Baig 2015

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Polyurethane-based

cation

exchange

composite

membranes:

Preparation,

characterization

and

its

application

in

development

of

ion-selective

electrode for

detection

of

copper(II)

Umair BaigQ1 a,b, Asif Ali Khan a,* a Analytical and Polymer Research Laboratory, Department of Applied Chemistry, Faculty of Engineering and Technology, Aligarh Muslim University, Aligarh

202002, UP, India bCenter of Excellence for Scientific Research Collaboration with MIT, King Fahd University of Petroleum and Minerals, Dhahran 31261, Saudi Arabia

Introduction

In the recent years, research focusing on polymer-based

composite ion-exchange membranes either by blending of

different polymers or by incorporating inorganic materials/ion-

exchanger

into

polymers,

has

attracted

considerable

attention

in

the academic and industries [1–4]. Composite ion-exchange

membranes with new or improved properties such as improved

mechanical, thermal, and ion-exchange properties may offer better

characteristics than their single-polymer material counterparts

[5,6]. Polymer based composite ion-exchanger/membranes are

now widely used for application in such fields as membrane

electrolysis, electrochemical separations, solid polymer electroly-

sis, fuel cells, separation of heavy toxic metal ions and in making

ion selective membrane electrodes [1–17].

Copper is broadly utilized as a part of mechanical, antimicrobial,

natural and ecological applications because of its properties of high

electrical conductivity, substance and warm soundness, pliancy and

ability to make composites with numerous metals. Copper is a vital

2component

on

account

of their

utilization

as

key

supplements

to

2amphibian

organic entities

and

is additionally

dangerous

at

high

3fixation (>15 mg day1), the maximum permissible concentration

3limits of copper is 2 mg day1 [18]. Copper insufficiency brings

3about weakness while its collection brings about human body

3dyslexia,

hypoglycemia,

liver

and

kidney

harm,

gastrointestinal

3issues and Wilson sickness (WD) [19]. In the point of view of such

3noxious effects of copper, its determination in ecological specimens

3is of utmost importance. A lot many analytical methods such as ion-

3exchange chromatography, neutron activation analysis, atomic

3absorption spectrometry (AAS), cold vapour AAS or flame atomic

3absorption spectrometry-electrothermal atomization (AASETA),

4gravimetry have generally been utilized for the determination of

4trace amount of copper in aqueous solutions and water bodies.Most

4of these methods suffer from many disadvantages such as time

4consuming, multiple sample manipulations, excessively costly and

4non-applicability infield work. Recently, the potentiometricmethod

4by using an ion sensor or ion-selective membrane electrode is an

4alternative, simple and low cost method for determination of

4copper. Thus, in this work, a new Cu(II) ion-selective electrode based

4on polyurethane-cerium(IV) phosphate cation exchange composite

4membrane is prepared and characterized for the potentiometric

5determination of Cu(II).

Journal of Industrial and Engineering Chemistry xxx (2015) xxx–xxx

* Corresponding author. Tel.: +91 571 2720323; fax: +91 9045462192.

E-mail addresses: [email protected], [email protected] (A.A. Khan).

A R T I C L E I N F O

Article history:

Received 23 February 2014

Received in revised form 18 November 2014

Accepted 31 December 2014

Available online xxx

Keywords:

Polymer

Composite membranes

Cation exchanger

Cu(II) selective electrode

A B S T R A C T

Polyurethane-cerium(IV) phosphate composite cation exchangemembraneswereprepared by solution

casting method in different stoicheometric ratios of polyurethane and cerium(IV) phosphate. The

structureandmorphology of thepreparedmembraneswere ascertainedby FTIR, SEM,

TGA andDTA.The

membrane having composition 1:2 (PU: cerium(IV) phosphate) shows best results for ion-exchange

capacity,water content, porosity, thicknessandswelling.The Cu(II)selectiveelectrodewas developedby

using this membranefor thedetermination of Cu(II) in solutions.The accuracy of theprocedurehasbeen

tested on drinking water samples spikedwith known amountsof Cu(II) and resultswere comparable to

those generated by Atomic Absorption Spectrophotometer.

2015 Published by Elsevier B.V. on behalf of The Korean Society of Industrial and Engineering

Chemistry.

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Please cite this article in press as: U. Baig, A.A. Khan, J. Ind. Eng. Chem. (2015), http://dx.doi.org/10.1016/j.jiec.2014.12.045

Contents

lists

available

at

ScienceDirect

Journal of Industrial and Engineering Chemistry

jou r n al h o mepag e: w ww.elsev ier .co m / locate / j iec

http://dx.doi.org/10.1016/j.jiec.2014.12.045

1226-086X/ 2015 Published by Elsevier B.V. on behalf of The Korean Society of Industrial and Engineering Chemistry.

