A polymer-encapsulated microsphere and its preparation method and application

Abstract

The present application discloses a polymer-encapsulated microsphere and its preparation method and application, which belongs to the field of separation science and technology. The polymer-encapsulated microsphere provided by the present application includes a base polymer and an extractant. The preparation method includes the following steps: adding the base polymer and the extractant to an organic solvent, stirring to obtain a dispersed phase; mixing sodium chloride with water to obtain a sodium chloride aqueous solution with a mass percentage concentration of 20-34% as a continuous phase; mixing sodium chloride with water to obtain a sodium chloride aqueous solution with a mass percentage concentration of 5-18% as a receiving phase; dispersing the dispersed phase in the continuous phase in the form of micro-liquid beads and transporting it to the receiving phase, desolventizing the micro-liquid beads, and obtaining polymer-encapsulated microspheres. The present application also provides the application of polymer-encapsulated microspheres in the separation and extraction of lithium resources. The polymer-encapsulated microspheres prepared by the present application have high selectivity and high extraction capacity, and can achieve rapid and highly selective separation and enrichment of low-concentration lithium resources.

Description

Technical Field

[0001] The present invention belongs to the field of separation science and technology, and specifically relates to a polymer-encapsulated microsphere and a preparation method and application thereof. Background Art

[0002] With the rapid development of the global new energy industry, the lithium-ion battery industry for power and energy storage has shown a rapid growth trend, and the demand for lithium resources in various industrial production has also continued to increase. Lithium resources mainly exist in minerals, underground brines and salt lake brines in nature. The commonly used methods for recovering lithium resources include precipitation, extraction, adsorption, calcination and membrane separation, which can obtain pure lithium brine and precipitate lithium in it.

[0003] However, as non-renewable natural resources continue to be consumed, the effective use of secondary resources has become an effective way to make up for this consumption. Whether it is natural resources or secondary resources, lithium often coexists with many other elements. In order to obtain lithium products with sufficient purity, lithium must be highly selectively separated and purified. However, due to the similarity of the physical and chemical properties of multiple elements with lithium, the difficulty of separation is increased.

[0004] In the mining and application of natural lithium ore, lepidolite, salt lake water, etc. are important mineral resources for extracting lithium. For lepidolite, sulfate roasting is one of the main methods for industrial production of lithium. However, the solution obtained by this method has low lithium ion content and high sodium ion content, and the sodium-lithium mass concentration ratio can reach 50:1 or even higher. In the subsequent preparation process of lithium carbonate, lithium is easily entrained by sodium sulfate crystals, resulting in large losses, which brings serious restrictions to the development of the process. Therefore, it is necessary to adopt certain technical means to separate lithium and sodium in a purified solution with high sodium and low lithium to improve the recovery efficiency of lithium.

[0005] In view of the above problems, there have been some studies on the selective separation and recovery of low-concentration lithium resources by extraction and adsorption methods. However, the existing technical methods still have some limitations. For example, CN116983964 discloses a preparation method and application of a lithium-sodium separation resin, which generates a polyaminophosphoric acid chelating resin containing multiple phosphate groups on the monomer through a Mannich reaction. Although this technology can effectively improve the separation effect under brine conditions with a lithium-sodium mass ratio of 0.008 to 1, its preparation process conditions are harsh, high temperature is required, and there is a problem of easy loss of the extractant, and this technology is only applicable to materials with a low lithium-sodium mass ratio and the system does not contain other interfering metal ions.

[0006] In addition, CN110656239B discloses a method for separating, purifying and extracting lithium by solvent extraction. The method uses a composite extractant for extraction and separation, and then performs back extraction and heat treatment to finally obtain a lithium product. However, the method requires the use of a large amount of organic solvents, which are flammable, volatile, and toxic. They are easily volatilized and entrained during use, resulting in increased costs, safety risks, and environmental pollution. The solid phase extractants reported in the patents often have a complicated preparation process and high cost.

[0007] Polymer-included microspheres (PIBs) are a new type of solid phase extractant developed based on polymer-included membrane (PIM) technology. PIBs are spherical polymer particles that encapsulate and support the organic liquid phase, i.e., the extractant, in their internal porous structure. By controlling the appropriate preparation conditions, a porous structure can also be formed on its surface. Since the liquid phase is fixed in a nano-sized channel network, PIBs are more stable than supported liquid membranes and certain macroporous resin materials. Compared with PIMs, PIBs have a larger specific surface area and can significantly reduce the separation and extraction time while maintaining selectivity. They can also be made into separation columns (or separation towers) in analytical or industrial separations, which is beneficial to the continuous operation of flow separation technology and pre-enrichment systems.

[0008] Therefore, there is an urgent need to develop polymer-encapsulated microspheres that can achieve rapid and highly selective separation and enrichment of low-concentration lithium resources under conditions of high impurity:lithium ratios, which have high selectivity and high extraction capacity and do not require organic solvents during use. Summary of the invention

[0009] In view of this, the present application provides a polymer-encapsulated microsphere and a preparation method and application thereof, which has high selectivity and high extraction capacity, and can achieve rapid and highly selective separation and enrichment of low-concentration lithium resources under conditions of high impurity:lithium ratio.

