Formation and control of bromate in sulfate radical-based oxidation processes for the treatment of waters containing bromide: A critical review.

Author(s) Guan, C.; Jiang, J.; Pang, S.; Zhou, Y.; Gao, Y.; Li, J.; Wang, Z.
Journal Water Res
Date Published 2020 Mar 16

Sulfate radical-based advanced oxidation processes (SR-AOPs) show a good prospect for effective elimination of organic contaminants in water due to the powerful oxidation capability and good adaptability of sulfate radical (SO). However, great concerns have been raised on occurrence of the carcinogenic byproduct bromate (BrO) in SR-AOPs. The present article aims to provide a critical review on BrO formation during bromine (Br)-containing water oxidation by various SR-AOPs. Potential reaction mechanisms are elaborated, mainly involving the sequential oxidation of bromide (Br) by SO to Br-containing radicals (e.g., bromine atom (Br•)) and then to hypobromous acid/hypobromite (HOBr/OBr), which acts as the requisite intermediate for BrO formation. Some key influencing factors on BrO formation are discussed. Particularly, dissolved organic matter (DOM) as a component ubiquitously present in aquatic environments shows a significant suppression effect on BrO formation, primarily attributed to the reduction of Br• by DOM to Br. The reaction of Br• with DOM can hardly produce organic brominated byproducts, while their formation is mainly due to the bromination of HOBr/OBr generated through nonradical pathways such as the direct reaction of Br with oxidants (e.g., peroxymonosulfate (PMS)) or other reactive species derived from catalytic activators (e.g., Co(III) in the Co(II)/PMS process). The debromination of brominated pollutants during their oxidation by SO results in the release of Br, which, however, is not further transformed to BrO until coexisting organic matters are mineralized nearly completely. Furthermore, possible strategies for control of BrO formation in SR-AOPs as well as the future research needs are proposed.

DOI 10.1016/j.watres.2020.115725
ISSN 1879-2448
Citation Water Res. 2020;176:115725.

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