JP4497512B2 - Method for selective separation of hydroiodic acid, method for producing hydroiodic acid, and method for producing alkali iodine salts - Google Patents

Description

  The present invention relates to a method for selectively separating hydroiodic acid in an aqueous solution by electrodialysis, a method for producing hydroiodic acid, and a method for producing iodine alkali salts.

  Hydroiodic acid and alkaline salts of iodine are important substances as chemical raw materials or pharmaceutical raw materials.

  Conventionally, as a method for producing hydroiodic acid, a reducing agent such as hypophosphorous acid is added to a suspension of iodine and water, and hydroiodic acid is distilled from the reaction solution by distillation after the reaction. Is known (for example, see Patent Document 1).

  As a method for producing iodine alkali salts, a method is known in which iodine is reduced using a reducing agent such as formic acid in the presence of an alkali (see, for example, Patent Document 2).

  Furthermore, as a raw material iodine production method, an oxidant such as chlorine is introduced into an aqueous solution that dissolves iodine ions to convert the iodine ions into free iodine, which is then expelled by air and absorbed into a reducing solution such as sodium bisulfite. And then concentrating (blowing out method), an oxidizing agent such as chlorine is introduced again to separate iodine ions as free iodine, and then purification is performed.

That is, in these conventional methods, an oxidizing agent is introduced into an aqueous solution in which iodine ions are dissolved to make free iodine, then reduced and concentrated, then oxidized again, isolated and purified as free iodine, and then reduced again. Thus, hydroiodic acid and iodine alkali salts are used.
JP-A-8-59205 (page 2-4) Japanese Patent Publication No. 5-80410 (page 1-3)

  However, in the conventional method for producing hydroiodic acid and iodine alkali salts, there are many production steps, oxidation and reduction are repeated, auxiliary materials are required, iodine vapor is generated, and processing of by-products is required. Yes. For this reason, in the manufacturing method of these hydriodic acid and iodine alkali salts, there exists a problem that manufacture of hydriodic acid and iodine alkali salts is not easy.

  The present invention has been made in view of the above points. A hydroiodic acid selective separation method, a hydroiodic acid production method, and an iodine alkali salt which can easily produce hydroiodic acid and iodine alkali salts. An object is to provide a manufacturing method.

The selective separation method of hydroiodic acid according to claim 1 is characterized in that, in addition to hydroiodic acid, hydrochloric acid (HCl), hydrobromic acid (HBr), sulfuric acid (H ₂ SO ₄ ), phosphorus as inorganic acids From an acid stock solution containing at least one of acid (H ₃ PO ₄ ) and sodium hydrogen sulfate (NaHSO ₄ ), disodium hydrogen phosphate (Na ₂ HPO ₄ ), and sodium iodide (NaI) as salts thereof, A hydriodic acid selective separation method for selectively separating hydroiodic acid by electrodialysis, wherein a cation exchange membrane is provided between a pair of electrode chambers from the positive electrode side to the electrode chamber to partition the polar liquid. Subsequently , the first anion exchange membrane and the first cation exchange membrane are alternately and repeatedly provided in the two sample chambers by the first anion exchange membrane and the first cation exchange membrane. The first anion of the alternately separated electrodialysis tank Exchange membrane and supplying the stock between the first cation exchange membrane, together with hydrogen ions in the stock solution (H ⁺⁾ is transmitted through the front Symbol first cation exchange membrane, iodine in the stock solution Ions (I ⁻ ) permeate through the first anion exchange membrane.

When a stock solution is supplied between the first anion exchange membrane and the first cation exchange membrane in the electrodialysis tank, hydrogen ions (H ⁺ ) in the stock solution are converted into the cation exchange membrane and the first cation. While passing through each of the exchange membranes, iodine ions (I ⁻ ) in the stock solution pass through the first anion exchange membrane. As a result, hydroiodic acid can be selectively separated from the acid stock solution by electrodialysis, there are few production steps, no repeated oxidation and reduction, no need for secondary materials, no generation of iodine vapor, Less processing of by-products. For this reason, hydroiodic acid can be manufactured easily.

The selective separation method of hydroiodic acid according to claim 2 is characterized in that, in addition to hydroiodic acid, hydrochloric acid (HCl), hydrobromic acid (HBr), sulfuric acid (H ₂ SO ₄ ), phosphorus as inorganic acids From an acid stock solution containing at least one of acid (H ₃ PO ₄ ) and sodium hydrogen sulfate (NaHSO ₄ ), disodium hydrogen phosphate (Na ₂ HPO ₄ ), and sodium iodide (NaI) as salts thereof, A hydroiodic acid selective separation method for selectively separating hydroiodic acid by electrodialysis, wherein a space between a pair of positive electrode chambers and a negative electrode chamber is connected from the positive electrode side to the electrode chamber. The first cation exchange membrane, the first anion exchange membrane, and the second cation exchange membrane are alternately and repeatedly provided to the cation exchange membrane that is supplied to Cation exchange membrane, first anion exchange membrane and second cation Supplying the stock solution during the on-exchange the first anion-exchange membrane electrodialysis bath partitioned alternately in three sample chamber at film and the second cation-exchange membrane, and the cation exchange membrane An aqueous solution of a strong acid is provided between the first cation exchange membrane and between the second cation exchange membrane and the adjacent first cation exchange membrane located on the negative electrode side of the second cation exchange membrane. The hydrogen ions (H ⁺ ) in the strong acid aqueous solution pass through the first cation exchange membrane, and the iodine ions (I ⁻ ) in the stock solution pass through the first anion exchange membrane. To do.

Then, a stock solution is supplied between the first anion exchange membrane and the second cation exchange membrane of the electrodialysis tank, and either the cation exchange membrane or the second cation exchange membrane and the first cation are supplied. When a strong acid aqueous solution is supplied to the exchange membrane, hydrogen ions (H ⁺ ) in the strong acid aqueous solution permeate the first cation exchange membrane and iodine ions (I ⁻ ) in the stock solution pass through the first cation exchange membrane. Permeates one anion exchange membrane. As a result, hydroiodic acid can be selectively separated from the acid stock solution by electrodialysis, there are few production steps, no repeated oxidation and reduction, no need for secondary materials, no generation of iodine vapor, Less processing of by-products. For this reason, hydroiodic acid can be manufactured easily.

