A novel composite membrane based on electrospinning-nonsolvent induced phase inversion technology and preparation method and application thereof

Abstract

This invention discloses a scaffold composite membrane constructed from electrospun polysulfone on a liquid polyvinylidene fluoride substrate, its preparation method, and its application, belonging to the field of membrane distillation technology. The composite membrane comprises a CAU-10-NH₂-doped PVDF substrate and a CAU-10-NH₂-doped PSF fiber scaffold layer constructed in situ on its surface using a handheld electrospinning gun before solvent-induced phase inversion. This method avoids the interlayer delamination problem of traditional multilayer membranes, utilizes PSF fibers to provide mechanical support and form a high-roughness surface, and combines the hydrophilicity and antifouling properties of CAU-10-NH₂ to significantly improve water flux, antifouling properties, and long-term stability. In simulated seawater desalination tests (3.5 wt% NaCl, 70 ℃), the membrane flux reached 42.8 L·m⁻²·h⁻¹, with a rejection rate of 99.2%. In the anti-wetting test (with SDBS surfactant), the flux remained stable at 32 L·m⁻²·h⁻¹ for 900 min, with a rejection rate of 99%. In the antifouling test: with humic acid (HA) as the pollutant, the flux reduction rate of the pure PVDF membrane was 75.76%, while that of the composite membrane of this invention was only 24.23%, with a flux recovery rate of 92.97% (pure PVDF membrane 67.69%); with sodium alginate (SA) as the pollutant, the flux reduction rate of the pure PVDF membrane was 85.70%, while that of this invention was only 30.38%, with a flux recovery rate of 89.98% (pure PVDF membrane 52.81%). The preparation process of this invention is simple, the structure is controllable, and the performance is excellent, showing good application prospects.

Description

Technical Field

[0001] This invention belongs to the field of membrane distillation technology, specifically relating to a novel composite membrane based on electrospinning-solvent-induced phase transformation technology and its preparation method, as well as the application of the composite membrane in seawater desalination. Background Technology

[0002] With the increasing scarcity of freshwater resources globally, seawater desalination has become an important way to solve the water crisis. Membrane distillation (MD), as an emerging heat-driven separation technology, has attracted widespread attention in the fields of seawater desalination and high-salinity wastewater treatment due to its advantages such as full utilization of low-grade heat sources, theoretical salt rejection rate of up to 100%, and low operating pressure. During membrane distillation, a temperature difference exists on both sides of the hydrophobic microporous membrane. Volatile water molecules evaporate on the hot side, pass through the membrane pores, and condense on the cold side, thereby achieving brine separation.

[0003] Currently, the membrane materials used in membrane distillation mainly include hydrophobic polymers such as polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), and polypropylene (PP). Among them, PVDF has become a research hotspot due to its good film-forming properties, mechanical strength, and thermal stability. However, traditional PVDF membranes still face the following challenges in membrane distillation applications: (1) Low flux: The pore structure of a single PVDF membrane is not ideal, and the water vapor mass transfer resistance is large, making it difficult to meet the permeate flux requirements of industrialization; (2) Membrane wetting problem: During long-term operation, low surface tension substances or surfactants can easily cause membrane pore wetting, resulting in a sharp drop in desalination rate; (3) Membrane fouling: Organic matter such as humic acid and sodium alginate in seawater can easily be adsorbed and deposited on the membrane surface, reducing the effective evaporation area and aggravating the wetting risk.

[0004] To improve membrane distillation performance, researchers have developed various modification strategies. For example, superhydrophobic coatings are constructed on the surface of PVDF-based membranes, or inorganic nanoparticles (such as SiO2 and TiO2) are introduced to enhance anti-wetting properties; or nanofiber membranes are prepared through electrospinning to increase porosity. However, electrospun fiber membranes often have poor mechanical strength and large pore sizes, making them prone to leakage when used alone. In recent years, metal-organic frameworks (MOFs) such as CAU-10-NH2, with their high specific surface area, tunable hydrophilicity / hydrophobicity, and abundant functional groups, have been explored for membrane modification.

