19F MAS-NMR Study of Structural Fluorine in Some Natural and Synthetic 2:1 Layer Silicates

Laurent Huve, Luc Delmotte, Pascal Martin, Ronan Le Dred, Jacques Baron and Daniel Saehr
Laboratoire de Matériaux Minéraux, URA-CNRS 0428, Ecole Nationale Supérieure de Chimie de Mulhouse 3 rue Alfred Werner, 68093 Mulhouse Cedex, France

Abstract: High-resolution solid-state, fluorine-19, magic-angle spinning-nuclear magnetic resonance spectroscopy (MAS-NMR) was used to study natural and synthetic fluorinated 2:1 layer silicates of known composition. This technique enabled us to determine directly the coordination of structural fluorine and it was found to be sensitive to both the chemical nature of the octahedral elements (Al, Mg, Li) and the type of octahedral sheet (di- or trioctahedral). The observed chemical shifts at −132, −152, −176 and −182 ppm (relative to CFCl3) were assigned to different environments of fluorine. The results were then used to characterize synthetic 2:1 layer silicates with unknown octahedral composition.

Key Words: Clay minerals • 19F MAS-NMR • Fluorine • Layer silicates • Silicates • Smectites

Clays and Clay Minerals; April 1992 v. 40; no. 2; p. 186-191; DOI: 10.1346/CCMN.1992.0400208
© 1992, The Clay Minerals Society
Clay Minerals Society (www.clays.org)