Bipolar electrodialysis apparatus for producing lithium hydroxide and sulfuric acid from lithium sulfate solution

Abstract

The present invention relates to a bipolar electrodialysis apparatus for producing lithium hydroxide and sulfuric acid from a lithium sulfate solution. A bipolar electrodialysis apparatus (100) for producing lithium hydroxide and sulfuric acid from lithium sulfate comprises: a positive electrode (20) and a negative electrode (30) that face each other; a first bipolar film (40), an anion-selective dialysis film (60), a cation-selective dialysis film (70), and a second bipolar film (50) that are disposed between the positive electrode (20) and the negative electrode (30); and a porous first nickel foam (80) disposed on the plane of the positive electrode (20) to be in close contact with each other and a porous second nickel foam (90) disposed on the plane of the negative electrode (30) to be in close contact with each other, wherein the nickel foams (80, 90) have a porosity of 50-90%.

Description

Bipolar electrodialysis device for producing lithium hydroxide and sulfuric acid from lithium sulfate solution

[0001] The present invention relates to a bipolar electrodialysis device for producing lithium hydroxide and sulfuric acid from a lithium sulfate solution, and more specifically, to a bipolar electrodialysis device for producing lithium hydroxide and sulfuric acid from a lithium sulfate solution that improves the production rate of lithium hydroxide and sulfuric acid.

[0002] Bipolar electrodialysis uses water H + Wow OH - Bipolar membranes are used for separation and have been utilized in high-value-added industries such as the pharmaceutical and food industries. Additionally, this method can produce or recover acids or bases from solutions and is environmentally friendly.

[0003] Recently, with the widespread use of IT devices such as smartphones and laptops, as well as electric vehicles (EVs) and energy storage systems (ESS), the global production of lithium-ion batteries is increasing. In parallel, research on technologies to recover and recycle valuable metals from spent lithium-ion batteries is also actively underway.

[0004] For example, a process for recovering valuable metals from spent lithium secondary batteries first leaches the lithium battery cathode active material with sulfuric acid and then recovers cobalt and nickel components by solvent extraction. After this recovery process, waste liquid containing lithium (Li2SO4) is generated, and this waste liquid contains about 2.5 to 3.0 g / L of lithium, which is higher than the concentration of lithium contained in brine (about 0.3 to 1.0 g / L) and is therefore sufficiently valuable for recycling.

[0005] When using a bipolar electrodialysis device to recover lithium from waste lithium sulfate solution, purified lithium hydroxide solution can be recovered directly from the lithium sulfate solution, which simplifies the process and is environmentally friendly; therefore, this method is gaining popularity.

[0006] The need for bipolar electrodialysis devices capable of increasing the production rate of lithium hydroxide and sulfuric acid from lithium sulfate solutions continues to grow in related industries.

[0007] [Prior Art Literature]

[0008] [Patent Literature]

[0009] (Patent Document 1) Republic of Korea Published Patent 10-2023-0094871

[0010] (Patent Document 2) Republic of Korea Published Patent 10-2024-0094902

[0011] (Patent Document 3) Republic of Korea Registered Patent 10-1433086

[0012] The present invention, devised to solve the aforementioned problems, provides a bipolar electrodialysis device with an improved rate of producing lithium hydroxide and sulfuric acid from a lithium sulfate solution.

[0013]

[0014] The objects of the present invention are not limited to those mentioned above, and other unmentioned objects and advantages of the present invention may be understood from the following description and will be more clearly understood by the embodiments of the present invention. Furthermore, it will be readily apparent that the objects and advantages of the present invention can be realized by the means and combinations thereof set forth in the claims.

[0015] To solve the above-mentioned problem, the present invention may provide a bipolar electrodialysis device (100) for producing lithium hydroxide and sulfuric acid from lithium sulfate, comprising: a positive electrode (20) and a negative electrode (30) facing each other; a first bipolar membrane (40), an anion-selective dialysis membrane (60), a cation-selective dialysis membrane (70), and a second bipolar membrane (50) disposed between the positive electrode (20) and the negative electrode (30); and a porous first nickel foam (80) disposed in close contact with each other on the plane of the positive electrode (20) and a porous second nickel foam (90) disposed in close contact with each other on the plane of the negative electrode (30), wherein the porosity of the nickel foams (80, 90) is 50% to 90%.

