Method for producing lithium solution

Abstract

A method for producing a lithium solution according to the present disclosure comprises igniting a mixture of alpha-spodumene and metallic aluminum to cause a thermite reaction and bringing the reaction product into contact with a leaching agent to obtain a lithium solution. The leaching agent may be water or sulfuric acid. When the leaching agent is water, it is also possible to obtain a lithium solution by bringing water into contact with the reaction product without subjecting the reaction product to a sulfation treatment.

Description

Lithium solution production method

[0001] The present disclosure relates to a method for producing a lithium solution.

[0002] Lithium is a resource recovered from brines in salt lakes or from an ore called spodumene. Lithium is contained in spodumene in the form of lithium aluminosilicate (LiAl(SiO3)2). Naturally occurring spodumene is in the α-spodumene state.

[0003] The sulfuric acid method is a well-known method for leaching lithium from spodumene (Non-Patent Documents 1 and 2). In the sulfuric acid method, α-spodumene undergoes a phase transition to β-spodumene in order to efficiently leach lithium from spodumene. Specifically, α-spodumene is heat-treated (calcined) at a temperature of approximately 1100°C to produce β-spodumene. The β-spodumene is then subjected to a sulfation treatment to convert the Li2O contained in the β-spodumene into Li2SO4. The β-spodumene is immersed in water to leach the Li2SO4 into the water. This produces an aqueous lithium sulfate solution. From the aqueous lithium sulfate solution, desired lithium compounds such as lithium carbonate and lithium hydroxide are produced.

[0004] Masao Kobayashi, "Lithium resources, production, and applications," Journal of the Mining Industry of Japan / 1001152 ('84-2) 115-122. Tian-ming Gao et al., "Lithium extraction from hard rock lithium ores (spodumene, lepidolite, zinnwaldite, petalite): Technology, resources, environment, and cost," China Geology, 6, 2023, 137-153.

[0005] Heat treatment for transforming α-spodumene into β-spodumene is generally carried out using a rotary kiln. Heat treatment using a rotary kiln requires a long time. Therefore, a technology for shortening the time required for transforming α-spodumene into β-spodumene is desired.

[0006] The present disclosure provides a method for producing a lithium solution, comprising: igniting a mixture of α-spodumene and metallic aluminum to cause a thermite reaction; and contacting the reaction product with a leaching agent to obtain a lithium solution.

[0007] According to the techniques of the present disclosure, the time required for the phase transition of α-spodumene to β-spodumene can be reduced.

[0008] Fig. 1 is a process diagram showing a method for producing a lithium solution according to an embodiment of the present disclosure. Fig. 2 is a graph showing the results of powder X-ray diffraction measurement of α-spodumene powder (lower row) and the reaction product of Example 1 (upper row). Fig. 3 is a graph showing the results of powder X-ray diffraction measurement of the reaction product of Example 1 (lower row) and the X-ray diffraction pattern of β-spodumene (upper row).

[0009] Hereinafter, embodiments of the present disclosure will be described with reference to the drawings. The present disclosure is not limited to the following embodiments.

[0010] 1 is a process diagram showing a method for producing a lithium solution according to an embodiment of the present disclosure. The lithium solution may be an aqueous solution containing lithium. Examples of aqueous solutions containing lithium include an aqueous lithium sulfate solution and an aqueous lithium hydroxide solution.

[0011] In step S1, α-spodumene and metallic aluminum are mixed together to obtain a mixture thereof.

[0012] The α-spodumene may be α-spodumene powder. The α-spodumene powder is obtained by crushing and beneficiating ore extracted from a mine. The average particle size of the α-spodumene powder is adjusted to, for example, a range of 5 mm or less. With this configuration, the phase transition from α-spodumene to β-spodumene can proceed efficiently. The average particle size of the α-spodumene powder is desirably 2 mm or less. The average particle size of the α-spodumene powder is, for example, greater than 300 μm.

[0013] The metallic aluminum may be metallic aluminum powder. The metallic aluminum powder has an average particle size adjusted to, for example, a range of 0.1 μm to 300 μm. With this configuration, the α-spodumene powder can be uniformly and quickly heated by the thermite reaction.

[0014] The average particle size of the metallic aluminum powder is desirably smaller than that of the α-spodumene powder. The method according to the present disclosure is a method for promoting the phase transition of spodumene by utilizing a thermite reaction. When the average particle size of the metallic aluminum powder is smaller than that of the α-spodumene powder, the metallic aluminum powder that causes the thermite reaction is likely to be dispersed and disposed around the α-spodumene powder, which is desirable from the viewpoint of efficiently progressing the phase transition.

