KR101766863B1 - Recovery of indium from the waste acid including indium - Google Patents

Abstract

The present invention provides a method of recovering indium from a waste acid containing indium comprising: a first step of reacting the waste acid containing indium with an organic acid by adding the organic acid after adjusting the waste acid to a pH of 1.5-2.5; a second step of adjusting the reaction mixture obtained by the first step to be at a pH of 5-6 by filtering the reaction mixture and adding a carbonic acid alkalizing agent to the filtered reaction mixture; and a third step of cleaning and drying a solid matter obtained by filtering the reaction mixture obtained by the second step. According to the present invention, the method of recovering indium from the waste acid containing indium is remarkably helpful for a follow-up filtering and cleaning step as a grain size of the solid matter obtained at cheap costs is large. In the case of electrowinning at a pH of 1-2 after dissolving the solid matter obtained by filtering and cleaning in an acid, a 99.9 percent pure indium (In) metal is obtained.

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for recovering indium from a waste acid containing indium,

The present invention relates to a method for recovering indium contained in waste acid.

Indium Tin Oxide (ITO) is a material having conductivity as well as transparency, and is used as a flat panel display such as a liquid crystal display (LCD), a plasma display panel (PDP), an organic light emitting device (OLED) The demand for transparent electrodes for manufacturing is continuously increasing. , And thus the amount of waste of ITO waste acid is also increasing.

However, since ITO is a very stable material, it requires a mixed acid solution of strong acids such as hydrochloric acid, nitric acid, and sulfuric acid to etch it. Since indium, which constitutes ITO, is an expensive metal, a lot of efforts have been made to recover indium from the waste ITO solution. The method for recovering indium is to neutralize the metal impurities by neutralizing with an alkaline agent, neutralize the filtrate, dissolve the precipitate in acid, add Al or Zn chips to collect indium metal by redox reaction or electrolyze by electrolysis A method of collecting an acid by using vacuum extraction distillation or dialysis, a method of collecting an acid by electrolytic sampling or an Al chip or the like A method of recovering indium by a reduction method is known.

However, the neutralizers used by these methods are expensive, have a high treatment cost, are accompanied by odor, and need to be improved by generating wastewater.

The present invention provides a method for recovering indium from a waste acid containing indium that can recover indium more economically with improved productivity.

The above-

Adding a carbonate-based alkalizing agent to the indium-containing waste acid to adjust the pH to 1.5 to 2.5, and then adding and reacting the organic acid;

A second step of firstly filtering the reaction mixture obtained according to the first step and adding a carbonic acid alkalizing agent to the filtrate to adjust the pH to 5 to 6; And

A second step of filtering the reaction mixture obtained in the second step, and a third step of washing and drying the obtained solid material, and recovering indium from the indium-containing waste acid.

And further performing an electrolytic harvesting or oxidation-reduction reaction of the product obtained in the third step to obtain indium.

According to the method of the present invention, it is possible to recover indium (In) metal having a purity of 99.99% or more while decreasing the filtration time from indium-containing waste acid at an inexpensive price.

BRIEF DESCRIPTION OF THE DRAWINGS Fig. 1 is a flow chart showing each step of a method for recovering high purity indium from an indium-containing waste acid according to the present invention.

Hereinafter, a method for recovering indium of high purity from indium-containing waste acid according to the present invention will be described in more detail.

Adding a carbonate-based alkalizing agent to the indium-containing waste acid to adjust the pH to 1.5 to 2.5, and then adding and reacting the organic acid;

A second step of filtering the reaction mixture obtained according to the first step and adding a carbonic acid alkalizing agent to the filtrate to adjust the pH to 5 to 6; And

And a third step of filtering the reaction mixture obtained according to the second step and washing and drying the obtained solid matter, and recovering indium from the indium-containing waste acid.

The indium-containing waste acid refers to a waste liquid generated after etching of an ITO film used as a conductor of a flat panel display, a touch panel, and a solar cell.

