Synthesis of chitosan cross-linked 3D network-structured hydrogel for methylene blue removal

TiO₂ loaded 2D montmorillonite (2DMMT)-chitosan-poly (acrylic acid) hydrogel with 3D network structure as a novel adsorbent for methylene blue (MB) removal was investigated. The hydrogel was formed via the polymerization and molecular forces between 2DMMT and polysaccharide. Physicochemical analysis and factor experiments were implemented on hydrogel. The results implied that hydrogel possessed a porous structure and high surface area, facilitating the access and removal of MB. A completely removal of MB could be achieved in a small hydrogel dose of 0.2 g/L within 120 min even after 5 regeneration cycles, which could lower costs and enhance efficiency dramatically. MB adsorption onto hydrogel was reasonably correlated with pseudo-second-order kinetic model and Redlich-Peterson isotherm model. MB adsorption mechanism onto hydrogel was analyzed by FTIR, EDS and XPS. It was found MB molecules reacted with carboxyl groups as well as substituted cation from 2DMMT. Such hydrogel could not only realize the green/sustainable application in water treatment, but also guide the preparation for polymer materials from polyelectrolyte and nanoclay.