Palygorskite-TiO₂ nanocomposites: Part 1. Synthesis and characterization

In this paper we describe the synthesis and characterization of small-sized TiO₂ particles supported on palygorskite (Pal) with Pal to TiO₂ mass ratios of 10:90, 20:80, 30:70, 40:60 and 50:50. The above Pal-TiO₂ nanocomposites were prepared by deposition of anatase form of TiO₂ on the Pal surfaces using a sol-gel method with titanium isopropoxide as a precursor under hydrothermal treatment at 180°C. Phase composition, particle morphology and physical properties of these samples were characterized using X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), attenuated total reflection using Fourier transform infrared spectroscopy (ATR-FTIR) and N₂ surface area analysis by BET. In order to investigate the absorption properties of the catalysts, UV-vis reflection spectra were measured. Preparation of Pal-TiO₂ nanocomposites led to good dispersion of TiO₂ on Pal surfaces. By increasing the amount of TiO₂, the deposited 3-10nm TiO₂ particles were found to be aggregated on the surfaces of the Pal particles. However, by decreasing the amount of TiO₂, the Pal particles were found to be aggregated. After treating with TiO₂, Pal samples largely showed interparticle mesopores of about 5.8nm. It was observed that the commercial titania P25 showed no absorption in visible light region. In contrast, the prepared Pal-TiO₂ samples showed gray color and absorption in visible light region.