A fluorine-containing polymer microsphere adsorbent for selectively adsorbing lithium, a structure control method thereof, and an application method thereof

Abstract

The present invention relates to the technical field of lithium adsorbent preparation, and in particular to a fluorine-containing polymer microsphere adsorbent for selectively adsorbing lithium, and a method for controlling its structure and an application method thereof, in order to solve the technical problems of poor selectivity, low adsorption capacity, high preparation cost and complex preparation process of existing lithium adsorbents. The present invention synthesizes a fluorine-containing polymer microsphere adsorbent material based on an emulsion polymerization method, which is simple to operate, low in cost, high in synthesis efficiency, can be prepared on a large scale, and has high selectivity and adsorption capacity. The adsorbent material of the present invention can efficiently and selectively adsorb lithium ions in lithium-containing wastewater containing a large number of monovalent and high-valent competitive ions. The adsorption of lithium ions is much better than the adsorption of sodium, potassium, cobalt, manganese and other ions, and the adsorption capacity of lithium ions can reach up to 38.5 mg / g.

Description

Technical Field

[0001] The present invention relates to the technical field of lithium adsorbent preparation, and in particular to a fluorine-containing polymer microsphere adsorbent for selectively adsorbing lithium, a structure control method thereof, and an application method thereof. Background Art

[0002] Lithium, known as a "high-energy metal" and the "white oil" of the new era, is a strategic metal driving the development of the new energy industry. As a lightweight, high-energy-density metallic element, lithium is widely used in batteries, ceramics, glass, and the nuclear industry. In recent years, the rapid commercialization of new energy vehicles and portable electronic devices has led to a rapid expansion of the lithium battery market, a sharp increase in demand for lithium resources, and potential risks to lithium supply. At the same time, according to the end-of-life cycle of power batteries, a wave of power battery retirements is currently underway. Improper handling of these retired power lithium batteries not only wastes lithium resources, but also causes secondary environmental pollution due to the nickel, cobalt, and manganese in the electrode materials. Therefore, the selective recovery of lithium from lithium-containing wastewater is crucial for the supply of lithium resources and the reduction of environmental pollution.

[0003] However, the composition of lithium-containing wastewater is relatively complex, containing a large number of coexisting monovalent and high-valent metal competing ions. Adsorption is a simple, efficient, highly selective, low-cost, and environmentally friendly method for lithium recovery. It uses lithium adsorbents to adsorb lithium from lithium-containing wastewater, then desorbs it using certain solvents, thereby recovering the lithium as a resource. Adsorbents are the core of lithium recovery using adsorption methods. Common lithium adsorbents include inorganic, organic, and composite adsorbents. Inorganic adsorbents include metal-based adsorbents and natural mineral-based adsorbents. Metal-based adsorbents primarily consist of aluminum, manganese, and titanium-based adsorbents. Aluminum-based adsorbents are technologically mature and have the greatest potential for industrial application, but their lithium selectivity is suboptimal. Manganese-based materials have excellent lithium adsorption properties, but manganese dissolution affects their long-term stability. Titanium-based adsorbents offer high adsorption efficiency, high lithium selectivity, good cyclic stability, and acid and alkali resistance, but their relatively high cost makes them unsuitable for large-scale industrial applications. Natural mineral-based adsorbents offer advantages such as excellent adsorption properties and sustainability, but their applicability is limited and they may contain impurities. Composite adsorbents combine the advantages of multiple adsorbents and have higher adsorption efficiency, but the preparation process may be more complicated and the cost is higher. Organic adsorbents, such as crown ethers and polymer ion exchange resins, are difficult to widely use due to the complex synthesis process.

[0004] Emulsion polymerization is a simple, low-cost, and highly tunable polymerization method. The morphology, particle size, number of chambers, and size of the microsphere adsorbent can be freely designed, making large-scale production easy and promising. Therefore, the design and preparation of microsphere adsorbent materials with stable structural properties, high adsorption capacity, high selectivity, and scalable production through emulsion polymerization has become a hot topic and a challenge in current research.

[0005] The information disclosed in this background technology section is only intended to deepen the understanding of the overall background technology of the present invention and should not be regarded as an admission or any form of suggestion that the information constitutes the prior art known to those skilled in the art. Summary of the Invention

[0006] The first technical problem to be solved by the present invention is to provide a fluorine-containing polymer microsphere adsorbent for selectively adsorbing lithium, so as to solve the technical problems of poor selectivity, low adsorption capacity, high preparation cost and complex preparation process of existing lithium adsorbents.

[0007] In order to achieve the above object, the technical solution adopted by the present invention is:

[0008] The fluorinated polymer microsphere adsorbent uses 2-(perfluorooctyl)ethyl methacrylate as the functional monomer and is produced via emulsion polymerization. This method uses an emulsion as the reaction medium to convert the monomer into polymer microspheres. Compared to traditional adsorbent material preparation methods, emulsion polymerization offers advantages such as simple operation, mild reaction conditions, large-scale production, and the ability to control the microsphere structure.

