Method for producing lithium hydroxide

Abstract

The present invention provides a method for producing lithium hydroxide that can reduce the burden of removing divalent or higher ions using an ion exchange resin. The method for producing lithium hydroxide includes the following steps (1) to (3). (1) Neutralization step: a step of adding an alkali to a first lithium chloride-containing liquid to obtain a neutralized liquid; (2) Ion exchange step: a step of contacting the neutralized liquid with an ion exchange resin to obtain a second lithium chloride-containing liquid; (3) Conversion step: a step of electrodialyzing the second lithium chloride-containing liquid to obtain a lithium hydroxide-containing liquid. According to this production method, divalent or higher ions can be roughly removed in the neutralization step, thereby reducing the burden of removing metals using an ion exchange resin.

Description

Technical Field

[0001] The present invention relates to a method for producing lithium hydroxide, and more particularly to a method for producing lithium hydroxide, which comprises obtaining a liquid containing lithium hydroxide from a liquid containing lithium chloride. Background Art

[0002] Lithium ion secondary batteries are often used as vehicle batteries due to their high energy density and high charge and discharge capacity. In addition, as positive electrode materials for lithium ion secondary batteries, the demand for nickel-based positive electrode materials, i.e., NCA, is increasing. When the NCA is used in lithium ion secondary batteries, it is preferred to supply lithium in the form of lithium hydroxide from an economical point of view.

[0003] Patent Document 1 discloses a method for producing high-purity lithium hydroxide from lithium chloride by bipolar membrane electrodialysis. In addition, the document discloses that lithium chloride is obtained by reacting lithium carbonate with hydrochloric acid, or by extracting lithium from a lithium-containing ore with hydrochloric acid, or by selectively adsorbing and separating from brine.

[0004] In the process of obtaining lithium hydroxide from lithium chloride by electrodialysis, the diaphragm used in the electrodialysis is, for example, a combination of a bipolar membrane, an anionic membrane, and a cationic membrane. For these diaphragms, when there are many ions with a valence of 2 or more, there is a risk of burdening the diaphragm and damaging the membrane. Therefore, the liquid before the electrodialysis needs to utilize an ion exchange resin to remove the above-mentioned ions with a valence of 2 or more.

[0005] Prior art literature

[0006] Patent Literature

[0007] Patent Document 1: Japanese Patent Application Publication No. 2009-269810. Summary of the invention

[0008] Problems to be solved by the invention

[0009] However, when there are a lot of ions with a valence of 2 or more, the removal by ion exchange resin will cause a load. Therefore, if you want to remove ions with a valence of 2 or more more reliably, you need to frequently replace the ion exchange resin. However, since ion exchange resin is expensive, the cost increases, and the load of the operation of replacing or regenerating the ion exchange resin increases.

[0010] The present invention has been made in view of the above circumstances, and an object of the present invention is to provide a method for producing lithium hydroxide which can reduce the burden of removing ions having a valence of two or more by using an ion exchange resin.

[0011] Technical solutions to problems

[0012] The first invention of the method for producing lithium hydroxide is characterized in that it includes the following steps (1) to (3): (1) a neutralization step: a step of adding an alkali to a first lithium chloride-containing liquid to obtain a neutralized liquid; (2) an ion exchange step: a step of contacting the neutralized liquid with an ion exchange resin to obtain a second lithium chloride-containing liquid; (3) a conversion step: a step of electrodialyzing the second lithium chloride-containing liquid to obtain a lithium hydroxide-containing liquid, wherein the first lithium chloride-containing liquid is obtained through an adsorption step and an elution step, wherein the adsorption step contacts a low-lithium content liquid with a lithium adsorbent obtained from lithium manganate to obtain adsorbed lithium manganate, and the elution step contacts the adsorbed lithium manganate with a hydrochloric acid solution to obtain the first lithium chloride-containing liquid.

[0013] The second invention of the method for producing lithium hydroxide is characterized in that it includes the following steps (1) to (4): (1) oxidation step: a step of adding an oxidant to a first lithium chloride-containing liquid to obtain an oxidized liquid; (2) neutralization step: a step of adding an alkali to the oxidized liquid to obtain a neutralized liquid; (3) ion exchange step: a step of contacting the neutralized liquid with an ion exchange resin to obtain a second lithium chloride-containing liquid; (4) conversion step: a step of electrodialyzing the second lithium chloride-containing liquid to obtain a lithium hydroxide-containing liquid, wherein the first lithium chloride-containing liquid is obtained through an adsorption step and an elution step, wherein the adsorption step contacts the low-lithium content liquid with a lithium adsorbent obtained from lithium manganate to obtain adsorbed lithium manganate, and the elution step contacts the adsorbed lithium manganate with a hydrochloric acid solution to obtain the first lithium chloride-containing liquid.

