Percarbonate mediated advanced oxidation completely degrades recalcitrant pesticide imidacloprid: Role of reactive oxygen species and transformation products

摘要

Pesticides are vital and indispensable especially in agricultural production. However, pesticide contamination is also a serious threat to human health and the environment. Imidacloprid (IMD), an archetypal neonicotinoid insecticide, is commonly used to protect a variety of crops worldwide. This study examined the destruction of IMD contaminant in wastewater via catalytic oxidation with sodium percarbonate (SPC). The process exemplified 100% removal at optimum condition. Rates of reaction were expressed in terms of the apparent rate constants (k(app)) and were observed to satisfactorily follow pseudo-first-order kinetics. Inhibitory effects of humic acid and various coexisting ions on IMD degradation were examined and the trend was observed as follows: NO2- > PO43- > NH4+ > Cl- > NO3-.In- addition, we elucidated the participation of center dot OH (hydroxyl), center dot O-2(-) (superoxyl), and HO2 center dot (perhydroxyl) radicals in the process by performing scavenging experiments for these reactive oxygen species. A likely IMD degradation pathway was proposed based on the intermediate species identified via gas chromatography/mass spectroscopy electron ionization procedure. Overall, the present study established SPC as a cleaner alternative to other oxidants for pesticide degradation as it is non-toxic, safe to handle, and produces by-products that inherently exist in the natural water matrix.