A lithium extraction adsorbent and its preparation method and application

Abstract

This article discloses a lithium extraction adsorbent, its preparation method, and application. This method uses in-situ polymerization to construct a COF-type cage structure on the surface of an adsorbent active component containing a cross-linked spherical morphology. This significantly reduces the powdering and dissolution loss of the prepared product even after repeated lithium extractions, and exhibits excellent cyclic stability. Furthermore, due to the large surface area buffer cavity design of the product structure, brine can be effectively infiltrated during the lithium extraction process, and the intercalation and deintercalation of lithium ions is not hindered, resulting in high adsorption efficiency. This product can achieve long-term recyclability in the industrial lithium extraction industry, meeting energy conservation and environmental protection requirements.

Description

Technical Field

[0001] This article relates to the field of material technology, and in particular to a lithium extraction adsorbent and its preparation method and application. Background Art

[0002] The methods for extracting lithium metal from liquid ore sources mainly include adsorption, precipitation, extraction and membrane separation. Among them, the adsorption method is more environmentally friendly and efficient. This method mainly uses manganese-based, titanium-based or aluminum-based lithium adsorbents to adsorb and extract lithium.

[0003] However, most of these adsorbents are in powder form, so they need to be granulated in advance when actually used. Although a binder is introduced during the granulation process to granulate the powder, the granulated product will frequently shrink / expand in volume due to the deintercalation of lithium ions during the adsorption and lithium extraction process, which will cause the binder structure to break. After multiple uses, the lithium extraction agent particles will become powdered and dissolved, resulting in a significant decrease in the lithium extraction rate. Summary of the Invention

[0004] The purpose of this article is to overcome the shortcomings of the above-mentioned existing technologies and provide a method for preparing a lithium extraction adsorbent. This method uses an in-situ polymerization method to construct a COF-type cage structure on the surface of an adsorption active component with a cross-linked spherical morphology, so that the prepared product has greatly improved pulverization and dissolution after multiple lithium extractions, and has good cycle stability; at the same time, due to the design of the large surface area buffer cavity of the product structure, brine can be effectively infiltrated during the lithium extraction process, and the deintercalation and insertion of lithium ions will not be hindered, and the adsorption efficiency is high.

[0005] To achieve the above objectives, the technical solutions adopted in this paper are:

[0006] A method for preparing a lithium-extraction adsorbent comprises the following steps:

[0007] The lithium-extracting adsorption active material is placed in a polar organic solvent containing a modified polymer, mixed evenly, dried and granulated, and the obtained mixed particles are placed in a cross-linking agent for cross-linking reaction to obtain cross-linked adsorption cores; the modified polymer includes a polymer with negatively charged groups and / or complexing groups;

[0008] TAPB (1,3,5-tris(4-aminophenyl)benzene), PDA (terephthalaldehyde), and BTCA (pyromellitic trimesic acid) are placed in a mixed solution of aniline and benzaldehyde and mixed and prepolymerized to obtain a prepolymerization reaction solution. Subsequently, a cross-linked adsorption core is added, mixed, and reacted at room temperature for 20 to 60 hours. The mixture is filtered, washed, and dried to obtain the lithium extraction adsorbent.

[0009] In the preparation method of the lithium extraction adsorbent described in this article, the lithium extraction adsorption active material is first in situ cross-linked with a specific modified polymer to prepare a cross-linked adsorption core, and then three monomers, TAPB, PDA and BTCA, are polymerized on the surface of the cross-linked adsorption core to form a COF cage structure. In this process, due to the specific modification of the surface of the cross-linked adsorption core, the lithium extraction adsorption active material will not be swollen and damaged by organic solvents such as aniline and benzaldehyde during the growth of the COF cage. The stably formed COF cage protective layer is not close to the cross-linked adsorption core, but forms a buffer gap in the middle. The gap allows the prepared product to be immersed in brine for lithium extraction. The brine can fully infiltrate and contact the lithium extraction adsorption active material, thereby achieving efficient lithium extraction. On the other hand, the COF cage layer has a rich pore structure, which can ensure the mass transfer effect of the brine and improve the lithium extraction cycle stability of the product without affecting the lithium extraction efficiency. Finally, the COF cage layer has high corrosion resistance, so even if the prepared product works multiple times in brine with high concentration, its structural integrity can still be guaranteed.