[0015] In this specification, the average particle size refers to the median size. The median size refers to the particle size (d50) corresponding to 50% cumulative volume in the particle size distribution of particles. The particle size distribution is measured, for example, by a laser diffraction / scattering particle size distribution analyzer.

[0016] In the mixture, the ratio (Wa / Ws) of the mass of metallic aluminum Wa to the mass of α-spodumene Ws is, for example, in the range of 0.2 to 2.5, preferably in the range of 0.2 to 1, and more preferably in the range of 0.2 to 0.5. From an economical standpoint, it is desirable to use as little metallic aluminum as possible.

[0017] In step S2, the mixture is ignited to cause a thermite reaction. Step S2 is carried out in an atmosphere containing oxygen gas, typically in an air atmosphere at atmospheric pressure. The aluminum metal burns violently, consuming oxygen contained in the atmosphere and oxygen contained in the α-spodumene. This reaction involving combustion is called the thermite reaction. The thermite reaction raises the temperature of the mixture to approximately 2000°C. The thermite reaction is completed in a short period of time.

[0018] It should be noted that the phase transition from α-spodumene to β-spodumene does not occur only during the thermite reaction. After the thermite reaction reaches its maximum temperature, the phase transition also progresses in a high-temperature environment, which is maintained by the time it takes for the temperature to decrease. This is because the phase transition from α-spodumene to β-spodumene can occur at temperatures above 900°C.

[0019] Through heat treatment due to the thermite reaction, α-spodumene undergoes a phase transition to β-spodumene. α-spodumene has a monoclinic crystal structure. β-spodumene has a tetragonal crystal structure. Therefore, the transformation from α-spodumene to β-spodumene can be confirmed by powder X-ray diffraction measurement.

[0020] According to a conventional method using a rotary kiln, α-spodumene needs to be heat-treated (calcined) at a temperature of about 1100°C for 3 to 4 hours. In contrast, according to the method of the present embodiment, which applies the thermite reaction, the time spent on external heating can be significantly reduced. As a result, it becomes possible to efficiently produce a lithium solution.

[0021] Furthermore, rotary kilns consume fossil fuels such as heavy oil, coal, and LPG. Reducing CO2 emissions has become an urgent issue in recent years, and there is a need to curb the use of fossil fuels and reduce CO2 emissions at lithium solution manufacturing sites as well. According to this embodiment, CO2 emissions can also be reduced because natural energy can be used to refine aluminum metal.

[0022] When using the thermite reaction of metallic aluminum, aluminum oxide (Al2O3) remains as an impurity in the reaction product. Aluminum oxide is a component of spodumene. Therefore, according to this embodiment, no special post-processing is required to remove the impurities.

[0023] In step S3, the reaction product is brought into contact with a leaching agent. The reaction product includes β-spodumene powder and aluminum oxide powder. By bringing the reaction product into contact with the leaching agent, lithium is leached from the β-spodumene powder. This results in a lithium solution. In this embodiment, the reaction product is immersed in a liquid leaching agent.

[0024] An example of a leaching agent is liquid water. The water is preferably purified water from which impurities have been removed by distillation or treatment using a separation membrane. Water is easy to handle as a leaching agent. When water is used as a leaching agent, an aqueous solution of lithium hydroxide is obtained as a lithium solution.

[0025] Another example of a leaching agent is sulfuric acid, which can be used to efficiently leach lithium from β-spodumene powder. When sulfuric acid is used as a leaching agent, an aqueous lithium sulfate solution is obtained as the lithium solution.

[0026] The concentration of sulfuric acid is not particularly limited, and sulfuric acid having a mass concentration of 10% to 98% can be used as appropriate.

[0027] The temperature of the leaching agent is, for example, 10° C. or higher and 98° C. or lower. The time for which the reaction product is brought into contact with the leaching agent (leaching time) is, for example, 0.1 hours or higher and 200 hours or lower. By appropriately adjusting the temperature of the leaching agent and the leaching time, the lithium concentration in the lithium solution can be increased.

[0028] One of the conventional methods for producing a lithium solution from α-spodumene is the sulfuric acid method. In the conventional sulfuric acid method, α-spodumene is subjected to a phase transition to β-spodumene, followed by a sulfation treatment to convert the LiO contained in the β-spodumene into LiSO. The sulfation treatment involves mixing β-spodumene powder with sulfuric acid and then heating the mixture at a temperature of approximately 250°C using a sulfuric acid roaster. By immersing the reaction product obtained through the sulfation treatment in water, LiSO leaches into the water, producing an aqueous lithium sulfate solution.