[0009] The particle size of the fluorinated polymer microsphere adsorbent is 12-17 μm; the pore size of the fluorinated polymer microsphere adsorbent is 50-200 nm, and the specific surface area is 100-300 m² / g. The perfluorooctyl group provides adsorption sites that attract lithium ions. The microporous structure allows the microsphere adsorbent to adsorb lithium ions, ensuring that lithium ions can pass smoothly and bind to the adsorption sites. The molecular formula of 2-(perfluorooctyl)ethyl methacrylate is C 14 H9F 17 O2, with a molecular weight of 532.19. This structure makes it a special fluorinated acrylate monomer. Its structure contains a methacrylate group and a perfluorooctylethyl group. The perfluorooctylethyl group is composed of a perfluorooctyl group connected to an ethyl group. The perfluorooctylethyl group itself has low surface energy, hydrophobicity and oleophobicity, which makes 2-(perfluorooctyl)ethyl methacrylate less soluble in water and the emulsification process more difficult. It is necessary to select a suitable emulsifier and emulsification process to ensure the stability of the emulsion system.

[0010] The present invention optimizes the monomer ratio, selects a suitable emulsifier and emulsification process, controls the stirring conditions, precisely controls the temperature, and adjusts the amount and type of initiator. On the basis of emulsion polymerization, the structure of the microspheres can be effectively adjusted to form a microsphere adsorbent with a uniform structure and obtain the most satisfactory microporous structure, thereby ensuring the selective adsorption effect of lithium ions.

[0011] The second technical problem to be solved by the present invention is to provide a method for controlling the structure of a fluorinated polymer microsphere adsorbent for selectively adsorbing lithium, by finely adjusting the preparation parameters to optimize the microporous structure of the fluorinated polymer microsphere adsorbent to achieve optimal selective lithium adsorption performance.

[0012] In order to achieve the above object, the technical solution adopted by the present invention is:

[0013] A method for controlling the structure of a fluorinated polymer microsphere adsorbent for selectively adsorbing lithium, for preparing the fluorinated polymer microsphere adsorbent, comprises the following steps:

[0014] S1 determines the preparation method and sets the initial parameters to carry out the emulsion polymerization reaction;

[0015] Preferably, in step S1, the preparation method comprises the following steps:

[0016] S11: adding an emulsifier to deionized water to prepare a uniformly dispersed aqueous solution; dissolving 2-(perfluorooctyl)ethyl methacrylate, ethylene glycol dimethacrylate, methacrylic acid, and azobisisobutyronitrile in chloroform to obtain a uniformly dispersed oil solution; slowly adding the oil solution dropwise to the aqueous solution under high-speed stirring to form a stable milky white oil-in-water emulsion;

[0017] Preferably, step S11 includes the following steps:

[0018] S111: Add deionized water and emulsifier to a three-necked flask, stir and mix thoroughly, and then ultrasonicate for 3-5 minutes to obtain a uniformly dispersed aqueous solution;

[0019] S112: Dissolve 2-(perfluorooctyl)ethyl methacrylate, ethylene glycol dimethacrylate, methacrylic acid, and azobisisobutyronitrile in chloroform, stir and mix thoroughly, and then ultrasonicate for 3-5 minutes to obtain a uniformly dispersed oil phase solution;

[0020] S113: The three-necked flask in step S111 is placed on a magnetic stirrer and stirred at a speed of 1200-1500 rpm, and then the oil phase solution obtained in step S12 is slowly added dropwise to the three-necked flask using a pipette. After the addition is completed, emulsification is continued for 8-10 minutes to obtain a stable milky white oil-in-water emulsion;

[0021] Preferably, the emulsifier is sodium lauryl sulfate; the mass ratio of the emulsifier to deionized water is 1-2:800, ensuring that the emulsifier is fully dispersed in the deionized water to form a stable aqueous solution. The amount of emulsifier is sufficient to encapsulate the oil droplets and prevent them from coalescing, while not excessive enough to cause excessive viscosity in the system and affect the emulsification effect.

[0022] Preferably, the molar ratio of the 2-(perfluorooctyl)ethyl methacrylate, the ethylene glycol dimethacrylate, and the methacrylic acid is 0.2-0.6:1.82-2.82:1; 2-(perfluorooctyl)ethyl methacrylate is used as a functional monomer to introduce fluorine atoms to improve the adsorption properties of the material. Methacrylic acid is used as a comonomer to adjust the hydrophilicity and ion exchange properties of the polymer, and ethylene glycol dimethacrylate is used as a cross-linking agent to improve the mechanical strength and stability of the microspheres. However, too much may cause the microspheres to be too dense, affecting the adsorption performance. The present invention can obtain the most satisfactory microporous structure by fitting and adjusting the parameters under the above-mentioned ratio limit to achieve the best adsorption effect for lithium ions.

[0023] The amount of methacrylic acid in chloroform is 33.33-50 g / L; that is, the volume ratio of the mass of methacrylic acid to chloroform is 1 g:(20 mL-30 mL); this ensures an appropriate concentration of methacrylic acid in the oil phase solution, which is neither too dilute nor too thick, and is conducive to its uniform distribution and effective copolymerization in the polymerization reaction.

