KR20060036629A - Method for manufacturing the high purity indium and the apparatus therefor - Google Patents

Abstract

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a purification method and apparatus for high purity of indium, which is a raw material of an indium tin oxide (ITO) target used in a transparent conductive film of a liquid crystal display.

The present invention relates to molten salt electrolytic refining in which tin separation efficiency and productivity are improved at least three times compared to conventional aqueous solution electrolytic refining in the high purity purification of tin containing tin as a main impurity. The present invention relates to a method and apparatus for purifying indium by electrolytic refining at a temperature not lower than the melting point of an electrolyte using indium monochloride or a complex compound of indium monochloride and zinc chloride as an electrolyte.

Indium, molten salt electrolytic, indium monochloride, zinc chloride

Description

Method for manufacturing the high purity Indium and the apparatus therefor}

1 is a molten salt electrolytic apparatus used in the present invention.

Explanation of symbols on the main parts of the drawings

1: electrolyzer 2: anode crucible 3: anode connector

4: anode indium 5: cathode indium 6: electrolyte

7: inner wall 8: heater 9: cover

10: anode inlet 11: anode inlet cover 12: gas outlet

13: indium outlet 14: rectifier

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a purification method and apparatus for high purity of indium, which is a raw material of an indium tin oxide (ITO) target used in a transparent conductive film of a liquid crystal display.

In general, purification of indium has used electrolytic refining using an insoluble anode or electrolytic refining using an indium containing indium as an anode.

Conventionally, a method in which wet tablets such as an acid dissolution method, an ion exchange method, a solvent extraction method, etc. are combined is used. For example, after washing and pulverizing ITO scrap, it is dissolved in nitric acid, hydrogen sulfide is blown into the solution, and tin, A method of precipitating and removing impurities such as lead and copper by sulfide, neutralizing by adding ammonia thereto, and recovering it as indium hydroxide is used.

Japanese Laid-Open Patent Publication No. 2001-240992 discloses a method for recovering indium by electrolytic purification, in order to prevent dendritic precipitates, which cause shorts, to adjust the conditions of the electrolytic solution and to prevent a decrease in current efficiency. An electropurification method of indium is disclosed which adjusts the chlorine ion concentration to 10 to 40 g / L using an alkali metal salt compound of hydrochloric acid, sodium chloride and potassium chloride in a liquid and indium chloride, and prevents the formation of dendritic electrodepositions.

U.S. Patent No. 4,287,030 discloses primary vacuum dissolution at 850-940 ° C for 1-5 hours, secondary dissolution at 950-1,100 ° C for 0.5-2 hours before electrolytic purification in hydrochloric acid solution. A method for re-dissolving in dissolving indium at 450 ° C is disclosed.

In addition, U.S. Patent No. 5,543,031 discloses a channel purification method using sulfuric acid solution as an anode solution in an anode chamber and an indium-containing aqueous solution as a cathode solution in a cathode chamber, and using an anion exchange membrane between both chambers. have.

The above methods use an aqueous solution in which indium is present in an ion state of In 3+ as an electrolyte, and obtain purified indium electrodeposited on the cathode by a current applied through a rectifier. Although aqueous solution electrolysis of indium has been studied for a long time and is a commercially proven method, since the current density range for obtaining high purity indium is low as 0.1-2.0 A / dm ² , a large number of products are required for mass production due to low productivity. An electrolyzer is needed.

Also, due to the recent development of the liquid crystal industry, ITO waste target scrap used in the liquid crystal transparent conductive film has been used as a raw material for indium refining. In this case, the main impurity must be separated. Since tin has a very similar chemical property to indium, the presence of tin in the electrolyte or anode indium acts as a factor that inhibits the purity of indium. Therefore, the process of removing tin before the aqueous solution electrolysis is essential. There was a problem.

The present invention has been made by the present inventors to solve the above problems of the conventional aqueous solution electrolysis, the purpose of the present invention is to provide a purification method and apparatus that can increase the productivity and directly purify indium having a high tin content. have.

