JP4967155B2 - Method for treating indium-containing solution - Google Patents

Description

  The present invention relates to a method for treating an indium-containing solution that recovers indium from the indium-containing solution.

  With the recent rapid development of flat panel displays, solar cells and the like, the demand for indium-tin oxide (hereinafter sometimes referred to as ITO) used as these transparent conductive films is remarkably increasing. However, since indium resources are limited worldwide, the indium recycling technology is important. Here, an ITO scrap material such as ITO target scrap is used as a raw material for producing the ITO film. Therefore, several methods for recovering indium using ITO scrap material as a raw material have been proposed. The present applicant also proposed a method for recovering indium with a purity of 99.99% or more from ITO scrap material as Patent Document 1.

Here, a method for treating an indium-containing solution according to the prior art will be described with reference to FIG.
FIG. 2 is a flowchart of a conventional method for treating an indium-containing solution.
First, hydrochloric acid is added to an indium-containing material such as an ITO scrap material, and indium and the like are dissolved in the hydrochloric acid and leached as an indium-containing solution.
The indium-containing solution is neutralized by adding an alkali agent, and first, tin is precipitated and removed as a hydroxide. Next, hydrogen sulfide gas is blown into the indium-containing solution to precipitate and remove copper, remaining tin, and lead as sulfides. The indium-containing solution from which copper, tin, and lead are removed is electrolyzed, and indium is collected as cathode indium metal. Then, by casting the cathode indium metal, indium is obtained at the same time as separating sodium from the cathode indium metal.
JP 2006-22407 A

The indium recovery method described in Patent Document 1 is a useful method that can recover 99.999% or more of high-purity indium in a simpler process and at a lower cost than other conventional methods.
However, as a result of further studies by the present inventors, in the method described in Patent Document 1, hydrogen sulfide is blown into a tin removal solution to which an alkaline agent is added, and copper, residual tin, and lead are converted into sulfide. It was conceived that part of indium dissolved in the solution also became starch. And since the said indium starch will be isolate | separated from the said liquid with the other starch, it discovered that the loss has arisen in the collection | recovery of indium.

  Here, the present inventors tried to suppress the generation of indium starch by reducing the amount of hydrogen sulfide blown in order to suppress the recovery loss of the indium. However, when the amount of hydrogen sulfide blown is reduced, it has now been found that other elements, particularly lead, are not sufficiently sulfided and cannot remain starch and remain dissolved in the liquid. . In this case, the lead in the liquid is not sufficiently separated, and when the indium-containing solution is electrolyzed, the lead concentration in the electrolytic base solution cannot be stably reduced to 0.1 mg / L or less. If the lead concentration in the electrolytic source solution is higher than 0.1 mg / L, the lead quality in the final product, indium, becomes high. In this case, since the quality of the recovered indium is lowered, it becomes difficult to recover the indium itself.

  Therefore, the problem to be solved by the present invention is to provide a method for treating an indium-containing solution that achieves both the suppression of indium loss and the maintenance of the quality of recovered indium.

In order to solve the above-mentioned problems, the present inventors conducted extensive research. And after adding an alkali to the indium-containing solution mentioned above and neutralizing and precipitating and removing tin ions as a hydroxide, activated carbon powder is added to the detinized indium-containing solution to remove lead by adsorption. I came up with it.
Then, hydrogen sulfide gas at a level that does not generate indium deposits is blown into the indium-containing solution that has undergone detinning and deleading, and copper and residual traces of tin and lead are removed as sulfides, thereby indium. The inventors have conceived that the quality of the recovered indium can be maintained while suppressing the loss, and the present invention has been completed.

That is, the first means for solving the above-described problem is:
Adding activated carbon to a solution containing lead and indium to adsorb lead;
Adding a sufficient amount of a sulfiding agent to sulfidize lead remaining in the solution into the solution, and removing the remaining lead as sulfides;
And a step of collecting indium from the solution from which the lead sulfide has been removed.

The second means is
In the step of adding activated carbon to the solution containing lead and indium to adsorb lead,
The method for treating an indium-containing solution according to the first means, wherein activated carbon is added in two or more portions.

The third means is
In the step of adding activated carbon to the solution containing lead and indium to adsorb lead,
The method for treating an indium-containing solution according to the first or second means, wherein the oxidation-reduction potential of the solution is kept higher than 300 mV.

The fourth means is
4. The method for treating an indium-containing solution according to any one of the first to third means, wherein the sulfurizing agent is hydrogen sulfide.

The fifth means is
The solution containing lead and indium further contains at least one or more of copper or tin of 10 PPM or less,
In the step of adding a sulphurizing agent in an amount sufficient to sulfidize lead remaining in the solution and removing the remaining lead as a sulfide in the solution, at least one of the contained copper or tin The method for treating an indium-containing solution according to any one of the first to fourth means, wherein the seed or more is removed as sulfide together with lead.

