Efficient Production of HO• and 3DOM* via Far-UVC Photolysis of Dissolved Organic Matter in Water

HO • and 3 DOM* that are photochemically produced from dissolved organic matter (DOM) affect the performance of UV-driven processes in water treatment. This study developed and applied a method to quantify the yields for HO • and 3 DOM* (expressed as ⌀ HO • and f TMP, respectively) from far-UVC (UV 222 ) photolysis of DOM. ⌀ HO • at 222 nm (0.64–0.82%) is 13–34 times higher than at 254 nm and 136–213 times higher than at >290 nm. f TMP at 222 nm (293–1011 M –1 ) is 3.6–8.4 times and 1.8–19 times greater than at 254 nm and >290 nm, respectively. Electron-accepting moieties (e.g., carbonyl-containing compounds) are likely the major precursors of 3 DOM* under UV 222 irradiation. Despite DOM’s light-screening and radical-scavenging effects, the high ⌀ HO • at 222 nm ensures that DOM has a negligible impact on HO • concentrations in the absence of other radical precursors (e.g., NO 3 – ). Concurrently, enhanced 3 DOM* generation accelerates the photosensitized activation of NH 2 Cl by 3-fold under UV 222 irradiation compared to UV 254 . Given the critical roles of HO • and 3 DOM* in micropollutant degradation, oxidant activation, and reactive species transformation, this work advances both the fundamental photochemistry and the practical application of far-UVC-driven water treatment technologies.