In order to achieve the above technical problem, the present invention provides a high-purity indium production method characterized by purifying indium with high purity by molten salt electrolysis using indium chloride (InCl) as a molten salt electrolyte.

In addition, the present invention provides a high-purity indium production method characterized in that it further comprises zinc chloride (ZnCl ₂ ) in the electrolyte of indium chloride (InCl).

In addition, the present invention provides a high-purity indium production method characterized in that the zinc chloride is 33 to 50 wt% compared to indium monochloride.

The present invention also provides a high-purity indium production method, characterized in that the temperature of the molten salt electrolyte is 200 ~ 350 ℃.

In addition, the present invention provides a high-purity indium production method characterized in that the current density during the molten salt electrolysis is 10 ~ 30 A / dm ² .

In addition, the present invention is made of a conductive material, the upper portion of the inner wall is insulated, the lower portion of the inner wall is not insulated, the upper surface is a cathode electrolytic cell sealed with a non-conductive cover having a charge in which the anode indium or the electrolyte is charged; A cathode crucible positioned inside the cathode electrolytic cell and accommodating anode indium; An indium outlet for continuously purifying indium under the cathode electrolyzer; A stop value for passing an electric current between the anode crucible and the cathode electrolyzer; It provides a high purity indium production apparatus, characterized in that consisting of; a heater for controlling the temperature of the cathode electrolyzer.

In addition, the present invention provides a high-purity indium production apparatus characterized by using a positive electrode connector for the positive electrode.

In addition, the present invention provides a high-purity indium production apparatus, characterized in that the anode connector is a group 4 to 6 metal or graphite on the periodic table.

Hereinafter, the structure of the manufacturing method of this invention is demonstrated in detail.

Among the indium compounds, chloride is most suitable for the composition of the electrolyte. Indium chloride includes indium chloride (InCl), indium dichloride (InCl ₂ ), and indium trichloride (InCl ₃ ) as an electrolyte to improve productivity. This is the best fit. Since indium in the molten indium chloride (InCl) is present as an indium monovalent ion (In ⁺ ), productivity is three times higher than that of an aqueous solution using In ³⁺ under the same current conditions.

The electrolyte may be used alone with indium monochloride. However, even when the tin content is greater than 0.01% or the tin content is less than 0.01%, if the tin component in the purified indium needs to be reduced to 2 ppm or less, the electrolyte may be used together with InCl. Two or more composite electrolytes are used by adding the compound of 2, i.e. chloride. Secondary chlorides other than InCl include NaCl, KCl PbCl ₂ , MgCl _2, and ZnCl ₂ , but ZnCl ₂ is most suitable in consideration of workability because ZnCl ₂ and InCl complex chloride have the lowest melting temperature. Three or more kinds of bichlorides are not preferable because the purification efficiency is not significantly improved and electrolyte management becomes difficult compared to two kinds of bichlorides, for example, InCl + ZnCl ₂ .

When InCl and ZnCl ₂ are used together as an electrolyte, the mixing ratio of ZnCl ₂ is 33 to 50 wt%, and InCl 57 wt and ZnCl ₂ 43 wt% are most suitable. This is because the melting point in the above ratio is the lowest, allowing operation at a relatively low temperature. When ZnCl ₂ is less than 33 wt%, the separation efficiency of tin is lowered, and when it is 50 wt% or more, there is a problem that the zinc component in the purified indium rapidly increases.

When electrolytic refining is possible, the temperature of the electrolyte may be higher than the melting temperature of the electrolyte at 137 ° C or higher. However, if the temperature is 200 ° C or lower, the fluidity of the molten electrolyte is poor and the refining effect and current efficiency are deteriorated. Although the loss is caused by the evaporation of the electrolyte, the temperature of the electrolyte is most appropriate between 200 ~ 350 ℃.

In the case of the negative electrode, the electrolytic cell itself can be used as the negative electrode.

