Transformation of 2,4,6-tribromophenol in the acetylperoxyl radical based oxidation process and formation of brominated byproducts

Abstract

Acetylperoxyl radical (CH3C(O)OO•), as a peracetic acid (PAA) derived specific radical, has a promising future in environmental remediation. However, the research about the transformation mechanism of halogenated organics with CH3C(O)OO• and the subsequent formation of disinfection byproducts (DBPs) is still in the gap stage. 2,4,6-tribromophenol (2,4,6-TBP) was chosen as a target brominated compound to study its transformation and the formation mechanism of brominated byproduct in the neutral Co(II)/PAA system. The results showed that 94.7 % of 2,4,6-TBP with 50 µM was transformed and its corresponding pseudo-first-order kinetic constant is about 0.540 min−1. Interestingly, CH3C(O)OO• and reactive bromine species were found to dominate 2,4,6-TBP transformation. 2,4,6-TBP had the best transformation under neutral conditions· H2O2, HCO3–, and natural organic matter (NOM) significantly inhibited 2,4,6-TBP transformation, while Cl− had little effect on 2,4,6-TBP transformation. In addition, the main transformation pathways of 2,4,6-TBP, including debromination, C–C coupling, self-coupling, and CH3C(O)OO• cross-coupling were proposed based on the analysis of transformation products by LC-MS/MS and DFT theoretical calculations. In identified intermediates, there are some DBPs, including bromate, bromoform, and dibromoacetic acid. These DBPs increased gradually in approximately 24 h, moreover, Suwannee River NOM improved DBPs production. Therefore, the formation mechanism of DBPs during the treatment of brominated organics with CH3C(O)OO• was proposed for the first time, which extended the theory of the formation mechanism of DBPs in CH3C(O)OO•-based water treatment.