Shuttle-shaped hetero-channel structure hydrophobic porous MXene-PVDF membrane and preparation method and application thereof

Abstract

The application discloses a shuttle-shaped heterogeneous channel structure hydrophobic porous MXene-PVDF membrane and a preparation method and application thereof. The preparation method of the membrane comprises the following steps: preparing MXene nanosheets by a wet chemical method; vacuum filtering a prepared MXene nanosheet solution to dry the MXene nanosheet solution on a base film to form an ordered layered MXene two-dimensional film; using an inducer to induce and control the porosity and pore shape of the MXene layer of the two-dimensional film, and reducing the oxygen-containing functional groups on the surface of the membrane to obtain a hydrophobic porous MXene-PVDF distillation membrane with a specific shuttle-shaped heterogeneous channel structure. The shuttle-shaped heterogeneous channel structure can realize high-speed passing of water vapor and effective interception of pollutants, the hydrophobic surface can relieve the membrane wetting to a certain extent, and finally effectively solve the problem of the trade-off effect between the flux and the anti-wetting performance, realize the synchronous improvement of the membrane flux and the anti-wetting performance, and realize long-term stable operation, and the membrane can be used in the field of salt water desalination treatment.

Description

TECHNICAL FIELD

[0001] The application belongs to the field of membrane separation technology, and particularly relates to a shuttle-shaped hetero-channel structure hydrophobic porous MXene-PVDF membrane and a preparation method and application thereof. BACKGROUND

[0002] Population explosion, rapid economic growth and water pollution have caused a serious water crisis. However, only about 3% of the global water resources is directly accessible, and most of the water resources exist in the form of high salinity water. Membrane distillation is a membrane separation technology driven by the vapor pressure difference between the two sides of a hydrophobic membrane, which only allows water vapor molecules to pass through the membrane pores during operation, and condenses into permeate by a cooling device, while pollutants and salts are intercepted. This technology can make full use of abundant high salinity water and convert it into fresh water, thereby alleviating the global water crisis. In actual production operation, the anti-wetting property and flux are important indicators for measuring the performance of the membrane. In order to prevent non-volatile pollutants and salts from passing through the membrane and to separate the feed and the permeate, the membrane must have good anti-wetting property; the membrane flux of membrane distillation also determines the water production efficiency and economic benefits. However, there is a trade-off effect between the flux and the anti-wetting property of membrane distillation. Therefore, it is urgent to develop advanced membrane materials to solve the trade-off effect between the flux and the anti-wetting property of membrane distillation, and to realize the simultaneous improvement of the membrane flux and the anti-wetting property.

[0003] Oxidized graphene (GO), covalent organic frameworks (COFs), metal-organic frameworks (MOFs) and transition metal carbide nitrides (MXenes) and other two-dimensional materials have become promising candidates for distillation membranes due to their unique nano-confined structures. When these materials are stacked on the surface of the membrane base, nano-confined channels are formed, which can reject salts and pollutants through ion sieving, thereby enhancing the anti-wetting property of the membrane. However, the narrow single-layer spacing and the rich oxygen-containing functional groups on the surface can react strongly with water molecules through hydrogen bonds, which is not conducive to the passage of water vapor and is prone to swelling in water. Ultimately, the anti-wetting property of the distillation membrane is improved, but the flux and stability are greatly reduced. MXene has a layered nanostructure and is composed of early transition metal carbides and / or carbonitrides, which stands out among two-dimensional materials due to its inherent excellent heat resistance and mechanical strength. MXene is prepared by a wet chemical method and a hydrofluoric acid (HF) etching method, and functional groups (such as -OH, -O and -F) are generated on the surface during the reaction process. Therefore, a shuttle-shaped hetero-channel structure is carefully designed between the MXene layers and the surface oxygen-containing functional groups are reduced, which allows water molecules to pass quickly while pollutants are intercepted, thereby strengthening the anti-swelling and anti-wetting properties and ensuring high flux and stable excellent desalination performance.

