Polyurethane composite membrane for embedding saponification cast macroporous polyamidoxime hydrogel particles as well as preparation method and application of polyurethane composite membrane

Abstract

The invention relates to the technical field of environmental energy chemistry and new materials, in particular to a polyurethane composite membrane for embedding saponification cast macroporous polyamidoxime hydrogel particles as well as a preparation method and application of the polyurethane composite membrane. According to the composite membrane, hydrogel particles with macroporous structures are formed through lauric acid saponification regulation and glutaraldehyde crosslinking, and compared with traditional microporous and mesoporous materials, the mass transfer efficiency and the adsorption rate of uranyl ions in seawater can be remarkably improved. The saponified cast macroporous polyamidoxime hydrogel particles are embedded in a polyurethane film, the thickness of the obtained composite film is only about 0.1 mm, and the composite film has good mass transfer efficiency on seawater and uranyl ions; the excellent uranyl ion adsorption performance is shown in real seawater. The material provided by the invention has significant application potential in large-scale seawater uranium extraction projects, and provides reliable technical support for efficient development of seawater uranium resources.

Description

Technical Field

[0001] This invention relates to the fields of environmental energy chemistry and new materials technology, specifically to a polyurethane composite membrane with embedded saponified cast macroporous poly(amine oxime) hydrogel particles, its preparation method, and its application. Background Technology

[0002] With increasing global emphasis on carbon neutrality and energy security, nuclear energy, with its high energy density, near-zero greenhouse gas emissions, and stable all-weather power generation capabilities, has once again become a key option in the energy transition strategies of various countries. Especially given that renewable energy sources are still struggling to fully meet baseload electricity demand, nuclear power is widely regarded as a crucial pillar for achieving a low-carbon power system. According to the latest forecasts from the International Atomic Energy Agency (IAEA) and several other authoritative energy agencies, the current global installed nuclear power capacity is approximately 398 GWe, and this figure is expected to grow to approximately 746 GWe by 2040, nearly doubling. This rapid expansion means a sharp increase in demand for nuclear fuel—particularly uranium resources. However, there are significant structural bottlenecks in terrestrial uranium resources. According to the Red Book jointly published by the Organization for Economic Cooperation and Development (OECD) and the Nuclear Energy Agency (NEA), the total amount of economically exploitable uranium resources globally at relatively low extraction costs (<130 USD / kg-U) is only close to 5.9 million tons. Even if existing mining capacity, stockpiles, and supplies from secondary sources such as decommissioned nuclear weapons are all taken into account, it is still difficult to fully cover the fuel gap caused by the large-scale expansion of nuclear power in the future.

[0003] Taking my country as an example, the contradiction between uranium resource supply and demand is particularly prominent. In recent years, with the rapid advancement of nuclear power construction, China's installed nuclear power capacity and the number of units under construction rank among the world's top. However, domestic uranium reserves are limited, the grade is low, and mining conditions are relatively difficult, resulting in domestic production being unable to meet the rapidly growing demand for nuclear fuel for a long time. To maintain nuclear power development, my country's dependence on imported uranium has continued to rise, and the risks to supply chain security and price fluctuations have also increased accordingly. my country faces potential uncertainties and strategic pressures in fuel acquisition. Therefore, developing new sources of uranium resources, expanding supply channels, and improving domestic nuclear fuel self-sufficiency have become important tasks to ensure the sustainable development of my country's nuclear energy and energy security.

[0004] Against this backdrop, uranium resources in the ocean have attracted significant attention due to their wide distribution and enormous total amount. Although the concentration of uranium in seawater is extremely low (averaging approximately 3.3 μg / L),... -1However, given the total volume of the global oceans is approximately 1.38 billion cubic kilometers, the theoretical uranium reserves are estimated at 4.5 billion tons, nearly a thousand times the recoverable reserves on land. This means that if uranium could be extracted from seawater economically and efficiently, it would fundamentally change the global uranium resource landscape and provide a near-unlimited fuel guarantee for the long-term sustainable development of nuclear power. For this reason, seawater uranium extraction has been listed as a strategic frontier technology by many countries. However, seawater uranium extraction still faces severe challenges in its engineering and commercialization. First, the extremely low uranium concentration requires adsorbent materials with extremely high affinity and selectivity. It must accurately identify and capture trace amounts of uranyl ions (UO2) in complex seawater containing a large number of competing ions (such as V, Fe, Zn, etc.). 2+ Secondly, the material must maintain structural stability and functional durability in harsh marine environments such as high salinity, high pH, ​​biofouling, and ocean current erosion. Furthermore, factors such as the elution and recovery efficiency after adsorption, the number of times the material can be recycled, and the overall energy consumption and cost control of the process collectively determine whether the technology has practical application value. Currently, although various adsorbents (such as amylopectin polymers, metal-organic frameworks, and bio-based materials) have shown good performance under laboratory conditions, their dynamic adsorption efficiency, long-term service capability, and economic feasibility in real seawater environments are still far from meeting industrialization standards.

