Structure of cetyltrimethylammonium intercalated hydrobiotite

Surfactant–clay mineral complexes obtained by intercalating cationic surfactants have attracted much scientific and industrial attention because of the wide applications in many fields. In this work we selected hydrobiotite to synthesize novel surfactant–clay mineral complexes with unique structures. Various amounts of cetyltrimethylammonium cations were intercalated into hydrobiotite and montmorillonite (for comparison). The structure of the surfactant–clay mineral complexes was characterized by X-ray diffraction, Fourier transform infrared spectroscopy and thermogravity analysis. Whereas the interlayer spaces of the montmorillonite were simultaneously intercalated and expanded by the surfactant cations, the hydrobiotite could only be intercalated and expanded layer by layer. Conformations of the intercalated surfactant cations on montmorillonite developed gradually from “liquidlike” to “solidlike” with increasing surfactant loading, whereas the intercalated surfactants on hydrobiotite adopted “solidlike” conformation even at very low surfactant loading stages. Both Coulombic interaction between the surfactant head groups and the clay mineral charge sites and van der Waals interaction between surfactant alkyl chains played important role for the intercalation of hydrobiotite. The unique structures of the surfactant–hydrobiotite may render them special properties and utilities.