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Abstract: The present work reports an interesting phenomena that the addition of hydrophobic ionic liquid, [C4mim]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 [C4mim][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 into the [C4mim]PF6 bottom phase in TLPS was proposed to be according with an anion exchange between and 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. [Copyright &y& Elsevier]

Abstract: This paper proposed a novel sugaring-out assisted three-liquid-phase system (TLPS) of diisopentyl sulfide (S201)–acetonitrile–glucose–water to extract and separate platinum, palladium and rhodium from their hydrochloric acid solution. Experimental results demonstrated that Pd(II), Pt(IV) and Rh(III) could be separated in one-step extraction process, respectively into the S201 organic top phase, sugaring-out acetonitrile-rich middle phase and aqueous bottom phase of the TLPS. The influences of different phase-forming agents, glucose concentration, HCl concentration in equilibrating aqueous phase and the initial volume ratio of added acetonitrile to aqueous glucose solution on partitions of platinum-group metal (PGM) ions were discussed. It was found that the three-liquid-phase partition behaviors of Pd(II), Pt(IV) and Rh(III) had a close relation with the phase-forming behavior of TLPS. The recovery of Pt and Pd were investigated. Sugaring-out assisted TLPS exhibited obvious advantages over the traditional salting-out systems. [Copyright &y& Elsevier]

Abstract: Salting-out induced three-liquid-phase system (TLPS) of diisopentyl sulfide (S201)−acetonitrile−NaCl−water was explored to extract and separate platinum, palladium and rhodium with one-step method. The influences of phase-forming behaviors of TLPS on partition of platinum-group metal (PGM) ions were investigated by changing the phase-forming salt and its concentration, HCl concentration in equilibrating salt aqueous phases and the initial volume ratio of acetonitrile to aqueous NaCl solution. Experimental results indicated Pd(II), Pt(IV) and Rh(III) were selectively concentrated into the S201 organic top phase, acetonitrile-rich middle phase and NaCl aqueous bottom phase respectively. The three-liquid-phase partition of platinum metal ions occurred with the salting-out induced two-phase splitting of acetonitrile–water mixtures. A micro-mechanism model is proposed to explain the influence of salting-out induced phase splitting behavior of three-liquid-phase system on mass transfer of PGM ions. Appearance of microscopic molecular aggregates accounts for the micro-phase enrichment of platinum metal ions. The competition of two opposite processes, salting-out induced dehydration of acetonitrile molecules in aqueous solutions while strong re-hydration of salting-out acetonitrile molecules in separated acetonitrile-rich phase, plays an important role in affecting the phase-forming behaviors and three-liquid-phase mass transfer of different platinum metal ions. [Copyright &y& Elsevier]