Functionalized fiber membrane for removing metal ions from a solution and method of making and use thereof

Abstract

This invention belongs to the field of functional membrane materials and semiconductor chemical purification technology, and relates to a functionalized fiber membrane for removing metal ions from solution, its preparation method, and its application. The preparation method includes: preparing a polyacrylonitrile nanofiber membrane by electrospinning; immersing the prepared polyacrylonitrile nanofiber membrane in an alkaline hydrolysis system for surface chemical modification; after the reaction is complete, washing and drying the fiber membrane to obtain the functionalized fiber membrane for removing metal ions from solution. The functionalized fiber membrane prepared by this invention has a stable overall structure and can maintain good chemical stability and mechanical integrity in organic solvents and complex chemical environments, reducing the loss of functional components and the risk of secondary pollution. Compared with traditional particulate ion exchange resins, the fiber membrane of this invention has significant advantages in adsorption kinetics, equipment integration, and operational reliability, and is of great significance for improving the performance and yield of semiconductor devices.

Description

Technical Field

[0001] This invention belongs to the field of functional membrane materials and semiconductor chemical purification technology, specifically relating to a functionalized fiber membrane for removing metal ions from solution, its preparation method, and its application. Background Technology

[0002] With the continuous advancement of semiconductor manufacturing processes, the feature size of semiconductor devices continues to shrink, leading to increasingly stringent requirements for material purity. The presence of trace impurities, especially mobile ion contamination (MIC), in the photoresist and related chemicals (such as developers and diluents) used in photolithography processes can significantly impact device performance. These mobile ions typically include alkali metal ions such as Na⁺ and K⁺, and transition metal ions such as Fe³⁺ and Cu²⁺. These ions exhibit high mobility under an electric field, easily drifting and accumulating within the device structure, causing problems such as threshold voltage drift, increased leakage current, and decreased dielectric layer reliability, severely affecting the stability and lifespan of semiconductor devices. Therefore, in advanced semiconductor manufacturing processes, the metal ion content in photoresists and related electronic chemicals is typically controlled at the ppb or even ppt level.

[0003] Currently, methods such as ion exchange resin adsorption, membrane separation, and chemical precipitation are commonly used to remove metal ions from solutions. Among these, ion exchange resins are widely used in water treatment and the purification of some fine chemicals due to their high exchange capacity. However, traditional ion exchange resins are usually granular with a relatively limited specific surface area and long internal diffusion paths, which restricts mass transfer and makes it difficult to achieve rapid and efficient removal of trace amounts of mobile ions. Furthermore, in high-purity electronic chemical systems, resin materials may also experience organic matter precipitation (Total Organic Carbon, TOC) and particulate shedding, introducing new sources of contamination and further affecting device performance.

[0004] On the other hand, membrane separation technologies (such as microfiltration, ultrafiltration, and nanofiltration) mainly rely on pore size sieving mechanisms, which have good removal effects on particulate pollutants. However, their removal capacity for migratable metal impurities existing in ionic form is limited, making it difficult to achieve highly selective separation. Therefore, single membrane filtration technologies are insufficient to meet the requirements of semiconductor-grade chemicals for ultra-low concentration control of migratable ions.

[0005] In recent years, nanofiber membranes prepared by electrospinning technology have attracted widespread attention in the field of separation and adsorption due to their high specific surface area, high porosity, and three-dimensional interconnected structure. These materials can significantly shorten mass transfer paths and improve separation efficiency. However, existing nanofiber membranes mostly focus on particle filtration or gas separation, and their surfaces typically lack the ability to specifically recognize and bind migratable ions, making it difficult to effectively control metal ion impurities.

[0006] In summary, current technologies still lack a material system that combines high mass transfer efficiency, low precipitation characteristics, and high selective adsorption capacity for migratable ions. Particularly in the fields of semiconductor photoresists and related electronic chemical purification, there is an urgent need to develop novel functional materials to achieve efficient removal of trace metal impurities, thereby meeting the stringent requirements of advanced processes for ultra-high purity chemicals. Summary of the Invention

[0007] In view of the shortcomings of the existing technology, the primary objective of the present invention is to provide a method for preparing a functionalized fiber membrane for removing metal ions from solution.

