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Extraction and separation of V(V) and Cr(VI) in the alkaline solution obtained from the Sub-molten Salt Method to treat the high chromium vanadium slags has been a thorny problem in the past decades. In this work, a new liquid-liquid solvent extraction strategy was proposed by using acidified primary amine N1923 (denoted as A-N1923) to separate V(V) from alkaline solution containing Cr(VI) and Al(III). It was indicated that co-extraction of Cr(VI) and Al(III) with V(V) can be avoided with the addition of trisodium citrate previously into the feed solutions. The influence from various factors, including the concentration of trisodium citrate, the initial aqueous pH value, concentration of A-N1923 in the organic phase, diluents in the organic phase, and the initial concentration ratio of V(V) to Cr(VI) in alkaline solutions, on the separation of V(V), Cr(VI) and Al(III) were investigated. The extraction loading capacity of V(V) in the organic phase could reach 6.67 g/L at 298 K. Al(III) in the organic phase can be stripped selectively using 0.18 mol/L trisodium citrate solution, and then V(V) can be recovered by 1.0 mol/L NaNO 3 solutions. The regeneration and reusability of the organic phases after stripping were discussed. The present work highlights a novel approach to separate and recover V(V) from alkaline leaching solution containing Cr(VI) and Al(III), especially being applicable for those strongly alkaline solution produced by treating the high chromium vanadium slags using the Sub-molten Salt Method. [ABSTRACT FROM AUTHOR]

Highlights: [•] A three-liquid-phase extraction approach for removal of Al, Fe, Si from rare earths. [•] Al, Fe and Si enriched in PEG middle phase and rare earths in bottom phase of TLPS. [•] Rare earths concentrated in bottom aqueous phase can be group separation by TLPS. [•] A new strategy for group separation of multiple target metals by TLPS. [ABSTRACT FROM AUTHOR]

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: A novel technique, gas-assisted three-liquid-phase extraction (GATE), was proposed to improve three-liquid-phase separation of p-nitrophenol (p-NP) and o-nitrophenol (o-NP) from wastewater. The partition behavior of p-NP and o-NP into a three-liquid-phase system composed of hexane–PEG2000–(NH4)2SO4–H2O at the aid of gas bubbling was discussed. It was demonstrated that the process of gas bubbling was effective for the mass transfer of p-NP and o-NP into PEG phase and hexane phase, respectively. Influences of various parameters including the phase-forming salt concentrations, gas flow rate, gas bubbling time, initial volume of hexane and PEG phase on distribution behavior of p-NP and o-NP were investigated. Under the optimal conditions for GATE, the removal ratio of p-NP and o-NP from wastewater could reach 81% and 90%, respectively. While the mass fraction of p-NP into PEG phase and o-NP into hexane phase arrived at 75% and 74%, respectively. The distribution ratio and concentration factor were all higher than conventional three-liquid-phase extraction system. During GATE processes, the dispersed PEG and hexane in (NH4)2SO4 aqueous solution can be captured by ascending gas streams. GATE is demonstrated to be an effective method for the simultaneously extraction and separation of two or more organic chemicals in one-step''s three-liquid-phase extraction, and also provides a technique to prevent loss of dispersed polymers and organic solvents in aqueous phase in extraction process for treatment of the phenolic wastewater. [Copyright &y& Elsevier]