This article was downloaded by: [Dicle University] On: 04 November 2014, At: 03:33
Publisher: Taylor & Francis
Informa Ltd Registered in England and Wales Registered Number: 1072954 Registered office: Mortimer House, 37-41 Mortimer Street, London W1T 3JH, UK
Journal of Dispersion Science and Technology
Publication details, including instructions for authors and subscription information: http://www.tandfonline.com/loi/ldis20Adsorption of Methylene Blue from Aqueous Solution
by Crosslinked Chitosan/Bentonite Composite
Yasemin Bulut a & Hatice Karaer a
a
Department of Chemistry, Faculty of Science , Dicle University , Diyarbakır , Turkey Accepted author version posted online: 10 Feb 2014.
To cite this article: Yasemin Bulut & Hatice Karaer (2015) Adsorption of Methylene Blue from Aqueous Solution
by Crosslinked Chitosan/Bentonite Composite, Journal of Dispersion Science and Technology, 36:1, 61-67, DOI: 10.1080/01932691.2014.888004
To link to this article: http://dx.doi.org/10.1080/01932691.2014.888004
PLEASE SCROLL DOWN FOR ARTICLE
Taylor & Francis makes every effort to ensure the accuracy of all the information (the “Content”) contained in the publications on our platform. However, Taylor & Francis, our agents, and our licensors make no
representations or warranties whatsoever as to the accuracy, completeness, or suitability for any purpose of the Content. Any opinions and views expressed in this publication are the opinions and views of the authors, and are not the views of or endorsed by Taylor & Francis. The accuracy of the Content should not be relied upon and should be independently verified with primary sources of information. Taylor and Francis shall not be liable for any losses, actions, claims, proceedings, demands, costs, expenses, damages, and other liabilities whatsoever or howsoever caused arising directly or indirectly in connection with, in relation to or arising out of the use of the Content.
This article may be used for research, teaching, and private study purposes. Any substantial or systematic reproduction, redistribution, reselling, loan, sub-licensing, systematic supply, or distribution in any
form to anyone is expressly forbidden. Terms & Conditions of access and use can be found at http:// www.tandfonline.com/page/terms-and-conditions
Adsorption of Methylene Blue from Aqueous Solution by
Crosslinked Chitosan/Bentonite Composite
Yasemin Bulut and Hatice Karaer
Department of Chemistry, Faculty of Science, Dicle University, Diyarbakır, Turkey GRAPHICAL ABSTRACT
This article reports the application of a crosslinked chitosan/bentonite composite as adsorbent for the removal of a cationic dye, methylene blue (MB), from aqueous solution. Batch experi-ments were conducted to study the effects of contact time, initial concentration of adsorbate (50–200 mg L1), temperature (298–313 K), agitation speed (90–150 rpm), and pH (2–10) on adsorption. The equilibrium experimental data were analyzed by the Freundlich and Langmuir models. The kinetic data obtained with different initial concentration and temperature were analyzed using a pseudo-first-order, pseudo-second-order, and intraparticle diffusion equations. Maximum adsorption capacity (Qm) was calculated at different temperatures (298, 308, and
313 K) as 95.24, 97.09, and 142.86 mg g1, respectively. The results showed that this novel adsorbent had a high adsorption capacity, making it suitable for use in the treatment MB-enriched wastewater.
Keywords Adsorption, clay, composite, methylene blue, super absorbent
1. INTRODUCTION
The presence of dyes in effluents is a major concern due to their adverse effects to many forms of life. The discharge of dyes in the environment is a matter of concern for both toxicological and esthetical reasons.[1,2] Wastewaters from industries like textile, dyeing, printing, cosmetics, food
coloring, papermaking, etc. are the major contributors of colored effluents. There are more than 105 commercially available dyes with over 7 105tons of dyes produced annually.[3]Discharging even a small amount of dye into water can affect aquatic life and food webs due to the carcinogenic and mutagenic effects of synthetic dyes.[4] Hence the removal of dyes from waste effluents becomes environmentally important.[5]Methylene blue (MB) is the most commonly used substance for dying cotton, wool, and silk. It can cause eye burns which may be responsible for permanent injury to the eyes of human and animals.[1] On inhalation, it can give rise to short periods of rapid or Received 25 December 2013; accepted 23 January 2014.
