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Potentiometric, Electrical Conductance and Self-Diffusion Measurements in Clay-Water Systems

Published online by Cambridge University Press:  01 January 2024

R. G. Gast  and
Peggy J. East
R. G. Gast
Affiliation:
Agricultural Research Laboratory of The University of Tennessee, Oak Ridge, Tennessee, USA
Peggy J. East
Affiliation:
Agricultural Research Laboratory of The University of Tennessee, Oak Ridge, Tennessee, USA
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Abstract

Potentiometric measurements using commercially available cationic glass electrodes, electrical conductance and self-diffusion measurements of cations and water were made in electrolyte-free 3–5 per cent Li, Na, K, Cs, Ca and Sr bentonite-water systems and bi-ionic systems with varying ratios of K and Ca. Activation energies for conductance in the homoionic clays were calculated using the Arrhenius equation.

The agreement between cation mobilities measured by diffusion and conductance indicates that the underlying mechanism is essentially the same for the two processes. But the activation energies for ion movement determined for conductance measurements do not explain the observed reduction in mobility. Only two clays, Li and Cs, gave values significantly higher than for the measured solution conductance and only the Cs clay gave a value higher than those calculated for ion conductance at infinite dilution.

Increasing Ca saturation in K-Ca clays from 1 to 99 per cent increased the self-diffusion coefficient or mobility of K by a factor of about 1.7 and Ca by a factor of about 30 reflecting the effect of the predominate accumulation of the divalent cation in regions of highest negative potential. The reduction in activity of monovalent cations calculated from the potentiometric measurements, although of the same order of magnitude, was consistently less than the corresponding reduction in mobility in both the homoionic and bi-ionic clays. This difference became greater with increasing mobility of K in the bi-ionic clays.

Type
General
Information
Clays and Clay Minerals (National Conference on Clays and Clay Minerals) , Volume 12 , February 1963 , pp. 297 - 310
Copyright
Copyright © The Clay Minerals Society 1963

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Footnotes

This manuscript is published with the permission of the Director of the University of Tennessee Agricultural Experiment Station, Knoxville.

Operated by the Tennessee Agricultural Experiment Station for the U.S. Atomic Energy Commission under Contract No. AT-40-1-GEN-242.

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