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.