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INTERNATIONAL JOURNAL OF ENVIRONMENTAL SCIENCES Volume 4, No 3, 2013
© Copyright by the authors - Licensee IPA- Under Creative Commons license 3.0
Research article ISSN 0976 – 4402
Received on September 2013 Published on November 2013 323
Studies on the behaviour of reactive dyes onto the cross-linked chitosan
using adsorption isotherms Deepika R, Venkateshprabhu. M, Pandimdevi. M
Department of Biotechnology, School of Bioengineering, SRM University, Kattankulathur
deepika.rangarajan@gmail.com
doi: 10.6088/ijes.2013040300010
ABSTRACT
The removal of textile reactive dyes in an aqueous media was studied by chitosan beads and
cross-linked chitosan beads. The chitosan beads were formed by dissolving in 0.3N acetic
acid and were cross-linked with 0.05M glutaraldehyde and 40% glyoxal. Their adsorption
capacity was evaluated by the removal of acid orange-10 and direct black-22 in the textile
wastewater. The effect of the parameters like biosorbent concentration, initial dye
concentration, contact time, temperature and pH were evaluated. The data for adsorption
isotherm was interpreted by the Langmuir equation and Langmuir constants was determined
for chitosan beads and cross- linked chitosan beads .The experimental data obtained for the
adsorption equilibrium from the chitosan beads and cross-linked chitosan beads were
correlated well with the Langmuir isotherm equation.
Keywords: Chitosan beads; cross-linked chitosan beads; glutaraldehyde; glyoxal; acid
orange-10; direct black-22; adsorption isotherm; Langmuir Isotherm.
1. Introduction
Water pollution is a common problem in worldwide due to economic and technological
development. Water pollution has become more and more serious especially regarding dyes.
Dyes mainly from dyeing industries, paper and pulp industries, textile industries, and many
other industries, have become serious threats to human beings and the aquatic ecosystem, due
to their toxicity and persistence after being released into the natural water. It was reported
that the textile wastewater contained a large variety of dyes and chemicals additions that
make the environmental challenge for textile industry not only as liquid waste but also in its
chemical composition (Venceslau et al., 1994). The main pollution in textile wastewater is
normally from dyeing and finishing processes. Large input of a wide range of chemicals and
dyestuffs, which generally are organic compounds of complex structure are used in these
processes. The textile materials does not adsorb all of them and the effluents caused disposal
problems. The major pollutants in textile wastewaters are high suspended solids, chemical
oxygen demand, heat, colour, acidity, and other soluble substances (Dae-Hee et al.,
1999).The removal of colour from textile industry and dyestuff manufacturing industry
wastewaters represents a major environmental concern. In addition, only 47% of 87 of
dyestuffs are biodegradable (Pagga and Brown, 1986).
1.1 Commonly used dyes
Dyes are divided into classes according to the types of fibers they are most compatible with.
The most notable are: acid dyes, premetalized acid dyes, chrome dyes (mordant dyes),
cationic dyes (basic dyes), direct dyes (substantive dyes), direct developed dyes, disperse
dyes, naphthol dyes, reactive dyes, sulfur dyes, and vat dyes (Price, Cohen, & Johnson, 2005).
Studies on the behaviour of reactive dyes onto the cross-linked chitosan using adsorption isotherms
Deepika R, Venkateshprabhu. M, Pandimdevi. M
International Journal of Environmental Sciences Volume 4 No.3, 2013 324
1.2 Acid Dyes
Acid dyes produce bright colors that have excellent fastness, or the ability of the dye to stay
on the fabric and not rub off or fade, to dry cleaning, but not necessarily to washing or light
and perspiration and have ionic interactions. Acid orange-10 is used in our studies.
Figure 1: Structure of Acid Orange – 10
1.3 Direct dyes
Direct dyes are used on cellulosic fibers and have excellent fastness to perspiration and dry
cleaning, but poor fastness to washing and varied light fastness and have intermolecular
forces. Direct black-22 is used in our studies.
Figure 2: Structure of Direct Black - 22
Some of the dyes are toxic and carcinogenic, use of these dye contaminated water without
any treatment may cause adverse effect on human health, domestic animals, wildlife and on
the environment. So it is necessary to treat or remove color from the wastewater before
discharge. Various treatment methods for removal of colour and dye are coagulation,
oxidation, flocculation, ozonation, biological treatment, adsorption and membrane processes.
Among these methods, adsorption method appears to offer the best prospect for overall
treatment of colour removal. Many adsorbents have been tested on the possibility to lower
dye concentrations from aqueous solutions, such as activated carbon(Mc Kay G, 1983, Allen
SJ, 1993), peat (Ramakrishna KR, Viraraghavan T,1997,Ho YS, McKay G, 1998), chitin
(McKay G, Blair HS, Gardner JR., 1983,Juang RS, Tseng RL, Wu FC, Lee SH. 1997), silica
(McKay G,1984), activated carbon (Tsai WT, Chang CY, Lin MC, Chien SF, Sun HF, Hsieh
MF., 2001).
