Lithium isotope concentration device and multistage lithium isotope concentration device, and lithium isotope concentration method

Abstract

A lithium isotope concentration device (10) has a treatment tank (1) divided into a supply tank (11) and a recovery tank (12) by an electrolyte membrane (2) having lithium ion conductivity, a main power source (51) connected between electrodes (31, 32) provided on both sides of the electrolyte membrane (2), and a sub power source (52) connected between a sub electrode (33) and the electrode (31), which alternately apply voltage, wherein the sub electrode (33) is provided in the supply tank (11) at a spaced interval from the electrolyte membrane (2).

Description

Technical Field

[0001] This invention relates to a lithium isotope concentration apparatus for separating lithium isotopes, a multi-stage lithium isotope concentration apparatus, and a lithium isotope concentration method. Background Technology

[0002] Lithium (Li) exists 7 Li and 6 The natural abundance ratio of these two stable isotopes, Li, is 92.41 mol% and 7.59 mol%, respectively. (Mass number 7) 7 Li and a mass number of 6 6 The properties of Li vary considerably, for example 7 Li is used to adjust the pH (hydrogen ion concentration) of the coolant in nuclear reactors. On the other hand, 6 Li is used in the production of tritium (tritium), a fuel for nuclear fusion reactors. Therefore, a technology has been developed to... 7 Li and 6 Li can be concentrated and separated into states with fewer isotopes of another substance. Known methods include amalgamation, molten salt methods, distillation, and selective recovery of lithium ions (Li) from seawater. + Methods such as adsorption and electrodialysis (e.g., Patent Document 1).

[0003] From an environmental impact perspective, adsorption or electrodialysis methods are superior to amalgamation methods (which use large amounts of mercury), molten salt methods (which involve heating lithium compounds at high temperatures), or distillation methods. Furthermore, these methods utilize the high-speed transport of large quantities of recovered materials due to their small mass. 6 Li + While the principle is similar, the isotope separation coefficient is small, resulting in low productivity as a concentration method. Therefore, the inventors conducted research to apply lithium recovery technology to the concentration of lithium isotopes, specifically a technique for selectively recovering Li from seawater or similar sources using electrodialysis with an electrolyte membrane that has lithium-ion conductivity (e.g., Patent Documents 2 and 3). Furthermore, it was found that in such Li recovery, the isotope separation coefficient is only relatively large for a short period after the start of operation, and a method was invented to improve efficiency by intermittently applying voltage or alternating between positive and negative voltages (Patent Document 4, Non-Patent Document 1). [Existing Technical Documents] [Patent Literature]

[0004] Patent Document 1: Japanese Invention Patent Publication No. 5429658 Patent Document 2: Japanese Invention Patent Publication No. 6233877 Patent Document 3: Japanese Patent Publication No. 2019-141807 Patent Document 4: Japanese Patent Publication No. 2019-141808 [Non-patent literature]

[0005] Non-patent document 1: Shunsuke Honda, Kiyoto Shin-mura, Kazuya Sasaki, "Lithiumisotope enrichment by electrochemical pumping using solid lithiumelectrolytes", Journal of the Ceramic Society of Japan, Volume 126, Issue 5, pp331-335, May 2018 Summary of the Invention [The technical problem the invention aims to solve]

[0006] In the method described in Patent Document 4, etc., when applying voltage intermittently, the effect is low unless the application stop time is set to a certain level or higher, thus raising concerns about reduced time efficiency. When applying positive and negative voltages alternately, the recovered voltage is higher when applying voltage in the opposite direction. 6 Li + Reverse flow occurs, so the voltage and application time need to be adjusted to suppress this as much as possible. There is still room for further improvement to increase productivity.

[0007] The present invention was made in view of the above-mentioned problems, and the technical problem to be solved is to provide a safe, efficient and productive lithium isotope concentration device and a multi-stage lithium isotope concentration device, as well as a lithium isotope concentration method. [Technical solutions used to solve technical problems]

[0008] After conducting in-depth research, the inventors realized that when the voltage for electrodialysis is applied intermittently, a potential difference can be formed in the Li aqueous solution (before isotope concentration) on the supply side during the period when the voltage application is stopped, so that even if the voltage application stop time is shortened, a high effect can be obtained.

[0009] That is, the lithium isotope concentration apparatus according to the present invention has a processing tank divided into a first tank and a second tank, and the second tank is used to extract lithium isotopes contained in the first tank in the form of lithium ions. 6 Li and 7 Li was recovered from an aqueous solution containing [a substance] compared to the aqueous solution. 6An apparatus for preparing aqueous solutions of lithium ions with a high isotope ratio of Li. Furthermore, the lithium isotope concentration apparatus according to the present invention is configured to have a lithium-ion conductive electrolyte membrane, porous electrodes, a secondary electrode, and a power supply device. The lithium-ion conductive electrolyte membrane separates the processing tank; the porous electrodes are configured to contact both sides of the lithium-ion conductive electrolyte membrane; the secondary electrodes are disposed within the first tank at intervals from the first tank side of the lithium-ion conductive electrolyte membrane and the porous electrodes; the power supply device alternately applies voltage between the porous electrodes and between the porous electrodes on the first tank side and the secondary electrode, with the porous electrodes on the first tank side being positive. Furthermore, the multi-stage lithium isotope concentration apparatus of the present invention is configured such that two or more lithium isotope concentration apparatuses are connected in such a way that the processing tanks are integrated, and the lithium-ion conductive electrolyte membranes of the lithium isotope concentration apparatuses are arranged apart from each other in such a way that the integrated processing tanks are divided into three or more tanks, and the second tank of one of the two adjacent lithium isotope concentration apparatuses also serves as the first tank of the other.

[0010] The lithium isotope concentration method of the present invention involves, in a processing tank divided into a first tank and a second tank by a lithium-ion conductive electrolyte membrane, extracting lithium isotopes contained in the first tank in the second tank. 6 Li and 7 Li was recovered from an aqueous solution containing [a substance] compared to the aqueous solution. 6 A method for preparing an aqueous solution of lithium ions with a high isotope ratio of Li. Furthermore, in the lithium isotope concentration method according to the present invention, steps 1 and 2 are performed alternately. In step 1, a positive voltage relative to the second tank side is applied to the first tank side of a porous electrode that is respectively in contact with both sides of the lithium-ion conductive electrolyte membrane. In step 2, a negative voltage relative to the porous electrode on the first tank side is applied to a secondary electrode disposed in the first tank at intervals from the surfaces of the porous electrode and the first tank side of the lithium-ion conductive electrolyte membrane. [Invention Effects]

[0011] The lithium isotope concentration apparatus and method according to the present invention can efficiently, safely, and with good productivity recover lithium isotopes. 6 Li isotope ratios are higher in aqueous solutions. Furthermore, the multi-stage lithium isotope concentration apparatus according to the present invention can further improve… 6 Isotope ratio of Li. Attached Figure Description

[0012] Figure 1 This is a schematic diagram illustrating the structure of the lithium isotope concentration apparatus according to the first embodiment of the present invention. Figure 2 This is a timing diagram illustrating the shift of the applied voltage of the power supply device of the lithium isotope enrichment apparatus according to the first embodiment of the present invention. Figure 3 This is a schematic diagram illustrating another structure of the lithium isotope concentration apparatus according to the first embodiment of the present invention. Figure 4 This describes the electrodialysis of lithium ions. Figure 1 A schematic diagram of a lithium isotope concentration device is shown. Figure 5A This is an explanation Figure 1 A magnified view of the main part of the movement of lithium ions in the initial state during the electrodialysis of lithium ions in the lithium isotope concentration apparatus shown. Figure 5B This is an explanation Figure 1 A magnified view of the main part of the movement of lithium ions after the initial movement has just begun during the electrodialysis of lithium ions in the lithium isotope concentration apparatus shown. Figure 5C This is an explanation Figure 1 A magnified view of the main part of the movement of lithium ions during the electrodialysis process of lithium ions in the lithium isotope concentration apparatus shown. Figure 5D This is to explain the passage. Figure 1 Enlarged view of the main part of the movement of lithium ions after their movement has stopped during electrodialysis of lithium ions in the lithium isotope concentration apparatus shown. Figure 6 It is a model that illustrates ion conduction in electrolytes. Figure 7 It is a graph illustrating the dependence of applied voltage on the amount of lithium ions moving per unit time and the isotope ratio in the electrodialysis obtained through simulation. Figure 8 This is a schematic diagram illustrating the structure of a lithium isotope concentration apparatus according to a modified example of the first embodiment of the present invention. Figure 9 This is a timing diagram illustrating the shift of the applied voltage of the power supply device of the lithium isotope enrichment apparatus according to a modified example of the first embodiment of the present invention. Figure 10 This is a schematic diagram illustrating the structure of the multi-stage lithium isotope concentration apparatus according to the first embodiment of the present invention. Figure 11A This is a schematic diagram illustrating a lithium isotope concentration method performed using a multi-stage lithium isotope concentration apparatus according to a modified embodiment of the first embodiment of the present invention. Figure 11BThis is a schematic diagram illustrating a lithium isotope concentration method performed using a multi-stage lithium isotope concentration apparatus according to a modified embodiment of the first embodiment of the present invention. Figure 12 This is a schematic diagram illustrating the structure of the multi-stage lithium isotope concentration apparatus according to the second embodiment of the present invention. Figure 13A This is to explain the passage. Figure 12 A schematic diagram of a lithium isotope concentration method performed in a multi-stage lithium isotope concentration apparatus. Figure 13B This is to explain the passage. Figure 12 A schematic diagram of a lithium isotope concentration method performed in a multi-stage lithium isotope concentration apparatus. Figure 13C This is to explain the passage. Figure 12 A schematic diagram of a lithium isotope concentration method performed in a multi-stage lithium isotope concentration apparatus. Figure 14 This is a schematic diagram illustrating the structure of the lithium isotope concentration apparatus according to the second embodiment of the present invention. Figure 15 This describes the electrodialysis of lithium ions in the lithium isotope concentration method. Figure 14 A schematic diagram of a lithium isotope concentration device is shown. Figure 16 This is a schematic diagram illustrating the structure of a lithium isotope concentration apparatus according to a first variation of the second embodiment of the present invention. Figure 17 This describes the electrodialysis of lithium ions in the lithium isotope concentration method. Figure 16 A schematic diagram of a lithium isotope concentration device is shown. Figure 18 This is a schematic diagram illustrating the structure of a lithium isotope concentration apparatus according to a second variation of the second embodiment of the present invention. Figure 19 This describes the electrodialysis of lithium ions in the lithium isotope concentration method. Figure 18 A schematic diagram of a lithium isotope concentration device is shown. Figure 20 It is a graph showing the amount of lithium ion movement and the lithium isotope separation coefficient involved in the examples and comparative examples. Detailed Implementation

[0013] Referring to the accompanying drawings, the methods for implementing the lithium isotope enrichment apparatus and method according to the present invention will be described. In the drawings, for clarity, the size of certain elements is sometimes exaggerated, or the shape is sometimes simplified. Furthermore, in the description of each embodiment, the same reference numerals are used for structural elements identical to those in the preceding embodiments, and descriptions are appropriately omitted.

[0014] [First Embodiment] (Lithium isotope concentration unit) like Figure 1 As shown, the lithium isotope concentration apparatus 10 according to the first embodiment of the present invention includes: a processing tank 1; an electrolyte membrane (lithium-ion conductive electrolyte membrane) 2 dividing the processing tank 1 into two; a first electrode 31 and a second electrode 32 (porous electrode) covering each surface of the electrolyte membrane 2; a third electrode (sub-electrode) 33; a power supply device 5; a stirrer (circulation mechanism) 6; and a cooling device 7. The processing tank 1 is divided by the electrolyte membrane 2 into a supply tank (first tank) 11 and a recovery tank (second tank) 12, wherein the supply tank (first tank) 11 contains an aqueous solution of Li (ASi), and the recovery tank (second tank) 12 contains... 6 The Li-containing aqueous solution ASi is used for Li recovery. The third electrode 33 is disposed in the supply tank 11 separately from the electrolyte membrane 2. The power supply device 5 includes a main power supply 51 and an auxiliary power supply 52, both DC power supplies, and a switching element 5s1. The main power supply 51 and auxiliary power supply 52 are alternately applied voltage by switching the switching element 5s1. The positive (+) terminal of the main power supply 51 is connected to the first electrode 31 disposed on the side of the supply tank 11, and the negative (-) terminal of the main power supply 51 is connected to the second electrode 32 disposed on the side of the recovery tank 12. The positive terminal of the auxiliary power supply 52 is connected to the first electrode 31, and the negative terminal of the auxiliary power supply 52 is connected to the third electrode 33. A stirrer 6 circulates the Li-containing aqueous solution ASi in the supply tank 11. A cooling device 7 cools the solution within the recovery tank 12. 6 The lithium isotope concentration apparatus according to the first embodiment of the present invention will be described below. The aqueous solution ASo is used to cool the electrolyte membrane 2 for Li recovery.

[0015] Treatment tank 1 consists of a Li-containing aqueous solution containing ASi and 6 The material used for Li recycling is made of a material that will not corrode or deteriorate upon contact with the aqueous solution ASo. Furthermore, the treatment tank 1 only needs to have a volume corresponding to the required processing capacity; its shape and other characteristics are not particularly limited.

[0016] Electrolyte membrane 2 is an electrolyte with lithium-ion conductivity, preferably without electron conductivity. - Furthermore, in the Li-containing aqueous solution ASi, Li is present. + In the case of metal ions other than those present, it is preferable that the electrolyte membrane 2 does not conduct these metal ions. More preferably, a ceramic electrolyte possessing these properties is preferred. Specifically, lithium lanthanum titanium oxide (La) can be cited as an example. 2 / 3-x Li 3x TiO3 (also known as LLTO), etc. Such an electrolyte membrane 2 has lattice defects at a certain ratio. Because the size of these lattice defect sites is small, it does not conduct electricity with a diameter greater than that of Li.+ Large metal ions. For example, in solid electrolytes like LLTO with a perovskite (ABO3) structure (A = Li, La or vacancy, B = Ti), a portion of the A sites have vacancies (A-site defects). Furthermore, as explained later in the section on lithium isotope enrichment methods, Li... + Infiltrating the A-position defect, Li + The defects at nearby A sites move between each other. Hereinafter, the sites that may contain Li, like the A site, will be called Li sites, and the Li sites with vacancies will be called Li site defects.

[0017] The first electrode 31 and the second electrode 32 are a pair of electrodes for applying a voltage between the two sides of the electrolyte membrane 2, and are respectively configured such that the first electrode 31 contacts the surface (hereinafter appropriately referred to as the surface) on the side of the supply tank 11 of the electrolyte membrane 2, and the second electrode 32 contacts the surface (hereinafter appropriately referred to as the back side) on the side of the recovery tank 12 of the electrolyte membrane 2. The first electrode 31 and the second electrode 32 have a porous structure such as a mesh to apply a voltage over a wide range of the electrolyte membrane 2, while the aqueous solutions ASi and ASo contact each surface of the electrolyte membrane 2 with a sufficiently large area.

[0018] The first electrode 31 is formed of an electrode material that is electronically conductive and stable when a voltage is applied in a Li-containing aqueous solution ASi, and is further preferably a material that is catalytically active relative to the reactions of formula (1) and formula (2). The second electrode 32 is formed of an electrode material that is electronically conductive and becomes Li-containing in the reaction. + of 6 The electrode material is formed to be stable when a voltage is applied in the aqueous solution ASo for Li recovery, and is further preferably a material that has catalytic activity relative to the reactions of the following formula (3) and the following formula (4). The first electrode 31 and the second electrode 32 are also preferably materials that are easy to process into the aforementioned shape. Platinum (Pt) is preferably used as such electrode material for the first electrode 31 and the second electrode 32, for example. Furthermore, in each formula, Li contained in the electrolyte membrane 2 is... + Represented as Li + (electrolyte). The following formula (2) represents the Li in the aqueous solution (containing Li aqueous solution ASi). + The reaction that moves to electrolyte membrane 2. Equation (4) below represents the reaction of Li in electrolyte membrane 2. + To aqueous solution ( 6 Li recovery uses aqueous solution (ASo) to move the reaction. [Chemical Formula 1] Li + →Li +(electrolyte)···(2) 2H2O+2e - →2OH-+H2↑···(3) Li + (electrolyte)→Li + ···(4)

[0019] The third electrode 33 is an electrode used to form a potential lower than the surface of the electrolyte membrane 2 in the Li-containing aqueous solution ASi. Therefore, the third electrode 33 is disposed in the supply tank 11 in a manner that does not contact the electrolyte membrane 2 and the first electrode 31, preferably disposed parallel to the first electrode 31. Furthermore, in order to suppress the voltage V2 applied between the third electrode 33 and the first electrode 31 to a small extent, as described later, the third electrode 33 is preferably disposed close to the first electrode 31 to the extent that it does not short-circuit. In addition, the third electrode 33 is preferably in a mesh or similar shape through which the aqueous solution can pass, thereby increasing the contact area between the third electrode 33 and the Li-containing aqueous solution ASi, and enabling continuous replacement of the Li-containing aqueous solution ASi in contact with the surface of the electrolyte membrane 2 (the first electrode 31) within the supply tank 11. Like the first electrode 31, the third electrode 33 is formed of an electrode material that is stable when a voltage is applied in the Li-containing aqueous solution ASi, and preferably a material that is easily processed into the aforementioned shape. Platinum (Pt) is preferably preferred for the third electrode 33, for example, but carbon (C) can also be used as such an electrode material.

[0020] The power supply unit 5 has two DC power supplies 51 and 52, as well as a switching element 5s1 and its drive circuit, etc., which alternately apply DC voltages from power supplies 51 and 52. The positive terminal of the main power supply 51 is connected to the first electrode 31, and the negative terminal of the main power supply 51 is connected to the second electrode 32. A positive voltage V1 (voltage + V1) is applied to the first electrode 31 relative to the second electrode 32. The positive terminal of the auxiliary power supply 52 is connected to the first electrode 31, and the negative terminal of the auxiliary power supply 52 is connected to the third electrode 33, as shown below. Figure 2 As shown, when the main power supply 51 is not supplied with voltage +V1, a negative voltage V2 (voltage -V2) is applied to the third electrode 33 relative to the first electrode 31. Therefore, the switching element 5s1 is configured to connect the first electrode 31 to either the positive terminal of the main power supply 51 or the positive terminal of the auxiliary power supply 52, or not to either. In other words, the power supply device 5 has two DC pulse power supplies that are synchronized with each other. Power supplies 51 and 52 preferably incorporate capacitors or the like to improve time responsiveness, so as to ideally output... Figure 2 The rectangular wave is shown. Furthermore, details regarding the magnitudes and application times of voltages V1 and V2 are described later, but it is preferred that voltage V2 be smaller than voltage V1.

[0021] Thus, the power supply device 5 only needs to be able to alternately apply voltages V1 and V2 of specified polarity and magnitude to the area between the first electrode 31 and the second electrode 32, and between the third electrode 33 and the first electrode 31, respectively. Figure 1 The circuit structure shown is an example. For example, as... Figure 3 As shown, it can also be a power supply device 5A having a variable power supply 51A and a switching element 5s1, wherein the variable power supply 51A can be switched to voltage levels V1 and V2, and the switching element 5s1 can switch the connection target of its negative terminal. Alternatively, the following structure (not shown) can be adopted: two DC power supplies are connected in series via the switching element, and voltage V1 is applied by the two power supplies respectively, and voltage V2 is applied by the one power supply. In addition, in Figure 1 and Figure 3 In the lithium isotope enrichment device 10 shown, when the power supply devices 5 and 5A apply a voltage V1 between the first electrode 31 and the second electrode 32, the third electrode 33 is in an open circuit state (see reference). Figure 4 When power supply devices 5 and 5A apply a voltage V2 between the third electrode 33 and the first electrode 31, the second electrode 32 is in an open-circuit state. Alternatively, it can be configured such that when power supply devices 5 and 5A apply a voltage +V1 between the first electrode 31 and the second electrode 32, the third electrode 33 is connected to the first electrode 31 at the same potential. Furthermore, it can be configured such that when a voltage -V2 is applied between the third electrode 33 and the first electrode 31, the second electrode 32 is connected to the first electrode 31 at the same potential.

