Simultaneous Control of Chlorite and Micropollutants in Drinking Water through Far-UVC Photolysis

Developing chemical-free approaches for the simultaneous control of micropollutants and disinfection byproducts aligns with sustainable development initiatives. We herein demonstrate that far-UVC radiation (UV₂₂₂) effectively degrades chlorite─a regulated disinfection byproduct of chlorine dioxide─as well as micropollutants in drinking water. The fluence-based photodecay rate constants of chlorite at 222 nm are 2.03-, 21.44-, and 20.22-fold higher than those at 254 nm in buffered deionized water, tap water, and surface water, respectively. Such enhancement is attributed to the 1.62-fold higher molar absorption coefficient and 1.44-fold higher apparent quantum yield at 222 nm compared to those at 254 nm. During UV₂₂₂ photolysis of chlorite (1.0 mg L⁻¹) in buffered deionized water (pH 7.0), HO• (2.61 (±0.22) × 10⁻¹⁵ M), Cl• (4.89 (±0.13) × 10⁻¹⁶ M), and ClO• (3.26 (±0.97) × 10⁻¹⁵ M) are generated. The values are 1.75-, 0.92-, and 3.01-fold higher than those produced under 254 nm irradiation. Nitrate has a negligible effect on chlorite photodecay and radical generation at 254 nm but exhibits a significant promoting effect at 222 nm. Additionally, natural organic matter suppresses chlorate formation during the UV₂₂₂ photolysis of chlorite. The findings advance the understanding of chlorite photochemistry and provide a sustainable strategy for micropollutant abatement in water.