Simulation degradation of bromophenolic compounds in chlorine-based advanced oxidation processes: Mechanism, microscopic and apparent kinetics, and toxicity assessment. (March 2022)

• Record Type: Journal Article
• Authors: Li, Mingxue; An, Zexiu; Huo, Yanru; Jiang, Jinchan; Zhou, Yuxin; Cao, Haijie; He, Maoxia
• Is Part Of: Chemosphere. Volume 291:Part 3(2022)
• Publication Date: 2022-03
• Subjects: Density functional theory -- Chlorine radical -- Hydroxyl radical -- Chlorine oxide radical -- UV/Chlorine -- UV/Chloramine; Pollution -- Periodicals; Pollution -- Physiological effect -- Periodicals; Environmental sciences -- Periodicals; Atmospheric chemistry -- Periodicals; 551.511
• DOI: 10.1016/j.chemosphere.2021.133034
• Languages: English
• ISSNs: 0045-6535

Abstract

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/H2 O2, UV/chlorine and UV/NH2 Cl. 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 10 7 M −1 s −1, and such rate constants dramatically increased to 10 10 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/NH2 Cl > UV/chlorine > UV/H2 O2, and UV/chlorine and UV/NH2 Cl were more effective for the removal of 246TBP and 246TBPT than UV/H2 O2 . UV and/or Cl dominated 246 TBA degradation under three AOPs. The main radicals mediating 246TBP and 246TBPT degradation are respectively HO under UV/H2 O2, ClO under UV/chlorine, and HO and Cl under UV/NH2 Cl. The transformation products of 246TBA, 246TBP and 246TBPT, especially methoxylated and hydroxylated polybrominated diphenyl ethers (MeO-PBDEs and HO-PBDEs), were still toxic pollutants. Graphical abstract: Image 1 Highlights: ClO exhibited similar but lower reactivity than HO . The deprotonation of 2, 4, 6-tribromophenol dramatically increased its reactivity. Addition was proven to dominate Cl initiated reactions by theoretical calculation. The apparent degradation kinetics of bromophenolic compounds were simulated. The formation pathways of hydroxylated polybrominated diphenyl ethers were calculated.