[0016] In one embodiment, the first bipolar membrane (40) faces the first nickel foam (80) disposed on the anode electrode (20), and an electrode solution is supplied to the first space (25) formed between the first nickel foam (80) and the first bipolar membrane (40); the anion-selective dialysis membrane (60) faces the first bipolar membrane (40), and deionized water is supplied to the acid chamber (45) formed between the first bipolar membrane (40) and the anion-selective dialysis membrane (60); the cation-selective dialysis membrane (70) faces the anion-selective dialysis membrane (60), and a lithium sulfate solution is supplied to the salt chamber (65) formed between the anion-selective dialysis membrane (60) and the cation-selective dialysis membrane (70); and the second bipolar membrane (50) is the DI water is supplied to a base chamber (75) formed between the cation-selective dialysis membrane (70) and the second bipolar membrane (50), and the second bipolar membrane (50) is opposed to the second nickel foam (90) placed on the cathode electrode (30), and an electrode solution can be supplied to a second space (55) formed between the second bipolar membrane (50) and the second nickel foam (90).

[0017] In one embodiment, the positive electrode (20) and the negative electrode (30) may be formed of nickel.

[0018] In one embodiment, the first nickel foam (80) and the second nickel foam (90) may undergo a loading process in hydrochloric acid of 1M to 3M.

[0019] In one embodiment, the loading process may continue for 12 to 24 hours.

[0020] In one embodiment, the nickel foam that has undergone the above-described loading process may undergo sonication treatment.

[0021] In one embodiment, a first gasket (32) disposed between the first bipolar membrane (40) and the anion-selective dialysis membrane (60); a second gasket (33) disposed between the anion-selective dialysis membrane (60) and the cation-selective dialysis membrane (70); and a third gasket (34) disposed between the cation-selective dialysis membrane (70) and the second bipolar membrane (50) are further included, wherein the thickness of the first nickel foam (80) and the second nickel foam (90) may be 30% to 40% thicker than the thickness of any one of the first gasket (32), the second gasket (33), and the third gasket (33).

[0022] In one embodiment, the thickness of the first nickel foam (80) and the second nickel foam (90) may be 330 to 570 μm.

[0023] In one embodiment, the first nickel foam (80) placed on the positive electrode (20) may be pressed onto the positive electrode (20), and the second nickel foam (90) placed on the negative electrode (30) may be pressed onto the negative electrode (30).

[0024] In one embodiment, the first nickel foam (80) and the second nickel foam (90) may undergo a support process in sulfuric acid or nitric acid.

[0025] In one embodiment, the electrode solution may be a lithium hydroxide solution having a concentration of 40 to 60 mS / cm.

[0026] In one embodiment, the first nickel foam (80) and the second nickel foam (90) may have a three-dimensional shape.

[0027] In one embodiment, the three-dimensional solid shape may be a rectangular prism with pores formed on at least three faces.

[0028] In one embodiment, the pore-forming plane of the first nickel foam (80) having a rectangular shape may be in close contact with the plane of the positive electrode (20), and the pore-forming plane of the second nickel foam (90) having a rectangular shape may be in close contact with the plane of the negative electrode (30).

[0029] In one embodiment, the voltage between the positive electrode (20) and the negative electrode (30) may be 10V.

[0030] According to various embodiments of the present invention, the production rate of lithium hydroxide and sulfuric acid in a bipolar electrodialysis device for producing lithium hydroxide and sulfuric acid from a lithium sulfate solution can be increased.

[0031] FIG. 1 is a conceptual diagram of a bipolar electrodialysis apparatus for producing lithium hydroxide and sulfuric acid from lithium sulfate according to an embodiment of the present invention.

[0032] Figure 2 is an enlarged conceptual diagram of the bipolar membrane of the bipolar electrodialysis device shown in Figure 1.

