JP2009155717A - Method for recovering indium - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method for recovering indium by which indium can be easily recovered efficiently at a low cost from indium-containing materials, such as waste electrical appliances, containing various organic compounds and inorganic compounds and having low indium content. <P>SOLUTION: As an indium-containing material, a waste electrical appliance, such as a waste liquid-crystal panel component, is crushed, and metals such as indium in the indium-containing material are leached with an acid solution. The resultant leachate is neutralized with alkali to form a precipitate and separated into the precipitate and a solution after neutralization by solid-liquid separation. Then, indium is recovered from the precipitate, and the solution after neutralization is used as the acid solution for use in the leaching of indium-containing materials. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a method for recovering indium, and more particularly to a method for recovering indium from waste electrical appliances containing metals such as indium, such as a liquid crystal display using a transparent conductive film made of indium tin oxide (ITO).

  In recent years, with the widespread use of flat panel displays such as liquid crystal displays, the demand for ITO transparent conductive films used for the electrodes has rapidly increased, and the demand for indium, which is a raw material for producing ITO, has increased greatly. However, since indium has no main ore, indium concentrated in neutralized gypsum by-produced in zinc smelting is recovered, or indium is recovered by a recycling technique.

  Conventionally, as a method for recovering indium from indium-containing materials such as ITO target waste, the indium-containing material obtained by pulverizing the ITO target waste is dissolved with hydrochloric acid, and an alkali is added to the solution to adjust the pH to 0. Neutralize to 5 ~ 4, deposit and remove predetermined metal ions in the solution as hydroxide, then blow in hydrogen sulfide gas to deposit metal ions harmful to electrolysis as sulfide After the removal, a method of electrolytically collecting indium metal using this solution as an electrolytic base solution has been proposed (see, for example, Patent Document 1). This method is extremely useful as a recycling method for ITO target scraps and the like because it can recover 99.999% or more of high-purity indium in a simple process and at low cost.

  In addition, as a method of recovering indium from the waste liquid crystal panel, the waste liquid crystal panel glass substrate is sorted according to the type of glass, the sorted waste liquid crystal panel is burned to decompose and remove organic substances, and the unburned residue including the glass substrate is removed. After crushing and peeling (removing) the thin film remaining on the glass substrate by a mechanical method, the thin film (metal powder) and the glass piece (glass cullet) are collected separately, from the metal powder such as indium A method for recovering metal has been proposed (see, for example, Patent Document 2).

JP 2000-169991 A (paragraph numbers 0005-0006) JP 2001-296508 A (paragraph number 0014-0019)

  However, the method of Patent Document 1 is an extremely useful method when recovering indium from an indium-containing material containing a large amount of metal such as indium, such as ITO target scrap. When recovering indium from indium-containing materials such as products, waste electrical appliances often contain components that include various organic and inorganic compounds, have complex shapes, and are intricately joined together. Therefore, by pulverizing and dissolving with an acid, leaching and collecting the metal requires a large amount of acid, resulting in an increase in the size of the apparatus and an increase in chemical cost and processing cost.

  On the other hand, the method of Patent Document 2 requires burning the waste liquid crystal panel and decomposing and removing organic substances. Therefore, when collecting indium from waste electrical appliances with a low content of rare metals such as indium, the apparatus is large. And cost increases.

  Therefore, in view of such conventional problems, the present invention is inexpensive, simple and efficient from indium-containing materials such as waste electrical appliances containing various organic compounds and inorganic compounds and low indium content. It is an object of the present invention to provide a method for recovering indium that can recover indium.

  As a result of diligent research to solve the above problems, the present inventors leached indium-containing materials with an acid solution composed of hydrochloric acid and alkali metal chloride, and produced the resulting leachate by neutralization with alkali. By recovering indium in the precipitate, indium can be recovered inexpensively, conveniently and efficiently from indium-containing materials such as waste electrical appliances containing various organic and inorganic compounds and low indium content. As a result, the present invention has been completed.

