Method for producing lithium hydroxide

Abstract

Provided is a method for producing lithium hydroxide, comprising the steps of: introducing a lithium salt solution into a salt solution compartment, and introducing water into an acidic solution compartment and a basic solution compartment; discharging, from the acidic solution compartment, a sulfuric acid solution including sulfuric acid ions separated from the lithium salt solution by an anion-selective ion exchange membrane and hydrogen ions generated by decomposing water through electrodialysis in a first bipolar membrane; discharging, from the basic solution compartment, a lithium hydroxide solution including lithium ions separated from the lithium salt solution by a cation-selective ion exchange membrane and hydroxide ions generated by decomposing water through electrolysis in a second bipolar membrane; and adding an additive to the lithium hydroxide solution discharged from the basic solution compartment to precipitate impurities and remove same.

Description

Method for manufacturing lithium hydroxide

[0001] The present invention relates to a method for manufacturing lithium hydroxide.

[0002] The global electric vehicle market is projected to grow from 2.3 million units in 2019 to 21.9 million units in 2030. Battery performance is also continuously improving through increased capacity and longer lifespan. Regarding cathode active materials for secondary batteries, the market share of high-energy-density High-Ni batteries is also predicted to rise to 76% by 2030. Consequently, the demand for lithium hydroxide, a raw material for High-Ni cathode active materials, is also expected to increase.

[0003] Lithium, which serves as a raw material for lithium-ion batteries, has conventionally been produced by extracting lithium carbonate from salt lakes, reacting it with lime to obtain a lithium hydroxide solution, and then crystallizing it. However, the lime process generates limestone as a byproduct, and the operation of kilns to recycle the limestone produces large amounts of carbon dioxide, posing an environmental problem. Alternatively, a lithium hydroxide solution can be produced using an electrodialysis method utilizing a bipolar membrane.

[0004] The objective of the present invention is to provide a method for producing lithium hydroxide that can increase the purity of lithium hydroxide obtained by crystallizing an aqueous lithium hydroxide solution and maintain a high production yield without increasing process costs.

[0005] 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.

[0006] In one embodiment of the present invention, a lithium salt aqueous solution is introduced into a bipolar electrodialysis device comprising sequentially an anode, a first bipolar membrane, an anion-selective ion exchange membrane, a cation-selective ion exchange membrane, a second bipolar membrane, and a cathode to obtain a lithium hydroxide aqueous solution; an acidic solution compartment formed between the first bipolar membrane and the anion-selective ion exchange membrane, in which an acidic solution is generated; a basic solution compartment formed between the second bipolar membrane and the cation-selective ion exchange membrane, in which a basic solution is generated; and a salt solution compartment formed between the anion-selective ion exchange membrane and the cation-selective ion exchange membrane; the lithium salt aqueous solution is introduced into the salt solution compartment, and water is introduced into the acidic solution compartment and the basic solution compartment, respectively. A method for producing lithium hydroxide is provided, comprising: a step of discharging a sulfuric acid aqueous solution obtained by including sulfate ions separated from the lithium salt aqueous solution by the anion-selective ion exchange membrane and hydrogen ions generated by the decomposition of water by electrodialysis in the first bipolar membrane from the acidic solution compartment; a step of discharging a lithium hydroxide aqueous solution obtained by including lithium ions separated from the lithium salt aqueous solution by the cation-selective ion exchange membrane and hydroxide ions generated by the decomposition of water by electrodialysis in the second bipolar membrane from the basic solution compartment; and a step of adding an additive to the lithium hydroxide aqueous solution discharged from the basic solution compartment to precipitate and remove impurities.

[0007] The amount of additive can be adjusted according to the ratio of the flow rate of water introduced into the basic solution compartment to the flow rate of water introduced into the acidic solution compartment.

[0008] The relationship between the amount of the additive added and the above flow rate ratio can be determined empirically.

[0009] The relationship between the input amount of the additive and the above flow rate ratio can be determined by linear regression analysis.

[0010] The relationship between the amount of additive added to the flow rate ratio can be calculated for each type of the anion exchange membrane or the cation exchange membrane.

[0011] The above impurities may include at least one selected from the group consisting of sulfate ions, carbonate ions, and combinations thereof.

[0012] The above additive may be selected as a compound capable of precipitating each type of impurity.

[0013] The above additive may include at least one selected from the group consisting of Ba(OH)2, Ca(OH)2, Pb(OH)2, AgOH, Sr(OH)2, and combinations thereof.

