Method for producing lithium adsorbent precursor
Patent Information
- Authority / Receiving Office
- WO · WO
- Patent Type
- Applications
- Current Assignee / Owner
- Filing Date
- 2026-01-22
- Publication Date
- 2026-08-13
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Abstract
Description
Method for producing lithium adsorbent precursors
[0001] This invention relates to a method for producing a precursor of a lithium adsorbent. More specifically, this invention relates to a method for producing a precursor of a lithium adsorbent by mixing manganese hydroxide and lithium hydroxide.
[0002] Lithium is widely used in industries such as ceramics and glass additives, glass flux for continuous steel casting, greases, pharmaceuticals, and batteries. In particular, lithium-ion batteries, a type of rechargeable battery, have high energy density and high voltage, and their use has recently expanded to include batteries for electronic devices such as laptop computers and automotive batteries for electric and hybrid vehicles, leading to a surge in demand. Consequently, the demand for lithium, the raw material for lithium, has also surged.
[0003] Lithium is found in salt lake brine or lithium-containing ores, such as sialite (Li ２ O / Al ２ O ３ / 2SiO ４ These materials have been used as raw materials and refined to produce lithium hydroxide or lithium carbonate. However, considering the manufacturing costs, a process that selectively recovers lithium from an aqueous solution containing impurities is desired, rather than a process that removes impurities other than lithium and leaves lithium in the aqueous solution.
[0004] A known process for selectively recovering lithium is to recover it as lithium manganate. Lithium manganate, which has a spinel structure, adsorbs lithium when pretreated by contacting it with an acid and exchanging lithium for hydrogen. Therefore, the adsorbent obtained by exchanging lithium for hydrogen in lithium manganate, i.e., manganese acid, has excellent selective adsorption ability for lithium, and manganese acid can repeatedly adsorb and elute lithium like an ion exchange resin.
[0005] Therefore, lithium manganate serves as a precursor for lithium adsorbents in processes for selectively recovering lithium. There are two methods for producing lithium manganate: a dry method using only calcination, and a wet method using an aqueous solution (see, for example, Patent Documents 1 and 2).
[0006] The wet method described in Patent Document 2 involves a hydrothermal reaction requiring pressurization, which is industrially disadvantageous due to its high cost and the need for safety considerations. Therefore, Patent Document 3 proposes obtaining lithium manganate by adding an oxidizing agent at low temperature to a raw material slurry containing a manganese source and a lithium source. This method is industrially advantageous because it does not require a pressure vessel and allows lithium manganate to be obtained under atmospheric pressure.
[0007] Japanese Patent Publication No. 2003-245542, Japanese Patent Publication No. 2001-157838, International Publication No. 2019 / 203274 (brochure)
[0008] As described above, the method described in Patent Document 3 does not require a pressure vessel and can obtain lithium manganate, which is a precursor to lithium adsorbent, under atmospheric pressure, making it an excellent method in terms of industrial production and safety. However, improvements in production efficiency are desired due to the low concentration of the manganese compound slurry and the need for lithium raw materials in amounts exceeding the stoichiometric ratio for the manganese compound. Furthermore, there is variability in the particle size of the obtained lithium manganate, and the fine particles have poor filterability, i.e., poor handling, and are prone to leakage during the manufacturing process, thus further improvements in production efficiency have been sought.
[0009] Therefore, the object of the present invention is to provide a method for producing lithium manganate, which serves as a precursor for a lithium adsorbent, having a narrow particle size distribution and excellent lithium adsorption performance, in an industrially advantageous manner. The present invention also aims to provide a precursor for a lithium adsorbent that has less particle size variation, excellent handling properties, fewer fine particles that tend to leak out during the manufacturing process, and further possesses excellent lithium adsorption performance.
[0010] In view of the above circumstances, the inventors conducted extensive research and found that the concentration of manganese relative to lithium in a raw material mixture slurry containing manganese and lithium compounds affects the adsorption performance. Furthermore, they discovered that by holding the raw material mixture slurry under heating for a certain period of time before carrying out the oxidation reaction, the particle size of the resulting lithium manganate becomes uniform, thus completing the present invention.
[0011] In other words, the present invention provides a method for producing a precursor of a lithium adsorbent, comprising: a mixing step of mixing a manganese hydroxide-containing slurry having a manganese hydroxide concentration of 7.5% by mass or more and 12% by mass or less with lithium hydroxide to obtain a raw material mixture slurry in which the molar amount of lithium is 1 to less than 4 times the molar amount of manganese; a heating and holding step of maintaining the raw material mixture slurry at a temperature of more than 60°C and less than 95°C for 0.5 hours or more and 12 hours or less; and an oxidation step of adding an oxidizing agent to the raw material mixture slurry after the heating and holding step to obtain an oxide.
[0012] The present invention provides a method for producing lithium manganate, which serves as a precursor to a lithium adsorbent, having a narrow particle size distribution and excellent lithium adsorption performance, in an industrially advantageous manner.
[0013] This is a flowchart showing a method for producing the precursor of the lithium adsorbent according to the present invention.
