Simultaneous production method of lithium hydroxide and sulfuric acid

Abstract

The present invention relates to a simultaneous production method of lithium hydroxide and sulfuric acid. Provided is a simultaneous production method of lithium hydroxide and sulfuric acid, the method comprising the steps of: preparing a bipolar membrane electrodialysis device including a first bipolar membrane, an anion exchange membrane, a cation exchange membrane, and a second bipolar membrane, wherein an acid chamber is formed between the first bipolar membrane and the anion exchange membrane, a salt chamber is formed between the anion exchange membrane and the cation exchange membrane, and a base chamber is formed between the cation exchange membrane and the second bipolar membrane; injecting a lithium sulfate aqueous solution into the salt chamber of the bipolar membrane electrodialysis device, injecting a sulfuric acid aqueous solution into the acid chamber, and injecting a lithium hydroxide aqueous solution into the base chamber; and discharging a desalted solution formed in the salt chamber of the bipolar membrane electrodialysis device, discharging the sulfuric acid aqueous solution formed in the acid chamber, and discharging the lithium hydroxide aqueous solution formed in the base chamber.

Description

Simultaneous production method of lithium hydroxide and sulfuric acid

[0001] The present invention relates to a method for simultaneously producing lithium hydroxide and sulfuric acid, and more particularly, to a method for simultaneously producing lithium hydroxide and sulfuric acid that can prevent a decrease in current efficiency of a bipolar membrane electrodialysis process and reduce electricity consumption.

[0002]

[0003] Driven by the recent rapid growth of the electric vehicle market, the lithium secondary battery market for electric vehicles is also experiencing explosive growth. Consequently, innovative technologies are being developed to economically produce lithium compounds, the raw material for lithium secondary batteries.

[0004] Among various methods for producing high-purity lithium hydroxide for electric vehicle batteries, electrochemical membrane separation technology for producing lithium hydroxide from lithium salts is being actively developed.

[0005] Lithium hydroxide (LiOH) and sulfuric acid (H2SO4) can be produced simultaneously from lithium salts using a bipolar membrane electrodialysis method. When a lithium sulfate (Li2SO4) aqueous solution is introduced into a bipolar membrane electrodialysis tank and a direct current is applied, lithium hydroxide (LiOH) and sulfuric acid (H2SO4) can be produced simultaneously. In this case, lithium ions (Li) dissociated from lithium sulfate + ) and sulfate ion (SO4 2- ) pass through the cation exchange membrane and the anion exchange membrane, respectively. Meanwhile, the bipolar membrane uses the applied current to decompose water (water dissociation) and produce protons (H + ) and hydroxide ions (OH - ) is generated, and the generated hydroxide ions move to the positive electrode (+) and meet with lithium ions to form lithium hydroxide, and the generated protons move to the negative electrode (-) and meet with sulfate ions to form sulfuric acid.

[0006] The ratio of the above-mentioned authorized current used to produce the target product can be expressed as current efficiency, and is calculated as follows.

[0007] Current efficiency (%) = 100 x (target ion production [mol]) x Faraday Constant [C / mol]) / (current density [A / m 2 ] x effective area of ​​the membrane [m 2 ] x authorization time [sec])

[0008] There are several factors that affect the current efficiency, and among them, the physical properties of the cation exchange membrane, anion exchange membrane, and bipolar membrane used are important.

[0009] Meanwhile, current efficiency is directly related to production cost, so technological development to increase current efficiency is necessary.

[0010]

[0011] One object of the present invention is to provide a method for efficiently simultaneously producing lithium hydroxide and sulfuric acid while increasing current efficiency. Specifically, the present invention provides a method for simultaneously producing lithium hydroxide and sulfuric acid using bipolar membrane electrodialysis, which can improve current efficiency by controlling the movement of water and lithium cations across an ion exchange membrane.

[0012]

[0013] A method for simultaneously producing lithium hydroxide and sulfuric acid according to one embodiment of the present invention comprises the steps of: preparing a bipolar membrane electrodialysis device including a first bipolar membrane, an anion exchange membrane, a cation exchange membrane, and a second bipolar membrane, wherein an acid chamber is formed between the first bipolar membrane and the anion exchange membrane, a salt chamber is formed between the anion exchange membrane and the cation exchange membrane, and a base chamber is formed between the cation exchange membrane and the second bipolar membrane; introducing a lithium sulfate aqueous solution into the salt chamber of the bipolar membrane electrodialysis device, introducing a sulfuric acid aqueous solution into the acid chamber, and introducing a lithium hydroxide aqueous solution into the base chamber; And it may include a step of discharging a demineralized solution formed in a salt chamber of the bipolar membrane electrodialysis device, discharging a sulfuric acid aqueous solution formed in an acid chamber, and discharging a lithium hydroxide aqueous solution formed in the base chamber.

[0014] Water (H2O) and lithium cations (Li) are exchanged in the cation exchange membrane of the above bipolar membrane electrodialysis device. + ) can have a movement weight ratio of 40 or less.