Address correspondence to Yasemin Bulut, Department of Chemistry, Faculty of Science, Dicle University, 21280 Diyarbakır, Turkey. E-mail: ybulut@dicle.edu.tr
Color versions of one or more of the figures in the article can be found online at www.tandfonline.com/ldis.
ISSN: 0193-2691 print=1532-2351 online DOI: 10.1080/01932691.2014.888004
61
difficult breathing while ingestion through the mouth produces a burning sensation and may cause nausea, vomiting, profuse sweating, mental confusion, and methemoglobinemia.[6,7] Therefore, the treatment of effluent containing such dye is of interest due to its harmful impacts on receiving waters.
Conventional treatment methods such as coagulation and flocculation, precipitation, ozonation, photocatalytic oxidation, electrochemical destruction, biological treat-ment and adsorption have been developed for water decontamination applications.[2,8]
Adsorption is recognized as a more efficient treatment process since it has the advantage of simplicity in oper-ation, low cost, flexibility, and intensitivity to toxic pollu-tants.[1,8,9] Various adsorbents have been used to remove different types of dyes. Activated carbons, plant, or ligno-cellulosic wastes, clays and biopolymers are among the common adsorbents used.[1,10–13] Chitosan (CS) can be used as an adsorbent to remove dyes due to the presence of amino and hydroxyl groups, which can serve as the active sites. However, CS is very sensitive to pH as it can either form gel or dissolve depending on the pH values.[10] To improve mechanical properties, adsorption capacity, or even to prevent dissolution of the CS in acidic medium, numerous studies have been devoted to the chemical modification of the CS surface by homogeneous or hetero-geneous crosslinking with di- or polyfunctional agents. On the other hand, CS-based composite materials have also been reported to exhibit enhanced mechanical, thermal, or adsorption properties comparative with any of its components used alone.[14]
Recently, the polymer=clay composite has received great attention because of its relatively low production cost and high adsorption capacity for some dyes.[15] CS composites such as bentonite, montmorillonite, activated clay, polyurethane, and oil palm ash have gained much attention, extensively studied and widely reported in the literature.[16–19]
In this study, we designed and characterized cross-linked chitosan=bentonite composite (CCSB) and analyzed its efficiency in adsorbing MB. The crosslinked CS composites were able to improve the CS performance as an adsorbent. A crosslinking agent can stabilize CS in acidic solutions so that CS becomes insoluble.[20,21] To the best of our knowledge, studies on the removal of MB from aqueous using crosslinked (ethyleneglycoledi-methacrylate) CS=bentonite as an adsorbent have yet to be reported. The factors influencing the adsorption capacity of the composite such as contact time, initial con-centration of MB, temperature, and pH were investigated. In order to examine the controlling mechanism of the adsorption process, the kinetics, adsorption isotherms, and thermodynamics parameters were evaluated.
2. MATERIALS AND METHODS 2.1. Materials
The bentonite was used as clay in this study and obtained from the town of Elazıg˘-Turkey. The sample was characterized by x-ray fluorescence. The chemical compositions of the bentonite were found to be as follows: 39.6% SiO2, 24.2% CaO, 9.57% Al2O3, 5.2% Fe2O3, 2.4%
MgO, 1.4% MnO, 0.9% K2O, 0.7% SrO, 0.6% TiO2, and
14.0% loss on ignition. After drying at 110C, the sample was pulverized to pass through a 150 mm sieve. Adsorption and desorption experiments were carried out using N2 at
77 K on a Quantochrome Autosorb-1-C=MS sorptiometer. Prior to each measurement, the sample was outgassed at 103Pa and 353 K for 3 hours. The N2isotherms were used
to determine the specific surface area (SA). The SA of bentonite micropowder was determined as 67 m2g1 by using multipoint Brunauer–Emmett–Teller (BET) methods. The cation-exchange capacity of the bentonite sample was determined according to the ammonium acetate saturation method and was found to be 0.61 meq g1 clay.[22] CS as powder was purchased from Fluka. MB (CI¼ 52,015; chemical formula: C16H18ClN3S; molecular weight¼
319.86 g mol1; maximum wavelength¼ 663 nm) supplied by Merck was used as adsorbate and was not purified prior to use. A stock solution of MB of 1000 mg L1 was prepared, which was diluted to the required initial concen-trations. Other agents used were all of analytical grade, and all solutions were prepared with distilled water. 2.2. Preparation of Adsorbents
CS solution was prepared by dissolving 1.0 g of CS powder in 100 mL of 1 M acetic acid solution. The mixture was kept stirred at room temperature for 24 hours. To the as-prepared homogeneous viscous solution, 1 mL of ethyle-neglycoledimethacrylate (EGDMA) was added, followed by the addition of 1.0 g of bentonite 10 minutes. The mixture was kept stirring at 60C for 4 hours. To prepare
CS=bentonite bead, the gel was dripped into a precipitation bath containing 250 mL of 20% ethanol–NaOH (2 M) solution by a disposable syringe. The CCSB gel thereby coagulated to uniform beads. The obtained CCSB beads were thoroughly rinsed with distilled water to remove any NaOH residue, afterwards were filtered and finally dried. The dry beads were then ground by a laboratory mill and sieved, and the beads with size of 80–100 mesh were used in this study.