Studies on the behaviour of reactive dyes onto the cross-linked chitosan using adsorption isotherms
Deepika R, Venkateshprabhu. M, Pandimdevi. M
International Journal of Environmental Sciences Volume 4 No.3, 2013 325
Recently, chitosan which is the second largest biopolymer next to cellulose has been
observed for the high potentials of the adsorption of dyes (Yoshida H, Okamoto A, Kataoka
T., 1993, Wu FC, Tseng RL, Juang RS., 2000), metal ions (Guibal E, Milot C, Tobin
JM.,1998,Liu XD, Tokura S, Haruki M, Nishi N, Sakairi N.2002,Oshita K, Oshima M, Gao
Y, Lee K-H, Motomizu S.,2003), proteins (Zeng XF, Ruckenstein E.,1998, Benesch J,
Tengvall P.,2002) and others (Matsumoto M, Shimizu T, Kondo K.,2004,Strand SP, Varum
KM.,2003). The adsorption of reactive dyes in neutral solutions using chitosan showed large
adsorption capacities of 1000–1100 g/kg (Wu FC, Tseng RL, Juang RS., 2000).
Chitosan is a linear polysaccharide composed of randomly distributed β-(1-4)-linked D-
glucosamine (deacetylated unit) and N-acetyl-D-glucosamine (acetylated unit). Chitosan is
produced by deacetylation of chitin, which is the structural element in the exoskeleton of
crustaceans (such as crabs and shrimp) and cell walls of fungi.
Figure 3: Structure of Chitin
Figure 4: Structure of Chitosan
Shrimp shell waste materials were collected and shrimp shells were scraped free of loose
tissue, washed with cold water and dried in sun for 2 days, and then Chitin was extracted
from shrimp shell by the following steps: Demineralizations of shells, was done using 4%
HCl and suspended at room temperature in the ratio of 1:14(w/v). After 36 hours, the shells
were quite squashy and were rinsed with water to remove acid and calcium chloride. The
demineralized shells were then treated with 5% NaOH at 90°C for 24 hours with a solvent to
solid ratio of 12:1(v/w). The residue was then collected and washed to neutrality in running
tap water. Then it was dried in sun and the product is chitin. The preparation of Chitosan is
simply deacetylation of chitin. Removal of acetyl groups from the chitin was achieved by
using 70% NaOH solution with a solid to solvent ratio of 1:14 (w/v) at room temperature for
72 hours. The mixture was stirred after some times for homogenous reaction. The resulting
chitosan were washed to neutrality in running tap water and rinsed with distilled water. Then
filtered and dried in sun.
Several Methods have been used to modify raw chitosan flake either physical (McKay G,
1984, Aksu Z., 2001) or chemical modifications (Namasivayam C, Kavitha D.,2002). These
Studies on the behaviour of reactive dyes onto the cross-linked chitosan using adsorption isotherms
Deepika R, Venkateshprabhu. M, Pandimdevi. M
International Journal of Environmental Sciences Volume 4 No.3, 2013 326
modifications were proposed in order to improve pore size, mechanical strength, and
chemical stability. Acid environments produce the partial dissolution of the polymer and to
make the polymer insoluble in acidic medium, modification by using cross- linking agents
used. Although cross-linking reduces the adsorption capacity but it enhance the resistance of
chitosan against acid, alkali and chemical (Robinson T, Chandran P, Nigam P.,2002). The
cross-linked chitosan also are very stable and maintain their strength even in acidic and basic
solutions (Namasivayam C, Kavitha D.,2002).These characteristics are very important for a
adsorbent so that it can be used in a lower pH environment. Cross-linking also can change the
crystalline nature of chitosan and enhance adsorption abilities (Annadurai G, Juang RS, Lee
DJ., 2002).
2. Materials and methods
Chitosan powder and reactive dyes, acid orange-10 and direct black-22 were commercially
purchased and the reagent namely sodium tri poly phosphate (TPP), glutaraldehyde, glyoxal,
hydrochloric acid, sodium hydroxide were purchased from Southern Indian Chemical
industries.
2.1 Preparation of chitosan Beads
3 grams of chitosan were dissolved 100ml of 0.3N acetic acid solution. Using a magnetic
stirrer it was stirred till a highly viscous solution was obtained. Chitosan solution was
dropped using syringe from a height of 20cm3 into the 1% TPP aqueous solution and the
beads were formed (Tapan Kumar Saha, Nikhil Chandra Bhoumik, Subarna Karmaker,
Mahmooda Ghani Ahmed, Hideki Ichikawa, Yoshinobu Fukumori, 2010), and the stability of
the beads were checked.
2.2 Preparation of cross-linked chitosan beads
The chitosan beads prepared were washed with deionized water and two different cross-
linking agents were used to modify chitosan at a ratio of 1 : 1 (chitosan: cross-linking agent),
they were suspended in 0.05 M glutaraldehyde and 40% glyoxal and were left standing for 24
hours and then the cross-linked chitosan beads were washed with distilled water and filtered
(W.S . WanNgah, C.S. Endud, R. Mayanar, 2002).
