JP4549501B2 - Indium recovery method - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a method for recovering indium from high-purity indium oxide-containing scrap generated during or after use of an indium-tin oxide (ITO) sputtering target.
[0002]
[Prior art]
In recent years, indium-tin oxide (ITO) sputtering targets have been widely used for transparent conductive thin films and gas sensors of liquid crystal display devices. In many cases, thin film forming means by sputtering is used on a substrate or the like. A thin film is formed.
Although the thin film forming means by this sputtering method is an excellent method, when a transparent conductive thin film is formed using a sputtering target, for example, the target is not consumed uniformly.
A part of the target that is heavily consumed is generally called an erosion part, but the sputtering operation is continued until the erosion part is consumed and the backing plate supporting the target is exposed. After that, it is replaced with a new target.
Therefore, many non-erosion portions, that is, unused target portions remain in the used sputtering target, and all of these become scrap. In addition, scrap is generated from the polishing powder and cutting powder during the production of the ITO sputtering target.
[0003]
Since a high-purity material is used for the ITO sputtering target material and the price is high, indium is generally recovered from such a scrap material.
As this indium recovery method, a method combining wet purification such as an acid dissolution method, an ion exchange method, and a solvent extraction method has been conventionally used.
For example, ITO scrap is washed and ground, dissolved in nitric acid, hydrogen sulfide is passed through the solution, and impurities such as zinc, tin, lead, copper are precipitated and removed as sulfides, and then ammonia is added to neutralize them. , A method of recovering as indium hydroxide.
However, indium hydroxide obtained by this method has poor filterability and takes a long time to operate, and there are many impurities such as Si, Al, etc., and indium hydroxide to be produced depends on its neutralization conditions and aging conditions, etc. Since the particle size and the particle size distribution fluctuate, there is a problem in that the characteristics of the ITO target cannot be stably maintained when manufacturing the ITO target thereafter.
[0004]
For this reason, the present inventor first reduced indium oxide-containing material such as ITO scrap in advance to 750-1200 ° C. using a reducing gas to form metallic indium, and then electrolytically purified the indium. A method for recovering indium was proposed (Japanese Patent Laid-Open No. 7-145432). According to this, it became possible to recover highly pure indium efficiently and stably.
However, the reduced metal is an indium-tin alloy. When indium is electrolytically purified using this indium-tin alloy as an anode, tin becomes an anode slime, suspends the bath, and there is a problem that impurities are mixed into the purified indium, so further improvement is necessary. there were.
[0005]
[Problems to be solved by the invention]
In order to solve the above-mentioned problems, the present invention is to provide a method for efficiently recovering indium from high-purity indium oxide-containing scrap generated at the time of production or after use of an ITO sputtering target.
[0006]
[Means for Solving the Problems]
The present invention
1. Dissolving ITO indium-containing scrap with hydrochloric acid to form an indium chloride solution, adding the sodium chloride aqueous solution to the indium chloride solution to remove tin contained in the scrap as tin hydroxide, 1. A method for recovering indium, which comprises replacing and recovering indium from zinc after removing tin hydroxide. 2. A method for recovering indium, characterized in that after replacing and recovering sponge indium together with solid sodium hydroxide to produce crude indium metal, the crude indium metal is further electrolytically purified to obtain high purity indium. When the ITO indium-containing scrap is melted with hydrochloric acid, the amount of hydrochloric acid is 300 to 600 L and the melting temperature is 100 to 110 ° C. with respect to 100 kg of the ITO indium-containing scrap. 3. Indium recovery method Sodium hydroxide aqueous solution is added to adjust the pH to 1.5 to 2.0, and tin contained in the scrap is removed as tin hydroxide. Collection method 5. 5. The method for recovering indium according to each of 1 to 4 above, wherein the pH of the indium chloride solution is adjusted to 1.5 to 2.5, and the solution temperature is adjusted to 5 to 50 ° C. 6. The indium chloride solution according to each of the above 1 to 4, wherein the pH of the indium chloride solution is adjusted to 1.7 to 2.0, and the liquid temperature is adjusted to 30 to 40 ° C. 7. The indium recovery method according to each of 1 to 6 above, wherein indium is replaced and recovered using a zinc plate. Using the crude indium metal as an anode, using a sulfuric acid bath, adjusting the pH to 1.8 to 2.0 and the chlorine ion concentration in the electrolytic purification solution to 20 to 30 g / L, and performing electrolytic purification, 8. The method for recovering indium according to each of items 7 to 9 9. The method for recovering indium as described in 8 above, wherein an alkali metal chloride such as hydrochloric acid or sodium chloride or potassium chloride and indium chloride are used as a chlorine ion source. 10. The indium recovery method according to 8 or 9 above, wherein the indium concentration in the electrolytic solution is adjusted to 45 to 55 g / L. The method for recovering indium according to each of 8 to 10 above, wherein the electrolysis temperature is adjusted to 25 to 50 ° C.
