Separation of Palladium(II) and Rhodium(III) Using a Polymer Inclusion Membrane Containing a Phosphonium-Based Ionic Liquid Carrier

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.