The pH is adjusted to 1.5 to 2.5 by adding a carbonic acid alkalizing agent to the indium-containing waste acid. If the pH is out of the above range, impurities may be contained in the finally obtained indium and the purity of indium may be lowered, which is not preferable.

Subsequently, the organic acid is added to the mixture, reacted for a predetermined time, and metal impurities, particularly lead, are removed through precipitation filtration. Here, the metal impurity acts as an obstacle in the electrolytic sampling step for obtaining indium, and it is preferable to remove lead, in particular.

A carbonic acid alkalizing agent is added to the filtrate to adjust the pH to 5 to 6, followed by filtration to obtain a solid. Here, when the pH is out of the above range, it is difficult to obtain a solid form, and the efficiency of recovering indium is lowered.

The indium may be recovered from the indium-containing waste acid further comprising the step of dissolving the product obtained in the third step in an acid, adjusting the pH to 1 to 2, and then conducting an electrolytic pickling or oxidation-reduction reaction to obtain indium .

In the conventional indium recovery method, expensive alkalizing agents such as caustic soda, caustic soda, and ammonia water are used for neutralization. Especially, when ammonia water is used, waste water is generated accompanied with odor, and particularly in the case of solid matters such as indium hydroxide The filtration property is poor and the productivity is low. Here, the indium hydroxide is poor in the filtration property because it is in the form of a weak flock. In addition, when the vacuum decompression distillation is used as the conventional indium recovery method, the energy cost is high. In the case of the dialysis, the installation and operation costs are large.

In contrast, in the present invention, the solid material has a mixture of indium carbonate and indium hydroxide [a mixture of In ₂ (CO 3) ₃ In (OH) ₃ ] or indium carbonate. Such solids exist in the form of flocs, and when they are carried out according to the conventional method, the crystal grains are larger than those of indium hydroxide, which has poor filtration property, so that the filtration property is greatly improved. And metal impurities derived from the use of the carbonate-based alkalizing agent can be effectively removed in the electrolytic harvesting step.

Hereinafter, with reference to Fig. 1, each step of the manufacturing method according to the present invention will be described in more detail.

First, the indium-containing waste acid is used as an indium-containing waste acid (mainly ITO waste etching solution used as a transparent conductor) generated in a flat panel display manufacturing process of a PDP, an LCD, an OLED, or a touch panel manufacturing process or a manufacturing process of a thin film solar cell .

The wastewater acid solution is introduced into the reaction tank and then the carbonate-based alkalizing agent is slowly added. In general, the ITO etching waste solution is a hard material that is not well etched by ITO, and is composed of strong acids such as hydrochloric acid, nitric acid, and sulfuric acid. In the neutralization, the amount of alkalizing agent consumed at the initial low pH is mostly, The alkaline agent should be added with caution when the pH is near 1 because the pH is elevated even when a little alkali is added.

The carbonic acid alkalizing agent may be, for example, potassium carbonate (K ₂ CO ₃ ), calcium carbonate (CaCO ₃ ), sodium carbonate (Na ₂ CO ₃ ), ammonium carbonate [(NH ₄ ) ₂ CO ₃ ] and sodium hydrogen carbonate ₃ , magnesium carbonate).

When the pH of the reaction tank is adjusted to 1.5 ~ 2.5, organic acid is added.

The organic acid may be, for example, citric acid, oxalic acid, malonic acid, malic acid, tartaric acid, acetic acid, fumaric acid, lactic acid, formic acid, propionic acid, butyric acid, iminodiacetic acid, glyoxylic acid, ascorbic acid, lactic acid, wherein the acid is selected from the group consisting of maleic acid, acrylic acid, valeric acid, pivalic acid, hexanoic acid, t-octanoic acid, 2- 2-ethyl-hexanoic acid, neodecanoic acid, lauric acid, stearic acid, oleic acid, naphthenic acid, dodecanoic acid, dodecanoic acid, and linoleic acid.

