Electrolytic cobalt was produced from a solution containing nickel and other metallic impurities employing solvent extraction - electrowinning. The solution was generated in batches by leaching superalloy scrap and was subsequently purified. It contained Co approx 7 -12 gpl, Ni approx 35-50 gpl, and Zn and Cu in small quantities. The organic extractant was partially neutralised PC 88A (2-ethylhexyl 2-ethylhexyl phosphonic acid) diluted in kerosene. Cobalt from the metal loaded organic phase was stripped by dilute H_2SO_4/acidic CoSO_4 solution and the resulting CoSO_4 solution, enriched to approx45 gpl Co tenor by recirculation, was used as electrolyte for electrowinning cobalt. The process parameters were first established in laboratory-scale tests and later in continuous bench-scale operation. The process was then tested in a large scale continuous pilot plant.
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