High-capacity selective removal of Sb(III) by magnetic molecularly imprinted polymers in water: Mechanistic insights from experiments and DFT calculations.

Selective removal of antimony(III)[Sb(III)] from aqueous environments remains challenging. Under circumneutral conditions, Sb(III) predominantly exists as the neutral species Sb(OH)3 and is poorly captured by conventional electrostatic adsorbents. A magnetic molecularly imprinted polymer (2-MMIP) was synthesized via surface imprinting on oleic acid-functionalized Fe3O4 nanoparticles, using 2-hydroxyethyl methacrylate as the monomer and Sb(III) as the template. The material exhibited a mesoporous core-shell structure and superparamagnetic properties, enabling magnetic separation within 3 s. 2-MMIP achieved a maximum Sb(III) adsorption capacity of 126.63 mg g-1. Adsorption followed pseudo-second-order kinetics, proceeded spontaneously and endothermically, and remained stable over pH 5.0-11.0. The material displayed selectivity for Sb(III) in the presence of competing metal ions, arsenite, and phosphate, and retained removal performance across five regeneration cycles. Effective Sb removal was confirmed in real mining wastewater without pH adjustment. FTIR and XPS analyses identified that hydroxyl and carbonyl groups within the imprinted cavities govern Sb(OH)3 binding through surface complexation. Density functional theory calculations revealed that the preorganized polymer cavity generates cooperative multi-site hydrogen bonding and charge transfer with Sb(OH)3 relative to isolated monomer binding. Collectively, these findings establish 2-MMIP as a selective, regenerable, and practically applicable material for Sb removal and recovery from complex aqueous matrices.