Aplicação e avaliação de três ânodos distintos (DDB/PT/OMM) na degradação de imidacloprido

Abstract

Imidacloprid (IMD) is a neonicotinoid insecticide widely used in agriculture. Due to its toxic effects, high solubility, and stability in water, it raises environmental concerns. Faced with this problem, the work aims to degrade imidacloprid in a commercial sample, by using advanced electrochemical oxidative processes with boron-doped diamond (DDB), platinum (Pt,) and mixed metal oxides (MMO) anodes, and as a catalyst a hybrid magnetic graphene (HMG). The HMG was synthesized and characterized through X-Ray Diffraction, RAMAN Scattering Spectroscopy, and FTIR analysis, which showed success in the formation of the material. The effect of pH (3, 5, and 7) and current density (33, 67, and 100 mA cm-2 ), showed better degradation results for DDB compared to Pt and OMM, with degradation rates of 99.8 % to pH 7, 67 mA cm-2 and at 60 min. The effect of the catalyst mass (0-1000 mg) added to the adsorption tests indicated that the Fenton reaction does not have a significant contribution to the degradation and the anodic material is the most important factor. The variation in the initial concentration (5, 25, and 50 mg L-1 ) did not imply a difference in the percentage of degradation of imidacloprid, and the use of NaCl as a support electrolyte replacing Na2SO4 promoted a significant increase in the percentage of degradation, in 60 min, of Pt (51.0 to 92.0%) and OMM (49.0 to 88.0%), while reducing DDB degradation from 99.9 to 93.0%. Through LC-MS analysis, it was possible to confirm the degradation of imidacloprid and propose the chemical structures for the formation of two by-products. In short, the best degradation results for the anodes can be presented as follows MMO<Pt<DDB.