[0005] Furthermore, the preparation of existing composite membranes for membrane distillation often employs a stepwise method (first preparing the substrate, then coating or spinning the functional layer), which is complex and suffers from poor interfacial compatibility. How to construct an integrated membrane for membrane distillation that is high-flux, anti-wetting, anti-fouling, and structurally stable while maintaining high hydrophobicity remains a pressing technical challenge in this field.

[0006] To address the aforementioned problems, this invention provides a scaffolded composite membrane based on electrospun polysulfone on a liquid polyvinylidene fluoride (PVDF) substrate. By directly electrospinning PSF fibers doped with CAU-10-NH2 onto the surface of the unsolidified PVDF liquid substrate, and then forming an interpenetrating network structure via NIPS, the hydrophobicity and mechanical strength of the PVDF substrate are preserved, while the high porosity and rough surface constructed by the polysulfone fibers enhances the long-term stability of the membrane. Simultaneously, the dual-doped CAU-10-NH2 provides a rapid water vapor transport channel, and the doping of CAU-10-NH2 effectively inhibits membrane wetting and fouling. This composite membrane exhibits high flux, anti-wetting, anti-fouling, and long-term stability in membrane distillation seawater desalination. Summary of the Invention

[0007] To address the problems of low flux, poor anti-wetting and anti-fouling properties of existing composite membranes used in membrane distillation, this invention provides a novel composite membrane based on electrospinning-solvent-induced phase inversion technology and its preparation method. This composite membrane achieves an integrated interpenetrating structure between the fiber layer and the substrate by directly electrospinning PSF fibers onto the surface of an unsolidified liquid PVDF substrate, followed by solvent-induced phase inversion curing. Furthermore, the hydrophilic modification of CAU-10-NH2 constructs a rapid water vapor transport channel, significantly improving the overall performance of the membrane.

[0008] To achieve the above-mentioned objectives, the present invention adopts the following technical solution: On one hand, the present invention provides a scaffold composite membrane, comprising: a PVDF substrate doped with CAU-10-NH2, and a PSF fiber scaffold layer also doped with CAU-10-NH2. The fiber scaffold layer is embedded in the surface of the substrate to form an interface-free three-dimensional network structure.

[0009] Preferably, the mass fraction of CAU-10-NH2 in the PVDF substrate is 0.25%, and the mass fraction of CAU-10-NH2 in the PSF fiber layer is 0.5%~1.5%.

[0010] Preferably, the PVDF substrate has a coating thickness of 200 μm and the fiber layer has a spinning time of 1-5 min.

[0011] On the other hand, the present invention provides a method for preparing the above-mentioned composite membrane, characterized by comprising the following steps: S1. Preparation of CAU-10-NH2: AlCl3·6H2O (5.5 mmol, 1.33 g) and isophthalic acid (5.5 mmol, 0.91 g) were dissolved in 16 mL of deionized water and 4 mL of N,N-dimethylformamide, respectively, and then mixed and stirred thoroughly. The mixture was placed in a stainless steel reactor lined with polytetrafluoroethylene and heated in an oven at 120 °C for 12 h. After the reaction was completed and cooled to room temperature, the resulting solid was redispersed in water by ultrasound. The mixture was then filtered and washed several times with deionized water and methanol. Finally, the product was dried in a vacuum oven at 150 °C for 12 h.

[0012] S2. Preparation of PVDF casting solution: PVDF, CAU-10-NH2, H2O and N,N-dimethylhexamethylenetetramine (DMAC) were mixed in a mass ratio of 15 : 0.25 : 1 : 83.75, stirred at 70 ℃ for 48 h, cooled to room temperature and allowed to stand to remove bubbles, thus obtaining PVDF casting solution; S3. Preparation of PSF spinning solution: PSF, CAU-10-NH2 and N,N-dimethylacetamide are mixed in a mass ratio of 23:1.0:76, ​​stirred at 60 ℃ for 48 h, cooled to room temperature and allowed to stand to remove bubbles, to obtain PSF electrospinning solution; S4. Coating the PVDF substrate: The casting solution from step S2 is coated onto a glass plate using a 15cm long scraper to form a film substrate with a thickness of 200 μm. S5. Electrospinning to construct the scaffold: Before the PVDF membrane substrate obtained in step S4 has solidified, a handheld electrospinning gun is used to spray the spinning solution from step S3 onto the surface of the PVDF membrane substrate under the conditions of 15 kV voltage and 10 cm receiving distance to form a PSF fiber scaffold layer. S6. Phase transformation curing: The composite liquid membrane obtained in step S5 is quickly immersed in a coagulation bath for NIPS process. After curing, it is taken out and thoroughly washed with deionized water to obtain the scaffold composite membrane.