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Experimental

Reagents and chemicals

For the preparation of cation exchange composite membranes

the

main

chemicals

were

used:

Polyurethane

(PU)

from

Research

design

and

standard

organization,

India,

tetrahydofuran,

ceric

sulfate (Ce(SO4)2.4H2O), orthophosphoric acid (H3PO4) were used

as received from Qualigens (India Ltd.). All other reagents and

chemicals

were

of

analytical

grade

(AR).

Synthesis

Cerium(IV)

phosphate

Preparation

of

cerium(IV)

phosphate

was

carried

out

by

taking

different ratios of 0.1 mol L 1 Ce(SO4)24H2O (prepared in

1 mol L 1 H2SO4 solution) and an aqueous solution of ortho

phosphoric

acid

(prepared

with

demineralized

water)

under

varying

conditions

given

in

Table

1

[20,21].

Preparation of polyurethane-cerium(IV) phosphate cation exchange

composite

membrane

Polyurethane-cerium(IV) phosphate cation exchange compos-ite membranes were prepared in various weight ratios of

cerium(IV)

phosphate

with

polyurethane

by

solution

casting

method.

500

mg

polyurethane

was

dissolved

in

tetrahydrofuran

(THF) at room temperature. A controlled amount of cerium(IV)

phosphate (200, 300, 400, 500, 800 and 1000 mg) were dispersed in

to

polyurethane

solution

in

THF.

Mechanical

stirring

was

applied

for

at

least

24

h

at

room

temperature

in

order

to

obtain

homogeneous cerium(IV) phosphate dispersed polyurethane

solution. The polymer dispersed was cast on to clean glass plates

and

kept

for

48

h

at

room

temperature

to

allow

complete

evaporation of THF. The resultant composite membranes were

cautiously peeled out of the glass plates and rinsed with doubly

distilled

water

on

both

sides

and

dried

at

room

temperature.

Polyurethane membrane was prepared with a similar method. Thedried polyurethane-cerium(IV) phosphate composite membranes

were converted into H+-form through immersion in 1 mol L 1

HNO3 for 2 days with occasional shaking intermittently replacing

the

supernatant

liquid

with

fresh

1

mol

L 1 HNO3 two to three

times. The excess was removed after several washings with DMW

and finally dried at room temperature. The condition of prepara-

tion

and

the

ion-exchange

capacity

(IEC),

of

the

cation

exchange

composite

membranes

are

given

in

Table

2.

Ion-exchange capacity measurement (IEC)

For

determination

of

ion

exchange

capacities

(IECs)

of

the

cation exchange composite membranes, accurately weighed dry

composite

membranes

were

converted

in

to

H+

-form

throughimmersion

in

1

mol

L 1HNO3 for 2 days. Excess HNO3was washed

9off

and

then

the

composite

membranes

were

immersed

in

200

mL

90.5

mol

L 1 NaNO3. The amount of H+ ion

was

determined

using

a

9titration with NaOH; cation exchange values were obtained and

9expressed as mequiv./g of dry exchanger (In H+ form). The cation

1exchange

composite

membrane

having

maximum

ion-exchange

1capacity

(1.79

mequiv./g)

was

selected

for

further

studies.

1Characterization

1Fourier

transform

infra

red

(FTIR)

studies1The FTIR spectrum of polyurethane membrane, cerium(IV)

1phosphate and polyurethane-cerium(IV) phosphate cation ex-

1change

composite

membrane

were

obtained

using

a

FTIR

1spectrophotometer

(Perkin-Elmer,

USA,

model

Spectrum-BX)

in

1the original form.

1Field

emission

scanning

electron

microscopy

(FE-SEM)

studies

1The

surface

morphology

of

the

original

form

of

polyurethane,

1cerium(IV) phosphate and polyurethane-cerium(IV) phosphate

1cation

exchange

composite

membrane

were

studied

by

field

1emission

scanning

electron

microscopy

(FE-SEM)

using

a

LEO

1microscope at various magnifications.

1Thermal

studies 1The

degradation

process

and

the

thermal

stability

of

polyure-

1thane membrane and polyurethane-cerium(IV) phosphate cation

1exchange composite membranes were investigated by thermo-

1gravimetic

analysis

(TGA)

and

differential

thermal

gravimetry

1(DTG)

using

thermal

analyzer-V2.2A

DuPont

9900.

