Lithium recovery apparatus and lithium recovery method

Abstract

The lithium recovery device (10C) has a treatment tank (1) divided into a supply tank (11) and a recovery tank (13) by a lithium ion-conducting electrolyte membrane (2), and moves Li + from an aqueous solution (SW) containing Li + and metal ions M n+ other than Li in the supply tank (11) to an aqueous solution (RS) in the recovery tank (13), has a first power source (51) and a sub power source (53), the first power source connects a first electrode (31) provided in a porous structure and in contact with the face of the supply tank (11) side of the electrolyte membrane (2) as a positive electrode between the first electrode (31) and a second electrode (32A) provided in the recovery tank (13); the sub power source (53) is connected in series with the positive electrode of the first power source (51), and connects the positive electrode with a sub electrode (41) provided in the supply tank (11) in a manner separated from the electrolyte membrane (2).

Description

TECHNICAL FIELD

[0001] The present application relates to a lithium recovery device and a lithium recover method for selectively recovering lithium ions from an aqueous solution. BACKGROUND

[0002] Lithium (Li) is a highly demanded resource as a raw material for lithium ion secondary batteries or fuel for nuclear fusion reactors, and a collection method that can stably supply and is more inexpensive is required. As a stable supply source of Li, there is seawater or the like in which Li + is dissolved as a cation. In addition, since lithium ion secondary batteries mainly contain Li in the form of lithium cobaltate (LiCoO2) or the like at the positive electrode, an inexpensive recovery technique for recovering from batteries discarded due to battery life or the like is desired. A recovery technique for recovering Li from seawater or the like has been applied to an adsorption method, but as a method with more excellent selectivity, a recovery method using electrodialysis is being developed, which uses an electrolyte membrane having lithium ion conductivity (for example, Patent Literature 1, Non-Patent Literature 1).

[0003] Reference Figure 11 will be made to a Li recovery method using electrodialysis described in Patent Literature 1 or the like. A lithium recovery device 100 is configured to divide a treatment tank 1 into a supply tank 11 and a recovery tank 13 by a lithium ion conductive electrolyte membrane (hereinafter, electrolyte membrane) 2, and a power supply 151 is connected with the electrode 131 as the positive electrode between the electrode 131 disposed in the supply tank 11 and the electrode 132 disposed in the recovery tank 13. A Li-containing aqueous solution SW such as seawater as a Li source is put in the supply tank 11, and a Li recovery aqueous solution RS such as pure water is put in the recovery tank 13.

[0004] When a voltage is applied by the power supply 151, a reaction of the following formula (1) occurs in the vicinity of the electrode 131 in the Li-containing aqueous solution SW of the supply tank 11 to generate water (H2O) and oxygen (O2). Also, in the case where the Li-containing aqueous solution SW contains a chloride ion (Cl - ), a reaction of the following formula (2) occurs in the vicinity of the electrode 131 to generate chlorine (Cl2). With the decrease of a hydroxide ion (OH - ), further, a Cl - ion or the like, in order to maintain the balance of electric charge, a Li +The electrochemical reaction of formula (3) involves the movement of Li into electrolyte membrane 2. Furthermore, in each formula, the Li contained in electrolyte membrane 2 (electrolyte, electrolyte) is... + Represented as Li + (electrolyte).

[0005] [Chemical Formula 1]

[0006]

[0007] 2Cl - →Cl2↑+2e - ··· (2)

[0008] Li + →Li + (electrolyte) ··· (3)

[0009] On the other hand, in the Li recovery aqueous solution RS in the recovery tank 13, the following reaction (4) occurs near the electrode 132 to generate hydrogen (H2) and OH. - Accompanied by OH - To maintain charge balance, an increase in the concentration of Li in electrolyte membrane 2 occurs on the surface of electrolyte membrane 2. + The electrochemical reaction of the following equation (5) is moved. As a result, the Li contained in the Li-containing aqueous solution SW, electrolyte membrane 2, and Li recovery aqueous solution RS are respectively + The electrochemical potential difference makes Li + The Li-containing aqueous solution SW migrates through electrolyte membrane 2 to the Li recovery aqueous solution RS. Because the lattice defect sites of electrolyte membrane 2 are small, they do not cause the diameter to be larger than that of the Li-containing aqueous solution. + Large Na + Ca 2+ The Li-containing aqueous solution SW contains Li excluding Li + Other metal ions M n+ Through. Therefore, Li + The Li-containing aqueous solution SW selectively moves to the Li recovery aqueous solution RS, enabling the recovery of Li in the recovery tank 13. + An aqueous solution (lithium hydroxide aqueous solution).

[0010] [Chemical Formula 2]

[0011] 2H2O+2e - →2OH - +H2↑ ··· (4)

[0012] Li + (electrolyte)→Li +(5)

[0013] In the recovery using the electrodialysis, the electrons e are moved from the aqueous solution SW containing Li to the electrode 131, and from the electrode 132 to the aqueous solution RS for recovery of Li - The more the amount of movement per unit time of Li + increases, the faster the reactions of the formula (1), the formula (4), and the like become, and the amount of movement per unit time of Li + (mobility of Li - ) in the electrolyte membrane 2 also increases. In addition, in order to form an electric field in the electrolyte membrane 2 in the thickness direction, the electrodes 131, 132 are preferably disposed in contact with the electrolyte membrane 2 (Patent Document 1), and at this time, the aqueous solutions SW, RS have a porous structure such as a mesh in contact with the electrolyte membrane 2. In addition, when the voltage of the power supply 151 is increased in order to increase the amount of movement per unit time of electrons e + , in reality, at a voltage up to a certain degree, the mobility of Li - does not easily increase further. This is considered to be because the electrolyte membrane 2 reaches a potential at which a part of the metal ions constituting the electrolyte is reduced by the excessively large potential difference applied to both surfaces, and thus the electrons e - are also conducted. When such a voltage is applied, the electrolyte membrane 2 moves a part of the electrons e - supplied from the negative electrode of the power supply 151 to the electrode 132 to the electrode 131. As a result, even if the amount of movement per unit time of the electrons e - moving from the electrode 131 to the electrode 132 via the power supply 151 increases by the increase in the applied voltage, the amount of movement per unit time of the electrons e + between the aqueous solution SW and the electrode 131, and between the electrode 132 and the aqueous solution RS does not significantly increase, and thus the mobility of Li - does not increase with the amount of increase in the applied voltage. Furthermore, the energy efficiency decreases due to the Joule heat generated by the conduction of the electrons e + in the electrolyte membrane 2. Therefore, it can be considered that there is a limit to the recovery method in terms of improving productivity.

[0014] Therefore, the present inventors and the like have developed a technology in which a circuit composed of electrodes separated from the electrolyte membrane is formed, and the potential difference of both surfaces of the electrolyte membrane is suppressed, without directly applying a voltage for electrodialysis from both surfaces of the electrolyte membrane, in order not to exhibit electron conductivity in the electrolyte membrane (Patent Document 2). In detail, as shown in FIG. 1, the aqueous solution SW containing Li is supplied to the electrode 131, and the aqueous solution RS for recovery of Li is supplied to the electrode 132. The electrodes 131, 132 are connected to the power supply 151, and the aqueous solutions SW, RS are connected to the aqueous solution reservoirs 141, 142, respectively. The aqueous solutions SW, RS are supplied to the aqueous solution reservoirs 141, 142, respectively, and the aqueous solutions SW, RS are supplied to the electrodes 131, 132, respectively, by the operation of the pumps 151, 152.As shown, the lithium recovery device 100 causes one of the electrodes 131, 132, here the electrode 132, to be disposed in the recovery tank 13 in a manner separated from the electrolyte membrane 2. According to such a structure, even if the voltage of the power supply 151 increases to a certain extent, the potential difference on both sides of the electrolyte membrane 2 does not significantly increase, and thus the electrolyte membrane 2 does not easily exhibit electronic conductivity, and it is possible to improve the Li + mobility.

[0015] [Related Art Documents]

[0016] [Patent Documents]

[0017] Patent Document 1: Japanese Patent No. 6233877

[0018] Patent Document 2: Japanese Patent Application Publication No. 2019-141807

[0019] [Non-Patent Documents]

[0020] Non-Patent Document 1: Kunugi S., Inaguma Y., Itoh M., "Electrochemical recovery and isotope separation of lithium ion employing lithium ion conductive perovskite-type oxides", Solid State Ionics, Vol. 122, Issues 1-4, pp. 35-39, July 1999 SUMMARY

[0021] [Problems to be Solved by the Invention]

[0022] As described above, in the recovery method using electrodialysis, as the applied voltage is increased, the Li + mobility increases. In addition, in the case where the Li-containing aqueous solution SW is seawater or the like containing chloride ions, in practice, the Li + mobility does not easily increase with respect to the voltage. Furthermore, the electrode 131 on the positive electrode side is preferably platinum (Pt) whose catalytic activity is excellent for the reaction of formula (1), but when the Li-containing aqueous solution SW contains chloride ions, the high catalytic activity of platinum as it is is affected by the formation of platinum chloride (PtCl2), the electrode reaction overvoltage increases, and the reaction speed of formula (1) decreases. In addition, in the recovery method using electrodialysis, the Li + mobility is limited by the diffusion of Li + to the surface of the electrolyte membrane, and thus, when the Li +When the Li concentration of the water solution in surface contact with the supply side is low, it is not easy to increase with respect to the applied voltage. When seawater is used as the Li source, the Li concentration is low, and therefore, even the recovery method described in Patent Literature 2 does not easily allow the recovery speed to be further increased. In addition, lithium recovery from used lithium ion secondary batteries and the like requires a recovery rate that is relatively close to 100%. However, when lithium recovery is performed, the Li concentration of the dissolved solution of the waste battery serving as the Li source decreases, and therefore the Li + mobility decreases, and the energy efficiency becomes extremely low when it is desired to make the Li remaining in the dissolved solution relatively close to 0. Therefore, these recovery methods have room for improvement in terms of productivity improvement. +

[0023] The present application was made in view of the above-described problems, and aims to provide a lithium recovery method and a lithium recovery apparatus that allow lithium to be recovered at high productivity from a low-concentration Li source such as seawater that contains chloride ions using electrodialysis.

[0024] [Technical Solution for Solving the Technical Problem]

[0025] The present inventors and others have found, through intensive research, that chloride ions adsorbed to the surface of the electrolyte membrane hinder the dissolution of lithium ions into the electrolyte membrane, and have conceived that by further providing an electrode having a high potential and separated from the electrolyte membrane in the Li-containing water solution on the positive electrode side, the chloride ions are drawn close to the electrode by electrostatic attraction, the concentration near the surface of the electrolyte membrane is reduced, and lithium ions are drawn close to the surface of the electrolyte membrane by electrostatic attraction, with the relative potential being lowered.

[0026] ​That is, the lithium recovery device according to the present application is a device having a treatment tank divided into a first tank and a second tank, and moving lithium ions from an aqueous solution containing lithium ions accommodated in the first tank to water or an aqueous solution accommodated in the second tank. Also, the lithium recovery device according to the present application is configured to have a lithium ion-conductive electrolyte membrane, a first electrode, a second electrode, a sub-electrode, a first power source, and a sub-power source, wherein the lithium ion-conductive electrolyte membrane divides the treatment tank; the first electrode has a porous structure and is disposed in contact with a surface of the first tank side of the lithium ion-conductive electrolyte membrane; the second electrode is disposed in the second tank in a manner separated from the lithium ion-conductive electrolyte membrane; the sub-electrode is disposed in the first tank and separated from the first electrode and the lithium ion-conductive electrolyte membrane; the first power source is connected between the first electrode and the second electrode in a manner that the first electrode is positive; and the sub-power source is connected in series with a positive electrode of the first power source and connects a positive electrode with the sub-electrode. In another lithium recovery device according to the present application, the second electrode has a porous structure and is disposed in contact with the lithium ion-conductive electrolyte membrane, and further has a third electrode and a second power source, wherein the third electrode is disposed in the second tank in a manner separated from the second electrode and the lithium ion-conductive electrolyte membrane; and the second power source is connected in series with a negative electrode of the first power source and connects a negative electrode with the third electrode.

[0027] The lithium recovery method according to the present application is a method of moving lithium ions from an aqueous solution containing lithium ions accommodated in a first tank to water or an aqueous solution accommodated in a second tank in a treatment tank divided into the first tank and the second tank. Also, in the lithium recovery method according to the present application, a voltage is applied by a first power source and a sub-power source, wherein the first power source is connected between a first electrode and a second electrode in a manner that the first electrode, which has a porous structure and is disposed in contact with a surface of a first tank side of a lithium ion-conductive electrolyte membrane dividing the treatment tank, is positive, and the second electrode is disposed in the second tank in a manner separated from the lithium ion-conductive electrolyte membrane; and the sub-power source is connected in series with a positive electrode of the first power source and connects a positive electrode with a sub-electrode disposed in the first tank in a manner separated from the lithium ion-conductive electrolyte membrane. In another lithium recovery method according to the present application, the second electrode has a porous structure and is disposed in contact with the lithium ion-conductive electrolyte membrane, and further a voltage is applied by a second power source connected in series with a negative electrode of the first power source and connecting a negative electrode with a third electrode disposed in the second tank in a manner separated from the second electrode and the lithium ion-conductive electrolyte membrane.

[0028] [Effects of Invention]

[0029] The lithium recovery device and the lithium recovery method according to the present application can selectively and at high speed recover lithium from an aqueous solution containing a chloride ion and having a very low concentration of lithium and coexisting with other metal ions, such as seawater, to improve productivity, and are less likely to reduce energy efficiency. BRIEF DESCRIPTION OF DRAWINGS

[0030] Figure 1 is a schematic diagram illustrating the structure of a lithium recovery device according to a first embodiment of the present application.

[0031] Figure 2 is a schematic diagram illustrating a lithium recovery method according to the first embodiment of the present application. Figure 1 of a lithium recovery device.

[0032] Figure 3 is a schematic diagram illustrating a lithium recovery method according to a modification of the first embodiment of the present application. Figure 1 is a circuit diagram of a lithium recovery device.

