This paper presents an approach to remove the dye using chitosan coated glass beads at various pH, temperature
and contact time. Dye decolorization using biopolymers are recent method of interest to remove the dyes from the
waste water. In this initial attempt, the chitosan was extracted from prawn shell wastes and applied in bio sorption
of azo dyes. This polymer was encapsulated over glass beads. The encapsulated glass beads were packed in a glass
column and azo dye decolorization was carried out and determined calorimetrically using UV-Visible
spectrophotometer and different isotherms were calculated. The isotherms such as Langmuir, Freundlich and
Temkin were examined and the appropriate model was identified. The interaction of the dye with chitosan was
studied using SEM and FTIR.
Ravi T.
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J. Chem. Pharm. Res., 2015, 7(3):695-703
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696
Preparation of bio- polymer and encapsulation over glass beads
The washed glass beads were drenched in Potassium di chromate solution and washed with water was dipped in a
bio-polymer for encapsulation and the encapsulate glass beads are taken in a Petri plate for drying purpose and this
encapsulate glass beads is dried in a room temperature [11].
Preparation of 1 ppm Dye Solution
Preparation of Dye solution is carried out by mixing 1 mg of azo dye namely "Acid Black" powder with 1 litre of
distilled water.
Figure -1: Structure of Acid black 24
Dye decolorization
For dye decolorization, 1
st
burette, the encapsulated chitosan glass beads which was filled to a certain height
(25cms), the burettes were filled with the dye solution (Acid Black) and studied the decolorization of dye by taking
samples in some fixed interval and analysed the change in the colour by using Varian Cary UV-Vis
Spectrophotometer [12-14].
Mathematical modelling study
Adsorption Isotherm design
Equilibrium sorption isotherms illustrate the ability of an adsorbent, distinguished by certain constants these values
defines the surface properties and affinity of the adsorbent [15-18].
Langmuir Isotherm
The Langmuir sorption isotherm has been the most extensively used isotherm and has been efficaciously applied to
many dye adsorption processes. Langmuir basic hypothesis was to adsorb a specific homogeneous site within the
adsorbent. The saturated monolayer adsorption isotherm can be represented as.
The Langmuir equation may be written as:
The Langmuir equation can be expressed in its linear form as:
Where Q
max
(mg/g) and K
L
(L/mg) are the Langmuir constants, indicating the highest adsorption ability for the solid
phase loading and the energy constant related to the heat of adsorption respectively. The values of Q
m
and K
L
can be
evaluated from the intercept and the slope of the linear plot of experimental data.
Freundlich Isotherm
Freundlich isotherm is an empirical isotherm that is used for non-ideal adsorption and is symbolized by the equation.
It is the relationship between the amounts of ligand adsorbed per unit mass of adsorbent, Q
e
, and the concentration
of the nickel at equilibrium, C
e.
The logarithmic form of the equation becomes,
Log q
e
=log K
f
+ (1/n) log Ce
Ravi T.
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J. Chem. Pharm. Res., 2015, 7(3):695-703
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697
Where K
f
n are the Freundlich constants, the features of the system. K
f
and n are the indicators of the adsorption
capacity and adsorption intensity, respectively. The ability of Freundlich model to fit the experimental data was
examined. For this case, the plot of log Ce vs. log qe was engaged to generate the intercept value of K
f
and the slope
of n.
Temkin isotherm
Tempkin isotherm assumes that the fall in the heat of sorption is a linear rather than the logarithmic, as implied in
the Freundlich equation. The equation is given by
q
e
= (RT/b) log (A C
e
)
A linear form of the Temkin isotherm can be expressed as:
q
e
= (RT/b) log A+ (RT/b) log C
e
q
e
= B log A+ B log C
e
The adsorption data can be analyzed according to Therefore a plot of q
e
versus logC
e
enables one to determine the
constants A and B.
