Recovery of platinum group metals from a spent automotive catalyst using polymer inclusion membranes containing an ionic liquid carrier

Spent automotive catalysts (SACs) are the most abundant secondary source of platinum group metals (PGMs), but the recycling of these materials is quite challenging. In the present study, we assessed the recovery of Pt, Pd, and Rh from a SAC leachate solution using polymer inclusion membranes (PIMs) containing the ionic liquid trioctyl (dodecyl) phosphonium chloride (P88812Cl). After pretreatment of the SAC using a reducing agent, metals could be extracted using relatively dilute acid solutions. The selective transport of PGMs from such solutions was demonstrated with two types of membranes having the same chemical composition: an isotropic dense membrane (ID-PIM) and an anisotropic porous membrane (AP-PIM). Using the ID-PIM, more than 90% of Pt and Pd in the SAC extraction solutions could be recovered with remarkably high purity. In contrast, the AP-PIM could recover Pt, Pd, and Rh in reasonable yields and purities with dramatically faster transport kinetics. Both membrane types demonstrated excellent durability with no loss of carrier molecules over a 10-day exposure to various harsh chemicals.

Automated summary

This study evaluated the recovery of Pt, Pd, and Rh from spent automotive catalysts using polymer inclusion membranes containing an ionic liquid. It was found that the isotropic dense membrane showed high purity recovery of Pt and Pd, while the anisotropic porous membrane recovered Pt, Pd, and Rh with faster transport kinetics. Both membrane types demonstrated excellent durability even after exposure to various harsh chemicals for 10 days.