A porous hybrid carbon nanofiber membrane, its preparation method and application

Abstract

This invention relates to the field of carbon materials technology, providing a porous hybrid carbon nanofiber membrane, its preparation method, and its applications. The invention proposes a "pore-hybrid dual-structure synergy" design concept, combining the pore-forming and flexibility-enhancing mechanism of PLA with a TEOS inorganic hybridization strategy. Using PAN as the carbon framework matrix, PLA as the pyrolytic pore-forming agent, TEOS as the silicon source, and lignin EHL as the hydrophilic modification component, a dual-structure synergistic flexible carbon nanofiber membrane is constructed. The resulting membrane exhibits stable separation performance, good separation cycle stability, and good durability, demonstrating broad applicability.

Description

Technical Field

[0001] This invention relates to the field of carbon materials technology, and in particular to a porous hybrid carbon nanofiber membrane, its preparation method, and its application.

[0002] Technical terms: TEOS refers to tetraethyl orthosilicate, DMF refers to N,N-dimethylformamide, PLA refers to polylactic acid, PAN refers to polyacrylonitrile, and EHL refers to enzymatically hydrolyzed lignin. Background Technology

[0003] With the acceleration of global industrialization, the resulting large amounts of oily wastewater are harming the ecological environment and human health. In particular, highly stable emulsified oil wastewater has become a serious challenge for water pollution and water resource recovery. For the treatment of emulsified oil wastewater, electrospun carbon nanofiber membrane separation technology, with its high porosity and tunable surface properties, shows great application potential. However, traditional PAN carbon nanofiber membranes face challenges in separating water-in-oil emulsified oil wastewater, which has a wide range of sources and large production volumes, due to their poor flexibility and hydrophobic-oleophilic properties.

[0004] To address the aforementioned issues, existing research has proposed two single modification strategies. However, these single strategies have significant limitations in improving the overall performance of carbon nanofiber membranes: while PLA pyrolysis pore formation can effectively enhance membrane flexibility, the resulting membrane skeleton lacks density, and its mechanical strength and chemical stability need to be improved; while TEOS-derived Si-O phases can strengthen the carbon matrix and optimize stress distribution, they are difficult to independently construct high-porosity structures, thus limiting the improvement of permeation flux. Summary of the Invention

[0005] The present invention aims to solve at least one of the above-mentioned technical problems and provides a porous hybrid carbon nanofiber membrane, its preparation method and application.

[0006] The first aspect of this invention provides a method for preparing a porous hybrid carbon nanofiber membrane, comprising the following steps: S1. Preparation of polymer nanofiber membranes: S11. Add TEOS to DMF and stir for a period of time to obtain a homogeneous solution; S12. Subsequently, PLA, PAN and EHL are added to the above homogeneous solution at the same time, and the mixture is stirred until completely dissolved to obtain a spinning solution. S13. The obtained spinning solution is loaded into a syringe for electrospinning, and the polymer film is collected by a collector. S14. After electrospinning is completed, the collected polymer membrane is taken out from the collector, dried, and polymer nanofiber membrane is obtained. S2. Preparation of porous hybrid carbon nanofiber membranes: S21. Pre-oxidation: The polymer nanofiber membrane is pre-oxidized in air at a certain heating rate to 200-300 ℃; S22. Carbonization: Under a protective atmosphere, the pre-oxidized polymer nanofiber membrane is carbonized at a certain heating rate to 600-1000 ℃ to obtain a porous hybrid carbon nanofiber membrane.

