Indian Journal of Chemical Technology
Vol. 22, September 2015, pp. 210-218
Adsorption studies of Cr+6 onto low- cost apple juice industry waste from
aqueous solution: Equilibrium, kinetics and thermodynamics
Piar Chand1, Mohit Sharma2 & Yogesh B Pakade1,*
1
Hill Area Tea Science Division, Academy of Scientific and Innovative Research (AcSIR),
CSIR-Central Road Research Institute (CRRI), Mathura Road, New Delhi 110 025, India
2
Natural Products Chemistry and Process Development
CSIR-Institute of Himalayan Bioresource Technology Palampur 176 061, H.P., India
E mail: [email protected]
Received 3 May 2013; accepted 14 February 2014
The potential use of apple pomace (AP) for the removal of Cr+6 ions from aqueous solution has been investigated under
optimized conditions. The adsorption influencing parameters such as dose, pH, time and concentrations have been
optimized. Langmuir, Freundlich and Temkin follow the adsorption data with r2 = 0.99, 0.94 and 0.99, qmax has been found
to be 7.89, 8.94 and 1.49 mg/g, respectively. Langmuir isotherm data is further supported with RL value from 0.658 to 0.088
from concentration range of 10-200 mg/L. The rate determining data follow pseudo-second order kinetics (r2=0.99-1) for
removal of Cr+6 using AP. The value of ∆Go (-7668.6 to -8917.6 J/mol), ∆Ho (3.503 KJ/mol/K) and ∆So (22.95 J/mol) show
that the adsorption process is found to be spontaneous, endothermic and increase in randomness during adsorption process is
observed. One of the interesting aspects of adsorption study is reutilization of adsorbent in multiple cycles; AP show
removal efficiency 78% of Cr+6 upto seven cycles. It reduces the operation cost and enhances the industrial application for
the removal of the chromium from aqueous solution.
Keywords: Apple pomace, Adsorption, Chromium, Equilibruim, Kinetics, Thermodynamics
Water contamination with various pollutant, due to
discharge of industrial wastewater is a matter of
global concern. Heavy metals contamination are one
of the serious water pollution because it related to the
public health even in small amount it causes the
mutagenic and carcinogenic effects to the human
body1. Heavy metals are persistent and non
biodegradable, and therefore, very difficult to
removed naturally from the environment. Chromium
metal contamination is the major pollution in water.
Chromium exists in its two forms Cr+3 and Cr+6, out
of which the later one is more toxic than former. The
maximum limit of Cr+6 in potable water is 0.05 mg
dm-3. The various kinds of industrial effluents which
discharge the Cr+6 into water are electroplating, metal
finishing, glass, dyes, chrome tanning, textiles and
pigment industries2.
Numerous methods including precipitations,
ion-exchange, membrane process and different
electrolytic methods are used for the removal and
recovery of metals from water. The adsorption of
metal ions onto insoluble compounds as adsorbent is
most effective than the above mentioned methods.
Activated carbon, charcoal and resin are used as
adsorbent but they are highly expensive, produce
large sludge, incomplete removal of metals etc. To
overcome the drawbacks associates with commercial
adsorbent, a low cost biosorbent materials using
waste has been developed for the removal of
Cr+6 metal ions from water3-10. Biosorption is fast,
economical, feasible and eco-friendly technique
which also utilized the waste generated from
industrial processing.
Recently, much attention is given to prepare
biosorbent using waste generated from industrial
processing. Apple juice industry produced large
amount of apple pomace (AP) which is dumped at the
industrial dumping sites. Since AP is locally available
industrial bi- product in Himachal Pradesh that can be
use as adsorbent for the removal of Cr+6 from water.
About 25-30% of AP is the left apart of the total
processed fruit, which is rich in polyphenols,
polysaccharides, pectins, cellulose, hemicellulose and
lignin11. The presence of these compounds causes AP
as a rich source of hydroxyl and phenolic groups
and these can be helpful in adsorption of Cr+6 onto
AP. In our previous study we explored the AP as
biosorbent for removal of Pb from water12.
