Development of a TiO₂/Sepiolite Photocatalyst for the Degradation of a Persistent Organic Pollutant in Aqueous Solution

A clay-based TiO₂ nanocomposite material was synthesized by a facile method, to investigate its structure and photocatalytic efficiency. The supported TiO₂ nanoparticles were generated using a sol-gel method, and subsequently, mixed with a suspension of sepiolite. The material was recovered in powder form (Mc-80) and then calcined to properly arrange the crystal lattice of the TiO₂ particles for use in heterogeneous photocatalysis (Mc-80-500). A powder X-ray diffractogram of Mc-80-500 revealed a dispersion of anatase and rutile phase TiO₂ particles on the clay surface, exhibiting a size in the order of 4-8 nm. TEM images of Mc-80-500 confirmed the presence of isolated TiO₂ beads on the surface of the fibrous sepiolite. The specific surface area of Mc-80-500 was larger than that of raw sepiolite and that of free TiO₂ nanoparticles. Mc-80-500 was found to be more efficient in heterogeneous photocatalysis compared to other TiO₂ materials based on sepiolite. Total depollution of a reactive dye (Orange G) was achieved after 1 h irradiation time, which is relatively quick compared to previous reports. The photocatalyst material can be washed with distilled water without chemical additives or calcination, and can be reused several times for photocatalysis, without loss of efficiency.