Alginic acid-polyacrylic acid composite ball coated with wax-cast macroporous polyamidoxime hydrogel particles as well as preparation method and application of alginic acid-polyacrylic acid composite ball

Abstract

The invention discloses an alginic acid-polyacrylic acid composite ball coated with wax-cast macroporous polyamidoxime hydrogel particles and a preparation method and application of the alginic acid-polyacrylic acid composite ball. The preparation method comprises the steps that firstly, molten wax serves as an oil phase, a polyamidoxime aqueous alkali solution is added, and stirring is conducted in a heating state to obtain uniform molten liquid; cooling the molten liquid to room temperature to obtain a solidified body, and naturally volatilizing at room temperature to completely remove moisture in the solidified body to obtain a shrunk solidified body; the contracted and solidified body is crushed, ground and dewaxed to obtain wax-cast polyamidoxime hydrogel particles with macroporous structures; the obtained wax-cast polyamidoxime hydrogel particles are coated in alginic acid-polyacrylic acid balls, so that the particles can be conveniently applied to extraction of uranium from seawater and recycling. The alginic acid-polyacrylic acid composite ball coated with the wax-cast macroporous polyamidoxime hydrogel particles has good adsorption capacity on uranyl ions, shows very high affinity and selectivity and good reusability, and can be applied to large-scale projects for extracting uranium from seawater.

Description

Technical Field

[0001] This invention relates to the fields of environmental energy chemistry and new materials technology, and more specifically, to an alginate-polyacrylic acid composite sphere coated with wax-cast macroporous polyamine oxime hydrogel particles, its preparation method and application. Background Technology

[0002] my country's uranium reserves are not abundant, with proven onshore uranium reserves of only about 200,000 tons, which is insufficient to meet the needs of my country's nuclear power development over the next 10-15 years. Meanwhile, high-quality uranium resources globally are concentrated in the hands of a few Western countries. Therefore, uranium resource supply has become a significant constraint on the large-scale development of nuclear power in my country. Developing unconventional uranium resources is of great strategic importance to ensure the sustainable development of my country's nuclear power industry.

[0003] The global uranium reserves in seawater are estimated at 4.5 billion tons, thousands of times greater than the proven uranium reserves on land, making it an inexhaustible resource. Currently, seawater uranium extraction is considered one of the most challenging yet most rewarding nuclear fuel resource development projects, and has even been named one of the "seven world-changing chemical separation technologies" by *Nature*. Research on seawater uranium extraction in my country began in the 1960s. In January 1967, the "671 Project Group," an inter-university project, was established based on the "Seawater Uranium Extraction" project group at East China Normal University. Unfortunately, due to various reasons, my country's seawater uranium extraction research was interrupted for a long period. Since 2011, with my country's positioning for future energy development and its focus on marine resource development, several domestic research institutions have successively carried out the design and development of materials for seawater uranium extraction in recent years.

[0004] Currently, there is a high level of global attention and efforts to advance research on seawater uranium extraction technology. However, the application of this technology still faces some insurmountable bottlenecks. Firstly, the poor uranium extraction capacity of the developed adsorption materials in real seawater is one of the most critical issues. Existing seawater uranium extraction materials have a theoretical adsorption capacity of over 1000 mg U / g, but their uranium extraction efficiency in real seawater is less than 1% of that. This is because uranium in seawater primarily exists as the highly stable uranyl tricarbonate complex ion [UO2(CO3)3]. 4- The presence of uranium in seawater, at extremely low concentrations (approximately 3.3 μg / L), makes it difficult for adsorbents to capture. Furthermore, the high concentrations of coexisting metal ions in seawater significantly reduce the material's adsorption capacity for uranium. Secondly, the overall cost of uranium extraction from seawater is high. Current assessments indicate that the cost of seawater uranium extraction is still far higher than that of uranium extraction from terrestrial mines, rendering it commercially unfeasible. Aside from the construction cost of the uranium extraction platform, the structural stability of the adsorbent material—whether it can withstand the challenges of the marine environment and maintain its structural stability and adsorption performance after a certain number of elution and regeneration processes—directly affects the cost of seawater uranium extraction.