[0024] The amount of azobisisobutyronitrile in chloroform is 3.33-4 g / L; that is, the volume ratio of azobisisobutyronitrile to chloroform is 1 g:(250 mL-300 mL). As an initiator, the concentration of azobisisobutyronitrile significantly influences the rate and extent of the polymerization reaction. This range ensures an appropriate initiator concentration, allowing the polymerization reaction to proceed smoothly while avoiding excessive initiator-induced over-polymerization and overheating.

[0025] The volume ratio of chloroform to deionized water is 1:2-3. This ratio helps form a stable oil-in-water emulsion. Chloroform, as the oil phase solvent, has a moderate volume relative to the water phase, ensuring sufficient dispersion of the oil phase in the water phase while preventing the emulsion from being too thin or too viscous.

[0026] S12: The three-necked flask in step S11 was sealed with a rubber stopper, one end was connected to an oil seal, and the other end was connected to a nitrogen source. Nitrogen was continuously introduced for 8-10 minutes to eliminate oxygen in the system and prevent the occurrence of oxidation reaction. The mixture was then placed in an oil bath at 70-80°C and a speed of 300-500 rpm for 10-12 hours to obtain a polymer microsphere mixed solution;

[0027] S13: After the reaction is completed, the polymer microspheres are recovered by centrifugation, washed with deionized water and ethanol multiple times, and dried to obtain dry microspheres;

[0028] Preferably, in step S13, the polymer microspheres are recovered by centrifugation, washed three times with deionized water, and then washed three times with ethanol to remove impurities such as unreacted monomers, emulsifiers and solvents to obtain a product, and then the washed microspheres are dried in a vacuum oven to constant weight; when washing the polymer microspheres, the amount of deionized water used is 33.33~40 g / L; the amount of ethanol used is 33.33~40 g / L, that is, the volume ratio of the mass of the polymer microspheres to deionized water or ethanol is 1g:(25mL~30mL), which helps to obtain pure polymer microspheres.

[0029] S14: Use ethanol and ethyl acetate solutions to perform solvent exchange on the dried microspheres respectively and then dry them to obtain a fluorine-containing polymer microsphere adsorbent material. Specifically, the dried microspheres are placed in a selected solvent, and the solvent is fully penetrated into the interior of the microspheres by stirring or ultrasonic treatment to exchange with the residual solvent and impurities. The number of exchanges and the time of each exchange need to be optimized according to the adsorption properties of the microspheres and the required degree of structural regulation. The main purpose of solvent exchange is to further remove the residual solvent and impurities in the microspheres, thereby achieving the purpose of micropore regulation. The residual solvent here refers to the residual solvent that has not been completely removed during the polymerization reaction or washing process, which complements the S13 step to ensure the purity and performance of the final fluorine-containing polymer microsphere adsorbent material. After the solvent exchange is completed, the microspheres are dried to remove the residual exchange solvent and fix the new structure of the microspheres.

[0030] Preferably, in steps S13 and S14, drying the microspheres includes placing the microspheres in a vacuum drying oven, drying them at a constant temperature of 40-50° C. for 24-25 h, and cooling them to room temperature to obtain dried microspheres.

[0031] S2 measures the pore size and specific surface area of ​​the resulting microspheres. Scanning electron microscopy (SEM) is used to characterize the microsphere morphology, observing their size, shape, and uniformity of distribution. Infrared spectroscopy (IR) analyzes the chemical structure of the microspheres to confirm the successful introduction of functional monomers and comonomers and the formation of cross-linked structures. Pore size and specific surface area are measured using gas adsorption.

[0032] S3 adjusts a single parameter, conducts multiple experiments, and records the results of each experiment;

[0033] S4 fits the empirical formula based on the experimental data and adjusts the parameters according to the fit;

[0034] Preferably, in step S4, the experimental data is imported into statistical analysis software for linear regression analysis to fit an empirical formula for pore size and specific surface area;

[0035] S5 repeats the above steps S1 to S4 until a satisfactory microporous structure is obtained to obtain a fluorine-containing polymer microsphere adsorbent.

[0036] Furthermore, in step S5, steps S1 to S4 are repeated, the experimental parameters are gradually adjusted, verification experiments are performed, and the preparation process is iteratively optimized to obtain a fluorine-containing polymer microsphere adsorbent with a satisfactory microporous structure.

[0037] The third technical problem to be solved by the present invention is to provide an application method of a fluorine-containing polymer microsphere adsorbent for selectively adsorbing lithium, wherein the fluorine-containing polymer microsphere adsorbent is added to lithium-containing wastewater to selectively adsorb lithium ions.

[0038] In order to achieve the above object, the technical solution adopted by the present invention is:

[0039] A method for applying a fluorinated polymer microsphere adsorbent for selectively adsorbing lithium comprises adding the fluorinated polymer microsphere adsorbent to lithium-containing wastewater to selectively adsorb lithium ions, and reacting at a constant temperature under stirring conditions, thereby achieving specific targeted recognition and ultra-high capacity adsorption of lithium ions.

[0040] Furthermore, the amount of the fluorine-containing polymer microsphere adsorbent added to the wastewater is 0.1-2 g / L, the reaction temperature is 25° C., the reaction time is 24 h, and the stirring speed is 180 rpm.