[0010] In a first aspect, the present application provides a polymer-encapsulated microsphere, wherein the polymer-encapsulated microsphere comprises a base polymer and an extractant; the base polymer is selected from at least one of polyvinyl chloride, polyvinylidene fluoride, polyvinylidene fluoride-hexafluoropropylene copolymer, polystyrene, and styrene-butadiene-styrene ternary block copolymer;

[0011] The extractant is selected from at least one of β-diketone extractants, organic phosphine oxide extractants, crown ether extractants, and ionic liquid extractants;

[0012] The mass percentage of the base polymer in the polymer-encapsulated microspheres is 29-80%; the mass percentage of the extractant in the polymer-encapsulated microspheres is 10-70%.

[0013] By adopting the above-mentioned technical scheme, the polymer-encapsulated microspheres of the present application have a porous structure inside and on the surface. This structure can provide a larger specific surface area, thereby increasing the chance of contact with lithium ions and improving the extraction efficiency. The organic liquid phase (i.e., the extractant) encapsulated inside the polymer-encapsulated microspheres of the present application is fixed in a nano-sized channel network, which can avoid the volatilization and loss of the organic phase in the traditional extraction process and improve the stability of the extractant. By selecting a suitable extractant, the present application can achieve highly selective adsorption of lithium ions, thereby effectively separating lithium in a high-impurity environment. The polymer-encapsulated microspheres of the present application can achieve efficient separation and enrichment of low-concentration lithium resources, and have high selectivity and high extraction capacity.

[0014] The specific basic polymer and extractant used in the present application can produce polymer-encapsulated microspheres with high selectivity and good stability, and can achieve efficient, stable and economical lithium ion separation.

[0015] The mass percentage of the base polymer in this application directly affects the porosity and pore size distribution of the microspheres, thereby affecting the adsorption performance. If the polymer content is too high, the internal porosity of the microspheres will be reduced, reducing the effective exposure area of ​​the extractant, thereby reducing the extraction efficiency. In addition, too much polymer will take up more space, reducing the amount of extractant that can be used to adsorb lithium ions, thereby reducing the overall adsorption capacity. If the polymer content is too low, the mechanical strength of the microspheres will be insufficient, and they will be easily broken or deformed, affecting their service life. In addition, too little polymer may not be able to fully wrap and fix the extractant, resulting in loss or instability of the extractant.

[0016] The appropriate amount of extractant in this application can maximize the adsorption sites and improve the adsorption efficiency of the microspheres. If the extractant content is too high, the mechanical strength of the microspheres will decrease, and they will not be fully fixed in the polymer skeleton, resulting in the loss of the extractant and affecting the adsorption performance. If the extractant content is too low, the adsorption capacity of the microspheres will be significantly reduced, and their high selectivity cannot be fully utilized, reducing the total adsorption capacity.

[0017] Optionally, the extractant is selected from at least one of 4,4,4-trifluoro-1-phenyl-1,3-butanedione (HBTA), trioctylphosphine oxide (TOPO), benzopentadecacrown-5 (B15C5), benzotwelvecacrown-4 (B12C4), LIX-54 extractant, 1-hexyl-3-methylimidazole bis(trifluoromethylsulfonyl)imide, and thenoyltrifluoroacetone.

[0018] Optionally, a reinforcing agent is also included;

[0019] The enhancer is selected from at least one of triphosphate, epoxy soybean oil, dioctyl phthalate, diphenyl 2-ethylhexyl phosphate, tri-n-butyl acetyl citrate, tri(2-ethylhexyl) acetyl citrate, di(2-ethylhexyl) sebacate, epoxy stearate octyl ester, and chlorinated paraffin.

[0020] By adopting the above technical solution, the present application adds an enhancer, which can improve the physical and chemical properties of the microspheres, improve the stability and adsorption efficiency of the extractant, and can also adjust the pore structure of the microspheres to further improve the extraction efficiency.

[0021] Optionally, based on the mass of the polymer-encapsulated microspheres, the mass percentage of the reinforcing agent is 0.1-15%.

[0022] In a second aspect, the present application provides a method for preparing the above-mentioned polymer-encapsulated microspheres, comprising the following steps:

[0023] Step S1, adding the base polymer and the extractant into an organic solvent, and then stirring to obtain a dispersed phase (or first liquid);

[0024] Step S2, mixing sodium chloride with water to prepare a sodium chloride aqueous solution with a mass percentage concentration of 20-34% as a continuous phase (or second liquid);

[0025] Step S3, mixing sodium chloride with water to prepare a sodium chloride aqueous solution with a mass percentage concentration of 5-18% as a receiving phase (or third liquid);

[0026] Step S4, dispersing the dispersed phase in the continuous phase in the form of micro-liquid beads and transporting them to the receiving phase, desolventizing the micro-liquid beads through solvent diffusion, and obtaining the polymer-encapsulated microspheres.

