Chlorination and chloramination of benzophenone-3 and benzophenone-4 UV filters

The objective of this research was to explore the fundamental reactions between chlorine/chloramine and 2-hydroxy1-4-methoxyl benzophenone (BP3)/2-hydroxyl-4-methoxyl benzophenone-sulfonic acid (BP4), which were the most common reactions in benzophenone-type UV filters during drinking water treatment processes. Both BP3 and BP4 could react with free chlorine and chloramine, with reactions following pseudo-first-order kinetics in excess of chlorine (HClO) and chloramine (NH2Cl). Generally, chlorination was more rapid than chloramination. BP4 was less reactive than BP3 toward both chlorine and chloramine, due to the presence of an electron-accepting sulfonate group. Therefore, BP3 had a significantly higher disinfection by-products (DBP) formation potential than BP4. Chlorination of BP3 and BP4 generated remarkably higher levels of DBPs than chloramination, with high pH conditions facilitating the formation of chloroform but inhibiting the formation of haloacetic acid (HAAs). Comparison of the reaction behavior of two different BP-type UV filters, i.e., BP3 and BP4, revealed that certain functional groups significantly affected the reactivity of BP-type UV filters in chlorination and chloramination processes. This contribution may provide new insights into the reaction behavior of UV filters during drinking water disinfection process using chlorine and/or chloramine as disinfectant, and provide guidelines for drinking water safety management.