[0007] This invention proposes a "pore-hybrid dual-structure synergy" design concept, combining the pore-forming and flexibility-enhancing mechanism of PLA with the inorganic hybridization strategy of TEOS. Using PAN as the carbon skeleton matrix, PLA as the pyrolytic pore-forming agent, TEOS as the silicon source, and lignin EHL as the hydrophilic modification component, a dual-structure synergistic flexible carbon nanofiber membrane is constructed. In this design, the porous structure formed by PLA decomposition endows the membrane material with compressibility and deformation capabilities, alleviating bending stress; the rigid SiO2 particles generated by TEOS hydrolysis synergistically inhibit carbonization shrinkage and buffer local stress concentration with the lignin-derived amorphous carbon domains; the Si-O amorphous phase serves as a flexible, chemically stable interface layer, achieving load redistribution and structural continuity; and the hydroxyl and carboxyl groups abundant in lignin directionally regulate the surface superhydrophilicity. This system, through molecular-level precursor composites, simultaneously addresses the bottlenecks of brittleness, oleophobicity, and high cost, achieving synergistic optimization of foldable flexibility, high permeability flux, and excellent separation selectivity.

[0008] This invention uses PLA, TEOS, PAN and lignin EHL as spinning precursors and employs a series of electrospinning, pre-oxidation and carbonization processes to prepare a flexible porous hybrid carbon nanofiber membrane with superhydrophilicity and underwater oleophobicity in one step.

[0009] Preferably, in step S11: The mass ratio of TEOS to DMF is (5-15):(200-250); The stirring temperature is 20-45℃, and the stirring time is 15-60 minutes.

[0010] Preferably, in step S12: The mass ratio of PLA, PAN, and EHL is (3-10):(10-20):(5-15); The mass ratio of TEOS to EHL is (5-15):(5-15); The temperature of the stirred mixture is 40-75 ℃.

[0011] Preferably, in step S13: The voltage for electrospinning is 18-20 kV; The feed rate for electrospinning is 1.5-2.0 mL / h; The distance between the syringe tip and the collector is 12-18 cm.

[0012] Preferably, in step S13: The temperature for electrospinning is 20-30 ℃; The relative humidity for electrospinning is 45%. The electrospinning time is 4-8 hours; The collector rotates at a speed of 120-2000 rpm.

[0013] Preferably, in step S14, drying is performed by drying overnight at room temperature.

[0014] Preferably, in step S21, the heating rate is 0.25-10.00 ℃ / min.

[0015] Preferably, in S22: The protective atmosphere is nitrogen, helium, or argon. The heating rate is 2-7.5 ℃ / min; Carbonize at 600-1000 ℃ for 1-3 hours.

[0016] A second aspect of the present invention provides a porous hybrid carbon nanofiber membrane, prepared according to any one of the above preparation methods.

[0017] A third aspect of the present invention is to provide an application of a porous hybrid carbon nanofiber membrane in water treatment.

[0018] This invention proposes a "pore-hybrid dual-structure synergy" design concept, combining the pore-forming and flexibility-enhancing mechanism of PLA with the inorganic hybridization strategy of TEOS. Using PAN as the carbon skeleton matrix, PLA as the pyrolytic pore-forming agent, TEOS as the silicon source, and lignin as the hydrophilic modification component, a dual-structure synergistic flexible carbon nanofiber membrane is constructed. In this design, the porous structure formed by PLA decomposition endows the membrane material with compressibility and deformation capabilities, alleviating bending stress; the rigid SiO2 particles generated by TEOS hydrolysis synergistically inhibit carbonization shrinkage and buffer local stress concentration with the lignin-derived amorphous carbon domains; the Si-O amorphous phase serves as a flexible, chemically stable interface layer, achieving load redistribution and structural continuity; and the hydroxyl and carboxyl groups abundant in lignin directionally regulate the surface superhydrophilicity. This system, through molecular-level precursor composites, simultaneously addresses the bottlenecks of brittleness, oleophobicity, and high cost, achieving synergistic optimization of foldable flexibility, high permeability flux, and excellent separation selectivity.

