Hyperbranched polyethyleneimine functionalized anti-fouling polyacrylonitrile fibers, and methods of making and using the same

Abstract

This invention belongs to the field of functional fiber materials technology, specifically relating to a hyperbranched polyethyleneimine-functionalized antifouling polyacrylonitrile fiber, its preparation method, and its applications. The preparation method includes grafting hyperbranched polyethyleneimine and guanidinoacetic acid onto polyacrylonitrile fiber as the main body, forming a three-dimensional network structure on the fiber surface. This material is easy to mass-produce and exhibits excellent mechanical strength. The surface-grafted hyperbranched polyethyleneimine contains a large number of amino groups, which not only improves the material's uranium extraction capability but also has a unique coordination effect on uranium. Simultaneously, the guanidino groups improve the material's antibacterial properties, cutting off microbial adhesion at the source.

Description

Technical Field

[0001] This invention belongs to the field of functional fiber materials technology, specifically relating to a hyperbranched polyethyleneimine-functionalized antifouling polyacrylonitrile fiber, its preparation method, and its application. Background Technology

[0002] To address the challenges of low uranium concentration and numerous competing ions, researchers have proposed various methods and technologies for uranium extraction, including chemical precipitation, adsorption, membrane separation, ion exchange, electrochemical methods, flotation, and bioaccumulation. Compared to other methods, adsorption offers advantages such as low cost, ease of operation, excellent material regeneration performance, and versatility, thus attracting widespread research. Many adsorbent materials have been developed, including porous organic frameworks, composite materials, fiber materials, and membrane materials.

[0003] Porous organic framework materials include metal-organic frameworks (MOFs), covalent organic frameworks (COFs), and porous aromatic frameworks (PAFs). Due to their advantages such as tunable composition, porosity, high chemical stability, and potential for functional group modification, they have been widely used in uranium extraction research in recent years. The Wu Fei research group at Lanzhou University introduced polyphenylacetylene (DAE), which possesses photoisomerization properties, into metal-organic frameworks (MOFs). Through dynamic adjustment via ultraviolet-visible light irradiation, DAE undergoes cis-trans isomerization, thereby regulating the pore size. Nature Communications 2025, 16, 2361 This material achieved uranium enrichment of 588.24 mg / g in natural seawater, with a U(VI) / V(V) separation factor ratio as high as 215. The team led by Luo Feng at East China University of Technology improved uranium extraction yield and selectivity by altering the stacking pattern of sulfonic acid-COF (covalent organic framework). J. Am. Chem. Soc. 2025, 147, 31340 31348 The comparison revealed that, compared to AA stacking, AB stacking of sulfonic acid COF forms a uranyl recognition pocket, which can accurately recognize uranyl through planar four-coordinate, thereby improving selectivity, with a U(VI) / V(V) separation factor ratio reaching 103. Professor Zhu Guangshan and Professor Jia Jiangtao's team synthesized an amide oxime-functionalized organic molecular cage and obtained two different crystalline phases through different hydrogen bonding methods. J. Am. Chem. Soc. 2025, 147, 2228 2236 HPOC-α, which forms open channels, achieved a uranium recovery rate of 11.97 mg / g in natural seawater within 30 days. However, the preparation process for such materials is often complex and the raw materials are expensive, which makes industrial-scale synthesis difficult; moreover, these materials are mostly in powder form, which also poses a great challenge to practical applications.

[0004] Composite materials are diverse and are currently widely used in uranium extraction research. Professor Chen Jiping's team at the Dalian Institute of Chemical Physics, Chinese Academy of Sciences, developed a novel macroporous PAO hydrogel particle and, through encapsulation technology, combined it with alginate-polyacrylic acid (A-PAA) microspheres to obtain A-PAA@WMPAO microspheres. Adv. Funct. Mater. 2024, 2418340 The microspheres achieved an adsorption capacity of 4.79 mg / g in seawater. To address the problems of poor macroscopic structure, limited mass transfer, and low functional group utilization in seawater uranium extraction materials, the team led by Wang Ning at Hainan University reported a honeycomb polyamide oxime adsorbent with a layered three-channel architecture, utilizing the structural characteristics of leaf veins and natural honeycombs. This material achieved a uranium adsorption capacity of 14.69 mg / g within 35 days without external energy input, while also exhibiting high ion selectivity, reusability, and cost-effectiveness. However, the preparation process of such materials is often complex, the synthesis process is difficult to control, and large-scale production for uranium extraction is challenging.