[0041] The beneficial effects of the present invention are:

[0042] (1) The functional monomer used in the method of the present invention is 2-(perfluorooctyl)ethyl methacrylate. 2-(perfluorooctyl)ethyl methacrylate contains rich fluorine elements and can provide more adsorption sites that can firmly bind to lithium ions. Through theoretical calculations and analysis of the interaction between fluorine elements and other monovalent metals, fluorine and lithium have the lowest binding energy, which indicates that the fluorine-containing functional monomer will preferentially bind to lithium ions and therefore has good selectivity; secondly, the synthesis of microsphere adsorbent materials using emulsion polymerization has been verified to be reasonable and highly feasible after long-term verification; finally, compared with other fluorine-containing functional monomers (2-(perfluorohexyl)ethyl methacrylate and 2-(perfluorodecyl)ethyl methacrylate), 2-(perfluorooctyl)ethyl methacrylate has the advantages of suitable boiling point reaction and cheaper price, so 2-(perfluorooctyl)ethyl methacrylate is selected as the reaction monomer.

[0043] (2) The present invention synthesizes a fluorine-containing polymer microsphere adsorbent material based on an emulsion polymerization method. The material is simple to operate, low in cost, has high synthesis efficiency, can be prepared on a large scale, and has high selectivity and adsorption capacity for lithium ions. The adsorbent material of the present invention can efficiently and selectively adsorb lithium ions from lithium-containing wastewater containing a large number of monovalent and high-valent competing ions. The adsorption capacity for lithium ions is far superior to that for sodium, potassium, cobalt, manganese, etc., and the adsorption capacity for lithium ions can reach up to 38.5 mg / g. BRIEF DESCRIPTION OF THE DRAWINGS

[0044] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the following briefly introduces the drawings required for use in the embodiments or the description of the prior art. Obviously, the drawings described below are only some embodiments recorded in the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative work.

[0045] Figure 1 This is a scanning electron microscope image of a fluorinated polymer microsphere adsorbent material prepared by emulsion polymerization in experiment 1;

[0046] Figure 2 A physical image of the stable oil-in-water emulsion prepared in Experiment 1, and a fluorescence microscopy image of the emulsion droplets stained with Nile red;

[0047] Figure 3 is the infrared spectrum;

[0048] Figure 4 This is a graph showing the nitrogen adsorption and desorption curves of a fluorinated polymer microsphere adsorbent material prepared by emulsion polymerization in Experiment 1.

[0049] Figure 5 This is the isothermal adsorption curve of the fluorine-containing polymer microsphere adsorbent material prepared by emulsion polymerization method in experiment 1;

[0050] Figure 6 This is a kinetic adsorption curve of a fluorine-containing polymer microsphere adsorbent material prepared by emulsion polymerization method in experiment 1;

[0051] Figure 7 To test the selective adsorption capacity of fluorinated polymer microspheres adsorbent material prepared by emulsion polymerization for lithium ions in a monovalent metal mixed solution;

[0052] Figure 8 This study aimed to test the selective adsorption capacity of fluorinated polymer microsphere adsorbent material prepared by emulsion polymerization for lithium ions in a mixed solution of high-valent metals. DETAILED DESCRIPTION

[0053] The technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, rather than all the embodiments.

[0054] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by those skilled in the art to which this invention pertains. The terms used in this specification are for the purpose of describing specific embodiments only and are not intended to limit the invention. The term "and / or" as used herein includes any and all combinations of one or more of the associated listed items.

[0055] A method for controlling the structure of a fluorinated polymer microsphere adsorbent for selectively adsorbing lithium, for preparing the fluorinated polymer microsphere adsorbent, comprises the following steps:

[0056] S1 determines the preparation method and sets initial parameters, including the type of emulsifier, the mass ratio of the emulsifier to deionized water, the molar ratio of each reactant, the reaction temperature, the reaction time, etc., to carry out the emulsion polymerization reaction;

[0057] Specific embodiment 1: This embodiment is a method for preparing a fluorine-containing polymer microsphere adsorbent based on an emulsion polymerization method, which is specifically carried out in the following steps:

[0058] S11. ① Add deionized water and an emulsifier to a three-necked flask, stir and mix thoroughly, and then ultrasonicate for 3-5 minutes to obtain a uniformly dispersed aqueous solution; the emulsifier is sodium lauryl sulfate; the mass ratio of the emulsifier to deionized water is (1-2):800;

[0059] ②. Dissolve 2-(perfluorooctyl)ethyl methacrylate, ethylene glycol dimethacrylate, methacrylic acid, and azobisisobutyronitrile in chloroform, stir and mix thoroughly, and then ultrasonicate for 3-5 minutes to obtain a uniformly dispersed oil phase solution; wherein the mass ratio of methacrylic acid to chloroform is 1 g:(20 mL-30 mL); the molar ratio of 2-(perfluorooctyl)ethyl methacrylate to methacrylic acid is (0.2-0.6):1; the molar ratio of ethylene glycol dimethacrylate to methacrylic acid is (1.82-2.82):1; the mass ratio of azobisisobutyronitrile to chloroform is 1 g:(250 mL-300 mL); and the volume ratio of chloroform to deionized water is 1:(2-3);

[0060] ③. Place the three-necked flask in step ① on a magnetic stirrer and stir at a speed of 1200-1500 rpm. Then, slowly add the oil phase solution obtained in step ② to the three-necked flask using a pipette. After the addition is completed, continue emulsification for 8-10 minutes to obtain a stable milky white oil-in-water emulsion;

[0061] S12. Seal the three-necked flask in step S11 with a rubber stopper, connect one end to an oil seal, and the other end to a nitrogen source, and continue to introduce nitrogen for 8-10 minutes. Then, place the mixture in an oil bath at 70-80°C and 300-500 rpm for 10-12 hours to obtain a mixed solution of polymer microspheres.

