JP2009084673A - Selective separation/recovery method for specified metal ion - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a selective separation/recovery method for a specified metal ion where, from a solution comprising two or more kinds of metal ions, only one kind of metal ion is selectively separated/recovered. <P>SOLUTION: By the contact of a compound forming a metal complex such as oxalic acid, control is performed in such a manner that metal ions other than one kind of metal ion as the object for separation/recovery are made into a nondissociated state, and thereafter, only at least one kind of metal ion in a dissociated state is selectively separated/recovered by a cation exchange means. This invention is industrially useful as the method where, from an etching waste liquid produced when the indium-containing material to be etched such as an ITO film is subjected to etching treatment with an oxalic acid solution, and in which metal components such as indium and tin are present as complex compounds together with oxalic acid, the indium whose separation/recovery are extremely difficult owing to its low concentration is selectively separated/recovered. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a selective separation and recovery method for specific metal ions in which only one metal ion is separated and recovered from a solution containing two or more types of metal ions, and in particular, selective separation and recovery of indium from indium-containing waste liquid. On how to do.

Indium ions are often distributed and contained at low concentrations in starches and liquids obtained from various metal smelting processes, liquid crystal manufacturing processes, and other chemical treatment processes. For example, the waste liquid discharged from the metal refining process usually contains a low concentration of indium ions, while it contains a very large amount of metal ions other than indium.
Such indium-containing waste liquid and starch are promising as a collection source for indium, which is an expensive rare metal.

  As a method for collecting indium from such an indium source, in the case of starch, a method is proposed in which this is dissolved in an acid to form a solution, and a solvent extraction method is applied to the resulting indium-containing solution. ing. For example, a method for concentrating indium by performing liquid-liquid extraction using an organic solvent such as isopropyl ether, tributyl phosphate, methyl isobutyl ketone, or tertiary saturated fatty acids as an extraction solvent has been reported.

Among these, the method using isopropyl ether, tributyl phosphate or methyl isobutyl ketone as an extraction solvent is an excellent method in that indium can be selectively extracted. However, as an aqueous phase condition during extraction, high concentration hydrochloric acid is used. In particular, isopropyl ether and methyl isobutyl ketone have a problem that they have a large amount of dissolution in an aqueous phase and a very short service life. In addition, the method using tertiary saturated fatty acid is excellent in that the solvent is inexpensive and the type of acid and the concentration of indium are not limited, but the extraction rate depends on the type and concentration of coexisting metal salts in the aqueous phase. There is a problem of a significant drop.
In addition, the solvent extraction method has a common problem that the solvent is taken in or dissolved in the form of droplets in the residual liquid.

  Therefore, conventionally, for example, after adjusting the pH using a method described in JP-B-1-43590, indium is recovered with a chelate resin. However, although chelate resins are generally expensive and have excellent selective adsorption ability for specific metal ions, there is a problem that regeneration efficiency is poor from the viewpoint of regeneration and recovery, and a large amount of regenerant must be used. .

By the way, as a transparent electrode of a liquid crystal display device, an electroluminescence (EL) display device or the like, an indium-containing material to be etched, for example, indium-tin-oxide (hereinafter abbreviated as ITO) film, has a predetermined pattern. Etching is used. The ITO transparent electrode is formed by forming an ITO film on a substrate such as glass, applying a resist mask, and etching the ITO film. Therefore, from such a liquid crystal manufacturing process, an etching waste liquid containing indium ions and other metal ions such as tin is discharged.
When etching an ITO film, an oxalic acid solution in which oxalic acid and a surfactant are mixed is generally used as an etching solution. This etching solution is used for etching, for example, by spraying on the ITO substrate, and is circulated until the etching rate becomes slow and cannot be used. Thereafter, the etching waste liquid whose etching ability is impaired is discharged out of the system and is usually discarded as it is.

In recent years, ITO, which is a transparent electrode, has attracted attention as an indispensable material for liquid crystal, organic EL, etc., and its demand continues to increase despite being a rare metal, and as a result, the price continues to rise. Therefore, discarding the etching waste liquid containing indium results in the disposal of indium, which is an expensive rare metal in the waste liquid, and there are problems in terms of cost and effective use of rare metal resources. However, a method that can be satisfactorily satisfied as a method for selectively separating and recovering indium from an etching waste liquid containing indium at a low concentration has not been provided.
Japanese Patent Publication No. 1-343590

  The present invention has been made in view of the above-described conventional situation, and from a solution containing two or more types of metal ions, only one specific type of metal ions can be efficiently and inexpensively used without using an organic solvent. An object is to provide a method of selectively separating and recovering.

  As a result of intensive studies to solve the above problems, the present inventor has made metal ions other than those intended for separation and recovery as a metal complex by adjusting the degree of ionization using the ease of formation of the complex. The present invention was completed by finding that the metal ions in the dissociated state can be efficiently separated and recovered by the cation exchange means.

  That is, the gist of the present invention is as follows.