[0022] A stirrer 6 is provided as needed. This stirrer 6 is a device that circulates the Li-containing aqueous solution ASi in the supply tank 11 by continuously replacing the Li-containing aqueous solution ASi in contact with the first electrode 31 during operation. The stirrer 6 can utilize known devices, such as rotating a screw, or using a pump to circulate the Li-containing aqueous solution ASi outside the processing tank 1. The lithium isotope concentration device 10 may also have a stirrer 6 in the recovery tank 12. 6 Li is recovered using an aqueous solution, ASo, in a recycling process.

[0023] A cooling device 7 is provided as needed to bring the electrolyte membrane 2 to a specified temperature. The cooling device 7 uses a Li-containing aqueous solution ASi or... 6 The electrolyte membrane 2 is cooled using an aqueous solution ASo for Li recovery. The cooling device 7 can be a known device for cooling liquids, preferably with temperature control functionality. In this embodiment, the cooling device 7 is an immersion type, with the refrigerant pipe (refrigerant pipe) immersed in the recovery tank 12. 6 The Li recovery system is set up using an aqueous solution ASo. The cooling device 7 only needs to maintain the electrolyte membrane 2 at a specified temperature; it is not necessary to use the Li-containing aqueous solution ASi. 6The aqueous solution ASi used for Li recovery is at a uniform liquid temperature. However, a stirrer may also be included depending on the volume of the processing tank 1. Similar to the processing tank 1, the refrigerant pipe of the cooling device 7 is connected to the Li-containing aqueous solution ASi. 6 The material used for Li recovery, ASi, is made of a material that will not corrode or deteriorate upon contact with the aqueous solution, and its shape is not particularly specified. For example, to efficiently cool the electrolyte membrane 2, the refrigerant tube is bent in a planar shape to correspond to the size of the plate-shaped electrolyte membrane 2, and is located near the larger area of ​​the electrolyte membrane 2 and arranged in an opposing manner. Alternatively, the refrigerant tube can be inserted into both the supply tank 11 and the recovery tank 12, depending on the thickness of the electrolyte membrane 2. Furthermore, the cooling device 7 can also be configured such that the processing tank 1 has a double-layer structure (casing) with refrigerant flowing inside (the casing). Alternatively, it can be configured to use a pump to circulate the Li-containing aqueous solution ASi or... 6 The aqueous solution ASo for Li recovery is circulated to the outside of treatment tank 1 and cooled by a heat exchanger.

[0024] The temperature of electrolyte membrane 2 will be described in detail later, ensuring it is below 30°C, for example, at... 6 The aqueous solution ASo for Li recovery is kept above 0°C at the start of operation (electrodialysis start) of the lithium isotope concentration unit 10, assuming it is pure water, to prevent the aqueous solutions ASi and ASo from freezing. This allows for measurement of the Li-containing aqueous solution ASi or... 6 The temperature of the aqueous solution ASo used for Li recovery is replaced by the temperature of the electrolyte membrane 2.

[0025] ASi, containing Li in an aqueous solution, is a Li source. 7 Li and 6 Li cations 7 Li + , 6 Li + An aqueous solution, such as a lithium hydroxide (LiOH) aqueous solution, is used at the start of operation of the lithium isotope concentration unit 10, containing at a natural abundance ratio. 7 Li + , 6 Li + Additionally, Li containing an aqueous solution of Li (ASi) is preferred. + The concentration is relatively high, and it is further preferred that the Li-containing aqueous solution ASi is Li at the start of operation of the lithium isotope concentration unit 10. + Saturated or supersaturated aqueous solutions. 6 Li recovery aqueous solution ASo is used to contain large quantities of lithium ions (Li) recovered from Li-containing aqueous solutions ASi. + ,especially 6 Li +The aqueous solution, for example, is pure water, at the start of operation of the lithium isotope concentration unit 10. Furthermore, in this specification, in... 7 Li and 6 Li ( 7 Li + and 6 Li + In the absence of distinction between them, they are collectively referred to as Li (Li + ).

[0026] The lithium isotope concentration device 10 may also include a liquid level sensor to detect the presence of Li-containing aqueous solutions (ASi) during operation. 6 Variations in the amount of the aqueous solution ASi and ASi used for Li recovery. Furthermore, to prevent accidental dissolution of atmospheric carbon dioxide (CO2) in the aqueous solutions ASi and ASi, resulting in the precipitation of lithium carbonate (Li2CO3), the lithium isotope concentration device 10 is preferably used to prevent the precipitation of Li-containing aqueous solutions ASi and ASi. 6 The lithium isotope recovery device 10 is configured such that the aqueous solution ASo is exposed to the atmosphere. In addition, from a safety point of view, it is preferable that the lithium isotope concentration device 10 has an exhaust mechanism for discharging the H2 and O2 generated during operation (generated by the reactions of formulas (1) and (3)) so that it does not fill the interior.

[0027] (Lithium isotope concentration method) The lithium isotope enrichment method according to the embodiments of the present invention is performed alternately: a first step, applying a positive voltage V1 relative to a second electrode 32 disposed on the back side to a first electrode 31 disposed on the surface of the electrolyte membrane 2; and a second step, applying a negative voltage V2 relative to the first electrode 31 to a third electrode 33. First, referring to... Figure 4 The electrodialysis of lithium ions performed using the lithium isotope concentration apparatus according to the first embodiment will be described. Furthermore, in Figure 4 The lithium isotope concentration device 10 shown omits the stirrer 6 and the cooling device 7.

[0028] like Figure 4 As shown, in the lithium isotope concentration apparatus 10, the main power supply 51 of the power supply unit 5 applies a positive voltage V1 (voltage + V1) to the first electrode 31 relative to the second electrode 32. Therefore, near the first electrode 31, hydroxide ions (OH-) from the Li aqueous solution ASi are concentrated. - The reaction of equation (1) occurs, causing electrons e to... - It is released to the first electrode 31, thereby producing water (H2O) and oxygen (O2). In the Li-containing aqueous solution ASi, as OH... - To reduce the charge and maintain charge balance, Li in the Li-containing aqueous solution ASi is reduced near electrolyte membrane 2. +The reaction of equation (2) moves into electrolyte membrane 2. Combining the reactions of equation (1) and (2), the reaction of equation (5) occurs near the first electrode 31. On the other hand, near the second electrode 32, through... 6 The H2O in the aqueous solution of Li recovery ASO is supplied with electrons (e.g., phospholipids). - The reaction shown in equation (3) occurs, thereby producing hydrogen (H2) and OH. - .exist 6 Li is recovered in an aqueous solution of ASO, along with OH... - To maintain charge balance, an increase in Li in electrolyte membrane 2 occurs near electrolyte membrane 2. + The reaction of the following equation (4) is moved over. If the reactions of the following equation (3) and the following equation (4) are combined, the reaction of the following equation (6) occurs near the second electrode 32. [Chemical Formula 2] Li + →Li + (electrolyte)···(2) 2H2O+2e - →2OH - +H2↑···(3) Li + (electrolyte)→Li + ···(4) 2Li + (electrolyte) + 2H₂O + 2e - →2OH-+H2↑+2Li + ···(6)

[0029] When these reactions occur, using an aqueous Li-containing solution ASi, an electrolyte membrane 2, and... 6 The Li recovered by aqueous solution ASo contains Li. + The electrochemical potential difference makes Li + From the Li-containing aqueous solution ASi, through the electrolyte membrane 2, to... 6 The Li-containing aqueous solution ASi moves to the first electrode 31 along with the electrons. - The amount of movement per unit time, from the second electrode 32 to 6 Li recovers electrons from aqueous solution ASO. - The greater the amount of movement per unit time, the faster these reactions occur. Therefore, the larger the voltage V1, the more Li moves from the first electrode 31 side to the second electrode 32 side in the electrolyte membrane 2.+ The more electrons per unit time (mobility), the greater the mobility. However, in reality, when the voltage V1 increases to a certain extent, the electrolyte membrane 2 also conducts electrons e. - Therefore, although Li + The mobility continues to increase, but the voltage dependence decreases. Here, refer to... Figures 5A-5C Detailed explanation of Li + Actions during passage through the electrolyte membrane 2. Figures 5A-5C This is an enlarged cross-sectional view of the vicinity of the electrolyte membrane 2 in the lithium isotope concentration device 10, showing that electrodes 31 and 32 are in partial contact with both sides of the electrolyte membrane 2. Additionally, in the aqueous solutions ASi and ASo, only those containing... 7 Li + , 6 Li + Use ○ to circle each one.

[0030] When no voltage is applied, such as Figure 5A As shown, 7 Li + , 6 Li + The sample is floated in a Li-containing aqueous solution ASi, and the adsorption onto and detachment from the surface of electrolyte membrane 2 are repeatedly performed. Starting from this state, as... Figure 5B As shown, a positive voltage V1 is applied to the first electrode 31, and a negative voltage V1 (voltage + V1) is applied to the second electrode 32. Furthermore, in the figure, positive charges are represented by + in circles, and negative charges are represented by - in circles. Thus, Li in the Li-containing aqueous solution ASi... + ( 7 Li + , 6 Li + The reaction described in equation (2) is intended to dissolve in the electrolyte membrane 2. At this time, Li adsorbed near the Li site defects on the surface of the electrolyte membrane 2... + The Li site defect is penetrated. Then, due to the electrodes 31 and 32, the electrolyte membrane 2 has a potential gradient on the back side that is lower than that on the surface, allowing the Li to penetrate the Li site defect on the surface. + The Li site defect near the deeper side of electrolyte membrane 2 jumps (jumps). Thus, Li... + Repeatedly moving from the Li site defect in electrolyte membrane 2 to the nearby Li site defect, ultimately as the reaction described in equation (4), such as Figure 5C As shown, the Li site defect on the back side moves to 6 Li is recovered in an aqueous solution of ASO.

[0031] Additionally, on the surface of electrolyte membrane 2, Li adsorbed near Li site defects +It moves deeper into the electrolyte membrane 2, thereby adsorbing another Li in its vicinity. + It moves over and dives into vacated Li site defects, or adsorbs new Li from Li-containing aqueous solutions (ASi). + And these Li + Similarly, it moves within electrolyte membrane 2. Furthermore, through Li... + Moving within electrolyte membrane 2, the Li site defects are affected by Li... + Whether it is filled in or vacated again, the newly generated Li site defects on the surface of electrolyte membrane 2 enable the adsorbed Li on the surface to be filled in or vacated again. + It begins to move towards the back side.

[0032] Reference Figure 6 To further explain Li in detail + Interpositional movement (jumping) within electrolyte membrane 2. Figure 6 This is a model illustrating ion conduction in an electrolyte, where x represents the position along the thickness direction of electrolyte membrane 2, and E... p This represents potential energy. In electrolyte membrane 2, Li... + ( 7 Li + , 6 Li + The Li site exists stably with minimal potential energy, but nearby Li sites are vacant (represented by dashed ○). When subjected to activation energy E... a At the above energy level, it is possible to overcome the energy barrier E between (jump) positions. m And move to that position defect (E) a =E D / 2+E m E D (Defect generation energy). Furthermore, it can be assumed that the ion undergoes thermal vibration at a frequency Γ0 at a location with minimal potential energy, thus enabling it to jump at a frequency (jump rate Γ) corresponding to that frequency (frequency factor) Γ0. The frequency Γ0 is inversely proportional to the square root of the ion's mass. 6 Li has a relatively small mass, and is 7 Li is 6 / 7 times, therefore the frequency Γ0 is 7 Li is (√(7 / 6)) times, as detailed below. The average moving velocity in electrolyte membrane 2 is 7 The speed of Li is (√(7 / 6)) times higher. Furthermore, for example, at a certain Li site defect relative to electrolyte membrane 2, two equidistant locations nearby exist respectively. 7 Li + and 6 Li + In this case, it is speculated that 6 Li + Redirect here first.

[0033] In addition, the Li sites in electrolyte membrane 2, i.e., in the ground state... 7 Li + , 6 Li + The potential energy rises to zero point oscillation hω I The quantity. Zero-point vibration hω I Dependent on isotopes, 6 Li + Compare 7 Li + Large. Similarly, in the excited state, 6 Li + Zero-point vibration hω S It is also larger. Therefore, its mass is greater than that of other substances. 7 Li + small 6 Li + In the ground state and excited state, considering the zero-point vibration hω I hω S Their potential energy is high. However, 6 Li + E is the energy barrier representing the potential difference between the excited state and the ground state. m Smaller (E) m ( 7 Li + )>E m ( 6 Li + )), that is, activation energy E a Smaller. As a result, 6 Li + Even if the energy received is higher 7 Li + Even small animals can jump. Li + The energy received relative to the activation energy E a The more residual electrolyte, the higher the mobility μ. Therefore, the greater the applied voltage V1 between the two sides of the electrolyte membrane 2, the higher the Li... + The amount of movement per unit of time increases.

[0034] in addition, 6 Li + By 7 Li + A small voltage V1 achieves the same relative activation energy E a The remaining energy, and at this time, 6 Li + The mobility μ is higher than the frequency Γ0 by a certain amount. Figure 7 The figure shows the simulation per unit time. 6 Li + , 7 Li +Quantity of movement and moving Li + The voltage dependence of the isotope ratio is applied. In the simulation, the activation energy E according to the Maxwell-Boltzmann distribution is represented by a normal distribution. a The distribution was approximated. Specifically, for each... 6 Li + , 7 Li + According to the activation energy E a The probability density of a normal distribution with average value is calculated based on the energy received each time, exceeding the activation energy E. a (set up 6 Li + < 7 Li + ) of Li + The ratio of isotopes is calculated, and its cumulative value is multiplied by the frequency Γ0 ratio to determine the relative value of mobility μ. 7 Li + and 6 Li + The abundance ratio was calculated by setting it to 1:1 in order to simplify the simulation.

[0035] like Figure 7 As shown, 6 Li + , 7 Li + The mobility increases from 0 in an S-shaped curve as the applied voltage increases, relative to... 7 Li + Activation energy E a small 6 Li + The voltage shifts towards the lower side, and the change is also higher than the frequency Γ0 ratio. Furthermore, Figure 7 limμ represents the value per unit time. 6 Li + The limit of the amount of movement. Therefore, applying voltage in order to make 6 Li + The smaller the range of movement within electrolyte membrane 2, the better. 6 Li + Compared to 7 Li + The more it moves. And, when the applied voltage increases... 6 Li + , 7 Li + When the mobility of each element converges, the difference between them decreases, and the isotope ratio converges to (√(7 / 6)) / (1+√(7 / 6)).

[0036] However, it is actually believed that when the voltage V1 is increased, 6 Li+ , 7 Li + The migration rate reaches Figure 7 Before reaching the limit shown, the voltage dependence decreases significantly. Specifically, as described above, when the voltage V1 applied between the two sides of the electrolyte membrane 2 increases to a certain value, a portion of the transition metal ions constituting the electrolyte membrane 2 are reduced (e.g., if the electrolyte membrane 2 is LLTO, then Ti...). 4+ +e - →Ti 3+ Electrolyte membrane 2 conducts electrons e from the recovery tank 12 side to the supply tank 11 side. - As a result, most of the electrical energy provided is consumed by electrons. - The conduction consumption, therefore Li + The voltage dependence of Li mobility decreases. + The energy efficiency during movement decreases. Furthermore, due to the reduction of some of the transition metal ions constituting electrolyte membrane 2, the ionic radius of the reduced ions increases (e.g., if electrolyte membrane 2 is LLTO, then Ti...). 4+ <Ti 3+ ), used for Li + The bottleneck of movement widens, thus making the movement of Li... + of 6 The lithium isotope ratio decreases sharply. Additionally, due to the electrons (e) conducted in electrolyte membrane 2... - The resulting Joule heating causes the temperature of electrolyte membrane 2 to rise, therefore, as described later, the moving Li + of 6 The lithium isotope ratio decreases.

[0037] Furthermore, the ion mobility μ is the relationship between the ion diffusion coefficient D and the following equation (7) (T: temperature (K), k: Boltzmann constant). The diffusion coefficient D, as shown in the following equation (8), is proportional to the hopping rate Γ (a: average distance between sites (hopping length), n...). c : carrier density, f: correlation coefficient determined by the ion and its surroundings, d: diffusion field size). Furthermore, the frequency factor Γ0 of equation (8) is proportional to temperature T, as shown in equation (9). Additionally, (Z s vib / Z I vib The frequency factor Γ0 is inversely proportional to the square root of the mass number m, therefore it is also inversely proportional to the square root of the mass number m (h: Planck's constant, Z). s vib Phonon allocation function of saddle point, Z I vib: Phonon distribution function in the initial state, C1: constant). According to equations (8) and (9), the diffusion coefficient D is represented by equation (10). Moreover, according to equations (7) and (10), the ion mobility μ is represented by equation (11) (C2: constant). As shown in equation (11), the mass number m and activation energy E a smaller 6 Li + ion mobility μ ratio 7 Li + high. [Mathematical Expression 1] kTμ=D···(7)

[0038] exist Figure 5B The image shows Li adsorbed on the surface of electrolyte membrane 2 after the initial application of voltage. + of 7 Li + and 6 Li has the property of reacting with Li in Li-containing aqueous solution ASi. + Equal isotope ratios. However, due to 7 Li + and 6 The difference in movement speed between Li 6 Li + The migration rate of Li site defects to electrolyte membrane 2 is greater than that of Li-containing aqueous solution ASi. 6 Li isotope ratio ( 6 Li / ( 7 Li+ 6 Li moves more. Furthermore, the movement between Li site defects in electrolyte membrane 2, and towards... 6 The movement of Li in the aqueous solution ASO during Li recovery is also... 6 Li + Faster. As a result, Li adsorbed on the surface of electrolyte membrane 2 + middle 6 Li + Reduced even more. Then, the new 7 Li + , 6 Li + The Li is adsorbed from the Li-containing aqueous solution ASi at vacated sites on the surface according to its isotopic ratio. By repeatedly performing this process, the Li remaining in the Li-containing aqueous solution ASi... + of 6 Li isotope ratio ( 6Li / ( 7 Li+ 6 Li gradually decreases, therefore, the newly moved Li + of 6 The lithium isotope ratio decreases. Specifically, the moving lithium... + of 6 The Li isotope ratio is at its maximum immediately after the application of voltage +V1, and thereafter decreases exponentially with the passage of time (see Patent Document 4).

[0039] Therefore, the lithium isotope enrichment method described in this embodiment repeatedly recovers small amounts of lithium isotopes by applying a voltage +V1 (step 1) for short periods of time. 6 Li with a high isotopic ratio. At the point in time immediately before the applied voltage stops, when the movement of Li reaches a certain extent due to the application of voltage +V1, as described above, it is assumed that the Li adsorbed on the surface of electrolyte membrane 2... + of 6 Li + It preferentially moves into electrolyte membrane 2, therefore at that time point, 6 The Li isotope ratio is lower than that of Li remaining in Li-containing aqueous solution ASi. + (Refer to Figure 5C Therefore, before the next application of voltage +V1, the adsorbed on the surface of electrolyte membrane 2 is... 7 Li + and 6 Li + Temporarily disconnected. When the applied voltage +V1 is stopped and the system is in a state of no application, Li... + The movement within electrolyte membrane 2 ceases, and the Li-containing aqueous solution ASi is neutralized. 6 Li is recovered from the aqueous solution ASo. + They are floated in aqueous solutions ASi and ASo, respectively, thereby repeatedly adsorbing onto and detaching from the surface and back of electrolyte membrane 2 (refer to...). Figure 5A However, in the Li-containing aqueous solution ASi, the Li adsorbed on the surface of electrolyte membrane 2 + Previously, the applied voltage +V1 was electroattracted to the deep side (back side) of the electrolyte membrane 2, so even if the applied voltage +V1 is stopped, Li + It will not immediately detach from the surface of electrolyte membrane 2.

