Enhanced photolysis of tetracycline by Zn(II): Role of complexation

Chang Xu; Shan Zhao; Shu-Guang Wang; Chao Song

doi:10.1016/j.scitotenv.2023.168484

Enhanced photolysis of tetracycline by Zn(II): Role of complexation

Sci Total Environ. 2024 Jan 20:909:168484. doi: 10.1016/j.scitotenv.2023.168484. Epub 2023 Nov 14.

Authors

Chang Xu¹, Shan Zhao¹, Shu-Guang Wang², Chao Song³

Affiliations

¹ Shandong Key Laboratory of Water Pollution Control and Resource Reuse, School of Environmental Science and Engineering, Shandong University, Qingdao, Shandong 266237, China; Shandong Key Laboratory of Environmental Processes and Health, School of Environmental Science and Engineering, Shandong University, Qingdao, Shandong 266237, China.
² Shandong Key Laboratory of Water Pollution Control and Resource Reuse, School of Environmental Science and Engineering, Shandong University, Qingdao, Shandong 266237, China; Shandong Key Laboratory of Environmental Processes and Health, School of Environmental Science and Engineering, Shandong University, Qingdao, Shandong 266237, China; Sino-French Research Institute for Ecology and Environment (ISFREE), School of Environmental Science and Engineering, Shandong University, Qingdao, Shandong 266237, China; WeiHai Research Institute of Industrial Technology of Shandong University, Weihai 264209, China.
³ Shandong Key Laboratory of Water Pollution Control and Resource Reuse, School of Environmental Science and Engineering, Shandong University, Qingdao, Shandong 266237, China; Shandong Key Laboratory of Environmental Processes and Health, School of Environmental Science and Engineering, Shandong University, Qingdao, Shandong 266237, China. Electronic address: songchao@sdu.edu.cn.

PMID: 37972777
DOI: 10.1016/j.scitotenv.2023.168484

Abstract

Zn(II) is a necessary additive during antibiotic production and aquaculture, leading to the coexistence of Zn(II) and antibiotics in aquatic environment, especially in receiving waters of pharmaceutical and aquaculture wastewater. However, the roles of Zn(II) in the photochemical behavior of antibiotics are still not clear, which limits the understanding of the fate of antibiotic in nature. In this study, tetracycline (TC) was selected as typical antibiotic to evaluate the effect of Zn(II) on antibiotic photolysis. The removal of TC was accelerated by 22.75 % with TC:Zn(II) molar ratio at 1:5. The mechanism of Zn(II)-induced TC photolysis was explored via reactive oxygen species (ROS) analysis and density functional theory (DFT) calculation for the first time. Zn(II) could enhance the formation of TC excited states and further produce more singlet oxygen (12.54 % higher than control group) to promote indirect photolysis. Besides, Zn(II) could react with TC via complexation, and the complex was more vulnerable to attack by reactive oxygen species due to more active sites. Furthermore, the structure and toxicity of intermediates were identified with mass spectrometer, T.E.S.T. and ECOSAR software. Zn(II) hardly changed the degradation path of TC, and TC was mainly degraded via ring opening, demethylation, deamidation, and hydrogen abstraction with more toxic intermediates than the parent molecule. This work is significant to better understand the environmental fate of antibiotics, and also provides new insight into wastewater treatment in the pharmaceutical and aquaculture industry.

Keywords: Antibiotics; DFT calculation; Degradation; ROS; Singlet oxygen.

MeSH terms

Anti-Bacterial Agents / analysis
Pharmaceutical Preparations
Photolysis
Reactive Oxygen Species
Tetracycline* / chemistry
Water Pollutants, Chemical* / analysis
Zinc / analysis

Substances

Reactive Oxygen Species
Tetracycline
Anti-Bacterial Agents
Pharmaceutical Preparations
Zinc
Water Pollutants, Chemical