A magnetic lithium extraction adsorbent, a preparation method and application thereof

Abstract

The present disclosure provides a magnetic lithium extraction adsorbent and a preparation method and application thereof, the preparation method comprising the following steps: (1) mixing iron salt, ferrous salt, aluminum salt and hydrophilic organic polymer with a solvent to obtain a mixed solution; (2) using a syringe pump, dropping the mixed solution into a base-lithium salt-ammonium carbonate salt-ethanol mixed solution through an electrostatic spraying device to obtain microspheres; (3) post-treating the microspheres to obtain the magnetic lithium extraction adsorbent. The adsorbent prepared by the method has magnetism, can realize solid-liquid separation through a magnet, and does not need to be filtered and the like, so that the lithium extraction process is more convenient.

Description

Technical Field

[0001] This disclosure belongs to the field of lithium extraction technology from salt lakes, and relates to a magnetic lithium extraction adsorbent, its preparation method and application. Background Technology

[0002] With the continuous advancement of science and technology, and the rapid development of new energy, metallurgy, and aerospace industries, the demand for lithium in various fields is constantly increasing. The content of lithium in the Earth's crust is very low; a small portion exists in rock deposits, while the majority is contained in salt lake brines. China is a major country in salt lake brine lithium resources, with salt lake lithium resources accounting for more than 80% of the country's total lithium resources and about one-third of the world's salt lake lithium resources. Preliminary estimates suggest lithium salt reserves of tens of millions of tons.

[0003] Currently, the main lithium extraction technologies in China include: electrodialysis, extraction, precipitation, calcination, and adsorption. Different salt lakes require different processes and preparation methods. The first four processes are more suitable for extracting high-concentration lithium resources from old brine in salt lakes; however, significant losses occur during the conversion of raw brine into old brine. Therefore, directly extracting lithium from raw brine can reduce resource waste, making the adsorption method highly competitive.

[0004] Traditional lithium adsorbents require granulation, but the granulated adsorbent particles are large and have a small specific surface area, making it difficult to fully utilize the lithium extraction capacity of the adsorbent.

[0005] CN111644145A discloses a method for preparing a magnetic adsorbent, in which an aluminum-based adsorbent is grown on the surface of a magnetic material. However, this bonding method relies solely on molecular bonds. During the adsorption process, the aluminum-based adsorbent undergoes volume expansion and contraction due to the insertion and extraction of lithium ions, making it easy for the outer layer and the core to separate.

[0006] CN108607503A discloses a magnetic adsorbent and its application method for lithium extraction from high magnesium-to-lithium ratio salt lake brine; zeolite powder with a particle size of 100-300 μm is screened, a manganese salt solution is added to it, and then lithium hydroxide is added to form a lithium ion adsorbent LiMn2O4 in the zeolite micropores using the zeolite powder as a template; the surface of the lithium ion adsorbent LiMn2O4 particles is coated with a nano-silica dispersion, and Fe3O4 or γ-Fe2O3 magnetic powder and calcium chloride are further adhered to it. Calcium silicate is formed by the nano-silica and calcium chloride, thereby firmly fixing the magnetic powder on the surface. After drying, a spherical outer layer of porous magnetic powder is obtained.

[0007] The magnetic adsorbent material prepared by the above method has poor structural stability, and the prepared adsorbent particles are small, making it difficult to separate by magnetic means when dissolved and dispersed in solution, resulting in adsorbent loss. Summary of the Invention

[0008] The following is an overview of the subject matter described in detail herein. This overview is not intended to limit the scope of the claims.

[0009] The purpose of this disclosure is to provide a magnetic lithium extraction adsorbent, its preparation method, and its application. The adsorbent prepared by the method described in this disclosure is magnetic and can achieve solid-liquid separation through a magnet, eliminating the need for brine filtration and other operations, thus simplifying the lithium extraction process.

[0010] To achieve this objective, the present disclosure adopts the following technical solution:

[0011] In a first aspect, this disclosure provides a method for preparing a magnetic lithium extraction adsorbent, the method comprising the following steps:

[0012] (1) Iron salt, ferrous salt, aluminum salt and hydrophilic organic polymer are mixed with solvent to obtain a mixed solution;

[0013] (2) Using an injection pump, the mixed solution is dripped into the alkali-lithium salt-ammonium carbonate-ethanol mixed solution through an electrostatic spraying device to obtain microspheres;

[0014] (3) The microspheres are post-processed to obtain the magnetic lithium adsorbent.

