JP4304254B2 - Recovery method of high purity indium - Google Patents

Description

【００１０】
【発明の効果】
本発明のインジウム回収方法によれば、従来の方法よりも簡単な工程でかつ安価に９９．９９９％以上の高純度のインジウムを回収できる。従って、本発明の方法は、ＩＴＯターゲット屑等のリサイクル法として極めて有用な方法である。
【図面の簡単な説明】
【図１】本発明のインジウム回収方法を示す工程図である。[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a method for recovering indium from an indium-containing material. More specifically, the present invention relates to a method for efficiently recovering high-purity indium metal from indium tin oxide (ITO) target scraps. This recovery method is useful as a recycling method for ITO target scraps and the like.
[0002]
[Prior art]
Due to the recent rapid development of liquid crystal technology, the demand for ITO used as a transparent conductive film of this liquid crystal has remarkably increased. An ITO target material is used as a raw material for producing the ITO film. Conventionally, several methods for recovering indium using ITO target scraps and the like as raw materials have been proposed. For example, there is a method using a solvent extraction method (Japanese Patent Laid-Open No. 8-91838). However, this method repeats extraction and back-extraction, which complicates the process, and uses an expensive solvent, resulting in high cost. . As another method, a metal indium plate is inserted into a solution in which indium is dissolved, and impurity ions in the solution are replaced and removed, and then indium metal is electrolytically collected using the solution as an electrolytic solution. (Japanese Patent Laid-Open No. 10-204673). Although this method is simple, the impurity ion concentration that can be removed by displacement deposition is limited, and the purity of the obtained indium metal is at most 99.99%.
[0003]
[Problems to be solved by the invention]
The present invention solves the above-mentioned problems in the conventional indium recovery method, and is a high-purity indium that has a simple process and surpasses the conventional method by a unit operation generally used in wet refining of metals. A method is proposed to recover the wastewater.
[0004]
[Means for Solving the Problems]
That is, the present invention includes a dissolution step of dissolving an indium-containing material with hydrochloric acid, neutralizing the resulting solution by adding an alkali to a predetermined value within a range of 0.5 to 4 and dissolving the solution. Neutralization process that deposits and removes predetermined metal ions in the liquid as hydroxide, and hydrogen sulfide gas is blown into the resulting post-neutralization liquid to deposit metal ions that are harmful to the next electrolysis process as sulfides This is a method for recovering high-purity indium, which includes a sulfiding step for removing, and an electrowinning step for electrolytically collecting indium metal using the obtained post-sulfurized solution as an electrolytic base solution. As the indium-containing material as a raw material, ITO target scraps can be suitably used. Moreover, the solution after electrolytic collection in the electrolytic collection step can be reused as the dissolution solution used in the dissolution step. Furthermore, it is desirable to prevent the accumulation of impurities in the system by extracting a part or all of the solution after electrolytic collection.
[0005]
DETAILED DESCRIPTION OF THE INVENTION
The outline of the recovery method according to the present invention is shown in the process diagram of FIG. As shown in the figure, the indium recovery method of the present invention involves dissolving an indium-containing material with hydrochloric acid, adding an alkali to the solution, and neutralizing the solution so that the pH becomes a predetermined value within a range of 0.5 to 4. Then, the predetermined metal ions in the solution are deposited and removed as hydroxides, and then hydrogen sulfide gas is blown into them to precipitate and remove metal ions harmful to the electrolysis of the next step as sulfides. This is a method for recovering high-purity indium by electrolytically collecting indium metal using a solution as an electrolyte.
[0006]
[Crushing step]: An ITO target is preferably used as the indium-containing material as a raw material, but is not limited thereto. The raw material is crushed to a size suitable for dissolution by a crusher.
[Dissolution step]: Hydrochloric acid is used as the solution. The amount of solution is adjusted so that the indium concentration is 20 to 200 g / l, and the acid amount is suitably 1.1 to 1.5 equivalents of the theoretical value. It is desirable to heat the solution to facilitate dissolution.
[Neutralization step]: An appropriate alkali is added to a solution obtained by dissolving an indium-containing material in hydrochloric acid to neutralize the solution to a predetermined value within a range of 0.5 to 4. The pH is set to 4 or less in order to prevent precipitation of indium hydroxide, and the pH is set to 0.5 or more in order to hydrolyze impurity ions and precipitate them as hydroxides. . In this process, most of tin, which is a main impurity in the ITO target scrap, is efficiently removed.
[Sulfurization step]: After removing hydroxides such as tin deposited in the neutralization step by filtration, hydrogen sulfide gas was blown into the solution. In addition to copper and lead, which are harmful to electrolysis in the next step, a small amount of tin is precipitated and removed as sulfides.
[Electrolytic collection step]: The cleaned indium solution is sent to the electrolytic collection step, and indium is recovered as a metal by electrolytic collection under appropriate electrolysis conditions.
[Casting process]: Since the recovered indium metal contains alkali metal such as sodium which is a component of the electrolytic solution as impurities, it is heated and mixed with solid caustic soda, and these alkali metals are dissolved and removed in molten caustic soda. Separate and cast metal into mold, cool and collect high purity indium.
[Solution treatment after electrolytic collection]: The solution after electrolytic collection is repeatedly used in the dissolution process, mixed with hydrochloric acid and reused. In order to prevent accumulation of metal ions that are lower than indium, such as aluminum and iron, a part or all of the solution after electrolytic collection is withdrawn out of the system.
[0007]
【Example】
After crushing 200 g of ITO target scrap, it was dissolved in 5 mol of hydrochloric acid to obtain 2 liters of indium solution. The solution composition of this solution is shown in Table 1.
Sodium carbonate was added to the solution to neutralize it until the pH reached 1.7. The precipitated hydroxide was removed by filtration to obtain a neutralized solution. The composition of this neutralized solution is shown in Table 1.
Hydrogen sulfide gas was blown into the solution after neutralization at a rate of 50 cc / min for 2 minutes. The precipitated sulfide was removed by filtration to obtain a solution after sulfidation. The liquid composition of this post-sulfurized liquid is shown in Table 1.
[0008]
Using the cleaned post-sulfurized solution as a base solution for electrowinning, indium metal was electrowinned under electrolysis conditions of a liquid temperature of 30 ° C. and a current density of 150 A / m ² . Table 1 shows the quality of the obtained electrowinning metal.
This electrolytically collected metal was heated and mixed and dissolved together with solid caustic soda, separated by specific gravity, poured into a mold, cooled, and cast indium was recovered. The quality of the obtained cast indium was as shown in Table 1, and was high purity of 99.999% or more.
[0009]
[Table 1]

