Microwave Assisted Synthesis Of Chitosan-graft-styrene For Efficient Cr(VI) Removal

UJ Nanomaterials Science Research Group, Department of Chemical Technology, University of Johannesburg, P.O. Box 17011, Doornfontien 2028, Johannesburg, South Africa

Adv. Mater. Lett., 2010, 1 (1), pp 59-66

DOI: 10.5185/amlett.2010.4120

Publication Date (Web): Apr 08, 2012

Copyright © IAAM-VBRI Press

 E-mail: amishra@uj.ac.za, ajits@uj.ac.za

Abstract

In this study, we have synthesized chitosan-grafted-styrene (Ch-g-sty) without any radical initiator or catalyst using microwave (MW) irradiation. Ch-g-sty was synthesized with 187% grafting using 80 % MW power in 40 second at (styrene) 0.13 M, (Chitosan) 0.1 g/25 mL. On the other hand, under similar condition of concentration of styrene and chitosan, 148% grafting was observed with potassium persulphate (K₂S₂O₈)/ascorbic acid as redox initiator and atmospheric oxygen as co-catalyst in 1 h using conventional method at 35^oC. Microwave synthesized Ch-g-sty copolymer was characterized by Fourier transform-Infrared (FTIR) spectroscopy, thermo gravimetric analysis (TGA), X-ray diffraction (XRD) measurement and scanning electron microscopy (SEM). Maximum grafting was optimized by varying the microwave power, exposure time and styrene/chitosan concentration. Ch-g-sty copolymer was found to be more efficient for Cr(VI) removal as compare to conventionally and parent chitosan in aqueous solution. Sorption of Cr(VI) was depending upon pH and concentration, with pH=3 being the optimum value. The equilibrium data followed the Langmuir isotherm model with maximum capacities of 526.3 mg/g, 312.5 mg/g and 166.7 mg/g for Ch-g-sty copolymer, conventional (thermostatic water bath) method and parent chitosan respectively.

Keywords

Microwave irradiation, chitosan-graft-styrene, ascorbic acid,adsorption