Recovery of metal values from waste printed circuit boards using an alkali fusion–leaching–separation process

• A novel alkaline process is developed to recover metal values from waste PCBs.
• Cu, nano-Cu2O, CaSnO3 and mixture of PbS–ZnS were obtained as the final products.
• Recoveries were 99% of Cu, 91% of Sn, 91% of Zn, and 79% of Pb, respectively.
• Precious metals were enriched in the residue with Au of 613 g/t, Ag of 2157 g/t.

An efficient alkali fusion–leaching–separation process is developed to recover metals in crushed metal enrichment (CME) which originated from waste printed circuit boards (PCBs). Impacts of fusion parameters on metals conversions were systematically investigated. In the fusion–leaching process, amphoteric metals such as tin, lead, zinc and aluminum in the CME were leached out, while leaving copper and precious metals in the residue. Subsequently, metals in solution were further extracted via precipitation processes, and metals in the residue were recovered using an acid leaching–electrowinning process. Cathode copper, nano-Cu2O, CaSnO3/CaSn(OH)6 crystal and mixture of PbS–ZnS were obtained as the final products of this process. By optimizing the experimental conditions, recoveries of 98.66% for Cu, 91.08% for Sn, 91.25% for Zn, 78.78% for Pb were achieved, respectively. And all precious metals were enriched in the final residue with grades of Au 613 g/t, and Ag 2157 g/t.