Synthesis of CeO_2/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.