Selective Electrochemical Leaching of Copper from Fragmented Waste Printed Circuit Boards in an Alkaline Sulfate–Glycine Electrolyte

Waste printed circuit boards (WPCBs) are a highly concentrated secondary source of copper. However, their complex and heterogeneous composition significantly complicates the selective extraction of metals. This study examined the feasibility of direct electrochemical leaching of copper from used PCB fragments in a sulfate–glycine alkaline electrolyte. The PCB fragments were used directly as a composite working electrode, without prior separation of the components or special surface preparation. It has been demonstrated that the electrochemical response of the composite PCB anode is similar to that of a pure copper electrode, which indicates the predominant role of the anodic dissolution of copper. A distinct potential window of 0.30 to 0.40 V relative to the Ag/AgCl electrode has been established, within which copper dissolves efficiently, while the dissolution of the associated metals (Sn, Pb, Ni, Fe) remains strongly inhibited. The maximum selectivity is reached at a potential of approximately 0.35 V. This is due to the formation of soluble and stable copper–glycine complexes, while the other metals remain in an alkaline medium in the form of poorly soluble phases. At more positive potentials (≥0.40–0.50 V), the co-dissolution of the associated metals begins, resulting in a sharp decrease in the selectivity of the process. Real-time potentiostatic experiments have shown that the selective leaching mode at 0.35 V is stable over long periods of operation and is characterized by continuous dissolution of copper with minimal release of other metals in solution.