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

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(n)mim][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 [C(8)mim][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.