Ion concentration device and ion concentration method

Abstract

In a lithium isotope concentration device (10) having a structure of a cross type cascade system using a recirculating electrodialysis method and having an n number of stages, each of 2n number of cells (1-n, ... , 1-2, 1-1, 1+1, 1+2, ... , 1+n) is partitioned into an anode chamber (2) and a cathode chamber (3) by a lithium-ion conductive electrolyte membrane, Li+ in an aqueous solution in the anode chamber (2) is moved to the cathode chamber (3) by application of a voltage, a Li source aqueous solution (9S) is supplied to the cathode chamber (3) of the cell (1-1) and the anode chamber (2) of the cell (1+1), and an aqueous solution (9D) is discharged from the anode chamber (2) of the cell (1-n) and an aqueous solution (9E) having a 6Li isotope ratio higher than that of the Li source aqueous solution (9S) is discharged from the cathode chamber (3) of the cell (1+n) at a flow rate lower than that of the aqueous solution (9D).

Description

Ion Concentration Device and Ion Concentration Method

[0001] The present invention relates to an ion concentration device and an ion concentration method.

[0002] Lithium (Li) 7 Li and 6 There are two stable isotopes of Li, and their natural abundance ratios are 92.41 mol% and 7.59 mol%. 7 Li with a mass number of 7 and 6 Li with a mass number of 6 have significantly different properties. For example, 7 Li is used to adjust the pH (hydrogen ion concentration) of the coolant in a nuclear reactor. On the other hand, 6 Li is used to produce tritium, the fuel of a fusion reactor. Therefore, 7 Li and 6 Li have been developed with technologies for concentrating and separating them into a state with less of the other isotope, including the amalgam method, molten salt method, distillation method, and the adsorption method and electrodialysis method (for example, Patent Document 1), which are also methods for selectively recovering lithium ions Li + from seawater and the like.

[0003] The adsorption method and the electrodialysis method 6 Li + because 7 Li + is smaller in mass than 6 Li and has a higher migration speed, and as a result, they utilize the fact that more is recovered. These methods are relatively superior in terms of environmental load and the like compared to the amalgam method that uses a large amount of mercury, the molten salt method and distillation method that heat lithium compounds and the like at high temperatures. However, on the other hand,

[0004] A method for enriching lithium isotopes using lithium recovery technology by electrodialysis will be explained with reference to Figure 44. The lithium isotope enrichment apparatus 101 is a lithium ion conductive electrolyte membrane (electrolyte membrane) 4 with electrodes 151 and 152 made of porous membranes attached to both sides, and the tank 107 is connected to the Li supply chamber 102. 6 The Li recovery chamber 103 is separated from the power supply chamber 102, and a power supply 106 is connected between electrodes 151 and 152. The positive electrode of the power supply 106 is connected to electrode 151 on the Li supply chamber 102 side, and the negative electrode is connected to 6 They are connected to the electrodes 152 on the Li recovery chamber 103 side. An aqueous solution 109a (for example, an aqueous lithium hydroxide (LiOH) solution with a natural isotopic ratio of Li) which serves as the Li source is introduced into the Li supply chamber 102. 6 Li recovery room 103 6 An aqueous solution 109c for Li recovery (for example, pure water at the start of operation) is added.

[0005] When a voltage V is applied by the power supply 106, the reaction shown in equation (1) below occurs near the electrode 151 in the aqueous solution 109a of the Li supply chamber 102, generating oxygen (O2) and hydroxide ions (OH) which are anions. - ) will decrease. On the other hand, 6 In the aqueous solution 109c of the Li recovery chamber 103, the reaction shown in equation (2) below occurs near the electrode 152, generating hydrogen (H2), and OH - The amount increases. Then, in order to maintain the charge balance in aqueous solutions 109a and 109c, the amount of Li in aqueous solution 109a increases. + The reaction shown in equation (3) below involves the movement of Li into the electrolyte membrane 4. + The reaction shown in equation (4) below occurs as the Li on both sides of the electrolyte membrane 4 moves to the aqueous solution 109c. + Due to the electrochemical potential difference, Li + It moves by permeating through the electrolyte membrane 4. Note that in each equation, the Li contained in the electrolyte membrane 4 (electrolyte) + Li + It is represented as (electrolyte).

[0006] From the Li supply chamber 102 side in the electrolyte membrane 4 6 Li to Li recovery room 103+ The movement is due to the difference in mass. 6 Li + The amount of movement per unit time (Li + (Mobility) 7 Li + It is more abundant than the lithium isotope enrichment device 101. 6 The Li isotope separation coefficient β (equation (5) below) is generally very small, less than 1.1, and the isotopic ratio is higher than that of natural Li. 6 It is difficult to obtain Li. In equation (5) below, X d , 1-X d This refers to the Li in aqueous solution 109a before operation of the lithium isotope enrichment apparatus 101. 6 Li 7 This represents the relative abundance of X c , 1-X c Li in aqueous solution 10⁹c 6 Li 7 Represents the ratio of abundance (0 < X) d <1, 0 <X c <1). β = (X c / (1-X) c )) / (X d / (1-X) d )) ... (5)

[0007] Therefore, after the operation of the lithium isotope enrichment device 101 is completed 6 By recovering the aqueous solution 109c from the Li recovery chamber 103, transferring it to the Li supply chamber 102, and repeating the operation, 6 The aqueous solution 109c in the Li recovery chamber 103 6 The Li isotope ratio can be increased in stages. Industrially, as shown in Figure 45, a multi-stage cascade lithium isotope enrichment apparatus 110 is applied, in which multiple lithium isotope enrichment apparatuses (cells) 101 are connected in series. Specifically, in the Li supply chamber 102 of the first stage cell 1011, Li is supplied as a Li source, with a Li isotope ratio equal to the natural ratio. + A Li source aqueous solution 9S (for example, a LiOH aqueous solution) containing is added. Then, after the start of operation, cell 1011 6The aqueous solution 1091 from the Li recovery chamber 103 is supplied to the Li supply chamber 102 of the second-stage cell 1012. Specifically, during operation, the first-stage cell 1011 6 The aqueous solution 1091 is circulated between the Li recovery chamber 103 and the Li supply chamber 102 of the second cell 1012. Then, the 6 The aqueous solution 1092 from the Li recovery chamber 103 is supplied to the Li supply chamber 102 of the third cell 1013. This process is repeated until the nth cell 101 n of 6 From Li recovery room 103 6 Aqueous solution with a high Li isotope ratio 10⁹ n It can be recovered.

[0008] In the lithium isotope enrichment apparatus 110, each of the cells 101 from the 1st stage to the (n-1)th stage contains: 6 A lithium-containing aqueous solution (e.g., a LiOH aqueous solution) with a lithium isotope ratio higher than the natural ratio but still not meeting the target level remains and is contained in the supplied lithium source. 6 Aqueous solution 109 recovered in relation to Li n inside 6 The amount of Li is low, resulting in poor material efficiency. Furthermore, the residual aqueous solution is a low-concentration LiOH solution, and in order to reuse it as a Li source, it requires processes such as evaporating the water to increase the concentration, which makes it inefficient to work with.

[0009] Here, a perfusion electrodialysis method is disclosed for separating ions of the same sign using the ion-selective permeability of the ion-exchange membrane in electrodialysis using an ion-exchange membrane (Non-Patent Documents 2, 3). For example, depending on the type, a cation exchange membrane has selective permeability between cations, and sodium ions (Na + ) against magnesium ions (Mg 2+ ) is 1.5 times more permeable, that is, Mg 2+ It has high selective permeability (selective permeability coefficient 1.5), Na + It is known to have low selective permeability. + , Mg 2+ From an aqueous solution containing Mg 2+To recover the ions, multiple cells divided into two chambers by such cation exchange membranes are connected, but in perfusion electrodialysis, the aqueous solutions from each of the two chambers of the cell are supplied to different cells. This method reduces waste in the supplied ion source.

[0010] Japanese Patent Publication No. 5429658, Japanese Patent Publication No. 6233877, Japanese Unexamined Patent Publication No. 2019-141807, International Publication No. 2022 / 009905, International Publication No. 2023 / 190771, Japanese Patent Publication No. 7029798, International Publication No. 2023 / 003044

[0011] Shunsuke Honda, Kiyoto Shin-mura, Kazuya Sasaki, “Lithium isotope enrichment by electrochemical pumping using solid lithium electrolytes”, Journal of the Ceramic Society of Japan, Volume 126, Issue 5, pp 331-335, May 2018. Haruhiko Ohya, Atsuo Hakamaya, Yasunobu Hiraoka, “Studies on the separation of same-charge ions by reflux electrodialysis I”, Journal of the Japan Society of Marine Science, Vol. 46, No. 1, pp. 27-36, 1992. H. Ohya, A. Hakamaya, Y. Hiraoka, Y. Negishi, “Theoretical studies on the separation of different ionic species of the same charge sign using cascaded electrodialysis with reflux”, Desalination, Volume 94, Issue 2, pp 167-199, December 1993.

[0012] The aforementioned perfusion electrodialysis method has a smaller separation coefficient relative to the number of cells compared to a serial cascade structure (Figure 45). In particular, 6 Li or 7Unlike the separation of heterogeneous metal ions using cation exchange membranes, the isotope separation coefficient in a single cell is extremely small in the concentration and separation of Li. Therefore, even if the number of cells is increased, the high isotope ratio required cannot be achieved. 6 Li 7 It is difficult to obtain Li.

[0013] The present invention has been made in view of the above-mentioned problems, and aims to provide an ion concentrator and an ion concentrator method suitable for separating and concentrating ions of ion species or isotopic species with small separation coefficients in a single cell, such as lithium isotope concentration.

[0014] In other words, the ion concentrator according to the present invention comprises an ion conductive membrane that allows multiple ion species or isotopic species to pass through, and has high or low selective permeability to some of the ion species or isotopic species, a power supply, and electrodes connected to the power supply, the ion concentrator is partitioned into a depletion chamber and a concentration chamber by the ion conductive membrane, and includes a cell in which the ions contained in the aqueous solution in the depletion chamber move to the aqueous solution in the concentration chamber by the voltage applied by the power supply, and is a device that supplies an ion source aqueous solution containing multiple ion species or isotopic species that permeate the ion conductive membrane, and recovers an aqueous solution in which the concentration ratio of some of the ions is higher than that of the ion source aqueous solution.

[0015] Furthermore, the first and second ion concentrators according to the present invention are equipped with 2n cells from the 1st to the 2nth (n: a natural number), and further comprising: a 0th cell consisting of a concentration chamber; a (2n+1)th cell consisting of a depletion chamber; an i-th channel (2≦i≦2n) that combines the aqueous solutions in the depletion chamber of the (i+1)th cell and the concentration chamber of the (i-2)th cell and branches them into the depletion chamber of the i-th cell and the concentration chamber of the (i-1)th cell, and the aqueous solution in the depletion chamber of the 2nd cell is supplied to the depletion chamber of the 1st cell The apparatus comprises a first channel that branches off and flows into the depletion chamber and the 0th cell, and a (2n+1)th channel that branches off and flows into the concentration chamber of the (2n-1)th cell and the (2n+1)th cell, wherein the ion source aqueous solution is supplied to the (n+1)th channel, and the aqueous solution is discharged from either the depletion chamber of the 1st cell or the concentration chamber of the 2nth cell, while an aqueous solution with a concentration ratio of some types of ions higher than that of the ion source aqueous solution is discharged from the other at a flow rate less than or equal to that of the aqueous solution. The first ion concentrator is configured such that, in the cell, the ion conductive membrane has high selective permeability of certain types of ions, and an aqueous solution with a high concentration ratio of certain types of ions is discharged from the concentration chamber of the 2nth cell, and the first cell has a larger flow rate of the aqueous solution discharged than the 2nth cell, a larger area of ​​the ion conductive membrane, a higher current density supplied to the ion conductive membrane by the power supply, and a higher temperature of the ion conductive membrane. The second ion concentrator is configured such that, in the cell, the ion conductive membrane has low selective permeability of certain types of ions, and an aqueous solution with a high concentration ratio of certain types of ions is discharged from the depletion chamber of the first cell, and the 2nth cell has a larger flow rate of the aqueous solution discharged than the first cell, a larger area of ​​the ion conductive membrane, a higher current density supplied to the ion conductive membrane by the power supply, and a higher temperature of the ion conductive membrane.

[0016] The third and fourth ion concentrators according to the present invention are provided with (2n+1) cells (n: natural number), and further comprising an i-th channel (2≦i≦2n) that merges the aqueous solutions in the depletion chamber of the (i+1)-th cell and the concentration chamber of the (i-1)-th cell and branches them into the depletion chamber and concentration chamber of the i-th cell, and a first channel that branches the aqueous solution in the depletion chamber of the second cell into the depletion chamber and concentration chamber of the first cell, The third ion concentrator comprises a (2n+1)th channel that branches the aqueous solution in the concentration chamber of the 2nth cell into the depletion chamber and the concentration chamber of the (2n+1)th cell, and supplies the ion source aqueous solution to the (n+1)th channel, discharging the aqueous solution from one of the depletion chamber of the 1st cell and the concentration chamber of the (2n+1)th cell, while discharging an aqueous solution from the other at a flow rate less than or equal to the aqueous solution, in which the concentration ratio of certain types of ions is higher than that of the ion source aqueous solution. The third ion concentrator comprises a cell in which the ion conductive membrane has high selective permeability of certain types of ions, and an aqueous solution with a high concentration ratio of certain types of ions is discharged from the concentration chamber of the (2n+1)th cell, and the 1st cell is configured to satisfy at least one of the following: a larger flow rate of the aqueous solution discharged than that of the (2n+1)th cell, a larger area of ​​the ion conductive membrane, a higher current density supplied to the ion conductive membrane by the power supply, and a higher temperature of the ion conductive membrane. The fourth ion concentrator is configured such that, in the cell, the ion conductive membrane has low selective permeability of certain types of ions and discharges an aqueous solution with a high concentration ratio of certain types of ions from the depletion chamber of the first cell, and the (2n+1)th cell has a larger flow rate of the aqueous solution discharged than the first cell, a larger area of ​​the ion conductive membrane, a higher current density supplied to the ion conductive membrane by the power supply, and a higher temperature of the ion conductive membrane.

[0017] The ion concentration method according to the present invention is a method in which a plurality of cells, each separated into a depletion chamber and a concentration chamber by an ion-conducting membrane that allows multiple ion species or isotopes to pass through and has high or low selective permeability to some of the ion species or isotopes, are connected by a channel, and an ion source aqueous solution containing multiple ion species or isotopes that permeate the ion-conducting membrane is supplied, and in each of the cells, a power supply connected to an electrode provided in the cell applies a voltage that moves the ions contained in the aqueous solution in the depletion chamber to the aqueous solution in the concentration chamber, thereby recovering an aqueous solution in which the concentration ratio of some of the ions is higher than that of the ion source aqueous solution.

[0018] Furthermore, the first and second ion concentration methods according to the present invention involve 2n cells (n: natural number) from the 1st to the 2nth, and a 0th cell consisting of a concentration chamber and a (2n+1)th cell consisting of a depletion chamber, where the aqueous solutions in the depletion chamber of the (i+1)th cell and the concentration chamber of the (i-2)th cell are merged and branched into the depletion chamber of the ith cell and the concentration chamber of the (i-1)th cell, respectively, forming an i-th channel (2≦i≦2n), and the aqueous solution in the depletion chamber of the 2nd cell is then depleted in the first cell. A first channel is connected to the chamber and the 0th cell, and a (2n+1)th channel is connected to the (2n+1)th cell, which is connected to the (2n-1)th cell, which is connected to the (2n+1)th cell, which is connected to the (n+1)th channel, which supplies the ion source aqueous solution to the (n+1)th channel, causing the aqueous solution to be discharged from one of the depletion chambers of the 1st cell and the concentration chamber of the 2nth cell, while the other channel discharges an aqueous solution at a flow rate less than or equal to the aqueous solution, in which the concentration ratio of some types of ions is higher than that of the ion source aqueous solution. The first ion concentration method involves discharging an aqueous solution from the concentration chamber of the 2nth cell in the cell, wherein the ion-conducting membrane has high selective permeability of certain types of ions and a high concentration ratio of certain types of ions, and the first cell satisfies at least one of the following conditions compared to the 2nth cell: the flow rate of the aqueous solution discharged is greater, the area of ​​the ion-conducting membrane is larger, the current density supplied to the ion-conducting membrane by the power supply is higher, and the temperature of the ion-conducting membrane is higher. The second ion concentration method involves discharging an aqueous solution from the depletion chamber of the first cell in the cell, wherein the ion-conducting membrane has low selective permeability of certain types of ions and a high concentration ratio of certain types of ions, and the 2nth cell satisfies at least one of the following conditions compared to the first cell: the flow rate of the aqueous solution discharged is greater, the area of ​​the ion-conducting membrane is larger, the current density supplied to the ion-conducting membrane by the power supply is higher, and the temperature of the ion-conducting membrane is higher.

[0019] The third and fourth ion concentration methods according to the present invention involve (2n+1) cells (n: natural number), an i-th channel (2≦i≦2n) through which the aqueous solutions in the depletion chamber of the (i+1)-th cell and the concentration chamber of the (i-1)-th cell are merged and branched into the depletion chamber and concentration chamber of the i-th cell, and a first channel (2≦i≦2n) through which the aqueous solution in the depletion chamber of the second cell is branched into the depletion chamber and concentration chamber of the first cell, and the 2n-th The aqueous solution in the concentration chamber of the cell is connected to the depletion chamber and the concentration chamber of the (2n+1)th cell by a (2n+1)th channel that branches off and flows into the concentration chamber, and the ion source aqueous solution is supplied to the (n+1)th channel to discharge the aqueous solution from one of the depletion chamber of the first cell and the concentration chamber of the (2n+1)th cell, and to discharge an aqueous solution at a flow rate less than or equal to the aqueous solution and in which the concentration ratio of certain types of ions is higher than that of the ion source aqueous solution from the other. The third ion concentration method is to ensure that in the cell, the ion conduction membrane has high selective permeability of certain types of ions and discharges an aqueous solution in which the concentration ratio of certain types of ions is high from the concentration chamber of the (2n+1)th cell, and the first cell satisfies at least one of the following conditions: the flow rate of the aqueous solution discharged is greater than that of the (2n+1)th cell, the area of ​​the ion conduction membrane is larger, the current density supplied to the ion conduction membrane by the power supply is higher, and the temperature of the ion conduction membrane is higher. The fourth ion concentration method involves discharging an aqueous solution from the depletion chamber of the first cell in which the ion-conducting membrane has low selective permeability of certain types of ions and a high concentration ratio of certain types of ions, and the (2n+1)th cell satisfies at least one of the following conditions compared to the first cell: a larger flow rate of the aqueous solution discharged, a larger area of ​​the ion-conducting membrane, a higher current density supplied to the ion-conducting membrane by the power supply, and a higher temperature of the ion-conducting membrane.

