CATION-EXCHANGE HYSTERESIS IN MONTMORILLONITE: A pH-DEPENDENT EFFECT
1975
Maes, A. | CREMERS, A.
The extent of irreversible adsorption of cobalt and zinc ions in sodium montmorillonite is shown to depend upon the composition of the solid phase and the pH. At low and intermediate occupancy of the divalent cation, the adsorption is perfectly reversible up to a pH value of about 6. At very high occupancies, approaching saturation, a significant portion of the adsorbed divalent cations become irreversibly fixed, but can be desorbed by a pH decrease. The consequences of the irreversible and nonstoichiometric uptake of these ions are analyzed and the phenomenon is discussed in terms of an adsorption process, involving either structural hydroxylgroups of the clay or hydroxyaluminum compounds.
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