JP2010029797A - Lithium isotope separation and condensation method, apparatus, measure, lithium ion selective permeation membrane, and lithium isotope concentrate - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method and an apparatus for lithium isotope separation and condensation as well as a separation film and a system for lithium isotope separation. <P>SOLUTION: A lithium ion selective permeation membrane which is a porous body impregnated with a lithium ion conductive ionic liquid, e.g. TMPA-TFSI of PP13-TFSI, is arranged while being brought into contact with a lithium solution containing<SP>6</SP>Li isotope and<SP>7</SP>Li isotope to separate<SP>6</SP>Li isotope and<SP>7</SP>Li isotope by dialysis. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

The present invention relates to a lithium isotope separation and concentration method, a lithium isotope separation and concentration apparatus, a ⁶ Li or ⁷ Li concentration recovery method, a lithium ion selective permeable membrane, and a ⁶ Li concentrate or ⁷ Li concentrate.

Natural isotopes of lithium are ⁷ Li ⁶ Li of about 7.6% is present at a rate of about 92.4%. Tritium which is a fuel of a fusion reactor is produced by nuclear reaction with 6- lithium ⁽⁶ Li) neutron, natural isotopic ratio in order to ensure the tritium amount required to retrieve the fusion energy Higher 30-90% concentrated ⁶ Li is required. On the other hand, 7-lithium ( ⁷ Li) is used for adjusting hydrogen ions in a pressurized water nuclear power plant, and in that case, it is required that ⁶ Li that generates tritium is not included.

In countries around the world, the development of nuclear fusion technology has been promoted actively, to ensure that for concentrated ⁶ Li resource has become essential as the future of energy. Concentrated ⁶ Li resources were considered to be procured from overseas in Japan, but with the decision to construct the International Thermonuclear Experimental Reactor (ITER), competition for fusion research became intense worldwide, making procurement impossible. It became.

Concentrated ⁶ Regarding the development of Li resource recovery technology, research based on various principles of Li isotope separation was actively conducted in the 1970s, but most of them have low isotope separation efficiency and are industrialized and mass-produced. Because it was difficult to scale up, it has not been put into practical use.

  As the lithium isotope separation, an amalgam method, molecular distillation, ion exchange method, electrophoresis method (molten salt method), and solvent extraction method are known. As other lithium isotope separation methods, a crown ether extraction method, a crown ether resin adsorption chromatographic method, a graphite intercalation method, a zirconium phosphate adsorption chromatographic method, and an electrochemical redox method are known.

Patent Document 1 describes a lithium isotope separation method and apparatus. That is, in this document, there is a method for separating ⁶ Li from raw materials in which ⁶ Li and ⁷ Li are mixed. An electric field is applied to a Li ion conductor, and the Li ions of ⁶ Li and ⁷ Li the difference in the ionic conductivity of the conductor, ⁶ Li and moving the Li ion conductor in the positive potential side to negative potential side, lithium isotope separation and separating the ⁶ Li from the raw material A method is described and the use of solid electrolyte ceramics is described. However, in this method, since it is necessary to keep the lithium raw material in a molten salt state, and in order to improve the lithium permeation separation efficiency of the Li ion conductor, a high temperature state is necessary. It was a method with a low lithium isotope separation factor.

JP 2002-79059 A

  The Li isotope separation method that has been put to practical use so far is an amalgam method using a countercurrent exchange reaction of a lithium isotope between a lithium hydroxide aqueous solution and a lithium amalgam (alloy of lithium and mercury) (Patent Document 2). is there. The lithium isotope separation factor by this amalgam method is in the range of 1.04-1.09. However, from the viewpoint of environmental pollution by mercury, research on Li isotope separation using an ion exchange membrane method and a molten salt method that does not use mercury has been actively conducted since the 1970s, and has come to this day. However, the ion exchange membrane method has a small isotope separation factor, and the molten salt method has a large energy consumption and is difficult to scale up to mass production. Even in other methods, the isotope separation factor was as small as 1.001 to 1.01.

  For the above reasons, there has been no industrial Li isotope separation method other than the amalgam method.

  The present invention has been made in view of the above points, and is a lithium isotope separation and enrichment method and apparatus that can be easily handled without using mercury and can significantly improve the isotope separation factor compared to the conventional method, and The purpose is to provide a system.

The present invention provides a lithium ion selective permeable membrane in which a porous body is impregnated and held with an ionic liquid having lithium ion conductivity or a mixture obtained by mixing and dissolving a crown ether compound having lithium selective adsorptivity in the ionic liquid. A lithium isotope separation and concentration method is provided, wherein a lithium solution containing a ⁶ Li isotope and a ⁷ Li isotope is placed in contact with each other, and the ⁶ Li isotope and the ⁷ Li isotope are separated by dialysis.

  The present invention also provides a lithium isotope separation and concentration method characterized by using an electrodialysis method or a salt concentration difference dialysis method as the dialysis method.

