Synergistic adsorption and oxidation of Sb(III) from mining wastewater using hybrid ZIF-8-Fe nanoparticles: Performance and mechanisms

The increasing release of antimony (Sb) into water environments due to anthropogenic activities poses significant ecological risks. This study developed a novel hybrid material, zeolitic imidazolate framework-8-iron nanoparticles (ZIF-8-Fe NPs), which demonstrates a synergistic adsorption-oxidation mechanism for efficient removal of Sb(III) from aqueous solutions. Major findings reveal that at an initial Sb(III) concentration of 1 mg L-1, ZIF-8-Fe NPs achieved a 73.3% removal efficiency within three hours through the dual processes of direct adsorption and oxidation of Sb(III) to Sb(V). Scanning electron microscopy-energy dispersive spectrometry (SEM-EDS), Fourier transform infrared spectroscopy (FTIR), and X-ray photoelectron spectroscopy (XPS) revealed that the removal mechanism involved both direct adsorption of Sb(III) by ZIF-8-Fe NPs and oxidation of Sb(III) to Sb(V), with two distinct morphologies of Sb adsorbed on the surface. The formation of covalent bonds (Zn-OH-Sb and Fe-O-Sb) was identified as the key factor in removing both Sb(III) and Sb(V) from aqueous solutions. The adsorption process conformed to the Langmuir adsorption isotherm and pseudo-second-order kinetics, with correlation coefficients (R²) of 0.959 and 0.999, respectively. The proposed mechanism suggests that the formation of Zn-OH-Sb and Fe-O-Sb covalent bonds plays a crucial role in Sb(III) removal. Significantly, ZIF-8-Fe NPs achieved removal efficiencies of 91.5% and 94.8% for Sb(III) at environmentally relevant concentrations of 100 µg L-1 and 20 µg L-1, in actual mining wastewater, demonstrating its practical applicability. This study establishes that ZIF-8-Fe NPs constitute an effective nanomaterial with significant potential for Sb(III) remediation in wastewater.