Lithium compound manufacturing method and lithium compound manufacturing device

Abstract

Provided is a method for producing a lithium compound, by which a high purity lithium compound can be efficiently produced from low quality lithium carbonate containing impurities such as salt water, the method comprising: mixing lithium carbonate, an acid such as an organic acid and water in a reaction tank 1 to produce an aqueous organic acid lithium compound solution containing an organic acid lithium compound; mixing the organic acid lithium compound and a metal hydroxide in a reaction tank 2 to produce an aqueous lithium hydroxide solution; returning an organic acid, which is regenerated by means of an electrochemical device from an organic acid metal compound by-produced when the aqueous lithium hydroxide solution is produced, to the reaction tank 1, and using this as the organic acid. Also provided is an apparatus for producing a lithium compound, the apparatus having the reaction tank 1, the reaction tank 2, the electrochemical device and a return pipe, each of which have a specific function.

Description

[Technical Field]

[0001] The present invention relates to a method and an apparatus for producing a lithium compound. [Background technology]

[0002] With the recent rapid spread of information-related devices and communication devices such as personal computers, video cameras, and mobile phones, the development of batteries to be used as their power sources has become increasingly important. Conventionally, batteries used for such applications have used electrolytes containing flammable organic solvents, but by making batteries all-solid-state, flammable organic solvents are not used in the battery, safety devices can be simplified, and manufacturing costs and productivity can be improved. Therefore, batteries in which the electrolyte is replaced with a solid electrolyte layer are being developed.

[0003] Lithium secondary batteries and the like are used for the above-mentioned applications, and in recent years, their use in hybrid cars and electric vehicles, which are being developed to comply with carbon dioxide emission regulations, has also been considered. Sulfide solid electrolytes are known as solid electrolytes used in lithium secondary batteries and the like. Sulfide solid electrolytes have high ionic conductivity and are useful for achieving high battery output. Because lithium sulfide is widely used as a raw material in the production of sulfide solid electrolytes, the demand for lithium sulfide has increased, along with the demand for lithium hydroxide, which is the raw material for lithium sulfide. One method for producing lithium hydroxide involves electrolyzing an aqueous lithium carbonate solution or suspension and passing the solution through an ion exchange membrane to produce a lithium hydroxide aqueous solution (see, for example, Patent Document 1). Another method for producing lithium hydroxide has been proposed, which includes a step of reacting lithium carbonate with an acid containing acetic acid to produce lithium acetate, and a step of reacting lithium acetate with a metal hydroxide to produce lithium hydroxide (see, for example, Patent Document 2).

[0004] Furthermore, as mentioned above, the use of lithium in hybrid cars and electric cars is being considered, and if this is put into practical use, it will be necessary to secure lithium more stably. In order to seek a wider range of lithium sources, techniques have been disclosed for recovering lithium from brine water of salt lakes using manganese oxide compounds as adsorbents (see, for example, Non-Patent Documents 1 and 2), and for recovering lithium by solar evaporation of brine (see, for example, Non-Patent Documents 1 and 3). [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Japanese Patent Application Laid-Open No. 2009-270188 [Patent Document 2] Japanese Patent Application Publication No. 2019-131448 [Non-patent literature]

[0006] [Non-Patent Document 1] "Fiscal 2008 Technical Support Project for On-site Needs, etc.: Joint Study Report on the Development of a Lithium Recovery System from Brine (Public Version)" (Japan Oil, Gas and Metals National Corporation, Mitsubishi Corporation), March 2010, pp. 31-32 [Non-patent document 2] Journal of MMIJ, 2019, Vol. 135, No. 9 [Non-patent document 3] "Lithium Production Technology Overview - Current Status and Future Trends," Metal Resources Report, March 29, 2019, 19-03-vol.48 Summary of the Invention [Problem to be solved by the invention]

[0007] When lithium hydroxide is obtained by the technique described in Patent Document 1, a dehydration step such as heating and concentration is required, which consumes a lot of energy, and reducing this energy is necessary to obtain lithium more cheaply. Furthermore, the method described in Patent Document 2 primarily uses acetic acid as the acid in the reaction with lithium carbonate, but with regard to the handling of potassium acetate and sodium acetate, which are by-products in the process of producing lithium hydroxide, the potassium acetate can be used as an antifreeze, etc., and it is mentioned that this has industrial utility. However, there is no proposal whatsoever for reusing by-products such as potassium acetate and sodium acetate in the method for producing lithium hydroxide, and the method lacks a perspective for efficiently producing lithium compounds, leaving significant room for improvement in production efficiency.

[0008] Furthermore, as demand for lithium used in solid electrolytes is expected to expand, a wider range of lithium sources will be required, including low-quality lithium sources containing impurities, which are obtained from a wide range of aqueous solutions, such as brine and geothermal water, as disclosed in Non-Patent Documents 1 to 3. However, in the technology described in Patent Document 1, when a low-quality lithium source is used, a problem arises in that electrolysis using an ion exchange membrane requires a large amount of energy consumption. Solving this problem is extremely important in the process of responding to the expanding demand for lithium and promoting industrialization. Similarly, improving the production efficiency of lithium compounds in the method described in Patent Document 2 is also extremely important.

[0009] The present invention has been made in view of the above circumstances, and an object of the present invention is to provide a method and an apparatus for producing a lithium compound, which are capable of efficiently producing a high-purity lithium compound from low-grade lithium carbonate containing impurities such as brine. [Means for solving the problem]

[0010] The method for producing a lithium compound according to the present invention comprises the steps of: mixing lithium carbonate, an acid containing an organic acid, and water in a reaction tank 1 to generate an aqueous solution of lithium organic acid containing a lithium organic acid; mixing the organic acid lithium aqueous solution and a metal hydroxide in a reaction tank 2 to produce a lithium hydroxide aqueous solution; and an organic acid regenerated from an organic acid metal by-produced in the production of the lithium hydroxide aqueous solution using an electrochemical device, and the regenerated organic acid is returned to the reaction tank 1 and used as the organic acid; a method for producing a lithium compound, is.

[0011] Furthermore, the lithium compound manufacturing apparatus according to the present invention comprises: The reactor 1 includes a reactor 2, an electrochemical device, and a return pipe. the reaction tank 1 is a tank in which lithium carbonate, an acid including an organic acid, and water are mixed to produce an aqueous solution of lithium organic acid, the reaction tank 2 is a tank in which the organic acid lithium aqueous solution and a metal hydroxide are mixed to produce a lithium hydroxide aqueous solution, the electrochemical device is a device for regenerating an organic acid used in producing the lithium organic acid aqueous solution from an aqueous solution obtained by removing lithium hydroxide from the lithium hydroxide aqueous solution, The return pipe is a pipe for returning the regenerated organic acid to the reaction tank 1. Lithium compound manufacturing equipment, is. [Effects of the Invention]

[0012] According to the present invention, it is possible to provide a method for producing a lithium compound and an apparatus for producing a lithium compound, which are capable of efficiently producing a high-purity lithium compound from low-grade lithium carbonate containing impurities such as brine. [Brief explanation of the drawings]

[0013] [Figure 1] FIG. 1 is a flow chart showing a preferred embodiment of a lithium compound production apparatus capable of carrying out the lithium compound production method of the present embodiment. [Figure 2] FIG. 1 is a flow chart showing a preferred embodiment of a lithium compound production apparatus capable of carrying out the lithium compound production method of the present embodiment. [Figure 3] FIG. 1 is a flow chart showing a preferred embodiment of a lithium compound production apparatus capable of carrying out the lithium compound production method of the present embodiment. [Figure 4] FIG. 1 is a flow chart showing a preferred embodiment of a lithium compound production apparatus capable of carrying out the lithium compound production method of the present embodiment. [Figure 5] FIG. 1 is a schematic diagram showing a preferred embodiment of an electrochemical device. DETAILED DESCRIPTION OF THE INVENTION

[0014] Hereinafter, a method for producing a lithium compound and an apparatus for producing a lithium compound according to one embodiment of the present invention (hereinafter referred to as "this embodiment") will be described. Note that the method for producing a lithium compound and the apparatus for producing a lithium compound according to one embodiment of the present invention are merely one embodiment of the method for producing a lithium compound and the apparatus for producing a lithium compound of the present invention, and the present invention is not limited to the method for producing a lithium compound and the apparatus for producing a lithium compound of the present embodiment. Furthermore, in this specification, lithium means both lithium and lithium ions, and should be interpreted appropriately unless technical contradiction arises.

[0015] In this specification, the upper and lower limit values ​​of a numerical range expressed as "greater than or equal to," "less than or equal to," and "to" can be arbitrarily combined, and the numerical values ​​in the examples can also be used as the upper and lower limit values. For example, when a certain numerical range is expressed as "A to B" and "C to D," the ranges "A to D" and "C to B" are also included. The same applies to the expressions "greater than or equal to," "less than or equal to," and "to."

[0016] (Findings gained by the inventors to arrive at the present invention) As a result of extensive research aimed at solving the above problems, the present inventors have discovered the following and have completed the present invention. As described in Patent Document 1, there have been conventional production methods for converting an aqueous solution of lithium carbonate or the like into an aqueous solution of lithium hydroxide using an electrochemical device with an ion exchange resin. However, this method has the problem that, although anions such as carbonate ions and sulfate ions can be removed by the ion exchange resin, the selectivity for metal ions is not high, and therefore a pretreatment step for sufficiently removing metal impurities is required to obtain a high-purity lithium compound.

[0017] Meanwhile, the present inventors have focused on a reaction in which an organic acid lithium is produced by mixing lithium carbonate, an organic acid such as acetic acid, and water, and a reaction in which an organic acid lithium aqueous solution is produced by mixing a metal hydroxide with the aqueous solution of the organic acid lithium. Regarding the reaction for producing lithium hydroxide, for example, attention can be paid to the reaction of producing lithium hydroxide by mixing lithium carbonate with calcium hydroxide. However, the reactivity between lithium carbonate and calcium hydroxide is not high, and heating is required to promote the reaction. Furthermore, due to the relationship with calcium hydroxide, it takes time to dissolve lithium carbonate and requires the use of a large amount of water. In this regard, in the present invention, the solubility of lithium carbonate is improved by adopting a reaction using an organic acid such as acetic acid, thereby reducing the amount of water used. Reducing the amount of water used leads to an increase in the overall efficiency of the production method. Furthermore, the reaction using an organic acid such as acetic acid is extremely reactive and does not require heating to promote the reaction, making it more advantageous than the reaction between lithium carbonate and calcium hydroxide.

[0018] Furthermore, in the present invention, lithium hydroxide is produced by mixing an organic acid lithium with a metal oxide, and the aqueous solution after recovering the lithium hydroxide contains an organic acid metal. By regenerating the organic acid from the organic acid metal, the organic acid can be reused for a reaction with lithium carbonate. The use of an electrochemical device to regenerate the organic acid from the organic acid metal was considered. An electrochemical device using an ion exchange membrane is also employed in the method of Patent Document 1. However, when using an electrochemical device to produce lithium hydroxide from lithium carbonate as in Patent Document 1, if low-grade lithium carbonate is used as a raw material, the concentration of lithium carbonate is low, and a large amount of energy is required to produce lithium hydroxide. In this regard, the present invention has a high content of organic acid metal, which allows for reduced energy consumption.

[0019] By employing the reaction using the above organic acid such as acetic acid, it is possible to reduce the energy consumption required for heating and decompression, as well as the energy consumption in the electrochemical device, and also to reduce the amount of water used. Therefore, it is considered that a high-purity lithium compound can be efficiently produced from low-grade lithium carbonate such as brine containing metals other than lithium as impurities. The present inventors have arrived at the present invention based on the above findings.

[0020] (Various aspects of this embodiment) A method for producing a lithium compound according to a first aspect of the present embodiment includes the steps of: mixing lithium carbonate, an acid containing an organic acid, and water in a reaction tank 1 to generate an aqueous solution of lithium organic acid containing a lithium organic acid; mixing the organic acid lithium aqueous solution and a metal hydroxide in a reaction tank 2 to produce a lithium hydroxide aqueous solution; and an organic acid regenerated from an organic acid metal by-produced in the production of the lithium hydroxide aqueous solution using an electrochemical device, and the regenerated organic acid is returned to the reaction tank 1 and used as the organic acid; a method for producing a lithium compound, is.