[0033] Figure 3 is an exploded perspective view of some components of the bipolar electrodialysis device of Figure 1.

[0034] Figure 4 shows a graph representing the change in current over time of a bipolar electrodialysis device according to experimental and comparative examples.

[0035] Figure 5 shows graphs representing the conductivity over time in the salt chamber (Fig. 5a), acid chamber (Fig. 5b), and base chamber (Fig. 5c) of a bipolar electrodialysis device according to experimental and comparative examples.

[0036] Figure 6 shows a graph representing the concentration of LiOH in the base chamber (Figure 6a) and the concentration of H2SO4 in the acid chamber (Figure 6b) over time in a bipolar electrodialysis device according to experimental and comparative examples.

[0037] The advantages and features of the present invention and the methods for achieving them will become clear by referring to the embodiments described below in detail together with the accompanying drawings. However, the present invention is not limited to the embodiments disclosed below but may be implemented in various different forms. These embodiments are provided merely to ensure that the disclosure of the present invention is complete and to fully inform those skilled in the art of the scope of the invention, and the present invention is defined only by the scope of the claims. Throughout the specification, the same reference numerals refer to the same components.

[0038] Although terms such as "first," "second," etc., are used to describe various components, it goes without saying that these components are not limited by these terms. These terms are used merely to distinguish one component from another, and unless specifically stated otherwise, the first component may also be the second component.

[0039] Throughout the specification, unless specifically stated otherwise, each component may be singular or plural.

[0040] In the following, the statement that any configuration is placed on the "upper (or lower)" of a component or on the "upper (or lower)" of a component may mean not only that any configuration is placed in contact with the upper (or lower) surface of said component, but also that another configuration may be interposed between said component and any configuration placed on (or below) said component.

[0041] In addition, where it is stated that one component is "connected," "combined," or "contacted" with another component, it should be understood that while the components may be directly connected or contacted with each other, another component may be "interposed" between each component, or each component may be "connected," "combined," or "contacted" through another component.

[0042] Singular expressions used in this specification include plural expressions unless the context clearly indicates otherwise. In this application, terms such as "composed of" or "comprising" should not be interpreted as necessarily including all of the various components or steps described in the specification, and should be interpreted as meaning that some of the components or steps may be omitted or additional components or steps may be included.

[0043] Throughout the specification, "A and / or B" means A, B, or A and B unless specifically stated otherwise, and "C to D" means C or more and D or less unless specifically stated otherwise.

[0044]

[0045] Hereinafter, a bipolar electrodialysis apparatus for producing lithium hydroxide and sulfuric acid from a lithium sulfate solution according to various embodiments will be described with reference to the attached drawings.

[0046]

[0047] FIG. 1 illustrates a conceptual diagram of a bipolar electrodialysis apparatus for producing lithium hydroxide and sulfuric acid from a lithium sulfate solution according to an embodiment of the present invention. As illustrated, the bipolar electrodialysis apparatus (100) according to an embodiment of the present invention includes a positive electrode (20) and a negative electrode (30) facing each other. The positive electrode (20) and the negative electrode (30) may be provided in the form of plates spaced apart so that their surfaces face each other.

[0048] A porous first nickel foam (80) is disposed on the positive electrode (20), and a porous second nickel foam (90) is disposed on the negative electrode (30). The first nickel foam (80) is disposed on the surface of the positive electrode (20) facing the negative electrode (30), and the second nickel foam (90) is disposed on the surface of the negative electrode (30) facing the positive electrode (20).

[0049] The above bipolar electrodialysis device (100) further includes a first bipolar membrane (40), an anion-selective dialysis membrane (60), a cation-selective dialysis membrane (70), and a second bipolar membrane (50) disposed between the positive electrode (20) and the negative electrode (30).

[0050] Preferably, the first bipolar membrane (40), the anion-selective dialysis membrane (60), the cation-selective dialysis membrane (70), and the second bipolar membrane (50) are arranged sequentially from the positive electrode (20) toward the negative electrode (30). The first bipolar membrane (40), the anion-selective dialysis membrane (60), the cation-selective dialysis membrane (70), and the second bipolar membrane (50) are spaced apart from each other along the direction in which they are arranged.