[0005] Given the technical problems of low adsorption efficiency, high production cost, and difficulty in recycling and reuse of existing uranium extraction materials, there is an urgent need to develop a uranium extraction material with high selectivity, high adsorption capacity, high adsorption rate, high affinity, and reusability. Summary of the Invention

[0006] The purpose of this invention is to overcome the above-mentioned defects in the prior art and provide an alginate-polyacrylic acid composite sphere coated with wax-cast macroporous poly(ammamine oxime) hydrogel particles, its preparation method, and its application. The alginate-polyacrylic acid composite sphere coated with wax-cast macroporous poly(ammamine oxime) hydrogel particles obtained by the preparation method of this invention has ideal adsorption capacity, selectivity, and affinity for uranium ions in simulated seawater and real seawater, thereby significantly optimizing and improving the seawater uranium extraction performance of the material and reducing the cost of use, which can provide technical reserves for the long-term development of my country's seawater uranium extraction industry.

[0007] To achieve the above objectives, the technical solution of the present invention is as follows:

[0008] A method for preparing alginate-polyacrylic acid composite spheres coated with wax-cast macroporous polyamine oxime hydrogel particles includes the following steps:

[0009] (1) Dissolve NH2OH·HCl in a solvent, then add Na2CO3 and NaOH to mix, and add polyacrylonitrile to react at 25℃~100℃ for 3h~72h to obtain a mixed solution;

[0010] (2) Add NH2OH·HCl, Na2CO3 and NaOH to the mixture and react at 25℃~100℃ for 3h~72h. After cooling the resulting reaction mixture to room temperature, pour it into deionized water to obtain flocculent precipitate. Collect the precipitate by filtration. Wash the precipitate until neutral and dry it to obtain polyamine oxime polymer powder.

[0011] (3) Dissolve the polyamine oxime polymer powder in an alkaline aqueous solution of NaOH, melt the wax taken from the candle at 50℃~90℃, then pour the obtained alkaline polyamine oxime aqueous solution into the melted wax and mix at 50℃~90℃, cool the obtained melt to room temperature to obtain a solidified solid, and allow it to evaporate naturally at room temperature to remove the water in the solidified solid to obtain a shrink solidified solid.

[0012] (4) The shrinkage solids are crushed and ground in sequence to obtain fine particles; then, the fine particles are extracted with acetone as solvent for 6h to 72h to remove wax, and dried to obtain wax-cast macroporous polyamine oxime hydrogel particles.

[0013] (5) Sodium alginate was dissolved in deionized water and the wax-cast macroporous polyamine oxime hydrogel particles were added and mixed at room temperature to obtain an alginate-wax-cast macroporous polyamine oxime hydrogel particle suspension.

[0014] (6) Dissolve polyacrylic acid and CaCl2 in deionized water to obtain a curing solution;

[0015] (7) The alginate-wax-cast macroporous polyamine oxime hydrogel particle suspension was added dropwise to the curing liquid and cured under stirring for 0.5h to 10h to obtain small balls. Then, the balls were washed, frozen and freeze-dried in sequence to obtain the alginate-polyacrylic acid composite balls coated with wax-cast macroporous polyamine oxime hydrogel particles.

[0016] Optionally, in step (1), the solvent includes DMF; the mixing temperature is 25℃~75℃; and the mixing time is 0.5h~5h.

[0017] Optionally, in step (1), the mass ratio of NH2OH·HCl, Na2CO3, NaOH and polyacrylonitrile is (2-20):(3-50):(0.2-20):(2-20); the mass-volume ratio of NH2OH·HCl and DMF is (2-20)g:(50-250)mL.

[0018] Optionally, in step (1), the average molecular weight of polyacrylonitrile is 150,000.

[0019] Optionally, in step (2), the mass ratio of the added NH2OH·HCl, Na2CO3 and NaOH is (0.3~15):(0.3~20):(0.1~10).

[0020] Optionally, in step (3), the mass ratio of the poly(ammoxime) polymer powder to the wax is (0.05-50):(0.25-25).

