Disaccharide/UiO-66(Zr) composites for selective dye adsorption: synergistic mechanisms

The global water crisis demands the use of efficient adsorbents to remove carcinogenic synthetic dyes from industrial wastewater. This study developed composites of disaccharides (lactose, maltose, sucrose) with UiO-66(Zr) and systematically evaluated their adsorption performance towards both cationic (methylene blue, MB; malachite green, MG; rhodamine B, RhB) and anionic (methyl orange, MO; and Congo red, CR) dyes. Comprehensive characterization, including PXRD, FT-IR, BET, TGA, XPS and zeta potential, confirmed the successful formation of the disaccharide/UiO-66(Zr) composites. Compared to the removal of cationic dyes, the disaccharide/UiO-66 composites showed superior performance in adsorbing anionic dyes. Sucrose/UiO-66 showed particularly outstanding results, exhibiting adsorption capacities of 54, 56, 37, 154 and 287 mg/g for MB, MG, RhB, MO and CR, respectively. This is likely because lactose and maltose are reducing disaccharides, while sucrose is non-reducing. The reducing property governs the adsorption capacity for anionic dyes. Furthermore, based on adsorption kinetics data, the dye adsorption process of these materials follows the pseudo-second-order kinetic model, with adsorption mechanisms involving electrostatic interactions, π-π stacking, size-selective, and dual-mode regenerability. Thus, disaccharide/UiO-66(Zr) exhibits immense application potential in environmental pollutant removal and also provides a valuable reference for the preparation and application of other MOF composites.