[0027] By adopting the above technical scheme, the preparation method of the polymer-encapsulated microspheres of the present application achieves rapid solidification and highly selective adsorption of the microspheres by controlling various conditions. The porous structure of the microspheres of the present application provides a large specific surface area, increases adsorption sites, and thus improves the extraction capacity. The extractant is fixed in the polymer skeleton, avoiding the volatilization and loss of the organic phase in the traditional extraction process, and improving the stability of the extractant.

[0028] In step S2 of the present application, a high concentration of sodium chloride aqueous solution helps to maintain the stability of the dispersed phase droplets and prevent them from merging. Step S3 further processes the dispersed phase droplets, and a lower concentration of sodium chloride aqueous solution helps to control the speed of solvent diffusion and avoid excessive solidification leading to uneven microsphere structure. The solvent diffusion in step S4 replaces the organic solvent in the dispersed phase, and finally forms solidified microspheres with a porous structure.

[0029] In the present application, in step S1, a base polymer, an extractant and an enhancer are added to an organic solvent to obtain polymer-encapsulated microspheres of the enhancer.

[0030] Optionally, in step S1, the organic solvent is tetrahydrofuran; and the mass percentage concentration of the base polymer in the dispersed phase is 0.1-10%.

[0031] By adopting the above technical solution, the specific mass percentage concentration of the base polymer in the dispersed phase of the present application can control the size of the microspheres and improve the flux of the preparation process. If the concentration is too low, the microsphere size may be too small, increasing the difficulty of solid-liquid separation, and the preparation process has a low flux and has no practical application value. If the concentration is too high, the viscosity of the dispersed phase may be too high, which is not conducive to the formation of uniform spherical micro-liquid beads.

[0032] Optionally, in step S1, the stirring temperature is 25-50° C., the stirring rate is 300-1000 rpm, and the stirring time is 2-30 h.

[0033] By adopting the above technical solution, the specific stirring temperature, stirring rate and stirring time of the present application can ensure that the preparation process of polymer-encapsulated microspheres is efficient and controllable, which helps to obtain a dispersed phase that is uniformly dissolved and well dispersed.

[0034] Optionally, in step S4, the dispersed phase is dispersed in the continuous phase in the form of micro-liquid beads using a microfluidic method or a membrane emulsification method.

[0035] By adopting the above technical solution, the present application uses microfluidics to accurately control the size and distribution of droplets, ensuring that the micro-liquid beads of the dispersed phase are evenly dispersed in the continuous phase. The present application uses membrane emulsification to ensure that the micro-liquid beads of the dispersed phase form a stable emulsion in the continuous phase.

[0036] Optionally, the microfluidic method includes delivering the first liquid and the second liquid to a divider by using a pump; the first liquid can be delivered by a syringe pump, and the second liquid can be delivered by a syringe pump or a peristaltic pump; the divider can be a three-way divider or a concentric capillary divider.

[0037] Optionally, during the microfluidic preparation process, the first liquid flow rate is 0.05~2 mL·min -1 The second liquid flow rate is 1.0~20.0 mL·min -1 ; and the ratio of the second liquid flow rate to the first liquid flow rate is greater than 7:1.

[0038] By adopting the above technical solution, the present application can form micro-liquid beads with uniform size and stability by accurately controlling the flow rate ratio of the dispersed phase and the continuous phase, thereby ensuring the consistency of the finally prepared microspheres.

[0039] Optionally, the membrane emulsification microsphere preparation method includes delivering the first liquid by means of a pump, wherein the third liquid acts as both a continuous phase and a receiving phase.

[0040] Optionally, the first liquid can be delivered by a syringe pump, a gear pump, or a diaphragm pump, and the flow rate of the first liquid is 1.0 to 100.0 mL min -1 .

[0041] By adopting the above technical solution, in the process of preparing polymer-encapsulated microspheres by membrane emulsification, the selection of a pump for conveying the dispersed phase and the flow control of the continuous phase are helpful to form microspheres with uniform size and excellent performance.

[0042] Optionally, in step S4, the average particle size of the polymer-encapsulated microspheres obtained is 1 to 300 μm.

[0043] By adopting the above technical solution, the average particle size of the polymer-encapsulated microspheres of the present application can provide sufficient specific surface area to improve selectivity; can provide sufficient adsorption sites to improve extraction capacity; and can also accelerate the adsorption process to improve extraction efficiency. If the average particle size is too small, the microspheres may easily aggregate, affecting the extraction efficiency; if the average particle size is too large, the specific surface area may be reduced, affecting selectivity and extraction capacity.

[0044] Optionally, in step S4, after the polymer-encapsulated microspheres are obtained, they are separated and dried; the drying temperature is 20-30° C., and the drying time is ≥12 h.

[0045] By adopting the above technical solution, the present application separates and dries the prepared polymer-encapsulated microspheres, and can remove the sodium chloride solution and moisture on the surface to ensure the stability and effectiveness of the microspheres in subsequent use and improve the extraction efficiency. Specific drying conditions can ensure that the moisture on the surface of the microspheres is completely removed without damaging the performance of the microspheres due to excessively high drying temperatures or excessively long drying times. If the drying temperature is too high, it may cause the loss of the extractant and deformation of the microspheres.

