Non-aqueous solvent extraction of rare-earth nitrates from ethylene glycol to n-dodecane by Cyanex 923

Abstract

Abstract A solvent extraction process comprising two immiscible organic phases has been developed for the extraction of rare earths. The more polar organic phase was ethylene glycol with dissolved rare-earth nitrate salts and lithium nitrate, while the less polar phase was a solution of the neutral extractant Cyanex® 923 dissolved in n -dodecane. The solvent extraction mechanism was determined by slope analysis and the main species in the organic phase was identified by Extended X-ray Absorption Fine Structure (EXAFS) studies. The extraction from the ethylene glycol solution was compared with extraction from an aqueous feed solution. When compared to aqueous feed solutions, the light rare-earth elements (LREEs) are less efficiently extracted and the heavy rare-earth elements (HREEs) more efficiently extracted from an ethylene glycol feed solution, resulting into the easy separation of HREEs from LREEs. The separation factors between neighboring elements are higher for this non-aqueous solvent extraction process than for extraction from an aqueous feed solution.