Sodium alginate grafted poly(N-vinyl formamide-co-acrylic acid)-bentonite clay hybrid hydrogel for sorptive removal of methylene green from wastewater

Abstract

The treatment of industrial effluents is highly desirable due to the presence of numerous toxic, non-biodegradable and water soluble dyes which adversely affect living organisms and the environment. Sorptive treatment of these contaminants by using hydrogel sorbents may be a fascinating approach due to facile operation, high efficacy, simple synthesis, rapid recovery and subsequent reuse of hydrogels. Therefore, a novel sodium alginate grafted and bentonite clay doped poly (N-vinyl formamide-co-acrylic acid-)[SA-g-p(VFA-co-AAc)/BC] hydrogel was fabricated from acrylic acid (AAc), N- vinyl formamide (VFA) and bentonite clay (BC). The percent swelling of hybrid material was comprehensively investigated at different pH in Milli-Q distilled water. The composite material absorbed water by Fickian diffusion and attained equilibrium in 23 h with corresponding maximum swelling capacity of 8049 %. The sorption potential of the anionic hydrogel was thoroughly inspected at pH 7 by using methylene green (MG) as a cationic probe dye in aqueous medium. During batch sorption experiments, conditions for maximum removal of MG were optimized by investigating the effect of agitation time, MG- concentration, solution temperature and pH. The resultant sorption data obeyed the pseudo second order kinetic and Langmuir isotherm models which unambiguously reflected chemisorption of MG onto the hybrid material owing to the ionic interaction of sorbent with the dye. The outstanding swelling (8049 %) and sorption capacities (2108 mg g−1) make the hybrid hydrogel a viable superabsorbent and sorbent for relevant industrial and environmental applications.