Polymer containing microsphere for separating thallium as well as preparation method and application of polymer containing microsphere

Abstract

The invention discloses a polymer containing microsphere for separating thallium as well as a preparation method and application of the polymer containing microsphere, and belongs to the technical field of separation science. The polymer-containing microsphere comprises a basic polymer and an extraction agent, the basic polymer forms polymer particles, the surfaces and the interiors of the polymer particles are provided with pores, and the extraction agent is arranged in the internal pores of the polymer particles; the basic polymer comprises at least one of polyvinyl chloride, polyvinylidene fluoride, a polyvinylidene fluoride-hexafluoropropylene copolymer, polystyrene and a styrene-butadiene-styrene ternary block copolymer; the extraction agent comprises at least one of a beta-diketone extraction agent, an organic amine extraction agent, an organic phosphorus extraction agent and an ionic liquid extraction agent; based on the mass of the polymer containing microspheres, the mass content of the basic polymer is 29-80%, and the mass content of the extracting agent is 10-70%. The polymer containing microspheres prepared by the invention have high selectivity and high extraction capacity, and can realize rapid high-selectivity separation and enrichment of low-concentration thallium.

Description

Technical Field

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

[0002] Thallium is a highly toxic element that poses a significant threat to human health. Consequently, countries around the world have stringent requirements for its content in food, beverages, and the environment. Furthermore, thallium is a strategic resource, crucial for the production of certain specialty materials. Thallium coexists with certain other elements in nature. During metal smelting, it must be removed as an impurity. Furthermore, thallium-containing wastewater generated by industrial processes such as mineral mining and metal smelting cannot be discharged directly; instead, thallium levels must be reduced to sufficiently low levels. Therefore, the separation and removal of thallium is a crucial issue, both from the perspective of thallium resource utilization and environmental protection.

[0003] To address these issues, research has been conducted on the selective separation and recovery of low-concentration thallium using pyrometallurgy, solvent extraction, metal displacement, and adsorption. However, pyrometallurgy generally consumes a lot of energy and can cause air pollution. Solvent extraction, due to the use of organic solvents, also poses pollution risks. Metal displacement and adsorption often produce metal mixtures, requiring further separation to obtain pure thallium.

[0004] Therefore, there is an urgent need to develop a polymer-encapsulated microsphere that can achieve rapid and highly selective separation and enrichment of low-concentration thallium resources. The microsphere has high selectivity and high extraction capacity and does not require special conditions such as organic solvents and high temperatures during use. Summary of the Invention

[0005] In view of this, the present application provides a polymer-encapsulated microsphere for separating thallium, and its preparation method and application. The polymer-encapsulated microsphere of the present application has high selectivity and high extraction capacity for thallium, and the separation process is relatively simple, which can achieve rapid and highly selective separation and enrichment of low-concentration thallium resources.

[0006] In the first aspect, the present application provides a polymer-encapsulated microsphere for separating thallium, the polymer-encapsulated microsphere comprising a base polymer and an extractant, the base polymer forming polymer particles, the surface and interior of the polymer particles having pores, and the extractant being arranged in the internal pores of the polymer particles; the base polymer comprising at least one of polyvinyl chloride, polyvinylidene fluoride, polyvinylidene fluoride-hexafluoropropylene copolymer, polystyrene, and styrene-butadiene-styrene ternary block copolymer; the extractant comprising at least one of β-diketone extractants, organic amines, organic phosphoric acid, organic phosphine oxide extractants, and ionic liquid extractants; based on the mass of the polymer-encapsulated microspheres, the mass content of the base polymer is 29%-80%, and the mass content of the extractant is 10%-70%.

[0007] By adopting the above-mentioned technical solution, the interior and surface of the polymer particles of the present application have a porous structure, which can provide a larger specific surface area, thereby increasing the chance of contact with thallium ions and improving the extraction efficiency. In addition, since the extractant is arranged inside the polymer particles, the volatilization and loss of the organic phase in the traditional extraction process can be avoided, and the stability of the extractant can be improved; and the above-mentioned extractant can achieve highly selective extraction of thallium ions, thereby effectively separating thallium in a high-impurity environment. The polymer-encapsulated microspheres of the present application can achieve efficient separation and enrichment of low-concentration thallium resources, and have high selectivity and high extraction capacity. In the present application, the mass content of the base polymer directly affects the porosity and pore size distribution of the polymer particles, thereby affecting the extraction performance. If the base polymer content is too high, the porosity inside 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 extract thallium ions, thereby reducing the overall extraction 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 of the extractant or instability. In this application, an appropriate amount of extractant can maximize the extraction sites and improve the extraction 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 loss of the extractant and affecting the extraction performance. If the extractant content is too low, the extraction capacity of the microspheres will be significantly reduced, and their high selectivity cannot be fully utilized, reducing the total extraction capacity.

[0008] Optionally, the β-diketone extractant includes at least one of 1-phenyl-1,3-butanedione, 1,3-diphenyl-1-3-propanedione, 4,4,4-trifluoro-1-phenyl-1,3-butanedione (HBTA), 4,4,4-trifluoro-1-(2-thiophene)1,3-butanedione, 2-hydroxy-4-isopropyl-2,4,6-cycloheptatrienol-1-one, 5,7-dichloro-8-quinoline, and 1,1,1-trifluoro-4-mercapto-4-(2-thiophene)3-butene-2-one.

[0009] Optionally, the organic amine extractant includes at least one of trioctylamine, triphenylmethaneamine, and 1-hexyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide.

[0010] Optionally, the organic phosphorus extractant includes at least one of trioctyl phosphate, di(2-ethylhexyl)phosphoric acid, 2-ethylhexyl mono-2-ethylhexyl phosphate, etc., and the organic phosphine oxide extractant includes trioctylphosphine oxide (TOPO).

