In this stuy, we report the separation of P(II) an Rh(III) in a chlorie solution using a polymer inclusion membrane (PIM). We esigne a trioctyl(oecyl) phosphonium chlorie (P88812Cl) ionic liqui as a metal carrier for the PIM separation system. The effects of PIM composition an experimental conitions were systematically investigate. The concentrations of hyrochloric aci in the fee solution an thiourea in the receiving solution were foun to play a crucial role in the success of selective separation. Uner the optimize conitions, P(II) coul be effectively separate from Rh(III) with a 98% recovery yiel an 99% purity. We also compare the performance of our esigne carrier, P88812Cl, to that of commercially available ionic liqui trihexyl(tetraecyl) phosphonium chlorie (P66614Cl) using a 7-cycle reusability test. The P88812Cl showe a more stable performance an better urability compare with those of the commercial ionic liqui carrier.