Chemical Engineering Journal 158 (2010) 393–401 Contents lists available at ScienceDirect Chemical Engineering Journal journal homepage: www.elsevier.com/locate/cej Adsorption of anionic dyes on chitosan grafted poly(alkyl methacrylate)s Vinod Kumar Konaganti a , Ramanjaneyulu Kota a , Satish Patil b , Giridhar Madras a,b,∗ a Department of Chemical Engineering, Indian Institute of Science, Bangalore, Karnataka 560012, India b Solid State and Structural Chemistry Unit, Indian Institute of Science, Bangalore, Karnataka 560012, India article info Article history: Received 16 November 2009 Received in revised form 3 January 2010 Accepted 4 January 2010 Keywords: Adsorption Kinetics Chitosan Chitosan grafting Poly(alkyl methacrylate)s abstract Chitosan grafted poly(alkyl methacrylate)s (namely chitosan grafted poly(methyl methacrylate) (ChgP- MMA), chitosan grafted poly(ethyl methacrylate) (ChgPEMA), chitosan grafted poly(butyl methacrylate) (ChgPBMA) and chitosan grafted poly(hexyl methacrylate) (ChgPHMA)) were synthesized and charac- terized by using FT-IR and 13 C NMR techniques. The adsorption batch experiments on these grafted copolymers were conducted by using an anionic sulfonated dye, Orange-G. A pseudo-second-order kinetic model was used to determine the kinetics of adsorption. The effect of grafting, effect of process variables and the effect of different sulfonated anionic dyes (Orange-G, Congo Red, Remazol Brill Blue R and Methyl Blue) on the adsorption kinetics was determined. The Langmuir and Freundlich models were used to fit the adsorption isotherms and from the values of correlation coefficients (R 2 ), it was observed that the experimental data fits very well to the Langmuir model. The values of the maximum adsorption capacity of the adsorbents follow the order: ChgPMMA > ChgPEMA > ChgPBMA > ChgPHMA > chitosan. © 2010 Elsevier B.V. All rights reserved. 1. Introduction Dye effluents discharged from textile and paper/pulp indus- tries are major sources of aquatic pollution. Several methods such as coagulation, biodegradation, adsorption, membrane separation, ion-exchange, incineration, etc. have been reported for waste water treatment. Among all these methods, adsorption is a both an effec- tive and economical method for the removal of dyes from aqueous solutions [1,2]. Even though the adsorption of dyes on to activated carbon is effective, its widespread use has been limited because of high cost and problems with its disposal [2]. Adsorption in presence of different biosorbent materials such as agricultural wastes, bacterial biomass and biopolymers have been reported in literature [3]. In particular, chitosan has proved to be an effective biosorbent for removing the dyes from aqueous solutions because of its non-toxicity, biocompatibility, biodegradability, anti- bacterial property and high sorption capacity [4]. Chitosan and their derivatives have a high affinity for adsorption towards reactive and disperse dyes [5–7]. A detailed review on dye removal from aque- ous solutions by adsorption using chitosan has been presented [1]. Chitosan is often grafted with polymers to improve its adsorp- tion and mechanical properties. Jayakumar et al. have presented a ∗ Corresponding author at: Department of Chemical Engineering, Indian Institute of Science, Bangalore, Karnataka 560012, India. Tel.: +91 80 22932321; fax: +91 80 23600683. E-mail addresses: giridhar@chemeng.iisc.ernet.in, giridharmadras@gmail.com (G. Madras). detailed review on graft copolymerized chitosan and their appli- cations [8]. Chitosan has been grafted with poly(acrylic acid) [9], poly(methacrylic acid) [10,11], poly(methyl methacrylate) [12] and modified with montmorillonite [13], -cyclodextrin [14], fatty acid glycidyl [15], and crosslinked with glutaraldehyde [16]. All these materials have been successfully used for the adsorption of metal ions and dyes. However, the effect of the alkyl group substituent of the grafted polymer on the adsorption kinetics has not been investigated. In the present study, a series of chitosan grafted poly(alkyl methacrylate)s has been synthesized and used for the adsorption of different types of sulfonated anionic dyes. The present study also determines the effect of process variables, grafting percentage and different dyes on the adsorption kinetics. 2. Experimental 2.1. Materials Chitosan (molecular weight of 300 kDa and 81% of degree of deacetylation) was purchased from Sigma Aldrich (USA) and used without any further purification. All the monomers methyl methacrylate (MMA), ethyl methacrylate (EMA), n-butyl methacry- late (BMA) and hexyl methacrylate (HMA) were purchased from Sigma Aldrich (USA) and used after washing with 5% alkali solution to remove phenolic inhibitor. Potassium persulfate from S. D. Fine Chemicals (India) and ascorbic acid from Sisco research laboratories (India) were used without further purification. Acetone and formic acid (90%) were obtained from Merck (India). The dyes, Orange-G 1385-8947/$ – see front matter © 2010 Elsevier B.V. All rights reserved. doi:10.1016/j.cej.2010.01.003