  The present invention also provides a method for separating and concentrating lithium isotopes, wherein the lithium ion selective permeable membrane is formed of a porous body having a dense surface and a rough inside.

The present invention includes a porous body including a body and a lithium ion conductive ionic liquid disposed in the body or a mixture of a ionic liquid and a crown ether compound having lithium selective adsorptivity. A lithium isotope separation / concentration apparatus comprising: a lithium ion selective permeation membrane that has been impregnated and a lithium solution bath containing ⁶ Li isotopes and ⁷ Li isotopes in contact with the lithium selective permeation membrane I will provide a.

In the present invention, the lithium isotope separation and concentration apparatus is arranged in multiple stages so that the lithium ion selective permeable membrane and the lithium solution tank are adjacent to each other, and a ⁶ Li concentrated solution or a ⁷ Li concentrated solution is provided. Cation exchange resin concentration recovery device is placed in the first process after that, and ⁶ Li or ⁷ Li is adsorbed and recovered by cation exchange resin from the generated ⁶ Li isotope concentrated solution or ⁷ Li isotope concentrated solution A high concentration ⁶ Li solution or a high concentration ⁷ Li solution collected by concentration by the cation exchange resin concentration and recovery device, and concentrated ⁶ Li or concentrated ⁷ Li by an electrodialysis concentration and recovery device. At the same time, and at the same time, hydrochloric acid is recovered on the anode side. Providing the third process that can eluting the adsorbed lithium ions, the ⁶ Li or ⁷ Li isotopic withers concentration recovery method or system characterized in that they are composed of more processes.

The present invention also provides a ⁶ Li concentrate or a ⁷ Li concentrate characterized by being concentrated and recovered by the ⁶ Li or ⁷ Li concentration recovery system.

In the present invention, the lithium isotope separation and concentration apparatus is arranged in multiple stages so that the lithium ion selective permeation membrane and the lithium solution tank are adjacent to each other, thereby forming a multistage Li isotope separation and concentration apparatus. The ⁶ Li or ⁷ Li isotope highly concentrated recovery system is characterized in that the multi-stage Li isotope separation and concentration apparatus is configured in cascade in multiple stages.

  The present invention also provides the lithium ion selective permeable membrane.

  The present invention also provides a lithium ion selective permeable membrane characterized in that the surface has a dense structure and the inside has a rough structure.

  In the present invention, a porous body is impregnated and held with an ionic solution having lithium ion conductivity typified by TMPA-TFSI or PP3-TFSI, which makes it easy to handle without using mercury, and isotope separation coefficient. Thus, it is possible to provide a lithium isotope separation and concentration method, apparatus and system which can be improved significantly compared to conventional methods.

  Embodiments of the present invention will be described below with reference to the drawings.

FIG. 1 is a diagram showing the principle of lithium isotope separation and concentration according to an embodiment of the present invention.
A lithium isotope separation and concentration apparatus 100 shown in FIG. 1 is composed of a body 1 and a lithium ion conductive ionic liquid disposed in the body or a crown ether compound having selective adsorptivity to lithium in the ionic liquid. Lithium ion selective permeable membrane 2 impregnated and held in a porous state with a dissolved one, and a lithium solution tank containing ⁶ Li isotopes and ⁷ Li isotopes in contact with the lithium ion selective permeable membrane 2 (lithium raw material solution tank) 3.

The other side of the lithium ion selectively permeable membrane 2 ⁶ Li separation concentration tank ^{4 6} Li is accommodated are separated concentrated is formed.

An anode electrode 5 is disposed in the lithium solution tank 3, and a cathode electrode 6 is disposed in the ⁶ Li separation / concentration tank 4. From the introduction path 8 and the ⁶ Li / ⁷ Li natural ratio solution for introducing the ⁶ Li / ⁷ Li natural ratio solution 7 such as lithium chloride (LiCl) in which ⁶ Li and ⁷ Li are mixed in the natural ratio in the lithium solution tank 3. A lead-out path 10 for leading out the ⁶ Li-depleted liquid 9 in which ⁶ Li is impaired is connected.

^{The 6} Li separation / concentration tank 4 is connected to an introduction path 12 for introducing, for example, a lithium chloride (LiCl) solution in which ⁶ Li and ⁷ Li are mixed in a natural ratio, and an outlet path 14 for deriving the ⁶ Li concentrated liquid 13. ^Then, 6 Li concentrated solution 13 in the ⁶ Li recovery 14 is made.

  The lithium ion selective permeable membrane 2 is a hydrophobic porous body (porous membrane formed by mixing and dissolving an ionic liquid having lithium ion conductivity or a crown ether compound having lithium selective adsorptivity in the ionic liquid. 15) is impregnated and held (ionic liquid impregnated and held 16).

