Integrated Oxygen Pressure Acid Leaching and Cyclone Electrowinning for Efficient Copper Recovery from Zn Hydrometallurgical Polymetallic Residues

The comprehensive recovery of copper from zinc hydrometallurgical residues is crucial for enhancing resource utilization and alleviating copper shortages. This study developed and optimized an integrated oxygen pressure acid leaching (OPAL)–cyclone electrowinning (CE) process to efficiently recover Cu, In, and Zn from polymetallic copper residues (PMCRs) produced in the zinc hydrometallurgy process. The OPAL parameters were optimized as follows: initial H2SO4 concentration, 135 g/L; temperature, 140°C, reaction time, 120 min; O2 partial pressure, 0.6 MPa; and liquid-to-solid ratio, 10:1. Phase evolution analysis confirmed the transformation of the dominant phases from Cu0/Cu2O/CuO/ZnO to S8/S6/SiO2/PbSO4, with negligible amounts of undissolved chalcopyrite (CuFe2S3). The leaching efficiencies achieved 99.94% Cu, 99.81% In, and 99.70% Zn, and Ag was enriched 33-fold in the residues (from 149.9 to 4946.7 g/t). A four-stage cascade CE process directly applied to the unpurified leachate (initial Cu2+: 74.76 g/L) reduced the Cu2+ concentration to 40.30 g/L (Stage I), 18.10 g/L (Stage II), 8.92 g/L (Stage III), and 1.74 g/L (Stage IV). This yielded cathode copper with 99.97–99.99% purity and 96.70% cumulative copper recovery. The staged current density control ensured a high average current efficiency of 98.2% throughout the process. The integrated OPAL-CE approach offers superior extraction efficiencies and a more streamlined process compared to conventional methods involving solvent extraction and provides a technically and economically viable route for the efficient recovery of valuable metals from the zinc hydrometallurgical residues.