CHAND et al.: ADSORPTION STUDIES OF Cr+6 ONTO LOW- COST APPLE JUICE INDUSTRY WASTE
Keep viewing these facts, the present study was
investigated for the removal of the Cr+6 from water
using AP as adsorbent. The characterization of
adsorbent was carried out by FTIR for functional
groups. Detailed batch adsorption, kinetics, isotherm
and thermodynamics study were conducted to
compute various adsorption parameters for AP.
Further, the regeneration protocol has been tested to
reuse the saturated adsorbent by multiple recycles.
211
FTIR analysis
The spectral analysis was done by Fourier
Transform Infrared Spectrophotometer (FTIR)
(Thermo Scientific Nicolet 6700, Madison, USA)
with KBr of IR spectroscopic grade from Sd-Fine
Chemical Limited, Mumbai. The samples were taken
in mortal pestle and crushed well with KBr (1:100)
and applied under pressure to make transparent
pellet. The IR spectra were recorded in the range of
400-4000 cm-1.
Experimental Section
Reagents and Chemicals
Potassium dichromate of analytical grade was
purchased from SDFCL, Mumbai, India. The stock
solution of 1000 mg/L was prepared by dissolving the
analytical grade of potassium dichromate (K2Cr2O7)
in water. All the desired concentration of Cr+6 ions
was prepared by diluting the stock solution. In order
to prevent metal contamination from glassware,
glassware was soaked overnight in 5% (v/v) HNO3
after each experiment.
Sample collection and preparation
Apple pomace was collected from Himachal Pradesh
Horticultural Produce Marketing and Processing
Corporation Ltd. (HPMC), Processing Unit Parwanoo,
District Solan, Himachal Pradesh, India.
Physico-chemical analysis
Physico-chemical parameters such as ash,
moisture, pH, electrical conductivity, organic matter,
nitrogen, phosphorus, calcium and sodium of AP were
analyzed. The pH was measured in the suspension of
AP:water ratio of 1:2. The organic carbon content was
determined by the Tyurin method and multiplied by
the coefficient of 1.724 to give the organic matter
content. The total nitrogen content was determined by
the Kjeldahl method. The phosphorus content was
determined by the ascorbic acid method after
decomposition with perchloric acid. The total
potassium, sodium and calcium were determined by
flame photometer (1381E, EI make, Chandigarh). The
total polyphenols13 and catechins14 were also
determined for preliminary study of apple pomace.
Particle size, Zeta Potential and Surface area of
the AP were measured using Malvern Zetasizer Nano
ZS instrument (U.K.) at 25°C and Micromeritics
ASAP-2000 by N2 adsorption method. The samples
were prepared using water in suspended form and
loaded into a pre washed cuvette for particle size and
gold plated U shaped cuvette for Zeta potential
measurement.
Batch Adsorption studies
Batch sorption experiment was performed for the
optimization of the dose, pH, time, and concentration
effect on adsorption of Cr+6 onto AP. The amount of
dose was ranged from 0.05 to 4.0 g in 50 mg/L of
Cr+6 ions concentration in 50 mL of chromium
contaminated synthetic water. The pH of the solution
was incresed from 2 to 9 and not extended beyond
9 because of metal precipitation. The pH of the
solution was adjusted with 0.1 M of NaOH and HCl
solution and measured by Cyberscan PC510, Eutech,
Singapore. The metal concentration and time was
optimized and ranged from 10 to 250 mg/L and 10 to
240 min, respectively. All the studies were conducted
in triplicate at the speed of 140 rpm. Metal analysis
was done with atomic absorption spectrophotometer
(AA-6300), Shimadzu, Tokyo, Japan with deuterium
background corrector (BGC-D2). The above optimized
parameters were used for conducting isotherm,
kinetics, thermodynamics and regeneration study.
Kinetic study
The kinetics study for the adsorption of the Cr+6
ions onto AP was investigated at the optimized
condition of dose, pH and concentration. The
concentration and time was investigated in the
range of the 10-100 mg/L and 5-35 min, respectively.