[0014] The method for producing lithium hydroxide according to the fourth invention is characterized in that, in the first invention or the second invention, the ion exchange resin used in the ion exchange step is an iminodiacetic acid type chelate resin or an iminodiacetate type chelate resin.

[0015] The method for producing lithium hydroxide of the fifth invention is characterized in that, in the fourth invention, the functional groups of the iminodiacetic acid type chelate resin and the iminodiacetate type chelate resin are sodium type.

[0016] The method for producing lithium hydroxide of the sixth invention is characterized in that, in any one of the first invention, the second invention, the fourth invention, and the fifth invention, the ion exchange step is carried out using a column, and the flow rate of the neutralized liquid passing through the column is greater than SV1 and less than SV7.

[0017] The method for producing lithium hydroxide according to the seventh invention is characterized in that, in the sixth invention, the flow rate of the neutralized liquid passing through the column is BV10 or more and BV35 or less.

[0018] The method for producing lithium hydroxide according to the eighth invention is characterized in that, in the first invention, the second invention, and the fourth to seventh inventions, the low-lithium content liquid is salt lake brine.

[0019] Effects of the Invention

[0020] According to the first invention, since a neutralization step of adding a base is provided before the ion exchange step using the ion exchange resin, ions having a valence of two or more can be roughly removed in the neutralization step, the load of metal removal using the ion exchange resin can be reduced.

[0021] In addition, the first lithium chloride-containing liquid is obtained through an adsorption step of adsorbing lithium using a lithium adsorbent obtained from lithium manganate and an elution step of eluting lithium from the adsorbed lithium manganate. Even if a part of manganese is dissolved in the elution step, the manganese is removed by the subsequent neutralization step or the combination of the oxidation step and the neutralization step. Therefore, high-purity lithium hydroxide can be obtained while using lithium manganate with excellent adsorption capacity.

[0022] According to the second invention, by providing an oxidation step of adding an oxidant and a neutralization step of adding an alkali before the ion exchange step using the ion exchange resin, manganese can be removed when the first lithium chloride-containing liquid contains manganese, and other ions with a valence of two or more can be roughly removed in the neutralization step, thereby further reducing the load of metal removal using the ion exchange resin.

[0023] In addition, the first lithium chloride-containing liquid is obtained through an adsorption step of adsorbing lithium using a lithium adsorbent obtained from lithium manganate and an elution step of eluting lithium from the adsorbed lithium manganate. Even if a part of manganese is dissolved in the elution step, the manganese is removed by the subsequent neutralization step or the combination of the oxidation step and the neutralization step. Therefore, high-purity lithium hydroxide can be obtained while using lithium manganate with excellent adsorption capacity.

[0024] According to the fourth invention, the ion exchange resin used in the ion exchange step is an iminodiacetic acid type chelate resin or an iminodiacetate type chelate resin, thereby improving the availability of the ion exchange resin.

[0025] According to the fifth invention, by making the functional group of the iminodiacetic acid type chelating resin or the like a sodium type, the pH of the liquid passing through will change when it is a hydrogen type, but when it is a sodium type, the pH does not change and the properties of the liquid during the reaction are stable.

[0026] According to the sixth invention, the ion exchange step is performed using a column, and by setting the flow rate in the column to be SV1 or more and SV7 or less, magnesium and calcium, which are divalent metals, can be removed more reliably.

[0027] According to the seventh invention, by setting the flow rate of the neutralized liquid passing through the column to be BV10 or more and BV35 or less, magnesium and calcium can be removed more reliably. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] Figure 1 This is a flow chart of the method for producing lithium hydroxide according to the first embodiment of the present invention.

[0029] Figure 2 This is a flow chart of a method for producing lithium hydroxide according to a second embodiment of the present invention.

[0030] Figure 3 This is a flow chart of a method for producing lithium hydroxide according to a third embodiment of the present invention.

