Rate Constants and Mechanisms for Reactions of Bromine Radicals with Trace Organic Contaminants.

Environ Sci Technol

School of Environmental Science and Engineering, Guangdong Provincial Key Laboratory of Environmental Pollution Control and Remediation Technology, Sun Yat-sen University, Guangzhou 510275, China.

Published: August 2021

Bromine radicals can pose great impacts on the photochemical transformation of trace organic contaminants in natural and engineered waters. However, the reaction kinetics and mechanisms involved are barely known. In this work, second-order reaction rate constants with Br and Br were determined for 70 common trace organic contaminants and for 17 model compounds using laser flash photolysis and steady-state competition kinetics. The values ranged from <10 to (2.86 ± 0.31) × 10 M s and the values from <10 to (1.18 ± 0.09) × 10 M s at pH 7.0. Six quantitative structure-activity relationships were developed, which allow predicting additional unknown and values. Single-electron transfer was shown to be a favored pathway for the reactions of Br and Br with trace organic contaminants, and this was supported by transient spectroscopy and quantum chemical calculations. This study is essential in advancing the scientific understanding of halogen radical-involved chemistry in contaminant transformation.

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http://dx.doi.org/10.1021/acs.est.1c02313DOI Listing

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