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Hydration States of Interlamellar Chromium Ions in Montmorillonite

Published online by Cambridge University Press:  02 April 2024

R. Melville Carr
R. Melville Carr*
Affiliation:
Chemistry Department, University of Otago, Dunedin, New Zealand
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Abstract

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Hydroxychromium montmorillonites were prepared from solutions containing chromium nitrate and varying amounts of NaOH. The reactant Cr ions were hydrolyzed and, in some experiments, were dimerized to a significant extent. The extent of polymerization in the product formed from a solution containing a maximum amount of [Cr2(H2O)8(OH)2]4+ was compared with that in products obtained from solutions containing monomer, [Cr(H2O)5OH]2+, and lesser amounts of the dimer. Despite the uncertainty about the nature and amounts of product interlamellar species, the catalytic effect of the montmorillonite interlayer on the hydrolysis and polymerization of Cr(III) appears to be independent of the nature of the reactant species. The validity of this conclusion depends to a large extent on the reliability of water determination in the clay mineral species, which is estimated to be no better than 5%. The assumption that H2O+ is 'combined’ and H2O— is 'free’ water is shown to be partially true, thereby causing some uncertainty in the interpretations of interlayer compositions.

Keywords

CatalysisChromiumHydrationInterlayerMontmorilloniteWater
Type
Research Article
Information
Clays and Clay Minerals , Volume 33 , Issue 4 , August 1985 , pp. 357 - 361
Copyright
Copyright © 1985, The Clay Minerals Society

References

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