Separation and storage of the long-lived isotope 99Tc in an appropriate and stable waste-form is an important issue for which metal oxide solid-state materials are considered. We are approaching the study of Tc speciation in metal oxides by employing polyoxometalates (POMs) as models. In this study, we examined the redox speciation of Tc incorporated into lacunary Wells-Dawson ions, a1-P2W17O6110- (a1 )and a2-P2W17O6110- (a2 ).  In the synthesis of the [TcVO(a1-P2W17O61)]7- (Tc V O-a 1 ) and  [TcVO(a2-P2W17O61)]7- (Tc V O-a 2 ), we observed the formation of Tc(IV) species (TcO2 and a Tc(IV) � oxo bridged dimer).  This study identifies the features in the synthesis that contribute to the formation of Tc(IV) species and identifies factors that optimize the formation of Tc V O-a2/ Tc V O-a1 .  EXAFS and XANES studies performed on non-optimized syntheses reveal that the parameters influencing the redox speciation of Tc V O-a2/ Tc V O-a1  are the precipitating agent (KCl or ethanol) and the amount of ethylene glycol, that is employed as a �transfer ligand� to prevent hydrolysis of the (NBu4) TcOCl4 starting reagent.

Considerations for the synthesis of polyoxometalates incorporating technetium

246th National Meeting (2013)

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