Enhanced heterogeneous photodegradation of VOC and dye using microwave synthesized TiO2/Clay nanocomposites: A comparison study of different type of clays

Supply of pure drinking water and air is a perquisite for sustaining of civilization and in this respect the clays are found to have significant importance as a semiconductor support material due to their layered morphology, chemical as well as mechanical stability, cation exchange capacity, non-toxic nature, low cost and availability. In spite of availability of technique very few studies have been done on the effect of clay structure on photocatalytic efficiency of semiconductor/clay nanocomposites. The TiO2/clay nanocomposites were synthesized from different clays having textural differences (1:1 and 2:1); by a simple and time as well as cost effective method under microwave conditions. Formation of anatase TiO2 nanoparticles on surface of different clays was achieved at 180 °C within 10 min of time. Phase composition, particle morphology, specific surface area, chemical bonding, etc. of those samples were characterized by using XRD, TEM, FESEM, FTIR and nitrogen gas adsorption-desorption (BET) methods. Formation of TiO2 nanoparticles on clay surface were confirmed by monitoring peaks of anatase TiO2 with crystallite size 10-20 nm in X-Ray diffraction pattern of TiO2/Clay nanocomposites. The TiO2/clay nanocomposites exhibited high surface area and uniform pore distribution compared to pure clays and TiO2 (Degussa P25, Germany). The photocatalytic activities of the nanocomposites were found to be depended on clay texture as well as optical characteristics apart from their surface area. The 2:1 clay (bentonite, kunipia-F) was observed to act as better support for TiO2 in comparison with 1:1 clay (kaolin); regarding its photo-catalytic degradation of methylene blue (MB) and volatile organic compound (VOC) such as chlorobenzene (CB) due to their different texture and optical properties. TiO2/bentonite nanocomposite has high optical absorbance under UV spectrum. It also showed surface area of 112 m2/g with high photocatalytic activity with a rate constant 0.02886 and 0.0460 min−1 for MB and CB degradations respectively. It had also been found that, the photocatalytic activity of the TiO2/bentonite nanocomposites were 8 and 5 times higher for MB and CB degradation respectively in compare with Degussa P25.