[0015] The ratio of the flow rate of the lithium hydroxide aqueous solution introduced to the flow rate of the lithium hydroxide aqueous solution discharged from the base chamber of the above bipolar membrane electrodialysis device may be 0.3 to 0.6.

[0016] The ratio of the flow rate of the sulfuric acid aqueous solution introduced to the flow rate of the sulfuric acid aqueous solution discharged from the acid chamber of the above bipolar membrane electrodialysis device may be 0.9 to 1.2.

[0017] The current density passing through the cation exchange membrane and anion exchange membrane of the above bipolar membrane electrodialysis device is 20 mA / cm 2 150 mA / cm 2 It could be.

[0018] The concentration of the lithium hydroxide aqueous solution introduced into the base chamber of the bipolar membrane electrodialysis device may be 0 mol / L to 1 mol / L, and the concentration of the lithium hydroxide aqueous solution discharged from the base chamber of the bipolar membrane electrodialysis device may be 1 mol / L to 5 mol / L.

[0019] The concentration of the sulfuric acid aqueous solution introduced into the acid chamber of the bipolar membrane electrodialysis device may be 0 mol / L to 0.5 mol / L, and the concentration of the sulfuric acid aqueous solution discharged from the acid chamber of the bipolar membrane electrodialysis device may be 0.5 mol / L to 3 mol / L.

[0020] The concentration of the lithium sulfate aqueous solution introduced into the salt chamber of the bipolar membrane electrodialysis device may be 0.5 mol / L to 2.5 mol / L, and the concentration of the lithium sulfate aqueous solution discharged from the salt chamber of the bipolar membrane electrodialysis device may be 0.1 mol / L to 2 mol / L.

[0021] The above bipolar membrane electrodialysis device may be a device that includes a first bipolar membrane, an anion exchange membrane, a cation exchange membrane, and a second bipolar membrane, and may be a device that connects two or more electrodialysis stacks in series, wherein an acid chamber is formed between the first bipolar membrane and the anion exchange membrane, a salt chamber is formed between the anion exchange membrane and the cation exchange membrane, and a base chamber is formed between the cation exchange membrane and the second bipolar membrane.

[0022] According to one embodiment of the present invention, the current efficiency of the bipolar membrane electrodialysis process can be increased by controlling the amount of movement of water and lithium cations in an ion exchange membrane in the bipolar membrane electrodialysis process.

[0023]

[0024] FIG. 1 schematically illustrates a bipolar membrane electrodialysis (BPED) device according to one embodiment of the present invention.

[0025] Figure 2 schematically illustrates a bipolar membrane electrodialysis (BPED) system used in the lithium hydroxide and sulfuric acid production experiment of the present invention.

[0026]

[0027] The terms first, second, and third, etc., are used to describe, but are not limited to, various parts, components, regions, layers, and / or sections. These terms are used only to distinguish one part, component, region, layer, or section from another part, component, region, layer, or section. Accordingly, a first part, component, region, layer, or section described below may be referred to as a second part, component, region, layer, or section without departing from the scope of the present invention.

[0028] The terminology used herein is for the purpose of describing particular embodiments only and is not intended to limit the present invention. As used herein, the singular forms "singular" and "comprising" include plural forms as well, unless the context clearly dictates otherwise. The word "comprising" as used herein specifies a particular feature, region, integer, step, operation, element, and / or component, but does not exclude the presence or addition of other features, regions, integers, steps, operations, elements, and / or components.

[0029] When a part is referred to as being "on" or "over" another part, it can be directly on or over the other part, or there may be other parts intervening. Conversely, when a part is referred to as being "directly on" another part, there are no other parts intervening.

[0030] Although not defined otherwise, all terms, including technical and scientific terms, used herein have the same meaning as commonly understood by those of ordinary skill in the technical field to which the present invention pertains. Terms defined in commonly used dictionaries are further interpreted to have meanings consistent with the relevant technical literature and the present disclosure, and are not to be construed as ideal or overly formal unless otherwise defined.

[0031] Also, unless otherwise stated, % means weight%, and 1 ppm is 0.0001 weight%.

[0032] In this specification, the term "combination(s) thereof" described in the expression in the Makushi format means one or more mixtures or combinations selected from the group consisting of the components described in the expression in the Makushi format, and means including any one or more selected from the group consisting of said components.

[0033] Hereinafter, embodiments of the present invention will be described in detail so that those skilled in the art can easily implement them. However, the present invention may be implemented in various different forms and is not limited to the embodiments described herein.

[0034]

[0035] FIG. 1 schematically illustrates a bipolar membrane electrodialysis (BPED) device according to one embodiment of the present invention.

[0036] Referring to FIG. 1, a bipolar membrane electrodialysis device according to one embodiment of the present invention may include a unit pair that is repeatedly stacked and positioned between an anode cell and a cathode cell. The unit pair may have a triplet configuration in which a bipolar membrane, an anion exchange membrane, and a cation exchange membrane are sequentially positioned. Specifically, the configuration may include a bipolar membrane, a spacer gasket, an anion exchange membrane, a spacer gasket, a cation exchange membrane, and a spacer gasket, which are sequentially positioned. The unit pairs of the configuration may be sequentially positioned adjacent to each other. Among two adjacent unit pairs, the spacer gasket positioned at the rear end of the cation exchange membrane of the unit pair positioned at the front may be positioned adjacent to the bipolar membrane of the unit pair positioned adjacent to the rear end.