[0014] The method may further include the step of obtaining lithium hydroxide by crystallizing the aqueous lithium hydroxide solution from which the above impurities have been removed.

[0015] In the case where the above lithium salt aqueous solution is a lithium sulfate aqueous solution, the lithium hydroxide aqueous solution can be produced together with the sulfuric acid aqueous solution by the following chemical formula 1 in the bipolar electrodialysis device.

[0016] <Chemical Formula 1>

[0017] Li2SO4 + 2H2O → H2SO4 + 2LiOH

[0018] By using constant values ​​a and b obtained by linear regression analysis on the correlation of Equation 1 below, where the above flow rate ratio is the independent variable X and the amount of sulfur (S) inflow from the lithium hydroxide aqueous solution discharged from the above basic solution compartment is the dependent variable Y, the content of sulfur (S), which is an impurity to be removed from the lithium hydroxide aqueous solution discharged from the above basic solution compartment, can be determined from the above flow rate ratio, and the equivalent value of the additive that precipitates the sulfur (S) of the above content can be calculated.

[0019] <Equation 1>

[0020] Y = aX + b

[0021] In the above formula 1, a may be 0.263 to 0.827 and b may be 0.018 to 0.153.

[0022] The above method for manufacturing lithium hydroxide allows the concentration of impurities in the lithium hydroxide obtained by crystallizing an aqueous lithium hydroxide solution to be controlled to a desired range.

[0023] The above method for manufacturing lithium hydroxide can reduce costs associated with the use of additives to remove impurities.

[0024] The above method for manufacturing lithium hydroxide can prevent a decrease in the production volume of lithium hydroxide by controlling the crystallization rate so that it does not drop even when high-concentration acid is generated depending on the operating conditions.

[0025] In addition to the effects described above, the specific effects of the present invention are described together with the specific details for implementing the invention below.

[0026] FIG. 1 schematically shows an exemplary structure of a bipolar electrodialysis device that can be used in the method for producing the lithium hydroxide above.

[0027] FIG. 2 schematically shows an exemplary structure of a bipolar electrodialysis device that can be used in the method for producing the lithium hydroxide above.

[0028] FIG. 3 schematically shows an exemplary structure of a bipolar electrodialysis device that can be used in the method for producing the lithium hydroxide above.

[0029] FIG. 4 is a schematic diagram showing the structure of a bipolar electrodialysis device fabricated as a laboratory-level evaluation device to perform and evaluate a method for producing lithium hydroxide according to one embodiment of the present invention.

[0030] Figure 5 is a table showing the production results obtained according to the operating conditions of the bipolar electrodialysis device of Figure 4.

[0031] Figure 6 is a graph showing the result of linear regression analysis of the relationship between the amount of S impurities entering according to the flow rate ratio in the table of Figure 5.

[0032] The aforementioned objectives, features, and advantages are described in detail below with reference to the attached drawings, thereby enabling those skilled in the art to easily implement the technical concept of the present invention. In describing the present invention, detailed descriptions of known technologies related to the present invention are omitted if it is determined that such descriptions would unnecessarily obscure the essence of the invention. Hereinafter, preferred embodiments according to the present invention will be described in detail with reference to the attached drawings. In the drawings, the same reference numerals are used to indicate the same or similar components.

[0033] 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.

[0034] In addition, where it is stated that one component is "connected," "combined," or "connected" to another component, it should be understood that while the components may be directly connected or connected to each other, another component may be "interposed" between each component, or each component may be "connected," "combined," or "connected" through another component.

[0035] In this specification, lithium, sulfur, magnesium, calcium, sodium, potassium, etc., may be in a form that exists in raw materials, extracts, or precipitates, and are collectively referred to as types of elements without being restricted to a form, such as metal atoms, atoms, ions, salts, etc., and when distinction is necessary, they may be understood as being in a state that exists according to the laws of nature.

