The removal of Sb from mine wastewater using biosynthesized Fe-Mn nanoparticles: Function and mechanism

Antimony (Sb) in mine wastewater poses a serious threat to surrounding ecosystems. In this study, biosynthesized iron-manganese nanoparticles (Fe-Mn NPs) were devised to remove Sb species. The resultant removal efficiencies were 100% for Sb(III) and 82.6% for Sb(V) utilizing a Sb(III) and Sb(V) concentration of 1mg·L-1. To understand the removal process, Fe-Mn NPs before and after exposure to Sb species were characterized by various advanced techniques, which indicated that while both Sb(III) and Sb(V) were adsorbed onto the surface of Fe-Mn NPs, Sb(III) was also partly oxidized to Sb(V). Furthermore, removal of both Sb(III) and Sb(V) followed pseudo-second-order kinetics and best fit the Freundlich adsorption isotherm model, suggesting that the removal process involved non-homogeneous chemisorption. These studies provided the evidence for an adsorption and oxidation mechanism for Sb(III) removal and an adsorption-dominated mechanism for Sb(V) removal by Fe-Mn NPs. When the produced Fe-Mn NPs were applied to remove Sb from mine wastewater, 92.7% removal was attained, demonstrating the significant practical potential of these nanoparticles to Sb species from mine wastewaters. This study provides novel insights for future exploration for Sb removal from mine wastewaters.