[0010] In one embodiment, the lithium extraction adsorption active substance is at least one of an aluminum-based lithium extraction adsorption active substance, a manganese-based lithium extraction adsorption active substance, and a titanium-based lithium extraction adsorption active substance.

[0011] In one embodiment, the modified polymer is sulfonic acid modified polyvinyl chloride (PVC-SO3H).

[0012] Furthermore, the weight average molecular weight of the sulfonic acid group-modified polyvinyl chloride is 80,000 to 120,000.

[0013] Specifically, the preparation method of the sulfonic acid modified polyvinyl chloride can be: polyvinyl chloride and sodium p-aminobenzenesulfonate are mixed in a mixed solvent of water and ethanol at a mass ratio of 1: (0.1-1) and reacted at 45-145° C. for 2-24 hours to obtain the obtained product.

[0014] On the other hand, the sulfonic acid group-modified polyvinyl chloride may also be a commercially available product.

[0015] In one embodiment, the modified polymer is amino-modified polyvinyl chloride (PVC-NH2).

[0016] In one embodiment, the polar organic solvent is at least one of dimethylformamide, N-methylpyrrolidone, and dimethyl sulfoxide.

[0017] Furthermore, the concentration of the modified polymer in the polar organic solvent is 0.05 to 0.5 g / mL.

[0018] In one embodiment, the mass ratio of the lithium-extraction adsorption active substance to the modified polymer is (1-3):(10-25).

[0019] In one embodiment, the mass ratio of the lithium extraction adsorption active material to the modified polymer is (1-2):18.

[0020] When the amount of modified polymer added is small, the cross-linked structure formed in situ is thinner, which makes it easy for the lithium extraction adsorption active substance to be corroded by the organic solvent during the COF cage formation process. When the amount of modified polymer added is too much, the lithium extraction capacity of the adsorbent will be reduced. When the addition amount of lithium extraction adsorption active substance and modified polymer is selected within the above range, the overall performance of the product is better.

[0021] In one embodiment, the crosslinking agent is at least one of ethylenediamine, polyethyleneimine, polymerized carbodiimide, tetramethylethylenediamine, glutaraldehyde, 1,4-butanediol diglycidyl ether, polypropylene glycol diglycidyl ether, 1,2-cyclohexanediol diglycidyl ether, ethylene glycol diglycidyl ether, diglycidyl ether, and bisphenol A diglycidyl ether.

[0022] Furthermore, the cross-linking reaction time is 5 to 10 hours.

[0023] The modified polymer is soaked in the cross-linking agent to cause a cross-linking reaction to occur, thereby forming a precursor complex with a cross-linked structure.

[0024] In one embodiment, the particle size of the cross-linked adsorption core is 0.2-3 mm.

[0025] In one embodiment, when TAPB, PDA, and BTCA are placed in a mixture of aniline and benzaldehyde, the concentration of TAPB is 7 to 15 mmol / L, the concentration of BTCA is 10 to 20 mmol / L, and the concentration of PDF is 7 to 15 mmol / L. In the mixture of aniline and benzaldehyde, the concentration of amino groups and aldehyde groups is 100 to 150 mmol / L.

[0026] Furthermore, the molar ratio of PDA to BTCA is (3:2) to (1:2).

[0027] In one embodiment, the solid-to-liquid ratio of the cross-linked adsorption core to the prepolymerization reaction liquid is 0.01-0.05 g / mL.

[0028] When the amount of prepolymer added is too much, or the amount of cross-linked adsorption core added is too little, the COF cage structure thickness is likely to be too large, affecting the adsorption capacity of the adsorbent; when the amount of prepolymer added is too little, or the amount of cross-linked adsorption core added is too much, the COF cage layer thickness will easily be too thin, and the degree of improvement in the product cycle stability needs to be strengthened. When the COF cage layer is prepared according to the said parameter conditions, the comprehensive performance of the prepared product is better.

