Extraction of rare-earth ions with an 8-hydroxyquinoline derivative in an ionic liquid

The extraction behavior of rare-earth ions with an 8-hydroxyquinoline derivative, HO8Q (5-octyloxymethyl-8-quinolinol), was studied using an ionic liquid, [C₈mim][Tf₂N] (1-octyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide), as the extracting phase. Compared with a conventional organic solvent, n-dodecane, the ionic liquid system showed a higher extraction ability for a heavy rare earth, Dy, and a better selectivity between Dy and Nd (separation factor β_Dy/Nd: 108). In the liquid-liquid extraction system, the color of the extracting phase changed from colorless to light yellow along with the extraction of rare-earth ions. Furthermore, the extraction efficiency was enhanced by the addition of TOPO (tri-n-octylphosphine oxide) as a co-extractant.