[0062] S13. After the reaction is completed, the polymer microspheres are recovered by centrifugation, washed three times with deionized water, and then washed three times with ethanol to obtain a product, and then the washed microspheres are dried in a vacuum oven to constant weight to obtain dry microspheres; the mass ratio of the polymer microspheres to the volume of deionized water is 1 g: (25 mL to 30 mL); the mass ratio of the polymer microspheres to the volume of ethanol is 1 g: (25 mL to 30 mL);

[0063] S14: Solvent exchange is performed on the dried microspheres using ethanol and ethyl acetate solutions, respectively, and then the dried microspheres are dried to obtain a fluorine-containing polymer microsphere adsorbent material.

[0064] Preferably, in steps S13 and S14, drying the microspheres includes placing the microspheres in a vacuum drying oven, drying them at a constant temperature of 40-50° C. for 24-25 h, and cooling them to room temperature to obtain a fluorine-containing polymer microsphere adsorbent material.

[0065] S2 measured the pore size and specific surface area of ​​the microspheres;

[0066] S3 adjusts a single parameter, conducts multiple experiments, and records the results of each experiment;

[0067] S4 fits the empirical formula based on the experimental data and adjusts the parameters according to the fit;

[0068] Specific embodiment 2: This embodiment differs from specific embodiment 1 in that the volume ratio of chloroform to deionized water in step S1 is 1:3. Other aspects are the same as specific embodiment 1.

[0069] Specific embodiment 3: This embodiment differs from specific embodiment 2 in that: in step S1, deionized water and an emulsifier are added to a three-necked flask, stirred and mixed, and then ultrasonically treated for 5 minutes to obtain a uniformly dispersed aqueous solution. Other aspects are the same as specific embodiments 1 or 2.

[0070] Specific embodiment 4: This embodiment differs from specific embodiment 3 in that in step S1, 2-(perfluorooctyl)ethyl methacrylate, ethylene glycol dimethacrylate, methacrylic acid, and azobisisobutyronitrile are dissolved in chloroform, stirred and mixed until uniform, and then ultrasonically treated for 5 minutes to obtain a uniformly dispersed oil phase solution. Other aspects are the same as those of specific embodiments 1 to 3.

[0071] Specific Embodiment 5: This embodiment differs from Specific Embodiment 4 in that, in step S1, the three-necked flask is placed on a magnetic stirrer and stirred at 1500 rpm. The oil phase solution obtained in step S2 is then slowly added dropwise to the three-necked flask using a pipette. After the addition is complete, emulsification is continued for 10 minutes to obtain a stable milky white oil-in-water emulsion. Otherwise, the same as in Specific Embodiments 1 to 4.

[0072] Specific Embodiment 6: This embodiment differs from Specific Embodiment 5 in that, in step S2, nitrogen is continuously introduced into the oil-in-water emulsion obtained in step S1 for 10 minutes, and then the mixture is placed in a 70°C oil bath at 500 rpm for 10 hours to obtain a polymer microsphere mixed solution. Otherwise, this embodiment is the same as Specific Embodiments 1 to 5.

[0073] Specific embodiment 7: This embodiment differs from specific embodiment 6 in that in step S3, the product obtained in step S2 is placed in a vacuum drying oven and dried at 40°C for 24 hours, followed by cooling to room temperature to obtain a fluorine-containing polymer microsphere adsorbent material based on an emulsion polymerization method. Other aspects are the same as specific embodiment 6.

[0074] S5 repeats the above steps S1 to S4 until a satisfactory microporous structure is obtained to obtain a fluorine-containing polymer microsphere adsorbent.

[0075] Specifically verify the present invention with the following test:

[0076] Experiment 1: This embodiment is a method for preparing a fluorinated polymer microsphere adsorbent based on an emulsion polymerization method, which is specifically carried out in the following steps:

[0077] S11. ① Add 60 mL of deionized water and 0.150 g of emulsifier to a three-necked flask, stir and mix thoroughly, and then ultrasonicate for 5 min to obtain a uniformly dispersed aqueous solution.

[0078] ② Dissolve 1.236 g of 2-(perfluorooctyl)ethyl methacrylate, 6.493 g of ethylene glycol dimethacrylate, 1.000 g of methacrylic acid, and 0.070 g of azobisisobutyronitrile in 20 mL of chloroform, stir to mix, and ultrasonicate for 5 min to obtain a uniformly dispersed oil phase solution;

[0079] ③. Place the three-necked flask in step ① on a magnetic stirrer and stir at 1500 rpm. Then, slowly add the oil phase solution obtained in step ② to the three-necked flask using a pipette. After the addition is completed, continue emulsification for 10 minutes to obtain a stable milky white oil-in-water emulsion.