[0004] In summary, in the field, it is desirable to develop a shuttle-shaped heterogeneous channel structure hydrophobic porous MXene-PVDF membrane, which can overcome the trade-off between membrane flux and anti-wetting performance in traditional membrane distillation systems, and prepare a stable and efficient two-dimensional membrane distillation composite membrane with high flux and high anti-wetting performance. SUMMARY

[0005] The purpose of the present application is to overcome the trade-off between membrane flux and anti-wetting performance in existing membrane distillation technology, and to provide a shuttle-shaped heterogeneous channel structure hydrophobic porous MXene-PVDF membrane and its preparation method and application. The shuttle-shaped heterogeneous channel structure hydrophobic porous MXene-PVDF membrane prepared by the method has strong anti-swelling and anti-wetting performance, can maintain high flux and stable excellent desalination performance, and can be used for the treatment of salt water desalination.

[0006] To solve the problems in the prior art, the technical scheme adopted by the present application is as follows:

[0007] A preparation method of a shuttle-shaped heterogeneous channel structure porous MXene-PVDF membrane, comprising the following steps:

[0008] Step 1: preparing a 1mg / ml MXene nanosheet solution by a wet chemical method

[0009] 1g LiF is added to 20ml 6-12M HCl solution, continuously stirred for 2-5min, and then 1g Ti3AlC2(MAX phase) powder is slowly added for reaction. During the reaction, small bubbles can be observed. Then the mixed solution is continuously stirred at 35℃ for 24 hours, and centrifuged at a speed of 3500-5000rpm for multiple times until the pH reaches 6. The obtained suspension is dispersed in 90ml DI water, and nitrogen is removed by ultrasonic treatment for 30-60min. The suspension is centrifuged again for 30-60min to obtain a 1mg / ml MXene nanosheet solution, which is stored at 4℃ for standby;

[0010] Step 2: vacuum filtration of the MXene nanosheet solution prepared in step 1 on the base film, and drying to form an ordered layered MXene two-dimensional membrane;

[0011] Step 3: using an inducer to induce and control the porosity and membrane pore shape of the MXene two-dimensional membrane obtained in step 2, and consuming the oxygen-containing functional groups on the membrane surface to obtain a shuttle-shaped heterogeneous channel structure hydrophobic porous MXene-PVDF membrane

[0012] The MXene two-dimensional film prepared in step 2 is uniformly coated with an inducing agent, and is sandwiched between two ceramic sheets, with part of the reaction expansion of the MXene two-dimensional film being left as a gap between the two ceramic sheets. The mixture is heated at 80-110 DEG C until the gas is completely released, and a shuttle-shaped hetero-channel structure porous MXene-PVDF film is obtained. As an improvement, the base film in step 2 is a PVDF film with a pore size of 0.22 microns.

[0013] As an improvement, the base film in step 2 is a hydrophobic PVDF film with a pore size of 0.22 microns.

[0014] As an improvement, the drying in step 2 is drying at natural room temperature for 24 hours.

[0015] As an improvement, the inducing agent in step 3 is hydrazine hydrate or sodium borohydride, wherein the volume of hydrazine hydrate ranges from 10-20 microliters, and the concentration of sodium borohydride ranges from 2-10 mg / L, and the volume is 10-20 microliters. Within this range of conditions, the generation of a shuttle-shaped hetero-channel structure can be effectively induced, and the oxygen-containing functional groups can be removed. Otherwise, the shuttle-shaped hetero-channel structure and the hydrophobic surface cannot be effectively constructed.

[0016] The shuttle-shaped hetero-channel structure porous MXene-PVDF film prepared by the above preparation method is characterized in that the narrow part of the shuttle-shaped channel in the shuttle-shaped hetero-channel structure porous MXene-PVDF film selectively repels Na+ ions, SDS and HA monomers with a high energy barrier, and allows water vapor molecules to pass through, thereby preventing the wetting of the membrane; the wider part ensures the rapid transport of water vapor, thereby increasing the water flux and preventing the aggregation of water vapor to cause the swelling of the membrane; at the same time, most of the oxygen-containing functional groups on the MXene surface disappear, effectively alleviating the wetting of the membrane, and under the synergistic action, the obtained shuttle-shaped hetero-channel structure hydrophobic porous MXene-PVDF film effectively solves the trade-off effect problem of flux and anti-wetting performance, realizes the simultaneous improvement of membrane flux and anti-wetting performance, and long-term stable operation.

[0017] As an improvement, the salt water is a solution with a salt content of 1-10%.

[0018] As an improvement, the solution with a salt content of 1-10% is a mixed solution containing one or more of sodium salt, magnesium salt, potassium salt, or calcium salt.

