New insight into the mechanism of electro-assisted pyrite minerals activation of peroxymonosulfate: Synergistic effects, activation sites and electron transfer

In recent years, sulfur-doped modified iron-based catalysts have been widely used to activate peroxymonosulfate (PMS) or peroxydisulfate (PDS) for the contamination elimination, however, the manufacturing complicated and costly limit further industrial application. Therefore, a new water purification technology using pyrite activation PMS with electro-assisted is developed, and the parameters are adjusted and underlying mechanism is clarified. It has been found PMS is effectively activated by FeS 2 , achieving ~90% tetracycline hydrochloride (TCH) removal. Sulfide is the main electron donor for activation PMS and mediates the regeneration of Fe(II) on the pyrite surface, and different sulfur conversion intermediates such as short-chain polysulfides S n 2− , elemental sulfur S 0 , and sulfate form from the oxidation of sulfides (S 2 2− ). Moreover, the iron ions in-situ generation from pyrite activation PMS involve in TCH degradation, and concurrently is greatly affected by current, PMS and pH. The production of hydroxyl radicals ( OH) and sulfate radicals (SO 4 − ) by pyrite-activated PMS is confirmed by electron paramagnetic resonance (ESR) and quenching tests. Finally, the mechanism is proved electro-oxidation, non-radical-oxidation and radical-oxidation synergistically eliminate TCH in EC/PMS/pyrite system. Overall, this study provides a new horizons for heterogeneous activation PMS and unveils the advantages and potential applications of sulfur-containing iron-based activators.