JPH0375223A - Recovery of indium - Google Patents

Abstract

PURPOSE:To enable ready recovery using a simple apparatus by adding oxalic acid and/or an oxalate to an In-containing aqueous solution while adjusting pH. CONSTITUTION:To (A) an aqueous solution obtained from a by-product, etc., in zinc smelting process and containing In in an amount of >=70% based on the total molar number of metallic ions, (B) oxalic acid and/or an oxalate (e.g. ammonium salt) is added in an amount of 0.5-2.5 time equivalent based on In in (A) component after or while adjusting pH to 0-2 by addition of an acid such as HCl or an alkali such as ammonia thereto and the resultant mixture is reacted at 10-60 deg.C to obtain a product (C). The (C) component is then separated by the centrifugal separation, etc., and the separated In oxalate is washed by pure water, etc., and subsequently burned, thus recovering In.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention relates to a method for recovering In, a valuable material, from an aqueous solution containing indium (in).

[Prior Art] Examples of aqueous solutions containing 1N as a main component include In solutions as smelting intermediates obtained as by-products of zinc smelting processes, and tin-doped In oxide (hereinafter referred to as ITO) sputtering targets. Examples include scrap dissolved in acid.

Currently, In is used in intermetallic compounds such as InP and 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] 1n is produced as a by-product of the zinc smelting process, etc., and its methods include methods using various chemical refining and electrolytic deposition,
These include ion exchange method, solvent extraction method, etc. All of these methods require large-scale equipment, are complicated to operate, and are difficult to adapt to changes in raw material composition.

In addition, electronic materials such as ITO have poor yields during the manufacturing process, and most of the In used becomes scrap.Therefore, recovery of valuable In from these scraps is expected, but there is still no satisfactory economic efficiency. There is no established method.

[Object of the Invention] The present invention has been made to solve the above-mentioned problems of the prior art, and its object is to provide a method for easily recovering In from an aqueous solution containing In using a simple device. purpose.

[Means for Solving the Problems] As a result of intensive study on a method for recovering In as an organic acid salt from an aqueous solution containing In, the present inventors found that oxalate is the most difficult among various types of In organic acid salts. Based on the knowledge that In is soluble, by adjusting the pH of the aqueous solution containing In and adjusting the amount of oxalic acid and/or oxalate to be added, it is possible to selectively generate 1N oxalate. Heading The invention has been completed.

That is, the present invention adjusts the pH of an aqueous solution containing In to O~2, or adds oxalic acid and/or oxalate to the aqueous solution while adjusting it, or adds oxalic acid and/or oxalate to an aqueous solution containing In. is added to adjust the pH of this aqueous solution to 0 to 2, and In is separated from the aqueous solution as oxalate.
This relates to the collection method. The present invention will be explained in more detail below.

In the present invention, the In-containing aqueous solution is, for example, an In solution of a smelting intermediate obtained as a by-product of a zinc smelting process, an I
This includes an acid solution of TO scrap.

Although there is no particular restriction on the content of In in the aqueous solution used here, the effects of the present invention are noticeable when 70% or more of the total number of moles of metal ions in the aqueous solution is In.

The higher the 1n content in the aqueous solution containing In compared to metal ions other than In, the more i can be obtained by the present invention.
The purity and recovery rate of n are also improved, and in the present invention, it is 99.99% (
It is possible to recover In with a purity higher than 4N (hereinafter referred to as 4N).

Next, an example using ITO scrap will be described in detail.

The acid solution of ITO scrap contains tin,
If this tin is separated by pretreatment of an acid solution and treated as an acid solution with a high In content by the method of the present invention, a highly purified 1n component can be obtained with a high recovery rate. Examples of the method for separating tin at this time include a method in which tin is precipitated and separated as a halogenostannate. That is, from an aqueous solution containing tin,
This is a method for selectively separating tin by producing halogenostannate under strong acidity and in the presence of halogen ions.

