KR100932706B1 - Method for recycling indium from indium containing waste solution - Google Patents

Abstract

PURPOSE: A high purity indium collecting method from indium waste water is provided to collect indium of the high purity by reforming the surface of the indium using phase transition catalyst and surface active agents. CONSTITUTION: A high purity indium collecting method from indium waste water comprises following steps. Alkali hydrate is put into the waste water including indium and an indium hydroxide is formed, precipitated, and separated. The indium hydroxide is dispersed in the deionized water and reducing agent, phase transition catalyst, and surface active agents are injected and the indium surface is reformed.

Description

Method for recycling indium from indium containing waste solution

The present invention relates to a method for recovering indium from a waste liquid containing indium with high purity, and to a method for recovering indium of high purity by reducing impurities in the indium recovery process by using a phase transfer catalyst and a fluorine-based surfactant. .

Indium Tin Oxide (ITO), a representative transparent-conductive material, is widely used as a transparent electrode such as a flat panel display device such as a liquid crystal display device, a plasma display panel, a field emission display device, an electron light emitting device, a solar cell, and a transparent heating wire. Tin oxide (SnO 2), zinc oxide (ZnO) and the like are also used as the transparent electrode material, but most representative materials are ITO coated with a small amount of InO 2 and SnO 2 coated on the base substrate in a thin film form. ITO thin films are manufactured by vapor deposition, sputtering, and the like, and are widely used as electrodes for liquid crystal display devices. When an ITO thin film is used in a flat panel display device, a sputtering method is most widely used because a large area uniform thin film is required.

The demand for ITO targets, the high density and sintered form of the sputtering method, is increasing, but the utilization rate of the target is only about 30% due to process problems.Indium, the main raw material of ITO targets, is hundreds of ppm in zinc ore. Since it is a very expensive element obtained at the level, the process of recycling the remaining 70% of the target after use is a very important technique.

As such a recovery and purification method, a method of electrolytic purification by dissolving ITO oxide in an acid after reduction treatment at a high temperature in a hydrogen atmosphere and a method of directly electrolytic purification of a metal before dissolution are reported. It also relates to the purification of indium and has been reported to synthesize indium sulfide and to obtain and purify the hydroxide under basic solution. In this purification method, the indium metal obtained after electrolysis remains a problem that may contain various impurities depending on the electrolytic conditions.

The present invention is a method for recovering high purity indium from a waste liquid containing indium, and since it contains a large amount of impurities, it is not easy to obtain high purity indium, and particularly tin (Sn), which is not easy to remove, remarkably It is an object of the present invention to provide a method capable of recovering high purity indium by reducing it.

The present invention to achieve the above object,

(a) adding alkaline hydroxide to a waste solution containing indium to form, precipitate and separate indium hydroxide;

(b) dispersing the indium hydroxide separated from step (a) in pure water and modifying the indium surface by adding a reducing agent, a phase transfer catalyst, and a fluorine-based surfactant;

(c) dissolving the indium surface-modified in the acid solution from step (b) and injecting aluminum metal to precipitate indium on the aluminum surface; And

(d) melting the indium precipitated on the aluminum surface from step (c) under an alkali salt at 200 to 600 ° C., and then solidifying the indium;

It is intended to provide a method for recovering high purity indium from an indium-containing waste liquid comprising a.

EMBODIMENT OF THE INVENTION Hereinafter, this invention is demonstrated in detail.

The present invention relates to a method for recovering high purity indium from a waste liquid containing indium. The waste liquid containing indium of the present invention includes a waste liquid obtained by treating ITO scrap with an acid solution. A waste liquid containing a large amount of indium in the step (etching, washing, etc.) or a waste liquid containing indium and impurities in an acidic solution of nitric acid solution.

Step (a) of the present invention is a step of neutralizing by adding an alkaline hydroxide to the waste solution of nitric acid solution containing indium, and forming indium to which a hydroxyl group (-OH) is introduced to separate in the form of a precipitate.

Examples of the alkaline hydroxide of step (a) of the present invention, 1 selected from ammonium hydroxide, sodium hydroxide, potassium hydroxide, lithium hydroxide, calcium hydroxide, magnesium hydroxide, hydroxylamine, monoethanolamine, diethanolamine and triethanolamine It is preferable that it is a species or more, and is not limited to the above-mentioned compound.