[0021] Optionally, in step (3), the concentration of the alkaline aqueous solution of NaOH is 0.1% to 10%.

[0022] Optionally, in step (3), the mass-to-volume ratio of the poly(ammonia oxime) polymer powder to the alkaline aqueous solution of NaOH is (0.05-50) g: (0.5-50) mL.

[0023] Optionally, in step (3), the solidified solid is white; the shrinkage solidified solid is pale yellow.

[0024] Optional, the candle is a white candle.

[0025] Optionally, in step (4), the particle size of the fine particles is 10μm to 100μm.

[0026] Optionally, in step (5), the mass-to-volume ratio of sodium alginate, deionized water, and wax-cast macroporous polyamine oxime hydrogel particles is (0.04–4) g: (4–400) mL: (0.2–20) g.

[0027] Optionally, in step (6), the mass-to-volume ratio of polyacrylic acid, CaCl2 and deionized water is (0.2-10) g: (0.4-20) g: (50-2000) mL; the average molecular weight of polyacrylic acid is 450,000.

[0028] Optionally, in step (7), the volume ratio of the alginate-wax-cast macroporous polyamine oxime hydrogel particle suspension to the curing liquid is (4-400):(50-2000).

[0029] The present invention also discloses an alginate-polyacrylic acid composite sphere coated with wax-cast macroporous polyamine oxime hydrogel particles prepared by the preparation method described above.

[0030] The present invention also discloses an alginate-polyacrylic acid composite sphere coated with wax-cast macroporous poly(ammonia oxime) hydrogel particles prepared by the preparation method described above, or the application of the alginate-polyacrylic acid composite sphere coated with wax-cast macroporous poly(ammonia oxime) hydrogel particles as described above in the enrichment and / or extraction of uranyl ions.

[0031] Optionally, the alginate-polyacrylic acid composite spheres coated with wax-cast macroporous polyamine oxime hydrogel particles can be used as adsorbent materials to enrich and / or extract low to medium concentrations of uranyl ions from simulated and real seawater.

[0032] Optionally, the concentration of the uranyl ion is 54.1 ppb to 1004.1 ppb.

[0033] Optionally, the alginate-polyacrylic acid composite spheres coated with wax-cast macroporous polyamine oxime hydrogel particles exhibit ideal affinity and selectivity for uranyl ions, and have high removal rates and adsorption capacities for uranyl ions in both simulated seawater and real seawater containing multiple coexisting ions.

[0034] Optionally, the concentration of U in the real seawater is approximately 4.1 ppb; the concentrations of U (330 ppb), V (200 ppb), Fe (150 ppb), Co (55 ppb), Ni (100 ppb), Cu (60 ppb), Zn (400 ppb), and Pb (3 ppb) in the prepared simulated seawater are all approximately 100 times the concentration levels of the real seawater, and Na (10.06 × 10⁻⁶) is also present. 6 ppb), Mg(1.23×10 6 ppb), K(3.53×10 5ppb), Ca(4.01×10 5 The ppb concentration level is the same as that of real seawater.

[0035] Implementing the embodiments of the present invention will have the following beneficial effects:

[0036] This invention uses inexpensive and readily available candle wax as raw material, and uses the molten wax as the oil phase to regulate the microstructure of poly(ammonia) oxime dissolved in the aqueous phase, thereby obtaining wax-cast poly(ammonia) oxime hydrogel particles with a macroporous structure. Compared with the microporous structure, the macroporous structure of this hydrogel particle is more conducive to the mass transfer of seawater and the adsorption of uranyl ions. Encapsulating the wax-cast poly(ammonia) oxime hydrogel particles in alginate-polyacrylic acid spheres facilitates their application in seawater uranium extraction and recycling.