[0029] The molar ratio of terephthalaldehyde to trimesic acid affects its performance. When the molar ratio of terephthalaldehyde to trimesic acid is controlled within the range of (3:2) to (1:2), the prepared product has better performance. If the proportion of terephthalaldehyde is too large, a hollow core-cage structure cannot be formed, resulting in an overly thick coating layer and reduced product adsorption capacity. If the proportion of terephthalaldehyde is too small, the formed cage layer is too thin, with too many holes, low strength, and easy to break during adsorption.

[0030] Another purpose of this article is to provide a lithium extraction adsorbent prepared by the preparation method of the lithium extraction adsorbent, which includes a cross-linked adsorption core and a polymer coating layer from the inside to the outside, and the polymer coating layer is obtained by polymerization of TAPB, PDA, and BTCA.

[0031] The lithium extraction adsorbent prepared as described in this article has a special core-cage structure. Unlike the general modified composite structure lithium extraction adsorbent, the two structural layers of this product are not completely tightly connected, and there is sufficient gap in the middle. It not only does not affect the infiltration and mass transfer of brine during lithium extraction, but also effectively prevents the lithium extraction active material from being pulverized and dissolved during the lithium extraction process, and has high recyclability and stability.

[0032] In one embodiment, the thickness of the polymer coating layer is 100-1000 nm, and the diameter of the surface pores is ≤10 nm; the particle size of the cross-linked adsorption core is 0.2-3 mm.

[0033] The polymer coating layer obtained by cross-linking these three specific monomers has moderate thickness, small pores and large specific surface area. It can fully serve as a transport and carrying intermediate for lithium ions in brine, and can even effectively improve the lithium extraction efficiency of lithium extraction active substances.

[0034] Another purpose of this article is to provide the application of the lithium extraction adsorbent in lithium extraction process.

[0035] Compared with the existing technology, the beneficial effects of this article are:

[0036] This article provides a method for preparing a lithium extraction adsorbent. This method uses an in-situ polymerization method to construct a COF-type cage structure on the surface of an adsorption active component with a cross-linked spherical morphology. The prepared product has greatly improved pulverization and dissolution after multiple lithium extractions, and has good cyclic stability. At the same time, due to the design of the large surface area buffer cavity of the product structure, brine can be effectively infiltrated during the lithium extraction process, and the deintercalation and insertion of lithium ions will not be hindered, resulting in high adsorption efficiency. DETAILED DESCRIPTION

[0037] To better illustrate the purpose, technical solutions and advantages of this article, this article will be further described below with reference to the accompanying drawings and specific embodiments.

[0038] Unless otherwise specified, the materials used in the examples and comparative examples can be obtained through commercial channels.

[0039] Example 1

[0040] An embodiment of the lithium extraction adsorbent and its preparation method and application described herein includes the following steps:

[0041] (1) 18 g of commercially available lithium-extraction adsorption active material LiCl·2Al(OH)3·nH2O was placed in a mixture containing 2 g of modified polymer PVC-SO3H modified polymer (Guangdong Xinxiang International Trading Co., Ltd., with a weight-average molecular weight of 100,000) and 100 mL of N-methylpyrrolidone, and the mixture was evenly mixed. The resulting mixed particles were spray-dried and granulated. The resulting mixed particles were immersed in a cross-linking agent tetramethylethylenediamine for a cross-linking reaction for 6 h to obtain cross-linked adsorption core particles with an average particle size of 1 mm.

