Green biopolymer stabilizer induced robust removal of vanadium (V) by sulfidated microscale zerovalent iron

Abstract

The in situ remediation of V(V) pollution in groundwater by the sulfidated microscale zero-valent iron (S-mZVI) is promising, while the practical application of S-mZVI faces a great challenge due to its gravitational sedimentation. Herein, we proposed an effective and environmentally friendly strategy to stabilize S-mZVI using xanthan gum (XG), and elucidated the mechanisms focused on the XG-induced stabilization, the removal of V(V) by S-mZVI and XG composites (S-mZVI@XG), and the XG-enhanced removal of V(V). First, S-mZVI@XG was fabricated with various XG concentrations, and the characterization confirmed the presence of the adsorbed and dispersed XG. Then, the stability of S-mZVI@XG was tested. It was found that as XG increased, the stability of S-mZVI@XG was improved due to electrostatic repulsion and steric-hinerance effect. Specifically, the settlement of S-mZVI@XG5 (XG = 5.0 g·L-1) was not found, and by contrast, more than 87.0 % of S-mZVI settled in 10 min. Finally, the application of S-mZVI@XG towards V(V) removal was studied. The results showed that the removal rate of V(V) reached 95.2 % by S-mZVI@XG5, greater than that by pristine S-mZVI (64.0 %). The reduction of V(V) to V(IV) and V(III) by Fe0, Fe2+, and S2- and the precipitation were major removal mechanisms. In addition, the XG-enhanced removal of V(V) was mainly ascribed to the stabilization and synergistic effects. These findings provided mechanical and technical insights into the practical application of stabilized S-mZVI for remediation of V(V) pollution in groundwater.