1Physicochemical characterization of polyurethane-cerium (IV)

1 phosphate

cation

exchange

composite

membranes

1The Water content (% total wet weight), porosity, thickness and

1swelling etc. were determined by the same method as discussed in

1our

previous

studies

[12–14].

Those

membrane

which

exhibited

1good

surface

qualities

like

porosity,

thickness

and

swelling

etc.

1were selected for further investigation.

1Fabrication

of

ion-selective

membrane

electrode

1Fabrication and conditioning of the ion-selective membrane

1electrode

was

done

by

the

same

method

as

we

have

described

1previously

[12–14].

The

membrane

sheet

of

0.20

mm

thickness

as

1obtained by the above procedure was cut in the shape of disk and

1mounted at the lower end of a Pyrex glass tube (outer diameter

10.8

cm,

internal

diameter

0.6

cm)

with

araldite.

Finally,

the

1assembly

was

allowed

to

dry

in

air

for

24

h.

The

glass

tube

was

1filled with 0.1 mol L 1 Cu(II) solution. Electrode was then

1equilibrated with Cu(II) solution (0.1 mol L 1) for 5–7 days. The

1tube

was

filled

3/4th

with

cupric

sulphate

solution

(0.1

mol

L 1)

1and

then

immersed

in

a

beaker

containing

the

test

solution

of

Table 1

Conditions of preparation and the ion-exchange capacity of cerium(IV)phosphate

cation exchanger.

Sample

code

Mixing volume ratios (%) Appearance

of the

sample

Na+ ion-exchange

capacity in

(mequiv./g)

Cerium

sulphate

(stock solution)

Ortho-phosphoric

acid

CP-1 1 1 (2 mol L 1) Light yellow 1.14



Table 2

Conditions of preparation and ion-exchange capacity of various Polyurethane-

cerium(IV) phosphate cation-exchange composite membranes.

Membrane

no.

Amount of

polyurethane

(PU) in mg

Amount of

cerium(IV)

phosphate

(mg)

Amount of

tetrahydofuran

(T.H.F) in ml

Stirring

time (h)

Ion-exchange

capacity

(mequiv./g)

PUCPM-1 500 200 50 24 0.95

PUCPM-2 500 300 50 24 1.16

PUCPM-3

500

400

50

24

1.19PUCPM-4 500 500 50 24 1.24

PUCPM-5 500 800 75 24 1.34

PUCPM-6 500 1000 75 24 1.79

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varying concentration of Cu(II) ion, keeping the level of inner filling

solution

higher

than

the

level

of

the

test

solution

to

avoid

any

reverse diffusion of the electrolyte.

Potential measurements

A

saturated

calomel

electrode

(SCE)

was

inserted

in

the

tube

for

electrical contact and another saturated calomel electrode (SCE)

was used as external reference electrode. All the potential

measurements

were

carried

out

using

the

following

cell

assembly:

SCEj0:1 mol L 1CuðIIÞjjMembranejjtest solutionjSCE

Potentiometric measurements were observed for a series of

standard solutions of cupric sulphate (1010 to 101mol L 1),

prepared by gradual dilution of the stock solution, as described by

IUPAC Commission for Analytical Nomenclature [22]. Potential

measurements were made in unbuffered solutions to avoid

interference from any foreign ion. In order to study the

characteristics of the electrode, the following parameters were

evaluated: lower detection limit, slope response curve, response

time and working pH range. The calibration graphs were plotted.

Characteristics

of

the

electrode

The characteristics of the fabricated membrane electrode, for

example,

effect

of

pH,

response

time,

potentiometric

selectivity

coefficient and storage of electrodes were measured by the

methods as described earlier [12–14].

1Effect of pH

1pH

solution

ranging

from

1

to

13

were

prepared

at

11 103mol L 1 constant ion concentration. The value of elec-

1trode potential at each pH was recorded and plot of electrode

1potential versus pH was plotted.

1The

response

time

1The method of determining response time in the present work

1is being outlined as follows: The electrode is first dipped in a

11 103mol L 1 solution of cupric sulphate and then 10 fold

1higher

concentrations.

The

potential

of

the

solution

was

read

at

1zero second; just after dipping of the electrode in the second

1solution and subsequently recorded at the intervals of 10 s. The

1potentials

were

then

plotted

vs.

the

time.

1Potentiometric selectivity coefficient of interfering anions

1One of the most important characteristics of a membrane

1sensor

is

its

response

for

the

primary

ion

in

the

presence

of

other

1foreign

ions,

which

is

measured

in

terms

of

the

potentiometric

1selectivity coefficient (K ABpot). In the present work we used the

1mixed solution method [23]. The selectivity coefficient was

1calculated

using

the

equation

given

below:

K v AB ¼ a A

ðaBÞ zA= zB

(1)

11where

a A and aB activities of primary and interfering ion and zA and

1 zB are charges on the ions.

