The multiple roles of chlorite on the concentrations of radicals and ozone and formation of chlorate during UV photolysis of free chlorine

Chlorine dioxide (ClO2) has emerged as a promising alternative to free chlorine for water disinfection and/or pre-oxidation due its reduced yields of chlorinated byproducts. ClO2 decomposes form chlorite (ClO2−), which influences the following advanced oxidation processes (AOPs) micropollutant abatement in drinking water. This study aims at investigating effects ClO2− on concentrations reactive species (e.g., radicals and ozone) formation chlorate UV/chlorine AOP. Results showed that concentration ClO· process remarkably decreased by 98.20–100.00% presence 0.1–1.0 mg·L−1 NaClO2. The HO· ozone 42.71–65.42% 22.02–64.31%, respectively, while Cl· was less affected (i.e., 31.00–36.21% reduction). overall were differentially impacted ClO2−’s multiple roles process. UV photolysis generated but not Cl·, or under relevant conditions. also competed with photons this effect minor (< 1.0%). radicals/ozone scavenging outcompeted above two lead decreasing species, consistency kinetic model predicted trends. reacted (ClO3−) perchlorate (ClO4−). played dominant role ClO3− formation. findings improved fundamental understanding inorganic byproduct other AOPs ClO2−-containing