[0021] As described above, the invention relating to the lithium compound manufacturing method of this embodiment focuses on two reactions: a reaction to produce an organic acid lithium by mixing lithium carbonate with an acid, including an organic acid such as acetic acid, and water, and a reaction to produce lithium hydroxide by mixing an aqueous solution of an organic acid lithium with a metal hydroxide. Because aqueous solutions of organic acids such as acetic acid have high solubility and reactivity with lithium carbonate, the reaction proceeds rapidly without heating. Furthermore, the aqueous solution of an organic acid lithium obtained by this reaction also has high reactivity with metal hydroxides, allowing lithium hydroxide to be easily produced. Furthermore, because lithium carbonate has high solubility in these reactions, the amount of water used to prepare the aqueous solution can be reduced, improving the overall efficiency of the manufacturing method.

[0022] Furthermore, after the reaction to produce lithium hydroxide is carried out and the lithium hydroxide is recovered, the aqueous solution contains an organic acid metal. This aqueous solution containing an organic acid metal can be used in an electrochemical device, specifically, by supplying it to an electrochemical device as a catholyte, to regenerate an organic acid such as acetic acid, which can then be used in a reaction with lithium carbonate. Furthermore, the aqueous solution obtained by regenerating an organic acid from the aqueous solution containing an organic acid metal contains a metal hydroxide, and the aqueous solution containing the metal hydroxide can be used in a reaction by mixing it with an organic acid lithium. By implementing this recycling via an organic acid such as acetic acid, it is possible to reuse the solution, thereby minimizing waste. The reduction of chemicals such as organic acids such as acetic acid and metal hydroxides, as well as the reduction of waste, can be said to be an advantage of focusing on the reaction due to mixing in an aqueous solution using an organic acid such as acetic acid.

[0023] The production method of this embodiment employs an electrochemical device, which consumes energy. However, because the organic acid metal content in the aqueous solution containing the organic acid metal that is supplied to the electrochemical device is high, the energy consumption required to recover an organic acid such as acetic acid from the aqueous solution can be kept lower than, for example, when producing lithium hydroxide from low-grade lithium carbonate using an electrochemical device. Therefore, the energy consumption in the electrochemical device can also be reduced.

[0024] Thus, according to the method for producing a lithium compound of this embodiment, even though low-grade lithium carbonate containing impurities such as brine is used, a highly reactive reaction is employed, thereby reducing energy consumption for heating and the like, and reducing the amount of water used. Furthermore, although an electrochemical device is employed, energy consumption is reduced, and by realizing recycling via an organic acid such as acetic acid, the solution can be reused, and waste can be minimized.

[0025] A method for producing a lithium compound according to a second aspect of the present embodiment is the same as the method for producing a lithium compound according to the first aspect, except that: The metal hydroxide is regenerated by the electrochemical device and returned to the reaction tank 2. That is it.

[0026] As described above, lithium hydroxide is generated and recovered, and then an aqueous solution containing an organic acid metal is supplied as a catholyte to an electrochemical device, whereby an organic acid such as acetic acid and a metal hydroxide are regenerated. Therefore, in a production method according to a second aspect, the metal hydroxide regenerated by the electrochemical device is used in a reaction with an organic acid lithium. In the production method according to the first aspect, an organic acid such as acetic acid regenerated by the electrochemical device is used in a reaction by mixing with lithium carbonate, thereby reducing waste. However, by using a metal hydroxide regenerated simultaneously with an organic acid such as acetic acid in a reaction with an organic acid lithium, it is possible to promote the production of lithium hydroxide and reduce waste.

[0027] A method for producing a lithium compound according to a third aspect of the present embodiment is the same as the method for producing a lithium compound according to the first or second aspect, Recovering only lithium ions from the lithium hydroxide aqueous solution into a recovery solution using a lithium ion separation device equipped with a Li selective permeable membrane. That is it.

[0028] In the production method of this embodiment, methods for obtaining high-purity lithium hydroxide from an aqueous lithium hydroxide solution include Method 1 (hereinafter sometimes simply referred to as "Method 1"), which involves recovering only lithium ions using a lithium ion separation device equipped with a Li permselective membrane, as described below, and Method 2 (hereinafter sometimes simply referred to as "Method 2"), which involves crystallization, solid-liquid separation, redissolution, and impurity removal. From the perspective of more efficiently obtaining high-purity lithium hydroxide, the method of recovering only lithium ions using a lithium ion separation device equipped with a Li permselective membrane is preferred.

[0029] For example, when adopting the above-mentioned method 2, crystallization can be performed using methods such as filtration, thermal concentration, and pH crystallization. However, as described below, pH crystallization is preferred in terms of efficiency and energy consumption. On the other hand, pH crystallization may require the use of chemicals such as potassium hydroxide, which poses a problem of increased chemical usage. In this regard, method 1, which recovers only lithium ions using a lithium ion separation device equipped with a Li-permselective membrane, is advantageous in that it does not require the use of chemicals and can produce highly pure lithium hydroxide.

[0030] Furthermore, when a lithium ion separation device equipped with a Li permselective membrane is used by Method 1, high-purity lithium hydroxide can be obtained by performing crystallization such as cooling crystallization or evaporation crystallization on the recovered solution from which only lithium ions have been recovered in the lithium ion separation device, followed by solid-liquid separation. Therefore, Method 1 is advantageous in that high-purity lithium hydroxide can be obtained more easily than Method 2, which requires re-dissolution, impurity removal, and the like in addition to crystallization and solid-liquid separation to obtain high-purity lithium hydroxide.

[0031] A fourth aspect of the present embodiment provides a method for producing a lithium compound according to the third aspect, comprising: Further, the recovered liquid recovered using the lithium ion separation device is crystallized and subjected to solid-liquid separation 1. That is it. This allows for the production of highly pure lithium hydroxide while reducing the amount of chemicals used. In this specification, "high purity" and "high purity" refer to a crystal purity of 99% or more.

[0032] A fifth aspect of the present embodiment provides a method for producing a lithium compound according to the third or fourth aspect, further comprising: the organic acid metal is supplied to the electrochemical device by a Li ion-removed aqueous solution obtained by recovering only lithium ions from the lithium hydroxide aqueous solution into the recovery solution using a lithium ion separation device equipped with the Li permselective membrane; That is it.

[0033] The reaction between the organic acid lithium and the metal hydroxide produces lithium hydroxide and an organic acid metal as a by-product, yielding an aqueous solution containing them. Removing the lithium hydroxide from the aqueous solution containing the lithium hydroxide and the organic acid metal by recovering only the lithium ions using a lithium ion separation device results in a Li-ion-removed aqueous solution containing the organic acid metal. In a fifth embodiment, an electrochemical device is used to recover an organic acid from the organic acid metal by-product produced by generating an aqueous lithium hydroxide solution. The by-product organic acid metal is supplied to the electrochemical device as an organic acid metal aqueous solution (Li-ion-removed aqueous solution), and an organic acid such as acetic acid is recovered from the organic acid metal aqueous solution (Li-ion-removed aqueous solution). In the case of Method 2, the separated liquid 1 obtained by crystallization and solid-liquid separation 1 from the aqueous solution containing the lithium hydroxide and the organic acid metal is supplied to the electrochemical device as the organic acid metal aqueous solution.

[0034] By reusing the organic acid metal aqueous solution (Li ion-removed aqueous solution or separation solution 1) containing the organic acid metal by-produced in the lithium ion separation device in this way, it is possible to reduce waste. The ability to reuse the organic acid metal aqueous solution (Li ion-removed aqueous solution or separation solution 1) can be said to be an advantage of focusing on the reaction using an organic acid such as acetic acid.

[0035] The method for producing a lithium compound according to a sixth aspect of the present embodiment is the same as any one of the first to fifth aspects, except that: Further, the method includes adding oxalic acid to the aqueous solution of lithium organic acid and performing solid-liquid separation 4. That is it.

[0036] By adding oxalic acid to the aqueous solution of organic acid lithium, heavy metals such as calcium and magnesium contained in the low-grade lithium carbonate can be precipitated, and the precipitated heavy metals can be removed by solid-liquid separation 4, so that an aqueous solution of organic acid lithium with few impurities can be obtained as separated liquid 4.

[0037] A seventh aspect of the present embodiment provides a method for producing a lithium compound according to the sixth aspect, further comprising: The lithium hydroxide aqueous solution is produced by reacting a separated liquid 4 obtained by performing solid-liquid separation 4 with a metal hydroxide. That is it.

[0038] As described above, in the seventh embodiment, the separated liquid 4 obtained by removing the precipitated heavy metals by solid-liquid separation 4 is an aqueous solution of lithium organic acid salt with few impurities. By using such separated liquid 4 to react with a metal hydroxide in reaction tank 2, the purity of lithium hydroxide is improved.

[0039] The method for producing a lithium compound according to an eighth aspect of the present embodiment is the same as any one of the third to seventh aspects, except that: Further, carbon dioxide is added to the recovered liquid to perform solid-liquid separation 5. Including, The lithium carbonate contained in the separated liquid 5 obtained by the solid-liquid separation 5 is used to generate the lithium organic acid aqueous solution. That is it.

[0040] The recovered liquid is obtained by recovering only lithium ions using the lithium ion separation device. As described above, the recovered liquid is an aqueous lithium hydroxide solution with few impurities. Therefore, by adding carbon dioxide to the recovered liquid, an aqueous solution containing lithium carbonate is obtained. By subjecting this to solid-liquid separation 5, high-purity lithium carbonate with few impurities is obtained. Furthermore, the separated liquid 5 obtained by solid-liquid separation 5 is a saturated aqueous lithium carbonate solution in which lithium carbonate is dissolved, and therefore can be used as lithium carbonate in producing an aqueous lithium acetate solution. By using the separated liquid 5 as a lithium carbonate source, it is possible to respond to a variety of operating conditions.

[0041] A ninth aspect of the present embodiment provides a method for producing a lithium compound according to the eighth aspect, further comprising: The carbon dioxide is generated by generating an aqueous solution of lithium organic acid. That is it. In producing an aqueous solution of lithium organic acid, carbon dioxide is produced together with the lithium organic acid by the reaction of an organic acid such as acetic acid with lithium carbonate. In the lithium ion separation device, only lithium ions are recovered and used as carbon dioxide to be added to the recovered solution, which is an aqueous lithium hydroxide solution with few impurities, thereby reducing the amount of carbon dioxide waste.

[0042] The method for producing a lithium compound according to a tenth aspect of the present embodiment is the same as any one of the first to ninth aspects, except that: Lithium hydroxide is obtained by solid-liquid separation 1. That is it.

[0043] The solid-liquid separation 1 is performed using a crystallized lithium hydroxide aqueous solution obtained by generating the lithium hydroxide aqueous solution, preferably a crystallized solution obtained by recovering the solution using the lithium ion separation apparatus of the fourth embodiment. Therefore, the separated solid 1-1 obtained by the solid-liquid separation 1 is lithium hydroxide with high purity. In other words, the tenth embodiment can be said to be an embodiment in which the lithium compound produced by the method for producing a lithium compound of the present embodiment is lithium hydroxide.

[0044] The method for producing a lithium compound according to an eleventh aspect of the present embodiment is the same as any of the eighth to tenth aspects, except that lithium carbonate is obtained by performing solid-liquid separation 5. In performing solid-liquid separation 5, as described above, only lithium ions are recovered using a lithium ion separation device, and carbon dioxide is added to the recovered solution, which is an aqueous lithium hydroxide solution with few impurities, to provide an aqueous solution containing lithium carbonate. Therefore, the separated solid 5 obtained by solid-liquid separation 5 is lithium carbonate with high purity. In other words, it can be said that the eleventh embodiment is an embodiment in which the lithium compound produced by the method for producing a lithium compound of the present embodiment is lithium carbonate.

[0045] The method for producing a lithium compound according to a twelfth aspect of the present embodiment is the same as any one of the first to eleventh aspects, except that: The metal that forms the metal hydroxide and the metal that forms the organic acid metal are the same. That is it. The metal hydroxide is used by generating the lithium hydroxide aqueous solution, and the organic acid metal is a by-product of generating the lithium hydroxide aqueous solution. By supplying the organic acid metal to an electrochemical device, an organic acid such as acetic acid is regenerated, and the metal is regenerated as a metal hydroxide. The recovered metal hydroxide is then used by generating a lithium hydroxide aqueous solution. In other words, the twelfth embodiment is an embodiment meaning that the metal is circulated, thereby reducing waste.

[0046] The method for producing a lithium compound according to a thirteenth aspect of the present embodiment is the same as any one of the first to twelfth aspects, except that: The metal is at least one selected from sodium, potassium, and barium. That is it. When the metal is one of these, the reaction for producing an aqueous lithium hydroxide solution proceeds more quickly and the metal is easily regenerated by an electrochemical device, making it possible to efficiently produce lithium hydroxide.

