SEPARATION OF EUROPIUM FROM SAMARIUM AND GADOLINIUM BY COMBINATION OF ELECTROCHEMICAL REDUCTION AND SOLVENT-EXTRACTION

The separation of Eu from Sm and Cd by combination of electrochemical reduction and solvent extraction was investigated. A two-compartment cell separated by a cation exchange membrane and equipped with a titanium plate electrode was used. Trivalent Eu was reduced to the divalent form by electroreduction in (NH4)2SO4 aqueous solution containing SmCl3, EuCl3 and GdCl3 to form EuSO4 precipitate selectively. The purity of Eu in the precipitate was more than 97%. The electro-reductive stripping of Eu was studied by using a two-compartment electrochemical cell. In two-phase systems consisting of metal-loaded di-5-methyl-2-(1-methylneohexyl)neodecanoyl phosphoric acid (DP-18) or bis(2-ethylhexyl)phosphoric acid (D2EHPA) diluted with xylene and (NH4)2SO4 aqueous solutions, Eu3+ was reduced at the aqueous phase/electrode interface and EuSO4 precipitated selectively in the aqueous phase. The recovery of Eu as EuSO4 from an organic solution containing equal amounts of the three elements was dependent on the aqueous-phase pH and attained up to 83.2% at pH 1.8 in the DP-18 system. The purity of Eu in the precipitate was more than 95%.