JPH0375224A - Method for purifying aqueous solution of indium - Google Patents

Abstract

PURPOSE:To readily enable purification of an aqueous solution of indium in a short time by adding counter ions of halogenostannate ions to an aqueous solution containing In and Sn coexisting with a strong acid group and halide ions. CONSTITUTION:Scraps, etc., of an In oxide sputtering target doped with Sn are dissolved in a concentrated HCl, etc., so as to provide >=0.5mmol/l proton concentration, a halogen concentration of >=50 times based on Sn and >=0.5mmol/l Sn concentration to afford an aqueous solution (A) containing In and Sn coexisting with a strong acid in >=1mmol/l HCl concentration and halogen ions. Counter ions (e.g. aqueous ammonia) (B) of a halogenostannate in an equimolar amount or more with the Sn in the component (A) is then added to the component (A) and reacted therewith at 5-60 deg.C to afford a reaction product (C), which is subsequently centrifuged, etc., to separate the halogenostannate (D). The resultant acidic aqueous solution of the In is then purified by an ion exchange method, etc., to produce a high-purity aqueous solution of the In.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention relates to a method for recovering indium, which is a valuable material, from an aqueous solution containing indium and tin.

[Prior Art] Examples of aqueous solutions containing indium (1n) and tin include those obtained by dissolving scraps of tin-doped In oxide (hereinafter referred to as ITO) sputtering targets in acid.

Currently, In is used in intermetallic compounds such as InP 5 InAs and transparent conductive thin films such as ITO, and the demand for In is expected to increase further in the future.

[Prior art and problems to be solved by the invention] [TO
Defective products during the manufacture of targets such as those with cracks during the manufacture of sintered bodies, those with insufficient sintering density,
It is expected that In, a valuable resource, can be recovered from scrap generated in the process of manufacturing transparent conductive thin films using ITO targets, and various methods have been proposed, but an economical method has not yet been established. be.

Generally, the method for separating tin and In from an aqueous solution containing In and tin is to raise the pH of the aqueous solution containing them to 12 or higher and precipitate In as a hydroxide, while tin is dissolved in the aqueous solution to separate them. There is a method of solid-liquid separation. However, this method has problems in terms of economy, such as the generated In hydroxide having extremely poor filterability and requiring a long time for the filtration operation.

There are also methods such as ion exchange and solvent extraction that use large-scale equipment, but these methods require rough separation through chemical purification in order to increase production efficiency, resulting in complicated processes.

[Object of the Invention] The present invention has been made to solve the above-mentioned problems of the prior art, and aims to provide a method for separating tin from an aqueous solution containing In and tin and recovering the In aqueous solution. purpose.

[Means for Solving the Problems] As a result of intensive study on a method for separating In and tin from an aqueous solution containing them, the present inventors found that by converting tin coexisting in an aqueous solution into a halogenostannate, tin The present invention was completed by discovering that it is possible to selectively separate only the following. That is, the present invention is a method for purifying an indium aqueous solution, which is characterized by adding a counter ion of a halogenostannate ion to an aqueous solution containing indium and tin in which a strong acid and a halide ion coexist to separate the halogenostannate. be.

The present invention will be explained in more detail below.

The starting material of the present invention can be widely used as long as it is an aqueous solution containing 1N and tin, but here, a case will be described in which a hydrochloric acid solution of ITo scrap is used.

When dissolving ITO scrap in an acid, acids such as hydrochloric acid, nitric acid, and sulfuric acid can be considered, but it is preferable to use hydrochloric acid because it can be dissolved most quickly. When using nitric acid, tin can be separated as metastannic acid, but the dissolution rate is extremely slow, and when using sulfuric acid, the dissolution rate is also inferior to that of hydrochloric acid. Further, the rate of dissolution of ITO scrap into hydrochloric acid becomes significantly faster when the dissolution is carried out at a high temperature, so it is preferable to carry out the dissolution at a temperature of 5 to 95°C.

