New insights into bromate removal by UV/sulfite process: Influencing factors, mechanism, and energy efficiency

Abstract

In recent years, the UV/sulfite process has shown high superiority in removing toxic halogenated organic compounds and oxyanions. Herein, the reduction of bromate (BrO3ˉ) in this process was reinvestigated. The reduction of BrO3ˉ in this process was influenced by some key coexisting species. A significant inhibition on the reduction of BrO3ˉ was observed in the presence of dissolved oxygen (DO). Nevertheless, increasing sulfite dosage could effectively mitigate the negative impact of DO on the reduction of BrO3ˉ. Humic acid (HA) could influence the reduction of BrO3ˉ through the enhancement of hydrated electron (eaqˉ) yield or the scavenging of eaqˉ. It should be noted that the presence of Cl− and HCO3− had an insignificant influence on the reduction of BrO3ˉ. In this process, besides eaqˉ, sulfite radical (SO3•−) also contributed to the reduction of BrO3ˉ, which was evidenced by scavenging experiments and fitting of a kinetic model. Moreover, the energy efficiency of this process for BrO3ˉ removal was found to be enhanced by increasing sulfite dosage, as indicated by calculation of electrical energy per order (EE/O). Meanwhile, this process was proven to be economical for BrO3ˉ removal. This study might provide a new outlook on the UV/sulfite process for real applications.