The current density during electrolysis is 10 ~ 30 A / dm ² , and the purification effect is improved at 10 A / dm ² or less, but there is a problem in productivity. If it is higher than 30 A / dm ^2, it is difficult to obtain high purity indium, especially copper (Cu More precious metal components than indium such as lead, lead (Pb) and tin (Sn). The current density is 5 ~ 300 times higher than the 0.1 ~ 2.0 A / dm ² used in the aqueous solution can be expected high productivity.

EMBODIMENT OF THE INVENTION Hereinafter, the apparatus of this invention as an Example which can implement said method invention is demonstrated in detail.

1 is a schematic diagram of the apparatus of the present invention. The electrolytic cell 1 is made of a conductive material and serves as a cathode, and the upper part of the inner wall is an insulating layer 7 insulated with an insulator such as quartz, and the lower part of the inner wall is not insulated, Is sealed with a non-conductive cover 9. The heater 8 is provided in the outer periphery of the side surface and the lower surface of the electrolytic cell 1.

The non-conductive cover 9 is provided with a charging inlet 10 into which the positive electrode indium 4 to be purified or the electrolyte 6 is charged, and the charging inlet 10 is provided with a lid 11 and a non-conductive cover. At any position of (9), a gas discharge port 12 through which product gas is discharged is provided.

An anode crucible 2 in which the anode indium 4 is accommodated is mounted inside the electrolytic cell 1. The cathode crucible 2 should not be reactive with the molten indium 4 and the indium compound. Pyrex or quartz are preferable as the material, and the cathode crucible 2 is preferably formed in a circular shape so as to balance the current.

In addition, a stop 14 for passing a current is disposed between the anode indium 4 and the electrolytic cell 1 as the cathode.

1 shows a molten salt electrolyzer of the type in which the conductor connector 3 is used.

Molten salt electrolysis basically uses indium to be purified as an anode, but may also provide a conductor connector 3 for connecting a stop from molten indium. The conductor connector 3 should be a conductor that is not reactive with molten indium and should have high corrosion resistance. As a usable material, graphite or a Group 4-6 element on the periodic table, that is, a refractory metal, is preferable as the conductor connector.

Hereinafter, the action of the molten salt device of the present invention will be described.

After charging the anode indium 4 into the anode crucible 2 through the injection hole 10 in the electrolytic cell 1, the electrolyte 6 is injected through the same injection hole 10. After that, the heater 8 is heated to adjust the temperature, and then a current is supplied from the stop 14 installed between the anode and the cathode. At this time, the positive electrode indium (4) may be supplied with a current directly, but the positive electrode connector (3) may be connected to supply current.

Gas generated during electrolysis is discharged through the gas outlet 12 to pass through a scrubber (not shown), and the purified indium 5 collected at the cathode is obtained through the indium outlet 13. The electrolytic apparatus has the advantage that the work can be continuously performed through the anode inlet 10 and the indium outlet (13).

EMBODIMENT OF THE INVENTION Hereinafter, the Example of this invention is described in detail.

Example 1

Among the impurities, molten salt electrolysis was performed using indium having a tin component of 30 ppm as an anode and using two kinds of electrolytes, InCl and InCl + ZnCl ₂ . After electrolytic refining at a current density of 10 A / dm ² and a temperature of 250 ° C., the purity of purified indium was analyzed by ICP. The results are shown in Table 1 below. In case of using InCl + ZnCl ₂ composite electrolyte, the removal efficiency of tin was higher than that of InCl alone, and both were purified to 99.998% or more.

TABLE 1Components of purified indium according to electrolyte

element Content (ppm) anode Purified Indium (InCl) Purified Indium (InCl + ZnCl ₂ ) Cu 2 <1 Not detected Pb 3 2 One Zn One <1 One CD One <1 Not detected Fe 2 <1 <1 As One Not detected Not detected Ni One Not detected Not detected Sb 2 One Not detected Ag One <1 <1 Al One <1 <1 Sn 29 5 One water(%) 99.99 99.998 99.999

Example 2

Molten salt electrolysis was carried out using indium with 10% tin in the impurity as an anode and InCl + ZnCl ₂ as an electrolyte. The current density was 10 A / dm ² and the temperature was 320 ° C. after electrolytic refining, the purity of the purified indium was analyzed by ICP. The results are shown in Table 2. Electrolytic refining of cobalt containing 10% tin content and purity up to 90% yielded 4N (99.99%) refined indium and found that InCl + ZnCl ₂ composite electrolyte is very effective for removing tin. Can be.