- When producing halogenostannate from such a solution, it is necessary to make the tin-containing solution strongly acidic. The acid concentration of this strongly acidic aqueous solution is 0.5 mo in proton concentration,
L/i or more is preferable, and 3 mo1/1 or more is particularly preferable. When the proton concentration is low, the required amount of halide ions and the required amount of cations serving as counterions of the halide stannate are increased, which is not only uneconomical, but also reduces the amount of precipitated tin compounds. Furthermore, if the proton concentration is too low, various metal ions in the solution will be produced as hydroxides, and at the same time In will also become hydroxides, making it difficult to selectively separate tin, and at the same time, the separability of the product will deteriorate. The type of acid used to adjust the proton concentration is not particularly limited, but strong acids such as hydrochloric acid, nitric acid, and sulfuric acid are preferred. Particularly when using acids containing halogens such as hydrofluoric acid, hydrochloric acid, and bromic acid,
This is preferable because the acid concentration and the halogen ion concentration can be adjusted at the same time.

Further, when precipitating a halogenostannate, the presence of halogen ions is required in the aqueous solution containing In and tin. In
The halogen ion concentration of the strongly acidic aqueous solution containing tin is preferably at least 50 times the molar content of tin, particularly preferably at least 80 times the molar content, although it depends on the type of halogen ions. 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.

In this way, an aqueous solution containing In and tin must contain halogen ions and be under strong acidity, so it is inevitable that a solution containing tin will contain halogen ions such as an aqueous solution of hydrochloric acid or an aqueous solution of hydrobromic acid. It is preferable to use a strongly acidic solution that does not contain halogen ions, such as a sulfuric acid aqueous solution that contains tin, as it is most economical and can simplify the operation.
This essential condition can also be achieved by adding a halogen ion source such as ammonium chloride, or by adding sulfuric acid to an aqueous solution containing halogen ions and tin.

Further, the tin referred to here may be either Sn'' or Sn'+.The tin removal effect is remarkable for both of these ions.Also, the tin concentration of the aqueous solution to be treated is 0.5
sIIoJ! / is preferably 1 or more, and when the tin concentration is low, the tin separation effect becomes small.

A counter ion of a halogenostannate ion is supplied to an aqueous solution containing In and tin in which a strong acid and a halide ion coexist to generate a halogenostannate. The amount of cations to be added that serve as counter ions to 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 counter ion added is small, the efficiency of precipitation of norogenostannate will be poor, and if it is more than necessary, it will be uneconomical. The cation may be added by any method as long as it acts as an electrolyte in an aqueous solution, and may be an inorganic or organic material. Inorganic substances include aqueous ammonia, sodium hydroxide, potassium hydroxide, calcium hydroxide,
Examples include bases such as magnesium hydroxide, and hydrochlorides, nitrates, and sulfates thereof. Examples of organic substances include bases such as methylamine, dimethylamine, ethylamine, and pyridine, and their hydrochlorides. It is preferable to generate the nologenostannate as an ammonium salt and/or a salt of amines. At this time, inorganic metal ions such as sodium ions and calcium ions are prevented from being mixed into the solution, and the effects of the present invention are improved. is also remarkable. However, considering economic efficiency, it is particularly preferable to produce it as an ammonium salt. When adding a base such as sodium hydroxide,
Since the proton concentration in the solution decreases, care must be taken not to make the proton concentration too low. There are ways to add electrolyte in the form of powder, slurry, aqueous solution, etc., but if an increase in the amount of liquid is expected, it is better to use powder, which also has the effect of separating tin. growing.

In this way, tin is selectively produced, but the temperature at which it is produced is not particularly limited, and is preferably 5 to 60°C.

If this temperature is too high, the solubility of the product will increase and the amount produced will decrease.

The halogenostannate is then separated from the resulting slurry containing the halogenostannate product. For this separation, conventional equipment such as centrifugal separators, belt filters, drum filters, etc. can be used.

The obtained product is a halogenostannate in which an anion complex in which a halogen ion is coordinated with a tin ion is produced using the added electrolyte such as ammonium ion, sodium ion, etc. as a counter ion. For example, ammonium chlorostannate,
These include ammonium bromostannate and sodium chlorostannate. In addition, the filtrate obtained by separating the product has a smaller amount of tin ions than In ions, and when such a solution is used in the present invention, the recovery rate and purity of In as oxalate are improved. .

