JP2010222641A - Method for producing rare metal - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a practicable method with which rare metal can efficiently be produced by utilizing a mechanochemical reaction. <P>SOLUTION: Rare metal oxide powder is mechanochemically reacted with silicon powder to obtain the rare metal and silicon oxide. As the rare metal oxide, the oxides of indium, tin and antimony, etc., can be used. The reaction of the rare metal oxide powder and the silicon powder can be applied while mechanically stirring-treating and this reaction can be applied under the atmosphere to be useful to recover the rare metal from the wasted liquid-crystal panel, etc. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

The present invention relates to a method for producing a rare metal using a rare metal oxide, and in particular, mechanochemically efficiently a rare metal contained in a transparent electrode used for a substrate such as a waste liquid crystal panel. It relates to an effective method for recovery.

For example, waste liquid crystal panels that are discarded in the manufacturing process of liquid crystal panels and plasma display panels, or products, information display devices, video display devices, etc. to which these panels are applied are dismantled and disposed of. The electrode contains valuable rare metals.

Therefore, various methods for treating the waste liquid crystal panel so as to be reused have been studied. In Patent Document 1, a glass plate of a waste liquid crystal panel is cut into a rectangular shape, the glass plate is removed from the liquid crystal panel, the liquid crystal is exposed, and the liquid crystal attached to the glass substrate is scraped and collected. It is disclosed that it is possible to recover rare metals and the like contained in However, the method for recovering the rare metal is not specifically disclosed here, and the process of scraping the liquid crystal from the glass plate cut into a fixed shape is troublesome.

Separately, as a method for recovering metallic indium, Patent Document 2 discloses that indium tin oxide (ITO) target scraps are pulverized, and this powder is dissolved with an acid such as hydrochloric acid, sulfuric acid or nitric acid, and then After neutralizing the pH of the solution with an alkali and aging the filtrate, hydrogen sulfide gas was blown in to precipitate and remove metal ions as sulfides. A method of electrowinning is disclosed. This method requires the use of difficult-to-handle chemicals such as strong acids and hydrogen sulfide, and the process is complicated and difficult to put into practical use.

Also, Patent Document 3 discloses a method for recovering metal indium from a substance containing indium and tin. Here too, an alloy of indium and tin is heated and dissolved in hydrochloric acid, sulfuric acid, or a mixed acid of hydrochloric acid and sulfuric acid. It was a thing and difficult to handle.

Therefore, as a method not using strong acid, there is an article in Non-Patent Document 1 that has developed a method for recovering rare metal indium by utilizing a mechanochemical reaction by pulverization from ITO. Since it can be carried out at room temperature and does not use a strong acid, it is easy to handle. However, since lithium nitride containing lithium, which is a rare metal, is used, there is a problem in safety and economy.
Japanese Patent No. 3589937 JP 2006-206990 A JP 2007-9274 A "Hebei Shinpo" dated July 26, 2007

An object of the present invention is to provide a method that can be put into practical use by utilizing a mechanochemical reaction as disclosed in Non-Patent Document 1 and capable of efficiently producing or recovering a rare metal.

The present inventors have found that a rare metal oxide powder can be reacted with a silicon powder under a specific atmosphere to obtain a rare metal and a silicon powder, and a patent application was filed as Japanese Patent Application No. 2008-206867. Thereafter, it was found that the mechanochemical reaction between the rare metal oxide powder and the silicon powder can be carried out effectively even in an atmosphere containing oxygen, and the present invention has been completed.

In the present invention, a rare metal oxide powder is mechanochemically reacted with silicon powder while stirring to obtain a rare metal and silicon oxide. Examples of the rare metal oxide include oxides of indium, tin, and antimony. Although it can be used, the mechanochemical reaction in the present invention may be carried out in an atmosphere containing oxygen or in an atmosphere containing no oxygen (an atmosphere of nitrogen, ammonia, carbon dioxide, etc.). It is economical to carry out in an air atmosphere.

The reaction between the rare metal oxide powder and the silicon powder is carried out while stirring with a ball mill or the like, but this reaction may be carried out at atmospheric pressure (about 1 atm, about 0.1 MPa) You may implement under pressure or pressure reduction. However, when carried out under reduced pressure, it may be 0.01 MPa or less, but it is usually preferred that the reduced pressure is about 0.01 MPa to 0.1 MPa.

A rare metal oxide is a group consisting of sodium hydroxide, potassium hydroxide, ammonium hydroxide, and sodium carbonate, in which cullet-like pulverized material such as the base of a waste liquid crystal panel is dissolved in hydrochloric acid and precipitated as chloride. The rare metal hydroxide or carbonate obtained by neutralizing with an alkaline aqueous solution containing a salt selected from the above can be obtained by drying and firing, and the present invention is useful for recovering rare metals from waste liquid crystal panels. It will be very useful.