[0015] This disclosure encapsulates magnetic materials and adsorbents into spheres using a hydrophilic organic polymer. The narrow particle size distribution of these microspheres ensures uniformity of the material composition and maintains excellent sphericity even after prolonged adsorption, minimizing breakage and dissolution. The electrostatic spraying method simplifies the granulation process of the aluminum-based adsorbent, combining granulation with synthesis. This allows the adsorbent to be synthesized during the granulation process, eliminating the need for subsequent powder granulation.

[0016] In one embodiment, the iron salt in step (1) includes any one or a combination of at least two of ferric chloride, ferric sulfate, or ferric nitrate.

[0017] In one embodiment, the ferrous salt includes any one or a combination of at least two of ferrous chloride, ferrous sulfate, or ferrous nitrate.

[0018] In one embodiment, the aluminum salt includes any one or a combination of at least two of aluminum chloride, aluminum sulfate, or aluminum nitrate.

[0019] In one embodiment, the hydrophilic organic polymer includes any one or a combination of at least two of polystyrene, epoxy resin, polymethyl methacrylate, polyvinyl chloride, chitosan, or chlorinated polyvinyl chloride.

[0020] In one embodiment, the solvent includes any one or a combination of at least two of N-methylpyrrolidone, acetone, or ethyl acetate.

[0021] In one embodiment, the molar ratio of ferrous ions in the ferrous salt and ferric ions in the ferric salt in step (1) is (1-1.5):(2-3), for example: 1:2, 1.2:2.5, 1.5:2.2, 1.8:2.5 or 1.5:3, etc.

[0022] In one embodiment, the total molar amount of iron in the ferrous and ferrous salts and the molar ratio of aluminum in the aluminum salts are (0.05 to 0.1):1, for example: 0.05:1, 0.06:1, 0.08:1, 0.09:1 or 0.1:1, etc.

[0023] In one embodiment, the solid-liquid ratio of the hydrophilic organic polymer to the solvent in step (1) is 5 to 20 mg / mL, for example: 5 mg / mL, 8 mg / mL, 10 mg / mL, 15 mg / mL or 20 mg / mL, etc.

[0024] In one embodiment, the mixing temperature in step (1) is 60 to 80°C, for example: 60°C, 65°C, 70°C, 75°C or 80°C.

[0025] In one embodiment, the mixing time is 5 to 10 hours, for example: 5 hours, 6 hours, 8 hours, 9 hours, or 10 hours.

[0026] In one embodiment, the flow rate of the mixed solution in the syringe pump in step (2) is 1 to 8 mL / h, for example: 1 mL / h, 2 mL / h, 4 mL / h, 6 mL / h or 8 mL / h, etc.

[0027] In one embodiment, the voltage of the electrostatic spraying device is 16 to 22 kV, for example: 16 kV, 18 kV, 20 kV, 21 kV or 22 kV, etc.

[0028] In one embodiment, the concentration of ammonium carbonate in the alkali-lithium salt-ammonium carbonate-ethanol mixed solution in step (2) is 0.1 to 0.5 mol / L, for example: 0.1 mol / L, 0.2 mol / L, 0.3 mol / L, 0.4 mol / L or 0.5 mol / L, etc.

[0029] In one embodiment, the concentration of alkali in the alkali-lithium salt-ammonium carbonate-ethanol mixed solution is 1 to 3 mol / L, for example: 1 mol / L, 1.5 mol / L, 2 mol / L, 2.5 mol / L or 3 mol / L, etc.

[0030] In one embodiment, the concentration of lithium salt in the alkali-lithium salt-ammonium carbonate-ethanol mixed solution is 0.1 to 1 mol / L, for example: 0.1 mol / L, 0.2 mol / L, 0.5 mol / L, 0.8 mol / L or 1 mol / L, etc.

[0031] In one embodiment, the alkali-lithium salt-ammonium carbonate-ethanol mixed solution in step (2) includes water.

[0032] In one embodiment, the volume ratio of ethanol to water is (2-5):1, for example: 2:1, 2.5:1, 3:1, 4:1 or 5:1, etc.

