Method of preparing hydroxide

Abstract

To provide an efficient method of preparing hydroxide including at least one element selected from a group consisting of nickel, cobalt, and manganese.SOLUTION: A method of preparing hydroxide comprises: a sulfuric acid-adding step of adding sulfuric acid to a material; a filtering step of filtering a liquid obtained in the sulfuric acid-adding step through an ultrafiltration membrane; a sodium hydroxide-adding step of adding sodium hydroxide to a mixed liquid containing the filtrate obtained in the filtering step; and a hydroxide concentration step of filtering, through the ultrafiltration membrane, a sodium sulfate-containing solution containing a hydroxide including the element and sodium sulfate. The ultrafiltration membrane in the hydroxide concentration step is a hollow fiber membrane, and a linear velocity at an inlet of the hollow fiber membrane is 0.3 m / sec or more and less than 1.5 m / sec.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The present invention relates to a method for producing hydroxides.

Background Art

[0002] In recent years, the demand for lithium-ion secondary batteries has been increasing as power sources for mobile devices such as mobile phones and notebook computers, and for electric vehicles and hybrid vehicles. Oxides containing cobalt elements, lithium elements, etc. are used as the positive electrode active material of lithium-ion batteries. Conventionally, as methods for producing hydroxides containing at least one element selected from the group consisting of nickel, cobalt, and manganese, the methods of Patent Documents 1 and 2 are known.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Patent Document 2

Summary of the Invention

Problems to be Solved by the Invention

[0004] Although Patent Documents 1 and 2 are methods for efficiently obtaining hydroxides containing at least one element selected from the group consisting of nickel, cobalt, and manganese, in recent years, a more efficient method, specifically, a manufacturing method that is less likely to clog during filtration even when the circulation amount of the liquid flowing during manufacturing is increased, has been demanded.

[0005] Therefore, an object of the present invention is to provide an efficient method for producing hydroxides containing at least one element selected from the group consisting of nickel, cobalt, and manganese.

Means for Solving the Problems

[0006] That is, the present invention is as follows. [1] A sulfuric acid addition step of adding sulfuric acid to a material containing at least one element selected from the group consisting of nickel, cobalt, and manganese, and / or an inorganic compound containing at least one element selected from the group consisting of nickel, cobalt, and manganese, A filtration step of filtering the liquid obtained in the sulfuric acid addition step through an ultrafiltration membrane, A sodium hydroxide addition step of adding sodium hydroxide to a mixed solution containing the filtrate obtained in the filtration step and containing ions of the element and SO4 2- ions, and A hydroxide concentration step of filtering the sodium sulfate-containing solution containing the hydroxide containing the element and sodium sulfate obtained in the sodium hydroxide addition step through an ultrafiltration membrane to concentrate the hydroxide, having The ultrafiltration membrane in the hydroxide concentration step is a hollow fiber membrane, and the linear velocity at the hollow fiber membrane inlet is 0.3 m / sec or more and less than 1.5 m / sec. A method for producing a hydroxide containing at least one element selected from the group consisting of nickel, cobalt, and manganese, characterized in that. [2] The manufacturing method according to [1], wherein the ultrafiltration membrane in the hydroxide concentration step is in a crossflow mode. [3] The manufacturing method according to [1] or [2], wherein the inner diameter of the hollow fiber membrane is 1.0 mm or more and 2.3 mm or less. [4] The manufacturing method according to any one of [1] to [3], wherein the linear velocity is 0.5 m / sec or more and less than 1.3 m / sec. [5] The manufacturing method according to any one of [1] to [4], wherein the concentration of the hydroxide in the sodium sulfate-containing solution is 300 g / L or more and less than 600 g / L. [6] The manufacturing method according to [4], wherein the concentration of the hydroxide in the sodium sulfate-containing solution is 600 g / L or more and less than 1200 g / L. [7] The production method according to any one of [1] to [6], wherein the particle size (D50) of the hydroxide in the sodium sulfate-containing solution is 1 μm or more and less than 12 μm. [8] The production method according to any one of [1] to [7], wherein the particle size (D50) D (unit: μm) of the hydroxide in the sodium sulfate-containing solution, the concentration C (unit: g / L) of the hydroxide in the sodium sulfate-containing solution, and the linear velocity S (unit: m / sec) at the hollow fiber membrane inlet satisfy the following relationship (1). 50 < D × C × S < 24000 ···(1)

Advantages of the Invention

[0007] According to the present invention, it is possible to provide a method for producing a hydroxide containing at least one element selected from the group consisting of nickel, cobalt, and manganese with high efficiency.

Brief Description of the Drawings

[0008]

Figure 1

Figure 2

Figure 3

Embodiments for Carrying Out the Invention

[0009] Hereinafter, embodiments for carrying out the present invention will be described in detail. Note that the present invention is not limited to the following description and can be variously modified and implemented within the scope of the gist.

[0010] [Method for Producing Hydroxide] The method for producing a hydroxide according to this embodiment includes a sulfuric acid addition step of adding sulfuric acid to a material containing at least one simple substance of an element selected from the group consisting of nickel, cobalt, and manganese, and / or an inorganic compound containing at least one element selected from the group consisting of nickel, cobalt, and manganese, a filtration step of filtering the liquid obtained in the sulfuric acid addition step through an ultrafiltration membrane, and the ions of the above elements and SO4 2- A sodium hydroxide addition step of adding sodium hydroxide to a mixed solution containing the filtrate obtained in the filtration step and containing the ions of the above elements and SO4 ions, and a hydroxide concentration step of filtering the sodium sulfate-containing solution containing the hydroxide containing the above elements and sodium sulfate obtained in the sodium hydroxide addition step through an ultrafiltration membrane to concentrate the hydroxide. The ultrafiltration membrane in the hydroxide concentration step is a hollow fiber membrane, and the linear velocity at the hollow fiber membrane inlet is 0.3 m / sec or more and less than 1.5 m / sec. Furthermore, a recovery step of recovering sulfuric acid and / or sodium hydroxide by at least one ion exchange membrane selected from the group consisting of an anion exchange membrane and a cation exchange membrane from the sodium sulfate solution separated in the hydroxide concentration step may be included. Also, it is preferable to reuse the sodium hydroxide recovered in the recovery step in the sodium hydroxide addition step. Further, it is preferable to reuse the sulfuric acid recovered in the recovery step in the sulfuric acid addition step.