[0033] Figure 4 is a schematic diagram illustrating the structure of a lithium recovery device according to a modification of the first embodiment of the present application.

[0034] Figure 5 is a schematic diagram illustrating a lithium recovery method according to a modification of the first embodiment of the present application. Figure 4 of a lithium recovery device.

[0035] Figure 6 is a schematic diagram illustrating the structure of a lithium recovery device and a lithium recovery method according to a modification of the first embodiment of the present application.

[0036] Figure 7 is a schematic diagram illustrating the structure of a lithium recovery device and a lithium recovery method according to a second embodiment of the present application.

[0037] Figure 8 is a schematic diagram illustrating a lithium recovery method according to the second embodiment of the present application. Figure 7 is a circuit diagram of a lithium recovery device.

[0038] Figure 9A is a graph showing the Li source LiOH concentration dependency of the amount of movement of lithium per unit time in examples and comparative examples according to the first embodiment of the present application.

[0039] Figure 9B is a graph showing the Li source LiOH concentration dependency of the amount of movement of lithium per unit time in examples and comparative examples according to the second embodiment of the present application.

[0040] Figure 10is a graph showing the amount of movement of lithium per unit time from a 0.001 mol / L aqueous LiOH solution and a 1.0 mol / L aqueous LiCl solution in the examples and comparative examples to which the present application relates.

[0041] Figure 11 is a schematic diagram of a lithium recovery apparatus of a lithium recovery method of the related art using an electrodialysis method. DETAILED DESCRIPTION

[0042] The manner of implementing the lithium recovery apparatus and lithium recovery method to which the present application relates will be described with reference to the drawings. In the drawings, the size and the like of a specific structural element are sometimes exaggerated for the sake of clear description, and the shape is sometimes simplified. In addition, in the description of each embodiment, the same reference numerals are attached to the same structural elements as those of the previous embodiment and the description is appropriately omitted.

[0043] [1st Embodiment]

[0044] (Lithium Recovery Apparatus)

[0045] As shown in Figure 1 , the lithium recovery apparatus 10 to which the 1st embodiment of the present application relates has a treatment tank 1, an electrolyte membrane (lithium ion conductive electrolyte membrane) 2 that separates the treatment tank 1, a 1st electrode 31 and a 2nd electrode 32 that cover each face of the electrolyte membrane 2, a 3rd electrode 33, a sub-electrode 41, and three power sources connected in series, i.e., a sub-power source 53, a 1st power source 51, and a 2nd power source 52. The lithium recovery apparatus 10 can also have a stirrer 72. The treatment tank 1 is separated into two tanks, i.e., a supply tank (1st tank) 11 that houses a Li-containing aqueous solution SW such as seawater and a recovery tank (2nd tank) 13 that houses a lithium recovery aqueous solution RS, by the electrolyte membrane 2, and the 1st electrode 31 is disposed on the supply tank 11 side and the 2nd electrode 32 is disposed on the recovery tank 13 side, respectively. The sub-electrode 41 is disposed in the supply tank 11 in a manner separated from the electrolyte membrane 2 and the 3rd electrode 33 is disposed in the recovery tank 13 in a manner separated from the electrolyte membrane 2, respectively. The positive (+) pole of the 1st power source 51 is connected to the 1st electrode 31 and the negative (-) pole is connected to the 2nd electrode 32. The 2nd power source 52 is connected in series with the negative pole of the 1st power source 51, i.e., the positive pole is connected to the 2nd electrode 32 and the negative pole is connected to the 3rd electrode 33. The sub-power source 53 is connected in series with the positive pole of the 1st power source 51, i.e., the negative pole is connected to the 1st electrode 31 and the positive pole is connected to the sub-electrode 41. Thus, the lithium recovery apparatus 10 to which the present embodiment relates is different from the lithium recovery apparatus of the related art (for example, the lithium recovery apparatus 100 shown in Figure 11 , which recovers lithium using an electrodialysis method) in that the 1st power source 51 Figure 11 ( the power source 151 of the 1st power source 51) directly applies a voltage between the two faces of the electrolyte membrane 2, and the electrodes 31, 32 Figure 11both of the electrodes 131, 132 are in contact with the electrolyte membrane 2, and a sub power supply 53 and a second power supply 52 connected in series with both poles of the first power supply 51, a sub electrode 41 connected to the positive pole of the sub power supply 53, and a third electrode 33 connected to the negative pole of the second power supply 52 are further added. Hereinafter, each structural element of the lithium recovery device involved in the embodiment constituting the present application will be described.

[0046] The treatment tank 1 is composed of a material which is not deteriorated such as corrosion even if it is in contact with the Li-containing aqueous solution SW and the Li recovery aqueous solution RS (for example, lithium hydroxide (LiOH) aqueous solution) containing Li after recovery. Also, the shape and the like of the treatment tank 1 are not particularly limited as long as it has a volume corresponding to the required treatment capacity.

[0047] The electrolyte membrane 2 is an electrolyte having lithium ion conductivity and not conducting metal ions M other than Li + n+ , and further preferably not conducting electrons e - . The metal ions M other than Li + n+ For example, in the case where the Li-containing aqueous solution SW is seawater, K + , Na + , Mg 2+ , Ca 2+ , and the like. It is further preferable that the electrolyte membrane 2 is an electrolyte of ceramic having these properties. Specifically, lithium lanthanum titanium oxide (La 2 / 3-x Li 3x TiO3, also called LLTO), and the like can be cited. Such an electrolyte membrane 2 has a crystal lattice defect at a certain ratio, and since the size of this crystal lattice defect site is small, it does not conduct metal ions having a larger diameter than Li + .

[0048] The first electrode 31 and the second electrode 32 are electrodes for applying a voltage between both faces of the electrolyte membrane 2 in pairs, and are respectively arranged so that the first electrode 31 is in contact with the face of the electrolyte membrane 2 on the supply tank 11 side, and the second electrode 32 is in contact with the face of the electrolyte membrane 2 on the recovery tank 13 side. Also, in the lithium recovery device 10 involved in the present embodiment, the first electrode 31 also applies a voltage in pairs with the third electrode 33 described later. It is preferable that the first electrode 31 and the second electrode 32 apply a voltage to a large area of the electrolyte membrane 2, and on the other hand, have a porous structure such as a mesh in a manner that the Li-containing aqueous solution SW or the Li recovery aqueous solution RS is in contact with the surface of the electrolyte membrane 2 with a sufficient area.

[0049] ​​The first electrode 31 is formed of an electrode material having catalytic activity and electron conductivity with respect to the reaction of the following formula (1) and the reaction of the following formula (3), and being stable even when a voltage is applied in the Li-containing aqueous solution SW, and further preferably a material that is easily processed into the shape. The second electrode 32 is formed of an electrode material having catalytic activity and electron conductivity with respect to the reaction of the following formula (5) and the reaction of the following formula (1), and being stable even when a voltage is applied in the Li-recovery aqueous solution RS that also contains Li after recovery of Li, and further preferably a material that is easily processed into the shape. As such an electrode material of the first electrode 31 and the second electrode 32, for example, platinum (Pt) is preferable. In addition, in the case where the Li-containing aqueous solution SW contains CI - , carbon (C) can also be applied. Furthermore, the following formula (3) represents the reaction of Li + in the aqueous solution (Li-containing aqueous solution SW) to move to the electrolyte membrane 2. The following formula (5) represents the reaction of Li + in the electrolyte membrane 2 to move to the aqueous solution (Li-recovery aqueous solution RS).

[0050] [Chemical Formula 3]

[0051]

[0052] Li + → Li + (electrolyte) ··· (3)

[0053] Li + (electrolyte) → Li + ··· (5)

[0054] The sub-electrode 41 is an electrode for forming a higher potential than the surface of the electrolyte membrane 2 in the Li-containing aqueous solution SW. Therefore, the sub-electrode 41 is disposed within the supply tank 11 in a manner not to contact the electrolyte membrane 2 and the first electrode 31, and is preferably disposed in a manner parallel to the first electrode 31. Also, in order to suppress the voltage V3 of the sub-power supply 53 to be small, as described later, the sub-electrode 41 is preferably disposed in close proximity to the first electrode 31 to the extent that short-circuiting does not occur. In addition, the sub-electrode 41 is preferably in a mesh-like shape or the like to increase the contact area with the Li-containing aqueous solution SW. The sub-electrode 41 is formed of an electrode material having catalytic activity and electron conductivity with respect to the reaction of the following formula (1), and being stable even when a voltage is applied in the Li-containing aqueous solution SW. In the case where the Li-containing aqueous solution SW contains halide ions, the sub-electrode 41 has catalytic activity with respect to the reaction of the following formula (2) with respect to the oxidation reaction thereof, for example, if the halide ions are chloride ions (CI - ). As such an electrode material of the sub-electrode 41, for example, carbon (C), platinum (Pt), or carbon on which platinum fine particles are catalytically supported is preferable.

[0055] [Chemical Formula 4]

[0056]

[0057] 2Cl - → Cl2↑ + 2e - ··· (2)

[0058] The third electrode 33 is an electrode for forming a potential lower than the surface of the electrolyte membrane 2 in the aqueous solution RS for Li recovery. Therefore, the third electrode 33 is arranged in the recovery tank 13 so as not to contact the electrolyte membrane 2 and the second electrode 32, and preferably is arranged in parallel with the second electrode 32. Also, in order to suppress the voltage V2 of the second power supply 52 to be small, as described later, the third electrode 33 is preferably arranged so as to approach the second electrode 32 to the extent that short-circuiting does not occur. In addition, the third electrode 33 is preferably in a mesh shape or the like so as to increase the contact area with the aqueous solution RS for Li recovery. The third electrode 33 is formed of an electrode material that has catalytic activity and electron conductivity with respect to the reaction of the following formula (4) and is stable even when a voltage is applied in the aqueous solution RS for Li recovery that also contains Li after recovery, and is, for example, preferably platinum (Pt). Alternatively, the third electrode 33 can also be a material that is stable at a potential lower than the potential generated by the reaction of the following formula (4), such as carbon (C), copper (Cu), or stainless steel, and more preferably a material in which fine particles of Pt that function as a catalyst are supported on the surface of these.

[0059] [Chemical Formula 5]

[0060] 2H2O + 2e - → 2OH - + H2↑ ··· (4)

[0061] The first power supply 51, the second power supply 52, and the sub power supply 53 are direct current power supply devices that apply prescribed voltages VI, V2, and V3, respectively, and the sub power supply 53, the first power supply 51, and the second power supply 52 are connected in series in this order from the positive electrode side. The positive electrode of the first power supply 51 is connected to the first electrode 31, and the negative electrode is connected to the second electrode 32. The positive electrode of the second power supply 52 is connected to the second electrode 32, and the negative electrode is connected to the third electrode 33. The positive electrode of the sub power supply 53 is connected to the sub electrode 41, and the negative electrode is connected to the first electrode 31. In other words, the connection node 5n1 between the first power supply 51 and the sub power supply 53 is connected to the first electrode 31, and the connection node 5n2 between the first power supply 51 and the second power supply 52 is connected to the second electrode 32 (see FIG. 1). Figure 2 The first power supply 51 applies a voltage VI between both faces of the electrolyte membrane 2, and causes the electrolyte membrane 2 to generate a potential for conducting Li +potential gradient. The second power supply 52 applies a voltage V2 to the Li recovery aqueous solution RS to form a lower potential than the surface of the electrolyte membrane 2, to inhibit the conduction of electrons e from the recovery tank 13 side to the supply tank 11 side of the electrolyte membrane 2 - . In addition, the first power supply 51 and the second power supply 52 connected in series as one main power supply apply a voltage (V1 + V2) larger than the voltage VI applied between the two faces of the electrolyte membrane 2, between the Li-containing aqueous solution SW and the Li recovery aqueous solution RS. The sub power supply 53 applies a voltage V3 to the Li-containing aqueous solution SW to form a higher potential than the surface of the electrolyte membrane 2, to cause Li + to exist in a large amount in the vicinity of the surface of the electrolyte membrane 2 where the potential is relatively low by electrostatic attraction, and to cause Cl - and the like to be far from the vicinity of the surface of the electrolyte membrane 2 where the potential is relatively low by electrostatic repulsion.

[0062] The agitator 72 is a device that circulates the Li-containing aqueous solution SW in the supply tank 11 in such a manner that the Li-containing aqueous solution SW is continuously replaced in contact with the first electrode 31 during operation, and is provided as necessary. Similarly, the agitator 72 can circulate the Li recovery aqueous solution RS in the recovery tank 13 in such a manner that the Li recovery aqueous solution RS is continuously replaced in contact with the second electrode 32. The agitator 72 can employ a publicly known device, for example, a structure in which a screw is rotated to agitate the aqueous solution SW, RS in the tank 11, 13 as shown in Figure 1 . In addition, it can be a circulation device 71 (see a modification example shown in Figure 4 ) that circulates the aqueous solution SW, RS between the tank 11, 13 and a circulation tank provided outside the treatment tank 1 by a pump, respectively.

[0063] The Li-containing aqueous solution SW is an aqueous solution containing Li as a source of Li, and contains metal ions M other than lithium ions Li + , such as K + , Na + , Ca 2+ , in addition to Li n+ . As such an aqueous solution, for example, seawater, waste brine after salt is collected from seawater, underground water such as hot spring water, and an aqueous solution obtained by pulverizing, calcining, and dissolving with an acid a used lithium ion secondary battery or the like, and adjusting the pH value as necessary can be cited.

[0064] The Li recovery aqueous solution RS is a solution for accommodating lithium ions Li + recovered from the Li-containing aqueous solution SW. In order to selectively obtain Li from metals, it is preferable that the Li recovery aqueous solution RS be an aqueous solution not containing metal ions (Na + , etc.) other than lithium ions Li + , and it is further preferable that it not contain OH -an aqueous solution of an anion other than fluoride, particularly a halide ion, or pure water. However, in order to smoothly perform the movement of Li + , it is preferable that the aqueous solution RS for Li recovery be an aqueous solution (aqueous lithium hydroxide (LiOH) solution) containing Li + at the start of recovery (at the start of application of power supply).

