Patent ID: 8888892

Claim:
A method for separating nickel, cobalt, and a rare earth element from a material containing positive and negative electrode active materials of a nickel-metal hydride battery, wherein a sulfide containing nickel and cobalt and a sulfate containing a rare earth element are obtained from the material containing positive and negative electrode active materials which constitutes the nickel-metal hydride battery, the method comprising: (1) a leaching step of mixing the material containing positive and negative electrode active materials with a sulfuric acid solution and dissolving therein, followed by separating a leachate from a residue, (2) a rare earth crystallization step of adding an alkali metal sulfate to the leachate obtained in the leaching step and thereby obtaining a mixed precipitate of double sulfate of a rare earth element and a rare-earth-element-free solution, and (3) a sulfide raw material recovery step of adding a sulfurizing agent to the rare-earth-element-free solution obtained in the rare earth crystallization step and thereby separating a nickel and cobalt sulfide raw material from a residual solution, and (4) a dezincification step of adding a sulfurizing agent to the rare-earth-element-free solution obtained in the rare earth crystallization step to separate zinc in the rare-earth-element-free solution as a sulfide precipitate, and supplying a residual solution after the separation as the rare-earth-element-free solution in the sulfide raw material recovery step.