CN112121648A - Polyvinylidene fluoride mixed matrix membrane with photocatalytic self-cleaning performance and preparation method and application thereof - Google Patents

Abstract

The invention relates to a polyvinylidene _fluoride mixed matrix film with photocatalytic self _- cleaning performance and a preparation method and application thereof. membrane liquid, and then a polyvinylidene fluoride mixed matrix membrane is prepared by a non-solvent-induced phase separation method; the mixed matrix membrane can be used to improve the anti-organic pollutant performance of the catalytic membrane reactor device. Compared with the prior art, in the present invention, SnO ₂ -Cu ₂ O is added to the polyvinylidene fluoride casting solution in the form of additives, and the PVDF membrane is modified by introducing the inorganic nanoparticle blending method and the NIPS method, which not only makes the composite membrane mechanically The strength is increased, while the hydrophilicity is also greatly enhanced, and it has better anti-fouling ability and retention performance.

Description

A polyvinylidene fluoride mixed matrix membrane with photocatalytic self-cleaning properties and its preparation Preparation method and application

technical field

The invention belongs to the technical field of membrane separation, and relates to a polyvinylidene fluoride mixed matrix membrane with photocatalytic self-cleaning performance and a preparation method and application thereof.

Background technique

Membrane separation technology is one of the preferred technologies in the field of water pollution control engineering. Because of its low cost, good effluent quality, high degree of intensification, simple equipment and convenient operation, it is widely used in drinking water purification and sewage treatment and reuse. . However, membrane fouling, especially organic fouling, often leads to the attenuation of membrane flux, the increase of operating cost and the shortening of membrane service life, thus becoming the main obstacle to the widespread application of membrane separation technology in drinking water, sewage and wastewater treatment.

Polyvinylidene fluoride (PVDF) is a vinylidene fluoride homopolymer or a copolymer of vinylidene fluoride and other small amounts of fluorine-containing vinyl monomers. It has good chemical resistance, high temperature resistance, radiation resistance and easy film formation. As a typical ultrafiltration membrane material, it is widely used in various water treatment fields, such as domestic sewage treatment, industrial wastewater treatment, etc. However, PVDF membrane materials have low surface energy and poor affinity with water. Hydrophobic organic pollutants such as proteins or oils are easily adsorbed to the membrane surface and cause membrane fouling, thereby affecting the economy and reliability of the membrane, restricting the Development, application and promotion of PVDF membrane materials. It is known that the fouling resistance of PVDF membranes can be improved by physical and chemical means, and the modification methods can be mainly divided into two categories: membrane surface modification and membrane material modification. Membrane material modification can be further divided into chemical modification and blending modification of membrane materials. The latter is a research hotspot in recent years because of its simple operation, and the hydrophilic group is not easy to fall off, which is convenient for large-scale promotion.

Photocatalysis technology is a relatively new, efficient and environmentally friendly technical means in the field of water treatment in recent years. This technology uses renewable light energy to generate active groups to achieve the degradation of organic pollutants in water. Therefore, the combination of photocatalytic technology and membrane modification technology to form a composite photocatalytic separation modified membrane can effectively improve the self-cleaning ability, hydrophilic performance and retention characteristics of the membrane. The technology of coupling photocatalysis and membrane separation is gradually being used in membrane separation research. Chinese patent CN103881122B has published a method for preparing a polyvinyl chloride/nano tin dioxide composite membrane with high visible light catalytic activity. The method is simple, the obtained composite film has excellent photocatalytic activity and stability under visible light, and can be easily separated and recovered from the degradation liquid, which is suitable for industrial application. However, the membrane prepared by this method has insufficient anti-fouling property to the organic pollutant pendimethalin, and has low retention efficiency.

SUMMARY OF THE INVENTION

The purpose of the present invention is to provide a polyvinylidene fluoride mixed matrix membrane with photocatalytic self-cleaning performance and its preparation method and application, which are used to solve the membrane pollution problem of the polyvinylidene fluoride membrane.

