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Accelerated Reduction of Bromate in Frozen Solution
journal contribution
posted on 2017-06-26, 00:00 authored by Dae Wi Min, Wonyong ChoiBromate is a common disinfection
byproduct formed during ozonation.
Reducing bromate into bromide can remove this toxic pollutant, however,
not many studies have been done for its environmental fate. In this
work, we demonstrate a new transformation pathway that bromate can
be efficiently reduced to bromide in frozen solution in the presence
of organic reductants like humic substances (HS). The results showed
that bromate in frozen solution could be removed by 30–40%
in dark condition and 80–90% in irradiation condition (λ
> 300 nm) in 24 h, while around 1% bromate was reduced in aqueous
solution. The bromate reduction by HS induced a partial oxidation
of HS, which was confirmed by X-ray photoelectron spectroscopic analysis
of the HS sample recovered from the frozen solution. Photoluminescence
analysis of HS revealed that the fluorescence quenching by bromate
was observed only with very high concentration of bromate (0.1–0.2
M) in aqueous solution whereas the quenching effect in frozen solution
was seen with much lower bromate concentration (5–100 μM).
The highly enhanced removal of bromate in ice is ascribed to the freeze
concentration effect that bromate and HS are concentrated by orders
of magnitude to accelerate the bimolecular transformation in the ice
grain boundary region. Freezing process in cold environments would
provide a unique chemical mechanism for the removal of persistent
bromate.
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Keywords
fluorescence quenchingice grain boundary regionhumic substancesbromate reduction300 nmPhotoluminescence analysisSolution Bromate24 hquenching effectdisinfection byproductFreezing processtransformation pathwaysolutionchemical mechanismX-ray photoelectron spectroscopic analysisHS samplefreeze concentration effect
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