Dissolution of oxidised Co-Cu ores using hydrochloric acid in the presence of ferrous chloride

An investigation of the dissolution of four oxidised Co-Cu ores, from the Democratic Republic of Congo (DRC, ex-Zaire), in hydrochloric acid and FeCl ₂ solution was conducted. Cobalt leaching in the absence of FeCl ₂ was < 36% but copper leaching was > 70%. Addition of FeCl₂ resulted in the reduction of Co³⁺ to soluble Co ²⁺. The leaching of cobalt was very rapid with only a slow rate of dissolution evident beyond 30 min. The ratio of ferrous ions to cobalt in the ore was important with a > 2:1 ratio required to achieve > 95% Co dissolution. Copper dissolution was also rapid and was not affected by the presence of ferrous ions. Both metals were present in several different minerals, of which only the most abundant, heterogenite and malachite, were detected by XRD.