[0005] Membrane-based adsorption materials possess abundant pore structures, high separation efficiency, and recyclability, making them widely used in water treatment applications and exhibiting excellent performance. Researchers Li Zhan and Tian Longlong from Lanzhou University obtained a 2D membrane by inserting transgenic E. coli expressing SUP into an MXene layer, and utilized the specific uranyl ion recognition ability of SUP to enhance the extraction of uranium (U) from seawater. Nano Lett. 2024, 24, 15151 15158 The results show that these membranes can accurately identify uranium ions and have excellent ion screening performance (SF). U / V ≈43, SF Na / U ≈158). A team led by Xing Lili and Xue Xinyu at the University of Electronic Science and Technology of China developed an Al-FEP-CTS@CF three-layer composite membrane. When water droplets from a salt lake come into contact with the membrane, mechanical energy is converted into electrical energy, driving the reduction of U(VI) adsorbed by chitosan (CTS) and the formation of uranate precipitates. In field experiments at the Qarhan Salt Lake in Qinghai, the four-stage cascade device reduced the uranium concentration in the salt lake water from 173 μg / L to 34 μg / L, achieving an extraction efficiency of 80.3%, and also improving the extraction efficiency for Mg. 2+ Na + The material exhibits excellent selectivity for coexisting ions with high abundance. Furthermore, it demonstrates superior stability; the superhydrophobic membrane maintains a contact angle >150° after 30 days, and the uranium extraction efficiency remains around 70% after five cycles of CTS@CF, combining high efficiency, selectivity, and potential for engineering applications. However, the membrane material is prone to clogging or fouling, requiring regular cleaning and complex maintenance.

[0006] Fiber materials possess advantages such as low cost, high mechanical strength, and stable chemical properties, making them more suitable for various aquatic environments compared to other powdered materials. Amine oximes, as a group with extremely high affinity for uranyl ions, are often used in fiber modification for practical uranium extraction. Professor Shi Bi's team at Sichuan University has developed a novel adsorbent material, BWT-AO-CFs, composed of collagen fibers (CFs) grafted with amine oxime groups (AO) and black chalcogenide (BWT). Desalination 2025, 600, 118471 BWT-AO-CFs combine the advantages of amine oxime groups and tannins, exhibiting high adsorption capacity, selectivity, and resistance to biofouling, making them suitable for long-term uranium extraction from seawater. This material achieved a uranium extraction capacity of 9.13 mg / g in simulated seawater and a uranium extraction rate as high as 89% in actual seawater, demonstrating its potential for industrial application. Although fiber adsorbents have made continuous breakthroughs in uranium extraction, problems such as insufficient selectivity for uranium and poor resistance to biofouling persist. Therefore, developing novel materials with excellent selectivity, good antibacterial properties, and rapid adsorption rates remains a key challenge for promoting the industrial application of this technology.

[0007] While porous organic framework materials offer high uranium extraction efficiency, their synthesis is complex, and they are often present in powder or particle form, limiting their practical applications. Composite materials, on the other hand, face challenges such as complex preparation processes and poor batch process control. Membrane-based adsorbents are prone to clogging or contamination, resulting in high maintenance costs. In comparison, fiber materials are the most widely used in uranium extraction, but their selectivity remains insufficient, and they are susceptible to microbial adhesion in marine environments, leading to low uranium extraction efficiency. Summary of the Invention

[0008] The purpose of this invention is to address the problem that while uranium extraction materials are diverse, they generally struggle to balance engineering application potential and adsorption performance. Using polyacrylonitrile fiber as the matrix, cyano groups are converted to carboxyl groups through alkali treatment, followed by an amide reaction to modify the fiber surface with hyperbranched polyethyleneimine, which has a unique coordinating effect on uranyl ions. Finally, the abundant amino groups on the polyethyleneimine surface undergo an amidation condensation reaction with guanidinoacetic acid to graft guanidino groups containing antifouling properties onto the fiber surface, thereby preparing a three-dimensional network antifouling fiber adsorbent material. This material not only retains the excellent mechanical properties of the fiber matrix but also endows it with the ability to selectively enrich uranyl ions, while possessing excellent antibacterial and bacteriostatic properties, making it promising for long-term stable uranium separation and enrichment applications in complex aquatic environments.

[0009] A first aspect of the present invention provides a method for preparing hyperbranched polyethyleneimine-functionalized antifouling polyacrylonitrile fibers, the method comprising: (a) Carboxylating polyacrylonitrile fibers to obtain carboxylated polyacrylonitrile fibers; (b) Acyl chloride is applied to carboxylated polyacrylonitrile fibers to obtain acyl chloride fibers; Hyperbranched polyethyleneimine was dissolved in anhydrous DMF (i.e., N,N-dimethylformamide) solution, and acyl chloride cellulose and anhydrous triethylamine were added. The mixture was refluxed at 68-72℃ for 10-14 h. After the reaction, the mixture was washed with water and dried to obtain polyethyleneimine-functionalized polyacrylonitrile fiber. (c) Dissolve guanidinoacetic acid in water, adjust the pH to 5-6, add carboxyl activator and stabilizer, activate, then adjust the pH to 7-8, add polyethyleneimine-functionalized polyacrylonitrile fiber, react at 38-42℃ for 18-30 h, rinse with deionized water and dry to obtain hyperbranched polyethyleneimine-functionalized antifouling polyacrylonitrile fiber.

