MEASURING THE SURFACE CONDUCTANCE OF KAOLINITE PARTICLES

In this paper we use a procedure devised by Dukhin and Shilov to derive a formula for the electric dipole strength of a disc-shaped particle with surface conductance Ks. The theory is then compared with experimental results obtained from complex conductivity measurements on a Na-kaolinite sol in the megahertz range. Ks is determined by fitting the experimental and theoretical curves of dipole strength as a function of frequency, assuming a particle aspect ratio of 0.1. The value of Ks obtained in this way is much greater than would be expected from the electrophoretic potential, indicating that a substantial fraction of the conductance comes from the ions below the shear plane in the kaolinite. Such “anomalous” conductance will have a profound effect on all electrokinetic properties of kaolinite. © 1993 Academic Press, Inc.