Comparative depiction of removal performance of Poly … depiction of removal performance of Poly (acrylamide-co-itaconic acid)/Charcoal and Chitosan/Charcoal composites for sorption

INTERNATIONAL JOURNAL OF ENVIRONMENTAL SCIENCES Volume 3, No 1, 2012

© Copyright by the authors - Licensee IPA- Under Creative Commons license 3.0

Research article ISSN 0976 – 4402

Received on May 2012 Published on July 2012 241

Comparative depiction of removal performance of Poly (acrylamide-co-

itaconic acid)/Charcoal and Chitosan/Charcoal composites for sorption of

Antibiotic drug from simulated wastewater Bajpai S.K, Shrivastava Sonia

Polymer Research

Laboratory, Department of Chemistry, Govt. Model Science College

Jabalpur, Madhya Pradesh, India

[email protected]

doi:10.6088/ijes.2012030131025

ABSTRACT

This study involves comparative study of equilibrium and kinetic sorption studies to remove

antibiotic drug Ciprofloxacin (CF) from aqueous solutions using poly (acrylamide-co-

itaconic acid)/charcoal composite i.e. [poly(AAm-co-IA)/Chl] and chitosan-charcoal

composite i.e. Cht/Chl as polymeric cation exchanger sorbent materials. The composites

prepared were characterized by FTIR spectroscopy and TGA analysis. In addition their

physicochemical parameters were also determined. The various isotherm models, when

applied to equilibrium sorption data at 25oC, followed the order of fitness as Temkin >

Langmuir≈ Freundlich and Temkin>Freundlich>Langmuir, respectively for [poly (AAm-co-

IA)/Chl] and Cht/Chl. The kinetic uptake data, obtained for [poly (AAm-co-IA)/Chl] and

Cht/Chl sorbents exhibited the order of fitness as: pseudo first order > Pore diffusion>

simple Elovich model> pseudo second order and Pseudo second order > pseudo first order >

pore diffusion > simple Elovich respectively. The sorption mean free energy from the

Dubinin–Raduschkevich (DR) isotherm was found to be nearly 12.91 kJ mol-1

and 5.59 kJ

mol-1

indicating an ion-exchange mechanism for drug uptake for only [poly (AAm-co-

IA)/Chl. The optimum pH value of sorbate solution for drug uptake was found to be around

6.0. Finally, the antibacterial action of drug was investigated and it was found that after

adsorption there was a decrease in bacterial growth inhibition efficiency of drug solution.

Keywords: Antibiotic drugs, Langmuir, Adsorption, toxicity, ion-exchange resin.

1. Introduction

Antibiotics are widely used in human and veterinary medicines for therapeutic purpose. They

are also largely used in animal operations for growth promotions and for disease prophylaxis

(Aksu, Tunc, 2005). They are often partially metabolized after administration and a

significant portion of the antibiotic can be excreted as parent compound or in conjugated

forms that can be converted back to the parent antibiotic. These residual antibiotics from

human and animal can enter the environment via various pathways, like wastewater effluent

discharge, runoff from land to which agricultural or human waste has been applied and

leaching. In fact it is widely accepted that waste water treatment plants (WWTPS) are the

main entry point of urban antibiotics in the aquatic environment. Recently, there has been

growing concern on this potential water pollution problem caused by antibiotics. Different

from conventional pollutant, these materials which are discharged daily have high polarity

and are easily soluble in water. So there are greater chances of their accumulation in aqueous

environment such as sea, river, ponds etc. and thus their chronic influence over human being

are of much concern (Seino et al, 2004; Ternes, 1998). In addition, their presence in water

Comparative depiction of removal performance of Poly (acrylamide-co-itaconic acid)/Charcoal and

Chitosan/Charcoal composites for sorption of Antibiotic drug from simulated wastewater

Bajpai S.K, Shrivastava Sonia International Journal of Environmental Sciences Volume 3 No.1, 2012

242

may cause death of micro-organisms which are effective in waste water treatment (Wang et al,

2008). A variety of antibiotics have been detected in waste effluents and natural waters at

mg/L to low µg/L levels (Segura et al, 2009). Antibiotic can remain in the tissues of the

animals, so that they can be considered as food pollutants. It has been suggested that these

compounds might trigger in occasions allergic reactions and contribute to select for

antibiotic-resistant bacteria in the human microbiota (Cabello, 2006). In addition, antibiotics

released to soils or waters can modify the local environmental microbiota, producing changes

in their composition or activity that are not fully understood. The alterations in the bacterial

populations include selection of resistant mutants in susceptible species, changes in the

distribution of antibiotic resistance genes present in gene-transfer units, and selection of

resistant species in such a way that overall composition of microbiota is modified. For

example, exposition to the ciprofloxacin of salt marsh sediment microbial communities

favors selection of sulphate-reducing and Gram-negative bacteria (Cordova-Kreylos, Scow,

2007). Apart from this consequence of antibiotic pollution, antibiotics can also produce

transient changes in the activity of microbial populations that might be relevant for their

productivity even at their sub-inhibitory concentration. It has been described that the

pollution of manure with silfatdiazine reduces microbial activity, mainly some processes in

nitrogen turnover, besides increasing resistance in soil (Ghosh, Lapara, 2007). Recently,

Kummerer (Kummerer, 2009) has reviewed the effect of antibiotics in the environment.

