Adsorptive removal of cationic dye by synthesized sustainable xanthan gum-g p(AMPS-co-AAm) hydrogel from aqueous media: Optimization by RSM-CCD model

Abstract

This research aims to treat toxic methylene blue (MB) dye from contaminated water due to its harmful effects on human health and the environment. For this purpose, xanthan gum-based hydrogel was prepared by grafting acrylamide (AAm) and 2-acrylamido-2-methly propane sulfonic acid (AMPS) onto xanthan gum (XG) with methylene bis acrylamide (MBA) as a crosslinking agent. With the introduction of sulfonate and carboxylate groups, the XG molecules were rearranged with better regularity, and based on rheology analysis; higher mechanical stability was approved. The central composite design (CCD) experimental design was used to evaluate the main and interaction effects of the independent hydrogel composition parameters (AMPS, AAm, and MBA concentration) and to derive a model from predicting optimization of the hydrogel composition to remove methylene blue (MB) dye. Accordingly, the concentrations of AAm (6 wt%), AMPS (4.09 wt%), and MBA (0.12 wt%) was found to be the optimum amount for the prepared pH-sensitive adsorbent to remove 98.85% of MB from an aqueous solution using CCD-RSM optimization. The fabrication of hydrogel and its interaction with monomers was specified by FTIR, TGA, rheology, FESEM, and ESEM techniques. The high porosity of hydrogel when swelled was confirmed based on ESEM images. A pseudo-first-order model and Langmuir isotherms best described the adsorption kinetics and adsorption equilibrium, respectively. The maximum equilibrium adsorption capacity of MB was obtained at 384.62 mg/g. The thermodynamic parameters indicated that the adsorption is endothermic and a process that increases irregularity. The hydrogel was regenerated for up to five cycles without significant reduction.