[0020] According to the ion concentrator and ion concentrating method of the present invention, an ion concentrator suitable for separating and concentrating ions of ion species and isotopic species with small separation coefficients in a single cell can be obtained. 6 Li or7 A multi-stage lithium isotope enrichment apparatus can be obtained that safely and productively recovers aqueous solutions with higher isotopic ratios of Li.

[0021] This is a schematic diagram illustrating the configuration of the lithium isotope enrichment apparatus according to the present invention. This is a schematic diagram illustrating the cell configuration of the lithium isotope enrichment apparatus according to the present invention and the lithium isotope enrichment method by electrodialysis. This is a schematic diagram illustrating the cell configuration of the lithium isotope enrichment apparatus according to the present invention, and is a horizontal cross-sectional view of the cell shown in Figure 2A. This is a horizontal cross-sectional view illustrating the cell configuration of the lithium isotope enrichment apparatus according to the present invention. This is a schematic diagram illustrating the configuration of the lithium isotope enrichment apparatus and the lithium isotope enrichment method according to the first embodiment of the present invention, and corresponds to an enlarged view of Figure 1. This is a graph showing an example of the flow rate ratio of each chamber of the lithium isotope enrichment apparatus shown in Figure 1. This is a schematic diagram illustrating the configuration of a modified lithium isotope enrichment apparatus shown in Figure 1. This is a schematic diagram illustrating the configuration of another lithium isotope enrichment apparatus according to the present invention. This is a schematic diagram illustrating the configuration of the lithium isotope enrichment apparatus and the lithium isotope enrichment method according to a modified example of the first embodiment of the present invention, and corresponds to an enlarged view of Figure 7. This is a graph showing an example of the flow rate ratio of each chamber of the lithium isotope enrichment apparatus shown in Figure 7. This is a schematic diagram illustrating the configuration of a modified lithium isotope enrichment apparatus shown in Figure 7. This is a schematic diagram illustrating the configuration of a modified lithium isotope enrichment apparatus shown in Figure 7. This is a schematic diagram illustrating the lithium isotope enrichment method according to the second embodiment of the present invention, and corresponds to an enlarged view of Figure 1. This is a schematic diagram illustrating the configuration of the lithium isotope enrichment apparatus and the lithium isotope enrichment method according to the third embodiment of the present invention, and corresponds to an enlarged view of Figure 1. This is a schematic diagram illustrating the configuration of the lithium isotope enrichment apparatus and the lithium isotope enrichment method according to a modified example of the third embodiment of the present invention, and corresponds to an enlarged view of Figure 7. This is a schematic diagram illustrating the configuration of the lithium isotope enrichment apparatus and the lithium isotope enrichment method according to the fourth embodiment of the present invention, and corresponds to an enlarged view of Figure 1. This is a schematic diagram illustrating the configuration of the lithium isotope enrichment apparatus and the lithium isotope enrichment method according to a modified example of the fourth embodiment of the present invention, and corresponds to an enlarged view of Figure 7. Simulation using a model of a cross-type cascade system structure, 6Graph of the stage-dependence of the overall separation factor of Li. By simulation using a model of a cross-type cascade system structure, 6 Graph of the stage-dependence of the Li recovery rate. By simulation using a model of a cross-type cascade system structure, 6 Graph of the flow rate ratio-dependence of the overall separation factor of Li. By simulation using a model of a cross-type cascade system structure, 6 Graph of the flow rate ratio-dependence of the Li recovery rate. By simulation using a model of a straight-type cascade system structure, 6 Graph of the stage-dependence of the overall separation factor of Li. By simulation using a model of a straight-type cascade system structure, 6 Graph of the stage-dependence of the Li recovery rate. By simulation using a model of a straight-type cascade system structure, 6 Graph of the flow rate ratio-dependence of the overall separation factor of Li. By simulation using a model of a straight-type cascade system structure, 6 Graph of the flow rate ratio-dependence of the Li recovery rate. A graph explaining the current asymmetry in a model of a cross-type cascade system structure. By simulation using the model shown in Fig. 26, 6 Graph of the current density-dependence of the overall separation factor of Li. A graph explaining the current asymmetry in a model of a cross-type cascade system structure. By simulation using the model shown in Fig. 28, 6 Graph of the current density-dependence of the overall separation factor of Li. A graph explaining the current asymmetry in a model of a cross-type cascade system structure. By simulation using the model shown in Fig. 30, 6 Graph of the current density-dependence of the overall separation factor of Li. A graph explaining the asymmetry of the electrolyte membrane area in a model of a cross-type cascade system structure. By simulation using the model shown in Fig. 32, 6 [[ID=X]]Graph of the current density-dependence of the overall separation factor of Li. By simulation using the model shown in Fig. 32, for different supply flow rates of the Li source aqueous solution 6It is a graph of the current density dependence of the overall separation factor of Li. By simulation using a model of a cross-type cascade system structure, 6 It is a graph of the flow rate ratio dependence of the overall separation factor of Li. By simulation using a model of a cross-type cascade system structure, 6 It is a graph of the flow rate ratio dependence of the Li recovery rate. By simulation using a model of a straight-type cascade system structure, 6 It is a graph of the flow rate ratio dependence of the overall separation factor of Li. By simulation using a model of a straight-type cascade system structure, 6 It is a graph of the flow rate ratio dependence of the Li recovery rate. By simulation using a model of a single cell structure, 6 It is a graph of the flow rate ratio dependence of the overall separation factor of Li. By simulation using a model of a single cell structure, 6 It is a graph of the flow rate ratio dependence of the Li recovery rate. By simulation using a model of a cross-type cascade system structure, 6 It is a graph of the current density dependence of the overall separation factor of Li. As shown in FIG. 41 6 It is a graph of the peak value of the overall separation factor of Li. By simulation using a model of a cross-type cascade system structure, 7 Of the Li-enriched aqueous solution 7 It is a graph of the current density dependence of the Li isotope ratio. It is a schematic diagram of a conventional lithium isotope enrichment device. It is a schematic diagram of a conventional multi-stage lithium isotope enrichment device.

[0022] A mode (embodiment) for implementing the ion concentration device and the ion concentration method according to the present invention will be described with reference to the drawings. In the drawings, for the sake of clarity of explanation, the size etc. of specific elements may be exaggerated, and the shape may be simplified. Also, in the description of each embodiment, the same elements as those in the previous embodiment are denoted by the same reference numerals, and the description will be omitted as appropriate.

[0023] [First Embodiment] (Lithium Isotope Concentrator) Figure 1 is a schematic diagram of a cross-type multi-stage cascade system using perfusion electrodialysis, and is a schematic diagram illustrating the structure of a lithium isotope concentrate (ion concentrate) 10 according to the first embodiment of the present invention. The lithium isotope concentrate 10 consists of a single-chamber cell 13 and 2n cells 1 -n ,1 -n+1 , ..., 1 -2 ,1 -1 ,1 +1 ,1 +2 , ..., 1 +n-1 ,1 +n (If not distinguished, refer to it as cell 1 as appropriate), single-chamber cell 12, and (2n+1) channels 8 connecting cells 13, 1, and 12. -n ,8 -n+1 , ..., 8 -2 ,8 -1 ,80,8 +1 ,8 +2 , ..., 8 +n-1 ,8 +n The lithium isotope enrichment apparatus 10 is equipped with the following: Cell 1 is divided into two chambers, and a specific ion (indicated by a white circle "〇" with a "+" inside in the figure) can move from the white chamber 2 on the left half of Figure 1 to the dot-patterned chamber 3 on the right half (see Figure 4), as shown by the white arrow. The lithium isotope enrichment apparatus 10 has the structure of a cross-type multi-stage cascade system using perfusion electrodialysis (see Non-Patent Literature 2). This structure is symmetrical in Figure 1, except that the arrangement of chambers 2 and 3 of cell 1 is aligned. Specifically, the lithium isotope enrichment apparatus 10 has the structure of an n-stage cross-type cascade system, as n cells 1 are arranged on both sides from the center. n is an arbitrary natural number, preferably 2 or more, and can be several tens to several hundred. The lithium isotope enrichment apparatus 10 has the nth and (n+1)th cell 1 in the center among 2n cells -1 ,1 +1 Li source aqueous solution (ion source aqueous solution) 9S is supplied from the outside via the flow path 80, and cells 1 at each end on both sides -n ,1 +n From aqueous solution 9a -n ,9c +n It discharges. The lithium isotope enrichment device 10 6 This is a lithium enrichment device.

[0024] Here, the subscripts 1 and 8, which indicate cells and flow paths, represent stages in the lithium isotope enrichment apparatus 10. As shown in Figure 1, starting from the flow path 80 to which the Li source aqueous solution 9S is supplied, the stages are -1, -2, ..., -n+1, ​​-n from left to right, and +1, +2, ..., +n-1, +n from right to left, with no cell 1 at stage 0. In the lithium isotope enrichment apparatus 10, the first cell 1 among 2n cells is the cell 1 of stage -n. -n , the nth cell 1 is the cell 1 of row -1 -1 , the (n+1)th cell 1 is the cell 1 of the +1 row. +1 , the 2nth cell 1 + the nth row cell 1 +n , and so on as appropriate. Also, in Figure 1, cell 1 on the left side (- side) of the flow path 80 -n ,1 -n+1 , ..., 1 -2 ,1 -1 And single-chamber cell 13 is the lithium-ion depletion region, and cell 1 on the right side (+ side) +1 ,1 +2 , ..., 1 +n-1 ,1 +n And the single-chamber cell 12 is the lithium ion concentration region. Figure 1 is a top view, and cells 13, 1 -n , ..., 1 -2 ,1 -1 ,1 +1 ,1 +2 , ..., 1 +n ,12 are arranged in a straight line in this order, but the flow path 8 -n , ..., 8 -2 ,8 -1 ,80,8 +1 ,8 +2 , ..., 8 +n (If not distinguished, the arrangement can be any arrangement depending on the shape of the flow path 8), and the cells 1 do not need to be aligned in the same direction.

[0025] The Li source aqueous solution 9S is a Li source that supplies Li, 7 Li and 6 Li cation 7 Li + , 6 Li + An aqueous solution containing, for example, 7 Li+ , 6 Li + This is an aqueous solution of lithium hydroxide (LiOH) containing Li in its natural abundance. Li source aqueous solution 9S is Li + A higher concentration is preferable, Li + It is even more preferable that it be a saturated or supersaturated aqueous solution of [the substance]. 7 Li and 6 Li ( 7 Li + and 6 Li + ) When they do not distinguish from each other, Li (Li + This is referred to as [the lithium isotope enrichment apparatus]. The following describes each element constituting the lithium isotope enrichment apparatus according to this embodiment.

[0026] As shown in Figure 2A, the cell 1 comprises an electrolyte membrane (lithium-ion conductive electrolyte membrane) 4 that divides the tank 7 into two chambers, an anode chamber (depletion chamber) 2 and a cathode chamber (concentration chamber) 3, a first electrode 51 and a second electrode 52 coated on both sides of the electrolyte membrane 4, and a power supply 6 connected between the electrodes 51 and 52. The power supply 6 has its positive (+) electrode connected to the first electrode 51 in the anode chamber 2 and its negative (-) electrode connected to the second electrode 52 in the cathode chamber 3. In the lithium isotope enrichment apparatus 10, the anode chamber 2 is Li + The depletion chamber and cathode chamber 3 are Li + This is the concentration chamber. As shown in Figure 2B, in cell 1, aqueous solution 9f1 flows into the anode chamber 2 and flows out as aqueous solution 9a, and aqueous solution 9f2 flows into the cathode chamber 3 and flows out as aqueous solution 9c. In Figures 1 and 4, the white area on the left half of cell 1 represents aqueous solution 9a, and the dotted area on the right half represents aqueous solution 9c.

[0027] Aqueous solutions 9a and 9c contain lithium ions (Li) recovered from the Li source aqueous solution 9S. +This is an aqueous solution for containing LiOH, and for example, at the start of operation of the lithium isotope enrichment apparatus 10 it is pure water, and after the start of operation it becomes an aqueous LiOH solution. As shown in Figure 2B, the aqueous solutions 9a and 9c are referred to as aqueous solutions 9f1 and 9f2 (if not distinguished, aqueous solution 9f) when they flow into the anode chamber 2 and cathode chamber 3 (chambers 2 and 3 as appropriate). As will be described later, in the anode chamber 2 of the same cell 1, aqueous solution 9a has a higher concentration of LiOH than aqueous solution 9f1. + Low concentration and containing Li + of 6 The Li isotope ratio is low. On the other hand, in the cathode chamber 3 of the same cell 1, aqueous solution 9c has a higher Li isotope ratio than aqueous solution 9f2. + High concentration and Li content + of 6 The Li isotope ratio is high. Also, in each cell, the Li of aqueous solutions 9f1 and 9f2 + concentration and 6 The Li isotope ratios are different.

[0028] The electrolyte membrane 4 is an electrolyte having lithium ion conductivity, and electron e - It is preferable that conduction does not occur. Furthermore, the Li source aqueous solution 9S is Li + If other metal ions are present, it is preferable that the electrolyte membrane 4 does not conduct these metal ions. More preferably, the electrolyte is made of ceramics having these properties. Specifically, lithium lanthanum titanium oxide (La 2 / 3-x Li 3x Examples include TiO3 (also called LLTO). Such electrolyte membranes 4 have a certain proportion of lattice defects, and because the size of these lattice defect sites is small, Li + Larger metal ions do not conduct. For example, in solid electrolytes having a perovskite (ABO3) structure (A = Li, La, or vacancy, B = Ti) such as LLTO, some A sites have vacancies (A site defects). And Li enters the A site defect. + It slipped in, and Li between the defects at nearby Site A + Li repeatedly moves +It permeates the electrolyte membrane 4. Hereinafter, sites where Li may exist, such as site A, will be called Li sites, and Li sites with vacancies will be called Li site defects. As will be explained in the lithium isotope enrichment method described later, this Li + In permeation through the electrolyte membrane 4, 7 Li + Smaller in mass 6 Li + It is easily permeable, that is, the electrolyte membrane 4 is 6 Li + It has high selective transparency, 7 Li + The selective transparency is low.

[0029] The first electrode 51 and the second electrode 52 are a pair of electrodes for applying a voltage between both sides of the electrolyte membrane 4. The first electrode 51 is located in the anode chamber 2 and connected to the positive electrode of the power supply 6, and the second electrode 52 is located in the cathode chamber 3 and connected to the negative electrode of the power supply 6. The first electrode 51 and the second electrode 52 are provided facing or in contact with the electrolyte membrane 4, preferably facing or in contact with a wider area of ​​the electrolyte membrane 4, and preferably both are provided in contact with the electrolyte membrane 4. In this case, the first electrode 51 and the second electrode 52 have a porous structure such as a mesh so that a voltage is applied to a wide area of ​​the electrolyte membrane 4, while aqueous solutions 9a and 9c come into contact with a sufficient area of ​​each surface of the electrolyte membrane 4.

[0030] The first electrode 51 is formed from an electrode material that has electronic conductivity and is stable even when a voltage is applied in an aqueous solution 9a, and is preferably made of a material that has catalytic activity for the reaction in formula (1) and the reaction in formula (3) below. The second electrode 52 is formed from an electrode material that has electronic conductivity and is stable even when a voltage is applied in an aqueous solution 9c, and is preferably made of a material that has catalytic activity for the reaction in formula (2) and the reaction in formula (4) below. The first electrode 51 and the second electrode 52 are further preferably made of a material that is easy to process into the above shapes. For the first electrode 51 and the second electrode 52, platinum (Pt) is preferred as such electrode material, for example. In each formula, Li contained in the electrolyte membrane 4 (electrolyte) + Li + It is expressed as (electrolyte). The following equation (3) shows Li in aqueous solution +This shows a reaction in which Li moves into the electrolyte membrane 4, and equation (4) below shows the Li in the electrolyte membrane 4 + This reaction shows that the substance moves into an aqueous solution (water).

[0031] Power supply 6 is a DC power supply, with the positive electrode connected to the first electrode 51 and the negative electrode connected to the second electrode 52. That is, power supply 6 applies a positive voltage V (voltage + V) to the first electrode 51 and to the second electrode 52. Power supply 6 applies a voltage between both sides of the electrolyte membrane 4, thereby supplying Li to the electrolyte membrane 4. + A potential gradient is generated to conduct electricity. The power supply 6 may be shared by multiple cells 1 and connected to their respective electrodes 51 and 52, as long as it is configured to apply a predetermined voltage V to each cell 1.

[0032] The tank 7 is made of a material that does not corrode or otherwise deteriorate even when in contact with aqueous solutions 9a and 9c (for example, an aqueous LiOH solution). As shown in Figure 2B, the tank 7 has through holes formed at a total of four locations in each of the two chambers 2 and 3 on two opposing sides, front and back, which communicate with the flow paths 82, 84, 83, and 85. Preferably, the flow paths 82 and 83 and the flow paths 84 and 85 are connected at two locations on the tank 7 that are spaced apart from each other in the in-plane direction of the electrolyte membrane 4, and through holes may also be formed at the bottom and top surfaces, and at two locations on the periphery of the side surfaces facing the electrolyte membrane 4. The tank 7 has a volume corresponding to the respective flow rates of the aqueous solutions 9f1 and 9f2, as will be described later, and specifically, it is preferable that the aqueous solutions 9f1 (9a) and 9f2 (9c) remain in the chambers 2 and 3 for a certain period of time before flowing out. Furthermore, it is preferable that the tank 7 has a shape in which the area of ​​the electrolyte membrane 4 is large relative to its volume, that is, a shape in which the height (vertical direction in Figure 2A) and / or depth (vertical direction in Figures 1 and 2B) is longer than the width (horizontal direction in Figures 1, 2A, and 2B).

[0033] In Figure 2A, the tank 7 is shown with an open top, but it is preferable that the tank is configured so that the aqueous solutions 9a and 9c are not exposed to the atmosphere in order to prevent carbon dioxide (CO2) from the atmosphere from unintentionally dissolving in the aqueous solutions 9a and 9c and causing lithium carbonate (Li2CO3) to precipitate. Furthermore, for safety reasons, it is preferable that the cell 1 is equipped with an exhaust means to exhaust hydrogen (H2) and oxygen (O2) generated during operation (by the reactions of formulas (1) and (2)) so that they do not fill the inside.

