Insights into DOM-Enhanced Periodate Degradation of Emerging Contaminants: The Organic Fenton-like Reactions

Emerging contaminants (ECs) pose ecological and health risks due to their persistence and bioaccumulation in aquatic environments. However, the effectiveness of chemical treatment processes for EC degradation is often hindered by the presence of dissolved organic matter (DOM) in real water systems. This study revealed that DOM enhanced the degradation of ECs such as bisphenol A in the DOM-mediated periodate (PI) oxidation system at neutral pH. The degradation of ECs followed biphasic pathways-an initial fast phase (<5 min) and a subsequent slowdown phase (>5 min). The ECs' degradation efficiency increased by 3 to 9 times with 20 mg_C L^-1 DOM present compared to that without DOM. In the DOM-mediated PI oxidation system, hydroxyl radicals (HO^•) were identified as the primary reactive species, with quantum chemical calculations confirming their generation via organic Fenton-like reaction pathways. The electron-donating moieties in DOM, such as hydroquinone, activated PI via single electron transfer and hydrogen transfer reactions, trigging rapid generation of HO^• in the initial fast phase. In the subsequent slowdown phase, PI activation was sustained by semiquinone-type radicals and dihydroxy-phenol derivatives formed from the initial reactions. This biphasic activation mechanism collectively enabled effective EC degradation throughout the oxidation process. This study reveals a novel PI activation pathway and provides theoretical guidance for the application of PI-based oxidation treatment processes in real water systems.