Advanced reduction of bromate by UV/TiO2-Bi process without external sacrificial agents: Mechanism and applications

Recently, the heterogeneous advanced reduction processes (ARPs) for bromate (BrO3-) degradation have attracted considerable attention due to its stable performance and easy combination with UV disinfection. In this study, a UV/TiO2-Bi advanced reduction process (ARP) was established for BrO3- removal without adding external sacrificial agents. In the UV/TiO2-Bi ARP, Bi nanoparticles (NPs) doped on the TiO2 acted as hole trapping centers, while TiO2 NPs were used as reduction centers for the reduction of BrO3-, which enhanced the charge carrier separation. The UV/TiO2-Bi-1% ARP exhibited the highest BrO3- removal rate without the addition of sacrificial agents in the reaction solution compared to UV/TiO2 ARP and the UV/TiO2-Bi ARP at other Bi/Ti ratios. The result of 72% removal of 200 µg/L BrO3- at 60 min by 0.2 g/L TiO2-Bi-1% in tap water at pH 6.8 and 7.71 mg/L dissolved oxygen (DO) demonstrates the promising potential of the UV/TiO2-Bi ARP for the removal of BrO3- in practical applications. Compared to the 99.5% removal in deionized (DI) water at 60 min, lower BrO3- reduction in tap water was likely attributed to the consumption of photo-generated electrons by NO3– and the adsorption of natural organic matter on the surface of TiO2-Bi-1% nanocomposites. The study provides not only a novel BrO3- removal system with good photo-reduction performance, but also some guidance for the influence of constituents in raw water on the treatment of BrO3-.