[0034] Single-chamber cell 13 is a -n stage cell 1 -n It is a single-chamber cell located at the negative end of the stage adjacent to the negative side (left side in Figures 1 and 4), and corresponds to the cathode chamber (concentration chamber) 3 of the (-n-1) stage cell. The single-chamber cell 12 is the cell 1 of the +n stage. +n This is a single-chamber cell located at the end of the stage adjacent to the positive side (right side in Figures 1 and 4), i.e., at the positive end, and corresponds to the anode chamber (depletion chamber) 2 of the (+n+1) stage cell. 2n cells 1 -n , ..., 1 -1 ,1 +1 , ..., 1 +n If cells 1 through 2n are the first to second cells, then single-chamber cell 13 is the 0th cell and single-chamber cell 12 is the (2n+1)th cell. As shown in Figure 3, single-chamber cell 13 consists of a tank 73 with through holes that communicate with the flow channels 83 and 85. Single-chamber cell 12 consists of a tank 72 with through holes that communicate with the flow channels 82 and 84. Tanks 72 and 73 can be made of the same material as tank 7, and preferably, tanks 72 and 73 have a closed structure.

[0035] The flow path 8 is provided to recirculate aqueous solutions 9a, 9c, and 9f (or aqueous solution 9 as appropriate if not distinguished) along a predetermined path between cells 1, and between cell 1 and single-chamber cell 13 or single-chamber cell 12. Like tank 7, flow path 8 is made of a material that does not deteriorate even when in contact with aqueous solution 9, and is formed to an inner diameter corresponding to the flow rate of aqueous solution 9. As will be described later, in the lithium isotope enrichment apparatus 10, the flow rates differ for each flow path 8, and in Figure 4, the amount of flow rate is represented by the thickness of the solid line indicating flow path 8. Also, in Figures 1 and 4, and in the drawings described later, the arrows attached to flow path 8 (82, 83, 84, 85, 87) indicate the direction of flow of aqueous solution 9.

[0036] -n stage (1st) and +n stage ((2n+1)th) flow path 8 -n ,8 +n Excluding flow path 8 -n+1 , ..., 8 -1 ,80,8 +1 , ..., 8 +n-1 As shown in Figure 1, it consists of flow paths 82, 83, 84, 85, 87 and control valves 81, 86. Flow paths 82, 83, 84, and 85 of flow path 8 are all connected to different cells 1 or single-chamber cells 13, 12. Specifically, in the i-th (2 ≤ i ≤ 2n) flow path 8, the inlet passage 83 is connected to the cathode chamber 3 of the (i-1)-th cell 1, the inlet passage 82 is connected to the anode chamber 2 of the i-th cell 1, the outlet passage 85 is connected to the cathode chamber 3 of the (i-2)-th cell 1, and the outlet passage 84 is connected to the anode chamber 2 of the (i+1)-th cell 1. The control valve 86 is provided at the junction of outlet passages 84 and 85 to allow aqueous solutions 9a and 9c to flow from the depletion chamber 2 to flow path 87 and from the cathode chamber 3 to flow path 87 without backflow through outlet passages 84 and 85. The control valve 81 is provided at the branching port from the flow path 87 to the inlet passage 82 and the inlet passage 83, so that the aqueous solution 9f (a mixture of aqueous solution 9a and aqueous solution 9c) does not flow back through the inlet passages 82 and 83 and flows into the anode chamber 2 and the cathode chamber 3 at a predetermined branching ratio. In other words, flow path 8 -n+1 , ..., 8 -1 ,80,8 +1 , ..., 8 +n-1 is, cell 13, 1 -n , ..., 1 -2 ,1 -1 ,1 +1 ,1 +2 , ..., 1 +n In the four adjacent cells 12, the aqueous solutions 9c and 9a in the cathode chamber 3 of the first cell and the anode chamber 2 of the fourth cell are merged from the negative side and flow into the cathode chamber 3 of the second cell 1 and the anode chamber 2 of the third cell 1 at a predetermined branching ratio. Furthermore, the central, i.e., the 0th stage ((n+1)th) flow path 80 of the lithium isotope enrichment apparatus 10 has a supply path 88 connected to the control valve 86, and the Li source aqueous solution 9S flows into cell 1 -1 Cathode chamber 3 and cell 1 +1 It flows into the anode chamber 2.

[0037] - nth stage (1st) flow path 8 -n This includes an inflow passage 83 connected to a single-chamber cell 13, and a cell 1 of the -n stage adjacent to the single-chamber cell 13. -n An inlet passage 82 connected to the anode chamber 2, a control valve 81 provided at the branching port of the inlet passage 82 and the inlet passage 83, and (-n+1) stage cell 1 -n+1 It consists of an outflow passage 84 connected between the anode chamber 2 and the control valve 81. +n stage ((2n+1)th) flow path 8 +n This includes an inflow passage 82 connected to a single-room cell 12, and a cell 1 of the +n stage adjacent to the single-room cell 12. +n An inlet passage 83 connected to the cathode chamber 3, a control valve 81 provided at the branching port of the inlet passage 82 and the inlet passage 83, and (+n-1) stage cell 1 +n-1 It consists of an outflow passage 85 connected to the cathode chamber 3.

[0038] - Cell 1 of row n -n Outlet passage 84 connected to anode chamber 2, +n stage cell 1 +n The outflow passage 85 connected to the cathode chamber 3 of the cell 1 is not connected to the flow paths that connect to the other cells 1, 13, and 12. As shown in Figure 4, cell 1 -n From the anode chamber 2, aqueous solution 9a -n but 6 As Li-depleted aqueous solution 9D, cell 1 +n From the cathode chamber 3, aqueous solution 9c +n but 6 Each is discharged as a concentrated Li aqueous solution 9E.

[0039] The flow path 8 is designed by the control valve 81 so that the amount of fluid flowing into the cathode chamber 3 (flow rate of inflow path 83) and the amount of fluid flowing into the anode chamber 2 (flow rate of inflow path 82) are in a predetermined ratio. The branching ratio may differ for each flow path 8. In the lithium isotope enrichment apparatus 10, cell 1 -n The flow rate in anode chamber 2, that is 6 Li-depleted aqueous solution 9D (aqueous solution 9a) -n The emissions from cell 1 +n The flow rate of the cathode chamber 3, that is 6 Li concentrated aqueous solution 9E (aqueous solution 9c +n The amount of discharged material should be greater than the amount of discharged material. Details regarding flow rate will be provided later.

[0040] The lithium isotope concentrator 10 may further include a temperature controller (not shown) that heats or cools one or both of the aqueous solutions 9a and 9c in the cell 1 to bring the electrolyte membrane 4 to a predetermined temperature. The temperature controller can be a known device for heating or cooling liquids, and preferably has a temperature control function. The temperature controller may control the temperature of the entire lithium isotope concentrator 10 as a whole, or it may be provided for each cell 1, or it may be provided in the flow path 8. Details regarding the temperature of the electrolyte membrane 4 will be described later, but it should be 30°C or lower, and to prevent the aqueous solutions 9 from freezing, for example, if the aqueous solutions 9a and 9c are pure water at the start of operation of the lithium isotope concentrator 10 (start of electrodialysis), it should be 0°C or higher. The temperature of the electrolyte membrane 4 can be measured by alternatively measuring the liquid temperature of the aqueous solutions 9a and 9c in the cell 1.

[0041] The lithium isotope enrichment apparatus 10 does not necessarily need to have single-chamber cells 13 and 12; in this case, the flow path 8 -n Flow path 83 and flow path 8 -n+1 Flow path 85, flow path 8 +n Flow channels 82 and 8 +n-1 The flow paths 84 are connected directly to each other (see the modified example of the third embodiment shown in Figure 12).

[0042] (Lithium Isotope Concentration Method) The lithium isotope concentration method (ion concentration method) according to the first embodiment of the present invention is a lithium isotope concentration apparatus 10 in which a Li source aqueous solution 9S is supplied to the flow path 80 while the cell 1 -n , ..., 1 -2 ,1 -1 ,1 +1 ,1 +2 , ..., 1 +n Each power supply 6 applies a voltage V to cell 1 +n Discharged from cathode chamber 3 6 The concentrated Li aqueous solution 9E is recovered. At that time, 6 Li concentrated aqueous solution 9E 6 The branching ratio of the control valve 81 of the flow path 8 is designed so that a large amount of the Li-depleting aqueous solution 9D is discharged.

[0043] Here, as shown in Figure 1, among the depleted areas, cell 1 kThe flow rate of anode chamber 2 for (-n+1 ≤ k ≤ -1) is F K+1,L This is expressed as (K = |k|), cell 1 -1 The flow rate of the cathode chamber 3 is F 1,R This is expressed as follows. Also, the flow rate of the single-chamber cell 13 is R L This is how it is expressed. Then, cell 1 -n The flow rate in anode chamber 2, that is 6 The amount of Li-depleting aqueous solution 9D discharged is (F n,L -R L ) can be expressed as. Also, cell 1 k The flow rate of cathode chamber 3 for (-n ≤ k ≤ -2) is (F K-1,L +R L -F n,L ) can be expressed as. On the other hand, among the concentrated regions, cell 1 k The flow rate of cathode chamber 3 for (+1 ≤ k ≤ +n - 1) is F K+1,R This is expressed as, cell 1 +1 The flow rate in anode chamber 2 is F 1,L This is expressed as follows. Also, the flow rate of the single-chamber cell 12 is R R This is how it is expressed. Then, cell 1 +n The flow rate of the cathode chamber 3, that is 6 The amount of discharged Li concentrated aqueous solution 9E is (F n,R -R R ) can be expressed as. Also, cell 1 k The flow rate in anode chamber 2 for (+2 ≤ k ≤ +n) is (F K-1,R +R R -F n,R ) can be expressed as follows. Also, if we represent the supply flow rate of the Li source aqueous solution 9S as F, then F n,L -R L +F n,R -R R The equation F holds true (Non-Patent Literature 2). It is assumed that the flow rates in chambers 2 and 3 of each cell 1 do not change during inflow and outflow. Hereafter, unless otherwise specified, F = 1, and these flow rates will be referred to as the flow rate ratio. Furthermore, the flow rate ratio R of single-chamber cells 13 and 12. L , R R This is called the reflux ratio.

[0044] The discharge amounts of aqueous solutions 9D and 9E are the same, i.e., F n,L -R L = F n,R -R RWhen = 0.5, the flow rate ratio of each chamber in the lithium isotope enrichment apparatus 10 (n≧2) will be symmetrical, as shown by the dotted line in Figure 5, for example. In this embodiment, F n,L -R L > F n,R -R R In Figure 5, F n,R -R R = 0.1, F n,L -R L When = 0.9, as an example, as shown by the dashed line, the total flow rate of the chambers in the depletion region (left half) is greater than that of the concentration region (right half), and cell 1 -n ,1 +n It is asymmetrical in other cases as well. Note that in Figure 5, F n,R -R R = 0.5 and 0.1 are both R L = R R Set = 0.5, and further, cell 1 -n+1 ~1 -2 Cell 1 +2 ~1 +n-1 Then, the same flow rate ratio was set for each. In this embodiment, the branching ratio of the control valve 81 is designed for each flow path 8 so that the aqueous solution 9 flows into each chamber at a predetermined flow rate ratio. Alternatively, cells 1 that discharge aqueous solutions 9D and 9E -n Flow path 84 and cell 1 +n Each flow rate of the flow path 85, and flow path 8 -n ,8 +n The branch ratio of the control valve 81 may be designed accordingly.

[0045] Before starting operation (before voltage is applied), the lithium isotope enrichment apparatus 10 contains, for example, pure water in the chambers 2 and 3 of cells 13, 1 and 12, and in the flow path 8. -n , ..., 1 -2 ,1 -1 ,1 +1 ,1 +2 , ..., 1 +n The voltage V is applied by each of the power supplies 6, and then, or simultaneously, the supply of the Li source aqueous solution 9S to the supply path 88 of the flow path 80 is started.

[0046] When Li source aqueous solution 9S is supplied from supply channel 88, Li in Li source aqueous solution 9S + Cell 1-1 Cathode chamber 3 and cell 1 +1 It flows into the anode chamber 2. Li + Furthermore, cell 1 -1 From cathode chamber 3 to cell 1 +1 Cathode chamber 3 and cell 1 +2 The anode chamber 2 flows into cell 1 +1 From anode chamber 2 to cell 1 -2 Cathode chamber 3 and cell 1 -1 It flows into the anode chamber 2. This is repeated sequentially, and Li flows into the aqueous solution 9 in chambers 2 and 3 of all cells 1, 13, and 12. + It contains.

[0047] In cell 1, Li is added to aqueous solution 9a (9f1) in anode chamber 2. + When it is present, as shown in Figure 2A, the following reaction occurs when a voltage V is applied. In the aqueous solution 9a of the anode chamber 2, near the first electrode 51, hydroxide ions (OH) in the aqueous solution 9a are reacted. - ) produces the reaction shown in equation (1) below, and electron e - The OH is released to the first electrode 51, generating water (H2O) and oxygen (O2). - As a result of the decrease, in order to maintain the balance of charge, Li in aqueous solution 9a + The reaction shown in equation (3) below occurs near the electrolyte membrane 4, in which the electrons e move into the electrolyte membrane 4. Meanwhile, in the aqueous solution 9c of the cathode chamber 3, the H2O in the aqueous solution 9c e - When supplied, the reaction shown in equation (2) below occurs, producing hydrogen (H2) and OH - Generates OH. - As the amount increased, in order to maintain the charge balance, Li in the electrolyte membrane 4 + The reaction shown in equation (4) below, in which the material moves, occurs near the electrolyte membrane 4.

[0048] From the reaction in equation (3) to the reaction in equation (4), that is, Li in aqueous solution 9a + Penetration from the surface to the interior of the electrolyte membrane 4, Li in the electrolyte membrane 4 + The movement of, and Li in the electrolyte membrane 4 + The transfer of to aqueous solution 9c proceeds as follows: Upon application of voltage V, the reaction of equation (3) occurs, and Li in aqueous solution 9a+ The Li penetrates into the Li site defects on the surface of the electrolyte membrane 4. Then, when a voltage V is applied, there is a potential gradient on the opposite side (cathode chamber 3 side) of the electrolyte membrane 4, so the Li that penetrated into the Li sites on the surface + It jumps (hops) to a nearby Li site defect on the deeper side of the electrolyte membrane 4. In this way, Li + The Li site in the electrolyte membrane 4 repeatedly moves from the Li site to nearby Li site defects, and finally moves from the Li site on the back side into the aqueous solution 9c as a reaction in equation (4). Then, the Li site on the surface of the electrolyte membrane 4 + As a result of the migration of one Li to the deeper part of the electrolyte membrane 4, another Li adsorbed in the vicinity moved into the now-empty Li site defect. + or Li in aqueous solution 9a + They sneak in, these Li + They similarly move through the electrolyte membrane 4.

[0049] 6 Li 7 Since its mass is 6 / 7 times smaller than that of Li, Li + In the inter-site movement (hopping) of the electrolyte membrane 4, 6 Li + but 7 Li + √(7 / 6) times faster, meaning a larger amount of movement per unit time (Li + High mobility (see Patent Document 4). Therefore, the electrolyte membrane 4 is 6 Li + It has high selective transparency, 7 Li + The selective permeability is low. As a result, Li that has moved from aqueous solution 9a (9f1) to aqueous solution 9c + of 6 The Li isotope ratio is the Li contained in aqueous solution 9f1. + It becomes higher than. As a result, in the anode chamber 2, the outflowing aqueous solution 9a contains Li + Not only does the concentration decrease, 6 The Li isotope ratio decreases, that is 7 ​The Li isotope ratio increases. On the other hand, in the cathode chamber 3, the aqueous solution 9c that flows out relative to the aqueous solution 9f2 that flows in contains Li + The concentration of Li increases, and this increase + teeth, 6 The Li isotope ratio is higher than that of aqueous solution 9f1.

[0050] In the lithium isotope enrichment apparatus 10, the aqueous solution 9a that flows out of the anode chamber 2 of cell 1 flows into the anode chamber 2 of the cell 1 in the next row on the negative side of cell 1 and into the cathode chamber 3 of the cell 1 in the next row, and the aqueous solution 9c that flows out of the cathode chamber 3 flows into the cathode chamber 3 of the cell 1 in the next row on the positive side and into the anode chamber 2 of the cell 1 in the next row.

[0051] Aqueous solution 9f k (-n+2≦k≦-2) is in cell 1 k-2 Aqueous solution 9c from cathode chamber 3 k-2 and cell 1 k+1 Aqueous solution 9a from anode chamber 2 k+1 It is a mixture of the above, and aqueous solution 9f -1 is cell 1 -3 Aqueous solution 9c from cathode chamber 3 -3 and cell 1 +1 Aqueous solution 9a from anode chamber 2 +1 It is a mixture of the following. Aqueous solution 9f -n+1 is cell 1 -n+1 Aqueous solution 9a from the anode chamber 2 via the single-chamber cell 13 -n+1 And, cell 1 -n+2 Aqueous solution 9a from anode chamber 2 -n+2 It is a mixture of and . And aqueous solution 9f k (-n+1 ≤ k ≤ -1) is in cell 1 k-1 Cathode chamber 3 and cell 1 k The aqueous solution 9f flows into the anode chamber 2. k (+2 ≤ k ≤ +n - 2) is in cell 1 k-1 Aqueous solution 9c from cathode chamber 3 k-1 And, cell 1 k+2 Aqueous solution 9a from anode chamber 2 k+2 It is a mixture of and an aqueous solution 9f +1 is cell 1 +1 Aqueous solution 9c from cathode chamber 3 -1 and cell 1 +3 Aqueous solution 9a from anode chamber 2+3 It is a mixture of the following. Aqueous solution 9f +n-1 is cell 1 +n-1 The aqueous solution 9c passed from the cathode chamber 3 through the single-chamber cell 12. +n-1 And, cell 1 +n-2 Aqueous solution 9c from cathode chamber 3 +n-2 It is a mixture of and . And aqueous solution 9f k (+1 ≤ k ≤ +n - 1) is in cell 1 k Cathode chamber 3 and cell 1 k+1 The aqueous solution 9f0 flows into the anode chamber 2. -2 Aqueous solution 9c from cathode chamber 3 -2 And, cell 1 +2 Aqueous solution 9a from anode chamber 2 +2 It is a mixture of Li source aqueous solution 9S and, cell 1 -1 Cathode chamber 3 and cell 1 +1 It flows into the anode chamber 2.