[0047] A lithium compound manufacturing apparatus according to a fourteenth aspect of the present embodiment includes: The reactor 1 includes a reactor 2, an electrochemical device, and a return pipe. the reaction tank 1 is a tank in which lithium carbonate, an acid including an organic acid, and water are mixed to produce an aqueous solution of lithium organic acid, the reaction tank 2 is a tank in which the organic acid lithium aqueous solution and a metal hydroxide are mixed to produce a lithium hydroxide aqueous solution, the electrochemical device is a device for regenerating an organic acid used in producing the lithium organic acid aqueous solution from an aqueous solution obtained by removing lithium hydroxide from the lithium hydroxide aqueous solution, The return pipe is a pipe for returning the regenerated organic acid to the reaction tank 1. Lithium compound manufacturing equipment, is.

[0048] The lithium compound production apparatus of this embodiment is suitable for use in the lithium compound production method of this embodiment because it can produce an aqueous solution of organic acid lithium (reaction tank 1), produce an aqueous solution of lithium hydroxide (reaction tank 2), regenerate an organic acid such as acetic acid from an organic acid metal by-produced in the production of the lithium hydroxide aqueous solution (electrochemical device), and return the regenerated organic acid to reaction tank 1 via a return pipe. That is, the lithium compound production apparatus of this embodiment can efficiently produce a high-purity lithium compound from low-grade lithium carbonate containing impurities such as brine.

[0049] The lithium compound manufacturing apparatus according to a fifteenth aspect of the present embodiment is the same as the fourteenth aspect, except that: The system further includes a lithium ion separation device equipped with a Li selective permeable membrane that recovers only lithium ions from the lithium hydroxide aqueous solution into a recovery liquid. That is it.

[0050] A lithium compound manufacturing apparatus according to a sixteenth aspect of the present embodiment is the same as the fifteenth aspect, except that: Further, a crystallizer for crystallizing the recovered liquid is provided. That is it. By providing a crystallizer, it becomes easier to obtain lithium hydroxide with higher purity.

[0051] As mentioned above, by providing a lithium ion separation device, it is possible to obtain high-purity lithium hydroxide without using chemicals, and high-purity lithium hydroxide can be easily obtained simply by crystallizing the recovered liquid.

[0052] [Method of manufacturing lithium compounds] The method for producing a lithium compound according to this embodiment will be described in further detail below. The method for producing a lithium compound according to the present embodiment includes the steps of: mixing lithium carbonate, an acid containing an organic acid, and water in a reaction tank 1 to generate an aqueous solution of lithium organic acid containing a lithium organic acid; mixing the organic acid lithium aqueous solution and a metal hydroxide in a reaction tank 2 to produce a lithium hydroxide aqueous solution; and an organic acid regenerated from an organic acid metal by-produced in the production of the lithium hydroxide aqueous solution using an electrochemical device, and the regenerated organic acid is returned to the reaction tank 1 and used as the organic acid; The present invention is characterized in that it comprises:

[0053] The method for producing a lithium compound according to this embodiment will be described with reference to FIGS. 1 to 4. FIGS. 1 to 4 are flow diagrams showing a preferred embodiment of a lithium hydroxide production apparatus capable of carrying out the method for producing a lithium compound according to this embodiment. FIGS. 1 and 2 show flow diagrams for the case where Method 2 is employed as a method for obtaining high-purity lithium hydroxide from an aqueous lithium hydroxide solution. FIG. 1 shows a flow diagram for the case where the ion exchange membrane used in the electrochemical device is an anion exchange membrane, and FIG. 2 shows a flow diagram for the case where the ion exchange membrane is a cation exchange membrane. FIG. 3 shows a flow diagram for the case where Method 1 is employed and the ion exchange membrane used in the electrochemical device is an anion exchange membrane, and FIG. 4 shows a flow diagram for the case where Method 1 is employed and the ion exchange membrane used in the electrochemical device is a cation exchange membrane.

[0054] 1 and 2 show that liquid 1 (an organic acid such as acetic acid) reacts with liquid 3 (a lithium carbonate liquid) containing crude lithium carbonate (low-grade lithium carbonate) as a raw material and separated liquid 5 obtained by solid-liquid separation 5 in reaction tank 1 to produce aqueous solution A (a lithium organic acid aqueous solution), which then reacts with aqueous solution B (a solution containing a metal hydroxide) in reaction tank 2 to produce aqueous solution C (a lithium hydroxide aqueous solution). In this way, in reaction tank 1, lithium carbonate reacts with an organic acid such as acetic acid to produce an aqueous solution of lithium organic acid containing the lithium organic acid, and in reaction tank 2, the lithium organic acid reacts with a metal hydroxide to produce an aqueous solution of lithium hydroxide.

[0055] When Method 1 is employed as a method for obtaining high-purity lithium hydroxide from a lithium hydroxide aqueous solution, the aqueous solution C produced in the reaction tank 2 is supplied as a stock solution to a lithium ion separation device 10 equipped with a Li permselective membrane 10c, where only lithium ions are recovered to form a Li-ion-removed aqueous solution, which is then supplied to the electrochemical device as an organic acid metal aqueous solution. When Method 2 is employed, the aqueous solution C undergoes crystallization and solid-liquid separation 1 to obtain lithium hydroxide as separated solid 1-2 and separated liquid 1-2, which is an aqueous solution containing metal acetate, and the separated liquid 1-2 is supplied to the electrochemical device as an organic acid metal aqueous solution.

[0056] In the electrochemical device having the anion exchange membrane of FIG. 1, an organic acid metal aqueous solution (separation liquid 1-2) is supplied as a catholyte, and aqueous solution A (aqueous solution of organic acid lithium) is supplied as an anolyte, and acetate ions are regenerated from the organic acid metal contained in the organic acid metal aqueous solution to form aqueous solution B (aqueous solution containing a metal hydroxide). On the other hand, aqueous solution A supplied to the electrochemical device becomes liquid 1 (acid containing an organic acid such as acetic acid) which further contains organic acid ions regenerated from the organic acid metal aqueous solution, and as described above, is used for reaction with lithium carbonate in reaction vessel 1. In this way, in the electrochemical device, organic acids such as acetic acid are regenerated from the organic acid metal which is a by-product of generating an aqueous lithium hydroxide solution.

[0057] When an electrochemical device having a cation exchange membrane (cation exchange membrane) as shown in FIG. 2 is used, the organic acid metal aqueous solution (separation liquid 1-2) is supplied as an anolyte, and metal ions are regenerated from the organic acid metal contained in the organic acid metal aqueous solution to form liquid 1 containing an organic acid. A portion of aqueous solution B, from which metal ions have been recovered from the organic acid metal aqueous solution in the electrochemical device, is circulated and supplied to the cathode chamber, and the non-circulated aqueous solution B is supplied to reaction chamber 2, and liquid 1 is used for the reaction with lithium carbonate in reaction chamber 1. In this way, whether an anion exchange membrane (anion exchange membrane) or a cation exchange membrane (cation exchange membrane) is used as the ion exchange membrane in the electrochemical device, organic acids such as acetic acid are regenerated from the organic acid metal by-produced by generating an aqueous lithium hydroxide solution.

[0058] In the lithium ion separation devices 10 shown in FIGS. 3 and 4, a recovered solution in which only lithium ions are recovered from an aqueous lithium hydroxide solution undergoes crystallization and solid-liquid separation 1 to become high-purity lithium hydroxide, or becomes high-purity lithium carbonate by reacting with a mixed gas containing carbon dioxide which is a by-product of the reaction caused by mixing an organic acid such as acetic acid with lithium carbonate in a reaction tank 1. The Li ion-removed aqueous solution obtained by recovering only lithium ions from the lithium hydroxide aqueous solution is supplied to the electrochemical device as an organic acid metal aqueous solution containing the organic acid metal produced in the reaction tank 2. As described above, the solution is supplied to the electrochemical device as either a catholyte or an anolyte, depending on the type of ion exchange membrane the electrochemical device has. The separated liquid 1-1 obtained after lithium hydroxide has been removed from the recovered solution through crystallization and solid-liquid separation 1 is an aqueous solution containing only a small amount of lithium hydroxide, and as shown in FIGS. 3 and 4, it may be supplied to the recovered liquid tank 10b of the lithium ion separation device 10.

[0059] (Generating an aqueous solution of lithium organic acid) The production method of this embodiment includes mixing lithium carbonate, an acid including an organic acid, and water in a reaction vessel 1 to generate an aqueous solution of lithium organic acid containing a lithium organic acid. Lithium carbonate is usually supplied in the form of a slurry, while acids including organic acids such as acetic acid are supplied as aqueous solutions. Therefore, an aqueous solution of lithium organic acid containing lithium acetate or other organic acid is obtained by reacting lithium carbonate with an acid including organic acids such as acetic acid in the aqueous solution. For example, when acetic acid is used as the organic acid, the reaction between lithium carbonate and an acid including acetic acid is shown in the following chemical reaction formula (1). The lithium acetate battery material produced by the following reaction dissolves in water in a reaction tank and exists in a dissociated state of acetate ions and lithium ions, forming a lithium ion-containing aqueous solution. Li2CO3+2CH3COOH→2CH3COOLi+CO2+H2O (1)

[0060] In addition to acetic acid, organic acids usable in the production method of this embodiment include those represented by the general formula R such as formic acid, propionic acid, and butanoic acid. 1 -COOH(R 1 is a hydrogen atom or an aliphatic hydrocarbon group; monocarboxylic acids having one carboxyl group represented by the general formula R 2 -(COOH)2(R 2 is a single bond or an aliphatic hydrocarbon group.) Dicarboxylic acids having two carboxyl groups, such as aconitic acid and citric acid; 3 -(COOH)3(R 3 is a single bond or an aliphatic hydrocarbon group. Preferred examples include trivalent carboxylic acids having three carboxyl groups, such as those represented by the following formula:

[0061] R in the general formula of monocarboxylic acid 1 As the aliphatic hydrocarbon group, alkyl groups and alkenyl groups are preferred, with alkyl groups being more preferred, taking into consideration reactivity when mixed with lithium carbonate, ease of availability, cost, etc. From the same viewpoint, a hydrogen atom is also preferred.

[0062] R 1The aliphatic hydrocarbon group may be either linear or branched, and is preferably linear in view of reactivity when mixed with lithium carbonate, ease of availability, cost, etc. From the same viewpoint, the number of carbon atoms in the aliphatic hydrocarbon group is preferably 1 or more, and the upper limit is preferably 8 or less, more preferably 4 or less, even more preferably 3 or less, and still more preferably 2 or less. Also, R 1 The aliphatic hydrocarbon group may be substituted with a halogen atom such as a fluorine atom or a chlorine atom, a hydroxyl group, or the like.

[0063] R in the general formula of dicarboxylic acid 2 As the aliphatic hydrocarbon group, alkylene (alkanediyl) groups and alkenylene (alkenediyl) groups are preferred, taking into consideration reactivity when mixed with lithium carbonate, ease of availability, cost, etc., and alkylene (alkanediyl) groups are more preferred. From the same viewpoint, a single bond is also preferred.

[0064] R 2 The aliphatic hydrocarbon group may be either linear or branched, and is preferably linear in view of reactivity when mixed with lithium carbonate, ease of availability, cost, etc. From the same viewpoint, the number of carbon atoms in the aliphatic hydrocarbon group is preferably 1 or more, and the upper limit is preferably 8 or less, more preferably 4 or less, even more preferably 3 or less, and still more preferably 2 or less. Also, R 2 The aliphatic hydrocarbon group may be substituted with a halogen atom such as a fluorine atom or a chlorine atom, a hydroxyl group, or the like.

[0065] R in the general formula of tricarboxylic acid 3 As the aliphatic hydrocarbon group, in consideration of reactivity when mixed with lithium carbonate, availability, cost, etc., an alkanetriyl group and an alkenetriyl group are preferred, with an alkanetriyl group being more preferred.

[0066] R 3The aliphatic hydrocarbon group may be either linear or branched, and is preferably linear in view of reactivity when mixed with lithium carbonate, ease of availability, cost, etc. From the same viewpoint, the number of carbon atoms in the aliphatic hydrocarbon group is preferably 1 or more, and the upper limit is preferably 8 or less, more preferably 4 or less, and even more preferably 3 or less. Also, R 3 The aliphatic hydrocarbon group may be substituted with a halogen atom such as a fluorine atom or a chlorine atom, a hydroxyl group, or the like, and is preferably substituted with a hydroxyl group.

[0067] As the organic acid that can be used in the manufacturing method of this embodiment, among the above organic acids, formic acid and acetic acid are preferred as monocarboxylic acids, and acetic acid is particularly preferred, oxalic acid is preferred as dicarboxylic acids, and citric acid is preferred as tricarboxylic acids.

