Swelling of Montmorillonite in Polar Organic Liquids

S. Olejnik*, A. M. Posner and J. P. Quirk
Department of Soil Science and Plant Nutrition, Institute of Agriculture, University of Western Australia, Nedlands, W.A. 6009
* Present address: CSIRO Division of Textile Physics, 338 Blaxland Road, Ryde, New South Wales, Australia.

Abstract: The crystalline and osmotic swelling of Na-, Cs-, Mg- and Ca-montmorillonite has been measured in dimethyl sulphoxide and in formamide, N-methyl formamide, dimethyl formamide, N-methyl acetamide and dimethyl acetamide. These liquids have similar dipole moments but their relative permittivities vary appreciably from values less than water to values greater than water.

Na-montmorillonite exhibits osmotic swelling (diffuse double layer development −d(001) ≫ 19 Å) in formamide and N-methyl formamide and Cs gives osmotic swelling behavior in formamide. Cs-montmorillonite in the crystalline swelling region give spacings greater than those found for water with all liquids. Mg- and Ca-montmorillonite did not give spacings greater than 19 Å in any of the liquids studied.

The swelling behavior of montmorillonite is affected by relative permittivity but for liquids with a similar relative permittivity methyl substitution in the molecule may prevent the development of diffuse double layers on the particle surfaces.

Clays and Clay Minerals; August 1974 v. 22; no. 4; p. 361-365; DOI: 10.1346/CCMN.1974.0220407
© 1974, The Clay Minerals Society
Clay Minerals Society (www.clays.org)