[0080] S12. Seal the three-necked flask in step S1 with a rubber stopper, connect one end to an oil seal, and the other end to a nitrogen source, and continue to introduce nitrogen for 10 minutes. Then, place the mixture in an oil bath at 70°C and 500 rpm for 10 hours to obtain a mixed solution of polymer microspheres.

[0081] S13, recovering the polymer microspheres by centrifugation, washing them three times with deionized water, and then washing them three times with ethanol to obtain a product; then placing the washed microspheres in a vacuum drying oven, drying them at 40°C for 24 hours, and cooling them to room temperature to obtain dry microspheres;

[0082] S14: The dried microspheres were subjected to solvent exchange with ethanol and ethyl acetate solutions respectively, and then dried to obtain a fluorine-containing polymer microsphere adsorbent material. The microspheres were then placed in a vacuum drying oven and dried at a constant temperature of 40°C for 24 hours. The microspheres were cooled to room temperature to obtain a fluorine-containing polymer microsphere adsorbent material.

[0083] Figure 1 This is a scanning electron microscope image of the fluorinated polymer microsphere adsorbent material prepared by emulsion polymerization in Experiment 1. It can be seen in the figure that the adsorbent material is spherical (a). Due to the evaporation of the oil phase after polymerization, the surface and interior are porous structures (b), which can expose more adsorption sites and accelerate mass transfer.

[0084] Figure 2 The actual image of the emulsion in step S1 of the experiment (a) and the fluorescence microscope image of the emulsion droplets stained with Nile red (b) show that the oil-in-water emulsion is uniformly milky white, indicating that the emulsion system has a certain stability (a). Figure 2 As can be seen in (b), the emulsion droplets are relatively uniform in size and well dispersed.

[0085] Figure 3 This is the infrared spectrum of the fluorinated polymer microsphere adsorbent material prepared by emulsion polymerization in Experiment 1. -1 The characteristic peak at 1725 cm corresponds to the stretching vibration of hydroxyl groups. -1 The characteristic peak at 1245 cm corresponds to the C=O in the ester group. -1 and 1147 cm -1 The two characteristic peaks at 1211 cm correspond to the ester group C(C=O)-O. -1 and 1112 cm -1They correspond to the asymmetric stretching vibration and symmetric contraction vibration of CF, respectively. This indicates that the fluorine-containing polymer microsphere adsorbent material based on emulsion polymerization was successfully prepared.

[0086] Figure 4 This is the nitrogen adsorption and desorption curve of the fluorinated polymer microsphere adsorbent material prepared by emulsion polymerization in Experiment 1. It was detected that the adsorbent had a nitrogen adsorption capacity of 258.94 m 2 The higher specific surface area of ​​​​the adsorbent (> 1.5 g) can prove the porous structure of the adsorbent, which can expose more adsorption sites.

[0087] The present invention also provides an application method of a fluorine-containing polymer microsphere adsorbent for selectively adsorbing lithium. The prepared fluorine-containing polymer microsphere adsorbent is added to lithium-containing wastewater to selectively adsorb lithium ions. The reaction is carried out at a constant temperature under stirring conditions, thereby achieving specific targeted recognition and ultra-high capacity adsorption of lithium ions.

[0088] Specifically, the fluorinated polymer microsphere adsorbent material prepared by the emulsion polymerization method in Experiment 1 was used to conduct adsorption experiments on lithium ion aqueous solutions with different concentrations. The test method is as follows:

[0089] (1) Prepare lithium nitrate aqueous solutions with lithium concentrations of 10 mg / L, 20 mg / L, 50 mg / L, 100 mg / L, 150 mg / L, 200 mg / L, 250 mg / L, 300 mg / L, 350 mg / L, 400 mg / L, 450 mg / L, and 500 mg / L, respectively; take 20 mL of each of these lithium-containing solutions with different concentrations and place them in 10 50 mL conical flasks;

[0090] (2) Weigh 20 mg of the fluorinated polymer microsphere adsorbent material prepared by emulsion polymerization in Experiment 1, and weigh a total of 10 portions. Place them in 50 mL conical flasks containing lithium ion aqueous solutions of different concentrations, and place them in a constant temperature oscillator with the parameters set at 25 °C, 180 rpm, and 24 h for adsorption experiment;

[0091] (3) taking the solution before and after adsorption from the conical flask respectively, and measuring the lithium ion concentration in the solution using an atomic absorption spectrometer (AAS);

[0092] Figure 5 The isothermal adsorption curve shows that the actual adsorption behavior of the adsorbent material for lithium ions is more consistent with the Langmuir model, indicating that the adsorption sites are distributed more evenly and monolayer adsorption occurs. The fitting shows that the maximum adsorption capacity Qmax of the fluorinated polymer microsphere adsorbent material based on emulsion polymerization for lithium ions is 38.5 mg / g.

