Effects of SiO₂ and CaO on Distributions of Platinum Group Metals Between Cu–CuO_0.5 and Pb–PbO-Based Slags at 1523 K

Platinum group metals (PGMs) are recovered using molten Cu or Pb as collector metals during pyrometallurgical recycling processes. The collector metal containing PGMs is oxidized to produce a PGM-enriched alloy and slag, primarily containing Cu or Pb oxide. Additionally, the slag comprises a considerable amount of PGMs. Therefore, it is returned to the upstream processes to be used as a secondary raw material, and some of PGMs remain in the recycling processes. Herein, the distributions of Rh, Pd, and Pt between molten metals (Cu, Pb) and corresponding metal oxide-based (CuO_0.5, PbO) slags were investigated at 1523 K. SiO₂ or CaO was added to the slag to a maximum concentration of 20 mass pct, thereby reducing the oxygen partial pressure in the system. Furthermore, the addition of an optimum amount of SiO₂ or CaO into various combinations of slags and collector metals reduced the concentrations of PGMs in the slags to less than approximately 1/10 of those without adding SiO₂ or CaO. Therefore, the addition of SiO₂ or CaO during the oxidation smelting process effectively reduced the dissolution of PGMs in the slag, resulting in a less amount of PGMs circulating in the recycling processes.