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Determination of iron oxidation states in clay minerals by x-ray absorption-edge fine-structure spectrometry

Published online by Cambridge University Press:  14 March 2018

C. G. Dodd  and
D. J. Kaup
C. G. Dodd
Affiliation:
University of Oklahoma, Norman, Oklahoma, U.S.A.
D. J. Kaup
Affiliation:
University of Oklahoma, Norman, Oklahoma, U.S.A.
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Abstract

The fine structure of the X-ray absorption spectrum observed on the high energy side of the iron K edge has been recorded with a modified commercial single-crystal X-ray spectrometer. Metallic iron samples exhibited no detectable fine structure, whereas Fe3+ in ferric oxide and Fe2+ in ferrous ammonium sulphate and ferrous sulphate produced significant fine-structure peaks due, presumably, to 1s→4p and 1s→5p electron transitions. The apex of the 1s→4p peak and the minimum between the two peaks were shifted to lower energies by the Fe2+ samples, and the corresponding apices and minima on fine-structure spectra of samples containing Fe3+ and Fe2+ were shifted by an amount which was approximately a linear function of composition. These observations have led to the development of an analytical procedure for the determination of ferric (or ferrous) iron in dry, ground or sedimented clay mineral samples. The lower limit of total iron concentration in the clay sample to which the method is applicable is approximately 1 per cent. The procedure appears promising as an indicator of the oxidation-reduction potential of the geological environment with which the clay mineral may have been in equilibrium, and as a tool of more general geochemical utility.

Type
Research Article
Information
Clay Minerals Bulletin , Volume 5 , Issue 30 , December 1963 , pp. 290 - 301
Copyright
Copyright © The Mineralogical Society of Great Britain and Ireland 1963

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