Application of ionic liquids for rare-earth recovery from waste electric materials

Rare-earth metals are essential for high-technology industries, and demands for rare-earth metals are increasing annually. Their stable supply must be ensured because the production of rare earths is limited to a few countries. Industrial waste and spent products, so-called «urban mines,» have been highlighted as valuable secondary resources. To promote metal recycling, highly efficient separation and recovery techniques are required. We have developed a novel separation technique based on liquid-liquid extraction using unique solvent ionic liquids. A newly synthesized extractant, diglycolamic acid, was used in the ionic-liquid systems. The extraction performance of rare-earth metals and selectivity to common metals were improved significantly. In this chapter, we describe the current state of recycling of rare earths, and summarize ionic-liquid-based extraction focusing on the recovery of rare-earth metals from waste electric materials. A liquid-membrane technique that uses ionic liquids is also introduced.