[0011] Also, the method for producing a hydroxide according to this embodiment includes a sulfuric acid addition step to a cobalt material of adding sulfuric acid to a cobalt material containing a simple substance of cobalt and / or an inorganic compound containing cobalt to obtain cobalt sulfate, a filtration step of cobalt sulfate of filtering the liquid obtained in the sulfuric acid addition step to the cobalt material through an ultrafiltration membrane, a sulfuric acid addition step to a nickel material of adding sulfuric acid to a nickel material containing a simple substance of nickel and / or an inorganic compound containing nickel to obtain nickel sulfate, a filtration step of nickel sulfate of filtering the liquid obtained in the sulfuric acid addition step to the nickel material through an ultrafiltration membrane, A step of adding sulfuric acid to a manganese material containing manganese in its elemental form and / or an inorganic compound containing manganese to obtain manganese sulfate, the step of adding sulfuric acid to the manganese material, A filtration step of manganese sulfate in which the liquid quality obtained in the step of adding sulfuric acid to the manganese material is filtered through an ultrafiltration membrane, The cobalt ions obtained in the filtration step of cobalt sulfate and SO4 2- The filtrate containing ions, the nickel ions obtained in the filtration step of nickel sulfate and SO4 2- The filtrate containing ions, and the manganese ions obtained in the filtration step of manganese sulfate and SO4 2- A mixing step of mixing the filtrates containing ions, A sodium hydroxide addition step of adding sodium hydroxide to the mixed solution obtained in the mixing step, An hydroxide concentration step of filtering the sodium sulfate-containing solution containing at least one element selected from the group consisting of nickel, cobalt, and manganese and sodium sulfate obtained in the sodium hydroxide addition step through an ultrafiltration membrane to concentrate the hydroxide, Furthermore, a recovery step of recovering sulfuric acid and / or sodium hydroxide from the sodium sulfate solution separated in the hydroxide concentration step by at least one ion exchange membrane selected from the group consisting of an anion exchange membrane and a cation exchange membrane, It may be a production method that may include. Furthermore, it is preferable to reuse the sodium hydroxide recovered in the recovery step in the sodium hydroxide addition step. Also, furthermore, it is preferable to reuse the sulfuric acid recovered in the recovery step in at least one step selected from the group consisting of the step of adding sulfuric acid to the cobalt material, the step of adding sulfuric acid to the nickel material, and the step of adding sulfuric acid to the manganese material.

[0012] In this specification, the solution before filtration supplied to the filtration membrane (preferably an ultrafiltration membrane in a crossflow mode) may be referred to as the feed solution, the solution purified through the filtration membrane as the filtrate (filtration liquid), and the solution discharged as it is without passing through the filtration membrane as the discharge solution.

[0013] Figs. 1 and 2 are schematic diagrams showing an example of the method for producing a hydroxide according to this embodiment. In the example of Fig. 1, in the method for producing a hydroxide according to this embodiment, sulfuric acid is added to the material (sulfuric acid addition step). Next, the liquid obtained in the sulfuric acid addition step is filtered by ultrafiltration (filtration step). The discharged liquid obtained in the filtration step may be returned to the sulfuric acid addition step and added to the above material again. That is, the above liquid may be a mixture of the above material, the above sulfuric acid, and the above discharged liquid. Next, sodium hydroxide is added to the filtrate obtained in the filtration step (sodium hydroxide addition step). In the sodium hydroxide addition step, ammonia may be added together with sodium hydroxide. Further, the discharged liquid of the hydroxide concentration step described later and the sodium hydroxide of the recovery step described later may be mixed. That is, the above mixed liquid may be a mixture of the above filtrate, sodium hydroxide, and the discharged liquid of the hydroxide concentration step. Next, the sodium sulfate-containing solution obtained in the sodium hydroxide addition step is filtered by ultrafiltration to concentrate the hydroxide contained in the sodium sulfate-containing solution (hydroxide concentration step). Here, when ammonia is added in the sodium hydroxide addition step, the sodium sulfate-containing solution may contain ammonium sulfate. Furthermore, sulfuric acid and sodium hydroxide may be recovered from the sodium sulfate solution, which is the filtrate of the hydroxide concentration step, by an ion exchange membrane and reused in the sulfuric acid addition step and the sodium hydroxide addition step. Here, when the sodium sulfate-containing solution contains ammonium sulfate, the sodium sulfate solution, which is the filtrate after ultrafiltration, may contain sodium sulfate and ammonium sulfate. Also, ammonium sulfate may be recovered by an ion exchange membrane.

[0014] Fig. 2 is a schematic diagram showing an example of the above hydroxide concentration step and the above recovery step. The sodium sulfate solution obtained in the hydroxide concentration step is once stored in a liquid tank and then sodium hydroxide and sulfuric acid are recovered using CW-1 including a cation exchange membrane and an anion exchange membrane. The recovered sodium hydroxide and sulfuric acid may be once stored in respective recovery tanks and then reused. In addition, when the sodium sulfate concentration in the sodium sulfate solution is low, it may be concentrated with a reverse osmosis membrane (RO membrane), and the concentrated sodium sulfate solution may be added to the above liquid phase. Also, the recovered hydroxide may be stored in a liquid storage tank once, and then dried or the like may be performed.

[0015] According to the method for producing hydroxide of the present embodiment, the amount of waste can be significantly reduced, so it is very excellent in terms of cost and environment. In addition, since purification is performed using an ultrafiltration membrane, a hydroxide with extremely little impurity contamination can be obtained. Also, when concentrating hydroxide in a circulation system, a hydroxide with a large particle size can be obtained. Further, when a sodium sulfate concentration step is provided, the water permeated through the reverse osmosis membrane can be reused, so the amount of water used can also be significantly reduced.