[0010] As a preferred embodiment, the preparation method of the above-mentioned hyperbranched polyethyleneimine functionalized antifouling polyacrylonitrile fiber includes step (a) as follows: immersing the polyacrylonitrile fiber in a sodium hydroxide solution, heating to 75-85℃ and maintaining the temperature for 60-84 hours, washing with water and drying to obtain carboxylated polyacrylonitrile fiber. As a further preferred embodiment, the mass fraction of the sodium hydroxide solution is 28%-32%; the amount of sodium hydroxide solution used is 120-180 mL relative to 1 g of polyacrylonitrile fiber. This sodium hydroxide concentration range ensures efficient hydrolysis of cyano groups to carboxyl groups while avoiding excessive degradation of the fiber backbone due to strong alkali and excessively high temperature, which is beneficial to maintaining the mechanical strength of the fiber; the above liquid-solid ratio ensures sufficient contact between the fiber and the alkaline solution, and the hydrolysis reaction is uniform and thorough, forming sufficient and evenly distributed carboxyl active sites on the fiber surface, laying a good foundation for subsequent acyl chlorination and functional grafting; the relatively mild temperature and time combination ensures carboxylation efficiency while taking into account the process energy consumption and the feasibility of mass production.

[0011] As a preferred embodiment, the preparation method of the above-mentioned hyperbranched polyethyleneimine-functionalized antifouling polyacrylonitrile fiber, step (b) to obtain acyl chloride fiber includes: immersing the carboxylated polyacrylonitrile fiber in anhydrous thionyl chloride, gradually heating to 70-80℃ for 2-4 h; filtering out the fiber after the reaction, and removing thionyl chloride by rotary evaporation to obtain acyl chloride fiber. This temperature range can efficiently convert carboxyl groups to acyl chloride in a short time, while avoiding side reactions and degradation of the fiber matrix or already generated acyl chloride groups at high temperatures; removing residual thionyl chloride by rotary evaporation can reduce byproducts and impurities during subsequent reactions with hyperbranched polyethyleneimine, which is beneficial to improving the amidation reaction efficiency and product purity.

[0012] As a preferred embodiment, in the above-mentioned method for preparing hyperbranched polyethyleneimine-functionalized antifouling polyacrylonitrile fibers, in step (b), relative to 1 g of carboxylated polyacrylonitrile fibers, the amount of anhydrous thionyl chloride is 80-120 mL, the amount of hyperbranched polyethyleneimine is 0.5-25 g, the amount of anhydrous DMF is 120-180 mL, and the amount of anhydrous triethylamine is 20-30 mL. As a further preferred embodiment, the amount of hyperbranched polyethyleneimine is 1-22 g, more preferably 5-22 g, especially at 8-12 g, where the adsorption performance is strongest. The amount of thionyl chloride used is 80-120 mL / g fiber: to ensure sufficient acylation of the carboxyl groups, while avoiding the recovery burden caused by excessive solvent. Within the aforementioned range of hyperbranched polyethyleneimine (PEI) dosage, a moderately dense three-dimensional PEI network structure can be formed on the fiber surface. This provides a large amount of amino groups for uranyl ion coordination while avoiding fiber pore blockage or agglomeration due to excessive grafting, thus maintaining good mass transfer performance. Experimental data show that the material's uranium adsorption capacity reaches its optimum when the PEI dosage is 8-12 g, demonstrating the crucial role of this optimal range in uranium extraction performance. DMF, as a good solvent, ensures the complete dissolution and uniform dispersion of PEI, while triethylamine, as an acid-binding agent, effectively neutralizes the HCl generated in the reaction, shifting the amidation equilibrium towards the product side.

[0013] As a preferred embodiment, in the above-mentioned method for preparing hyperbranched polyethyleneimine-functionalized antifouling polyacrylonitrile fibers, step (b) uses hyperbranched polyethyleneimine with a weight-average molecular weight of 10,000. This molecular weight balances the degree of branching and the flexibility of chain segments, which is beneficial for forming a stable three-dimensional network structure on the fiber surface, providing abundant coordination sites while maintaining the overall structural stability and mechanical properties of the material.

[0014] As a preferred embodiment, in the above-mentioned method for preparing hyperbranched polyethyleneimine-functionalized antifouling polyacrylonitrile fibers, in step (c), the amount of polyethyleneimine-functionalized polyacrylonitrile fibers used is 280-320 mg relative to 300 mg guanidinoacetic acid. This ensures that after guanidinoacetic acid is activated, it can fully and uniformly undergo an amidation reaction with the amino groups on the PEI surface of the fiber; it avoids excessive guanidinoacetic acid leading to unreacted monomers remaining in the solution, or insufficient fiber usage leading to uneven surface grafting and localized excessive cross-linking, thereby ensuring that the material obtains stable and uniform antifouling (antibacterial) properties.