[0040] Therefore, in the lithium isotope concentration method of this embodiment, when the applied voltage +V1 is stopped, a voltage V2 (voltage -V2) that is negative relative to the first electrode 31 is applied to the third electrode 33 via the auxiliary power supply 52 (step 2). By applying voltage -V2, a potential gradient is generated in the Li-containing aqueous solution ASi, with the area near the surface of the electrolyte membrane 2 being positive and the area near the third electrode 33 being negative. Therefore, as Figure 5D As shown, Li adsorbed on the surface of electrolyte membrane 2 + They quickly detach due to electrostatic repulsion.

[0041] Because applying voltage -V2 can make Li... + It detaches from the surface of electrolyte membrane 2, therefore, when the applied voltage -V2 is stopped and the applied voltage +V1 is resumed by the main power supply 51, as... Figure 5B As shown, there is a new Li + The Li is adsorbed onto the surface of electrolyte membrane 2. + Having Li in the aqueous solution ASi at this time + The isotopic ratios are identical. Therefore, the 6Li isotopic ratio becomes higher than it was immediately before the last applied voltage +V1 was stopped (see reference). Figure 5C Li adsorbed on the surface of electrolyte membrane 2 + As a result, even when a voltage of +V1 was applied for a short period of time, it was able to recover [the energy / resources]. 6 Li has a high isotope ratio. Thus, by alternately applying a voltage +V1 (step 1) between the two surfaces of the electrolyte membrane 2 (between the first electrode 31 and the second electrode 32) and a voltage -V2 (step 2) between the third electrode 33 and the first electrode 31 for a short period of time, a larger amount of Li can be recovered compared to the case of continuously applying voltage +V1. 6 Li has a high isotope ratio.

[0042] As mentioned above, the larger the voltage V1, the more Li + The higher the mobility, the more Li per unit time + The amount of movement increases. However, when the voltage V1 increases above a certain value, the electrolyte membrane 2 exhibits electronic conductivity, resulting in the inability to improve the Li... + The energy efficiency of mobility decreases, and in addition, the moving Li + of 6 The lithium isotope ratio decreases sharply. On the other hand, the smaller the voltage V1, the lower the lithium isotope ratio. 6 Li + Compared to 7 Li +The higher the mobility, the greater the isotope separation coefficient. Therefore, the voltage V1 is preferably a voltage that prevents the electrolyte membrane 2 from exhibiting electronic conductivity, and more preferably a smaller voltage. However, since a smaller voltage V1 results in lower Li... + The lower the mobility, the better; therefore, it is preferable to set it to a level that does not excessively reduce productivity. Specifically, it depends on the electronic conductivity of the electrolyte membrane 2, the electrode performance that determines the electrode reaction overvoltage, etc., but if a voltage exceeding 2.0V is applied, electronic conductivity can be exhibited in the electrolyte membrane 2. On the other hand, the lower limit of the voltage V1 is not particularly limited, as long as it can make Li... + Movement within electrolyte membrane 2 is possible; although this lower limit depends on the electronic conductivity of electrolyte membrane 2, the hydrogen ion concentration of the aqueous solution ASi and ASo, etc., it is preferably set within a range of 0.5V or higher. Preferably, it is determined according to the desired... 6 The effect of Li concentration, compared to the duration of a single continuous application (during electrodialysis) t ED The voltage V1 is set by combining the following methods.

[0043] Furthermore, the larger the voltage V2, the greater the electric field applied to the Li-containing aqueous solution ASi between the surface of the electrolyte membrane 2 and the third electrode 33, thus increasing the Li... + Li is attracted at high speed to the third electrode 33, and thus adsorbed onto the surface of the electrolyte membrane 2. + It can disengage in a shorter time. On the other hand, when the voltage V2, i.e., the potential difference between the first electrode 31 and the third electrode 33, becomes a certain value or higher, the electrolysis reaction of H2O occurs in the Li-containing aqueous solution ASi (reactions of formulas (1) and (3)), and the energy efficiency decreases. Therefore, the voltage V2 is preferably set to a value that prevents the electrolysis reaction of H2O from occurring, and the voltage V2 is a large value but smaller than the voltage V1. The third electrode 33 is preferably configured to be shortly spaced from the first electrode 31 so that the electric field between the surface of the electrolyte membrane 2 and the third electrode 33 increases relative to the voltage V2 mentioned above.

[0044] The duration of a single continuous application of voltage +V1 (during electrodialysis) t ED and the continuous application time of voltage V2 (during reset) t RST Unless otherwise specified, it is preferred to set them separately to make 6 The recovery efficiency of Li is sufficiently high. During electrodialysis, t ED The shorter the length, the more Li is recovered. 6 The higher the Li isotope ratio, specifically, preferably less than 1 second, and more preferably around 0.5 seconds. During the reset period t RST In the process, the Li adsorbed on the surface of electrolyte membrane 2 is caused by the previously applied voltage +V1. + Full separation, preferably complete separation, is sufficient, even if the period is further prolonged. 6The recovery efficiency of Li will not improve during electrodialysis. ED Relative to period t CYC The ratio decreases, thus reducing time efficiency (productivity). The larger the voltage V2, and the shorter the interval between the third electrode 33 and the first electrode 31, the longer the reset period t... RST The faster the results are achieved, the better.

[0045] Furthermore, it is preferable not to apply voltage +V1 and voltage -V2 simultaneously. This is because by applying voltage -V2, Li... + The concentration of electrolyte membrane 2 near the surface in the Li-containing aqueous solution ASi is relatively low. Therefore, if a voltage -V2 is applied when a voltage +V1 is applied, then Li + From Li-containing aqueous solution ASi to 6 The movement of ASO in the aqueous solution for Li recovery is hindered, thereby reducing energy efficiency. In particular, it is preferable to apply the moving Li at the very beginning. + of 6 After the voltage +V1, which represents the highest Li isotope ratio, no voltage -V2 is applied. Alternatively, there could be a period t during which neither +V1 nor -V2 is applied. int1 t int2 However, if there is no application period t int1 t int2 If the duration is too long, productivity will decrease. Therefore, it is preferable to stop applying voltage +V1 (t during electrodialysis). ED After that, voltage -V2 is applied (during reset t). RST )(t int1 ≥0), more preferably, after stopping the application of voltage +V1, the application of voltage -V2 is started more rapidly, and even more preferably, the application of voltage -V2 is started at the same time as stopping the application of voltage +V1 (t int1 =0). Additionally, it is preferable to stop applying voltage -V2 (during reset t) RST After that, voltage +V1 (during electrodialysis) is applied. ED )(t int2 ≥0), more preferably, the voltage +V1 is applied after the applied voltage -V2 is stopped. int2 >0). The start and stop times of voltage +V1 and voltage -V2 are preferably set according to the time accuracy of the power supply device 5 so that voltage +V1 and voltage -V2 are not applied simultaneously.

[0046] In the lithium isotope concentration method according to this embodiment, the Li in the electrolyte membrane 2 + The migration rate varies with the Li-containing aqueous solution ASi on the supply side. + The concentration increases, thereby enhancing... 6The concentration rate of Li. Therefore, the Li-containing aqueous solution ASi preferably has a high Li concentration. + Concentration, more preferably Li + Saturated or supersaturated aqueous solutions. Therefore, in order to suppress the Li in Li-containing aqueous solutions ASi... + The concentration decreases over time, for example, preferably after a predetermined operating application time, or within... 6 Li recovery from aqueous solution ASO. + After the concentration decreases to the specified value, the Li-containing aqueous solution ASi in the supply tank 11 is replaced. Preferably, the Li-containing aqueous solution ASi is always circulated outside the treatment tank 1 during operation. Furthermore, by replacing the Li-containing aqueous solution ASi in this way, the accompanying Li... + Li remaining in the Li-containing aqueous solution ASi due to migration + of 6 Li isotope ratio ( 6 Li / ( 7 Li+ 6 The decrease in Li) thus inhibits the new movement of Li. + of 6 The reduction in the lithium isotope ratio allows for more efficient concentration. 6 Li. Furthermore, it can compensate for the reduction in liquid volume caused by the reaction of Li-containing aqueous solution ASi according to formula (1). Additionally, for 6 Since the volume of the aqueous solution ASo used for Li recovery decreases due to the reaction in formula (3), it is preferable to add water (H2O) or the like to the recovery tank 12 as needed. In the lithium isotope concentration device 10, it is preferable to keep the liquid levels in the supply tank 11 and the recovery tank 12 consistent during operation.

[0047] Furthermore, as shown in equation (11) above, the ion mobility μ also depends on the temperature T, and the degree of its dependence is affected by the activation energy E. a The impact. 7 Li + , 6 Li + The mobility increases exponentially with increasing temperature, but the activation energy E a big 7 Li + The temperature dependence is greater. As a result, as the temperature increases, the low mobility decreases. 7 Li + With high mobility 6 Li + The ratio decreases. Therefore, the more Li... + Low mobility at low temperatures, moving Li + of 6The higher the Li isotope ratio, the better. In this embodiment, the applicable temperature range is above the freezing point and below the boiling point of the aqueous solutions ASi and ASo. 6 The aqueous solution ASo for Li recovery is at 0–100°C when it is pure water at the start of electrodialysis. Therefore, the temperature of the electrolyte membrane 2 is preferably below 20°C, more preferably below 15°C, even more preferably below 10°C, and even more preferably below 5°C.

[0048] for 6 After Li concentration is complete 6 Li recovery uses an aqueous solution ASo. For example, if water is evaporated to concentrate Li, it can be precipitated by generating lithium carbonate (Li₂CO₃) through bubbling with carbon dioxide (CO₂). This allows for the recovery of Li. 6 Li can be recovered. Alternatively, after the formation of lithium carbonate, lithium hydroxide (LiOH) can be generated in a supersaturated state through cooling or water evaporation, causing it to precipitate. 6 Li is recycled.

[0049] (Modified Example) In the lithium isotope concentration apparatus described in the above embodiments, when the voltage applied between the two sides of the electrolyte membrane is stopped, a high potential gradient is formed in the Li-containing aqueous solution in the supply tank, causing lithium ions adsorbed on the surface of the electrolyte membrane to detach efficiently. However, at the point when the voltage is applied between the two sides of the electrolyte membrane again, the lithium ion concentration in the Li-containing aqueous solution near the surface of the electrolyte membrane is relatively low. Therefore, it takes time for lithium ions to adsorb onto the surface of the electrolyte membrane, and the mobility of lithium ions in the electrolyte membrane does not increase after the voltage is applied again, resulting in insufficient energy efficiency. Therefore, in order to eliminate the low concentration of lithium ions near the surface of the electrolyte membrane after the lithium ions are temporarily detached from the surface of the electrolyte membrane and before the voltage is applied between the two sides of the electrolyte membrane is applied again, the following structure is adopted. Hereinafter, refer to Figure 8 and Figure 9 The lithium isotope concentration apparatus and lithium isotope concentration method according to a modified example of the first embodiment of the present invention will be described.

[0050] like Figure 8As shown, the lithium isotope concentration apparatus 10B according to a modification of the first embodiment of the present invention includes: a processing tank 1; an electrolyte membrane (lithium-ion conductive electrolyte membrane) 2 dividing the processing tank 1 into two; a first electrode 31 and a second electrode 32 (porous electrode) covering each surface of the electrolyte membrane 2; a third electrode (auxiliary electrode) 33; a power supply device 5B; a stirrer (circulation unit) 6; and a cooling device 7. The power supply device 5B has a main power supply 51 and an auxiliary power supply 52B, which applies voltage with alternating polarities. The main power supply 51 is connected to the first electrode 31 and the second electrode 32, and the auxiliary power supply 52B is connected to the first electrode 31 and the third electrode 33. Therefore, the lithium isotope concentration apparatus 10B according to this modification is relative to... Figure 1 The lithium isotope enrichment apparatus 10 of the embodiment shown in the diagram has a structure in which the auxiliary power supply 52, which serves as a DC power supply, is replaced with an auxiliary power supply 52B.

[0051] The power supply device 5B has a main power supply 51 and an auxiliary power supply 52B. The main power supply 51 is a DC power supply, and the auxiliary power supply 52B can apply voltage with alternating polarities. It also includes a switching element 5s1 and its drive circuit, etc., to allow the main power supply 51 and auxiliary power supply 52B to apply voltage alternately by switching. The main power supply 51 is the same as in the above embodiment, with its positive terminal connected to the first electrode 31 and its negative terminal connected to the second electrode 32. A positive voltage V1 (voltage + V1) is intermittently applied to the first electrode 31 relative to the second electrode 32. The auxiliary power supply 52B is connected to the first electrode 31 and the third electrode 33, applying a DC voltage V2 with its polarities alternately reversed. More specifically, as... Figure 9 As shown, when the main power supply 51 does not apply voltage +V1, during one stop period of voltage +V1, the auxiliary power supply 52B first applies a negative voltage V2 (voltage -V2) to the third electrode 33 relative to the first electrode 31, and then reverses the polarity, applying a positive voltage V2 (voltage +V2) to the third electrode 33 relative to the first electrode 31. The details of the application time of voltages V1 and V2 will be described later.

[0052] Alternatively, the power supply device 5B may also have a variable power supply 51A (see reference). Figure 3 The structure of the switching element that switches the connection targets at their two poles. Furthermore, in Figure 8In the lithium isotope enrichment apparatus 10B shown, similar to the embodiment described above, when the power supply device 5B applies a voltage +V1 between the first electrode 31 and the second electrode 32, the third electrode 33 is in an open-circuit state; when a voltage -V2 or +V2 is applied between the third electrode 33 and the first electrode 31, the second electrode 32 is in an open-circuit state. Alternatively, it can be configured such that when the power supply device 5B applies a voltage +V1 between the first electrode 31 and the second electrode 32, the third electrode 33 is connected to the first electrode 31 at the same potential. Furthermore, it can also be configured such that when a voltage -V2 or +V2 is applied between the third electrode 33 and the first electrode 31, the second electrode 32 is connected to the first electrode 31 at the same potential.

[0053] (Lithium isotope concentration method) The lithium isotope concentration method according to the modified embodiments of the present invention is repeated sequentially as follows: a first step of applying a positive voltage V1 relative to a second electrode 32 disposed on the back side of a first electrode 31 disposed on the surface of the electrolyte membrane 2; a second step of applying a negative voltage V2 relative to the first electrode 31 to a third electrode 33; and a third step of applying a positive voltage V2 relative to the first electrode 31 to the third electrode 33. The first step (during electrodialysis t) ED ) and step 2 (reset period t) RST ) and the above-described implementation method (refer to Figure 2 The same as described in [reference needed]. In this modified example, the lithium isotope enrichment method sets a preparation period t after step 2 and before the next step 1. PREP As the third step.

[0054] As described in the above embodiment, after applying voltage +V1 (step 1), by applying voltage -V2 (step 2), as... Figure 5D As shown, Li adsorbed on the surface of electrolyte membrane 2 + Detachment. In detail, Li + The Li in the Li-containing aqueous solution ASi detaches from the surface of the positively charged electrolyte membrane 2 through electrostatic repulsion. + Due to the non-uniform distribution of electrostatic attraction near the third electrode 33, as a result, Li... + The concentration of lithium isotopes is relatively reduced. In the lithium isotope concentration method involved in this variation, after applying voltage -V2 through the auxiliary power supply 52B in step 2, the polarity of the auxiliary power supply 52B is reversed, and a voltage V2 (voltage +V2) that is positive relative to the first electrode 31 is applied to the third electrode 33 (step 3). By applying voltage +V2, a potential gradient is generated in the Li-containing aqueous solution ASi, which is negative near the surface of the electrolyte film 2 and positive near the third electrode 33. Thus, the Li that is unevenly distributed near the third electrode 33 in step 2 is reduced.+ Due to electrostatic repulsion, it quickly leaves the third electrode 33, and also rapidly releases Li. + The electrostatic repulsion between Li and the surface of electrolyte membrane 2 eliminates the Li + The concentration of Li is relatively low near the surface of electrolyte membrane 2. Furthermore, the Li is unevenly distributed near the third electrode 33. + Li and Li floating in Li-containing aqueous solution ASi + Attracted by electrostatic attraction to the surface of the negatively charged electrolyte membrane 2, thus increasing the concentration in that vicinity; additionally, some Li... + The Li is adsorbed onto the surface. At this time, the Li adsorbed on the surface of electrolyte membrane 2 + Having Li in the aqueous solution ASi at this time + Equal isotope ratios.

[0055] When the applied voltage +V2 is stopped and the applied voltage +V1 is restarted through the main power supply 51, as follows: Figure 5B and Figure 5C As shown, Li adsorbed on the surface of electrolyte membrane 2 + It moves into the electrolyte membrane 2. Thus, by applying a voltage -V2 between the third electrode 33 and the first electrode 31, then reversing the polarity to apply a voltage +V2, and then applying a voltage +V1 between the two sides of the electrolyte membrane 2 (between the first electrode 31 and the second electrode 32), a large amount of electrolyte can be recovered immediately after the application of voltage +V1. 6 Li has a high isotope ratio.

[0056] In steps 2 and 3, the magnitude of the voltage applied between the third electrode 33 and the first electrode 31 can be different. In step 3, the larger the voltage V2, the larger the electric field applied to the Li-containing aqueous solution ASi between the surface of the electrolyte membrane 2 and the third electrode 33, thus increasing the Li... + The Li exits the third electrode 33 at high speed and is attracted to the surface of the electrolyte membrane 2, thereby eliminating the Li near the surface of the electrolyte membrane 2 in a shorter time. + At low concentrations, and capable of converting Li + Adsorbed onto the surface of electrolyte membrane 2. On the other hand, as described in the above embodiment, it is preferably set to a degree to which the electrolytic reaction of H2O does not occur in the Li-containing aqueous solution ASi.

[0057] The continuous application time (preparation period) of voltage +V2 PREP There are no specific regulations regarding the duration of electrodialysis. ED and reset period t RST Similarly, preferred by 6 The Li recovery efficiency is set in a way that maximizes efficiency. During the preparation period, tPREP As long as the Li- ions near the surface of the electrolyte membrane 2 that were affected by the previously applied voltage -V2 are eliminated... + Low concentration is acceptable, with Li being the preferred option. + A high concentration of Li is present near the surface of electrolyte membrane 2, and more of it is adsorbed on the surface. However, even with a large amount of Li adsorbed on the surface of electrolyte membrane 2... + Li after the initial application of voltage +V1 + There are also limits to improving the migration rate. Additionally, if the preparation period t... PREP The longer the electrodialysis period (t) ED With period t CYC The ratio decreases accordingly, leading to a decrease in productivity. Preparation period t PREP During the reset period t RST Similarly, the larger the voltage V2 and the shorter the interval between the third electrode 33 and the first electrode 31, the shorter the time it takes to achieve the desired effect.

[0058] If the reset period t RST During the preparation period t PREP If the period during which neither voltage -V2 nor +V2 is applied between the third electrode 33 and the first electrode 31 is prolonged, productivity decreases. Therefore, after stopping the application of voltage -V2, it is preferable to start applying voltage +V2 more quickly, such as... Figure 9 As shown, it is more preferable to start applying voltage +V2 at the same time as stopping the application of voltage -V2. Furthermore, if the application of voltage +V2 (during the preparation period t) PREP After stopping, the application of the starting voltage +V1 (during electrodialysis, t) ED The period of no application up to t int3 If the application time is too long, productivity decreases, and consequently, the effect of applying voltage +V2 is reduced. Therefore, it is preferable to start applying voltage +V1 more quickly after stopping applying voltage +V2, and more preferably, to start applying voltage +V1(t) simultaneously with stopping applying voltage +V2. int3 =0). Alternatively, it can be done when applying voltage +V1 (during electrodialysis t). ED Apply voltage +V2. Therefore, after starting to apply voltage +V1, the application of voltage +V2 can be stopped. In this case, the preparation period t PREP It is considered to be the period from the start of applying voltage +V2 to the start of applying voltage +V1.