[0037] Experimental results show that the alginate-polyacrylic acid composite spheres coated with wax-cast macroporous poly(amine oxime) hydrogel particles prepared in this invention have an ideal adsorption capacity for uranyl ions. Simultaneously, this material exhibits high affinity and selectivity for uranyl ions, demonstrating ideal adsorption capacity and removal rate for uranyl ions in both simulated and real seawater containing multiple coexisting metal ions. Furthermore, this material exhibits good reusability during uranyl ion adsorption. This material significantly improves upon the bottleneck problems of poor selectivity, low adsorption capacity, and poor reusability of uranium extraction materials in real seawater, showing great application potential and prospects in large-scale seawater uranium extraction projects. Attached Figure Description

[0038] Figure 1 The results of the dynamic adsorption and kinetic model fitting of uranyl ions by alginate-polyacrylic acid composite spheres coated with wax-cast macroporous polyamine oxime hydrogel particles in Example 1 of this invention under three different initial concentrations (U, 10, 20, 40 ppm).

[0039] Figure 2 The alginate-polyacrylic acid composite spheres of the wax-cast macroporous polyamine oxime hydrogel particles described in Example 1 of this invention exhibit uranyl ion (U, C) ion retention during five adsorption-desorption cycles. o The adsorption capacity and desorption efficiency results (20 ppm) were obtained.

[0040] Figure 3 The adsorption results of the alginate-polyacrylic acid composite spheres coated with wax-cast macroporous polyamine oxime hydrogel particles in simulated seawater containing multiple competing adsorption ions are shown in Example 1 of this invention.

[0041] Figure 4 The alginate-polyacrylic acid composite spheres of Embodiment 1 of this invention, which are coated with wax-cast macroporous polyamine oxime hydrogel particles, are in the presence of different concentrations of humic acid (HA, C). oUranyl ions (U, C = 0, 5, 10, 15, 20, 25 ppm) o The adsorption capacity of U in a solution of 20 ppm (=20 ppm) is calculated.

[0042] Figure 5 The results of the adsorption and removal rates of U by the alginate-polyacrylic acid composite spheres coated with wax-cast macroporous polyamine oxime hydrogel particles of Example 1 of the present invention in real seawater with different concentrations of uranyl ions (U, 50, 100, 200, 500, 1000 ppb) added in standard form are shown.

[0043] Figure 6 The results show the adsorption capacity of alginate-polyacrylic acid composite spheres coated with wax-cast macroporous polyamine oxime hydrogel particles in Example 1 of this invention for U in 10L of real seawater over 15 days. Detailed Implementation

[0044] The present invention will be further described below with reference to specific embodiments, but this does not limit the present invention in any way.

[0045] Example 1

[0046] A method for preparing alginate-polyacrylic acid composite spheres of coated wax-cast macroporous polyamine oxime hydrogel particles that selectively enrich and extract uranyl ions includes the following steps:

[0047] (1) Dissolve 11.46g NH2OH·HCl in 100mL DMF at 75℃, gradually add 9.0g Na2CO3 and 2.28g NaOH and continue stirring for 2h, then add 6.0g polyacrylonitrile and stir at 65℃ for 24h. After the reaction is completed, add 3.98g NH2OH·HCl, 3.6g Na2CO3 and 0.812g NaOH to the mixture and continue stirring at 65℃ for 24h. Finally, pour the reaction mixture cooled to room temperature into deionized water to obtain flocculent precipitate. Filter the precipitate, wash it until neutral, and dry it to obtain poly(amine oxime) polymer powder.

[0048] (2) Dissolve 0.75g of the poly(xime) polymer powder obtained in step (1) in 5mL of an alkaline aqueous solution containing 50mg NaOH. Melt 1.5g of wax from a white candle at 75°C. Then pour the obtained alkaline poly(xime) aqueous solution into the melted wax and stir continuously at 75°C until a homogeneous melt is obtained. Cool the melt to room temperature to obtain a white solid. Remove the water from the solid by natural evaporation at room temperature to obtain a hard, pale yellow shrinkage solid. Crush and grind the obtained shrinkage solid to obtain fine particles (50μm in diameter). Then, use acetone as a solvent to Soxhlet extract the obtained fine particles for 24h to remove the wax. Dry the obtained material to obtain wax-cast macroporous poly(xime) hydrogel particles.