[0008] Another object of the present invention is to provide a functionalized fiber membrane for removing metal ions from solution, prepared by the above method. The functionalized fiber membrane achieves efficient adsorption and removal of metal ions by constructing a nanofiber structure with a high specific surface area and introducing functional groups with ion exchange and / or chelation effects on its surface. The functionalized fiber membrane combines high mass transfer efficiency, high selectivity, and low fouling characteristics, overcoming the problems of slow mass transfer rate and easy precipitation fouling of traditional particulate ion exchange resins, as well as the insufficient removal capacity of conventional membrane materials for dissolved ions.

[0009] Another object of the present invention is to provide the application of the above-mentioned functionalized fiber membrane for removing metal ions from solution.

[0010] To achieve the above objectives, the technical solution adopted by the present invention is as follows:

[0011] A method for preparing a functionalized fiber membrane for removing metal ions from solution includes the following steps:

[0012] S1. Preparation of polyacrylonitrile (PAN) nanofiber membrane: Polyacrylonitrile powder was dissolved in an organic solvent to obtain a polyacrylonitrile spinning solution, which was then spun using an electrospinning method. After spinning, the solution was dried to remove unvolatile solvent and obtain a polyacrylonitrile nanofiber membrane.

[0013] S2. Surface functionalization of polyacrylonitrile nanofiber membranes: The prepared polyacrylonitrile nanofiber membranes are immersed in an alkaline hydrolysis system, causing the cyano groups in the polyacrylonitrile nanofiber membranes to undergo surface chemical modification with the reaction solution, thereby introducing active groups with ion exchange or chelation effects on the surface of the polyacrylonitrile nanofibers. After the reaction is complete, the membranes are washed with a washing solution to remove the residual reaction solution. After washing, the polyacrylonitrile functionalized fiber membranes are dried to obtain polyacrylonitrile functionalized fiber membranes capable of removing trace metal ions.

[0014] The organic solvent in step S1 is at least one of N,N-dimethylformamide, N,N-dimethylacetamide, and acetone; preferably N,N-dimethylformamide.

[0015] Preferably, the mass concentration of polyacrylonitrile in the spinning solution in step S1 is 10-20 wt%. Preferably, the weight-average molecular weight of the polyacrylonitrile is 50,000-300,000, more preferably 120,000-180,000.

[0016] Preferably, the parameters of the electrospinning method in step S1 include: a spinning voltage range of 10~15kV, a spinning receiving distance of 15~25cm, a syringe advance speed of 0.4~1mL / h, a collecting roller rotation speed of 100~400rpm, a spinning ambient temperature of 20~40℃, and a relative humidity of 20~80RH.

[0017] Preferably, the drying temperature in step S1 is 40~60℃, and the drying time is 12~24h.

[0018] Preferably, in step S2, the polyacrylonitrile fiber membrane is cut into squares with a side length of 2-10 cm and then immersed in an alkaline hydrolysis system.

[0019] Preferably, the alkaline hydrolysis system in step S2 is one of the following: NaOH / ethanol-water mixed solution, hydrazine hydrate / ethanol / water mixed solution, organic solution system containing ethylenediaminetetraacetic dianhydride, chlorosulfonic acid solution, and acid anhydride reagent.

[0020] More preferably, the concentration of NaOH in the NaOH / ethanol-water mixed solution is 0.1~2 mol / L, the concentration of hydrazine hydrate in the hydrazine hydrate / ethanol / water mixed solution is 5~50 wt%, the concentration of ethylenediaminetetraacetic dianhydride in the organic solution system containing ethylenediaminetetraacetic dianhydride is 0.01~0.2 mol / L, the concentration of chlorosulfonic acid in the chlorosulfonic acid solution is 1~10 wt%, and the concentration of acid anhydride reagent in the acid anhydride reagent is 0.1~1.0 mol / L.

[0021] Preferably, the surface chemical modification temperature in step S2 is 25~60℃; the reaction time is 6~12h.

[0022] Preferably, the active group having ion exchange or chelation function in step S2 is at least one of carboxyl, amide, hydrazine, amino, EDTA chelating group, and sulfonic acid group, depending on the selected reaction solution.