As an example of an organic acid, oxalic acid is used. The content of the organic acid is 2.5 to 12.5 equivalents, for example, 5 to 10 equivalents, relative to 1 equivalent of lead (Pb). After the organic acid is added, the mixture is agitated for 4 to 6 hours, aged and subjected to the first filtration.

The aging is carried out, for example, at 45 to 70 ° C. The aging time depends on the aging temperature, but ranges, for example, from 1.5 to 4 hours.

Primary neutralization is carried out at a pH of 1.5 to 2.5 and an organic acid such as oxalic acid is added to remove metal impurities such as Pb and then carbonic acid alkali is added to obtain a solid having a high crystal grain size and good filtration property.

The filtrate is neutralized to a pH of 5 to 6 by slowly adding a carbonic acid alkali to the filtrate. The solid precipitates precipitate, which is in the form of flocs, unlike indium hydroxide, which is poor in filtration, and has a large grain size and greatly improved filtration. This solid is washed with purified water and dried to give a product.

The drying is carried out, for example, at 20 to 60 ° C, for example, at 25 to 50 ° C.

The filtration time required for the second filtration of the solid after neutralization to pH 5 to 6 is 40 minutes or less, for example, 20 to 35 minutes. Thus, the time required for filtration is remarkably reduced as compared with the conventional method.

According to the indium recovery method of the present invention, an In metal having a purity of 99% or more, preferably 99.99% or more can be obtained.

The indium-containing solid obtained according to the above process may be subjected to an electrolytic picking reaction and / or an oxidation-reduction reaction to conduct high purity indium.

The electrolytic picking reaction and the oxidation-reduction reaction are carried out according to a method commonly used in the art.

Electrolytic sampling is a process in which metal ions present in a solution are precipitated by externally applying a voltage. Indium can be effectively recovered by adjusting the current density during electrolysis.

In the electrolytic picking reaction, the indium-containing solid obtained according to the above procedure is dissolved in an acid to adjust the pH to 1 to 2, and then electrolyzed to obtain high purity indium.

The redox reaction is to deposit an aluminum (Al) chip or a zinc (Zn) chip to precipitate indium by redox.

Hereinafter, the present invention will be described in more detail with reference to the following examples, but the present invention is not limited thereto.

The indium-containing waste acid used in this experiment was a thin film transistor-

transistor liquid crystal display (TFT-LCD) manufacturing process, and the composition shown in Table 1 below

ingredient Total
(as H2SO4) Hydrochloric acid Sulfuric acid nitric acid content(%) 19.8 8.7 7 1.4 ingredient Fe Cu Sn Al Pb Zn In Content (ppm) 8 1.2 5 0.4 22 24 376

Example  One

Sodium carbonate (soda ash) was added to 2 liters of an In-containing spent acid having the composition shown in Table 1 to adjust the pH of the mixture to about 2.1. Then, 2 g of oxalic acid (content of oxalic acid relative to 1 equivalent of lead (Pb) in the indium-containing waste acid was 7.46 equivalent) was added to the mixture, followed by stirring for 5 hours and filtration. The pH of the mixture was adjusted to 5.6 by addition of sodium carbonate to the filtrate.

The reaction mixture was stirred slowly for about 3 hours to form crystals. The obtained crystals were filtered, and the filtered solid was washed once with distilled water, then placed in an oven maintained at 50 ° C, and dried. 0.5 g of the dried product was dissolved in 50 ml of a 50% hydrochloric acid solution, and the solution was appropriately diluted and analyzed by ICP-OES (Model: Plasma 7000 DV, Perkin Elmer, USA).

Example  2

2 g of oxalic acid (content of oxalic acid relative to 1 equivalent of lead (Pb) in the indium-containing waste acid is 7.46 equivalent) was added to 2 liters of indium-containing waste acid to adjust the pH to about 2.0 by adding soda ash After agitation, filtration was carried out. Soda ash was added to the filtrate again to adjust the pH to 5.5, and the mixture was slowly stirred for 3 hours to form crystals. The resulting solid was filtered.

