Hydrogel from crosslinked polyacrylamide/guar gum graft copolymer for sorption of hexavalent chromium ion

A new sorbent material based on guar gum (GG) was prepared by the polymerization grafting of acrylamide (Aam) onto guar gum, using potassium bromate/thiourea dioxide redox system for initiating the polymerization reaction. The so prepared polyacrylamide/guar gum graft copolymer (PAamGG) was further crosslinked with glutaraldehyde (GA) to obtain the sorbent material in the form of hydrogel. The so-obtained hydrogel was used for removal of hexavalent chromium ion (Cr(VI)) from its aqueous solution. Factors affecting metal sorption, such as pH, sorbent concentration, immersion duration and Cr(VI) solution concentration were extensively investigated. It was found from the study that the sorption of Cr(VI) by the hydrogel is pH-dependent and maximum sorption was obtained at pH 3. The sorption data obeyed Langmuir and Freundlich sorption isotherms. The Langmuir sorption capacity (Q(max)) was found to be 588.24 mg/g. Freundlish constants, K-F and n, were found to be 55.03 and 2.835, respectively. (C) 2011 Elsevier Ltd. All rights reserved.