Method for preparing lithium hydroxide from lithium-containing source

Abstract

A method for preparing lithium hydroxide, according to one embodiment of the present invention, comprises the steps of: injecting a lithium-containing source material into a roasting device and subjecting same to sulfuric acid-roasting; leaching the roasted lithium-containing source material so as to obtain a solution including lithium sulfate; purifying the leaching solution; and putting the purified solution into a bipolar electrodialysis device so as to obtain a lithium hydroxide aqueous solution, wherein the dilute sulfuric acid solution discharged from the bipolar electrodialysis device is concentrated by a concentrator so that the concentrated sulfuric acid is circulated and supplied to the roasting device, and the concentration ratio (Li / S) of lithium (Li) and sulfur (S) in the dilute sulfuric acid solution injected into the concentrator is 0.07 or less.

Description

Method for producing lithium hydroxide from raw materials containing lithium

[0001] One embodiment of the present invention can provide a method for producing lithium hydroxide from a lithium-containing raw material. Specifically, one embodiment of the present invention can provide a method for producing lithium hydroxide from a lithium-containing raw material by electrodialysis, which stably concentrates and recycles diluted sulfuric acid produced in the electrodialysis process, as a method for stable operation of an electrodialysis process and a sulfuric acid concentration process.

[0002]

[0003] With the recent rapid growth of the IT and electric vehicle markets, demand for lithium, a key raw material for secondary batteries, is expected to increase significantly. The lithium market for secondary batteries is heavily concentrated in Korea, China, and Japan. However, Korea relies entirely on imports, necessitating a stable supply and demand mechanism. Therefore, development of lithium extraction technologies from ore and brine is underway, and a demonstration plant for the production of lithium carbonate and lithium hydroxide from ore is in operation in Korea. Several companies in South America and China are producing large quantities of lithium, and research into the production of lithium compounds, such as lithium hydroxide, is also underway in Korea.

[0004] Conventional techniques for producing lithium hydroxide can be classified into a lithium leaching process and a process for obtaining lithium hydroxide.

[0005] First, the process of leaching lithium from ore involves first calcining the ore to change its phase structure into a crystal structure suitable for lithium extraction, then acid-roasting to change the ore into a form suitable for lithium extraction. Next, leaching yields an acidic solution containing lithium.

[0006] In the above process, the acid used for the oxidation reaction is primarily sulfuric acid (H2SO4). Some processes use hydrochloric acid (HCl), but due to environmental concerns, sulfuric acid is currently used in almost all commercial processes. The resulting lithium-containing acid solution is obtained in the form of an aqueous lithium sulfate (Li2SO4) solution, a known technology used in most processes for extracting lithium from ore.

[0007] The lithium sulfate aqueous solution obtained after the above lithium sulfate extraction process contains various impurities (Mg, Ca, Fe, Ni, Mn, Si, Al, etc.) originating from the ore. To be input into the subsequent process, the lithium sulfate aqueous solution is purified to obtain a purified lithium sulfate aqueous solution, which is then converted into lithium hydroxide through base treatment, etc.

[0008] Secondly, a method utilizing electrolysis or electrodialysis, which is another process for obtaining lithium hydroxide from lithium sulfate, is known. A process is known in which a lithium sulfate solution is directly introduced into an electrolysis or electrodialysis device to produce a lithium hydroxide solution, or a method is known in which phosphoric acid (H3PO4) is introduced to obtain lithium phosphate (Li3PO4), which is then converted back into lithium sulfate and introduced into an electrolysis or electrodialysis device to obtain a lithium hydroxide aqueous solution.

[0009] Meanwhile, a technology combining the above two technologies can extract lithium from ore in the form of a lithium sulfate aqueous solution, convert it into a lithium hydroxide aqueous solution using electrodialysis, and crystallize the lithium hydroxide aqueous solution to produce lithium hydroxide monohydrate (LiOH-H2O). Here, the electrodialysis process is a key process that converts the lithium sulfate aqueous solution into a lithium hydroxide aqueous solution, and dilute sulfuric acid is produced as a by-product.