[0023] Preferably, step S2 can be repeated multiple times, with surface chemical modification performed in different alkaline hydrolysis systems to introduce various active groups onto the surface of polyacrylonitrile fibers. In this step, the following operations can be repeated: immersion in an alkaline hydrolysis system for surface chemical modification—washing—drying. Different alkaline hydrolysis systems can be selected to synergistically introduce multiple functional groups (such as carboxyl, amino, sulfonic acid, and chelating groups) onto the nanofiber surface. This allows ion exchange, coordination chelation, and electrostatic interactions to work synergistically, ensuring their stable presence on the fiber surface without detachment or deactivation, thereby significantly improving the adsorption capacity for metal ions. For example, the PAN nanofiber substrate membrane is first placed in a hydrazine hydrate / ethanol / water mixed solution for surface amination treatment, washed and dried, and then subjected to carboxyl functionalization modification with anhydride reagents. Finally, the carboxylated PAN nanofiber membrane is added to chlorosulfonic acid solution for surface sulfonation reaction. Alternatively, the PAN nanofiber membrane is first placed in a NaOH / ethanol-water mixed solution for carboxylation modification treatment, then the carboxylated functional fiber membrane is pre-wetted in deionized water, and then the treated carboxylated functional fiber membrane is placed in an organic solution system containing ethylenediaminetetraacetic dianhydride for graft modification.

[0024] Preferably, the washing solution in step S2 is DMF, deionized water, ethanol, or a mixture thereof, used to remove unreacted reagents and residual impurities.

[0025] Preferably, the drying process in step S2 is carried out at a temperature of 40-60°C for 12-24 hours.

[0026] The present invention also provides a functionalized fiber membrane for removing metal ions from solution, prepared by the above method. The fiber membrane has a diameter of 50 nanometers to 1000 nanometers and has a three-dimensional interconnected porous structure with a porosity of 70% to 95%.

[0027] Furthermore, the functionalized fiber membrane includes a nanofiber substrate and a functionalized layer disposed on the surface of the nanofiber substrate. The nanofiber substrate is made of a polymeric material, polyacrylonitrile, and the functionalized layer contains active groups with ion exchange or chelation functions. These active groups are functional groups capable of providing ion exchange sites or coordination sites. The active groups with ion exchange or chelation functions contained in the functionalized layer are selected from at least one of oxygen-containing coordinating groups (carboxyl groups), strong acidic groups (sulfonic acid groups), and multidentate chelating groups (ethylenediaminetetraacetic acid groups).

[0028] The functionalized fiber membrane described in this invention can be used to remove trace (ppb level) metal ions from solutions.

[0029] Preferably, the metal ion is selected from one or more of sodium ions, potassium ions, copper ions, iron ions, calcium ions, or magnesium ions, and the metal ion is selected from one or more of sodium ions, potassium ions, copper ions, iron ions, calcium ions, or magnesium ions. + K + Fe 3+ The removal rate is ≥90%. The concentration of metal ions in the solution can be in the ppb range (e.g., 10-500 ppb).

[0030] Preferably, the solution is an electronic chemical system, including photoresist, developer, or organic solvent system.

[0031] Compared with the prior art, the present invention has the following advantages and beneficial effects:

[0032] 1. This invention constructs a functionalized layer with ion exchange and coordination functions by introducing active sites such as carboxyl, amino, sulfonic acid, and chelating groups on the surface of nanofibers. This significantly enhances the adsorption capacity of metal ions in solution and improves the removal efficiency of trace metal impurities, achieving high-efficiency removal even at ppb-level metal ion concentrations.

[0033] 2. This invention uses electrospinning technology to construct a three-dimensional interconnected porous nanofiber membrane. The fibers form a continuous open pore network, which can effectively shorten the mass transfer path, increase the diffusion rate of metal ions, thereby improving the adsorption kinetics performance and reducing fluid resistance.

[0034] 3. Compared with traditional granular ion exchange resins, the functionalized fiber membrane of the present invention has a higher specific surface area and better interfacial contact efficiency, which avoids the problems of easy shedding of particulate materials and secondary pollution while maintaining high removal efficiency.

