Adsorptive removal of lead and cadmium ions using cross-linked CMC Schiff base: Isotherm, kinetics and catalytic activity

Article abstract of DOI:10.13005/ojc/320150

Water plays a vital role to human and other living organisms. Due to the effluent coming from chemical industries, the industrial activity, contamination of ground water level is goes on increasing nowadays. Therefore, there is a need to develop technolog

Full text of DOI:10.13005/ojc/320150

ISSN: 0970-020 X
CODEN: OJCHEG
2016, Vol. 32, No. (1):
Pg. 441-453
ORIENTAL JOURNAL OF CHEMISTRY
An International Open Free Access, Peer Reviewed Research Journal
www.orientjchem.org
Adsorptive Removal of Lead and Cadmium Ions using
Cross-Linked CMC Schiff Base: Isotherm, Kinetics and
Catalytic Activity
P. MOGANAVALLY1, M. DEEPA2 *, P. N. SUDHA3 and R. SURESH4
1Research and Development Centre, Bharathiyar University, Coimbatore, India.
2Department of Chemistry, Muthurangam Govt. Arts College, Vellore, India.
3PG & Research Department of Chemistry, D.K.M College for Women, Vellore, India.
4Government Polytechnic College, Nagapadi, Thiruvannamalai, India.
*Corresponding author E-Mail: deeparam79@gmail.com
http://dx.doi.org/10.13005/ojc/320150
(Received: January 21, 2016; Accepted: March 08, 2016)
ABSTRACT
Water plays a vital role to human and other living organisms. Due to the effluent coming from
chemical industries, the industrial activity, contamination of ground water level is goes on increasing
nowadays. Therefore, there is a need to develop technologies that can remove toxic pollutants in
wastewater. Hence the cross linked Carboxymethyl chitosan(CMC)/ 2,3-dimethoxy Benzaldehyde
Schiff base complex has been synthesized and characterized by using FT-IR and SEM analysis.
All these results revealed that cross linked Schiff base has formed with high adsorption capacity.
The prepared effective adsorbent used for the removal of heavy metals like lead (II) and cadmium
(II) ions from aqueous solution and the adsorption data follow the Freundlich model, which follows
pseudo first order kinetics.Effect of various parameters like solution pH, adsorbent dose and contact
time for the removal of heavy metals has been studied.The synthesized sample undergoes catalytic
oxidation process significantly at 24 hrs. The results showed that cross linked Schiff base is an
effective, eco-friendly, low-cost adsorbent.
Key words: Carboxymethyl chitosan; Gluteraldehyde; adsorption; catalytic activity;
INTRODUCTION
industry. Chitosan is an inexpensive and renewable
material with many applications in cosmetics,
Chitosan, the most abundant natural
polysaccharide, is produced by the deacetylation
of chitin which is one of the key constituents of the
shells of crustaceans and a byproduct of the fishing
pharmaceuticals, food science and biotechnology
1-2
.
Due to the poor solubility of chitosan, O-
carboxymethyl chitosan, which is a water soluble
chitosan derivative, have attracted much attention