[0065] The lithium recovery device 10 can also have a heating device for heating the electrolyte membrane 2 to a prescribed temperature via the aqueous Li-containing solution SW or the aqueous solution RS for Li recovery. The heating device can employ a publicly known heater for heating a liquid, and preferably has a temperature adjustment function. The heating device is, for example, of the immersion type, and is disposed so as to be immersed in the aqueous solution RS for Li recovery in the recovery tank 13. Thus, as with the treatment tank 1, the heating portion of the heating device that is immersed in the aqueous solution RS for Li recovery is composed of a material that does not deteriorate, such as corrosion, even when in contact with the aqueous solution RS for Li recovery. The heating device can not make the aqueous Li-containing solution SW or the aqueous solution RS for Li recovery a uniform liquid temperature, as long as it is capable of heating the electrolyte membrane 2 to a prescribed temperature. However, depending on the volume of the treatment tank 1 and the like, it can also not have the agitator 72. The temperature of the electrolyte membrane 2 can be any temperature that is equal to or higher than the freezing point and lower than the boiling point of the aqueous solutions SW, RS, and is preferably a high temperature as described later.

[0066] The lithium recovery device 10 can also have a liquid level sensor or the like for sensing fluctuations in the amount of the aqueous Li-containing solution SW or the aqueous solution RS for Li recovery during operation. Also, when carbon dioxide (CO2) in the atmosphere is unexpectedly dissolved in the aqueous solution RS for Li recovery during operation, lithium carbonate (Li2CO3) is precipitated, the conductivity of the aqueous solution RS for Li recovery decreases, and this is not preferable, so in order to prevent this, it is preferable that the lithium recovery device 10 be configured so that the aqueous solution RS for Li recovery is not exposed to the atmosphere. Also, from the viewpoint of safety, it is preferable that the lithium recovery device 10 have an exhaust mechanism that exhausts the gases (O2, H2, and Cl2 and the like generated by the reactions of formula (1), formula (4), and formula (2)) generated by operation in a manner that does not fill the interior, and also that the Cl2 and the like generated from the aqueous Li-containing solution SW be recovered as a byproduct. Thus, it is preferable that the lithium recovery device 10 have a one-way valve provided in, for example, the supply tank 11 and the recovery tank 13 of the treatment tank 1, so as to exhaust the gases generated from the aqueous solutions SW, RS to the outside of the treatment tank 1, and so as not to allow the inflow of outside air.

[0067] (Lithium recovery method)

[0068] The lithium recovery method according to the first embodiment of the present application will be described with reference to Figure 2 and Figure 3 . The lithium recovery method according to the first embodiment of the present application is a method for recovering lithium from an aqueous solution containing lithium ions, and is a method for recovering lithium from an aqueous solution containing lithium ions byFigure 1 The lithium recovery device 10 according to the first embodiment shown is operated in the following manner. Further, in the following description, the stirrer 72 is omitted. Figure 2

[0069] In the lithium recovery device 10, the sub power supply 53, the first power supply 51, and the second power supply 52 connected in series can be regarded as one power supply (referred to as power supply 50). Also, the first power supply 51 and the second power supply 52 can be regarded as one power supply (referred to as main power supply 51-52). The power supply 50 applies a voltage (V3+V1+V2) positive with respect to the third electrode 33 to the sub electrode 41. Meanwhile, the main power supply 51-52 applies a voltage (V1+V2) positive with respect to the third electrode 33 to the first electrode 31. Thus, in the Li-containing aqueous solution SW supplied to the supply tank 11, the following reactions occur. In the vicinity of each of the sub electrode 41 and the first electrode 31, the hydroxide ion (OH - ) in the Li-containing aqueous solution SW undergoes the following reaction (1) to release an electron e - and generate water (H2O) and oxygen (O2) and the like, and the electron e - is released to the sub electrode 41 and the first electrode 31. In the case where the Li-containing aqueous solution SW contains a halide ion, such as a chloride ion (Cl - ), the following reaction (2) further occurs to release an electron e - and generate chlorine (Cl2) and the like, and a gas is generated depending on the kind of anion contained in the Li-containing aqueous solution SW. In the Li-containing aqueous solution SW, with the decrease in OH - or other anions, in order to maintain the balance of electric charges, the following reaction (3) of Li + in the Li-containing aqueous solution SW moves into the electrolyte membrane 2.

[0070] [Chemical Formula 6]

[0071]

[0072] 2Cl - → Cl2↑ + 2e - ··· (2)

[0073] Li + → Li + (electrolyte) ··· (3)

[0074] Here, in the Li-containing aqueous solution SW, by applying the voltage V3 by the sub power supply 53, a potential gradient is formed in which the potential of the sub electrode 41 is higher than the surface of the electrolyte membrane 2 (the first electrode 31). Thus, OH - and Cl - ​by the electrostatic attraction. In addition, since the potential of the sub-electrode 41 is sufficiently high, Cl - is easily oxidized, and thus the reaction of formula (2) easily occurs at a high speed. Therefore, in the vicinity of the sub-electrode 41, Cl - is reduced by the reaction of formula (2). Thus, Cl - is further pulled toward the sub-electrode 41 by the electrostatic attraction. As a result, in the vicinity of the first electrode 31 having a lower potential than the sub-electrode 41, Cl - becomes relatively low, which causes the reaction of formula (1) to mainly occur.

[0075] On the other hand, the following reaction occurs in the Li recovery aqueous solution RS of the recovery tank 13. In the vicinity of the third electrode 33, H2O in the Li recovery aqueous solution RS is supplied with electrons e - by the application of voltage (V1+V2) by the main power supply 51-52, and the reaction of the following formula (4) occurs, generating hydrogen gas (H2) and OH - . Thus, H + is reduced in the vicinity of the third electrode 33, and thus the reaction of the following formula (5) occurs in the electrolyte membrane 2 in the vicinity of the second electrode 32 to which Li + in the Li recovery aqueous solution RS moves. In addition, at the same time, the second power supply 52 applies a positive voltage V2 of a prescribed magnitude based on the voltages V1, V3 to the second electrode 32 with respect to the third electrode 33. Thus, in the vicinity of the second electrode 32, OH - in the Li recovery aqueous solution RS occurs the reaction of the following formula (1) to release electrons e - to the second electrode 32, generating H2O and O2. As a result, in the vicinity of the second electrode 32, cations are in excess due to the reaction of formula (1) and the reaction of formula (5), and an imbalance of charges occurs. However, in order to compensate for the deficiency of cations that occurs in the vicinity of the third electrode 33 due to the reaction of formula (4), Li + moves from the second electrode 32 to the vicinity of the third electrode 33 at a high speed, and as a result, the imbalance of charges in the Li recovery aqueous solution RS can be eliminated. Furthermore, the relative relationship between the magnitude of the voltage V1 and the voltage V2 will be described later.

[0076] [Chemical Formula 7]

[0077] 2H2O + 2e - → 2OH - + H2↑ ··· (4)

[0078] Li + (electrolyte) → Li + ··· (5)

[0079]

[0080] From the reaction of formula (3) to the reaction of formula (5), Li in the Li-containing aqueous solution SW + intruding from the surface of the electrolyte membrane 2 into the inside, Li + moving in the electrolyte membrane 2 and Li in the electrolyte membrane 2 + moves to the Li recovery aqueous solution RS as follows. By applying a voltage (V1+V2) by the main power supply 51-52, as the reaction of formula (3), Li in the Li-containing aqueous solution SW + intrudes into the lattice defect site of the surface of the electrolyte membrane 2. Then, by applying a voltage V1 by the first power supply 51, the electrolyte membrane 2 has a potential gradient in which the potential of the face on the opposite side (the recovery tank 13 side) is low, so Li that intrudes into the surface of the lattice defect site + jumps (hops) to the lattice defect site in the vicinity of the deep side of the electrolyte membrane 2. In this way, Li + repeatedly moves from the lattice defect site of the electrolyte membrane 2 to the lattice defect site in the vicinity thereof, and finally moves from the lattice defect site of the face on the recovery tank 13 side to the Li recovery aqueous solution RS as the reaction of formula (5). Then, Li of the lattice defect site of the face on the supply tank 11 side of the electrolyte membrane 2 + moves to the deep part of the electrolyte membrane 2, and intrudes into the vacant lattice defect site with another Li adsorbed in the vicinity thereof + or Li in the Li-containing aqueous solution SW + , these Li + move in the electrolyte membrane 2 as well.

[0081] In the lithium recovery device 10 related to the present embodiment, as described above, by applying a voltage V3 by the sub power supply 53, a potential gradient is formed in the Li-containing aqueous solution SW, even if the Li-containing aqueous solution SW contains Cl - , the Cl in the vicinity of the electrolyte membrane 2 - has a relatively low concentration. Therefore, the adsorption of Cl - to the surface of the electrolyte membrane 2 is small, and the reaction of formula (3) is inhibited. In addition, in the Li-containing aqueous solution SW, according to the potential gradient, Li + as a cation is pulled toward the surface of the electrolyte membrane 2 (the first electrode 31) by electrostatic attraction, and the concentration becomes relatively high in the vicinity. Therefore, even if the Li + concentration of the Li-containing aqueous solution SW is low, Li + is able to sufficiently diffuse to the surface of the electrolyte membrane 2. Furthermore, between the two faces of the electrolyte membrane 2, in terms of the Li + concentration of the Li-containing aqueous solution SW, a large Li + concentration gradient is formed, and as a result of this Li+ The concentration gradient generates a large chemical potential difference, thus promoting the intercalation of Li at lattice defect sites in the electrolyte membrane 2. + The movement.

[0082] Furthermore, by applying a voltage V2 from the second power source 52, a potential gradient is formed in the Li recovery aqueous solution RS, with the gradient being positive near the surface of the electrolyte membrane 2 and negative near the third electrode 33. Therefore, Li + The Li particles near the surface of the electrolyte membrane 2 are pulled towards the vicinity of the third electrode 33 by electrostatic attraction. + The concentration decreases. As a result, due to the Li... + The concentration gradient widens, resulting in a larger chemical potential difference, which further promotes the Li-C content at lattice defect sites in electrolyte membrane 2. + The movement.

[0083] Thus, Li in electrolyte membrane 2 + The movement of Li in electrolyte membrane 2 + The greater the concentration gradient, the faster the reaction becomes. Therefore, the stronger the electric field generated by the voltage V3 of the auxiliary power source 53 in the Li-containing aqueous solution SW, and the stronger the electric field generated by the voltage V2 of the second power source 52 in the Li recovery aqueous solution RS, the faster the reactions in equation (3) and equation (5) become, enabling the Li in the Li-containing aqueous solution SW to be processed. + The Li is further recovered by high-speed movement of the Li-containing aqueous solution RS into the electrolyte membrane 2. Furthermore, the stronger the electric field generated in the Li-containing aqueous solution SW, the more even the Li in the Li-containing aqueous solution SW will be recovered. + Even at lower concentrations, the reaction in equation (3) can be accelerated. Furthermore, in the Li-containing aqueous solution SW containing Cl... - In the case where the electric field generated in the Li-containing aqueous solution SW is stronger, the reaction of equation (3) is less likely to be affected by Cl. - Obstruction. Li in electrolyte membrane 2 + The movement of OH- also increases with the greater the potential gradient in electrolyte membrane 2, i.e., the greater the voltage V1 of the first power source 51. Furthermore, as the voltage V1 increases, the difference in reaction rates between equation (4) and equation (1) in the Li recovery aqueous solution RS also increases. - The rate of increase becomes faster, therefore the reaction in equation (5) becomes faster, which can accelerate the reaction of Li in electrolyte membrane 2. + The aqueous solution RS is moved towards Li recovery.

[0084] As mentioned above, the larger the voltages V1 and V2 are, and the stronger the electric field achieved by voltage V3, then Li +the amount of movement per unit time increases. In addition, in order to increase the electric field, the voltage V3 is made large, and when the voltage at which water is generated by electrolysis is reached, the reaction of the following formula (4) occurs in the vicinity of the 1st electrode 31 in the Li-containing aqueous solution SW to generate H2. Since this reaction acquires electrons e - , the movement of the electrons e - is promoted (refer to Figure 2 ) in opposition to the reaction of the above formula (1) in the vicinity of the 1st electrode 31. When the potential of the vicinity of the 1st electrode 31, that is, the face of the supply groove 11 side of the electrolyte membrane 2, is the potential at which H2 is generated, regardless of the magnitude of the applied voltage V1 between the two faces of the electrolyte membrane 2, the potential at which a part of the metal ions constituting the electrolyte membrane 2 is reduced (for example, if the electrolyte membrane 2 is LLTO, Ti 4+ + e - → Ti 3+ ) is reached, and the electrolyte membrane 2 exhibits electron conductivity. Thus, the electrons e - conducted in the electrolyte membrane 2 generate Joule heat, and therefore, the energy efficiency of the movement of Li + decreases drastically. Moreover, the effect of suppressing the electrolyte membrane 2 from exhibiting electron conductivity by the application of the voltage V2 described later decreases. Therefore, the voltage V3 is made smaller than the voltage at which water is generated by electrolysis, and it is preferable that the voltage be large within this range. Furthermore, the voltage at which water is generated by electrolysis is actually a value that is several hundred mV larger than the theoretical voltage (1.229 V, 25°C) depending on the electrode performance of the respective electrodes in determining the electrode reaction overvoltage of the two electrodes (the 1st electrode 31 and the sub-electrode 41 for the voltage V3), and the like. Moreover, in the present embodiment, even if the voltage V3 is equal to or larger than the above value, when the voltage V2 is larger than the voltage V3 by a certain degree or more, the potential of the face of the supply groove 11 side of the electrolyte membrane 2 does not decrease to the potential at which H2 is generated or less, and water is not generated by electrolysis, and therefore, the voltage V3 can be set to a larger value.