[0029] In contrast, according to one embodiment of the present disclosure, a lithium solution can be obtained by bringing water into contact with the reaction product without subjecting the reaction product to a sulfation treatment. That is, according to this embodiment, it is possible to omit the sulfation treatment and produce a lithium solution without using sulfuric acid. Even without performing the sulfation treatment and without using sulfuric acid as a leaching agent, a lithium solution having a lithium concentration close to that of an aqueous lithium sulfate solution obtained by a conventional sulfuric acid method can be obtained. Because lithium oxide readily reacts with water, lithium oxide contained in β-spodumene can be eluted into water according to the reaction of the following formula (1). Because other elements such as Fe and Mg cannot be eluted into water, a lithium aqueous solution with higher purity can be obtained compared to when sulfuric acid is used.

[0030] Li2O+H2O→2Li + +2OH - ...(1)

[0031] In step S4, solid-liquid separation is performed. The liquid phase of the slurry obtained through step S3 contains a lithium solution. The solid phase of the slurry contains solid matter such as β-spodumene residue, aluminum oxide, and unreacted metallic aluminum. The lithium solution and solid matter can be separated by a separation method such as centrifugation or membrane separation. As a result, the target lithium solution is obtained.

[0032] When the lithium solution is a lithium sulfate aqueous solution, lithium carbonate can be obtained in the form of a precipitate by adding sodium carbonate to the lithium sulfate aqueous solution. A lithium hydroxide aqueous solution can be obtained by adding calcium hydroxide to the lithium sulfate aqueous solution. Lithium carbonate and lithium hydroxide are, for example, raw materials for the active material of lithium-ion secondary batteries.

[0033] (Other Embodiments) (Additional Notes) The above description of the embodiments discloses the following techniques.

[0034] (Technology 1) A method for producing a lithium solution, comprising: igniting a mixture of α-spodumene and metallic aluminum to cause a thermite reaction; and contacting the reaction product with a leaching agent to obtain a lithium solution.

[0035] According to the techniques of the present disclosure, the time required for the phase transition of α-spodumene to β-spodumene can be reduced.

[0036] (Technology 2) The method for producing a lithium solution according to Technology 1, wherein the leaching agent is water. Water as the leaching agent is easy to handle.

[0037] (Technology 3) The method for producing a lithium solution according to Technology 1, wherein the leaching agent is sulfuric acid. When sulfuric acid is used, lithium can be efficiently leached from β-spodumene powder.

[0038] (Technology 4) The method for producing a lithium solution according to any one of Technologies 1 to 3, wherein the metallic aluminum is metallic aluminum powder, and the metallic aluminum powder has an average particle size in the range of 0.1 μm or more and 300 μm or less. With this configuration, the α-spodumene powder can be uniformly and quickly heated by the thermite reaction.

[0039] (Technology 5) The method for producing a lithium solution according to Technology 4, wherein the α-spodumene is α-spodumene powder, and the metallic aluminum powder has an average particle size smaller than that of the α-spodumene powder. When the metallic aluminum powder has an average particle size smaller than that of the α-spodumene powder, the metallic aluminum powder that causes the thermite reaction is likely to be dispersed and disposed around the α-spodumene powder, which is desirable from the viewpoint of efficiently progressing the phase transition.

[0040] (Technology 6) The method for producing a lithium solution according to any one of Technologies 1 to 5, wherein the temperature of the leaching agent is 10°C or higher and 98°C or lower, and the time for which the reaction product is brought into contact with the leaching agent is 0.1 hours or higher and 200 hours or lower. By appropriately adjusting the temperature of the leaching agent and the leaching time, the lithium concentration in the lithium solution can be increased.

[0041] (Technology 7) The method for producing a lithium solution according to Technology 2, wherein the reaction product is brought into contact with water to obtain the lithium solution without subjecting the reaction product to a sulfation treatment. According to the technology of the present disclosure, it is possible to omit the sulfation treatment and to produce a lithium solution without using sulfuric acid.

[0042] (Technology 8) The method for producing a lithium solution according to Technology 2 or 7, which satisfies at least one selected from the group consisting of: a ratio of the iron content in the lithium solution to the lithium content in the lithium solution being 50% or less on a mass basis; a ratio of the manganese content in the lithium solution to the lithium content in the lithium solution being 50% or less on a mass basis; and a ratio of the nickel content in the lithium solution to the lithium content in the lithium solution being 50% or less on a mass basis. A low content of other metal elements is desirable from the viewpoint of producing a high-purity lithium compound.

