Bromide (Br–) is ubiquitous in aquatic environment. Bromine atoms (Br*) and dibromine radical ions (Br2*–) can be thus generated through multiple routes in environmental relevant waters. The interactions of Br* and Br2*– with dissolved organic matter (DOM) affect the removal efficiency of micropollutants, and potentially yield undesirable brominated byproducts in advanced oxidation processes (AOPs). However, the kinetic information for reactions of Br* and Br2*– with DOM, and the radical–induced formation of brominated byproducts have been rarely reported. These gaps were systematically explored in the present work. The second–order reaction rate constants of dozens DOM isolates with Br* and Br2*– were determined using both laser flash photolysis and steady–state UV irradiation. DOM showed high reactivity toward Br* with rate constants from 8.75×107 to 5.47×108 MC–1s–1 (7.29×103 to 4.56×104 mgC–1 L s–1). The reaction rate constants between Br2*– and DOM ranged from 1.15×105 to 2.25×106 MC–1s–1 (10 to 187 mgC–1 L s–1). DOM with higher aromatic carbon contents (SUVA254), higher electron-donating capacity (EDC) and lower E2/E3 values exhibited higher reactivity toward Br2*–. By using laser flash photolysis, the formation of brominated organic byproducts during reactions of DOM with Br* and Br2*– were quantified, and the formation mechanism involved were investigated. This study provides fundamental data for the modeling prediction of both micropollutant removal and brominated organic byproducts formation in AOPs.

Reactivity of Br* and Br2*– with dissolved organic matter and the formation of brominated organic byproducts

ACS Spring Meeting 2021

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