"Formation of Bromate During Ferrate(VI) Oxidation of Bromide in Water" by Xin Huang, Yang Deng et al.
 

Formation of Bromate During Ferrate(VI) Oxidation of Bromide in Water

Document Type

Article

Publication Date

7-1-2016

Journal / Book Title

Chemosphere

Abstract

Ferrate (VI) is traditionally recognized as a safe oxidant without production of disinfection byproducts (DBPs). However, here we detected probable carcinogenic bromate (BrO 3 - ) during ferrate(VI) oxidation of bromide (Br - )-containing water, and evaluated the effects of pH, ferrate(VI) dose, initial Br - concentration, and co-existing anions on the BrO 3 - formation. BrO 3 - was produced at a moderately-weakly acidic pH condition and in the absence of phosphate that was commonly applied as a buffer and stabilizing agent in previous ferrate(VI) studies. At pH 5.0, the produced BrO 3 - was increased from 12.5 to 273.8 μg/L with the increasing initial Br - concentration from 200 to 1000 μg/L at 10 mg/L Fe(VI), corresponding to an increase in the molar conversion ([BrO 3 - ]/initial [Br - ]) from 2.3% to 10.3%, in a bicarbonate-buffered solution. As pH increased to 7.0, the BrO 3 - concentration gradually dropped. The BrO 3 - production appeared to be associated with the oxidation by high valence iron species (i.e. Fe(VI), Fe(V) and Fe(IV)). Two key intermediate products (i.e. hypobromous acid/hypobromite (HOBr/OBr - ) and hydrogen peroxide (H 2 O 2 )) relevant to the bromate formation were identified. The production of HOBr, a requisite intermediate for the ensuing bromate formation, was indirectly validated through identification of bromine-containing trihalomethanes and haloacetic acids during ferrate oxidation in a natural water, though these bromo-organic DBPs produced were insignificant. Furthermore, the inhibition effects of various anions on the formation of BrO 3 - followed chloride < sulfate < silicate < phosphate. More H 2 O 2 was detected at higher phosphate concentration. It could reduce HOBr to Br - , thereby inhibiting the bromate formation.

DOI

10.1016/j.chemosphere.2016.04.093

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