The present invention is a method of adding the alkaline hydroxide of step (a) to the waste solution containing indium, it is subjected to a two-step process. As the first step, the alkaline hydroxide is added so that the pH is 1 to 4, stirred for about 30 minutes to 4 hours, and left to be filtered. The reason is that the alkaline hydroxide is contained in the waste liquid containing indium of the present invention. When the tin has a pH of 1 to 4, a part of tin is oxidized to tin oxide to form a precipitate. At this time, a part of tin may be removed as a precipitate. The filtrate from which part of the tin was removed in the first step was the second step, and the same as the alkaline hydroxide added in the previous step was added. At this time, the pH was added to be 8-12 and stirred for about 1 hour to 4 hours. It is preferable to filter by infiltration, and when the pH of the waste liquid containing indium is 8-12, indium hydroxide is formed. The indium hydroxide may be separated in the form of a precipitate. Step (b) of the present invention is preferably carried out at 30 to 80 ℃, more preferably carried out at 40 to 60 ℃.

In the step (b) of the present invention, the indium hydroxide precipitate is separated and dispersed in deionized water without impurities, and a reducing agent is added to desorb and reduce the hydroxyl group (—OH) from indium. Examples of the reducing agent may be one or more selected from sodium borohydride, formaldehyde, hydrazine and sodium hypophosphite. In addition to the reducing agent exemplified above, any reducing agent having excellent reducing ability against indium hydroxide may be used, and impurities It is preferable not to work.

When the indium reduced by the reducing agent is left as it is, it acts as an impurity by oxidizing or includes impurities between fine particles due to agglomeration between indium particles, so that it is not easy to remove impurities in a subsequent process.

Therefore, step (b) of the present invention is performed by adding a phase transfer catalyst and a fluorine-based surfactant after addition of a reducing agent, and the addition of a phase transfer catalyst and a fluorine-based surfactant has the greatest technical features of the present invention. The phase transfer catalyst and the fluorine-based surfactant of step (b) of the present invention are capping the surface of the indium particles with a fluorine-based surfactant to prevent agglomeration between the indium particles and to prevent oxidation or impurity loading. Has In the prior art, in the manufacturing process of indium due to agglomeration between indium due to wet indium production process and impurity contained between particles, the process cost increases due to the need for further purification process such as vacuum purification in the final step. There was this.

In addition, after the reduction in the step (b) of the present invention, the process of modifying the indium surface by adding a phase transfer catalyst and a fluorine-based surfactant is carried out under micro vibration conditions such as ultrasonic vibration, jet air, etc. It can be obtained effectively. In particular, the ultrasonic vibration may use ultrasonic vibration in the range of 1W to 100W.

The reducing agent, the phase transfer catalyst and the fluorine-based surfactant added in the step (b) of the present invention are 20 to 100 parts by weight of the reducing agent, 50 to 200 parts by weight of the phase transfer catalyst, and 100 to 400 parts by weight of the fluorine-based surfactant based on 100 parts by weight of indium hydroxide. It is preferable to add in an amount, and it is more preferable to add in an amount of 30 to 50 parts by weight of a reducing agent, 100 to 150 parts by weight, and 200 to 300 parts by weight of a fluorine-based surfactant based on 100 parts by weight of indium oxide. The present invention is excellent in dispersibility of the indium, the surface capping effect, etc. to be added in the above input ratio range, the input amount is effective compared to the effect. When added below the above range, the desired dispersibility or capping effect cannot be obtained, and when exceeding the above range, it is difficult to expect a larger effect.

Phase transfer catalyst introduced in step (b) of the present invention, quaternary ammonium salts such as tetrabutylammonium chloride and benzyltributylammonium chloride; Quaternary phosphonium salts such as tetrabutylphosphonium chloride and tetraphenylphosphonium bromide and the like; Crown ethers such as dibenzo-18-crown-6-ether and dicyclohexyl-18-crown-6-ether and the like; Cryphrends, such as [2, 2, 2] -cretate, and the like can be mentioned.