[0011] Optionally, the ionic liquid extractant includes at least one of a quaternary ammonium salt ionic liquid extractant, an imidazole ionic liquid extractant, a pyridine ionic liquid extractant, and an organophosphorus ionic liquid; wherein the quaternary ammonium salt ionic liquid extractant includes trioctylmethylammonium chloride, the imidazole ionic liquid extractant includes 1-butyl-3-methylimidazolinium hexafluorophosphate; the pyridine ionic liquid extractant includes hexadecylpyridinium bromide, and the organophosphorus ionic liquid includes octyltributylphosphonium chloride, hexadecyltributylphosphonium bromide, etc.

[0012] In one possible implementation, the polymer-encapsulated microspheres further include a reinforcing agent. The reinforcing agent includes at least one of triphosphate, epoxy soybean oil, dioctyl phthalate, 2-ethylhexyl diphenyl phosphate, tri-n-butyl acetyl citrate, tri(2-ethylhexyl) acetyl citrate, di(2-ethylhexyl) sebacate, octyl epoxy stearate, and chlorinated paraffin.

[0013] In the above technical solution, the enhancer can improve the physical and chemical properties of the polymer particles, increase the stability and extraction efficiency of the extractant, and can also adjust the pore structure of the polymer particles to further improve the extraction efficiency.

[0014] In a possible implementation, the mass content of the reinforcing agent is 0.1%-15% based on the mass of the polymer-enclosed microspheres.

[0015] In a possible implementation, the average particle size of the polymer particles is 1 μm to 300 μm.

[0016] In the above technical solution, polymer particles with an average particle size that meets the above conditions can provide sufficient specific surface area, thereby improving selectivity for thallium, and can also provide sufficient extraction sites, thereby increasing the extraction capacity for thallium. In addition, polymer particles with an average particle size that meets the above conditions can accelerate the extraction process and improve extraction efficiency. If the average particle size is too small, the polymer particles may easily aggregate, affecting extraction efficiency; if the average particle size is too large, the specific surface area may be reduced, affecting selectivity and extraction capacity.

[0017] In a second aspect, the present application provides a method for preparing the above-mentioned polymer-encapsulated microspheres for separating thallium, comprising the following steps: dispersing a dispersed phase in a continuous phase to form liquid droplets, and then transferring the liquid droplets to a receiving phase for solidification; the continuous phase is a 20wt%~34wt% sodium chloride aqueous solution, and the receiving phase is a 5wt%~18wt% sodium chloride aqueous solution; the dispersed phase includes a solute and an organic solvent, the solute includes a base polymer and an extractant, the base polymer includes at least one of polyvinyl chloride, polyvinylidene fluoride, polyvinylidene fluoride-hexafluoropropylene copolymer, polystyrene, and styrene-butadiene-styrene terblock copolymer; the extractant includes at least one of a β-diketone extractant, an organic amine extractant, an organic phosphoric acid extractant, an organic phosphine oxide extractant, and an ionic liquid extractant; the organic solvent is tetrahydrofuran; based on the total mass of the solute, the mass content of the base polymer is 29%~80%, and the mass content of the extractant is 10%~70%.

[0018] In the above technical solution, the solute in the dispersed phase is dissolved in the organic solvent tetrahydrofuran. The inventors have discovered that because the organic solvent is tetrahydrofuran, when the dispersed phase is dispersed in the form of liquid droplets in a sodium chloride aqueous solution with a higher concentration (i.e., the continuous phase), the liquid droplets are highly stable and are not easily merged, and the organic solvent is not easily diffused. Moreover, when the liquid droplets are transferred to a sodium chloride aqueous solution with a lower concentration (i.e., the receiving phase), the organic solvent in the liquid droplets diffuses at an appropriate rate, which not only allows the liquid droplets to solidify, but also avoids excessively rapid solidification that would result in an uneven structure of the polymer microspheres.

[0019] In a third aspect, the present application provides the use of the above-mentioned polymer-encapsulated microspheres for separating thallium in separating and extracting thallium resources.

[0020] By employing the above-described technical solution, the polymer-encapsulated microspheres of this application can separate thallium from different materials, improving its recovery rate and purity. Furthermore, they avoid the use of organic solvents, eliminating the operational hazards and environmental pollution associated with highly toxic solvents. The polymer-encapsulated microspheres of this application can also be reused multiple times, reducing application costs.

[0021] In one possible implementation, the application of polymer-encapsulated microspheres in the separation and extraction of thallium resources includes the following steps: placing the polymer-encapsulated microspheres in a thallium-containing liquid for extraction, then separating the polymer-encapsulated microspheres and placing the polymer-encapsulated microspheres in a stripping agent and stirring to obtain a stripping solution, and concentrating and / or converting the stripping solution to obtain a thallium product.

[0022] By adopting the above technical solution, the present application places polymer-encapsulated microspheres into a thallium-containing liquid for agitation extraction. The polymer-encapsulated microspheres are then separated and placed in a stripping agent for further processing, ultimately yielding a thallium product through concentration and / or conversion. The efficient extraction and multiple uses of the polymer-encapsulated microspheres in thallium resource separation and extraction improve the extraction efficiency of thallium ions, avoid the use of highly toxic organic solvents, and reduce environmental impact.

[0023] In one possible implementation, the application of polymer-encapsulated microspheres in the separation and extraction of thallium resources includes the following steps: placing the polymer-encapsulated microspheres in a filling column to form an extraction column, and allowing the thallium-containing liquid to flow through the extraction column; then using a stripping agent to flow through the extraction column to obtain a stripping liquid, and concentrating and / or converting the stripping liquid to obtain a thallium product.

[0024] 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.

[0025] The beneficial effects of this application are as follows: 1. The polymer-encapsulated microspheres of this application can achieve efficient separation and enrichment of low-concentration thallium resources with high selectivity and high extraction capacity.

[0026] 2. The polymer particles 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 thallium ions and improving extraction efficiency.

[0027] 3. The preparation method of the polymer-encapsulated microspheres of the present application can rapidly solidify to form polymer-encapsulated microspheres by controlling various conditions, and the obtained polymer-encapsulated microspheres have highly selective extraction.

