均相Co/PMS系统降解吡虫啉的影响因素及降解途径研究

过渡态Co^2+-催化分解KHSO₅(Co/PMS)系统是一种新型的高级氧化技术,其反应体系可以产生强氧化性的硫酸自由基(SO^·-₄).以杀虫剂吡虫啉为目标污染物,重点研究了溶液中PMS浓度、Co^2+-浓度和无机阴离子(H₂PO^-₄、HCO^-₃、NO^-₃和Cl^-)对Co/PMS系统降解吡虫啉的影响.结果表明,吡虫啉的降解遵循准一级动力学,其降解速率与氧化剂PMS浓度和催化剂Co^2+-的浓度呈正相关.吡虫啉的降解速率随着PMS和Co^2+-浓度的增加而增大,但是当PMS与吡虫啉的摩尔比大于20时,增加PMS的浓度对吡虫啉的降解速率反而有一定程度的抑制.H₂PO^-₄能促进Co/PMS系统对虫啉的降解;低浓度的HCO^-₃促进吡虫啉的降解,高浓度则为抑制作用;Cl^-抑制吡虫啉的降解,而NO^-₃则对整个降解过程影响不明显.研究中采用GC/MS分析吡虫啉降解的中间产物,得到了6-氯烟酸和6-氯烟酰胺2种主要的中间产物,并由此推测其可能的降解途径.

Influential Factors and Degradation Pathway of Imidacloprid by Homogeneous Co/PMS System

Cobaltous-mediated decomposition of peroxymonosulfate (Co/PMS) system is one of novel advanced oxidation technologies (AOTs), which leads to the formation of very strong oxidizing species in aqueous phase. Effects of PMS concentrations, Co2+ concentrations and various inorganic anions (H2PO4-, HCO3-, NO3-, Cl-) on the degradation of Imidacloprid induced by Co/PMS system was investigated as emphasis. The degradation kinetics of imidacloprid followed pseudo first-order kinetics and reaction rates related to PMS and Co2+, concentrations. The reaction rates increased with increasing PMS] and Co2+] when the other parameters were constant. However, the decrease of degradation rates was found when the molar ratio of PMS versus imidacloprid was over 20. The effects of H2PO4- had positive effect on the degradation of Imidacloprid, low concentration HCO3- had positive effect and high concentration HCO3- had negative effect, Cl- had negative effect, while NO3- had little effect. Based on the results of GC/MS, two main intermediates were identified, 6-chloronicotinic acid and 6-chloronicotinamide, and the reaction pathway for SO4*- induced by homogeneous Co/PMS was proposed accordingly.