Green synthesis and characterization of spinel CoAl₂O₄ nanoparticles: Efficient photocatalytic degradation of organic dyes

CoAl₂O₄ nanoparticles (NPs) were synthesized using the sol–gel method and employed for the photocatalytic degradation of Direct Blue 129 (DB129) and Direct Red 31 (DR31) in an aqueous solution. The synthesized CoAl₂O₄ NPs have been fully characterized by X-ray powder diffraction (XRD), UV–vis diffuse reflectance spectroscopy (UV–vis DRS), Fourier transform infrared spectroscopy (FT-IR), scanning electron microscopy with an energy-dispersive X-ray spectroscope (SEM-EDS), transmission electron microscope (TEM), and Brunauer Emmett Teller (BET). The experiment investigated the optimal conditions for photocatalysis, including the amount of photocatalyst dosage, contact time, visible light irradiation, pH, and initial dye concentration. The results demonstrated that CoAl₂O₄ nanoparticles have great potential for efficiently photodegradation of direct blue 129 (DB129) and direct red 31 (DR31). Furthermore, the use of radical scavenger agents helped to clarify the mechanism by which the dyes are degraded through photodegradation.