JP6428441B2 - Acid waste liquid treatment apparatus and treatment method - Google Patents

Description

  The present invention relates to a processing apparatus and a processing method for an acid waste solution containing metal ions, and more specifically, from an acid waste solution containing metal ions such as iron (Fe), cobalt (Co), and nickel (Ni), to a cation exchange membrane. The present invention relates to an apparatus and a method for efficiently removing the metal ions by electrodialysis using a slag. The present invention particularly relates to nuclear power generation such as decontamination waste liquid generated by acid decontamination of metal pipes and equipment in nuclear power plants, and eluent obtained by eluting metal ions from ion exchange resins used in nuclear power plants. It is suitably used for the treatment of acid waste liquid containing metal ions generated from places.

  In a nuclear power plant, a large amount of decontamination waste liquid is generated when the radioactive material is chemically removed from the primary cooling system equipment and piping contaminated with the radioactive material and the metal member surface of the system including these. These decontamination waste liquids contain metal ions, particularly iron group metal ions such as Fe, Co or Ni, and also contain a large amount of radioactive substances such as Co-60 (cobalt 60) and Ni-63 (nickel 63). . Usually, the decontamination waste liquid is reused as a decontamination liquid after the ionic components dissolved by the ion exchange resin are removed. For this reason, there exists a problem that the waste of the ion exchange resin containing many radioactive substances generate | occur | produces.

  In nuclear power plants, etc., ion exchange resins used to purify cooling water systems containing radioactive materials by directly touching fuel rods such as the reactor water purification system (CUW) and the fuel storage pool water purification system (FPC) Because it absorbs a lot of radioactive material, it is stored as a high dose rate waste in a resin tank installed at the power plant.

  Waste containing these radioactive substances is finally kneaded with a solidification aid such as cement and stabilized, and then buried. The cost for disposal is different depending on the amount of radioactive material contained, and the higher the concentration of radioactive material, the higher the cost. For this reason, it is economical to reduce the volume of waste with a high dose rate as much as possible and then use it as a solid waste. Specifically, it is desirable in terms of volume reduction if the radioactive substance can be separated from the ion exchange resin as a solid and the solid can be enclosed in a shielding container. Waste ion exchange resin from which radioactive materials have been removed is a low-dose rate waste with low disposal costs, and if the radioactive materials can be removed to a level where incineration of the waste ion exchange resin can be achieved, incineration will significantly Volume reduction can be achieved.

  As a method for treating such high-dose waste resin, there are methods of decomposing waste resin by wet oxidation such as Fenton method and supercritical water oxidation as proposed in Patent Document 1 and Patent Document 2. In this case, a large amount of waste liquid with a high dose rate is generated. When the waste liquid with a high dose rate is finally disposed of, it is necessary to stabilize it as a solidified body by a method such as evaporating and concentrating and kneading the concentrated liquid with cement. In this case, since a solidification aid such as cement is newly added, there is a problem that the amount of waste at a high dose rate to be finally disposed increases and the amount of waste cannot be reduced.

  Patent Document 3 discloses a technique in which sulfuric acid is passed through waste resin, ionic radioactive substances are eluted, radioactive substances are separated from the eluent by diffusion dialysis, and sulfuric acid is circulated and reused. Patent Document 4 discloses a waste resin treatment method in which waste resin is immersed in an oxalic acid aqueous solution to dissolve the metal clad on the surface, and metal ions adsorbed on the resin are eluted into the oxalic acid aqueous solution. Yes. In these cases as well, waste liquid containing radioactive substances is generated, but the solidification process is not covered.

  On the other hand, as a method for removing radioactive substances from waste liquid containing ionic radioactive substances, Patent Document 5 discloses that a decontamination solution in which radioactive cations are dissolved is energized while passing through an electrodeposition cell, and the radioactive cations are used. Has been disclosed in which a decontamination solution is regenerated and reused by depositing as a radioactive metal particle on a cathode. At that time, the cathode on which radioactive metal particles are deposited is described as pouring catholyte over the entire cathode to desorb the radioactive metal particles.

  However, in this method, the catholyte property changes depending on the property of the decontamination waste liquid, and therefore the catholyte cannot be adjusted to a liquid property suitable for electrodeposition. When the decontamination solution is an acidic waste solution, the radioactive metal component deposited on the cathode surface is dissolved again in the acidic waste solution, so that no precipitation occurs or the deposition rate is significantly reduced. In addition, when the waste liquid is neutral or alkaline, a hydroxide precipitate is formed in the vicinity of the cathode surface, and it becomes difficult to recover by depositing radioactive metal on the cathode surface. For this reason, in order to efficiently recover radioactive substances from the waste liquid by the electrodeposition method, it is not preferable to introduce the waste liquid directly into the cathode chamber, and it is important to make the catholyte liquid suitable for electrodeposition. Become.

  In view of this, the inventors of the Japanese Patent Application No. 2013-221322 efficiently used iron group metal ions without being affected by the liquid properties of the iron group metal ion-containing waste liquid in the electrodeposition treatment of the iron group metal ion-containing liquid. A processing method and a processing device for iron group metal ion-containing waste liquid, which are deposited and removed from the liquid, were proposed. Specifically, iron group metal ion-containing waste liquid is introduced into the anode chamber of the electrodeposition tank in which the anode chamber with the anode and the cathode chamber with the cathode are separated by a cation exchange membrane, and the catholyte is introduced into the cathode chamber. Then, by applying current between the anode and the cathode, the iron group metal ions in the liquid in the anode chamber are moved into the catholyte in the cathode chamber so that the iron group metal is deposited on the cathode. The iron group metal can be electrodeposited and removed under appropriate electrodeposition conditions without being influenced by the liquid properties of the group metal ion-containing waste liquid.

Japanese Patent Publication No. 61-9599 Japanese Patent No. 3657747 JP 2004-28697 A JP 2013-44588 A Japanese Patent No. 4438898 Japanese Patent Application No. 2013-221322

By the technique of Japanese Patent Application No. 2013-221322, the iron group metal can be electrodeposited and removed under appropriate electrodeposition conditions without being influenced by the liquid property of the iron group metal ion-containing waste liquid. As a result of the examination, if the metal ions in the acid waste liquid are to be electrodeposited and removed according to Japanese Patent Application No. 2013-221322, the metal ions in the acid waste liquid are transferred through the cation exchange membrane to the electrodeposition liquid. It was confirmed that the acid group anion migrates to the electrodeposition liquid side through the cation exchange membrane.
Here, the acid group is also called an acid radical, and refers to a remaining atom or atomic group obtained by removing one or more hydrogen atoms that can be ionized as hydrogen ions from various inorganic and organic acid molecules. For example, it refers to Cl in hydrochloric acid, SO ₄ in sulfuric acid, and HSO ₄ . Further, the acid anion refers the molecules of the organic and inorganic various acids, anions consisting of the remainder of the atoms or atomic groups a hydrogen atom capable of ionizing excluding one or more as a hydrogen ion, such as Cl in hydrochloric acid ^- And SO ₄ ²⁻ and HSO ₄ ⁻ in sulfuric acid.