The object of the present invention can be realized through the following technical solutions:

A preparation method of a polyvinylidene fluoride (PVDF) mixed matrix film with photocatalytic self-cleaning performance, comprising: mixing SnO ₂ -Cu ₂ O nanocomposite material and polyvinylidene fluoride and preparing a casting liquid, and then passing through Polyvinylidene fluoride mixed matrix membranes were prepared by non-solvent induced phase separation (NIPS).

Further, the preparation method of the SnO ₂ -Cu ₂ O nanocomposite material includes: preparing a mixed solution of copper salt, tin salt and hydrochloric acid, adjusting the pH to 7-12, then adding a reducing agent and carrying out the process at room temperature After the reaction, the obtained product undergoes the processes of centrifugation, washing, drying and calcination in sequence, and the SnO ₂ -Cu ₂ O nanocomposite material is obtained.

Further, the copper salt includes cuprous chloride, and the tin salt includes stannous chloride;

The mol ratio of described copper salt and tin salt is (1-4): (0.1-2);

The addition of described hydrochloric acid is 10-30mL/mol Cu, and the concentration of hydrochloric acid is 30-40mol/L;

The preparation method of the mixed solution includes: adding copper salt, tin salt and hydrochloric acid into deionized water, and ultrasonicating for 15-45min;

The reducing agent includes hydrazine hydrate, and the addition of the hydrazine hydrate is 10-30 mL/mol Cu;

In the reduction reaction, the reaction time is 1-4h.

Further, in the described washing process, the detergent is ethanol;

The drying process includes vacuum drying at 40-80°C;

In the calcination process, the calcination atmosphere includes argon gas, the calcination temperature is 100-400° C., and the calcination time is 1-4 hours.

Further, the preparation method of the casting solution includes: adding SnO ₂ -Cu ₂ O nanocomposite material, porogen and polyvinylidene fluoride into N,N-dimethylformamide, stirring evenly, The casting liquid is obtained after defoaming.

Further, the porogen includes polyvinylpyrrolidone;

The mass ratio of the SnO ₂ -Cu ₂ O nanocomposite material, porogen and polyvinylidene fluoride is (0.1-1.6):1:(14-20);

During the stirring process, the stirring temperature is 30-80℃, and the stirring time is 8-18h;

In the process of standing and defoaming, the standing time is 5-12h.

Further, the non-solvent-induced phase separation method comprises: scraping the film casting liquid on the substrate, and placing it in a gel bath for phase separation to obtain the polyvinylidene fluoride mixed matrix film.

Further, the thickness of the scraping film is 100-260 μm;

The gel bath includes a mixed solution of ethanol and water in a volume ratio of (0.5-1.5):(0.8-1.3), and the temperature of the gel bath is 14-30°C.

A polyvinylidene fluoride mixed matrix membrane with photocatalytic self-cleaning performance, prepared by the method as described above, can be used for anti-organic pollutants, specifically for improving the anti-organic pollutant performance of a catalytic membrane reactor device .

The SnO ₂ -Cu ₂ O photocatalyst-modified PVDF ultrafiltration membrane of the present invention can be used in a catalytic membrane reactor device to degrade organic pollutants on the membrane surface under the irradiation of a visible light lamp, thereby inhibiting membrane fouling. Utilize the SnO ₂ -Cu ₂ O photocatalyst modified PVDF ultrafiltration membrane of the present invention to realize the anti-pollution method under visible light irradiation as follows:

A catalytic membrane reactor device was constructed, the PVDF ultrafiltration membrane modified by the SnO ₂ -Cu ₂ O photocatalyst after pollution was fixed on the membrane module, and the LED visible light lamp was fixed on the surface of the membrane. After photocatalysis for 30 min, the SnO ₂ - The Cu ₂ O photocatalyst-modified PVDF ultrafiltration membrane continued to be used in the water flux experiment, which achieved resistance to organic pollution and enhanced flux recovery under LED visible light irradiation. The organic pollutants include pendimethalin.

