Hectorite-Modified Sodium Alginate/γ-Cyclodextrin Microspheres with Tunable Interlayers for Dye Removal

Dye wastewater is characterized by its complex composition, high chromaticity, and significant toxicity, posing a major challenge in industrial wastewater treatment. Adsorption has emerged as an indispensable technology for dye removal due to its operational simplicity, environmental compatibility, and cost-effectiveness. In this work, a gel microsphere adsorbent (PS/P-γ-CD/Hec-XTAB) was prepared by incorporating sodium alginate with epichlorohydrin-crosslinked γ-cyclodextrin polymer and hectorite modified with cationic surfactants of varying chain lengths. The adsorbent was applied to remove typical cationic dyes─methylene blue (MB) and rhodamine B (RhB)─from aqueous solution. The optimized material, PS/P-γ-CD/Hec-CTAB0.4, exhibited a high specific surface area (374.7008 m2/g) and showed maximum adsorption capacities of 139.1564 mg/g and 122.663 mg/g for methylene blue and rhodamine B respectively at pH 7 and 25 °C. The adsorption kinetics followed a pseudo-first-order model, while equilibrium data were well described by the Langmuir isotherm. The process was found to be endothermic and spontaneous, mainly governed by hydrogen bonding, electrostatic interactions, host−guest encapsulation, and pore filling. Overall, this study presents an eco-friendly and economically viable adsorbent with promising potential for practical application in dye wastewater treatment.