  If the acid group anion in the acid waste liquid moves to the electrodeposition liquid side, the acid concentration of the acid waste liquid decreases, so the acid waste liquid after removing metal ions can be effectively reused as the acid liquid. Not only does this disappear, but the pH of the electrodeposition solution decreases, which may cause poor electrodeposition when the metal ions are electrodeposited and removed from the electrodeposition solution.

  The present invention suppresses permeation of the acid group anion in the acid waste liquid through the cation exchange membrane in removing the metal ion in the acid waste liquid through the cation exchange membrane by electrodialysis using a cation exchange membrane, It is an object of the present invention to provide a treatment apparatus and a treatment method for an acid waste liquid that can be efficiently treated without reducing the acid concentration of the acid waste liquid and without causing poor electrodeposition.

As a result of intensive studies to solve the above problems, the present inventors use a cation exchange membrane having a film thickness of a predetermined value or more to prevent acid group anions from permeating through the cation exchange membrane. The present invention has been completed.
That is, the gist of the present invention is as follows.

[1] An acid waste liquid treatment apparatus for removing metal ions in an acid waste liquid by permeation through a cation exchange membrane by electrodialysis, wherein the film thickness of the cation exchange membrane is 0.25 to 1 mm. Waste liquid treatment equipment.

[2] In [1], the acid waste liquid is a radioactive acid waste liquid containing a radioactive metal ion generated when acid cleaning or acid elution of a radioactive metal pollutant is performed with an acidic decontamination liquid. The apparatus for treating an acid waste liquid, wherein the radioactive acid waste liquid from which the radioactive metal ions have been removed is reused as the acidic decontamination liquid.

[3] In [1] or [2], the metal ion in the acid waste liquid passes through the cation exchange membrane and forms a ligand-containing liquid containing a ligand that forms a complex with the metal ion. An acid waste liquid treatment apparatus characterized by being transferred.

[4] A method for treating an acid waste liquid, comprising removing metal ions in the acid waste liquid by electrodialysis through a cation exchange membrane having a thickness of 0.25 to 1 mm.

[5] In [4], the acid waste liquid is a radioactive acid waste liquid generated when acid cleaning or acid elution of a radioactive metal contaminant is performed with an acid decontamination liquid, and the radioactive acid waste liquid is obtained by a treatment method of the acid waste liquid. A method for treating an acid waste liquid, wherein the radioactive metal ions are removed and then reused as the acidic decontamination liquid.

[6] In [4] or [5], the metal ion in the acid waste liquid is passed through the cation exchange membrane to form a ligand-containing liquid containing a ligand that forms a complex with the metal ion. A method for treating an acid waste liquid, comprising transferring the acid waste liquid.

  According to the acid waste liquid treatment apparatus and method of the present invention, the acid group anion in the acid waste liquid is lost through the cation exchange membrane, thereby preventing the acid concentration of the acid waste liquid from being lowered. Can do. For this reason, the acid waste liquid after a metal ion removal process can be effectively reused as an acid liquid. Further, when metal ions are allowed to pass through the cation exchange membrane and transferred to the electrodeposition solution, inhibition of electrodeposition due to a decrease in pH of the electrodeposition solution due to the acid group anion permeating the cation exchange membrane is also prevented.

  Metal ions that permeate the cation exchange membrane from the acid waste liquid are transferred to a ligand-containing liquid containing a ligand that forms a soluble complex with the metal ion, thereby allowing the metal to permeate the cation exchange membrane. Ions can be prevented from precipitating as hydroxide or clogging the cation exchange membrane. According to the present invention, when an organic acid or organic acid salt is used as the ligand-containing liquid, Since it can also prevent that the acid group of an organic acid permeate | transmits a cation exchange membrane and transfers to the acid waste liquid side, the stable electrodeposition process can be performed continuously.

It is a systematic diagram of the processing apparatus which shows an example of embodiment of this invention. It is a systematic diagram of the processing apparatus which shows the other example of embodiment of this invention. It is a systematic diagram of the processing apparatus which shows another example of embodiment of this invention. It is a systematic diagram of the test apparatus used in the Example. It is a graph which shows the time-dependent change of the TOC density | concentration in the simulated acid waste liquid in Example 1 and Comparative Example 1. It is a graph which shows a time-dependent change of Fe density | concentration in the simulated acid waste liquid in Example 1 and Comparative Example 1.

  Hereinafter, embodiments of the present invention will be described in detail.

The acid waste liquid to be treated according to the present invention is not particularly limited as long as it is an acid waste liquid containing metal ions such as iron group metal ions such as iron, cobalt, and nickel, but the present invention includes the following (1), (2 It is suitable for the treatment of acid waste liquid.
(1) Primary cooling system equipment and piping contaminated with radioactive materials at nuclear power plants, acid waste solution in which radioactive materials are acid-dissolved from the surface of metal parts of systems containing them (2) Used ion exchange at nuclear power plants Resin (Ion exchange resin used for purification of cooling water system containing radioactive material by directly touching fuel rods such as reactor water purification system (CUW) and fuel storage pool water purification system (FPC)) Eluted acid waste solutions that have been acid-eluted to remove radioactive metal ions from the waste solution (ion exchange resin used to remove radioactive metal ions from the waste solution). Usually these acid waste solutions are strong acid waste solutions having a pH of 5 or less, preferably pH 2 or less. is there.

  Since the decontamination acid waste liquid and the elution acid waste liquid contain radioactive cobalt which is one of iron group ions, according to the present invention, the radioactive cobalt in these acid waste liquids is bulky on the cathode of the electrodeposition tank. There is an advantage that it can be stably fixed as a small metal state, and the acid waste solution after the removal of radioactive cobalt can be effectively reused as the acid solution for the above decontamination and acid elution.