[0049] (3) Dissolve 400 mg of sodium alginate in 40 mL of deionized water, add 1.6 g of wax-cast macroporous polyamine oxime hydrogel particles obtained in step (2), and stir continuously at room temperature until a uniform alginate-wax-cast macroporous polyamine oxime hydrogel particle suspension is obtained.

[0050] (4) Dissolve 1.44g of polyacrylic acid and 2.52g of CaCl2 in 400mL of deionized water and stir until homogeneous to obtain a curing solution.

[0051] (5) 40 mL of the alginate-wax-cast macroporous polyamine oxime hydrogel particle suspension obtained in step (3) was dripped into 400 mL of the curing solution obtained in step (4) using a syringe; after curing for 2 h under stirring, small balls were obtained, washed with deionized water, then rapidly frozen in liquid nitrogen, and freeze-dried by a freeze dryer to finally obtain alginate-polyacrylic acid composite balls coated with wax-cast macroporous polyamine oxime hydrogel particles.

[0052] Example 2

[0053] The dynamic adsorption of the alginate-polyacrylic acid composite spheres coated with wax-cast macroporous poly(ammonia oxime) hydrogel particles prepared in Example 1 was evaluated. Three 20 mg portions of the alginate-polyacrylic acid composite spheres coated with wax-cast macroporous poly(ammonia oxime) hydrogel particles prepared in Example 1 were accurately weighed and dispersed into 500 mL glass Erlenmeyer flasks containing uranyl ion aqueous solutions of three different initial concentrations (U, 10, 20, and 40 ppm; pH = 7). The Erlenmeyer flasks were placed in a constant temperature water bath at 25°C and continuously shaken at a speed of 150 rpm. Starting from the start of oscillation timing, 0.5 mL of solution was taken from the Erlenmeyer flask at time points of 1, 2, 3, 5, 7, 10, 15, 20, 30, 40, 50, 60, 80, 100, 120, 150, and 180 hours. Using azoarsin III as the colorimetric reagent, the remaining concentration of uranyl ions in the solution was determined by UV-Vis spectroscopy. The adsorption capacity of the adsorbent material for uranyl ions at the aforementioned time points was then calculated. The final dynamic adsorption and kinetic model fitting results are shown below. Figure 1 As shown. By Figure 1 It is evident that the alginate-polyacrylic acid composite spheres coated with wax-cast macroporous poly(ammidine oxime) hydrogel particles of the present invention possess an ideal adsorption capacity for uranyl ions. In the above three aqueous solutions of uranyl ions with different initial concentrations, adsorption equilibrium was reached within 150 h, with equilibrium adsorption capacities for U reaching as high as 224.3, 450.9, and 657.9 mg / g, respectively. Kinetic model fitting indicates that the adsorption of uranyl ions by the alginate-polyacrylic acid composite spheres coated with wax-cast macroporous poly(ammidine oxime) hydrogel particles of the present invention conforms more closely to the pseudo-second-order kinetic model.

[0054] Example 3

[0055] Accurately weigh 4 mg of the alginate-polyacrylic acid composite spheres coated with wax-cast macroporous polyamine oxime hydrogel particles prepared in Example 1 and place them into a 100 mL solution of uranyl ion (U, C) aqueous solution. o=20 ppm; pH=7) in a glass Erlenmeyer flask. The Erlenmeyer flask was placed in a constant temperature water bath at 25℃ and continuously shaken at 150 rpm for 150 h. After that, 0.5 mL of solution was taken out and the residual concentration of uranyl ions in the solution was determined by UV-Vis spectroscopy using azoarsin III as the colorimetric reagent, so as to calculate the adsorption capacity of the adsorbent material for uranyl ions. After the adsorption was completed, the alginate-polyacrylic acid composite spheres coated with wax-cast macroporous poly(amine oxime) hydrogel particles were taken out and placed in a glass Erlenmeyer flask containing 100 mL of 0.5 M HNO3 aqueous solution. The Erlenmeyer flask was placed in a constant temperature water bath at 25℃ and continuously shaken at 150 rpm for 2 h. After that, 0.5 mL of solution was taken out and the concentration of uranyl ions in the solution was determined by UV-Vis spectroscopy using azoarsin III as the colorimetric reagent, so as to calculate the elution efficiency of uranyl ions. After elution, the alginate-polyacrylic acid composite spheres coated with wax-cast macroporous polyamine oxime hydrogel particles were removed, washed with deionized water until neutral, and the adsorption-elution experiment was repeated according to the above steps. This process was repeated for a total of 5 cycles. The adsorption capacity and elution efficiency results are as follows: Figure 2 As shown. By Figure 2 It can be seen that the adsorption capacity of the prepared material only decreased to a low extent after being reused 5 times, and good elution efficiency was obtained in all cases. This indicates that the alginate-polyacrylic acid composite spheres coated with wax-cast macroporous polyamine oxime hydrogel particles prepared in this invention have good reusability for adsorbing uranyl ions.

