Dowa Mining Co., Ltd.

Unitika Ltd.

Tanaka Kikinzoku Kogyo K.k.

Kosaka Smelting & Refining Co., Ltd.

Hitoshi Masuda

Hiroshi Inoue

Nobuyasu Ezawa

Masahide Hirai

Norihito Ishimori

Kunio Sekine

Kaoru Saruta

Shozo Tomoshige

Kozo Kondo

Shoei Takada

Kodo Ishibashi

A method for directly leaching a zinc concentrate in one of the stages contained in the hydrometallurgical process for the production of electrolytic zinc. The method comprises: a neutral leach step, a zinc concentrate leach step, and an iron oxidation step. In the zinc concentrate leach step, a neutral leach residue and an iron sediment returned from the iron oxidation step are repulped by the spent electrolyte followed by adding thereto zinc concentrate to extract zinc from the zinc concentrate by carrying out a leaching under atmospheric pressure and at a temperature of not lower than 90&deg; C., but not higher than the boiling point of the solution. According to this method, the concentration of Fe(III) ions in the zinc concentrate leach solution is significantly increased. Due to this Fe(III) ion concentration, the leaching rate of the zinc concentrate is enhanced.

Method of leaching zinc concentrate

A process of recovering a platinum group metal from a waste catalyst comprising a first step which comprises heating and melting the catalyst impregnated with the platinum group metal, copper and/or the oxide of copper, a flux component and a reductant component to form a layer containing the metal copper into which the platinum group metal is absorbed and another layer of the oxide, and then separating the metal copper; and a second step which comprises supplying air or oxygen as an oxidant to the separated metal copper for oxidizing under heating and melting to form a layer of partially oxidized metal copper and another layer of the metal copper containing the concentrated platinum group metal, and separating it. This process enables the economical recovery of the platinum group metal from the waste catalyst in a short period of time with high recovery rate.

Process of recovering platinum group metal

A novel method is disclosed which enables gallium and/or indium to be selectively separated and concentrated from a solution containing them in very low concentrations together with many other metal ions in rather high concentrations. The solution is passed through a bed of a chelating ion exchange resin having an amino carboxylic acid group either immediately or after the pH adjustment. Gallium and/or indium adsorbed on the chelate resin is desorbed by eluting with a mineral acid. The eluate, after the pH adjustment, is passed through another bed of a chelating ion exchange resin having an amino carboxylic acid group, and the resin is treated with a mineral acid to elute the metal ions adsorbed on the resin to thereby recover gallium and/or indium in the form of a concentrated solution.

Method of selective separation and concentration of gallium and/or

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Akita, Japan

Hitoshi Masuda