In the present invention, when removing metal ions from the acid waste solution containing metal ions by electrodialysis using the cation exchange membrane through the cation exchange membrane, the film thickness of the cation exchange membrane is 0. The thing of 25-1 mm is used. By using a relatively thick cation exchange membrane having a film thickness of 0.25 mm or more as the cation exchange membrane, the acid group anion in the acid waste liquid permeates through the cation exchange membrane and the acid concentration of the acid waste liquid decreases, or electrodeposition When the pH of the solution is lowered or further contains an organic acid or organic acid salt described later in the electrodeposition solution, these acid group anions permeate the cation exchange membrane from the electrodeposition solution side to the acid waste solution side. It is possible to prevent migration. From the viewpoint of preventing the permeation of acid group anions, the cation exchange membrane is preferably thicker, but if the cation exchange membrane is excessively thick, the membrane resistance increases and the power consumption increases. It is not preferable.
The thickness of the cation exchange membrane is preferably 0.30 to 0.80 mm, more preferably 0.35 to 0.50 mm.
Normally, in electrodialysis, a thin film having a thickness of 0.20 mm or less is used in order to reduce the membrane resistance by reducing the film thickness of the ion exchange membrane as much as possible. In the present invention, in order to prevent permeation of acid group anions, a cation exchange membrane having the above thickness is used.

  The smaller the exchange group density of the cation exchange membrane used in the present invention, the higher the effect of inhibiting the acid group anion in the acid waste liquid from permeating the cation exchange membrane. Further, when the electrodeposition liquid contains an organic acid or organic acid salt described later, the acid group anion permeates the cation exchange membrane from the electrodeposition liquid side as the exchange group density of the cation exchange membrane is smaller. The effect which suppresses shifting to the side is high. However, when the exchange group density of the cation exchange membrane is excessively reduced, the permeation rate of metal ions in the cation exchange membrane is reduced, the membrane resistance is increased, and the power consumption is increased. For these reasons, the cation exchange membrane used in the present invention preferably has an exchange group density of 1.0 to 2 meq / g-dry membrane, and 1.5 to 1.8 meq / g-dry membrane. Is more preferable.

Hereinafter, the present invention will be described in more detail with reference to the drawings. In one embodiment of the present invention,
An anode chamber having an anode and a cathode chamber having a cathode are separated by a cation exchange membrane, an acid waste solution containing metal ions is introduced into the anode chamber, and a catholyte (electrodeposition solution) is introduced into the cathode chamber. The metal ions in the acid waste liquid in the anode chamber are transferred to the liquid in the cathode chamber by passing electricity between the anode and the cathode, and the metal is deposited on the cathode. Acid waste liquid treatment method,
And an electrode chamber having an anode chamber having an anode, a cathode chamber having a cathode, a cation exchange membrane separating the anode chamber and the cathode chamber, and an energizing means for energizing between the anode and the cathode, The anode chamber has a liquid passing means for passing an acid waste solution containing metal ions, and a liquid passing means for passing a catholyte (electrodeposition liquid) to the cathode chamber, and is energized between the anode and the cathode. An acid waste liquid treatment apparatus for causing metal ions in the acid waste liquid in the anode chamber to pass through the cation exchange membrane and moving into the liquid in the cathode chamber, and depositing the metal on the cathode,
Thus, the metal ions in the acid waste liquid are removed.

In another aspect of the present invention,
An acid waste solution containing metal ions and an electrodeposition solution containing a ligand that forms a complex with the metal ions are introduced into an electrodialysis tank provided with a plurality of cation exchange membranes, and the metal ions in the acid waste solution Is transferred to the electrodeposition liquid through the cation exchange membrane to remove metal ions in the acid waste liquid, and an electrodeposition liquid containing metal ions flowing out of the electrodialysis tank. An electrodeposition step in which the metal ion in the electrodeposition solution is electrodeposited on the cathode to remove the metal ions from the electrodeposition solution; A method for treating an acid waste liquid, comprising: an electrodeposition liquid circulation step for feeding the electrodeposition liquid from which metal ions have been removed in the step to the electrodialysis step;
And an electrodialysis tank having an anode chamber provided with an anode, a cathode chamber provided with a cathode, and a plurality of cation exchange membranes provided between the anode and the cathode chamber, an anode of the electrodialysis tank, and An energizing means for energizing between the cathodes, an acid waste solution containing metal ions in the electrodialysis tank, and a means for passing an electrodeposition solution containing a ligand that forms a complex with the metal ions, An electrodialyzer that removes the metal ions in the acid waste liquid by allowing the metal ions in the acid waste liquid to pass through the cation exchange membrane and transfer to the electrodeposition liquid; an anode chamber equipped with an anode; An electrodeposition tank having a cathode chamber provided with a cathode; a cation exchange membrane separating the anode chamber and the cathode chamber; energization means for energizing between the anode and the cathode; Means for passing the electrodeposition liquid containing the metal ions flowing out from the dialysis tank, An electrodeposition apparatus for removing the metal ions from the electrodeposition liquid by electrodepositing the metal in the electrodeposition liquid containing ions onto the cathode; and an electrode from which the metal ions flowing out of the electrodeposition tank have been removed. An acid waste liquid treatment apparatus comprising: a means for feeding the liquid to the electrodialysis tank;
Thus, the metal ions in the acid waste liquid are removed.

In the another aspect, more specifically, the following (I) or (II) can be used as the electrodialysis tank.
(I) an anode and a cathode, a first bipolar film disposed opposite to the anode, a second bipolar film disposed opposite to the cathode, the first bipolar film and the second A plurality of cation exchange membranes arranged between the bipolar membranes and a third bipolar membrane arranged between the cation exchange membranes, wherein the gap between the anode and the first bipolar membrane is An anode chamber, a cathode chamber is provided between the cathode and the second bipolar membrane, and a deionization chamber is provided between the cation exchange membrane and the bipolar membrane provided on the anode side of the cation exchange membrane. A concentration chamber is formed between the cation exchange membrane and the bipolar membrane provided on the cathode side of the cation exchange membrane, and the acid waste liquid is passed through the deionization chamber and What was comprised so that the said electrodeposition liquid might flow.
(II) an anode and a cathode, a first hydrogen permselective cation exchange membrane disposed against the anode, a second hydrogen permselective cation exchange membrane disposed against the cathode, A plurality of cation exchange membranes arranged between the first hydrogen selective permeable cation exchange membrane and the second hydrogen selective permeable cation exchange membrane, and a third arranged between the cation exchange membranes. A hydrogen selective permeation type cation exchange membrane, and a space between the anode and the first hydrogen selective permeation type cation exchange membrane between an anode chamber and the cathode and the second hydrogen selective permeation type cation exchange membrane. Is a cathode chamber, and a space between the cation exchange membrane and the hydrogen selective permeable cation exchange membrane provided on the anode side of the cation exchange membrane is a deionization chamber, the cation exchange membrane and the cation exchange membrane. The hydrogen permselective cation exchange provided on the cathode side of Film has become a concentrating compartment between, as well as liquid permeability of the acid waste liquid deionizing chamber, which is configured to liquid passage the electrodeposition solution in the concentrating compartment.

