Cobalt and copper recovery from the ancient flotation tailings by selective sulfation roast – Leaching process

J. Min. Metall. Sect. B-Metall. 55 (3) B (2019) 315-324. DOI:10.2298/JMMB190304043O
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The ancient flotation tailings from Lefke, Cyprus, have a potential for non-ferrous metals such as cobalt and copper from more than 9.5 million tons of reserves containing 0.38% Cu, 0.032% Co, and 22.6% Fe. Recovery of cobalt and copper from these tailings can provide great benefits from economic and environmental perspectives. While the ancient tailings were kept long time in storage in dumps, the characteristics of the material has become different from the common Co and Cu bearing ores. In order to extract these valuable metals, a process involving combination of roasting and leaching was applied in this study. Since this process responded to recovery to some extent, an innovative technique of using Na2SO4 as a promoter during roasting was proposed. Utilizing of Na2SO4 did not provide only higher metal extractions, but also resulted in high selectivity. In the scope of the study, following the determination of the mineralogy and chemical composition of the tailings, certain processes such as direct leaching and sulfation roasting with/without additives before leaching were applied. Since low metal extractions were obtained from direct leaching, a selective sulfation process was applied on the tailings before leaching in order to produce a pregnant solution containing higher amounts of Co and Cu metals by reducing the iron concentration. When sulfation roasting was performed without any additive, the desired selectivity could not be provided, since the sample was considerably oxidized under the atmospheric conditions in the past. Therefore, the usage of Na2SO4 as an additive with the amount of 25% at a roasting temperature of 700ºC was tested. Consequently, Na2SO4 improved the sulfation and resulted in higher cobalt (90.1%) and copper (71.2%) recovery during leaching. Beside this, an improvement with a selective sulfation was obtained by combined effect of Na2SO4 addition and temperature, and the iron extraction decreased from 26.1% to 3.9%.
Keywords: Flotation tailings; Cobalt; Copper, Roasting; Selective sulfation; Sodium sulfate

Correspondence Address:
M. Ozer, Istanbul Technical University, Mining Faculty,
Mineral Processing Engineering Department, Maslak, Istanbul

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