[0035] 4. This invention uses surface chemical modification to stably fix active groups on the fiber surface, which improves the structural stability and service life of the material and enables it to maintain good adsorption performance and good structural stability in multiple uses or continuous flow systems.

[0036] 5. The preparation process of this invention is simple, the conditions are mild and highly controllable, and it is suitable for large-scale preparation. Moreover, the functionalized fiber membrane prepared has good application prospects in the field of electronic chemical purification, and can effectively reduce the content of metal ions in the solution and improve the purity of the system. Attached Figure Description

[0037] Figure 1 The image shows a scanning electron microscope (SEM) image of the carboxylated functional fiber membrane prepared in Example 1, which shows a uniform and continuous fiber structure.

[0038] Figure 2 The image shows a scanning electron microscope (SEM) image of the EDTA-functionalized nanofiber membrane prepared in Example 3, which reveals a uniform and continuous fiber structure. Detailed Implementation

[0039] The present invention will now be described in further detail with reference to embodiments and accompanying drawings, but the embodiments of the present invention are not limited thereto. The raw materials used in the design of this invention can all be purchased directly from the market, and for process parameters that are not particularly well-known, conventional techniques can be referred to.

[0040] Example 1:

[0041] This embodiment provides a method for preparing a carboxylated functional fiber membrane and its application in metal ion adsorption. The method specifically includes the following steps:

[0042] (1) Preparation of PAN nanofiber-based membranes:

[0043] Polyacrylonitrile (PAN, weight average molecular weight approximately 150,000) was dissolved in N,N-dimethylformamide (DMF) to prepare a homogeneous spinning solution with a mass fraction of 12 wt%. The solution was magnetically stirred at room temperature for 10 h to ensure complete dissolution of PAN, resulting in a uniform and transparent electrospinning precursor solution.

[0044] Nanofiber membranes were prepared using electrospinning technology, with the following specific process parameters: applied voltage: 15kV; injection rate: 1.0mL / h; distance between needle and receiving plate: 15cm; ambient temperature: 25℃; relative humidity: 40%.

[0045] The PAN nanofiber membranes were collected and dried under vacuum at 60°C for 12 hours to remove residual solvent, and then set aside for use.

[0046] (2) Carboxylation modification treatment:

[0047] The above-mentioned PAN nanofiber membrane was subjected to alkaline hydrolysis treatment in a NaOH / ethanol-water mixed solution. The NaOH concentration was 1.0 mol / L, and the volume ratio of ethanol to water was 1:1. The reaction was carried out at 30℃ for 4 hours, causing partial hydrolysis of the cyano groups (–C≡N) in the PAN molecular chain, gradually converting them into amide groups and carboxylates, thereby introducing carboxyl (–COOH) functional sites onto the fiber surface.

[0048] After the reaction was completed, the fiber membrane was removed and repeatedly washed with large amounts of deionized water until the pH of the washing solution was neutral to remove residual alkali and byproducts. It was then dried under vacuum at 60°C for 12 hours to obtain the carboxylated functional fiber membrane.

[0049] (3) Metal ion adsorption performance test:

[0050] The obtained carboxylated functional fiber membrane was cut into 1cm × 1cm samples and placed in a simulated wastewater solution containing metal ions for adsorption experiments. The metal ions included Cu. 2+ Fe 3+ and Na + Their initial concentrations were Cu 2+ 100 mg / L; Fe 3+ 100 mg / L; Na + The concentration of the compound was 100 mg / L, the pH of the solution was controlled at 6, and the reaction temperature was 25℃. The adsorption reaction was carried out under isothermal shaking conditions for 30 min.

