Hydroxylation of some emerging disinfection byproducts (DBPs) in water environment: Halogenation induced strong pH-dependency

Zexiu An; Dongchen Yang; Mingxue Li; Yanru Huo; Jinchan Jiang; Yuxin Zhou; Yuhui Ma; Wenlong Hou; Jinlin Zhang; Maoxia He

doi:10.1016/j.jhazmat.2023.131233

Hydroxylation of some emerging disinfection byproducts (DBPs) in water environment: Halogenation induced strong pH-dependency

J Hazard Mater. 2023 Jun 15:452:131233. doi: 10.1016/j.jhazmat.2023.131233. Epub 2023 Mar 20.

Authors

Zexiu An¹, Dongchen Yang², Mingxue Li³, Yanru Huo³, Jinchan Jiang³, Yuxin Zhou³, Yuhui Ma³, Wenlong Hou³, Jinlin Zhang⁴, Maoxia He⁵

Affiliations

¹ College of Plant Protection, Hebei Agricultural University, Baoding 071000, China; Environment Research Institute, Shandong University, Qingdao 266237, China.
² College of Plant Protection, Hebei Agricultural University, Baoding 071000, China.
³ Environment Research Institute, Shandong University, Qingdao 266237, China.
⁴ College of Plant Protection, Hebei Agricultural University, Baoding 071000, China. Electronic address: zhangjinlin@hebau.edu.cn.
⁵ Environment Research Institute, Shandong University, Qingdao 266237, China. Electronic address: hemaox@sdu.edu.cn.

PMID: 36948122
DOI: 10.1016/j.jhazmat.2023.131233

Abstract

In this work, the hydroxylation mechanisms and kinetics of some emerging disinfection byproducts (DBPs) have been systematically investigated through theoretical calculation methods. Five chlorophenols and eleven halogenated pyridinols were chosen as the model compounds to study their pH-dependent reaction laws in UV/H₂O₂ system. For the reactions of HO^• with 37 different dissociation forms, radical adduct formation (RAF) was the main reaction pathway, and the reactivity decreased with the increase of halogenation degree. The k_app values (at 298 K) increased with the increase of pH from 0 to 10, and decreased with the increase of pH from 10 to 14. Compared with phenol, the larger the chlorination degree in chlorophenols was, the stronger the pH sensitivity of the k_app values; compared with chlorophenols, the pH sensitivity in halogenated pyridinols was further enhanced. As the pH increased from 2 to 10.5, the degradation efficiency increased at first and then decreased. With the increase of halogenation degree, the degradation efficiency range increased, the pH sensitivity increased, the optimal degradation efficiency slightly increased, and the optimal degradation pH value decreased. The ecotoxicity and bioaccumulation of most hydroxylated products were lower than their parental compounds. These findings provided meaningful insights into the strong pH-dependent hydroxylation of emerging DBPs on molecular level.

Keywords: Halogenated aromatic DBPs; Health risk; UV/H(2)O(2) system; pH-dependency.