[0015] As a preferred embodiment, in the above-mentioned method for preparing hyperbranched polyethyleneimine-functionalized antifouling polyacrylonitrile fiber, step (c) involves adjusting the pH to 5-6 using 1 M hydrochloric acid. This acidic environment is conducive to the formation of a highly active intermediate between the carboxyl activator (EDC) and the stabilizer (NHS), thereby improving the activation efficiency of guanidinoacetic acid. The pH is then adjusted to 7-8 using 2 M sodium hydroxide solution. Under near-neutral or weakly alkaline conditions, the amino groups on the polyethyleneimine maintain appropriate nucleophilicity, which is beneficial for the amidation reaction with activated guanidinoacetic acid. Simultaneously, strong alkali is avoided to prevent degradation of the fiber or grafted functional groups, ensuring reaction selectivity and material stability.

[0016] As a preferred embodiment, in the above-mentioned method for preparing hyperbranched polyethyleneimine-functionalized antifouling polyacrylonitrile fibers, in step (c), for activation, the carboxyl activator is 1-ethyl-3-(3-dimethylaminopropyl)carbodiimide hydrochloride; the stabilizer is N-hydroxysuccinimide; the activation temperature is 0-5℃; and the activation time is 1.5-2.5 h. The EDC / NHS system can efficiently activate carboxyl groups under mild conditions, forming stable active ester intermediates, significantly improving the condensation efficiency of guanidinoacetic acid and amino groups on the fiber surface. Low temperature conditions are beneficial for suppressing the hydrolysis side reactions of the activator and active ester intermediates, improving activation efficiency and reaction selectivity; the 1.5-2.5 h time window can ensure sufficient activation of guanidinoacetic acid, while avoiding increased energy consumption and potential side reactions caused by excessively long reaction times.

[0017] A second aspect of the present invention provides a hyperbranched polyethyleneimine-functionalized antifouling polyacrylonitrile fiber, which is prepared by the above-described preparation method.

[0018] A third aspect of the present invention provides the application of the above-mentioned hyperbranched polyethyleneimine-functionalized antifouling polyacrylonitrile fiber in the separation and extraction of uranium.

[0019] Compared with the prior art, the present invention has at least the following beneficial effects: This invention uses polyacrylonitrile fibers as the main body, grafting hyperbranched polyethyleneimine and guanidinoacetic acid sequentially to form a three-dimensional network structure on the fiber surface. This material is easy to mass-produce and exhibits excellent mechanical strength. The surface-grafted hyperbranched polyethyleneimine contains a large number of amino groups, which not only improves the material's uranium extraction capability but also has a unique coordination effect on uranium. Simultaneously, the guanidino groups improve the material's antibacterial properties, cutting off microbial adhesion at the source.

[0020] The above description is merely an overview of the technical solution of the present invention. In order to better understand the technical means of the present invention and to implement it in accordance with the contents of the specification, and in order to make the above and other objects, features and advantages of the present invention more apparent and understandable, specific embodiments of the present invention are described below. Attached Figure Description

[0021] Figure 1 This paper presents a preparation route for a three-dimensional fiber brush PAN-PEI-GAA with polyethyleneimine / guanidine bifunctionalization; Figure 2 The following images show (A) SEM plot and (B) SEM mapping plot of PAN-PEI-GAA-3.

[0022] Figure 3 The infrared spectra and zeta potentials of different materials are shown in (A) and (B).

[0023] Figure 4 XPS (A) N1s and (B) O1s spectra of different materials are shown.

[0024] Figure 5 The effects of (A) pH value and (B) adsorbent dosage on the adsorption efficiency of uranyl by PAN-PEI-GAA-3 are shown (Experimental conditions: (A)). C O(U) = 11.9 ppm, adsorbent dosage 0.5 g / L, 72 h, 298 K; (B) C O(U) = 11.9 ppm, adsorbent dosage 0.05~0.6 g / L, pH 6 ± 0.1, 600 h, 298 K).

[0025] Figure 6 The following figures illustrate the (A) adsorption kinetics, (B) pseudo-first-order kinetics, and (C) pseudo-second-order kinetics fittings for uranium adsorption by PAN-PEI-GAA-3; and the (D) adsorption isotherm and (E) Langmuir model and (F) Freundlich model fittings for uranium adsorption by PAN-PEI-GAA-3 (experimental conditions: (A)). C O(U) = 11.9 ppm, adsorbent dosage 0.1 g / L, pH 6 ± 0.1, 200 h, 298 K; (D) C O(U) = 2.7~45.9 ppm, adsorbent dosage 0.1 g / L, pH 6 ± 0.1, 200 h, 298 K).

[0026] Figure 7 The adsorption capacities of PAN-PEI-GAA-3 for different ions are shown. q e and (B) allocation coefficient K d (C) Effect of salinity on adsorption performance; (D) Antibacterial effect of different materials and (E) Antibacterial rate (Experimental conditions: (A) Initial concentration of metal ions is 2×10⁻⁶) -6mol / L, adsorbent dosage 0.0317 g / L, pH = 6, 1200 h, 298 K; (C) C O(U) = 11.9 ppm, adsorbent dosage 0.5 g / L, pH 6 ± 0.1, 48 h, 298 K).

