Method and apparatus for separating and concentrating lithium

Abstract

The objective of this method and apparatus for separating and concentrating lithium from water containing both lithium and anions using electrodialysis is to avoid a voltage increase during electrodialysis even when the lithium concentration in the treated water flowing through the treated water chamber decreases, thereby enabling efficient separation and concentration of lithium. [Solution] A method for separating and concentrating lithium, characterized by treating water to be treated, in which lithium ions and anions coexist, with an electrodialysis apparatus in which an ion exchange resin is filled in the water flow path of the water to be treated. The water to be treated chamber of the electrodialysis apparatus is filled with a mixed resin of anion exchange resin and cation exchange resin.

Description

Technical Field

[0001] The present invention relates to a method and apparatus for separating and concentrating lithium from water in which lithium and anions coexist, and particularly to a method and apparatus for separating and concentrating lithium using an electrodialysis apparatus.

Background Art

[0002] Lithium is an important target for separation and concentration because it is a main material of lithium batteries.

[0003] As a method for concentrating water in which cations and anions coexist, there is a method using a reverse osmosis membrane (RO membrane) or a nanofiltration membrane. In this method, concentration is carried out in a state where cations and anions coexist, and there is a risk of scale formation due to the combination of cations and anions.

[0004] Patent Document 1 describes a method for recovering lithium as lithium hydroxide from lithium sulfate-containing water using an electrodialysis apparatus with bipolar electrodes. According to this method, lithium ions and anions can be separated using an electrodialysis apparatus. However, when the concentrations of cations and anions in the water to be treated are low, the electric resistance increases, the current value decreases, the applied voltage increases, and the separation efficiency decreases.

[0005] That is, in an electrodialysis apparatus, the water to be treated flows through the water chamber to be treated toward the outlet side, and as the concentration of ions decreases, the current becomes difficult to flow, so the voltage applied between the anode and cathode of the electrodialysis increases. In addition, the lithium ions remaining in the desalted treated water do not become sufficiently low.

Prior Art Documents

Patent Documents

[0006]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0007] The present invention aims to provide a method and apparatus for separating and concentrating lithium from water containing both lithium and anions using electrodialysis, in which an increase in the electrodialysis voltage is avoided even when the lithium concentration of the water flowing through the water treatment chamber decreases, thereby enabling efficient separation and concentration of lithium. [Means for solving the problem]

[0008] The gist of this invention is as follows:

[0009] [1] A method for separating and concentrating lithium, characterized by treating water to be treated in which lithium ions and anions coexist using an electrodialysis apparatus in which an ion exchanger is filled in the flow path of the water to be treated.

[0010] [2] The method for separating and concentrating lithium according to [1], characterized in that the ion exchange material is a mixed resin.

[0011] [3] The method for separating and concentrating lithium as described in [1],[2], wherein the anion is a carbonate ion.

[0012] [4] The method for separating and concentrating lithium according to [1] to [3], wherein the lithium ion concentration in the water to be treated is 1,000 mg / L or more.

[0013] [5] The lithium separation and concentration method described in [3],[4] wherein the carbonate ion concentration in the water to be treated is 10,000 mg / L or more.

[0014] [6] A method for separating and concentrating lithium according to any one of [1] to [5], wherein the flow rate of cation-concentrated water or anion-concentrated water is 1 / 2 or less of the supply flow rate of the water to be treated.

[0015] [7] A method for separating and concentrating lithium according to any one of [1] to [5], wherein the flow rate of cation-concentrated water or anion-concentrated water is 1 / 10 or less of the supply flow rate of the water to be treated.

[0016] [8] The method for separating and concentrating lithium according to any one of [1] to [5], wherein the flow rate of the anion-concentrated water is 10 to ○○ times the supply flow rate of the water to be treated.

[0017] [9] An electrodialysis apparatus for subjecting water to be treated containing lithium ions and anions to electrodialysis treatment, an anode and a cathode, an anode chamber constituting diaphragm adjacent to the anode through an anode chamber, a cathode chamber constituting diaphragm adjacent to the cathode through a cathode chamber, between the anode chamber constituting diaphragm and the cathode chamber constituting diaphragm, at least A. an anion exchange membrane or a bipolar membrane, B. a cation exchange membrane, and C. an anion exchange membrane or a bipolar membrane are arranged in this order from the anode side to the cathode side a water to be treated chamber formed between A and B, a cation concentration chamber formed between B and C, and an ion exchanger filled in the water to be treated chamber, wherein the anode chamber constituting diaphragm is a cation exchange membrane or a bipolar membrane, and the cathode chamber constituting diaphragm is an anion exchange membrane or a bipolar membrane, An electrodialysis apparatus for subjecting water to be treated containing lithium ions and anions to electrodialysis treatment.

[0018] [(Regarding 10)] The anode chamber constituting diaphragm is a cation exchange membrane, the cathode chamber constituting diaphragm is an anion exchange membrane, the ion exchanger filled in the water to be treated chamber is a mixed resin, an anion-concentrated water chamber, a water to be treated chamber, and a cation-concentrated water chamber formed by arranging an anion exchange membrane and a cation exchange membrane in this order from the anode side to the cathode side between the anode constituting diaphragm and the cathode constituting diaphragm, a mixed resin or a cation exchange resin filled in the anode chamber, a mixed resin or an anion exchange resin filled in the anion-concentrated water chamber, a mixed resin or a cation exchange resin filled in the cation-concentrated water chamber, The mixed resin filled in the cathode chamber and An electrodialysis apparatus according to [9].

[0019]

[11] The anode chamber forming diaphragm is a cation exchange membrane, Each membrane forming the cathode chamber is an anion exchange membrane, The ion exchanger filled in the water to be treated chamber is a mixed resin, and Between the anode chamber forming diaphragm and the cathode chamber forming diaphragm, one or more sets of an anion concentrated water chamber, a water to be treated chamber, and a cation concentrated water chamber formed by arranging an anion exchange membrane, a cation exchange membrane, and a bipolar membrane in this order from the anode side to the cathode side are arranged, Between the bipolar membrane farthest from the anode side and the cathode chamber forming diaphragm, an anion concentrated water chamber, a water to be treated chamber, and a cation concentrated water chamber formed by arranging an anion exchange membrane and a cation exchange membrane in this order from the anode side to the cathode side, The mixed resin or cation exchange resin filled in the anode chamber, The mixed resin or anion exchange resin filled in each anion concentrated water chamber, The mixed resin or cation exchange resin filled in each cation concentrated water chamber, The mixed resin filled in the cathode chamber and An electrodialysis apparatus according to [9].

