Adsorption and intercalation processes of ionic surfactants on montmorillonite associated with their ionic charge

The adsorption of sodium dodecylsulfate (SDS) and cetyltrimethylammonium bromide (CTAB) by montmorillonite (MMT), respectively, in aqueous solution and their resulting intercalating structures after removal of water were investigated. The former adsorption results from the Donnan equilibrium for ions leading to hydrophilic nature of SDS/MMT hybrid, whereas the latter results from the Coulomb attraction or so-called cation exchange leading to hydrophobic nature of CTAB/MMT. X-ray scattering and transmission electron microscopy investigations on the dried SDS/MMT hybrids reveal that the adsorbed SDS neither substantially increases the interlayer distance nor changes the rough spherical texture of pristine MMT, whereas the adsorbed cetyltrimethyl ammonium cations significantly increase the interlayer distance of MMT resulting a well-integrated CTAB/MMT lamellar structure.