Insights into the oxidation of bisphenol A by peracetic acid enhanced with bromide: The role of free bromine

Abstract

Peracetic acid (PAA) has received great attention in wastewater treatment as an alternative to free chlorine. However, wastewater constituents such as bromide (Br−) may affect the PAA-based oxidation process. In this study, we reported a detailed kinetic and mechanistic study on bisphenol A (BPA, 20 μM) oxidation by PAA in the presence of Br−. When the concentration of Br− was increased from 20 to 100 μM, the removal rate of BPA was significantly increased, which was attributed to the formation of secondary oxidant hypobromous acid. When BPA was treated with 5 mM PAA in the presence of 100 µM Br− at pH 7.0, ∼26 % of bromide was converted into organic bromine in 24 h. Brominated disinfection byproducts (Br-DBPs) accounted for ∼8.2 % of total organic bromine generated, among them the concentrations of bromoform (CHBr3), dibromoacetic acid (DBAA), and tribromoacetic acid (TBAA), were determined to be 0.94, 0.99, and 0.21 µM, respectively. A total of 23 transformation products were identified by high-resolution mass spectrometry (HRMS) analyses. Three transformation pathways, including CC (C1-C2 and C2-C4) bridge bond cleavage, phenyl ring bromination, and stepwise oxidation were proposed and rationalized by theoretical calculations. In conclusion, the presence of Br− can enhance the degradation efficiency of BPA in the PAA disinfection process; however, the formation of potentially carcinogenic brominated intermediates in Br−-containing wastewaters should be scrutinized.