The role of bromides upon electrochemical mineralization of bisphenol A with boron-doped diamond anode

Anodic oxidation with boron-doped diamond (BDD) has been regarded as outstanding option for wastewater treatment. However, in the presence of halide, the extreme promise of the technology may be hampered by the formation of toxic halogenated by-products. While the behaviors of chloride are relatively understood, little is currently known about the role of bromide and its effect on the generation of brominated transformation by-products (BTPs). Herein, we reported for the first time the bromide-mediated electrochemical mineralization of bisphenol A with BDD anodes. Firstly, we employed statistical methodology to determine the impacts of the main operating variables on the mineralization performance, and the novel and peculiar roles of bromides during the electrolytic oxidations were identified. Next, LC/MS analysis was used to identify the reaction intermediates, and plenty of BTPs (including oligomers of complex structures) were thus detected. Detailed transformation mechanisms responsible for the BTPs were also proposed. Lastly, we used ECOSAR program to determine the ecological toxicity of all detected by-products, and the structure-toxicity relation involved was discussed. Overall, the above results are of particular interest to understand BTPs formation mechanism in electrochemical oxidation processes, which as well provide guidelines to minimize potential risks of BDD technology for phenolic wastewater treatment.