Electrochemical removal of imidacloprid on different anodes with in-situ H2O2 generation: Optimizing conditions for rapid degradation and safe byproducts

Imidacloprid is a neonicotinoid insecticide with the highest detection frequency in aquatic environments. To address its issue, the degradation of imidacloprid present in a commercial sample was investigated through the efficiencies of BDD, Pt, and MMO-RuO2-TiO2 anodes, using electrochemical oxidation with hydrogen peroxide electrogeneration (EO-H2O2), and employing a gas diffusion electrode (GDE) as the cathode. Among the anodes tested, BDD provided the best results, with complete degradation of imidacloprid after 40 min using pH 7, 67 mA cm-2, and Na2SO4 as the supporting electrolyte, for all the initial imidacloprid concentrations investigated. Additionally, tests were performed using IMD at low concentrations in different matrices. Replacing Na2SO4 with NaCl as the supporting electrolyte resulted in significantly increased degradation using the Pt (51.0-92.0 %) and MMO (49.0-88.0 %) anodes. LC-MS analyses confirmed the complete degradation of imidacloprid, with the data obtained enabling the proposal of the structures of two degradation products. Toxicity analysis using ECOSAR software showed that imidacloprid could cause acute and chronic toxicity for the organisms studied, while degradation product I did not show any toxicity, and degradation product II was classified as harmful to fish. The findings indicated that under optimized conditions, the three anodes have a high potential for use in EO-H2O2 systems for the removal of imidacloprid present in water matrices.