[0010]

[0011] One object of the present invention is to provide a method for producing lithium hydroxide, which can stably concentrate and recycle dilute sulfuric acid produced in an electrodialysis process, thereby ensuring stable operation of the electrodialysis process and extending the lifespan of an ion exchange membrane.

[0012]

[0013] A method for producing lithium hydroxide according to one embodiment of the present invention comprises the steps of: introducing a lithium-containing raw material into a roasting device and roasting it with sulfuric acid; an leaching step of leaching the roasted lithium-containing raw material to obtain a solution containing lithium sulfate; a step of purifying the leaching solution; and a step of introducing the purified solution into a bipolar electrodialysis device to obtain a lithium hydroxide aqueous solution. A diluted sulfuric acid solution discharged from the bipolar electrodialysis device is introduced into a concentrator, and the concentrated sulfuric acid obtained is circulated and supplied to the roasting device, and the concentration ratio (Li / S) of lithium (Li) and sulfur (S) in the diluted sulfuric acid solution introduced into the concentrator is 0.07 or less.

[0014] The concentration of the above dilute sulfuric acid solution is 6.0 to 15.0 wt%, and the above dilute sulfuric acid solution is concentrated to a concentration of 90 wt% or more.

[0015] In the process of concentrating the dilute sulfuric acid solution discharged from the above bipolar electrodialysis device, no precipitates are generated.

[0016] The step of purifying the above-mentioned leaching solution includes a first purification step of purifying the above-mentioned leaching solution, wherein the pH is 7.1 to 9.5; and a second purification step of purifying the above-mentioned first purified solution, wherein the pH is 9 to 11.

[0017] The above lithium-containing raw material is a lithium-containing ore.

[0018] It further includes a step of calcining the lithium-containing raw material at 950 to 1100°C before acid oxidation.

[0019] The step of dissolving the lithium-containing raw material in sulfuric acid uses concentrated sulfuric acid having a concentration of 95% or higher.

[0020] In the step of acid-calcining the lithium-containing raw material, the sulfuric acid equivalent is added in a weight ratio of 200 to 300% based on the weight of lithium, the calcination temperature is 180 to 300°C, and the calcination time is 40 to 120 minutes.

[0021] The leaching step of leaching the above-described lithium-containing raw material to obtain a solution containing lithium sulfate is a leaching step using water or diluted sulfuric acid.

[0022] The above water is purified water, and the dilute sulfuric acid is recycled from the step of obtaining a lithium hydroxide aqueous solution by bipolar electrodialysis of the purified solution.

[0023] As a first purification step for purifying the above-mentioned leaching solution, the first purification step having a pH of 7.1 to 9.5 is a step for purifying by adjusting the pH using a non-Na alkaline source.

[0024] The above non-Na alkaline source is calcium hydroxide (Ca(OH)2).

[0025] The second purification step of purifying the first purified solution, wherein the pH is 9 to 11, is a step of purifying by adjusting the pH using an alkali metal carbonate source.

[0026] It further includes a step of additional purification using an ion exchange resin to remove trace amounts of impurities remaining in the second purified solution generated in the second purification step.

[0027] The method further includes a step of obtaining a lithium hydroxide aqueous solution by subjecting the second purified solution generated in the second purification step to bipolar electrodialysis; and a step of crystallizing the obtained lithium hydroxide aqueous solution thereafter.

[0028] The above crystallization step includes a step of obtaining lithium hydroxide monohydrate through primary crystallization; a step of redissolving the obtained lithium hydroxide monohydrate; and a step of secondarily crystallizing the redissolved solution to obtain the final lithium hydroxide monohydrate.

[0029]

[0030] A method for producing lithium hydroxide according to one embodiment of the present invention has the advantage of being able to stably and efficiently operate an electrodialysis process and a sulfuric acid concentration process.

[0031] A method for producing lithium hydroxide according to one embodiment of the present invention has the advantage of increasing the lifespan of an ion exchange membrane through stable operation of an electrodialysis process.

[0032]

[0033] Figure 1 is a flow chart of a lithium hydroxide manufacturing process according to one embodiment of the present invention.