[0052] Based on these findings, aqueous solution 9f k-1 Aqueous solution 9f k of 6 The Li isotope ratio increases (-n+2 ≤ k ≤ +n-1). Consequently, aqueous solution 9a k-1 Aqueous solution 9a k of 6 The Li isotope ratio increases. Furthermore, cell 1 -n Aqueous solution 9a flowing out from the anode chamber 2 -n ( 6 Li-depleted aqueous solution 9D) is in cell 1 of the adjacent row. -n+1 Aqueous solution 9a flowing out from the anode chamber 2 -n+1 Cell 1 -n Li + Since it has been moved, aqueous solution 9a -n+1 Rather 6 The Li isotope ratio is low. Similarly, aqueous solution 9c k-1 Aqueous solution 9c k of 6 The Li isotope ratio increases (-n+2 ≤ k ≤ +n). That is, as the step progresses towards the negative side, the aqueous solution 9a from the anode chamber 2 of cell 1 6 As the Li isotope ratio decreases and the step progresses towards the positive side, the aqueous solution 9c from the cathode chamber 3 of cell 1 6 The Li isotope ratio increases. As a result, cell 1-n From anode chamber 2 6 Li-depleting aqueous solution 9D is discharged, cell 1 +n From cathode chamber 3 6 Li concentrated aqueous solution 9E is discharged.

[0053] Lithium isotope enrichment device 10 6 The Li isotope separation coefficient (hereinafter referred to as the overall separation coefficient) ω is larger as the number of stages n increases. The overall separation coefficient ω is expressed by the following equation (6). In the following equation (6), X S , 1-X S Li in Li source aqueous solution 9S 6 Li 7 Ratio of existence, X E , 1-X E teeth 6 Li in Li concentrated aqueous solution 9E 6 Li 7 This represents the relative abundance of ω = (X E / (1-X) E )) / (X S / (1-X) S )) ... (6)

[0054] Furthermore, in the lithium isotope enrichment method according to this embodiment, as described above, 6 The amount of Li concentrated aqueous solution 9E is greater than the amount of Li discharged. 6 The discharge volume of the Li-depleting aqueous solution 9D is high, and therefore the total flow rate in the depletion chamber of the lithium isotope enrichment device 10 is higher than that in the enrichment chamber. As a result, the overall separation coefficient ω of the lithium isotope enrichment device 10 becomes even larger. Cell 1 +n Flow rate ratio of cathode chamber 3 (F n,R -R R The lower the value of ), the larger the overall separation coefficient ω. On the other hand, the supply amount of Li source aqueous solution 9S is 6 Since the amount of Li concentrated aqueous solution 9E recovered will be small, the supplied Li source aqueous solution 9S will contain 6 Recovered amount of Li 6 Li concentrated aqueous solution 9E contains 6 Li amount ( 6 The Li recovery rate (r6) decreases. 6 The Li recovery rate r6 is expressed by the following equation (7). C S , C EThese are, respectively, Li source aqueous solution 9S, 6 This is the Li concentration of the Li-concentrated aqueous solution 9E. Note that in Figure 5, cell 1 -n+1 ~1 -2 Cell 1 +2 ~1 +n-1 Although the same flow rate ratio is set for each, a slope may be provided. In this case, F K,L ≤ F K+1,L (K=|k|, -n+1≦k≦1), F K,R ≥ F K+1,R It is preferable to set K = |k|, 1 ≤ k ≤ +n - 1. Also, the reflux ratio R L , R R r6 is not limited to 0.5. E C E (F n,R -R R ) / (X S C S F) ... (7)

[0055] In the lithium isotope enrichment method according to this embodiment, by setting the applied voltage V to a voltage equal to or greater than the voltage at which the electrolysis reaction of water occurs, the reactions of formula (1) and formula (2) occur, and Li + The molecules move through the electrolyte membrane 4. The voltage at which the electrolysis reaction of water occurs (electrolysis voltage) is +1.229V (25°C) when aqueous solution 9a and aqueous solution 9c have the same pH (hydrogen ion concentration). In reality, due to the electrode performance that determines the electrode reaction overpotential of each electrode 51 and 52, it is necessary to apply a voltage several hundred mV greater than the theoretical voltage of 1.229V. Also, the higher the pH of aqueous solution 9a compared to aqueous solution 9c, the lower the electrolysis voltage becomes, and conversely, the lower the pH of aqueous solution 9a compared to aqueous solution 9c, the higher the electrolysis voltage becomes.

[0056] In cell 1, the larger the current I / S supplied per unit area from power supply 6 to the electrolyte membrane 4, that is, the larger the voltage V of power supply 6, the greater the amount of Li moving per unit time in the electrolyte membrane 4. + The amount is large (Li + (High mobility), Li in aqueous solution 9c + The concentration increases (S: area of ​​electrolyte membrane 4). Li + If the mobility is too low, Li between chambers 2 and 3 in cell 1+ It will be discharged from cell 1 before its movement is effectively completed. On the other hand, as the voltage V increases, Li + As mobility increases, Cell 1 6 The Li isotope separation coefficient (hereinafter referred to as the head separation coefficient as appropriate) β decreases (approaches 1) (see Patent Document 4). Note that in the operation of the lithium isotope enrichment apparatus 10, the electrolyte membrane 4 is electron e - Li instead + Since current is conducted, the current I supplied to the electrolyte membrane 4 can be measured by an ammeter connected between the first electrode 51 or the second electrode 52 in contact with the electrolyte membrane 4 and the power supply 6 (connected in series with the power supply 6), or connected between the electrodes 51 and 52 (connected in parallel with the power supply 6).

[0057] Furthermore, when the voltage applied between both sides of the electrolyte membrane 4 exceeds a certain value, some of the transition metal ions constituting the electrolyte membrane 4 are reduced (for example, if the electrolyte membrane 4 is LLTO, Ti 4+ +e - →Ti 3+ ), the electrolyte membrane 4 moves electrons e from the cathode chamber 3 side to the anode chamber 2 side - It becomes conductive. As a result, most of the given electrical energy is conducted by electrons e - Since it is consumed in conduction, Li + The voltage dependence of the mobility of Li decreases, + The energy efficiency in the movement of ions decreases. Furthermore, some of the transition metal ions constituting the electrolyte membrane 4 are reduced, and the ionic radius of these reduced ions increases (for example, if the electrolyte membrane 4 is LLTO, Ti 4+ <Ti 3+ ), Li + The bottleneck for moving Li will widen, so + of 6 The Li isotope ratio will decrease rapidly. Therefore, the voltage V will be Li + Within the range in which it can move through the electrolyte membrane 4, and furthermore, while the aqueous solution 9 remains in cell 1 (chambers 2 and 3), a certain amount of Li + The range in which it moves from anode chamber 2 to cathode chamber 3 should be small.

[0058] Also, Li + Mobility also depends on temperature, increasing exponentially as the temperature T of the electrolyte membrane 4 increases, but the head separation coefficient β decreases (see Patent Document 4). Therefore, it is preferable that the temperature T of the electrolyte membrane 4 be lower than the range between the freezing point and the boiling point of the aqueous solution 9. Furthermore, the aqueous solution 9 may contain a solute that lowers the freezing point to below 0°C, and the solute can be added to the Li source aqueous solution 9S and the aqueous solution 9 contained in the cell 1 before starting operation. Such a solute is Li + To avoid hindering the movement of the solute, an aqueous solution containing the solute should be selected that does not permeate the electrolyte membrane 4 and does not corrode the electrolyte membrane 4 or electrodes 51 and 52. Specifically, examples include salts of sodium chloride (NaCl, table salt), magnesium chloride (MgCl2), calcium chloride (CaCl2), potassium chloride (KCl), etc., which are used as antifreeze agents, or organic solvents such as ethylene glycol. Sodium chloride is particularly preferred because it does not produce precipitates other than lithium carbonate (carbonates) even when carbon dioxide is dissolved in it, and it has a large freezing point depression.

[0059] recovered 6 Li concentrated aqueous solution 9E is desired 6 If the Li isotope ratio is not satisfied, 6 The Li-concentrated aqueous solution 9E may be supplied to the lithium isotope enrichment apparatus 10 as the Li source aqueous solution 9S for the next operation. 6 Before supplying the concentrated Li aqueous solution 9E, evaporate the water to remove the Li + It is preferable to increase the concentration. The series of operations is desired 6 Li isotope ratio 6 Repeat the process until a concentrated Li aqueous solution 9E is obtained.

[0060] Desired 6 The Li isotope ratio was reached. 6 For the concentrated Li aqueous solution 9E, for example, after concentrating Li by evaporating the water as needed, lithium carbonate (Li2CO3) is generated and precipitated by carbon dioxide (CO2) bubbling or the like. 6 Li can be recovered. Or, 6By cooling or evaporating the water in the concentrated Li aqueous solution 9E to create a supersaturated state, lithium hydroxide (LiOH) is generated and precipitated, 6 Li can also be recovered.

[0061] 6 If a salt other than sodium chloride, such as magnesium chloride, is added to the concentrated Li aqueous solution 9E to lower the freezing point, it is preferable to evaporate the water before bubbling carbon dioxide, and remove the salt precipitated by the reduction in water by a general method such as filtration before bubbling. Alternatively, before bubbling carbon dioxide, Li may be selectively recovered in pure water by performing a normal electrodialysis (see, for example, Japanese Patent Publication No. 2019-141807) at a temperature of 0°C or higher, for example, above room temperature.

[0062] (Variation) In the lithium isotope enrichment apparatus 10, cell 1 -n Aqueous solution 9a in the anode chamber 2 -n Cell 1 +n aqueous solution 9c in cathode chamber 3 +n A configuration may be used in which a portion of each is discharged and the remainder is recirculated (see Non-Patent Document 3). That is, as shown in Figure 6, the lithium isotope enrichment apparatus 10G has a flow path 8 -n However, cell 1 -n Aqueous solution 9a in the anode chamber 2 -n It is configured so that a portion of it flows in. Similarly, channel 8 +n However, cell 1 +n aqueous solution 9c in cathode chamber 3 +n It is configured so that a portion of it flows in.

[0063] Therefore, the lithium isotope enrichment device 10G uses flow path 8 -n ,8 +n Each of these is equipped with a control valve 86, similar to the other flow paths 8, and further equipped with a control valve 89. The control valve 89, similar to the control valve 81, branches one flow path into two, and discharges aqueous solution from one of the branches in a predetermined ratio or predetermined amount. -n-stage cell 1 -n The outflow passage 84 connected to the anode chamber 2 is branched by a control valve 89, and aqueous solution 9a -n However, from one of the branches 6 ​It is discharged as a Li-depleted aqueous solution 9D. The other branched outflow channel 84 is the -n stage (1st) flow path 8 -n Connected to the control valve 86, aqueous solution 9a -n Cell 1 of the (-n+1) row -n+1 Aqueous solution 9a in the anode chamber 2 -n+1 It merges with it. Similarly, cell 1 of +n rows +n The outflow passage 85 connected to the cathode chamber 3 is branched by a control valve 89, and the aqueous solution 9c +n However, from one of the branches 6 It is discharged as a concentrated Li aqueous solution 9E. The other branched outflow channel 85 is a +n stage ((2n+1)th) flow path 8 +n Connected to the control valve 86, aqueous solution 9c +n Cell 1 of the (+n-1)th row +n-1 aqueous solution 9c in cathode chamber 3 +n-1 It merges with the other components of the lithium isotope enrichment device 10G and the configuration of cell 1 are the same as those of the lithium isotope enrichment device 10 (see Figures 1, 2A, 2B, and 3).

[0064] In the lithium isotope enrichment device 10G, as shown in Figure 6, cell 1 in the depletion area k The flow rate of anode chamber 2 for (-n ≤ k ≤ -1) is F K+1,L This is expressed as (K = |k|), cell 1 -1 The flow rate of the cathode chamber 3 is F 1,R This is how it is represented. Also, cell 1 -n Aqueous solution 9a that flowed out from the anode chamber 2. -n Of these, the flow rate that is returned without being discharged is R. L It is represented as '. Then, 6 The amount of Li-depleting aqueous solution 9D discharged is (F n+1,L -R L It can be expressed as '). Also, cell 1 k The flow rate of cathode chamber 3 for (-n ≤ k ≤ -2) is (F K-1,L +R L '-F n+1,L ), flow rate of single-chamber cell 13 (R L ) is (F n,L +R L '-F n+1,L ) can be expressed as. On the other hand, cell 1 in the concentrated region k The flow rate of cathode chamber 3 for (+1 ≤ k ≤ +n) is F K+1,R This is expressed as, cell 1+1 The flow rate in anode chamber 2 is F 1,L This is how it is represented. Also, cell 1 +n Aqueous solution 9c that flowed out from cathode chamber 3. +n Of these, the flow rate that is returned without being discharged is R. R It is represented as '. Then, 6 The amount of discharged Li concentrated aqueous solution 9E is (F n+1,R -R R It can be expressed as '). Also, cell 1 k The flow rate in anode chamber 2 for (+2 ≤ k ≤ +n) is (F K-1,R +R R '-F n+1,R ), flow rate of single-chamber cell 12 (R R ) is (F n,R +R R '-F n+1,R ) can be expressed as follows. Also, if we represent the supply flow rate of the Li source aqueous solution 9S as F, then F n+1,L -R L '+F n+1,R -R R ' = F holds true (Non-Patent Document 3). As in the above embodiment, unless otherwise specified, F = 1, and these flow rates are referred to as the flow rate ratio, R L ', R R The value ' is called the reflux ratio.

[0065] In this modified example, similar to the above embodiment (see Figure 4), 6 Li depletion aqueous solution 9D 6 The amount of discharged is greater than that of Li concentrated aqueous solution 9E, that is, F n+1,L -R L '>F n+1,R -R R The branching ratio of the control valve 81 is designed for each flow path 8, or cell 1 -n Flow path 84 and cell 1 +n Design the flow rates for each channel 85.

[0066] The lithium isotope enrichment method in the lithium isotope enrichment apparatus 10G is the same as that of the lithium isotope enrichment apparatus 10. That is, while supplying the Li source aqueous solution 9S to the flow path 80, the power supply 6 of each of the 2n cells 1 applies a voltage V, and cell 1 +n Discharged from cathode chamber 3 6 The concentrated Li aqueous solution 9E is recovered. At that time, 6Li concentrated aqueous solution 9E 6 The branching ratio for each of the 8 channels is designed so that a large amount of the Li-depleting aqueous solution 9D is discharged. The reaction caused by the application of voltage V in cell 1 is as described in the above embodiment.

[0067] In this modified example, cell 1 of the final stage (+n stages) on the concentration side +n Aqueous solution 9c that flowed out from cathode chamber 3. +n A portion of the same cell 1 +n Cathode chamber 3 and cell 1 +n Since it is being recirculated to the anode chamber 2 (via single-chamber cell 12), even 6 The Li isotope separation coefficient is large. 6 The concentrated Li aqueous solution 9E can be recovered. Therefore, aqueous solution 9c +n The aqueous solution 9a is refluxed. -n A configuration that does not reflux is also acceptable. In this case, the lithium isotope enrichment device 10G has a flow path 8 -n However, the aqueous solution 9a has the same structure as the embodiment described above (see Figure 1). -n All 6 It is discharged as Li-depleted aqueous solution 9D.

[0068] The lithium isotope enrichment apparatus according to the present invention may have the structure of a straight-type multi-stage cascade system using perfusion electrodialysis (see Non-Patent Literature 2). Figure 7 is a schematic diagram of a straight-type multi-stage cascade system using perfusion electrodialysis, and is a schematic diagram illustrating the structure of a lithium isotope enrichment apparatus (ion enrichment apparatus) 10A according to a modification of the first embodiment of the present invention. The lithium isotope enrichment apparatus 10A has (2n+1) cells 1 -n ,1 -n+1 , ..., 1 -2 ,1 -1 ,10,1 +1 ,1 +2 , ..., 1 +n-1 ,1 +n , and (2n+1) channels 8 connecting them -n ,8 -n+1 , ..., 8 -2 ,8 -1 ,80,8 +1 ,8 +2 , ..., 8 +n-1 ,8+n It is equipped with the following. The straight-type multi-stage cascade system is symmetrical in Figure 7, except that the arrangement of chambers 2 and 3 of cell 1 is aligned. In the lithium isotope enrichment apparatus 10A, the first cell 1 among (2n+1) cells is the -n stage cell 1 -n The (n+1)th cell 1 is cell 10 of row 0, and the (2n+1)th cell 1 is cell 1 of row +n. +n , as may be referred to. The lithium isotope enrichment apparatus 10A has the structure of an n-stage straight-type cascade system, with the (n+1)th cell 10 in the center and n cells 1 on each side. n is any natural number, preferably 2 or more, and specifically can be several tens to several hundred. The lithium isotope enrichment apparatus 10A is supplied with an aqueous Li source solution (aqueous ion source solution) 9S from the outside via a flow path 80 to the central cell 10, and the cells 1 at each end on both sides -n ,1 +n From aqueous solution 9a -n ,9c +n It discharges. In Figure 7, cell 1 -n ,1 -n+1 , ..., 1 -1 , and the chamber 2 of cell 10 is Li + This is a depleted area, and is the chamber 3 of cell 10, and cell 1 +1 , ..., 1 +n-1 ,1 +n Li + This is the concentrated region.

[0069] Cell 1 has the same structure as the embodiment shown in Figures 2A and 2B. However, in the lithium isotope enrichment apparatus 10A, the same aqueous solution 9f flows into the anode chamber 2 and the cathode chamber 3.

[0070] As shown in Figure 8, the flow path 8 is the same as in the embodiment described above. -n+1 , ..., 8 -2 ,8 -1 ,80,8 +1 ,8 +2 , ..., 8 +n-1 This consists of flow paths 82, 83, 84, 85, 87 and control valves 81, 86. However, in this modified example, flow path 8 k (-n+1 ≤ k ≤ +n-1) is the case where inflow channels 82 and 83 are the same cell 1k It is connected to the anode chamber 2 and cathode chamber 3, and is the cell 1 of the adjacent row on the negative side (left side in Figures 7 and 8). k-1 The outflow path 85 is connected to the cathode chamber 3, and the cell 1 of the adjacent stage on the + side (right side in Figures 7 and 8) k+1 The outflow passage 84 is connected to the anode chamber 2. In other words, the flow path 8 -n+1 , ..., 8 -1 ,80,8 +1 , ..., 8 +n-1 In this system, the aqueous solutions 9c and 9a in the cathode chamber 3 of the negative-side cell 1 and the anode chamber 2 of the positive-side cell 1 are merged in three adjacent cells 1 and flowed into the anode chamber 2 and cathode chamber 3 of the central cell 1 at a predetermined branching ratio. Furthermore, a supply passage 88 is connected to the control valve 86 of the flow path 80. -n is cell 1 -n Inflow passages 82, 83, and cell 1 are connected to the anode chamber 2 and cathode chamber 3. -n+1 It consists of an outflow passage 84 connected to the anode chamber 2 and a control valve 81. +n is cell 1 +n Inflow passages 82, 83, and cell 1 are connected to the anode chamber 2 and cathode chamber 3. +n-1 It consists of an outflow passage 85 connected to the cathode chamber 3 and a control valve 81.

