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Production of Layered Double Hydroxides for Anion Capture and Storage

Published online by Cambridge University Press:  31 January 2011

Jonathan Phillips  and
Luc Vandeperre
Jonathan Phillips
Affiliation:
jp504@ic.ac.uk, Imperial College London, Department of Materials, London, United Kingdom
Luc Vandeperre
Affiliation:
l.vandeperre@imperial.ac.uk, Imperial College London, Department of Materials, London, United Kingdom
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Abstract

Technetium has a long half life of up to 2.13×105 years. It is separated from liquid waste streams with tetraphenylphosphonium bromide [1], which upon degradation releases Tc as the pertechnetate anion, TcO4−. Pertechnetate is highly mobile in groundwater and it is therefore highly desirable to capture and immobilise this anion within a solid for interim and ultimately long term storage. Layered Double Hydroxide (LDH) materials are known to possess excellent anion sorption capabilities due to their structure which consists of ordered positively charged sheets intercalated with interchangeable hydrated anions. The composition can be tailored to produce suitable precursors for ceramic phases by varying the divalent and trivalent cations and the anions. LDHs with the general formula Ca1-x (Fe1-y, Aly)x (OH)2 (NO3)x . nH2O were produced by a co-precipitation method from a solution of mixed nitrates. Calcination leads to the formation of Brownmillerite Ca2(Al,Fe)2O5 like compounds for temperatures as low as 400°C, this is close to the lowest temperature at which Tc is known to volatilise (310.6 °C Tc2O7). It was shown that after calcining up to 600°C, the LDH structure is recovered in water allowing rapid ion capture to occur. This suggests that these materials have potential for both capture and as a storage medium for Tc.

Keywords

layeredadsorptionwaste management
Type
Research Article
Information
MRS Online Proceedings Library (OPL) , Volume 1215: Symposium V – Materials Research Needs to Advance Nuclear Energy , 2009 , 1215-V11-04
Copyright
Copyright © Materials Research Society 2010

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References

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