Industrial rare earth separation factors

In Table 1, typical extracting reagents used for separation and enrichment of inorganic elements are summarized. Organophosphorus extractants are often used because of their solubility properties. Di(2-ethylhexyl) phosphoric acid is commonly applied to industrial separations because of its high extractability and high separation factors between many inorganic elements, especially for rare earth elements. Other metal ions are extracted as well as the trivalent metal ions. 

The purity of rare earth oxides is an important factor for the reliability on the characterization of their basic properties. In some earlier works, the presence of impurities in the oxides led to erroneous determinations of stmcture and polymorphism. However, due to development of effective separation technologies such as liquid/liquid extraction and precipitation/crystallization purification processes, high purity rare earth oxides can now be easily supplied for higher reliability studies as well as industrial manufacturing. 

Several ionic liquid-based extraction systems for the separation of and recycling rare-earth elements (REEs) have been reviewed in this chapter. There is a great interest in applying ILs to the REE recycling process [14]. However, before IL-based extractions of REEs can be carried out on an industrial scale, there are certain IL factors that need to be considered comprehensively, such as cost, purity, acidity stability, viscosity solubility, density, electrical conductivity, electrochemical windows, extraction efficiency, selectivity, extraction mechanism, stripping ratio, and methods of recycling [14]. The continuing studies in the above areas are warranted. 

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