Degradation of 2- (2-hydroxy-5-methylphenyl) benzotriazole (UV-P) by ferrate(VI): key factors, reaction pathway, and toxicity assessment

2-(2-Hydroxy-5-methylphenyl) benzotriazole (UV-P), a high-production and structurally complex benzotriazole derivative, has an uncertain degradation pathway and transformation dynamics in aquatic environments, raising concerns about its potential toxicological risks to human health and the ecological systems. This study investigated the oxidative degradation of UV-P by ferrate(VI) in aqueous solution under controlled experimental conditions. The results demonstrated that ferrate(VI) efficiently degraded UV-P under alkaline conditions, achieving a maximum removal efficiency of 91.76 % at pH 8.0. Furthermore, the influence of various environmental factors, including pH, oxidant dosages, inorganic ions (HCO 3 − , Cl − , Br − , NO 3 − , Ca 2+ , K + , Mg 2+ , and NH 4 + ), and humic acid, on the ferrate(VI)-mediated oxidative degradation of UV-P were systematically examined. The results indicated that although inorganic ions and humic acid partially inhibited the degradation process, a satisfactory degradation efficiency was still attained. The intermediate identification results indicated that the ferrate(VI)-mediated oxidative degradation of UV-P primarily proceeded via bond cleavage, oxygen atom transfer, and radical coupling reactions, resulting in the formation of cleavage products, hydroxylated derivatives, and polymeric compounds. The oxidative degradation pathway of UV-P and key reactive sites targeted in the ferrate(VI) degradation system were examined through quantum chemical methods, including analyses of atomic charge distribution and frontier electron density. The toxicity assessment highlighted the need to focus on the chronic toxicity of specific aminated degradation products. This study is essential for elucidating the degradation mechanism of the benzotriazole compound UV-P in aquatic environments and comprehensively assessing its potential biotoxicity.