The flask of each concentration 10, 20, 40, 60, 80 and
100 mg/L was removed at the regular interval and
filtered out for the rest of the metals ions.
Thermodynamics
Thermodynamics study was done by varying the
temperature range from 25-50°C at optimized
condition of dose (2.8 g), pH (5.0) and time (80 min)
in 50 mg/L of Cr+6 in 50 mL of water. The
temperature range was maintained from 25-50°C in
incubator cum shaker INNOVA 44, New Brunswick
Scientific, New Jersey, USA. Once the pre set time
reached the flasks were removed and filter out for
the residual metal concentration. The value of ∆Ho
INDIAN J. CHEM. TECHNOL., SEPTEMBER 2015
212
and ∆So were calculated from equation (1) called
Van’t Hoff equation:
log k d =
∆S ° ∆H °
−
R
RT
… (1)
where (Kd) is determined by using the equation
Kd =
qe
ce
… (2)
where qe, is the amount of the metal ions adsorbed
and Ce is the concentration of the metals ions at
equilibrium. The thermodynamics parameters such as
∆Ho and ∆So are calculated by using the Van’t Hoff
equation by plotting a graph between log Kd vs 1/T,
where slope gives the value of ∆Ho and intercept
represent for ∆So The Gibbs free energy change is
calculated by using the equation, ∆Go = ‒RT ln Kd,
R = universal constant (8.314 J/mol/K) and T is
temperature in Kelvin.
Desorption and regeneration study
Recyclability of the AP was done first by
adsorption followed by desorption with 0.5 M HNO3
solution. The desorption study was done at dose of
2.8 g, pH = 5, time 80 min and concentration of 50
mg/L in 50 mL water. The small amount of the acid
was added for desorption of the metal ions, shaked
and filtered out for the residual metal concentration.
After that the adsorbent was washed with deionized
water to remove the excess of the acid and dried at
room temperature for repeated adsorption cycles. This
process was repeated until its removal efficiency
decreased to its half.
Results and Discussion
Physico-chemical characterization of AP
The physico-chemical parameters were studied for
the preliminary characteristics of AP and compiled in
Table 1. The amount of nitrogen, phosphorous,
potassium, organic contents, calcium and sodium
were found to be 0.94 g/Kg, 0.075 g/Kg, 0.584 g/Kg,
19.78%, 1.47 mg/Kg and 0.014 mg/Kg. The AP was
found acidic in nature with pH of 3.22. The parameters
such as ash, moisture, electrical conductivity and bulk
density were found 1.85, 8.6%, 7.15 mmhos/cm and
0.572 g/mL, respectively. Physical parameter such as
surface area was found to be 0.7129 m2/g. The major
chemical constituents polyphenols and catechins were
found to be 6.51 and 3.12% which might be
responsible for metal binding.
Spectral data of AP before and after adsorption
The 13 different peaks were observed signify the
adsorptive nature of the AP (Fig. 1). The different
peaks in AP were found in the region of 3409.4,
2923.9, 2854.2, 1733.7, 1635.7, 1558.1, 1540.9,
1456.6, 1374.8, 1318.4, 1159.6, 1031.6 and 576.9 cm-1.
The broad band in the region of 3200-3600 cm-1 was
observed because of overlapping of –OH and –NH
groups. The peaks at 2923.9 and 2854.2 cm-1 are
attributed to the asymmetric and symmetric stretching
of –CH2 groups. These may be methyl, methylene
and methoxy groups15. The peaks at 1733.7 and
1637.7 cm-1 were attributed to –COO and –CO,
respectively. These groups might be from cellulose,
hemicelluloses, lignin and pectin in AP. The bands
at 1558.1, 1540.9 and 1456.6 cm-1 are due to –C–H
stretching in aromatic skeleton, -N-H deformation
and –N-H bending, respectively. The other IR peaks
at 1318.4, 1159.6, 1031.6 and 576.9 cm-1 were
attributed to –C-O-C–, –C-N, –C-O and –C-C groups
stretching, respectively. The IR band which are either
disappeared or decreases in intensity after adsorption
might involved in metals binding (Table 2)16. These
major peaks are –OH and –NH, esters
(–COO), ethers (–C-O-C), amide (–CONH2) and
amine (–NH2) containing groups responsible for the
Cr+6 binding onto AP surface. The particle size and
zeta potential of AP were found to be 220.3 d.nm and
-23.6 mV, respectively. The negative value of zeta
potential tells that the surface of the AP was
negatively charged because of the presence of –OH,
–NH2 and –COOH groups.
