A lithium ion sieve adsorbent and its preparation method and application

Abstract

The present invention relates to the field of ion sieve adsorbent materials, and discloses a lithium-extracting ion sieve adsorbent, and its preparation method and application. The method comprises: in the presence of an organic solvent, dropping acryloyl chloride into a mixed solution I containing spiropyran and triethylamine to carry out a mixing reaction I to obtain polyspiropyran; relative to 1g of the mixed solution I; dropping the mixed solution Ⅰ containing the polyspiropyran into a metal salt solution to carry out a mixing reaction Ⅰ to obtain the lithium-extracting ion sieve adsorbent; the mixed solution Ⅰ also contains a ligand for synthesizing MOFs; the metal salt solution contains at least two of iron salts, zirconium salts and zinc salts. The lithium-extracting ion sieve adsorbent obtained by the preparation method provided by the present invention can reversibly adsorb and desorb adsorbed ions, and can efficiently extract Li from brine. + , to Na + Mg 2+ and Ca 2+ It also has high selectivity; and the lithium ion sieve adsorbent has good cycle performance.

Description

Technical Field

[0001] The present invention relates to the field of ion sieve adsorbent materials, and in particular to a lithium extraction ion sieve adsorbent and a preparation method and application thereof. Background Art

[0002] In recent years, the rapid development of industries such as glass, ceramics, grease, batteries, refrigerants, and medical has significantly increased demand for lithium resources. Nearly 80% of the world's lithium is stored in salt lake brines. Current methods for extracting lithium from these brines include precipitation, evaporative crystallization, solvent extraction, selective membrane separation, and ion adsorption. Precipitation and evaporative crystallization are only suitable for extracting lithium from salt lake brines with low Mg / Li ratios and pose significant environmental risks during operation. Ion adsorption, on the other hand, has attracted widespread attention from researchers due to its high recovery rate and high selectivity for lithium ions.

[0003] Currently, reports on lithium ion adsorbents from salt lakes focus on ion exchange resins, manganese-based, titanium-based, and aluminum-based ion sieves. Ion exchange resins offer ion selectivity but have low lithium absorption capacity. Aluminum-based adsorbents offer some improvement, but lithium absorption capacity remains low. Titanium-based and manganese-based ion sieves offer high ion selectivity and lithium absorption capacity, but require acid washing during synthesis and subsequent desorption, leading to the loss of titanium and magnesium ions. Furthermore, these processes pose environmental risks and require long adsorbent regeneration times.

[0004] As a new functional porous material in recent years, MOFs have a uniform pore structure and adjustable pore size, high porosity and large specific surface area, making them an ideal reagent for selective ion adsorption. At the same time, polyspiropyran (PSP) as a photoisomer can be converted into a zwitterionic state under dark conditions to adsorb anions and cations from salt water, and release the adsorbed anions and cations under light to achieve rapid regeneration of the adsorbent. For example, CN115888667A discloses a method for preparing a photosensitive regenerated lithium adsorbent, which is a method for heating a metal organic framework MOF and spiropyran SP with an initiator to obtain a photosensitive regenerated lithium ion adsorbent PSP-MOF with high selectivity for lithium and magnesium. The adsorbed material is desorbed and regenerated by sunlight, showing excellent stability. However, the photosensitive regenerated lithium adsorbent has poor separation effect on lithium and sodium ions, low adsorption capacity for lithium, and difficult adsorbent recovery.

[0005] Therefore, it is urgent to prepare a material with high lithium ion selectivity, large adsorption capacity, easy regeneration, good cycle performance and stable structure for the extraction of lithium ions from salt lakes. Summary of the Invention

[0006] The purpose of the present invention is to overcome the defects of the prior art lithium ion sieve, such as poor stability, regeneration waste liquid pollution and recycling difficulty.