[0028] 4. The polymer-encapsulated microspheres of the present application can separate thallium from different materials and improve the recovery rate and purity of thallium.

[0029] 5. This application can avoid the use of highly toxic organic solvents, eliminating the operational hazards, environmental pollution and other problems caused by highly toxic solvents. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] In order to more clearly illustrate the technical solutions of the embodiments of the present application, the following is a brief introduction to the drawings required for use in the embodiments of the present application. It should be understood that the following drawings only show certain embodiments of the present application and therefore should not be regarded as limiting the scope. For ordinary technicians in this field, other relevant drawings can be obtained based on these drawings without creative work.

[0031] Figure 1 It is a structural diagram of a device equipped with a co-core capillary divider; Figure 2 It is a schematic diagram of the structure of the membrane emulsifier device; Figure 3 This is a field emission scanning electron micrograph of the polymer-encapsulated microspheres prepared in Example 1; Figure 4 This is the Fourier transform infrared spectrum of the polymer-encapsulated microspheres prepared in Example 1. DETAILED DESCRIPTION

[0032] In order to make the purpose, technical solutions and advantages of this application more clear, the following further describes this application in detail with reference to the embodiments. It should be understood that the specific embodiments described herein are only used to explain this application and are not intended to limit this application.

[0033] The inventors of this application discovered in their research on separating thallium resources that the current pyrometallurgical, solvent extraction, and adsorption methods for selectively separating and recovering low-concentration thallium still face some difficult-to-overcome technical challenges. For example, pyrometallurgical processes require harsh high temperatures, while solvent extraction methods suffer from the problem of easy loss of the extractant and are only applicable to the separation and recovery of thallium of varying concentrations in liquid materials. For example, CN202310205228.3 discloses a method for separating thallium from thallium-containing sulfide waste slag using a pyrometallurgical method, wherein the calcination temperature is 650-750°C and the calcination time is not less than 1 hour. The adsorption method often produces a metal mixture. If pure thallium is to be obtained, re-separation is required. For example, CN202010060828.1 discloses a method for removing and recovering thallium from industrial wastewater, which requires re-separation; US5296204A discloses a method for separating and recovering thallium from industrial waste by solid-phase extraction. When adsorbing thallium, certain other elements such as cadmium will be co-adsorbed, and a replacement reaction is required to obtain thallium. Moreover, the solid-phase extraction agent used often has a complex preparation process and high cost.

[0034] To address the above-mentioned issues, this application proposes a polymer-encapsulated microsphere for separating thallium. The microsphere has high selectivity and high extraction capacity for thallium, enabling rapid and highly selective separation and enrichment of low-concentration thallium resources. Furthermore, the process for separating thallium using the microsphere is relatively simple and the conditions are mild. The following is a detailed description of the present application: In a first aspect, the polymer-encapsulated microspheres of the present application comprise a base polymer and an extractant. The base polymer forms polymer particles having pores on the surface and interior of the polymer particles, and the extractant is disposed within the pores of the polymer particles. The base polymer comprises at least one of polyvinyl chloride, polyvinylidene fluoride, polyvinylidene fluoride-hexafluoropropylene copolymer, polystyrene, and styrene-butadiene-styrene terblock copolymer. The extractant comprises at least one of a β-diketone extractant, an organic amine extractant, an organic phosphoric acid extractant, an organic phosphine oxide extractant, and an ionic liquid extractant. Based on the mass of the polymer-encapsulated microspheres, the mass content of the base polymer is 29%-80%, and the mass content of the extractant is 10%-70%. The polymer particles have a porous structure both inside and on the surface, which provides a large specific surface area, thereby increasing the contact opportunity with thallium ions and improving extraction efficiency. Furthermore, since the extractant is disposed within the polymer particles, it avoids the volatilization and loss of the organic phase during traditional extraction processes, improving the stability of the extractant. Furthermore, the extractant can achieve highly selective extraction of thallium ions, thereby effectively separating thallium in a high-impurity environment. The polymer-encapsulated microspheres of the present application can achieve efficient separation and enrichment of low-concentration thallium resources with high selectivity and high extraction capacity. In the present application, the mass content of the base polymer directly affects the porosity and pore size distribution of the polymer particles, thereby affecting the extraction performance. If the base 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 available for extracting thallium ions, thereby reducing the overall extraction capacity. If the polymer content is too low, too little polymer may not be able to fully wrap and fix the extractant, and affect the dispersibility of the microspheres, and cause the extractant to be lost or unstable. In the present application, an appropriate amount of extractant can maximize the extraction site and improve the extraction 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 poor microsphere dispersibility and loss of extractant, affecting the extraction performance. If the extractant content is too low, the extraction capacity of the microspheres will be significantly reduced, and their high selectivity cannot be fully utilized, reducing the total extraction capacity.

[0035] In some embodiments of the present application, the β-diketone extractant includes at least one of 1-phenyl-1,3-butanedione, 1,3-diphenyl-1-3-propanedione, 4,4,4-trifluoro-1-phenyl-1,3-butanedione (HBTA), 4,4,4-trifluoro-1-(2-thiophene)-1,3-butanedione, 2-hydroxy-4-isopropyl-2,4,6-cycloheptatrienol-1-one, 5,7-dichloro-8-quinoline, and 1,1,1-trifluoro-4-mercapto-4-(2-thiophene)-3-butene-2-one. The organic amine extractant includes at least one of trioctylamine and 1-hexyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide. Organophosphorus extractants include at least one of trioctyl phosphate, di(2-ethylhexyl)phosphoric acid, octyltributylphosphine chloride, and hexadecyltributylphosphine bromide. Organophosphine oxide extractants include at least one of trioctylphosphine oxide (TOPO) and di-(2-ethylhexyl)phosphoric acid (D2EHPA). Ionic liquid extractants include at least one of quaternary ammonium salt ionic liquid extractants, imidazole ionic liquid extractants, and pyridine ionic liquid extractants. Quaternary ammonium salt ionic liquid extractants include trioctylmethylammonium chloride, imidazole ionic liquid extractants include 1-butyl-3-methylimidazolinium hexafluorophosphate, and pyridine ionic liquid extractants include N-hexadecylpyridinium bromide.

