Method for manufacturing nickel and cobalt-containing solution from hydroxide containing nickel and cobalt

A method of manufacturing a cobalt-nickel-containing solution, the method comprising:

• preparing at least one of a crude nickel hydroxide and a crude cobalt hydroxide as a starting material,
• the crude nickel hydroxide containing cobalt and nickel, and one or more elements of magnesium, calcium, iron, silicon, manganese, zinc, copper, aluminum, and chromium other than the cobalt and nickel as impurities, and containing the nickel more than the cobalt, and
• the crude cobalt hydroxide containing cobalt and nickel, and one or more elements of magnesium, calcium, iron, silicon, manganese, zinc, copper, aluminum, and chromium other than the cobalt and nickel as impurities, and containing the cobalt more than the nickel,
• a water-washing process of adding water to the starting material, stirring and mixing it to form a slurry, filtering the slurry to obtain a sediment, washing the sediment with water to reduce one or more of the impurities from the sediment, thereby obtaining a post-water-washing crude hydroxide;
• a leaching process of subjecting the post-water-washing crude hydroxide to leaching with an acid to obtain a post-leaching solution containing cobalt and nickel;
• a neutralization process of adding a pH adjusting agent the post-leaching solution to perform neutralization, and subjecting it to solid-liquid separation to remove a post-neutralization residue, thereby obtaining a post-neutralization solution;
• an extraction process of subjecting the post-neutralization solution obtained to solvent extraction with an extractant, thereby obtaining a post-extraction solution containing both cobalt and nickel with the impurities reduced;
• a washing process of back-extracting a part of nickel and cobalt contained in a post-extraction organic phase obtained in the extraction process into an aqueous phase to remove one or more of manganese, magnesium, calcium, zinc, and copper as the impurities into a post-washing organic phase as an organic phase, thereby obtaining a post-washing solution as the aqueous phase containing nickel and cobalt with the impurities reduced;
• and
• a back extraction process of further subjecting the post-washing organic phase to back extraction to back-extract manganese, magnesium, calcium, zinc, and copper as the impurities into an aqueous phase and to remove the impurities into a post-back-extraction solution as the aqueous phase, thereby obtaining a post-back-extraction organic phase with the impurities reduced.