Lithium ion extractant for lithium, magnesium ion separation and preparation method thereof

Abstract

The application discloses a lithium ion extractant for lithium and magnesium ion separation and a preparation method thereof, and belongs to the technical field of lithium and magnesium ion separation. The lithium ion extractant for lithium and magnesium ion separation is an organic acid root ion doped aluminum lithium bimetallic hydroxide, and a structural formula of the lithium ion extractant is LiX*2Al(OH)3*YH2O, wherein X is an organic acid root ion, Y is the number of crystal water contained in a phase, and the adsorption capacity of the extractant for lithium ions is 8-16 mg / g. The preparation method of the lithium ion extractant takes a sodium aluminate solution and an alkaline lithium salt solution as raw materials, adopts a coprecipitation method to prepare the lithium ion extractant, and simultaneously adds an organic acid as a doping modifier to form a complex ion with lithium ions. The lithium ion extractant can effectively improve the adsorption capacity for lithium ions, thereby improving the separation effect of lithium ions and magnesium ions, and can be effectively applied to direct extraction of lithium ions in a high magnesium-lithium ratio solution such as salt lake brine.

Description

Technical Field

[0001] This invention belongs to the field of lithium and magnesium ion separation technology, and more specifically, relates to a lithium ion extractant for lithium and magnesium ion separation and its preparation method. Background Technology

[0002] With the rapid development of the new energy industry, the demand for batteries continues to rise, and lithium is considered a key metal affecting global economic development. Lithium resources include brine, lepidolite ore, and recycled lithium-ion batteries. Due to its lower extraction cost compared to lepidolite and lithium ore, salt lake brine is the most important lithium resource, accounting for approximately 70% of the world's industrially available lithium resources.

[0003] Salt lake brine is generally a chloride solution system with a LiCl content of approximately 265–1888 mg / L. The main cations in the brine are Li. + Na + K + Mg 2+ Ca 2+ The main anion is Cl. - SO4 2- CO3 2- HCO3 - NO3 - The pH of the solution before lithium extraction is approximately 5–11. The key to lithium extraction from brine solutions is Li... + and Mg 2+ Existing methods for lithium ion separation often involve magnesium extraction followed by lithium extraction, resulting in the loss of lithium resources. Therefore, direct extraction of lithium ions from solutions with a high magnesium-to-lithium ratio is of great significance. Lithium-aluminum layered double hydroxides are excellent lithium ion extractants and can be used to adsorb lithium ions from high magnesium solutions.

[0004] The literature Li Y, Tang N, Zhang L, et al, Colloids and Surfaces A: Physicochemical and Engineering Aspects, 2023, 658: 130641 describes a one-pot method for processing Fe... 3+ Doping and Li + Intercalation reaction coupling was used to prepare Li + and Mg 2+ Li-Al-Fe-Cl LDH with a separation coefficient of 35.83; Li was prepared by co-precipitation method as described in the literature Zhong J, Lin S, Yu J, Desalination, 2021, 505:114983. + and Mg 2+Li / Al-LDHs with a separation coefficient of 125; The literature Zhong J, Lin S, Yu J, Separation And Purification Technology, 2021, 256:117780 describes a novel granulation method for preparing Li… + and Mg 2+ Granulated Li / Al-LDHs (GLDHs) with a separation coefficient of 156.1. Reference Chen J, Lin S, Yu J, Separation and Purification Technology, 2021, 255:117710 describes the preparation of magnetic lithium-aluminum layered double hydroxides (MLDHs) via a fractional co-precipitation method at a solid-liquid ratio of 1:40. + and Mg 2+ The separation coefficient was 153.51. Chinese patent CN108854996A prepared Li by modifying the surface of aluminum hydroxide with a coupling agent. + and Mg 2+ Lithium adsorbent with a separation coefficient of 27.5–29.8.

[0005] Comparative analysis of the above research findings shows that the lithium-ion extractants prepared by existing methods are effective against Li-ion contamination. + and Mg 2+ The separation coefficient still needs to be further improved, and existing lithium-ion extractants cannot effectively solve the problem of efficient separation of lithium ions and magnesium ions in salt lake brine. Summary of the Invention

[0006] 1. The problem to be solved

[0007] The purpose of this invention is to provide a lithium ion extractant for the separation of lithium and magnesium ions and its preparation method, thereby solving the problem in the prior art that lithium ions cannot be directly and efficiently extracted from solutions with a high magnesium-to-lithium ratio, such as salt lake brine.