[0020]

[12] The anode chamber forming diaphragm is a cation exchange membrane, The cathode chamber forming diaphragm is an anion exchange membrane, The ion exchanger filled in the water to be treated chamber is a mixed resin, and Between the anode forming diaphragm and the cathode forming diaphragm, one or more sets of an anion concentrated water chamber, a water to be treated chamber, a cation concentrated water chamber, and a pure water chamber formed by arranging an anion exchange membrane, a cation exchange membrane, an anion exchange membrane, and a cation exchange membrane in this order from the anode side to the cathode side are arranged. Between the cation exchange membrane farthest from the anode side and the cathode chamber forming diaphragm, an anion concentrated water chamber, a water to be treated chamber, and a cation concentrated water chamber formed by arranging an anion exchange membrane and a cation exchange membrane in this order from the anode side to the cathode side, The anode chamber is filled with a mixed resin or cation exchange resin, A mixed resin or anion exchange resin is filled into each anion concentration water chamber, A mixed resin or cation exchange resin is filled into each cation-concentrated water chamber, The mixed resin filled in the aforementioned pure water chamber, The mixed resin filled in the cathode chamber and An electrodialysis machine having [9].

[0021]

[13] The anode chamber diaphragm and the cathode chamber diaphragm are both bipolar membranes, The ion exchange material filled in the water chamber to be treated is a mixed resin, Between the anode chamber diaphragm and the cathode chamber diaphragm, a treated water chamber and a cation-concentrated water chamber are formed according to any of the following a to b: A mixed resin or cation exchange resin filled in the cation-concentrated water chamber, An electrodialysis machine having [9]. a. A cation exchange membrane is provided, with a water to be treated chamber on the anode side of the cation exchange membrane and a cation-concentrated water chamber on the cathode side of the cation exchange membrane. b. Between the anode chamber diaphragm and the cathode chamber diaphragm, one or more sets of treated water chambers and cation-concentrated water chambers are arranged by arranging a cation exchange membrane and a bipolar membrane in that order from the anode side to the cathode side, and between the bipolar membrane furthest from the anode side and the cathode chamber diaphragm, there are treated water chambers and cation-concentrated water chambers formed by arranging a cation exchange membrane. [Effects of the Invention]

[0022] In this invention, lithium and anions can be efficiently separated and concentrated by using an electrodialysis apparatus in which an ion exchanger is filled into the water treatment chamber (desalination chamber).

[0023] In one aspect of the present invention, a mixed resin, which is a mixture of anion exchange resin and a cation exchange resin, is filled into the water to be treated chamber as an ion exchange resin. Even if the lithium concentration decreases as the water to be treated flows through this water to be treated chamber (desalination chamber), the water dissociates due to the action of the mixed resin, generating hydrogen ions and hydroxide ions, so that a sufficient current flows and a voltage increase is avoided. [Brief explanation of the drawing]

[0024] [Figure 1] This is a diagram showing the configuration of an electrodialysis apparatus used in a lithium separation and concentration method according to an embodiment. [Figure 2] This is a diagram showing the configuration of an electrodialysis apparatus used in a lithium separation and concentration method according to an embodiment. [Figure 3] This is a diagram showing the configuration of an electrodialysis apparatus used in a lithium separation and concentration method according to an embodiment. [Figure 4] This is a diagram showing the configuration of an electrodialysis apparatus used in a lithium separation and concentration method according to an embodiment. [Figure 5] This is a diagram showing the configuration of an electrodialysis apparatus used in the lithium separation and concentration method described in the comparative example. [Modes for carrying out the invention]

[0025] The present invention will be described in more detail below.

[0026] In this invention, lithium-containing water is treated with an electrodialysis apparatus to obtain lithium-containing water with a high lithium concentration. Examples of lithium-containing water include, but are not limited to, lithium-containing water discharged from the manufacturing process of lithium-ion batteries and the recycling process of waste lithium batteries, as well as water from salt lakes and ore deposits used for lithium resource extraction.

[0027] The lithium concentration in the lithium-containing treated water is preferably 0.5 mg / L or more, particularly 5 mg / L or more, and especially 50 mg / L or more, and also preferably 50,000 mg / L or less, particularly 10,000 mg / L or less, and especially 3,000 mg / L or less.

[0028] If the lithium concentration in the lithium-containing water to be treated is outside the above range, membrane concentration treatment or dilution treatment may be performed as necessary.

[0029] The lithium-containing treated water may also contain cations other than lithium. Examples of cations other than lithium include, but are not limited to, sodium ions, potassium ions, ammonium ions, magnesium ions, nickel ions, cobalt ions, manganese ions, aluminum ions, and iron ions.

[0030] The lithium-containing treated water preferably contains a cation such as lithium and a corresponding anion. Examples of such anions include, but are not limited to, chloride ions, fluoride ions, sulfate ions, carbonate ions, nitrate ions, phosphate ions, and acetate ions.

[0031] The pH of the lithium-containing treated water is preferably between 2 and 13, particularly between 3 and 12, and especially between 4 and 9. If the pH is outside this range, the pH may be adjusted by adding acids such as hydrochloric acid, sulfuric acid, or nitric acid, or alkalis such as sodium hydroxide, potassium hydroxide, calcium hydroxide, or magnesium hydroxide.

[0032] Prior to electrodialysis treatment of lithium-containing water using an electrodialysis machine, the lithium-containing water may be subjected to solid content removal treatments such as filtration and sedimentation.

[0033] The following describes an example configuration of an electrodialysis machine with reference to the diagrams.

[0034] <First example of an electrodialysis machine> Figure 1 is a diagram showing an example of an electrodialysis apparatus used in the embodiment.