[0085] [Chemical Formula 8]

[0086] 2H2O + 2e - → 2OH - + H2↑ · · · (4)

[0087]

[0088] Here, the aqueous solution of the portion of the Li-containing aqueous solution SW that is sandwiched by the 1st electrode 31 and the sub-electrode 41 is denoted by the reference sign "SW E ", and the aqueous solution of the portion of the Li-recovery aqueous solution RS that is sandwiched by the 2nd electrode 32 and the 3rd electrode 33 is denoted by the reference sign "RS E ". As Figure 3As shown, the lithium recovery device 10 according to the present embodiment includes the 2nd power supply 52, the 1st power supply 51, the sub power supply 53, the Li-containing aqueous solution SW E , the electrolyte membrane 2, the Li recovery aqueous solution RS E , the 2nd power supply 52 in this order in a closed circuit connected in a ring shape. In this closed circuit (1st circuit), the current I3, I1, I2 flows in the counterclockwise direction as shown by the broken line arrows, through the power supplies 53, 51, 52 (power supply 50) connected in series. Further, in the electrolyte membrane 2, Li + instead of the electron e - moves in the opposite direction (in the same direction as the current I1). In addition, in the Li-containing aqueous solution SW, OH - instead of a part of the electron e - moves. Also, in the Li recovery aqueous solution RS, OH - instead of a part of the electron e - moves in the opposite direction, Li + and H + move.

[0089] In the lithium recovery device 10, the positive electrode of the 1st power supply 51 and the negative electrode of the sub power supply 53 (connection node 5n1) are connected to the electrolyte membrane 2 and the Li-containing aqueous solution SW E via the 1st electrode 31, respectively. In addition, the negative electrode of the 1st power supply 51 and the positive electrode of the 2nd power supply 52 (connection node 5n2) are connected to the electrolyte membrane 2 and the Li recovery aqueous solution RS E via the 2nd electrode 32, respectively. Therefore, in the lithium recovery device 10, the current can flow in any one of the directions from the connection node 5n1 to the electrolyte membrane 2, or from the Li-containing aqueous solution SW E or the electrolyte membrane 2 to the connection node 5n1. Also, in the lithium recovery device 10, the current can flow in any one of the directions from the connection node 5n2 to the Li recovery aqueous solution RS E , or from the electrolyte membrane 2 to the connection node 5n2. The resistance of the electrolyte membrane 2 (the resistance between the 1st electrode 31 and the 2nd electrode 32, the moving resistance of Li + is denoted as R EL , the resistance of the Li-containing aqueous solution SW E (the resistance between the 1st electrode 31 and the sub electrode 41) is denoted as R SW , and the resistance of the Li recovery aqueous solution RS E (the resistance between the 2nd electrode 32 and the 3rd electrode 33) is denoted as R RS . In addition, the lithium recovery device 10 further includes the reaction resistance R of the reaction of the sub electrode 41 based on the reaction of formula (1) (generation of O2), the reaction of formula (2) (generation of Cl2).c41 , the reaction resistance R of the reaction of the formula (2) based on the reaction of the formula (1) of the 1st electrode 31 c31 .

[0090] In the lithium recovery device 10, as described above, the electron e is moved or not moved from the Li-containing aqueous solution SW to the 1st electrode 31 in such a manner that the reaction of the formula (4) does not occur in the 1st electrode 31 - , the current flows or does not flow from the connection node 5n1 connected to the positive electrode of the 1st power source 51 to the 1st electrode 31. Therefore, the lithium recovery device 10 includes a closed circuit connected in a ring shape in the order of the 2nd power source 52, the 1st power source 51, the electrolyte membrane 2, the Li-recovery aqueous solution RS E , the 2nd power source 52 as the 2nd circuit. In this closed circuit, as shown by the gray arrows, the current I4, I1, I2 flows through the 1st power source 51 and the 2nd power source 52 (main power sources 51-52) connected in series. The current flowing from the current I1 (from the connection node 5n1) to the electrolyte membrane 2 via the 1st electrode 31 is denoted as I4. In the lithium recovery device 10, as long as the voltage V3 is set in such a manner that the current I4 flows or does not flow (does not flow in the opposite direction) in such a direction, that is, in such a manner that I4 ≥ 0. For the current I4, since the relation I3 + I4 = I1 holds, as long as I1 ≥ I3, it is sufficient. Figure 3

[0091] Therefore, the lithium recovery device 10 can connect, for example, current meters in series with the 1st power source 51 and the sub power source 53 (not shown), and apply the voltages V1, V3 while measuring the currents I1, I3. In addition, the smaller the reaction resistance R SW , the reaction resistance R of the sub electrode 41 c41 , the reaction resistance R of the sub electrode 41 c41 , the reaction of the formula (1) of the sub electrode 41. The reaction resistance R SW , the reaction of the formula (1) of the sub electrode 41. The reaction resistance R SW , the reaction of the formula (1) of the sub electrode 41. The reaction resistance R

[0092] As described above, the stronger the electric field generated in the Li-containing aqueous solution SW by the voltage V3, the faster the movement speed of Li + , the reaction of the formula (1) of the sub electrode 41. The reaction resistance R + ​The faster the concentration increases, the more it inhibits the Cl contained in the Li-containing aqueous solution SW. - Hinder Li + Movement. Additionally, the total amount of the reactions of formula (1) or further formula (2) in the first electrode 31 that cause current I4 to flow from the positive terminal (connection node 5n1) of the first power source 51 to the first electrode 31, and the reactions of formula (1) and formula (2) in the secondary electrode 41, combined with the Li moving in the electrolyte membrane 2. + The amount is directly related to the current, and the amount of Li moving in electrolyte membrane 2 is equivalent to (I3+I4). + Therefore, to increase the Li recovery rate, the total current (I3+I4), i.e., the current I1, should be as large as possible. Furthermore, in terms of energy efficiency, a smaller I4 is preferable, and most preferably I4 = 0 (I1 = I3). However, during operation, to prevent I1 < I3, it is preferable to make I1 > I3, including a margin. Additionally, to maximize the Li recovery rate, it is preferable to make I1 > I3 (I4 > 0), even if O2 is generated in the first electrode 31. Moreover, even if the voltage V3 is less than the voltage required for water electrolysis, if the voltage V1 is not a certain value relative to V3, the current I4 flows in the opposite direction (I4 < 0), and the electrolyte membrane 2 exhibits electronic conductivity (see the second embodiment described later). In this embodiment, as explained below, the magnitude of the voltage V1 can be set sufficiently.

[0093] In the lithium recovery method involved in this invention, the larger the voltage V1, the more Li... + The amount of movement increases. However, when the voltage V1, i.e., the potential difference between the two sides of the electrolyte membrane 2, is reduced to a portion of the metal ions constituting the electrolyte membrane 2 (for example, if the electrolyte membrane 2 is LLTO, then Ti...), the reduction... 4+ +e - →Ti 3+ When the voltage (appropriately referred to as the electrolyte reduction voltage) is above a certain value, the electrolyte membrane 2 can conduct electrons e from the recovery tank 13 side to the supply tank 11 side. - (Refer to Patent Document 2). Therefore, even if the voltage V1 is further increased, Li will not... + The increase in the amount of movement increases the increase in voltage V1, and the energy efficiency decreases.

[0094] However, in this embodiment, a voltage V2 is applied by a second power supply 52 connected between the second electrode 32 and the third electrode 33, generating an appropriate potential difference with the second electrode 32 as the positive electrode. Thus, electrons e supplied to Li using the aqueous solution RS are recovered from the third electrode 33. -Moving from the second electrode 32 on the surface of the electrolyte membrane 2 towards the positive terminal of the second power supply 52, the potential of the second electrode 32 is maintained at a relatively high level at the potential for O2 generation. Since the potential for O2 generation is higher than the reduction potential of the metal ions constituting the electrolyte membrane 2, no electrons (e) will be conducted regardless of the potential difference between the two surfaces of the electrolyte membrane 2. - Therefore, the voltage V1 can be set to a value greater than or equal to the electrolyte reduction voltage of the electrolyte membrane 2. In other words, if such a large voltage V1 is applied without applying a voltage V2, electrons e are gained from the negative electrode side (recovery tank 13 side) of the electrolyte membrane 2. - This reduces metal ions. This phenomenon is particularly common with transition metal ions. However, in this embodiment, as described above, by applying a voltage V2, the electrolyte membrane 2 is prevented from reaching the reduction potential of the metal ions, thus preventing the electrolyte membrane 2 from conducting electrons e. - .

[0095] Thus, in the lithium recovery method according to this embodiment, electrons e are released from the aqueous solution RS for Li recovery to the second electrode 32. - Therefore, the current flows from the positive terminal of the second power source 52 through the second electrode 32 to the aqueous solution RS for Li recovery. E Flow. Therefore, the lithium recovery device 10 includes a second power source 52 and an aqueous solution RS for Li recovery. E The closed circuit formed serves as the third circuit, through which currents I5 and I2 flow via the second power supply 52, as indicated by the hollow arrow. The current flowing from the branch of current I2 (from the connection node 5n2) to the second electrode 32 is denoted as I5. Regarding the lithium recovery device 10, it is configured such that current I5 flows in such a direction or does not flow (does not flow in the opposite direction), that is, in such a way that I5 ≥ 0, as follows.

[0096] For the current I5, since the relationship I1 + I5 = I2 holds, the voltages V1 and V2 are set with I1 ≤ I2 to ensure I5 ​​≥ 0. The resistance of the electrolyte membrane 2 (the resistance between the first electrode 31 and the second electrode 32, Li...) is... + The moving resistance is represented as R. EL Li is recovered using an aqueous solution RS E The resistance (the resistance between the second electrode 32 and the third electrode 33) is expressed as R. RS In addition, the lithium recovery device 10 also includes a reaction resistor R of the third electrode 33 based on the reaction (generation of H2) of formula (4). c33 The reaction resistance R of the second electrode 32 based on equation (1) (generating O2) c32Thus, for the first circuit, the following equation (6) is established, for the second circuit, the following equation (7) is established, and for the third circuit, the following equation (8) is established. Also, in this case, the resistance of the electrodes 31, 32, 41, 33 or the wiring is ignored.

[0097] [Math. 1]

[0098] V1+V2+V3=I2x(R RS +R c33 )+I3x(R SW +R c41 )+I1xR EL ... (6)

[0099] V1+V2=I2x(R RS +R c33 )+I1xR EL +I4xR C31

[0100] =I2x(R RS +R c33 )+I1x(R EL +R C31 )-I3xR C31 ... (7)

[0101] V2=I2x(R RS +R c33 )+I5xR C32

[0102] =I2x(R RS +R c33 +R c32 )-I1xR C32 ... (8)

[0103] The following equation (9) is obtained from equation (6) and equation (7), and the following equation (10) is obtained from equation (7) and equation (8). The current I1 is represented by the following equation (11) from equation (10). The current I2 is represented by the following equation (12) from equation (8). The current I3 is represented by the following equation (13) from equation (9). In order to make I1 < I2, the following equation (14) can be established. When equation (14) is solved, it becomes the following equation (15). Also, when I2 of equation (12) is substituted into equation (11), and I3 of equation (13) is substituted into I3 to solve I1, it becomes the following equation (16). When equation (16) is substituted into equation (15), it becomes the following equation (17).

[0104] [Math. 2]

[0105] V3=I3x(R SW +R c31+ R c41 ) - I1x R c31 ... (9)

[0106] V1= I1x (R EL + R c31 + R c32 ) - I2x R c32 - I3x R c31 ... (10)

[0107]

[0108]

[0109]

[0110]

[0111]

[0112] I1x {A}... (16)

[0113] = (R SW + R c31 + R c41 ) x (R RS + R c32 + R c33 ) x V1

[0114] + (R SW + R c31 + R c41 ) x R c32 x V2 + (R RS + R c32 + R c33 ) x R c31 x V3

[0115] {A}

[0116] = (R RS + R c33 ) x [(R EL + R c32 ) x (R SW + R c31 + R c41 ) + R c31 x (R SW + R c41 )]

[0117] + (R EL R SW + R EL R c31 + R EL R c41+R SW R c31 +R c31 R c41 ) x R c32

[0118]

[0119]

[0120] Thus, as the voltage VI of the first power source 51 and the voltage V3 of the sub power source 53 are larger, the voltage V2 of the second power source 52 is set larger in correspondence therewith. Therefore, the lithium recovery device 10 can connect, for example, a current meter in series with the first power source 51 and the second power source 52 (not shown) and apply the voltages VI, V2 while measuring the currents II, I2. Further, as the resistance R RS between the second electrode 32 and the third electrode 33 and the reaction resistance R c33 of the third electrode 33 are lower, a higher effect can be obtained even if the voltage V2 is smaller. The reaction resistance R c33 becomes lower as the area of the third electrode 33 immersed in the lithium recovery aqueous solution RS is larger or the catalytic activity of the reaction of formula (4) of the third electrode 33 is larger. The resistance R RS becomes lower as the areas of the second electrode 32 and the third electrode 33 immersed in the lithium recovery aqueous solution RS are larger or the distance between them is shorter. Further, the resistance R RS becomes lower as the electron conductivity of the lithium recovery aqueous solution RS is higher.

[0121] Further, the reaction amount of the reaction of formula (1) that occurs in the second electrode 32, that is, the magnitude of the current I5 (≧0) is not directly related to the movement amount of Li + On the other hand, when the voltage V2 is insufficient with respect to the voltages VI, V3 and formula (17) does not hold, I5 < 0 is made, and the current flows from the second electrode 32 to the negative electrode of the sub power source 53, and the reaction of formula (4) also occurs in the second electrode 32. At this time, for the voltage VI, the following formula (18) is expressed. R c32 ' is the reaction resistance of the reaction (generation of H2) of formula (4) of the second electrode 32. However, even if I5 < 0, as long as the potential of the face of the electrolyte membrane 2 on the recovery tank 13 side is higher than the reduction potential of the metal ion that constitutes the electrolyte membrane 2 (Ti c32 → Ti 4+ ; -0.488 V vs. SHE) determined by (|I5| x R 3+ ') is made, |I5| can be made small.

