A nickel-hydrogen battery used for metal recovery method

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PROBLEM TO BE SOLVED : To provide a method for treatment of used nickel-metal hydride battery capable of separating nickel, cobalt, rare-earth elements and other coexisting metal elements from the positive- and negative-electrode active materials obtained by scrapping the above used battery, particularly capable of recovering high-content nickel and rare-earth elements in the form reusable as materials for battery. SOLUTION : The recovering method includes the following steps (1) to (6) : (1) a cleaning step of cleaning the positive- and negative-electrode active materials; (2) a reduction step of reducing the mixture of an after-cleaning residue obtained by the above cleaning step and a leachate obtained by the following leaching step; (3) a leaching step of leaching out a reduction residue obtained by the above reduction step; (4) a rare earth recovery step of subjecting a reduction liquid obtained by the reduction step to double salt formation of the rare earth elements; (5) an oxidation/neutralization step of oxidizing/neutralizing a filtrate obtained by the rare earth recovery step; and (6) a solvent extraction step of extracting the liquid after oxidation/neutralization obtained by the step (5) with a solvent. COPYRIGHT : (C)2010, JPO&INPIT