[0014] The present invention provides a method for producing a precursor of a lithium adsorbent (hereinafter also referred to as "the precursor") (hereinafter also referred to as "the production method"), comprising: a mixing step (hereinafter also referred to as "the mixing step"), in which a manganese hydroxide-containing slurry having a manganese hydroxide concentration of 7.5% by mass or more and 12% by mass or less is mixed with lithium hydroxide to obtain a raw material mixture slurry in which the molar amount of lithium is 1 to less than 4 times the molar amount of manganese; a heating and holding step (hereinafter also referred to as "the heating and holding step"), in which the raw material mixture slurry is maintained at a temperature of more than 60°C and less than 95°C for 0.5 hours or more and 12 hours or less; and an oxidation step (hereinafter also referred to as "the oxidation step"), in which an oxidizing agent is added to the raw material mixture slurry after the heating and holding step to obtain an oxide.
[0015] This mixing process yields a raw material mixture slurry in which the molar amount of lithium is between 1 and 4 times the molar amount of manganese. From the viewpoint of reducing the amount of lithium used, it is preferable that the molar amount of lithium in the raw material mixture slurry is between 1.3 and 3.8 times the molar amount of manganese in the raw material mixture slurry.
[0016] The manganese hydroxide-containing slurry is a slurry containing manganese hydroxide, in which manganese hydroxide is dispersed and flowing in the solvent described below. From the viewpoint of the production efficiency of this adsorbent, the concentration of manganese hydroxide in the slurry is preferably 7.8% by mass or more and 10.3% by mass or less, and particularly preferably 8.1% by mass or more and 9.6% by mass or less.
[0017] The solvent for the slurry may be an aqueous solvent, an organic solvent, or a mixture thereof, and an aqueous solvent is preferred from the viewpoint of ease of handling and cost. Examples of aqueous solvents include pure water, deionized water, industrial water, tap water, and distilled water. Of these, pure water and deionized water are particularly preferred from the viewpoint of preventing contamination with impurities.
[0018] The manganese hydroxide-containing slurry may be a commercially available manganese hydroxide-containing slurry, or it may be a slurry prepared by mixing commercially available manganese hydroxide with the solvent, or it may be a slurry prepared by mixing separately synthesized manganese hydroxide with the solvent. When separately synthesized manganese hydroxide is used, manganese hydroxide obtained by the reaction of manganese sulfate or manganese nitrate with alkali hydroxide is preferred.
[0019] One method for obtaining manganese hydroxide by the aforementioned synthesis is to mix manganese sulfate or manganese nitrate with an alkali hydroxide. More specifically, this method involves using solutions of each compound and mixing them, or mixing solid manganese sulfate or manganese nitrate with an alkali hydroxide in a solvent such as water. The solvent used may be the same solvent as that used in the slurry.
[0020] When manganese sulfate or manganese nitrate is used as an aqueous solution, its concentration should be less than or equal to the solubility of each substance. The same applies when alkali hydroxide is used as an aqueous solution.
[0021] Examples of alkali hydroxides used when obtaining manganese hydroxide by the above synthesis include sodium hydroxide, potassium hydroxide, and lithium hydroxide.
[0022] When manganese hydroxide is obtained by synthesis as described above, the resulting liquid containing manganese hydroxide may be used directly as the manganese hydroxide slurry, or the manganese hydroxide may be recovered in solid form and then the solvent may be added separately to form a slurry. From the viewpoint of workability, it is preferable to use the liquid containing manganese hydroxide obtained by synthesis directly as the manganese hydroxide slurry. In this case, the manganese concentration in the manganese hydroxide slurry may be appropriately adjusted to fall within the above range before being used in the mixing step.
[0023] The lithium hydroxide used in this mixing step may be a commercially available product or may be synthesized separately. If synthesized separately, it can be synthesized by reactions such as the reaction of lithium oxide with water or the reaction of lithium carbonate with calcium hydroxide. In this mixing step, solid lithium hydroxide may be added to the manganese hydroxide-containing slurry, or a solution of lithium hydroxide or a slurry containing lithium hydroxide may be mixed with the manganese hydroxide-containing slurry. The slurry containing lithium hydroxide is a state in which lithium hydroxide is dispersed and flowing in the following solvent.
[0024] The solvent for the slurry containing lithium hydroxide may be an aqueous solvent, an organic solvent, or a mixture thereof. From the viewpoint of ease of handling and cost, an aqueous solvent is preferred. Examples of aqueous solvents include pure water, deionized water, industrial water, tap water, and distilled water. Of these, pure water and deionized water are particularly preferred from the viewpoint of preventing contamination with impurities.
[0025] In this mixing step, the manganese hydroxide concentration in the manganese hydroxide-containing slurry is 7.5% by mass or more and 12% by mass or less. During this mixing step, if necessary, the concentration of the manganese hydroxide-containing slurry is adjusted to the above concentration before mixing with lithium hydroxide.
[0026] From the viewpoint of reaction efficiency, it is preferable to mix the manganese hydroxide-containing slurry with the lithium hydroxide by mixing solid lithium hydroxide with the manganese hydroxide-containing slurry. The solid lithium hydroxide is more preferably lithium hydroxide powder, which is lithium hydroxide powder. The manganese hydroxide-containing slurry and lithium hydroxide may be mixed together at once, gradually added to one, or added in small amounts while mixing. This mixing step is preferably carried out while stirring with a stirring bar, blade, or the like.
[0027] The mixing of the manganese hydroxide-containing slurry and the lithium hydroxide is preferably carried out at a temperature of 20°C to 95°C, and more preferably at a temperature of 40°C to 80°C, from the viewpoint of efficiently dissolving the lithium hydroxide. The temperature may be set to the desired temperature from the beginning of the mixing process and the mixing of the manganese hydroxide-containing slurry and the lithium hydroxide may be started, or the temperature may be raised to the desired temperature after the two have been mixed. When the mixing process is carried out at the above temperature, the mixing process may be carried out at a constant temperature, or the temperature may be adjusted as appropriate while observing the mixing state.