[0093] The fluorinated polymer microsphere adsorbent material prepared by the emulsion polymerization method in Experiment 1 was used to conduct a kinetic adsorption experiment on a lithium ion aqueous solution. The test method is as follows:

[0094] (1) Prepare a lithium nitrate aqueous solution with a lithium concentration of 500 mg / L and place 100 mL of the lithium-containing solution in a 250 mL beaker;

[0095] (2) Weigh 100 mg of the fluorinated polymer microsphere adsorbent material prepared by emulsion polymerization in Experiment 1 and place it in a beaker of aqueous solution with a lithium concentration of 500 mg / L; stir magnetically at 500 rpm, 25 °C, and for 180 min;

[0096] (3) At the time of 0, 1, 3, 5, 10, 30, 60, 90, 150, and 180 min, 1 mL of the solution was taken from the beaker and the lithium ion concentration in the solution was measured using an atomic absorption spectrometer (AAS);

[0097] Figure 6 The kinetic adsorption curve shows that the adsorbent material reaches kinetic adsorption equilibrium in 60 minutes. The pseudo-second-order kinetic model is more consistent with the actual kinetic adsorption process, indicating that chemical adsorption plays a dominant role in the adsorption process between lithium ions and the adsorbent.

[0098] The adsorption selectivity of lithium ions in a monovalent metal mixed solution was analyzed using the fluorinated polymer microsphere adsorbent material based on the emulsion polymerization method prepared in Experiment 1. The test method is as follows:

[0099] (1) Prepare a 20 mL mixed aqueous solution containing 40 mMol / L lithium ions, 40 mMol / L sodium ions, and 40 mMol / L potassium ions; place the solution in a 50 mL conical flask;

[0100] (2) Weigh 20 mg of the fluorinated polymer microsphere adsorbent material prepared by emulsion polymerization in Experiment 1 and place it in a mixed aqueous solution containing 40 mMol / L lithium ions, 40 mMol / L sodium ions, and 40 mMol / L potassium ions. Place it in a constant temperature oscillator with the parameters set at 25 °C, 180 rpm, and 24 h for adsorption experiment;

[0101] (3) taking the ion solution before and after adsorption in the conical flask, and using inductively coupled plasma mass spectrometry (ICP MS) to determine the concentrations of lithium ions, sodium ions, and potassium ions in the solution;

[0102] Figure 7The selective adsorption capacity of the fluorinated polymer microsphere adsorbent material based on the emulsion polymerization method for lithium ions in a monovalent metal mixed solution shows that the fluorinated polymer microsphere adsorbent material based on the emulsion polymerization method can separate lithium ions from a mixed solution containing sodium ions and potassium ions, indicating that the adsorbent material can also excellently complete the separation and recovery of lithium ions in a monovalent metal mixed solution containing sodium ions, potassium ions, etc. with a charge state similar to that of lithium ions.

[0103] The adsorption selectivity of lithium ions in a mixed solution of high-valent metals was analyzed using the fluorinated polymer microsphere adsorbent material based on the emulsion polymerization method prepared in Experiment 1. The test method is as follows:

[0104] (1) Prepare a 20 mL mixed aqueous solution containing 40 mMol / L lithium ions, 40 mMol / L cobalt ions, and 40 mMol / L manganese ions; place the solution in a 50 mL conical flask;

[0105] (2) Weigh 20 mg of the fluorinated polymer microsphere adsorbent material prepared by emulsion polymerization in Experiment 1 and place it in a mixed aqueous solution containing 40 mMol / L lithium ions, 40 mMol / L cobalt ions, and 40 mMol / L manganese ions. Place it in a constant temperature oscillator with the parameters set at 25 °C, 180 rpm, and 24 h for adsorption experiment;

[0106] (3) taking the ion solution before and after adsorption in the conical flask, and using inductively coupled plasma mass spectrometry (ICP MS) to determine the concentrations of lithium ions, cobalt ions, and manganese ions in the solution;

[0107] Figure 8 The selective adsorption ability of the fluorinated polymer microsphere adsorbent material based on the emulsion polymerization method for lithium ions in a mixed solution of high-valent metals can be seen. It can be seen that the fluorinated polymer microsphere adsorbent material based on the emulsion polymerization method can separate lithium ions from a mixed solution containing cobalt ions and manganese ions, indicating that the adsorbent material can excellently complete the separation and recovery of lithium ions in a mixed solution containing high-valent metals such as cobalt ions and manganese ions.

[0108] Those skilled in the art will appreciate that the present invention is not limited to the foregoing embodiments. The foregoing embodiments and descriptions are merely illustrative of the principles of the present invention. Various changes and modifications may be made to the present invention without departing from the spirit and scope of the present invention. Such changes and modifications are intended to fall within the scope of the present invention. The scope of the present invention is defined by the appended claims and their equivalents.