[0056] Example 4

[0057] 4 mg of the alginate-polyacrylic acid composite spheres coated with wax-cast macroporous poly(amine oxime) hydrogel particles prepared in Example 1 were accurately weighed and dispersed into 500 mL of simulated seawater containing a variety of competing adsorption ions (U, 330 ppb; V, 200 ppb; Fe, 150 ppb; Co, 55 ppb; Ni, 100 ppb; Cu, 60 ppb; Zn, 400 ppb; Pb, 3 ppb; Na, 10.06 × 10⁻⁶). 6 ppb; Mg, 1.23 × 10⁻⁶ 6 ppb; K, 3.53 × 10 5 ppb; Ca, 4.01 × 10⁻⁶ 5 The solution was placed in a glass Erlenmeyer flask containing ppb, and then continuously shaken at 150 rpm for 150 h in a constant temperature water bath at 25℃. 0.1 mL of the solution was then taken out, diluted 50 times, and the remaining concentrations of U, V, Fe, Co, Ni, Cu, Zn, and Pb were simultaneously determined by ICP-MS. The adsorption capacity of the adsorbent material for these elements was then calculated. The results are as follows: Figure 3 As shown. By Figure 3It is evident that the alginate-polyacrylic acid composite spheres coated with wax-cast macroporous polyamine oxime hydrogel particles prepared in this invention exhibit good affinity and adsorption capacity for uranyl ions in the prepared simulated seawater, with an adsorption capacity for U as high as 8.23 ​​mg / g, demonstrating ideal performance.

[0058] Example 5

[0059] The antifouling performance of the alginate-polyacrylic acid composite spheres coated with wax-cast macroporous polyamine oxime hydrogel particles prepared in Example 1 was evaluated. 4 mg of the alginate-polyacrylic acid composite spheres coated with wax-cast macroporous polyamine oxime hydrogel particles prepared in Example 1 were accurately weighed and placed into 100 mL of a solution containing humic acid (HA, C). o Uranyl ion aqueous solutions (U, C = 0, 5, 10, 15, 20, 25 ppm) o =20ppm; pH=7) in a glass Erlenmeyer flask. The flask was placed in a constant temperature water bath at 25℃ and continuously shaken at 150 rpm for 150 h. 0.5 mL of the solution was then taken out, and the remaining concentration of uranyl ions in the solution was determined by UV-Vis spectroscopy using azoarsin III as the colorimetric reagent, thereby calculating the adsorption capacity of the adsorbent material for uranyl ions. Figure 4 It can be seen that the adsorption capacity of the prepared material for U decreases to a certain extent with the increase of HA concentration, but it no longer decreases when the HA concentration is higher than 20 ppm, indicating that the alginate-polyacrylic acid composite spheres coated with wax-cast macroporous polyamine oxime hydrogel particles prepared in this invention have good anti-fouling properties.