[0036] In one embodiment of the present invention,

[0037] A lithium salt aqueous solution is introduced into a bipolar electrodialysis device comprising, in sequence, an anode, a first bipolar membrane, an anion-selective ion exchange membrane, a cation-selective ion exchange membrane, a second bipolar membrane, and a cathode to obtain a lithium hydroxide aqueous solution, and

[0038] An acidic solution compartment formed between the first bipolar membrane and the anion-selective ion exchange membrane, in which an acidic solution is generated; a basic solution compartment formed between the second bipolar membrane and the cation-selective ion exchange membrane, in which a basic solution is generated; and a salt solution compartment formed between the anion-selective ion exchange membrane and the cation-selective ion exchange membrane; are formed,

[0039] A step of introducing the lithium salt aqueous solution into the salt solution compartment and introducing water into the acidic solution compartment and the basic solution compartment, respectively;

[0040] A step of discharging an aqueous sulfuric acid solution obtained by including sulfate ions separated from the above lithium salt aqueous solution by the above anion-selective ion exchange membrane and hydrogen ions generated by the decomposition of water by electrodialysis in the above first bipolar membrane from the acidic solution compartment;

[0041] A step of discharging the lithium hydroxide aqueous solution obtained by including lithium ions separated from the lithium salt aqueous solution by the cation-selective ion exchange membrane and hydroxide ions generated by the decomposition of water by electrodialysis in the second bipolar membrane from the basic solution compartment; and

[0042] A method for producing lithium hydroxide is provided, comprising the step of adding an additive to the aqueous lithium hydroxide solution discharged from the basic solution compartment to precipitate and remove impurities.

[0043] The method for manufacturing the above lithium hydroxide may further include the step of obtaining lithium hydroxide by crystallizing the aqueous lithium hydroxide solution from which the impurities have been removed.

[0044] The method for manufacturing the above lithium hydroxide involves adding an additive to the aqueous lithium hydroxide solution obtained from the bipolar electrodialysis device to remove impurities, and then performing a crystallization step. That is, by performing a step of removing impurities before performing the crystallization step, the method for manufacturing the above lithium hydroxide can increase the crystallization rate by removing impurities that may affect the crystallization rate.

[0045] The above method for manufacturing lithium hydroxide allows the concentration of impurities in the lithium hydroxide obtained by crystallizing an aqueous lithium hydroxide solution to be controlled to a desired range by predetermining and adding an additive to remove impurities.

[0046] The above method for manufacturing lithium hydroxide can reduce costs by predetermining the amount of additive to be added to remove impurities, thereby allowing the use of the necessary amount of additive.

[0047] The above method for manufacturing lithium hydroxide can prevent a decrease in the production volume of lithium hydroxide by controlling the crystallization rate so that it does not drop even when high-concentration acid is generated depending on the operating conditions.

[0048] Figure 1 schematically shows an exemplary structure of the bipolar electrodialysis device.

[0049] Specifically, the bipolar electrodialysis device comprises: an anode (1), a first bipolar membrane (3), an anion-selective ion exchange membrane (4), a cation-selective ion exchange membrane (5), a second bipolar membrane (6) and a cathode (2) in sequence; an acidic solution compartment (11) formed between the first bipolar membrane (3) and the anion-selective ion exchange membrane (4) and in which an acidic solution is generated; a basic solution compartment (12) formed between the second bipolar membrane (6) and the cation-selective ion exchange membrane (5) and in which a basic solution is generated; and a salt solution compartment (13) formed between the anion-selective ion exchange membrane (4) and the cation-selective ion exchange membrane (5).

[0050] The lithium salt aqueous solution (10) can be introduced into the salt solution compartment (13). Water (90) is introduced into the acidic solution compartment (11) and the basic solution compartment (12). An electrode solution (80) is introduced between the anode (1) and the first bipolar membrane (3) and between the cathode (2) and the second bipolar membrane (6). The electrode solution (80) may be water or an aqueous solution.

[0051] In one embodiment, the lithium salt aqueous solution (10) may be an aqueous solution of lithium sulfate (Li2SO4).

[0052] When the above lithium salt aqueous solution (10) is introduced, lithium ions (Li) in the above lithium salt aqueous solution + ) passes through the cation-selective ion exchange membrane (5) and sulfate ions (SO4) 2- Anions such as ) pass through the anion-selective ion exchange membrane (4), and the desalinated lithium salt aqueous solution (10') is discharged from the salt solution compartment (13).

[0053] When voltage is applied to the positive electrode (1) and the negative electrode (2), water is converted into hydrogen ions (H₂) by electrodialysis in the first bipolar membrane (3) and the second bipolar membrane (6). + ) and hydroxide ions (OH -It is decomposed into ) and hydrogen ions (H) into the acidic solution compartment (11) by electric force. + ) moves, and hydroxide ions (OH) move to the basic solution compartment (12). - ) will move.

