JP2889890B2 - Production method of indium oxide - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for producing indium oxide, and more particularly to a method for producing a high-purity inorganic indium oxide solution from an indium-containing material, for example, a scrap material of indium tin oxide (hereinafter referred to as ITO). The present invention relates to a method for producing high-purity indium oxide from a solution in a high yield.

[0002]

2. Description of the Related Art Conventionally, IT used for a transparent conductive film has been used.
O is formed by a sputtering method or a vapor deposition method, and an ITO sintered body is widely used as a target material used at this time. The usage rate of these ITO sintered compact targets is as low as about 30%, and most of them are collected as scrap.

[0003] The recovered ITO scrap is contaminated by contamination of impurities during production of the target, adhesion of brazing material for bonding to the backing plate, adhesion of impurities during film formation, and contamination of impurities during scrap grinding. When the impurities are used as a transparent conductive film, the scraps cannot be recycled as ITO as they are because they impair light transmittance and conductivity.

On the other hand, in the production of an ITO sintered body, indium metal is generally dissolved with an inorganic acid, and an alkali agent is added to the obtained indium solution to generate indium hydroxide, which is roasted and oxidized. Indium oxide or the indium solution directly roasted to form indium oxide is mixed with a predetermined amount of SnO ₂ powder to obtain ITO raw material powder.

There is also a method in which a predetermined amount of a tin solution such as SnCl ₂ is added to an indium solution and coprecipitated, and the coprecipitate is roasted to obtain ITO raw material powder. The ITO raw material powder thus obtained is molded and fired to obtain ITO
A sintered body is manufactured.

[0006] Metal indium is usually recovered as a by-product of zinc smelting and is metallized by recovering indium, which is usually contained in a trace amount in zinc ore, by electrolysis or the like. Dependent on the production, and its output is naturally limited.

[0007] Against this background, the recovery of high-purity indium from ITO scrap in high yield is important from the viewpoint of effective use of scarce resources.

Various methods have been proposed as conventional methods for recovering and refining ITO scrap. In general, pretreatment, electrolytic refining to produce metal indium, and various treatments such as dissolution in the ITO production process are performed. After that, the raw material powder is used as an ITO raw material powder and then reused.

The purification method is roughly classified into a wet method and a dry method. (1) In the wet method, a pretreatment utilizing an oxidation-reduction reaction (for example, JP-A-55-158125 and JP-A-55-158125) 1955-
158126) and electrolytically collecting the recovered indium. (2) On the other hand, as a dry method, a method has been proposed in which a chlorinating agent is added to an indium-containing substance, and heat treatment is performed to generate indium chloride and then volatilize and recover.

However, the above-described conventional techniques have the following problems. (1) Wet pretreatment-electrolysis sampling method In this method, a large number of filtration steps are required in the pretreatment step, and complete separation from other metals is very difficult at this time. In this case, the power consumption is large and the process is complicated, resulting in high running costs. Further, when recovered as metal indium by this method, it is necessary to further dissolve it in an inorganic acid when producing ITO, which has a drawback that the process becomes extremely complicated.

(2) Dry method In the case of the chloride recovery method, chlorides of other elements such as arsenic and phosphorus volatilize together with indium, so that separation accuracy is extremely poor.

[0012]

SUMMARY OF THE INVENTION The present invention solves the conventional problems and produces a high-purity inorganic indium solution from an indium-containing material such as ITO scrap material.
The present invention proposes a method for producing high-purity indium oxide from the solution at high yield and at low cost.

[0013]

The inventors of the present invention leached indium-containing materials such as ITO scrap with nitric acid and precipitated and separated tin as insoluble stannic acid by an oxidation reaction.
Impurities are removed from a high-concentration indium solution containing impurities by performing solvent extraction alone or in combination in two stages using an organic solvent such as an alkyl phosphate ester type and a carboxylic acid type as an extractant, thereby obtaining a high-purity inorganic acid. With the knowledge that an indium solution can be obtained, the present invention has been accomplished.