  FIG. 1 is a system diagram showing an example of an embodiment of an acid waste liquid treatment apparatus of the present invention, and shows an example in which the present invention is applied to a decontamination process of a waste ion exchange resin used in a nuclear power plant. .

  The apparatus of FIG. 1 includes an eluent storage tank 30 for storing an eluent obtained by eluting metal ions from a waste ion exchange resin, an elution tank 8 that is a packed tower filled with a waste ion exchange resin 40, and an elution tank 8. Acid waste liquid storage tank 10 for storing acid waste liquid containing metal ions to be discharged, electrodeposition tank 1 into which acid waste liquid from acid waste liquid storage tank 10 is introduced, and cathode for storing catholyte supplied to electrodeposition tank 1 A liquid storage tank 20. The electrodeposition tank 1 has a structure in which an anode chamber 2A having an anode 2 and a cathode chamber 3A having a cathode 3 are separated by a cation exchange membrane 5, and the acid waste liquid from the acid waste liquid storage tank 10 is supplied to the anode chamber 2A. The catholyte is passed through the cathode chamber 3A. 9A and 9B are heat exchangers.

Eluent of the eluent storage tank 30 is a heat exchanger 9A 60 ° C. or higher in the process of being delivered to the elution tank 8 through the pipe 31 by the pump _{P 3,} preferably 70 to 120 ° C., more preferably 80 to 100 After being heated to ° C., the elution tank 8 is passed upwardly, and the effluent (acid waste liquid) passes through the pipe 32, and the cation exchange membrane 8 in the electrodeposition tank 4 is deteriorated by the heat exchanger 9B. After being cooled to a small temperature of less than 60 ° C., for example, 10 ° C. or more and less than 60 ° C., the acid waste solution storage tank 10 is fed. Acid waste acid waste liquid storage tank 10 by the pump P ₁ is introduced into the anode chamber 2A of the through pipe 11 electrodeposition tank 1, electrodeposition processing liquid is circulated in the eluent reservoir 30 from the pipe 34, re as eluent Used.

On the other hand, the catholyte in the catholyte storage tank 20 is introduced into the cathode chamber 3A of the electrodeposition tank ₁ through the pipe 21 by the pump P2, and returned to the catholyte storage tank 20 through the pipe 22.
The eluent storage tank 30 is appropriately replenished with acid through a pipe 33, and the catholyte storage tank 20 is replenished with a catholyte through a pipe 23.

In this apparatus, by passing the heated eluent through the elution tank 8 filled with the waste ion exchange resin 40, the ionic radionuclide adsorbed on the waste ion exchange resin 40 is eluted and removed. Then, the clad mixed in the waste ion exchange resin 40 or entering the resin particles is dissolved and removed. In contact with the waste ion exchange resin 40, an eluent (acid waste liquid) containing ionic radionuclides and clad melt is introduced into the anode chamber 2 </ b> A of the electrodeposition tank 1 through the acid waste liquid storage tank 10. By energizing the anode 2 and the cathode 3 of the electrodeposition tank 1, metal ions such as radioactive metal ions in the acid waste liquid and iron ions derived from the cladding permeate the cation exchange membrane 5 and move to the cathode chamber 3A. Electrodeposited on the cathode 3. The acid waste liquid treatment liquid from which metal ions have been removed in the electrodeposition tank 1 is returned to the eluent storage tank 30 and recycled.
The catholyte in the cathode chamber 3 </ _b > A is circulated between the catholyte storage tank 20 by the pump P < _b > _2, and the reduced amount of the catholyte is circulated and reused while being added to the catholyte storage tank 20.

  The pH of the catholyte used in the present invention is preferably from 1 to 9, and more preferably from 2 to 8. When the pH of the catholyte is too low, re-dissolution of the electrodeposited metal occurs on the cathode, which may reduce the electrodeposition rate. On the other hand, when the pH of the catholyte is too high, metal hydroxide is likely to be generated as a suspended substance in the liquid. Therefore, when the pH of the catholyte is out of the above range, it is preferable to adjust the pH appropriately with an alkali or an acid. However, in the present invention, the acid waste liquid is obtained by using the cation exchange membrane having the above-mentioned thickness. The pH drop of the catholyte due to permeation of acid group anions from the cation exchange membrane is prevented.

  The catholyte preferably contains a ligand capable of forming a complex with a metal ion that has permeated the cation exchange membrane, and in order to make such a ligand exist, a complex that forms a complex with the metal ion. It is preferable to add an agent (hereinafter sometimes referred to as “the complexing agent of the present invention”).

The complexing agent of the present invention includes dicarboxylic acid having two carboxyl groups in the molecule and a salt thereof (hereinafter sometimes referred to as “dicarboxylic acid (salt)”), and three carboxyl groups in the molecule. Those selected from the tricarboxylic acid and salts thereof (hereinafter sometimes referred to as “tricarboxylic acid (salt)”) are preferable. These may use only 1 type and may mix and use 2 or more types. Dicarboxylic acids (salts) and tricarboxylic acids (salts) suppress the generation of suspended substances during electrodeposition due to their chelating effects, and have an excellent effect in improving the electrodeposition effect.
In contrast, a monocarboxylic acid having one carboxyl group in the molecule has a weak binding force with metal ions, and a suspended substance composed of a metal hydroxide is generated in the liquid. Problems such as not wearing. Further, when a carboxylic acid having four or more carboxyl groups in the molecule is used, there is a problem that the binding force with metal ions is too strong, the metal is retained in the liquid, and the electrodeposition rate is significantly reduced. .

  As the dicarboxylic acid (salt) and tricarboxylic acid (salt), those represented by the following formula (1) are particularly preferable in that suspended substances are hardly generated and electrodeposition proceeds rapidly. The dicarboxylic acid (salt) or tricarboxylic acid (salt) represented by the following formula (1) has 1 to 3 carbon atoms between the carboxyl groups in the molecule, and is derived from its shape. Thus, it is estimated that an appropriate binding force can be obtained with the metal ion.

