JP4952899B2 - Indium recovery method - Google Patents

Description

The present invention relates to a method for recovering indium that efficiently deposits spongy metallic indium from an indium solution obtained by acid leaching of an indium-containing material, for example, an indium chloride solution.

An indium-tin oxide (ITO) thin film is widely used as a semiconductor material, and this thin film is generally formed by a sputtering method. An ITO high-density sintered body is used as a sputtering target material, and a large amount of ITO scrap is generated as a used target material. Since high-purity materials are used for ITO sintering and the price is high, indium is recovered from such scrap materials. As this indium recovery method, a method of recovering indium after dissolving ITO scrap in hydrochloric acid, adding sodium hydroxide to the solution to separate and separate tin in the solution by tin hydroxide precipitation is known. (Patent Documents 1, 2, and 3).

As the conventional indium recovery method, there are known a method of recovering metal indium by electrowinning and a method of recovering sponge indium by displacement deposition. In the electrowinning method, the pH of the indium chloride solution separated from tin in the solution by precipitation with tin hydroxide is adjusted to precipitate indium hydroxide, which is recovered by filtration and dissolved in sulfuric acid. It is a method of collecting metal indium by electrolysis, a method of adjusting the pH of the indium chloride solution to neutral (pH 5-6) to precipitate indium hydroxide (Patent Document 1), and adjusting the pH of the indium chloride solution to alkaline ( A method (Patent Document 2) in which indium hydroxide is aggregated and precipitated by adjusting the pH to 7-9) is known. On the other hand, the method for recovering sponge indium is a method in which zinc is added to an indium chloride solution from which tin hydroxide has been removed to displace and deposit sponge-like metal indium (Patent Document 3).

In the conventional method for recovering indium, the method of precipitating indium hydroxide and filtering it out is poor in filterability of the precipitate, and the process of dissolving the recovered indium hydroxide in sulfuric acid followed by electrolysis is complicated. It is.

On the other hand, in the conventional indium recovery method in which sponge indium is deposited by displacement precipitation, the pH of the indium solution obtained by leaching the indium-containing material is adjusted to 1.5 to 2.5 so that indium hydroxide does not precipitate. And adding zinc powder to deposit sponge-like metal indium (Patent Document 4), adjusting the pH to 0.5 to 1.5 and immersing the aluminum plate to deposit sponge-like metal indium A method (Patent Document 5) is known.

However, any of the conventional displacement deposition methods has a problem that the reaction does not proceed smoothly when the concentration of indium in the liquid is high. That is, in the conventional method of performing zinc substitution, when the indium concentration is 100 g / L or more, a thin indium film is formed on the surface of the zinc plate, hindering elution of zinc and inhibiting the substitution reaction between zinc and indium. The stationation will not progress. In addition, the aluminum substitution has a problem that when the indium concentration is high, the reaction is intense and the aluminum piece is entrained in the sponge indium, so that metal indium with few impurities cannot be obtained.
JP 2002-69684 A JP 2002-201025 A JP 2002-69544 A JP-A-11-269570 JP 09-268334 A

The present invention solves the above-mentioned conventional problems in a method for recovering sponge indium, and starts high-concentration indium solution by switching between zinc substitution and aluminum substitution according to the concentration of indium ions in the liquid. Provided is a method for efficiently recovering sponge-like metal indium in a short time as a raw material.

According to the present invention, a method for recovering indium that solves the above-described problems is provided by the following configuration.
[1] In a method of depositing metal indium by adding a base metal than indium to an indium solution obtained by acid leaching of indium-containing material, after adding zinc to the solution and depositing metal indium Furthermore, in place of zinc, aluminum is added to deposit metal indium, and a method for recovering indium.
[2] In the method of [1] above, first, zinc is added to the solution to deposit indium metal until the indium ion concentration is less than 1 g / L, and then aluminum is added to the solution instead of zinc. And a method for recovering indium by depositing metal indium until the indium ion concentration is less than 10 mg / L.
[3] In the method of [1] or [2] above, indium ions and indium hydroxide coexist in the liquid, and zinc is first added to the liquid until the indium ion concentration is less than 1 g / L. indium to precipitate, then, instead of the zinc was added to the aluminum in the solution, a method for recovering indium for depositing metal indium to indium ion concentration is less than 10 mg / L.
[4] In the method described in any one of [1] to [3] above, an indium chloride solution is used, the pH of the solution is adjusted to 2.5 to 3.5, and indium hydroxide is generated. A zinc plate is immersed in an indium chloride solution at an indium ion initial concentration of 60 to 85 g / L and an initial indium hydroxide amount (In conversion) of 5 to 60 g / L (total indium concentration of 90 to 120 g / L). Then, metal indium is precipitated until the indium ion concentration in the solution is less than 1 g / L, and then the pH of the indium chloride solution is adjusted to less than 0.5, and an aluminum plate is added to the solution instead of the zinc plate. A method for recovering indium in which metallic indium is deposited until the concentration of indium ions in the liquid becomes less than 10 mg / L.

