The Coordination of Aluminum Ions in the Palygorskite Structure

Necip Güven, Jean-Baptiste d'Espinose de la Caillerie and Jose J. Fripiat
Department of Geosciences, Texas Tech University P.O. Box 4109, Lubbock, Texas 79409
Department of Chemistry and Laboratory for Surface Studies University of Wisconsin-Milwaukee, P.O. Box 413, Milwaukee, Wisconsin 53201

Abstract: NMR spectra of PF1-1 Floridan palygorskite strongly suggest that Al3+ occurs only in octahedral coordination. X-ray microanalysis of the palygorskite fibers indicate a chemical composition defined by the atomic ratios: Mg/Si = 0.34, Al/Si = 0.27, and Fe/Si = 0.04. Considering the NMR and CEC data in this report along with the previously published results of IR and Mössbauer spectroscopic studies, the following structural formula is proposed for PF1-1 palygorskite: ( Mg 2.12 Al 1.68 Fe 3+ 0.96 )Si 8 O 20 (OH) 2 ( OH 2 ) 4 where □ represents the vacant Ml octahedral sites in the structure, and Al3+ and Fe3+ are all exclusively assigned to the octahedral sites.

Key Words: Al-coordination • MAS-NMR • Palygorskite

Clays and Clay Minerals; August 1992 v. 40; no. 4; p. 457-461; DOI: 10.1346/CCMN.1992.0400410
© 1992, The Clay Minerals Society
Clay Minerals Society (www.clays.org)