[0059] In the lithium isotope concentration method according to this embodiment and its variations, as described above, the lower the temperature of the electrolyte membrane 2, the higher the efficiency. 6 Li isotope ratios can be used to recover it, but this requires the use of Li-containing aqueous solutions (ASi). 6Li recovery using aqueous solution ASO is cooled above its freezing point in a way that prevents freezing. Therefore, aqueous solutions ASi, ASO, especially... 6 The aqueous solution ASo for Li recovery can also contain a solute that does not permeate the electrolyte membrane 2, so that the freezing point is lowered to below 0°C. Such a solute is one in which the aqueous solution ASi or ASo will not corrode the electrolyte membrane 2, electrodes 31, 32, etc. Specifically, examples include salts such as sodium chloride (NaCl, table salt), magnesium chloride (MgCl2), calcium chloride (CaCl2), and potassium chloride (KCl), or organic solvents such as ethylene glycol. As mentioned above, in order to recover from the end of electrodialysis... 6 Li recovery using aqueous solution ASO recovery 6 Li and carbon dioxide are bubbled, and in this case, sodium chloride, which does not produce precipitates (carbonates) other than lithium carbonate and has a significantly lower freezing point, is particularly preferred. Furthermore, 6 In the case where the aqueous solution ASo for Li recovery concentrates Li by evaporating water before bubbling carbon dioxide, it is preferable to remove the salts precipitated due to water reduction using conventional methods such as filtration before bubbling. Alternatively, for the recovery... 6 The Li recovery aqueous solution ASo can also selectively recover Li in pure water or the like by performing conventional electrodialysis at a temperature above 0°C, such as room temperature, before carbon dioxide bubbling (see, for example, Patent Document 3). According to this method, the electrolyte membrane 2 can be cooled to below 0°C, more preferably to below 0°C, thereby further improving… 6 Li isotopes can be concentrated more efficiently.

[0060] [Multi-stage lithium isotope concentration unit] (First Embodiment) The lithium isotope enrichment devices 10 and 10B involved in the embodiments and their modifications (see reference) Figure 1 , Figure 8 Obtaining a substance containing [a certain substance] in recycling tank 12 6 The Li isotope ratio is higher than that of the Li aqueous solution containing Li-Si in the supply tank 11. 6 Li recovery aqueous solution (ASo). After recovering this Li... 6 The Li recovery aqueous solution ASo is added to an empty supply tank 11 and operated to obtain Li containing 6 An aqueous solution of Li with a further high Li isotope ratio. Therefore, by forming a cascade structure in which the recovery tank 12 of the lithium isotope concentration device 10 is integrated with the supply tank 11 of another lithium isotope concentration device 10, staged concentration is possible. 6 Li. The following is for reference only. Figure 10 The multi-stage lithium isotope concentration apparatus according to the first embodiment of the present invention will be described.

[0061] The multi-stage lithium isotope concentration apparatus 20 according to the first embodiment of the present invention includes: a processing tank 1A; four electrolyte membranes (lithium-ion conductive electrolyte membranes) 22, 23, 24, and 25, which are arranged in parallel at intervals to divide the processing tank 1A into five tanks 11, 12, 13, 14, and 15 in one direction; a first electrode 31 and a second electrode 32 (a porous electrode) covering both sides of the electrolyte membranes 22, 23, 24, and 25; a third electrode (sub-electrode) 33, which is arranged opposite to the first electrode 31 in the tanks 11, 12, 13, and 14; four power supply units 5; and a stirrer (circulation mechanism) 6, which is arranged in each of the tanks 11, 12, 13, and 14. The multi-stage lithium isotope concentration unit 20 is a structure that connects four lithium isotope concentration units 10 in such a way that each processing tank 1 is integrated with the processing tank 1A. The recovery tank 12 of one of two adjacent lithium isotope concentration units 10 also serves as the supply tank 11 of the other. The electrolyte membranes 22, 23, 24, and 25 can each have the same structure as the electrolyte membrane 2 of the lithium isotope concentration unit 10, and are appropriately referred to as electrolyte membrane 2 unless there is a special need to identify them.

[0062] Similar to the lithium isotope concentration device 10, the supply tank 11 side of the lithium isotope concentration device 10 ( Figure 10 The left side of the (hereinafter referred to as the supply side) is the supply tank 11 at the end of the ( ), which contains an aqueous solution of Li, ASi. Tanks 12, 13, 14, and 15 respectively contain 6 Li recovery uses aqueous solutions AS1, AS2, AS3, and ASo. 6 Li recovery uses aqueous solutions AS1, AS2, AS3, and ASo, along with lithium isotope concentration unit 10. 6 The aqueous solution ASi used for Li recovery is the same as that used to contain lithium ions (Li) recovered from the Li-containing aqueous solution ASi. + The aqueous solution, for example, is pure water, at the start of operation of the multi-stage lithium isotope concentration unit 20. Additionally, the recovery tank 12 side of the lithium isotope concentration unit 10 ( Figure 10 The right side of the tank is called the recovery side. In the multi-stage lithium isotope concentration device 20, the tank 15 at one end of the recovery side is called the recovery tank.

[0063] In the multi-stage lithium isotope concentration apparatus 20, a second electrode 32, a third electrode 33, and a first electrode 31 are sequentially arranged in each of the tanks 12, 13, and 14 (excluding the tanks 11 and 15 at both ends) from the supply side. In the same tank, the second electrode 32 and the first electrode 31 are arranged with sufficient spacing between them, that is, the four electrolyte membranes 2 are arranged with sufficient spacing between them. Furthermore, the second electrode 32 and the third electrode 33 in the same tank are arranged separately from each other, and more preferably with sufficient spacing between them. Therefore, tanks 12, 13, and 14 are arranged in the separation direction of the processing tank 1A (the connection direction of the lithium isotope concentration apparatus 10). Figure 10 The length is designed to be sufficient in the left-right direction. On the other hand, as explained in the structure of the lithium isotope concentration device 10, the third electrode 33 and the first electrode 31 in the same tank are preferably arranged close to each other to the extent that they do not short-circuit.

[0064] As described in the structure of the lithium isotope enrichment apparatus 10, the power supply unit 5 has a main power supply 51 and an auxiliary power supply 52, and is configured such that these power supplies do not operate simultaneously. Furthermore, in the multi-stage lithium isotope enrichment apparatus 20, it is preferable to configure it so that the four power supply units 5 can be driven independently; in other words, the main power supply 51 is connected to electrodes 31 and 32, the auxiliary power supply 52 is connected to electrodes 31 and 33, and each power supply unit 5 is independently connected. In the case of identifying the four power supply units 5 in the multi-stage lithium isotope enrichment apparatus 20, as... Figure 10 As shown, from the supply tank 11 side, they are sequentially referred to as power supply devices 5(1), 5(2), 5(3), and 5(4). Furthermore, in this embodiment, the power supply device 5 has two linked switching elements 5s1 and 5s3. As explained in the structure of the lithium isotope concentration apparatus 10, the switching element 5s1 switches the connection target of the first electrode 31. The switching element 5s3 switches the connection / disconnection of the third electrode 33 and the auxiliary power supply 52, that is, switches the connection / disconnection of the auxiliary power supply 52. ​​In addition, in the multi-stage lithium isotope concentration apparatus 20, it is preferable that the power supplies 51 and 52 are floating power supplies, or only one of the power supplies 51 and 52 may be grounded. For example, it may be configured such that the positive terminal of the main power supply 51 and the negative terminal of the auxiliary power supply 52 of the power supply device 5(1) are grounded during their respective operation, so that the Li-containing aqueous solution ASi in the supply tank 11 is grounded to a reference potential. However, if the resistance between the second electrode 32 and the first electrode 31 in each of the slots 12, 13 and 14 is high enough, it is also possible to ground two or more power supplies 51 and 52 respectively.

[0065] The agitator 6 circulates the aqueous solutions ASi, AS1, AS2, and AS3 in tanks 11, 12, 13, and 14, respectively. The multi-stage lithium isotope concentration device 20 can also have an agitator 6 in the recovery tank 15, which... 6Li is recovered using an aqueous solution ASo cycle. The multi-stage lithium isotope concentration unit 20 may also include a cooling device 7 for cooling electrolyte membranes 22, 23, 24, and 25 (see reference). Figure 1 (Not shown). When the agitator 6 and the submersible cooling device 7 are installed in the tanks 12, 13, and 14, it is preferable that the agitator 6 and the submersible cooling device 7 are positioned between the second electrode 32 (electrolyte membrane 2) and the third electrode 33. All other elements are the same as those described in the structure of the lithium isotope concentration devices 10 and 10B.

[0066] (Lithium isotope concentration method using a multi-stage lithium isotope concentration device) The lithium isotope concentration method performed by the multi-stage lithium isotope concentration apparatus 20 according to this embodiment is the same as the method performed by the lithium isotope concentration apparatus 10. In the figure, a lithium isotope concentration of a naturally occurring ratio is added to the supply tank 11 at the left end. 7 Li, 6 Li-containing aqueous solution ASi is prepared by adding pure water to tanks 12, 13, 14, and 15 respectively. As described above, the Li-containing aqueous solution on the upstream side (supply side) contains... + The higher the concentration, the more Li in electrolyte membrane 2 + The higher the mobility, the better. Therefore, from an energy efficiency perspective, it is preferable to maximize Li mobility immediately after the initial operation begins. + The Li-containing aqueous solution ASi in the supply tank 11 is moved to the pure water, i.e., the aqueous solution AS1, in the tank 12, that is, the Li is only in the electrolyte membrane 22. + Movement to increase Li in aqueous solution AS1 + Concentration. Therefore, only the power supply device 5(1) is driven. And, when the aqueous solution AS1 reaches the specified Li + The concentration, preferably after reaching saturation concentration, is then driven by the power supply device 5(2) to start Li + The movement of aqueous solution AS1 from aqueous solution AS1 to aqueous solution AS2 in tank 13.

[0067] Simultaneously, Li is processed from Li-containing aqueous solution ASi to aqueous solution AS1. + The movement of Li from aqueous solution AS1 to aqueous solution AS2 + Move, and when the Li in the aqueous solution AS2 + The concentration of Li reached the specified level + After concentration, the power supply unit 5(3) is then driven to start Li + The aqueous solution AS2 moves to the aqueous solution AS3 in tank 14. This process is repeated until all power supply units 5 driving the multi-stage lithium isotope concentration unit 20 are activated, thus concentrating the Li... +Moving from left to right in the diagram, the aqueous solutions AS1, AS2, AS3, and ASo in tanks 12, 13, 14, and 15 change from pure water at the start of operation to solutions containing different concentrations of... 6 LiOH aqueous solutions of Li with different Li isotope ratios. 6 The lithium isotope ratios increase in the order Asi < As1 < As2 < As3 < Aso. Therefore, even due to Li + Even when the isotope separation coefficient achieved by moving within an electrolyte membrane 2 is not large, it is still possible to recover from the recovery tank 15. 6 Li has a high isotope ratio, which can prevent Li from + Mobility is drastically reduced due to low temperature or low voltage, which can improve productivity.

[0068] The multi-stage lithium isotope concentration apparatus 20 is designed, for example, such that when a voltage +V1 is applied between the first electrode 31 and the second electrode 32 covering both sides of the electrolyte membrane 23 by the main power supply 51 of the driving power supply device 5 (2), even if the main power supply 51 or the auxiliary power supply 52 of other power supply devices 5 is driven, no electric field is substantially generated between the first electrode 31 and the third electrode 33 or the second electrode 32 in the tank 12, or between the second electrode 32 and the third electrode 33 or the first electrode 31 in the tank 13. Alternatively, it is designed so that even if an electric field is generated, it is small enough not to hinder the reactions of equations (1) and (3) near the electrodes 31 and 32 on both sides of the electrolyte membrane 23. Therefore, as described above, the spacing between the electrolyte membranes 2 and the spacing between the second electrode 32 and the third electrode 33 are configured to be sufficiently wide. With such a structure, two or more adjacent power supply devices 5 can be driven simultaneously. For example, the power supplies 51 and 52 of four power supply devices 5 can be synchronized, such as Figure 10 As shown, it can simultaneously drive the main power supply 51, or simultaneously drive the main power supply 51 and the auxiliary power supply 52 of different power supply devices 5.

[0069] In the multi-stage lithium isotope concentration unit 20, the number of electrolyte membranes 2 is not specifically specified; the more membranes 2 connected, the more lithium isotope concentration units 10 can be connected, and the more lithium isotope can be recovered. 6 Li has a high isotope ratio. Additionally, in Figure 10 In the structure where the lithium isotope concentration device 10 is connected in one direction, all adjacent electrolyte membranes 2, 2 are arranged opposite each other. However, for example, they can also be connected by bending at 90° at one or more points, so that adjacent electrolyte membranes 2, 2 are arranged perpendicular to each other. In the groove of the bent portion separated by the mutually perpendicularly arranged electrolyte membranes 2, 2, the third electrode 33 is arranged parallel to and close to the first electrode 31 covering the surface of the electrolyte membrane 2 on the recovery side.

[0070] (Modified Example) The multi-stage lithium isotope concentrator 20 can also be a structure that connects multiple lithium isotope concentrators 10B, that is, it has a power supply unit 5B instead of a power supply unit 5.

[0071] In the multi-stage lithium isotope concentration apparatus 20 described in the above embodiments, in order to enable Li + The lithium isotope concentrator 10 moves simultaneously between adjacent electrolyte membranes 2, and the spacing between the electrolyte membranes 2 is relatively wide. Therefore, a longer processing tank 1A is required in the connection direction of the lithium isotope concentrator 10. Here, the lithium isotope concentrator 10 intermittently applies voltage between the two sides of the electrolyte membrane 2. Therefore, by staggering the timing of applying voltage to adjacent electrolyte membranes 2, the multi-stage lithium isotope concentrator 20 can minimize the impact on the reaction near electrodes 31 and 32 when voltage is applied between the two sides of the electrolyte membrane 2. Hereinafter, refer to... Figure 11A and Figure 11B A multi-stage lithium isotope concentration apparatus according to a variation of the first embodiment of the present invention will be described.

[0072] The multi-stage lithium isotope concentration apparatus 20A according to the first embodiment of the present invention is the same as the multi-stage lithium isotope concentration apparatus 20 according to the above embodiment. It is a structure in which four lithium isotope concentration apparatus 10 are connected in such a way that each processing tank 1 is integrated with the processing tank 1A. However, it has a power supply device 50, which includes four power supply devices 5 (see reference 1). Figure 10 In addition, the multi-stage lithium isotope concentration device 20A, like the multi-stage lithium isotope concentration device 20, includes a stirrer 6 and a cooling device 7 (not shown) as needed. In this modified example, the cooling device 7 is preferably a structure in which the processing tank 1A is used as a jacket tank to allow the refrigerant to flow.

[0073] The power supply device 50 includes: a main power supply 51 connected between the first electrode 31 and the second electrode 32 on both sides of each electrolyte membrane 2; and an auxiliary power supply 52 connected between the third electrode 33 and the first electrode 31, which are arranged facing each other in the same tank of tanks 11, 12, 13, and 14, configured such that the main power supply 51 and the auxiliary power supply 52, which are connected to the same first electrode 31, alternately apply voltage. That is, the power supply device 50 has four power supply devices 5 (see reference 50). Figure 10 Furthermore, in the case of identifying these main power supplies 51, such as... Figure 11A and Figure 11BAs shown, from the supply tank 11 side, they are sequentially referred to as main power supplies 51(1), 51(2), 51(3), and 51(4). Similarly, they are referred to as auxiliary power supplies 52(1), 52(2), 52(3), and 52(4). Furthermore, the power supply device 50 is configured to not simultaneously drive the main power supply 51 connected to the electrodes 31 and 32 on both sides of the adjacent electrolyte membrane 2 (it is not connected to the electrodes 31 and 32). Therefore, the power supply device 50 groups two or more adjacent power supply devices 5 of the connected lithium isotope concentration device 10 together, and alternately drives the Li in each group. + Movement. At this point, it is preferable to synchronize one unit in each group; here, two units are arranged as a group. Therefore, main power supply 51(1) is synchronized with main power supply 51(3), and main power supply 51(2) is synchronized with main power supply 51(4). Therefore, it is preferable that the period t of all power supply devices 5 is... CYC The same, and during the electrodialysis period t ED Set to less than the period t CYC 1 / 2(t) ED <t CYC / 2), during the reset period t RST Set as period t CYC less than 1 / 2 (t) RST ≤t CYC / 2). In addition, similar to the multi-stage lithium isotope enrichment device 20, the power supplies 51 and 52 are preferably floating power supplies, or in the multi-stage lithium isotope enrichment device 20A, only one of the power supplies 51 and 52 may be grounded.

[0074] (Lithium isotope concentration method using a multi-stage lithium isotope concentration device) Reference Figure 11A and Figure 11B The lithium isotope enrichment method performed by the multi-stage lithium isotope enrichment apparatus 20A according to this modified example will be described. This modified example is the same as the above-described embodiment, except for the timing when voltages +V1 and -V2 are applied by the power supply device 50.

[0075] like Figure 11A As shown, when the main power supplies 51(1) and 51(3) are connected, the power supply device 50 disconnects the main power supplies 51(2) and 51(4). Accordingly, a voltage +V1 is applied between the two sides of each of the electrolyte membranes 22 and 24. Therefore, Li... + The Li-containing aqueous solution ASi from supply tank 11 moves through electrolyte membrane 22 to aqueous solution AS1 in tank 12, and the aqueous solution AS2 from tank 13 moves through electrolyte membrane 24 to aqueous solution AS3 in tank 14. On the other hand, Li... +The electrolyte membrane 23 (between aqueous solution AS1 and aqueous solution AS2) and electrolyte membrane 25 (between aqueous solution AS3 and aqueous solution ASo) do not move. Furthermore, at this time, by connecting auxiliary power supplies 52(2) and 52(4), a voltage -V2 can be applied between the third electrode 33 and the first electrode 31 within tanks 12 and 14. Accordingly, as indicated by the dotted arrows in the figure, a voltage -V2 is generated from Li + The surfaces of the stationary electrolyte membranes 23 and 25 (first electrode 31) face the electric field E2 on the supply side, and Li adsorbed on the surfaces of the electrolyte membranes 23 and 25 + Disengage (refer to) Figure 5D ).

[0076] Next, as Figure 11B As shown, the power supply device 50 disconnects the main power supplies 51(1), 51(3) and the auxiliary power supplies 52(2), 52(4), and connects the main power supplies 51(2), 51(4). Accordingly, a voltage +V1 is applied between the two sides of each of the electrolyte membranes 23 and 25. Therefore, Li... + The aqueous solution AS1 in tank 12 moves through the electrolyte membrane 23 to the aqueous solution AS2 in tank 13. + The aqueous solution AS3 in tank 14 moves through the electrolyte membrane 25 to the aqueous solution ASo in tank 15. On the other hand, Li + It does not move within electrolyte membrane 22 (between aqueous solution ASi and aqueous solution AS1) and electrolyte membrane 24 (between aqueous solution AS2 and aqueous solution AS3). Furthermore, at this time, by connecting auxiliary power supplies 52(1) and 52(3), a voltage -V2 can be applied between the third electrode 33 and the first electrode 31 within tanks 11 and 13. Accordingly, as indicated by the dotted arrows in the figure, a voltage -V2 is generated from Li + The surfaces of the stationary electrolyte membranes 22 and 24 (first electrode 31) face the electric field E2 on the supply side, and Li adsorbed on the surfaces of the electrolyte membranes 22 and 24 + Disengage (refer to) Figure 5D ).

[0077] And after that, as Figure 11A As shown, power supply device 50 disconnects main power supplies 51(2), 51(4) and auxiliary power supplies 52(1), 52(3), connects main power supplies 51(1), 51(3), and connects auxiliary power supplies 52(2), 52(4). Thus, by alternately connecting main power supplies 51(1), 51(3) and main power supplies 51(2), 51(4), Li + They move intermittently and alternately within electrolyte membranes 22, 24 and electrolyte membranes 23, 25, respectively. Furthermore, correspondingly, by alternately connecting auxiliary power supplies 52(2), 52(4) and auxiliary power supplies 52(1), 52(3), Li can be... +Quickly from before Li + The moved electrolyte membrane 2 detaches from its surface. Furthermore, similar to the embodiment described above, it is preferable to drive only the power supply device 5 (1) after initial operation and only in the electrolyte membrane 22 to allow Li to dissolve. + After the movement, power supply devices 5(2), 5(3), and 5(4) are added to each unit in stages to drive it.

