Int J Electrochem Sci 8 (2013) 5067 - 5085

International Journal of

ELECTROCHEMICAL SCIENCE

wwwelectrochemsciorg

Ionic Conductivity and Thermophysical Properties of 1-Butyl-1-

Methylpyrrolidinium Butyl Sulfate and its Binary Mixtures with

Poly(ethylene glycol) at Various Temperatures

Tzi-Yi Wu Lin Hao Pin-Rong Chen Jian-Wei Liao

Department of Chemical and Materials Engineering National Yunlin University of Science and

Technology Yunlin 64002 Taiwan ROC

E-mail wutyyuntechedutw

Received 18 February 2013 Accepted 16 March 2013 Published 1 April 2013

The work studies the synthesis and thermophysical characterization of butylsulfate-based Ionic Liquid

(IL) [PyrMB][BuSO4] The synthesized IL is characterized by NMR spectroscopy elemental analysis

and Karl Fischer titration Thermophysical properties such as density viscosity and conductivity

for the binary mixture of butylsulfate-based IL [PyrMB][BuSO4] with poly(ethylene glycol) (PEG)

[Mw = 200] are measured over the whole composition range The thermal expansion coefficient of neat

[PyrMB][BuSO4] and its binary mixtures is ascertained using the experimental density results and

their excess volume expansivity is also estimated The temperature dependence of viscosity and

conductivity over the whole composition range can be described by the Vogel-Tammann-Fulcher

(VTF) equation and the maximum of conductivity is located at xPEG200 = 059 and corresponds to a

value of 171 mS cmminus 1

at 33315 K The excess properties and deviations are fitted to the Redlich-Kister polynomial equation to obtain the binary coefficients and the standard errors The variation of

these properties with composition of the binary mixtures is discussed in terms of molecular

interactions between components and structural effects

Keywords ionic liquids binary mixture viscosity conductivity Vogel-Tammann-Fulcher equation

excess properties deviations

1 INTRODUCTION

Room temperature ionic liquids (ILs) are typically salts that contain at least one organic cation

or anion and have melting points below or not far above ambient temperatures [1] The

physicochemical properties of ILs can be molecularly designed to positively affect different kinds of

processes by varying these anions and cations [2-5] During the past decade ionic liquids (ILs) have

attracted increasing attention and intensive investigation and witnessed a steady growth from the

Int J Electrochem Sci Vol 8 2013

5068

academics to industry due to their distinctive properties such as wide temperature range of application

high thermal stability [3-5] nonflammability wide electrochemical window [6-9] and high electrical

conductivity [10-13] They have been used in a broad variety of synthesis [1415] corrosion inhibition

[16-20] biotechnology [21-24] and nano technology [25-32] especially as promising ldquogreenrdquo

electrolyte for electrochemical devices such as dye-sensitized solar cells [33ndash38] lithium ion batteries

[39-42] sensors [43-55] and fuel cells [56] but experimental data of physicochemical properties [57-

61] are still scarce Alkylsulfate-based ILs are some of the most promising ILs to be applied in

academic investigations and industrial processes since most of these ILs can be easily synthesized at a

reasonable cost [62] So far the viscosity of sulfate-based ILs are 1 to 3 orders of magnitude greater

than those of traditional organic liquids which affect the rate of mass transfer leading to much more

power needed for mixing in liquid reactions or separation processes In some current studies the

problem of high viscosity can be resolved partially by means of adding organic solvents to pure ionic

liquid [63] Although the addition of organic solvents into ILs decreases the viscosity of mixture

significantly the conventional organic solvents has high volatility due to their boiling temperature are

below 80 oC Accordingly some scientists studied the thermodynamic properties of ethylene glycol

derivatives instead of conventional organic solvents Poly(ethylene glycol) (PEG) is one of the

ethylene glycol derivatives PEG of various molecular weights have been widely used in processes

across many industrial sectors as a result of being non-toxic biodegradable inexpensive widely

available and with a very low volatility [6465] Low molecular weight PEG (Mw = 200) is liquid at

room temperature making it easy to combine with ILs generate solvent systems and thus use in

advanced environmentally friendly processes [65]

In the present research the density viscosity and conductivity of a sulfate-based IL

([PyrMB][BuSO4]) and its binary mixture with PEG200 over the whole composition range and

temperatures between (29315 and 35315) K at atmospheric pressure are estimated From these

experimental results excess molar volume excess volume expansivity and viscosity deviations from

the ideal behavior were characterized The excess properties were calculated and then correlated at

each temperature as a function of composition by a Redlich-Kister-type equation The impact nature

of the solute on the ionic conductivity and thermophysical properties of binary mixture was

investigated in detail

2 EXPERIMENTAL

21 Materials

Poly(ethylene glycol)s dibutyl sulfate and 1-methylpyrrolidine were obtained from

commercial suppliers and used without further purification The poly(ethylene glycol)s of average

molar mass 200 was purchased from Showa Chemical Industry Co Ltd Japan dibutyl sulfate (95 )

and 1-methylpyrrolidine (gt98 ) was purchased from Tokyo Chemical Industry Co Ltd

Int J Electrochem Sci Vol 8 2013

5069

22 1-Butyl-1-methylpyrrolidinium butyl sulfate ([PyrMB][BuSO4])

Dibutyl sulfate (757 g 360 mmol) was added dropwise to a solution of equal molar amounts of

1-methylpyrrolidine (3065 g 360 mmol) in 200 mL toluene and then cooled in an ice-bath under

nitrogen at a rate that maintained the reaction temperature below 31315 K (highly exothermic

reaction) The reaction mixture was stirred at room temperature for 4h After the reaction stopped the

upper organic phase of the resulting mixture was decanted and the lower ionic liquid phase was

washed with ethyl acetate (4 x 70 mL) After the last washing the remaining ethyl acetate was

removed by rotavapor under reduced pressure The IL obtained was dried by heating at (34315 to

35315) K and stirring under a high vacuum (2 10-1

Pa) for 48 h In order to reduce the water content

to negligible values (lower than 003 mass ) a vacuum (2 x 10-1

Pa) and moderate temperature

(34315 K) were applied to the IL for 2 days The IL was kept in bottles under an inert gas The

structure of [PyrMB][BuSO4] is shown in Figure 1

Yield 91 1H NMR (300 MHz D2O ppm) 395 (t 2H -CH2SO4) 338 (m 4H N-CH2-)

321 (m 2H N-CH2-) 292 (s 3H N-CH3) 210 (m 4H N-CH2CH2-) 167 (m 2H -CH2CH2SO4)

155 (m 2H N-CH2CH2-) 128 (m 4H N-CH2CH2CH2- and -CH2CH2CH2SO4) 082 (m 6H N-

CH2CH2CH2CH3 and CH3CH2CH2CH2SO4) Elem Anal Calcd for C13H29NO4S C 5285 H 989

N 474 Found C 5268 H 979 N 465

NC4H9SO4

Figure 1 Molecular structure of 1-butyl-1-methylpyrrolidinium butyl sulfate ([PyrMB][BuSO4])

23 Measurements

The conductivity () of the ionic liquids was systematically measured with a conductivity

meter (LF 340 WTW Germany) and a standard conductivity cell (TetraCon 325 WTW Germany)

The cell constant was determined by calibration after each sample measurement using an aqueous 001

M KCl solution The density of the ILs was measured with a dilatometer which was calibrated by

measuring the density of neat glycerin at 30 40 50 60 70 and 80 oC The dilatometer was placed in a

thermostatic water bath (TV-4000 TAMSON) whose temperature was regulated to within plusmn 001 K

To measure density IL or a binary mixture was placed into the dilatometer up to the mark the top of

the capillary tube (located on the top of the dilatometer) was sealed and the dilatometer (with capillary

tube) was placed into a temperature bath for 10 min to allow the temperature to equilibrate The main

interval between the two marks in the capillary tube was 001 cm3 and the minor interval between two

marks was 0001 cm3 From the correction coefficient of glycerin in capillary tube at various

temperatures we can calculate the density of neat IL or binary system by the expanded volume of

liquid in the capillary tube at various temperatures Each sample was measured at least three times to

determine an average value and the values of the density were plusmn00001 gmL The viscosity (η) of the

Int J Electrochem Sci Vol 8 2013

5070

IL was measured using a calibrated modified Ostwald viscometer (Cannon-Fenske glass capillary

viscometers CFRU 9721-A50) The viscometer capillary diameter was 12 mm as measured using a

caliper (model No PD-153) with an accuracy of plusmn 002 mm The viscometer was placed in a

thermostatic water bath (TV-4000 TAMSON) whose temperature was regulated to within plusmn 001 K

The flow time was measured using a stopwatch with a resolution of 001 s For each IL the

experimental viscosity was obtained by averaging three to five flow time measurements The water

content of synthesized IL [PyrMB][BuSO4] was determined using the KarlndashFischer method the

content was below 300 ppm The nuclear magnetic resonance (NMR) spectra of the synthesized IL

were recorded on a BRUKER AV300 spectrometer and calibrated with tetramethylsilane (TMS) as the

internal reference

3 RESULTS AND DISCUSSION

31 Density and excess molar volume

The densities of neat IL [PyrMB][BuSO4] neat PEG200 and PEG200 (1) + [PyrMB][BuSO4]

(2) binary mixture over the temperature range (29315 to 35315) K and at atmospheric pressure are

presented in Table 1 and Figure 2 As shown in Figure 2 the trend of density for the binary system

with respect to temperature was decreased with increasing temperature The variations of the densities

with concentration at the different temperatures studied are shown in Figure 3 from analysis of the

data it was found that the densities depend more strongly on the mole fraction of PEG200 in the

mixture than on temperature

Figure 2 ρ vs T plot of the PEG200 (1) + [PyrMB][BuSO4] (2) binary system

A third-order polynomial was found to satisfactorily correlate the change of density with various

compositions

T K

290 300 310 320 330 340 350 360

g

cm

-3

109

110

111

112

113

114

x1 = 00000

x1 = 01452

x1 = 01942

x1 = 02912

x1 = 03897

x1 = 04893

x1 = 05890

x1 = 06903

x1 = 07922

x1 = 08958

Int J Electrochem Sci Vol 8 2013

5071

ρ = a0 + a1 x1 + a2 x12 + a3 x1

3 (1)

where x1 is the mole fractions of PEG200 and a0 a1 a2 and a3 refer to the fit coefficients Fit

parameters are listed in Table 2 for the mixtures

Table 1 Experimental density () and excess molar volume (VmE) for the binary system PEG200 (1)

+ [PyrMB][BuSO4] (2)

x1

29315 29815 30315 30815 31315 31815 32315 32815 33315 33815 34315 34815 35315

ρg middotcm-3

0 11258 11228 11199 11169 11140 11111 11082 11053 11025 10996 10968 10940 10912

01452 11288 11259 11230 11200 11171 11142 11112 11083 11053 11024 10995 10965 10936

01942 11305 11275 11245 11216 11186 11157 11127 11097 11068 11038 11008 10979 10949

02912 11334 11304 11274 11243 11213 11183 11153 11123 11092 11062 11032 11002 10972

03897 11352 11321 11291 11260 11229 11199 11168 11138 11107 11076 11046 11015 10984

04893 11356 11325 11294 11263 11232 11201 11170 11139 11108 11077 11046 11015 10984

05890 11350 11319 11288 11256 11225 11193 11162 11131 11099 11068 11036 11005 10973

06903 11331 11299 11267 11235 11203 11172 11140 11108 11076 11044 11012 10980 10948

07922 11318 11285 11252 11219 11186 11153 11120 11087 11054 11021 10988 10956 10923

08958 11312 11278 11243 11208 11174 11139 11104 11070 11035 11000 10966 10931 10896

1 11312 11273 11234 11195 11157 11119 11081 11044 11007 10970 10933 10896 10860

E

mV cm3 mol-1

0 00000 00000 00000 00000 00000 00000 00000 00000 00000 00000 00000 00000 00000

01452 -05572 -05884 -06161 -06404 -06613 -06787 -06925 -07028 -07096 -07127 -07123 -07081 -07003

01942 -08575 -08917 -09225 -09498 -09737 -09942 -10111 -10245 -10343 -10406 -10432 -10422 -10375

02912 -13539 -13931 -14289 -14614 -14903 -15159 -15379 -15564 -15714 -15828 -15906 -15947 -15952

03897 -15730 -16197 -16630 -17029 -17394 -17726 -18022 -18284 -18511 -18702 -18858 -18978 -19061

04893 -14983 -15521 -16026 -16498 -16936 -17341 -17711 -18047 -18348 -18615 -18846 -19041 -19201

05890 -12361 -12970 -13547 -14090 -14601 -15078 -15522 -15931 -16306 -16647 -16953 -17224 -17459

06903 -07359 -08013 -08634 -09222 -09777 -10300 -10788 -11243 -11663 -12049 -12400 -12717 -12997

07922 -03606 -04235 -04831 -05394 -05923 -06418 -06878 -07304 -07695 -08051 -08371 -08655 -08903

08958 -01410 -01915 -02384 -02818 -03216 -03578 -03903 -04192 -04443 -04656 -04832 -04969 -05068

1 00000 00000 00000 00000 00000 00000 00000 00000 00000 00000 00000 00000 00000

Figure 3 ρ of the PEG200 (1) + [PyrMB][BuSO4] (2) binary system as a function of concentration

at various temperatures

The correlation constants for Eq (1) were established using the least square method and are

presented in Table 2 along with the standard deviation estimated using the following equation

2

exp cal 1 2( - )

[ ]Z Z

n

(2)

x1

00 02 04 06 08 10

g c

m-3

106

108

110

112

114

29315 K

30315 K

31315 K

32315 K

33315 K

34315 K

35315 K

Int J Electrochem Sci Vol 8 2013

5072

where n is the number of experimental points and Zexp and Zcal are the experimental and

calculated values respectively

Table 2 Coefficients of polynomiala for the correlation of the density (ρgmiddotcm

-3) in function of

concentration at different temperatures of the binary systems PEG200 (1) + [PyrMB][BuSO4]

(2)

TK a0 g cm

-3 a1 g cm

-3 a2 g cm

-3 a3 g cm

-3

29315 11248 00455 -00638 0024 0000840

29815 11219 00447 -00617 00217 0000800

30315 1119 00439 -00596 00195 0000764

30815 11161 00431 -00575 00173 0000732

31315 11132 00422 -00554 00152 0000704

31815 11103 00413 -00533 00132 0000680

32315 11075 00403 -00512 00112 0000660

32815 11046 00393 -00492 00093 0000640

33315 11018 00382 -00471 00074 0000625

33815 10989 00372 -0045 00055 0000613

34315 10961 0036 -0043 00037 0000606

34815 10933 00349 -00409 0002 0000596

35315 10905 00337 -00389 00003 0000592

a ρ = a0 + a1 x1 + a2 x1

2 + a3 x1

3

As can be seen from the Table 1 the value of the density decreases with increasing temperature

eventhough the variation is very small If the variation of the density with the temperature is

considered as linear then the change in the calculated thermal expansion coefficient values becomes

nearly constant In order to have an improved accuracy a second order polynomial of the eqn (3) was

used to correlate the variation of the density with the temperature for PEG200 (1) + [PyrMB][BuSO4]

(2) binary system

ρ = b0 + b1 T + b2 T2 (3)

where T is the temperature and b0 b1 and b2 are the correlation coefficients The correlation

coefficients are listed in Table 3 together with the standard deviations (σ) calculated using Eq (2)

Excess thermodynamic properties are of great importance for understanding the nature of

molecular interaction in binary mixtures The excess molar volume E

mV which is the difference

between the real and ideal mixing behaviors is defined by

m m 1 1 2 2 E o o

V V xV x V (4)

where Vm represents the volume of a mixture containing one mole of (PEG200 +

[PyrMB][BuSO4]) x1 and x2 are the mole fractions of components 1 (PEG200) and 2

([PyrMB][BuSO4]) respectively and V10 and V2

0 are the molar volumes of the pure components The

Int J Electrochem Sci Vol 8 2013

5073

excess molar volumes of mixtures over the entire composition range were calculated from our

measurements of density according to the following equation

Table 3 The adjustable parameters of density (ρ = b0 + b1 T + b2 T2) at various temperature for neat

PEG200 (x1 = 1) [PyrMB][BuSO4] (x1 = 0) and binary system PEG200 (1) + [PyrMB][BuSO4]

(2)

x1 b0 b1 b2

0 1326 -000077105 00000003 000003

01452 1301 -0000588 0 000023

01942 1304 -0000593 0 000032

02912 131 -0000604 0 000047

03897 1315 -0000613 0 000009

04893 1318 -0000621 0 000034

05890 1319 -0000629 0 000045

06903 132 -0000639 0 000046

07922 1325 -0000658 0 000036

08958 1335 -0000694 0 000030

1 1405 -000108 000000051 000112

Figure 4 Excess molar volumes for the binary system PEG200 (1) + [PyrMB][BuSO4] (2) and

fitted curves using the Redlich-Kister parameters

1 1 2 2 1 1 2 2m

1 2

E

Vx M x M x M x M

(5)

where ρ1 ρ2 and ρ are the densities of neat PEG200 [PyrMB][BuSO4] and their mixture

respectively M1 and M2 are the molar masses of PEG200 and [PyrMB][BuSO4] respectively The E

mV

values of mixtures are summarized in Table 1 The excess molar volumes of mixtures versus the mole

x1

00 02 04 06 08 10

Vm

E

cm

3 m

ol-1

-20

-15

-10

-05

00

30315 K

31315 K

32315 K

33315 K

Int J Electrochem Sci Vol 8 2013

5074

fraction of PEG200 from 29315 to 35315 K are plotted in Figure 4 The excess molar volume of the

binary system is mainly concerned with the weak chemical interactions the physical and structural

characteristics of the system components If the chemical or nonchemical interaction of the same

components is the dominant way of the interaction the excess volume of the mixture should be

positive If the molecules of the components have a more effective packing in the mixture than that in

the pure component that is the attracting interaction between the molecules of two components is the

dominant way the excess molar volume of the binary system should be negative [66] As shown in

Figure 4 the excess molar volumes are asymmetric and negative for all of the systems studied over the

entire composition range the minimum of E

mV is reached at a mole fraction of PEG200 near x1 = 04

and the absolute values of the excess volume increase with increasing temperature The molar volume

for [PyrMB][BuSO4] is 26243 cm3 mol

-1 at T = 29315 K which is greater than the molar volumes of

PEG200 (17681 cm3 mol

-1) at T = 29315 K The large difference between molar volumes of the

molecular liquid and [PyrMB][BuSO4] indicates that it is possible that the relatively small organic

molecules fit into the interstices upon mixing Therefore the filling effect of organic molecular liquids

in the interstices of ionic liquids and the ionndashdipole interactions between poly(ethylene glycol)

oligomer and the butylsulfate-based ionic liquids all contribute to the negative values of the molar

excess volumes

32 Volume expansivity and excess volume expansivity

Density results for the PEG200 and [PyrMB][BuSO4] binary system studied in current work were

also used to derive the coefficient of thermal expansion From the relationship of vs T the volume

expansivity (coefficient of thermal expansion) α is defined as

1 1

( ) ( )p p

V

TV T

(6)

where subscript p indicates constant pressure The α values of pure [PyrMB][BuSO4] and

PEG200 and their mixture are summarized in Table 4 The values indicate that the thermal expansion

coefficient of this binary mixture (PEG200 + [PyrMB][BuSO4]) increases with increasing temperature

and increases with increasing mole fraction of the PEG200

The corresponding excess function (excess volume expansivity) was calculated using

E id id

1 1 2 2 (7)

where id

1 is an ideal volume fraction given by the following relation

1 m11

1 m1 2 m2

id xV

xV x V

(8)

Int J Electrochem Sci Vol 8 2013

5075

where Vmi is the molar volume of pure component i

Table 4 Experimental volume expansivity (α) and the excess volume expansivity (αE) for the binary

system PEG200 (1) + [PyrMB][BuSO4] (2)

x1

29315 29815 30315 30815 31315 31815 32315 32815 33315 33815 34315 34815 35315

104 αK-1

0 51245 51380 51516 51651 51787 51922 52058 52193 52329 52464 52600 52735 52871

01452 52053 52189 52325 52462 52600 52739 52878 53018 53159 53300 53443 53586 53730

01942 52438 52576 52715 52854 52994 53135 53276 53418 53561 53705 53850 53995 54141

02912 53299 53443 53586 53731 53877 54023 54170 54318 54466 54616 54766 54917 55069

03897 53973 54120 54268 54417 54567 54717 54869 55021 55174 55328 55483 55638 55795

04893 54667 54818 54971 55124 55278 55433 55589 55745 55903 56061 56221 56381 56542

05890 55372 55527 55683 55840 55998 56157 56317 56477 56639 56801 56965 57129 57294

06903 56358 56517 56677 56838 57000 57163 57327 57492 57657 57824 57992 58160 58330

07922 58175 58344 58515 58687 58860 59033 59208 59384 59561 59739 59918 60098 60279

08958 61313 61502 61691 61882 62074 62268 62462 62658 62855 63053 63252 63453 63655

1 66532 66763 66993 67224 67455 67685 67916 68146 68377 68607 68838 69069 69299

104 αEK-1

0 00000 00000 00000 00000 00000 00000 00000 00000 00000 00000 00000 00000 00000

01452 -00762 -00772 -00782 -00792 -00800 -00808 -00815 -00822 -00827 -00832 -00837 -00840 -00843

01942 -00942 -00954 -00966 -00977 -00987 -00997 -01006 -01014 -01021 -01028 -01033 -01038 -01043

02912 -01259 -01275 -01289 -01302 -01315 -01327 -01339 -01349 -01359 -01368 -01376 -01383 -01389

03897 -01870 -01889 -01908 -01926 -01943 -01959 -01975 -01989 -02003 -02016 -02028 -02040 -02050

04893 -02576 -02600 -02623 -02646 -02668 -02689 -02709 -02728 -02746 -02764 -02780 -02796 -02811

05890 -03382 -03412 -03441 -03470 -03497 -03524 -03550 -03574 -03598 -03621 -03644 -03665 -03685

06903 -04064 -04100 -04136 -04170 -04204 -04236 -04268 -04299 -04329 -04358 -04386 -04413 -04439

07922 -04073 -04110 -04146 -04181 -04214 -04247 -04279 -04310 -04339 -04368 -04396 -04422 -04448

08958 -02968 -02998 -03026 -03053 -03079 -03104 -03128 -03151 -03172 -03192 -03211 -03228 -03245

1 00000 00000 00000 00000 00000 00000 00000 00000 00000 00000 00000 00000 00000

Figure 5 Plot of excess volume expansivity αE of the PEG200 (1) + [PyrMB][BuSO4] (2) binary

system versus mole fraction x1 at various temperatures

Typical concentration dependencies of excess volume expansivity are given in Figure 5 for the

PEG200 + [PyrMB][BuSO4] binary system The values of excess thermal coefficient αE are found to

x1

00 02 04 06 08 10

10

4

E K

-1

-04

-03

-02

-01

00

29315 K

30315 K

31315 K

32315 K

33315 K

34315 K

35315 K

Temp

Int J Electrochem Sci Vol 8 2013

5076

be negative over the whole composition range for the binary system at 29315 ~ 35315 K The curves

are asymmetrical with the minimum located at the IL mole fraction of about 08 In general negative

αE values indicate the presence of strong interaction between the components in the mixtures [67] The

trends observed in αE values for the present mixtures suggest the formation of H-bonding between

unlike molecules which is stronger in PEG200 + [PyrMB][BuSO4] binary system The increasing

negative αE values for PEG200 + [PyrMB][BuSO4] with increase in temperature indicate enhanced

unlike interaction between components of the mixture that is more destruction of order during mixing

contributes negatively to αE

33 Viscosity

Since ILs are more viscous than conventional solvents in most applications they can be used in

mixtures with other less viscous compounds Therefore the viscosity of pure ILs and their mixtures

with PEG oligomer (or conventional solvents) is an important property and their knowledge is

primordial for each industrial processes [6869] The measured dynamic viscosities for the neat

PEG200 neat [PyrMB][BuSO4] and PEG200 + [PyrMB][BuSO4] binary mixture as a function of

temperature over the whole composition range are shown in Figure 6 and their data are listed in Table

5 the viscosities of the mixtures decrease rapidly when PEG oligomer are added to the ionic liquid

especially at lower temperatures The fitting lines in Figure 6 were calculated with the following

fourth-order polynomial equation

= c0 + c1 x1 + c2 x12 + c3 x1

3 + c4 x1

4 (9)

where x1 is the mole fractions of PEG200 and c0 c1 c2 c3 and c4 refer to the fit coefficients

The parameters of correlation are shown in Table 6

Figure 6 Dynamic viscosity for the PEG200 (1) + [PyrMB][BuSO4] (2) binary system as a

function of mole fractions of the PEG200 at different temperatures Lines represent the

polynomial correlation

x1

00 02 04 06 08 10

mP

a s

0

200

400

600

800

1000

1200

1400

29315 K

30315 K

31315 K

32315 K

33315 K

34315 K

35315 K

Int J Electrochem Sci Vol 8 2013

5077

Table 5 Experimental dynamic viscosity (η) and viscosity deviation (Δη) for the binary system

PEG200 (1) + [PyrMB][BuSO4] (2)

x1

29315 29815 30315 30815 31315 31815 32315 32815 33315 33815 34315 34815 35315

ηmPamiddots

0 13209 9343 6745 4961 3712 2821 2176 1700 1345 1077 871 712 587

01452 5907 4362 3294 2539 1992 1589 1286 1055 876 735 623 533 460

01942 4656 3475 2656 2072 1647 1331 1091 907 763 649 557 483 422

02912 3134 2395 1870 1489 1205 991 826 697 594 512 445 390 345

03897 2367 1846 1463 1177 959 792 660 557 474 406 351 306 269

04893 1799 1396 1104 887 723 598 501 424 362 312 272 238 210

05890 1540 1194 941 753 611 502 418 351 298 255 220 191 167

06903 1185 926 736 594 485 402 336 284 242 209 181 158 139

07922 954 742 589 475 389 323 271 231 198 172 150 132 117

08958 811 639 512 415 342 285 240 204 175 151 132 116 102

1 629 505 410 337 280 235 199 170 146 126 110 97 85

ΔηmPamiddots

0 00 00 00 00 00 00 00 00 00 00 00 00 00

01452 -5475 -3698 -2530 -1751 -1221 -857 -602 -423 -295 -204 -137 -89 -54

01942 -6111 -4152 -2859 -1991 -1398 -988 -700 -496 -347 -244 -166 -110 -68

02912 -6411 -4374 -3030 -2126 -1507 -1077 -774 -558 -391 -288 -204 -142 -103

03897 -5940 -4053 -2813 -1982 -1415 -1022 -745 -547 -405 -300 -223 -166 -123

04893 -5254 -3622 -2541 -1811 -1255 -957 -708 -528 -396 -299 -227 -173 -131

05890 -4260 -2944 -2073 -1484 -1034 -796 -594 -448 -341 -262 -203 -158 -124

06903 -3340 -2316 -1636 -1176 -826 -634 -475 -360 -275 -212 -165 -129 -101

07922 -2289 -1599 -1138 -823 -579 -449 -320 -257 -197 -152 -118 -92 -72

08958 -1129 -787 -559 -404 -277 -220 -152 -126 -96 -74 -58 -45 -35

1 00 00 00 00 00 00 00 00 00 00 00 00 00

Table 6 Coefficients of polynomiala for the correlation of the viscosity ( mPa s) in function of

concentration at different temperatures of the binary systems PEG200 (1) + [PyrMB][BuSO4]

(2)

TK c0 mPa s c1 mPa s c2 mPa s c3 mPa s C4 mPa s

29315 13154 -68701 15960 -16688 63543 1075

29815 93069 -46703 10681 -11113 42269 727

30315 67211 -32185 72085 -74396 28222 497

30815 49454 -22431 48886 -49866 18828 343

31315 37016 -15772 33175 -33281 12474 238

31815 28146 -1116 22406 -21947 81322 165

32315 21713 -7923 14947 -1413 51409 114

32815 16975 -56244 97349 -870 30666 077

33315 13435 -39753 60667 -4908 16219 051

33815 10756 -27812 34718 -22519 61382 033

34315 87026 -19098 16304 -39091 -88892 021

34815 71108 -12698 32285 90904 -5763 016

35315 58636 -79728 -60345 18103 -91096 017 a = c0 + c1 x1 + c2 x1

2 + c3 x1

3 + c4 x1

4

The temperature dependence becomes distinctly nonlinear especially at high [PyrMB][BuSO4]

content The Vogel-Tammann-Fulcher (VTF) equation [70-75] suitably correlates the nonlinear

behavior as a function of the temperature not only the viscosities of the neat IL but also the viscosities

of the mixtures for the binary systems through the composition range

Int J Electrochem Sci Vol 8 2013

5078

exp[ ]( )

o

o

B

T T

(10)

where ηo B and To are constants The parameter To is the ideal glass transition temperature which

should be slightly below the experimental glass transition temperature Tg [76] The adjustable

parameters obtained from the VTF correlation were presented in Table 7 The obtained parameters o

and B change smoothly with composition for binary mixtures

Table 7 The VTF equation parameters of viscosity ( 1 exp[ ]( )

o

o

B

T T

) and conductivity

(

exp[ ]( )

o

o

B

T T

) for neat PEG200 (x1 = 1) [PyrMB][BuSO4] (x1 = 0) and binary system

PEG200 (1) + [PyrMB][BuSO4] (2)

x1

ηo (mPa s) To (K) B (K) R2a

o (mS cm-1

) To (K) Brsquo (K) R2a

0 027 1810 9540 0999 792 1788 6854 0999

01452 026 1712 9413 0999 577 1699 6268 0999

01942 043 1788 7975 0999 401 1792 5297 0999

02912 053 1794 7264 0999 521 1662 6031 0999

03897 026 1629 8902 0999 274 1803 4381 0999

04893 023 1666 8455 0999 177 1951 3272 0999

05890 015 1648 8865 0999 216 1883 3672 0999

06903 015 1647 8572 0999 88 2174 2000 0999

07922 017 1717 7702 0999 92 2020 2578 0999

08958 012 1642 8360 0999 43 2110 2088 0999

1 014 1649 7868 0999 556 1928 9815 0999

a Correlation coefficient

The viscosities of the mixtures decrease rapidly when organic oligomers are added to the ionic

liquid this decrease is particularly evident in dilute solutions of organic oligomers in the ionic liquid

The strong coulomb interactions between the [BuSO4]- anion and [PyrMB]

+ cation are weakened upon

mixing with the polar organic oligomers which leads to a higher mobility of the ions and a lower

viscosity of the mixtures [77] This indicates that the viscosity of ILs could be therefore tuned for

several applications by adding an organic solvent or by changing temperature [78]

Due to the wide range of possible molecular interactions between the two components

deviations can occur from ideal behavior These viscosity deviations can be quantified by the viscosity

deviation Δη also known as ldquoexcess viscosityrdquo in other sources

1 1 2 2 (mPa s) x x (11)

Int J Electrochem Sci Vol 8 2013

5079

where x1 and x2 are the mole fractions of PEG200 and [PyrMB][BuSO4] respectively and 1

and 2 are the viscosities (mPa middot s) of the solution the pure solvent and the pure IL respectively

Figure 7 shows the viscosity deviations as a function of the PEG200 mole fraction composition x1 and

temperature for the PEG200 + [PyrMB][BuSO4] binary mixture The values of viscosity deviations

are compared with those obtained from the RedlichndashKister polynomial equation The viscosity

deviation for the mixture show negative deviations from ideality over the whole mole fraction range

Figure 7 also shows that the negative values of viscosity deviations decrease with increasing

temperature this can be attributed to the specific interactions in mixtures typically hydrogen bonds break-

up as the temperature increases [79] The minimum value of Δη is observed at about x1 asymp 03 and the

viscosity deviation depends on molecular interactions as well as on the size and shape of the molecules

[80]

Figure 7 Viscosity deviations Δη versus the mole fraction at various temperatures for the binary

mixture PEG200 (1) + [PyrMB][BuSO4] (2)

34 Conductivity

The experimental data of conductivity of the neat ILs [PyrMB][BuSO4] neat PEG200 and

binary system are plotted against the x1 at various temperatures in Figure 8 together with lines

calculated with the four-order polynomial equation

= d0 + d1 x1 + d2 x12 + d3 x1

3 + d4 x1

4 (12)

where x1 is the mole fractions of PEG200 and d0 d1 d2 d3 and d4 refer to the fit coefficients

The parameters of correlation are shown in Table 8 The conductivities of neat IL [PyrMB][BuSO4]

neat PEG200 and binary system at various temperatures were fitted using the VTF equation

exp[ ]

( )o

o

B

T T

(13)

x1

00 02 04 06 08 10

m

Pa s

-700

-600

-500

-400

-300

-200

-100

0

29315 K

30315 K

31315 K

32315 K

33315 K

34315 K

35315 K

Int J Electrochem Sci Vol 8 2013

5080

where T is the absolute temperature and Brsquo and To are adjustable parameters The best-fit

mS cm-1 Brsquo (K) and To (K) parameters are given in Table 7 Neat [PyrMB][BuSO4] neat

PEG200 and binary system were very well fit by the VTF model over the temperature range studied

Figure 8 Plot of conductivity of the PEG200 (1) + [PyrMB][BuSO4] (2) binary system versus

mole fraction x1 at various temperatures

Table 8 Coefficients of polynomiala for the correlation of the conductivity ( mS cm

-1) in function

of concentration at different temperatures of the binary systems PEG200 (1) +

[PyrMB][BuSO4] (2)

TK d0 mS cm

-1 d1 mS cm

-1 d2 mS cm

-1 d3 mS cm

-1 d4 mS cm

-1

29315 02019 09622 -01679 0734 -17284 00095

29815 02588 11031 -02503 09086 -20181 00109

30315 03255 12119 -01935 08565 -21971 00125

30815 04025 13165 -01329 0767 -23477 00141

31315 04904 13712 01238 03677 -23439 00156

31815 05894 15032 -00006 04737 -25518 00171

32315 06999 15802 00743 0265 -25986 00188

32815 08221 16427 01595 00089 -26032 00208

33315 09562 16373 04858 -06207 -24165 00233

a = d0 + d1 x1 + d2 x1

2 + d3 x1

3 + d4 x1

4

As shown in Figure 8 it can be seen that the conductivity of the binary mixture increases with

increasing amount of PEG200 goes through a maximum and then goes down to the specific

conductivity of the neat PEG200 The conductivity is related to the ion mobility and the number of

charge carriers [81] At a fixed concentration the ions move faster at higher temperature due to the

relatively lower viscosity of the mixture On the other hand the composition influences both the ion

mobility and the number of charge carriers at a fixed temperature At the beginning the number of

charge and the ion mobility increase with increasing PEG oligomer composition the maximum of

conductivity is located at x1 = 059 and corresponds to a value of 171 mS cmminus 1

at 33315 K It can also

be observed that the conductivity increases as the temperature increases The higher temperature may

x1

00 02 04 06 08 10

mS

cm

-1

00

05

10

15

20

29315 K

29815 K

30315 K

30815 K

31315 K

31815 K

32315 K

32815 K

33315 K

Int J Electrochem Sci Vol 8 2013

5081

weaken the influence of aggregation to the conductivity which suggests that a higher temperature is

better for the ILs to act as electrolytes

Table 9 RedlickndashKister fitting coefficients Ak and the standard deviation of the VE and ∆for the

binary mixture of PEG200 (1) + [PyrMB][BuSO4] (2) system

TK A0 A1 A2 A3 A4

VEcm

3 mol

-1

29315 -5979 -4906 6585 5754 -1717 002687

29815 -6200 -4760 6464 5767 -2022 002693

30315 -6408 -4612 6345 5774 -2276 002698

30815 -6602 -4461 6229 5774 -2476 002701

31315 -6782 -4310 6116 5767 -2623 002701

31815 -6948 -4155 6006 5753 -2716 002699

32315 -7100 -3999 5899 5732 -2754 002692

32815 -7239 -3840 5795 5704 -2738 002683

33315 -7363 -3679 5694 5669 -2666 002670

33815 -7472 -3515 5596 5626 -2538 002654

34315 -7568 -3350 5501 5576 -2353 002634

34815 -7648 -3182 5409 5518 -2111 002611

35315 -7714 -3011 5320 5452 -1812 002586

∆mPa s

29315 -20414 -17226 -15592 -95544 -75863 399496

29815 -14035 -11558 -10713 -62192 19493 340180

30315 -98261 -78407 -73734 -40709 58145 286725

30815 -69922 -53591 -50601 -2676 67556 235258

31315 -48876 -39537 -41051 -14118 16739 079245

31815 -36917 -25169 -22939 -11646 51047 146189

32315 -27415 -1721 -12581 -92603 21498 104339

32815 -20441 -11703 -77538 -38334 -81478 090708

33315 -15382 -67274 -31134 -47585 -18255 059539

33815 -11664 -44928 -15533 -22312 -05591 037855

34315 -89038 -24163 68654 -15007 -10347 024263

34815 -68279 -91813 23131 -10367 -18636 017759

35315 -52525 -24051 26474 15498 -85341 018640

35 Redlich-Kister Equation for Binary System

The binary excess property ( E

mV ) and deviations (Δ) at several temperatures were fitted to a

Redlich-Kister-type equation [82]

1 1 1

0

(or ) (1 ) (1 2 )j

E i

i

i

Y Y x x A x

(14)

Int J Electrochem Sci Vol 8 2013

5082

where ΔY (YE) represents E

mV (cm3 mol

minus1) and Δ

(mPa s)x1 denotes the mole fraction of

PEG200 Ai represents the polynomial coefficients and j is the degree of the polynomial expansion

The correlated results for excess molar volumes ( E

mV ) viscosity deviations (Δ) including the values

of the fitting parameters Ai together with the standard deviation σ are given in Table 9 where the

tabulated standard deviation σ [83] is defined as

2

exp cal 1 2( )

[ ]Y Y

m n

(15)

where m is the number of experimental data points and n is the number of estimated

parameters The subscripts ldquoexprdquo and ldquocalrdquo denote the values of the experimental and calculated

property respectively As shown in Table 9 the experimentally derived E

mV and Δη values were

correlated satisfactorily by the Redlich-Kister equation

4 CONCLUSIONS

This paper is a systematic characterizations of thermophysical properties for IL binary system

Density viscosity and conductivity for (PEG200 + [PyrMB][BuSO4]) binary system are presented as a

function of temperature at atmospheric pressure it was demonstrated that viscosity and conductivity

were more sensitive to the changes in PEG content or temperature than density and the viscosity and

conductivity of pure IL and (PEG200 + [PyrMB][BuSO4]) binary system at different temperature are

fitted using the VogelndashTammannndashFulcher (VTF) equation with good accuracy The excess molar

volumes excess volume expansivity and viscosity deviations show negative deviations from the ideal

solution the results are interpreted in terms of molecular interactions in the (PEG200 +

[PyrMB][BuSO4]) binary mixture The conductivity increases to a maximum value when the

concentration of PEG200 is increased and decreases after the maximum the data obtained will be

helpful for the application of the ionic liquids as electrolytes and also useful for the ionic liquids

database

ACKNOWLEDGEMENTS

The authors would like to thank the National Science Council of the Republic of China for financially

supporting this project

References

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2 TY Wu IW Sun ST Gung MW Lin BK Chen HP Wang SG Su J Taiwan Inst Chem

Eng 42 (2011) 513

Int J Electrochem Sci Vol 8 2013

5083

3 TY Wu SG Su KF Lin YC Lin HP Wang MW Lin ST Gung IW Sun Electrochim

Acta 56 (2011) 7278

4 B Baek S Lee C Jung Int J Electrochem Sci 6 (2011) 6220

5 PN Tshibangu SN Ndwandwe ED Dikio Int J Electrochem Sci 6 (2011) 2201

6 TY Wu SG Su HP Wang IW Sun Electrochem Commun 13 (2011) 237

7 TY Wu SG Su HP Wang YC Lin ST Gung MW Lin IW Sun Electrochim Acta 56

(2011) 3209

8 IW Sun YC Lin BK Chen CW Kuo CC Chen SG Su PR Chen TY Wu Int J

Electrochem Sci 7 (2012) 7206

9 TY Wu SG Su ST Gung MW Lin YC Lin CA Lai IW Sun Electrochim Acta 55

(2010) 4475

10 AN Soriano AM Agapito LJLI Lagumbay AR Caparanga MH Li J Taiwan Inst Chem

Eng 42 (2011) 258

11 TY Wu IW Sun ST Gung BK Chen HP Wang SG Su J Taiwan Inst Chem Eng 42

(2011) 874

12 S Ibrahim MR Johan Int J Electrochem Sci 6 (2011) 5565

13 TY Wu SG Su YC Lin HP Wang MW Lin ST Gung IW Sun Electrochim Acta 56

(2010) 853

14 H Wang LX Wu YC Lan JQ Zhao JX Lu Int J Electrochem Sci 6 (2011) 4218

15 FF Liu SQ Liu QJ Feng SX Zhuang JB Zhang P Bu Int J Electrochem Sci 7 (2012)

4381

16 HA Barham SA Brahim Y Rozita KA Mohamed Int J Electrochem Sci 6 (2011) 181

17 SK Shukla LC Murulana EE Ebenso Int J Electrochem Sci 6 (2011) 4286

18 NV Likhanova O Olivares-Xometl D Guzman-Lucero MA Dominguez-Aguilar N Nava

M Corrales-Luna MC Mendoza Int J Electrochem Sci 6 (2011) 4514

19 A Zarrouk M Messali H Zarrok R Salghi AA Ali B Hammouti SS Al-Deyab F Bentiss

Int J Electrochem Sci 7 (2012) 6998

20 BS Ali BH Ali R Yusoff MK Aroua Int J Electrochem Sci 7 (2012) 3835

21 MH Lin YJ Liu ZH Yang YB Huang ZH Sun Y He CL Ni Int J Electrochem Sci 7

(2012) 965

22 CH Su MH Chung HJ Hsieh YK Chang JC Ding HM Wu J Taiwan Inst Chem Eng

43 (2012) 573

23 H Shekaari A Kazempour J Taiwan Inst Chem Eng 43 (2012) 650

24 ZJ Wei Y Li D Thushara YX Liu QL Ren J Taiwan Inst Chem Eng 43 (2012) 363

25 GQ Zhang HW Yang JF Gao HK Zhang CB Zheng YL Cao YH Wang KQ Ding

Int J Electrochem Sci 7 (2012) 7547

26 P Norouzi MR Ganjali F Faridbod SJ Shahtaheri HA Zamani Int J Electrochem Sci 7

(2012) 2633

27 F Faridbod MR Ganjali M Hosseini P Norouzi Int J Electrochem Sci 7 (2012) 1927

28 MR Ganjali Z Rafiei-Sarmazdeh T Poursaberi SJ Shahtaheri P Norouzi Int J

Electrochem Sci 7 (2012) 1908

29 A Babaei DJ Garrett AJ Downard Int J Electrochem Sci 7 (2012) 3141

30 MR Ganjali T Alizade P Norouzi Int J Electrochem Sci 7 (2012) 4800

31 MR Ganjali T Alizade B Larijani F Faridbod P Norouzi Int J Electrochem Sci 7 (2012)

4756

32 P Norouzi B Larijani MR Ganjali Int J Electrochem Sci 7 (2012) 7313

33 TY Wu MH Tsao SG Su HP Wang YC Lin FL Chen CW Chang IW Sun J Braz

Chem Soc 22 (2011) 780

34 MH Tsao TY Wu HP Wang IW Sun SG Su YC Lin CW Chang Mater Lett 65

(2011) 583

Int J Electrochem Sci Vol 8 2013

5084

35 SY Ku SY Lu Int J Electrochem Sci 6 (2011) 5219

36 TY Wu MH Tsao FL Chen SG Su CW Chang HP Wang YC Lin IW Sun J Iran

Chem Soc 7 (2010) 707

37 IW Sun HP Wang H Teng SG Su YC Lin CW Kuo PR Chen TY Wu Int J

Electrochem Sci 7 (2012) 9748

38 TY Wu MH Tsao FL Chen SG Su CW Chang HP Wang YC Lin WC Ou-Yang

IW Sun Int J Mol Sci 11 (2010) 329

39 YX An PJ Zuo XQ Cheng LX Liao GP Yin Int J Electrochem Sci 6 (2011) 2398

40 LC Xuan YX An W Fang LX Liao YL Ma ZY Ren GP Yin Int J Electrochem Sci

6 (2011) 6590

41 HM Wang SQ Liu K Huang XG Yin YN Liu SJ Peng Int J Electrochem Sci 7

(2012) 1688

42 HM Wang SQ Liu NF Wang YN Liu Int J Electrochem Sci 7 (2012) 7579

43 H Ganjali MR Ganjali T Alizadeh F Faridbod P Norouzi Int J Electrochem Sci 6 (2011)

6085

44 MR Ganjali MH Eshraghi S Ghadimi SM Moosavi M Hosseini H Haji-Hashemi P

Norouzi Int J Electrochem Sci 6 (2011) 739

45 MR Ganjali T Poursaberi M Khoobi A Shafiee M Adibi M Pirali-Hamedani P Norouzi

Int J Electrochem Sci 6 (2011) 717

46 P Norouzi M Hosseini MR Ganjali M Rezapour M Adibi Int J Electrochem Sci 6 (2011)

2012

47 MR Ganjali MR Moghaddam M Hosseini P Norouzi Int J Electrochem Sci 6 (2011)

1981

48 MR Ganjali M Hosseini M Pirali-Hamedani HA Zamani Int J Electrochem Sci 6 (2011)

2808

49 MR Ganjali M Rezapour SK Torkestani H Rashedi P Norouzi Int J Electrochem Sci 6

(2011) 2323

50 P Norouzi M Pirali-Hamedani SO Ranaei-Siadat MR Ganjali Int J Electrochem Sci 6

(2011) 3704

51 F Faridbod HA Zamani M Hosseini M Pirali-Hamedani MR Ganjali P Norouzi Int J

Electrochem Sci 6 (2011) 3694

52 MR Ganjali SO Ranaei-Siadat H Rashedi M Rezapour P Norouzi Int J Electrochem Sci

6 (2011) 3684

53 TH Tsai KC Lin SM Chen Int J Electrochem Sci 6 (2011) 2672

54 MR Ganjali T Alizadeh F Azimi B Larjani F Faridbod P Norouzi Int J Electrochem

Sci 6 (2011) 5200

55 R Mirshafian MR Ganjali P Norouzi Int J Electrochem Sci 7 (2012) 1656

56 J Gao JG Liu WM Liu B Li YC Xin Y Yin ZG Zou Int J Electrochem Sci 6 (2011)

6115

57 TY Wu BK Chen L Hao KF Lin IW Sun J Taiwan Inst Chem Eng 42 (2011) 914

58 TY Wu BK Chen L Hao CW Kuo IW Sun J Taiwan Inst Chem Eng 43 (2012) 313

59 SW Peng AN Soriano RB Leron MH Li J Taiwan Inst Chem Eng 42 (2011) 233

60 TY Wu IW Sun MW Lin BK Chen CW Kuo HP Wang YY Chen SG Su J Taiwan

Inst Chem Eng 43 (2012) 58

61 TY Wu BK Chen CW Kuo L Hao YC Peng IW Sun J Taiwan Inst Chem Eng 43

(2012) 860

62 A Arce H Rodriguez A Soto Green Chem 9 (2007) 247

63 TY Wu HC Wang SG Su ST Gung MW Lin CB Lin J Taiwan Inst Chem Eng 41 (2010)

315 64 X Li M Hou Z Zhang B Han G Yang X Wang L Zou Green Chem 10 (2008) 879

Int J Electrochem Sci Vol 8 2013

5085

65 J Chen SK Spear JG Huddleston RD Rogers Green Chem 7 (2005) 64

66 U Domanska M Laskowska J Solution Chem 38 (2009) 779

67 K Tamura M Nakamura S Murakami J Solution Chem 26 (1997) 1199

68 Z Yu H Gao H Wang L Chen J Chem Eng Data 56 (2011) 2877

69 KN Marsh JA Boxall R Lichtenthaler Fluid Phase Equilib 219 (2004) 93

70 TY Wu SG Su ST Gung MW Lin YC Lin WC Ou-Yang IW Sun CA Lai J Iran

Chem Soc 8 (2011) 149

71 TY Wu L Hao CW Kuo YC Lin SG Su PL Kuo IW Sun Int J Electrochem Sci 7

(2012) 2047

72 TY Wu L Hao PR Chen JW Liao Int J Electrochem Sci 8 (2013) 2606

73 CW Kuo CW Huang BK Chen WB Li PR Chen TH Ho CG Tseng TY Wu Int J

Electrochem Sci 8 (2013) 3834

74 CW Kuo WB Li PR Chen JW Liao CG Tseng TY Wu Int J Electrochem Sci 8

(2013) 5007

75 TY Wu BK Chen L Hao YC Lin HP Wang CW Kuo IW Sun Int J Mol Sci 12

(2011) 8750

76 H Rodriguez JF Brennecke J Chem Eng Data 51 (2006) 2145

77 Y Tian X Wang J Wang J Chem Eng Data 53 (2008) 2056

78 TY Wu HC Wang SG Su ST Gung MW Lin CB Lin J Chin Chem Soc 57 (2010)

44

79 TY Wu BK Chen L Hao YC Peng IW Sun Int J Mol Sci 12 (2011) 2598

80 H Eyring MS John Significant Liquid Structure Wiley New York 1969

81 H Every AG Bishop M Forsyth DR MacFarlane Electrochim Acta 45 (2000) 1279 82 O Redlich AT Kister Ind Eng Chem 40 (1948) 345

83 A Paul P Kumar A Samanta J Phys Chem B 109 (2005) 9148

copy 2013 by ESG (wwwelectrochemsciorg)

Int J Electrochem Sci Vol 8 2013

5069

22 1-Butyl-1-methylpyrrolidinium butyl sulfate ([PyrMB][BuSO4])

Dibutyl sulfate (757 g 360 mmol) was added dropwise to a solution of equal molar amounts of

1-methylpyrrolidine (3065 g 360 mmol) in 200 mL toluene and then cooled in an ice-bath under

nitrogen at a rate that maintained the reaction temperature below 31315 K (highly exothermic

reaction) The reaction mixture was stirred at room temperature for 4h After the reaction stopped the

upper organic phase of the resulting mixture was decanted and the lower ionic liquid phase was

washed with ethyl acetate (4 x 70 mL) After the last washing the remaining ethyl acetate was

removed by rotavapor under reduced pressure The IL obtained was dried by heating at (34315 to

35315) K and stirring under a high vacuum (2 10-1

Pa) for 48 h In order to reduce the water content

to negligible values (lower than 003 mass ) a vacuum (2 x 10-1

Pa) and moderate temperature

(34315 K) were applied to the IL for 2 days The IL was kept in bottles under an inert gas The

structure of [PyrMB][BuSO4] is shown in Figure 1

Yield 91 1H NMR (300 MHz D2O ppm) 395 (t 2H -CH2SO4) 338 (m 4H N-CH2-)

321 (m 2H N-CH2-) 292 (s 3H N-CH3) 210 (m 4H N-CH2CH2-) 167 (m 2H -CH2CH2SO4)

155 (m 2H N-CH2CH2-) 128 (m 4H N-CH2CH2CH2- and -CH2CH2CH2SO4) 082 (m 6H N-

CH2CH2CH2CH3 and CH3CH2CH2CH2SO4) Elem Anal Calcd for C13H29NO4S C 5285 H 989

N 474 Found C 5268 H 979 N 465

NC4H9SO4

Figure 1 Molecular structure of 1-butyl-1-methylpyrrolidinium butyl sulfate ([PyrMB][BuSO4])

23 Measurements

The conductivity () of the ionic liquids was systematically measured with a conductivity

meter (LF 340 WTW Germany) and a standard conductivity cell (TetraCon 325 WTW Germany)

The cell constant was determined by calibration after each sample measurement using an aqueous 001

M KCl solution The density of the ILs was measured with a dilatometer which was calibrated by

measuring the density of neat glycerin at 30 40 50 60 70 and 80 oC The dilatometer was placed in a

thermostatic water bath (TV-4000 TAMSON) whose temperature was regulated to within plusmn 001 K

To measure density IL or a binary mixture was placed into the dilatometer up to the mark the top of

the capillary tube (located on the top of the dilatometer) was sealed and the dilatometer (with capillary

tube) was placed into a temperature bath for 10 min to allow the temperature to equilibrate The main

interval between the two marks in the capillary tube was 001 cm3 and the minor interval between two

marks was 0001 cm3 From the correction coefficient of glycerin in capillary tube at various

temperatures we can calculate the density of neat IL or binary system by the expanded volume of

liquid in the capillary tube at various temperatures Each sample was measured at least three times to

determine an average value and the values of the density were plusmn00001 gmL The viscosity (η) of the

Int J Electrochem Sci Vol 8 2013

5070

IL was measured using a calibrated modified Ostwald viscometer (Cannon-Fenske glass capillary

viscometers CFRU 9721-A50) The viscometer capillary diameter was 12 mm as measured using a

caliper (model No PD-153) with an accuracy of plusmn 002 mm The viscometer was placed in a

thermostatic water bath (TV-4000 TAMSON) whose temperature was regulated to within plusmn 001 K

The flow time was measured using a stopwatch with a resolution of 001 s For each IL the

experimental viscosity was obtained by averaging three to five flow time measurements The water

content of synthesized IL [PyrMB][BuSO4] was determined using the KarlndashFischer method the

content was below 300 ppm The nuclear magnetic resonance (NMR) spectra of the synthesized IL

were recorded on a BRUKER AV300 spectrometer and calibrated with tetramethylsilane (TMS) as the

internal reference

3 RESULTS AND DISCUSSION

31 Density and excess molar volume

The densities of neat IL [PyrMB][BuSO4] neat PEG200 and PEG200 (1) + [PyrMB][BuSO4]

(2) binary mixture over the temperature range (29315 to 35315) K and at atmospheric pressure are

presented in Table 1 and Figure 2 As shown in Figure 2 the trend of density for the binary system

with respect to temperature was decreased with increasing temperature The variations of the densities

with concentration at the different temperatures studied are shown in Figure 3 from analysis of the

data it was found that the densities depend more strongly on the mole fraction of PEG200 in the

mixture than on temperature

Figure 2 ρ vs T plot of the PEG200 (1) + [PyrMB][BuSO4] (2) binary system

A third-order polynomial was found to satisfactorily correlate the change of density with various

compositions

T K

290 300 310 320 330 340 350 360

g

cm

-3

109

110

111

112

113

114

x1 = 00000

x1 = 01452

x1 = 01942

x1 = 02912

x1 = 03897

x1 = 04893

x1 = 05890

x1 = 06903

x1 = 07922

x1 = 08958

Int J Electrochem Sci Vol 8 2013

5071

ρ = a0 + a1 x1 + a2 x12 + a3 x1

3 (1)

where x1 is the mole fractions of PEG200 and a0 a1 a2 and a3 refer to the fit coefficients Fit

parameters are listed in Table 2 for the mixtures

Table 1 Experimental density () and excess molar volume (VmE) for the binary system PEG200 (1)

+ [PyrMB][BuSO4] (2)

x1

29315 29815 30315 30815 31315 31815 32315 32815 33315 33815 34315 34815 35315

ρg middotcm-3

0 11258 11228 11199 11169 11140 11111 11082 11053 11025 10996 10968 10940 10912

01452 11288 11259 11230 11200 11171 11142 11112 11083 11053 11024 10995 10965 10936

01942 11305 11275 11245 11216 11186 11157 11127 11097 11068 11038 11008 10979 10949

02912 11334 11304 11274 11243 11213 11183 11153 11123 11092 11062 11032 11002 10972

03897 11352 11321 11291 11260 11229 11199 11168 11138 11107 11076 11046 11015 10984

04893 11356 11325 11294 11263 11232 11201 11170 11139 11108 11077 11046 11015 10984

05890 11350 11319 11288 11256 11225 11193 11162 11131 11099 11068 11036 11005 10973

06903 11331 11299 11267 11235 11203 11172 11140 11108 11076 11044 11012 10980 10948

07922 11318 11285 11252 11219 11186 11153 11120 11087 11054 11021 10988 10956 10923

08958 11312 11278 11243 11208 11174 11139 11104 11070 11035 11000 10966 10931 10896

1 11312 11273 11234 11195 11157 11119 11081 11044 11007 10970 10933 10896 10860

E

mV cm3 mol-1

0 00000 00000 00000 00000 00000 00000 00000 00000 00000 00000 00000 00000 00000

01452 -05572 -05884 -06161 -06404 -06613 -06787 -06925 -07028 -07096 -07127 -07123 -07081 -07003

01942 -08575 -08917 -09225 -09498 -09737 -09942 -10111 -10245 -10343 -10406 -10432 -10422 -10375

02912 -13539 -13931 -14289 -14614 -14903 -15159 -15379 -15564 -15714 -15828 -15906 -15947 -15952

