Dissolution, solvation as well as the chemistry of f-element cations in conventional solvents are nowadays quite well understood as extensive studies have been undertaken in the past. In contrast, little is known about lanthanide ions in ionic liquids (ILs). However, ILs are of particular interest with respect the separation and purification of lanthanides by extraction methods as well as for the production of elemental lanthanide metal by electrodepositon. Hydrophobic ILs have been already been successfully applied in the extraction of lanthnides from aqueous, acidic solutions. Here a clear benefit is the high tunablility of both the physico-chemical properties as well as the complexation behaviour of the IL by the choice of the cation-anion combination.     The electrodeposition of rare earth metals using a classical high temperature molten salt process is well established. However, ionic liquids, especially room temperature ionic liquids, hence room temperature molten salts, RTILs, offer the advantage of much lower working temperatures, but it it not trivial to find ionic liquids that have a suitable. It may be possible to reduce the rare earth oxide to the metal directly by electrolysis in ionic liquids. But there are certain challenges such as the dissolution (and solubility) of rare earth oxides and oxo-compounds in ILs, the chemical and electrochemical stability of the ILs, the conductivity and viscosity of the IL and many more. Task-specific ILs for the dissolution and electrochemical deposition of ILs will be presented. Clear connections can be made between the IL acidity and the dissolution capability on the one hand and the IL basicity and the lanthanide metal reduction potential on the other.

Rare earth chemistry in ionic liquids

248th National Meeting (2014)

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