Fig. 1. FTIR spectra of polyurethane (a), cerium(IV)phosphate (b) and polyurethane-cerium(IV) phosphate cation exchange composite membrane (c).

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Storage

of

electrodes

The polyurethane-cerium(IV) phosphate composite membrane

electrode was stored in distilled water when not in use for more

than

one

day.

It

was

activated

with

(0.1

mol

L 1)

Cu(II)

solution

by

keeping

immersed

in

it

for

2

h,

before

use,

to

compensate

for

any

loss of metal ions in the membrane phase that might have taken

place

due

to

a

long

storage

in

distilled

water.

Electrode

was

thenwashed

thoroughly

with

DMW

before

use.

Results and discussion

Various

samples

of

organic–inorganic

polyurethane-cerium(IV)

phosphate

cation

exchange

composite

membranes

were

prepared

by solution casting method under different stoichiometric ratios. A

variety of cation exchange composite membranes by varying the

stoichiometry

between

polyurethane

and

cerium

(IV)

phosphate

were

prepared,

but

highest

ion-exchange

capacity

was

observed

in

1:2 stoichiometry (Table 2). The cation exchange membrane

(sample PUCPM-6) possessed better Na+ ion exchange capacity

(1.79

mequiv./g)

as

compared

to

the

inorganic

particles

(sample

CP-1)

of

cerium(IV)phosphate

(1.14

mequiv./g)

[20,21]. Due

to

Fig. 2. SEM image of pure polyurethane (a), cerium(IV) phosphate (b) and polyurethane-cerium(IV) phosphate composite membrane at different magnifications (c).

0 10 20 30 40 50 60 70 80 90

0

500

1000

1500

2000

2500

3000

3500

4000

I n t e n s i t y ( a . u . )

2Theta (Degree)

Polyurethane

Polyurethane-ce(IV)phosphate

Fig. 3. X-ray diffraction pattern of polyurethane and polyurethane-cerium(IV)

phosphate

cation

exchange

composite

membrane.


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higher ion exchange capacity, and thermal stabilities, sample

PUCPM-6 (Table 2) was selected for further studies.

The FTIR spectra of polyurethane, cerium(IV)phosphate, and

polyurethane-cerium(IV) phosphate cation exchange composite

membrane are shown in Fig. 1. In the polyurethane spectrum, the

absorption

band

at

3333

cm1 corresponds

to

NH

stretching.

The

sharp peaks at 2874 cm1 and 2959 cm1 are associated with –CH2stretching, while other modes of –CH2 vibrations are identified by

the

bands

at

1457,

1415,

1311,

and

1228

cm1.

In

addition,

the

absorption

band

at

1735

cm1 is

associated

with

a

C55O group in

polyurethane. The group of NH vibrations is identified by the bands

at 1532 cm1. The band at 1703 cm1 is assigned to hydrogen

bonding

between

N–H

and

C55O groups in the hard segment and

the ester or ester-oxygen groups of the soft segments of urethanelinkage. The presence of cerium(IV) phosphate in the polyure-

thane-cerium(IV) phosphate composite membrane is further

2strengthen from the presence of broad band at 3137 cm1 which

2may be due to the vibration of hydroxyl groups, the broadness of

2this hump may also be due to the presence of occluded water

2molecule. The band between 1200 and 800 cm1 with a peak of

2intensity at 1066 cm1 may be assigned to symmetric and

2antisymentric

stretching

of

the

P–O

bond

in

PO3 groups [24].

(a)

(b)