[0051] The first bipolar film (40) is spaced apart from and facing the first nickel foam (80) disposed on the positive electrode (20). The first nickel foam (80) and the first bipolar film (40) define a first space (25) provided between them.

[0052] The anion-selective dialysis membrane (60) is spaced apart from and faces the first bipolar membrane (40). The first bipolar membrane (40) and the anion-selective dialysis membrane (60) define an acid compartment (45) provided between them.

[0053] The cation-selective dialysis membrane (70) is spaced apart from and faces the anion-selective dialysis membrane (60). The anion-selective dialysis membrane (60) and the cation-selective dialysis membrane (70) define a salt compartment (65) provided between them.

[0054] The second bipolar membrane (50) is spaced apart from and faces the cation-selective dialysis membrane (70). The cation-selective dialysis membrane (70) and the second bipolar membrane (50) define a base compartment (75) provided between them.

[0055] The second bipolar film (50) is spaced apart from and faces the second nickel foam (90) disposed on the cathode electrode (30). The second bipolar film (50) and the second nickel foam (90) define a second space (55) provided between them.

[0056] Electrode solution is supplied to the first space (25) and the second space (55). The electrode solution may be, for example, a lithium hydroxide solution, and its concentration may be, for example, 40 mS / cm or more and 60 mS / cm or less. If the concentration is less than 40 mS / cm, the electrode solution is insufficient to perform the required function, and if the concentration exceeds 60 mS / cm, the function of the electrode solution is not improved, and only the concentration increases. Preferably, the concentration of the lithium hydroxide solution may be about 48 mS / cm.

[0057] Next, deionized water can be supplied to the acid chamber (45) formed between the first bipolar membrane (40) and the anion-selective dialysis membrane (60).

[0058] Next, a lithium sulfate (Li2SO4) solution can be supplied to the salt chamber (65) formed between the anion-selective dialysis membrane (60) and the cation-selective dialysis membrane (70).

[0059] Next, DI water can be supplied to the base chamber (75) formed between the cation-selective dialysis membrane (70) and the second bipolar membrane (50).

[0060] Referring to FIG. 2, an enlarged conceptual diagram of the first and second bipolar membranes (40, 50) illustrated in FIG. 1 is shown. Each of the first and second bipolar membranes (40, 50) includes an anion-selective dialysis membrane (41, 51) and a cation-selective dialysis membrane (42, 52) that are spaced apart from each other by a predetermined gap and face each other. The DI water supplied between the anion-selective dialysis membrane (41, 51) and the cation-selective dialysis membrane (42, 52) is H + Wow OH - It dissociates into, and as described, H + It is moved to the right in the drawing (into the birth chamber (45) and the second space (55)) through the cation-selective permeable membranes (42, 52) of the first and second bipolar membranes (40, 50), and OH - It is moved to the left in the drawing (into the first space (25) and base chamber (75)) through an anion-selective permeable membrane (41, 51). This reaction can be carried out, for example, at 0.83V.

[0061] Referring again to FIG. 1, the porous first and second nickel foams (80, 90) are further described. As illustrated, each of the first and second nickel foams (80, 90) is placed in close contact with the planar surface of the positive electrode (20) and the negative electrode (30), and the porosity of the nickel foams (80, 90) may be about 50% to 90% (the pores formed in the nickel foams (80, 90) in FIG. 1 are exaggerated for ease of understanding). When the porosity of the nickel foams (80, 90) is within this range, the electrode liquid can flow without resistance between the pores formed in the nickel foams (80, 90). Thus, the amount of electrolyte that comes into physical or chemical contact or interacts with the nickel foam can be increased, and the surface area of ​​the nickel foam that comes into physical or chemical contact or interacts with the electrolyte can be increased. Thus, the efficiency of the bipolar electrodialysis device can be increased.

