OPTIONS FOR THE SEPARATION OF RARE EARTH ELEMENTS

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OPTIONS FOR THE SEPARATION OF RARE EARTH ELEMENTS
J.R. Goode
J.R. Goode and Associates, Suite 1010, 65 Spring Garden Ave.,
Toronto, Ontario, Canada, M2N 6H9
([email protected])
ABSTRACT
This paper reviews options for the separation of a mixture of rare earth elements (REE) into its
component elements. The original crude separations used selective chemistry such as double salt
precipitation and reductive/oxidative processes - methods that still have a place in the industry.
Fractional crystallization was developed for more complete separations of adjacent REE. The latter
method was replaced by ion exchange (IX) which was in turn replaced by solvent extraction (SX). Two
main SX chemistries are in use (solvation and cation exchangers) with several variants (mixed solvents,
ionic liquids, etc.) under development. Plant configurations have evolved including advanced techniques
like “hyperlinking”, novel saponification methods, and alternative stripping techniques. The classic mixer
settler is the most commonly employed device although centrifugal contactors are also used. Nondispersive SX options, including microfluidic devices and membrane-assisted SX techniques, are being
developed and could revolutionize the SX option.
Other REE separation techniques now being studied, and discussed in this paper, include Molecular
Recognition Technology (MRT) and Free Flow Electrophoresis (FFE), and newer ion exchange based
separation systems.
Separation plant feed composition, purity targets, separation system chemistry, reagent demands,
environmental issues, control systems, and economics are compared and discussed.
KEYWORDS
Rare earth separation, solvent extraction, SX, solvent, mixer-settler, centrifugal contactor, non-dispersive
SX, microfluidics, membrane supported SX, Molecular Recognition Technology, MRT, Free Flow
Electrophoresis, FFE, environment, economics
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