[0054] Lithium ions (Li) that have passed through the cation-selective ion exchange membrane (5) above + ) and hydroxide ions (OH) formed from water by electrodialysis in the second bipolar membrane (6) - An aqueous lithium hydroxide (LiOH) solution (30) formed including ) is discharged from the basic solution compartment (12). At least a portion of the aqueous lithium hydroxide (LiOH) solution (30) discharged from the basic solution compartment (12) can be reintroduced into the basic solution compartment (12) and circulated. In FIG. 1, the aqueous lithium hydroxide (LiOH) solution (31) represents the aqueous lithium hydroxide (LiOH) solution that is circulated and introduced.

[0055] Anions that have passed through the above anion-selective ion exchange membrane (4), for example, sulfate ions (SO4 2- ) and hydrogen ions (H) formed from water by electrodialysis in the first bipolar membrane (3) + An acidic aqueous solution (20) formed including ) is discharged from the acidic solution compartment (11) as a byproduct. For example, if the lithium salt aqueous solution (10) is a lithium sulfate (Li2SO4) aqueous solution, the acidic aqueous solution (20) may be a sulfuric acid (H2SO4) aqueous solution (20). At least a portion of the sulfuric acid (H2SO4) aqueous solution (20) discharged from the acidic solution compartment (11) may be reintroduced into the acidic solution compartment (11) and circulated. In FIG. 1, the sulfuric acid (H2SO4) aqueous solution (21) represents the sulfuric acid (H2SO4) aqueous solution that is circulated and introduced.

[0056] For example, if the lithium salt aqueous solution (10) is an aqueous solution of lithium sulfate (Li2SO4), an aqueous solution of lithium hydroxide (30) is discharged from the basic solution compartment (12), and an aqueous solution of sulfuric acid (H2SO4) (20) is discharged from the acidic solution compartment (11). At this time, the reaction in the bipolar electrodialysis device can be represented by the following chemical formula 1. That is, in the bipolar electrodialysis device, the aqueous solution of lithium hydroxide (LiOH) is produced together with the aqueous solution of sulfuric acid (H2SO4) by the following chemical formula 1.

[0057] <Chemical Formula 1>

[0058] Li2SO4 + 2H2O → H2SO4 + 2LiOH

[0059]

[0060] In one embodiment, the bipolar electrodialysis device may include a structure in which a plurality of stacks are repeated, with an acidic solution compartment (11), a salt solution compartment (13), and a basic solution compartment (12) formed by a first bipolar membrane (3), an anion-selective ion exchange membrane (4), a cation-selective ion exchange membrane (5), and a second bipolar membrane (6) as one stack unit.

[0061] The above-described bipolar electrodialysis device may include at least 2, for example, 2 to 100, for example, 2 to 50, for example, 2 to 20, for example, 2 to 10 stacks.

[0062] FIG. 2 schematically illustrates an exemplary structure of the bipolar electrodialysis device comprising a plurality (n) of stacks.

[0063] In FIG. 1, the bipolar membranes (3, 6) are named 'first' or 'second' for convenience of explanation, but the bipolar membranes (3, 6) are hydrogen ions (H) generated from water by electrodialysis. + ) and hydroxide ions (OH -Since it performs the same function of moving according to the direction of voltage application, it is not distinguished as the 1st to nth order bipolar film in FIG. 2 but is indicated as a bipolar film (3 / 6).

[0064] In FIG. 2, for example, if the bipolar electrodialysis device includes n stacks, it may include n anion-selective ion exchange membranes (4), n cation-selective ion exchange membranes (5), and n+1 bipolar membranes (3 / 6).

[0065] FIG. 3 schematically illustrates an exemplary structure of the bipolar electrodialysis device that can be used in one embodiment of the present invention.

[0066]

[0067] In one embodiment, when the bipolar electrodialysis device comprises two or more stacks, the membrane facing the outermost anode (1) and the cathode (2) may sequentially be a bipolar membrane (3 / 6), an anion-selective ion exchange membrane (4), or a cation-selective ion exchange membrane (5). For example, depending on the structural design of the bipolar electrodialysis device, the compartment following the compartment through which the electrode solution (80) passes may be any one of an acidic solution compartment (11), a salt solution compartment (13), and a basic solution compartment (12), and accordingly, the type of membrane facing the electrode may be determined.

[0068] In one embodiment, following the anode (1), a cation-selective ion exchange membrane (5) is first arranged, and then (bipolar membrane (3 / 6), anion-selective ion exchange membrane (4), and cation-selective ion exchange membrane (5)) are arranged sequentially, and after these are repeated, finally, a cation-selective ion exchange membrane (5) and a cathode (2) can be arranged sequentially. The structure is arranged sequentially as follows: anode (1) - basic solution compartment (12) - acidic solution compartment (11) - salt solution compartment (13) - basic solution compartment (12) - … - basic solution compartment (12) - cathode (2).