There are many methods that have been employed in recent past for the removal of

antibiotics from water sources which include use of nanofiltration membrane (Koyuncu et al,

2008), coagulation (Choi et al, 2008), membrane bioreactor (Radjenovic, 2007), nanoscale

iron particles (Gauch et al, 2009), activated carbon (Dutta et al, 1997), bentonite clay

(Budyanto et al, 2008), polysaccharide (Adriano et al, 2005) etc. In recent past, a number of

polymeric sorbents have been employed for the purpose of removing antibiotic drugs from

aqueous solutions. For example, Pisarev et al. (Pisarev et al, 2009) have studied sorption of

antibiotic erythromycin using co-polymer of methacrylic acid and ethylene glycol

dimethacrylate. Similarly a co-polymer of methacrylic acid and n-vinyl-2-pyrrolidone has

been used as imprinting polymer for effective and selective removal of antibiotic

sulfamethoxazole (Valtchev et al, 2009). The removal efficiency was found to be nearly 90%.

Similarly, polyaniline has been exploited for effective removal of diclofenac sodium from

aqueous solution (Bajpai, Bhowmik, 2010). The overall sorption mechanism was found to be

diffusion controlled. Apart from synthetic polymers, natural polymers like pectin have been

used in the form of beads to remove ciprofloxacin (Khoder et al, 2009).

The natural biopolymer chitosan (cht) contains amino group which, in acid medium has a

strong tendency to protonate as –NH3+, thus acting as cation exchanger. Likewise, the

synthetic co-polymer polyacrylamide-co-itaconic acid P(AAm-co-IA) is also a cationic

polymer. We, in preliminary studies, observed that both don’t give reproducible results for

Sorptive removal of cationic drug ciprofloxacin. This was probably due to agglomerating

tendency of sorbent particles in aqueous sorption medium. So, we developed their composite

with charcoal and found that these composite sorbents yielded satisfactory reproducibility in

preliminary sorption studies. Therefore the present work describes a comparison between

sorption efficiency of these two sorbents for removal of cationic drug ciprofloxacin

hydrochloride.

2. Materials and method

2.1 Materials




243

Monomers acrylamide (AAm), and itaconic acid (IA), crosslinker N,N’methylene

bisacrylamide (MB) (Fig.1) , initiator potassium persulphate (KPS) and activated charcoal

were purchased from Hi Media chemicals, Mumbai, India ,and were used as received except

AAm which was recrystallized in methanol to remove the inhibitor. The adsorbents animal

charcoal and chitin were purchased from CDH chemicals, Mumbai, India. The co adsorbent

chitosan was obtained by deacetylation of chitin as reported in our previous study (Bajpai,

Johnson, 2005) .The degree of deacetylation was found to be 98%.The model drug

Ciprofloxacin (CF) (molecular weight 367.80, formula C17H18FN3O3.HCl, Batch no.CFP-

007), was obtained from Karnataka Antibiotics Pharmaceuticals Limited (A Govt. of India

Enterprise).The aqueous solution of drug was used throughout the investigations.

2.2(a) Preparation of P (AAm-co-IA)/Chl composite

The polymer/activated carbon composite were prepared by carrying out free-radical induced

aqueous polymerization of AAm and IA in the presence of uniformly dispersed fine Chl. In

brief 105.514 mM of monomer AAm, 3.843 mM of IA, 1.784 mM of crosslinker MBis was

dissolved in distilled water to give a total volume of 35 ml. To this, 0.3 g of activated

charcoal was added. Finally the reaction was initiated by addition of 0.647 mM of KPS and

1800 µl of catalyst TEMED under vigorous shaking. After the whole reaction mixture gelled,

it was put in an electric oven (Tempstar, India) at 600C to ensure the complete polymerization.

The resulting poly (AAm-Co-IA)/Chl composite was washed thoroughly in distilled water to

remove the unreacted salts and then dried at 500Cin a dust free chamber. The dried mass was

grinded and passed through standard sieves to get sorbent particles with the average

geometrical mean diameter of 695µm. The composite sorbent particles were stored in a dry

place for further use.

2.2 (b) Preparation of chitosan/charcoal (Cht/Chl) composite

The Cht/Chl composite was prepared by precipitation of dissolved chitosan (figure 1) in the

presence of charcoal particles. In a typical method, chitosan solution, with a concentration of

3% (w/v), was prepared in 2% (v/v) acetic acid solution and to 25 ml of this; 0.5g of charcoal

was mixed under vigorous stirring for a period of 1h to ensure complete mixing. Finally, the

suspension was poured into 5% (w/v) solution of sodium hydroxide under vigorous shaking

at 250C.The precipitate, so obtained, was allowed to dry in an electric oven (Tempstar, India)

at 500C till it attained a constant weight. The composite particles were allowed to pass

through standard sieves to obtain particles with geometrical mean diameter of 695 µm.