[0033] In one embodiment, the post-processing in step (3) includes washing and drying.

[0034] In one embodiment, the detergent used for washing includes ultrapure water.

[0035] In one embodiment, the microspheres are washed until the pH is neutral.

[0036] In one embodiment, the median particle size D50 of the magnetic lithium extraction adsorbent is 100–1000 μm, for example: 100 μm, 200 μm, 500 μm, 800 μm or 1000 μm, etc.

[0037] In a second aspect, this disclosure provides a magnetic lithium extraction adsorbent, which is prepared by the method described in the first aspect.

[0038] The adsorbent prepared by the method described in this disclosure is magnetic, and solid-liquid separation can be achieved through a magnet, eliminating the need for brine filtration and other operations, thus simplifying the lithium extraction process.

[0039] Thirdly, this disclosure provides an application of the magnetic lithium extraction adsorbent as described in the second aspect, wherein the magnetic lithium extraction adsorbent is used for lithium extraction from salt lakes.

[0040] Compared with the prior art, this disclosure has the following beneficial effects:

[0041] (1) The adsorbent particles prepared by the method described in this disclosure have smaller particle sizes and larger specific surface areas compared to traditional granulation methods, which is more conducive to the contact between the adsorbent and the brine. Furthermore, the hydrophilic organic polymer facilitates the wetting of the adsorbent by the brine. In addition, the ammonium carbonate salt decomposes during the drying process to generate gas, creating pores in the microspheres, which further increases the specific surface area of ​​the adsorbent. All of these factors contribute to increasing the lithium extraction capacity of the adsorbent.

[0042] (2) The adsorption capacity described in this disclosure can reach more than 9.54 mg / g, and the capacity retention rate of the lithium-extracting adsorbent after 100 cycles can reach more than 96.84%.

[0043] After reading and understanding the accompanying diagrams and detailed descriptions, the other aspects can be understood. Attached Figure Description

[0044] The accompanying drawings are used to provide a further understanding of the technical solutions in this paper and form part of the specification. They are used together with the embodiments of this application to explain the technical solutions in this paper and do not constitute a limitation on the technical solutions in this paper.

[0045] Figure 1 This is a SEM image of the magnetic lithium extraction adsorbent prepared in Example 1 of this disclosure.

[0046] Figure 2 This is a hysteresis curve of the magnetic lithium extraction adsorbent prepared in Example 1 of this disclosure. Detailed Implementation

[0047] The technical solutions of this disclosure will be further illustrated below through specific embodiments. Those skilled in the art should understand that the embodiments described are merely illustrative of this disclosure and should not be construed as specific limitations thereof.

[0048] Example 1

[0049] This embodiment provides a magnetic lithium extraction adsorbent, and the preparation method of the magnetic lithium extraction adsorbent is as follows:

[0050] (1) Mix 0.02 mol ferrous sulfate and 0.0175 mol ferric sulfate (Fe) 2+ :Fe 3+ =1.5:2.65) and 10g of epoxy resin and 1mol of aluminum sulfate were added to 1L of acetone and stirred at 60℃ for 10h to prepare a homogeneous solution;

[0051] (2) Microspheres were obtained by dripping the above homogenized solution into a mixed solution of alkali-lithium salt-ammonium carbonate-ethanol using an injection pump (5 mL / h) and an electrostatic spray device. The concentration of ammonium bicarbonate was 0.2 mol / L, the concentration of sodium hydroxide was 2 mol / L, the concentration of lithium chloride was 0.2 mol / L, the volume ratio of ethanol to water was 2.5:1, and the voltage of the electrostatic spray device was 20 kV.

[0052] (3) After filtering the microspheres, wash them with ultrapure water until the pH is about 7, and dry them at 80℃ for 10h to obtain a magnetic lithium extraction adsorbent with a D50 of 300μm.

[0053] The SEM image of the magnetic lithium extraction adsorbent is shown below. Figure 1 As shown, by Figure 1 It can be seen that the magnetic lithium extraction adsorbent is spherical with a narrow particle size distribution, which can ensure the uniformity of the material composition.