That is, the first invention comprises a first step of leaching an indium-containing substance with nitric acid to obtain an indium nitrate solution;
A second step of extracting the indium ion from the solution obtained in the step with an organic solvent, back-extracting the obtained extract to obtain an indium solution, and hydrolyzing the solution obtained in the second step. A third step of roasting the indium hydroxide to obtain indium oxide, the method comprising the steps of:

The second invention comprises a first step of leaching the indium-containing substance with nitric acid to obtain an indium nitrate solution, and solvent-extracting indium ions from the solution obtained in the first step with an alkyl phosphate ester-based extractant; A second step of back-extracting the obtained extract with an inorganic acid to obtain an indium solution, and solvent-extracting indium ions from the solution obtained in the second step with a carboxylic acid-based extractant; A third step of back-extracting with an inorganic acid to obtain an indium solution, and a fourth step of reacting the solution obtained in the third step with an alkali and roasting the obtained indium hydroxide to obtain indium oxide. A method for producing indium oxide, comprising:

According to a third aspect of the present invention, there is provided a first step in which an indium-containing substance is leached with nitric acid to obtain an indium nitrate solution, and indium ions are solvent-extracted from the solution obtained in the first step with a carboxylic acid-based extractant. A second step of back-extracting the extracted liquid with an inorganic acid to obtain an indium solution, and solvent-extracting indium ions from the solution obtained in the second step with an alkyl phosphate ester-based extractant. A third step of back-extracting with an inorganic acid to obtain an indium solution, and a fourth step of reacting the solution obtained in the third step with an alkali and roasting the obtained indium hydroxide to obtain indium hydride. And a method for producing indium oxide.

In the above invention, the indium-containing substance is indium tin oxide, the alkyl phosphate ester-based extractant is dialkyl phosphate, and the inorganic acid is hydrochloric acid,
Preferably, it is one selected from sulfuric acid and nitric acid.

According to the present invention, the indium-containing material, for example, ITO scrap is combined with the precipitation separation method and the solvent extraction method, and the separation conditions are set to predetermined conditions. Can be produced at a high yield, and a high-purity indium oxide powder as an ITO raw material powder can be produced from the solution at a low cost and a high yield.

Next, the present invention will be described in detail.・ IT such as sputtering target used for film formation
A first step of producing an insoluble stannic acid by leaching O scrap material with nitric acid, separating tin and obtaining an indium nitrate solution;

The indium nitrate solution containing metal impurities obtained in the first step is subjected to solvent extraction of indium ions with an organic solvent containing an alkyl phosphate, preferably a dialkyl phosphate, to separate metal impurity ions in the residual liquid. A second step of back-extracting indium ions in the organic solvent with an inorganic acid such as hydrochloric acid or sulfuric acid to obtain an inorganic acid indium solution,

Indium ions are solvent-extracted from the solution obtained in the second step using a carboxylic acid, preferably a tertiary carboxylic acid as an extracting agent, and metal impurity ions are separated from the remaining solution. A third step of back-extracting indium ions in an organic solvent using at least one inorganic acid as a back-extracting agent to obtain a high-purity and high-concentration inorganic acid indium solution;

An alkali agent is added to the high-purity and high-concentration indium solution obtained in the third step to generate indium hydroxide, and the obtained indium hydroxide is roasted to obtain high-purity indium oxide. The second step is to obtain high-purity indium oxide from ITO scrap at high yield and low cost.

A treatment method in which the second step and the third step of the second invention are reversed is a third invention. The first to third invention methods are applicable not only to ITO scrap but also to other indium-containing substances. Needless to say, this is sufficiently applicable.

The ITO scrap referred to in the present invention is a sintered body containing, for example, 0 to 30 wt% of tin in terms of SnO ₂ ,
A target material used for forming a film as an ITO target and removed from a backing plate. This scrap is made of brazing material, backing plate,
Contains metal impurities from the sintered body manufacturing process and the film forming process.

Table 1 shows an example of the component analysis value of ITO scrap.

[0026]

[Table 1]

It should be noted that the method of the present invention can be applied not only to scraps used for film formation as scrap but also to compacts, powders, etc. The present invention is not limited to ITO scrap alone, but can be applied to other indium-containing materials.