2.3. Determination of Point of Zero Charge of Adsorbent
The point of zero charge (pHPZC) of samples was
deter-mined by the solid addition method.[3]To a series of 100 mL conical flasks, 45 mL of KNO3solution of known strength
62 Y. BULUT AND H. KARAER
was transferred. The pH0 values of the solution were
roughly adjusted from 2 to 12 by adding either 0.1 mol L1 HNO3 or NaOH (Mettler Toledo). The total
volume of the solution in each flask was made exactly to 50 mL by adding the KNO3solution of the same strength.
The pH of the solutions was then accurately noted, and 0.1 g of samples was added to each flask, which were securely capped immediately. The suspensions were then manually shaken and allowed to equilibrate for 48 hours with intermittent manual shaking. The pH values of the supernatant liquid were noted. The difference between the initial (pH0) and final pH (pHf) values (pH0–pHf) was
plotted versus the pH. The point of intersection of the resulting curve at which pH gave the pHPZC. The procedure
was repeated for different concentrations of KNO3.
2.4. Adsorption Studies
MB adsorption from aqueous solutions was investigated in batch experiments. The experimental solution with desired MB concentration was obtained by successive dilution of a stock solution of MB with deionized water. To determine the calibration curve of MB, absorbance of solutions with predetermined MB concentrations at kmax¼
663 nm was detected by a UV-vis spectrophotometer (Cary 100 Bio UV-visible). In the following adsorption experiments, the concentration of the MB solution after absorption was determined by using this calibration curve, and the amount of MB that has been absorbed can then be calculated accordingly. Adsorption experiments were carried out on thermostated shaker (Julabo SW23) at a constant known speed with 50 mL MB solution of known concentration, pH, and adsorbent dosage was added into a 50 mL stoppered conical flask. Thus, 0.01 g of composite was placed in a flask and contacted with 50 mL of aqueous solution of MB at different initial concentrations (50, 100, and 200 mg L1), temperatures (298, 303, and 313 K) and agitation speed (90, 120, and 150 rpm).
The equilibrium concentration of the MB was measured at different contact durations. The contact time ranged between 2 and 36 hours.
For isotherm studies, a series of flasks with MB solution in the range of 25–250 mg L1 at pH (original pH¼ 5.11) and then the adsorbent were added to each flask. The mixtures were agitated at constant temperature of 298, 303, and 313 K for 120 minutes. Adsorption of dye by 1 g of CCSB composite was determined by the following mass balance equation (1):
q¼ Cð i CfÞ
V
W ½1
where q represents the amount of dye adsorbed, Ci
and Cf are the initial and final concentration (mg L1),
respectively, of dye after adsorption. V is the volume
(mL) of experimental solution, and W is the weight (g) of the adsorbent.[23–26]
3. RESULTS AND DISCUSSION 3.1. Adsorption Kinetics
3.1.1. Effect of Contact Time and Initial Concentration Figure 1 shows the influences of the initial MB concen-tration for the adsorption kinetics of the MB on the CCSB at 298 K. As the initial dye concentration was increased from 50 to 200 mg L1, the dye adsorption capacity increased from 57.95 to 126.56 mg g1. This can be attribu-ted to mass transfer effects and the driving force of the con-centration gradient being directly proportional to the initial concentrations.[27] Figure 1 demonstrated that the higher adsorption rates were observed at the beginning. The adsorption rate may be higher because of an increase in the number of vacant sites initially available, resulting in an increased concentration gradient between the sorbate in the solution and that at the sorbent surface. In time, the concentration gradient is reduced owing to the adsorp-tion of the dye molecules onto the vacant sites, leading to decreased adsorption during the later stages.[5] Conse-quently, the equilibrium time is 120 minutes in our experi-ment for the adsorption of MB onto adsorbent. Time-rate adsorption curve is single and continuous, suggesting the possibility of monolayer coverage of MB onto surface of the adsorbent.[4]
3.1.2. Effect of Temperature
Effect of temperature on the adsorption of MB by CCSB is shown in Figure 2 The equilibrium adsorption capacity was affected by temperature, with the amount of MB adsorbed increasing from 72.45 to 89.95 mg g1when
FIG. 1. Effect of contact time on the adsorption of MB onto CCSB at different initial MB concentrations at 298 K (m¼ 0.01 g, V ¼ 50 mL, speed¼ 120 rpm, pH ¼ original).