[0037] Referring to Fig. 1, an acid chamber may be formed between the first bipolar membrane and the anion exchange membrane, and a salt chamber may be formed between the anion exchange membrane and the cation exchange membrane. Additionally, a base chamber may be formed between the cation exchange membrane and the second bipolar membrane.

[0038] Hereinafter, a manufacturing method for simultaneously manufacturing lithium hydroxide and sulfuric acid according to one embodiment of the present invention will be described.

[0039] First, a lithium salt aqueous solution, specifically a lithium sulfate aqueous solution, is introduced into the salt chamber of the unit pair, a low-concentration sulfuric acid aqueous solution containing a sulfuric acid concentration of 0, which is an acid chamber reaction solution, is introduced into the acid chamber, and a low-concentration lithium hydroxide aqueous solution containing a lithium hydroxide concentration of 0, which is a base chamber reaction solution, is introduced into the base chamber to perform bipolar electrodialysis.

[0040] At this time, when a direct current voltage is applied to the bipolar membrane electrodialysis device to cause current to flow, a sulfuric acid (H2SO4) aqueous solution is formed in the acid chamber between the first bipolar membrane and the anion exchange membrane, a lithium hydroxide (LiOH) aqueous solution is formed in the base chamber between the cation exchange membrane and the second bipolar membrane, and a demineralized solution containing residual lithium salt that did not move from the introduced lithium salt aqueous solution is formed in the salt chamber between the cation exchange membrane and the anion exchange membrane.

[0041]

[0042] Specifically, the formation process of the sulfuric acid (H2SO4) and lithium hydroxide (LiOH) is as follows.

[0043] When electricity is applied to the first bipolar membrane, water entering the membrane from the acid and base chambers is dissociated to form hydrogen ions (H + ) and hydroxide ions (OH - ) is made. At this time, hydroxide ions (OH) are generated by water decomposition. - ) migrates to the base chamber on the positive (+) cell side, and the generated hydrogen ions (H + ) migrates to the acid chamber between the first bipolar membrane and the anion exchange membrane. Meanwhile, the anions of the lithium salt solution injected between the anion exchange membrane and the cation exchange membrane pass through the anion exchange membrane and migrate between the first bipolar membrane and the anion exchange membrane. And, the hydrogen ions (H + ) and the anions are concentrated between the first bipolar membrane and the anion exchange membrane to form a high-concentration sulfuric acid (H2SO4) aqueous solution. In the present invention, the acid chamber reaction solution may specifically be a mixture of a sulfuric acid (H2SO4) aqueous solution and deionized water (DI water).

[0044] Next, the process of forming a lithium hydroxide (LiOH) solution is as follows. The second bipolar membrane decomposes water coming from the base and acid chambers to produce hydrogen ions (H + ) and hydroxide ions (OH - ) is made. At this time, hydrogen ions (H) are generated by water decomposition. + ) moves to the acid chamber on the negative (-) cell side, and the decomposed hydroxide ions (OH - ) moves to the base chamber between the second bipolar membrane and the anion exchange membrane. Meanwhile, lithium ions (Li) of the lithium salt solution injected between the anion exchange membrane and the cation exchange membrane + ) passes through the cation exchange membrane and moves to the base chamber. Then, the hydroxide ions (OH - ) and the lithium ion (Li + ) is concentrated in the base chamber to form a high-concentration lithium hydroxide (LiOH) aqueous solution. In the present invention, the base chamber solution may specifically be a lithium hydroxide (LiOH) aqueous solution or / and deionized water (DI water).

[0045]

[0046] More specifically, the sulfate anion (SO4 2- ) is hydrogen ion (H) that is produced by water dissociation in the bipolar membrane on the anode cell side. + ) and is converted into acid (H2SO4), and lithium ions (Li) move to the cathode through the cation exchange membrane. + ) is a hydroxyl radical (OH) generated in the bipolar membrane - ) reacts with lithium and converts to lithium hydroxide (LiOH).

[0047] In one embodiment of the present invention, the lithium salt may be specifically sulfate (Li2SO4), and the acid may be sulfuric acid (H2SO4). Meanwhile, the acid chamber reaction solution may be low-concentration sulfuric acid (H2SO4) or water (deionized water), and the base chamber reaction solution may be low-concentration lithium hydroxide aqueous solution or water (deionized water).

[0048] At this time, the overall reaction formula may be as follows.

[0049] Li2SO4(aq) ⇔ 2Li + (Move to base chamber) + SO4 2- (Move to acid chamber)

[0050] H2O ⇔ H + (Move to acid chamber) + OH - (Move to base chamber)

[0051] Li2SO4(aq)+ 2H2O ⇔ 2LiOH(aq, base chamber) + H2SO4(aq, acid chamber)

[0052]

[0053] At this time, the high-concentration lithium salt aqueous solution injected into the salt chamber is released by the movement of lithium ions and acid groups, and a low-concentration lithium salt aqueous solution, i.e., a deionized solution, is generated and can be discharged outside the electrodialysis device.

