Determination of surface free energy of kaolinite

Abstract--The adsorption of n-octane and water vapor on natural kaolinite was measured. From ad-sorption isotherms film pressures were determined which were then used to calculate the dispersion and nondispersion components of the kaolinite surface free energy. In addition, thermodesorption of water from the kaolinite surface was determined. These results uggest that physically adsorbed water emained on the kaolinite surface, even at temperatures a great as 125"(2. Therefore, experimentally determined dispersion and nondispersion components appear to relate to the surface precovered with a film of water. These values are: ~gw) = 34.4 mJ/m 2 for dispersion i teractions and ~gw) = 60.2 mJ/m 2 for nondispersion interactions. Assuming a kaolinite surface precovered with a film of water, which decreased the free energy by the work of spreading, the following components of the energy for the bare surface were calculated: ~s = 67.6 mJ/m 2 and 3' ~ = 103.4 mJ/m 2, for dispersion and nondispersion components, respectively