[0013] The advantages of this invention are: 1. MOF Dual Doping Constructs Rapid Water Vapor Transport Channels, Simultaneously Enhancing Anti-wetting and Anti-fouling Capabilities: This invention incorporates CAU-10-NH2 doping into both the PVDF substrate and the PSF fiber layer. CAU-10-NH2 possesses well-defined sub-nanometer-scale pores (approximately 5.7 Å) and abundant amino functional groups, enabling the construction of a continuous hydrophilic microporous network within the membrane. During membrane distillation, water vapor molecules preferentially diffuse rapidly along the MOF pores in a skip-like manner, significantly shortening the mass transfer path and thus substantially increasing flux. Experiments show that after CAU-10-NH2 doping, the water flux of the composite membrane is more than doubled compared to the pure PVDF membrane. Furthermore, the negative charge on the CAU-10-NH2 surface causes the membrane to exhibit electrostatic repulsion against common negatively charged pollutants in seawater (such as humic acid and sodium alginate) and anionic surfactants (at a neutral pH with a Zeta potential of -23.32 mV), effectively preventing pollutant adsorption and the intrusion of low surface energy substances into the membrane pores. This electrostatic shielding effect endows the membrane with excellent anti-wetting properties and resistance to organic fouling. Even under long-term operation or high-concentration brine conditions, it can still maintain a stable desalination rate, avoiding the salt leakage problem caused by pore wetting that is prone to occur in traditional hydrophobic membranes.

[0014] 2. Electrospun PSF fiber layer constructs a rough surface, endowing the membrane with excellent hydrophobicity and long-term operational stability: This invention employs a handheld electrospinning gun to deposit a polysulfone (PSF) fiber layer in situ on the surface of a liquid PVDF substrate. The intrinsic contact angle of PSF material is approximately 80-90°, but the three-dimensional porous fiber network formed by electrospinning exhibits a micro-nano-level layered rough structure on its surface. According to the Cassie-Baxter model, this rough surface can effectively trap air, increasing the apparent contact angle of the composite membrane to over 120°, achieving a hydrophobic or even highly hydrophobic state. During membrane distillation, this hydrophobic rough layer effectively prevents liquid water from entering the membrane pores while allowing water vapor to pass freely. More importantly, after a non-solvent-induced phase transformation, the fiber layer and the liquid substrate form an integrated interpenetrating structure, eliminating the interlayer delamination risk common in traditional multilayer composite membranes. Even during long-term membrane distillation operation, the water flux and desalination rate of this composite membrane show no significant decrease, demonstrating excellent mechanical and chemical stability.

[0015] 3. Simple Preparation Process: This invention eliminates the complex multi-step processes in traditional membrane preparation, creatively combining electrospinning with non-solvent-induced phase inversion (NIPS). First, all materials (PVDF, PSF, CAU-10-NH2) are commercially available or synthesized via conventional hydrothermal methods, requiring no special atmosphere or ultra-high temperature treatment. Second, the handheld electrospinning equipment is small and flexible, allowing for short-term (1-5 min) spraying directly onto the freshly coated liquid membrane surface. Subsequently, immersion in a coagulation bath completes the phase inversion, with the entire process being continuous and controllable. Furthermore, the doping of CAU-10-NH2 can be achieved through simple blending. Therefore, this invention is not only easily reproducible on a laboratory scale but also possesses potential for large-scale production and industrial application. Attached Figure Description

