Preparation and use method of anti-pollution membrane with coupling piezoelectric catalysis and ultra-infiltration characteristics
By introducing PVDF and hydroxyl-containing nanofillers into the casting solution, an antifouling membrane with both piezoelectric catalysis and superwetting properties was prepared, solving the problem of easy fouling of separation membranes and achieving simplified preparation and improved antifouling ability.
Patent Information
- Application Number
- CN202511666138.X
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2025-11-13
- Publication Date
- 2026-02-24
AI Technical Summary
In existing technologies, separation membranes are easily contaminated during use, leading to performance degradation and shortened service life. Furthermore, existing methods are complex and have poor anti-fouling and stability, making it difficult to achieve synergistic effects of catalysis and superwetting properties by controlling the preparation process.
By introducing PVDF, styrene-maleic anhydride, and hydroxyl-containing nanofillers into the casting solution, a composite casting solution was prepared. Combined with thin-layer casting solution composite technology, an antifouling membrane with piezoelectric catalysis and superwetting properties was prepared. The interaction and esterification reaction between nanomaterials and PVDF were used to form a multi-scale structure to enhance the membrane's antifouling ability.
This method achieves a long-lasting antifouling effect by generating free radicals through piezoelectric catalysis to remove pollutants, thereby improving the membrane's antifouling ability and stability and simplifying the preparation process.
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Figure CN121550862A_ABST
Abstract
Description
Technical Field
[0001] This invention belongs to the field of new material preparation, specifically a synergistic preparation method for a super-wetting antifouling membrane that simultaneously couples piezoelectric catalysis and superwetting properties. Background Technology
[0002] Due to their advantages such as high separation precision and no secondary pollution, separation membranes have shown many important applications in chemical, environmental, and other fields. However, membrane fouling is an unavoidable problem during use, which greatly reduces membrane performance and shortens membrane lifespan. Currently, methods such as superwetting modification and the introduction of catalytically active materials can significantly improve the antifouling ability of separation membranes. However, these methods all require post-treatment of the membrane, and methods for preparing antifouling membranes during the membrane curing process are rare. Such post-treatment methods are prone to the following problems: First, post-treatment methods not only increase the complexity of the membrane fabrication process, which is not conducive to the large-scale preparation of antifouling membranes; second, there are compatibility issues between the antifouling functional layer and the base membrane material, resulting in poor long-term antifouling performance and stability.
[0003] In recent years, introducing polymerizable molecules into the casting solution has become an important method to improve the hydrophilicity of membranes and prepare durable antifouling membranes. However, relying solely on improving hydrophilicity to enhance the antifouling properties of membranes still faces problems such as insufficient durable antifouling. Therefore, if improving hydrophilicity can be coupled with introducing catalytic properties, the membrane fouling problem faced by separation membranes may be solved.
[0004] Although there are studies on coupling superwetting and catalytic properties into the membrane simultaneously through post-treatment, these are all achieved through post-treatment methods, so problems such as complex post-treatment technology and poor compatibility still exist.
[0005] Therefore, a search revealed no existing technologies that could synergistically prepare separation membranes with both catalytic and superwetting properties by controlling the membrane preparation process. Summary of the Invention
[0006] In view of this, the purpose of the present invention is to provide an antifouling membrane that can be easily prepared, has both piezoelectric catalytic and superwetting properties, and has good stability, so as to solve the current membrane fouling problem.
[0007] To achieve the above objectives, the following technical solution is adopted:
[0008] PVDF, pore-forming additives, and solvents are mixed together to prepare support layer casting solution A.
[0009] Functional layer casting solution B was prepared by blending PVDF, styrene maleic anhydride (SMA), solvent, and hydroxyl-containing nanofiller together.
[0010] First, casting solution A is applied to a glass plate. Then, casting solution B with a thickness of about 0.01-0.03 mm is applied to casting solution A to prepare a composite casting solution. Finally, the solution is placed in a coagulation bath to solidify according to the phase inversion method.
[0011] Preferably, the solvent is one or a mixture of dimethylacetamide, dimethylformamide, triethyl phosphate, and dimethyl sulfoxide.
[0012] Preferably, the nanofiller is one or more of the nanomaterials rich in hydroxyl groups, such as hydroxylated carbon nanotubes, chloroform nanotubes, and hydroxylated graphene.