[0062] When the porosity of the nickel foam is 30% or less, the nickel foam has a very dense structure like a general electrode, making it difficult for the electrode solution to penetrate into the pores of the nickel foam. When the porosity of the nickel foam exceeds 90%, the electrolyte can flow without resistance, but the density of the nickel foam is low, making it similar to having no nickel foam.

[0063] The first and / or second nickel foam (80, 90) may have a three-dimensional shape, and pores may be formed on at least three faces of the three-dimensional shape. For example, the nickel foam (80, 90) may be formed in a rectangular shape as illustrated, and pores may be formed on at least three faces (a face in contact with the electrode, a face opposite thereto, and at least one of the remaining faces) of the six faces of the rectangular shape. Alternatively, for example, the nickel foam (80, 90) may be formed in a truncated cone or cylinder shape, and pores may be formed on at least a portion of three faces, namely an upper circular face, a lower circular face, and a perimeter face. In this case, the contact area may be increased compared to a two-dimensional mesh shape.

[0064] Nickel foam (80, 90) can be immersed in a 1 to 3 M hydrochloric acid (HCl) solution for 12 to 24 hours. Through this immersion process, the wettability of the nickel foam (80, 90) is improved. In this immersion process, sulfuric acid or nitric acid may be used instead of hydrochloric acid.

[0065] The nickel foam (80, 90) that has undergone the loading process described above may undergo sonication treatment.

[0066] Referring to FIG. 3, which shows an exploded perspective view of some components of a bipolar electrodialysis device for producing lithium hydroxide and sulfuric acid from a conventional lithium sulfate solution, the conventional bipolar electrodialysis device may be similar to the bipolar electrodialysis device (100) according to one embodiment of the present invention, except that it lacks nickel foam (80, 90). As illustrated in FIG. 3, a conventional electrodialysis device may include an electrode gasket (31) placed in front of a first bipolar membrane (340), a gasket (32) placed between the first bipolar membrane (340) and an anion-selective dialysis membrane (360), a gasket (33) placed between the anion-selective dialysis membrane (360) and a cation-selective dialysis membrane (370), a gasket (34) placed between the cation-selective dialysis membrane (370) and a second bipolar membrane (50), and an electrode gasket (35) placed between the second bipolar membrane (350) and a second nickel foam (90).

[0067] A bipolar electrodialysis device (100) according to one embodiment of the present invention may include first and second nickel foams (80, 90) respectively disposed at the gasket (31, 35) position shown in FIG. 3. The first nickel foam (80) disposed on the positive electrode (20) and the second nickel foam (90) disposed on the negative electrode (30) may be formed to be about 30 to 40% thicker than the thickness of the gasket (31, 35) described above. For example, the thickness of the nickel foam (80, 90) may be 330 to 570 μm. Preferably, the thickness of the nickel foam (80, 90) may be about 450 μm. When the nickel foam (80, 90) has a thickness within this range, the nickel foam (80, 90) can be pressed against the electrode (20, 30) by a fastening force during assembly of the bipolar electrodialysis device (100). Due to this pressing force, after assembly, the electrode (20, 30) and the nickel foam (80, 90) can be closely attached to each other, and the density of the nickel foam (80, 90) increases at this attachment point, thereby promoting the transfer of electrons.

[0068] If the nickel foam has a thickness greater than the range described above, the nickel foam may be damaged during the fastening process for assembling the bipolar electrodialysis device (100), or the electrode fluid may not flow smoothly within the nickel foam. Conversely, if the nickel foam has a thickness smaller than the range described above, a gap may form between the electrode and the nickel foam after assembly, or the density of the nickel foam may not increase, thereby reducing the expected effect.

[0069] Referring again to FIG. 1, the dialysis process occurring within the bipolar electrodialysis device (100) will be explained.

[0070] A lithium sulfate solution (Li2SO4) can be supplied to a salt chamber (65) formed between an anion-selective dialysis membrane (60) and a cation-selective dialysis membrane (70). The concentration of lithium sulfate can be, for example, 66 mS / cm. By the electricity (e.g., 10 V) (constant current is also possible) applied to the electrodes (20, 30) of the bipolar electrodialysis device (100), lithium sulfate is SO4 2- wa Li + It dissociates into SO4 2- is moved into the birthing chamber (45) through the anion-selective dialysis membrane (60), and Li + It is moved into the base chamber (75) through the cation-selective dialysis membrane (70).