[0007] In order to achieve the above object, the first aspect of the present invention provides a method for preparing a lithium ion sieve adsorbent, the method comprising:

[0008] (1) In the presence of an organic solvent, acryloyl chloride is added dropwise to a mixed solution I containing spiropyran and triethylamine to perform a mixing reaction I to obtain polyspiropyran;

[0009] The acryloyl chloride is added at a flow rate of 1-3 mL / min relative to 1 g of the mixed solution I;

[0010] (2) adding the mixed solution Ⅰ containing the polyspiropyran dropwise to a metal salt solution to carry out a mixing reaction Ⅰ to obtain the lithium ion sieve adsorbent; the mixed solution Ⅰ also contains a ligand for synthesizing MOFs;

[0011] The metal salt solution contains at least two of iron salt, zirconium salt and zinc salt;

[0012] The addition rate of the mixed solution Ⅰ is 3-10 mL / min relative to 1 g of the metal salt solution; the average pore size of the lithium ion sieve adsorbent is 0.6-1.3 nm, and the specific surface area is 869-1438 m 2 / g.

[0013] The second aspect of the present invention provides a lithium ion sieve adsorbent prepared by the method described in the first aspect.

[0014] The third aspect of the present invention provides the use of the lithium ion extraction sieve adsorbent described in the second aspect in the extraction of lithium ions from salt lake brine.

[0015] Through the above technical solution, the present invention has at least the following advantages:

[0016] (1) The method for preparing a lithium ion sieve adsorbent provided by the present invention has a low preparation cost and can rapidly synthesize a lithium ion sieve adsorbent in large quantities at room temperature.

[0017] (2) The lithium ion sieve adsorbent provided by the present invention can efficiently extract Li from brine in a wide pH range. + , to Na + Mg 2+ and Ca 2+ It also has high selectivity.

[0018] (3) The lithium ion sieve adsorbent provided by the present invention can be used to reversibly adsorb and desorb the adsorbed ions through simple brightness adjustment, with good cycle performance, and no waste liquid is generated during the desorption process, which is environmentally friendly.

[0019] (4) The lithium ion sieve adsorbent provided by the present invention is easy to recover and can be separated from the solution by a magnet. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] Figure 1 This is a flow chart of the preparation method of the lithium ion sieve adsorbent according to Example 1 of the present invention;

[0021] Figure 2 Schematic diagram of the adsorption and desorption principle of the lithium ion sieve adsorbent prepared in Example 1 of the present invention;

[0022] Figure 3 Schematic diagram of the recovery of the lithium ion sieve adsorbent prepared in Example 1 of the present invention;

[0023] Figure 4 The lithium ion sieve adsorbent prepared in Example 1 of the present invention is Li in a 1000ppm solution under different pH conditions. + 、Na + Mg 2+ , Ca 2+ Adsorption capacity diagram;

[0024] Figure 5 The lithium ion sieve adsorbent prepared in Example 1 of the present invention is Li + 、Na + Mg 2+ , Ca 2+ Adsorption kinetics curve;

[0025] Figure 6 The lithium ion sieve adsorbent prepared in Example 1 of the present invention is Li + Desorption kinetics curve;

[0026] Figure 7 The adsorption capacity and ion selectivity curves of the lithium ion sieve adsorbent prepared in Example 1 of the present invention in solutions with different ion concentrations;

[0027] Figure 8 This is a cyclic stability curve of the lithium ion sieve adsorbent prepared in Example 1 of the present invention under continuous operation in a 1000 ppm solution at pH = 12. DETAILED DESCRIPTION

[0028] The endpoints of the ranges and any values disclosed herein are not limited to the precise ranges or values, and these ranges or values should be understood to include values close to these ranges or values. For numerical ranges, the endpoints of each range, the endpoints of each range and individual point values, and the individual point values can be combined with each other to obtain one or more new numerical ranges, which should be considered to be specifically disclosed herein.

[0029] In the present invention, MOFs is an organic-inorganic hybrid material, also known as a coordination polymer. It is different from both inorganic porous materials and general organic complexes, and has both the rigidity of inorganic materials and the flexibility of organic materials.

[0030] In the present invention, spiropyran is a photochromic dye.