[0005] CN112871144A discloses a method for preparing a uranium adsorbent material, which involves impregnating a nonpolar macroporous resin in an alkaline aqueous solution of poly(xime)amine oxime to obtain a uranium adsorbent material composed of a nonpolar macroporous resin loaded with poly(xime)amine oxime; the nonpolar macroporous resin is macroporous resin D101, macroporous resin HP-20, macroporous resin HPD-300, macroporous resin NKA, or macroporous resin AB-8; the mass ratio of poly(xime)amine oxime to nonpolar macroporous resin is 3-25:100. CN112547026A discloses a uranium adsorbent material composed of a nonpolar macroporous resin loaded with poly(xime)amine oxime. CN116459802A discloses a high-strength, three-dimensional continuous, ultra-large porous uranium adsorption hydrogel. It comprises a first polymer network formed by low-temperature crystallization polymerization and crosslinking of polyvinyl alcohol and water-soluble bio-based macromolecules; a second polymer network formed by random copolymerization and crosslinking of poly(amine oxime) and hydrophilic vinyl monomers on the basis of the first network; and a third polymer network formed by self-assembly of polyaniline on the surface of the second network. Nano-silica is uniformly distributed in the gel phase of the hydrogel. The hydrogel has a three-dimensional continuous open ultra-large porous structure with pore sizes ranging from 10 μm to 200 μm. However, the overall proportion of amine oxime groups in this material is relatively low, and the spatial distribution of the groups is limited, ultimately making it difficult to obtain a high adsorption capacity.

[0006] The inventor's previous patent CN202411410451.2 disclosed alginate-polyacrylic acid composite spheres coated with wax-cast macroporous polyamine oxime hydrogel particles, which showed good adsorption capacity for uranyl ions in simulated seawater. However, the adsorption kinetics of this material were slow, and its adsorption capacity in real seawater was not ideal. This was because the composite spheres had a large particle size of about 3 mm, and the pore size of the alginate-polyacrylic acid spheres was small, which limited the diffusion of seawater or uranyl ions into the material and resulted in low utilization of the wax-cast macroporous polyamine oxime hydrogel particles inside the material.

[0007] Therefore, it is necessary to develop materials with higher adsorption capacity and faster adsorption kinetics for uranyl ions in real seawater environments. Summary of the Invention

[0008] This invention aims to overcome the shortcomings of existing seawater uranium extraction materials in terms of adsorption performance, structural stability, and engineering applicability. It provides a novel method for preparing a polyurethane composite membrane with embedded saponified cast macroporous poly(amine oxime) hydrogel particles and its application in seawater uranium extraction. The composite membrane prepared using the method described in this invention exhibits good adsorption performance for uranyl ions (UO2) in a real seawater environment. 2+ All exhibit excellent adsorption capacity, rapid adsorption rate, ideal affinity and selectivity, and good regeneration performance. The preparation process proposed in this invention is simple and cost-controllable, and possesses good mechanical strength and processability, facilitating large-scale production and significantly improving its deployment feasibility in actual marine environments.

[0009] To achieve the above objectives, the technical solution of the present invention is as follows:

[0010] A method for preparing a polyurethane composite membrane with embedded saponified cast macroporous polyamine oxime hydrogel particles includes the following steps:

[0011] (1) Lauric acid was added to the alkaline aqueous solution of polyamine oxime for saponification reaction, then glutaraldehyde was added, mixed evenly, and cooled to obtain solidified solid. The water in the obtained solidified solid was removed to obtain shrink solidified solid.

[0012] (2) After the shrinkage solids are crushed and ground, the resulting particles are extracted with organic solvents to remove laurates and dried to obtain saponified cast macroporous polyamine oxime hydrogel particles.

[0013] (3) The macroporous poly(xime) hydrogel particles cast by saponification and polyurethane solution are mixed evenly. The resulting suspension is loaded into a mold and immersed in water. The non-solvent-induced phase separation process causes the suspension to solidify and be demolded to obtain a composite membrane. The membrane is washed and dried to obtain a polyurethane composite membrane containing macroporous poly(xime) hydrogel particles cast by saponification.

[0014] This invention utilizes the property that sodium laurate, formed after saponification, can co-melt with an alkaline aqueous solution of poly(xylene oxime) at a relatively high temperature and spontaneously solidify at room temperature, thus achieving good interface control of the poly(xylene oxime) alkaline aqueous solution. After the material is dehydrated, the poly(xylene oxime) phase disperses within the soap phase, realizing a "phase inversion" process. Removing sodium laurate enables hard mold casting of the poly(xylene oxime), obtaining macroporous poly(xylene oxime) hydrogel particles. The added glutaraldehyde can react with the amino groups of the xylene oxime, causing cross-linking of the poly(xylene oxime), which can significantly improve the strength and reusability of the macroporous poly(xylene oxime) hydrogel particles.

