Adsorption behavior of a cationic surfactant on montmorillonite

Adsorption of cationic surfactants onto clay is of interest in cosmetic applications as well as in environmental issues. Adsorption of alkyl(C13-15) benzyldimethylammonium chloride (ABDAC) onto montmorillonite-type clay is investigated in this work. Variation in the concentration of exchangeable cations of the clay in solution as a function of the amount of ABDAC adsorbed showed the adsorption process to be controlled by the surface charge density of the clay. Basal spacing of the clay increased stepwise by 7 Å during the adsorption process, indicating a final bilayer arrangement within the interlayers. Surface compaction of the alkyl chains determined by IR absorption at 2912 Å were in full agreement with the variation in specific reduced surface excess n1?(n)/m. Enthalpy of desorption of water from organo-clay complexes showed the surfaces to be hydrophobic even at low surface coverage, owing to flat-lying alkyl chains. © 1995