Decolorization of Ponceau Red 4R with TiO ₂ / ZnO : Effect of calcination temperature and Fe addition

The photocatalytic degradation of azo dyes using semiconductor oxides has emerged as a promising strategy for wastewater remediation. In this study, pure, mixed, and Fe‐doped oxide catalysts based on Zinc Oxide and Titanium Dioxide were synthesized and evaluated for the degradation of Ponceau 4R under ultraviolet irradiation. The catalysts were characterized by X‐ray diffraction, scanning electron microscopy/energy dispersive X‐ray, Fourier Transform Infrared Spectroscopy, N 2 adsorption–desorption, photoacoustic spectroscopy, and point of zero charge analyses. Fe incorporation reduced the band gap energy of the catalysts to values close to 2.0 eV, indicating enhanced visible‐light absorption. However, photocatalytic experiments demonstrated that Fe doping did not improve catalyst performance. Among all evaluated materials, commercial ZnO exhibited the highest activity, achieving 100% dye decolorization with pseudo‐first‐order rate constants of up to 0.0506 min −1 . Calcination at 400°C generally enhanced photocatalytic activity, whereas Fe addition reduced the performance of ZnO‐based systems, likely due to increased charge recombination and particle agglomeration. Kinetic analyses showed that the pseudo‐first‐order model best described the degradation process. The results demonstrate that pure ZnO remains more effective than Fe‐doped and mixed oxide systems for Ponceau 4R degradation under the investigated condition.