[0015] Further, in step (1), the polyamine oxime alkaline aqueous solution is obtained by dissolving the polyamine oxime polymer in an alkaline aqueous solution, and the alkaline aqueous solution is a solution of NaOH and / or KOH with a concentration of 0.01-0.1 g / mL, preferably, the concentration of NaOH and / or KOH is 0.02-0.04 g / mL; even further, the ratio of polyamine oxime polymer to alkaline aqueous solution is 1 g: 10-20 mL.

[0016] Further, in step (1), the mass ratio of poly(xime) polymer powder, lauric acid, and glutaraldehyde is 1g:1-2g:0.1-0.3; preferably, the mass ratio of poly(xime) polymer powder, lauric acid, and glutaraldehyde is 1g:1.4-1.6g:0.2-0.25; even further, the saponification reaction temperature is 20-60℃, preferably 30-50℃, for example, 40℃; the cooling is to 10-25℃; the removal of moisture from the solidified solid is by natural evaporation at room temperature. The solidified solid is white, and the shrunken solidified solid is brownish-yellow.

[0017] Further, in step (1), the preparation of the poly(gamma-amine oxime) polymer is well known in the art. In one embodiment of the present invention, NH2OH·HCl, Na2CO3, and NaOH are reacted in DMF solvent at 30-125°C, preferably 50-90°C, for example, 65-75°C. Then, polyacrylonitrile is added, and the reaction is continued at this temperature for 12-24 hours. NH2OH·HCl, Na2CO3, and NaOH are then added, and the reaction is continued at this temperature for another 12-24 hours. The resulting mixture is poured into water to obtain a white flocculent precipitate, which is filtered and dried to obtain the poly(gamma-amine oxime) polymer. Further, the mass ratio of NH2OH·HCl, Na2CO3, NaOH, and polyacrylonitrile is 5-50:5-40:1-10:3-30, preferably 30-40:20-30:5-8:10-15. Further still, the amount of NH2OH·HCl, Na2CO3, and NaOH added accounts for 20-30 wt% of their respective raw materials. The weight-average molecular weight of polyacrylonitrile ranges from 150,000 to 500,000.

[0018] Further, in step (2), the particle size after crushing and grinding is 20-80 μm; the organic solvent is selected from at least one of ethanol and propanol; the organic solvent extraction is preferably Soxhlet extraction.

[0019] Further, in step (3), the polyurethane is a polyether-type polyurethane, such as at least one of BASF 1185A, BASF 1175AU, BASF 1180A, Covestro 785A, Covestro 790A, and UZ3-71D; the concentration of the polyurethane solution is 0.1-0.5 g / mL, preferably 0.2-0.3 g / mL, and the solvent is selected from at least one of N,N-dimethylacetamide, N,N-dimethylformamide, and dimethyl sulfoxide. The mass ratio of the macroporous poly(amine oxime) hydrogel particles and the polyurethane in the saponification casting is 1:0.5-1.5, preferably 1:0.75-1.

[0020] Further, in step (3), the mold is made of polytetrafluoroethylene (PTFE) with a thickness of 0.05-0.2 mm. The thickness of the mold determines the thickness of the film. The planar shape of the mold is not particularly limited, such as quadrilateral, circle, ellipse, rectangle, or trapezoid. In one specific embodiment of the invention, the mold is a cube of 10-100 mm × 10-100 mm × 0.05-0.2 mm, for example, 20 × 20 × 0.1 mm. The immersion time in water is 1-60 minutes, preferably 10-20 minutes. Washing is done with water, and drying is done by freeze drying.

[0021] The second objective of this invention is to provide a composite membrane prepared by the above-described method for use in the enrichment and / or extraction of uranyl ions in water.

[0022] Furthermore, the water body is seawater, and the concentration of uranyl ions in the water body is 1-3000 μg / L. -1 Preferably 1-100 μg / L -1 The polyurethane composite membrane with embedded saponified cast macroporous poly(amine oxime) hydrogel particles obtained in this invention exhibits ideal affinity and selectivity for uranyl ions, and shows satisfactory removal rate and adsorption capacity for uranyl ions in both simulated seawater and real seawater containing multiple coexisting ions.

[0023] The concentration of U in the actual seawater was approximately 4 μg / L. -1 The simulated seawater contained U (330 μg / L) was prepared. -1 ), V (150 μg / L) -1 ), Fe (150 μg L) -1 ), Co (55 μg L) -1 Ni (100 μg L) -1 Cu (60 μg L) -1), Zn (400 μg L) -1 Pb (3 μg L) -1 The concentrations of Na (10.06 × 10⁻⁶) were approximately 100 times higher than the actual seawater concentration levels. 6 μg L -1 ), Mg (1.23×10 6 μg L -1 K (3.53×10) 5 μg L -1 ), Ca (4.01×10 5 μg L -1 The concentration level is the same as that of real seawater.

