Oxidative pressurized acid leaching of waste printed circuit boards

The amount of waste printed circuit board (WPCB) increases continuously. There is an economic and environmental need to recover valuable metals from WPCBs. In this study, the applicability of oxidative pressurized acid leaching of WPCBs rich in copper and tin was investigated. The effect of leaching parameters such as temperature, partial oxygen pressure and chloride concentration on metal dissolution from WPCBs was studied in sulfuric acid media. It was shown that non-metallic elements present in WPCBs initiated gas formation, namely CO2 and CO, during oxidized pressure acid leach. Decomposition of plastic components already started at 90 °C with 1.5 MPa oxygen overpressure in the presence of 1 g/dm3 chlorides. Gas formation was shown to have a negative impact on the process since copper extraction was reduced to 27% compared to 80-90% extraction achieved from anode slimes used as a reference material. It was suggested that gas formation related to plastic components could have a severe impact on metal yields. The highest dissolution of tin equal to 36% was achieved at room temperature. It was found that higher temperature promoted tin hydrolysis.