Harnessing Outer-Sphere Hydrogen Bonding Interactions for Enhancing Ln(III) Selectivity with Alcohol Phase Modifiers.
Allison A Peroutka1, Amanda J Carr2, Ilya A Shkrob2
1Department of Chemistry, Colorado School of Mines, 1500 Illinois St, Golden, Colorado 80401, United States.
Inorganic Chemistry
|March 4, 2026
Summary
Phase modifiers like alcohols enhance lanthanide (Ln) separation by influencing outer-sphere interactions, not inner-sphere coordination. This study reveals how alcohol structure impacts Ln extraction and selectivity in solvent extraction systems.
Area of Science:
- Radiochemistry
- Separation Science
- Coordination Chemistry
Background:
- N,N,N',N'-tetraoctyldiglycolamide (TODGA) exhibits high lanthanide (Ln) selectivity.
- Selectivity is linked to outer-sphere interactions involving TODGA, counteranions, and solvent molecules.
- Phase modifiers, such as alcohols, can affect Ln extraction but their mechanism is unclear.
Purpose of the Study:
- Investigate the influence of alcohol structure on Ln extraction by TODGA.
- Elucidate the mechanism of alcohol interaction in Ln separation.
- Explore the impact of alcohols on Ln speciation in HNO3 and HCl systems.
Main Methods:
- Solvent extraction experiments using TODGA in n-dodecane/alcohol mixtures.
- Spectroscopic analyses including UV-Vis-NIR, TRFS, EXAFS, and NMR.
- Investigation of lanthanide extraction in nitric acid and hydrochloric acid media.
Main Results:
- Alcohols significantly enhance Ln selectivity, increasing separation factors.
- Alcohols associate in the outer sphere, preserving the 1:3 [Ln(TODGA)3]3+ complex.
- Alcohol alkyl chain structure influences Ln extraction and speciation.
Conclusions:
- Alcohols act as effective phase modifiers to enhance Ln selectivity in TODGA-based extraction.
- Outer-sphere interactions with alcohols provide a novel strategy for controlling Ln separation.
- Understanding alcohol influence is key to optimizing solvent extraction processes for lanthanides.
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