[0069]

[0070] The bipolar electrodialysis device of Fig. 1 corresponds to the case where n=1 in Fig. 2, and the previously described explanation with reference to Fig. 1 may be applicable not only to the cases of Figs. 2 and 3, but also to cases where the type of membrane facing the electrode is not a bipolar membrane but a cation-selective ion exchange membrane or an anion-selective exchange membrane.

[0071]

[0072] In one embodiment, the amount of additive can be adjusted according to the ratio of the flow rate of water introduced into the basic solution compartment to the flow rate of water introduced into the acidic solution compartment.

[0073] The method for manufacturing the above lithium hydroxide can empirically determine the relationship between the amount of the additive added to the flow rate ratio and, accordingly, determine the amount of the additive added.

[0074] The relationship between the amount of the additive added to the flow rate ratio in the above method of manufacturing lithium hydroxide may be affected by the type of the anion exchange membrane or the cation exchange membrane. Therefore, the relationship between the amount of the additive added to the flow rate ratio can be calculated for each type of the anion exchange membrane or the cation exchange membrane.

[0075] In the above method for producing lithium hydroxide, the lithium hydroxide (LiOH) aqueous solution (30) obtained by discharging from the bipolar electrodialysis device contains sulfate ions (SO4) as impurities. 2- ), carbonate ions (CO3 2- It may include at least one type of sulfate ion (SO4) etc. 2- ), carbonate ions (CO3 2-Additives capable of forming precipitates with impurities such as ) to precipitate them may be, for example, Ba(OH)2, Ca(OH)2, Pb(OH)2, AgOH, Sr(OH)2, etc. In this way, the additive can be selected as a compound capable of precipitating each type of impurity. By using a hydroxide as the additive, additional impurities may not be generated.

[0076] In one embodiment, the additive may include at least one selected from the group consisting of Ba(OH)2, Ca(OH)2, Pb(OH)2, AgOH, Sr(OH)2, and combinations thereof. For example, the additive may include sulfate ions (SO4 2- Regarding ), BaSO4, CaSO4, PbSO4, Ag2SO4, and SrSO4 can be formed and precipitated. The above additive is carbonate ions (CO3 2- Regarding ), BaCO3, CaCO3, PbCO3, Ag2CO3, and SrCO3 can be formed and precipitated. The precipitated material can be separated and removed by solid-liquid separation, and if necessary, it can be recovered and used.

[0077] The above method for manufacturing lithium hydroxide can prevent the unnecessary overuse of additives or prevent situations where impurities are not sufficiently removed due to a lack of additives by determining and adding an appropriate amount of additive to be added in advance according to the above flow rate ratio to remove these impurities.

[0078] Accordingly, the method for manufacturing the lithium hydroxide described above can prevent cost waste by preventing the excessive use of additives while increasing the crystallization rate, by predetermining and using an appropriate amount of additive.

[0079] The above bipolar electrodialysis device has a change in the concentration of the acidic aqueous solution (20) discharged from the acidic solution compartment (11) depending on the operating conditions. When the concentration of the acidic aqueous solution (20) circulating in the acidic solution compartment (11) is high depending on the operating conditions, sulfate ions (SO4) in the acidic solution compartment (11) 2- Anions such as ) may pass through the bipolar membranes (3, 6) by diffusion and enter the basic solution compartment (12), or pass through the cation-selective ion exchange membrane (5) in reverse and be included as impurities in the basic solution compartment (12), to a higher degree. In such cases, the impurity sulfate ions (SO4) 2- Since the concentration of ) has increased, the amount of additive added must be increased.

[0080] In Figure 1, the arrows indicated by dashed lines passing through the membrane represent the movement of ions by diffusion, and the arrows indicated by solid lines passing through the membrane represent the movement of ions by electric force.

[0081] The concentration of the acidic solution compartment (11) is closely related to the flow rate of water introduced into the acidic solution compartment.

[0082] Meanwhile, since the bipolar electrodialysis device maintains overall balance, when changing the water flow rate that controls the concentration of the acidic solution compartment (11), the water flow rate introduced into the basic solution compartment (12) may also need to be changed. For example, when lowering the water flow rate introduced into the acidic solution compartment (11), if the concentration of the acidic solution compartment (11) is high, the hydrogen ions (H) flowing into the basic solution compartment (12) + ) increases, and hydrogen ions become hydroxide ions (OH - Since it may not be possible to reach the target concentration of the basic solution by meeting with ) and generating water, the flow rate of water introduced into the basic solution compartment (12) may need to be changed.

