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Calcium Vanadinite: An Alternative Apatite Host for Cl-rich Wastes

Published online by Cambridge University Press:  03 July 2014

M. R. Gilbert*
Affiliation:
AWE, Aldermaston, Reading, RG7 4PR, UK.
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Abstract

Apatites are often seen as good potential candidates for the immobilization of halide-rich wastes and, in particular, chlorapatite (Ca5(PO4)3Cl) has received much attention in recent years. However, synthesis of chlorapatite waste-forms can produce a complicated multi-phase system, with a number of secondary phases forming, including β-TCP (Ca3(PO4)2), spodiosite (Ca2(PO4)Cl) and pyrophosphate (Ca2P2O7), many of which require elevated temperatures and extended calcinations times to reduce. Calcium vanadinite (Ca5(VO4)3Cl) demonstrates a much simpler phase system, with calcination at 750 °C yielding Ca5(VO4)3Cl together a small quantity of a Ca2V2O7 secondary phase, the formation of which can be retarded by the addition of excess CaCl2. Characterization of compositions doped with SmCl3 as an inactive analogue for AnCl3 show the Cl to be immobilized in the vanadinite whilst the Sm forms a wakefieldite (SmVO4) phase.

Type
Articles
Copyright
Copyright © Materials Research Society 2014 

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References

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