Potassium- and Ammonium-Treated Montmorillonites. I. Interstratified Structures with Ethylene Glycol and Water

Blahoslav Číčel and Daniel Machajdík
Institute of Inorganic Chemistry, Slovak Academy of Sciences Dúbravská cesta, 809 34 Bratislava, Czechoslovakia

Abstract: Monoionic K- and NH4-smectites saturated with ethylene glycol form mixed-layer structures which usually consist of three kinds of layers: a 10-Å, non-expanded layer; a 14-Å, partly expanded layer; and a 16.8-Å, completely expanded layer. In some samples, the 14-Å layers formed 60–70% of all layers present. When saturated with water vapor the smectites commonly consisted of three kinds of layers (10-, 12.6-, and 15.5-Å). Generally these samples contained fewer expanded layers than those saturated with ethylene glycol. This result is attributed to the smaller dipole moment of water compared with that of ethylene glycol. The greater solvation energy of NH4+ in comparison with that of K+ causes the expansion of a part of layers which did not expand in the K forms. This result indicates that there is an inhomogeneous distribution of layer charge in the smectite structure. The prevalent type of mixed layering in the studied samples is that of random distribution of layers.

Key Words: Ethylene glycol complex • Interstratification • Layer charge • Mixed layer • Montmorillonite

Clays and Clay Minerals; February 1981 v. 29; no. 1; p. 40-46; DOI: 10.1346/CCMN.1981.0290106
© 1981, The Clay Minerals Society
Clay Minerals Society (www.clays.org)