[0024] Implementing the embodiments of the present invention will have the following beneficial effects:

[0025] The polyurethane composite membrane with embedded saponified cast macroporous poly(ammidine oxime) hydrogel particles obtained after implementing this invention has significant structural and performance advantages. The macroporous hydrogel particles formed through lauric acid saponification and glutaraldehyde crosslinking significantly improve the mass transfer efficiency and adsorption rate of uranyl ions in seawater compared to traditional microporous and mesoporous materials. Embedding these saponified cast macroporous poly(ammidine oxime) hydrogel particles in a polyurethane film results in a composite membrane with a thickness of only about 0.1 mm, exhibiting excellent mass transfer efficiency for both seawater and uranyl ions. Simultaneously, this composite membrane also possesses good mechanical stability and ease of operation, facilitating practical applications for uranium extraction and recycling from seawater. Experimental results show that this composite membrane exhibits excellent uranyl ion adsorption performance in both simulated and real seawater. The material has high affinity and selectivity for uranyl ions, achieving efficient removal even in environments with multiple coexisting metal ions, and can be repeatedly recycled while maintaining stable performance, effectively overcoming the technical bottlenecks of poor selectivity, low adsorption capacity, and poor reusability of existing materials in practical applications. In summary, the material of this invention has significant application potential in large-scale seawater uranium extraction projects, providing reliable technical support for the efficient development of seawater uranium resources.

[0026] Compared to the inventor's previous patent CN202411410451.2, the composite membrane prepared by the method of this invention has faster adsorption kinetics, requiring only 50 hours instead of 150 hours previously; it also exhibits better adsorption performance in real seawater, with a significantly improved adsorption capacity. Attached Figure Description

[0027] Figure 1 The results are SEM characterization of the surface (a, scale bar length 1 μm) and cross section (b, scale bar length 10 μm) of the polyurethane composite membrane with embedded saponified cast macroporous polyamine oxime hydrogel particles prepared in Example 1, as well as the mercury porosimetry test results (c).

[0028] Figure 2 The effect of different contents of saponified cast macroporous poly(ammonia oxime) hydrogel particles on the tensile properties of the polyurethane composite membrane with embedded saponified cast macroporous poly(ammonia oxime) hydrogel particles prepared in Example 1.

[0029] Figure 3 The polyurethane composite membrane with embedded saponified cast macroporous polyamine oxime hydrogel particles prepared in Example 1 was tested at three different initial uranium concentrations (U, C0 = 10, 20, and 40 mg L). -1 Dynamic adsorption curves and kinetic model fitting results at pH = 6.

[0030] Figure 4 The polyurethane composite membrane of embedded saponified cast macroporous poly(amine oxime) hydrogel particles in Example 1 exhibited good uranyl ion (U, CO = 20 mg / L) retention in 8 consecutive adsorption-desorption cycles. -1 The adsorption capacity and desorption efficiency at pH = 6.

[0031] Figure 5 The polyurethane composite membrane of embedded saponified cast macroporous polyamine oxime hydrogel particles described in Example 1 was used in experiments with different concentrations of humic acid (HA, CO = 0, 5, 10, 15, 20 and 25 mg L). -1 Uranyl ion solution (U, CO = 20 mg / L) -1 Changes in adsorption capacity at pH = 6.

[0032] Figure 6 The polyurethane composite membrane of embedded saponified cast macroporous poly(amine oxime) hydrogel particles in Example 1 exhibits selective adsorption performance of uranyl ions in simulated seawater containing multiple competing ions.

[0033] Figure 7 The polyurethane composite membrane of the embedded saponified cast macroporous poly(amine oxime) hydrogel particles described in Example 1 showed different concentrations of spiked real seawater for uranyl ions (U, CO = 54, 104, 204, 504, 1004, and 2004 μg / L). -1 The adsorption amount and removal rate of ).

[0034] Figure 8 The polyurethane composite membrane of embedded saponified cast macroporous poly(amine oxime) hydrogel particles from Example 1 was tested in 10 L of real seawater over 20 days for U (U, CO = 4 μg / L). -1 The adsorption capacity results were obtained.

[0035] Figure 9 The polyurethane composite membrane of embedded saponified cast macroporous polyamine oxime hydrogel particles from Example 1 was tested in 50 L of real seawater over 25 days for U (U, CO = 4 μg / L).-1 The adsorption capacity results were obtained. Detailed Implementation

[0036] The present invention will be further described below with reference to specific embodiments, but this does not limit the present invention in any way.

[0037] Example 1

[0038] (1) 22.92 g NH2OH·HCl, 18 g Na2CO3 and 4.56 g NaOH were added sequentially to a 500 mL flask, followed by 200 mL DMF. The mixture was stirred continuously at 65 °C for 1 h. Then 12 g polyacrylonitrile was added, and the mixture was stirred at 65 °C for 24 h. Subsequently, 7.96 g NH2OH·HCl, 7.20 g Na2CO3 and 1.62 g NaOH were added to the reaction mixture, and the mixture was stirred at 65 °C for another 24 h. After the reaction was completed, the resulting mixture was poured into a large amount of deionized water to obtain a white flocculent precipitate. The precipitate was filtered, repeatedly washed until neutral, and vacuum dried to obtain poly(amine oxime) polymer powder.

