Unraveling the enhancement of sulfidation on microscale zerovalent iron toward removal of vanadium(V) from groundwater

Abstract

Sulfidation has been regarded as an effective strategy to enhance the sequestration of contaminants by zerovalent iron (ZVI). However, the effect of sulfidation on ZVI for V(V) removal has not been explored, and the mechanism has not been fully elucidated. Here, this study evaluated V(V) removal by sulfidated microscale ZVI (S-mZVI) and sufficiently ascertained its underlying mechanism. First, the sulfidation of mZVI was studied and the characterization confirmed a uniformly-distributed FeSx shell fabricated on mZVI. Then, applying S-mZVI for V(V) removal was tested as a function of S/Fe molar ratios, pH, dissolved oxygen, and common anions. The greatest removal (98.1%) of V(V) was achieved by S-mZVI prepared under S/Fe of 0.05, 98 times higher than that by mZVI. The decreased pH showed a positive effect and V(V) removal reached 100% at pH 3.0. The common anions (Cl−, SO42−, NO3− and HCO3−) showed slight inhibition on V(V) removal. Finally, V(V) removal by S-mZVI was clarified to be mediated via a combined function of reduction from V(V) to V(IV) and V(III), adsorption, and precipitation. These findings provided valuable insights into applying ZVI materials for V(V) removal.