[0054] The hysteresis curve of the magnetic lithium extraction adsorbent is as follows: Figure 2 As shown, by Figure 2 It can be seen that the specific saturation magnetization of the magnetic lithium extraction adsorbent is 10.89 ecm / g. The magnetic lithium extraction adsorbent exhibits good magnetism, and the hysteresis loop shows a rapid increase with increasing magnetic field strength, followed by a gradual plateauing, which is consistent with the characteristics of strongly magnetic materials. The specific saturation magnetization of the magnetic lithium extraction adsorbent is slightly lower than that of the magnetic titanium-based adsorbent, possibly because the magnetic lithium extraction adsorbent is an amorphous crystal, and the magnetization phenomenon of this component is not obvious.

[0055] Example 2

[0056] This embodiment provides a magnetic lithium extraction adsorbent, and the preparation method of the magnetic lithium extraction adsorbent is as follows:

[0057] (1) Mix 0.015 mol ferrous sulfate and 0.019 mol ferric sulfate (Fe) 2+ :Fe 3+ A homogeneous solution was prepared by adding 5g of polystyrene and 1mol of aluminum sulfate (r=1:2.5) to 1L of acetone and stirring at 60℃ for 10h.

[0058] (2) Microspheres were obtained by dripping the above homogenized solution into a mixed solution of alkali-lithium salt-ammonium carbonate-ethanol using an injection pump (1 mL / h) and an electrostatic spray device. The concentration of ammonium bicarbonate was 0.1 mol / L, the concentration of sodium hydroxide was 1 mol / L, the concentration of lithium chloride was 0.1 mol / L, the volume ratio of ethanol to water was 2:1, and the voltage of the electrostatic spray device was 16 kV.

[0059] (3) After filtering the microspheres, wash them with ultrapure water until the pH is about 7, and dry them at 80℃ for 10h to obtain a magnetic lithium extraction adsorbent with a D50 of 100μm.

[0060] Example 3

[0061] This embodiment provides a magnetic lithium extraction adsorbent, and the preparation method of the magnetic lithium extraction adsorbent is as follows:

[0062] (1) Mix 0.02 mol ferrous sulfate and 0.03 mol ferric sulfate (Fe) 2+ :Fe 3+ A homogeneous solution was prepared by adding 20g of polymethyl methacrylate (PMMA) and 1mol of aluminum sulfate to 1L of ethyl acetate and stirring at 70°C for 8 hours.

[0063] (2) Microspheres were obtained by dripping the above homogenized solution into a mixed solution of alkali-lithium salt-ammonium carbonate-ethanol using an injection pump (8 mL / h) and an electrostatic spray device. The concentration of ammonium bicarbonate was 0.5 mol / L, the concentration of sodium hydroxide was 3 mol / L, the concentration of lithium chloride was 1 mol / L, the volume ratio of ethanol to water was 5:1, and the voltage of the electrostatic spray device was 22 kV.

[0064] (3) After filtering the microspheres, wash them with ultrapure water until the pH is about 7, and dry them at 80℃ for 10h to obtain a magnetic lithium extraction adsorbent with a D50 of 1000μm.

[0065] Example 4

[0066] The only difference between this embodiment and Embodiment 1 is that Fe 2+ :Fe 3+ =1:1, and other conditions and parameters are exactly the same as in Example 1.

[0067] Example 5

[0068] The only difference between this embodiment and Embodiment 1 is that Fe 2+ :Fe 3+ =1:4, and other conditions and parameters are exactly the same as in Example 1.

[0069] Example 6

[0070] The only difference between this embodiment and Embodiment 1 is that the mass of the epoxy resin is 3g; all other conditions and parameters are exactly the same as in Embodiment 1.

[0071] Example 7

[0072] The only difference between this embodiment and Embodiment 1 is that the mass of the epoxy resin is 30g, while the other conditions and parameters are exactly the same as in Embodiment 1.

[0073] Example 8

[0074] The only difference between this embodiment and Embodiment 1 is that the volume ratio of ethanol to water is 1:2, while the other conditions and parameters are exactly the same as in Embodiment 1.

[0075] Example 9

[0076] The only difference between this embodiment and Embodiment 1 is that the electrostatic spray voltage is 10kV, while the other conditions and parameters are exactly the same as in Embodiment 1.