[0036] In some embodiments of the present application, the polymer-encapsulated microspheres further include an enhancer. The enhancer includes at least one of triphosphate, epoxy soybean oil, dioctyl phthalate, 2-ethylhexyl diphenyl phosphate, tri-n-butyl acetyl citrate, tri-(2-ethylhexyl) acetyl citrate, di-(2-ethylhexyl) sebacate, octyl epoxy stearate, and chlorinated paraffin. The enhancer can improve the physical and chemical properties of the polymer particles, enhance the stability and extraction efficiency of the extractant, and regulate the pore structure of the polymer particles, further improving extraction efficiency. By way of example, in some embodiments of the present application, the enhancer content is 0.1%-15% by weight based on the mass of the polymer-encapsulated microspheres.

[0037] In some embodiments of the present application, the average particle size of the polymer particles is 1 μm to 300 μm. Polymer particles with an average particle size that meets the above conditions can provide sufficient specific surface area, improve selectivity for thallium, and provide sufficient extraction sites, thereby increasing the thallium extraction capacity. Furthermore, polymer particles with an average particle size that meets the above conditions can accelerate the extraction process and improve extraction efficiency. If the average particle size is too small, the polymer particles may easily aggregate, affecting extraction efficiency. If the average particle size is too large, the specific surface area may be reduced, affecting selectivity and extraction capacity.

[0038] In a second aspect, the present application provides a method for preparing polymer-encapsulated microspheres, which specifically comprises the following steps: S1. Adding a solute into an organic solvent and then stirring to obtain a dispersed phase; wherein the solute includes a base polymer and an extractant.

[0039] In this step, the specific types of the base solvent and the extractant are as described above in this application and will not be repeated here. Moreover, based on the total mass of the solute, the mass content of the base polymer is 29% to 80%, and the mass content of the extractant is 10% to 70%. The organic solvent is tetrahydrofuran, which is miscible with water and facilitates the subsequent solidification of the dispersed phase to form particles. In addition, in some embodiments of the present application, the solute may also include an enhancer, the specific types of the enhancer are as described above in this application; and the mass content of the enhancer is 0.1% to 20% based on the total mass of the solute.

[0040] In some embodiments of the present application, in order to better control the size of the polymer particles in the subsequently formed polymer-encapsulated microspheres and improve the throughput of the preparation process, the mass percentage concentration of the base polymer in the dispersed phase is 0.1% to 10%. If the concentration of the base polymer is too low, the size of the subsequently formed polymer particles may be too small, affecting the dispersibility of the dispersed phase micro-liquid beads in the continuous phase, and the preparation process throughput is low, which has no practical application value. If the concentration of the base polymer is too high, the viscosity of the dispersed phase may be too high, which is not conducive to the subsequent formation of uniform liquid beads.

[0041] Furthermore, in some embodiments of the present application, the dispersed phase is prepared at a stirring temperature of 25°C to 50°C, a stirring rate of 300 rpm to 1000 rpm, and a stirring time of 2 hours to 30 hours. This facilitates obtaining a uniformly dissolved and well-dispersed dispersed phase. It should also be noted that, in the subsequent content of this document, the dispersed phase may also be referred to as the first liquid.

[0042] S2. Mixing sodium chloride with water to prepare a sodium chloride aqueous solution with a mass concentration of 20% to 34% to obtain a continuous phase. In the following content of this article, the continuous phase may also be referred to as the second liquid.

[0043] S3. Mixing sodium chloride with water to prepare a sodium chloride aqueous solution with a mass percent concentration of 5% to 18% to obtain a receiving phase. In the following content of this article, the receiving phase may also be referred to as the third liquid.

[0044] S4. Dispersing the dispersed phase in the continuous phase to form liquid droplets, then transporting the liquid droplets to the receiving phase, desolvating the liquid droplets through solvent diffusion, thereby solidifying, and obtaining polymer-encapsulated microspheres.

[0045] In this step, the inventors discovered that because the organic solvent is tetrahydrofuran, when the dispersed phase is dispersed in the form of liquid droplets in a highly concentrated sodium chloride aqueous solution (i.e., the continuous phase), the liquid droplets are highly stable and are not easily merged, nor is the organic solvent easily diffused. Furthermore, when the liquid droplets are transferred to a less concentrated sodium chloride aqueous solution (i.e., the receiving phase), the organic solvent in the liquid droplets diffuses at an appropriate rate, which not only allows the liquid droplets to solidify but also prevents excessively rapid solidification from causing structural inhomogeneity in the polymer particles within the polymer microspheres.

[0046] In this step, the microfluidics method or the membrane emulsification method can be used for preparation. Specifically, when the microfluidics method is used, a pump will be used to deliver the first liquid and the second liquid to the divider; the first liquid can be delivered by a syringe pump or a constant flow pump, and the second liquid can be delivered by a syringe pump, a constant flow pump or a peristaltic pump; the divider can be a three-way divider or a concentric capillary divider. The flow rate of the first liquid is 0.05~2 mL·min-1. The flow rate of the second liquid is 1.0~20.0 mL·min-1; and the ratio of the flow rate of the second liquid to the flow rate of the first liquid is greater than 7:1. The microfluidics method can accurately control the flow ratio of the dispersed phase and the continuous phase, and can form micro-liquid beads of uniform size and stability, thereby ensuring the consistency of the finally prepared microspheres. The structural schematic diagram of the concentric capillary divider device used in the preparation process is shown in the figure. Figure 1 shown.

[0047] When using membrane emulsification, a pump is used to deliver the first liquid, while the third liquid acts as both the continuous phase and the receiving phase. The first liquid can be delivered using a syringe pump, gear pump, constant flow pump, or diaphragm pump, with a flow rate of 1.0-100.0 mL·min-1. The schematic diagram of the membrane emulsifier used in the preparation process is shown below. Figure 2 shown.

