|Abstract or Summary
- The influence of pH (titration method) and of salt concentration
and drying (drying method) upon the formation of synthetic AI, Fe,
and Mg interlayers in montmorillonite and vermiculite was investigated.
Interlayer formation was evaluated by X-ray diffraction
measurements of basal spacings using a natural chlorite for comparison.
The titration method was superior to the drying method with
respect to aluminum, ferric iron, and magnesium interlayer formation.
The various interlayers formed in montmorillonite by titration
method were more stable than those produced in vermiculite.
The most stable interlayers were made with magnesium and
aluminum in montmorillonite by the titration method. The synthetic
material, like the natural chlorite, did not show any expansion and
exhibited practically no collapse after K treatment and heating to 300° and 550°C.
In montmorillonite, aluminum interlayers were formed in both
acid and alkaline media, but those produced when the OH/AI solution
ratio was less than 1.00 and the pH less than 5.8 exhibited the greatest
stability. When the OH/Al ratio exceeded 1.00, the interlayered
montmorillonite exhibited a gradual expansion toward 17 A[superscript °] on solvation
and partial collapse upon K treatment and heating. Magnesium
interlayers were formed only in alkaline media at pH of about 10.0
Increase in pH produced a slight dissolution of magnesium interlayers.
Ferric iron interlayers were also formed in both acid and alkaline
media. They always exhibited expansion upon solvation with ethylene
gIycoI. The material retained a basal spacing of approximately 14 A[superscript °] at 300°C. They showed also a slight resistance to collapse at 550°C.
The diffraction patterns of Fe-interlayered materials exhibited broad
basal spacings and plateaus compared to AI and Mg interlayers.
In vermiculite, only magnesium interlayers showed stability
after K saturation and K saturation plus heating at 300°C. However,
this material showed no resistance to collapse at 550°C. Aluminum
and iron interlayers did not show this degree of perfection, for they
exhibited a partial collapse after K saturation, a slight resistance to
collapse at 300°C, and no resistance at 550°C.
Aluminum and ferric iron interlayers were formed in montmorillonite
and vermiculite with one drying cycle.