As society becomes more dependent on materials and technologies that utilize f-elements, the necessity of improved ways of acquiring these metals increases. While mining rare earth element (REE) ores provides a main source of f-elements, these processes are often cumbersome and produce large amounts of hazardous waste. This has led toward a goal of improving the separations processes that occur during mining to make them more efficient and environmentally conscious. Research in this area also has the potential to increase the viability of new sources of f-elements, such as from the recycling of electronics that contain valuable lanthanide metals. A series of ligands employing three phenyl substituted carbamoylmethylphosphine oxide (CMPO) groups connected through a trialkyl amine ligand capping scaffold has been prepared for selective extraction of f-elements from aqueous solution. Previous work conducted by our group has revealed fluctuation in metal extraction selectivity based on variation in the liquid-liquid extraction parameters (i.e., stir time and ligand concentration). This study will further investigate the stir time dependency of a tris(2-aminoethyl)amine capped ligand derivative with respect to extraction of Gd(III) from aqueous solution. Preliminary results also indicate that an extractant possessing a larger, more flexible tris(3-aminopropyl)amine cap exhibits a high extraction efficiency with respect to the separation of Th(IV). This study will further investigate the extraction selectivity of this ligand utilizing a mixture containing thorium, uranium, and all REEs (excluding promethium) and how the selectivity is affected by ligand concentration. Finally, photophysical studies of select lanthanide complexes of these CMPO ligands aimed at investigating the metal ion coordination environment in solution will be presented.

Variation of a liquid-liquid extraction protocol employing tripodal CMPO-based ligands for f-element recovery

ACS Spring Meeting 2021

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