The SnO ₂ -Cu ₂ O photocatalyst modified PVDF ultrafiltration membrane of the present invention can activate the SnO ₂ -Cu ₂ O photocatalyst on the surface of the membrane under visible light irradiation to generate oxidative active oxygen radicals, and the active oxygen radicals It can degrade organic pollutants and mineralize pollutants into CO ₂ and H ₂ O.

When the polyvinylidene fluoride mixed matrix membrane of the present invention is treated with a pendimethalin solution, the membrane exhibits excellent anti-fouling property, and the retention rate is significantly improved. This is because during the phase separation process, the inorganic nanomaterials are embedded in the concave surface of the hybrid membrane surface, resulting in a smoother membrane surface, and the smooth membrane surface is less likely to accumulate contaminants. On the other hand, with the enhancement of hydrophilicity, the "hydration layer" on the membrane surface effectively prevents the fouling from approaching, making the fouling accumulation in the membrane pores more difficult, and showing higher antifouling performance. At the same time, because the modified membrane has a complex structure of uniform sponge pores and a pore size smaller than that of pendimethalin, it can also effectively intercept pendimethalin molecules, showing a high rejection rate.

The preparation method of the present invention is to add the prepared SnO ₂ -Cu ₂ O to the polyvinylidene fluoride casting solution in the form of an additive, and modifying the PVDF membrane by introducing the inorganic nanoparticle blending method and the NIPS method not only makes the composite membrane mechanically The strength is improved, and the hydrophilicity is also greatly improved, and it has better anti-fouling ability and interception performance. Blending is the simplest and most commonly used membrane modification method. Compared with other methods, blending modification has the following advantages: modification and film formation are carried out simultaneously, the process is simple, and no complicated post-processing steps are required; the additive can cover the membrane surface and the inner wall of the membrane hole at the same time without causing damage to the membrane structure. .

Compared with the prior art, the present invention has the following characteristics:

1) Compared with the traditional PVDF ultrafiltration membrane, the SnO ₂ -Cu ₂ O photocatalyst modified PVDF ultrafiltration membrane provided by the present invention has higher hydrophilicity and has remarkable photocatalytic performance; SnO ₂ -Cu ₂ O photocatalyst Among them, the combination of Cu ₂ O and SnO ₂ can form a heterojunction structure, which can improve the photoresponse performance of the two and avoid the photocorrosion phenomenon of SnO ₂ , while the addition of Cu ₂ O improves its electron transport rate, effectively promoting The visible light responsiveness of SnO ₂ -Cu ₂ O has a good anti-fouling effect under visible light irradiation, which can effectively reduce the membrane fouling phenomenon and slow down the decline rate of membrane flux;

2) Compared with the PVDF membrane modified by the SnO ₂ -Cu ₂ O photocatalyst provided by the present invention, the energy consumption and cost are significantly reduced compared with the PVDF membrane modified by the ultraviolet photocatalyst (such as TiO ₂ );

3) The method for preparing the SnO ₂ -Cu ₂ O photocatalyst-modified PVDF ultrafiltration membrane of the present invention is simple and easy to operate. , which can be widely used in the preparation of photocatalyst modified PVDF membranes;

4) The method for preparing the SnO ₂ -Cu ₂ O photocatalyst-modified PVDF ultrafiltration membrane of the present invention is a blending modification method, and the photocatalyst SnO ₂ -Cu ₂ O in the modified membrane is not easy to dissolve with the water flow during use. , to avoid poisoning and potential secondary pollution to the water body, and ensure the durability and stability of the membrane structure.

Description of drawings

1 is a scanning electron microscope image of SnO ₂ -Cu ₂ O particles prepared in Example 1;

Fig. 2 is the sectional scanning electron microscope picture of the uniform polyvinylidene fluoride film prepared in embodiment 4;

Figure 3 shows the water flux of the SnO ₂ -Cu ₂ O photocatalyst-modified PVDF membrane (M4-M8) prepared in Example 4-8 and the original PVDF membrane M0 degrading pendimethalin solution over time under visible light irradiation changing curve;

FIG. 4 is a comparison diagram of the water flux and rejection rate of the SnO ₂ -Cu ₂ O photocatalyst-modified PVDF membrane (M4-M8) prepared in Example 4-8 and the original PVDF membrane M0.

