Eco-friendly recovery of copper from copper slag via magnetic separation followed by flotation: Experimental and mechanistic insights

Copper slag (CS) is a typical industrial waste generated during the smelting of copper sulphide concentrates. It contains numerous valuable metals, particularly copper. CS stockpiling results in resource wastage and environmental pollution. In this study, an innovative eco-friendly process involving magnetic separation followed by froth flotation was proposed to efficiently recover copper from CS. The grinding properties and magnetic separation behaviour as well as froth flotation behaviour, kinetics and mechanisms of CS were thoroughly investigated. The findings demonstrated that non-magnetic metallic copper and chalcocite in CS could be efficiently separated and recovered through magnetic separation, while the copper-bearing minerals in the magnetic separation tailings could be further recovered via froth flotation. The ethylenediamine (EDA)-enhanced sulphide- induced flotation mechanism revealed that EDA facilitated the dissolution of the copper oxide film present on the surface of copper sulphide minerals, exposing a fresh hydrophobic surface. The dissolved Cu2+ subsequently reacted with S2- to form coarse-grained CuS particles that selectively adsorbed onto the copper-bearing minerals, thereby accelerating copper froth flotation and improving copper recovery. In this combined process, the copper recovery was increased from approximately 90 % for the conventional flotation process to 97.59 %. In addition, the copper grade in the final tailings was found to have significantly reduced from over 0.3 % to 0.14 %. Compared with the conventional froth flotation process, the proposed novel approach increases revenue by 79.18 CNY per metric ton of CS.