[0078] In this modified example, the auxiliary power supply 52 is connected to Li + A voltage -V2 is applied between the third electrode 33 and the first electrode 31 in the tank on the recovery side of the moving electrolyte membrane 2. Accompanying this, a gap is designed to be left between the second electrode 32 and the third electrode 33 so as not to substantially generate an electric field between the third electrode 33 and the opposing second electrode 32, or even if an electric field is generated, it is small enough not to hinder the reaction of equation (3) near the second electrode 32 caused by the applied voltage +V1. Specifically, it is preferable to configure the third electrode 33 and the first electrode 31 in the same tank with a sufficiently short gap to obtain the desired electric field E2 with a small voltage V2. Accordingly, even without a wider gap between the second electrode 32 and the third electrode 33, the reaction near the second electrode 32 will not be hindered by the applied voltage -V2. With such a structure, the multi-stage lithium isotope concentration apparatus 20A according to this modification can shorten the gap between the electrolyte membranes 2 and reduce the size and miniaturize the lithium isotope concentration apparatus 10 in the connection direction.

[0079] The multi-stage lithium isotope enrichment unit 20A, like the multi-stage lithium isotope enrichment unit 20, can also be a structure connecting multiple lithium isotope enrichment units 10B. Therefore, the power supply unit 50 replaces the auxiliary power supply 52, thus having an auxiliary power supply 52B (see reference). Figure 8 In this case, for example, when the main power supplies 51(1) and 51(3) are connected, the auxiliary power supplies 52(2) and 52(4) are connected with their polarities reversed midway. Therefore, during the reset period t RST During the preparation period t PREP The sum is preferably set to a period t. CYC less than 1 / 2 (t) RST +t PREP ≤t CYC / 2).

[0080] (Second Implementation) The lithium isotope enrichment devices 10 and 10B involved in the above embodiments and their modifications (refer to...) Figure 1 , Figure 8As in the first embodiment and its variations, in a multi-stage lithium isotope concentration apparatus in which each processing tank 1 and processing tank 1A are connected in an integrated manner, as described above, the recovery tank 12 of one of two adjacent lithium isotope concentration apparatuses 10, 10 also serves as the supply tank 11 of the other. Furthermore, the third electrode 33 and the second electrode 32, respectively provided in the integrated supply tank 11 and recovery tank 12, can be integrated. Hereinafter, refer to... Figure 12 The multi-stage lithium isotope concentration apparatus according to the second embodiment of the present invention will be described.

[0081] The multi-stage lithium isotope concentration apparatus 20B according to the second embodiment of the present invention includes: a processing tank 1A; six electrolyte membranes (lithium-ion conductive electrolyte membranes) 22, 23, 24, 25, 26, and 27, which are arranged in parallel at intervals to divide the processing tank 1A into seven tanks 11, 12, 13, 14, 15, 16, and 17 in one direction; a first electrode 31 and a second electrode 32 (porous electrode) covering both sides of the electrolyte membranes 22, 23, 24, 25, 26, and 27; a third electrode (sub-electrode) 33, which is arranged opposite to the first electrode 31 in the tank 11; and a power supply device 50C. Furthermore, similar to the multi-stage lithium isotope concentration apparatus 20, the multi-stage lithium isotope concentration apparatus 20B may, as needed, include a stirrer (circulation mechanism) 6 or a cooling device 7 (not shown). The multi-stage lithium isotope concentration unit 20B is a structure in which six lithium isotope concentration units 10B are connected in such a way that each processing tank 1 is integrated with the processing tank 1A. The recovery tank 12 of one of two adjacent lithium isotope concentration units 10B also serves as the supply tank 11 of the other. Furthermore, the second electrode 32 in the recovery tank 12 of one unit also serves as the third electrode 33 in the supply tank 11 of the other unit. Therefore, the multi-stage lithium isotope concentration unit 20B only has a third electrode 33, separate from the electrolyte membrane 22, in the supply tank 11 at the supply side. The electrolyte membranes 22, 23, 24, 25, 26, and 27 can have the same structure as the electrolyte membrane 2 of the lithium isotope concentration units 10 and 10B, respectively, and are appropriately referred to as electrolyte membrane 2 without special identification. Additionally, the cooling device 7 is preferably a structure in which the processing tank 1A is used as a jacketed box for refrigerant circulation.

[0082] As described above, in the multi-stage lithium isotope concentration apparatus 20B, since the second electrode 32 disposed in tanks 12, 13, 14, 15, and 16 respectively also serves as the third electrode 33 in the same tank, it is preferable that the electrolyte membranes 2 be spaced shortly apart so that the second electrode 32, as the third electrode 33, is disposed close to the opposing first electrode 31 to the extent that it does not short-circuit. That is, tanks 12, 13, 14, 15, and 16, except for the tanks 11 and 17 at both ends, are preferably shorter in the separation direction of the processing tank 1A (the connection direction of the lithium isotope concentration apparatus 10B). With this structure, the multi-stage lithium isotope concentration apparatus 20B can reduce the number of components and reduce its size in the connection direction, thus achieving miniaturization.

[0083] The power supply unit 50C comprises six power supply units 5C1, 5C2, 5C3, 5C4, 5C5, and 5C6 sequentially from the supply side. Each of these six power supply units has a main power supply 51 and an auxiliary power supply 52. ​​Power supply units 5C1, 5C2, 5C3, 5C4, 5C5, and 5C6 are equivalent to power supply unit 5B of the lithium isotope enrichment unit 10B, and are appropriately referred to as power supply unit 5C unless otherwise specified. Like power supply unit 5B, power supply unit 5C alternately applies DC voltage to the main power supply 51 and the auxiliary power supply 52, and the polarity of the auxiliary power supply 52 is reversed. In detail, the power supply unit 5C repeats the steps alternately in the following order: Step 1: Connect the positive and negative terminals of the main power supply 51 to the first electrode 31 and the second electrode 32, respectively, and apply a voltage +V1; Step 2: Disconnect the main power supply 51, and connect the positive and negative terminals of the auxiliary power supply 52 to the first electrode 31, the third electrode 33, or the adjacent second electrode 32 on the supply side, respectively, and apply a voltage -V2; Step 3: Alternately connect the positive and negative terminals of the auxiliary power supply 52, and apply a voltage +V2. Therefore, the power supply device 5C also has switching elements 5s1, 5s2, and 5s3 for switching the connection targets of the electrodes 31, 32, and 33. However, since the second electrode 32 of one of the adjacent lithium isotope enrichment devices 10B also serves as the third electrode 33 of the other, in addition to the power supply device 5C1, the switching element 5s3 also serves as the switching element 5s2 of the adjacent power supply device 5C on the supply side. In addition, in the multi-stage lithium isotope enrichment device 20B, power supplies 51 and 52 are preferably floating power supplies, or only one of power supplies 51 and 52 may be grounded.

[0084] In the multi-stage lithium isotope enrichment apparatus 20B, it is preferable not only to enrich Li by applying a voltage +V1, but also to enrich Li +In the supply-side tank of the moving electrolyte membrane 2, and in the recovery-side tank, no voltage -V2 is applied between the third electrode 33 or the second electrode 32 and the first electrode 31. When a potential gradient with a positive value near the surface of the electrolyte membrane 2 is generated in the aqueous solution in the recovery-side tank, Li + The movement of the lithium isotope is hindered, reducing energy efficiency. Therefore, the power supply unit 50C groups three or more adjacent power supply units 5C connected to the lithium isotope enrichment unit 10B, and alternately powers the lithium isotope enrichment unit 5C in each group. + Movement. Here, the switching elements 5s1, 5s2, and 5s3 are set in a group of three, which are switching elements that simultaneously perform the on / off operation of three positions.

[0085] Switching element 5s1 is a three-pole switch that switches the connection target of the first electrode 31 to the positive terminal of the main power supply 51, the positive terminal of the auxiliary power supply 52, or the negative terminal of the auxiliary power supply 52. ​​Switching element 5s2 connects / disconnects the second electrode 32 from the negative terminal of the main power supply 51. Switching element 5s3 is a two-pole switch that switches the connection target of the third electrode 33 to the positive terminal of the auxiliary power supply 52, the negative terminal of the auxiliary power supply 52, or no connection. Switching element 5s2, which also functions as switching element 5s3, is a two-pole switch that switches the connection target of the second electrode 32 to the negative terminal of the main power supply 51 and the positive terminal of the auxiliary power supply 52 of the adjacent power supply device 5C on the recovery side, the negative terminal of the auxiliary power supply 52, or no connection.

[0086] Furthermore, it is preferable to synchronize one unit in each group, in this case, three units per group. Therefore, power supply unit 5C1 is synchronized with power supply unit 5C4, power supply unit 5C2 with power supply unit 5C5, and power supply unit 5C3 with power supply unit 5C6, respectively. Thus, the period t of all power supply units 5C is... CYC The same and during the electrodialysis period t ED During the reset period t RST and preparation period t PREP They are respectively set to be less than the period t CYC 1 / 3 (t) ED <t CYC / 3、t RST <t CYC / 3、t PREP <t CYC / 3). Furthermore, during electrodialysis, power supplies 5C1, 5C4, 5C2, 5C5, 5C3, and 5C6 are used to control the flow rate. ED Driven in a non-repetitive manner.

[0087] (Lithium isotope concentration method using a multi-stage lithium isotope concentration device) Reference Figure 13A , Figure 13B and Figure 13C The lithium isotope concentration method performed using the multi-stage lithium isotope concentration apparatus 20B according to this embodiment will be described. Furthermore, in Figure 13A , Figure 13B and Figure 13C In the diagram, the main power supply 51 and auxiliary power supply 52 of the power supply devices 5C1, 5C2, 5C3, 5C4, 5C5, and 5C6 are represented as main power supply 51(1), 51(2), 51(3), 51(4), 51(5), 51(6) and auxiliary power supply 52(1), 52(2), 52(3), 52(4), 52(5), 52(6).

[0088] like Figure 13A As shown, when power supply devices 5C1 and 5C4 are connected to the main power supply 51(1) and 51(4), the other power supply devices 5C2, 5C3, 5C5, and 5C6 are disconnected from the main power supply 51. Accordingly, a voltage +V1 is applied between the two sides of each of the electrolyte membranes 22 and 25. O2 is then generated near the first electrode 31 covering the surface of the electrolyte membranes 22 and 25, and H2 is generated near the second electrode 32 covering the back surface. Figure 13A The middle part is omitted; please refer to the following: Figure 4 Then, Li + The Li-containing aqueous solution ASi from supply tank 11 moves through electrolyte membrane 22 to aqueous solution AS1 in tank 12, and the aqueous solution AS3 from tank 14 moves through electrolyte membrane 25 to aqueous solution AS4 in tank 15. On the other hand, Li... + It does not move within the other electrolyte membranes 23, 24, 26, and 27. Additionally, at this time, power supply devices 5C2 and 5C5 are connected to auxiliary power supplies 52(2) and 52(5), enabling the Li... + A voltage +V2 is applied between the second electrode 32 and the first electrode 31 within the tanks 12 and 15 on the recovery side of the moving electrolyte membranes 22 and 25. Accordingly, as indicated by the dotted arrows in the figure, an electric field E2 (electric field +E2) is generated in the aqueous solutions AS1 and AS4 towards the recovery side. Due to Li... + Li in aqueous solutions AS1 and AS4 moves along the electric field. + The Li is attracted to the vicinity of the first electrode 31 on the recovery side (near the surface of electrolyte membranes 23 and 26). Additionally, Li moving within electrolyte membranes 22 and 25... + The electrolyte rapidly leaves the back surface of electrolyte membranes 22 and 25 (second electrode 32) and moves towards the recovery side in aqueous solutions AS1 and AS4. As a result, the Li near the back surface of electrolyte membranes 22 and 25... + As the concentration decreases, the concentration gradient with the vicinity of the surface increases, and the Li in electrolyte membranes 22 and 25... + The migration rate increases.

[0089] Furthermore, at this time, power supply devices 5C3 and 5C6 are connected to auxiliary power supplies 52(3) and 52(6), enabling the application of voltage -V2 between the second electrode 32 and the first electrode 31 within slots 13 and 16. Accordingly, as indicated by the dotted arrows in the figure, a voltage -V2 is generated from Li... + The surfaces of the unmoved electrolyte membranes 24 and 27 (first electrode 31) face the electric field E2 (electric field -E2) on the supply side, causing the Li+ adsorbed on the surfaces of the electrolyte membranes 24 and 27 to rapidly detach (refer to...). Figure 5D ).

[0090] Next, as Figure 13B As shown, power supply devices 5C1 and 5C4 disconnect the main power supplies 51(1) and 51(4) and connect the auxiliary power supplies 52(1) and 52(4), and power supply devices 5C2 and 5C5 disconnect the auxiliary power supplies 52(2) and 52(5) and connect the main power supplies 51(2) and 51(5). Furthermore, power supply devices 5C3 and 5C6 reverse the polarity of the auxiliary power supplies 52(3) and 52(6). Accordingly, a voltage +V1 is applied between the two sides of each of the electrolyte membranes 23 and 26. Then, O2 and H2 are generated near the electrodes 31 and 32 covering the two sides of the electrolyte membranes 23 and 26, respectively. Figure 13B The middle part is omitted; please refer to the following: Figure 4 Then, Li + The aqueous solution AS1 in tank 12 moves through electrolyte membrane 23 to the aqueous solution AS2 in tank 13, and the aqueous solution AS4 in tank 15 moves through electrolyte membrane 26 to the aqueous solution AS5 in tank 16. Meanwhile, in other electrolyte membranes 22, 24, 25, and 27, Li... + Do not move. Additionally, at this time, due to the influence of Li... + A voltage +V2 is applied between the second electrode 32 and the first electrode 31 within the tanks 13 and 16 on the recovery side of the moving electrolyte membranes 23 and 26. Therefore, as shown by the dotted arrows in the figure, an electric field +E2 is generated in the aqueous solutions AS2 and AS5. Through the electric field +E2, a voltage -V2 is applied within tanks 13 and 16 (refer to...) Figure 13A This causes the Li in the aqueous solutions AS2 and AS5 to be unevenly located near the second electrode 32 on the supply side. + Moving towards the recovery side reduces the Li content near the back surface of electrolyte membranes 23 and 26. + Concentration. Furthermore, since a voltage +V2 (refer to...) was just applied in the tanks 12 and 15 on the supply side of the electrolyte membranes 23 and 26 prior to this... Figure 13A Therefore, in aqueous solutions AS1 and AS4, the Li near the surfaces of electrolyte films 23 and 26... + The concentration increased. As a result, in electrolyte membranes 23 and 26, Li... + The concentration gradient of Li increases,+ The migration rate increases.

[0091] Furthermore, at this time, just before this, Li + The electrolyte membranes moved to 22, 25 (reference) Figure 13A A voltage -V2 is applied between the third electrode 33 and the first electrode 31 in tank 11 on the supply side and between the second electrode 32 and the first electrode 31 in tank 14. Therefore, as shown by the dotted arrows in the figure, an electric field -E2 is generated in the aqueous solutions ASi and AS3. Consequently, the Li adsorbed on the surfaces of the electrolyte membranes 22 and 25... + Get out quickly (refer to) Figure 5D ).

[0092] Next, as Figure 13C As shown, power supply devices 5C2 and 5C5 disconnect the main power supplies 51(2) and 51(5) and connect the auxiliary power supplies 52(2) and 52(5), while power supply devices 5C3 and 5C6 disconnect the auxiliary power supplies 52(3) and 52(6) and connect the main power supplies 51(3) and 51(6). Furthermore, power supply devices 5C1 and 5C4 reverse the polarity of the auxiliary power supplies 52(1) and 52(4). Accordingly, a voltage +V1 is applied between the two sides of each of the electrolyte membranes 24 and 27. As a result, O2 and H2 are generated near the electrodes 31 and 32 covering the two sides of the electrolyte membranes 24 and 27, respectively. Figure 13C The middle part is omitted; please refer to the following: Figure 4 Then, Li + The aqueous solution AS2 in tank 13 moves through electrolyte membrane 24 to aqueous solution AS3 in tank 14, and the aqueous solution AS5 in tank 16 moves through electrolyte membrane 27 to aqueous solution ASo in tank 17. Meanwhile, in other electrolyte membranes 22, 23, 25, and 26, Li... + It does not move. Furthermore, at this time, due to the interaction between the third electrode 33 and the first electrode 31 within the groove 11, and Li... + A voltage +V2 is applied between the second electrode 32 and the first electrode 31 within the tank 14 on the recovery side of the moving electrolyte membrane 24. Therefore, as shown by the dotted arrows in the figure, an electric field +E2 is generated in the aqueous solutions ASi and AS3. Through the electric field +E2, a voltage -V2 is applied within the tanks 11 and 14 (refer to...) Figure 13B This causes the Li atoms near electrodes 33 and 32 on the supply side to be unevenly distributed in aqueous solutions ASi and AS3. + Move towards the recovery side. Additionally, since a voltage +V2 (refer to...) was just applied in the tanks 13 and 16 on the supply side of the electrolyte membranes 24 and 27 prior to this... Figure 13B Therefore, in aqueous solutions AS2 and AS5, the Li near the surfaces of electrolyte membranes 24 and 27 +The concentration increased. As a result, in electrolyte membranes 24 and 27, Li... + The concentration gradient of Li increases, + The migration rate increases.

[0093] At this time, because Li had just been... + Electrolyte membranes 23 and 26 moved to (reference) Figure 13B A voltage -V2 is applied between the second electrode 32 and the first electrode 31 in tanks 12 and 15 on the recovery side. Therefore, as shown by the dotted arrows in the figure, an electric field -E2 is generated in the aqueous solutions AS1 and AS4. Consequently, the Li adsorbed on the surfaces of electrolyte membranes 23 and 26... + Get out quickly (refer to) Figure 5D ).

[0094] And after that, as Figure 13A As shown, power supply devices 5C3 and 5C6 disconnect the main power supplies 51(3) and 51(6) and connect the auxiliary power supplies 52(3) and 52(6), while power supply devices 5C1 and 5C4 disconnect the auxiliary power supplies 52(1) and 52(4) and connect the main power supplies 51(1) and 51(4). Furthermore, power supply devices 5C2 and 5C5 reverse the polarity of the auxiliary power supplies 52(2) and 52(5). Thus, in the multi-stage lithium isotope concentration apparatus 20C, operation is performed by switching the on / off state of power supplies 51 and 52 by alternating power supply devices 5C1, 5C4, 5C2, 5C5, and 5C3, 5C6. Accordingly, each electrolyte membrane 2 is alternately and intermittently subjected to a voltage +V1 on both sides. Then, in the tank on the supply side of the electrolyte membrane 2, after stopping the application of voltage +V1, a voltage -V2 is applied, causing the Li adsorbed on the surface of the electrolyte membrane 2 to... + Li disengages rapidly, while Li disengages by applying voltage +V2 before the next application of voltage +V1. + The lithium isotopes are attracted to the surface of the electrolyte membrane 2, thus achieving a high concentration. Therefore, the multi-stage lithium isotope concentration unit 20C is a compact device that is reduced in size along the separation direction of the processing tank 1A, while simultaneously enabling efficient recovery from the recovery tank 17 in terms of time. 6 Li has a high isotope ratio.

[0095] Similar to the multi-stage lithium isotope concentration device 20, the lithium isotope concentration device 10B can also be connected by bending at one or more points by 90°, and the adjacent electrolyte membranes 2, 2 are arranged perpendicularly to each other. In the groove of the bend separated by the mutually perpendicularly arranged electrolyte membranes 2, 2, the second electrode 32 does not also serve as the third electrode 33, that is, not only are electrodes 31, 32 arranged, but also the third electrode 33 is arranged, and the third electrode 33 is arranged parallel and close to the first electrode 31 covering the surface of the electrolyte membrane 2 on the recovery side.