An acid or alkali is added to the thus obtained aqueous solution containing In as a main component to adjust the pH. The optimum range for pH adjustment depends on the concentration of In, temperature, and the amount of oxalic acid and/or oxalate to be added, but it is preferably adjusted to a range of pH 2 or less. However, if this pH is too low than necessary, In
The solubility of oxalate increases and the recovery rate of the In component decreases. Also, in the In oxalate obtained when pn is too high! n
A large amount of other metals are mixed in, reducing the purification effect. p
The type of acid added during H adjustment is not particularly limited, and examples thereof include mineral acids such as hydrochloric acid, sulfuric acid, and nitric acid. Furthermore, there are no restrictions on the type of alkali to be added, but examples include alkali metal hydroxides, alkaline earth metal hydroxides, ammonia, and the like. In this case, when ammonia is used, metal ions such as sodium ions and potassium ions are not mixed into the aqueous solution containing In as a main component, so it is particularly preferable when recovering high-purity In. The acid or alkali may be added in any form such as an aqueous solution, slurry, powder, or gas, but it is preferable to use the acid or alkali in the form of a slurry, powder, or gas because there is no increase in liquid volume and the recovery of In is effective. It is preferable because it improves rate and productivity.

In the present invention, the oxalic acid and/or oxalate added to generate In as oxalate from an aqueous solution containing In include alkali metal salts, alkaline earth metal salts, ammonium salts, etc. as oxalate; Ion-free salts are preferred for recovering highly pure In, and ammonium salts are particularly preferred.

Oxalic acid and/or oxalate can be added in the form of an aqueous solution, powder, or slurry, and may also be added as an alcoholic solution in which oxalic acid and/or oxalate has a high solubility. The amount of oxalic acid and/or oxalate added depends on the temperature of the solution, 90%
% Although it varies appropriately depending on the In concentration, the concentration of metal ions other than In, etc., it is preferably 0.5 to 2.5 times equivalent to In. If this amount is less than the above range, the recovery rate of In will decrease, and if it is more, metal ions other than In will be generated together.

For example, when recovering as in of about 4N, i
When the content of n is high, increase the amount of oxalic acid added and adjust the pH to 1.
oxalate in the range of ~2.

Conversely, if the In content in the solution is low compared to other metals, reduce the amount of oxalic acid and adjust the pH to a range of 0 to 1.
n is produced as oxalate.

Addition of acid or alkali to aqueous solution containing In and oxalic acid and/or
Alternatively, the order of addition of oxalate is not particularly limited, but the simplest method is to adjust the pH of an aqueous solution containing 1N to a range of 0 to 2, and then add oxalic acid and/or oxalate. In this case, the slower the addition rate of oxalic acid and/or oxalate, the more the co-generation of metal ions other than In can be suppressed, and the more pure In oxalate can be obtained. When the aqueous solution containing In is strongly acidic, the pH may be adjusted first, but oxalic acid and/or oxalate may be added first, and then the pH may be adjusted to 0 to 2 with an alkali. In this case as well, the slower the alkali addition rate, that is, the more the pH is gradually raised, the higher the purity of the oxalate of 10 can be obtained. Also, I
Adding an alkali to an aqueous solution containing n as a main component and converting the metal ions in the aqueous solution into a gel-like product slurry of hydroxide,
It is also possible to generate In oxalate by adding oxalic acid and/or oxalate to this slurry, and then adding an acid to adjust the pH to a range of 0 to 2. In this case, very fine and highly purified in oxalate is obtained. In this way, In oxalate is produced, but the reaction temperature is not particularly limited and is 1
0 to 60°C is preferred.

Next, In oxalate is separated and recovered from the obtained slurry containing In oxalate. For separation at this time, conventional equipment such as a centrifugal separator, belt filter, drum filter, etc. can be used.

In oxalate has extremely good filterability and can be easily separated into solid and liquid in a short time.

The obtained In oxalate is preferably washed with pure water, a dilute acid aqueous solution, a dilute oxalic acid aqueous solution, or the like to remove metal salts other than In adhering to the In oxalate.

The 1N oxalate thus obtained can be used as an In oxide by sintering or the like.

[Effect of the invention] Conventionally, large-sized equipment such as ion exchange towers, electrolytic cells, and solvent extraction tanks were used to purify In, but the present invention purifies In with a concentration of 4 or more using simple equipment and operations. In addition, since it is relatively unaffected by the amount of metal ions other than In, it can be well applied to a method for recovering In from scrap containing In.