Table 1 ― Physico-chemical characterization of apple pomace
Properties
Values
Ash
Moisture
pH
Electrical conductivity (EC) at 12°C
Particle size
Zeta potential
Surface area
Bulk Density
Nitrogen (N)
Phosphorus (P)
Potassium (K)
Organic matter (C)
Calcium (Ca)
Sodium (Na)
Total polyphenols
Catechin31
1.85 %
8.6 %
3.22
7.15 mmhos/cm
220.2 d .nm
-23.6 mV
0.7129 m2/g
0.572 g/mL
0.94 g/Kg
0.075 g/Kg
0.584 g/Kg
19.78 %
1.47 mg/Kg
0.014 mg/Kg
6.51 %
3.12 %
CHAND et al.: ADSORPTION STUDIES OF Cr+6 ONTO LOW- COST APPLE JUICE INDUSTRY WASTE
213
Fig. 1 ― FTIR spectra of apple pomace before (a) and after (b) adsorption of Cr+6 ions.
Table 2 ― Overlay FTIR spectra of AP before and after adsorption of Cr+6 ions from water
IR peaks
Before adsorption
After adsorption
Differences
1
2
3
4
5
6
7
8
9
10
11
12
13
3409.4
2923.9
2854.2
1733.7
1635.7
1558.1
1540.9
1456.6
1374.8
1318.4
1159.6
1031.6
576.9
3401.8
2923.4
2852.5
Disappeared
1642.5
Disappeared
Disappeared
Disappeared
1373.9
Disappeared
1157.7
1024.4
579.9
-7.6
-0.5
-1.7
Unknown
6.8
Unknown
Unknown
Unknown
-0.9
Unknown
-1.9
-7.2
3
Effect of sorption time and kinetics study
The time study was done to determine the required
equilibrium for the adsorption of Cr+6 onto AP. The
time was varied from 10-240 min, at the pH of 5 and
constant dose 2.8 g in 50 mg/L of metal ions
concentration in 50 mL of synthetic water. It was
Functional groups
-OH and –NH str in bonded form
-CH2 asymmetric str.
-CH2 symmetric str.
-COO str. of ester group
-CO groups of carbonyl
-C-H str.
-N-H deformation
-N-H bending
-C-O-C of ether group
-C-H bending in CH3
Amine (-C-N stretching)
-C-O str.
-C-C- group stretching
observed that the adsorption process was fast and
about 60-91% adsorption takes place in between the
time periods of 10-30 min, given in Fig. 2. The
maximum adsorption of 91% was observed upto
30 min and steady state obtained by further increased
of time.
214
INDIAN J. CHEM. TECHNOL., SEPTEMBER 2015
Table 3 ― Pseudo-second order of kinetics study for adsorption
of Cr+6 ions onto apple pomace
Fig. 2 ― Effect of time on removal of Cr+6 from aqueous solution
using AP
The adsorption data was applied to pseudo second
order kinetics by using equation17.
t
1
t
=
+
2
q t Kq e
qe
… (3)
where, K is the pseudo-second order kinetics,
qe and qt are the amount of metals adsorbed at
equilibrium and at time t, respectively. The graph
between t/qt vs t was plotted to find the value of
K and qe from intercept and slope respectively.