[0122] [Mathematical formula 3]

[0123] V1 = I1 x R EL + I4 x R c31 - I5 x R c32

[0124] = I1 x (R EL + R c31 + R c32 ') - I2 x R c32 - I3 x R c31 ... (18)

[0125] As described above, as the voltage V2 is larger, the Li + concentration gradient in the electrolyte membrane 2 is larger, and the movement of Li + in the electrolyte membrane 2 is accelerated. However, as the voltage V2 becomes larger with respect to the voltage V2 at which I1 = I2 (the minimum value of the equation (17)), the current I5 increases, and the generation of O2 in the vicinity of the 2nd electrode 32 (the reaction of the equation (1)) and the generation of H2 in the vicinity of the 3rd electrode 33 (the reaction of the equation (4)) increase more than the increase in the amount of movement of Li + . On the other hand, even if the voltage V2 is I1 > I2, as described above, if the difference |I5| between I1 and I2 is small enough, the electrolyte membrane 2 does not exhibit electronic conductivity, and the voltage V2 can be set to such a value at a minimum. However, in the operation of the lithium recovery device 10, the currents I1 and I2 are not easily maintained constantly, for example, due to the decrease in the resistance R RS due to the increase in the Li + concentration of the Li recovery aqueous solution RS, and the like, and thus it is preferable to set the voltage V2 in such a manner that I1 < I2 as a margin. For example, at the start of the operation of the lithium recovery device 10, the voltage V2 is set to be larger by a difference of 0.5 V or more, preferably more than 0 V and 1 V or less or (V1 / 10) or less, with respect to the voltage V2 at which I1 = I2.

[0126] In the lithium recovery method according to the present application, the liquid amounts of the Li-containing aqueous solution SW and the Li recovery aqueous solution RS decrease as the operation time elapses, and thus it is preferable to replenish the supply tank 11 with the Li-containing aqueous solution SW periodically or all the time. Alternatively, as described later, it is more preferable to circulate the Li-containing aqueous solution SW outside the treatment tank 1 all the time during the operation. For the Li recovery aqueous solution RS, it is preferable to add water (H2O) or the like to the recovery tank 13 periodically or all the time. In the lithium recovery device 10, it is preferable that the liquid levels of the supply tank 11 and the recovery tank 13 coincide with each other during the operation.

[0127] ​For the aqueous solution RS for Li recovery after operation, for example, Li can be concentrated by evaporating water as needed, after which lithium carbonate (Li2CO3) is generated by bubbling carbon dioxide (CO2) or the like, and precipitated, thereby recovering Li. Alternatively, after lithium carbonate is generated, lithium hydroxide (LiOH) can be further generated in a supersaturated state by cooling or evaporating water or the like, and precipitated, thereby recovering Li. In addition, in the case where the aqueous solution SW containing Li contains Cl - , since Cl2is generated on the side of the supply tank 11, it can be recovered together with O2generated at the same time, and separated and recovered by a known method using the difference in boiling point (O2: -183.0°C, Cl2: -101.5°C) or the like.

[0128] In the present application, a sub power supply 53 is connected in series with the positive electrode of the first power supply 51 that applies a voltage VI between both faces of the electrolyte membrane 2, and by providing a sub electrode 41 having a higher potential than the surface of the electrolyte membrane 2 in the aqueous solution SW containing Li, Li + is made to exist in large quantities in the vicinity of the electrolyte membrane 2, and on the other hand, Cl - is made to move away from the electrolyte membrane 2. As a result, the hindrance of the dissolution of Li - in the aqueous solution SW containing Li due to the adsorption of Cl + to the surface of the electrolyte membrane 2 is suppressed. Therefore, it is possible to use a source of Li containing Cl - at a high concentration such as seawater as the aqueous solution SW containing Li, and efficiently recover Li + . In addition, since the concentration of Li + is relatively high in the vicinity of the electrolyte membrane 2 in the aqueous solution SW containing Li, a concentration gradient of Li + is efficiently formed in the electrolyte membrane 2, and the movement of Li + in the electrolyte membrane 2 can be accelerated. This effect is more significant when the concentration of Li + in the aqueous solution SW containing Li is low.

[0129] Furthermore, in the present embodiment, in addition to the first power supply 51 that applies a voltage VI between both faces of the electrolyte membrane 2, a second power supply 52 is connected in series with the negative electrode thereof, and by providing a third electrode 33 having a lower potential than the surface of the electrolyte membrane 2 in the aqueous solution RS for Li recovery, and setting the potential difference, that is, the voltage V2 of the second power supply 52, in correspondence with the voltage VI, even when a large potential difference reaching the reduction potential of the metal ion thereof is generated between both faces of the electrolyte membrane 2, the conduction of electrons e - is not facilitated. As a result, Li +The recovery rate becomes high in response to the potential gradient of the electrolyte membrane 2. Furthermore, by having the first electrode 31 and the second electrode 32 in contact with both sides of the electrolyte membrane 2, the first power source 51 efficiently forms a potential gradient on the electrolyte membrane 2, allowing the Li in the electrolyte membrane 2 to be recovered. + The movement speed becomes high. Furthermore, as the voltage V2 of the second power supply 52 increases in response to the increase in the voltage V1 of the first power supply 51, Li is further efficiently formed on the electrolyte membrane 2. + The concentration gradient can further enable Li + The movement within the electrolyte membrane 2 is accelerated.

[0130] In addition to voltage V1, the Li in electrolyte membrane 2 + The movement of the electrolyte membrane increases with higher temperature. Therefore, a higher temperature for the electrolyte membrane 2 is preferred. Additionally, the resistance R of the electrolyte membrane 2 and the aqueous solutions SW and RS... EL R SW R RS The reaction resistances of electrodes 31, 32, 41, and 33 decrease with increasing temperature. The applicable temperature range is above the freezing point and below the boiling point of the aqueous solutions SW and RS, preferably above 20°C.

[0131] (Modified Example)

[0132] In the lithium recovery apparatus described in the above embodiment, since the Li source containing chloride ions is in direct contact with the surface of the electrolyte membrane on the supply tank side, even if the chloride ions are driven away from the first electrode disposed on that surface of the electrolyte membrane by the electrostatic repulsion formed by the voltage applied from the auxiliary power source, the catalytic activity will be impaired to some extent during long-term operation. Furthermore, in Li recovery using electrodialysis, as the Li in the electrolyte membrane... + The higher the pH of the aqueous solution on the supply side compared to the aqueous solution on the recovery side, the better the Li + The higher the migration rate, the better. For example, when seawater is used as the Li source, it is weakly alkaline. In contrast, the aqueous solution on the recovery side changes from pure water to a LiOH aqueous solution as the process progresses, increasing the concentration and pH value. This makes the Li... + The migration rate decreases. Therefore, the following structure is achieved in a way that prevents chloride ions from contacting the electrolyte membrane and allows for a high pH value in the aqueous solution that is in contact with the supply side of the electrolyte membrane. (Refer to the following...) Figure 4 and Figure 5 The lithium recovery apparatus and lithium recovery method involved in the modified examples of the first embodiment of the present invention will be described.

[0133] like Figure 4As shown, the lithium recovery device 10A according to the modification of the first embodiment of the present application has the treatment tank 1, the electrolyte membrane (lithium ion conductive electrolyte membrane) 2 and the ion exchange membrane 62 that divide the treatment tank 1, the first electrode 31 and the second electrode 32 that cover each surface of the electrolyte membrane 2, the third electrode 33, the sub-electrode 41, and the three power supplies 53, 51, and 52 connected in series. The lithium recovery device 10A can also have the circulation device (circulation mechanism) 71 and the agitator 72. The treatment tank 1 is divided into three tanks, namely, the supply tank (first tank) 11 that accommodates the Li-containing aqueous solution SW such as seawater, the intermediate tank 12 that accommodates the Li-containing aqueous solution AS, and the recovery tank (second tank) 13 that accommodates the Li recovery aqueous solution RS, in one direction by the ion exchange membrane 62 and the electrolyte membrane 2. In detail, the ion exchange membrane 62 is used to divide the supply tank 11 and the intermediate tank 12, and the electrolyte membrane 2 is used to divide the intermediate tank 12 and the recovery tank 13. The sub-electrode 41 is provided in the supply tank 11. The third electrode 33 is provided in the recovery tank 13 in a manner separated from the electrolyte membrane 2. Thus, the lithium recovery device 10A according to the modification is a lithium recovery device 10A that is capable of recovering lithium from seawater or the like, in which the supply tank 11, the intermediate tank 12, and the recovery tank 13 are divided by the ion exchange membrane 62 and the electrolyte membrane 2, and the third electrode 33 is provided in the recovery tank 13 in a manner separated from the electrolyte membrane 2. Figure 1 As shown, the lithium recovery device 10 according to the embodiment is additionally provided with the ion exchange membrane 62 that divides the treatment tank 1 between the sub-electrode 41 and the first electrode 31, and the structure in which the supply tank 11 is further divided into the supply tank 11 and the intermediate tank 12 by the ion exchange membrane 62.

[0134] The ion exchange membrane 62 is used to conduct at least the cation of Li + . The ion exchange membrane 62 can be used to make the Li-containing aqueous solution AS of the intermediate tank 12 not contain halide ions such as Cl - . The ion exchange membrane 62 can be a cation exchange membrane that allows the cation to pass through and cuts off the anion, or a cation exchange membrane that allows only Li + , K + , and Na +a monovalent cation-selective permselective ion exchange membrane, a bipolar monovalent ion-selective permselective ion exchange membrane, and the like. These ion exchange membranes can employ known ion exchange membranes, for example, as a cation exchange membrane, SELEMION (registered trademark) CMV (manufactured by AGC Engineering, Inc.), NEOSEPTA CSE (manufactured by Asahi Glass Co., Ltd. can be employed, as a monovalent cation-selective permselective ion exchange membrane, SELEMION (registered trademark) CSO (manufactured by AGC Engineering, Inc.) can be employed, and as a bipolar monovalent ion-selective permselective ion exchange membrane, NEOSEPTA CIMS (manufactured by Asahi Glass Co., Ltd.) can be employed. In the lithium recovery device 10A as well, it is preferable that the sub electrode 41 be short in interval from the first electrode 31, and thus it is preferable that the ion exchange membrane 62 be short in interval from the electrolyte membrane 2 (the first electrode 31), and thus it is preferable that the intermediate tank 12 be short in the direction of separation of the treatment tank 1.

[0135] The circulation device 71 has, for example, a pump, a filter that removes dust and the like, and the like. In particular, in the case where the Li-containing aqueous solution SW is seawater or hot spring water, or the like, it is preferable to apply a voltage while circulating the Li-containing aqueous solution SW from these supply sources into the supply tank 11. With such a structure, even if the recovery of Li + is performed, the Li + concentration of the Li-containing aqueous solution SW can be maintained substantially constant, and even if the Li-containing aqueous solution is a low-concentration Li aqueous solution, the Li recovery speed is not easily reduced, and long-term continuous operation is possible. Alternatively, the Li-containing aqueous solution SW in the supply tank 11 can be replaced by the circulation device 71 at regular intervals. In addition, the lithium recovery device 10A can be a structure in which the supply tank 11 is open to the outside (for example, the sea) via a filter or the like.

[0136] The Li-containing aqueous solution AS is an aqueous solution in which anions other than Cl - and OH - are removed from the Li-containing aqueous solution SW housed in the supply tank 11. The Li-containing aqueous solution AS, at the start of recovery (at the start of application of power), as with the Li recovery aqueous solution RS, can employ pure water, and is preferably an aqueous solution containing Li + (LiOH aqueous solution).

[0137] The sub power supply 53, as with the embodiment, applies a voltage V3 to cause the Li-containing aqueous solution AS in contact with the supply side of the electrolyte membrane 2 to have a higher potential than the surface of the electrolyte membrane 2, and to cause Li +A large amount of Li exists near the surface of the electrolyte membrane 2 due to electrostatic attraction. In this modified example, a high potential difference is further generated between the two sides of the ion exchange membrane 62, namely between the Li-containing aqueous solution SW and the Li-containing aqueous solution AS, on the side of the supply tank 11, so that the Li-containing aqueous solution SW contains a large amount of Li. + The cations migrate toward the Li-containing aqueous solution AS.

[0138] In the lithium recovery device 10A, a circulation device 71 or a stirrer 72 can also be installed in the intermediate tank 12. The circulation device 71 for circulating the Li-containing aqueous solution AS can be equipped with a function to remove Li from the Li-containing aqueous solution AS. + Other than the cation precipitation tank and the filter used to prevent the precipitate from returning to the intermediate tank 12.

[0139] Reference Figure 5 This section will explain the lithium recovery method according to a variation of the first embodiment of the present invention. Furthermore, in... Figure 5 In this variation, the circulation device 71 and the stirrer 72 are omitted. The lithium recovery method involved in this modification can be achieved through... Figure 4 The lithium recovery apparatus 10A shown in the modified example of the first embodiment is performed in the same manner as the lithium recovery method of the first embodiment.

[0140] In the lithium recovery device 10A, a voltage V3 is applied through the auxiliary power supply 53 to cause the Li in the Li-containing aqueous solution SW to... + Cations migrate through ion exchange membrane 62 into the Li-containing aqueous solution AS. Furthermore, as described in the embodiment, the potential gradient achieved by voltage V3 causes Li to... + The Li is drawn towards the surface of the electrolyte membrane 2 (first electrode 31) by electrostatic attraction. The reactions occurring due to the applied voltages V1, V2, and V3 are as described in the embodiment. Furthermore, in the case where the ion exchange membrane 62 is a monovalent cation-selective ion exchange membrane or a bipolar monovalent ion-selective ion exchange membrane, only Li moves in the Li-containing aqueous solution AS. + K + Na + Equal 1 cation, without moving to Ca 2+ The solution contains divalent and trivalent cations. Therefore, it can reduce the amount of precipitate in the Li-containing aqueous solution AS that is in surface contact with the supply side of the electrolyte membrane 2, without hindering the absorption of Li. + The movement from the Li-containing aqueous solution AS to the Li recovery aqueous solution RS.

