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 (UV 254 ) to emerging Far-UVC at 222 nm (UV 222 ), 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 SO 4 •- 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 UV 222 /PDS AOP in surface water are predicted to be 1.94-13.71 times higher than those by the UV 254 /PDS AOP. Among the tested water matrix components, chloride and nitrate decrease SO 4 •- but increase HO • concentration in the UV 222 /PDS AOP. Compared to the UV 254 /PDS AOP, the UV 222 /PDS AOP decreases the formation potentials of carbonaceous disinfection byproducts (DBPs) but increases the formation potentials of nitrogenous DBPs.