[0027] Figure 8 The following are shown: (A) Uranyl elution efficiency with different eluents; (B) Regeneration performance of PAN-PEI-GAA-3 using 0.05 M Na2CO3 solution as eluent (experimental conditions). C O(U) = 11.9 ppm, adsorbent dosage 0.5 g / L, 48 h, 298 K).

[0028] Figure 9 The adsorption kinetics of PAN-PEI-3 are shown (experimental conditions: C O(U) = 11.9 ppm, adsorbent dosage 0.1 g / L, pH 6 ± 0.1, 400 h, 298 K). Detailed Implementation

[0029] The following description provides numerous specific details to offer a more thorough understanding of the technical solutions provided by this invention. However, it will be apparent to those skilled in the art that the technical solutions provided by this invention can be implemented without one or more of these details.

[0030] The following describes some of the content involved in the embodiments: (1) Synthesis of adsorbent This invention uses polyacrylonitrile fibers as a substrate. The cyano groups on the fiber surface are converted to carboxyl groups via alkaline hydrolysis, and then polyethyleneimine is modified onto the fiber surface using an amide reaction. Subsequently, the abundant amino groups on the polyethyleneimine undergo an amidation condensation reaction with guanidinoacetic acid. For the specific synthesis process, please refer to [reference needed]. Figure 1 .

[0031] (2) Adsorption test The adsorption performance of the material for uranium was investigated from the aspects of adsorbent dosage, adsorption kinetics, isotherm, and selectivity.

[0032] (3) Repeatability and stability Elution and regeneration experiments were conducted on the material using a sodium carbonate solution of appropriate concentration to investigate the reproducibility of uranium extraction. The regenerated adsorbent was characterized by infrared spectroscopy to examine the stability of its chemical structure.

[0033] (4) Seawater adsorption experiment Five mg of material was placed in an adsorption column, and a seawater (40 L) experiment was carried out using a self-made dynamic adsorption device. The adsorption capacity was calculated by measuring the uranium concentration of the solution before and after adsorption using ICP-MS.

[0034] Example 1 (1) Synthesis of adsorbent material PAN-PEI-GAA (a) Immerse 1 g of polyacrylonitrile fiber in sodium hydroxide solution (30% by mass, 150 mL), heat to 80°C and maintain for 72 h, wash with water and dry to obtain carboxylated polyacrylonitrile fiber for later use.

[0035] (b) Carboxylated polyacrylonitrile fiber (1 g) was immersed in anhydrous thionyl chloride (100 mL) and the temperature was gradually increased to 75 °C for 3 h. After the reaction, the fiber was filtered out, and the thionyl chloride was removed by rotary evaporation to obtain acyl chloride fiber. Hyperbranched polyethyleneimine (10 g, Mw=10000) was dissolved in anhydrous DMF (150 mL) solution, and acyl chloride fiber and anhydrous triethylamine (25 mL) were added. The mixture was heated to 70 °C and refluxed for 12 h. After the reaction, the fiber was washed with water and dried to obtain polyethyleneimine-functionalized polyacrylonitrile fiber (PAN-PEI). By changing the amount of polyethyleneimine, a series of polyethyleneimine-functionalized polyacrylonitrile fibers were prepared (Table 1).

[0036] Table 1. Raw material feed ratio for PAN-PEI preparation

[0037] (c) Guanidoacetic acid (300 mg) was dissolved in water, and the pH was adjusted to 5-6 using 1 M hydrochloric acid. 980 mg of 1-ethyl-3-(3-dimethylaminopropyl)carbodiimide hydrochloride (EDC) and 590 mg of N-hydroxysuccinimide (NHS) were added. The mixture was activated at 0°C for 2 h, and then the pH was adjusted to 7-8 using 2 M sodium hydroxide solution. PAN-PEI fiber (300 mg) was then added. After reacting at 40°C for 24 h, the mixture was rinsed with deionized water and dried to obtain PAN-PEI-GAA fiber.

[0038] Scanning electron microscopy (SEM) characterization results Figure 2 A) shows that the surface of polyacrylonitrile fibers is smooth and flat; after grafting with polyethyleneimine (PEI), the fiber surface becomes rough and wrinkles increase; further grafting with guanidine groups increases the surface roughness of the fibers. Elemental distribution diagram ( Figure 2 B) shows that the three elements C, N, and O are evenly distributed on the surface of the material.

