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

The separation of Eu from Sm and Gd by a combination of photochemical reduction and solvent extraction was investigated. A low-pressure mercury lamp having emission peaks of 184.9 nm and 253.7 nm was used as a light source. The trivalent Eu was reduced to the divalent state by photoreduction in (NH4)2SO4 aqueous solution containing SmCl3, EuCl3, GdCl3 and scavenger (2-propanol or isopropyl formate) to make EuSO4 Precipitate selectively. The purity of Eu in the precipitate was more than 97%. The photoreductive stripping of Eu was studied by using a two-compartment cell separated by a sintered glass filter. In a two-phase system consisting of bis(2-ethylhexyl)phosphoric acid (D2EHPA)/xylene containing the three elements and (NH4)2SO4 aqueous solution, Eu3+ Was reduced in the aqueous phase using isopropyl formate as scavenger, and EuSO4 Precipitated selectively. The recovery of Eu as EuSO4 from the organic solution containing equal amounts of the three elements was dependent on the aqueous-phase pH and reached 68% at pH 0.4. The purity of Eu in the precipitate was more than 95%.