[0083] In addition, on the other hand, the concentration of impurities in the basic solution compartment (12) is also affected by the volume of the lithium hydroxide aqueous solution. If the volume of the lithium hydroxide aqueous solution is small, the same amount of sulfate ions (SO4 2- Even if ) is introduced, it may form a higher impurity concentration.

[0084] In order to consider the complex relationship between the concentration of the acidic solution compartment (11) and the concentration of the basic solution compartment (12) as described above, the method of manufacturing the lithium hydroxide above applies the relationship between the flow rate ratio of the water introduced into the basic solution compartment to the flow rate of the water introduced into the acidic solution compartment and the amount of the additive introduced.

[0085] The relationship between the above flow rate ratio and the amount of additive added can be determined by a linear regression analysis method.

[0086] Specifically, constants a and b obtained by linear regression analysis on the correlation of Equation 1 below, where the above flow rate ratio is the independent variable X and the amount of sulfur (S) inflow from the lithium hydroxide aqueous solution discharged from the above basic solution compartment is the dependent variable Y, can be used.

[0087] <Equation 1>

[0088] Y = aX + b

[0089]

[0090] In one embodiment, a may be 0.263 to 0.827 and b may be 0.018 to 0.153.

[0091] When Equation 1, in which constants a and b are specified as the correlation between the above flow rate ratio and the amount of sulfur (S) flowing into the above lithium hydroxide aqueous solution, is determined, the amount of sulfur (S) flowing into the obtained lithium hydroxide aqueous solution at a predetermined flow rate ratio can be calculated through Equation 1. The numerical value in g of the equivalent amount of additive that precipitates the calculated amount of sulfur (S) can be obtained by multiplying the molar ratio of the specific additive and sulfur (S).

[0092] In one embodiment, by using the correlation of Equation 1 specified by linear regression analysis, the content of sulfur (S), which is an impurity to be removed from the lithium hydroxide aqueous solution discharged from the basic solution compartment, can be determined from the flow rate ratio, and the equivalent value of the additive that precipitates the sulfur (S) can be calculated.

[0093] For example, if the additive is Ba(OH)2, Ca(OH)2, Pb(OH)2, AgOH, or Sr(OH)2, sulfate ions (SO4 2- The molar ratio of sulfur (S), an impurity introduced into ), is equal to the molar ratio (x / S) listed in Table 1. x in the molar ratio (x / S) represents each additive.

[0094] The above has explained the impurity sulfur (S), but carbonate ions (CO4 2- For carbon (C), an impurity introduced into the above-mentioned basic solution compartment, the constants a and b obtained by linear regression analysis on the correlation of Equation 1, in which the above flow rate ratio is the independent variable X and the amount of carbon (C) introduced into the lithium hydroxide aqueous solution discharged from the above-mentioned basic solution compartment is the dependent variable Y, can be used in the same manner. It is obvious that the values ​​of a and b obtained at this time will be different from the constants a and b obtained for sulfur (S) mentioned above. Depending on the operating conditions, the values ​​of the constants a and b obtained from the linear regression analysis results may be obtained differently.

[0095] For example, if the additive is Ba(OH)2, Ca(OH)2, Pb(OH)2, AgOH, or Sr(OH)2, carbonate ions (CO4 2- The molar ratio of carbon (C), an impurity introduced into ), is equal to the molar ratio (x / S) listed in Table 1. x in the molar ratio (x / S) represents each additive.

[0096] Additive Molecular Weight g / mol Molar Ratio (x / S) Molar Ratio (x / C) Ba(OH)217 1.3 5.3 4 14.28 Ca(OH)27 4.1 2.3 16.17 Pb(OH)224 1.2 7.5 220.10 AgOH12 4.9 3.9 0 10.41 Sr(OH)212 1.6 3.7 9 10.14

