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Inhibition of Sintering by Si During the Conversion of Si-Rich Ferrihydrite to Hematite

Published online by Cambridge University Press:  28 February 2024

Susan M. Glasauer ,
Paul Hug ,
Peter G. Weidler  and
Andreas U. Gehring
Susan M. Glasauer
Affiliation:
Lehrstuhl für Bodenkunde, Technische Universität München, 85350 Freising-Weihenstephan, Germany
Paul Hug
Affiliation:
Institut für Anorganische Chemie, Universität Zürich, CH-8057 Zürich, Switzerland
Peter G. Weidler
Affiliation:
Institut für Terrestrische Ökologie, ETH Zürich, CH-8952 Schlieren, Switzerland
Andreas U. Gehring
Affiliation:
Institut für Terrestrische Ökologie, ETH Zürich, CH-8952 Schlieren, Switzerland
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Abstract

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The distribution and chemical state of Si in a synthetic 2-line ferrihydrite with a Si/(Si + Fe) molar ratio of 0.11 was studied. Heat treatment under oxidizing conditions shows that Si-rich ferrihydrite is stable to 400°C. The transformation to hematite and the formation of a polymerized amorphous-silica phase occur at 850°C. At this temperature, the specific surface area decreases greatly and the average pore diameter increases, which is indicative of sintering. Heating under severe reducing conditions causes a segregation of Si from Fe and results in a mixture of elemental Fe and SiO2. Surface and structural data suggest that Si is located near the particle surface where it limits the rearrangement of Fe octahedra to form hematite.

Keywords

BETFerrihydriteSiSinteringXPS
Type
Research Article
Information
Clays and Clay Minerals , Volume 48 , Issue 1 , February 2000 , pp. 51 - 56
Copyright
Copyright © 2000, The Clay Minerals Society

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