[0096] (Modified Example) The multi-stage lithium isotope concentration unit 20B can also be a structure that connects multiple lithium isotope concentration units 10. In this case, instead of applying voltage +V2 (step 3) to the auxiliary power supply 52, a period is set in which no voltage is applied (application is stopped) between the third electrode 33 or the second electrode 32 and the first electrode 31 in the same tank.

[0097] [Second Implementation] As described in the first embodiment, during operation, the Li-containing aqueous solution ASi preferably maintains a high Li content. + Concentration. Therefore, except for replacing the Li-containing aqueous solution ASi in the supply tank 11 or circulating it with the external environment of the treatment tank 1, the Li concentration in the Li-containing aqueous solution ASi should be maintained for good operability and without significantly expanding the equipment. + Concentration, and adopt the following structure. See below for reference. Figure 14 The lithium isotope concentration apparatus according to the second embodiment of the present invention will be described.

[0098] (Lithium isotope concentration unit) The lithium isotope concentration apparatus 10C according to the second embodiment of the present invention includes: a processing tank 1B; an electrolyte membrane (lithium-ion conductive electrolyte membrane for lithium replenishment) 21; an electrolyte membrane (lithium-ion conductive electrolyte membrane) 22; a first electrode (porous electrode) 31; a second electrode (porous electrode) 32; a third electrode (sub-electrode) 33; a fourth electrode (first electrode for lithium replenishment) 41; a fifth electrode (second electrode for lithium replenishment) 42; a power supply device 5 with a built-in main power supply 51 and a sub-power supply 52; a power supply (power supply for lithium replenishment) 53; a stirrer (circulation structure) 6; and a cooling device 7. The processing tank 1B is sequentially divided by the electrolyte membranes 21 and 22 into a replenishment tank (lithium replenishment tank) 12 containing an aqueous solution of Li AS', a supply tank (first tank) 11 containing an aqueous solution of Li Si, and a cooling device 7. 6 The three are: the recovery tank (second tank) 12 for the Li recovery aqueous solution ASo; and the lithium isotope concentration device 10C, which is relative to the lithium isotope concentration device 10 of the first embodiment (see reference 10). Figure 1 The device includes an electrolyte membrane 21 that separates the processing tank 1B from the supply tank 11 side of the electrolyte membrane 22, a replenishment tank 1z separated from the supply tank 11 by the electrolyte membrane 21, electrodes 41 and 42 disposed in each tank of the supply tank 11, and a power supply 53 connected between the electrodes 41 and 42. Apart from these components, the structure is the same as that of the lithium isotope concentration apparatus 10 according to the first embodiment. Depending on the requirements, it may also include a liquid level sensor, an exhaust mechanism, etc.

[0099] The lithium isotope concentration apparatus 10C, consisting of a replenishment tank 1z, a supply tank 11, an electrolyte membrane 21 separating them, electrodes 41 and 42, and a power supply 53, is similar to that of the lithium isotope concentration apparatus 10. It is a lithium recovery apparatus based on a lithium recovery method using an electrolyte membrane with lithium-ion conductivity (e.g., Patent Documents 2 and 3). This lithium recovery apparatus enables Li... + The Li-containing aqueous solution AS' contained in the replenishment tank 1z is moved to the Li-containing aqueous solution ASi contained in the supply tank 11. That is, the lithium isotope concentration apparatus 10C according to this embodiment is a cascade structure that integrates and connects the processing tanks of the lithium recovery apparatus described above and the lithium isotope concentration apparatus 10 according to the first embodiment in the supply tank 11.

[0100] Electrolyte membrane 22 has the same structure as the electrolyte membrane 2 of the lithium isotope concentration apparatus 10 described in the above embodiments. Electrolyte membrane 21 may also have the same structure as electrolyte membrane 22.

[0101] The fourth electrode 41 and the fifth electrode 42 are arranged in pairs and are used to apply a voltage between the two sides of the electrolyte membrane 21. The fourth electrode 41 is in the replenishment tank 1z, and the fifth electrode 42 is in the supply tank 11, respectively contacting or opposite to the electrolyte membrane 21. Preferably, one or both of the fourth electrode 41 and the fifth electrode 42 have a porous structure and are in contact with the electrolyte membrane 21, more preferably one of them is in contact with the electrolyte membrane 21, and even more preferably... Figure 14 As shown, the fourth electrode 41 is in contact with the electrolyte membrane 21 (see Patent Document 3). By contacting at least one of the electrodes 41 and 42 with the electrolyte membrane 21, a voltage can be applied over a wide range of the electrolyte membrane 21. Moreover, since one of the electrodes 41 and 42 is in contact with the electrolyte membrane 21 while the other is away from it, even if the voltage V3 applied by the power supply 53 connected between the electrodes 41 and 42 is large enough, the potential difference between the two sides of the electrolyte membrane 21 can be suppressed, and as will be described later, the Li in the electrolyte membrane 21 can be suppressed. + Reduced energy efficiency during movement.

[0102] As described above, the fourth electrode 41 is disposed in contact with the surface of the electrolyte membrane 21 on the side of the replenishment tank 1z, and a voltage is applied over a large area of ​​the electrolyte membrane 21. On the other hand, the fourth electrode 41, like electrodes 31 and 32, has a porous structure such as a mesh, so that the Li-containing aqueous solution AS′ contacts the surface of the electrolyte membrane 21 over a sufficiently large area. The fourth electrode 41 is formed of an electrode material that has electronic conductivity and is stable when a voltage is applied in the Li-containing aqueous solution AS′. It is further preferred to use a material that has catalytic activity for the reaction of formula (1) and the reaction of formula (2) as the first electrode 31, and it is further preferred to use a material that is easy to process into the above shape. Platinum (Pt) is preferred, for example, as such an electrode material for the fourth electrode 41. [Chemical Formula 3] Li + →Li + (electrolyte)···(2)

[0103] The fifth electrode 42 is disposed within the supply tank 11 in a manner that does not contact the electrolyte membrane 21. On the other hand, it is preferable that the distance between it and the electrolyte membrane 21 is not long, and it is also preferable that it is disposed parallel to the electrolyte membrane 21. Similar to the third electrode 33, the fifth electrode 42 is preferably shaped such as a mesh to allow aqueous solution to pass through, thereby increasing the contact area with the Li-containing aqueous solution ASi, and enabling continuous replacement of the Li-containing aqueous solution ASi in contact with the surface of the electrolyte membrane 21 within the supply tank 11. The fifth electrode 42 is formed of an electrode material that has electronic conductivity and is stable when a voltage is applied in the Li-containing aqueous solution ASi. It is further preferred to use a material that has catalytic activity for the reaction of the following formula (3). For example, platinum (Pt) is preferred as such an electrode material. Alternatively, the fifth electrode 42 can also be made of carbon (C), copper (Cu), or stainless steel that is stable at a potential lower than the potential at which the reaction of the following formula (3) occurs, and it is more preferable to support Pt particles that act as a catalyst on their surface. Furthermore, the fifth electrode 42 can also have a porous structure like the fourth electrode 41 and be disposed in contact with the electrolyte membrane 21. [Chemical Formula 4] 2H2O+2e - →2OH - +H2↑···(3)

[0104] Furthermore, in the lithium isotope concentration apparatus 10C, a fifth electrode 42, a third electrode 33, and a first electrode 31 are arranged within a supply tank 11. The length of the supply tank 11 in the separation direction (between electrolyte membranes 21 and 22) is designed to be sufficiently long so that the fifth electrode 42 and the third electrode 33 or the first electrode 31 are sufficiently spaced apart from each other. Specifically, it is designed so that even if the first electrode 31 is connected to the main power supply 51, or the electrodes 33 and 31 are connected to the auxiliary power supply 52, and the fifth electrode 42 is connected to the power supply 53, no substantial electric field is generated between the fifth electrode 42 and the first electrode 31 or the third electrode 33, or even if an electric field is generated, it is small enough not to hinder the reaction in the vicinity of the fifth electrode 42 and the first electrode 31.

[0105] Power supply 53, like main power supply 51, is a DC power supply. Its positive terminal is connected to the fourth electrode 41, and its negative terminal is connected to the fifth electrode 42. A voltage V3 (voltage + V3) that is positive relative to the fifth electrode 42 is applied to the fourth electrode 41. Alternatively, power supply 53 can be a variable power supply to adjust the Li in the electrolyte membrane 21. + Migration rate.

[0106] Similar to the first embodiment, the stirrer 6 circulates the Li-containing aqueous solution AS' in the supply tank 11. The lithium isotope concentration device 10C may also have a stirrer 6 in the replenishment tank 12 to circulate the Li-containing aqueous solution AS', or it may also have a stirrer 6 in the recovery tank 12 to circulate the Li-containing aqueous solution AS'. 6 Li recovery uses an aqueous solution, ASo, for recycling. Furthermore, if a cooling device 7 is provided in the lithium isotope concentration unit 10C, it is preferable not to cool the electrolyte membrane 21 to prevent Li from accumulating in the electrolyte membrane 21. + The migration rate decreases. Therefore, for example, as Figure 14 As shown, the cooling device 7 is an immersion type, and the refrigerant pipe is arranged to be immersed in the recovery tank 12. 6 Li is recovered in an aqueous solution ASo and is opposite to the electrolyte membrane 22.

[0107] Li-containing aqueous solution AS' is used to maintain its high Li content by supplying Li to the Li-containing aqueous solution ASi during the operation of the lithium isotope concentration unit 10C. + Concentration of Li source. The Li-containing aqueous solution AS' is based on the ratio of naturally occurring Li to... 7 Li and 6 Li cations 7 Li + , 6 Li + The aqueous solution, similar to the Li-containing aqueous solution ASi, is, for example, an aqueous solution of lithium hydroxide (LiOH). Additionally, because when Li... + Li in electrolyte membrane 21 at low concentration +The mobility decreases, therefore, at the start of operation of the lithium isotope concentration unit 10C, it is preferable to use Li containing an aqueous solution of Li AS'. + Higher concentration, preferably Li + A saturated or supersaturated aqueous solution. Similar to the first embodiment, at the start of operation of the lithium isotope concentration device 10C, an aqueous solution containing Li, ASi, and... 6 Li recovery uses aqueous solutions of ASO, such as saturated or supersaturated aqueous solutions of LiOH, as well as pure water.

[0108] (Lithium isotope concentration method) Reference Figure 15 A lithium isotope concentration method performed using the lithium isotope concentration apparatus according to the second embodiment of the present invention will be described. Furthermore, in Figure 15 In this embodiment, the stirrer 6 and cooling device 7 are omitted. In the lithium isotope concentration apparatus 10C according to this embodiment, Li... + From the Li-containing aqueous solution Asi in the supply tank 11 to the recovery tank 12 6 The movement of the aqueous solution ASO for Li recovery is the same as in the first embodiment (see [reference]). Figure 4 , Figures 5A to 5D Furthermore, Li + The movement of the Li-containing aqueous solution AS′ from the replenishment tank 1z to the Li-containing aqueous solution ASi from the supply tank 11 is related to the application of voltage +V1 to make Li... + From Li-containing aqueous solution ASi to 6 The movement of Li in the aqueous solution of ASO is the same.

[0109] That is, such as Figure 15 As shown, in the lithium isotope concentration apparatus 10C, the power supply 53 applies a positive voltage V3 (voltage + V3) to the fourth electrode 41 relative to the fifth electrode 42. Therefore, near the fourth electrode 41, OH- ions in the Li-containing aqueous solution AS′... - The reaction of equation (1) occurs, causing electrons e to... - Released to electrode 41, producing H2O and O2, OH - Decrease. In Li-containing aqueous solution AS′, as OH... - To reduce charge and maintain charge balance, LiO2 decreases on the surface of electrolyte membrane 21, near the fourth electrode 41. + The reaction of formula (2) dissolved in electrolyte membrane 21. On the other hand, near the fifth electrode 42, H2O in the Li-containing aqueous solution ASi donates electrons e. - This leads to the reaction described in equation (3), which produces H2 and OH. - Therefore, with OH -To maintain charge balance, an increase in Li in the electrolyte membrane 21 occurs near the back side of the electrolyte membrane 21. + The reaction of the following equation (4) is transferred. As a result, due to the Li contained in the Li-containing aqueous solution AS′, electrolyte membrane 21 and the Li-containing aqueous solution ASi near electrolyte membrane 21 respectively. + The electrochemical potential difference of Li + It permeates through the electrolyte membrane 21 from the Li-containing aqueous solution AS′ and moves into the Li-containing aqueous solution ASi. [Chemical Formula 5] Li + →Li + (electrolyte)···(2) 2H2O+2e - →2OH - +H2↑···(3) Li + (electrolyte)→Li + ···(4)

[0110] From the reaction in equation (2) to the reaction in equation (4), that is, the Li in the Li-containing aqueous solution AS' + Li enters the interior of electrolyte membrane 21 from the surface of electrolyte membrane 21 and is present in electrolyte membrane 21. + The movement and Li in electrolyte membrane 21 + The migration to Li-containing aqueous solution ASi is related to the Li in Li-containing aqueous solution ASi. + via electrolyte membrane 22 (electrolyte membrane 2) to 6 The movement of the aqueous solution ASo for Li recovery is the same, and as described in the first embodiment.

[0111] As the voltage V3 increases, the Li in the electrolyte membrane 21... + The higher the migration rate (refer to...) Figure 7 Therefore, it is preferable to use Li in the electrolyte membrane 22. + The mobility is used to set the voltage V3. Furthermore, since power supply 53 can be continuously powered, Li... + The movement from the Li-containing aqueous solution AS' to the Li-containing aqueous solution ASi and the intermittent energization of the main power supply 51 cause Li to... + From Li-containing aqueous solution ASi to 6 Compared to the movement of ASO in the aqueous solution used for Li recovery, this method can increase the average amount of movement per unit time. Additionally, as... Figure 15As shown, during the operation of the lithium isotope concentration device 10C (driven by the main power supply 51), the power supply 53 can be continuously driven to replenish Li to the Li-containing aqueous solution ASi. + However, it can also drive the power supply 53 for short periods at regular intervals, applying a large voltage V3 to make Li + It moves at high speed in Li-containing aqueous solution ASi.

[0112] Here, when the voltage V3 is large, and the potential difference between the two sides is a portion of the transition metal ions that reduce the electrolyte membrane 21 (for example, if the electrolyte membrane 21 is LLTO, then it is Ti), the potential difference between the two sides is large. 4+ +e - →Ti 3+ When the voltage exceeds a certain threshold, electron conductivity is exhibited in the electrolyte membrane 21. Therefore, electrons e are conducted in the electrolyte membrane 21. - Joule heating is generated, therefore Li + The energy efficiency of the mobile circuit drops sharply, and even with a further increase in voltage V3, Li + The mobility will not increase to a level corresponding to an increase in voltage V3. Specifically, although it also depends on the electronic conductivity of the electrolyte membrane 21 and the electrode performance that determines the electrode reaction overvoltage, electronic conductivity can be exhibited in the electrolyte membrane 21 when a voltage exceeding 2.0V is applied between the two sides. In the lithium isotope concentration apparatus 10C, since one side of the electrodes 41, 42 that hold the electrolyte membrane 21 from both sides is positioned away from the electrolyte membrane 21, it is difficult for the potential difference between the two sides of the electrolyte membrane 21 to reach the aforementioned voltage even if the voltage V3 is increased to a certain extent. However, since the aforementioned voltage will be reached when the voltage is further increased, it is preferable to set it below this voltage.

[0113] According to the lithium isotope concentration apparatus 10C of this embodiment, since the lithium isotope is constantly or periodically replenished in the Li-containing aqueous solution ASi... 6 Li isotope ratio is the same as the natural ratio of Li + Therefore, it is possible to convert Li containing Li aqueous solution ASi into Li + Maintaining a high concentration and slowing down 6 The rate of decrease in the Li isotope ratio allows for long-term continuous operation even without external circulation of the Li-containing aqueous solution (ASi). However, beyond a certain point in the long-term operation, a large amount of residual Li in the Li-containing aqueous solution (ASi) leads to... 7 Li + This significantly reduces the 6Li isotope ratio compared to the natural ratio. Additionally, Li containing Li aqueous solution AS'... + The concentration decreases, causing the Li in the electrolyte membrane 21 relative to the voltage V3 to decrease. +The reduced mobility leads to a decrease in energy efficiency, therefore it is preferable to replace the Li-containing aqueous solutions AS' and ASi in the replenishment tank 1z and the supply tank 11.

[0114] (First variation) The lithium isotope concentration device 10C involved in this embodiment replenishes Li to a Li-containing aqueous solution ASi using a known lithium recovery method. + Therefore, Li can also be recovered from seawater and other sources to replenish Li-containing aqueous solutions (ASi). + However, in seawater with low Li content... + In aqueous solutions of concentration, Li + Mobility via Li + Diffusion to the surface of electrolyte membrane 21 is rate-limited, thus the mobility is difficult to increase relative to voltage V3, resulting in low energy efficiency. Furthermore, chloride ions in seawater degrade the catalytic activity of the fourth electrode 41; additionally, chloride ions adsorbed on the surface of electrolyte membrane 21 further degrade the catalytic activity of Li. + The migration rate decreases. Therefore, in order to reduce the concentration of Li... + Efficiently replenishing Li in aqueous solution + The following structure is adopted.

[0115] like Figure 16 As shown, the lithium isotope concentration apparatus 10D according to the first modification of the second embodiment of the present invention includes: a processing tank 1B; an electrolyte membrane (lithium-ion conductive electrolyte membrane for lithium replenishment) 21; an electrolyte membrane (lithium-ion conductive electrolyte membrane) 22; a first electrode (porous electrode) 31; a second electrode (porous electrode) 32; a third electrode (sub-electrode) 33; a fourth electrode (first electrode for lithium replenishment) 41; a fifth electrode (second electrode for lithium replenishment) 42; a sixth electrode 44; a power supply device 5 with a built-in main power supply 51 and a sub-power supply 52; a power supply (power supply for lithium replenishment) 53; a power supply 55; an ion exchange membrane 8; and a stirrer (circulation mechanism) 6. The processing tank 1B is divided into four sections via ion exchange membranes 8 and electrolyte membranes 21 and 22, in the following order: a raw material tank 1y containing a Li-containing aqueous solution SW; a replenishment tank (lithium replenishment tank) 1z containing a Li-containing aqueous solution AS'; a supply tank (first tank) 11 containing a Li-containing aqueous solution ASi; and a recovery tank (second tank) 12 containing a 6Li recovery aqueous solution ASo. The lithium isotope concentration device 10D is relative to the lithium isotope concentration device 10C according to the second embodiment (see...). Figure 14The lithium isotope concentration apparatus 10D adds an ion exchange membrane 8 that separates the processing tank 1B from the replenishment tank 1z side of the electrolyte membrane 21, a sixth electrode 44 disposed in the raw material tank 1y separated from the replenishment tank 1z by the ion exchange membrane 8, and a power supply 55 connected between the electrodes 44 and 41. Furthermore, in the lithium isotope concentration apparatus 10D, the fourth electrode 41 is configured to be in surface contact with the replenishment tank 1z side of the electrolyte membrane 21. Other than this, the structure is the same as that of the lithium isotope concentration apparatus 10C according to the above embodiment, and may also include a cooling device 7, a liquid level sensor, an exhaust mechanism, etc., as needed.