T e m p C e l

700.0600.0500.0400.0300.0200.0100.0

T G

%

10 0 .0

90.0

80.0

70.0

60.0

50.0

40.0

30.0

20.0

10 .0

0 .0

T G

%

10 0 .0

9 0 .0

8 0 .0

7 0 .0

6 0 .0

5 0 .0

4

0

.0

3 0 .0

2 0 .0

10 .0

0 .0

D

T G

m g / m i n

1.0 0 0

0 .5 0 0

0 .0 0 0

-0 .5 0 0

-1.0 0 0

-1.5 0 0

-2 .0 0 0

T e m p C e l

7 0 0 . 06 0 0 . 05 0 0 . 04 0 0 . 03 0 0 . 02 0 0 . 01 0 0 . 0

T G %

10 0 .0

9 5 .0

9 0 .0

8 5 .0

8

0

.0

7 5 .0

7 0 .0

6 5 .0

6 0 .0

5 5 .0

5 0 .0

4 5 .0

T G %

10 0 .0

9 5 .0

9 0 .0

8 5 .0

8

0

.0

7 5 .0

7 0 .0

6 5 .0

6 0 .0

5 5 .0

5 0 .0

4 5 .0

D T G u g / m i n

2 0 0 .0

10 0 .0

0

.0

-10 0 .0

-2 0 0 .0

-3 0 0 .0

-4 0 0 .0

Fig. 4. TGA and DTA curves of polyurethane (a) and polyurethane-cerium(IV) phosphate cation exchange composite membrane (b).

Table 3

Physicochemical characterization of Polyurethane-cerium(IV)phosphate cation

exchange composite membranes.

Membrane No. Thickness (mm) Total wet

weight (%)

Porosity Swelling (%)

PUCPM-1 0.165 1.906 0.0019 0.3412

PUCPM-2 0.174 1.813 0.0021 0.3682

PUCPM-3 0.182 1.983 0.0022 0.4352

PUCPM-4 0.194 1.997 0.0021 0.4561

PUCPM-5 0.199 1.772 0.0023 0.5672

PUCPM-6 0.201 1.476 0.0017 0.1201

12 10 8 6 4 2 0

300

350

400

450

500

550

E l e c t r o d e P o t e n t i a l ( m V )

-log [Cu2+

]

Fig. 5. Calibration curve for polyurethane-cerium(IV) phosphate cation exchange

composite

membrane

(PUCPM-6)

electrode

in

aqueous

solution

of

Cu(NO3)2.


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Compared with Fig. 2(a), some peaks are shifted in the polyure-

thane-cerium(IV) phosphate composite membrane from 1228,

1415, 609, 508 cm1, to 1224, 1401, 616, 539 cm1 respectively,

indicating the formation of polyurethane-cerium(IV) phosphate

composite membrane.

Fig. 2(a–c) shows the FE-SEM image of pure polyurethane,

cerium(IV) phosphate and polyurethane-cerium(IV) phosphate

composite membrane at different magnifications, indicating the

binding of inorganic material, i.e. silica gel with organic polymer,

i.e. polyurethane. The pictures showed that the difference in

surface morphology of organic polymer, inorganic material and

composite membrane. It has been revealed that after binding of

polyurethane with cerium(IV) phosphate, the morphology has

been changed. It is also observed in Fig. 2(c) that the prepared

organic-inorganic polyurethane-cerium(IV) phosphate composite

membrane is homogeneous and dense.

Fig. 3 illustrates the diffractograms of pure polyurethane and

polyurethane-cerium(IV) phosphate composite membrane in the

2u range between 58 and 808. In the diffractogram of pure

polyurethane there are no sharp diffraction peaks, confirming their

amorphous nature. The polyurethane is known to be an amorphous

polymer and shows a broad diffraction peak at 2u values 10–308.

On the addition of cerium(IV)phosphate in the polyurethane

matrix, the intensity of the peak 10–308 become shifted. These

intensity changes in the composite membrane due to the

interaction between polyurethane and cerium(IV)phosphate andsome small peaks are situated in the diffractogram of polyure-

thane-cerium(IV) phosphate composite membrane at 2u values

28.28, 32.18, 428

and

488.

Fig. 4 shows the thermogravimetric stability data of polyure-

thane and polyurethane-cerium(IV) phosphate composite mem-

brane.

It

can

be

concluded

from

this

figure

that

the

thermal

2stability of polyurethane-cerium(IV) phosphate composite mem-

2brane is higher than that of pure polyurethane. At 800 8C the2percentage of residual weight of polyurethane and polyurethane-

2cerium(IV) phosphate composite membrane is 0.00% and 44.00%

2respectively. Therefore the addition of cerium(IV) phosphate

2cation exchanger improves the thermal stability of composite

2membrane.

2The thickness, swelling, porosity, water content capacity, etc. of

2the polyurethane-cerium (IV) phosphate cation exchange com-

2posite membrane was investigated and the results are summarized

2in Table 3. Thus, the low orders of water content, swelling and

2porosity with less thickness of this membrane suggest that the

2interstices are negligible and diffusion across the membrane would

2occur mainly through the exchange sites. Hence, membrane

Table 4

Potentiometric response of five independent polyurethane-cerium(IV)phosphate

membrane electrodes for Cu2+.