  That is, in the method for recovering indium according to the present invention, an indium-containing material is leached with an acid solution composed of hydrochloric acid and an alkali metal chloride, and the obtained leachate is neutralized with an alkali to recover indium in the generated precipitate. It is characterized by doing. In this indium recovery method, solid-liquid separation is carried out after neutralization, and the post-neutralization liquid separated by solid-liquid separation is used as an acid solution, and indium is collected in the solid matter separated by solid-liquid separation. Is preferred. Further, the indium-containing material is a waste electrical appliance containing indium, and the waste electrical appliance is preferably crushed before leaching, and the waste electrical appliance is preferably a waste liquid crystal panel component containing glass. Further, the alkali is preferably an alkali metal hydroxide, and the alkali metal chloride is preferably sodium chloride or potassium chloride.

  According to the present invention, various substances can be obtained by leaching indium-containing material with an acid solution composed of hydrochloric acid and alkali metal chloride, neutralizing the obtained leachate with alkali, and collecting indium in the generated precipitate. Indium can be easily and efficiently recovered at low cost from indium-containing materials such as waste electrical appliances that contain various organic and inorganic compounds and have a low indium content.

  Hereinafter, an embodiment of the indium recovery method according to the present invention will be described with reference to the process diagram of FIG.

  As shown in FIG. 1, after crushing a waste electrical appliance containing indium as an indium-containing material as a raw material, for example, a waste liquid crystal panel component, a metal such as indium in the indium-containing material is leached with an acid solution, The obtained leachate is neutralized with an alkali to form a precipitate, separated into a precipitate and a neutralized solution by solid-liquid separation, and indium is recovered from the precipitate. In addition, you may use the liquid after neutralization as an acid solution in the case of the leaching of an indium containing material.

  As the indium-containing material as a raw material, waste electrical appliances used in households, mining industries, or other industries can be used. Waste electrical appliances include structural parts, electronic parts, other functional parts, decorative parts, and the like, and include various metal elements and organic and inorganic compositions. When recovering metals from such waste electrical appliances, the mutual effects of the contained metal elements and compositions are complex, and it was difficult to obtain the desired metal. In the embodiment, it is possible to recover indium easily and efficiently from such waste electrical appliances at low cost. Also, as waste electrical appliances, electrical appliances using liquid crystals such as liquid crystal televisions or liquid crystal panel parts disassembled from liquid crystal televisions can be used, and these are leached after being crushed into small pieces by a crusher or the like. Is preferred. Although a liquid crystal television contains a small amount of indium metal, it has been difficult to recover indium because of its dense and complex structure. However, in the embodiment of the indium recovery method according to the present invention, Indium can also be leached and recovered from a liquid crystal television at low cost, simply and efficiently.

  When crushing waste electrical appliances into small pieces with a crusher, etc., the dimensions of the small pieces may be set as appropriate depending on the capacity of the equipment, etc., but in order to facilitate leaching and handling, strips with a maximum length of about 200 mm or less It is preferable to use a small piece, and it is more preferable to use a strip-shaped piece having a maximum length of 50 mm or less. For this crushing, a widely used crusher such as a single-screw crusher, a multi-axis crusher, or a ball mill can be used. In order to improve the recovery rate of indium, after the waste electrical appliance is crushed, pretreatment such as incineration or decomposition of organic matter by acid may be performed.

  As the acid solution, a solution obtained by mixing alkali metal chloride with hydrochloric acid (HCl) is used. The concentration of hydrochloric acid may be determined according to the amount of raw material to be dissolved and the content of indium. By using an acid solution in which hydrochloric acid and an alkali metal chloride are mixed, a metal such as indium is dissolved from the waste electrical appliance and is leached into the acid solution. As the alkali metal chloride, sodium chloride (NaCl) or potassium chloride (KCl) is preferably used. The mixing ratio of hydrochloric acid and alkali metal chloride is preferably 1 to 5 equivalents of alkali metal chloride with respect to 1N hydrochloric acid in order to suppress the use of chemicals in the entire process and the increase in equipment.

