Synthesis of bicrystalline TiO2 supported sepiolite fibers and their photocatalytic activity for degradation of gaseous formaldehyde

Bicrystalline TiO2 supported acid activated sepiolite (TiO2/AAS) fibers have been successfully synthesized by a simple method at low temperature. The as-prepared TiO2/AAS composites were characterized by X-ray diffraction (XRD), nitrogen adsorption/desorption method, UV–vis diffuse reflectance spectrum (UV–vis DRS), scanning electron microscope (SEM), high-resolution transmission electron microscopy (HRTEM) and Fourier transform infrared (FT-IR) spectroscopy. The X-ray diffraction analysis indicates that the binary mixtures of anatase and rutile exist in the TiO2/AAS composites. The specific surface area of the TiO2/AAS composites is much larger than that of raw sepiolite and acid activated sepiolite (AAS) fibers. The photocatalytic activities of the TiO2/AAS composites were evaluated by the degradation of gaseous formaldehyde (a main indoor air pollutant) under UV light irradiation. The result indicates that the photocatalytic activity of the TiO2/AAS composites is excellent and superior to that of the TiO2/sepiolite (raw sepiolite) and pure TiO2. The high photocatalytic activity of the TiO2/AAS composites can be attributed to the anatase–rutile mixed phase and bimodal pore structure in the TiO2/AAS composites.