Dissolved organic matter (DOM) in aquatic, marine, or engineered water treatment systems is known to participate in important photochemical reactions via the formation of excited triplet states. Recent studies have shown that triplet-DOM can then react with halides, oxidizing them to generate radical halogen species. These radicals, in turn, may play an important role in the formation of disinfection byproducts, especially when utilizing ultraviolet (UV) light for advanced oxidation processes. Here, cationic fullerene derivatives and Rose Bengal are used as model triplet-sensitizers to investigate the effects of halides on photosensitization processes. Laser flash photolysis is used to measure the triplet lifetimes of fullerenes in the presence of halides. Electron paramagnetic resonance is used to identify and explore the halide radical species present. Photodegradation experiments of probe compounds are also used to estimate quantities of singlet oxygen or other radicals in the system. Further, MS2 bacteriophage inactivation will provide a microbiological indicator of the disinfection potential of radicals present. These results are considered in the context of disinfection byproduct formation and the prospective use chlorine photolysis as a novel advanced oxidation process. Finally, the assumptions of past studies utilizing cationic fullerenes with halide counter-ions are questioned and discussed.

Exploring the role of photoexcited triplet states in the formation of halide radicals: implications for advanced oxidation processes

2019 Spring National Meeting

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