On the Application of Organic–Inorganic Composite Materials Based on Nickel(II) and Cobalt(II) Ferrites As Catalysts for the Oxidative Decomposition of Organic Dyes

The possibilities of synthesizing composite organic-inorganic materials from agricultural waste (biochars based on rice husks, sunflower husks, and ferrites of the composition MFe₂O₄ (M = Ni, Co) are studied. The synthesis of materials is carried out using the sol-gel method. It is established that the nature of the biochar influences the product yield: for a composite with biochar from rice husk, the yield of the composite material is approximately 25% higher than for sunflower husk. This fact is explained by the loose structure of biochar obtained from sunflower husks, which ensures more complete contact of the surface with oxygen during heat treatment and leads to the partial burnout of the biochar during the synthesis of the composite material. The synthesized materials are characterized by X-ray diffraction analysis, scanning electron microscopy, and Fourier transform infrared spectroscopy. Cobalt(II) and nickel(II) ferrites crystallize on the surface of the organic carrier in the form of a film. The composite material has significant catalytic properties in the reaction of destruction of the organic dye (methyl orange) under the influence of hydrogen peroxide and daylight: complete removal of the azo dye from the solution in the presence of the cobalt(II) ferrite/sunflower catalyst is achieved after just 60 min.