Determination of Surface Free Energy of Kaolinite

Emil Chibowski and Piotr Staszczuk
Department of Physical Chemistry, Institute of Chemistry Maria Curie-Skłodowska University, M. Curie-Słodowska Sq. 3 20-031 Lublin, Poland

Abstract: The adsorption of n-octane and water vapor on natural kaolinite was measured. From adsorption 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 suggest that physically adsorbed water remained on the kaolinite surface, even at temperatures as great as 125°C. Therefore, experimentally determined dispersion and nondispersion components appear to relate to the surface precovered with a film of water. These values are: γ Sf(w) d = 34.4 mJ/m2 for dispersion interactions and γ Sf(w) n = 60.2 mJ/m2 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: γ S d = 67.6 mJ/m2 and γ S n = 103.4 mJ/m2, for dispersion and nondispersion components, respectively.

Key Words: Adsorption • Film pressure • Free energy • Kaolinite • n-Octane • Surface • Water

Clays and Clay Minerals; October 1988 v. 36; no. 5; p. 455-461; DOI: 10.1346/CCMN.1988.0360511
© 1988, The Clay Minerals Society
Clay Minerals Society (www.clays.org)