03897 -15730 -16197 -16630 -17029 -17394 -17726 -18022 -18284 -18511 -18702 -18858 -18978 -19061

04893 -14983 -15521 -16026 -16498 -16936 -17341 -17711 -18047 -18348 -18615 -18846 -19041 -19201

05890 -12361 -12970 -13547 -14090 -14601 -15078 -15522 -15931 -16306 -16647 -16953 -17224 -17459

06903 -07359 -08013 -08634 -09222 -09777 -10300 -10788 -11243 -11663 -12049 -12400 -12717 -12997

07922 -03606 -04235 -04831 -05394 -05923 -06418 -06878 -07304 -07695 -08051 -08371 -08655 -08903

08958 -01410 -01915 -02384 -02818 -03216 -03578 -03903 -04192 -04443 -04656 -04832 -04969 -05068

1 00000 00000 00000 00000 00000 00000 00000 00000 00000 00000 00000 00000 00000

Figure 3 ρ of the PEG200 (1) + [PyrMB][BuSO4] (2) binary system as a function of concentration

at various temperatures

The correlation constants for Eq (1) were established using the least square method and are

presented in Table 2 along with the standard deviation estimated using the following equation

2

exp cal 1 2( - )

[ ]Z Z

n

(2)

x1

00 02 04 06 08 10

g c

m-3

106

108

110

112

114

29315 K

30315 K

31315 K

32315 K

33315 K

34315 K

35315 K

Int J Electrochem Sci Vol 8 2013

5072

where n is the number of experimental points and Zexp and Zcal are the experimental and

calculated values respectively

Table 2 Coefficients of polynomiala for the correlation of the density (ρgmiddotcm

-3) in function of

concentration at different temperatures of the binary systems PEG200 (1) + [PyrMB][BuSO4]

(2)

TK a0 g cm

-3 a1 g cm

-3 a2 g cm

-3 a3 g cm

-3

29315 11248 00455 -00638 0024 0000840

29815 11219 00447 -00617 00217 0000800

30315 1119 00439 -00596 00195 0000764

30815 11161 00431 -00575 00173 0000732

31315 11132 00422 -00554 00152 0000704

31815 11103 00413 -00533 00132 0000680

32315 11075 00403 -00512 00112 0000660

32815 11046 00393 -00492 00093 0000640

33315 11018 00382 -00471 00074 0000625

33815 10989 00372 -0045 00055 0000613

34315 10961 0036 -0043 00037 0000606

34815 10933 00349 -00409 0002 0000596

35315 10905 00337 -00389 00003 0000592

a ρ = a0 + a1 x1 + a2 x1

2 + a3 x1

3

As can be seen from the Table 1 the value of the density decreases with increasing temperature

eventhough the variation is very small If the variation of the density with the temperature is

considered as linear then the change in the calculated thermal expansion coefficient values becomes

nearly constant In order to have an improved accuracy a second order polynomial of the eqn (3) was

used to correlate the variation of the density with the temperature for PEG200 (1) + [PyrMB][BuSO4]

(2) binary system

ρ = b0 + b1 T + b2 T2 (3)

where T is the temperature and b0 b1 and b2 are the correlation coefficients The correlation

coefficients are listed in Table 3 together with the standard deviations (σ) calculated using Eq (2)

Excess thermodynamic properties are of great importance for understanding the nature of

molecular interaction in binary mixtures The excess molar volume E

mV which is the difference

between the real and ideal mixing behaviors is defined by

m m 1 1 2 2 E o o

V V xV x V (4)

where Vm represents the volume of a mixture containing one mole of (PEG200 +

[PyrMB][BuSO4]) x1 and x2 are the mole fractions of components 1 (PEG200) and 2

([PyrMB][BuSO4]) respectively and V10 and V2

0 are the molar volumes of the pure components The

Int J Electrochem Sci Vol 8 2013

5073

excess molar volumes of mixtures over the entire composition range were calculated from our

measurements of density according to the following equation

Table 3 The adjustable parameters of density (ρ = b0 + b1 T + b2 T2) at various temperature for neat

PEG200 (x1 = 1) [PyrMB][BuSO4] (x1 = 0) and binary system PEG200 (1) + [PyrMB][BuSO4]

(2)

x1 b0 b1 b2

0 1326 -000077105 00000003 000003

01452 1301 -0000588 0 000023

01942 1304 -0000593 0 000032

02912 131 -0000604 0 000047

03897 1315 -0000613 0 000009

04893 1318 -0000621 0 000034

05890 1319 -0000629 0 000045

06903 132 -0000639 0 000046

07922 1325 -0000658 0 000036

08958 1335 -0000694 0 000030

1 1405 -000108 000000051 000112

Figure 4 Excess molar volumes for the binary system PEG200 (1) + [PyrMB][BuSO4] (2) and

fitted curves using the Redlich-Kister parameters

1 1 2 2 1 1 2 2m

1 2

E

Vx M x M x M x M

(5)

where ρ1 ρ2 and ρ are the densities of neat PEG200 [PyrMB][BuSO4] and their mixture

respectively M1 and M2 are the molar masses of PEG200 and [PyrMB][BuSO4] respectively The E

mV

values of mixtures are summarized in Table 1 The excess molar volumes of mixtures versus the mole

x1

00 02 04 06 08 10

Vm

E

cm

3 m

ol-1

-20

-15

-10

-05

00

30315 K

31315 K

32315 K

33315 K

Int J Electrochem Sci Vol 8 2013

5074

fraction of PEG200 from 29315 to 35315 K are plotted in Figure 4 The excess molar volume of the

binary system is mainly concerned with the weak chemical interactions the physical and structural

characteristics of the system components If the chemical or nonchemical interaction of the same

components is the dominant way of the interaction the excess volume of the mixture should be

positive If the molecules of the components have a more effective packing in the mixture than that in

the pure component that is the attracting interaction between the molecules of two components is the

dominant way the excess molar volume of the binary system should be negative [66] As shown in

Figure 4 the excess molar volumes are asymmetric and negative for all of the systems studied over the

entire composition range the minimum of E

mV is reached at a mole fraction of PEG200 near x1 = 04

and the absolute values of the excess volume increase with increasing temperature The molar volume

for [PyrMB][BuSO4] is 26243 cm3 mol

-1 at T = 29315 K which is greater than the molar volumes of

PEG200 (17681 cm3 mol

-1) at T = 29315 K The large difference between molar volumes of the

molecular liquid and [PyrMB][BuSO4] indicates that it is possible that the relatively small organic

molecules fit into the interstices upon mixing Therefore the filling effect of organic molecular liquids

in the interstices of ionic liquids and the ionndashdipole interactions between poly(ethylene glycol)

oligomer and the butylsulfate-based ionic liquids all contribute to the negative values of the molar

excess volumes

32 Volume expansivity and excess volume expansivity

Density results for the PEG200 and [PyrMB][BuSO4] binary system studied in current work were

also used to derive the coefficient of thermal expansion From the relationship of vs T the volume

expansivity (coefficient of thermal expansion) α is defined as

1 1

( ) ( )p p

V

TV T

(6)

where subscript p indicates constant pressure The α values of pure [PyrMB][BuSO4] and

PEG200 and their mixture are summarized in Table 4 The values indicate that the thermal expansion

coefficient of this binary mixture (PEG200 + [PyrMB][BuSO4]) increases with increasing temperature

and increases with increasing mole fraction of the PEG200

The corresponding excess function (excess volume expansivity) was calculated using

E id id

1 1 2 2 (7)

where id

1 is an ideal volume fraction given by the following relation

1 m11

1 m1 2 m2

id xV

xV x V

(8)

Int J Electrochem Sci Vol 8 2013

5075

where Vmi is the molar volume of pure component i

Table 4 Experimental volume expansivity (α) and the excess volume expansivity (αE) for the binary

system PEG200 (1) + [PyrMB][BuSO4] (2)

x1

29315 29815 30315 30815 31315 31815 32315 32815 33315 33815 34315 34815 35315

104 αK-1

0 51245 51380 51516 51651 51787 51922 52058 52193 52329 52464 52600 52735 52871

01452 52053 52189 52325 52462 52600 52739 52878 53018 53159 53300 53443 53586 53730

01942 52438 52576 52715 52854 52994 53135 53276 53418 53561 53705 53850 53995 54141

02912 53299 53443 53586 53731 53877 54023 54170 54318 54466 54616 54766 54917 55069

03897 53973 54120 54268 54417 54567 54717 54869 55021 55174 55328 55483 55638 55795

04893 54667 54818 54971 55124 55278 55433 55589 55745 55903 56061 56221 56381 56542

05890 55372 55527 55683 55840 55998 56157 56317 56477 56639 56801 56965 57129 57294

06903 56358 56517 56677 56838 57000 57163 57327 57492 57657 57824 57992 58160 58330

07922 58175 58344 58515 58687 58860 59033 59208 59384 59561 59739 59918 60098 60279

08958 61313 61502 61691 61882 62074 62268 62462 62658 62855 63053 63252 63453 63655

1 66532 66763 66993 67224 67455 67685 67916 68146 68377 68607 68838 69069 69299

104 αEK-1

0 00000 00000 00000 00000 00000 00000 00000 00000 00000 00000 00000 00000 00000

01452 -00762 -00772 -00782 -00792 -00800 -00808 -00815 -00822 -00827 -00832 -00837 -00840 -00843

01942 -00942 -00954 -00966 -00977 -00987 -00997 -01006 -01014 -01021 -01028 -01033 -01038 -01043

02912 -01259 -01275 -01289 -01302 -01315 -01327 -01339 -01349 -01359 -01368 -01376 -01383 -01389

03897 -01870 -01889 -01908 -01926 -01943 -01959 -01975 -01989 -02003 -02016 -02028 -02040 -02050

04893 -02576 -02600 -02623 -02646 -02668 -02689 -02709 -02728 -02746 -02764 -02780 -02796 -02811

05890 -03382 -03412 -03441 -03470 -03497 -03524 -03550 -03574 -03598 -03621 -03644 -03665 -03685

06903 -04064 -04100 -04136 -04170 -04204 -04236 -04268 -04299 -04329 -04358 -04386 -04413 -04439

07922 -04073 -04110 -04146 -04181 -04214 -04247 -04279 -04310 -04339 -04368 -04396 -04422 -04448

08958 -02968 -02998 -03026 -03053 -03079 -03104 -03128 -03151 -03172 -03192 -03211 -03228 -03245

1 00000 00000 00000 00000 00000 00000 00000 00000 00000 00000 00000 00000 00000

Figure 5 Plot of excess volume expansivity αE of the PEG200 (1) + [PyrMB][BuSO4] (2) binary

system versus mole fraction x1 at various temperatures

Typical concentration dependencies of excess volume expansivity are given in Figure 5 for the

PEG200 + [PyrMB][BuSO4] binary system The values of excess thermal coefficient αE are found to

x1

00 02 04 06 08 10

10

4

E K

-1

-04

-03

-02

-01

00

29315 K

30315 K

31315 K

32315 K

33315 K

34315 K

35315 K

Temp

Int J Electrochem Sci Vol 8 2013

5076

be negative over the whole composition range for the binary system at 29315 ~ 35315 K The curves

are asymmetrical with the minimum located at the IL mole fraction of about 08 In general negative

αE values indicate the presence of strong interaction between the components in the mixtures [67] The

trends observed in αE values for the present mixtures suggest the formation of H-bonding between

unlike molecules which is stronger in PEG200 + [PyrMB][BuSO4] binary system The increasing

negative αE values for PEG200 + [PyrMB][BuSO4] with increase in temperature indicate enhanced

unlike interaction between components of the mixture that is more destruction of order during mixing

contributes negatively to αE

33 Viscosity

Since ILs are more viscous than conventional solvents in most applications they can be used in

mixtures with other less viscous compounds Therefore the viscosity of pure ILs and their mixtures

with PEG oligomer (or conventional solvents) is an important property and their knowledge is

primordial for each industrial processes [6869] The measured dynamic viscosities for the neat

PEG200 neat [PyrMB][BuSO4] and PEG200 + [PyrMB][BuSO4] binary mixture as a function of

temperature over the whole composition range are shown in Figure 6 and their data are listed in Table

5 the viscosities of the mixtures decrease rapidly when PEG oligomer are added to the ionic liquid

especially at lower temperatures The fitting lines in Figure 6 were calculated with the following

fourth-order polynomial equation

= c0 + c1 x1 + c2 x12 + c3 x1

3 + c4 x1

4 (9)

where x1 is the mole fractions of PEG200 and c0 c1 c2 c3 and c4 refer to the fit coefficients

The parameters of correlation are shown in Table 6

Figure 6 Dynamic viscosity for the PEG200 (1) + [PyrMB][BuSO4] (2) binary system as a

function of mole fractions of the PEG200 at different temperatures Lines represent the

polynomial correlation

x1

00 02 04 06 08 10

mP

a s

0

200

400

600

800

1000

1200

1400

29315 K

30315 K

31315 K

32315 K

33315 K

34315 K

35315 K

Int J Electrochem Sci Vol 8 2013

5077

Table 5 Experimental dynamic viscosity (η) and viscosity deviation (Δη) for the binary system

PEG200 (1) + [PyrMB][BuSO4] (2)

x1

29315 29815 30315 30815 31315 31815 32315 32815 33315 33815 34315 34815 35315

ηmPamiddots

0 13209 9343 6745 4961 3712 2821 2176 1700 1345 1077 871 712 587

01452 5907 4362 3294 2539 1992 1589 1286 1055 876 735 623 533 460

01942 4656 3475 2656 2072 1647 1331 1091 907 763 649 557 483 422

02912 3134 2395 1870 1489 1205 991 826 697 594 512 445 390 345

03897 2367 1846 1463 1177 959 792 660 557 474 406 351 306 269

04893 1799 1396 1104 887 723 598 501 424 362 312 272 238 210

05890 1540 1194 941 753 611 502 418 351 298 255 220 191 167

06903 1185 926 736 594 485 402 336 284 242 209 181 158 139

07922 954 742 589 475 389 323 271 231 198 172 150 132 117

08958 811 639 512 415 342 285 240 204 175 151 132 116 102

1 629 505 410 337 280 235 199 170 146 126 110 97 85

ΔηmPamiddots

0 00 00 00 00 00 00 00 00 00 00 00 00 00

01452 -5475 -3698 -2530 -1751 -1221 -857 -602 -423 -295 -204 -137 -89 -54

01942 -6111 -4152 -2859 -1991 -1398 -988 -700 -496 -347 -244 -166 -110 -68

02912 -6411 -4374 -3030 -2126 -1507 -1077 -774 -558 -391 -288 -204 -142 -103

03897 -5940 -4053 -2813 -1982 -1415 -1022 -745 -547 -405 -300 -223 -166 -123

04893 -5254 -3622 -2541 -1811 -1255 -957 -708 -528 -396 -299 -227 -173 -131

05890 -4260 -2944 -2073 -1484 -1034 -796 -594 -448 -341 -262 -203 -158 -124

06903 -3340 -2316 -1636 -1176 -826 -634 -475 -360 -275 -212 -165 -129 -101

07922 -2289 -1599 -1138 -823 -579 -449 -320 -257 -197 -152 -118 -92 -72

08958 -1129 -787 -559 -404 -277 -220 -152 -126 -96 -74 -58 -45 -35

1 00 00 00 00 00 00 00 00 00 00 00 00 00

Table 6 Coefficients of polynomiala for the correlation of the viscosity ( mPa s) in function of

concentration at different temperatures of the binary systems PEG200 (1) + [PyrMB][BuSO4]

(2)

TK c0 mPa s c1 mPa s c2 mPa s c3 mPa s C4 mPa s

29315 13154 -68701 15960 -16688 63543 1075

29815 93069 -46703 10681 -11113 42269 727

30315 67211 -32185 72085 -74396 28222 497

30815 49454 -22431 48886 -49866 18828 343

31315 37016 -15772 33175 -33281 12474 238

31815 28146 -1116 22406 -21947 81322 165

32315 21713 -7923 14947 -1413 51409 114

32815 16975 -56244 97349 -870 30666 077

33315 13435 -39753 60667 -4908 16219 051

33815 10756 -27812 34718 -22519 61382 033

34315 87026 -19098 16304 -39091 -88892 021

34815 71108 -12698 32285 90904 -5763 016

35315 58636 -79728 -60345 18103 -91096 017 a = c0 + c1 x1 + c2 x1

2 + c3 x1

3 + c4 x1

4

The temperature dependence becomes distinctly nonlinear especially at high [PyrMB][BuSO4]

content The Vogel-Tammann-Fulcher (VTF) equation [70-75] suitably correlates the nonlinear

behavior as a function of the temperature not only the viscosities of the neat IL but also the viscosities

of the mixtures for the binary systems through the composition range

Int J Electrochem Sci Vol 8 2013

5078

exp[ ]( )

o

o

B

T T

(10)

where ηo B and To are constants The parameter To is the ideal glass transition temperature which

should be slightly below the experimental glass transition temperature Tg [76] The adjustable

parameters obtained from the VTF correlation were presented in Table 7 The obtained parameters o

and B change smoothly with composition for binary mixtures

Table 7 The VTF equation parameters of viscosity ( 1 exp[ ]( )

o

o

B

T T

) and conductivity

(

exp[ ]( )

o

o

B

T T

) for neat PEG200 (x1 = 1) [PyrMB][BuSO4] (x1 = 0) and binary system

PEG200 (1) + [PyrMB][BuSO4] (2)

x1

ηo (mPa s) To (K) B (K) R2a

o (mS cm-1

) To (K) Brsquo (K) R2a

0 027 1810 9540 0999 792 1788 6854 0999

01452 026 1712 9413 0999 577 1699 6268 0999

01942 043 1788 7975 0999 401 1792 5297 0999

02912 053 1794 7264 0999 521 1662 6031 0999

03897 026 1629 8902 0999 274 1803 4381 0999

04893 023 1666 8455 0999 177 1951 3272 0999

05890 015 1648 8865 0999 216 1883 3672 0999

06903 015 1647 8572 0999 88 2174 2000 0999

07922 017 1717 7702 0999 92 2020 2578 0999

08958 012 1642 8360 0999 43 2110 2088 0999

1 014 1649 7868 0999 556 1928 9815 0999

a Correlation coefficient

The viscosities of the mixtures decrease rapidly when organic oligomers are added to the ionic

liquid this decrease is particularly evident in dilute solutions of organic oligomers in the ionic liquid

The strong coulomb interactions between the [BuSO4]- anion and [PyrMB]

+ cation are weakened upon

mixing with the polar organic oligomers which leads to a higher mobility of the ions and a lower

viscosity of the mixtures [77] This indicates that the viscosity of ILs could be therefore tuned for

several applications by adding an organic solvent or by changing temperature [78]

Due to the wide range of possible molecular interactions between the two components

deviations can occur from ideal behavior These viscosity deviations can be quantified by the viscosity

deviation Δη also known as ldquoexcess viscosityrdquo in other sources

1 1 2 2 (mPa s) x x (11)

Int J Electrochem Sci Vol 8 2013

5079

where x1 and x2 are the mole fractions of PEG200 and [PyrMB][BuSO4] respectively and 1

and 2 are the viscosities (mPa middot s) of the solution the pure solvent and the pure IL respectively

Figure 7 shows the viscosity deviations as a function of the PEG200 mole fraction composition x1 and

temperature for the PEG200 + [PyrMB][BuSO4] binary mixture The values of viscosity deviations

are compared with those obtained from the RedlichndashKister polynomial equation The viscosity

deviation for the mixture show negative deviations from ideality over the whole mole fraction range

Figure 7 also shows that the negative values of viscosity deviations decrease with increasing

temperature this can be attributed to the specific interactions in mixtures typically hydrogen bonds break-

up as the temperature increases [79] The minimum value of Δη is observed at about x1 asymp 03 and the

viscosity deviation depends on molecular interactions as well as on the size and shape of the molecules

[80]

Figure 7 Viscosity deviations Δη versus the mole fraction at various temperatures for the binary

mixture PEG200 (1) + [PyrMB][BuSO4] (2)

34 Conductivity

The experimental data of conductivity of the neat ILs [PyrMB][BuSO4] neat PEG200 and

binary system are plotted against the x1 at various temperatures in Figure 8 together with lines

calculated with the four-order polynomial equation

= d0 + d1 x1 + d2 x12 + d3 x1

3 + d4 x1

4 (12)

where x1 is the mole fractions of PEG200 and d0 d1 d2 d3 and d4 refer to the fit coefficients

The parameters of correlation are shown in Table 8 The conductivities of neat IL [PyrMB][BuSO4]

neat PEG200 and binary system at various temperatures were fitted using the VTF equation

exp[ ]

( )o

o

B

T T

(13)

x1

00 02 04 06 08 10

m

Pa s

-700

-600

-500

-400

-300

-200

-100

0

29315 K

30315 K

31315 K

32315 K

33315 K

34315 K

35315 K

Int J Electrochem Sci Vol 8 2013

5080

where T is the absolute temperature and Brsquo and To are adjustable parameters The best-fit

mS cm-1 Brsquo (K) and To (K) parameters are given in Table 7 Neat [PyrMB][BuSO4] neat

PEG200 and binary system were very well fit by the VTF model over the temperature range studied

Figure 8 Plot of conductivity of the PEG200 (1) + [PyrMB][BuSO4] (2) binary system versus

mole fraction x1 at various temperatures

Table 8 Coefficients of polynomiala for the correlation of the conductivity ( mS cm

-1) in function

of concentration at different temperatures of the binary systems PEG200 (1) +

[PyrMB][BuSO4] (2)

TK d0 mS cm

-1 d1 mS cm

-1 d2 mS cm

-1 d3 mS cm

-1 d4 mS cm

-1

29315 02019 09622 -01679 0734 -17284 00095

29815 02588 11031 -02503 09086 -20181 00109

30315 03255 12119 -01935 08565 -21971 00125

30815 04025 13165 -01329 0767 -23477 00141

31315 04904 13712 01238 03677 -23439 00156

31815 05894 15032 -00006 04737 -25518 00171

32315 06999 15802 00743 0265 -25986 00188

32815 08221 16427 01595 00089 -26032 00208

33315 09562 16373 04858 -06207 -24165 00233

a = d0 + d1 x1 + d2 x1

2 + d3 x1

3 + d4 x1

4

As shown in Figure 8 it can be seen that the conductivity of the binary mixture increases with

increasing amount of PEG200 goes through a maximum and then goes down to the specific

conductivity of the neat PEG200 The conductivity is related to the ion mobility and the number of

charge carriers [81] At a fixed concentration the ions move faster at higher temperature due to the

relatively lower viscosity of the mixture On the other hand the composition influences both the ion

mobility and the number of charge carriers at a fixed temperature At the beginning the number of

charge and the ion mobility increase with increasing PEG oligomer composition the maximum of

conductivity is located at x1 = 059 and corresponds to a value of 171 mS cmminus 1

at 33315 K It can also

be observed that the conductivity increases as the temperature increases The higher temperature may

x1

00 02 04 06 08 10

mS

cm

-1

00

05

10

15

20

29315 K

29815 K

30315 K

30815 K

31315 K

31815 K

32315 K

32815 K

33315 K

Int J Electrochem Sci Vol 8 2013

5081

weaken the influence of aggregation to the conductivity which suggests that a higher temperature is

better for the ILs to act as electrolytes

Table 9 RedlickndashKister fitting coefficients Ak and the standard deviation of the VE and ∆for the

binary mixture of PEG200 (1) + [PyrMB][BuSO4] (2) system

TK A0 A1 A2 A3 A4

VEcm

3 mol

-1

29315 -5979 -4906 6585 5754 -1717 002687

29815 -6200 -4760 6464 5767 -2022 002693

30315 -6408 -4612 6345 5774 -2276 002698

30815 -6602 -4461 6229 5774 -2476 002701

31315 -6782 -4310 6116 5767 -2623 002701

31815 -6948 -4155 6006 5753 -2716 002699

32315 -7100 -3999 5899 5732 -2754 002692

32815 -7239 -3840 5795 5704 -2738 002683

33315 -7363 -3679 5694 5669 -2666 002670

33815 -7472 -3515 5596 5626 -2538 002654

34315 -7568 -3350 5501 5576 -2353 002634

34815 -7648 -3182 5409 5518 -2111 002611

35315 -7714 -3011 5320 5452 -1812 002586

∆mPa s

29315 -20414 -17226 -15592 -95544 -75863 399496

29815 -14035 -11558 -10713 -62192 19493 340180

30315 -98261 -78407 -73734 -40709 58145 286725

30815 -69922 -53591 -50601 -2676 67556 235258

31315 -48876 -39537 -41051 -14118 16739 079245

31815 -36917 -25169 -22939 -11646 51047 146189

32315 -27415 -1721 -12581 -92603 21498 104339

32815 -20441 -11703 -77538 -38334 -81478 090708

33315 -15382 -67274 -31134 -47585 -18255 059539

33815 -11664 -44928 -15533 -22312 -05591 037855

34315 -89038 -24163 68654 -15007 -10347 024263

34815 -68279 -91813 23131 -10367 -18636 017759

35315 -52525 -24051 26474 15498 -85341 018640

35 Redlich-Kister Equation for Binary System

The binary excess property ( E

mV ) and deviations (Δ) at several temperatures were fitted to a

Redlich-Kister-type equation [82]

1 1 1

0

(or ) (1 ) (1 2 )j

E i

i

i

Y Y x x A x

(14)

Int J Electrochem Sci Vol 8 2013

5082

where ΔY (YE) represents E

mV (cm3 mol

minus1) and Δ

(mPa s)x1 denotes the mole fraction of

PEG200 Ai represents the polynomial coefficients and j is the degree of the polynomial expansion

The correlated results for excess molar volumes ( E

mV ) viscosity deviations (Δ) including the values

of the fitting parameters Ai together with the standard deviation σ are given in Table 9 where the

tabulated standard deviation σ [83] is defined as

2

exp cal 1 2( )

[ ]Y Y

m n

(15)

where m is the number of experimental data points and n is the number of estimated

parameters The subscripts ldquoexprdquo and ldquocalrdquo denote the values of the experimental and calculated

property respectively As shown in Table 9 the experimentally derived E

mV and Δη values were

correlated satisfactorily by the Redlich-Kister equation

4 CONCLUSIONS

This paper is a systematic characterizations of thermophysical properties for IL binary system

Density viscosity and conductivity for (PEG200 + [PyrMB][BuSO4]) binary system are presented as a

function of temperature at atmospheric pressure it was demonstrated that viscosity and conductivity

were more sensitive to the changes in PEG content or temperature than density and the viscosity and

conductivity of pure IL and (PEG200 + [PyrMB][BuSO4]) binary system at different temperature are

fitted using the VogelndashTammannndashFulcher (VTF) equation with good accuracy The excess molar

volumes excess volume expansivity and viscosity deviations show negative deviations from the ideal

solution the results are interpreted in terms of molecular interactions in the (PEG200 +

[PyrMB][BuSO4]) binary mixture The conductivity increases to a maximum value when the

concentration of PEG200 is increased and decreases after the maximum the data obtained will be

helpful for the application of the ionic liquids as electrolytes and also useful for the ionic liquids

database

ACKNOWLEDGEMENTS

The authors would like to thank the National Science Council of the Republic of China for financially

supporting this project

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Chem Soc 22 (2011) 780

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Chem Soc 7 (2010) 707

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38 TY Wu MH Tsao FL Chen SG Su CW Chang HP Wang YC Lin WC Ou-Yang

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39 YX An PJ Zuo XQ Cheng LX Liao GP Yin Int J Electrochem Sci 6 (2011) 2398

40 LC Xuan YX An W Fang LX Liao YL Ma ZY Ren GP Yin Int J Electrochem Sci

6 (2011) 6590

41 HM Wang SQ Liu K Huang XG Yin YN Liu SJ Peng Int J Electrochem Sci 7

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42 HM Wang SQ Liu NF Wang YN Liu Int J Electrochem Sci 7 (2012) 7579

43 H Ganjali MR Ganjali T Alizadeh F Faridbod P Norouzi Int J Electrochem Sci 6 (2011)

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44 MR Ganjali MH Eshraghi S Ghadimi SM Moosavi M Hosseini H Haji-Hashemi P

Norouzi Int J Electrochem Sci 6 (2011) 739

45 MR Ganjali T Poursaberi M Khoobi A Shafiee M Adibi M Pirali-Hamedani P Norouzi

Int J Electrochem Sci 6 (2011) 717

46 P Norouzi M Hosseini MR Ganjali M Rezapour M Adibi Int J Electrochem Sci 6 (2011)

2012

47 MR Ganjali MR Moghaddam M Hosseini P Norouzi Int J Electrochem Sci 6 (2011)

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48 MR Ganjali M Hosseini M Pirali-Hamedani HA Zamani Int J Electrochem Sci 6 (2011)

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49 MR Ganjali M Rezapour SK Torkestani H Rashedi P Norouzi Int J Electrochem Sci 6

(2011) 2323

50 P Norouzi M Pirali-Hamedani SO Ranaei-Siadat MR Ganjali Int J Electrochem Sci 6

(2011) 3704

51 F Faridbod HA Zamani M Hosseini M Pirali-Hamedani MR Ganjali P Norouzi Int J

Electrochem Sci 6 (2011) 3694

52 MR Ganjali SO Ranaei-Siadat H Rashedi M Rezapour P Norouzi Int J Electrochem Sci

6 (2011) 3684

53 TH Tsai KC Lin SM Chen Int J Electrochem Sci 6 (2011) 2672

54 MR Ganjali T Alizadeh F Azimi B Larjani F Faridbod P Norouzi Int J Electrochem

Sci 6 (2011) 5200

55 R Mirshafian MR Ganjali P Norouzi Int J Electrochem Sci 7 (2012) 1656

56 J Gao JG Liu WM Liu B Li YC Xin Y Yin ZG Zou Int J Electrochem Sci 6 (2011)

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57 TY Wu BK Chen L Hao KF Lin IW Sun J Taiwan Inst Chem Eng 42 (2011) 914

58 TY Wu BK Chen L Hao CW Kuo IW Sun J Taiwan Inst Chem Eng 43 (2012) 313

59 SW Peng AN Soriano RB Leron MH Li J Taiwan Inst Chem Eng 42 (2011) 233

60 TY Wu IW Sun MW Lin BK Chen CW Kuo HP Wang YY Chen SG Su J Taiwan

Inst Chem Eng 43 (2012) 58

61 TY Wu BK Chen CW Kuo L Hao YC Peng IW Sun J Taiwan Inst Chem Eng 43

(2012) 860

62 A Arce H Rodriguez A Soto Green Chem 9 (2007) 247

63 TY Wu HC Wang SG Su ST Gung MW Lin CB Lin J Taiwan Inst Chem Eng 41 (2010)

315 64 X Li M Hou Z Zhang B Han G Yang X Wang L Zou Green Chem 10 (2008) 879

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65 J Chen SK Spear JG Huddleston RD Rogers Green Chem 7 (2005) 64

66 U Domanska M Laskowska J Solution Chem 38 (2009) 779

67 K Tamura M Nakamura S Murakami J Solution Chem 26 (1997) 1199

68 Z Yu H Gao H Wang L Chen J Chem Eng Data 56 (2011) 2877

69 KN Marsh JA Boxall R Lichtenthaler Fluid Phase Equilib 219 (2004) 93

70 TY Wu SG Su ST Gung MW Lin YC Lin WC Ou-Yang IW Sun CA Lai J Iran

Chem Soc 8 (2011) 149

71 TY Wu L Hao CW Kuo YC Lin SG Su PL Kuo IW Sun Int J Electrochem Sci 7

(2012) 2047

72 TY Wu L Hao PR Chen JW Liao Int J Electrochem Sci 8 (2013) 2606

73 CW Kuo CW Huang BK Chen WB Li PR Chen TH Ho CG Tseng TY Wu Int J

Electrochem Sci 8 (2013) 3834

74 CW Kuo WB Li PR Chen JW Liao CG Tseng TY Wu Int J Electrochem Sci 8

(2013) 5007

75 TY Wu BK Chen L Hao YC Lin HP Wang CW Kuo IW Sun Int J Mol Sci 12

(2011) 8750

76 H Rodriguez JF Brennecke J Chem Eng Data 51 (2006) 2145

77 Y Tian X Wang J Wang J Chem Eng Data 53 (2008) 2056

78 TY Wu HC Wang SG Su ST Gung MW Lin CB Lin J Chin Chem Soc 57 (2010)

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79 TY Wu BK Chen L Hao YC Peng IW Sun Int J Mol Sci 12 (2011) 2598

80 H Eyring MS John Significant Liquid Structure Wiley New York 1969

81 H Every AG Bishop M Forsyth DR MacFarlane Electrochim Acta 45 (2000) 1279 82 O Redlich AT Kister Ind Eng Chem 40 (1948) 345

83 A Paul P Kumar A Samanta J Phys Chem B 109 (2005) 9148

copy 2013 by ESG (wwwelectrochemsciorg)

Int J Electrochem Sci Vol 8 2013

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IL was measured using a calibrated modified Ostwald viscometer (Cannon-Fenske glass capillary

viscometers CFRU 9721-A50) The viscometer capillary diameter was 12 mm as measured using a

caliper (model No PD-153) with an accuracy of plusmn 002 mm The viscometer was placed in a

thermostatic water bath (TV-4000 TAMSON) whose temperature was regulated to within plusmn 001 K

The flow time was measured using a stopwatch with a resolution of 001 s For each IL the

experimental viscosity was obtained by averaging three to five flow time measurements The water

content of synthesized IL [PyrMB][BuSO4] was determined using the KarlndashFischer method the

content was below 300 ppm The nuclear magnetic resonance (NMR) spectra of the synthesized IL

were recorded on a BRUKER AV300 spectrometer and calibrated with tetramethylsilane (TMS) as the

internal reference

3 RESULTS AND DISCUSSION

31 Density and excess molar volume

The densities of neat IL [PyrMB][BuSO4] neat PEG200 and PEG200 (1) + [PyrMB][BuSO4]

(2) binary mixture over the temperature range (29315 to 35315) K and at atmospheric pressure are

presented in Table 1 and Figure 2 As shown in Figure 2 the trend of density for the binary system

with respect to temperature was decreased with increasing temperature The variations of the densities

with concentration at the different temperatures studied are shown in Figure 3 from analysis of the

data it was found that the densities depend more strongly on the mole fraction of PEG200 in the

mixture than on temperature

Figure 2 ρ vs T plot of the PEG200 (1) + [PyrMB][BuSO4] (2) binary system

A third-order polynomial was found to satisfactorily correlate the change of density with various

compositions

T K

290 300 310 320 330 340 350 360

g

cm

-3

109

110

111

112

113

114

x1 = 00000

x1 = 01452

x1 = 01942

x1 = 02912

x1 = 03897

x1 = 04893

x1 = 05890

x1 = 06903

x1 = 07922

x1 = 08958

Int J Electrochem Sci Vol 8 2013

5071

ρ = a0 + a1 x1 + a2 x12 + a3 x1

3 (1)

where x1 is the mole fractions of PEG200 and a0 a1 a2 and a3 refer to the fit coefficients Fit

parameters are listed in Table 2 for the mixtures

Table 1 Experimental density () and excess molar volume (VmE) for the binary system PEG200 (1)

+ [PyrMB][BuSO4] (2)

x1

29315 29815 30315 30815 31315 31815 32315 32815 33315 33815 34315 34815 35315

ρg middotcm-3

0 11258 11228 11199 11169 11140 11111 11082 11053 11025 10996 10968 10940 10912

01452 11288 11259 11230 11200 11171 11142 11112 11083 11053 11024 10995 10965 10936

01942 11305 11275 11245 11216 11186 11157 11127 11097 11068 11038 11008 10979 10949

02912 11334 11304 11274 11243 11213 11183 11153 11123 11092 11062 11032 11002 10972

03897 11352 11321 11291 11260 11229 11199 11168 11138 11107 11076 11046 11015 10984

04893 11356 11325 11294 11263 11232 11201 11170 11139 11108 11077 11046 11015 10984

05890 11350 11319 11288 11256 11225 11193 11162 11131 11099 11068 11036 11005 10973

06903 11331 11299 11267 11235 11203 11172 11140 11108 11076 11044 11012 10980 10948

07922 11318 11285 11252 11219 11186 11153 11120 11087 11054 11021 10988 10956 10923

08958 11312 11278 11243 11208 11174 11139 11104 11070 11035 11000 10966 10931 10896

1 11312 11273 11234 11195 11157 11119 11081 11044 11007 10970 10933 10896 10860

E

mV cm3 mol-1

0 00000 00000 00000 00000 00000 00000 00000 00000 00000 00000 00000 00000 00000

01452 -05572 -05884 -06161 -06404 -06613 -06787 -06925 -07028 -07096 -07127 -07123 -07081 -07003

01942 -08575 -08917 -09225 -09498 -09737 -09942 -10111 -10245 -10343 -10406 -10432 -10422 -10375

02912 -13539 -13931 -14289 -14614 -14903 -15159 -15379 -15564 -15714 -15828 -15906 -15947 -15952

03897 -15730 -16197 -16630 -17029 -17394 -17726 -18022 -18284 -18511 -18702 -18858 -18978 -19061

04893 -14983 -15521 -16026 -16498 -16936 -17341 -17711 -18047 -18348 -18615 -18846 -19041 -19201

05890 -12361 -12970 -13547 -14090 -14601 -15078 -15522 -15931 -16306 -16647 -16953 -17224 -17459

06903 -07359 -08013 -08634 -09222 -09777 -10300 -10788 -11243 -11663 -12049 -12400 -12717 -12997

07922 -03606 -04235 -04831 -05394 -05923 -06418 -06878 -07304 -07695 -08051 -08371 -08655 -08903

08958 -01410 -01915 -02384 -02818 -03216 -03578 -03903 -04192 -04443 -04656 -04832 -04969 -05068

1 00000 00000 00000 00000 00000 00000 00000 00000 00000 00000 00000 00000 00000

Figure 3 ρ of the PEG200 (1) + [PyrMB][BuSO4] (2) binary system as a function of concentration

at various temperatures

The correlation constants for Eq (1) were established using the least square method and are

presented in Table 2 along with the standard deviation estimated using the following equation

2

exp cal 1 2( - )

[ ]Z Z

n

(2)

x1

00 02 04 06 08 10

g c

m-3

106

108

110

112

114

29315 K

30315 K

31315 K

32315 K

33315 K

34315 K

35315 K

Int J Electrochem Sci Vol 8 2013

5072

where n is the number of experimental points and Zexp and Zcal are the experimental and

calculated values respectively

Table 2 Coefficients of polynomiala for the correlation of the density (ρgmiddotcm

-3) in function of

concentration at different temperatures of the binary systems PEG200 (1) + [PyrMB][BuSO4]

(2)

TK a0 g cm

-3 a1 g cm

-3 a2 g cm

-3 a3 g cm

-3

29315 11248 00455 -00638 0024 0000840

29815 11219 00447 -00617 00217 0000800

30315 1119 00439 -00596 00195 0000764

30815 11161 00431 -00575 00173 0000732

31315 11132 00422 -00554 00152 0000704

31815 11103 00413 -00533 00132 0000680

32315 11075 00403 -00512 00112 0000660

32815 11046 00393 -00492 00093 0000640

33315 11018 00382 -00471 00074 0000625

33815 10989 00372 -0045 00055 0000613

34315 10961 0036 -0043 00037 0000606

34815 10933 00349 -00409 0002 0000596

35315 10905 00337 -00389 00003 0000592

a ρ = a0 + a1 x1 + a2 x1

2 + a3 x1

3

As can be seen from the Table 1 the value of the density decreases with increasing temperature

eventhough the variation is very small If the variation of the density with the temperature is

considered as linear then the change in the calculated thermal expansion coefficient values becomes

nearly constant In order to have an improved accuracy a second order polynomial of the eqn (3) was

used to correlate the variation of the density with the temperature for PEG200 (1) + [PyrMB][BuSO4]

(2) binary system

ρ = b0 + b1 T + b2 T2 (3)

where T is the temperature and b0 b1 and b2 are the correlation coefficients The correlation

coefficients are listed in Table 3 together with the standard deviations (σ) calculated using Eq (2)

Excess thermodynamic properties are of great importance for understanding the nature of

molecular interaction in binary mixtures The excess molar volume E

mV which is the difference

between the real and ideal mixing behaviors is defined by

m m 1 1 2 2 E o o

V V xV x V (4)

where Vm represents the volume of a mixture containing one mole of (PEG200 +

[PyrMB][BuSO4]) x1 and x2 are the mole fractions of components 1 (PEG200) and 2

([PyrMB][BuSO4]) respectively and V10 and V2

0 are the molar volumes of the pure components The

Int J Electrochem Sci Vol 8 2013

5073

excess molar volumes of mixtures over the entire composition range were calculated from our

measurements of density according to the following equation

Table 3 The adjustable parameters of density (ρ = b0 + b1 T + b2 T2) at various temperature for neat

PEG200 (x1 = 1) [PyrMB][BuSO4] (x1 = 0) and binary system PEG200 (1) + [PyrMB][BuSO4]

(2)

x1 b0 b1 b2

0 1326 -000077105 00000003 000003

01452 1301 -0000588 0 000023

01942 1304 -0000593 0 000032

02912 131 -0000604 0 000047

03897 1315 -0000613 0 000009

04893 1318 -0000621 0 000034

05890 1319 -0000629 0 000045

06903 132 -0000639 0 000046

07922 1325 -0000658 0 000036

08958 1335 -0000694 0 000030

1 1405 -000108 000000051 000112

Figure 4 Excess molar volumes for the binary system PEG200 (1) + [PyrMB][BuSO4] (2) and

fitted curves using the Redlich-Kister parameters

1 1 2 2 1 1 2 2m

1 2

E

Vx M x M x M x M

(5)

where ρ1 ρ2 and ρ are the densities of neat PEG200 [PyrMB][BuSO4] and their mixture

respectively M1 and M2 are the molar masses of PEG200 and [PyrMB][BuSO4] respectively The E

mV

values of mixtures are summarized in Table 1 The excess molar volumes of mixtures versus the mole

x1

00 02 04 06 08 10

Vm

E

cm

3 m

ol-1

-20

-15

-10

-05

00

30315 K

31315 K

32315 K

33315 K

Int J Electrochem Sci Vol 8 2013

5074

fraction of PEG200 from 29315 to 35315 K are plotted in Figure 4 The excess molar volume of the

binary system is mainly concerned with the weak chemical interactions the physical and structural

characteristics of the system components If the chemical or nonchemical interaction of the same

components is the dominant way of the interaction the excess volume of the mixture should be

positive If the molecules of the components have a more effective packing in the mixture than that in

the pure component that is the attracting interaction between the molecules of two components is the

dominant way the excess molar volume of the binary system should be negative [66] As shown in

Figure 4 the excess molar volumes are asymmetric and negative for all of the systems studied over the

entire composition range the minimum of E

mV is reached at a mole fraction of PEG200 near x1 = 04

and the absolute values of the excess volume increase with increasing temperature The molar volume

for [PyrMB][BuSO4] is 26243 cm3 mol

-1 at T = 29315 K which is greater than the molar volumes of

PEG200 (17681 cm3 mol

-1) at T = 29315 K The large difference between molar volumes of the

molecular liquid and [PyrMB][BuSO4] indicates that it is possible that the relatively small organic

molecules fit into the interstices upon mixing Therefore the filling effect of organic molecular liquids

in the interstices of ionic liquids and the ionndashdipole interactions between poly(ethylene glycol)

oligomer and the butylsulfate-based ionic liquids all contribute to the negative values of the molar

excess volumes

32 Volume expansivity and excess volume expansivity

Density results for the PEG200 and [PyrMB][BuSO4] binary system studied in current work were

also used to derive the coefficient of thermal expansion From the relationship of vs T the volume

expansivity (coefficient of thermal expansion) α is defined as

1 1

( ) ( )p p

V

TV T

(6)

where subscript p indicates constant pressure The α values of pure [PyrMB][BuSO4] and

PEG200 and their mixture are summarized in Table 4 The values indicate that the thermal expansion

coefficient of this binary mixture (PEG200 + [PyrMB][BuSO4]) increases with increasing temperature

and increases with increasing mole fraction of the PEG200

The corresponding excess function (excess volume expansivity) was calculated using

E id id

1 1 2 2 (7)

where id

1 is an ideal volume fraction given by the following relation

1 m11

1 m1 2 m2

id xV

xV x V

(8)

Int J Electrochem Sci Vol 8 2013

5075

where Vmi is the molar volume of pure component i

Table 4 Experimental volume expansivity (α) and the excess volume expansivity (αE) for the binary

system PEG200 (1) + [PyrMB][BuSO4] (2)

x1

29315 29815 30315 30815 31315 31815 32315 32815 33315 33815 34315 34815 35315

104 αK-1

0 51245 51380 51516 51651 51787 51922 52058 52193 52329 52464 52600 52735 52871

01452 52053 52189 52325 52462 52600 52739 52878 53018 53159 53300 53443 53586 53730

01942 52438 52576 52715 52854 52994 53135 53276 53418 53561 53705 53850 53995 54141

02912 53299 53443 53586 53731 53877 54023 54170 54318 54466 54616 54766 54917 55069

03897 53973 54120 54268 54417 54567 54717 54869 55021 55174 55328 55483 55638 55795

04893 54667 54818 54971 55124 55278 55433 55589 55745 55903 56061 56221 56381 56542

05890 55372 55527 55683 55840 55998 56157 56317 56477 56639 56801 56965 57129 57294

06903 56358 56517 56677 56838 57000 57163 57327 57492 57657 57824 57992 58160 58330

07922 58175 58344 58515 58687 58860 59033 59208 59384 59561 59739 59918 60098 60279

08958 61313 61502 61691 61882 62074 62268 62462 62658 62855 63053 63252 63453 63655

1 66532 66763 66993 67224 67455 67685 67916 68146 68377 68607 68838 69069 69299

104 αEK-1

0 00000 00000 00000 00000 00000 00000 00000 00000 00000 00000 00000 00000 00000

01452 -00762 -00772 -00782 -00792 -00800 -00808 -00815 -00822 -00827 -00832 -00837 -00840 -00843

01942 -00942 -00954 -00966 -00977 -00987 -00997 -01006 -01014 -01021 -01028 -01033 -01038 -01043

02912 -01259 -01275 -01289 -01302 -01315 -01327 -01339 -01349 -01359 -01368 -01376 -01383 -01389

03897 -01870 -01889 -01908 -01926 -01943 -01959 -01975 -01989 -02003 -02016 -02028 -02040 -02050

04893 -02576 -02600 -02623 -02646 -02668 -02689 -02709 -02728 -02746 -02764 -02780 -02796 -02811

05890 -03382 -03412 -03441 -03470 -03497 -03524 -03550 -03574 -03598 -03621 -03644 -03665 -03685

06903 -04064 -04100 -04136 -04170 -04204 -04236 -04268 -04299 -04329 -04358 -04386 -04413 -04439

07922 -04073 -04110 -04146 -04181 -04214 -04247 -04279 -04310 -04339 -04368 -04396 -04422 -04448

08958 -02968 -02998 -03026 -03053 -03079 -03104 -03128 -03151 -03172 -03192 -03211 -03228 -03245

1 00000 00000 00000 00000 00000 00000 00000 00000 00000 00000 00000 00000 00000

Figure 5 Plot of excess volume expansivity αE of the PEG200 (1) + [PyrMB][BuSO4] (2) binary

system versus mole fraction x1 at various temperatures

Typical concentration dependencies of excess volume expansivity are given in Figure 5 for the

PEG200 + [PyrMB][BuSO4] binary system The values of excess thermal coefficient αE are found to

x1

00 02 04 06 08 10

10

4

E K

-1

-04

-03

-02

-01

00

29315 K

30315 K

31315 K

32315 K

33315 K

34315 K

35315 K

Temp

Int J Electrochem Sci Vol 8 2013

5076

be negative over the whole composition range for the binary system at 29315 ~ 35315 K The curves

are asymmetrical with the minimum located at the IL mole fraction of about 08 In general negative

αE values indicate the presence of strong interaction between the components in the mixtures [67] The

trends observed in αE values for the present mixtures suggest the formation of H-bonding between

unlike molecules which is stronger in PEG200 + [PyrMB][BuSO4] binary system The increasing

negative αE values for PEG200 + [PyrMB][BuSO4] with increase in temperature indicate enhanced

unlike interaction between components of the mixture that is more destruction of order during mixing

contributes negatively to αE

33 Viscosity

Since ILs are more viscous than conventional solvents in most applications they can be used in

mixtures with other less viscous compounds Therefore the viscosity of pure ILs and their mixtures

with PEG oligomer (or conventional solvents) is an important property and their knowledge is

primordial for each industrial processes [6869] The measured dynamic viscosities for the neat

PEG200 neat [PyrMB][BuSO4] and PEG200 + [PyrMB][BuSO4] binary mixture as a function of

temperature over the whole composition range are shown in Figure 6 and their data are listed in Table

5 the viscosities of the mixtures decrease rapidly when PEG oligomer are added to the ionic liquid

especially at lower temperatures The fitting lines in Figure 6 were calculated with the following

fourth-order polynomial equation

= c0 + c1 x1 + c2 x12 + c3 x1

3 + c4 x1

4 (9)

where x1 is the mole fractions of PEG200 and c0 c1 c2 c3 and c4 refer to the fit coefficients

The parameters of correlation are shown in Table 6

Figure 6 Dynamic viscosity for the PEG200 (1) + [PyrMB][BuSO4] (2) binary system as a

function of mole fractions of the PEG200 at different temperatures Lines represent the

polynomial correlation

x1

00 02 04 06 08 10

mP

a s

0

200

400

600

800

1000

1200

1400

29315 K

30315 K

31315 K

32315 K

33315 K

34315 K

35315 K

Int J Electrochem Sci Vol 8 2013

5077

Table 5 Experimental dynamic viscosity (η) and viscosity deviation (Δη) for the binary system

PEG200 (1) + [PyrMB][BuSO4] (2)

x1

29315 29815 30315 30815 31315 31815 32315 32815 33315 33815 34315 34815 35315

ηmPamiddots

0 13209 9343 6745 4961 3712 2821 2176 1700 1345 1077 871 712 587

01452 5907 4362 3294 2539 1992 1589 1286 1055 876 735 623 533 460

01942 4656 3475 2656 2072 1647 1331 1091 907 763 649 557 483 422

02912 3134 2395 1870 1489 1205 991 826 697 594 512 445 390 345

03897 2367 1846 1463 1177 959 792 660 557 474 406 351 306 269

04893 1799 1396 1104 887 723 598 501 424 362 312 272 238 210

05890 1540 1194 941 753 611 502 418 351 298 255 220 191 167

06903 1185 926 736 594 485 402 336 284 242 209 181 158 139

07922 954 742 589 475 389 323 271 231 198 172 150 132 117

08958 811 639 512 415 342 285 240 204 175 151 132 116 102

1 629 505 410 337 280 235 199 170 146 126 110 97 85

ΔηmPamiddots

0 00 00 00 00 00 00 00 00 00 00 00 00 00

01452 -5475 -3698 -2530 -1751 -1221 -857 -602 -423 -295 -204 -137 -89 -54

01942 -6111 -4152 -2859 -1991 -1398 -988 -700 -496 -347 -244 -166 -110 -68

02912 -6411 -4374 -3030 -2126 -1507 -1077 -774 -558 -391 -288 -204 -142 -103

03897 -5940 -4053 -2813 -1982 -1415 -1022 -745 -547 -405 -300 -223 -166 -123

04893 -5254 -3622 -2541 -1811 -1255 -957 -708 -528 -396 -299 -227 -173 -131

05890 -4260 -2944 -2073 -1484 -1034 -796 -594 -448 -341 -262 -203 -158 -124

06903 -3340 -2316 -1636 -1176 -826 -634 -475 -360 -275 -212 -165 -129 -101

07922 -2289 -1599 -1138 -823 -579 -449 -320 -257 -197 -152 -118 -92 -72

08958 -1129 -787 -559 -404 -277 -220 -152 -126 -96 -74 -58 -45 -35

1 00 00 00 00 00 00 00 00 00 00 00 00 00

Table 6 Coefficients of polynomiala for the correlation of the viscosity ( mPa s) in function of

concentration at different temperatures of the binary systems PEG200 (1) + [PyrMB][BuSO4]

(2)

TK c0 mPa s c1 mPa s c2 mPa s c3 mPa s C4 mPa s

29315 13154 -68701 15960 -16688 63543 1075

29815 93069 -46703 10681 -11113 42269 727

30315 67211 -32185 72085 -74396 28222 497

30815 49454 -22431 48886 -49866 18828 343

31315 37016 -15772 33175 -33281 12474 238

31815 28146 -1116 22406 -21947 81322 165

32315 21713 -7923 14947 -1413 51409 114

32815 16975 -56244 97349 -870 30666 077

33315 13435 -39753 60667 -4908 16219 051

33815 10756 -27812 34718 -22519 61382 033

34315 87026 -19098 16304 -39091 -88892 021

34815 71108 -12698 32285 90904 -5763 016

35315 58636 -79728 -60345 18103 -91096 017 a = c0 + c1 x1 + c2 x1

2 + c3 x1

3 + c4 x1

4

The temperature dependence becomes distinctly nonlinear especially at high [PyrMB][BuSO4]

content The Vogel-Tammann-Fulcher (VTF) equation [70-75] suitably correlates the nonlinear

behavior as a function of the temperature not only the viscosities of the neat IL but also the viscosities

of the mixtures for the binary systems through the composition range

Int J Electrochem Sci Vol 8 2013

5078

exp[ ]( )

o

o

B

T T

(10)

where ηo B and To are constants The parameter To is the ideal glass transition temperature which

should be slightly below the experimental glass transition temperature Tg [76] The adjustable

parameters obtained from the VTF correlation were presented in Table 7 The obtained parameters o

and B change smoothly with composition for binary mixtures

Table 7 The VTF equation parameters of viscosity ( 1 exp[ ]( )

o

o

B

T T

) and conductivity

(

exp[ ]( )

o

o

B

T T

) for neat PEG200 (x1 = 1) [PyrMB][BuSO4] (x1 = 0) and binary system

PEG200 (1) + [PyrMB][BuSO4] (2)

x1

ηo (mPa s) To (K) B (K) R2a

o (mS cm-1

) To (K) Brsquo (K) R2a

0 027 1810 9540 0999 792 1788 6854 0999

01452 026 1712 9413 0999 577 1699 6268 0999

01942 043 1788 7975 0999 401 1792 5297 0999

02912 053 1794 7264 0999 521 1662 6031 0999

03897 026 1629 8902 0999 274 1803 4381 0999

04893 023 1666 8455 0999 177 1951 3272 0999

05890 015 1648 8865 0999 216 1883 3672 0999

06903 015 1647 8572 0999 88 2174 2000 0999

07922 017 1717 7702 0999 92 2020 2578 0999

08958 012 1642 8360 0999 43 2110 2088 0999

1 014 1649 7868 0999 556 1928 9815 0999

a Correlation coefficient

The viscosities of the mixtures decrease rapidly when organic oligomers are added to the ionic

liquid this decrease is particularly evident in dilute solutions of organic oligomers in the ionic liquid

The strong coulomb interactions between the [BuSO4]- anion and [PyrMB]

+ cation are weakened upon

mixing with the polar organic oligomers which leads to a higher mobility of the ions and a lower

viscosity of the mixtures [77] This indicates that the viscosity of ILs could be therefore tuned for

several applications by adding an organic solvent or by changing temperature [78]

Due to the wide range of possible molecular interactions between the two components

deviations can occur from ideal behavior These viscosity deviations can be quantified by the viscosity

deviation Δη also known as ldquoexcess viscosityrdquo in other sources

1 1 2 2 (mPa s) x x (11)

Int J Electrochem Sci Vol 8 2013

5079

where x1 and x2 are the mole fractions of PEG200 and [PyrMB][BuSO4] respectively and 1

and 2 are the viscosities (mPa middot s) of the solution the pure solvent and the pure IL respectively

Figure 7 shows the viscosity deviations as a function of the PEG200 mole fraction composition x1 and

temperature for the PEG200 + [PyrMB][BuSO4] binary mixture The values of viscosity deviations

are compared with those obtained from the RedlichndashKister polynomial equation The viscosity

deviation for the mixture show negative deviations from ideality over the whole mole fraction range

Figure 7 also shows that the negative values of viscosity deviations decrease with increasing

temperature this can be attributed to the specific interactions in mixtures typically hydrogen bonds break-

up as the temperature increases [79] The minimum value of Δη is observed at about x1 asymp 03 and the

viscosity deviation depends on molecular interactions as well as on the size and shape of the molecules

[80]

Figure 7 Viscosity deviations Δη versus the mole fraction at various temperatures for the binary

mixture PEG200 (1) + [PyrMB][BuSO4] (2)

34 Conductivity

The experimental data of conductivity of the neat ILs [PyrMB][BuSO4] neat PEG200 and

binary system are plotted against the x1 at various temperatures in Figure 8 together with lines

calculated with the four-order polynomial equation

= d0 + d1 x1 + d2 x12 + d3 x1

3 + d4 x1

4 (12)

where x1 is the mole fractions of PEG200 and d0 d1 d2 d3 and d4 refer to the fit coefficients