[0071] SO4 moved into the birthing chamber (45) 2- H dissociated from DI water by the first bipolar membrane (40) + It combines with to form H2SO4. The concentration in the acid chamber (45) can be 0.02 mS / cm.

[0072] Li moved into the base chamber (75) + OH dissociated from DI water by the second bipolar membrane (50) - It combines with to form LiOH. The concentration in the base chamber (75) can be 0.02 mS / cm.

[0073]

[0074] [Experimental Example]

[0075] To verify the effectiveness of the bipolar electrodialysis device (100) shown in Fig. 1, an experiment was conducted under the following conditions.

[0076]

[0077] <Experimental Conditions>

[0078] 1) Nickel foam porosity: 85%

[0079] 2) Nickel foam thickness: 450μm

[0080] 3) Immobilization process: Performed in 2M HCl for 12 hours

[0081] 4) A structure consisting of three repeating sets of bipolar membranes, anion-selective dialysis membranes, and cation-selective dialysis membranes

[0082] 5) Applied voltage: 10V

[0083] 6) Salt solution chamber (65) concentration: Li2SO4=66 mS / cm

[0084] 7) Acid chamber (45) and base chamber (75) concentration: 0.02 mS / cm (DI water)

[0085] 8) Electrode solution: 48 mS / cm LiOH

[0086]

[0087] [Comparative Examples 1 and 2]

[0088] To compare with the experimental example, the experiment was conducted under the following conditions.

[0089]

[0090] <Experimental Conditions>

[0091] The experimental conditions of Comparative Examples 1 and 2 were the same as those of the experimental examples described above, except for the nickel foam. That is, in the case of Comparative Example 1, no nickel foam was used, and in the case of Comparative Example 2, nickel foam with a porosity of 25-30% was used.

[0092]

[0093] Hereinafter, experimental results for experimental examples and comparative examples will be explained with reference to FIGS. 4 to 6.

[0094]

[0095] Referring to FIG. 4, a graph showing the change in current over time of a bipolar electrodialysis device according to the experimental conditions described above is shown. It can be seen that the graph (blue) corresponding to the pre-treated nickel foam (porosity 85%) (Experimental Example) rose and converged more rapidly than the graph (orange) corresponding to the Standard (Comparative Example 1) without nickel foam, and the final current value was also higher. In the case of the graph (gray) corresponding to Comparative Example 2 (porosity of nickel foam 25 to 30%), the rate of rise and the final current value were actually lower than those of Comparative Example 1. Through these results, it can be seen that in the case of the Experimental Example, electron transfer in the nickel foam is smooth, and as a result, ions move rapidly inside, thereby reducing the resistance of the bipolar electrodialysis device.

[0096] Referring to FIG. 5, a graph showing the conductivity of the salt compartment (65) (Fig. 5a), acid compartment (45) (Fig. 5b), and base compartment (75) (Fig. 5c) over time in a bipolar electrodialysis device according to the experimental conditions described above is shown. Generally, conductivity is dependent on the concentration of ions. Referring to FIG. 5a, initially, the salt compartment (65) is mostly a Li2SO4 solution, and as the operation of the bipolar electrodialysis device (100) progresses, SO4 2- Ions and Li +It can be seen that ions are moved through the anion-selective dialysis membrane (60) and the cation-selective dialysis membrane (70), respectively. For the production of H2SO4 and LiOH to proceed smoothly, these ions must be moved well to the base chamber (75) and the acid chamber (45), respectively. As shown, the graph (blue) of the experimental example (porosity 85%) shows the fastest decrease in conductivity, which means that the ions in the salt chamber (65) moved quickly to the base chamber (75) and the acid chamber (45). However, in Comparative Example 2 (porosity 25-30%) (gray), desalination is slower than in Comparative Example 1 because the movement of electron ions from the electrode solution is not smooth, and it shows the highest conductivity value even after 60 minutes.

