Photocatalytic Oxidation of Aqueous Cyanide with TiO2/SiO2 Mixed Oxides

R. van Grieken, M.-J. López-Muñoz, J. Aguado, and J. Marugán (Spain)

Keywords

Photocatalysis, silica, titania, solgel, cyanide

Abstract

The use of titania-silica materials as catalysts in photocatalytic processes has been proposed as an alternative to the conventional TiO2 materials, in order to facilitate the separation of the solids after the reaction. However, despite the large number of works in this field, up to date it is not totally clarified the mechanism governing the photocatalytic activity of these materials. In the present work several titania-silica materials have been prepared through a sol-gel method controlling the main variables to obtain materials with different textural properties, degree of incorporation and dispersion of titanium species and crystallinity of titanium dioxide. Characterization of the catalysts and correlation with the activity for the photocatalytic oxidation of cyanide in comparison with the traditional 100% titania photocatalysts have allowed to identify the main features that determine the photoactivity of these materials. The reaction tests for the photocatalytic oxidation of cyanide show that anatase formation is absolutely required. The correlation between the photonic efficiency and the results of characterization of the materials by diffuse reflectance UV/vis spectroscopy and powder X-ray diffraction shows that the activity of the TiO2/SiO2 photocatalysts could be attributed to the formation of TiO2 nanocrystals of suitable band gap energy.

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