TMPA-TFSI (formal chemical name: N, N, N-Trimethyl-N-propylammonium bis (trifluoromethanesulfonyl) imide) or PP3-TFSI (formal chemical name: N-Methyl-N-propylpiperidinium) as an ionic liquid having lithium ion selectivity bis (trifluoromethanesulfonyl) imide) is used, but other ionic liquids may be used. Other ionic liquids, for example
The 1-Alkyl-3methylimidazolium TFSI anion as cation _{((CF 3 SO 2) 2} N -) as an ionic liquid which is a combination of, or 1-Ethyl-3methylimidazolium bis (trifluoromethanesulfonyl ) imide, 1-Ethyl -2,3methylimidazolium bis (trifluoromethanesulfonyl ) imide and other imidazolium-based ionic liquids, such as 1-Ethylpyridinium bis (trifluoromethanesulfonyl) imide and 1-Butylpyridinium bis (trifluoromethanesulfonyl) imide, trimethylphosphonium bis (trifluoromethanesulfonyl) imide, Polyethyleneoxide (PEO) bis (trifluoromethanesulfonyl) ) Ionic liquids such as imide, sulfonic acid type Zwitterion, carboxylic acid type Zwitterion, imidoic acid type Zwitterion, borate type Zwitterion, TFSI anion ionic liquid, and the above lithium ion conductive ionic liquid, TFSI anion The inclusions have good lithium ion conductivity.
Furthermore, 12-crown-4-ether is suitable as a crown ether compound which is mixed and dissolved in these ionic liquids to enhance lithium isotope separation characteristics. In any case, in this example, in separating ⁶ Li ions and ⁷ Li ions, an ionic liquid that is an aqueous solution or a crown ether was mixed and dissolved in the ionic liquid to separate lithium isotopes. It is characterized by using things.

  As the permeation method, an electropermeation method or a chlorine concentration dialysis method is used, but other dialysis methods may be used.

FIG. 2 shows an example in which the lithium selective permeable membrane 2 is formed in a cylindrical shape.
As shown in FIG. 2 (a), a lithium ion selective permeable membrane 2 configured in a cylindrical shape is disposed around the central portion of a cylindrical body 1, a ⁶ Li solution tank 3 on the outer peripheral portion, and a lithium ion A ⁶ Li concentration tank 4 is formed at the center of the selective permeable membrane 2, that is, at the center of the body 1. ^{The 6} Li separation / concentration tank 4 is connected to an introduction path 12 for the lithium solution 13 and a lead-out path 14 for the ⁶ Li concentrated solution 13 as in FIG.

  As shown in FIG. 2B, the lithium ion selective permeable membrane 2 has a cylindrical shape, and an ionic liquid impregnated portion 16A in which a hydrophobic porous membrane 15 (FIG. 1) is impregnated and held 16 (FIG. 1). Constitute. It is formed of an ionic liquid impregnated porous diaphragm. As a material of the porous diaphragm, a water repellent material such as Teflon (registered trademark) is desirable.

  FIG. 2C shows an enlarged cross-sectional view of the A part in FIG. In FIG. 2C, the ionic liquid is impregnated into a filter-like substance of a porous body (including a porous film) having a dense structure on the surface (outer surface, inner surface) and a rough structure on the inside, It is possible to reduce or prevent the ionic liquid from desorbing from the porous body at the inner and outer surface portions by allowing ions to move relatively freely in the impregnated portion of the rough portion. Adhering a hydrophobic porous membrane to the inner and outer surfaces of the cylinder is also effective in preventing the ionic liquid from being detached.

  In the example shown in FIG. 2, the lithium ion selective permeable membrane 2 is formed in a cylindrical shape. However, the lithium ion selective permeable membrane 2 can be formed in a flat plate shape to have a flat plate-like diaphragm configuration, and the configuration is the same as in FIG. be able to.

The present invention is characterized by using a porous membrane impregnated with an ionic liquid or a mixture of a crown ether compound and dissolved in an ionic liquid when selectively separating and recovering Li ion isotopes, The principle is to separate into ⁶ Li ions and ⁷ Li ions by a dialysis method using an inorganic or organic porous membrane impregnated with an ionic liquid having selective permeability of Li ions. ⁶ Li ions and ⁷ Li ions not only have slightly different ionic radii, but the ion mobility depends on the mass of the ions, so that there is a difference in the ionic conduction velocity for each Li isotope in the ionic liquid-impregnated porous diaphragm. As a result, ⁶ Li having a high conduction speed is selectively recovered through an ionic liquid-impregnated porous diaphragm (particularly an organic porous diaphragm).

As shown in FIG. 1, natural Li isotope ratio Li aqueous solution ( ⁶ Li / ⁷ Li natural ratio solution 7, anode side) and ⁶ Li permeate solution ( ⁶ Li / ⁷ Li natural ratio solution 11, cathode side) In the meantime, by applying a potential to both sides of a porous membrane (lithium ion selective permeable membrane 2) impregnated with an ionic liquid having selective adsorptivity to Li ions, only Li ions move through the ionic liquid-impregnated porous membrane. . During movement, ⁶ Li ions move faster than ⁷ Li ions, so ⁶ Li ions move quickly to the ⁶ Li separation and concentration tank 4, and ⁷ Li remains in the lithium solution tank 3 in a large amount. After ⁶ Li moved, ⁶ Li becomes enriched solution at the cathode side, whereas lithium solution is the original solution ⁶ Li is ^impaired, the 7 Li concentration than the ratio of ⁶ Li ^/ 7 Li before movement Increased state.