[0097] Now, referring to FIG. 5b, a graph of conductivity over time in the birthing chamber (45) is shown. SO4 in the birthing chamber (45) 2- Although ions are present, the most influential factor in improving conductivity is H₂ generated by water dissociation in the bipolar membrane (40). + It is an increase of. However, H + It cannot occur alone and SO4 2- As such, it is dominant to the counterion (or anion). Therefore, an improvement in conductivity means that H2SO4 is being formed. When considered in conjunction with Fig. 5(a), the SO4 from the acid chamber (45) that has come over from the salt chamber (65) 2- Ions are generated as H2SO4 along with the water splitting of the bipolar membrane (40), and conductivity is improved. It can be seen that the graph (blue) of the experimental example with nickel foam having an appropriate porosity inserted shows the fastest improvement in conductivity, and that sulfuric acid is produced much faster than in Comparative Example 1, which did not insert nickel foam. On the other hand, SO4 in the salt solution chamber of Comparative Example 2, which has nickel foam with an inappropriate porosity inserted 2- Ions did not move properly, so sulfuric acid was not formed well, and conductivity was measured to be the lowest.

[0098] Now, referring to FIG. 5c, a graph of conductivity over time in the base chamber (75) is shown. In the base chamber (75) as well, similar to the acid chamber (45), the Li that escaped from the salt chamber (65) + OH generated in the bipolar membrane (50) - Conductivity is determined by OH - It can be seen that the generation of over time is fastest in the experimental example. However, in the case of Comparative Example 2, the formation of the electrode solution's flow path is hindered and electron transfer is not easy, resulting in OH - It can be seen that the formation is lower than Comparative Example 1, which does not include nickel foam.

[0099] From the graph in Fig. 5c, it can be seen that in the experimental example, electron transfer is facilitated by the insertion of nickel foam with an appropriate porosity, so the resistance to ion movement is minimized, and therefore the production of LIOH is also fastest.

[0100] Referring to Fig. 6, graphs showing the concentration of LiOH in the base chamber (Fig. 6a) and the concentration of H2SO4 in the acid chamber (Fig. 6b) over time in a bipolar electrodialysis apparatus according to the experimental conditions described above are shown. The concentrations were obtained by operating the bipolar electrodialysis apparatus to acquire samples and analyzing them via ICP (Inductively Coupled Plasma). In Fig. 6a, it can be seen that the experimental example (blue) produces LiOH the fastest. In Fig. 6b, it can be seen that the experimental example (blue) produces H2SO4 the fastest.

[0101]

[0102] Although the present invention has been described above with reference to the illustrated drawings, the present invention is not limited by the embodiments and drawings disclosed in this specification, and it is obvious that various modifications can be made by a person skilled in the art within the scope of the technical concept of the present invention. Furthermore, even if the effects of the configuration of the present invention were not explicitly described while explaining the embodiments of the present invention above, it is natural to acknowledge that the effects predictable by said configuration should also be recognized.

[0103]

[0104] [Explanation of the symbol]

[0105] 100: Bipolar electrodialysis device 20: Positive electrode

[0106] 25: First space 30: Cathode electrode

[0107] 31-35: Gasket 40: First bipolar membrane

[0108] 41, 51: Anion-selective dialysis membrane

[0109] 42, 52: Cation-selective dialysis membrane

[0110] 45: Birthing chamber 50: Second bipolar membrane

[0111] 55: Second space 60: Anion-selective dialysis membrane

[0112] 65: Saline chamber 70: Cation-selective dialysis membrane

[0113] 75: Base chamber 80: First nickel foam

[0114] 90: Secondary Nickel Form

Claims

1. A bipolar electrodialysis device (100) for producing lithium hydroxide and sulfuric acid from lithium sulfate, Positive electrode (20) and negative electrode (30) facing each other; A first bipolar membrane (40), an anion-selective dialysis membrane (60), a cation-selective dialysis membrane (70), and a second bipolar membrane (50) disposed between the anode electrode (20) and the cathode electrode (30); and It includes a porous first nickel foam (80) disposed in close contact with each other on the plane of the positive electrode (20) and a porous second nickel foam (90) disposed in close contact with each other on the plane of the negative electrode (30), A bipolar electrodialysis device having a porosity of 50% to 90% of the nickel foam (80, 90).