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MOGANAVALLY et al., Orient. J. Chem., Vol. 32(1), 441-453 (2016)
as it widened its applications. Carboxymethyl Synthesis of Carboxymethyl chitosan Schiff
chitosan is not only a good solubility, but also possess Bases (CMC-SB)
unique chemical, physical and biological properties
The Carboxymethyl chitosan Schiff base is
3. Carboxymethyl chitosan is formed by means of prepared already and reported in the literature 11
carboxymethylation, as some of the –OH of chitosan
.
were replaced by –CH2COOH groups. Therefore, Synthesis of cross-linked Carboxymethyl
the reactive ligands like –COOH and –NH2 groups chitosan Schiff Bases (CMC-SB)
are still ready to undergo chemical modifications
The synthesized Carboxymethyl chitosan
to improve its physical properties. In comparison Schiff base product was dissolved in water and stirred
to chitosan, CMC has higher moisture absorption, at room temperature for 30 min. Then gluteraldehyde
retention, better biological, chelating and sorption was added to the mixture. The mixture was stirred
properties 4-6. Generally, Schiff based material and heated at 60°C for 12 h under water bath heating.
exhibits wide range of applications, hence the water After cooling, the crude product was washed with
soluble CMC has to be modified into Schiff base with ethanol to the point of colorless filtrate. The product
2,3 -dimethoxy Benzaldehyde.
was dried at 60°C in vacuum for 24 h 12. The cross
linked Carboxymethyl chitosan Schiff base (GLU-
Crosslinking is another method adopted to CMC-SB) structure is shown in Figure-1.
improve the properties of Carboxymethyl chitosan
Schiff bases. Crosslinking agents are generally Characterization of CMC & C-CMC Schiff base
structured in many forms like rings, straight chains, complex
and branched chains. There are several crosslinking
FT-IR spectroscopy was measured to
agents like gluteraldehyde, formaldehyde, glyoxal determine the type of bonds. Fourier transform
etc. In general, adsorption capacity decreases infrared spectra of CMC-Schiff base and its
with the extent of crosslinking, as it decreases the cross linked derivatives using KBR pellet method
reactive sites on the polymer. But in some cases it were recorded in the frequency range of 400 –
also improves the adsorption capacity, depending on 4000 cm-1 using Thermo Nicolet AVATAR 330
the functional groups in the crosslinking agent 7.The spectrophotometer. X – ray diffractograms of
chitosanandchitosancrosslinkedwithgluteraldehyde samples were obtained using an X – ray powder
has reported in the previous literatures 8-9 and their diffractometer (XRD – SHIMADZU XD – D1) with
application in the removal of heavy metals10 and Ni – filter and Cu Ká radiation source. The relative
biological property have been discussed. The intensity was recorded in the scattering range 2è,
metal selected for our study is lead and cadmium. varying from 10o to 90o. The surface morphology and
Therefore in the present work, Chitosan modified to cross section morphology of CMC- Schiff base and its
Carboxymethyl chitosan, by considering the solubility cross-linked derivatives were observed with scanning
the modification made and to improve in applications, electron microscopy to verify the compatibility of
it has been crosslinked. Carboxymethyl chitosan the mixtures of CMC-SB derivatives.To analyze the
/2,3-dimethoxy Benzaldehyde Schiff base was cross samples, the films were cut into pieces of various
linked by using gluteraldehyde has been synthesized sizes and wiped with a thin gold – palladium layer
and characterized using the techniques like FT-IR, by a sputter coater unit (UG – microtech, UCK field,
XRD, SEM, Catalytic activity and investigated for its UK) and the cross section topography was analyzed
adsorption capacity and its kinetics.
with Cambridge Stereoscan 440 Scanning Electron
Microscope (Leica, Cambridge UK).
MATERIALS AND METHODS
Catalytic activity
Carboxymethyl chitosan were purchased
Theoxidationofcyclohexanewasperformed
from India Sea Foods, Cochin, Kerala, India. The under the aerobic conditions.10 mmol 30% hydrogen
aldehyde such as 2, 3- dimethoxy Benzaldehyde and peroxide solution was added to the Schiff base
gluteraldehyde were purchased from Sigma Aldrich, complex (0.05 g) in 10 ml of acetonitrile in a 25 ml
India. All the chemicals used were of analytical ûask equipped with a magnetic stirrer and ûtted
grade.
with water condenser. With this reaction mixture,

