哒嗪硫磷在液相中的光化学降解

以高压汞灯为光源,研究了哒嗪硫磷在液相中的光化学降解及影响因素.结果表明,哒嗪硫磷浓度为5mg·L-1时,在纯水中光解半衰期为9.82h,哒嗪硫磷在不同有机溶剂中的光解速率大小依次为正己烷>乙酸乙酯>甲醇>乙腈,在碱性溶液中比中性和酸性溶液中光解快.在2～20mg·L-1浓度范围内,哒嗪硫磷在水与甲醇中光解速率均随初始浓度的增加而降低.硝酸盐对哒嗪硫磷水中光解有一定的光敏化作用,而表面活性剂(SDS)则表现出显著的光猝灭作用,且猝灭作用与剂量比正相关.Fe3+和Fe2+对哒嗪硫磷水中光解有极强的光敏作用,并且光敏效应随着离子浓度的提高表现出先增加后减小的现象.光解产物的HPLC-MS检测表明,哒嗪硫磷在水中光解主要的途径是发生光氧化和光异构化作用.

Photochemical degradation of pyridaphenthione in various solvents

The photochemical degradation of pyridaphenthione in various solvents and the relevant effect factors were studied under the irradiation of high-pressure mercury lamp. The results showed that the half-life of pyridaphenthione in distilled water was 9.82 hours at the concentration of 5 mg·L^-1. The photolytic rates of pyridaphenthione in different organic solvents showed the following sequence: n-hexane > ethyl acetate > methanol > acetonitrile. The photolytic rate of pyridaphenthione in alkaline buffer solution was much faster than in acid or in neutral buffer solution. The photolytic rate became slower with increasing concentration of pyridaphenthione in aqueous solution and methanol in ranges from 2 mg·L^-1 to 20 mg·L^-1. In aqueous solutions, nitrate showed photosensitizing effect on the photodegradation of pyridaphenthione, but surfactant (SDS) obviously quenched its photodegradation and the quenching effect was proportional to the dosage ratio. We also found that Fe³⁺ and Fe²⁺ could have an intense photosensitizing effect on photolysis of pyridaphenthione. As the concentration of ions increased, the photosensitive efficiency increased in the beginning and then decreased. Detecting the photoproducts by HPLC-MS indicated that two main photolytic pathways of pyridaphenthione in aqueous solutions were photo-oxidation and photo-isomerization.