Far-UVC Photolysis of Peroxydisulfate for Micropollutant Degradation in Water

Increasing radical yields to reduce UV fluence requirement for achieving targeted removal of micropollutants in water would make UV-based advanced oxidation processes (AOPs) less energy demanding in the context of United Nations' Sustainable Development Goals and carbon neutrality. We herein demonstrate that, by switching the UV radiation source from conventional low-pressure UV at 254 nm (UV₂₅₄) to emerging Far-UVC at 222 nm (UV₂₂₂), the fluence-based concentration of HO^• in the UV/peroxydisulfate (UV/PDS) AOP increases by 6.40, 2.89, and 6.00 times in deionized water, tap water, and surface water, respectively, with increases in the fluence-based concentration of SO₄^•- also by 5.06, 5.81, and 55.47 times, respectively. The enhancement to radical generation is confirmed using a kinetic model. The pseudo-first-order degradation rate constants of 16 micropollutants by the UV₂₂₂/PDS AOP in surface water are predicted to be 1.94-13.71 times higher than those by the UV₂₅₄/PDS AOP. Among the tested water matrix components, chloride and nitrate decrease SO₄^•- but increase HO^• concentration in the UV₂₂₂/PDS AOP. Compared to the UV₂₅₄/PDS AOP, the UV₂₂₂/PDS AOP decreases the formation potentials of carbonaceous disinfection byproducts (DBPs) but increases the formation potentials of nitrogenous DBPs.