[0016] Figure 1 The XRD patterns are of the M(0.25)e P(1.0)-3 membrane in Example 1 and the PVDF membrane in Comparative Example 1. Figure 2 SEM image of the M(0.25)e P(1.0)-3 membrane in Example 1; Figure 3 Here is a SEM image of the PVDF membrane in Comparative Example 1; Figure 4 The image shows the AFM pattern of the M(0.25)e P(1.0)-3 membrane in Example 1. Figure 5 AFM image of the PVDF membrane in Comparative Example 1; Figure 6 WCA of the M(0.25)e P(1.0)-3 membrane in Example 1 and the PVDF membrane in Comparative Example 1; Figure 7 The zeta potentials of the M(0.25)e P(1.0)-3 membrane in Example 1 and the PVDF membrane in Comparative Example 1 are shown. Figure 8 The graph shows the vacuum membrane distillation (VMD) performance of the M(0.25)e P(1.0)-3 membrane in Example 1 and the PVDF membrane in Comparative Example 1 in simulated seawater at 30-70°C. Figure 9 The anti-wetting properties of sodium dodecylbenzenesulfonate (SDBS) on the M(0.25)e P(1.0)-3 membrane of Example 1 and the PVDF membrane of Comparative Example 1 were tested at 60°C. Figure 10 The antifouling properties of the M(0.25)e P(1.0)-3 membrane in Example 1 and the PVDF membrane in Comparative Example 1 were tested at 60°C for humic acid (HA). Figure 11The antifouling properties of the M(0.25)e P(1.0)-3 membrane in Example 1 and the PVDF membrane in Comparative Example 1 were tested at 60°C using sodium alginate (SA). Figure 12 The flowchart and conceptual diagram of the preparation of the M(0.25)e P(1.0)-3 membrane in Example 1 are shown. Note: M represents PVDF; M(0.25) represents PVDF containing 0.25 wt% CAU-10-NH2; P(1.0) represents PSF spinning solution doped with 1 wt% CAU-10-NH2; e represents electrospinning; the number represents spinning time (min); n represents non-solution induced phase inversion (NIPS). Detailed Implementation

[0017] The present invention will be further described below with reference to specific embodiments. It should be noted that the following embodiments are for illustrative purposes only and are not intended to limit the scope of protection of the invention.

[0018] Example 1: Preparation of scaffold composite membrane (1) Preparation of CAU-10-NH2: AlCl3·6H2O (5.5 mmol, 1.33 g) and isophthalic acid (5.5 mmol, 0.91 g) were dissolved in 16 mL of deionized water and 4 mL of N,N-dimethylformamide, respectively, and then mixed and stirred thoroughly. The mixture was placed in a stainless steel reactor lined with polytetrafluoroethylene and heated in an oven at 120 °C for 12 h. After the reaction was completed and cooled to room temperature, the resulting solid was redispersed in water by ultrasound. The mixture was then filtered and washed several times with deionized water and methanol. Finally, the product was dried in a vacuum oven at 150 °C for 12 h.

[0019] (2) Preparation of PVDF casting solution: PVDF, CAU-10-NH2, H2O and N,N-dimethylhexamethylene amide (DMAC) were mixed in a mass ratio of 15:0.25:1:83.75, stirred at 70 °C for 48 h, cooled to room temperature and allowed to stand to remove bubbles to obtain PVDF casting solution; (3) Preparation of PSF spinning solution: PSF, CAU-10-NH2 and N,N-dimethylacetamide were mixed at a mass ratio of 23:1.0:76, ​​stirred at 60 °C for 48 h, cooled to room temperature and allowed to stand to remove bubbles, and PSF spinning solution was obtained. (4) Preparation of composite membrane: The PVDF casting solution was coated onto a glass plate with a 15 cm long doctor blade to form a membrane substrate with a thickness of 200 μm. Before the PVDF membrane substrate on the glass plate solidified, the PSF spinning solution was sprayed onto the surface of the PVDF membrane substrate with a handheld electrospinning gun under the conditions of 15 kV voltage, 10 ml / h spinning speed and 10 cm receiving distance to form a PSF fiber scaffold layer. The composite liquid membrane obtained by spinning was quickly immersed in a coagulation bath for NIPS process. After solidification, it was taken out and thoroughly washed with deionized water to obtain the scaffold composite membrane.