[0008] 2. Technical Solution

[0009] To solve the above problems, the technical solution adopted by the present invention is as follows:

[0010] This invention provides a lithium-ion extractant for the separation of lithium and magnesium ions. The lithium-ion extractant is an aluminum-lithium bimetallic hydroxide doped with organic acid anions, with the structural formula LiX·2Al(OH)3·YH2O, where X is an organic acid anion and Y has a value of 1.0-3.0. The extractant has an adsorption capacity of 8-16 mg / g for lithium ions.

[0011] Furthermore, the organic acid anions are acetate ions, butyrate ions, or acetic acid ions, with butyrate ions providing the best separation effect for lithium ions and magnesium ions.

[0012] Furthermore, the extractant has a nanosheet structure with a specific surface area of ​​9-15 m². 2 / g, the thickness of the sheet-like structure is 180-220nm.

[0013] Furthermore, the extractant is prepared by co-precipitation using sodium aluminate solution and alkaline lithium salt solution as raw materials, with the addition of organic acid as a dopant modifier.

[0014] The present invention also provides a method for preparing the above-mentioned lithium-ion extractant, which uses sodium aluminate solution and alkaline lithium salt solution as raw materials and adopts a co-precipitation method to prepare the lithium-ion extractant, while adding organic acid as a dopant modifier to form complex ions with lithium ions.

[0015] Furthermore, the amount of organic acid added is 1-5 g / L of reaction solution.

[0016] Furthermore, the reaction synthesis temperature is 25-80℃, the reaction time is 3-10 min, the aging temperature is 50-100℃, and the aging time is 1-7 h.

[0017] Furthermore, the alkaline lithium salt solution is a lithium carbonate, lithium bicarbonate, or lithium hydroxide solution.

[0018] Furthermore, the concentration of alumina in the sodium aluminate solution is 80-150 g / L, and the molecular ratio of the solution is 1.0-5.0.

[0019] Furthermore, the concentration of lithium ions in the alkaline lithium salt solution is 1-20 g / L.

[0020] 3. Beneficial effects

[0021] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0022] (1) The lithium ion extractant of the present invention is an aluminum-lithium bimetallic hydroxide doped with organic acid ions. By doping with organic acid ions, the adsorption capacity for lithium ions can be effectively improved, thereby improving the separation effect of lithium ions and magnesium ions, so that it can be effectively applied to the direct extraction of lithium ions in solutions with high magnesium-to-lithium ratios, such as salt lake brine.

[0023] (2) This invention uses sodium aluminate solution and alkaline lithium salt solution as raw materials and prepares aluminum-lithium bimetallic hydroxide by coprecipitation method. By adding a certain organic acid as a doping modifier, the form of lithium ions in the solution can be changed, so that the acid radical ions and lithium ions form complex ions. The formation of complex ions allows acid radical ions to be smoothly doped between the aluminum-lithium LDH layers, which is beneficial to the preparation of acid radical ion doped aluminum-lithium bimetallic hydroxide with nanosheet structure, thus further ensuring the separation effect of lithium ions and magnesium ions.

[0024] (3) The adsorption capacity of the acetic acid-doped lithium aluminum hydride LDH synthesized in this invention can be higher than 16.0 mg / g, and the adsorption capacity of the butyric acid-doped lithium aluminum hydride LDH material can be higher than 13.74 mg / g. Moreover, the separation coefficient of butyric acid-doped lithium aluminum hydride LDH for magnesium ions and lithium ions can be as high as 3.64 × 10⁻⁶. 6 . Attached Figure Description

[0025] Figure 1 The image shows a comparison of the XRD patterns of the lithium-ion extractant synthesized in Example 1 before and after adsorption.

[0026] Figure 2 The image shows a comparison of the XRD patterns of the lithium-ion extractant synthesized in Example 2 before and after adsorption.

[0027] Figure 3 The image shows a comparison of the XRD patterns of the lithium-ion extractant synthesized in Example 3 before and after adsorption.

[0028] Figure 4 The images show a comparison of the microstructures of the lithium-ion extractants synthesized in Examples 1-3 and Comparative Example 1.