MOGANAVALLY et al., Orient. J. Chem., Vol. 32(1), 441-453 (2016)
443
5 mmol of cyclohexane was added and allowed
to stir magnetically under 70 C at atmospheric
The conversion percentage of cyclohexane
was calculated as below:
0
pressure conditions for 12 h.Aliquots were collected
separately at 8 h and 12 h for the product analyses.
Two separate blank experiments were also carried
out, one without metal complex and one without
H2O2, by keeping other experimental conditions
unaltered to prove the importance of catalyst
and H2O2 in the reaction. The collected product
samples were analyzed with a Hewlett–Packard gas
chromatogram (HP 6890) having FID detector. The
conditions followed in the product analysis were,
capillary column: HP-5, carrier gas: nitrogen, and
ûow rate:0.5 cm3 min-1. In the same way cross linked
CMC Schiff base derivative also prepared.
Conversion % of cyclohexane = 100 × [Initial %-
Final%] /Initial%
Heavy metal removal by batch adsorption
studies
Synthetic solutions of Pb (II) ions and Cd (II)
ions were taken in stopper bottles and agitated with
schiff base and its crosslinked schiff base separately
at 30oC in orbit shaker at fixed speed of 160rpm.
The extent of heavy metal removal was investigated
separately by changing adsorbent dose, contact time
OCH3
H 3
C
O
CH2OCH2COOH
O
O
OHC
NH
2
OH
O
OH
NH2
O
n
CH2OCH2COOH
OCH3
OCH3
OCH3
OCH3
O
O
CH2OCH2COOH
O
CH2OCH2COOH
O
H
H
O
O
OH
OH
N
N
O
O
O
OH
OH
O
n
CH2OCH2COOH
NH2
NH2
CH2OCH2COOH
OCH3
OCH3
OCH3
OCH3
CH2OCH2COOH
O
CH2OCH2COOH
O
O
O
OH
OH
N
O
N
O
O
O
OH
OH
n
CH2OCH2COOH
N
CH2OCH2COOH
N
CH2OCH2COOH
O
CH2OCH2COOH
O
O
O
N
N
OH
OH
O
OH
O
O
OH
O
CH2OCH2COOH
O
N
n
CH2OCH2COOH
N
OCH3
OCH3
H3CO
H3CO
Fig. 1: Structure of CMC-SB and GLU-CMC-SB complex

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MOGANAVALLY et al., Orient. J. Chem., Vol. 32(1), 441-453 (2016)
of shaking and changing pH of the solution. After In and linearised form of the Freundlich equation
attaining the equilibrium adsorbent was separated was used.
by filtration using filter paper and aqueous phase
concentration of metal was determined with atomic
adsorption spectrophotometer (Varian AAA 220 where
log Cads = log P + 1/n log Ceq
FS).
Cads = amount of metal ion adsorbed (mg/g)
Ceq= equilibrium concentration in solution (mg/dm3)
1/n = Freundlich constant (mg.g-1)
Adsorption isotherm studies
At the optimum conditions of adsorbent P = Freundlich constant (g.dm-3)
dose and pH, the synthetic solutions of Pb ions were
agitated for one hour at various initial concentrations Temkin model
and amount of unadsorbed lead in the filtrate were
The Temkin model is linearly represented
analysed.The same procedure is followed to analyse and generally applied in the form:
the Cd (II) ions.The values were fitted into Langmuir,
Freundlich, Temkin and Dubinin – Radushkevich (D
– R) adsorption isotherms.
qe=B ln A + B ln Ce
T
Where A and B are the Temkin isotherm
constant (L/g) and heat of sorption (KJ/mol)
respectively. R is the gas constant (J/mol/k), b is
Langmuir adsorption isotherm
In this study the following linearised form of the Temkin isotherm constant linked to the energy
the Langmuir isotherm was used.
Ceq / Cads = bCeq / KL + 1/ KL and Cmax = KL/b
parameter, B, T is the absolute temperature in kelvin
as shown on equation:
b = RT/B
Where
Cads = amount of metal ion adsorbed (mg/g)
Ceq= equilibrium concentration of metal ion in solution
(mg/dm3)
KL =Langumir constant (dm3/g)
b = Langumir constant (dm3.mg)
Cmax= maximum metal ion to adsorb onto 1g chitosan
(mg/g).
Dubinin-Radhushkevich isotherm
Dubinin – Radushkevich (D – R) isotherm
helps to determine the nature of bonding either
physisorption (or) chemisorption,
ln qe = ln qs – Kade2
qm is the maximum adsorption capacity (mg/g).Kads
is a D-R constant related to the energy of adsorption
and å is the Polanyi potential.
Freundlich adsorption isotherm
The Freundlich equation which is used is
expressed as:
e = RT ln [1+(1/Ce)]
1/n
Cads = P Ceq
The mean free energy of adsorption (E)
calculated using eqn,
E= (2K)-0.5
3500
3000
2500
2000
1500
Wavenumber cm-1
1000
500
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Fig. 2: FTIR spectrum of Carboxymethyl Chitosan