^{_{M 1 OOC- (CHX 1) a}} - (NH) b - (CX 2 X 4) c -CX 3 X 5 -COOM 2
... (1)
(In the formula (1), X ¹ , X ² and X ³ each independently represent H or OH, X ⁴ and X ⁵ each independently represent H, OH or COOM ³ , M ¹ , M ² , M ³ each independently represent H, monovalent alkali metal or ammonium ion, and a, b, and c each independently represent an integer of 0 or 1. However, in Formula (1), X ⁴ and X ⁵ are simultaneously COOM ³ will never be reached.)

Suitable dicarboxylic acids in the present invention, for example, oxalic acid (ethanedioic acid, HOOC-COOH), malonic acid (propanedioic acid, _HOOC-CH 2 -COOH), succinic acid (butanedioic acid, HOOC-CH ₂ -CH ₂ -COOH), glutaric acid (pentanedioic _{acid, HOOC-CH 2 -CH 2 -CH} 2 -COOH), malic acid (2-hydroxybutanedioic _{acid, HOOC-CH 2 -CH (OH} ) -COOH) , Tartaric acid (2,3-dihydroxybutanedioic acid, HOOC—CH (OH) —CH (OH) —COOH), iminodiacetic acid (HOOC—CH ₂ —NH—CH ₂ —COOH), etc. Acid, succinic acid, malic acid, tartaric acid and iminodiacetic acid are particularly preferred. Examples of the tricarboxylic acid include citric acid (HOOC—CH ₂ —COH (COOH) —CH ₂ —COOH), 1,2,3-propanetricarboxylic acid, and citric acid is particularly preferable. In addition, examples of salts of these dicarboxylic acids and tricarboxylic acids include alkali metal salts such as sodium salts and potassium salts, and ammonium salts.

  In the present invention, when the acid waste liquid contains a plurality of types of metal ions, it is preferable that an ammonium salt coexists with a dicarboxylic acid (salt) and / or a tricarboxylic acid (salt). For example, when an acid waste solution containing Co and Fe is treated according to the present invention, when no ammonium salt is added, Co is usually faster in electrodeposition than Fe, and Fe is deposited on the Co electrodeposition layer. An electrodeposition layer is formed, but by adding an ammonium salt, the electrodeposition rates of Co and Fe become substantially equal, and Co and Fe are electrodeposited in an alloy form. When the electrodeposition rates of Co and Fe are different and electrodeposition is performed by separating the Co layer and the Fe layer, the electrodeposition tends to float or peel off due to the difference in the physical properties of Co and Fe, and continuous electrodeposition processing is performed. There is a risk that it will not be possible.

  Any ammonium salt may be used as long as it produces ammonium ions in the liquid. For example, ammonium chloride, ammonium sulfate, ammonium oxalate, and ammonium citrate are preferable. These ammonium salts may be used alone or in combination of two or more. In particular, when ammonium dicarboxylate such as ammonium oxalate or ammonium tricarboxylate such as ammonium citrate is used, the ammonium salt and the complexing agent of the present invention can be used, and suspension due to the chelating effect of dicarboxylic acid or tricarboxylic acid It is possible to obtain the effect of suppressing the generation of substances and the effect of adjusting the electrodeposition rate of Co and Fe with one agent.

The concentration of the complexing agent of the present invention in the catholyte used in the present invention is not particularly limited, but it is introduced into the cathode chamber with respect to the total molar concentration of metal ions in the acid waste solution introduced into the anode chamber. It is preferable that the molar concentration of the complexing agent of the present invention in the catholyte is 0.1 to 50 times, particularly 0.5 to 10 times. As the catholyte, for example, the complexing agent of the present invention is used. An aqueous solution having a pH of 1 to 9, preferably 2 to 8 containing 0.01 to 20% by weight, preferably 0.1 to 5% by weight is used. If the amount of the complexing agent of the present invention is too small, the effect of inhibiting suspended substances due to the use of the complexing agent of the present invention cannot be sufficiently obtained. The landing speed is reduced.
The complexing agent of the present invention is oxidatively decomposed when it comes into contact with the anode of the electrodeposition tank. However, in the present invention, the cation exchange membrane separates the anode chamber and the cathode chamber, and therefore the complexing agent is included. Since the electrodeposition liquid does not come into direct contact with the anode, the complexing agent is not oxidized and wasted, and it is contained in the catholyte by using a cation exchange membrane having the above-mentioned film thickness. It is also possible to prevent the complexing agent passing through the cation exchange membrane from being transferred to the acid waste liquid and lost. Therefore, in the present invention, the amount of complexing agent to be replenished in the catholyte may be very small, and the amount of chemicals used can be reduced.

  When an ammonium salt is used, the ammonium salt is preferably used in an amount such that the concentration in the catholyte is 0.01 to 20% by weight, preferably 0.1 to 5% by weight. If the concentration of the ammonium salt is too low, the above effect due to the use of the ammonium salt cannot be sufficiently obtained, and if it is too high, the effect is not improved and the amount of chemicals used increases.

  The electrodeposition conditions (current value, current density, temperature, etc.) are not particularly limited, but the current density is preferably 5 to 600 mA / cm 2 with respect to the cathode area in view of electrodeposition efficiency.

In the apparatus of FIG. 1, it is preferable to use an acid eluent heated to 60 ° C. or higher as the eluent used for decontamination of the waste ion exchange resin. radioactive metal ions adsorbed on the cation exchange resin of the ion exchange resin is possible to eliminate eluted replace H ⁺ ions and ions, can also be effectively dissolve and remove the cladding mixed in the waste ion-exchange resin It becomes.

  As the acid eluent, an aqueous solution of an inorganic acid such as sulfuric acid, hydrochloric acid or nitric acid, or an organic acid such as formic acid, acetic acid or oxalic acid can be used. These acids may be used alone or as a mixture of two or more, but sulfuric acid and / or oxalic acid that does not easily volatilize when heated and used and does not fall under hazardous materials is used. It is preferable.

