JP2000169991A - Recovering method of high purity indium - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method to recover high purity indium with a simple process from an indium-contg. material such as ITO target waste. SOLUTION: An indium-contg. material is dissolved in hydrochloric acid, and an alkali is added to the dissolved liquid to neutralize to obtain a specified pH range from 0.5 to 4 so as to precipitate specified metal ions as hydroxides in the dissolved liquid. Then hydrogen sulfide gas is blown into the liquid to precipitate and remove metal ions as sulfides which are harmful in the succeeding electrolysis process. Then the dissolved liquid is used as an electrolytic source soln. to recover indium metal by electrolysis. By this method, indium of >=99.999% purity can be recovered from an ITO target waste.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for recovering indium from a substance containing indium. More specifically, the present invention relates to a method for efficiently recovering high-purity indium metal from indium tin oxide (ITO) target waste. This recovery method is useful as a recycling method for ITO target waste and the like.

[0002]

2. Description of the Related Art Due to the recent rapid development of liquid crystal technology, demand for ITO used as a transparent conductive film for this liquid crystal has been remarkably growing. As a raw material for producing this ITO film, ITO
Target material is used. Conventionally, several methods of recovering indium using ITO target waste as a raw material have been proposed. For example, there is a method using a solvent extraction method (JP-A-8-91838).
The process becomes complicated due to repeated extraction and back extraction,
High cost due to use of expensive solvent. As another method, a method in which a metal indium plate is inserted into a solution in which indium is dissolved to replace and remove impurity ions in the solution and then removed, and then the indium metal is electrolytically collected using the solution as an electrolytic solution. (JP-A-10-204673). This method has a simple process, but has a limit on the impurity ion concentration that can be removed by displacement precipitation, and the purity of the obtained indium metal is at most 99.99%.

[0003]

SUMMARY OF THE INVENTION The present invention has been made to solve the above-mentioned problems in the conventional indium recovery method, and requires a simple process by a unit operation generally used in wet refining of metals. The present invention proposes a method capable of recovering high-purity indium that exceeds the conventional method.

[0004]

That is, the present invention provides a dissolving step of dissolving an indium-containing substance with hydrochloric acid, and adding an alkali to the obtained dissolving solution to adjust the pH to a predetermined value within a range of 0.5 to 4. Neutralization so that a predetermined metal ion in the solution is precipitated as hydroxide and removed, and a hydrogen sulfide gas is blown into the obtained neutralized solution to perform the next electrolysis step. This is a method for recovering high-purity indium, which includes a sulfurization step of precipitating and removing harmful metal ions as sulfides and an electrowinning step of electrowinning indium metal using the obtained post-sulfidation solution as an electrolysis source solution. As the indium-containing material serving as a raw material, ITO target waste can be suitably used. In addition, the solution after electrowinning in the electrowinning step can be reused as the lysis solution used in the lysis step. Furthermore, it is desirable to prevent the accumulation of impurities in the system by extracting a part or the whole amount of the solution after the electrolytic sampling.

[0005]

DESCRIPTION OF THE PREFERRED EMBODIMENTS 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 dissolves indium-containing substances with hydrochloric acid,
An alkali is added to the solution to neutralize the solution so that the pH becomes a predetermined value in a range of 0.5 to 4, and a predetermined metal ion in the solution is precipitated and removed as a hydroxide, and then removed. ,
This is a method for recovering high-purity indium in which hydrogen sulfide gas is blown thereinto to precipitate and remove metal ions harmful to electrolysis in the next step as sulfides, and then use this solution as an electrolytic solution to electrolytically extract indium metal.