[0054] In addition, the lithium salt solution formed in the salt chamber can be injected into a unit pair located adjacent to the rear end to perform the same electrodialysis as the unit pair of the front end.

[0055] At this time, in order to increase the current efficiency when producing lithium hydroxide aqueous solution and sulfuric acid aqueous solution from lithium salt aqueous solution as described above, the speed of dissociation of water (pure water) in the bipolar membrane and the speed of migration of lithium ions and anions contained in the lithium-containing aqueous solution must be appropriately controlled. If the above speeds are not appropriately controlled, for example, if the speed of dissociation of pure water (or deionized water) is faster than the speed of migration of lithium ions and anions contained in the lithium-containing aqueous solution, the dissociated hydrogen ions and hydroxide ions will not be able to meet their counter ions. Accordingly, ion migration will occur to maintain electrical neutrality. Meanwhile, the direction of ion migration must consider both the direction of electric migration and the direction of diffusion migration due to the concentration difference. For example, the hydroxyl ion (OH) in the base chamber of the cation exchange membrane - ) concentration of hydroxyl groups (OH) in the salt chamber - ) concentration, the diffusion of hydroxyl ions from the base chamber to the acid chamber occurs. Since this diffusion movement direction is opposite to the direction of electrical movement, it reduces the current efficiency. The cation exchange membrane can suppress the back diffusion of hydroxyl anions (also called back dissipation because it is in the opposite direction to the direction of electrical movement) to a certain extent due to the Donnan exclusion power of the fixed anions (co-anions) inside. However, as the concentration of hydroxyl in the base chamber increases, the back diffusion to the acid chamber also increases, which can gradually reduce the current efficiency.

[0056] Therefore, in order to increase the current efficiency of lithium hydroxide production, it is important to appropriately control the properties of the anion exchange membrane, bipolar membrane, and cation exchange membrane, thereby controlling the water decomposition rate and the lithium ion and anion movement rate in the bipolar membrane, and to maintain an appropriate balance between the moved ions and the movement rate of water (H2O) in the exchange membrane.

[0057] Lithium cations (OH) through the cation exchange membrane - ) moves, water moves with it. If the amount of water (H2O) that moves with it is too large, the density of fixed anions in the cation exchange membrane decreases due to swelling of the cation exchange membrane, and hydroxyl anions (OH - ) reduces the donnan exclusion power, which ultimately increases the back migration of anions and reduces the current efficiency.

[0058]

[0059] In one embodiment of the present invention, the cation exchange membrane may be at least one selected from CM2, CMB, CSE of Astom, CD100, CH100 of W-Scocpe, TWEDC1S of Shandong Tienwei, and CT-4, CTG-10 of Hangzhou Lanran.

[0060] Water (H2O) and lithium cations (Li) in the cation exchange membrane of the electrodialysis device + ) weight ratio of the displacement (ω) C ) may be 40 or less, specifically 35 or less, and more specifically 20 to 35.

[0061] The weight ratio (ω) of the movement of water and lithium cations per unit time in the above cation exchange membrane C ) can be expressed by the following equation.

[0062] ω C = H2O movement (g) / Li + Movement (g) (1)

[0063] Water (H2O) and lithium cations (Li) in a cation exchange membrane + ) weight ratio of the displacement (ω) C ) When the value is 40, it is possible to prevent a significant decrease in the efficiency of the current applied to produce lithium hydroxide and reduce the amount of electrical energy consumed.

[0064] In the present invention, the ωC can be adjusted depending on the type of polymer constituting the cation exchange membrane, the type of fixed ion group, the ion exchange capacity, the thickness of the membrane, etc. Even if the polymer constituting the membrane, the type of fixed ion, and the thickness of the membrane are the same, ωC can change if the ion exchange capacity (milli-equivalent / g-dry polymer), which is the ratio of the amount (molar number) of fixed ion groups to the dry weight of the membrane, changes. In addition, the ωC can also change depending on the process conditions of the bipolar membrane electrodialysis device, i.e., temperature, concentration, etc.

[0065] In another embodiment of the present invention, the ratio (Q) of the supply flow rate of the low-concentration lithium hydroxide (LiOH) aqueous solution fed as a raw material to the discharge flow rate of the high-concentration lithium hydroxide (LiOH) aqueous solution produced in the base chamber of the bipolar membrane electrodialysis device LH in / Q LH out ) may be 0.3 to 0.6. The above ratio (Q LH in / Q LH out ) value is less than 0.3, the concentration of the lithium hydroxide solution increases, which may result in a decrease in current efficiency due to increased reverse migration by diffusion of hydroxide ions (OH-) through the cation exchange membrane, and the above ratio (Q LH in / Q LH out) value is greater than 0.6, there is a problem that the amount of water to be removed in the subsequent crystalline lithium hydroxide manufacturing process increases, which lowers the overall productivity. Meanwhile, in the present invention, the concentration of the high-concentration lithium hydroxide (LiOH) aqueous solution generated in the base chamber may range from 1 mol / L to 5 mol / L, and the concentration of the low-concentration lithium hydroxide (LiOH) aqueous solution input as a raw material may range from 0 mol / L to 1 mol / L. If the concentration of the generated lithium hydroxide (LiOH) aqueous solution is within 1 mol / L, the economic feasibility is poor, and if the concentration of the generated lithium hydroxide is 5 mol / L or more, the reverse diffusion through the cation exchange membrane increases excessively, resulting in a decrease in current efficiency. The lithium hydroxide (LiOH) aqueous solution input as a raw material may be pure (lithium hydroxide concentration 0 mol / L), and if the concentration exceeds 1 mol / L, lithium hydroxide is consumed excessively, resulting in a decrease in economic feasibility.

