Separation of rare earths by split-anion extraction with ionic liquids

There are two main challenges in the field of separation of rare earths by solvent extraction: (1) the development of a highly selective extraction agent that can remove one rare-earth element from a mixture without co-extraction of the other elements; (2) the development of a process that allows extraction of rare earths from a chloride solution to an organic phase by a solvating extractant. Extraction from chloride solution is preferred by industry because hydrochloric acid is much cheaper than nitric acid, and because waste water treatment is simpler in case of chlorides compared to nitrates. Solvating extractants are the preferred type of extractants, because of the possibility of loading a high concentration of rare earths in the organic phase and the easy back extraction of the rare earths from the organic phase by water instead of strong acids. Within the framework of the FP7 project EURARE on the exploitation of European rare-earth deposits, Prof. Binnemans invented a new process, called “split anion extraction” with makes the extraction of rare earths from a chloride solution possible by extraction with a nitrate ionic liquid via a solvating mechanism.

References:

• Separation of rare earths by split-anion extraction
  Larsson and K. Binnemans
  Hydrometallurgy 156, 206–214 (2015).
  DOI: 10.1016/j.hydromet.2015.04.020

• Process for extraction and separation of rare earths by split-anion extraction with ionic liquids
  Binnemans and K. Larsson
  Patent application WO 2015106324 A1 (see link here)