Research Center of Analytical Instrumentation, Northwest University, Xi'an, Shaanxi 710069, China; Key Laboratory of Synthetic and Natural Functional Molecule Chemistry of Ministry of Education, College of Chemistry & Materials Science, Northwest University, Xi'an, Shaanxi 710069, China.
Research Center of Analytical Instrumentation, Northwest University, Xi'an, Shaanxi 710069, China; Key Laboratory of Synthetic and Natural Functional Molecule Chemistry of Ministry of Education, College of Chemistry & Materials Science, Northwest University, Xi'an, Shaanxi 710069, China.
Sci Total Environ. 2020 Jul 10;725:138487. doi: 10.1016/j.scitotenv.2020.138487. Epub 2020 Apr 6.
Fipronil and its metabolites are potentially harmful to the ecological environment and have chronic neurotoxic effects, which makes it to be classified as class C carcinogens. Fipronil has been banned from agricultural use in China since 2009, but its residue remains in the environment. Therefore, an efficient and economical method is urgently needed to degrade fipronil residues in the environment. Herein, the degradation of fipronil in water solution using argon microwave-induced plasma (MIP) system was studied and a plausible reaction pathway was proposed in combination with Density Functional Theory (DFT) calculations. The degradation of fipronil by MIP system was optimized in terms of input power, plasma-sample distance, initial concentration and gas flow rate. After short time MIP treatment with an input power of 150 W, as high as 85.62% degradation efficiency was achieved for the fipronil at concentration of 20 mg·L under the optimized conditions, and the corresponding energy efficiency was 1334.8 mg·kwh. Optical emission spectrometry (OES) was employed to characterize the distribution and intensity of OH, H and O species which play key roles in the degradation of fipronil by plasma, and it revealed that the degradation reaction mainly occurs at gas-liquid interface where the highest intensity of OH, H and O species was observed. High resolution mass spectrometric analysis in combination quantum chemical calculations indicate that a wide diversity of reaction processes occurred for fipronil degradation under MIP treatment, involving oxidation or reduction, nitro reduction, oxidative dichlorination, reductive dichlorination, hydration, dehydration and thiourea to urea. The possible degradation mechanism and pathways were proposed based on the degrading species identified by high resolution Mass Spectrometry (HRMS) and the thermodynamic profiles.
氟虫腈及其代谢物对生态环境具有潜在危害，且具有慢性神经毒性作用，因此被归类为 C 类致癌物质。自 2009 年以来，中国已禁止将氟虫腈用于农业用途，但它的残留物仍存在于环境中。因此，迫切需要一种高效、经济的方法来降解环境中的氟虫腈残留。本研究采用氩气微波诱导等离子体（MIP）系统降解水溶液中的氟虫腈，结合密度泛函理论（DFT）计算提出了可能的反应途径。从输入功率、等离子体-样品距离、初始浓度和气体流速等方面优化了 MIP 系统对氟虫腈的降解。在输入功率为 150 W 的短时间 MIP 处理后，在优化条件下，浓度为 20 mg·L 的氟虫腈降解效率高达 85.62%，相应的能量效率为 1334.8 mg·kwh。采用发射光谱（OES）来表征在等离子体降解氟虫腈过程中起关键作用的 OH、H 和 O 物质的分布和强度，结果表明降解反应主要发生在气-液界面，在此处观察到 OH、H 和 O 物质的强度最高。高分辨质谱分析结合量子化学计算表明，在 MIP 处理下，氟虫腈的降解涉及氧化或还原、硝基还原、氧化二氯代、还原二氯代、水合、脱水和硫脲到脲等多种反应过程。根据高分辨质谱（HRMS）鉴定的降解产物和热力学曲线，提出了可能的降解机制和途径。
