Solvometallurgical Recovery of Platinum

Extraction and separation of platinum group metals (PGMs) from secondary raw materials are usually carried out via hydrometallurgical processes. These processes use strongly oxidizing acidic solutions, such as aqua regia or hydrochloric acid in the presence of chlorine gas, which may have negative environmental impacts and are dangerous. In this paper, a solvometallurgical approach was developed for the sustainable recovery of PGMs from spent automotive exhaust catalysts. The PGMs were leached using FeCl3 or CuCl2 as oxidizing agents in the organic solvents dimethyl sulfoxide (DMSO) or acetonitrile (CH3CN). Palladium was quantitatively dissolved in CuCl2/CH3CN, CuCl2/DMSO, and FeCl3/DMSO with only 10−20% codissolution of Pt and Rh. By adjusting the concentration of the oxidizing agent in CH3CN, Pd was selectively leached with 0.01 mol L−1 FeCl3, whereas Pt and Rh could be dissolved in a more concentrated FeCl3 solution (0.3 mol L−1). The solvoleaching of PGMs was investigated in depth by UV−vis spectra and electrochemical properties. The closed-loop solvoleaching of PGMs with less-hazardous chemicals avoids the emission of toxic or flammable gases while reducing the consumption of acids and bases and limiting the generation of wastewater.