[0007]
DETAILED DESCRIPTION OF THE INVENTION
In the present invention, indium-containing scrap such as polishing powder of an ITO target is dissolved with hydrochloric acid. In this case, the amount of hydrochloric acid is set to 300 L to 600 L with respect to 100 kg of the ITO indium-containing scrap and melted at a temperature of 100 to 110 ° C. This melting temperature is in a boiling state. The dissolution time is about 3 to 5 hours, and is adjusted as appropriate.
The amount of hydrochloric acid is 300L to 600L. 300 L is a reaction equivalent, and adding more than 600 L is useless because the reaction is not particularly accelerated. By adjusting the amount of hydrochloric acid and dissolving at a temperature of 100 to 110 ° C., the undissolved residue can be reduced as much as possible.
Next, in order to neutralize and remove tin in the scrap as tin hydroxide, the pH of the indium chloride solution is adjusted using an aqueous sodium hydroxide solution or the like, and the pH of the indium chloride solution is set to 1.5 to 2.5. To do. In addition to the aqueous sodium hydroxide solution, potassium hydroxide can also be used.
The reason for setting the pH to 1.5 to 2.5 is that if the pH is less than 1.5, tin hydroxide is not completely formed, and if it exceeds 2.5, indium hydroxide (In (OH) _{This is because 3} ) is not preferable. Preferably, the pH of the indium chloride solution is adjusted to 1.7 to 2.0.
[0008]
Next, this tin hydroxide is removed by filtration. This is used as a raw material for substitution with zinc.
The liquid temperature of the indium chloride solution at this time is adjusted to 5 to 50 ° C. The reason for adjusting the solution temperature of the indium chloride solution to 5 to 50 ° C is that the reaction is slow when the temperature is less than 5 ° C, and the amount of water evaporation increases and the solution concentration becomes unstable when the temperature exceeds 50 ° C. This is because it is not possible to perform a proper reaction. Preferably, the liquid temperature of the indium chloride solution is adjusted to 30 to 40 ° C.
The indium chloride solution is replaced with indium using a zinc plate or the like. In this case, it is only necessary to leave it for about 16 hours.
[0009]
After replacement, solid-liquid separation, water washing, and drying are performed to obtain sponge indium. Further, the recovered sponge indium is melted together with solid sodium hydroxide to produce a crude indium metal.
Next, this indium metal is melted and cast to form an anode for electrolytic purification. Further, the indium metal anode is adjusted to pH 1.8 to 2.0 and the chlorine ion concentration to 20 to 35 g / L using a sulfuric acid bath, and electrolytically purified to recover high purity indium. As the chlorine ion source, hydrochloric acid or alkali metal chlorides such as sodium chloride and potassium chloride and indium chloride can be used.
In the electrolytic purification of indium, chlorine ions are added to the electrolytic purification solution to prevent the formation of dendritic electrodeposits (dendrites), and as a result, short-circuiting between electrodes is suppressed, and indium is recovered by electrolytic purification. This is because it is possible to effectively prevent a decrease in current efficiency.
Further, it is desirable to adjust the electrolysis temperature to 25 to 50 ° C. and to adjust the indium concentration in the electrolytic solution to 45 to 55 g / L.
As described above, the electrolysis temperature is adjusted to 25 to 50 ° C., and the indium concentration in the electrolytic solution is adjusted to 45 to 55 g / L. This is because it is not preferable. Moreover, even if it exceeds 55 g / L, there is no particular problem in electrolysis, but there is a problem that the residual amount in the system increases, so it is desirable that the amount be 55 g / L or less.
[0010]
No special electrolysis device is required. For example, electrolysis may be performed using indium to be purified as an anode and a titanium plate or the like as a cathode base plate. Among the impurities in the anode, those more precious than indium, such as tin, precipitate as slime, and those lower than indium dissolve in the electrolyte and do not deposit on the cathode.
In this case, it is desirable to provide a diaphragm between the anode and the cathode in order to avoid the incorporation of slime into the precipitate.
A surfactant such as glue, gelatin and PEG can be added to the electrolytic solution to further reduce the amount of dendritic precipitates.
The pH of the electrolytic solution is preferably adjusted to 1.0 to 2.0. A pH of less than 1.0 is not preferable because hydrogen generation increases and current efficiency decreases. On the other hand, if the pH exceeds 2.0, indium forms a hydroxide and precipitates, which is not preferable. A more preferable range is PH1.5 to 1.8.
[0011]
Current density is desirably adjusted to 0.1~2.0A / dm ^2. When the current density is less than 0.1 A / dm ² , the production efficiency is lowered. On the other hand, when the current density exceeds 2.0 A / dm ² , hydrogen gas generation increases and electrodeposition is not preferable.
