Understanding Mechanism of Adsorption in the Decolorization of Aqueous Methyl Violet (6B) Solution by Okra Polysaccharides: Experiment and Theory

Optimal conditions for ultrasonic-assisted extraction of polysaccharide from Chinese okra were found using response surface methodology. The okra polysaccharide (OPS) was used for the adsorption of methyl violet 6B (MV). Conditions for maximal adsorption efficiency of MV were established. The mechanism of MV adsorption was investigated by the characterization and physicochemical analysis of OPS before and after the adsorption of MV. Both infrared (IR) analysis and molecular dynamics (MD) simulation suggest that MV adsorption by OPS was an electrostatic interaction between MV and oxygen-containing groups of OPS. Further, the results of first-principles calculation were in agreement with IR spectroscopy measurements and MD simulation, which were all consistent with the suggested adsorption mechanism. Optimization of okra extraction conditions, maximized efficiency of MV adsorption by OPS, and the understanding of the adsorption mechanism are the highlights of this work, providing a reference for promising applications of OPS in the treatment of wastewater in textile, paper, and other industries.