[0048] In addition, in the preparation method of the present application, the polymer-encapsulated microspheres in S3 are usually post-treated, as follows; S4. Dry the polymer-encapsulated microspheres at a temperature of 20°C to 30°C for a drying time of ≥12 h.

[0049] This step removes any sodium chloride solution and moisture from the surface, ensuring the stability and effectiveness of the microspheres during subsequent use and improving extraction efficiency. Maintaining an appropriate drying temperature ensures complete removal of moisture from the microsphere surface while also preventing loss of extractant or deformation of the polymer particles due to excessively high drying temperatures or prolonged drying times, which could compromise the performance of the polymer-encapsulated microspheres.

[0050] Thirdly, the present application also provides the use of polymer-encapsulated microspheres in the separation and extraction of thallium resources.

[0051] Polymer-encapsulated microspheres can be used to directly extract thallium-containing liquids using a batch process or packed into extraction columns for continuous extraction. In batch extraction, the polymer-encapsulated microspheres are placed in the thallium-containing liquid and stirred for extraction. The polymer-encapsulated microspheres are then separated and placed in a stripping agent and stirred to produce a stripping solution. The stripping solution is then concentrated to produce the thallium product. In continuous extraction, the polymer-encapsulated microspheres are placed in a packed column to form an extraction column. The thallium-containing liquid is continuously passed through the extraction column. A stripping agent is then continuously passed through the column to produce a stripping solution. The stripping solution is then concentrated and / or converted to produce the thallium product.

[0052] The polymer-encapsulated microspheres of the present application are particularly suitable for separation and extraction of low-concentration thallium solutions. Specifically, the mass concentration of thallium in the thallium-containing solution can be as low as 5 ppb to 10%.

[0053] In addition, during separation and extraction, the stripping agent includes a reducing agent with a concentration of 0.001~1M (M is mol / L) and an acid solution of 0.001-5 M. The reducing agent may include at least one of ascorbic acid, hydrazine hydrate, hydroxylamine hydrochloride, thiourea, sodium sulfite, and sodium thiosulfate, and the acid solution may include at least one of hydrochloric acid, sulfuric acid, and nitric acid.

[0054] In addition, the back-extraction liquid can be heated and evaporated to obtain a concentrated liquid for concentration; and the conversion can be carried out by ion exchange reaction to obtain an inorganic salt of a specific thallium.

[0055] The solution of this application is described below with reference to the following specific embodiments.

[0056] The specific information of the raw materials used in the examples of this application is shown in Table 1: Table 1 Specific embodiments Example 1 This embodiment provides polymer-encapsulated microspheres, comprising a base polymer and an extractant; the base polymer is polyvinyl chloride (PVC), and the extractant is trioctylphosphine oxide (TOPO), with the weight proportions being 60% and 40%, respectively. The base polymer forms polymer particles, each having pores on the surface and within the polymer particles, and the extractant is disposed within the internal pores of the polymer particles. The method for preparing the polymer-encapsulated microspheres of this embodiment comprises the following steps: 0.60 g of polyvinyl chloride and 0.40 g of trioctylphosphine oxide were added to 30 mL of tetrahydrofuran and stirred at 400 rpm and 50°C for 4 h to obtain the dispersed phase (first liquid). The continuous phase (second liquid) consisted of a 20% by mass sodium chloride aqueous solution. The receiving phase (third liquid) consisted of a 10% by mass sodium chloride aqueous solution. The third liquid column consisted of a 60 mm inner diameter and 400 mm height glass column filled with 500 mL of the third liquid. The column was connected to a concentric capillary divider at its bottom. The first tube had an inner diameter of 500 μm and an outer diameter of 700 μm; the second tube had an inner diameter of 1200 μm and an outer diameter of 2000 μm. Syringe pumps were used to deliver the first and second liquids to the divider's first and second tubes, respectively, at flow rates of 0.2 mL / min and 1.6 mL / min, respectively. At the outlet of the first tube, the second liquid flow gathers the first liquid flow at the entrance of the micropore through the fluid dynamic focusing effect and divides it into discontinuous and equal-length sections. At the outlet of the micropore, due to the pore expansion and interfacial tension, the droplets become larger and form spherical micro-beads. At this time, the first liquid micro-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 micro-spheres. Finally, the polymer-encapsulated micro-spheres are filtered and separated, washed with water to remove NaCl attached to the surface, and air-dried at 25°C to obtain polymer-encapsulated micro-spheres. The field emission scanning electron microscope (FESEM) image is as follows Figure 3 Its Fourier infrared spectrum is shown as follows Figure 4 shown.

[0058] Low concentration Tl 3+ Enrichment: Weigh 0.18 g of the prepared polymer-encapsulated microspheres and place them in 50 mL of 1.0 mg / L 3+ and 50 mg / L Li + Add hydrochloric acid to the liquid to 0.1 M. Extraction was carried out at 25 ° C and 800 rpm for 90 minutes. Samples were taken to determine the Tl 3+ He Li + The extraction efficiency was calculated by back-extracting Tl with 0.1 M hydroxylamine hydrochloride. 3+ , get Li-free + Tl 3+ The solution is further processed (concentrated, converted) to obtain thallium products.

