Solar Activation of Peroxymonosulfate by Chromophoric Dissolved Organic Matter Enables Predictable Micropollutant Attenuation in Real Waters

Abstract

Solar-driven activation of peroxymonosulfate (PMS) is a promising advanced oxidation process for water and wastewater treatment; however, the kinetics of emerging contaminant removal in real water matrices remain poorly understood. In this study, we investigated PMS photosensitization in three environmentally relevant water matrices and evaluated its role in the abatement of 42 pharmaceuticals and personal care products (PPCPs). Under simulated solar irradiation, CDOM promoted PMS transformation and generated multiple photochemically produced reactive intermediates (PPRIs). A multiple-probe chemical method was employed to quantify the cumulative exposure doses of HO•, SO4•–, Cl2•–, CO3•–, and 1O2. Across the tested matrices, PPRI exposure doses followed the order CO3•– > 1O2 > Cl2•– ∼ SO4•– > HO•. The measured PPRI exposure doses, together with second-order rate constants, reasonably predicted PPCP removal in the solar/PMS/CDOM system. For several phenolic and aniline-containing PPCPs, DOM-mediated inhibition was observed and was attributed to reductive back-reaction of one-electron oxidation intermediates; incorporating inhibition factors improved the agreement between calculated and experimental removal efficiencies. Furthermore, four commonly detected PPCPs, sucralose, metformin, caffeine, and carbamazepine, were first identified as practical indicator compounds for estimating PPRI exposure without adding external probe chemicals. These findings provide a mechanistic framework for predicting PPCP attenuation during solar/PMS treatment in CDOM-rich waters and highlight the importance of secondary radicals in real aquatic matrices.