Development of Ammonium-Saponites from Gels with Variable Ammonium Concentration and Water Content at Low Temperatures*

J. Theo Kloprogge1, **, Johan Breukelaar2, J. Ben H. Jansen1, *** and John W. Geus3
1 Department of Geochemistry, Institute of Earth Sciences, University of Utrecht, Budapestlaan 4, P.O. Box 80.021, 3508 TA Utrecht, The Netherlands
2 Koninklijke/Shell-Laboratorium Amsterdam (Shell Research B.V.), P.O. Box 3003, 1003 AA Amsterdam, The Netherlands
3 Department of Inorganic Chemistry, University of Utrecht, P.O. Box 80.083, 3508 TB Utrecht, The Netherlands
* This paper is a joint contribution from the Debye Institute, University of Utrecht, The Netherlands, and Shell Research B.V., Amsterdam.
** Present address: Plastics and Rubber Institute TNO, P.O. Box 108, 3700 AC Zeist, The Netherlands.
*** Present address: Bowagemi, Prinses Beatrixlaan 20, 3972 AN Driebergen, The Netherlands.

Abstract: Ammonium-saponite is hydrothermally grown at temperatures below 300°C from a gel with an overall composition corresponding to (NH4)0.6Mg3Si3.4Al0.6O10(OH)2. The synthetic saponite and co-existing fluid have been characterized by means of X-ray powder diffraction, X-ray fluorescence, Induced Coupled Plasma-Atomic Emission Spectroscopy, thermogravimetric analysis, transmission electron microscopy, CEC determination using an ammonia selective electrode, and pH measurement. In the crystallization model developed, crystallization started with the growth of individual tetrahedral layers with an aluminum substitution not controlled by the AlIV/AlVI ratio in the gel and hydrothermal fluid, on which the octahedral Mg layers can grow. During the synthesis, individual sheets stacked to form thicker flakes while lateral growth also took place. The remaining AlVI partly replaced ammonium as the interlayer cation.

Key Words: Cation exchange capacity • Infrared spectroscopy • Saponite • Synthesis • Thermal analysis • Transmission electron microscopy • X-ray powder diffraction

Clays and Clay Minerals; February 1993 v. 41; no. 1; p. 103-110; DOI: 10.1346/CCMN.1993.0410111
© 1993, The Clay Minerals Society
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