[0077] Example 10

[0078] The only difference between this embodiment and Embodiment 1 is that the flow rate of the syringe pump is 20 mL / h, while the other conditions and parameters are exactly the same as in Embodiment 1.

[0079] Comparative Example 1

[0080] This comparative example provides a magnetic lithium extraction adsorbent, and the preparation method of the magnetic lithium extraction adsorbent is as follows:

[0081] Using iron(III) oxide with a D50 of 150 nm as the core, it was dispersed in a 1 mol / L aluminum chloride solution with a solid-liquid ratio of 1 mg / mL. Then, a 2 mol / L sodium hydroxide solution was added, with the amount of sodium hydroxide added being three times the amount of aluminum chloride. Subsequently, lithium chloride with a molar amount equal to that of aluminum chloride was added. After dispersion and reaction, the mixture was stirred for 1 h to obtain an aluminum adsorbent with an internal magnetic core.

[0082] Comparative Example 2

[0083] The only difference between this comparative example and Example 1 is that no hydrophilic organic polymer is added; all other conditions and parameters are exactly the same as in Example 1.

[0084] Performance testing:

[0085] The adsorption performance test method is static adsorption. This adsorbent was used for Li + Lithium was extracted from brine with a concentration of 500 ppm. 20 g of deionized water and 2 g of lithium adsorbent were mixed and extracted at room temperature for 10 h. The concentration of brine before and after adsorption was measured, and the adsorption capacity was calculated according to the following formula.

[0086] The adsorption capacity of the adsorbent is: Q = V(C0 - C) / m;

[0087] Q is the adsorption capacity, mg / g; V is the adsorption liquid volume, L; m is the adsorbent mass, g; C0 and C are the lithium ion concentrations in the brine before and after adsorption, mg / L, respectively.

[0088] The ratio of the adsorption capacity to the initial adsorption capacity after 100 cycles is used to obtain the capacity retention rate after 100 cycles.

[0089] The test results are shown in Table 1:

[0090] Table 1

[0091]

[0092]

[0093] As can be seen from Table 1, as obtained from Examples 1-3, the adsorption capacity of the present disclosure can reach more than 9.54 mg / g, and the capacity retention rate of the lithium extraction adsorbent after 100 cycles can reach more than 96.84%.

[0094] A comparison of Examples 1 and 4-5 shows that the molar ratio of ferrous salt to ferric salt affects the performance of the magnetic lithium extraction adsorbent disclosed in this invention. Controlling the molar ratio of ferrous salt to ferric salt to (1-1.5):(2-3) results in a better performance of the adsorbent. If the ratio of ferrous salt to ferric salt is not within this range, it is difficult to form iron(III) oxide in the alcohol solution, which reduces the magnetism of the lithium extraction adsorbent and increases the difficulty of solid-liquid separation after lithium extraction.

[0095] A comparison of Examples 1 and 6-7 shows that the solid-liquid ratio of the hydrophilic organic polymer to the solvent affects the performance of the magnetic lithium extraction adsorbent disclosed in this invention. Controlling the solid-liquid ratio of the hydrophilic organic polymer to the solvent to 5-20 mg / mL results in a better performance of the adsorbent. If the amount of hydrophilic organic polymer added is too large, the adsorption capacity of the adsorbent will be reduced. If the amount of hydrophilic organic polymer added is too small, the brine cannot fully wet the adsorbent, which is not conducive to the performance of its adsorption capacity.

[0096] A comparison of Examples 1 and 8 shows that during the preparation of the magnetic lithium adsorbent disclosed herein, when the ethanol content in the alkali-lithium salt-ammonium carbonate-ethanol mixed solution in step (2) is low, the ferrous ions and ferric ions in the mixed solution are unlikely to undergo the above-mentioned reaction, thus affecting the magnetism of the adsorbent.

[0097] A comparison of Examples 1 and 9 shows that in the preparation process of the magnetic lithium extraction adsorbent described in this disclosure, the electrostatic spraying voltage is low, resulting in a larger spherical particle size, which reduces the specific surface area of ​​the material and affects the adsorption capacity. Increasing the voltage does not further affect the particle size, therefore there is no need to set a higher voltage to increase energy consumption.

[0098] A comparison of Examples 1 and 10 shows that during the preparation of the magnetic lithium extraction adsorbent described in this disclosure, if the injection pump flow rate is too high, it will disrupt the balance of fluid surface tension, gravity, and electric field, resulting in an irregular spherical structure that is easily dissolved during adsorption.