the temperature was raised from 298 to 313 K. This increase in MB removal indicates not only that tempera-ture has a significant effect on adsorption, but also that the adsorption of MB on composite surface is an endo-thermic process. The mobility of molecules increases gener-ally with a rise in temperature, thereby facilitating the formation of surface monolayers.[28]
3.1.3. Effect of Stirring
Agitation is an important parameter in adsorption phenomena influencing the distribution of the solute in the bulk solution and the formation of the external bound-ary film. Agitation speeds of 90, 120, and 150 rpm were used within contact time of 240 minutes. With the increase of speed from 90 to 150 rpm, the removal of MB increased from 65 to 99 mg g1(Figure 3). An increase in agitation speed reduced the film boundary layer around the particles, and as a result the external film transfer coefficient increased. Similar results were reported by Purkait.[29] 3.1.4. Adsorption Kinetics
In order to understand the process of adsorption, three kinetic models were applied to analyze experimental data[22,23]: log qð e qtÞ ¼ log qe kpft ½2 t qt ¼ 1 kpsq2e þ t qe ½3 qt¼ kipt1=2 ½4
In Equations (1)–(4), qe(mg g1) and qt(mg g1) are the
amounts of MB adsorbed at equilibrium and at any
contact time of adsorption t (min), respectively; kpf
(min1), kps(g mg1min1), and kip(mg g1min1=2) are
the pseudo-first-order, pseudo-second-order, and intrapar-ticle diffusion rate constants, respectively. According to Equation (1), the plot of ln (qe– qt) versus t, and according
to Equation (2) the plot of t=qtversus t and according to
Equation (3) the plot of qt versus t ½
should each give a straight line for the respective model to be applicable. The rate constant qe and corresponding linear regression
correlation coefficient values, R, are given in Table 1. The high values of R2 (0.9949–0.9994) for all concentra-tions, temperatures, and stirring indicate that the adsorp-tion data conform well to pseudo-second-order kinetics. In addition, the calculated qe values agreed with the
experimental data in the case of the pseudo-second-order model. Similar results have been observed in the adsorption of MB onto CS-g-poly (acrylic acid)=vermiculite hydrogel composites,[4]and crosslinked succinyl CS.[8]
3.1.5. Activation Parameters
From three of the pseudo-second-order rate constants, ks, each at a different temperature, and using the Arrhenius
equation (5), it is possible to gain some insight into the type of adsorption.
ln kpsm ¼ ln A EaRT ½5
where Ea is the activation energy (J mol1), kpsm is
the pseudo-second-order rate constant for adsorption (g mol1min1), A is the temperature-independent Arrhenius factor (g mol1min1), R is the gas constant (8.314 J K1mol1), and T is the solution temperature (K). The slope of the plot of ln kpsmversus T1 can then
be used to evaluate Ea. Low activation energies
(5–40 kJ mol1) are characteristic of physical adsorption, FIG. 3. Effect of speed on the adsorption of MB onto CCSB for a solution initially containing 100 mg L1of MB as a function of time at 298 K (m¼ 0.01 g, V ¼ 50 mL, speed ¼ 120 rpm, pH ¼ original).
FIG. 2. Effect of temperature on the adsorption of MB onto CCSB for a solution initially containing 100 mg L1of MB as a function of time (m¼ 0.01 g, V ¼ 50 mL, speed ¼ 120 rpm, pH ¼ original).