The parameters of correlation are shown in Table 8 The conductivities of neat IL [PyrMB][BuSO4]

neat PEG200 and binary system at various temperatures were fitted using the VTF equation

exp[ ]

( )o

o

B

T T

(13)

x1

00 02 04 06 08 10

m

Pa s

-700

-600

-500

-400

-300

-200

-100

0

29315 K

30315 K

31315 K

32315 K

33315 K

34315 K

35315 K

Int J Electrochem Sci Vol 8 2013

5080

where T is the absolute temperature and Brsquo and To are adjustable parameters The best-fit

mS cm-1 Brsquo (K) and To (K) parameters are given in Table 7 Neat [PyrMB][BuSO4] neat

PEG200 and binary system were very well fit by the VTF model over the temperature range studied

Figure 8 Plot of conductivity of the PEG200 (1) + [PyrMB][BuSO4] (2) binary system versus

mole fraction x1 at various temperatures

Table 8 Coefficients of polynomiala for the correlation of the conductivity ( mS cm

-1) in function

of concentration at different temperatures of the binary systems PEG200 (1) +

[PyrMB][BuSO4] (2)

TK d0 mS cm

-1 d1 mS cm

-1 d2 mS cm

-1 d3 mS cm

-1 d4 mS cm

-1

29315 02019 09622 -01679 0734 -17284 00095

29815 02588 11031 -02503 09086 -20181 00109

30315 03255 12119 -01935 08565 -21971 00125

30815 04025 13165 -01329 0767 -23477 00141

31315 04904 13712 01238 03677 -23439 00156

31815 05894 15032 -00006 04737 -25518 00171

32315 06999 15802 00743 0265 -25986 00188

32815 08221 16427 01595 00089 -26032 00208

33315 09562 16373 04858 -06207 -24165 00233

a = d0 + d1 x1 + d2 x1

2 + d3 x1

3 + d4 x1

4

As shown in Figure 8 it can be seen that the conductivity of the binary mixture increases with

increasing amount of PEG200 goes through a maximum and then goes down to the specific

conductivity of the neat PEG200 The conductivity is related to the ion mobility and the number of

charge carriers [81] At a fixed concentration the ions move faster at higher temperature due to the

relatively lower viscosity of the mixture On the other hand the composition influences both the ion

mobility and the number of charge carriers at a fixed temperature At the beginning the number of

charge and the ion mobility increase with increasing PEG oligomer composition the maximum of

conductivity is located at x1 = 059 and corresponds to a value of 171 mS cmminus 1

at 33315 K It can also

be observed that the conductivity increases as the temperature increases The higher temperature may

x1

00 02 04 06 08 10

mS

cm

-1

00

05

10

15

20

29315 K

29815 K

30315 K

30815 K

31315 K

31815 K

32315 K

32815 K

33315 K

Int J Electrochem Sci Vol 8 2013

5081

weaken the influence of aggregation to the conductivity which suggests that a higher temperature is

better for the ILs to act as electrolytes

Table 9 RedlickndashKister fitting coefficients Ak and the standard deviation of the VE and ∆for the

binary mixture of PEG200 (1) + [PyrMB][BuSO4] (2) system

TK A0 A1 A2 A3 A4

VEcm

3 mol

-1

29315 -5979 -4906 6585 5754 -1717 002687

29815 -6200 -4760 6464 5767 -2022 002693

30315 -6408 -4612 6345 5774 -2276 002698

30815 -6602 -4461 6229 5774 -2476 002701

31315 -6782 -4310 6116 5767 -2623 002701

31815 -6948 -4155 6006 5753 -2716 002699

32315 -7100 -3999 5899 5732 -2754 002692

32815 -7239 -3840 5795 5704 -2738 002683

33315 -7363 -3679 5694 5669 -2666 002670

33815 -7472 -3515 5596 5626 -2538 002654

34315 -7568 -3350 5501 5576 -2353 002634

34815 -7648 -3182 5409 5518 -2111 002611

35315 -7714 -3011 5320 5452 -1812 002586

∆mPa s

29315 -20414 -17226 -15592 -95544 -75863 399496

29815 -14035 -11558 -10713 -62192 19493 340180

30315 -98261 -78407 -73734 -40709 58145 286725

30815 -69922 -53591 -50601 -2676 67556 235258

31315 -48876 -39537 -41051 -14118 16739 079245

31815 -36917 -25169 -22939 -11646 51047 146189

32315 -27415 -1721 -12581 -92603 21498 104339

32815 -20441 -11703 -77538 -38334 -81478 090708

33315 -15382 -67274 -31134 -47585 -18255 059539

33815 -11664 -44928 -15533 -22312 -05591 037855

34315 -89038 -24163 68654 -15007 -10347 024263

34815 -68279 -91813 23131 -10367 -18636 017759

35315 -52525 -24051 26474 15498 -85341 018640

35 Redlich-Kister Equation for Binary System

The binary excess property ( E

mV ) and deviations (Δ) at several temperatures were fitted to a

Redlich-Kister-type equation [82]

1 1 1

0

(or ) (1 ) (1 2 )j

E i

i

i

Y Y x x A x

(14)

Int J Electrochem Sci Vol 8 2013

5082

where ΔY (YE) represents E

mV (cm3 mol

minus1) and Δ

(mPa s)x1 denotes the mole fraction of

PEG200 Ai represents the polynomial coefficients and j is the degree of the polynomial expansion

The correlated results for excess molar volumes ( E

mV ) viscosity deviations (Δ) including the values

of the fitting parameters Ai together with the standard deviation σ are given in Table 9 where the

tabulated standard deviation σ [83] is defined as

2

exp cal 1 2( )

[ ]Y Y

m n

(15)

where m is the number of experimental data points and n is the number of estimated

parameters The subscripts ldquoexprdquo and ldquocalrdquo denote the values of the experimental and calculated

property respectively As shown in Table 9 the experimentally derived E

mV and Δη values were

correlated satisfactorily by the Redlich-Kister equation

4 CONCLUSIONS

This paper is a systematic characterizations of thermophysical properties for IL binary system

Density viscosity and conductivity for (PEG200 + [PyrMB][BuSO4]) binary system are presented as a

function of temperature at atmospheric pressure it was demonstrated that viscosity and conductivity

were more sensitive to the changes in PEG content or temperature than density and the viscosity and

conductivity of pure IL and (PEG200 + [PyrMB][BuSO4]) binary system at different temperature are

fitted using the VogelndashTammannndashFulcher (VTF) equation with good accuracy The excess molar

volumes excess volume expansivity and viscosity deviations show negative deviations from the ideal

solution the results are interpreted in terms of molecular interactions in the (PEG200 +

[PyrMB][BuSO4]) binary mixture The conductivity increases to a maximum value when the

concentration of PEG200 is increased and decreases after the maximum the data obtained will be

helpful for the application of the ionic liquids as electrolytes and also useful for the ionic liquids

database

ACKNOWLEDGEMENTS

The authors would like to thank the National Science Council of the Republic of China for financially

supporting this project

References

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2 TY Wu IW Sun ST Gung MW Lin BK Chen HP Wang SG Su J Taiwan Inst Chem

Eng 42 (2011) 513

Int J Electrochem Sci Vol 8 2013

5083

3 TY Wu SG Su KF Lin YC Lin HP Wang MW Lin ST Gung IW Sun Electrochim

Acta 56 (2011) 7278

4 B Baek S Lee C Jung Int J Electrochem Sci 6 (2011) 6220

5 PN Tshibangu SN Ndwandwe ED Dikio Int J Electrochem Sci 6 (2011) 2201

6 TY Wu SG Su HP Wang IW Sun Electrochem Commun 13 (2011) 237

7 TY Wu SG Su HP Wang YC Lin ST Gung MW Lin IW Sun Electrochim Acta 56

(2011) 3209

8 IW Sun YC Lin BK Chen CW Kuo CC Chen SG Su PR Chen TY Wu Int J

Electrochem Sci 7 (2012) 7206

9 TY Wu SG Su ST Gung MW Lin YC Lin CA Lai IW Sun Electrochim Acta 55

(2010) 4475

10 AN Soriano AM Agapito LJLI Lagumbay AR Caparanga MH Li J Taiwan Inst Chem

Eng 42 (2011) 258

11 TY Wu IW Sun ST Gung BK Chen HP Wang SG Su J Taiwan Inst Chem Eng 42

(2011) 874

12 S Ibrahim MR Johan Int J Electrochem Sci 6 (2011) 5565

13 TY Wu SG Su YC Lin HP Wang MW Lin ST Gung IW Sun Electrochim Acta 56

(2010) 853

14 H Wang LX Wu YC Lan JQ Zhao JX Lu Int J Electrochem Sci 6 (2011) 4218

15 FF Liu SQ Liu QJ Feng SX Zhuang JB Zhang P Bu Int J Electrochem Sci 7 (2012)

4381

16 HA Barham SA Brahim Y Rozita KA Mohamed Int J Electrochem Sci 6 (2011) 181

17 SK Shukla LC Murulana EE Ebenso Int J Electrochem Sci 6 (2011) 4286

18 NV Likhanova O Olivares-Xometl D Guzman-Lucero MA Dominguez-Aguilar N Nava

M Corrales-Luna MC Mendoza Int J Electrochem Sci 6 (2011) 4514

19 A Zarrouk M Messali H Zarrok R Salghi AA Ali B Hammouti SS Al-Deyab F Bentiss

Int J Electrochem Sci 7 (2012) 6998

20 BS Ali BH Ali R Yusoff MK Aroua Int J Electrochem Sci 7 (2012) 3835

21 MH Lin YJ Liu ZH Yang YB Huang ZH Sun Y He CL Ni Int J Electrochem Sci 7

(2012) 965

22 CH Su MH Chung HJ Hsieh YK Chang JC Ding HM Wu J Taiwan Inst Chem Eng

43 (2012) 573

23 H Shekaari A Kazempour J Taiwan Inst Chem Eng 43 (2012) 650

24 ZJ Wei Y Li D Thushara YX Liu QL Ren J Taiwan Inst Chem Eng 43 (2012) 363

25 GQ Zhang HW Yang JF Gao HK Zhang CB Zheng YL Cao YH Wang KQ Ding

Int J Electrochem Sci 7 (2012) 7547

26 P Norouzi MR Ganjali F Faridbod SJ Shahtaheri HA Zamani Int J Electrochem Sci 7

(2012) 2633

27 F Faridbod MR Ganjali M Hosseini P Norouzi Int J Electrochem Sci 7 (2012) 1927

28 MR Ganjali Z Rafiei-Sarmazdeh T Poursaberi SJ Shahtaheri P Norouzi Int J

Electrochem Sci 7 (2012) 1908

29 A Babaei DJ Garrett AJ Downard Int J Electrochem Sci 7 (2012) 3141

30 MR Ganjali T Alizade P Norouzi Int J Electrochem Sci 7 (2012) 4800

31 MR Ganjali T Alizade B Larijani F Faridbod P Norouzi Int J Electrochem Sci 7 (2012)

4756

32 P Norouzi B Larijani MR Ganjali Int J Electrochem Sci 7 (2012) 7313

33 TY Wu MH Tsao SG Su HP Wang YC Lin FL Chen CW Chang IW Sun J Braz

Chem Soc 22 (2011) 780

34 MH Tsao TY Wu HP Wang IW Sun SG Su YC Lin CW Chang Mater Lett 65

(2011) 583

Int J Electrochem Sci Vol 8 2013

5084

35 SY Ku SY Lu Int J Electrochem Sci 6 (2011) 5219

36 TY Wu MH Tsao FL Chen SG Su CW Chang HP Wang YC Lin IW Sun J Iran

Chem Soc 7 (2010) 707

37 IW Sun HP Wang H Teng SG Su YC Lin CW Kuo PR Chen TY Wu Int J

Electrochem Sci 7 (2012) 9748

38 TY Wu MH Tsao FL Chen SG Su CW Chang HP Wang YC Lin WC Ou-Yang

IW Sun Int J Mol Sci 11 (2010) 329

39 YX An PJ Zuo XQ Cheng LX Liao GP Yin Int J Electrochem Sci 6 (2011) 2398

40 LC Xuan YX An W Fang LX Liao YL Ma ZY Ren GP Yin Int J Electrochem Sci

6 (2011) 6590

41 HM Wang SQ Liu K Huang XG Yin YN Liu SJ Peng Int J Electrochem Sci 7

(2012) 1688

42 HM Wang SQ Liu NF Wang YN Liu Int J Electrochem Sci 7 (2012) 7579

43 H Ganjali MR Ganjali T Alizadeh F Faridbod P Norouzi Int J Electrochem Sci 6 (2011)

6085

44 MR Ganjali MH Eshraghi S Ghadimi SM Moosavi M Hosseini H Haji-Hashemi P

Norouzi Int J Electrochem Sci 6 (2011) 739

45 MR Ganjali T Poursaberi M Khoobi A Shafiee M Adibi M Pirali-Hamedani P Norouzi

Int J Electrochem Sci 6 (2011) 717

46 P Norouzi M Hosseini MR Ganjali M Rezapour M Adibi Int J Electrochem Sci 6 (2011)

2012

47 MR Ganjali MR Moghaddam M Hosseini P Norouzi Int J Electrochem Sci 6 (2011)

1981

48 MR Ganjali M Hosseini M Pirali-Hamedani HA Zamani Int J Electrochem Sci 6 (2011)

2808

49 MR Ganjali M Rezapour SK Torkestani H Rashedi P Norouzi Int J Electrochem Sci 6

(2011) 2323

50 P Norouzi M Pirali-Hamedani SO Ranaei-Siadat MR Ganjali Int J Electrochem Sci 6

(2011) 3704

51 F Faridbod HA Zamani M Hosseini M Pirali-Hamedani MR Ganjali P Norouzi Int J

Electrochem Sci 6 (2011) 3694

52 MR Ganjali SO Ranaei-Siadat H Rashedi M Rezapour P Norouzi Int J Electrochem Sci

6 (2011) 3684

53 TH Tsai KC Lin SM Chen Int J Electrochem Sci 6 (2011) 2672

54 MR Ganjali T Alizadeh F Azimi B Larjani F Faridbod P Norouzi Int J Electrochem

Sci 6 (2011) 5200

55 R Mirshafian MR Ganjali P Norouzi Int J Electrochem Sci 7 (2012) 1656

56 J Gao JG Liu WM Liu B Li YC Xin Y Yin ZG Zou Int J Electrochem Sci 6 (2011)

6115

57 TY Wu BK Chen L Hao KF Lin IW Sun J Taiwan Inst Chem Eng 42 (2011) 914

58 TY Wu BK Chen L Hao CW Kuo IW Sun J Taiwan Inst Chem Eng 43 (2012) 313

59 SW Peng AN Soriano RB Leron MH Li J Taiwan Inst Chem Eng 42 (2011) 233

60 TY Wu IW Sun MW Lin BK Chen CW Kuo HP Wang YY Chen SG Su J Taiwan

Inst Chem Eng 43 (2012) 58

61 TY Wu BK Chen CW Kuo L Hao YC Peng IW Sun J Taiwan Inst Chem Eng 43

(2012) 860

62 A Arce H Rodriguez A Soto Green Chem 9 (2007) 247

63 TY Wu HC Wang SG Su ST Gung MW Lin CB Lin J Taiwan Inst Chem Eng 41 (2010)

315 64 X Li M Hou Z Zhang B Han G Yang X Wang L Zou Green Chem 10 (2008) 879

Int J Electrochem Sci Vol 8 2013

5085

65 J Chen SK Spear JG Huddleston RD Rogers Green Chem 7 (2005) 64

66 U Domanska M Laskowska J Solution Chem 38 (2009) 779

67 K Tamura M Nakamura S Murakami J Solution Chem 26 (1997) 1199

68 Z Yu H Gao H Wang L Chen J Chem Eng Data 56 (2011) 2877

69 KN Marsh JA Boxall R Lichtenthaler Fluid Phase Equilib 219 (2004) 93

70 TY Wu SG Su ST Gung MW Lin YC Lin WC Ou-Yang IW Sun CA Lai J Iran

Chem Soc 8 (2011) 149

71 TY Wu L Hao CW Kuo YC Lin SG Su PL Kuo IW Sun Int J Electrochem Sci 7

(2012) 2047

72 TY Wu L Hao PR Chen JW Liao Int J Electrochem Sci 8 (2013) 2606

73 CW Kuo CW Huang BK Chen WB Li PR Chen TH Ho CG Tseng TY Wu Int J

Electrochem Sci 8 (2013) 3834

74 CW Kuo WB Li PR Chen JW Liao CG Tseng TY Wu Int J Electrochem Sci 8

(2013) 5007

75 TY Wu BK Chen L Hao YC Lin HP Wang CW Kuo IW Sun Int J Mol Sci 12

(2011) 8750

76 H Rodriguez JF Brennecke J Chem Eng Data 51 (2006) 2145

77 Y Tian X Wang J Wang J Chem Eng Data 53 (2008) 2056

78 TY Wu HC Wang SG Su ST Gung MW Lin CB Lin J Chin Chem Soc 57 (2010)

44

79 TY Wu BK Chen L Hao YC Peng IW Sun Int J Mol Sci 12 (2011) 2598

80 H Eyring MS John Significant Liquid Structure Wiley New York 1969

81 H Every AG Bishop M Forsyth DR MacFarlane Electrochim Acta 45 (2000) 1279 82 O Redlich AT Kister Ind Eng Chem 40 (1948) 345

83 A Paul P Kumar A Samanta J Phys Chem B 109 (2005) 9148

copy 2013 by ESG (wwwelectrochemsciorg)

Int J Electrochem Sci Vol 8 2013

5071

ρ = a0 + a1 x1 + a2 x12 + a3 x1

3 (1)

where x1 is the mole fractions of PEG200 and a0 a1 a2 and a3 refer to the fit coefficients Fit

parameters are listed in Table 2 for the mixtures

Table 1 Experimental density () and excess molar volume (VmE) for the binary system PEG200 (1)

+ [PyrMB][BuSO4] (2)

x1

29315 29815 30315 30815 31315 31815 32315 32815 33315 33815 34315 34815 35315

ρg middotcm-3

0 11258 11228 11199 11169 11140 11111 11082 11053 11025 10996 10968 10940 10912

01452 11288 11259 11230 11200 11171 11142 11112 11083 11053 11024 10995 10965 10936

01942 11305 11275 11245 11216 11186 11157 11127 11097 11068 11038 11008 10979 10949

02912 11334 11304 11274 11243 11213 11183 11153 11123 11092 11062 11032 11002 10972

03897 11352 11321 11291 11260 11229 11199 11168 11138 11107 11076 11046 11015 10984

04893 11356 11325 11294 11263 11232 11201 11170 11139 11108 11077 11046 11015 10984

05890 11350 11319 11288 11256 11225 11193 11162 11131 11099 11068 11036 11005 10973

06903 11331 11299 11267 11235 11203 11172 11140 11108 11076 11044 11012 10980 10948

07922 11318 11285 11252 11219 11186 11153 11120 11087 11054 11021 10988 10956 10923

08958 11312 11278 11243 11208 11174 11139 11104 11070 11035 11000 10966 10931 10896

1 11312 11273 11234 11195 11157 11119 11081 11044 11007 10970 10933 10896 10860

E

mV cm3 mol-1

0 00000 00000 00000 00000 00000 00000 00000 00000 00000 00000 00000 00000 00000

01452 -05572 -05884 -06161 -06404 -06613 -06787 -06925 -07028 -07096 -07127 -07123 -07081 -07003

01942 -08575 -08917 -09225 -09498 -09737 -09942 -10111 -10245 -10343 -10406 -10432 -10422 -10375

02912 -13539 -13931 -14289 -14614 -14903 -15159 -15379 -15564 -15714 -15828 -15906 -15947 -15952

03897 -15730 -16197 -16630 -17029 -17394 -17726 -18022 -18284 -18511 -18702 -18858 -18978 -19061

04893 -14983 -15521 -16026 -16498 -16936 -17341 -17711 -18047 -18348 -18615 -18846 -19041 -19201

05890 -12361 -12970 -13547 -14090 -14601 -15078 -15522 -15931 -16306 -16647 -16953 -17224 -17459

06903 -07359 -08013 -08634 -09222 -09777 -10300 -10788 -11243 -11663 -12049 -12400 -12717 -12997

07922 -03606 -04235 -04831 -05394 -05923 -06418 -06878 -07304 -07695 -08051 -08371 -08655 -08903

08958 -01410 -01915 -02384 -02818 -03216 -03578 -03903 -04192 -04443 -04656 -04832 -04969 -05068

1 00000 00000 00000 00000 00000 00000 00000 00000 00000 00000 00000 00000 00000

Figure 3 ρ of the PEG200 (1) + [PyrMB][BuSO4] (2) binary system as a function of concentration

at various temperatures

The correlation constants for Eq (1) were established using the least square method and are

presented in Table 2 along with the standard deviation estimated using the following equation

2

exp cal 1 2( - )

[ ]Z Z

n

(2)

x1

00 02 04 06 08 10

g c

m-3

106

108

110

112

114

29315 K

30315 K

31315 K

32315 K

33315 K

34315 K

35315 K

Int J Electrochem Sci Vol 8 2013

5072

where n is the number of experimental points and Zexp and Zcal are the experimental and

calculated values respectively

Table 2 Coefficients of polynomiala for the correlation of the density (ρgmiddotcm

-3) in function of

concentration at different temperatures of the binary systems PEG200 (1) + [PyrMB][BuSO4]

(2)

TK a0 g cm

-3 a1 g cm

-3 a2 g cm

-3 a3 g cm

-3

29315 11248 00455 -00638 0024 0000840

29815 11219 00447 -00617 00217 0000800

30315 1119 00439 -00596 00195 0000764

30815 11161 00431 -00575 00173 0000732

31315 11132 00422 -00554 00152 0000704

31815 11103 00413 -00533 00132 0000680

32315 11075 00403 -00512 00112 0000660

32815 11046 00393 -00492 00093 0000640

33315 11018 00382 -00471 00074 0000625

33815 10989 00372 -0045 00055 0000613

34315 10961 0036 -0043 00037 0000606

34815 10933 00349 -00409 0002 0000596

35315 10905 00337 -00389 00003 0000592

a ρ = a0 + a1 x1 + a2 x1

2 + a3 x1

3

As can be seen from the Table 1 the value of the density decreases with increasing temperature

eventhough the variation is very small If the variation of the density with the temperature is

considered as linear then the change in the calculated thermal expansion coefficient values becomes

nearly constant In order to have an improved accuracy a second order polynomial of the eqn (3) was

used to correlate the variation of the density with the temperature for PEG200 (1) + [PyrMB][BuSO4]

(2) binary system

ρ = b0 + b1 T + b2 T2 (3)

where T is the temperature and b0 b1 and b2 are the correlation coefficients The correlation

coefficients are listed in Table 3 together with the standard deviations (σ) calculated using Eq (2)

Excess thermodynamic properties are of great importance for understanding the nature of

molecular interaction in binary mixtures The excess molar volume E

mV which is the difference

between the real and ideal mixing behaviors is defined by

m m 1 1 2 2 E o o

V V xV x V (4)

where Vm represents the volume of a mixture containing one mole of (PEG200 +

[PyrMB][BuSO4]) x1 and x2 are the mole fractions of components 1 (PEG200) and 2

([PyrMB][BuSO4]) respectively and V10 and V2

0 are the molar volumes of the pure components The

Int J Electrochem Sci Vol 8 2013

5073

excess molar volumes of mixtures over the entire composition range were calculated from our

measurements of density according to the following equation

Table 3 The adjustable parameters of density (ρ = b0 + b1 T + b2 T2) at various temperature for neat

PEG200 (x1 = 1) [PyrMB][BuSO4] (x1 = 0) and binary system PEG200 (1) + [PyrMB][BuSO4]

(2)

x1 b0 b1 b2

0 1326 -000077105 00000003 000003

01452 1301 -0000588 0 000023

01942 1304 -0000593 0 000032

02912 131 -0000604 0 000047

03897 1315 -0000613 0 000009

04893 1318 -0000621 0 000034

05890 1319 -0000629 0 000045

06903 132 -0000639 0 000046

07922 1325 -0000658 0 000036

08958 1335 -0000694 0 000030

1 1405 -000108 000000051 000112

Figure 4 Excess molar volumes for the binary system PEG200 (1) + [PyrMB][BuSO4] (2) and

fitted curves using the Redlich-Kister parameters

1 1 2 2 1 1 2 2m

1 2

E

Vx M x M x M x M

(5)

where ρ1 ρ2 and ρ are the densities of neat PEG200 [PyrMB][BuSO4] and their mixture

respectively M1 and M2 are the molar masses of PEG200 and [PyrMB][BuSO4] respectively The E

mV

values of mixtures are summarized in Table 1 The excess molar volumes of mixtures versus the mole

x1

00 02 04 06 08 10

Vm

E

cm

3 m

ol-1

-20

-15

-10

-05

00

30315 K

31315 K

32315 K

33315 K

Int J Electrochem Sci Vol 8 2013

5074

fraction of PEG200 from 29315 to 35315 K are plotted in Figure 4 The excess molar volume of the

binary system is mainly concerned with the weak chemical interactions the physical and structural

characteristics of the system components If the chemical or nonchemical interaction of the same

components is the dominant way of the interaction the excess volume of the mixture should be

positive If the molecules of the components have a more effective packing in the mixture than that in

the pure component that is the attracting interaction between the molecules of two components is the

dominant way the excess molar volume of the binary system should be negative [66] As shown in

Figure 4 the excess molar volumes are asymmetric and negative for all of the systems studied over the

entire composition range the minimum of E

mV is reached at a mole fraction of PEG200 near x1 = 04

and the absolute values of the excess volume increase with increasing temperature The molar volume

for [PyrMB][BuSO4] is 26243 cm3 mol

-1 at T = 29315 K which is greater than the molar volumes of

PEG200 (17681 cm3 mol

-1) at T = 29315 K The large difference between molar volumes of the

molecular liquid and [PyrMB][BuSO4] indicates that it is possible that the relatively small organic

molecules fit into the interstices upon mixing Therefore the filling effect of organic molecular liquids

in the interstices of ionic liquids and the ionndashdipole interactions between poly(ethylene glycol)

oligomer and the butylsulfate-based ionic liquids all contribute to the negative values of the molar

excess volumes

32 Volume expansivity and excess volume expansivity

Density results for the PEG200 and [PyrMB][BuSO4] binary system studied in current work were

also used to derive the coefficient of thermal expansion From the relationship of vs T the volume

expansivity (coefficient of thermal expansion) α is defined as

1 1

( ) ( )p p

V

TV T

(6)

where subscript p indicates constant pressure The α values of pure [PyrMB][BuSO4] and

PEG200 and their mixture are summarized in Table 4 The values indicate that the thermal expansion

coefficient of this binary mixture (PEG200 + [PyrMB][BuSO4]) increases with increasing temperature

and increases with increasing mole fraction of the PEG200

The corresponding excess function (excess volume expansivity) was calculated using

E id id

1 1 2 2 (7)

where id

1 is an ideal volume fraction given by the following relation

1 m11

1 m1 2 m2

id xV

xV x V

(8)

Int J Electrochem Sci Vol 8 2013

5075

where Vmi is the molar volume of pure component i

Table 4 Experimental volume expansivity (α) and the excess volume expansivity (αE) for the binary

system PEG200 (1) + [PyrMB][BuSO4] (2)

x1

29315 29815 30315 30815 31315 31815 32315 32815 33315 33815 34315 34815 35315

104 αK-1

0 51245 51380 51516 51651 51787 51922 52058 52193 52329 52464 52600 52735 52871

01452 52053 52189 52325 52462 52600 52739 52878 53018 53159 53300 53443 53586 53730

01942 52438 52576 52715 52854 52994 53135 53276 53418 53561 53705 53850 53995 54141

02912 53299 53443 53586 53731 53877 54023 54170 54318 54466 54616 54766 54917 55069

03897 53973 54120 54268 54417 54567 54717 54869 55021 55174 55328 55483 55638 55795

04893 54667 54818 54971 55124 55278 55433 55589 55745 55903 56061 56221 56381 56542

05890 55372 55527 55683 55840 55998 56157 56317 56477 56639 56801 56965 57129 57294

06903 56358 56517 56677 56838 57000 57163 57327 57492 57657 57824 57992 58160 58330

07922 58175 58344 58515 58687 58860 59033 59208 59384 59561 59739 59918 60098 60279

08958 61313 61502 61691 61882 62074 62268 62462 62658 62855 63053 63252 63453 63655

1 66532 66763 66993 67224 67455 67685 67916 68146 68377 68607 68838 69069 69299

104 αEK-1

0 00000 00000 00000 00000 00000 00000 00000 00000 00000 00000 00000 00000 00000

01452 -00762 -00772 -00782 -00792 -00800 -00808 -00815 -00822 -00827 -00832 -00837 -00840 -00843

01942 -00942 -00954 -00966 -00977 -00987 -00997 -01006 -01014 -01021 -01028 -01033 -01038 -01043

02912 -01259 -01275 -01289 -01302 -01315 -01327 -01339 -01349 -01359 -01368 -01376 -01383 -01389

03897 -01870 -01889 -01908 -01926 -01943 -01959 -01975 -01989 -02003 -02016 -02028 -02040 -02050

04893 -02576 -02600 -02623 -02646 -02668 -02689 -02709 -02728 -02746 -02764 -02780 -02796 -02811

05890 -03382 -03412 -03441 -03470 -03497 -03524 -03550 -03574 -03598 -03621 -03644 -03665 -03685

06903 -04064 -04100 -04136 -04170 -04204 -04236 -04268 -04299 -04329 -04358 -04386 -04413 -04439

07922 -04073 -04110 -04146 -04181 -04214 -04247 -04279 -04310 -04339 -04368 -04396 -04422 -04448

08958 -02968 -02998 -03026 -03053 -03079 -03104 -03128 -03151 -03172 -03192 -03211 -03228 -03245

1 00000 00000 00000 00000 00000 00000 00000 00000 00000 00000 00000 00000 00000

Figure 5 Plot of excess volume expansivity αE of the PEG200 (1) + [PyrMB][BuSO4] (2) binary

system versus mole fraction x1 at various temperatures

Typical concentration dependencies of excess volume expansivity are given in Figure 5 for the

PEG200 + [PyrMB][BuSO4] binary system The values of excess thermal coefficient αE are found to

x1

00 02 04 06 08 10

10

4

E K

-1

-04

-03

-02

-01

00

29315 K

30315 K

31315 K

32315 K

33315 K

34315 K

35315 K

Temp

Int J Electrochem Sci Vol 8 2013

5076

be negative over the whole composition range for the binary system at 29315 ~ 35315 K The curves

are asymmetrical with the minimum located at the IL mole fraction of about 08 In general negative

αE values indicate the presence of strong interaction between the components in the mixtures [67] The

trends observed in αE values for the present mixtures suggest the formation of H-bonding between

unlike molecules which is stronger in PEG200 + [PyrMB][BuSO4] binary system The increasing

negative αE values for PEG200 + [PyrMB][BuSO4] with increase in temperature indicate enhanced

unlike interaction between components of the mixture that is more destruction of order during mixing

contributes negatively to αE

33 Viscosity

Since ILs are more viscous than conventional solvents in most applications they can be used in

mixtures with other less viscous compounds Therefore the viscosity of pure ILs and their mixtures

with PEG oligomer (or conventional solvents) is an important property and their knowledge is

primordial for each industrial processes [6869] The measured dynamic viscosities for the neat

PEG200 neat [PyrMB][BuSO4] and PEG200 + [PyrMB][BuSO4] binary mixture as a function of

temperature over the whole composition range are shown in Figure 6 and their data are listed in Table

5 the viscosities of the mixtures decrease rapidly when PEG oligomer are added to the ionic liquid

especially at lower temperatures The fitting lines in Figure 6 were calculated with the following

fourth-order polynomial equation

= c0 + c1 x1 + c2 x12 + c3 x1

3 + c4 x1

4 (9)

where x1 is the mole fractions of PEG200 and c0 c1 c2 c3 and c4 refer to the fit coefficients

The parameters of correlation are shown in Table 6

Figure 6 Dynamic viscosity for the PEG200 (1) + [PyrMB][BuSO4] (2) binary system as a

function of mole fractions of the PEG200 at different temperatures Lines represent the

polynomial correlation

x1

00 02 04 06 08 10

mP

a s

0

200

400

600

800

1000

1200

1400

29315 K

30315 K

31315 K

32315 K

33315 K

34315 K

35315 K

Int J Electrochem Sci Vol 8 2013

5077

Table 5 Experimental dynamic viscosity (η) and viscosity deviation (Δη) for the binary system

PEG200 (1) + [PyrMB][BuSO4] (2)

x1

29315 29815 30315 30815 31315 31815 32315 32815 33315 33815 34315 34815 35315

ηmPamiddots

0 13209 9343 6745 4961 3712 2821 2176 1700 1345 1077 871 712 587

01452 5907 4362 3294 2539 1992 1589 1286 1055 876 735 623 533 460

01942 4656 3475 2656 2072 1647 1331 1091 907 763 649 557 483 422

02912 3134 2395 1870 1489 1205 991 826 697 594 512 445 390 345

03897 2367 1846 1463 1177 959 792 660 557 474 406 351 306 269

04893 1799 1396 1104 887 723 598 501 424 362 312 272 238 210

05890 1540 1194 941 753 611 502 418 351 298 255 220 191 167

06903 1185 926 736 594 485 402 336 284 242 209 181 158 139

07922 954 742 589 475 389 323 271 231 198 172 150 132 117

08958 811 639 512 415 342 285 240 204 175 151 132 116 102

1 629 505 410 337 280 235 199 170 146 126 110 97 85

ΔηmPamiddots

0 00 00 00 00 00 00 00 00 00 00 00 00 00

01452 -5475 -3698 -2530 -1751 -1221 -857 -602 -423 -295 -204 -137 -89 -54

01942 -6111 -4152 -2859 -1991 -1398 -988 -700 -496 -347 -244 -166 -110 -68

02912 -6411 -4374 -3030 -2126 -1507 -1077 -774 -558 -391 -288 -204 -142 -103

03897 -5940 -4053 -2813 -1982 -1415 -1022 -745 -547 -405 -300 -223 -166 -123

04893 -5254 -3622 -2541 -1811 -1255 -957 -708 -528 -396 -299 -227 -173 -131

05890 -4260 -2944 -2073 -1484 -1034 -796 -594 -448 -341 -262 -203 -158 -124

06903 -3340 -2316 -1636 -1176 -826 -634 -475 -360 -275 -212 -165 -129 -101

07922 -2289 -1599 -1138 -823 -579 -449 -320 -257 -197 -152 -118 -92 -72

08958 -1129 -787 -559 -404 -277 -220 -152 -126 -96 -74 -58 -45 -35

1 00 00 00 00 00 00 00 00 00 00 00 00 00

Table 6 Coefficients of polynomiala for the correlation of the viscosity ( mPa s) in function of

concentration at different temperatures of the binary systems PEG200 (1) + [PyrMB][BuSO4]

(2)

TK c0 mPa s c1 mPa s c2 mPa s c3 mPa s C4 mPa s

29315 13154 -68701 15960 -16688 63543 1075

29815 93069 -46703 10681 -11113 42269 727

30315 67211 -32185 72085 -74396 28222 497

30815 49454 -22431 48886 -49866 18828 343

31315 37016 -15772 33175 -33281 12474 238

31815 28146 -1116 22406 -21947 81322 165

32315 21713 -7923 14947 -1413 51409 114

32815 16975 -56244 97349 -870 30666 077

33315 13435 -39753 60667 -4908 16219 051

33815 10756 -27812 34718 -22519 61382 033

34315 87026 -19098 16304 -39091 -88892 021

34815 71108 -12698 32285 90904 -5763 016

35315 58636 -79728 -60345 18103 -91096 017 a = c0 + c1 x1 + c2 x1

2 + c3 x1

3 + c4 x1

4

The temperature dependence becomes distinctly nonlinear especially at high [PyrMB][BuSO4]

content The Vogel-Tammann-Fulcher (VTF) equation [70-75] suitably correlates the nonlinear

behavior as a function of the temperature not only the viscosities of the neat IL but also the viscosities

of the mixtures for the binary systems through the composition range

Int J Electrochem Sci Vol 8 2013

5078

exp[ ]( )

o

o

B

T T

(10)

where ηo B and To are constants The parameter To is the ideal glass transition temperature which

should be slightly below the experimental glass transition temperature Tg [76] The adjustable

parameters obtained from the VTF correlation were presented in Table 7 The obtained parameters o

and B change smoothly with composition for binary mixtures

Table 7 The VTF equation parameters of viscosity ( 1 exp[ ]( )

o

o

B

T T

) and conductivity

(

exp[ ]( )

o

o

B

T T

) for neat PEG200 (x1 = 1) [PyrMB][BuSO4] (x1 = 0) and binary system

PEG200 (1) + [PyrMB][BuSO4] (2)

x1

ηo (mPa s) To (K) B (K) R2a

o (mS cm-1

) To (K) Brsquo (K) R2a

0 027 1810 9540 0999 792 1788 6854 0999

01452 026 1712 9413 0999 577 1699 6268 0999

01942 043 1788 7975 0999 401 1792 5297 0999

02912 053 1794 7264 0999 521 1662 6031 0999

03897 026 1629 8902 0999 274 1803 4381 0999

04893 023 1666 8455 0999 177 1951 3272 0999

05890 015 1648 8865 0999 216 1883 3672 0999

06903 015 1647 8572 0999 88 2174 2000 0999

07922 017 1717 7702 0999 92 2020 2578 0999

08958 012 1642 8360 0999 43 2110 2088 0999

1 014 1649 7868 0999 556 1928 9815 0999

a Correlation coefficient

The viscosities of the mixtures decrease rapidly when organic oligomers are added to the ionic

liquid this decrease is particularly evident in dilute solutions of organic oligomers in the ionic liquid

The strong coulomb interactions between the [BuSO4]- anion and [PyrMB]

+ cation are weakened upon

mixing with the polar organic oligomers which leads to a higher mobility of the ions and a lower

viscosity of the mixtures [77] This indicates that the viscosity of ILs could be therefore tuned for

several applications by adding an organic solvent or by changing temperature [78]

Due to the wide range of possible molecular interactions between the two components

deviations can occur from ideal behavior These viscosity deviations can be quantified by the viscosity

deviation Δη also known as ldquoexcess viscosityrdquo in other sources

1 1 2 2 (mPa s) x x (11)

Int J Electrochem Sci Vol 8 2013

5079

where x1 and x2 are the mole fractions of PEG200 and [PyrMB][BuSO4] respectively and 1

and 2 are the viscosities (mPa middot s) of the solution the pure solvent and the pure IL respectively

Figure 7 shows the viscosity deviations as a function of the PEG200 mole fraction composition x1 and

temperature for the PEG200 + [PyrMB][BuSO4] binary mixture The values of viscosity deviations

are compared with those obtained from the RedlichndashKister polynomial equation The viscosity

deviation for the mixture show negative deviations from ideality over the whole mole fraction range

Figure 7 also shows that the negative values of viscosity deviations decrease with increasing

temperature this can be attributed to the specific interactions in mixtures typically hydrogen bonds break-

up as the temperature increases [79] The minimum value of Δη is observed at about x1 asymp 03 and the

viscosity deviation depends on molecular interactions as well as on the size and shape of the molecules

[80]

Figure 7 Viscosity deviations Δη versus the mole fraction at various temperatures for the binary

mixture PEG200 (1) + [PyrMB][BuSO4] (2)

34 Conductivity

The experimental data of conductivity of the neat ILs [PyrMB][BuSO4] neat PEG200 and

binary system are plotted against the x1 at various temperatures in Figure 8 together with lines

calculated with the four-order polynomial equation

= d0 + d1 x1 + d2 x12 + d3 x1

3 + d4 x1

4 (12)

where x1 is the mole fractions of PEG200 and d0 d1 d2 d3 and d4 refer to the fit coefficients

The parameters of correlation are shown in Table 8 The conductivities of neat IL [PyrMB][BuSO4]

neat PEG200 and binary system at various temperatures were fitted using the VTF equation

exp[ ]

( )o

o

B

T T

(13)

x1

00 02 04 06 08 10

m

Pa s

-700

-600

-500

-400

-300

-200

-100

0

29315 K

30315 K

31315 K

32315 K

33315 K

34315 K

35315 K

Int J Electrochem Sci Vol 8 2013

5080

where T is the absolute temperature and Brsquo and To are adjustable parameters The best-fit

mS cm-1 Brsquo (K) and To (K) parameters are given in Table 7 Neat [PyrMB][BuSO4] neat

PEG200 and binary system were very well fit by the VTF model over the temperature range studied

Figure 8 Plot of conductivity of the PEG200 (1) + [PyrMB][BuSO4] (2) binary system versus

mole fraction x1 at various temperatures

Table 8 Coefficients of polynomiala for the correlation of the conductivity ( mS cm

-1) in function

of concentration at different temperatures of the binary systems PEG200 (1) +

[PyrMB][BuSO4] (2)

TK d0 mS cm

-1 d1 mS cm

-1 d2 mS cm

-1 d3 mS cm

-1 d4 mS cm

-1

29315 02019 09622 -01679 0734 -17284 00095

29815 02588 11031 -02503 09086 -20181 00109

30315 03255 12119 -01935 08565 -21971 00125

30815 04025 13165 -01329 0767 -23477 00141

31315 04904 13712 01238 03677 -23439 00156

31815 05894 15032 -00006 04737 -25518 00171

32315 06999 15802 00743 0265 -25986 00188

32815 08221 16427 01595 00089 -26032 00208

33315 09562 16373 04858 -06207 -24165 00233

a = d0 + d1 x1 + d2 x1

2 + d3 x1

3 + d4 x1

4

As shown in Figure 8 it can be seen that the conductivity of the binary mixture increases with

increasing amount of PEG200 goes through a maximum and then goes down to the specific

conductivity of the neat PEG200 The conductivity is related to the ion mobility and the number of

charge carriers [81] At a fixed concentration the ions move faster at higher temperature due to the

relatively lower viscosity of the mixture On the other hand the composition influences both the ion

mobility and the number of charge carriers at a fixed temperature At the beginning the number of

charge and the ion mobility increase with increasing PEG oligomer composition the maximum of

conductivity is located at x1 = 059 and corresponds to a value of 171 mS cmminus 1

at 33315 K It can also

be observed that the conductivity increases as the temperature increases The higher temperature may

x1

00 02 04 06 08 10

mS

cm

-1

00

05

10

15

20

29315 K

29815 K

30315 K

30815 K

31315 K

31815 K

32315 K

32815 K

33315 K

Int J Electrochem Sci Vol 8 2013

5081

weaken the influence of aggregation to the conductivity which suggests that a higher temperature is

better for the ILs to act as electrolytes

Table 9 RedlickndashKister fitting coefficients Ak and the standard deviation of the VE and ∆for the

binary mixture of PEG200 (1) + [PyrMB][BuSO4] (2) system

TK A0 A1 A2 A3 A4

VEcm

3 mol

-1

29315 -5979 -4906 6585 5754 -1717 002687

29815 -6200 -4760 6464 5767 -2022 002693

30315 -6408 -4612 6345 5774 -2276 002698

30815 -6602 -4461 6229 5774 -2476 002701

31315 -6782 -4310 6116 5767 -2623 002701

31815 -6948 -4155 6006 5753 -2716 002699

32315 -7100 -3999 5899 5732 -2754 002692

32815 -7239 -3840 5795 5704 -2738 002683

33315 -7363 -3679 5694 5669 -2666 002670

33815 -7472 -3515 5596 5626 -2538 002654

34315 -7568 -3350 5501 5576 -2353 002634

34815 -7648 -3182 5409 5518 -2111 002611

35315 -7714 -3011 5320 5452 -1812 002586

∆mPa s

29315 -20414 -17226 -15592 -95544 -75863 399496

29815 -14035 -11558 -10713 -62192 19493 340180

30315 -98261 -78407 -73734 -40709 58145 286725

30815 -69922 -53591 -50601 -2676 67556 235258

31315 -48876 -39537 -41051 -14118 16739 079245

31815 -36917 -25169 -22939 -11646 51047 146189

32315 -27415 -1721 -12581 -92603 21498 104339

32815 -20441 -11703 -77538 -38334 -81478 090708

33315 -15382 -67274 -31134 -47585 -18255 059539

33815 -11664 -44928 -15533 -22312 -05591 037855

34315 -89038 -24163 68654 -15007 -10347 024263

34815 -68279 -91813 23131 -10367 -18636 017759

35315 -52525 -24051 26474 15498 -85341 018640

35 Redlich-Kister Equation for Binary System

The binary excess property ( E

mV ) and deviations (Δ) at several temperatures were fitted to a

Redlich-Kister-type equation [82]

1 1 1

0

(or ) (1 ) (1 2 )j

E i

i

i

Y Y x x A x

(14)

Int J Electrochem Sci Vol 8 2013

5082

where ΔY (YE) represents E

mV (cm3 mol

minus1) and Δ

(mPa s)x1 denotes the mole fraction of

PEG200 Ai represents the polynomial coefficients and j is the degree of the polynomial expansion

The correlated results for excess molar volumes ( E

mV ) viscosity deviations (Δ) including the values

of the fitting parameters Ai together with the standard deviation σ are given in Table 9 where the

tabulated standard deviation σ [83] is defined as

2

exp cal 1 2( )

[ ]Y Y

m n

(15)

where m is the number of experimental data points and n is the number of estimated

parameters The subscripts ldquoexprdquo and ldquocalrdquo denote the values of the experimental and calculated

property respectively As shown in Table 9 the experimentally derived E

mV and Δη values were

correlated satisfactorily by the Redlich-Kister equation

4 CONCLUSIONS

This paper is a systematic characterizations of thermophysical properties for IL binary system

Density viscosity and conductivity for (PEG200 + [PyrMB][BuSO4]) binary system are presented as a

function of temperature at atmospheric pressure it was demonstrated that viscosity and conductivity

were more sensitive to the changes in PEG content or temperature than density and the viscosity and

conductivity of pure IL and (PEG200 + [PyrMB][BuSO4]) binary system at different temperature are

fitted using the VogelndashTammannndashFulcher (VTF) equation with good accuracy The excess molar

volumes excess volume expansivity and viscosity deviations show negative deviations from the ideal

solution the results are interpreted in terms of molecular interactions in the (PEG200 +

[PyrMB][BuSO4]) binary mixture The conductivity increases to a maximum value when the

concentration of PEG200 is increased and decreases after the maximum the data obtained will be

helpful for the application of the ionic liquids as electrolytes and also useful for the ionic liquids

database

ACKNOWLEDGEMENTS

The authors would like to thank the National Science Council of the Republic of China for financially

supporting this project

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1 P Wasserscheid T Welton Ionic Liquids in Synthesis Second ed Weinheim VCH 2003

2 TY Wu IW Sun ST Gung MW Lin BK Chen HP Wang SG Su J Taiwan Inst Chem

Eng 42 (2011) 513

Int J Electrochem Sci Vol 8 2013

5083

3 TY Wu SG Su KF Lin YC Lin HP Wang MW Lin ST Gung IW Sun Electrochim

Acta 56 (2011) 7278

4 B Baek S Lee C Jung Int J Electrochem Sci 6 (2011) 6220

5 PN Tshibangu SN Ndwandwe ED Dikio Int J Electrochem Sci 6 (2011) 2201

6 TY Wu SG Su HP Wang IW Sun Electrochem Commun 13 (2011) 237

7 TY Wu SG Su HP Wang YC Lin ST Gung MW Lin IW Sun Electrochim Acta 56

(2011) 3209

8 IW Sun YC Lin BK Chen CW Kuo CC Chen SG Su PR Chen TY Wu Int J

Electrochem Sci 7 (2012) 7206

9 TY Wu SG Su ST Gung MW Lin YC Lin CA Lai IW Sun Electrochim Acta 55

(2010) 4475

10 AN Soriano AM Agapito LJLI Lagumbay AR Caparanga MH Li J Taiwan Inst Chem

Eng 42 (2011) 258

11 TY Wu IW Sun ST Gung BK Chen HP Wang SG Su J Taiwan Inst Chem Eng 42

(2011) 874

12 S Ibrahim MR Johan Int J Electrochem Sci 6 (2011) 5565

13 TY Wu SG Su YC Lin HP Wang MW Lin ST Gung IW Sun Electrochim Acta 56

(2010) 853

14 H Wang LX Wu YC Lan JQ Zhao JX Lu Int J Electrochem Sci 6 (2011) 4218

15 FF Liu SQ Liu QJ Feng SX Zhuang JB Zhang P Bu Int J Electrochem Sci 7 (2012)

4381

16 HA Barham SA Brahim Y Rozita KA Mohamed Int J Electrochem Sci 6 (2011) 181

17 SK Shukla LC Murulana EE Ebenso Int J Electrochem Sci 6 (2011) 4286

18 NV Likhanova O Olivares-Xometl D Guzman-Lucero MA Dominguez-Aguilar N Nava

M Corrales-Luna MC Mendoza Int J Electrochem Sci 6 (2011) 4514

19 A Zarrouk M Messali H Zarrok R Salghi AA Ali B Hammouti SS Al-Deyab F Bentiss

Int J Electrochem Sci 7 (2012) 6998

20 BS Ali BH Ali R Yusoff MK Aroua Int J Electrochem Sci 7 (2012) 3835

21 MH Lin YJ Liu ZH Yang YB Huang ZH Sun Y He CL Ni Int J Electrochem Sci 7

(2012) 965

22 CH Su MH Chung HJ Hsieh YK Chang JC Ding HM Wu J Taiwan Inst Chem Eng

43 (2012) 573

23 H Shekaari A Kazempour J Taiwan Inst Chem Eng 43 (2012) 650

24 ZJ Wei Y Li D Thushara YX Liu QL Ren J Taiwan Inst Chem Eng 43 (2012) 363

25 GQ Zhang HW Yang JF Gao HK Zhang CB Zheng YL Cao YH Wang KQ Ding

Int J Electrochem Sci 7 (2012) 7547

26 P Norouzi MR Ganjali F Faridbod SJ Shahtaheri HA Zamani Int J Electrochem Sci 7

(2012) 2633

27 F Faridbod MR Ganjali M Hosseini P Norouzi Int J Electrochem Sci 7 (2012) 1927

28 MR Ganjali Z Rafiei-Sarmazdeh T Poursaberi SJ Shahtaheri P Norouzi Int J

Electrochem Sci 7 (2012) 1908

29 A Babaei DJ Garrett AJ Downard Int J Electrochem Sci 7 (2012) 3141

30 MR Ganjali T Alizade P Norouzi Int J Electrochem Sci 7 (2012) 4800

31 MR Ganjali T Alizade B Larijani F Faridbod P Norouzi Int J Electrochem Sci 7 (2012)

4756

32 P Norouzi B Larijani MR Ganjali Int J Electrochem Sci 7 (2012) 7313

33 TY Wu MH Tsao SG Su HP Wang YC Lin FL Chen CW Chang IW Sun J Braz

Chem Soc 22 (2011) 780

34 MH Tsao TY Wu HP Wang IW Sun SG Su YC Lin CW Chang Mater Lett 65

(2011) 583

Int J Electrochem Sci Vol 8 2013

5084

35 SY Ku SY Lu Int J Electrochem Sci 6 (2011) 5219

36 TY Wu MH Tsao FL Chen SG Su CW Chang HP Wang YC Lin IW Sun J Iran

Chem Soc 7 (2010) 707

37 IW Sun HP Wang H Teng SG Su YC Lin CW Kuo PR Chen TY Wu Int J

Electrochem Sci 7 (2012) 9748

38 TY Wu MH Tsao FL Chen SG Su CW Chang HP Wang YC Lin WC Ou-Yang

IW Sun Int J Mol Sci 11 (2010) 329

39 YX An PJ Zuo XQ Cheng LX Liao GP Yin Int J Electrochem Sci 6 (2011) 2398

40 LC Xuan YX An W Fang LX Liao YL Ma ZY Ren GP Yin Int J Electrochem Sci

6 (2011) 6590

41 HM Wang SQ Liu K Huang XG Yin YN Liu SJ Peng Int J Electrochem Sci 7

(2012) 1688

42 HM Wang SQ Liu NF Wang YN Liu Int J Electrochem Sci 7 (2012) 7579

43 H Ganjali MR Ganjali T Alizadeh F Faridbod P Norouzi Int J Electrochem Sci 6 (2011)

6085

44 MR Ganjali MH Eshraghi S Ghadimi SM Moosavi M Hosseini H Haji-Hashemi P

Norouzi Int J Electrochem Sci 6 (2011) 739

45 MR Ganjali T Poursaberi M Khoobi A Shafiee M Adibi M Pirali-Hamedani P Norouzi

Int J Electrochem Sci 6 (2011) 717

46 P Norouzi M Hosseini MR Ganjali M Rezapour M Adibi Int J Electrochem Sci 6 (2011)

2012

47 MR Ganjali MR Moghaddam M Hosseini P Norouzi Int J Electrochem Sci 6 (2011)

1981

48 MR Ganjali M Hosseini M Pirali-Hamedani HA Zamani Int J Electrochem Sci 6 (2011)

2808

49 MR Ganjali M Rezapour SK Torkestani H Rashedi P Norouzi Int J Electrochem Sci 6

(2011) 2323

50 P Norouzi M Pirali-Hamedani SO Ranaei-Siadat MR Ganjali Int J Electrochem Sci 6

(2011) 3704

51 F Faridbod HA Zamani M Hosseini M Pirali-Hamedani MR Ganjali P Norouzi Int J

Electrochem Sci 6 (2011) 3694

52 MR Ganjali SO Ranaei-Siadat H Rashedi M Rezapour P Norouzi Int J Electrochem Sci

6 (2011) 3684

53 TH Tsai KC Lin SM Chen Int J Electrochem Sci 6 (2011) 2672

54 MR Ganjali T Alizadeh F Azimi B Larjani F Faridbod P Norouzi Int J Electrochem

Sci 6 (2011) 5200

55 R Mirshafian MR Ganjali P Norouzi Int J Electrochem Sci 7 (2012) 1656

56 J Gao JG Liu WM Liu B Li YC Xin Y Yin ZG Zou Int J Electrochem Sci 6 (2011)

6115

57 TY Wu BK Chen L Hao KF Lin IW Sun J Taiwan Inst Chem Eng 42 (2011) 914

58 TY Wu BK Chen L Hao CW Kuo IW Sun J Taiwan Inst Chem Eng 43 (2012) 313

59 SW Peng AN Soriano RB Leron MH Li J Taiwan Inst Chem Eng 42 (2011) 233

60 TY Wu IW Sun MW Lin BK Chen CW Kuo HP Wang YY Chen SG Su J Taiwan

Inst Chem Eng 43 (2012) 58

61 TY Wu BK Chen CW Kuo L Hao YC Peng IW Sun J Taiwan Inst Chem Eng 43

(2012) 860

62 A Arce H Rodriguez A Soto Green Chem 9 (2007) 247

63 TY Wu HC Wang SG Su ST Gung MW Lin CB Lin J Taiwan Inst Chem Eng 41 (2010)

315 64 X Li M Hou Z Zhang B Han G Yang X Wang L Zou Green Chem 10 (2008) 879

Int J Electrochem Sci Vol 8 2013

5085

65 J Chen SK Spear JG Huddleston RD Rogers Green Chem 7 (2005) 64

66 U Domanska M Laskowska J Solution Chem 38 (2009) 779

67 K Tamura M Nakamura S Murakami J Solution Chem 26 (1997) 1199

68 Z Yu H Gao H Wang L Chen J Chem Eng Data 56 (2011) 2877

69 KN Marsh JA Boxall R Lichtenthaler Fluid Phase Equilib 219 (2004) 93

70 TY Wu SG Su ST Gung MW Lin YC Lin WC Ou-Yang IW Sun CA Lai J Iran

Chem Soc 8 (2011) 149

71 TY Wu L Hao CW Kuo YC Lin SG Su PL Kuo IW Sun Int J Electrochem Sci 7

(2012) 2047

72 TY Wu L Hao PR Chen JW Liao Int J Electrochem Sci 8 (2013) 2606

73 CW Kuo CW Huang BK Chen WB Li PR Chen TH Ho CG Tseng TY Wu Int J

Electrochem Sci 8 (2013) 3834

74 CW Kuo WB Li PR Chen JW Liao CG Tseng TY Wu Int J Electrochem Sci 8

(2013) 5007

75 TY Wu BK Chen L Hao YC Lin HP Wang CW Kuo IW Sun Int J Mol Sci 12

(2011) 8750

76 H Rodriguez JF Brennecke J Chem Eng Data 51 (2006) 2145

77 Y Tian X Wang J Wang J Chem Eng Data 53 (2008) 2056

78 TY Wu HC Wang SG Su ST Gung MW Lin CB Lin J Chin Chem Soc 57 (2010)

44

79 TY Wu BK Chen L Hao YC Peng IW Sun Int J Mol Sci 12 (2011) 2598

80 H Eyring MS John Significant Liquid Structure Wiley New York 1969

81 H Every AG Bishop M Forsyth DR MacFarlane Electrochim Acta 45 (2000) 1279 82 O Redlich AT Kister Ind Eng Chem 40 (1948) 345

