Unlocking the Full Potential of Zinc Oxide/Cerium Oxide Composite Nanoparticles for Removal of Mixed Pharmaceutical and Dye Pollutants in Water

ABSTRACT The widespread presence of pharmaceutical residues and dye contaminants in wastewater necessitates the development of efficient, low‐cost photocatalysts. Here, zinc oxide/cerium oxide (ZnO/CeO 2 ) composite nanoparticles were synthesized via a simple hydrothermal method, and their CeO 2 content was optimized for the simultaneous degradation of ciprofloxacin (CIP), tetracycline (TC), methylene blue (MB), and methyl orange (MO). X‐ray diffraction shows that ZnO retains its hexagonal wurtzite structure, while secondary CeO 2 reflections appear at ≥ 5 mol% CeO 2 , indicating a ZnO/CeO 2 composite. The composites exhibit pronounced morphology changes relative to pristine ZnO and a moderate increase in specific surface area at optimal CeO 2 loading. Optical analysis reveals only slight band gap variations (3.13–3.16 eV) with increasing CeO 2 content, whereas photoluminescence increases progressively, with ZnO/CeO 2 ‐5 showing the lowest PL among Ce‐containing samples, suggesting a favourable balance between charge separation and recombination. Consequently, the 5 mol% ZnO/CeO 2 composite displays superior photocatalytic performance in single‐pollutant tests, binary mixtures (CIP + TC, MB + MO), and a four‐pollutant mixture, demonstrating efficient removal of complex antibiotic–dye systems. The enhanced activity is attributed to the combined effects of Ce 3+ /Ce 4+ redox chemistry, oxygen‐vacancy‐related surface states, and intimate ZnO/CeO 2 interfacial contact.