Scenarios for Sustainable Management of a Solid Release from a Hydrometallurgical Zinc Treatment in the Democratic Republic of Congo

The treatment of zinc ores at the UZK (Kolwezi Zinc Factory), in the DRC (Democratic Republic of Congo), has generated a deposit of solid releases rich in recoverable metals, but presented an environmental risk given the conditions of its storage. The results of chemical analyses by X-ray fluorescence have shown the presence of base metals recoverable in significant proportions in these releases, which contain on average 17% zinc and 3.5% copper. In addition, X-ray diffraction analyses have identified the main minerals: franklinite, willemite and sphalerite. The environmental risks are real, because the results of the availability tests for leaching have revealed significant zinc and copper extraction rates for a liquid to solid ratio of 100 and those of landfill compliances show that although under European Directive 2003/33/EC, these discharges are dangerous and must be treated under conditions which respect the environment. Following an environmental risk assessment, two scenarios for reprocessing these discharges are envisaged and will be compared from a technical, economic and environmental point of view, including their feasibility in the context of the DRC. The two processes would be on the one hand a hot acid attack in two or three stages and on the other hand a mixed digestion-roasting treatment followed by leaching with water.