Fe(IV)/Fe(V)-mediated polyferric sulfate/periodate system: A novel coagulant/oxidant strategy in promoting micropollutant abatement

Strategic modulation of the advanced oxidation processes for the selective oxidation of micropollutants has attracted accumulating attention in water decontamination. This study first reported the combination of the coagulant polyferric sulfate (PFS) and oxidant periodate (PI) to accomplish synergistic abatement of the antibiotic sulfamethoxazole (SMX). The oxidizing performance of SMX by this system was almost unaffected by coexisting water constituents, indicating the great promise of selective oxidation. Different from the current hydroxyl radicals (•OH)-mediated coagulant/oxidant systems (e.g., PFS/H2O2 and PFS/ozone), the dominance of high-valent Fe(IV)/Fe(V) intermediates was unambiguously verified in the PFS/PI treatment. The PFS colloids before and after the oxidation were characterized and the iron speciation was analyzed. The transformation of monomeric iron configurations (Fe(a)) to oligomeric iron configurations (Fe(b)) could maintain the homeostasis of surface-bound Fe(III) and Fe(II). The interaction mechanisms included the production of reactive species and dynamic reaction equilibrium for micropollutant degradation. Finally, the transformation pathways of SMX and carbamazepine (CMZ) in the PFS/PI system were postulated. Overall, this study provided a novel coagulant/oxidant strategy to achieve selective and sustainable water purification.