Feasibilities for hydrometallurgical recovery of precious metals from waste printed circuit boards in Lithuania

Abstract

Given the current trends in the WPCBs generation and precious metal value in the market, it can be concluded that recovery of precious metals from WPCBs is beneficial both economically and environmentally. Leaching by thiourea demonstrated the feasibility of Au, Cu, Ag and Pd recovery. Also the importance of pre-treatment was confirmed. The metal leaching rate for preliminarily cut and thermally treated WPCBs was 18–100% higher in comparison with that of untreated WPCBs. It can be explained by the removal of a protective soldermask layer, also by partial change of the mass and chemical structure of the WPCB matrix. After the thermal treatment, WPCBs become more crumble, they can decrease consumption of reagents and facilitate cutting. Also it was confirmed that the metal content in the old (age >20 years) WPCBs is significantly higher than in the currently generated WPCBs what is caused by the development of PCB production technology.