Hydrothermal synthesis of Na-beidellite

J. Theo Kloprogge; Ad M.J. van der Eerden; J. Ben H. Jansen; John W. Geus

J. Theo Kloprogge Department of Geochemistry, Institute of Earth Sciences, University of Utrecht, Budapestlaan 4, P. 0. Box 80.021, 3508 TA Utrecht, The Netherlands
Ad M.J. van der Eerden Department of Geochemistry, Institute of Earth Sciences, University of Utrecht, Budapestlaan 4, P. 0. Box 80.021, 3508 TA Utrecht, The Netherlands
J. Ben H. Jansen Department of Geochemistry, Institute of Earth Sciences, University of Utrecht, Budapestlaan 4, P. 0. Box 80.021, 3508 TA Utrecht, The Netherlands
John W. Geus Department of Inorganic Chemistry, Analytical Chemical Laboratory, University of Utrecht, Croesestraat 77a, 3522 AD Utrecht, The Netherlands

Keywords: Na-beidellite, hydrothermal synthesis

Abstract

Na-beidellite was hydrothermally synthesized using various starting materials at a range of P-T conditions. The best crystallized Na-beidellite was carefully investigated with XRD, SEM, TGA, MAS-NMR and IR-spectroscopy. Cell parameters are: a = 5.18 ± 0.005 Å; b = 8.96 ± 0.008 Å; c = 12,54 ± 0.011Å; V = 581.9 ± 0.5 Å3. Indexing is based on an orthorhombic cell. 29Si MAS-NMR reveal three peak positions: - 92.7 ppm (Si-OAl); - 88.4 ppm (Si-1Al); - 82.3 ppm (Si-2Al), indicating an AlIV/Si ratio of 0.106 per unit cell. The presence of small amounts of F in the hydrothermal fluid causes a significant increase in crystallinity. Na-beidellite is the only crystalline product applying a starting gel of composition Na0.7Al4.7Si7.3O22. A Na1.0Al5.0Si7O22 gel results in Na-beidellite + paragonite and gels with higher Na content produce only paragonite.