Preparation and properties of TiO2/montmorillonite composites

TiO2/montmorillonite composites were prepared by reaction of montmorillonite with a TiO2 sol formed by hydrolyzing titanium iso-propoxide, at 50–80 °C. The composites showed expanding and broadening of the basal reflections of montmorillonite indicating a partial intercalation of the smaller colloidal TiO2 particles and increased disorder. The reaction temperature affected largely the amount of TiO2 hydrolyzed and the resulting pore sizes. Both properties increased with increasing reaction temperature; the TiO2 content from 24.2 to 46.6 mass% and the average pore size from 2 to 20 nm. The colloidal TiO2 particles consisted of anatase up to 1000 °C without transforming into rutile. The growth of the TiO2 particles was suppressed by the montmorillonite particles. Adsorption of methylene blue (MB) was higher in the composite prepared at 80 °C than in that at 50 °C because of the larger pore size. Photocatalytic decomposition of 1,4-dioxane by the composites was higher than for pure anatase due to the synergy effect of adsorption for 1,4-dioxane and photodecomposed intermediates by montmorillonite and its photodecomposition by TiO2.