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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
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
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
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
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
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)
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
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.
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
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
.
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
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.
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
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
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
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.
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
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
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
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
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
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.
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
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
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
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
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
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
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
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
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