Ultraviolet photolysis of chlorine (UV/chlorine), an emerging advanced oxidation process (AOP), has multiple functions for the control of contaminants via the production of hydroxyl radicals (HO*) and reactive chlorine species (RCS), such as Cl, ClO and Cl2–. This paper centers around the radical chemistry of RCS and HO* in different water matrices and their roles and mechanisms in the abatement of contaminants. The concentrations of Cl, ClO and Cl2– are comparable or higher than those of HO* (10-14 ~ 10-13 M). The reactivities of RCS are more selective than HO* with a broader range of second order rate constants (k). The k values of Cl* toward most aromatics are higher or similar as compared to HO*, while those of Cl2– and ClO are less reactive but more selective toward aromatics containing electron-donating functional groups. Their major reaction mechanisms with Cl* are electron transfer and addition, while those with ClO and Cl2– primarily involve electron transfer. As for aliphatics, their reactivities with both HO* and RCS are much lower than aromatics. The reaction mechanisms for most of them with Cl and Cl2– are hydrogen abstraction, except for olefins, which are addition. In addition, RCS greatly contribute to the inactivation of microbial contaminants.

Efficiency and mechanisms of oxidation and disinfection by the UV/chlorine process

Fall 2022 abstracts, posters, and presentations will launch in mid-September.

ACS Fall 2022

The official archive and repository for all ACS Meetings & Expositions abstracts and select posters or presentations.