Hereinafter, the present invention will be described in more detail in the case of ITO scrap as a typical example of the indium-containing material.

First, the first step of nitric acid leaching of ITO scrap and the step of separating tin will be described. The ITO scrap is pulverized and heated and leached with stirring in a nitric acid solution in order to accelerate the dissolution rate. At this time, the ITO scrap particle size is preferably 1 mm or less, the nitric acid concentration is 40% or more,
The heating temperature is preferably 90 ° C. or higher.

In addition, the leaching time and the amount of nitric acid are appropriately adjusted depending on the amount of the ITO scrap, the indium content, the tin content, and the like. However, the ITO scrap is sufficiently leached and dissolved to completely precipitate tin as stannic acid. Set conditions.

The thus obtained solution is subjected to operations such as precipitation separation and filtration separation to obtain an indium nitrate solution (containing a trace amount of metal impurities) from which the tin component has been almost completely removed. The concentration of indium in this solution can be set as appropriate, but is adjusted so as to balance with the amount of charge and withdrawal in the solvent extraction step as the next step.

Next, the solvent extraction and purification step as the second and third steps will be described. The indium solution obtained in the first step is a nitric acid acidic solution, and the amount of indium contained therein is naturally higher than that of a solution obtained by zinc refining or the like.

In consideration of these facts, the present inventors have conducted various studies on an extractant for selectively extracting high-concentration indium in a nitric acid system. Was found to satisfy the condition.

The alkyl phosphate is represented by the general formula: Is a dialkyl phosphate ester represented by

The carboxylic acid has the general formula Is a tertiary carboxylic acid represented by Here, R is an alkyl group represented by CnH _{2n + 1} .

When these extractants come into contact with an indium solution containing metal impurities, cations are extracted by a cation exchange reaction. The extraction rate of each cation is set p
It has a specific extraction rate depending on H, and a high-concentration indium solution is finally purified by a known solvent extraction method utilizing this characteristic.

As examples of the respective pH-extraction ratio curves, FIG. 1 shows a pH-extraction ratio curve for a dialkyl phosphate ester system, and FIG. 2 shows a pH-extraction ratio curve for a tertiary carboxylic acid system. . As can be seen from these figures, the pH of the aqueous solution
Is in the range of about 0.3 to 4.0, indium ions are extracted by these extractants.

The actual solvent extraction step is carried out by a known continuous multi-stage contact method, a continuous batch method, or a counter-current type multi-stage extraction method. For example, by performing continuously using an apparatus such as a mixer settler, indium is removed. It is selectively purified and extracted.

By contacting the solvent from which only indium was extracted at a high concentration with an inorganic acid as a back-extracting agent, the indium in the solvent was back-extracted into a water-retentate to obtain a high-purity and high-concentration solution. The resulting inorganic acid indium solution is obtained.

Here, a diluent or a phase separation accelerator may be added to the extractant, and the volume ratio (O / A ratio) of the extractant to the aqueous metal salt solution, the contact method, the number of extraction stages, etc. ,
Based on the indium concentration in the indium solution, the amount of impurity metal contained, and the like, conditions are set so that indium ions are extracted at a high concentration in the extraction solvent and are separated from the impurity metal.

The inorganic acid dissolved as a back-extracting agent is preferably hydrochloric acid or sulfuric acid in the alkyl phosphate ester-based extractant of the second step, and hydrochloric acid or sulfuric acid in the case of the carboxylic acid-based extractant of the third step. Sulfuric acid or nitric acid is preferred.

The concentration of the inorganic acid at this time may be adjusted so as to be equivalent to the indium ion to be back-extracted. Conversely, by changing the concentration, an inorganic acid solution of indium having an arbitrary concentration can be obtained.

The reason that the purification step using an alkyl phosphate ester-based extractant and the purification step using a carboxylic acid-based extractant are performed in two stages is that the extraction ability of each metal impurity is different, and on the other hand, it is difficult to separate indium from indium. This is because metal impurities that are difficult to perform are complemented on the other hand.

