Chemical characterization, structural features, and thermal behavior of sodium and hydrogen octosilicate

G. Borbély, H. K. Beyer, H. G. Karge, W. Schwieger, A. Brandt, K. H. Bergk

Research output: Contribution to journalArticle

43 Citations (Scopus)

Abstract

The chemical composition and the thermal behavior of sodium and hydrogen octosilicate was studied by chemical and thermal analysis, infrared (IR), magic-angle-spinning nuclear magnetic resonance (MAS-NMR) spectroscopy, and X-ray diffractometry. Both compounds are layer silicates with basal spacings of 11.10 and 7.38 Å, respectively. In both forms the ratio of Q4 silicon (connected via oxygen bridges with four silicon atoms) to Q3 silicon (connected with only three other Si atoms) is I. At least a small part of the Q4 silicon can be substituted by aluminum. Elimination of water coordinated to the cations in sodium octosilicate results in a concomitant structural collapse. Replacement of the sodium ions by protons affects the atomic arrangement in the sheets only to a minor degree, but results in a decrease of the periodicity along the crystallographic c axis. Upon heat treatment an endothermal structural rearrangement occurs at about 360 K as revealed by significant changes of the IR and 29Si MAS-NMR spectra. Reexchange with Na ions largely, but not completely, restores the structure of the parent octo- silicate. The X-ray diffraction pattern of sodium octosilicate was indexed in the monoclinic system with a = 7.345 Å, b = 12.74 Å, c = 11.25 Å and β = 99.3°. Based on conclusions drawn from the results of the present study, the X-ray pattern of hydrogen oclosilicate was tentatively indexed in the monoclinic system with a = 7.345 Å, b = 12.74 Å, c = 8.51 Å and β = 119.8°.

Original languageEnglish
Pages (from-to)490-497
Number of pages8
JournalClays and Clay Minerals
Volume39
Issue number5
DOIs
Publication statusPublished - Oct 1991

Keywords

  • MAS-NMR spectroscopy
  • Octosilicate
  • Sheet silicates
  • Thermal behavior

ASJC Scopus subject areas

  • Water Science and Technology
  • Soil Science
  • Geochemistry and Petrology
  • Earth and Planetary Sciences (miscellaneous)

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