Extraction of REE(III) and Am(III) from a Nitric Acid Solution with Fe(III) and Mn(II) Dibutyl Phosphoric Acid Compounds

The behavior of a number of REE and Am(III) during their extraction from nitric acid solutions with iron and manganese dibutyl phosphoric acid (HDBP) compounds in various diluents was studied. An increase in the concentration of iron and manganese in the organic phase leads to an increase in the REE distribution ratios and, in some cases, to a noticeable change in the element separation factors. The element separation factors significantly differ depending on the diluent. The increase in the separation factors of pairs of elements can reach high values. For example, the Er/Dy separation factor in toluene increases by a factor of 5, and the Dy/Tb separation factor in chloroform, by a factor of 7. The use of decalin as a diluent leads in most cases to a maximum increase in the REE distribution ratios. In the system with an o-nitrotoluene (ONT) diluent, at a certain ratio of HDBP to Fe(III), the separation factors of americium and REE (except cerium) are high enough to allow their separation. The influence of the transition metal and solvent on the distribution and separation of REE is discussed.