Copper Separation and Recovery from Solutions: Conventional and Membrane-Based Methods

Cu is central to electrification and low-carbon technologies, while declining ore grades and environmental pressures increase interest in recovery from secondary liquid resources. This review critically evaluates copper separation from mine-affected waters, copper-smelting waste acids, electroplating wastewaters, and secondary-material leachates. Cu is the principal target; co-occurring metals are treated as competitors or sequential recovery targets. Feed origin, Cu concentration and speciation, pH/free acidity, ionic strength, ligands, and polymetallic composition are related to process performance and product form. Conventional precipitation, solvent extraction, ion exchange, and electrowinning are compared with microfiltration, ultrafiltration, nanofiltration, reverse osmosis, electrodialysis, supported liquid membranes, emulsion liquid membranes, and polymer inclusion membranes. High Cu removal or rejection does not by itself demonstrate Cu-selective recovery. MF and UF require conversion of dissolved Cu into retainable species; NF and RO mainly recover water and preconcentrate metals; ED becomes more selective with speciation control; and carrier-mediated membranes can fractionate metals but face stability constraints. Most membrane processes generate a Cu-rich retentate, concentrate, or stripping solution rather than metallic Cu and therefore require downstream crystallisation or electrowinning. Key gaps are long-term operation with variable industrial feeds, fouling and scaling control, mass balances and product-purity reporting, membrane/carrier durability, and consistent techno-economic validation.