The solids were washed once with distilled water and then placed in an oven maintained at 50 < 0 > C and allowed to dry. 0.5 g of the dried product was dissolved in 50 ml of a 50% hydrochloric acid solution, and the solution was appropriately diluted and analyzed by ICP-OES (Model: Plasma 7000 DV, Perkin Elmer, USA).

Example  3

Except that the content of oxalic acid was changed to 1.34 g (1 equivalent of lead (Pb) in indium-containing waste acid to 5 equivalents of oxalic acid).

Example  4

Except that the content of oxalic acid was changed to 2.01 g (the content of oxalic acid was 7.5 equivalents relative to 1 equivalent of lead (Pb) in the indium-containing waste acid)).

Example  5

Except that the content of oxalic acid was changed from 2.68 g (1 equivalent of lead (Pb) in the indium-containing waste acid to 10 equivalent of oxalic acid).

Example  6

Except that the content of oxalic acid was changed from 0.67 g (1 equivalent of lead (Pb) in indium-containing waste acid to 2.5 equivalents of oxalic acid).

Example  7

Except that the content of oxalic acid was changed from 3.35 g (1 equivalent of lead (Pb) in the indium-containing waste acid to 12.5 equivalents of oxalic acid).

Comparative Example  One

Sodium carbonate (soda ash) was added to 2 liters of the impurity-containing waste acid having the composition shown in Table 1 to adjust the pH of the mixture to about 2.2. The pH of the mixture was then adjusted to 5.7 by the addition of sodium carbonate to the mixture.

The reaction mixture was stirred slowly for about 3 hours to form crystals. The obtained crystals were filtered, and the filtered solid was washed once with distilled water, then placed in an oven maintained at 50 ° C, and dried. 0.5 g of the dried product was dissolved in 50 ml of a 50% hydrochloric acid solution, and the solution was appropriately diluted and analyzed by ICP-OES (Model: Plasma 7000 DV, Perkin Elmer, USA).

Comparative Example  2

The pH was adjusted to about 1 by using sodium hydroxide (caustic soda) in the form of flakes in 2 liters of the impurity containing In having the composition shown in Table 1, neutralized to pH 2.0 with 50% sodium hydroxide solution (caustic soda) Respectively. The filtrate was adjusted to pH 5.4 using a liquid 50% caustic soda and stirred slowly for 3 hours to obtain a solid. The obtained solid was subjected to filtration in the same manner as in Example 2.

Evaluation example  1: Inductive coupling plasma  Spectrometer ( ICP- OES (Inductively Coupled Plasma Optical Emission Spectrometer: ICP- OES ) analysis

The products obtained in accordance with Example 1 and Comparative Example 1 were analyzed using an inductively coupled plasma spectrometer. As the inductively coupled plasma spectrometer, ICP-OES (Model: Plasma 7000 DV) manufactured by Perkin Elmer of USA was used.

The results of the analysis are shown in Table 2 below.

ingredient In recovery rate In
(%) Fe
(ppm) Cu
(ppm) Sn
(ppm) Al
(ppm) Pb
(ppm) Zn
(ppm) Example 1 91.1% 30.42 3,378 122 1,920 40 17 27,100 Comparative Example 1 91.3% 30.37 3,573 1375 1,857 41 23,400 26,300

Referring to Table 2, it was found that the effect of oxalic acid on the removal of Pb adversely affecting electrolytic harvesting was very good.

2) Example 2-6

When carried out according to Examples 2 to 6, the final product obtained

ICP-OES analysis was performed. The content of lead identified through ICP-OES analysis is shown in Table 3 below. Lead is a major metal component that acts as an obstruction in electrolytic harvesting.

