Basic Research on Batchwise Multi-stage Extractions Using TODGA for Dy/Nd Separation

The mutual separation of lanthanides has been studied by multi-stage extraction using an extractant, DGA (diglycolamide) compounds. N,N,N′,N′-tetraoctyl-DGA (TODGA) has a high extractability to lanthanides and a relatively high separation factor (SF) between Dy and Nd (SF of over 20) from HNO3 media. Complete separation with such SF values can be achieved by multi-stage extraction. Less information on multi-stage extraction compared to batch extraction has been presented up to now. We thus conducted a basic study. By confirming the experimental data to be identical to calculations, the sample solution including both metals was employed for batchwise multi-stage extraction. Ninety-seven percent of Dy with under detection limit of Nd could be recovered into the organic phase from Nd with a ten-times higher concentration than Dy using the condition, 0.1 M TODGA/n-dodecane and 0.3 M HNO3 by the multi extraction of 9 × 9 stages for organic and aqueous phases.