[0034] Figure 2 shows the results of an experiment on the change in the Li / H2SO4 concentration ratio in a solution according to the concentration ratio in an embodiment of the present invention.

[0035]

[0036] In this specification, the terms first, second, and third, etc. are used to describe various parts, components, regions, layers, and / or sections, but are not limited thereto. 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.

[0037] 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.

[0038] 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.

[0039] Also, unless otherwise stated, % means weight%, and 1 ppm is 0.0001 weight%.

[0040] 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.

[0041] 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.

[0042] Figure 1 is a flow chart of a lithium hydroxide manufacturing process according to one embodiment of the present invention.

[0043] Referring to Figure 1, each step of the lithium hydroxide manufacturing process of the present invention will be examined in detail.

[0044] One embodiment of the present invention provides a method for producing lithium hydroxide using an ore containing lithium, specifically, spodumene concentrate.

[0045]

[0046] First, a step of introducing lithium-containing raw material into a combustion device and performing sulfuric acid combustion is performed.

[0047] Specifically, the ore raw material containing lithium is calcined to change the crystal state of the ore from the initial α phase to the β phase, which is easy to roast and leach. The calcination temperature may range from 950 to 1100°C. If calcined at a temperature lower than the above temperature, microcalcination occurs, and if calcined at a temperature higher than the above temperature, microcalcination occurs, resulting in undercalcination, which reduces the efficiency of lithium leaching.

[0048] Acid roasting is performed on the ore for which the above calcination is completed. At this time, the acid roasting process uses concentrated sulfuric acid (or anhydrous sulfuric acid) of 95% or more, and the equivalent amount of sulfuric acid added is 200 to 300% by weight based on the weight of lithium contained in the ore. The roasting temperature is 180 to 300°C, and the roasting time can be 40 to 120 minutes.

[0049] The above concentrated sulfuric acid can be recycled as dilute sulfuric acid (6-15% H2SO4) generated in the bipolar electrodialysis described below to reduce process costs and utilize by-products.

[0050] In one embodiment of the present invention, the dilute sulfuric acid solution discharged from the bipolar electrodialysis device is concentrated in a concentrator to form concentrated sulfuric acid, and the concentrated sulfuric acid can be circulated and supplied to the combustion device for use. In one embodiment of the present invention, the dilute sulfuric acid (6-15%) generated in the bipolar electrodialysis step is mixed with purified water and sulfate SO42- ) is included.

[0051] At this time, the concentration ratio (Li / S) of lithium (Li) and sulfur (S) in the dilute sulfuric acid solution injected into the concentrator can be adjusted to 0.0766 or less.

[0052] By controlling the concentration ratio of lithium (Li) and sulfur (S) in the dilute sulfuric acid solution (Li / S) to 0.0766 or less, precipitates do not occur during the concentration process, so the concentration process can be operated smoothly, which is desirable.

[0053] Specifically, when the concentration ratio (Li / S) of lithium (Li) and sulfur (S) in the dilute sulfuric acid discharged from the bipolar electrodialysis device exceeds 0.0766, the concentration ratio can be adjusted to 0.0766 or less by mixing in dilute sulfuric acid.

[0054] The dilute sulfuric acid generated in the above bipolar electrodialysis mainly contains lithium as an impurity, and as the lifespan of the anion membrane or bipolar membrane of the electrodialysis process approaches, the concentration of lithium impurities in the dilute sulfuric acid increases.

[0055] When the ratio of lithium impurity concentration to sulfuric acid concentration of dilute sulfuric acid increases, when it exceeds a certain ratio, precipitates such as lithium sulfate (Li2SO4) are generated in the sulfuric acid concentration equipment during concentration, which makes the dilute sulfuric acid circulation utilization process not smooth, and the operating rate of the electrodialysis process itself decreases, resulting in a problem of lowering the overall lithium hydroxide productivity.

[0056] Meanwhile, in the above concentrator, the dilute sulfuric acid solution is concentrated into concentrated sulfuric acid with a sulfuric acid concentration of up to 95 wt%, and can be mixed with concentrated sulfuric acid used as a raw material in the sulfuric acid roasting step and fed into the roasting device.

