Simulation degradation of bromophenolic compounds in chlorine-based advanced oxidation processes: Mechanism, microscopic and apparent kinetics, and toxicity assessment

Mingxue Li; Zexiu An; Yanru Huo; Jinchan Jiang; Yuxin Zhou; Haijie Cao; Maoxia He

doi:10.1016/j.chemosphere.2021.133034

Simulation degradation of bromophenolic compounds in chlorine-based advanced oxidation processes: Mechanism, microscopic and apparent kinetics, and toxicity assessment

Chemosphere. 2022 Mar;291(Pt 3):133034. doi: 10.1016/j.chemosphere.2021.133034. Epub 2021 Nov 22.

Authors

Mingxue Li¹, Zexiu An¹, Yanru Huo¹, Jinchan Jiang¹, Yuxin Zhou¹, Haijie Cao², Maoxia He³

Affiliations

¹ Environment Research Institute, Shandong University, Qingdao, 266237, PR China.
² Institute of Materials for Energy and Environment, School of Materials Science and Engineering, Qingdao University, Qingdao, 266071, PR China.
³ Environment Research Institute, Shandong University, Qingdao, 266237, PR China. Electronic address: hemaox@sdu.edu.cn.

PMID: 34822870
DOI: 10.1016/j.chemosphere.2021.133034

Abstract

Chlorine-based advanced oxidation processes (AOPs) have been extensively studied to remove contaminants through generating HO^• and reactive chlorine species, including ClO^• and Cl^•. In this work, 2,4,6-tribromoanisole (246TBA) and 2,4,6-tribromophenol (246TBP) were selected as model to investigate the reaction mechanisms and micro-kinetics of brominated contaminants with HO^•, ClO^• and Cl^• in chlorine-based AOPs. Also, the apparent degradation kinetics of two compounds were simulated at pH 3.0-9.5 under UV/H₂O₂, UV/chlorine and UV/NH₂Cl. Calculated results showed that neutral 246TBA and 246TBP exhibited similar reactivity to HO^• and ClO^•, which was different from anionic 2,4,6-tribromophenolate (246TBPT): radical adduct formation (RAF) and H atom abstraction (HAA) were predominant mechanisms for the HO^• and ClO^• initiated reactions of 246TBA and 246TBP, while RAF and single electron transfer (SET) for 246TBPT; the reaction rate constants of 246TBA and 246TBP with HO^• and ClO^• were lower than 10⁷ M^-1 s^-1, and such rate constants dramatically increased to 10¹⁰ M^-1 s^-1 once 246TBP was deprotonated to 246TBPT. The apparent degradation kinetics of 246TBA at pH 3.0-9.5 was simulated in the order of UV/NH₂Cl > UV/chlorine > UV/H₂O₂, and UV/chlorine and UV/NH₂Cl were more effective for the removal of 246TBP and 246TBPT than UV/H₂O₂. UV and/or Cl^• dominated 246 TBA degradation under three AOPs. The main radicals mediating 246TBP and 246TBPT degradation are respectively HO^• under UV/H₂O₂, ClO^• under UV/chlorine, and HO^• and Cl^• under UV/NH₂Cl. The transformation products of 246TBA, 246TBP and 246TBPT, especially methoxylated and hydroxylated polybrominated diphenyl ethers (MeO-PBDEs and HO-PBDEs), were still toxic pollutants.

Keywords: Chlorine oxide radical; Chlorine radical; Density functional theory; Hydroxyl radical; UV/Chloramine; UV/Chlorine.

MeSH terms

Chlorine
Hydrogen Peroxide
Kinetics
Oxidation-Reduction
Ultraviolet Rays
Water Pollutants, Chemical* / analysis
Water Purification*

Substances

Water Pollutants, Chemical
Chlorine
Hydrogen Peroxide