Removal of textile dyes from single and ternary solutions using poly(acrylamide-co-N-methylacrylamide) grafted katira gum hydrogel

A novel hydrogel poly(acrylamide-co-poly-N-methylacrylamide) grafted katira gum (KG) was synthesized via free radical copolymerization using a mixture of acrylamide and N-methylacrylamide in presence of N,N'-methylene-bis-acrylamide as a cross-linking agent. A series of hydrogels (KG-1 to KG-6) were prepared by varying amount of acrylamide and N-methylacryamide. Poly-acrylamide-g-katira gum (PAM-g-KG) and poly-N-methylacrylamide-g-katira gum (PNMA-g-KG) hydrogels were also prepared using same crosslinking agent. Swelling characteristics of all the prepared hydrogels in water were evaluated and the hydrogel with best swelling property (KG-6) was identified. The hydrogel KG-6 was characterized by FTIR, X-ray diffractometer, and scanning electron microscopy and was used for the adsorption of textile dyes namely methylene blue (MB), malachite green (MG), and congo red (CR) from single and ternary solutions. Adsorption dynamics, kinetics, isotherm, and thermodynamics of all the prepared hydrogels were studied in the ternary dye solutions. The sorption kinetics data were fitted well to pseudo-second order and the equilibrium adsorption data were found to follow Freundlich isotherm model. The thermodynamics studies showed that the adsorption process was spontaneous and exothermic in nature. The preferential dye adsorption by the hydrogel was followed in the order MB > MG > CR. (C) 2017 Wiley Periodicals, Inc.