1.3 Effect of biosorbent concentration
10mg/L of the dye concentration at pH 7 and temperature 32oC were standardized. Varying
biosorbent concentration from 1g/L to 5g/L was prepared and 100mL of the cross-linkers was
taken for each biosorbent concentration, then they were kept in a shaker at 200 rpm. Finally
O.D at 477nm for acid orange-10 and at 484nm for direct black-22 was measured using UV-
Vis spectrophotometer for 0th time and different time interval.
1.4 Effect of dye concentration
1g/L of the biosorbent concentration at pH 7 and temperature 32oC were standardized. Dye
concentration from 10mg/L to 50mg/L was prepared and 100mL of the cross-linkers was
taken for each initial dye concentration. They were kept in a shaker at 200 rpm, and the
optical density at 477nm for acid orange-10 and at 484nm for direct black-22 was measured
using UV-Vis spectrophotometer for 0th time and different time interval.
Studies on the behaviour of reactive dyes onto the cross-linked chitosan using adsorption isotherms
Deepika R, Venkateshprabhu. M, Pandimdevi. M
International Journal of Environmental Sciences Volume 4 No.3, 2013 327
1.5 Effect of temperature
1g/L of the biosorbent concentration and 10mg/l of dye concentration at pH 7 and
temperature 32oC were standardized. Temperature was varied from 30oC to 70oC. 100mL of
the cross-linkers was taken and was standardized. They were kept in a shaker at 200 rpm. The
O.D at 477nm for acid orange-10 and at 484nm for direct black-22 was measured using UV-
Vis spectrophotometer for 0th time and different time interval.
1.6 Effect of pH
1g/l of the biosorbent concentration and 10mg/l of dye concentration at temperature 32oC
were standardized. pH was adjusted using 1N HCl and 1N NaOH and then was varied from 2
to 9. 100mL of the cross-linkers was taken and was standardized. They were kept in a shaker
at 200 rpm. The O.D at 477nm for acid orange-10 and at 484nm for direct black-22 was
measured using UV-Vis spectrophotometer for 0th time and different time interval.
3. Results and discussions
Parameters like biosorbent concentration, dye concentration, temperature, pH were selected
at constant agitation speed to conduct experiment on the reduction of acid orange-10 and
direct dye-22 dye in textile waste water.
3.1 % Removal
a) The % Removal of the reactive dye was calculated using the formula:
% Removal = Co – Cr *100
Co
Where, Co = Initial concentration
Cr = Residual concentration
b) Using the above formula % removal was found and was tabulated.
c) A graph was drawn between time and % removal.
3.2 Effect of biosorbent concentration
Table 1 and Table 2 indicates that the optimum biosorbent concentration is attained at 1 g/L
for both acid orange-10 and direct black-22 of chitosan which can also be inferred from
Figure 6 and Figure 7.
Table 1: Effect of acid orange -10 on chitosan biosorbent
Conc.
(g/L)
30
(mins)
60
(mins)
120
(mins)
180
(mins)
1440
(mins)
2880
(mins)
1 48.67 56.45 58.31 59.97 63.29 63.46
2 51.01 63.30 63.64 66.66 68.69 68.86
3 58.60 68.95 69.12 70.95 77.63 77.96
4 56.11 66.02 66.19 67.79 71.68 71.86
5 62.95 76.12 76.43 77.21 78.76 79.06
Studies on the behaviour of reactive dyes onto the cross-linked chitosan using adsorption isotherms
Deepika R, Venkateshprabhu. M, Pandimdevi. M
International Journal of Environmental Sciences Volume 4 No.3, 2013 328
Figure 6: Effect of biosorbent concentration on the removal of acid orange - 10
Table 2: Effect of direct black -22 on chitosan biosorbent
Conc.
(g/L)
30
(mins)
60
(mins)
120
(mins)
180
(mins)
1440
(mins)
2880
(mins)
1 28.24 41.18 49.41 54.12 62.35 62.35
2 26.83 36.59 40.24 45.12 85.37 85.37
3 24.68 31.17 49.35 53.25 84.42 84.42
4 23.96 60.00 60.42 60.50 80.21 81.25
5 27.78 45.56 60.00 65.56 74.44 74.44
Figure 7: Effect of biosorbent concentration on the removal of direct black-22
It also shows that equilibrium is attained at 4 g/L for Acid orange and 5 g/L for Direct black
of chitosan-glutaraldehyde from Table 3 and Table 4 which is also observed from the Figure
8 and Figure 9.
Studies on the behaviour of reactive dyes onto the cross-linked chitosan using adsorption isotherms
Deepika R, Venkateshprabhu. M, Pandimdevi. M
International Journal of Environmental Sciences Volume 4 No.3, 2013 329
Table 3: Effect of acid orange -10 on cross-linked chitosan-glutaraldehyde biosorbent
Conc.
