Clays and Clay Minerals, Vol. 57, No. 2, 227–233, 2009.
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Authors
Bzdek, Bryan R.
Mcguire, Molly M.
Issue Date
2009
Type
Article
Language
Keywords
Periodicals , Geology , ATR-FTIR , Infrared Spectroscopy , NAu-1 , NAu-2 , Nontronite , Reduction
Alternative Title
Polarized Atr-ftir Investigation Of Fe Reduction In The Uley Nontronites
Abstract
Reductionof structural Fe insmectites affects the surface chemical behavior of the clay, but the underlying mechanism and changes in clay structure are still in need of investigation, particularly with respect to changes in the tetrahedral sheet. The purpose of this study was to probe changes in the tetrahedral sheet that occur when structural Fe is reduced in the Uley nontronites, NAu-1 and NAu-2, using polarized attenuated total internal reflection Fourier-transform infrared spectroscopy. Despite the differences in their structures - NAu-2 has tetrahedral Fe3+ while NAu-1 does not - the changes observed in the Si-O stretching region were quite similar. Reduction results in a shift of the in-plane Si-O stretching modes to lower frequencies, while the out-of-plane Si-O stretch shifts to higher frequencies. The magnitude of these shifts is greater inNAu-2 thaninNAu-1, but the crystallinity of the tetrahedral silicate sheet of NAu-2 is preserved upon reduction. In both nontronites, the orientation of the out-of-plane Si-O bond changes and becomes completely perpendicular to the basal (001) surface of the clay, indicating the formation of trioctahedral domains wherein the individual tetrahedra reorient relative to the plane of the clay layer.\
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gsccm57209-bzd.pdf: 281KB
Citation
Clays and Clay Minerals, Vol. 57, No. 2, 227–233, 2009.
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