Organic-solvent/water/ionic-liquid triphasic system for the fractional extraction of divalent metal cations.

A novel cyclohexane/water/ionic-liquid (1-butyl-3-methylimidazolium hexafluorophosphate, [bmim][PF6]) triphasic extraction system was studied for a possible fractional extraction of divalent metal cations with co-using 8-quinolinol (HQ) and tri-n-octylphosphine oxide (TOPO) as competitive extractants. In this system, Ni2+ was extracted into the [bmim][PF6] phase as a Q(-)-complex, whereas each of Mn2+, Zn2+, Cd2+ and Pb2+ was extracted into the cyclohexane phase as an ion-pair of a cationic TOPO-complex and PF6-. A suitable selection of extractants and ionic liquid can result in developing a powerful triphasic fractional extraction system.