[0019] Beneficial effects:

[0020] Compared with the prior art, the shuttle-shaped hetero-channel structure hydrophobic porous MXene-PVDF film and the preparation method and application thereof have the following advantages:

[0021] 1. This invention prepares a heterogeneous, spindle-shaped, hydrophobic, porous two-dimensional membrane using an inducing agent-induced regulation method. The resulting layered two-dimensional membrane forms numerous spindle-shaped channels, with the narrower end regions capable of sieving and retaining salt or contaminants, while the wider middle region facilitates rapid water vapor transport. Furthermore, the reduced number of oxygen-containing functional groups on the surface enhances the stability of the heterogeneous, spindle-shaped, hydrophobic, porous two-dimensional membrane in water, enabling long-term stable prevention of salt or contaminant intrusion.

[0022] 2. The dual-functional pores of the spindle-shaped heterogeneous channel structure hydrophobic porous MXene-PVDF membrane of the present invention achieve simultaneous improvement in flux, anti-wetting ability and stability.

[0023] 3. The spindle-shaped heterogeneous channel structure porous MXene-PVDF membrane of this invention exhibits a significantly higher flux than ordinary commercial membranes when treating simulated seawater solutions with a salt content of 3.5%, with a flux 2.5 times that of commercial PVDF membranes. Simultaneously, this membrane also demonstrates excellent stability during operation. Attached Figure Description

[0024] Figure 1 (a) The flux and rejection rate of the MF24 membrane in Example 1 and the MF24-1 membrane in Example 2 of the present invention, respectively;

[0025] Figure 1 (b) is the 12-hour operating flux of the spindle-shaped heterochannel porous MXene-PVDF membrane prepared in the comparative examples and Examples 1, 3-6 of this invention for treating a simulated seawater solution with a salt content of 3.5%;

[0026] Figure 1 (c) The conductivity of the spindle-shaped heterochannel porous MXene-PVDF membrane prepared in the comparative examples and Examples 1, 3-6 of this invention after 12 hours of operation in a simulated seawater solution with a salt content of 3.5%.

[0027] Figure 2 (a) The flux of the spindle-shaped heterochannel porous MXene-PVDF membrane prepared in the comparative example and Example 1 of the present invention when treating brine containing surfactant (SDS);

[0028] Figure 2 (b) The anti-wetting properties of the spindle-shaped heterochannel porous MXene-PVDF membrane prepared in the comparative example and Example 1 of the present invention when treating salt water containing surfactant (SDS);

[0029] Figure 2 (c) The flux of the spindle-shaped heterochannel porous MXene-PVDF membrane prepared in the comparative example and Example 1 of the present invention when treating brine containing surfactant organic matter (HA);

[0030] Figure 2 (d) shows the operation and anti-wetting properties of the spindle-shaped heterochannel porous MXene-PVDF membrane prepared in the comparative example and Example 1 of this invention when treating brine containing surfactant organic matter (HA);

[0031] Figure 3 (a) is the average throughput of MF24 in Example 1 of the present invention after 12 hours of operation when processing 3.5% NaCl, 3.5% NaCl+3% MgCl2, 3.5% NaCl+3% MgCl2+3% KCl, and 3.5% NaCl+3% MgCl2+3% KCl+3% CaCl2.

[0032] Figure 3 (b) is the average throughput of MF24-1 in Example 2 when processing 3.5% NaCl, 3.5% NaCl+3% MgCl2, 3.5% NaCl+3% MgCl2+3% KCl, and 3.5% NaCl+3% MgCl2+3% KCl+3% CaCl2 over 12 hours.

[0033] Figure 4 (a) is a scanning electron microscope (SEM) image of the M24 film at the 200 nm scale in Example 1 of the present invention;

[0034] Figure 4 (b) is a scanning electron microscope (SEM) image of the MF24-1 film treated with sodium borohydride at the 200 nm scale in Example 2 of the present invention;

[0035] Figure 4 (c) is a scanning electron microscope (SEM) image of the MF24 film treated with hydrazine hydrate at the 200 nm scale in Example 1 of the present invention;

[0036] Figure 4 (d) is the (002) lattice diffraction pattern of the MF24 film in Example 1 of the present invention;

[0037] Figure 4 (e) shows the water contact angle test results of the M24 and MF24 membranes of Example 1 and the MF24-1 membrane of Example 2 of the present invention;

[0038] Figure 5 (a)-(d) are morphological images of the M24 and MF24 films prepared in Example 1 of the present invention before and after ultrasonication for 600s after running for 12 hours.