[0028] This mixing step involves mixing the manganese hydroxide-containing slurry, which has a manganese hydroxide concentration of 7.5% by mass or more and 12% by mass or less, with the lithium hydroxide to obtain a raw material mixture slurry in which the molar amount of lithium is 1 to less than 4 times the molar amount of manganese. In this mixing step, it is sufficient to mix the raw material mixture slurry so that the molar amount of lithium in the slurry is 1 to less than 4 times the molar amount of manganese. For example, the raw material mixture slurry may be obtained by mixing the manganese hydroxide-containing slurry with lithium hydroxide in an amount of 1 to less than 4 times the molar amount of manganese hydroxide, or the manganese hydroxide-containing slurry and lithium hydroxide may be mixed, and manganese hydroxide or lithium hydroxide, or both, may be added as needed, so that the molar amount of lithium in the resulting raw material mixture slurry is 1 to less than 4 times the molar amount of manganese.
[0029] For example, if a manganese hydroxide-containing slurry with a manganese hydroxide concentration of 7.5% by mass or more and 12% by mass or less is mixed with lithium hydroxide, and the molar amount of lithium in the resulting mixed slurry is four times or more the molar amount of manganese, then a compound containing manganese, such as manganese hydroxide, may be added. Alternatively, if a manganese hydroxide-containing slurry with a manganese hydroxide concentration of 7.5% by mass or more and 15% by mass or less is mixed with lithium hydroxide, and the molar amount of lithium in the resulting mixed slurry is less than one time the molar amount of manganese, then a compound containing lithium, such as lithium hydroxide, may be added.
[0030] From the viewpoint of ease of operation, the mixing process is preferably a mixing step in which a manganese hydroxide-containing slurry having a manganese hydroxide concentration of 7.5% by mass or more and 12% by mass or less is mixed with lithium hydroxide in an amount of 1 to 4 times the molar amount of manganese hydroxide to obtain a raw material mixture slurry. From the viewpoint of the production efficiency of this precursor, a mixing step is more preferably a mixing step in which lithium hydroxide in an amount of lithium element of 1.3 to 3.8 times the molar amount of manganese element in the manganese hydroxide-containing slurry is mixed to obtain a raw material mixture slurry. The molar amounts of manganese element and lithium element in the raw material mixture slurry can be determined from the amounts of manganese hydroxide and lithium hydroxide used in the mixing process, respectively.
[0031] The inventors have found that by using a manganese hydroxide-containing slurry with a manganese hydroxide concentration of 7.5% to 12% by mass, and by setting the molar amount of lithium in the raw material mixture slurry obtained in this mixing step to 1 to less than 4 times the molar amount of manganese, it is possible to reduce the amount of lithium used, and the lithium adsorbent obtained from this precursor exhibits excellent selective lithium adsorption performance. From the viewpoint of excellent lithium adsorption capacity of the lithium adsorbent obtained from this precursor, a molar amount of lithium in the raw material mixture slurry of 1.3 to 3.8 times the molar amount of manganese is particularly preferable. Furthermore, this manufacturing method, in which the molar amount of lithium hydroxide is within the above range, can reduce the amount of lithium used compared to conventional methods for producing lithium adsorbent precursors, and is therefore more preferable from the viewpoint of green chemistry.
[0032] This heating and holding step maintains the raw material mixture slurry obtained in the mixing step at a temperature between 60°C and 95°C for 0.5 hours to 12 hours. The inventors have found that by going through this heating and holding step, the resulting precursor has a narrow particle size distribution and excellent filterability, i.e., handling properties. From the viewpoint of obtaining a precursor with a more uniform particle size, the heating temperature in this heating and holding step is preferably between 65°C and 90°C. The temperature in this heating and holding step may fluctuate within the above range, but from the viewpoint of obtaining a precursor with a uniform particle size, it is preferable that the temperature in this heating and holding step remain constant within the above temperature range.
[0033] The heating and holding time is preferably 1 hour to 3 hours, from the viewpoint of obtaining the precursor having a more uniform particle size. This heating and holding may be completed in a single operation, or it may be performed multiple times as long as the total time is within this range, provided that the effects of the present invention are not impaired. This heating and holding step may be performed under standing conditions, but it is preferable to perform it under stirring, from the viewpoint of obtaining the precursor having a more uniform particle size and preventing the generation of by-products. Stirring is usually performed with a stirring bar or stirring blade.
[0034] If necessary, after this mixing step, the temperature of the raw material mixture slurry may be raised to the temperature of this heating and holding step. From the viewpoint of obtaining the present precursor having a more uniform particle size and the fact that a rapid heating rate affects the quality of the present precursor, the heating rate is preferably 0.1 °C / min or more and 10 °C / min or less, and more preferably 1 °C / min or more and 5 °C / min or less.
[0035] After this heating and holding step, it is preferable to cool the heated and held raw material mixture slurry from the viewpoints of shortening the time for carrying out the next step within an appropriate temperature range, suppressing the denaturation of the present precursor obtained due to the heat history, and reducing the influence on the quality of the present precursor. When cooling after this heating and holding step, the temperature drop rate is preferably 0.1 °C / min or more and 10 °C / min or less, and particularly preferably 1 °C / min or more and 5 °C / min or less, from the viewpoints of shortening the time for carrying out the next step within an appropriate temperature range, suppressing the denaturation of the present precursor obtained due to the heat history, and reducing the influence on the quality of the present precursor due to the temperature drop. Methods for controlling the temperature drop rate to be within the above range include purging the atmosphere with room temperature or cooled gas, and cooling the reaction vessel housing with cooling water or the like.
