Separation of rare earth metals using a supported liquid membrane with DTPA

The separation of La, Pr and Nd (Ln) using a supported liquid membrane system was studied. A water-soluble chelating agent, diethylenetriaminepentaacetic acid (DTPA), was added to the feed or stripping phase to improve permeation rates and selectivities. In the presence of DTPA in the feed phase, La was recovered selectively and the selectivity of Pr with respect to Nd attained was 2.5. However, when DTPA was added to the stripping phase, Ln could permeate even in the pH range in the stripping phase where permeation was hardly detected without DTPA. These phenomena were explained by the difference in the stabilities of chelate formation of Ln ions with DTPA.