Circular Economy Approaches for Copper Recovery from Mining Waste: A Systematic Review of Leaching Technologies

Mining activities generate large volumes of waste that pose both environmental liabilities and potential secondary resource value. A significant fraction of these materials still contains recoverable copper, making leaching a promising strategy for reprocessing and valorization, given the natural decline in ore grade. This study presents a PRISMA-based systematic review of recent literature on leaching technologies applied to mining waste, with emphasis on technical performance, environmental implications, and economic feasibility. The reviewed residues include tailings, slags, copper smelter dusts, sludges, waste rock, leaching residues, and other secondary mining and metallurgical wastes. The main leaching routes identified were acidic, biological, alkaline, and hybrid systems, including conventional H2SO4 leaching, pressure oxidative leaching, chloride-based systems, glycine- and ammonia-based alkaline media, organic acids, deep eutectic solvents, and biologically mediated processes. Reported Cu recoveries ranged from low values in refractory systems to near-complete extraction under optimized conditions. Overall, copper recovery was controlled primarily by the mineralogical occurrence of Cu rather than by leaching category alone. In contrast, the highest recoveries were generally associated with intensified conditions capable of overcoming sulfide- and silicate-related constraints. Environmental and circular economy benefits were frequently claimed but less often demonstrated through direct evidence, while economic assessment remained limited. Future research should better integrate mineralogical interpretation, environmental verification, and economic feasibility.