Reactions of neonicotinoids with peroxydisulfate: The generation of neonicotinoid anion radicals and activation pathway to form sulfate radicals

Yangjian Zhou; Yu Lei; Qingqing Kong; Xin Lei; Jianglin Peng; Yufeng Xie; Shuangshuang Cheng; Yanpeng Gao; Junlang Qiu; Xin Yang

doi:10.1016/j.jhazmat.2023.131081

Reactions of neonicotinoids with peroxydisulfate: The generation of neonicotinoid anion radicals and activation pathway to form sulfate radicals

J Hazard Mater. 2023 May 15:450:131081. doi: 10.1016/j.jhazmat.2023.131081. Epub 2023 Feb 24.

Authors

Yangjian Zhou¹, Yu Lei², Qingqing Kong¹, Xin Lei¹, Jianglin Peng¹, Yufeng Xie³, Shuangshuang Cheng¹, Yanpeng Gao³, Junlang Qiu⁴, Xin Yang⁵

Affiliations

¹ School of Environmental Science and Engineering, Guangdong Provincial Key Laboratory of Environmental Pollution Control and Remediation Technology, Sun Yat-sen University, Guangzhou 510275, China.
² School of Environmental Science and Engineering, Guangdong Provincial Key Laboratory of Environmental Pollution Control and Remediation Technology, Sun Yat-sen University, Guangzhou 510275, China; Key Laboratory of Photochemistry, Institute of Chemistry Chinese Academy of Sciences, Beijing National Laboratory for Molecular Sciences, Beijing 100190, China.
³ Guangdong-Hong Kong-Macao Joint Laboratory for Contaminants Exposure and Health, Guangdong Key Laboratory of Environmental Catalysis and Health Risk Control, School of Environmental Science and Engineering, Institute of Environmental Health and Pollution Control, Guangdong University of Technology, Guangzhou 510006, China.
⁴ School of Environmental Science and Engineering, Guangdong Provincial Key Laboratory of Environmental Pollution Control and Remediation Technology, Sun Yat-sen University, Guangzhou 510275, China. Electronic address: qiujlang@mail.sysu.edu.cn.
⁵ School of Environmental Science and Engineering, Guangdong Provincial Key Laboratory of Environmental Pollution Control and Remediation Technology, Sun Yat-sen University, Guangzhou 510275, China. Electronic address: yangx36@mail.sysu.edu.cn.

PMID: 36848840
DOI: 10.1016/j.jhazmat.2023.131081

Abstract

To activate persulfate to generate reactive species such as sulfate radical (SO₄^•-) for micropollutants abatement, external energy or chemicals are often needed. In this study, a novel SO₄^•- formation pathway was reported during the oxidation of neonicotinoids by peroxydisulfate (S₂O₈^2-, PDS) without any other chemical additions. Thiamethoxam (TMX) was used as a representative neonicotinoid and SO₄^•- was the dominant specie contributing to its degradation during PDS oxidation at neutral pH. TMX anion radical (TMX^•-) was found to activate PDS to generate SO₄^•- with the second-order reaction rate constant determined to be (1.44 ± 0.47)× 10⁶ M^-1s^-1 at pH 7.0 by using laser flash photolysis. TMX^•- was generated from the TMX reactions with superoxide radical (O₂^•-), which was formed from the hydrolysis of PDS. This indirect PDS activation pathway via anion radicals was also applicable to other neonicotinoids. The formation rates of SO₄^•- were found to negatively linearly correlated with E_gap (LUMO-HOMO). The DFT calculations indicated the energy barrier of anion radicals to activate PDS was greatly reduced compared to the parent neonicotinoids. The pathway of anion radicals' activation of PDS to form SO₄^•- improved the understanding of PDS oxidation chemistry and provided some guidance to enhance oxidation efficiency in field applications.

Keywords: Chemical oxidation; Electron transfer; Neonicotinoid anion radicals; Peroxydisulfate; Sulfate radical.