Electrochemically-assisted aqueous reduction of gold from printed circuit boards leached with cupric chloride

Efficient use of secondary raw materials and the development of electrified refining processes are both key enablers of more sustainable and circular hydrometallurgy. Waste printed circuit boards (PCBs), common e-waste deriving from devices such as smartphones and computers, are a prime example of a secondary feed that societies produce in increasing amounts and that contain relatively high concentration of key metals like copper, tin, and gold. This work advances hydrometallurgical processing of PCBs by showing how the recently developed electrochemically-assisted aqueous reduction (EAR) can achieve selective gold recovery from cyanide-free, cupric chloride PCB leachates. In the current study, both copper and gold are leached simultaneously from PCBs in cupric chloride media. Results show that EAR can recover gold from the leachate, with deposits containing up to ≥ 99 wt% gold, despite gold being present at several orders of magnitude lower concentration compared to more abundant metals (e.g. Cu, Fe, Al, Ni, Zn, Sn). This is the first study employing EAR in a real leach solution and thus provides insight into the performance of such tailored electrochemical recovery methods in complex solution matrixes.