[0116] Ion exchange membrane 8 conducts at least Li + The cation. Accordingly, the Li-containing aqueous solution AS' in the replenishment tank 1z is free of Cl. - Isohalide ions. Ion exchange membrane 8 is suitable for use as a cation exchange membrane that allows cations to pass through while shielding anions; it only allows Li... + K + Na + The ion exchange membranes include monovalent cation-selective ion exchange membranes that allow monovalent cations to pass through, and bipolar monovalent ion-selective ion exchange membranes that allow monovalent ions to pass through. These ion exchange membranes can be made of known membranes; for example, as cation exchange membranes, SELEMION CMV (manufactured by AGC Engineering Co., Ltd.) and NEOSEPTA CSE (manufactured by ASTOM Co., Ltd.) can be used; as monovalent cation-selective ion exchange membranes, SELEMION CSO (manufactured by AGC Engineering Co., Ltd.) can be used; and as bipolar monovalent ion-selective ion exchange membranes, NEOSEPTACIMS (manufactured by ASTOM Co., Ltd.) can be used. In the lithium isotope concentration apparatus 10D, it is preferable that the interval between the sixth electrode 44 and the fourth electrode 41 is short. Therefore, it is preferable that the ion exchange membrane 8 is arranged such that the interval between it and the electrolyte membrane 21 (the fourth electrode 41) is shortened. Therefore, it is preferable that the replenishment tank 1z is short in the separation direction of the processing tank 1B.

[0117] The sixth electrode 44 is arranged in pair with the fourth electrode 41, and is used to make the Li-containing aqueous solution SW contain Li. +The cations move into the Li-containing aqueous solution AS', and in the Li-containing aqueous solution AS', the surface of the electrolyte membrane 21 becomes an electrode with a relatively low potential. The sixth electrode 44 is preferably arranged parallel to the fourth electrode 41 in the feed tank 1y, and is also preferably arranged in a way that shortens the interval with the fourth electrode 41 by being separated by an ion exchange membrane 8. In addition, the sixth electrode 44 is preferably shaped like a mesh to increase the contact area with the Li-containing aqueous solution SW. The sixth electrode 44 is formed of an electrode material that has electronic conductivity and is stable when a voltage is applied in the Li-containing aqueous solution SW, and is further preferably a material that has catalytic activity for the reaction of the following formula (1). In the case that the Li-containing aqueous solution SW contains halide ions, the sixth electrode 44 is preferably also subjected to its oxidation reaction, for example, if it is chloride ions (Cl). - The material is catalytically active for the reaction of the following formula (12). As such an electrode material, the sixth electrode 44 is preferably, for example, carbon (C), platinum (Pt), or carbon with platinum particles supported on it. [Chemical Formula 6] 2Cl - →Cl2↑+2e - ···(12)

[0118] Power supply 55, like power supply 53, is a DC power supply. Its positive terminal is connected to the sixth electrode 44, and its negative terminal is connected to the fourth electrode 41, i.e., connected in series with the positive terminal of power supply 53. Power supply 55 applies a voltage V5, generating an electric field E3 (refer to...) in the Li-containing aqueous solutions SW and AS′. Figure 17 ), so that the Li-containing aqueous solution SW contains Li + The cations migrate towards the Li-containing aqueous solution AS′, thereby creating a relatively low potential on the surface of the electrolyte membrane 21 within the Li-containing aqueous solution AS′, allowing the Li... + The surface becomes non-uniform due to electrostatic attraction. Power supplies 53 and 55 are preferably configured to be switched on (ON) and switched off (OFF) independently of each other.

[0119] The Li-containing aqueous solution SW is used in the operation of the lithium isotope concentration unit 10D to convert Li into Li in the Li-containing aqueous solution ASi. + The Li source, whose concentration is maintained at a high level, supplies Li to the Li-containing aqueous solution ASi via the Li-containing aqueous solution AS′. The Li-containing aqueous solution SW is a Li source other than lithium-ion Li. + In addition, it also contains K + Na + Ca 2+ Other metal ions M n+An aqueous solution. Examples of such an aqueous solution include seawater, waste brine from seawater after salt collection, groundwater such as hot spring water, and aqueous solutions after the pH of used lithium-ion batteries have been dissolved in acid and then adjusted. The Li-containing aqueous solution AS′ is the same as described above, but contains a naturally occurring proportion of... 7 Li and 6 Li cations 7 Li + , 6 Li + An aqueous solution, such as a lithium hydroxide (LiOH) aqueous solution, is used. However, in this modified example, pure water may also be used before the operation (isotope concentration) of the lithium isotope concentration apparatus 10D begins. Similar to the first embodiment, at the start of operation of the lithium isotope concentration apparatus 10D, an aqueous solution containing Li, ASi, and... 6 Li recovery uses aqueous solutions of ASO, such as saturated or supersaturated aqueous solutions of LiOH, as well as pure water.

[0120] Reference Figure 17 A lithium isotope concentration method according to the lithium isotope concentration apparatus according to the first modification of the second embodiment of the present invention will be described. In the lithium isotope concentration apparatus 10D according to this modification, it is preferable to contain pure water as a Li-containing aqueous solution AS′ in the replenishment tank 1z. First, the power supply 55 is driven to make the Li-containing aqueous solution AS′... + Cations move from the Li-containing aqueous solution SW contained in the raw material tank 1y, and Li in the Li-containing aqueous solution AS′ + Once a certain concentration is reached, power supply 53 is further activated. The following describes the Li... + The movement of the Li-containing aqueous solution AS′ in the replenishment tank 1z to the Li-containing aqueous solution ASi in the supply tank 11 will be explained. Furthermore, in Figure 17 The mixer 6 is omitted from the text.

[0121] In the lithium isotope concentration apparatus 10D, power supplies 55 and 53, connected in series, can be considered as a single power supply (referred to as power supply 55-53). Power supply 55-53 applies a positive voltage (V5+V3) relative to the fifth electrode 42 to the sixth electrode 44. Simultaneously, power supply 53 applies a positive voltage V3 relative to the fifth electrode 42 to the fourth electrode 41. Thus, the following reactions occur in the feed tank 1y and the replenishment tank 1z. Near the sixth electrode 44 and the fourth electrode 41, OH- ions from the Li aqueous solutions SW and AS′ react... - The reaction shown in equation (1) occurs, releasing electrons e. - This produces H2O and O2, releasing electrons (e) to the 6th electrode 44 and the 4th electrode 41. - In the Li-containing aqueous solution SW containing Cl -In the case of the reaction of equation (12) occurring further near the sixth electrode 44, electrons e are released. - Cl2 is produced. In Li-containing aqueous solutions SW and AS′, as OH... - Due to the reduction of other anions, in order to maintain charge balance, Li in the Li-containing aqueous solution AS′ occurs on the surface of electrolyte membrane 21, i.e., near the fourth electrode 41. + The reaction of equation (2) that moves into electrolyte membrane 21. [Chemical Formula 7] 2Cl - →Cl2↑+2e - ···(12) Li + →Li + (electrolyte)···(2)

[0122] Furthermore, between electrodes 44 and 41 containing the Li aqueous solution SW and AS′, an electric field E3 is generated by applying a voltage V5 from the power supply 55, creating a potential gradient at the sixth electrode 44 that is higher than the surface of the electrolyte membrane 21 where the fourth electrode 41 is located. Therefore, the OH- in the Li aqueous solution SW... - and Cl - It is attracted by the sixth electrode 44 due to electrostatic attraction. On the other hand, the Li-containing aqueous solution SW contains Li. + The cations move along the electric field E3 and are attracted to the surface of the electrolyte membrane 21 through the ion exchange membrane 8.

[0123] On the other hand, similar to the above embodiment, the following reaction occurs in the supply tank 11. Near the fifth electrode 42, H2O in the Li-containing aqueous solution ASi supplies electrons e. - This leads to the reaction shown in equation (3), which produces H2 and OH. - Therefore, with OH - The increase in charge leads to the formation of Li in the electrolyte membrane 21 near the electrolyte membrane 21 in order to maintain charge balance. + The reaction of the following formula (4) is moved. [Chemical Formula 8] 2H2O+2e - →2OH - +H2↑···(3) Li + (electrolyte)→Li + ···(4)

[0124] In the lithium isotope concentration apparatus 10D of this modified example, as described above, a voltage V5 is applied by a power supply 55 to form a potential gradient in the Li-containing aqueous solution AS′, thereby allowing Li to act as a cation. + The Li is attracted to the surface of the electrolyte membrane 21 (the fourth electrode 41) by electrostatic attraction, resulting in a relatively high concentration in its vicinity. Therefore, even Li containing Li aqueous solution AS′ + Low concentration, Li + It can also diffuse sufficiently to the surface of the electrolyte membrane 21, and the Li in the electrolyte membrane 21 + The migration rate will not decrease.

[0125] The stronger the electric field E3, the more Li + The more Li is attracted to the surface of the electrolyte membrane 21, the higher the concentration of Li in the electrolyte membrane 21 can be. + Mobility. However, in order to enhance the electric field E3 and increase the voltage V5, when the voltage required for water electrolysis (+1.229V vs. SHE, 25℃) is reached, the reaction of formula (3) occurs near the fourth electrode 41 in the Li-containing aqueous solution AS′, producing H2. Because this reaction accepts electrons e - Therefore, electron e - The movement is opposite to the reaction in equation (1) above near the fourth electrode 41. When the surface near the fourth electrode 41, i.e., the side of the replenishment tank 1z of the electrolyte membrane 21, is at the potential for H2 generation, regardless of the potential difference between the two surfaces of the electrolyte membrane 21, a portion of the transition metal ions constituting the electrolyte membrane 21 is reduced (e.g., if the electrolyte membrane 21 is LLTO, then Ti 4+ +e - →Ti 3+ The potential of ) exhibits electron transport on the electrolyte membrane 21. As a result, as described above, Li + The energy efficiency of movement within the electrolyte membrane 21 decreases sharply. Therefore, the voltage V5 is less than the voltage at which water electrolysis occurs.

[0126] Furthermore, even if the voltage V5 is less than the voltage at which water electrolysis occurs, if it exceeds a certain magnitude relative to the voltage V3, current flows from the fourth electrode 41 to the negative terminal of the power supply 55, meaning the fourth electrode 41 accepts electrons e. - The reaction of formula (3) occurs nearby, producing H2. As a result, electron transport is exhibited in the electrolyte membrane 21. Therefore, the voltage V5 is preferably larger in the range where the current does not flow from the fourth electrode 41 to the negative terminal of the power supply 55. Therefore, for example, a galvanometer can be connected in series with the fourth electrode 41 (the galvanometer is connected between the connection between the power supply 55 and the power supply 53 and the fourth electrode 41), and the voltages V3 and V5 can be applied while measuring the current.

[0127] In this modified example, the feed tank 1y of the lithium isotope concentration apparatus 10D can also be opened to the sea through a filter or the like. Furthermore, the lithium isotope concentration apparatus 10D does not have an ion exchange membrane 8, meaning it is similar to the lithium isotope concentration apparatus 10C described in the above embodiment. The processing tank 1B can be divided into three sections, and seawater or the like can be contained in the replenishment tank 1z as a Li-containing aqueous solution AS'. By applying a voltage V5, Cl in the Li-containing aqueous solution AS' is... - Anions are far from the fourth electrode 41 and the electrolyte membrane 21, therefore even without the ion exchange membrane 8, Cl - It is also difficult to adsorb onto the surface of the electrolyte membrane 21. In addition, the fourth electrode 41 is difficult to adsorb onto the surface of the electrolyte membrane 21 due to Cl. - And deterioration, therefore Li in electrolyte membrane 21 + The migration rate will not decrease. Additionally, the Li in the Li-containing aqueous solution AS' + The Li is attracted to the surface of the fourth electrode 41, i.e., the electrolyte membrane 21, thereby increasing the concentration of Li in the electrolyte membrane 21. + Mobility. Furthermore, since there is no ion exchange membrane 8 between the 6th electrode 44 and the 4th electrode 41, the electric field E3 can be made stronger relative to the voltage V5. Additionally, even without the ion exchange membrane 8, a LiOH aqueous solution can be contained in the replenishment tank 1z as a Li-containing aqueous solution AS', similar to the embodiment described above. Even with the Li-containing aqueous solution AS', the Li... + The concentration of Li in electrolyte membrane 21 decreased over time. + The mobility is also difficult to reduce, thus reducing the replacement frequency of the Li-containing aqueous solution AS'. In this case, when the Li in the Li-containing aqueous solution AS'... + When the concentration drops below a certain value, voltage V5 can be applied by power supply 55.

[0128] According to the lithium isotope enrichment device 10D involved in this modification, it is possible to replenish Li from Li-containing aqueous solutions SW, such as seawater, to Li-containing aqueous solutions ASi. + Therefore, for the Li-containing aqueous solution ASi, pure water can also be contained in the supply tank 11 before the start of operation (isotope concentration) of the lithium isotope concentration device 10D, and Li can be transferred from the Li-containing aqueous solution SW through the Li-containing aqueous solution AS'. + The lithium isotope concentration device 10D is a cascaded lithium recovery and isotope concentration composite device that integrates a lithium recovery device, a lithium isotope concentration device 10, and a processing tank. In this case, firstly, the driving power supplies 53 and 55 are used to process the lithium isotope concentration device 10, which is a lithium recovery and isotope concentration composite device that integrates a lithium recovery device, a lithium isotope concentration device 10, and a processing tank. + A LiOH aqueous solution (e.g., a LiOH saturated aqueous solution) with the target concentration is prepared, and then the power supply device 5 is driven to start isotope concentration.

[0129] (Second variation) The lithium isotope concentration device 10D involved in the above-described modification can be a lithium recovery and isotope concentration combined device. However, in order to convert pure water into a high concentration of LiOH saturated aqueous solution... + Aqueous solutions require a large amount of Li + The movement, from the initial stage to the start of isotope concentration, takes time. Therefore, in order to improve Li without exhibiting electron transport in electrolyte membrane 21... + Mobility is calculated using the following structure.

[0130] like Figure 18 As shown, the lithium isotope concentration apparatus 10E according to the second variation of the second embodiment of the present invention includes a processing tank 1B, an electrolyte membrane (lithium-ion conductive electrolyte membrane for lithium replenishment) 21, an electrolyte membrane (lithium-ion conductive electrolyte membrane) 22, a first electrode (porous electrode) 31, a second electrode (porous electrode) 32, a third electrode (sub-electrode) 33, a fourth electrode (first electrode for lithium replenishment) 41, a fifth electrode (second electrode for lithium replenishment) 42A, a sub-electrode 43, a sixth electrode 44, a power supply device 5 with a built-in main power supply 51 and a sub-power supply 52, a power supply (power supply for lithium replenishment) 53, a power supply 54, a power supply 55, an ion exchange membrane 8, and a stirrer (circulation mechanism) 6. The processing tank 1B is divided into four sections via ion exchange membranes 8 and electrolyte membranes 21 and 22, in the following order: a raw material tank 1y containing a Li-containing aqueous solution SW; a replenishment tank (lithium replenishment tank) 1z containing a Li-containing aqueous solution AS'; a supply tank (first tank) 11 containing a Li-containing aqueous solution ASi; and a recovery tank (second tank) 12 containing a 6Li recovery aqueous solution ASo. The lithium isotope concentration device 10E is the lithium isotope concentration device 10D according to the first modification of the second embodiment (see reference). Figure 16 An additional structure is added, in which the fifth electrode 42A, like the fourth electrode 41, has a porous structure and is in contact with the electrolyte membrane 21. A secondary electrode 43 is disposed in the supply tank 11 opposite to and away from the electrolyte membrane 21 and the fifth electrode 42A. A power supply 54 is connected between the electrodes 42A and 43. Other than this, the structure is the same as that of the lithium isotope concentration apparatus 10D described in the above-described modification. Depending on the requirements, it may also include a cooling device 7, a liquid level sensor, an exhaust mechanism, etc.

[0131] The fifth electrode 42A is arranged in pair with the fourth electrode 41 and is used to apply a voltage between the two sides of the electrolyte membrane 21. Furthermore, in the Li-containing aqueous solution ASi, it is the electrode that makes the potential of the side (back side) of the electrolyte membrane 21 on the supply tank 11 side relatively higher. Therefore, the fifth electrode 42A has a porous structure and is arranged to contact the side of the electrolyte membrane 21 on the supply tank 11 side. The fifth electrode 42A is formed of an electrode material that has electronic conductivity and is stable when a voltage is applied in the Li-containing aqueous solution ASi. More preferably, it is a material that has catalytic activity for the reactions of formula (1) and formula (4), and even more preferably, it is a material that is easily processed into the above shape. For example, platinum (Pt) is preferably used as such an electrode material for the fifth electrode 42A. [Chemical Formula 9] Li + (electrolyte)→Li + ···(4)

[0132] The secondary electrode 43 is an electrode used to form a potential lower than the back surface of the electrolyte membrane 21 in the Li-containing aqueous solution ASi. It is also an electrode paired with the fourth electrode 41 for applying a voltage. Therefore, in the supply tank 11, the secondary electrode 43 is preferably configured not to contact the electrolyte membrane 21 and the fifth electrode 42A, and is positioned opposite the fifth electrode 42A, preferably parallel to it. Furthermore, as described later, the secondary electrode 43 is preferably positioned close to the fifth electrode 42A to the extent that it does not short-circuit. Additionally, the secondary electrode 43 is preferably of a mesh-like shape to increase the contact area with the Li-containing aqueous solution ASi. The secondary electrode 43 is formed of an electrode material that has electronic conductivity and is stable when a voltage is applied in the Li-containing aqueous solution ASi; more preferably, it is a material that has catalytic activity for the reaction of formula (3). Platinum (Pt) is preferred, for example, as such an electrode material for the secondary electrode 43. Alternatively, the secondary electrode 43 can also be made of carbon (C), copper (Cu) or stainless steel that is stable at a potential lower than the potential at which the reaction of the following formula (3) occurs, and more preferably, Pt particles that act as catalysts are supported on their surfaces. [Chemical Formula 10] 2H2O+2e - →2OH - +H2↑···(3)

[0133] Power supply 54, like power supply 53, is a DC power supply. Its positive terminal is connected to the fifth electrode 42A, and its negative terminal is connected to the secondary electrode 43, i.e., it is connected in series with the negative terminal of power supply 53. Power supply 54 applies a voltage V4, which creates a potential in the Li-containing aqueous solution ASi that is lower than the back surface of the electrolyte membrane 21, thereby suppressing the electronic conductivity of the electrolyte membrane 21.

[0134] Reference Figure 19 A lithium isotope concentration method according to a second modification of the second embodiment of the present invention will be described. In the lithium isotope concentration apparatus 10E according to this modification, pure water is contained in the replenishment tank 1z and the supply tank 11 as a Li-containing aqueous solution AS′, ASi. Furthermore, compared with the lithium isotope concentration apparatus 10D according to the first modification (see...),... Figure 17 Similarly, preferably, the power supply 55 is driven first to make the Li-containing + Cations move from the Li-containing aqueous solution SW contained in the raw material tank 1y, and Li in the Li-containing aqueous solution AS′ + Once a certain concentration is reached, power supplies 53 and 54 are then activated. The following discussion concerns Li... + The movement of the Li-containing aqueous solution AS′ in the replenishment tank 1z to the Li-containing aqueous solution ASi in the supply tank 11 will be explained. Furthermore, in Figure 19 The mixer 6 is omitted from the text.