[0039] Figure 5 (e)-(f) show the flux rejection of the M24 and MF24 membranes prepared in Example 1 of the present invention after soaking in HCl and NaOH for 5 days;

[0040] Figure 6 This is a schematic diagram illustrating the mechanism of action of a spindle-shaped heterostructure hydrophobic porous MXene-PVDF membrane. Detailed Implementation

[0041] The following embodiments are provided to enable those skilled in the art to more fully understand the present invention, but do not limit the invention in any way.

[0042] Unless otherwise specified, in the embodiments of this specification, the term "ambient temperature" specifically refers to 15℃-30℃; the term "min" specifically refers to a unit of time measurement: minutes; the term "h" specifically refers to a unit of time measurement: hours; the term "ml" specifically refers to a unit of volume: milliliters; the term "mg" specifically refers to a unit of weight: milligrams; the term "g" specifically refers to a unit of weight: grams; the term "μm" specifically refers to a unit of length: micrometers; the term "nm" specifically refers to a unit of length: nanometers; and the term "L" specifically refers to a unit of volume: liters.

[0043] In this invention, the MXene nanosheet solution is prepared as follows: 1 g of LiF is added to 20 ml of 6M HCl solution and stirred continuously for 5 min. Then, 1 g of Ti3AlC2 (MAX phase) powder is slowly added to the resulting solution to complete the reaction. Tiny bubbles can be observed during this process. The mixed solution is continuously stirred at 280 rpm at 35°C for 24 hours, and then the above product is centrifuged multiple times at 5000 rpm until the pH reaches 6. The resulting suspension is dispersed in 90 ml of DI water, and nitrogen gas is applied by sonication for 30 min to remove the multilayer nanosheets, followed by centrifugation for another 50 min. The supernatant is stored as a 1 mg / ml MXene nanosheet solution at 4°C.

[0044] Comparative Example

[0045] The comparative examples are a commercial PVDF membrane and a membrane M24 made by loading MXene onto PVDF without hydrazine hydrate induction treatment.

[0046] Take 200 ml of alcohol and add 24 ml of 1 mg / ml MXene solution. Sonicate for 40 minutes to form a homogeneous MXene alcohol dispersion solution. Then, vacuum filter the above MXene solution with a commercial PVDF membrane with a pore size of 0.22 μm and dry it overnight at ambient temperature to obtain an MXene layered two-dimensional membrane labeled M24.

[0047] Example 1

[0048] Take 24 ml of a 1 mg / ml MXene nanosheet solution. The specific preparation method is as follows:

[0049] (1) 24 mL of 1 mg / mL MXene nanosheet solution prepared by vacuum filtration (1) using a commercial PVDF membrane with a pore size of 0.22 μm was placed on the base membrane and dried to form an ordered layered MXene two-dimensional membrane.

[0050] (2) The porosity and pore shape of the two-dimensional MXene membrane obtained in step (2) were controlled by using hydrazine hydrate induction to obtain a spindle-shaped heterochannel structure hydrophobic porous MXene-PVDF membrane. 10 μL of hydrazine hydrate was uniformly coated on the surface of the MXene two-dimensional membrane obtained in (2), and sandwiched between two ceramic plates (leaving some space between the two ceramic plates for the reaction expansion of the membrane) and heated at 90°C for several hours to obtain a spindle-shaped heterochannel structure porous membrane, denoted as MF24.

[0051] Example 2

[0052] Take 24 ml of a 1 mg / ml MXene nanosheet solution. The specific preparation method is as follows:

[0053] (1) 24 mL of 1 mg / mL MXene nanosheet solution prepared by vacuum filtration (1) using a commercial PVDF membrane with a pore size of 0.22 μm was placed on the base membrane and dried to form an ordered layered MXene two-dimensional membrane.

[0054] (2) The porosity and pore shape of the two-dimensional MXene membrane obtained in step (2) were controlled by using sodium borohydride-induced method to obtain a spindle-shaped heterochannel porous MXene-PVDF membrane. The surface of the MXene two-dimensional membrane obtained in (2) was uniformly coated with sodium borohydride with a concentration of 5 mg / L and a volume of 10 μL, and sandwiched between two ceramic plates (leaving some space between the two ceramic plates for the reaction expansion of the membrane). The membrane was heated at 90°C for several hours to obtain a spindle-shaped heterochannel porous membrane, denoted as MF24-1.