[0060] Example 6

[0061] The enrichment and extraction efficiency of uranyl ions by alginate-polyacrylic acid composite spheres coated with wax-cast macroporous poly(ammonia oxime) hydrogel particles prepared in Example 1 was evaluated in a real seawater environment. 25 mg of the alginate-polyacrylic acid composite spheres coated with wax-cast macroporous poly(ammonia oxime) hydrogel particles prepared in Example 1 were accurately weighed and dispersed into 100 mL of real seawater containing standard added uranyl ions (U, 50, 100, 200, 500, 1000 ppb) (the original U concentration in the seawater was determined to be 4.1 ppb by ICP-MS). The flasks were placed in a constant temperature water bath at 25°C and continuously shaken at 150 rpm for 240 h. Subsequently, the concentration of residual U in the real seawater was determined by ICP-MS. The final residual U concentration and adsorption efficiency are shown below. Figure 5 As shown. By Figure 5 It is known that the alginate-polyacrylic acid composite spheres coated with wax-cast macroporous polyamine oxime hydrogel particles prepared in this invention have good affinity and extraction effect on medium and low concentrations of uranyl ions (U, 4.1~1004.1ppb) in complex seawater environments, and the final extraction efficiency of uranyl ions is above 95%.

[0062] Example 7

[0063] The uranium extraction performance of the alginate-polyacrylic acid composite spheres coated with wax-cast macroporous poly(ammonia oxime) hydrogel particles prepared in Example 1 was evaluated in real seawater. 4 mg of the alginate-polyacrylic acid composite spheres coated with wax-cast macroporous poly(ammonia oxime) hydrogel particles prepared in Example 1 was accurately weighed and placed in a glass jar containing 10 L of filtered real seawater (the initial U concentration in the seawater was determined to be 4.1 ppb by ICP-MS), and stirred for adsorption at room temperature. On days 3, 5, 7, 10, and 15, 2 mL of seawater was taken from the glass jar, and the concentration of remaining U in the real seawater was determined by ICP-MS. The final adsorption capacity of the alginate-polyacrylic acid composite spheres coated with wax-cast macroporous poly(ammonia oxime) hydrogel particles for U was obtained as follows: Figure 6 As shown. By Figure 6 It is known that the alginate-polyacrylic acid composite spheres coated with wax-cast macroporous polyamine oxime hydrogel particles prepared in this invention achieved an adsorption capacity of 4.79 mg g of U in 10 L of real seawater within 15 days. -1 This further demonstrates that the material has good affinity and selectivity for uranyl ions, and can be applied to the efficient extraction of uranyl ions from real seawater.

[0064] In summary, the alginate-polyacrylic acid composite spheres coated with wax-cast macroporous poly(amine oxime) hydrogel particles prepared by the method of this invention exhibit ideal adsorption capacity for uranyl ions. Simultaneously, this material demonstrates extremely high affinity and selectivity for uranyl ions, exhibiting ideal adsorption capacity and removal rate for uranyl ions in both simulated and real seawater containing multiple coexisting metal ions. Furthermore, this material demonstrates good reusability during the uranyl ion adsorption process. This material significantly improves upon the bottleneck problems of poor selectivity, low adsorption capacity, and poor reusability of uranium extraction materials in real seawater, and can be applied to large-scale seawater uranium extraction projects.

[0065] The embodiments described above are merely illustrative of several implementations of the present invention, and while the descriptions are specific and detailed, they should not be construed as limiting the scope of the patent application. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of the present invention, and these all fall within the scope of protection of the present invention. Therefore, the scope of protection of this patent should be determined by the appended claims.