[0141] The voltages V1, V2, and V3 are set as described in the embodiment. However, the Li-containing aqueous solution SW E resistance R SWThis is the sum of the resistances of the Li-containing aqueous solution SW, AS, and the ion exchange membrane 62 between the first electrode 31 and the secondary electrode 41. Additionally, at the start of recovery, the Li-containing aqueous solution AS is pure water (containing no Li). + When using a low-concentration LiOH aqueous solution, it is preferable to first activate only the auxiliary power supply 53 to activate Li. + After moving to the Li-containing aqueous solution AS and reaching the specified concentration, the first power supply 51 and the second power supply 52 are further activated.

[0142] According to the lithium recovery apparatus of this modified example, since anions such as chloride ions are blocked from the Li-containing aqueous solution in the supply tank, it is less likely that the aqueous solution in contact with the supply side of the electrolyte membrane will contain anions, thus further preventing the first electrode disposed on that side of the electrolyte membrane from deteriorating. Furthermore, even if the Li-containing aqueous solution in the supply tank has a low pH value (acidic to weakly alkaline), the aqueous solution in contact with the supply side of the electrolyte membrane can be kept at a high pH value, preventing the Li... + Mobility increases the applied voltage, thus improving energy efficiency.

[0143] The lithium recovery device involved in this modification can have two or more functions for conducting lithium-containing materials. + The ion exchange membrane for cations is divided into four or more processing tanks, with two or more intermediate tanks located between the supply tanks and recovery tanks at both ends. In this lithium recovery device, all ion exchange membranes are held between a first electrode and a secondary electrode within the supply tank. By having multiple ion exchange membranes, anions such as chloride ions are further blocked from the Li-containing aqueous solution in the supply tank. Therefore, it is less likely that the aqueous solution in contact with the supply side of the electrolyte membrane will contain anions, further reducing the risk of degradation of the first electrode on that side of the electrolyte membrane. Additionally, the aqueous solution in contact with the supply side of the electrolyte membrane can have a higher pH value, further improving energy efficiency.

[0144] Furthermore, monovalent cation-selective ion exchange membranes and bipolar monovalent ion-selective ion exchange membranes (appropriately collectively referred to as monovalent ion-selective ion exchange membranes) generally do not have sufficient tolerance to strong alkalinity. On the other hand, the aqueous solution after removing anions from the Li-containing aqueous solution SW tends to become strongly alkaline when the cation concentration is high. Therefore, in the lithium recovery apparatus 10A according to the modified example, when the ion exchange membrane 62 uses a monovalent ion-selective ion exchange membrane to move only monovalent cations to the Li-containing aqueous solution AS in the intermediate tank 12, it is necessary to prevent the Li-containing aqueous solution AS from becoming too alkaline before the cation concentration increases. + The Li is moved to the aqueous solution RS for Li recovery, or by making Li... +Other than monovalent cations, precipitation or other methods are used to remove them from the Li-containing aqueous solution AS, and the pH value of the Li-containing aqueous solution AS is adjusted to below a predetermined value. The lithium recovery device according to this modification may have a combination of a cation exchange membrane for conducting cations containing multivalent ions and a monovalent ion-selective permeable ion exchange membrane. On the other hand, when the number of ion exchange membranes increases, the resistance between the first electrode and the secondary electrode becomes high, and the voltage applied by the secondary power supply is less than the voltage for water electrolysis, making it difficult to form a strong electric field. Therefore, it is preferable to arrange only a portion of the multiple ion exchange membranes between the first electrode and the secondary electrode connected to the secondary power supply, and to apply voltage to the other ion exchange membranes by additional secondary power supplies.

[0145] That is, such as Figure 6 As shown, another variation of the first embodiment of the present invention relates to a lithium recovery device 10B, which includes a processing tank 1, an electrolyte membrane (lithium-ion conductive electrolyte membrane) 2 separating the processing tank 1, ion exchange membranes 61 and 62, a first electrode 31 and a second electrode 32, a third electrode 33, auxiliary electrodes 41, 42, and 43, three power supplies 53, 51, and 52 connected in series, and an auxiliary power supply 54. Depending on the requirements, the lithium recovery device 10B may also include a circulation device 71 and a stirrer 72 (see reference). Figure 1 , Figure 4 The processing tank 1 is divided into four tanks along one direction by two ion exchange membranes 61 and 62 and an electrolyte membrane 2: a supply tank (tank 1) 11 containing a Li-containing aqueous solution SW, an intermediate tank 12a containing a Li-containing aqueous solution AS′, an intermediate tank 12b containing a Li-containing aqueous solution AS, and a recovery tank (tank 2) 13 containing a Li recovery aqueous solution RS. Specifically, ion exchange membrane 61 separates the supply tank 11 and the intermediate tank 12a, ion exchange membrane 62 separates the intermediate tank 12a and the intermediate tank 12b, and electrolyte membrane 2 separates the intermediate tank 12b and the recovery tank 13. A third electrode 33 is disposed in the recovery tank 13 separately from the electrolyte membrane 2. Secondary electrodes 41 and 43 are disposed separately from each other in the intermediate tank 12a, with secondary electrode 41 facing the ion exchange membrane 62 and secondary electrode 43 facing the ion exchange membrane 61. Secondary electrode 42 is disposed in the supply tank 11. The positive terminal of the auxiliary power supply 54 is connected to the auxiliary electrode 42, and the negative terminal is connected to the auxiliary electrode 43. Therefore, the lithium recovery device 10B involved in this modification is relative to... Figure 4 The lithium recovery apparatus 10A shown in the modified example adds an ion exchange membrane 61 that separates the processing tank 1 on the supply side of the secondary electrode 41, a secondary power supply 54 for applying voltage between the two sides of the ion exchange membrane 61, and secondary electrodes 42 and 43 connected to the secondary power supply 54.

[0146] Similar to ion exchange membrane 62, ion exchange membrane 61 is disposed relative to electrolyte membrane 2 on Li+ of the supply side, for conducting at least Li + Cations. The ion exchange membrane 61 can apply the same ion exchange membrane as the ion exchange membrane 62. Alternatively, one of the ion exchange membranes 61, 62 can apply a cation exchange membrane that conducts cations containing multivalent cations, and the other can apply a monovalent cation-selective ion exchange membrane or a bipolar monovalent ion-selective ion exchange membrane.

[0147] The sub-electrode 42 and the sub-electrode 43 are connected to the sub-power supply 54, and are electrodes for applying a voltage that generates a high potential difference between the two faces of the ion exchange membrane 61 on the supply tank 11 side. Therefore, the sub-electrode 42 is disposed in the supply tank 11, and the sub-electrode 43 is disposed in the intermediate tank 12a, each in a manner opposite to the ion exchange membrane 61. It is preferable that the sub-electrode 42 and the sub-electrode 43 are disposed in parallel to each other. In addition, it is preferable that the sub-electrode 42 and the sub-electrode 43 are in a mesh shape or the like through which an aqueous solution passes, so as to continuously replace the aqueous solution SW, AS' in contact with the surface of the ion exchange membrane 61 in the supply tank 11 and the intermediate tank 12a. In the present modification, the sub-electrode 41 is formed of an electrode material that is stable when a voltage is applied in the Li-containing aqueous solution AS' including Li recovered, and the same applies to the sub-electrode 43. The sub-electrode 42 is formed of an electrode material that is stable when a voltage is applied in the Li-containing aqueous solution SW, like the sub-electrode 41 of the first embodiment. In addition, the sub-electrode 43 is disposed separately from the sub-electrode 41 disposed in the same intermediate tank 12a, and therefore, the same intermediate tank 12a, that is, the interval between the ion exchange membrane 61 and the ion exchange membrane 62 is designed to be a sufficient length in the left-right direction of the treatment tank 1. Figure 6

[0148] The sub-power supply 54 applies a voltage V4 that generates a high potential difference between the two faces of the ion exchange membrane 61, that is, between the Li-containing aqueous solution SW and the Li-containing aqueous solution AS', so as to move the cations containing Li + in the Li-containing aqueous solution SW to the Li-containing aqueous solution AS'. The sub-power supply 54 is a direct current power supply like the sub-power supply 53, and the positive electrode is connected to the sub-electrode 42 in the supply tank 11, and the negative electrode is connected to the sub-electrode 43 in the intermediate tank 12a.

[0149] The Li-containing aqueous solution AS' is an aqueous solution in which Cl - and the like are removed from the Li-containing aqueous solution SW housed in the supply tank 11, except for OH - . The Li-containing aqueous solution AS' can apply pure water at the start of recovery (at the start of power application), like the Li-containing aqueous solution AS or the Li recovery aqueous solution RS, and it is preferable to be an aqueous solution containing Li + (LiOH aqueous solution).

[0150] ​Here, as mentioned above, monovalent ion-selective permeable ion exchange membranes typically do not possess sufficient tolerance to strong alkalinity. In this modified example, when only Li is used... + When monovalent cations move into the Li-containing aqueous solution AS in the intermediate tank 12b, the ion exchange membrane 61 is a monovalent ion-selective permeable ion exchange membrane. Preferably, acid is pre-added in a manner that prevents the Li-containing aqueous solution AS′ from becoming strongly alkaline due to cations moving from the Li-containing aqueous solution SW. The acid added to the Li-containing aqueous solution AS′ is selectively added to prevent the Li-containing cations from becoming strongly alkaline. + The precipitated acid, and avoiding Cl, which affects the catalytic activity of the platinum electrode that easily generates gas through oxidation reactions. - The preferred form is nitric acid or sulfuric acid. Even if the Li-containing aqueous solution AS′ contains NO3... - Anions, due to being cleaved by the ion exchange membrane 62, are not present in the Li-containing aqueous solution AS in contact with the electrolyte membrane 2. On the other hand, because sometimes OH- ions are not present... - The Li-containing aqueous solution AS, which contains anions other than those mentioned above, becomes strongly alkaline. Therefore, it is preferable to use a cation exchange membrane with high alkali resistance for the ion exchange membrane 62. With this structure, the Li-containing aqueous solution AS in contact with the surface of the electrolyte membrane 2 at the supply tank 11 side can be effectively treated. + The concentration is high enough to achieve high Li + The high mobility allows for efficient Li recovery.

[0151] The lithium recovery method performed by lithium recovery device 10B in this variation and the lithium recovery method performed by lithium recovery device 10A in the aforementioned variation (see reference) Figure 5 Similarly, this can be achieved by applying voltages from power supplies 51, 52, and 53, and also by applying voltages from auxiliary power supply 54. The voltages V1, V2, and V3 are set as described in the modified example. Furthermore, the larger the voltage V4 applied by auxiliary power supply 54, the stronger the electric field generated by the aqueous solutions SW and AS′ between auxiliary electrodes 42 and 43, thus increasing the Li-containing aqueous solution SW's Li content. + The amount of cations that migrate per unit time to the Li-containing aqueous solution AS′ increases. When the Li + When the amount of movement per unit time is small, the Li in the aqueous solution AS′ containing Li + The concentration decreased, and the Li containing Li aqueous solution AS + The concentration decreases, therefore Li + The migration rate is throttled.

[0152] On the other hand, when the voltage V4 is above a certain value, the reaction of formula (1) occurs near the secondary electrode 42 to generate O2, and when the Li-containing aqueous solution SW contains Cl... -Cl2is generated by the reaction of the following formula (2). At the same time, H2is generated by the reaction of the following formula (4) in the vicinity of the sub-electrode 43. Since the more the reaction amount of these reactions is, the more the energy efficiency is reduced, it is preferable that the Li + The voltage V4 is made smaller in a range where the mobility is not limited. In addition, the electric field generated by the voltage V4 becomes stronger with respect to the voltage V4 as the interval between the sub-electrodes 42, 43 and the ion exchange membrane 61 is shorter, and as the electronic conductivity of the Li-containing aqueous solution SW, AS' is higher. Therefore, by making the Li-containing aqueous solution AS' an ion-containing aqueous solution at the time of starting the operation or by the arrangement of the sub-electrodes 42, 43, it is possible to increase the movement amount of the like cations per unit time with respect to the voltage V4. +

[0153] [Chemical Formula 9]

[0154]

[0155] 2Cl - → Cl2↑ + 2e - ··· (2)

[0156] 2H2O + 2e - → 2OH - + H2↑ ··· (4)

[0157] In addition, as in the modification example, at the time of starting the recovery, when the Li-containing aqueous solution AS is pure water or a low-concentration LiOH aqueous solution, first, it is preferable that the sub-power sources 53, 54 are operated to make the Li + After the Li-containing aqueous solution AS moves toward the Li-containing aqueous solution AS and reaches a prescribed concentration, the first power source 51 and the second power source 52 are further operated. According to the lithium recovery device 10B, it is possible to individually set the voltages applied between the two surfaces of the ion exchange membrane 61 and between the two surfaces of the ion exchange membrane 62. Therefore, it is easy to individually manage the pH values of the Li-containing aqueous solutions AS', AS during the operation.

[0158] In the lithium recovery device 10B related to the present modification example, it is also possible to make the ion exchange membrane 61 apply a cation exchange membrane that conducts cations containing polyvalent cations, and to make the ion exchange membrane 62 apply a monovalent ion-selective permeable ion exchange membrane. By such a structure, it is possible to recover only the polyvalent cations contained in the cations contained in the Li-containing aqueous solution SW from the Li-containing aqueous solution AS' of the intermediate tank 12a. In addition, it is possible to recover Li + ​Other than monovalent ions. However, in order to ensure that the Li-containing aqueous solutions AS′ and AS in contact with both sides of the ion exchange membrane 62 are not strongly alkaline, it is preferable to drive the power supplies 51, 52, 53, and 54 in a manner where the cation concentration is not high, or to recover Li from the Li-containing aqueous solutions AS′ and AS in a timely manner. + Other than cations. Alternatively, the lithium recovery apparatus 10B according to this modification can be configured with three ion exchange membranes, sequentially having a cation exchange membrane, a monovalent ion-selective permeable ion exchange membrane, and a cation exchange membrane, with an intermediate tank for the three tanks. Moreover, acid is added to the aqueous solution of the first and second intermediate tanks from the supply side without making it strongly alkaline. With such a structure, the Li in the aqueous solution in contact with the electrolyte membrane 2 of the intermediate tank of the third tank can be made more soluble in Li. + It has a high concentration and can recover polyvalent cations from the intermediate tank of the first tank.

