Transport and separation of iron(III) from nickel(II) with the ionic liquid trihexyl(tetradecyl)phosphonium chloride

Iron(III) was efficiently extracted from a 6 M hydrochloride solution with the ionic liquid trihexyl(tetradecyl)phosphonium chloride, Cyphos® IL101, dissolved in chloroform. Spectroscopical data revealed that iron exists as tetrachloroferrate species in the organic phase. In contrast, nickel(II) was not extracted under experimental conditions. Satisfying back extraction of Fe(III) was achieved with a 0.5 M HCl solution.Consequent time-dependent transport studies with Cyphos IL101 as ionic liquid carrier in chloroform (0.01 M), showed a successful quantitative transport of 0.1 M Fe(III) from a 6 M hydrochloride source phase to a 0.5 M hydrochloride receiving phase and a favorable separation from Ni(II). The transport of Fe(III) through the bulk liquid membrane (BLM) was assumed to follow a nonsteady kinetic regime with two consecutive and irreversible first-order reactions. With an initial Fe(III)/Cyphos IL101 concentration ratio of 10, an apparent rate constant ks of 31.4 × 10−3 min−1 was obtained for the Fe(III) transport from the membrane- to the receiving phase, whereas the rate constant kf for the Fe(III) transport from the source- to the membrane phase was 11.8 × 10−3 min−1.