[0059] Example 2 This embodiment provides polymer-encapsulated microspheres, comprising a base polymer and an extractant; the base polymer is polyvinylidene fluoride (PVDF), the extractant is 4,4,4-trifluoro-1-benzene-1,3-butanedione (BTA), and the promoter is trioctyl phosphate (TOP), with the mass proportions being 50%, 40%, and 10%, respectively. The base polymer forms polymer particles, which have pores on the surface and inside, and the extractant is disposed in the internal pores of the polymer particles. The method for preparing polymer-encapsulated microspheres of this embodiment comprises the following steps: 0.50 g of PVDF, 0.40 g of 4,4-trifluoro-1-phenyl-1,3-butanedione, and 0.1 g of trioctyl phosphate were added to 30 ml of tetrahydrofuran and stirred at 400 rpm and 50°C for 12 h to obtain a dispersed phase (first liquid). The continuous phase (second liquid) consisted of a 25% by mass sodium chloride aqueous solution. The receiving phase (third liquid) consisted of a 15% by mass sodium chloride aqueous solution. The third liquid column consisted of a 60 mm inner diameter, 400 mm high glass column filled with 500 mL of the third liquid. A concentric capillary divider with the same dimensions as in Example 1 was connected to its bottom. Syringe pumps were used to deliver the first and second liquids to the first and second tubes of the divider, respectively, at flow rates of 0.2 mL / min and 1.8 mL / min. At the outlet of the first tube, the second liquid flow was hydrodynamically focused onto the micropores, dividing the first liquid flow into discrete segments. At this point, the first-liquid microbeads and the second liquid are both contained within the third liquid. The tetrahydrofuran in the microbeads rapidly diffuses into the third liquid, desolvating the microbeads and ultimately yielding solid polymer microspheres. Finally, the polymer-encapsulated microspheres are separated by filtration, washed with water, and air-dried at 25°C to obtain the polymer-encapsulated microspheres.

[0060] Polymer-encapsulated microspheres were used to separate thallium from a mixture of thallium, sodium, and potassium: 1 g of polymer-encapsulated microspheres was filled into a 9 mm diameter glass column and both ends were blocked with absorbent cotton. + , Na + , K + The concentrations were 1.0 mg·L -1 , 50.0 mg·L -1 , 40.0 mg·L -1 ) Use a peristaltic pump to pump the solution through the separation column. After the solution is pumped, back-extract the thallium with 2 M hydrochloric acid. Use a peristaltic pump to pump 10 mL of 2 M hydrochloric acid through the separation column to obtain a sodium- and potassium-free thallium solution.

[0061] Example 3 This embodiment provides polymer-encapsulated microspheres, comprising a base polymer and an extractant; the base polymer is polyvinylidene fluoride-hexafluoropropylene copolymer (PVDF-HFP), and the extractant is P204, with the weight proportions being 55% and 45%, respectively. The base polymer forms polymer particles, each having pores on the surface and within the polymer particles, and the extractant is disposed within the internal pores of the polymer particles. The method for preparing the polymer-encapsulated microspheres of this embodiment comprises the following steps: 5.5 g of PVDF-HFP and 4.5 g of P204 were added to 200 ml of tetrahydrofuran and stirred at a stirring rate of 600 rpm and a stirring temperature of 50 °C for 15 h to obtain a dispersed phase (first liquid). The third liquid was a sodium chloride aqueous solution with a mass percentage concentration of 15%. 6000 mL of the third liquid was placed in a glass column with an inner diameter of 200 mm and a height of 400 mm (such as Figure 2 (as shown). A gear pump is used to transport the first liquid to a membrane emulsifier. The membrane emulsifier disperses the first liquid into microdroplets, which are then dispersed in a third liquid. The tetrahydrofuran in the microdroplets rapidly diffuses into the third liquid, desolvating the microdroplets and ultimately producing solid polymer microspheres. The microspheres are separated by filtration, washed with water, and air-dried at 25°C to obtain polymer-encapsulated microspheres.

[0062] Polymer-encapsulated microspheres are used to separate thallium (III) from a mixture of thallium (III), sodium, potassium, and boron: 1 g of polymer-encapsulated microspheres is filled in a 9 mm diameter glass column and both ends are blocked with absorbent cotton. 3+ 、Na + , K + 、B 3+ (Concentrations were 1.0 mg·L -1 , 50.0 mg·L -1 , 40.0 mg·L -1 , 10 mg·L -1 ) The mixed solution was transported through the separation column by a peristaltic pump, and after the transport was completed, Tl was back-extracted with 2 M hydrochloric acid. 3+ A peristaltic pump was used to deliver 10 mL of 2 M hydrochloric acid through the separation column to obtain a thallium solution free of sodium, potassium, and boron.

[0063] Example 4 This embodiment provides polymer-encapsulated microspheres, comprising a base polymer, an extractant, and a reinforcing agent; the base polymer is polyvinylidene fluoride (PVDF), the extractant is trioctylamine (TOA), and the reinforcing agent is tributyl phosphate (TBP), with the mass proportions being 55%, 40%, and 5%, respectively. The base polymer forms polymer particles, which have pores on the surface and inside, and the extractant is disposed in the internal pores of the polymer particles. The method for preparing the polymer-encapsulated microspheres of this embodiment comprises the following steps: 11 g of polyvinyl chloride, 8.0 g of TOA extractant, and 1.0 g of TBP were added to 600 ml of tetrahydrofuran and stirred at 400 rpm and 50°C for 12 hours to obtain a dispersed phase (the first liquid). The third liquid was a 10% by mass sodium chloride aqueous solution.

[0064] Place 5000 mL of the third liquid in a glass column with an inner diameter of 200 mm and a height of 400 mm (e.g. Figure 2 (as shown). A constant-flow pump is used to deliver the first liquid to a membrane emulsifier. The membrane emulsifier disperses the first liquid into microbeads, which are then dispersed in a third liquid. The tetrahydrofuran in the microbeads rapidly diffuses into the third liquid, desolvating the microbeads and ultimately producing solid polymer microspheres. The microspheres are separated by filtration, washed with water, and air-dried at 25°C to obtain polymer-encapsulated microspheres.

[0065] Low concentration of Tl in high Tl / Li ratio brine 3+ Enrichment: Weigh 1.0 g of the prepared polymer-encapsulated microspheres and add them to 200 mL of 0.5 mg·L -1 Tl 3+ and 350 mg·L -1 Li + The extraction was carried out at 25 °C and 800 rpm for 50 min. 3+ The extraction rate is 88%, achieving T1 3+ With Li + separation.

