Preparation method of inner and outer coating graded porous polymer microspheres for ocean uranium extraction

Abstract

The invention discloses a preparation method of graded porous polymer microspheres with inner and outer coatings for ocean uranium extraction. The preparation method comprises the following steps: curing ethoxylated trimethylolpropane triacrylate multiple emulsion particles containing polyvinyl alcohol inner liquid drops into graded porous polymer microspheres; the graded porous polymer microspheres are dispersed in a polyacrylonitrile solution, the polyacrylonitrile solution serves as an inner phase, silicone oil serves as an outer phase, and a capillary tube is used for absorbing the inner phase; an injection pump is used for controlling the flow velocity of the inner phase and the outer phase, the inner phase is sheared by the outer phase at the flow focusing position to form solid-water-oil composite emulsion particles, and the solid-water-oil composite emulsion particles flow out into a rotary evaporation bottle filled with the outer phase in advance through a collecting pipe of a flow focusing type capillary tube generator; and curing the solid-water-oil liquid drops to obtain the porous polymer microspheres with graded inner and outer coatings. The large specific surface area of the graded porous polymer microspheres is utilized, functionalization of polyacrylonitrile is achieved, and the polyacrylonitrile has the function of adsorbing uranium ions through follow-up modification.

Description

Technical Field

[0001] The present invention belongs to the technical field of microfluidic preparation of new materials, and more specifically, relates to a method for preparing graded porous polymer microspheres with inner and outer coatings for uranium extraction from the ocean. Background Art

[0002] With the rapid growth of global energy demand and the increasingly serious environmental pollution caused by the use of fossil fuels, the development of clean and efficient energy has become an important task that needs to be solved in the world today. Among clean energy, nuclear energy has attracted much attention due to its high efficiency and environmental protection characteristics. However, the development of nuclear energy is inseparable from nuclear fuel, of which uranium is one of the most important raw materials. The ocean is a huge uranium resource reservoir, containing billions of tons of uranium, far exceeding the reserves on land. Therefore, it is particularly urgent to efficiently extract uranium from seawater. As an important adsorption material, polymers play an important role in the extraction of uranium from seawater. Among them, polyacrylonitrile has extremely excellent adsorption properties after being modified with hydroxylamine and is widely used in the field of uranium extraction from seawater. However, the adsorption efficiency of traditional polyacrylonitrile fibers is limited due to their small surface area. In recent years, researchers have developed a hierarchical porous polymer microsphere with a highly interconnected pore network that can significantly increase the specific surface area. However, the characteristics of polyacrylonitrile limit the possibility of directly producing hierarchical porous polymer microspheres by photocuring. Summary of the invention

[0003] An object of the present invention is to solve at least the above problems and / or disadvantages and to provide at least the advantages which will be described hereinafter.

[0004] In order to achieve these purposes and advantages according to the present invention, a method for preparing inner and outer coated graded porous polymer microspheres for marine uranium extraction is provided, comprising the following steps:

[0005] Step 1: preparing an ethoxylated trimethylolpropane triacrylate (ETPTA) solution and a polyvinyl alcohol aqueous solution to which 2-hydroxy-2-methyl-1-phenyl-1-propanone (HMPP) was added, and using a two-step coaxial capillary generator to prepare ETPTA multiple emulsions containing 1 to 4 polyvinyl alcohol inner droplets;

[0006] Step 2: curing the ETPTA multiple emulsion particles with ultraviolet light to obtain graded porous polymer microspheres with a grade number of 1 to 4;

[0007] Step 3, dispersing the graded porous polymer microspheres in a polyacrylonitrile solution, placing the microspheres in a closed container and evacuating the container to ensure that the pores are filled with the polyacrylonitrile solution, using the polyacrylonitrile solution as the inner phase and silicone oil as the outer phase, using a capillary to absorb the inner phase, and using a polydimethylsiloxane soft channel to tightly connect the capillary to the injection tube of the flow focusing capillary generator; at the same time, using a hose to tightly connect the outer phase to the continuous phase inlet of the flow focusing capillary generator;