The acid concentration in the eluent has a suitable concentration depending on the acid used. For example, the sulfuric acid concentration is preferably 5 to 40% by weight, more preferably 10 to 30% by weight. The oxalic acid concentration is preferably 0.1 to 40% by weight, more preferably 1 to 20% by weight. When the acid concentration is lower than the above range, the dissolution efficiency of hematite (α-Fe ₂ O ₃ ), which is the main component of the cladding, is lowered. That is, the clad is present in a form mixed in or entering the waste ion exchange resin, the main component of which is hardly soluble hematite, and it is difficult to dissolve with a low concentration of acid. If the acid concentration in the eluent is high, the amount of hydrogen generated in the subsequent electrodeposition tank becomes excessive, and the electrodeposition efficiency decreases.

  In the apparatus of FIG. 1, radioactive substances are highly concentrated by electrodepositing on the cathode what becomes a metal cation, such as cobalt-60 and nickel-63 contained in the radioactive waste ion exchange resin. can do. On the other hand, it is possible to obtain a waste ion exchange resin whose radiation dose is reduced to an extremely low level, and the treated waste ion exchange resin can be incinerated. Then, the amount of waste can be reduced to a capacity of 1/100 to 1/200 by incinerating the waste ion exchange resin into incineration ash.

  In the apparatus of FIG. 1, the electrodeposition tank 1 is a closed system. However, since hydrogen gas is generated from the cathode, it is preferable to use an open system with the upper part opened. In addition, when replacing the cathode electrodeposited with metal, the replacement is easier if the upper part of the electrodeposition tank is open. Further, the eluent is passed through the elution tank 8 in an upward flow, but may be a downward flow. However, when the waste ion exchange resin is in the form of a powder, it is preferable to make the flow upward because the differential pressure is likely to increase during liquid flow. In the electrodeposition tank 1, the acid waste liquid and the catholyte may be passed through the cation exchange membrane 5 in the opposite directions. Furthermore, it is possible to exchange heat between the eluent introduced into the elution tank 8 and the discharged acid waste liquid.

2 and 3 are system diagrams showing an example of another embodiment of the acid waste liquid treatment apparatus of the present invention.
The treatment apparatus of FIG. 1 performs permeation of metal ions through a cation exchange membrane and electrodeposition of metal ions in one tank of an electrodeposition tank 1, while FIGS. 2 and 3 show an electrodialysis tank and an electrodeposition tank. Are separately provided, the cation exchange membrane of metal ions is permeated in the electrodialysis tank, the electrodeposition of metal ions is performed in the electrodeposition tank, and further, a plurality of cation exchange membranes are provided in the electrodialysis tank. It is an improvement in efficiency.

The acid waste liquid treatment apparatus of FIG. 2 includes an electrodialysis tank 50 and an electrodeposition tank 60.
First, the electrodialysis tank 50 will be described. In the electrodialysis tank 50, the bipolar membrane BP and the cation exchange membrane CM are alternately arranged between the anode 51A and the cathode 52A.
A bipolar film (first bipolar film) BP is disposed to face the anode 51A, and an anode chamber 51 is formed between the anode 51A and the first bipolar film BP.
A bipolar film BP (second bipolar film) BP is disposed opposite the cathode 52A, and a cathode chamber 52 is formed between the cathode 52A and the second bipolar film BP.

  A plurality of (three in FIG. 2) cations are provided at a predetermined interval between the first bipolar film BP that partitions the anode chamber 51 and the second bipolar film BP that partitions the cathode chamber 52. The exchange membrane CM is arranged, and the bipolar membrane (third bipolar membrane) BP is arranged at a further interval between the cation exchange membranes CM, whereby a liquid passage chamber is formed.

  The chamber on the anode 51A side of the cation exchange membrane CM is a deionization chamber 53 through which the acid waste liquid is passed, and the chamber on the cathode 52A side of the cation exchange membrane CM is a concentration chamber 54 through which the electrodeposition solution is passed. is there.

  The bipolar membrane BP is an ion exchange membrane having a structure in which a cation exchange membrane layer and an anion exchange membrane layer are laminated, and the anion exchange membrane layer is disposed on the anode 51A side and the cation exchange membrane layer is disposed on the cathode 52A side. Is done. Even if a voltage is applied, the bipolar membrane BP does not transmit cations or anions, and is energized by dissociating water into hydrogen ions and hydroxide ions in the bipolar membrane BP.

  For this reason, in the electrodialysis tank 50 of FIG. 2, when a voltage is applied between the anode 51A and the cathode 52A, the metal ions in the acid waste liquid flowing through the deionization chamber 53 permeate the cation exchange membrane CM. Then, it moves into the electrodeposition liquid flowing through the concentration chamber 54. Thereby, the metal ion in an acid waste liquid is removed. Although the acid group anions (here, sulfate ions and hydrogen sulfate ions) in the acid waste liquid are electrically attracted to the anode 51A side, the bipolar membrane BP does not permeate the acid group anions, and therefore remains in the acid waste liquid. The solution after dialysis can be reused as an acid solution.

In FIG. 2, the acid waste liquid introduced into the deionization chamber 53 of the electrodialysis tank 50 through the lines L ₁ , L _1A , L _1B and the line L _1C has metal ions removed by electrodialysis in the electrodialysis tank 50. Then, it is returned to the decontamination process through the lines L _2A , L _2B , L _2C and the line L ₂ and reused.

On the other hand, the electrodeposition liquid from the electrodeposition solution storage tank 80 by a pump _{P 1,} line _{L 3} and the line _{L 3A,} L _3B, is introduced through the _{L 3C} to concentrating compartment 54 of the electrodialysis cell 50. Electrodeposition liquid containing metal ions that have permeated through the cation exchange membrane CM from the deionization chamber 53 and moved to the concentration chamber 54 by electrodialysis in the electrodialysis tank 50 passes through the lines L _4A , L _4B , L _4C and the line L ₄ . After that, it is returned to the electrodeposition liquid storage tank 80. As described later, since the metal ions in the electrodeposition liquid storage tank 80 are removed in the electrodeposition tank 60, the electrodeposition liquid from which the metal ions have been removed is supplied to the electrodialysis tank 50. Is done. As the electrodeposition liquid, the same one as the catholyte in FIG. 1 is used.

  An electrode solution containing an electrolyte is circulated in the anode chamber 51 and the cathode chamber 52 of the electrodialysis tank 50. It is necessary to select an electrolyte that does not cause oxidation at the anode 51A, reduction at the cathode 52A, or precipitation at the cathode 52A, and sulfuric acid or an alkali metal salt of sulfuric acid is preferable.