[0039] The chemical structure of the material was characterized by Fourier transform infrared spectroscopy (FT-IR). Figure 3A). Polyacrylonitrile fibers at 2235 cm -1 A sharp absorption peak exists at [value missing], attributed to the characteristic stretching vibration of the cyano group (-C≡N). After alkali treatment, the intensity of this absorption peak significantly decreases, while the peaks at 1552 and 1400 cm⁻¹ also weaken. -1 Two new absorption peaks appeared at the point, which were attributed to carboxylate ions (-COO-). - Asymmetric and symmetric stretching vibrations; furthermore, at 3335 cm -1 A broad peak appears at 1650 cm⁻¹, corresponding to the OH stretching vibration, confirming successful carboxylation of the polyacrylonitrile fibers. After grafting with polyethyleneimine (PEI), the peak at 1650 cm⁻¹ appears in the spectrum. -1 A C=O stretching vibration peak of the amide I band appeared at 3335 cm⁻¹. -1 The significantly enhanced broad peak at this location is attributed to the superposition of OH and NH stretching vibrations, proving that PEI has been successfully grafted onto the fiber surface. Grafting guanidine groups further enhances the amide bond strength, indicating the successful synthesis of PAN-PEI-GAA-1~4. Zeta potential results show ( Figure 3 (B) With PEI modification and guanidinium functionalization, the zeta potential of the material gradually increases. This is because amine and guanidinium groups readily undergo protonation in water, thereby increasing the surface positive charge density of the material, thus proving that guanidinium groups were successfully modified onto the material surface.

[0040] In the high-resolution XPS spectrum of N 1s ( Figure 4 In A), PAN-COOH exhibits a single characteristic peak at 399.8 eV, attributed to a cyano group (-C≡N). After introducing PEI, the spectrum decomposes into four peaks at 399.1 eV, 399.7 eV, 401.0 eV, and 402.0 eV, corresponding to primary / secondary amines (-NH₂ / -NH⁻), cyano groups (-C≡N), amide bonds (-CONH⁻), and protonated amines (-NH₃⁺), respectively. + After GAA modification, a new peak appeared at 398.6 eV, indicating the formation of an imine bond (-C=N-), while the intensity of the free amine decreased relatively, confirming the successful grafting of the guanidine group. Furthermore, the O 1s energy spectrum ( Figure 4 B) This further confirms the successful synthesis of the above reaction, with the carboxylate group (-COO) in PAN-COOH positioned at 531.3 eV. - The main component is PEI and GAA. After modification with PEI and GAA, a significant -CONH- peak was observed at 532.2–532.3 eV.

[0041] (2) Study on the adsorption properties of modified polyacrylonitrile fiber A measured amount of PAN-PEI-GAA-3 was dispersed in uranyl nitrate solutions of different concentrations and heated to 25°C. oAfter adsorption equilibrium at C, the solution was filtered, and the uranium content in the solution was detected by ICP-OES / ICP-MS to calculate the adsorption efficiency and adsorption capacity.

[0042] (a) Effects of pH and adsorbent dosage on adsorption The effect of pH on uranium adsorption was investigated in uranium solutions with different initial pH values. Figure 5 A). PAN-PEI-GAA-3 exhibits optimal adsorption performance at pH 6, with an adsorption efficiency of 99.9%. Below pH 6, the adsorption performance decreases, attributed to the amine matrix protonation on the material surface under low pH conditions, leading to electrostatic repulsion between the amine and uranyl ions in the solution. At pH 9.0, the adsorption efficiency also decreases, possibly due to the formation of stable complexes between carbonate ions introduced by the sodium bicarbonate solution used to adjust the pH and uranyl ions. However, the material maintains an adsorption efficiency of 94.3% at pH 8.0, indicating that PAN-PEI-GAA-3 is suitable for uranium extraction in seawater environments. Adsorbent dosage test results ( Figure 5 B) shows that as the amount of adsorbent increases, the adsorption capacity gradually decreases, while the adsorption efficiency of uranium increases rapidly. When the amount of adsorbent is 0.6 mg / mL, the adsorption efficiency reaches 99.9%, indicating that the material has a high affinity for uranium.

[0043] (b) Adsorption kinetics and isotherms To further investigate the adsorption behavior of uranium on the fibers, the adsorption kinetics of PAN-PEI-GAA-1~4 were examined under optimal pH conditions. Experimental results ( Figure 6 A) indicates that the adsorption kinetics of the four materials are similar, with the adsorption capacity gradually increasing over time and reaching equilibrium after about 200 h.

[0044] The equilibrium adsorption capacities of PAN-PEI-GAA-1 to 4 were 94.1, 98.1, 113.3, and 112.5 mg / g, respectively, corresponding to adsorption efficiencies of 75.7%, 81.0%, 92.8%, and 92.2%. Among them, PAN-PEI-GAA-3 showed the highest adsorption capacity; therefore, the adsorption kinetics fitting results of this material were selected for subsequent adsorption experiments. Figure 6 (B, 6C) indicates that the correlation coefficient of the pseudo-second-order kinetic model is higher than that of the pseudo-first-order kinetic model (Table 2), suggesting that chemisorption dominates the entire adsorption process. With increasing initial uranium concentration, the adsorption capacity of PAN-PEI-GAA-3 for uranium gradually increases (…). Figure 6 D). The adsorption isotherms were fitted and analyzed using the Langmuir model and the Freundlich model, respectively. Figure 6(E, 6F, Table 3) The results show that the adsorption behavior of uranium on PAN-PEI-GAA-3 is more consistent with the Freundlich isotherm model, indicating that the adsorption process is mainly multilayer adsorption. At the same time, the 1 / n value is less than 0.5, indicating that uranium forms a strong complexation with multiple active sites on the fiber surface, and the adsorption process is easy to carry out.

