Effects of SiO2 and CaO on Distributions of Platinum Group Metals Between Cu–CuO0.5 and Pb–PbO-Based Slags at 1523 K

Abstract

AbstractPlatinum 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 (CuO0.5, 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.