Ionic liquid based three-liquid-phase partitioning and one-step separation of Pt (IV), Pd (II) and Rh (III)

The present work reports an interesting phenomena that the addition of hydrophobic ionic liquid, [C(4-)mim]PF6, into the oil-water two phase system of diisopentyl sulfide (S201)-nonane organic solutions and hydrochloric acid aqueous solutions containing Pt (IV), Pd (II) and Rh (III) chloric-complexing anions could induce the formation of a stable liquid-liquid-liquid three layered liquids coexisting medium for extraction and one-step separation of platinum, palladium and rhodium. The influences of H+ and Cl- concentrations in equilibrating aqueous solutions, the initial Pt (IV) concentration, the volume ratio of added [C(4)mim][PF6] to hydrochloric acid aqueous solution and the different salt ions in equilibrating aqueous solutions on the three-liquid-phase partitioning behaviors of three platinum metal ions were evaluated. The transferring of PtCl62- into the [C(4)mim]PF6 bottom phase in TLPS was proposed to be according with an anion exchange between PtCl62- and PF6- in ionic liquid. Therefore, the separated ionic liquid phase is not the solvent of organic extractants, but provides an extended separation capacity than the literature reported ionic liquid based two-phase extraction systems. The present work indicated that this ionic liquid based three-liquid system can be used to separate multi-metal coexisting solutions. (C) 2013 Elsevier B.V. All rights reserved.