Adsorption kinetics
To examine the adsorption kinetics on Chitosan, the pseudo-first-order and pseudo-second-order models were used
to measure the experimental results [19-22].
Pseudo first order equation
The first order equation of Lagergren is generally expressed as follows. Lagergren's kinetics equation has been
most widely used for the adsorption of an adsorbate from an aqueous solution.
dq/dt = k
1
(q
e
- q
t
)
where q
e
is the amount of dye adsorbed at equilibrium (mg/g), q
t
is the amount of dye adsorbed at time t (min
-1
), and
k
1
is the rate constant of pseudo-first-order adsorption. If it supposed that q=0 at t=0, then:
log (q
e
- q
t
) = log q
e
- k
1
t
Pseudo-second-order
If the rate of sorption is a second order mechanism, the pseudo-second order chemisorption kinetic rate equation is
expressed as follows
dq
t
/dt= k
2
(q
e
- q
t
)
2
Where k
2
is the rate constant of pseudo-second-order reaction (g/mg/min). The integrated form of Equation when
(t=0
t and qt=0
qe) the following expression is obtained:
Where q
e
, q
t
are the amounts of adsorbent at equilibrium and at time t (mmol g
-1
), k
1
is the rate constant of pseudo-
first order kinetics equation (min
-1
), and k
2
is the pseudo-second order rate constant (g mmol
-1
min
-1
).
Characterization of Chitosan (C)
Scanning Electron Microscope (SEM) [23-24]
The scanning electron microscope (SEM) is a type of electron microscope that uses a focused beam of high-energy
electrons in producing a variety of signals at the surface of a solid specimen. The carefully chosen effective samples
were placed in SEM module, Hitachi 5415 A, and micrographs were taken at different magnification.
FTIR analysis
The absorbance FT-IR spectra of the samples were documented using an FT-IR PerkinElmer spectrometer. The
spectra were collected within a scanning range of 400-4000 cm
- 1
.
Ravi T.
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J. Chem. Pharm. Res., 2015, 7(3):695-703
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698
RESULTS AND DISCUSSION
Effect of pH
Solutions of dye (acid black) with different pH was prepared, the effect of pH variation from 4.0 - 9.0 was studied
by adjusting the pH of dye solution using 0.1N HCl or NaOH and it was shown that % removal of dye was
maximum at pH 8. The initial and final concentration was observed by using U-V spectroscopy.
The Graph is drawn between pH and % removal of Chitosan.
Fig 1: Variation of % Removal at different pH at 100ppm
Effect of Contact Time
The effect of contact time for dye adsorption on chitosan glass beads is shown in fig.4.2 and it was observed that in
the 1
st
hour the %removal was very high. After 4
th
hour equilibrium attains so there is negligible % Removal.
Fig 2: % Removal of dye at different time interval
From the above figure -2 which is plot between time and % removal, shows that equilibrium attains at 4
th
hour and
after that there is no change in the percentage removal.
Ravi T.
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J. Chem. Pharm. Res., 2015, 7(3):695-703
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699
Langmuir isotherm
Fig3: Langmuir equilibrium isotherm model for the absorption of the dye on chitosan (C) glass beads at pH 8
The Langmuir isotherm model was selected for the evaluation of highest adsorption ability corresponding to
complete monolayer coverage on the glass beads surface
Table 1 Linear Langmuir isotherm parameters
Bio Polymer
q
m
K
L
R
2
C
2.336 0.216 0.9965
Freundlich Isotherm
Fig 4 Freundlich equilibrium isotherm model for the adsorption of the dyes on Chitosan (C) beads at pH 8
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700
Table 2 Freundlich equilibrium isotherm model for the adsorption of the dyes on chitosan (C) glass beads at pH 8
Concentration (ppm)
% Removal
Ce
q
e
logc
e
logq
e
100 87
13
1.74
1.113
0.24
80
90
8 1.44 0.90 0.15
50
94
3 0.94 0.46 -0.027
The Freundlich model was chosen to estimate the adsorption intensity of the adsorbate on the adsorbent surface. The
experimental data from the batch adsorption indicates that the dye removal is plotted logarithmically using the linear
Freundlich isotherm equation.