[0068] Since lithium carbonate and acids including organic acids such as acetic acid are highly reactive, the reaction proceeds quickly, and therefore heating is not necessary, although heating may be performed as necessary. In this case, the reaction temperature is from room temperature (23°C) to 120°C, preferably from room temperature (23°C) to 80°C. As shown in the above chemical reaction formula (1), the amount of organic acid such as acetic acid used may be twice the molar ratio of lithium carbonate, or may be supplied in excess, for example, about 2 to 5 times. Supplying an excess improves the yield of lithium acetate, allowing for more efficient production of lithium hydroxide.

[0069] The lithium carbonate used in producing the aqueous solution of lithium organic acid is a starting material in the production method of this embodiment, that is, a material for producing lithium hydroxide. Examples of lithium carbonate include low-grade lithium carbonate obtained from brines such as salt lake brine and geothermal brine, as well as seawater, mining wastewater, lithium-containing treated water extracted from treatment components of lithium secondary batteries, etc. As such, the lithium carbonate used in the production method of this embodiment does not need to be special reagent grade.

[0070] The low-grade lithium carbonate obtained from the brine or the like and usable in the production method of this embodiment contains moisture resulting from moisture absorption or brine, as well as various other impurities. For example, low-grade lithium carbonate typically contains lithium, boron, sodium, potassium, magnesium, calcium, and the like, with the metal atom contents typically being 5,000 to 300,000 ppm by mass, 10 to 200 ppm by mass, 300 to 2,000 ppm by mass, 100 to 800 ppm by mass, 200 to 1,500 ppm by mass, or 1,500 to 4,500 ppm by mass. In addition to the above, low-grade lithium carbonate may also contain chlorine, with the chlorine content typically being 300 to 2,000 ppm by mass. It may also contain aluminum, zinc, lead, and the like, with the metal atom contents typically being 0.5 to 50 ppm by mass, 0.1 to 10 ppm by mass, or 0.1 to 20 ppm by mass. Furthermore, the brine may contain sulfate, usually at a content of 50 to 1,000 ppm by mass as SO. Note that the low-grade lithium carbonate used in the production method of the present embodiment varies depending on the properties of the brine, and therefore, it goes without saying that the low-grade lithium carbonate may not be limited to the above.

[0071] The acid containing an organic acid such as acetic acid may contain the organic acid such as acetic acid described above, and may contain an acid other than an organic acid such as acetic acid, as long as the reaction represented by the chemical reaction formula (1) proceeds. From the viewpoint of obtaining lithium hydroxide more efficiently, it is preferable that the entire amount is an organic acid such as acetic acid, and in this case, the organic acids described above may be used alone or in combination. In addition, as the acid other than the organic acid such as acetic acid, inorganic acids such as hydrochloric acid, sulfuric acid, etc. may be used. Also, a plurality of organic acids may be used.

[0072] In the production method of this embodiment, the method for supplying lithium carbonate, water, and an organic acid to the reaction tank 1 is not particularly limited as long as they can be mixed in the reaction tank 1 as a result. For example, water may be added to low-grade lithium carbonate to supply the mixture to the reaction tank 1 in the form of a slurry; the organic acid may be directly supplied to the reaction tank 1; or the organic acid may be mixed with water, and the mixture may be added to low-grade lithium carbonate to supply the mixture to the reaction tank 1 in the form of a slurry.

[0073] (Generating an aqueous solution of lithium hydroxide) The production method of this embodiment includes reacting an organic lithium acid such as lithium acetate with a metal hydroxide to produce an aqueous lithium hydroxide solution. For example, when acetic acid is used as the organic acid and the organic acid lithium becomes lithium acetate, the reaction between lithium acetate and a metal hydroxide is represented by the following chemical reaction formula (2). CH3COOLi+MeOH+H2O→CH3COOMe+LiOH·H2O (2) (Me stands for metal.)

[0074] As mentioned above, the reaction proceeds quickly because lithium organic acids such as lithium acetate and metal hydroxides are highly reactive, similar to the reaction between lithium carbonate and organic acids such as acetic acid. Therefore, heating is not necessary, but heating may be performed as necessary. In this case, the temperature is room temperature (23°C) to 120°C, preferably room temperature (23°C) to 80°C. Although room temperature is written as 23°C for convenience, this is merely for convenience, and the above temperature condition does not mean a temperature above 23°C. When heating, the temperature means a temperature above room temperature (ambient temperature).

[0075] Preferred examples of metal hydroxides include sodium hydroxide, potassium hydroxide, and barium hydroxide, with sodium hydroxide and potassium hydroxide being more preferred, and potassium hydroxide being even more preferred. By using such metal hydroxides, the reaction represented by the above chemical reaction formula (2) can be easily carried out, and lithium hydroxide can be efficiently obtained. These metal hydroxides can be used alone or in combination, but from the viewpoint of simplifying the production method and improving efficiency, it is preferable to use a single metal hydroxide, i.e., a single metal hydroxide.

[0076] (Electrochemical Equipment) In the production method of this embodiment, an organic acid such as acetic acid used in generating the aqueous solution of lithium organic acid containing lithium organic acid such as lithium acetate is regenerated from "CHCOOMe" in the above chemical reaction formula (2), i.e., an organic acid metal such as metal acetate, which is a by-product of generating an aqueous solution of lithium hydroxide, using an electrochemical device. The electrochemical device is not particularly limited as long as it is capable of electrolysis. For example, a membrane electrochemical device equipped with an ion exchange membrane capable of recovering organic acids such as acetic acid from organic acid metals such as metal acetate is preferably used. The ion exchange membrane may be a cation exchange membrane or an anion exchange membrane. Bipolar membrane electrochemical devices may also be used. In this case, an anion exchange membrane (anion exchange membrane), a cation exchange membrane (cation exchange membrane), or a bipolar ion exchange membrane (a membrane consisting of an anion exchange layer and a cation exchange layer) is used. Among these, a cation exchange membrane (cation exchange membrane) is preferred as the ion exchange membrane.

[0077] The anion exchange membrane can be any membrane that can recover organic acid ions such as acetate ions, and preferred examples thereof include anion exchange membranes using a strongly basic anion exchange resin or a weakly basic anion exchange resin having an amino group as a functional group, or a strongly basic anion exchange resin having a quaternary ammonium group. The cation exchange membrane can be any membrane capable of recovering sodium ions and the like, and preferred examples thereof include strongly acidic cation exchange membranes in which sulfonic groups have been introduced into a fluororesin matrix, such as Nafion 115, Nafion 212, and Nafion 350 (manufactured by Chemrous Chemicals); strongly acidic cation exchange membranes in which sulfonic groups have been introduced into a styrene-divinylbenzene copolymer matrix, such as Neosepta CSE (manufactured by Astom Chemicals); and hydrocarbon cation exchange membranes such as Selemion (manufactured by AGC Engineering).

[0078] As the electrochemical device, for example, a device as shown in Fig. 5 is preferably used. The electrochemical device shown in Fig. 5 includes an anode 1, a cathode 2, and a plurality of anion exchange membranes 3. The liquid 2 supplied as a catholyte to the cathode side of the electrochemical device, the aqueous solution A supplied as an anolyte to the anode side, and the liquid 1 and aqueous solution B discharged from the electrochemical device correspond to Fig. 1 in which the ion exchange membrane is an anion exchange membrane. Although not shown in the present specification, even when the ion exchange membrane of the electrochemical device is a cation exchange membrane, the device may have a plurality of cation exchange membranes, as in the case of an anion exchange membrane.

[0079] Liquid 2, supplied as the catholyte and anolyte, is an aqueous solution containing an organic acid metal, such as metal acetate, by-produced in the production of a lithium hydroxide aqueous solution. Preferably, it is an aqueous solution containing an organic acid metal, such as metal acetate, by-produced after recovering lithium hydroxide from the aqueous solution obtained by producing the lithium hydroxide aqueous solution. More specifically, liquid 2 contains an organic acid metal aqueous solution, as shown in FIGS. 1 to 4. When Method 1 is employed to obtain high-purity lithium hydroxide from a lithium hydroxide aqueous solution, the organic acid metal aqueous solution contains a Li-ion-removed aqueous solution containing an organic acid metal, obtained by removing lithium hydroxide from the lithium hydroxide aqueous solution by recovering only lithium ions using a lithium ion separation device (see FIGS. 3 and 4). When Method 2 is employed, the lithium hydroxide aqueous solution is crystallized, followed by solid-liquid separation 1, to obtain separated liquid 1-2. In the electrochemical device, organic acid ions, such as acetate ions, are recovered into the anolyte from the organic acid metal, such as metal acetate, contained in the catholyte (see FIGS. 1 and 2).

[0080] 1 and 3, when an anion exchange membrane is used as the ion exchange membrane of the electrochemical device, liquid 2 that becomes the catholyte may contain aqueous solution B together with the Li-ion-removed aqueous solution obtained by the lithium ion separation device or the separated liquid 1-2 obtained by solid-liquid separation 1. On the other hand, when a cation exchange membrane is used as the ion exchange membrane of the electrochemical device, liquid 2 that becomes the anolyte is the Li-ion-removed aqueous solution obtained by the lithium ion separation device or the separated liquid 1-2 obtained by solid-liquid separation 1, as shown in FIGS.

[0081] 1 and 3 has an anion exchange membrane, it is preferable to use, as the anolyte, an aqueous solution of lithium organic acid obtained by generating the aqueous solution of lithium organic acid and potassium hydroxide (aqueous solution A) by circulating them. By using an aqueous solution with a high salt concentration, for example, when a diaphragm-type electrochemical device is employed, it is possible to reduce the power required for diaphragm electrolysis and also reduce waste. When the electrochemical device has a cation exchange membrane and method 2 in FIG. 2 is adopted, a separated liquid 1-2 obtained by crystallizing an aqueous lithium hydroxide solution and performing solid-liquid separation 1 is used as the anolyte, whereas when the lithium ion separation device in FIG. 4 is adopted, a Li ion-removed aqueous solution (aqueous organic acid metal solution) is used.

[0082] Aqueous solution B discharged from the cathode side of the electrochemical device is a residual solution resulting from the recovery of organic acid ions from the organic acid metal contained in solution 2 when the electrochemical device has the anion exchange membrane of FIG. 1, or a solution resulting from the recovery of metal ions from the organic acid metal contained in solution 2 when the electrochemical device has the cation exchange membrane of FIG. 2, and is an aqueous solution containing metal hydroxide formed by the metal contained in the organic acid metal. In either case, aqueous solution B is an aqueous solution containing metal hydroxide, and therefore, from the viewpoint of reducing waste, it is preferably used for the reaction with the organic acid lithium in reaction tank 2. When the lithium ion separation device of FIGS. 3 and 4 is employed, aqueous solution B may also vary depending on the type of ion exchange membrane of the electrochemical device, and in either case, it is an aqueous solution containing metal hydroxide.

[0083] In the cases of Figures 1 and 2, the metal contained in the metal hydroxide undergoes a reaction in reaction tank 2 from metal hydroxide (aqueous solution B) to become an organic acid metal (aqueous solution C, separated liquid 1-2), as described above, and then in the electrochemical device, the organic acid metal (liquid 2) is converted to metal hydroxide (aqueous solution B), so the metal is circulated. Furthermore, in the case of the lithium ion separation device of Figures 3 and 4, the metal contained in the metal hydroxide becomes organic acid metal (aqueous solution C), as in the cases of Figures 1 and 2 above. Next, the metal is discharged from the lithium ion separation device as a Li ion-removed aqueous solution (organic acid metal aqueous solution), and in the electrochemical device, the organic acid metal (liquid 2) is converted to metal hydroxide (aqueous solution B), so the metal is circulated. Therefore, the circulating metal is the same as the metal contained in the metal hydroxide. Preferred examples of the metal contained in the metal hydroxide include sodium, potassium, barium, etc., more preferably sodium and potassium, and even more preferably potassium. These metals may be used alone or in combination.

[0084] Liquid 1 discharged from the electrochemical device becomes an aqueous solution containing a large amount of organic acid such as acetic acid, after organic acid ions have been recovered from the organic acid metal contained in liquid 2 (FIG. 1) or after metal ions contained in liquid 2 have been removed (FIG. 2). In the production method of this embodiment, liquid 1 is used as an organic acid such as acetic acid that reacts with lithium carbonate. The same applies when using the lithium ion separation device shown in FIGS. 3 and 4.

