Degradation of atrazine by ionizing radiation coupled with persulfate oxidation: Mechanism, pathway and toxicity assessment

Abstract

The ubiquitous existence of atrazine (ATZ) in aquatic environments has aroused intense concerns, regarding its potential harmful effects on human health and ecology safety. Ionizing radiation has now drawn increasing attention in wastewater treatment. However, its unsatisfactory mineralization performance has significantly hindered the practical applications. Herein, the gamma radiation combined with persulfate oxidation (gamma/PS) system has been innovatively engineered to facilitate the removal of ATZ. Results showed that ATZ (10 mg/L) can be completely removed by gamma radiation with 1.0 kGy dose, and the pseudo-first-order kinetic model provided an good fit for the degradation. Gamma radiation can effectively remove ATZ with initial concentrations ranging from 5–20 mg/L, over a broad pH range (3.2–10.5), with the co-existence of inorganic anions (including CO32-, NO3-, and SO42-) and humic acid, and in actual waters (tap water and surface water). Degradation pathways of ATZ were proposed according to density functional theory (DFT) calculation and LC-MS analysis, including alkylic-hydroxylation, alkylic-oxidation, and dechlorination-hydroxylation. Moreover, gamma radiation was promising to reduce the toxicity of ATZ. Compared with the gamma radiation alone process, the gamma/PS system exhibited satisfactory ATZ removal performance. The k value rose by 4.78 times when PS (1 mM) was added, and TOC removal efficiency increased from 6.48 % to 34.53 % when PS was 4 mM. •OH and SO4•- participated in ATZ degradation, with •OH dominating. These results demonstrated that gamma/PS is a potential approach to degrade ATZ.