[0008] Step 4: Using a syringe pump to control the flow rates of the inner phase and the outer phase, the inner phase is sheared by the outer phase at the flow focusing point to form a solid-water-oil composite emulsion, and flows out through the collection tube of the flow focusing capillary generator into a rotary evaporator pre-filled with the outer phase;

[0009] Step 5: Use a rotary evaporator to solidify the solid-water-oil droplets in the rotary evaporation bottle to obtain graded porous polymer microspheres with inner and outer coatings.

[0010] Preferably, in the step 1, ETPTA is replaced by trimethylolpropane triacrylate (TMPTA) or ethylene glycol dimethacrylate (EGDMA).

[0011] Preferably, in the step 1, the molecular weight of the polyvinyl alcohol used is in the range of 13000 to 146000, the degree of hydrolysis is in the range of 86% to 99%, and the mass concentration is in the range of 1% to 5%; the mass concentration of the ethoxylated trimethylolpropane triacrylate solution to which 2-hydroxy-2-methyl-1-phenyl-1-propanone is added is 0.1 to 5wt%; and the volume ratio of the ethoxylated trimethylolpropane triacrylate solution to the polyvinyl alcohol aqueous solution is 1:11.

[0012] Preferably, in step 2, the ultraviolet light power is greater than or equal to 200 W, and the irradiation time is greater than or equal to 5 minutes.

[0013] Preferably, in step three, the molecular weight of polyacrylonitrile is in the range of 10,000 to 500,000; the mass volume ratio of the graded porous polymer microspheres to the polyacrylonitrile solution is 0.1 to 10 g:1 mL; and the viscosity of the silicone oil is 50 to 500 cs.

[0014] Preferably, in step 3, the solvent for dissolving polyacrylonitrile is N,N-dimethylformamide or dimethyl sulfoxide, and the mass concentration of polyacrylonitrile is 1% to 10%.

[0015] Preferably, in step 3, the inner diameter of the capillary is the same as the inner diameter of the injection tube of the flow focusing capillary generator;

[0016] The collecting tube of the flow focusing capillary generator is a hydrophobic capillary.

[0017] Preferably, in step 4, the flow rate ratio of the external phase to the internal phase is greater than or equal to 1; the external phase is pre-filled with silicone oil accounting for 20% to 30% of the volume of the rotary evaporator.

[0018] Preferably, in step five, the inner wall of the rotary evaporator is subjected to a hydrophobic treatment, and the hydrophobic treatment comprises coating the inner wall of the rotary evaporator with polytetrafluoroethylene or silane; the rotation speed of the rotary evaporator is 5 to 30 rpm, and the curing temperature is 20 to 50°C.

[0019] The invention discloses an application of porous polymer microspheres with graded inner and outer coatings for extracting uranium from the ocean. The porous polymer microspheres with graded inner and outer coatings for extracting uranium from the ocean are applied to extracting uranium from the ocean.

[0020] The present invention includes at least the following beneficial effects: The present invention adopts a new strategy: first, a photosensitive resin material (2-hydroxy-2-methyl-1-phenyl-1-propanone) is selected, and a hierarchical porous polymer microsphere matrix is ​​prepared by microfluidics and photocuring, and then a droplet of a polyacrylonitrile coating solution is prepared to encapsulate the hierarchical porous polymer microsphere, and finally, a hierarchical porous polymer microsphere with inner and outer coatings of polyacrylonitrile is obtained by rotary evaporation. This strategy not only utilizes the large specific surface area of ​​the hierarchical porous polymer microspheres, but also realizes the functionalization of polyacrylonitrile, so that it has the function of subsequent modification to adsorb uranium ions. It is worth mentioning that the polyacrylonitrile coating solution in this strategy can also be expanded to solutions of other functionalized materials. Therefore, the hierarchical porous polymer microspheres prepared by this method are not only suitable for specific fields such as uranium extraction from seawater, but also can play an important role in other fields, providing more possibilities for the future development of hierarchical porous polymer microspheres, and are expected to show broader application prospects in the fields of adsorption, separation, catalysis, etc.