The adsorption data was followed the pseudosecond order kinetics with r2= 0.999 and 1 for all
metal ion concentration (Table 3). Most of the
adsorption study of metals ions onto adsorbent surface
follows pseudo-second order of kinetics18. The
experimental K value for the concentration 10, 20, 40,
60, 80 and 100 was found 5.051, 0.943, 0.653, 0.586,
0.442 and 0.558, respectively. The value of
K was decreased as the concentration of Cr+6
increases. The larger the value of K the faster is
the rate of adsorption19. The kinetics study thus
indicated that the AP was capable for the removal
of 90% of Cr+6 contaminated water within time
periods of 5-35 min.
Effect of pH on adsorption
The removal of metal ions from aqueous solution
using adsorbent is pH dependent. As pH (H+)
increases the adsorption of the metals ions increases
due to lesser number of H+ ions and a greater number
of surface ligand with negative charges19. At low pH
(H+) ions it providing the more ligands for metal
binding and hence adsorption increased20. The result
revealed that the adsorption of Cr+6 was increased
Conc
Equation
r2
qe(mg/g)
K
10
20
40
60
80
100
y=7.6692x+11.619
y=4.228x+18.876
y=2.9516x+13.312
y=1.1741x+2.3519
y=0.8902x+1.7956
y=0.7049x+0.8901
0.99
0.99
0.99
0.99
0.99
0.99
0.1304
0.237
0.339
0.852
1.123
1.419
5.051
0.943
0.653
0.586
0.442
0.558
as pH increases from 2 to 5 respectively. The
steady state was obtained by further increase in
pH upto 8. The maximum adsorption of the Cr+6 ions
was found to be 97.8% at pH 5. Similar observation
was found during adsorption of Cr+6 onto maple
sawdust 21.
Effect of dose on adsorption
The metal adsorption increases as the amount of
dose increases because of the more surface area was
available due to increase in active sites on
adsorbent22. It was observed that as the adsorbent
dose increased, the % removal of Cr+6 also increases
upto 2.8 g/50 mL. The steady state was observed by
further increased in the dose of adsorbent towards
Cr+6 metal ions adsorption. This may be due that as
the adsorbent dose increases, the availability of
binding site is more and further increased in doses, it
gets aggregated and resulted less in number of
binding site available. The adsorbent dose of 2.8
g/mL was selected for further adsorption studies.
Effect of initial concentration and adsorption isotherm
The effect of initial metal concentration for Cr+6
was investigated in the concentration ranged of
10-250 mg/L. It showed that the AP proved an excellent
adsorbent at 250 mg/L of metal concentration
even with removal efficiency of 87.9% and after
that the adsorption efficiency decreases as
concentration increases because of the saturation
of the binding sites.
The study of adsorption isotherms indicates the
adsorption capacities of adsorbent at experimental
conditions. The most commonly applied isotherms are
Langmuir, Freundlich and Temkin. It is also helpful
to determine the adsorptive capacity of adsorbent and
performance of adsorption process.
The Langmuir and Freundlich adsorption isotherm
was applied to the above obtained data for the
determination of the adsorption capacity (qmax) in mg/g23.
Langmuir isotherm model:
CHAND et al.: ADSORPTION STUDIES OF Cr+6 ONTO LOW- COST APPLE JUICE INDUSTRY WASTE
1
1
1
=
+
qe C e qmax b qmax
... (4)
where, qe is the metal ions adsorbed (mg/g), ce is
metal concentration at equilibrium, qmax is the
maximum adsorption capacity (mg/g) and b is the
Langmuir constant (L/gm). A graph between 1/qe vs
1/ Ce was plotted and value of qmax and b were
calculated from its intercept and slope, respectively.
