Diluent Effects in the Extraction of Amine From Nitric Acid Solutions by Selected Carbamoylphosphoryl Extractants and Related Monofunctional Compounds*

The extraction of Am(III) from nitric acid solutions by a series of bifunctional extractants containing the carbamoylphosphoryl moiety and of monofunctional extractants containing the P=O donor group, has been investigated using a number of different diluents. In some diluents, such as chloroform, dichloroethane and nitrobenzene, the existence of an apparently anomalous order of Am(III) extraction (that is higher metal extraction for lower basicity of the extractant) has been confirmed with phenyl substituted carbamoylmethylphosphine oxides. No evidence of anomalies was found in other diluents, for example carbon tetrachloride, tetrachloroethylene and o-xylene. While it seems unlikely that the “anomalous aryl strengthening” effect, recently reported in the soviet literature, can account for the extraction behavior of Am(III) by the bifunctional extractants and diluents investigated in this work, the apparent anomalies have been simply explained by strong solvation effects between the diluent and the very basic extractants.