Interactinide separations

In these extractants, HNO3 interaction with the extractant occurs with the carbamoyl portion of the molecule (Horwitz etal. 1981), leaving the solvating phosphorus portion of the molecule to interact with the metal ion. These compounds are indeed more efficient extractants of the trivalent metal ions from acidic solutions, able to extract trivalent actinide and lanthanide ions from relatively dilute nitric-acid solutions. Horwitz et al. (1981) have studied the separation of the lanthanides and trivalent actinides from Am to Fm (table 2) using dihexyl-N, N-diethylcarbamoyl-methylphosphonate (DHDECMP) and aqueous nitrate solutions. Steadily decreasing distribution ratios are observed for the lanthanides, but nearly constant D s are found for the trivalent actinides. Group separation does not appear feasible while interlanthanide (but probably not interactinide) separations are possible. However, substitu-... 

Tertiary amines are poor extractants for lanthanides and actinides from dilute nitrate media, but extract these metal ions strongly from concentrated nitrate solutions of low acidity (as was true of TBP). Similar observations have been made for extraction from chloride media. Figure 1 indicates that for 30% Alamine 336/xylene/ll M LiCl group separations are good, some interactinide separations are possible, but lanthanide separation factors are small. Weaver briefly discusses the application of the TRAMEX (tertiary amine extraction) process for the purification of... 

Based on earlier research on the separation of the lanthanides, ion exchange separations were also done using citric add as a complexant. Because the citrate eluent is plagued by relatively slow kinetics, other hydroxy-carboxylic adds were tested as elutriants for the higher actinide elements. Lactic add was among the first spedes tried, but better interactinide separations were observed using a-hydroxyisobutyric acid... 

A sampling of the methods which are (or could be) used for interlanthanide or interactinide separations are shown in figs. 4 and 5, respectively. These should not be... 

Fig. 5. Interactinide separation factors (relative to Am) for selected methods HDEHP and TTA dam from Stary (1966), AHIB (a-hydroxyisobutyric acid/Dowex 50) data from Choppin et al. (1956), and Smith and Hoffman (1956), DHDECMP (dihexyl -N, N-diethyl-carbamoylmethylphosphonate) data from Horwitz etal.(1981).

---