Synchronous degradation of aqueous benzotriazole and bromate reduction in catalytic ozonation: Effect of matrix factor, degradation mechanism and application strategy in water treatment

Yuting Zhang; Haodong Ji; Wen Liu; Zhenbei Wang; Zilong Song; Yiping Wang; Chao Liu; Bingbing Xu; Fei Qi

doi:10.1016/j.scitotenv.2020.138696

Synchronous degradation of aqueous benzotriazole and bromate reduction in catalytic ozonation: Effect of matrix factor, degradation mechanism and application strategy in water treatment

Sci Total Environ. 2020 Jul 20:727:138696. doi: 10.1016/j.scitotenv.2020.138696. Epub 2020 Apr 15.

Authors

Yuting Zhang¹, Haodong Ji², Wen Liu², Zhenbei Wang¹, Zilong Song¹, Yiping Wang¹, Chao Liu¹, Bingbing Xu³, Fei Qi⁴

Affiliations

¹ Beijing Key Lab for Source Control Technology of Water Pollution, College of Environmental Science and Engineering, Beijing Forestry University, Beijing 100083, PR China.
² The Key Laboratory of Water and Sediment Sciences, Ministry of Education, College of Environmental Sciences and Engineering, Peking University, Beijing 100871, PR China.
³ State Key Laboratory of Environmental Criteria and Risk Assessment, Chinese Research Academy of Environmental Sciences, Beijing 100012, PR China.
⁴ Beijing Key Lab for Source Control Technology of Water Pollution, College of Environmental Science and Engineering, Beijing Forestry University, Beijing 100083, PR China. Electronic address: qifei@bjfu.edu.cn.

PMID: 32344259
DOI: 10.1016/j.scitotenv.2020.138696

Abstract

Ozone-based technologies are used for micro-pollutants removal in wastewater treatment. However, the generation of the toxic by-product bromate (BrO₃^-) is of a great concern. LaCoO₃ (LCO) catalytic ozonation has been used to overcome this significant drawback in the sole ozonation, achieving better BrO₃^- elimination efficiency. However, a key challenge is how to enhance micro-pollutant (benzotriazole, BZA) degradation efficiency and to eliminate formed BrO₃^- synchronously under various water qualities in drinking water or wastewater treatment. Therefore, the objective of this study is to propose a practical strategy of BZA removal and BrO₃^- reduction synchronously in water or wastewater treatment. In this study, important factors influencing BZA removal and BrO₃^- reduction were investigated, including [catalyst], [BZA], initial pH solution, [NH₄⁺-N] and [(bi)carbonate alkalinity]. Based on the performance and mechanism of these effects, a practical strategy for BZA degradation and BrO₃^- elimination with and without Br^- in the influent was developed. Additionally, the density functional theory (DFT) calculation successfully predicted the attack site on BZA by molecular ozone and formed hydroxyl radical (HO·) during LCO catalytic ozonation. Fukui indexes of f⁺ and f⁰ were calculated to forecast direct ozone molecule and HO· attack, respectively. Combination of DFT calculation with intermediates that identified through liquid chromatography-quadrupole time-of-flight mass spectrometry (LC-Q-TOF-MS), BZA degradation pathway was established more accurately. Additionally, four new intermediates were identified in this study. Overall, this study proposes a useful strategy for synchronous micro-pollutants degradation and BrO₃^- elimination, while also suggesting the feasibility of LCO catalytic ozonation for water or wastewater purification.

Keywords: Benzotriazole; Bromate; Catalytic ozonation; Matrix factor; Theoretical computations.