Amidoxime-based macroporous resin as well as preparation method and application thereof

Abstract

The invention discloses amidoxime-based macroporous resin as well as a preparation method and application thereof, and belongs to the technical field of functional polymer material preparation. The preparation method comprises the following steps: introducing an organic phase containing an organic monomer mixture, an initiator, a photocuring agent and a pore-foaming agent and a water phase containing a stabilizer into a micro-fluidic chip to generate monodisperse liquid drops, and then initiating polymerization curing by illumination to obtain precursor resin microspheres with uniform size and adjustable pore structure, and finally, introducing a functional group through amidoximation reaction. According to the method, accurate control of liquid drops is realized by utilizing a microfluidic technology, rapid curing is realized by combining photopolymerization, and the size, morphology, aperture and functional group distribution of the resin can be synergistically regulated from the source. The prepared resin has high monodispersity, a through macroporous structure and uniformly distributed amidoxime groups, and shows high adsorption capacity, rapid adsorption kinetics and good cycle stability to uranyl ions.

Description

Technical Field

[0001] This invention belongs to the field of functional polymer material preparation technology, and relates to a macroporous adsorption resin with uniform size and a methylamine oxime functional group, specifically to a methylamine oxime-based macroporous resin and its preparation method and application. Background Technology

[0002] Due to their unique strong coordination ability with metal ions such as uranium, vanadium, and gallium, amine oxime resins have significant application value in fields such as hydrometallurgy, nuclear fuel cycle, and wastewater treatment. Their performance largely depends on the resin's physical structure (such as particle morphology, size distribution, pore size, and specific surface area) and chemical structure (type, density, and uniformity of functional groups).

[0003] Currently, the conventional methods for preparing amylopectin-based resins mainly consist of two steps: first, obtaining a precursor resin (usually a polyacrylonitrile resin) through suspension polymerization or dispersion polymerization, followed by the introduction of amylopectin groups through chemical modification. However, these traditional polymerization methods rely on mechanical stirring to disperse monomer droplets, and the droplet size is controlled by the stirring shear force, resulting in a wide size distribution and irregular morphology of the final resin particles. This can easily cause problems such as uneven fluid distribution, increased pressure drop, and decreased mass transfer efficiency in practical applications (such as packed columns). In addition, traditional methods have limited ability to finely control the porous structure inside the resin, making it difficult to achieve uniform pore size design and uniform loading of functional groups while maintaining a high specific surface area.

[0004] CN118930688A discloses a method for preparing amine oxime materials using microfluidic control, in which a polyacrylonitrile solution is added dropwise to a coagulation bath via a microfluidic pump to achieve physical molding. While this method can obtain particles with relatively uniform size, it is essentially a reprocessing and molding of existing polymers, rather than starting with polymerization reactions and structural construction from monomers. Therefore, this method has inherent limitations in simultaneously and precisely controlling the crosslinking network structure, pore size distribution, and chemical environment of functional groups in the resin.

[0005] Therefore, developing a new method that integrates precise fluid manipulation with controllable polymerization chemical reactions to prepare functional resins with designable structures and excellent performance is of significant research value and application demand. Summary of the Invention

[0006] The technical problem to be solved by this invention is how to achieve precise and controllable construction of resin microspheres in terms of size and morphology starting from the monomer source, so as to solve the problems of unevenness of traditional suspension polymerization products and the fact that existing microfluidic technology can only physically shape existing polymers and cannot simultaneously control the chemical structure.

[0007] To achieve the above-mentioned objectives, the technical solution adopted in this application is as follows.

[0008] In a first aspect, the present invention provides a method for preparing a methine oxime-based macroporous resin, comprising the following steps: S1. Preparation of the organic phase: Acrylonitrile, divinylbenzene, and styrene are mixed as an organic monomer mixture; An initiator, a photocuring agent, and a porogen are added to a mixture of organic monomers and mixed thoroughly to obtain an organic phase. S2. Preparation of the aqueous phase: Prepare an aqueous solution of polyvinyl alcohol as the aqueous phase; S3. Preparation of monodisperse droplets: The organic phase obtained in step S1 and the aqueous phase obtained in step S2 are passed into a microfluidic chip to generate monodisperse droplets; S4. Photopolymerization and curing: Under light irradiation, the monomers in the monodisperse droplets obtained in step S3 are polymerized. After curing, the monomers are washed once, Soxhlet extracted, washed twice, and dried to obtain macroporous resin precursor microspheres. S5. Amine oxime reaction: The macroporous resin precursor microspheres obtained in step S4 are reacted with hydroxylamine reagent until the reaction is complete. After washing and drying, amine oxime-based macroporous resin is obtained.