[0071] Similar to the above embodiment, -n stage cell 1 -n Outlet passage 84 connected to anode chamber 2, +n stage cell 1 +n The outflow passages 85 connected to the cathode chamber 3 are not connected to the flow paths that connect to other cells 1. As shown in Figure 8, cell 1 -n From the anode chamber 2, aqueous solution 9a -n but 6 As Li-depleted aqueous solution 9D, cell 1 +n From the cathode chamber 3, aqueous solution 9c +n but 6 Each is discharged as a concentrated Li aqueous solution 9E.

[0072] In the lithium isotope enrichment device 10A, as shown in Figure 7, in the depleted region, cell 1 k The flow rate of anode chamber 2 for (-n+1 ≤ k ≤ 0) is F K+1,L This is expressed as (K = |k|), cell 1 -n The flow rate of the cathode chamber 3 is R LThis is expressed as follows. On the other hand, among the concentrated regions, cell 1 k The flow rate of cathode chamber 3 for (0 ≤ k ≤ +n - 1) is F K+1,R This is expressed as, cell 1 +n The flow rate in the anode chamber 2 is R R This is expressed as follows. Then, similar to the above embodiment (cross type), cell 1 -n The flow rate in anode chamber 2, that is 6 The amount of Li-depleting aqueous solution 9D discharged is (F n,L -R L ) can be expressed as. Also, cell 1 k The flow rate of cathode chamber 3 for (-n+1 ≤ k ≤ -1) is (F K,L +R L -F n,L ) can be expressed as. Cell 1 +n The flow rate of the cathode chamber 3, that is 6 The amount of discharged Li concentrated aqueous solution 9E is (F n,R -R R ) can be expressed as. Also, cell 1 k The flow rate in anode chamber 2 for (+1 ≤ k ≤ +n - 1) is (F K,R +R R -F n,R ) can be expressed as F n,L -R L +F n,R -R R = F holds true. As in the above embodiment, unless otherwise specified, F = 1, and these flow rates are referred to as the flow rate ratio, R L , R R This is called the reflux ratio.

[0073] The discharge amounts of aqueous solutions 9D and 9E are the same, i.e., F n,L -R L = F n,R -R R When = 0.5, the flow rate ratio of each chamber in the lithium isotope enrichment apparatus 10A (n≧2) will be symmetrical, as shown by the dotted line in Figure 9, for example. In this modified example, as in the above embodiment, F n,L -R L > F n,R -R R In Figure 9, F n,R -R R = 0.1, F n,L -R LIn the case of =0.9, as an example, as shown by the dashed line, the total flow rate of the chambers in the depletion region (left half) is greater than that of the concentration region (right half), resulting in an asymmetrical appearance. Note that in Figure 9, F n,R -R R = 0.5 and 0.1 are both R L = R R Set = 0.5, and further, cell 1 -n+1 ~1 -1 Cell 1 +1 ~1 +n-1 Then, the same flow rate ratio was set for each. In this modified example as in the above embodiment, the branching ratio of the control valve 81 was designed for each flow path 8 so that the aqueous solution 9 flows into each chamber at a predetermined flow rate ratio, or cell 1 -n Flow path 84 and cell 1 +n The flow rates of each channel 85 are designed. Also, in Figure 8, as in Figure 4, the thickness of the solid line representing channel 8 indicates the amount of flow.

[0074] The lithium isotope enrichment method in the lithium isotope enrichment apparatus 10A is the same as that of the lithium isotope enrichment apparatus 10. That is, while supplying the Li source aqueous solution 9S to the flow path 80, the power supply 6 of each of the (2n+1) cells 1 applies a voltage V, and cell 1 +n Discharged from cathode chamber 3 6 The concentrated Li aqueous solution 9E is recovered. At that time, 6 Li concentrated aqueous solution 9E 6 The branching ratio for each of the flow paths 8 is designed so that a large amount of the Li-depleting aqueous solution 9D is discharged. The reaction caused by the application of voltage V in cell 1 is as described in the above embodiment. In the lithium isotope enrichment apparatus 10A, the same aqueous solution 9f flows into chambers 2 and 3 of cell 1. Similar to the above embodiment, in the anode chamber 2, the aqueous solution 9a that flows out relative to the incoming aqueous solution 9f is Li + The pigment decreases, and 6 The Li isotope ratio decreases. On the other hand, in the cathode chamber 3, the outflowing aqueous solution 9c is Li compared to the incoming aqueous solution 9f. + Concentration increases, and 6 The Li isotope ratio increases.

[0075] In the lithium isotope enrichment apparatus 10A, cell 1 kAqueous solution 9a that flowed out from anode chamber 2 (-n+1 ≤ k ≤ +n) k This is the cell 1 k Cell 1 of the row next to the - side k-1 The aqueous solution 9c flows into the anode chamber 2 and cathode chamber 3, and flows out of the cathode chamber 3. k The cell in the row next to the + side is cell 1. k+1 It flows into the anode chamber 2 and the cathode chamber 3.

[0076] Aqueous solution 9f k (-n+1 ≤ k ≤ +n-1) is in cell 1 k-1 Aqueous solution 9c from cathode chamber 3 k-1 and cell 1 k+1 Aqueous solution 9a from anode chamber 2 k+1 It is a mixture of the above, and cell 1 k It flows into the anode chamber 2 and cathode chamber 3. However, aqueous solution 9f0 is aqueous solution 9c -1 ,9a +1 Further, Li source aqueous solution 9S is mixed in. Also, cell 1 -n The anode chamber 2 and cathode chamber 3 contain cell 1 -n+1 Aqueous solution 9a from anode chamber 2 -n+1 It flows in. Cell 1 +n The anode chamber 2 and cathode chamber 3 contain cell 1 +n-1 Aqueous solution 9c from cathode chamber 3 +n-1 It flows in.

[0077] Based on these findings, similar to the above embodiment, aqueous solution 9f k-1 Aqueous solution 9f k of 6 The Li isotope ratio increases (-n+2 ≤ k ≤ +n-1), and aqueous solution 9a k-1 Aqueous solution 9a k of 6 The Li isotope ratio is high, and the aqueous solution is 9c k-1 Aqueous solution 9c k of 6 The Li isotope ratio increases (-n+2 ≤ k ≤ +n). As a result, cell 1 -n From anode chamber 2 6 Li-depleting aqueous solution 9D is discharged, cell 1 +n From cathode chamber 3 6 Li concentrated aqueous solution 9E is discharged.

[0078] Furthermore, similar to the above embodiment, the total flow rate in the depletion region of the lithium isotope enrichment apparatus 10A is greater than that in the enrichment region. In this modified example as well, cell 1 +n Flow rate ratio of cathode chamber 3 (F n,R -R R The lower the value of ), the larger the overall separation coefficient ω becomes, while on the other hand, 6 The Li recovery rate r6 decreases.

[0079] In the lithium isotope enrichment apparatus 10A, as in the lithium isotope enrichment apparatus 10G (see Figure 6), cell 1 -n Aqueous solution 9a in the anode chamber 2 -n Cell 1 +n aqueous solution 9c in cathode chamber 3 +n A configuration may be used in which a portion of each is discharged and the remainder is recirculated (see Non-Patent Document 3). That is, as shown in Figure 10, the lithium isotope enrichment apparatus 10H has a flow path 8 -n However, cell 1 -n Aqueous solution 9a in the anode chamber 2 -n It is configured so that a portion of it flows in. Similarly, channel 8 +n However, cell 1 +n aqueous solution 9c in cathode chamber 3 +n It is configured so that a portion of it flows in.

[0080] Therefore, the lithium isotope enrichment device 10H uses flow path 8 -n ,8 +n Each of these is equipped with a control valve 86, similar to the other flow paths 8, and further equipped with a control valve 89. -n-stage cell 1 -n The outflow passage 84 connected to the anode chamber 2 is branched by a control valve 89, and aqueous solution 9a -n However, from one of the branches 6 It is discharged as a Li-depleted aqueous solution 9D. The other branched outflow channel 84 is the -n stage (1st) flow path 8 -n Connected to the control valve 86, aqueous solution 9a -n Cell 1 of the (-n+1) row -n+1 Aqueous solution 9a in the anode chamber 2 -n+1 It merges with it. Similarly, cell 1 of +n rows +n The outflow passage 85 connected to the cathode chamber 3 is branched by a control valve 89, and the aqueous solution 9c +n However, from one of the branches 6It is discharged as a concentrated Li aqueous solution 9E. The other branched outflow channel 85 is a +n stage ((2n+1)th) flow path 8 +n Connected to the control valve 86, aqueous solution 9c +n Cell 1 of the (+n-1)th row +n-1 aqueous solution 9c in cathode chamber 3 +n-1 It merges with the other components of the lithium isotope enrichment device 10H and the configuration of cell 1 are the same as those of the lithium isotope enrichment device 10A (see Figures 7, 2A, 2B, and 3).

[0081] In the lithium isotope enrichment device 10H, as shown in Figure 10, cell 1 of the depletion region k The flow rate of anode chamber 2 for (-n ≤ k ≤ 0) is F K+1,L This is expressed as (K = |k|). Also, cell 1 -n Aqueous solution 9a that flowed out from the anode chamber 2. -n Of these, the flow rate that is returned without being discharged is R. L This is represented as '. On the other hand, cell 1 in the concentrated region k The flow rate of cathode chamber 3 for (0 ≤ k ≤ + n) is F K+1,R This is how it is represented. Also, cell 1 +n Aqueous solution 9c that flowed out from cathode chamber 3. +n Of these, the flow rate that is returned without being discharged is R. R It is represented as '. Then, 6 The amount of Li-depleting aqueous solution 9D discharged is (F n+1,L -R L It can be expressed as '). Also, cell 1 k The flow rate of cathode chamber 3 for (-n ≤ k ≤ -1) is (F K,L +R L '-F n+1,L ) can be expressed as follows. 6 The amount of discharged Li concentrated aqueous solution 9E is (F n+1,R -R R It can be expressed as '). Also, cell 1 k The flow rate in anode chamber 2 for (+1 ≤ k ≤ +n) is (F K,R +R R '-F n+1,R ) can be expressed as follows. Also, if we represent the supply flow rate of the Li source aqueous solution 9S as F, then F n+1,L -R L '+F n+1,R -R R' = F holds true (Non-Patent Document 3). As in the above embodiment, unless otherwise specified, F = 1, and these flow rates are referred to as the flow rate ratio, R L ', R R The value ' is called the reflux ratio.

[0082] In this modified example, similar to the previous modified example (see Figure 8), 6 Li depletion aqueous solution 9D 6 The amount of discharged is greater than that of Li concentrated aqueous solution 9E, that is, F n+1,L -R L '>F n+1,R -R R The branching ratio of the control valve 81 is designed for each flow path 8, or cell 1 -n Flow path 84 and cell 1 +n Design the flow rates for each channel 85.

[0083] The lithium isotope enrichment method in the lithium isotope enrichment apparatus 10H is the same as that of the lithium isotope enrichment apparatus 10. That is, while supplying the Li source aqueous solution 9S to the flow path 80, the power supply 6 of each of the 2n cells 1 applies a voltage V, and cell 1 +n Discharged from cathode chamber 3 6 The concentrated Li aqueous solution 9E is recovered. At that time, 6 Li concentrated aqueous solution 9E 6 The branching ratio for each of the 8 channels is designed so that a large amount of the Li-depleting aqueous solution 9D is discharged. The reaction caused by the application of voltage V in cell 1 is as described in the above embodiment.

[0084] In this modified example, cell 1 of the final stage (+n stages) on the concentration side +n Aqueous solution 9c that flowed out from cathode chamber 3. +n A portion of the same cell 1 +n Since the current is being recirculated to the cathode chamber 3 and anode chamber 2, 6 The Li isotope separation coefficient is large. 6 The Li-concentrated aqueous solution 9E can be recovered. Therefore, similar to the lithium isotope enrichment apparatus 10G, aqueous solution 9c +n The aqueous solution 9a is refluxed. -n A configuration that does not allow for recirculation is also acceptable.

[0085] The lithium isotope enrichment apparatus 10H can also have a structure with n=0, i.e., one cell 1 (10). That is, as shown in Figure 11, the lithium isotope enrichment apparatus 10I comprises a cell 10 and a flow channel 80, and is configured such that a portion of the aqueous solutions 9a0 and 9c0 flowing out from chambers 2 and 3 of cell 10 is discharged as aqueous solutions 9D and 9E, the remainder merges in the flow channel 80 and branches into chambers 2 and 3. For this purpose, the lithium isotope enrichment apparatus 10I is further equipped with control valves 89a and 89c in the flow channel 80, which branch out into outflow passages 84 and 85.

[0086] In the lithium isotope enrichment apparatus 10I, similar to the lithium isotope enrichment apparatus 10H, the flow rate of chambers 2 and 3 of cell 10 is set to F 1,L , F 1,R This is expressed as follows, and of the aqueous solutions 9a0 and 9c0 that flow out from chambers 2 and 3, the flow rate that is returned without being discharged is R. L ', R R This is represented as '. Then the amount of discharged from aqueous solutions 9D and 9E is (F 1,L -R L ´), (F 1,R -R R It can be expressed as '). Also, if we represent the supply flow rate of the Li source aqueous solution 9S as F, then F 1,L -R L '+F 1,R -R R The equation ' = F holds true.

[0087] In this modified example, similar to the previous modified example (see Figure 8), 6 Li depletion aqueous solution 9D 6 The amount of discharged is greater than that of Li concentrated aqueous solution 9E, that is, F 1,L -R L '>F 1,R -R R The branching ratio of the control valve 81 of the flow path 80 is designed to be such that, or the branching ratios of the control valves 89a and 89c (the flow rate ratios of the flow paths 84 and 85 of cell 10) are designed. In Figure 11, as in Figure 4, the thickness of the solid line representing the flow path 80 indicates the amount of flow. Note that, similar to the lithium isotope enrichment apparatus 10H, it is also possible to have a configuration in which the aqueous solution 9c0 is refluxed and the aqueous solution 9a0 is not refluxed.

[0088] Lithium isotope enrichment apparatuses 10, 10G, 10A, 10H, and 10I can be configured to increase the head separation coefficient β for cell 1. For example, in addition to the applied voltage V and the temperature of the electrolyte membrane 4, Li + As a configuration to reduce mobility, one of the anode chamber 2 or cathode chamber 3 is provided with a porous electrode in contact with the electrolyte membrane 4 and an electrode facing it at a distance, with a power supply 6 connected between these electrodes, and an electrode short-circuited to the porous electrode is provided in the other chamber. With both sides of the electrolyte membrane 4 at the same potential, Li + Li + By moving Li + The mobility is reduced (Patent Document 5). Furthermore, the power supply 6 is configured to intermittently apply voltage, alternating between short-term voltage application and shutdown. With this configuration, 6 Li + and 7 Li + The difference in mobility is significant, and Li is transferred from anode chamber 2 to cathode chamber 3 only for a short time immediately after the voltage is applied. + Move it (Patent Documents 6, 7, Non-Patent Document 1).

[0089] According to the lithium isotope enrichment apparatus and lithium isotope enrichment method of the first embodiment and its modified form, lithium isotope enrichment can be performed safely and productively by electrodialysis. 6 Aqueous solutions with a higher Li isotope ratio can be recovered.

[0090] [Second Embodiment] A lithium isotope enrichment apparatus with a multi-stage cascade system structure using perfusion electrodialysis is not limited to flow rate asymmetry, and Li between the two chambers of each cell + By making the amount of migration asymmetric, the overall separation coefficient ω of the lithium isotope enrichment apparatus can be increased. The lithium isotope enrichment method according to the second embodiment of the present invention will be described below.

[0091] (Lithium Isotope Concentration Method) The lithium isotope concentration method (ion concentration method) according to the second embodiment of the present invention, as shown in Figure 12, is similar to the first embodiment, in the lithium isotope concentration apparatus 10, while supplying a Li source aqueous solution 9S to the flow path 80, a voltage V is applied to each of the 2n cells 1 power supplies 6, and cell 1 +n Discharged from cathode chamber 3 6 The concentrated Li aqueous solution 9E is recovered. At that time, 6 Li concentrated aqueous solution 9E 6 The branching ratio is set for each channel 8 so that a large amount of the Li-depleted aqueous solution 9D is discharged. In Figure 12, as in Figure 4, the arrows attached to the channels 8 indicate the direction of flow of the aqueous solution 9, and the thickness of the solid line representing the channel 8 indicates the amount of flow.

[0092] In this embodiment, further, cell 1 +n Voltage V +n Cell 1 -n Voltage V -n It is set to be smaller than, preferably, cell 1 k The voltage V applied by power supply 6 k However, cell 1 of the row next to that - side k-1 Voltage V k-1 The following is (V -n >V +n , V k-1 ≧V k , V -1 ≧V +1 , 1-n ≤ k ≤ -1, +2 ≤ k ≤ +n). For example, set the voltage V of all cells 1 to be different so that the voltage V gradually decreases each time the stage moves from the negative end to the positive end. Then, as you approach the positive end, Li in cell 1 + Mobility decreases. Note that in Figure 12, Li from anode chamber 2 to cathode chamber 3 + The size of the white arrow indicating the movement of Li + This represents the degree of mobility. As a result, the overall separation coefficient ω of the lithium isotope enrichment device 10 becomes even larger.

[0093] As described in the first embodiment, the voltage V is Li +It is restricted to the range above the voltage at which it moves in the electrolyte membrane 4 and below the voltage at which the electrolyte membrane 4 exhibits electron conductivity. Therefore, in order for the voltage V of all the cells 1 to be within this range, it is not necessary for all the cells 1 to have different voltages V from each other. For example, in a plurality of consecutive stages of cells 1, the same voltage V can be used.

