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 3–10 nm 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 5.8 nm. 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.