83 A Paul P Kumar A Samanta J Phys Chem B 109 (2005) 9148

copy 2013 by ESG (wwwelectrochemsciorg)

Int J Electrochem Sci Vol 8 2013

5072

where n is the number of experimental points and Zexp and Zcal are the experimental and

calculated values respectively

Table 2 Coefficients of polynomiala for the correlation of the density (ρgmiddotcm

-3) in function of

concentration at different temperatures of the binary systems PEG200 (1) + [PyrMB][BuSO4]

(2)

TK a0 g cm

-3 a1 g cm

-3 a2 g cm

-3 a3 g cm

-3

29315 11248 00455 -00638 0024 0000840

29815 11219 00447 -00617 00217 0000800

30315 1119 00439 -00596 00195 0000764

30815 11161 00431 -00575 00173 0000732

31315 11132 00422 -00554 00152 0000704

31815 11103 00413 -00533 00132 0000680

32315 11075 00403 -00512 00112 0000660

32815 11046 00393 -00492 00093 0000640

33315 11018 00382 -00471 00074 0000625

33815 10989 00372 -0045 00055 0000613

34315 10961 0036 -0043 00037 0000606

34815 10933 00349 -00409 0002 0000596

35315 10905 00337 -00389 00003 0000592

a ρ = a0 + a1 x1 + a2 x1

2 + a3 x1

3

As can be seen from the Table 1 the value of the density decreases with increasing temperature

eventhough the variation is very small If the variation of the density with the temperature is

considered as linear then the change in the calculated thermal expansion coefficient values becomes

nearly constant In order to have an improved accuracy a second order polynomial of the eqn (3) was

used to correlate the variation of the density with the temperature for PEG200 (1) + [PyrMB][BuSO4]

(2) binary system

ρ = b0 + b1 T + b2 T2 (3)

where T is the temperature and b0 b1 and b2 are the correlation coefficients The correlation

coefficients are listed in Table 3 together with the standard deviations (σ) calculated using Eq (2)

Excess thermodynamic properties are of great importance for understanding the nature of

molecular interaction in binary mixtures The excess molar volume E

mV which is the difference

between the real and ideal mixing behaviors is defined by

m m 1 1 2 2 E o o

V V xV x V (4)

where Vm represents the volume of a mixture containing one mole of (PEG200 +

[PyrMB][BuSO4]) x1 and x2 are the mole fractions of components 1 (PEG200) and 2

([PyrMB][BuSO4]) respectively and V10 and V2

0 are the molar volumes of the pure components The

Int J Electrochem Sci Vol 8 2013

5073

excess molar volumes of mixtures over the entire composition range were calculated from our

measurements of density according to the following equation

Table 3 The adjustable parameters of density (ρ = b0 + b1 T + b2 T2) at various temperature for neat

PEG200 (x1 = 1) [PyrMB][BuSO4] (x1 = 0) and binary system PEG200 (1) + [PyrMB][BuSO4]

(2)

x1 b0 b1 b2

0 1326 -000077105 00000003 000003

01452 1301 -0000588 0 000023

01942 1304 -0000593 0 000032

02912 131 -0000604 0 000047

03897 1315 -0000613 0 000009

04893 1318 -0000621 0 000034

05890 1319 -0000629 0 000045

06903 132 -0000639 0 000046

07922 1325 -0000658 0 000036

08958 1335 -0000694 0 000030

1 1405 -000108 000000051 000112

Figure 4 Excess molar volumes for the binary system PEG200 (1) + [PyrMB][BuSO4] (2) and

fitted curves using the Redlich-Kister parameters

1 1 2 2 1 1 2 2m

1 2

E

Vx M x M x M x M

(5)

where ρ1 ρ2 and ρ are the densities of neat PEG200 [PyrMB][BuSO4] and their mixture

respectively M1 and M2 are the molar masses of PEG200 and [PyrMB][BuSO4] respectively The E

mV

values of mixtures are summarized in Table 1 The excess molar volumes of mixtures versus the mole

x1

00 02 04 06 08 10

Vm

E

cm

3 m

ol-1

-20

-15

-10

-05

00

30315 K

31315 K

32315 K

33315 K

Int J Electrochem Sci Vol 8 2013

5074

fraction of PEG200 from 29315 to 35315 K are plotted in Figure 4 The excess molar volume of the

binary system is mainly concerned with the weak chemical interactions the physical and structural

characteristics of the system components If the chemical or nonchemical interaction of the same

components is the dominant way of the interaction the excess volume of the mixture should be

positive If the molecules of the components have a more effective packing in the mixture than that in

the pure component that is the attracting interaction between the molecules of two components is the

dominant way the excess molar volume of the binary system should be negative [66] As shown in

Figure 4 the excess molar volumes are asymmetric and negative for all of the systems studied over the

entire composition range the minimum of E

mV is reached at a mole fraction of PEG200 near x1 = 04

and the absolute values of the excess volume increase with increasing temperature The molar volume

for [PyrMB][BuSO4] is 26243 cm3 mol

-1 at T = 29315 K which is greater than the molar volumes of

PEG200 (17681 cm3 mol

-1) at T = 29315 K The large difference between molar volumes of the

molecular liquid and [PyrMB][BuSO4] indicates that it is possible that the relatively small organic

molecules fit into the interstices upon mixing Therefore the filling effect of organic molecular liquids

in the interstices of ionic liquids and the ionndashdipole interactions between poly(ethylene glycol)

oligomer and the butylsulfate-based ionic liquids all contribute to the negative values of the molar

excess volumes

32 Volume expansivity and excess volume expansivity

Density results for the PEG200 and [PyrMB][BuSO4] binary system studied in current work were

also used to derive the coefficient of thermal expansion From the relationship of vs T the volume

expansivity (coefficient of thermal expansion) α is defined as

1 1

( ) ( )p p

V

TV T

(6)

where subscript p indicates constant pressure The α values of pure [PyrMB][BuSO4] and

PEG200 and their mixture are summarized in Table 4 The values indicate that the thermal expansion

coefficient of this binary mixture (PEG200 + [PyrMB][BuSO4]) increases with increasing temperature

and increases with increasing mole fraction of the PEG200

The corresponding excess function (excess volume expansivity) was calculated using

E id id

1 1 2 2 (7)

where id

1 is an ideal volume fraction given by the following relation

1 m11

1 m1 2 m2

id xV

xV x V

(8)

Int J Electrochem Sci Vol 8 2013

5075

where Vmi is the molar volume of pure component i

Table 4 Experimental volume expansivity (α) and the excess volume expansivity (αE) for the binary

system PEG200 (1) + [PyrMB][BuSO4] (2)

x1

29315 29815 30315 30815 31315 31815 32315 32815 33315 33815 34315 34815 35315

104 αK-1

0 51245 51380 51516 51651 51787 51922 52058 52193 52329 52464 52600 52735 52871

01452 52053 52189 52325 52462 52600 52739 52878 53018 53159 53300 53443 53586 53730

01942 52438 52576 52715 52854 52994 53135 53276 53418 53561 53705 53850 53995 54141

02912 53299 53443 53586 53731 53877 54023 54170 54318 54466 54616 54766 54917 55069

03897 53973 54120 54268 54417 54567 54717 54869 55021 55174 55328 55483 55638 55795

04893 54667 54818 54971 55124 55278 55433 55589 55745 55903 56061 56221 56381 56542

05890 55372 55527 55683 55840 55998 56157 56317 56477 56639 56801 56965 57129 57294

06903 56358 56517 56677 56838 57000 57163 57327 57492 57657 57824 57992 58160 58330

07922 58175 58344 58515 58687 58860 59033 59208 59384 59561 59739 59918 60098 60279

08958 61313 61502 61691 61882 62074 62268 62462 62658 62855 63053 63252 63453 63655

1 66532 66763 66993 67224 67455 67685 67916 68146 68377 68607 68838 69069 69299

104 αEK-1

0 00000 00000 00000 00000 00000 00000 00000 00000 00000 00000 00000 00000 00000

01452 -00762 -00772 -00782 -00792 -00800 -00808 -00815 -00822 -00827 -00832 -00837 -00840 -00843

01942 -00942 -00954 -00966 -00977 -00987 -00997 -01006 -01014 -01021 -01028 -01033 -01038 -01043

02912 -01259 -01275 -01289 -01302 -01315 -01327 -01339 -01349 -01359 -01368 -01376 -01383 -01389

03897 -01870 -01889 -01908 -01926 -01943 -01959 -01975 -01989 -02003 -02016 -02028 -02040 -02050

04893 -02576 -02600 -02623 -02646 -02668 -02689 -02709 -02728 -02746 -02764 -02780 -02796 -02811

05890 -03382 -03412 -03441 -03470 -03497 -03524 -03550 -03574 -03598 -03621 -03644 -03665 -03685

06903 -04064 -04100 -04136 -04170 -04204 -04236 -04268 -04299 -04329 -04358 -04386 -04413 -04439

07922 -04073 -04110 -04146 -04181 -04214 -04247 -04279 -04310 -04339 -04368 -04396 -04422 -04448

08958 -02968 -02998 -03026 -03053 -03079 -03104 -03128 -03151 -03172 -03192 -03211 -03228 -03245

1 00000 00000 00000 00000 00000 00000 00000 00000 00000 00000 00000 00000 00000

Figure 5 Plot of excess volume expansivity αE of the PEG200 (1) + [PyrMB][BuSO4] (2) binary

system versus mole fraction x1 at various temperatures

Typical concentration dependencies of excess volume expansivity are given in Figure 5 for the

PEG200 + [PyrMB][BuSO4] binary system The values of excess thermal coefficient αE are found to

x1

00 02 04 06 08 10

10

4

E K

-1

-04

-03

-02

-01

00

29315 K

30315 K

31315 K

32315 K

33315 K

34315 K

35315 K

Temp

Int J Electrochem Sci Vol 8 2013

5076

be negative over the whole composition range for the binary system at 29315 ~ 35315 K The curves

are asymmetrical with the minimum located at the IL mole fraction of about 08 In general negative

αE values indicate the presence of strong interaction between the components in the mixtures [67] The

trends observed in αE values for the present mixtures suggest the formation of H-bonding between

unlike molecules which is stronger in PEG200 + [PyrMB][BuSO4] binary system The increasing

negative αE values for PEG200 + [PyrMB][BuSO4] with increase in temperature indicate enhanced

unlike interaction between components of the mixture that is more destruction of order during mixing

contributes negatively to αE

33 Viscosity

Since ILs are more viscous than conventional solvents in most applications they can be used in

mixtures with other less viscous compounds Therefore the viscosity of pure ILs and their mixtures

with PEG oligomer (or conventional solvents) is an important property and their knowledge is

primordial for each industrial processes [6869] The measured dynamic viscosities for the neat

PEG200 neat [PyrMB][BuSO4] and PEG200 + [PyrMB][BuSO4] binary mixture as a function of

temperature over the whole composition range are shown in Figure 6 and their data are listed in Table

5 the viscosities of the mixtures decrease rapidly when PEG oligomer are added to the ionic liquid

especially at lower temperatures The fitting lines in Figure 6 were calculated with the following

fourth-order polynomial equation

= c0 + c1 x1 + c2 x12 + c3 x1

3 + c4 x1

4 (9)

where x1 is the mole fractions of PEG200 and c0 c1 c2 c3 and c4 refer to the fit coefficients

The parameters of correlation are shown in Table 6

Figure 6 Dynamic viscosity for the PEG200 (1) + [PyrMB][BuSO4] (2) binary system as a

function of mole fractions of the PEG200 at different temperatures Lines represent the

polynomial correlation

x1

00 02 04 06 08 10

mP

a s

0

200

400

600

800

1000

1200

1400

29315 K

30315 K

31315 K

32315 K

33315 K

34315 K

35315 K

Int J Electrochem Sci Vol 8 2013

5077

Table 5 Experimental dynamic viscosity (η) and viscosity deviation (Δη) for the binary system

PEG200 (1) + [PyrMB][BuSO4] (2)

x1

29315 29815 30315 30815 31315 31815 32315 32815 33315 33815 34315 34815 35315

ηmPamiddots

0 13209 9343 6745 4961 3712 2821 2176 1700 1345 1077 871 712 587

01452 5907 4362 3294 2539 1992 1589 1286 1055 876 735 623 533 460

01942 4656 3475 2656 2072 1647 1331 1091 907 763 649 557 483 422

02912 3134 2395 1870 1489 1205 991 826 697 594 512 445 390 345

03897 2367 1846 1463 1177 959 792 660 557 474 406 351 306 269

04893 1799 1396 1104 887 723 598 501 424 362 312 272 238 210

05890 1540 1194 941 753 611 502 418 351 298 255 220 191 167

06903 1185 926 736 594 485 402 336 284 242 209 181 158 139

07922 954 742 589 475 389 323 271 231 198 172 150 132 117

08958 811 639 512 415 342 285 240 204 175 151 132 116 102

1 629 505 410 337 280 235 199 170 146 126 110 97 85

ΔηmPamiddots

0 00 00 00 00 00 00 00 00 00 00 00 00 00

01452 -5475 -3698 -2530 -1751 -1221 -857 -602 -423 -295 -204 -137 -89 -54

01942 -6111 -4152 -2859 -1991 -1398 -988 -700 -496 -347 -244 -166 -110 -68

02912 -6411 -4374 -3030 -2126 -1507 -1077 -774 -558 -391 -288 -204 -142 -103

03897 -5940 -4053 -2813 -1982 -1415 -1022 -745 -547 -405 -300 -223 -166 -123

04893 -5254 -3622 -2541 -1811 -1255 -957 -708 -528 -396 -299 -227 -173 -131

05890 -4260 -2944 -2073 -1484 -1034 -796 -594 -448 -341 -262 -203 -158 -124

06903 -3340 -2316 -1636 -1176 -826 -634 -475 -360 -275 -212 -165 -129 -101

07922 -2289 -1599 -1138 -823 -579 -449 -320 -257 -197 -152 -118 -92 -72

08958 -1129 -787 -559 -404 -277 -220 -152 -126 -96 -74 -58 -45 -35

1 00 00 00 00 00 00 00 00 00 00 00 00 00

Table 6 Coefficients of polynomiala for the correlation of the viscosity ( mPa s) in function of

concentration at different temperatures of the binary systems PEG200 (1) + [PyrMB][BuSO4]

(2)

TK c0 mPa s c1 mPa s c2 mPa s c3 mPa s C4 mPa s

29315 13154 -68701 15960 -16688 63543 1075

29815 93069 -46703 10681 -11113 42269 727

30315 67211 -32185 72085 -74396 28222 497

30815 49454 -22431 48886 -49866 18828 343

31315 37016 -15772 33175 -33281 12474 238

31815 28146 -1116 22406 -21947 81322 165

32315 21713 -7923 14947 -1413 51409 114

32815 16975 -56244 97349 -870 30666 077

33315 13435 -39753 60667 -4908 16219 051

33815 10756 -27812 34718 -22519 61382 033

34315 87026 -19098 16304 -39091 -88892 021

34815 71108 -12698 32285 90904 -5763 016

35315 58636 -79728 -60345 18103 -91096 017 a = c0 + c1 x1 + c2 x1

2 + c3 x1

3 + c4 x1

4

The temperature dependence becomes distinctly nonlinear especially at high [PyrMB][BuSO4]

content The Vogel-Tammann-Fulcher (VTF) equation [70-75] suitably correlates the nonlinear

behavior as a function of the temperature not only the viscosities of the neat IL but also the viscosities

of the mixtures for the binary systems through the composition range

Int J Electrochem Sci Vol 8 2013

5078

exp[ ]( )

o

o

B

T T

(10)

where ηo B and To are constants The parameter To is the ideal glass transition temperature which

should be slightly below the experimental glass transition temperature Tg [76] The adjustable

parameters obtained from the VTF correlation were presented in Table 7 The obtained parameters o

and B change smoothly with composition for binary mixtures

Table 7 The VTF equation parameters of viscosity ( 1 exp[ ]( )

o

o

B

T T

) and conductivity

(

exp[ ]( )

o

o

B

T T

) for neat PEG200 (x1 = 1) [PyrMB][BuSO4] (x1 = 0) and binary system

PEG200 (1) + [PyrMB][BuSO4] (2)

x1

ηo (mPa s) To (K) B (K) R2a

o (mS cm-1

) To (K) Brsquo (K) R2a

0 027 1810 9540 0999 792 1788 6854 0999

01452 026 1712 9413 0999 577 1699 6268 0999

01942 043 1788 7975 0999 401 1792 5297 0999

02912 053 1794 7264 0999 521 1662 6031 0999

03897 026 1629 8902 0999 274 1803 4381 0999

04893 023 1666 8455 0999 177 1951 3272 0999

05890 015 1648 8865 0999 216 1883 3672 0999

06903 015 1647 8572 0999 88 2174 2000 0999

07922 017 1717 7702 0999 92 2020 2578 0999

08958 012 1642 8360 0999 43 2110 2088 0999

1 014 1649 7868 0999 556 1928 9815 0999

a Correlation coefficient

The viscosities of the mixtures decrease rapidly when organic oligomers are added to the ionic

liquid this decrease is particularly evident in dilute solutions of organic oligomers in the ionic liquid

The strong coulomb interactions between the [BuSO4]- anion and [PyrMB]

+ cation are weakened upon

mixing with the polar organic oligomers which leads to a higher mobility of the ions and a lower

viscosity of the mixtures [77] This indicates that the viscosity of ILs could be therefore tuned for

several applications by adding an organic solvent or by changing temperature [78]

Due to the wide range of possible molecular interactions between the two components

deviations can occur from ideal behavior These viscosity deviations can be quantified by the viscosity

deviation Δη also known as ldquoexcess viscosityrdquo in other sources

1 1 2 2 (mPa s) x x (11)

Int J Electrochem Sci Vol 8 2013

5079

where x1 and x2 are the mole fractions of PEG200 and [PyrMB][BuSO4] respectively and 1

and 2 are the viscosities (mPa middot s) of the solution the pure solvent and the pure IL respectively

Figure 7 shows the viscosity deviations as a function of the PEG200 mole fraction composition x1 and

temperature for the PEG200 + [PyrMB][BuSO4] binary mixture The values of viscosity deviations

are compared with those obtained from the RedlichndashKister polynomial equation The viscosity

deviation for the mixture show negative deviations from ideality over the whole mole fraction range

Figure 7 also shows that the negative values of viscosity deviations decrease with increasing

temperature this can be attributed to the specific interactions in mixtures typically hydrogen bonds break-

up as the temperature increases [79] The minimum value of Δη is observed at about x1 asymp 03 and the

viscosity deviation depends on molecular interactions as well as on the size and shape of the molecules

[80]

Figure 7 Viscosity deviations Δη versus the mole fraction at various temperatures for the binary

mixture PEG200 (1) + [PyrMB][BuSO4] (2)

34 Conductivity

The experimental data of conductivity of the neat ILs [PyrMB][BuSO4] neat PEG200 and

binary system are plotted against the x1 at various temperatures in Figure 8 together with lines

calculated with the four-order polynomial equation

= d0 + d1 x1 + d2 x12 + d3 x1

3 + d4 x1

4 (12)

where x1 is the mole fractions of PEG200 and d0 d1 d2 d3 and d4 refer to the fit coefficients

The parameters of correlation are shown in Table 8 The conductivities of neat IL [PyrMB][BuSO4]

neat PEG200 and binary system at various temperatures were fitted using the VTF equation

exp[ ]

( )o

o

B

T T

(13)

x1

00 02 04 06 08 10

m

Pa s

-700

-600

-500

-400

-300

-200

-100

0

29315 K

30315 K

31315 K

32315 K

33315 K

34315 K

35315 K

Int J Electrochem Sci Vol 8 2013

5080

where T is the absolute temperature and Brsquo and To are adjustable parameters The best-fit

mS cm-1 Brsquo (K) and To (K) parameters are given in Table 7 Neat [PyrMB][BuSO4] neat

PEG200 and binary system were very well fit by the VTF model over the temperature range studied

Figure 8 Plot of conductivity of the PEG200 (1) + [PyrMB][BuSO4] (2) binary system versus

mole fraction x1 at various temperatures

Table 8 Coefficients of polynomiala for the correlation of the conductivity ( mS cm

-1) in function

of concentration at different temperatures of the binary systems PEG200 (1) +

[PyrMB][BuSO4] (2)

TK d0 mS cm

-1 d1 mS cm

-1 d2 mS cm

-1 d3 mS cm

-1 d4 mS cm

-1

29315 02019 09622 -01679 0734 -17284 00095

29815 02588 11031 -02503 09086 -20181 00109

30315 03255 12119 -01935 08565 -21971 00125

30815 04025 13165 -01329 0767 -23477 00141

31315 04904 13712 01238 03677 -23439 00156

31815 05894 15032 -00006 04737 -25518 00171

32315 06999 15802 00743 0265 -25986 00188

32815 08221 16427 01595 00089 -26032 00208

33315 09562 16373 04858 -06207 -24165 00233

a = d0 + d1 x1 + d2 x1

2 + d3 x1

3 + d4 x1

4

As shown in Figure 8 it can be seen that the conductivity of the binary mixture increases with

increasing amount of PEG200 goes through a maximum and then goes down to the specific

conductivity of the neat PEG200 The conductivity is related to the ion mobility and the number of

charge carriers [81] At a fixed concentration the ions move faster at higher temperature due to the

relatively lower viscosity of the mixture On the other hand the composition influences both the ion

mobility and the number of charge carriers at a fixed temperature At the beginning the number of

charge and the ion mobility increase with increasing PEG oligomer composition the maximum of

conductivity is located at x1 = 059 and corresponds to a value of 171 mS cmminus 1

at 33315 K It can also

be observed that the conductivity increases as the temperature increases The higher temperature may

x1

00 02 04 06 08 10

mS

cm

-1

00

05

10

15

20

29315 K

29815 K

30315 K

30815 K

31315 K

31815 K

32315 K

32815 K

33315 K

Int J Electrochem Sci Vol 8 2013

5081

weaken the influence of aggregation to the conductivity which suggests that a higher temperature is

better for the ILs to act as electrolytes

Table 9 RedlickndashKister fitting coefficients Ak and the standard deviation of the VE and ∆for the

binary mixture of PEG200 (1) + [PyrMB][BuSO4] (2) system

TK A0 A1 A2 A3 A4

VEcm

3 mol

-1

29315 -5979 -4906 6585 5754 -1717 002687

29815 -6200 -4760 6464 5767 -2022 002693

30315 -6408 -4612 6345 5774 -2276 002698

30815 -6602 -4461 6229 5774 -2476 002701

31315 -6782 -4310 6116 5767 -2623 002701

31815 -6948 -4155 6006 5753 -2716 002699

32315 -7100 -3999 5899 5732 -2754 002692

32815 -7239 -3840 5795 5704 -2738 002683

33315 -7363 -3679 5694 5669 -2666 002670

33815 -7472 -3515 5596 5626 -2538 002654

34315 -7568 -3350 5501 5576 -2353 002634

34815 -7648 -3182 5409 5518 -2111 002611

35315 -7714 -3011 5320 5452 -1812 002586

∆mPa s

29315 -20414 -17226 -15592 -95544 -75863 399496

29815 -14035 -11558 -10713 -62192 19493 340180

30315 -98261 -78407 -73734 -40709 58145 286725

30815 -69922 -53591 -50601 -2676 67556 235258

31315 -48876 -39537 -41051 -14118 16739 079245

31815 -36917 -25169 -22939 -11646 51047 146189

32315 -27415 -1721 -12581 -92603 21498 104339

32815 -20441 -11703 -77538 -38334 -81478 090708

33315 -15382 -67274 -31134 -47585 -18255 059539

33815 -11664 -44928 -15533 -22312 -05591 037855

34315 -89038 -24163 68654 -15007 -10347 024263

34815 -68279 -91813 23131 -10367 -18636 017759

35315 -52525 -24051 26474 15498 -85341 018640

35 Redlich-Kister Equation for Binary System

The binary excess property ( E

mV ) and deviations (Δ) at several temperatures were fitted to a

Redlich-Kister-type equation [82]

1 1 1

0

(or ) (1 ) (1 2 )j

E i

i

i

Y Y x x A x

(14)

Int J Electrochem Sci Vol 8 2013

5082

where ΔY (YE) represents E

mV (cm3 mol

minus1) and Δ

(mPa s)x1 denotes the mole fraction of

PEG200 Ai represents the polynomial coefficients and j is the degree of the polynomial expansion

The correlated results for excess molar volumes ( E

mV ) viscosity deviations (Δ) including the values

of the fitting parameters Ai together with the standard deviation σ are given in Table 9 where the

tabulated standard deviation σ [83] is defined as

2

exp cal 1 2( )

[ ]Y Y

m n

(15)

where m is the number of experimental data points and n is the number of estimated

parameters The subscripts ldquoexprdquo and ldquocalrdquo denote the values of the experimental and calculated

property respectively As shown in Table 9 the experimentally derived E

mV and Δη values were

correlated satisfactorily by the Redlich-Kister equation

4 CONCLUSIONS

This paper is a systematic characterizations of thermophysical properties for IL binary system

Density viscosity and conductivity for (PEG200 + [PyrMB][BuSO4]) binary system are presented as a

function of temperature at atmospheric pressure it was demonstrated that viscosity and conductivity

were more sensitive to the changes in PEG content or temperature than density and the viscosity and

conductivity of pure IL and (PEG200 + [PyrMB][BuSO4]) binary system at different temperature are

fitted using the VogelndashTammannndashFulcher (VTF) equation with good accuracy The excess molar

volumes excess volume expansivity and viscosity deviations show negative deviations from the ideal

solution the results are interpreted in terms of molecular interactions in the (PEG200 +

[PyrMB][BuSO4]) binary mixture The conductivity increases to a maximum value when the

concentration of PEG200 is increased and decreases after the maximum the data obtained will be

helpful for the application of the ionic liquids as electrolytes and also useful for the ionic liquids

database

ACKNOWLEDGEMENTS

The authors would like to thank the National Science Council of the Republic of China for financially

supporting this project

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10 AN Soriano AM Agapito LJLI Lagumbay AR Caparanga MH Li J Taiwan Inst Chem

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(2011) 874

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(2010) 853

14 H Wang LX Wu YC Lan JQ Zhao JX Lu Int J Electrochem Sci 6 (2011) 4218

15 FF Liu SQ Liu QJ Feng SX Zhuang JB Zhang P Bu Int J Electrochem Sci 7 (2012)

4381

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18 NV Likhanova O Olivares-Xometl D Guzman-Lucero MA Dominguez-Aguilar N Nava

M Corrales-Luna MC Mendoza Int J Electrochem Sci 6 (2011) 4514

19 A Zarrouk M Messali H Zarrok R Salghi AA Ali B Hammouti SS Al-Deyab F Bentiss

Int J Electrochem Sci 7 (2012) 6998

20 BS Ali BH Ali R Yusoff MK Aroua Int J Electrochem Sci 7 (2012) 3835

21 MH Lin YJ Liu ZH Yang YB Huang ZH Sun Y He CL Ni Int J Electrochem Sci 7

(2012) 965

22 CH Su MH Chung HJ Hsieh YK Chang JC Ding HM Wu J Taiwan Inst Chem Eng

43 (2012) 573

23 H Shekaari A Kazempour J Taiwan Inst Chem Eng 43 (2012) 650

24 ZJ Wei Y Li D Thushara YX Liu QL Ren J Taiwan Inst Chem Eng 43 (2012) 363

25 GQ Zhang HW Yang JF Gao HK Zhang CB Zheng YL Cao YH Wang KQ Ding

Int J Electrochem Sci 7 (2012) 7547

26 P Norouzi MR Ganjali F Faridbod SJ Shahtaheri HA Zamani Int J Electrochem Sci 7

(2012) 2633

27 F Faridbod MR Ganjali M Hosseini P Norouzi Int J Electrochem Sci 7 (2012) 1927

28 MR Ganjali Z Rafiei-Sarmazdeh T Poursaberi SJ Shahtaheri P Norouzi Int J

Electrochem Sci 7 (2012) 1908

29 A Babaei DJ Garrett AJ Downard Int J Electrochem Sci 7 (2012) 3141

30 MR Ganjali T Alizade P Norouzi Int J Electrochem Sci 7 (2012) 4800

31 MR Ganjali T Alizade B Larijani F Faridbod P Norouzi Int J Electrochem Sci 7 (2012)

4756

32 P Norouzi B Larijani MR Ganjali Int J Electrochem Sci 7 (2012) 7313

33 TY Wu MH Tsao SG Su HP Wang YC Lin FL Chen CW Chang IW Sun J Braz

Chem Soc 22 (2011) 780

34 MH Tsao TY Wu HP Wang IW Sun SG Su YC Lin CW Chang Mater Lett 65

(2011) 583

Int J Electrochem Sci Vol 8 2013

5084

35 SY Ku SY Lu Int J Electrochem Sci 6 (2011) 5219

36 TY Wu MH Tsao FL Chen SG Su CW Chang HP Wang YC Lin IW Sun J Iran

Chem Soc 7 (2010) 707

37 IW Sun HP Wang H Teng SG Su YC Lin CW Kuo PR Chen TY Wu Int J

Electrochem Sci 7 (2012) 9748

38 TY Wu MH Tsao FL Chen SG Su CW Chang HP Wang YC Lin WC Ou-Yang

IW Sun Int J Mol Sci 11 (2010) 329

39 YX An PJ Zuo XQ Cheng LX Liao GP Yin Int J Electrochem Sci 6 (2011) 2398

40 LC Xuan YX An W Fang LX Liao YL Ma ZY Ren GP Yin Int J Electrochem Sci

6 (2011) 6590

41 HM Wang SQ Liu K Huang XG Yin YN Liu SJ Peng Int J Electrochem Sci 7

(2012) 1688

42 HM Wang SQ Liu NF Wang YN Liu Int J Electrochem Sci 7 (2012) 7579

43 H Ganjali MR Ganjali T Alizadeh F Faridbod P Norouzi Int J Electrochem Sci 6 (2011)

6085

44 MR Ganjali MH Eshraghi S Ghadimi SM Moosavi M Hosseini H Haji-Hashemi P

Norouzi Int J Electrochem Sci 6 (2011) 739

45 MR Ganjali T Poursaberi M Khoobi A Shafiee M Adibi M Pirali-Hamedani P Norouzi

Int J Electrochem Sci 6 (2011) 717

46 P Norouzi M Hosseini MR Ganjali M Rezapour M Adibi Int J Electrochem Sci 6 (2011)

2012

47 MR Ganjali MR Moghaddam M Hosseini P Norouzi Int J Electrochem Sci 6 (2011)

1981

48 MR Ganjali M Hosseini M Pirali-Hamedani HA Zamani Int J Electrochem Sci 6 (2011)

2808

49 MR Ganjali M Rezapour SK Torkestani H Rashedi P Norouzi Int J Electrochem Sci 6

(2011) 2323

50 P Norouzi M Pirali-Hamedani SO Ranaei-Siadat MR Ganjali Int J Electrochem Sci 6

(2011) 3704

51 F Faridbod HA Zamani M Hosseini M Pirali-Hamedani MR Ganjali P Norouzi Int J

Electrochem Sci 6 (2011) 3694

52 MR Ganjali SO Ranaei-Siadat H Rashedi M Rezapour P Norouzi Int J Electrochem Sci

6 (2011) 3684

53 TH Tsai KC Lin SM Chen Int J Electrochem Sci 6 (2011) 2672

54 MR Ganjali T Alizadeh F Azimi B Larjani F Faridbod P Norouzi Int J Electrochem

Sci 6 (2011) 5200

55 R Mirshafian MR Ganjali P Norouzi Int J Electrochem Sci 7 (2012) 1656

56 J Gao JG Liu WM Liu B Li YC Xin Y Yin ZG Zou Int J Electrochem Sci 6 (2011)

6115

57 TY Wu BK Chen L Hao KF Lin IW Sun J Taiwan Inst Chem Eng 42 (2011) 914

58 TY Wu BK Chen L Hao CW Kuo IW Sun J Taiwan Inst Chem Eng 43 (2012) 313

59 SW Peng AN Soriano RB Leron MH Li J Taiwan Inst Chem Eng 42 (2011) 233

60 TY Wu IW Sun MW Lin BK Chen CW Kuo HP Wang YY Chen SG Su J Taiwan

Inst Chem Eng 43 (2012) 58

61 TY Wu BK Chen CW Kuo L Hao YC Peng IW Sun J Taiwan Inst Chem Eng 43

(2012) 860

62 A Arce H Rodriguez A Soto Green Chem 9 (2007) 247

63 TY Wu HC Wang SG Su ST Gung MW Lin CB Lin J Taiwan Inst Chem Eng 41 (2010)

315 64 X Li M Hou Z Zhang B Han G Yang X Wang L Zou Green Chem 10 (2008) 879

Int J Electrochem Sci Vol 8 2013

5085

65 J Chen SK Spear JG Huddleston RD Rogers Green Chem 7 (2005) 64

66 U Domanska M Laskowska J Solution Chem 38 (2009) 779

67 K Tamura M Nakamura S Murakami J Solution Chem 26 (1997) 1199

68 Z Yu H Gao H Wang L Chen J Chem Eng Data 56 (2011) 2877

69 KN Marsh JA Boxall R Lichtenthaler Fluid Phase Equilib 219 (2004) 93

70 TY Wu SG Su ST Gung MW Lin YC Lin WC Ou-Yang IW Sun CA Lai J Iran

Chem Soc 8 (2011) 149

71 TY Wu L Hao CW Kuo YC Lin SG Su PL Kuo IW Sun Int J Electrochem Sci 7

(2012) 2047

72 TY Wu L Hao PR Chen JW Liao Int J Electrochem Sci 8 (2013) 2606

73 CW Kuo CW Huang BK Chen WB Li PR Chen TH Ho CG Tseng TY Wu Int J

Electrochem Sci 8 (2013) 3834

74 CW Kuo WB Li PR Chen JW Liao CG Tseng TY Wu Int J Electrochem Sci 8

(2013) 5007

75 TY Wu BK Chen L Hao YC Lin HP Wang CW Kuo IW Sun Int J Mol Sci 12

(2011) 8750

76 H Rodriguez JF Brennecke J Chem Eng Data 51 (2006) 2145

77 Y Tian X Wang J Wang J Chem Eng Data 53 (2008) 2056

78 TY Wu HC Wang SG Su ST Gung MW Lin CB Lin J Chin Chem Soc 57 (2010)

44

79 TY Wu BK Chen L Hao YC Peng IW Sun Int J Mol Sci 12 (2011) 2598

80 H Eyring MS John Significant Liquid Structure Wiley New York 1969

81 H Every AG Bishop M Forsyth DR MacFarlane Electrochim Acta 45 (2000) 1279 82 O Redlich AT Kister Ind Eng Chem 40 (1948) 345

83 A Paul P Kumar A Samanta J Phys Chem B 109 (2005) 9148

copy 2013 by ESG (wwwelectrochemsciorg)

Int J Electrochem Sci Vol 8 2013

5073

excess molar volumes of mixtures over the entire composition range were calculated from our

measurements of density according to the following equation

Table 3 The adjustable parameters of density (ρ = b0 + b1 T + b2 T2) at various temperature for neat

PEG200 (x1 = 1) [PyrMB][BuSO4] (x1 = 0) and binary system PEG200 (1) + [PyrMB][BuSO4]

(2)

x1 b0 b1 b2

0 1326 -000077105 00000003 000003

01452 1301 -0000588 0 000023

01942 1304 -0000593 0 000032

02912 131 -0000604 0 000047

03897 1315 -0000613 0 000009

04893 1318 -0000621 0 000034

05890 1319 -0000629 0 000045

06903 132 -0000639 0 000046

07922 1325 -0000658 0 000036

08958 1335 -0000694 0 000030

1 1405 -000108 000000051 000112

Figure 4 Excess molar volumes for the binary system PEG200 (1) + [PyrMB][BuSO4] (2) and

fitted curves using the Redlich-Kister parameters

1 1 2 2 1 1 2 2m

1 2

E

Vx M x M x M x M

(5)

where ρ1 ρ2 and ρ are the densities of neat PEG200 [PyrMB][BuSO4] and their mixture

respectively M1 and M2 are the molar masses of PEG200 and [PyrMB][BuSO4] respectively The E

mV

values of mixtures are summarized in Table 1 The excess molar volumes of mixtures versus the mole

x1

00 02 04 06 08 10

Vm

E

cm

3 m

ol-1

-20

-15

-10

-05

00

30315 K

31315 K

32315 K

33315 K

Int J Electrochem Sci Vol 8 2013

5074

fraction of PEG200 from 29315 to 35315 K are plotted in Figure 4 The excess molar volume of the

binary system is mainly concerned with the weak chemical interactions the physical and structural

characteristics of the system components If the chemical or nonchemical interaction of the same

components is the dominant way of the interaction the excess volume of the mixture should be

positive If the molecules of the components have a more effective packing in the mixture than that in

the pure component that is the attracting interaction between the molecules of two components is the

dominant way the excess molar volume of the binary system should be negative [66] As shown in

Figure 4 the excess molar volumes are asymmetric and negative for all of the systems studied over the

entire composition range the minimum of E

mV is reached at a mole fraction of PEG200 near x1 = 04

and the absolute values of the excess volume increase with increasing temperature The molar volume

for [PyrMB][BuSO4] is 26243 cm3 mol

-1 at T = 29315 K which is greater than the molar volumes of

PEG200 (17681 cm3 mol

-1) at T = 29315 K The large difference between molar volumes of the

molecular liquid and [PyrMB][BuSO4] indicates that it is possible that the relatively small organic

molecules fit into the interstices upon mixing Therefore the filling effect of organic molecular liquids

in the interstices of ionic liquids and the ionndashdipole interactions between poly(ethylene glycol)

oligomer and the butylsulfate-based ionic liquids all contribute to the negative values of the molar

excess volumes

32 Volume expansivity and excess volume expansivity

Density results for the PEG200 and [PyrMB][BuSO4] binary system studied in current work were

also used to derive the coefficient of thermal expansion From the relationship of vs T the volume

expansivity (coefficient of thermal expansion) α is defined as

1 1

( ) ( )p p

V

TV T

(6)

where subscript p indicates constant pressure The α values of pure [PyrMB][BuSO4] and

PEG200 and their mixture are summarized in Table 4 The values indicate that the thermal expansion

coefficient of this binary mixture (PEG200 + [PyrMB][BuSO4]) increases with increasing temperature

and increases with increasing mole fraction of the PEG200

The corresponding excess function (excess volume expansivity) was calculated using

E id id

1 1 2 2 (7)

where id

1 is an ideal volume fraction given by the following relation

1 m11

1 m1 2 m2

id xV

xV x V

(8)

Int J Electrochem Sci Vol 8 2013

5075

where Vmi is the molar volume of pure component i

Table 4 Experimental volume expansivity (α) and the excess volume expansivity (αE) for the binary

system PEG200 (1) + [PyrMB][BuSO4] (2)

x1

29315 29815 30315 30815 31315 31815 32315 32815 33315 33815 34315 34815 35315

104 αK-1

0 51245 51380 51516 51651 51787 51922 52058 52193 52329 52464 52600 52735 52871

01452 52053 52189 52325 52462 52600 52739 52878 53018 53159 53300 53443 53586 53730

01942 52438 52576 52715 52854 52994 53135 53276 53418 53561 53705 53850 53995 54141

02912 53299 53443 53586 53731 53877 54023 54170 54318 54466 54616 54766 54917 55069

03897 53973 54120 54268 54417 54567 54717 54869 55021 55174 55328 55483 55638 55795

04893 54667 54818 54971 55124 55278 55433 55589 55745 55903 56061 56221 56381 56542

05890 55372 55527 55683 55840 55998 56157 56317 56477 56639 56801 56965 57129 57294

06903 56358 56517 56677 56838 57000 57163 57327 57492 57657 57824 57992 58160 58330

07922 58175 58344 58515 58687 58860 59033 59208 59384 59561 59739 59918 60098 60279

08958 61313 61502 61691 61882 62074 62268 62462 62658 62855 63053 63252 63453 63655

1 66532 66763 66993 67224 67455 67685 67916 68146 68377 68607 68838 69069 69299

104 αEK-1

0 00000 00000 00000 00000 00000 00000 00000 00000 00000 00000 00000 00000 00000

01452 -00762 -00772 -00782 -00792 -00800 -00808 -00815 -00822 -00827 -00832 -00837 -00840 -00843

01942 -00942 -00954 -00966 -00977 -00987 -00997 -01006 -01014 -01021 -01028 -01033 -01038 -01043

02912 -01259 -01275 -01289 -01302 -01315 -01327 -01339 -01349 -01359 -01368 -01376 -01383 -01389

03897 -01870 -01889 -01908 -01926 -01943 -01959 -01975 -01989 -02003 -02016 -02028 -02040 -02050

04893 -02576 -02600 -02623 -02646 -02668 -02689 -02709 -02728 -02746 -02764 -02780 -02796 -02811

05890 -03382 -03412 -03441 -03470 -03497 -03524 -03550 -03574 -03598 -03621 -03644 -03665 -03685

06903 -04064 -04100 -04136 -04170 -04204 -04236 -04268 -04299 -04329 -04358 -04386 -04413 -04439

07922 -04073 -04110 -04146 -04181 -04214 -04247 -04279 -04310 -04339 -04368 -04396 -04422 -04448

08958 -02968 -02998 -03026 -03053 -03079 -03104 -03128 -03151 -03172 -03192 -03211 -03228 -03245

1 00000 00000 00000 00000 00000 00000 00000 00000 00000 00000 00000 00000 00000

Figure 5 Plot of excess volume expansivity αE of the PEG200 (1) + [PyrMB][BuSO4] (2) binary

system versus mole fraction x1 at various temperatures

Typical concentration dependencies of excess volume expansivity are given in Figure 5 for the

PEG200 + [PyrMB][BuSO4] binary system The values of excess thermal coefficient αE are found to

x1

00 02 04 06 08 10

10

4

E K

-1

-04

-03

-02

-01

00

29315 K

30315 K

31315 K

32315 K

33315 K

34315 K

35315 K

Temp

Int J Electrochem Sci Vol 8 2013

5076

be negative over the whole composition range for the binary system at 29315 ~ 35315 K The curves

are asymmetrical with the minimum located at the IL mole fraction of about 08 In general negative

αE values indicate the presence of strong interaction between the components in the mixtures [67] The

trends observed in αE values for the present mixtures suggest the formation of H-bonding between

unlike molecules which is stronger in PEG200 + [PyrMB][BuSO4] binary system The increasing

negative αE values for PEG200 + [PyrMB][BuSO4] with increase in temperature indicate enhanced

unlike interaction between components of the mixture that is more destruction of order during mixing

contributes negatively to αE

33 Viscosity

Since ILs are more viscous than conventional solvents in most applications they can be used in

mixtures with other less viscous compounds Therefore the viscosity of pure ILs and their mixtures

with PEG oligomer (or conventional solvents) is an important property and their knowledge is

primordial for each industrial processes [6869] The measured dynamic viscosities for the neat

PEG200 neat [PyrMB][BuSO4] and PEG200 + [PyrMB][BuSO4] binary mixture as a function of

temperature over the whole composition range are shown in Figure 6 and their data are listed in Table

5 the viscosities of the mixtures decrease rapidly when PEG oligomer are added to the ionic liquid

especially at lower temperatures The fitting lines in Figure 6 were calculated with the following

fourth-order polynomial equation

= c0 + c1 x1 + c2 x12 + c3 x1

3 + c4 x1

4 (9)

where x1 is the mole fractions of PEG200 and c0 c1 c2 c3 and c4 refer to the fit coefficients

The parameters of correlation are shown in Table 6

Figure 6 Dynamic viscosity for the PEG200 (1) + [PyrMB][BuSO4] (2) binary system as a

function of mole fractions of the PEG200 at different temperatures Lines represent the

polynomial correlation

x1

00 02 04 06 08 10

mP

a s

0

200

400

600

800

1000

1200

1400

29315 K

30315 K

31315 K

32315 K

33315 K

34315 K

35315 K

Int J Electrochem Sci Vol 8 2013

5077

Table 5 Experimental dynamic viscosity (η) and viscosity deviation (Δη) for the binary system

PEG200 (1) + [PyrMB][BuSO4] (2)

x1

29315 29815 30315 30815 31315 31815 32315 32815 33315 33815 34315 34815 35315

ηmPamiddots

0 13209 9343 6745 4961 3712 2821 2176 1700 1345 1077 871 712 587

01452 5907 4362 3294 2539 1992 1589 1286 1055 876 735 623 533 460

01942 4656 3475 2656 2072 1647 1331 1091 907 763 649 557 483 422

02912 3134 2395 1870 1489 1205 991 826 697 594 512 445 390 345

03897 2367 1846 1463 1177 959 792 660 557 474 406 351 306 269

04893 1799 1396 1104 887 723 598 501 424 362 312 272 238 210

05890 1540 1194 941 753 611 502 418 351 298 255 220 191 167

06903 1185 926 736 594 485 402 336 284 242 209 181 158 139

07922 954 742 589 475 389 323 271 231 198 172 150 132 117

08958 811 639 512 415 342 285 240 204 175 151 132 116 102

1 629 505 410 337 280 235 199 170 146 126 110 97 85

ΔηmPamiddots

0 00 00 00 00 00 00 00 00 00 00 00 00 00

01452 -5475 -3698 -2530 -1751 -1221 -857 -602 -423 -295 -204 -137 -89 -54

01942 -6111 -4152 -2859 -1991 -1398 -988 -700 -496 -347 -244 -166 -110 -68

02912 -6411 -4374 -3030 -2126 -1507 -1077 -774 -558 -391 -288 -204 -142 -103

03897 -5940 -4053 -2813 -1982 -1415 -1022 -745 -547 -405 -300 -223 -166 -123

04893 -5254 -3622 -2541 -1811 -1255 -957 -708 -528 -396 -299 -227 -173 -131

05890 -4260 -2944 -2073 -1484 -1034 -796 -594 -448 -341 -262 -203 -158 -124

06903 -3340 -2316 -1636 -1176 -826 -634 -475 -360 -275 -212 -165 -129 -101

07922 -2289 -1599 -1138 -823 -579 -449 -320 -257 -197 -152 -118 -92 -72

08958 -1129 -787 -559 -404 -277 -220 -152 -126 -96 -74 -58 -45 -35

1 00 00 00 00 00 00 00 00 00 00 00 00 00

Table 6 Coefficients of polynomiala for the correlation of the viscosity ( mPa s) in function of

concentration at different temperatures of the binary systems PEG200 (1) + [PyrMB][BuSO4]

(2)

TK c0 mPa s c1 mPa s c2 mPa s c3 mPa s C4 mPa s

29315 13154 -68701 15960 -16688 63543 1075

29815 93069 -46703 10681 -11113 42269 727

30315 67211 -32185 72085 -74396 28222 497

30815 49454 -22431 48886 -49866 18828 343

31315 37016 -15772 33175 -33281 12474 238

31815 28146 -1116 22406 -21947 81322 165

32315 21713 -7923 14947 -1413 51409 114

32815 16975 -56244 97349 -870 30666 077

33315 13435 -39753 60667 -4908 16219 051

33815 10756 -27812 34718 -22519 61382 033

34315 87026 -19098 16304 -39091 -88892 021

34815 71108 -12698 32285 90904 -5763 016

35315 58636 -79728 -60345 18103 -91096 017 a = c0 + c1 x1 + c2 x1

2 + c3 x1

3 + c4 x1

4

The temperature dependence becomes distinctly nonlinear especially at high [PyrMB][BuSO4]

content The Vogel-Tammann-Fulcher (VTF) equation [70-75] suitably correlates the nonlinear

behavior as a function of the temperature not only the viscosities of the neat IL but also the viscosities

of the mixtures for the binary systems through the composition range

Int J Electrochem Sci Vol 8 2013

5078

exp[ ]( )

o

o

B

T T

(10)

where ηo B and To are constants The parameter To is the ideal glass transition temperature which

should be slightly below the experimental glass transition temperature Tg [76] The adjustable

parameters obtained from the VTF correlation were presented in Table 7 The obtained parameters o

and B change smoothly with composition for binary mixtures

Table 7 The VTF equation parameters of viscosity ( 1 exp[ ]( )

o

o

B

T T

) and conductivity

(

exp[ ]( )

o

o

B

T T

) for neat PEG200 (x1 = 1) [PyrMB][BuSO4] (x1 = 0) and binary system

PEG200 (1) + [PyrMB][BuSO4] (2)

x1

ηo (mPa s) To (K) B (K) R2a

o (mS cm-1

) To (K) Brsquo (K) R2a

0 027 1810 9540 0999 792 1788 6854 0999

01452 026 1712 9413 0999 577 1699 6268 0999

01942 043 1788 7975 0999 401 1792 5297 0999

02912 053 1794 7264 0999 521 1662 6031 0999

03897 026 1629 8902 0999 274 1803 4381 0999

04893 023 1666 8455 0999 177 1951 3272 0999

05890 015 1648 8865 0999 216 1883 3672 0999

06903 015 1647 8572 0999 88 2174 2000 0999

07922 017 1717 7702 0999 92 2020 2578 0999

08958 012 1642 8360 0999 43 2110 2088 0999

1 014 1649 7868 0999 556 1928 9815 0999

a Correlation coefficient

The viscosities of the mixtures decrease rapidly when organic oligomers are added to the ionic

liquid this decrease is particularly evident in dilute solutions of organic oligomers in the ionic liquid

The strong coulomb interactions between the [BuSO4]- anion and [PyrMB]

+ cation are weakened upon

mixing with the polar organic oligomers which leads to a higher mobility of the ions and a lower

viscosity of the mixtures [77] This indicates that the viscosity of ILs could be therefore tuned for

several applications by adding an organic solvent or by changing temperature [78]

Due to the wide range of possible molecular interactions between the two components

deviations can occur from ideal behavior These viscosity deviations can be quantified by the viscosity

deviation Δη also known as ldquoexcess viscosityrdquo in other sources

1 1 2 2 (mPa s) x x (11)

Int J Electrochem Sci Vol 8 2013

5079

where x1 and x2 are the mole fractions of PEG200 and [PyrMB][BuSO4] respectively and 1

and 2 are the viscosities (mPa middot s) of the solution the pure solvent and the pure IL respectively

Figure 7 shows the viscosity deviations as a function of the PEG200 mole fraction composition x1 and

temperature for the PEG200 + [PyrMB][BuSO4] binary mixture The values of viscosity deviations

are compared with those obtained from the RedlichndashKister polynomial equation The viscosity

deviation for the mixture show negative deviations from ideality over the whole mole fraction range

Figure 7 also shows that the negative values of viscosity deviations decrease with increasing

temperature this can be attributed to the specific interactions in mixtures typically hydrogen bonds break-

up as the temperature increases [79] The minimum value of Δη is observed at about x1 asymp 03 and the

viscosity deviation depends on molecular interactions as well as on the size and shape of the molecules

[80]

Figure 7 Viscosity deviations Δη versus the mole fraction at various temperatures for the binary

mixture PEG200 (1) + [PyrMB][BuSO4] (2)

34 Conductivity

The experimental data of conductivity of the neat ILs [PyrMB][BuSO4] neat PEG200 and

binary system are plotted against the x1 at various temperatures in Figure 8 together with lines

calculated with the four-order polynomial equation

= d0 + d1 x1 + d2 x12 + d3 x1

3 + d4 x1

4 (12)

where x1 is the mole fractions of PEG200 and d0 d1 d2 d3 and d4 refer to the fit coefficients

The parameters of correlation are shown in Table 8 The conductivities of neat IL [PyrMB][BuSO4]

neat PEG200 and binary system at various temperatures were fitted using the VTF equation

exp[ ]

( )o

o

B

T T

(13)

x1

00 02 04 06 08 10

m

Pa s

-700

-600

-500

-400

-300

-200

-100

0

29315 K

30315 K

31315 K

32315 K

33315 K

34315 K

35315 K

Int J Electrochem Sci Vol 8 2013

5080

where T is the absolute temperature and Brsquo and To are adjustable parameters The best-fit

mS cm-1 Brsquo (K) and To (K) parameters are given in Table 7 Neat [PyrMB][BuSO4] neat

PEG200 and binary system were very well fit by the VTF model over the temperature range studied

Figure 8 Plot of conductivity of the PEG200 (1) + [PyrMB][BuSO4] (2) binary system versus

mole fraction x1 at various temperatures

Table 8 Coefficients of polynomiala for the correlation of the conductivity ( mS cm

-1) in function

of concentration at different temperatures of the binary systems PEG200 (1) +

[PyrMB][BuSO4] (2)

TK d0 mS cm

-1 d1 mS cm

-1 d2 mS cm

-1 d3 mS cm

-1 d4 mS cm

-1

29315 02019 09622 -01679 0734 -17284 00095

29815 02588 11031 -02503 09086 -20181 00109

30315 03255 12119 -01935 08565 -21971 00125

30815 04025 13165 -01329 0767 -23477 00141

31315 04904 13712 01238 03677 -23439 00156

31815 05894 15032 -00006 04737 -25518 00171

32315 06999 15802 00743 0265 -25986 00188

32815 08221 16427 01595 00089 -26032 00208

33315 09562 16373 04858 -06207 -24165 00233

a = d0 + d1 x1 + d2 x1

2 + d3 x1

3 + d4 x1

4

As shown in Figure 8 it can be seen that the conductivity of the binary mixture increases with

increasing amount of PEG200 goes through a maximum and then goes down to the specific

conductivity of the neat PEG200 The conductivity is related to the ion mobility and the number of

charge carriers [81] At a fixed concentration the ions move faster at higher temperature due to the

relatively lower viscosity of the mixture On the other hand the composition influences both the ion

mobility and the number of charge carriers at a fixed temperature At the beginning the number of

charge and the ion mobility increase with increasing PEG oligomer composition the maximum of

conductivity is located at x1 = 059 and corresponds to a value of 171 mS cmminus 1

at 33315 K It can also

be observed that the conductivity increases as the temperature increases The higher temperature may

x1

00 02 04 06 08 10

mS

cm

-1

00

05

10

15

20

29315 K

29815 K

30315 K

30815 K

31315 K

31815 K

32315 K

32815 K

33315 K

Int J Electrochem Sci Vol 8 2013

5081

weaken the influence of aggregation to the conductivity which suggests that a higher temperature is

better for the ILs to act as electrolytes

Table 9 RedlickndashKister fitting coefficients Ak and the standard deviation of the VE and ∆for the

binary mixture of PEG200 (1) + [PyrMB][BuSO4] (2) system

TK A0 A1 A2 A3 A4

VEcm

3 mol

-1

29315 -5979 -4906 6585 5754 -1717 002687

29815 -6200 -4760 6464 5767 -2022 002693

30315 -6408 -4612 6345 5774 -2276 002698

30815 -6602 -4461 6229 5774 -2476 002701

31315 -6782 -4310 6116 5767 -2623 002701

31815 -6948 -4155 6006 5753 -2716 002699

32315 -7100 -3999 5899 5732 -2754 002692

32815 -7239 -3840 5795 5704 -2738 002683

33315 -7363 -3679 5694 5669 -2666 002670

33815 -7472 -3515 5596 5626 -2538 002654

34315 -7568 -3350 5501 5576 -2353 002634

34815 -7648 -3182 5409 5518 -2111 002611

35315 -7714 -3011 5320 5452 -1812 002586

∆mPa s

29315 -20414 -17226 -15592 -95544 -75863 399496

29815 -14035 -11558 -10713 -62192 19493 340180

30315 -98261 -78407 -73734 -40709 58145 286725

30815 -69922 -53591 -50601 -2676 67556 235258

31315 -48876 -39537 -41051 -14118 16739 079245

31815 -36917 -25169 -22939 -11646 51047 146189

32315 -27415 -1721 -12581 -92603 21498 104339

32815 -20441 -11703 -77538 -38334 -81478 090708

33315 -15382 -67274 -31134 -47585 -18255 059539

33815 -11664 -44928 -15533 -22312 -05591 037855

34315 -89038 -24163 68654 -15007 -10347 024263

34815 -68279 -91813 23131 -10367 -18636 017759

35315 -52525 -24051 26474 15498 -85341 018640

35 Redlich-Kister Equation for Binary System

The binary excess property ( E

mV ) and deviations (Δ) at several temperatures were fitted to a

Redlich-Kister-type equation [82]

1 1 1

0

(or ) (1 ) (1 2 )j

E i

i

i

Y Y x x A x

(14)

Int J Electrochem Sci Vol 8 2013

5082

where ΔY (YE) represents E

mV (cm3 mol

minus1) and Δ

(mPa s)x1 denotes the mole fraction of

PEG200 Ai represents the polynomial coefficients and j is the degree of the polynomial expansion

