Assessment of the Effect of Zn Co-Doping on Fe/TiO2 Supports in the Preparation of Catalysts by Wet Impregnation for Photodegradation Reactions of Food Coloring Effluents

This study explores the photocatalytic efficiency of Zn/Fe/TiO2 catalysts, synthesized via the wet impregnation method, for degrading the food colorings Allura Red and Tartrazine Yellow. A 22 factorial design with a central point replication guided the catalyst synthesis. Characterization involved BET surface area analysis, SEM-EDX, XRD, and PZC determination. Photocatalytic tests were conducted in batch mode under natural sunlight with 10 mg L−1 food coloring solutions. Kinetic modeling and statistical analysis were performed, and catalyst reuse was evaluated under artificial light. Results showed that low calcination temperatures (200–273 °C) and Zn loadings of 2–10% led to nearly 99% discoloration and degradation efficiency. The Behnajady–Modirshahla–Ghanbery kinetic model best described the discoloration data, confirming the significant impact of both variables. The optimal catalyst for Allura Red degradation was 2%Zn/2%Fe/TiO2 calcined at 200 °C, while for Tartrazine Yellow, 6%Zn/2%Fe/TiO2 calcined at 300 °C was most effective. Both catalysts exhibited excellent stability, maintaining efficiency over four reuse cycles. These findings demonstrate the potential of Zn/Fe/TiO2 catalysts for sustainable wastewater treatment.