[0057] In the present invention, if the dilute sulfuric acid discharged from the bipolar electrodialysis device can be efficiently concentrated into the desired concentrated sulfuric acid, there is no limitation on the concentrator and the concentration method.

[0058]

[0059] Next, a leaching step is performed to leach the lithium-containing raw material to obtain a solution containing lithium sulfate.

[0060] In the step of leaching the above-mentioned ore, the solvent used may be purified water or dilute sulfuric acid that does not contain impurities. The purified water is fresh water treated with RO, etc., and the dilute sulfuric acid may be recycled from dilute sulfuric acid (6-15% H2SO4) generated during bipolar electrodialysis to reduce process costs and utilize byproducts.

[0061] The aqueous solution that has gone through the leaching process as described above is obtained as a solution whose main component is lithium sulfate (Li2SO4). Various impurities (Al, Si, Ca, Mg, Fe, Ni, Na, K, etc.) originating from the ore raw material are present in the solution, and thus it goes through the purification step described below.

[0062]

[0063] Next, a step of purifying the leaching solution is performed.

[0064] The above lithium sulfate solution may be purified through a two-step chemical purification process. The first purification step may use a non-Na-based alkaline source, and the pH of the first purification step may be 7.1 to 9.5. In other words, the first purification step may be performed in a pH range exceeding the pH range of 5 to 7, which is the pH range in which Al and Si impurities are precipitated and purified.

[0065] In addition, in one embodiment of the present invention, the first purification step can use calcium hydroxide (Ca(OH)2) as a non-Na-based alkali source. This process has a stable pH fluctuation compared to a process using NaOH as an alkali source. However, in the case of NaOH, the pH rises rapidly at the beginning of the injection due to the rapid reaction, and then decreases again repeatedly, so it has the disadvantage of being difficult to control the pH during the process (pH fluctuation of 4 to 9). In contrast, when a non-Na-based alkali source, i.e., calcium hydroxide, is used, the pH immediately increases to 8 or higher after the injection, and the pH of the solution is maintained at 7.1 or higher even after 2 hours from the injection. That is, the pH does not fall below 7.1, which is the pH range of the first purification process used in the developed process configuration, and since the reaction time of the process of the present invention is within 1 hour, the pH of the solution does not change rapidly and can be stably maintained at 7.1.

[0066] At this time, since calcium hydroxide has low solubility, it can be supplied in a slurry state for smooth supply. The solid-liquid ratio of the calcium hydroxide slurry is 5:1 in weight ratio of 'water: calcium hydroxide', and a ±20% input variation is allowed for the above 5:1 condition. In other words, the solid-liquid ratio can be 4:1 to 6:1. OH according to the variation in the mixing ratio of the slurry - The molar ratio of OH- can also allow for a variation of ±20% with respect to the target amount of 0.13 mol. That is, the molar ratio of OH- can be between 0.104 and 0.156.

[0067] Typically, the theoretical maximum precipitation pH range for pure Al material is between 5 and 7. However, in the case of the lithium sulfate aqueous solution obtained by the above leaching, various impurity ions exist within the solution, and the common ion effect and interaction with suspended oxide particles due to these impurity ions are at work. Accordingly, the pH range for Al precipitation in the lithium sulfate aqueous solution may be between pH 7.1 and 9.5, which is slightly higher than the theoretical precipitation pH range, and the process disclosed in the present invention is characterized by using the above pH range.

[0068] Furthermore, the above-described leaching and first purification steps are described as two separate processes. However, in an actual process, the leaching and first purification steps can be performed in a single reactor. That is, the leaching and first purification steps can be performed simultaneously by introducing the slurry of the leachate into a single reactor, followed by the leachate and then reacting it with a non-Na alkaline source slurry. The leachate can be purified water or dilute sulfuric acid, as described above.

[0069] Next, a second purification step is performed, and the second purification step may be a step for removing trace impurity elements that were not removed in the first purification step and residual metal (e.g., Ca) components derived from the non-Na-based alkaline source (e.g., calcium hydroxide) that was added. In the second purification step, trace impurities remaining in the form of carbonate may be removed by raising the pH to a range of 9 to 11 using an alkali metal carbonate. Specifically, the alkali metal carbonate may be Na2CO3.

