Hydrometallurgical separation of Co(II) from Ni(II) from model and real waste solutions

This paper presents sustainable hydrometallurgical recovery of Co(II) from wastewater, achieved by application of two ionic liquids (Cyphos IL 101 or 104) and an acidic extractant (Cyanex 272). The separation of Co(II) is carried out from model aqueous chloride and sulfate solutions, as well as from a real waste sulfate solution containing also Ni(II). The extractants were investigated both as single carriers and as synergic mixtures, the latter giving no positive synergistic effect. Cyanex 272 does not allow Co(II) to be transferred from chloride solutions effectively, while extraction from sulfate mixtures reaches totally up to 100% after two stages. Cyphos IL 101 does not give satisfactory results of Co(II) recovery from sulfate solutions, while both Co(II) and Ni(II) are transferred efficiently from chloride ones. Stripping of Co(II) from the loaded organic phases with 1 M H2SO4 is very efficient (95-100%), regardless of the type of extractant (Cyanex 272 or Cyphos IL 104) and its concentration. Application of 1 M H2SO4 allows Co(II) to be recovered from the loaded organic phase (up to 100%) in one stage of stripping and to be enriched even three-to fivefold relative to that in the feed. It also allows the organic phase to be reused for further extractions. Theoretical considerations of economic feasibility of the process proposed indicated that the value of cobalt in solutions after proposed steps increases from 0.32 USD/dm(3) (after two stages of extraction) to 1.42 USD/dm(3) after stripping. The major novelty of this work is the design of hydrometallurgical recovery of Co(II) from real sulfate wastewater in the presence of Ni(II), which permits sustainable processing of waste, recycling and recovery of critical element and also regeneration and reuse of organic chemicals applied for extraction. (C) 2019 Elsevier Ltd. All rights reserved.