Ultraviolet (UV)-based advanced oxidation processes (AOPs) such as UV/hydrogen peroxide, UV/chlorine, and UV/persulfate are promising technologies to destroy a wide variety of organic compounds due to the formation of reactive radical species such as hydroxyl radicals, chlorine radicals, and sulfate radicals. However, the presence of background dissolved organic matter (DOM) can affect the performance of UV-based AOPs and decrease the efficiency of target organic compound degradations because of the interaction of photons and active radical species with background DOM. This study aims to understand the molecular level DOM transformation induced by UV irradiation and various reactive radical species. As a start, we used Suwannee River Fulvic and Humic Acids as DOM standard surrogates and studied the transformation of DOM induced by both photolysis and different radicals. A combination of a Thermo Scientific Orbitrap Elite Hybrid Ion Trap Mass Spectrometer in negative-ion mode and an ion chromatography provided the unique transformation of elemental ratios of H/C and O/C, double bond equivalence, and the formation of low molecular weight organic acids as transformation products. For example, an aliphatic portion of DOM was significantly transformed by hydroxyl and chlorine radicals and formed low molecular weight organic acids. In contrast, sulfate radicals selectively react with an aromatic component of DOM and destroyed the ring structure but did not produce low molecular weight organic acids. Steady-state concentrations of different radical species determined by different probe compounds provided quantitative insight into the contribution of each radical reaction. This is the first study that investigated the molecular-level DOM transformation during various UV-based AOPs.

Transformation of dissolved organic matter in engineered ultraviolet (UV) photolysis and UV-based advanced oxidation processes

255th National Meeting (2018)

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