A task-specific ionic liquid based on hydroxypyridinone for lanthanide separation

A 1,2-hydroxypyridinone (HOPO) grafted ionic liquid (HOPO-IL) was synthesized for the first time and characterized by NMR spectroscopy and mass spectrometry. The solvent extraction of this HOPO-IL used as an extractant for lanthanide separation in various ionic liquids (ILs) and organic solvent was investigated, revealing enhanced extraction performance in the IL solvents. The extraction performance increased by ∼2 folds in ILs than in organic solvent. The extraction behavior of this HOPO-IL extractant was also compared in aqueous solutions under different acidities. The effects of aqueous phase acidity and the additions of an IL's cation or anion to the aqueous phase on separation properties of lanthanides are studied, indicating a strong pH-dependence and a dominant cation-exchange mechanism of lanthanide extraction. Notice: This manuscript has been authored by UT-Battelle, LLC, under contract DE-AC05-00OR22725 with the US Department of Energy (DOE). The US government retains and the publisher, by accepting the article for publication, acknowledges that the US government retains a nonexclusive, paid-up, irrevocable, worldwide license to publish or reproduce the published form of this manuscript, or allow others to do so, for US government purposes. DOE will provide public access to these results of federally sponsored research in accordance with the DOE Public Access Plan (https://energy.gov/downloads/doe-public-access-plan).