The correlated results for excess molar volumes ( E

mV ) viscosity deviations (Δ) including the values

of the fitting parameters Ai together with the standard deviation σ are given in Table 9 where the

tabulated standard deviation σ [83] is defined as

2

exp cal 1 2( )

[ ]Y Y

m n

(15)

where m is the number of experimental data points and n is the number of estimated

parameters The subscripts ldquoexprdquo and ldquocalrdquo denote the values of the experimental and calculated

property respectively As shown in Table 9 the experimentally derived E

mV and Δη values were

correlated satisfactorily by the Redlich-Kister equation

4 CONCLUSIONS

This paper is a systematic characterizations of thermophysical properties for IL binary system

Density viscosity and conductivity for (PEG200 + [PyrMB][BuSO4]) binary system are presented as a

function of temperature at atmospheric pressure it was demonstrated that viscosity and conductivity

were more sensitive to the changes in PEG content or temperature than density and the viscosity and

conductivity of pure IL and (PEG200 + [PyrMB][BuSO4]) binary system at different temperature are

fitted using the VogelndashTammannndashFulcher (VTF) equation with good accuracy The excess molar

volumes excess volume expansivity and viscosity deviations show negative deviations from the ideal

solution the results are interpreted in terms of molecular interactions in the (PEG200 +

[PyrMB][BuSO4]) binary mixture The conductivity increases to a maximum value when the

concentration of PEG200 is increased and decreases after the maximum the data obtained will be

helpful for the application of the ionic liquids as electrolytes and also useful for the ionic liquids

database

ACKNOWLEDGEMENTS

The authors would like to thank the National Science Council of the Republic of China for financially

supporting this project

References

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2 TY Wu IW Sun ST Gung MW Lin BK Chen HP Wang SG Su J Taiwan Inst Chem

Eng 42 (2011) 513

Int J Electrochem Sci Vol 8 2013

5083

3 TY Wu SG Su KF Lin YC Lin HP Wang MW Lin ST Gung IW Sun Electrochim

Acta 56 (2011) 7278

4 B Baek S Lee C Jung Int J Electrochem Sci 6 (2011) 6220

5 PN Tshibangu SN Ndwandwe ED Dikio Int J Electrochem Sci 6 (2011) 2201

6 TY Wu SG Su HP Wang IW Sun Electrochem Commun 13 (2011) 237

7 TY Wu SG Su HP Wang YC Lin ST Gung MW Lin IW Sun Electrochim Acta 56

(2011) 3209

8 IW Sun YC Lin BK Chen CW Kuo CC Chen SG Su PR Chen TY Wu Int J

Electrochem Sci 7 (2012) 7206

9 TY Wu SG Su ST Gung MW Lin YC Lin CA Lai IW Sun Electrochim Acta 55

(2010) 4475

10 AN Soriano AM Agapito LJLI Lagumbay AR Caparanga MH Li J Taiwan Inst Chem

Eng 42 (2011) 258

11 TY Wu IW Sun ST Gung BK Chen HP Wang SG Su J Taiwan Inst Chem Eng 42

(2011) 874

12 S Ibrahim MR Johan Int J Electrochem Sci 6 (2011) 5565

13 TY Wu SG Su YC Lin HP Wang MW Lin ST Gung IW Sun Electrochim Acta 56

(2010) 853

14 H Wang LX Wu YC Lan JQ Zhao JX Lu Int J Electrochem Sci 6 (2011) 4218

15 FF Liu SQ Liu QJ Feng SX Zhuang JB Zhang P Bu Int J Electrochem Sci 7 (2012)

4381

16 HA Barham SA Brahim Y Rozita KA Mohamed Int J Electrochem Sci 6 (2011) 181

17 SK Shukla LC Murulana EE Ebenso Int J Electrochem Sci 6 (2011) 4286

18 NV Likhanova O Olivares-Xometl D Guzman-Lucero MA Dominguez-Aguilar N Nava

M Corrales-Luna MC Mendoza Int J Electrochem Sci 6 (2011) 4514

19 A Zarrouk M Messali H Zarrok R Salghi AA Ali B Hammouti SS Al-Deyab F Bentiss

Int J Electrochem Sci 7 (2012) 6998

20 BS Ali BH Ali R Yusoff MK Aroua Int J Electrochem Sci 7 (2012) 3835

21 MH Lin YJ Liu ZH Yang YB Huang ZH Sun Y He CL Ni Int J Electrochem Sci 7

(2012) 965

22 CH Su MH Chung HJ Hsieh YK Chang JC Ding HM Wu J Taiwan Inst Chem Eng

43 (2012) 573

23 H Shekaari A Kazempour J Taiwan Inst Chem Eng 43 (2012) 650

24 ZJ Wei Y Li D Thushara YX Liu QL Ren J Taiwan Inst Chem Eng 43 (2012) 363

25 GQ Zhang HW Yang JF Gao HK Zhang CB Zheng YL Cao YH Wang KQ Ding

Int J Electrochem Sci 7 (2012) 7547

26 P Norouzi MR Ganjali F Faridbod SJ Shahtaheri HA Zamani Int J Electrochem Sci 7

(2012) 2633

27 F Faridbod MR Ganjali M Hosseini P Norouzi Int J Electrochem Sci 7 (2012) 1927

28 MR Ganjali Z Rafiei-Sarmazdeh T Poursaberi SJ Shahtaheri P Norouzi Int J

Electrochem Sci 7 (2012) 1908

29 A Babaei DJ Garrett AJ Downard Int J Electrochem Sci 7 (2012) 3141

30 MR Ganjali T Alizade P Norouzi Int J Electrochem Sci 7 (2012) 4800

31 MR Ganjali T Alizade B Larijani F Faridbod P Norouzi Int J Electrochem Sci 7 (2012)

4756

32 P Norouzi B Larijani MR Ganjali Int J Electrochem Sci 7 (2012) 7313

33 TY Wu MH Tsao SG Su HP Wang YC Lin FL Chen CW Chang IW Sun J Braz

Chem Soc 22 (2011) 780

34 MH Tsao TY Wu HP Wang IW Sun SG Su YC Lin CW Chang Mater Lett 65

(2011) 583

Int J Electrochem Sci Vol 8 2013

5084

35 SY Ku SY Lu Int J Electrochem Sci 6 (2011) 5219

36 TY Wu MH Tsao FL Chen SG Su CW Chang HP Wang YC Lin IW Sun J Iran

Chem Soc 7 (2010) 707

37 IW Sun HP Wang H Teng SG Su YC Lin CW Kuo PR Chen TY Wu Int J

Electrochem Sci 7 (2012) 9748

38 TY Wu MH Tsao FL Chen SG Su CW Chang HP Wang YC Lin WC Ou-Yang

IW Sun Int J Mol Sci 11 (2010) 329

39 YX An PJ Zuo XQ Cheng LX Liao GP Yin Int J Electrochem Sci 6 (2011) 2398

40 LC Xuan YX An W Fang LX Liao YL Ma ZY Ren GP Yin Int J Electrochem Sci

6 (2011) 6590

41 HM Wang SQ Liu K Huang XG Yin YN Liu SJ Peng Int J Electrochem Sci 7

(2012) 1688

42 HM Wang SQ Liu NF Wang YN Liu Int J Electrochem Sci 7 (2012) 7579

43 H Ganjali MR Ganjali T Alizadeh F Faridbod P Norouzi Int J Electrochem Sci 6 (2011)

6085

44 MR Ganjali MH Eshraghi S Ghadimi SM Moosavi M Hosseini H Haji-Hashemi P

Norouzi Int J Electrochem Sci 6 (2011) 739

45 MR Ganjali T Poursaberi M Khoobi A Shafiee M Adibi M Pirali-Hamedani P Norouzi

Int J Electrochem Sci 6 (2011) 717

46 P Norouzi M Hosseini MR Ganjali M Rezapour M Adibi Int J Electrochem Sci 6 (2011)

2012

47 MR Ganjali MR Moghaddam M Hosseini P Norouzi Int J Electrochem Sci 6 (2011)

1981

48 MR Ganjali M Hosseini M Pirali-Hamedani HA Zamani Int J Electrochem Sci 6 (2011)

2808

49 MR Ganjali M Rezapour SK Torkestani H Rashedi P Norouzi Int J Electrochem Sci 6

(2011) 2323

50 P Norouzi M Pirali-Hamedani SO Ranaei-Siadat MR Ganjali Int J Electrochem Sci 6

(2011) 3704

51 F Faridbod HA Zamani M Hosseini M Pirali-Hamedani MR Ganjali P Norouzi Int J

Electrochem Sci 6 (2011) 3694

52 MR Ganjali SO Ranaei-Siadat H Rashedi M Rezapour P Norouzi Int J Electrochem Sci

6 (2011) 3684

53 TH Tsai KC Lin SM Chen Int J Electrochem Sci 6 (2011) 2672

54 MR Ganjali T Alizadeh F Azimi B Larjani F Faridbod P Norouzi Int J Electrochem

Sci 6 (2011) 5200

55 R Mirshafian MR Ganjali P Norouzi Int J Electrochem Sci 7 (2012) 1656

56 J Gao JG Liu WM Liu B Li YC Xin Y Yin ZG Zou Int J Electrochem Sci 6 (2011)

6115

57 TY Wu BK Chen L Hao KF Lin IW Sun J Taiwan Inst Chem Eng 42 (2011) 914

58 TY Wu BK Chen L Hao CW Kuo IW Sun J Taiwan Inst Chem Eng 43 (2012) 313

59 SW Peng AN Soriano RB Leron MH Li J Taiwan Inst Chem Eng 42 (2011) 233

60 TY Wu IW Sun MW Lin BK Chen CW Kuo HP Wang YY Chen SG Su J Taiwan

Inst Chem Eng 43 (2012) 58

61 TY Wu BK Chen CW Kuo L Hao YC Peng IW Sun J Taiwan Inst Chem Eng 43

(2012) 860

62 A Arce H Rodriguez A Soto Green Chem 9 (2007) 247

63 TY Wu HC Wang SG Su ST Gung MW Lin CB Lin J Taiwan Inst Chem Eng 41 (2010)

315 64 X Li M Hou Z Zhang B Han G Yang X Wang L Zou Green Chem 10 (2008) 879

Int J Electrochem Sci Vol 8 2013

5085

65 J Chen SK Spear JG Huddleston RD Rogers Green Chem 7 (2005) 64

66 U Domanska M Laskowska J Solution Chem 38 (2009) 779

67 K Tamura M Nakamura S Murakami J Solution Chem 26 (1997) 1199

68 Z Yu H Gao H Wang L Chen J Chem Eng Data 56 (2011) 2877

69 KN Marsh JA Boxall R Lichtenthaler Fluid Phase Equilib 219 (2004) 93

70 TY Wu SG Su ST Gung MW Lin YC Lin WC Ou-Yang IW Sun CA Lai J Iran

Chem Soc 8 (2011) 149

71 TY Wu L Hao CW Kuo YC Lin SG Su PL Kuo IW Sun Int J Electrochem Sci 7

(2012) 2047

72 TY Wu L Hao PR Chen JW Liao Int J Electrochem Sci 8 (2013) 2606

73 CW Kuo CW Huang BK Chen WB Li PR Chen TH Ho CG Tseng TY Wu Int J

Electrochem Sci 8 (2013) 3834

74 CW Kuo WB Li PR Chen JW Liao CG Tseng TY Wu Int J Electrochem Sci 8

(2013) 5007

75 TY Wu BK Chen L Hao YC Lin HP Wang CW Kuo IW Sun Int J Mol Sci 12

(2011) 8750

76 H Rodriguez JF Brennecke J Chem Eng Data 51 (2006) 2145

77 Y Tian X Wang J Wang J Chem Eng Data 53 (2008) 2056

78 TY Wu HC Wang SG Su ST Gung MW Lin CB Lin J Chin Chem Soc 57 (2010)

44

79 TY Wu BK Chen L Hao YC Peng IW Sun Int J Mol Sci 12 (2011) 2598

80 H Eyring MS John Significant Liquid Structure Wiley New York 1969

81 H Every AG Bishop M Forsyth DR MacFarlane Electrochim Acta 45 (2000) 1279 82 O Redlich AT Kister Ind Eng Chem 40 (1948) 345

83 A Paul P Kumar A Samanta J Phys Chem B 109 (2005) 9148

copy 2013 by ESG (wwwelectrochemsciorg)

Int J Electrochem Sci Vol 8 2013

5074

fraction of PEG200 from 29315 to 35315 K are plotted in Figure 4 The excess molar volume of the

binary system is mainly concerned with the weak chemical interactions the physical and structural

characteristics of the system components If the chemical or nonchemical interaction of the same

components is the dominant way of the interaction the excess volume of the mixture should be

positive If the molecules of the components have a more effective packing in the mixture than that in

the pure component that is the attracting interaction between the molecules of two components is the

dominant way the excess molar volume of the binary system should be negative [66] As shown in

Figure 4 the excess molar volumes are asymmetric and negative for all of the systems studied over the

entire composition range the minimum of E

mV is reached at a mole fraction of PEG200 near x1 = 04

and the absolute values of the excess volume increase with increasing temperature The molar volume

for [PyrMB][BuSO4] is 26243 cm3 mol

-1 at T = 29315 K which is greater than the molar volumes of

PEG200 (17681 cm3 mol

-1) at T = 29315 K The large difference between molar volumes of the

molecular liquid and [PyrMB][BuSO4] indicates that it is possible that the relatively small organic

molecules fit into the interstices upon mixing Therefore the filling effect of organic molecular liquids

in the interstices of ionic liquids and the ionndashdipole interactions between poly(ethylene glycol)

oligomer and the butylsulfate-based ionic liquids all contribute to the negative values of the molar

excess volumes

32 Volume expansivity and excess volume expansivity

Density results for the PEG200 and [PyrMB][BuSO4] binary system studied in current work were

also used to derive the coefficient of thermal expansion From the relationship of vs T the volume

expansivity (coefficient of thermal expansion) α is defined as

1 1

( ) ( )p p

V

TV T

(6)

where subscript p indicates constant pressure The α values of pure [PyrMB][BuSO4] and

PEG200 and their mixture are summarized in Table 4 The values indicate that the thermal expansion

coefficient of this binary mixture (PEG200 + [PyrMB][BuSO4]) increases with increasing temperature

and increases with increasing mole fraction of the PEG200

The corresponding excess function (excess volume expansivity) was calculated using

E id id

1 1 2 2 (7)

where id

1 is an ideal volume fraction given by the following relation

1 m11

1 m1 2 m2

id xV

xV x V

(8)

Int J Electrochem Sci Vol 8 2013

5075

where Vmi is the molar volume of pure component i

Table 4 Experimental volume expansivity (α) and the excess volume expansivity (αE) for the binary

system PEG200 (1) + [PyrMB][BuSO4] (2)

x1

29315 29815 30315 30815 31315 31815 32315 32815 33315 33815 34315 34815 35315

104 αK-1

0 51245 51380 51516 51651 51787 51922 52058 52193 52329 52464 52600 52735 52871

01452 52053 52189 52325 52462 52600 52739 52878 53018 53159 53300 53443 53586 53730

01942 52438 52576 52715 52854 52994 53135 53276 53418 53561 53705 53850 53995 54141

02912 53299 53443 53586 53731 53877 54023 54170 54318 54466 54616 54766 54917 55069

03897 53973 54120 54268 54417 54567 54717 54869 55021 55174 55328 55483 55638 55795

04893 54667 54818 54971 55124 55278 55433 55589 55745 55903 56061 56221 56381 56542

05890 55372 55527 55683 55840 55998 56157 56317 56477 56639 56801 56965 57129 57294

06903 56358 56517 56677 56838 57000 57163 57327 57492 57657 57824 57992 58160 58330

07922 58175 58344 58515 58687 58860 59033 59208 59384 59561 59739 59918 60098 60279

08958 61313 61502 61691 61882 62074 62268 62462 62658 62855 63053 63252 63453 63655

1 66532 66763 66993 67224 67455 67685 67916 68146 68377 68607 68838 69069 69299

104 αEK-1

0 00000 00000 00000 00000 00000 00000 00000 00000 00000 00000 00000 00000 00000

01452 -00762 -00772 -00782 -00792 -00800 -00808 -00815 -00822 -00827 -00832 -00837 -00840 -00843

01942 -00942 -00954 -00966 -00977 -00987 -00997 -01006 -01014 -01021 -01028 -01033 -01038 -01043

02912 -01259 -01275 -01289 -01302 -01315 -01327 -01339 -01349 -01359 -01368 -01376 -01383 -01389

03897 -01870 -01889 -01908 -01926 -01943 -01959 -01975 -01989 -02003 -02016 -02028 -02040 -02050

04893 -02576 -02600 -02623 -02646 -02668 -02689 -02709 -02728 -02746 -02764 -02780 -02796 -02811

05890 -03382 -03412 -03441 -03470 -03497 -03524 -03550 -03574 -03598 -03621 -03644 -03665 -03685

06903 -04064 -04100 -04136 -04170 -04204 -04236 -04268 -04299 -04329 -04358 -04386 -04413 -04439

07922 -04073 -04110 -04146 -04181 -04214 -04247 -04279 -04310 -04339 -04368 -04396 -04422 -04448

08958 -02968 -02998 -03026 -03053 -03079 -03104 -03128 -03151 -03172 -03192 -03211 -03228 -03245

1 00000 00000 00000 00000 00000 00000 00000 00000 00000 00000 00000 00000 00000

Figure 5 Plot of excess volume expansivity αE of the PEG200 (1) + [PyrMB][BuSO4] (2) binary

system versus mole fraction x1 at various temperatures

Typical concentration dependencies of excess volume expansivity are given in Figure 5 for the

PEG200 + [PyrMB][BuSO4] binary system The values of excess thermal coefficient αE are found to

x1

00 02 04 06 08 10

10

4

E K

-1

-04

-03

-02

-01

00

29315 K

30315 K

31315 K

32315 K

33315 K

34315 K

35315 K

Temp

Int J Electrochem Sci Vol 8 2013

5076

be negative over the whole composition range for the binary system at 29315 ~ 35315 K The curves

are asymmetrical with the minimum located at the IL mole fraction of about 08 In general negative

αE values indicate the presence of strong interaction between the components in the mixtures [67] The

trends observed in αE values for the present mixtures suggest the formation of H-bonding between

unlike molecules which is stronger in PEG200 + [PyrMB][BuSO4] binary system The increasing

negative αE values for PEG200 + [PyrMB][BuSO4] with increase in temperature indicate enhanced

unlike interaction between components of the mixture that is more destruction of order during mixing

contributes negatively to αE

33 Viscosity

Since ILs are more viscous than conventional solvents in most applications they can be used in

mixtures with other less viscous compounds Therefore the viscosity of pure ILs and their mixtures

with PEG oligomer (or conventional solvents) is an important property and their knowledge is

primordial for each industrial processes [6869] The measured dynamic viscosities for the neat

PEG200 neat [PyrMB][BuSO4] and PEG200 + [PyrMB][BuSO4] binary mixture as a function of

temperature over the whole composition range are shown in Figure 6 and their data are listed in Table

5 the viscosities of the mixtures decrease rapidly when PEG oligomer are added to the ionic liquid

especially at lower temperatures The fitting lines in Figure 6 were calculated with the following

fourth-order polynomial equation

= c0 + c1 x1 + c2 x12 + c3 x1

3 + c4 x1

4 (9)

where x1 is the mole fractions of PEG200 and c0 c1 c2 c3 and c4 refer to the fit coefficients

The parameters of correlation are shown in Table 6

Figure 6 Dynamic viscosity for the PEG200 (1) + [PyrMB][BuSO4] (2) binary system as a

function of mole fractions of the PEG200 at different temperatures Lines represent the

polynomial correlation

x1

00 02 04 06 08 10

mP

a s

0

200

400

600

800

1000

1200

1400

29315 K

30315 K

31315 K

32315 K

33315 K

34315 K

35315 K

Int J Electrochem Sci Vol 8 2013

5077

Table 5 Experimental dynamic viscosity (η) and viscosity deviation (Δη) for the binary system

PEG200 (1) + [PyrMB][BuSO4] (2)

x1

29315 29815 30315 30815 31315 31815 32315 32815 33315 33815 34315 34815 35315

ηmPamiddots

0 13209 9343 6745 4961 3712 2821 2176 1700 1345 1077 871 712 587

01452 5907 4362 3294 2539 1992 1589 1286 1055 876 735 623 533 460

01942 4656 3475 2656 2072 1647 1331 1091 907 763 649 557 483 422

02912 3134 2395 1870 1489 1205 991 826 697 594 512 445 390 345

03897 2367 1846 1463 1177 959 792 660 557 474 406 351 306 269

04893 1799 1396 1104 887 723 598 501 424 362 312 272 238 210

05890 1540 1194 941 753 611 502 418 351 298 255 220 191 167

06903 1185 926 736 594 485 402 336 284 242 209 181 158 139

07922 954 742 589 475 389 323 271 231 198 172 150 132 117

08958 811 639 512 415 342 285 240 204 175 151 132 116 102

1 629 505 410 337 280 235 199 170 146 126 110 97 85

ΔηmPamiddots

0 00 00 00 00 00 00 00 00 00 00 00 00 00

01452 -5475 -3698 -2530 -1751 -1221 -857 -602 -423 -295 -204 -137 -89 -54

01942 -6111 -4152 -2859 -1991 -1398 -988 -700 -496 -347 -244 -166 -110 -68

02912 -6411 -4374 -3030 -2126 -1507 -1077 -774 -558 -391 -288 -204 -142 -103

03897 -5940 -4053 -2813 -1982 -1415 -1022 -745 -547 -405 -300 -223 -166 -123

04893 -5254 -3622 -2541 -1811 -1255 -957 -708 -528 -396 -299 -227 -173 -131

05890 -4260 -2944 -2073 -1484 -1034 -796 -594 -448 -341 -262 -203 -158 -124

06903 -3340 -2316 -1636 -1176 -826 -634 -475 -360 -275 -212 -165 -129 -101

07922 -2289 -1599 -1138 -823 -579 -449 -320 -257 -197 -152 -118 -92 -72

08958 -1129 -787 -559 -404 -277 -220 -152 -126 -96 -74 -58 -45 -35

1 00 00 00 00 00 00 00 00 00 00 00 00 00

Table 6 Coefficients of polynomiala for the correlation of the viscosity ( mPa s) in function of

concentration at different temperatures of the binary systems PEG200 (1) + [PyrMB][BuSO4]

(2)

TK c0 mPa s c1 mPa s c2 mPa s c3 mPa s C4 mPa s

29315 13154 -68701 15960 -16688 63543 1075

29815 93069 -46703 10681 -11113 42269 727

30315 67211 -32185 72085 -74396 28222 497

30815 49454 -22431 48886 -49866 18828 343

31315 37016 -15772 33175 -33281 12474 238

31815 28146 -1116 22406 -21947 81322 165

32315 21713 -7923 14947 -1413 51409 114

32815 16975 -56244 97349 -870 30666 077

33315 13435 -39753 60667 -4908 16219 051

33815 10756 -27812 34718 -22519 61382 033

34315 87026 -19098 16304 -39091 -88892 021

34815 71108 -12698 32285 90904 -5763 016

35315 58636 -79728 -60345 18103 -91096 017 a = c0 + c1 x1 + c2 x1

2 + c3 x1

3 + c4 x1

4

The temperature dependence becomes distinctly nonlinear especially at high [PyrMB][BuSO4]

content The Vogel-Tammann-Fulcher (VTF) equation [70-75] suitably correlates the nonlinear

behavior as a function of the temperature not only the viscosities of the neat IL but also the viscosities

of the mixtures for the binary systems through the composition range

Int J Electrochem Sci Vol 8 2013

5078

exp[ ]( )

o

o

B

T T

(10)

where ηo B and To are constants The parameter To is the ideal glass transition temperature which

should be slightly below the experimental glass transition temperature Tg [76] The adjustable

parameters obtained from the VTF correlation were presented in Table 7 The obtained parameters o

and B change smoothly with composition for binary mixtures

Table 7 The VTF equation parameters of viscosity ( 1 exp[ ]( )

o

o

B

T T

) and conductivity

(

exp[ ]( )

o

o

B

T T

) for neat PEG200 (x1 = 1) [PyrMB][BuSO4] (x1 = 0) and binary system

PEG200 (1) + [PyrMB][BuSO4] (2)

x1

ηo (mPa s) To (K) B (K) R2a

o (mS cm-1

) To (K) Brsquo (K) R2a

0 027 1810 9540 0999 792 1788 6854 0999

01452 026 1712 9413 0999 577 1699 6268 0999

01942 043 1788 7975 0999 401 1792 5297 0999

02912 053 1794 7264 0999 521 1662 6031 0999

03897 026 1629 8902 0999 274 1803 4381 0999

04893 023 1666 8455 0999 177 1951 3272 0999

05890 015 1648 8865 0999 216 1883 3672 0999

06903 015 1647 8572 0999 88 2174 2000 0999

07922 017 1717 7702 0999 92 2020 2578 0999

08958 012 1642 8360 0999 43 2110 2088 0999

1 014 1649 7868 0999 556 1928 9815 0999

a Correlation coefficient

The viscosities of the mixtures decrease rapidly when organic oligomers are added to the ionic

liquid this decrease is particularly evident in dilute solutions of organic oligomers in the ionic liquid

The strong coulomb interactions between the [BuSO4]- anion and [PyrMB]

+ cation are weakened upon

mixing with the polar organic oligomers which leads to a higher mobility of the ions and a lower

viscosity of the mixtures [77] This indicates that the viscosity of ILs could be therefore tuned for

several applications by adding an organic solvent or by changing temperature [78]

Due to the wide range of possible molecular interactions between the two components

deviations can occur from ideal behavior These viscosity deviations can be quantified by the viscosity

deviation Δη also known as ldquoexcess viscosityrdquo in other sources

1 1 2 2 (mPa s) x x (11)

Int J Electrochem Sci Vol 8 2013

5079

where x1 and x2 are the mole fractions of PEG200 and [PyrMB][BuSO4] respectively and 1

and 2 are the viscosities (mPa middot s) of the solution the pure solvent and the pure IL respectively

Figure 7 shows the viscosity deviations as a function of the PEG200 mole fraction composition x1 and

temperature for the PEG200 + [PyrMB][BuSO4] binary mixture The values of viscosity deviations

are compared with those obtained from the RedlichndashKister polynomial equation The viscosity

deviation for the mixture show negative deviations from ideality over the whole mole fraction range

Figure 7 also shows that the negative values of viscosity deviations decrease with increasing

temperature this can be attributed to the specific interactions in mixtures typically hydrogen bonds break-

up as the temperature increases [79] The minimum value of Δη is observed at about x1 asymp 03 and the

viscosity deviation depends on molecular interactions as well as on the size and shape of the molecules

[80]

Figure 7 Viscosity deviations Δη versus the mole fraction at various temperatures for the binary

mixture PEG200 (1) + [PyrMB][BuSO4] (2)

34 Conductivity

The experimental data of conductivity of the neat ILs [PyrMB][BuSO4] neat PEG200 and

binary system are plotted against the x1 at various temperatures in Figure 8 together with lines

calculated with the four-order polynomial equation

= d0 + d1 x1 + d2 x12 + d3 x1

3 + d4 x1

4 (12)

where x1 is the mole fractions of PEG200 and d0 d1 d2 d3 and d4 refer to the fit coefficients

The parameters of correlation are shown in Table 8 The conductivities of neat IL [PyrMB][BuSO4]

neat PEG200 and binary system at various temperatures were fitted using the VTF equation

exp[ ]

( )o

o

B

T T

(13)

x1

00 02 04 06 08 10

m

Pa s

-700

-600

-500

-400

-300

-200

-100

0

29315 K

30315 K

31315 K

32315 K

33315 K

34315 K

35315 K

Int J Electrochem Sci Vol 8 2013

5080

where T is the absolute temperature and Brsquo and To are adjustable parameters The best-fit

mS cm-1 Brsquo (K) and To (K) parameters are given in Table 7 Neat [PyrMB][BuSO4] neat

PEG200 and binary system were very well fit by the VTF model over the temperature range studied

Figure 8 Plot of conductivity of the PEG200 (1) + [PyrMB][BuSO4] (2) binary system versus

mole fraction x1 at various temperatures

Table 8 Coefficients of polynomiala for the correlation of the conductivity ( mS cm

-1) in function

of concentration at different temperatures of the binary systems PEG200 (1) +

[PyrMB][BuSO4] (2)

TK d0 mS cm

-1 d1 mS cm

-1 d2 mS cm

-1 d3 mS cm

-1 d4 mS cm

-1

29315 02019 09622 -01679 0734 -17284 00095

29815 02588 11031 -02503 09086 -20181 00109

30315 03255 12119 -01935 08565 -21971 00125

30815 04025 13165 -01329 0767 -23477 00141

31315 04904 13712 01238 03677 -23439 00156

31815 05894 15032 -00006 04737 -25518 00171

32315 06999 15802 00743 0265 -25986 00188

32815 08221 16427 01595 00089 -26032 00208

33315 09562 16373 04858 -06207 -24165 00233

a = d0 + d1 x1 + d2 x1

2 + d3 x1

3 + d4 x1

4

As shown in Figure 8 it can be seen that the conductivity of the binary mixture increases with

increasing amount of PEG200 goes through a maximum and then goes down to the specific

conductivity of the neat PEG200 The conductivity is related to the ion mobility and the number of

charge carriers [81] At a fixed concentration the ions move faster at higher temperature due to the

relatively lower viscosity of the mixture On the other hand the composition influences both the ion

mobility and the number of charge carriers at a fixed temperature At the beginning the number of

charge and the ion mobility increase with increasing PEG oligomer composition the maximum of

conductivity is located at x1 = 059 and corresponds to a value of 171 mS cmminus 1

at 33315 K It can also

be observed that the conductivity increases as the temperature increases The higher temperature may

x1

00 02 04 06 08 10

mS

cm

-1

00

05

10

15

20

29315 K

29815 K

30315 K

30815 K

31315 K

31815 K

32315 K

32815 K

33315 K

Int J Electrochem Sci Vol 8 2013

5081

weaken the influence of aggregation to the conductivity which suggests that a higher temperature is

better for the ILs to act as electrolytes

Table 9 RedlickndashKister fitting coefficients Ak and the standard deviation of the VE and ∆for the

binary mixture of PEG200 (1) + [PyrMB][BuSO4] (2) system

TK A0 A1 A2 A3 A4

VEcm

3 mol

-1

29315 -5979 -4906 6585 5754 -1717 002687

29815 -6200 -4760 6464 5767 -2022 002693

30315 -6408 -4612 6345 5774 -2276 002698

30815 -6602 -4461 6229 5774 -2476 002701

31315 -6782 -4310 6116 5767 -2623 002701

31815 -6948 -4155 6006 5753 -2716 002699

32315 -7100 -3999 5899 5732 -2754 002692

32815 -7239 -3840 5795 5704 -2738 002683

33315 -7363 -3679 5694 5669 -2666 002670

33815 -7472 -3515 5596 5626 -2538 002654

34315 -7568 -3350 5501 5576 -2353 002634

34815 -7648 -3182 5409 5518 -2111 002611

35315 -7714 -3011 5320 5452 -1812 002586

∆mPa s

29315 -20414 -17226 -15592 -95544 -75863 399496

29815 -14035 -11558 -10713 -62192 19493 340180

30315 -98261 -78407 -73734 -40709 58145 286725

30815 -69922 -53591 -50601 -2676 67556 235258

31315 -48876 -39537 -41051 -14118 16739 079245

31815 -36917 -25169 -22939 -11646 51047 146189

32315 -27415 -1721 -12581 -92603 21498 104339

32815 -20441 -11703 -77538 -38334 -81478 090708

33315 -15382 -67274 -31134 -47585 -18255 059539

33815 -11664 -44928 -15533 -22312 -05591 037855

34315 -89038 -24163 68654 -15007 -10347 024263

34815 -68279 -91813 23131 -10367 -18636 017759

35315 -52525 -24051 26474 15498 -85341 018640

35 Redlich-Kister Equation for Binary System

The binary excess property ( E

mV ) and deviations (Δ) at several temperatures were fitted to a

Redlich-Kister-type equation [82]

1 1 1

0

(or ) (1 ) (1 2 )j

E i

i

i

Y Y x x A x

(14)

Int J Electrochem Sci Vol 8 2013

5082

where ΔY (YE) represents E

mV (cm3 mol

minus1) and Δ

(mPa s)x1 denotes the mole fraction of

PEG200 Ai represents the polynomial coefficients and j is the degree of the polynomial expansion

The correlated results for excess molar volumes ( E

mV ) viscosity deviations (Δ) including the values

of the fitting parameters Ai together with the standard deviation σ are given in Table 9 where the

tabulated standard deviation σ [83] is defined as

2

exp cal 1 2( )

[ ]Y Y

m n

(15)

where m is the number of experimental data points and n is the number of estimated

parameters The subscripts ldquoexprdquo and ldquocalrdquo denote the values of the experimental and calculated

property respectively As shown in Table 9 the experimentally derived E

mV and Δη values were

correlated satisfactorily by the Redlich-Kister equation

4 CONCLUSIONS

This paper is a systematic characterizations of thermophysical properties for IL binary system

Density viscosity and conductivity for (PEG200 + [PyrMB][BuSO4]) binary system are presented as a

function of temperature at atmospheric pressure it was demonstrated that viscosity and conductivity

were more sensitive to the changes in PEG content or temperature than density and the viscosity and

conductivity of pure IL and (PEG200 + [PyrMB][BuSO4]) binary system at different temperature are

fitted using the VogelndashTammannndashFulcher (VTF) equation with good accuracy The excess molar

volumes excess volume expansivity and viscosity deviations show negative deviations from the ideal

solution the results are interpreted in terms of molecular interactions in the (PEG200 +

[PyrMB][BuSO4]) binary mixture The conductivity increases to a maximum value when the

concentration of PEG200 is increased and decreases after the maximum the data obtained will be

helpful for the application of the ionic liquids as electrolytes and also useful for the ionic liquids

database

ACKNOWLEDGEMENTS

The authors would like to thank the National Science Council of the Republic of China for financially

supporting this project

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2 TY Wu IW Sun ST Gung MW Lin BK Chen HP Wang SG Su J Taiwan Inst Chem

Eng 42 (2011) 513

Int J Electrochem Sci Vol 8 2013

5083

3 TY Wu SG Su KF Lin YC Lin HP Wang MW Lin ST Gung IW Sun Electrochim

Acta 56 (2011) 7278

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7 TY Wu SG Su HP Wang YC Lin ST Gung MW Lin IW Sun Electrochim Acta 56

(2011) 3209

8 IW Sun YC Lin BK Chen CW Kuo CC Chen SG Su PR Chen TY Wu Int J

Electrochem Sci 7 (2012) 7206

9 TY Wu SG Su ST Gung MW Lin YC Lin CA Lai IW Sun Electrochim Acta 55

(2010) 4475

10 AN Soriano AM Agapito LJLI Lagumbay AR Caparanga MH Li J Taiwan Inst Chem

Eng 42 (2011) 258

11 TY Wu IW Sun ST Gung BK Chen HP Wang SG Su J Taiwan Inst Chem Eng 42

(2011) 874

12 S Ibrahim MR Johan Int J Electrochem Sci 6 (2011) 5565

13 TY Wu SG Su YC Lin HP Wang MW Lin ST Gung IW Sun Electrochim Acta 56

(2010) 853

14 H Wang LX Wu YC Lan JQ Zhao JX Lu Int J Electrochem Sci 6 (2011) 4218

15 FF Liu SQ Liu QJ Feng SX Zhuang JB Zhang P Bu Int J Electrochem Sci 7 (2012)

4381

16 HA Barham SA Brahim Y Rozita KA Mohamed Int J Electrochem Sci 6 (2011) 181

17 SK Shukla LC Murulana EE Ebenso Int J Electrochem Sci 6 (2011) 4286

18 NV Likhanova O Olivares-Xometl D Guzman-Lucero MA Dominguez-Aguilar N Nava

M Corrales-Luna MC Mendoza Int J Electrochem Sci 6 (2011) 4514

19 A Zarrouk M Messali H Zarrok R Salghi AA Ali B Hammouti SS Al-Deyab F Bentiss

Int J Electrochem Sci 7 (2012) 6998

20 BS Ali BH Ali R Yusoff MK Aroua Int J Electrochem Sci 7 (2012) 3835

21 MH Lin YJ Liu ZH Yang YB Huang ZH Sun Y He CL Ni Int J Electrochem Sci 7

(2012) 965

22 CH Su MH Chung HJ Hsieh YK Chang JC Ding HM Wu J Taiwan Inst Chem Eng

43 (2012) 573

23 H Shekaari A Kazempour J Taiwan Inst Chem Eng 43 (2012) 650

24 ZJ Wei Y Li D Thushara YX Liu QL Ren J Taiwan Inst Chem Eng 43 (2012) 363

25 GQ Zhang HW Yang JF Gao HK Zhang CB Zheng YL Cao YH Wang KQ Ding

Int J Electrochem Sci 7 (2012) 7547

26 P Norouzi MR Ganjali F Faridbod SJ Shahtaheri HA Zamani Int J Electrochem Sci 7

(2012) 2633

27 F Faridbod MR Ganjali M Hosseini P Norouzi Int J Electrochem Sci 7 (2012) 1927

28 MR Ganjali Z Rafiei-Sarmazdeh T Poursaberi SJ Shahtaheri P Norouzi Int J

Electrochem Sci 7 (2012) 1908

29 A Babaei DJ Garrett AJ Downard Int J Electrochem Sci 7 (2012) 3141

30 MR Ganjali T Alizade P Norouzi Int J Electrochem Sci 7 (2012) 4800

31 MR Ganjali T Alizade B Larijani F Faridbod P Norouzi Int J Electrochem Sci 7 (2012)

4756

32 P Norouzi B Larijani MR Ganjali Int J Electrochem Sci 7 (2012) 7313

33 TY Wu MH Tsao SG Su HP Wang YC Lin FL Chen CW Chang IW Sun J Braz

Chem Soc 22 (2011) 780

34 MH Tsao TY Wu HP Wang IW Sun SG Su YC Lin CW Chang Mater Lett 65

(2011) 583

Int J Electrochem Sci Vol 8 2013

5084

35 SY Ku SY Lu Int J Electrochem Sci 6 (2011) 5219

36 TY Wu MH Tsao FL Chen SG Su CW Chang HP Wang YC Lin IW Sun J Iran

Chem Soc 7 (2010) 707

37 IW Sun HP Wang H Teng SG Su YC Lin CW Kuo PR Chen TY Wu Int J

Electrochem Sci 7 (2012) 9748

38 TY Wu MH Tsao FL Chen SG Su CW Chang HP Wang YC Lin WC Ou-Yang

IW Sun Int J Mol Sci 11 (2010) 329

39 YX An PJ Zuo XQ Cheng LX Liao GP Yin Int J Electrochem Sci 6 (2011) 2398

40 LC Xuan YX An W Fang LX Liao YL Ma ZY Ren GP Yin Int J Electrochem Sci

6 (2011) 6590

41 HM Wang SQ Liu K Huang XG Yin YN Liu SJ Peng Int J Electrochem Sci 7

(2012) 1688

42 HM Wang SQ Liu NF Wang YN Liu Int J Electrochem Sci 7 (2012) 7579

43 H Ganjali MR Ganjali T Alizadeh F Faridbod P Norouzi Int J Electrochem Sci 6 (2011)

6085

44 MR Ganjali MH Eshraghi S Ghadimi SM Moosavi M Hosseini H Haji-Hashemi P

Norouzi Int J Electrochem Sci 6 (2011) 739

45 MR Ganjali T Poursaberi M Khoobi A Shafiee M Adibi M Pirali-Hamedani P Norouzi

Int J Electrochem Sci 6 (2011) 717

46 P Norouzi M Hosseini MR Ganjali M Rezapour M Adibi Int J Electrochem Sci 6 (2011)

2012

47 MR Ganjali MR Moghaddam M Hosseini P Norouzi Int J Electrochem Sci 6 (2011)

1981

48 MR Ganjali M Hosseini M Pirali-Hamedani HA Zamani Int J Electrochem Sci 6 (2011)

2808

49 MR Ganjali M Rezapour SK Torkestani H Rashedi P Norouzi Int J Electrochem Sci 6

(2011) 2323

50 P Norouzi M Pirali-Hamedani SO Ranaei-Siadat MR Ganjali Int J Electrochem Sci 6

(2011) 3704

51 F Faridbod HA Zamani M Hosseini M Pirali-Hamedani MR Ganjali P Norouzi Int J

Electrochem Sci 6 (2011) 3694

52 MR Ganjali SO Ranaei-Siadat H Rashedi M Rezapour P Norouzi Int J Electrochem Sci

6 (2011) 3684

53 TH Tsai KC Lin SM Chen Int J Electrochem Sci 6 (2011) 2672

54 MR Ganjali T Alizadeh F Azimi B Larjani F Faridbod P Norouzi Int J Electrochem

Sci 6 (2011) 5200

55 R Mirshafian MR Ganjali P Norouzi Int J Electrochem Sci 7 (2012) 1656

56 J Gao JG Liu WM Liu B Li YC Xin Y Yin ZG Zou Int J Electrochem Sci 6 (2011)

6115

57 TY Wu BK Chen L Hao KF Lin IW Sun J Taiwan Inst Chem Eng 42 (2011) 914

58 TY Wu BK Chen L Hao CW Kuo IW Sun J Taiwan Inst Chem Eng 43 (2012) 313

59 SW Peng AN Soriano RB Leron MH Li J Taiwan Inst Chem Eng 42 (2011) 233

60 TY Wu IW Sun MW Lin BK Chen CW Kuo HP Wang YY Chen SG Su J Taiwan

Inst Chem Eng 43 (2012) 58

61 TY Wu BK Chen CW Kuo L Hao YC Peng IW Sun J Taiwan Inst Chem Eng 43

(2012) 860

62 A Arce H Rodriguez A Soto Green Chem 9 (2007) 247

63 TY Wu HC Wang SG Su ST Gung MW Lin CB Lin J Taiwan Inst Chem Eng 41 (2010)

315 64 X Li M Hou Z Zhang B Han G Yang X Wang L Zou Green Chem 10 (2008) 879

Int J Electrochem Sci Vol 8 2013

5085

65 J Chen SK Spear JG Huddleston RD Rogers Green Chem 7 (2005) 64

66 U Domanska M Laskowska J Solution Chem 38 (2009) 779

67 K Tamura M Nakamura S Murakami J Solution Chem 26 (1997) 1199

68 Z Yu H Gao H Wang L Chen J Chem Eng Data 56 (2011) 2877

69 KN Marsh JA Boxall R Lichtenthaler Fluid Phase Equilib 219 (2004) 93

70 TY Wu SG Su ST Gung MW Lin YC Lin WC Ou-Yang IW Sun CA Lai J Iran

Chem Soc 8 (2011) 149

71 TY Wu L Hao CW Kuo YC Lin SG Su PL Kuo IW Sun Int J Electrochem Sci 7

(2012) 2047

72 TY Wu L Hao PR Chen JW Liao Int J Electrochem Sci 8 (2013) 2606

73 CW Kuo CW Huang BK Chen WB Li PR Chen TH Ho CG Tseng TY Wu Int J

Electrochem Sci 8 (2013) 3834

74 CW Kuo WB Li PR Chen JW Liao CG Tseng TY Wu Int J Electrochem Sci 8

(2013) 5007

75 TY Wu BK Chen L Hao YC Lin HP Wang CW Kuo IW Sun Int J Mol Sci 12

(2011) 8750

76 H Rodriguez JF Brennecke J Chem Eng Data 51 (2006) 2145

77 Y Tian X Wang J Wang J Chem Eng Data 53 (2008) 2056

78 TY Wu HC Wang SG Su ST Gung MW Lin CB Lin J Chin Chem Soc 57 (2010)

44

79 TY Wu BK Chen L Hao YC Peng IW Sun Int J Mol Sci 12 (2011) 2598

80 H Eyring MS John Significant Liquid Structure Wiley New York 1969

81 H Every AG Bishop M Forsyth DR MacFarlane Electrochim Acta 45 (2000) 1279 82 O Redlich AT Kister Ind Eng Chem 40 (1948) 345

83 A Paul P Kumar A Samanta J Phys Chem B 109 (2005) 9148

copy 2013 by ESG (wwwelectrochemsciorg)

Int J Electrochem Sci Vol 8 2013

5075

where Vmi is the molar volume of pure component i

Table 4 Experimental volume expansivity (α) and the excess volume expansivity (αE) for the binary

system PEG200 (1) + [PyrMB][BuSO4] (2)

x1

29315 29815 30315 30815 31315 31815 32315 32815 33315 33815 34315 34815 35315

104 αK-1

0 51245 51380 51516 51651 51787 51922 52058 52193 52329 52464 52600 52735 52871

01452 52053 52189 52325 52462 52600 52739 52878 53018 53159 53300 53443 53586 53730

01942 52438 52576 52715 52854 52994 53135 53276 53418 53561 53705 53850 53995 54141

02912 53299 53443 53586 53731 53877 54023 54170 54318 54466 54616 54766 54917 55069

03897 53973 54120 54268 54417 54567 54717 54869 55021 55174 55328 55483 55638 55795

04893 54667 54818 54971 55124 55278 55433 55589 55745 55903 56061 56221 56381 56542

05890 55372 55527 55683 55840 55998 56157 56317 56477 56639 56801 56965 57129 57294

06903 56358 56517 56677 56838 57000 57163 57327 57492 57657 57824 57992 58160 58330

07922 58175 58344 58515 58687 58860 59033 59208 59384 59561 59739 59918 60098 60279

08958 61313 61502 61691 61882 62074 62268 62462 62658 62855 63053 63252 63453 63655

1 66532 66763 66993 67224 67455 67685 67916 68146 68377 68607 68838 69069 69299

104 αEK-1

0 00000 00000 00000 00000 00000 00000 00000 00000 00000 00000 00000 00000 00000

01452 -00762 -00772 -00782 -00792 -00800 -00808 -00815 -00822 -00827 -00832 -00837 -00840 -00843

01942 -00942 -00954 -00966 -00977 -00987 -00997 -01006 -01014 -01021 -01028 -01033 -01038 -01043

02912 -01259 -01275 -01289 -01302 -01315 -01327 -01339 -01349 -01359 -01368 -01376 -01383 -01389

03897 -01870 -01889 -01908 -01926 -01943 -01959 -01975 -01989 -02003 -02016 -02028 -02040 -02050

04893 -02576 -02600 -02623 -02646 -02668 -02689 -02709 -02728 -02746 -02764 -02780 -02796 -02811

05890 -03382 -03412 -03441 -03470 -03497 -03524 -03550 -03574 -03598 -03621 -03644 -03665 -03685

06903 -04064 -04100 -04136 -04170 -04204 -04236 -04268 -04299 -04329 -04358 -04386 -04413 -04439

07922 -04073 -04110 -04146 -04181 -04214 -04247 -04279 -04310 -04339 -04368 -04396 -04422 -04448

08958 -02968 -02998 -03026 -03053 -03079 -03104 -03128 -03151 -03172 -03192 -03211 -03228 -03245

1 00000 00000 00000 00000 00000 00000 00000 00000 00000 00000 00000 00000 00000

Figure 5 Plot of excess volume expansivity αE of the PEG200 (1) + [PyrMB][BuSO4] (2) binary

system versus mole fraction x1 at various temperatures

Typical concentration dependencies of excess volume expansivity are given in Figure 5 for the

PEG200 + [PyrMB][BuSO4] binary system The values of excess thermal coefficient αE are found to

x1

00 02 04 06 08 10

10

4

E K

-1

-04

-03

-02

-01

00

29315 K

30315 K

31315 K

32315 K

33315 K

34315 K

35315 K

Temp

Int J Electrochem Sci Vol 8 2013

5076

be negative over the whole composition range for the binary system at 29315 ~ 35315 K The curves

are asymmetrical with the minimum located at the IL mole fraction of about 08 In general negative

αE values indicate the presence of strong interaction between the components in the mixtures [67] The

trends observed in αE values for the present mixtures suggest the formation of H-bonding between

unlike molecules which is stronger in PEG200 + [PyrMB][BuSO4] binary system The increasing

negative αE values for PEG200 + [PyrMB][BuSO4] with increase in temperature indicate enhanced

unlike interaction between components of the mixture that is more destruction of order during mixing

contributes negatively to αE

33 Viscosity

Since ILs are more viscous than conventional solvents in most applications they can be used in

mixtures with other less viscous compounds Therefore the viscosity of pure ILs and their mixtures

with PEG oligomer (or conventional solvents) is an important property and their knowledge is

primordial for each industrial processes [6869] The measured dynamic viscosities for the neat

PEG200 neat [PyrMB][BuSO4] and PEG200 + [PyrMB][BuSO4] binary mixture as a function of

temperature over the whole composition range are shown in Figure 6 and their data are listed in Table

5 the viscosities of the mixtures decrease rapidly when PEG oligomer are added to the ionic liquid

especially at lower temperatures The fitting lines in Figure 6 were calculated with the following

fourth-order polynomial equation

= c0 + c1 x1 + c2 x12 + c3 x1

3 + c4 x1

4 (9)

where x1 is the mole fractions of PEG200 and c0 c1 c2 c3 and c4 refer to the fit coefficients

The parameters of correlation are shown in Table 6

Figure 6 Dynamic viscosity for the PEG200 (1) + [PyrMB][BuSO4] (2) binary system as a

function of mole fractions of the PEG200 at different temperatures Lines represent the

polynomial correlation

x1

00 02 04 06 08 10

mP

a s

0

200

400

600

800

1000

1200

1400

29315 K

30315 K

31315 K

32315 K

33315 K

34315 K

35315 K

Int J Electrochem Sci Vol 8 2013

5077

Table 5 Experimental dynamic viscosity (η) and viscosity deviation (Δη) for the binary system

PEG200 (1) + [PyrMB][BuSO4] (2)

x1

29315 29815 30315 30815 31315 31815 32315 32815 33315 33815 34315 34815 35315

ηmPamiddots

0 13209 9343 6745 4961 3712 2821 2176 1700 1345 1077 871 712 587

01452 5907 4362 3294 2539 1992 1589 1286 1055 876 735 623 533 460

01942 4656 3475 2656 2072 1647 1331 1091 907 763 649 557 483 422

02912 3134 2395 1870 1489 1205 991 826 697 594 512 445 390 345

03897 2367 1846 1463 1177 959 792 660 557 474 406 351 306 269

04893 1799 1396 1104 887 723 598 501 424 362 312 272 238 210

05890 1540 1194 941 753 611 502 418 351 298 255 220 191 167

06903 1185 926 736 594 485 402 336 284 242 209 181 158 139

07922 954 742 589 475 389 323 271 231 198 172 150 132 117

08958 811 639 512 415 342 285 240 204 175 151 132 116 102

1 629 505 410 337 280 235 199 170 146 126 110 97 85

ΔηmPamiddots

0 00 00 00 00 00 00 00 00 00 00 00 00 00

01452 -5475 -3698 -2530 -1751 -1221 -857 -602 -423 -295 -204 -137 -89 -54

01942 -6111 -4152 -2859 -1991 -1398 -988 -700 -496 -347 -244 -166 -110 -68

02912 -6411 -4374 -3030 -2126 -1507 -1077 -774 -558 -391 -288 -204 -142 -103

03897 -5940 -4053 -2813 -1982 -1415 -1022 -745 -547 -405 -300 -223 -166 -123

04893 -5254 -3622 -2541 -1811 -1255 -957 -708 -528 -396 -299 -227 -173 -131

05890 -4260 -2944 -2073 -1484 -1034 -796 -594 -448 -341 -262 -203 -158 -124

06903 -3340 -2316 -1636 -1176 -826 -634 -475 -360 -275 -212 -165 -129 -101

07922 -2289 -1599 -1138 -823 -579 -449 -320 -257 -197 -152 -118 -92 -72

08958 -1129 -787 -559 -404 -277 -220 -152 -126 -96 -74 -58 -45 -35

1 00 00 00 00 00 00 00 00 00 00 00 00 00

Table 6 Coefficients of polynomiala for the correlation of the viscosity ( mPa s) in function of

concentration at different temperatures of the binary systems PEG200 (1) + [PyrMB][BuSO4]

(2)

TK c0 mPa s c1 mPa s c2 mPa s c3 mPa s C4 mPa s

29315 13154 -68701 15960 -16688 63543 1075

29815 93069 -46703 10681 -11113 42269 727

30315 67211 -32185 72085 -74396 28222 497

30815 49454 -22431 48886 -49866 18828 343

31315 37016 -15772 33175 -33281 12474 238

31815 28146 -1116 22406 -21947 81322 165

32315 21713 -7923 14947 -1413 51409 114

32815 16975 -56244 97349 -870 30666 077

33315 13435 -39753 60667 -4908 16219 051

33815 10756 -27812 34718 -22519 61382 033

34315 87026 -19098 16304 -39091 -88892 021

34815 71108 -12698 32285 90904 -5763 016

35315 58636 -79728 -60345 18103 -91096 017 a = c0 + c1 x1 + c2 x1

2 + c3 x1

3 + c4 x1

4

The temperature dependence becomes distinctly nonlinear especially at high [PyrMB][BuSO4]

content The Vogel-Tammann-Fulcher (VTF) equation [70-75] suitably correlates the nonlinear

behavior as a function of the temperature not only the viscosities of the neat IL but also the viscosities

of the mixtures for the binary systems through the composition range

Int J Electrochem Sci Vol 8 2013

5078

exp[ ]( )

o

o

B

T T

(10)

where ηo B and To are constants The parameter To is the ideal glass transition temperature which

should be slightly below the experimental glass transition temperature Tg [76] The adjustable

parameters obtained from the VTF correlation were presented in Table 7 The obtained parameters o

and B change smoothly with composition for binary mixtures

Table 7 The VTF equation parameters of viscosity ( 1 exp[ ]( )

o

o

B

T T

) and conductivity

(

exp[ ]( )

o

o

B

T T

) for neat PEG200 (x1 = 1) [PyrMB][BuSO4] (x1 = 0) and binary system

PEG200 (1) + [PyrMB][BuSO4] (2)

x1

ηo (mPa s) To (K) B (K) R2a

o (mS cm-1

) To (K) Brsquo (K) R2a

0 027 1810 9540 0999 792 1788 6854 0999

01452 026 1712 9413 0999 577 1699 6268 0999

01942 043 1788 7975 0999 401 1792 5297 0999

02912 053 1794 7264 0999 521 1662 6031 0999

03897 026 1629 8902 0999 274 1803 4381 0999

04893 023 1666 8455 0999 177 1951 3272 0999

05890 015 1648 8865 0999 216 1883 3672 0999

06903 015 1647 8572 0999 88 2174 2000 0999

07922 017 1717 7702 0999 92 2020 2578 0999

08958 012 1642 8360 0999 43 2110 2088 0999

1 014 1649 7868 0999 556 1928 9815 0999

a Correlation coefficient

The viscosities of the mixtures decrease rapidly when organic oligomers are added to the ionic

liquid this decrease is particularly evident in dilute solutions of organic oligomers in the ionic liquid

The strong coulomb interactions between the [BuSO4]- anion and [PyrMB]

+ cation are weakened upon

mixing with the polar organic oligomers which leads to a higher mobility of the ions and a lower

viscosity of the mixtures [77] This indicates that the viscosity of ILs could be therefore tuned for

several applications by adding an organic solvent or by changing temperature [78]

Due to the wide range of possible molecular interactions between the two components

deviations can occur from ideal behavior These viscosity deviations can be quantified by the viscosity

deviation Δη also known as ldquoexcess viscosityrdquo in other sources

1 1 2 2 (mPa s) x x (11)

Int J Electrochem Sci Vol 8 2013

5079

where x1 and x2 are the mole fractions of PEG200 and [PyrMB][BuSO4] respectively and 1

and 2 are the viscosities (mPa middot s) of the solution the pure solvent and the pure IL respectively

Figure 7 shows the viscosity deviations as a function of the PEG200 mole fraction composition x1 and

temperature for the PEG200 + [PyrMB][BuSO4] binary mixture The values of viscosity deviations

are compared with those obtained from the RedlichndashKister polynomial equation The viscosity

deviation for the mixture show negative deviations from ideality over the whole mole fraction range

Figure 7 also shows that the negative values of viscosity deviations decrease with increasing

temperature this can be attributed to the specific interactions in mixtures typically hydrogen bonds break-

up as the temperature increases [79] The minimum value of Δη is observed at about x1 asymp 03 and the

viscosity deviation depends on molecular interactions as well as on the size and shape of the molecules

[80]

Figure 7 Viscosity deviations Δη versus the mole fraction at various temperatures for the binary

mixture PEG200 (1) + [PyrMB][BuSO4] (2)

34 Conductivity

The experimental data of conductivity of the neat ILs [PyrMB][BuSO4] neat PEG200 and

binary system are plotted against the x1 at various temperatures in Figure 8 together with lines

calculated with the four-order polynomial equation

= d0 + d1 x1 + d2 x12 + d3 x1

3 + d4 x1

4 (12)

where x1 is the mole fractions of PEG200 and d0 d1 d2 d3 and d4 refer to the fit coefficients