[0070] Next, if trace amounts of Ca and Mg remain in the lithium sulfate aqueous solution that has undergone the second purification step, an additional purification step may be performed using an ion exchange resin. The criterion for performing the additional purification step is when the concentrations of Ca and Mg in the lithium sulfate aqueous solution exceed 10 ppm each after the second purification step. If the concentrations are below this, the additional purification step is not performed.

[0071]

[0072] Next, a step of introducing the purified solution into a bipolar electrodialysis device to obtain a lithium hydroxide aqueous solution is performed.

[0073] In order to convert the purified lithium sulfate aqueous solution obtained through the first and second purification steps (additional purification steps as necessary) into lithium hydroxide (LiOH), a bipolar electrodialysis step is performed. The bipolar electrodialysis step is a step for converting the lithium sulfate aqueous solution introduced into a bipolar electrodialyzer into a lithium hydroxide aqueous solution and a sulfuric acid solution.

[0074] The concentration of lithium hydroxide produced in the above bipolar electrodialysis step is characterized by 2 to 3 mol%, and the concentration of the obtained sulfuric acid can be adjusted to the level of 5 to 15 wt%. In addition, some of the desalted water produced can be recycled in the process of obtaining lithium carbonate through dilution of the primary crystallizer purge solution. In addition, the obtained dilute sulfuric acid can be concentrated and fed to a catalytic converter. Since the method of concentrating the dilute sulfuric acid solution discharged from the bipolar electrodialysis device in a concentrator and recycling it to the catalytic converter has been described in detail above, it is omitted here.

[0075]

[0076] A method for producing lithium hydroxide according to one embodiment of the present invention may further include a crystallization step for solidifying and purifying the lithium hydroxide aqueous solution obtained through the bipolar electrodialysis step. The crystallization step may include a step of obtaining lithium hydroxide monohydrate through a first crystallization, a step of redissolving the same, and a step of obtaining the final lithium hydroxide monohydrate through a second crystallization.

[0077] In the crystallization step, as a means for removing Na and K ions, which are monovalent ion impurities contained in the lithium ore; the amount of purge solution of the crystallizer of the first crystallization step can be set to 17 to 18% based on the inlet lithium concentration. At this time, in order to recover lithium in the purge solution, lithium in the purge solution can be fixed as lithium carbonate. At this time, since the purge solution generated from the crystallizer is a saturated lithium hydroxide solution, de-salted water generated from bipolar electrodialysis is used to dilute it to an appropriate concentration range of <30 g / L based on the lithium concentration, and since the diluted purge solution is in an alkaline state, it can be manufactured into lithium carbonate using carbon dioxide (CO2). The manufactured lithium carbonate is purified through washing, and Na and K ions, which are monovalent ion impurities derived from the ore, can be discharged through the washing water.

[0078]

[0079] Hereinafter, embodiments of the present invention will be described in more detail through examples. However, the following examples are merely preferred embodiments of the present invention, and the present invention is not limited to the following examples.

[0080]

[0081] (Example)

[0082] Lithium hydroxide was produced using spodumene concentrate from lithium-containing ore. The production method was carried out according to the method disclosed above.

[0083] A concentration experiment was conducted according to the sulfuric acid concentration and lithium concentration in the dilute sulfuric acid solution discharged from the above bipolar electrodialysis device.

[0084] The total concentrations of sulfuric acid (H2SO4) and lithium sulfate (Li2SO4) according to the concentration ratio are shown in Table 1 below.

[0085] In the present invention, the concentration rate is expressed in wt% and is calculated from the following equation (1).

