Pyrometallurgical production of molten copper generates large volumes of slag that commonly contain several wt.% Cu, often at grades exceeding those of primary copper ores. Understanding Cu speciation is essential for reducing copper losses, yet industrial slags commonly contain substantial X-ray amorphous material that cannot be characterised by conventional X-ray diffraction (XRD), while electron microscopy provides only local information.
This study investigates slags from an electric slag-cleaning furnace (EF), a flash furnace (FF) and a converter (CT) using quantitative XRD, Cu K-edge X-ray absorption spectroscopy (XAS) and SEM-EDS to determine Cu speciation and bulk mineralogy.
The EF slag contains ~61 wt% X-ray amorphous material and Cu occurs predominantly as metallic Cu. In the CT slag, chalcocite is the only Cu-bearing crystalline phase (~12 wt%), consistent with XAS indicating Cu mainly as crystalline Cu2S. The FF slag contains ~33 wt% amorphous material, with XRD identifying ~8 wt% metallic Cu, ~2 wt% delafossite and ~6 wt% cuprite. XANES linear-combination fitting indicates that 54% of Cu is associated with Cu2O, 12% with CuFeO2, 3% with CuO and 32% with metallic Cu, showing that Cu+ species dominate in the FF slag.
These results demonstrate that Cu speciation varies systematically between process units and is closely linked to both crystalline and amorphous components. The combined XRD–XAS approach provides a robust framework for characterising Cu deportment in industrial copper slags and supports improved understanding of copper retention during pyrometallurgical processing.