Oxidative debromination of 2,2-bis(bromomethyl)-1,3-propanediol by UV/persulfate process and corresponding formation of brominated by-products

Jianliang Sun; Yu Chen; Yingying Xiang; Li Ling; Jingyun Fang; Chii Shang

doi:10.1016/j.chemosphere.2019.04.168

Oxidative debromination of 2,2-bis(bromomethyl)-1,3-propanediol by UV/persulfate process and corresponding formation of brominated by-products

Chemosphere. 2019 Aug:228:735-743. doi: 10.1016/j.chemosphere.2019.04.168. Epub 2019 Apr 26.

Authors

Jianliang Sun¹, Yu Chen², Yingying Xiang², Li Ling², Jingyun Fang³, Chii Shang⁴

Affiliations

¹ School of Chemistry & Environment, South China Normal University, Guangzhou, China; Department of Civil and Environmental Engineering, The Hong Kong University of Science and Technology, Clear Water Bay, Kowloon, Hong Kong.
² Department of Civil and Environmental Engineering, The Hong Kong University of Science and Technology, Clear Water Bay, Kowloon, Hong Kong.
³ Guangdong Provincial Key Laboratory of Environmental Pollution Control and Remediation Technology, School of Environmental Science and Engineering, Sun Yat-Sen University, Guangzhou, China. Electronic address: fangjy3@mail.sysu.edu.cn.
⁴ Department of Civil and Environmental Engineering, The Hong Kong University of Science and Technology, Clear Water Bay, Kowloon, Hong Kong; Hong Kong Branch of Chinese National Engineering Research Center for Control & Treatment of Heavy Metal Pollution, The Hong Kong University of Science and Technology, Clear Water Bay, Kowloon, Hong Kong. Electronic address: cechii@ust.hk.

PMID: 31071560
DOI: 10.1016/j.chemosphere.2019.04.168

Abstract

This study investigated the oxidative debromination of 2,2-bis(bromomethyl)-1,3-propanediol (BBMP), a widely used brominated flame retardant, and the corresponding formation of brominated by-products by the UV/persulfate process. The debromination of BBMP by the UV/persulfate process was primarily driven by sulfate radicals (SO₄^-) at pHs 4.0-6.0 and hydroxyl radicals (HO) at pHs 9.0-12.0. The debromination rate increased with increasing pH from 4.0 to 9.0 and remained the same at pHs 9.0 and 12.0. Bromate was formed through the oxidation of bromide released from BBMP mainly by SO₄^-, with free bromine as a key intermediate. Bromate formation increased with increasing pH from 4.0 to 6.0, while it remarkably decreased with increasing pH from 6.0 to 12.0. This was mainly due to the transformation of SO₄^- to HO and also the quenching of bromine atoms that were the key intermediate for the formation of free bromine, by hydroxyl ions at the alkaline pH. In addition, the oxidative debromination of BBMP resulted in a significant decrease in the concentrations of total organic bromine, but the formation of brominated acetic acids and unknown brominated organic by-products. The concentrations of brominated organic by-products firstly increased and then decreased with prolonged reaction time. Also, the formation of brominated organic by-products and genotoxicity at pH 9.0 were much lower than that at pH 6.0. In this study, we propose that the UV/persulfate process under mildly alkaline conditions not only debrominates BBMP efficiently but also eliminates the formation of bromate and brominated organic by-products and genotoxicity.

Keywords: Advanced oxidation processes; Bromate; Brominated by-products; Brominated flame retardants; Debromination; Sulfate radicals.

MeSH terms

Bromates / chemistry
Bromides / chemistry
Bromine / chemistry
Flame Retardants* / radiation effects
Halogenation
Hydroxyl Radical
Oxidation-Reduction
Propylene Glycols / chemistry*
Propylene Glycols / radiation effects
Sulfates / chemistry
Ultraviolet Rays
Water Pollutants, Chemical / chemistry*
Water Pollutants, Chemical / radiation effects

Substances

Bromates
Bromides
Flame Retardants
Propylene Glycols
Sulfates
Water Pollutants, Chemical
sulfate radical
2,2-bis(bromomethyl)-1,3-propanediol
Hydroxyl Radical
Bromine