[0066] Example 5 This embodiment provides polymer-encapsulated microspheres, comprising a base polymer, an extractant, and a reinforcing agent; the base polymer is PVC, the extractant is Aliquat 336, and the reinforcing agent is epoxidized soybean oil, with the weight proportions being 50%, 45%, and 5%, respectively. The base polymer forms polymer particles, each having pores on the surface and within the polymer particles, and the extractant is disposed within the internal pores of the polymer particles. The method for preparing the polymer-encapsulated microspheres of this embodiment comprises the following steps: 1 g of PVC, 0.9 g of Aliquat 336, and 0.1 g of epoxidized soybean oil were added to 50 ml of tetrahydrofuran and stirred at 400 rpm and 50°C for 4 hours to obtain a dispersed phase (first liquid). The second liquid was a 20% sodium chloride aqueous solution, and the third liquid was a 10% sodium chloride aqueous solution.

[0067] Place 500 mL of the third liquid in a glass column with an inner diameter of 60 mm and a height of 400 mm (e.g. Figure 1 As shown in Figure 2 , the first and second liquids were delivered to the first and second tubes of the separator using syringe pumps, respectively, at flow rates of 0.2 mL / min and 2.0 mL / min. At the outlet of the first tube, the second liquid stream converged the first liquid stream at the micropore inlet through hydrodynamic focusing, dividing it into discrete, equal-length segments. At the micropore outlet, pore expansion and interfacial tension caused the droplets to expand and form spherical microbeads. Both the first liquid microbeads and the second liquid were now immersed in a third liquid. Due to the high solubility and diffusion coefficient of tetrahydrofuran in the third liquid, the tetrahydrofuran in the microbeads rapidly diffused into the third liquid, desolvating the microbeads and ultimately yielding solid polymer microspheres. Finally, the polymer-encapsulated microspheres were separated by filtration, washed with water to remove surface NaCl, and air-dried at 25°C to obtain the polymer-encapsulated microspheres.

[0068] Low concentration of Tl in complex raw material solution 3+ Separation and enrichment: Weigh 0.50 g of the prepared polymer-encapsulated microspheres and place them in a plastic tube with an inner diameter of 3 mm. Both ends are plugged with absorbent cotton to prepare a separation column. 3+ (1 mgL -1 ) and Na + (1000 mg L -1 ), K + (500 mg L -1 ),Mg 2+ (200 mg L -1 ), Ca 2+ (200 mg L -1 ), Fe 3+ (100 mgL -1 ), Ni 2+ (100 mg L -1 ), Cu 2+ (100 mg L -1 ), 50 mL of HCl (2 M) stock solution was transported through the separation column at a flow rate of 0.5 mL min -1The concentrations of various elements in the effluent were determined, and the extraction efficiency of Tl and the separation factor of Tl / M were calculated. The obtained Tl extraction efficiency was 82%, and the separation factors were greater than 20.

[0069] Example 6 This embodiment provides a polymer-encapsulated microsphere, comprising a base polymer, an extractant, and a reinforcing agent; the base polymer is PVC, the extractant is TBHDPB, and the reinforcing agent is TBP, with the mass proportions being 50%, 45%, and 5%, respectively. The base polymer forms polymer particles, the surface and interior of the polymer particles have pores, and the extractant is provided in the internal pores of the polymer particles. The preparation method of the polymer-encapsulated microspheres of this embodiment is basically the same as that of Example 5, except for adaptively adjusting the type and content of the solute; the application steps are the same as those of Example 5. The obtained Tl extraction rate is 79%, and the separation factors are all greater than 20.

[0070] Example 7 This embodiment provides a polymer-encapsulated microsphere, comprising a base polymer and an extractant; the base polymer is PVDF-HFP and the extractant is BMIMPF6, accounting for 55% and 45% by mass, respectively. The base polymer forms polymer particles, the surface and interior of the polymer particles have pores, and the extractant is disposed in the internal pores of the polymer particles. The preparation method of the polymer-encapsulated microspheres of this embodiment is substantially the same as that of Example 5, except for adaptively adjusting the type and content of the solute; the application steps are the same as those of Example 5. The obtained Tl extraction rate is 85%, and the separation factors are all greater than 26.

[0071] Comparative Example 1 The difference between the polymer-encapsulated microspheres in this comparative example and Example 1 is that in the polymer-encapsulated microspheres, the base polymer is polyvinyl chloride (PVC) and the extractant is trioctylphosphine oxide (TOPO), and the mass proportions of the base polymer and the extractant are 25% and 75%, respectively.

[0072] Comparative Example 2 The difference between the polymer-encapsulated microspheres in this comparative example and Example 1 is that in the polymer-encapsulated microspheres, the base polymer is polyvinyl chloride (PVC) and the extractant is TOPO, with the mass proportions being 85% and 15%, respectively.

[0073] Comparative Example 3 The polymer-encapsulated microspheres in this comparative example differ from those in Example 1 in that, in the polymer-encapsulated microspheres, the base polymer is polyvinyl chloride (PVC) and the total concentration of the extractant (TOPO) in tetrahydrofuran is 6%.

[0074] In addition, the inventors have also tried to use other organic solvents including methyltetrahydrofuran, acrylonitrile, acetone, N,N-dimethylformamide, toluene and the like instead of tetrahydrofuran, or to use other alkali metal salts or halogen salts instead of sodium chloride, but the polymer cannot be dissolved well or liquid droplets are formed during the preparation process, or the liquid droplets cannot be diffused well and thus solidified, so polymer-enclosed microspheres cannot be prepared. For example, using methyltetrahydrofuran as a solvent, although the polymer and the extractant can be dissolved and dispersed in the continuous phase to form micro-liquid droplets, the solubility of the solvent in the aqueous phase is too low, and the solvent cannot effectively diffuse into the receiving phase, so it is not possible to effectively desolvate and solidify to obtain solid phase particles. For another example, using N,N-dimethylformamide as a solvent, although the polymer and the extractant can be dissolved well, the solvent is too miscible with the second liquid and the third liquid used, and an interface cannot be formed, so micro-liquid droplets and microspheres cannot be formed. For another example, using sodium nitrate instead of sodium chloride, because tetrahydrofuran and any concentration of sodium nitrate aqueous solution cannot form a suitable interface and interfacial tension, micro-liquid droplets and microspheres cannot be formed.