[0094] (Modified Example) In the lithium isotope enrichment method according to this embodiment, for each cell 1, Li + In order to make the mobilities different, the temperature T of the electrolyte membrane 4 may be made different for each cell 1. That is, for the cell 1 +n the temperature T of the electrolyte membrane 4 +n is set to be lower than the temperature T of the electrolyte membrane 4 of the cell 1 -n and preferably, the temperature T of the electrolyte membrane 4 of the cell 1 -n is set to be lower than the temperature T of the electrolyte membrane 4 of the cell 1 in the adjacent stage on that side, k and preferably, the temperature T of the electrolyte membrane 4 of the cell 1 k is lower than the temperature T of the electrolyte membrane 4 of the cell 1 in the adjacent stage on the adjacent side on that side, k-1 and preferably, the temperature T of the electrolyte membrane 4 of the cell 1 k-1 is less than or equal to the temperature T of the electrolyte membrane 4 of the cell 1 in the adjacent stage on the adjacent side on that side (T -n > T +n , T k-1 ≧ T k , T -1 ≧ T +1 , 1 - n ≦ k ≦ -1, +2 ≦ k ≦ +n). Therefore, the lithium isotope enrichment apparatus 10 includes a temperature regulator for each cell 1. Note that the aqueous solutions 9 flowing out from each of the chambers 2 and 3 of the cell 1 flow into the cells 1 in the adjacent stages on both sides and further into the cells 1 in the adjacent stages on each side. In particular, since the flow rate ratio in the cathode chamber 3 is low, more of the aqueous solution 9 flows into the cells 1 in the stage on one side, so the temperatures of the cells 1 in the adjacent stages are likely to affect each other. Taking this into account, it is preferable to adjust the temperature of the aqueous solution 9 in the cell 1. Furthermore, both the voltage V and the temperature T may be made different for each cell 1.

[0095] In the lithium isotope enrichment method according to this embodiment, by making the voltage V and / or the temperature T different for each cell 1, the discharge amounts of the aqueous solutions 9D and 9E are the same, that is, F n,L -R L = F n,R -R R = 0.5, and the flow rates may be symmetric. However, Li +Under conditions of high mobility (high voltage V, high temperature T), the head separation coefficient β is small, and furthermore, as mentioned above, the voltage V and temperature T are limited in range, so when the number of stages n is large, it is difficult to create a difference for each cell, making it difficult to increase the effectiveness. Also, the asymmetry of the flow rate and Li + By combining this with mobility asymmetry, the effect can be further enhanced.

[0096] The lithium isotope enrichment method according to this embodiment can also be applied to lithium isotope enrichment apparatuses 10G, 10A, and 10H (see Figures 6, 7, 8, and 10) according to a modification of the first embodiment. Furthermore, similar to the modification of the first embodiment, a configuration for increasing the head separation coefficient β can be applied to cell 1 of the lithium isotope enrichment apparatuses 10, 10G, 10A, and 10H.

[0097] [Third Embodiment] In the second embodiment, Li between the two chambers for each cell + In order to make the amount of movement different, the Li of the electrolyte membrane + Although the mobility is different, the area of ​​the lithium ion conductive electrolyte membrane may also be different. Below, a lithium isotope enrichment apparatus and lithium isotope enrichment method according to a third embodiment of the present invention will be described.

[0098] (Lithium Isotope Enrichment Apparatus) The lithium isotope enrichment apparatus (ion enrichment apparatus) 10B according to the third embodiment of the present invention has the same structure as the lithium isotope enrichment apparatus 10 according to the first embodiment, an n-stage cross-type cascade system shown in Figure 1. Furthermore, as shown in Figure 13, the lithium isotope enrichment apparatus 10B has a cell 1 -n , ..., 1 -2 ,1 -1 ,1 +1 ,1 +2 , ..., 1 +n However, in this order, the size increases, and more specifically, the depth increases, meaning the area S of the electrolyte membrane 4 is large. The other components of the lithium isotope enrichment apparatus 10B are the same as those of the lithium isotope enrichment apparatus 10.

[0099] Cell 1 has the same structure as the first embodiment shown in Figures 2A and 2B, except for its size. In the lithium isotope enrichment apparatus 10B, cell 1 +n Area S of the electrolyte membrane 4 +n Cell 1 -n Area S of the electrolyte membrane 4 -n Designed to be smaller than, preferably, cell 1 k Area S of the electrolyte membrane 4 k However, cell 1 of the row next to that - side k-1 Area S of the electrolyte membrane 4 k-1 The following is (S -n > S +n , S k-1 ≥S k , S -1 ≥S +1 , 1-n ≤ k ≤ -1, +2 ≤ k ≤ +n). For example, all cells 1 are set to be different in size so that the area S of the electrolyte membrane 4 gradually decreases each time a step is moved from the negative end to the positive end. Then, as you approach the positive end, Li in cell 1 + The amount of movement decreases. Note that in Figure 13, the depth of cell 1 is changed, but the height may also be changed, or both. Also, as shown in Figure 13, the lithium isotope enrichment apparatus 10B is configured such that the cells 1 have the same width and the volume differs in proportion to the area S of the electrolyte membrane 4, but it may also be configured so that the width is changed and the volume is the same. Also, in the lithium isotope enrichment apparatus 10B, the area S of the electrolyte membrane 4 of all cells 1 does not have to be different from each other, for example, they can be the same size in multiple consecutive stages of cells 1. In that case, cell 1 -n Cell 1 -n+1 Larger than (S -n > S -n+1 ) is preferable, and cell 1 +n Cell 1 +n-1 Smaller than (S +n-1 > S +n ) is preferable.

[0100] (Lithium Isotope Concentration Method) The lithium isotope concentration method (ion concentration method) according to the third embodiment of the present invention, as shown in Figure 13, in the lithium isotope concentration apparatus 10B, similar to the first embodiment, while supplying a Li source aqueous solution 9S to the flow path 80, a voltage V is applied to each power supply 6 of 2n cells 1, and cell 1 +n Discharged from cathode chamber 3 6 The concentrated Li aqueous solution 9E is recovered. At that time, 6 Li concentrated aqueous solution 9E 6 The branching ratio is set for each channel 8 so that a large amount of the Li-depleted aqueous solution 9D is discharged. In Figure 13, as in Figure 4, the arrows attached to the channels 8 indicate the direction of flow of the aqueous solution 9, and the thickness of the solid line representing the channel 8 indicates the amount of flow.

[0101] According to the lithium isotope enrichment method of this embodiment, the overall separation coefficient ω is large, similar to the first embodiment, and furthermore, because the area S of the electrolyte membrane 4 differs for each cell 1, the overall separation coefficient ω becomes even larger.

[0102] (Modified Example) The lithium isotope enrichment apparatus according to this embodiment is a lithium isotope enrichment apparatus 10G (see Figure 6), with cell 1 -n Aqueous solution 9a in the anode chamber 2 -n Cell 1 +n aqueous solution 9c in cathode chamber 3 +n A configuration may be used in which a portion of each is discharged and the remainder is recirculated.

[0103] The lithium isotope enrichment apparatus according to this embodiment has a minimum of +n cells 1 +n Area S of the electrolyte membrane 4 +n If it is 0, that is, cell 1 +n It may not be necessary. As shown in Figure 14, the lithium isotope enrichment apparatus (ion enrichment apparatus) 10C according to a modification of the third embodiment of the present invention has cell 1 +n Furthermore, there are no single-chamber cells 13 and 12. Therefore, in the lithium isotope enrichment apparatus 10C, cell 1 -n+1 Aqueous solution 9a that flowed out from the anode chamber 2. -n+1 Part of the flow path 8 -n+1 It merges with the aqueous solution 9f. +n-1 Part of it is cell 1+n flows into the flow path 8 instead of flowing into the anode chamber 2 +n-2 and merges with it. Then, the aqueous solution 9c +n-1 flowing out from the cathode chamber 3 of the cell 1 +n-1 partially flows directly into the cathode chamber 3 of the cell 1 +n instead of flowing in, and is discharged as the Li-enriched aqueous solution 9E, while the remaining part merges with the flow path 8 6 . Other configurations of the lithium isotope enrichment device 10C are the same as those of the lithium isotope enrichment device 10B. +n-1

[0104] The lithium isotope enrichment device according to the present embodiment may have a structure of a straight multi-stage cascade system. That is, the lithium isotope enrichment device (ion enrichment device) 10D according to the modified example of the third embodiment of the present invention has the same structure as the lithium isotope enrichment device 10A (see FIG. 7) according to the modified example of the first embodiment, which is an n-stage straight cascade system structure. Further, as shown in FIG. 15, in the lithium isotope enrichment device 10D, the cells 1 -n , …, 1 -1 , 10, 1[[ID=2|1]] +1 , …, 1 +n are larger in size in this order, that is, the area S of the electrolyte membrane 4 is larger. Other configurations of the lithium isotope enrichment device 10D are the same as those of the lithium isotope enrichment device 10A. Also, the lithium isotope enrichment device according to this modified example may have a configuration in which a part of each of the aqueous solution 9a -n in the anode chamber 2 of the cell 1 -n , the aqueous solution 9c +n in the cathode chamber 3 of the cell 1 +n is discharged, and the remaining part is refluxed, similar to the lithium isotope enrichment device 10H (see FIG. 10).

[0105] Similar to the modified example of the first embodiment, the lithium isotope enrichment devices 10B, 10C, and 10D can apply a configuration for increasing the head separation factor β to the cell 1.

[0106] The lithium isotope enrichment method according to the present embodiment is such that in the lithium isotope enrichment devices 10B, 10C, and 10D, the discharge amounts of the aqueous solutions 9D and 9E are the same, that is, F n,L - R L = F n,R - RR It may also be a symmetrical flow rate of =0.5. However, the asymmetry of the flow rate and Li + By combining this with the asymmetry of the amount of migration, the effect can be further enhanced. In addition, by combining this with the lithium isotope enrichment method according to the second embodiment, the voltage V (I / S) and / or the temperature T of the electrolyte membrane 4 may be made different for each cell 1.

[0107] [Fourth Embodiment] The lithium isotope enrichment apparatus according to the present invention is 7 It can also be used as a lithium concentration device. Cell 1 of the -n stage of a multi-stage (n-stage) cascade system (Figures 1 and 7) using perfusion electrodialysis. -n Aqueous solution 9a discharged from the anode chamber 2 -n It is better than Li source aqueous solution 9S 6 The Li isotope ratio is low, that is 7 High Li isotope ratio 7 It can be said to be a concentrated Li aqueous solution. And by creating an asymmetric multi-stage cascade structure as follows, 7 Aqueous solutions with a higher Li isotope ratio can be recovered.

[0108] (Lithium Isotope Concentrator) As shown in Figure 16, the lithium isotope concentrate (ion concentrate) 10E according to the fourth embodiment of the present invention has the same n-stage cross-type cascade system structure as the lithium isotope concentrate 10 according to the first embodiment, as shown in Figure 1. The lithium isotope concentrate 10E is supplied with an aqueous Li source solution (aqueous ion source solution) 9S from the outside via the flow path 80, and cells 1 at each end on both sides -n ,1 +n from 7 Li concentrated aqueous solution 9E, 7 Discharge the Li-depleted aqueous solution 9D. For details, see Cell 1. -n From the anode chamber 2, aqueous solution 9a -n but 7 As Li concentrated aqueous solution 9E, cell 1 +n From the cathode chamber 3, aqueous solution 9c +n but 7 They are each discharged as Li-depleted aqueous solution 9D.

[0109] Furthermore, the lithium isotope enrichment device 10E is cell 1+n The flow rate of the cathode chamber 3, that is 7 Emissions from Li-depleting aqueous solution 9D (F n,R -R R ) is cell 1 -n The flow rate in anode chamber 2, that is 7 Discharge volume of Li concentrated aqueous solution 9E (F n,L -R L (F n,L -R L <F n,R -R R The branching ratio for each flow path 8 is set by the control valve 81. In Figure 16, the amount of flow is represented by the thickness of the solid line indicating the flow path 8. The other configurations of the lithium isotope enrichment apparatus 10E are the same as those of the lithium isotope enrichment apparatus 10. Therefore, the lithium isotope enrichment apparatus 10E is a configuration in which the flow rate ratio of each chamber is swapped (left and right reversed) between the negative and positive sides of the lithium isotope enrichment apparatus 10 (Figure 4), or in other words, a configuration in which the polarity of the applied voltage to all cells 1 is reversed.

[0110] (Lithium Isotope Concentration Method) The lithium isotope concentration method (ion concentration method) according to the fourth embodiment of the present invention, as shown in Figure 16, in the lithium isotope concentration apparatus 10E, similar to the first embodiment, while supplying a Li source aqueous solution 9S to the flow path 80, a voltage V is applied to each of the 2n cells 1 power supplies 6, and cell 1 -n Discharged from anode chamber 2 7 The concentrated Li aqueous solution 9E is recovered. At that time, 7 Li concentrated aqueous solution 9E (aqueous solution 9a -n ) 7 Li-depleting aqueous solution 9D (aqueous solution 9c +n The branching ratio for each of the eight flow paths is designed to ensure that a large amount of waste is discharged.

[0111] As shown in Figure 2B, in cell 1, when a voltage V is applied, the aqueous solution 9a that flows out in the anode chamber 2 relative to the aqueous solution 9f1 that flows in contains Li + The concentration decreases, 7 The Li isotope ratio increases. On the other hand, in the cathode chamber 3, the aqueous solution 9c that flows out relative to the aqueous solution 9f2 that flows in contains Li + The concentration of increases,7 The Li isotope ratio decreases.

[0112] (Modified Example) The lithium isotope enrichment apparatus according to this embodiment is a lithium isotope enrichment apparatus 10G (see Figure 6), with cell 1 -n Aqueous solution 9a in the anode chamber 2 -n Cell 1 +n aqueous solution 9c in cathode chamber 3 +n A configuration may be used in which a portion of each is discharged and the remainder is recirculated. In this modified example, aqueous solution 9a -n By recirculating a portion (the remainder), 7 The Li isotope separation coefficient is large. 7 The concentrated Li aqueous solution 9E can be recovered. Therefore, aqueous solution 9a -n Recirculate to 9c +n A configuration that does not allow for recirculation is also acceptable.

[0113] The lithium isotope enrichment apparatus according to this embodiment may have a straight-type multi-stage cascade system structure. That is, as shown in Figure 17, the lithium isotope enrichment apparatus (ion enrichment apparatus) 10F according to a modification of the fourth embodiment of the present invention has the same n-stage straight-type cascade system structure as the lithium isotope enrichment apparatus 10A (see Figure 7) according to a modification of the first embodiment. Furthermore, the lithium isotope enrichment apparatus 10F, similar to the fourth embodiment, has a cell 1 +n The flow rate of the cathode chamber 3, that is 7 Emissions from Li-depleting aqueous solution 9D (F n,R -R R ) is cell 1 -n The flow rate in anode chamber 2, that is 7 Discharge volume of Li concentrated aqueous solution 9E (F n,L -R L (F n,L -R L <F n,R -R RThe branching ratio for each flow path 8 is set by the control valve 81. The other configurations of the lithium isotope enrichment device 10F are the same as those of the lithium isotope enrichment device 10A. Therefore, the lithium isotope enrichment device 10F is a configuration in which the flow rate ratio of each chamber is reversed (left and right inverted) compared to the lithium isotope enrichment device 10A (see Figure 8), or in other words, a configuration in which the polarity of the applied voltage to all cells 1 is reversed.

[0114] The lithium isotope enrichment apparatus according to this modified example is a lithium isotope enrichment apparatus 10H (see Figure 10), with cell 1 -n Aqueous solution 9a in the anode chamber 2 -n Cell 1 +n aqueous solution 9c in cathode chamber 3 +n A configuration may be used in which a portion of each is discharged and the remainder is refluxed. Furthermore, a structure comprising a single cell 1 (10), such as the lithium isotope enrichment apparatus 10I (see Figure 11), is also possible. Also, aqueous solution 9a -n Recirculate to 9c +n A configuration that does not allow for recirculation is also acceptable.

[0115] Similar to the modification of the first embodiment, the lithium isotope enrichment apparatus 10E and 10F can be configured to increase the head separation coefficient β in cell 1.

[0116] 7 The lithium isotope enrichment apparatus, which serves as the Li enrichment apparatus, may have different voltages V (I / S) and / or temperatures T of the electrolyte membrane 4 for each cell 1, similar to the second embodiment. In this embodiment, cell 1 -n Li in + Mobility is Cell 1 +n It is set to be lower than, preferably, cell 1 k-1 Li in + The cell in the row next to the positive side of the mobility k The following is (V -n <V +n , V k-1 ≤ V k , V -1 ≤ V +1 , T -n <T +n , T k-1 ≦T​k , T -1 ≦T +1 , 1-n ≤ k ≤ -1, +2 ≤ k ≤ +n). Also, similar to the third embodiment, the area S of the electrolyte membrane 4 may be different for each cell 1. In this embodiment, cell 1 -n Area S of the electrolyte membrane 4 -n Cell 1 +n Area S of the electrolyte membrane 4 +n Designed to be smaller than, preferably, cell 1 k-1 Area S of the electrolyte membrane 4 k-1 However, cell 1 in the row next to the + side k Area S of the electrolyte membrane 4 k The following applies, and also, cell 1 -n Cell 1 -n+1 Smaller than, and cell 1 +n Cell 1 +n-1 Larger than (S -n <S +n , S k-1 ≤S k , S -1 ≤S +1 , S -n <S -n+1 , S +n-1 <S +n , 1-n ≤ k ≤ -1, +2 ≤ k ≤ +n). That is, the lithium isotope enrichment apparatus is configured such that the polarity of the applied voltage to all cells 1 is reversed for lithium isotope enrichment apparatuses 10B, 10C, and 10D. Furthermore, in the case where at least one of the voltage V (I / S), the temperature T of the electrolyte membrane 4, and the area S of the electrolyte membrane 4 differs for each cell 1 (asymmetrical), the lithium isotope enrichment method according to this embodiment results in the discharge amount of aqueous solutions 9D and 9E being the same, i.e., F n,L -R L = F n,R -R R A symmetrical flow rate of =0.5 may also be used.

[0117] The ion concentrator and ion concentrating method according to the present invention are not limited to lithium ion isotope concentration, but can be applied to the concentration and separation of heterogeneous ions and isotopes that can be concentrated and separated by electrodialysis. Specifically, in a multi-stage cascade system using reflux electrodialysis, equipped with cells separated by ion-conducting membranes corresponding to the ions to be concentrated, the flow rate and / or ion transfer rate are configured asymmetrically. When the ions to be concentrated are anions, the anode chamber 2 of cell 1 is the ion concentration chamber, and the cathode chamber 3 is the ion depletion chamber. According to the present invention, the overall separation coefficient can be increased.

