Enhanced chlorination of diclofenac using ABTS as electron shuttle: Performance, mechanism and applicability

Jiaxin Xu; Jing Zou; Jianying Wu; Huiping Zeng; Yixin Huang; Jingxin Yang; Chunming Gong; Siying Chen; Jun Ma

doi:10.1016/j.scitotenv.2023.168117

Enhanced chlorination of diclofenac using ABTS as electron shuttle: Performance, mechanism and applicability

Sci Total Environ. 2024 Jan 10:907:168117. doi: 10.1016/j.scitotenv.2023.168117. Epub 2023 Oct 25.

Authors

Jiaxin Xu¹, Jing Zou², Jianying Wu³, Huiping Zeng⁴, Yixin Huang³, Jingxin Yang⁵, Chunming Gong⁶, Siying Chen³, Jun Ma⁷

Affiliations

¹ Xiamen Key Laboratory of Municipal and Industrial Solid Waste Utilization and Pollution Control, College of Civil Engineering, Huaqiao University, Xiamen, Fujian 361021, China; Key Laboratory of Water Quality Science and Water Environment Recovery Engineering, Beijing University of Technology, Beijing 100124, China.
² Xiamen Key Laboratory of Municipal and Industrial Solid Waste Utilization and Pollution Control, College of Civil Engineering, Huaqiao University, Xiamen, Fujian 361021, China. Electronic address: zoujing@hqu.edu.cn.
³ Xiamen Key Laboratory of Municipal and Industrial Solid Waste Utilization and Pollution Control, College of Civil Engineering, Huaqiao University, Xiamen, Fujian 361021, China.
⁴ Key Laboratory of Water Quality Science and Water Environment Recovery Engineering, Beijing University of Technology, Beijing 100124, China.
⁵ Key Laboratory for Water Quality and Conservation of the Pearl River Delta, Ministry of Education, Institute of Environmental Research at Greater Bay, Guangzhou University, Guangzhou 510006, China.
⁶ Xiamen Institute of Environmental Science, Xiamen, Fujian 361005, China.
⁷ State Key Laboratory of Urban Water Resource and Environment, School of Environment, Harbin Institute of Technology, Harbin, Heilongjiang 150090, China.

PMID: 37890637
DOI: 10.1016/j.scitotenv.2023.168117

Abstract

Chlorination, one of the most common oxidation strategies, performed limited degradation capacity towards many emerging organic contaminants under neutral pH conditions. In this study, 2,2'-azinobis(3-ethylbenzothiazoline)-6-sulfonate (ABTS) was discovered to possess an outstanding activation property towards free available chlorine (FAC) during the chlorination of diclofenac (DCF) among pH 6.0-9.5. ABTS radical (ABTS^•+) primarily accounted for the elimination of DCF in the ABTS/FAC system, although hydroxyl radicals, reactive chlorine species, and singlet oxygen were also generated via the self-decomposition of FAC. ABTS acted as the electron shuttle to degrade DCF in the ABTS/FAC system, where ABTS was firstly oxidized by FAC to ABTS^•+ via single electron transfer, and followed by the elimination of DCF with the generated ABTS^•+. Eight DCF degradation intermediates were identified by LC/Q-TOF/MS, and four DCF degradation pathways were proposed. Real water bodies, humic acid, and the coexistent anions of Cl^-, HCO₃^-, NO₃^-, and SO₄^2- performed negligible influence on DCF removal in ABTS/FAC system. ABTS/FAC system was much superior to sole chlorination in terms of toxicity reduction and anti-interference capacity. Overall, this study innovatively introduced ABTS as the electron shuttle to enhance the oxidative capacity of FAC under neutral pH conditions and provided a new insight that the ABTS-like organic/synthetic components might play an important role in degrading emerging organic contaminants by chlorination in water treatment.

Keywords: ABTS; Chlorination; Diclofenac; Electron shuttle; Free available chlorine.

MeSH terms

Chlorides
Chlorine / chemistry
Diclofenac / chemistry
Electrons
Halogenation
Kinetics
Oxidation-Reduction
Water Pollutants, Chemical* / analysis
Water Purification*

Substances

Chlorine
Diclofenac
2,2'-azino-di-(3-ethylbenzothiazoline)-6-sulfonic acid
Chlorides
Water Pollutants, Chemical