JP2001011549A - METHOD FOR LEACHING In FROM In-CONTAINING OXIDE - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method capable of extracting In from In-contg. scrap contg. In in the state of In oxide under mild acid treating conditions. SOLUTION: In-contg. scrap is subjected to mechanochemical treatment, e.g. of being subjected to dry pulverizing for a prescribed time by a planetary mill in the coexistence of ceramic powder of alumina (Al2O3), or the like, the crystal structure of In oxide (In2O3) is made amorphous, and after that, it is leached into a sulfuric acid of about 1 to 5N, by which In can be leached at >=80% high leaching ratio from the In-contg. scrap even at room temp. In this way, compared to the case of the conventional methods acid or alkali of high temp. and high concn., the intrusion of impurities from a melting tank is made small, there is no need of particularly increasing the acid resistance of the material of the melting tank, and the operating environment is moreover improved. The separability between In and Al in the leaching is also better.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a method for leaching In from an In-containing oxide, and more particularly to a method for leaching In from an In-containing oxide.
IT generated at the time of cleaning of a sputtering machine which is industrially implemented to form a TO transparent conductive film
The present invention relates to a method for leaching In from an In-containing oxide such as O scrap.

[0002]

2. Description of the Related Art Conventionally, as a method for leaching In from a scrap containing In in the form of In oxide, it is common to dissolve it with a high-temperature, high-concentration alkali or acid.

[0003]

However, in the leaching method under such conditions, the recovery rate of In is low and impurities are mixed in from the dissolution tank. An extra step of separating contaminant components is required. On the other hand, in order to avoid such contamination, there is a problem that expensive equipment is required due to the need to increase the acid resistance of the material of the tank, and furthermore, there is a problem that the working environment is not preferable.

The present invention provides a method for leaching and extracting In under relatively mild conditions from indium-containing oxides such as In-containing scraps in order to solve the problems of the conventional methods as described above. It is intended for.

[0005]

Means for Solving the Problems In order to achieve the above object, as a result of intensive studies, the present inventor has performed a mechanochemical treatment on an indium-containing oxide such as an In-containing scrap for a predetermined time to obtain an In-containing oxide (In ₂ oxide). to destroy the crystal structure of O _3, etc.) instead of the leach easily form found that can effectively leach in by leaching it to low concentration acid. Furthermore, in the mechanochemical treatment, alumina (A
The present inventors have found that the coexistence of a ceramic powder having a high hardness, such as l ₂ O ₃ ), improves the leaching efficiency of In.

That is, according to the present invention, firstly, an In-containing oxide is subjected to a mechanochemical treatment in the presence of a ceramic powder to change the crystal structure of the In-containing oxide, and then at room temperature. A method for leaching In from an In-containing oxide, characterized by leaching in a low-concentration acid; secondly, from the In-containing oxide according to the first aspect, wherein the mechanochemical treatment is a dry pulverization treatment. Third, the low-concentration acid is sulfuric acid having a concentration of 5 N or less, wherein the low-concentration acid is sulfuric acid having a concentration of 5 N or less; 5. The method for leaching In from an In-containing oxide according to any one of the first to third aspects, wherein the powder is alumina powder, and the low-concentration acid is sulfuric acid at room temperature of 1 N or less; ,
The crystal structure of the In-containing oxide after the mechanochemical treatment is at least partially amorphous, and the In-containing oxide according to any of the first to fourth aspects is characterized in that:
Sixth, the method for leaching In from an In-containing oxide according to any one of the first to fifth aspects, wherein the In-containing oxide is scrap.

[0007]

DETAILED DESCRIPTION OF THE INVENTION According to the knowledge of the present inventors, ITO
In in In-containing oxides such as In-containing scraps such as scraps, In is contained in a crystalline structure of a Sn-doped In oxide (for example, composed of In ₂ O ₃ and a small amount of In ₂ SnO ₅ ). In the presence of ceramic powder having high hardness such as alumina, zirconia, etc., the crystal structure of the In oxide is destroyed by subjecting it to a dry grinding treatment with a high energy grinding machine such as a ball mill including a planetary mill, in the presence of a ceramic powder having a high hardness. Can be leached at a high rate by using a low-concentration acid such as sulfuric acid of 5N or less. At the time of this mechanochemical treatment, the coexisting ceramic powder has an effect of effectively destroying the crystal structure of the In oxide, promoting amorphousness, and enhancing the acid leaching effect. In this case, In can be easily and sufficiently leached with low-concentration sulfuric acid of 1N or less.

