Surface conductance related to electrolyte concentration in bentonite pastes

Abstract

The present paper describes a method of obtaining experimentally the relationship between surface conductance and electrolyte concentration for a bentoniteJNaC1 system over a wide range of clay content. The method exploits the natural tendency of clay suspensions to form oriented films upon drying, in order to build up oriented pastes within a conductivity cell. Work previously reported in the literature has been concerned with disordered clay systems. In such systems, changes in salt concentration cause differences in internal structure of the paste which prevent a satisfactory approach to the required relationship. Surface conductance decreases with increasing electrolyte content at all interparticle spacings and it has a maximum value, in relation to paste porosity, for each electrolyte level. This maximum occurs at lower spacings as the salt content increases. The results are explained in terms of the dissociation and overlap of opposing counter-ion layers in the paste.