METHOD FOR PRODUCING COBALT SOLUTION

A method for producing a cobalt solution by removing magnesium ions from a cobalt-containing solution obtained by subjecting battery powder resulting from lithium ion battery waste to at least a leaching process, the cobalt-containing solution containing magnesium ions, wherein the method includes: a magnesium separation step of extracting cobalt ions from the cobalt-containing solution using a solvent containing a carboxylic acid-based extracting agent to separate the magnesium ions, and then stripping the cobalt ions from the solvent to obtain the cobalt solution as a stripped solution.