KR20150078431A - Method for recycling indium from ITO scrap - Google Patents

Abstract

The present invention relates to a method for collecting indium from an ITO scrap and, specifically, to a method for collecting high-purity indium from an ITO scrap, by effectively removing tin or the like using potassium iodide. A method for collecting indium from an indium tin oxide (ITO) scrap comprises: a step of leaching an indium tin oxide (ITO) scrap into hydrochloric acid or sulfuric acid (step 1); a step of precipitating impurities by adding potassium iodide (KI) to the leach solution (step 2); a step of removing the impurities from the leach solution (step 3); and a step of collecting indium by electrowinning the leach solution (step 4).

Description

METHOD FOR RECOVERING INDIUM FROM ITO SCRAPS

The present invention relates to a method for recovering indium in high purity from ITO scrap.

The present invention relates to a method for recovering indium from ITO scrap at a high purity, wherein ITO is a ceramic material having a cubic structure of In _(2-x) Sn _x O ₃ , wherein a part of the indium element is substituted with tin, And thus it is widely used as a transparent electrode material of a display device.

In particular, indium, which is a main component of ITO, is a metal that is used in various fields such as optical materials, optoelectronic materials, and compound semiconductors. However, since it is expensive, it is necessary to recycle indium from recovered materials or waste containing indium.

One of the important considerations in the method of recovering indium is the purity of indium. Since the recycling value is extremely low when the purity of indium is lowered, the removal of the remaining components other than indium should be considered important when the indium is recovered.

In particular, when indium is recovered from ITO scrap, it is necessary to remove tin, which is a main component other than indium. Conventionally, as a conventional tin removal method, a sulphation method and a solvent extraction method are known, but the above method has a low tin removal rate and a low recovery rate of indium, and thus has a limited application on an industrial scale.

The inventors of the present invention have made intensive studies on the method of recovering indium from ITO scrap at a high purity. As a result, it has been confirmed that indium can be recovered in high purity by a method of precipitating and removing tin as an insoluble compound by using potassium iodide, .

The present invention is to provide a method for recovering indium from ITO scraps in high purity.

In order to solve the above problems, the present invention provides a method for recovering indium from indium tin oxide (ITO) scrap comprising the steps of:

The step of leaching indium tin oxide (ITO) scrap into hydrochloric acid or sulfuric acid (step 1);

Adding potassium iodide (KI) to the leaching solution to precipitate the impurities (Step 2);

Removing the impurities from the leach solution (step 3); And

And collecting the leached solution by electrolysis to recover indium (Step 4).

The present invention relates to a method for recovering high-purity indium from an ITO scrap using an electrolytic extraction method, wherein an ITO scrap is leached with hydrochloric acid or sulfuric acid to remove impurities by neutralization reaction and / or potassium iodide addition and then recovering high purity indium by electrolytic harvesting Method. In the electrolytic extraction method, indium of high purity can be obtained only by removing tin in which the reduction potential is noble than indium in the preliminary process (impurity removal step before electrolysis). Although existing methods of sulphurization and solvent extraction are disclosed as methods for removing tin, the present invention is characterized in that a method of precipitating and removing with an insoluble compound (tin iodide) is used by using potassium iodide. According to one embodiment of the present invention, tin was removed in a preliminary process (step), and electrolysis was performed to obtain indium having a purity of 99.9%. Hereinafter, each step will be described in detail.

The step 1 is a step of leaching indium tin oxide (ITO) scrap with hydrochloric acid or sulfuric acid to prepare an extract.

When the ITO scrap is reacted with hydrochloric acid or sulfuric acid, the components of the ITO scrap are dissolved. In addition to indium, tin, zinc, iron, copper, nickel and the like are leached out as main leaching components. Particularly, tin is leached in a considerable amount, and in order to recover high purity indium, removal of tin is required, which is tin-free in step 2 of the present invention to be described below.

The step 1 may further include filtering the leach solution. When leaching into hydrochloric acid or sulfuric acid, impurities other than the leaching solution may be contained, which may reduce the efficiency of the electrolytic harvesting method described below.

The method may further include the step of controlling the pH of the leaching solution to 1 to 3 after filtering the leaching solution. Since it leaches into hydrochloric acid or sulfuric acid, the leachate is in a strong acid state. When the pH of the leach solution is adjusted to 1 to 3, some of the components other than indium precipitate, so that the remaining components other than indium can be partially removed through pH control.

Step 2 is a step of adding potassium iodide to the leaching solution of step 1 to precipitate impurities. Due to the addition of potassium iodide, the remaining components other than indium become insoluble compounds and precipitation occurs. For example, tin present in a large amount in the leach solution reacts with potassium iodide to become tin iodide (SnI) and precipitate. The tin present in the leach can be removed by removing the precipitate.

The added amount of potassium iodide is preferably 0.1 to 10 g per liter (liter) of the leach solution.

Step 3 is a step of removing the impurities from the leach solution. Since the impurities exist in the form of a precipitate, they can be removed by filtration. Accordingly, most of the components other than indium can be removed from the leach solution.

In step 4, the leached solution is electrolyzed to recover indium. The term " electrolytic harvesting " used in the present invention is a step of precipitating metal ions present in a solution by externally applying a voltage. In the present invention, since indium is substantially present only in the leach solution, indium can be recovered in high purity through electrolysis. Indium can be effectively recovered by adjusting the current density during the electrolytic collection. In the present invention, a current density of 1 to 20 ASD can be used. More preferably, a current density of 1 to 5 ASD can be used.