Figure 1: Structures of monomers and drug




244

2.3 Characterization of sorbent

2.3.1 Physicochemical parameters

The co-polymeric composite sorbents were analyzed for measurement of their

physicochemical parameters. The method of determination was adopted from our previous

report (Bajpai, tankhiwale, 2008) using n-heptane as a non-sorbent. The values obtained, are

given in Table

Table 1: Various physical parameters obtained for sorbents S.No. Parameters Poly( AAm-co-

IA)/chl

Chi/chl composite

1. Particle size 695 µm 695 µm

2. Percent porosity 55 % 55%

3. True density 1.0 ml/g 2.5 ml/g

4. apparent density 0.45 ml/g 0.5 ml/g

2.3.2 Thermogravimetric analysis of composite sorbents

The TGA was performed in Indian Institute of Technology, Mumbai, India, using

thermogravimetric analyzer (Perkin Elmer Thermal Analyser). About 12.0 mg of powdered

composite sorbents were placed in ceramic crucible and analysed over the temperature range

from 25oC to1000

oC at the rate 10

oC min

-1under a dry flow of nitrogen at the rate of 50 ml

min-1

.

2.3.3 FTIR spectral analysis

The FTIR (Fourier Transform Infrared) spectrum of polymer-charcoal composite sorbents P

(AAm-co-IA)/Chl and Cht/Chl was recorded on FTIR spectrophotometer (Shimadzu, 8400S)

using KBr.

2.4 Adsorption experiments

Sorption studies were carried out in thermo stated water bath shaker (Rivotek, India) at 25oC,

with a shaking speed of 200 rpm using Erlenmeyer flasks of 250 ml capacity. Batch

experiments were performed by equilibrating 0.06 g and 0.08 g of adsorbents Chi/Chl and P

(AAm-co-IA)/Chl respectively with 50 ml of drug aqueous solution of pre-determined

concentrations. The required pH was obtained by adding a few drops of 0.1 M HCl or 0.1 M

NaOH. The sorption system was agitated at 200 rpm for a period of 1 hr and was centrifuged

and the supernatant was analyzed spectrophotometrically (Systronics 2201- UV-

spectrophotometer) at 273 nm. The amounts of drug adsorbed qe, in mg per g of sorbent and

percent sorption were determined using following equations (Amin et al, 2008)

(((( ))))W

Vx C - C q eoe ====

……. (1)

and

% Removal

(((( ))))100x

C

C - C

o

eo====

…… (2)




245

where Co and Ce are initial and final concentrations of drug solutions (mg L-1

) respectively;

and V and W are volume of sorbate solution study (in litre) and amount of sorbent used (in g)

respectively. The concentrations of drug in the solutions were estimated using Lambert-

Beers-Law plotted for drug solutions of known concentrations.

All the experiments were carried out in triplicate and average values have been reported in

the data with standard deviation of 2 percent .In the experiments, where higher deviation was

observed, the data was discarded and new experiment was conducted.

2.5 Antibacterial study

The effect of drug (CF) adsorption on its antibacterial action was investigated on E.coli using

well method (Vimala et al, 2009). This is based on the principle that when drug is placed

inside the well of suitable nutrient agar medium inoculated with test bacterium, there is radial

diffusion of drug outwards through the agar thus creating antibiotic concentration gradient.

The concentration of drug is more near the well and decreases on moving outwards. Finally

an inhibition zone is produced around the antibiotic well, whose width is measure of

susceptibility of pathogen.

For this nutrient agar media was prepared and then sterilized by autoclaving it in conical flask

for 30 minutes. With this media, agar plates were prepared by transferring the media to these

sterilized petriplates. After solidification of the media, E. coli culture was spread on the solid

surface of the media and then wells of diameter 70 mm were punched in it. To this inoculated

Petridish l00 µl of drug solution was filled in the well and then incubated for 2 days at 37oC

in the incubation chamber. The presences of inhibition zones containing bacterial culture

around the well were observed. The diameters of each inhibition zone were measured in mm.

3 Results and discussion

3.1 Characterization of sorbents

3.1.1 Physicochemical parameters

Table-I describes the physicochemical parameters of synthesized co-polymeric composite

sorbent P (AAm-co-IA/Chl) and natural biopolymer composite sorbent (Chi/Chl). Here it is

interesting to see that, the % porosity is around 55% and 80% respectively which suggests not

only the porous nature of the sorbents but also possibility of occurrence of intraparticle

diffusion phenomenon.

3.1.2 Thermo gravimetric analysis of co-polymeric sorbent

The thermo gravimetric analysis of composite sorbents was performed to investigate their

thermal stability. The results, as depicted in figure 2 shows that the initial decomposition

temperature (Tid) for P (AAm-co-IA/Chl) is nearly 210oC while the final decomposition

temperature Tfd is approximately 570oC.This suggests that the polymer is fairly stable upto

200oC. In figure 2 the TGA for Chi/Chl shows initial decomposition starts at 150

oC-180

oC

(Tid) while only 49% of composite decomposes at nearly 1000oC. This suggests that however

initial decomposition of composite starts at relatively lower temperature (180oC), polymer

composite overall is quite stable.




246

Figure 2(a): TGA curve of P(AAm-co-IA)/chl composite

Figure 2(b): TGA curve of Chi/Chl composite

3.1.3 FTIR spectral analysis

The FTIR spectra of plain composite sorbent [poly(acrylamide-co-itaconic acid)/Chl] as

depicted in figure 3 clearly indicates a narrow band appeared at 3190 cm-1

, due to the

overlapping of O-H and N-H stretching of acid and amide respectively. The symmetric and

asymmetric >CH2 stretching of methylene occurs near 2930 and 2856 cm-1

respectively. A

prominent peak at 1650 cm-1

corresponding to >C=O stretching vibration of amide. Another

band arising for C-O stretching appears near about 1325 cm-1

.