[0042] (2) TAPB, PDA, and BTCA are placed in a mixture of aniline and benzaldehyde, mixed, and subjected to a prepolymerization reaction for 3 minutes to obtain a prepolymerization reaction solution, and then a cross-linked adsorption core is added according to a solid-liquid ratio of 0.03 g / mL, and the mixture is stirred and mixed at a rate of 300 r / min and reacted at room temperature for 48 hours, filtered, washed, and dried to obtain the lithium extraction adsorbent; wherein the concentrations of TAPB and BTCA in the polymerization reaction solution are 10 mmol / L, the concentration of PDA is 15 mmol / L, and the concentrations of amino groups and aldehyde groups in the mixture of aniline and benzaldehyde are both 120 mmol / L.

[0043] The lithium extraction adsorbent includes cross-linked adsorption core particles and a polymer coating layer. The thickness of the polymer coating layer is 600 nm, and the pore diameter of the surface is less than 10 nm.

[0044] Example 2

[0045] An embodiment of the lithium extraction adsorbent, preparation method, and application thereof described herein differs from Example 1 only in that the amount of the modified polymer added is 1 g.

[0046] Example 3

[0047] An embodiment of the lithium extraction adsorbent, preparation method, and application thereof described herein differs from Example 1 only in that the amount of the modified polymer added is 0.5 g.

[0048] Example 4

[0049] An embodiment of the lithium extraction adsorbent, preparation method, and application thereof described herein differs from Example 1 only in that the amount of the modified polymer added is 3 g.

[0050] Example 5

[0051] An embodiment of the lithium extraction adsorbent, preparation method, and application thereof described herein differs from Example 1 only in that the amount of the modified polymer added is 4 g.

[0052] Example 6

[0053] An embodiment of the lithium extraction adsorbent, preparation method, and application thereof described herein differs from Example 1 only in that the molar ratio of terephthalaldehyde to trimesic acid is 1:3, and other conditions and parameters are exactly the same as those in Example 1.

[0054] Example 7

[0055] An embodiment of the lithium extraction adsorbent, preparation method, and application thereof described herein differs from Example 1 only in that the molar ratio of terephthalaldehyde to trimesic acid is 1:5, and other conditions and parameters are exactly the same as those in Example 1.

[0056] Example 8

[0057] An embodiment of the lithium extraction adsorbent, preparation method, and application thereof described herein differs from Example 1 only in that the molar ratio of terephthalaldehyde to trimesic acid is 3:1, and other conditions and parameters are exactly the same as those in Example 1.

[0058] Example 9

[0059] An embodiment of the lithium extraction adsorbent, preparation method, and application thereof described herein differs from Example 1 only in that the molar ratio of terephthalaldehyde to trimesic acid is 5:1, and other conditions and parameters are exactly the same as those in Example 1.

[0060] Example 10

[0061] An embodiment of the lithium extraction adsorbent, preparation method, and application described herein differs from Example 1 only in that the modified polymer is PVC-NH2 with a molecular weight of 100,000. The modified polymer is prepared by dissolving 5g of polyvinyl chloride (PVC) and 2g of 4-aminothiophenol in 100mL of N-methylpyrrolidone, stirring uniformly, and refluxing at 50°C for 12 hours. After the reaction is complete, the mixture is continuously washed with deionized water and then dried at 60°C to obtain PVC-NH2 with a molecular weight of 100,000.

[0062] Comparative Example 1

[0063] A lithium extraction adsorbent and its preparation method and application, which differ from Example 1 only in that the cross-linked adsorption core is used as a lithium extraction adsorbent after preparation.

[0064] Comparative Example 2

[0065] A lithium extraction adsorbent and its preparation method and application, the preparation method comprising the following steps:

[0066] (1) Commercially available lithium-extraction adsorption active material LiCl·2Al(OH)3·nH2O, PVDF, and N-methylpyrrolidone were mixed uniformly in a mass ratio of 100:5:150, spray-dried, and granulated to obtain cross-linked adsorption core particles with an average particle size of 1.5 mm;

[0067] (2) Prepare a lithium extraction adsorbent in the same manner as in Example 1.

