Radionuclide Extraction by 2,6‐Pyridinedicarboxylamide Derivatives and Chlorinated Cobalt Dicarbollide

Abstract

The extraction properties of diamide derivatives of dipicolinamide (2,6‐pyridinedicarboxylamide or DPA, (R′R″NCO)₂C₅NH₃) in mixtures containing chlorinated cobalt dicarbollide in the acid form (HCCD), with and without a substituted polyethylene glycol (PEG), have been investigated. Distribution ratios of Cs, Sr, U, Eu and Am have been measured for various concentrations of diamide, PEG, aqueous phase nitric acid, with various HCCD:diamide ratios, and using different organic diluents. In the absence of HCCD, the diamides show little affinity for the extraction of Am or Eu from nitric acid solutions (distributions typically <1). Addition of HCCD with the diamide extractants indicates a pronounced synergistic effect with regard to actinide and lanthanide extraction; the observed Am and Eu distribution ratios typically increase by several orders of magnitude. Cesium is also appreciably extracted by the HCCD in the presence of the various diamides. Addition of PEG (to simultaneously extract Sr) with HCCD and diamide has minimal impacts on the Eu and Am distribution ratios. The initial data indicate that alkyl substituted DPA derivatives weakly affect the extraction properties with regard to actinides and lanthanides, while aryl substituents decrease extraction ability of the mixture. The results of this preliminary work indicate that numerous HCCD‐PEG‐DPA systems are promising and effective for the simultaneous extraction Cs, Sr, Am, and Eu from acidic solutions.

Keywords:

• Cobalt dicarbollide
• diamides of dipicolinamide
• extraction
• cesium
• strontium
• actinides
• lanthanides