[0035] Between the anode (positive electrode) 11 and the cathode (negative electrode) 12, a cation exchange membrane 13, anion exchange membrane 14, a cation exchange membrane 15 as an anode chamber diaphragm, and an anion exchange membrane 16 as a cathode chamber diaphragm are arranged in this order. From the anode 11 toward the cathode 12, the anode chamber 21, anion concentrated water chamber 22, treated water chamber (desalination chamber) 23, cation concentrated water chamber 24, and cathode chamber 25 are formed in this order. Each chamber 21 to 25 is filled with a resin (mixed resin) which is a mixture of anion exchange resin and cation exchange resin. The ratio of anion exchange resin in the mixed resin is preferably about 40 to 80 volume percent. Note that the anode chamber 21 and the cation concentrated water chamber 24 may be filled with cation exchange resin only, and the anion concentrated water chamber 22 may be filled with anion exchange resin only.

[0036] The water to be treated, containing lithium ions, etc., is passed through the water to be treated chamber 23. Pure water is passed through the anion-concentrated water chamber 22 and the cation-concentrated water chamber 24 in a countercurrent with respect to the water to be treated chamber 13. Pure water is passed through the anode chamber 21 and the cathode chamber 25 as electrode water.

[0037] When a voltage is applied between the anode 11 and the cathode 12, and the water to be treated, pure water, and electrode water are passed through as described above, the anions contained in the water to be treated in the water to be treated chamber 13 move towards the anode 11, permeate the anion exchange membrane 14, and move to the anion concentrated water chamber 22. Then, the anion concentrated water containing these anions is recovered from the anion concentrated water chamber 22.

[0038] Cations such as Li in the water to be treated in the water to be treated chamber 23 (however, H + Ions are excluded. The same applies to the following cations.) They move to the cathode 12 side and permeate the cation exchange membrane 15. Then, the cation-concentrated water (lithium hydroxide aqueous solution) containing these cations is recovered from the cation-concentrated water chamber 24.

[0039] Even though anions and cations in the water to be treated move to the anion-concentrated water chamber 22 and the cation-concentrated water chamber 24 in this manner, the water to be treated chamber 23 is filled with a mixed resin, so a sufficient current flows through the water to be treated chamber 23, and the applied voltage between the anode 11 and the cathode 12 hardly increases. In other words, when anions and cations in the water to be treated move to the acidic water extraction chamber and the alkaline water extraction chamber, the conductivity of the water in the water to be treated decreases and it becomes difficult for current to flow, but due to the action of the mixed resin in the water to be treated chamber, H is released due to the dissociation of water. + and OH - This occurs. As a result, the reduced conductivity can be compensated for by the generated hydrogen ions and hydroxide ions. In this way, it is possible to reduce the concentration of anions and cations in the treated water to a sufficiently low level without significantly increasing the applied voltage.

[0040] <Second example of an electrodialysis machine> Figure 2 is a configuration diagram showing a second example of an electrodialysis apparatus used in the embodiment. This electrodialysis apparatus is configured to have multiple water treatment chambers (desalination chambers) and to separate them with bipolar membranes so that cations that have permeated the cation exchange membrane and anions that have permeated the anion exchange membrane do not mix.

[0041] Between the anode (positive electrode) 31 and the cathode (negative electrode) 32, a cation exchange membrane 33, anion exchange membrane 34, cation exchange membrane 35, bipolar membrane 36, anion exchange membrane 37, cation exchange membrane 38 as diaphragms constituting the anode chamber, and anion exchange membrane 39 as a diaphragm constituting the cathode chamber are arranged in this order. From the anode 31 toward the cathode 32, the anode chamber 41, anion concentrated water chamber 42, treated water chamber (desalination chamber) 43, cation concentrated water chamber 44, anion concentrated water chamber 45, treated water chamber (desalination chamber) 46, cation concentrated water chamber 47, and cathode chamber 48 are formed in this order. Each chamber 41 to 48 is filled with a resin (mixed resin) which is a mixture of anion exchange resin and cation exchange resin. Note that the anode chamber 41 and the cation concentrated water chambers 44 and 47 may be filled with cation exchange resin only, and the anion concentrated water chambers 42 and 45 may be filled with anion exchange resin only.

[0042] The water to be treated, containing lithium ions, etc., is passed through the water to be treated chambers 43 and 46. Pure water is passed through the anion-concentrated water chambers 42 and 45 and the cation-concentrated water chambers 44 and 47 in the countercurrent direction to the water to be treated chambers 43 and 46. Pure water is passed through the anode chamber 41 and the cathode chamber 46 as electrode water.

[0043] When a voltage is applied between the anode 31 and the cathode 32, and the water to be treated, pure water, and electrode water are passed through as described above, the anions contained in the water to be treated in the water to be treated chambers 43 and 46 move towards the anode 41, permeate the anion exchange membranes 34 and 37 respectively, move to the anion-concentrated water chambers 42 and 45, and flow out into each chamber 42 and 45. Note that the anions in the anion-concentrated water chamber 45 do not move to the cation-concentrated water chamber 44 because the bipolar membrane 36 is present on the anode 31 side.

[0044] Cationic cations in the water to be treated in the water to be treated chambers 43 and 46 move towards the cathode 32 and permeate through the cation exchange membranes 35 and 38. Then, cation-concentrated water (aqueous lithium hydroxide solution) containing these cations flows out from the cation-concentrated water chambers 44 and 47. Cationic cations in the cation-concentrated water chamber 44 do not move to the anion-concentrated water chamber 45 because the bipolar membrane 35 is present on the cathode 32 side.

[0045] Even if anions and cations in the treated water move from the treated water chambers 43 and 46 to the adjacent chamber and exit, the treated water chambers 43 and 46 are filled with a mixed resin, so hydrogen ions and hydroxide ions are generated by the dissociation of water, and a sufficient current flows through the treated water chambers 43 and 46. Therefore, the applied voltage between the anode 31 and cathode 32 hardly rises, making it possible to sufficiently reduce the concentration of anions and cations in the treated water.