(g/L)
30
(mins)
60
(mins)
120
(mins)
180
(mins)
1 9.74 12.82 12.31 12.56
2 4.26 7.02 7.27 7.52
3 1.91 4.09 4.91 4.91
4 4.24 4.78 5.37 5.37
5 4.12 5.93 6.44 6.96
Figure 8: Effect of % removal of acid orange-10 by cross-linked chitosan glutaraldehyde
Table 4: Effect of direct black -22 on the cross-linked chitosan-glutaraldehyde biosorbent
Conc.
(g/L)
30
(mins)
60
(mins)
120
(mins)
180
(mins)
1 15.63 25 27.08 28.13
2 10.31 14.43 16.50 17.53
3 13.33 16.67 17.78 17.78
4 37.37 40.40 44.44 45.46
5 44.57 48.91 52.17 52.17
Figure 9: Effect of % removal of direct black-22 by cross-linked chitosan-glutaraldehyde
Studies on the behaviour of reactive dyes onto the cross-linked chitosan using adsorption isotherms
Deepika R, Venkateshprabhu. M, Pandimdevi. M
International Journal of Environmental Sciences Volume 4 No.3, 2013 330
It is seen from Table 5 and Table 6 that acid orange-10 and direct black-22 attains
equilibrium at 3 g/L of chitosan-glyoxal which can also be compared in Figure 10 and Figure
11.
Table 5: Effect of acid orange-10 on cross-linked chitosan-glyoxal biosorbent
Conc.
(g/L)
30
(mins)
60
(mins)
120
(mins)
180
(mins)
1 6.00 6.87 7.97 8.51
2 3.97 5.46 5.71 5.71
3 3.73 4.52 4.79 5.05
4 6.03 7.54 8.04 8.04
5 6.94 8.74 9.25 9.51
Figure 10: Effect of % removal of acid orange-10 by cross-linked chitosan-glyoxal
Table 6: Effect of direct black-22 dye on the cross-linked chitosan-glyoxal biosorbent
Conc.
(g/L)
30
(mins)
60
(mins)
120
(mins)
180
(mins)
1 7.96 12.50 14.77 14.77
2 4.60 6.90 9.20 10.35
3 9.41 11.77 14.12 14.12
4 6.38 12.77 15.96 15.96
5 9.38 15.39 17.58 18.68
Studies on the behaviour of reactive dyes onto the cross-linked chitosan using adsorption isotherms
Deepika R, Venkateshprabhu. M, Pandimdevi. M
International Journal of Environmental Sciences Volume 4 No.3, 2013 331
Figure 11: Effect of % removal of direct black-22 by cross-linked chitosan-glyoxal
3.3 Effect of dye concentration
Table 7 and Table 8 data shows that the optimum initial dye concentration of chitosan is 30
mg/L for acid orange-10 and 20 mg/L for direct black-22 which can also be concluded from
the Figure 12 and Figure 13.
Table 7: Effect of acid orange-10 dye on chitosan
Conc.
(mg/L)
30
(mins)
60
(mins)
120
(mins)
180
(mins)
10 31.54 43.15 43.57 43.98
20 38.61 46.69 47.01 47.17
30 43.96 50.55 50.77 50.99
40 9.62 12.41 12.76 13.11
50 45.33 49.69 50.00 50.16
Figure 12: Effect of dye concentration on the removal of acid orange-10 by chitosan
Studies on the behaviour of reactive dyes onto the cross-linked chitosan using adsorption isotherms
Deepika R, Venkateshprabhu. M, Pandimdevi. M
International Journal of Environmental Sciences Volume 4 No.3, 2013 332
Table 8: Effect of direct black-22 dye on chitosan
Conc.
(mg/L)
30
(mins)
60
(mins)
120
(mins)
180
(mins)
10 4.76 6.35 7.41 7.94
20 1.80 5.76 6.47 6.47
30 2.84 6.03 6.38 6.74
40 5.30 12.88 13.64 14.39
50 6.42 9.17 10.09 10.09
Figure 13: Effect of dye concentration on the removal of direct black-22 by chitosan
From Table 9 and Table 10 equilibrium is attained at 20 mg/L for acid orange-10 and direct
black-22 of chitosan-glutaraldehyde which is observed from the Figure 14 and Figure 15.
Table 9: Effect of acid orange-10 dye on the cross-linked chitosan-glutaraldehyde
Conc.
(mg/L)
30
(mins)
60
(mins)
120
(mins)
180
(mins)
10 3.35 4.64 5.16 5.41
20 1.79 2.55 3.06 3.06
30 3.69 4.42 4.67 4.91
40 2.15 3.34 3.82 4.06
50 1.14 2.35 2.82 2.82
Studies on the behaviour of reactive dyes onto the cross-linked chitosan using adsorption isotherms
Deepika R, Venkateshprabhu. M, Pandimdevi. M
International Journal of Environmental Sciences Volume 4 No.3, 2013 333
Figure 14: Effect of dye concentration on the removal of acid orange-10 by cross-linked
chitosan-glutaraldehyde
Table 10: Effect of direct black-22 dye on the cross-linked chitosan-glutaraldehyde
Conc.