Example 3 Example 4 Example 5 Example 6 Example 7 Oxalic acid dosage 5 eq.
(1.34 g) 7.5 equivalent
(2.01 g) 10 equivalent
(2.68 g) 2.5 eq.
(0.67 g) 12.5 equivalent
(3.35 g) Pb (ppm) 23 21 18 55 18

As shown in Table 3, when the content of oxalic acid is in the range of 2.5 to 12.5 equivalents, the lead (Pb) removal effect is excellent, and in particular, 5 to 10 equivalents are most suitable.

Evaluation example  2: Filtration time

The filtration time of the solid material was examined in accordance with Example 2 and Comparative Example 2, and the results are shown in Table 4 below.

Filtration time Example 2 Comparative Example 2 minute 31 92

As shown in Table 4, it can be seen that the time taken for filtration is significantly reduced as compared with Comparative Example 2 when it is carried out according to Example 2.

The filtration time required for filtration was the same as in Example 2, when the filtration was carried out according to Example 1 and Examples 2 to 6 above. As described above, it was confirmed that the filtration time of Example 1-6 was much shorter than that of Comparative Example 2.

Evaluation example  3: Purity of indium

The indium-containing solids prepared in Example 1-6 were dissolved in hydrochloric acid to adjust the pH to about 1 and electrolysis was performed. As for the electrolytic sampling conditions, a Pt mesh electrode was used as an anode, a Cu plate was used as a cathode, an electrolytic temperature was about 25 ° C, and a current density was adjusted to 1.0 to 5 ASD.

The purity of indium recovered through electrolysis was confirmed by ICP.

As a result, it was found that the In metal having a purity of 99.99% or more can be recovered by using the indium-containing solid produced according to Example 1-6.

While the present invention has been particularly shown and described with reference to exemplary embodiments thereof, it is to be understood that the invention is not limited to the exemplary embodiments or constructions. It will be apparent to those skilled in the art that various modifications and variations are possible in light of the above teachings will be. Accordingly, the scope of protection of the present invention should be determined by the appended claims.

Claims (6)

Adding a carbonate-based alkalizing agent to the indium-containing waste acid to adjust the pH to 1.5 to 2.5, adding an organic acid to react, and aging at 45 to 70 ° C for 1.5 to 4 hours;
A second step of firstly filtering the reaction mixture obtained according to the first step and adding a carbonic acid alkalizing agent to the filtrate to adjust the pH to 5 to 6; And
And a third step of washing and drying a mixture of indium carbonate (In ₂ (CO 3) ₃ ) and indium hydroxide (In (OH) ₃ ) obtained by filtering the reaction mixture obtained in the second step In addition,
The step of dissolving the product obtained in the third step in an acid, adjusting the pH to 1 to 2, and conducting an electrolytic pickling or redox reaction to obtain indium,
The organic acid recovers indium from the indium-containing waste acid added in an amount corresponding to 5 to 10 equivalents based on 1 equivalent of the existing lead (Pb) present in the indium-containing waste acid,
The organic acid may be selected from the group consisting of citric acid, oxalic acid, malonic acid, malic acid, tartaric acid, acetic acid, fumaric acid, lactic acid But are not limited to, formic acid, propionic acid, butyric acid, iminodiacetic acid, glyoxylic acid, ascorbic acid, lactic acid, Maleic acid, acrylic acid, valeric acid, pivalic acid, hexanoic acid, t-octanoic acid, 2-ethyl-hexanoic acid 2-ethyl-hexanoic acid, neodecanoic acid, lauric acid, stearic acid, oleic acid, naphthenic acid, dodecanoic acid, , Linoleic acid, and the like. The method according to claim 1,
The carbonic acid alkalizing agent used in the first and second steps may be potassium carbonate (K ₂ CO ₃ ), calcium carbonate (CaCO ₃ ), sodium carbonate (Na ₂ CO ₃ ), ammonium carbonate (NH ₄ ) ₂ CO ₃ , And sodium hydrogencarbonate (NaHCO ₃ , magnesium carbonate). delete delete delete delete

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