[0051] Experimental results show that this carboxylated functional fiber membrane has a positive effect on Cu 2+ and Fe 3+ It exhibits strong adsorption capacity, with a more significant adsorption effect on high-valence metal ions, while the adsorption effect on Na+ is relatively strong. + The adsorption capacity is relatively weak, indicating that it has a certain degree of selective adsorption characteristics. Under the above experimental conditions, the removal effects on different metal ions are as follows: After 30 min of adsorption, the removal rates of each metal ion were as follows: Cu 2+ : 94.6%; Fe 3+ 96.2%; Na + 18.7%

[0052] (4) Description of technical effects:

[0053] Compared with unmodified PAN nanofiber membranes, the carboxylated functional fiber membranes prepared in this embodiment have a large number of carboxyl functional groups introduced on their surface, which can interact with metal ions through electrostatic interaction and complexation, thereby significantly improving the removal efficiency of heavy metal ions.

[0054] Meanwhile, this method is simple, operates under mild conditions, and is easy to scale up, making it suitable for the rapid adsorption and separation of heavy metal pollutants in water.

[0055] Example 2:

[0056] This embodiment provides a method for preparing a multifunctional group-grafted polyacrylonitrile (PAN) nanofiber functional membrane for removing metal ions from solution. The method includes the following steps:

[0057] (1) Preparation of PAN nanofiber membranes:

[0058] Polyacrylonitrile (PAN, weight average molecular weight approximately 150,000) was dissolved in N,N-dimethylformamide (DMF) to prepare a homogeneous spinning solution with a mass fraction of 12 wt%. The solution was magnetically stirred at room temperature for 10 h until completely dissolved, resulting in a uniform and transparent solution.

[0059] Nanofiber membranes were prepared using electrospinning technology with the following parameters: applied voltage: 15kV; feed rate: 1mL / h; distance between needle and receiving plate: 15cm; ambient temperature: 25℃; relative humidity: 60%.

[0060] The PAN nanofiber membranes were collected and dried in a vacuum drying oven at 40°C for 12 hours for later use.

[0061] (2) Amination treatment of PAN nanofiber surface

[0062] The above-mentioned PAN nanofiber membrane was placed in a mixed solution of hydrazine hydrate / ethanol / water, wherein the mass fraction of hydrazine hydrate was 80% and the volume ratio of ethanol to water was 1:1. The reaction was carried out at 40-60℃ for 4 hours, causing the cyano groups in the PAN molecular chain to undergo hydrazinolysis, generating acylhydrazine structures and some amine functional groups.

[0063] After the reaction was completed, the membrane was repeatedly washed with deionized water and ethanol until neutral, and then dried at 60°C to obtain an amination PAN nanofiber membrane.

[0064] (3) Carboxyl functionalization modification

[0065] Amine-modified PAN nanofiber membranes were immersed in a solution of N,N-dimethylformamide containing maleic anhydride (which can be replaced with succinic anhydride) at a concentration of 1 mol / L, with 0.8% (w / w) of 4-dimethylaminopyridine (DMAP) added as a catalyst. The reaction was carried out at 60 °C for 6 h to allow the anhydride to undergo a ring-opening reaction with the amino groups on the fiber surface, introducing carboxyl functional groups. After the reaction was complete, the membranes were washed sequentially with N,N-dimethylformamide and deionized water, and then vacuum dried at 60 °C to obtain carboxylated PAN nanofiber membranes.

[0066] (4) Sulfonic acid group introduction modification

[0067] The carboxylated PAN nanofiber membrane was placed in an ice bath (2°C) and a chlorosulfonic acid solution (3 wt%) was slowly added to carry out a surface sulfonation reaction. The reaction time was controlled at 20 min to avoid damage to the fiber structure. After the reaction was completed, the sample was immediately transferred to a large amount of ice water to terminate the reaction and repeatedly washed until neutral. Then, it was vacuum dried at 40°C to obtain a multifunctional modified PAN nanofiber membrane.

[0068] (5) Fiber membrane adsorption performance test

[0069] The adsorption performance of the fiber membrane was tested by cutting the multifunctional modified PAN nanofiber membrane prepared in Example 2 into samples with a size of 2 cm × 2 cm. Each sample was placed in 50 mL of a metal ion solution of a certain concentration (Cu). 2+ Pb 2+ Fe 3+ The initial concentration of all samples was 50 mg / L. Adsorption was performed at 25℃ with shaking for 4 h at a shaking rate of 150 rpm. After adsorption, the solution was filtered or the supernatant was collected, and the residual metal ion concentration was determined by inductively coupled plasma optical emission spectrometry (ICP-OES). The adsorption amount was calculated using the following formula:

[0070]

[0071] Multifunctional modified PAN nanofiber membrane for Cu 2+ Pb 2+ Fe 3+ All exhibited excellent adsorption performance, among which Pb 2+ It exhibits the highest adsorption capacity, with a maximum adsorption amount reaching 165 mg / g, significantly higher than unmodified materials and materials modified with a single functional group.