[0036] The present oxidation step carried out after the present heating and holding step is a step of adding an oxidizing agent to the raw material mixture slurry after heating and holding to obtain an oxide. Examples of the oxidizing agent include sodium hypochlorite, potassium hypochlorite, sodium chlorite, potassium chlorite, hypochlorous acid, chlorous acid, ammonium peroxydisulfate, sodium peroxydisulfate, and the like. The raw material mixture slurry after heating and holding contains manganese hydroxide and lithium hydroxide. By adding an oxidizing agent, the reaction of manganese hydroxide and lithium hydroxide proceeds, and lithium manganate, that is, the present precursor, is obtained. Among the above oxidizing agents, sodium hypochlorite, potassium hypochlorite, ammonium peroxydisulfate, and sodium peroxydisulfate are particularly preferable in that the reaction to lithium manganate proceeds efficiently and they are industrially inexpensive and easily available.
[0037] In this oxidation step, it is preferable to add the oxidizing agent to make the redox potential of the raw material mixture slurry -100 mV or more and 1000 mV or less with a silver / silver chloride electrode. When the oxidizing agent is not added in the oxidation step, the redox potential of the raw material mixture slurry is usually -250 mV or less with a silver / silver chloride electrode. By adding the oxidizing agent to make the redox potential of the raw material mixture slurry within the above range, this oxidation step can proceed smoothly. When the redox potential is less than -100 mV, the yield of lithium manganate obtained may decrease. Also, when the redox potential is greater than 1000 mV, it may be necessary to make the equipment for the oxidation step capable of withstanding such a large redox potential. It is more preferable to add the oxidizing agent so that the redox potential of the raw material mixture slurry is 0 mV or more and 500 mV or less with a silver / silver chloride electrode.
[0038] If the redox potential of the solution is preferably -100 mV or more and 1000 mV or less, more preferably 0 mV or more and 500 mV or less with a silver / silver chloride electrode, there is no need for special equipment to achieve a high potential, the cost of the equipment can be suppressed, and lithium manganate can be obtained in a high yield. The redox potential can be controlled within the above range by adjusting the addition amount of the oxidizing agent.
[0039] In this oxidation step, it is preferable to add the oxidizing agent little by little gradually. The oxidizing agent is consumed when oxidizing manganese. Therefore, it is preferable to add the oxidizing agent so that the value of the redox potential of the raw material mixture slurry is within the above range. When the oxidizing agent is added, the redox potential temporarily rises, but when the oxidizing agent is consumed when oxidizing manganese, the redox potential decreases accordingly. It is more preferable to add the oxidizing agent so that the redox potential of the raw material mixture slurry is -100 mV or more and 1000 mV or less, and further 0 mV or more and 500 mV or less with a silver / silver chloride electrode. After the addition of the oxidizing agent is completed and the raw material mixture slurry is sufficiently mixed, if the redox potential is within the above range, it can be regarded as the end of this oxidation step.
[0040] The oxidation process is preferably carried out at 40°C or higher, particularly 45°C or higher. In the oxidation process, lithium is intercalated to produce lithium manganate. If the temperature of the oxidation process is below 40°C, the reaction rate of intercalation may not increase sufficiently. By carrying out the oxidation process at 40°C or higher, this reaction rate can be effectively increased. Furthermore, since it may be necessary to change the equipment for the oxidation process to one with higher heat resistance, the temperature of the oxidation process is preferably 60°C or lower. From the viewpoint of efficiency of the oxidation process, it is preferable to add the oxidizing agent for 20 minutes or more. From the viewpoint of production efficiency of the precursor, it is preferable to add the oxidizing agent for 40 minutes or less.
[0041] In this oxidation process, it is preferable that the oxidizing agent is added to the raw material mixture slurry after heating and holding while the slurry is maintained at a temperature of 40°C to 60°C, particularly 45°C to 55°C. In this state, the raw material mixture slurry and the oxidizing agent are stirred, thereby oxidizing the manganese in the raw material mixture slurry.
[0042] Furthermore, in order to reliably produce lithium manganate oxide, it is preferable to continue stirring and mixing at the aforementioned temperature for three hours or more after adding the oxidizing agent. This oxidation process is usually carried out under atmospheric pressure.
[0043] The precursor, which is an oxide produced in the oxidation process, namely lithium manganate, is separated into solid and liquid forms and becomes a powder.
[0044] Preferably, this manufacturing method further includes a calcination step in which the oxide obtained in the oxidation step is calcined. By performing the calcination step, the oxidation of the raw material mixture slurry is carried out more reliably.
[0045] The firing temperature in the firing process is preferably 300 ° C or higher and 600 ° C or lower, and more preferably 450 ° C or higher and 550 ° C or lower. By setting the firing temperature within the above range, oxidation of manganese can be carried out while suppressing a decrease in specific surface area due to growth of the obtained particles of the present precursor. The firing time is appropriately selected, but from the viewpoint of obtaining lithium manganate with a high main phase rate having uniform particle size, it is preferably 2 hours or more and 10 hours or less, and more preferably 4 hours or more and 6 hours or less. The firing atmosphere is not particularly limited, and either an air atmosphere or an oxygen atmosphere may be used.
