Selective Separation of Platinum Group Metals via Sequential Transport through Polymer Inclusion Membranes Containing an Ionic Liquid Carrier

Mutual separation of platinum group metals (PGMs) is a particularly challenging issue in metal recovery technology. In this study, we report the successful separation of Pt(IV), Pd(II), and Rh(III) by sequential transport through polymer inclusion membranes (PIMs) containing the ionic liquid trioctyl(dodecyl) phosphonium chloride (P88812Cl) as a metal carrier. This study describes the screening of suitable receiving solutions, optimization of the operating conditions, establishing a possible transport mechanism, and evaluation of the membrane stability. In the first transport sequence, Pt(IV) was selectively transported into the receiving solution with a recovery of >95%, while Pd(II) and Rh(III) remained in the feed solution. In the second transport sequence, high-purity Pd(II) was transported into the receiving solution with a recovery of >95%, while Rh(III) remained completely in the feed solution. Furthermore, the PIM exhibited a stable performance with multiple uses over a 4-week period during which four Pt(IV) and Pd(II) sequential transport cycles were continuously carried out.