[0021] The present invention adopts a two-step capillary generator to prepare porous polymer microspheres with a classification number of 1-4, and prepares corresponding solid-water-oil composite emulsion particles through a flow focusing capillary generator, and obtains graded porous polymer microspheres with inner and outer coatings by rotary evaporation solidification, thereby broadening the scope of functional application of graded porous polymer microspheres.

[0022] The invention can accurately control the outer diameter and the number of grades of porous polymer microspheres by assembling two-step capillary generators with different tube diameters and adjusting the three-phase flow rate.

[0023] The present invention can accurately control the thickness of the inner and outer coatings of the graded porous polymer microspheres by assembling flow focusing capillary generators with different tube diameters and adjusting the two-phase flow rate.

[0024] In addition to using polyacrylonitrile for uranium extraction from the ocean, the inner and outer coating materials of the present invention can also be changed according to different functional requirements and can be applied to adsorption, separation, catalysis and other fields.

[0025] The advantages, objectives and features of the present invention will be embodied in part through the following description, and in part will be understood by those skilled in the art through study and practice of the present invention. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] Figure 1 This is a high-speed photograph of the solid-water-oil composite emulsion formation process when porous polymer microspheres with a classification number of 3 are used as the solid phase in the flow focusing capillary generator in Example 1;

[0027] Figure 2 This is a scanning electron microscope photograph of the cross section of the porous polymer microspheres with inner and outer coatings and a classification number of 3 obtained in Example 1 after being cut in half by femtosecond laser;

[0028] Figure 3 This is an enlarged view of the red frame in Example 1. DETAILED DESCRIPTION

[0029] The present invention is further described in detail below in conjunction with the accompanying drawings so that those skilled in the art can implement the invention with reference to the description.

[0030] It should be understood that the terms such as “having”, “including” and “comprising” used herein do not exclude the existence or addition of one or more other elements or combinations thereof.

[0031] Example 1

[0032] This embodiment provides a method for preparing hierarchical porous polymer microspheres with inner and outer coatings, comprising the following steps:

[0033] Step 1: prepare 5 mL of ETPTA solution to which 0.5 wt% HMPP was added and 55 mL of 1 wt% polyvinyl alcohol aqueous solution, wherein the molecular weight of the polyvinyl alcohol is in the range of 13,000 to 23,000 and the degree of hydrolysis is 86%; prepare ETPTA multiple emulsions containing three polyvinyl alcohol inner droplets using a two-step coaxial capillary generator; wherein the multiple emulsions using a two-step coaxial capillary generator are prior art, for details, refer to Acta Physica Sinica, "Study on the Size Control Law of Double Emulsions in Microfluidic Technology", Vol. 66, No. 4 (2017) 046801.

[0034] Step 2: irradiate the ETPTA multiple emulsion particles with ultraviolet light of 200 W for 5 minutes to solidify and obtain porous polymer microspheres with an outer diameter of 850 μm and a classification number of 3;

[0035] Step 3: Disperse 1 g of graded porous polymer microspheres in 10 mL of 4 wt% polyacrylonitrile / N,N-dimethylformamide solution, place in a closed container and evacuate to ensure that the pores are filled with polyacrylonitrile / N,N-dimethylformamide solution, the molecular weight of polyacrylonitrile is 80,000; Figure 1 As shown, polyacrylonitrile / N,N-dimethylformamide solution is used as the inner phase, silicone oil with a viscosity of 100 cs is used as the outer phase, 50 third-level porous polymer microspheres are sucked by a capillary, and the capillary is tightly connected to the injection tube of the flow focusing capillary generator by a polydimethylsiloxane soft channel, and the inner diameter of the capillary is the same as the inner diameter of the injection tube of the flow focusing capillary generator; at the same time, a hose is used to tightly connect the outer phase solution to the continuous phase inlet of the flow focusing capillary generator;

