Separation of samarium and europium by solvent extraction with an undiluted quaternary ammonium ionic liquid: towards high-purity medical samarium-153

Abstract

Long-lived europium-154 impurities are formed during the production of medical samarium-153 in a high-flux nuclear reactor. A method to separate these europium impurities from samarium was investigated using the hydrophobic quaternary ammonium ionic liquid Aliquat 336 nitrate. The separation method consists of the selective reduction of Eu³⁺ by zinc metal in an aqueous feed solution containing a high nitrate salt concentration. Subsequent extraction using undiluted Aliquat 336 nitrate leads to an efficient separation of both lanthanides in a relatively short time frame. Sm³⁺ was extracted to the neat ionic liquid phase much more efficiently than Eu²⁺. An initial approach using the addition of dicyclohexano-18-crown-6 to capture Eu²⁺ in the ionic liquid phase was less efficient.