Journal
ENVIRONMENTAL SCIENCE & TECHNOLOGY
Volume 55, Issue 15, Pages 10502-10513Publisher
AMER CHEMICAL SOC
DOI: 10.1021/acs.est.1c02313
Keywords
Br-center dot and Br-2(center dot-); trace organic contaminants (TrOCs); kinetics; quantitative structure-activity relationships (QSARs); transient absorption spectroscopy; single-electron transfer; advanced oxidation processes (AOPs)
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Funding
- National Key Research and Development Program of China [2017YFE0133200]
- National Natural Science Foundation of China [21876210]
- China Postdoctoral Science Foundation [2020M683055]
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This study determined the reaction kinetics parameters of bromine radicals in the photochemical transformation of trace organic contaminants in natural and engineered waters. It was found that bromine radicals mainly react with contaminants through a single-electron transfer pathway.
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-center dot and Br-2(center dot-) were determined for 70 common trace organic contaminants and for 17 model compounds using laser flash photolysis and steady-state competition kinetics. The k(Br)center dot values ranged from <108 to (2.86 +/- 0.31) x 10(10) M-1 s(-1) and the k(Br2 center dot)- values from <10(5) to (1.18 +/- 0.09) x 10(9) M-1 s(-1) at pH 7.0. Six quantitative structure-activity relationships were developed, which allow predicting additional unknown k(Br)center dot and k(Br2)center dot- values. Single-electron transfer was shown to be a favored pathway for the reactions of Br center dot and Br-2 center dot- 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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