Table 2 Components of Purified Indium according to Electrolyte

element Content (ppm) anode Refined indium Cu 90 <1 Pb 130 2 Zn 10 One CD 10 3 Fe 100 <1 As 5 Not detected Ni 20 Not detected Sb 5 One Ag 100 <1 Al 5 2 Sn 10 (%) 87 water(%) 90 99.99

Example 3

In general, molten salt electrolysis was performed using 99.9% 3N (three nine) indium indium, which is the purity of indium recovered first from indium scrap, as an anode, and InCl + ZnCl ₂ as an electrolyte. The current density was 15 A / dm ² , and the temperature was 280 ° C. After electrolytic refining, the purity of purified indium was analyzed by ICP. The results are shown in Table 3 below. The purity after purifying 3N of indium satisfies 99.998%, the purity required for ITO.

Table 3 Components of Purified Indium according to Electrolyte

element Content (ppm) anode Refined indium Cu 39 <1 Pb 13 One Zn 5 7 CD One One Fe 5 Not detected As One Not detected Ni 20 Not detected Sb 9 One Ag 5 Not detected Al One <1 Sn 470 2 water(%) 99.9 99.998

Comparative Example

The purified indium was analyzed by ICP after electrolysis using an anode used in Example 3 at a temperature of 30 ° C. in an aqueous solution of indium at a concentration of 40 g / l and a chlorine concentration of 100 g / l using a current density of 2 A / dm ² . The results are shown in Table 4. According to the results below, the aqueous solution electrolysis has a purification effect, but it can be confirmed that the concentration of impurities is higher than that of molten salt electrolysis.

Table 4 Components of Purified Indium after Electrolytic Solution

element Content (ppm) anode Refined indium Cu 39 4 Pb 13 3 Zn 5 <1 CD One 2 Fe 5 4 As One 3 Ni 20 2 Sb 9 4 Ag 5 2 Al One 2 Sn 470 8 water(%) 99.9 99.996

As described above, according to the present invention, low indium containing a large amount of impurities, including tin, has an excellent effect of producing high purity indium up to 99.999% with high tin separation efficiency and high productivity.

Molten salt electrolysis has the advantage that it does not require a large amount of electrolyte solution, such as aqueous solution electrolysis, and pH control is also unnecessary.

Claims (8)

A high purity indium production method characterized by purifying indium with high purity by molten salt electrolysis using indium monochloride (InCl) as a molten salt electrolyte. The method of claim 1, further comprising zinc chloride (ZnCl ₂ ) in the electrolyte of indium monochloride (InCl). The method according to claim 2, The zinc chloride is a high purity indium production method, characterized in that 33 to 50 wt% compared to indium monochloride. The method according to any one of claims 1 to 3, A high purity indium production method, characterized in that the temperature of the molten salt electrolyte is 200 ~ 350 ℃. The method according to any one of claims 1 to 3, High purity indium production method characterized in that the current density during the molten salt electrolysis is 10 ~ 30 A / dm ² . A cathode electrolyzer made of a conductive material, the upper portion of the inner wall is insulated, and the lower portion of the inner wall is not insulated, and the upper surface is sealed with a non-conductive cover having a charging hole into which an anode indium or an electrolyte is charged; A cathode crucible positioned inside the cathode electrolytic cell and accommodating anode indium; An indium outlet for continuously purifying indium under the cathode electrolyzer; A stop value for passing an electric current between the anode crucible and the cathode electrolyzer; A heater controlling a temperature of the cathode electrolyzer; High purity indium production apparatus, characterized in that consisting of. The method according to claim 6, High purity indium production apparatus, characterized in that for use in the positive electrode connector. The method according to claim 7, The anode connector is a high purity indium manufacturing apparatus, characterized in that the graphite or a Group 4 to 6 metal on the periodic table.

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