⁶ Li liquid separated enriched is taken as ⁶ Li recovery solution ⁽⁶ Li ^/ 7 Li natural ratio LiCl solution) to accompanied being by ⁶ Li concentrated liquid 13 ^is 6 Li recovered 14. On the other hand, from the lithium solution in which ⁶ Li is depleted ( ⁶ Li depleted solution 9), ⁷ Li having a relatively increased concentration with the loss of ⁶ Li is recovered as a ⁷ Li concentrated solution.

  FIG. 3 shows the Li isotope separation test effect when TMPA-TESI or PP13-TFSI is used as the ionic liquid.

In FIG. 3, X-axis represents the intensity of the current to be applied, Y axis represents the ⁶ Li separation factor. In order to obtain a Li isotope separation concentrate, it is desirable that the Li isotope separation factor is high and the amount of recovered Li is large. When the current to be applied is increased, a ⁶ Li separation coefficient that is significantly higher than that of the conventional example can be obtained in any case. If it is 30 mA or more, a large ⁶ Li separation coefficient cannot be obtained, but a ⁶ Li separation coefficient much higher than that of the conventional example can be obtained within 10 mA. In the case of PP13-TFSI, a very high ⁶ Li separation factor of 1.20 is obtained at about 3 mA. ⁶ Li separation factor of the amalgam method, which is a conventional method is 1.04 to 1.09, compared with 1.001 to 1.01 of an ion exchange method, very is ⁶ Li separation factor in the case of the present invention high 1. It can be seen that ⁶ Li can be separated and recovered with an efficiency of 15 to 1.40.

FIG. 4 is a Li isotope separation test result showing the value of ⁶ Li isotope separation coefficient with respect to the intensity of dialysis current according to this example. Even under this condition, as in FIG. 3, a ⁶ Li isotope separation factor much higher than that of the conventional example is obtained. Therefore, it can be seen that there is a remarkably high ⁶ Li isotope separation efficiency.

FIG. 5 shows the ⁶ Li isotope separation factor obtained when the type of ionic liquid is changed and the diaphragm thickness, permeation current, and LiCl concentration of the lithium ion selective permeable membrane are changed. For the ionic liquid used in this case (TMPA-TFSI), a ⁶ Li isotope separation factor lower than that of FIG. 4, ⁶ Li isotope separation factor of about similar as compared to the amalgam method of the prior art is obtained However, the ionic liquid (TMPA-TFSI) in this case is characterized by a high yield of ⁶ Li. Therefore, it can be seen that there is a remarkably high ⁶ Li isotope separation efficiency.

FIG. 6 also shows the result of obtaining the same ⁶ Li isotope separation efficiency. In this figure displays a LiCl concentration of lithium solution tank to the X-axis, and displays the ⁶ Li isotope separation factor in the Y-axis.

  FIG. 7 shows a Li isotope separation and concentration apparatus (multistage Li isotope separation and concentration apparatus) 200 having a multistage electrodialysis cell structure. The multi-stage Li isotope separation and concentration apparatus 200 is configured by multi-stages the lithium isotope separation and concentration apparatus 100 having a single cell type electrodialysis structure shown in FIG.

  In FIG. 7, a multistage Li isotope separation / concentration device 200 is configured by incorporating a large number of single-cell type lithium isotope separation / concentration devices 100 (single cells) into the body 1. An example incorporating 100 is shown.

  The body 1 is connected to an introduction path 22 for introducing the polar liquid 21 and a discharge path 24 for discharging 23. As shown in FIG. 1, a cathode electrode 6A and an anode electrode 5A are provided in the periphery of the body 1 where the polar liquid is present.

The single cell 100 is composed of a lithium solution tank 3, a ⁶ Li separation / concentration tank 4, and a lithium selective permeable membrane 2 therebetween, which is indicated as K ^Li in the figure, and a known organic diaphragm electrodialysis method is used. Applicable.

During the unit cell 100, that is, between the lithium solution chamber 3 and the adjacent ⁶ Li separating and concentrating tank 4 Yes by arranging anion permeable membrane 25, in the drawings are indicated as A.

The adjacent lithium solution tanks 3 between the single cells are connected by connection pipes 26, and the ⁶ Li separation and concentration tanks 4 are connected by connection pipes 27, respectively. As shown, the connecting pipe 26 and the connecting pipe 27 are adapted to countercurrent, thus lithium solution and ⁶ Li separated concentrate flow direction, will flow in the opposite direction.

An introduction path 32 for introducing the LiCl solution 31 is connected to the lithium solution tank 3 on the desalting side, and a lead-out path 35 for discharging low salt ( ⁷ Li concentrated) 38A is connected to the lithium solution tank 3 on the concentration side. Is done.