[0009] In step S1 above, the mass ratio of acrylonitrile, divinylbenzene and styrene in the organic monomer mixture is 5~7:2~3:1~2.

[0010] In step S1 above, the amount of initiator added is 0.5 to 2% of the total mass of the organic monomer mixture.

[0011] In step S1 above, the initiator is azobisisobutyronitrile.

[0012] In step S1 above, the amount of the photocuring agent added is 0.1 to 1% of the total mass of the organic monomer mixture.

[0013] In step S1 above, the photocuring agent is any one of benzoin dimethyl ether, acetophenone derivatives, acylphosphine oxides, thioxanthones, and 4-isobutylphenyl-4'-methylphenyliodonium hexafluorophosphate.

[0014] In step S1 above, the mass ratio of the organic monomer mixture to the porogen is 2~5:1.

[0015] In step S1 above, the pore-forming agent is at least one of kerosene, liquid paraffin, xylene, cyclohexanone, polyvinylpyrrolidone, and gasoline.

[0016] In step S2 above, the mass concentration of the polyvinyl alcohol aqueous solution is 2-10%.

[0017] In step S3 above, the droplet generation unit of the microfluidic chip is a flow focusing structure or a T-shaped structure; the diameter of the monodisperse droplet is 50~500μm.

[0018] In step S3 above, the inlet rate of the organic phase is 5~100 μL / min, the inlet rate of the aqueous phase is 10~200 μL / min, and the inlet rate of the aqueous phase is always greater than that of the organic phase.

[0019] In step S4 above, the illumination condition is ultraviolet light with a wavelength of 365nm.

[0020] In step S5 above, the mass-to-volume ratio of the macroporous resin precursor microspheres to the hydroxylamine reagent is 1g:10~50mL.

[0021] In step S5 above, the hydroxylamine reagent is an alkaline solution of hydroxylamine hydrochloride prepared from hydroxylamine hydrochloride and sodium hydroxide; wherein the concentration of hydroxylamine hydrochloride is 1~5 mol / L, and the molar ratio of sodium hydroxide to hydroxylamine hydrochloride is 1~1.5:1.

[0022] In step S5 above, the reaction temperature of the amylated oxime reaction is 60~90℃, and the reaction time is 4~12 hours.

[0023] Secondly, the present invention provides a methaminoxime macroporous resin prepared by the above preparation method.

[0024] Thirdly, the present invention provides the application of the above-mentioned amineoxime macroporous resin in the adsorption of uranium, gallium, and vanadium metal ions in aqueous solution.

[0025] The beneficial effects of this invention are as follows: This invention achieves precise generation and solidification of precursor droplets through microfluidic chip technology, resulting in resin particles with high size uniformity and a particle size distribution significantly superior to traditional suspension polymerization products. This method allows for precise control of the resin's crosslinking degree, pore size distribution, and specific surface area by adjusting microfluidic parameters and the composition of the reaction system. Due to the regular morphology and good internal pore connectivity of the precursor microspheres, the reactants can diffuse fully and uniformly into the particle interior during subsequent amine oxime modification, thereby significantly improving the grafting efficiency and distribution uniformity of functional groups. These structural advantages collectively contribute to the resin exhibiting high adsorption capacity, rapid adsorption kinetics, and good cycling stability for target metal ions such as uranyl ions. Furthermore, this process can achieve high-throughput preparation based on a parallel chip structure, possessing significant potential for industrial scalability. Attached Figure Description

[0026] Figure 1 The monodisperse droplets prepared in Example 1; Figure 2 The photocurable resin prepared in Example 1; Figure 3 This is a scanning electron microscope image of the amylopyridine macroporous resin prepared in Example 1. Detailed Implementation

[0027] To make the technical problems, solutions, and beneficial effects of this application clearer, the following detailed description is provided in conjunction with the embodiments. Unless otherwise defined, all technical terms used herein have the same meaning as understood by one of ordinary skill in the art.

