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Green rust as a precursor for magnetite: an in situ synchrotron based study

Published online by Cambridge University Press:  05 July 2018

A. Sumoondur ,
S. Shaw ,
I. Ahmed  and
L. G. Benning
A. Sumoondur*
Affiliation:
Earth and Biosphere Institute, School of Earth and Environment, University of Leeds, Leeds, LS2 9JT, UK
S. Shaw
Affiliation:
Earth and Biosphere Institute, School of Earth and Environment, University of Leeds, Leeds, LS2 9JT, UK
I. Ahmed
Affiliation:
Earth and Biosphere Institute, School of Earth and Environment, University of Leeds, Leeds, LS2 9JT, UK
L. G. Benning
Affiliation:
Earth and Biosphere Institute, School of Earth and Environment, University of Leeds, Leeds, LS2 9JT, UK
*
*E-mail: [email protected]
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Abstract

In this study, direct evidence for the formation of magnetite via a green rust intermediate is reported. The Fe(II) induced transformation of ferrihydrite, was quantified in situ and under O2-free conditions using synchrotron-based time-resolved energy dispersive X-ray diffraction. At pH 9 and Fe(II)/Fe(III) ratios of 0.5 and 1, rapid growth (6 min) of sulphate green rust and its subsequent transformation to magnetite was observed. Electron microscopy confirmed these results, showing the initial rapid formation of hexagonal sulphate green rust particles, followed by the corrosion of the green rust as magnetite growth occurred, indicating that the reaction proceeds via a dissolution-reprecipitation mechanism. At pH 7 and Fe(II)/Fe(III) ratio of 0.5, sulphate green rust was the stable phase, with no transformation to magnetite.

Keywords

magnetitegreen rustnanoparticulatesynchrotrondiffraction
Type
Research Article
Information
Mineralogical Magazine , Volume 72 , Issue 1 , February 2008 , pp. 201 - 204
Copyright
Copyright © The Mineralogical Society of Great Britain and Ireland 2008

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