[0019] This invention uses PLA, TEOS, PAN, and lignin as spinning precursors and employs a one-step process of electrospinning, pre-oxidation, and carbonization to prepare a flexible porous hybrid carbon nanofiber membrane with superhydrophilicity and underwater oleophobicity. The resulting membrane exhibits stable separation performance, good separation cycle stability and durability, and has wide applicability. Attached Figure Description

[0020] Figure 1 Images of porous hybrid carbon nanofiber membranes being bent and folded; Figure 2 (a) Stress-strain curves and (b) modulus of porous hybrid carbon nanofiber membranes with different pre-oxidation heating rates; Figure 3 (a) Stress-strain curves and (b) modulus of porous hybrid carbon nanofiber membranes at different carbonization temperatures; Figure 4 (a) An image of the rapid permeation process of water droplets on the surface of a porous hybrid carbon nanofiber membrane; Figure 4 (b) Contact angle of porous hybrid carbon nanofiber membrane with oil in air; CCNFMs-5.0-z Figure 4 (c) Immersion time in air; Figure 4 (d) Underwater oil contact angle; Figure 4 (e) Underwater oil contact angles for different oil agents; Figure 4 (f) Digital photograph of the underwater oil adhesion resistance of CCNFM-5.0-600; Figure 4 (g) Water contact angle in air for lignin-free carbon nanofiber membranes; Figure 4 (h) Image of the rapid penetration process of oil droplets on the CCNFM surface; Figure 5 Separation flux and separation efficiency for separating oil-water mixtures using gravity-driven devices: (a) SFM and (b) SSE; (c) Permeation flux and separation efficiency of CCNFM-5.0-600 for different oil-based SSEs under gravity drive; (d) Optical microscopic images and digital photographs of oil-in-water emulsions before (left) and after (right) separation using porous hybrid carbon nanofiber membranes; (e) Schematic diagram of the SSE and SFM permeation processes. Detailed Implementation

[0021] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0022] Example 1:

[0023] 1. Preparation of polymer nanofiber membranes: First, 1.0 g of TEOS was added to 23 g of DMF and stirred at room temperature for 30 minutes to obtain a homogeneous solution. Then, 0.6 g of PLA, 1.4 g of PAN, and 1.0 g of EHL were simultaneously added to the above solution, and the mixture was stirred at 60 °C until completely dissolved. The resulting spinning solution was then loaded into a syringe, and electrospinning was performed at a feed rate of 1.8 mL / h under a voltage of 18–20 kV, with the tip 15 cm from the collector. The electrospinning process was carried out for 6 hours at 25 °C and 45% relative humidity, with the collector rotating at 150 rpm. After electrospinning, the polymer film was removed from the collector and dried overnight at room temperature.

[0024] 2. Preparation of porous hybrid carbon nanofiber membranes: To investigate the effects of pre-oxidation heating rate and carbonization temperature on the mechanical properties and surface wettability of CCNFMs, the following steps were performed for pre-oxidation and carbonization: First, the polymer nanofiber membrane was pre-oxidized in air at a heating rate of 5.00 °C / min to 250 °C. Then, the resulting membrane was further carbonized for 2 h at a heating rate of 5 °C / min to 800 °C under a nitrogen atmosphere to obtain a porous hybrid carbon nanofiber membrane. The resulting material is denoted as CCNFM-XY, where X represents the pre-oxidation heating rate and Y represents the carbonization temperature.

[0025] The material obtained in this embodiment is designated CCNFM-5.00-800. Images of the porous hybrid carbon nanofiber membrane under bending and folding are shown below. Figure 1 As shown, the material obtained in this embodiment has good flexibility and remains intact after being bent and folded.

[0026] Example 2:

[0027] The heating rate for pre-oxidation was 0.25 °C / min, and the rest was the same as in Example 1.

[0028] The resulting material is denoted as CCNFM-0.25-800.

[0029] Example 3:

[0030] The heating rate for pre-oxidation was 1.00 °C / min, and the rest was the same as in Example 1.

[0031] The obtained material is denoted as CCNFM-1.00-800.

[0032] Example 4:

[0033] The pre-oxidation heating rate was 3.00 °C / min, and the rest was the same as in Example 1.

[0034] The obtained material is denoted as CCNFM-3.00-800.

[0035] Example 5:

[0036] The heating rate for pre-oxidation was 10.00 °C / min, and the rest was the same as in Example 1.