That is, the substrate that has been cut and crushed to recover rare metals contained in transparent electrodes used in the substrate of waste liquid crystal panels (for example, waste liquid crystal panels, waste plasma display panels, and waste solar cells). The transparent electrode film formed above is dissolved in a hydrochloric acid and nitric acid mixed solution and then neutralized with an alkaline solution to recover the metal that is a component of the transparent electrode film as chloride, hydroxide, and carbonate. After the rare metal compound is precipitated, it is recovered as a metal oxide by firing, and the obtained metal oxide and silicon can be stirred together under atmospheric pressure to deposit the rare metal oxide as a rare metal. It is.

In this method, waste liquid crystal panels, etc. (waste liquid crystal panels, waste plasma display panels, waste solar cells, etc.) are crushed as necessary. The process includes removing organic substances from the panel, and dissolving the thin film material formed on the substrate from the pulverized cullet-like substrate with chemicals, and purifying the thin film material formed on the substrate. Good and efficient recovery.

In the present invention, it is preferable to collect the rare metal after depositing the rare metal by an agitation treatment in an air atmosphere and then adding water to the treatment tank and performing a water washing treatment.

In the method of the present invention, a rare metal (such as indium) can be directly produced economically and with high purity by using a rare metal oxide without using heat and special chemicals. Such a method of the present invention is also effective for recovering rare metals from wastes containing rare metals. For example, when applied to a method for treating waste liquid crystal panels, the substrate material (glass) has a metal thin film attached thereto. It can be reused as a substitute material for silica.
Therefore, by utilizing the present invention, it is possible to recycle almost no waste, and it is possible to provide an ideal waste panel processing method and the like.
In addition, since the silicon (Si) used in the present invention can be used as a waste silicon wafer which has become defective in the semiconductor manufacturing process or a waste product in the silicon ingot manufacturing process, the method of the present invention is very environmentally friendly Can be said to be a good method.

FIG. 1 is a flowchart showing an example of the method of the present invention. FIG. 2 is an X-ray diffraction (XRD) diagram of the powder in the example of the present invention, (A) is a measurement result before In ₂ O ₃ + Si mechanochemical reaction treatment, and (B) is a mechanochemical reaction treatment. The measurement result after is shown.

One embodiment of the present invention will be described with reference to FIG.
<S1> Pre-treatment process waste liquid crystal panel etc. (for example, waste liquid crystal panel discarded in a liquid crystal panel manufacturing factory, waste liquid crystal panel discarded in a liquid crystal display assembly factory, disassembled and discharged, and in the market For waste liquid crystal panels etc. that are discharged after dismantling the discarded products), exclude plastic members, metal members, organic films, etc. other than the base materials.
<S2> Panel cutting step The substrate that has been pretreated is cut.
<S3> Grinding step The cut substrate is pulverized into a cullet shape.
<S4> Dissolving and neutralizing the thin film with acid, removing the thin film formed on the glass substrate with a mixture of calcined hydrochloric acid and nitric acid, and dissolving the rare metal contained in the transparent electrode formed on the substrate into the mixed liquid After that, it is neutralized with an alkali solution, and the obtained rare metal hydroxide or carbonate is fired to obtain a rare metal oxide.
<S5> Mechanochemical reaction The cullet-like base material containing the rare metal oxide is reacted with silicon (purity 99.9%) in an air atmosphere in a reaction vessel. This reaction is preferably carried out with stirring at 1 atm (0.10 MPa). By this reaction, the rare metal oxide is deposited as a rare metal (for example, indium), and silicon is deposited as silicon oxide.
<S6> Cleaning / Separation The above reaction product is placed in a 10% KOH aqueous solution at 50 ° C. and treated with stirring for 2 hours to dissolve silicon oxide. By this treatment, indium (solid) and a silicon oxide KOH aqueous solution (K ₂ SiO ₃ ) are separated into solid and liquid, and the produced indium is recovered.
<S7> Inspection A purity inspection of the generated indium is performed.

First, plastic materials other than the base material, metal members, organic films, etc. are excluded from the waste liquid crystal panel discarded in the manufacturing process of the liquid crystal panel, then the base is cut, and the cut base is crushed into a cullet shape. The base material (with transparent electrode material attached) is dissolved in an acid mainly composed of hydrochloric acid and precipitated as a chloride, and an alkaline aqueous solution (NaOH, NH ₄ OH, Na ₂ CO ₃ ) is injected into it. To neutralize and stabilize as hydroxide or carbonate.
At this time, it is considered that the chemical reaction shown in (chemical reaction formulas 1 to 4) occurs.

(Chemical reaction formula 1) In ₂ O ₃ + 6HCl-> 2InCl ₃ + 3H ₂ O
(Chemical reaction formula 2) InCl ₃ + 3NaOH-> In (OH) ₃ + 3NaCl
(Chemical reaction formula 3) InCl ₃ + 3NH ₄ OH-> In (OH) ₃ + 3NH ₄ Cl
(Chemical reaction formula 4) InCl ₃ + 3Na ₂ CO _3- > In ₂ (CO) ₃ + 6NaCl

The obtained precipitates, indium hydroxide In (OH) ₃ and indium carbonate In ₂ (CO) ₃ are dried and fired (at 600 ° C. to 700 ° C. for 2 hours) to produce indium oxide (In ₂ O ₃ ). Store in a stable form.