[0086]

[0087] Concentration rate [%] = {(H2SO4 [g] + Li2SO4 [g]) / (mass of total solution [g])} X 100 [%] (1)

[0088]

[0089] Sulfuric acid solution S1 S2 S3 S4 S5 S6 S7 Li (g / L) 0.15 2 5 0.5 1.5 3 5 Initial (actual) H2SO4 (wt%) 7.5 5 7.1 8 7.6 1 1 1.0 9 1 1.5 9 1 1.7 6 1 1.8 3 Concentration 50% H2SO4 + Li2SO4 (wt%) 48.4 1 5 4.8 5 1.9 5 4 7.5 9 5 0.9 8 5 0.0 7 4 7.6 3 Concentration 70% H2SO4 + Li2SO4 (wt%) 69.8 4 7 4.4 6 9.1 9 6 9.3 8 7 1.3 7 0.6 5 4 2.0 5 Concentration 80% H2SO4+Li2SO4(wt%)76.2985.7681.4380.4282.2080.3542.69 Concentration 95% H2SO4+Li2SO4(wt%)95.5895.2989.2195.4394.5495.2559.65

[0090] The Li / S concentration ratio in the solution according to the concentration ratio is shown in Table 2 below.

[0091] Sulfuric acid solution S1 S2 S3 S4 S5 S6 S7 Li(g / L) 0.15 25 0.5 1.53 5 Initial Li / S 0.00 40 20.06 20 40.14 0 9 20.01 33 70.03 17 8 0.05 45 50.08 8 48 Concentration 50% Li / S 0.00 57 0 0.06 76 10.12 7 44 0.01 35 50.03 63 60.05 9 6 30.08 750 Concentration 70% Li / S 0.00 52 6 0.06 6 5 30.08 41 6 0.01 28 30.03 63 6 0.06 25 6 0.06 5 19 Concentration 80%Li / S0.006020.070180.099610.012600.036840.065120.09412 Concentration rate 95%Li / S0.005450.064710.109540.011580.035950.063070.09474

[0092] The cells marked in bold in Tables 1 and 2 above are cases where precipitation occurred due to concentration.

[0093] Referring to Tables 1 and 2 above, it was confirmed that the concentration of lithium (Li) and the concentration of sulfuric acid (H2SO4) in the solution before concentration affected the precipitation.

[0094] The Li / H2SO4 concentration ratio in the solution according to the concentration ratio in Table 2 above is shown in Figure 2.

[0095] Referring to Figure 2, precipitation occurred in the area shaded in gray.

[0096] Referring to the results of this graph, if a fitting line is drawn based on the point where the first precipitation occurred in each experiment, the trend equation is as shown in Equation 1 below.

[0097] [Formula 1]

[0098] y = 1E-5x 2 - 0.0021x + 0.1207,

[0099] R² of Equation 1 = 0.5214,

[0100] Y is Li / H2SO4, x is the concentration ratio.

[0101]

[0102] Therefore, it can be expected that precipitation is likely to occur during concentration when the Li / H2SO4 ratio is 0.025 (Li / S 0.07) or higher and the concentration rate is 40% or higher (above the fitting line).

[0103] In the lithium hydroxide production process according to the present invention, when the state of the membrane of the bipolar electrodialysis device ages or its performance deteriorates, and the amount of Li impurities in the produced dilute sulfuric acid increases, when the Li / S concentration ratio reaches 0.07, a certain amount of high-concentration sulfuric acid is added before the concentration process to dilute the Li / S concentration ratio to 0.07 or less, thereby suppressing the formation of precipitates in the concentration process.

[0104] Meanwhile, the high-concentration sulfuric acid for dilution may be commercial sulfuric acid of 50% or more, or already high-concentration sulfuric acid may be used.

[0105] That is, in the concentration process of the present invention, when the Li / S concentration ratio is higher than 0.07 before adding dilute sulfuric acid, a certain amount of high-concentration sulfuric acid is added to adjust the Li / S concentration ratio to 0.07 or less, so that even if sulfuric acid with a concentration of 90% or more or 95% or more is produced in the concentration process, the occurrence of precipitates can be prevented.

[0106]

[0107] Although the preferred embodiments of the present invention have been described above, the present invention is not limited thereto, and various modifications can be made within the scope of the patent claims, the detailed description of the invention, and the attached drawings, and it is obvious that this also falls within the scope of the present invention.

[0108] Accordingly, the actual scope of the present invention is defined by the appended claims and their equivalents.