⁶ Li separation outlet passage 39 to the concentration tank 4 for collecting the ⁶ Li concentrated solution 38 in the ⁶ Li separation concentration tank 4 in the desalting side is connected introduction passage 37 for introducing the LiCl solution 36 is connected on the concentration-side Is done.

By applying an organic diaphragm electrodialysis method using an ionic liquid from a lithium solution in each cell 100, ⁶ Li is separated, and sequentially flows through ⁶ Li separation and concentration 4 through each connection pipe 27, and finally increases the concentration. recovered from ⁶ Li separating and concentrating tank 4 desalting side of the step as a ⁶ Li concentrated solution 38, is a ⁶ Li high concentrate 39 by multistage ⁶ Li concentration treatment.

On the other hand, ⁷ Li concentrated by the separation of ⁶ Li in each cell 100 flows through the connection pipe 26 and is recovered from the lithium concentration tank 3 on the concentration side. ^When viewed from ⁶ Li, it is a ⁶ Li depleted solution, and when viewed from ⁷ Li, it is a ⁷ Li concentrated solution.

Recovered ⁷ Li enriched solution is similarly to ⁷ Li concentrated solution 38A and ⁶ Li concentrated solution 38, are multistage ⁷ Li concentration treatment, are increased sequentially enrichment ⁷ Li High concentrate 39A.

In this way, electrodialysis cells having an ionic liquid-impregnated organic diaphragm separating ⁶ Li ions and ⁷ Li ions are arranged in multiple stages (cascades), and these multistage electrodialysis cells are alternately connected to each other, and an aqueous Li solution having a natural isotope ratio. the passed through and by applying a potential to the ^electrodes, 6 Li is high ⁶ Li enriched stream concentrated in the concentration ⁽⁷ Li depleted stream) and a high concentration of ⁷ Li enriched ^{stream 6} Li is impaired is obtained.

The following matters are mentioned as the merit of the organic diaphragm electrodialysis method.
· Industrialized easily method, scaleable, high productivity economical method, isotope separation factor less high, the multistage Li isotope separation concentrator 200 of the present system shown in FIG. 7 K ^{Li -A} composite membrane This is called a system electrodialysis cell.

FIG. 8 shows a modification of the multistage Li isotope separation and concentration apparatus 200 shown in FIG. The same number is attached | subjected to the same structure. In the multistage Li isotope separation / concentration apparatus 200 shown in FIG. 8, the anion dialysis membrane 25 shown by “A” in FIG. 7 is used only in the immediate vicinity of the cathode electrode, and the others are lithium selective shown by K ^Li. Only permeable membranes are used. ⁶ Li is permeated one after another to the adjacent lithium lithium solution tank and ⁶ Li separation / concentration tank to be highly concentrated. In this example, ⁶ Li is highly concentrated, but similarly ⁷ Li can be highly concentrated. Hereinafter, the multi-stage Li isotope separation / concentration device 200 of this system shown in FIG. 8 is referred to as a K ^Li diaphragm type electrodialysis cell.

FIG. 9 shows an electrodialysis multi-stage ⁶ Li isotope separation system constituted by the multi-stage Li isotope separation and concentration apparatus 200 shown in FIG. 7, a concentrated ⁶ Li isotope recovery system 301 by ion exchange resin concentration, and electrodialysis. ⁶ shows a ⁶ Li highly concentrated recovery system 300 that is connected to the electrodialyzed ⁶ LiOH recovery system 302 to obtain a ⁶ Li highly concentrated solution. Although FIG. 9 shows a system for recovering the ⁶ Li concentrated solution, the ⁷ Li concentrated solution is recovered in the same manner.

In FIG. 9, the configuration of the multistage Li isotope separation and concentration apparatus 200 is the same as that shown in FIG. In this figure, LiCl powders 41 and 42 are an Li solution (desalting side) 31 and a LiCl solution (concentration side) 36 of an aqueous solution, in which case Li concentration and ⁶ Li / ⁷ Li ratio analysis 43 and 44 are performed, respectively. It becomes data of Li isotope separation concentrate collection.

The concentrated ⁶ Li isotope recovery system 301 is constituted by a cation exchange resin concentration recovery device 50 using a cation exchange resin 51. In the figure, two towers of cation exchange resin concentration recovery apparatus 50 are shown.

The ⁶ Li concentrated solution 38 recovered by the multistage Li isotope separation / concentration device 200 is introduced through the pipe 52 to the lower part of each cation exchange resin concentration recovery device 50. The concentrated ⁶ Li component is adsorbed by the cation exchange resin 51. Regeneration liquid is desorbed by a solution of hydrochloric acid as a 53, ⁶ Li high concentration recovery solution from the cation exchange resin concentration recovery device 50 the top for the cation exchange resin, eluting ⁶ Li component adsorbed is introduced through a pipe 54 56 is collected.

^{The 6} Li highly concentrated recovery liquid 56 is guided to the electrodialysis ⁶ LiOH recovery system 302 via the pipe 55.