[0075] Experimental testing Test items and methods Average particle size and particle size dispersion index: Laser particle size analyzer is used to detect particle size and particle size dispersion index; The average particle size, particle size dispersion index and single T1 of the polymer-encapsulated microspheres prepared in Examples 1-7 and Comparative Examples 1-2 were measured. 3+ / Tl + The extraction rate was tested and the test results are shown in Table 2.

[0076] Table 2

[0077] From the test results in Table 2, it can be seen that the polymer-encapsulated microspheres prepared by the preparation method of the present application have high sphericity, the diameter can be adjusted within the range of 50-220 μm, and the particle size dispersion index is between 6% and 36%. + The extraction separation was performed with an extraction rate of more than 90%. The polymer-encapsulated microspheres prepared in the other embodiments can selectively extract T1 3+ , capable of achieving efficient separation of thallium. In all embodiments, the polymer-encapsulated microspheres achieved a high separation factor (>20) of Tl against other elements.

[0078] The mass content of the base polymer in Comparative Example 1 is 25%, and the mass content of the extractant is only 48%. This is mainly because the extractant content in the microspheres is too high, resulting in their high viscosity and agglomeration, which reduces their surface area and thus significantly reduces the extraction rate.

[0079] In Comparative Example 2, the mass content of the base polymer is greater than 80%, the content of the extractant is too low, and the extraction rate of thallium by the obtained polymer-encapsulated microspheres is also very low.

[0080] In Comparative Example 3, the concentration of polymer and extractant in the dispersed phase was 6%, and polymer-encapsulated microspheres with a particle size of 220 μm were obtained. However, the extraction rate of thallium was relatively low.

[0081] Other examples show no significant differences in the performance of the three base polymers used. This, of course, is also due to the extraction solvent used. PVDF has poorer solubility in THF than PVC, requiring longer dissolution times. PVDF-HFP also has even worse solubility than PVDF, requiring prolonged heating and stirring.

[0082] The above are only preferred embodiments of the present application and are not intended to limit the present application. Any modifications, equivalent replacements, and improvements made within the principles of the present application should be included in the scope of protection of the present application.

Claims

1. A polymer-encapsulated microsphere for separating thallium, characterized in that: The polymer-enclosed microspheres include a base polymer and an extractant, wherein the base polymer forms polymer particles having a microporous structure on the surface and inside, and the extractant is disposed in the internal pores of the polymer particles; the base polymer includes at least one of polyvinyl chloride, polyvinylidene fluoride, polyvinylidene fluoride-hexafluoropropylene copolymer, polystyrene, and styrene-butadiene-styrene ternary block copolymer; The extractant includes at least one of a β-diketone extractant, an organic amine extractant, an organic phosphoric acid extractant, an organic phosphine oxide extractant, and an ionic liquid extractant; Based on the mass of the polymer-enclosed microspheres, the mass content of the base polymer is 29%-80%, and the mass content of the extractant is 10%-70%.

2. The polymer-encapsulated microspheres for separating thallium according to claim 1, characterized in that: It also includes a reinforcing agent; the polymer particles contain the reinforcing agent; The enhancer includes at least one of triphosphate, epoxy soybean oil, isooctyl alcohol, dioctyl phthalate, 2-ethylhexyl diphenyl phosphate, acetyl tri-n-butyl citrate, acetyl tri(2-ethylhexyl) citrate, di(2-ethylhexyl) sebacate, epoxy octyl stearate, and chlorinated paraffin.

3. The polymer-encapsulated microspheres for separating thallium according to claim 2, characterized in that: Based on the mass of the polymer-enclosed microspheres, the mass content of the reinforcing agent is 0.1%-20%.

4. The polymer-encapsulated microspheres for separating thallium according to claim 1, characterized in that: The average particle size of the polymer particles is 1 μm to 300 μm.

5. A method for preparing polymer-encapsulated microspheres for separating thallium according to any one of claims 1 to 4, characterized in that: The following steps are involved: Dispersing the dispersed phase in the continuous phase to form liquid droplets, and then transferring the liquid droplets to a receiving phase for desolventizing and solidification; the continuous phase is a 20 wt% to 34 wt% sodium chloride aqueous solution, and the receiving phase is a 5 wt% to 18 wt% sodium chloride aqueous solution; The dispersed phase includes a solute and an organic solvent, the solute includes a base polymer and an extractant, the base polymer includes at least one of polyvinyl chloride, polyvinylidene fluoride, polyvinylidene fluoride-hexafluoropropylene copolymer, polystyrene, and styrene-butadiene-styrene ternary block copolymer; the extractant includes at least one of a β-diketone extractant, an organic amine extractant, an organic phosphoric acid extractant, an organic phosphine oxide extractant, and an ionic liquid extractant; the organic solvent is tetrahydrofuran; based on the total mass of the solute, the mass content of the base polymer is 29% to 80%, and the mass content of the extractant is 10% to 70%.

6. The method for preparing polymer-encapsulated microspheres for separating thallium according to claim 5, wherein: The mass content of the base polymer is 0.1%-10% based on the mass of the dispersed phase.

7. The method for preparing polymer-encapsulated microspheres for separating thallium according to claim 5, characterized in that: The solute further includes an enhancer; optionally, based on the total mass of the solute, the mass content of the enhancer is 0.1% to 20%.

8. Use of the polymer-encapsulated microspheres for separating thallium according to any one of claims 1 to 4 in separating and extracting thallium.

9. Use of the polymer-encapsulated microspheres for separating thallium according to claim 8 in separating and extracting thallium resources, characterized in that: The method comprises the following steps: placing the polymer-enclosed microspheres into a thallium-containing liquid for extraction, separating the polymer-enclosed microspheres, placing the polymer-enclosed microspheres into a stripping agent and stirring to obtain a stripping solution, and concentrating the stripping solution to obtain a thallium product.

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

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