Water and Ion Movement in Thin Films as Influenced by the Electrostatic Charge and Diffuse Layer of Cations Associated With Clay Mineral Surfaces

Abstract

Abstract Theory is developed and the effect of the ions and the electrostatic charge associated with clay platelets on the movement of water and ions in thin films between particles or on particle surfaces is calculated for several systems. Under postulated conditions which probably exist in fairly dry soils and compacted shales, movement of water was restricted by as much as 50% and movement of free electrolyte by more than 90%. Data are presented which illustrate this “salt‐sieving” effect and provide a “semiquantitative” check on the theory and calculations. Increases in apparent intrinsic permeability with increasing hydraulic pressure gradients in clay systems, which have been noted previously, are of an order which could be explained by the phenomena considered in this study.