[0020] Comparative Example 1: PVDF membrane without fiber support The only difference from Example 1 is that the electrospinning step is not performed, and the PVDF casting solution is directly immersed in the coagulation bath for NIPS without adding CAU-10-NH2 to obtain a pure PVDF membrane. Morphological and structural characterization: Figure 1 The images show the XRD patterns of the M(0.25)e P(1.0)-3 membrane from Example 1 and the PVDF membrane from Comparative Example 1. Figure 1 It can be seen that the M(0.25)e P(1.0)-3 film shows obvious CAU-10-NH2 characteristic diffraction peaks at positions such as 8.2 ° and 14.8 °, indicating that MOF was successfully doped into the PVDF film substrate and PSF spinning solution.

[0021] Figure 2 The image shows the SEM images of the M(0.25)e P(1.0)-3 membrane in Example 1. As can be seen from the images at different magnifications: the surface (100 μm and 20 μm) shows that the PSF spun fibers and the PVDF substrate are interwoven, forming a tight interpenetrating network structure; the cross-sections (100 μm and 50 μm) further confirm that there are no obvious interfacial gaps between the PSF fiber layer and the upper surface of the PVDF substrate, indicating a strong bond and high degree of integration between the two.

[0022] Figure 3 The image shows the SEM images of the PVDF membrane in Comparative Example 1. As can be seen from the images at different magnifications, the surface (100 μm and 20 μm) exhibits a typical dense skin structure with a smooth and flat surface; the cross-section (100 μm and 50 μm) shows a uniform sponge-like or finger-like porous structure, and the entire membrane layer is a homogeneous substrate formed in one piece.

[0023] Figure 4 and Figure 5 The images show AFM images of the M(0.25)e P(1.0)-3 membrane in Example 1 and the PVDF membrane in Comparative Example 1, respectively. Figure 4As can be seen, the composite film surface exhibits a distinct three-dimensional undulating structure, with the network structure formed by the interwoven PSF fibers leading to a significant increase in surface roughness. AFM height map analysis shows that the root mean square roughness (Rq) of the composite film is approximately 101.2 nm, and the average roughness (Ra) is approximately 80.5 nm. In comparison, Figure 5 The PVDF membrane shown has a relatively smooth surface, with an Rq of approximately 41.23 nm and a Ra of approximately 30.7 nm. This result indicates that the PSF fiber layer constructed by electrospinning effectively increases the roughness of the membrane surface, which is beneficial for forming a stable air layer (Cassie-Baxter state) during membrane distillation, thereby improving the membrane's anti-wetting properties and long-term operational stability.

[0024] Figure 6 The figures show the water contact angle data of the M(0.25)e P(1.0)-3 membrane in Example 1 and the PVDF membrane in Comparative Example 1. As can be seen from the figure, the water contact angle of the membrane is greatly improved due to the increased roughness of the membrane caused by spinning. The contact angle of the M(0.25)e P(1.0)-3 membrane is 126.9°, which is nearly 40° higher than that of the PVDF membrane (87.5°).

[0025] Figure 7 The figure shows the zeta potential curves of the M(0.25)e P(1.0)-3 membrane in Example 1 and the PVDF membrane in Comparative Example 1 as a function of pH. As can be seen from the figure, both membranes exhibit negative surface charge within the test pH range (3-10), and the negative charge gradually increases with increasing pH. Specifically, the zeta potential of the pure PVDF membrane is approximately -5 mV at pH=7, with a relatively low absolute value across the entire pH range; while the zeta potential of the M(0.25)e P(1.0)-3 membrane is significantly more negative under the same conditions, approximately -20 mV at pH=7. This is because the CAU-10-NH2 metal-organic framework material doped in the composite membrane is rich in amino ligands, which carry a permanent negative charge on its surface, and the electrospun PSF fiber layer increases the specific surface area, allowing for more complete exposure of the negatively charged groups. The composite membrane's stronger negative charge gives it a stronger electrostatic repulsion capability: on the one hand, it can effectively repel negatively charged organic matter (such as humic acid and sodium alginate) and surfactants in seawater, inhibiting pollutant adsorption and membrane pore wetting, thereby improving antifouling and antiwetting performance; on the other hand, this electronegativity helps maintain a stable gas-liquid interface during membrane distillation, extending the membrane's service life. Membrane distillation performance test comparison: The performance tests (temperature 30 ℃-70 ℃), SDBS anti-wetting test (temperature 60 ℃, time 900 min), and anti-fouling test (temperature 60 ℃, time 900 min) of Example 1 and Comparative Example 1 were conducted in a self-made membrane tank.