  As the acid solution, a solution in which hydrochloric acid and alkali metal chloride are mixed in advance may be used, but during leaching, alkali metal chloride may be added to hydrochloric acid continuously or intermittently, and hydrochloric acid may be added depending on the reaction state. The reaction may be controlled by adding an alkali metal chloride. By such control, the medicine can be used efficiently and the cost can be suppressed.

  The amount of the acid solution may be set according to the content of indium contained in the waste electrical appliance. For acid leaching, it is only necessary to put the waste electrical appliance into the acid solution. If the temperature of the acid solution during leaching is 50 to 90 ° C., the leaching time can be shortened and the efficiency can be improved.

  As the leaching reaction progresses, the acid solution changes into a waste residue of the waste electrical appliance and a leachate in which the metal is dissolved. However, the dissolution residue increases the volume of the solution, so it is separated from the solution by filtration or the like. It is preferable to remove it. By removing the dissolved residue in this way, it is possible to reduce the scale of the apparatus in the subsequent process, and even when the dissolved residue contains hard glass or the like, it is possible to prevent breakage or wear of the pump or the like. it can. However, if the volume of the dissolved residue is small in the subsequent steps and there is little influence on each chemical reaction, filtration may be omitted.

  In the acid leaching, if one or both of the waste electrical appliance and the acid solution are continuously added to the container, the leaching can be continuously performed and the efficiency can be further improved. In particular, when there are a large amount of waste electrical appliances to be processed, the waste electrical appliances may be stored in a container, an acid solution may be introduced into the container, and leaching may be performed by repeating the bottoming and re-feeding cycles.

  It is preferable to use caustic soda (NaOH) or potassium hydroxide (KOH) as the alkali used for neutralization. In particular, caustic soda becomes sodium chloride when added to hydrochloric acid, and can be reused for acid leaching, so that the amount of sodium chloride used can be suppressed and costs can be reduced.

  In the neutralization, when the liquid temperature is 15 to 90 ° C. and the pH is 4 to 9, a neutralized product (precipitate) of indium is generated and can be efficiently recovered. Moreover, efficiency can be improved by stirring.

  After neutralization, in order to separate the post-neutralization solution and the indium deposit, solid-liquid separation is performed by filtration or the like. Since the neutralized solution contains an alkali metal chloride, it can be used for acid leaching, and the precipitate becomes a raw material for recovering a metal such as indium as it is. In order to obtain indium metal, there are a method of reducing after firing, and a method of dissolving the precipitate in an acid or the like and adjusting it to an electrolytic solution to obtain indium metal by an electrolytic method.

  Examples of the indium recovery method according to the present invention will be described in detail below.

[Example 1]
First, as an indium-containing material as a raw material, a waste liquid crystal panel component in which an electronic component or the like was bonded to a glass substrate was prepared, and the waste liquid crystal panel component was crushed to a size of about 200 mm square by a crusher. In addition, in this waste liquid crystal panel component after crushing, electronic components and the like are held while being bonded to the crushed glass substrate.

  Table 1 shows the results of chemical analysis of the metal composition contained in the waste liquid crystal panel parts after crushing. In addition, the unit of Table 1 has shown the conversion mass (mg) by the chemical analysis value per dry raw material (kg).

  Next, 200 g of waste liquid crystal panel parts after crushing are collected, put into an acid solution (mixed solution of 0.3 N hydrochloric acid and 32 g of sodium chloride) prepared in advance in a 1 L beaker, and at atmospheric pressure under atmospheric pressure. The leaching was carried out by standing at 20 ° C. for 6 hours.

