Influence of exchangeable cations on the stability and water retention of montmorillonite
1999
Ahmad, M.M. (National Agricultural Research Centre, Islamabad (Pakistan)) | Karube, J.
The stability of montmorillonite was determined under NaCl solution combined with CaCl2, MgCl2, or AlCl3. When the pH changed from 5.8 to 8.0, the stability increased considerably for all combinations except AlCl3 due to the point of zero change of the edge being at about pH 6.5. Montmorillonite dispersed at low electrical conductivity (EC) even when the sodium adsorption ratio (SAR) was low. At high pH, the system required high EC for coagulation under the same SAR. The water retention of montmorillonite treated with NaCl, NH4Cl, KCl, CaCl2, MgCl2, and AlCl3 was measured to estimate the effect on the structure. Clay saturated with Na(+) exhibited almost the same water retention in both drying and wetting processes, while with NH4(+), K(+), Ca(2+), and Al(3+), it showed inversibility once air dried. The basal spacing of air-dried montmorillonite measured by X-ray diffraction (XRD) followed the order of the hydrated ion radius within the same valence. The greater interlayer opening of air-dired clay with Ca(2+), Mg(2+), and Al(3+) indicated the formation of a porous structure
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