The method for selective separation of hydroiodic acid according to claim 3 is that in addition to hydroiodic acid, hydrochloric acid (HCl), hydrobromic acid (HBr), sulfuric acid (H ₂ SO ₄ ), phosphorus as inorganic acids From an acid stock solution containing at least one of acid (H ₃ PO ₄ ) and sodium hydrogen sulfate (NaHSO ₄ ), disodium hydrogen phosphate (Na ₂ HPO ₄ ), and sodium iodide (NaI) as salts thereof, A hydroiodic acid selective separation method for selectively separating hydroiodic acid by electrodialysis, wherein a space between a pair of positive electrode chambers and a negative electrode chamber is connected from the positive electrode side to the electrode chamber. The first anion exchange membrane, the first cation exchange membrane, the second anion exchange membrane, and the second cation exchange membrane are alternately supplied to the cation exchange membrane that is supplied to These first anion exchange membranes and first cations provided repeatedly The first anion exchange membrane and the first cation exchange membrane of an electrodialysis tank partitioned alternately into four sample chambers by an exchange membrane, a second anion exchange membrane and a second cation exchange membrane And the second anion exchange membrane and the second cation exchange membrane are supplied with the stock solution, the other is supplied with an aqueous solution of strong acid, and iodine ions (I ^- ) And hydrogen ion (H ⁺ ) in an aqueous solution of the strong acid, hydroiodic acid is produced by a double displacement dialysis reaction.

Then, the stock solution is applied between the first anion exchange membrane and the first cation exchange membrane and between the second anion exchange membrane and the second cation exchange membrane in the electrodialysis tank. When a strong acid aqueous solution is supplied to the other side, hydroiodic acid is generated by double displacement dialysis reaction from iodine ion (I ⁻ ) in the stock solution and hydrogen ion (H ⁺ ) in the strong acid aqueous solution. As a result, hydroiodic acid can be selectively separated from the acid stock solution by electrodialysis, there are few production steps, no repeated oxidation and reduction, no need for secondary materials, no generation of iodine vapor, Less processing of by-products. For this reason, hydroiodic acid can be manufactured easily.

The selective separation method of hydroiodic acid according to claim 4 uses a monovalent anion selective permeation membrane as the anion exchange membrane in the selective separation method of hydroiodic acid according to any one of claims 1 to 3. is there.

  Then, by using a monovalent anion selective permeable membrane as the anion exchange membrane, hydroiodic acid can be more easily separated from the stock solution.

The selective separation method of hydroiodic acid according to claim 5 is the selective separation method of hydroiodic acid according to any one of claims 1 to 4 , wherein an iodine absorbing solution produced by a blowing-out method is used as a stock solution. is there.

  And using the iodine absorption liquid manufactured by the blowing out method as a stock solution, hydroiodic acid is selectively separated from this stock solution by the electrodialysis method. As a result, hydroiodic acid can be more easily produced, so hydroiodic acid can be obtained more economically.

The method for producing hydroiodic acid according to claim 6 is an electrodialysis method from an aqueous solution containing hydroiodic acid and other inorganic ions by the method for selectively separating hydroiodic acid according to any one of claims 1 to 5. a separation step for selectively separating hydriodic acid at, is obtained by including a purification step of distilling purified aqueous solution containing a selected separated hydroiodic acid in the separation step.

Then, hydroiodic acid is selectively separated from an aqueous solution containing hydroiodic acid and other inorganic ions by electrodialysis as a separation step. Thereafter, distilled purified water solution containing hydriodic acid obtained in this separation step as a purification step. As a result, there are fewer manufacturing steps, no repeated oxidation and reduction, no need for by-products, no generation of iodine vapor, and fewer by-product treatments, so high purity hydroiodic acid can be easily and more easily produced. Can be manufactured economically.

The method for producing hydroiodic acid according to claim 7 is the method for producing hydroiodic acid according to claim 6, wherein the aqueous solution obtained in the separation step comprises at least hydroiodic acid, sulfuric acid and sulfate. At least one of barium hydroxide and barium salt other than sulfuric acid is added to the aqueous solution obtained in this separation step, and at least one of sulfuric acid and sulfate contained in the aqueous solution is precipitated as barium salt. A precipitation step to be removed is provided, and the hydroiodic acid aqueous solution after removing at least one of sulfuric acid and sulfate in the precipitation step is purified by distillation in the purification step.

The method for producing an alkali iodine salt according to claim 8 is a method for producing hydroiodic acid according to claim 6 or 7 , and hydroiodic acid distilled and purified in a purification step of the method for producing hydroiodic acid. And a production process for producing an alkali iodine salt by neutralizing with alkali hydroxide.

  Then, hydroiodic acid distilled and purified in the purification step of the hydroiodic acid production method according to claim 6 is neutralized with alkali hydroxide as a production step to produce alkali iodine salts. As a result, since this iodine alkali salt can be manufactured easily, this iodine alkali salt can be manufactured more economically.

According to the present invention, in addition to hydroiodic acid, hydrochloric acid (HCl), hydrobromic acid (HBr), sulfuric acid (H ₂ SO ₄ ), phosphoric acid (H ₃ PO ₄ ) and these as inorganic acids Hydroiodic acid from an acid stock solution containing at least one of sodium hydrogen sulfate (NaHSO ₄ ), disodium hydrogen phosphate (Na ₂ HPO ₄ ), and sodium iodide (NaI) as a salt of By selectively separating the hydriodic acid, the production process is small, the oxidation and reduction are not repeated, no auxiliary materials are required, iodine vapor is not generated, and the treatment of by-products is reduced. Easy to manufacture.

  Hereinafter, the configuration of the electrodialysis tank according to the first embodiment of the present invention will be described with reference to FIG.

  In FIG. 1, 1 is an electrodialysis tank as an electrodialysis apparatus, and this electrodialysis tank 1 is a set of two chambers configured by being alternately partitioned into two sample chambers. Specifically, a pair of electrodes 1a and 1b are disposed on both sides of the electrodialysis tank 1. One of the pair of electrodes 1a and 1b, that is, the electrode 1a is used as an anode as a positive electrode. Here, platinum (Pt), titanium (Ti) / platinum, carbon (C), nickel (Ni), ruthenium (Ru) / titanium, iridium (Ir) / titanium, etc. are used as the electrode 1a of the anode. It is done.

  The other of the pair of electrodes 1a and 1b, that is, the electrode 1b is used as a cathode as a negative electrode. Here, as the cathode electrode 1b, iron (Fe), nickel, platinum, titanium / platinum, carbon, chromium (Cr) steel as stainless steel, or the like is used. The electrodes 1a and 1b are formed in a long rectangular flat plate shape such as a groove plate shape, a mesh shape, or a lattice shape.