[0046] In the firing process, the firing may be carried out a plurality of times. For example, the oxide obtained in the present oxidation process may be fired, and then the pulverized product obtained by cooling and pulverizing the fired product may be fired again.
[0047] After the firing process, the fired product is appropriately cooled, and if necessary, pulverization, disintegration, classification, etc. are carried out, and Li <OOOOOO5>Mn ｙ O ４ The present precursor, which is lithium manganate represented by, is obtained. In the above formula, x and y can take various numerical values depending on the crystal states of lithium and manganese, but usually, x is 1 or more and 2 or less, and y is 1 or more and 2 or less.
[0048] By the present production method, the present precursor, which is an excellent precursor of a lithium adsorbent, is obtained. The present precursor thus obtained is subjected to an exchange reaction of lithium and hydrogen by contacting with an acid such as hydrochloric acid, and H ａ Mn ｂ O ４ It becomes a compound represented by, and it becomes possible to adsorb lithium. In the above formula, a and b can take various values depending on the obtained present precursor, but usually, a is 1 or more and 2 or less, and b is 1 or more and 2 or less.
[0049] In the present production method, the present mixing step, the present heating and holding step, and the present oxidation step, and if necessary, the firing step may be continuously carried out. After separation and recovery for each step, the recovered product may be supplied to the next step. Further, the present production method may have steps such as washing, purification, and classification in addition to the present mixing step, the present heating and holding step, and the present oxidation step, and each step may be repeated a plurality of times as necessary.
[0050] The inventors have found that the particle size distribution of the precursor obtained by the above-described manufacturing method is narrow, resulting in excellent handling properties, fewer fine particles that tend to leak out during the manufacturing process, and furthermore, the lithium adsorbent obtained from this precursor exhibits excellent lithium adsorption performance. The width of the particle size distribution of the precursor is preferably such that, in the volume frequency particle size distribution measured by laser diffraction scattering, D10 is the particle size at which the cumulative volume value reaches 10%, D50 is the particle size at which the cumulative volume value reaches 50%, and D90 is the particle size at which the cumulative volume value reaches 90%, the particle size distribution index satisfies the following formula (1): ((D90 - D10) / D50) ≤ 1.2 (1)
[0051] Precursors of lithium adsorbents include lithium manganate, lithium titanate, manganese-lithium titanate, and magnesium manganate. These salts become acids when treated with acid, and all of them adsorb lithium. Among these lithium adsorbent precursors, lithium manganate is preferred from the viewpoint of its excellent lithium adsorption performance.
[0052] It is particularly preferable that the precursor of the lithium adsorbent has individual particles of similar size, thereby increasing the filtration rate and shortening the working time, i.e., improving production efficiency, and that the precursor satisfies the following formula (2): ((D90 - D10) / D50) ≤ 1 (2)
[0053] The D50 of this precursor is preferably 2 μm to 6 μm in size, and more preferably 3 μm to 5 μm in size, from the viewpoint of production efficiency and from the viewpoint of improving lithium adsorption performance when this precursor is used as a lithium adsorbent.
[0054] The BET specific surface area of this precursor is set to 3m from the viewpoint of improving the lithium adsorption performance when this precursor is used as a lithium adsorbent. ２ / g or more 30m ２ Preferably less than / g, and 5m ２ / g or more 20m ２A value of less than or equal to / g is even more preferable. The BET specific surface area is the specific surface area determined by the BET method, and can be determined by adsorption measurement of an inert gas such as nitrogen gas. The BET specific surface area can be measured, for example, using a specific surface area measuring device.
[0055] The precursor satisfying formula (1) can be produced by the manufacturing method described above, and by setting the manufacturing method to the preferred range described above, the formula (2), D50, and BET specific surface area can be obtained.
[0056] This precursor, when brought into contact with an acid such as hydrochloric acid, becomes an acid, and both types of acids adsorb lithium. When this precursor is lithium manganate, an exchange reaction occurs between lithium and hydrogen, and H ａ Mn ｂ O ４ The compound represented by the formula becomes capable of adsorbing lithium. In the above formula, a and b can take various values depending on the obtained precursor, but usually a is between 1 and 2, and b is between 1 and 2. Lithium titanate, manganese-lithium titanate, and magnesium manganate are known as precursors of lithium adsorbents, and similarly, these also become lithium adsorbents that adsorb lithium by becoming acidic.
[0057] Magnesium manganate is Mg ２ MnO ４ and MgMn ２ O ４ Its composition is known, and by oxidation with a suitable oxidizing agent, it becomes manganic acid, which acts as a lithium adsorbent that adsorbs lithium.
[0058] As described above, the precursor obtained by this manufacturing method is a lithium adsorbent capable of adsorbing lithium. For example, it can be suitably used in processes for efficiently recovering lithium from aqueous solutions containing lithium and impurities other than lithium, such as alkali metals like sodium and potassium, and alkaline earth metals like magnesium and calcium.
[0059] The present invention has been described above. However, the present invention is not limited to the configuration of the above embodiments. The present invention may have additional steps in the configuration of the above embodiments, or may be replaced with any other steps that produce a similar effect.
[0060] The present invention will be described below with reference to examples, but the present invention is not limited to these examples.
[0061] (1) Particle size distribution index was measured by laser diffraction scattering method using the MT3000II from Microtrac Bell to measure D50, D90, and D10 in the volume frequency particle size distribution of the sample powder, and the particle size distribution index ((D90 - D10) / D50) was determined. (2) BET specific surface area was measured using a flow-type automatic specific surface area measuring device (Flowsorb, Shimadzu Corporation).