[0043] [Preparation of α-spodumene powder] α-Spodumene (manufactured by Albemarle) was pulverized in a mortar to obtain α-spodumene powder. Powder X-ray diffraction measurement of the α-spodumene powder was carried out. The results are shown in Figure 2. The same α-spodumene powder was used in the following examples and comparative examples.

[0044] Example 1 A mixture was prepared by mixing 0.2 g of α-spodumene powder and 0.5 g of metallic aluminum powder (manufactured by Fujifilm Wako Pure Chemical Industries, Ltd., with 80% or more of the powder having a particle size of 53 μm to 150 μm). The mixture was placed in a carbon crucible and ignited to cause a thermite reaction, yielding a reaction product. The reaction product was allowed to cool naturally, and then subjected to powder X-ray diffraction measurement. The results are shown in Figure 2.

[0045] The reaction product was immersed in 50 mL of pure water at 25° C. for 168 hours. Then, solid-liquid separation was performed by filtration. Thus, the lithium solution of Example 1 was obtained.

[0046] [X-ray Diffraction Measurement] The conditions for powder X-ray diffraction measurement of the α-spodumene powder and the reaction product of Example 1 were as follows.

[0047] Powder X-ray diffractometer: Rigaku MiniFlex600 X-ray source: CuKα ray Scanning speed: 10 deg / min

[0048] (Example 2) A lithium solution of Example 2 was obtained in the same manner as in Example 1, except that the reaction product obtained through the thermite reaction was immersed in 50 mL of sulfuric acid at 25°C for 168 hours. As the sulfuric acid, sulfuric acid with a mass concentration of 50% was used.

[0049] (Comparative Example 1) Using a heating furnace, 0.2 g of α-spodumene powder was heat-treated at 1000°C for 4 hours. This resulted in β-spodumene powder. The β-spodumene powder was immersed in 50 mL of pure water at 25°C for 168 hours. Thereafter, solid-liquid separation was carried out by filtration. This resulted in the lithium solution of Comparative Example 1.

[0050] (Comparative Example 2) Using a heating furnace, 0.2 g of α-spodumene powder was heat-treated at 1000°C for 4 hours. As a result, β-spodumene powder was obtained. The β-spodumene powder was immersed in 50 mL of sulfuric acid at 25°C for 168 hours. The sulfuric acid used had a mass concentration of 50%. Thereafter, solid-liquid separation was performed by filtration. As a result, a lithium solution of Comparative Example 2 was obtained.

[0051] Comparative Example 3 0.2 g of α-spodumene powder was immersed in 50 mL of pure water at 25° C. for 168 hours. Then, solid-liquid separation was carried out by filtration. Thus, a lithium solution of Comparative Example 3 was obtained.

[0052] (Comparative Example 4) Using a microwave decomposition system (BLADE, manufactured by CEM), 0.2 g of α-spodumene powder was immersed in 10 mL of sulfuric acid at 250°C for 60 seconds. Then, solid-liquid separation was carried out by filtration. As a result, a lithium solution of Comparative Example 4 was obtained.

[0053] [ICP Optical Emission Spectroscopy] The lithium solutions of the examples and comparative examples were diluted with pure water to a concentration within the calibration curve to prepare samples. The lithium concentration (mg / L) of each sample was measured using an ICP optical emission spectrometer (iCAP PRO XP ICP-OES, manufactured by Thermo Fisher Scientific). The results are shown in Table 1.

[0054]

[0055] Fig. 2 is a graph showing the results of powder X-ray diffraction measurement of α-spodumene powder (lower row) and the reaction product of Example 1 (upper row). The reaction product of Example 1 is a reaction product obtained via a thermite reaction. Fig. 3 is a graph showing the results of powder X-ray diffraction measurement of the reaction product of Example 1 (lower row) and the X-ray diffraction pattern of β-spodumene (upper row). The results of powder X-ray diffraction measurement of the reaction product of Example 1 are common to Fig. 2 and Fig. 3. The X-ray diffraction pattern of β-spodumene is literature data.

[0056] As can be seen from a comparison of the X-ray diffraction pattern in the lower row of FIG. 2 with the X-ray diffraction pattern in the upper row of FIG. 2, the crystal structure of spodumene changed significantly due to the thermite reaction.

[0057] As can be seen from a comparison of the X-ray diffraction pattern in the lower row of Figure 3 with the X-ray diffraction pattern in the upper row of Figure 3, the X-ray diffraction pattern of the reaction product obtained via the thermite reaction contained a peak derived from β-spodumene, a peak derived from metallic aluminum, and a peak derived from aluminum oxide. This result indicates that α-spodumene was converted to β-spodumene via the thermite reaction.

