School of Environmental Science and Engineering, Guangdong Provincial Key Laboratory of Environmental Pollution Control and Remediation Technology, Sun Yat-sen University, Guangzhou 510275, China.
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.
J Hazard Mater. 2023 May 15;450:131081. doi: 10.1016/j.jhazmat.2023.131081. Epub 2023 Feb 24.
To activate persulfate to generate reactive species such as sulfate radical (SO) for micropollutants abatement, external energy or chemicals are often needed. In this study, a novel SO formation pathway was reported during the oxidation of neonicotinoids by peroxydisulfate (SO, PDS) without any other chemical additions. Thiamethoxam (TMX) was used as a representative neonicotinoid and SO 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 SO with the second-order reaction rate constant determined to be (1.44 ± 0.47)× 10 Ms at pH 7.0 by using laser flash photolysis. TMX was generated from the TMX reactions with superoxide radical (O), 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 SO were found to negatively linearly correlated with E (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 SO improved the understanding of PDS oxidation chemistry and provided some guidance to enhance oxidation efficiency in field applications.
为了激活过硫酸盐生成硫酸根自由基（SO）等活性物种以去除微量污染物，通常需要外部能量或化学物质。在这项研究中，在中性 pH 下过二硫酸盐（SO、PDS）氧化新烟碱类杀虫剂时，无需添加任何其他化学物质，报告了一种新的 SO 生成途径。噻虫嗪（TMX）被用作代表性的新烟碱类杀虫剂，在 PDS 氧化过程中，SO 是其降解的主要物质。发现噻虫嗪阴离子自由基（TMX）可以激活 PDS 生成 SO，通过激光闪光光解在 pH 7.0 下确定的二级反应速率常数为（1.44±0.47）×10 Ms。TMX 是由 PDS 水解产生的超氧自由基（O）与 TMX 反应生成的。这种通过阴离子自由基的间接 PDS 激活途径也适用于其他新烟碱类杀虫剂。SO 的生成速率与 E（LUMO-HOMO）呈负线性相关。DFT 计算表明，与母体新烟碱类杀虫剂相比，阴离子自由基激活 PDS 的能垒大大降低。阴离子自由基激活 PDS 形成 SO 的途径提高了对 PDS 氧化化学的理解，并为提高现场应用中的氧化效率提供了一些指导。