64 Y. BULUT AND H. KARAER
while higher ones (40–800 kJ mol1) suggest chemisorp-tions.[28] The present results give Ea¼ 6.11 kJ mol1 for
the adsorption of MB onto CCSB (Figure 4), indicating that the adsorption has a low potential barrier and corre-sponds therefore to physisorption. The value is consistent with those found in the literature for the adsorption of dyes onto many adsorbents, for example, maxilon blue GRL onto sepiolite (34 kJ mol1),[30] and MB onto perlite (14 kJ mol1).[31]
3.2. Adsorption Equilibrium
Adsorption isotherms are important for the description of how molecules of adsorbate interact with adsorbent surface. Hence, the correlation of equilibrium data using either a theoretical or empirical equation is essential for the adsorption interpretation and prediction of the extent
of adsorption.[3] The equilibrium adsorption data were generally interpreted using Langmuir and Freundlich models which are represented by the following equations, respectively[22,25,32,33]: Ce qe ¼ 1 KLQm þCe Qm ½6 qe¼ KfCe1=n ½7
where Qm(mg=g) and KL(L=mg) are Langmuir isotherm
coefficients. The value of Qm represents the maximum
adsorption capacity. Kf (mg=g) and n are Freundlich
constants. Two adsorption isotherms were constructed by plotting the Ce=qe versus Ce, logqe versus logCe,
respect-ively. The dimensionless separation factor, RL, is an
essen-tial characteristic of Langmuir isotherm, which is defined as Equation (8)[4];
RL¼
1 1þ KLC0
ð Þ ½8
where KL is the Langmuir constant, and Cois the highest
initial MB concentration. The value of RL indicates the
type of the isotherm to be either favorable (0 < RL<1),
unfavorable (RL>1), linear (RL¼ 1) or irreversible
(RL¼ 0).[3] Isotherms for the studied system at different
temperatures are presented in Figure 5. Langmuir and Freundlich parameters computed from Equations (6) and (7) are listed in Table 2. The best fit isotherm model for the system was compared by judging the correlation coeffi-cients R2values. The Langmuir isotherm was found to fit quite well with the experimental data for three different temperatures in comparison with the linear correlation coefficients (R2). The results of Table 2 also show that with FIG. 4. Plot of ln kpsmversus T1estimation of the activation energy
for the adsorption of MB on CCSB.
TABLE 1
Kinetic data of different kinetic models for the adsorption MB on SSCB
PF PS IP= Co (mg L1) T (K) Speed (rpm) qe (mg g1) qe (mg g1) kpf (min1) R2 qe (mg g1) kps (g mg1min1) R2 kid (g mg1min1=2) R2 50 298 120 57.95 49.84 0.0138 0.9503 63.69 0.0004157 0.9949 23521 0.9446 100 72.45 41.64 0.0106 0.9211 75.76 0.0005792 0.9962 20228 0.9621 200 126.56 57.68 0.0219 0.7812 128.04 0.0011798 0.9994 13705 0.9128 100 298 120 72.45 41.64 0.0106 0.9211 75.19 0.0005881 0.9963 20228 0.9621 303 81,00 45.72 0.0124 0.9434 84.75 0.0006129 0.9988 22757 0.9035 313 89.95 40.55 0.0094 0.8135 91.74 0.0006619 0.9978 21769 0.8667 100 298 90 65.5 45.27 0.0173 0.9472 68.97 0.0007889 0.9982 17796 0.921 120 72.45 41.64 0.0106 0.9211 75.19 0.0005881 0.9963 20228 0.9621 150 100.00 41.75 0.0134 0.8282 102.04 0.0008942 0.9984 15771 0.9431 qe: experimental.
