Influence of Exchangeable Cations on the Surface Free Energy of Kaolinite as Determined from Contact Angles

Jańczuk Bronisław1, Emil Chibowski1, Mieczysław Hajnos2, Tomasz Białopiotrowicz1 and Janusz Stawiński2
1 Department of Physical Chemistry, Institute of Chemistry Maria Curie-Skłodowska University, 20-031 Lublin, Poland
2 Institute of Agrophysics, Polish Academy of Sciences, Lublin, Poland

Abstract: The influence of adsorbed H+, Na+, K+, Ca2+, Mg2+, Ba2+, and Al3+ ions on the wettability of a kaolinite surface was determined from contact angles, which were measured in kaolinite-water drop- air (saturated water vapor) and kaolinite-diiodomethane drop-air systems. From the results and using a modified Young equation, the dispersion and nondispersion components of the free energy of the kaolinite hydrated surface were determined. The dispersion component of all the tested samples was between 32.8 and 38.9 mJ/m2, but the nondispersion component changed almost linearly from 53 to 95.9 mJ/m2 with the change of the entropy of hydration of the adsorbed ions, except for K+ and Ba2+. The latter ions were exceptions, probably due to their large ionic radii.

Key Words: Contact angle • Dispersion • Kaolinite • Surface free energy • Wettability

Clays and Clay Minerals; June 1989 v. 37; no. 3; p. 269-272; DOI: 10.1346/CCMN.1989.0370311
© 1989, The Clay Minerals Society
Clay Minerals Society (www.clays.org)