In the present invention, tin is separated as a halogenostannate from such an aqueous solution containing In and tin. Tin in an aqueous solution can be produced as a halogenostannate in the presence of a halogenostannate ion and its counter ion, but the purification efficiency depends on the acid concentration in the aqueous solution, the halide ion concentration, and the concentration of halogenostannate. It depends on the concentration of the cation that serves as the counter ion. The proton concentration corresponding to the acid concentration of an aqueous solution containing In and tin is 0.
．． 5mm.

Preferably 1/1 or more, more preferably 3moJ! /j! The above is particularly preferable. If this proton concentration is low, the required amount of halogen ions and the required amount of cations serving as counter ions of the halogenostannate are increased, which is not only uneconomical, but also reduces the amount of tin compounds produced, which makes it difficult to use in the present invention. effectiveness decreases. Furthermore,
If the proton concentration is too low, various metal ions in the solution will become hydroxides, and at the same time, in will also become hydroxides.
Selective separation of tin becomes difficult, and the filterability of the product becomes poor, significantly reducing the effectiveness of the present invention. The type of acid for adjusting the proton concentration is not particularly limited, but strong acids such as hydrochloric acid, nitric acid, and sulfuric acid are preferred, and halogen-containing acids such as hydrofluoric acid, hydrochloric acid, and bromic acid are more preferred. When using an acid containing a halogen, the acid concentration and the halogen ion concentration can be adjusted at the same time.

In addition, in the present invention, when producing halogenostannate, I
The halogen ion concentration of a strongly acidic aqueous solution containing n and tin is
Although it depends on the type of halogen ion, it is preferably at least 50 times molar relative to tin, particularly preferably at least 80 times molar. At this time, the halogen ions may be adjusted by adding an acid containing halogen ions, such as hydrochloric acid, or by adding a salt containing halogen ions such as sodium chloride or ammonium chloride. good.

In this way, the aqueous solution containing In and tin in the present invention must have halogen ions and be under strong acidity. A strongly acidic solution containing halogen ions is preferred because it is the most economical and can simplify the operation. The above essential conditions can also be achieved by adding sulfuric acid, or by adding sulfuric acid to a solution containing halogen ions and tin.

In the present invention, tin may be either Sn2+ or Sn4+. The effect of the present invention is remarkable for both of these ions. Further, the tin concentration of the aqueous solution treated in the present invention is preferably 0.5 mmoi/1 or more. At this time, if the tin concentration is low, the effect of the present invention will be reduced.

A method for preparing such a solution containing in and tin is, for example, when dissolving a scrap ITO target in concentrated hydrochloric acid, since halogen ions are already present and the environment is strongly acidic, the hydrochloric acid concentration should be reduced to 1 moJ! /J! Above, preferably 3
Dissolve the target so that it is more than IIIOili,
Examples include a method of adjusting the halogen ion concentration and acid concentration.

A counter ion of a halogenostannate ion is supplied to an aqueous solution containing 1N and tin in which such a strong acid and a halide ion coexist to generate a halogenostannate. The amount of cations to be added that serve as counter ions for halogen stannate depends on the halogen ion concentration and acid concentration, but it should be added so that the counter ions of halogen stannate are at least equimolar to tin. Things are good.

If the amount of this counterion added is small, the production efficiency of halogenostannate will be poor, and if it is too much than necessary, it will be uneconomical. The method for adding cations at this time may be any method as long as it acts as an electrolyte in an aqueous solution, and may be an inorganic or organic material. Examples of inorganic substances include bases such as aqueous ammonia, sodium hydroxide, potassium hydroxide, calcium hydroxide, and magnesium hydroxide, and their hydrochlorides, nitrates, and sulfates. As organic matter,
Examples include bases such as methylamine, dimethylamine, ethylamine, and pyridine, and their hydrochlorides.