[0045] Table 2 Adsorption kinetics fitting of PAN-PEI-GAA-3

[0046] Table 3. Adsorption isotherm fitting of PAN-PEI-GAA-3

[0047] (3) Selectivity, salinity, resistance to biofouling and regenerability studies The adsorption selectivity of PAN-PEI-GAA-3 was studied in uranium solutions containing multiple competing ions. For example... Figure 7 As shown in Figure A, the adsorption capacity of PAN-PEI-GAA-3 for uranium is significantly higher than that of other competing ions, reaching 11 times that of vanadium. Simultaneously, the partition coefficient of PAN-PEI-GAA-3 for uranium (…) K d Up to 2.3×10 4 mL / g ( Figure 7 B), significantly higher than other ions, indicates good selectivity of the material. Since high salt concentrations in seawater or salt lakes affect the adsorption performance of the material, the effect of different salinities on uranium extraction efficiency was studied. The results show that at 10... -4 In a ~0.5 M salt solution, PAN-PEI-GAA-3 can still maintain a 99% uranium adsorption efficiency. Figure 7 (C) indicates that salinity has little effect on the material. The uranium extraction process generates a large number of microorganisms that adhere to the material surface, thereby reducing its mechanical and adsorption properties. Therefore, we selected representative bacteria from seawater, the Gram-negative bacterium *Escherichia coli* and the Gram-positive bacterium *Staphylococcus aureus*, to investigate the material's antibacterial properties. The results are as follows... Figure 7 As shown in Figures D and 7E, PAN-PEI-GAA-3 exhibits good inhibitory effects on both *Escherichia coli* and *Staphylococcus aureus*, with inhibition rates reaching 99%, higher than the 20.3% and 20.3% of the original PAN fiber, respectively. This indicates that grafting hyperbranched polyethyleneimine and guanidinoacetic acid can effectively enhance the antibacterial properties of the material, thereby reducing the impact of bioadhesion on material loss and adsorption performance, and improving the material's antifouling performance in uranium extraction. The antibacterial properties of this material mainly stem from the protonation of hyperbranched polyethyleneimine and the strong positive charge of the guanidino group, achieving an antibacterial effect by disrupting the bacterial cell membrane structure.

[0048] To reduce costs, the number of times the adsorbent material can be reused needs to be considered. Therefore, we conducted desorption experiments on the material that had adsorbed uranyl using different eluents. The results showed that the elution efficiencies of 0.05M Na₂CO₃ and HCl solutions reached 99.9% and 99.5%, respectively, only slightly lower than those of higher concentrations of HCl and Na₂CO₃. Considering both elution efficiency and economic cost, 0.05M Na₂CO₃ solution was selected as the eluent. The reusability of PAN-PEI-GAA-3 was investigated through six adsorption-desorption cycles, and the results are as follows: Figure 8 As shown in Figure B, the adsorption efficiency of the material for uranium gradually decreases with increasing cycle number, maintaining 74% of the initial adsorption efficiency after the sixth cycle. Repeated adsorption and desorption may cause conformational changes in the polymer chains on the material surface, resulting in the embedding of some grafted functional groups and thus reducing the effective contact area. Furthermore, repeated cycles may lead to the shedding of a small number of functional groups, further reducing adsorption efficiency. However, overall, PAN-PEI-GAA-3 maintains a 74% adsorption efficiency after 6 cycles, indicating good reusability and potential for practical applications.

[0049] Due to its high adsorption capacity, PAN-PEI-GAA-3 was selected for uranium extraction from natural seawater in this study to evaluate its application potential. A self-made circulating dynamic adsorption device was used. 5 mg of the material was packed into the adsorption column, and 40 L of natural seawater was circulated between the adsorption column and a water tank using a peristaltic pump. After 12 days of cyclic adsorption, the material's adsorption capacity for uranium reached 11.3 mg / g, higher than most reported adsorbents, indicating that this material has good application potential in the field of uranium extraction from seawater.

[0050] Comparative Example 1 Using PAN-PEI-3 (PEI-modified material) as a comparative example, its uranium adsorption performance was evaluated. The results are as follows: Figure 9 As shown, under the conditions of pH=6, initial uranium concentration (C0) of 11.9 ppm and solid-liquid ratio of 0.1 mg / mL, after adsorption for about 400 h, the material reached equilibrium and the adsorption capacity of uranium was 105.9 mg / g, with a removal rate of 85.0%, which is slightly lower than PAN-PEI-GAA-3's 113.3 mg / g and corresponding removal rate (92.8%).

