Extraction of precious metals by synergetic smelting of spent automotive catalysts and waste printed circuit boards

Spent automotive catalysts (SACs) and waste printed circuit boards (WPCBs) are the most important secondary resource containing precious metals (PMs). A resource-saving process of extracting PMs from SACs and WPCBs by synergistic smelting of these two wastes was proposed. The main feature of the process was to use metal components in WPCBs as the collector metal of PMs and use carrier components in SACs as the slag formative. A SiO2-FeO-Al2O3-MgO-CaO slag system was first designed for the synergistic smelting by analyzing phase diagrams and liquid phase formation. On this basis, the laboratory -scale synergistic smelting experiments of these two wastes were carried out. Under the optimal conditions of 1350 degrees C, FeO/SiO2 mass ratio = 1.0, WPCBs/SACs mass ratio = 0.25, 5 wt% CaO content in the slag, and 3 h smelting time, the extraction efficiencies of Pd, Rh, Ag and Au were 90.5%, 93.2%, 98.9% and 94.5%, respectively. In the collected crude Cu ingot after synergistic smelting, PMs were mainly concentrated in the Cu-Sn phase. Also, a potential industrial system for the synergistic-smelting process based on a top-blown injection smelting furnace was proposed. The novel process will provide an effective way for extracting PMs from secondary resources.