[0118] The lithium isotope enrichment apparatus and lithium isotope enrichment method according to the present invention have been described above, and embodiments for carrying out the present invention have been described below. It should be noted that the present invention is not limited to these embodiments and the embodiments described above, and various modifications and alterations based on these descriptions are also included in the spirit of the present invention.

[0119] Regarding the lithium isotope enrichment apparatus and lithium isotope enrichment method according to the embodiment of the present invention, the overall separation coefficient ω was calculated by simulation using a model that simulates the lithium isotope enrichment apparatus. In doing so, first, using a sample that simulates the cell shown in Figure 2A, 6 The Li isotope separation coefficient was measured and defined as the head separation coefficient β.

[0120] (Cell fabrication) The cells of the lithium isotope enrichment apparatus use a plate-shaped La as the electrolyte membrane, measuring 50 mm x 50 mm and 0.5 mm thick. 0.57 Li 0.29TiO3 (lithium-ion conductive ceramic LLTO, manufactured by Toho Titanium Co., Ltd.) was used. On the center of each side of this electrolyte membrane, grid-like electrodes measuring 19.5 mm x 20.5 mm were formed as the first and second electrodes, with a thickness of 10 μm, a width of 0.5 mm, and a spacing of 0.5 mm. Two lead wires were also formed to connect to these electrodes, for a total of four. The first electrode, the second electrode, and the lead wires were formed by screen printing Pt paste onto the surface of the electrolyte membrane and firing it in air at 900°C for 1 hour. The electrolyte membrane with the electrodes formed was installed in a processing tank made of acrylic plate and divided into two chambers. The processing tank was housed in a constant temperature bath with a temperature control function. A power supply was connected between the pairs of lead wires connected to the first and second electrodes, with the first electrode as the positive electrode, and an ammeter was connected to the other pair, forming a cell for a lithium isotope enrichment apparatus.

[0121] A 1 mol / L lithium hydroxide aqueous solution was prepared as the Li source aqueous solution. 7 Li, 6 The amount of Li was measured using an inductively coupled plasma mass spectrometer (ICP-MS) (Agilent 8800, manufactured by Agilent Technologies, Inc.). 130 ml of this lithium hydroxide aqueous solution was added to the chamber on the first electrode side (the side connected to the positive electrode of the power supply) of the cell, and 130 ml of pure water was added to the chamber on the second electrode side, ensuring that both electrodes were completely submerged. The temperatures of the lithium hydroxide aqueous solution and the pure water in the cell were then adjusted in a constant temperature bath (20, 30, 40, 50°C).

[0122] (Lithium isotope enrichment experiment using a single cell) To remove the isotope bias caused by Li present in the electrolyte membrane (LLTO), a DC voltage of 2.0 V was applied for 24 hours as a pretreatment. After the pretreatment, the aqueous solutions in the two chambers of the cell were replaced with fresh ones, and a DC voltage of 2.0 V was applied for 1 hour. After the experiment, the aqueous solution in the chamber on the second electrode side was collected, and the aqueous solution was... 7 Li, 6 The amount of Li was measured using an ICP-MS device. Electrodialysis, including pretreatment, was performed by switching the liquid temperature in the cell.

[0123] In the Li source aqueous solution and the aqueous solution recovered after the experiment, 6Li abundance ratio X d , X c Calculate the following for each temperature: 6 The Li isotope separation coefficient was calculated. Table 1 shows the head separation coefficient β and the average current value at 1h for each temperature. β = (X c / (1-X) c )) / (X d / (1-X) d )) ... (5)

[0124]

[0125] [Evaluation of Multistage Cascade System Models] From Table 1, assuming a head separation coefficient β = 1.06, in the models of cross-type and straight-type multistage cascade system structures (see Figures 1 and 7), 6 Flow rate of Li concentrated aqueous solution 9E, Li + Concentration C E , and 6 Li abundance ratio X E This was obtained by solving the mass balance equation using simulation (see Non-Patent Documents 2 and 3). The cell had an active area of ​​9 cm × 9 cm for the electrolyte membrane (LLTO) and two chambers with widths of 4 mm each. The Li source aqueous solution was, 6 Li and 7 Initial isotope ratio of Li X S , 1-X S The values ​​were set to 0.0759 and 0.9241 respectively, and the Li concentration to 200 mol / m³. 3 The supply flow rate F is 1.667 × 10 -7 I understand 3 The value was set to / s. In the simulation, the calculation was repeated at least 150 times, C E , X E The square of the remainder is 10 each -8 mol / m 3 The following and 10 -12 The session ended when the following conditions were met.

[0126] (Example 1) In a model of a cross-type and straight-type cascade system structure for n=1 to 5, the flow rate (F) of the cathode chamber (concentration chamber) of the +n stage cell n,R -R RThe peak value of the overall separation coefficient ω is obtained by varying the flow rate F=1 of the Li source aqueous solution within the range of 0.5 to 0.001. 6 The Li recovery rate r6 was calculated. Table 2 shows the flow rate ratio for each chamber in each stage for the cross type, and Table 3 shows the flow rate ratio for the straight type. Also, Figure 5 shows the flow rate for the cross type, and Figure 9 shows the flow rate for the straight type. n,R -R R This shows the flow rate ratios for each chamber at values ​​of 0.5 and 0.1, respectively.

[0127]

[0128]

[0129] The peak value of the overall separation coefficient ω in the cross-type model and 6 The graphs showing the dependence of the Li recovery rate r6 on the number of stages are shown in Figures 18 and 19, and the graphs showing the dependence on the flow rate ratio are shown in Figures 20 and 21, respectively. The peak value of the overall separation coefficient ω in the straight-type model and 6 The graphs showing the dependence of the Li recovery rate r6 on the number of stages are shown in Figures 22 and 23, and the graphs showing the dependence on the flow rate ratio are shown in Figures 24 and 25.

[0130] As shown in Figures 18, 19, 22, and 23, the overall separation coefficient ω increases as the number of stages n increases. 6 The Li recovery rate r6 increased in both cases. In particular, the overall separation coefficient ω of the cross-type apparatus showed a high dependence, being larger than that of the straight-type apparatus for n≧2, and the difference widened further as the number of stages n increased compared to the straight-type apparatus.

[0131] As shown in Figures 20 and 24, the flow rate ratio (F) of the cathode chamber of the +n stage cell n,R -R R As the asymmetry of the flow rate is reduced (the asymmetry of the flow rate is increased), the overall separation coefficient ω increases, and for both the cross-type and straight-type, when n≧2, F n,R -R R When the value was ≤0.04, it was possible to make it larger than the head separation coefficient β (1.06). On the other hand, as shown in Figures 21 and 25, when the asymmetry of the flow rate was increased, 6 The Li recovery rate r6 decreased, but the decline has stabilized.

[0132] (Example 2) In Example 1, a five-stage cross-type cascade system structure (see Figure 1), the overall separation coefficient ω (peak value) was calculated by changing the applied voltage (current supplied per unit area to the electrolyte membrane) for each cell at a flow rate ratio of 0.001 in the +5 cell of Example 1. Case (reference example) 2-0 is an example in which only the flow rate ratio of Example 1 is asymmetrical. As shown in Figure 26, in Case (comparative example) 2-1, the current of Example 1-1 is set to 1, and the negative cell (cell 1 -5 , ..., 1 -2 ,1 -1 The current of the + side cell (cell 1) is set to 2, and the current of the + side cell (cell 1) +1 ,1 +2 , ..., 1 +5 In this case, the current of the negative-side cell is set to 0.5, or 1 / 4 of the negative-side current. In Case 2-2, conversely, the current of the negative-side cell is set to 0.5 and the current of the positive-side cell is set to 2. Figure 27 shows the graph of the current density dependence of each overall separation coefficient ω.

[0133] As shown in Figure 27, in Example 1-1, where only the flow rate is asymmetrical, the overall separation coefficient ω increases as the current increases, reaching 10 A / m 2 The current peaked in the vicinity and then gradually decreased thereafter. On the other hand, in comparative example 2-1, where the current of the positive cell was increased, the overall separation coefficient ω was 3 A / m 2 The value peaked in the vicinity, and in the low current region below that, it was slightly larger than in Example 1-1, but because the peak current was small, the peak value was small. In contrast, in Example 2-2, where the current of the negative cell was increased, the overall separation coefficient ω was small in the low current region, but 3 A / m 2 The above results are larger than those in Example 1-1, and the measurement range is (~15 A / m). 2 It continued to increase in ).

[0134] Furthermore, as shown in Figure 28, the overall separation coefficient ω was calculated for Case (Reference Example) 3-0 and Case (Example) 3-1, 3-2, and 3-3, in which the current for each stage was varied so that the sum of the currents of the 10 cells matched. Also, as shown in Figure 30, the overall separation coefficient ω was calculated for Case (Example) 3-4 to 3-7 to confirm the effect of reducing the current of the positive-side stage. Figures 29 and 31 show graphs of the current density dependence of the overall separation coefficient ω.

[0135] As shown in Figure 29, the steeper the current change, the larger the peak value of the overall separation coefficient ω. Also, as shown in Figure 31, when the current is changed only in the stages near the end of the positive side, the overall separation coefficient ω is relatively large in the low current region. On the other hand, when the current is changed in stages with smaller levels, the peak value of the overall separation coefficient ω increases, but there was also a tendency for the peak current to increase.

[0136] Here, when the current density is high, that is, when the voltage between both sides of the electrolyte membrane is large, the electrolyte membrane exhibits electronic conductivity, as described above. In the lithium isotope enrichment experiment using a single cell, the current density was 6.92 A / m². 2 Since the liquid temperature is 50°C, it is preferable to operate within a range that does not significantly exceed this temperature. Therefore, 10 A / m 2 It is preferable that the overall separation coefficient ω is large in the following current range.

[0137] (Example 3) In Example 1, with a 5-stage cross-type cascade system structure (see Figure 1), the flow rate ratio of the cathode chambers of the 5th stage cell was 0.001. As shown in Figure 32, the flow path length (vertical length in Figure 1) was varied for each cell so that the total volume of the 10 cells and the area of ​​the electrolyte membrane matched. The supply current per unit area to the electrolyte membrane of each of the 10 cells was made equal, and the flow rate F of the Li source aqueous solution was set to 3 × 10⁻⁶. -8 I understand 3 The overall separation coefficient ω was calculated using a constant value of / s. Figure 33 shows the current density dependence of the overall separation coefficient ω for Case (Example) 4-1, 4-2, and Case (Reference Example) 4-0, which has the same cell size. Figure 34 shows the current density dependence of the overall separation coefficient ω for Example 4-2 when the supply flow rate F of the Li source aqueous solution is changed.

[0138] As shown in Figure 33, by increasing the area of ​​the electrolyte membrane in the negative-side cell, it was possible to reduce the peak current without significantly changing the peak value of the overall separation coefficient ω. Furthermore, as shown in Figure 34, a lower supply flow rate F of the Li source aqueous solution allows for a higher overall separation coefficient ω.

[0139] (Example 4) In a 5-stage cross-type and straight-type cascade system structure, the effect of refluxing the aqueous solution that flowed out from the anode chamber of the -5-stage cell and the cathode chamber of the +5-stage cell was confirmed. Without reflux (R L ' = R R ' = 0) (See Figures 1 and 7), recirculation on the depleted side (R L ' = 0.2, R R '=0), reflux on the concentration side (R L ' = 0, R R ' = 0.2), reflux on both sides (R L ' = 0.2, R R For each of the values ​​of ' = 0.2) (see Figures 6 and 10), the flow rate (F) of the cathode chamber (concentration chamber) of the +5 stage cell is the same as in Example 1. 5,R -R R The peak value of the overall separation coefficient ω is obtained by varying the value of ') within the range of 0.5 to 0.001 relative to the flow rate F = 1 of the Li source aqueous solution. 6 The Li recovery rate r6 was calculated. Similarly, a 0-stage straight-type (single-cell) model was also evaluated. The peak value of the overall separation coefficient ω and 6 Graphs showing the flow rate ratio dependence of the Li recovery rate r6 are shown in Figures 35 and 36 for the cross-type model, in Figures 37 and 38 for the 5-stage straight-type model, and in Figures 39 and 40 for the 0-stage straight-type model.

[0140] As shown in Figures 35 and 37, refluxing a portion of the aqueous solution that flows out from the concentration side (+5 stage) increased the peak value of the overall separation coefficient ω, and this was more pronounced at lower flow rates. Furthermore, the effect was greater in the straight type than in the cross type. On the other hand, as shown in Figures 36 and 38, when the flow rate ratio was low (F 5,R -R R <0.01), 6The Li recovery rate r6 decreased. Furthermore, little effect was observed from recirculating the aqueous solution that flowed out from the depleted side (-5 stage).

[0141] In a single cell, as shown in Figures 39 and 40, refluxing a portion of the aqueous solution that flows out from the concentration side increases the peak value of the overall separation coefficient ω, and also, 6 The Li recovery rate r6 increased.

[0142] (Example 5) For a 5-stage cross-type cascade system structure (see Figure 1), (1) the flow rate ratio of the cathode chambers of the 5-stage cell is 0.001, (2) the current is that of Example 3-3 in Figure 25, and (3) the cell length is that of Example 4-2 in Figure 29, and the overall separation coefficient ω for the combinations of (1) + (2), (1) + (3), (2) + (3), and (1) + (2) + (3) is 1 × 10⁻¹⁰. The flow rate F of the Li source aqueous solution is 1 × 10⁻¹⁰. -8 I understand 3 The calculation is performed using the formula / s, and Figure 41 shows the graph of the current density dependence of the overall separation coefficient ω, while Figure 42 shows the peak value of the overall separation coefficient ω.

[0143] As shown in Figures 41 and 42, the asymmetry effect is low for (2) or (3) alone, and for (2) + (3), the effect can be increased by combining (1) with (2) or (3), and the effect can be further increased by combining (1) with both (2) and (3).

[0144] (Example 6) Lithium isotope enrichment apparatus and lithium isotope enrichment method according to the present invention 7 The effect of Li concentration was confirmed. In the model of the five-stage cross-type cascade system structure in Example 1 (see Figure 1), the flow rate F of the Li source aqueous solution was set to 1 × 10⁻⁶. -7 I understand 3 Let / s be the flow rate (F) of the anode chamber of the -5 stage cell. 5,L -R L ) is set to 0.5 (F) relative to the flow rate F = 1 of the Li source aqueous solution. 5,R -R R =0.5), 0.01(F 5,R -R R =0.99), 0.99(F 5,R -R R= 0.01). The flow rate ratios for each chamber are as shown in Table 2 of Example 1 (n=5). - Discharged from the anode chamber (depletion chamber) of the 5-stage cell 7 Li concentrated aqueous solution 7 The relative abundance of Li was obtained using simulation, similar to Example 1. Figure 43 shows: 7 The graph shows the current density dependence of Li isotope ratios.

[0145] As shown in Figure 43, the flow rate ratio (F) of the anode chamber of the -5 stage cell 5,L -R L By lowering the flow rate and making it asymmetrical, it is possible to achieve a more symmetrical configuration than with a symmetrical one. 7 We were able to recover an aqueous solution with a high Li isotope ratio. Conversely, the flow rate ratio (F 5,L -R L The high flow rate ratio (F) of the cathode chamber of a +5 stage cell, i.e., the high flow rate ratio (F) of the cathode chamber. 5,R -R R If we consider an asymmetrical configuration with a low degree of ) compared to a symmetrical configuration, 7 Li concentrated aqueous solution 7 The Li isotope ratio was low. This composition is, 6 It is for lithium enrichment.

[0146] 10, 10A-10I Lithium Isotope Concentrator (Ion Concentrator) 1 Cell 12, 13 Single-chamber cell 2 Anode chamber (Depletion chamber) 3 Cathode chamber (Concentration chamber) 4 Electrolyte membrane (Lithium ion conductive electrolyte membrane, Ion conductive membrane) 51 First electrode (electrode) 52 Second electrode (electrode) 6 Power supply 7 Tank 8 Flow path 81, 86, 89, 89a, 89c Control valve 82, 83 Inflow path (flow path) 84, 85 Outflow path (flow path) 87 Flow path 88 Supply path 9D 6 Li-depleted aqueous solution, 7 Li-depleted aqueous solution 9E 6 Li concentrated aqueous solution, 7 Li-concentrated aqueous solution 9S Li-source aqueous solution (ion source aqueous solution)

Claims

1. The apparatus comprises an ion-conducting membrane that allows multiple ion species or isotope species to pass through, and has high selective permeability to some of the ion species or isotope species, a power supply, and electrodes connected to the power supply, and is divided into a depletion chamber and a concentration chamber by the ion-conducting membrane, and has 2n cells from the 1st to the 2nth (n: natural number), in which the ions contained in the aqueous solution in the depletion chamber move to the aqueous solution in the concentration chamber by the voltage applied by the power supply, and further comprises a 0th cell consisting of a concentration chamber, a (2n+1)th cell consisting of a depletion chamber, and an i-th channel (2≦i≦2n) that merges the aqueous solutions in the depletion chamber of the (i+1)th cell and the concentration chamber of the (i-2)th cell and branches them into the depletion chamber of the i-th cell and the concentration chamber of the (i-1)th cell, respectively. An ion concentrator comprising: a first channel that branches and flows the aqueous solution in the depletion chamber of the second cell to the depletion chamber of the first cell and the 0th cell; and a (2n+1)th channel that branches and flows the aqueous solution in the concentration chamber of the (2n-1)th cell to the concentration chamber of the 2nth cell and the (2n+1)th cell, wherein an ion source aqueous solution containing multiple ion species or isotopic ions that permeate the ion conductive membrane is supplied to the (n+1)th channel to discharge the aqueous solution from the depletion chamber of the first cell, and discharges an aqueous solution from the concentration chamber of the 2nth cell at a flow rate less than or equal to the aqueous solution, in which the concentration ratio of some types of ions is higher than that of the ion source aqueous solution, An ion concentrator characterized in that the first cell has a larger flow rate of the aqueous solution discharged than the second nth cell, a larger area of ​​the ion conductive membrane, a higher current density supplied to the ion conductive membrane by the power supply, and a higher temperature of the ion conductive membrane.

2. The ion concentrator according to claim 1, wherein a portion of the aqueous solution in the concentration chamber of the 2nth cell is discharged, and the remainder merges with the aqueous solution in the concentration chamber of the (2n-1)th cell in the (2n+1)th flow path.

