Ultraviolet (UV)-based advanced oxidation processes (AOPs) are increasingly used for the degradation of micropollutants in water and wastewater. This study reports a novel UVA/chlorine dioxide (ClO2) AOP based on the photolysis of ClO2 using energy-efficient UV radiation sources in the UVA range (e.g., UVA-LEDs). At a ClO2 dosage of 74 μM (5.0 mg L–1 as ClO2) and a UV fluence at 47.5 mJ cm–2, the UVA365/ClO2 AOP generated a spectrum of reactive species, including chlorine oxide radicals, chlorine atoms, hydroxyl radicals, and ozone at a concentration of ~10–13, ~10–15, ~10–14, and ~10–7 M, respectively. A kinetic model to simulate the reactive species generation in the UVA365/ClO2 AOP was established, validated against the experimental results, and used to predict the pseudo-first-order rate constants and relative contributions of different reactive species to the degradation of 19 micropollutants in the UVA365/ClO2 AOP. Compared to the well-documented UVC254/chlorine AOP, the UVA365/ClO2 AOP produced similar levels of reactive species at similar oxidant dosages but was much less pH-dependent and required much lower energy input, with much lower formation of chloro-organic byproducts and marginal formation of chlorite and chlorate.

Degradation of micropollutants in water by a novel UVA/ClO2 advanced oxidation process

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