Reduction of Imidacloprid by Sponge Iron and Identification of its Degradation Products

In this study, imidacloprid was degraded by sponge iron in aqueous solution via chemical reduction. The effects of initial pH, reaction time, and operating model were investigated. Lower of pH was advantageous to the reduction degradation reaction. The influence of agitation was investigated in terms of reaction kinetics and degradation yield. Imidacloprid degradation with agitation showed first-order reaction kinetics with a reaction rate of 0.0235 min(-1), and degradation without agitation possessed two distinctive kinetics regimes; a rapid reduction in the initial stage and a slower process until removal was complete. Both stages of the degradation showed first-order reaction kinetics with reaction rates of 0.0122 min(-1) and 0.0030 min(-1), respectively. Transformation products were identified using high-performance liquid chromatography-mass spectrometry (HPLC-MS). HPLC-MS exhibited nine fragment ions at m/z 97, 155.9, 174.9, 196.9, 211.1, 269.9, 266.1, 279, and 301.1. Finally, a degradation pathway of imidacloprid was proposed.