[0031] In the present invention, 2-methylimidazole is an organic compound in the form of a white or off-white crystalline powder, which is easily soluble in water, alcohol solutions, and acetone, but poorly soluble in organic solutions such as benzene.

[0032] As mentioned above, the first aspect of the present invention provides a method for preparing a lithium ion sieve adsorbent, the method comprising:

[0033] (1) In the presence of an organic solvent, acryloyl chloride is added dropwise to a mixed solution I containing spiropyran and triethylamine to perform a mixing reaction I to obtain polyspiropyran;

[0034] The acryloyl chloride is added at a flow rate of 1-3 mL / min relative to 1 g of the mixed solution I;

[0035] (2) adding the mixed solution Ⅰ containing the polyspiropyran dropwise to a metal salt solution to carry out a mixing reaction Ⅰ to obtain the lithium ion sieve adsorbent; the mixed solution Ⅰ also contains a ligand for synthesizing MOFs;

[0036] The metal salt solution contains at least two of iron salt, zirconium salt and zinc salt;

[0037] The addition rate of the mixed solution Ⅰ is 3-10 mL / min relative to 1 g of the metal salt solution; the average pore size of the lithium ion sieve adsorbent is 0.6-1.3 nm, and the specific surface area is 869-1438 m 2 / g.

[0038] The inventors of the present invention discovered that by using spiropyran, ligands for synthesizing MOFs and metal salts as raw materials and controlling the process steps and reaction parameters, a lithium ion sieving adsorbent can be successfully prepared. The adsorbent has a high ion sieving ability and has a large pore cavity that can fix the photosensitive adsorbent therein, making the functionalized MOFs have good stability during actual use.

[0039] Preferably, the ligand used to synthesize MOFs is 2-methylimidazole, and the metal salt solution contains zinc salt and iron salt.

[0040] Preferably, the molar ratio of the zinc salt to the iron salt is 1:0.1-0.6.

[0041] Preferably, the zinc salt is zinc acetate; and the iron salt is ferrous chloride.

[0042] Preferably, the ligand used to synthesize MOFs is terephthalic acid, and the metal salt solution contains zirconium salt and iron salt.

[0043] Preferably, the molar ratio of the zirconium salt to the iron salt is 1:0.5-1.

[0044] Preferably, the zirconium salt is zirconium chloride; and the iron salt is ferrous chloride.

[0045] Preferably, the ligand used to synthesize MOFs is trimesic acid, and the metal salt solution contains zirconium salt and iron salt.

[0046] Preferably, the molar ratio of the zirconium salt to the iron salt is 1:0.1-0.4.

[0047] Preferably, the zirconium salt is zirconium chloride; and the iron salt is ferrous chloride.

[0048] Preferably, in step (1), the molar ratio of the spiropyran to the triethylamine is 1:7-12.

[0049] Preferably, in step (1), the mixing reaction I includes a first mixing reaction I and a second mixing reaction I carried out sequentially, wherein the conditions of the first mixing reaction I include: temperature of -2 to 10°C, and time of 0.5-3h; the conditions of the second mixing reaction I include: temperature of 18-22°C, and time of 1-3h.

[0050] Preferably, in step (1), the organic solvent is dichloromethane.

[0051] Preferably, the method further comprises: in step (1), removing impurities from the product obtained from the mixed reaction I to obtain the polyspiropyran.

[0052] More preferably, the impurity removal treatment comprises filtering, washing and extracting performed in sequence.

[0053] More preferably, the extraction is performed using a basic alumina column.

[0054] Preferably, in step (2), in the mixed solution Ⅱ, the molar ratio of the polyspiropyran to the ligand for synthesizing MOFs is 0.3-0.8:1.

[0055] Preferably, in step (2), the conditions of the mixing reaction Ⅰ include: temperature of 25-50° C. and time of 0.5-10 h.

[0056] Preferably, the method further comprises: in step (2), washing the product obtained from the mixed reaction Ⅰ to obtain the lithium-extracting ion sieve adsorbent.

[0057] More preferably, the solvent used for the washing is selected from any one of methanol, ethanol, N,N-dimethylformamide and water.