[0046] In a third aspect, the present application provides the use of the above-mentioned polymer-encapsulated microspheres in the separation and extraction of lithium resources.

[0047] By adopting the above technical solution, the polymer-encapsulated microspheres of the present application can achieve the separation of lithium from different materials, improve the recovery rate and purity of lithium. In addition, the use of organic solvents is avoided, eliminating the operational hazards and environmental pollution caused by highly toxic solvents. The polymer-encapsulated microspheres of the present application can also be used multiple times to reduce the application cost.

[0048] Optionally, the method comprises the following steps: placing the polymer-encapsulated microspheres into a lithium-containing liquid for lithium extraction; after the lithium extraction is completed, separating the polymer-encapsulated microspheres, placing them into a stripping agent, stirring them to obtain a stripping solution, and concentrating and converting the stripping solution to obtain a lithium product.

[0049] By adopting the above technical solution, the present application puts the polymer-encapsulated microspheres into the lithium-containing liquid for stirring and extraction, then separates the polymer-encapsulated microspheres and puts them into the stripping agent for further treatment, and finally obtains the lithium product by concentration and conversion. The efficient adsorption and multiple use of the polymer-encapsulated microspheres in the separation and extraction of lithium resources improves the extraction efficiency of lithium ions, avoids the use of highly toxic organic solvents, and reduces the impact on the environment.

[0050] Optionally, the method comprises the following steps: placing the polymer-encapsulated microspheres in a filling column to form an extraction column, and allowing a lithium-containing liquid to flow through the extraction column; and then allowing a stripping agent to flow through the extraction column to obtain a stripping liquid, and concentrating and converting the stripping liquid to obtain a lithium product.

[0051] By adopting the above technical solution, the present application can achieve continuous operation through the extraction column, improve the extraction efficiency, and the fixed extraction column is easy to manage and control.

[0052] Optionally, the lithium-containing solution includes a mass concentration of 0.0001~10% Li + of solution.

[0053] Optionally, the stripping agent includes an acid solution with a molar concentration of 0.001 to 5 M (mol / L), and the acid can be selected from at least one of hydrochloric acid, sulfuric acid, and nitric acid.

[0054] Optionally, the concentration can be carried out by heating and evaporating the stripping solution to obtain a concentrated solution; the conversion can be carried out by adding sodium carbonate to the concentrated solution to react and obtain lithium carbonate.

[0055] In summary, the present invention includes at least one of the following beneficial technical effects:

[0056] 1. The polymer-encapsulated microspheres of the present application can achieve efficient separation and enrichment of low-concentration lithium resources, and have high selectivity and high extraction capacity.

[0057] 2. The polymer-encapsulated microspheres of the present application have a porous structure inside and on the surface, which can provide a larger specific surface area, thereby increasing the chance of contact with lithium ions and improving the extraction efficiency.

[0058] 3. The preparation method of polymer-encapsulated microspheres of the present application achieves rapid solidification and highly selective adsorption of the microspheres by controlling various conditions.

[0059] 4. The polymer-encapsulated microspheres of the present application can separate lithium from different materials and improve the recovery rate and purity of lithium.

[0060] 5. This application can avoid the use of highly toxic organic solvents and eliminate the operational hazards, environmental pollution and other problems caused by highly toxic solvents. BRIEF DESCRIPTION OF THE DRAWINGS

[0061] Figure 1 It is a schematic diagram of the structure of a preparation device equipped with a co-core capillary divider;

[0062] Figure 2 It is a schematic diagram of the structure of the preparation device equipped with a membrane emulsifier;

[0063] Figure 3 This is a field emission scanning electron microscope image of the polymer-encapsulated microspheres prepared in Example 1;

[0064] Figure 4 This is the Fourier transform infrared spectrum of the polymer-encapsulated microspheres prepared in Example 1. DETAILED DESCRIPTION

[0065] In order to make the purpose, technical solution and advantages of the present application more clear, the present application is further described in detail below in conjunction with the embodiments. It should be understood that the specific embodiments described here are only used to explain the present application and are not used to limit the present application.

[0066] The inventors of this application found in their research on separating lithium resources that the preparation process of the prior art is harsh, requires high temperature, and has the problem of easy loss of the extractant, and is only applicable to materials with a low sodium / lithium mass ratio and the system does not contain other interfering metal ions. Solvent extraction requires the use of a large amount of organic solvents to separate and purify lithium. These organic solvents are flammable, volatile, and toxic. They are easy to evaporate and carry over during use, posing safety risks and environmental pollution problems. In addition, the solid phase extractants reported in existing patents often have a complex preparation process and high cost.

