Characterization and photocatalytic activity of TiO 2 supported sepiolite catalysts

Abstract

This study focuses on structural and photocatalytic properties of TiO 2 supported sepiolite and sodium ion treated sepiolite catalysts, prepared by a sol–gel method in aqueous solution of acetic acid. The structural features of the catalysts have been investigated by thermal gravimetric analysis (TGA), X-ray diffraction (XRD), atomic force microscopy (AFM), scanning electron microscopy SEM with energy dispersive X-ray analysis (EDX) and surface area (BET) measurements. XRD analysis exhibited characteristic anatase reflections and supplied information about the crystalline sizes of TiO 2 nanoparticles. AFM and SEM images revealed obvious variations in the surface morphology of raw sepiolite after TiO 2 loading. Sodium chloride treatment enhanced the attraction of sepiolite support through TiO 2 nanoparticles. The efficiency of the supported catalysts has been elucidated using β-Naphthol as a model compound. High Performance Liquid Chromatography (HPLC) analyses were used for measuring the concentration of β-Naphthol remaining in solution during the experimental runs. All prepared catalysts exhibited higher activities than commercial Degussa P-25 and bare TiO 2. Dark adsorption capacities and photocatalytic activities of all supported catalysts were found to vary in the same trend. Langmuir–Hinshelwood model was used to explain the pseudo-first-order kinetics of β-Naphthol degradation. Also, a mechanism was postulated for the route of degradation.