  The electrodialysis tank 1 further includes a chamber frame 2 as a frame body having a notch (not shown), and a pair of electrodes 1a and 1b are attached to the inside of both end portions along the longitudinal direction of the chamber frame 2. ing. In the chamber frame 2, a cation exchange membrane K that partitions the polar liquid P supplied to the electrode chamber 11a on the positive electrode side from the positive electrode side where the electrode 1a of the chamber frame 2 is disposed. Subsequently, the first anion exchange membranes A1 and the first cation exchange membranes K1 are alternately arranged in a state of being spaced apart at equal intervals along the longitudinal direction.

  In addition, each of the first anion exchange membrane A1 and the first cation exchange membrane K1 is used to give tension to the first anion exchange membrane A1 and the first cation exchange membrane K1. The both ends of each of the first anion exchange membrane A1 and the first cation exchange membrane K1 are fastened and fixed to both side surfaces of the chamber frame 2 while being pulled along the longitudinal direction.

  Furthermore, on the inner surface of each of the chamber frames 2 partitioned by the first anion exchange membrane A1 and the first cation exchange membrane K1, a liquid supply port (not shown) communicating with the interior of the chamber frame 2 and Each of the liquid outlets is provided. Further, in the chamber frame 2, a spacer (not shown) having a flow distribution action for making the thickness in the chamber frame 2 uniform is provided.

  As a result, the electrodes 1a and 1b in the electrodialysis tank 1 are alternately partitioned by the first anion exchange membrane A1 and the first cation exchange membrane K1.

  Here, as the first anion exchange membrane A1, for example, a general strongly basic styrene-divinylbenzene-based homogeneous anion exchange membrane is used. Then, by using a monovalent anion selective permeable membrane which is a membrane having enhanced monovalent anion selective permeability as the first anion exchange membrane A1, the selective permeability of iodine ions (I−) is higher. Therefore, it is more effective. Further, as the monovalent anion selective permeable membrane, for example, Selemion ASV membrane (manufactured by Asahi Glass Co., Ltd.), Aciplex A-192 membrane (manufactured by Asahi Kasei Co., Ltd.), Neoceptor ACS membrane (manufactured by Tokuyama Co., Ltd.), etc. .

  Further, as the first cation exchange membrane K1, for example, a strongly acidic styrene-divinylbenzene-based homogeneous cation exchange membrane is used. Further, by using a hydrogen ion selective permeation membrane that is a membrane having enhanced hydrogen ion permselectivity as the first cation exchange membrane K1, the hydrogen ion selective permeation rate becomes higher, which is more effective. . Further, as the hydrogen ion selective permeable membrane, for example, there is a Selemion HSV membrane (manufactured by Asahi Glass Co., Ltd.).

  On the other hand, the inside of the chamber frame 2 in which the electrodes 1a and 1b in the electrodialysis tank 1 are housed and both sides are partitioned by the cation exchange membrane K becomes electrode chambers 11a and 11b as polar liquid chambers. Further, the inside of the chamber frame 2 partitioned by the cation exchange membrane K and the first anion exchange membrane A1 between the electrode chambers 11a and 11b is a concentration chamber 13 as a sample chamber. Further, the inside of the chamber frame 2 partitioned by the first anion exchange membrane A1 and the first cation exchange membrane K1 between the electrode chambers 11a and 11b is a stock solution chamber 12 as a sample chamber.

  In other words, in the stock solution chamber 12, the anode side of the pair of electrodes 1a and 1b is partitioned by the first anion exchange membrane A1, and the cathode side is partitioned by the first cation exchange membrane K1. Further, in the concentration chamber 13, the anode side of the pair of electrodes 1a and 1b is partitioned by a cation exchange membrane K, and the cathode side is partitioned by a first anion exchange membrane A1. These stock solution chambers 12 and concentration chambers 13 are alternately formed. Furthermore, the electrode chambers 11a and 11b are located on both sides in the width direction of the stock solution chamber 12 and the concentration chamber 13 which are alternately formed.

  The electrode chamber 11a on the anode side is partitioned by a cation exchange membrane K. Further, the cathode-side electrode chamber 11b is partitioned by the first cation exchange membrane K1. The liquid supply port and the liquid discharge port located on both side surfaces of the chamber frame 2 along the longitudinal direction of the electrode chambers 11a and 11b are the polar liquid inlet and the polar liquid outlet that serve as the inlet and outlet of the polar liquid P, respectively. ing.

  Further, the liquid supply port and the liquid discharge port located on both side surfaces of the chamber frame 2 along the longitudinal direction of the stock solution chamber 12 are a stock solution inlet and a stock solution outlet that serve as an inlet and an outlet for the stock solution D, respectively. Therefore, this stock solution D is supplied to the stock solution chamber 12 between the first anion exchange membrane A1 and the first cation exchange membrane K1. Further, the liquid supply port and the liquid discharge port located on both side surfaces of the chamber frame 2 along the longitudinal direction of the concentration chamber 13 serve as a concentration liquid inlet and a concentration liquid outlet, which serve as an inlet and an outlet for the concentrated liquid C, respectively.

  Next, a stock solution D, which is an aqueous solution of an acid containing hydroiodic acid, is introduced into the stock solution chamber 12 from the stock solution inlet. Further, the concentrate C is introduced into the concentration chamber 13 from the concentrate inlet. Furthermore, an anolyte and a catholyte P as a catholyte are introduced into the electrode chambers 11a and 11b located at both ends in contact with the electrodes 1a and 1b from the polar liquid inlet.

  Here, the number of repetitions n of the arrangement of the first anion exchange membrane A1 and the first cation exchange membrane K1 in the chamber frame 2 of the electrodialysis tank 1 can be selected according to the purpose, and preferably 10 or more and 1000. The number of repetitions is about the following. The supply of each of the polar solution P, the stock solution D, and the concentrate C to the electrode chambers 11a, 11b, the stock solution chamber 12, and the concentration chamber 13 of the electrodialysis tank 1 is continuously performed.

  Further, an external tank (not shown) for supplying these polar solution P, undiluted solution D and concentrated solution C is provided, and these polar solution P, undiluted solution D and concentrated solution C are connected to electrode chambers 11a and 11b, undiluted solution chamber 12 and concentrated chamber 13, respectively. You may circulate each between external tanks. Further, the stock solution D is an aqueous solution of an acid containing hydroiodic acid and at least one of other inorganic acids and salts thereof, that is, hydroiodic acid and other inorganic acids, for example, in a blowing out method. An iodine absorbing solution prepared in the above manner or an aqueous solution containing hydroiodic acid obtained by hydrolyzing an organic iodine compound with an acid is preferable.