  According to the present invention, in the treatment of an indium-containing solution, both the suppression of indium loss and the maintenance of the quality of recovered indium can be realized.

Here, a method for treating an indium-containing solution according to the prior art will be described with reference to FIG. FIG. 1 is a flowchart of a method for treating an indium-containing solution according to the present invention.
Also in the present invention, hydrochloric acid is first added to an indium-containing material such as an ITO scrap material, and indium and the like are dissolved in the hydrochloric acid to be leached as an indium-containing solution. Then, an alkali agent is added to the indium-containing solution for neutralization, and first, tin is precipitated and removed as a hydroxide.

Next, activated carbon is added to the indium-containing solution, and lead in the solution is adsorbed and removed by the activated carbon. Here, commercially available activated carbon can be used. As a form, a powdery thing is preferable in the case of addition and reaction. Furthermore, the activated carbon which adsorb | sucked the said lead can be collect | recovered with lead by reprocessing of acid dissolution and roasting.
Although the amount of the activated carbon added depends on the content of lead in the indium-containing solution, it may be about several mass% with respect to the liquid.
However, the lead concentration in the indium-containing solution before addition of activated carbon is preferably 1 ppm or less. As long as normal ITO scrap material is used as a raw material, the lead concentration in the indium-containing solution at this stage is 1 ppm or less. However, if the lead concentration is high for some reason, the indium at the stage is previously prepared by a method such as a sulfide precipitation method. It is preferable to keep the lead concentration in the contained solution at 1 ppm or less.

  As for the method of adding activated carbon, the whole amount may be added at one time, but it is more preferable to add it in several times. It is because it becomes easy to react with the unreacted lead in a solution by adding in several times. The removal of lead further proceeds by collecting the activated carbon and setting the oxidation-reduction potential of the solution to 300 mV or more, preferably about 600 mV. In order to increase the oxidation-reduction potential, an oxidizing agent such as hydrogen peroxide may be added to the solution.

Thus, in this invention, it uses, after removing a certain impurity like the liquid after neutralization. In other words, the liquid after removing impurities to some extent has a high concentration of the desired recovered metal. As a result, the concentration of impurities becomes relatively low relative to the concentration of recovered metal. In this case, in the separation of the overwhelmingly recovered metal and impurities, it becomes more difficult to separate only the impurities without losing only the recovered metal during processing. In such a case, the method of the present invention is more useful. Here, examples of the impurities include copper, tin, and the like in addition to the above-described lead, and these are elements contained in the ITO scrap.
As described above, since the lead concentration in the indium-containing solution is preferably set to 1 ppm or less, when the lead concentration in the indium-containing solution is set to 1 ppm or less in advance, the concentration of copper, tin, etc. is also 10 ppm. Since this will be described below, the present invention can be applied as it is thereafter.

By the above-mentioned operation, lead is co-precipitated and removed from the activated carbon, and copper and tin are also removed, but they are not completely removed but remain in the indium-containing solution. Hydrogen sulfide gas is blown into the indium-containing liquid, and copper, remaining tin, and lead are precipitated and removed as sulfides.
The amount of hydrogen sulfide gas blown at this time is about equivalent to the amount of impurities and sulfur. With the configuration in which the hydrogen sulfide gas was blown into an equivalent amount, indium in the indium-containing solution could remain in the solution without becoming a starch. On the other hand, copper, tin, and lead remaining in the solution are precipitated and removed as sulfides.

  Cathode indium metal is extracted from the indium-containing solution from which the copper, tin, and lead have been removed by electrowinning. Furthermore, sodium can be separated by casting the cathode indium metal. Through the above processing steps, indium having a purity of 99.99% or more can be recovered from the ITO scrap material as a recycled raw material with a yield of almost 100%.

Example 1
The ITO scrap material was dissolved and leached with hydrochloric acid, and the obtained leachate was neutralized by adding an alkali to adjust the pH to 2 or less, followed by filtration. The components of the neutralized solution obtained by filtration are shown in Table 1. The neutralized solution was used as the indium-containing solution according to this example. Table 1 shows the contents of indium, lead, tin, and copper in the indium-containing solution.
To 300 ml of the indium-containing solution containing lead, indium and the like, 3 g of activated carbon powder was added, and the mixture was pulped by stirring with a flat blade at 60 ° C. for 1 hour.
The obtained pulp was No. Solid-liquid separation was performed using 5C filter paper (1.0 μm). The solution obtained by the solid-liquid separation was used as a sulfurization source solution. The sulfurization source solution was adjusted to a redox potential of 340 to 350 mV by adding an alkali during the neutralization.
Next, the equivalent amount of hydrogen sulfide in which lead in the sulfidation source liquid is precipitated is calculated as equivalent to lead, copper, tin in terms of sulfur, and the equivalent amount of hydrogen sulfide is blown into the sulfidation source solution, Lead, tin, copper and the like were removed as starch to obtain an electrolysis solution.
Table 2 shows the concentrations of indium and lead in the neutralized solution, the sulfurization original solution after the activated carbon treatment, and the electrolytic original solution.
As is clear from the results in Table 2, by adding activated carbon to the solution after neutralization, lead can be separated in the sulfurization source solution, and the lead concentration in the electrolytic solution can be 0.1 ppm or less. And lead was remarkably separated. As a result, indium having a quality of 99.99% by mass or more could be obtained after casting.