[0068] Comparative Example 3

[0069] A lithium extraction adsorbent and its preparation method and application, the preparation method comprising the following steps:

[0070] The commercially available lithium extraction adsorption active material LiCl·2Al(OH)3·nH2O, PVDF and N-methylpyrrolidone were mixed evenly in a mass ratio of 100:5:150, spray dried and granulated to obtain a lithium extraction adsorbent with an average particle size of 1.5 mm.

[0071] Comparative Example 4

[0072] A lithium extraction adsorbent and its preparation method and application, the preparation method comprising the following steps:

[0073] (1) Prepare cross-linked adsorption cores according to the same protocol as in Example 1;

[0074] (2) Nano-silica with a D50 of 200 nm and a cross-linked adsorption core were dissolved in ethanol at a mass ratio of 1:10 and a solid-liquid mass ratio of 1:5, and a lithium adsorbent was obtained by spray drying.

[0075] Effect Example 1

[0076] In order to verify the lithium extraction effect of the lithium extraction adsorbent described in this article, the products of each embodiment and comparative example were used to extract lithium: 1000 mL of each product was measured with a measuring cylinder and loaded into an ion exchange column with an inner diameter of 70 mm and a length of 500 mm. + 10 bv (1 bv is 1000 mL) of brine with a concentration of 0.5 g / L was passed through, and then 10 bv of deionized water was passed through, which was one cycle. After 100 cycles, the volume of the finished product of each embodiment was measured with a graduated cylinder.

[0077] 100-week dissolution rate (%) = (volume of finished product after 1-100 cycles (mL) / original volume (mL)) * 100%;

[0078] The adsorption performance test method is the static adsorption method. This adsorbent is used for Li +To extract lithium from brine with a concentration of 500 ppm, take 20 g of deionized water and mix it with 2 g of lithium adsorbent. Extract lithium at room temperature for 10 hours. Measure the brine concentration before and after adsorption, and calculate the adsorption capacity according to the following formula.

[0079] The adsorption capacity of the adsorbent is: Q = V (C0-C) / m;

[0080] Q is the adsorption capacity, mg / g; V is the volume of the adsorption liquid, L; m is the mass of the adsorbent, g; C0 and C are the lithium ion concentrations in the brine before and after adsorption, respectively, mg / L.

[0081] The cycle stability was obtained by measuring the ratio of the adsorption capacity after 100 cycles to the initial adsorption capacity.

[0082] The results are shown in Table 1.

[0083] Table 1

[0084]

[0085]

[0086] As can be seen from Table 1, the adsorption capacity of the products of each embodiment can reach more than 9 mg / g, and the capacity stability after 100 cycles can be maintained at more than 95%. According to the performance of the products of Examples 1 to 5, it can be seen that as the amount of modified polymer added increases, the degree of erosion of the lithium extraction adsorption active substance during the synthesis of the COF cage becomes lower, but if the amount added is too much, the lithium extraction capacity of the prepared lithium extraction adsorbent will be reduced. According to Examples 1 and 6 to 9, it can be seen that as the molar ratio of terephthalaldehyde and trimesic acid changes, the thickness of the COF cage structure will also change, but if the thickness is too thick, it will directly reduce the adsorption capacity of the product, and if the thickness is too thin, the degree of improvement in the stability of the product will be insufficient. In contrast, the product of Comparative Example 1 has not undergone any modification, and the dissolution loss rate during lithium extraction is high, and the product cannot be recycled well; the product of Comparative Example 3 does not introduce the COF cage structure, and only uses conventional PVDF binder for granulation. Not only is the lithium extraction stability not improved, but the adsorption capacity is relatively reduced; the product of Comparative Example 2 introduces the COF cage structure on the basis of using PVDF as a binder. Although the lithium extraction stability is improved, the degree is very limited, and the adsorption capacity is also low; and although the product of Comparative Example 4 prepares a cross-linked adsorption core, it does not construct a COF cage structure to improve the stability of the product. Instead, it uses conventional nano-silica as a physical coating layer. Although it also has a certain effect, it is not as good as the performance of the products in each embodiment.

