Equilibrium Theory of the Kaolinite-Water System at Low Moisture Contents, with Some Remarks Concerning Adsorption Hysteresis
A microscopic theory of the kaolinite-water system is presented, based upon the assumption that the clay-water interaction may be envisioned as partly hydration of the exchangeable cations and partly adsorption by the oxygen and hydroxyl surfaces. The theory treats exchangeable cation hydration quantum-mechanically as an ion-dipole phenomenon and considers water adsorption by the mineral surface as a problem in hydrogen bonding. A statistical mechanical model incorporating the quantum-theoretical results is then invoked to find the contribution of each component interaction to the initial portion of the adsorption isotherm for homoionic kaolinite. Good agreement between the theoretical calculations and available experimental data is achieved for water vapor adsorption by Li-, Na-, K-, and Mg-kaolinite, without the use of ad hoc empirical parameters. The concordance, in turn, is used to suggest that the basis for adsorption hysteresis in kaolinite-water vapor systems is the irreversible transition: mineral surface water → cation hydration water.
Unable to display preview. Download preview PDF.
- Fox, J. J., and Martin, A. E. (1940) Investigations of infrared spectra (2.5-7.5 µ). Absorption of water, Proc. Royal Soc. (London), 174A, 234–62.Google Scholar
- Herzberg, G. (1945) Molecular Spectra and Molecular Structure. II. D. Van Nostrand, New York.Google Scholar
- Hill, T. L. (1960) An Introduction to Statistical Thermodynamics, Addison-Wesley, Reading, Massachusetts.Google Scholar
- Longuet-Escard, J., Mering, J., and Brindley, G. W. (1960) Étude des profiles des bandes de diffraction dans la Montmorillonite—Influence de l’hydration et de la nature des cations échangeables, Proc. Intern. Geol. Congress (Copenhagen) 24, 17–27.Google Scholar
- Martin, R. T. (1959) Water-vapor sorption on kaolinite: Hysteresis, Clays and Clay Minerals, Proc. 6th Conf., Pergamon Press, New York, 259–78.Google Scholar
- Pauling, L. (1960) The Nature of the Chemical Bond, Cornell University Press, Ithaca, New York, 3rd ed.Google Scholar
- Sposito, G. (1965) On the General Theory of the Clay-Water Interaction, Unpublished Ph.D. thesis, University of California, Berkeley, California.Google Scholar