[0036] Step 4: Use a syringe pump to control the flow rate of the inner phase to 10 mL / h and the flow rate of the outer phase to 40 mL / h. At the flow focusing point, the inner phase is sheared by the outer phase to form a solid-water-oil composite emulsion, and flows out through the collection tube of the flow focusing capillary generator into a rotary evaporator pre-filled with 200 mL of the outer phase solution;

[0037] Step 5: Use a rotary evaporator to solidify the solid-water-oil droplets in the rotary evaporation bottle. The rotation speed is 5 rpm and the rotary evaporation temperature is 50° C. After curing for 2 days, 3-level porous polymer microspheres with inner and outer coatings are obtained.

[0038] The scanning electron microscope photograph of the cross section of the hierarchical porous polymer microspheres with inner and outer coatings prepared in this example after being cut in half by femtosecond laser is shown in FIG. Figure 2 and Figure 3 As shown, Figure 3 for Figure 2 The enlarged image of the red box in the middle, from Figure 2 and Figure 3 It can be seen that polyacrylonitrile was successfully coated on the outer surface of the ETPTA microspheres and the inner surface of the three holes, which provided support for the subsequent modification of the polyacrylonitrile coating to adsorb uranium ions.

[0039] Example 2

[0040] This embodiment provides a method for preparing hierarchical porous polymer microspheres with inner and outer coatings. Compared with Example 1, ETPTA is replaced with trimethylolpropane triacrylate (TMPTA), and the process parameters of the remaining steps are the same as those of Example 1.

[0041] Example 3

[0042] This embodiment provides a method for preparing hierarchical porous polymer microspheres with inner and outer coatings. Compared with Example 1, ETPTA is replaced by ethylene glycol dimethacrylate (EGDMA), and the process parameters of the remaining steps are the same as those in Example 1.

[0043] The number of devices and processing scales described here are used to simplify the description of the present invention. Applications, modifications and variations of the present invention will be obvious to those skilled in the art.

[0044] Although the embodiments of the present invention have been disclosed as above, they are not limited to the applications listed in the specification and the implementation modes, and they can be fully applied to various fields suitable for the present invention. For those familiar with the art, additional modifications can be easily implemented. Therefore, without departing from the general concept defined by the claims and the scope of equivalents, the present invention is not limited to the specific details and the illustrations shown and described herein.

Claims

1. A method for preparing porous polymer microspheres with inner and outer coatings for uranium extraction from the ocean, characterized in that: The following steps are involved: Step 1: preparing an ethoxylated trimethylolpropane triacrylate solution and a polyvinyl alcohol aqueous solution to which 2-hydroxy-2-methyl-1-phenyl-1-propanone is added, and using a two-step coaxial capillary generator to prepare ethoxylated trimethylolpropane triacrylate multiple emulsions containing 1 to 4 polyvinyl alcohol inner droplets; Step 2: curing the ethoxylated trimethylolpropane triacrylate multiple emulsion particles with ultraviolet light to obtain hierarchical porous polymer microspheres with a hierarchical number of 1 to 4; Step 3, dispersing the graded porous polymer microspheres in a polyacrylonitrile solution, placing the microspheres in a closed container and evacuating the container to ensure that the pores are filled with the polyacrylonitrile solution, using the polyacrylonitrile solution as the inner phase and silicone oil as the outer phase, using a capillary to absorb the inner phase, and using a polydimethylsiloxane soft channel to tightly connect the capillary to the injection tube of the flow focusing capillary generator; at the same time, using a hose to tightly connect the outer phase to the continuous phase inlet of the flow focusing capillary generator; Step 4: Using a syringe pump to control the flow rates of the inner phase and the outer phase, the inner phase is sheared by the outer phase at the flow focusing point to form a solid-water-oil composite emulsion, and flows out through the collection tube of the flow focusing capillary generator into a rotary evaporator pre-filled with the outer phase; Step 5: Use a rotary evaporator to solidify the solid-water-oil droplets in the rotary evaporation bottle to obtain graded porous polymer microspheres with inner and outer coatings.