From the above viewpoint, the particle size of the coexisting ceramic powder is preferably from 5 to 500 μm, particularly preferably from 10 to 50 μm. The coexisting ceramic powder may be mixed in the indium-containing oxide at the time when scrap can be formed, or may be added to and mixed with the scrap. In addition, the dry pulverization is preferably performed by a ball mill. Furthermore, the temperature of the leaching solution during acid leaching is preferably room temperature,
This normal temperature means non-heating, and means 10 to 40 ° C. More preferable liquid temperature is about 20 to 30 ° C. around room temperature.
It is. As the acid used for leaching, mineral products such as sulfuric acid, nitric acid, and hydrochloric acid can be used, but sulfuric acid is particularly preferable.

[0009] Mechanochemical generally refers to mechanical energy added to a solid material, such as shear, compression, impact,
The surface of a solid material undergoes physicochemical changes due to crushing, bending, stretching, etc., causing a chemical change to the gas or liquid material existing around it, or directly inducing a chemical change between them and the surface of the solid material. It is known as a phenomenon that affects the chemical state by promoting or promoting.
The In leaching solution thus obtained is further subjected to a conventionally known extraction means such as a solvent extraction method, an ion exchange method, and an electrolysis method, so that In can be easily recovered at a high rate.

[0010]

EXAMPLE An ITO scrap sample containing mechanochemically treated alumina (Al ₂ O ₃ );
In ₂ O ₃ sample by reagent, In ₂ O ₃ and Al by reagent
_The mechanochemical treatment effect was investigated for the mixed sample of ₂ O ₃ . Table 1 shows the chemical composition of the sample ITO scrap.

[0011]

[Table 1]

As shown in Table 1, ITO scrap contains mainly oxides such as In ₂ O _{3 and} alumina (Al ₂ O ₃ ) by sandblasting powder used at the time of cleaning of a sputtering apparatus. And its average diameter was about 15 μm. In addition, an In ₂ O ₃ sample (purity: 99.9%, average diameter: about 15 μm) was used as a reagent powder sample.
m) and an Al ₂ O ₃ sample (purity: 99.9%, average diameter: about 32 μm) were prepared, and a weight ratio (In ₂ O ₃ ) of the In ₂ O ₃ alone sample and both reagents were substantially the same as the ITO scrap composition.
An O ₃ sample: an Al ₂ O ₃ sample = 1: 9) was prepared as a mixed model sample.

The test was performed according to the flowchart shown in FIG. 1A shows an ITO scrap sample, and FIG. 1B shows a model mixed sample (In ₂ O ₃ + Al ₂ O ₃ ), all of which were tested by the same procedure. Dry grinding using a planetary mill (Fritch, Pulverisette-7) was used for mechanochemical treatment of the ITO scrap sample and the model mixed sample. In this planetary mill, two mill pots (made of zirconia, capacity: 50 ml) are arranged at a position with a radius of rotation of 70 mm on a disk that rotates horizontally clockwise,
The mill pot itself can rotate at the same rotation speed in the counterclockwise direction. In one mill pot, 4 g of a powder sample and a zirconia ball (diameter ×
Number: 15mm x 7) and mill rotation speed 700r
The mechanochemical treatment was performed at a constant pm for a maximum of 120 minutes. All the samples, including the untreated samples, which had been subjected to the mechanochemical treatment for a predetermined time were collected from the mill pot, and their constituent phases and crystallinity were evaluated by a powder X-ray diffraction method.

The mechanochemical treatment time (pulverization time) of the ITO scrap sample and the average particle size of the obtained particles (50% by a laser diffraction / scattering type particle size distribution analyzer)
The relationship with the average particle size D50) is shown in FIG. The average particle size decreases to about 1 μm in the first 15 minutes of treatment,
Even if the treatment time was further extended, no decrease in the particle size was observed, and the particle size became almost constant, and it is assumed that the particle size of the sample reached the pulverization limit value. As is apparent from this figure, it is preferable to set the processing time so that the particle size becomes 1 μm or less by the mechanochemical processing.

