Beyond TiO2: Cerium-Doped Zinc Oxide as a New Photocatalyst for the Photodegradation of Persistent Pollutants

We prepared via hydrothermal synthesis zinc oxide samples doped with cerium. The samples were characterized via powder X-Ray Diffraction measurements, Diffuse Reflectance UV Vis spectroscopy, Scanning Electron Microscopy and Transmission Electron Microscopy with EDX (Energy Dispersive X-Ray spectroscopy) analysis, and BET (Brunauer-Emmett-Teller) surface area analysis. XRD measurements reveal the formation of highly crystalline materials; wurtzite is the most important. All materials were tested using phenol as model molecule and their performances were compared with TiO2 P25. The material showing the best performance, namely Ce-doped ZnO, was then used to abate some emerging pollutants. We chose three iodinated X-ray contrast agent (ICM), iopromide, iopamidol and diatrizoate, known to be recalcitrant to traditional advanced oxidation processes. In the presence of TiO2 P25, all ICM exhibited a slow degradation, with t(1/2) ranging from 30 min (iopamidol) to 120 min (diatrizoate) and several hours are required for their complete disappearance. The employment of Ce-doped ZnO leads to a sharp increase in their disappearance, with t(1/2) obtained within 15 min (iopamidol) or 25 min (diatrizoate) and the complete abatement is achieved within 2 h.