  The resin regeneration waste liquid 57 discharged from the cation exchange resin concentration recovery apparatus 50 is recovered through the pipe 57 and reused as the LiCl solution 31 or the regeneration liquid 53 for cation exchange resin elution in the figure.

Electrodialysis ^{6 The} LiOH recovery system 302 is constituted by an electrodialysis recovery device 60. As the electrodialysis concentration recovery apparatus 60, a known electrodialysis apparatus is employed.

In the electrodialysis concentration recovery apparatus 60, an anion dialysis membrane is used for A, and a cation dialysis membrane is used for K. The cathode reaction and anode reaction of the electrodialyzer 60 are as follows.
[Cathode reaction] 2Li ⁺ + 2H ₂ O + 2e ⁻ → 2LiOH + H ₂ ↑
[Anode Reaction] 2Cl ⁻ + H ₂ O-2e ⁻ → 2HCl + 1 / 2O ₂ ↑
^{6 The} LiOH recovery liquid 61 is recovered from the pipe 62.

In the electrodialysis concentration recovery device 60, the coexisting chlorine ions are removed and recovered, and the target high concentration LiOH is recovered. This high-concentration LiOH solution is heated to remove moisture and dried to obtain the target LiOH · H ₂ O powder 65. The concentrated LiOH · _{H 2} O ^becomes concentrated ⁷ LiOH · _{H 2} O in concentrated ⁶ LiOH · _{H 2} O or ⁷ Li of 6 Li.

  In the electrolytic dialysis concentration recovery device 60, the chlorine ions generated by the dialysis reaction at the anion dialysis membrane are converted into hydrochloric acid 63 and recovered as a regenerated solution 53 for elution of the cation exchange resin via the pipe 64.

The concentrated ⁶ LiOH recovery liquid 61 is dried to obtain concentrated ⁶ LiOH.H ₂ O powder 65. In these systems, Li concentration and ⁶ Li / ⁷ Li ratio analysis 43-49 is performed for each solution.

By introducing an aqueous solution of lithium chloride LiCl having a natural lithium isotope ratio as a raw material into a multi-stage single cell of the multi-stage Li isotope separation and concentration apparatus 200, and separating ⁶ Li and ⁷ Li in each cell, ⁶ Li is ⁷ Li enriched ^{stream 7} Li depleted stream and ⁶ Li and concentrating is impaired is obtained. After obtaining a predetermined concentrated ⁶ Li aqueous solution in a multi-stage single cell, the ⁶ Li concentrated Li component is collected with a cation exchange resin, and the collected ⁶ Li concentrated Li component is eluted with hydrochloric acid or the like to be highly concentrated. ⁶ Li-concentrated Li component is obtained. Further, this highly concentrated ⁶ Li concentrated Li component is decomposed and recovered into a lithium hydroxide (LiOH) solution and a hydrochloric acid solution by electrodialysis. As a result, the LiOH solution recovered on the cathode side of the electrodialysis tank contains a ⁶ Li-concentrated Li component. On the anode side of the electrodialysis tank, hydrochloric acid is recovered by electrodialysis treatment. The recovered hydrochloric acid is reused as an eluent for recovering the ⁶ Li-concentrated Li component collected by the cation exchange resin in the previous stage.

On the other hand, a concentrated ⁷ LiOH recovery liquid and further concentrated ⁷ LiOH and H ₂ O powders are obtained from the ⁷ Li concentrated liquid obtained by depletion of ⁶ Li by the application of a cation exchange resin and electrodialysis.

In this way, the lithium isotope separation and concentration apparatus 100 is arranged in multiple stages so that the lithium ion selective permeable membrane 2 and the lithium solution tank 3 are adjacent to each other, thereby producing a ⁶ Li concentrate or a ⁷ Li concentrate. The cation exchange resin recovery device 50 for concentrating and recovering ⁶ Li or ⁷ Li from the produced ⁶ Li concentrate or ⁷ Li concentrate by the cation exchange resin 51 and electrodialysis for further concentration recovery by the electrodialysis process A concentration recovery device 60 is provided to recover the concentrated ⁶ Li or ⁷ Li. The ⁶ Li or ⁷ Li concentrated recovery system 300 constituting the ⁶ Li or ⁷ Li high concentration recovery system 300 constitutes the ⁶ Li concentrate or ⁷ Li concentration. Things are collected.

The data of ⁶ Li separation concentrate 38 is as follows.

Li natural isotope ratio = ⁶ Li (7.59%): ⁷ Li (92.41%)
⁶ Li isotope separation factor of single ^cell: 1.20 (6 Li9.11%)
⁶ Li isotope separation factor in the case of a 10-stage continuous concentration cell: 6.19 ( ⁶ Li 47.0%)
The data of ⁶ Li separation concentrate 56 is as follows.

The Li concentration (for example, 0.2 M / L) in the solution of ⁶ Li isotope (47.0%) in the case of the 10-stage continuous concentration cell is increased 10 to 25 times to be 2.0 to 5.0 M / L. The highly concentrated Li solution is recovered.