[0031] Figure 4 This is a flow chart of a method for producing lithium hydroxide according to a fourth embodiment of the present invention. DETAILED DESCRIPTION

[0032] Hereinafter, embodiments of the present invention will be described based on the accompanying drawings. However, the embodiments shown below list the methods for producing lithium hydroxide for embodying the technical concept of the present invention, and the present invention does not limit the methods for producing lithium hydroxide to the following. It should be noted that the contents described in some embodiments and embodiments may also be used in other embodiments, embodiments, etc.

[0033] The method for producing lithium hydroxide of the present invention comprises the following steps (1) to (3): (1) a neutralization step: a step of adding an alkali to a first lithium chloride-containing liquid to obtain a neutralized liquid; (2) an ion exchange step: a step of contacting the neutralized liquid with an ion exchange resin to obtain a second lithium chloride-containing liquid; (3) a conversion step: a step of subjecting the second lithium chloride-containing liquid to electrodialysis to obtain a lithium hydroxide-containing liquid. With this configuration, ions with a valence of two or more can be roughly removed in the neutralization step, and thus the load of removing metals by the ion exchange resin can be reduced.

[0034] In addition, the method for producing lithium hydroxide of the present invention includes the following steps (1) to (4): (1) oxidation step: adding an oxidant to a first lithium chloride-containing liquid to obtain an oxidized liquid; (2) neutralization step: adding an alkali to the oxidized liquid to obtain a neutralized liquid; (3) ion exchange step: contacting the neutralized liquid with an ion exchange resin to obtain a second lithium chloride-containing liquid; (4) conversion step: subjecting the second lithium chloride-containing liquid to electrodialysis to obtain a lithium hydroxide-containing liquid. With this configuration, manganese can be removed when manganese is contained in the first lithium chloride-containing liquid, and other ions with a valence of two or more can be roughly removed in the neutralization step, thereby further reducing the load of metal removal by the ion exchange resin.

[0035] In addition, it is preferred that the first liquid containing lithium chloride is obtained through an adsorption step of bringing the low-lithium content liquid into contact with a lithium adsorbent obtained from lithium manganate to obtain adsorbed lithium manganate, and an elution step of bringing the adsorbed lithium manganate into contact with a hydrochloric acid solution to obtain a first liquid containing lithium chloride. With this configuration, even if a portion of manganese is dissolved in the elution step, the manganese is removed by the subsequent neutralization step or the combination of the oxidation step and the neutralization step, so that high-purity lithium hydroxide can be obtained while using lithium manganate having excellent adsorption capacity.

[0036] In addition, the ion exchange resin used in the ion exchange process is preferably an iminodiacetic acid type chelate resin or an iminodiacetate type chelate resin. Through this structure, the availability of the ion exchange resin is improved.

[0037] In addition, the functional group of described iminodiacetic acid type resin and described iminodiacetic acid salt type resin is preferably sodium type.Through this formation, when the functional group of resin is hydrogen type, the pH of the liquid through can change, and when being sodium type, the properties of liquid are stable when pH does not change and reaction.

[0038] In addition, the ion exchange step is performed using a column, and the flow rate of the neutralized liquid passing through the column is preferably greater than SV1 and less than SV7. With this configuration, magnesium and calcium, which are divalent metals, can be removed more reliably.

[0039] In addition, the flow rate of the neutralized liquid passing through the column is preferably BV10 or more and BV35 or less. With this configuration, magnesium and calcium can be removed more reliably.

[0040] (First Embodiment)

[0041] Figure 1 A flow chart showing a method for producing lithium hydroxide according to a first embodiment of the present invention is shown. The method for producing lithium hydroxide according to this embodiment includes three steps: a neutralization step, an ion exchange step, and a conversion step.

[0042] <Neutralization process>

[0043] Figure 1The neutralization process shown is a process of adding an alkali to the first lithium chloride-containing liquid to obtain a neutralized liquid. Through this process, a neutralized precipitate containing impurities other than lithium chloride is obtained. Here, the first lithium chloride-containing liquid refers to a liquid containing lithium chloride when the liquid is crystallized. For example, a liquid obtained by reacting lithium carbonate with hydrochloric acid, a liquid obtained by extracting from a lithium-containing ore with hydrochloric acid, or a liquid obtained by selectively adsorbing and separating lithium from brine can be cited. It should be noted that, as described later in other embodiments, the first lithium chloride-containing liquid is preferably a liquid obtained by selectively adsorbing and separating lithium from brine.