The fluorine-based surfactant added in the step (b) of the present invention may use a known fluorine-based surfactant. Anionics such as perfluoroalkyl carboxylates, perfluoroalkyl sulfonates, perfluoroalkyl sulfates, perfluoroalkyl phosphates, and the like; Cationic systems such as perfluoroalkyl amine salts, perfluoroalkyl quaternized ammonium salts, and the like; Amphoteric ionic systems such as perfluoroalkyl carboxy betaine, perfluoroalkyl sulfobetaine and the like; And nonionics such as fluorinated alkyl polyoxyethylene, perfluoroalcohol polyoxyethylene, and the like.

The surface modified indium obtained from step (b) of the present invention is washed and filtered several times with pure water.

In the step (c) of the present invention, after the step (b), the washed and filtered surface-modified indium is dissolved in an acid solution. The acid solution may be nitric acid, sulfuric acid, hydrochloric acid, and the like, and aluminum is added to the acid solution as a precipitation metal. As the precipitation metal of the present invention, aluminum is not limited in shape or form, but for example, aluminum particles or granules having an average particle diameter of 0.01 to 1 mm, or aluminum metal bars may be used. After the indium surface-modified with the fluorine-based surfactant is added to the acid solution, the indium can be deposited on the aluminum metal surface by adding the aluminum metal to the acid solution. Indium capped with a fluorine-based surfactant is added to the acid solution and the fluorine-based surfactant is peeled off, causing the indium particles to precipitate on the aluminum metal surface due to the difference in ionization tendency. In addition to aluminum, zinc may be used as a metal capable of depositing indium on the metal surface by using an ionization tendency difference. Step (c) of the present invention is preferably carried out at 40 to 100 ℃, more preferably carried out at 70 to 100 ℃.

The step (d) of the present invention is a step of obtaining the indium precipitated on the aluminum surface from the step (c), the peeling means may be peeled using a known technique such as ultrasonic vibration or air jet, Rather, it is preferable to heat-treat under alkaline salt conditions because acid is present between the indium particles due to the acid treatment in the previous step and the particles are not dense. The alkali salt heat treatment preferably uses an alkali salt having a melting point of 300 ° C. or higher, for example, sodium hydroxide, potassium hydroxide, lithium hydroxide, magnesium hydroxide, calcium hydroxide, and the like, and preferably sodium hydroxide. . In the alkali salt heat treatment step, the indium precipitated on the aluminum surface is added to the heat treatment furnace containing the alkali salt as it is without in particular peeling off the indium, and the molten indium is separated from the alkali salt. The heat treatment is carried out through a heat treatment furnace equipped with a special filtering device inside the furnace. The alkali salt heat treatment temperature is preferably heat treated within a range that exceeds the melting point of indium and does not exceed the melting point of the alkali salt, more preferably performed in the temperature range of 200 to 600 ℃, it is preferably carried out in the temperature range of 200 to 300 ℃ Most preferred. The alkali salt heat treatment may remove the acid and improve the purity of indium, wherein the purity of the indium obtained after the alkali salt heat treatment may be 99.8% or more. The purity of the indium of the present invention is carried out using ICP (Inductively Coupled Plasma; ELAN 9000 from Perkin Elmer).

After the step (d), the present invention can further improve the purity of indium by a known melt hydrolysis method. The apparatus for melt hydrolysis may use a molten salt electrolysis apparatus common in the art, for example, the apparatus shown in FIG. As the molten salt, InCl + ZnCl ₂ can be used as an electrolyte, and molten salt electrolysis is performed using indium as an anode and graphite as a cathode. The molten salt electrolysis is carried out at 200 to 300 ℃.

According to the present invention, after the molten salt electrolysis, as a result of measuring the purity of indium through ICP analysis, 99.999% or more of indium could be prepared.

The present invention is a technology capable of minimizing the content of impurities by preventing the impurity carried between the indium particles by improving the dispersibility of the indium from the waste solution containing indium by using a phase transfer catalyst and a fluorine-based surfactant, the final molten salt electrolyte It is an indium recovery technique that yields 99.999% 5N by the process.