Claims

1. A fluorine-containing polymer microsphere adsorbent for selectively adsorbing lithium, characterized in that: The fluorinated polymer microsphere adsorbent uses 2-(perfluorooctyl)ethyl methacrylate as a functional monomer and is produced by emulsion polymerization. The particle size of the fluorinated polymer microsphere adsorbent is 12-17 μm. The pore size of the fluorinated polymer microsphere adsorbent is 50-200 nm, and the specific surface area is 100-300 m² / g, ensuring that lithium ions can pass through smoothly and bind to adsorption sites. The fluorinated polymer microsphere adsorbent has a better adsorption performance for lithium ions than for sodium, potassium, cobalt, and manganese ions. The method for controlling the structure of the fluorine-containing polymer microsphere adsorbent comprises the following steps: S1: preparing an aqueous phase solution with deionized water and an emulsifier; dissolving 2-(perfluorooctyl)ethyl methacrylate, ethylene glycol dimethacrylate, and methacrylic acid as oil phase monomers and azobisisobutyronitrile as an initiator in chloroform to obtain an oil phase solution; determining a preparation method and setting initial parameters to conduct an emulsion polymerization reaction; S2 measured the pore size and specific surface area of ​​the microspheres; S3 adjusts a single parameter, conducts multiple experiments, and records the results of each experiment; S4 fits the empirical formula based on the experimental data and adjusts the parameters according to the fit; S5 repeats the above steps S1 to S4, gradually adjusts the experimental parameters, conducts verification experiments, iteratively optimizes the preparation process, and obtains a fluorine-containing polymer microsphere adsorbent.

2. The fluorine-containing polymer microsphere adsorbent for selectively adsorbing lithium according to claim 1, characterized in that: In step S1, the preparation method includes the following steps: S11: adding an emulsifier to deionized water to prepare a uniformly dispersed aqueous solution; dissolving 2-(perfluorooctyl)ethyl methacrylate, ethylene glycol dimethacrylate, methacrylic acid, and azobisisobutyronitrile in chloroform to obtain a uniformly dispersed oil solution; slowly adding the oil solution dropwise to the aqueous solution under high-speed stirring to form a stable milky white oil-in-water emulsion; S12: The three-necked flask in step S11 was sealed with a rubber stopper, one end was connected to an oil seal, and the other end was connected to a nitrogen source, and nitrogen was continuously introduced for 8-10 minutes. The mixture was then placed in an oil bath at 70-80°C and a speed of 300-500 rpm for 10-12 hours to obtain a polymer microsphere mixed solution; S13: After the reaction is completed, the polymer microspheres are recovered by centrifugation, washed with deionized water and ethanol multiple times, and dried to obtain dry microspheres; S14: Solvent exchange is performed on the dried microspheres using ethanol and ethyl acetate solutions, respectively, and then the dried microspheres are dried to obtain a fluorine-containing polymer microsphere adsorbent material.

3. The fluorine-containing polymer microsphere adsorbent for selectively adsorbing lithium according to claim 2, characterized in that: In steps S13 and S14, the drying of the microspheres includes placing the microspheres in a vacuum drying oven, drying them at a constant temperature of 40-50° C. for 24-25 hours, and cooling them to room temperature to obtain dried microspheres.

4. The fluorine-containing polymer microsphere adsorbent for selectively adsorbing lithium according to claim 2, characterized in that: Step S11 includes the following steps: S111: Add deionized water and emulsifier to a three-necked flask, stir and mix thoroughly, and then ultrasonicate for 3-5 minutes to obtain a uniformly dispersed aqueous solution; S112: Dissolve 2-(perfluorooctyl)ethyl methacrylate, ethylene glycol dimethacrylate, methacrylic acid, and azobisisobutyronitrile in chloroform, stir and mix thoroughly, and then ultrasonicate for 3-5 minutes to obtain a uniformly dispersed oil phase solution; S113: Place the three-necked flask in step S111 on a magnetic stirrer and stir at a speed of 1200-1500 rpm, then slowly add the oil phase solution obtained in step S12 into the three-necked flask using a pipette. After the addition is completed, continue emulsification for 8-10 minutes to obtain a stable milky white oil-in-water emulsion.

5. The fluorine-containing polymer microsphere adsorbent for selectively adsorbing lithium according to claim 4, characterized in that: The emulsifier is sodium lauryl sulfate; the mass ratio of the emulsifier to deionized water is 1-2:800; the molar ratio of the 2-(perfluorooctyl)ethyl methacrylate, the ethylene glycol dimethacrylate, and the methacrylic acid is 0.2-0.6:1.82-2.82:1; the amount of the methacrylic acid in the chloroform is 33.33-50 g / L; the amount of the azobisisobutyronitrile in the chloroform is 3.33-4 g / L; and the volume ratio of the chloroform to deionized water is 1:2-3.

6. The fluorine-containing polymer microsphere adsorbent for selectively adsorbing lithium according to claim 2, characterized in that: In step S13, when washing the polymer microspheres, the amount of deionized water used is 33.33-40 g / L; the amount of ethanol used is 33.33-40 g / L.

7. A method for applying a fluorinated polymer microsphere adsorbent for selectively adsorbing lithium, comprising adding the fluorinated polymer microsphere adsorbent prepared in claim 1 to lithium-containing wastewater to selectively adsorb lithium ions, characterized in that: By reacting at a constant temperature under stirring conditions, specific targeted recognition and ultra-high capacity adsorption of lithium ions can be achieved.

8. The method for applying a fluorinated polymer microsphere adsorbent for selectively adsorbing lithium according to claim 7, characterized in that: The amount of the fluorine-containing polymer microsphere adsorbent added to the wastewater is 0.1-2 g / L, the reaction temperature is 25° C., the reaction time is 24 h, and the stirring speed is 180 rpm.

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