[0046] Furthermore, although Figure 2 shows two treated water chambers 43 and 46, it is also possible to provide three or more treated water chambers by providing three or more combinations of anion-concentrated water chamber, treated water chamber, and cation-concentrated water chamber. To provide three or more treated water chambers, two or more sets of anion-concentrated water chamber 42, anion-exchange membrane 34, treated water chamber 43, cation-exchange membrane 35, cation-concentrated water chamber 44, and bipolar membrane 36 can be arranged between the cation exchange membrane 33 and the anion exchange membrane 39, from the anode 31 side to the cathode 32 side. After that, the anion-concentrated chamber 45, anion-exchange membrane 37, treated water chamber 46, cation-exchange membrane 38, and cation-concentrated water chamber 47 can be arranged.

[0047] <Third example of an electrodialysis machine> In the electrodialysis apparatus shown in Figure 2, a bipolar membrane 36 is interposed between the cation-concentrated water chamber 44 and the anion-concentrated water chamber 45 to prevent ion movement between the two chambers. However, as shown in the third example of the electrodialysis apparatus in Figure 3, an anion exchange membrane 50, a pure water chamber 52, and a cation exchange membrane 51 may be placed instead of the bipolar membrane 36.

[0048] The other components in Figure 3 are the same as those in Figure 2, and the same reference numerals indicate the same parts.

[0049] In the electrodialysis apparatus shown in Figure 3, cations in the cation-concentrated water chamber 44 do not move to the pure water chamber 52 because an anion exchange membrane 50 is present on the cathode 32 side. Similarly, anions in the anion-concentrated water chamber 45 do not move to the pure water chamber 52 because a cation exchange membrane 51 is present on the anode 31 side.

[0050] Although the anion and cation concentrations in the pure water within the pure water chamber 52 are extremely low, the chamber is filled with a mixed resin, and hydrogen ions and hydroxide ions are generated by the dissociation of water, allowing sufficient current to flow.

[0051] The other operating modes and effects of the electrodialysis apparatus in Figure 3 are the same as those of the electrodialysis apparatus in Figure 2.

[0052] <Fourth example of an electrodialysis machine> Figure 4 is a configuration diagram showing a fourth example of an electrodialysis apparatus used in the embodiment.

[0053] Between the anode (positive electrode) 61 and the cathode (negative electrode) 62, a bipolar membrane 63, a cation exchange membrane 64, a bipolar membrane 65, a cation exchange membrane 66, and a bipolar membrane 67, which serve as diaphragms for the anode chamber and cathode chamber respectively, are arranged in this order. From the anode 61 toward the cathode 62, the anode chamber 71, the water to be treated chamber 72, the cation concentrated water chamber 73, the water to be treated chamber 74, the cation concentrated water chamber 75, and the cathode chamber 76 are formed in this order. Each chamber 71 to 76 is filled with a resin (mixed resin) which is a mixture of anion exchange resin and cation exchange resin. Note that the anode chamber 71 and the cation concentrated water chambers 73 and 75 may be filled with cation exchange resin only.

[0054] The water to be treated, containing cations and anions such as lithium ions, is passed through the water to be treated chambers 72 and 74. Pure water is passed through the cation-concentrated water chambers 73 and 75 in the countercurrent direction to the water to be treated chambers 72 and 74. Pure water or an aqueous sodium sulfate solution is passed through the anode chamber 71 and cathode chamber 76 as electrode water. Since bipolar membranes 63 and 67 are used, sulfate ions and sodium ions do not move to adjacent chambers even when an aqueous sodium sulfate solution is passed through as electrode water.

[0055] When a voltage is applied between the anode 61 and the cathode 62, and the treated water, pure water, and electrode water are passed through as described above, the cations contained in the treated water in the treated water chambers 72 and 74 move towards the cathode 62, permeate the cation exchange membranes 64 and 66 respectively, and move to the cation concentrated water chambers 73 and 75. Then, the cation concentrated water (lithium hydroxide aqueous solution) containing these cations is recovered from the cation concentrated water chambers 73 and 75.

[0056] Anions in the water to be treated in the water to be treated chambers 72 and 74 attempt to move toward the anode 61, but this movement is prevented by the bipolar membranes 63 and 65. As a result, acidic water containing these anions is recovered from the water to be treated chambers 72 and 74.

[0057] Even though the cations in the water to be treated move to the cation-concentrated water chambers 73 and 75, the water to be treated chambers 72 and 74 are filled with mixed resin, and water dissociation generates water ions and hydroxide ions, so a sufficient current flows through the water to be treated chambers 62 and 64. Consequently, the applied voltage between the anode 61 and cathode 62 hardly rises, and cation-concentrated water with a high concentration of LiOH as the main component is extracted from the cation-concentrated water chambers 73 and 75.

[0058] Although Figure 4 shows two treated water chambers 72 and 74, the combination of a cation-concentrated water chamber and a treated water chamber may be combined into one treated water chamber, or three or more combinations of cation-concentrated water chambers and treated water chambers may be provided, resulting in three or more treated water chambers. If there is only one treated water chamber, the treated water chamber 72, cation exchange membrane 64, and cation-concentrated water chamber 73 should be arranged between the bipolar membrane 63 and the bipolar membrane 67. When installing three or more water treatment chambers, two or more sets of water treatment chambers 72, cation exchange membrane 64, cation concentrated water chamber 73, and bipolar membrane 65 are arranged between bipolar membranes 63 and 67, with the water treatment chamber 72, cation exchange membrane 64, cation concentrated water chamber 73, and bipolar membrane 65 forming one set, moving from the anode 61 side toward the cathode 62. In this arrangement, a cation exchange membrane 66 is placed between the bipolar membrane furthest from the anode 61 and bipolar membrane 67 to provide water treatment chambers 74 and cation concentrated water chambers 75.

[0059] In the electrodialysis apparatus shown in Figures 1-4 above, the water to be treated and the pure water are in countercurrent flow, but parallel flow (co-current flow) is also acceptable.

[0060] Furthermore, in the electrodialysis apparatus shown in Figures 1-3, a cation exchange membrane and an anion exchange membrane are provided as the anode chamber diaphragm and cathode chamber diaphragm, respectively, but either one or both may be changed to bipolar membranes. If bipolar membranes are used, the electrode chambers in contact with the bipolar membranes may or may not be filled with ion exchange resin. However, if ion exchange resin is not filled, an aqueous solution containing an electrolyte such as sodium sulfate solution must be used in the electrode chambers.

