Microstructural changes of reference montmorillonites by cationic surfactants

The characteristics of montmorillonites modified with the cationic surfactant hexadecyltrimethylammonium (HDTMA) were evaluated by investigating adsorption isotherms and microstructures. The interlayer structure of montmorillonite intercalated with alkylammonium cations was affected by several factors: the density of the layer charge, degree of exchange, and mutual interaction between alkyl chains. Especially, the surface charge appeared to have an influence on interlayer expansion as a function of surface coverage. Our transmission electron microscopy (TEM) data on the montmorillonite treated with HDTMA revealed that different types of organic derivatives with distinct swelling patterns occurred as a result of the different layer charge densities or distributions on the clay mineral.