Detailed ways

The present invention will be described in detail below with reference to the accompanying drawings and specific embodiments.

A preparation method of a polyvinylidene fluoride (PVDF) mixed matrix membrane with photocatalytic self-cleaning performance, comprising the following steps:

1) Preparation of SnO ₂ -Cu ₂ O nanocomposite: cuprous chloride (CuCl ₂ ), stannous chloride dihydrate (SnCl ₂ ·2H ₂ O) and hydrochloric acid were added to deionized water, and sonicated for 15- After 45 minutes, a mixed solution was obtained, then the pH of the mixed solution was adjusted to 7-12, a reducing agent hydrazine hydrate was added and the reaction was carried out at room temperature for 1-4 hours. After drying under vacuum, and finally calcining at 100-400 ° C for 1-4 h in an argon atmosphere, SnO ₂ -Cu ₂ O nanocomposite is obtained;

Wherein, the molar ratio of CuCl ₂ to SnCl ₂ ·2H ₂ O is (1-4): (0.1-2); the addition of hydrochloric acid is 10-30mL/mol Cu, and the concentration of hydrochloric acid is 30-40mol/L; hydrazine hydrate The addition amount is 10-30mL/mol Cu;

2) Preparation of casting solution: SnO ₂ -Cu ₂ O nanocomposite, porogen polyvinylpyrrolidone (PVP) and polyvinylidene fluoride (PVDF) were added to N,N-dimethylformamide (DMF) and stirring at 30-80°C for 8-18h, and after standing for defoaming, the casting liquid is obtained;

Wherein, the mass ratio of SnO ₂ -Cu ₂ O nanocomposite, porogen and polyvinylidene fluoride is (0.1-1.6):1:(14-20);

3) Preparation of polyvinylidene fluoride mixed matrix film by non-solvent-induced phase separation method: Scratch the casting liquid on a glass plate, the thickness of the scraped film is 100-260 μm, and place it in a volume ratio of ethanol and water (0.5-1.5 μm). ): (0.8-1.3) to conduct phase separation in a gel bath at 14-30° C. to obtain a polyvinylidene fluoride mixed matrix membrane.

The following are more detailed implementation cases, which further illustrate the technical solutions of the present invention and the technical effects that can be obtained.

Example 1:

This embodiment is used to prepare SnO ₂ -Cu ₂ O nanocomposite materials, and the specific preparation method is as follows:

1) adding 0.01mol CuCl ₂ , 0.005mol SnCl ₂ 2H ₂ O and 0.2mL 35mol/L hydrochloric acid to 200mL deionized water, and ultrasonically treating for 30min to obtain a mixed solution;

2) Ammonia water was added to the mixed solution until pH=9.0, then 0.2 mL of hydrazine hydrate was added, and the reduction reaction was carried out at room temperature for 2 hours;

3) After the obtained product was washed with ethanol, vacuum-dried at 60° C., and then the dried powder was calcined at 200° C. for 2 h under argon protection to obtain SnO ₂ -Cu ₂ O nanocomposite.

The obtained SnO ₂ -Cu ₂ O nanocomposite was characterized by scanning electron microscope, and the results are shown in Fig. 1 .

Example 2:

This embodiment is used to prepare SnO ₂ -Cu ₂ O nanocomposite materials, and the specific preparation method is as follows:

1) adding 0.04mol CuCl ₂ , 0.004mol SnCl ₂ ·2H ₂ O and 0.4mL 30mol/L hydrochloric acid to 200mL deionized water, and ultrasonically treating for 15min to obtain a mixed solution;

2) Ammonia water was added to the mixed solution until pH=9.0, then 0.4 mL of hydrazine hydrate was added, and the reduction reaction was carried out at room temperature for 1 h;

3) After the obtained product was washed with ethanol, it was vacuum-dried at 40° C., and then the dried powder was calcined at 100° C. for 1 h under argon protection to obtain SnO ₂ -Cu ₂ O nanocomposite.

