Separation of the trivalent actinides and lanthanides remains a challenging task in the implementation of a fully closed nuclear fuel cycle.  Recently, variations of the standard Trivalent Actinide-Lanthanide Separations by Phosphorous-reagent Extraction from Aqueous Komplexes (TALSPEAK) method have been proposed, substituting bis(2-ethylhexyl)phosphoric acid (HDEHP) with 2-ethylhexylphosphonic acid mono-2-ethylhexl ester (HEH[EHP]).  Several advantages in what has been deemed as Advanced TALSPEAK can be noted by using HEH(EHP) rather than HDEHP, including a flatter pH profile, more predictable thermodynamic extraction behavior, and faster extraction kinetics relative to traditional TALSPEAK.  The work presented here attempts to extend Advanced TALSPEAK from the traditional lactate media to a malonate buffer system, allowing separations using lower pH ranges than normally required with lactic acid.  The partitioning and separation of the trivalent lanthanide elements and americium between an aqueous phase and n-dodecane diluent using a combination of HEHEHP, malonic acid, and N-(hydroxyethyl)-ethylenediaminetriacetic acid (HEDTA) are reported.  A thermodynamic model for the prediction of the extraction behavior at various conditions and the role of ternary complexes present in the aqueous phase are also discussed.

Development of a malonate buffer system for use in advanced TALSPEAK separations

248th National Meeting (2014)

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