Highly efficient mutual separation of Nd-Pr by the selective dissolution of Nd into an ionic liquid containing1,1,1,2,2,3,3-heptafluoro-7,7-dimethyl-4,6-octanedione

The separation of Nd from Pr in the mixture is one of the challenging tasks. The present investigation exhibited the unprecedented mutual separation of Nd and Pr from the physical mixture of Nd<inf>2</inf>O<inf>3</inf> and Pr<inf>6</inf>O<inf>11</inf> by selective dissolution of Nd into an ionic liquid, 1-butyl-3-methylimidazolium bis (trifluoromethanesulfonyl) imide) ([C<inf>4</inf>mim]NTf<inf>2</inf>) phase containing 1,1,1,2,2,3,3-heptafluoro-7,7-dimethyl-4,6-octanedione (HFOD) for stabilizing Nd³⁺ by enolate ion complexing in the ionic liquid phase. The water content of ionic liquid, the concentration of HFOD, and the frequency of stirring improved the extent of dissolution. However, Pr dissolution in measurable quantity showed detrimental effect in their mutual separation. The sintering of the precursors led to agglomeration of the particles obtaining bigger in size with low defect fraction thereby resulting in the reduction in the extent of dissolution due to the availability of lower surface area. The relative composition of Nd<inf>2</inf>O<inf>3</inf> and Pr<inf>6</inf>O<inf>11</inf> influenced the mutual separation as also observed for the total amount of solid required to be process with respect to the unit ionic liquid phase volume. The dissolution being exothermic, the extent of dissolution reduced at higher temperature thereby registering an impact on the mutual separation. The nature of the ionic liquid also influenced the dissolution characteristics with a trend in the mutual separation as [C<inf>4</inf>mim]NTf<inf>2</inf> < [C<inf>6</inf>mim]NTf<inf>2</inf> < [C<inf>8</inf>mim]NTf<inf>2</inf>.