The FTIR spectra of Chi/Chl composite as depicted in figure 3 shows a band at 3449cm-1

which corresponds to N-H stretch, a peak at 3257cm-1

due to O-H stretch, bands at 2932 and

1407 cm-1

corresponding to C-H stretch and bend respectively, peak at 1646 cm-1

corresponds

to N-H- II stretch, band arising due to C-O stretch appears near about 1162 and 1029 cm-1

.




247

Figure 3(a): FTIR spectra of P(AAm-co-IA)/Chl composite

Figure 3(b): FTIR curve of Chi/Chl composite

3.2 Effects of sorbent/sorbate ratio (mg/ml) on drug uptake

The results, as shown in figure 4, reveal that the P (AAm-co-IA)/Chl sorbent shows a

maximum drug uptake of nearly 52 percent at solid/liquid ratio of 1.4 while the optimum

percent uptake of nearly 67 percent at the solid/ liquid ratio of 1.6. The initial increase in drug

uptake with solid/ liquid ratio is attributable to the increased number of sites available for

drug molecules to be adsorbed. However, beyond certain value of solid/liquid ratio, the drug

uptake reached saturation value. Here it is noteworthy that chitosan/charcoal composite

demonstrates higher percent sorption as compared to the other sorbent. This could probably

be attributed to greater porosity of Cht/Chl sorbent which offers greater number of active

sites exposed to the incoming drug molecules. Based on these results, it was decided to

maintain a solid liquid ratio of 1.4 and 1.6 in the whole investigation for P (AAm-co-IA)/Chl

and Cht/Chl sorbents respectively.




248

Figure 4: Effect of solid-liquid ratio of P (AAm-co-IA)/Chl and Cht/Chl composites on drug

uptake

3.3 Effect of pH on drug sorption

pH of a sorption system plays a significant role in affecting the extent of adsorption,

particularly when both sorbent and sorbate molecules are ionic in nature (Bajpai & Bajpai,

1995). In the present study, both P (AAm-co-IA)/Chl and Chi/Chl, the sorbents and

ciprofloxacin the sorbate are ionic in nature and therefore pH of the sorption system was

expected to play a significant role in obtaining optimum drug adsorption. In order to

investigate this, drug solution of a known concentration was prepared in the pH range of 1.5

to 12.2 and agitated with appropriate quantity of sorbent at 25oC. The percent drug sorption

versus pH of the solution profiles are shown in Figure 5. It can clearly be seen that for the

sorbents, namely P(AAm-co-IA)/Chl and Cht/Chl, the maximum percent sorption values of

52 and 81 are obtained respectively at the solution pH of nearly 6.0. However both of the

sorbents show different trends i.e. there is remarkable decrease in percent drug sorption on

either side along the pH axis for Cht/Chl while for P (AAm-co-IA)/Chl sorbent sorption

decreases below pH 6.0 but remain constant beyond the pH 6.0. However, there percent

uptake differ remarkably i.e. nearly 52 and 81 percent respectively. The observed findings

may be explained as follows: The sorbate ciprofloxacin has pka value at nearly 6.4 [Pisal et al,

2004] and at the same pH the two carboxylic groups of itaconic acid moieties also remain in

fully ionized state [Betancourt et al, 2010]. Therefore, there occurs effective ion-exchange

process between the cationic drug molecules and free H+ ions present within the P (AAm-co-

IA)/Chl sorbent particles. When pH of the solution is reduced to 5.0, the ionization of the

carboxylic groups is decreased (pka2= 5.40), thus lowering the concentration of exchangeable

H+ ions within the polymer composite. In addition, the unionized –COOH group also produce

additional cross links, thus making the gel structure more compact. This results in lower drug

uptake. Where pH is further reduced to, say 3.0, the pH is below the pka value of itaconic acid

(i.e. 3.85) and hence ionization of first carboxylic group is also suppressed. This further

reduces the number of counter or free H+ ions in the network. Hence extent of ion exchange

process is further suppressed, thus lowering the drug uptake. On further decreasing the pH

below 3.0 the ionization of carboxylic acid was almost nil. This brought the drug uptake to

almost minimal value. On the other hand, when pH is increased beyond 6.0, no appreciable

increase in drug uptake was observed which could be due to fact that ionization was almost

complete. The sorbent Cht/Chl showed somewhat different behavior. When the pH of the




249

solution is sufficiently low i.e. around 2.0, the degree of drug sorption is quite low. Although

at this pH drug ciprofloxacin exists as cations, and chitosan also has protonated amino groups

(i.e. –NH3+) but there is low degree of adsorption because at low pH chitosan is in dissolved

state. However, as the pH increases to around 6.0, the chitosan becomes insoluble and it

exists within the Cht/Chl composite particles. The observed maximum drug uptake would be

probably be due to electrostatic interactions such as –OH---O, -OH---F existing between

chitosan and drug molecules. However, when pH is further increased beyond 6.0, the

ciprofloxacin exists as zwitter-ionic species (pk1 and pk2 are 6.1 and 7.7 for ciprofloxacin) as

the protonated amino group of the piperazine moiety and ionized –COO- groups exists in the

drug molecules. Under this condition, the electrostatic interactions decrease and causes low

drug uptake. Thus we see that although both of the sorbents show optimal pH value of 6.0,

but their sorption capacities differ appreciably from each other, Cht/Chl showing higher drug

removal.