[0044] In the neutralization process, alkali is added to remove metals other than lithium. Ion exchange resins are mainly used to remove metal ions with a valence of more than 2. However, if the liquid before contacting the ion exchange resin contains a lot of metal ions with a valence of more than 2, there will be a need to frequently replace the ion exchange resin. However, since ion exchange resins are expensive, the cost of manufacturing lithium hydroxide increases, and the load of replacing the ion exchange resin increases. In addition, the load of the operation of regenerating the ion exchange resin also increases. Therefore, in the neutralization process, alkali is added to remove part of the metals other than lithium. As metals other than lithium, divalent magnesium, manganese, etc. can be cited. Specifically, in the neutralization process, sodium hydroxide is added to the first lithium chloride-containing liquid to precipitate magnesium and manganese in the form of magnesium hydroxide and manganese hydroxide, and the precipitate is recovered to remove metals other than lithium. When precipitating to remove magnesium, etc., it is sufficient to be alkaline, but when the pH is too high, the cost of the neutralizer increases, which is not preferred. Therefore, the pH of the neutralized liquid after the neutralization process is preferably above 8.5 and below 12.

[0045] <Ion exchange process>

[0046] Figure 1 The ion exchange step shown is a step of contacting the neutralized liquid with an ion exchange resin to obtain a second lithium chloride-containing liquid. In the ion exchange step, calcium that was not removed in the neutralization step, aluminum that remains depending on the pH of the neutralization step, and very small amounts of manganese and magnesium that were not completely removed in the neutralization step are removed.

[0047] Ion exchange resin is a kind of synthetic resin, and a part of its molecular structure has a structure that is ionized as an ion exchange group. In the ion exchange process, it is preferred to remove the ion exchange resin of the metal ion of more than 2 valences that cannot be trapped in the neutralization process, i.e., iminodiacetic acid type chelate resin or iminodiacetate type chelate resin. The pH of the liquid after the neutralization in the ion exchange process is determined to a preferred value by the ion exchange resin. However, it is preferred that the liquid after the neutralization obtained in the neutralization process is directly subjected to the ion exchange process.

[0048] Furthermore, in the iminodiacetic acid type chelate resin and the iminodiacetate type chelate resin, the functional group is preferably a sodium type.

[0049] By using an iminodiacetic acid type chelate resin or an iminodiacetate type chelate resin as the ion exchange resin used in the ion exchange step, the availability of the ion exchange resin can be improved.

[0050] In addition, by making the functional group of the iminodiacetic acid type chelate resin or the like a sodium type, the pH of the liquid passing therethrough changes when it is a hydrogen type, but when it is a sodium type, the pH does not change and the properties of the liquid during the reaction are stable.

[0051] The contact method between the ion exchange resin and the neutralized solution is preferably a column method, but a batch mixing method may be adopted.

[0052] In the case of using a column method, the liquid flow rate of the neutralized liquid through the column is preferably above SV1 and below SV7. SV is the abbreviation of space velocity (Space Velocity), which represents the liquid flow rate per unit time (1 hour) (unit is BV described below). When the liquid flow rate is less than SV1, the manufacturing efficiency of lithium hydroxide deteriorates. In addition, when the liquid flow rate is greater than SV7, the flow of the liquid becomes too fast, and there is a situation where the metal cannot be captured. By setting it to this liquid flow rate, magnesium and calcium as divalent metals can be more reliably removed.

[0053] In addition, the flow rate of the neutralized liquid through the column is preferably above BV10 and below BV35. BV is the abbreviation of bed volume (BedVolume), which is a unit indicating that it is several times the volume of the ion exchange resin in the column. When the flow rate is less than BV10, the manufacturing efficiency of lithium hydroxide deteriorates. In addition, when the flow rate is greater than BV35, it may exceed the metal capture capacity of the ion exchange resin and cause penetration, resulting in the inability to capture metals. By setting it to this flow rate, magnesium and calcium can be further reliably removed.

[0054] The ion exchange resin used in the ion exchange step can be regenerated, and the captured metals can be eluted by immersing the used ion exchange resin in a liquid having an acid hydrogen concentration of 0.3 mol / L or more and 2.0 mol / L or less.

