Excerpt
Ravi T.
et al
J. Chem. Pharm. Res., 2015, 7(3):695-703
______________________________________________________________________________
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.
et al
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.
et al
J. Chem. Pharm. Res., 2015, 7(3):695-703
______________________________________________________________________________
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.
et al
J. Chem. Pharm. Res., 2015, 7(3):695-703
______________________________________________________________________________
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
Ravi T.
et al
J. Chem. Pharm. Res., 2015, 7(3):695-703
______________________________________________________________________________
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
Ravi T.
et al
J. Chem. Pharm. Res., 2015, 7(3):695-703
______________________________________________________________________________
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.
Ravi T.
et al
J. Chem. Pharm. Res., 2015, 7(3):695-703
______________________________________________________________________________
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.
et al
J. Chem. Pharm. Res., 2015, 7(3):695-703
______________________________________________________________________________
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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