J . Phys. Chem. 1988, 92, 6489-6492
6489
Double-Layer Ion Correlation Forces Restrict Calcium-Clay Swelling R. Kjellander, S. MarEelja, Department of Applied Mathematics. Research School of Physical Sciences, Australian National University, Canberra, ACT 2601, Australia
R. M. Pashley,* Department of Chemistry, Australian National University, Canberra, ACT 2601, Australia
and J. P. Quirk Waite Agricultural Research Institute, University of Adelaide, Glen Osmond. S A 5064, Australia (Received: July 14, 1988)
An advanced statistical mechanical method has been used to calculate the diffuse electrical double-layer interaction between clay mineral surfaces in divalent electrolyte solutions. The prediction of a strongly attractive region in the swelling pressure curve was found to be in close agreement with direct experimental measurements of the force between mica surfaces under similar solution conditions. These results present the first quantitative explanation of the marked effect of calcium ions in preventing the swelling of clays.
Introduction The short-range (
