Properties of Decylammonium Chloride and Cesium Perfluorooctanoate at Interfaces and Standard Free Energy of Their Adsorption

Measurements of the surface tension of aqueous solutions of decylammonium chloride (DACl) and cesium perfluorooctanoate (CsPFO) and the interfacial tension of DACl (CsPFO) solution-decane and DACl (CsPFO) solution-benzene systems were made at 293 and 303 K. On the basis of these measurements, the adsorption isotherms and the standard free energies of adsorption were determined. Also, the standard free energy of adsorption was determined from the surface free energy of the tails of DACl and CsPFO and the interfacial free energy of the tail-water system. It was found that the standard free energy of adsorption at a given temperature only slightly depends on the type of phase in contact with the solutions of the surfactants and can be determined on the basis of the surface and interfacial free energy of systems including the tails of the surfactants. It was also found that standard free energy of adsorption depends on temperature, and is considerably smaller for CsPFO than for DACl. Copyright 1997Academic Press