The Langmuir adsorption isotherm can be
expressed by dimensionless constant called the
dimensionless parameters RL, by following equation:
RL =
1
1 + bC0
215
Langmuir Freundlich and Temkin adsorption
isotherm (Figs. 3 A, B, C ) was applied to obtained
data and found that the adsorption data well fitted to
all isotherms with r2 = 0.99 0.94 and 0.99,
respectively. The Langmuir and Temkin isotherm
... (5)
where b is Langmuir constant obtained from above
equation, Co is the initial concentration of metal ions,
RL is the equilibrium parameters and its value must be
in between the 0-1 support the Langmuir model and
indicated the favorable adsorption. There are four
possibility of RL value 1) when RL is in between
0-1, adsorption process is favorable 2) RL >1 tells
the unfavorable adsorption, 3) RL = 1 for linear
adsorption and 4) RL= 0, irreversible process24, 25.
Freundlich isotherm model:
log q e = log K +
1
log ce
n
... (6)
While in Freundlich equation, qe is the amount of
the metals ions adsorbed (mg/g), Ce is the
concentration at equilibrium and, K and n are the
Freundlich constant which represents the adsorption
capacity (mg/g) and adsorption intensity were
calculated by plotting the graph between log qe vs log
Ce. The slope of the graph gives the value of n while
the intercept gives the value of K, respectively.
Temkin model explain the effect of some indirect
interaction of adsorbent-adsorbate on adsorption
isotherm and also suggested that due to interaction,
the heat of adsorption of all the molecules in the layer
would linearly decrease with coverage26. The Temkin
isotherm has been applied in the following equation:
q e = B ln C e + B ln K t
... (7)
where qe is the amount of metal absorbed (mg/g),
Ce is the concentration at equilibrium (mg/L) B and
Kt is the Temkin isotherm constants. Linear graph
was plotted between qe vs lnCe whose slope is
directly proportional B value and intercept gives the
value of Kt.
Fig. 3 ― Adsorption isotherm (A) Langnuir (B) Freundlich
(C) Temkin for removal Cr+6 from aqueous solution
INDIAN J. CHEM. TECHNOL., SEPTEMBER 2015
216
fitted to the best as with adsorption capacity of 7.89,
8.49 and 1.49 mg/g, respectively (Table 4). The qmax
value of AP was greater than all the reported
adsorbent (Table 5) for removal of Cr+6 from water.
The Langmuir adsorption isotherm was further
supported by dimensionless constant RL. The RL value
was found between 0.658-0.071 for concentration
range of 10-250 mg/L. The maximum value of RL for
Cr+6 was found to be 0.150, suggesting the adsorption
was favorable on coconut charcoal10. All the value of
RL for concentration 10-250 mg/L was found greater
than zero and less than unity indicates the favorable
adsorption process for Cr+6 by apple pomace.
In Freundlich equation the value of 1/n is less than
unity represents the favorable adsorption process27.
The value of n less than unity tells that nature of
adsorption is chemical while greater than unity tells
the physical adsorption. The value of n was found to
be 1.388 (Table 4) indicated that adsorption of
chromium takes place by physical bonding28.
temperature dependant and endothermic in nature
which was further supported by the positive value of
∆Ho (3.503 J/mol/K). The others thermodynamics
parameters as ∆Go and ∆So were calculated to
evaluate the feasibility of the adsorption process
(Table 6).
The Gibbs free energy (∆Go) at temperature 298,
303, 313 and 323 K was found to be -7668.6, -7939.9,
-8546.3 and -8917.6 J/mol, respectively. The value of
∆Go was negative and its values increased as the
temperature increases, indicated the feasibility and
spontaneity of the Cr+6 ions adsorption process onto
AP surface 29. The positive value of the ∆Ho indicated
the endothermic nature of the adsorption and
positive value of ∆So indicated the increases in
randomness during adsorption process. The value of
∆Go (-7668.6 J/mol), ∆Ho (3.503 KJ/mol/K) and ∆So
(22.95 J/mol) showed that the adsorption process
was found spontaneous, endothermic and increase
in randomness.