[0072] Example 3:

[0073] The preparation of functional fiber membranes incorporating EDTA chelating groups and their adsorption properties for metal ions are described, specifically including the following steps:

[0074] (1) Pretreatment of carboxylated fiber membranes:

[0075] The carboxylated functional fiber membrane prepared in Example 1 was cut to an appropriate size for later use. To improve the exposure of active sites in the subsequent grafting reaction, the carboxylated functional fiber membrane could be pre-wetted in deionized water for 20 minutes to allow the fibers to swell fully and improve the uniformity of the reaction.

[0076] (2) Grafting modification of EDTA groups:

[0077] The pretreated carboxylated functional fiber membrane was placed in an organic solution system containing ethylenediaminetetraacetic dianhydride (EDTA dianhydride) for grafting reaction. N,N-dimethylformamide (DMF) or dimethyl sulfoxide (DMSO) could be used as the solvent for the EDTA dianhydride solution, with a mass concentration of 2 wt%. In the reaction system, the carboxyl groups (–COOH) on the fiber surface underwent a ring-opening acylation reaction with the EDTA dianhydride, further forming a stable amide / ester bond structure, thereby covalently grafting the EDTA multidentate chelating groups onto the fiber surface.

[0078] The reaction conditions are as follows: reaction temperature: room temperature to 50℃; reaction time: 6 hours;

[0079] Slight oscillation or magnetic stirring can improve mass transfer efficiency.

[0080] (3) Post-processing and purification:

[0081] After the reaction was completed, the fiber membrane was washed sequentially with N,N-dimethylformamide or dimethyl sulfoxide, ethanol and deionized water to thoroughly remove unreacted EDTA dianhydride and low molecular weight byproducts.

[0082] After washing, the fiber membrane was dried under vacuum at 60°C for 12 hours to obtain an EDTA-functionalized nanofiber membrane (PAN-COOH-EDTA functionalized fiber membrane).

[0083] (4) Evaluation of metal ion adsorption performance:

[0084] The obtained EDTA functionalized fiber membrane was cut into 1cm × 1cm samples and placed in a simulated wastewater solution containing various metal ions for adsorption experiments. The metal ions included Cu. 2+ Pb 2+ Fe 3+ and Zn 2+ The initial concentration of each metal ion was 100 mg / L to ensure comparability of adsorption performance among different metal ions. The solution pH was controlled at 6, and the temperature was 25℃. The adsorption reaction was carried out under isothermal shaking conditions for 30 min, and the residual metal ion concentration was measured periodically.

[0085] Experimental results show that the EDTA-functionalized fiber membrane exhibits excellent adsorption performance for a variety of divalent and trivalent metal ions, with high adsorption capacity and fast adsorption kinetics, especially for Cu. 2+ and Pb 2+ It exhibits significant selective enrichment ability. Specific data are as follows: Adsorption capacity (Cu) 2+ ): 192 mg / g; adsorption capacity (Pb) 2+): 218 mg / g, removal rate: >95%.

[0086] (6) Technical effect description:

[0087] Compared to the single carboxylated fiber membrane of Example 1, this example introduces an EDTA multidentate chelate structure, transforming the fiber surface from a single coordination site to a multidentate cooperative coordination structure. This structure can simultaneously form stable chelate complexes with metal ions through nitrogen and oxygen atoms, thereby significantly improving the metal ion binding capacity and selective adsorption performance, and effectively enhancing the kinetic adsorption rate of the material. Furthermore, this method features mild reaction conditions and simple operation, making it suitable for the large-scale preparation of functionalized nanofiber membranes.

[0088] Example 4

[0089] This embodiment provides a dynamic filtration method for multifunctional group-grafted polyacrylonitrile nanofiber functional membranes in trace metal ion systems and its recycling performance evaluation.