[0067] In order to solve the above problems, the present application proposes a polymer-encapsulated microsphere, wherein the polymer-encapsulated microsphere comprises a base polymer and an extractant; the base polymer is selected from at least one of polyvinyl chloride, polyvinylidene fluoride, polyvinylidene fluoride-hexafluoropropylene copolymer, polystyrene, and styrene-butadiene-styrene ternary block copolymer;

[0068] The extractant is selected from at least one of β-diketone extractants, organic phosphine oxide extractants, crown ether extractants, and ionic liquid extractants;

[0069] The mass percentage of the base polymer in the polymer-encapsulated microspheres is 29-80%; the mass percentage of the extractant in the polymer-encapsulated microspheres is 10-70%.

[0070] The preparation method comprises the following steps:

[0071] Step S1, adding the base polymer and the extractant into an organic solvent, and then stirring to obtain a dispersed phase;

[0072] Step S2, mixing sodium chloride with water to prepare a sodium chloride aqueous solution with a mass percentage concentration of 20-34% as a continuous phase;

[0073] Step S3, mixing sodium chloride with water to prepare a sodium chloride aqueous solution with a mass percentage concentration of 5-18% as a receiving phase;

[0074] Step S4, dispersing the dispersed phase in the continuous phase in the form of micro-liquid beads and transporting them to the receiving phase, desolventizing the micro-liquid beads through solvent diffusion, and obtaining the polymer-encapsulated microspheres.

[0075] The invention also provides the application of polymer-encapsulated microspheres in separating and extracting lithium resources.

[0076] The solution of the present application is described below in conjunction with the following specific embodiments.

[0077] The specific information of the raw materials used in the examples of this application is shown in Table 1:

[0078] Table 1

[0079] Specific embodiments

[0081] Example 1

[0082] The present embodiment provides a polymer-encapsulated microsphere, including a base polymer and an extractant; in terms of weight percentage, the base polymer is polyvinyl chloride (PVC), and the extractant is LIX-54 extractant and trioctylphosphine oxide (TOPO), with weight percentages of 40%, 40% and 20%, respectively.

[0083] The preparation method comprises the following steps:

[0084] Step S1, adding 0.24 g of polyvinyl chloride, 0.24 g of LIX-54 extractant, and 0.12 g of trioctylphosphine oxide into 20 ml of tetrahydrofuran, stirring for 4 h at a stirring rate of 400 rpm and a stirring temperature of 40° C., and ultrasonically treating for 10 min to obtain a dispersed phase (first liquid);

[0085] Step S2, the continuous phase (second liquid) is a sodium chloride aqueous solution with a mass percentage concentration of 20%;

[0086] Step S3, the receiving phase (third liquid) is a sodium chloride aqueous solution with a mass percentage concentration of 10%;

[0087] Step S4, the third liquid column is a glass column with an inner diameter of 60mm and a height of 400mm, filled with 500mL of the third liquid, and its bottom is connected to a co-core capillary divider, the inner diameter of the first tube is 500μm, and the outer diameter is 700μm; the inner diameter of the second tube is 1200μm, and the outer diameter is 2000μm. The first liquid and the second liquid are respectively delivered to the first tube and the second tube of the divider by a delivery pump, and the flow rates of the first liquid and the second liquid are 0.2mL / min and 1.6mL / min, respectively. At the outlet of the first tube, the second liquid flow gathers the first liquid flow at the micropore entrance through fluid dynamic focusing and divides it into discontinuous and equal-length sections. At the outlet of the micropore, due to the expansion of the pores and the interfacial tension, the droplets become larger and form spherical micro-liquid beads. At this time, the first liquid micro-liquid beads and the second liquid are both in the third liquid. Since tetrahydrofuran has a high solubility and diffusion coefficient in the third liquid, the tetrahydrofuran in the micro beads will quickly diffuse into the third liquid, thereby desolvating the micro beads and finally obtaining solid polymer microspheres. Finally, the polymer-encapsulated microspheres are filtered and separated, washed with water to remove NaCl attached to the surface, and air-dried at 25°C to obtain the polymer-encapsulated microspheres. The field emission scanning electron microscope (FESEM) image is shown below: Figure 3 Its Fourier infrared spectrum is shown as Figure 4 shown.

[0088] Low concentration Li + Enrichment: Weigh 0.18 g of the prepared polymer-encapsulated microspheres and place them in 50 mL of 1.0 mg / L Li + and 50mg / L Na + The pH of the solution was adjusted to 4, and the extraction was carried out at 25°C and 800 rpm for 90 minutes. The Li + and Na + The concentration of is calculated and the extraction efficiency is calculated. To prepare lithium carbonate, the LiCl solution is heated and evaporated to concentrate, and an appropriate amount of sodium carbonate is added to obtain lithium carbonate, which is crystallized, filtered, and dried to obtain the final product.

[0089] Example 2

[0090] This embodiment provides a polymer-encapsulated microsphere, comprising a base polymer and an extractant; in terms of mass percentage, the base polymer is polyvinylidene fluoride (PVDF), and the extractant is an ionic liquid [(B12C4)C 6 im][TTA], the mass proportions are 50% and 50% respectively.

[0091] Among them, [(B12C4)C 6im][TTA] was prepared from 1-hexyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide ([C6mim][NTf2]), benzododecacrown-4, and thenoyltrifluoroacetone.