[0051] Representative Gram-negative bacteria (Escherichia coli) and Gram-positive bacteria (Staphylococcus aureus) from the seawater environment were selected as test strains to evaluate the antibacterial properties of the material. The results are as follows: Figure 7As shown in Figures D and 7E, PAN-PEI-3 exhibited good inhibitory effects against both *Escherichia coli* and *Staphylococcus aureus*, with inhibition rates reaching 99.3% and 93.6%, respectively. Although this antibacterial effect was slightly lower than that of Example 1, it was still far superior to that of unmodified PAN fibrils. These results indicate that grafting hyperbranched polyethyleneimine can significantly improve the antibacterial properties of the material. This effect is mainly attributed to the fact that a large number of amine groups in the PEI structure become positively charged after protonation in aqueous solution. These groups adsorb and disrupt the negatively charged bacterial cell membranes through electrostatic interactions, leading to leakage of intracellular substances and thus achieving highly efficient antibacterial activity.

[0052] The above are merely preferred embodiments of the present invention and are not intended to limit the present invention. Various modifications and variations can be made to the present invention by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A method for preparing a stain-resistant polyacrylonitrile fiber functionalized with hyperbranched polyethyleneimine, characterized in that, The preparation method includes: (a) Carboxylating polyacrylonitrile fibers to obtain carboxylated polyacrylonitrile fibers; (b) Acyl chloride is applied to carboxylated polyacrylonitrile fibers to obtain acyl chloride fibers; Hyperbranched polyethyleneimine was dissolved in anhydrous DMF solution, and acyl chloride cellulose and anhydrous triethylamine were added. The mixture was refluxed at 68-72℃ for 10-14 h. After the reaction, the mixture was washed with water and dried to obtain polyethyleneimine-functionalized polyacrylonitrile fiber. (c) Dissolve guanidinoacetic acid in water, adjust the pH to 5-6, add carboxyl activator and stabilizer, activate, then adjust the pH to 7-8, add polyethyleneimine-functionalized polyacrylonitrile fiber, react at 38-42℃ for 18-30 h, rinse with deionized water and dry to obtain hyperbranched polyethyleneimine-functionalized antifouling polyacrylonitrile fiber.

2. The method for preparing hyperbranched polyethyleneimine-functionalized antifouling polyacrylonitrile fiber according to claim 1, characterized in that, Step (a) includes: Polyacrylonitrile fibers were immersed in a sodium hydroxide solution, heated to 75-85℃ and maintained for 60-84 hours, washed with water and dried to obtain carboxylated polyacrylonitrile fibers.

3. The method for preparing hyperbranched polyethyleneimine-functionalized antifouling polyacrylonitrile fiber according to claim 2, characterized in that, The mass fraction of sodium hydroxide solution is 28%-32%; The amount of sodium hydroxide solution used is 120-180 mL relative to 1 g of polyacrylonitrile fiber.

4. The method for preparing hyperbranched polyethyleneimine-functionalized antifouling polyacrylonitrile fiber according to claim 1, characterized in that, Step (b) to obtain acyl chloride cellulose includes: Carboxylated polyacrylonitrile fibers are immersed in anhydrous thionyl chloride and the temperature is gradually raised to 70-80℃ for 2-4 hours. After the reaction, the fibers are filtered out and the thionyl chloride is removed by rotary evaporation to obtain acyl chloride fibers.

5. The method for preparing hyperbranched polyethyleneimine-functionalized antifouling polyacrylonitrile fiber according to claim 4, characterized in that, In step (b), at least one of the following characteristics must be satisfied: For every 1 g of carboxylated polyacrylonitrile fiber, the amount of anhydrous thionyl chloride used is 80-120 mL, the amount of hyperbranched polyethyleneimine used is 0.5-25 g, the amount of anhydrous DMF used is 120-180 mL, and the amount of anhydrous triethylamine used is 20-30 mL. The weight-average molecular weight of hyperbranched polyethyleneimine is 10,000.

6. The method for preparing hyperbranched polyethyleneimine-functionalized antifouling polyacrylonitrile fiber according to claim 1, characterized in that, In step (c), the amount of polyethyleneimine-functionalized polyacrylonitrile fiber used is 280-320 mg relative to 300 mg guanidinoacetic acid.

7. The method for preparing hyperbranched polyethyleneimine-functionalized antifouling polyacrylonitrile fiber according to claim 1, characterized in that, In step (c), at least one of the following characteristics must be satisfied: Adjust the pH to 5-6 using 1 M hydrochloric acid; Adjust the pH to 7-8 using a 2 M sodium hydroxide solution.

8. The method for preparing hyperbranched polyethyleneimine-functionalized antifouling polyacrylonitrile fiber according to claim 1, characterized in that, In step (c), at least one of the following characteristics must be satisfied: The carboxyl activator is 1-ethyl-3-(3-dimethylaminopropyl)carbodiimide hydrochloride; The stabilizer is N-hydroxysuccinimide; The activation temperature is 0-5℃; The activation time is 1.5-2.5 h.

9. A type of antifouling polyacrylonitrile fiber functionalized with hyperbranched polyethyleneimine, characterized in that, It is prepared by the preparation method described in any one of claims 1-8.

10. The application of the hyperbranched polyethyleneimine-functionalized antifouling polyacrylonitrile fiber according to claim 9 in the separation and extraction of uranium.

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