Electrode Nerstian slope

(mV/decade)

(n= 6)

Linear range RSD (%)

(n = 6)

1 30.00 1 101 to 1 108molL 1 1.5

2 29.96 1 101 to 1 108molL 1 1.6

3 29.95 1 101 to 1 108molL 1 1.5

4 29.95

1

10

1

to

1

10

8

molL

1

1.55 29.96 1 101 to 1 108molL 1 1.8

0 1 2 3 4 5 6 7 8 9 10

380

400

420

440

460

480

500


pH

Fig. 6. Effect of pH on electrode potential of polyurethane-cerium(IV) phosphate

cation

exchange composite

membrane

(PUCPM-6))

electrode

at

1

10

3

M

Cu

2+

ion.

0 10 20 30 40 50 60

400

405

410

415

420

425

430

435

440


Time (Sec)

Fig. 7. Dynamic response time of polyurethane-cerium(IV) phosphate cation

exchange composite membrane electrode for Cu2+ ions.

Table 5

The selectivity coefficient of various interfering cations for Cu2+ selective

polyurethane-cerium(IV) phosphate membrane electrode.

Interfering ion (Mn+) Selectivity

coefficients (K MSM)

K+ 2.8 103

Na+ 1.89 103

Mg2+ 5.5 103

Ca2+ 2.9 103

Mn2+ 2.15 103

Fe2+ 1.56 104

Zn2+ 0.98 104

Cd2+ 0.87 104

Pb2+ 1.30 105

Hg2+ 0.56 105

Table 6

Determination of Cu2+ added to a drinking water sample containing different

concentrations of copper.

Added

Cu2+

(mgL 1)

Detected

Cu2+ by

membrane

electrode

(mg L 1)

RSD (%)

(n = 5)

Recovery

by membrane

electrode (%)

Detected

Cu2+ By AAS

(mg L 1)

RSD (%)

(n= 5)

Recovery

by AAS (%)

2.0 1.88 1.05 94.00 1.93 1.01 96.00

4.0 3.76 1.11 94.00 3.82 1.03 95.50

6.0 5.69 1.07 94.83 5.75 1.01 95.88

8.0 7.62 1.08 95.25 7.80 1.02 97.50

10.0 9.69 1.04 96.90 9.81 1.03 98.10


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sample PUCPM-6 (thickness 0.201 mm) was selected for the

preparation of an ion-selective electrode for further studies.

Performance

of

Cu(II)

selective

membrane

electrode

Working concentration range and slope

Using

the

optimized

membrane

composition

described

above,

the potentiometric response of the membrane electrode was

studied for Cu2+ in the concentration range of 1012mol L 1 to

101mol

L 1 at

25

8C

as

shown

in

Fig.

5. The

results

showed

a

Nernstian

response

of

30.00

mV/decade

of

Cu2+ concentration,

and

the wide linear range within the concentration range from108mol L 1 to 101mol L 1 of Cu2+ ions. All the potentiomertic

measurements

were

conducted

a

number

of

times

(n

=

10)

to

check

the

reproducibility

of

the

results.

EMFs

were

plotted

against

log

of

activities of copper ions and calibration curves were drawn for five

sets of experiments. The relative standard deviation (RSD) of a

single

electrode

(within

electrode

variation)

was

also

determined.

The

relative

standard

deviation

(RSD)

of

a

single

electrode

was

found to be 1.5%, shows good reproducibility behavior and the

homogenous nature of the proposed membrane electrode. The

detection

limit

of

membrane

electrode

was

determined

according

to

IUPAC

recommendations

from

the

intersection

of

two

extrapo-

lated linear portions of the curve [25] and was found to be

1 108.

The reproducibility of the optimized membrane electrode wasalso

studied

by

measuring

the

potentiometric

response

of

five

independent Cu2+ ion selective membrane electrodes with the

same composition. These measurements were additionally done in

six

replicates.

The

relative

standard

deviation

(between

electrode

variations),

slope

and

linear

range

were

investigated

and

the

results are summarized in Table 4.

Effect

of

pH

on

electrode

potential

and

response

time

The

pH

effect

on

the

potential

response

of

the

electrode

was

measured for 1 103mol L 1 Cu2+ ion concentration at different

pH values. The pH was adjusted with hydrochloric acid and sodium

hydroxide.

Fig.

6

depicts

that

the

pH

dependence

of

the

potential

is

insignificant

in

the

pH

range

2.5–6.5

which

can

be

taken

as

a

working

pH

range

for

the

electrode.

Another

important

factor

is

thepromptness

of

the

response

of

the

ion-selective

membrane

electrode.

The

average

response

time

is

defined

as

the

time

required for the electrode to reach a stable potential.

