Nippon Mining Co., Ltd.

Tsumoru Fujii

Takashi Ogata

Shoichiro Namihisa

An acid solution containing cobalt and nickel is contacted with an organic extraction medium comprising alkyl phosphonic acid mono alkyl ester where said alkyl group has 8-10 carbon atoms in two or more stages, wherein the contact at a first stage is carried out at a pH value not exceeding 5.0 and at a second and further stages being carried out at a pH range of 5.5-7.0. Thereby cobalt may effectively and selectively be extracted into the organic extraction medium from the solution without excess rise in viscosity. Cobalt and nickel may be separately recovered with high purity.

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Hitachi, Japan

Tsumoru Fujii