[1] A method for selectively separating and recovering a specific metal ion by separating and recovering only one metal ion from a solution containing two or more metal ions, wherein the solution is brought into contact with a compound that forms a metal complex. Thus, the metal ions excluding the one kind of metal ions in the solution are adjusted to be in a non-dissociated state, and then only the one kind of metal ions in the dissociated state are selectively separated and recovered by cation exchange means. A method for selectively separating and recovering a specific metal ion.

[2] The method for selectively separating and recovering a specific metal ion according to [1], wherein the compound that forms the metal complex is oxalic acid.

[3] The method for selectively separating and recovering specific metal ions according to [1] or [2], wherein the one metal ion to be selectively separated and recovered has a smaller complex formation constant than other metal ions.

[4] The method for selectively separating and recovering a specific metal ion according to any one of [1] to [3], wherein the one metal ion to be selectively separated and recovered is an indium ion.

[5] The method for selectively separating and recovering a specific metal ion according to any one of [1] to [4], wherein the cation exchange means contains a cation exchange resin.

  According to the method of the present invention, it is possible to easily and efficiently selectively separate and recover only one metal ion from a solution containing two or more metal ions without using an organic solvent.

  The formation of the non-dissociated state of the metal by the formation of the metal complex in the present invention will be described below by exemplifying a solution containing indium ions and tin ions.

When oxalic acid is added to such a solution as a compound that forms a metal complex (hereinafter sometimes referred to as a “metal complex forming agent”), indium ions (In ³⁺ ) and tin ions (Sn ²⁺ ) are each oxalic acid. A complex with the ion (: COO ⁻ ) ₂ is generated, and the complex itself becomes an anion. However, due to the difference in complex formation constant, indium with a small complex formation constant is partially dissociated into indium ions, while tin hardly dissociates and exists as a complex. Therefore, since anionic metal oxalate complexes (indium oxalate complex, tin oxalate complex) and indium ions are present in the system, only indium ions can be selectively separated and recovered by cation exchange means. Can do.

  Hereinafter, embodiments of the selective separation and recovery method for specific metal ions of the present invention will be described in detail.

  The selective separation and recovery method for a specific metal ion of the present invention is a dissociation state by a cation exchange means under the condition that a metal ion except for one kind of metal ion for separation and recovery purpose in a solution to be treated is in a non-dissociation state. This is a method for selectively separating and recovering only one kind of metal ion for the purpose of separation and recovery. Specifically, by adding oxalic acid as a metal complex forming agent, a specific purpose of separation and recovery is specified. A non-dissociable complex is generated with respect to metal ions other than metal ions, and then specific metal ions for separation and recovery are selectively separated and recovered by cation exchange means.

  As the metal species to be selectively separated and recovered in the present invention, indium which is an expensive rare metal is preferable because it is usually contained and discharged in an etching waste liquid and is very difficult to separate and recover due to its low concentration.

In the present invention, the metal species to be brought into a non-dissociated state is not particularly limited. However, when the metal species is brought into a non-dissociated state by complex formation, it is necessary to be a metal ion having a complex formation constant larger than the metal ion intended for separation and recovery. is there. In this case, the larger the difference in complex formation constant between the metal ion intended for separation and recovery and the other metal ions, the better. For example, complex formation constant of ^{Fe 3+} and ^{Cu 2+} with respect to citric acid is from ^{Fe 3+} is 11.9, ^{Cu 2+} is 5.2, citric acid tends to generate ^{Fe 3+} complexes than ^{Cu 2+.}

Moreover, in this invention, oxalic acid is used suitably as a metal complex production | generation agent. However, the metal complex generating agent is not limited to oxalic acid, and any metal complex generating agent may be used as long as it can easily generate a metal complex other than the metal ion intended for separation and recovery.
Two or more metal complex forming agents may be used in combination. The amount of the metal complex forming agent used may be an amount such that metal ions other than the metal ions for separation / recovery in the solution are in a non-dissociated state and the metal ions for separation / recovery are present in a dissociated state.

  Examples of cation exchange means effective for the present invention include cation exchange resins, chelate resins, and electroregenerative deionizers. However, chelate resins are expensive and have low regeneration efficiency. In the type deionizer, it is difficult to obtain a sufficient effect in the treatment with a high flow rate, and there is a problem that precipitation occurs in some cases, so that cation exchange resin is used, and metal ions other than metal ions for separation and recovery are in a non-dissociated state. A method in which a liquid in which only metal ions for separation and recovery are in a dissociated state is brought into contact with the cation exchange resin by passing the liquid through a cation exchange resin packed column is preferable.