[0016] (Sulfuric acid addition step) In the above sulfuric acid addition step, as the material to which sulfuric acid is added, it may be only a simple substance of at least one element selected from the group consisting of nickel, cobalt, and manganese, and / or only an inorganic compound containing at least one element selected from the group consisting of nickel, cobalt, and manganese, or it may be a mixture further containing the effluent obtained in the filtration step described later, etc., or a mixture further containing other additives, etc.

[0017] As the at least one element selected from the group consisting of nickel, cobalt, and manganese, it may be the three kinds of nickel, cobalt, and manganese, and among them, cobalt is preferable.

[0018] Examples of the inorganic compound include metal compounds containing at least one element selected from the group consisting of nickel, cobalt, and manganese, such as minerals containing the above elements.

[0019] In the sulfuric acid addition step, examples of the material to which sulfuric acid is added include cobalt alone and / or a cobalt material containing cobalt, nickel alone and / or a nickel material containing nickel, manganese alone and / or a manganese material containing manganese, and the like. The cobalt material may be cobalt alone and / or only an inorganic compound containing cobalt, or may be a mixture further containing the effluent obtained in the filtration step described below, a mixture further containing other additives, or the like. It is preferable that the cobalt material does not contain nickel and manganese. The nickel material may be nickel alone and / or only an inorganic compound containing nickel, or may be a mixture further containing the effluent obtained in the filtration step described below, a mixture further containing other additives, or the like. It is preferable that the nickel material does not contain cobalt and manganese. The manganese material may be manganese alone and / or only an inorganic compound containing manganese, or may be a mixture further containing the effluent obtained in the filtration step described below, a mixture further containing other additives, or the like. It is preferable that the manganese material does not contain cobalt and nickel.

[0020] The concentrations of cobalt, nickel, and manganese in the above materials are not particularly limited. For example, as long as a hydroxide having an iron content (mass ratio) of 0.1 ppm or less can be obtained by the method of this embodiment.

[0021] The above material may be liquid or solid.

[0022] The amount of sulfuric acid added in the sulfuric acid addition step, the amount of sulfuric acid added in the sulfuric acid addition step to the cobalt material, the amount of sulfuric acid added in the sulfuric acid addition step to the nickel material, and the amount of sulfuric acid added in the sulfuric acid addition step to the manganese material are not particularly limited, and sulfuric acid may be sequentially added until each material is completely dissolved.

[0023] In the sulfuric acid addition step, stirring may or may not be performed during the addition of sulfuric acid.

[0024] In the sulfuric acid addition step, after adding sulfuric acid, the pH may be adjusted to precipitate an element having a different ionization tendency from the above element, and impurities may be removed more efficiently in the filtration step described later.

[0025] By the sulfuric acid addition step, a liquid mass containing a sulfide (for example, cobalt sulfate, nickel sulfate, and / or manganese sulfate) containing at least one element contained in the above material selected from the group consisting of nickel, cobalt, and manganese can be obtained.

[0026] (Filtration step) In the filtration step, the liquid mass obtained in the sulfuric acid addition step is supplied to ultrafiltration, and filtration is performed to obtain a filtrate from which impurity metals such as iron have been removed. Further, if there is a solution that is discharged without being filtered by ultrafiltration, it may be circulated and used in the sulfuric acid addition step.

[0027] The ultrafiltration membrane used in the filtration step may be a crossflow type or a dead-end type (total volume filtration type). Among them, when there are many impurities in the feed liquid (for example, 0.1 mass% or more), the crossflow type is preferable, and when there are few impurities in the feed liquid (for example, less than 0.1 mass%), the dead-end type is preferable. In the case of an ultrafiltration membrane of the crossflow type, the discharge liquid that has not been filtered and discharged is preferably mixed with the above liquid mass obtained in the sulfuric acid addition step and filtered again with the ultrafiltration membrane.

[0028] The ultrafiltration may be an internal pressure type or an external pressure type. In the case of the crossflow filtration type, internal pressure filtration is preferable, and in the case of the dead-end filtration type, external pressure filtration is preferable. Among them, from the viewpoint of being less likely to have turbidity adhere to the membrane surface and being able to efficiently filter a high-concentration liquid, internal pressure filtration of the crossflow type is preferable.

[0029] The retention pore size of the ultrafiltration membrane is preferably 3,000 to 1,000,000 in terms of the molecular weight cut-off, and more preferably 6,000 to 100,000.

[0030] As the ultrafiltration membrane, for example, "Microza UF" (manufactured by Asahi Kasei Corporation) or the like can be used.

[0031] In the above filtration step, from the viewpoint of more efficiently removing impurities such as iron, it is preferable to replace the solution when the iron concentration in the feed liquid supplied to the ultrafiltration membrane or the discharge liquid discharged from the ultrafiltration membrane becomes high. Among them, it is preferable to replace the solution when the mass ratio of iron hydroxide in 100% by mass of the above feed liquid or discharge liquid reaches 5% by mass, and when the iron hydroxide in the feed liquid is extremely small, it may be replaced when it reaches 0.1% by mass. The above iron concentration can be measured by providing a measuring instrument for measuring the iron concentration near the supply port or the discharge port of the ultrafiltration membrane. In addition, the solution to be replaced may be mixed with the mixed liquid in the sodium hydroxide addition step described later after removing iron components by a filtration membrane of the total amount filtration method or the like.

[0032] In the filtration step of the above cobalt sulfate, the filtration step of the above nickel sulfate, and the filtration step of the above manganese sulfate, the same ultrafiltration membrane and filtration conditions as above are preferable.

[0033] The filtrate obtained in the above filtration step may be continuously used in the subsequent mixing step or sodium hydroxide addition step, or may be used after being stored in a storage tank or the like.

[0034] By the above filtration step, a filtrate containing ions of at least one element selected from the group consisting of nickel, cobalt, and manganese, and SO4 2- ions can be obtained.