[0039] (2) 10g of the poly(ammoxime) polymer powder obtained in step (1) was added to 200 mL of an aqueous solution containing 2g of NaOH and stirred at 40°C to dissolve. Then, 14g of lauric acid was added and the mixture was stirred until the solution became clear. Finally, 10 mL of glutaraldehyde aqueous solution (25% by mass) was added and stirred for 30 minutes to obtain a homogeneous solution. The solution was cooled to room temperature to obtain a white solid. The water in the solid was completely removed by natural evaporation at room temperature to obtain a hard, brownish-yellow shrinkage solid. The shrinkage solid was crushed and ground to obtain fine particles (approximately 50μm in diameter). The fine particles were then extracted with ethanol for 24 hours using a Soxhlet extractor to remove sodium laurate. The obtained material was dried to obtain saponified cast macroporous poly(ammoxime) hydrogel particles.

[0040] (3) Dissolve 1g of polyurethane in 5 mL of DMAc, then add 0.75g of the saponified casting macroporous polyamine oxime hydrogel particles obtained in step (2), and stir continuously at room temperature until a uniform polyurethane-saponified casting macroporous polyamine oxime hydrogel particle suspension is obtained.

[0041] (4) The polyurethane-saponification casting macroporous polyamine oxime hydrogel particle suspension obtained in step (3) is poured into a customized polytetrafluoroethylene template (20×20×0.1 mm). Then the entire template is immersed in deionized water and soaked for 10 minutes to allow the poured suspension to solidify. After demolding, the obtained ultrafilm is washed with deionized water and freeze-dried to obtain a polyurethane composite membrane with embedded saponification casting macroporous polyamine oxime hydrogel particles.

[0042] (5) such as Figure 1 As shown in Figure a, the surface of the polyurethane composite membrane with embedded saponified cast macroporous poly(amine oxime) hydrogel particles is covered with macropores, which is very conducive to seawater entering the interior of the composite membrane; as Figure 1 As shown in b, the polyurethane composite membrane with embedded saponified cast macroporous poly(amine oxime) hydrogel particles also exhibits finger-shaped macropores formed by a non-solvent-induced phase separation process, which is highly beneficial for seawater mass transfer within the membrane; such as Figure 1 As shown in c, the mercury porosimetry results of the polyurethane composite membrane with embedded saponified cast macroporous poly(amine oxime) hydrogel particles also prove that the composite membrane has an ideal macroporous structure.

[0043] Example 2

[0044] The effect of different saponified cast macroporous poly(xylamine oxime) hydrogel particles on the tensile strength of the polyurethane composite membrane with embedded saponified cast macroporous poly(xylamine oxime) hydrogel particles prepared in Example 1 was evaluated. In step (3) of Example 1, 1 g of polyurethane was dissolved in 5 mL of DMAc, and then different masses (0.25, 0.50, 0.75, 1.00, 1.25 and 1.50 g) of saponified cast macroporous poly(xylamine oxime) hydrogel particles were added to form suspensions. Finally, polyurethane composite membranes with different contents of saponified cast macroporous poly(xylamine oxime) hydrogel particles were prepared using the same method as in step (4) of Example 1, and tensile tests were performed on them. Figure 2 As shown, the tensile strength of the composite membrane gradually decreases with the increase of the content of saponified casting macroporous poly(ammonia oxime) hydrogel particles. A high content of saponified casting macroporous poly(ammonia oxime) hydrogel particles can obtain a higher uranium adsorption capacity, but the decrease in tensile strength is not conducive to the practical application of the material in the marine environment. Finally, the amount of saponified casting macroporous poly(ammonia oxime) hydrogel particles added in step (3) of Example 1 (0.75g) was selected.

[0045] Example 3

[0046] The dynamic adsorption performance of the polyurethane composite membrane with embedded saponified cast macroporous poly(xime) hydrogel particles prepared in Example 1 was evaluated. Five precisely weighed polyurethane composite membranes with embedded saponified cast macroporous poly(xime) hydrogel particles were placed in 500 mL Erlenmeyer flasks, and 500 mL of an aqueous solution containing U (U, CO = 10, 20, or 40 mg / L) was added to each flask. -1 (pH = 6). The system was continuously shaken at 150 rpm under a constant temperature of 25 ℃. 0.5 mL samples were taken at preset time points (0.5, 1, 2, 3, 5, 7, 10, 15, 20, 30, 40, 50, 70, and 100 h). The residual U concentration in the solution was determined using the azoarsine III colorimetric method and UV-Vis spectrophotometry, and the adsorption capacity per unit mass (g) of adsorbent at each time point was calculated accordingly. Figure 3 As shown, the composite membrane exhibits rapid and efficient uranium adsorption capacity at three initial concentrations. The adsorption process tends to reach equilibrium within 50 hours, with corresponding equilibrium adsorption capacities of 111.33, 224.47, and 332.58 mg g, respectively. -1 Further kinetic model fitting of the experimental data showed that the pseudo-second-order kinetic model had a much higher goodness of fit than the pseudo-first-order model, confirming that the adsorption process is mainly controlled by the chemisorption mechanism.