[0037] The obtained material is denoted as CCNFM-10.00-800.

[0038] Example 6:

[0039] The carbonization temperature was 600 °C, and the rest was the same as in Example 1.

[0040] The resulting material is denoted as CCNFM-1.00-600.

[0041] Example 7:

[0042] The carbonization temperature was 700 °C, and the rest was the same as in Example 1.

[0043] The resulting material is denoted as CCNFM-5.00-700.

[0044] Example 8:

[0045] The carbonization temperature was 900 °C, and the rest was the same as in Example 1.

[0046] The obtained material is denoted as CCNFM-5.00-900.

[0047] Example 9:

[0048] The carbonization temperature was 1000 ℃, and the rest was the same as in Example 1.

[0049] The resulting material is denoted as CCNFM-5.00-1000.

[0050] Example 10:

[0051] The pre-oxidation heating rate was 1.00 °C / min, the carbonization temperature was 900 °C, and the rest was the same as in Example 1.

[0052] The obtained material is denoted as CCNFM-1.00-900.

[0053] Example 11:

[0054] 1. Preparation of polymer nanofiber membranes: First, 1.2 g of TEOS was added to 22 g of DMF and stirred at room temperature for 30 minutes to obtain a homogeneous solution. Then, 0.5 g of PLA, 1.5 g of PAN, and 0.75 g of EHL were simultaneously added to the solution, and the mixture was stirred at 60 °C until completely dissolved. The resulting spinning solution was then loaded into a syringe, and electrospinning was performed at a feed rate of 1.8 mL / h under a voltage of 18-20 kV, with the tip 15 cm from the collector. The electrospinning process was carried out for 6 hours at 25 °C and 45% relative humidity, with the collector rotating at 150 rpm. After electrospinning, the polymer film was removed from the collector and dried overnight at room temperature.

[0055] 2. Preparation of porous hybrid carbon nanofiber membranes: To investigate the effects of pre-oxidation heating rate and carbonization temperature on the mechanical properties and surface wettability of CCNFMs, the following steps were performed for pre-oxidation and carbonization: First, the polymer nanofiber membrane was pre-oxidized in air at a heating rate of 1.00 °C / min to 200 °C. Then, the resulting membrane was further carbonized for 2 h at a heating rate of 3.5 °C / min to 900 °C under a nitrogen atmosphere.

[0056] The resulting material is denoted as 1-CCNFM-1.00-900.

[0057] Example 12:

[0058] 1. Preparation of polymer nanofiber membranes: First, 0.8 g of TEOS was added to 24 g of DMF and stirred at room temperature for 30 minutes to obtain a homogeneous solution. Then, 0.75 g of PLA, 1.3 g of PAN, and 1.2 g of EHL were simultaneously added to the above solution, and the mixture was stirred at 60 °C until completely dissolved. The resulting spinning solution was then loaded into a syringe, and electrospinning was performed at a feed rate of 1.8 mL / h under a voltage of 18-20 kV, with the tip 15 cm from the collector. The electrospinning process was carried out for 6 hours at 25 °C and 45% relative humidity, with the collector rotating at 150 rpm. After electrospinning, the polymer film was removed from the collector and dried overnight at room temperature.

[0059] 2. Preparation of porous hybrid carbon nanofiber membranes: To investigate the effects of pre-oxidation heating rate and carbonization temperature on the mechanical properties and surface wettability of CCNFMs, the following steps were performed for pre-oxidation and carbonization: First, the polymer nanofiber membrane was pre-oxidized in air at a heating rate of 1.00 °C / min to 300 °C. Then, the resulting membrane was further carbonized for 2 h at a heating rate of 6 °C / min to 900 °C under a nitrogen atmosphere.

[0060] The resulting material is denoted as 2-CCNFM-1.00-900.

[0061] Comparative Example 1: EHL was not added (PLA, TEOS, and PAN were used as raw materials), and everything else was the same as in Example 1. The resulting material was denoted as 1-CCNFM.

