Quick Search:    advanced search

GSW Home   GeoRef Home   My GSW Alerts   Contact GSW   About GSW   Journals List   Help

This Article Figures Only Full Text Full Text (PDF) Alert me when this article is cited Alert me if a correction is posted Citation Map Services Email this article to a friend Similar articles in this journal Similar articles in ISI Web of Science Alert me to new issues of the journal Download to citation manager Citing Articles Citing Articles via HighWire Citing Articles via ISI Web of Science (12) Citing Articles via Google Scholar Google Scholar Articles by Weir, M. R. Articles by Detellier, C. Search for Related Content GeoRef GeoRef Citation

SOLID-STATE NUCLEAR MAGNETIC RESONANCE STUDY OF SEPIOLITE AND PARTIALLY DEHYDRATED SEPIOLITE

Ottawa-Carleton Chemistry Institute, Department of Chemistry, University of Ottawa, Ottawa, Ontario, Canada K1N 6N5

^* E-mail address of corresponding author: dete{at}science.uottawa.ca

The assignment of the ²⁹Si CP/MAS-NMR spectrum of naturally-occurring sepiolite clay was re-examined using ²⁹Si COSY and ¹H-²⁹Si HETCOR pulse sequences. Each of the three main resonances at –92.1, –94.6 and –98.4 ppm has been attributed to one of the three pairs of equivalent Si nuclei in the basal plane, and the resonance at –85 ppm to Q²(Si-OH) Si nuclei. On the basis of the COSY experiment, the resonance at –92.1 ppm is unambiguously assigned to the intermediate, near-edge Si sites. The HETCOR experiment revealed that the resonance at –94.6 ppm cross-polarizes almost entirely from the Mg–OH protons, and therefore is assigned to the central Si position. The remaining resonance at –98.4 ppm correlates strongly to the protons of the structural water molecules and therefore is assigned to the edge Si sites. Nearly complete rehydration was achieved at room temperature by exposing sepiolite samples that had been partially dehydrated at 120°C to water vapor or to D₂O vapor. The rehydration results support the ²⁹Si NMR peak assignments that were made on the basis of the COSY and HETCOR experiments.

The ²⁹Si CP/MAS-NMR spectrum corresponding to the folded sepiolite structure in which approximately one half of the structural water has been removed by heating to 350°C is reported for the first time. The chemical shift values and relative intensities are significantly different compared to the resonances that are observed in the corresponding spectrum of the true sepiolite anhydride. These observations support the earlier claim that sepiolite heated to ~350°C exists as a distinct phase to be differentiated from that of the completely dehydrated state.

Key Words: Dehydrated Sepiolite • Magic Angle Spinning NMR • Sepiolite • ²⁹Si CP/MAS-NMR • ²⁹Si NMR Signals Assignment • 2-Dimensional Solid State NMR

This article has been cited by other articles:

				J. E. Post, D. L. Bish, and P. J. Heaney Synchrotron powder X-ray diffraction study of the structure and dehydration behavior of sepiolite American Mineralogist, January 1, 2007; 92(1): 91 - 97. [Abstract] [Full Text] [PDF]

				W. Kuang, W. Kuang, G. A. Facey, and C. Detellier DEHYDRATION AND REHYDRATION OF PALYGORSKITE AND THE INFLUENCE OF WATER ON THE NANOPORES Clays and Clay Minerals, October 1, 2004; 52(5): 635 - 642. [Abstract] [Full Text] [PDF]

				B. Hubbard, B. Hubbard, W. Kuang, A. Moser, G. A. Facey, and C. Detellier STRUCTURAL STUDY OF MAYA BLUE: TEXTURAL, THERMAL AND SOLID-STATE MULTINUCLEAR MAGNETIC RESONANCE CHARACTERIZATION OF THE PALYGORSKITE-INDIGO AND SEPIOLITE-INDIGO ADDUCTS Clays and Clay Minerals, June 1, 2003; 51(3): 318 - 326. [Abstract] [Full Text] [PDF]