Characterization and photocatalytic activity of TiO2 supported sepiolite catalysts

This study focuses on structural and photocatalytic properties of TiO2 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 TiO2 nanoparticles. AFM and SEM images revealed obvious variations in the surface morphology of raw sepiolite after TiO2 loading. Sodium chloride treatment enhanced the attraction of sepiolite support through TiO2 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 TiO2. 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.