Claims

1. A step of introducing lithium-containing raw material into a combustion device and combustion with sulfuric acid; A leaching step of leaching the lithium-containing raw material that has been disintegrated to obtain a solution containing lithium sulfate; A step of purifying the above-mentioned leaching solution; and A step of introducing the purified solution into a bipolar electrodialysis device to obtain a lithium hydroxide aqueous solution; The concentrated sulfuric acid obtained by pouring the diluted sulfuric acid solution discharged from the above bipolar electrodialysis device into the concentrator is circulated and supplied to the combustion device. The concentration ratio (Li / S) of lithium (Li) and sulfur (S) in the diluted sulfuric acid solution fed into the above concentrator is 0.07 or less. Method for producing lithium hydroxide.

2. In paragraph 1, The concentration of the above diluted sulfuric acid solution is 6.0 to 15.0 wt%. Method for producing lithium hydroxide.

3. In paragraph 1, Concentrating the above diluted sulfuric acid solution to a concentration of 90 wt% or more, Method for producing lithium hydroxide.

4. In paragraph 1, In the process of concentrating the dilute sulfuric acid solution discharged from the above bipolar electrodialysis device, no precipitates are generated. Method for producing lithium hydroxide.

5. In paragraph 1, The step of purifying the above-mentioned leaching solution is: As a first purification step for purifying the above-mentioned leaching solution, the first purification step having a pH of 7.1 to 9.5; and A second purification step for purifying the first purified solution generated in the first purification step, comprising a second purification step having a pH of 9 to 11; Method for producing lithium hydroxide.

6. In paragraph 1, The above lithium-containing raw material is a lithium-containing ore. Method for producing lithium hydroxide.

7. In paragraph 1, Further comprising a step of calcining the lithium-containing raw material at 950 to 1100°C before acid oxidation. Method for producing lithium hydroxide.

8. In paragraph 1, The step of dissolving the lithium-containing raw material in sulfuric acid uses concentrated sulfuric acid having a concentration of 95% or higher. Method for producing lithium hydroxide.

9. In paragraph 1, In the step of acidifying the lithium-containing raw material; The sulfuric acid equivalent is added in a weight ratio of 200 to 300% based on the weight of lithium, the roasting temperature is 180 to 300°C, and the roasting time is 40 to 120 minutes. Method for producing lithium hydroxide.

10. In paragraph 1, A leaching step for leaching the lithium-containing raw material that has been disintegrated to obtain a solution containing lithium sulfate; The stage of leaching using water or diluted sulfuric acid, Method for producing lithium hydroxide.

11. In paragraph 10, The above water is purified water, The above diluted sulfuric acid is recycled from the step of obtaining a lithium hydroxide aqueous solution by bipolar electrodialysis of the above purified solution. Method for producing lithium hydroxide.

12. In paragraph 5, As a first purification step for purifying the above-mentioned leaching solution, the first purification step having a pH of 7.1 to 9.5; is a step for purifying by adjusting the pH using a non-Na alkaline source. Method for producing lithium hydroxide.

13. In paragraph 11, The above non-Na alkaline source is calcium hydroxide (Ca(OH)2). Method for producing lithium hydroxide 14. In paragraph 5, The second purification step of purifying the first purified solution, wherein the second purification step has a pH of 9 to 11; is a step of purifying by controlling the pH using an alkali metal carbonate source. Method for producing lithium hydroxide.

15. In paragraph 5, In order to remove trace amounts of impurities remaining in the second purified solution generated in the second purification step, a step of additional purification using an ion exchange resin is further included. Method for producing lithium hydroxide.

16. In paragraph 5, A step of obtaining a lithium hydroxide aqueous solution by performing bipolar electrodialysis on the second purified solution generated in the second purification step; thereafter A step of crystallizing the obtained lithium hydroxide aqueous solution; further comprising; Method for producing lithium hydroxide.

17. In paragraph 16, The above crystallization step is a step of obtaining lithium hydroxide monohydrate through primary crystallization; A step of redissolving the obtained lithium hydroxide monohydrate; Comprising a step of secondary crystallizing the above re-dissolved solution to obtain the final lithium hydroxide monohydrate. Method for producing lithium hydroxide.

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