[0159] [Second Implementation]

[0160] In the lithium recovery apparatus according to the described embodiment, by providing a third electrode in the recovery tank in a manner separate from the electrolyte membrane, the voltage applied between the two sides of the electrolyte membrane is increased, resulting in a high Li recovery rate. Alternatively, Li can be recovered at a low rate by operating with a lower voltage. Hereinafter, refer to... Figure 7 The lithium recovery apparatus and lithium recovery method according to the second embodiment of the present invention will be explained.

[0161] (Lithium recovery device)

[0162] like Figure 7 As shown, the lithium recovery device 10C according to the second embodiment of the present invention includes a processing tank 1, an electrolyte membrane (lithium-ion conductive electrolyte membrane) 2 that divides the processing tank 1 into a supply tank (first tank) 11 and a recovery tank (second tank) 13, a first electrode 31 covering the surface of the electrolyte membrane 2 on the side of the supply tank 11, a second electrode 32A disposed in the recovery tank 13, a secondary electrode 41 disposed in the supply tank 11, and a secondary power supply 53 and a first power supply 51 connected in series. Depending on the needs, the lithium recovery device 10C may also include a circulation device 71 and a stirrer 72 (see reference 1). Figure 1 , Figure 4 The lithium recovery device 10C involved in this embodiment is relative to... Figure 1 The lithium recovery apparatus 10 shown in the first embodiment omits the second power supply 52 and the third electrode 33, and instead has a structure with a second electrode 32A separated from the electrolyte membrane 2. In the lithium recovery apparatus 10C, the first power supply 51 serves as the main power supply alone, applying a voltage V1 between both sides of the electrolyte membrane 2, and between the Li-containing aqueous solution SW and the Li recovery aqueous solution RS.

[0163] As with the second electrode 32 of the first embodiment, the second electrode 32A is an electrode used in pairs with the first electrode 31 to apply a voltage between both faces of the electrolyte membrane 2. The second electrode 32A is disposed in the recovery tank 13 in a manner not in contact with the electrolyte membrane 2, but is preferably not spaced apart from the electrolyte membrane 2, and is preferably disposed in parallel with the electrolyte membrane 2. As with the third electrode 33 of the first embodiment, the second electrode 32A is preferably in a mesh shape or the like to increase the contact area with the aqueous solution RS for Li recovery. Also as with the second electrode 32 of the first embodiment, the second electrode 32A can have a porous structure and be disposed in contact with the electrolyte membrane 2. The second electrode 32A has catalytic activity and electron conductivity with respect to the reaction of the following formula (4), is formed of an electrode material stable also when a voltage is applied to the aqueous solution RS for Li recovery including Li recovery, and is preferably, for example, platinum (Pt).

[0164] [Chemical Formula 10]

[0165] 2H2O + 2e - → 2OH - + H2↑ · · · (4)

[0166] (Li recovery method)

[0167] Referring to Figure 7 , a Li recovery method according to a second embodiment of the present application will be described. The Li recovery method according to the second embodiment is performed by the Li recovery device 10C according to the second embodiment in the following manner.

[0168] In the Li recovery device 10C, the sub power supply 53 and the first power supply 51 connected in series can be regarded as one power supply (referred to as power supply 53-51). The power supply 53-51 applies a voltage (V3 + VI) positive with respect to the second electrode 32A to the sub electrode 41. At the same time, the first power supply 51 applies a voltage VI positive with respect to the second electrode 32A to the first electrode 31. Thus, in the Li-containing aqueous solution SW supplied to the supply tank 11, as with the first embodiment, in the vicinity of each of the sub electrode 41 and the first electrode 31, OH - in the Li-containing aqueous solution SW reacts to release electrons e - to generate H2O and O2, and the like, and the electrons e - are released to the sub electrode 41 and the first electrode 31. In the case where the Li-containing aqueous solution SW contains Cl - , in the vicinity of the sub electrode 41, a reaction of the following formula (2) further occurs to release electrons e - to generate Cl2. In the Li-containing aqueous solution SW, in association with the generation of OH -, other anions decrease, in order to maintain the balance of charge, Li in the Li-containing aqueous solution SW moves to the surface of the electrolyte membrane 2, i.e., the vicinity of the 1st electrode 31 + The reaction of the following formula (3) moves to the electrolyte membrane 2.

[0169] [Chemical formula 11]

[0170]

[0171] 2Cl - → Cl2↑ + 2e - ··· (2)

[0172] Li + → Li + (electrolyte) ··· (3)

[0173] On the other hand, in the Li recovery aqueous solution RS of the recovery tank 13, in the vicinity of the 2nd electrode 32A, the reaction of the following formula (4) occurs by H2O in the Li recovery aqueous solution RS being supplied with electrons e - , and H2 and OH - are generated. Thus, with the increase of OH - , in order to maintain the balance of charge, the reaction of the following formula (5) occurs in the electrolyte membrane 2, in which Li in the electrolyte membrane 2 moves. +

[0174] [Chemical formula 12]

[0175] 2H2O + 2e - → 2OH - + H2↑ ··· (4)

[0176] Li + (electrolyte) → Li + ··· (5)

[0177] From the reaction of formula (3) to the reaction of formula (5), i.e., Li in the Li-containing aqueous solution SW + intrudes from the surface of the electrolyte membrane 2 into the inside, Li + moves in the electrolyte membrane 2, and Li + ​The movement of the aqueous solution RS for Li recovery is as described in the first embodiment. In this embodiment, when the potential difference between the two sides of the electrolyte membrane 2 obtained by applying voltage V1 is greater than or equal to the electrolyte reduction voltage of the electrolyte membrane 2, the electrolyte membrane 2 exhibits electronic conductivity, and even if the voltage V1 is further increased, the Li recovery rate does not increase by the amount of voltage V1 increase, and the energy efficiency decreases sharply (see Patent Document 2). Specifically, although the electrode performance, such as the electrode reaction overvoltage, is also determined based on the electronic conductivity of the electrolyte membrane 2, the electrolyte membrane 2 can exhibit electronic conductivity when a voltage exceeding 2.0V is applied between the two sides. Therefore, in this embodiment, it is preferable to set the voltage V1 applied by the first power supply 51 such that the potential difference between the two sides of the electrolyte membrane 2 is less than or equal to the electrolyte reduction voltage. In the lithium recovery apparatus 10C according to this embodiment, since the second electrode 32A is provided separately from the electrolyte membrane 2, the voltage V1 can be set to be greater than the electrolyte reduction voltage of the electrolyte membrane 2 by a certain extent.

[0178] Furthermore, similar to the first embodiment, the voltage V3 is made lower than the voltage required for water electrolysis. In this embodiment, even if the voltage V3 is greater than or equal to the theoretical voltage for water electrolysis (1.229V) plus the value obtained from electrode performance, etc., water electrolysis will not occur when the voltage V1 is significantly greater than the voltage V3. However, even if the voltage V3 is less than the voltage required for water electrolysis, the electrolyte membrane 2 exhibits electronic conductivity when it exceeds the voltage V1 by a certain amount. Here, the portion of the aqueous solution containing Li aqueous solution SW held between the first electrode 31 and the secondary electrode 41 is referred to as "SW" in the accompanying drawings. E The portion of the aqueous solution RS used for Li recovery, which is held between the electrolyte membrane 2 and the second electrode 32A, is denoted as "RS" in the attached diagram. E " indicates. For example Figure 8 As shown, the lithium recovery device 10C according to this embodiment includes a first power source 51, an auxiliary power source 53, and a Li-containing aqueous solution SW. E 2. Electrolyte membrane, 3. Aqueous solution for Li recovery (RS) E (Illustration omitted) A closed circuit in which the first power supply 51 is connected in a loop. In this closed circuit (the first circuit), the first power supply 51 and the auxiliary power supply 53 (power supply 53-51) connected in series flow currents I3 and I1 in a counterclockwise direction, as indicated by the dashed arrows.

[0179] Furthermore, in the lithium recovery device 10C, the positive terminal of the first power source 51 and the negative terminal (connection node 5n1) of the auxiliary power source 53 are connected to the electrolyte membrane 2 and the Li-containing aqueous solution SW via the first electrode 31, respectively. Econnected. Therefore, in the lithium recovery device 10C, the current can flow in either direction from the connection node 5n1 to the electrolyte membrane 2, or from the Li-containing aqueous solution SW E or the electrolyte membrane 2 to the connection node 5n1, but is configured so that the current I4 flows or does not flow from the connection node 5n1 to the electrolyte membrane 2, as explained in the first embodiment. Therefore, the lithium recovery device 10C includes a closed circuit composed of the first power supply 51, the electrolyte membrane 2, and the Li recovery aqueous solution RS E (omitted from the drawing) as the second circuit, and the current I4, I1 flows in the counterclockwise direction as shown by the gray arrows by the first power supply 51. The current flowing from the current I1 branch (from the connection node 5n1) to the electrolyte membrane 2 via the first electrode 31 is denoted as I4.

[0180] In the lithium recovery device 10C, the voltage V3 can be set so that the current I4 flows in this direction or does not flow (does not flow in the opposite direction), that is, so that I4 > 0. For the current I4, since the relationship I3 + I4 = I1 holds, it can be I1 > I3. The resistance of the electrolyte membrane 2 (the resistance between the first electrode 31 and the second electrode 32A, the moving resistance of Li + is denoted as R EL , and the resistance of the Li-containing aqueous solution SW E (omitted from the drawing) as the second circuit, and the current I4, I1 flows in the counterclockwise direction as shown by the gray arrows by the first power supply 51. The current flowing from the current I1 branch (from the connection node 5n1) to the electrolyte membrane 2 via the first electrode 31 is denoted as I4. SW In the present embodiment, the resistance R EL is the resistance of the electrolyte membrane 2 (the resistance between the electrolyte membrane 2 and the second electrode 32A) and the resistance of the Li recovery aqueous solution RS E (omitted from the drawing) as the second circuit, and the current I4, I1 flows in the counterclockwise direction as shown by the gray arrows by the first power supply 51. The current flowing from the current I1 branch (from the connection node 5n1) to the electrolyte membrane 2 via the first electrode 31 is denoted as I4. E In the present embodiment, the resistance R c41 , the reaction resistance R c31 of the second electrode 32A based on the reaction of formula (4). c32 Thus, for the first circuit, it is represented by the following formula (19), and for the second circuit, it is represented by the following formula (20). Here, the resistance of the electrodes 31, 32A, 41 or the wiring is ignored.

[0181] [Math. 4]

[0182] V1 + V3 = I1 x (R EL + R c32 ') + I3 x (R SW + R c41) · · · (19)

[0183] V1= I1x (R EL +R c32 ') + I4x R C31

[0184] = I1x (R EL +R c31 + R c32 ') - I3x R C31 · · · (20)

[0185] The following equation (9) is obtained from equation (19) and equation (20). The current I1 is represented by the following equation (21) from equation (20). The current I3 is represented by the following equation (13) from equation (9). In order to make I1 > I3, the following equation (22) is established. When solving the following equation (22), it becomes the following equation (23). In addition, when solving I1 by substituting I3 of the following equation (21) into the following equation (13), it becomes the following equation (24). When substituting the following equation (24) into the following equation (23), it becomes the following equation (25).

[0186] [Equation 5]

[0187] V3= I3x (R SW +R c31 +R c41 ) - I1x R c31 ···(9)

[0188]

[0189]

[0190]

[0191]

[0192] I1x [(R SW +R c41 ) x (R EL +R c31 +R c32 ') + (R EL +R c32 ') x R c31 ]

[0193] = (R SW +R c31 +R c41 ) x V1 + R c31 x V3···(24)

[0194]

[0195] In this way, the voltage V3 of the auxiliary power supply 53 is made less than the voltage required for water electrolysis, and is set to a certain value below the voltage V1 of the first power supply 51, preferably larger than this value, in a manner consistent with equation (25). Therefore, the lithium recovery device 10C can, for example, connect a galvanometer in series with the first power supply 51 and the auxiliary power supply 53 (not shown), respectively, and apply voltages V1 and V3 while measuring currents I1 and I3. Furthermore, the voltage V1 and V3 are adjusted according to the resistance R between the first electrode 31 and the auxiliary electrode 41. SW The reaction resistance R of the secondary electrode 41 c41 The lower the voltage, the stronger the electric field generated in the Li-containing aqueous solution SW, even with a smaller voltage V3, resulting in a higher effect. Reaction resistance R c41 The resistance R decreases as the area of ​​the secondary electrode 41 immersed in the Li-containing aqueous solution SW increases or the catalytic activity of the reaction of the secondary electrode 41 according to formula (1) increases. SW The resistance decreases as the area of ​​the first electrode 31 and the secondary electrode 41 immersed in the Li-containing aqueous solution SW increases or the spacing between them decreases. Additionally, the resistance R... SW The electron conductivity of SW containing Li aqueous solution decreases as the conductivity increases.

[0196] Similar to the first embodiment, in this embodiment, a secondary power supply 53 is connected in series with the positive electrode of the first power supply 51 that applies voltage between the two sides of the electrolyte membrane 2. By providing a secondary electrode 41 with a potential higher than that of the surface of the electrolyte membrane 2 in a Li-containing aqueous solution SW, seawater or other materials containing high concentrations of Cl can be used. - Li source or Li + Low-concentration Li sources, used as Li-containing aqueous solutions (SW), are highly efficient for the treatment of Li. + Recycling.

[0197] (Modified Example)

[0198] and Figure 4 , Figure 6 Similar to the lithium recovery apparatuses 10A and 10B involved in the variations of the first embodiment shown, the lithium recovery apparatus involved in this embodiment may have ion exchange membranes 61 and 62, and has a structure that divides the processing tank 1 into three or more sections.