[0058] As mentioned above, the second aspect of the present invention provides a lithium ion sieve adsorbent prepared by the method described in the first aspect.

[0059] As mentioned above, the third aspect of the present invention provides the use of the lithium ion extraction sieve adsorbent described in the second aspect in the extraction of lithium ions from salt lake brine.

[0060] The present invention will be described in detail below through examples.

[0061] In the following examples, unless otherwise specified, the instruments, reagents, materials, etc. involved are conventional instruments, reagents, materials, etc., which can be obtained through conventional commercial channels. In addition, unless otherwise specified, the reagents used are commercially available analytical grade products.

[0062] Acryloyl chloride was purchased from Shanghai MacLean Biochemical Technology Co., Ltd. with a CAS number of 814-68-6 and a purity of 96%.

[0063] Spiropyran was purchased from Beijing Huawei Ruike Chemical Co., Ltd. with a purity of 97%.

[0064] 2-Methylimidazole was purchased from Shanghai Aladdin Biochemical Technology Co., Ltd. with a CAS number of 693-98-1 and a purity of 98%.

[0065] Example 1

[0066] (1) In a 250 mL round-bottom flask, in the presence of 75 mL of an organic solvent (dichloromethane), acryloyl chloride was added dropwise to a mixed solution I containing spiropyran and triethylamine, and stirred to sequentially perform a first mixing reaction I (temperature: 0°C, time: 1 h) and a second mixing reaction I (temperature: 20°C, time: 2 h);

[0067] The product obtained from the second mixed reaction I was filtered to remove salt precipitation, diluted with 50 mL of dichloromethane, and then washed three times with 50 mL of saturated NaHCO3 solution and once with 50 mL of brine;

[0068] The washed product was dried with MgSO4, added with 15 mL of methanol, and extracted through a basic alumina column;

[0069] Finally, the remaining solvent was evaporated using a rotary evaporator at 40° C. and 90-100 kPa to obtain the polyspiropyran PSP.

[0070] (2) adding two or more metal salts to 5 mL of water and stirring uniformly to obtain a metal salt solution;

[0071] The aforementioned polyspiropyran and the ligand for synthesizing MOFs were added to 5 mL of water and stirred evenly to obtain a mixed solution containing polyspiropyran and the ligand for synthesizing MOFs ⅠⅠ;

[0072] The mixed solution Ⅰ containing polyspiropyran was added dropwise to the metal salt solution to carry out a mixing reaction Ⅰ (temperature of 25° C., time of 0.5 h), and the product obtained by the mixing reaction Ⅰ was washed three times with deionized water to obtain a lithium ion sieve adsorbent.

[0073] The present invention is exemplified in Figure 1 A flow chart for preparing the lithium ion sieve adsorbent in this embodiment is provided in FIG.

[0074] The raw material ratio and process conditions of this embodiment are shown in Table 1.

[0075] Unless otherwise specified, Examples 2 and 3 were carried out using a method similar to that of Example 1, except that the raw material ratios and process conditions were different. See Table 1 for details.

[0076] Table 1 (the amount of mixed solution I is 1g, the amount of metal salt solution is 1g)

[0077]

[0078]

[0079] Example 4

[0080] This example is carried out using a method similar to that of Example 1, except that, in this example, the ligand used to synthesize MOFs is 2-methylimidazole, and the metal salt is a combination of 1 mol nickel acetate and 0.5 mol copper chloride.

[0081] The lithium ion sieve adsorbent was obtained, with an average pore size of 1.12 nm and a specific surface area of 1326 m 2 / g.

[0082] Example 5

[0083] This example was carried out using a method similar to that of Example 3, except that, in this example, the ligand used to synthesize MOFs was trimesic acid, and the metal salt was a combination of 1 mol of zinc acetate and 0.8 mol of cuprous chloride.

[0084] The obtained lithium ion sieve adsorbent has an average pore size of 0.84nm and a specific surface area of 1035m 2 / g.