In the present invention, it is preferable that the halogenostannate be produced as an ammonium salt and/or a salt of amines, and in this case, mixing of inorganic metal ions such as sodium ions and calcium ions into the solution can be avoided, and the present invention The effect is also significant. However, considering economic efficiency, it is particularly preferable to produce it as an ammonium salt. When adding a base such as sodium hydroxide, the proton concentration in the solution will decrease, so care must be taken to adjust the proton concentration. These can be added in the form of powder, slurry, aqueous solution, etc., but if an increase in liquid volume is expected, powder form is preferable and improves the effect of separating and producing tin.

In this way, tin is selectively produced, but the reaction temperature at this time is not particularly limited and is preferably 5 to 60°C. If this temperature is too high, the amount of product produced decreases, probably because the solubility of the product increases.

The halogenostannate is then separated from the resulting slurry containing the halogenostannate product. For this separation, conventional equipment such as centrifuges, belt filters, drum filters, etc. can be used. In the present invention, the separation of the product at this time is extremely good, and solid-liquid separation can be easily performed in a short time. The separated product obtained here is a halogenostannate, such as chlorostannic acid, which is produced by an anion complex in which a halide ion is coordinated with a tin ion, using the added electrolyte ammonium ion, sodium ion, etc. as a counter ion. Ammonium, ammonium brostannate, sodium chlorostannate, etc. These tin salts have high solubility in water, and it was generally thought that they could only be obtained by methods such as evaporation of a solution to dryness. It can be easily separated by adjusting the concentration of cations that serve as counter ions to stannate ions.

In this way, an acidic aqueous solution of in, in which tin is separated from an aqueous solution containing in and tin, can be obtained. However, this solution may contain impurities other than tin, such as iron, calcium, sodium, and zirconium.
In such a case, a highly purified In aqueous solution can be obtained by methods such as electrolytic deposition, ion exchange, and chemical purification.

Here, when the solution is purified by electrolytic deposition, since tin, which has a higher deposition potential than In, is removed by the present invention, a large amount of metal, which has a higher deposition potential than In, is removed from the In aqueous solution. As long as it is not mixed, in can be recovered as a metal by electrolytic deposition. At this time, for example, if the acid concentration of the In aqueous solution is high, hydrogen generation occurs simultaneously with the electrolytic deposition of In, resulting in a low current efficiency.

In addition, if the acid concentration is too low, 1N hydroxide will be generated, so the solution containing In treated with the present invention should be adjusted to pH 3.5,
Preferably, the value is adjusted to 1 to 3.5, and In is recovered from the solution by electrolysis.

In addition, in the case of purification by an ion exchange method, for example, when separating using an eluent such as ethylenediaminetetraacetic acid (EDTA), tin, which is adjacent to In in the elution order, is removed in the present invention, so it is easy to perform separation. It is possible to separate In from other metals and recover high-purity In.

In addition, methods for recovering indium by removing metal impurities other than tin through chemical refining include methods for recovering indium as oxalate, methods for recovering as hydroxide, and methods for recovering indium as organic acid salts such as formate. be.

A method for recovering In as oxalate is to add acid or alkali to an acidic aqueous solution containing In treated according to the present invention.
This is a method in which oxalic acid and/or oxalate is added after adjustment, and 1N is recovered as oxalate. The optimum range for pH adjustment at this time depends on the concentration of In, temperature, and the amount of oxalic acid and/or oxalate to be added, but it is preferable to adjust the pH to a range of ~2. If this pH is too low, the solubility of In oxalate increases and the recovery rate decreases. Moreover, if this pH is too high, a large amount of metals other than In will be mixed into the obtained In oxalate, reducing the purification effect. The type of acid to be added is not particularly limited, and examples include mineral acids such as hydrochloric acid, sulfuric acid, and nitric acid. There are no restrictions on the type of alkali to be added, but examples include alkali metal hydroxides, alkaline earth metal hydroxides, and ammonia.