an increase in temperature from 298 to 313 K, adsorption capacity (Qm) increased from 95.24 to 142.86 mg=g,
respectively. The Qm values of MB on CCSB have been
compared with those of other adsorbents (Table 3).[34,35] According to the RL values, all the systems correspond to
favorable adsorption processes (Table 2). 3.3. Thermodynamic Studies
The thermodynamic parameters are important for a better understanding of the effect of temperature. Since the KL Langmuir constant is essentially an equilibrium
constant, the variation of KL with temperature (Table 2)
can be used to estimate the enthalpy change accompanying adsorption, DHo, that is, the standard enthalpy change of adsorption at a fixed surface coverage.[28] The standard Gibbs’ free energy change of adsorption, DGo, can be related to the equilibrium Langmuir constant, KL, by
DGo¼ RT ln KL ½9
where R is the gas constant (R¼ 8.314 J=mol K). A convenient form of the Van’t Hoff equation then relates
KL to the standard enthalpy and entropy changes of
adsorption DHo and DSo, respectively, ln KL¼
DH0
RT þ DS0
R ½10
On the basis of a plot of ln KL versus T1Equation (10),
DHocan be estimated from the slope and DSofrom inter-cept of what should be a straight line passing through the points. The DHo and DSo values are thus found to be þ23.9 kJ mol1 and 153 J K1, respectively, while the DGo values are 21.77, 22.75, and 22.94 kJ mol1 (at 298, 303, and 313 K), respectively. These are values that correspond to spontaneous physical processes, while those with values in the80 to 400 kJ mol1range correspond to chemisorptions.[33] As DGo changed from 21.77 to 22.94 kJ mol1 when the temperature increased from 298 to 313 K, it can be concluded that the adsorption mechanism is dominated by physisorption.[21] These findings suggest that the adsorption is rapid and more spontaneous at higher temperature. The positive value of DHo confirms the endothermic nature of the adsorption process, as has been found in most cases.[21,26]This feature may be an indication of the occurrence of monolayer composite-solution interface during adsorption.[14]
3.4. Effect of pH
Many studies suggest that pH is an important factor in the adsorption process.[28] Some experiments were there-fore performed at 25C with 100 mg L1solutions to study
the MB adsorption on CCSB as a function of solution pH. The amount and the percentage of MB adsorbed from solu-tions were as follows: unbuffered, 57.20 mg g1, 24.40%; pH 2, 63.7 mg g1, 27.2%; pH 6, 71.8 mg g1, 30.8%; pH 6, 122.00 mg g1, 50.50%; pH 8, 132.30 mg g1, 57.3% pH 10, 200.00 mg g1, 82.40%; pH 12. Hence it is clear that the adsorption process is dependent on the pH of the solution, the percentage of MB adsorbed increasing with pH and being at a maximum at pH 11. MB produces molecular cations in aqueous solution. The adsorption of MB on the CCSB surface is primarily influenced by the surface charge on the TABLE 2
The adsorption parameters of Langmuir and Freundlich at different temperatures
T (K) Langmuir isotherm model Freundlich isotherm model Qm KL R2 RL KF 1=n R2 298 95.24 0.020376 0.9928 0.197 18.62 0.842 0.9667 303 97.09 0.025971 0.9971 0.162 24.54 0.856 0.9762 313 142.86 0.017322 0.9928 0.224 28.84 0.861 0.9765 FIG. 5. Adsorption isotherm for the adsorption of MB onto CCSB at different temperatures.
TABLE 3
Comparison of maximum monolayer capacity for MB on the other different adsorbents
Adsorbents Qm(mg=g) References
CCSB 95–142 This work
Fly ash 13.42 29
Rice husk 40.58 30
Pleurotus ostreatus (Jacq.) P. Kumm
70 11
Rice husk ash 18.149 12
66 Y. BULUT AND H. KARAER
adsorbent. Silanol groups on this surface become increasingly deprotonated as the pH of the adsorption system rises, thereby increasing the number of negatively charged adsorb-ent sites. Reduced adsorption of MB at acidic pH reflects the presence of excess Hþions that compete with dye cations for the adsorption sites.[28] The experimental results show that the pHPZCvalue of CCSB is 9.49.
4. CONCLUSION
In the present study, the removal of MB from aqueous solution was investigated by using as an adsorbent cross-linked CCSB. This adsorbent has been demonstrated to be highly effective for the removal of the cationic dye MB from aqueous solution. Both kinetics and thermodynamic parameters of the adsorption process were estimated. These data indicated an endothermic spontaneous adsorption pro-cess. Equilibrium experiments fitted well with the Langmuir isotherm model, and the maximum monolayer adsorption capacity for the MB was 95.24 mg g1at 298 K. The kinetic measurements showed that the process was rapid and followed a pseudo-second-order model. In conclusion, it can be said that the composite is quite effective adsorbents for the removal of MB from aqueous solution and has good potential for further application in effluent treatment.
REFERENCES
[1] Rafatullah, M., Sulaiman, O., Hashim, R., and Ahmad, A. (2010) J. Hazard. Mater., 177: 70–80.
[2] Santhi, T. and Manonmani, S. (2011) Clean Soil Air Water, 39: 162–170.
[3] Wang, L., Zhang, J., and Wang, A. (2011) Desalination, 266: 33–39.
[4] Liu, Y., Zheng, Y., and Wang, A. (2010) J. Environ. Sci., 22: 486–493.
