Toward the Recovery of Platinum Group Metals from a Spent Automotive Catalyst with Supported Ionic Liquid Phases

Abstract

We present a novel approach for the separation and recovery of Pt and Pd leached from a spent automotive catalyst relying on conventional and polymerized supported ionic liquid phases (SILPs and polySILPs, respectively). A variety of parameters with possible effects on the separation behavior, namely, acidity and concentration of the platinum group metal (PGM) containing solution, as well as different SILP and polySILP loadings, were evaluated for the separation of PGMs in the presence of high concentrations of Al, Fe, Zn, and Ce. The polySILP material demonstrated the ability to separate the PGMs from major accompanying interferences in a single separation step, while problems arising from ionic liquid leaching in the case of SILPs could be avoided. Moreover, the use of supported ionic liquid phases allowed the drastic reduction of the amount of required ionic liquid compared to conventional liquid–liquid separation, while avoiding problems arising from emulsion formation. Subsequent stripping experiments lead to further purification of the PGMs and finally desorption from the solid material into a pure solution. Eventually, the concept of chemisorbed polySILPs provides a new and convenient approach for the recycling of platinum group metals.

Liquid‐ and Solid‐based Separations Employing Ionic Liquids for the Recovery of Platinum Group Metals Typically Encountered in Catalytic Converters: A Review

“…Variation in the H + concentration does not markedly affect the maximum Pt uptake, which is in line with the independency of protonation of the phosphonium groups from the acidity of the solution, implying acidity has no effect on the ion-exchange mechanism. On the other hand, at Cl À 1.0 m sorption capacity reaches its [216] Open access, CC BY license 4.0, https://creativecommons.org/licenses/by/4.0/. maximum.…”

“…By employing the conditions that favor Rh retention on the real leachate experiments and with the application of selective stripping, pure Pt and Pd could be recovered in solution, with respective recoveries of 86 and 96 %. Additionally, the comparison between polymerized IL covalently bound on silica (polySILP) and ILs physisorbed on silica (SILPs) (Figure 48) proved the merit of the former over the latter; more efficient separation of the PGMs is achieved with the polySILP and significantly less amount of IL is leaching out of the solid support during the metal loading and stripping of the sorbent material [216] …”

“…Figure48. Evaluated supported IL phases for PGM separation [216]. Open access, CC BY license 4.0, https://creativecommons.org/licenses/by/4.0/.…”

A Combined Deep Eutectic Solvent–Ionic Liquid Process for the Extraction and Separation of Platinum Group Metals (Pt, Pd, Rh)

“…Mixtures of imidazolium ILs have demonstrated high selectivity toward Pt from multi-element solutions [ 28 ], while their functionalization dramatically increases the selectivity for Pd, which is quantitatively extracted from multi-element mixtures [ 29 ]. Phosphonium-based ILs have already been applied in PGM recovery and separation from model solutions [ 26 , 30 , 31 ], and car catalyst acidic liquor [ 32 , 33 ]. The hydrophobic ILs based on phosphonium cations are thermally stable and, therefore, suitable for applications in a wide temperature range.…”

Towards Understanding the Cathode Process Mechanism and Kinetics in Molten LiF–AlF3 during the Treatment of Spent Pt/Al2O3 Catalysts

“…Dendrimer-based adsorbents were found suitable for the recovery of precious metals due to their well-defined molecular composition with N-bearing functionalities, which led to selective extraction of metal ions from aqueous and non-aqueous solutions [13]. A supported ionic liquid-based method for the separation of platinum group metals was proposed by Lanaridi et al [14]. Separation of Pt and Pd from Rh and other interfering elements and recovery of Pt (86%) and Pd (96%) in solution was successfully performed with acidified thiourea solutions.…”