Karaya gum-grafted-poly( N,N'-dimethylacrylamide) gel: A pH responsive potential adsorbent for sequestration of cationic dyes

Abstract A polysaccharide based hydrogel, Karaya gum grafted with N,N'-dimethylacrylamide (KG-g-PDMA) was synthesized and studied as single efficient adsorbent for removal of multiple cationic dyes from aqueous solution. The adsorbent material was synthesised via microwave assisted free radical polymerization process and was characterized by FTIR, TGA, BET and SEM techniques. Swelling studies of adsorbent was performed using buffer solutions of pH 4.0, 7.0 and 9.2 and the viability of KG-g-PDMA, as an adsorbent for removal of basic dyes, methylene blue (MB), crystal violet (CV), rhodamine (Rh B) and toluidine blue (TB) from aqueous solution has been studied. The effect of various parameters on dye adsorption has been investigated. The maximum dye adsorption capacities of the KG-g-PDMA for TB, MB, CV and Rh B were found to be 472.86, 468.38, 447.12 and 433.02 mg/g respectively which were appreciably high compared to other reported materials such as activated carbon, gypsum and Moroccan clay etc. The pseudo second order kinetic model and Freundlich isotherm models provide better correlation with the experimental data for the adsorption of all the dyes on KG-g-PDMA. The thermodynamic studies indicated the nature of dye adsorption to be endothermic and spontaneous. Desorption studies indicated that maximum desorption occurs at acidic pH conditions. Overall this work throws light on design and development of single efficient adsorbent material for the adsorption of multiple cationic dyes and possible reuse of the material.