2. In Claim 1, The first bipolar film (40) is positioned opposite to the first nickel foam (80) disposed on the positive electrode (20), and an electrode solution is supplied to the first space (25) formed between the first nickel foam (80) and the first bipolar film (40). The anion-selective dialysis membrane (60) is opposite to the first bipolar membrane (40), and deionized water is supplied to the acid chamber (45) formed between the first bipolar membrane (40) and the anion-selective dialysis membrane (60). The above cation-selective dialysis membrane (70) faces the above anion-selective dialysis membrane (60), and a lithium sulfate solution is supplied to the salt chamber (65) formed between the above anion-selective dialysis membrane (60) and the above cation-selective dialysis membrane (70). The second bipolar membrane (50) faces the cation-selective dialysis membrane (70), and DI water is supplied to the base chamber (75) formed between the cation-selective dialysis membrane (70) and the second bipolar membrane (50). A bipolar electrodialysis device in which the second bipolar membrane (50) faces the second nickel foam (90) disposed on the cathode electrode (30), and an electrode solution is supplied to the second space (55) formed between the second bipolar membrane (50) and the second nickel foam (90).

3. In Claim 1, A bipolar electrodialysis device in which the positive electrode (20) and the negative electrode (30) are formed of nickel.

4. In Claim 1, The first nickel foam (80) and the second nickel foam (90) are a bipolar electrodialysis device that has undergone a support process in hydrochloric acid of 1M to 3M.

5. In Claim 4, The above-mentioned impregnation process is a bipolar electrodialysis device that lasts for 12 to 24 hours.

6. In Claim 5, The nickel foam that has undergone the above-mentioned impregnation process is a bipolar electrodialysis device that has undergone sonication treatment.

7. In Claim 2, A first gasket (32) disposed between the first bipolar membrane (40) and the anion-selective dialysis membrane (60); A second gasket (33) disposed between the anion-selective dialysis membrane (60) and the cation-selective dialysis membrane (70); and It further includes a third gasket (34) disposed between the cation-selective dialysis membrane (70) and the second bipolar membrane (50), wherein A bipolar electrodialysis device in which the thickness of the first nickel foam (80) and the second nickel foam (90) is 30% to 40% thicker than the thickness of any one of the first gasket (32), the second gasket (33), and the third gasket (33).

8. In Claim 7, A bipolar electrodialysis device having a thickness of 330 to 570 μm for the first nickel foam (80) and the second nickel foam (90).

9. In Claim 1, A bipolar electrodialysis device in which the first nickel foam (80) placed on the positive electrode (20) is pressed onto the positive electrode (20), and the second nickel foam (90) placed on the negative electrode (30) is pressed onto the negative electrode (30).

10. In Claim 1, The first nickel foam (80) and the second nickel foam (90) are a bipolar electrodialysis device that has undergone a support process in sulfuric acid or nitric acid.

11. In Claim 2, A bipolar electrodialysis device in which the electrode solution is a lithium hydroxide solution having a concentration of 40 to 60 mS / cm.

12. In Claim 1, The first nickel foam (80) and the second nickel foam (90) are a bipolar electrodialysis device having a three-dimensional shape.

13. In Claim 12, A bipolar electrodialysis device in which the above three-dimensional solid shape is a rectangular parallelepiped having pores formed on at least three faces.

14. In Claim 13, The plane in which the pores are formed of the first nickel foam (80) having the shape of a rectangular parallepiped is in close contact with the plane of the anode electrode (20), A bipolar electrodialysis device in which the pore-forming plane of the second nickel foam (90) having the shape of a rectangular parallepiped is in close contact with the plane of the cathode electrode (30).

15. In Claim 1, A bipolar electrodialysis device in which the voltage between the positive electrode (20) and the negative electrode (30) is 10V.

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