Therefore, if the contained metal impurities can be purified by one extraction system, either one of the extraction steps can be omitted. In addition, the order of the extraction step using the alkyl phosphate ester-based extractant and the extraction step using the carboxylic acid-based extractant is as follows: the extraction process with the carboxylic acid-based extractant in the second step, and the alkyl phosphate ester-based extractant in the third step. May be performed. However, as described above, the inorganic acid that can be used for back extraction after the extraction treatment with the alkyl phosphate ester-based extractant is either hydrochloric acid or sulfuric acid. Few.

Next, in the fourth step of producing indium oxide powder, an alkali solution is added to the high-purity inorganic indium solution obtained through the second to third steps to produce indium hydroxide. After solid-liquid separation, high-purity indium oxide is produced by roasting at a temperature at which indium hydroxide decomposes.

As the alkaline agent used in the fourth step,
Normal alkali agents such as NH ₄ OH and NaOH may be used, but those having good separability of generated indium hydroxide are preferable, and those having less impurity residue in the finally produced indium oxide are preferable.

As described above, an alkali agent which has good separability from indium hydroxide or volatilizes during roasting and does not remain in indium oxide is suitable.

Thus, the indium oxide powder obtained by the method of the present invention obtained in a relatively simple process has a purity equivalent to or higher than that produced from a conventional high-purity indium metal.

Also, an appropriate amount of a tin solution is added to the high-purity indium inorganic acid solution to cause coprecipitation, and solid-liquid separation is followed by roasting to produce the desired ITO powder.

As described above, according to the present invention, the steps are much simpler than those of the conventional method, so that the cost can be reduced. Since a known continuous production apparatus can be applied to the extraction step, an indium solution can be produced industrially at low cost. Next, examples of the present invention will be described.

[0051]

【Example】

Example 1 Sample No. 1 in Table 1 was used. After 200 g of ITO scrap having the component composition shown in 1 was collected and pulverized, it was charged into a test reactor together with about 500 ml of industrial nitric acid, heated and leached with stirring at 95 ° C. for 24 hours, then filtered and solid-liquid separated.
(First step)

[0052]

[Table 1]

The composition of the obtained solution is shown in Table 2 1
And no tin ions were detected.

[0054]

[Table 2]

Next, the indium nitrate solution was brought into contact with a solvent containing 60% of a dialkyl phosphate extractant at an O / A ratio of 3/1, and then the extraction solvent layer was separated to substantially remove indium ions. Back-extract with an equivalent amount of hydrochloric acid. (2nd process)

This indium chloride solution was contacted with a solvent containing 60% of a tertiary carboxylic acid extractant at an O / A ratio of 3/1, and the extraction step of phase separation was repeated 10 times to selectively extract indium. The solvent layer was separated, nitric acid was added in an amount approximately equivalent to indium ion, and back-extraction was performed.
A high-purity indium nitrate solution having the composition shown in No. 1 was obtained. (3rd step)

[0057]

[Table 3]

Aqueous ammonia (NH ₄ OH) was added to this solution while stirring until pH 8 was reached, and indium hydroxide was formed and solid-liquid separated. The obtained indium hydroxide was roasted at about 800 ° C. Thus, indium oxide was obtained. (4th process)

The purity of the obtained indium oxide was 99.9.
At 9% or more, the impurity metal amount was 10 ppm or less.

Example 2 The sample Nos. 200 g of ITO scrap having the composition shown in Fig. 2 was collected and pulverized, and then charged into a test reactor together with about 500 ml of industrial nitric acid.
After heating and leaching while stirring for 4 hours, the mixture was filtered and solid-liquid separated. (First step)

The composition of the obtained solution is as follows:
o. As shown in FIG. 2, no tin ion was detected.