Figure 5: Effect of pH on drug sorption by Poly (AAm-Co-IA)/Chl and Chi/Chl composite

3.4 Equilibrium sorption studies

The study of equilibrium sorption is essential to design a plant based on sorptive removal

process (Chandra et al, 2006). The sorption equilibrium indicates how the sorbate molecules

distribute themselves between the liquid phase (solution) and the solid phase (sorbent) at the

equilibrium state (Hameed et al, 2007). In order to describe sorption equilibrium data of CF

on composite sorbents, Langmuir, Freundlich and Temkin isotherm models were used which

may described as below:

Langmuir model (Langmuir, 1918) assumes monolayer coverage of sorbate over a

homogeneous sorbent surface and is given as

eooe C

1.

bQ

1

Q

1

q

1++++====

……(3)

where Qo (mg g-1

) is the maximum sorption capacity corresponding to complete monolayer

coverage on the sorbent surface and b (L mg-1

) is the langmuir constant related to the heat of

sorption.




250

Freundlich isotherm (Freudlich, 1906) assumes that adsorption process takes place on

heterogeneous surface and is given as

FK log eC log

n

1 eq log ++++====

……(4)

where KF (mg/g (L/mg)1/n

) is Freundlich constant related to sorption capacity and n refers to

sorption intensity.

Finally, Temkin isotherm (Temkin, pyzhev, 1940) considers the effects of some indirect

sorbent/sorbate interactions on uptake process and is given as

e

T

T

T

e lnCb

RT.lnA

b

RTq ++++====

……(5)

where AT and bT are Temkin constants.

Figure 6, 7 and 8 show comparative profiles for Langmuir, Freundlich and Temkin isotherms

for P(AAm-co-IA)/Chl composite and Chi/Chl composite respectively, drawn using

equilibrium uptake data obtained with initial concentrations of drug solutions in the range of

5 to 50 mg L-1

at 27oC. It was found that all the three isotherm models fitted well on uptake

data and, based on their regression values, the order of fitness for P (AAm-co-IA)/Chl was

Temkin > Langmuir > Freundlich and for Chi/Chl composite it was

Temkin>Freundlich>Langmuir .The various isotherms parameters have been given in Table-

II. Chi/chl showed a fair maximum sorption capacity value of 111.11 mg g-1

(i.e. Qo) which

indicates high removal efficiency of the Chi/Chl sorbent as compared to a lower value of

31.25mg g-1

for poly (AAm-co-IA)/Chl.

Finally, in order to investigate the mode of uptake process i.e. whether physical or chemical

sorption, the equilibrium sorption data was also applied to Dubinin-Radushkevich (D-R)

isotherm model this is given as (Ahmad et al, 2002)

)2.exp(-BmC ad

C εεεε==== ……(6)

where Cad is amount of sorbate adsorbed in moles g-1

, Cm is the maximum amount of drug that

could be adsorbed on sorbent under the optimized experimental conditions, B is a constant

with a dimension of energy, and Polyanyi potential, ε = RT ln(1 + 1/Ce) where R is the gas

constant in kJ mol-1

K-1

, T is the absolute temperature in K and Ce is the equilibrium

concentration (mol L-1

) of drug solution .The linearized form may be written as

2B-mC ln ad

C ln εεεε==== …… (7)

When lnCad was plotted against ε2, a linear plot was observed (figure 9) with fairly high

regression value of 0.99 for Chi/Chl composite and a value of 0.97 for P (AAm-co-IA)/Chl.

The computed value of B from the slope of straight line was found to be 3 × 10-3

kJ mol-2

for

P (AAm-co-IA)/Chl and 1.6× 10-3

kJ mol-2

for Chi/Chl composite. From the calculated value

of B, the mean sorption energy was computed as




251

2B

1E

−−−−====

……(8)

which is the free energy transfer of one mole of solute from infinity to the surface of sorbent.

The numerical value of E, as evaluated using Eq. (8) was found to be 12.91 kJ mol-1

for

poly(AAm-co-IA)/Chl which lies within the prescribed range of 8-16 kJ mol-1

for ion-

exchange and the value of E for Chi/Chl was found to be 5.59kJ mol-1

.In this way it may be

concluded that sorption of drug is mainly governed by ion-exchange process in case of

poly(AAm-co-IA)/Chl composite as also predicted in a previous section while discussing pH

effect.

Figure 6: Langmuir plot for sorption of drug onto P (AAm-co-IA)/chl and Chi/Chl

composite

Figure 7: Freundlich plot for sorption of drug onto P(AAm-co-IA)/chl and Chi/Chl

composite




252

Figure 8: Temkin plot for sorption of drug onto P (AAm-co-IA)/chl and Chi/Chl Composite

Figure 9: D-R isotherm plot for sorption of drug onto P (AAm-co-IA)/chl and Chi/Chl

composite

3.5 Dynamic sorption studies

The effect of contact time on drug sorption was studied for sorbate solutions with initial

concentrations of 25 mg L-1

at 27oC.The results, as depicted in the figure 10 show that for

both the sorbents, drug uptake increases with time and attains an optimum value of 26 and 44

for P (AAm-co-IA)/Chl and Chi/Chl respectively. The Chi/Chl sorbent shows higher drug

uptake, probably due to porous nature of composite sorbent and availability of greater

number of active sites for drug uptake.