In Figure 2, electrodeposition tank 60 and anolyte provided a common electrodeposition solution storage tank 70, the electrode solution of the electrodeposition liquid storage tank 70 to the anode chamber 51 of the electrodialysis cell 50 via line L ₅ by the pump P ₂ After the introduction, it is introduced into the cathode chamber 52 via the line L ₆ , the circulation system returning to the electrodeposition liquid storage tank 70 via the line L _7, and the electrode liquid in the electrodeposition liquid storage tank 70 are supplied to the line L ₈ by the pump P _3. introduced into the anode chamber 61 of the electrodeposition tank 60 through, but to form a circulation passage for returning the electrodeposition solution storage tank 70 via line L _9, is not limited in any way to this embodiment, the electrodes An electrode solution storage tank may be provided for each chamber.

  In the electrodialysis tank 50 of FIG. 2, three cation exchange membranes CM are provided and three deionization chambers 53 are formed. However, the number of cation exchange membranes CM is not limited to three, and two cation exchange membranes CM can be used. Four or more may be used. As the number of cation exchange membranes in the electrodialysis tank increases, the cation exchange membrane area can be increased relative to the electrode area, and the permeation rate of metal ions can be increased without increasing the current value. When the number is increased, the resistance of the entire electrodialysis tank is increased, the power consumption is increased, and the temperature in the electrodialysis tank is increased. If the temperature of the electrodialysis tank becomes 40 ° C. or higher, the cation exchange membrane or the bipolar membrane may deteriorate. Therefore, when the temperature of the electrodialysis tank tends to increase, the temperature in the electrodialysis tank does not exceed 40 ° C. Thus, it is preferable to cool the acid waste solution, the electrodeposition solution, or the electrode solution as necessary.

  In FIG. 2, the acid waste liquid in the deionization chamber 53 and the electrodeposition liquid in the concentration chamber 54 are passed in the same direction, but they may be passed in opposite directions. Moreover, there is no restriction | limiting in particular also about the flowing direction of the electrode liquid of the anode chamber 51 and the cathode chamber 52. FIG.

  In addition, it is preferable to provide an appropriate spacer between the cation exchange membrane CM and the bipolar membrane BP of the electrodialysis tank 50 so that the membranes are in close contact with each other due to membrane deflection or the like and the flow path is not blocked. The shape of the spacer is not particularly limited as long as the flow path is secured, and any shape such as a net shape, a honeycomb shape, or a ball shape can be adopted. The material of the spacer is preferably selected according to the properties of the liquid to be passed, and when the acid waste liquid is treated, a material having acid resistance is selected.

Next, the electrodeposition tank 60 will be described.
As the electrodeposition tank, as shown in FIG. 2, a two-chamber electrodeposition tank 60 in which an anode chamber 61 in which an anode 61A is disposed and a cathode chamber 62 in which a cathode 62A is disposed is partitioned by a cation exchange membrane CM. Is preferably used. It electrodeposition solution which contains metal ions sent to the electrodialysis cell 50 color electrodeposition solution storage tank 80 is introduced to the cathode chamber 62 of the via line L ₁₀ by the pump P ₄ electrodeposition tank 60. By applying a voltage between the anode 61A and the cathode 62A of the electrodeposition tank 60, the metal ions in the electrodeposition liquid are deposited as metal on the cathode 62A and are electrodeposited and immobilized.

  As in the electrodialysis tank 50, an electrolyte solution that does not oxidize at the anode 61A is used as the anolyte in the electrodeposition tank 60. In FIG. 2, the anolyte in the electrodeposition tank 60 and the electrode liquid in the electrodialysis tank 50 are shared, but these may be separated.

  As in the electrodialysis tank 50, the direction in which the anolyte flows in the anode chamber 61 and the direction in which the electrodeposition liquid flows in the cathode chamber 62 may be the same as shown in FIG. May be.

  In the electrodialysis tank 50, the ion exchange membrane disposed between the cation exchange membranes does not transmit metal ions (if a membrane that allows metal ions to pass through is used, the ion exchange membrane passes through the cation exchange membrane and moves to the electrodeposition solution. Metal ions permeate through the membrane and return to the acid waste liquid) and do not permeate the acid group anion (when a membrane through which the acid group anion permeates is used, the acid group anion penetrates the membrane, It is a condition that the electrode solution is transferred to the electrodeposition solution or the electrode solution in the anode chamber, and the acid waste solution cannot be reused as the acid solution). From such a point, not only a bipolar membrane but also a hydrogen selective cation exchange membrane can be used. The hydrogen selective permeation type cation exchange membrane is a cation exchange membrane having a high hydrogen ion transport number (ratio in which the movement of hydrogen ions contributes to the current) and satisfies the above-mentioned required characteristics. As a hydrogen selective permeation type cation exchange membrane, AGC Engineering's Selemion CMF or the like can be adopted as a commercial product.

  FIG. 3 differs from the electrodialysis tank 50 in that a hydrogen selective permeation type cation exchange membrane HCM is used instead of the bipolar membrane BP, and other configurations are the same as those in FIG. In FIG. 2, members having the same functions as those in FIG.

As shown in FIGS. 2 and 3, by separately providing the electrodialysis tank and the electrodeposition tank, the metal ion dialysis speed in the electrodialysis tank and the metal ion electrodeposition speed in the electrodeposition tank are optimal. Conditions such as current density can be set so that
The current density of the electrodialysis tank that performs dialysis of metal ions is 10 to 400 mA / mm with respect to the cathode area, regardless of whether a bipolar membrane or a hydrogen selective permeation cation exchange membrane is used. it is preferably cm ^2, and more preferably 20~200mA / cm ^2.
Moreover, it is preferable that it is 5-200 mA / cm < ² > with respect to a cathode area, and, as for the current density of an electrodeposition tank, it is more preferable that it is 10-150 mA / cm < ² >.

  Also, as shown in FIGS. 2 and 3, the electrodialysis tank and the electrodeposition tank are provided separately, thereby simplifying the structure of the electrodeposition tank, and replacing the cathode on which metal is deposited and deposited by electrodeposition. In this case, the replacement work can be easily performed without the work being hindered by complicated constituent members.

  In this way, when the treatment apparatus having the electrodialysis tank and the electrodeposition tank is applied to the decontamination process of the waste ion exchange resin used in the nuclear power plant, the waste ion exchange is performed as in FIG. An eluent storage tank for storing an eluent obtained by eluting radioactive metal ions from a resin, an elution tank that is a packed tower filled with a waste ion exchange resin, and an acid waste liquid storage tank for storing an acid waste liquid discharged from the elution tank The acid waste liquid from the acid waste liquid storage tank is passed through the deionization chamber 53 of the electrodialysis tank 50 to remove the metal ions, and then circulated to the eluent storage tank to be reused as the eluent.

