Photocatalytic Decolorization of Methyl Orange by Silica-Supported TiO2 Composites

Abstract

Immobilization of TiO₂ on silica gel has been proposed to enable easy separation of the catalyst in aqueous systems after photocatalytic reaction. Our simple synthesizing method reduces production cost, and the photocatalyst could find economical application in wastewater treatment. Silica-supported TiO₂ composites were prepared by molten salt method at 500, 600 and 700 °C for 60 min. The obtained samples were characterized by scanning electron microscopy (SEM), X-ray diffraction (XRD), diffuse reflectance spectroscopy and X-ray fluorescence. SEM results showed a heterogeneous surface covered with spherical particles. According to XRD findings, the only phase of the prepared TiO₂/SG nanocomposites at all temperatures was pure anatase. The average crystallite size of anatase was roughly 25, 42, 44 and 53 nm for nanocomposites prepared at 550, 600, 700 and 800 °C, respectively. The samples taken at 500 and 600 ºC showed a band gap value of 2.98 eV, and for sample synthesized at 700 ºC the band gap was 2.95 eV. The decolorization activity has been evaluated by Methyl orange (MO) oxidation in liquid phase. The results showed that the sample obtained at 700 °C had the highest photocatalytic decolorization efficiency activity, and the sample prepared at 500 °C had the lowest. The decolorization activity of photocatalyst prepared at 700 °C did not change during stability experiment.