253

Figure 10: qt vs t plot at 25 mg/l concentration plot for sorption of drug onto P(AAm-co-

IA)/chl and Chi/Chl Composite

3.6 Sorption kinetic models

The most commonly used kinetic models, namely pseudo first order and pseudo second order

were employed to make quantitative interpretation of the kinetic data displayed in figure 10.

A simple pseudo first order kinetic model (Lagergren et al, 1898) is given as

t2.303

klogq)qlog(q sad

ete −−−−====−−−− ……(9)

where qt (mg g-1

) is the amount of drug sorbed on the surface of composite sorbents at time t

and kads (min-1

) is the equilibrium rate constant of pseudo first order sorption. Utilizing the

uptake data, displayed in figure 10 we plotted graph between log (qe-qt) and t which were

found to be almost linear, as depicted in figure 11, for both P (AAm-co-IA)/Chl and Chi/Chl

composites with linear regressions of 0.960 and 0.989 respectively . In addition to pseudo

first order, use of pseudo second order is also very common. There are four types of linear

pseudo second order kinetic models (Ho, Mckay, 1998), of which most popular linear form is

tq

1

qK

1

q

t

e

2

e2adst

++++====

…… (10)

Where qe is the amount of drug sorbed at equilibrium, k2ads is second order rate constant

(g/mg min). The kinetic drug uptake data, when applied on above Eq. (10) yielded linear

plots between t/qt and t showing fair regression of 0.99 and 0.93 for P(AAm-co-IA)/Chl and

Chi/Chl composites at initial concentration of 25 mg L-1

respectively (figure 12).

Now, using slopes and intercepts of these linear plots, obtained for pseudo first order and

second order kinetic models, adsorption rate constants and equilibrium drug uptake were

evaluated and are given in the Table III. It can be seen that regression values, obtained for

first order kinetic plots are much higher than those obtained for pseudo second order kinetic

plots. In this way, it may be concluded that first order kinetic model describes the kinetic

uptake data most successfully. Here, it is also worth mentioning that we also applied simple




254

Elovich model (Badmus, 2007) on uptake data and the regression was good for lower

concentrations (Table III).

Figure 11: Lagergren plot for P(AAm-co-IA)/chl and Chi/Chl Composite at 25 mg/l

Figure 12: Pseudo second order plot for P(AAm-co-IA)/chl and Chi/Chl Composite at 25

mg/l

Table 3: Various kinetic parameters for adsorbents

Adsorbent Pseudo first order Pseudo second order Elovich model Intra particle

diffusion

model

K1×10-3

(sec-

1)

Qe(m

gg-1

)

R2 K2(g

mg-

1sec

-1)

Qe(

mgg-

1)

R2 α

(mgg-

1min

-

1)

β R2 Kid C R

2

P(AAm-

co-IA)/chl

41.4 27.6 0.97 0.57 41.6 0.91 6.16 6.8 0.9

7

3.7 -4.28 0.97

Cht/chl 101.0 51.5 0.96 1.34 55.5 0.98 -4.6 11.

8

0.9

8

6.2 0.21 0.97




255

3.7 Macro and micro-pore diffusion

The uptake mechanism of a sorbate onto the sorbent follows three steps viz. film diffusion,

pore diffusion and intraparticle transport (Vishwanathan, meenakshi, 2008). The slowest of

the three steps controls the overall rate of the sorption process. Generally, pore diffusion and

intraparticle diffusion are often rate limiting in a batch reactor (Vimala et al, 2009). The

adsorption rate parameter which controls the batch process for most of the contact time is the

intraparticle diffusion. The possibility of intraparticle diffusion resistance affecting

adsorption was explored by using the intraparticle diffusion model, given as (Cheung et al,

2007)

Itkq 2/1

idt ++++==== ……(11)

where kid (mg g-1

min-1/2

) is the intraparticle diffusion rate constant and I is the intercept of

plot of qt versus t1/2

. If this linear plot passes through origin then intraparticle diffusion is the

rate controlling step. In case the straight line does not pass through origin, it indicates that

there is difference between the rate of mass transfer in the initial and final steps of adsorption,

and some other mechanism along with intraparticle diffusion is also involved (Baral et al,

2006). To investigate this, qt versus t1/2

plots were obtained for dynamic uptake of drug from

solutions with initial concentration of 25 mg L-1

. The results, as shown in the figure 13 for

P(AAm-co-IA)/Chl and Chi/Chl sorbents indicate that both the plots are almost linear and

pass through origin. The values of intraparticle diffusion rate constants kid, as determined for

both the sorbents using slopes of the linear plots were found to be 3.72 and 6.24 mg g-1

min-

1/2 respectively. The regression values were found to be 0.97 and 0.97 respectively.