[0061] Furthermore, in the electrodialysis apparatus shown in Figure 4, bipolar membranes are used for both the anode chamber diaphragm and the cathode chamber diaphragm. However, the combination of the anode chamber diaphragm and the cathode chamber diaphragm can be any of the following: cation exchange membrane and bipolar membrane, cation exchange membrane and anion exchange membrane, or bipolar membrane and anion exchange membrane. When a bipolar membrane is used for the electrode chamber diaphragm, the electrode chamber in contact with the bipolar membrane may or may not be filled with ion exchange resin. However, if ion exchange resin is not filled, an aqueous solution containing an electrolyte such as sodium sulfate solution must be used in the electrode chamber.

[0062] The above-mentioned pure water can include desalinated water from an electrodialysis unit, permeate from an RO unit, treated water from cation exchange resins and anion exchange resins, pure water from a separately installed pure water production device, and other types of water. Among these, desalinated water from an electrodialysis unit, permeate from an RO unit, and treated water from cation exchange resins and anion exchange resins are preferred.

[0063] [Effects of using an electrodialysis machine] In the electrodialysis apparatus shown in Figures 1-4, lithium ions contained in the water to be treated are affected by the electric field, permeate the cation exchange membrane on the cathode side, and mix with hydroxide ions that have permeated the adjacent anion exchange membrane, recovering as alkaline cation-concentrated water. On the other hand, anions such as carbonate ions contained in the water to be treated are affected by the electric field, permeate the anion exchange membrane on the anode side, and mix with hydrogen ions that have permeated the adjacent cation exchange membrane, recovering as acidic anion-concentrated water.

[0064] When cations and anions move within the water being treated, the conductivity of the water decreases, making it difficult for current to flow. However, because a mixed resin is present in the flow path, the water dissociates, generating hydrogen ions and hydroxide ions. As a result, the current does not decrease, and the concentrations of cations and anions in the water being treated become sufficiently low.

[0065] In this way, the electrodialysis apparatus shown in Figures 1-4 above yields cation-concentrated water with a high concentration of lithium, and hydrogen ions and hydroxide ions are generated in the water treatment chamber by electrolysis of water, thus preventing a voltage increase in the electrodialysis apparatus.

[0066] Furthermore, in the electrodialysis apparatus shown in Figures 1-4 above, ion exchange resin is packed into the cation-concentrated water chamber and the anion-concentrated water chamber, which accelerates ion transfer by retaining ions in the ion exchange resin. In addition, electrolysis can be used to supplement the current medium in areas where concentration is insufficient.

[0067] Note that filling the cation concentrate chamber and the anion concentrate chamber with ion exchange resin is not mandatory and can be omitted. If filling with ion exchange resin is omitted, it is preferable to supply water containing the target components of each concentrate chamber to each chamber, rather than pure water. For the water supplied to the cation concentrate chamber, a mixture of a portion of the cation concentrate discharged from the cation concentrate chamber and pure water can be used, but is not limited to this. For the water supplied to the anion concentrate chamber, a mixture of a portion of the anion concentrate discharged from the anion concentrate chamber and pure water can be used, but is not limited to this.

[0068] In the electrodialysis apparatus described above, by setting the flow rate of the cation-concentrated water chamber to 50% or less of the flow rate of the desalination chamber, particularly to 50-20%, and especially to 20-5%, the cations can be concentrated to more than twice their original volume.

[0069] [Reference example] Figure 5 shows an electrodialysis apparatus without ion exchange resin. In this electrodialysis apparatus, a bipolar membrane 73, anion exchange membrane 74, a cation exchange membrane 75, and a bipolar membrane 76 are arranged in this order between the anode 71 and the cathode 72 to form an anode chamber 81, anion concentrated water chamber 82, water to be treated chamber 83, cation concentrated water chamber 84, and cathode chamber 85. None of the chambers 81 to 85 are filled with packing materials such as ion exchange resin.

[0070] In this electrodialysis apparatus, lithium ions contained in the water to be treated are affected by the electric field, permeate the cation exchange membrane 75 on the cathode 72 side, and mix with hydroxide ions generated from the adjacent bipolar membrane 76 to be recovered as alkaline cation-concentrated water (lithium hydroxide aqueous solution). On the other hand, anions such as carbonate ions contained in the water to be treated are affected by the electric field, permeate the anion exchange membrane 74 on the anode 71 side, and mix with hydrogen ions generated from the adjacent bipolar membrane 73 to be recovered as acidic anion-concentrated water. As cations and anions move in the water to be treated, the conductivity of the water decreases, making it difficult for electricity to flow. Therefore, a higher voltage is required to reduce these ions, and the energy consumption also increases. Furthermore, it is necessary to ensure safety against high voltage and the durability of the components. In addition, applying high voltage can cause problems such as hydrogen ions breaking through the electrostatic barrier of the anion exchange membrane and passing through.

[0071] Furthermore, in addition to the presence or absence of ion exchange resin filling, the electrodialysis apparatus in Figures 1 and 5 differs in that the diaphragm adjacent to the electrode chamber in Figure 5 is a bipolar membrane, allowing sodium sulfate aqueous solution to be passed through as electrode water. If the ion exchange resin is removed from the electrodialysis apparatus in Figure 1, which uses pure water to pass through the electrode chamber, the electrical resistance of the electrode chamber will increase. If sodium sulfate aqueous solution is used as electrode water to reduce the electrical resistance of the electrode chamber, ions will permeate through the ion exchange membrane and mix into the adjacent chamber. For example, if sodium sulfate aqueous solution is passed through as electrode water in an apparatus like Figure 1, which uses an anion exchange membrane as the diaphragm adjacent to the cathode chamber, sulfate ions will pass through the anion exchange membrane, contaminating the cation-concentrated water and lithium ion water. For this reason, Figure 5 uses a bipolar membrane as the diaphragm adjacent to the electrode chamber.

[0072] [Recovery of lithium from lithium-concentrated water] From the electrodialysis apparatus described above, cation-concentrated water (lithium hydroxide aqueous solution) containing a high concentration of lithium can be obtained.