[0035] (Mixing Step) When the filtration step is divided into a plurality of steps such as the filtration step of cobalt sulfate, the filtration step of nickel sulfate, and the filtration step of manganese sulfate, a mixing step may be provided to mix the filtrates and the like obtained in each step before the sodium hydroxide addition step described later. For example, in the above mixing step, the cobalt ions and SO4 obtained in the filtration step of cobalt sulfate, 2- the filtrate containing ions, the nickel ions and SO4 obtained in the filtration step of nickel sulfate, 2- the filtrate containing ions, and the manganese ions and SO4 obtained in the filtration step of manganese sulfate, 2- the filtrate containing ions may be mixed to obtain a mixed solution, or the cobalt ions and SO4 obtained in the filtration step of cobalt sulfate, 2- the filtrate containing ions, the nickel ions and SO4 obtained in the filtration step of nickel sulfate, 2- the filtrate containing ions, and the liquid quality obtained in the sulfuric acid addition step to the manganese material may be mixed to obtain a mixed solution, or further other additives, the discharge liquid obtained in the hydroxide concentration step described later, etc. may be mixed. Note that when using the liquid quality obtained in the sulfuric acid addition step to the manganese material and not performing the filtration of manganese sulfate, the filtration step of manganese sulfate may not be provided.

[0036] In the above mixed solution, the filtrate containing cobalt ions and SO4 2- ions, the filtrate containing nickel ions and SO4 2- ions, and the solution or filtrate containing manganese ions and SO4 2- ions may not have an equal mass ratio. For example, from the perspective of suppressing the usage amount of expensive cobalt, the amount of the filtrate containing nickel ions may be increased and the amount of the filtrate containing cobalt ions may be decreased. Specifically, the mass ratio of the filtrate containing nickel in the 100% by mass of the mixed solution may be 35 - 90% by mass.

[0037] The mixed solution obtained in the above mixing step may be continuously used in the sodium hydroxide addition step described later, or may be used after being stored in a storage tank or the like.

[0038] (Sodium Hydroxide Addition Step) In the sodium hydroxide addition step, ions of at least one element selected from the group consisting of nickel, cobalt, and manganese and SO4 2-A mixed solution containing the filtrate obtained in the above filtration step containing ions, or sodium hydroxide is added to the mixed solution obtained in the above mixing step to obtain a sodium sulfate-containing solution containing the hydroxide of the above element and sodium sulfate. In the above sodium hydroxide addition step, from the viewpoint of controlling the reaction rate and particle shape, it is preferable to add ammonia in addition to sodium hydroxide. Sodium hydroxide and ammonia may be added separately or may be mixed in advance and then added. Here, it is preferable that the above hydroxide contains all of at least one element selected from the group consisting of nickel, cobalt, and manganese contained in the material used in the sulfuric acid addition step. In addition, when an element is added in an intermediate step, it may further contain the added element.

[0039] The above mixed solution may be only the above filtrate, or may be a mixed solution in which the filtrate is mixed with the discharge liquid obtained in the hydroxide concentration step described later, the above other additives, etc. That is, the above filtrate may contain the discharge liquid containing the above hydroxide discharged from the ultrafiltration membrane in the hydroxide concentration step. The above mixed solution preferably contains a hydroxide containing at least one element selected from the group consisting of nickel, cobalt, and manganese, and the ratio of the above hydroxide in 100% by mass of the above mixed solution is preferably 10% by mass or more. The ratio of the above hydroxide in the above mixed solution can be increased by mixing and circulating the discharge liquid of the hydroxide concentration step into the above mixed solution, adjusting the ratio of sodium hydroxide, ammonia, ammonium sulfate, and the filtrate in the mixed solution, etc. In the sodium hydroxide addition step, the ratio of the total added mass of ammonia and ammonium sulfate to the added mass of sodium hydroxide (100% by mass) is preferably 10 to 80% by mass.

[0040] In the above sodium hydroxide addition step, it is preferable to continue adding sodium hydroxide until precipitation stops. In the above sodium hydroxide addition step, it is preferable to continue adding ammonia until precipitation stops.

[0041] In the above sodium hydroxide addition step, stirring may or may not be performed during the addition of sodium hydroxide.

[0042] As the temperature at the time of adding sodium hydroxide in the above sodium hydroxide addition step, from the viewpoint of suppressing the crystallization of sodium sulfate, it is preferably 32°C or higher, more preferably 40°C or higher. In the method for producing a hydroxide of the present embodiment, the temperature of the solution containing sodium sulfate is preferably 32°C or higher. Specifically, the mixed solution obtained by mixing the sodium sulfate-containing solution, the sodium sulfate solution, and the discharge liquid of the hydroxide concentration step is preferably 32°C or higher.

[0043] (Hydroxide concentration step) In the above hydroxide concentration step, a sodium sulfate-containing solution containing at least one element selected from the group consisting of nickel, cobalt, and manganese obtained in the above sodium hydroxide addition step and sodium sulfate is filtered through an ultrafiltration membrane, and separated into a sodium sulfate solution (filtrate) excluding the hydroxide and a solution containing the hydroxide (discharge liquid). Here, when ammonia is added in the sodium hydroxide addition step, the sodium sulfate-containing solution may contain at least one element selected from the group consisting of nickel, cobalt, and manganese obtained in the sodium hydroxide addition step, sodium sulfate, and ammonium sulfate, and can be filtered through an ultrafiltration membrane to be separated into a sodium sulfate solution (filtrate) containing sodium sulfate and ammonium sulfate excluding the hydroxide and a solution containing the hydroxide (discharge liquid).