[0047] Example 4

[0048] To evaluate the renewability of the polyurethane composite membrane with embedded saponified cast macroporous poly(ammonia oxime) hydrogel particles prepared in Example 1 in practical applications, eight consecutive adsorption-desorption cycle experiments were conducted. A sample of the polyurethane composite membrane with embedded saponified cast macroporous poly(ammonia oxime) hydrogel particles was weighed and placed in 100 mL of an aqueous solution containing uranyl ions (CO = 20 mg / L). -1 The membrane was placed in a glass Erlenmeyer flask (pH = 6.0) and kept at 25°C and 150 rpm for 50 h to reach adsorption equilibrium. Then, a 0.5 mL sample was taken, and the remaining U concentration in the solution was determined by UV-Vis spectrophotometry using the azoarsine III colorimetric method, and the adsorption capacity was calculated. After adsorption, the membrane material was transferred to another Erlenmeyer flask containing 100 mL of 0.5 M HNO3 aqueous solution and shaken for 30 min at the same temperature and speed for desorption. A 0.5 mL sample was taken to determine the U concentration in the eluent, and the elution efficiency was calculated accordingly. After desorption, the membrane was repeatedly rinsed with deionized water until neutral and reused in the next adsorption-desorption cycle. The above process was repeated a total of 8 times. Figure 4As shown, the adsorption capacity of the composite membrane decreased slightly after the first cycle, but gradually stabilized from the second cycle onwards. After eight consecutive uses, its adsorption capacity for uranyl ions remained above 69% of the initial value, while the elution efficiency in each cycle was above 92%, indicating that uranyl ions could be released efficiently and the functional groups could be effectively regenerated.

[0049] Example 5

[0050] The antifouling performance of the polyurethane composite membrane with embedded saponified cast macroporous poly(xime) hydrogel particles prepared in Example 1 was evaluated. One precisely weighed sample of the polyurethane composite membrane with embedded saponified cast macroporous poly(xime) hydrogel particles was placed in a 100 mL glass Erlenmeyer flask, and 100 mL of a solution containing a fixed concentration of uranyl ions (U, CO = 20 mg / L) was added. -1 (pH = 6) and different concentrations of humic acid (HA, CO = 0, 5, 10, 15, 20 and 25 mg L / L) -1 An aqueous solution of azoarsine III was prepared. The system was subjected to isothermal shaking at 25°C and 150 rpm for 50 h for adsorption. Subsequently, a 0.5 mL sample was taken, and the concentration of residual U in the solution was determined by UV-Vis spectrophotometry using azoarsine III as the colorimetric reagent. The adsorption capacity of the membrane material was then calculated. Figure 5 As shown, the adsorption capacity of the composite membrane for uranyl ions decreases slowly with increasing HA concentration, indicating that humic acid has a certain degree of competitive or shielding effect on uranium adsorption. However, even at HA concentrations as high as 25 mg / L, the adsorption capacity of the composite membrane for uranium ions increases. -1 Even at relatively high levels in typical natural water bodies, the uranium adsorption capacity of the material can still be maintained at more than 67% of that of the control group without HA. This result fully demonstrates that the polyurethane composite membrane with embedded saponified cast macroporous poly(amine oxime) hydrogel particles has excellent resistance to organic pollution and can effectively enrich uranyl ions in real seawater or natural water bodies rich in humus.

[0051] Example 6

[0052] To investigate the selectivity of the polyurethane composite membrane with embedded saponified cast macroporous poly(ammonia oxime) hydrogel particles prepared in Example 1 for uranyl ions in a complex ionic environment, a simulated seawater competitive adsorption experiment was conducted. 0.5 pieces of the polyurethane composite membrane with embedded saponified cast macroporous poly(ammonia oxime) hydrogel particles were accurately weighed and placed in a 500 mL Erlenmeyer flask. 500 mL of a prepared simulated seawater solution (CO(U) = 330 μg / L) was added. -1 C0(V) = 150 μg L -1 CO(Fe) = 150 μg / L -1 CO(Co) = 55 μg / L -1 C0(Ni) = 100 μg L -1 C0(Cu) = 60 μg / L-1 C0(Zn) = 400 μg / L -1 C0(Pb) = 3 μg / L -1 C0(Na) = 10.06 × 10 6 μg L -1 C0(K) = 3.53 × 10 5 μg L -1 C0(Ca) = 4.01 × 10 5 μg L -1 C0(Mg) = 1.23 × 10⁻⁶ 6 μg L -1 The system was placed in a 25°C constant temperature water bath and continuously shaken at 150 rpm for 50 h. After adsorption, 0.1 mL of the supernatant was taken, diluted 50 times, and the remaining concentrations of U, V, Fe, Co, Ni, Cu, Zn, and Pb were simultaneously determined by ICP-MS, and the adsorption capacity of the material for each metal ion was calculated accordingly. Figure 6 As shown, the polyurethane composite membrane with embedded saponified cast macroporous poly(amine oxime) hydrogel particles exhibits a significant preferential adsorption capacity for uranyl ions in simulated seawater with high salinity and multiple ion coexistence, with a uranium adsorption capacity of 7.15 mg / g.