[0073] The method for recovering lithium from this lithium hydroxide aqueous solution is not particularly limited, and various methods can be employed. For example, a method can be used in which sodium carbonate is added to the lithium hydroxide aqueous solution to precipitate and separate lithium carbonate. [Examples]

[0074] The following describes some examples.

[0075] [Example 1] Using the electrodialysis apparatus shown in Figure 1, the treated water, consisting of an aqueous chloride solution (lithium chloride and sodium chloride in Example 1), was subjected to electrodialysis under the following conditions.

[0076] <Water to be treated> Lithium ion concentration: 2600 mg / L Sodium ion concentration: 200 mg / L Chloride ion concentration: 13700 mg / L pH: 5.56

[0077] <Electrode water> pure water

[0078] <Ion exchange membrane> Anion exchange membrane: Astom-manufactured anion exchange membrane (AHA) Cation exchange membrane: Cation exchange membrane (CMB) manufactured by ASTOM

[0079] <Mixed resin> Kurita Water Industries' ion exchange resin (KR-UM1) Membrane area: 100cm 2 Distance between anode and cathode: 3.5 cm

[0080] <Driving conditions> Membrane area: 100cm 2 Treated water flow rate: 3.7mL / min Cation-concentrated water flow rate: 1.6 mL / min Anion concentrate flow rate: 1.6 mL / min Electrode water flow rate: 250mL / min Initial voltage upon power-on: 15.0V Initial current when power is applied: 4.0A

[0081] <Result> After 60 hours of operation, the following was observed:

[0082] Voltage: 13.6V Current: 4.5A Lithium ion concentration in desalination water: 230 mg / L Sodium ion concentration in desalinated water: 12 mg / L Chloride ion concentration in desalinated water: 21 mg / L Lithium ion concentration in cation-concentrated water: 6,200 mg / L Sodium ion concentration in cation-concentrated water: 470 mg / L Chloride ion concentration in anion-concentrated water: 32,300 mg / L

[0083] The flow rates of cation-concentrated water and anion-concentrated water were less than half the flow rate of the water being treated, and calculations based on their reciprocals suggested a 2.3-fold ion concentration. In reality, lithium ions, sodium ions, and chloride ions were concentrated 2.4 times, achieving the expected values.

[0084] [Example 2] In Example 1, a chloride aqueous solution of the following concentration was used as the water to be treated, and the treatment was carried out under the same conditions as in Example 1, except that the flow rates of the water to be treated and each concentrated water were as follows.

[0085] <Water to be treated> Lithium ion concentration: 8.2 mg / L Chloride ion concentration: 38.7 mg / L pH: 5.76

[0086] <Water flow conditions> Treated water flow rate: 78mL / min Cation-concentrated water flow rate: 4.8 mL / min Anion concentrate flow rate: 7.3 mL / min

[0087] <Result> After 60 hours of operation, the following was observed:

[0088] Voltage: 7.3V Current: 0.50A Lithium ion concentration in desalinated water: 0.1 mg / L Chloride ion concentration in desalinated water: 0.0 mg / L Lithium ion concentration in cation-concentrated water: 149 mg / L Chloride ion concentration in anion-concentrated water: 443 mg / L

[0089] The flow rates of cation-concentrated water and anion-concentrated water were less than 1 / 10 of the flow rate of the water to be treated, and theoretically, lithium ions were expected to be concentrated 16 times and chloride ions 11 times. In reality, lithium ions were concentrated 18 times and chloride ions 11 times, obtaining the expected values.

[0090] [Comparative Example 1] An electrodialysis treatment of a lithium chloride aqueous solution was performed using the electrodialysis apparatus shown in Figure 5 under the following conditions.

[0091] <Water to be treated> Lithium ion concentration: 8.3 mg / L Chloride ion concentration: 38.9 mg / L pH: 5.58

[0092] <Electrode water> 15 wt% sodium sulfate aqueous solution <Ion exchange membrane area, electrode area> Anion exchange membrane: Astom-manufactured anion exchange membrane (AHA) Cation exchange membrane: Cation exchange membrane (CMB) manufactured by ASTOM Bipolar membrane: Bipolar membrane manufactured by Astrom Membrane area: 50cm 2 Distance between anode and cathode: 0.4 cm

[0093] <Driving conditions> Treated water flow rate: 81mL / min Cation-concentrated water flow rate: 4.3 mL / min Anion concentrate flow rate: 7.8 mL / min Electrode water flow rate: 8.0mL / min Initial voltage upon power-on: 15.0V Initial current when power is applied: 0.11A

[0094] <Result> After 6 hours of operation, the following was observed:

[0095] Voltage: 15.0V Current: 0.13A Lithium ion concentration in desalinated water: 4.2 mg / L Chloride ion concentration in desalinated water: 30.7 mg / L Lithium ion concentration in cation-concentrated water: 77.3 mg / L Chloride ion concentration in anion-concentrated water: 38.9 mg / L

[0096] The lithium ion concentration in the desalination water was higher compared to Example 2, and the voltage reached 15.01V, making it difficult for current to flow. This shows that in electrodialysis, the efficiency of concentration and separation decreases when the ion concentration in the desalination water decreases.

[0097] [Example 3] In Example 1, a chloride aqueous solution of the following concentration was used as the water to be treated, and the treatment was carried out under the same conditions as in Example 1, except that the flow rates of the water to be treated and each concentration were as follows.

[0098] <Water to be treated> Lithium ion concentration: 0.81 mg / L Chloride ion concentration: 3.8 mg / L pH: 4.54 <Driving conditions> Treated water flow rate: 75mL / min Cation-concentrated water flow rate: 3.5 mL / min Anion concentrate flow rate: 6.3 mL / min Initial voltage upon power-on: 3.2V Initial current when power is applied: 0.025A

[0099] <Result> After 60 hours of operation, the results were as follows:

[0100] Voltage: 3.4V Current: 0.025A Lithium ion concentration in desalinated water: 0.0 mg / L Chloride ion concentration in desalinated water: 0.1 mg / L Lithium ion concentration in cation-concentrated water: 15.8 mg / L Chloride ion concentration in anion-concentrated water: 42.1 mg / L

[0101] The flow rates of cation-concentrated water and anion-concentrated water were less than 1 / 10 of the flow rate of the water to be treated, and theoretically, lithium ions were expected to be concentrated 21 times and chloride ions 12 times. In reality, lithium ions were concentrated 20 times and chloride ions 11 times, obtaining the expected values.