When producing In as oxalate from the In-containing acidic aqueous solution treated in the present invention, oxalic acid and/or oxalate is added, and the oxalate used is an alkali metal salt, an alkaline earth metal salt, or an ammonium salt. However, in order to recover highly pure in, it is preferable to use a salt that does not contain metal ions, and ammonium salts are particularly preferable. The amount of oxalic acid and/or oxalate added depends on the temperature, pHs I
Although it depends on the n concentration, the concentration of metal ions other than In, etc.
The equivalent amount is preferably 0.5 to 2.5 times. If this amount is too small, the recovery rate of In will decrease, and if it is too large, metal ions other than In will also be produced, which is not preferable.

Next, In oxalate is separated and recovered from the obtained slurry containing In oxalate. The obtained In oxalate is purified water,
It is preferable to wash with a dilute acid aqueous solution or a dilute oxalic acid aqueous solution to remove metal salts other than In attached to the In oxalate.

On the other hand, when in is recovered as a hydroxide, an acidic aqueous solution containing In treated according to the present invention is neutralized to pH 3 to 5 with an alkali in the presence of a reducing agent, and In is recovered as a hydroxide. At this time, the presence of a reducing agent reduces impurity metal ions such as iron, zinc, tellurium, etc., and by adjusting the pH so that these hydroxides are difficult to grow, the hydroxides of in are selectively removed. It can be generated. The type of alkali added here is not limited, but examples include alkali metal hydroxides, alkaline earth metal hydroxides, ammonia, and the like. When using ammonia, I treated according to the present invention
Since metal ions such as sodium ions and potassium ions are not mixed into the acidic aqueous solution containing n, this method is particularly preferable when recovering high-purity in.

When producing In as a hydroxide from the acidic aqueous solution containing In treated in the present invention, reducing agents such as hydrazine,
Ascorbic acid, sodium sulfite, sulfur dioxide, etc. are used, but hydrazine and ascorbic acid, which do not contain sodium, sulfur, etc., are preferred. The amount of reducing agent added varies depending on the type of reducing agent, but for example, if the impurity is iron and the reducing agent is ascorbic acid, it is sufficient to add twice the amount of iron. In this way, iron is converted from Pe” to Fe2+
By changing to ferrous hydroxide, it is possible to obtain ferrous hydroxide with relatively high solubility.

The method for neutralizing an acidic aqueous solution containing In treated according to the present invention is as follows:
Although not particularly limited, it is preferable to perform acid neutralization and neutralization for precipitation of In hydroxide separately. The acid may be neutralized using alkali at a high concentration or alkali at a low concentration, but in order to prevent an increase in the amount of liquid and improve production efficiency, it is preferable to use alkali at a high concentration. The high concentration of alkali mentioned here is not particularly limited, but it is preferably a concentration of 5N or more. Neutralization of this acid takes pH ~3
It shall end within the range of . p at the time when neutralization of the acid is completed
The step of adding alkali from H to I) H5 is called neutralization for precipitation of In hydroxide.

During acid neutralization, the temperature of the liquid increases due to the heat of neutralization.
It is preferable to lower the liquid temperature before proceeding to neutralization for precipitation of In hydroxide. If neutralization is performed to precipitate In hydroxide at a high temperature, the generated In hydroxide becomes gel-like, resulting in extremely poor filterability. Therefore, neutralization for precipitation of In hydroxide is preferably carried out at 5 to 60°C, particularly preferably at 5 to 35°C.

Further, it is preferable that the reducing agent is added after the neutralization of the acid is completed and before the neutralization for precipitation of In hydroxide is performed. If a long time elapses after adding the reducing agent, the reduced metal ions will be oxidized by dissolved oxygen in the aqueous solution, and the effect of adding the reducing agent will decrease.

