Degradation of atrazine (ATZ) by ammonia/chlorine synergistic oxidation process

Chlorination is widely used for disinfection of water and wastewater. Ammonia/chlorine co-exposure can be easily achieved when ammonia is present in water. In this study, ammonia and chlorine showed synergistic effect on atrazine (ATZ) degradation. A degradation efficiency of 50.2% was obtained in 10 min with a Cl/N molar ratio of 1.6. By contrast, free chlorine and chloramines barely degraded ATZ. The synergistic effect involved formation of hydroxyl radicals ( OH) and reactive chlorine species. The radical concentrations followed the order of ClO (4.8 × 10 −13 M) >  OH (4.1 × 10 −13 M) >  Cl (3.0 × 10 −15 M). The dominant radical was OH (>80% contribution), followed by ClO (less than18% contribution), which had relatively lower reactivity with ATZ. The synergism was pH dependent, with OH largely suppressed by 98% when the pH was acidic or basic rather than neutral, resulting in a decrease in ATZ degradation. The transformation products detected indicated that ATZ degradation involved dealkylation and dechlorination–hydroxylation, and lower yields of oxidation byproducts were obtained by ammonia/chlorine synergistic oxidation process compared to direct chlorination.