[0026] Figure 8 The graphs show the permeate flux versus feed temperature during vacuum membrane distillation (VMD) in simulated seawater (3.5 wt% NaCl) using the M(0.25)e P(1.0)-3 membrane of Example 1 and the PVDF membrane of Comparative Example 1. The results show that the flux of both membranes increases significantly with increasing temperature (30 °C to 70 °C), consistent with the vapor pressure difference-driven mass transfer law in membrane distillation. At all test temperatures, the flux of the M(0.25)e P(1.0)-3 composite membrane is significantly higher than that of the pure PVDF membrane. For example, at 60 °C, the flux of the pure PVDF membrane is approximately 13.25 kg·m⁻²·h⁻¹, while the flux of the composite membrane reaches approximately 32.43 kg·m⁻²·h⁻¹. This is attributed to the three-dimensional porous structure constructed by the electrospun PSF fiber layer in the membrane reducing the water vapor mass transfer resistance, while the doping of CAU-10-NH₂ provides a fast transport channel for water vapor. The results demonstrate that the composite membrane of the present invention has a significant high-throughput advantage in vacuum membrane distillation.

[0027] Figure 9 The figures show flux variation curves of the M(0.25)e P(1.0)-3 membrane of Example 1 and the PVDF membrane of Comparative Example 1 during membrane distillation in feed solutions containing different concentrations of sodium dodecylbenzenesulfonate (SDBS). The results show that as the SDBS concentration increases from 0 to 1.2 mmol / L, the flux of the pure PVDF membrane begins to decline rapidly at lower concentrations, dropping to below 60% of the initial flux at 0.6 mmol / L, indicating significant wetting of the membrane pores. In contrast, the flux decline of the M(0.25)e P(1.0)-3 composite membrane is significantly reduced within the same SDBS concentration range, maintaining a high flux (approximately 85% of the initial flux) even at a high concentration of 1.2 mmol / L. Therefore, the composite membrane of this invention exhibits excellent anti-wetting properties and is suitable for seawater desalination scenarios containing low surface tension pollutants.

[0028] Figure 10 The graphs show the membrane distillation flux changes over time for the M(0.25)e P(1.0)-3 membrane of Example 1 and the PVDF membrane of Comparative Example 1 before and after the addition of humic acid (HA). The test process included three stages: initial pure water flux, fouling stage after the addition of HA, and flux recovery stage after cleaning. The results showed that after the addition of HA, the flux of the pure PVDF membrane decreased rapidly, with a flux reduction rate of approximately 75.8% at the end of the fouling stage; while the flux reduction rate of the composite membrane was only 24.2%, indicating that its surface antifouling ability was significantly enhanced. After physical cleaning, the flux recovery rate of the composite membrane reached 92.97%, which was much higher than the 67.69% of the pure PVDF membrane.

[0029] Figure 11The graphs show the changes in membrane distillation flux of the M(0.25)e P(1.0)-3 membrane in Example 1 and the PVDF membrane in Comparative Example 1 before and after the addition of sodium alginate (SA). The test results show that after adding SA, the flux decrease of the pure PVDF membrane is extremely significant, reaching 85.70%; while the flux decrease of the composite membrane is only 30.38%. After physical cleaning, the flux recovery rate of the composite membrane is as high as 89.98%, while that of the pure PVDF membrane only recovers to 52.81%.

[0030] Based on the above test data, it can be seen that the present invention significantly improves the overall performance of the composite membrane in membrane distillation seawater desalination through the synergistic regulation of the PSF fiber support layer, CAU-10-NH2. (1) Synergistic enhancement of water vapor flux: The macroscopic porous structure of the PSF fiber layer is responsible for collecting and guiding water vapor into the membrane interior rapidly, while the high hydrophilicity of CAU-10-NH2 is responsible for high-speed water vapor transport within the pores of the substrate. The series connection of macroscopic and microscopic dual-level channels makes the overall mass transfer efficiency far exceed that of the finger pore structure of pure PVDF membrane.

