Phenol and its derivatives are persistent, toxic organic pollutants commonly found in industrial wastewater. This study investigates the synthesis, characterization, and visible-light photocatalytic activity of ZnO, α-Fe₂O₃, and ZnFe₂O₄-based composites (75Zn:25Fe, 50Zn:50Fe, and 25Zn:75Fe) for the degradation of phenol in aqueous solution. The photocatalysts were prepared via a simple co-precipitation method followed by calcination at 1000 °C and characterized by X-ray fluorescence (XRF), X-ray diffraction (XRD), and UV-V is spectroscopy. Photocatalytic experiments were conducted under natural sunlight and a 500 W halogen lamp (visible light) using 100 mg L⁻¹ phenol solutions. Among the catalysts, pure α-Fe₂O₃ exhibited the highest photocatalytic efficiency, achieving 86% phenol degradation with a rate constant of 0.3108 min⁻¹. The activity order was α-Fe₂O₃ > 25Zn:75Fe > 50Zn:50Fe > 75Zn:25Fe > ZnO. Optimal conditions included acidic pH, 1.5 g L⁻¹ catalyst loading, and low initial phenol concentration. Adsorption played a significant role and degradation followed the Langmuir–Hinshelwood kinetic model. These results demonstrated that low-cost, visible-light-active α-Fe₂O₃-based materials are promising for the treatment of phenolic wastewater using solar or artificial visible light.
Fatuase et al. (Sat,) studied this question.