[0085] Comparative Example 1

[0086] This comparative example was carried out in a manner similar to that of Example 1, except that the amount of mixed solution I in this comparative example was kept unchanged and the dripping flow rate of acryloyl chloride was adjusted to 5 mL / min.

[0087] The obtained lithium ion sieve adsorbent has an average pore size of 1.11nm and a specific surface area of 1027m 2 / g.

[0088] Comparative Example 2

[0089] This comparative example was carried out in a manner similar to that of Example 1, except that the amount of the metal salt solution in this comparative example was kept unchanged and the addition flow rate of the mixed solution Ⅰ was adjusted to 1 mL / min.

[0090] The obtained lithium ion sieve adsorbent has an average pore size of 1.06nm and a specific surface area of 1236m 2 / g.

[0091] Test Case

[0092] The performance test of the lithium ion sieve adsorbent prepared in the above examples was carried out, including the adsorbent's performance on Li + 、Na + Mg 2+ , Ca 2+ The adsorption capacity of the adsorbent for Li at pH = 12 + 、Na + Mg 2+ , Ca 2+ The adsorption kinetics test, desorption kinetics test of the adsorbent in LiCl solution, adsorption capacity and ion selectivity test of the adsorbent in solutions with different ion concentrations, and cyclic stability test of the adsorbent during continuous operation.

[0093] Some test results are shown in Table 2.

[0094] The ion concentration is analyzed by ICP-AES; the adsorption amount Q is calculated by the ion concentration in the solution before and after ICP-AES analysis, and the formula is: Q t =(C0-C t )×V / (m×M);

[0095] In the formula, Q tis the ion adsorption capacity at any time t, C0 is the initial salt solution ion concentration, unit is mg / L; C t is the ion concentration of the salt solution at any time t, in mg / L; m is the mass of the adsorbent, in g; V is the volume of the salt solution, in L; M is the relative molecular mass of the metal ion.

[0096] Table 2

[0097]

[0098] The present invention is exemplified in Figure 2 A schematic diagram of the adsorption and desorption principle of the lithium ion sieve adsorbent prepared in Example 1 is provided. Figure 2 It can be seen that under dark conditions, the lithium ion sieve adsorbent can be used as a water-absorbing material to quickly absorb Ca 2+ Mg 2+ Screening, Li + and Na + After the adsorption is completed, the material is exposed to visible light and its hydrophobic properties are reversed to a hydrophobic material (the hydrophobic angle changes from 56° to 107°), and desorption and regeneration begin.

[0099] The present invention is exemplified in Figure 3 A schematic diagram of the recovery of the lithium ion sieve adsorbent prepared in Example 1 is provided. Figure 3 It can be seen that the lithium ion sieve adsorbent has a great effect on the Ca 2+ Mg 2+ 、Li + and Na + After adsorption, it is transferred to visible light and the adsorbent can be adsorbed by a magnet, thereby achieving rapid separation, desorption and regeneration, avoiding the use of acidic regeneration eluents and causing environmental pollution.

[0100] The present invention is exemplified in Figure 4 The lithium ion sieve adsorbent prepared in Example 1 is provided for Li under different pH conditions in a 1000 ppm solution. + 、Na + Mg 2+ , Ca 2+ Adsorption capacity diagram. Figure 4 It can be seen that with the increase of pH, the adsorption capacity of the adsorbent for cations in the salt solution gradually increases. When pH = 12, the lithium ion sieve adsorbent has the largest cation adsorption capacity, and its adsorption capacity remains basically unchanged as the alkalinity of the salt solution continues to increase.

[0101] The present invention is exemplified in Figure 5 The lithium ion sieve adsorbent prepared in Example 1 is provided for Li+ 、Na + Mg 2+ , Ca 2+ Adsorption kinetics curve. Figure 5 It can be seen that Na + 、Li + After 40 minutes, the adsorption reached saturation, and Ca 2+ Mg 2+ Adsorption saturation was reached after 10 min.

[0102] The present invention is exemplified in Figure 6 The lithium ion sieve adsorbent prepared in Example 1 is provided for Li + Desorption kinetics curve. Figure 6 It can be seen that Li + Complete desorption can be achieved after 8 minutes.

