Chitosan/smectite spheres for methylene blue removal: preparation and characterization

Effluent treatment and water body decontamination are pressing global challenges due to high water consumption and industrial effluent generation. This study focused on developing efficient, cost-effective adsorbents for the removal of methylene blue, a widely used dye known for its toxicity. Chitosan (CS) and smectite clay composites were prepared and characterized using FTIR, XRD, and pHpzc analyses. FTIR confirmed the preservation of the functional groups of both materials in the prepared composite, whereas the diffractograms indicated a superficial interaction, as evidenced by the absence of shifts in the diffractogram peaks. The point of zero charge pH on the surface of the CS/Clay-180 and CS/Clay-580 composites was evaluated as 8.5 and 8.4, respectively. Adsorption experiments covered a pH range of 3 - 11, exposure times of up to 600 min and dye concentrations from 5 - 350 mg L-1. Kinetic data followed first and second-order models, while the Freundlich model best described the experimental isotherms. Our composites exhibited excellent adsorption capacities, with maximum values of 45.4 mg g-1 for CS/Clay-180 and 42.7 mg g-1 for CS/Clay-580, at pH 10 and a contact time of 300 min. Therefore, the prepared CS/clay spheres proved to be effective and environmentally friendly adsorbents for the removal of methylene blue, contributing to the development of sustainable solutions for water purification.