  In order to separate and recover metal ions for separation and recovery using a cation exchange resin, a solution in which metal ions for separation and recovery exist in a dissociated state and other metal ions exist in a non-dissociated state in the cation exchange resin ( Hereinafter referred to as “liquid to be treated”), and only the dissociated metal ions may be adsorbed and separated by the cation exchange resin. In this case, the cation exchange resin may be added to the liquid to be treated and mixed with stirring, or the column may be filled with the cation exchange resin and the liquid to be treated may be passed. In any case, only the metal ions in the dissociated state are adsorbed and separated on the cation exchange resin, and the other metal ions in the non-dissociated state are not adsorbed on the cation exchange resin and are present in the liquid to be treated as they are. Only metal ions for separation and recovery are selectively separated.

  As described above, when a cation exchange resin is used as a cation exchange means, the separation and recovery performance is saturated by adsorbing the metal ions in a non-dissociated state, so that a regenerant is periodically passed through. Need to play. As this regenerant, about 2 to 10% by weight of strong acid such as hydrochloric acid can be used. Thus, the metal ions for separation and recovery are concentrated and eluted in the regeneration waste solution, and can be easily recovered.

  In the present invention, when the pH of the solution to be treated is strongly acidic, oxalic acid cannot exist as ions and exists in a molecular state, so that a metal complex cannot be generated, leading to a reduction in metal ion recovery rate. Therefore, in such a case, it is preferable to carry out the present invention after adjusting the pH to a neutral range (for example, 6.5 to 8.0) by adding an acid or alkali to the liquid to be treated and neutralizing it beforehand. .

  In the method of the present invention, in particular, when the liquid to be treated is an ITO etching waste liquid, oxalic acid as an etching component already exists, so it is not necessary to newly add a chemical substance as a metal complex forming agent. It is advantageous. However, you may add a metal complex production | generation agent further as needed.

  Here, the oxalic acid etching waste liquid is a waste liquid generated when an indium-containing material to be etched such as an ITO film is etched with an oxalic acid solution as described above. In this oxalic acid etching waste liquid, metal components such as indium and tin are present as a complex compound together with oxalic acid. However, as described above, indium has a smaller complex formation constant than tin, so that a part of it is dissociated to form indium ions. Therefore, selective separation and recovery by cation exchange means becomes possible.

  Hereinafter, the present invention will be described more specifically with reference to Examples and Comparative Examples.

Example 1
10 ml of a cation exchange resin (“Dow 650C” manufactured by Dow Chemical Co., Ltd.) was weighed in a beaker and charged into 100 ml of an ITO etching waste solution (4% by weight oxalic acid aqueous solution, indium concentration 180 ppm, tin concentration 50 ppm). Subsequently, after stirring for 30 minutes at 300 rpm, the mixture was filtered with a filter paper having a gap of 0.45 μm, and the test using the filtrate as a sample to measure the In concentration and the Sn concentration with an ICP-luminescence spectrometer was performed three times. The results shown in Table 1 were obtained.

  Moreover, when this resin was packed in a column, and 30 ml of 5% by weight hydrochloric acid was passed through it, and then extruded with 70 ml of pure water (total liquid volume: 100 ml), elution of indium in hydrochloric acid was confirmed. The concentrations shown in Table 1 were obtained.

Comparative Example 1
A test was conducted in the same manner as in Example 1 except that a chelate resin (“CR20” manufactured by Mitsubishi Chemical Corporation) was used instead of the cation exchange resin, and the results are shown in Table 1.

  As is clear from Table 1, the ITO etching waste liquid in which the metal complex is formed with oxalic acid is treated with a cation exchange resin and then eluted with hydrochloric acid to selectively recover only indium ions as indium chloride. I was able to.

  When a chelate resin is used in place of the cation exchange resin, although the amount of indium ions adsorbed is larger than that of the cation exchange resin, tin ions are also adsorbed, and the selective adsorptivity to indium is low and indium is selectively absorbed. It could not be recovered.

  The selective separation / recovery method for specific metal ions of the present invention is such that indium, tin, and other metal components generated when an indium-containing material to be etched such as an ITO film is etched with an oxalic acid solution are combined with oxalic acid as a complex compound. This is industrially useful as a method for selectively separating and recovering indium, which is an expensive rare metal, which is extremely difficult to separate and recover from existing etching waste liquid because of its low concentration.

Claims (5)

A method for selectively separating and recovering a specific metal ion, wherein only one metal ion is separated and recovered from a solution containing two or more metal ions,
The solution is adjusted so that the metal ions except the one metal ion in the solution are brought into a non-dissociated state by bringing the solution into contact with a compound that forms a metal complex. A method for selectively separating and recovering specific metal ions, wherein only one kind of metal ions is selectively separated and recovered.   The method for selectively separating and recovering a specific metal ion according to claim 1, wherein the compound that forms the metal complex is oxalic acid.   3. The method for selectively separating and recovering a specific metal ion according to claim 1, wherein the one metal ion to be selectively separated and recovered has a smaller complex formation constant than the other metal ions.   4. The method for selectively separating and collecting specific metal ions according to claim 1, wherein the one kind of metal ions to be selectively separated and recovered is indium ions.   5. The selective separation and recovery method for specific metal ions according to claim 1, wherein the cation exchange means includes a cation exchange resin.