[0028] This invention provides a microfluidic method for preparing uniformly sized amineoxime-based macroporous resins, which mainly includes the following steps. The core of the method lies in combining the precise physical manipulation of fluids (droplets) using microfluidic technology with photo-initiated in-situ chemical polymerization of monomers, thereby achieving synergistic control over the size, morphology, and internal structure of resin microspheres from the monomer source. Following efficient amineoxime modification, a high-performance adsorbent material is ultimately obtained.

[0029] Step 1, Preparation of the organic phase: Acrylonitrile, divinylbenzene, and styrene are mixed in a mass ratio ranging from 5:3:2 to 7:2:1 to form an organic monomer mixture. Acrylonitrile is the monomer that provides the cyano (-CN) group necessary for the subsequent amylopyrification reaction; divinylbenzene acts as a crosslinking agent to construct the three-dimensional network framework of the resin, providing mechanical strength and stability; styrene acts as a comonomer, helping to adjust the hydrophilicity / hydrophobicity of the resin and the flexibility of the polymer chains. Then, a porogen is added to the above organic monomer mixture, with the mass ratio of the organic monomer mixture to the porogen controlled at 2:1 to 5:1. The porogen can be one or more combinations of kerosene, liquid paraffin, xylene, cyclohexanone, polyvinylpyrrolidone, gasoline, etc. Its function is to induce phase separation during polymerization, thereby forming and maintaining a continuous macroporous structure in the polymer network. Subsequently, 0.5-2% by mass of an oil-soluble free radical initiator and 0.1-1% by mass of a photocuring agent are added to the organic monomer mixture. The initiator is azobisisobutyronitrile (AIBN); the photocuring agent is any one of benzoin dimethyl ether, acetophenone derivatives (α-hydroxy ketones, such as 1173), acylphosphine oxides (TPO, 819), thioxanthones (ITX), and 4-isobutylphenyl-4'-methylphenyliodonium hexafluorophosphate. AIBN can act as a thermally assisted initiation site in subsequent photopolymerization, while benzoin dimethyl ether is the main photosensitizer that absorbs ultraviolet light to generate free radicals, initiating rapid polymerization. All components are stirred and dissolved uniformly to obtain a homogeneous and transparent organic phase solution.

[0030] Step 2, Preparation of the aqueous phase: Prepare an aqueous dispersion containing a stabilizer, such as a 2-10% (w / w) polyvinyl alcohol (PVA) aqueous solution. This aqueous phase serves as a continuous phase that is immiscible with the organic phase during the microfluidic process. The stabilizer it contains helps form a stable oil / water interface within the chip and prevents the generated droplets from coalescing during subsequent collection.

[0031] Step 3: Microfluidic generation of monodisperse droplets: The prepared organic phase solution and aqueous phase solution are introduced into the microfluidic chip at flow rates of 5~100 μL / min and 10~200 μL / min respectively (with the aqueous phase flow rate always greater than the organic phase flow rate) to generate monodisperse droplets. The droplet generation unit of the chip is preferably a flow focusing structure or a T-shaped structure. The principle is to utilize the balance of shear force and interfacial tension between the two-phase fluids within a microscale channel to continuously and precisely cut the organic phase into uniformly sized droplets, which are then dispersed in the aqueous phase. By adjusting the flow rate ratio of the two phases and the size of the chip channel, the diameter of the generated droplets can be controlled within the range of 50 μm to 500 μm.

[0032] Step 4: UV-Initiated Polymerization and Curing: Monodisperse droplets are collected in a transparent container and irradiated under 365nm UV light. Under UV excitation, the photocuring agent (benzoin dimethyl ether) and initiator (AIBN) in the organic phase generate a large number of free radicals, rapidly initiating copolymerization and cross-linking reactions of monomers such as acrylonitrile, divinylbenzene, and styrene within the droplets. This photopolymerization process is rapid and uniform, enabling the entire droplet to solidify into solid microspheres from the outside in within a short time, forming uniformly sized poly(acrylonitrile-styrene-divinylbenzene) macroporous resin precursor microspheres. After curing, the microspheres are washed and subjected to Soxhlet extraction to remove the aqueous phase and surface impurities, followed by drying to obtain dried precursor resin microspheres.