  Hereinafter, the present invention will be described more specifically with reference to examples.

[Example 1, Comparative Examples 1 and 2]
Using the test apparatus shown in FIG. 4, metal ion permeation and electrodeposition experiments of a cation exchange membrane were performed. In FIG. 4, parts having the same functions as those in the apparatus shown in FIG.
In this test apparatus, an anode chamber 2A provided with an anode 2 in an electrodeposition tank 1 and a cathode chamber 3A provided with a cathode 3 are separated by a cation exchange membrane 5, and an acid waste solution is passed through the anode chamber 2A. By passing a catholyte through the cathode chamber 3A and energizing between the anode 2 and the cathode 3, the metal ions in the solution in the anode chamber 2A are transmitted through the cation exchange membrane 5 to enter the solution in the cathode chamber 3A. The metal is deposited on the cathode 3 by being moved.

CoSO ₄ · 7H ₂ O and Fe ₂ (SO ₄ ) ₃ · nH ₂ O and 10% by weight sulfuric acid were dissolved in water to prepare simulated acid waste liquids having the properties shown in Table 1 (SO ₄ concentration in total, H ₂ sO ₄ was prepared) so as to be 5 wt% in terms of also simulating the electrodeposition liquid (catholyte having properties of ammonium citrate tribasic were dissolved in water are shown in Table 1) were prepared, the apparatus of FIG. 1 Was used for the electrodeposition test of Co and Fe. The electrodeposition conditions are as shown in Table 1. The anode used was a Pt-plated Ti plate, and the cathode used a Cu plate.
As the cation exchange membrane, those shown in Table 2 were used. The cation exchange membranes A to C are all homogeneous membranes that are polymerized after impregnating the raw material monomer solution into the reinforcing body, and are hydrocarbon-based Na-type cation exchange membranes.
The sulfate ion concentration and pH in the electrodeposition solution after energization for 16 hours were examined, and the results are shown in Table 2.
Moreover, the time-dependent change of the TOC density | concentration of the simulation acid waste liquid in Example 1 and the comparative example 1 is shown in FIG. 5, and the time-dependent change of Fe density | concentration is shown in FIG.

From Table 2, in Example 1 using the thick cation exchange membrane A, it was possible to suppress the sulfuric acid in the simulated acid waste liquid from passing through the cation exchange membrane and transferring to the electrodeposition solution. I understand.
From FIG. 5, in Comparative Example 1, citric acid added as a complexing ligand of iron and cobalt to the electrodeposition solution permeated the cation exchange membrane and transferred to the simulated acid waste solution. Although the TOC concentration increased with time, it can be seen that in Example 1, the cation exchange membrane permeation of citric acid was also suppressed.
Further, FIG. 6 shows that, in Example 1, the Fe concentration in the simulated acid waste liquid can be removed quickly even though the cation exchange membrane is thick.
The reason why Example 1 has a higher permeation rate of the Fe cation exchange membrane than Comparative Example 1 is unclear, but from this result, a sufficient permeation rate can be obtained even with a large cation exchange membrane. all right.
When the cathode surface was confirmed after energization for 16 hours, silver white metallic Fe and Co were electrodeposited with good adhesion in Example 1, but in Comparative Examples 1 and 2, the entire cathode surface was It was covered with a peelable black deposit. This is considered to be due to the fact that in Comparative Examples 1 and 2, the sulfuric acid concentration in the electrodeposition liquid increased and the pH decreased, and thus electrodeposition inhibition occurred. Since the black deposit is attached to the magnet, it is considered that Fe was deposited as magnetite.
As is clear from the above results, in the present invention, radioactive metal ions such as radioactive cobalt can be electrodeposited on the cathode with good adhesion and in a stable metal state. Therefore, the present invention is applied to radioactive acid waste liquid. Especially effective in cases.

DESCRIPTION OF SYMBOLS 1 Electrodeposition tank 2 Anode 2A Anode chamber 3 Cathode 3A Cathode chamber 4 Power supply 5 Cation exchange membrane 8 Elution tank 9A, 9B Heat exchanger 10 Acid waste liquid storage tank 20 Catholyte storage tank 30 Eluent storage tank 40 Waste ion exchange resin 50 Electrodialysis tank 51 Anode Chamber 51A Anode 52 Cathode Chamber 52A Cathode 53 Deionization Chamber 54 Concentration Chamber 60 Electrodeposition Tank 61 Anode Chamber 61A Anode 62 Cathode Chamber 62A Cathode 70 Electrode Liquid Storage Tank 80 Electrodeposition Liquid Storage CM Cation Exchange Membrane BP Bipolar Membrane CHM Hydrogen Selection Permeable cation exchange membrane

Claims (6)

Metal acid in acid waste liquid is removed by permeation through a cation exchange membrane by electrodialysis , and in the acid waste liquid treatment apparatus that reuses the acid waste liquid from which the metal ions have been removed as an acid liquid, the film thickness of the cation exchange membrane Is a treatment apparatus for acid waste liquid, wherein   2. The acid waste liquid according to claim 1, wherein the acid waste liquid is a radioactive acid waste liquid containing radioactive metal ions generated when acid cleaning or acid elution of a radioactive metal pollutant is performed with an acidic decontamination liquid. The radioactive acid waste liquid from which ions have been removed is reused as the acidic decontamination liquid.   3. The metal ion in the acid waste liquid according to claim 1, wherein the metal ion permeates the cation exchange membrane and is transferred to a ligand-containing liquid containing a ligand that forms a complex with the metal ion. Characteristic acid waste liquid treatment equipment. Metal ions in the acid waste liquid are removed by permeation through a cation exchange membrane having a film thickness of 0.25 to 1 mm by electrodialysis , and the acid waste liquid from which the metal ions have been removed is reused as an acid solution. Treatment method of acid waste liquid.   5. The acid waste liquid according to claim 4, wherein the acid waste liquid is a radioactive acid waste liquid generated when acid cleaning or acid elution of a radioactive metal pollutant is performed with an acid decontamination liquid. A method for treating an acid waste liquid, wherein the acid ion decontamination liquid is reused after removing metal ions.   6. The metal ion in the acid waste liquid according to claim 4, wherein the metal ion is transferred to a ligand-containing liquid containing a ligand that forms a complex with the metal ion through the cation exchange membrane. A method for treating acid waste liquid.

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