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

Abstract

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 the 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 the removal of 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, respectively, in actual mining wastewater, demonstrating their practical applicability. This study establishes that ZIF-8-Fe NPs constitute an effective nanomaterial with significant potential for Sb(III) remediation in wastewater.