Extraction of Lanthanides(III) and Am(III) by Mixtures of Malonamide and Dialkylphosphoric Acid |
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Authors: | Benoît Gannaz Mark R. Antonio Clément Hill Gérard Cote |
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Affiliation: | 1. CEA‐Valrh?, DEN/VRH/DRCP/SCPS/LCSE , Bagnols‐sur‐Cèze, France;2. Chemistry Division, Argonne National Laboratory , Argonne, IL, USA;3. Ecole Nationale Supérieure de Chimie de Paris‐ENSCP , Université Pierre et Marie Curie‐Paris6 , Paris, France |
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Abstract: | Abstract N,N′‐dimethyl‐N,N′‐dioctylhexylethoxymalonamide, DMDOHEMA, and di‐n‐hexylphosphoric acid, HDHP, are the extractants of reference for the French DIAMEX–SANEX process for the separation of trivalent actinide ions from the lanthanide ions. In this work, the extraction of Eu3+ and Am3+ by the two extractants, alone or in mixtures, has been investigated under a variety of experimental conditions. The two cations are extracted by HDHP as the M(DHP · HDHP)3 complexes with an Eu/Am separation factor of ~10. With DMDOHEMA, Eu3+ and Am3+ are extracted as the M(NO3)3(DMDOHEMA)2 disolvate species with an Am/Eu separation factor of ~2. The metal distribution ratios measured with a mixture of the two reagents indicated that almost all lanthanides are extracted equally well. The extraction of Eu3+ and Am3+ by HDHP‐DMDOHEMA mixtures exhibits a change of extraction mechanism and a reversal of selectivity taking place at ~1 M HNO3 in the aqueous phase. Below this aqueous acidity, HDHP dominates the metal extraction by the mixture, whereas DMDOHEMA is the predominant extractant at higher aqueous acidities. Some measurements indicated apparent modest antagonism between the two extractants in the extraction of Eu3+ and synergism in the extraction of Am3+. These data were interpreted as resulting from the formation in the organic phase of mixed HDHP‐DMDOHEMA species containing two HDHP and five DMDOHEMA molecules. |
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Keywords: | Malonamides di-n-hexylphosphoric acid Am(III) Eu(III) extraction separation |
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