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Iron substitution in aluminosilicate sols synthesized at low pH

Published online by Cambridge University Press:  09 July 2018

M. B. McBride ,
V. C. Farmer ,
J. D. Russell ,
J. M. Tait  and
B. A. Goodman
M. B. McBride
Affiliation:
Department of Agronomy, Cornell University, Ithaca, NY14853, USA
V. C. Farmer
Affiliation:
The Macaulay Institute for Soil Research, Craigiebuckler, Aberdeen AB9 2QJ, UK
J. D. Russell
Affiliation:
The Macaulay Institute for Soil Research, Craigiebuckler, Aberdeen AB9 2QJ, UK
J. M. Tait
Affiliation:
The Macaulay Institute for Soil Research, Craigiebuckler, Aberdeen AB9 2QJ, UK
B. A. Goodman
Affiliation:
The Macaulay Institute for Soil Research, Craigiebuckler, Aberdeen AB9 2QJ, UK
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Abstract

The procedure for synthesizing proto-imogolite (an acid-soluble hydroxy-aluminium orthosilicate complex) and imogolite (a tubular aluminosilicate mineral) was used to produce ferruginous aluminosilicates over a range of Al/Fe ratios to determine whether Fe3+ can be incorporated in the imogolite structure. Analysis of the synthesized products by transmission electron microscopy, electron diffraction, and IR spectroscopy indicated that, while imogolite was formed in the presence of iron, increased Fe3+ in the systems caused the formation of ferrihydrite and poorly-organized aluminosilicates resembling proto-imogolite allophane. Treatment of these materials with Na-citrate/dithionite/bicarbonate dissolved the ferrihydrite and poorly-organized aluminosilicate, and concentrated products with tubular morphology. Analysis of the structural Fe3+ by ESR spectroscopy suggested that little or no Fe3+ was incorporated in the structure of imogolite, although the less crystalline proto-imogolite allophane may have accommodated some structural Fe3+. A separate iron-rich product, identified as ferrihydrite, was formed at low Al/Fe ratios. Mössbauer spectroscopic analysis of 57Fe3+ doped at very low levels into proto-imogolite and imogolite indicated that the sites of substitution were better defined in the latter. At least part of this Fe3+ may have been incorporated in the structure of boehmite, an impurity formed during synthesis.

Type
Research Article
Information
Clay Minerals , Volume 19 , Issue 1 , February 1984 , pp. 1 - 8
Copyright
Copyright © The Mineralogical Society of Great Britain and Ireland 1984

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References

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