高压电场低温等离子体对马拉硫磷的降解效能及降解途径

为探索高压电场低温等离子体对水中马拉硫磷的降解效能特性,以电压、作用时间及农药初始浓度为试验因素,采用气相色谱测定马拉硫磷的残留并建立降解动力学模型,利用气相串联质谱分析鉴定马拉硫磷降解产物,并结合傅里叶红外光谱研究低温等离子体对马拉硫磷的降解效能,解析其降解途径。结果表明:马拉硫磷在水中的降解效率随着低温等离子体电压强度及作用时间的延长显著增加(P<0.05);在初始浓度为0.1 μg/mL,50 Hz、80 kV处理180 s后,马拉硫磷降解效率达到79.62%±2.97%。马拉硫磷降解趋势符合一级动力学模型,产生的主要中间降解产物为马拉氧磷、磷酸三乙酯、顺-丁烯二酸二乙酯、反-丁烯二酸二乙酯、O,O,S-三甲基二硫代磷酸酯及2-二甲氧基膦硫酰磺基-4-乙氧基-4-氧丁酸。其中毒性较高的马拉氧磷可进一步降解为毒性较低的磷酸三乙酯。马拉硫磷降解过程中中间产物的形成主要经历了P=S键的氧化及C-S键的断裂两种途径。研究为降解水中农药残留研究提供了新的方法参考。

Degradation Efficiency and Pathway of Malathion Treated by High Voltage Electric Field Cold Plasma

The degradation efficiency of malathion by high voltage electric field cold plasma was studied by using the high-voltage electric field voltage intensity,treatment time and initial concentration of pesticide as experimental parameters. Gas chromatographic(GC)was used to determine the residue of malathion and a degradation kinetic model was established. Gas chromatography tandem mass spectrometry(GC-MS)was used to identify malathion degradation products. Combined with Fourier transform infrared spectros’copy(FT-IR),the degradation efficiency of malathion by cold plasma was studied and its degradation pathway was analyzed. The results showed that the degradation efficiency of malathion in water significantly increased with the increase of cold plasma voltage intensity and treatment time(P<0.05). When the initial concentration was 0.1 μg/mL,the degradation efficiency of malathion reached 79.62%±2.97% by the treatment of 50 Hz,80 kV for 180 s. The degradation products were malaoxon,triethyl phosphate,2-butenedioic acid(Z)-,diethyl ester,2-butenedioic acid(E)-,diethyl ester,O,O,S-trimethyl phosphorodithioate and 2-dimethoxyphosphinothioylsulfanyl-4-ethoxy-4-oxobutanoic acid. Malathion could be degraded into triethyl phosphate with lower toxicity by further processing. And the formation of intermediates in the degradation of malathion mainly by two pathways of oxidation of P=S bond and fracture of C-S bond. The study provides a new method for the study of degradation of pesticide residues in water.