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

BrO3- formation was investigated over beta-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 beta-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 center dot-/O-2(center dot-) 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 center dot-/O-2(center dot-), 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. (C) 2013 Elsevier B.V. All rights reserved.