[0055] <Conversion process>

[0056] like Figure 1As shown, in the conversion process, the lithium chloride contained in the second lithium chloride-containing liquid is converted into lithium hydroxide to obtain a lithium hydroxide-containing liquid in which lithium hydroxide is dissolved. Lithium chloride is dissolved in the second lithium chloride-containing liquid. In this process, these liquids are converted into a lithium hydroxide-containing liquid containing lithium hydroxide and hydrochloric acid, for example, by electrodialysis using a bipolar membrane. That is, by performing electrodialysis, the lithium chloride in the second lithium chloride-containing liquid is decomposed, and the lithium ions of the lithium chloride are combined with hydroxide ions through a cation membrane to form lithium hydroxide, and for example, chloride ions are converted into hydrochloric acid through an anion membrane. The recovered hydrochloric acid can be recycled in the elution process. As a result, the amount of hydrochloric acid used can be reduced.

[0057] In addition, in the conversion step, in addition to the electrodialysis using a bipolar membrane, for example, there can be mentioned the electrodialysis using an ion exchange membrane. When a cation exchange membrane is used as the ion exchange membrane, lithium hydroxide is generated in the cathode chamber.

[0058] In this embodiment, a neutralization step of adding a base is provided before the ion exchange step using the ion exchange resin. Thus, since ions with a valency of two or more can be roughly removed in the neutralization step, the load of metal removal using the ion exchange resin can be reduced.

[0059] <Process after conversion process>

[0060] When the liquid containing lithium hydroxide obtained in the conversion step is evaporated, dried and solidified, lithium hydroxide is obtained. However, there are alkali metals such as sodium or potassium in the liquid containing lithium hydroxide. If it is directly evaporated, dried and solidified, the solid obtained thereby contains a large amount of hydroxides other than lithium hydroxide. Therefore, it is preferred to set a crystallization step to solidify the lithium hydroxide dissolved in the liquid containing lithium hydroxide after the conversion step.

[0061] In the crystallization process, solid lithium hydroxide is obtained by solidifying the lithium hydroxide dissolved in the liquid containing lithium hydroxide. A crystallization mother liquor is obtained together with the solid lithium hydroxide. In the conversion process, lithium becomes lithium hydroxide, and alkali metals such as sodium and potassium also become hydroxides. Therefore, these are also included in the liquid containing lithium hydroxide obtained in the conversion process. In addition, chloride ions as anions also pass through the membrane and are included in the liquid containing lithium hydroxide. In the crystallization process, the difference in solubility of each hydroxide is utilized to solidify the lithium hydroxide and separate the impurities contained.

[0062] In the crystallization step, the liquid containing lithium hydroxide is heated and concentrated. At this time, the concentration of metal ions contained in the liquid rises, and first, the lithium hydroxide with lower solubility precipitates and solidifies. The precipitated lithium hydroxide is recovered in the form of solid lithium hydroxide. At this time, sodium hydroxide and potassium hydroxide with higher solubility do not precipitate and remain in the liquid. Thus, the purity of the recovered lithium hydroxide is improved.

[0063] For example, it is known that the solubility of lithium hydroxide is 13.2 g / 100 g-water at 60°C, which is very low compared to 174 g / 100 g-water of sodium hydroxide and 154 g / 100 g-water of potassium hydroxide. Since the chloride ion is 2 g / L even when the heating concentration operation is performed, it will not precipitate in lithium hydroxide as an alkali metal chloride.

[0064] In industry, the crystallization process can be performed by continuous crystallization using a crystallization tank. In addition, it can be performed by batch crystallization. The crystallization mother liquor produced in the crystallization process is a concentrated alkaline aqueous solution. It should be noted that, since the crystallization mother liquor contains a certain amount of lithium hydroxide, the recovery rate of lithium is increased by repeating the process before the neutralization process. In addition, the cost of the neutralizing agent is reduced.

[0065] (Second Embodiment)

[0066] Figure 2 A flow chart showing a method for producing lithium hydroxide according to a second embodiment of the present invention is shown. The difference between this embodiment and the first embodiment is that an oxidation step is provided in the previous stage of the neutralization step. Other aspects are the same as the first embodiment. The oxidation step as a difference is described below.