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

Example 1 A 36% aqueous hydrochloric acid solution IJ, 2°Og of ITO target scrap, and 107g of ammonium chloride were placed in an 11 separable flask equipped with a stirrer, and the mixture was 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. Hydrochloric acid concentration: 8.5 moJ / IIn:
1.14 Sn: 10. in+mo1/JC
a: 1.1 // re: 1.9 ” Zr: 1.1 l/ Zn: 2.2 Na: 3. 100 mj of this target solution was heated in a 500-meter separator equipped with a stirrer. Transfer to a flask and add H
2C204・H2O30g is 318mJ! An oxalic acid solution dissolved in pure water was added. Next, while stirring this solution,
28% aqueous ammonia was added to adjust the pH of the solution to 1.1 to obtain In oxalate, and stirring was continued for 2 hours. The temperature at this time was 25°C. Next, it was suction filtered through No. 5G filter paper and washed with a 62% oxalic acid aqueous solution to obtain 1N oxalate. The filterability is very good and the IJL in the filtrate is 10
The recovery rate was 91%. After drying the obtained cake, it was baked at 700° C. for 3 hours to obtain In oxide. The obtained In oxide was redissolved in hydrochloric acid, and metal elements other than In were analyzed using an inductively coupled plasma emission spectrometer (hereinafter referred to as 1 cP), and the concentration was 10 ppm or less relative to In oxide. However, Na was measured using an atomic absorption spectrometer.

Comparative Example 1 100 mA of the target solution of Example 1 was placed in a 1000 m 1 separable flask equipped with a stirrer, and 2060 g of H2C204'' H was added to [132ffij
! An oxalic acid solution dissolved in pure water was added. Next, while stirring this solution, 28% ammonia water was added, and the pH of the solution was
In oxalate was produced by adjusting H to 1.1. Stirring was then continued for 2 hours. The temperature at this time was 25°C. Next, the mixture was suction filtered using No. 5G filter paper and washed with a 0.2% oxalic acid aqueous solution to obtain In oxalate. The filterability was very good, and the recovery rate of In from Inff1 in the filtrate was 99%. The obtained cake was made into In oxide in the same manner as in Example 1, redissolved in hydrochloric acid, and analyzed for metal elements other than In. Sn: 85 LO ppm and Ca: 3 relative to In oxide.
00ppm SFe: 500ppm, Zr: 700
ppm, Zn: 990 ppm.

Since it contained 2QOppm of Na and the amount of oxalic acid added was large, the yield increased, but many other impurities were co-precipitated.

Comparative Example 2 A 100-liter of the target solution of Example 1 was placed in a 500-liter separable flask equipped with a stirrer, and further added with H2C.
An oxalic acid solution in which 2030 g of 204.H was dissolved in 316-pure water was added. Next, while stirring this solution, 28% ammonia water was added, the pH of the solution was adjusted to 0 or less, and I
n oxalate was produced. Stirring was then continued for 2 hours.

The temperature at this time was 25°C. Next, the mixture was suction filtered using No. 5C filter paper and washed with a 0.2% oxalic acid aqueous solution to obtain In oxalate. Although the filterability was very good, the pH was too low, so the In recovery rate was 26%.

Comparative Example 3 This target solution was heated to
0IIl, g into a separable flask, and further add H2
An oxalic acid solution in which 30 g of C20a.H2O was dissolved in 316-pure water was added. Next, while stirring this solution, 28
% aqueous ammonia was added and the pH of the solution was adjusted to 3.1 to form In oxalate, and stirring was continued for 2 hours. The temperature at this time was 25°C. Next, the mixture was suction filtered using No. 5C filter paper and washed with a 0.2% oxalic acid aqueous solution to obtain In oxalate. The filterability was very good, and the In recovery rate was 99% based on the 1N amount in the filtrate. The resulting cake was treated in the same manner as in Example 1 to obtain In oxide, which was redissolved in hydrochloric acid and analyzed for metal elements other than In. Sn: 9100 relative to In oxide.
1) pIII, Ca:290+) I3In, P(
3:510p1)m, Zr:890ppn+SZn
Since the pH was too high, the yield was improved, but many other impurities were co-precipitated.

Claims (1)

[Claims] Adjusting the pH of the aqueous solution containing indium to 0 to 2, or adding oxalic acid and/or oxalate to the aqueous solution while adjusting it, or adding oxalic acid and/or oxalate to the aqueous solution containing indium, and adjusting the pH of the aqueous solution. A method for recovering indium, which comprises adjusting the pH to 0 to 2 and separating indium in an aqueous solution as oxalate.