FIGS. 3 and 4 show the X-ray diffraction patterns of the sample for each mechanochemical treatment time. FIG. 3 shows an X-ray diffraction pattern of the ITO scrap sample, and FIG. 4 shows an X-ray diffraction pattern of the In ₂ O ₃ single powder sample. First, from FIG. 3, the change in the diffraction peak intensity of alumina (Al ₂ O ₃ ) constituting the ITO scrap is small with the extension of the processing time.
It can be seen that the diffraction peak intensities of In ₂ O _{3 and} In ₂ SnO ₅ gradually decreased, and almost disappeared by the treatment for 60 minutes. This is because of the above-mentioned I by the mechanochemical treatment.
This indicates that the n-oxide crystal was destroyed and became amorphous.

On the other hand, FIG._TwoO_ThreeIn case of single powder
Is In even after mechanochemical treatment. _TwoO_ThreeDiffraction pattern
No remarkable change was observed, and the crystallinity was observed even after treatment for 60 minutes.
It can be seen that is maintained. 3 and 4 above
The difference is mainly in the presence or absence of alumina in the test sample.
3 clearly shows the effect of breaking the crystal of the In oxide in FIG.
This is probably due to the coexistence of alumina. To confirm this
First, a mechanochemical treatment was performed on the model mixed sample.
As a result, the result shown in FIG. 5 was obtained. That is, processing time
Along with the extension of alumina (Al_TwoO_Three) Diffraction peak intensity
Changes were small, but In_TwoO_ThreeThe diffraction peak intensity of
It shows a tendency to decrease, and agrees well with the result of FIG.
It turned out to be perfect. With this, ITO scraper
Aluminum contained in the mechanochemical treatment process
The powder effectively destroys the crystal structure of the In oxide,
It has been confirmed that it plays an important role in shaping.

Acid leaching treatment From the mechanochemically-treated powder sample obtained in the above-mentioned treatment, 0.5 g of each sample was taken, and sulfuric acid of various concentrations (50 m
l) and leaching test was performed at room temperature. In this leaching test, after stirring for 1 hour with a magnetic stirrer,
The suspension was separated by filtration through filter paper (No. 5C), and the concentrations of dissolved elements, particularly In, Sn and Al, in the filtrate were analyzed by ICP.

For the ITO scrap sample (untreated, 0 minutes) and the sample subjected to the mechanochemical treatment for 30 minutes and 60 minutes, the leaching rate of In with respect to the leaching solution with different concentrations of sulfuric acid was investigated. 6 is shown. From FIG. 6, it can be seen that the In leaching rate rapidly increases up to a sulfuric acid concentration of about 1 N at any treatment time, but only slightly increases in a higher concentration region, and hardly changes at about 5 N or more. You can see that it is in a state.

Next, with respect to the ITO scrap sample, the sulfuric acid concentration was kept constant at 1 N, and the change of the leaching rates of In, Sn and Al due to the mechanochemical treatment time (pulverization time) was investigated. The obtained results are shown in FIG. Indicated. In this FIG.
I from untreated (milling time: 0 min) ITO scrap
The n leaching rate is as low as about 45%, but exceeds about 80% after 15 minutes treatment, and rises to 90% or more after 30 minutes treatment. However, the improvement of the In leaching rate is not recognized in a further long-time treatment, and conversely, it tends to slightly decrease. On the other hand, S
The leaching rate is about 20% in the untreated state,
It becomes 45% by the minute treatment, and tends to decrease when the treatment time is further extended. In addition, separation of In and Sn is carried out at pH
It is possible by adjustment and there is no particular problem in processing. Regarding Al, the leaching rate was as low as several percent even in the treatment range up to 60 minutes, and it can be seen that the dissolution of alumina into sulfuric acid was slight.

Next, the In ₂ O ₃ single sample and the model mixed sample (In
₂ O ₃ + 90% Al ₂ O ₃ )
A leaching test was performed. The results obtained are shown in FIG. FIG.
In the results shown in the above, first, in the case of the In ₂ O ₃ single sample, the In leaching rate was 10 to 15 even when the mechanochemical treatment was performed.
%, And no significant improvement in leaching rate is observed. However, the In leaching rate from the model mixed sample increased linearly with the treatment time at first, and increased to 80
% Is reached. It can be seen that this result is similar to the result of the scrap sample of FIG. However,
With further mechanochemical treatment, the In leaching rate tends to decrease, and the result is similar to that of the ITO scrap sample. Although the reason why the In leaching rate is reduced by a long-time mechanochemical treatment is not necessarily clear,
It is possible that the crystal structure of n ₂ O ₃ has been changed to the structure of α-Al ₂ O ₃ by mechanical treatment.

