This research project addresses the problem of establishing an accurate theoretical model of the electrical double layer at the surface of a 2:1 layer type clay mineral (e.g., montmorillonite) in contact with an aqueous electrolyte solution. The results are expected to clarify the interpretation of experimental data on clay particle surface potentials, anion exclusion, cation adsorption, and swelling. A theoretical investigation of the 2:1 clay mineral/aqueous solution interface will be undertaken with four objectives: (1) rigourous application of modified Gouy- Chapman theory to a disc-shaped clay particle suspended in a 1-1 electrolyte solution, (2) calculation of the relation between the electrophoretic mobility and zeta-potential for the clay particle considered in objective (1), (3) calculation of the electrostatic interaction between planar charged surfaces contacting a non- uniform dielectric continuum containing different-sized ions, and (4) extension of modified Gouy-Chapman theory to calculate surface potentials and the electrostatic interaction between planar charged surfaces based on recent integral equation methods in statistical mechanics.
