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pH Dependence of the Aqueous Dissolution Rates of Perovskite and Zirconolite at 90°C

Published online by Cambridge University Press:  15 February 2011

Peter J McGlinn
Affiliation:
Australian Nuclear Science and Technology Organisation (ANSTO) Private Mail Bag 1, Menai, New South Wales, Australia, 2234.
K. P. Hart
Affiliation:
Australian Nuclear Science and Technology Organisation (ANSTO) Private Mail Bag 1, Menai, New South Wales, Australia, 2234.
E. H. Loi
Affiliation:
Australian Nuclear Science and Technology Organisation (ANSTO) Private Mail Bag 1, Menai, New South Wales, Australia, 2234.
E. R. Vance
Affiliation:
Australian Nuclear Science and Technology Organisation (ANSTO) Private Mail Bag 1, Menai, New South Wales, Australia, 2234.
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Abstract

Perovskite and zirconolite are two of the major phases of the Synroc titanate mineral assemblage. Their aqueous durability under a range of pH conditions at 90°C has been examined. Solution analysis, electron microscopy and X-ray diffraction have been used to investigate the dissolution behaviour of these phases, and a perovskite phase doped with Nd, Sr and Al, using buffered solutions at pH levels of 2.1, 3.7, 6.1, 7.9 and 12.9. After 43 days of leaching, Ca and Ti extractions from perovskite and zirconolite show only a weak pH-dependence.

SEM investigation of the samples leached at pH 2.1, 6.1 and 12.9 showed that a titanaceous surface layer formed on the perovskite specimens. XRD analysis of the perovskite samples showed that anatase formed on the leached surface at acidic and neutral pHs, but not under alkaline conditions, and that minor amounts of rutile also formed. In the leached perovskite specimens doped with Nd, Sr and Al, no rutile was found by XRD and anatase was only detected in the sample leached at pH 2.1. There were no detectable changes in the leached zirconolite samples examined by SEM and XRD.

Type
Research Article
Copyright
Copyright © Materials Research Society 1995

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References

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