[0092] The preparation method comprises the following steps:

[0093] Step S1, 0.50 g of PVDF, [(B12C4)C 6 im][TTA] 0.50 g was added to 30 ml of tetrahydrofuran, and stirred for 12 h at a stirring rate of 400 rpm and a stirring temperature of 50° C. to obtain a dispersed phase (first liquid);

[0094] Step S2, the continuous phase (second liquid) is a sodium chloride aqueous solution with a mass percentage concentration of 25%;

[0095] Step S3, the receiving phase (third liquid) is a sodium chloride aqueous solution with a mass percentage concentration of 15%;

[0096] Step S4, the third liquid column is a glass column with an inner diameter of 60mm and a height of 400mm, filled with 500mL of the third liquid, and its bottom is connected to a co-core capillary divider, and its size is the same as that of Example 1. The first liquid and the second liquid are respectively transported to the first tube and the second tube of the divider by a syringe pump, and the flow rates of the first liquid and the second liquid are 0.2mL / min and 1.8mL / min, respectively. At the outlet of the first tube, the second liquid flow gathers the first liquid flow at the micropores and divides it into discontinuous sections through fluid dynamic focusing. At this time, the first liquid micro beads and the second liquid are both in the third liquid. The tetrahydrofuran in the micro beads quickly diffuses into the third liquid, thereby desolvating the micro beads and finally obtaining solid polymer microspheres. Finally, the polymer-encapsulated microspheres are filtered and separated, washed with water, and air-dried at 25°C to obtain the polymer-encapsulated microspheres.

[0097] Polymer-encapsulated microspheres are used to separate lithium from a mixture of lithium, sodium and potassium: 1 g of polymer-encapsulated microspheres is filled in a glass column with a diameter of 9 mm and both ends are blocked with absorbent cotton. + , Na + , K + The concentration was 1.0 mg·L -1 , 50.0mg·L -1 , 40.0mg·L -1) Use a peristaltic pump to transport the solution through a separation column. After the transport is completed, use 0.2 M hydrochloric acid to extract lithium. Use a peristaltic pump to transport 10 mL of 0.2 M hydrochloric acid through a separation column to obtain a lithium solution free of sodium and potassium. To prepare lithium carbonate, heat the LiCl solution for evaporation and concentration, add an appropriate amount of sodium carbonate to obtain lithium carbonate, crystallize, filter, and dry to obtain the final product.

[0098] Example 3

[0099] The present embodiment provides a polymer-encapsulated microsphere, comprising a base polymer and an extractant; in terms of weight percentage, the base polymer is polyvinylidene fluoride-hexafluoropropylene copolymer (PVDF-HFP), and the extractant is 4,4,4-trifluoro-1-benzene-1,3-butanedione (HBTA) and trioctylphosphine oxide (TOPO), with weight percentages of 50%, 25% and 25%, respectively.

[0100] The preparation method comprises the following steps:

[0101] Step S1, adding 10.0 g of PVDF-HFP, 5.0 g of HBTA and 5.0 g of TOPO into 500 ml of tetrahydrofuran, stirring for 15 h at a stirring rate of 600 rpm and a stirring temperature of 50° C. to obtain a dispersed phase (first liquid).

[0102] Step S2: The third liquid is a sodium chloride aqueous solution with a mass percentage concentration of 15%.

[0103] Step S3, place 6000 mL of the third liquid in a glass column with an inner diameter of 200 mm and a height of 400 mm (eg Figure 2 As shown). The first liquid is transported to the membrane emulsifier by a gear pump. The first liquid is dispersed into micro beads by the membrane emulsifier and dispersed in the third liquid. Tetrahydrofuran in the micro beads quickly diffuses into the third liquid, thereby desolvating the micro beads and finally obtaining solid polymer microspheres. After the microspheres are filtered and separated, they are washed with water and air-dried at 25°C to obtain the polymer-encapsulated microspheres.

[0104] Polymer-encapsulated microspheres are used to separate lithium from a mixture of lithium, sodium, potassium, and boron: 1 g of polymer-encapsulated microspheres is filled in a glass column with a diameter of 9 mm and both ends are blocked with absorbent cotton. + 、Na + , K + , B 3+ (Concentrations were 1.0 mg·L -1 , 50.0mg·L -1 , 40.0mg·L -1 , 10mg·L -1) The mixed solution is transported through a separation column by a peristaltic pump, and after the transport is completed, lithium is extracted with 0.2M hydrochloric acid. 10mL of 0.2M hydrochloric acid is transported through a separation column by a peristaltic pump to obtain a lithium solution free of sodium, potassium, and boron. To prepare lithium carbonate, the LiCl solution is heated and evaporated, and an appropriate amount of sodium carbonate is added to obtain lithium carbonate, which is crystallized, filtered, and dried to obtain the final product.

[0105] Example 4

[0106] The present embodiment provides a polymer-encapsulated microsphere, comprising a base polymer, an extractant and a reinforcing agent; in terms of mass percentage, the base polymer is polyvinyl chloride (PVC), the extractant is trioctylphosphine oxide (TOPO), and the reinforcing agent is epoxidized soybean oil, with mass percentages of 55%, 40% and 5%, respectively.