Here, the concentration of hydroiodic acid in the stock solution D is generally in the range of 0.1% by mass or more and 30% by mass or less because the selectivity decreases when it is dilute. Further, inorganic acids other than hydroiodic acid or salts thereof contained in the stock solution D are generally hydrochloric acid (HCl), hydrobromic acid (HBr), sulfuric acid (H ₂ SO _4). ), Phosphoric acid (H ₃ PO ₄ ), sodium hydrogen sulfate (NaHSO ₄ ), disodium hydrogen phosphate (Na ₂ HPO ₄ ), sodium iodide (NaI), etc. The concentration of these inorganic acids or their salts is , 0.01 mass% or more and 10 mass% or less.

  The stock solution chamber 12 is supplied with an aqueous solution containing hydroiodic acid and another inorganic acid or a salt thereof, that is, a stock solution D, from the stock solution inlet. The concentration of hydroiodic acid in the stock solution D in the stock solution chamber 12 is lowered by continuing electrodialysis in the stock solution chamber 12. For this reason, a solution in which the concentration of hydroiodic acid is sufficiently reduced is appropriately extracted from the stock solution outlet as a treatment solution, and the stock solution D is newly replenished. Further, it is possible to perform continuous operation in which the processing solution is continuously extracted from the stock solution outlet and the stock solution D is replenished from the stock solution inlet.

  Further, a concentrate C such as a hydroiodic acid aqueous solution is supplied to the concentration chamber 13 from the concentrate inlet. The concentration of hydroiodic acid in the concentrate C supplied to the concentration chamber 13 is an aqueous solution of about 0.1% to 5% in the initial state of electrodialysis. Further, the concentrated solution C in the concentration chamber 13 is subjected to electrodialysis in the concentration chamber 13, whereby hydroiodic acid that has permeated through the first anion exchange membrane A 1 is used to generate iodine in the concentrated solution C. The concentration of hydrofluoric acid increases. Therefore, a concentrated hydroiodic acid aqueous solution can be obtained by withdrawing the concentrated liquid C, which is a treatment liquid having an increased concentration of hydroiodic acid, from the concentrated liquid outlet as necessary or continuously. Can do.

  Further, as the polar liquid P supplied to the electrode chambers 11a and 11b, an aqueous solution of sulfuric acid, phosphoric acid, or a salt thereof of about 0.1% to 10% is used. The operating current density during electrodialysis supplied between the electrodes 1a and 1b of the electrode chambers 11a and 11b is set to be equal to or lower than the limit current density after the limit current density is measured in advance. The temperatures of the stock solution D, concentrated solution C, and polar solution P during electrodialysis in the electrodialysis tank 1 are usually in the range of 5 ° C. or higher and 70 ° C. or lower, preferably 20 ° C. or higher and 50 ° C. or lower.

  Next, the method for separating hydroiodic acid according to the first embodiment will be described.

  First, the polar solution P is supplied to the electrode chambers 11 a and 11 b of the electrodialysis tank 1, the stock solution D is supplied to the stock solution chamber 12, and the concentrate C is supplied to the concentration chamber 13.

  In this state, a current equal to or lower than the limit current density measured in advance is supplied between the electrodes 1a and 1b of the electrode chambers 11a and 11b.

Then, as shown in FIG. 1, hydrogen ions (H ⁺ ) in the stock solution chamber 12 permeate the first cation exchange membrane K 1 and iodine ions in the stock solution chamber 12 pass through the first anion exchange. Permeates through the membrane A1.

At this time, the iodine ion, anion such as sulfate ion (SO ₄ ²⁻ ), phosphate ion (PO ₄ ³⁻ ), and chlorine ion (Cl ⁻ ) are converted into the cation exchange membrane K and the first cation. It cannot penetrate each of the exchange membranes K1. Further, hydrogen ions cannot permeate the first anion exchange membrane A1.

  For this reason, the concentration of hydroiodic acid in the concentrate C in the concentration chamber 13 increases. Thereafter, the treatment liquid in which the concentration of hydroiodic acid in the concentration chamber 13 is increased, that is, the concentrated liquid C is extracted from the concentration chamber 13, whereby a high concentration hydroiodic acid aqueous solution can be obtained.

  As described above, according to the first embodiment, the stock solution D is supplied to the stock solution chamber 12 between the first anion exchange membrane A1 and the first ion exchange membrane K1 of the electrodialysis tank 1. To do. As a result, by supplying current between the electrodes 1a and 1b of the electrodialysis tank 1, hydroiodic acid is selectively separated from the stock solution D into the concentrating chamber 13 by electrodialysis, and this concentration is performed. The concentration of hydroiodic acid in the concentrate C in the chamber 13 increases.

  As a result, for example, an oxidant is introduced into an aqueous solution in which iodine ions are dissolved to convert iodine ions into free iodine, then expelled with air, absorbed into a sulfurous acid aqueous solution, reduced and concentrated, and then oxidized again. Compared to the conventional method of once liberating and isolating and purifying as iodine, and then reducing again to obtain hydroiodic acid or an alkali salt of iodine, there are fewer steps, and without repeating the oxidation and reduction, the auxiliary raw material can be obtained. There is no need, no generation of iodine vapor, and less by-product processing.

  Therefore, hydroiodic acid can be easily selectively separated by electrodialysis from an acid stock solution D containing at least one of inorganic acids and salts thereof in addition to hydroiodic acid. Acid can be produced. Therefore, hydroiodic acid can be produced very efficiently and economically.

  Further, by using a monovalent anion selective permeation membrane as the first anion exchange membrane A1, iodine ions can be further permeated and separated from the stock solution D. Therefore, hydroiodic acid can be more efficiently removed from the stock solution D. Can be selectively separated. Furthermore, hydroiodic acid can be more easily produced by using the iodine absorbing solution produced by the blowing-out method as the stock solution D, so that hydroiodic acid can be obtained more economically.

  Next, a second embodiment of the present invention will be described with reference to FIG.

  The electrodialysis tank 1 shown in FIG. 2 is basically the same as the electrodialysis tank 1 shown in FIG. 1, but the electrode chambers 11a and 11b arranged at both ends of the electrodialysis tank 1 are connected to the positive electrode side. Next, the cation exchange membrane K that partitions the polar liquid P from the first is exchanged with the first cation exchange membrane K1, the first anion exchange membrane A1, and the second cation exchange membrane K2 so that three A set of three sample chambers formed by alternately partitioning into sample chambers is provided with a plurality, preferably 5 or more and 500 or less repetition times n selected according to the purpose.

  The electrodialysis tank 1 includes a first solution chamber 21 which is a sample chamber as a stock solution chamber 12 adjacent to the electrode chamber 11b on the cathode side. The first solution chamber 21 is partitioned on the cathode side by the second cation exchange membrane K2 and on the anode side by the first anion exchange membrane A1. The first solution chamber 21 is supplied with a stock solution D which is an aqueous solution of an acid containing hydroiodic acid and other inorganic acids and any of these salts.