[0044] As a method for suppressing the deposition of adhering substances on the membrane surface of the ultrafiltration membrane, various methods are known. As one technique, a method of performing filtration at a high linear velocity (for example, 2.0 m / sec or higher) is known. In particular, when the feed liquid is a slurry, the adhering substances are likely to deposit on the membrane surface, and the filtration efficiency is likely to decrease. The sodium sulfate-containing solution is a slurry. The inventors have tried various methods from the perspective of suppressing the deposition of deposited substances on the membrane surface and increasing efficiency in the method for producing a hydroxide containing at least one element selected from the group consisting of nickel, cobalt, and manganese described above, and as one of them, filtration at a high linear velocity was also tried. Surprisingly, in a sodium sulfate-containing solution containing a hydroxide containing at least one element selected from the group consisting of nickel, cobalt, and manganese, it was found that when filtration is performed at a high linear velocity, the membrane surface is damaged and stable production is difficult. In membrane filtration of a slurry, even when filtration is performed at a high linear velocity, the membrane surface is not damaged, which is a problem peculiar to the method for producing a hydroxide containing at least one element selected from the group consisting of nickel, cobalt, and manganese. Further, it was found that even when filtration is performed at a low linear velocity, deposited substances are less likely to accumulate on the membrane surface. Then, when further examination was carried out on the linear velocity in the hydroxide concentration step in the method for producing a hydroxide containing at least one element selected from the group consisting of nickel, cobalt, and manganese described above, it was found that particularly when filtration is performed in the range where the linear velocity at the hollow fiber membrane inlet is 0.3 m / sec or more and less than 1.5 m / sec, the efficiency is good. Further, by performing filtration at a low linear velocity, the power of the pump can be reduced.

[0045] The linear velocity at the hollow fiber membrane inlet is preferably 0.5 m / sec or more and less than 1.3 m / sec, more preferably 0.5 to 1.2 m / sec. The inventors conducted studies on the linear velocity and found a suitable combination of the hydroxide concentration in the sodium sulfate-containing solution, which is the feed solution for ultrafiltration, and the linear velocity. Specifically, when the concentration of the hydroxide in the sodium sulfate-containing solution is 300 g / L or more and less than 600 g / L, it was found that the hydroxide can be produced more efficiently when the linear velocity at the hollow fiber membrane inlet is 0.3 m / sec or more and less than 1.5 m / sec (more preferably 0.4 to 1.4 m / sec, and even more preferably 0.5 to 1.3 m / sec). Further, when the concentration of the hydroxide in the sodium sulfate-containing solution is 600 g / L or more and less than 1200 g / L, it was found that the hydroxide can be produced more efficiently when the linear velocity at the hollow fiber membrane inlet is 0.5 m / sec or more and less than 1.3 m / sec (more preferably 0.5 to 1.2 m / sec, and even more preferably 0.7 to 1.1 m / sec). Incidentally, the linear velocity at the hollow fiber membrane inlet is calculated by dividing the circulation flow rate (m 3 / s) by the total opening area (m 2 ) of the hollow fiber membranes contained in the membrane module. Also, the concentration of the hydroxide in the sodium sulfate-containing solution can be measured using the feed solution to the ultrafiltration membrane as a sample.

[0046] The ultrafiltration membrane is a hollow fiber membrane. A module in which a plurality of hollow fiber membranes are bundled and housed in a case may be used. Incidentally, when a plurality of hollow fiber membranes are used, the linear velocity at the hollow fiber membrane inlet, the inner diameter of the hollow fiber membrane described later, etc. may be the average value of each hollow fiber membrane.

[0047] From the viewpoint of more efficiently producing the hydroxide, the inner diameter of the hollow fiber membrane is preferably 1.0 mm or more and 2.3 mm or less, more preferably 1.1 to 2.0 mm, and even more preferably 1.3 to 1.9 mm.

[0048] The concentration of the hydroxide in the sodium sulfate-containing solution supplied to the ultrafiltration membrane is preferably 300 to 1500 g / L, more preferably 300 to 1300 g / L, and even more preferably 300 to 1200 g / L.

[0049] The particle size (D50) of the hydroxide in the sodium sulfate-containing solution supplied to the ultrafiltration membrane is preferably 1 μm or more and less than 12 μm, more preferably 2 to 11 μm, and even more preferably 3 to 10 μm. The particle size (D50) can be measured by the method described in the examples below.

[0050] In the hydroxide concentration step, from the viewpoint that the surface of the ultrafiltration membrane is less likely to be scraped and the hydroxide can be produced more efficiently, the particle size (D50) D (unit: μm) of the hydroxide in the sodium sulfate-containing solution, the concentration C (unit: g / L) of the hydroxide in the sodium sulfate-containing solution, and the linear velocity S (unit: m / sec) at the inlet of the hollow fiber membrane preferably satisfy the following relationship (1), more preferably satisfy the following relationship (2), and even more preferably satisfy the following relationship (3). 50 < D × C × S < 24000 ···(1) 200 < D × C × S < 18000 ···(2) 400 < D × C × S < 14000 ···(3)

[0051] In the hydroxide concentration step, from the viewpoint of more efficiently producing the hydroxide, the pressure (Pi) at the inlet of the ultrafiltration membrane is preferably 0.1 to 0.3 MPa, more preferably 0.13 to 0.2 MPa. Also, from the viewpoint of more efficiently producing the hydroxide, the pressure (Po) at the outlet of the ultrafiltration membrane is preferably 0.01 to 0.08 MPa, more preferably 0.02 to 0.06 MPa. The pressure at the inlet or outlet of the ultrafiltration membrane can be measured by pressure gauges installed on the inlet side and outlet side of the circulation.

[0052] The ultrafiltration membrane may be an organic membrane or an inorganic membrane. Examples of the organic membrane include membranes made of resins such as polyvinylidene fluoride (PVDF), polyethylene (PE), polysulfone (PSF), polyacrylonitrile (PAN), polyethersulfone (PES), polytetrafluoroethylene (PTFE), ethylene tetrafluoroethylene (ETFE), cellulose, cellulose triacetate, and polyamide. Examples of the inorganic membrane include ceramic membranes made from metal oxides such as alumina, mullite, titania, and zirconia, etc.

[0053] In the ultrafiltration membrane in the hydroxide concentration step, a crossflow ultrafiltration membrane is preferred. For the crossflow ultrafiltration membrane, it is preferable to mix the discharged liquid that is discharged without being filtered into the above-mentioned mixed liquid in the sodium hydroxide addition step.

[0054] In the hydroxide concentration step, it is preferable to keep the hydroxide concentration in the feed liquid supplied to the ultrafiltration membrane or the discharged liquid discharged from the ultrafiltration membrane at a certain level or higher. The mass ratio of the hydroxide in the feed liquid or discharged liquid per 100% by mass is preferably 1 to 40% by mass, more preferably 10 to 20% by mass. The hydroxide concentration may be measured by providing a device for measuring the concentration near the feed port or discharge port of the ultrafiltration membrane.

