Copper Recovery from Printed Circuit Boards Using Ammonia–Ammonium Sulphate System: A Sustainable Approach

Purpose The present study intends to provide a more established understanding of copper ammoniacal leaching and electrowinning in the presence of organic matter from WPCBs. Because the recirculation of the spent solutions is a matter of great importance from economic and environmental points of view in the hydrometallurgical processes, it was evaluated. Methods This work evaluates copper, zinc and nickel recoveries using ammonia–ammonium solutions to leach WPCBs samples; in samples free electronic components, namely electrolytic capacitors; and in samples after calcination at 550 °C. The electrowinning efficiency from pregnant solutions obtained was also evaluated and tests on successive leaching—electrowinning cycles were done to follow the recirculating potential of those solutions. Results Pre-treatments to reduce organic compounds in WPCBs showed not significantly influence metals leaching efficiencies compared to WPCBs in all and apparently do not benefit copper electrowinning from the pregnant solutions. WPCBs shredding is crucial for obtaining high copper, zinc and nickel leaching recoveries. Electrowinning copper was carried out with extraction efficiencies above 98% in 5 to 6 h of electrolysis time; the copper deposits showed 89.2% copper and nearly 1% zinc and nickel. The recirculation of spent solutions was done with four leaching—electrowinning cycles, showing high copper recoveries up to reaching a pH below 7, which corresponded to a very low ammonia concentration of about 12 mg L −1 . Conclusion Ammonia/ammonium leaching of WPCBs is attractive from the selective dissolution of copper, zinc and nickel. The pregnant solutions can be used directly for electrowinning and have high purity of copper products. Being the recirculation of solutions is a focal step in the hydrometallurgical processes. Graphical Abstract