Separation of metals from Ni-Cu-Ag-Pd-Bi-Sn multi-metal system of e-waste by leaching and stepwise potential-controlled electrodeposition

Electronic waste, as hazardous waste, contains a large amount of metals, which is of great recovery value. However, they are difficult to separate due to wide variety and complex distribution. Most of current recycling methods are environmentally-unfriendly or complicated. In this study, a simple, efficient and green approach for metals separation from Ni-Cu-Ag-Pd-Bi-Sn multi-metal system of e-waste was proposed combining mild leaching and stepwise potential-controlled electrodeposition. The leaching efficiencies of Ni, Ag, Pd, Cu and Bi were 99.16%, 99.09%, 94.91%, 99.61% and 23.76% with 1 mol/L HNO3 at 80 degrees C. The leaching process was analyzed. It showed that the existence of Ag-Pd continuous solid solution in the alloy lowered the oxidation potential of Pd, which facilitated its leaching. Sn precipitated as SnO2. Then Ag-Pd alloy and Cu-Bi alloy were separately extracted from the leaching solution by stepwise electrodeposition. 97.72% of Ag and 98.05% of Pd were recycled after 5 h with potential of 0.35 V. The recovery efficiencies of Cu and Bi were 97.87% and 97.33% after 7 h with potential of 0.05 V. The EDS results showed high purity property of Ag-Pd and Cu-Bi alloy. This process can achieve cleaner and efficient extraction of metals from multi-metal system in e-waste.

Automated summary

In this study, a simple, efficient and green approach for metals separation from Ni-Cu-Ag-Pd-Bi-Sn multi-metal system of e-waste was proposed combining mild leaching and stepwise potential-controlled electrodeposition. The leaching process was analyzed, showing the existence of Ag-Pd continuous solid solution in the alloy lowering the oxidation potential of Pd facilitating its leaching. The results indicated high purity property of Ag-Pd and Cu-Bi alloy after extraction. This process can achieve cleaner and efficient extraction of metals from multi-metal system in e-waste.