M.Tech. / Recent studies have explored the capabilities of sulphur dioxide (SO2), a reducing agent that shows great potential to enhance the leaching efficiency of cobalt from mixed Co-Cu oxidized ores. The research study reported in this dissertation was conducted to further explore the efficacy of SO2 as a suitable reagent to improve the cobalt yield in solution from mixed Co-Cu oxidised ores. Four mixed Co-Cu oxidised ores were used in this study; namely, high cobalt ore (34% Co), low cobalt ore with mica (4% Co), low cobalt ore without mica (3% Co) and high copper ore (0.5% Co). The mechanistic leaching pathways of cobalt from these ores with and without SO2 were investigated and monitored using Ultra-Violet/Visible spectroscopy. Mineralogical studies of these ores was carried out by X - ray diffraction (XRD), X - ray fluorescence (XRF) and flame atomic absorption spectroscopy (AAS). Microwave processing of these ores prior to leaching experiments was also investigated. The experimental work was carried out on a laboratory scale and highlights of results obtained are summarized as follows:  Although not much information pertaining to Co2+ bearing minerals in mixed Co-Cu oxidised ores was derived from XRD results, two forms of heterogenite minerals (CoOOH-2H and CoOOH-3R), which bear cobalt as Co3+ were noted in the low cobalt ores.  High percentage cobalt dissolutions (85% to 95%) were achieved when leaching mixed Co-Cu oxidised ores in the presence of SO2.  UV/Visible spectroscopy confirmed concentrations of Co3+ and Co2+ before and after SO2 treatment of mixed Co-Cu oxidised ores.  Percentage cobalt dissolutions improved by 10% to 20% in microwave irradiated mixed Co-Cu oxidised ores  The presence of iron and copper in leach solutions can limit the dissolution of cobalt from mixed Co-Cu oxidised ores to a certain extent.

A study of the reduction of black cobalt oxide, using hydrogen as the reductant, showed that the temperature and time used for reduction exerted a profound influence on the proportions of face centred cubic (a) and hexagonal close packed (e) cobalt allotropes obtained in the reduced metal powder. Reduction under certain conditions yielded a faulted hexagonal cobalt powder product which contained stacking faults. The influence of oxygen and titanium on cobalt materials showed that these impurities did not stabilise the proportions of either the cubic or hexagonal phases under the conditions, which were used. The grinding of cobalt powders from different sources showed different tendencies towards agglomeration, when acetome was used as the milling fluid. It was found that powders which contained an initially higher proportion of the hexagonal phase -had a strong tendency towards agglomeration during the initial stages of grinding. The importance of the different phases of cobalt present in the metal powders, and their different agglomeration tendencies on grinding, on the milling required for satisfactory densification of cobalt - tungsten carbide compacts has been shown; it was (iv) found that hard metal alloys prepared using powders with an initially higher proportion of the hexagonal phase required less milling to achieve a given sintered density, than did mixtures prepared with other cobalt powder*;. A correlation analysis between the properties of the milled hard metal powders and the properties of the sintered compacts was carried out; it was found that the most important correlation was between the specific surface area of the milled hard metal powder and the coercivity of the sintered product.