FIG. 10 shows a system flow for the ⁶ Li or ⁷ Li highly concentrated recovery system shown in FIG.

  In the example shown in FIG. 10, an electrodialysis method or a salt concentration gradient dialysis method is used as the dialysis method. These can be used together to form a system flow.

The ⁶ Li or ⁷ Li high concentration recovery method using the ⁶ Li or ⁷ Li (including ⁶ Li and ⁷ Li) high concentration recovery system 300 configured as described above can perform isotope separation and concentration operation at room temperature. Yes, low power consumption, high isotope separation factor, and highly concentrated recovery of ⁶ Li and ⁷ Li.

  According to the present invention, not only the scale-up for mass production of Li isotopes is easy, but also a separation factor exceeding the isotope separation factor (about 1.06) of the mercury amalgam method which has been put to practical use until now. Can be obtained.

Figure 11 shows an example of the system as ^K Li -A composite diaphragm type electrodialysis cell 200 and Li isotope separation cascade 400 constructed using the ^{K Li} diaphragm type electrodialysis cell 200 shown in FIG. 8 as shown in FIG. 7 .

In FIG. 11, the Li isotope separation cascade 400 uses a K ^Li -A composite diaphragm type electrodialysis cell 200 for 1-stage concentration and 2-stage concentration of ⁶ Li, and K ^{Li for} multi-stage concentration, which is the final stage in this example. A diaphragm type electrodialysis cell 200 is used. Since each electrodialysis cell has been described with reference to FIGS. 7 and 8, the detailed internal description is omitted and the connection relationship will be described. In this example, three ^KLi- A composite diaphragm type electrodialysis cells 200 are used for one-stage concentration and two-stage concentration, but the number is not limited. In any case, as the number of stages increases, the number of electrodialysis cells 200 used decreases in relation to the amount of solution. The first stage concentrating ⁶ Li401 obtained in one stage concentrate is branched into two, is the second stage of the ^K Li -A composite membrane system LiCl solution electrodialysis cell 200 ⁽⁶ Li concentrated side) lithium solution bath is introduced into the 3, it is the (one-stage concentrate ⁶ Li402 is merged or branched with 2-stage ^K Li -A composite membrane system LiCl solution electrodialysis cell 200 ⁽⁶ Li ^{concentrated,} 7 Li desalination side) ⁶ It is introduced into the Li separation / concentration tank 4. The discharged ⁷ Li is recovered by the ⁷ Li recovery system 403.

Similarly, the two-stage concentration 404 obtained by the two-stage concentration is mixed or branched into the LiCl solution of the third stage K ^Li diaphragm type electrodialysis cell 200 and introduced into the lithium solution tank 3 to form ⁶ Li. concentrate ^{4 (6} Li ^{concentrated,} 7 Li desalination side) obtained. ⁶ Li impairment solution of 2-3-stage ⁽⁶ Li ^desalting, 7 Li concentration side) ^{6 K} Li another system as Li recovery system 405, 407 -A composite diaphragm type electrodialysis cell 200 or 1-2, It is introduced into the ⁶ Li separation / concentration liquid 3 at the stage and ⁶ Li is recovered again.
In this way, the cascading is ⁶ Li high concentrate from the final stage 406 is recovered.
Although this example shows the recovery of ⁶ Li, ⁷ Li can also be configured and recovered in the same cascade.

The applicability of the present invention will be described as follows.
Concentrated ⁶ Li preparation of high efficiency of the present invention contribute to the realization of nuclear fusion, in order to contribute to ensuring the necessary tritium as fuel for fusion reactors, can overcome the major challenges towards a fusion reactor achieved.
Application to other nuclear fields In another field of nuclear energy research and development, ⁷ Li, which is a tritium isotope, is a form of ⁷ LiOH in the pressurized water nuclear power generation system that controls the concentration of hydrogen ions to reduce structural material corrosion. are used which are but, since the thermal neutron absorption cross section of the Li isotope ⁶ Li is ^940b, 7 Li is ^{0.037B, 7} content of 6 Li is less 0.001% Li (enrichment 99 .99% or more) must be used, but this can be accommodated.
Application to Lithium Battery Since ⁶ Li in a Li solution has higher mobility than ⁷ Li, an improvement in Li ion conductivity is expected in a Li solution containing a large amount of ⁶ Li. This characteristic can be utilized in a Li ion battery, and a Li ion battery using concentrated ⁶ Li can be expected to realize a powerful Li battery that surpasses the performance of conventional Li ion batteries using natural Li.

