Photolysis at the Speed of Light: Chemical Free Degradation of Trace Organic Contaminants by Bespoke Photolysis Using High Intensity UV LEDs

UV LEDs have demonstrated effectiveness in disinfection applications and proven suitability at scale for disinfection in municipal wastewater and drinking water. Technological advances in materials design and electrical efficiency have made high-intensity light delivery by UV C LEDs a reality and now poise these traditionally disinfection system to serve a dual purpose for targeted remediation of trace contaminants. This work investigated the effectiveness of UV C light emission tailoring on the photodegradation dynamics of select trace organic compounds (TrOCs). Degradation kinetics and quantum yields of target compounds under 275 nm irradiation were governed by molar absorbance and chemical structure, and kinetics followed estrone (E1) > tryptophan > caffeine ≈ pCBA > urea. Secondary experiments compared the efficacy of a 275 nm UV LED and medium-pressure mercury vapour (MP UV) system for photodegradation of two steroid estrogens, E1 & 17B-estradiol (17B-E2). Use of the 275 nm UV LED system substantially reduced fluence requirements to achieve 90% degradation of both compounds. LC-MS/MS analysis of E1 photodegradation products showed that the UV LED system was more effective in eliminating both the E1 and its associated photoproduct compared to the MP UV system. This work demonstrates the effective use of UV LEDs for tailored photolysis of TrOCs and provides evidence for their use potential in applications outside of water disinfection.