[0029] Wherein: (a) is the morphology of the comparative synthesis of lithium aluminum LDH; (b) is the morphology of the butyric acid-doped lithium aluminum LDH synthesized in Example 1; (c) is the morphology of the butyric acid-doped lithium aluminum LDH synthesized in Example 2; and (d) is the morphology of the butyric acid-doped lithium aluminum LDH synthesized in Example 3. Detailed Implementation

[0030] This invention uses sodium aluminate solution, alkaline lithium salt solution, and organic acids as reactants to prepare organic acid anion-doped aluminum-lithium bimetallic hydroxides via a co-precipitation method. After doping modification, the adsorption capacity for lithium ions and the separation effect between lithium ions and magnesium ions are effectively improved, thus enabling the selective separation and extraction of lithium ions in high magnesium-to-lithium ratio solutions such as salt lake brine. The organic acids in this invention include acetic acid, butyric acid, and acetic acid, while the alkaline lithium salt solution includes lithium carbonate, lithium bicarbonate, and lithium hydroxide solutions. During the synthesis process, organic solvents such as ethanol and dichloromethane, which are miscible with water, are used, with the amount of organic solvent added accounting for 1% to 10% of the volume ratio of the aqueous solution. The organic acids can be added to either the sodium aluminate solution or the alkaline lithium salt solution.

[0031] Organic acid anions in the solution alter the form of lithium ions. Lithium ions and acid anions can form complex ion pairs. Organic acid anion-doped lithium aluminum LDH is prepared during the co-precipitation process of lithium ions and aluminate ions. The conversion equations between aluminate ions are shown in equations (1) and (2). Taking butyrate ions as an example, the reaction equations for the formation of complex ions between lithium ions and acid anions are shown in equations (3), (4), and (5). The reaction equations for complex anion-doped lithium aluminum LDH are shown in equations (6), (7), and (8), where X represents organic acid anions.

[0032]

[0033]

[0034] C3H7COOH + LiOH = C3H7COO - ·Li + +H2O (3)

[0035] Li + ·4H2O+C3H7COO - =Li + ·3H2O·C3H7COO-+H2O (4)

[0036] Li + ·4H2O+C3H7COO - =Li + ·2H2O·C3H7COO-+2H2O (5)

[0037]

[0038]

[0039]

[0040] It should also be noted that the X in the LiX·2Al(OH)3·YH2O prepared by this invention not only contains organic acid anions, but may also be doped with a certain amount of OH. - , but OH - Since the doping amount of ions cannot be precisely measured, OH has been omitted in this application. - Ion doping.

[0041] The present invention will be further described below with reference to specific embodiments.

[0042] Example 1

[0043] The preparation method of the lithium-ion extractant for lithium and magnesium ion separation in this embodiment includes the following steps:

[0044] (1) Prepare a sodium aluminate solution with an aluminum oxide concentration of 150 g / L and a solution molecular ratio (molar ratio of sodium oxide to aluminum oxide in the sodium aluminate solution) of 1.5;

[0045] (2) Prepare a lithium hydroxide solution with a lithium ion concentration of 2 g / L;

[0046] (3) Add butyric acid to sodium aluminate solution at a concentration of 4 g / L;

[0047] (4) Butyric acid-doped lithium aluminum LDH was prepared by mixing sodium aluminate solution and lithium hydroxide solution with a constant flow pump at a mixing temperature of 25°C and a synthesis time of 5 minutes; the aging temperature was 70°C and the aging time was 7 hours. The butyric acid-doped lithium aluminum LDH prepared in this example is LiC3H7COO·2Al(OH)3·2.8H2O.

[0048] Example 2

[0049] The preparation method of the lithium-ion extractant for lithium and magnesium ion separation in this embodiment includes the following steps:

[0050] (1) Prepare a sodium aluminate solution with an aluminum oxide concentration of 80 g / L and a molecular ratio of 1.2.

[0051] (2) Prepare a lithium hydroxide solution with a lithium ion concentration of 2 g / L;

[0052] (3) Add butyric acid to sodium aluminate solution at a concentration of 2 g / L;

[0053] (4) Butyric acid-doped lithium aluminum hydride (LDH) was prepared by mixing sodium aluminate solution and lithium hydroxide solution using a constant flow pump at a mixing temperature of 25°C and a synthesis time of 5 minutes; the aging temperature was 70°C and the aging time was 7 hours. The butyric acid-doped lithium aluminum hydride (LDH) prepared in this embodiment is LiC3H7COO·2Al(OH)3·2H2O.