Hereinafter, the present invention will be described in more detail based on the following examples. However, the following examples are not intended to limit the invention only.

Example 1

500 ml of the waste solution containing indium, tin and other impurities was kept at 40 ° C. and ammonium hydroxide was added so that the pH of the solution was 4. At this time, if there is tin in the solution, the solution becomes cloudy. The solution is filtered to remove tin oxide and ammonium hydroxide is added so that the pH of the filtrate is 11. At this time, when the solution became turbid, indium hydroxide was formed, which was filtered and washed several times with anhydrous hexane, thereby obtaining 72 g of indium hydroxide. Disperse this indium hydroxide in pure water, add 20 g of sodium hypophosphite, stir at 80 ° C. for 2 hours, add 72 g of tetrabutylammonium and 150 g of fluorinated surfactant (3M Novec FC-4430) at the same time. Stir enough for about an hour. Thereafter, the solid is filtered and washed with water, dispersed in a nitric acid solution, and then aluminum granules (average particle diameter: 1 mm) are added to precipitate indium. NaOH granules were placed in a heat treatment furnace equipped with a filtration device, and aluminum granules having indium precipitated on the surface thereof were added thereto, followed by heat treatment at 250 ° C., whereby molten indium was obtained and cooled to obtain an indium ingot. Can be. In this case, the purity of indium analyzed by ICP was 99.9%. In order to obtain higher purity indium, the indium ingot was InCl and ZnCL ₂ as a molten salt, indium was used as an anode, graphite was electrolyzed, and a current density of 20 A / dm ² was performed at 250 ° C. The molten salt electrolyte gave indium of 99.999% purity.

1 is an indium recovery process diagram of the present invention,

2 is a molten salt electrolytic apparatus diagram.

Claims (9)

(a) adding alkaline hydroxide to a waste solution containing indium to form, precipitate and separate indium hydroxide; (b) dispersing the indium hydroxide separated from step (a) in pure water and modifying the indium surface by adding a reducing agent, a phase transfer catalyst, and a fluorine-based surfactant; (c) dissolving the indium surface-modified in the acid solution from step (b) and injecting aluminum metal to precipitate indium on the aluminum surface; And (d) melting the indium precipitated on the aluminum surface from step (c) under an alkali salt at 200 to 600 ° C., and then solidifying the indium; Method for recovering high purity indium from indium-containing waste liquid containing The method of claim 1, The alkaline hydroxide of step (a) is at least one selected from ammonium hydroxide, sodium hydroxide, potassium hydroxide, lithium hydroxide, calcium hydroxide, magnesium hydroxide, hydroxylamine, monoethanolamine, diethanolamine and triethanolamine Recovery method of high purity indium The method of claim 1, 20 to 100 parts by weight of a reducing agent, 50 to 200 parts by weight of the phase transfer catalyst, and 100 to 400 parts by weight of the fluorine-based surfactant in the step (b) in 100 parts by weight of the indium hydroxide recovery method The method of claim 3, wherein Reducing agent of step (b) is a high purity indium recovery method, characterized in that at least one selected from sodium borohydride, formaldehyde, hydrazine and sodium hypophosphite The method of claim 3, wherein The phase transfer catalyst of step (b) is at least one selected from crown ethers, quaternary ammonium salts and quaternary phosphonium salts. The method of claim 3, wherein The fluorine-based surfactant of step (b) is an anionic system of perfluoroalkyl carboxylate, fluoroalkyl sulfonate, perfluoroalkyl sulfate, perfluoroalkyl phosphate; Cationic systems of perfluoroalkyl amine salts and perfluoroalkyl quaternized ammonium salts; Amphoteric ionic systems of perfluoroalkyl carboxybetaine and perfluoroalkyl sulfobetaine; And a nonionic system of fluorinated alkyl polyoxyethylene and perfluoroalcohol polyoxyethylene. The method of claim 1, Indium surface modification step of the step (b) is a high purity indium recovery method characterized in that carried out under ultrasonic vibration conditions The method of claim 1, After the step (d), the method of recovering high purity indium further comprising the step of molten hydrolysis of indium The method of claim 8, Molten salt is a recovery method of high purity indium characterized in that using InCl + ZnCl ₂

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