[0097] For example, if the additive is Ba(OH)2 and the impurity to be removed by precipitation is sulfate ions, the flow rate ratio is measured, and then the amount of sulfur (S) inflow is calculated by Equation 1, in which the constant values ​​a and b are determined in advance through linear regression analysis, and then multiplied by 5.34, which is the molar ratio (x / S) of Ba(OH)2, the required numerical value of Ba(OH)2 in g is obtained. That is, when the g amount of Ba(OH)2 obtained is added to the lithium hydroxide aqueous solution, sulfur (S) corresponding to the amount of sulfur (S) inflow calculated by Equation 1 forms a precipitate and precipitates, which can then be removed by solid-liquid separation. For example, if the additive is Ca(OH)2 and the impurity to be removed by precipitation is carbonate ions, the flow rate ratio is measured, and then the amount of carbon (C) inflow is calculated by Equation 1, in which the constant values ​​a and b are determined in advance through linear regression analysis. By multiplying this by 6.17, which is the molar ratio (x / C) of Ca(OH)2, the required numerical value of Ca(OH)2 in g units is obtained. That is, when the g amount of Ca(OH)2 obtained is added to the lithium hydroxide aqueous solution, carbon (C) corresponding to the amount of carbon (C) inflow calculated by Equation 1 forms a precipitate and precipitates, which can then be removed by solid-liquid separation.

[0098] Examples and comparative examples of the present invention are described below. The following examples are merely embodiments of the present invention, and the present invention is not limited to the following examples.

[0099]

[0100] (Example)

[0101] Example 1

[0102] The quality of the obtained solution was analyzed by simulating a laboratory-level evaluation device manufactured with a single-stage stack as shown in Fig. 4 as a bipolar electrodialysis device. For the bipolar electrodialysis device, AD100 / CH100 / BHD15 from W-Scope Korea (WSK) was used as the anion-selective exchange membrane / cation-selective exchange membrane / bipolar membrane.

[0103] The laboratory-scale evaluation device circulated salt, basic, and acidic solutions via fed-batch operation, and the experiment was conducted by adding deionized water to lower the concentration whenever the concentration of the basic or acidic solution reached a certain level.

[0104] As for the salt solution, an aqueous lithium sulfate solution was added to the lithium salt solution, and the amount of Ba(OH)2 added as an additive to remove sulfate ions, which are impurities, from the obtained aqueous lithium hydroxide solution was calculated.

[0105] The input flow rate of deionized water is important to maintain the production concentrations of the basic solution (aqueous lithium hydroxide solution) and the acidic solution (aqueous sulfuric acid solution) at levels close to the starting concentrations. As the acidic solution with a higher concentration is produced, the input flow rate of deionized water must decrease; accordingly, the flow rate of the basic solution also required some adjustment.

[0106] FIG. 5 is a table showing the production results obtained according to the operating conditions of the bipolar electrodialysis device. In FIG. 5, the impurity is sulfate ions (SO4 2- The results of measuring the sulfur (S) content attributable to ) are shown.

[0107] In the table of Fig. 5, an experimental formula for the amount of S impurity inflow according to the flow rate ratio (corresponding to 'amount of S inflow' in the table of Fig. 5) was derived by linear regression analysis, and Fig. 6 is a graph of the results according to the linear regression analysis.

[0108] In Fig. 6, Equation 2, where the independent variable X is the flow rate ratio and the dependent variable Y is the S inflow, was obtained as follows (a=0.7932, b=0.139).

[0109] <Equation 2>

[0110] Y = 0.7932 X + 0.139

[0111] Therefore, by using the above Equation 2, the amount of S inflow for a given flow rate ratio can be predicted, and the amount of additive required to remove the predicted amount of S inflow can be calculated for each type of additive using the molar ratio in Table 1.

[0112] The required number of g units of Ba(OH)2 calculated above was added to the aqueous lithium hydroxide solution obtained from the bipolar electrodialysis device of Fig. 4 to precipitate and remove impurities.

[0113]

[0114] Although the present invention has been described above with reference to embodiments, the present invention is not limited by the embodiments 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 describing the embodiments of the present invention above, it is natural to acknowledge that the effects predictable by said configuration should also be recognized.