[0053] Example 7

[0054] The enrichment and extraction efficiency of uranyl ions by the polyurethane composite membrane with embedded saponified cast macroporous poly(ammonia oxime) hydrogel particles prepared in Example 1 was evaluated in a real seawater environment. Two polyurethane composite membranes with embedded saponified cast macroporous poly(ammonia oxime) hydrogel particles were accurately weighed and placed in several 100 mL glass Erlenmeyer flasks. Real seawater was added to each flask beforehand, and uranyl standard solutions of different concentrations were artificially added to make the initial total uranium concentrations 54, 104, 204, 504, 1004, and 2004 μg / L, respectively. -1 (The actual background uranium concentration in seawater was determined by ICP-MS to be 4 μg / L) -1 All Erlenmeyer flasks were continuously shaken at 150 rpm in a 25°C constant temperature water bath for 120 hours. After adsorption was complete, samples were taken and the residual uranium concentration in each system was determined by ICP-MS. The adsorption efficiency was calculated accordingly, and the results are as follows. Figure 7 As shown. The results show that the polyurethane composite membrane of saponified cast macroporous poly(amine oxime) hydrogel particles developed in this invention can withstand low to medium concentrations (54~2004 μg / L) in complex real seawater environments. -1 The uranyl ions exhibit excellent affinity and high extraction efficiency, with uranium removal rates exceeding 99%.

[0055] Example 8

[0056] The uranium extraction performance of the polyurethane composite membrane with embedded saponified cast macroporous poly(ethyleneamine oxime) hydrogel particles prepared in Example 1 was evaluated in real seawater. 0.5 pieces of this composite membrane were accurately weighed and placed in a glass tank containing 10 L of pre-filtered real seawater (the background uranium concentration in the seawater was determined to be 4 μg / L by ICP-MS). -1 The material was subjected to dynamic adsorption with continuous stirring at room temperature. At days 1, 3, 5, 7, 10, 15, and 20 of adsorption, 1 mL seawater samples were taken from the system, and the residual uranium concentration was determined by ICP-MS. The uranium adsorption capacity of the material over time was then calculated. Figure 8 It is evident that, within a 15-day adsorption period, the composite membrane achieved a cumulative adsorption capacity of 6.17 mg g for uranium in 10 L of real seawater. -1 During the 20-day adsorption period, the composite membrane achieved a cumulative adsorption capacity of 6.59 mg g for uranium in 10 L of real seawater. -1 This result fully demonstrates that the polyurethane composite membrane developed in this invention, with its highly functional saponified cast macroporous poly(amine oxime) hydrogel microparticles, exhibits excellent affinity and selectivity for uranyl ions in real seawater, and has the potential for efficient extraction of uranium resources in actual marine environments.

[0057] Example 9

[0058] The uranium extraction performance of the polyurethane composite membrane with embedded saponified cast macroporous poly(ethyleneamine oxime) hydrogel particles prepared in Example 1 was evaluated in real seawater. 0.5 pieces of this composite membrane were accurately weighed and placed in a circulation device containing 50 L of pre-filtered real seawater (the background uranium concentration in the seawater was determined to be 4 μg / L by ICP-MS). -1 The system was continuously cyclically induced to undergo dynamic adsorption at room temperature. At days 5, 10, 15, 20, and 25 of adsorption, 1 mL seawater samples were taken from the system, and the residual uranium concentration was determined by ICP-MS. The uranium adsorption capacity of the material over time was then calculated. Figure 9 It is evident that, within a 25-day adsorption period, the composite membrane achieved a cumulative adsorption capacity of 9.14 mg g for uranium in 50 L of real seawater. -1 This result further demonstrates that the polyurethane composite membrane developed in this invention, with its highly functional saponified cast macroporous poly(amine oxime) hydrogel microparticles, exhibits extremely ideal affinity and selectivity for uranium ions in real seawater, and has the potential for efficient extraction of uranium resources in actual marine environments.