[0066] In another embodiment of the present invention, the ratio (Q) of the supply flow rate of low-concentration sulfuric acid (H2SO4) aqueous solution fed as a raw material to the discharge flow rate of high-concentration sulfuric acid (H2SO4) aqueous solution generated in the acid chamber of a bipolar membrane electrodialysis device HS in / Q HS out ) can be 0.9 to 1.2. The above ratio (Q HS in / Q HS out ) value is less than 0.9, the concentration of sulfuric acid (H2SO4) produced may become too high, which may increase the reverse movement of hydrogen ions (protons) through the anion exchange membrane and lower the current efficiency. In addition, the ratio (Q HS in / Q HS out) value is 1.2 or more, there is a problem that the concentration of the produced sulfuric acid (H2SO4) becomes too diluted, so that the usability of the produced sulfuric acid as a product is reduced. Meanwhile, in the present invention, the concentration of the high-concentration sulfuric acid (H2SO4) aqueous solution produced in the acid chamber may be in the range of 0.5 mol / L to 3 mol / L, and the concentration of the low-concentration sulfuric acid (H2SO4) aqueous solution introduced as a raw material may be in the range of 0 mol / L to 0.5 mol / L. If the concentration of the produced sulfuric acid aqueous solution is 0.5 mol / mol or less, the economic feasibility is reduced, and if the concentration is 3 mol / L or more, the reverse diffusion of hydrogen ions (H+) through the anion exchange membrane becomes excessive, lowering the current efficiency. The sulfuric acid (H2SO4) aqueous solution used as a raw material can be pure (sulfuric acid concentration 0 mol / L), and if it exceeds 0.5 mol / L, excessive sulfuric acid consumption occurs, resulting in poor economic efficiency.

[0067]

[0068] Meanwhile, in the present invention, the concentration of the lithium sulfate aqueous solution introduced into the salt chamber of the bipolar membrane electrodialysis device may be 0.5 mol / L to 2.5 mol / L, and the concentration of the lithium sulfate aqueous solution discharged from the salt chamber of the electrodialysis device may be 0.1 mol / L to 2 mol / L. If the concentration of the introduced lithium sulfate aqueous solution is less than 0.5 mol / L, the resistance of the salt solution increases, making operation difficult. If the concentration exceeds 2.5 mol / L, the solubility limit in water is approached, making operation difficult. In addition, if the concentration of the lithium sulfate aqueous solution (desalination solution) discharged from the salt chamber of the electrodialysis device is less than 0.1 mol / L, the resistance of the salt solution excessively increases, making operation difficult at a high current density. If the concentration exceeds 2 mol / L, the size of the device is excessively required, reducing economic feasibility.

[0069]

[0070] In another embodiment of the present invention, the current density passing through the membrane (cation exchange membrane and anion exchange membrane) is 20 mA / cm 2 150 mA / cm 2 (based on the effective area) and specifically 50 mA / cm 2 100 mA / cm 2 It can be. The current density is 20mA / cm 2 In case of less than 0.01%, the production volume of lithium hydroxide (LiOH) or sulfuric acid (H2SO4) produced per effective membrane area (kg / m) 2 -hr) is too low, and the current density is 150mA / cm 2 If it exceeds , the resistance becomes too large, which causes a problem of deterioration (blistering, delamination, aging, etc.) of the ion exchange membrane, especially the bipolar membrane.

[0071] In the invention, the above membrane current density can be supplied through a rectifier considering the effective membrane area. At this time, the current density must be within a range that does not cause temperature rise or membrane deterioration due to various resistances that may occur in a bipolar membrane electrodialysis device.

[0072] Figure 2 schematically illustrates a bipolar membrane electrodialysis (BPED) system used in the lithium hydroxide and sulfuric acid production experiment of the present invention.

[0073] In one embodiment of the present invention, a bipolar membrane electrodialysis (BPED) system may include an electrodialysis stack including one or more pairs of a cation exchange membrane (C), an anion exchange membrane (A), and a bipolar membrane (BP) arranged sequentially.

[0074] Additionally, two or more of the above stacks may be connected in series. In this case, the membrane current density of the series-connected stacks may gradually decrease.