Claims

1. A method for preparing alginate-polyacrylic acid composite beads coated with wax-cast macroporous polyaminoxide hydrogel particles, characterized by, Includes the following steps: (1) Dissolve NH2OH·HCl in a solvent, then add Na2CO3 and NaOH to mix, and add polyacrylonitrile to react at 25℃~100℃ for 3h~72h to obtain a mixed solution; (2) Add NH2OH·HCl, Na2CO3 and NaOH to the mixture and react at 25℃~100℃ for 3h~72h. After cooling the resulting reaction mixture to room temperature, pour it into deionized water to obtain flocculent precipitate. Collect the precipitate by filtration, wash the precipitate until neutral, dry it and obtain polyamine oxime polymer powder. (3) Dissolve the polyamine oxime polymer powder in an alkaline aqueous solution of NaOH, melt the wax taken from the candle at 50℃~90℃, then pour the obtained alkaline polyamine oxime aqueous solution into the melted wax and mix at 50℃~90℃, cool the obtained melt to room temperature to obtain a solidified solid, and allow it to evaporate naturally at room temperature to remove the water in the solidified solid to obtain a shrink solidified solid. (4) The shrinkage solids are crushed and ground in sequence to obtain fine particles; then, the fine particles are extracted with acetone as solvent for 6h to 72h to remove wax, and dried to obtain wax-cast macroporous polyamine oxime hydrogel particles. (5) Sodium alginate was dissolved in deionized water and the wax-cast macroporous polyamine oxime hydrogel particles were added and mixed at room temperature to obtain an alginate-wax-cast macroporous polyamine oxime hydrogel particle suspension. (6) Dissolve polyacrylic acid and CaCl2 in deionized water to obtain a curing solution; (7) The alginate-wax-cast macroporous polyamine oxime hydrogel particle suspension was added dropwise to the curing liquid and cured under stirring for 0.5h to 10h to obtain small balls. Then, the balls were washed, frozen and freeze-dried in sequence to obtain the alginate-polyacrylic acid composite balls coated with wax-cast macroporous polyamine oxime hydrogel particles.

2. The preparation method according to claim 1, characterized in that, In step (1), the solvent includes DMF; The mixing temperature is 25℃~75℃; the mixing time is 0.5h~5h; The mass ratio of NH2OH·HCl, Na2CO3, NaOH and polyacrylonitrile is (2~20):(3~50):(0.2~20):(2~20); The mass-to-volume ratio of NH2OH·HCl to DMF is (2-20) g : (50-250) mL; The average molecular weight of polyacrylonitrile is 150,000.

3. The preparation method according to claim 1, characterized in that, In step (2), the mass ratio of the added NH2OH·HCl, Na2CO3 and NaOH is (0.3~15):(0.3~20):(0.1~10).

4. The preparation method according to claim 1, characterized in that, In step (3), the mass ratio of poly(ammonia oxime) polymer powder to wax is (0.05-50):(0.25-25); The concentration of the alkaline aqueous solution of NaOH is 0.1% to 10%. The mass-to-volume ratio of poly(ammonia oxime) polymer powder to alkaline aqueous solution of NaOH is (0.05–50) g ​​: (0.5–50) mL; The solidified solid is white; the shrunken solidified solid is pale yellow; the candle is a white candle.

5. The preparation method according to claim 1, characterized in that, In step (4), the particle size of the fine particles is 10μm to 100μm; In step (5), the mass-to-volume ratio of sodium alginate, deionized water, and wax-cast macroporous polyamine oxime hydrogel particles is (0.04-4) g: (4-400) mL: (0.2-20) g.

6. The preparation method according to claim 1, characterized in that, In step (6), the mass-to-volume ratio of polyacrylic acid, CaCl2, and deionized water is (0.2–10) g: (0.4–20) g: (50–2000) mL; the average molecular weight of polyacrylic acid is 450,000. In step (7), the volume ratio of the alginate-wax casting macroporous polyamine oxime hydrogel particle suspension to the curing liquid is (4-400):(50-2000).

7. An alginate-polyacrylic acid composite sphere coated with wax-cast macroporous poly(amine oxime) hydrogel particles prepared by the preparation method according to any one of claims 1-6.

8. An alginate-polyacrylic acid composite sphere coated with wax-cast macroporous poly(ammonia oxime) hydrogel particles prepared by any one of claims 1-6, or the alginate-polyacrylic acid composite sphere coated with wax-cast macroporous poly(ammonia oxime) hydrogel particles as described in claim 7, in the enrichment and / or extraction of uranyl ions.

9. The application according to claim 8, characterized in that, The alginate-polyacrylic acid composite spheres coated with wax-cast macroporous polyamine oxime hydrogel particles are used as adsorbent materials for enriching and / or extracting low to medium concentrations of uranyl ions from simulated and real seawater.

10. The application according to claim 8, characterized in that, The concentration of uranyl ions is 54.1 ppb to 1004.1 ppb.

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