Cryptands on a Solid Support for the Separation of Europium from Gadolinium

With the great demand for europium in green-energy technologies comes the need for innovative methods to isolate the elements. We introduce a solid-liquid extraction method using a 2.2.2-cryptand-modified solid support to separate europium from gadolinium using their differences in electrochemical potential. The method overcomes challenges associated with the separation of those two ions that have similar coordination chemistry in the +3 oxidation state. A competitive adsorption study in the cryptand system between Eu^II/Eu^III and Gd^III shows greater affinity for Eu^II relative to Gd^III. After separation from Gd^III, Eu was released by oxidizing Eu^II to Eu^III with 99.3% purity. The purity of separated Eu is unaffected by pH between pH 3.0 and 5.5. Overall, we demonstrate that by modifying a solid support with 2.2.2-cryptand, divalent europium can be separated from trivalent gadolinium based on the differences of affinities of 2.2.2-cryptand for the two ions.