With the rapid development of science and technology, rare earths (REs) are playing a vital role in economic and social development due to their unique electronic structure and physicochemical properties. REs are widely used in lighting, electrical, and magnetic field as a crucially strategic resource. Being the upstream of the RE industry supply chain, RE separation is crucial throughout the whole industry. The primary issues about RE separation are reviewed in this chapter. Conventional organic solvent extractants expose some inherent questions in the long-term application, while ionic liquids as "green solvents" show great potential in the separation processes. This chapter also overviewed RE resources in the world and the issues associated with these separation processes. A brief introduction to ionic liquid-based RE functional materials has been also made.
Rare EarthsThe rare earths (REs) are a group of chemically similar elements in the entire periodic table, consisting of scandium (Sc), yttrium (Y), and the lanthanides. The lanthanides are the series of elements with atomic numbers from 57 to 71, including lanthanum (La), cerium (Ce), praseodymium (Pr), neodymium (Nd), samarium (Sm), europium (Eu), gadolinium (Gd), terbium (Tb), dysprosium (Dy), holmium (Ho), erbium (Er), thulium (Tm), ytterbium (Yb), and lutetium (Lu).Based on the electronic structure and physicochemical properties, REs can be classified as light REs and heavy REs. Light REs are also called "cerium subgroup," including La, Ce, Pr, Nd, Sm, Eu, and Gd. Heavy REs are also called "yttrium