(mg/L)
30
(mins)
60
(mins)
120
(mins)
180
(mins)
10 4.35 13.04 15.22 16.30
20 8.08 14.14 17.17 19.19
30 6.42 12.84 15.60 17.43
40 6.78 11.02 15.25 15.25
50 4.80 10.40 12.00 12.80
Figure 15: Effect of dye concentration on the removal of direct black-22 by cross-linked
chitosan-glutaraldehyde.
Studies on the behaviour of reactive dyes onto the cross-linked chitosan using adsorption isotherms
Deepika R, Venkateshprabhu. M, Pandimdevi. M
International Journal of Environmental Sciences Volume 4 No.3, 2013 334
Table 11 and Table 12 indicate equilibrium is attained at 30mg/L for acid orange-10 and
direct black-22 of chitosan-glyoxal which can also be seen from the Figure 16 and Figure 17.
Table 11: Effect of acid orange-10 dye on the cross-linked chitosan-glyoxal
Conc.
(mg/L)
30
(mins)
60
(mins)
120
(mins)
180
(mins)
10 3.90 5.29 6.69 6.96
20 1.37 2.74 3.84 4.11
30 2.11 2.64 2.90 3.17
40 1.56 3.38 3.90 3.90
50 1.79 3.32 4.34 4.59
Figure 16: Effect of dye concentration on the removal of acid orange-10 by cross-linked
chitosan-glyoxal
Table 12: Effect of direct black-22 dye on cross-linked chitosan-glyoxal
Conc.
(mg/L)
30
(mins)
60
(mins)
120
(mins)
180
(mins)
10 16.47 23.53 27.06 29.41
20 14.74 16.84 20.00 21.05
30 8.26 11.00 13.76 13.76
40 6.78 11.02 14.41 15.25
50 5.60 12.00 12.80 12.80
Studies on the behaviour of reactive dyes onto the cross-linked chitosan using adsorption isotherms
Deepika R, Venkateshprabhu. M, Pandimdevi. M
International Journal of Environmental Sciences Volume 4 No.3, 2013 335
Figure 17: Effect of dye concentration on the removal of Direct Black-22 by cross-linked
Chitosan–Glyoxal
3.4 Effect of temperature
Table 13 and Table 14 shows the optimum temperature of chitosan was 40°C for acid orange-
10 and 50°C for direct black-22 which is confirmed from the Figure 18 and Figure 19.
Table 13: Effect of temperature on the adsorption of acid orange-10 on chitosan
Temperature
(°C)
30
(mins)
60
(mins)
120
(mins)
180
(mins)
30 27.36 29.85 30.35 30.35
40 25.41 27.03 27.57 28.11
50 3.19 6.91 8.51 8.51
60 3.87 4.97 6.08 6.63
70 9.52 11.91 12.86 13.33
Figure 18: Effect of temperature on the removal of acid orange-10 by chitosan
Studies on the behaviour of reactive dyes onto the cross-linked chitosan using adsorption isotherms
Deepika R, Venkateshprabhu. M, Pandimdevi. M
International Journal of Environmental Sciences Volume 4 No.3, 2013 336
Table 14: Effect of temperature on the adsorption of direct black-22 on chitosan
Temperature
(°C)
30
(mins)
60
(mins)
120
(mins)
180
(mins)
30 12.20 14.63 15.85 17.07
40 9.38 15.63 18.75 18.75
50 19.44 30.56 38.89 38.89
60 15.52 27.59 32.76 34.48
70 15.00 30.00 37.50 37.50
Figure 19: Effect of temperature on the removal of direct black-22 by chitosan
Table 15 and Table 16 presents results that the equilibrium is attained at 70°C for acid
orange-10 and direct black-22 of chitosan-glutaraldehyde which is also confirmed from the
Figure 20 and Figure 21.
Table 15: Effect of temperature on the adsorption of acid orange-10 on cross-linked
chitosan-glutaraldehyde
Temperature
(°C)
30
(mins)
60
(mins)
120
(mins)
180
(mins)
30 1.65 4.96 8.68 8.68
40 5.70 47.80 51.75 51.75
50 3.81 46.67 48.57 49.05
60 43.00 46.00 49.50 49.50
70 6.78 14.41 19.49 20.34
Studies on the behaviour of reactive dyes onto the cross-linked chitosan using adsorption isotherms
Deepika R, Venkateshprabhu. M, Pandimdevi. M
International Journal of Environmental Sciences Volume 4 No.3, 2013 337
0
10
20
30
40
50
60
30 60 120 180% D
ye
Rem
ova
l 30°C
40°C
50°C
60°C
70°C
Time (mins)
Figure 20: Effect of temperature on the removal of acid orange-10 by cross-linked chitosan-
glutaraldehyde
Table 16: Effect of temperature on the adsorption of direct black-22 on chitosan-glyoxal
Temperature
(°C)
30
(mins)
60
(mins)
120
(mins)
180
(mins)
30 3.68 8.09 11.77 11.77
40 4.17 9.72 11.11 11.81
50 1.65 7.44 9.92 10.74
60 5.00 19.00 22.00 22.00
70 6.59 12.09 13.19 14.29
0
5
10
15
20
25
30 60 120 180
% D
ye
Rem
oval
30°C
40°C
50°C
60°C
70°C
Time (mins)
Figure 21: Effect of temperature on the removal of direct black-22 by cross-linked chitosan-
glutaraldehyde
Table 17 and Table 18 shows equilibrium is at70°C, 60°C for acid orange-10 and direct
black-22 respectively of chitosan-glyoxal which can also be inferred from the Figure 22 and
Figure 23.
