Activation of peroxymonosulfate by natural pyrite for efficient degradation of V(IV)-citrate complex in groundwater.

The V(IV)-organic complexes are difficult to be removed from water by the traditional water treatment processes due to their strong mobility, high stability, and possible formation of V(V) with stronger toxicity during oxidation. In this study, we applied a natural iron-based ore, pyrite, to catalyze peroxymonosulfate (PMS) activation assisted with alkali precipitation to remove V(IV) containing complexes. The effects of initial V(IV)-citrate concentration, PMS concentration, ore dosage and natural anions were comprehensively investigated using citric acid as a model ligand. Results showed that pyrite can effectively purify V(IV)-citrate. Specifically, 99.4 ± 0.4% of total vanadium and 73.6 ± 0.9% of total organic carbon are removed, and the pyrite maintained high catalytic activity after multiple uses. Characterization analyses revealed that free metal ions including Fe and V(IV) ions in the solution were removed by subsequent alkali precipitation. Radical quenching experiments indicated that sulfate radical (SO4•-) and hydroxyl radical (HO•) were generated and SO4•- is the primary reactive oxygen species. This study provides an effective strategy treating V(IV)-citrate complexes in contaminated water using low-cost natural ore.