A novel process of extracting precious metals from waste printed circuit boards: Utilization of gold concentrate as a fluxing material

Waste printed circuit boards (PCBs) are highly toxic materials because of the hazardous substances that are incorporated into them. An advanced recycling technology based on pyrometallurgical treatment using Au concentrate as a flux material was developed in this study. The benefits of employing roasted gold concentrate (RGC) in the smelting process of waste PCBs were demonstrated through high-temperature experiments. The major oxide compositions of PCBs (CaO, Al2O3, and SiO2) were fluxed using oxidized Au concentrate composed of FetO and SiO2. Quaternary slag systems (CaO-FetO-Al2O3-SiO2) were formed during the smelting process, which rendered the process of separation of oxide impurities from Cu-based alloys easier. Precious metals (Au and Ag) were effectively recovered from waste PCBs and Au concentrate in the form of a metal alloy that required further treatment by leaching and extraction. Residual S in the RGC significantly changed the alloy phases. A large quantity of S was formulated into a matte phase, while a small amount of S was dissolved into a Cu-Fe metal alloy. The subsequent hydrometallurgical process was optional. Electrorefining or pressure leaching could be applied depending on the type of Cu alloy.