Enrichment of precious metals by hydrometallurgical separation of Bi and Fe from platinum palladium concentrate

The platinum palladium concentrate from copper anode slime was used as raw material. According to its mineral characteristics, HCl was selected as leaching agent to remove the main base metals such as Bi, Fe and enrich the precious metals such as Au, Ag, Pt and Pd. The composition distribution of Bi(Ⅲ) and Fe(Ⅲ) in hydrochloric acid system was plotted by thermodynamic calculation. The influences of the concentrations of HCl and Cl-, reaction temperature and time, and other factors leaching on efficiencies of Bi and Fe were investigated experimentally. The results show that the leaching efficiencies of Bi and Fe are 96.24% and 93.08%, respectively, when the HCl concentration is 2 mol/L, no chloride ion is added, the liquid-solid ratio is 20: 1 and at 50℃ for 1 h. Bi (Ⅲ) and Fe (Ⅲ) in the leaching solution are mainly in the forms of [BiCl6]3- and [FeCl2]+ complexes. The main components of the leaching residue are Ag, Ti, Fe and Te, with the contents of 20.22%, 15.25%, 5.87% and 4.57%. The grades of Au, Pt and Pd are 2930 g/t, 1980 g/t and 1330 g/t. The SEM images show that the leached residue is granular with uneven size. The EDS images show that the leached residue contains Fe, Ti, Ag and other metal elements. The results of XRD show that the main phase of the residue is AgCl, which realizes the separation of impurities and the enrichment of precious metals. © 2021, Science Press. All right reserved.