MOGANAVALLY et al., Orient. J. Chem., Vol. 32(1), 441-453 (2016)
445
Kinetics Studies
Inthepresentstudykineticswerecalculated
for both pseudo-first order, the pseudo second order
kinetic models applied and expressed as follows.
intermolecular hydrogen bond O-H, N-H stretching
and polymeric association with gluteraldehyde.The
asymmetic C-H stretching was indicated by the peak
at 2918 cm-1 for CMC, 2921 cm-1 for CMC-SB, and
2928 cm-1 for Glu-CMC-SB, this corresponding peak
shift to the higher position reveals the incorporation
of aromatic C-H bonds of aldehyde13.
Pseudo-first order kinetics
Rate expression is
log(qe-qt) = log qe – (k/2.303)t
The peak at 1725 cm-1 in CMC has shifted
to the lower wavenumber 1604 cm-1 in CMC-SB
and 1631 cm-1 in Glu-CMC-SB complex. This
band is most probably composed of amide band
of Carboxymethyl chitosan, C=N stretching band
of Schiff base were cross-linked with –CHO of
gluteraldehyde 14. Moreover, it is not observed any
band at ~ 1715 related to free aldehyde group 15. The
absorption at 1418 cm-1 in Glu-CMC-SB represents
the –CH- bending of –CH2- in gluteraldehyde, which
is not present in CMC-SB complex. The FTIR
spectrum of CMC, CMC-SB and Glu-CMC-SB
showed its characteristic Schiff base formation peaks
were in the range of 1598 – 1650 cm-1, confirming
the presence of imine bond was formed between
-NH group of carboxymethyl chitosan matrix and
with the C=O group of gluteraldehyde.The decrease
in the intensity of the peak for -NH2 group content,
which indicates the participation of the amino
group of the CMC polymer matrix with the aromatic
aldehyde to form Schiff bases and crosslinked with
gluteraldehyde 16. All these characteristics prove the
formation of crosslinked CMC-SB has been prepared
successfully.
qt and qe are the amounts of ion adsorbed at time
t and at equilibrium (mg/g), k1 = rate constant
(min-1)
Pseudo-Second order Kinetics
Rate expression is
t/qt = 1/k2qe2 + t/qe
where, k2 = second order kinetic constant
(gmg-1min-1).
RESULTS AND DISCUSSION
FTIR studies
Figure-2, 3 and 4 shows the FT- IR
spectrum of the Carboxymethyl chitosan (CMC)
and Carboxymethyl chitosan/2,3-dimethoxy
Benzaldehyde Schiff base (CMC-SB) and cross
linked gluteraldehyde Schiff base (Glu-CMC-SB)
complex. The spectrum shows a broad peak at
3420 and 3418 cm-1 for CMC and CMC-SB, but in
case of cross linked Schiff base complex appeared
at 3436 cm-1 slightly higher, which indicates the
3500
3000
2500
2000
1500
Wavenumber cm-1
1000
500
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Fig. 3: FTIR spectrum of Carboxymethyl Chitosan/2,
3 -dimethoxy Benzaldehyde Schiff base derivative

MOGANAVALLY et al., Orient. J. Chem., Vol. 32(1), 441-453 (2016)
446
XRD studies
The X-ray diffraction of CMC, CMC-SB
nature 17. Thus the interaction detected in this work
decreases the membrane crystallinity.
and Glu-CMC-SB were shown in Figure -5, 6 and
7.The peaks of CMC obtained at 2è = 20°, 29° and
46° were broad. For CMC-SB the peak was shifted
to 2è = 28°, 47° and 56°, this indicates the formation
of Schiff base.The peaks are broad, which indicates
that the prepared schiff base has semi crystalline
nature. The XRD spectra of Glu -CMC-SB exhibits
two broad peaks around 20° and 40°, indicates that
the sample is going form crystalline to amorphous
SEM Analysis
The surface morphology of CMC, CMC-
SB and Glu-CMC-SB complexes were shown in
the Figure-8. From the SEM image we conclude
that CMC shows a homogeneous smooth surface
and CMC-SB shows rough surface due to the
addition of aromatic aldehyde. Further, the rough
porous surface is increased due to the addition of
3500
3000
2500
2000
1500
Wavenumber cm-1
1000
500
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Fig. 4: FTIR spectrum of Carboxymethyl Chitosan/2,3 -dimethoxy
Benzaldehyde/Gluteraldehyde Schiff base derivative
Fig. 5: XRD pattern of Carboxymethyl Chitosan