[0062] Comparative Example 2: PLA was not added (EHL, TEOS, and PAN were used as raw materials), and the rest was the same as in Example 1. The resulting material was denoted as 2-CCNFM.

[0063] The following are the performance tests and structural characterizations.

[0064] I. Mechanical properties and microstructure: like Figure 2 As shown in (a) and (b), as the pre-oxidation heating rate increased from 0.25 ℃ / min to 5.00 ℃ / min, the tensile stress of the porous hybrid carbon nanofiber membrane decreased from 2.04 MPa to 1.54 MPa, the tensile strain increased from 1.46% to 2.03%, and the Young's modulus decreased from 148.9 MPa to 76.1 MPa. This result indicates that the increase in the pre-oxidation heating rate reduced the tensile strength of the porous hybrid carbon nanofiber membrane, but increased the fracture deformation and improved the flexibility. This may be because the pores generated by the pyrolysis of PLA during pre-oxidation can deflect and disperse the stress, thereby alleviating the stress concentration phenomenon when the nanofibers are under stress, and thus increasing the tensile strain of the porous hybrid carbon nanofiber membrane. When the pre-oxidation heating rate was further increased from 5.00 ℃ / min to 10.0 ℃ / min, the tensile stress of the porous hybrid carbon nanofiber membrane did not change significantly, but the tensile strain decreased significantly from 2.03% to 1.32%, and the Young's modulus increased from 76.1 MPa to 137.12 MPa. This result indicates that further increasing the pre-oxidation heating rate did not significantly change the tensile strength of the porous hybrid carbon nanofiber membrane, but significantly reduced its fracture deformation capacity and flexibility.

[0065] As shown in Table 1, the pore volume of the porous hybrid carbon nanofiber membrane first decreases and then increases with the increase of the pre-oxidation heating rate. This indicates that either too slow or too fast a pre-oxidation heating rate promotes the formation of pores in the porous hybrid carbon nanofiber membrane. This is because when the pre-oxidation heating rate is slow, the pre-oxidation process is prolonged, and PLA undergoes more complete pyrolysis during the heating process; while when the pre-oxidation heating rate is too fast, the PLA pyrolysis process and gas escape are accelerated, leading to the formation of more pores.

[0066] Table 1. Pore structure of porous hybrid carbon nanofiber membranes with different pre-oxidation heating rates .

[0067] like Figure 3 As shown in (a) and (b), as the carbonization temperature increased from 600 ℃ to 900 ℃, the tensile stress of the porous hybrid carbon nanofiber membrane decreased from 2.29 MPa to 1.41 MPa, the tensile strain increased from 1.65% to 2.38%, and the Young's modulus decreased from 141.2 MPa to 62.1 MPa. This result indicates that the increase in carbonization temperature reduced the tensile strength of the porous hybrid carbon nanofiber membrane, but increased the fracture deformation and improved the flexibility. This may be because the porosity generated by the pyrolysis of PLA and lignin during heat treatment increases with the increase in carbonization temperature. The pyrolysis of lignin is more complete, and more pores are generated. These pores can deflect and disperse the stress, thereby alleviating the stress concentration phenomenon when the nanofibers are under stress. This increases the tensile strain and improves the flexibility of the porous hybrid carbon nanofiber membrane. When the carbonization temperature was further increased to 1000 ℃, the tensile stress of the porous hybrid carbon nanofiber membrane increased to 1.68 MPa, but the tensile strain decreased from 2.38% to 2.15%, and the Young's modulus increased from 62.1 MPa to 81.3 MPa. This result indicates that further increases in carbonization temperature slightly increased the tensile strength of the porous hybrid carbon nanofiber membrane, but decreased its fracture deformation capacity and flexibility. This may be because, with further increases in carbonization temperature, the graphitization degree of the porous hybrid carbon nanofiber membrane further increased, weakening the plastic deformation capacity of the carbon matrix and increasing the fracture stress. At the same time, further increases in temperature caused further pyrolysis of lignin, further increasing the pore structure of the porous hybrid carbon nanofiber membrane. Excessive pore structure has a degrading effect on the deformation capacity of the porous hybrid carbon nanofiber membrane.