Figure 13: Pore diffusion plot for P(AAm-co-IA)/chl and Chi/Chl composite at 25 mg/l

3.10 Antibacterial study

The major disadvantage of presence of drugs in aquatic system is that they kill micro-

organisms like bacteria, fungi which take up toxic metal ions and thus help to protect the

aquatic environment. So, the presence of drugs increases the metal ion toxicity by reducing

the micro-organisms. Figure 14 (a) shows the growth of bacteria in petridishes, supplemented




256

with drug solution of concentration 3.0 mg L-1

and figure 14 (b) that containing drug solution

left after adsorption. It is clear that the petridish containing original drug solution shows

greater inhibitory action of drug. Whereas, there is larger population of colonies in the

petridish containing drug solution remained after adsorption.

Figure 14: Antibacterial study: zone of inhibition in the petridishes supplemented with (a)

original drug solution (b) drug solution left after adsorption.

4. Conclusion

From the above study it may be concluded that both, P(AAm-co-IA)/Chl and Chi/Chl

sorbents have capacity to remove ciprofloxacin from waste water. The two sorbents show

maximum sorption value of 31.25 of 111.11 respectively, thus showing better removal

tendency of Chi/Chl. The removal mechanism involves ion exchange and electrostatic

bindings respectively. The Lagergren kinetics model is best fitted onto kinetic drug uptake

data. Since chitosan is far cheaper than polyacrylamide and itaconic acid and other related

chemicals involved in copolymer formation, and it has greater removal capacity of drug, it is

more advantageous to Opt Chi/Chl composite as a potential sorbent for removal of

ciprofloxacin from waste water.

Acknowledgement

Authors are thankful to Dr. O. P. Sharma for his unconditional support and for providing

necessary facilities

5. References

1. Adriano, W.S., Veredas, V., Santana, C.C., Goncalves, L.R.B., (2005), Adsorption

of amoxicillin on chitosan beads: kinetics, equilibrium and validation of finite bath

models, Biochemical engineering journal, 27, pp 132-137.

2. Aksu, Z., Tunc, O., (2005), Application of biosorption for penicillin G removal:

comparison with activated carbon, Process biochemistry, 40(2), pp 831-847.

3. Anirudhan, T.S., Suchithra, P.S., Radhakrishnan, P.G., (2009), Synthesis and

characterization of humic acid immobilized-polymer/bentinite composites and their




257

ability to adsorb basic dyes from aqueous solutions, Applied clay science., 43, pp

1336-1342.

4. Badmus, M.A.O., Audu, T.O.K., Anyata, B.U., (2007), Removal of lead ions from

industrial wastewaters by activated carbon prepared from periwinkle shells

(Typanotonus fuscatus), Turkish journal of engineering and environmental sciences,

31, pp 251-263.

5. Bajpai, A.K., Bajpai, S.K., (1995), Dynamic measurements of adsorption of

hydrolyzed polyacrylamide (HPAM) onto hematite, Colloid and interface science,

273(11), pp 1028-1032.

6. Bajpai, S.K., Bhowmik, M., (2010), Adsorption of diclofenac sodium from aqueous

solution using polyaniline as a potential sorbent. I. Kinetic studies. , Journal of

applied polymer science, 117(6), pp 3615-3622.

7. Bajpai, S.K., Johnson, S., (2005), Superabsorbent hydrogels for removal of divalent

toxic ions. Part I: Synthesis and swelling characterization, Reactive and functional

polymers, 62(3), pp 271-283.

8. Bajpai, S.K., Tankiwale, R., (2008), Preparation,characterization and preliminary

calcium release study of floating sodium alginate/dextran- based hydrogel beads:

part-I , Polymer international., 57(1), pp 57-65

9. Baral, S.S., Das, S.N., Rath, P., (2006), Hexavalent chromium removal from

aqueous solution by adsorption on treated sawdust, Biochemical engineering journal,

31(3), pp 216-222.

10. Betancourt T, Pardo J, Soo K, Peppas N.A., (2010), Characterization of pH-

responsive hydrogels of poly (itaconic acid-g-ethylene glycol) prepared by UV-

initiated free radical polymerization as biomaterials for oral delivery of bioactive

agents., journal of biomedical Material Research A., 93(1), pp 175-88

11. Budyanto, S., Soedjono, S., Irawaty, W., Indraswati, N., (2008), Studies of

adsorption equilibria and kinetics of amoxicillin from simulated wastewater using

activated carbon and natural bentonite, Journal of environmental protection science,

2, pp 72-80.

12. Cabello, F.C., (2006), Heavy use of prophylactic antibiotics in aquaculture: a

growing problem for human and animal health and for the environment,

Environmental microbiology, 8, pp 1137-1144.

13. Chandra, T.C., Mirna, M.M., Surdayanto, Y., Ismadji, S., (2006), Adsorption of

basic dye onto activated carbon prepared from durian shell: studies of adsorption

equilibrium and kinetics, Chemical engineering journal, 127, pp 121-129.

14. Cheung, W.H., Szeto, Y.S., McKay, G., (2007), Intraparticle diffusion processes

during acid dye adsorption onto chitosan bioresource technology, 98 (15), pp 2897-

2904.

15. Choi, K., Kim, S., Kim, S-H., (2008), Removal of antibiotics by coagulation and

granular activated carbon filtration, Journal of hazardous materials, 151(1), pp 38-43.