[0055] By recovering the hydroxide concentrated in the hydroxide concentration step, a hydroxide containing at least one element selected from the group consisting of nickel, cobalt, and manganese can be obtained. When mixing the discharged liquid discharged without being filtered in the hydroxide concentration step into the above-mentioned mixed liquid in the sodium hydroxide addition step, from the viewpoint of suppressing the decrease in the water permeation performance of ultrafiltration, when the mass ratio of the hydroxide in the feed liquid or discharged liquid per 100% by mass to the ultrafiltration membrane during the hydroxide concentration step reaches 50% by mass, it is preferable to recover the solution. The obtained solution may be further purified and concentrated by centrifugation, drying, filter press, etc. to obtain the hydroxide.

[0056] Recovery process In the above recovery process, sulfuric acid and sodium hydroxide are separated and recovered from the sodium sulfate solution separated in the above hydroxide concentration process and reused, so that the amount of the solution to be discarded can be significantly reduced, the cost associated with the discard can be reduced, and the environmental pollution associated with the discard can be reduced. When ammonium sulfate is contained in the sodium sulfate solution, ammonium sulfate may be separated and recovered.

[0057] As the ion exchange membrane used in the above recovery process, at least one selected from the group consisting of an anion exchange membrane and a cation exchange membrane is preferable, and it is more preferable to use an anion exchange membrane and a cation exchange membrane. For example, the sodium sulfate solution is passed between an anion exchange membrane and a cation exchange membrane in a container whose interior is separated by an anion exchange membrane and a cation exchange membrane, and by diffusion dialysis, SO4 2- ions are concentrated by the anion exchange membrane, and Na + is concentrated by the cation exchange membrane, so that it may be separated into sulfuric acid and sodium hydroxide (CW-1 in FIG. 2). The anion exchange membrane and the cation exchange membrane may be used alone or in combination of a plurality of types.

[0058] When sodium hydroxide is recovered by a cation exchange membrane in the recovery process, it is preferable to reuse the recovered sodium hydroxide in the above sodium hydroxide addition process. The recovered sodium hydroxide may be reused in its entirety or partially. The metal content in 100% by mass of the recovered sodium hydroxide is preferably 1 ppm or less. The mass ratio of the sodium hydroxide recovered in the above recovery process to 100% by mass of the total amount of sodium hydroxide added in the above sodium hydroxide addition process is preferably 20% by mass or more. When sulfuric acid is recovered by an anion exchange membrane in the recovery step, the recovered sulfuric acid is preferably reused in the sulfuric acid addition step described above. The entire amount or a part of the recovered sulfuric acid may be reused. The metal content in 100% by mass of the recovered sulfuric acid is preferably 1 ppm or less. The mass ratio of the sulfuric acid recovered in the recovery step to 100% by mass of the total amount of sulfuric acid added in the sulfuric acid addition step is preferably 20% by mass or more. When ammonium sulfate is recovered by an ammonium sulfate recovery device in the recovery step, the recovered ammonium sulfate can be reused as a fertilizer or the like. Since the recovered sodium hydroxide and / or sulfuric acid contains only the components obtained by removing the impurity metal components from the raw materials used for the production of the hydroxide of the present embodiment, it is a solution suitable for the method for producing the hydroxide of the present embodiment, in which unintended impurities and impurity metal components are very small.

[0059] The method for producing a hydroxide according to the present embodiment may further include a sodium sulfate concentration step of concentrating the sodium sulfate solution with a reverse osmosis membrane when the concentration of sodium sulfate in 100% by mass of the sodium sulfate solution separated in the hydroxide concentration step is less than 15% by mass, so that the concentration of sodium sulfate in 100% by mass of the sodium sulfate solution becomes 15% by mass or more (Figure 2). The sodium sulfate concentration step can be provided, for example, between the hydroxide concentration step and the recovery step. By using the concentrated sodium sulfate solution in the recovery step, sulfuric acid and sodium hydroxide can be recovered more efficiently.

[0060] In the method for producing a hydroxide according to the present embodiment, the hydroxide obtained is Ni x Co y Mn z (OH)2 (wherein x, y, and z satisfy x + y + z = 1) is preferably a hydroxide represented by. As the above x, 0 ≦ x < 1 may be satisfied, preferably 0.2 ≦ x ≦ 0.9, and more preferably 0.5 ≦ x ≦ 0.8. As for the above y, it may be 0 ≦ y ≦ 1, and preferably 0 ≦ y ≦ 0.4. Also, y is preferably smaller than x. As for the above z, it may be 0 ≦ z < 1, and preferably 0 ≦ z ≦ 0.4.

[0061] The hydroxide obtained by the method for producing a hydroxide of the present embodiment can be used, for example, as a raw material for a positive electrode active material of a lithium ion battery or the like.

[0062] [Method for producing a positive electrode active material] The hydroxide obtained by the method for producing a hydroxide of the above-described present embodiment can be used for the production of a positive electrode active material. Examples of the method for producing the positive electrode active material include a method including a lithium compound mixing step of mixing the above hydroxide and a lithium compound to form a lithium mixture, and a firing step of firing the lithium mixture obtained in the lithium compound mixing step.

[0063] The above positive electrode active material can be used in a lithium ion battery or the like.