[0033] Step 5, Amine Oxime Functional Modification: The dried precursor resin microspheres are reacted with an alkaline solution of hydroxylamine hydrochloride to introduce amine oxime functional groups. Specifically, an alkaline solution of hydroxylamine hydrochloride with a concentration of 1-5 mol / L (the molar ratio of sodium hydroxide to hydroxylamine hydrochloride is controlled at 1:1 to 1.5:1) is mixed with the precursor resin microspheres at a mass-to-volume ratio of 1:10 g / mL to 1:50 g / mL. The reaction system temperature is maintained at 60-90℃ for 4-12 hours. Under these conditions, the cyano groups on the polymer chains of the precursor microspheres undergo a nucleophilic addition reaction with hydroxylamine, transforming into amine oxime groups with strong chelating ability for metal ions. Due to the uniform size and interconnected macropores of the precursor microspheres, the reaction reagents can diffuse evenly and fully into the interior of each microsphere, thereby achieving a high degree of uniformity in the distribution of functional groups throughout the resin particles, greatly improving the grafting efficiency and utilization rate of functional groups. After the reaction was completed, the product was thoroughly washed to remove residual reagents and dried to finally obtain uniformly sized amylopyram macroporous resin.

[0034] The amylopectin-based macroporous resin prepared by the above steps consists of spherical microspheres with a particle size variation coefficient (CV) of less than 5%, significantly lower than that of traditional methods (typically >15%). This resin possesses a regular morphology, controllable macroporous structure, and uniformly distributed high-density amylopectin groups, making it ideal for adsorbing uranyl ions (UO2) in aqueous solutions. 2+ Gallium ion (Ga(OH)4) - ) or vanadate ions (VO4) 3- When it is used, it exhibits high adsorption capacity, rapid adsorption kinetics and good recycling performance.

[0035] The following specific embodiments will be provided to explain the solution of the present invention. Those skilled in the art will understand that the following embodiments are for illustrative purposes only and should not be considered as limiting the scope of the invention. Where specific techniques or conditions are not specified in the embodiments, they are performed according to the techniques or conditions described in the literature in the field or according to the product instructions. Reagents or instruments whose manufacturers are not specified are all conventional products that can be obtained commercially.

[0036] Example 1: Microfluidic preparation of a methylamine oxime macroporous resin, the specific steps are as follows.

[0037] (1) Mix 5g of acrylonitrile, 3g of divinylbenzene and 2g of styrene. Add 5.0g of xylene, 0.1g of AIBN and 0.03g of benzoin dimethyl ether to the mixture. Stir thoroughly until all components are completely dissolved to obtain a homogeneous and transparent organic phase solution.

[0038] (2) Prepare a 2% (w / w) aqueous solution of polyvinyl alcohol (PVA-1788) to obtain the aqueous phase.

[0039] (3) A polydimethylsiloxane (PDMS) microfluidic chip with a flow focusing structure was used. The prepared organic phase and aqueous phase were injected into the chip at flow rates of 50 μL / min and 150 μL / min, respectively, using a syringe pump to generate monodisperse droplets with a diameter of approximately 200 μm (e.g., Figure 1 As shown), the samples were collected in a quartz glass bottle. The quartz glass bottle was placed under a 365nm ultraviolet light source and cured for 10 minutes (as shown). Figure 2 (As shown). After curing, the obtained solid microspheres were repeatedly washed with deionized water, and then continuously extracted with ethanol in a Soxhlet extractor for 24 hours. Finally, the microspheres were vacuum dried at 60°C to obtain macroporous resin precursor microspheres.

[0040] (4) Weigh 1.0 g of macroporous resin precursor microspheres and place them in a reaction vessel. Add 20 mL of hydroxylamine hydrochloride base solution (containing 3 mol / L hydroxylamine hydrochloride and 3.3 mol / L sodium hydroxide). Place the reaction system in an 80°C constant temperature water bath for 8 hours. After the reaction is complete, filter the product and wash it sequentially with deionized water, 0.1 mol / L dilute hydrochloric acid, and deionized water until neutral. Finally, vacuum dry the product at 60°C to obtain the final amylopectin macroporous resin product.