258

16. Cordova-Kreylos, A.I., Scow, K.M., (2007), Effects of ciprofloxacin on salt marsh

sediment microbial communities, International society for microbial ecology journal,

1(7), pp 585-595.

17. Dutta, M., Baruah, R., Dutta, and N.N., (1997), Adsorption of 6-aminopenicillanic

acid on activated carbon, Separation and purification technology, 12(2), pp 99-108.

18. Freundlich, H., (1906) , U¨ ber die adsorption in lo¨sungen [Adsorption in solution]”

Zeitschrift für Physikalische Chemie, 57, pp 384-470.

19. Gauch, A., Tuqan, A., Assi, H.A., (2009), Antibiotic removal from water:

Elimination of amoxicillin and ampicillin by microscale and nanoscale iron particles,

Environmental pollution, 157(5), pp 1626-1635.

20. Ghosh, S., Lapara, T.M., (2007), The effects of subtherapeutic antibiotic use in farm

animals on the proliferation and persistence of antibiotic resistance among soil

bacteria, society for microbial ecology journal, (1), pp 191-203.

21. Hameed, B.H., Din, A.T.M., Ahmad, A.L., (2007), Adsorption of methylene blue

onto bamboo-based activated carbon: Kinetics and equilibrium studies journal of

hazardous materials, 141(3), pp 819-825.

22. Ho, Y.S., McKay, G., (1998), Sorption of dye from aqueous solution by peat,

Chemical engineering journal, 70(2), pp 115-124.

23. Khoder, M., Tsapis, N., Hugust, H., Besnard, N., Gueutin, C., Fattal, E., (2009),

Removal of ciprofloxacin in simulated digestive media by activated charcoal

entrapped within zinc-pectinate beads, International journal of pharmaceutics, 379,

pp 251-259.

24. Koyuncu, I., Arikan, O.A., Wiesner, M.R., Rice, C., (2008), Removal of hormones

and antibiotics by nanofiltration membranes, Journal of membrane science, 309(1-2),

pp 94-101.

25. Kummerer, K. (2009), Antibiotics in the aquatic environment -A review -Part I,

Chemosphere, 75, pp 417-434.

26. Lagergren, S., Vetenskapsakademiens, K.S., (1898), Zur theorie der sogenannten

adsorption gelöster stoffe, Handlingar, 24(4), pp 1-39.

27. Langmuir, I., (1918), The adsorption f gases on plane surfaces of glass, mica and

platinum, Journal of American chemical society, 40(9), pp 1361-1403 .

28. Pisal, S., Zainmuddin, R., Nalawade, P., Mahadik, K., Kadam, S., (2004), Drug

release of polyethylene-glycol-treated ciprofloxacin-Indion 234 complexes,

American association of pharmaceutical scientists Pharma. Sci. Tech., 5(4).

29. Pisarev, O.A., Ezhova, N.M., Garkushina, I.S., (2009) Russian journal of physical

chemistry, 83(1), pp 17-27.




259

30. Radjenovic, J., Petrovic, M., Barcelo, D., (2007), Analysis of

pharmaceuticals in wastewater and removal using a membrane bioreactor, Analytical

and bioanalytical chemistry, 387(4), pp 1365-1377.

31. Segura, P.A., Francois, M., Gagnon, C., Sauve, S., (2009), Review of the occurrence

of Anti-infectives in Contaminated wastewaters and natural and drinking waters,

Environmental health perspectives, 117(5), pp 675-684.

32. Seino, A., Hasegawa, Y., Masunaga, S., (2004), Distribution of Antibioticresistant E.

Coli in Kaname, Tsurumi, and Tama Rivers, Journal of Japan society on water

environment, 27(11), pp 693-698.

33. S-Z. E., El-Ashtoukhy, Amin, N.K., Abdelwahab, O., (2008), Removal of lead (II)

and copper (II) from aqueous solution using pomegranate peel as a new adsorbent,

Desalination, 223(1-3), pp 162-173.

34. Temkin, M.J., Pyzhev, V., (1940), Recent modifications to Langmuir Isotherms,

Acta Physiochemica, 12, pp 217-222.

35. Ternes, T.A., (1998), Occurrence of drugs in German sewage treatment plants and

rivers, Water research, 32(11), pp 3245-3260.

36. Valtchev, M., Palm, B.S., Schiller, M., Steinfeld, U., (2009), Development of

sulfamethoxazole-imprinted polymers for the selective extraction from waters,

Journal of hazardous materials, 170, pp 722-728.

37. Vimala, V., Sivudu, K.S., Mohan, Y.M., Sreedhar, B., Raju, K.M., (2009),

Permeation of sodiumDdecyl sulfate through polyaniline-modified cellulose acetate

membranes, Carbohydrate polymers, 75, pp 463-471.

38. Vishwanathan, N., Meenakshi, S., (2008), Selective sorption of fluoride using Fe(III)

loaded carboxylated chitosan beads, Journal of fluorine chemistry, 129(6), pp 503-

509.

39. Wang, Q.L., Ding, De-Xin., Hu, E., Yu, R., Qlu, G., (2008), Transactions of

nonferrous metals society of China, 18(6), pp 1529-1532.

Documents

Comparative depiction of removal performance of Poly … depiction of removal performance of Poly (acrylamide-co-itaconic acid)/Charcoal and Chitosan/Charcoal composites for sorption