[0085] Furthermore, when the organic acid ions are recovered using an electrochemical device, hydrogen is generated from the anode and oxygen is generated from the cathode. The generated hydrogen and oxygen accompany the liquid 1 discharged from the electrochemical device and are generated as a mixed gas together with carbon dioxide when an aqueous solution of organic acid lithium is produced. As described above, carbon dioxide can be added as a mixed gas to a separated liquid 2, which is an aqueous solution of lithium hydroxide with reduced impurities, to obtain lithium carbonate (see also Figures 1 and 2). Furthermore, when a lithium ion separation device is provided, the mixed gas can be added to the recovered liquid discharged from the lithium ion separation device to obtain lithium carbonate, as shown in Figure 3.

[0086] (Lithium ion separation device equipped with a Li-permselective membrane) In the production method of this embodiment, it is preferable to use a lithium ion separator equipped with a Li permselective membrane to separate the lithium hydroxide aqueous solution obtained by generating the lithium hydroxide aqueous solution, and recover only the lithium ions into a recovered solution. By using the lithium ion separator, high-purity lithium hydroxide can be obtained without the need for chemicals, and high-purity lithium hydroxide can be easily obtained simply by crystallizing the recovered solution.

[0087] As shown in FIGS. 3 and 4, the lithium ion separation device 10 includes a raw solution tank 10a for supplying aqueous solution C (lithium hydroxide aqueous solution), a recovery solution tank 10b for storing a recovery solution, and a Li-permselective membrane 10c that selectively allows only lithium ions to pass through. As shown in FIGS. 3 and 4, lithium ions contained in the aqueous solution C (lithium hydroxide aqueous solution) supplied to the raw solution tank 10a pass through the Li-permselective membrane 10c and are recovered in the recovery solution. The lithium ion separation device 10 also includes a first electrode 10d (anode) in one tank (the raw solution tank 10a side) and a second electrode 10e (cathode) in the other tank (the recovery solution tank 10b side). In this way, lithium ions move from the anode side to the cathode side, thereby transferring from the aqueous solution C (lithium hydroxide aqueous solution) supplied to the raw solution tank 10a to the recovery solution in the recovery solution tank 10b. Next, the lithium ions recovered in the recovery solution are separated from lithium hydroxide produced in crystallization such as evaporation crystallization or cooling crystallization, and the filtrate is separated by solid-liquid separation or the like, and the lithium hydroxide is further dried as necessary to obtain high-purity lithium hydroxide.

[0088] The lithium ion separation device 10 may have a storage tank (not shown) for storing the raw solution and the recovered solution in the raw solution tank 10a and the recovered solution tank 10b. By having the storage tank, the raw solution and the recovered solution can be stored as needed, and the raw solution and the recovered solution can be circulated between the raw solution tank 10a and the storage tank, respectively, and therefore, it is possible to respond to various situations.

[0089] For example, if a storage tank for the recovered liquid is provided, the recovered liquid from which lithium ions have been recovered in the lithium ion separation device 10 can be circulated and temporarily stored in the storage tank, and when the concentration of lithium ions contained in the recovered liquid in the storage tank reaches a certain level or higher, the recovered liquid can be crystallized from the storage tank and subjected to necessary treatments such as solid-liquid separation to obtain lithium hydroxide as a product. Furthermore, it becomes easier to adjust the distribution of the recovered liquid depending on the required amounts of lithium hydroxide and lithium carbonate as products. Furthermore, for example, if a storage tank for the raw solution is provided, the raw solution can be circulated, and depending on the operating conditions of the lithium ion separation device, the aqueous solution C from the reaction tank 2 can be temporarily stored and then supplied to the raw solution tank 10a of the lithium ion separation device 10. Also, depending on the operating conditions of the electrochemical device, the Li ion-removed aqueous solution after lithium ions have been recovered in the lithium ion separation device 10 can be temporarily stored in the storage tank and then supplied to the electrochemical device.

[0090] The lithium ion separation device 10 used in the manufacturing method of this embodiment may be in the form of a single tank separated into a raw liquid tank 10a and a recovered liquid tank 10b by a Li-selective permeable membrane 10c, as shown in Figures 3 and 4, or may be in the form of two tanks, the raw liquid tank 10a and the recovered liquid tank 10b, connected via the Li-selective permeable membrane 10c.

[0091] The Li-permselective membrane is a membrane that has the function of transferring Li ions in the raw solution C (lithium hydroxide aqueous solution) to the recovered solution, and is usually installed to separate the raw solution C (lithium hydroxide aqueous solution) from the recovered solution (see Figures 3 and 4). The Li-permselective membrane preferably comprises a Li-permselective membrane body made of a super Li-ion conductor (ion conductor) with particularly high ionic conductivity, and a Li-adsorption layer formed as a thin layer on the side where the aqueous solution C (lithium hydroxide aqueous solution) serving as the raw solution is supplied.

[0092] Using a super Li-ion conductor as the Li-permselective membrane body can increase the ionic current of Li ions flowing between the electrodes, thereby improving the Li recovery efficiency. Here, the Li ions contained in the aqueous solution exist as Li hydrated ions, with water molecules coordinating around them. Therefore, in order to further increase the ionic current, it is effective to create a condition where water molecules can be easily removed from the surface of the Li-permselective membrane (the interface between the Li-permselective membrane and the raw solution). For this reason, it is preferable that a Li adsorption layer that adsorbs Li ions (excluding hydrates) in the Li ion extract is formed on the surface of the Li permselective membrane. That is, it is preferable that the Li permselective membrane is one that has been subjected to a surface Li adsorption treatment. As the Li adsorption layer, as will be described later, one that is formed by modifying the surface of the material that constitutes the Li permselective membrane is preferred.

[0093] Preferred materials for the Li permselective membrane body include, for example, the following oxides, oxynitrides, etc. containing Li. That is, the Li permselective membrane preferably contains the following oxides, oxynitrides, etc. containing Li. Examples of oxides containing Li include lithium lanthanum titanate (Li x ,La y )TiO z (where x=3a-2b, y=2 / 3-a, z=3-b, 0<a≦1 / 6、0≦b≦0.06、x> 0) (hereinafter also referred to as "LLTO"), lithium lanthanum zirconate: Li7La3Zr2O 12 (hereinafter also referred to as "LLZO"), lithium lanthanum niobate: Li5La3Nb2O 12 , lithium lanthanum tantalate: Li5La3Ta2O 12 The LLTO is more specifically Li 0.29 La 0.57 TiO3 (a≒0.1, b≒0) can be used.

[0094] These materials can be obtained as sintered bodies by mixing particles made of these materials with sintering aids and sintering the mixture at high temperatures (above 1000°C). In this case, the surface of the Li-permselective membrane can be configured as a porous structure in which fine particles made of LLTO are bonded (sintered), thereby increasing the effective surface area of ​​the Li-permselective membrane itself. This is true not only for LLTO, but also for other Li-containing oxides and oxynitrides, which will be described later.

[0095] As the super Li ion conductor that can be used as the material for constituting the Li permselective membrane body, in addition to the above-mentioned LLTO, LLZO, etc. as an oxide containing Li, for example, Li substituted NASICON (Na Super Ionic Conductor) type crystal, 1+x+y Al x (Ti,Ge) 2-x Si y P 3-y O 12 (where 0≦x≦0.6, 0≦y≦0.6) (Li2O-Al2O3-SiO2-P2O5-TiO2-GeO2 system, hereinafter also referred to as "LASiPTiGeO") and the like are also included.

[0096] Preferred examples of oxynitrides containing Li include lithium phosphate oxynite (Li3PON, hereinafter also referred to as "LiPON"), nitride of LLTO (LLTON), nitride of LLZO (LLZON), nitride of LASiPTiGeO (LASiPTiGeON), and the like.

[0097] The above-mentioned super Li-ion conductors, such as oxides and oxynitrides containing Li, contain Li as one of their constituent elements, and exhibit ionic conductivity when Li ions outside the crystal move between Li sites in the crystal. Li ions flow through the Li-selective membrane itself, but sodium ions cannot flow within the Li-selective membrane. In this case, it is the Li ions (Li + ) and the Li hydrate ions present in the original solution along with the Li ions cannot enter the Li sites and therefore do not conduct through the crystal. In this respect, it is the same as the Li permselective membrane described in WO2015 / 020121.

[0098] Here, if a large amount of lithium ions in particular are adsorbed onto the surface of the Li permselective membrane body by the Li adsorption layer, the water molecules of the lithium hydrated ions are removed during adsorption, leaving only lithium ions, thereby increasing the lithium ion conduction efficiency (ionic current flowing through the Li permselective membrane body) from the raw liquid side to the recovered liquid side in the Li permselective membrane body.

[0099] The Li-permselective membrane may not have an anode or a cathode, as shown in Figure 3, or may have an anode and a cathode bonded to it. When an anode and a cathode are provided, it is preferable that the anode be provided on the source liquid side of the Li-permselective membrane and the cathode be provided on the recovered liquid side. With this configuration, the solid-liquid interfaces on the source liquid side and recovered liquid side of the Li-permselective membrane are maintained at positive and negative potentials, respectively, enabling the recovery of lithium ions. The anode and cathode may be made of metal materials that do not undergo electrochemical reactions in the raw solution and recovered solution, such as SUS, Ti, Pt, Ni, Ti-Ir alloys, and alloys thereof.

[0100] Although the above materials used as Li-permselective membranes are solids, they are known to exhibit conductivity due to the flow of Li ions within the crystals in a form similar to free electrons. Therefore, when the anode is at a positive potential and the cathode is at a negative potential, Li ions (positive ions) in the source solution on the anode side that reach the cathode side of the Li-permselective membrane will flow by ionic conduction from the anode side (source solution) of the Li-permselective membrane to the cathode side (recovered solution). Li ions that reach the cathode side of the Li-permselective membrane are recovered in the recovered solution. Therefore, after a certain time has passed, the Li-ion concentration in the source solution decreases, while the Li-ion concentration in the recovered solution increases.

[0101] The Li adsorption layer is formed as a thin layer on the surface of the Li permselective membrane body by chemically treating the Li permselective membrane body. Specifically, it is formed by acid treatment of one main surface of the Li permselective membrane body (for example, LLTO), for example by exposing this surface to hydrochloric acid or nitric acid for 5 days. By this treatment, Li, which is particularly susceptible to oxidation among the constituent elements of the Li permselective membrane body (for example, LLTO), is replaced with hydrogen in the acid, and the Li adsorption layer is formed as H 0.29 La 0.57It is presumed that a layer of material (HLTO) with a composition similar to TiO3 is formed. The formation of a thin surface layer (HLTO) is supported by the X-ray diffraction results in WO2017 / 131051, which show peaks that are different from those of the Li permselective membrane itself (e.g., LLTO).

[0102] The H sites in HLTO were originally intended for Li, so H is particularly susceptible to substitution by Li ions, but is difficult to substitute by other ions (such as sodium ions). For this reason, HLTO functions as a Li adsorption layer. Furthermore, because HLTO is produced by a reaction with acid, it is only formed on the outermost surface of the Li permselective membrane itself.

[0103] The lithium ion separation device may also include a heater for heating the recovery liquid. Heating the recovery liquid increases the solubility of lithium ions in the recovery liquid, and the increased solubility of lithium ions is supplied from the lithium hydroxide aqueous solution that serves as the raw solution, allowing a large amount of lithium ions to be recovered.

[0104] (Operating conditions of lithium ion separator) When the recovery liquid is heated, the heating temperature is preferably 50° C. or higher, more preferably 60° C. or higher, even more preferably 70° C. or higher, and particularly preferably 80° C. or higher, and the upper limit is preferably 100° C. or lower, more preferably 95° C. or lower, and even more preferably 90° C. or lower. When the heating temperature is within the above range, lithium ions can be recovered more efficiently. The type of heater is not particularly limited, and for example, a jacket type or heater type heat exchanger using electricity or a heat medium can be used. Also, a part of the recovered liquid can be heated by circulating it through a heater, in which case a shell-tube type heat exchanger can also be used.

[0105] In the manufacturing method of this embodiment, the pH of the aqueous solution C (lithium hydroxide aqueous solution) that serves as the stock solution may be controlled. By controlling the pH, lithium ions can be efficiently recovered. In this case, it is preferable to adjust the pH to within a range of 12 to 14. Note that a pH of 12 to 14 is an adjustment target. In this embodiment, a pH of 12 to 14 includes, for the pH of the stock solution, a value of 12 includes a value of 11.5 to less than 12.5, and a pH of 14 includes a value of 13.5 to less than 14.5, and essentially means a range of 11.5 to less than 14.5.