It is assumed that the result of In leaching with sulfuric acid from the In-containing oxide described above is closely related to the change in the crystal structure (amorphization) of the material as shown in FIGS. That is, the crystal structure of the In-containing oxide did not change much by the treatment when alumina powder was not present, and the In leaching rate was low.
In the case of O scrap, In ₂ O ₃
Amorphous crystal structure is promoted, and a high In leaching rate is exhibited in the subsequent sulfuric acid leaching. Further, even when the In-containing scrap containing In in the In-containing oxide form does not initially contain ceramic powder such as alumina, the same effect can be obtained by adding the ceramic powder such as alumina and performing the mechanochemical treatment. Things.

[0022]

According to the method of the present invention, the crystal structure of an In-containing oxide such as In-containing scrap can be made amorphous, and a low-concentration acid of 5N or less, such as 1N, can be obtained at room temperature from the In-containing oxide. Leaching with sulfuric acid at room temperature below
There is an effect that leaching can be effectively performed at the above high leaching rate. In addition, by performing leaching under such mild acid treatment conditions of 5 N or less, preferably 1 N or less, contamination of impurities from the dissolution tank is reduced as compared with the conventional leaching method using a high-temperature and high-concentration acid or alkali. Therefore, there is no need to particularly increase the acid resistance of the material of the melting tank, and the working environment is improved. Further, according to the method of the present invention, In can be selectively leached with respect to Al in the acid leaching, so that there is also an effect that the separation and removal of Al in a subsequent processing step becomes easy. Furthermore, by using a dry pulverizing means such as a ball mill including a planetary mill, there is an effect that mechanochemical treatment of an In-containing oxide such as an In-containing scrap can be easily performed.

[Brief description of the drawings]

FIG. 1 is a flowchart showing a test procedure according to an embodiment of the present invention.

FIG. 2 is a graph showing a relationship between a pulverization time and an average particle size for an ITO scrap sample in Examples.

FIG. 3 is a diagram showing X-ray diffraction patterns of ITO scrap samples having different grinding times in Examples.

FIG. 4 is a diagram showing X-ray diffraction patterns of In ₂ O ₃ samples having different pulverization times in Examples.

FIG. 5 is a diagram showing X-ray diffraction patterns of model mixed samples (90% Al ₂ O ₃ + 10% In ₂ O ₃ ) having different grinding times in Examples.

FIG. 6 is a graph showing a relationship between an In leaching rate and a sulfuric acid concentration from ITO scrap samples having different grinding times in Examples.

FIG. 7 is a graph showing a relationship between each leaching rate of In, Sn, and Al from an ITO scrap sample with 1N sulfuric acid and a pulverization time in Examples.

FIG. 8 is a graph showing the relationship between the In leaching rate and the pulverization time from a single sample of In ₂ O ₃ and a model mixed sample with 1N sulfuric acid in Examples.

 ────────────────────────────────────────────────── ─── Continued on the front page (72) Inventor Takeshi Aoyagi 2-11-17 Shinmachi, Sanbongi-cho, Shida-gun, Miyagi F-term (reference) 4K001 AA15 BA22 CA01 DB03

Claims (6)

[Claims] 1. A method of subjecting an In-containing oxide to a mechanochemical treatment in the presence of a ceramic powder to change the crystal structure of the In-containing oxide, and then leaching the low-concentration acid at room temperature. A method for leaching In from an In-containing oxide. 2. The method for leaching In from an In-containing oxide according to claim 1, wherein the mechanochemical treatment is a dry pulverization treatment. 3. The method for leaching In from an In-containing oxide according to claim 1, wherein the low-concentration acid is sulfuric acid having a concentration of 5 N or less. 4. The method according to claim 1, wherein said ceramic powder is alumina powder and said low-concentration acid is sulfuric acid at room temperature of 1 N or less. Leaching method. 5. The leaching of In from the In-containing oxide according to claim 1, wherein at least a part of a crystal structure of the In-containing oxide after the mechanochemical treatment is amorphous. Method. 6. The method for leaching In from an In-containing oxide according to claim 1, wherein the In-containing oxide is scrap.