[5] Chen, A.H. and Huang, Y.Y. (2010) J. Hazard. Mater., 177: 668–675.
[6] Ghosh, D. and Bhattacharyya, K.G. (2002) Appl. Clay Sci., 20: 295–300.
[7] Tan, I.A.W., Ahmad, A.L., and Hameed, B.H. (2008) J. Hazard. Mater., 154: 337–346.
[8] Huang, X.Y., Bu, H.T., Jiang, G.B., and Zeng, M.H. (2011) Int. J. Biol. Macromol., 49: 643–651.
[9] Tran, H.V., Tran, L.D., and Nguyen, T.N. (2010) Mater. Sci. Eng. C., 30: 304–310.
[10] Wan Ngaha, W.S., Teonga, L.C., and Hanafiaha, M.A.K.M. (2011) Carbohyd. Polym., 83: 1446–1456.
[11] Islek, C., Sinag, A., and Akata, I. (2008) Clean Soil Air Water, 36: 387–392.
[12] Chowdhury, A.K., Sarkar, A.D., and Bandyopadhyay, A. (2009) Clean Soil Air Water, 37: 581–392.
[13] Zanjanchi, MA., Sajjadi, H., Arvand, M., Mohammad-Khah, A., and Ghalami-Choobar, B. (2011) Clean Soil Air Water, 39: 1007–1013.
[14] Dinu, M.V. and Dragan, E.S. (2010) Chem. Eng. J., 160: 157–163.
[15] Wang, L., Zhang, J.P., and Wang, A.Q. (2008) Colloids Surf. A: Physicochem. Eng. Aspects, 22: 47–53.
[16] Wang, L. and Wang, A. (2007) J. Hazard. Mater., 147: 979–985.
[17] Won, S.L., Lee, H.C., Jeong, Y.G., Min, B.G., and Lee, S.C. (2009) Fiber. Polym., 10: 636–642.
[18] Lin, S.H., Juang, R.S., and Wang, Y.H. (2004) J. Hazard. Mater., B113: 195–200.
[19] Wei, J.M., Zhu, R.L., Zhu, J.X., Ge, F., Yuan, P., and He, H.P. (2009) J. Hazard. Mater., 166: 195–199.
[20] Crini, G. (2006) Bioresour. Technol., 97: 1061–1085. [21] Crini, G. and Badot, P.M. (2008) Prog. Polym. Sci., 33:
399–447.
[22] Bulut, Y., Akc¸ay, G., Elma, D., and Serhatlı, I.E. (2009) J. Hazard. Mater., 171: 717–723.
[23] Ngah, W.S.W., Ariff, N.F.M., and Hashim, A., and Hanafiah, M.A.K.M. (2010) Clean Soil Air Water, 38: 394–400.
[24] Aydin, A.H., Bulut, Y., and Yavuz, O¨ . (2004) Int. J. Environ. Pollut., 21: 97–104.
[25] Bulut, Y. and Yokus, B. (2007) Cell. Chem. Technol., 41: 443–450.
[26] Bulut, Y. and Aydın, H. (2006) Desalination, 194: 259–267. [27] Wan, M.W., Kan, C.C., Rogel, B.D., and Dalida, M.L.P.
(2010) Carbohydr. Polym., 80: 891–899.
[28] Almeida, C.A.P., Debacher, N.A., Downs, A.J., Cottet, L., and Mello, C.A.D. (2009) J. Colloid Interface Sci., 332: 46–53.
[29] Nandi, B.K., Goswami, A., and Purkait, M.K. (2009) Appl. Clay Sci., 42: 583–590.
[30] Dog˘an, M., Alkan, M., Demirbas, O¨ ., O¨zdemir, Y., and O¨ zmetin, C. (2006) Chem. Eng. J., 124: 89–101.
[31] Dog˘an, M., Alkan, M., Tu¨rkyilmaz, A., and O¨ zdemir, Y. (2004) J. Hazard. Mater., 109: 141–148.
[32] Bulut, Y. and Tez, Z. (2007) J. Hazard. Mater., 149: 35–41.
[33] Seki, Y. and Yurdakoc¸, K. (2006) Adsorption, 12: 89–100. [34] Wang, S., Boyjoo, Y., and Choueib, A. (2005) Chemosphere,
60: 1401–1407.
[35] Vadivelan, V. and Kumar, K.V. (2005) J. Colloids Interface Sci., 286: 90–100.