(Example 2)
Activated charcoal powder was added 6 times, 0.5 g every 10 minutes, to 300 ml of the neutralized solution similar to Example 1. And it stirred with the flat blade for 1 hour at 60 degreeC from the time of the first activated carbon addition, and the pulp which concerns on Example 2 was obtained. Other conditions and operations were performed in the same manner as in Example 1.
Table 2 shows the concentrations of indium and lead in the obtained neutralized solution, sulfurization source solution, and electrolysis source solution.
As in Example 2, the addition of the activated carbon to the solution after neutralization was performed in a plurality of times, so that lead could be further separated and the lead concentration in the sulfurization source solution could be reduced. As a result, it was possible to reduce the amount of hydrogen sulfide used for blowing, to reduce raw material costs and to improve the yield of indium. Furthermore, indium having a quality of 99.99% by mass or more could be obtained after casting.

(Example 3)
3 g of activated carbon powder was added to 300 ml of the neutralized solution similar to Example 1 and stirred with a flat blade at 60 ° C. for 1 hour to obtain a pulp. Here, during the stirring, hydrogen peroxide water was added to the pulp, and the oxidation-reduction potential (Ag / AgCl electrode) of the pulp was kept at 600 mV or more.
The obtained pulp was No. Solid-liquid separation was performed using 5C filter paper (opening diameter: 1.0 μm). Thereafter, the same operation as in Example 1 was performed.
Table 2 shows the concentrations of indium and lead in the post-neutralization solution, the activated sulfur solution after activated carbon treatment, and the electrolysis solution according to Example 3.
As in Example 3, by keeping the oxidation-reduction potential of the pulp at 500 mV or higher, lead can be further separated, and the lead concentration in the sulfidizing liquid can be reduced. As a result, it was possible to reduce the amount of hydrogen sulfide used for blowing, to reduce raw material costs and to improve the yield of indium. Furthermore, indium having a quality of 99.99% by mass or more could be obtained after casting.

(Comparative Example 1)
The activated sulfur powder was added to 300 ml of the neutralized solution similar to Example 1 without adding activated carbon powder. Thereafter, the same operation as in Example 1 was performed.
Table 2 shows the concentrations of indium and lead in the post-neutralization solution, the activated sulfur solution after the activated carbon treatment, and the electrolytic solution according to Comparative Example 1.
Like Comparative Example 1, by making the sulfurization source liquid without adding activated carbon powder to the liquid after neutralization,
In order to remove lead, it was necessary to increase the amount of sulfiding agent added. As the addition amount of the sulfurizing agent increased, indium was also sulfided and turned into starch, resulting in loss of indium.
On the other hand, it was difficult to sufficiently separate lead without causing loss of indium.

It is process drawing which shows the indium collection | recovery method concerning this invention. It is process drawing which shows the indium collection | recovery method based on a prior art.

Claims (5)

Adding activated carbon to a solution containing lead and indium to adsorb lead;
Adding a sufficient amount of a sulfiding agent to sulfidize lead remaining in the solution into the solution, and removing the remaining lead as sulfides;
And a step of collecting indium from the solution from which the lead sulfide has been removed. In the step of adding activated carbon to the solution containing lead and indium to adsorb lead,
The method for treating an indium-containing solution according to claim 1, wherein the activated carbon is added in two or more times. In the step of adding activated carbon to the solution containing lead and indium to adsorb lead,
The method for treating an indium-containing solution according to claim 1 or 2, wherein the oxidation-reduction potential of the solution is maintained at a state higher than 300 mV.   The method for treating an indium-containing solution according to any one of claims 1 to 3, wherein the sulfurizing agent is hydrogen sulfide. The solution containing lead and indium further contains at least one or more of copper or tin of 10 PPM or less,
In the step of adding a sulphurizing agent in an amount sufficient to sulfidize lead remaining in the solution and removing the remaining lead as a sulfide in the solution, at least one of the contained copper or tin The method for treating an indium-containing solution according to any one of claims 1 to 4, wherein seeds or more are removed as sulfide together with lead.

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