[0102] [Example 4] In Example 1, a chloride aqueous solution of the following concentration was used as the water to be treated, and the treatment was carried out under the same conditions as in Example 1, except that the flow rates of the water to be treated and each concentration were as follows.

[0103] <Water to be treated> Lithium ion concentration: 2,400 mg / L Sodium ion concentration: 12,000 mg / L Chloride ion concentration: 18,000 mg / L Carbonate ion concentration: 13,000 mg / L pH: 11.17 <Driving conditions> Treated water flow rate: 2.4mL / min Cation-concentrated water flow rate: 0.85 mL / min Anion concentrate water flow rate: 85 mL / min Initial voltage upon power-on: 13.1V Initial current when power is applied: 4.5A

[0104] <Result> After 60 hours of operation, the results were as follows:

[0105] Voltage: 12.4V Current: 4.5A Lithium ion concentration in desalinated water: 320 mg / L Sodium ion concentration in desalinated water: 860 mg / L Chloride ion concentration in desalinated water: 180 mg / L Carbonate ion concentration in desalinated water: 1,800 mg / L Lithium ion concentration in cation-concentrated water: 4,900 mg / L Sodium ion concentration in cation-concentrated water: 26,000 mg / L Chloride ion concentration in anion-concentrated water: 440 mg / L Carbonate ion concentration in anion-concentrated water: 3.1 mg / L

[0106] The flow rate of the cation-concentrated water was less than half the flow rate of the water being treated, and theoretically, the lithium ions were expected to be concentrated 2.8 times based on the flow rate ratio. In reality, lithium remained in the desalination water as well, resulting in a 2.4-fold concentration in the cation-concentrated water. The flow rate of the anion-concentrated water was 35 times the flow rate of the water being treated, which resulted in a lower carbonate ion concentration in the anion-concentrated water and suppressed the generation of carbon dioxide.

[0107] [Comparative Example 2] An electrodialysis treatment of a lithium chloride aqueous solution was performed using the electrodialysis apparatus shown in Figure 5 under the following conditions.

[0108] <Water to be treated> Lithium ion concentration: 2,600 mg / L Sodium ion concentration: 12,000 mg / L Chloride ion concentration: 17,000 mg / L Carbonate ion concentration: 10,000 mg / L pH: 11.39 <Electrode water> 15 wt% sodium sulfate aqueous solution (same as Comparative Example 1) <Ion exchange membrane and electrode> Same as Comparative Example 1

[0109] <Driving conditions> Treated water flow rate: 2.7mL / min Cation-concentrated water flow rate: 1.1 mL / min Anion concentrate flow rate: 79 mL / min Initial voltage upon power-on: 15.0V Initial current when power is applied: 3.5A

[0110] <Result> After 6 hours of operation, the following was observed:

[0111] Voltage: 13.3V Current: 4.5A Lithium ion concentration in desalination water: 1,200 mg / L Sodium ion concentration in desalinated water: 4,300 mg / L Chloride ion concentration in desalinated water: 2,700 mg / L Carbonate ion concentration in desalinated water: 7,600 mg / L Lithium ion concentration in cation-concentrated water: 3,400 mg / L Sodium ion concentration in cation-concentrated water: 18,000 mg / L Chloride ion concentration in anion-concentrated water: 640 mg / L Carbonate ion concentration in anion-concentrated water: 100 mg / L

[0112] The lithium ion content in the desalinated water was higher compared to Example 4, indicating insufficient separation and concentration.

[0113] [Comparative Example 3] Comparative Example 2 has half the membrane area compared to Example 4. Therefore, the demineralized water from Comparative Example 2 was placed in a tank, and this demineralized water (water quality as described below) was used as the water to be treated and passed through the same electrodialysis apparatus as in Comparative Example 2 under the following conditions.

[0114] <Water to be treated> Lithium ion concentration: 1,200 mg / L Sodium ion concentration: 4,400 mg / L Chloride ion concentration: 2,600 mg / L Carbonate ion concentration: 6,100 mg / L pH: 12.62 <Electrode water> 15 wt% sodium sulfate aqueous solution (same as Comparative Example 2) <Driving conditions> Treated water flow rate: 2.7mL / min Cation-concentrated water flow rate: 1.1 mL / min Anion concentrate flow rate: 81 mL / min

[0115] <Result> After 6 hours of operation, the following was observed:

[0116] Voltage: 15.0V Current: 1.1A Lithium ion concentration in desalination water: 550 mg / L Sodium ion concentration in desalinated water: 1,600 mg / L Chloride ion concentration in desalinated water: 470 mg / L Carbonate ion concentration in desalinated water: 3,000 mg / L Lithium ion concentration in cation-concentrated water: 1,600 mg / L Sodium ion concentration in cation-concentrated water: 6,800 mg / L Chloride ion concentration in anion-concentrated water: 80 mg / L Carbonate ion concentration in anion-concentrated water: 120 mg / L

[0117] The lithium ion concentration in the desalination water was higher compared to Example 4, and the voltage reached 15.0V, making it difficult for current to flow. This indicates that in electrodialysis, a lower ion concentration in the desalination water reduces the efficiency of concentration and separation. The power consumption was also higher in Example 4 (55.8W), Comparative Example 2 (59.9W), and Comparative Example 3 (16.5W). [Explanation of Symbols]

[0118] 11,31,61,71 Anode 12,32,62,72 cathode 15,33,35,38,51,64,66,75 Cation exchange membrane 14,34,37,39,51,74 Anion exchange membrane 13,36,63,65,67,73,76 Bipolar film 21,41,71,81 Anode chamber 25, 48, 76, 85 Cathode chamber

Claims

1. A method for separating and concentrating lithium, characterized by treating water to be treated, in which lithium ions and anions coexist, with an electrodialysis apparatus in which an ion exchange resin is filled into the water flow path.