[0106] The temperature of the aqueous solution C (lithium hydroxide aqueous solution) that serves as the raw solution may be adjusted, specifically, heated, in the same manner as the recovery solution. This makes it easier to adjust the temperature of the recovery solution to 50°C or higher, enabling highly efficient recovery of lithium ions. When adjusting the temperature of the raw solution, the adjusted temperature should be within the temperature adjustment range of the recovery solution.

[0107] (Crystallization and solid-liquid separation 1) In the production method of this embodiment, when the lithium ion separation device of the above-mentioned method 1 is used, it is preferable to crystallize the recovered solution obtained by recovering only lithium ions from the lithium hydroxide aqueous solution in the lithium ion separation device. By crystallization, lithium hydroxide can be purified and its purity can be improved. In this case, that is, when Method 1 is adopted in which high-purity lithium hydroxide is obtained from an aqueous lithium hydroxide solution by recovering only lithium ions using a lithium ion separation device equipped with a Li permselective membrane, the crystallization method is not particularly limited as long as lithium hydroxide can be obtained from the recovered solution. Preferred examples include filtration, cooling crystallization, evaporation crystallization, pH crystallization, and the like, and from the viewpoint of more efficiently obtaining high-purity lithium hydroxide, evaporation crystallization is more preferred.

[0108] In the lithium ion separation device, when the aqueous solution C (lithium hydroxide aqueous solution) that serves as the recovered solution or raw solution is heated, evaporation crystallization is preferably employed because it can reduce the energy required for evaporation. In the case of evaporation crystallization, the specific method is not particularly limited as long as it is carried out by a conventional evaporation crystallization technique, and for example, it is preferable to carry out the evaporation crystallization while adjusting the temperature preferably to 80° C. or higher and 100° C. or lower. From the viewpoint of carrying out evaporation crystallization more efficiently, the adjusted temperature is more preferably 85° C. or higher, and even more preferably 90° C. or higher.

[0109] From the viewpoint of more efficient evaporation and crystallization, evaporation and crystallization is preferably carried out under a reduced pressure atmosphere. By reducing the pressure, water vapor generated in the system can be discharged and added to the recovered liquid or the like for reuse. When reducing the pressure, there are no particular limitations on the pressure, and the vacuum pressure is usually about 0.05 to 10 kPa, and from the viewpoint of more efficient evaporation and crystallization, it is preferably 0.1 to 5 kPa, more preferably 0.2 to 1 kPa.

[0110] The evaporation and crystallization may be carried out while supplying an inert gas, such as nitrogen gas or argon gas. From the viewpoint of suppressing carbonation, the gas may contain oxygen as long as the concentration of carbon monoxide, carbon dioxide, or hydrocarbon is 10 ppm or less. To obtain lithium hydroxide with higher purity, the concentration is preferably 1 ppm or less, and more preferably 0.1 ppm.

[0111] The liquid from which lithium hydroxide has been crystallized, obtained by the above crystallization, is subjected to solid-liquid separation 1 to obtain lithium hydroxide as separated solid 1-1. It is preferable to remove impurities from the separated solid 1-1 by washing with ethanol or the like. Solid-liquid separation 1 may be carried out using a commonly used solid-liquid separation device, such as a vacuum filter, a pressure filter, a centrifuge, a belt press, a screw press, etc. The same applies to solid-liquid separations 2 to 5 described below.

[0112] Next, the ethanol is removed, preferably by drying at room temperature, to obtain purified lithium hydroxide. The lithium hydroxide of separated solid 1-1 has high purity and can be handled as a product produced by the production method of this embodiment. In addition, in this case (when method 1 is adopted), the recovered solution obtained in the lithium ion separation device recovers only lithium ions, so the amount of impurities is extremely small, and treatments such as redissolution in a redissolution tank and purification using a metal remover, which are preferably adopted in method 2, are not necessary. Furthermore, in the solid-liquid separation 1, the separated liquid 1-1, which is the liquid obtained after separating the lithium hydroxide from the separated solid 1-1, is an aqueous solution containing a trace amount of lithium hydroxide that could not be separated by crystallization. The separated liquid 1-1 may be supplied to a recovery liquid tank of a lithium ion separation device, as shown in Figures 3 and 4.

[0113] Furthermore, when the above-mentioned Method 2 is employed in the production method of this embodiment, the lithium hydroxide aqueous solution obtained by generating the above-mentioned lithium hydroxide aqueous solution may be crystallized. By crystallization, the lithium hydroxide can be purified and its purity can be improved. In this case, that is, when high-purity lithium hydroxide is obtained from an aqueous lithium hydroxide solution, if Method 2 is adopted in which an aqueous lithium hydroxide solution is obtained through crystallization, solid-liquid separation, redissolution, and impurity removal without using a lithium ion separation device, examples of the crystallization method include a filtration method, a heat concentration method, and a pH crystallization method, and from the viewpoints of efficiency and suppression of energy consumption, the pH crystallization method is preferred.

[0114] pH crystallization can be carried out, for example, by dropping an aqueous solution containing a metal hydroxide into an aqueous solution of lithium organic acid. Specifically, aqueous solution A (aqueous solution of lithium organic acid) or, if solid-liquid separation 4 is performed, separation liquid 4 is dropped into an aqueous solution containing a metal hydroxide (e.g., aqueous solution B such as an aqueous potassium hydroxide solution) obtained from an electrochemical device so that the molar ratio of potassium to lithium is preferably 0.5 times or more, more preferably 0.75 times or more, even more preferably equimolar (1.0 times) or more, and preferably 4.0 times or less, more preferably 3.5 times or less, even more preferably 3.0 times or less, to crystallize lithium hydroxide hydrate. In this case, the dropwise addition time of the aqueous solution of lithium organic acid and the aqueous potassium hydroxide solution is preferably 1 to 6 hours. Next, the liquid in which lithium hydroxide hydrate has crystallized due to the dropwise addition is preferably stirred for 15 minutes to 2 hours to mature the lithium hydroxide crystals.

[0115] 1 and 2, the crystallizer is shown as an independent device, but from the viewpoint of efficiency, in Method 2, it is preferable that the reaction tank 2 also serves as the crystallizer. As described above, crystallization can be carried out by adding dropwise the aqueous solution A or the separation liquid 4 that will serve as seed crystals to the aqueous solution B that will serve as the mother liquid. Therefore, as long as the reaction tank 2 is equipped with a means for adding dropwise the aqueous solution A or the separation liquid 4, the reaction between the organic acid lithium and the metal hydroxide and the crystallization can be carried out simultaneously, and therefore there is no need to provide a separate crystallizer.

[0116] The liquid in which lithium hydroxide crystals have been aged and in which lithium hydroxide has crystallized is subjected to solid-liquid separation 1, and the separated solid 1-2 obtained is preferably washed with ethanol or the like to remove impurities. In the case of Method 2, solid-liquid separation 1 may be carried out using a commonly used solid-liquid separation device, similar to solid-liquid separation 1 in Method 1 above. Examples of solid-liquid separation devices that can be used include a vacuum filter, a pressure filter, a centrifuge, a belt press, and a screw press.

[0117] Next, purified lithium hydroxide is obtained by removing the ethanol, preferably by drying at room temperature, etc. The lithium hydroxide of the separated solid 1-2 has high purity and can be handled as a product produced by the production method of this embodiment. Furthermore, the purity of the lithium hydroxide is improved by undergoing a treatment such as redissolution described below, so it is of course possible to handle the lithium hydroxide that has undergone this treatment as a product.

[0118] Furthermore, the separated liquid 1-2 obtained by the solid-liquid separation 1 is an aqueous solution containing an organic acid metal as described above, and is supplied to an electrochemical device, where organic acid ions are recovered from the organic acid metal, and the resulting aqueous solution (aqueous solution B) containing the metal hydroxide is used in a reaction with an organic acid lithium to obtain lithium hydroxide.

[0119] (Redissolution and solid-liquid separation 2) In the production method of this embodiment, when Method 2 is employed to obtain high-purity lithium hydroxide from an aqueous lithium hydroxide solution, it is preferable to include producing an aqueous lithium hydroxide solution using the lithium hydroxide (separated solid 1-2) obtained by the above crystallization and solid-liquid separation 1, adding a metal remover that removes metals that form organic acid metals to the aqueous solution, and performing solid-liquid separation 2. Producing an aqueous lithium hydroxide solution using the lithium hydroxide that is separated solid 1-2 is also referred to as "redissolution," because lithium hydroxide is converted back into an aqueous lithium hydroxide solution. By redissolving the lithium hydroxide, adding a metal remover, and performing solid-liquid separation 2, impurities such as metals that form organic acid metals, which may be contained in the lithium hydroxide purified by the above crystallization, can be removed, and lithium hydroxide with higher purity can be obtained.

[0120] For the redissolution, pure water can be supplied as needed to dissolve the lithium hydroxide, or a separated liquid 3 obtained by solid-liquid separation 3 described below can be used. The aqueous solution D obtained by redissolution is an aqueous solution containing highly pure lithium hydroxide.

[0121] The re-melting may be carried out at room temperature, or may be carried out with heating as necessary. Heating allows for faster re-melting, which improves time efficiency, but leads to a loss of thermal energy, which reduces energy efficiency. Therefore, the need for heating can be determined according to the requirements. When heating is performed, the heating temperature is not particularly limited and cannot be determined in general because it may vary depending on the properties of the low-grade lithium carbonate that is the starting material, the scale of the apparatus, and the like. However, in consideration of the balance between the time and the consumption of thermal energy, the heating temperature is preferably 40°C or higher, more preferably 60°C or higher, and the upper limit is preferably 90°C or lower, more preferably 85°C or lower.

[0122] Redissolution may be carried out with stirring. Stirring allows for faster redissolution, improving time efficiency, but it also leads to energy loss, reducing energy efficiency. Therefore, the need for stirring can be determined based on the user's needs. In the case of stirring, the stirring time (time required for redissolution) is not particularly limited, and cannot be determined in general because it may vary depending on the properties of the low-grade lithium carbonate that is the starting material, the scale of the apparatus, and the like. However, in consideration of the balance between time and energy consumption, the stirring time is preferably 10 minutes or more, more preferably 30 minutes or more, and the upper limit is preferably 3 hours or less, more preferably 2 hours or less, and even more preferably 1.5 hours or less.

[0123] The metal remover to be added to the aqueous solution D obtained by redissolution may be selected appropriately depending on the metal to be removed. For example, when the metal to be removed is potassium, which is particularly preferred in the production method of this embodiment, hexafluorosilicic acid (HSiF) or the like can be preferably used.

[0124] The separated solid 2 obtained by the solid-liquid separation 2 contains impurities such as potassium and magnesium that may be contained in the lithium hydroxide of the separated solid 1-2. Furthermore, the separated liquid 2 obtained by the solid-liquid separation 2 is an aqueous solution containing highly pure lithium hydroxide from which these impurities have been removed.

[0125] (Cooling and solid-liquid separation 3) In the production method of this embodiment, when Method 2 is employed to obtain high-purity lithium hydroxide from an aqueous lithium hydroxide solution, cooling the aqueous solution containing high-purity lithium hydroxide, which is separated liquid 2 obtained by solid-liquid separation 2, causes the lithium hydroxide to recrystallize, and by performing solid-liquid separation 3, high-purity lithium hydroxide is obtained as separated solid 3. The lithium hydroxide in separated solid 3 is the product produced by the production method of this embodiment.

[0126] The separated liquid 3 obtained by solid-liquid separation 3 is a saturated aqueous solution containing lithium hydroxide that did not recrystallize upon the cooling. From the viewpoint of reducing waste, the separated liquid 3 may be used for the redissolution. Although the separated liquid 3 is a saturated aqueous solution containing lithium hydroxide, during redissolution, the temperature of the separated liquid 3 naturally rises to the temperature before cooling, making it possible to dissolve further lithium hydroxide. The separated liquid 3 may be heated before use, if necessary.

[0127] When lithium hydroxide is produced by the production method of this embodiment, separated solids 1-2 and 3 obtained by solid-liquid separation 1 and solid-liquid separation 3 can be used as products. These lithium hydroxides are usually monohydrates (LiOH HO). The obtained lithium hydroxide can be used as is depending on the application, or can be further dehydrated before use. The dehydration of lithium hydroxide monohydrate may be carried out by conventional drying methods such as heating and vacuuming.

[0128] (Oxalic acid addition and solid-liquid separation 4) As shown in FIGS. 1 and 2 , the production method of this embodiment preferably further includes adding oxalic acid to an aqueous solution of lithium organic acid (aqueous solution A) obtained by generating an aqueous solution of lithium organic acid, and performing solid-liquid separation 4. By adding oxalic acid, calcium and other heavy metals that may be contained in the low-grade lithium carbonate contained in the organic acid lithium aqueous solution (aqueous solution A) can be precipitated. Then, the precipitated impurities can be removed as separated solids 4 by solid-liquid separation 4.