[0115]

[0116] [Explanation of the symbol]

[0117] 1: Positive electrode

[0118] 2: Cathode

[0119] 3: First bipolar membrane

[0120] 4: Anion-selective ion exchange membrane

[0121] 5: Cation-selective ion exchange membrane

[0122] 6: Second bipolar membrane

[0123] 3 / 6: Bipolar membrane

[0124] 10: Aqueous solution of lithium salt

[0125] 10': Aqueous solution of lithium salt

[0126] 11: Acidic solution compartment

[0127] 12: Basic solution compartment

[0128] 13: Salt solution compartment

[0129] 20: Aqueous solution of sulfuric acid (H2SO4)

[0130] 21: Aqueous solution of sulfuric acid (H2SO4)

[0131] 30: Aqueous solution of lithium hydroxide (LiOH)

[0132] 31: Aqueous solution of lithium hydroxide (LiOH)

[0133] 80: Electrode solution

[0134] 90: Water

Claims

1. An aqueous lithium salt solution is introduced into a bipolar electrodialysis device comprising, in sequence, an anode, a first bipolar membrane, an anion-selective ion exchange membrane, a cation-selective ion exchange membrane, a second bipolar membrane, and a cathode to obtain an aqueous lithium hydroxide solution, and An acidic solution compartment formed between the first bipolar membrane and the anion-selective ion exchange membrane, in which an acidic solution is generated; a basic solution compartment formed between the second bipolar membrane and the cation-selective ion exchange membrane, in which a basic solution is generated; and a salt solution compartment formed between the anion-selective ion exchange membrane and the cation-selective ion exchange membrane; are formed, A step of introducing the lithium salt aqueous solution into the salt solution compartment and introducing water into the acidic solution compartment and the basic solution compartment, respectively; A step of discharging an aqueous sulfuric acid solution obtained by including sulfate ions separated from the above lithium salt aqueous solution by the above anion-selective ion exchange membrane and hydrogen ions generated by the decomposition of water by electrodialysis in the above first bipolar membrane from the acidic solution compartment; A step of discharging the lithium hydroxide aqueous solution obtained by including lithium ions separated from the lithium salt aqueous solution by the cation-selective ion exchange membrane and hydroxide ions generated by the decomposition of water by electrodialysis in the second bipolar membrane from the basic solution compartment; and A step comprising: adding an additive to the aqueous lithium hydroxide solution discharged from the basic solution compartment to precipitate and remove impurities. Method for manufacturing lithium hydroxide.

2. In Paragraph 1, The amount of additive added is adjusted according to the ratio of the flow rate of water added to the basic solution compartment to the flow rate of water added to the acidic solution compartment. Method for manufacturing lithium hydroxide.

3. In Paragraph 2, Empirically determining the relationship between the input amount of the additive and the above flow rate ratio Method for manufacturing lithium hydroxide.

4. In Paragraph 3, Determining the relationship between the input amount of the additive and the above flow rate ratio by linear regression analysis Method for manufacturing lithium hydroxide.

5. In Paragraph 2, Calculating the relationship between the amount of additive added and the flow rate ratio for each type of the anion exchange membrane or the cation exchange membrane. Method for manufacturing lithium hydroxide.

6. In Paragraph 1, The above impurity comprises at least one selected from the group consisting of sulfate ions, carbonate ions, and combinations thereof. Method for manufacturing lithium hydroxide.

7. In Paragraph 1, The above additive is selected as a compound capable of precipitating each type of impurity. Method for manufacturing lithium hydroxide.

8. In Paragraph 1, The above additive comprises at least one selected from the group consisting of Ba(OH)2, Ca(OH)2, Pb(OH)2, AgOH, Sr(OH)2, and combinations thereof. Method for manufacturing lithium hydroxide.

9. In Paragraph 1, The method further comprises the step of obtaining lithium hydroxide by crystallizing the aqueous lithium hydroxide solution from which the above impurities have been removed. Method for manufacturing lithium hydroxide.

10. In Paragraph 1, The above lithium salt aqueous solution is a lithium sulfate aqueous solution, and In the above-described bipolar electrodialysis device, the aqueous lithium hydroxide solution is produced together with the aqueous sulfuric acid solution according to the following chemical formula 1. Method for manufacturing lithium hydroxide. <Chemical Formula 1> Li2SO4 + 2H2O → H2SO4 + 2LiOH 11. In Paragraph 2, Using the constant values ​​a and b obtained by linear regression analysis on the correlation of Equation 1 below, where the above flow rate ratio is the independent variable X and the amount of sulfur (S) inflow from the lithium hydroxide aqueous solution discharged from the above basic solution compartment is the dependent variable Y, Determining the content of sulfur (S), an impurity to be removed from the lithium hydroxide aqueous solution discharged from the basic solution compartment, from the above flow rate ratio, and calculating the equivalent value of an additive that precipitates the sulfur (S) of the above content. Method for manufacturing lithium hydroxide. <Equation 1> Y = aX + b 12. In Paragraph 11, The above a is 0.263 to 0.827 and the above b is 0.018 to 0.153 Method for manufacturing lithium hydroxide.

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