Bromate formation on the non-porous TiO 2 photoanode in the photoelectrocatalytic system

Abstract

The increasing use of ozone in water disinfection processes has been the focus of considerable concern in regards to inorganic disinfection by product formation of bromate in waters containing bromide. Due to the public health risk caused by the presence of bromate as a suspected carcinogen, attention had been addressed to the conditions under which bromate is formed. In this study, photoanodic bromine generation and bromate ( BrO 3 - ) formation were investigated using a TiO 2 electrode in a photoelectrocatalytic (PEC) treatment process. The separation of anodic and cathodic reactions in the PEC system resulted in a pH decrease from 9.3 to 3.0 in the photoanode compartment and an increase to 11.0 in the cathode compartment. Under a photo-illumination intensity of 5.7 mW cm −2 UV, a biasing potential of +1.0 V vs SCE, a pH of 6.0 and at a NaBr concentration of 1.0 × 10 −2 M, active bromine formation increased over time with 2.4 × 10 −6 M min −6 rate and reached a steady-state concentration of 1.44 × 10 −4 M in 60 min. Bromate formation was detected after a lag-period of 15 min and exhibited a continuous increasing trend with respect to irradiation time. No bromate formation was observed below pH 6.5 whereas an increasing bromate concentrations and pH up to pH = 8.5 were noted.