After adding the reducing agent, an alkali is added again to generate In hydroxide. It is preferable that the alkali be added so that the pH of the In-containing acidic aqueous solution treated according to the present invention is in the range of 3 to 5. If the pH is too high, impurities such as iron will co-produce with in, and if the pH is too low, the efficiency of indium hydroxide production will be low. The concentration of the alkali added is preferably low, and preferably 5N or less. If the alkali concentration is too high, impurities will be included in the In hydroxide produced, resulting in a decrease in the purity of the resulting In.

Next, from the obtained slurry containing In hydroxide, 1n
Separate and recover the hydroxide. For this separation, conventional equipment such as a centrifugal separator, belt filter, drum filter, etc. can be used.

The filterability of In hydroxide is extremely good, and it can be easily separated into solid and liquid in a short time.

The obtained In hydroxide is washed using pure water, an aqueous solution of a dilute acid, or an aqueous solution containing a reducing agent such as ascorbic acid,
It is preferable to remove metal salts other than In attached to the In hydroxide.

The In hydroxide thus obtained can be dried and fired to form In oxide. In addition, even higher purity In
In order to recover In metal, the obtained hydroxide may be dissolved in an acid and recovered as In metal by electrolytic deposition, or an ion exchange method or a solvent extraction method may be used.

For example, when recovering In metal, first, In hydroxide is dissolved in acid. The acid used here may be an inorganic acid such as hydrochloric acid, nitric acid, or sulfuric acid, or an organic acid such as formic acid, citric acid, or tartaric acid. In is electrolytically extracted using such an acid aqueous solution containing In as an electrolyte. The pH of this electrolyte
The higher the pH, the more hydrogen generation can be suppressed and the current efficiency can be improved, but if the pH is too high, hydrolysis of in will occur. The pH of the electrolytic solution at this time is preferably O to 3.5, although it depends on the concentration of metal ions other than In. In addition, electrolysis can be carried out at a temperature ranging from room temperature to below the boiling point of the electrolyte used, but generally speaking, the higher the temperature, the faster the dissolution rate of metals in acids, so it is more efficient to carry out electrolysis at a lower temperature. . Preferably, electrolysis is carried out at a temperature ranging from room temperature to 60°C.

The cathode where In is recovered is preferably In metal, and 1
The cathode electrodeposited with n can be made into an ingot as it is. Further, any anode can be used as long as it is not corroded by the electrolyte, but from the viewpoint of durability, it is possible to use PT, graphite, or the like. However, when the electrolytic cell is partitioned by an anion exchange membrane, the anode may be a soluble one because it is not affected by metal ions dissolved from the anode.

However, since the anions in the electrolyte pass through the anion exchange membrane and move from the anode to the cathode, it is preferable that the electrolyte in the anode compartment has the same anions as the electrolyte in the cathode compartment. For example, when the cathode electrolyte is a formic acid 1N solution, the anode electrolyte is a formic acid solution or an ammonium formate solution. Also,
When the cathode electrolyte is a hydrochloric acid solution of In chloride, the anode electrolyte is an aqueous hydrochloric acid solution, an ammonium chloride solution, or a sodium chloride solution. When the electrolyte at the anode is a formic acid solution, by using In metal as the anode, an In formic acid solution can be generated in the anode chamber while indium is electrolytically deposited and recovered in the cathode chamber. By doing this, 1. Current can be used efficiently, and the In formic acid solution obtained in the anode chamber is
It can be used as a raw material for producing TO targets.

[Effects of invention Next, the effects of the present invention will be listed.

(1) Halogenostannates, which were conventionally thought to be difficult to produce in acidic solutions due to their high solubility, can be easily produced by selecting the production conditions.

(2) The present invention can separate only tin in a strongly acidic region, and
Since there is no co-production of In, an aqueous solution with a large proportion of In can be easily obtained from a mixed aqueous solution of tin and In, which is a valuable material.

(3) Since the halogenostannate product is crystalline, it has extremely good filterability, and the filtration operation is easy and takes only a short time.

