Photodegradation of Organophosphorus Pesticides on Magnetically Recyclable Core-Shell Nanocatalyst

Abstract

Magnetically recyclable nanoparticle catalysts, in particular, Fe₃O₄, TiO₂@Fe₃O₄, SiO₂@Fe₃O₄, TiO₂–SiO₂@Fe₃O₄ and silver doped TiO₂–SiO₂@Fe₃O₄ (Ag–TiO₂–SiO₂@Fe₃O₄) were synthesized by sol-gel and modified sol-gel synthesis methods. These nanoparticle catalysts were prepared from metal salts and alkoxide precursor salts. Photocatalytic activity of these catalysts was studied in the degradation of organophosphorus pesticides Glyphosate, and Malathion in water. A detailed study of photodegradation of these organic compounds under UV radiation was performed. The physicochemical characterization of the synthesized nanoparticles was performed using TEM (Transmission electron microscopy), EDX (energy dispersive X-ray), ICP-AES (inductively coupled plasma−atomic emission spectroscopy), XRD (X-ray diffraction) and BET surface area measurement techniques. The degradation reactions of organic pesticides were performed in a specially designed photo-batch reactor. The use of H₂O₂ as an oxidant in the reaction was found to enhance the catalytic performance towards degradation and subsequent mineralization of the organophosphorus pesticides. Silver-doped nanocatalyst exhibits high recycling efficiency and stability over several subsequent runs. The course of the reactions was studied using COD (chemical oxygen demand) removal and HPLC (high-performance liquid chromatography) methods of water before and after the photodegradation reactions. More than 95% reduction in the COD was observed in the treated water sample using Ag–TiO₂–SiO₂@Fe₃O₄.