Transforming Copper Smelting Waste into Metal-Depleted Material via Density Separation and High-Temperature Settling

This research examines transforming contaminated mining waste into mineralogically stable material using density separation and high-temperature settling. Samples with elevated metal concentrations were collected from century-old landfill sites, separated from overburden and organic material, and subjected to density separation and thermal treatment at 1300 and 1400 °C. This process significantly reduced heavy metal content, lowering cumulative lead, cadmium, and arsenic concentrations from 2440 g/t to below 60 g/t, and efficiently removed volatile elements such as arsenic and zinc. Sulfur content decreased from 1.67 wt% to 0.21 wt% after treatment at 1400 °C, while oxygen content increased from 31.9 wt% to 36.29 wt% and 34.2 wt% after treatment at 1300 °C and 1400 °C, respectively. Mineralogical, differential thermal and chemical analyses confirmed the thermal stability of the resulting material up to at least 350 °C, with fayalite and magnetite as the predominant minerals. Final concentrations of heavy metals were below EU natural soil background levels, supporting the material’s safe and sustainable reuse in environmental applications. By focusing on remediation of metal-rich hotspots, this approach enables practical reclamation of mining waste areas and supports the valorization of legacy copper slag deposits, advancing environmental restoration and circular economy goals.