CHARGE CHARACTERISTICS OF CLAYS EVALUATED WITH CAESIUM CHLORIDE IN SPECIAL REFERENCE TO DISPERSION BEHAVIOR

概要

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A method to determine negative and positive charge of clays applying Cs^+ and Cl^- as an index cation and anion respectively was proposed. Special attention was paid for pH and electrolyte concentration in equilibrium solution so as to relate the charge characteristics with dispersion behavior of clays. In order to establish the proposed method as suitable charge determination, interlayer fixation of Cs^+ was compared with that of K^+ and Na^+ by using some reference and soil clays including vermiculite and mica. As a result, Cs^+ was not virtually fixed by any type of clays unless drying process was included. The flocculating effect of Cs^+ enabled negative charge determination in the systems with high pH and low electrolyte concentration which was difficult to quantify with Na^+ due to the dispersion of fine particles. The charge characteristics evaluated by the proposed method indicated that the montmorillonite was the typical clay mineral with permanent charge. In contrast, pH and electrolyte concentration dependence of the sericite suggested the characteristic property of variable charge rather than permanent. This observation was discussed from the aspect of the assumed heterogeneity of surface charge sites in the sericite.
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