[0107] The preparation method comprises the following steps:

[0108] Step S1, adding 11 g of polyvinyl chloride, 8.0 g of TOPO extractant and 1.0 g of epoxidized soybean oil into 600 ml of tetrahydrofuran, stirring at a stirring rate of 400 rpm and a stirring temperature of 50° C. for 4 h to obtain a dispersed phase (first liquid).

[0109] Step S2: The third liquid is a sodium chloride aqueous solution with a mass percentage concentration of 10%.

[0110] Step S3, placing 5000 mL of the third liquid in a glass column with an inner diameter of 200 mm and a height of 400 mm (eg Figure 2 As shown). The first liquid is transported to the membrane emulsifier by a gear pump. The first liquid is dispersed into micro beads by the membrane emulsifier and dispersed in the third liquid. Tetrahydrofuran in the micro beads quickly diffuses into the third liquid, thereby desolvating the micro beads and finally obtaining solid polymer microspheres. After the microspheres are filtered and separated, they are washed with water and air-dried at 25°C to obtain the polymer-encapsulated microspheres.

[0111] Low Li concentration in high Mg / Li ratio brines + Enrichment: Weigh 1.0 g of the prepared polymer-encapsulated microspheres and add them to 200 mL of 0.5 mg·L -1 Li + and 350mg·L -1 Mg 2+ The extraction was carried out at 25°C and 800 rpm for 50 minutes. The extraction rate of Li was 85%, and the separation factor of Li and Mg was 260. To prepare lithium carbonate, the LiCl solution was heated and evaporated, and an appropriate amount of sodium carbonate was added to obtain lithium carbonate, which was crystallized, filtered, and dried to obtain the final product.

[0112] Comparative Example 1

[0113] The difference between Comparative Example 1 and Example 1 is that the polymer-encapsulated microspheres of Comparative Example 1 include a base polymer and an extractant; in terms of mass percentage, the base polymer is polyvinyl chloride (PVC), and the extractant is LIX-54 extractant and trioctylphosphine oxide (TOPO), and the mass proportions are 25%, 40% and 35%, respectively.

[0114] Comparative Example 2

[0115] The difference between Comparative Example 2 and Example 1 is that the polymer-encapsulated microspheres of Comparative Example 2 include a base polymer and an extractant; in terms of mass percentage, the base polymer is polyvinyl chloride (PVC), and the extractant is LIX-54 extractant and trioctylphosphine oxide (TOPO), and the mass percentages are 85%, 10% and 5%, respectively.

[0116] Experimental testing

[0117] Test items and test methods

[0118] Average particle size and particle size dispersion index: The diameter of the prepared polymer-encapsulated microspheres was observed and measured using a microscope. The diameters of 100 microspheres were measured and their average value and particle size dispersion index were calculated.

[0119] The polymer-encapsulated microspheres prepared in Examples 1 to 4 and Comparative Examples 1 to 2 were measured for average particle size, particle size dispersion index, and single Li + The extraction rate was tested and the test results are shown in Table 2.

[0120] Table 2

[0121]

[0122] From the test results in Table 2, it can be seen that the polymer-encapsulated microspheres prepared by the preparation method of the present invention have high sphericity, the diameter can be adjusted within the range of 50-120 μm, and the particle size dispersion index is between 8-15%. The polymer-encapsulated microspheres prepared in Examples 1-4 are used for the separation of lithium from different feed liquids, and the extraction rate is not less than 85%. The polymer-encapsulated microspheres prepared in Examples 1-4 have high selectivity and can achieve efficient separation of lithium.

[0123] In Comparative Example 1, the mass percentage of the base polymer is less than 29%, and the mass percentage of the extractant is greater than 70%. The lithium extraction rate of the obtained polymer-encapsulated microspheres is significantly reduced.

[0124] The mass percentage of the base polymer in Comparative Example 2 is greater than 80%, and the lithium extraction rate of the obtained polymer-encapsulated microspheres is also reduced.

[0125] Embodiments 5 to 8

[0126] Example 5

[0127] The difference between Example 5 and Example 3 is that the polymer-encapsulated microspheres of Example 5 include a base polymer, an extractant and a reinforcing agent; in terms of mass percentage, the base polymer is polyvinylidene fluoride-hexafluoropropylene copolymer (PVDF-HFP), the extractant is 4,4,4-trifluoro-1-benzene-1,3-butanedione (HBTA) and trioctylphosphine oxide (TOPO), and the reinforcing agent is dioctyl phthalate (DOP), and the mass percentages are 50%, 25%, 10% and 15%, respectively.

[0128] Example 6

[0129] The difference between Example 6 and Example 3 is that the polymer-encapsulated microspheres of Example 6 include a base polymer, an extractant and a reinforcing agent; calculated by mass percentage, the base polymer is polyvinylidene fluoride-hexafluoropropylene copolymer (PVDF-HFP), the extractant is 4,4,4-trifluoro-1-benzene-1,3-butanedione (HBTA) and trioctylphosphine oxide (TOPO), and the reinforcing agent is dioctyl phthalate, and the mass proportions are 50%, 25%, 17% and 8% respectively.