[0013] Principles and advantages of this invention:
[0014] Casting solution A mainly serves a mechanical support function, providing mechanical strength for the antifouling membrane;
[0015] In casting solution B, the reaction between SMA and the hydroxyl groups on the nanomaterials can improve the dispersibility of the nanomaterials in the casting solution. At the same time, due to the interaction between the nanomaterials and PVDF and its polymer molecular chains, the state of the PVDF molecular chains in the entire casting solution can be affected.
[0016] By further combining thin-layer casting solution composite technology and limiting the thickness of the functional layer casting solution B to between 0.01 and 0.03 mm, the full-domain control of the multi-scale structure of the functional layer can be achieved.
[0017] The prepared membrane surface possesses abundant micro- and nano-structures, which facilitates the preparation of a superwetting membrane, thus preventing contaminant adhesion. Simultaneously, the antifouling membrane exhibits a high content of β-crystals, displaying excellent piezoelectric responsiveness. Under pulsed pressure stimulation, it generates a piezoelectric catalytic effect, producing free radicals with strong oxidizing properties, thereby removing contaminants adhering to the membrane surface. Ultimately, the antifouling membrane achieves a long-lasting antifouling effect through the organic synergy of superwetting and piezoelectric catalysis. Attached Figure Description
[0018] Figure 1 a to Figure 1 b is a SEM image of the membrane surface;
[0019] Figure 2 Figure showing the results of underwater oleophobicity test of the membrane.
[0020] Figure 3 a to Figure 3 b shows the XRD and FTIR spectra of the membrane;
[0021] Figure 4 a to Figure 4 c is the membrane PFM test diagram;
[0022] Figure 5 a to Figure 5 c is the free radical ESR test graph;
[0023] Figure 6 a to Figure 6 c is a graph showing the oil-water separation performance of the membrane. Detailed Implementation
[0024] The embodiments of the present invention will be described in detail below. It should be emphasized that the following description is merely exemplary and is not intended to limit the scope and application of the present invention.
[0025] Example 1
[0026] A uniform and transparent support layer casting solution was prepared by dissolving 22g PVDF, 10g polyethylene glycol, and 4g dodecyltrimethylammonium chloride in 64g DMAC. A uniform and transparent functional layer casting solution was prepared by dissolving 8g PVDF, 6g SMA, and 0.32g travertine nanotubes in 86g DMAC. First, a 0.3mm thick support layer casting solution was applied to a glass plate, followed by a 0.02mm thick functional layer casting solution applied on top of the support layer casting solution, resulting in a composite casting solution. Finally, the solution was cured in a 30℃ water bath to form a film.
[0027] Example 2
[0028] Similar to Example 1, the composition of the casting solution for the support layer and the film-forming conditions remain unchanged. The only change is that the travertine nanotubes in the casting solution for the functional layer are replaced with hydroxylated carbon nanotubes.
[0029] Example 3
[0030] Similar to Example 1, the composition of the casting solution for the support layer and the film-forming conditions remain unchanged. The only change is that the travertine nanotubes in the casting solution for the functional layer are replaced with hydroxylated graphene.
[0031] Compare with Example 1
[0032] Similar to Example 1, the composition of the casting solution for the support layer and the film-forming conditions remain unchanged. The only change is that the thickness of the casting solution for the functional layer is adjusted to 0.1 mm.
[0033] Compare with Example 2
[0034] Similar to Example 1, the composition of the casting solution for the support layer and the film-forming conditions remain unchanged. The only change is that the travertine nanotubes in the casting solution for the functional layer are replaced with carbon nanotubes (without hydroxyl groups).
[0035] Compare with Example 3
[0036] Similar to Example 1, the composition of the casting solution for the support layer and the film-forming conditions remain unchanged. The only change is that the travertine nanotubes in the casting solution for the functional layer are replaced with activated carbon (without hydroxyl groups).
[0037] Performance testing: The antifouling membranes prepared in Examples 1-3 and Control Examples 1-3 were characterized for their hydrophilicity, lipophilicity, and basic crystal structure properties. The specific results are shown in the table below:
[0038] Table 1
[0039] Results analysis: Figure 1 (ab) is a SEM image of Example 1. It can be seen that the surface of the PVDF film in Example 1 has a fish-scale structure. Further magnification reveals that the surface of the PVDF film has a spherical structure with abundant micro- and nano-protrusions. According to the Wenzel-Cassie theory, this structure is beneficial to improving the wettability of the material.