The indium nitrate solution and a solvent containing 60% of a dialkyl phosphate extractant were mixed at an O / A ratio of 3 /
After repeating the extraction operation of contacting with 1 and separating the phases three times,
The extraction solvent layer was separated and back-extracted with hydrochloric acid in an amount approximately equivalent to indium ion. (2nd process)

The step of contacting the obtained indium chloride solution with a solvent containing 60% of a tertiary carboxylic acid extractant at an O / A ratio of 3/1 to perform phase separation was repeated seven times, and then indium was selectively extracted. The separated solvent layer was separated and back-extracted with hydrochloric acid in an amount approximately equivalent to indium ion. A high-purity indium chloride solution having the composition shown in FIG. 2 was obtained. (3rd step)

Aqueous ammonia (NH ₄ OH) was added to this solution with stirring until pH 8 was reached, and indium hydroxide was formed. After solid-liquid separation, the obtained indium hydroxide was roasted at 1000 ° C. Indium oxide was obtained. (4th process)

The purity of the obtained indium oxide was 99.9.
At 9% or more, the impurity metal amount was 10 ppm or less.

[0066]

According to the present invention, indium-containing materials such as IT
It is possible to produce a high-purity and high-concentration indium oxide solution with a relatively simple process from O scrap material or the like, and to produce high-purity indium oxide from this solution at a high yield and at low cost.

[Brief description of the drawings]

FIG. 1. p with dialkyl phosphate ester solvent extractant
It is an H-extraction rate curve diagram.

FIG. 2 is a diagram showing a pH-extraction rate curve with a tertiary carboxylic acid-based solvent extractant.

(72) Inventor Koichiro Ejima 1-8-2 Marunouchi, Chiyoda-ku, Tokyo Dowa Mining Co., Ltd. (72) Inventor Ichiro Nishimoto 1-8-2 Marunouchi, Chiyoda-ku, Tokyo Dowa Mining Co., Ltd. (56) References JP-A-63-60242 (JP, A) JP-A-3-199122 (JP, A) JP-A-58-135128 (JP, A) JP-A-58-60619 (JP, A) (58) Fields investigated (Int. Cl. ⁶ , DB name) C01G 1/00-57/00

Claims (6)

(57) [Claims] 1. A first step in which an indium-containing substance is leached with nitric acid to obtain an indium nitrate solution, and the solution obtained in the first step is extracted with an organic solvent to extract indium ions, and the obtained extract is back-extracted. A second step of obtaining an indium solution by hydrolyzing the solution obtained in the second step, and roasting the obtained indium hydroxide to obtain indium oxide. A method for producing indium oxide. 2. A first step in which an indium-containing substance is leached with nitric acid to obtain an indium nitrate solution, and indium ions are extracted from the solution obtained in the first step by solvent extraction using an alkyl phosphate ester-based extractant. A second step of back-extracting the extract with an inorganic acid to obtain an indium solution, and solvent-extracting indium ions from the solution obtained in the second step with a carboxylic acid-based extractant, and extracting the resulting extract with an inorganic acid. A third step of back-extracting to obtain an indium solution, and a fourth step of reacting the solution obtained in the third step with an alkali and roasting the obtained indium hydroxide to obtain indium oxide. A method for producing indium oxide, comprising: 3. A first step in which an indium-containing substance is leached with nitric acid to obtain an indium nitrate solution, and indium ions are solvent-extracted from the solution obtained in the first step with a carboxylic acid-based extractant, and the resulting extract is obtained. A second step of back-extracting the indium solution with an inorganic acid to obtain an indium solution, and solvent-extracting indium ions from the solution obtained in the second step with an alkyl phosphate ester-based extractant, and extracting the resulting extract with an inorganic acid. A third step of back-extracting to obtain an indium solution, and a fourth step of reacting the solution obtained in the third step with an alkali and roasting the obtained indium hydroxide to obtain indium oxide. A method for producing indium oxide, comprising: 4. The method for producing indium oxide according to claim 1, wherein said indium-containing substance is indium tin oxide. 5. The indium oxide according to claim 2, wherein the alkyl phosphate extractant is a dialkyl phosphate ester, and the carboxylic acid extractant is a tertiary carboxylic acid. Manufacturing method. 6. The method for producing indium oxide according to claim 2, wherein the inorganic acid is at least one selected from hydrochloric acid, sulfuric acid, and nitric acid.