Combination of oxidative and reductive effects of phenolic compounds on the degradation of aniline disinfection by-products by free radicals

Abstract

In this study, we selected 13 phenolic compounds containing -COOH, -CHO, -OH, and -COCH3 functional groups as model compounds for dissolved organic matter (DOM), and explored the redox reactions during the co-degradation of phenolic compounds with aniline disinfection by-products (DBPs) at the molecular level. When phenolic compounds and aniline DBPs were degraded, phenoxy radicals and aniline radicals were the most important intermediates. Phenoxy radicals can degrade aniline DBPs via hydrogen atom abstraction (HAA) reactions, and the reaction rates were related to the reduction potentials of the compounds. Compounds containing electron-withdrawing groups were more likely to oxidize aniline DBPs. Aniline DBPs were more easily degraded by phenoxy radicals when they contained electron-donating groups, and the increase in the number of chlorine atoms inhibited the reaction rates of aniline DBPs degradation by phenoxy radicals. Although phenolic compounds can reduce aniline DBPs, there was no significant correlation between the reaction rates and the reduction potentials of the compounds. Considering the redox effects of phenolic compounds on aniline DBPs, co-degradation simulations showed that phenolics inhibited the degradation efficiency of aniline DBPs. This work provided new insights into the transformation mechanisms and degradation efficiencies of DOM and aniline DBPs when they were co-degraded.