[0068] As shown in Table 2, the pore volume of the porous hybrid carbon nanofiber membrane exhibits a trend of first increasing and then stabilizing with increasing carbonization temperature. This indicates that when the carbonization temperature is in the range of 600 ℃ to 900 ℃, higher carbonization temperatures promote the formation of pores in the porous hybrid carbon nanofiber membrane. This is because the increased carbonization temperature intensifies the pyrolysis of the PLA component as a sacrificial phase, leading to more complete decomposition of lignin (EHL), the release of more gaseous products, and the formation of more pores. Simultaneously, the carbon skeletons of polyacrylonitrile (PAN) and lignin (EHL) are further etched and activated, promoting the development of micropores and mesopores, resulting in an overall increase in pore structure. When the carbonization temperature is in the range of 900 ℃ to 1000 ℃, the change in pore structure is not significantly observed. Combined with the above description of mechanical properties, the increased tensile stress at fracture, the decreased fracture deformation and flexibility are mainly caused by the synergistic effect of increased graphitization and micro / mesoporous structure.

[0069] Table 2. Pore structures of porous hybrid carbon nanofiber membranes at different carbonization temperatures .

[0070] II. Wetting properties: Choosing the right wettability, including superhydrophilicity and high underwater oleophobicity, is a key requirement for oil-water separation applications. Figure 4 (a) illustrates the rapid permeation process of water droplets on the surface of a porous hybrid carbon nanofiber membrane. Figure 4 (b) shows its oil contact angle in air, by Figure 4 (c) It can be seen that the time for water droplets to wet porous hybrid carbon nanofiber membranes with different carbonization temperatures in the air is less than 0.2 seconds, which indicates that porous hybrid carbon nanofiber membranes with different carbonization temperatures all exhibit good superhydrophilicity.

[0071] like Figure 4 As shown in (d), the underwater oil contact angle (OCA) of the porous hybrid carbon nanofiber membrane for petroleum ether exceeded 147°, indicating that the porous hybrid carbon nanofiber membrane exhibits high underwater oleophobicity. Furthermore, at a carbonization temperature of 600 °C, it achieved a superoleophobic effect underwater (OCA = 150.5°). CCNFM-5.0-600 also showed good underwater oleophobicity for vegetable oil (OCA = 145.1°) and n-hexadecane (OCA = 148.7°). Figure 4 (e)).

[0072] The underwater oil-repellent properties of porous hybrid carbon nanofiber membranes are as follows: Figure 4As shown in (f), in the underwater oil anti-adhesion test, a jet of dyed petroleum ether rapidly impacted the underwater CCNFM-5.0-600 and then bounced completely without any adhesion. To further investigate the source of the surface hydrophilicity of the porous hybrid carbon nanofiber membrane, a lignin-free sample was prepared as a control (Comparative Example 1). The lignin-free carbon nanofiber membrane exhibited the typical hydrophobicity inherent in carbon nanofiber membranes in air. Figure 4 (g)) and superlipophilic ( Figure 4 (h) indicates that the superhydrophilicity of CCNFMs may originate from the incorporation of lignin.

[0073] Surface wettability tests showed that Comparative Example 1, without lignin, exhibited typical hydrophobic (WCA=129.5°) and oleophilic properties inherent to carbon materials in air (using PLA, TEOS, and PAN as raw materials). In contrast, the sample with added lignin exhibited stable superhydrophilicity in air within a carbonization temperature range of 600-1000 °C, indicating that the addition of lignin significantly altered the wettability of the carbon nanofiber membrane. The porous hybrid carbon nanofiber membrane exhibited good underwater anti-adhesion and underwater superoleophobicity (OCA=150.5°) to petroleum ether, and also showed high underwater oleophobicity to n-hexadecane and vegetable oils.