  Here, as this stock solution D, for example, an iodine absorbing solution produced by a blowing-out method or a hydroiodic acid-containing aqueous solution obtained by hydrolyzing an organic iodine compound with an acid is used. Further, the concentration of hydroiodic acid in the stock solution D is usually about 1% by mass or more and 30% by mass or less because the current value decreases and the production efficiency decreases when the stock solution D is dilute.

  Further, on the anode side of the first solution chamber 21, a second solution chamber 22 which is a sample chamber as the concentration chamber 13 is provided. The second solution chamber 22 is partitioned on the cathode side by the first anion exchange membrane A1 and on the anode side by the first cation exchange membrane K1. The second solution chamber 22 is supplied with a concentrated solution C that is an aqueous solution of hydroiodic acid. Here, the concentrate C is intended, and the concentration of hydroiodic acid in the concentrate C is usually about 0.1% by mass to 5% by mass at the start of electrodialysis. .

Further, on the anode side of the second solution chamber 22, a third solution chamber 23 which is a sample chamber as an acid chamber is provided . In the third solution chamber 23, the cathode side is partitioned by the first cation exchange membrane K1, and the anode side is partitioned by either the cation exchange membrane K or the second cation exchange membrane K2 that partitions the polar liquid P. It is partitioned. The third solution chamber 23 is supplied with an aqueous solution of strong acid such as hydrochloric acid, sulfuric acid, and phosphoric acid. The acid concentration in this aqueous solution is usually about 1% by mass or more and 20% by mass or less because the current value is low and the production efficiency of hydroiodic acid is reduced when it is dilute.

  Next, the method for separating hydroiodic acid according to the second embodiment will be described.

  First, as a separation step, the polar solution P is supplied to the electrode chambers 11a and 11b, the stock solution D is supplied to the first solution chamber 21, the concentrated solution C is supplied to the second solution chamber 22, and the third solution An aqueous solution of an inorganic acid is supplied to the solution chamber 23.

  In this state, a current equal to or lower than the limit current density measured in advance is supplied between the electrodes 1a and 1b of the electrode chambers 11a and 11b.

  Then, as shown in FIG. 2, hydrogen ions in the first solution chambers 21 pass through the second cation exchange membranes K <b> 2, and iodine ions in the first solution chambers 21 are in the first solution chambers 21. It passes through the anion exchange membrane A1.

  At this time, iodine ions, sulfate ions, phosphate ions, chloride ions, and other anions cannot pass through each second cation exchange membrane K2. Further, hydrogen ions cannot permeate each first anion exchange membrane A1.

  On the other hand, hydrogen ions in the third solution chamber 23 pass through the first cation exchange membrane K1 and move to the second solution chamber 22 on the cathode side.

  Therefore, the concentration of hydroiodic acid in the concentrate C in each second solution chamber 22 increases.

  Thereafter, by extracting the concentrated liquid C in which the concentration of hydroiodic acid in each of the second solution chambers 22 is increased, a higher concentration hydroiodic acid aqueous solution can be obtained efficiently.

  That is, the iodine ion of hydroiodic acid in the stock solution D supplied into the first solution chamber 21 and the aqueous solution supplied into the third solution chamber 23 by electrodialysis in a batch method using the electrodialysis tank 1. Hydroiodic acid is generated from the hydrogen ion of the acid by a double displacement dialysis reaction, and the concentration of hydroiodic acid in the concentrate C in the second solution chamber 22 increases.

  Further, by continuing the electrodialysis in the electrodialysis tank 1, the concentration of hydroiodic acid in the stock solution D in the first solution chamber 21 is lowered. When the concentration of hydroiodic acid in the stock solution D in the first solution chamber 21 is sufficiently lowered, the electrodialysis in the electrodialysis tank 1 is temporarily stopped, and the first solution chamber 21 and the third solution in the raw material system are stopped. After an appropriate amount of the stock solution D and the acid aqueous solution in the solution chamber 23 is extracted as a processing solution, the stock solution D and the acid aqueous solution, which are raw material solutions, are respectively added to the first solution chamber 21 and the third solution chamber 23. refill.

  Further, the concentrated liquid C, which is the product liquid in the second solution chamber 22 of the production system, is left for use as a raw material for the next electrodialysis, and the remainder is extracted as the product liquid. Therefore, by repeating the above steps, a high concentration aqueous solution of hydroiodic acid can be obtained.

  Next, a third embodiment of the present invention will be described with reference to FIG.

  The electrodialysis tank 1 shown in FIG. 3 is basically the same as the electrodialysis tank 1 shown in FIG. 1, but the electrode chambers 11a and 11b disposed at both ends of the electrodialysis tank 1 are connected to the positive electrode side. The cation exchange membrane K partitioning the polar liquid P from the first cation exchange membrane A1, the first cation exchange membrane K1, the second anion exchange membrane A2, and the second cation exchange membrane K2 A set of four chambers formed by alternately partitioning into four sample chambers by partitioning at a plurality of sample chambers selected according to the purpose, preferably with a repetition number n of about 5 to 500. It is what was done.

  The electrodialysis tank 1 includes a first solution chamber 31 which is a sample chamber as a stock solution chamber 12 adjacent to the electrode chamber 11b on the cathode side. In the first solution chamber 31, the cathode side is partitioned by the second cation exchange membrane K2, and the anode side is partitioned by the second anion exchange membrane A2. The stock solution D is supplied to the first solution chamber 31.

  Further, on the anode side of the first solution chamber 31, a second solution chamber 32 that is a sample chamber serving as the concentration chamber 13 is provided. In the second solution chamber 32, the cathode side is partitioned by the second anion exchange membrane A2, and the anode side is partitioned by the first cation exchange membrane K1. The concentrated solution C is supplied to the second solution chamber 32.

  Further, on the anode side of the second solution chamber 32, a third solution chamber 33 which is a sample chamber as an acid chamber is provided. In the third solution chamber 33, the cathode side is partitioned by the first cation exchange membrane K1, and the anode side is partitioned by the first anion exchange membrane A1. In the third solution chamber 33, an aqueous solution of a strong acid such as hydrochloric acid, sulfuric acid or phosphoric acid is used.

Further, on the anode side of the third solution chamber 33, a fourth solution chamber 34 which is a sample chamber as the concentration chamber 13 is provided. The fourth solution chamber 34 is partitioned on the cathode side by the first anion exchange membrane A1, and on the anode side by the cation exchange membrane K and the second cation exchange membrane K2 that partition the polar liquid P. Yes. The fourth solution chamber 34 is supplied with an acid or salt aqueous solution by-produced corresponding to the acid supplied to the third solution chamber 33. The concentration in the aqueous solution is usually about 0.1% by mass to 5% by mass at the start of electrodialysis.