[0087] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of this article and are not intended to limit the scope of protection of this article. Although this application has been described in detail with reference to the preferred embodiments, those skilled in the art should understand that the technical solutions of this article may be modified or replaced by equivalents without departing from the essence and scope of the technical solutions of this article.

Claims

1. A method for preparing a lithium extraction adsorbent, characterized in that: The following steps are involved: The lithium-extracting adsorption active material is placed in a polar organic solvent containing a modified polymer, mixed evenly, dried and granulated, and the obtained mixed particles are placed in a cross-linking agent for cross-linking reaction to obtain cross-linked adsorption cores; the modified polymer includes a polymer with negatively charged groups and / or complexing groups; 1,3,5-tris(4-aminophenyl)benzene (TAPB), terephthalaldehyde (PDA), and trimesic acid (BTCA) are placed in a mixed solution of aniline and benzaldehyde, mixed, and subjected to a prepolymerization reaction to obtain a prepolymerization reaction solution. Subsequently, a cross-linked adsorption core is added, mixed, and reacted at room temperature for 20 to 60 hours, filtered, washed, and dried to obtain the lithium extraction adsorbent.

2. The method for preparing a lithium extraction adsorbent according to claim 1, wherein: The lithium extraction adsorption active substance is at least one of an aluminum-based lithium extraction adsorption active substance, a manganese-based lithium extraction adsorption active substance, and a titanium-based lithium extraction adsorption active substance.

3. The method for preparing a lithium extraction adsorbent according to claim 1, wherein: The modified polymer is sulfonic acid group-modified polyvinyl chloride and / or amino group-modified polyvinyl chloride.

4. The method for preparing a lithium extraction adsorbent according to claim 1, wherein: The polar organic solvent is at least one of dimethylformamide, N-methylpyrrolidone, and dimethyl sulfoxide.

5. The method for preparing a lithium extraction adsorbent according to claim 1, wherein: The concentration of the modified polymer in the polar organic solvent is 0.05-0.5 g / mL; the mass ratio of the lithium extraction adsorption active substance to the modified polymer is (1-3): (10-25).

6. The method for preparing a lithium extraction adsorbent according to claim 1, wherein: The crosslinking agent is at least one of ethylenediamine, polyethyleneimine, polymerized carbodiimide, tetramethylethylenediamine, glutaraldehyde, 1,4-butanediol diglycidyl ether, polypropylene glycol diglycidyl ether, 1,2-cyclohexanediol diglycidyl ether, ethylene glycol diglycidyl ether, diglycidyl ether, and bisphenol A diglycidyl ether.

7. The method for preparing a lithium extraction adsorbent according to claim 1, wherein: When TAPB, PDA, and BTCA are placed in a mixture of aniline and benzaldehyde, the concentration of TAPB is 7-15 mmol / L, the concentration of BTCA is 10-20 mmol / L, and the concentration of PDA is 7-15 mmol / L. In the mixture of aniline and benzaldehyde, the concentrations of amino groups and aldehyde groups are 100-150 mmol / L.

8. The method for preparing a lithium extraction adsorbent according to claim 1, wherein: The molar ratio of PDA to BTCA is (3:2) to (1:2).

9. The method for preparing a lithium extraction adsorbent according to claim 1, wherein: The solid-to-liquid ratio of the cross-linked adsorption core to the prepolymerization reaction liquid is 0.01-0.05 g / mL.

10. The lithium extraction adsorbent prepared by the method for preparing a lithium extraction adsorbent according to any one of claims 1 to 9, characterized in that: From the inside to the outside, it includes a cross-linked adsorption core and a polymer coating layer, and the polymer coating layer is obtained by polymerizing TAPB, PDA, and BTCA.

11. The lithium extraction adsorbent according to claim 10, characterized in that The thickness of the polymer coating layer is 100-1000 nm, and the diameter of the surface pores is ≤10 nm; the particle size of the cross-linked adsorption core is 0.2-3 mm.

12. Use of the lithium extraction adsorbent according to claim 10 or 11 in lithium extraction process.

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