Nano Structured Ni and Ru Impregnated TiO2 Photocatalysts: Synthesis, Characterization and Photocatalytic Degradation of Neonicotinoid Insecticides

Titania by sol gel and Ni-Ru titania catalysts by wet impregnation methods were prepared and characterized by XRD, UV-DRS, BET and TEM techniques. Catalytic activities of the photocatalysts were evaluated towards the degradation of three widely used neonicotinoids type insecticides namely acetamiprid, imidacloprid and thiamethoxam under UV, Visible and solar irradiations. The reaction parameters such as initial concentration of the insecticide, weight of the catalyst and pH of the system were found to influence the reaction rate. The results indicated that the metal impregnated catalysts were found to be more active than pure TiO2. Ni/TiO2 or Ru/TiO2 catalysts degraded all the insecticides completely even under visible irradiation. The observed visible activity of the catalysts was attributed to their lower band gap values. HPLC and TOC analyses revealed that mineralisation of the insecticides occurred through dearomatization by multiple hydroxylation and oxidation. The degradation pathway and the kinetics were also discussed in detail.