Synthesis of Zeolites from Thermally Activated Kaolinite. Some Observations on Nucleation and Growth

M. Murat, A. Amokrane, J. P. Bastide and L. Montanaro*
Institut National des Sciences Appliquées (INSA) de Lyon, Groupe Métallurgie Physique et Physique des Matériaux (UA CNRS N° 341), Laboratoire de Chimie-Physique Appliquée et Environnement, and Laboratoire de Thermochimie Minérale, 20 Av. Albert Einstein, 69621 Villeurbanne, France
* Politecnico di Torino, Dipartimento dei Materiali ed Ingegneria Chimica, Corso Duca degli Abruzzi 24, 10129 Torino, Italia

Abstract: Depending on the preparation temperature and the origin of the raw mineral, the products obtained by thermal activation of kaolinite lead, by hydrothermal treatment with sodium hydroxide at 102°C, either to zeolite 4A, or to cubic zeolite P, or to a mixture of cubic and tetragonal zeolite P. The change in the type of zeolite obtained was explained on the basis of a radical change of the zeolite nucleation process due to either the presence of soluble potassium or high silica content resulting from dehydration of muscovite (an impurity in the raw-kaolinite), or from “segregation” associated with the first step of the metakaolinite to mullite transformation. These phenomena occur at a lower calcination temperature with poorly-crystallized kaolinite, and iron in such a sample promotes a sensitive decrease in the formation rate of zeolite crystals. Such results could be used to characterize the crystallinity of kaolinites.

Clay Minerals; March 1992 v. 27; no. 1; p. 119-130; DOI: 10.1180/claymin.1992.027.1.12
© 1992, The Mineralogical Society
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