  That is, the iodine ion of hydroiodic acid in the stock solution D supplied into the first solution chamber 31 and the aqueous solution supplied into the third solution chamber 33 by electrodialysis in a batch method using the electrodialysis tank 1. Hydroiodic acid is generated from the hydrogen ion of the acid by double displacement dialysis reaction, and the concentration of hydroiodic acid in the concentrate C in the second solution chamber 32 increases, and the fourth solution chamber The acid or salt concentration in the aqueous solution in 34 increases.

  For this reason, the concentration of hydroiodic acid in the stock solution D in the first solution chamber 31 of the raw material system and the concentration of the acid in the aqueous solution in the third solution chamber 33 gradually decrease, and this decrease in concentration. Along with this, the current value decreases.

  When the current value is sufficiently reduced, the electrodialysis using the electrodialysis tank 1 is temporarily stopped, and the stock solution D and the acid in the first solution chamber 31 and the third solution chamber 33 of the raw material system are stopped. After extracting an appropriate amount of the aqueous solution as the treatment liquid, the first solution chamber 31 and the third solution chamber 33 are respectively replenished with the stock solution D and the acid aqueous solution as the raw material solution.

  Further, a part of each of the concentrated liquid C and the aqueous solution in the second solution chamber 32 and the fourth solution chamber 34 of the production system is left for use as a raw material for the next electrodialysis, and the remainder is extracted as a production liquid. . Therefore, by repeating the above steps, a high concentration aqueous solution of hydroiodic acid can be obtained.

  At this time, the aqueous solution of hydroiodic acid obtained by the electrodialysis method in the electrodialysis tank 1 contains at least one of a small amount of hydrochloric acid and sulfuric acid. For this reason, when this aqueous solution of hydroiodic acid is distilled as it is, at least one of iodine and sulfur is produced by the reaction of hydroiodic acid and sulfuric acid, and the distillate becomes cloudy.

Therefore, it is necessary to remove sulfuric acid before distilling the aqueous solution of hydroiodic acid. The removal of sulfuric acid is performed by adding a barium hydroxide or barium salt other than sulfuric acid to an aqueous solution of hydroiodic acid containing a small amount of sulfuric acid, and precipitating and separating the sulfuric acid as a barium salt. And Here, among barium compounds to be used, barium salts other than sulfuric acid include barium carbonate (BaCO ₃ ), barium chloride (BaCl ₂ ), and the like.

  Furthermore, the addition amount of this barium compound is usually about equal to or higher than that of sulfuric acid contained in the hydroiodic acid aqueous solution, that is, about 1 to 1.5 times. That is, when the amount of the barium compound added is small, sulfuric acid remains in the hydroiodic acid aqueous solution. On the other hand, when the amount of barium compound added is large, it is not economical. The treatment temperature at this time is usually in the range of room temperature to 60 ° C., and the treatment time is usually from 30 minutes to 3 hours.

  And since the produced | generated barium sulfate turns into a fine white crystal | crystallization, this is isolate | separated by filtration or centrifugal sedimentation. At this time, a part of barium sulfate is dissolved in an aqueous solution of hydroiodic acid, but it is deposited as a white slurry in the residue of the distillation pot without causing any adverse effect in the distillation step described later. By returning this white slurry to the barium sulfate separation step, the entire amount of barium sulfate is circulated and removed. As a result, since sulfuric acid and sulfate can be efficiently removed from an aqueous solution of hydroiodic acid, high-purity hydroiodic acid can be easily produced.

  Next, the hydroiodic acid aqueous solution after removing a small amount of sulfuric acid as a barium salt still contains a small amount of hydrochloric acid. The separation of hydrochloric acid from the aqueous solution of hydroiodic acid can be easily performed by distillation as a purification step as a distillation step. At this time, since the distillation can be performed at a low temperature, vacuum distillation is desirable, and the distillation is usually performed under a reduced pressure of about 50 mmHg. After separating the fraction containing hydrochloric acid as the initial fraction, an azeotropic fraction of hydroiodic acid and water having a concentration of about 57% by mass or more and 58% by mass or less can be obtained. Hydroiodic acid is very easily oxidized and easily colored, so it is necessary to avoid contact with air as much as possible during operation. For this reason, the distillation operation is preferably performed under a nitrogen stream. As a result, extremely high purity hydroiodic acid can be obtained.

  Moreover, various iodine alkali salts can be obtained by the manufacturing process which neutralizes after adding various alkali hydroxides to this aqueous solution of hydroiodic acid. Here, examples of the alkali include sodium, potassium, lithium, and ammonium. In the neutralization reaction, an aqueous solution of alkali hydroxide may be added to the aqueous solution of hydroiodic acid, or an aqueous solution of hydroiodic acid may be added to the aqueous solution of alkali hydroxide. And the pH at the time of this neutralization is the range of 4-10, Preferably it is the range of 6-8. As a result, since this iodine alkali salt can be manufactured easily, this iodine alkali salt can be manufactured more economically.

  In each of the above embodiments, the electrodialysis tank 1 in which the cation exchange membranes and the anion exchange membranes are alternately arranged in the chamber frame 2 has been described. However, hydroiodic acid is selectively selected by electrodialysis. An electrodialyzer having any configuration may be used as long as it can be separated.

  The iodine absorbing solution produced by the blowing-out method is used as a stock solution D, and the CH-O type electrodialysis tank 1 (number of built-in membranes 10 pairs, effective membrane area 0.022 m 2 / sheet) manufactured by Asahi Glass Co., Ltd. shown in FIG. Electrodialysis was performed.

  At this time, a selemion HSV membrane (manufactured by Asahi Glass Co., Ltd.), which is a hydrogen ion selective permeable membrane, was used as the first cation exchange membrane K1. Further, as the first anion exchange membrane A1, a selemion ASV membrane (manufactured by Asahi Glass Co., Ltd.), which is a monovalent anion selective permeable membrane, was used.

  Then, a stock solution D1000 g having a composition of hydroiodic acid is 9.2% by mass, sodium hydrogensulfate is 5.5% by mass, and hydrochloric acid is 0.3% by mass is supplied to the stock solution chamber 12, Concentrate C, which is 700 g of a 1% by mass hydroiodic acid aqueous solution, was supplied to the concentration chamber 13. Further, a polar liquid P1000 g, which is a 10% by mass sulfuric acid aqueous solution, was supplied to each electrode chamber 11a, 11b.

