HOME HELP FEEDBACK SUBSCRIPTIONS ARCHIVE SEARCH TABLE OF CONTENTS		QUICK SEARCH:   [advanced] Author: Keyword(s): Year:  Vol:  Page:

This Article Full Text (PDF) Alert me when this article is cited Alert me if a correction is posted Services Similar articles in this journal Alert me to new issues of the journal Download to citation manager Citing Articles Citing Articles via Google Scholar Google Scholar Articles by Verburg, K. Articles by McBride, M. B. Search for Related Content PubMed Articles by Verburg, K. Articles by McBride, M. B. Agricola Articles by Verburg, K. Articles by McBride, M. B.

Cation-Exchange Hysteresis and Dynamics of Formation and Breakdown of Montmorillonite Quasi-Crystals

CSIRO Division of Soils, Cunningham Laboratory, 306 Carmody Road, St Lucia, Qld 4067, Australia

Philippe Baveye^* and Murray B. McBride

Dep. of Soil, Crop and Atmospheric Sciences, Cornell Univ., Ithaca, NY 14853

*Corresponding author (pcb2{at}cornell.edu).

ABSTRACT

The phenomenon of cation-exchange hysteresis seems to suggest that a number of cation-exchange reactions are characterized by an extremely slow kinetic. This, however, is in direct conflict with the fast equilibration times that have been reported in the literature in recent years. These seemingly contradictory observations have been reconciled recently in a conceptual model in which the exchanger is assumed to first undergo a fast reaction, followed by a much slower, second kinetic stage. This conceptual model links cation-exchange hysteresis to hysteresis in the formation and breakdown of quasicrystals during the forward and backward exchange reactions. Because the results in the literature on the kinetics of these processes are contradictory, the objective of this study was to assess their dynamics and long-term kinetics. Initial rates of quasi-crystal formation and breakdown were found to be fast, but the processes proceeded thereafter for at least 5 mo at a slower rate. The results also suggest that the slow kinetics of quasi-crystal formation and breakdown is related to the presence of activation energy barriers for intercrystalline swelling and can cause quasi-crystals to be inherited from the preparation procedure.

Contribution of Dep. Soil, Crop and Atmospheric Sciences, Cornell Univ.

Received for publication August 10, 1994.