Mechanism of Ionic Diffusion in Dense Bentonite

Abstract

ABSTRACTA new model based on ionic diffusion in surface (bound) and interstitial (free) water in compacted bentonite systems has been developed. The model is supported by data obtained from flow-through diffusion experiments using Cs+, I- and Cl-. The results show that diffusion depends on the charge of the diffusing species: cations are attracted to the clay particle surface, but are not immobilized, whereas anions are repelled from the clay particle surface. Cations diffuse through both surface and interstitial water, and anions diffuse mainly through interstitial water. The clay structure has been found to affect the diffusion of cations and anions.