[0064] [Apparatus for producing a hydroxide] Examples of the apparatus used in the method for producing the hydroxide of the present embodiment described above include, for example, a reaction vessel A used in a sulfuric acid addition step of adding sulfuric acid to a material containing a simple substance of the above element and / or an inorganic compound containing the above element; an ultrafiltration membrane A used in a filtration step of filtering the above liquid mass; a liquid path A connecting the reaction vessel A and the ultrafiltration membrane A; a reaction vessel B used in a sodium hydroxide addition step of adding sodium hydroxide to a mixed solution containing the filtrate of the ultrafiltration membrane used in the above filtration step; a liquid path connecting the ultrafiltration membrane A and the reaction vessel B and passing the filtrate of the ultrafiltration membrane A; an ultrafiltration membrane B used in a hydroxide concentration step of filtering a sodium sulfate-containing solution containing the hydroxide containing the above element and sodium sulfate; a liquid path B connecting the reaction vessel B and the ultrafiltration membrane B; a container C including at least one ion exchange membrane selected from the group consisting of an anion exchange membrane and a cation exchange membrane used in a recovery step of recovering sulfuric acid and sodium hydroxide from the sodium sulfate solution separated by the ultrafiltration membrane B; a liquid path connecting the ultrafiltration membrane B and the container C and passing the filtrate of the ultrafiltration membrane B; a liquid path for transferring the sulfuric acid recovered in the recovery step to the reaction vessel A; a liquid path for transferring the sodium hydroxide recovered in the recovery step to the reaction vessel B; and the like. Here, the reaction vessel B may be a reaction vessel used in a sodium hydroxide addition step of adding sodium hydroxide and ammonia. The ultrafiltration membrane B may be an ultrafiltration membrane used in a hydroxide concentration step of filtering a sodium sulfate-containing solution containing the hydroxide containing the above element, sodium sulfate, and ammonium sulfate. The container C may be a container including at least one ion exchange membrane selected from the group consisting of an anion exchange membrane and a cation exchange membrane used in a recovery step of recovering sulfuric acid, sodium hydroxide, and ammonium ammonia from the sodium sulfate solution separated by the ultrafiltration membrane B. In particular, when the ultrafiltration membrane is of the crossflow type, a circulation liquid path A for circulating the discharge liquid of the ultrafiltration membrane A to the reaction vessel A, a circulation liquid path B for circulating the discharge liquid of the ultrafiltration membrane B to the reaction vessel B, and the like may be provided.

Example

[0065] Hereinafter, the present invention will be described in more detail based on examples, but the present invention is not limited to these examples.

[0066] (Experimental Example 1) Metallic nickel (produced by Sato Metal Co., Ltd., nickel ingot), metallic cobalt (produced by Zhejiang Huayou Cobalt Co., Ltd., cobalt ingot), and metallic manganese (manganese ingot) were dissolved in sulfuric acid to prepare a sulfuric acid solution. Cobalt, nickel, and manganese were mixed so that the molar ratio was 1:1:1. Then, the pH was adjusted, and the mixture was filtered through a 5A filter paper, a 0.1 μm F filter, and a microza UF (ultrafiltration membrane). The obtained filtrate was poured into the circulation tank shown in Fig. 3. As shown in Fig. 3, the above-mentioned circulation tank was also poured with the discharge liquid discharged without passing through the filter membrane in the filtration in the hydroxide concentration step described later. In addition, the filtrate obtained by the filtration in the hydroxide concentration step described later was also poured into the above-mentioned circulation tank. By adding the above-mentioned discharge liquid and filtrate containing sodium hydroxide to the above-mentioned circulation tank, Ni x Co y Mn z (OH)2 (ternary hydroxide) was reacted to obtain a sodium sulfate-containing solution containing a hydroxide containing nickel, cobalt, and manganese elements and sodium sulfate. Using the membrane filtration device shown in Fig. 3, the sodium sulfate-containing solution was filtered. The flow rate of the filtrate when circulating through the UF module at a constant linear velocity was measured. For the above filtration, a UF membrane module (model SIP-1053, manufacturer Asahi Kasei Corporation) with a membrane material of polysulfone, a fractional molecular weight of 6000, a hollow fiber inner diameter of 1.4 mm, 140 filled numbers, and a hollow part opening area of 0.0002 m 2 was used. The average filtration pressure ((Pi + Po) ÷ 2) was 0.1 MPa, the filtration temperature was 40 to 50 °C, and the amount of solution in the circulation tank was made constant at 10 L. The particle size (D50) of the hydroxide in the sodium sulfate-containing solution was 3.7 μm, and the hydroxide concentration was 300 g / L. When filtration was carried out at a linear velocity of 0.5 m / s at the hollow fiber membrane inlet (circulation flow rate 6.5 L / min), the filtration flow rate was almost constant and stable even 12 hours after the start of filtration. In addition, 12 hours after the start of filtration, the UF module was taken out and the hollow fiber membrane was visually inspected. As a result, the membrane surface was in the same state as before filtration. In addition, the linear velocity in Example 1 can be calculated as follows. Circulation flow rate 6.5 L / min = 0.000108 m 3 / s Total opening area of the hollow fiber membranes contained in the membrane module = 3.14 × (1.4 / 2) 2 × 140 = 0.000215 m 2 Linear velocity = Circulation flow rate (m 3 / s) / Total opening area of the hollow fiber membranes contained in the membrane module (m 2 ) = 0.50 m / s

[0067] (Experimental Example 2) Filtration was carried out in the same manner as in Example 1, except that the linear velocity was 1.3 m / s (circulation flow rate 16.9 L / min). Even 12 hours after the start of filtration, the filtration flow rate was almost constant and stable. In addition, 12 hours after the start of filtration, the UF module was taken out and the hollow fiber membrane was visually inspected. As a result, the membrane surface was in the same state as before filtration.

[0068] (Experimental Example 3) Filtration was carried out in the same manner as in Example 1, except that the linear velocity was 0.4 m / s (circulation flow rate 5.2 L / min). 12 hours after the start of filtration, the filtration flow rate tended to decrease slightly, but it was within the range where the operation was not affected. In addition, 12 hours after the start of filtration, the UF module was taken out and the hollow fiber membrane was visually inspected. As a result, the membrane surface was in the same state as before filtration.

[0069] (Experimental Example 4) Filtration was carried out in the same manner as in Example 1, except that the linear velocity was 1.4 m / s (circulation flow rate 18.2 L / min). 12 hours after the start of filtration, the filtration flow rate tended to decrease slightly, but it was within the range where the operation was not affected. Also, 12 hours after the start of filtration, the UF module was taken out and the hollow fiber membrane was visually inspected. As a result, the membrane surface was in the same state as before filtration.