According to an embodiment of the present invention, the purity of indium can be recovered to at least about 95%, preferably at least 97%, more preferably at least 99% by the above method.

INDUSTRIAL APPLICABILITY The method for recovering indium according to the present invention can effectively recover indium from ITO scrap by removing tin and the like by using potassium iodide.

Fig. 1 schematically shows a method of recovering indium of the present invention.

Hereinafter, the present invention will be described in more detail with reference to Examples. These examples are for further illustrating the present invention, and the scope of the present invention is not limited by these examples.

Example

Hereinafter, the entire process of the embodiment is schematically shown in FIG. 1, and specifically performed as follows.

1) Impurity analysis

20 g of abrasive scrap of ITO (indium tin oxide) and IZTO (indium zinc tin oxide) were leached out with hydrochloric acid and analyzed by ICP. 30 g of ITO sludge was leached with hydrochloric acid and the composition after leaching was as shown in Table 1 below.

ingredient In Sn Zn Fe Cu Ni mg / L 15939 2966 13.8 9.2 3.7 3.1

2) Removal of impurities by addition of potassium iodide

Potassium iodide (KI) was added to the solution changed pH in the leaching solution, and the iodide reaction of the impurities caused precipitation of the iodine compound. The precipitate was filtered to remove the impurities in the solution. The amount of KI and pH were controlled as follows.

I) Without KI

pH Removal rate (%) Zn Sn Fe Cu Ni 1.0 0.1 0.7 2.2 8.1 6.5 1.5 0.7 38.8 15.2 27.0 22.6 2.0 0.5 60.0 29.3 48.6 45.2 2.5 0.6 85.2 43.5 67.6 64.5 3.0 0.1 95.0 50.0 81.1 87.1

Ii) Addition of KI 0.1 g / L

pH Removal rate (%) Zn Sn Fe Cu Ni 1.0 0.2 10.1 5.4 18.9 3.2 1.5 1.2 77.5 19.6 32.4 22.6 2.0 38.2 92.6 32.6 48.6 48.4 2.5 47.9 98.0 48.9 56.8 67.7 3.0 60.4 100 54.3 86.5 80.6

Iii) Addition of KI 1.0 g / L

pH Removal rate (%) Zn Sn Fe Cu Ni 1.0 0.07 59.4 15.2 21.6 0 1.5 0.4 89.9 28.3 35.1 19.4 2.0 42.8 100 41.3 48.6 54.8 2.5 50.7 100 57.6 70.3 71.0 3.0 63.9 100 76.1 94.6 77.4

Iv) Addition of KI 10.0 g / L

pH Removal rate (%) Zn Sn Fe Cu Ni 1.0 0.27 100 37.0 48.6 6.5 1.5 0.47 100 51.1 59.5 22.6 2.0 54.1 100 67.4 73.0 51.6 2.5 63.5 100 79.3 81.1 67.7 3.0 78.4 100 95.7 99.4 77.4

3) Electrolytic recovery

Electrolytic recovery (electrowinning) was performed at 10 g / L potassium iodide (KI), pH 1.0. The solution composition and electrolysis conditions under these conditions were as shown in Tables 6 and 7 below.

ingredient In Zn Sn Fe Cu Ni mg / L 13667 13 0 5.8 1.9 2.9

Electrolytic recovery condition Anode material Pt / Ti mesh Cathode material Al plate Electrolysis temperature 40 ℃ Stirring speed 500 rpm Current density 1.0 to 20 ASD

20 g of indium was recovered by the above electrolytic recovery method and the impurities were analyzed by ICP. The results are shown in Table 8 below.

Current density (ASD) Zn (ppm) Sn (ppm) Fe (ppm) Cu (ppm) Ni (ppm) Indium purity Current efficiency One 0 0 0 1.851 0 99.988% 90% 2 0 0 0 1.855 0 99.987% 88% 5 0 0 0 1.887 0.075 99.922% 85% 10 0 0 0.149 1.828 0.104 97.411% 80% 20 5.649 0 0.203 1.810 0.177 95.737% 69%

As shown in Table 8, indium can be recovered to a purity of about 95% or more by the method according to the present invention. In addition, when the current density was adjusted to 1 to 5 ASD, the purity of indium could be recovered to about 99% or more.

Claims (6)

The step of leaching indium tin oxide (ITO) scrap into hydrochloric acid or sulfuric acid (step 1);
Adding potassium iodide (KI) to the leaching solution to precipitate the impurities (Step 2);
Removing the impurities from the leach solution (step 3); And
And recovering the indium from the electrolytic solution by withdrawing the leaching solution (Step 4).
A method for recovering indium from indium tin oxide (ITO) scrap.
2. The method of claim 1, wherein step 1 further comprises filtering the leach solution.
3. The method of claim 2, further comprising filtering the leach solution and then adjusting the pH of the leach solution to 1-3.
The method according to claim 1, wherein the amount of potassium iodide added in step 2 is 0.1 to 10 g per liter (liter) of the leach solution.
The method according to claim 1, wherein the step 3 is performed by filtering the leach solution.
The method of claim 1, wherein the current density of the electrolytic harvesting in step 4 is from 1 to 20 ASD.

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