[0103] The present invention is exemplified in Figure 7 The adsorption capacity and ion selectivity curves of the lithium ion sieve adsorbent prepared in Example 1 in solutions with different ion concentrations are provided. Figure 7 It can be seen that as the salt concentration gradually increases, the adsorbent has a + 、Na + Mg 2+ , Ca 2+ The adsorption capacity increases accordingly. When the ion concentration in the solution exceeds 10000ppm, the adsorption capacity remains basically unchanged. When the ion concentration is 5000ppm, the adsorbent has the largest Li + Selectivity, continue to increase the salt concentration, the ion selectivity remains basically unchanged.

[0104] The present invention is exemplified in Figure 8 The cyclic stability curve of the lithium ion sieve adsorbent prepared in Example 1 under continuous operation in a 1000 ppm solution at pH = 12 is provided. Figure 8 It can be seen that after multiple adsorption-desorption tests, the adsorption capacity of the lithium ion sieve adsorbent did not decrease significantly.

[0105] From the above results, it can be seen that the lithium ion sieve adsorbent prepared by the method for preparing the lithium ion sieve adsorbent provided by the present invention can reversibly adsorb and desorb the adsorbed ions, and can efficiently extract Li from brine. + , to Na + Mg 2+ and Ca 2+ It also has high selectivity; and the lithium ion sieve adsorbent has good cycle performance.

[0106] The preferred embodiments of the present invention have been described in detail above, but the present invention is not limited thereto. Within the technical concept of the present invention, various simple variations of the technical solution of the present invention may be made, including combining the various technical features in any other appropriate manner. These simple variations and combinations should also be regarded as disclosed in the present invention and fall within the scope of protection of the present invention.

Claims

1. A method for preparing a lithium ion sieve adsorbent, characterized in that: The method includes: (1) In the presence of an organic solvent, acryloyl chloride is added dropwise to a mixed solution I containing spiropyran and triethylamine to perform a mixing reaction I to obtain polyspiropyran; The acryloyl chloride is added at a flow rate of 1-3 mL / min relative to 1 g of the mixed solution I; (2) adding the mixed solution Ⅰ containing the polyspiropyran dropwise to a metal salt solution for a mixing reaction Ⅰ to obtain the lithium ion sieve adsorbent; the mixed solution Ⅰ also contains a ligand for synthesizing MOFs; The ligand used to synthesize MOFs is 2-methylimidazole, and the metal salt solution contains zinc salt and iron salt; the molar ratio of the zinc salt to the iron salt is 1:0.1-0.6; The addition rate of the mixed solution Ⅰ is 3-10 mL / min relative to 1 g of the metal salt solution; the average pore size of the lithium ion sieve adsorbent is 0.6-1.3 nm, and the specific surface area is 869-1438 m 2 / g.

2. The method according to claim 1, wherein The zinc salt is zinc acetate; the iron salt is ferrous chloride.

3. The method according to claim 1, wherein In step (1), the molar ratio of the spiropyran to the triethylamine is 1:7-12.

4. The method according to any one of claims 1 to 3, wherein: In step (1), the mixing reaction I includes a first mixing reaction I and a second mixing reaction I carried out in sequence, wherein the conditions of the first mixing reaction I include: temperature of -2 to 10°C, time of 0.5-3h; the conditions of the second mixing reaction I include: temperature of 18-22°C, time of 1-3h.

5. The method according to any one of claims 1 to 3, wherein: In step (2), in the mixed solution Ⅰ, the molar ratio of the polyspiropyran to the ligand for synthesizing MOFs is 0.3-0.8:

1.

6. The method according to any one of claims 1 to 3, wherein: In step (2), the conditions of the mixed reaction Ⅱ include: temperature of 25-50°C and time of 0.5-10h.

7. A lithium ion sieve adsorbent prepared by the method according to any one of claims 1 to 6.

8. Use of the lithium ion extraction sieve adsorbent according to claim 7 in extracting lithium ions from salt lake brine.

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