Hydrometallurgical Copper Recovery Routes from Waste PCBs: Cementation vs. Solvent Extraction

The high demand for electronic devices is generating a substantial amount of electronic waste, which contains spent printed circuit boards (PCBs). PCBs are mainly composed of metals, with copper (Cu) being the most representative. The Cu scarcity in the Earth crust and the so-called digital and energy transition create additional stress to find innovative approaches to overcome this global problem.In this study, Cu recovery from mechanically pre-concentrated PCBs residues was studied using sulfuric acid–hydrogen peroxide leaching followed by two alternative downstream routes: (i) direct cementation using steel wool and (ii) solvent extraction (SX) with the oxime-based extractant LIX 984N followed by stripping and cementation. Optimized leaching achieved 98±0.05% Cu extraction with high Zn co-leaching (93±0.02%). Direct cementation recovered 99±0.01% of dissolved Cu, corresponding to approximately 506g of Cu/ kg of concentrate, with 2% of Zn co-cementation. The SX–stripping–cementation route achieved high individual stage efficiencies (SX 93±0.003%), stripping 90±0.02%, cementation 91±0.01%) without Zn losses. On the other hand, with low overall Cu recovery - 390g of Cu/ kg of concentrate - due to dilution and cumulative transfer losses.The results demonstrate a clear trade-off between maximum Cu yield (direct cementation) and higher Cu/Zn selectivity (SX route), highlighting the importance of normalized mass balance comparison in PCBs recycling flowsheet design.