[0067] <Oxidation process>

[0068] The oxidation process is a process of oxidizing the manganese in the first lithium chloride-containing liquid into insoluble manganese dioxide by adding an oxidant such as air, oxygen, sodium hypochlorite, etc. to the first lithium chloride-containing liquid, so as to precipitate and remove the manganese dissolved in the liquid. Although manganese can also be removed in the neutralization process, by setting up the oxidation process, manganese is removed before the neutralization process, so the load of removing manganese in the neutralization process can be reduced. In addition, the manganese precipitated and removed in the oxidation process can be reused. The type of oxidant used in the oxidation process can be air, oxygen, sodium hypochlorite, etc. The redox potential of the first lithium chloride-containing liquid is set to the pH and potential located in the manganese dioxide region in the potential pH diagram.

[0069] (Third Embodiment)

[0070] Figure 3 A flow chart showing a method for producing lithium hydroxide according to a third embodiment of the present invention is shown. The difference between this embodiment and the first embodiment is that an adsorption step and an elution step are provided in the previous stage of the neutralization step, and the first lithium chloride-containing liquid is obtained by passing through these adsorption steps and elution steps. Other aspects are the same as the first embodiment. The adsorption step and the elution step as the differences are described below.

[0071] <Adsorption process>

[0072] Figure 3 The adsorption process shown is a process of contacting a lithium adsorbent with a low-lithium content liquid such as salt lake brine, so that lithium is selectively adsorbed from the low-lithium content liquid to the lithium adsorbent. The reaction formula in the adsorption process is shown in Formula 1. Here, H is used as a lithium adsorbent. 1.6 Mn 1.6 O4 reaction formula, but is not particularly limited thereto. For example, other lithium adsorbents obtained from lithium manganate having other spinel structures can also be used. In addition, these lithium adsorbents are preferably manganese oxides that make lithium manganate contact with acid to remove lithium from the lithium manganate.

[0073] Formula 1

[0074] H 1.6 Mn 1.6 O4+1.6LiCl→Li 1.6 Mn 1.6 O4+1.6HCl

[0075] There is no particular limitation on the method of making these contacts. For example, as the contact method, a column method and a batch mixing method can be cited. In the column method, when the lithium adsorbent is used as a fine powder, generally, the resistance to liquid flow is high and it is difficult to continuously pass the liquid. Therefore, it is preferred to use particles made by kneading the lithium adsorbent (including the case of a precursor before becoming a lithium adsorbent) and a binder such as an alumina binder, and sintering them.

[0076] In the adsorption process, the pH of the low-lithium content liquid is preferably above 3 and below 10. Since the reaction in the adsorption process is a reaction in which lithium is adsorbed to generate acid, when the pH of the liquid is low, there is a case where the reaction rate slows down or the reaction itself does not occur. Therefore, it is preferred to increase the pH of the low-lithium content liquid before contacting the low-lithium content liquid with the lithium adsorbent. However, in the case where the low-lithium content liquid contains magnesium, magnesium hydroxide precipitates when the pH is too high, and when the magnesium hydroxide covers the surface of the lithium adsorbent, the adsorption reaction of lithium is physically hindered. In particular, when a column method is adopted as a contact method, there are more cases where blockage occurs in the column due to magnesium hydroxide. Therefore, the pH of the first lithium chloride-containing liquid is preferably below 10.

[0077] In addition, after the column is passed through, when the pH is below 3, there is a possibility that the lower part of the column cannot efficiently adsorb lithium. It should be noted that in the circulation method, it is preferred to add a neutralizing agent to the effluent after the column is passed through, and return it to the column after adjusting to the above pH range. In the case of a column method, the flow rate can be changed according to the required processing volume. In the case of a precipitate after neutralization, the column can be passed through smoothly by appropriately using a filtering device such as a filter press or a check filter.

[0078] After the adsorption operation, the lithium adsorbent after lithium adsorption is washed with water as needed in order to carry out the elution process of the next process. In the case of column liquid passing, after the low-lithium content liquid is passed, distilled water with higher purity is passed through the column to squeeze out and wash the low-lithium content liquid remaining inside. In the case of batch mixing, after solid-liquid separation, water is added to the lithium adsorbent after lithium adsorption to remove the low-lithium content liquid attached.

