A zinc recovery method includes an alkali fusion step (102) of, at a temperature equal to or higher than a melting point of sodium hydroxide, bringing a material (1) and molten sodium hydroxide being sodium hydroxide (5) or (14) in a molten state into contact with each other to decompose the zinc ferrite contained in the material (1) into zinc oxide components and iron oxide components in the molten sodium hydroxide, a water leaching step (103) of, at a temperature lower than a boiling point of water, bringing water into contact with sodium hydroxide being the molten sodium hydroxide with a decreased temperature, the zinc oxide components, and the iron oxide components and leaching the zinc oxide components in a sodium hydroxide aqueous solution.
According to the present invention, an electrolytic product collecting method and an electrolytic product collecting system involve: leaching, with a sodium hydroxide aqueous solution (2), a zinc-containing substance derived from zinc-containing dust (1) to obtain a zinc-containing sodium hydroxide aqueous solution (3); performing electrolysis by using an electrolysis device (E) comprising an electrolysis tank (30) that accommodates an electrolysis bath (32) using an anode (10), a cathode (20) that faces the anode (10) and that is made of pure magnesium or a magnesium alloy, and the zinc-containing sodium hydroxide aqueous solution (3); and, in the electrolysis tank (30), bringing contact members (44), sequentially at a prescribed time interval, into contact with a plurality of portions of a zinc electrodeposition substance (4) obtained as an electrolytic product in an electrolysis step (102), to thereby peel off the zinc electrodeposition substance (4) from the cathode (20).
In this zinc recovery method or zinc ferrite decomposition method, zinc ferrite is decomposed into a zinc oxide component and an iron oxide component by: bringing a starting material (1) that contains a zinc component and zinc ferrite, or a processed starting material (3), which is obtained by processing the starting material (1), into contact with an aqueous alkali hydroxide solution (5, 14); heating the starting material (1) or the processed starting material (3) and the aqueous alkali hydroxide solution (5, 14) in contact with each other until the temperatures of the starting material (1) or the processed starting material (3) and the aqueous alkali hydroxide solution (5, 14) reach the boiling point of water having boiling-point elevation; retaining the concentration of an alkaline agent in the aqueous alkali hydroxide solution (5, 14) when evaporation of the water content in the aqueous alkali hydroxide solution (5, 14) has stopped after the temperature thereof reached the boiling point; and bringing the alkaline agent, the concentration of which is retained in a concentration retention step (102c), and zinc ferrite in the starting material (1) or in the processed starting material (3) into contact with each other.
The present zinc recovery method is characterized in including a dissolving process of treating a raw material containing zinc with an alkaline fluid at a temperature equal to or higher than 100° C. to dissolve zinc contained in the raw material, and a recovering process of recovering zinc extracted from the raw material by the dissolving process.
A zinc production method further includes chlorine-concentration adjusting processes 101, 101′, and 105 of using an alkali hydroxide aqueous solution as an extraction solvent for selectively extracting zinc components in a zinc-containing aqueous-solution generating process 102, and separating chlorine components contained in electric arc furnace dust or secondary dust to decrease the chlorine concentration of a zinc-containing aqueous solution at a stage prior to an electrolyzing process 103.
A zinc recovery method comprising: an alkaline melting step 102 for bringing, at a temperature equal to or higher than the melting point of sodium hydroxide, a material (1) and the like into contact with molten sodium hydroxide which is sodium hydroxide (5), (14) in a molten state to break up zinc ferrite contained in the material (1) and the like in the molten sodium hydroxide into zinc oxide components and ferric oxide components; a water dissolution step (103) for bringing, into contact with water and at a temperature not higher than the boiling point of water, the ferric oxide components, the zinc oxide components, and sodium hydroxide obtained as a result of lowering the temperature of the molten sodium hydroxide, and dissolving the zinc oxide components into a sodium hydroxide aqueous solution to obtain a zinc-containing aqueous solution (8) containing zinc components and to obtain an insoluble substance (9) including ferric oxide components that would not be dissolved in the sodium hydroxide aqueous solution; and a zinc recovery step (105), (108) for recovering the zinc components derived from the zinc-containing aqueous solution (8).
This zinc recovery method is characterized by comprising: a dissolution step for dissolving zinc contained in a raw material by treating a zinc-containing raw material with an alkaline fluid having a temperature of at least 100 °C; and a recovery step for recovering zinc extracted from the raw material in the dissolution step.
A zinc production method, according to the present invention, further comprises chlorine concentration adjustment steps 101, 101', and 105 for using a hydroxylated alkaline aqueous solution as an extraction solvent for selectively extracting a zinc component during a zinc-containing aqueous solution generation step 102, and separating the chlorine component contained in electrical-furnace dust or secondary dust at a stage prior to an electrolysis step 103 so as to reduce the chlorine concentration in a zinc-containing aqueous solution.
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