METHOD FOR PRODUCING HIGH-PURITY COBALT SULFATE SOLUTION, AND METHOD FOR PRODUCING COBALT SULFATE

摘要

The present invention is a method for producing, from a cobalt sulfate solution including nickel ions, a high-purity cobalt sulfate solution having a higher purity level of cobalt compared to the aforementioned cobalt sulfate solution. The cobaltickel concentration ratio of the cobalt sulfate solution is 100 or greater. This method includes a nickel separation step in which: the cobalt sulfate solution is brought into contact with a solvent containing a bis(2,4,4-trimethylpentyl)phosphinic acid so as to adjust pH; with nickel ions included in the cobalt sulfate solution left in the liquid, cobalt ions are extracted into the solvent; and subsequently, the cobalt ions that have been extracted into the solvent are back-extracted with a sulfuric acid.