[0075] In Fig. 2, for convenience, the material discharged from the shear stack is illustrated as being directly fed into the rear stack. However, a portion of the material discharged from the shear stack may be separated externally and only the remaining portion may be supplied to the rear stack. In addition, additional raw materials may be mixed with the material discharged from the shear stack and supplied to the rear stack. This is not particularly limited as long as the purpose of the present invention can be achieved.

[0076]

[0077] (Experiment on the production of lithium hydroxide and sulfuric acid)

[0078] A pair of cation exchange membranes (C), anion exchange membranes (A), and bipolar membranes (BP) arranged sequentially (effective membrane area 0.5 m 2 ) were stacked 40 times and connected in series to form a BPED system.

[0079] Figure 2 schematically illustrates the BPED system used in the lithium hydroxide and sulfuric acid production experiment of the present invention.

[0080] The above cation exchange membrane C may be at least one selected from CM2, CMB, CSE of Astom, CD100, CH100 of W-Scocpe, TWEDC1S of Shandong Tienwei, CT-4, CTG-10 of Hangzhou Lanran, and the cation exchange membranes used in stacks 1 to 3 may be the same or different.

[0081] The above anion exchange membrane A may be at least one selected from among ASE, AID, ACD of Astom, AD100 of W-Scocpe, TWEDA1R of Shandong Tienwei, and ATD of Hangzhou Lanran, and the anion exchange membranes used in stacks 1 to 3 may be the same or different.

[0082] The above bipolar membrane BP may be at least one selected from BP-1, BPU of Astom, FBM of Fumatech, TRJBM of Beijing Tingrun, and BP-2 of Hangzhou Lanran, and the bipolar membranes used in stacks 1 to 3 may be the same or different.

[0083]

[0084] The flow of the solution within the stack is specifically described with reference to Fig. 2.

[0085] Between the anion exchange membrane (A) and the cation exchange membrane (C), a lithium sulfate (Li2SO4) salt solution with a Li concentration of 10 g / L is supplied (lithium sulfate supply amount: Q LS in (kg / hr)), a mixture of water (deionized water (DIW) or lithium hydroxide aqueous solution and water (DIW)) is supplied between the cation exchange membrane (C) and the bipolar membrane (BP) (supply amount: Q LH in (kg / hr)), water (DIW) or a mixture of water and sulfuric acid solution is supplied between the bipolar membrane (BP) and the anion exchange membrane (A) (supply amount: Q HS in (kg / hr)). Based on the salt chamber supplying lithium sulfate salt, positive (+) direct current is applied to the electrode located at the end of the stack on the anion exchange membrane (A) side, and negative (-) direct current is applied to the electrode located at the end of the stack on the cation exchange membrane (C) side.

[0086] Specifically, stack 1 has an ion exchange membrane current density of 77 mA / cm 2 , stack 2 has an ion exchange membrane current density of 73 mA / cm 2 , stack 3 has an ion exchange membrane current density of 60 mA / cm 2 The amount of lithium hydroxide (LiOH) produced and discharged by applying electricity of the size of Q LH out (kg / hr)) and the amount of sulfuric acid (H2SO4) (Q HS out (kg / hr)) was measured.

[0087] Lithium ions (Li) in the produced lithium hydroxide + ) and the content of sulfur in sulfuric acid were measured using the ICP (Ion coupled chromatography) method.

[0088] The lithium content in lithium hydroxide is mostly lithium ions (Li) that have moved through the cation exchange membrane. + ) value (Q Li+ C (kg / hr)), and the S value in sulfuric acid is mostly converted to sulfate ion (SO4) through the anion exchange membrane. 2- ) moved value (Q) SO4(2-) A (kg / hr)). The amount of sulfate transport is calculated from the amount of sulfur transport.

[0089]

[0090] The amount of water (Q) that moved with lithium ions through the cation exchange membrane H2O C (kg / hr)) can be calculated as follows.

[0091] (Q H2O C ) = (Q LH out ) - (Q LH in ) - (Q Li+ C ) (2)

[0092]

[0093] However, the amount of water (H2O) flowing into the bipolar membrane from the base chamber and the amount of hydroxide ions (OH) produced by water decomposition in the bipolar membrane and supplied to the base chamber - ) can be seen as negligible in normal conditions as they cancel each other out.

[0094]

[0095] The weight ratio of water and lithium ions moving through the cation exchange membrane (parameter, ω) C ) is calculated as follows:

[0096] ω C = (Q H2O C ) / (Q Li+ C ) (3)

[0097]

[0098] The amount of water (Q) that moved with sulfate ions through the anion exchange membrane H2O A (kg / hr)) can be calculated as follows.

[0099] (Q H2O A ) = (Q HS out ) - (Q HS in ) - (Q SO4(2-) A ) (4)

[0100]

[0101] However, the amount of water flowing into the bipolar membrane in the acid chamber and the hydrogen ions (H) produced by water decomposition in the bipolar membrane and supplied to the acid chamber + ) can be considered negligible in normal conditions as they cancel each other out.

