Effect of Bromide Ions on the Transformation of Natural Organic Matter and the Formation of Halogenated Byproducts in the UV/chlorine Oxidation Process
Journal Title: Energy Environmental Protection - Year 2025, Vol 39, Issue 1
Abstract
The UV/chlorine advanced oxidation process (AOP), which generates various highly reactive radical species, effectively degrades micropollutants and inactivates microorganisms. The ubiquitous presence of natural organic matter (NOM) in water leads to the generation of chlorinated disinfection byproducts, while the presence of bromide induces the generation of brominated disinfection byproducts, which are known to pose threats to ecological safety and human health. However, research has primarily focused on conventional disinfection byproducts due to the complexities associated with NOM, the diversity of halogenated byproducts, and the limitations of analytical techniques. In this study, Fourier transform ion cyclotron resonance mass spectrometry (FT-ICR MS) was applied to elucidate the influence of bromide ions on the transformation of NOM and the generation of halogenated byproducts in the UV/chlorine AOP. The introduction of bromide in the UV/chlorine AOP facilitated the generation of hypobromous acid and bromine-containing radicals (such as Brâ¢, BrOâ¢, \begin{document}$\mathrm{Br}_2^{{\bullet} -} $\end{document}, and BrOHâ¢â). This alteration in radical speciation led to significant transformations of CHO compounds in NOM, particularly those with higher aromaticity. The newly generated CHO compounds were mainly tannin-like and alicyclic molecules rich in carboxyl groups. A total of 222 bromine-containing compounds (CHOBr) were detected after the UV/chlorine AOP. Compared with the CHOBr compounds detected in dark chlorination, these CHOBr compounds had significantly lower carbon numbers and AImod values. Analysis of the precursors of these CHOBr, considering both addition reactions (AR) and substitution reactions (SR) as pathways, showed that these precursors had low O/C ratios or high H/C ratios. These precursors were predominantly lignin-like compounds and highly unsaturated and phenolic compounds. The SR precursors had lower aromaticity compared to AR precursors. The majority of CHOBr compounds generated during chlorination were removed during the post-chlorination process, while most of the CHOBr compounds generated in the UV/chlorine AOP remained during the post-chlorination phase. In addition to CHOBr compounds, the number of CHOCl compounds identified in the UV/chlorine AOP in the presence of bromide ions was significantly lower than that in the absence of bromide ions. For example, there were 333 one-chlorine-containing compounds in the UV/chlorine AOP without bromide ions, but only 33 CHOCl1 compounds with the presence of bromide ions. Meanwhile, compounds containing both Cl and Br were also detected in this study. This study characterizes the formation of unknown brominated byproducts at the molecular level and elucidates the transformation mechanisms of their precursors. These findings highlight the importance of brominated byproducts and provide a reference for addressing critical issues in the practical application of the UV/chlorine AOP.
Authors and Affiliations
Xiaoxue RUAN,Yingying XIANG,Xin YANG,
Keywords
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- EP ID EP762196
- DOI 10.20078/j.eep.20241105
- Views 12
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