BACKGROUND Recycling of spent platinum group metals (PGMs) has attracted much attention in order to overcome the problems associated with the low natural abundance of these resources. To recycle such metals, efficient hydrometallurgical processes are required. To improve the efficiency of these processes, we have designed a new phosphonium‐based ionic liquid as an extraction solvent. This paper reports on the potential use of the ionic liquid for extraction and separation of PGMs, namely Pt(IV), Pd(II), and Rh(III). RESULTS An ionic liquid, trioctyl(dodecyl)phosphonium chloride, P88812Cl, which was newly synthesized, showed highly efficient extraction for Pt(IV), Pd(II), and Rh(III). P88812Cl features several advantages as an extraction solvent, such as high hydrophobicity and low viscosity compared with those features of a commercial analogue, trihexyl(tetradecyl)phosphonium chloride (P66614Cl). The favorable features of our novel ionic liquid were reflected by its high extraction efficiency and low release of phosphorus from the ionic liquid into the aqueous feed solution. Stripping operations were possible, and the high reusability of the ionic liquid was confirmed. CONCLUSION The novel ionic liquid P88812Cl is potentially useful as an extraction solvent for PGMs. Results highlight the strengths of ionic liquids and the tuneability of their properties through design of their molecular structure. © 2017 Society of Chemical Industry

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The recovery of platinum group metals (PGMs) from automotive exhaust catalysts is important, and hydrometallurgical extraction is an effective approach. In the present study, a newly designed phosphonium-based ionic liquid (IL) was applied to the separation and recovery of PGMs from an automobile catalyst leach liquor in conjunction with varying pH levels. This IL, trioctyldodecyl phosphonium chloride (P 8,8,8,12 Cl), allows quantitative extraction of Pd(II) at any HCl concentration, with almost 80% removal of Rh(III) at 1 mol L −1 HCl after two extractions. Significant amounts of Fe(III) were extracted into the IL phase, but could be removed using 1 mol L −1 Na 2 SO 3 . The Pd(II) and Rh(III) were selectively recovered from the IL using 1 mol L −1 CS(NH 2 ) 2 and 5 mol L −1 HCl, respectively. This work therefore demonstrated the selective recovery of PGMs through optimization of various parameters and shows the significant potential of this IL with regard to recycling PGMs from leach liquor.

Fibrous silica ZSM-5 (FZSM-5) with a novel dendrimeric morphology was synthesized using a CTAB-based microemulsion system. The dendrimers increased the active site accessibility and enhanced the catalytic activity for large molecule hydrocracking and ethylbenzene dehydrogenation.

In this study, we report the separation of Pd(II) and Rh(III) in a chloride solution using a polymer inclusion membrane (PIM). We designed a trioctyl(dodecyl) phosphonium chloride (P 88812 Cl) ionic liquid as a metal carrier for the PIM separation system. The effects of PIM composition and experimental conditions were systematically investigated. The concentrations of hydrochloric acid in the feed solution and thiourea in the receiving solution were found to play a crucial role in the success of selective separation. Under the optimized conditions, Pd(II) could be effectively separated from Rh(III) with a 98% recovery yield and 99% purity. We also compared the performance of our designed carrier, P 88812 Cl, to that of commercially available ionic liquid trihexyl(tetradecyl) phosphonium chloride (P 66614 Cl) using a 7-cycle reusability test. The P 88812 Cl showed a more stable performance and better durability compared with those of the commercial ionic liquid carrier.

Platinum group metals (PGMs) play an important role in the automotive industry as key components of exhaust catalysts. Recycling of PGMs from secondary resources, such as waste products, is encouraged to ensure their sustainability. A highly e cient and environmentally benign technique for the separation of PGMs is currently required. In the present study, the recovery of PGMs from a spent automotive catalyst was investigated using the trioctyldodecyl phosphonium chloride (P 8,8,8,12 Cl) ionic liquid (IL) as the PGM extraction solvent. First, leaching from the catalyst was investigated. Pt and Pd are selectively extracted into undiluted P 8,8,8,12 Cl from the 5 mol L 1 HCl leachate containing various metals together with Pt, Pd, and Rh. Subsequently, Rh is extracted into fresh P 8,8,8,12 Cl from the ra nate adjusted to an appropriate HCl concentration. Mutual separation of Pt and Pd is possible by stripping processes. Some common metals coextracted with PGMs, such as Fe, Cu, and Zn, are removed by each stripping process. Recovery of high purity Pt, Pd, and Rh is achieved by the proposed recycling process. The results demonstrate that separation using phosphonium-based ILs is useful for recycling PGMs.

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