Bromate Formation from Bromide Oxidation by the UV/Persulfate Process

• Published in: Environmental science & technology Vol. 46; no. 16; pp. 8976 - 8983
• Main Authors: Fang, Jing-Yun, Shang, Chii
• Format: Journal Article
• Language: English
• Published: Washington, DC American Chemical Society 21.08.2012
• Subjects: Acidity; Applied sciences; Biological and physicochemical phenomena; Bromates - chemistry; Bromides - chemistry; bromine; Chemical compounds; Chemical reactions; Drinking water and swimming-pool water. Desalination; Earth sciences; Earth, ocean, space; Engineering and environment geology. Geothermics; Exact sciences and technology; free radicals; Natural water pollution; organic matter; Oxidation; Oxidation-Reduction; photolysis; Pollutants; Pollution; Pollution, environment geology; sulfates; Sulfates - chemistry; Ultraviolet radiation; Ultraviolet Rays; Water treatment and pollution; Carcinogen; Ultraviolet radiation; Bromates; Pollutant formation; Bromides; Reaction mechanism; Oxidation; Water pollution; Photochemical reaction; Photooxidation
• ISSN: 0013-936X; 1520-5851; 1520-5851
• DOI: 10.1021/es300658u

Bromate formation from bromide oxidation by the UV/persulfate process was investigated, along with changes in pH, persulfate dosages, and bromide concentrations in ultrapure water and in bromide-spiked real water. In general, the bromate formation increased with increasing persulfate dosage and bromide concentration. The bromate formation was initiated and primarily driven by sulfate radicals (SO4 •–) and involved the formation of hypobromous acid/hypobromite (HOBr/OBr–) as an intermediate and bromate as the final product. Under the test conditions, the rate of the first step driven by SO4 •– is slower than that of the second step. Direct UV photolysis of HOBr/OBr– to form bromate and the photolysis of bromate are insignificant. The bromate formation was similar for pH 4–7 but decreased over 90% with increasing pH from 7 to above 9. Less bromate was formed in the real water sample than in ultrapure water, which was primarily attributable to the presence of natural organic matter that reacts with bromine atoms, HOBr/OBr– and SO4 •–. The extent of bromate formation and degradation of micropollutants are nevertheless coupled processes unless intermediate bromine species are consumed by NOM in real water.