  After leaching for 6 hours, the liquid in the beaker was filtered with a filter paper and separated into a dissolution residue mainly made of glass and a leachate. Table 2 shows the leaching conditions, indium elution amount, non-elution amount, and leaching rate. As shown in Table 2, the infiltration rate of indium was 93%, which was very high.

  Next, caustic soda (NaOH) was added as an alkali to the obtained leachate, and the pH was raised to 9 with stirring to neutralize at a liquid temperature of 20 ° C. After confirming that a precipitate was formed and the pH was stable, neutralization was completed. In addition, NaOH was added so that it might become 0.4 equivalent Na with respect to the chlorine in the acid at the time of leaching.

  After this neutralization was completed, the solid and liquid were separated by filtration, and separated into a precipitate and a neutralized solution. This precipitate is mainly indium hydroxide, the amount of indium in the precipitate (the amount of indium recovered in the precipitate (elution amount)), the amount of indium in the solution after neutralization (the precipitate) Table 3 shows the amount of indium that was not recovered (the amount of undissolved)) and the recovery rate of indium. As shown in Table 3, the indium recovery was as high as 98%, and an excellent indium raw material with high indium quality could be obtained.

  On the other hand, the neutralized solution contains 8.8% by mass of sodium chloride and can be used for leaching after crushing the waste liquid crystal panel parts, thus suppressing the amount of new sodium chloride used for leaching. Can reduce costs. When the obtained neutralized solution was used for leaching, the indium recovery rate was 99%, and an extremely high recovery rate could be maintained. In addition, since the liquid after neutralization contained a little indium, the actual yield after subtracting this amount was also 98%, and it was found that the actual yield was improved.

[Example 2]
Indium was recovered in the same manner as in Example 1 except that the amount of sodium chloride in the acid solution used for leaching was changed to 48 g. As a result, the indium leaching rate was 92%, and the indium recovery rate was 98%. Table 2 shows leaching conditions, indium elution amount, non-elution amount, and leaching rate.

[Comparative Examples 1 and 2 and Examples 3 to 12]
The hydrochloric acid in the acid solution used for leaching was 0.8N hydrochloric acid, the liquid temperature during leaching was 19 ° C, 50 ° C, 75 ° C or 90 ° C, respectively, and the reaction time was 1 hour, 3 hours or 6 hours, Indium was leached by the same method as in Example 1. Table 4 shows the leaching conditions, indium elution amount, non-elution amount, and leaching rate.

[Comparative Examples 3 and 4]
A waste liquid crystal panel component similar to that of Example 1 was prepared. In Comparative Example 3, crushing as in Example 1 was not performed, and in Comparative Example 4, crushing as in Example 1 was performed, and then each acid solution ( Leaching was carried out in the same manner as in Example 1 except that 1.4N hydrochloric acid (without NaCl) was used. Table 5 shows the leaching conditions and the elution and inelution amounts of indium. As shown in Table 5, the infiltration rate of indium can be greatly improved by crushing the waste liquid crystal panel components before leaching.

It is process drawing which shows embodiment of the recovery method of indium by this invention.

Claims (6)

A method for recovering indium characterized by leaching an indium-containing material with an acid solution comprising hydrochloric acid and an alkali metal chloride, neutralizing the obtained leachate with an alkali, and recovering indium in the generated precipitate. . Solid-liquid separation is performed after the neutralization, and the post-neutralization liquid separated by solid-liquid separation is used as an acid solution, and indium is recovered in the solid matter separated by solid-liquid separation. The method for recovering indium according to claim 1. The method for recovering indium according to claim 1 or 2, wherein the indium-containing material is a waste electrical appliance containing indium, and the waste electrical appliance is crushed before the leaching. The method for recovering indium according to claim 3, wherein the waste electrical appliance is a waste liquid crystal panel component containing glass. The indium recovery method according to claim 1, wherein the alkali is an alkali metal hydroxide. The method for recovering indium according to any one of claims 1 to 5, wherein the alkali metal chloride is sodium chloride or potassium chloride.

Images