Influence du milieu de synthèse sur la cristallisation de saponite : proposition de mécanisme réactionnel en milieux acide et basique

Influence of the synthesis medium on the saponite crystallisation: formation mechanism in acidic and basic media. The present work is relative to the hydrothermal synthesis of saponite, a clay mineral having the following chemical formula per half unit cell : MxMg3 (Si4-xAlx)O10(OH,F)2, 0.2 < x < 1.20, where M is an hydrated exchangeable cation and x is the layer charge. Syntheses were performed in fluorine medium in the pH range 1 to 12. Two mechanisms can be proposed: in acidic medium, tetrahedral polysilicic acid incorporate Al3+ cations and, in basic medium, silica polycondensation occurs around a [Mg(OH)2] brucite-like layer. To cite this article: M. Jaber, J. Miéhé-Brendlé, C. R. Chimie 8 (2005).