Degradation of 1H-benzotriazole by UV/H2O2 and UV/TiO2: kinetics, mechanisms, products and toxicologyElectronic supplementary information (ESI) available. See DOI: 10.1039/c8ew00116b

Benzotriazoles are emerging contaminants widespread in environmental waters. As they are robust against conventional biological wastewater treatment, it is desirable to develop cost-effective and safe treatment methods for benzotriazole removal. The current study attempted to investigate the degradation of water dissolved 1 H -benzotriazole (1H-BTA) with UV/H 2 O 2 and UV/TiO 2 . Pseudo-first order degradation kinetics were observed in low power 280 nm UV/H 2 O 2 and UV/TiO 2 systems (UV intensity = 0.023 mW cm −2 , k app reached 1.63 × 10 −3 s −1 and 1.87 × 10 −3 s −1 , respectively), and radical oxidation was the dominant reaction mechanism with k &z.rad;OH-BTA at (7.1 ± 0.8) × 10 9 M −1 s −1 and (6.9 ± 0.7) × 10 9 M −1 s −1 . Both systems were affected by the pH value, natural organic matter and anions, leading to incomplete mineralization in actual water treatment processes. As the reaction proceeded, 1H-BTA was progressively transformed into eight organic products. The number of preliminary hydroxylated products ( e.g. C 6 H 5 N 3 O) increased rapidly at the early stage, while the further open-loop products ( e.g. C 4 H 3 N 3 O 4 ) were dominant at the later stage. Based on the proteomics analysis, the significant activation of ribosome, transporter and tricarboxylic acid cycle metabolisms in Escherichia coli , which exposed to the later degradation product mixture, suggested that the toxicity of 1H-BTA decreased. In conclusion, incomplete mineralization using hydroxyl radical oxidation likewise has potential for thedetoxification of 1H-BTA. Benzotriazoles are emerging contaminants widespread in environmental waters.