[0031] (2) Synergistic enhancement of antiwetting: The rough surface of PSF provides a physical barrier (air layer), while the negative charge of CAU-10-NH2 provides a chemical barrier (electrostatic repulsion). The two work together to maintain high flux even under high concentration of SDBS (1.2 mmol / L), while the pure PVDF membrane is severely wetted at 0.6 mmol / L.

[0032] (3) Synergistic enhancement of antifouling and stability: The negative charge of CAU-10-NH2 electrostatically repels humic acid (HA) and sodium alginate (SA), which are also negatively charged, reducing the initial adhesion of pollutants to the membrane surface; the rough surface of PSF reduces the actual contact area between pollutants and the membrane, weakening the deposition of pollutants in the boundary layer. During cleaning, the loose fiber layer makes it easier for physical rinsing to remove pollutants attached to the surface, thus the flux recovery rate is as high as 92.97% (HA) and 89.98% (SA).

[0033] The synergistic effect of the two results in Example 1 being significantly superior to Comparative Example 1 in terms of membrane distillation flux, long-term stability, anti-wetting properties, and anti-fouling properties, thus verifying the feasibility of the technical solution of the present invention and the synergistic control mechanism.

[0034] The above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention. 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 novel composite membrane based on electrospinning-solvent-induced phase inversion technology is characterized by, include: A PVDF substrate, wherein the substrate is doped with CAU-10-NH2 metal-organic framework material and a finger film structure is formed by NIPS; The PSF fiber support layer, which is also doped with CAU-10-NH2, is spun onto the surface of the PVDF substrate using a handheld electrospinning gun before NIPS spinning, forming an integrated interpenetrating structure with the substrate.

2. The composite membrane according to claim 1, characterized in that, The mass fraction of CAU-10-NH2 in the PVDF substrate is 0.25%.

3. The composite membrane according to claim 1, characterized in that, The mass fraction of CAU-10-NH2 in the PSF fiber scaffold layer is 0.5%~1.5%.

4. The composite membrane according to claim 2, characterized in that, The PVDF substrate has a coating thickness of 200 μm and a coating size of 15 cm * 20 cm.

5. The PSF fiber scaffold layer according to claim 3, characterized in that, The PSF fiber was spun using a handheld electrospinning gun at a voltage of 15 KV and a spinning speed of 10 ml / h.

6. A method for preparing a composite membrane as described in any one of claims 1 to 5, characterized in that, Includes the following steps: S1. Preparation of PVDF casting solution: PVDF, CAU-10-NH2, H2O and N,N-dimethylhexamethylene amide (DMAC) are mixed in a mass ratio of 15:0.25:1:83.75, stirred at 70 °C for 48 h, cooled to room temperature and allowed to stand to remove bubbles to obtain PVDF casting solution; S2. Preparation of PSF spinning solution: PSF, CAU-10-NH2 and N,N-dimethylacetamide are mixed in a mass ratio of 23:1.0:76, ​​stirred at 60 ℃ for 48 h, cooled to room temperature and allowed to stand to remove bubbles, to obtain PSF electrospinning solution; S3. Coating the PVDF substrate: The casting solution from step S1 is coated onto a glass plate using a 15 cm long scraper to form a film substrate with a thickness of 200 μm. S4. Electrospinning to construct the scaffold: Before the PVDF membrane substrate obtained in step S3 has solidified, a handheld electrospinning gun is used to spray the spinning solution from step S2 onto the surface of the PVDF membrane substrate under the conditions of 15 kV voltage and 10 cm receiving distance to form a PSF fiber scaffold layer. S5. Phase transformation curing: The composite liquid membrane obtained in step S4 is quickly immersed in a coagulation bath for NIPS process. After curing, it is taken out and thoroughly washed with deionized water to obtain the scaffold composite membrane.

7. The composite membrane according to claim 1, characterized in that, The coagulation bath used in the NIPS process of the composite membrane is deionized water, the temperature is 20~40 ℃, and the time is 24 h.

8. The composite membrane according to claim 1, characterized in that, The PSF fiber is spun using a handheld electrospinning gun for 1-5 minutes.

9. The application of a scaffold composite membrane as described in any one of claims 1 to 5 in seawater desalination.

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