[0010]
【The invention's effect】
According to the indium recovery method of the present invention, 99.999% or more of high-purity indium can be recovered in a simpler process and at a lower cost than conventional methods. Therefore, the method of the present invention is an extremely useful method as a recycling method for ITO target scraps and the like.
[Brief description of the drawings]
FIG. 1 is a process diagram showing an indium recovery method of the present invention.

Claims (3)

The step of dissolving the ITO target waste with hydrochloric acid, and neutralizing the obtained solution by adding an alkali to a predetermined value in the range of 0.5 to 4, and tin ions in the solution A step of depositing and removing as hydroxide, a step of depositing and removing at least copper and lead ions as sulfides with hydrogen sulfide gas from the obtained post-neutralized solution, And a step of electrolytically collecting indium metal as a liquid. The step of dissolving the ITO target waste with hydrochloric acid, and neutralizing the obtained solution by adding an alkali to a predetermined value in the range of 0.5 to 4, and tin ions in the solution A step of depositing and removing as hydroxide, a step of depositing and removing at least copper and lead ions as sulfides with hydrogen sulfide gas from the obtained post-neutralized solution, A method for recovering indium, comprising: a step of electrolytically collecting indium metal as a liquid; and a step of repeating the step of dissolving the obtained liquid after electrolytic collection. The method for recovering indium according to claim 1 or 2, wherein accumulation of impurities in the system is prevented by extracting at least a part of the solution after electrolytic collection in the electrolytic collection step.

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