  In this state, after electrodialysis for 1.5 hours at a constant voltage of 10 V, the liquid composition in each chamber was analyzed by ion chromatography. As a result, the ion concentration of the stock solution D in the stock solution chamber 12 is an iodine ion concentration of 1.4% by mass, a sulfate ion concentration of 4.3% by mass, a chlorine ion concentration of 0.2% by mass, and sodium ions. The concentration was 1.0% by mass.

  The concentration of the concentrated liquid C in the concentration chamber 13 is such that the iodine ion concentration is 11.9% by mass, the sulfate ion concentration is 0.4% by mass, the chlorine ion concentration is 0.1% by mass, sodium ion The concentration was 0.2% by mass.

  As a result, the separation rate of hydroiodic acid from the stock solution D was 85.3%, and the selectivity of hydroiodic acid to the acid and salt transferred to the concentrate C was 87.8 mol%.

  Next, the iodine absorption solution manufactured by the blowing-out method is used as the stock solution D, and the electrodialysis tank 1 (3 chambers / set, 10 sets of built-in membranes, effective membrane area) modified from Asahi Kasei Co., Ltd. G4 type shown in FIG. 0.02 m 2 / sheet) was used for electrodialysis.

  At this time, an Aciplex K-501 membrane (manufactured by Asahi Kasei Corporation), which is a cation exchange membrane, was used as the first cation exchange membrane K1 and the second cation exchange membrane K2. In addition, an Aciplex A-192 membrane (manufactured by Asahi Kasei Corporation), which is a monovalent anion selective permeable membrane, was used as the first anion exchange membrane A1.

  A stock solution D1000 g having a composition of hydroiodic acid of 9.2% by mass, sodium hydrogensulfate of 5.5% by mass, and hydrochloric acid of 0.3% by mass in the first solution chamber 21. Supplied. At the same time, 700 g of concentrated liquid C, which is a 1% by mass hydroiodic acid aqueous solution, was supplied to the second solution chamber 22, and an aqueous acid solution, 1000 g of 10% by mass sulfuric acid aqueous solution, was supplied to the third solution chamber 23. In addition, the electrode chamber 11a, 11b was supplied with 800 g of polar solution P, which is a 10% by mass sulfuric acid aqueous solution.

  In this state, after electrodialysis for 3 hours at a constant voltage of 10 V, the liquid composition in each chamber was analyzed by ion chromatography. As a result, the ion concentration of the stock solution D in the first solution chamber 21 is 1.0 mass% for the iodine ion, 4.7 mass% for the sulfate ion concentration, and 0.3 mass% for the chlorine ion concentration. Sodium ion concentration was 1.1 mass%.

  Further, the ion concentration of the concentrated liquid C in the second solution chamber 22 is that the iodine ion concentration is 11.5% by mass, the sulfate ion concentration is 0.4% by mass, and the chlorine ion concentration is 0.1% by mass. The sodium ion concentration was 0.03% by mass. Further, the ion concentration of the aqueous solution in the third solution chamber 23 was 9.1% by mass for the sulfate ion concentration and 0.1% by mass for the sodium ion concentration.

  As a result, the separation rate of hydroiodic acid from the stock solution D was 90.5%, and the selectivity of hydroiodic acid to the acid and salt transferred to the concentrate C was 90.3 mol%.

  Next, an iodine absorbing solution produced by the blowing-out method is used as a stock solution D, and an Asahi Kasei Co., Ltd. G4 type electrodialysis tank 1 shown in FIG. 02m2 / sheet) was electrodialyzed.

  At this time, an Aciplex K-501 membrane (manufactured by Asahi Kasei Corporation), which is a cation exchange membrane, was used as the first cation exchange membrane K1 and the second cation exchange membrane K2. As the first anion exchange membrane A1 and the second anion exchange membrane A2, Aciplex A-192 membrane (manufactured by Asahi Kasei Corporation), which is a monovalent anion selective permeable membrane, was used.

  Then, 2890 g of a stock solution D having a composition of 9.2% by weight of hydroiodic acid, 5.5% by weight of sodium hydrogensulfate, and 0.3% by weight of hydrochloric acid is added to the first solution chamber 31. Then, 600 g of concentrated liquid C, which is a 1 mass% hydroiodic acid aqueous solution, was supplied to the second solution chamber 32. At the same time, 2000 g of an acid aqueous solution as a 10% by mass sulfuric acid aqueous solution was supplied to the third solution chamber 33, and 600 g of a salt aqueous solution as a 1% by mass sodium hydrogen sulfate aqueous solution was supplied to the fourth solution chamber 34. Each electrode chamber 11a, 11b was supplied with 1000 g of polar liquid P, which is a 5% by mass sodium hydrogen sulfate aqueous solution.

  In this state, after electrodialysis for 2 hours at a constant voltage of 10 V, the liquid composition in each chamber was analyzed by ion chromatography. As a result, the ion concentration of the stock solution D in the first solution chamber 31 is such that the iodine ion concentration is 0.5 mass%, the sulfate ion concentration is 4.8 mass%, and the chlorine ion concentration is 0.3 mass%. The sodium ion concentration was 1.0% by mass.

  The ion concentration of the concentrated liquid C in the second solution chamber 32 is that the iodine ion concentration is 24.3% by mass, the sulfate ion concentration is 1.1% by mass, and the chloride ion concentration is 0.1% by mass. there were. Furthermore, the ion concentration of the aqueous solution in the third solution chamber 33 was 0.6% by mass as the sulfate ion concentration. The ion concentration of the aqueous solution in the fourth solution chamber 34 was 18.5% by mass for the sulfate ion concentration and 0.7% by mass for the sodium ion concentration.

  As a result, the separation rate of hydroiodic acid from the stock solution D was 95.7%, and the selectivity of hydroiodic acid to the acid and salt transferred to the concentrate C was 93.5 mol%.

  Next, a concentrated solution C1058 g having a composition of 2.03 mol of iodine ion, 0.12 mol of sulfate ion and 0.02 mol of chloride ion obtained in Example 3 was weighed into a three-necked flask, and nitrogen was added. Under a stream of air, room temperature and stirring, 41.0 g of barium hydroxide octahydrate was added.

  Then, after stirring for 30 minutes, the precipitated crystals were filtered and washed with a small amount of water to obtain 1150 g of a filtrate. As a result of analyzing the composition of the filtrate by ion chromatography, iodine ions were 22.1% by mass, chlorine ions were 0.1% by mass, and sulfate ions were not detected at all.

  Next, the filtrate obtained in Example 4 was transferred to a distillation flask and concentrated under reduced pressure under a nitrogen stream using a magnetized Rasig packed tower (not shown) having an inner diameter of 18 mm and a tower height of 1 m. After distillation to separate the first fraction, 328 g of a fraction of 50 mmHg and 65 ° C. to 66 ° C. was obtained. At this time, when the obtained fraction was analyzed, the concentration of hydroiodic acid was 58% by mass, and no other inorganic salt was observed in the analysis by ion chromatography.