[0059] In summary, the polyurethane composite membrane with embedded saponified cast macroporous poly(amine oxime) hydrogel microparticles obtained by the preparation method provided in this invention exhibits excellent comprehensive performance in uranyl ion adsorption. This material not only possesses high adsorption capacity but also demonstrates extremely strong affinity and selectivity for uranyl ions. Even in simulated and real seawater systems containing multiple competing metal ions, it can efficiently enrich and remove uranium, maintaining ideal levels of both adsorption capacity and removal rate. Furthermore, the composite membrane exhibits good stability and reusability in multiple adsorption-desorption cycles. These advantages effectively overcome the three major bottlenecks commonly found in traditional seawater uranium extraction materials—poor selectivity for uranyl ions in real seawater, low adsorption capacity, and poor recyclability. Therefore, this material demonstrates significant technological advancement and engineering feasibility in practical applications, possessing the potential for large-scale, sustainable seawater uranium extraction projects.

Claims

1. A method for preparing a polyurethane composite membrane with embedded saponified cast macroporous poly(amine oxime) hydrogel particles, characterized in that, Includes the following steps: (1) Lauric acid was added to the alkaline aqueous solution of polyamine oxime for saponification reaction, then glutaraldehyde was added, mixed evenly, and cooled to obtain solidified solid. The water in the obtained solidified solid was removed to obtain shrink solidified solid. (2) After the shrinkage solids are crushed and ground, the resulting particles are extracted with organic solvents to remove laurates and dried to obtain saponified cast macroporous polyamine oxime hydrogel particles. (3) Mix the saponified macroporous polyamine oxime hydrogel particles and polyurethane solution evenly, put the resulting suspension into a mold and immerse it in water. The non-solvent-induced phase separation process causes the suspension to solidify and be demolded to obtain a composite membrane. Wash and dry to obtain a polyurethane composite membrane with saponified macroporous polyamine oxime hydrogel particles embedded in the product.

2. The preparation method according to claim 1, characterized in that, In step (1), the polyamine oxime alkaline aqueous solution is obtained by dissolving the polyamine oxime polymer in an alkaline aqueous solution. The alkaline aqueous solution is a solution of NaOH and / or KOH with a concentration of 0.01-0.1 g / mL. Preferably, the concentration of NaOH and / or KOH is 0.02-0.04 g / mL. Furthermore, the ratio of polyamine oxime polymer to alkaline aqueous solution is 1 g: 10-20 mL.

3. The preparation method according to claim 1, characterized in that, In step (1), the mass ratio of poly(ammonia oxime) polymer powder, lauric acid, and glutaraldehyde is 1g:1-2g:0.1-0.

3.

4. The preparation method according to claim 1, characterized in that, In step (1), the mass ratio of poly(ammonia oxime) polymer powder, lauric acid, and glutaraldehyde is 1g:1.4-1.6g:0.2-0.25; furthermore, the saponification reaction temperature is 20-60℃, preferably 30-50℃; the cooling is to 10-25℃; the removal of solidified moisture is to allow it to evaporate naturally at room temperature.

5. The preparation method according to claim 1, characterized in that, In step (1), the preparation method of poly(ammonia oxime) polymer includes the following steps: NH2OH·HCl, Na2CO3 and NaOH are reacted in DMF solvent at 30-125℃, preferably 50-90℃, then polyacrylonitrile is added, and the reaction is continued at this temperature for 12-24h. NH2OH·HCl, Na2CO3 and NaOH are then added, and the reaction is continued at this temperature for 12-24h. The resulting mixture is poured into water to obtain a white flocculent precipitate, which is filtered and dried to obtain the poly(ammonia oxime) polymer. Further, the mass ratio of NH2OH·HCl, Na2CO3, NaOH and polyacrylonitrile is 5-50:5-40:1-10:3-30, preferably 30-40:20-30:5-8:10-15. Even further, the amount of NH2OH·HCl, Na2CO3 and NaOH added accounts for 20-30 wt% of their respective raw materials. The weight-average molecular weight of polyacrylonitrile ranges from 150,000 to 500,000.

6. The preparation method according to claim 1, characterized in that, In step (2), the particle size after crushing and grinding is 20-80 μm; the organic solvent is selected from at least one of ethanol and propanol; the organic solvent extraction is preferably Soxhlet extraction.

7. The preparation method according to claim 1, characterized in that, In step (3), the polyurethane is a polyether-type polyurethane, such as at least one of BASF 1185A, BASF 1175AU, BASF 1180A, Covestro 785A, Covestro 790A, and UZ3-71D; the concentration of the polyurethane solution is 0.1-0.5 g / mL, preferably 0.2-0.3 g / mL, and the solvent is selected from at least one of N,N-dimethylacetamide, N,N-dimethylformamide, and dimethyl sulfoxide.

8. The preparation method according to claim 1, characterized in that, In step (3), the mass ratio of macroporous polyamine oxime hydrogel particles and polyurethane in the saponification casting is 1:0.5-1.5, preferably 1:0.75-1.

9. A composite membrane, characterized in that, It is prepared by the method described in any one of claims 1-8.

10. The application of the composite membrane prepared by the method according to any one of claims 1-8 in the enrichment and / or extraction of uranyl ions in water; further, the water is seawater, and the concentration of uranyl ions in the water is 1-3000 μg / L. -1 Preferably 1-100 μg / L -1 .

Images