Debromination of polybrominated diphenyl ethers (PBDEs) and their conversion to polybrominated dibenzofurans (PBDFs) by UV light: Mechanisms and pathways

Rui Wang; Ting Tang; Jianbing Xie; Xueqin Tao; Kaibo Huang; Mengyao Zou; Hua Yin; Zhi Dang; Guining Lu

doi:10.1016/j.jhazmat.2018.04.057

Debromination of polybrominated diphenyl ethers (PBDEs) and their conversion to polybrominated dibenzofurans (PBDFs) by UV light: Mechanisms and pathways

J Hazard Mater. 2018 Jul 15:354:1-7. doi: 10.1016/j.jhazmat.2018.04.057. Epub 2018 Apr 25.

Authors

Rui Wang¹, Ting Tang¹, Jianbing Xie², Xueqin Tao², Kaibo Huang¹, Mengyao Zou², Hua Yin³, Zhi Dang³, Guining Lu⁴

Affiliations

¹ School of Environment and Energy, South China University of Technology, Guangzhou 510006, China.
² School of Environmental Science and Engineering, Zhongkai University of Agriculture and Engineering, Guangzhou 510225, China.
³ School of Environment and Energy, South China University of Technology, Guangzhou 510006, China; The Key Lab of Pollution Control and Ecosystem Restoration in Industry Clusters, Ministry of Education, Guangzhou 510006, China.
⁴ School of Environment and Energy, South China University of Technology, Guangzhou 510006, China; The Key Lab of Pollution Control and Ecosystem Restoration in Industry Clusters, Ministry of Education, Guangzhou 510006, China. Electronic address: lutao@scut.edu.cn.

PMID: 29715617
DOI: 10.1016/j.jhazmat.2018.04.057

Abstract

Polybrominated diphenyl ethers (PBDEs) are typical flame retardant that have arose widely environmental concerns. Previous studies have found that PBDEs can generate lower BDEs and polybrominated dibenzofuran (PBDFs) under UV exposure, but these two processes were not well understood. In this study, we have investigated them through the case study of three BDE congeners (i.e. BDE-29, BDE-25 and BDE-21), which all have an ortho-, a meta- and a para-bromine substituents. The results shows that the vulnerability rank order of brominated position for these three BDE congeners are totally different, the bromine substituent at each position (ortho-, meta- or para-) can be preferentially removed, indicating it is not scientific to summarize the debromination pathways of PBDEs by comparing the brominated position. The lowest unoccupied molecular orbital (LUMO) of PBDEs in first excited state are well consistent with their actual debromination pathways, suggesting it is a good descriptor to predict the photodebromination pathways of PBDEs. In addition, the PBDEs with an ortho-bromine substituent can generate lower PBDFs, and the first step is to generate lower BDEs with an ortho-carbon radical, followed by ring closure reaction to generate PBDFs.

Keywords: Debromination; PBDEs; PBDFs; Photolysis; Predicting descriptor.