According to the method of the present invention, in the substitution deposition of metal indium, after zinc is added to the solution to deposit metal indium, aluminum is added instead of zinc to deposit metal indium, and zinc substitution and aluminum substitution are performed. By performing two-stage substitution, sponge metal indium can be efficiently deposited in a relatively short time according to the concentration of indium ions in the liquid.

Specifically, for example, first, zinc is added to the solution, and the cementation with zinc is advanced until the indium ion concentration is less than 1 g / L. Thereafter, aluminum is added to the solution instead of zinc, and the indium concentration is increased. In the latter half, when the indium ion concentration is less than 10 mg / L, the precipitation of metal indium in the high-concentration region is rapidly advanced in the first half zinc substitution step, and the second half aluminum substitution step. In this case, it is possible to stably deposit metal indium in a low concentration region.

The method of the present invention can be carried out in combination with a method of depositing metal indium in a state where indium ions and indium hydroxide coexist in the liquid. Specifically, the pH of the indium solution is adjusted to convert some of the indium ions in the solution to indium hydroxide, and in the state where indium ions and indium hydroxide coexist in the solution, zinc is first added to the solution. Then, metal indium is deposited until the indium ion concentration is less than 1 g / L, and then aluminum is added to the liquid instead of zinc, and the metal indium is deposited until the indium ion concentration is less than 10 mg / L. According to this method, in the first half of zinc substitution, the indium ion concentration in the solution can be increased while maintaining the indium ion concentration in the range suitable for cementation, and the zinc plate is prevented from becoming insoluble and stable. Indium can be deposited on the substrate.

Sponge-like metal indium recovered by the method of the present invention contains almost no indium hydroxide or zinc hydroxide in the first zinc replacement step, and aluminum entrainment also occurs in the second aluminum replacement step. And metal indium with few impurities can be obtained.

Hereinafter, the present invention will be specifically described together with examples.
The method of the present invention is a method of depositing metal indium by adding a base metal rather than indium to an indium solution obtained by acid leaching of indium-containing material, and depositing metal indium by adding zinc to the solution. Then, in addition to zinc, aluminum is further added to deposit metal indium to precipitate indium.

The indium solution is a solution in which an indium-containing material is dissolved in sulfuric acid, hydrochloric acid, nitric acid, and the like. For example, ITO scrap is dissolved in hydrochloric acid, and the residue in the liquid is filtered and separated by tin hydroxide precipitation. . Specifically, ITO scrap is dissolved in hydrochloric acid under heating. This solution can be obtained by adding an alkali (sodium hydroxide or the like) to adjust the pH to 1.5 to 2.5 to produce a tin hydroxide precipitate, and then separating the solid and liquid to remove the tin hydroxide precipitate. it can. Hereinafter, an indium chloride solution will be described as an example.

In the method of the present invention, for example, in an indium chloride solution, first, zinc is added to the solution to deposit indium metal until the indium ion concentration is less than 1 g / L, and then aluminum is substituted into the solution instead of zinc. Add and deposit metallic indium until the indium ion concentration is less than 10 mg / L.

When aluminum substitution is performed at a stage where the concentration of indium in the first half is high, the reaction is so intense that aluminum is entrained in the spongy metallic indium on which aluminum is deposited, resulting in an increase in impurities. First, zinc substitution is performed to deposit metal indium until the indium ion concentration is less than 1 g / L, and then switching from zinc substitution to aluminum substitution can stably promote the deposition of metal indium. The aluminum substitution is preferably performed until the indium ion concentration is less than 10 mg / L. If zinc substitution is performed until this indium ion concentration is reached, zinc has a smaller ionization tendency than aluminum, and the substitution reaction is slow, so that the deposition time is considerably long, which is not practical.

