Electrical Potential Between Dissimilar Clay Double Layers

A. K. Helmy, I. M. Natale and M. E. Mandolesi
Universidad Nacional del Sur, 8000 Bahía Blanca, Argentina

Abstract: A model describing the electric double layers in clay-electrolyte systems containing particles with different surface charge densities was developed and used to calculate the film thickness of water present in a clay paste. The average water film thicknesses (∼18 Å) calculated by considering the clay to contain 9 groups of particles of different charge densities did not differ from those calculated by assuming one average charge density; provided the minimum potential between particles remained constant. These values, however, were higher than those obtained from gravimetric water determinations by about 30%. The overestimation of the average thickness of the water films by the theoretical model is most likely due to the assumption of a complete parallel arrangement of particles in the paste and the validity of the Gouy theory for double layers on clays.

Key Words: Double layer • Electrolyte • Film thickness • Montmorillonite • Surface charge • Water

Clays and Clay Minerals; February 1982 v. 30; no. 1; p. 49-54; DOI: 10.1346/CCMN.1982.0300106
© 1982, The Clay Minerals Society
Clay Minerals Society (www.clays.org)