[0090] (1) Preparation of functionalized fiber membranes

[0091] The functionalized nanofiber membrane was prepared using the method described in Example 3, resulting in a multifunctionalized PAN nanofiber membrane (denoted as PAN-COOH-EDTA) with ethylenediaminetetraacetic acid (EDTA) groups. The obtained fiber membrane was cut into circular sheets with a diameter of 3 cm and a thickness of approximately 200 μm, and fixed in a dead-end filtration device as a filter medium.

[0092] (2) Preparation of simulated low-concentration metal ion solutions

[0093] Prepare a solution simulating an electronic chemical system using deionized water or an isopropanol / water mixture (volume ratio 1:1) as the solvent. The solution contains trace amounts of metal ions, including Cu. 2+ Fe 3+ And Na + Its initial concentration is: Cu 2+ 100 ppb; Fe 3 + 100 ppb; Na + 500 ppb. Adjust the solution pH to 5.5 ± 0.2.

[0094] (3) Dynamic filtration experiment

[0095] The above solution was filtered through the prepared functionalized nanofiber membrane (PAN-COOH-EDTA) under constant pressure driving conditions. The specific operating parameters were as follows: operating pressure: 0.08 MPa; filtration flux: 200 L·m³. -2 ·h -1Filtration temperature: 25℃; Processing volume: 100mL.

[0096] During the filtration process, permeate samples were collected at regular intervals, and the concentration of metal ions was determined by inductively coupled plasma mass spectrometry (ICP-MS).

[0097] (4) Comparative experiment

[0098] To verify the technical effect of the present invention, an unmodified PAN nanofiber membrane (the fiber membrane prepared in step (1) of Example 3) and a carboxylated PAN fiber membrane (the fiber membrane prepared in Example 1) were set as control groups and filtration experiments were carried out under the same conditions.

[0099] Experimental results show that:

[0100] Unmodified PAN nanofiber membranes showed a 24% removal rate for metal ions; carboxylated PAN nanofiber membranes showed a 24% removal rate for Cu ions. 2+ and Fe 3+ The removal rates were 78% and 82%, respectively; the PAN-COOH-EDTA functionalized fiber membrane in Example 3 showed good removal rates for Cu. 2+ and Fe 3+ The removal rates were 96% and 94%, respectively; meanwhile, the removal rates of Na... + The removal rate was relatively low, only 18%, indicating that the material has higher selectivity for multivalent metal ions.

[0101] (5) Cyclic regeneration performance test

[0102] The PAN-COOH-EDTA functionalized fiber membrane, after adsorption saturation, was immersed in 0.5 mol / L dilute hydrochloric acid solution for 30 min for desorption treatment, followed by washing with deionized water until neutral and drying. The adsorption-desorption cycle experiment was repeated 5 times, and the results showed that:

[0103] After 5 cycles, the membrane for Cu 2+ The removal rate remained above 85%; the material structure showed no obvious damage, indicating that it has good stability and reusability.

[0104] (6) Description of technical effects

[0105] The multifunctionalized PAN nanofiber membrane prepared by this invention exhibits excellent removal capabilities in trace metal ion systems, and can further reduce the concentration of metal ions in the solution from the ppb level to an even lower level, meeting the application requirements of high-purity chemicals.

[0106] Compared to traditional granular ion exchange resins, this invention achieves effective introduction of functional groups under mild conditions by adjusting process parameters, while maintaining the three-dimensional interconnected porous structure of the fibers, thus avoiding nanofiber structure collapse and breakage. The prepared multifunctionalized PAN nanofiber membrane, relying on its three-dimensional interconnected porous structure and high-density active sites on the surface, significantly improves mass transfer efficiency and adsorption kinetics performance, while reducing fluid resistance.