[0102] The weight ratio of water and sulfate ions moving through the anion exchange membrane (parameter, ω) A ) is calculated as follows:

[0103] ω A = (Q H2O A ) / (Q SO4(2-) A ) (5)

[0104]

[0105] It was operated in rectifier mode with similar voltage sum control, and the current efficiency was calculated from the amount of lithium produced as follows.

[0106] Current efficiency (%) = 100 x {Li production (mol) x Faraday Constant (C / mol)}

[0107] / {Current density (A / m 2 ) x membrane area (m) 2 ) x time (sec)} (6)

[0108]

[0109] (Example 1)

[0110] In Example 1, CH100 from W-Scope was used as a cation exchange membrane, A100 from W-Scope was used as an anion exchange membrane, and BPU from Astom was used as a bipolar membrane to produce lithium hydroxide and sulfuric acid. Meanwhile, the same cation exchange membrane, anion exchange membrane, and bipolar membrane were used in Stacks 1 to 3.

[0111] Meanwhile, the ratio of the supply lithium hydroxide aqueous solution flow rate to the discharged lithium hydroxide aqueous solution flow rate from the stack (Q LH in / Q LH out ) is 0.36, and the ratio of the flow rate of the supplied sulfuric acid solution to the flow rate of the discharged sulfuric acid solution (Q HS in / Q HS out ) is 1.03.

[0112]

[0113] (Example 2)

[0114] In Example 2, lithium hydroxide and sulfuric acid were produced using CD100 from W-Scope as a cation exchange membrane, AD100 from W-Scope as an anion exchange membrane, and FBM from Pumatech as a bipolar membrane. Meanwhile, the same cation exchange membrane, anion exchange membrane, and bipolar membrane were used in Stacks 1 to 3.

[0115] Meanwhile, the ratio of the supply lithium hydroxide aqueous solution flow rate to the discharged lithium hydroxide aqueous solution flow rate from the stack (Q LH in / Q LH out ) is 0.43, and the ratio of the flow rate of the supplied sulfuric acid solution to the flow rate of the discharged sulfuric acid solution (Q HS in / Q HS out ) is 1.05.

[0116]

[0117] (Example 3)

[0118] In Example 3, CH100 from W-Scope was used as a cation exchange membrane, AD100 from W-Scope was used as an anion exchange membrane, and FBM from Pumatech was used as a bipolar membrane to produce lithium hydroxide and sulfuric acid. Meanwhile, the same cation exchange membrane, anion exchange membrane, and bipolar membrane were used in Stacks 1 to 3.

[0119] Meanwhile, the ratio of the supply lithium hydroxide aqueous solution flow rate to the discharged lithium hydroxide aqueous solution flow rate from the stack (Q LH in / Q LH out ) is 0.53, and the ratio of the flow rate of the supplied sulfuric acid solution to the flow rate of the discharged sulfuric acid solution (Q HS in / Q HS out ) is 0.95.

[0120]

[0121] (Comparative Example 1)

[0122] In Comparative Example 1, a membrane (CH100') with a modified ion exchange capacity from W-Scope was used as a cation exchange membrane, AD100 from W-Scope was used as an anion exchange membrane, and FBM from Pumatech was used as a bipolar membrane to produce lithium hydroxide and sulfuric acid. Meanwhile, the same cation exchange membrane, anion exchange membrane, and bipolar membrane were used in Stacks 1 to 3.

[0123] Meanwhile, the ratio of the supply lithium hydroxide aqueous solution flow rate to the discharged lithium hydroxide aqueous solution flow rate from the stack (Q LH in / Q LH out ) is 0.28, and the ratio of the flow rate of the supplied sulfuric acid solution to the flow rate of the discharged sulfuric acid solution (Q HS in / Q HS out ) is 1.27.

[0124]

[0125] Flow rates and parameters (ω) measured in Examples 1 to 3 and Comparative Example 1 C , ω A ) The calculation results are shown in Table 1 below.

[0126] LiOH solutionH2SO4solutionCation exchange membraneAnion exchange membraneVoltageTotal(V)Current efficiency(%)Q LH in(kg / hr)QLH out(kg / hr)QLi+ C(kg / hr)QH2O C(kg / hr)Q HS in(kg / hr)QHS out(kg / hr)S out A(g / L)QH2O A(kg / hr)ωc(by wt)ωA(by wt)Example 1650180737.31119.73113302035.8-397.430.0-3.725356Example 27501728309483250308031.9-446.631.6-4.728350Example 3950178431.4802.63100327030.4-109.925.6-1.228253.5 Comparative example 1550193430.21353.83520277038.3-1045.944.8-9.226741.7

[0127] Referring to Table 1 above, ω C In the case of Comparative Example 1, where the value was 44.8, the cation exchange membrane CH100' current efficiency was 41.7%, which was significantly lower than Examples 1 to 3. The cation exchange membrane has the so-called Donnan Exclusion Effect, which blocks the movement of anions by repelling them by anions (co-ions) fixed inside the membrane. It is known that the higher the density of fixed anions, the higher the Donnan Exclusion Effect. However, ω C When the value is 44.8, the cation exchange membrane is excessively swollen by water, which lowers the density of fixed anions inside the cation exchange membrane, ultimately leading to anions (OH - ) is judged to have a significantly reduced theft exclusion effect.

