Inhibition of bromate formation by surface reduction in catalytic ozonation of organic pollutants over β-FeOOH/Al2O3

Abstract

BrO3− formation was investigated over β-FeOOH/Al2O3 during the catalytic ozonation of Br−-containing water. The effect of several representative compounds in aqueous environment such as 2,4-dichlorophenoxyacetic acid (2,4-D), phenazone (PZ), diphenhydramine (DP), amitrole (AMT) and Br−-containing raw drinking water was examined on the formation of BrO3−. No significant BrO3− formation and higher removal of total organic carbon (TOC) were observed during the catalytic ozonation of the tested samples except AMT. Moreover, it was found that the adsorbed BrO3− was reduced to Br−, which was greatly enhanced by the degradation of organics according to the order AMT<DP<PZ<2,4-D. The surface Fe(II) of β-FeOOH/Al2O3 was responsible for the reduction of BrO3− on the basis of in situ diffuse reflection UV–vis spectra and the determination of surface Fe(II) under different conditions. It was generated from the reaction of surface Fe(III) with HO2−/O2− during the catalytic ozonation of different pollutants. Furthermore, FTIR and GC–MS analysis verified that the complexation of surface Fe(III) with the oxygen-containing functional groups (OH, COOH) of pollutants or their intermediates enhanced the reaction of Fe(III) with HO2−/O2−, resulting in more surface Fe(II) to cause higher BrO3− reduction rate. The catalyst still showed effectiveness for the inhibition of BrO3− formation and TOC removal for a Br−-containing raw drinking water under the realistic conditions. These findings could be applied to the minimization of BrO3− formation in catalytic ozonation of Br−-containing drinking water.