Table 3: Freundlich isotherm parameters
Bio polymer
1/n
K
f
R
2
C
0.4079 0.6092 0.999
Temkin isotherm
Table 4: Temkin equilibrium isotherm model for the adsorption of the dyes on chitosan (C) glass beads
Concentration (ppm)
% Removal
C
e
q
e
log
C
e
100 87
13
1.74
1.113
80 90
8
1.44
0.90
50 94
3
0.94
0.46
Fig 5: Temkin equilibrium isotherm model for the adsorption of the dyes on Chitoson (C) glass beads at pH 8
Table 5: Temkin isotherm parameters
Biopolymer K
T
B
T
R
2
(C) 2.03
1.2118
0.997
Adsorption kinetics
Table 6: Kinetic models for the adsorption of dye on Chitosan (C) glass beads
Time (hr)
q
t
q
e
-q
t
log(q
e
-q
t
)
1 1.48
0..26
-0.585
2 1.6
0.14
-0.853
3 1.68
0.06
-1.22
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701
Fig 6 Kinetic models for the adsorption of dye on Chitosan (C) glass beads
Table 7: Kinetic models for the adsorption of dye on Chitosan (C) glass beads
Time (hr)
q
t
t/q
t
1 1.48
0.67
2 1.6
1.25
3 1.68
1.78
Fig 7: Kinetic models for the adsorption of dye on Chitosan (C) glass beads
The q
e, exp
for C is 1.72 and using 1
st
order kinetics the value of q
e, calc
is 0.56 which is having very large difference
with q
e, expt
whereas by using 2
nd
order kinetics the value of q
e, calc
is 1.8 which is closer to q
e, expt
so it follows 2
nd
order kinetics.
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J. Chem. Pharm. Res., 2015, 7(3):695-703
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702
Table 8: Parameters of the kinetic models for the adsorption dye onto Chitosan glass beads
Pseudo 1st order
Pseudo 2nd order
Biopolymer Q
e, exp
k
1
Q
e, cal
R
2
k
2
Q
e, cal
h R
2
(C)
1.72 0.3175 0.56 0.992 2.49 1.8 8.082 0.9993
Characterization of Extracted Chitosan
Characterization is carried out to know quantitatively the elements present in the bio polymer. It is carried out by
using Scanning Electron Microscope (SEM), Fourier Transform Infrared Spectroscopy (FTIR).
Scanning Electron Microscope (SEM)
The scanning electron microscope shows a changes in the structure of chitosan coated glass slide that was treated
with the dye. The smooth surface of the chitosan was disturbed after attachment of the dye.
(a)
(b)
Fig 8: SEM images (a) before adsorption of dye with Chitosan (b) after adsorption of dye
Fig 9: EDAX peaks
The EDAX shows higher concentration of Si, C, O Cl and Ca and traces of Na, Al and Mg.
Fourier Transform Infrared Spectroscopy
The FTIR spectrum of a control dye and chitosan sorbent (24 hours) was compared. The spectrum of the control dye
displayed a peaks at 1023.42, 3352.82, 2916, 1544.22 and 1259.77cm
-1
for cyclohexane vibration, OH stretch, -CH
stretch, NO stretch respectively. The stretching between1573 to 2600 was commonly seen by the Chitosan sorbent
Ravi T.
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703
which represent C O-, C N and C N. The major stretch were shown in 1020.59, 3299.01 2649 etc that
representing the CC- stretch, C-H stretch were seen.
(a)
(b)
Fig 9: FTIR images for (a) chitosan before removal of dye (b) after removal of dye
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Frequently asked questions
What is the procedure for preparing bio-polymer and encapsulation over glass beads?
