Synthesis, characterization, and photocatalytic activity of aluminum doped spinel ferrite nanoparticles for the photodegradation of Congo red

Abstract

In this study, the photocatalytic degradation of Congo red dye was investigated using aluminum-doped nickel cadmium manganese prepared from a sol–gel auto-combustion process and characterized by X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), and scanning electron microscopy coupled with energy-dispersive X-ray spectroscopy (SEM–EDX) for morphological and chemical studies. UV–Vis spectroscopic investigations were performed to explore the optical properties of the synthesised spinel ferrite. The results show that the particle size decreases, the surface area increases, and the band gap energy of ferrite nanoparticles decreases with aluminum doping, which is responsible for their enhanced photocatalytic activity under visible light irradiation. The photodegradation efficiency of the aluminum-doped catalyst was found to be remarkable, up to 99.54% for Congo red after 60 min as compared to undoped 56.78% in 60 min under normal conditions. At optimized conditions Congo red dye (10 ppm) was degraded by 100% in 30 min under pH 3, 40 °C, 100 mg/100 mL catalyst dosage, 200 W light intensity conditions. Superoxide radicals, together with hydroxyl radicals and holes, appear to be key species in the degradation mechanisms, as determined in previous studies. Therefore, the recycled catalyst showed excellent stability and reusability over five cycles of photocatalytic performance.