Three-phase nanocomposites of two nanoclays and TiO2: Synthesis, characterization and photacatalytic activities

For the first time two different nanoclay minerals were combined with nanophase anatase for the synthesis of three-phase nanocomposites with improved photocatalytic properties. The novel halloysite (H) + palygorskite (Pal)-TiO2 nanocomposites were prepared using palygorskite and halloysite from Greece. Three nanocomposites were synthesized using [Hal + Pal] to TiO2 mass ratios of [10 + 20]:70, [15 + 15]:70 and [20 + 10]:70, respectively by depositing anatase form of TiO2 on the clay surfaces using titanium isopropoxide as a precursor under hydrothermal treatment at 180 degrees C. Phase composition, particle morphology and physical properties of these three-phase nanocomposites were characterized by XRD, ATR-FTIR, SEM, TEM, DR-UV-Vis, N-2-adsorption/desorption isotherms. The photocatalytic activities of three-phase clay-titania nanocomposites in decomposing NOx gas and toluene vapor were determined. The three-phase clay-titania nanocomposites showed significantly higher photocatalytic activity in decomposing inorganic and organic pollutants compared to that of either palygorskite- or halloysite-TiO2 nanocomposites under both UV- and visible-light irradiation. These studies led to a new class of clay-based nanocomposite materials with advanced photocatalytic properties. (C) 2013 Elsevier B.V. All rights reserved.