Minimizing bromate formation with cerium dioxide during ozonation of bromide-containing water

This work investigated the effect of several metal oxides including α-FeOOH, α-Fe₂O₃, γ-FeOOH, and CeO₂ on bromate formation potential (BFP) during ozonation of bromide-containing water. Results indicate that CeO₂ could most effectively minimize the BFP among these metal oxides taking ozonation alone as control. The BFP minimization by O₃/CeO₂ favored a relatively low Br^- concentration (i.e., <1.0 mg L^-1) and pH < 7. Water temperature ranging from 5 to 25 °C had no significant impact on the percent reduction of BrO₃^-. Further investigation indicates that the effective BFP minimization can be ascribed to neither the surface adsorption of BrO₃^- or Br^- on CeO₂ nor the surface reduction of BrO₃^- to HOBr/OBr^- by CeO₂. It seems to have relationship with the activity of surface Ce(IV) sites. The CeO₂ can lower the concentration of H₂O₂ which is formed during ozone decomposition and promotes BrO₃^- formation. Another possible reason for the BFP minimization is that the CeO₂ could possibly reduce BrO^{{radical dot}} to HOBr/OBr^- during the decomposition of H₂O₂.