Relation Between Swelling, Water Properties and b-Dimension in Montmorillonite-Water Systems

Abstract

Abstract-The b-dimensions of the unit cells of six different Na-saturated montmorillonites were determined by X-ray diffraction at water Contents ranging from 0 to 20 g per g of montmorillonite.In every case, the b-dimension increased progressively with water content from its initial value, which was characteristic of each dry montmorillonite, to a final value of -9.0 A, which was common to all montmorillonites. The latter value was reached when the water contents of the respective montmorillonites were equal to those at maximal swelling. When these water contents were plotted against the corresponding changes in b-dimension, a straight line that passed through the origin was obtained.Different structure-sensitive properties of the water in montmorillonite-water systems (i.e. the partial specific volume, the amount remaining unfrozen at -5~ and the activation energy required for ions to move through it) were available, as functions of the species of exchangeable cation, from previous studies. Relevant b-dimensions were determined in the present study. It was found that all of these water properties were correlated with the b-dimension of the associated montmorillonite.Our results indicate that epitaxy exists between the crystal lattices of montmorillonite and adsorbed water and that these lattices undergo mutual adjustment with each increment of water. The resulting loss of free energy causes water adsorption, i.e. swelling, to occur spontaneously. Swelling stops when no further adjustment takes place. This does not happen until the adsorbed water is several hundred angstroms thick and has achieved a preferred configuration.

The effect of mineral-ion interactions on soil hydraulic conductivity

“…Solutions enriched in K + can improve soil HC, possibly through Na + displacement (Chen et al, 1983;Levy and Torrento, 1995;Ravina and Low, 1972;Ravina and Markus, 1975). However, additions of K + led to reductions in HC in an illite soil and a low cation exchange capacity (CEC) montmorillonite soil (Chen et al, 1983;Laurenson et al, 2011).…”

Direct Measurement of the Relation Between Swelling Pressure and Interlayer Distance in Li-Vermiculite

“…The general view is that swelling is due to excess osmotic pressure in the solution between the superimposed silicate layers and that it can be described by doublelayer theory (Schofield, 1946;Norrish, 1954;Bolt and Miller, 1955;Warkentin et aL, 1957;Norrish and Rausell-Colom, 1963;van Olphen, 1963;Quirk, 1968). A second view, which has been held primarily by Low and his coworkers (Low and Deming, 1953;Hemwall and Low, 1956;Ravina and Low, 1972;Low and Margheim, 1979;Low, 1980Low, , 1981Viani et al, 1983) and by Derjaguin and his coworkers (Derjaguin et al, 1954;Derjaguin and Churaev, 1974) is that surface hydration also contributes to the swelling of clays and other colloids. The latter view has been advanced recently by Israelachvili and Adams (1978) and Pasbley (1981aPasbley ( , 1981b.…”

Exchangeable Cation—Structural Parameter Relationships in Montmorillonite

“…Therefore, several mechanisms are probably responsible for the changes in b-dimension. It should be noted that in five out of the six montmorillonites used by Ravina and Low (1972) the b-dimension versus water content shows a shoulder in the range of 3-5 g H20]g clay. This shoulder may indicate that there are two or more mechanisms affecting the b-dimension, each of which is dominant within a different range of water content.…”

“…Low et al (1970) and Ravina and Low (1972) showed that the b-dimension in six different montmorillonites increased progressively with water content from 0 to 10-15 gm H20/g clay. The mechanism proposed in the present study can explain changes in the bdimension as a function of water content up to about 2-3 gm H~O/g clay.…”

“…Most of these studies were limited to relatively dry clays. Low et al (1970) and Ravina and Low (1972) reported that the b-dimension of montmorillonite depends on the moisture content of the system, up to relatively high water contents. They explain this effect by the existence of epitaxy between the montmorillonite crystal and the adsorbed water and by mutual adjustment between the two with each increment of water.…”