Advances in Treatment of Brominated Hydrocarbons by Heterogeneous Catalytic Ozonation and Bromate Minimization

Abstract

The formation of carcinogenic bromate ions is a constraint when ozone is used for the remediation of water containing brominated organic materials. With its strong oxidizing ability, ozone rapidly transforms bromide in aqueous media to bromate, through a series of reactions involving hydroxyl radicals. Several strategies, such as limiting the ozone concentration, maintaining pH < 6, or the use of ammonia or hydrogen peroxide were explored to minimize bromate generation. However, most of the above strategies had a negative effect on the ozonation efficiency. The advanced oxidation processes, using catalysts together with ozone, have proven to be a promising technology for the degradation of pollutants in wastewater, but very few studies have been conducted to find ways to minimize bromate formation during this approach. The proposed article, therefore, presents a comprehensive review on recent advances in bromate reduction in water by catalytic ozonation and proposes reaction mechanisms associated with the catalytic process. The main aim is to highlight any gaps in the reported studies, thus creating a platform for future research and a quest to find environment friendly and efficacious catalysts for minimizing bromate formation in aqueous media during ozonation of brominated organic compounds.

Keywords: bromate minimization; bromide; catalytic ozonation; metal oxides.

Figure 1

Bromate formation pathways [14].

Figure 2

Formation route for bromate.

Scheme 1

Reaction pathway for formation of protonated/deprotonated Fe-Co surface in water.

Scheme 2

Pathway for inhibition/formation of bromate in catalytic ozonation.

Scheme 3

Reaction pathways for bromate formation during Fe-Co catalysed ozonation and degradation of 2,4,6-TBP in water.