[0107] Furthermore, while existing technologies demonstrate that PAN materials can incorporate different functional groups through various reactions, achieving the synergistic introduction of multiple functional groups (such as carboxyl, amino, sulfonic acid, and chelating groups) within the same nanofiber system, and ensuring their stable presence on the fiber surface without detachment or deactivation, remains a significant technical challenge. This invention overcomes these difficulties. The prepared multifunctionalized PAN nanofiber membrane exhibits excellent structural stability, can operate stably in continuous filtration systems, and possesses good regeneration performance, making it suitable for applications requiring extremely high metal ion content, such as electronic chemical purification and ultrapure water treatment.

[0108] The above embodiments are preferred embodiments of the present invention, but the embodiments of the present invention are not limited to the above embodiments. Any changes, modifications, substitutions, combinations, or simplifications made without departing from the spirit and principle of the present invention shall be considered equivalent substitutions and shall be included within the protection scope of the present invention.

Claims

1. A method for preparing a functionalized fiber membrane for removing metal ions from solution, characterized in that, Includes the following steps: S1. Polyacrylonitrile powder is dissolved in an organic solvent to obtain a polyacrylonitrile spinning solution, which is then spun using an electrospinning method. After spinning, the solution is dried to obtain a polyacrylonitrile nanofiber membrane. S2. The prepared polyacrylonitrile nanofiber membrane is immersed in an alkaline hydrolysis system for surface chemical modification. After the reaction is complete, the fiber membrane is washed and dried to obtain the functionalized fiber membrane used to remove metal ions from the solution.

2. The preparation method according to claim 1, characterized in that, The organic solvent mentioned in step S1 is at least one of N,N-dimethylformamide, N,N-dimethylacetamide, and acetone; In step S1, the mass concentration of polyacrylonitrile in the spinning solution is 10-20 wt%; the weight-average molecular weight of the polyacrylonitrile is 50,000-300,000. The parameters of the electrospinning method described in step S1 include: a spinning voltage range of 10~15kV, a spinning receiving distance of 15~25cm, a syringe advance speed of 0.4~1mL / h, a collecting roller rotation speed of 100~400rpm, a spinning ambient temperature of 20~40℃, and a relative humidity of 20~80%RH%. The drying temperature in step S1 is 40~60℃, and the drying time is 12~24h.

3. The preparation method according to claim 1, characterized in that, The alkaline hydrolysis system mentioned in step S2 is one of the following: NaOH / ethanol-water mixed solution, hydrazine hydrate / ethanol / water mixed solution, organic solution system containing ethylenediaminetetraacetic dianhydride, chlorosulfonic acid solution, and acid anhydride reagent solution.

4. The preparation method according to claim 3, characterized in that, In the alkaline hydrolysis system, the concentration of NaOH in the NaOH / ethanol-water mixed solution is 0.1~2 mol / L, the concentration of hydrazine hydrate in the hydrazine hydrate / ethanol / water mixed solution is 5~50 wt%, the concentration of ethylenediaminetetraacetic acid dianhydride in the organic solution system containing ethylenediaminetetraacetic acid dianhydride is 0.01~0.2 mol / L, the concentration of chlorosulfonic acid in the chlorosulfonic acid solution is 1~10 wt%, and the concentration of acid anhydride reagent in the acid anhydride reagent solution is 0.1~1.0 mol / L.

5. The preparation method according to claim 1, characterized in that, The surface chemical modification temperature in step S2 is 25~60℃; the reaction time is 6~12h.

6. The preparation method according to claim 1, characterized in that, The washing solution used in step S2 is at least one of DMF, deionized water, and ethanol; The drying process in step S2 is carried out at a temperature of 40~60℃ for 12~24h.

7. The preparation method according to claim 1, characterized in that, The operation of step S2 was repeated several times, and surface chemical modification was carried out in different alkaline hydrolysis systems to introduce a variety of different active groups on the surface of polyacrylonitrile fibers.

8. A functionalized fiber membrane for removing metal ions from a solution, prepared by the method according to any one of claims 1-7.

9. The use of the functionalized fiber membrane of claim 7 or 8 in the removal of trace metal ions from a solution.

10. The application according to claim 9, characterized in that, The metal ion is selected from one or more of sodium ion, potassium ion, copper ion, iron ion, calcium ion or magnesium ion, and the concentration of the metal ion in the solution is at the ppb level; The solution is an electronic chemical system, including photoresist, developer, or organic solvent system.

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