Temperature effect on the acid-base behaviour of Na-montmorillonite.
We report a study of the acid-base properties of Na-montmorillonite suspensions at temperatures from 25 degrees C to 80 degrees C, by continuous and batch potentiometric methods, combined with analysis of the dissolved and readsorbed species. The batch titration curves reveal that the dissolution processes of Na-montmorillonite and silica-rich secondary phases are increasingly predominant, respectively at acid and basic pH, and according to the temperature. The continuous titration curves are less affected by these side reactions. In the absence of a common intersection point, the thermodynamic analysis of the curves was based on the shift of the PZNPC with the ionic strength. This shift was not significantly altered by the temperature, by comparison with the dissociation product of water in the same conditions. Therefore we concluded that protonation-deprotonation of the dissociable sites at the edges of the clay platelets is not significantly temperature dependent.
Duc
Myriam
M
Laboratory of Physical Chemistry and Microbiology for the Environment, Nancy University, CNRS, 405 rue de Vandoeuvre, F-54600 Villers-lès-Nancy, France.
Carteret
Cédric
C
Thomas
Fabien
F
Gaboriaud
Fabien
F