2. The method for separating and concentrating lithium according to claim 1, characterized in that the ion exchange resin is a mixed resin.

3. The method for separating and concentrating lithium according to claim 1 or 2, wherein the anion is a carbonate ion.

4. A method for separating and concentrating lithium according to claims 1 to 3, wherein the lithium ion concentration in the water to be treated is 1,000 mg / L or more.

5. The lithium separation and concentration method according to claims 3 and 4, wherein the carbonate ion concentration in the water to be treated is 10,000 mg / L or more.

6. A method for separating and concentrating lithium according to any one of claims 1 to 5, wherein the flow rate of cation-concentrated water or anion-concentrated water is 1 / 2 or less of the supply flow rate of water to be treated.

7. A method for separating and concentrating lithium according to any one of claims 1 to 5, wherein the flow rate of cation-concentrated water or anion-concentrated water is 1 / 10 or less of the supply flow rate of the water to be treated.

8. A method for separating and concentrating lithium according to any one of claims 1 to 5, wherein the flow rate of the anion-concentrated water is 10 to 100 times the supply flow rate of the water to be treated.

9. An electrodialysis apparatus for electrodialysis treatment of water to be treated containing lithium ions and anions, anode and cathode, The anode is adjacent to the anode chamber via an anode chamber, and the anode chamber is composed of a diaphragm, The cathode is adjacent to the cathode chamber via a cathode chamber, and the cathode chamber is composed of a diaphragm, Between the anode chamber diaphragm and the cathode chamber diaphragm, at least A. anion exchange membrane or bipolar membrane, B. cation exchange membrane, and C. anion exchange membrane or bipolar membrane are arranged in this order from the anode side to the cathode side. A water treatment chamber formed between A and B, A cation concentration chamber formed between B and C, The water chamber to be treated is filled with an ion exchanger, The anode chamber diaphragm is a cation exchange membrane or a bipolar membrane. The cathode chamber diaphragm is an anion exchange membrane or a bipolar membrane. An electrodialysis apparatus for electrodialysis treatment of water containing lithium ions and anions.

10. The anode chamber diaphragm is a cation exchange membrane. The cathode chamber diaphragm is an anion exchange membrane. The ion exchange material filled in the water chamber to be treated is a mixed resin, Between the anode diaphragm and the cathode diaphragm, an anion exchange membrane and a cation exchange membrane are arranged in this order from the anode side to the cathode side to form an anion-concentrated water chamber, a water chamber to be treated, and a cation-concentrated water chamber. The anode chamber is filled with a mixed resin or cation exchange resin, The mixed resin or anion exchange resin filled in the anion concentration water chamber, A mixed resin or cation exchange resin filled in the cation-concentrated water chamber, The mixed resin filled in the cathode chamber and An electrodialysis apparatus according to claim 9, having the following features.

11. The anode chamber diaphragm is a cation exchange membrane. Each membrane constituting the cathode chamber is an anion exchange membrane. The ion exchange material filled in the water chamber to be treated is a mixed resin, Between the anode chamber diaphragm and the cathode chamber diaphragm, one or more sets of anion-concentrated water chambers, a water-to-treatment chamber, and a cation-concentrated water chamber are arranged, each formed by arranging an anion exchange membrane, a cation exchange membrane, and a bipolar membrane in that order from the anode side to the cathode side. Between the bipolar membrane furthest from the anode and the cathode chamber diaphragm, an anion-concentrated water chamber, a water-to-treatment chamber, and a cation-concentrated water chamber are formed by arranging an anion exchange membrane and a cation exchange membrane in that order from the anode side to the cathode side. The anode chamber is filled with a mixed resin or cation exchange resin, A mixed resin or anion exchange resin is filled into each anion concentration water chamber, A mixed resin or cation exchange resin is filled into each cation-concentrated water chamber, The mixed resin filled in the cathode chamber and An electrodialysis apparatus according to claim 9, having the following features.

12. The anode chamber diaphragm is a cation exchange membrane. The cathode chamber diaphragm is an anion exchange membrane. The ion exchange material filled in the water chamber to be treated is a mixed resin, Between the anode diaphragm and the cathode diaphragm, one or more sets of anion-concentrated water chambers, a water-to-treat chamber, a cation-concentrated water chamber, and a pure water chamber are arranged by arranging anion exchange membrane, cation exchange membrane, anion exchange membrane, and cation exchange membrane in this order from the anode side to the cathode side, and between the cation exchange membrane furthest from the anode side and the cathode chamber diaphragm, anion-concentrated water chamber, a water-to-treat chamber, and a cation-concentrated water chamber are formed by arranging anion exchange membrane and cation exchange membrane in this order from the anode side to the cathode side, The anode chamber is filled with a mixed resin or cation exchange resin, A mixed resin or anion exchange resin is filled into each anion concentration water chamber, A mixed resin or cation exchange resin is filled into each cation-concentrated water chamber, The mixed resin filled in the aforementioned pure water chamber, The mixed resin filled in the cathode chamber and An electrodialysis apparatus according to claim 9, having the following features.

13. The anode chamber diaphragm and the cathode chamber diaphragm are both bipolar membranes, The ion exchange material filled in the water chamber to be treated is a mixed resin, Between the anode chamber diaphragm and the cathode chamber diaphragm, a water to be treated chamber and a cation-concentrated water chamber are formed according to any of the following a to b: A mixed resin or cation exchange resin filled in the cation-concentrated water chamber, An electrodialysis apparatus according to claim 9, having the following features. a. A single cation exchange membrane is provided, with a water to be treated chamber on the anode side of the cation exchange membrane and a cation-concentrated water chamber on the cathode side of the cation exchange membrane. b. Between the anode chamber diaphragm and the cathode chamber diaphragm, one or more sets of treated water chambers and cation-concentrated water chambers are arranged by arranging a cation exchange membrane and a bipolar membrane in that order from the anode side to the cathode side, and between the bipolar membrane furthest from the anode side and the cathode chamber diaphragm, there are also treated water chambers and cation-concentrated water chambers formed by arranging a cation exchange membrane.

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