Efficient degradation of imidacloprid in soil by thermally activated persulfate process: Performance, kinetics, and mechanisms

Imidacloprid (IMI) as a first-generation commercial neonicotinoid has been frequently detected in the environment in recent years. In this study, the efficient degradation of IMI in soil by a thermally activated persulfate (PS) process was investigated. The degradation efficiencies of IMI were in the range of 82–97% with the PS dosage of 10 mM, when the initial concentrations of IMI were 5–50 mg/kg in the soil. Degradation of the IMI was fitted with a pseudo-first-order kinetic model under different reaction temperatures. Inhibition effects of the common inorganic anions on the IMI degradation in the system followed the order Cl - > HCO 3 - > H 2 PO 4 - > NO 3 - . Soil pH and soil organic matter were also main factors affecting the degradation of IMI. The degradation efficiencies (64–97%) of three other typical neonicotinoids (acetamiprid, clothianidin, and dinotefuran) indicated that the thermally activated persulfate process could be used for remediation of neonicotinoid-contaminated soil. Quenching experiments indicated that the major reactive species in IMI degradation were SO 4 •- , O 2 •- , and •OH. Six degradation intermediates of IMI were inferred in the soil, and degradation pathways of IMI included hydroxylation, denitrification, C-N bond break and further oxidation. • Thermally activated PS process can efficiently degrade IMI in the contaminated soil. • Degradation of the IMI was fitted with a pseudo-first-order kinetic model. • Degradation rates of four neonicotinoids followed the order CLO > IMI > ACE > DIN. • Reactive species SO 4 •- , O 2 •- and •OH were involved in the degradation process of IMI. • Degradation pathways of IMI were proposed based on identified products.