Impact of coexisting components in acid mine drainage on Sb(III) oxidation by biosynthesized iron nanoparticles*

Despite the oxidation mechanism of antimonite (Sb(III)) by biosynthesized iron nanoparticles (Fe NPs) has been reported, the impact of coexisting components in acid mine drainage (AMD) on the Sb(III) oxidation by Fe NPs is unknown. Herein, how the coexisting components in AMD affect Sb(III) oxidation by Fe NPs was investigated. Firstly, Fe NPs achieved complete oxidation of Sb(III) (100%), while only 65.0% of Sb(III) was oxidized when As (III) was added, due to competitive oxidation between As(III) and Sb(III), which was verified by characterization analysis. Secondly, the decline in solution pH improved Sb(III) oxidation from 69.5% (pH 4) to 100% (pH 2), which could be attributed to the rise of Fe3+ in solution promoting the electron transfer between Sb(III) and Fe NPs. Thirdly, the oxidation efficiencies of Sb(III) fell by 14.9 and 44.2% following the addition of oxalic and citric acid, respectively, resulting from the fact that these two acids reduced the redox potential of Fe NPs, thereby inhibiting Sb(III) oxidation by Fe NPs. Finally, the interference effect of coexisting ions was studied, where PO43-significantly reduced Sb(III) oxidation efficiency due to the occupation of the surface-active sites on Fe NPs. Overall, this study has significant implications for the prevention of Sb contamination in AMD.