The adsorption of anionic and cationic surfactants by the different clay minerals: FTIR spectroscopic study

The adsorption of an anionic surfactant LABS (Linear alkyl benzene-sulphonate) and a cationic surfactant DDAC (Distearly dimethyl ammonium chloride) by kaolinite, bentonite and sepiolite clays was investigated by vibrational spectroscopy. The samples prepared at different concentrations, and clay-surfactant spectra in the natural state, were recorded. The spectroscopic results indicate that the LABS and DDAC adsorbed on sepiolite and kaolinite. Bentonites are coordinated to either surface hydroxyls by H-bonding interaction (sepiolite) or to exchangeable catoins (kaolinite, bentonite) through both sulphur and nitrogen atoms as ligands. Interactions of both surfactants showed similarities, in that LABS was coordinated on clay surfaces with broken ends, and the DDAC molecule was adsorbed on the clay surface.