Structural modifications in Au/Al₂O₃–CeO₂ mixed oxides as a function of Ce⁴⁺ content and its effects in the mineralization of the herbicide diuron
2012
Galindo-Hernández, F. | Wang, J.A. | Gómez, R. | Bokhimi, X. | Lartundo, L. | Mantilla, A.
Nanocrystalline Au/Al₂O₃–CeO₂ photocatalysts with different CeO₂ contents were prepared by the sol–gel method. Gold was deposited by a deposition–precipitation approach. Nitrogen adsorption, X-ray diffraction, Rietveld refinement, radial distribution functions, UV–vis spectroscopy (diffuse reflectance), FT-IR and transmission electron microscopy (TEM) techniques were used for the characterization of the synthesized Au/Al₂O₃–CeO₂ samples. The photodegradation of the herbicide diuron (C₉H₁₀Cl₂N₂O) in aqueous media using an UV light emission source was used to evaluate the photocatalytic behavior of these nanomaterials. High specific surface areas (326–124m²/g) and a band gap in the UV region 3.25–3.15eV were obtained in these solids. XRD patterns showed that Au/Al₂O₃–CeO₂ mixed oxides contain crystal structures of ceria and γ-alumina. Although, both ceria and γ-alumina are cubic structures, ceria phase is remarkably predominant with respect to the alumina phase. Mineralization of diuron was determined by measuring the total organic carbon (TOC) remaining in the irradiated solution. All the samples, including bare Au/Al₂O₃ solid, are quite active for the decomposition of the herbicide; however, the analysis of the TOC after 2.5h in irradiation showed that only photocatalysts containing CeO₂ are capable to reach up to 77% of mineralization of the herbicide.
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