Abatement of Structurally Diverse Micropollutants by the UV/Permanganate Process: Roles of Hydroxyl Radicals and Reactive Manganese Species

The UV/permanganate process was recently reported to be an innovative advanced oxidation process (AOP) that generates HO^• and reactive manganese species (RMnS) of Mn­(V). This study further identified that Mn­(V) is first generated by UV/permanganate, followed by its transformation into Mn­(III) and the final production of MnO₂. The UV/permanganate process was effective for the degradation of 26 structurally diverse micropollutants, with k_obs′ ranging from 0.05 to 1.8 min^–1. HO^• was active in the degradation of all micropollutants, while Mn­(V) was selective toward aromatics containing carboxylic groups. The roles of Mn­(III) and MnO₂ formed in situ were not important for the degradation of micropollutants under neutral conditions; however, under acidic conditions, in situ-formed MnO₂ was attributable to the abatement of phenolics, anilines, and propranolol as a catalyst of permanganate. HO^• was scavenged by water matrix components, such as (bi)­carbonate, bromide, and natural organic matter (NOM) while simultaneously forming CO₃^•–, Br^•/Br₂^•–, and Mn­(III)–NOM complexes that promoted micropollutant degradation. The electrical energy per order (EE/O) for 90% micropollutant transformation by UV/permanganate was comparable with that by UV/H₂O₂ in simulated drinking water. This study comprehensively elucidates the roles of HO^• and diverse RMnS in micropollutant degradation by UV/permanganate under practical conditions.