Lattice Expansion and Rheological Behavior Relationships in Water-Montmorillonite Systems

Abstract

Some divergent experimental data have been reported on the swelling behavior of sodium montmorillonite. At water contents above 50 percent (based on the weight of dry clay) the basal reflection of sodium montmorillonite at 19.2 Å becomes weak and very diffuse; some workers have stated that it disappears altogether while others report a persistent weak line even at very high water content. The pronounced differences in physical properties of sodium and calcium montmorillonite suggest that their lattice expansions should also be dissimilar. This paper describes some X-ray diffraction experiments using purified lithium, sodium, and potassium montmorillonites dispersed in water and in salt solutions which were conducted for the purpose of resolving some of these disputed points. The X-ray diffraction instrument employed was a General Electric geiger counter spectrometer unit with a copper tube and nickel filters. The knowledge thus gained has provided some insight into other properties of these clays, such as their rheological behavior.A recording Couette-type viscometer designed to provide a wide spectrum of shear rates and shearing stresses has been used to examine the rheological transformations which occur in passing from states of maximum dispersion to states of varying degrees of agglomeration as a result of interactions between LiCl, NaCl, KCl, and CaCl₂, and the Li, Na, K, and Ca salts of montmorillonite in terms of certain ideal rheological models. Filtration characteristics of these systems have also been explored using a standard technique.