Studies on the behaviour of reactive dyes onto the cross-linked chitosan using adsorption isotherms
Deepika R, Venkateshprabhu. M, Pandimdevi. M
International Journal of Environmental Sciences Volume 4 No.3, 2013 338
Table 17: Effect of temperature on the adsorption of acid orange-10 on chitosan-glyoxal
Temperature
(°C)
30
(mins)
60
(mins)
120
(mins)
180
(mins)
30 6.86 11.77 13.73 14.71
40 5.56 11.11 16.67 17.78
50 3.66 9.76 14.63 14.63
60 8.45 15.49 19.72 21.13
70 7.69 15.39 16.72 16.72
0
5
10
15
20
25
30 60 120 180
% D
ye
Rem
ova
l
30°C
40°C
50°C
60°C
70°C
Time (mins)
Figure 22: Effect of temperature on the removal of acid orange-10 by cross-linked chitosan-
glyoxal
Table 18: Effect of temperature on the adsorption of direct black-22 on cross-linked
chitosan-glyoxal
Temperature
(°C)
30
(mins)
60
(mins)
120
(mins)
180
(mins)
30 9.43 22.64 24.53 24.53
40 14.58 20.83 27.08 31.25
50 11.29 17.74 20.97 20.97
60 18.42 26.32 31.58 34.21
70 47.62 57.14 76.19 80.95
Studies on the behaviour of reactive dyes onto the cross-linked chitosan using adsorption isotherms
Deepika R, Venkateshprabhu. M, Pandimdevi. M
International Journal of Environmental Sciences Volume 4 No.3, 2013 339
0102030405060708090
30 60 120 180
% D
ye
Rem
oval
30°C
40°C
Time (mins)
Figure 23: Effect of temperature on the removal of direct black-22 by cross-linked chitosan-
glyoxal
3.5 Effect of pH
Table 19 and Table 20 depicts that the optimum pH value is 3pH and 4pH for acid orange-10
and direct black-22 respectively of chitosan which can also be inferred from the Figure 24
and Figure 25.
Table 19: Effect of pH on the adsorption of acid orange-10 on Chitosan
pH 30
(mins)
60
(mins)
120
(mins)
180
(mins)
2 6.25 16.35 18.27 18.75
3 7.41 13.23 14.81 14.81
4 8.57 13.88 18.78 19.18
5 2.97 11.44 15.25 15.25
6 5.20 13.60 19.60 20.00
7 8.91 16.19 21.05 21.46
8 10.97 13.08 18.99 18.99
9 7.19 19.42 21.22 21.58
Figure 24: Effect of pH on the removal of acid orange-10 by chitosan
Studies on the behaviour of reactive dyes onto the cross-linked chitosan using adsorption isotherms
Deepika R, Venkateshprabhu. M, Pandimdevi. M
International Journal of Environmental Sciences Volume 4 No.3, 2013 340
Table 20: Effect of pH on the adsorption of direct black-22 on chitosan
pH 30
(mins)
60
(mins)
120
(mins)
180
(mins)
2 4.46 15.29 17.83 18.47
3 3.43 11.43 17.71 18.29
4 5.00 12.00 19.00 19.00
5 2.61 12.00 21.57 22.22
6 6.02 15.04 24.81 24.81
7 4.55 14.55 24.55 25.46
8 5.36 11.90 20.24 20.83
9 5.35 11.23 17.65 17.65
Figure 25: Effect of pH on the removal of direct black-22 by chitosan
Table 21 and Table 22 data confirms that equilibrium is attained at 8pH for acid orange-10
and 6pH for direct black-22 of chitosan-glutaraldehyde which is also seen from the Figure 26
and Figure 27.
