Geometallurgy of Cobalt Black Ores in the Katanga Copperbelt (Ruashi Cu-Co Deposit): A New Proposal for Enhancing Cobalt Recovery

Abstract

Copper-cobalt deposits in the Central African Copperbelt belong to the Sediment-Hosted Stratiform Copper (SHSC) type and are situated in the Neoproterozoic Katanga Supergroup. This paper describes in detail the geology, geochemistry and hydrometallurgy of cobalt, with a special focus on the Black Ore Mineralised Zone (BOMZ) unit from the Ruashi Cu-Co deposit as a case study. Based on results from fieldwork and laboratory testing, it was concluded that the BOMZ consists of a succession of massive and stratified dolostones, which are weathered into carbonaceous clay dolostones and clays. The Lower “Calcaire à Minéreaux Noirs Formation” (Lower CMN Formation) consists of stratified and finely laminated dolostones, which are weathered at the surface into clayey to siliceous dolostones. The cobalt concentration in the weathering zone is due to supergene enrichment, a process that is linked to the formation of a cobalt cap. The ore consists of heterogenite associated with minor amounts of chrysocolla and malachite. Minor carrollite, chalcopyrite, chalcocite and bornite are present in unweathered fragments. The cobalt grade in both the BOMZ and Lower CMN decreases within depth while the copper grade increases. These grade changes reflect the variation in mineralogy with depth from heterogenite with minor amounts of malachite and chrysocolla to malachite, chrysocolla with traces of heterogenite, spherocobaltite, chalcocite, chalcopyrite, carrollite and bornite. Based on the Cu (100xAS Cu/TCu) and Co ratio (100 xAS Co/TCo), which is related to the ore mineralogy, oxide ores (Cu ratio ≥ 75%) and oxide dominant mixed ores (Cu ratio < 75%, containing the copper sulphide chalcocite) can be differentiated in both the BOMZ and Lower CMN. The absence of talc and the low concentration of Ni, Mn and Fe, on the one hand, and the high-grade Cu in the BOMZ, on the other hand, facilitate the hydrometallurgy of cobalt but require a specific processing. Consequently, the recovery of Co from the BOMZ requires the application of a processing method that is based on sulphuric acid (30 g/L) leaching under reducing conditions (300–350 mV) and the removal of impurities (Cu > 95% and Mn ≈ 99%) from the pregnant leach solution (PLS) by solvent extraction (SX) prior to the precipitation of cobalt as a high-grade hydroxide (40.5%). The sulphuric acid leaching of the BOMZ enabled achieving, after 8 h of magnetic stirring (500 rpm), a highest yield of 93% Co, with other major elements Mn (84%) and Cu (40%). The latter forms a main co-product of the Co exploitation. In contrast, the highest leaching yield for Fe remained smaller than 5%.

Sustainable Approach for Critical Metals Recovery through Hydrometallurgical Processing of Spent Batteries Using Organic Acids

“…As observed by the characterization of the cell battery, there is a high concentration of Co (21.1%), which is at least 50 times higher than that in natural sources. 34,35 The cathode material represents 35.4% of the cell battery, which is the main economic value. It is estimated that 87% of the economic value is due to the Co content, where for each ton of this cell battery, up to US$ 12,769 may be recovered, 90% of the cathode.…”

Additive-Free Aqueous Extraction of Copper and Zinc from Sulfidic Tailings Using Fast Microwave-Assisted Pre- and Post-Treatments

“…These results confirmed that the removal of Fe, together with As, was achieved under hydrothermal conditions with no significant removal of the other metals. The remaining solutions can be utilized to further refine the contained metals such as Cu, Zn, and Co ,, or to directly isolate them by precipitation or electrodeposition (e.g., electrowinning). , …”

“…In hydrometallurgical methods, use of chemicals in aqueous solution for metal extraction is often the practice . The most commonly used chemicals are ammonia, ,,, or other bases, − acids − and their salts, as well as oxidation agents , that enable selective leaching of the targeted metals from either pretreated or untreated material. On the other hand, pure water is seldom used as a lixiviant due to its low selectivity and poor mineral solubility. , …”

Are Ecological Risk Indices for Trace Metals Relevant for Characterizing Polluted Substrates in the Katangese Copperbelt (DR Congo) and for Assessment of the Performance of Remediation Trials?

“…Mining activities in the Katangese Copperbelt (KCB, DR Congo) for more than a century generated great quantities of mining waste. These result from ore extraction in mines and metallurgical processes for ore purification; a typology of mining waste in the KCB is provided in the literature [1][2][3]. Mining is responsible for metal dissemination and the related pollution of the environment, as reported by numerous studies.…”