[0054] Example 3

[0055] The preparation method of the lithium-ion extractant for lithium and magnesium ion separation in this embodiment includes the following steps:

[0056] (1) Prepare a sodium aluminate solution with an aluminum oxide concentration of 150 g / L and a molecular ratio of 1.5.

[0057] (2) Prepare a lithium hydroxide solution with a lithium ion concentration of 2 g / L;

[0058] (3) Add butyric acid to sodium aluminate solution at a concentration of 1 g / L, and add 10% ethanol to lithium hydroxide solution;

[0059] (4) Butyric acid-doped lithium aluminum hydride (LDH) was prepared by mixing sodium aluminate solution and lithium hydroxide solution using a constant flow pump at a mixing temperature of 25°C and a synthesis time of 5 minutes; the aging temperature was 70°C and the aging time was 7 hours. The butyric acid-doped lithium aluminum hydride (LDH) prepared in this embodiment is LiC3H7COO·2Al(OH)3·1.8H2O.

[0060] Comparative Example

[0061] The preparation method of the lithium-ion extractant in this comparative example includes the following steps:

[0062] (1) Prepare a sodium aluminate solution with an aluminum oxide concentration of 150 g / L and a molecular ratio of 1.5.

[0063] (2) Prepare a lithium hydroxide solution with a lithium ion concentration of 2 g / L;

[0064] (3) Aluminum lithium LDH was prepared by mixing sodium aluminate solution and lithium hydroxide solution with a constant flow pump at a mixing temperature of 25°C and a synthesis time of 5 minutes; the aging temperature was 70°C and the aging time was 7 hours.

[0065] (4) The adsorption liquid-solid ratio was 20 ml / g, the adsorption time was 60 min, the adsorption temperature was 25℃, and the lithium ion adsorption capacity was 5.80 mg / g.

[0066] Figures 1-3 XRD analysis showed that the phase after lithium ion adsorption remained as lithium aluminum hydride (LDH), indicating that the lithium ion adsorption-desorption process did not change the phase structure of the material. In Example 1, the highest characteristic peak position of the butyrate-doped lithium aluminum hydride LDH was 11.60°; in Example 2, it was 11.64°; and in Example 3, it was 11.69°. A smaller peak position indicates a larger interlayer spacing; increased interlayer spacing is beneficial for lithium ion adsorption, therefore Example 1 exhibits better adsorption performance. Lithium ions were extracted using the lithium ion adsorbents obtained in Examples 1-3 and Comparative Example 1, with a lithium ion concentration of 301.2 mg·L⁻¹ in the original adsorption solution. -1 The magnesium ion concentration was 102.05 g·L⁻¹. -1 The adsorption liquid-to-solid ratio was 20 ml / g, the adsorption time was 60 min, and the adsorption temperature was 25℃. The adsorption results are shown in Table 1 below. As can be seen from the table, the separation effect of lithium ions and magnesium ions can be effectively improved by organic acid doping modification. Simultaneously, combined with... Figure 4It can be seen that after modification with organic acid doping, a smaller sheet-like structure can be formed, thus providing more active adsorption sites.

[0067] Table 1. Adsorption capacity of magnesium and lithium ions and magnesium-lithium separation effect of the materials used to prepare lithium aluminum LDH.

[0068]

[0069] Example 4

[0070] The preparation method of the lithium-ion extractant for lithium and magnesium ion separation in this embodiment includes the following steps:

[0071] (1) Prepare a sodium aluminate solution with an aluminum oxide concentration of 95 g / L and a molecular ratio of 5.

[0072] (2) Prepare a lithium carbonate solution with a lithium ion concentration of 20 g / L;

[0073] (3) Add acetic acid to sodium aluminate solution at a concentration of 5 g / L, and add ethanol at a volume ratio of 10% to lithium carbonate solution.

[0074] (4) Acetic acid-doped lithium aluminum ether (LDH) was prepared by mixing sodium aluminate solution and lithium carbonate solution using a constant flow pump at a mixing temperature of 80°C and a synthesis time of 3 minutes; the aging temperature was 100°C and the aging time was 5 hours.