[0070] (Experimental Example 5) Filtration was carried out in the same manner as in Example 1, except that the molar ratios of the metal nickel, metal cobalt, metal manganese, and sulfuric acid used were changed, and the particle size (D50) of the hydroxide in the sodium sulfate-containing solution was 10.7 μm and the hydroxide concentration was 1200 g / L. Even 12 hours after the start of filtration, the filtration flow rate was almost constant and stable. Also, 12 hours after the start of filtration, the UF module was taken out and the hollow fiber membrane was visually inspected. As a result, the membrane surface was in the same state as before filtration.

[0071] (Experimental Example 6) Filtration was carried out in the same manner as in Example 5, except that the linear velocity was 1.2 m / s (circulation flow rate 15.6 L / min). Even 12 hours after the start of filtration, the filtration flow rate was almost constant and stable. Also, 12 hours after the start of filtration, the UF module was taken out and the hollow fiber membrane was visually inspected. As a result, the membrane surface was in the same state as before filtration.

[0072] (Comparative Example 1) Filtration was carried out in the same manner as in Example 1, except that the linear velocity was 0.2 m / s (circulation flow rate 2.6 L / min). Immediately after the start of filtration, the slurry blocked the hollow part of the hollow fiber membrane in the UF membrane module, the filtration flow rate gradually decreased, and stable operation could not be performed. 24 hours after the start of filtration, filtration was almost impossible. 12 hours after the start of filtration, the UF module was taken out and the hollow fiber membrane was visually inspected. As a result, the membrane surface was in the same state as before filtration.

[0073] (Comparative Example 2) Filtration was carried out in the same manner as in Example 1, except that the linear velocity was 1.7 m / s (circulation flow rate 22.1 L / min). The filtration flow rate continuously decreased gradually from the start of filtration and was not stable. 24 hours after the start of filtration, filtration was almost impossible. Also, 12 hours after the start of filtration, the UF module was taken out and the hollow fiber membrane was visually inspected. As a result, the membrane surface was damaged.

[0074] (Comparative Example 3) Filtration was carried out in the same manner as in Example 5 except that the linear velocity was 0.2 m / s (circulation flow rate 2.6 L / min). Immediately after the start of filtration, the slurry blocked the hollow part of the hollow fiber membrane in the UF membrane module, the filtration flow rate gradually decreased, and stable operation could not be achieved. 24 hours after the start of filtration, filtration was almost impossible. 12 hours after the start of filtration, the UF module was taken out and the hollow fiber membrane was visually inspected. As a result, the membrane surface was in the same state as before filtration.

[0075] (Comparative Example 4) Filtration was carried out in the same manner as in Example 5 except that the linear velocity was 1.7 m / s (circulation flow rate 22.1 L / min). The filtration flow rate continuously decreased gradually from the start of filtration and was not stable. 24 hours after the start of filtration, filtration was almost impossible. Also, 12 hours after the start of filtration, the UF module was taken out and the hollow fiber membrane was visually inspected. As a result, the membrane surface was damaged.

[0076] (Comparative Example 5) Filtration was carried out in the same manner as in Example 1 except that a colloidal silica-containing solution was used instead of the filtrate containing metallic nickel, metallic cobalt, and metallic manganese. The above colloidal silica-containing solution is a solution that does not contain nickel, cobalt, or manganese. The particle size (D50) of the particles in the above colloidal silica-containing solution was 0.1 μm, and the particle concentration was 3000 g / L. Immediately after the start of filtration, the slurry blocked the hollow part of the hollow fiber membrane in the UF membrane module, the filtration flow rate gradually decreased, and stable operation could not be achieved. 12 hours after the start of filtration, filtration was almost impossible.

[0077] (Comparative Example 6) Filtration was carried out in the same manner as in Comparative Example 5, except that the linear velocity was 1.7 m / s (circulation flow rate: 22.1 L / min). Even 12 hours after the start of filtration, the filtration flow rate was almost constant and stable.

Claims

1. A sulfuric acid addition step of adding sulfuric acid to a material containing at least one simple substance of an element selected from the group consisting of nickel, cobalt, and manganese, and / or an inorganic compound containing at least one element selected from the group consisting of nickel, cobalt, and manganese, A filtration step of filtering the liquid obtained in the sulfuric acid addition step through an ultrafiltration membrane, The ions of the above elements and SO ４ ２－ A sodium hydroxide addition step of adding sodium hydroxide to a mixed solution containing the filtrate obtained in the above filtration step containing ions and SO ions, and A hydroxide concentration step of filtering the sodium sulfate-containing solution containing the hydroxide containing the element and sodium sulfate obtained in the sodium hydroxide addition step through an ultrafiltration membrane to concentrate the hydroxide, having, wherein the ultrafiltration membrane in the hydroxide concentration step is a hollow fiber membrane, and the linear velocity at the hollow fiber membrane inlet is 0.3 m / sec or more and less than 1.5 m / sec, A method for producing a hydroxide containing at least one element selected from the group consisting of nickel, cobalt, and manganese, characterized by this.

2. The production method according to Claim 1, wherein the ultrafiltration membrane in the hydroxide concentration step is in a crossflow mode.

3. The production method according to Claim 1 or 2, wherein the inner diameter of the hollow fiber membrane is 1.0 mm or more and 2.3 mm or less.

4. The production method according to Claim 1 or 2, wherein the linear velocity is 0.5 m / sec or more and less than 1.3 m / sec.

5. The production method according to Claim 1 or 2, wherein the concentration of the hydroxide in the sodium sulfate-containing solution is 300 g / L or more and less than 600 g / L.

6. The production method according to Claim 4, wherein the concentration of the hydroxide in the sodium sulfate-containing solution is 600 g / L or more and less than 1200 g / L.

7. The production method according to Claim 1 or 2, wherein the particle size (D50) of the hydroxide in the sodium sulfate-containing solution is 1 μm or more and less than 12 μm.

8. The production method according to Claim 1 or 2, wherein the particle size (D50) D (unit: μm) of the hydroxide in the sodium sulfate-containing solution, the concentration C (unit: g / L) of the hydroxide in the sodium sulfate-containing solution, and the linear velocity S (unit: m / sec) at the hollow fiber membrane inlet satisfy the following relationship (1). 50 < D × C × S < 24000... (1)

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