Table 21: Effect of pH on the adsorption of acid orange-10 on chitosan-glutaraldehyde
pH 30
(mins)
60
(mins)
120
(mins)
180
(mins)
2 1.25 4.15 5.81 5.81
3 1.67 3.77 4.60 5.02
4 1.79 4.02 5.36 5.36
5 3.23 5.53 7.37 7.83
6 2.04 4.08 5.31 5.31
7 2.16 3.88 5.17 5.60
8 3.83 5.74 6.70 6.70
9 1.49 5.47 6.97 7.46
Studies on the behaviour of reactive dyes onto the cross-linked chitosan using adsorption isotherms
Deepika R, Venkateshprabhu. M, Pandimdevi. M
International Journal of Environmental Sciences Volume 4 No.3, 2013 341
Figure 26: Effect of pH on the removal of acid orange-10 by cross-linked chitosan-
glutaraldehyde
Table 22: Effect of pH on the adsorption of direct black-22 on chitosan-glutaraldehyde
pH 30
(mins)
60
(mins)
120
(mins)
180
(mins)
2 2.30 5.17 8.05 8.05
3 3.73 6.83 8.70 9.32
4 3.25 5.84 7.79 8.44
5 3.82 6.37 7.64 7.64
6 3.45 5.00 6.21 6.21
7 5.30 9.09 11.36 12.12
8 4.96 9.09 10.74 10.74
9 7.56 10.08 14.29 15.13
Figure 27: Effect of pH on the removal of direct black-22 by cross-linked chitosan-
glutaraldehyde
Table 23 and Table 24 indicate equilibrium is attained at 4pH, 3pH for acid orange-10 and
direct black-22 respectively of chitosan-glyoxal which can also be seen from the Figure 28
and Figure 29.
Studies on the behaviour of reactive dyes onto the cross-linked chitosan using adsorption isotherms
Deepika R, Venkateshprabhu. M, Pandimdevi. M
International Journal of Environmental Sciences Volume 4 No.3, 2013 342
Table 23: Effect of pH on the adsorption of acid orange-10 on chitosan-glyoxal
pH 30
(mins)
60
(mins)
120
(mins)
180
(mins)
2 2.10 5.59 7.69 8.39
3 2.17 5.80 7.97 7.97
4 2.07 4.83 6.90 6.90
5 5.30 9.09 12.12 12.88
6 3.97 6.35 11.11 11.11
7 1.64 4.10 6.56 7.38
8 1.74 4.35 6.09 6.09
9 2.73 6.36 8.18 8.18
Figure 28: Effect of pH on the removal of acid orange-10 by cross-linked chitosan-glyoxal
Table 24: Effect of pH on the adsorption of direct black-22 on cross-linked chitosan-glyoxal
pH 30
(mins)
60
(mins)
120
(mins)
180
(mins)
2 2.06 7.23 11.34 11.34
3 2.17 5.44 10.87 10.87
4 4.94 8.64 13.58 14.82
5 5.33 9.33 13.33 14.67
6 6.25 9.38 14.06 14.06
7 2.78 9.72 15.28 16.67
8 5.17 12.07 17.24 17.24
9 9.09 18.18 29.55 29.55
Studies on the behaviour of reactive dyes onto the cross-linked chitosan using adsorption isotherms
Deepika R, Venkateshprabhu. M, Pandimdevi. M
International Journal of Environmental Sciences Volume 4 No.3, 2013 343
Figure 29: Effect of pH on the removal of direct black-22 by cross-linked chitosan-glyoxal
3.6 Langmuir isotherm
a) It is represented as:
Where, Ce = Equilibrium concentration of dye solution
qe= Metal ion adsorbed (mg/g)
b, qmax = Langmuir constants
The adsorption of the reactive dyes onto the chitosan beads and cross-linked chitosan beads
showed a contact time of 60 minutes. Figure 30 and Figure 31 shows adsorption equilibrium
data fitted much better to Langmuir isotherm, where in both acid orange-10 and direct black-
22 reactive dyes, the chitosan-glyoxal cross-linked beads showed better adsorption of the
reactive dyes when compared to the chitosan and chitosan-glutaraldehyde cross-linked beads,
though cross-linked chitosan beads have the advantage that they can be used in a low pH
(acidic) solution, where chitosan beads dissolve.
Table 25: Langmuir isotherm of acid orange-10-Chitosan
Initial dye concⁿ
(Co) mg/l
Final dye concⁿ
(Ce) mg/l
qe=(Co-Ce) V ̸ W
(mg/g) Ce/qe
5 2 3 0.7
10 7.1 2.9 2.45
15 11.5 3.5 3.29
20 17.9 2.1 8.5
25 22.6 2.4 9.4
30 27.7 2.3 12.04
35 32.7 2.3 14.2
40 37.6 2.4 15.67
45 42.1 2.9 14.52
50 47.8 2.2 21.73
Ce= 1 * Ce + 1
qe qmax b.qmax
Studies on the behaviour of reactive dyes onto the cross-linked chitosan using adsorption isotherms
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International Journal of Environmental Sciences Volume 4 No.3, 2013 344
R2 = 0.959
Figure 30: Adsorption isotherm of acid orange-10 by chitosan
Table 26: Langmuir isotherm of direct black-22-Chitosan
Initial dye concⁿ
(Co) mg/l
Final dye concⁿ
(Ce) mg/l
qe=(Co-Ce) V / W
(mg/g) Ce/qe
5 2.8 2.2 1.27
10 8.4 1.6 5.25
15 13.4 1.6 8.38
20 18.68 1.52 15.67
25 23.9 1.1 21.7