[0055] Example 3

[0056] Except for the addition of 16 mg of MXene (i.e., 16 ml of MXene solution), the rest was the same as in Example 1, and the resulting spindle-shaped heterochannel porous membrane was labeled MF16.

[0057] Example 4

[0058] Except for the addition of 20 mg of MXene (i.e., 20 ml of MXene solution), the rest was the same as in Example 1, and the resulting spindle-shaped heterochannel porous membrane was labeled MF20.

[0059] Example 5

[0060] Except for the addition of 28 mg of MXene (i.e., 28 ml of MXene solution), the rest was the same as in Example 1, and the resulting spindle-shaped heterochannel porous membrane was labeled MF28.

[0061] Example 6

[0062] Except for the addition of MXene at a mass of 32 mg, i.e., the volume of the added MXene solution was 32 ml, everything else was the same as in Example 1, and the resulting spindle-shaped heterochannel porous membrane was labeled MF32.

[0063] Test Example 1

[0064] The membranes prepared in Examples 1-6 and the comparative examples were tested to compare the flux, effluent conductivity and operational stability of the membranes prepared under different conditions when treating simulated seawater solutions with a salt content of 3.5%.

[0065] The flux is calculated as shown in equation (1):

[0066]

[0067] In the formula: F represents the solvent permeation flux (Kg·m -2 ·h -1 ), t represents the running time (h), M represents the mass change of the solvent during the running time t (kg), and A represents the effective area of ​​the membrane during operation (m²). 2 ).

[0068] The conductivity is recorded in real time by a conductivity meter. The lower the conductivity, the higher the salt rejection rate.

[0069] The retention rate is calculated as shown in equation (2):

[0070]

[0071] In the formula: R represents the membrane rejection rate (%), C f and C p These represent the conductivity of the feed solution and the permeate solution, respectively.

[0072] Test results are as follows Figure 1 As shown, when treating 3.5% NaCl solution, the MF24 membrane exhibits better flux than the MF24-1 membrane, with both showing salt rejection rates approaching 100%. Furthermore, the membranes treated with hydrazine hydrate demonstrate superior flux and salt rejection rates compared to those without hydrazine hydrate treatment. Among the hydrazine hydrate-treated membranes, the MF24 membrane achieves the best flux of 55.59 kg / m³. 2 The salt rejection rate is 99.99%. This membrane flux is comparable to that of commercial PVDF membranes (22.79 kg m³ / h). -2 h -1The flux of the M24 membrane is 2.5 times that of commercial PVDF membranes, and its long-term salt rejection rate and anti-wetting performance are significantly improved. The flux of the untreated M24 membrane is 15.56 kg / m³. 2 h, and after a long period of operation, flux and salt rejection rate decrease due to the easy swelling and peeling of MXene in water.

[0073] Test Example 2

[0074] The test compares the performance of the spindle-shaped heterochannel hydrophobic porous membranes of Examples 1-6 in the same salt solutions as in Test Example 1, with 50 mg / L surfactant SDS and 30 mg / L organic HA, respectively. The conductivity was recorded in real time by a conductivity meter, and the flux and salt rejection rate were calculated in the same way as in Test Example 1.

[0075] like Figure 2 As shown, MF24 operates stably for extended periods in salt solutions containing SDS or HA, achieving fluxes of 50.81 and 47.2 kg / (m²), respectively. 2 h). Commercial PVDF membranes began to gradually wet after about 6 hours of operation and were fully wetted after 12 hours. M24 membranes without hydrazine hydrate treatment also began to show decreased anti-wetting properties, flux, and salt rejection after 6 hours of operation due to the swelling and exfoliation of MXene.