[0128] Therefore, OH in the produced lithium hydroxide aqueous solution - The anion-swollen cation exchange membrane overcomes the anion exclusion effect by the anion (co-ion) and significantly back migrates toward the lithium sulfate salt solution, and the back-migrated OH -It is thought that the current efficiency decreases because the amount of applied current is consumed in proportion to the amount of negative ions.

[0129] Table 1 above shows the ratio (ω) of the amount of water and sulfate moving through the anion exchange membrane. A ) is indicated as a negative number (-). The amount of water (H2O) flowing into the bipolar membrane from the acid chamber and the hydrogen ions (H2O) decomposed in the bipolar membrane are expressed as + ) are calculated assuming that the production amounts of hydrogen ions can offset each other, but in reality, it appears that the amount of water inflow is greater than the amount of hydrogen ion outflow.

[0130] The present invention is not limited to the above-described embodiments, but can be manufactured in a variety of different forms. Those skilled in the art will appreciate that the present invention can be implemented in other specific forms without altering the technical spirit or essential characteristics of the present invention. Therefore, the embodiments described above should be understood as illustrative in all respects and not restrictive.

Claims

1. A step of preparing a bipolar membrane electrodialysis device, comprising a first bipolar membrane, an anion exchange membrane, a cation exchange membrane, and a second bipolar membrane, wherein an acid chamber is formed between the first bipolar membrane and the anion exchange membrane, a salt chamber is formed between the anion exchange membrane and the cation exchange membrane, and a base chamber is formed between the cation exchange membrane and the second bipolar membrane; A step of injecting a lithium sulfate aqueous solution into the salt chamber of the bipolar membrane electrodialysis device, injecting a sulfuric acid aqueous solution into the acid chamber, and injecting a lithium hydroxide aqueous solution into the base chamber; and A step of discharging a demineralized solution formed in a salt chamber of the bipolar membrane electrodialysis device, discharging a sulfuric acid aqueous solution formed in an acid chamber, and discharging a lithium hydroxide aqueous solution formed in the base chamber; including; Water (H2O) and lithium cations (Li) are exchanged in the cation exchange membrane of the above bipolar membrane electrodialysis device. + ) has a movement weight ratio of 40 or less. A method for simultaneously producing lithium hydroxide and sulfuric acid.

2. In paragraph 1, The ratio of the flow rate of the lithium hydroxide aqueous solution introduced to the flow rate of the lithium hydroxide aqueous solution discharged from the base chamber of the above bipolar membrane electrodialysis device is 0.3 to 0.

6. A method for simultaneously producing lithium hydroxide and sulfuric acid.

3. In paragraph 1, The ratio of the flow rate of the sulfuric acid aqueous solution fed to the flow rate of the sulfuric acid aqueous solution discharged from the acid chamber of the above bipolar membrane electrodialysis device is 0.9 to 1.

2. A method for simultaneously producing lithium hydroxide and sulfuric acid.

4. In paragraph 1, The current density passing through the cation exchange membrane and anion exchange membrane of the above bipolar membrane electrodialysis device is 20 mA / cm 2 150 mA / cm 2 It is, A method for simultaneously producing lithium hydroxide and sulfuric acid.

5. In paragraph 1, The concentration of the lithium hydroxide aqueous solution injected into the base chamber of the above bipolar membrane electrodialysis device is 0 mol / L to 1 mol / L, The concentration of the lithium hydroxide aqueous solution discharged from the base chamber of the above bipolar membrane electrodialysis device is 1 mol / L to 5 mol / L. A method for simultaneously producing lithium hydroxide and sulfuric acid.

6. In paragraph 1, The concentration of the sulfuric acid aqueous solution injected into the acid chamber of the above bipolar membrane electrodialysis device is 0 mol / L to 0.5 mol / L, The concentration of the sulfuric acid aqueous solution discharged from the acid chamber of the above bipolar membrane electrodialysis device is 0.5 mol / L to 3 mol / L. A method for simultaneously producing lithium hydroxide and sulfuric acid.

7. In paragraph 1, The concentration of the lithium sulfate aqueous solution injected into the salt chamber of the above bipolar membrane electrodialysis device is 0.5 mol / L to 2.5 mol / L, The concentration of the lithium sulfate aqueous solution discharged from the salt chamber of the above bipolar membrane electrodialysis device is 0.1 mol / L to 2 mol / L. A method for simultaneously producing lithium hydroxide and sulfuric acid.

8. In paragraph 1, The above bipolar membrane electrodialysis device, An electrodialysis stack comprising two or more electrodialysis stacks connected in series, wherein the electrodialysis stack comprises a first bipolar membrane, an anion exchange membrane, a cation exchange membrane, and a second bipolar membrane, wherein an acid chamber is formed between the first bipolar membrane and the anion exchange membrane, a salt chamber is formed between the anion exchange membrane and the cation exchange membrane, and a base chamber is formed between the cation exchange membrane and the second bipolar membrane. Method for producing lithium hydroxide.

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