Assessing the viability of magnetic separator tailings as a secondary source of nickel, cobalt and copper: a case study for Tati Nickel Mining Company

Abstract To date, the recovery of nickel and cobalt sulphide minerals from low-grade ores poses significant challenges in mineral processing due to their complex nature. With the decline of rich ore bodies, a paradigm shift to low-grade ores and secondary sources exists for these critical metals, particularly in the renewable energy sector, i.e. storage batteries. This study explores the potential consideration of the magnetic separator tailings obtained from Tati Nickel Mining Company in Botswana as a lucrative base metal secondary resource for the recovery of nickel, cobalt and copper. It becomes a dual approach to obtain valuable base metals while economically handling the waste material to ease the environmental challenges it was posing to the mine and the community. Characterisation of the samples obtained through crystallographic analysis, mineralogy and mapping, and elemental analysis showed the presence of nickel and copper minerals to a degree by which they can be economically extracted through hydrometallurgical means. Cobalt concentration in the sample was in trace amounts as it could only be detectable through the destructive technique. Concentration through froth flotation was conducted post characterisation, with emphasis on flotation time. The optimum flotation time was determined to be 3 minutes, giving metal recoveries of 15.56%, 27.40% and 52% for cobalt, nickel and copper respectively, with an enrichment ratio of 7.39 for copper. However, the yield obtained was 7.04% highlighting the ineffectiveness of the traditional concentration route previously practised in the mine. It was recommended therefore to re-design the flotation process and tailor it for the magnetic separator tailings, concentrating on the effects of pH and particle size distribution primarily, before the other factors, e.g. collectors, modifiers, etc. In conclusion, it was noted that the recovery of nickel, copper and the by-product iron was feasible; therefore, a recommendation was made to apply the Activox technology.