[0130] Example 7

[0131] The difference between Example 7 and Example 6 is that in step S1 of Example 7, stirring is performed at a stirring rate of 650 rpm and a stirring temperature of 35° C. for 16 h.

[0132] Example 8

[0133] The difference between Example 8 and Example 6 is that in step S1 of Example 8, stirring is performed at a stirring rate of 1000 rpm and a stirring temperature of 50° C. for 30 h.

[0134] The average particle size, particle size dispersion index and single Li + The extraction rate was tested and the test results are shown in Table 3.

[0135] Table 3

[0136]

[0137] From the test results in Table 3, it can be seen that the Example 5 and the Example 6 further added a reinforcing agent, the particle size dispersion index of the obtained polymer-encapsulated microspheres was reduced, and the extraction rate of lithium was increased. Among them, the particle size dispersion index of the polymer-encapsulated microspheres obtained in the Example 6 was the lowest, and the extraction rate of lithium was the highest.

[0138] The difference between Example 7 and Example 8 and Example 6 is that the stirring parameters are different, and the particle size dispersion index of the polymer-encapsulated microspheres prepared in Example 7 is the lowest.

[0139] The above description is only a preferred embodiment of the present application and is not intended to limit the present application. Any modifications, equivalent substitutions and improvements made within the principles of the present application should be included in the protection scope of the present application.

Claims

1. A polymer-encapsulated microsphere, characterized in that: The polymer-encapsulated microspheres include a base polymer and an extractant; the base polymer is selected from at least one of polyvinyl chloride, polyvinylidene fluoride, polyvinylidene fluoride-hexafluoropropylene copolymer, polystyrene, and styrene-butadiene-styrene terblock copolymer; The extractant is selected from at least one of β-diketone extractants, organic phosphine oxide extractants, crown ether extractants, and ionic liquid extractants; The mass percentage of the base polymer in the polymer-encapsulated microspheres is 29-80%; the mass percentage of the extractant in the polymer-encapsulated microspheres is 10-70%; The polymer-encapsulated microspheres also include a reinforcing agent; The enhancer is selected from at least one of triphosphate, epoxy soybean oil, dioctyl phthalate, diphenyl 2-ethylhexyl phosphate, tri-n-butyl acetyl citrate, tri(2-ethylhexyl) acetyl citrate, di(2-ethylhexyl) sebacate, epoxy stearate, and chlorinated paraffin; Based on the mass of the polymer-encapsulated microspheres, the mass percentage of the reinforcing agent is 0.1-15%.

2. A method for preparing polymer-encapsulated microspheres according to claim 1, characterized in that: The following steps are involved: Step S1, adding the base polymer, the extractant, and the enhancer into an organic solvent, and then stirring to obtain a dispersed phase; Step S2, mixing sodium chloride with water to prepare a sodium chloride aqueous solution with a mass percentage concentration of 20-34% as a continuous phase; Step S3, mixing sodium chloride with water to prepare a sodium chloride aqueous solution with a mass percentage concentration of 5-18% as a receiving phase; Step S4, dispersing the dispersed phase in the continuous phase in the form of micro-liquid beads and transporting them to the receiving phase, desolventizing the micro-liquid beads through solvent diffusion, and obtaining the polymer-encapsulated microspheres.

3. The method for preparing polymer-encapsulated microspheres according to claim 2, characterized in that: In the step S1, the organic solvent is tetrahydrofuran; and the mass percentage concentration of the base polymer in the dispersed phase is 0.1-10%.

4. The method for preparing polymer-encapsulated microspheres according to claim 2, characterized in that: In the step S1, the stirring temperature is 25-50° C., the stirring speed is 300-1000 rpm, and the stirring time is 2-30 h.

5. The method for preparing polymer-encapsulated microspheres according to claim 2, characterized in that: In the step S4, the average particle size of the polymer-encapsulated microspheres obtained is 1-300 μm.

6. Use of the polymer-encapsulated microspheres according to claim 1 in separating and extracting lithium resources.

7. The use of the polymer-encapsulated microspheres according to claim 6 in separating and extracting lithium resources, characterized in that: The method comprises the following steps: placing the polymer-encapsulated microspheres into a lithium-containing liquid to extract lithium; after the lithium extraction is completed, separating the polymer-encapsulated microspheres, placing them into a stripping agent, stirring them to obtain a stripping solution, and concentrating and converting the stripping solution to obtain a lithium product.

8. The use of the polymer-encapsulated microspheres according to claim 6 in separating and extracting lithium resources, characterized in that: The method comprises the following steps: placing the polymer-encapsulated microspheres in a filling column to form an extraction column, and allowing a lithium-containing feed liquid to flow through the extraction column; and then allowing a stripping agent to flow through the extraction column to obtain a stripping liquid, and concentrating and converting the stripping liquid to obtain a lithium product.

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