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MOGANAVALLY et al., Orient. J. Chem., Vol. 32(1), 441-453 (2016)
gluteraldehyde. Comparing the bare Schiff base the conversion percentage of cyclohexane is also
with its Glu-CMC-SB complexes, the image of cross increased. The results reveals the catalytic activity
linked Schiff base complex shows the rough and of CMC-SB complex was more pronounced at 12 h
dense surfaces with large number of pores. These and the yield is 49% compared to the cross linked
large rough surfaces were more suitable for greater Schiff base complex (yield is 47 %) which shows a
adsorbing property and biomedical applications.
bright future in industrial applications.
Catalytic activity
Removal of lead (II) and Cadmium (II) ions
The efficiencies of the CMC-SB and
Optimum metal adsorption was determined
Glu-CMC-SB complex as catalysts for oxidation of by investigating the parameters such as initial
cyclohexane to cyclohexanol is shown in theTable -1 concentration of metal ions, sorbent dosage, pH
and Figure-9. When the reaction time is increased, and contact time of solution at constant temperature.
Fig. 6: XRD pattern of Carboxymethyl Chitosan/2,3 -dimethoxy
Benzaldehyde Schiff base derivative
Fig. 7: XRD pattern of Carboxymethyl Chitosan/2,3 -dimethoxy
Benzaldehyde/GluteraldehydeSchiff base derivative

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MOGANAVALLY et al., Orient. J. Chem., Vol. 32(1), 441-453 (2016)
The equilibrium data were fit into Langumir model, Effect of adsorbent dose
Freundlich, Temkin and Dubinin – Radushkevich
(D-R) adsorption isotherms.
The adsorption dependence of Pb (II)
and Cd (II) was studied by varying the amount of
adsorbents from 1 – 6 gms, while keeping the pH
Fig. 8: SEM image of (a)CMC, (b) CMC-SB and (c) Crosslinked CMC-SB
and contact time as constant. From the Figure-10
and 11, the influence of adsorption process can
be observed by increasing its adsorbent dosage.
The removal efficiency increases with increase in
the amount of adsorbent dosage; this is due to the
greater availability of the exchangeable sites for the
ions 18. After a certain amount of adsorbent (5-6gms),
there is no further increase in adsorption. This
Table 1: Catalytic activity of CMC-SB
Samples
% Conversion to Cyclohexanol
4Hrs
8Hrs
12Hrs
CMC-SB
Glu-CMC-SB
27
23
34
32
49
47
Table 2: Adsorption isotherm constant,
Cmax and correlation coefficients
Table 3: Coefficients of Freundlich
isotherm model
Langmuir constants
Metal
ions
Freundlich constants
Metal
ions
KL
b
Cmax
(mg/g)
R2
KF (mg/g)
n
R2
(dm3/g) (dm3/mg)
Pd (II)
Cd(II)
2.2336
2.2699
1.6529
1.5873
0.988
0.992
Pd(II)
Cd(II)
0.8432
0.9814
0.008432
0.009814
100
100
0.772
0.827
Table 5: D-R Isotherm Parameters
D-R isotherm parameters
Table 4: Coefficients of Temkin isotherm model
Metal
ions
Temkin isotherm parameters
B (KJ/mol) AT (L/g) bT
Metal
ions
qs
Kads
E
R2
R2
(mg/g)
(mol2/J2) (KJ/mol)
Pd(II)
Cd(II)
0.01425
0.01542
0.2324 173.86
0.2398 160.67
0.8080
0.842
Pd(II)
Cd(II)
27.31
28.80
4x10-6
4x10-6
0.35361
0.35361
0.542
0.563