[0076] Test Example 3

[0077] The operation of the MF24 membrane in Test Example 1 and the MF24-1 membrane in Test Example 2 was tested in various salt ion solutions. The ion rejection rate was measured using an ion specificity (ISE) meter, and the flux was calculated using the same method as in Test Example 1. Figure 3 As shown, MF24 achieved an average flux of 55.59 kg / m³ after 12 hours of operation when processing 3.5% NaCl, 3.5% NaCl + 3% MgCl₂, 3.5% NaCl + 3% MgCl₂ + 3% KCl, and 3.5% NaCl + 3% MgCl₂ + 3% KCl + 3% CaCl₂. 2 h, 52.06 kg / m 2 h, 47.02kg / m 2 h, 41.71 kg / m 2 h, the rejection rate for each ion was close to 100%; while MF24-1 achieved an average flux of 43.27 kg / m³ after 12 hours of operation when treating 3.5% NaCl, 3.5% NaCl + 3% MgCl₂, 3.5% NaCl + 3% MgCl₂ + 3% KCl, and 3.5% NaCl + 3% MgCl₂ + 3% KCl + 3% CaCl₂. 2 h, 41.36 kg / m 2 h, 37.05kg / m2 h, 30.87 kg / m 2 h, the rejection rate for each ion is close to 100%. This is likely due to the large thickness and small spindle size of the MF24-1 membrane, resulting in greater resistance to water vapor transport and lower flux. This demonstrates the high efficiency of the MF24 membrane in removing multiple salt ions.

[0078] Test Example 4

[0079] The M24 and MF24 films prepared in Example 1 and the MF24-1 film prepared in Example 2 were characterized by scanning electron microscopy (SEM) and X-ray diffraction (XRD). The results are as follows: Figure 4 As shown in (a)-(d).

[0080] in, Figure 4 (a) is a scanning electron microscope (SEM) image of the M24 film at the 200 nm scale. The MXene-modified layer of the M24 film consists of a single layer of MXene nanosheets with a dense and parallel arrangement.

[0081] Figure 4 (b) is a scanning electron microscope (SEM) image of the MF24-1 film at the 200 nm scale. After treatment with sodium borohydride, gas is generated and expands in the parallel interlayer, forming numerous spindle-shaped pores. The average maximum lateral size of the pores is approximately 50 nm, and the average maximum longitudinal size is approximately 30 nm. The film thickness also increases from 200 nm to approximately 800 nm. This signifies the successful fabrication of a porous membrane with a spindle-shaped heterochannel structure, where the narrow portions of the spindle-shaped channels have high energy barriers that selectively repel Na+. + The membrane contains ions, SDS and HA monomers, and allows the passage of H2O molecules, thus preventing membrane wetting, while the larger portion ensures rapid transport of water vapor.

[0082] Figure 4 (c) is a scanning electron microscope (SEM) image of the MF24 membrane treated with hydrazine hydrate at the 200 nm scale. After treatment with hydrazine hydrate, gas is generated and expands in the parallel interlayer, forming a large number of spindle-shaped pores with an average maximum lateral size of about 200 nm and an average maximum longitudinal size of about 60 nm. The membrane thickness increases from 200 nm to about 600 nm. This signifies the successful preparation of a porous membrane with a spindle-shaped heterochannel structure. The narrow portion of the spindle-shaped channel has a high energy barrier that selectively repels Na+ ions, SDS, and HA monomers while allowing H2O molecules to pass through, thus preventing membrane wetting. The larger portion ensures rapid water vapor transport. The MF membrane treated with hydrazine hydrate forms a larger spindle-shaped pore area and a greater difference in size between the narrow and wide portions.

[0083] Figure 4(d) is the (002) lattice diffraction pattern of the MF24 film. The leftward shift of the (002) lattice in the lattice diffraction pattern further indicates the increase in inter-film spacing and the expansion of film volume.

[0084] Figure 4 (e) shows the water contact angle test results of M24, MF24 and MF24-1 membranes. It can be seen that after reduction treatment with hydrazine hydrate and sodium borohydride, the water contact angle of the membrane increases and the hydrophobicity is improved. This is because the number of hydroxyl groups on the membrane surface is reduced by reduction. Among them, the membrane treated with hydrazine hydrate has stronger hydrophobicity.

[0085] Test Example 5

[0086] The stability of the MF24 membranes prepared in the comparative example and Example 1 was tested.

[0087] like Figure 5 As shown in (a)-(b), after 12 hours of operation in Example 1, the color of MXene changed from dark black to dark green, indicating that MXene swelled and detached from the membrane, while the color of the MF24 membrane remained unchanged, indicating that the reduction of oxygen-containing functional groups made the membrane structurally stable in solution.

[0088] like Figure 5 As shown in (c)-(d), after ultrasonication in water for 600 s, the MF membrane structure remained intact without any visible defects, while the MXene membrane detached from the PVDF substrate and rapidly disintegrated. This indicates that hydrazine-induced treatment improved the membrane's resistance to water flow shear forces and its long-term operational stability.