[0199] Example

[0200] The foregoing has described a method for implementing the lithium recovery apparatus and method of the present invention. The following describes embodiments that confirm the effectiveness of the present invention. Furthermore, the present invention is not limited to these embodiments and methods; various modifications and alterations made based on these descriptions are naturally included within the scope of the present invention.

[0201] against Figure 1The lithium recovery device according to the first embodiment of the present application and Figure 7 The lithium recovery device according to the second embodiment of the present application, and

[0202] (Fabrication of lithium recovery device)

[0203] The lithium recovery device used a plate-shaped La 0.57 Li 0.29 TiO3 (lithium ion conductive ceramic LLTO, manufactured by Toho Titanium Co., Ltd.) as an electrolyte film. In the respective central portions of both faces of the electrolyte film, a lattice-shaped electrode having a thickness of 10 μm, a width of 0.5 mm, and a pitch of 0.5 mm was formed in a size of 19.5 mm x 20.5 mm as a first electrode and a second electrode, and a lead wire for connection with a power source connected to the electrode was also formed. The first electrode, the second electrode, and the lead wire were formed by screen printing of a Pt paste on the surface of the electrolyte film and firing at 900°C for 1 h in the atmosphere. In addition, a Pt mesh electrode of 20 mm x 20 mm was used as a sub-electrode, and a Ni mesh electrode of 20 mm x 20 mm was used as a third electrode. The electrolyte film on which the electrodes and the like were formed was installed in a treatment tank made of an acrylic plate, and a supply tank and a recovery tank were partitioned, and the sub-electrode was disposed in the supply tank and the third electrode was disposed in the recovery tank in such a manner that the electrodes on the surface of the electrolyte film faced each other (sub-electrode-electrolyte film distance: 50 mm). Furthermore, the treatment tank was housed in a thermostat tank having a temperature adjustment function. Then, the lithium recovery device was fabricated in such a manner that the first electrode was connected to a first power source as a positive electrode, a sub-power source was connected in series with the positive electrode of the first power source and the positive electrode thereof was connected to the sub-electrode, and a second power source was connected in series with the negative electrode of the first power source and the negative electrode thereof was connected to the third electrode between the first electrode and the second electrode. In addition, a current meter was inserted between the first power source and the first electrode, the second power source and the first power source and the third electrode (between the second power source 52 and the connection node 5n2), and the sub-power source and the sub-electrode, respectively. Figure 2

[0204] ​A 0.1 mol / L lithium hydroxide aqueous solution was prepared as a Li-containing aqueous solution (Li source) and 150 ml was supplied to the supply tank of the lithium recovery device so that the first electrode and the auxiliary electrode were completely immersed. In addition, a 0.1 mol / L lithium hydroxide aqueous solution was prepared as a Li recovery aqueous solution and 150 ml was supplied to the recovery tank of the lithium recovery device so that the second electrode and the third electrode were completely immersed. Furthermore, for both the Li-containing aqueous solution and the Li recovery aqueous solution, the same concentration of lithium hydroxide aqueous solution was stored in the Li-containing aqueous solution supply tank and the Li recovery aqueous solution supply tank provided outside the treatment tank of the lithium recovery device in the constant-temperature tank, and the temperature was adjusted to 40°C (= 313.15 K), which was the same as the temperature of the lithium hydroxide aqueous solution in the supply tank and the recovery tank.

[0205] (Lithium recovery experiment)

[0206] As Example 1 relating to the first embodiment of the present application (see Figure 1 ), the direct current voltages shown in Table 1 were applied for 1 h by the first power source (voltage V1), the second power source (voltage V2), and the auxiliary power source (voltage V3). In order to suppress changes in the concentration of the lithium hydroxide aqueous solution in the supply tank and the recovery tank accompanying the electrodialysis, while the voltages were being applied, the aqueous solutions were supplied at a certain rate from the supply tanks to the supply tank and the recovery tank by the liquid feeding pumps, and the lithium hydroxide aqueous solutions were withdrawn at the same rate. Then, the Li concentrations of the aqueous solutions in the recovery tank after the voltages were applied and the lithium hydroxide aqueous solutions withdrawn from the recovery tank were measured by an inductively coupled plasma optical emission spectrometry (ICP-OES) device (Optima 7000DV, manufactured by PerkinElmer), and the amount of Li moved by the application of the voltages for 1 h was calculated. The amount of Li moved per unit time is shown in Table 1.

[0207] As Example 2 relating to the second embodiment of the present application (see Figure 7 ), the direct current voltages shown in Table 1 were applied for 1 h by the first power source (voltage V1) and the auxiliary power source (voltage V3). In addition, as Comparative Example 1, the voltages were applied for 1 h by the first power source (voltage V1) and the second power source (voltage V2). As Comparative Example 2, the voltages were applied for 1 h by only the first power source (voltage V1). As with the experiment, while the voltages were being applied, the lithium hydroxide aqueous solutions of the same concentration were supplied from the supply tanks to the supply tank and the recovery tank, and the lithium hydroxide aqueous solutions were withdrawn at the same rate. The Li concentrations of the aqueous solutions in the recovery tank after the voltages were applied and the lithium hydroxide aqueous solutions withdrawn from the recovery tank were measured, and the amount of Li moved per unit time was calculated and is shown in Table 1.

[0208] A 1.0 mol / L lithium chloride (LiCl) aqueous solution was prepared as the Li-containing aqueous solution (Li source), and a 1.0 mol / L lithium hydroxide aqueous solution was prepared as the aqueous solution for Li recovery. The lithium recovery experiment was performed in the same manner as in the case of the lithium hydroxide aqueous solution. In addition, a 1.0 mol / L lithium chloride (LiCl) aqueous solution was prepared as the Li-containing aqueous solution (Li source), and a 0.1 mol / L lithium hydroxide aqueous solution was prepared as the aqueous solution for Li recovery. The lithium recovery experiment was performed in the same manner as in the case of the lithium hydroxide aqueous solution. The Li concentration of the aqueous solution in the recovery tank after the application of voltage and the lithium hydroxide aqueous solution drawn from the recovery tank were measured, and the amount of Li moved per unit time was calculated. The results are shown in Table 1.

[0209] In Figure 9A , a graph showing the Li source LiOH concentration dependence of the amount of Li moved per unit time as a lithium hydroxide aqueous solution is shown for Example 1 and Comparative Example 1. In Figure 9B , a graph showing Example 2 and Comparative Example 2 is shown. In addition, in Figure 10 , graphs showing the amount of Li moved per unit time as a 0.001 mol / L lithium hydroxide aqueous solution and a 1.0 mol / L lithium chloride aqueous solution, respectively, are shown for the examples and comparative examples.

[0210] [Table 1]

[0211]

[0212]

[0213] When Example 1 is compared with Comparative Example 1 and Example 2 is compared with Comparative Example 2, respectively, as shown in Table 1, Figure 9A and Figure 9B , the effects of Example 1 and Example 2 according to the present application are high when the concentration of the lithium hydroxide aqueous solution as the Li source is low. In addition, as shown in Table 1 and Figure 10 , the effects of Example 1 and Example 2 according to the present application are also high when a lithium chloride aqueous solution is used as the Li source. In addition, when Example 1 is compared with Example 2, by providing the third electrode at a low potential on the side of the recovery tank, the applied voltage V1 between the two surfaces of the electrolyte membrane can be increased, and the recovery rate of Li can be made high.

[0214] Accordingly, it can be confirmed that the lithium recovery device and the lithium recovery method according to the embodiments of the present application achieve a high speed of recovery from a Li source having a low Li concentration or a Li source containing Cl - .

[0215] [Reference Signs Description]

[0216] 10, 10A, 10B, 10C: lithium recovery device; 1: treatment tank; 11: supply tank (1st tank); 12: intermediate tank; 12a, 12b: intermediate tank; 13: recovery tank (2nd tank); 2: electrolyte membrane (lithium ion conductive electrolyte membrane); 31: 1st electrode; 32, 32A: 2nd electrode; 33: 3rd electrode; 41: sub-electrode; 42, 43: sub-electrode; 51: 1st power supply; 52: 2nd power supply; 53: sub-power supply; 54: sub-power supply; 61, 62: ion exchange membrane; AS: Li-containing aqueous solution; RS: Li recovery aqueous solution; SW: Li-containing aqueous solution

Claims

1. A lithium recovery apparatus comprising a processing tank divided into a first tank and a second tank, wherein lithium ions are moved from an aqueous solution containing lithium ions contained in the first tank to water or an aqueous solution contained in the second tank, characterized in that, It comprises a lithium-ion conductive electrolyte membrane, a first electrode, a second electrode, a secondary electrode, a first power source, and a secondary power source, wherein... The lithium-ion conductive electrolyte membrane separates the processing tank; The first electrode has a porous structure and is arranged in such a way that it is in surface contact with the first groove side of the lithium-ion conductive electrolyte membrane; The second electrode is disposed in the second tank in a manner that separates it from the lithium-ion conductive electrolyte membrane; The secondary electrode is disposed in the first tank and is separated from the first electrode and the lithium-ion conductive electrolyte membrane; The first power source is connected between the first electrode and the second electrode with the first electrode being positive; The auxiliary power source is connected in series with the positive terminal of the first power source, and the positive terminal is connected to the auxiliary electrode.

2. A lithium recovery apparatus comprising a processing tank divided into a first tank and a second tank, wherein lithium ions are moved from an aqueous solution containing lithium ions contained in the first tank to water or an aqueous solution contained in the second tank, characterized in that, It comprises a lithium-ion conductive electrolyte membrane, a first electrode, a second electrode, a secondary electrode, a third electrode, a first power source, a secondary power source, and a second power source, wherein... The lithium-ion conductive electrolyte membrane separates the processing tank; The first electrode has a porous structure and is disposed in contact with the surface of the first tank side of the lithium-ion conductive electrolyte membrane; the second electrode is disposed in contact with the surface of the second tank side. The secondary electrode is disposed in the first tank and is separated from the first electrode and the lithium-ion conductive electrolyte membrane; The third electrode is disposed in the second tank in a manner separate from the second electrode and the lithium-ion conductive electrolyte membrane; The first power source is connected between the first electrode and the second electrode with the first electrode being positive; The auxiliary power supply is connected in series with the positive terminal of the first power supply, and the positive terminal is connected to the auxiliary electrode. The second power source is connected in series with the negative terminal of the first power source, and the negative terminal is connected to the third electrode.

3. The lithium recovery device according to claim 2, characterized in that, The voltage of the first power source is a voltage applied to the lithium-ion conductive electrolyte membrane that reaches or exceeds the reduction potential of at least one metal element contained in the lithium-ion conductive electrolyte membrane.

4. The lithium recovery device according to any one of claims 1 to 3, characterized in that, It also has one or more ion exchange membranes, which are used to conduct cations containing at least lithium ions. The processing tank is sequentially divided into the first tank, one or more intermediate tanks, and the second tank along one direction. The lithium-ion conductive electrolyte membrane divides the processing tank into the second tank and the adjacent intermediate tank. The ion exchange membrane divides the treatment tank into the intermediate tank and its adjacent intermediate tank or the first tank. Lithium ions are moved from the aqueous solution containing lithium ions contained in the first tank to the water or aqueous solution contained in the intermediate tank to the water or aqueous solution contained in the second tank.

5. The lithium recovery device according to any one of claims 1 to 3, characterized in that, It has a circulation mechanism that circulates an aqueous solution containing lithium ions between the outside and the first tank.

6. A lithium recovery method, comprising moving lithium ions from an aqueous solution containing lithium ions contained in the first tank to water or an aqueous solution contained in the second tank in a processing tank divided into a first tank and a second tank, characterized in that, Voltage is applied by the first power source and the auxiliary power source, wherein, The first power source is connected in a positive manner between the first electrode and a second electrode disposed in the second tank in a manner that is separated from the lithium-ion conductive electrolyte membrane, with the first electrode having a porous structure and being disposed in a positive manner with the first electrode in a manner that is in contact with the surface of the first tank side of the lithium-ion conductive electrolyte membrane that separates the processing tank. The auxiliary power source is connected in series with the positive electrode of the first power source, and the positive electrode is connected to the auxiliary electrode disposed in the first tank in a manner separate from the lithium-ion conductive electrolyte membrane.

7. A lithium recovery method, comprising moving lithium ions from an aqueous solution containing lithium ions contained in the first tank to water or an aqueous solution contained in the second tank in a processing tank divided into a first tank and a second tank, characterized in that, Voltage is applied by the first power source, the auxiliary power source, and the second power source, wherein, The first power source is connected between the first electrode and the second electrode, which has a porous structure and is arranged in a positive manner to contact the surface of the lithium-ion conductive electrolyte membrane separating the processing tank on the first tank side. The auxiliary power source is connected in series with the positive electrode of the first power source, and the positive electrode is connected to the auxiliary electrode disposed in the first tank in a manner separate from the lithium-ion conductive electrolyte membrane. The second power source is connected in series with the negative electrode of the first power source, and the negative electrode is connected to the third electrode disposed in the second tank in a manner separate from the second electrode and the lithium-ion conductive electrolyte membrane.

8. The lithium recovery method according to claim 7, characterized in that, The first power source applies a voltage to the lithium-ion conductive electrolyte membrane that reaches or exceeds the reduction potential of at least one metal element contained in the lithium-ion conductive electrolyte membrane.

9. The lithium recovery method according to any one of claims 6 to 8, characterized in that, The processing tank is sequentially divided into the first tank, one or more intermediate tanks, and the second tank along one direction. The intermediate tank and its adjacent intermediate tank or the first tank are separated by an ion exchange membrane for conducting cations containing at least lithium ions. The second tank and its adjacent intermediate tank are separated by the lithium-ion conductive electrolyte membrane. Lithium ions are moved from the lithium-ion-containing aqueous solution contained in the first tank to the water or aqueous solution contained in the intermediate tank and then to the water or aqueous solution contained in the second tank.

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