Enhanced inhibition of bromate formation in catalytic ozonation of organic pollutants over Fe–Al LDH/Al2O3

Abstract

Fe–Al layered double hydroxides (Fe–Al LDH, the molar ratio of Fe(II) to Fe(III) was about 1:10) was successfully supported and highly dispersed on mesoporous Al2O3 based on the X-ray diffraction (XRD) and X-ray photoelectron spectroscopy (XPS) analysis. Fe–Al LDH/Al2O3 was more efficient in inhibiting BrO3− formation and removing organic pollutant taking ozonation alone as control. Further investigation indicated that BrO3− reduction by surface Fe(II) was responsible to the complete inhibition of BrO3− formation. Fe(II) was reduced from the Fe(III)-intermediates complex via an electron transfer process and the reaction of Fe(III) and HO2−/O2− in catalytic ozonation. The amount of surface Fe(II) in catalytic ozonation of amitrole (AMT), phenazone (PZ) and 2,4-dichlorophenoxyacetic acid (2,4-D) was 0.34, 2.47 and 3.30μmol/g, which proved that most of Fe(II) was generated from the reaction of ozone and Fe–Al LDH/Al2O3 since 0.33μmol/g of Fe(II) existed within the catalyst. The increase of ozone amount and the formation of Fe(III)-intermediates complex could enhance the Fe(II) generation, leading to more efficient inhibition of BrO3− formation. Finally, Fe–Al LDH/Al2O3 still showed effectiveness in the inhibition of BrO3− and TOC removal for a raw drinking water under the realistic conditions, which could be applied to the BrO3− mineralization in catalytic ozonation of Br−-containing drinking water.