Photosensitized Transformation of Peroxymonosulfate in Dissolved Organic Matter Solutions under Simulated Solar Irradiation

Sulfate radical (SO4 center dot-)-mediated advanced oxidation processes via peroxymonosulfate (PMS) activation have been extensively investigated. However, the phototransformation of PMS in sunlit dissolved organic matter (DOM) solution has not been previously examined. For the first time, the photosensitized transformation of PMS in DOM-enriched solutions under simulated solar irradiation was observed. The generation of reactive species, including O-1(2), SO4 center dot-, and (OH)-O-center dot, was confirmed by electron paramagnetic resonance and quantified by chemical probes. SO(4)(center dot- )was the primary reactive species generated via the reaction of excited triplet DOM ( 3 DOM*) with PMS. ((DOM)-D-3*) acted as a reactive reductant and was quickly oxidized by PMS, with an estimated reaction rate constant of (4.09 +/- 0.21) x 10(8) M-1 s(-1). Compared to 3 DOM*, one-electron-reducing DOM center dot- (DOM center dot-) was a minor contributor to the photosensitized transformation of PMS, and the contribution of DOM center dot- relied on the phenolic constituents. In addition, a series of different types of DOM center dot- including terrestrial DOM center dot- autochthonous DOM center dot- and effluent organic matter and its fractions, were employed to examine the photosensitized transformation kinetics of PMS. Overall, the photosensitized transformation of PMS by irradiated DOM could be a useful and economical approach to generate SO4 center dot- under environmentally relevant conditions.