Platinum(IV), Palladium(II), and Rhodium(III) Recovery from Mixed Acidic Chloride Solutions Using Chelating Ion Exchange Resin Puromet MTS9600

The chelating ion exchange resin Puromet MTS9600 was employed for the separation of platinum group metals (PGMs), specifically Pt(IV), Pd(II), and Rh(III) from acidic chloride media (0.1-9.0 M HCl). The study investigated the impact of hydrochloric acid, temperature, PGM concentrations, and contact time on the recovery of the PGM-chloro complexes from dilute mixed PGM solutions as could be expected from the leaching of spent automotive catalysts. PGM adsorption onto the resin and loading isotherms were examined. Kinetic and diffusion-based models studies revealed that adsorption of PGM-chloro complexes onto the resin obeys the Ho pseudo-second order model, and intraparticle diffusion is a predominant mechanism controlling the sorption process. PGM desorption from the loaded resins was performed using various eluants. The effective recovery of Pt(IV) and Pd(II) was achieved through the utilization of thiourea, while the elution of Rh(III) did not yield promising results within the applied desorption conditions. A separation flowsheet is proposed for the recovery of Pt(IV) and Pd(II) from chloride solution over Rh(III) using a short contact time. In this process, adsorbed Pd(II) can be completely recovered using a 5 M NH3 solution, while Pt(IV) is eluted with 1 M thiourea. Less than 4% of Rh(III) is recovered in the eluates and mostly remains in the initial PGM solution.