(4) In aqueous solution treated with the present invention and ion exchange method,
High purity (99.9% or more) metal In and/or In compounds can be easily obtained by combining electrolytic deposition, chemical refining, etc.

[Example] Examples, comparative examples, and reference examples of the present invention are shown below, but the present invention is not limited to these.

Example 1 A 36% hydrochloric acid aqueous solution tg and 200 g of a scrap ITO target were placed in a 21 separable flask equipped with a stirrer, and the mixture was stirred at 80° C. for 3 hours to dissolve the target. The resulting solution was filtered, the residue was removed, and the composition was analyzed. Hydrochloric acid concentration: 6.5 moJ / l11n ion concentration: 1.25 filo 1 / R Tin ion concentration: 102 mmoB iron ion concentration
: 2 mmoJ! / 1 Zirconium ion concentration: 1.1 mmoj! / J! Met.

200 IIl.g of this target solution was placed in a 300 ml separable flask equipped with a stirrer, and while stirring, 10+nJ of 28% ammonia water was added to form a halogenostannate precipitate, followed by stirring for 1 hour. The temperature of the aqueous solution at this time was 25°C. Next, the slurry is NO.
, 5C filter paper. The filtration property was very good, and when the obtained filtrate was analyzed by IPC, In concentration: 1.2 mob/Ostin concentration
: 10.8 tn mol / 1 iron ion concentration : 1.9 m oR / zirconium ion concentration:
1. I IIlmoJ / ,! ! Met.

Example 2 The target solution of Example 1 was used as LOOmJ! 200+J with a stirrer! 10 ml of a 14N aqueous sodium hydroxide solution was added to the mixture in a separable flask with stirring to form a precipitate of halogenostannate, and the mixture was stirred for 1 hour. The temperature at this time was 25°C.

Next, the slurry was suction filtered through NO, 5G filter paper.

The filterability was very good, and when the obtained filtrate was analyzed by IPC, the In concentration was 1.1 moJ! / 1,
The tin concentration is 58 mmoj/J! Met.

Example 3 The target solution LooIII,e from Example 1 was placed in a 200III,e separable flask equipped with a stirrer, and 3.9 g of ammonium chloride was added while stirring to form a precipitate of halogenostannate. , and stirred for 1 hour. The temperature at this time was 25°C. Next, the slurry is NO.
, 5G filter paper. The filterability was very good, and when the obtained filtrate was analyzed by IPC, the In concentration was 1.2 moi/J! , tin concentration is 15.1 mm
oJ! / It was 1.

Example 4 100 m, e of the target solution of Example 1 was added to 200 I! equipped with a stirrer! li separable flask, 5.8 g of ammonium nitrate was added with stirring to form a halogenostannate Ω precipitate, and the mixture was stirred for 1 hour. The temperature at this time was 25°C. Next, the slurry was mixed with NO.5
The mixture was suction-filtered using C filter paper. The filterability was very good, and when the obtained filtrate was analyzed by IPC, the In concentration was 1.
2 tnol/1, tin concentration is 20.511II
IIOjl, e teatuta.

Comparative Example 1 100 nl of the target solution of Example 1 was heated to 200 ra with a stirrer, i! into a separable flask, add 40 mA of 28% ammonia water while stirring, and add 1
Although the mixture was stirred for several hours, the amount of ammonia added was too large and the aqueous solution disappeared under strong acidity, so no precipitate was formed.

Comparative Example 2 12N sulfuric acid aqueous solution 500IIIJ was placed in 11 separable flasks equipped with a stirrer! and 100 g of scrap ITO target were added and stirred at 80° C. for 3 hours to dissolve the target. The obtained solution was filtered to remove the residue, and the composition was analyzed. The results were as follows: Sulfuric acid concentration: 7.5 ioJ/1in ion concentration: 1.05 moj/j Tin ion concentration: 92 rmoj/j.