In the method of the present invention, preferably, an alkali such as sodium hydroxide is added to the indium chloride solution to adjust the pH of the solution to 2.5 to 3.5 to generate indium hydroxide. If the pH is lower than 2.5, indium hydroxide precipitates are not sufficiently formed. If this pH is higher than 3.5, most of the indium ions are precipitated by indium hydroxide, and the concentration of indium ions in the liquid becomes too low. Cementation with zinc in the first half is carried out in the state where indium ions and indium hydroxide coexist in the pH range.

When cementation is performed by immersing a zinc plate in an indium chloride solution, the initial concentration of indium ions is preferably in the range of about 70 g / L. If the initial concentration of indium ions is higher than this, for example, about 150 g / L, a thin indium film is formed on the surface of the zinc plate, hindering zinc elution and inhibiting the substitution reaction between zinc and indium. The stationation will not progress. On the other hand, if the indium ion concentration in the liquid is significantly lower than the initial concentration, it takes time to deposit metal indium, and the efficiency is lowered.

In addition, since the indium ion concentration in the liquid gradually decreases as the deposition of metal indium proceeds, when cementation is performed in the range where the initial concentration of indium ions is around 70 g / L, a sufficient amount without replenishing indium ions. In order to obtain this metal indium, a large amount of initial liquid is required, and indium loss in the final process increases.

The recovery method of the present invention adjusts the pH of the indium chloride solution to 2.5 to 3.5 to produce indium hydroxide, and deposits metal indium in the state where indium ions and indium hydroxide coexist in the liquid. Therefore, it is possible to perform cementation while increasing the indium concentration of the entire solution including indium hydroxide while maintaining the concentration of indium ions in the solution within a concentration range suitable for cementation, so that the zinc plate is insolubilized. Indium can be stably deposited.

Specifically, the initial concentration of indium chloride in the indium chloride solution used for cementation is in the range of indium ion concentration of 60 to 100 g / L, preferably 60 to 85 g / L, the amount of indium hydroxide in the liquid (In conversion) 5 A range of 60 g / L and therefore a total indium concentration of 90 to 120 g / L is preferred. A zinc plate is immersed in an indium chloride solution in this concentration range to perform a substitution reaction between indium and zinc. When the substitution reaction proceeds and the indium ion concentration in the liquid decreases, indium hydroxide in the liquid dissolves and indium ions are supplied into the liquid, and the equilibrium of the indium ion concentration is maintained.

In the pH range where the cementation is carried out (pH 2.5 to 3.5), the reaction of zinc ions eluted in the liquid binding to hydroxyl groups to generate zinc hydroxide does not proceed. Indium does not contain zinc hydroxide.

By adding sodium hydroxide or the like to the indium chloride solution and adjusting the pH to the above range, indium hydroxide is generated and the liquid becomes cloudy. When a zinc plate is immersed in this, the substitution reaction proceeds, and sponge-like metal indium precipitates and accumulates at the bottom of the container. On the other hand, as indium ions are consumed in the substitution reaction, the indium hydroxide in the solution is in chemical equilibrium. The solution gradually becomes transparent after dissociating from the solution. Since all the indium hydroxide is consumed and zinc ions do not produce zinc hydroxide, the deposited metal indium does not contain indium hydroxide and zinc hydroxide.

As described above, the pH of the indium chloride solution is adjusted to produce indium hydroxide, the initial concentration of indium ions and the amount of indium hydroxide are adjusted to the above ranges, the zinc plate is immersed in the indium chloride solution, Metal indium is deposited until the indium ion concentration of 1 g / L. In this state, almost all of indium hydroxide is consumed.

After zinc substitution, the pH of the indium chloride solution is adjusted to less than 0.5, an aluminum plate is added to the solution instead of the zinc plate, and indium metal is added until the indium ion concentration in the solution is less than 10 mg / L. Precipitate. In this aluminum replacement step, the pH of the indium chloride solution is adjusted to less than 0.5. If the pH is higher than 0.5, it takes too much time for cementation and it is not industrial. This is remarkable in the low concentration region of indium in the liquid.

Since the aluminum substitution proceeds in a relatively short time until the indium ion concentration in the liquid becomes less than 10 mg / L, the recovery rate of indium can be increased by switching from zinc substitution to aluminum substitution. On the other hand, if aluminum substitution is performed from the stage where the indium ion concentration is high, the substitution reaction is so intense that the amount of aluminum taken into the deposited spongy metallic indium is not preferable. If the aluminum content exceeds 1%, explosion may occur in the alkali melting in the next step.

