Removal of methylene blue from water with montmorillonite nanosheets/chitosan hydrogels as adsorbent

In this work, self-assembled hydrogels were prepared with exfoliated montmorillonite nanosheets (MMTNS) and chitosan (CS) as the adsorbent for removing methylene blue (MB) from water. Adsorption properties were determined by studying the kinetics and thermodynamic of MB adsorption onto the hydrogels from aqueous solutions, and AFM, FTIR, SEM, and XPS were used for the characterization of the MMTNS and hydrogels. The experimental results have shown that the montmorillonite nanosheets/chitosan hydrogels were superb adsorbents for removing MB from water, reaching the maximum adsorption capacity of 530 mg/g. The adsorption well followed the pseudo-second-order kinetics and Langmuir isotherm, and was spontaneous endothermic. The adsorption of MB on the hydrogels could be easily realized through cation exchange and hydrogen binding. It was also found that the hydrogels prepared with lower solid concentration of MMTNS had a looser stratified structure and thus a greater adsorption capacity for MB in aqueous solutions.