[0062] (Example 1) <Mixing Process> 598.7 g of water was prepared in a 2 L Teflon-lined stainless steel beaker, and 156.0 g of powdered manganese sulfate monohydrate (manganese sulfate: 0.923 mol) was added and stirred with a Teflon-lined stirring blade to dissolve it. Then, the mixture was heated on a cooking heater to a temperature of 60°C. Subsequently, 169.2 g of a 48% sodium hydroxide aqueous solution (sodium hydroxide: 2.03 mol) was added to prepare a manganese hydroxide slurry with a concentration of 8.9% by mass. 123.9 g of powdered lithium hydroxide monohydrate (lithium hydroxide: 2.95 mol) was added to this manganese hydroxide slurry, and the slurry was heated on a cooking heater to a temperature of 60°C while stirring to obtain a raw material mixture slurry. The ratio of lithium to manganese (Li / Mn) in this raw material mixture slurry was 3.2.
[0063] <Heating and Holding Process> The raw material mixture slurry was heated on a cooking heater while being stirred and mixed until the slurry reached a temperature of 80°C, after which it was stirred and held for 2 hours.
[0064] <Oxidation Process> After heating and holding, the slurry was allowed to cool to 50°C. Then, a 12% sodium hypochlorite aqueous solution was added dropwise at a constant flow rate so that the final dropwise time was 30 minutes, until the oxidation-reduction potential at the silver / silver chloride electrode reached 300 mV or higher. 588.8 g of sodium hypochlorite aqueous solution was required to achieve a stable oxidation-reduction potential of 300 mV or higher. Stirring and mixing were continued for 3 hours. During stirring and mixing, heating was continued using a cooking heater to prevent the temperature from falling below 50°C. This operation yielded a black powder. After stirring was complete, the powder was separated into solid and liquid components and recovered by suction filtration using a Buchner funnel with a circular quantitative filter paper (ADVANTEC, No. 5C) with a diameter of 110 mm, a thickness of 0.22 mm, and a particle retention capacity of 1 μm. The time required for this suction filtration was 10 minutes. The recovered powder was washed with pure water to remove any adhering liquid, and then dried in the air at 110°C for approximately 24 hours.
[0065] <Casturing Process> The dried powder was calcined at 500°C for 5 hours in an air atmosphere to obtain 92 g of lithium manganate powder (precursor of lithium adsorbent). The particle size distribution index ((D90 - D10) / D50) and BET specific surface area of the obtained lithium manganate powder were measured and the results are shown in Table 1.
[0066] (Example 2) <Mixing Step> The same procedure as in Example 1 was followed up to preparing a manganese hydroxide slurry with a concentration of 8.9% by mass. To this manganese hydroxide slurry, 108.4 g of powdered lithium hydroxide monohydrate (lithium hydroxide: 2.58 mol) was added to obtain a raw material mixture slurry. The ratio of lithium to manganese (Li / Mn) in this raw material mixture slurry was 2.8.
[0067] The subsequent heating and holding, oxidation, and calcination processes were carried out in the same manner as in Example 1 to obtain 92 g of lithium manganate powder. The time required for suction filtration was the same as in Example 1. The particle size distribution index ((D90 - D10) / D50) and BET specific surface area of the obtained lithium manganate powder were measured and the results are shown in Table 1.
[0068] (Example 3) The same procedure as in Example 1 was followed, except that the slurry temperature was set to 80°C in the heating and holding step, followed by stirring and heating for 4 hours, to obtain 93 g of lithium manganate powder. The time required for suction filtration was the same as in Example 1. The particle size distribution index ((D90 - D10) / D50) and BET specific surface area of the obtained lithium manganate powder were measured and the results are shown in Table 1.
[0069] (Comparative Example 1) <Mixing Process> 906.3 g of water was prepared in a 2 L Teflon-lined stainless steel beaker, and 156.0 g of powdered manganese sulfate monohydrate (manganese sulfate: 0.923 mol) was added and stirred with a Teflon-lined stirring blade to dissolve it. Then, the mixture was heated on a cooking heater to a temperature of 40°C. 169.2 g of a 48% sodium hydroxide aqueous solution (sodium hydroxide: 2.03 mol) was added to prepare a 6.7% by mass manganese hydroxide slurry. 154.9 g of powdered lithium hydroxide monohydrate (lithium hydroxide: 3.69 mol) was added to the manganese hydroxide slurry to obtain a raw material mixture slurry. The ratio of lithium to manganese (Li / Mn) in this raw material mixture slurry was 4.0.
[0070] <Heating and Holding Process> The heating and holding process was not performed.
[0071] <Oxidation Process> The raw material mixture slurry obtained in the mixing process was heated to 50°C. A 12% sodium hypochlorite aqueous solution was then added dropwise at a constant flow rate so that the final dropping time was 30 minutes, until the oxidation-reduction potential at the silver / silver chloride electrode reached 300 mV or higher. 588.8 g of sodium hypochlorite aqueous solution was required to achieve a stable oxidation-reduction potential of 300 mV or higher. Stirring and mixing were continued for 3 hours. During stirring and mixing, heating was continued using a cooking heater to prevent the temperature from falling below 50°C. This operation yielded a black powder. After stirring was complete, the powder was separated into solid and liquid components and recovered by suction filtration using a Buchner funnel with a circular quantitative filter paper (ADVANTEC, No. 5C) having a diameter of 110 mm, a thickness of 0.22 mm, and a particle retention capacity of 1 μm. The time required for this suction filtration was 200 minutes. The recovered powder was washed with pure water to remove any adhering liquid, and then dried in the air at 110°C for approximately 24 hours.
