Resource potential of slags from Zambian copper smelters

Abstract

Millions of tonnes of pyrometallurgical slags from copper smelters in the Copperbelt Province and North-Western Province of Zambia have been deposited on dumps near mining and ore processing operations and represent potential sources of valuable elements for the future. Here, we analysed archived and freshly collected copper slag samples (n = 48) from five historical and currently operating Zambian copper smelters to assess their chemical compositions, solid speciation of valuable elements, and resource potential. Elevated values of Cu (mean: 1.43 wt%, up to 9.5 wt %), Co (mean: 4450 mg/kg, up to 2.4 wt%), Ni (mean: 69.2 mg/kg, up to 935 mg/kg) and Mo (mean: 169 mg/kg, up to 422 mg/kg) were detected, predominantly bound in the entrapped matte and metallic droplets. The image analysis of scanning electron micrographs (SEM) was used for the assessment of the size distribution of sulfide/metallic droplets and indicated that copper slags from Nkana (Kitwe) and Mufulira, with the most abundant fraction >100 mu m, are the best candidates for further reprocessing by crushing, milling, and flotation. Nevertheless, slag reprocessing must be carried out in an environmentally friendly way to limit dust generation, which can have implications for the environment (soil systems) and human health.