The washed glass beads are drenched in Potassium di chromate solution and washed with water, then dipped in a bio-polymer for encapsulation. The encapsulate glass beads are then taken in a Petri plate for drying at room temperature.
How is the 1 ppm Dye Solution prepared?
The dye solution is prepared by mixing 1 mg of azo dye, specifically "Acid Black" powder, with 1 litre of distilled water.
How is Dye decolorization carried out in this study?
Encapsulated chitosan glass beads are filled in a burette to a height of 25cms. The burettes are filled with the dye solution (Acid Black), and decolorization is studied by taking samples at fixed intervals. Changes in color are analyzed using a Varian Cary UV-Vis Spectrophotometer.
What is the purpose of the Adsorption Isotherm design in this study?
Equilibrium sorption isotherms illustrate the ability of an adsorbent, distinguished by certain constants that define surface properties and affinity.
Describe the Langmuir Isotherm used in the mathematical modeling study.
The Langmuir sorption isotherm is used extensively for dye adsorption. It assumes adsorption occurs at specific homogeneous sites within the adsorbent, forming a saturated monolayer.
What is the mathematical equation for the Langmuir Isotherm?
The Langmuir equation is used to determine Qmax (mg/g) and KL (L/mg), indicating the maximum adsorption capacity and energy constant respectively.
Describe the Freundlich Isotherm used in the mathematical modeling study.
The Freundlich isotherm is an empirical isotherm used for non-ideal adsorption. It relates the amount of ligand adsorbed per unit mass of adsorbent, Qe, to the concentration of the nickel at equilibrium, Ce.
What is the logarithmic form of the Freundlich Isotherm equation?
Log qe = log Kf + (1/n) log Ce , where Kf and n are the Freundlich constants indicating adsorption capacity and intensity.
Describe the Temkin isotherm.
Tempkin isotherm assumes that the fall in the heat of sorption is linear.
How can the constants A and B be determined from the Temkin isotherm?
A plot of qe versus logCe allows determination of constants A and B.
What kinetic models were used to examine adsorption on Chitosan?
Pseudo-first-order and pseudo-second-order models were used.
What is the Pseudo first order equation of Lagergren used for?
Lagergren's first order equation, dq/dt = k1 (qe - qt), where qe is the amount adsorbed at equilibrium, qt at time t, and k1 is the rate constant, is widely used for adsorption from aqueous solutions.
What is the Pseudo-second-order kinetic rate equation?
The pseudo-second order chemisorption kinetic rate equation is dqt/dt= k2 (qe - qt)2 , where k2 is the rate constant of pseudo-second-order reaction
How was the Chitosan characterized in this study?
Characterization involved Scanning Electron Microscopy (SEM) and FTIR analysis.
What does Scanning Electron Microscope (SEM) analysis reveal?
SEM uses a focused beam of high-energy electrons to produce signals at the surface of the sample for imaging at different magnifications.
What is the scanning range for FTIR analysis?
FTIR spectra were collected within a scanning range of 400-4000 cm-1.
What was the effect of pH on dye removal in the experiment?
The percentage removal of dye was maximum at pH 8.
What was the effect of contact time on dye adsorption?
The percentage removal was high in the first hour, reaching equilibrium around the 4th hour.
Which isotherm model was used for evaluating highest adsorption ability?
The Langmuir isotherm model was selected to evaluate highest adsorption ability corresponding to complete monolayer coverage.
How was Freundlich model used in the experiment?
The Freundlich model estimates the adsorption intensity of the adsorbate on the adsorbent surface, plotted logarithmically using the linear Freundlich isotherm equation.
What were the kinetic results obtained?
The process follows 2nd order kinetics
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- Ravi Thiyagarajan et al. (Autor:in), 2015, Extraction of chitosan from prawn shell waste and its application in dye decolorization, München, GRIN Verlag, https://www.hausarbeiten.de/document/334712
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