Selective recovery and separation of copper and iron from fine materials of electronic waste processing

Abstract

As electronic waste (e-waste) is increasing, its by-products such as flue dust and wastewater, which are generated during its treatment process, are also increasing. In this study, the fine material generated in the processing of e-waste by both mechanical and thermal methods was investigated for the effective recovery and separation of valuable metals, including Cu and Fe, using both physical and chemical methods. The Fe in this sample was present mostly as magnetite, as determined by XRD, and was removed by magnetic separation. Three different acid solutions (HNO3, HCl, and H2SO4) were used for selective Cu recovery. All experiments were conducted with varying length of time (1–10 h) and temperature ranges (20–60 °C). The kinetics of Cu dissolution in HNO3 was studied, based on the shrinking core model, and the activation energy was about 5.0 kcal/mol. The dissolution of Cu in HNO3 was faster than that of other metals such as Fe and Al. In the case of H2SO4, dissolution of Cu was not observed, while Fe was completely dissolved after about 4 h at 60 °C. Based on the results of various leaching and the kinetic study, a two-step process was performed for selective metal recovery. H2SO4 was used to dissolve Fe as the first leaching process and HNO3 was used for Cu dissolution as the second leaching process. Through this two-step process, Fe and Cu leaching efficiencies were obtained at approximately 90% and 98%, respectively.