In the present invention, a method for recovering a rare metal includes firstly, in a sealed container under an air atmosphere, a compound powder made of a metal oxide containing a predetermined metal, a silicon (Si) powder, a grinding ball, Enclose. After the sealing, the sealed container is rotated at a predetermined speed for a predetermined time to mix and pulverize the compound powder and the silicon powder. Thereby, a mixed powder containing a predetermined metal can be generated. The generated mixed powder is dissolved in silicon oxide using a KOH aqueous solution, so that the indium (solid) and the KOH aqueous solution of silicon oxide are separated into solid and liquid, and the generated predetermined metal indium can be recovered. .

As described above, the metal recovery method according to the embodiment of the present invention can recover a high-quality metal efficiently by a simple method called a pulverization operation in an air atmosphere. Since a predetermined metal can be recovered as a powder, handling is easy. In addition, it uses a mechanochemical reaction that promotes a chemical reaction by applying mechanical energy to the raw material, and the reaction is a sealed system and does not require any special heating during the reaction. Since it is not heated in this way, temperature control, safety equipment, etc. are unnecessary, the apparatus can be miniaturized, and industrial implementation is easy.

Using the metal recovery method according to the embodiment of the present invention, a test for recovering indium from indium oxide was performed in an air atmosphere. A sealed zirconia mill pot was filled with 24 zirconia balls for pulverization, 2 g of indium oxide powder, and 0.61 g of silicon powder, and completely sealed with a stainless steel overpot. Next, a ball collision was induced by rotating the sealed container at 700 rpm for 3 hours with a pulverizer. When the powder thus produced was analyzed by X-ray diffraction (XRD), it was confirmed that it contained indium as shown in FIG. 2 (In ₂ O in the chart of (B) after the mechanochemical reaction treatment). ₃ and Si diffraction images could not be confirmed, only metal In diffraction images were observed).

The indium-containing powder and pure water were filled in a sealed container together with a grinding ball, and washed with water by rotating at 300 rpm for 10 minutes with a grinding device. Since the powder thus produced is a fine indium powder and a silicon oxide powder, only a predetermined metal was separated and recovered. At this time, it is considered that the chemical reaction shown in (chemical reaction formula 5) occurs.

(Chemical reaction formula 5) 2In ₂ O ₃ + 3Si → 4In + 3SiO ₂

In the above mechanochemical reaction, the change in Gibbs free energy before and after the chemical reaction is a negative chemical reaction of -906 KJ / mol.

As described above, if the change in Gibbs free energy before and after the chemical reaction is negative, the metal can be recovered by the metal recovery method of the embodiment of the present invention. The following chemical reaction formulas 6 and 7 are listed as examples.

(Chemical reaction formula 6) 2SnO ₂ + 2Si → 2SiO ₂ + 2Sn; ΔG ° f = −674KJ / mol
(Chemical reaction formula 7) 2Sb ₂ O ₃ + 3Si → 3SiO ₂ + 4Sb ΔG ° f = -2,823KJ / mol

In addition, the transparent conductive film (Indium Tin oxide) is composed of In ₂ O ₃ : SnO ₂ = 9: 1. However, as a method of recovering indium from this, it is possible to recover indium and tin mixed with hydrochloric acid solution. Sodium hydroxide is added to the solution to precipitate Sn (OH) ₂ at pH 2, and sodium hydroxide is further added to precipitate In (OH) ₃ at pH 4-5, which are separated and fired. Thus, In (OH) _{3 is changed} to In ₂ O ₃ and this is reacted with silicon powder in an air atmosphere in the same manner as in Example 1 to recover indium.

Claims (6)

A rare metal oxide powder is obtained by causing a mechanochemical reaction while stirring with a silicon powder to obtain a rare metal and silicon oxide, wherein the rare metal is indium, tin or antimony. Method. The manufacturing method of Claim 1 which implements the said mechanochemical reaction in the atmosphere containing oxygen. The manufacturing method according to claim 2, wherein the atmosphere is air. The manufacturing method of any one of Claims 1-3 which implements the said mechanochemical reaction under atmospheric pressure. The process according to any one of claims 1 to 4, wherein the reaction product is treated with a KOH aqueous solution, and the rare metal and silicon oxide are solid-liquid separated using silicon oxide as the KOH aqueous solution. The rare metal oxide dissolves the cullet-like pulverized material of the base of the waste liquid crystal panel, the waste plasma display panel and the waste solar cell in hydrochloric acid, and precipitates the rare metal as a chloride. Neutralized with an alkaline aqueous solution containing a salt selected from the group consisting of potassium hydroxide, ammonium hydroxide and sodium carbonate, and obtained by drying and firing the obtained rare metal hydroxide or carbonate. The manufacturing method of any one of Claims 1-5.

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