Investigation of Performance of Imidazolium Ionic Liquid in the Extraction and Separation of Rare Earth Elements from Aqueous Solution

In this study, ionic liquids for extraction and separation of rare earth elements such as cerium, samarium, gadolinium and dysprosium have been studied and tested. The results showed that pure ionic fluids [C6MIM]PF6 and [C6MIM]NTf2, as the solvent, could extract rare earth metals without an extractant. But, the extraction efficiency was low (19.54% for cerium extraction with [C6MIM]PF6, and 11.11% with [C6MIM]PF6). The use of TOPO extractant in these ionic liquids led to the higher extraction efficiency (higher than 80% for extraction of ions with a mixture of TOPO and [C6MIM]PF6. Since ionic liquids are high viscosity solvents, their application in liquid-liquid extraction columns will be complicated, so the combination of ionic liquids with TOPO and TBP solvent was studied. The experimental results showed that the mixture of three compounds TOPO, TBP, and [C6MIM]NTf2 was better than the mixture with [C6MIM]PF6. But, in the mixture of two components, TOPO and [C6MIM]PF6 was more appropriate for ion extraction. The result showed in continuous applications with high volume, the mixture of these three substances can lead to the extraction of rare earth metals with a high extraction efficiency.