Formation of titanium dioxide nanostructures in the interlayer space of clay minerals

Kaolin and montmorillonite are intercalated through their consecutive two-stage treatment with dimethyl sulfoxide (DMSO) and TiCl₄ vapors. It is established that, at 293 K, this process is kinetically hindered irrespective of the mobility of adjacent structural layers in the minerals. As the temperature is elevated to 393 K, the first stage markedly accelerates, thus making it possible to synthesize kaolin-DMSO and montmorillonite-DMSO intercalates in real time with interplanar spacings d ₀₀₁ = 11.4 and 23.18 Å, respectively, and the degree of intercalant incorporation up to 40 wt %. The replacement of DMSO by TiCl₄ leads to the formation of kaolin-TiCl₄ (d ₀₀₁ = 13.1 Å) and montmorillonite-TiCl₄ (d ₀₀₁ = 15.3 Å) intercalates, amorphization of the minerals, subsequent hydrolysis of intercalated TiCl₄, and the formation of hydrated titanium dioxide. The thermal transformation of the latter within a temperature range of 573–673 K is accompanied by the formation of anatase nanoclusters possessing high photocatalytic activity.