Eurasian Resources Group’s (ERG) Metalkol operation in the Democratic Republic of the Congo (DRC) produces copperCopper cathode and cobaltCobalt hydroxide from the retreatment of historic copperCopper-cobaltCobalt tailingsTailings left by previous mining operators in the Kingamyambo tailingsTailings Dam and Musonoi River System. The dynamic behaviour of this river system has caused distinct areas with high variability in terms of the particle size distribution, and clay and impurity content that need to be managed carefully to ensure a controlled feed to processingProcessing. Higher levels of cadmiumCadmium and zinc in this material are of concern due to pressure from end users to reduce these impurities in the Co(OH)2 product. Selective precipitationPrecipitation with an organo dithiophosphate, as used in the phosphoric acidPhosphoric acid industry for heavy metalsMetals removal, has been investigated for the treatment of the cobaltCobalt (Co) solution. Bench scale experiments, continuous pilot plant, and plant trials have shown that cadmium removalCadmium removal efficiencies of > 98% can be achieved. Key technical and economic considerations relate to the solids content of the dosing point and the base metalMetals content of the streams, which greatly affect the dosing requirements to achieve the cadmium removalCadmium removal target. The difference in performance between reagents was established, and the choice between reagents would depend on the specific priorities and requirements of the process, such as the desired Cd concentration in the downstream product and the acceptable level of Co loss.