Degradation of benzotriazole and benzothiazole with the UV-activated peracetic acid process: performance, mechanism and transformation pathway

• Published in: Environmental science water research & technology 2024-03, Vol.1 (4), p.982-994
• Main Authors: Lai, Webber Wei-Po, Gu, Fang-Yi, Tai, Wan-Lun, Tang, Zih-Syuan
• Format: Article
• Language: English
• Subjects: Aquatic environment; Aqueous environments; Benzene; Benzothiazole; Benzotriazole; Constants; Degradation; Dissolved organic matter; Hydroxylation; Kinetics; Oxidation; Peracetic acid; Photolysis; Rate constants; Reaction kinetics; Ring opening; Toxicity; Ultraviolet radiation; Wastewater
• ISSN: 2053-1400; 2053-1419
• DOI: 10.1039/d3ew00838j

Benzotriazole (BT) and benzothiazole (BTH) are two high-production chemicals that are recalcitrant and have been commonly detected in aquatic environments worldwide, posing potential threats to ecosystems. The main purpose of this study was to utilize the UV-activated peracetic acid (UV/PAA) process to degrade BT and BTH in aqueous environments and explore the reaction kinetics and mechanisms involved. Both BT and BTH were efficiently degraded by UV/PAA, with pseudo first-order rate constants ( k ) of 0.155 and 0.059 min −1 , respectively. The k values for BT and BTH decreased with increasing solution pH (3.0-11.0) and initial compound concentrations (0.04-0.24 mM), while k exhibited a positive and proportional relationship with the PAA dose (5-30 mg L −1 ). The degradation of BT and BTH via the UV/PAA reaction was mainly attributed to ·OH attack; UV photolysis, carbon-centered radicals (R-C·) and PAA oxidation also made contributions. The contributions of 1 O 2 to BT and BTH degradation were negligible despite the formation of 1 O 2 in the UV/PAA system. The effects of coexisting water components (dissolved organic matter, HCO 3 − , Cl − and NO 3 − ) and the impact of actual wastewater matrix on BT and BTH degradation were also investigated. During the UV/PAA reaction, BT was degraded into products through pathways involving i) hydroxylation, ii) triazole ring opening and iii) benzene ring opening, while BTH underwent a continuous hydroxylation reaction. The results from a toxicity assessment indicated that BT and BTH were degraded and decomposed into less toxic products with the UV/PAA process, demonstrating the potential of the UV/PAA reaction for BT and BTH removal from aqueous environments. The UV-activated peracetic acid process (UV/PAA) exhibited efficient degradation and detoxification of benzotriazole (BT) and benzothiazole (BTH). Detailed mechanistic insights into the UV/PAA degradation of BT and BTH have been thoroughly explored.