The parameters of correlation are shown in Table 8 The conductivities of neat IL [PyrMB][BuSO4]

neat PEG200 and binary system at various temperatures were fitted using the VTF equation

exp[ ]

( )o

o

B

T T

(13)

x1

00 02 04 06 08 10

m

Pa s

-700

-600

-500

-400

-300

-200

-100

0

29315 K

30315 K

31315 K

32315 K

33315 K

34315 K

35315 K

Int J Electrochem Sci Vol 8 2013

5080

where T is the absolute temperature and Brsquo and To are adjustable parameters The best-fit

mS cm-1 Brsquo (K) and To (K) parameters are given in Table 7 Neat [PyrMB][BuSO4] neat

PEG200 and binary system were very well fit by the VTF model over the temperature range studied

Figure 8 Plot of conductivity of the PEG200 (1) + [PyrMB][BuSO4] (2) binary system versus

mole fraction x1 at various temperatures

Table 8 Coefficients of polynomiala for the correlation of the conductivity ( mS cm

-1) in function

of concentration at different temperatures of the binary systems PEG200 (1) +

[PyrMB][BuSO4] (2)

TK d0 mS cm

-1 d1 mS cm

-1 d2 mS cm

-1 d3 mS cm

-1 d4 mS cm

-1

29315 02019 09622 -01679 0734 -17284 00095

29815 02588 11031 -02503 09086 -20181 00109

30315 03255 12119 -01935 08565 -21971 00125

30815 04025 13165 -01329 0767 -23477 00141

31315 04904 13712 01238 03677 -23439 00156

31815 05894 15032 -00006 04737 -25518 00171

32315 06999 15802 00743 0265 -25986 00188

32815 08221 16427 01595 00089 -26032 00208

33315 09562 16373 04858 -06207 -24165 00233

a = d0 + d1 x1 + d2 x1

2 + d3 x1

3 + d4 x1

4

As shown in Figure 8 it can be seen that the conductivity of the binary mixture increases with

increasing amount of PEG200 goes through a maximum and then goes down to the specific

conductivity of the neat PEG200 The conductivity is related to the ion mobility and the number of

charge carriers [81] At a fixed concentration the ions move faster at higher temperature due to the

relatively lower viscosity of the mixture On the other hand the composition influences both the ion

mobility and the number of charge carriers at a fixed temperature At the beginning the number of

charge and the ion mobility increase with increasing PEG oligomer composition the maximum of

conductivity is located at x1 = 059 and corresponds to a value of 171 mS cmminus 1

at 33315 K It can also

be observed that the conductivity increases as the temperature increases The higher temperature may

x1

00 02 04 06 08 10

mS

cm

-1

00

05

10

15

20

29315 K

29815 K

30315 K

30815 K

31315 K

31815 K

32315 K

32815 K

33315 K

Int J Electrochem Sci Vol 8 2013

5081

weaken the influence of aggregation to the conductivity which suggests that a higher temperature is

better for the ILs to act as electrolytes

Table 9 RedlickndashKister fitting coefficients Ak and the standard deviation of the VE and ∆for the

binary mixture of PEG200 (1) + [PyrMB][BuSO4] (2) system

TK A0 A1 A2 A3 A4

VEcm

3 mol

-1

29315 -5979 -4906 6585 5754 -1717 002687

29815 -6200 -4760 6464 5767 -2022 002693

30315 -6408 -4612 6345 5774 -2276 002698

30815 -6602 -4461 6229 5774 -2476 002701

31315 -6782 -4310 6116 5767 -2623 002701

31815 -6948 -4155 6006 5753 -2716 002699

32315 -7100 -3999 5899 5732 -2754 002692

32815 -7239 -3840 5795 5704 -2738 002683

33315 -7363 -3679 5694 5669 -2666 002670

33815 -7472 -3515 5596 5626 -2538 002654

34315 -7568 -3350 5501 5576 -2353 002634

34815 -7648 -3182 5409 5518 -2111 002611

35315 -7714 -3011 5320 5452 -1812 002586

∆mPa s

29315 -20414 -17226 -15592 -95544 -75863 399496

29815 -14035 -11558 -10713 -62192 19493 340180

30315 -98261 -78407 -73734 -40709 58145 286725

30815 -69922 -53591 -50601 -2676 67556 235258

31315 -48876 -39537 -41051 -14118 16739 079245

31815 -36917 -25169 -22939 -11646 51047 146189

32315 -27415 -1721 -12581 -92603 21498 104339

32815 -20441 -11703 -77538 -38334 -81478 090708

33315 -15382 -67274 -31134 -47585 -18255 059539

33815 -11664 -44928 -15533 -22312 -05591 037855

34315 -89038 -24163 68654 -15007 -10347 024263

34815 -68279 -91813 23131 -10367 -18636 017759

35315 -52525 -24051 26474 15498 -85341 018640

35 Redlich-Kister Equation for Binary System

The binary excess property ( E

mV ) and deviations (Δ) at several temperatures were fitted to a

Redlich-Kister-type equation [82]

1 1 1

0

(or ) (1 ) (1 2 )j

E i

i

i

Y Y x x A x

(14)

Int J Electrochem Sci Vol 8 2013

5082

where ΔY (YE) represents E

mV (cm3 mol

minus1) and Δ

(mPa s)x1 denotes the mole fraction of

PEG200 Ai represents the polynomial coefficients and j is the degree of the polynomial expansion

The correlated results for excess molar volumes ( E

mV ) viscosity deviations (Δ) including the values

of the fitting parameters Ai together with the standard deviation σ are given in Table 9 where the

tabulated standard deviation σ [83] is defined as

2

exp cal 1 2( )

[ ]Y Y

m n

(15)

where m is the number of experimental data points and n is the number of estimated

parameters The subscripts ldquoexprdquo and ldquocalrdquo denote the values of the experimental and calculated

property respectively As shown in Table 9 the experimentally derived E

mV and Δη values were

correlated satisfactorily by the Redlich-Kister equation

4 CONCLUSIONS

This paper is a systematic characterizations of thermophysical properties for IL binary system

Density viscosity and conductivity for (PEG200 + [PyrMB][BuSO4]) binary system are presented as a

function of temperature at atmospheric pressure it was demonstrated that viscosity and conductivity

were more sensitive to the changes in PEG content or temperature than density and the viscosity and

conductivity of pure IL and (PEG200 + [PyrMB][BuSO4]) binary system at different temperature are

fitted using the VogelndashTammannndashFulcher (VTF) equation with good accuracy The excess molar

volumes excess volume expansivity and viscosity deviations show negative deviations from the ideal

solution the results are interpreted in terms of molecular interactions in the (PEG200 +

[PyrMB][BuSO4]) binary mixture The conductivity increases to a maximum value when the

concentration of PEG200 is increased and decreases after the maximum the data obtained will be

helpful for the application of the ionic liquids as electrolytes and also useful for the ionic liquids

database

ACKNOWLEDGEMENTS

The authors would like to thank the National Science Council of the Republic of China for financially

supporting this project

References

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2 TY Wu IW Sun ST Gung MW Lin BK Chen HP Wang SG Su J Taiwan Inst Chem

Eng 42 (2011) 513

Int J Electrochem Sci Vol 8 2013

5083

3 TY Wu SG Su KF Lin YC Lin HP Wang MW Lin ST Gung IW Sun Electrochim

Acta 56 (2011) 7278

4 B Baek S Lee C Jung Int J Electrochem Sci 6 (2011) 6220

5 PN Tshibangu SN Ndwandwe ED Dikio Int J Electrochem Sci 6 (2011) 2201

6 TY Wu SG Su HP Wang IW Sun Electrochem Commun 13 (2011) 237

7 TY Wu SG Su HP Wang YC Lin ST Gung MW Lin IW Sun Electrochim Acta 56

(2011) 3209

8 IW Sun YC Lin BK Chen CW Kuo CC Chen SG Su PR Chen TY Wu Int J

Electrochem Sci 7 (2012) 7206

9 TY Wu SG Su ST Gung MW Lin YC Lin CA Lai IW Sun Electrochim Acta 55

(2010) 4475

10 AN Soriano AM Agapito LJLI Lagumbay AR Caparanga MH Li J Taiwan Inst Chem

Eng 42 (2011) 258

11 TY Wu IW Sun ST Gung BK Chen HP Wang SG Su J Taiwan Inst Chem Eng 42

(2011) 874

12 S Ibrahim MR Johan Int J Electrochem Sci 6 (2011) 5565

13 TY Wu SG Su YC Lin HP Wang MW Lin ST Gung IW Sun Electrochim Acta 56

(2010) 853

14 H Wang LX Wu YC Lan JQ Zhao JX Lu Int J Electrochem Sci 6 (2011) 4218

15 FF Liu SQ Liu QJ Feng SX Zhuang JB Zhang P Bu Int J Electrochem Sci 7 (2012)

4381

16 HA Barham SA Brahim Y Rozita KA Mohamed Int J Electrochem Sci 6 (2011) 181

17 SK Shukla LC Murulana EE Ebenso Int J Electrochem Sci 6 (2011) 4286

18 NV Likhanova O Olivares-Xometl D Guzman-Lucero MA Dominguez-Aguilar N Nava

M Corrales-Luna MC Mendoza Int J Electrochem Sci 6 (2011) 4514

19 A Zarrouk M Messali H Zarrok R Salghi AA Ali B Hammouti SS Al-Deyab F Bentiss

Int J Electrochem Sci 7 (2012) 6998

20 BS Ali BH Ali R Yusoff MK Aroua Int J Electrochem Sci 7 (2012) 3835

21 MH Lin YJ Liu ZH Yang YB Huang ZH Sun Y He CL Ni Int J Electrochem Sci 7

(2012) 965

22 CH Su MH Chung HJ Hsieh YK Chang JC Ding HM Wu J Taiwan Inst Chem Eng

43 (2012) 573

23 H Shekaari A Kazempour J Taiwan Inst Chem Eng 43 (2012) 650

24 ZJ Wei Y Li D Thushara YX Liu QL Ren J Taiwan Inst Chem Eng 43 (2012) 363

25 GQ Zhang HW Yang JF Gao HK Zhang CB Zheng YL Cao YH Wang KQ Ding

Int J Electrochem Sci 7 (2012) 7547

26 P Norouzi MR Ganjali F Faridbod SJ Shahtaheri HA Zamani Int J Electrochem Sci 7

(2012) 2633

27 F Faridbod MR Ganjali M Hosseini P Norouzi Int J Electrochem Sci 7 (2012) 1927

28 MR Ganjali Z Rafiei-Sarmazdeh T Poursaberi SJ Shahtaheri P Norouzi Int J

Electrochem Sci 7 (2012) 1908

29 A Babaei DJ Garrett AJ Downard Int J Electrochem Sci 7 (2012) 3141

30 MR Ganjali T Alizade P Norouzi Int J Electrochem Sci 7 (2012) 4800

31 MR Ganjali T Alizade B Larijani F Faridbod P Norouzi Int J Electrochem Sci 7 (2012)

4756

32 P Norouzi B Larijani MR Ganjali Int J Electrochem Sci 7 (2012) 7313

33 TY Wu MH Tsao SG Su HP Wang YC Lin FL Chen CW Chang IW Sun J Braz

Chem Soc 22 (2011) 780

34 MH Tsao TY Wu HP Wang IW Sun SG Su YC Lin CW Chang Mater Lett 65

(2011) 583

Int J Electrochem Sci Vol 8 2013

5084

35 SY Ku SY Lu Int J Electrochem Sci 6 (2011) 5219

36 TY Wu MH Tsao FL Chen SG Su CW Chang HP Wang YC Lin IW Sun J Iran

Chem Soc 7 (2010) 707

37 IW Sun HP Wang H Teng SG Su YC Lin CW Kuo PR Chen TY Wu Int J

Electrochem Sci 7 (2012) 9748

38 TY Wu MH Tsao FL Chen SG Su CW Chang HP Wang YC Lin WC Ou-Yang

IW Sun Int J Mol Sci 11 (2010) 329

39 YX An PJ Zuo XQ Cheng LX Liao GP Yin Int J Electrochem Sci 6 (2011) 2398

40 LC Xuan YX An W Fang LX Liao YL Ma ZY Ren GP Yin Int J Electrochem Sci

6 (2011) 6590

41 HM Wang SQ Liu K Huang XG Yin YN Liu SJ Peng Int J Electrochem Sci 7

(2012) 1688

42 HM Wang SQ Liu NF Wang YN Liu Int J Electrochem Sci 7 (2012) 7579

43 H Ganjali MR Ganjali T Alizadeh F Faridbod P Norouzi Int J Electrochem Sci 6 (2011)

6085

44 MR Ganjali MH Eshraghi S Ghadimi SM Moosavi M Hosseini H Haji-Hashemi P

Norouzi Int J Electrochem Sci 6 (2011) 739

45 MR Ganjali T Poursaberi M Khoobi A Shafiee M Adibi M Pirali-Hamedani P Norouzi

Int J Electrochem Sci 6 (2011) 717

46 P Norouzi M Hosseini MR Ganjali M Rezapour M Adibi Int J Electrochem Sci 6 (2011)

2012

47 MR Ganjali MR Moghaddam M Hosseini P Norouzi Int J Electrochem Sci 6 (2011)

1981

48 MR Ganjali M Hosseini M Pirali-Hamedani HA Zamani Int J Electrochem Sci 6 (2011)

2808

49 MR Ganjali M Rezapour SK Torkestani H Rashedi P Norouzi Int J Electrochem Sci 6

(2011) 2323

50 P Norouzi M Pirali-Hamedani SO Ranaei-Siadat MR Ganjali Int J Electrochem Sci 6

(2011) 3704

51 F Faridbod HA Zamani M Hosseini M Pirali-Hamedani MR Ganjali P Norouzi Int J

Electrochem Sci 6 (2011) 3694

52 MR Ganjali SO Ranaei-Siadat H Rashedi M Rezapour P Norouzi Int J Electrochem Sci

6 (2011) 3684

53 TH Tsai KC Lin SM Chen Int J Electrochem Sci 6 (2011) 2672

54 MR Ganjali T Alizadeh F Azimi B Larjani F Faridbod P Norouzi Int J Electrochem

Sci 6 (2011) 5200

55 R Mirshafian MR Ganjali P Norouzi Int J Electrochem Sci 7 (2012) 1656

56 J Gao JG Liu WM Liu B Li YC Xin Y Yin ZG Zou Int J Electrochem Sci 6 (2011)

6115

57 TY Wu BK Chen L Hao KF Lin IW Sun J Taiwan Inst Chem Eng 42 (2011) 914

58 TY Wu BK Chen L Hao CW Kuo IW Sun J Taiwan Inst Chem Eng 43 (2012) 313

59 SW Peng AN Soriano RB Leron MH Li J Taiwan Inst Chem Eng 42 (2011) 233

60 TY Wu IW Sun MW Lin BK Chen CW Kuo HP Wang YY Chen SG Su J Taiwan

Inst Chem Eng 43 (2012) 58

61 TY Wu BK Chen CW Kuo L Hao YC Peng IW Sun J Taiwan Inst Chem Eng 43

(2012) 860

62 A Arce H Rodriguez A Soto Green Chem 9 (2007) 247

63 TY Wu HC Wang SG Su ST Gung MW Lin CB Lin J Taiwan Inst Chem Eng 41 (2010)

315 64 X Li M Hou Z Zhang B Han G Yang X Wang L Zou Green Chem 10 (2008) 879

Int J Electrochem Sci Vol 8 2013

5085

65 J Chen SK Spear JG Huddleston RD Rogers Green Chem 7 (2005) 64

66 U Domanska M Laskowska J Solution Chem 38 (2009) 779

67 K Tamura M Nakamura S Murakami J Solution Chem 26 (1997) 1199

68 Z Yu H Gao H Wang L Chen J Chem Eng Data 56 (2011) 2877

69 KN Marsh JA Boxall R Lichtenthaler Fluid Phase Equilib 219 (2004) 93

70 TY Wu SG Su ST Gung MW Lin YC Lin WC Ou-Yang IW Sun CA Lai J Iran

Chem Soc 8 (2011) 149

71 TY Wu L Hao CW Kuo YC Lin SG Su PL Kuo IW Sun Int J Electrochem Sci 7

(2012) 2047

72 TY Wu L Hao PR Chen JW Liao Int J Electrochem Sci 8 (2013) 2606

73 CW Kuo CW Huang BK Chen WB Li PR Chen TH Ho CG Tseng TY Wu Int J

Electrochem Sci 8 (2013) 3834

74 CW Kuo WB Li PR Chen JW Liao CG Tseng TY Wu Int J Electrochem Sci 8

(2013) 5007

75 TY Wu BK Chen L Hao YC Lin HP Wang CW Kuo IW Sun Int J Mol Sci 12

(2011) 8750

76 H Rodriguez JF Brennecke J Chem Eng Data 51 (2006) 2145

77 Y Tian X Wang J Wang J Chem Eng Data 53 (2008) 2056

78 TY Wu HC Wang SG Su ST Gung MW Lin CB Lin J Chin Chem Soc 57 (2010)

44

79 TY Wu BK Chen L Hao YC Peng IW Sun Int J Mol Sci 12 (2011) 2598

80 H Eyring MS John Significant Liquid Structure Wiley New York 1969

81 H Every AG Bishop M Forsyth DR MacFarlane Electrochim Acta 45 (2000) 1279 82 O Redlich AT Kister Ind Eng Chem 40 (1948) 345

83 A Paul P Kumar A Samanta J Phys Chem B 109 (2005) 9148

copy 2013 by ESG (wwwelectrochemsciorg)

Int J Electrochem Sci Vol 8 2013

5076

be negative over the whole composition range for the binary system at 29315 ~ 35315 K The curves

are asymmetrical with the minimum located at the IL mole fraction of about 08 In general negative

αE values indicate the presence of strong interaction between the components in the mixtures [67] The

trends observed in αE values for the present mixtures suggest the formation of H-bonding between

unlike molecules which is stronger in PEG200 + [PyrMB][BuSO4] binary system The increasing

negative αE values for PEG200 + [PyrMB][BuSO4] with increase in temperature indicate enhanced

unlike interaction between components of the mixture that is more destruction of order during mixing

contributes negatively to αE

33 Viscosity

Since ILs are more viscous than conventional solvents in most applications they can be used in

mixtures with other less viscous compounds Therefore the viscosity of pure ILs and their mixtures

with PEG oligomer (or conventional solvents) is an important property and their knowledge is

primordial for each industrial processes [6869] The measured dynamic viscosities for the neat

PEG200 neat [PyrMB][BuSO4] and PEG200 + [PyrMB][BuSO4] binary mixture as a function of

temperature over the whole composition range are shown in Figure 6 and their data are listed in Table

5 the viscosities of the mixtures decrease rapidly when PEG oligomer are added to the ionic liquid

especially at lower temperatures The fitting lines in Figure 6 were calculated with the following

fourth-order polynomial equation

= c0 + c1 x1 + c2 x12 + c3 x1

3 + c4 x1

4 (9)

where x1 is the mole fractions of PEG200 and c0 c1 c2 c3 and c4 refer to the fit coefficients

The parameters of correlation are shown in Table 6

Figure 6 Dynamic viscosity for the PEG200 (1) + [PyrMB][BuSO4] (2) binary system as a

function of mole fractions of the PEG200 at different temperatures Lines represent the

polynomial correlation

x1

00 02 04 06 08 10

mP

a s

0

200

400

600

800

1000

1200

1400

29315 K

30315 K

31315 K

32315 K

33315 K

34315 K

35315 K

Int J Electrochem Sci Vol 8 2013

5077

Table 5 Experimental dynamic viscosity (η) and viscosity deviation (Δη) for the binary system

PEG200 (1) + [PyrMB][BuSO4] (2)

x1

29315 29815 30315 30815 31315 31815 32315 32815 33315 33815 34315 34815 35315

ηmPamiddots

0 13209 9343 6745 4961 3712 2821 2176 1700 1345 1077 871 712 587

01452 5907 4362 3294 2539 1992 1589 1286 1055 876 735 623 533 460

01942 4656 3475 2656 2072 1647 1331 1091 907 763 649 557 483 422

02912 3134 2395 1870 1489 1205 991 826 697 594 512 445 390 345

03897 2367 1846 1463 1177 959 792 660 557 474 406 351 306 269

04893 1799 1396 1104 887 723 598 501 424 362 312 272 238 210

05890 1540 1194 941 753 611 502 418 351 298 255 220 191 167

06903 1185 926 736 594 485 402 336 284 242 209 181 158 139

07922 954 742 589 475 389 323 271 231 198 172 150 132 117

08958 811 639 512 415 342 285 240 204 175 151 132 116 102

1 629 505 410 337 280 235 199 170 146 126 110 97 85

ΔηmPamiddots

0 00 00 00 00 00 00 00 00 00 00 00 00 00

01452 -5475 -3698 -2530 -1751 -1221 -857 -602 -423 -295 -204 -137 -89 -54

01942 -6111 -4152 -2859 -1991 -1398 -988 -700 -496 -347 -244 -166 -110 -68

02912 -6411 -4374 -3030 -2126 -1507 -1077 -774 -558 -391 -288 -204 -142 -103

03897 -5940 -4053 -2813 -1982 -1415 -1022 -745 -547 -405 -300 -223 -166 -123

04893 -5254 -3622 -2541 -1811 -1255 -957 -708 -528 -396 -299 -227 -173 -131

05890 -4260 -2944 -2073 -1484 -1034 -796 -594 -448 -341 -262 -203 -158 -124

06903 -3340 -2316 -1636 -1176 -826 -634 -475 -360 -275 -212 -165 -129 -101

07922 -2289 -1599 -1138 -823 -579 -449 -320 -257 -197 -152 -118 -92 -72

08958 -1129 -787 -559 -404 -277 -220 -152 -126 -96 -74 -58 -45 -35

1 00 00 00 00 00 00 00 00 00 00 00 00 00

Table 6 Coefficients of polynomiala for the correlation of the viscosity ( mPa s) in function of

concentration at different temperatures of the binary systems PEG200 (1) + [PyrMB][BuSO4]

(2)

TK c0 mPa s c1 mPa s c2 mPa s c3 mPa s C4 mPa s

29315 13154 -68701 15960 -16688 63543 1075

29815 93069 -46703 10681 -11113 42269 727

30315 67211 -32185 72085 -74396 28222 497

30815 49454 -22431 48886 -49866 18828 343

31315 37016 -15772 33175 -33281 12474 238

31815 28146 -1116 22406 -21947 81322 165

32315 21713 -7923 14947 -1413 51409 114

32815 16975 -56244 97349 -870 30666 077

33315 13435 -39753 60667 -4908 16219 051

33815 10756 -27812 34718 -22519 61382 033

34315 87026 -19098 16304 -39091 -88892 021

34815 71108 -12698 32285 90904 -5763 016

35315 58636 -79728 -60345 18103 -91096 017 a = c0 + c1 x1 + c2 x1

2 + c3 x1

3 + c4 x1

4

The temperature dependence becomes distinctly nonlinear especially at high [PyrMB][BuSO4]

content The Vogel-Tammann-Fulcher (VTF) equation [70-75] suitably correlates the nonlinear

behavior as a function of the temperature not only the viscosities of the neat IL but also the viscosities

of the mixtures for the binary systems through the composition range

Int J Electrochem Sci Vol 8 2013

5078

exp[ ]( )

o

o

B

T T

(10)

where ηo B and To are constants The parameter To is the ideal glass transition temperature which

should be slightly below the experimental glass transition temperature Tg [76] The adjustable

parameters obtained from the VTF correlation were presented in Table 7 The obtained parameters o

and B change smoothly with composition for binary mixtures

Table 7 The VTF equation parameters of viscosity ( 1 exp[ ]( )

o

o

B

T T

) and conductivity

(

exp[ ]( )

o

o

B

T T

) for neat PEG200 (x1 = 1) [PyrMB][BuSO4] (x1 = 0) and binary system

PEG200 (1) + [PyrMB][BuSO4] (2)

x1

ηo (mPa s) To (K) B (K) R2a

o (mS cm-1

) To (K) Brsquo (K) R2a

0 027 1810 9540 0999 792 1788 6854 0999

01452 026 1712 9413 0999 577 1699 6268 0999

01942 043 1788 7975 0999 401 1792 5297 0999

02912 053 1794 7264 0999 521 1662 6031 0999

03897 026 1629 8902 0999 274 1803 4381 0999

04893 023 1666 8455 0999 177 1951 3272 0999

05890 015 1648 8865 0999 216 1883 3672 0999

06903 015 1647 8572 0999 88 2174 2000 0999

07922 017 1717 7702 0999 92 2020 2578 0999

08958 012 1642 8360 0999 43 2110 2088 0999

1 014 1649 7868 0999 556 1928 9815 0999

a Correlation coefficient

The viscosities of the mixtures decrease rapidly when organic oligomers are added to the ionic

liquid this decrease is particularly evident in dilute solutions of organic oligomers in the ionic liquid

The strong coulomb interactions between the [BuSO4]- anion and [PyrMB]

+ cation are weakened upon

mixing with the polar organic oligomers which leads to a higher mobility of the ions and a lower

viscosity of the mixtures [77] This indicates that the viscosity of ILs could be therefore tuned for

several applications by adding an organic solvent or by changing temperature [78]

Due to the wide range of possible molecular interactions between the two components

deviations can occur from ideal behavior These viscosity deviations can be quantified by the viscosity

deviation Δη also known as ldquoexcess viscosityrdquo in other sources

1 1 2 2 (mPa s) x x (11)

Int J Electrochem Sci Vol 8 2013

5079

where x1 and x2 are the mole fractions of PEG200 and [PyrMB][BuSO4] respectively and 1

and 2 are the viscosities (mPa middot s) of the solution the pure solvent and the pure IL respectively

Figure 7 shows the viscosity deviations as a function of the PEG200 mole fraction composition x1 and

temperature for the PEG200 + [PyrMB][BuSO4] binary mixture The values of viscosity deviations

are compared with those obtained from the RedlichndashKister polynomial equation The viscosity

deviation for the mixture show negative deviations from ideality over the whole mole fraction range

Figure 7 also shows that the negative values of viscosity deviations decrease with increasing

temperature this can be attributed to the specific interactions in mixtures typically hydrogen bonds break-

up as the temperature increases [79] The minimum value of Δη is observed at about x1 asymp 03 and the

viscosity deviation depends on molecular interactions as well as on the size and shape of the molecules

[80]

Figure 7 Viscosity deviations Δη versus the mole fraction at various temperatures for the binary

mixture PEG200 (1) + [PyrMB][BuSO4] (2)

34 Conductivity

The experimental data of conductivity of the neat ILs [PyrMB][BuSO4] neat PEG200 and

binary system are plotted against the x1 at various temperatures in Figure 8 together with lines

calculated with the four-order polynomial equation

= d0 + d1 x1 + d2 x12 + d3 x1

3 + d4 x1

4 (12)

where x1 is the mole fractions of PEG200 and d0 d1 d2 d3 and d4 refer to the fit coefficients

The parameters of correlation are shown in Table 8 The conductivities of neat IL [PyrMB][BuSO4]

neat PEG200 and binary system at various temperatures were fitted using the VTF equation

exp[ ]

( )o

o

B

T T

(13)

x1

00 02 04 06 08 10

m

Pa s

-700

-600

-500

-400

-300

-200

-100

0

29315 K

30315 K

31315 K

32315 K

33315 K

34315 K

35315 K

Int J Electrochem Sci Vol 8 2013

5080

where T is the absolute temperature and Brsquo and To are adjustable parameters The best-fit

mS cm-1 Brsquo (K) and To (K) parameters are given in Table 7 Neat [PyrMB][BuSO4] neat

PEG200 and binary system were very well fit by the VTF model over the temperature range studied

Figure 8 Plot of conductivity of the PEG200 (1) + [PyrMB][BuSO4] (2) binary system versus

mole fraction x1 at various temperatures

Table 8 Coefficients of polynomiala for the correlation of the conductivity ( mS cm

-1) in function

of concentration at different temperatures of the binary systems PEG200 (1) +

[PyrMB][BuSO4] (2)

TK d0 mS cm

-1 d1 mS cm

-1 d2 mS cm

-1 d3 mS cm

-1 d4 mS cm

-1

29315 02019 09622 -01679 0734 -17284 00095

29815 02588 11031 -02503 09086 -20181 00109

30315 03255 12119 -01935 08565 -21971 00125

30815 04025 13165 -01329 0767 -23477 00141

31315 04904 13712 01238 03677 -23439 00156

31815 05894 15032 -00006 04737 -25518 00171

32315 06999 15802 00743 0265 -25986 00188

32815 08221 16427 01595 00089 -26032 00208

33315 09562 16373 04858 -06207 -24165 00233

a = d0 + d1 x1 + d2 x1

2 + d3 x1

3 + d4 x1

4

As shown in Figure 8 it can be seen that the conductivity of the binary mixture increases with

increasing amount of PEG200 goes through a maximum and then goes down to the specific

conductivity of the neat PEG200 The conductivity is related to the ion mobility and the number of

charge carriers [81] At a fixed concentration the ions move faster at higher temperature due to the

relatively lower viscosity of the mixture On the other hand the composition influences both the ion

mobility and the number of charge carriers at a fixed temperature At the beginning the number of

charge and the ion mobility increase with increasing PEG oligomer composition the maximum of

conductivity is located at x1 = 059 and corresponds to a value of 171 mS cmminus 1

at 33315 K It can also

be observed that the conductivity increases as the temperature increases The higher temperature may

x1

00 02 04 06 08 10

mS

cm

-1

00

05

10

15

20

29315 K

29815 K

30315 K

30815 K

31315 K

31815 K

32315 K

32815 K

33315 K

Int J Electrochem Sci Vol 8 2013

5081

weaken the influence of aggregation to the conductivity which suggests that a higher temperature is

better for the ILs to act as electrolytes

Table 9 RedlickndashKister fitting coefficients Ak and the standard deviation of the VE and ∆for the

binary mixture of PEG200 (1) + [PyrMB][BuSO4] (2) system

TK A0 A1 A2 A3 A4

VEcm

3 mol

-1

29315 -5979 -4906 6585 5754 -1717 002687

29815 -6200 -4760 6464 5767 -2022 002693

30315 -6408 -4612 6345 5774 -2276 002698

30815 -6602 -4461 6229 5774 -2476 002701

31315 -6782 -4310 6116 5767 -2623 002701

31815 -6948 -4155 6006 5753 -2716 002699

32315 -7100 -3999 5899 5732 -2754 002692

32815 -7239 -3840 5795 5704 -2738 002683

33315 -7363 -3679 5694 5669 -2666 002670

33815 -7472 -3515 5596 5626 -2538 002654

34315 -7568 -3350 5501 5576 -2353 002634

34815 -7648 -3182 5409 5518 -2111 002611

35315 -7714 -3011 5320 5452 -1812 002586

∆mPa s

29315 -20414 -17226 -15592 -95544 -75863 399496

29815 -14035 -11558 -10713 -62192 19493 340180

30315 -98261 -78407 -73734 -40709 58145 286725

30815 -69922 -53591 -50601 -2676 67556 235258

31315 -48876 -39537 -41051 -14118 16739 079245

31815 -36917 -25169 -22939 -11646 51047 146189

32315 -27415 -1721 -12581 -92603 21498 104339

32815 -20441 -11703 -77538 -38334 -81478 090708

33315 -15382 -67274 -31134 -47585 -18255 059539

33815 -11664 -44928 -15533 -22312 -05591 037855

34315 -89038 -24163 68654 -15007 -10347 024263

34815 -68279 -91813 23131 -10367 -18636 017759

35315 -52525 -24051 26474 15498 -85341 018640

35 Redlich-Kister Equation for Binary System

The binary excess property ( E

mV ) and deviations (Δ) at several temperatures were fitted to a

Redlich-Kister-type equation [82]

1 1 1

0

(or ) (1 ) (1 2 )j

E i

i

i

Y Y x x A x

(14)

Int J Electrochem Sci Vol 8 2013

5082

where ΔY (YE) represents E

mV (cm3 mol

minus1) and Δ

(mPa s)x1 denotes the mole fraction of

PEG200 Ai represents the polynomial coefficients and j is the degree of the polynomial expansion

The correlated results for excess molar volumes ( E

mV ) viscosity deviations (Δ) including the values

of the fitting parameters Ai together with the standard deviation σ are given in Table 9 where the

tabulated standard deviation σ [83] is defined as

2

exp cal 1 2( )

[ ]Y Y

m n

(15)

where m is the number of experimental data points and n is the number of estimated

parameters The subscripts ldquoexprdquo and ldquocalrdquo denote the values of the experimental and calculated

property respectively As shown in Table 9 the experimentally derived E

mV and Δη values were

correlated satisfactorily by the Redlich-Kister equation

4 CONCLUSIONS

This paper is a systematic characterizations of thermophysical properties for IL binary system

Density viscosity and conductivity for (PEG200 + [PyrMB][BuSO4]) binary system are presented as a

function of temperature at atmospheric pressure it was demonstrated that viscosity and conductivity

were more sensitive to the changes in PEG content or temperature than density and the viscosity and

conductivity of pure IL and (PEG200 + [PyrMB][BuSO4]) binary system at different temperature are

fitted using the VogelndashTammannndashFulcher (VTF) equation with good accuracy The excess molar

volumes excess volume expansivity and viscosity deviations show negative deviations from the ideal

solution the results are interpreted in terms of molecular interactions in the (PEG200 +

[PyrMB][BuSO4]) binary mixture The conductivity increases to a maximum value when the

concentration of PEG200 is increased and decreases after the maximum the data obtained will be

helpful for the application of the ionic liquids as electrolytes and also useful for the ionic liquids

database

ACKNOWLEDGEMENTS

The authors would like to thank the National Science Council of the Republic of China for financially

supporting this project

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2 TY Wu IW Sun ST Gung MW Lin BK Chen HP Wang SG Su J Taiwan Inst Chem

Eng 42 (2011) 513

Int J Electrochem Sci Vol 8 2013

5083

3 TY Wu SG Su KF Lin YC Lin HP Wang MW Lin ST Gung IW Sun Electrochim

Acta 56 (2011) 7278

4 B Baek S Lee C Jung Int J Electrochem Sci 6 (2011) 6220

5 PN Tshibangu SN Ndwandwe ED Dikio Int J Electrochem Sci 6 (2011) 2201

6 TY Wu SG Su HP Wang IW Sun Electrochem Commun 13 (2011) 237

7 TY Wu SG Su HP Wang YC Lin ST Gung MW Lin IW Sun Electrochim Acta 56

(2011) 3209

8 IW Sun YC Lin BK Chen CW Kuo CC Chen SG Su PR Chen TY Wu Int J

Electrochem Sci 7 (2012) 7206

9 TY Wu SG Su ST Gung MW Lin YC Lin CA Lai IW Sun Electrochim Acta 55

(2010) 4475

10 AN Soriano AM Agapito LJLI Lagumbay AR Caparanga MH Li J Taiwan Inst Chem

Eng 42 (2011) 258

11 TY Wu IW Sun ST Gung BK Chen HP Wang SG Su J Taiwan Inst Chem Eng 42

(2011) 874

12 S Ibrahim MR Johan Int J Electrochem Sci 6 (2011) 5565

13 TY Wu SG Su YC Lin HP Wang MW Lin ST Gung IW Sun Electrochim Acta 56

(2010) 853

14 H Wang LX Wu YC Lan JQ Zhao JX Lu Int J Electrochem Sci 6 (2011) 4218

15 FF Liu SQ Liu QJ Feng SX Zhuang JB Zhang P Bu Int J Electrochem Sci 7 (2012)

4381

16 HA Barham SA Brahim Y Rozita KA Mohamed Int J Electrochem Sci 6 (2011) 181

17 SK Shukla LC Murulana EE Ebenso Int J Electrochem Sci 6 (2011) 4286

18 NV Likhanova O Olivares-Xometl D Guzman-Lucero MA Dominguez-Aguilar N Nava

M Corrales-Luna MC Mendoza Int J Electrochem Sci 6 (2011) 4514

19 A Zarrouk M Messali H Zarrok R Salghi AA Ali B Hammouti SS Al-Deyab F Bentiss

Int J Electrochem Sci 7 (2012) 6998

20 BS Ali BH Ali R Yusoff MK Aroua Int J Electrochem Sci 7 (2012) 3835

21 MH Lin YJ Liu ZH Yang YB Huang ZH Sun Y He CL Ni Int J Electrochem Sci 7

(2012) 965

22 CH Su MH Chung HJ Hsieh YK Chang JC Ding HM Wu J Taiwan Inst Chem Eng

43 (2012) 573

23 H Shekaari A Kazempour J Taiwan Inst Chem Eng 43 (2012) 650

24 ZJ Wei Y Li D Thushara YX Liu QL Ren J Taiwan Inst Chem Eng 43 (2012) 363

25 GQ Zhang HW Yang JF Gao HK Zhang CB Zheng YL Cao YH Wang KQ Ding

Int J Electrochem Sci 7 (2012) 7547

26 P Norouzi MR Ganjali F Faridbod SJ Shahtaheri HA Zamani Int J Electrochem Sci 7

(2012) 2633

27 F Faridbod MR Ganjali M Hosseini P Norouzi Int J Electrochem Sci 7 (2012) 1927

28 MR Ganjali Z Rafiei-Sarmazdeh T Poursaberi SJ Shahtaheri P Norouzi Int J

Electrochem Sci 7 (2012) 1908

29 A Babaei DJ Garrett AJ Downard Int J Electrochem Sci 7 (2012) 3141

30 MR Ganjali T Alizade P Norouzi Int J Electrochem Sci 7 (2012) 4800

31 MR Ganjali T Alizade B Larijani F Faridbod P Norouzi Int J Electrochem Sci 7 (2012)

4756

32 P Norouzi B Larijani MR Ganjali Int J Electrochem Sci 7 (2012) 7313

33 TY Wu MH Tsao SG Su HP Wang YC Lin FL Chen CW Chang IW Sun J Braz

Chem Soc 22 (2011) 780

34 MH Tsao TY Wu HP Wang IW Sun SG Su YC Lin CW Chang Mater Lett 65

(2011) 583

Int J Electrochem Sci Vol 8 2013

5084

35 SY Ku SY Lu Int J Electrochem Sci 6 (2011) 5219

36 TY Wu MH Tsao FL Chen SG Su CW Chang HP Wang YC Lin IW Sun J Iran

Chem Soc 7 (2010) 707

37 IW Sun HP Wang H Teng SG Su YC Lin CW Kuo PR Chen TY Wu Int J

Electrochem Sci 7 (2012) 9748

38 TY Wu MH Tsao FL Chen SG Su CW Chang HP Wang YC Lin WC Ou-Yang

IW Sun Int J Mol Sci 11 (2010) 329

39 YX An PJ Zuo XQ Cheng LX Liao GP Yin Int J Electrochem Sci 6 (2011) 2398

40 LC Xuan YX An W Fang LX Liao YL Ma ZY Ren GP Yin Int J Electrochem Sci

6 (2011) 6590

41 HM Wang SQ Liu K Huang XG Yin YN Liu SJ Peng Int J Electrochem Sci 7

(2012) 1688

42 HM Wang SQ Liu NF Wang YN Liu Int J Electrochem Sci 7 (2012) 7579

43 H Ganjali MR Ganjali T Alizadeh F Faridbod P Norouzi Int J Electrochem Sci 6 (2011)

6085

44 MR Ganjali MH Eshraghi S Ghadimi SM Moosavi M Hosseini H Haji-Hashemi P

Norouzi Int J Electrochem Sci 6 (2011) 739

45 MR Ganjali T Poursaberi M Khoobi A Shafiee M Adibi M Pirali-Hamedani P Norouzi

Int J Electrochem Sci 6 (2011) 717

46 P Norouzi M Hosseini MR Ganjali M Rezapour M Adibi Int J Electrochem Sci 6 (2011)

2012

47 MR Ganjali MR Moghaddam M Hosseini P Norouzi Int J Electrochem Sci 6 (2011)

1981

48 MR Ganjali M Hosseini M Pirali-Hamedani HA Zamani Int J Electrochem Sci 6 (2011)

2808

49 MR Ganjali M Rezapour SK Torkestani H Rashedi P Norouzi Int J Electrochem Sci 6

(2011) 2323

50 P Norouzi M Pirali-Hamedani SO Ranaei-Siadat MR Ganjali Int J Electrochem Sci 6

(2011) 3704

51 F Faridbod HA Zamani M Hosseini M Pirali-Hamedani MR Ganjali P Norouzi Int J

Electrochem Sci 6 (2011) 3694

52 MR Ganjali SO Ranaei-Siadat H Rashedi M Rezapour P Norouzi Int J Electrochem Sci

6 (2011) 3684

53 TH Tsai KC Lin SM Chen Int J Electrochem Sci 6 (2011) 2672

54 MR Ganjali T Alizadeh F Azimi B Larjani F Faridbod P Norouzi Int J Electrochem

Sci 6 (2011) 5200

55 R Mirshafian MR Ganjali P Norouzi Int J Electrochem Sci 7 (2012) 1656

56 J Gao JG Liu WM Liu B Li YC Xin Y Yin ZG Zou Int J Electrochem Sci 6 (2011)

6115

57 TY Wu BK Chen L Hao KF Lin IW Sun J Taiwan Inst Chem Eng 42 (2011) 914

58 TY Wu BK Chen L Hao CW Kuo IW Sun J Taiwan Inst Chem Eng 43 (2012) 313

59 SW Peng AN Soriano RB Leron MH Li J Taiwan Inst Chem Eng 42 (2011) 233

60 TY Wu IW Sun MW Lin BK Chen CW Kuo HP Wang YY Chen SG Su J Taiwan

Inst Chem Eng 43 (2012) 58

61 TY Wu BK Chen CW Kuo L Hao YC Peng IW Sun J Taiwan Inst Chem Eng 43

(2012) 860

62 A Arce H Rodriguez A Soto Green Chem 9 (2007) 247

63 TY Wu HC Wang SG Su ST Gung MW Lin CB Lin J Taiwan Inst Chem Eng 41 (2010)

315 64 X Li M Hou Z Zhang B Han G Yang X Wang L Zou Green Chem 10 (2008) 879

Int J Electrochem Sci Vol 8 2013

5085

65 J Chen SK Spear JG Huddleston RD Rogers Green Chem 7 (2005) 64

66 U Domanska M Laskowska J Solution Chem 38 (2009) 779

67 K Tamura M Nakamura S Murakami J Solution Chem 26 (1997) 1199

68 Z Yu H Gao H Wang L Chen J Chem Eng Data 56 (2011) 2877

69 KN Marsh JA Boxall R Lichtenthaler Fluid Phase Equilib 219 (2004) 93

70 TY Wu SG Su ST Gung MW Lin YC Lin WC Ou-Yang IW Sun CA Lai J Iran

Chem Soc 8 (2011) 149

71 TY Wu L Hao CW Kuo YC Lin SG Su PL Kuo IW Sun Int J Electrochem Sci 7

(2012) 2047

72 TY Wu L Hao PR Chen JW Liao Int J Electrochem Sci 8 (2013) 2606

73 CW Kuo CW Huang BK Chen WB Li PR Chen TH Ho CG Tseng TY Wu Int J

Electrochem Sci 8 (2013) 3834

74 CW Kuo WB Li PR Chen JW Liao CG Tseng TY Wu Int J Electrochem Sci 8

(2013) 5007

75 TY Wu BK Chen L Hao YC Lin HP Wang CW Kuo IW Sun Int J Mol Sci 12

(2011) 8750

76 H Rodriguez JF Brennecke J Chem Eng Data 51 (2006) 2145

77 Y Tian X Wang J Wang J Chem Eng Data 53 (2008) 2056

78 TY Wu HC Wang SG Su ST Gung MW Lin CB Lin J Chin Chem Soc 57 (2010)

44

79 TY Wu BK Chen L Hao YC Peng IW Sun Int J Mol Sci 12 (2011) 2598

80 H Eyring MS John Significant Liquid Structure Wiley New York 1969

81 H Every AG Bishop M Forsyth DR MacFarlane Electrochim Acta 45 (2000) 1279 82 O Redlich AT Kister Ind Eng Chem 40 (1948) 345

83 A Paul P Kumar A Samanta J Phys Chem B 109 (2005) 9148

copy 2013 by ESG (wwwelectrochemsciorg)

Int J Electrochem Sci Vol 8 2013

5077

Table 5 Experimental dynamic viscosity (η) and viscosity deviation (Δη) for the binary system

PEG200 (1) + [PyrMB][BuSO4] (2)

x1

29315 29815 30315 30815 31315 31815 32315 32815 33315 33815 34315 34815 35315

ηmPamiddots

0 13209 9343 6745 4961 3712 2821 2176 1700 1345 1077 871 712 587

01452 5907 4362 3294 2539 1992 1589 1286 1055 876 735 623 533 460

01942 4656 3475 2656 2072 1647 1331 1091 907 763 649 557 483 422

02912 3134 2395 1870 1489 1205 991 826 697 594 512 445 390 345

03897 2367 1846 1463 1177 959 792 660 557 474 406 351 306 269

04893 1799 1396 1104 887 723 598 501 424 362 312 272 238 210

05890 1540 1194 941 753 611 502 418 351 298 255 220 191 167

06903 1185 926 736 594 485 402 336 284 242 209 181 158 139

07922 954 742 589 475 389 323 271 231 198 172 150 132 117

08958 811 639 512 415 342 285 240 204 175 151 132 116 102

1 629 505 410 337 280 235 199 170 146 126 110 97 85

ΔηmPamiddots

0 00 00 00 00 00 00 00 00 00 00 00 00 00

01452 -5475 -3698 -2530 -1751 -1221 -857 -602 -423 -295 -204 -137 -89 -54

01942 -6111 -4152 -2859 -1991 -1398 -988 -700 -496 -347 -244 -166 -110 -68

02912 -6411 -4374 -3030 -2126 -1507 -1077 -774 -558 -391 -288 -204 -142 -103

03897 -5940 -4053 -2813 -1982 -1415 -1022 -745 -547 -405 -300 -223 -166 -123

04893 -5254 -3622 -2541 -1811 -1255 -957 -708 -528 -396 -299 -227 -173 -131

05890 -4260 -2944 -2073 -1484 -1034 -796 -594 -448 -341 -262 -203 -158 -124

06903 -3340 -2316 -1636 -1176 -826 -634 -475 -360 -275 -212 -165 -129 -101

07922 -2289 -1599 -1138 -823 -579 -449 -320 -257 -197 -152 -118 -92 -72

08958 -1129 -787 -559 -404 -277 -220 -152 -126 -96 -74 -58 -45 -35

1 00 00 00 00 00 00 00 00 00 00 00 00 00

Table 6 Coefficients of polynomiala for the correlation of the viscosity ( mPa s) in function of

concentration at different temperatures of the binary systems PEG200 (1) + [PyrMB][BuSO4]

(2)

TK c0 mPa s c1 mPa s c2 mPa s c3 mPa s C4 mPa s

29315 13154 -68701 15960 -16688 63543 1075

29815 93069 -46703 10681 -11113 42269 727

30315 67211 -32185 72085 -74396 28222 497

30815 49454 -22431 48886 -49866 18828 343

31315 37016 -15772 33175 -33281 12474 238

31815 28146 -1116 22406 -21947 81322 165

32315 21713 -7923 14947 -1413 51409 114

32815 16975 -56244 97349 -870 30666 077

33315 13435 -39753 60667 -4908 16219 051

33815 10756 -27812 34718 -22519 61382 033

34315 87026 -19098 16304 -39091 -88892 021

34815 71108 -12698 32285 90904 -5763 016

35315 58636 -79728 -60345 18103 -91096 017 a = c0 + c1 x1 + c2 x1

2 + c3 x1

3 + c4 x1

4

The temperature dependence becomes distinctly nonlinear especially at high [PyrMB][BuSO4]

content The Vogel-Tammann-Fulcher (VTF) equation [70-75] suitably correlates the nonlinear

behavior as a function of the temperature not only the viscosities of the neat IL but also the viscosities

of the mixtures for the binary systems through the composition range

Int J Electrochem Sci Vol 8 2013

5078

exp[ ]( )

o

o

B

T T

(10)

where ηo B and To are constants The parameter To is the ideal glass transition temperature which

should be slightly below the experimental glass transition temperature Tg [76] The adjustable

parameters obtained from the VTF correlation were presented in Table 7 The obtained parameters o

and B change smoothly with composition for binary mixtures

Table 7 The VTF equation parameters of viscosity ( 1 exp[ ]( )

o

o

B

T T

) and conductivity

(

exp[ ]( )

o

o

B

T T

) for neat PEG200 (x1 = 1) [PyrMB][BuSO4] (x1 = 0) and binary system

PEG200 (1) + [PyrMB][BuSO4] (2)

x1

ηo (mPa s) To (K) B (K) R2a

o (mS cm-1

) To (K) Brsquo (K) R2a

0 027 1810 9540 0999 792 1788 6854 0999

01452 026 1712 9413 0999 577 1699 6268 0999

01942 043 1788 7975 0999 401 1792 5297 0999

02912 053 1794 7264 0999 521 1662 6031 0999

03897 026 1629 8902 0999 274 1803 4381 0999

04893 023 1666 8455 0999 177 1951 3272 0999

05890 015 1648 8865 0999 216 1883 3672 0999

06903 015 1647 8572 0999 88 2174 2000 0999

07922 017 1717 7702 0999 92 2020 2578 0999

08958 012 1642 8360 0999 43 2110 2088 0999

1 014 1649 7868 0999 556 1928 9815 0999

a Correlation coefficient

The viscosities of the mixtures decrease rapidly when organic oligomers are added to the ionic

liquid this decrease is particularly evident in dilute solutions of organic oligomers in the ionic liquid

The strong coulomb interactions between the [BuSO4]- anion and [PyrMB]

+ cation are weakened upon

mixing with the polar organic oligomers which leads to a higher mobility of the ions and a lower

viscosity of the mixtures [77] This indicates that the viscosity of ILs could be therefore tuned for

several applications by adding an organic solvent or by changing temperature [78]

Due to the wide range of possible molecular interactions between the two components

deviations can occur from ideal behavior These viscosity deviations can be quantified by the viscosity

deviation Δη also known as ldquoexcess viscosityrdquo in other sources

1 1 2 2 (mPa s) x x (11)

Int J Electrochem Sci Vol 8 2013

5079

where x1 and x2 are the mole fractions of PEG200 and [PyrMB][BuSO4] respectively and 1

and 2 are the viscosities (mPa middot s) of the solution the pure solvent and the pure IL respectively

Figure 7 shows the viscosity deviations as a function of the PEG200 mole fraction composition x1 and

temperature for the PEG200 + [PyrMB][BuSO4] binary mixture The values of viscosity deviations

are compared with those obtained from the RedlichndashKister polynomial equation The viscosity

deviation for the mixture show negative deviations from ideality over the whole mole fraction range

Figure 7 also shows that the negative values of viscosity deviations decrease with increasing

temperature this can be attributed to the specific interactions in mixtures typically hydrogen bonds break-

up as the temperature increases [79] The minimum value of Δη is observed at about x1 asymp 03 and the

viscosity deviation depends on molecular interactions as well as on the size and shape of the molecules

[80]

Figure 7 Viscosity deviations Δη versus the mole fraction at various temperatures for the binary

mixture PEG200 (1) + [PyrMB][BuSO4] (2)

34 Conductivity

The experimental data of conductivity of the neat ILs [PyrMB][BuSO4] neat PEG200 and

binary system are plotted against the x1 at various temperatures in Figure 8 together with lines

calculated with the four-order polynomial equation

= d0 + d1 x1 + d2 x12 + d3 x1

3 + d4 x1

4 (12)

where x1 is the mole fractions of PEG200 and d0 d1 d2 d3 and d4 refer to the fit coefficients

The parameters of correlation are shown in Table 8 The conductivities of neat IL [PyrMB][BuSO4]

neat PEG200 and binary system at various temperatures were fitted using the VTF equation

exp[ ]

( )o

o

B

T T

(13)

x1

00 02 04 06 08 10

m

Pa s

-700

-600

-500

-400

-300

-200

-100

0

29315 K

30315 K

31315 K

32315 K

33315 K

34315 K

35315 K

Int J Electrochem Sci Vol 8 2013

5080

where T is the absolute temperature and Brsquo and To are adjustable parameters The best-fit

mS cm-1 Brsquo (K) and To (K) parameters are given in Table 7 Neat [PyrMB][BuSO4] neat

PEG200 and binary system were very well fit by the VTF model over the temperature range studied

Figure 8 Plot of conductivity of the PEG200 (1) + [PyrMB][BuSO4] (2) binary system versus

mole fraction x1 at various temperatures

Table 8 Coefficients of polynomiala for the correlation of the conductivity ( mS cm

-1) in function

of concentration at different temperatures of the binary systems PEG200 (1) +

[PyrMB][BuSO4] (2)

TK d0 mS cm

-1 d1 mS cm

-1 d2 mS cm

-1 d3 mS cm

-1 d4 mS cm

-1

29315 02019 09622 -01679 0734 -17284 00095

29815 02588 11031 -02503 09086 -20181 00109

30315 03255 12119 -01935 08565 -21971 00125

30815 04025 13165 -01329 0767 -23477 00141

31315 04904 13712 01238 03677 -23439 00156

31815 05894 15032 -00006 04737 -25518 00171

32315 06999 15802 00743 0265 -25986 00188

32815 08221 16427 01595 00089 -26032 00208

33315 09562 16373 04858 -06207 -24165 00233

a = d0 + d1 x1 + d2 x1

2 + d3 x1

3 + d4 x1

4

As shown in Figure 8 it can be seen that the conductivity of the binary mixture increases with

increasing amount of PEG200 goes through a maximum and then goes down to the specific

conductivity of the neat PEG200 The conductivity is related to the ion mobility and the number of

charge carriers [81] At a fixed concentration the ions move faster at higher temperature due to the

relatively lower viscosity of the mixture On the other hand the composition influences both the ion

mobility and the number of charge carriers at a fixed temperature At the beginning the number of

charge and the ion mobility increase with increasing PEG oligomer composition the maximum of

conductivity is located at x1 = 059 and corresponds to a value of 171 mS cmminus 1

at 33315 K It can also

be observed that the conductivity increases as the temperature increases The higher temperature may

x1

00 02 04 06 08 10

mS

cm

-1

00

05

10

15

20

29315 K

29815 K

30315 K

30815 K

31315 K

31815 K

32315 K

32815 K

33315 K

Int J Electrochem Sci Vol 8 2013

5081

weaken the influence of aggregation to the conductivity which suggests that a higher temperature is

better for the ILs to act as electrolytes

Table 9 RedlickndashKister fitting coefficients Ak and the standard deviation of the VE and ∆for the

binary mixture of PEG200 (1) + [PyrMB][BuSO4] (2) system

TK A0 A1 A2 A3 A4

VEcm

3 mol

-1

29315 -5979 -4906 6585 5754 -1717 002687

29815 -6200 -4760 6464 5767 -2022 002693

30315 -6408 -4612 6345 5774 -2276 002698

30815 -6602 -4461 6229 5774 -2476 002701

31315 -6782 -4310 6116 5767 -2623 002701

31815 -6948 -4155 6006 5753 -2716 002699

32315 -7100 -3999 5899 5732 -2754 002692

32815 -7239 -3840 5795 5704 -2738 002683

33315 -7363 -3679 5694 5669 -2666 002670

33815 -7472 -3515 5596 5626 -2538 002654

34315 -7568 -3350 5501 5576 -2353 002634

34815 -7648 -3182 5409 5518 -2111 002611

35315 -7714 -3011 5320 5452 -1812 002586

∆mPa s

29315 -20414 -17226 -15592 -95544 -75863 399496

29815 -14035 -11558 -10713 -62192 19493 340180

30315 -98261 -78407 -73734 -40709 58145 286725

30815 -69922 -53591 -50601 -2676 67556 235258

31315 -48876 -39537 -41051 -14118 16739 079245

31815 -36917 -25169 -22939 -11646 51047 146189

32315 -27415 -1721 -12581 -92603 21498 104339

32815 -20441 -11703 -77538 -38334 -81478 090708

33315 -15382 -67274 -31134 -47585 -18255 059539

33815 -11664 -44928 -15533 -22312 -05591 037855

34315 -89038 -24163 68654 -15007 -10347 024263

34815 -68279 -91813 23131 -10367 -18636 017759

35315 -52525 -24051 26474 15498 -85341 018640

35 Redlich-Kister Equation for Binary System

The binary excess property ( E

mV ) and deviations (Δ) at several temperatures were fitted to a

Redlich-Kister-type equation [82]

1 1 1

0

(or ) (1 ) (1 2 )j

E i

i

i

Y Y x x A x

(14)

Int J Electrochem Sci Vol 8 2013

5082

where ΔY (YE) represents E

mV (cm3 mol

minus1) and Δ

(mPa s)x1 denotes the mole fraction of

PEG200 Ai represents the polynomial coefficients and j is the degree of the polynomial expansion