The figure explaining the principle of this invention. The figure which shows one example of the lithium ion selective permeable membrane structure used for this invention. The figure which shows the effect by the Example of this invention. The figure which shows a Li isotope separation test result. The figure which shows a Li isotope separation test result. The figure which shows a Li isotope separation test result. The figure which shows the structure of the multistage Li isotope separation and concentration apparatus which is an Example of this invention. The figure which shows the modification of the multistage type Li isotope separation and concentration apparatus shown in FIG. It shows a ⁶ Li or ⁷ Li high concentration recovery system which is an embodiment of the present invention. View showing an example of a system flow of ⁶ Li or ⁷ Li high concentration recovery system. The figure which shows one example of the Li isotope separation cascade which is an Example of this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Body, 2 ... Lithium ion selective permeable membrane, 3 ... Lithium solution tank, 4 ... ⁶ Li separation concentration tank, 5 ... Anode electrode, 6 ... Cathode electrode, 7 ... ⁶ Li / ⁷ Li natural ratio solution, 9 ... ⁶ Li depleted solution, 13 ... ⁶ Li concentrated solution, 26, 27 ... Connection piping, 50 ... Cation exchange resin, 51 ... Cation exchange resin concentrated recovery device, 60 ... Electrodialysis concentration recovery device, 61 ... ⁶ LiOH recovery solution , 100 ... Lithium isotope separation / concentration device (single cell), 200 ... Li-isotope separation / concentration device (multi-stage Li isotope separation / concentration device, multi-stage cell) having a multistage electrodialysis cell structure, 300 ... ⁶ Li high concentration recovery system ⁽⁶ Li or ⁷ Li-rich recovery system), 301 ... ion exchange resin concentration by concentrating ⁶ Li isotope recovery system (concentrated ⁶ Li or ⁷ Li isotope recovery system), 302 ... electrodialysis LiOH recovery system (electrolysis transmission ⁶ LiOH or ⁷ LiOH recovery system).

Claims (11)

An ionic liquid having lithium ion conductivity of the lithium ion selectively permeable membrane impregnated held in the porous body, disposed in contact with the lithium solution containing ⁶ Li isotopic and ⁷ Li isotope, ⁶ Li isotopic by dialysis And a ⁷ Li isotope are separated from each other. ⁶ Li isotopes and ⁷ Li are applied to a lithium ion selective permeation membrane in which a porous body is impregnated and held by mixing and dissolving a crown ether compound having selective adsorptivity to lithium in an ionic liquid having lithium ion conductivity. lithium isotope separation concentration method, characterized in that arranged in contact with the lithium solution containing isotope, separating ⁶ Li isotopic and ⁷ Li isotopic by dialysis.   3. The lithium isotope separation and concentration method according to claim 1 or 2, wherein an electrodialysis method or a salt concentration difference dialysis method is used as the dialysis method.   3. The lithium isotope separation and enrichment method according to claim 1, wherein the lithium ion selective permeable membrane is formed of a porous body having a dense surface and a rough inside. A body, a lithium ion selective permeable membrane in which the porous body is impregnated and held with an ionic liquid having lithium ion conductivity, and a ⁶ Li isotope in contact with the lithium selective permeable membrane And a lithium solution tank containing ⁷ Li isotopes. Lithium ion selection in which a porous body is impregnated and retained by mixing and dissolving a fuselage and a crown ether compound having selective adsorptivity to lithium in an ionic liquid having lithium ion conductivity disposed in the fuselage And a lithium solution bath containing a ⁶ Li isotope and a ⁷ Li isotope in contact with the lithium ion selective permeable membrane. The lithium isotope separation / concentration device according to claim 5 or 6 is arranged in multiple stages so that the lithium ion selective permeation membrane and the lithium solution tank are adjacent to each other, thereby constituting a multistage Li isotope separation / concentration device A ⁶ Li or ⁷ Li isotope highly concentrated recovery system, wherein the multi-stage Li isotope separation and concentration apparatus is configured in cascade in multiple stages. The lithium isotope separation and concentration apparatus according to claim 5 or 6 is arranged in multiple stages so that the lithium ion selective permeation membrane and the lithium solution tank are adjacent to each other, and a ⁶ Li concentrated solution or a ⁷ Li concentrated solution adsorption but first process spawned by ⁶ Li isotopic enrichment solution or ⁷ Li isotopic enrichment solution from ⁶ Li or ⁷ Li cation exchange resins produced by placing the cation intercourse resin concentration recovery device to a subsequent stage Second concentration to be recovered, concentrated ⁶ Li solution or concentrated ⁷ Li solution recovered by concentrating by the cation exchange resin concentration and recovery device, and concentrated ⁶ Li or concentrated ⁷ Li to lithium hydroxide by electrodialysis concentration and recovery device The solution is recovered on the cathode side, and at the same time, hydrochloric acid is recovered on the anode side. ⁶ Li or ⁷ Li isotopic withers concentration recovery method, characterized in that it comprises a third process that can eluting the adsorbed lithium ions device. ⁶ Li or ⁷ Li ⁶ Li concentrate, characterized in that concentrated recovered by concentrating recovery method or ⁷ Li concentrate of claim 8.   The lithium ion selective permeable membrane according to any one of claims 1 to 9.   11. The lithium ion selective permeable membrane according to claim 10, wherein the surface has a dense structure and the inside has a rough structure.

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