Synthesis of CeO2/fly ash cenospheres composites as novel photocatalysts by modified pyrolysis process

A novel fly ash cenospheres (FACs)-supported CeO2 composite (CeO2/FACs) was successfully synthesized by the modified pyrolysis process. The prepared composites were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), X-ray photoelectron spectroscopy (XPS), and diffuse reflection spectra (DRS) techniques. XRD results indicated that the CeO2 film coated on cenospheres was a face-centered cubic structure. SEM images confirmed that the CeO2 film was relatively compact. XPS results showed that Ce was present as both Ce4+ and Ce3+ oxidation states in CeO2 film coated on FACs substrate. The bandgap of the composite was narrower compared with the pure CeO2. The as-prepared material exhibited good photocatalytic activity for the decolorization of methylene blue (MB) under visible light irradiation, and the first-order reaction rate constant (k) of 0.0028 min−1 for CeO2/FACs composite was higher than 0.0015 min−1 of pure CeO2. The fact that they floated on water meant that CeO2/FACs composites were easily recovered from water by filtration after the reaction. The recycling test revealed that the composites were quite stable during the MB photocatalytic decolorization. The CeO2/ FACs catalyst was therefore promising for practical use in the degradation of pollutants or water cleanup.

Graphical AbstractSEM micrographs of a pristine FAC (a); some FACs (b) at low magnification; CeO2/FAC at low (c) and high (d) magnification; cross-section of CeO2/FACs (e); some pieces of coatings of CeO2/FACs (f); EDX spectra of pristine FACs (g) and CeO2/FACs samples (h)Figure optionsDownload full-size imageDownload as PowerPoint slide