[0058] In Table 1, "Li leaching rate (%)" represents the ratio of each measured value to the measured value of Comparative Example 2.

[0059] As shown in Table 1, the lithium solution of Example 2 exhibited a lithium concentration approximately equal to that of the lithium solution of Comparative Example 2 obtained by heat treatment at 1000° C. for 4 hours.

[0060] The lithium solution of Example 1 exhibited a lithium concentration that was approximately half of that of the lithium solution of Comparative Example 2. The lithium solution of Example 1 was obtained using water as the leaching agent. Nevertheless, the lithium solution of Example 1 exhibited a lithium concentration that was comparable to that of the lithium solution of Comparative Example 2.

[0061] The lithium concentration in the lithium solution of Comparative Example 1 was less than 1 / 10 of the lithium concentration in the lithium solution of Comparative Example 2. The lithium solution of Comparative Example 1 was obtained through heat treatment at 1000° C. for 4 hours. However, because pure water was used as the leaching agent in Comparative Example 1, almost no lithium could be leached from the spodumene.

[0062] The lithium concentrations in the lithium solutions of Comparative Examples 3 and 4 were less than 1 / 10 of the lithium concentration in the lithium solution of Comparative Example 2. In Comparative Examples 3 and 4, since no heat treatment was performed, almost no lithium could be leached from the α-spodumene.

[0063] The iron, manganese and nickel contents in the lithium solutions of Examples 1 and 2 were as shown in Table 2.

[0064]

[0065] As shown in Table 2, the contents of iron, manganese, and nickel in the lithium solution of Example 1 were all lower than the contents of iron, manganese, and nickel in the lithium solution of Example 2. In other words, the method of Example 1 was more advantageous in suppressing the leaching of other metal elements from β-spodumene than the method of Example 2. A low content of other metal elements is desirable from the viewpoint of producing a high-purity lithium compound.

[0066] The lithium solutions in each example were obtained at a stage in which lithium was leached from β-spodumene. In the lithium solution of Example 1, the ratio of the iron content to the lithium content (Fe / Ni) was 50% or less by mass. The lower limit of the ratio (Fe / Ni) is not particularly limited and may be, for example, 10%. However, the iron content in the lithium solution may be below the detection limit of the ICP optical emission spectrometer. In the lithium solution of Example 1, the ratio of the manganese content to the lithium content (Mn / Li) was 50% or less by mass. The lower limit of the ratio (Mn / Li) depends on the detection limit of the ICP optical emission spectrometer, but is generally zero. In the lithium solution of Example 1, the ratio of the nickel content to the lithium content (Ni / Li) was 50% or less by mass. The lower limit of the ratio (Ni / Li) is not particularly limited and may be, for example, 10%. However, the nickel content in the lithium solution may be below the detection limit of the ICP optical emission spectrometer.

[0067] The techniques of the present disclosure are useful for recovering lithium from ores.

Claims

1. A method for producing a lithium solution, comprising: igniting a mixture of α-spodumene and metallic aluminum to cause a thermite reaction; and contacting the reaction product with a leaching agent to obtain a lithium solution.

2. The method for producing a lithium solution according to claim 1, wherein the leaching agent is water.

3. The method for producing a lithium solution according to claim 1, wherein the leaching agent is sulfuric acid.

4. The method for producing a lithium solution according to claim 1, wherein the metallic aluminum is metallic aluminum powder, and the metallic aluminum powder has an average particle size in the range of 0.1 μm or more and 300 μm or less.

5. The method for producing a lithium solution according to claim 4, wherein the α-spodumene is α-spodumene powder, and the average particle size of the metallic aluminum powder is smaller than the average particle size of the α-spodumene powder.

6. The method for producing a lithium solution according to claim 1, wherein the temperature of the leaching agent is 10°C or higher and 98°C or lower, and the time for which the reaction product is brought into contact with the leaching agent is 0.1 hours or higher and 200 hours or lower.

7. The method for producing a lithium solution according to claim 2, wherein the reaction product is brought into contact with the water to obtain the lithium solution without subjecting the reaction product to a sulfation treatment.

8. The method for producing a lithium solution according to claim 2, wherein at least one of the following is satisfied: a ratio of the iron content in the lithium solution to the lithium content in the lithium solution is 50% or less on a mass basis; a ratio of the manganese content in the lithium solution to the lithium content in the lithium solution is 50% or less on a mass basis; and a ratio of the nickel content in the lithium solution to the lithium content in the lithium solution is 50% or less on a mass basis.

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