The correlated results for excess molar volumes ( E

mV ) viscosity deviations (Δ) including the values

of the fitting parameters Ai together with the standard deviation σ are given in Table 9 where the

tabulated standard deviation σ [83] is defined as

2

exp cal 1 2( )

[ ]Y Y

m n

(15)

where m is the number of experimental data points and n is the number of estimated

parameters The subscripts ldquoexprdquo and ldquocalrdquo denote the values of the experimental and calculated

property respectively As shown in Table 9 the experimentally derived E

mV and Δη values were

correlated satisfactorily by the Redlich-Kister equation

4 CONCLUSIONS

This paper is a systematic characterizations of thermophysical properties for IL binary system

Density viscosity and conductivity for (PEG200 + [PyrMB][BuSO4]) binary system are presented as a

function of temperature at atmospheric pressure it was demonstrated that viscosity and conductivity

were more sensitive to the changes in PEG content or temperature than density and the viscosity and

conductivity of pure IL and (PEG200 + [PyrMB][BuSO4]) binary system at different temperature are

fitted using the VogelndashTammannndashFulcher (VTF) equation with good accuracy The excess molar

volumes excess volume expansivity and viscosity deviations show negative deviations from the ideal

solution the results are interpreted in terms of molecular interactions in the (PEG200 +

[PyrMB][BuSO4]) binary mixture The conductivity increases to a maximum value when the

concentration of PEG200 is increased and decreases after the maximum the data obtained will be

helpful for the application of the ionic liquids as electrolytes and also useful for the ionic liquids

database

ACKNOWLEDGEMENTS

The authors would like to thank the National Science Council of the Republic of China for financially

supporting this project

References

1 P Wasserscheid T Welton Ionic Liquids in Synthesis Second ed Weinheim VCH 2003

2 TY Wu IW Sun ST Gung MW Lin BK Chen HP Wang SG Su J Taiwan Inst Chem

Eng 42 (2011) 513

Int J Electrochem Sci Vol 8 2013

5083

3 TY Wu SG Su KF Lin YC Lin HP Wang MW Lin ST Gung IW Sun Electrochim

Acta 56 (2011) 7278

4 B Baek S Lee C Jung Int J Electrochem Sci 6 (2011) 6220

5 PN Tshibangu SN Ndwandwe ED Dikio Int J Electrochem Sci 6 (2011) 2201

6 TY Wu SG Su HP Wang IW Sun Electrochem Commun 13 (2011) 237

7 TY Wu SG Su HP Wang YC Lin ST Gung MW Lin IW Sun Electrochim Acta 56

(2011) 3209

8 IW Sun YC Lin BK Chen CW Kuo CC Chen SG Su PR Chen TY Wu Int J

Electrochem Sci 7 (2012) 7206

9 TY Wu SG Su ST Gung MW Lin YC Lin CA Lai IW Sun Electrochim Acta 55

(2010) 4475

10 AN Soriano AM Agapito LJLI Lagumbay AR Caparanga MH Li J Taiwan Inst Chem

Eng 42 (2011) 258

11 TY Wu IW Sun ST Gung BK Chen HP Wang SG Su J Taiwan Inst Chem Eng 42

(2011) 874

12 S Ibrahim MR Johan Int J Electrochem Sci 6 (2011) 5565

13 TY Wu SG Su YC Lin HP Wang MW Lin ST Gung IW Sun Electrochim Acta 56

(2010) 853

14 H Wang LX Wu YC Lan JQ Zhao JX Lu Int J Electrochem Sci 6 (2011) 4218

15 FF Liu SQ Liu QJ Feng SX Zhuang JB Zhang P Bu Int J Electrochem Sci 7 (2012)

4381

16 HA Barham SA Brahim Y Rozita KA Mohamed Int J Electrochem Sci 6 (2011) 181

17 SK Shukla LC Murulana EE Ebenso Int J Electrochem Sci 6 (2011) 4286

18 NV Likhanova O Olivares-Xometl D Guzman-Lucero MA Dominguez-Aguilar N Nava

M Corrales-Luna MC Mendoza Int J Electrochem Sci 6 (2011) 4514

19 A Zarrouk M Messali H Zarrok R Salghi AA Ali B Hammouti SS Al-Deyab F Bentiss

Int J Electrochem Sci 7 (2012) 6998

20 BS Ali BH Ali R Yusoff MK Aroua Int J Electrochem Sci 7 (2012) 3835

21 MH Lin YJ Liu ZH Yang YB Huang ZH Sun Y He CL Ni Int J Electrochem Sci 7

(2012) 965

22 CH Su MH Chung HJ Hsieh YK Chang JC Ding HM Wu J Taiwan Inst Chem Eng

43 (2012) 573

23 H Shekaari A Kazempour J Taiwan Inst Chem Eng 43 (2012) 650

24 ZJ Wei Y Li D Thushara YX Liu QL Ren J Taiwan Inst Chem Eng 43 (2012) 363

25 GQ Zhang HW Yang JF Gao HK Zhang CB Zheng YL Cao YH Wang KQ Ding

Int J Electrochem Sci 7 (2012) 7547

26 P Norouzi MR Ganjali F Faridbod SJ Shahtaheri HA Zamani Int J Electrochem Sci 7

(2012) 2633

27 F Faridbod MR Ganjali M Hosseini P Norouzi Int J Electrochem Sci 7 (2012) 1927

28 MR Ganjali Z Rafiei-Sarmazdeh T Poursaberi SJ Shahtaheri P Norouzi Int J

Electrochem Sci 7 (2012) 1908

29 A Babaei DJ Garrett AJ Downard Int J Electrochem Sci 7 (2012) 3141

30 MR Ganjali T Alizade P Norouzi Int J Electrochem Sci 7 (2012) 4800

31 MR Ganjali T Alizade B Larijani F Faridbod P Norouzi Int J Electrochem Sci 7 (2012)

4756

32 P Norouzi B Larijani MR Ganjali Int J Electrochem Sci 7 (2012) 7313

33 TY Wu MH Tsao SG Su HP Wang YC Lin FL Chen CW Chang IW Sun J Braz

Chem Soc 22 (2011) 780

34 MH Tsao TY Wu HP Wang IW Sun SG Su YC Lin CW Chang Mater Lett 65

(2011) 583

Int J Electrochem Sci Vol 8 2013

5084

35 SY Ku SY Lu Int J Electrochem Sci 6 (2011) 5219

36 TY Wu MH Tsao FL Chen SG Su CW Chang HP Wang YC Lin IW Sun J Iran

Chem Soc 7 (2010) 707

37 IW Sun HP Wang H Teng SG Su YC Lin CW Kuo PR Chen TY Wu Int J

Electrochem Sci 7 (2012) 9748

38 TY Wu MH Tsao FL Chen SG Su CW Chang HP Wang YC Lin WC Ou-Yang

IW Sun Int J Mol Sci 11 (2010) 329

39 YX An PJ Zuo XQ Cheng LX Liao GP Yin Int J Electrochem Sci 6 (2011) 2398

40 LC Xuan YX An W Fang LX Liao YL Ma ZY Ren GP Yin Int J Electrochem Sci

6 (2011) 6590

41 HM Wang SQ Liu K Huang XG Yin YN Liu SJ Peng Int J Electrochem Sci 7

(2012) 1688

42 HM Wang SQ Liu NF Wang YN Liu Int J Electrochem Sci 7 (2012) 7579

43 H Ganjali MR Ganjali T Alizadeh F Faridbod P Norouzi Int J Electrochem Sci 6 (2011)

6085

44 MR Ganjali MH Eshraghi S Ghadimi SM Moosavi M Hosseini H Haji-Hashemi P

Norouzi Int J Electrochem Sci 6 (2011) 739

45 MR Ganjali T Poursaberi M Khoobi A Shafiee M Adibi M Pirali-Hamedani P Norouzi

Int J Electrochem Sci 6 (2011) 717

46 P Norouzi M Hosseini MR Ganjali M Rezapour M Adibi Int J Electrochem Sci 6 (2011)

2012

47 MR Ganjali MR Moghaddam M Hosseini P Norouzi Int J Electrochem Sci 6 (2011)

1981

48 MR Ganjali M Hosseini M Pirali-Hamedani HA Zamani Int J Electrochem Sci 6 (2011)

2808

49 MR Ganjali M Rezapour SK Torkestani H Rashedi P Norouzi Int J Electrochem Sci 6

(2011) 2323

50 P Norouzi M Pirali-Hamedani SO Ranaei-Siadat MR Ganjali Int J Electrochem Sci 6

(2011) 3704

51 F Faridbod HA Zamani M Hosseini M Pirali-Hamedani MR Ganjali P Norouzi Int J

Electrochem Sci 6 (2011) 3694

52 MR Ganjali SO Ranaei-Siadat H Rashedi M Rezapour P Norouzi Int J Electrochem Sci

6 (2011) 3684

53 TH Tsai KC Lin SM Chen Int J Electrochem Sci 6 (2011) 2672

54 MR Ganjali T Alizadeh F Azimi B Larjani F Faridbod P Norouzi Int J Electrochem

Sci 6 (2011) 5200

55 R Mirshafian MR Ganjali P Norouzi Int J Electrochem Sci 7 (2012) 1656

56 J Gao JG Liu WM Liu B Li YC Xin Y Yin ZG Zou Int J Electrochem Sci 6 (2011)

6115

57 TY Wu BK Chen L Hao KF Lin IW Sun J Taiwan Inst Chem Eng 42 (2011) 914

58 TY Wu BK Chen L Hao CW Kuo IW Sun J Taiwan Inst Chem Eng 43 (2012) 313

59 SW Peng AN Soriano RB Leron MH Li J Taiwan Inst Chem Eng 42 (2011) 233

60 TY Wu IW Sun MW Lin BK Chen CW Kuo HP Wang YY Chen SG Su J Taiwan

Inst Chem Eng 43 (2012) 58

61 TY Wu BK Chen CW Kuo L Hao YC Peng IW Sun J Taiwan Inst Chem Eng 43

(2012) 860

62 A Arce H Rodriguez A Soto Green Chem 9 (2007) 247

63 TY Wu HC Wang SG Su ST Gung MW Lin CB Lin J Taiwan Inst Chem Eng 41 (2010)

315 64 X Li M Hou Z Zhang B Han G Yang X Wang L Zou Green Chem 10 (2008) 879

Int J Electrochem Sci Vol 8 2013

5085

65 J Chen SK Spear JG Huddleston RD Rogers Green Chem 7 (2005) 64

66 U Domanska M Laskowska J Solution Chem 38 (2009) 779

67 K Tamura M Nakamura S Murakami J Solution Chem 26 (1997) 1199

68 Z Yu H Gao H Wang L Chen J Chem Eng Data 56 (2011) 2877

69 KN Marsh JA Boxall R Lichtenthaler Fluid Phase Equilib 219 (2004) 93

70 TY Wu SG Su ST Gung MW Lin YC Lin WC Ou-Yang IW Sun CA Lai J Iran

Chem Soc 8 (2011) 149

71 TY Wu L Hao CW Kuo YC Lin SG Su PL Kuo IW Sun Int J Electrochem Sci 7

(2012) 2047

72 TY Wu L Hao PR Chen JW Liao Int J Electrochem Sci 8 (2013) 2606

73 CW Kuo CW Huang BK Chen WB Li PR Chen TH Ho CG Tseng TY Wu Int J

Electrochem Sci 8 (2013) 3834

74 CW Kuo WB Li PR Chen JW Liao CG Tseng TY Wu Int J Electrochem Sci 8

(2013) 5007

75 TY Wu BK Chen L Hao YC Lin HP Wang CW Kuo IW Sun Int J Mol Sci 12

(2011) 8750

76 H Rodriguez JF Brennecke J Chem Eng Data 51 (2006) 2145

77 Y Tian X Wang J Wang J Chem Eng Data 53 (2008) 2056

78 TY Wu HC Wang SG Su ST Gung MW Lin CB Lin J Chin Chem Soc 57 (2010)

44

79 TY Wu BK Chen L Hao YC Peng IW Sun Int J Mol Sci 12 (2011) 2598

80 H Eyring MS John Significant Liquid Structure Wiley New York 1969

81 H Every AG Bishop M Forsyth DR MacFarlane Electrochim Acta 45 (2000) 1279 82 O Redlich AT Kister Ind Eng Chem 40 (1948) 345

83 A Paul P Kumar A Samanta J Phys Chem B 109 (2005) 9148

copy 2013 by ESG (wwwelectrochemsciorg)

Int J Electrochem Sci Vol 8 2013

5078

exp[ ]( )

o

o

B

T T

(10)

where ηo B and To are constants The parameter To is the ideal glass transition temperature which

should be slightly below the experimental glass transition temperature Tg [76] The adjustable

parameters obtained from the VTF correlation were presented in Table 7 The obtained parameters o

and B change smoothly with composition for binary mixtures

Table 7 The VTF equation parameters of viscosity ( 1 exp[ ]( )

o

o

B

T T

) and conductivity

(

exp[ ]( )

o

o

B

T T

) for neat PEG200 (x1 = 1) [PyrMB][BuSO4] (x1 = 0) and binary system

PEG200 (1) + [PyrMB][BuSO4] (2)

x1

ηo (mPa s) To (K) B (K) R2a

o (mS cm-1

) To (K) Brsquo (K) R2a

0 027 1810 9540 0999 792 1788 6854 0999

01452 026 1712 9413 0999 577 1699 6268 0999

01942 043 1788 7975 0999 401 1792 5297 0999

02912 053 1794 7264 0999 521 1662 6031 0999

03897 026 1629 8902 0999 274 1803 4381 0999

04893 023 1666 8455 0999 177 1951 3272 0999

05890 015 1648 8865 0999 216 1883 3672 0999

06903 015 1647 8572 0999 88 2174 2000 0999

07922 017 1717 7702 0999 92 2020 2578 0999

08958 012 1642 8360 0999 43 2110 2088 0999

1 014 1649 7868 0999 556 1928 9815 0999

a Correlation coefficient

The viscosities of the mixtures decrease rapidly when organic oligomers are added to the ionic

liquid this decrease is particularly evident in dilute solutions of organic oligomers in the ionic liquid

The strong coulomb interactions between the [BuSO4]- anion and [PyrMB]

+ cation are weakened upon

mixing with the polar organic oligomers which leads to a higher mobility of the ions and a lower

viscosity of the mixtures [77] This indicates that the viscosity of ILs could be therefore tuned for

several applications by adding an organic solvent or by changing temperature [78]

Due to the wide range of possible molecular interactions between the two components

deviations can occur from ideal behavior These viscosity deviations can be quantified by the viscosity

deviation Δη also known as ldquoexcess viscosityrdquo in other sources

1 1 2 2 (mPa s) x x (11)

Int J Electrochem Sci Vol 8 2013

5079

where x1 and x2 are the mole fractions of PEG200 and [PyrMB][BuSO4] respectively and 1

and 2 are the viscosities (mPa middot s) of the solution the pure solvent and the pure IL respectively

Figure 7 shows the viscosity deviations as a function of the PEG200 mole fraction composition x1 and

temperature for the PEG200 + [PyrMB][BuSO4] binary mixture The values of viscosity deviations

are compared with those obtained from the RedlichndashKister polynomial equation The viscosity

deviation for the mixture show negative deviations from ideality over the whole mole fraction range

Figure 7 also shows that the negative values of viscosity deviations decrease with increasing

temperature this can be attributed to the specific interactions in mixtures typically hydrogen bonds break-

up as the temperature increases [79] The minimum value of Δη is observed at about x1 asymp 03 and the

viscosity deviation depends on molecular interactions as well as on the size and shape of the molecules

[80]

Figure 7 Viscosity deviations Δη versus the mole fraction at various temperatures for the binary

mixture PEG200 (1) + [PyrMB][BuSO4] (2)

34 Conductivity

The experimental data of conductivity of the neat ILs [PyrMB][BuSO4] neat PEG200 and

binary system are plotted against the x1 at various temperatures in Figure 8 together with lines

calculated with the four-order polynomial equation

= d0 + d1 x1 + d2 x12 + d3 x1

3 + d4 x1

4 (12)

where x1 is the mole fractions of PEG200 and d0 d1 d2 d3 and d4 refer to the fit coefficients

The parameters of correlation are shown in Table 8 The conductivities of neat IL [PyrMB][BuSO4]

neat PEG200 and binary system at various temperatures were fitted using the VTF equation

exp[ ]

( )o

o

B

T T

(13)

x1

00 02 04 06 08 10

m

Pa s

-700

-600

-500

-400

-300

-200

-100

0

29315 K

30315 K

31315 K

32315 K

33315 K

34315 K

35315 K

Int J Electrochem Sci Vol 8 2013

5080

where T is the absolute temperature and Brsquo and To are adjustable parameters The best-fit

mS cm-1 Brsquo (K) and To (K) parameters are given in Table 7 Neat [PyrMB][BuSO4] neat

PEG200 and binary system were very well fit by the VTF model over the temperature range studied

Figure 8 Plot of conductivity of the PEG200 (1) + [PyrMB][BuSO4] (2) binary system versus

mole fraction x1 at various temperatures

Table 8 Coefficients of polynomiala for the correlation of the conductivity ( mS cm

-1) in function

of concentration at different temperatures of the binary systems PEG200 (1) +

[PyrMB][BuSO4] (2)

TK d0 mS cm

-1 d1 mS cm

-1 d2 mS cm

-1 d3 mS cm

-1 d4 mS cm

-1

29315 02019 09622 -01679 0734 -17284 00095

29815 02588 11031 -02503 09086 -20181 00109

30315 03255 12119 -01935 08565 -21971 00125

30815 04025 13165 -01329 0767 -23477 00141

31315 04904 13712 01238 03677 -23439 00156

31815 05894 15032 -00006 04737 -25518 00171

32315 06999 15802 00743 0265 -25986 00188

32815 08221 16427 01595 00089 -26032 00208

33315 09562 16373 04858 -06207 -24165 00233

a = d0 + d1 x1 + d2 x1

2 + d3 x1

3 + d4 x1

4

As shown in Figure 8 it can be seen that the conductivity of the binary mixture increases with

increasing amount of PEG200 goes through a maximum and then goes down to the specific

conductivity of the neat PEG200 The conductivity is related to the ion mobility and the number of

charge carriers [81] At a fixed concentration the ions move faster at higher temperature due to the

relatively lower viscosity of the mixture On the other hand the composition influences both the ion

mobility and the number of charge carriers at a fixed temperature At the beginning the number of

charge and the ion mobility increase with increasing PEG oligomer composition the maximum of

conductivity is located at x1 = 059 and corresponds to a value of 171 mS cmminus 1

at 33315 K It can also

be observed that the conductivity increases as the temperature increases The higher temperature may

x1

00 02 04 06 08 10

mS

cm

-1

00

05

10

15

20

29315 K

29815 K

30315 K

30815 K

31315 K

31815 K

32315 K

32815 K

33315 K

Int J Electrochem Sci Vol 8 2013

5081

weaken the influence of aggregation to the conductivity which suggests that a higher temperature is

better for the ILs to act as electrolytes

Table 9 RedlickndashKister fitting coefficients Ak and the standard deviation of the VE and ∆for the

binary mixture of PEG200 (1) + [PyrMB][BuSO4] (2) system

TK A0 A1 A2 A3 A4

VEcm

3 mol

-1

29315 -5979 -4906 6585 5754 -1717 002687

29815 -6200 -4760 6464 5767 -2022 002693

30315 -6408 -4612 6345 5774 -2276 002698

30815 -6602 -4461 6229 5774 -2476 002701

31315 -6782 -4310 6116 5767 -2623 002701

31815 -6948 -4155 6006 5753 -2716 002699

32315 -7100 -3999 5899 5732 -2754 002692

32815 -7239 -3840 5795 5704 -2738 002683

33315 -7363 -3679 5694 5669 -2666 002670

33815 -7472 -3515 5596 5626 -2538 002654

34315 -7568 -3350 5501 5576 -2353 002634

34815 -7648 -3182 5409 5518 -2111 002611

35315 -7714 -3011 5320 5452 -1812 002586

∆mPa s

29315 -20414 -17226 -15592 -95544 -75863 399496

29815 -14035 -11558 -10713 -62192 19493 340180

30315 -98261 -78407 -73734 -40709 58145 286725

30815 -69922 -53591 -50601 -2676 67556 235258

31315 -48876 -39537 -41051 -14118 16739 079245

31815 -36917 -25169 -22939 -11646 51047 146189

32315 -27415 -1721 -12581 -92603 21498 104339

32815 -20441 -11703 -77538 -38334 -81478 090708

33315 -15382 -67274 -31134 -47585 -18255 059539

33815 -11664 -44928 -15533 -22312 -05591 037855

34315 -89038 -24163 68654 -15007 -10347 024263

34815 -68279 -91813 23131 -10367 -18636 017759

35315 -52525 -24051 26474 15498 -85341 018640

35 Redlich-Kister Equation for Binary System

The binary excess property ( E

mV ) and deviations (Δ) at several temperatures were fitted to a

Redlich-Kister-type equation [82]

1 1 1

0

(or ) (1 ) (1 2 )j

E i

i

i

Y Y x x A x

(14)

Int J Electrochem Sci Vol 8 2013

5082

where ΔY (YE) represents E

mV (cm3 mol

minus1) and Δ

(mPa s)x1 denotes the mole fraction of

PEG200 Ai represents the polynomial coefficients and j is the degree of the polynomial expansion

The correlated results for excess molar volumes ( E

mV ) viscosity deviations (Δ) including the values

of the fitting parameters Ai together with the standard deviation σ are given in Table 9 where the

tabulated standard deviation σ [83] is defined as

2

exp cal 1 2( )

[ ]Y Y

m n

(15)

where m is the number of experimental data points and n is the number of estimated

parameters The subscripts ldquoexprdquo and ldquocalrdquo denote the values of the experimental and calculated

property respectively As shown in Table 9 the experimentally derived E

mV and Δη values were

correlated satisfactorily by the Redlich-Kister equation

4 CONCLUSIONS

This paper is a systematic characterizations of thermophysical properties for IL binary system

Density viscosity and conductivity for (PEG200 + [PyrMB][BuSO4]) binary system are presented as a

function of temperature at atmospheric pressure it was demonstrated that viscosity and conductivity

were more sensitive to the changes in PEG content or temperature than density and the viscosity and

conductivity of pure IL and (PEG200 + [PyrMB][BuSO4]) binary system at different temperature are

fitted using the VogelndashTammannndashFulcher (VTF) equation with good accuracy The excess molar

volumes excess volume expansivity and viscosity deviations show negative deviations from the ideal

solution the results are interpreted in terms of molecular interactions in the (PEG200 +

[PyrMB][BuSO4]) binary mixture The conductivity increases to a maximum value when the

concentration of PEG200 is increased and decreases after the maximum the data obtained will be

helpful for the application of the ionic liquids as electrolytes and also useful for the ionic liquids

database

ACKNOWLEDGEMENTS

The authors would like to thank the National Science Council of the Republic of China for financially

supporting this project

References

1 P Wasserscheid T Welton Ionic Liquids in Synthesis Second ed Weinheim VCH 2003

2 TY Wu IW Sun ST Gung MW Lin BK Chen HP Wang SG Su J Taiwan Inst Chem

Eng 42 (2011) 513

Int J Electrochem Sci Vol 8 2013

5083

3 TY Wu SG Su KF Lin YC Lin HP Wang MW Lin ST Gung IW Sun Electrochim

Acta 56 (2011) 7278

4 B Baek S Lee C Jung Int J Electrochem Sci 6 (2011) 6220

5 PN Tshibangu SN Ndwandwe ED Dikio Int J Electrochem Sci 6 (2011) 2201

6 TY Wu SG Su HP Wang IW Sun Electrochem Commun 13 (2011) 237

7 TY Wu SG Su HP Wang YC Lin ST Gung MW Lin IW Sun Electrochim Acta 56

(2011) 3209

8 IW Sun YC Lin BK Chen CW Kuo CC Chen SG Su PR Chen TY Wu Int J

Electrochem Sci 7 (2012) 7206

9 TY Wu SG Su ST Gung MW Lin YC Lin CA Lai IW Sun Electrochim Acta 55

(2010) 4475

10 AN Soriano AM Agapito LJLI Lagumbay AR Caparanga MH Li J Taiwan Inst Chem

Eng 42 (2011) 258

11 TY Wu IW Sun ST Gung BK Chen HP Wang SG Su J Taiwan Inst Chem Eng 42

(2011) 874

12 S Ibrahim MR Johan Int J Electrochem Sci 6 (2011) 5565

13 TY Wu SG Su YC Lin HP Wang MW Lin ST Gung IW Sun Electrochim Acta 56

(2010) 853

14 H Wang LX Wu YC Lan JQ Zhao JX Lu Int J Electrochem Sci 6 (2011) 4218

15 FF Liu SQ Liu QJ Feng SX Zhuang JB Zhang P Bu Int J Electrochem Sci 7 (2012)

4381

16 HA Barham SA Brahim Y Rozita KA Mohamed Int J Electrochem Sci 6 (2011) 181

17 SK Shukla LC Murulana EE Ebenso Int J Electrochem Sci 6 (2011) 4286

18 NV Likhanova O Olivares-Xometl D Guzman-Lucero MA Dominguez-Aguilar N Nava

M Corrales-Luna MC Mendoza Int J Electrochem Sci 6 (2011) 4514

19 A Zarrouk M Messali H Zarrok R Salghi AA Ali B Hammouti SS Al-Deyab F Bentiss

Int J Electrochem Sci 7 (2012) 6998

20 BS Ali BH Ali R Yusoff MK Aroua Int J Electrochem Sci 7 (2012) 3835

21 MH Lin YJ Liu ZH Yang YB Huang ZH Sun Y He CL Ni Int J Electrochem Sci 7

(2012) 965

22 CH Su MH Chung HJ Hsieh YK Chang JC Ding HM Wu J Taiwan Inst Chem Eng

43 (2012) 573

23 H Shekaari A Kazempour J Taiwan Inst Chem Eng 43 (2012) 650

24 ZJ Wei Y Li D Thushara YX Liu QL Ren J Taiwan Inst Chem Eng 43 (2012) 363

25 GQ Zhang HW Yang JF Gao HK Zhang CB Zheng YL Cao YH Wang KQ Ding

Int J Electrochem Sci 7 (2012) 7547

26 P Norouzi MR Ganjali F Faridbod SJ Shahtaheri HA Zamani Int J Electrochem Sci 7

(2012) 2633

27 F Faridbod MR Ganjali M Hosseini P Norouzi Int J Electrochem Sci 7 (2012) 1927

28 MR Ganjali Z Rafiei-Sarmazdeh T Poursaberi SJ Shahtaheri P Norouzi Int J

Electrochem Sci 7 (2012) 1908

29 A Babaei DJ Garrett AJ Downard Int J Electrochem Sci 7 (2012) 3141

30 MR Ganjali T Alizade P Norouzi Int J Electrochem Sci 7 (2012) 4800

31 MR Ganjali T Alizade B Larijani F Faridbod P Norouzi Int J Electrochem Sci 7 (2012)

4756

32 P Norouzi B Larijani MR Ganjali Int J Electrochem Sci 7 (2012) 7313

33 TY Wu MH Tsao SG Su HP Wang YC Lin FL Chen CW Chang IW Sun J Braz

Chem Soc 22 (2011) 780

34 MH Tsao TY Wu HP Wang IW Sun SG Su YC Lin CW Chang Mater Lett 65

(2011) 583

Int J Electrochem Sci Vol 8 2013

5084

35 SY Ku SY Lu Int J Electrochem Sci 6 (2011) 5219

36 TY Wu MH Tsao FL Chen SG Su CW Chang HP Wang YC Lin IW Sun J Iran

Chem Soc 7 (2010) 707

37 IW Sun HP Wang H Teng SG Su YC Lin CW Kuo PR Chen TY Wu Int J

Electrochem Sci 7 (2012) 9748

38 TY Wu MH Tsao FL Chen SG Su CW Chang HP Wang YC Lin WC Ou-Yang

IW Sun Int J Mol Sci 11 (2010) 329

39 YX An PJ Zuo XQ Cheng LX Liao GP Yin Int J Electrochem Sci 6 (2011) 2398

40 LC Xuan YX An W Fang LX Liao YL Ma ZY Ren GP Yin Int J Electrochem Sci

6 (2011) 6590

41 HM Wang SQ Liu K Huang XG Yin YN Liu SJ Peng Int J Electrochem Sci 7

(2012) 1688

42 HM Wang SQ Liu NF Wang YN Liu Int J Electrochem Sci 7 (2012) 7579

43 H Ganjali MR Ganjali T Alizadeh F Faridbod P Norouzi Int J Electrochem Sci 6 (2011)

6085

44 MR Ganjali MH Eshraghi S Ghadimi SM Moosavi M Hosseini H Haji-Hashemi P

Norouzi Int J Electrochem Sci 6 (2011) 739

45 MR Ganjali T Poursaberi M Khoobi A Shafiee M Adibi M Pirali-Hamedani P Norouzi

Int J Electrochem Sci 6 (2011) 717

46 P Norouzi M Hosseini MR Ganjali M Rezapour M Adibi Int J Electrochem Sci 6 (2011)

2012

47 MR Ganjali MR Moghaddam M Hosseini P Norouzi Int J Electrochem Sci 6 (2011)

1981

48 MR Ganjali M Hosseini M Pirali-Hamedani HA Zamani Int J Electrochem Sci 6 (2011)

2808

49 MR Ganjali M Rezapour SK Torkestani H Rashedi P Norouzi Int J Electrochem Sci 6

(2011) 2323

50 P Norouzi M Pirali-Hamedani SO Ranaei-Siadat MR Ganjali Int J Electrochem Sci 6

(2011) 3704

51 F Faridbod HA Zamani M Hosseini M Pirali-Hamedani MR Ganjali P Norouzi Int J

Electrochem Sci 6 (2011) 3694

52 MR Ganjali SO Ranaei-Siadat H Rashedi M Rezapour P Norouzi Int J Electrochem Sci

6 (2011) 3684

53 TH Tsai KC Lin SM Chen Int J Electrochem Sci 6 (2011) 2672

54 MR Ganjali T Alizadeh F Azimi B Larjani F Faridbod P Norouzi Int J Electrochem

Sci 6 (2011) 5200

55 R Mirshafian MR Ganjali P Norouzi Int J Electrochem Sci 7 (2012) 1656

56 J Gao JG Liu WM Liu B Li YC Xin Y Yin ZG Zou Int J Electrochem Sci 6 (2011)

6115

57 TY Wu BK Chen L Hao KF Lin IW Sun J Taiwan Inst Chem Eng 42 (2011) 914

58 TY Wu BK Chen L Hao CW Kuo IW Sun J Taiwan Inst Chem Eng 43 (2012) 313

59 SW Peng AN Soriano RB Leron MH Li J Taiwan Inst Chem Eng 42 (2011) 233

60 TY Wu IW Sun MW Lin BK Chen CW Kuo HP Wang YY Chen SG Su J Taiwan

Inst Chem Eng 43 (2012) 58

61 TY Wu BK Chen CW Kuo L Hao YC Peng IW Sun J Taiwan Inst Chem Eng 43

(2012) 860

62 A Arce H Rodriguez A Soto Green Chem 9 (2007) 247

63 TY Wu HC Wang SG Su ST Gung MW Lin CB Lin J Taiwan Inst Chem Eng 41 (2010)

315 64 X Li M Hou Z Zhang B Han G Yang X Wang L Zou Green Chem 10 (2008) 879

Int J Electrochem Sci Vol 8 2013

5085

65 J Chen SK Spear JG Huddleston RD Rogers Green Chem 7 (2005) 64

66 U Domanska M Laskowska J Solution Chem 38 (2009) 779

67 K Tamura M Nakamura S Murakami J Solution Chem 26 (1997) 1199

68 Z Yu H Gao H Wang L Chen J Chem Eng Data 56 (2011) 2877

69 KN Marsh JA Boxall R Lichtenthaler Fluid Phase Equilib 219 (2004) 93

70 TY Wu SG Su ST Gung MW Lin YC Lin WC Ou-Yang IW Sun CA Lai J Iran

Chem Soc 8 (2011) 149

71 TY Wu L Hao CW Kuo YC Lin SG Su PL Kuo IW Sun Int J Electrochem Sci 7

(2012) 2047

72 TY Wu L Hao PR Chen JW Liao Int J Electrochem Sci 8 (2013) 2606

73 CW Kuo CW Huang BK Chen WB Li PR Chen TH Ho CG Tseng TY Wu Int J

Electrochem Sci 8 (2013) 3834

74 CW Kuo WB Li PR Chen JW Liao CG Tseng TY Wu Int J Electrochem Sci 8

(2013) 5007

75 TY Wu BK Chen L Hao YC Lin HP Wang CW Kuo IW Sun Int J Mol Sci 12

(2011) 8750

76 H Rodriguez JF Brennecke J Chem Eng Data 51 (2006) 2145

77 Y Tian X Wang J Wang J Chem Eng Data 53 (2008) 2056

78 TY Wu HC Wang SG Su ST Gung MW Lin CB Lin J Chin Chem Soc 57 (2010)

44

79 TY Wu BK Chen L Hao YC Peng IW Sun Int J Mol Sci 12 (2011) 2598

80 H Eyring MS John Significant Liquid Structure Wiley New York 1969

81 H Every AG Bishop M Forsyth DR MacFarlane Electrochim Acta 45 (2000) 1279 82 O Redlich AT Kister Ind Eng Chem 40 (1948) 345

83 A Paul P Kumar A Samanta J Phys Chem B 109 (2005) 9148

copy 2013 by ESG (wwwelectrochemsciorg)

Int J Electrochem Sci Vol 8 2013

5079

where x1 and x2 are the mole fractions of PEG200 and [PyrMB][BuSO4] respectively and 1

and 2 are the viscosities (mPa middot s) of the solution the pure solvent and the pure IL respectively

Figure 7 shows the viscosity deviations as a function of the PEG200 mole fraction composition x1 and

temperature for the PEG200 + [PyrMB][BuSO4] binary mixture The values of viscosity deviations

are compared with those obtained from the RedlichndashKister polynomial equation The viscosity

deviation for the mixture show negative deviations from ideality over the whole mole fraction range

Figure 7 also shows that the negative values of viscosity deviations decrease with increasing

temperature this can be attributed to the specific interactions in mixtures typically hydrogen bonds break-

up as the temperature increases [79] The minimum value of Δη is observed at about x1 asymp 03 and the

viscosity deviation depends on molecular interactions as well as on the size and shape of the molecules

[80]

Figure 7 Viscosity deviations Δη versus the mole fraction at various temperatures for the binary

mixture PEG200 (1) + [PyrMB][BuSO4] (2)

34 Conductivity

The experimental data of conductivity of the neat ILs [PyrMB][BuSO4] neat PEG200 and

binary system are plotted against the x1 at various temperatures in Figure 8 together with lines

calculated with the four-order polynomial equation

= d0 + d1 x1 + d2 x12 + d3 x1

3 + d4 x1

4 (12)

where x1 is the mole fractions of PEG200 and d0 d1 d2 d3 and d4 refer to the fit coefficients

The parameters of correlation are shown in Table 8 The conductivities of neat IL [PyrMB][BuSO4]

neat PEG200 and binary system at various temperatures were fitted using the VTF equation

exp[ ]

( )o

o

B

T T

(13)

x1

00 02 04 06 08 10

m

Pa s

-700

-600

-500

-400

-300

-200

-100

0

29315 K

30315 K

31315 K

32315 K

33315 K

34315 K

35315 K

Int J Electrochem Sci Vol 8 2013

5080

where T is the absolute temperature and Brsquo and To are adjustable parameters The best-fit

mS cm-1 Brsquo (K) and To (K) parameters are given in Table 7 Neat [PyrMB][BuSO4] neat

PEG200 and binary system were very well fit by the VTF model over the temperature range studied

Figure 8 Plot of conductivity of the PEG200 (1) + [PyrMB][BuSO4] (2) binary system versus

mole fraction x1 at various temperatures

Table 8 Coefficients of polynomiala for the correlation of the conductivity ( mS cm

-1) in function

of concentration at different temperatures of the binary systems PEG200 (1) +

[PyrMB][BuSO4] (2)

TK d0 mS cm

-1 d1 mS cm

-1 d2 mS cm

-1 d3 mS cm

-1 d4 mS cm

-1

29315 02019 09622 -01679 0734 -17284 00095

29815 02588 11031 -02503 09086 -20181 00109

30315 03255 12119 -01935 08565 -21971 00125

30815 04025 13165 -01329 0767 -23477 00141

31315 04904 13712 01238 03677 -23439 00156

31815 05894 15032 -00006 04737 -25518 00171

32315 06999 15802 00743 0265 -25986 00188

32815 08221 16427 01595 00089 -26032 00208

33315 09562 16373 04858 -06207 -24165 00233

a = d0 + d1 x1 + d2 x1

2 + d3 x1

3 + d4 x1

4

As shown in Figure 8 it can be seen that the conductivity of the binary mixture increases with

increasing amount of PEG200 goes through a maximum and then goes down to the specific

conductivity of the neat PEG200 The conductivity is related to the ion mobility and the number of

charge carriers [81] At a fixed concentration the ions move faster at higher temperature due to the

relatively lower viscosity of the mixture On the other hand the composition influences both the ion

mobility and the number of charge carriers at a fixed temperature At the beginning the number of

charge and the ion mobility increase with increasing PEG oligomer composition the maximum of

conductivity is located at x1 = 059 and corresponds to a value of 171 mS cmminus 1

at 33315 K It can also

be observed that the conductivity increases as the temperature increases The higher temperature may

x1

00 02 04 06 08 10

mS

cm

-1

00

05

10

15

20

29315 K

29815 K

30315 K

30815 K

31315 K

31815 K

32315 K

32815 K

33315 K

Int J Electrochem Sci Vol 8 2013

5081

weaken the influence of aggregation to the conductivity which suggests that a higher temperature is

better for the ILs to act as electrolytes

Table 9 RedlickndashKister fitting coefficients Ak and the standard deviation of the VE and ∆for the

binary mixture of PEG200 (1) + [PyrMB][BuSO4] (2) system

TK A0 A1 A2 A3 A4

VEcm

3 mol

-1

29315 -5979 -4906 6585 5754 -1717 002687

29815 -6200 -4760 6464 5767 -2022 002693

30315 -6408 -4612 6345 5774 -2276 002698

30815 -6602 -4461 6229 5774 -2476 002701

31315 -6782 -4310 6116 5767 -2623 002701

31815 -6948 -4155 6006 5753 -2716 002699

32315 -7100 -3999 5899 5732 -2754 002692

32815 -7239 -3840 5795 5704 -2738 002683

33315 -7363 -3679 5694 5669 -2666 002670

33815 -7472 -3515 5596 5626 -2538 002654

34315 -7568 -3350 5501 5576 -2353 002634

34815 -7648 -3182 5409 5518 -2111 002611

35315 -7714 -3011 5320 5452 -1812 002586

∆mPa s

29315 -20414 -17226 -15592 -95544 -75863 399496

29815 -14035 -11558 -10713 -62192 19493 340180

30315 -98261 -78407 -73734 -40709 58145 286725

30815 -69922 -53591 -50601 -2676 67556 235258

31315 -48876 -39537 -41051 -14118 16739 079245

31815 -36917 -25169 -22939 -11646 51047 146189

32315 -27415 -1721 -12581 -92603 21498 104339

32815 -20441 -11703 -77538 -38334 -81478 090708

33315 -15382 -67274 -31134 -47585 -18255 059539

33815 -11664 -44928 -15533 -22312 -05591 037855

34315 -89038 -24163 68654 -15007 -10347 024263

34815 -68279 -91813 23131 -10367 -18636 017759

35315 -52525 -24051 26474 15498 -85341 018640

35 Redlich-Kister Equation for Binary System

The binary excess property ( E

mV ) and deviations (Δ) at several temperatures were fitted to a

Redlich-Kister-type equation [82]

1 1 1

0

(or ) (1 ) (1 2 )j

E i

i

i

Y Y x x A x

(14)

Int J Electrochem Sci Vol 8 2013

5082

where ΔY (YE) represents E

mV (cm3 mol

minus1) and Δ

(mPa s)x1 denotes the mole fraction of

PEG200 Ai represents the polynomial coefficients and j is the degree of the polynomial expansion

The correlated results for excess molar volumes ( E

mV ) viscosity deviations (Δ) including the values

of the fitting parameters Ai together with the standard deviation σ are given in Table 9 where the

tabulated standard deviation σ [83] is defined as

2

exp cal 1 2( )

[ ]Y Y

m n

(15)

where m is the number of experimental data points and n is the number of estimated

parameters The subscripts ldquoexprdquo and ldquocalrdquo denote the values of the experimental and calculated

property respectively As shown in Table 9 the experimentally derived E

mV and Δη values were

correlated satisfactorily by the Redlich-Kister equation

4 CONCLUSIONS

This paper is a systematic characterizations of thermophysical properties for IL binary system

Density viscosity and conductivity for (PEG200 + [PyrMB][BuSO4]) binary system are presented as a

function of temperature at atmospheric pressure it was demonstrated that viscosity and conductivity

were more sensitive to the changes in PEG content or temperature than density and the viscosity and

conductivity of pure IL and (PEG200 + [PyrMB][BuSO4]) binary system at different temperature are

fitted using the VogelndashTammannndashFulcher (VTF) equation with good accuracy The excess molar

volumes excess volume expansivity and viscosity deviations show negative deviations from the ideal

solution the results are interpreted in terms of molecular interactions in the (PEG200 +

[PyrMB][BuSO4]) binary mixture The conductivity increases to a maximum value when the

concentration of PEG200 is increased and decreases after the maximum the data obtained will be

helpful for the application of the ionic liquids as electrolytes and also useful for the ionic liquids

database

ACKNOWLEDGEMENTS

The authors would like to thank the National Science Council of the Republic of China for financially

supporting this project

References

1 P Wasserscheid T Welton Ionic Liquids in Synthesis Second ed Weinheim VCH 2003

2 TY Wu IW Sun ST Gung MW Lin BK Chen HP Wang SG Su J Taiwan Inst Chem

Eng 42 (2011) 513

Int J Electrochem Sci Vol 8 2013

5083

3 TY Wu SG Su KF Lin YC Lin HP Wang MW Lin ST Gung IW Sun Electrochim

Acta 56 (2011) 7278

4 B Baek S Lee C Jung Int J Electrochem Sci 6 (2011) 6220

5 PN Tshibangu SN Ndwandwe ED Dikio Int J Electrochem Sci 6 (2011) 2201

6 TY Wu SG Su HP Wang IW Sun Electrochem Commun 13 (2011) 237

7 TY Wu SG Su HP Wang YC Lin ST Gung MW Lin IW Sun Electrochim Acta 56

(2011) 3209

8 IW Sun YC Lin BK Chen CW Kuo CC Chen SG Su PR Chen TY Wu Int J

Electrochem Sci 7 (2012) 7206

9 TY Wu SG Su ST Gung MW Lin YC Lin CA Lai IW Sun Electrochim Acta 55

(2010) 4475

10 AN Soriano AM Agapito LJLI Lagumbay AR Caparanga MH Li J Taiwan Inst Chem

Eng 42 (2011) 258

11 TY Wu IW Sun ST Gung BK Chen HP Wang SG Su J Taiwan Inst Chem Eng 42

(2011) 874

12 S Ibrahim MR Johan Int J Electrochem Sci 6 (2011) 5565

13 TY Wu SG Su YC Lin HP Wang MW Lin ST Gung IW Sun Electrochim Acta 56

(2010) 853

14 H Wang LX Wu YC Lan JQ Zhao JX Lu Int J Electrochem Sci 6 (2011) 4218

15 FF Liu SQ Liu QJ Feng SX Zhuang JB Zhang P Bu Int J Electrochem Sci 7 (2012)

4381

16 HA Barham SA Brahim Y Rozita KA Mohamed Int J Electrochem Sci 6 (2011) 181

17 SK Shukla LC Murulana EE Ebenso Int J Electrochem Sci 6 (2011) 4286

18 NV Likhanova O Olivares-Xometl D Guzman-Lucero MA Dominguez-Aguilar N Nava

M Corrales-Luna MC Mendoza Int J Electrochem Sci 6 (2011) 4514

19 A Zarrouk M Messali H Zarrok R Salghi AA Ali B Hammouti SS Al-Deyab F Bentiss

Int J Electrochem Sci 7 (2012) 6998

20 BS Ali BH Ali R Yusoff MK Aroua Int J Electrochem Sci 7 (2012) 3835

21 MH Lin YJ Liu ZH Yang YB Huang ZH Sun Y He CL Ni Int J Electrochem Sci 7

(2012) 965

22 CH Su MH Chung HJ Hsieh YK Chang JC Ding HM Wu J Taiwan Inst Chem Eng

43 (2012) 573

23 H Shekaari A Kazempour J Taiwan Inst Chem Eng 43 (2012) 650

24 ZJ Wei Y Li D Thushara YX Liu QL Ren J Taiwan Inst Chem Eng 43 (2012) 363

25 GQ Zhang HW Yang JF Gao HK Zhang CB Zheng YL Cao YH Wang KQ Ding

Int J Electrochem Sci 7 (2012) 7547

26 P Norouzi MR Ganjali F Faridbod SJ Shahtaheri HA Zamani Int J Electrochem Sci 7

(2012) 2633

27 F Faridbod MR Ganjali M Hosseini P Norouzi Int J Electrochem Sci 7 (2012) 1927

28 MR Ganjali Z Rafiei-Sarmazdeh T Poursaberi SJ Shahtaheri P Norouzi Int J

Electrochem Sci 7 (2012) 1908

29 A Babaei DJ Garrett AJ Downard Int J Electrochem Sci 7 (2012) 3141

30 MR Ganjali T Alizade P Norouzi Int J Electrochem Sci 7 (2012) 4800

31 MR Ganjali T Alizade B Larijani F Faridbod P Norouzi Int J Electrochem Sci 7 (2012)

4756

32 P Norouzi B Larijani MR Ganjali Int J Electrochem Sci 7 (2012) 7313

33 TY Wu MH Tsao SG Su HP Wang YC Lin FL Chen CW Chang IW Sun J Braz

Chem Soc 22 (2011) 780

34 MH Tsao TY Wu HP Wang IW Sun SG Su YC Lin CW Chang Mater Lett 65

(2011) 583

Int J Electrochem Sci Vol 8 2013

5084

35 SY Ku SY Lu Int J Electrochem Sci 6 (2011) 5219

36 TY Wu MH Tsao FL Chen SG Su CW Chang HP Wang YC Lin IW Sun J Iran

Chem Soc 7 (2010) 707

37 IW Sun HP Wang H Teng SG Su YC Lin CW Kuo PR Chen TY Wu Int J

Electrochem Sci 7 (2012) 9748

38 TY Wu MH Tsao FL Chen SG Su CW Chang HP Wang YC Lin WC Ou-Yang

IW Sun Int J Mol Sci 11 (2010) 329

39 YX An PJ Zuo XQ Cheng LX Liao GP Yin Int J Electrochem Sci 6 (2011) 2398

40 LC Xuan YX An W Fang LX Liao YL Ma ZY Ren GP Yin Int J Electrochem Sci

6 (2011) 6590

41 HM Wang SQ Liu K Huang XG Yin YN Liu SJ Peng Int J Electrochem Sci 7

(2012) 1688

42 HM Wang SQ Liu NF Wang YN Liu Int J Electrochem Sci 7 (2012) 7579

43 H Ganjali MR Ganjali T Alizadeh F Faridbod P Norouzi Int J Electrochem Sci 6 (2011)

6085

44 MR Ganjali MH Eshraghi S Ghadimi SM Moosavi M Hosseini H Haji-Hashemi P

Norouzi Int J Electrochem Sci 6 (2011) 739

45 MR Ganjali T Poursaberi M Khoobi A Shafiee M Adibi M Pirali-Hamedani P Norouzi

Int J Electrochem Sci 6 (2011) 717

46 P Norouzi M Hosseini MR Ganjali M Rezapour M Adibi Int J Electrochem Sci 6 (2011)

2012

47 MR Ganjali MR Moghaddam M Hosseini P Norouzi Int J Electrochem Sci 6 (2011)

1981

48 MR Ganjali M Hosseini M Pirali-Hamedani HA Zamani Int J Electrochem Sci 6 (2011)

2808

49 MR Ganjali M Rezapour SK Torkestani H Rashedi P Norouzi Int J Electrochem Sci 6

(2011) 2323

50 P Norouzi M Pirali-Hamedani SO Ranaei-Siadat MR Ganjali Int J Electrochem Sci 6

(2011) 3704

51 F Faridbod HA Zamani M Hosseini M Pirali-Hamedani MR Ganjali P Norouzi Int J

Electrochem Sci 6 (2011) 3694

52 MR Ganjali SO Ranaei-Siadat H Rashedi M Rezapour P Norouzi Int J Electrochem Sci

6 (2011) 3684

53 TH Tsai KC Lin SM Chen Int J Electrochem Sci 6 (2011) 2672

54 MR Ganjali T Alizadeh F Azimi B Larjani F Faridbod P Norouzi Int J Electrochem

Sci 6 (2011) 5200

55 R Mirshafian MR Ganjali P Norouzi Int J Electrochem Sci 7 (2012) 1656

56 J Gao JG Liu WM Liu B Li YC Xin Y Yin ZG Zou Int J Electrochem Sci 6 (2011)

6115

57 TY Wu BK Chen L Hao KF Lin IW Sun J Taiwan Inst Chem Eng 42 (2011) 914

58 TY Wu BK Chen L Hao CW Kuo IW Sun J Taiwan Inst Chem Eng 43 (2012) 313

59 SW Peng AN Soriano RB Leron MH Li J Taiwan Inst Chem Eng 42 (2011) 233

60 TY Wu IW Sun MW Lin BK Chen CW Kuo HP Wang YY Chen SG Su J Taiwan

Inst Chem Eng 43 (2012) 58

61 TY Wu BK Chen CW Kuo L Hao YC Peng IW Sun J Taiwan Inst Chem Eng 43

(2012) 860

62 A Arce H Rodriguez A Soto Green Chem 9 (2007) 247

63 TY Wu HC Wang SG Su ST Gung MW Lin CB Lin J Taiwan Inst Chem Eng 41 (2010)

315 64 X Li M Hou Z Zhang B Han G Yang X Wang L Zou Green Chem 10 (2008) 879

Int J Electrochem Sci Vol 8 2013

5085

65 J Chen SK Spear JG Huddleston RD Rogers Green Chem 7 (2005) 64

66 U Domanska M Laskowska J Solution Chem 38 (2009) 779

67 K Tamura M Nakamura S Murakami J Solution Chem 26 (1997) 1199

68 Z Yu H Gao H Wang L Chen J Chem Eng Data 56 (2011) 2877

69 KN Marsh JA Boxall R Lichtenthaler Fluid Phase Equilib 219 (2004) 93

70 TY Wu SG Su ST Gung MW Lin YC Lin WC Ou-Yang IW Sun CA Lai J Iran

Chem Soc 8 (2011) 149

71 TY Wu L Hao CW Kuo YC Lin SG Su PL Kuo IW Sun Int J Electrochem Sci 7

(2012) 2047

72 TY Wu L Hao PR Chen JW Liao Int J Electrochem Sci 8 (2013) 2606

73 CW Kuo CW Huang BK Chen WB Li PR Chen TH Ho CG Tseng TY Wu Int J

Electrochem Sci 8 (2013) 3834

74 CW Kuo WB Li PR Chen JW Liao CG Tseng TY Wu Int J Electrochem Sci 8

(2013) 5007

75 TY Wu BK Chen L Hao YC Lin HP Wang CW Kuo IW Sun Int J Mol Sci 12

(2011) 8750

76 H Rodriguez JF Brennecke J Chem Eng Data 51 (2006) 2145

77 Y Tian X Wang J Wang J Chem Eng Data 53 (2008) 2056

78 TY Wu HC Wang SG Su ST Gung MW Lin CB Lin J Chin Chem Soc 57 (2010)

44

79 TY Wu BK Chen L Hao YC Peng IW Sun Int J Mol Sci 12 (2011) 2598

80 H Eyring MS John Significant Liquid Structure Wiley New York 1969

81 H Every AG Bishop M Forsyth DR MacFarlane Electrochim Acta 45 (2000) 1279 82 O Redlich AT Kister Ind Eng Chem 40 (1948) 345

83 A Paul P Kumar A Samanta J Phys Chem B 109 (2005) 9148

copy 2013 by ESG (wwwelectrochemsciorg)

Int J Electrochem Sci Vol 8 2013

5080

where T is the absolute temperature and Brsquo and To are adjustable parameters The best-fit

mS cm-1 Brsquo (K) and To (K) parameters are given in Table 7 Neat [PyrMB][BuSO4] neat

PEG200 and binary system were very well fit by the VTF model over the temperature range studied

Figure 8 Plot of conductivity of the PEG200 (1) + [PyrMB][BuSO4] (2) binary system versus

mole fraction x1 at various temperatures

Table 8 Coefficients of polynomiala for the correlation of the conductivity ( mS cm

-1) in function

of concentration at different temperatures of the binary systems PEG200 (1) +

[PyrMB][BuSO4] (2)

TK d0 mS cm

-1 d1 mS cm

-1 d2 mS cm

-1 d3 mS cm

-1 d4 mS cm

-1

29315 02019 09622 -01679 0734 -17284 00095

29815 02588 11031 -02503 09086 -20181 00109

30315 03255 12119 -01935 08565 -21971 00125

30815 04025 13165 -01329 0767 -23477 00141

31315 04904 13712 01238 03677 -23439 00156

31815 05894 15032 -00006 04737 -25518 00171

32315 06999 15802 00743 0265 -25986 00188

32815 08221 16427 01595 00089 -26032 00208

33315 09562 16373 04858 -06207 -24165 00233

a = d0 + d1 x1 + d2 x1

2 + d3 x1

3 + d4 x1

4

As shown in Figure 8 it can be seen that the conductivity of the binary mixture increases with

increasing amount of PEG200 goes through a maximum and then goes down to the specific

conductivity of the neat PEG200 The conductivity is related to the ion mobility and the number of

charge carriers [81] At a fixed concentration the ions move faster at higher temperature due to the

relatively lower viscosity of the mixture On the other hand the composition influences both the ion

mobility and the number of charge carriers at a fixed temperature At the beginning the number of

charge and the ion mobility increase with increasing PEG oligomer composition the maximum of

conductivity is located at x1 = 059 and corresponds to a value of 171 mS cmminus 1

at 33315 K It can also

be observed that the conductivity increases as the temperature increases The higher temperature may

x1

00 02 04 06 08 10

mS

cm

-1

00

05

10

15

20

29315 K

29815 K

30315 K

30815 K

31315 K

31815 K

32315 K

32815 K

33315 K

Int J Electrochem Sci Vol 8 2013

5081

weaken the influence of aggregation to the conductivity which suggests that a higher temperature is

better for the ILs to act as electrolytes

Table 9 RedlickndashKister fitting coefficients Ak and the standard deviation of the VE and ∆for the

binary mixture of PEG200 (1) + [PyrMB][BuSO4] (2) system

TK A0 A1 A2 A3 A4

VEcm

3 mol

-1

29315 -5979 -4906 6585 5754 -1717 002687

29815 -6200 -4760 6464 5767 -2022 002693

30315 -6408 -4612 6345 5774 -2276 002698

30815 -6602 -4461 6229 5774 -2476 002701

31315 -6782 -4310 6116 5767 -2623 002701

31815 -6948 -4155 6006 5753 -2716 002699

32315 -7100 -3999 5899 5732 -2754 002692

32815 -7239 -3840 5795 5704 -2738 002683

33315 -7363 -3679 5694 5669 -2666 002670

33815 -7472 -3515 5596 5626 -2538 002654

34315 -7568 -3350 5501 5576 -2353 002634

34815 -7648 -3182 5409 5518 -2111 002611

35315 -7714 -3011 5320 5452 -1812 002586

∆mPa s

29315 -20414 -17226 -15592 -95544 -75863 399496

29815 -14035 -11558 -10713 -62192 19493 340180

30315 -98261 -78407 -73734 -40709 58145 286725

30815 -69922 -53591 -50601 -2676 67556 235258

31315 -48876 -39537 -41051 -14118 16739 079245

31815 -36917 -25169 -22939 -11646 51047 146189

32315 -27415 -1721 -12581 -92603 21498 104339

32815 -20441 -11703 -77538 -38334 -81478 090708

33315 -15382 -67274 -31134 -47585 -18255 059539

33815 -11664 -44928 -15533 -22312 -05591 037855

34315 -89038 -24163 68654 -15007 -10347 024263

34815 -68279 -91813 23131 -10367 -18636 017759

35315 -52525 -24051 26474 15498 -85341 018640

35 Redlich-Kister Equation for Binary System

The binary excess property ( E

mV ) and deviations (Δ) at several temperatures were fitted to a

Redlich-Kister-type equation [82]

1 1 1

0

(or ) (1 ) (1 2 )j

E i

i

i

Y Y x x A x

(14)

