Adsorption of sodium dodecyl sulfate on kaolin from different alcohol-water mixtures

The adsorption of sodium dodecyl sulfate (SDS) onto kaolin from different alcohol-water mixtures has been studied. The alcohols used were 1-propanol, 1-butanol, 1-pentanol, and 1-decanol containing 3.5 or 7 wt% water. In all cases the adsorption isotherms show a rather steep rise at low surfactant concentrations, Thereafter, there is a more or less continuous leveling off. The plateau adsorption of SDS on kaolin is found to increase with increasing chain length of the alcohol in the alcohol - water solvent. The adsorption properties are discussed in relation to the dielectric constant of the solvents; the aggregation properties of the surfactant in the bulk phase and the molecular packing of the surfactant in the adsorbed state are also considered. (C) 1996 Academic Press, Inc.