The response time in contact with 1 103mol L 1 Cu2+

solution

was

determined,

and

the

results

are

shown

in

Fig.

7. It

is

clear

from

the

figure,

that

the

response

time

of

the

membrane

is

14 s.

Lifetime and durability of the ion-selective electrode is one of

the

important

factors

in

choosing

the

appropriateness

of

ion-

selective

electrode.

Durability

of

the

proposed

ion-selective

membrane electrode was evaluated by monitoring the change in

the slope and linear range with time. These measurements were

also done in six replicates. The lifetime of the electrode was

determined

by

reading

its

potentials

and

plotting

the

calibration

3curves for a period of 6 months, while this period the electrode

3were used extensively (one hour per weeks). During this time no

3significant

changes

in

the

slope

were

observed.

Thus,

The

3membrane

electrode

could

be

successfully

used

up

to

6

months

3without any notable drift in potential during which the potential

3slope is reproducible within 1 mV per concentration decade.

3Whenever

a

drift

in

the

potential

is

observed,

the

membrane

is

re-

3equilibrated with 0.1 mol L 1 cupric sulfate solutions for 3–4 days.

3Potentiometric

selectivity

3The selectivity behavior is obviously one of the important3characteristics of the ion-selective electrodes, determining wheth-

3er

reliable

measurement

in

the

target

sample

is

possible

or

not.

The

3selectivity

preference

of

the

membrane

for

an

interfering

ion

3relative to Cu2+ was determined by the mixed solution method

3(MSM). It is evident from Table 5 that most of the interfering ions

3showed

low

values

of

selectivity

coefficient,

indicating

no

3interference

in

the

performance

of

the

membrane

electrode

3assembly. Such remarkable selectivity of the proposed ion-

3selective electrode over other ions reflects the high affinity of

3the

membrane

toward

the

Cu2+ ions.

3 Accuracy

3The proposed membrane electrode was found to work well3under

laboratory

conditions.

To

evaluate

the

accuracy,

an

Cu2+ ion

3selective electrode was satisfactorily applied for the determination

3of Cu2+ ions in various samples of drinking water containing

3different

amount

of

Cu2+ spiked

with

increasing

known

concen-

3tration

of

Cu2+ ranging

from

2

to

10

mg

L 1,

Each

sample

was

3analyzed in five replicate measurements by membrane electrode

3and the results was tested by the standard addition method. The

3results

are

given

in

Table

6, shows

that

the

amount

of

Cu2+

3recovered

with

the

help

of

the

membrane

electrode

is

in

good

3agreement with that determined by atomic absorption spectros-

3copy (AAS), thereby reflecting the utility of the proposed method

3for

the

analysis

of

real

water

samples.

3Table

7

compares

the

working

concentration

range,

response

3time,

life

time,

pH

range

and

detection

limit

of

the

proposed3electrode

with

other

reported

Cu2+ ion-selective

electrode

[26–29].

3The

results

clearly

indicated

the

superiority

of

the

proposed

3electrode in terms of linear range, pH, response behavior and

3detection limit.

3Conclusion

3The proposed potentiometric sensor of polyurethane-ceriu-

3m(IV)

phosphate

composite

membrane

showed

good

operating

3characteristics

including

Nernstian

response,

reasonable

detection

3limit, relatively high selectivity, wide dynamic range and fast

3response. These characteristics and the typical applications

3presented

in

this

paper

makes

this

sensor

suitable

for

measuring

3Cu(II)

content

in

real

samples

without

a

significant

interaction

Table 7

Comparison of the proposed Cu(II) ion membrane electrode with the reported electrodes.

Refs. Electroactive material Response

time (s)

Linear range pH range Nerstian slope

(mV/decade)

Detection limit

[26] Diaminopyridine and o-vanilin

Schiff base

30 s 105 to 101mol L 1 1.0–5.3 29.6 4.7 106mol L 1

[27] Dithiane,2-(4-methoxyphenyl) 5 s 105 to 102mol L 1 1.3–5.5 29.5 1 1 106molL 1

[28] Quinolinoxymethyl)-trimethylbenzene 30 s 106 to 101mol L 1 1.0–6.0 30 4.0 107molL 1

[29] Tetrathiabicyclo[9.2.1] tetradeca-diene 10 s 106 to 101mol L 1 0.6–6.0 28 1 3.2 107mol L 1

Present

work

Polyurethane-cerium(IV)

phosphate

14

s

1.0

10

8

to

1.0

10

1

mol

L

1

2.5–6.5

30.00

1.0

10

8

molL

1


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from cationic species. A comparison between the response

characteristics

of

the

proposed

potentiometric

sensor

and

those

of previously reported Cu (II) ion-selective electrode indicated that

the present sensor is invariably superior.

