The Effect of Unequal Ionic Size on the Swelling Pressure in Clays

Abstract

Abstract--In this paper, we use the unequal radius modified Gouy-Chapman theory to evaluate the effect of the ionic size of the electrolyte on the swelling pressures (H) in different clay systems immersed in electrolytic solutions. First the model is applied to a l:l electrolyte to show that the coion size is only important at surface charge densities much lower than those found in typical clay systems. The swelling pressure is calculated and the results are compared with experimental data. Literature ionic radii values are used to show the dependence of the swelling pressure on the specific counterions present. Next the model is applied to a 1:1 and 2:1 electrolyte mixture with unequal-sized counterions to show the swelling pressure is highly dependent on both counterion sizes. The unequal and same-sized cases are compared.

Ionic size effects on the force between planar electrical double layers

“…This effect has been studied previously by Huerta et al,12 who solved the modified Gouy-Chapman theory for a number of ionic sizes using a constant surface charge density model. 12 The modified Gouy-Chapman (MGC) theory treats the electrolyte as point ions except in its interaction with the surface, where an excluded region, equal in thickness to the radius of the ion, exists near the surface. The second way in which the ion size will affect the results is through the short-range ion-ion correlations.…”

Influence of Particle Orientation on One-Dimensional Compression of Montmorillonite

“…The model developed in this study is extension of the basic model implied in the studies of Bolt (7), Low (13), Callaghan and Ottewill (8), and Huerta et al (12). For example, Bolt (7) assumed that particles were parallel to FIG.…”

“…Thus, the measured Several attempts have in the past been made to model the electric conductivity of a kaolinite/water/electrolyte system is one-dimensional compression behavior of clays purely on a function of the manner in which the kaolinite particles are the basis of interparticle double-layer repulsive force (7, 8, arranged; A e Å 1 for random fabric and A e ú 1 for fabric 12,13). In these studies, the clay platelets have been as-where the particles are arranged with their faces predominantly sumed to be arranged parallel to each other in a volume of parallel to a horizontal plane.…”

“…Some of these factors are dure, illustrated in Fig. 3, the double-layer interaction is limited to what was referred to as the ''zone of interaction'' (i) effect of ions' size and unequal size (12), (ii) threedimensional nature of soil fabric, (iii) swelling due to inter-(ZOI). The definition of ZOI in two dimensions is illustrated in Fig.…”