[0041] The properties of the obtained amylopyridine macroporous resin product were characterized, and its SEM images are shown below. Figure 3 As shown in the figure, the resin microspheres have good sphericity and a porous surface structure. The statistically measured number-average particle size is 198 μm, the standard deviation of particle size distribution is 6 μm, and the calculated CV value is 3.0%. BET testing shows that the specific surface area of ​​the resin is 350 m² / g. 2 The resin has an average pore size of 120 nm. Elemental analysis results show that the nitrogen content of the resin is 12.5%, based on which the content of amine oxime groups on the resin is calculated to be approximately 3.8 mmol / g.

[0042] The resulting amylopyridine macroporous resin was subjected to pH=5.0 and UO2. 2+ Adsorption experiments were conducted in a solution with an initial concentration of 100 mg / L. The test results showed that the resin had a saturated adsorption capacity of 180 mg / g for uranyl ions, and reached 90% of the saturated adsorption capacity within 30 minutes.

[0043] Example 2: Microfluidic preparation of a methylamine oxime macroporous resin, the specific steps are as follows.

[0044] (1) Same as Example 1.

[0045] (2) Same as Example 1.

[0046] (3) The only difference from Example 1 is that the prepared organic phase and aqueous phase were injected into the chip at flow rates of 5 μL / min and 50 μL / min respectively using a syringe pump to generate monodisperse droplets with a diameter of approximately 80 μm. Other curing, washing, and drying conditions were the same as in Example 1 to obtain macroporous resin precursor microspheres.

[0047] (4) Same as Example 1.

[0048] The properties of the obtained amine oxime-based macroporous resin product were characterized. The resin had a diameter of approximately 80 μm, a particle size distribution standard deviation of 5 μm, and a calculated CV value of 2.8%. BET testing showed that the resin had a specific surface area of ​​300 m² / g. 2 The resin has an average pore size of 108 nm. Elemental analysis results show that the nitrogen content of the resin is 10%, based on which the content of amine oxime groups on the resin is calculated to be approximately 3.04 mmol / g.

[0049] The resulting amylopyridine macroporous resin was subjected to pH=5.0 and UO2. 2+ Adsorption experiments were conducted in a solution with an initial concentration of 100 mg / L. The test results showed that the resin had a saturated adsorption capacity of 144 mg / g for uranyl ions, and reached 90% of the saturated adsorption capacity within 45 minutes.

[0050] Comparative Example: Preparation of amylopectin resins by conventional suspension polymerization Using the same monomer formulation as in Example 1 (5g acrylonitrile, 3g divinylbenzene, 2g styrene, 5g xylene, 0.1g AIBN, 0.03g benzoin dimethyl ether), conventional suspension polymerization was carried out. The organic phase was added to an aqueous phase containing a dispersant, and droplets were formed by mechanical stirring. Polymerization was initiated by heating to obtain resin particles. The resin particles were modified under the same amylopyridine oxime conditions as in Example 1 (hydroxylamine hydrochloride alkaline solution, 80°C, 8 hours), and after washing and drying, amylopyridine oxime resin was obtained.

[0051] The properties of the obtained resin product were characterized. Its particle size distribution ranged from 100 to 400 μm, and the CV value was >20%, indicating an extremely wide particle size distribution and irregular morphology. BET testing showed that the resin's specific surface area was only 36 m². 2 / g, significantly lower than the product in the examples. Elemental analysis showed that the nitrogen content of the resin was 5%, and the calculated content of amine oxime groups on the resin was approximately 1.52 mmol / g.

[0052] The resulting resin was subjected to pH=5.0 and UO2. 2+ Adsorption experiments were conducted in a solution with an initial concentration of 100 mg / L. The test results showed that the resin had a saturated adsorption capacity of 77 mg / g for uranyl ions, and the time required to reach 90% of the saturated adsorption capacity was 90 minutes.

