Platinum(IV) Recovery from HCl Solutions using Amberlite XAD-7 Impregnated with a Tetraalkyl Phosphonium Ionic Liquid

An ionic liquid (IL) (tetradecyl(trihexyl)phosphonium chloride) was immobilized in Amberlite XAD-7 for preparing extractant impregnated resins (EIRs). The IL content was varied between 59 and 586 mg IL g−1. The EIRs were used for Pt(IV) recovery from (0.01 − 8 M) HCl solutions. Platinum sorption efficiency increased with IL loading (>99% for EIRs in 0.01 M HCl) but slightly decreased with HCl concentration (84% in 8 M HCl). Metal ions were extracted by an ion exchange mechanism involving the binding of the chlorocomplex to IL phosphonium cation. SEM-EDS analysis showed that IL and platinum were homogeneously distributed in the whole mass of the EIRs. Sorption isotherms were fitted with the Langmuir equation and maximum sorption capacity increased with extractant loading (up to 74.6 mg Pt g−1, for an EIR with 291 mg IL g−1 in 0.01 M HCl solution). Sorption kinetics was not affected by agitation speed: the resistance to film diffusion is not the limiting step. Uptake kinetics was controlled by the resistanc...