Visible light-responsive Ce-doped ZnO ceramic nanostructures as effective photocatalysts for removal of persistent organic pollutants from contaminated waters

Cerium-doped zinc oxide (ZnO) ceramic nanostructures were conceived and prepared by means of electrospinning-calcination method. Morphological analysis based on scanning electron microscopy (SEM) disclosed a transition from spherical to rod-shaped features in ZnO ceramic nanostructures upon cerium (Ce) doping amount. Powder X-ray diffraction (XRD) indicated that the unit cell parameters remained unchanged for doped ZnO, while a new diffraction peak at 2 theta = 28.57 occurred above 0.5% Ce, corresponding to cubic CeO2. The results are further supported by X-ray Photoelectron Spectroscopy (XPS) investigations, which clearly confirmed the occurrence of Ce4+ ions upon the increase of Ce incorporation during the synthesis. Photocatalytic screening assays for methylene blue (MB) degradation using a visible light source, demonstrated superior performance for the doped material with 0.1% Ce content, yielding the highest pseudo-first-order rate constant (k = 4.795 x 10-2 min-1). Additionally, the best catalyst ZnO:Ce (0.1%), showed rate constants of 1.018 x 10-2 min-1 and 3.675 x 10-2 min-1 for photodegradation of metronidazole (MNZ) and ciprofloxacin (CIP), respectively, under the established optimal conditions. The catalyst stability was confirmed through multiple reuse cycles. The present study points out the effective Ce-doped ZnO nanostructures for versatile photocatalytic applications.