Effect of temperature and thermodynamics study
Desorption and regeneration
The effect of temperature study was done by
varying the temperature from 25-50°C at 50 mg/L
of metals ions solution in 50 mL of synthetic water at
pH of 5. The result revealed that as the temperature
increases percent adsorption of Cr+6 also increased
which confirms the adsorption process was
Adsorption and desorption is one of the most
important factor which makes an adsorbent more
economically feasible in industrial application. To test
the reusability of AP, adsorption and desorption
cycles were repeated eight times using same
adsorbent. Figure 4 showed that the adsorption
Table 4 ― Langmuir, Freundlich and Temkin adsorption isotherm for Cr+6 adsorption onto AP
Adsorbent
Langmuir
Freundlich
K (mg/g)
n
8.49
1.388
qmax (mg/g)
b
r
7.89
0.052
0.99
AP
Temkin
2
2
B
Kt (mg/g)
r2
0.94
0.856
1.49
0.99
r
+6
Table 5 ― Various biosorbent used for the removal of Cr ions from aqueous solution
S.No
1
2
3
4
5
6
7
8
Biosorbent
Dolochar
Exhausted coffee
Sugar industry waste
Distillery sludge
Activated carbon of coconut tree sawdust
Coal and Cactus
Coconut charcoal
Apple pomace
Qmax (mg/g)
Reference
2.1
1.4
4.35
5.7
3.46
6.78 and 7.082
3.973
7.81
[4]
[5]
[6]
[7]
[8]
[9]
[10]
Present study
Table 6 ― Thermodynamics study for adsorption of Cr+6 ions onto AP
Equation
T(K)
1/T
Kc
lnKc
log Kc
∆G˚(J/mol)
r2
y= -421.39x+2.7613
298
303
313
323
0.0034
0.0033
0.0032
0.0031
22.09
23.38
26.69
27.68
3.095
3.152
3.284
3.321
1.344
1.369
1.426
1.442
-7668.6
-7939.9
-8546.3
-8917.6
0.98
∆H (KJ/mol/K) ∆S(J/mol)
3.503
22.95
CHAND et al.: ADSORPTION STUDIES OF Cr+6 ONTO LOW- COST APPLE JUICE INDUSTRY WASTE
217
78%, which make the AP more economical than the
other adsorbent reported.
Acknowledgements
The authors are thankful to the Director, Dr. P. S.
Ahuja, CSIR-Institute of Himalayan Bioresource
Technology, Palampur (India) for providing required
research facilities and the one of the authors Mr. Piar
Chand acknowledges to the Council of Scientific &
Industrial Research (CSIR), government of India for
providing Senior Research Fellowship (SRF) ack no:
131338/2k11/1 and Academy of Scientific and
Innovative Research (AcSIR).
References
Fig. 4 ― Reusability of AP for removal of Cr
aqueous solution
+6
ions from
capacity of Cr+6 slightly decreases with increase in
adsorption-desorption cycles. The study revealed
that the AP can be use upto seven cycles with
removal efficiency of 78% and further increase in
cycle resulted reduction in the removal efficiency
upto 51%. The removal of Cr+6 ions was found to
64% at sixth cycles using coconut charcoal10.
However the complete desorption with acid
was not possible in all cycles because of the
non-electrostatic forces between adsorbent and
metals ions30. Due to more recyclability of AP,
the operational cost is decrease and indicates its
industrial application for the removal of the
chromium from aqueous solution.
Conclusion
The AP which is apple juice industrial waste
could be used as a potential adsorbent for removal
of Cr+6 ions from aqueous solution. The dose of
2.8 g, pH of 5.0 and contact time of 30 min are
optimized for removal of Cr+6 from aqueous
solution. The FTIR analysis of AP before and
after adsorption gives better understanding on
sorption mechanism. The adsorption data fit
reasonably well to adsorption isotherm, time kinetics
and thermodynamics. Langmuir adsorption isotherm
for AP which further supported by dimensionless
constant value (RL), is found to be more suitable.
Pseudo-second order of kinetics is followed by the
Cr+6 ions with correlation coefficient (r2 = 0.999 to 1)
for all the concentration. The best and most
important part of this study is regeneration of
AP upto seven cycles with removal efficiency of
1
2
3
4
5
6
7
8
9
10
11
12
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14
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