[0072] <Casturing Process> The dried powder was calcined at 500°C for 5 hours in an air atmosphere to obtain 86 g of lithium manganate powder. The particle size distribution index ((D90 - D10) / D50) and BET specific surface area of the obtained lithium manganate powder were measured and the results are shown in Table 1.
[0073] (Comparative Example 2) <Mixing Process> 906.3 g of water was prepared in a 2 L Teflon-lined stainless steel beaker, and 156.0 g of powdered manganese sulfate monohydrate (manganese sulfate: 0.923 mol) was added and stirred with a Teflon-lined stirring blade to dissolve it. Then, the mixture was heated on a cooking heater to a temperature of 40°C. 169.2 g of a 48% sodium hydroxide aqueous solution (sodium hydroxide: 2.03 mol) was added to prepare a 6.7% by mass manganese hydroxide slurry. 108.4 g of powdered lithium hydroxide monohydrate (lithium hydroxide: 2.58 mol) was added to the manganese hydroxide slurry to obtain a raw material mixture slurry. The ratio of lithium to manganese (Li / Mn) in this raw material mixture slurry was 2.8.
[0074] <Heating and Holding Process> The same procedure as in Example 1 was performed.
[0075] <Oxidation Process> After heating and holding, the slurry was allowed to cool to 50°C. Then, a 12% sodium hypochlorite aqueous solution was added dropwise at a constant flow rate so that the final dropwise time was 30 minutes, until the oxidation-reduction potential at the silver / silver chloride electrode reached 300 mV or higher. 588.8 g of sodium hypochlorite aqueous solution was required to achieve a stable oxidation-reduction potential of 300 mV or higher. Stirring and mixing were continued for 3 hours. During stirring and mixing, heating was continued using a cooking heater to prevent the temperature from falling below 50°C. This operation yielded a black powder. After stirring was complete, the powder was separated into solid and liquid components and recovered by suction filtration using a Buchner funnel with a circular quantitative filter paper (ADVANTEC, No. 5C) with a diameter of 110 mm, a thickness of 0.22 mm, and a particle retention capacity of 1 μm. The time required for this suction filtration was 20 minutes. The recovered powder was washed with pure water to remove any adhering liquid, and then dried in the air at 110°C for approximately 24 hours.
[0076] <Casturing Process> The dried powder was calcined at 500°C for 5 hours in an air atmosphere to obtain 96 g of lithium manganate powder. The particle size distribution index ((D90 - D10) / D50) and BET specific surface area of the obtained lithium manganate powder were measured and the results are shown in Table 1.
[0077] (Comparative Example 3) <Mixing Step> The same procedure as in Example 1 was followed up to preparing a manganese hydroxide slurry with a concentration of 8.9% by mass. To this manganese hydroxide slurry, 108.4 g of powdered lithium hydroxide monohydrate (lithium hydroxide: 2.58 mol) was added to obtain a raw material mixture slurry. The ratio of lithium to manganese (Li / Mn) in this raw material mixture slurry was 2.8.
[0078] <Heating and Holding Process> The heating and holding process was not performed.
[0079] <Oxidation Process> After the temperature of the raw material mixture slurry obtained in the mixing process was set to 50°C, a 12% sodium hypochlorite aqueous solution was added dropwise at a constant flow rate so that the final dropping time was 30 minutes, until the oxidation-reduction potential at the silver / silver chloride electrode reached 300 mV or higher. 588.8 g of sodium hypochlorite aqueous solution was required to finally achieve a stable oxidation-reduction potential of 300 mV or higher. Stirring and mixing were continued for 3 hours. During stirring and mixing, heating was continued using a cooking heater to prevent the temperature from falling below 50°C. This operation yielded a black powder. After stirring was complete, the powder was recovered by solid-liquid separation using a Buchner funnel and suction filtration with a circular quantitative filter paper (ADVANTEC, No. 5C) with a diameter of 110 mm, a thickness of 0.22 mm, and a particle retention capacity of 1 μm. The time required for this suction filtration was 30 minutes. The recovered powder was washed with pure water to remove any adhering liquid, and then dried in the air at 110°C for approximately 24 hours.
[0080] <Casturing Process> The dried powder was calcined at 500°C for 5 hours in an air atmosphere to obtain 92 g of lithium manganate powder. The particle size distribution index ((D90 - D10) / D50) and BET specific surface area of the obtained lithium manganate powder were measured and the results are shown in Table 1.
[0081] (Comparative Example 4) In the mixing process, 291.0 g of water was prepared in a 2 L Teflon-lined stainless steel beaker, and 156.0 g of powdered manganese sulfate monohydrate (manganese sulfate: 0.923 mol) was added and stirred with a Teflon-lined stirring blade to dissolve it. Then, the mixture was heated on a cooking heater to a temperature of 40°C. 169.2 g of a 48% sodium hydroxide aqueous solution (sodium hydroxide: 2.03 mol) was added to prepare a 13.3% by mass manganese hydroxide slurry. However, the viscosity of the slurry was too high, making stirring impossible, and further operations could not be carried out.
