title: Bromide oxidation by ferrate(VI): The formation of active bromine and bromate.
abstract: Ferrate (VI) (abbreviated as Fe(VI)) has long been considered as a green oxidant that does not produce any known hazardous byproducts. However, this work shows that Fe(VI) can slowly oxidize bromide forming active bromine (HOBr/OBr(-)) and bromate, and in natural waters total organic bromine (TOBr) can also be detected. Results showed that the highest levels of active bromine and bromate were formed at lower pHs and in the absence of phosphate. Hydrogen peroxide, which forms from the reaction of Fe(VI) and water, plays an essential role in suppressing bromate formation by reducing active bromine back to bromide. Fe(VI) decomposition products (assumed to be particulate phase Fe(III)) can catalyze the decomposition of hydrogen peroxide by Fe(VI). Phosphate had a substantial inhibiting effect on the formation of active bromine, but less so on bromate formation. The presence of the raw water matrix in natural water suppressed bromate formation. For a natural water spiked with 0.1 mg/L of bromide, the bromate and TOBr concentrations after Fe(VI) oxidation were below 3.0 and 15 μg/L, respectively. No consistent trend regarding the effect of pH or buffer ions on TOBr formation was observed due to the competition between Fe(VI), hydrogen peroxide, and natural organic matter (NOM) for reaction with active bromine. Under environmentally relevant conditions, the formation of bromate and TOBr would not be a problem for Fe(VI) application as their concentration levels are quite low.
authors.affiliation: Department of Civil and Environmental Engineering, University of Massachusetts, Amherst, MA 01003, United States. Electronic address: yanjunj@umass.edu.
authors.forename: Yanjun
authors.initials: Y
authors.lastname: Jiang
authors.affiliation: Department of Civil and Environmental Engineering, University of Massachusetts, Amherst, MA 01003, United States; Department of Civil and Environmental Engineering, Worcester Polytechnic Institute, Worcester, MA 01609, United States.
authors.forename: Joseph E
authors.initials: JE
authors.lastname: Goodwill
authors.affiliation: Department of Civil and Environmental Engineering, University of Massachusetts, Amherst, MA 01003, United States.
authors.forename: John E
authors.initials: JE
authors.lastname: Tobiason
authors.affiliation: Department of Civil and Environmental Engineering, University of Massachusetts, Amherst, MA 01003, United States.
authors.forename: David A
authors.initials: DA
authors.lastname: Reckhow
mesh_terms: D001959:Bromates / Q000737:chemistry*; D001965:Bromides / Q000737:chemistry*; D001966:Bromine; D005290:Ferric Compounds; D010084:Oxidation-Reduction; D018508:Water Purification
chemical_list: D001959:Bromates; D001965:Bromides; D005290:Ferric Compounds; D001966:Bromine
keywords: Bromate; Bromine; Ferrate; Oxidation; Total organic bromine