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Clays and Clay Minerals

, Volume 3, Issue 1, pp 205–220 | Cite as

The Relation between Composition and Swelling in Clays

  • Margaret D. Foster
Article

Abstract

The phenomenon of swelling is associated with the hydration of clay; however, all clays do not swell when hydrated. Steps in the mechanism of hydration and swelling of different types of clays as observed and interpreted by several investigators and some theories proposed as to the cause of hydration and swelling are reviewed.

The concept of clays as colloidal electrolytes that dissociate to a greater or less extent when dispersed in water seems to explain most satisfactorily the significant relation between the degree of swelling on hydration and the composition of the clay minerals. In the kaolinite group, in which there are generally no replacements, the small number of exchangeable cations associated with the clay structure are presumed to be held by broken bonds on the edges of the sheets. Even though kaolinite, as shown by Marshall, is more highly ionized than montmorillonite, this greater ionization, because of the small number of cations present and their location on the edges of the sheets, cannot pry the units apart or leave the sheets sufficiently charged to cause the mineral to exhibit the phenomenon of swelling.

In the montmorillonite structure, on the other hand, isomorphous replacements, most commonly of magnesium and ferrous iron for aluminum in the octahedral layer, and, to a slight degree, replacement of aluminum for silicon in the tetrahedral layer, give the structure a net residual charge of 0.7 to 1.10 milliequivalents, which is neutralized by cations held electrostatically and located, for the most part, between the sheets. On hydration such a structure tends to ionize, the degree of ionization depending on (a) the nature of the exchangeable cation and (b) the kind and extent of isomorphous replacements. The characteristically great swelling of sodium montmorillonite as compared with calcium montmorillonite can be correlated with its much greater ionization. The differences in swelling of different montmorillonites have been correlated with the nature and extent of octahedral substitution and are attributed to the effect of these replacements on the anionic strength of the structural unit and its consequent degree of ionization as influenced by the changes in polarization throughout the structure caused by these replacements.

Hydrous mica, with the same structure as montmorillonite, is characterized by even a greater degree of isomorphous replacements and, consequently, a greater charge. However, a large part of this charge is neutralized by fixed, nonexchangeable and nonionizable potassium, and ionization of the exchangeable cations is unable to overcome the effect of this fixed potassium. It is probable that the greater replacements in the hydrous mica structure, as in the montmorillonite structure, have a depressing effect on ionization. The result is that hydrous micas are characterized by a very low degree of swelling.

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References

  1. Baver, L. D. (1929) The effect of the amount and nature of exchangeable cations on the structure of a colloidal clay: Missouri Agri. Exp. Sta. Res. Bull. 129.Google Scholar
  2. Bernai, J. D., and Fowler, R. H. (1933) A theory of water in ionic solution with particular reference to hydrogen and hydroxyl ions: Jour. Chem. Physics, vol. 1, pp. 515–548.CrossRefGoogle Scholar
  3. Bradfield, R. (1923) The chemical nature of colloidal clay: Missouri Agri. Exp. Sta. Res. Bull. 60.Google Scholar
  4. Foster, Margaret D. (1953) Geochemical studies of clay minerals. II. Relation between ionic substitution and swelling in montmorillonite: Am. Mineral., vol. 38, pp. 994–1006.Google Scholar
  5. Grim, R. E. (1935) Properties of clay: Recent marine sediments: London, Thos. Murby and Co., pp. 466–495.Google Scholar
  6. Grim, R. E. (1942) Modern concepts of clay minerals: Jour. Geology, vol. 50, pp. 225–275.CrossRefGoogle Scholar
  7. Hartley, G. S. (1935) Application of the Debye-Hückel theory to colloidal electrolytes: Faraday Soc. Trans., vol. 31, p. 68.Google Scholar
  8. Hendricks, S. B., Nelson, R. A., and Alexander, L. T. (1940) Hydration mechanism of the clay mineral montmorillonite saturated with various cations: Am. Ceramic Soc. Jour., vol. 62, pp. 1457–1464.CrossRefGoogle Scholar
  9. Houwink, R. (1937) On the structure of the hydration hull of inorganic soil colloids: Zeitschr. Koll., vol. 93, pp. 110–114.Google Scholar
  10. Kelley, W. P. (1943) Mattson’s paper on “The laws of soil colloidal behavior” — review and comments: Soil Sci., vol. 56, pp. 443–456.CrossRefGoogle Scholar
  11. Marshall, C. E. (1936) Soil science and mineralogy: Soil Sci. Soc. America Proc., vol. 1, pp. 23–31.CrossRefGoogle Scholar
  12. Marshall, C. E, (1948) Ionwation of calcium from soil colloids and its bearing on soil relationships: Soil Sci., vol. 65, pp. 57–68.CrossRefGoogle Scholar
  13. Marshall, C. E. (1949) The colloid chemistry of the silicate minerals: New York, Academic Press, Inc., p. 162.Google Scholar
  14. Marshall, C. E., and Gupta, R. S. (1933) Base exchange equilibria in clays: Soc. Chem. Industry Jour., vol. 52, p. 433T.Google Scholar
  15. Marshall, C. E., and Krinbill, C. A. (1942) The clays as colloidal electrolytes: Jour. Phys. Chemistry, vol. 46, pp. 1077–1090.CrossRefGoogle Scholar
  16. Mattson, S. (1929) The laws of soil colloidal behavior. I: Soil Sci., vol. 28, pp. 179–220.CrossRefGoogle Scholar
  17. Mattson, S. (1932) The laws of soil colloidal behavior. VIII. Forms and functions of water: Soil Sci., vol. 33, pp. 301–322.CrossRefGoogle Scholar
  18. Mering, J. (1946) The hydration of montmorillonite: Faraday Soc. Trans., vol. 42B, pp. 205–219.CrossRefGoogle Scholar
  19. Spiel, S. (1940) Effect of adsorbed electrolytes on the properties of mono-disperse clay-water systems: Am. Ceramic Soc. Jour., vol. 23, pp. 33–38.CrossRefGoogle Scholar
  20. Wiegner, G. (1931) Some physico-chemical properties of clays. I. Base exchange or ionic interchangle. II. Hydrogen clays: Soc. Chem. Industry Jour., vol. 50, pp. 65–71, 103-112T.CrossRefGoogle Scholar

Copyright information

© The Clay Minerals Society 1954

Authors and Affiliations

  • Margaret D. Foster
    • 1
  1. 1.U.S. Geological SurveyUSA

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