30 28.7 1.3 22.07
35 33.5 1.5 22.33
40 38.7 1.3 22.76
45 43.9 1.1 39.9
50 48.9 1.1 44.46
R2= 0.9169
Figure 31: Langmuir isotherm of direct black-22 by chitosan
Studies on the behaviour of reactive dyes onto the cross-linked chitosan using adsorption isotherms
Deepika R, Venkateshprabhu. M, Pandimdevi. M
International Journal of Environmental Sciences Volume 4 No.3, 2013 345
Table 27: Langmuir isotherm of acid orange-10-cross-linked chitosan-glutaraldehyde
Initial dye concⁿ
(Co) mg/l
Final dye concⁿ
(Ce) mg/l
qe=(Co-Ce) V / W
(mg/g) Ce/qe
5 3 2 1.5
10 7.5 2.5 3
15 12 3 4
20 18 2 9
25 22.8 2.2 10.4
30 28 2 19
35 33 2 16.5
40 37.6 2.4 15.7
45 42 3 14
50 48 2 24
R2= 0.8461
Figure 32: Langmuir isotherm of acid orange-10 by cross-linked chitosan-glutaraldehyde
Table 28: Langmuir isotherm of direct black-22-cross-linked chitosan-glutaraldehyde
Initial dye concⁿ
(Co) mg/l
Final dye concⁿ
(Ce) mg/l
qe=(Co-Ce) V / W
(mg/g) Ce/qe
5 3 2 1.5
10 8.7 1.3 6.7
15 13.5 1.5 9
20 18 2 9
25 23.8 1.2 19.8
30 28 2 19
35 33 2 16.5
40 38.8 1.2 32.3
45 43.5 1.5 29
50 48.5 1.5 32.3
Studies on the behaviour of reactive dyes onto the cross-linked chitosan using adsorption isotherms
Deepika R, Venkateshprabhu. M, Pandimdevi. M
International Journal of Environmental Sciences Volume 4 No.3, 2013 346
R2= 0.9132
Figure 33: Langmuir isotherm of direct black-22 by cross-linked chitosan-glutaraldehyde
Table 29: Langmuir isotherm of acid orange-10-cross-linked chitosan-glyoxal
Initial dye concⁿ
(Co) mg/l
Final dye concⁿ
(Ce) mg/l
qe=(Co-Ce) V / W
(mg/g) Ce/qe
5 3.5 1 2.3
10 8 1.5 4
15 12.5 2 5
20 18.2 1 10.1
25 23 1.5 11.5
30 28.3 1 16.7
35 33.5 1 22.3
40 38 1.5 19
45 43 1.5 21.5
50 48.5 1 32.3
R2= 0.937
Figure 34: Langmuir isotherm of acid orange-10 by cross-linked chitosan-glyoxal
Studies on the behaviour of reactive dyes onto the cross-linked chitosan using adsorption isotherms
Deepika R, Venkateshprabhu. M, Pandimdevi. M
International Journal of Environmental Sciences Volume 4 No.3, 2013 347
Table 30: Langmuir isotherm of direct black-22-cross-linked chitosan-glyoxal
Initial dye concⁿ
(Co) mg/l
Final dye concⁿ
(Ce) mg/l
qe=(Co-Ce) V / W
(mg/g) Ce/qe
5 4 1 4
10 8.5 1.5 5.7
15 13 2 6.5
20 19 1 19
25 23.5 1.5 15.7
30 29 1 29
35 34 1 34
40 38.5 1.5 25.7
45 43.5 1.5 29
50 49 1 49
R2= 0.8618
Figure 35: Langmuir isotherm of direct black – 22 by cross-linked chitosan-glyoxal
3.7 Comparative Studies
Figure 36: Comparison of Langmuir isotherm: Acid orange-10
Studies on the behaviour of reactive dyes onto the cross-linked chitosan using adsorption isotherms
Deepika R, Venkateshprabhu. M, Pandimdevi. M
International Journal of Environmental Sciences Volume 4 No.3, 2013 348
Figure 37: Comparison of Langmuir isotherm: Direct black – 22
5. Conclusion
The percentage removal of dyes, acid orange-10 and direct black-22 were controlled by
factors affecting adsorption capacity such as biosorbent concentration, dye concentration,
contact time, pH, temperature. From this study it was concluded using Langmuir isotherm
that the cross-linked chitosan with glyoxal showed good adsorption capacity of dyes when
compared to the cross-linked chitosan with glutaraldehyde and non-cross-linked chitosan, and
the cross-linked chitosan have the advantage that they can be used in low pH (acidic) solution
where-in non-cross-linked chitosan beads dissolve. The highest percentage removal of Acid
orange-10 was achieved at pH 4, in contact time of 60 minutes, by biosorbent dose of 3g/L of
30mg/L dye concentration, whereas the highest percentage removal of Direct black-22 was
achieved at pH 3 in contact time of 60 minutes by biosorbent dose of 3g/L of 30mg/L dye
concentration, thus the decrease in efficiency was not due to deactivation of binding sites but
due to loss of adsorbent mass during desorption process.
Acknowledgment
The authors would like to thank SRM University, Kattankulathur for providing experimental
facilities and also take the immense pleasure to thank the staff and technicians for their
guidance for the completion of this study.
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