Recovery of metals from waste printed circuit boards by selective leaching combined with cyclone electrowinning process

•An innovative waste printed circuit boards (wPCBs) treatment technique is presented.•Selective separating and recycling of metals form wPCBs has been successful implementation.•95.20% Sn and 95.72% Cu can be selective leached out.•Copper and stannic acid were obtained as the final products. This paper provides a benign process that realized the metals separation and recovery from wPCBs in an efficient and low cost way. The chemical active order and potential-pH diagram of the metals enlightened us to apply stepwise leaching to selective separation of the metals from the wPCBs. The results indicated that the selective separation of Fe, Al, Zn; Sn and Cu can be achieved by the dilute sulfuric acid leaching, displacement leaching using copper sulphate and sulfuric acid leaching with air-oxidization, respectively. Under the optimal conditions, the leaching efficiency of Fe, Al, Zn, Sn and Cu were 92.59%, 90.51%, 89.73%, 1.44% and 0.82%, respectively, in the dilute sulfuric acid leaching. In the displacement leaching, the displacement efficiency of Sn was as high as 95.20%, with little Cu leached. The data of sulfuric acid leaching with air-oxidization experiments shows that the leaching efficiency of Cu reached 95.72%. In order to recover the Sn and Cu in the solutions, the hydrolysis precipitation and cyclone electrowinning were introduced. With these techniques, 92.75% Sn was precipitated and the smooth cathode copper (purity 99.98%) was obtained with the current efficiency was 94.96%. Moreover, the analysis of the mass distribution about the process demonstrated that the H+ and Cu2+ were consumed, but also produced in different procedure, that means the process is a simple and eco-friendly technology, not only due to its high recovery efficiency, but also high reagents recyclable.