[0075] (5) Lithium ions were extracted using the lithium ion extractant synthesized in this embodiment. The lithium ion concentration in the adsorption solution was 301.2 mg·L⁻¹. -1 The magnesium ion concentration was 102.05 g·L⁻¹. -1 The adsorption liquid-to-solid ratio was 20 ml / g, the adsorption time was 60 min, the adsorption temperature was 25℃, the adsorption capacity for lithium ions was 16.0 mg / g, the adsorption capacity for magnesium ions was 0.60 mg / g, and the separation coefficient was 81177.38.

[0076] Example 5

[0077] The preparation method of the lithium-ion extractant for lithium and magnesium ion separation in this embodiment includes the following steps:

[0078] (1) Prepare a sodium aluminate solution with an aluminum oxide concentration of 110 g / L and a molecular ratio of 1.0.

[0079] (2) Prepare a lithium bicarbonate solution with a lithium ion concentration of 5 g / L;

[0080] (3) Add oxalic acid to sodium aluminate solution at a concentration of 3.5 g / L, and add 10% ethanol by volume to lithium bicarbonate solution.

[0081] (4) Oxalic acid-doped lithium aluminum DH was prepared by mixing sodium aluminate solution and lithium bicarbonate solution with a constant flow pump at a mixing temperature of 35°C and a synthesis time of 10 minutes; the aging temperature was 50°C and the aging time was 6 hours.

[0082] (5) Lithium ions were extracted using the lithium ion extractant synthesized in this embodiment. The lithium ion concentration in the adsorption solution was 301.2 mg·L⁻¹. -1 The magnesium ion concentration was 102.05 g·L⁻¹. -1 The adsorption liquid-to-solid ratio was 20 ml / g, the adsorption time was 60 min, the adsorption temperature was 25℃, the adsorption capacity for lithium ions was 11.0 mg / g, the adsorption capacity for magnesium ions was 0.40 mg / g, and the separation coefficient was 23949.74.

Claims

1. A lithium-ion extractant for separating lithium and magnesium ions, characterized in that, The lithium-ion extractant is an aluminum-lithium bimetallic hydroxide doped with organic acid anions, with the structural formula LiX·2Al(OH)3·YH2O, where X is an organic acid anion and Y has a value of 1.0-3.

0. The extractant has an adsorption capacity of 8-16 mg / g for lithium ions; the organic acid anion is acetate ion, butyrate ion, or oxalate ion.

2. The lithium-ion extractant for separating lithium and magnesium ions according to claim 1, characterized in that, The extractant has a nanosheet structure with a specific surface area of ​​9-15 m². 2 / g, the thickness of the sheet-like structure is 180-220nm.

3. The lithium-ion extractant for separating lithium and magnesium ions according to claim 2, characterized in that, The extractant is prepared by co-precipitation using sodium aluminate solution and alkaline lithium salt solution as raw materials, with the addition of organic acid as a dopant modifier.

4. A method for preparing a lithium-ion extractant for separating lithium and magnesium ions as described in any one of claims 1-3, characterized in that, The lithium ion extractant was prepared by co-precipitation using sodium aluminate solution and alkaline lithium salt solution as raw materials, while organic acid was added as a dopant to form complex ions with lithium ions.

5. The method for preparing the lithium-ion extractant for lithium and magnesium ion separation according to claim 4, characterized in that, The amount of organic acid added is 1-5 g / L of reaction solution.

6. The method for preparing the lithium-ion extractant for lithium and magnesium ion separation according to claim 5, characterized in that, The reaction synthesis temperature is 25-80℃, the reaction time is 3-10 min, the aging temperature is 50-100℃, and the aging time is 1-7 h.

7. The method for preparing the lithium-ion extractant for lithium and magnesium ion separation according to any one of claims 4-6, characterized in that, The alkaline lithium salt solution is a lithium carbonate, lithium bicarbonate, or lithium hydroxide solution.

8. The method for preparing the lithium-ion extractant for lithium and magnesium ion separation according to any one of claims 4-6, characterized in that, The concentration of alumina in the sodium aluminate solution is 80-150 g / L, and the molecular ratio of the solution is 1.0-5.

0.

9. The method for preparing the lithium-ion extractant for lithium and magnesium ion separation according to any one of claims 4-6, characterized in that, The concentration of lithium ions in the alkaline lithium salt solution is 1-20 g / L.

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