Far UV light in water treatment via producing reactive oxidative species

Abstract Far UV light at 222 nm (UV 222 ) is gaining much attention for water treatment due to its high disinfection efficiency and safety to human, and the mechanism is deemed direct photolysis. We found that UV 222 is much more efficient than UV 254 for the abatement of 18 organic micropollutants and inactivation of pathogens, and the phenomenon is related to the production of reactive oxidative species (ROS). Multiple ROS are identified, including hydroxyl radical (HO • ), singlet oxygen ( 1 O 2 ), superoxide radical anion ( • O 2 − ) and ozone (O 3 ). The degradation of micropollutants is mainly due to HO • , which results from water homolysis and oxygen (O2) photodissociation. The quantum yield of HO• is 0.893, and the concentration of HO • reaches 10 -13 M under neutral conditions. This study is the first that reports the efficient production of ROS upon UV 222 photolysis, which facilitates chemical-free advanced oxidation processes in water.