Acknowledgements

The

author

Dr.

Umair

Baig

gratefully

acknowledges

to

University

Grant

Commission,

Government

of

India,

[42-336/2013 (SR)] for financial support and Department of Applied

Chemistry, Z.H. College of Engineering and Technology, A.M.U.,

(Aligarh) for providing research facilities. The support of this work

by KFUPM through the project # R15-CW-11 (MIT-13104, 13105)

under the Center of Excellence for Scientific Collaboration with MIT

is also gratefully acknowledged.

References

[1] Y. Xiuhua, M. Yingfeng, Yuezhong, ACS Appl. Mater. Interfaces 5 (2013)1414–1422.

[2] S.M. Hosseini, M. Askari, P. Koranian, S.S. Madaeni, A.R. Moghadassi, J. Ind.Q2 Eng.Chem. (2013) (in press).

[3] M.K. Arsalan, M.A. Mohammad, A. Rafiuddin, Desalination 318 (2013) 97–106.[4] T.S. Chung, L.Y. Jian, Y. Li, S. Kulprathipanja, Prog. Polym. Sci. 32 (2007) 483–507.[5] A. Khan, A.M. Asiri, M.A. Rub, N. Azum, A.A.P. Khan, S.B. Khan, M.M. Rahman, I.

Khan, Composites Part B 45 (2013) 1486–1490.

3[6] C.F. Nørgaard, U.G. Nielsen, E.M. Skou, Solid State Ionics 213 (2012) 76–82.3[7] B.P. Tripathi, V.K. Shahi, Prog. Polym. Sci. 36 (2011) 945–979.3[8] J.X. Leong,W.R.W. Daud,M.Ghasemi, K.B. Liew,M. Ismail, Ren. Sust. Ener.Rev. 283(2013) 575–587.4[10] V.V. Volkov, T.A. Kravchenko, I .R. Vyacheslav, Rus. Chem. Rev. 82 (2013)4465–482.4[11] X. Zuo, S. Yu, W. Shi, Desalination 290 (2012) 83–88.4[12] A.A. Khan, U. Baig, J. Ind. Eng. Chem. 18 (2012) 1937–1944.4[13] A.A. Khan, U. Baig, Desalination 319 (2013) 10–17.4[14] A.A. Khan, U. Baig, Desalination 289 (2012) 21–26.4[15] A.A. Khan, U. Baig, M. Khalid, J. Ind. Eng. Chem. 4 (2013) 1226–1233.

4[16] A.A. Khan, L. Paquiza, J. Ind. Eng. Chem. 6 (2014) 4261–4266. 4[17] A.A. Khan, L. Paquiza, J. Ind. Eng. Chem. (2014) (in press).4[18] N. Wang, C. Wu, Y. Cheng, T. Xu, Inter. J. Pharma 408 (2011) 39–49.4[19] S.D. Faust, O.M. Aly, Adsorption Processes for Water Treatment, Butterworth,4London, 1987.4[20] A.A. Khan, U. Baig, Composites B 56 (2014) 862–868.4[21] A.A. Khan, R. Ahmad, A. Khan, P.K. Mondal, Am. J. Chem. 157 (2011) 122–129.4[22] Recommendation for publishing manuscripts on ion-selective electrodes (pre-4pared for publication by G.G. Guilbault), Commission on Analytical Nomencla-4ture, Analytical chemistry Division, IUPAC, Ion-Sel El Rev 1969;1:139.4[23] A.K. Jain, R.P. Singh, C. Bala, Anal. Lett. 15 (1982) 1557–1563.4[24] Peahkovaskii VV, Melnikova RY, Dzyuva ED. Atlas of Infra red spectra of phos-4phate, orthophosphate. Moscow: Nauka; 1985.4[25] Y. Umezawa, K. Umezawa, H. Sato, Pure Appl. Chem. 67 (1995) 507.4[26] L.P. Singh, J.M. Bhatnagar, Talanta 64 (2004) 313–319.4[27] A. Abbaspour, M.A. Kamyabi, Anal. Chim. Acta 455 (2002) 225–231.4[28] S.K. Mittal, S.K.A.Kumar, N. Gupta, S. Kaur, S. Kumar,Anal.Chim.Acta 585 (2007)4161–170.4[29] M.H. Mashhadizadeh,A. Mostafavi, R. Razavi, M. Shamsipur, Sens. ActuatorsB 86

4(2002) 222–228.


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