Degradation of Imidacloprid，Acetamiprid and Triazophos in Aqueous Solution by Dielectric Barrier Discharge Low-Temperature Plasma

In order to explore the degradation of imidacloprid, acetamiprid and triazophos by dielectric barrier discharge low-temperature plasma, the aqueous solution was established to study the effects of the discharge voltage, discharge time, initial pesticide concentration and pH of solution on degradation. The degradation kinetics model was also analyzed and the degradation path was proposed based on the degradation products identification. The results showed that the low-temperature plasma technology could effectively degrade the three pesticide residues in the aqueous solution and triazophos was much more labile to low-temperature plasma treatment than imidacloprid and acetamiprid. Under the conditions of this study, the increase of discharge voltage and discharge time, and the decrease of initial pesticides concentration benefitted the increase of degradation rate. Alkaline conditions were conducive to the degradation of imidacloprid and acetamiprid, and acidic conditions benefitted the degradation of triazophos. The maximum degradations rates were 62.5% for imidacloprid (pH9.0), 42.4% for acetamiprid (pH9.0) and 94.5% for triazophos (pH3.0) after the treatment at 13.6 kV for 5 min at the initial concentration of 1.9 mg/L. The degradation kinetics of all pesticides were fitted to the first-order kinetics model well (R²≥0.90). Seven and five degradation products of imidacloprid and acetamiprid were identified respectively. The formation of imidacloprid and acetamiprid degradation products mainly experienced the breaking of C-H, C-N bonds and the oxidation and substitution of hydroxyl radicals.