[0082] [Evaluation] A lithium adsorbent was prepared from the lithium manganate obtained in the above examples and comparative examples by performing the following procedure, and a lithium adsorption test was conducted. <Preparation of lithium adsorbent (acid treatment)> 5 g of lithium manganate was placed in a 300 mL beaker, and 75 mL of hydrochloric acid aqueous solution prepared by diluting hydrochloric acid (manufactured by Wako Pure Chemical Industries, Ltd.) with pure water to a concentration of 0.5 mol / L was added, and the mixture was stirred for 30 minutes. After mixing and stirring, the slurry was filtered by suction using a Buchner funnel to separate the solid and liquid, and the powder was recovered.
[0083] The recovered powder was placed back into a 300 mL beaker, and 75 mL of a 0.5 mol / L hydrochloric acid aqueous solution was added. The mixture was then mixed and stirred for 30 minutes. After mixing and stirring, the slurry was filtered by suction using a Buchner funnel to separate the solids and recover the powder. The recovered powder was washed with approximately 150 mL of pure water to remove any adhering liquid.
[0084] <Lithium Adsorption Test> Lithium chloride, sodium chloride, magnesium chloride, potassium chloride, calcium chloride dihydrate, boric acid, sodium sulfate, and 1 mol / L hydrochloric acid were dissolved in pure water to prepare aqueous solutions with lithium concentration of 0.71 g / L, sodium concentration of 72 g / L, magnesium concentration of 17 g / L, potassium concentration of 19 g / L, and calcium concentration of 0.4 g / L. 300 mL of the prepared aqueous solution and 5 g of the adsorbent prepared by the acid treatment were placed in a 300 mL beaker and stirred for 3 hours. As lithium was adsorbed, the pH of the aqueous solution decreased, so a 1 mol / L sodium hydroxide aqueous solution was added during stirring to adjust the pH to 8.5. After stirring, solid-liquid separation was performed by suction filtration of the slurry using a Buchner funnel.
[0085] The powder obtained by solid-liquid separation was placed in a 300 mL beaker and subjected to acid treatment using the same procedure as for the preparation of the lithium adsorbent (acid treatment). The amount of lithium adsorbed was calculated by analyzing the lithium concentration in the resulting filtrate using ICP-AES. The results are shown in Table 1.
[0086]
[0087] From the results in Table 1, it can be seen that the lithium manganate obtained in each example had a (D90 - D10) / D50 of 1.2 or less, indicating that there were many particles with a particle size close to D50 (average particle size). Furthermore, it can be seen that the lithium adsorbent obtained by acid treatment of the lithium manganate obtained in each example had a higher lithium adsorption capacity compared to the comparative examples. Therefore, the lithium adsorbent obtained by acid treatment of lithium manganate obtained by this manufacturing method has excellent lithium adsorption performance. In addition, the particle size distribution of the obtained lithium manganate is narrow, resulting in excellent handling properties. This is related to the time required for suction filtration in each example and comparative example. Compared to each example, where D50 is within an appropriate range and the particle size distribution index is 1.2 or less, the comparative examples, which contained many fine powders and had inconsistent particle sizes, required longer filtration times, indicating that each example is superior in terms of production efficiency.
Claims
1. A method for producing a precursor of a lithium adsorbent, comprising: a mixing step of mixing a manganese hydroxide-containing slurry having a manganese hydroxide concentration of 7.5% by mass or more and 12% by mass or less with lithium hydroxide to obtain a raw material mixture slurry in which the molar amount of lithium is 1 to less than 4 times the molar amount of manganese; a heating and holding step of maintaining the raw material mixture slurry at a temperature of more than 60°C and less than 95°C for 0.5 hours or more and 12 hours or less; and an oxidation step of adding an oxidizing agent to the raw material mixture slurry after the heating and holding step to obtain an oxide.
2. The method for producing a precursor of a lithium adsorbent according to claim 1, wherein in the mixing step, the manganese hydroxide-containing slurry and lithium hydroxide are mixed at a temperature of 20°C to 95°C.
3. A method for producing a precursor of a lithium adsorbent according to claim 1 or 2, wherein the raw material mixture slurry obtained in the mixing step is heated to the temperature of the heating and holding step at a heating rate of 0.1°C / min or more and 10°C / min or less.
4. A method for producing a precursor of a lithium adsorbent according to claim 1 or 2, wherein, after the heating and holding step, the raw material mixture slurry is cooled at a cooling rate of 0.1°C / min or more and 10°C / min or less, and then subjected to an oxidation step.
5. A method for producing a precursor of a lithium adsorbent according to claim 1, further comprising a calcination step of calcining the oxide after the oxidation step.
6. The method for producing a precursor of a lithium adsorbent according to claim 1 or 2, wherein the manganese hydroxide in the manganese hydroxide-containing slurry is obtained by the reaction of manganese sulfate or manganese nitrate with alkali hydroxide.
7. A method for producing a precursor of a lithium adsorbent according to claim 1 or 2, wherein the oxidizing agent is at least one selected from the group consisting of sodium hypochlorite, potassium hypochlorite, sodium chlorite, potassium chlorite, hypochlorous acid, chlorous acid, ammonium peroxodisulfate, and sodium peroxodisulfate.
8. The method for producing a precursor of a lithium adsorbent according to claim 1 or 2, wherein the addition of the oxidizing agent in the oxidation step is carried out under conditions of 40°C to 60°C.
9. A method for producing a precursor of a lithium adsorbent according to claim 1 or 2, wherein in the oxidation step, the oxidizing agent is added to set the oxidation-reduction potential of the raw material mixture slurry to -100 mV or more and 1000 mV or less at a silver / silver chloride electrode.