[Crushing step] An ITO target is preferably used as an indium-containing material as a raw material, but the present invention is not limited to this. The raw material is crushed by a crusher to a size suitable for dissolution. [Dissolution step]: Hydrochloric acid is used as the dissolution solution. The amount of the dissolving solution is adjusted so that the indium concentration becomes 20 to 200 g / l, and the amount of the acid is adjusted from 1.1 to 1.5 of the theoretical value.
Double equivalents are appropriate. It is desirable to heat the lysis solution to promote lysis. [Neutralization step]: An appropriate alkali is added to a solution obtained by dissolving the indium-containing substance in hydrochloric acid to neutralize the solution to a predetermined value within a range of 0.5 to 4. The reason for setting the pH to 4 or less is to prevent precipitation of indium hydroxide, and the reason for setting the pH to 0.5 or more is to hydrolyze impurity ions and precipitate as hydroxide. .
In this step, most of tin, which is a major impurity in the ITO target waste, is efficiently removed. [Sulfurization step]: After removing the hydroxide such as tin precipitated in the neutralization step by filtration, hydrogen sulfide gas was blown into this solution. In addition to copper and lead harmful to electrolysis in the next step, a trace amount of tin is precipitated and removed as sulfide. [Electrolysis sampling step]: The cleaned indium solution is sent to an electrolysis sampling step, and indium is recovered as metal by electrolysis under appropriate electrolysis conditions. [Casting process]: Since the recovered indium metal contains an alkali metal such as sodium which is a component of the electrolytic solution as an impurity, it is heated and mixed together with solid caustic soda to dissolve and remove these alkali metals in molten caustic soda.
The metal is cast into a mold after being separated by specific gravity, cooled, and high-purity indium is recovered. [Liquid treatment after electrolytic collection]: The liquid after electrolytic collection is repeated in the dissolving step, mixed with hydrochloric acid and reused. In order to prevent accumulation of metal ions, such as aluminum and iron, which are more noble than indium, part or all of the liquid after the electrolytic extraction is extracted out of the system.

[0007]

EXAMPLE After 200 g of ITO target waste was crushed, it was dissolved in 5 mol of hydrochloric acid to obtain a 2 liter indium solution. The solution composition of this solution is shown in Table 1. Sodium carbonate was added to this solution to neutralize it until the pH reached 1.7. The precipitated hydroxide was removed by filtration to obtain a neutralized solution. Table 1 shows the composition of the solution after neutralization. Hydrogen sulfide gas was blown into the liquid after the neutralization at a rate of 50 cc / min for 2 minutes. The precipitated sulfide was removed by filtration to obtain a post-sulfidation liquid. Table 1 shows the liquid composition of the liquid after sulfurization.

Using the cleaned solution after sulfidation 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. The electrowinning metal was mixed with solid caustic soda by heating and dissolved, and the specific gravity was separated. The metal component was poured into a mold, cooled, and the cast indium was recovered. The quality of the cast indium obtained was as shown in Table 1, and was high purity of 99.999% or more.

[0009]

[Table 1]

[0010]

According to the method for recovering indium of the present invention,
It is a simpler and cheaper process than the conventional method.
% Or more of highly pure indium can be recovered. Therefore, the method of the present invention is an extremely useful method for recycling ITO target waste.

[Brief description of the drawings]

FIG. 1 is a process chart showing an indium recovery method of the present invention.

 ──────────────────────────────────────────────────続 き Continued on front page (72) Inventor Shigeru Ogasawara 1-8-2 Marunouchi, Chiyoda-ku, Tokyo Dowa Mining Co., Ltd. (72) Inventor Jun Komori 1-8-2 Marunouchi, Chiyoda-ku, Tokyo Same as above F Mining in WA Mining Co., Ltd. (Reference) 4K001 AA42 BA22 DB04 DB19 DB21 DB23 4K058 AA21 BA07 BB04 FC07 FC12 FC21 FC27

Claims (4)

[Claims] 1. A dissolving step of dissolving an indium-containing substance with hydrochloric acid, and adding an alkali to the obtained dissolving solution to adjust the pH to 0.1.
A neutralization step of neutralizing to a predetermined value in the range of 5 to 4 and precipitating and removing a predetermined metal ion in the solution as a hydroxide; High purity including a sulfurization step of blowing hydrogen gas to precipitate and remove harmful metal ions as sulfides in the next electrolysis step, and an electrowinning step of electrowinning indium metal using the obtained post-sulfidation liquid as an electrolysis source liquid How to recover indium. 2. The method for recovering high-purity indium according to claim 1, wherein the indium-containing material as a raw material is ITO target waste. 3. The method for recovering high-purity indium according to claim 1, wherein the solution after the electrowinning in the electrowinning step is reused as the lysis solution used in the lysing step. 4. The method according to claim 1, wherein at least a part of the solution after the electrowinning in the electrowinning step is extracted to prevent accumulation of impurities in the system.