[0053] As can be seen from the comparison of the above embodiments and comparative examples, the amylopectin-based macroporous resin prepared by microfluidic control in this invention has significant advantages. Regarding size uniformity, the CV values ​​of the products in the embodiments are all less than 5%, while the CV values ​​of the products prepared by the conventional method in the comparative examples are greater than 20%; regarding pore structure, the specific surface area of ​​the products in the embodiments can reach 300-350 m² / g. 2 / g, while the comparative product was only 36m 2 / g; Regarding the efficiency of functional group introduction, the content of the amylopectin groups in the product of the examples was 3.04~3.8 mmol / g, which was much higher than the 1.52 mmol / g of the comparative example; Regarding the adsorption performance, the saturated adsorption capacity of the product of the examples was 144~180 mg / g, which was significantly better than the 77 mg / g of the comparative example, and the adsorption kinetics were faster. These results indicate that the method of the present invention achieves precise control of resin size, morphology and pore structure through microfluidic technology, thereby significantly improving the efficiency of functional group introduction and adsorption performance.

Claims

1. A method for preparing a geminioxime-based macroporous resin, characterized in that, Includes the following steps: S1. Preparation of the organic phase: Acrylonitrile, divinylbenzene and styrene are mixed to obtain a mixture of organic monomers; An initiator, a photocuring agent, and a porogen are added to a mixture of organic monomers and mixed thoroughly to obtain an organic phase. S2. Preparation of the aqueous phase: Prepare an aqueous solution of polyvinyl alcohol as the aqueous phase; S3. Preparation of monodisperse droplets: The organic phase obtained in step S1 and the aqueous phase obtained in step S2 are passed into a microfluidic chip to generate monodisperse droplets; S4. Photopolymerization and curing: Under light irradiation, the monomers in the monodisperse droplets obtained in step S3 are polymerized. After curing, the monomers are washed once, Soxhlet extracted, washed twice, and dried to obtain macroporous resin precursor microspheres. S5. Amine oxime reaction: The macroporous resin precursor microspheres obtained in step S4 are reacted with hydroxylamine reagent until the reaction is complete. After washing and drying, amine oxime-based macroporous resin is obtained.

2. The preparation method according to claim 1, characterized in that, In step S1, at least one of the following conditions must be met: The mass ratio of acrylonitrile, divinylbenzene and styrene in the organic monomer mixture is 5~7:2~3:1~2; The amount of initiator added is 0.5-2% of the total mass of the organic monomer mixture; The initiator is azobisisobutyronitrile; The amount of the photocuring agent added is 0.1% to 1% of the total mass of the organic monomer mixture; The photocuring agent is any one of benzoin dimethyl ether, acetophenone derivatives, acylphosphine oxides, thioxanthones, and 4-isobutylphenyl-4'-methylphenyliodonium hexafluorophosphate; The mass ratio of the organic monomer mixture to the porogen is 2~5:1; The pore-forming agent is at least one of kerosene, liquid paraffin, xylene, cyclohexanone, polyvinylpyrrolidone, and gasoline.

3. The preparation method according to claim 1, characterized in that: In step S2, the mass concentration of the polyvinyl alcohol aqueous solution is 2-10%.

4. The preparation method according to claim 1, characterized in that, In step S3, at least one of the following conditions must be met: The droplet generation unit of the microfluidic chip is a flow focusing structure or a T-shaped structure; The diameter of the monodisperse droplets is 50~500μm; The influent rate of the organic phase is 5~100 μL / min, and the influent rate of the aqueous phase is 10~200 μL / min, with the influent rate of the aqueous phase always being greater than that of the organic phase.

5. The preparation method according to claim 1, characterized in that: In step S4, the illumination condition is ultraviolet light with a wavelength of 365nm.

6. The preparation method according to claim 1, characterized in that: In step S5, the mass-to-volume ratio of the macroporous resin precursor microspheres to the hydroxylamine reagent is 1g:10~50mL.

7. The preparation method according to claim 1, characterized in that: In step S5, the hydroxylamine reagent is a hydroxylamine hydrochloride alkaline solution prepared by hydroxylamine hydrochloride and sodium hydroxide; The concentration of hydroxylamine hydrochloride is 1~5 mol / L, and the molar ratio of sodium hydroxide to hydroxylamine hydrochloride is 1~1.5:

1.

8. The preparation method according to claim 1, characterized in that: In step S5, the reaction temperature of the amylated oxime reaction is 60~90℃, and the reaction time is 4~12 hours.

9. A methylamine oxime macroporous resin prepared by the preparation method according to any one of claims 1 to 8.

10. The application of the amine oxime macroporous resin according to claim 9 in the adsorption of uranium, gallium, and vanadium metal ions in aqueous solution.

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