Int J Electrochem Sci Vol 8 2013

5082

where ΔY (YE) represents E

mV (cm3 mol

minus1) and Δ

(mPa s)x1 denotes the mole fraction of

PEG200 Ai represents the polynomial coefficients and j is the degree of the polynomial expansion

The correlated results for excess molar volumes ( E

mV ) viscosity deviations (Δ) including the values

of the fitting parameters Ai together with the standard deviation σ are given in Table 9 where the

tabulated standard deviation σ [83] is defined as

2

exp cal 1 2( )

[ ]Y Y

m n

(15)

where m is the number of experimental data points and n is the number of estimated

parameters The subscripts ldquoexprdquo and ldquocalrdquo denote the values of the experimental and calculated

property respectively As shown in Table 9 the experimentally derived E

mV and Δη values were

correlated satisfactorily by the Redlich-Kister equation

4 CONCLUSIONS

This paper is a systematic characterizations of thermophysical properties for IL binary system

Density viscosity and conductivity for (PEG200 + [PyrMB][BuSO4]) binary system are presented as a

function of temperature at atmospheric pressure it was demonstrated that viscosity and conductivity

were more sensitive to the changes in PEG content or temperature than density and the viscosity and

conductivity of pure IL and (PEG200 + [PyrMB][BuSO4]) binary system at different temperature are

fitted using the VogelndashTammannndashFulcher (VTF) equation with good accuracy The excess molar

volumes excess volume expansivity and viscosity deviations show negative deviations from the ideal

solution the results are interpreted in terms of molecular interactions in the (PEG200 +

[PyrMB][BuSO4]) binary mixture The conductivity increases to a maximum value when the

concentration of PEG200 is increased and decreases after the maximum the data obtained will be

helpful for the application of the ionic liquids as electrolytes and also useful for the ionic liquids

database

ACKNOWLEDGEMENTS

The authors would like to thank the National Science Council of the Republic of China for financially

supporting this project

References

1 P Wasserscheid T Welton Ionic Liquids in Synthesis Second ed Weinheim VCH 2003

2 TY Wu IW Sun ST Gung MW Lin BK Chen HP Wang SG Su J Taiwan Inst Chem

Eng 42 (2011) 513

Int J Electrochem Sci Vol 8 2013

5083

3 TY Wu SG Su KF Lin YC Lin HP Wang MW Lin ST Gung IW Sun Electrochim

Acta 56 (2011) 7278

4 B Baek S Lee C Jung Int J Electrochem Sci 6 (2011) 6220

5 PN Tshibangu SN Ndwandwe ED Dikio Int J Electrochem Sci 6 (2011) 2201

6 TY Wu SG Su HP Wang IW Sun Electrochem Commun 13 (2011) 237

7 TY Wu SG Su HP Wang YC Lin ST Gung MW Lin IW Sun Electrochim Acta 56

(2011) 3209

8 IW Sun YC Lin BK Chen CW Kuo CC Chen SG Su PR Chen TY Wu Int J

Electrochem Sci 7 (2012) 7206

9 TY Wu SG Su ST Gung MW Lin YC Lin CA Lai IW Sun Electrochim Acta 55

(2010) 4475

10 AN Soriano AM Agapito LJLI Lagumbay AR Caparanga MH Li J Taiwan Inst Chem

Eng 42 (2011) 258

11 TY Wu IW Sun ST Gung BK Chen HP Wang SG Su J Taiwan Inst Chem Eng 42

(2011) 874

12 S Ibrahim MR Johan Int J Electrochem Sci 6 (2011) 5565

13 TY Wu SG Su YC Lin HP Wang MW Lin ST Gung IW Sun Electrochim Acta 56

(2010) 853

14 H Wang LX Wu YC Lan JQ Zhao JX Lu Int J Electrochem Sci 6 (2011) 4218

15 FF Liu SQ Liu QJ Feng SX Zhuang JB Zhang P Bu Int J Electrochem Sci 7 (2012)

4381

16 HA Barham SA Brahim Y Rozita KA Mohamed Int J Electrochem Sci 6 (2011) 181

17 SK Shukla LC Murulana EE Ebenso Int J Electrochem Sci 6 (2011) 4286

18 NV Likhanova O Olivares-Xometl D Guzman-Lucero MA Dominguez-Aguilar N Nava

M Corrales-Luna MC Mendoza Int J Electrochem Sci 6 (2011) 4514

19 A Zarrouk M Messali H Zarrok R Salghi AA Ali B Hammouti SS Al-Deyab F Bentiss

Int J Electrochem Sci 7 (2012) 6998

20 BS Ali BH Ali R Yusoff MK Aroua Int J Electrochem Sci 7 (2012) 3835

21 MH Lin YJ Liu ZH Yang YB Huang ZH Sun Y He CL Ni Int J Electrochem Sci 7

(2012) 965

22 CH Su MH Chung HJ Hsieh YK Chang JC Ding HM Wu J Taiwan Inst Chem Eng

43 (2012) 573

23 H Shekaari A Kazempour J Taiwan Inst Chem Eng 43 (2012) 650

24 ZJ Wei Y Li D Thushara YX Liu QL Ren J Taiwan Inst Chem Eng 43 (2012) 363

25 GQ Zhang HW Yang JF Gao HK Zhang CB Zheng YL Cao YH Wang KQ Ding

Int J Electrochem Sci 7 (2012) 7547

26 P Norouzi MR Ganjali F Faridbod SJ Shahtaheri HA Zamani Int J Electrochem Sci 7

(2012) 2633

27 F Faridbod MR Ganjali M Hosseini P Norouzi Int J Electrochem Sci 7 (2012) 1927

28 MR Ganjali Z Rafiei-Sarmazdeh T Poursaberi SJ Shahtaheri P Norouzi Int J

Electrochem Sci 7 (2012) 1908

29 A Babaei DJ Garrett AJ Downard Int J Electrochem Sci 7 (2012) 3141

30 MR Ganjali T Alizade P Norouzi Int J Electrochem Sci 7 (2012) 4800

31 MR Ganjali T Alizade B Larijani F Faridbod P Norouzi Int J Electrochem Sci 7 (2012)

4756

32 P Norouzi B Larijani MR Ganjali Int J Electrochem Sci 7 (2012) 7313

33 TY Wu MH Tsao SG Su HP Wang YC Lin FL Chen CW Chang IW Sun J Braz

Chem Soc 22 (2011) 780

34 MH Tsao TY Wu HP Wang IW Sun SG Su YC Lin CW Chang Mater Lett 65

(2011) 583

Int J Electrochem Sci Vol 8 2013

5084

35 SY Ku SY Lu Int J Electrochem Sci 6 (2011) 5219

36 TY Wu MH Tsao FL Chen SG Su CW Chang HP Wang YC Lin IW Sun J Iran

Chem Soc 7 (2010) 707

37 IW Sun HP Wang H Teng SG Su YC Lin CW Kuo PR Chen TY Wu Int J

Electrochem Sci 7 (2012) 9748

38 TY Wu MH Tsao FL Chen SG Su CW Chang HP Wang YC Lin WC Ou-Yang

IW Sun Int J Mol Sci 11 (2010) 329

39 YX An PJ Zuo XQ Cheng LX Liao GP Yin Int J Electrochem Sci 6 (2011) 2398

40 LC Xuan YX An W Fang LX Liao YL Ma ZY Ren GP Yin Int J Electrochem Sci

6 (2011) 6590

41 HM Wang SQ Liu K Huang XG Yin YN Liu SJ Peng Int J Electrochem Sci 7

(2012) 1688

42 HM Wang SQ Liu NF Wang YN Liu Int J Electrochem Sci 7 (2012) 7579

43 H Ganjali MR Ganjali T Alizadeh F Faridbod P Norouzi Int J Electrochem Sci 6 (2011)

6085

44 MR Ganjali MH Eshraghi S Ghadimi SM Moosavi M Hosseini H Haji-Hashemi P

Norouzi Int J Electrochem Sci 6 (2011) 739

45 MR Ganjali T Poursaberi M Khoobi A Shafiee M Adibi M Pirali-Hamedani P Norouzi

Int J Electrochem Sci 6 (2011) 717

46 P Norouzi M Hosseini MR Ganjali M Rezapour M Adibi Int J Electrochem Sci 6 (2011)

2012

47 MR Ganjali MR Moghaddam M Hosseini P Norouzi Int J Electrochem Sci 6 (2011)

1981

48 MR Ganjali M Hosseini M Pirali-Hamedani HA Zamani Int J Electrochem Sci 6 (2011)

2808

49 MR Ganjali M Rezapour SK Torkestani H Rashedi P Norouzi Int J Electrochem Sci 6

(2011) 2323

50 P Norouzi M Pirali-Hamedani SO Ranaei-Siadat MR Ganjali Int J Electrochem Sci 6

(2011) 3704

51 F Faridbod HA Zamani M Hosseini M Pirali-Hamedani MR Ganjali P Norouzi Int J

Electrochem Sci 6 (2011) 3694

52 MR Ganjali SO Ranaei-Siadat H Rashedi M Rezapour P Norouzi Int J Electrochem Sci

6 (2011) 3684

53 TH Tsai KC Lin SM Chen Int J Electrochem Sci 6 (2011) 2672

54 MR Ganjali T Alizadeh F Azimi B Larjani F Faridbod P Norouzi Int J Electrochem

Sci 6 (2011) 5200

55 R Mirshafian MR Ganjali P Norouzi Int J Electrochem Sci 7 (2012) 1656

56 J Gao JG Liu WM Liu B Li YC Xin Y Yin ZG Zou Int J Electrochem Sci 6 (2011)

6115

57 TY Wu BK Chen L Hao KF Lin IW Sun J Taiwan Inst Chem Eng 42 (2011) 914

58 TY Wu BK Chen L Hao CW Kuo IW Sun J Taiwan Inst Chem Eng 43 (2012) 313

59 SW Peng AN Soriano RB Leron MH Li J Taiwan Inst Chem Eng 42 (2011) 233

60 TY Wu IW Sun MW Lin BK Chen CW Kuo HP Wang YY Chen SG Su J Taiwan

Inst Chem Eng 43 (2012) 58

61 TY Wu BK Chen CW Kuo L Hao YC Peng IW Sun J Taiwan Inst Chem Eng 43

(2012) 860

62 A Arce H Rodriguez A Soto Green Chem 9 (2007) 247

63 TY Wu HC Wang SG Su ST Gung MW Lin CB Lin J Taiwan Inst Chem Eng 41 (2010)

315 64 X Li M Hou Z Zhang B Han G Yang X Wang L Zou Green Chem 10 (2008) 879

Int J Electrochem Sci Vol 8 2013

5085

65 J Chen SK Spear JG Huddleston RD Rogers Green Chem 7 (2005) 64

66 U Domanska M Laskowska J Solution Chem 38 (2009) 779

67 K Tamura M Nakamura S Murakami J Solution Chem 26 (1997) 1199

68 Z Yu H Gao H Wang L Chen J Chem Eng Data 56 (2011) 2877

69 KN Marsh JA Boxall R Lichtenthaler Fluid Phase Equilib 219 (2004) 93

70 TY Wu SG Su ST Gung MW Lin YC Lin WC Ou-Yang IW Sun CA Lai J Iran

Chem Soc 8 (2011) 149

71 TY Wu L Hao CW Kuo YC Lin SG Su PL Kuo IW Sun Int J Electrochem Sci 7

(2012) 2047

72 TY Wu L Hao PR Chen JW Liao Int J Electrochem Sci 8 (2013) 2606

73 CW Kuo CW Huang BK Chen WB Li PR Chen TH Ho CG Tseng TY Wu Int J

Electrochem Sci 8 (2013) 3834

74 CW Kuo WB Li PR Chen JW Liao CG Tseng TY Wu Int J Electrochem Sci 8

(2013) 5007

75 TY Wu BK Chen L Hao YC Lin HP Wang CW Kuo IW Sun Int J Mol Sci 12

(2011) 8750

76 H Rodriguez JF Brennecke J Chem Eng Data 51 (2006) 2145

77 Y Tian X Wang J Wang J Chem Eng Data 53 (2008) 2056

78 TY Wu HC Wang SG Su ST Gung MW Lin CB Lin J Chin Chem Soc 57 (2010)

44

79 TY Wu BK Chen L Hao YC Peng IW Sun Int J Mol Sci 12 (2011) 2598

80 H Eyring MS John Significant Liquid Structure Wiley New York 1969

81 H Every AG Bishop M Forsyth DR MacFarlane Electrochim Acta 45 (2000) 1279 82 O Redlich AT Kister Ind Eng Chem 40 (1948) 345

83 A Paul P Kumar A Samanta J Phys Chem B 109 (2005) 9148

copy 2013 by ESG (wwwelectrochemsciorg)

Int J Electrochem Sci Vol 8 2013

5081

weaken the influence of aggregation to the conductivity which suggests that a higher temperature is

better for the ILs to act as electrolytes

Table 9 RedlickndashKister fitting coefficients Ak and the standard deviation of the VE and ∆for the

binary mixture of PEG200 (1) + [PyrMB][BuSO4] (2) system

TK A0 A1 A2 A3 A4

VEcm

3 mol

-1

29315 -5979 -4906 6585 5754 -1717 002687

29815 -6200 -4760 6464 5767 -2022 002693

30315 -6408 -4612 6345 5774 -2276 002698

30815 -6602 -4461 6229 5774 -2476 002701

31315 -6782 -4310 6116 5767 -2623 002701

31815 -6948 -4155 6006 5753 -2716 002699

32315 -7100 -3999 5899 5732 -2754 002692

32815 -7239 -3840 5795 5704 -2738 002683

33315 -7363 -3679 5694 5669 -2666 002670

33815 -7472 -3515 5596 5626 -2538 002654

34315 -7568 -3350 5501 5576 -2353 002634

34815 -7648 -3182 5409 5518 -2111 002611

35315 -7714 -3011 5320 5452 -1812 002586

∆mPa s

29315 -20414 -17226 -15592 -95544 -75863 399496

29815 -14035 -11558 -10713 -62192 19493 340180

30315 -98261 -78407 -73734 -40709 58145 286725

30815 -69922 -53591 -50601 -2676 67556 235258

31315 -48876 -39537 -41051 -14118 16739 079245

31815 -36917 -25169 -22939 -11646 51047 146189

32315 -27415 -1721 -12581 -92603 21498 104339

32815 -20441 -11703 -77538 -38334 -81478 090708

33315 -15382 -67274 -31134 -47585 -18255 059539

33815 -11664 -44928 -15533 -22312 -05591 037855

34315 -89038 -24163 68654 -15007 -10347 024263

34815 -68279 -91813 23131 -10367 -18636 017759

35315 -52525 -24051 26474 15498 -85341 018640

35 Redlich-Kister Equation for Binary System

The binary excess property ( E

mV ) and deviations (Δ) at several temperatures were fitted to a

Redlich-Kister-type equation [82]

1 1 1

0

(or ) (1 ) (1 2 )j

E i

i

i

Y Y x x A x

(14)

Int J Electrochem Sci Vol 8 2013

5082

where ΔY (YE) represents E

mV (cm3 mol

minus1) and Δ

(mPa s)x1 denotes the mole fraction of

PEG200 Ai represents the polynomial coefficients and j is the degree of the polynomial expansion

The correlated results for excess molar volumes ( E

mV ) viscosity deviations (Δ) including the values

of the fitting parameters Ai together with the standard deviation σ are given in Table 9 where the

tabulated standard deviation σ [83] is defined as

2

exp cal 1 2( )

[ ]Y Y

m n

(15)

where m is the number of experimental data points and n is the number of estimated

parameters The subscripts ldquoexprdquo and ldquocalrdquo denote the values of the experimental and calculated

property respectively As shown in Table 9 the experimentally derived E

mV and Δη values were

correlated satisfactorily by the Redlich-Kister equation

4 CONCLUSIONS

This paper is a systematic characterizations of thermophysical properties for IL binary system

Density viscosity and conductivity for (PEG200 + [PyrMB][BuSO4]) binary system are presented as a

function of temperature at atmospheric pressure it was demonstrated that viscosity and conductivity

were more sensitive to the changes in PEG content or temperature than density and the viscosity and

conductivity of pure IL and (PEG200 + [PyrMB][BuSO4]) binary system at different temperature are

fitted using the VogelndashTammannndashFulcher (VTF) equation with good accuracy The excess molar

volumes excess volume expansivity and viscosity deviations show negative deviations from the ideal

solution the results are interpreted in terms of molecular interactions in the (PEG200 +

[PyrMB][BuSO4]) binary mixture The conductivity increases to a maximum value when the

concentration of PEG200 is increased and decreases after the maximum the data obtained will be

helpful for the application of the ionic liquids as electrolytes and also useful for the ionic liquids

database

ACKNOWLEDGEMENTS

The authors would like to thank the National Science Council of the Republic of China for financially

supporting this project

References

1 P Wasserscheid T Welton Ionic Liquids in Synthesis Second ed Weinheim VCH 2003

2 TY Wu IW Sun ST Gung MW Lin BK Chen HP Wang SG Su J Taiwan Inst Chem

Eng 42 (2011) 513

Int J Electrochem Sci Vol 8 2013

5083

3 TY Wu SG Su KF Lin YC Lin HP Wang MW Lin ST Gung IW Sun Electrochim

Acta 56 (2011) 7278

4 B Baek S Lee C Jung Int J Electrochem Sci 6 (2011) 6220

5 PN Tshibangu SN Ndwandwe ED Dikio Int J Electrochem Sci 6 (2011) 2201

6 TY Wu SG Su HP Wang IW Sun Electrochem Commun 13 (2011) 237

7 TY Wu SG Su HP Wang YC Lin ST Gung MW Lin IW Sun Electrochim Acta 56

(2011) 3209

8 IW Sun YC Lin BK Chen CW Kuo CC Chen SG Su PR Chen TY Wu Int J

Electrochem Sci 7 (2012) 7206

9 TY Wu SG Su ST Gung MW Lin YC Lin CA Lai IW Sun Electrochim Acta 55

(2010) 4475

10 AN Soriano AM Agapito LJLI Lagumbay AR Caparanga MH Li J Taiwan Inst Chem

Eng 42 (2011) 258

11 TY Wu IW Sun ST Gung BK Chen HP Wang SG Su J Taiwan Inst Chem Eng 42

(2011) 874

12 S Ibrahim MR Johan Int J Electrochem Sci 6 (2011) 5565

13 TY Wu SG Su YC Lin HP Wang MW Lin ST Gung IW Sun Electrochim Acta 56

(2010) 853

14 H Wang LX Wu YC Lan JQ Zhao JX Lu Int J Electrochem Sci 6 (2011) 4218

15 FF Liu SQ Liu QJ Feng SX Zhuang JB Zhang P Bu Int J Electrochem Sci 7 (2012)

4381

16 HA Barham SA Brahim Y Rozita KA Mohamed Int J Electrochem Sci 6 (2011) 181

17 SK Shukla LC Murulana EE Ebenso Int J Electrochem Sci 6 (2011) 4286

18 NV Likhanova O Olivares-Xometl D Guzman-Lucero MA Dominguez-Aguilar N Nava

M Corrales-Luna MC Mendoza Int J Electrochem Sci 6 (2011) 4514

19 A Zarrouk M Messali H Zarrok R Salghi AA Ali B Hammouti SS Al-Deyab F Bentiss

Int J Electrochem Sci 7 (2012) 6998

20 BS Ali BH Ali R Yusoff MK Aroua Int J Electrochem Sci 7 (2012) 3835

21 MH Lin YJ Liu ZH Yang YB Huang ZH Sun Y He CL Ni Int J Electrochem Sci 7

(2012) 965

22 CH Su MH Chung HJ Hsieh YK Chang JC Ding HM Wu J Taiwan Inst Chem Eng

43 (2012) 573

23 H Shekaari A Kazempour J Taiwan Inst Chem Eng 43 (2012) 650

24 ZJ Wei Y Li D Thushara YX Liu QL Ren J Taiwan Inst Chem Eng 43 (2012) 363

25 GQ Zhang HW Yang JF Gao HK Zhang CB Zheng YL Cao YH Wang KQ Ding

Int J Electrochem Sci 7 (2012) 7547

26 P Norouzi MR Ganjali F Faridbod SJ Shahtaheri HA Zamani Int J Electrochem Sci 7

(2012) 2633

27 F Faridbod MR Ganjali M Hosseini P Norouzi Int J Electrochem Sci 7 (2012) 1927

28 MR Ganjali Z Rafiei-Sarmazdeh T Poursaberi SJ Shahtaheri P Norouzi Int J

Electrochem Sci 7 (2012) 1908

29 A Babaei DJ Garrett AJ Downard Int J Electrochem Sci 7 (2012) 3141

30 MR Ganjali T Alizade P Norouzi Int J Electrochem Sci 7 (2012) 4800

31 MR Ganjali T Alizade B Larijani F Faridbod P Norouzi Int J Electrochem Sci 7 (2012)

4756

32 P Norouzi B Larijani MR Ganjali Int J Electrochem Sci 7 (2012) 7313

33 TY Wu MH Tsao SG Su HP Wang YC Lin FL Chen CW Chang IW Sun J Braz

Chem Soc 22 (2011) 780

34 MH Tsao TY Wu HP Wang IW Sun SG Su YC Lin CW Chang Mater Lett 65

(2011) 583

Int J Electrochem Sci Vol 8 2013

5084

35 SY Ku SY Lu Int J Electrochem Sci 6 (2011) 5219

36 TY Wu MH Tsao FL Chen SG Su CW Chang HP Wang YC Lin IW Sun J Iran

Chem Soc 7 (2010) 707

37 IW Sun HP Wang H Teng SG Su YC Lin CW Kuo PR Chen TY Wu Int J

Electrochem Sci 7 (2012) 9748

38 TY Wu MH Tsao FL Chen SG Su CW Chang HP Wang YC Lin WC Ou-Yang

IW Sun Int J Mol Sci 11 (2010) 329

39 YX An PJ Zuo XQ Cheng LX Liao GP Yin Int J Electrochem Sci 6 (2011) 2398

40 LC Xuan YX An W Fang LX Liao YL Ma ZY Ren GP Yin Int J Electrochem Sci

6 (2011) 6590

41 HM Wang SQ Liu K Huang XG Yin YN Liu SJ Peng Int J Electrochem Sci 7

(2012) 1688

42 HM Wang SQ Liu NF Wang YN Liu Int J Electrochem Sci 7 (2012) 7579

43 H Ganjali MR Ganjali T Alizadeh F Faridbod P Norouzi Int J Electrochem Sci 6 (2011)

6085

44 MR Ganjali MH Eshraghi S Ghadimi SM Moosavi M Hosseini H Haji-Hashemi P

Norouzi Int J Electrochem Sci 6 (2011) 739

45 MR Ganjali T Poursaberi M Khoobi A Shafiee M Adibi M Pirali-Hamedani P Norouzi

Int J Electrochem Sci 6 (2011) 717

46 P Norouzi M Hosseini MR Ganjali M Rezapour M Adibi Int J Electrochem Sci 6 (2011)

2012

47 MR Ganjali MR Moghaddam M Hosseini P Norouzi Int J Electrochem Sci 6 (2011)

1981

48 MR Ganjali M Hosseini M Pirali-Hamedani HA Zamani Int J Electrochem Sci 6 (2011)

2808

49 MR Ganjali M Rezapour SK Torkestani H Rashedi P Norouzi Int J Electrochem Sci 6

(2011) 2323

50 P Norouzi M Pirali-Hamedani SO Ranaei-Siadat MR Ganjali Int J Electrochem Sci 6

(2011) 3704

51 F Faridbod HA Zamani M Hosseini M Pirali-Hamedani MR Ganjali P Norouzi Int J

Electrochem Sci 6 (2011) 3694

52 MR Ganjali SO Ranaei-Siadat H Rashedi M Rezapour P Norouzi Int J Electrochem Sci

6 (2011) 3684

53 TH Tsai KC Lin SM Chen Int J Electrochem Sci 6 (2011) 2672

54 MR Ganjali T Alizadeh F Azimi B Larjani F Faridbod P Norouzi Int J Electrochem

Sci 6 (2011) 5200

55 R Mirshafian MR Ganjali P Norouzi Int J Electrochem Sci 7 (2012) 1656

56 J Gao JG Liu WM Liu B Li YC Xin Y Yin ZG Zou Int J Electrochem Sci 6 (2011)

6115

57 TY Wu BK Chen L Hao KF Lin IW Sun J Taiwan Inst Chem Eng 42 (2011) 914

58 TY Wu BK Chen L Hao CW Kuo IW Sun J Taiwan Inst Chem Eng 43 (2012) 313

59 SW Peng AN Soriano RB Leron MH Li J Taiwan Inst Chem Eng 42 (2011) 233

60 TY Wu IW Sun MW Lin BK Chen CW Kuo HP Wang YY Chen SG Su J Taiwan

Inst Chem Eng 43 (2012) 58

61 TY Wu BK Chen CW Kuo L Hao YC Peng IW Sun J Taiwan Inst Chem Eng 43

(2012) 860

62 A Arce H Rodriguez A Soto Green Chem 9 (2007) 247

63 TY Wu HC Wang SG Su ST Gung MW Lin CB Lin J Taiwan Inst Chem Eng 41 (2010)

315 64 X Li M Hou Z Zhang B Han G Yang X Wang L Zou Green Chem 10 (2008) 879

Int J Electrochem Sci Vol 8 2013

5085

65 J Chen SK Spear JG Huddleston RD Rogers Green Chem 7 (2005) 64

66 U Domanska M Laskowska J Solution Chem 38 (2009) 779

67 K Tamura M Nakamura S Murakami J Solution Chem 26 (1997) 1199

68 Z Yu H Gao H Wang L Chen J Chem Eng Data 56 (2011) 2877

69 KN Marsh JA Boxall R Lichtenthaler Fluid Phase Equilib 219 (2004) 93

70 TY Wu SG Su ST Gung MW Lin YC Lin WC Ou-Yang IW Sun CA Lai J Iran

Chem Soc 8 (2011) 149

71 TY Wu L Hao CW Kuo YC Lin SG Su PL Kuo IW Sun Int J Electrochem Sci 7

(2012) 2047

72 TY Wu L Hao PR Chen JW Liao Int J Electrochem Sci 8 (2013) 2606

73 CW Kuo CW Huang BK Chen WB Li PR Chen TH Ho CG Tseng TY Wu Int J

Electrochem Sci 8 (2013) 3834

74 CW Kuo WB Li PR Chen JW Liao CG Tseng TY Wu Int J Electrochem Sci 8

(2013) 5007

75 TY Wu BK Chen L Hao YC Lin HP Wang CW Kuo IW Sun Int J Mol Sci 12

(2011) 8750

76 H Rodriguez JF Brennecke J Chem Eng Data 51 (2006) 2145

77 Y Tian X Wang J Wang J Chem Eng Data 53 (2008) 2056

78 TY Wu HC Wang SG Su ST Gung MW Lin CB Lin J Chin Chem Soc 57 (2010)

44

79 TY Wu BK Chen L Hao YC Peng IW Sun Int J Mol Sci 12 (2011) 2598

80 H Eyring MS John Significant Liquid Structure Wiley New York 1969

81 H Every AG Bishop M Forsyth DR MacFarlane Electrochim Acta 45 (2000) 1279 82 O Redlich AT Kister Ind Eng Chem 40 (1948) 345

83 A Paul P Kumar A Samanta J Phys Chem B 109 (2005) 9148

copy 2013 by ESG (wwwelectrochemsciorg)

Int J Electrochem Sci Vol 8 2013

5082

where ΔY (YE) represents E

mV (cm3 mol

minus1) and Δ

(mPa s)x1 denotes the mole fraction of

PEG200 Ai represents the polynomial coefficients and j is the degree of the polynomial expansion

The correlated results for excess molar volumes ( E

mV ) viscosity deviations (Δ) including the values

of the fitting parameters Ai together with the standard deviation σ are given in Table 9 where the

tabulated standard deviation σ [83] is defined as

2

exp cal 1 2( )

[ ]Y Y

m n

(15)

where m is the number of experimental data points and n is the number of estimated

parameters The subscripts ldquoexprdquo and ldquocalrdquo denote the values of the experimental and calculated

property respectively As shown in Table 9 the experimentally derived E

mV and Δη values were

correlated satisfactorily by the Redlich-Kister equation

4 CONCLUSIONS

This paper is a systematic characterizations of thermophysical properties for IL binary system

Density viscosity and conductivity for (PEG200 + [PyrMB][BuSO4]) binary system are presented as a

function of temperature at atmospheric pressure it was demonstrated that viscosity and conductivity

were more sensitive to the changes in PEG content or temperature than density and the viscosity and

conductivity of pure IL and (PEG200 + [PyrMB][BuSO4]) binary system at different temperature are

fitted using the VogelndashTammannndashFulcher (VTF) equation with good accuracy The excess molar

volumes excess volume expansivity and viscosity deviations show negative deviations from the ideal

solution the results are interpreted in terms of molecular interactions in the (PEG200 +

[PyrMB][BuSO4]) binary mixture The conductivity increases to a maximum value when the

concentration of PEG200 is increased and decreases after the maximum the data obtained will be

helpful for the application of the ionic liquids as electrolytes and also useful for the ionic liquids

database

ACKNOWLEDGEMENTS

The authors would like to thank the National Science Council of the Republic of China for financially

supporting this project

References

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2 TY Wu IW Sun ST Gung MW Lin BK Chen HP Wang SG Su J Taiwan Inst Chem

Eng 42 (2011) 513

Int J Electrochem Sci Vol 8 2013

5083

3 TY Wu SG Su KF Lin YC Lin HP Wang MW Lin ST Gung IW Sun Electrochim

Acta 56 (2011) 7278

4 B Baek S Lee C Jung Int J Electrochem Sci 6 (2011) 6220

5 PN Tshibangu SN Ndwandwe ED Dikio Int J Electrochem Sci 6 (2011) 2201

6 TY Wu SG Su HP Wang IW Sun Electrochem Commun 13 (2011) 237

7 TY Wu SG Su HP Wang YC Lin ST Gung MW Lin IW Sun Electrochim Acta 56

(2011) 3209

8 IW Sun YC Lin BK Chen CW Kuo CC Chen SG Su PR Chen TY Wu Int J

Electrochem Sci 7 (2012) 7206

9 TY Wu SG Su ST Gung MW Lin YC Lin CA Lai IW Sun Electrochim Acta 55

(2010) 4475

10 AN Soriano AM Agapito LJLI Lagumbay AR Caparanga MH Li J Taiwan Inst Chem

Eng 42 (2011) 258

11 TY Wu IW Sun ST Gung BK Chen HP Wang SG Su J Taiwan Inst Chem Eng 42

(2011) 874

12 S Ibrahim MR Johan Int J Electrochem Sci 6 (2011) 5565

13 TY Wu SG Su YC Lin HP Wang MW Lin ST Gung IW Sun Electrochim Acta 56

(2010) 853

14 H Wang LX Wu YC Lan JQ Zhao JX Lu Int J Electrochem Sci 6 (2011) 4218

15 FF Liu SQ Liu QJ Feng SX Zhuang JB Zhang P Bu Int J Electrochem Sci 7 (2012)

4381

16 HA Barham SA Brahim Y Rozita KA Mohamed Int J Electrochem Sci 6 (2011) 181

17 SK Shukla LC Murulana EE Ebenso Int J Electrochem Sci 6 (2011) 4286

18 NV Likhanova O Olivares-Xometl D Guzman-Lucero MA Dominguez-Aguilar N Nava

M Corrales-Luna MC Mendoza Int J Electrochem Sci 6 (2011) 4514

19 A Zarrouk M Messali H Zarrok R Salghi AA Ali B Hammouti SS Al-Deyab F Bentiss

Int J Electrochem Sci 7 (2012) 6998

20 BS Ali BH Ali R Yusoff MK Aroua Int J Electrochem Sci 7 (2012) 3835

21 MH Lin YJ Liu ZH Yang YB Huang ZH Sun Y He CL Ni Int J Electrochem Sci 7

(2012) 965

22 CH Su MH Chung HJ Hsieh YK Chang JC Ding HM Wu J Taiwan Inst Chem Eng

43 (2012) 573

23 H Shekaari A Kazempour J Taiwan Inst Chem Eng 43 (2012) 650

24 ZJ Wei Y Li D Thushara YX Liu QL Ren J Taiwan Inst Chem Eng 43 (2012) 363

25 GQ Zhang HW Yang JF Gao HK Zhang CB Zheng YL Cao YH Wang KQ Ding

Int J Electrochem Sci 7 (2012) 7547

26 P Norouzi MR Ganjali F Faridbod SJ Shahtaheri HA Zamani Int J Electrochem Sci 7

(2012) 2633

27 F Faridbod MR Ganjali M Hosseini P Norouzi Int J Electrochem Sci 7 (2012) 1927

28 MR Ganjali Z Rafiei-Sarmazdeh T Poursaberi SJ Shahtaheri P Norouzi Int J

Electrochem Sci 7 (2012) 1908

29 A Babaei DJ Garrett AJ Downard Int J Electrochem Sci 7 (2012) 3141

30 MR Ganjali T Alizade P Norouzi Int J Electrochem Sci 7 (2012) 4800

31 MR Ganjali T Alizade B Larijani F Faridbod P Norouzi Int J Electrochem Sci 7 (2012)

4756

32 P Norouzi B Larijani MR Ganjali Int J Electrochem Sci 7 (2012) 7313

33 TY Wu MH Tsao SG Su HP Wang YC Lin FL Chen CW Chang IW Sun J Braz

Chem Soc 22 (2011) 780

34 MH Tsao TY Wu HP Wang IW Sun SG Su YC Lin CW Chang Mater Lett 65

(2011) 583

Int J Electrochem Sci Vol 8 2013

5084

35 SY Ku SY Lu Int J Electrochem Sci 6 (2011) 5219

36 TY Wu MH Tsao FL Chen SG Su CW Chang HP Wang YC Lin IW Sun J Iran

Chem Soc 7 (2010) 707

37 IW Sun HP Wang H Teng SG Su YC Lin CW Kuo PR Chen TY Wu Int J

Electrochem Sci 7 (2012) 9748

38 TY Wu MH Tsao FL Chen SG Su CW Chang HP Wang YC Lin WC Ou-Yang

IW Sun Int J Mol Sci 11 (2010) 329

39 YX An PJ Zuo XQ Cheng LX Liao GP Yin Int J Electrochem Sci 6 (2011) 2398

40 LC Xuan YX An W Fang LX Liao YL Ma ZY Ren GP Yin Int J Electrochem Sci

6 (2011) 6590

41 HM Wang SQ Liu K Huang XG Yin YN Liu SJ Peng Int J Electrochem Sci 7

(2012) 1688

42 HM Wang SQ Liu NF Wang YN Liu Int J Electrochem Sci 7 (2012) 7579

43 H Ganjali MR Ganjali T Alizadeh F Faridbod P Norouzi Int J Electrochem Sci 6 (2011)

6085

44 MR Ganjali MH Eshraghi S Ghadimi SM Moosavi M Hosseini H Haji-Hashemi P

Norouzi Int J Electrochem Sci 6 (2011) 739

45 MR Ganjali T Poursaberi M Khoobi A Shafiee M Adibi M Pirali-Hamedani P Norouzi

Int J Electrochem Sci 6 (2011) 717

46 P Norouzi M Hosseini MR Ganjali M Rezapour M Adibi Int J Electrochem Sci 6 (2011)

2012

47 MR Ganjali MR Moghaddam M Hosseini P Norouzi Int J Electrochem Sci 6 (2011)

1981

48 MR Ganjali M Hosseini M Pirali-Hamedani HA Zamani Int J Electrochem Sci 6 (2011)

2808

49 MR Ganjali M Rezapour SK Torkestani H Rashedi P Norouzi Int J Electrochem Sci 6

(2011) 2323

50 P Norouzi M Pirali-Hamedani SO Ranaei-Siadat MR Ganjali Int J Electrochem Sci 6

(2011) 3704

51 F Faridbod HA Zamani M Hosseini M Pirali-Hamedani MR Ganjali P Norouzi Int J

Electrochem Sci 6 (2011) 3694

52 MR Ganjali SO Ranaei-Siadat H Rashedi M Rezapour P Norouzi Int J Electrochem Sci

6 (2011) 3684

53 TH Tsai KC Lin SM Chen Int J Electrochem Sci 6 (2011) 2672

54 MR Ganjali T Alizadeh F Azimi B Larjani F Faridbod P Norouzi Int J Electrochem

Sci 6 (2011) 5200

55 R Mirshafian MR Ganjali P Norouzi Int J Electrochem Sci 7 (2012) 1656

56 J Gao JG Liu WM Liu B Li YC Xin Y Yin ZG Zou Int J Electrochem Sci 6 (2011)

6115

57 TY Wu BK Chen L Hao KF Lin IW Sun J Taiwan Inst Chem Eng 42 (2011) 914

58 TY Wu BK Chen L Hao CW Kuo IW Sun J Taiwan Inst Chem Eng 43 (2012) 313

59 SW Peng AN Soriano RB Leron MH Li J Taiwan Inst Chem Eng 42 (2011) 233

60 TY Wu IW Sun MW Lin BK Chen CW Kuo HP Wang YY Chen SG Su J Taiwan

Inst Chem Eng 43 (2012) 58

61 TY Wu BK Chen CW Kuo L Hao YC Peng IW Sun J Taiwan Inst Chem Eng 43

(2012) 860

62 A Arce H Rodriguez A Soto Green Chem 9 (2007) 247

63 TY Wu HC Wang SG Su ST Gung MW Lin CB Lin J Taiwan Inst Chem Eng 41 (2010)

315 64 X Li M Hou Z Zhang B Han G Yang X Wang L Zou Green Chem 10 (2008) 879

Int J Electrochem Sci Vol 8 2013

5085

65 J Chen SK Spear JG Huddleston RD Rogers Green Chem 7 (2005) 64

66 U Domanska M Laskowska J Solution Chem 38 (2009) 779

67 K Tamura M Nakamura S Murakami J Solution Chem 26 (1997) 1199

68 Z Yu H Gao H Wang L Chen J Chem Eng Data 56 (2011) 2877

69 KN Marsh JA Boxall R Lichtenthaler Fluid Phase Equilib 219 (2004) 93

70 TY Wu SG Su ST Gung MW Lin YC Lin WC Ou-Yang IW Sun CA Lai J Iran

Chem Soc 8 (2011) 149

71 TY Wu L Hao CW Kuo YC Lin SG Su PL Kuo IW Sun Int J Electrochem Sci 7

(2012) 2047

72 TY Wu L Hao PR Chen JW Liao Int J Electrochem Sci 8 (2013) 2606

73 CW Kuo CW Huang BK Chen WB Li PR Chen TH Ho CG Tseng TY Wu Int J

Electrochem Sci 8 (2013) 3834

74 CW Kuo WB Li PR Chen JW Liao CG Tseng TY Wu Int J Electrochem Sci 8

(2013) 5007

75 TY Wu BK Chen L Hao YC Lin HP Wang CW Kuo IW Sun Int J Mol Sci 12

(2011) 8750

76 H Rodriguez JF Brennecke J Chem Eng Data 51 (2006) 2145

77 Y Tian X Wang J Wang J Chem Eng Data 53 (2008) 2056

78 TY Wu HC Wang SG Su ST Gung MW Lin CB Lin J Chin Chem Soc 57 (2010)

44

79 TY Wu BK Chen L Hao YC Peng IW Sun Int J Mol Sci 12 (2011) 2598

80 H Eyring MS John Significant Liquid Structure Wiley New York 1969

81 H Every AG Bishop M Forsyth DR MacFarlane Electrochim Acta 45 (2000) 1279 82 O Redlich AT Kister Ind Eng Chem 40 (1948) 345

83 A Paul P Kumar A Samanta J Phys Chem B 109 (2005) 9148

copy 2013 by ESG (wwwelectrochemsciorg)

Int J Electrochem Sci Vol 8 2013

5083

3 TY Wu SG Su KF Lin YC Lin HP Wang MW Lin ST Gung IW Sun Electrochim

Acta 56 (2011) 7278

4 B Baek S Lee C Jung Int J Electrochem Sci 6 (2011) 6220

5 PN Tshibangu SN Ndwandwe ED Dikio Int J Electrochem Sci 6 (2011) 2201

6 TY Wu SG Su HP Wang IW Sun Electrochem Commun 13 (2011) 237

7 TY Wu SG Su HP Wang YC Lin ST Gung MW Lin IW Sun Electrochim Acta 56

(2011) 3209

8 IW Sun YC Lin BK Chen CW Kuo CC Chen SG Su PR Chen TY Wu Int J

Electrochem Sci 7 (2012) 7206

9 TY Wu SG Su ST Gung MW Lin YC Lin CA Lai IW Sun Electrochim Acta 55

(2010) 4475

10 AN Soriano AM Agapito LJLI Lagumbay AR Caparanga MH Li J Taiwan Inst Chem

Eng 42 (2011) 258

11 TY Wu IW Sun ST Gung BK Chen HP Wang SG Su J Taiwan Inst Chem Eng 42

(2011) 874

12 S Ibrahim MR Johan Int J Electrochem Sci 6 (2011) 5565

13 TY Wu SG Su YC Lin HP Wang MW Lin ST Gung IW Sun Electrochim Acta 56

(2010) 853

14 H Wang LX Wu YC Lan JQ Zhao JX Lu Int J Electrochem Sci 6 (2011) 4218

15 FF Liu SQ Liu QJ Feng SX Zhuang JB Zhang P Bu Int J Electrochem Sci 7 (2012)

4381

16 HA Barham SA Brahim Y Rozita KA Mohamed Int J Electrochem Sci 6 (2011) 181

17 SK Shukla LC Murulana EE Ebenso Int J Electrochem Sci 6 (2011) 4286

18 NV Likhanova O Olivares-Xometl D Guzman-Lucero MA Dominguez-Aguilar N Nava

M Corrales-Luna MC Mendoza Int J Electrochem Sci 6 (2011) 4514

19 A Zarrouk M Messali H Zarrok R Salghi AA Ali B Hammouti SS Al-Deyab F Bentiss

Int J Electrochem Sci 7 (2012) 6998

20 BS Ali BH Ali R Yusoff MK Aroua Int J Electrochem Sci 7 (2012) 3835

21 MH Lin YJ Liu ZH Yang YB Huang ZH Sun Y He CL Ni Int J Electrochem Sci 7

(2012) 965

22 CH Su MH Chung HJ Hsieh YK Chang JC Ding HM Wu J Taiwan Inst Chem Eng

43 (2012) 573

23 H Shekaari A Kazempour J Taiwan Inst Chem Eng 43 (2012) 650

24 ZJ Wei Y Li D Thushara YX Liu QL Ren J Taiwan Inst Chem Eng 43 (2012) 363

25 GQ Zhang HW Yang JF Gao HK Zhang CB Zheng YL Cao YH Wang KQ Ding

Int J Electrochem Sci 7 (2012) 7547

26 P Norouzi MR Ganjali F Faridbod SJ Shahtaheri HA Zamani Int J Electrochem Sci 7

(2012) 2633

27 F Faridbod MR Ganjali M Hosseini P Norouzi Int J Electrochem Sci 7 (2012) 1927

28 MR Ganjali Z Rafiei-Sarmazdeh T Poursaberi SJ Shahtaheri P Norouzi Int J

Electrochem Sci 7 (2012) 1908

29 A Babaei DJ Garrett AJ Downard Int J Electrochem Sci 7 (2012) 3141

30 MR Ganjali T Alizade P Norouzi Int J Electrochem Sci 7 (2012) 4800

31 MR Ganjali T Alizade B Larijani F Faridbod P Norouzi Int J Electrochem Sci 7 (2012)

4756

32 P Norouzi B Larijani MR Ganjali Int J Electrochem Sci 7 (2012) 7313

33 TY Wu MH Tsao SG Su HP Wang YC Lin FL Chen CW Chang IW Sun J Braz

Chem Soc 22 (2011) 780

34 MH Tsao TY Wu HP Wang IW Sun SG Su YC Lin CW Chang Mater Lett 65

(2011) 583

Int J Electrochem Sci Vol 8 2013

5084

35 SY Ku SY Lu Int J Electrochem Sci 6 (2011) 5219

36 TY Wu MH Tsao FL Chen SG Su CW Chang HP Wang YC Lin IW Sun J Iran

Chem Soc 7 (2010) 707

37 IW Sun HP Wang H Teng SG Su YC Lin CW Kuo PR Chen TY Wu Int J

Electrochem Sci 7 (2012) 9748

38 TY Wu MH Tsao FL Chen SG Su CW Chang HP Wang YC Lin WC Ou-Yang

IW Sun Int J Mol Sci 11 (2010) 329

39 YX An PJ Zuo XQ Cheng LX Liao GP Yin Int J Electrochem Sci 6 (2011) 2398

40 LC Xuan YX An W Fang LX Liao YL Ma ZY Ren GP Yin Int J Electrochem Sci

6 (2011) 6590

41 HM Wang SQ Liu K Huang XG Yin YN Liu SJ Peng Int J Electrochem Sci 7

(2012) 1688

42 HM Wang SQ Liu NF Wang YN Liu Int J Electrochem Sci 7 (2012) 7579

43 H Ganjali MR Ganjali T Alizadeh F Faridbod P Norouzi Int J Electrochem Sci 6 (2011)

6085

44 MR Ganjali MH Eshraghi S Ghadimi SM Moosavi M Hosseini H Haji-Hashemi P

Norouzi Int J Electrochem Sci 6 (2011) 739

45 MR Ganjali T Poursaberi M Khoobi A Shafiee M Adibi M Pirali-Hamedani P Norouzi

Int J Electrochem Sci 6 (2011) 717

46 P Norouzi M Hosseini MR Ganjali M Rezapour M Adibi Int J Electrochem Sci 6 (2011)

2012

47 MR Ganjali MR Moghaddam M Hosseini P Norouzi Int J Electrochem Sci 6 (2011)

1981

48 MR Ganjali M Hosseini M Pirali-Hamedani HA Zamani Int J Electrochem Sci 6 (2011)

2808

49 MR Ganjali M Rezapour SK Torkestani H Rashedi P Norouzi Int J Electrochem Sci 6

(2011) 2323

50 P Norouzi M Pirali-Hamedani SO Ranaei-Siadat MR Ganjali Int J Electrochem Sci 6

(2011) 3704

51 F Faridbod HA Zamani M Hosseini M Pirali-Hamedani MR Ganjali P Norouzi Int J

Electrochem Sci 6 (2011) 3694

52 MR Ganjali SO Ranaei-Siadat H Rashedi M Rezapour P Norouzi Int J Electrochem Sci

6 (2011) 3684

53 TH Tsai KC Lin SM Chen Int J Electrochem Sci 6 (2011) 2672

54 MR Ganjali T Alizadeh F Azimi B Larjani F Faridbod P Norouzi Int J Electrochem

Sci 6 (2011) 5200

55 R Mirshafian MR Ganjali P Norouzi Int J Electrochem Sci 7 (2012) 1656

56 J Gao JG Liu WM Liu B Li YC Xin Y Yin ZG Zou Int J Electrochem Sci 6 (2011)

6115

57 TY Wu BK Chen L Hao KF Lin IW Sun J Taiwan Inst Chem Eng 42 (2011) 914

58 TY Wu BK Chen L Hao CW Kuo IW Sun J Taiwan Inst Chem Eng 43 (2012) 313

59 SW Peng AN Soriano RB Leron MH Li J Taiwan Inst Chem Eng 42 (2011) 233

60 TY Wu IW Sun MW Lin BK Chen CW Kuo HP Wang YY Chen SG Su J Taiwan

Inst Chem Eng 43 (2012) 58

61 TY Wu BK Chen CW Kuo L Hao YC Peng IW Sun J Taiwan Inst Chem Eng 43

(2012) 860

62 A Arce H Rodriguez A Soto Green Chem 9 (2007) 247

63 TY Wu HC Wang SG Su ST Gung MW Lin CB Lin J Taiwan Inst Chem Eng 41 (2010)

315 64 X Li M Hou Z Zhang B Han G Yang X Wang L Zou Green Chem 10 (2008) 879

Int J Electrochem Sci Vol 8 2013

5085

65 J Chen SK Spear JG Huddleston RD Rogers Green Chem 7 (2005) 64

66 U Domanska M Laskowska J Solution Chem 38 (2009) 779

67 K Tamura M Nakamura S Murakami J Solution Chem 26 (1997) 1199

68 Z Yu H Gao H Wang L Chen J Chem Eng Data 56 (2011) 2877

69 KN Marsh JA Boxall R Lichtenthaler Fluid Phase Equilib 219 (2004) 93

70 TY Wu SG Su ST Gung MW Lin YC Lin WC Ou-Yang IW Sun CA Lai J Iran

Chem Soc 8 (2011) 149

71 TY Wu L Hao CW Kuo YC Lin SG Su PL Kuo IW Sun Int J Electrochem Sci 7

(2012) 2047

72 TY Wu L Hao PR Chen JW Liao Int J Electrochem Sci 8 (2013) 2606

73 CW Kuo CW Huang BK Chen WB Li PR Chen TH Ho CG Tseng TY Wu Int J

Electrochem Sci 8 (2013) 3834

74 CW Kuo WB Li PR Chen JW Liao CG Tseng TY Wu Int J Electrochem Sci 8

(2013) 5007

75 TY Wu BK Chen L Hao YC Lin HP Wang CW Kuo IW Sun Int J Mol Sci 12

(2011) 8750

76 H Rodriguez JF Brennecke J Chem Eng Data 51 (2006) 2145

77 Y Tian X Wang J Wang J Chem Eng Data 53 (2008) 2056

78 TY Wu HC Wang SG Su ST Gung MW Lin CB Lin J Chin Chem Soc 57 (2010)

44

79 TY Wu BK Chen L Hao YC Peng IW Sun Int J Mol Sci 12 (2011) 2598

80 H Eyring MS John Significant Liquid Structure Wiley New York 1969

81 H Every AG Bishop M Forsyth DR MacFarlane Electrochim Acta 45 (2000) 1279 82 O Redlich AT Kister Ind Eng Chem 40 (1948) 345

83 A Paul P Kumar A Samanta J Phys Chem B 109 (2005) 9148

copy 2013 by ESG (wwwelectrochemsciorg)

Int J Electrochem Sci Vol 8 2013

5084

35 SY Ku SY Lu Int J Electrochem Sci 6 (2011) 5219

36 TY Wu MH Tsao FL Chen SG Su CW Chang HP Wang YC Lin IW Sun J Iran

Chem Soc 7 (2010) 707

37 IW Sun HP Wang H Teng SG Su YC Lin CW Kuo PR Chen TY Wu Int J

Electrochem Sci 7 (2012) 9748

38 TY Wu MH Tsao FL Chen SG Su CW Chang HP Wang YC Lin WC Ou-Yang

IW Sun Int J Mol Sci 11 (2010) 329

39 YX An PJ Zuo XQ Cheng LX Liao GP Yin Int J Electrochem Sci 6 (2011) 2398

40 LC Xuan YX An W Fang LX Liao YL Ma ZY Ren GP Yin Int J Electrochem Sci

6 (2011) 6590

41 HM Wang SQ Liu K Huang XG Yin YN Liu SJ Peng Int J Electrochem Sci 7

(2012) 1688

42 HM Wang SQ Liu NF Wang YN Liu Int J Electrochem Sci 7 (2012) 7579

43 H Ganjali MR Ganjali T Alizadeh F Faridbod P Norouzi Int J Electrochem Sci 6 (2011)

6085

44 MR Ganjali MH Eshraghi S Ghadimi SM Moosavi M Hosseini H Haji-Hashemi P

Norouzi Int J Electrochem Sci 6 (2011) 739

45 MR Ganjali T Poursaberi M Khoobi A Shafiee M Adibi M Pirali-Hamedani P Norouzi

Int J Electrochem Sci 6 (2011) 717

46 P Norouzi M Hosseini MR Ganjali M Rezapour M Adibi Int J Electrochem Sci 6 (2011)

2012

47 MR Ganjali MR Moghaddam M Hosseini P Norouzi Int J Electrochem Sci 6 (2011)

1981

48 MR Ganjali M Hosseini M Pirali-Hamedani HA Zamani Int J Electrochem Sci 6 (2011)

2808

49 MR Ganjali M Rezapour SK Torkestani H Rashedi P Norouzi Int J Electrochem Sci 6

(2011) 2323

50 P Norouzi M Pirali-Hamedani SO Ranaei-Siadat MR Ganjali Int J Electrochem Sci 6

(2011) 3704

51 F Faridbod HA Zamani M Hosseini M Pirali-Hamedani MR Ganjali P Norouzi Int J

Electrochem Sci 6 (2011) 3694

52 MR Ganjali SO Ranaei-Siadat H Rashedi M Rezapour P Norouzi Int J Electrochem Sci

6 (2011) 3684

53 TH Tsai KC Lin SM Chen Int J Electrochem Sci 6 (2011) 2672

54 MR Ganjali T Alizadeh F Azimi B Larjani F Faridbod P Norouzi Int J Electrochem

Sci 6 (2011) 5200

55 R Mirshafian MR Ganjali P Norouzi Int J Electrochem Sci 7 (2012) 1656

56 J Gao JG Liu WM Liu B Li YC Xin Y Yin ZG Zou Int J Electrochem Sci 6 (2011)

6115

57 TY Wu BK Chen L Hao KF Lin IW Sun J Taiwan Inst Chem Eng 42 (2011) 914

58 TY Wu BK Chen L Hao CW Kuo IW Sun J Taiwan Inst Chem Eng 43 (2012) 313

59 SW Peng AN Soriano RB Leron MH Li J Taiwan Inst Chem Eng 42 (2011) 233

60 TY Wu IW Sun MW Lin BK Chen CW Kuo HP Wang YY Chen SG Su J Taiwan

Inst Chem Eng 43 (2012) 58

61 TY Wu BK Chen CW Kuo L Hao YC Peng IW Sun J Taiwan Inst Chem Eng 43

(2012) 860

62 A Arce H Rodriguez A Soto Green Chem 9 (2007) 247

63 TY Wu HC Wang SG Su ST Gung MW Lin CB Lin J Taiwan Inst Chem Eng 41 (2010)

315 64 X Li M Hou Z Zhang B Han G Yang X Wang L Zou Green Chem 10 (2008) 879

Int J Electrochem Sci Vol 8 2013

5085

65 J Chen SK Spear JG Huddleston RD Rogers Green Chem 7 (2005) 64

66 U Domanska M Laskowska J Solution Chem 38 (2009) 779

67 K Tamura M Nakamura S Murakami J Solution Chem 26 (1997) 1199

68 Z Yu H Gao H Wang L Chen J Chem Eng Data 56 (2011) 2877

69 KN Marsh JA Boxall R Lichtenthaler Fluid Phase Equilib 219 (2004) 93

70 TY Wu SG Su ST Gung MW Lin YC Lin WC Ou-Yang IW Sun CA Lai J Iran

Chem Soc 8 (2011) 149

71 TY Wu L Hao CW Kuo YC Lin SG Su PL Kuo IW Sun Int J Electrochem Sci 7

(2012) 2047

72 TY Wu L Hao PR Chen JW Liao Int J Electrochem Sci 8 (2013) 2606

73 CW Kuo CW Huang BK Chen WB Li PR Chen TH Ho CG Tseng TY Wu Int J

Electrochem Sci 8 (2013) 3834

74 CW Kuo WB Li PR Chen JW Liao CG Tseng TY Wu Int J Electrochem Sci 8

(2013) 5007

75 TY Wu BK Chen L Hao YC Lin HP Wang CW Kuo IW Sun Int J Mol Sci 12

(2011) 8750

76 H Rodriguez JF Brennecke J Chem Eng Data 51 (2006) 2145

77 Y Tian X Wang J Wang J Chem Eng Data 53 (2008) 2056

78 TY Wu HC Wang SG Su ST Gung MW Lin CB Lin J Chin Chem Soc 57 (2010)

44

79 TY Wu BK Chen L Hao YC Peng IW Sun Int J Mol Sci 12 (2011) 2598

80 H Eyring MS John Significant Liquid Structure Wiley New York 1969

81 H Every AG Bishop M Forsyth DR MacFarlane Electrochim Acta 45 (2000) 1279 82 O Redlich AT Kister Ind Eng Chem 40 (1948) 345

83 A Paul P Kumar A Samanta J Phys Chem B 109 (2005) 9148

copy 2013 by ESG (wwwelectrochemsciorg)

Int J Electrochem Sci Vol 8 2013

5085

65 J Chen SK Spear JG Huddleston RD Rogers Green Chem 7 (2005) 64

66 U Domanska M Laskowska J Solution Chem 38 (2009) 779

67 K Tamura M Nakamura S Murakami J Solution Chem 26 (1997) 1199

68 Z Yu H Gao H Wang L Chen J Chem Eng Data 56 (2011) 2877

69 KN Marsh JA Boxall R Lichtenthaler Fluid Phase Equilib 219 (2004) 93

70 TY Wu SG Su ST Gung MW Lin YC Lin WC Ou-Yang IW Sun CA Lai J Iran

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