3. The apparatus comprises an ion-conducting membrane that allows multiple ion species or isotope species to pass through, but has low selective permeability to some of the ion species or isotope species, a power supply, and electrodes connected to the power supply, and is divided into a depletion chamber and a concentration chamber by the ion-conducting membrane, and has 2n cells from the 1st to the 2nth (n: natural number), in which the ions contained in the aqueous solution in the depletion chamber move to the aqueous solution in the concentration chamber by the voltage applied by the power supply, further comprising a 0th cell consisting of a concentration chamber, a (2n+1)th cell consisting of a depletion chamber, and an i-th channel (2≦i≦2n) that merges the aqueous solutions in the depletion chamber of the (i+1)th cell and the concentration chamber of the (i-2)th cell and branches them into the depletion chamber of the i-th cell and the concentration chamber of the (i-1)th cell, respectively. An ion concentrator comprising: a first channel that branches and flows the aqueous solution in the depletion chamber of the second cell to the depletion chamber of the first cell and the 0th cell; and a (2n+1)th channel that branches and flows the aqueous solution in the concentration chamber of the (2n-1)th cell to the concentration chamber of the 2nth cell and the (2n+1)th cell, wherein an ion source aqueous solution containing multiple ion species or isotopic ions that permeate the ion conductive membrane is supplied to the (n+1)th channel to discharge the aqueous solution from the concentration chamber of the 2nth cell, and discharges an aqueous solution from the depletion chamber of the first cell at a flow rate less than or equal to the aqueous solution, in which the concentration ratio of some types of ions is higher than that of the ion source aqueous solution, An ion concentrator characterized in that the 2nth cell has a larger flow rate of the aqueous solution discharged than the first cell, a larger area of ​​the ion conductive membrane, a higher current density supplied to the ion conductive membrane by the power supply, and a higher temperature of the ion conductive membrane.

4. The ion concentrator according to claim 3, wherein a portion of the aqueous solution in the depletion chamber of the first cell is discharged, and the remainder merges with the aqueous solution in the depletion chamber of the second cell in the first flow path.

5. The ion concentrator according to claim 1 or 2, characterized in that the area of ​​the ion conductive membrane of the first cell is larger than that of the second cell, and / or the area of ​​the ion conductive membrane of the (2n-1)th cell is larger than that of the 2nth cell.

6. The ion concentrator according to claim 3 or 4, characterized in that the area of ​​the ion conductive membrane of the second cell is larger than that of the first cell, and / or the area of ​​the ion conductive membrane of the 2n-th cell is larger than that of the (2n-1)-th cell.

7. The apparatus comprises an ion-conducting membrane that allows multiple ion species or isotope species to pass through, and has high selective permeability to some of the ion species or isotope species, a power supply, and electrodes connected to the power supply, and is divided into a depletion chamber and a concentration chamber by the ion-conducting membrane, and comprises (2n+1) cells (n: natural number) in which the ions contained in the aqueous solution in the depletion chamber move to the aqueous solution in the concentration chamber by the voltage applied by the power supply, further comprising an i-th channel (2≦i≦2n) that merges the aqueous solutions in the depletion chamber of the (i+1)-th cell and the concentration chamber of the (i-1)-th cell and branches off to flow into the depletion chamber and concentration chamber of the i-th cell, and a first channel that branches off to flow into the depletion chamber of the second cell and concentration chamber of the first cell, An ion concentrator comprising: a (2n+1)th channel that branches and flows the aqueous solution in the concentration chamber of the 2nth cell into the depletion chamber and the concentration chamber of the (2n+1)th cell; an ion source aqueous solution containing a plurality of ion species or isotopic species that permeate the ion conduction membrane into the (n+1)th channel, thereby discharging the aqueous solution from the depletion chamber of the first cell and discharging an aqueous solution from the concentration chamber of the (2n+1)th cell at a flow rate less than or equal to the aqueous solution, in which the concentration ratio of some types of ions is higher than that of the ion source aqueous solution; wherein the first cell satisfies at least one of the following: a larger flow rate of the aqueous solution to be discharged than that of the (2n+1)th cell; a larger area of ​​the ion conduction membrane; a higher current density supplied to the ion conduction membrane by the power supply; and a higher temperature of the ion conduction membrane.

8. The ion concentrator according to claim 7, wherein a portion of the aqueous solution in the concentration chamber of the (2n+1)th cell is discharged, and the remainder merges with the aqueous solution in the concentration chamber of the 2nth cell in the (2n+1)th flow path.

9. The apparatus comprises an ion-conducting membrane that allows multiple ion species or isotope species to pass through, but has low selective permeability to some of the ion species or isotope species, a power supply, and electrodes connected to the power supply, and is divided into a depletion chamber and a concentration chamber by the ion-conducting membrane, and comprises (2n+1) cells (n: natural number) in which the ions contained in the aqueous solution in the depletion chamber move to the aqueous solution in the concentration chamber by the voltage applied by the power supply, and further comprises an i-th channel (2≦i≦2n) that merges the aqueous solutions in the depletion chamber of the (i+1)-th cell and the concentration chamber of the (i-1)-th cell and branches off to flow into the depletion chamber and concentration chamber of the i-th cell, and a first channel that branches off to flow into the depletion chamber of the second cell and concentration chamber of the first cell, An ion concentrator comprising: a (2n+1)th channel that branches the aqueous solution in the concentration chamber of the 2nth cell into the depletion chamber and the concentration chamber of the (2n+1)th cell, wherein an ion source aqueous solution containing a plurality of ion species or isotopic species that permeate the ion conduction membrane is supplied to the (n+1)th channel, the aqueous solution is discharged from the concentration chamber of the (2n+1)th cell, and an aqueous solution with a concentration ratio of some types of ions higher than that of the ion source aqueous solution is discharged from the depletion chamber of the 1st cell at a flow rate less than or equal to that of the aqueous solution, characterized in that the (2n+1)th cell satisfies at least one of the following: the flow rate of the aqueous solution to be discharged is greater than that of the 1st cell, the area of ​​the ion conduction membrane is larger, the current density supplied to the ion conduction membrane by the power supply is higher, and the temperature of the ion conduction membrane is higher.

10. The ion concentrator according to claim 9, wherein a portion of the aqueous solution in the depletion chamber of the first cell is discharged, and the remainder merges with the aqueous solution in the depletion chamber of the second cell in the first flow path.

11. The ion concentrator according to claim 7 or 8, characterized in that the area of ​​the ion conductive membrane of the first cell is larger than that of the second cell, and / or the area of ​​the ion conductive membrane of the 2n-th cell is larger than that of the (2n+1)-th cell.

12. The ion concentrator according to claim 9 or 10, characterized in that the area of ​​the ion conductive membrane of the second cell is larger than that of the first cell, and / or the area of ​​the ion conductive membrane of the (2n+1)th cell is larger than that of the 2nth cell.

13. An ion concentrator comprising: an ion-conducting membrane that allows multiple ion species or isotopic species to pass through and has high selective permeability to some of the ion species or isotopic species; a power supply; and electrodes connected to the power supply, the ion concentrator being divided into a depletion chamber and a concentration chamber by the ion-conducting membrane, and the ions contained in the aqueous solution in the depletion chamber moving into the aqueous solution in the concentration chamber by a voltage applied by the power supply; and a channel that branches a portion of the aqueous solution in the concentration chamber of the cell into the concentration chamber and the depletion chamber, wherein an ion source aqueous solution containing multiple ion species or isotopic species that permeate the ion-conducting membrane is supplied to the channel, the aqueous solution being discharged from the depletion chamber of the cell, and an aqueous solution being discharged from the concentration chamber at a flow rate less than that of the aqueous solution, with a concentration ratio of some of the ions higher than that of the ion source aqueous solution.

14. An ion concentrator comprising: an ion-conducting membrane that allows multiple ion species or isotopic species to pass through but has low selective permeability to some of the ion species or isotopic species; a power supply; and electrodes connected to the power supply, the ion concentrator being divided into a depletion chamber and a concentration chamber by the ion-conducting membrane, and the ions contained in the aqueous solution in the depletion chamber moving into the aqueous solution in the concentration chamber by a voltage applied by the power supply; and a channel that branches a portion of the aqueous solution in the depletion chamber of the cell into the depletion chamber and the concentration chamber, wherein an ion source aqueous solution containing multiple ion species or isotopic species that permeate the ion-conducting membrane is supplied to the channel, the aqueous solution is discharged from the concentration chamber of the cell, and an aqueous solution with a concentration ratio of some of the ions higher than that of the ion source aqueous solution is discharged from the depletion chamber at a flow rate less than that of the aqueous solution.

15. The ion-conducting membrane is a lithium-ion conductive electrolyte membrane, and the ion source aqueous solution is 6 Li and 7 It is an aqueous solution containing lithium ions of Li, and is more than the aforementioned ion source aqueous solution. 6 Li or 7 An ion concentrator according to any one of claims 1 to 14, for recovering an aqueous solution containing lithium ions with a high isotopic ratio of Li.

16. An ion-conducting membrane that allows permeation of multiple ion species or isotope species, and has high selective permeability of some of these ion species or isotope species, comprising 2n cells from the 1st to the 2nth (n: natural number) divided into a depletion chamber and a concentration chamber, a 0th cell consisting of a concentration chamber, and a (2n+1)th cell consisting of a depletion chamber, where the aqueous solutions in the depletion chamber of the (i+1)th cell and the concentration chamber of the (i-2)th cell are combined, resulting in the ith The following channels are connected: an i-th channel (2 ≤ i ≤ 2n) that branches off and flows into the depletion chamber of the cell and the concentration chamber of the (i-1)th cell; a first channel that branches off and flows into the depletion chamber of the second cell and the depletion chamber of the first cell and the 0th cell; and a (2n+1)th channel that branches off and flows into the concentration chamber of the (2n-1)th cell and the concentration chamber of the 2nth cell and the (2n+1)th cell. An ion concentration method comprising supplying an ion source aqueous solution containing multiple ion species or isotope species of ions that permeate the ion conductive membrane to the (n+1)th channel, and in each of the cells, a power supply connected to an electrode provided in the cell applies a voltage that moves the ions contained in the aqueous solution in the depletion chamber to the aqueous solution in the concentration chamber, thereby discharging the aqueous solution from the depletion chamber of the first cell and discharging an aqueous solution from the concentration chamber of the 2nth cell at a flow rate less than or equal to the aqueous solution, in which the concentration ratio of some types of ions is higher than that of the ion source aqueous solution, characterized in that the first cell satisfies at least one of the following: the flow rate of the aqueous solution to be discharged is greater than that of the 2nth cell, the area of ​​the ion conductive membrane is larger, the current density supplied to the ion conductive membrane by the power supply is higher, and the temperature of the ion conductive membrane is higher.

17. The ion concentration method according to claim 16, wherein a portion of the aqueous solution in the concentration chamber of the 2nth cell is discharged, and the remainder merges with the aqueous solution in the concentration chamber of the (2n-1)th cell in the (2n+1)th flow path.

18. An ion-conducting membrane that allows permeability of multiple ion species or isotope species, but has low selective permeability of some of these ion species or isotope species, comprising 2n cells (n: natural number) from the 1st to the 2nth, each partitioned into a depletion chamber and a concentration chamber, a 0th cell consisting of a concentration chamber, and a (2n+1)th cell consisting of a depletion chamber, where the aqueous solutions in the depletion chamber of the (i+1)th cell and the concentration chamber of the (i-2)th cell are combined to form the ith The following channels are connected: an i-th channel (2 ≤ i ≤ 2n) that branches off and flows into the depletion chamber of the cell and the concentration chamber of the (i-1)th cell; a first channel that branches off and flows into the depletion chamber of the second cell and the depletion chamber of the first cell and the 0th cell; and a (2n+1)th channel that branches off and flows into the concentration chamber of the (2n-1)th cell and the concentration chamber of the 2nth cell and the (2n+1)th cell. An ion concentration method comprising supplying an ion source aqueous solution containing multiple ion species or isotope species that permeate the ion conductive membrane to the (n+1)th channel, and in each of the cells, a power supply connected to an electrode provided in the cell applies a voltage that moves the ions contained in the aqueous solution in the depletion chamber to the aqueous solution in the concentration chamber, thereby discharging the aqueous solution from the concentration chamber of the 2nth cell and discharging an aqueous solution from the depletion chamber of the 1st cell at a flow rate less than or equal to the aqueous solution, in which the concentration ratio of some types of ions is higher than that of the ion source aqueous solution, characterized in that the 2nth cell satisfies at least one of the following: the flow rate of the aqueous solution to be discharged is greater than that of the 1st cell, the area of ​​the ion conductive membrane is larger, the current density supplied to the ion conductive membrane by the power supply is higher, and the temperature of the ion conductive membrane is higher.

19. The ion concentration method according to claim 18, wherein a portion of the aqueous solution in the depletion chamber of the first cell is discharged, and the remainder merges with the aqueous solution in the depletion chamber of the second cell in the first flow path.

20. An ion-conducting membrane that allows permeation of multiple ion species or isotope species, while exhibiting high selective permeability to some of these ion species or isotope species, wherein (2n+1) cells, each partitioned into a depletion chamber and a concentration chamber (n: natural number), are connected by an i-th channel (2≦i≦2n) that merges the aqueous solutions in the depletion chamber of the (i+1)-th cell and the concentration chamber of the (i-1)-th cell, and branches them into the depletion chamber and concentration chamber of the i-th cell (2≦i≦2n), a first channel that branches the aqueous solution in the depletion chamber of the second cell into the depletion chamber and concentration chamber of the first cell, and a (2n+1)-th channel that branches the aqueous solution in the concentration chamber of the 2n-th cell into the depletion chamber and concentration chamber of the (2n+1)-th cell. An ion concentration method comprising supplying an ion source aqueous solution containing multiple ion species or isotope species that permeate the ion conductive membrane to the (n+1)th channel, and in each of the cells, a power supply connected to an electrode provided in the cell applies a voltage that moves the ions contained in the aqueous solution in the depletion chamber to the aqueous solution in the concentration chamber, thereby discharging the aqueous solution from the depletion chamber of the first cell and discharging an aqueous solution from the concentration chamber of the (2n+1)th cell at a flow rate less than or equal to the aqueous solution, in which the concentration ratio of some types of ions is higher than that of the ion source aqueous solution, characterized in that the first cell satisfies at least one of the following: the flow rate of the aqueous solution to be discharged is greater than that of the (2n+1)th cell, the area of ​​the ion conductive membrane is larger, the current density supplied to the ion conductive membrane by the power supply is higher, and the temperature of the ion conductive membrane is higher.

21. The ion concentration method according to claim 20, wherein a portion of the aqueous solution in the concentration chamber of the (2n+1)th cell is discharged, and the remainder merges with the aqueous solution in the concentration chamber of the 2nth cell in the (2n+1)th flow path.

22. An ion-conducting membrane that allows permeability of multiple ion species or isotopic species, but has low selective permeability to some of these ion species or isotopic species, wherein (2n+1) cells, each partitioned into a depletion chamber and a concentration chamber (n: natural number), are connected by an i-th channel (2≦i≦2n) that merges the aqueous solutions in the depletion chamber of the (i+1)-th cell and the concentration chamber of the (i-1)-th cell, and branches them into the depletion chamber and concentration chamber of the i-th cell (2≦i≦2n), a first channel that branches the aqueous solution in the depletion chamber of the second cell into the depletion chamber and concentration chamber of the first cell, and a (2n+1)-th channel that branches the aqueous solution in the concentration chamber of the 2n-th cell into the depletion chamber and concentration chamber of the (2n+1)-th cell. An ion concentration method comprising supplying an ion source aqueous solution containing multiple ion species or isotope species that permeate the ion conductive membrane to the (n+1)th channel, and in each of the cells, a power supply connected to an electrode provided in the cell applies a voltage that moves the ions contained in the aqueous solution in the depletion chamber to the aqueous solution in the concentration chamber, thereby discharging the aqueous solution from the concentration chamber of the (2n+1)th cell, and discharging an aqueous solution from the depletion chamber of the first cell at a flow rate less than or equal to the aqueous solution, in which the concentration ratio of some types of ions is higher than that of the ion source aqueous solution, characterized in that the (2n+1)th cell satisfies at least one of the following: the flow rate of the aqueous solution to be discharged is greater than that of the first cell, the area of ​​the ion conductive membrane is larger, the current density supplied to the ion conductive membrane by the power supply is higher, and the temperature of the ion conductive membrane is higher.

23. The ion concentration method according to claim 22, wherein a portion of the aqueous solution in the depletion chamber of the first cell is discharged, and the remainder merges with the aqueous solution in the depletion chamber of the second cell in the first flow path.

24. An ion concentration method comprising: an ion-conducting membrane that allows multiple ion species or isotope species to pass through, but has high selective permeability to some of the ion species or isotope species, in a cell divided into a depletion chamber and a concentration chamber, the aqueous solution in the concentration chamber being connected by a channel that branches and flows into the concentration chamber and the depletion chamber, an ion source aqueous solution containing multiple ion species or isotope species that permeate the ion-conducting membrane being supplied to the channel, and a power supply connected to electrodes provided in the cell applying a voltage that moves the ions contained in the aqueous solution in the depletion chamber to the aqueous solution in the concentration chamber, thereby discharging the aqueous solution from the depletion chamber and discharging an aqueous solution from the concentration chamber at a flow rate less than that of the aqueous solution, in which the concentration ratio of some of the ions is higher than that of the ion source aqueous solution.

25. An ion concentration method comprising a cell partitioned into a depletion chamber and a concentration chamber by an ion-conducting membrane that permeates multiple ion species or isotope species but has low selective permeability to some of the ion species or isotope species, wherein the aqueous solution in the depletion chamber is connected by a channel that branches and flows into the depletion chamber and the concentration chamber, and an ion source aqueous solution containing multiple ion species or isotope species that permeate the ion-conducting membrane is supplied to the channel, and a power supply connected to electrodes provided in the cell applies a voltage that moves the ions contained in the aqueous solution in the depletion chamber to the aqueous solution in the concentration chamber, thereby discharging the aqueous solution from the concentration chamber and discharging an aqueous solution from the depletion chamber at a flow rate less than that of the aqueous solution, in which the concentration ratio of some of the ions is higher than that of the ion source aqueous solution.

26. The ion-conducting membrane is a lithium-ion conductive electrolyte membrane, and the ion source aqueous solution is 6 Li and 7 It is an aqueous solution containing lithium ions of Li, and is more than the aforementioned ion source aqueous solution. 6 Li or 7 An ion concentration method according to any one of claims 16 to 25, for recovering an aqueous solution containing lithium ions with a high isotopic ratio of Li.

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