Distribution behavior of platinum group metals between liquid metal and molten slag in the Cu-Cu₂O and Pb-PbO systems at 1523 K

In the pyrometallurgical process of recycling platinum group metals (PGMs), PGMs are recovered using collector metals such as copper and lead. The collector metal containing the PGMs is oxidized to produce a PGMs-enriched alloy phase and a slag containing the collector metal oxide as the main component. A small amount of PGMs dissolves in the slag. The slag is again treated as secondary raw materials, and the PGMs in the slag stay in a recycling process. In the present work, considering the oxidation process of PGMs recycling, the distribution ratios of rhodium, palladium, and platinum between molten copper or lead and molten CuO_0.5or PbO slag were first investigated at 1523 K. Next, we determined the distribution of PGMs between CuO_0.5or PbO slag with 0 to 20 mass-% SiO₂or CaO and liquid copper or lead. The oxygen potential in the samples was measured with an oxygen concentration cell using a ZrO₂solid electrolyte. The addition of SiO₂or CaO reduced the oxygen partial pressure and the distribution ratios of PGMs between the slag and liquid Cu or Pb. From these results, the addition of SiO₂or CaO to the slag is effective in reducing the dissolution of the PGMs in the oxidation smelting slag and reducing the amount of the PGMs circulating in the recycling process.