Such a process will lower the operating cost of cobalt production as it will eliminate the need of reducing agents. īecause of the aforementioned difficulties with the reductive leaching method, it is critical to develop a process that can recover copper and cobalt in a short period of time without the use of reducing agents.

Įxpensive, but they also cause major environmental problems, and when used in large quantities, SO 2 has an impact on copper recovery. Common copper and cobalt minerals found in central African Copperbelt region. Reducing agents, such as SO 2, are not only For example, at Shituru Plant in the DRC, reducing agents accounted for 47% of the total operating cost per tonne of cobalt metal produced. Authors and stated that the high consumption of reducing agents during leaching makes the production of cobalt an expensive process. Additionally, reducing agents used for Co 3+ minerals increase the operating cost.

Īlthough the reductive leaching method has been well established in many metallurgical plants of the DRC and Zambia, the leaching time of 8 hours in some hydrometallurgical plants in the DRC is undesirable. The leaching of the copper-cobalt ores from the DRC normally takes 2 hours but in some cases, the leaching time can go up to 8 hours. A typical reaction for the dissolution of Co 3+ using SO 2 as the reducing agent is represented by Equation (1). Commonly used reducing agents for Co 3+ minerals include sulphur dioxide (SO 2), sodium metabisulphite (SMBS), ferrous ions and hydrogen peroxide (H 2O 2). As already stated, reducing agents are added to the leaching system in order to convert the acid insoluble Co 3+ to soluble Co 2+ for easy leaching. While most copper oxide and cobalt (II) oxide minerals dissolve in sulphuric acid, Co 3+ does not dissolve in acid during the direct acid leaching. The hydrometallurgical processing of copper-cobalt oxide minerals from the DRC involves leaching the ore/concentrate in sulphuric acid (H 2SO 4). The main gangue minerals include dolomite (CaMg(CO 3) 2) and quartz (SiO 2). Table 1 shows the main copper and cobalt oxide minerals from the Central African Copperbelt region of Zambia and the DRC. Malachite (Cu 2CO 3(OH) 2), azurite (Cu 3(CO 3) 2(OH) 2) and chrysocolla (CuOSiO 2♲H 2O) are some of the copper oxide minerals found in the oxidised deposits of the DRC. H 2O) or in amorphous state as heterogenite (CoO♲Co 2O 3♶H 2O).The common cobalt (III) minerals exist either in crystalline state as Stainierite (Co 2O 3 Cobalt (III) is the major form in which cobalt exists and from which most of the cobalt is produced. Cobalt carbonate readily dissolves in acid while trivalent cobalt (Co 3+) is insoluble in acid and requires a reducing agent to convert it to divalent cobalt (Co 2+). In the oxidised deposits of the DRC, the main cobalt oxide minerals are cobalt carbonate and cobalt (III) oxide. The Central African Copperbelt region of the Democratic Republic of Congo (DRC) and Zambia accounts for more than 50% of the world’s cobalt (Co) reserves and one tenth of the world’s copper (Cu) reserves. The outcome of this work has shown that the sulphuric acid bake-leach process is a possible alternative to the reductive leaching method for copper-cobalt oxide ores. Both copper and cobalt were extracted from the baked material within short leaching times and without the addition of reducing agents. The dissolutions of copper and cobalt were dependent on acid concentration with cobalt showing more sensitivity to the amount of acid. The reacted samples were then subjected to water leaching at room temperature to determine the leachability of copper and cobalt from the baked material. Baking tests were conducted at different conditions such as temperature, time, and varying amounts of acid. Sulphuric acid bake-leach process of the mixed copper-cobalt oxide ore was carried out by mixing the sample with sulphuric acid followed by baking of the mixture in a muffle furnace. A sulphuric acid bake–leach method for the treatment of mixed copper-cobalt oxide minerals was investigated as an alternative to the reductive leaching method.

Copper and cobalt