[0040] so, Figure 2 This indicates that the PVDF membrane in Example 1 has excellent underwater superoleophobicity, and it exhibits superoleophobicity to a variety of different types of oil.
[0041] Figure 3 As shown in Figure a, the α-crystal form disappeared and the β-crystal form became dominant in the XRD pattern of the PVDF film in Example 1. Further FTIR analysis revealed this. Figure 3 b) Based on the Lambert-Beer law, it was found that the PVDF film in Example 1 had a β-crystal ratio as high as 83.2%.
[0042] Figure 4 In the PFM test, a significant piezoelectric response signal was obtained in the amplitude and phase of the antifouling membrane. When a voltage of ±10V was applied to the membrane surface, a significant hysteresis phenomenon and a 180° phase change, as well as a typical butterfly-shaped amplitude curve, were clearly observed. 33 The coefficient is as high as 88pm V -1 The d33 coefficient is higher than that of many traditional inorganic piezoelectric materials and organic-inorganic composite materials, and even exceeds that of PVDF films prepared by electrospinning, which indicates that the film in Example 1 has excellent piezoelectric properties.
[0043] Table 1 further reveals that PVDF films prepared from nanomaterials with hydroxyl functional groups and a thin functional layer casting solution (0.02 mm) (Examples 1-3) exhibit high hydrophilicity, underwater superoleophobicity, and a β-crystal ratio greater than 80%.
[0044] However, for nanomaterials with excessively thick functional layer casting solutions (Comparative Example 1) and those lacking hydroxyl functional groups (Comparative Examples 2-3), the hydrophilicity, underwater oleophobicity, and β-crystal content of the prepared PVDF films all decreased significantly. This indicates that the thickness of the functional layer casting solution has a significant impact on the formation of antifouling films. We found that antifouling films prepared with functional layer casting solution thicknesses between 0.01-0.03 mm exhibit superwetting properties and a β-crystal content greater than 80%.
[0045] In addition, the hydroxyl groups on the surface of nanomaterials also have an important influence. The esterification reaction between SMA and the hydroxyl groups on nanomaterials can promote the dispersion of nanomaterials in the casting solution, which is beneficial to the preparation of antifouling membranes with superwetting properties and a β-crystal ratio of more than 80%.
[0046] The membranes prepared in the above examples and comparative examples were subjected to oil-water separation experiments.
[0047] The preparation method of the oil-in-water (O / W) emulsion was as follows: 1 mL of oil and 0.25 g of emulsifier were added to 250 mL of water, followed by mechanical stirring for 24 h. Four types of oils were used in the emulsification process: n-hexane, cyclohexane, petroleum ether, and soybean oil. The separation process was completed using a self-made dead-end flow apparatus. The oil-water separation experimental steps were as follows: First, deionized water was pre-pressurized at 0.2 MPa for 15 min, then the deionized water was replaced with the oil-in-water (O / W) emulsion, and the oil-water separation experiment was started at a pressure of 0.1 MPa. During the experiment, the peristaltic pump was adjusted as needed to maintain a stable transmembrane pressure of 0.1 MPa.
[0048] For the hexane oil-water emulsion separation experiment, during a continuous test lasting 30 minutes, the flux decline rate and flux recovery rate of the example and the control example are shown in Table 2 below:
[0049] Table 2 Example Flux decay rate (%) Flux recovery rate (%) Example 1 63.4 83.4 Example 2 59.3 85.9 Example 3 61.5 84.4 Compare with Example 1 83.1 51.3 Compare with Example 2 83.5 48.7 Compare with Example 3 81.7 51.5
[0050] As can be seen from Table 2, compared with Comparative Examples 1-3, the PVDF membranes in Examples 1-3 have a lower flux decay rate and a higher flux recovery rate, which indicates that the superoleophobic antifouling membrane has better antifouling ability.
