METHOD FOR SEPARATING NIKEL AND COBALT FROM ACTIVE MATERIALS CONTAINED IN SPENT NICKEL-HYDROGEN BATT

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The present invention addresses the problem of providing a method for separating and recovering nickel, cobalt and rare earth elements (RE) from positive- and negative-electrode active materials that constitute a nickel-hydrogen secondary battery. The above problem can be solved by a method wherein nickel, cobalt and RE are recovered in the form of a sulfide that contains both nickel and cobalt and an RE-containing sulfate form a material which contains positive- and negative-electrode active materials that constitute a nickel-hydrogen secondary battery, said method including the following three steps : (1) a leaching step of subjecting a material which contains positive- and negative-electrode active materials to mixing with a sulfuric acid solution and dissolving therein, and then separating the resultant system into a leachate and a residue; (2) an RE crystallization step of adding an alkali metal sulfate to the leachate to obtain both a precipitate of an RE composite sulfate mixture and a RE-free fluid; and (3) a sulfide raw material recovery step of adding a sulfurizing agent to the RE-free fluid and thereby separating the RE-free fluid into a nickel/cobalt sulfide raw material and a residual fluid.