Next, using the fraction obtained in Example 5 above, neutralized with various alkali hydroxides to pH 6 or more and 8 or less, and concentrated and dried to obtain alkali iodine salts.

  As a result, crystals having the composition shown in Table 1 could be obtained.

It is explanatory drawing which shows the electrodialysis tank of the 1st Embodiment of this invention. It is explanatory drawing which shows 2nd Embodiment of the electrodialysis tank of this invention. It is explanatory drawing which shows 3rd Embodiment of the electrodialysis tank of this invention.

1 Electrodialysis tank
11a, 11b Electrode chamber A1 1st anion exchange membrane A2 2nd anion exchange membrane K cation exchange membrane K1 1st cation exchange membrane K2 2nd cation exchange membrane D Stock solution P Polar solution

Claims (8)

In addition to hydroiodic acid, hydrochloric acid (HCl), hydrobromic acid (HBr), sulfuric acid (H ₂ SO ₄ ), phosphoric acid (H ₃ PO ₄ ) as an inorganic acid, and hydrogen sulfate as a salt thereof Hydroiodic acid is selectively separated by electrodialysis from an acid stock solution containing at least one of sodium (NaHSO ₄ ), disodium hydrogen phosphate (Na ₂ HPO ₄ ), and sodium iodide (NaI). A method for selectively separating hydroiodic acid,
The first anion exchange membrane and the first cation exchange membrane are alternately and repeatedly provided following the cation exchange membrane that partitions the polar liquid supplied to the electrode chamber from the positive electrode side between the pair of electrode chambers. , between these first anion-exchange membrane and the first of the first anion-exchange membrane electrodialysis bath partitioned alternately to two of the sample chamber at the cation exchange membrane and the first cation-exchange membrane In between, supply the stock solution,
Together with hydrogen ions in the stock solution (H ⁺⁾ is transmitted through the front Symbol first cation exchange membrane, iodine ions in the stock solution ^- characterized in that is transmitted through the first anion-exchange membrane (I) A selective separation method of hydroiodic acid. In addition to hydroiodic acid, hydrochloric acid (HCl), hydrobromic acid (HBr), sulfuric acid (H ₂ SO ₄ ), phosphoric acid (H ₃ PO ₄ ) as an inorganic acid, and hydrogen sulfate as a salt thereof Hydroiodic acid is selectively separated by electrodialysis from an acid stock solution containing at least one of sodium (NaHSO ₄ ), disodium hydrogen phosphate (Na ₂ HPO ₄ ), and sodium iodide (NaI). A method for selectively separating hydroiodic acid,
The first cation exchange membrane and the first cation exchange membrane are separated from the pair of positive electrode chambers and negative electrode chambers by partitioning the polar liquid supplied to the electrode chamber from the positive electrode side . Anion exchange membranes and second cation exchange membranes are alternately and repeatedly provided, and these first cation exchange membrane, first anion exchange membrane, and second cation exchange membrane provide three sample chambers. The stock solution is supplied between the first anion exchange membrane and the second cation exchange membrane of the electrodialysis tank alternately divided into two, and the cation exchange membrane and the first cation exchange membrane Supplying an aqueous solution of a strong acid between and between the second cation exchange membrane and the adjacent first cation exchange membrane located on the negative electrode side of the second cation exchange membrane ;
Hydrogen ions (H ⁺ ) in the strong acid aqueous solution permeate the first cation exchange membrane, and iodine ions (I ⁻ ) in the stock solution permeate the first anion exchange membrane. A selective separation method of hydroiodic acid. In addition to hydroiodic acid, hydrochloric acid (HCl), hydrobromic acid (HBr), sulfuric acid (H ₂ SO ₄ ), phosphoric acid (H ₃ PO ₄ ) as an inorganic acid, and hydrogen sulfate as a salt thereof Hydroiodic acid is selectively separated by electrodialysis from an acid stock solution containing at least one of sodium (NaHSO ₄ ), disodium hydrogen phosphate (Na ₂ HPO ₄ ), and sodium iodide (NaI). A method for selectively separating hydroiodic acid,
The first anion exchange membrane and the first anion exchange membrane are separated from the pair of the positive electrode chamber and the negative electrode chamber by the cation exchange membrane that partitions the polar liquid supplied to the electrode chamber from the positive electrode side . A cation exchange membrane, a second anion exchange membrane, and a second cation exchange membrane are alternately and repeatedly provided. The first anion exchange membrane, the first cation exchange membrane, and the second anion. Between the first anion exchange membrane and the first cation exchange membrane of the electrodialysis tank alternately divided into four sample chambers by an exchange membrane and a second cation exchange membrane, and the second anion Supplying the stock solution to any one of the ion exchange membrane and the second cation exchange membrane, and supplying an aqueous solution of a strong acid to the other;
Selective separation of hydroiodic acid, characterized in that hydroiodic acid is produced by double displacement dialysis reaction from iodine ion (I ⁻ ) in the stock solution and hydrogen ion (H ⁺ ) in the strong acid aqueous solution. Method. The method for selectively separating hydroiodic acid according to any one of claims 1 to 3, wherein a monovalent anion selective permeable membrane is used as the anion exchange membrane. The method for selective separation of hydroiodic acid according to any one of claims 1 to 4, wherein an iodine absorbing solution produced by a blowing-out method is used as a stock solution. A separation step of selectively separating hydroiodic acid by electrodialysis from an aqueous solution containing hydroiodic acid and other inorganic ions by the method for selectively separating hydroiodic acid according to any one of claims 1 to 5. When,
Method for producing hydroiodic acid, characterized in that the aqueous solution containing a selected separated hydroiodic acid in the separation process was and a purification step of distillation purification. The aqueous solution obtained in the separation step contains hydroiodic acid and at least one of sulfuric acid and sulfate,
A precipitation step in which at least one of barium hydroxide and barium salt other than sulfuric acid is added to the aqueous solution obtained in this separation step, and at least one of sulfuric acid and sulfate contained in the aqueous solution is precipitated and removed as a barium salt; Prepared,
The aqueous hydroiodic acid solution after removing at least one of sulfuric acid and sulfate in this precipitation step is purified by distillation in the purification step
The method for producing hydroiodic acid according to claim 6. A method for producing hydroiodic acid according to claim 6 or 7 ,
A production process for producing iodine alkali salts by neutralizing hydroiodic acid distilled and purified in the purification process of the method for producing hydroiodic acid with alkali hydroxide, Manufacturing method.

Images