[0135] In the lithium isotope concentration apparatus 10E, the power supplies 55, 53, and 54 connected in series can be considered as a single power supply (referred to as power supply 55-53-54). Similarly, power supplies 53 and 54 can be considered as a single power supply (referred to as power supply 53-54). Power supply 55-53-54 applies a positive voltage (V5+V3+V4) relative to the sub-electrode 43 to the sixth electrode 44. At the same time, power supply 53-54 applies a positive voltage (V3+V4) relative to the sub-electrode 43 to the fourth electrode 41. Thus, in the raw material tank 1y and the replenishment tank 1z, similar to the lithium isotope concentration apparatus 10D described above, the reaction of formula (1) occurs near the sixth electrode 44 and the fourth electrode 41, and the reaction of formula (12) occurs near the sixth electrode 44. Accompanying this, Li in the Li aqueous solution AS′ containing Li occurs near the fourth electrode 41. + The reaction of equation (2) that moves into electrolyte membrane 21. [Chemical Formula 11] 2Cl - →Cl2↑+2e - ···(12) Li + →Li + (electrolyte)···(2)

[0136] On the other hand, the following reaction occurs in the supply tank 11. Near the secondary electrode 43, H2O in the Li-containing aqueous solution ASi is supplied with electrons by applying a voltage (V3+V4) from the power supply 53-54. -This leads to the reaction shown in equation (3), producing H2 and OH. - Therefore, H + The amount of Li in the electrolyte membrane 21 decreases near the secondary electrode 43, thereby causing Li to form on the back side of the electrolyte membrane 21, i.e., near the fifth electrode 42A. + The reaction proceeds to the Li-containing aqueous solution ASi as shown in equation (4). Simultaneously, power supply 54 applies a positive voltage V4 relative to the secondary electrode 43 to the fifth electrode 42A. This voltage V4 is based on the specified magnitudes of voltages V3 and V5. Therefore, near the fifth electrode 42A, OH- in the Li-containing aqueous solution ASi reacts... - The reaction shown in equation (1) occurs, thereby transferring electrons e - Released to the fifth electrode 42A, thereby producing H2O and O2. As a result, near the fifth electrode 42A, an imbalance of excess cation charge arises due to the reactions of equation (1) and (4). However, to compensate for the deficiency of cations generated near the secondary electrode 43 due to the reaction of equation (3), Li + Along the electric field E4 generated by the applied voltage V4, the electric field rapidly moves from the vicinity of the fifth electrode 42A to the vicinity of the secondary electrode 43, thereby eliminating the charge imbalance in the Li-containing aqueous solution ASi. Furthermore, the relative magnitudes of voltages V3 and V4 will be described later. [Chemical Formula 12] 2H2O+2e - →2OH - +H2↑···(3) Li + (electrolyte)→Li + ···(4)

[0137] In the lithium isotope enrichment apparatus 10E according to this modification, the effect of applying voltage V5 is the same as that of the lithium isotope enrichment apparatus 10D according to the first modification. In this modification, by further applying voltage V4, an appropriate potential difference with the fifth electrode 42A as the positive electrode is generated in the Li-containing aqueous solution ASi. Therefore, electrons e supplied from the secondary electrode 43 to the Li-containing aqueous solution ASi... - The fifth electrode 42A moves from the back side of the electrolyte membrane 21 towards the positive terminal of the power supply 54, and the potential of the fifth electrode 42A is maintained at the O2 generation potential. Since the O2 generation potential is higher than the reduction potential of the transition metal ions constituting the electrolyte membrane 21, no electrons are conducted regardless of the potential difference between the two sides of the electrolyte membrane 21. -Therefore, the voltage V3 can be set to a voltage greater than the applied voltage required to bring the electrolyte membrane 21 to the reduction potential of at least one transition metal ion constituting the electrolyte membrane 21. In other words, when such a large voltage V3 is applied without applying voltage V4, electrons e are captured from the negative electrode side (supply tank 11 side) of the electrolyte membrane 21. - The electrolyte membrane 21 is used to reduce transition metal ions. However, in this modified example, as described above, by applying voltage V4, the electrolyte membrane 21 does not reach the reduction potential of the transition metal ions, and the electrolyte membrane 21 does not transfer electrons e. - .

[0138] When voltage V4 is not sufficiently large relative to voltage V3, current flows from the fifth electrode 42A to the negative terminal of power supply 53, that is, the fifth electrode 42A receives electrons e. - The reaction of formula (3) occurs near it, thereby producing H2. As a result, electron transport is exhibited in the electrolyte membrane 21. Therefore, the voltage V4 is set to a value such that no current flows from the fifth electrode 42A to the negative electrode of the power supply 53. The lower the resistance (resistance of the Li aqueous solution ASi) between the fifth electrode 42A and the secondary electrode 43, the smaller the voltage V4 can be. Therefore, it is preferable that the distance between the fifth electrode 42A (electrolyte membrane 21) and the secondary electrode 43 is short. However, as the voltage V4 becomes larger at such a value, the current flowing from the power supply 54 to the fifth electrode 42A increases, and the occurrence of O2 near the fifth electrode 42A (reaction of formula (1)) and the occurrence of H2 near the secondary electrode 43 (reaction of formula (3)) increase to the value of Li + As the amount of movement increases, energy efficiency decreases. Therefore, for example, a galvanometer can be connected in series to the fifth electrode 42A (the connection between the galvanometer and the power supply 53 and 54 is between the galvanometer and the fifth electrode 42A) to apply voltage V4 while measuring the current.

[0139] When Li-containing aqueous solution ASi is used as Li + When the target concentration is, for example, a saturated LiOH aqueous solution, the power supply device 5 is used to initiate isotope concentration. Additionally, as described in the above embodiments, Li₂ concentration is achieved in the electrolyte membrane 21 through continuous energization of the power supply 53. + The movement of Li and the Li generated in the electrolyte membrane 22 due to the intermittent energization of the main power supply 51 + Compared to other methods, this allows for a greater amount of movement at regular intervals. Therefore, after isotope enrichment begins, the voltage V3 can be reduced, and the voltage V5 can be reduced as needed, and power supply 54 can be stopped (see reference). Figure 18 , Figure 17 ).

[0140] The lithium isotope enrichment devices 10C, 10D, and 10E according to the second embodiment and its modifications can also be configured as the lithium isotope enrichment device 10B according to the modification of the first embodiment (see [reference]). Figure 8 The supply tank 11 is connected to the lithium isotope concentration unit 10C, 10D, 10E. Similarly, the lithium isotope concentration units 10C, 10D, 10E can also be configured to connect with the multi-stage lithium isotope concentration units 20, 20A, 20B (see reference). Figure 10 , Figure 11A and Figure 11B , Figure 12 The supply tank 11 is connected. [Example]

[0141] The foregoing has described the methods for implementing the present invention, including the lithium isotope enrichment apparatus and method. The following describes embodiments that demonstrate the effectiveness of the present invention. Furthermore, the present invention is not limited to these embodiments and methods; various modifications and alterations made based on these descriptions are naturally included within the scope of the present invention.

[0142] against Figure 1 and Figure 8 The lithium isotope enrichment apparatus shown in the embodiments and variations of the present invention measures the change in the lithium isotope ratio by changing the applied voltage conditions.

[0143] (Construction of a lithium isotope concentration device) The lithium isotope enrichment device used 50mm×50mm, 0.5mm thick plate-shaped La... 0.57 Li 0.29 TiO3 (lithium-ion conductive ceramic LLTO, manufactured by Toho Titanium Co., Ltd., Japan) is used as the electrolyte membrane. On the central portion of each of the two sides of this electrolyte membrane, 10 μm thick, 0.5 mm wide, and spaced 0.5 mm apart, grid-like electrodes of 19.5 mm × 20.5 mm are formed as the first and second electrodes (porous structure electrodes). Leads for connecting to a power source are also formed on these electrodes. The first electrode, second electrode, and lead are formed by screen printing Pt paste onto the surface of the electrolyte membrane and firing at 900°C for 1 hour in atmospheric air. A 20 mm × 20 mm Pt mesh electrode is used as the third electrode (sub-electrode). The electrolyte membrane with the electrodes is mounted in a processing tank made of acrylic resin plate, which is divided into a supply tank and a recovery tank. In the supply tank, the third electrode is positioned directly opposite the first electrode on the surface of the electrolyte membrane (distance between the third electrode and the electrolyte membrane: 50 mm). The processing tank is then housed in a thermostatic bath with temperature control. A main power supply is then connected between the first and second electrodes, with the first electrode as the positive terminal, and an auxiliary power supply is connected between the third and first electrodes, thus creating a lithium isotope concentration device.

[0144] Input into the supply tank of the lithium isotope concentration unit 7 Li: 92.23 mol%, 6 A lithium hydroxide aqueous solution containing 7.77 mol% and 1 mol / L of Li is used as the Li-containing aqueous solution. 150 ml of pure water is added to each of the recovery tanks as... 6 The lithium recovery aqueous solution was used to completely immerse the first, second, and third electrodes. Then, the liquid temperature of the lithium hydroxide aqueous solution and pure water in the treatment tank was adjusted to 20°C.

[0145] (Lithium isotope concentration experiment) The voltage V1 applied between the first and second electrodes by the main power supply is set to: LLTO (electrolyte membrane) display Li + Conductivity, and exhibiting no electronic conductivity or sufficiently low electronic conductivity, is 2.0V. Additionally, the applied voltage V2, supplied by the auxiliary power supply between the third and first electrodes, is set to 1.0V (equivalent to 200V / m). As Example 1, this is performed alternately and repeatedly in a manner that alternates between applying a 1.0-second voltage +V1 (the first electrode is the positive terminal of the main power supply) and applying a 0.5-second voltage -V2 (the third electrode is the negative terminal of the auxiliary power supply) with a 0.5-second voltage-free period (see reference). Figure 2 (See Table 1). As Example 2, the process was repeated in the following order: applying voltage +V1 for 1.0 second, applying voltage -V2 for 0.5 seconds, and applying voltage +V2 for 0.5 seconds (the third electrode is the positive terminal of the auxiliary power supply) during a period of no voltage application with a 0.5-second interval before and after applying voltage +V1 (see Table 1). Figure 9 (See Table 1). Additionally, as Comparative Example 1, the application of voltage +V1 for 1.0 seconds and the cessation of application for 1.5 seconds were performed alternately and repeatedly. Examples 1, 2, and Comparative Example 1 were performed until the cumulative application time of voltage +V1 reached 3600 seconds. Furthermore, as Comparative Example 2, voltage +V1 was continuously energized for 1 hour (3600 seconds). The aqueous solutions in the supply tank and recovery tank were stirred during the voltage application period. Table 1 shows voltage V1, V2, voltage application period, and running time. In Table 1, the voltage application period is indicated by parentheses () indicating the application time; time alone indicates no application period.

[0146] After the experiment, the aqueous solution in the recovery tank was recovered, and the concentration of [unspecified substance] in the aqueous solution was determined using an inductively coupled plasma mass spectrometry (ICP-MS) device (Elan drc-e, manufactured by PerkinElmer Co., Ltd.). 7 Li, 6 The amount of Li. 7 Li, 6 Li is used to calculate the cumulative applied time of voltage + V1 per hour. +Movement ( 7 Li, 6 (total amount of Li), Li per hour of operation time + Movement and 6 Li isotope segregation coefficient. 6 The Li isotope separation coefficient is (the aqueous solution in the recovery tank after applying voltage) 6 Li / 7 Li) molar ratio) / (Li hydroxide aqueous solution in the supply tank before voltage application) 6 Li / 7 Li (molar ratio). See Table 1 and... Figure 20 Li + The displacement (Li of the average application time (energizing time) per voltage + V1) + Movement, Li + Migration rate), average Li per runtime + Movement and 6 Li isotope segregation coefficient.

[0147] [Table 1]

[0148] As shown in Table 1 and Figure 20 As shown, compared to Comparative Example 2, which was continuously energized, Examples 1, 2, and 1, in which a voltage +V1 was intermittently applied between the two sides of the electrolyte membrane, showed improvements. 6 The Li isotope separation coefficients were all high. Furthermore, in Examples 1 and 2, where a voltage -V2 was applied between the third and first electrodes of the Li-containing aqueous solution in the supply tank during the period when the applied voltage +V1 was stopped, compared to Comparative Example 1 where no voltage was applied, 6 Li has a high isotope separation coefficient. Therefore, it can be considered that in a Li-containing aqueous solution, by applying a negative voltage to a third electrode located away from the electrolyte membrane surface relative to the electrolyte membrane surface, it is possible to ionize the Li adsorbed on the electrolyte membrane surface. + It is easier to disengage, and this is further enhanced by intermittently applying voltage +V1. 6 Li concentration effect. Furthermore, in Example 2, where voltage +V2 is applied after voltage -V2 is applied, and the applied voltage +V2 is applied during the period when voltage +V1 is stopped, Li... + The mobility was significantly higher than that of Example 1, approximately 3.7 times, with an average Li per runtime. + The movement is also approximately three times greater. Therefore, it can be considered that by applying voltage +V2, the Li distortion that occurred immediately after resuming the application of voltage +V1 due to the application of voltage -V2 can be eliminated. + The decrease in mobility, and further improvement of Li + Mobility, thereby enabling simultaneous improvement in both time and energy efficiency. [Explanation of reference numerals in the attached figures]

[0149] 10, 10B, 10C, 10D, 10E: Lithium isotope concentration unit; 20, 20A, 20B: Multi-stage lithium isotope concentration unit; 1, 1A, 1B: Processing tank; 11: Supply tank (tank 1); 12: Recovery tank (tank 2); 1z: Replenishment tank (lithium replenishment tank); 2: Electrolyte membrane (lithium-ion conductive electrolyte membrane); 21: Electrolyte membrane (lithium-ion conductive electrolyte membrane for lithium replenishment); 22, 23, 24, 25, 26, 27: Electrolyte membrane (lithium-ion conductive electrolyte membrane); 31: ... 1. Electrode (porous structure electrode); 32. Second electrode (porous structure electrode); 33. Third electrode (secondary electrode); 41. Fourth electrode (first electrode for lithium replenishment); 42, 42A. Fifth electrode (second electrode for lithium replenishment); 50, 50C. Power supply; 5, 5A, 5B. Power supply; 51. Main power supply; 51A. Variable power supply; 52, 52B. Secondary power supply; 53. Power supply (power supply for lithium replenishment); 6. Stirrer (circulation mechanism); 7. Cooling device; ASi: Li-containing aqueous solution; ASo: 6 Li recovery using aqueous solution.

Claims

1. A lithium isotope concentration apparatus having a processing tank divided into a first tank and a second tank, wherein lithium isotopes contained in the first tank are processed in the second tank. 6 Li and 7 Li was recovered from an aqueous solution containing [a substance] compared to the aqueous solution. 6 An aqueous solution of lithium ions with a high isotopic ratio of Li, characterized in that... It comprises a lithium-ion conductive electrolyte membrane, porous electrodes, a secondary electrode, and a power supply device, wherein... The lithium-ion conductive electrolyte membrane separates the processing tank; The porous electrode is configured to contact both sides of the lithium-ion conductive electrolyte membrane. The secondary electrode is disposed in the first tank in a manner that separates it from the surface of the lithium-ion conductive electrolyte membrane on the first tank side and the electrode of the porous structure. The power supply device alternately applies a voltage with the first slot side as the positive terminal to the electrodes of the porous structure, and applies a voltage with the secondary electrode as the negative terminal to the electrode of the porous structure on the first slot side and the secondary electrode. Each time a voltage is applied between the electrodes of the porous structure, lithium ions move from the first tank side to the second tank side in the lithium ion conductive electrolyte membrane; each time a voltage is applied between the electrode of the porous structure and the secondary electrode on the first tank side, lithium ions contained in the aqueous solution in the first tank detach from the surface of the lithium ion conductive electrolyte membrane.

2. The lithium isotope concentration apparatus according to claim 1, characterized in that, The power supply device applies a voltage between the electrode and the secondary electrode of the porous structure on the first slot side, with the electrode of the porous structure on the first slot side being positive, then applies a voltage with the secondary electrode being positive, and then applies a voltage between the electrodes of the porous structure.

3. The lithium isotope concentration apparatus according to claim 1 or 2, characterized in that, The power supply device has a main power supply and a secondary power supply. The main power supply connects the first slot side as the positive electrode between the electrodes of the porous structure. The secondary power supply connects the electrodes of the porous structure on the first slot side and the secondary electrode.

4. The lithium isotope concentration apparatus according to claim 1 or 2, characterized in that, It has a circulation mechanism that circulates the aqueous solution contained in the first tank.

5. The lithium isotope concentration apparatus according to claim 1 or 2, characterized in that, The processing tanks are divided in the order of lithium replenishment tank, the first tank, and the second tank. It also includes a lithium-ion conductive electrolyte membrane for lithium replenishment, a first electrode for lithium replenishment, a second electrode for lithium replenishment, and a power supply for lithium replenishment, wherein... The lithium replenishment tank is separated from the first tank by a lithium-ion conductive electrolyte membrane. The first electrode for lithium replenishment is disposed inside the lithium replenishment tank; The second electrode for lithium replenishment is disposed in the first tank in a manner that is in contact with or opposite to the lithium-ion conductive electrolyte membrane for lithium replenishment; The lithium replenishment power supply uses the first lithium replenishment electrode as the positive electrode and connects it between the first lithium replenishment electrode and the second lithium replenishment electrode. Lithium ions are released from the lithium replenishment tank in the form of lithium ions. 6 Li and 7 The aqueous solution of Li moves toward the aqueous solution contained in the first tank.

6. The lithium isotope concentration apparatus according to claim 1 or 2, characterized in that, It has a cooling device that cools the lithium-ion conductive electrolyte membrane.

7. A multi-stage lithium isotope concentration apparatus, comprising connecting two or more lithium isotope concentration apparatuses as described in claim 1 or 2 in such a manner that the processing tank is integrated, characterized in that, The lithium-ion conductive electrolyte membranes of the lithium isotope concentration device are spaced apart from each other in such a way that the integrated processing tank is divided into three or more tanks. The second tank of one of the two adjacent lithium isotope concentration units also serves as the first tank of the other.

8. The multi-stage lithium isotope concentration device according to claim 7, characterized in that, The power supply devices of the two lithium isotope concentration devices do not simultaneously apply voltage to the electrodes of the porous structure between each other.

9. The multi-stage lithium isotope concentration device according to claim 8, characterized in that, The porous electrode on the second tank side of one of the two lithium isotope concentration devices also serves as the secondary electrode of the other.

10. The multi-stage lithium isotope concentration device according to claim 9, characterized in that, It has a circulation mechanism that circulates the aqueous solution contained in at least one of the separated treatment tanks. In a tank containing an aqueous solution circulated by the circulation mechanism, the secondary electrode is spaced apart from the lithium-ion conductive electrolyte membrane.

11. The multi-stage lithium isotope concentration device according to claim 7, characterized in that, It also includes a lithium-ion conductive electrolyte membrane for lithium replenishment, a first electrode for lithium replenishment, a second electrode for lithium replenishment, and a power supply for lithium replenishment, wherein... The lithium replenishment lithium-ion conductive electrolyte membrane further separates the separated processing tanks by providing a lithium replenishment tank at the end of the first tank side; The first electrode for lithium replenishment is disposed inside the lithium replenishment tank; The second electrode for lithium replenishment is in contact with or opposite to the lithium-ion conductive electrolyte membrane for lithium replenishment in the first tank adjacent to the lithium replenishment tank; The lithium replenishment power supply uses the first lithium replenishment electrode as the positive electrode and connects it between the first lithium replenishment electrode and the second lithium replenishment electrode. Lithium ions are released from the lithium replenishment tank in the form of lithium ions. 6 Li and 7 The aqueous solution of Li moves to the aqueous solution contained in the adjacent first tank of the lithium replenishment tank.

12. The multi-stage lithium isotope concentration device according to claim 7, characterized in that, It has a cooling device that cools the aqueous solution contained in at least one of the separated treatment tanks.

13. A method for concentrating lithium isotopes, comprising, in a processing tank divided into a first tank and a second tank by a lithium-ion conductive electrolyte membrane, extracting lithium isotopes contained in the first tank in the second tank from a sample in the first tank in the form of lithium ions. 6 Li and 7 Li was recovered from an aqueous solution containing [a substance] compared to the aqueous solution. 6 An aqueous solution of lithium ions with a high isotopic ratio of Li, characterized in that... Alternate between steps 1 and 2. In the first step, a positive voltage relative to the second tank side is applied to the first tank side of the porous electrode that is in contact with both sides of the lithium-ion conductive electrolyte membrane, in such a way that lithium ions move from the first tank side to the second tank side in the lithium-ion conductive electrolyte membrane. In the second step, a negative voltage is applied to the sub-electrode disposed in the first tank, which is spaced apart from the porous electrode and the first tank side of the lithium ion conductive electrolyte membrane, in such a way that lithium ions contained in the aqueous solution in the first tank are detached from the surface of the lithium ion conductive electrolyte membrane.

14. The lithium isotope concentration method according to claim 13, characterized in that, The third step involves applying a positive voltage to the secondary electrode relative to the electrode of the porous structure on the first trench side. Repeat the steps in the order of step 1, step 2, and step 3.

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