In the next alkali melting step, the recovered metal indium is mixed with metal indium and caustic soda and heated to melt, and the impurities in the metal indium are transferred to the caustic soda phase to recover 99.9% or more of indium. If the metal indium contains about 1% or more of aluminum by this alkali melting, sodium aluminate is generated from caustic soda and aluminum, and the viscosity of the melt is increased. Originally, this melt also contains volatile impurities, which gradually escape as gas during melting. However, if the viscosity of the melt is high, the degassing is suppressed by its internal pressure, and if this exceeds the limit, the degassing is ejected all at once and a so-called explosion occurs. To cope with this, the amount of caustic soda to be used must be extremely increased or the amount of indium must be decreased, which is not industrial. Therefore, it is preferable that the metal indium recovered by the aluminum replacement has as little aluminum content as possible. According to the method of the present invention, metallic indium having an aluminum content of 1% or less can be obtained by first proceeding with zinc substitution and then switching to aluminum substitution.

Examples of the present invention are shown below together with comparative examples.
[Example 1]
Sodium hydroxide is added to 6500 liters of indium chloride solution to adjust the pH to 2.8 to produce indium hydroxide. The amount of indium hydroxide in the solution (In conversion) is 25 g / L, the amount of free indium ions is 69 g / L (total) A cloudy solution having an indium concentration of 94 g / L was obtained. A plurality of zinc plates (area: 1200 cm ² ) were immersed in this solution under the above pH and left for 72 hours to become a transparent solution, and a precipitate was deposited on the bottom of the container. The indium ion concentration of the solution was 0.8 g / L. After filtering this and collecting the precipitate, an aluminum plate is immersed in the filtrate instead of the zinc plate and left until the indium ion concentration of the solution reaches 7 mg / L, and the sediment deposited on the bottom of the container is recovered by dehydration. did. These deposits were dehydrated and dried to obtain 611 kg of sponge-like metal indium. Indium hydroxide and zinc hydroxide contained in the metal indium were below the detection limit, and aluminum was 0.3%. The results are shown in Table 1.

[Example 2, Comparative Examples 1 and 2]
Sponge-like metal indium was obtained in the same manner as in Example 1 except that the pH of the indium chloride solution was adjusted to the value shown in Table 1. The results are shown in Table 1.

As shown in Table 1, Examples 1 and 2 of the present invention have a large amount of recovered metal indium and a small amount of impurities contained in the recovered metal indium. On the other hand, Comparative Example 1 has an indium recovery rate of about 1% lower than that of the Example. In Comparative Example 2, the substitution reaction was intense at first, and it was necessary to peel the metal sponge-like indium from the aluminum plate. In addition, aluminum pieces were scattered in the recovered metal indium, and 1.2% aluminum was contained at an average concentration.

Claims (4)

In a method of depositing metal indium by adding a base metal than indium to an indium solution obtained by acid leaching of indium-containing material, zinc is added to the solution to deposit metal indium, and then zinc is further added. A method for recovering indium, wherein aluminum is added instead to deposit metal indium.
2. The method of claim 1, wherein zinc is first added to the solution to deposit indium metal until the indium ion concentration is less than 1 g / L, and then aluminum is added to the solution in place of zinc. Indium recovery method in which metal indium is deposited until the amount of the metal becomes less than 10 mg / L.
3. The method according to claim 1 or 2, wherein indium ions and indium hydroxide coexist in the liquid, zinc is first added to the liquid to deposit indium metal until the indium ion concentration is less than 1 g / L, and then instead of the zinc was added to the aluminum in the solution, a method for recovering indium for depositing metal indium to indium ion concentration is less than 10 mg / L.
The method according to any one of claims 1 to 3, wherein an indium chloride solution is used and the pH of the solution is adjusted to 2.5 to 3.5 to produce indium hydroxide, and an initial indium ion concentration of 60 to 85 g. / L, initial indium hydroxide amount (In conversion) 5-60g / L (total indium concentration 90-120g / L) concentration range, soak zinc plate in indium chloride solution, indium ion concentration in the liquid Indium metal is precipitated until the concentration of the indium chloride is less than 1 g / L, and then the pH of the indium chloride solution is adjusted to less than 0.5, and an aluminum plate is added to the solution instead of the zinc plate, and the indium ion concentration in the solution Indium recovery method in which metal indium is deposited until the amount of the metal becomes less than 10 mg / L.