Influence of weak magnetic field and tartrate on the oxidation and sequestration of Sb(III) by zerovalent iron: Batch and semi-continuous flow study

Highlights: • Oxidation of Sb(III)-tartrate and Sb(III) in the Fe⁰-H₂O-O₂ system was studied. • WMF greatly enhanced Sb(III)-tartrate and Sb(III) removal by ZVI. • WMF also increased the removal capacity of Sb(III)-tartrate and Sb(III) by ZVI. • Tartrate significantly retarded Sb(III) removal by ZVI. • The mechanisms of the inhibiting effect of tartrate were clarified. - Abstract: The influence of weak magnetic field (WMF) and tartrate on the oxidation and sequestration of Sb(III) by zerovalent iron (ZVI) was investigated with batch and semi-continuous reactors. The species analysis of antinomy in aqueous solution and solid precipitates implied that both Sb(III) adsorption preceding its conversion to Sb(V) in solid phase and Sb(III) oxidation to Sb(V) preceding its adsorption in aqueous phase occurred in the process of Sb(III) sequestration by ZVI. The application of WMF greatly increased the rate constants of Sb_tot (total Sb) and Sb(III) disappearance during Sb(III)-tartrate and uncomplexed-Sb(III) sequestration by ZVI. The enhancing effect of WMF was primarily due to the accelerated ZVI corrosion in the presence of WMF, as evidenced by the influence of WMF on the change of solution and solid properties with reaction. However, tartrate greatly retarded Sb removal by ZVI. It was because tartrate inhibited ZVI corrosion, competed with Sb(III) and Sb(V) for the active surface sites, increased the negative surface charge of the generated iron (hydr)oxides due to its adsorption, and formed soluble complexes with Fe(III). The positive effect of WMF on Sb(III)-tartrate and uncomplexed-Sb(III) removal by ZVI was also verified with a magnetic semi-continuous reactor.