[0079] <Washing process>

[0080] like Figure 3 As shown, in the elution process, the adsorbed lithium manganate that has adsorbed lithium is contacted with hydrochloric acid to obtain a first lithium chloride-containing liquid. The adsorbed lithium manganate is, for example, in the form of lithium manganate, and the lithium is eluted by contacting the adsorbed lithium manganate with hydrochloric acid. The contact method is usually a column method, but it can also be a batch mixing method, and can be any contact method. The reaction formula when lithium is eluted is shown in Formula 2.

[0081] Formula 2

[0082] Li 1.6 Mn 1.6 O4+1.6HCl→H 1.6 Mn 1.6 O4+1.6LiCl

[0083] Here, Li is shown as lithium manganate. 1.6 Mn 1.6 O4, but is not particularly limited thereto. For example, a lithium adsorbent obtained from lithium manganate having other spinel structures can also be used. The concentration of hydrochloric acid only needs to be sufficient to elute lithium. When the concentration is too high, the lithium manganate will dissolve and be lost. In addition, when the concentration is too low, lithium will not be eluted. The concentration of hydrochloric acid is preferably above 0.3 mol / L and below 2.0 mol / L. In the case of a column method, the liquid flow rate can be changed according to the required processing volume.

[0084] The eluate obtained in this process, i.e., the first lithium chloride-containing liquid, contains a small amount of sodium, potassium, magnesium, and calcium associated with the adsorption process. In addition, when the lithium adsorbent is lithium manganate, it also contains manganese eluted from the lithium adsorbent. In addition, when the granules using an alumina binder are used as lithium adsorbents, aluminum is contained in the second lithium chloride-containing liquid. Among these impurities, polyvalent metals other than sodium and potassium will cause defects such as shortened membrane life in the subsequent conversion process, so they are removed in the above-mentioned neutralization process or the combination of the oxidation process and the neutralization process. It should be noted that through the elution operation, the lithium adsorbent after lithium adsorption is changed back to a lithium adsorbent, and becomes a state that can adsorb lithium again. Therefore, it can be used again in the adsorption process. When reused, the lithium adsorbent is preferably washed with water.

[0085] (Fourth Embodiment)

[0086] Figure 4 A flow chart showing a method for producing lithium hydroxide according to a fourth embodiment of the present invention is shown. This embodiment differs from the second embodiment in that an adsorption step and an elution step are provided in the previous stage of the neutralization step. Other aspects are the same as the second embodiment. In addition, the details of the adsorption step and the elution step are the same as those of the third embodiment described above.

[0087] Example

[0088] Hereinafter, specific examples of the method for producing lithium hydroxide of the present invention will be described, but the present invention is not limited to these examples.

[0089] (Example 1)

[0090] <Neutralization process>

[0091] An alkali is added to the first lithium chloride-containing liquid to obtain a neutralized liquid. The first lithium chloride-containing liquid is obtained by eluting the lithium adsorbed by the lithium adsorbent with hydrochloric acid. The alkali used in the neutralization process is sodium hydroxide. The weight per unit volume of the metal ions contained in the obtained neutralized liquid is shown in Table 1. The metal concentration is analyzed by ICP-AES. In the neutralization process, the weight per unit volume of aluminum, magnesium, and manganese is small. However, the weight per unit volume of calcium is a very high value.

[0092] Table 1

[0093] Al Ca Mg Mn g / L g / L g / L g / L 0.001 0.42 0.001 0.001

[0094] <Ion exchange process>

[0095] Use iminodiacetic acid type chelating resin CR11 (Mitsubishi Chemical Corporation system) as ion exchange resin.Pack this chelating resin 20ml in the glass column of diameter 20mm, to implement ion exchange process.The flow rate at this moment is SV5 (capacity is 20ml, is therefore 100ml / h).The weight per unit volume of above-mentioned metal ion is measured every BV5 (volume is 20ml, is therefore 100ml).Measure with ICP-AES in the same manner as in the mensuration and after liquid.The results are shown in Table 2.

[0096] Table 2

[0097]

[0098] Till BV35, the weight per unit volume of four kinds of metal ions is the lower limit value 0.00005g / L of the assay device of measuring usefulness, and it can be known that these metals are trapped by resin in the ion exchange process.But when BV surpassed 40, thought to surpass the trapping capacity of resin, each metal ion and the weight per unit volume in the neutralization back liquid equal or approach this value.

[0099] (Comparative Example 1)

[0100] The neutralization step and the ion exchange step were carried out under the same conditions as in Example 1 except that the flow rate in the ion exchange step was SV10 (200 ml / h) and the weight per unit volume was measured every BV10.

