In ongoing efforts to investigate the utility of ionic liquids (ILs) as diluents and/or extractants for metal ion separations, functionalized ILs (FILs) represent a combination of both these characteristics. The choice of ions that comprise a room temperature IL can result in a liquid salt under ambient conditions. Both the anion and cation can modify the hydrophobicity/hydrophilicity, bestowing specific solvation properties of an IL diluent for incorporation of a metal ion ligand. Our studies have set out to synthesize a set of FILs designed to complex actinyl cations, typified by U(VI), through chemical incorporation of the chelator dipicolinic acid (DPA) in its dianionic state. New FILs were synthesized by converting the halide salts of various organic cations to their hydroxide form via an anion exchange resin, followed by simple acid-base metathesis with DPA. Purified products were characterized by a host of techniques, including 1HNMR, FTIR, HPLC-UV, Karl Fischer titration, and elemental analysis, to ensure their composition and evaluate their physicochemical properties. By combining various hydrophobic cations, with the somewhat polar DPA, the properties can be modulated systematically. The FILs are being studied for their behavior in the extraction of uranium (as a representative light actinide) from aqueous solutions, and various other f-element cations will be examined. The results of these experiments will inform further synthesis of FILs in efforts to make rational choices in the design of metal ion extraction systems for separation and preconcentration of metal ions.

Synthesis and evaluation of a series of ionic liquids functionalized with dipicolinate complexants

253rd National Meeting (2017)

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