Ionic Liquid and Silica Sol-Gel Composite Materials Doped with N,N,N′,N′-tetra(n-octyl)diglycolamide for Extraction of La³⁺ and Ba²⁺

Abstract

Sol-gel processed silica materials, which incorporated ionic liquids and N,N,N′,N′-tetra(n-octyl)diglycolamide (TODGA), were prepared and used as sorbents for extraction of La³⁺ and Ba²⁺ from aqueous solutions. Imidazolium-based ionic liquids (ILs), 1-alkyl-3-methylimidazolium bis(trifluoromethane)sulfonimide ([C_nmim][NTf₂], n = 2, 4, 6, 8, 10) were entrapped in these monolithic composite sol-gel sorbents. The corresponding extraction efficiencies were found to be dependent on both the volume of IL used in the silica matrix and the alkyl chain length of the IL cation. The silica composite sorbent containing [C₈mim][NTf₂] exhibited the best extraction efficiency for La³⁺ and the best separation factor for La³⁺/Ba²⁺. The separation results were analyzed by both Langmuir and Freundlich adsorption isotherm models and the Freundlich model was found to give better fit.

Keywords:

• ionic liquids
• La³⁺/Ba²⁺
• silica sol-gel composite
• TODGA

ACKNOWLEDGEMENTS

This research was supported by the U.S. Department of Energy, the Office of Nuclear Physics, the Office of Basic Energy Sciences, Division of Chemical Sciences, Geosciences, and Biosciences under Contract DE-AC05-0096OR22725 with Oak Ridge National Laboratory, managed by UT-Battelle, LLC. BY and JRB acknowledge the Oak Ridge Associated Universities (ORAU) for postdoctoral fellowships.