MOGANAVALLY et al., Orient. J. Chem., Vol. 32(1), 441-453 (2016)
shows that the maximum adsorption has attained Effect of pH
449
and hence the ions attached to the adsorbent and
the amount of free ions remains constant 19. The
maximum % removal of Pb2+ was 87.7 % and 94.2
% in CMC-SB and Glu-CMC-SB respectively. In the
removal of Cd (II) ions, the percentage of removal is
87.9 % and 94.1 % for CMC-SB and Glu-CMC-SB.
The result reveals that the cross linked Schiff base
complex exhibits more removal compared to the
Schiff base.
The Figure – 12 and 13 shows the pH
dependence in the removal efficiency of the lead
and cadmium ions in the aqueous solution. Studies
revealed that the system is strongly pH dependent,
due to the nature of the chemical interactions with
the functional group on the Carboxymethyl chitosan
matrix. The optimum removal was obtained at pH 6
for Schiff base complex and pH 5 for cross linked
Schiff base complex. With increase in the pH the
adsorption also increases, due to the decrease in
the competition between the H+ and the lead and
cadmium ions for the same functional group. After
Fig. 10: Effect of adsorbent dose on the
removal of Pb2+
Fig. 9: Catalytic activity of CMC-SB
Fig. 12: Effect of pH on the removal of Pb2+
Fig. 11: Effect of adsorbent dose on the
removal of Cd2+
Fig. 13: Effect of pH on the removal of Cd2+
Fig. 14: Effect of contact time on the removal
of Pb2+

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MOGANAVALLY et al., Orient. J. Chem., Vol. 32(1), 441-453 (2016)
the certain level of pH, the adsorption decreases due increased with increase in contact time to some
the insoluble hydroxide ions precipitating from the extent, due to high transfer rate of the metal ions
solution making the adsorption studies impossible.
to the surface of the adsorbent particles. Further
increases in contact time, the equilibrium have been
The Contact time is an important factor, attained and hence no further increase in adsorption
which is useful for the wastewater treatment system. 20-21. Thus the results illustrated that the optimum
The influence of the contact time for the removal of contact time for maximum removal of Pb2+ and Cd2+
the Pb2+ and Cd2+ ions was analysed by keeping the were 360 min.
initial solution concentration 200 mg Metal (II)/L, pH
5 & 6 and adsorbent dosage 1g as constant. The Adsorption Isotherms
observed results are presented in Figure-14 & 15. It
The adsorption isotherm is fundamental in
was found that the removal efficiency of metal ions describing the interactive behaviour between solutes
Fig. 16: Langmuir isotherm model for Pb2+
Fig. 18: Freundlich isotherm model for Pb2+
Fig. 20:Temkin isotherm model for Pb2+
Fig. 15: Effect of contact time on the removal
of Cd2+
Fig. 17: Langmuir isotherm model for Cd2+
Fig. 19: Freundlich isotherm model for Cd2+

MOGANAVALLY et al., Orient. J. Chem., Vol. 32(1), 441-453 (2016)
451
and adsorbent, which express the surface properties
and affinity of the adsorbent 22. The adsorption
isotherm and its kinetics of CMC-SB complex for the
removal of Pb (II) is already reported in the literature
11. Hence adsorption isotherm and kinetic study for
the cross linking of CMC-SB complex is discussed
below.
made up of elementary sites 23. Another assumption
is that there is no reaction between molecules
adsorbed on neighbouring sites 24.
The linearised Langmuir isotherm allows
the calculation of adsorption capacities and Langmuir
constant “b” and “KL”.With the help of the slope and
intercept of linear plot of Ceq/Cads against Ceq shown
in the Figure-16 &17, the Langmuir constants KL and
b can be calculated and given in the Table-2.
Langmuir adsorption isotherm
The Langmuir adsorption isotherm is one
of the most widely used isotherms, proposed for
the adsorption of a solid at a solid-liquid interface.
It is assumed that each of which can adsorb one
adsorbate molecule, i.e., monolayer adsorption
Freundlich isotherm
The linearised Freundlich equation plot
of log qe vs log Ce yielded a straight line as shown
Fig. 22: D-R isotherm model for Pb2+
Fig. 21:Temkin isotherm model for Cd2+
Fig. 23: D-R isotherm model for Cd2+
Fig. 24: Comparison between Correlation
Coefficients of four Isotherms
Fig. 25: Pseudo-first order kinetics model
Fig. 26: Pseudo-second order kinetics model