[0074] III. Oil-water separation performance: Different oily wastewaters were prepared, specifically surfactant-free oil-water mixtures (SFM) and SDS-stabilized oil-in-water emulsions (SSE), to evaluate the separation performance of porous hybrid carbon nanofiber membranes. Separation performance was tested using a glass separation apparatus. The oil-water mixture and the oil-in-water emulsion were placed in the upper glass apparatus, and the lignin-based carbon nanofiber membrane obtained in the above examples was placed at the junction of the two glass apparatuses. The oil-water mixture and the oil-in-water emulsion were separated under gravity, and the filtrate was collected in the lower glass apparatus.

[0075] like Figure 5 As shown in (a), as the carbonization temperature increases from 600 °C to 1000 °C, the permeation flux of the porous hybrid carbon nanofiber membrane to SFM increases from 4060.5 ± 358.4 L·m -2 ·h -1 It decreased to 1510.7 ± 201.3 L·m -2 ·h -1 However, CCNFMs still maintain a separation efficiency of over 99% for SFM. Figure 5 As shown in (b), as the carbonization temperature increases from 600 °C to 1000 °C, the permeation flux of the porous hybrid carbon nanofiber membrane to SSE increases from 1560.0 ± 158.3 L·m⁻¹. -2 ·h -1Decreased to 910.7 ± 101.1 L·m -2 ·h -1 The porous hybrid carbon nanofiber membrane maintained a separation efficiency of over 98% for SSE. This result indicates that the porous hybrid carbon nanofiber membrane treated at a lower carbonization temperature exhibits better flux when separating SFM and SSE. This is likely because at lower carbonization temperatures, lignin is not fully decomposed, and the carbon nanofiber membrane retains more hydrophilic groups. These hydrophilic groups enhance the affinity and preferential adsorption of water molecules, reducing the mass transfer resistance of the aqueous phase within the membrane pores, thereby significantly improving the flux of the oil-in-water emulsion.

[0076] Compared to separating SSE, porous hybrid carbon nanofiber membranes exhibit higher flux and separation efficiency for SFM. This is because oil droplets in SSE accumulate on the surface of the porous hybrid carbon nanofiber membrane, forming an oil film that hinders water passage and significantly reduces permeation flux. Figure 5 (e)). And as Figure 5 As shown in (c), the separation flux and efficiency for separating vegetable oil-based SSEs were 1029.3 L·m⁻¹. -2 ·h -1 And 98.9%; when separating n-hexadecyl SSE, the separation flux and efficiency were 1309.6 L·m⁻¹, respectively. -2 ·h -1 And 98.5%. Figure 5 (d) shows optical microscope images and digital photographs of the SSE and the corresponding filtrate. Numerous oil droplets with diameters of several micrometers can be observed in the emulsion, but these droplets are not visible in the clearer filtrate, indicating that the porous hybrid carbon nanofiber membrane has a good purification effect on emulsified oily wastewater.

[0077] Comparative Example 2, without the addition of PLA (using EHL, TEOS, and PAN as raw materials), yielded a carbon nanofiber membrane with a separation flux and efficiency of 525.1 L·m⁻¹ for separating SSE. -2 ·h -1 And 97.5%; when separating SFM, the separation flux and efficiency were 1002.3 L·m⁻¹, respectively. -2 ·h -1 And 98.3%.

[0078] Oil-water separation performance tests showed that, without the addition of PLA, the separation flux of Comparative Example 2 for both SSE and SSE was significantly lower than that of Example 1. The addition of PLA significantly improved the separation performance of the porous hybrid carbon nanofiber membrane for oily wastewater.

[0079] IV. Circulation separation performance: Cyclic separation experiments were conducted on the separation performance of the porous hybrid carbon nanofiber membrane CCNFM-5.00-600. The results showed that the separation effect of the porous hybrid carbon nanofiber membrane on SFM remained stable within five cycles. After five cycles, the SFM flux recovery efficiency of CCNFM-5.00-600 remained above 95%. Before and after separation, the surface morphology and porosity of CCNFM-5.00-600 showed no significant changes, demonstrating good separation cycle stability.

