Sustainable recovery of Cu, Fe and Zn from end-of-life printed circuit boards

The circularity represents the key strategy of the modern economy, where the waste becomes a raw material, ready to be reprocessed for a second life. In this context, the main aim of the present work was the development of a sustainable process for the recovery of Cu and Zn from end-of-life printed circuit boards (PCBs). The exploitation of this hazardous waste produces a double effect the recovery of metals, suitable for the current metal market, and the avoided disposal of scraps produced worldwide. The process allowed to exceed the limits of several approaches reported in the literature, mainly due to the highest consumptions (both energy and raw materials) and the loss of Zn content. The best identified conditions, suitable for the treatment of both chemical and bio- leach liquor included: the Fe precipitation with sodium hydroxide, followed by the Cu cementation with Zn (Zn/Cu molar ratio of 1.1) and a final Zn precipitation with oxalic acid (0.A./Zn molar ratio of 1.5). The metals showed recovery efficiencies higher than 95% and purifies up to 95%. An efficient recirculation system contributes to the sustainability growth, as confirmed by the carbon footprint assessment, towards the implementation of a zero waste treatment. Future perspective should include the further exploitation of the residue, rich in precious metals.