[0129] The separated liquid 4 obtained by solid-liquid separation 4 is an aqueous solution of lithium organic acid (aqueous solution A) from which impurities have been removed as separated solid 4. Therefore, it is preferable to generate an aqueous solution of lithium hydroxide by reacting separated liquid 4 with a metal oxide. Since the amount of impurities in solid-liquid separation 4 is small, lithium hydroxide with improved purity can be obtained as a result.

[0130] When the lithium ion separation devices of FIGS. 3 and 4 are employed, it is advisable to add aqueous solution B (aqueous solution containing metal hydroxide) discharged from the cathode side of the electrochemical device instead of oxalic acid.

[0131] (Addition of carbon dioxide and solid-liquid separation 5) 3 and 4, the production method of this embodiment further includes adding carbon dioxide to the recovered liquid and performing solid-liquid separation 5, and the lithium carbonate contained in the separated liquid 5 obtained by performing solid-liquid separation 5 can be used to produce the lithium organic acid aqueous solution. When Method 2 is used to obtain high-purity lithium hydroxide from an aqueous lithium hydroxide solution, as shown in FIGS. 1 and 2, carbon dioxide is added to the separated liquid 2 in the same manner as the recovered liquid, and the separated liquid 5 is performed, and the lithium carbonate contained in the separated liquid 5 obtained by performing solid-liquid separation 5 can be used to produce the lithium organic acid aqueous solution.

[0132] The recovered liquid and separated liquid 2 are aqueous solutions containing highly pure lithium hydroxide, and when carbon dioxide is added to the recovered liquid and separated liquid 2, highly pure lithium carbonate is obtained. By performing solid-liquid separation 5, highly pure lithium carbonate is obtained as separated solid 5. The lithium carbonate of separated solid 5 is a product produced by the production method of this embodiment.

[0133] Carbon dioxide is preferably generated by producing an aqueous solution of lithium organic acid. According to the above chemical reaction formula (1), carbon dioxide is generated by reacting lithium carbonate with an organic acid such as acetic acid. Although the carbon dioxide can be disposed of as is, from the viewpoint of reducing waste, it is preferable to use it when producing lithium carbonate from lithium hydroxide. As shown in Figures 1 and 2, in reaction vessel 1, liquid 1 (an acid containing an organic acid such as acetic acid) reacts with liquid 3 (lithium carbonate liquid), and carbon dioxide is added to separated liquid 2 in the form of a mixed gas.

[0134] [Lithium compound manufacturing equipment] The lithium compound manufacturing apparatus of this embodiment includes: The reactor 1 includes a reactor 2, an electrochemical device, and a return pipe. the reaction tank 1 is a tank in which lithium carbonate, an acid including an organic acid, and water are mixed to produce an aqueous solution of lithium organic acid, the reaction tank 2 is a tank in which the organic acid lithium aqueous solution and a metal hydroxide are mixed to produce a lithium hydroxide aqueous solution, the electrochemical device is a device for regenerating an organic acid used in producing the lithium organic acid aqueous solution from an aqueous solution obtained by removing lithium hydroxide from the lithium hydroxide aqueous solution, The return pipe is a pipe for returning the regenerated organic acid to the reaction tank 1. This is a manufacturing device.

[0135] The functions of reaction tank 1, reaction tank 2, and the electrochemical device, namely, reaction tank 1 performs the function of mixing lithium carbonate with an acid including an organic acid such as acetic acid to cause a reaction and thereby produce an aqueous solution of lithium organic acid, reaction tank 2 performs the function of mixing the aqueous solution of lithium organic acid with a metal hydroxide to cause a reaction and thereby produce an aqueous solution of lithium hydroxide, and the electrochemical device performs the function of regenerating an organic acid such as acetic acid used in producing the aqueous solution of lithium organic acid from an aqueous solution obtained by removing lithium hydroxide from the aqueous solution of lithium hydroxide, are as described above in the method for producing a lithium compound of this embodiment.

[0136] The types of reaction tanks 1 and 2 are not particularly limited as long as they are tanks that can cause the above reaction by mixing, and ordinary tank-shaped reaction tanks may be used. Furthermore, in order to perform mixing in these reaction tanks, they may be equipped with a stirrer or heating equipment as necessary. The configuration of the electrochemical device is as explained in the method for producing a lithium compound of this embodiment.

[0137] Carbon dioxide is produced as a by-product by the reaction caused by mixing an organic acid such as acetic acid with lithium carbonate in the reaction tank 1, and the by-product carbon dioxide is added to the separated liquid 2 as a mixed gas, but some of the carbon dioxide is dissolved in the aqueous solution A (aqueous solution of lithium organic acid) supplied from the reaction tank 1. The carbon dioxide dissolved in the aqueous solution A causes lithium carbonate to be produced in the subsequent reaction tank 2, or in the redissolution tank when Method 2 is employed. Lithium carbonate can be an impurity when lithium hydroxide is produced by the production method of this embodiment. Therefore, it is preferable that the reaction tank 2 is provided with a means for supplying an inert gas as a means for removing carbon dioxide from the aqueous solution. In this case, it is preferable that the inert gas supply means is designed to supply the inert gas by bubbling.

[0138] Regarding the production of lithium carbonate using carbon dioxide, it is preferable that the downstream of the reaction tank 2 and the redissolving tank, i.e., the solid-liquid separation tanks 2, 3, and 5, have an inert gas supply means that can create an inert gas atmosphere. It is also preferable to bubble an inert gas in the redissolving tank. By providing such a means, when lithium carbonate can become an impurity, carbon dioxide, which is a cause of the impurity, can be removed, thereby suppressing the production of lithium carbonate.

[0139] (crystallizer) The lithium compound production apparatus of this embodiment preferably further includes a crystallizer for crystallizing the recovered solution. When Method 2 is employed to obtain high-purity lithium hydroxide from an aqueous lithium hydroxide solution, the apparatus preferably includes a crystallizer for crystallizing the aqueous lithium hydroxide solution. By including a crystallizer, the purity of the lithium hydroxide can be improved.

[0140] The crystallization device included in the lithium compound production apparatus of this embodiment is as described above in the lithium compound production method of this embodiment. For example, when Method 2 is employed to obtain high-purity lithium hydroxide from an aqueous lithium hydroxide solution, as described above, the reaction tank 2 in the production apparatus of this embodiment can also be used, and in terms of efficiency, it is preferable to use the reaction tank 2 for both purposes. If the reaction tank 2 is equipped with a stirrer for stirring the aqueous solution B that serves as the mother liquor and the aqueous solution A to be dropped, and is equipped with a means for dropping the aqueous solution A, etc., it can also function as a crystallization device. In this case, a separate, independent crystallization device is not required. The crystallization performed in the crystallizer is as explained in the method for producing a lithium compound of this embodiment, and there are no particular limitations on the type of crystallizer as long as it can perform the crystallization method to be adopted. When Method 1 is adopted to obtain high-purity lithium hydroxide from an aqueous lithium hydroxide solution, it is preferable to adopt a crystallizer that can perform evaporative crystallization, and when Method 2 is adopted, it is preferable to adopt a crystallizer that can perform pH crystallization.

[0141] (Other devices) The production apparatus of this embodiment is required to include a reaction vessel 1, a reaction vessel 2, an electrochemical device, and a return pipe, and preferably includes a lithium ion separation device equipped with a Li-permselective membrane, and a crystallization device. Here, the lithium ion separation device equipped with a Li permselective membrane is a device employed when Method 1 is employed to obtain high-purity lithium hydroxide from a lithium hydroxide aqueous solution. The configuration of the lithium ion separation device is as described above in the lithium compound production method of this embodiment. By including the lithium ion separation device, the production device of this embodiment can obtain high-purity lithium hydroxide without the need for chemicals, and can easily produce high-purity lithium hydroxide simply by crystallizing the recovered liquid. In this case, the production device may also be equipped with a crystallizer for crystallizing the recovered liquid, a solid-liquid separator, and, if necessary, a dryer for drying, etc.

[0142] When Method 2 is adopted to obtain high-purity lithium hydroxide from an aqueous lithium hydroxide solution, a crystallizer may be used. Furthermore, as shown in Figures 1 to 4, the production apparatus of this embodiment may also include, in addition to the above, a solid-liquid separation apparatus capable of performing solid-liquid separations 1 to 5, a means for supplying an organic acid such as oxalic acid, a means for supplying a metal-removing agent, a redissolving tank for redissolving lithium hydroxide, and a means for cooling lithium hydroxide. These devices and the like may be provided depending on the method employed in the method for producing a lithium compound according to the present embodiment.

[0143] (storage tank) The manufacturing apparatus of this embodiment may be provided with a storage tank (not shown) as needed. For example, as described above, when a lithium ion separation device is used, a storage tank for storing the raw solution and the recovered solution can be provided. By providing storage tanks for the raw solution and the recovered solution, various operations can be accommodated.

[0144] The provision of a storage tank for the recovered solution facilitates the circulation of the recovered solution, the storage of the recovered solution until the lithium ions contained in the recovered solution reach a predetermined concentration or higher, and the adjustment of the distribution of the recovered solution in accordance with the required amounts of lithium hydroxide and lithium carbonate to be used as products, thereby improving the operability of the production apparatus of this embodiment. On the other hand, the provision of a storage tank for the raw solution facilitates the circulation of the raw solution and the temporary storage of the aqueous solution C and the Li ion-removed aqueous solution in accordance with the operating conditions of the lithium ion separation device and the electrochemical device, thereby improving the operability of the production apparatus of this embodiment.

[0145] In addition to the above, examples of storage tanks include storage tanks for storing the liquid 2 and aqueous solutions A and B, which are liquids to be supplied to the electrochemical device. Providing storage tanks for storing the liquids to be supplied to the electrochemical device makes it easy to adjust the supply amount depending on the operating status of the electrochemical device, thereby improving the operability of the manufacturing device of this embodiment.

[0146] Pure water may be supplied to the lithium ion separation device and the electrochemical device as needed, but by supplying the water to a storage tank first and then to the electrochemical device, the supply of pure water can be easily managed, improving the operability of the manufacturing device of this embodiment.

[0147] The reactor may be equipped with a storage tank for storing the raw materials, i.e., lithium carbonate, water, and organic acid. For example, in Figures 1 to 4, water is shown to be supplied to the lithium carbonate line. The raw material low-grade lithium carbonate (crude lithium carbonate) is supplied in the form of a slurry as described above, but a storage tank for adjusting the slurry may be provided. In this case, the raw material low-grade lithium carbonate (crude lithium carbonate) and water may be supplied, mixed in advance, and supplied to the reaction tank 1 in the form of a slurry. By providing a storage tank, the supply amount of the low-grade lithium carbonate slurry can be adjusted depending on the mixing status in the reaction tank 1, thereby improving the operability of the production apparatus of this embodiment.

[0148] 1 to 4, the organic acid is shown to be supplied directly to the reaction tank 1. The organic acid is also temporarily stored in a storage tank in advance, and the supply amount of the organic acid can be adjusted depending on the mixing condition in the reaction tank 1, etc., thereby improving the operability of the production apparatus of this embodiment. [Example]

[0149] The present invention will now be described in detail with reference to examples, but the present invention is not limited to these examples in any way.

[0150] (measurement of atomic content) After weighing the sample, dilute nitric acid (3% by mass aqueous solution) was added to dissolve it, and the content of various atoms contained in the sample, such as the lithium ion extract, was measured using an ICP optical emission spectrometer (model number "5100 ICP-OES", manufactured by Agilent Technologies, Inc.).

[0151] (Purity measurement) The purity of the lithium hydroxide was calculated by weighing the lithium hydroxide obtained in the examples in a glove box (dew point: approximately −100°C, nitrogen atmosphere), dissolving it in water, and measuring the purity using a potentiometric titrator ("COM-1600 (model number)" manufactured by Hiranuma Sangyo Co., Ltd.).

[0152] Example 1 Low-grade lithium carbonate containing the elements shown in Table 1, prepared according to the following (Preparation of low-grade lithium carbonate), was prepared, and lithium hydroxide and lithium carbonate were produced using the lithium compound production apparatus shown in FIG. 1. The purity of the obtained lithium hydroxide was 99.9%, meaning that lithium hydroxide of extremely high purity was obtained. The operation of each step in each device in the lithium compound production apparatus was carried out as follows.