[0099] As can be seen from the comparison between Example 1 and Comparative Example 1, the adsorbent particles that directly use iron oxide as the magnetic core have a smaller particle size. During the magnetic adsorption process, some particles may be dispersed in the solution and cannot be attracted by the magnet. In comparison, the particle size of this disclosure is more suitable, which can ensure both the specific surface area of ​​the adsorbent and the efficiency of solid-liquid separation.

Claims

1. A method for preparing a magnetic lithium extraction adsorbent, comprising the following steps: (1) mixing a ferric salt, a ferrous salt, an aluminum salt and a hydrophilic organic polymer with a solvent to obtain a mixed solution; (2) using a syringe pump, dropping the mixed solution into a base-lithium salt-ammonium carbonate salt-ethanol mixed solution through an electrostatic spraying device to obtain microspheres; (3) post-treating the microspheres to obtain the magnetic lithium extraction adsorbent; the hydrophilic organic polymer comprises any one or a combination of at least two of polystyrene, epoxy resin, polymethyl methacrylate, polyvinyl chloride, chitosan or chlorinated polyvinyl chloride.

2. The production method according to claim 1, wherein the ferric salt in step (1) comprises any one or a combination of at least two of ferric chloride, ferric sulfate or ferric nitrate.

3. The production method according to claim 1, wherein the ferrous salt comprises any one or a combination of at least two of ferrous chloride, ferrous sulfate or ferrous nitrate.

4. The production method according to claim 1, wherein the aluminum salt comprises any one or a combination of at least two of aluminum chloride, aluminum sulfate or aluminum nitrate.

5. The production method according to claim 1, wherein the solvent comprises any one or a combination of at least two of N-methyl pyrrolidone, acetone or ethyl acetate.

6. The production method according to claim 1, wherein the molar ratio of ferrous ions in the ferrous salt to trivalent iron ions in the ferric salt in step (1) is (1-1.5) :(2-3).

7. The production method according to claim 1, wherein the total molar amount of iron elements in the ferric salt and the ferrous salt to the molar amount of aluminum elements in the aluminum salt is (0.05-0.1) :

1.

8. The production method according to claim 1, wherein the solid-liquid ratio of the hydrophilic organic polymer to the solvent is 5-20 mg / mL.

9. The production method as claimed in claim 1, wherein, the stirring temperature of the mixing in step (1) is 60-80℃.

10. The production method according to claim 9, wherein the stirring time of the mixing is 5-10 h.

11. The production method as claimed in claim 1, wherein, the flow rate of the mixed solution in the syringe pump in step (2) is 1-8 mL / h.

12. The production method as claimed in claim 1, wherein, the voltage of the electrostatic spraying device is 16-22 kV.

13. The production method according to claim 1, wherein the concentration of the ammonium carbonate salt in the base-lithium salt-ammonium carbonate salt-ethanol mixed solution in step (2) is 0.1-0.5 mol / L.

14. The production method according to claim 1, wherein the concentration of the base in the base-lithium salt-ammonium carbonate salt-ethanol mixed solution is 1-3 mol / L.

15. The production method according to claim 1, wherein the concentration of the lithium salt in the base-lithium salt-ammonium carbonate salt-ethanol mixed solution is 0.1-1 mol / L.

16. The production method as claimed in claim 1, wherein, the base-lithium salt-ammonium carbonate salt-ethanol mixed solution in step (2) comprises water.

17. The production method according to claim 16, wherein the volume ratio of the ethanol to the water is (2-5) :

1.

18. The production method as claimed in claim 1, wherein, the post-treatment in step (3) comprises washing and drying.

19. The production method according to claim 18, wherein the washing agent for the washing comprises ultrapure water.

20. The production method according to claim 19, wherein the pH of the microspheres after the washing is neutral.

21. The production method as claimed in claim 1, wherein, the median particle size D50 of the magnetic lithium extraction adsorbent is 100-1000 μm. 22.A magnetic lithium extraction adsorbent prepared by the method according to any one of claims 1-21. 23.Use of the magnetic lithium extraction adsorbent according to claim 22 for lithium extraction from salt lakes.

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