[0051] To further enhance the antifouling ability of the PVDF membrane in this embodiment, based on its excellent piezoelectric response, ultrasound was introduced to stimulate the PVDF antifouling membrane to produce a piezoelectric catalytic effect. The experimental steps are as follows: First, the membrane was pre-pressurized with deionized water at 0.2 MPa for 15 min. Then, the deionized water was replaced with an oil-in-water (O / W) emulsion. The membrane element was placed in the ultrasonic chamber, the ultrasound was turned on, and the oil-water separation experiment was started at a pressure of 0.1 MPa. During the experiment, the peristaltic pump was adjusted as needed to maintain a stable transmembrane pressure of 0.1 MPa.
[0052] Figure 5 a to Figure 5 c is the ESR test diagram of the antifouling membrane under ultrasound in Example 1. It can be seen that ultrasound can stimulate the antifouling membrane to generate hydroxyl radicals, superoxide radicals and singlet oxygen with strong oxidizing effects, which is beneficial to the oxidative degradation of pollutants.
[0053] therefore, Figure 6 a to Figure 6 c shows that the antifouling membrane has excellent antifouling effect on oil-water emulsions stabilized by three different charged surfactants. In an oil-water separation experiment lasting up to 400 minutes, the membrane flux decay rate was only 13% at most.
[0054] In summary, this invention employs a simple thin-layer casting solution composite technology to prepare an antifouling membrane that simultaneously couples piezoelectric catalysis and superoleophobic properties, thereby enhancing the antifouling ability of the membrane. Furthermore, by applying ultrasound, the antifouling membrane can be stimulated to generate free radicals with strong oxidizing effects, which degrade pollutants, thereby further enhancing the broad-spectrum antifouling ability of the membrane.
[0055] It will be apparent to those skilled in the art that the present invention is not limited to the details of the exemplary embodiments described above, and that the invention can be implemented in other specific forms without departing from the spirit or essential characteristics of the invention. Therefore, the embodiments should be considered in all respects as exemplary and non-limiting, and the scope of the invention is defined by the appended claims rather than the foregoing description. Thus, it is intended that all variations falling within the meaning and scope of equivalents of the claims be included within the present invention.
Claims
1. A method for preparing a PVDF antifouling membrane coupled with piezoelectric catalysis and superwetting properties, characterized in that, Includes the following steps: (1) Mix PVDF, pore-forming additives and solvents to prepare support layer casting solution A; (2) PVDF, styrene maleic anhydride (SMA), solvent and hydroxyl-containing nanofiller are blended to prepare functional layer casting solution B; (3) First, the casting solution A is applied to the glass plate, and then the casting solution B with a thickness of 0.01-0.03 mm is applied to the surface of the casting solution A to form a composite casting solution; (4) The composite casting liquid is placed in a coagulation bath and solidified using the phase inversion method to obtain an antifouling membrane.
2. The preparation method according to claim 1, characterized in that, The solvent is one or a mixture of dimethylacetamide, dimethylformamide, triethyl phosphate, and dimethyl sulfoxide.
3. The preparation method according to claim 1, characterized in that, The hydroxyl-containing nanofiller is one or more of hydroxylated carbon nanotubes, chloroform nanotubes, and hydroxylated graphene.
4. The preparation method according to claim 1, characterized in that, The composition of the support layer casting solution A in step (1) is: 22-25 parts PVDF, 8-12 parts pore-forming additive, and 60-65 parts solvent (by mass).
5. The preparation method according to claim 1, characterized in that, The composition of the functional layer casting solution B in step (2) is: 6-10 parts PVDF, 4-8 parts SMA, 0.2-0.5 parts hydroxyl-containing nanofiller, and 80-90 parts solvent (by mass).
6. The preparation method according to claim 1, characterized in that, In step (3), the coating thickness of casting solution A is 0.1-0.6 mm.
7. The preparation method according to claim 1, characterized in that, In step (4), the coagulation bath is composed of one or more mixtures of water and glycerin, and the coagulation bath temperature is 15-35℃.
8. A PVDF antifouling membrane with coupled piezoelectric catalysis and superwetting properties prepared by the method of any one of claims 1-7, characterized in that, The membrane has a β-crystal content ≥80%, an air water contact angle ≤15°, and an underwater oil contact angle ≥150°. 33 Coefficient ≥ 85pm·V -1 .
9. The application of the antifouling membrane according to claim 8 in oil-water separation, characterized in that, The application includes the separation of water-in-oil emulsions containing different charged surfactants under ultrasonic assistance.