Rice flour-assisted synthesis of magnetic CoFe ₂ O ₄ nanoparticles for photoactivation of oxalic acid to degrade aqueous methylene blue

In this study, we synthesized reusable CoFe2O4 nanoparticles via a simple sol–gel method with the assistance of rice flour as a sustainable agricultural resource, and explored the effects of calcination temperatures. The synthesized magnetic samples were characterized and compared to CoFe2O4 powders prepared by conventional ceramic and coprecipitation techniques. Their catalytic activities were assessed through methylene blue degradation in the presence of oxalic acid. All CoFe2O4 samples demonstrated significant H2C2O4 photoactivation capabilities, effectively degrading methylene blue under both UVA and visible light. Among the synthesis methods and calcination temperatures, the rice flour-assisted sol–gel method with calcination at 600 °C proved to be the most effective for producing single-phase spinel crystalline CoFe2O4 nanoparticles with a large specific surface area, enhanced surface metal content, and weakened surface metal–oxygen bonds. These properties not only resulted in superior catalytic activity but also imparted strong magnetism, enabling efficient recovery and reuse over multiple cycles.