Mutual Separation of Fe(II) and Fe(III) Using Cyclohexane/Water/Ionic-liquid Triphasic Extraction System with 2,2′-Bipyridine and Tri-n-octylphosphine Oxide

Abstract

The triphasic extraction system with two extract phases can be used to separate two materials simultaneously into each phase. In this article, a possible mutual separation of Fe(II) and Fe(III) was studied using the cyclohexane/water/ionic liquid (IL) triphasic extraction system for Fe speciation. For Fe(II) and Fe(III) extraction, 2,2′-bipyridine (bpy) and tri-n-octylphosphine oxide (TOPO) were selected as extractants, respectively. It was suggested that [Fe^II(bpy)₃]²⁺ and Fe^III(TOPO)₄³⁺·3Tf₂N⁻ were extracted into the IL (1-butyl-3-methylimidazolium bis(trifluoromethanesulfonyl)imide, C₄mimTf₂N) phase and the cyclohexane phase, respectively, and both of the extractants also acted as masking agents. On simultaneous separation using the triphasic system, Fe(II) and Fe(III) were quantitatively extracted into the IL phase and the cyclohexane phase, respectively, and their mutual separation was achieved.