Mechanistic insight into the role of typical microplastics in chlorination disinfection: Precursors and adsorbents of both MP-DOM and DBPs

Zhihao Yan; Hanyang Qian; Juanjuan Yao; Meng Guo; Xiong Zhao; Naiyun Gao; Zhi Zhang

doi:10.1016/j.jhazmat.2023.132716

Mechanistic insight into the role of typical microplastics in chlorination disinfection: Precursors and adsorbents of both MP-DOM and DBPs

J Hazard Mater. 2024 Jan 15:462:132716. doi: 10.1016/j.jhazmat.2023.132716. Epub 2023 Oct 5.

Authors

Zhihao Yan¹, Hanyang Qian¹, Juanjuan Yao², Meng Guo¹, Xiong Zhao¹, Naiyun Gao³, Zhi Zhang¹

Affiliations

¹ Key Laboratory of Three Gorges Reservoir Region's Eco-Environment, Ministry of Education, Chongqing University, Chongqing 400045, China.
² Key Laboratory of Three Gorges Reservoir Region's Eco-Environment, Ministry of Education, Chongqing University, Chongqing 400045, China. Electronic address: yaojuanjuan@cqu.edu.cn.
³ State Key Laboratory of Pollution Control and Resources Reuse, Tongji University, Shanghai 200092, China.

PMID: 37820530
DOI: 10.1016/j.jhazmat.2023.132716

Abstract

Microplastics (MPs) in drinking water are predominantly < 10 µm. The leaching of MPs derived dissolved organic matters (MP-DOM) from 5 µm polypropylene MPs (PP-MPs) and polystyrene MPs (PS-MPs) and the formation of MP-DOM derived disinfection byproducts during chlorination disinfection were first investigated. Comparably, PS-MPs are more vulnerable to chlorination and the primary attacks are on para C in aromatic side-chains via electrophilic Cl-substitution and oxidation by two-electron transfer. The O/C and Cl/C ratio of polystyrene MPs was linear and exponential versus initial available Cl₂ concentrations, respectively. The significant PS-DOM leaching was observed with initial available Cl₂ of 4.0 mg/L (USEPA recommended upper dose). As the initial available Cl₂ concentration increased to 8.0 mg/L, the adsorption of chloro-phenolic-components of 200 Daltons in PS-DOM by 5 µm PS-MPs was observed for the first time. Trichloromethane (TCM) was identified as the dominant disinfection byproduct with a formation potential of 60.3 ± 7.8 and 73.7 ± 9.8 μg/mg for PS-DOM and PP-DOM, respectively. The derived TCM could adsorb onto PS-MPs followed the pseudo-second-order kinetic and Langmuir isotherm models. Extreme chlorination could reduce the maximal adsorption capacity of TCM on 5 µm PS-MPs from 196.68 ± 48.66 to 146.02 ± 32.98 μg/g. Thus, PS-MPs act as precursors and carriers of TCM in chlorination.

Keywords: Chlorination; Disinfection by-products and adsorption; Dissolved organic matters; Leaching; Microplastics.