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Table 6: Comparison between Lagergren pseudo-first-order and
pseudo-second-order kinetic models
Pseudo-first-order
kinetic model
Experimental
valueqe
Pseudo-second order
kinetic model
Metal
ion
qe
(mg/g)
k1
(min-1)
R2
(mg/g)
qe
(mg/g)
k2 (g mg-1
min-1)
R2
Pb (II)
Cd(II)
274.79
289.73
0.09212
0.01152
0.927
0.939
187
182
333.33
333.33
1.5075x10-5
1.3119 x10-5
0.995
0.993
better describes the adsorption process very
effectively when compared to the other models.
Hence Freundlich model was followed and multilayer
adsorption was suggests for the removal of metal
ions by the Glu-CMC-SB.Further it can be proved by
comparing the Temkin and D-R isotherm ‘E’ values,
the mean free energy and the heat of adsorption
values for Pb (II) and Cd (II) ions are lower than 20KJ/
mol. According to Atkins, when the energy values
are lower than 20KJ/mol, confirms the physisorption
mechanism is followed. Physisorption is also called
non-specific adsorption which occurs as a result
of long range weak Van der waals forces between
adsorbates and adsorbents 26
in Figure –18 & 19 and Table-3. The Freundlich
isotherm model proposed a monolayer adsorption
with a heterogeneous energetic distribution of active
sites, and/or interactions between adsorbed species.
Using mathematical calculation that an ‘n’ value
between 1 and 10 represents beneficial adsorption
25
.
Temkin Isotherm
TheTemkin isotherm takes into account the
interactions between adsorbents and metal ions to
be adsorbed and is based on the adsorption, that
the free energy of adsorption is simply a function of
surface coverage. By plotting the quantity adorbed
qe against ln Ce and the constants were determined
from the slope and intercept shown in Figure-20 &
21 and calculated parameters in Table-4. From the
figures, we determine the heat of adsorption (B) for
Pb (II) and Cd (II) is 14.25 J /mol and 15.42 J/mol.
Adsorption Kinetics
The adsorption data of lead (II) and Cd
(II) ion uptake by Glu-CMC-SB complex was fitted
using Lagregren pseudo first order (Figure – 25) and
pseudo second order model (Figure – 26).
The maximum binding energy (A ) for Pb (II) and Cd
T
(II) is 0.2324 and 0.2398 L/g.
A comparison between two kinetic models
suggested in Table -6 and Figure -25 & 26, the
correlation coefficient (R2) for the pseudo-second
order kinetic model is much higher in comparison
to pseudo-first order model. The close agreement
between the experimental qe mg/g) values and the
estimated qe (mg/g) values from pseudo-second
order kinetic model. These facts suggest that
obtained kinetic data followed the pseudo-second
Dubinin – Radushkevich (D – R) sorption
isotherm
Dubinin – Radushkevich model (Dubinin
and Radushkevich, (1947) is postulated within
a sorption space close to the sorbent surface to
evaluate the sorption free energy and to help to
determine the nature of bonding either physisorption
(or) chemisorptions.By plotting the quantity adsorbed
2 against lnYe and Kads shown in Figure-22 & 23, qs
and E were determined from the slope, intercept and
given in Table - 5.
order kinetic model 27
.
CONCLUSION
The cross linked Carboxymethyl chitosan
Schiff base complex was successfully synthesized
using gluteraldehyde. The FTIR result proves the
cross linking of Schiff base and XRD shows that the
sample goes from crystalline to amorphous nature,
Comparison between Adsorption Isotherms
TheTable-2-5illustratesthelinearregression
coefficient of four isotherms. On comparing these
isotherm models in Figure -24, the observed R2
values of Freundlich isotherm (0.988 and 0.992)

453
MOGANAVALLY et al., Orient. J. Chem., Vol. 32(1), 441-453 (2016)
which makes the material suitable for waste water adsorption efficiency of the Crosslinked biopolymer
treatment. The SEM results clearly indicates the can be further used for the study of waste water
rough and porous nature of cross linked sample tannery effluent. From the regression coefficient,
compared to the other samples, which increases we conclude the adsorption follows Freundlich model
the adsorption process and helps in the removal rather than the others. The adsorption follows the
of heavy metals. All these results reveals that the physisorption also concluded from the Temkin and
prepared crosslinked Carboxymethyl chitosan Schiff D-R models. Through kinetic studies we confirmed
base acts as a efficient biosorbent with good metal- that the adsorption process follows pseudo second
binding capacity for the removal of heavy metals like order kinetic model. The oxidation of cyclohexane
lead and cadmium ions from aqueous solutions, The was performed and it also increased upto 12h, which
is very useful in industrial applications in future.
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