100mJ of this target solution! was placed in a 200+nJ separable flask equipped with a stirrer, 5 mfl of 28% aqueous ammonia was added while stirring, and the mixture was stirred for 1 hour, but no precipitate was formed because no halogen ions were present. The temperature of the aqueous solution at this time was 25°C.

Reference Example 1 The solution 100n+,e from which tin was separated in Example 1 was placed in a 500 rAi separable flask equipped with a stirrer, and while stirring, 28% ammonia water was added, the pH of the solution was adjusted to 2, and the solution was heated at 25°C. It was left to cool until Thereafter, 440 mg of ascorbic acid was added and stirred, and then 2.8% aqueous ammonia was added to generate In hydroxide.

The pH of the slurry was 4.2, and the temperature was 28°C. Next, the slurry was suction filtered through NO, 5C filter paper.

The filterability was very good.The obtained cake was dissolved in hydrochloric acid and IC
When analyzed by P, tin is 40oooo compared to In.
ppm1 iron is 110 ppm, zirconium is 500 ppm
It was ppm.

Reference Example 2 100+n1 of the solution from which tin was separated in Example 1 was transferred to a 500mj! equipped with a stirrer. into a separable flask and add 28% ammonia water while stirring to adjust the pH of the solution to 2.
The mixture was cooled to 25°C. Thereafter, 2.8% ammonia water was added to generate In hydroxide. The pH of the slurry was 4.2 and the temperature was 28°C. next,
The slurry was suction filtered through NO, 5C filter paper. The filterability was very good. When the resulting cake was dissolved in hydrochloric acid and analyzed by ICP, it was found that tin was 4000 ppm relative to In.
, 780ppm of iron, 300ppffl of zirconium
Since no reducing agent was added, the iron content was higher than in Example 5.

Reference Example 3 The target solution toomj of Example 1 was placed in a 500 mJ separable flask equipped with a stirrer, and while stirring, 28% ammonia water was added to adjust the pH of the solution to 2, and the solution was allowed to cool to 25°C. Thereafter, 2.8% aqueous ammonia was added to generate 1N hydroxide.

The pl of the slurry was 4.2 and the temperature was 28°C.

Next, the slurry was suction filtered using No. 5C filter paper.

When the obtained cake was dissolved in hydrochloric acid and analyzed by ICP, it was found that tin was 80,200 ppm and iron was 500 ppm relative to In.
ppm1 zirconium was 300 ppm, and since tin was not separated, the tin content was extremely high.

Reference Example 4 In an electrolytic cell in which both the anode and the cathode were metal 1N electrodes and a fluorine-based anion exchange membrane 5F-34 manufactured by Tosoh Corporation was arranged as a diaphragm, the electrolyte on the anode side was a 20% formic acid aqueous solution,
The electrolyte on the cathode side was treated in the same manner as in Example 5 to
A hydroxide cake of n was produced, and the cake was dissolved in a 20% formic acid aqueous solution, and the resulting product was used for electrolysis.

The electrolysis temperature was 25℃, and the current density was 20IIIAlcfl.
It was set to 12. During electrolysis, the voltage between the electrodes was stable, the current efficiency on the anode side was 105%, and the current efficiency on the cathode side was 98%. The reason why the current efficiency on the anode side is 1 (IOX or more) is due to the natural dissolution of metal 1n.

Next, the metal In deposited on the cathode was dissolved in hydrochloric acid and the impurity content was examined by ICP.
401) pm, iron was 10 ppm or less, zirconium was 10 ppm or less, and it was possible to recover 3N In metal. On the other hand, the electrolyte in the anode chamber is heated and concentrated, and In
of In formate and then convert the resulting In formate to 7
By firing at 00℃ for 5 hours, the average particle size is 0.2μm.
of In oxide was obtained.

Claims (1)

[Claims] A counter ion of a halogenostannate ion is added to an aqueous solution containing indium and tin in which a strong acid and a halogen ion coexist.
A method for purifying an aqueous indium solution characterized by separating halogenostannate.