[0080] V. Durability: Durability tests showed that even with a separation time extended to 30 minutes, the SFM separation flux and flux recovery rate of CCNFM-5.00-600 remained at 4015.27 L·m⁻¹. -2 ·h -1 It achieves a separation efficiency of 98.8%, and its separation efficiency for different oil-based SSEs remains above 98%, demonstrating good versatility.

[0081] After being soaked in acid (pH=2) and alkali (pH=12) for 30 days, CCNFM-5.00-600 maintained a separation efficiency of over 99% with no significant change in elastic modulus. The surface morphology and porosity of the CCNFM-5.00-600 fiber membrane showed no significant changes after acid and alkali treatment, demonstrating good durability. After being soaked in water at 0 ℃ and 95 ℃ for half an hour, CCNFM-5.00-600 also maintained a separation efficiency of over 99%, demonstrating good durability and stability.

[0082] Finally, it should be noted that the above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art can still modify the technical solutions described in the foregoing embodiments or make equivalent substitutions for some of the technical features. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A method for preparing a porous hybrid carbon nanofiber membrane, characterized in that, Includes the following steps: S1. Preparation of polymer nanofiber membranes S11. Add TEOS to DMF and stir for a period of time to obtain a homogeneous solution; S12. Subsequently, PLA, PAN and EHL are added to the above homogeneous solution at the same time, and the mixture is stirred until completely dissolved to obtain a spinning solution. S13. The obtained spinning solution is loaded into a syringe for electrospinning, and the polymer film is collected by a collector. S14. After electrospinning is completed, the collected polymer membrane is taken out from the collector, dried, and polymer nanofiber membrane is obtained. S2. Preparation of porous hybrid carbon nanofiber membranes S21. Pre-oxidation: The polymer nanofiber membrane is pre-oxidized in air at a certain heating rate to 200-300 ℃; S22. Carbonization: Under a protective atmosphere, the pre-oxidized polymer nanofiber membrane is carbonized at a certain heating rate to 600-1000 ℃ to obtain a porous hybrid carbon nanofiber membrane.

2. The method for preparing a porous hybrid carbon nanofiber membrane according to claim 1, characterized in that, In step S11: The mass ratio of TEOS to DMF is (5-15):(200-250); The stirring temperature is 20-45℃, and the stirring time is 15-60 minutes.

3. The method for preparing a porous hybrid carbon nanofiber membrane according to claim 1, characterized in that, In step S12: The mass ratio of PLA, PAN, and EHL is (3-10):(10-20):(5-15); The mass ratio of TEOS to EHL is (5-15):(5-15); The temperature of the stirred mixture is 40-75 ℃.

4. The method for preparing a porous hybrid carbon nanofiber membrane according to claim 1, characterized in that, In step S13: The voltage for electrospinning is 18-20 kV; The feed rate for electrospinning is 1.5-2.0 mL / h; The distance between the syringe tip and the collector is 12-18 cm.

5. The method for preparing a porous hybrid carbon nanofiber membrane according to claim 1, characterized in that, In step S13: The temperature for electrospinning is 20-30 ℃; The relative humidity for electrospinning is 45%. The electrospinning time is 4-8 hours; The collector rotates at a speed of 120-2000 rpm.

6. The method for preparing a porous hybrid carbon nanofiber membrane according to claim 1, characterized in that, In step S14: drying is performed overnight at room temperature.

7. The method for preparing a porous hybrid carbon nanofiber membrane according to claim 1, characterized in that, In S21, the heating rate is 0.25-10.00 ℃ / min.

8. The method for preparing a porous hybrid carbon nanofiber membrane according to claim 1, characterized in that, In S22: The protective atmosphere is nitrogen, helium, or argon. The heating rate is 2-7.5 ℃ / min; Carbonize at 600-1000 ℃ for 1-3 hours.

9. A porous hybrid carbon nanofiber membrane, characterized in that, Prepared by the method according to any one of claims 1-8.

10. The application of a porous hybrid carbon nanofiber membrane according to claim 9 in water treatment.

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