Cation-exchanged montmorillonites characterization

The exchange and thermodynamic characterization of complex cations in montmorillonites present no problem with regard to the accessibility and the accomodation of the complexes, regardless of the extent of exchange. 

Clay deposits are composed principally of fine quartz and clay minerals. The three major clay minerals are kaolinite, illite and montmorillonite. Both kaolinite and illite have non-expansive lattices, whereas that of montmorillonite is expansive. In other words, montmorillonite is characterized by its ability to swell and by its notable cation exchange properties. 

The present paper reports on the preparation and characterization of pillcu ed montmorillonites prepared by cation exchange of the montmorillonite with hydrothermally treated solutions contsuning ACH in admixture with chlorides of La, Ce, Pr, Nd, or a commercial mixture of RE-cations. 

Smectite clay - Like mica, smectite cl (commonly called bentonite) has either a pyrophyllite or talc structure. Montmorillonite, a common high-aliunimun smectite, can be characterized by die pyrophyllite crystal structure with a small amount of octahedral Al replaced by Mg. The resulting charge imbalance is compensated by exchangeable cations, usually Na or Ca, between the laminae. In addition to diese counterions, oriented water, similar to that in vermiculite, occupies the interlaminar space. When Ca is the exchangeable cation, there are two water l ers, as in vermiculite when Na is the counterion, there is usually just one water layer. Figure 18 shows the montmorillonite structure. 

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