Direct and indirect photolysis of triclocarban in the presence of dissolved organic matter

Abstract

Abstract Photolysis is an important attenuation pathway for the removal of wastewater effluent organic micropollutants from surface waters. In this work, direct and indirect processes leading to the degradation of the disinfectant, triclocarban were studied. Photo-irradiation experiments were conducted in water collected from Old Woman Creek (OWC) a tributary of Lake Erie near Huron, OH, USA and in solutions of fulvic acids isolated from the Suwannee River, Georgia, USA (SRFA), Old Woman Creek (OWCFA) and Pony Lake, Antarctica (PLFA). Photodegradation of triclocarban proceeded faster in the presence of all three fulvic acids relative to deionized water. PLFA, an autochthonous dissolved organic matter (DOM) was found to be more reactive than the other fulvic acids, while the mostly allochthonous SRFA exhibited the lowest reactivity toward triclocarban. The later observation can be in part explained by anti-oxidant moieties present in SRFA. Photosensitized triclocarban degradation in whole water DOM from OWC was entirely attributable to the fulvic acid fraction and suggests that this component is the most photo-reactive fraction of the DOM. Anoxic and methanol-quenched experiments revealed unexpected results whereby the former suggests oxidation through reaction with triplet DOM, while the later is indicative of reaction with photo-generated hydroxyl radicals. It is possible that methanol can quench excited DOM species, which would shut down the triplet oxidation pathway. Finally, we observed no enhancement of triclocarban-photosensitized degradation through the addition of iron.

Keywords

• triclocarban
• photolysis
• DOM