Moreover, it is desirable to perform electrolysis by adjusting the electrolysis temperature to 10 to 75 ° C. If the electrolysis temperature is less than 10 ° C, the current efficiency is undesirably lowered. Conversely, when the electrolysis temperature exceeds 75 ° C., the evaporation of the electrolyte increases, and the concentration of indium in the electrolyte varies, which is not preferable. A more preferable electrolysis temperature is 25 to 50 ° C.
With the above electrolysis conditions, dendritic precipitation that causes a short circuit can be prevented, thereby preventing a decrease in current efficiency, and indium can be efficiently recovered by electrolytic purification.
[0012]
【Example】
Next, examples will be described. In addition, a present Example is for showing an example of invention, This invention is not restrict | limited to these Examples. That is, other aspects and modifications included in the technical idea of the present invention are included.
As an ITO indium-containing scrap material, 2 kg of indium oxide-tin oxide (ITO scrap) was used. In this scrap, In was 73.6 wt% and Sn was 8.6 wt%. To this scrap material, 10 liters of concentrated hydrochloric acid was added and heated at 110 ° C. for 4 hours. The liquid was in a boiling state.
After dissolution, 3.4 liters of 6.5N sodium hydroxide was added to the solution that was about 6 liters, and neutralized to pH 2.0 to produce tin hydroxide.
[0013]
Next, this was filtered, the residue (tin hydroxide) was scrapped, and about 10 liters of filtrate was obtained. To this, 20 liters of water was added to adjust the reducing solution to about 30 liters.
The In concentration at this time was 48.6 g / L.
11 zinc plates of 12 cm × 15 cm were immersed in this reducing solution and left for 16 hours.
The area of the zinc plate at this time was 3960 cm ² .
Thereafter, solid-liquid separation was performed. The waste liquid at this time contained Zn 46.2 g / L and In 0.2 g / L. This was washed with water and dried. Zn quality in In was 460 ppm. This was melted and cast to obtain 1421 g of an electrolytic purification anode.
Next, electrolytic purification was performed in a sulfuric acid bath. The electrolysis conditions are as follows.
pH 1.8-2.0
Chlorine 20-30g / L
In concentration 45 to 55 g / L
Temperature 40 ° C
Thereby, the tin quality of the purified indium obtained was <10 ppm (weight). From the above, it was possible to remove tin, which occupies most of the impurities in the indium oxide-tin oxide (ITO) scrap, and it was possible to recover high purity indium.
[0014]
【The invention's effect】
INDUSTRIAL APPLICATION This invention has the outstanding effect that an indium can be efficiently collect | recovered from the high purity indium oxide containing scrap generated at the time of manufacture of an ITO sputtering target or after use.
[Brief description of the drawings]
FIG. 1 is a process chart of indium recovery.

Claims (10)

  Dissolving ITO indium-containing scrap with hydrochloric acid to form an indium chloride solution, adding sodium hydroxide aqueous solution to the indium chloride solution to remove tin contained in the scrap as tin hydroxide, After the removal, the step of substituting and recovering indium from zinc, recovering the replacement indium sponge together with solid sodium hydroxide to produce crude indium metal, and then electrolytically purifying the crude indium metal to obtain high purity A method for recovering indium, comprising obtaining indium.   2. The indium according to claim 1, wherein when the ITO indium-containing scrap is melted with hydrochloric acid, the amount of hydrochloric acid is 300 to 600 L and the melting temperature is 100 to 110 ° C. with respect to 100 kg of the ITO indium-containing scrap. Recovery method.   The recovery of indium according to claim 1 or 2, wherein an aqueous sodium hydroxide solution is added to adjust the pH to 1.5 to 2.5, and tin contained in the scrap is removed as tin hydroxide. Method. The method for recovering indium according to any one of claims 1 to 3, wherein the pH of the indium chloride solution is adjusted to 1.5 to 2.5 and the liquid temperature is adjusted to 5 to 50 ° C. The method for recovering indium according to any one of claims 1 to 3, wherein the pH of the indium chloride solution is adjusted to 1.7 to 2.0, and the liquid temperature is adjusted to 30 to 40 ° C. The indium recovery method according to any one of claims 1 to 5, wherein indium is replaced and recovered using a zinc plate. The crude indium metal is used as an anode, and using a sulfuric acid bath, the pH is adjusted to 1.0 to 2.0, and the chlorine ion concentration in the electrolytic purification solution is adjusted to 20 to 35 g / L, and the electrolytic purification is performed. The method for recovering indium according to any one of -6.   8. The method for recovering indium according to claim 7, wherein alkali metal chlorides such as hydrochloric acid or sodium chloride and potassium chloride and indium chloride are used as a chlorine ion source.   The method for recovering indium according to claim 7 or 8, wherein an indium concentration in the electrolytic solution is adjusted to 45 to 55 g / L. The method for recovering indium according to any one of claims 7 to 9, wherein the electrolysis temperature is adjusted to 25 to 50 ° C.

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