[0101] Table 3

[0102]

[0103] From the time when BV reached 10, the weight per unit volume of all metal ions increased and became close to the weight per unit volume in the neutralized solution. This is considered to be because the liquid flow rate was so fast that it exceeded the value of SV7, so the metal could not be captured by the ion exchange resin.

[0104] (Comparative Example 2)

[0105] The neutralization step and the ion exchange step were carried out under the same conditions as in Example 1 except that the flow rate in the ion exchange step was SV25 (500 ml / h) and the weight per unit volume was measured every BV50.

[0106] Table 4

[0107]

[0108] From the time when BV reached 25, the weight per unit volume of all metal ions increased and became close to the weight per unit volume in the neutralized solution. This is considered to be because the liquid flow rate was so fast that it exceeded the value of SV7, so the metal could not be captured by the ion exchange resin.

Claims

1. A method for producing lithium hydroxide, characterized in that: The process comprises the following steps (1) to (3): (1) Neutralization step: a step of adding alkali to the first lithium chloride-containing liquid to obtain a neutralized liquid; (2) Ion exchange step: a step of contacting the neutralized liquid with an ion exchange resin to obtain a second liquid containing lithium chloride; (3) a conversion step: a step of subjecting the second liquid containing lithium chloride to electrodialysis using a bipolar membrane to obtain a liquid containing lithium hydroxide, The first lithium chloride-containing liquid is obtained through an adsorption process and an elution process. The adsorption process allows the low-lithium content liquid to contact with a lithium adsorbent obtained from lithium manganate to obtain adsorbed lithium manganate; The elution step allows the adsorbed lithium manganate to contact with a hydrochloric acid solution to obtain the first liquid containing lithium chloride. The ion exchange step is carried out using a column. The flow rate of the neutralized liquid passing through the column is greater than SV1 and less than SV7, The flow rate of the neutralized liquid passing through the column is greater than or equal to BV10 and less than or equal to BV35.

2. A method for producing lithium hydroxide, characterized in that: The process comprises the following steps (1) to (4): (1) Oxidation step: a step of adding an oxidant to the first lithium chloride-containing liquid to obtain an oxidized liquid; (2) Neutralization step: a step of adding alkali to the oxidized liquid to obtain a neutralized liquid; (3) Ion exchange step: a step of contacting the neutralized liquid with an ion exchange resin to obtain a second liquid containing lithium chloride; (4) a conversion step: a step of subjecting the second liquid containing lithium chloride to electrodialysis to obtain a liquid containing lithium hydroxide, The first lithium chloride-containing liquid is obtained through an adsorption process and an elution process. The adsorption process allows the low-lithium content liquid to contact with a lithium adsorbent obtained from lithium manganate to obtain adsorbed lithium manganate; The elution step allows the adsorbed lithium manganate to contact with a hydrochloric acid solution to obtain the first liquid containing lithium chloride.

3. The method for producing lithium hydroxide according to claim 1, wherein The ion exchange resin used in the ion exchange step is an iminodiacetic acid type chelate resin or an iminodiacetate type chelate resin.

4. The method for producing lithium hydroxide according to claim 2, wherein The ion exchange resin used in the ion exchange step is an iminodiacetic acid type chelate resin or an iminodiacetate type chelate resin.

5. The method for producing lithium hydroxide according to claim 3, wherein The functional groups of the iminodiacetic acid type chelating resin and the iminodiacetate type chelating resin are sodium type.

6. The method for producing lithium hydroxide according to claim 4, wherein The functional groups of the iminodiacetic acid type chelating resin and the iminodiacetate type chelating resin are sodium type.

7. The method for producing lithium hydroxide according to any one of claims 2, 4 and 6, wherein: The ion exchange step is carried out using a column. The flow rate of the neutralized liquid passing through the column is greater than or equal to SV1 and less than or equal to SV7.

8. The method for producing lithium hydroxide according to claim 7, wherein The flow rate of the neutralized liquid passing through the column is greater than or equal to BV10 and less than or equal to BV35.

9. The method for producing lithium hydroxide according to any one of claims 1 to 6 and 8, characterized in that: The low lithium content liquid is salt lake brine.

10. The method for producing lithium hydroxide according to claim 7, wherein The low lithium content liquid is salt lake brine.

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