[0153] (Preparation of low-grade lithium carbonate) The low-grade lithium carbonate used as the starting material was prepared by adding metals such as Ca and Mg as impurity components to lithium carbonate (commercially available), assuming that the lithium carbonate was derived from brine, to prepare the product shown in Table 1. The purity of the lithium carbonate in the low-grade lithium carbonate was 90.7% by mass.

[0154] (Reaction tank 1 and oxalic acid treatment) In reaction vessel 1, acetic acid was mixed with the aqueous solution containing the above-mentioned low-grade lithium carbonate (lithium carbonate content: 99.0 mol%) so that the molar ratio of acetic acid to lithium carbonate was 1.1 times, to prepare a 4.72 mol / L lithium acetate solution (aqueous solution A). The Ca content of the lithium acetate solution (aqueous solution A) was 0.90 mol%. Next, oxalic acid was added in an amount 1.1 times the molar ratio of the Ca concentration in aqueous solution A, and the resulting white solid (separated solid 4) was separated by filtration (solid-liquid separation 4). The above treatment was carried out at room temperature (25°C). Here, filtration (solid-liquid separation 4) was performed by vacuum filtration. A common commercially available filter paper ("No. 5 (model number)" manufactured by Advantech Toyo Co., Ltd.) was used, and filtration was performed under reduced pressure in a polypropylene container. A tabletop diaphragm-type dry vacuum pump was used. The other solid-liquid separations 1 to 3 and 5, which will be described later, were also performed using the same method as this solid-liquid separation 4.

[0155] (Reaction tank 2) The mixing ratio of potassium hydroxide and lithium acetate was adjusted as follows depending on the molar ratio of potassium to lithium (K / Li metal molar ratio): While stirring a 50 mass % aqueous solution of potassium hydroxide (aqueous solution B, mother liquid) supplied from an electrochemical device at a stirring speed of 30 rpm, the lithium acetate solution (separated liquid 4) obtained in solid-liquid separation 4 was added dropwise until the molar ratio of potassium to lithium (K / Li metal molar ratio) reached 1.5, and stirring was continued for 24 hours to crystallize and mature lithium hydroxide crystals.

[0156] (Re-dissolving tank and solid-liquid separation 2) In a redissolution tank, 30 g of lithium hydroxide (separated solid 1) obtained by the above crystallization and aging was redissolved in 70 ml of pure water to prepare 100 g of lithium hydroxide aqueous solution. Next, hexafluorosilicic acid was added to the prepared solution (aqueous solution D) in a molar ratio of 0.5 times the potassium in the solution, and after stirring for 2 hours, the product (white solid) was separated by filtration (solid-liquid separation 2). The purified lithium hydroxide aqueous solution was left to cool overnight at approximately 10°C, and the cooled solution was filtered (solid-liquid separation 3) to obtain lithium hydroxide (white crystals).

[0157] (Electrochemical Equipment) The electrochemical device used was an iridium-coated titanium plate for the anode plate (oxygen generating electrode), a stainless steel plate for the cathode plate, and an AHO membrane (manufactured by Asahi Glass Co., Ltd.) for the anion exchange membrane. A portion of the lithium acetate solution (aqueous solution A) obtained in reaction vessel 1 was supplied to the anode side, and separated liquid 1 obtained from reaction vessel 2 (crystallization) and solid-liquid separation 1 was supplied to the cathode side, and the electrochemical reaction was carried out at a constant current of 1 A. The diaphragm layer capacity of the electrochemical device was 200 ml, and the effective electrode area was 4.0 × 3.0 cm. 2 is.

[0158] (Lithium carbonate production) A mixed gas mainly containing carbon dioxide (CO2) generated in the reaction vessel 1 was blown into the separated liquid 2 (aqueous lithium hydroxide solution) obtained by the solid-liquid separation 2 for 30 minutes so that the molar ratio of carbon dioxide (CO2) relative to the lithium hydroxide in the separated liquid 2 became 0.5, and the solution was then filtered (solid-liquid separation 5) to obtain white crystals (lithium carbonate) as separated solid 5. The purity of the obtained lithium carbonate was 99.5%, and the yield was 30%.

[0159] Example 2 Lithium carbonate was obtained in the same manner as in Example 1, except that the crystallization in reaction tank 2 was carried out by adding a lithium acetate solution (separation liquid 4) dropwise until the molar ratio of potassium to lithium (K / Li metal molar ratio) became 2.5. The purity of the obtained lithium carbonate was 99.5%, and the yield was 45%.

[0160] [Table 1]

[0161] Example 3 Using the lithium compound production apparatus shown in FIG. 3, the lithium hydroxide aqueous solution obtained in reaction tank 2 was supplied to the lithium ion separation apparatus as follows. In Example 1, in a reaction tank 2 containing 200 mL of the lithium acetate battery material solution (separated liquid 4) obtained in solid-liquid separation 4, a 5 M aqueous sodium hydroxide solution (aqueous solution B, mother liquid) was added dropwise while stirring at a stirring speed of 30 rpm until the pH reached 13, thereby obtaining an aqueous lithium hydroxide solution containing lithium ions. The obtained aqueous solution C was placed in a stock solution tank as a stock solution, and a 0.1 M aqueous lithium hydroxide solution was placed in a recovery solution tank as a recovery solution. A voltage of 5 V was applied between the two electrodes, and Li ions were recovered in the recovery solution. After applying voltage for 240 hours, the recovered solution from which Li ions were recovered was subjected to evaporation and crystallization. The precipitated solid matter was subjected to X-ray diffraction (XRD) measurement, and it was confirmed that only lithium hydroxide monohydrate was produced (purity: 99.9%).

[0162] Example 4 In Example 3, an electrochemical device equipped with a cation exchange membrane was used, and 200 mL of the Li-ion-removed aqueous solution after recovering lithium ions was placed in the anode chamber of the electrochemical device, and 200 mL of a 0.1 M aqueous sodium hydroxide solution was placed in the cathode chamber, and an electrochemical reaction was carried out for 24 hours at a constant current of 1 A. The sodium concentrations in the aqueous sodium hydroxide solution placed in the cathode side before and after the electrochemical reaction were 0.1 M and 3.5 M, respectively. The lithium compound production device used in Example 4 is shown in FIG. 4.

[0163] After the electrochemical reaction, the aqueous solution on the cathode side was supplied to reaction tank 2 as aqueous solution B, and the pH in reaction tank 2 became 13.2. This aqueous solution from reaction tank 2 was supplied to a lithium ion separation device, and a voltage of 5 V was applied between the two electrodes for 24 hours, recovering the lithium ions in the recovery solution and conducting evaporation and crystallization. X-ray diffraction (XRD) measurement of the precipitated solid confirmed that only lithium hydroxide monohydrate was produced (purity: 99.9%). From the results of Examples 3 and 4 above, it was confirmed that high-purity lithium hydroxide can be obtained regardless of whether an anion exchange membrane or a cation exchange membrane is used as the ion exchange membrane provided in the electrochemical device.

[0164] (Preparation Example 1) In a reaction vessel 1, formic acid was mixed with the aqueous solution containing low-grade lithium carbonate used in Example 1 (lithium carbonate content: 99.0 mol%) so that the molar amount was 1.1 times that of lithium carbonate, to prepare a 4.72 mol / L lithium formate solution.

[0165] (Preparation Example 2) In a reaction vessel 1, citric acid was mixed with the aqueous solution containing low-grade lithium carbonate used in Example 1 (lithium carbonate content: 99.0 mol%) so that the molar amount of citric acid was 1.1 times that of lithium carbonate, to prepare a 4.72 mol / L lithium citrate solution.

[0166] (Reference example 1) To the lithium acetate solution (4.7 mol%) used in reaction tank 1 of Example 1, an aqueous solution of sodium hydroxide (sodium hydroxide concentration: 1 mol%) was added so that the amount of Na was 1.5 times the amount (moles) of lithium contained in the lithium organic acid solution, and the resulting solution was subjected to evaporation crystallization. The precipitated salt was separated into solid and liquid by filtration, and the separated liquid was evaporated and dried. X-ray diffraction (XRD) measurement of the powder sample confirmed that lithium hydroxide monohydrate had been produced.

[0167] Example 5 The lithium formate solution obtained in Preparation Example 1 was subjected to solid-liquid separation of the salt obtained in the same manner as in Reference Example 1 above, and the separated liquid was evaporated and dried to obtain a powder sample. X-ray diffraction (XRD) measurement was then performed on the powder sample, and it was confirmed that lithium hydroxide monohydrate was produced. Therefore, it is believed that when formic acid is used as the organic acid, high-purity lithium hydroxide can be obtained, just like when acetic acid is used.

[0168] From the examples, it was confirmed that the lithium compound production method and production apparatus of the present embodiment can efficiently produce a high-purity lithium compound from low-grade lithium carbonate containing impurities such as brine, etc. Furthermore, it was found that organic acids such as formic acid, oxalic acid, and citric acid can also be used to efficiently produce high-purity lithium compounds, similar to acetic acid.

Claims

1. mixing lithium carbonate, an acid containing an organic acid, and water in a reaction tank 1 to generate an aqueous solution of lithium organic acid containing a lithium organic acid; The lithium organic acid and the metal hydroxide are mixed in a reaction tank 2 to produce an aqueous lithium hydroxide solution; and an organic acid regenerated from an organic acid metal by-produced in the production of the lithium hydroxide aqueous solution using an electrochemical device, and the regenerated organic acid is returned to the reaction tank 1 and used as the organic acid; A method for producing a lithium compound, comprising:

2. 2. The method for producing a lithium compound according to claim 1, wherein the metal hydroxide is regenerated by the electrochemical device and returned to the reaction vessel (2).

3. 3. The method for producing a lithium compound according to claim 1, further comprising recovering only lithium ions from the aqueous lithium hydroxide solution into a recovery solution using a lithium ion separation device equipped with a Li permselective membrane.

4. The method for producing a lithium compound according to claim 3 , further comprising crystallizing the recovered solution recovered using the lithium ion separation device to perform solid-liquid separation 1.

5. 4. The method for producing a lithium compound according to claim 3, wherein the organic acid metal is supplied to the electrochemical device from a Li ion-removed aqueous solution obtained by recovering only lithium ions from the lithium hydroxide aqueous solution into the recovery solution using a lithium ion separation device including the Li permselective membrane.

6. 2. The method for producing a lithium compound according to claim 1, further comprising adding oxalic acid to the aqueous solution of lithium organic acid and performing solid-liquid separation (4).

7. 7. The method for producing a lithium compound according to claim 6, wherein the lithium hydroxide aqueous solution is produced by reacting a separated liquid 4 obtained by performing the solid-liquid separation 4 with the metal hydroxide.

8. Further, carbon dioxide is added to the recovered liquid to perform solid-liquid separation 5. Including, The lithium carbonate contained in the separated liquid 5 obtained by the solid-liquid separation 5 is used to generate the lithium organic acid aqueous solution. The method for producing a lithium compound according to claim 3 .

9. 9. The method for producing a lithium compound according to claim 8, wherein the carbon dioxide is generated by producing the aqueous solution of lithium organic acid.

10. The method for producing a lithium compound according to claim 4, wherein lithium hydroxide is obtained by carrying out the solid-liquid separation 1.

11. The method for producing a lithium compound according to claim 8, wherein lithium carbonate is obtained by performing the solid-liquid separation (5).

12. 2. The method for producing a lithium compound according to claim 1, wherein the metal forming the metal hydroxide and the metal forming the organic acid metal are the same.

13. 2. The method for producing a lithium compound according to claim 1, wherein the metal is at least one selected from the group consisting of sodium, potassium, and barium.

14. The reactor 1 includes a reactor 2, an electrochemical device, and a return pipe. the reaction tank 1 is a tank in which lithium carbonate, an acid including an organic acid, and water are mixed to produce an aqueous solution of lithium organic acid, the reaction tank 2 is a tank in which the organic acid lithium aqueous solution and a metal hydroxide are mixed to produce a lithium hydroxide aqueous solution, the electrochemical device is a device for regenerating an organic acid used in producing the lithium organic acid aqueous solution from an aqueous solution obtained by removing lithium hydroxide from the lithium hydroxide aqueous solution, The return pipe is a pipe for returning the regenerated organic acid to the reaction tank 1. Lithium compound manufacturing equipment.

15. 15. The lithium compound manufacturing apparatus according to claim 14, further comprising a lithium ion separation device equipped with a Li selective permeable membrane for recovering only lithium ions from the lithium hydroxide aqueous solution into a recovery liquid.

16. The apparatus for producing a lithium compound according to claim 15, further comprising a crystallizer for crystallizing the recovered solution.

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