Solid-State Nuclear Magnetic Resonance Spectroscopy on Synthetic Ammonium/Aluminum-Saponites*

J. T. Kloprogge1, **, J. Breukelaar2, A. E. Wilson2, J. W. Geus3 and J. B. H. Jansen1, ***
1 Department of Geochemistry, Institute of Earth Sciences, University of Utrecht Budapestlaan 4, P.O. Box 80.021, 3508 TA Utrecht, The Netherlands
2 Koninklijke/Shell-Laboratorium Amsterdam (Shell Research B.V.) P.O. Box 3003, 1003 AA Amsterdam, The Netherlands
3 Department of Inorganic Chemistry, University of Utrecht P.O. Box 80.083, 3508 TB Utrecht, The Netherlands
* This paper is a joint contribution from the Debye Institute, University of Utrecht, The Netherlands, and Shell Research B.V.
** Present address: TNO-Institute of Applied Physics TU Delft, Department of Inorganic Materials Chemistry, P.O. Box 595, 5600 AN Eindhoven, The Netherlands.
*** Present Address: Bowagemi B.V., Prinses Beatrixlaan 20, 3972 AN Driebergen, The Netherlands.

Abstract: Ammonium-saponite is hydrothermally grown at temperatures below 300°C from a gel with an overall composition corresponding to (NH4)0.6Mg3Al0.6Si3.4O10(OH)2. Using 27Al and 29Si solid-state Magic Angle Spinning NMR techniques it is demonstrated that synthetic ammonium-saponites have a rather constant Si/AlIV ratio (≈5.5) and an AlIV/AlVI ratio that varies between 1.5 and 3.8. The above ratios are independent of the synthesis temperature, although an increasing amount of Si, N, and, to a lesser extent, Al are incorporated in an amorphous phase with increasing temperature. 27Al MAS-NMR is unable to differentiate between Al at octahedral and Al3+ at interlayer sites. CEC, XRD, and the inability to swell prove the AlVI to be mainly on the interlayer sites. Based on the NH4- exchange capacity, X-ray fluorescence, 27Al and 29Si MAS-NMR, it is possible to calculate a relatively accurate structural formula.

Key Words: 27Al/29Si MAS-NMR • Saponite • Synthesis

Clays and Clay Minerals; August 1994 v. 42; no. 4; p. 416-420; DOI: 10.1346/CCMN.1994.0420406
© 1994, The Clay Minerals Society
Clay Minerals Society (www.clays.org)