2. The method for preparing the internal and external coating graded porous polymer microspheres for uranium extraction from the ocean as claimed in claim 1, characterized in that: In the step 1, ethoxylated trimethylolpropane triacrylate is replaced by trimethylolpropane triacrylate and ethylene glycol dimethacrylate.

3. The method for preparing the internal and external coating graded porous polymer microspheres for uranium extraction from the ocean as claimed in claim 1, characterized in that: In the step 1, the molecular weight of the polyvinyl alcohol used is in the range of 13000 to 146000, the degree of hydrolysis is in the range of 86% to 99%, and the mass concentration is in the range of 1% to 5%; the mass concentration of the ethoxylated trimethylolpropane triacrylate solution to which 2-hydroxy-2-methyl-1-phenyl-1-propanone is added is 0.1 to 5wt%; and the volume ratio of the ethoxylated trimethylolpropane triacrylate solution to the polyvinyl alcohol aqueous solution is 1:

11.

4. The method for preparing the internal and external coating graded porous polymer microspheres for uranium extraction from the ocean as claimed in claim 1, characterized in that: In the step 2, the ultraviolet light power is greater than or equal to 200 W, and the irradiation time is greater than or equal to 5 minutes.

5. The method for preparing the internal and external coating graded porous polymer microspheres for uranium extraction from the ocean as claimed in claim 1, characterized in that: In the step 3, the molecular weight of polyacrylonitrile is in the range of 10,000 to 500,000; the mass volume ratio of the graded porous polymer microspheres to the polyacrylonitrile solution is 0.1 to 10 g:1 mL; and the viscosity of the silicone oil is 50 to 500 cs.

6. The method for preparing the internal and external coating graded porous polymer microspheres for uranium extraction from the ocean as claimed in claim 1, characterized in that: In the step 3, the solvent for dissolving polyacrylonitrile is N,N-dimethylformamide or dimethyl sulfoxide, and the mass concentration of polyacrylonitrile is 1% to 10%.

7. The method for preparing the internal and external coating graded porous polymer microspheres for uranium extraction from the ocean as claimed in claim 1, characterized in that: In the step 3, the inner diameter of the capillary is the same as the inner diameter of the injection tube of the flow focusing capillary generator; The collecting tube of the flow focusing capillary generator is a hydrophobic capillary.

8. The method for preparing the internal and external coating graded porous polymer microspheres for uranium extraction from the ocean as claimed in claim 1, characterized in that: In the step 4, the flow rate ratio of the external phase to the internal phase is greater than or equal to 1; the pre-filled external phase specifically comprises pre-filled silicone oil accounting for 20% to 30% of the volume of the rotary evaporator.

9. The method for preparing the internal and external coating graded porous polymer microspheres for uranium extraction from the ocean as claimed in claim 1, characterized in that: In the step 5, the inner wall of the rotary evaporator is subjected to hydrophobic treatment; the rotary evaporator rotates at a speed of 5 to 30 rpm, and the curing temperature is 20 to 50°C.

10. An application of porous polymer microspheres with graded inner and outer coatings for uranium extraction from the ocean, wherein the porous polymer microspheres with graded inner and outer coatings for uranium extraction from the ocean are prepared by the method for preparing porous polymer microspheres with graded inner and outer coatings for uranium extraction from the ocean according to any one of claims 1 to 9, characterized in that: The internal and external coating graded porous polymer microspheres for extracting uranium from the ocean are used for extracting uranium from the ocean.

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