[0089] like Figure 5 As shown in (e)-(f), after immersing M24 and MF24 membranes in HCl for 5 days, the two membranes were used to treat a 3.5% NaCl solution. The flux of the M24 membrane decreased significantly by 32.7%, while the flux of the MF24 membrane decreased by only 8.6%. The rejection rate of the M24 membrane decreased to 83%, while the rejection rate of the MF24 membrane remained as high as 97%. Similarly, after immersing both membranes in NaOH for 5 days, their performance in treating a 3.5% NaCl solution was measured. The flux and salt rejection rate of the M24 membrane were 50.81 kg / m³. 2 h and 87%, while the flux and rejection rate of MF24 membrane were 52.13 kg / m³. 2 The h and 99% indicate that the modified membrane has significantly improved acid and alkali resistance.

[0090] In summary, this invention prepares a heterogeneous, spindle-shaped, hydrophobic, porous two-dimensional membrane using an inducing agent-induced regulation method. The resulting layered two-dimensional membrane forms numerous spindle-shaped channels, with the narrower end regions capable of sieving and retaining salt or contaminants, while the wider middle region facilitates rapid water vapor transport, achieving a simultaneous improvement in flux, anti-wetting ability, and stability. When treating simulated seawater solutions with a salt content of 3.5%, the membrane flux is significantly higher than that of ordinary commercial membranes, reaching 2.5 times that of commercial PVDF membranes. Furthermore, this membrane exhibits excellent stability during operation, providing long-term, stable protection against salt or contaminant intrusion.

[0091] The embodiments described above are some, but not all, embodiments of the present invention. The detailed description of the embodiments of the present invention is not intended to limit the scope of the claimed invention, but merely to illustrate selected embodiments. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without inventive effort are within the scope of protection of the present invention.

Claims

1. A method for preparing a spindle-shaped heterochannel structure hydrophobic porous MXene-PVDF membrane, characterized in that, Includes the following steps: Step 1: Prepare a 1 mg / mL MXene nanosheet solution using a wet chemical method. Add 1g LiF to 20 mL of 6-12 M HCl solution and stir continuously for 2-5 min. Then slowly add 1g Ti3AlC2 powder to react. Tiny bubbles can be observed during the reaction. Stir the mixture continuously at 35℃ for 24 hours. Centrifuge multiple times at 3500-5000 rpm until the pH reaches 6. Disperse the resulting suspension in 90 mL of DI water. Use nitrogen gas to sonicate for 30-60 min to remove the multilayer nanosheets. Centrifuge again for 30-60 min to obtain a 1 mg / mL MXene nanosheet solution. Store at 4℃ for later use. Step 2: The MXene nanosheet solution obtained in Step 1 is vacuum filtered onto the base film and dried to form an ordered layered MXene two-dimensional film; wherein, the base film is a hydrophobic PVDF film with a pore size of 0.22 μm. Step 3: The porosity and pore shape of the MXene two-dimensional membrane obtained in Step 2 are induced and controlled by an inducing agent to obtain a spindle-shaped heterochannel porous MXene-PVDF membrane; wherein the inducing agent is 10-20 μL of hydrazine hydrate or sodium borohydride with a concentration of 2-10 mg / L and a volume of 5-10 μL. The surface of the MXene two-dimensional membrane obtained in step 2 is uniformly coated with an inducing agent and sandwiched between two ceramic sheets, leaving some gaps between the two ceramic sheets for the reaction expansion of the MXene two-dimensional membrane. It is heated at 80-110℃ until the gas completely escapes to obtain a spindle-shaped heterochannel porous MXene-PVDF membrane.

2. The method for preparing a spindle-shaped heterostructure hydrophobic porous MXene-PVDF membrane according to claim 1, characterized in that, The drying in step 2 is performed at room temperature for 24 hours.

3. The application of a spindle-shaped heterostructure hydrophobic porous MXene-PVDF membrane prepared by the preparation method described in claim 1 in brine desalination.

4. The application according to claim 3, characterized in that, The brine is a solution with a salt content of 1-10%.

5. The application according to claim 4, characterized in that, The solution with a salt content of 1-10% is a mixed solution containing one or more of sodium, magnesium, potassium, and calcium salts.

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