Example 3:

This embodiment is used to prepare SnO ₂ -Cu ₂ O nanocomposite materials, and the specific preparation method is as follows:

1) adding 0.07mol CuCl ₂ , 0.035mol SnCl ₂ ·2H ₂ O and 2.1 mL of 40 mol/L hydrochloric acid to 200 mL of deionized water, and ultrasonically treated for 45 min to obtain a mixed solution;

2) Add ammonia water to the mixed solution until pH=9.0, then add 2.1 mL of hydrazine hydrate, and carry out reduction reaction at room temperature for 4 hours;

3) After the obtained product was washed with ethanol, vacuum dried at 80°C, and then the dried powder was calcined at 400°C for 4 h under argon protection to obtain SnO ₂ -Cu ₂ O nanocomposite.

Example 4:

In this example, the SnO ₂ -Cu ₂ O nanocomposite material in Example 1 is used to further prepare a polyvinylidene fluoride mixed matrix film, and the specific preparation method is as follows:

1) Dissolve SnO ₂ -Cu ₂ O nanocomposite, PVP and PVDF in DMF at a mass ratio of 0.3:1:15, stir at 60°C for 10h until fully dissolved, and then stand for defoaming for 6h to obtain a cast film liquid;

2) Scraping the casting liquid on the glass plate, the thickness of the scraping film is 250 μm;

3) Immerse the glass plate with the membrane liquid in a mixture of 15°C ethanol and deionized water in a volume ratio of 1.0:1.2 for phase separation;

4) Transfer the phase-separated membrane to deionized water for soaking to remove excess solvent, and then put it into clean deionized water for preservation to obtain a polyvinylidene fluoride mixed matrix membrane, which is recorded as an M4 ultrafiltration membrane.

The obtained M4 ultrafiltration membrane was characterized by cross-sectional scanning electron microscopy, and the results are shown in Figure 2. It can be seen from the figure that the surface of the membrane section is dense, but has larger membrane pores.

Example 5:

In this example, the SnO ₂ -Cu ₂ O nanocomposite material in Example 1 is used to further prepare a polyvinylidene fluoride mixed matrix film, and the specific preparation method is as follows:

1) Dissolve SnO ₂ -Cu ₂ O nanocomposite, PVP and PVDF in DMF at a mass ratio of 0.8:1:15, stir at 70°C for 10h until fully dissolved, and then stand for defoaming for 10h to obtain a cast film liquid;

2) Scratch the casting liquid on the glass plate, and the thickness of the scraped film is 150 μm;

3) Immerse the glass plate with the membrane liquid in a mixture of ethanol and deionized water at a volume ratio of 0.8:1.0 at 20°C for phase separation;

4) Transfer the phase-separated membrane to deionized water for immersion to remove excess solvent, and then put it into clean deionized water for preservation to obtain a polyvinylidene fluoride mixed matrix membrane, which is denoted as M5 ultrafiltration membrane.

Example 6:

In this example, the SnO ₂ -Cu ₂ O nanocomposite material in Example 1 is used to further prepare a polyvinylidene fluoride mixed matrix film, and the specific preparation method is as follows:

1) Dissolve SnO ₂ -Cu ₂ O nanocomposite, PVP and PVDF in DMF at a mass ratio of 1.5:1:15, stir at 50°C for 10h until fully dissolved, and then stand for degassing for 8h to obtain a cast film liquid;

2) Scratch the casting liquid on the glass plate, and the thickness of the scraped film is 130 μm;

3) Immerse the glass plate with the membrane liquid in a mixture of ethanol and deionized water at a volume ratio of 1.2:1.0 at 25°C for phase separation;

4) Transfer the phase-separated membrane to deionized water and soak it in deionized water to remove excess solvent, and then put it into clean deionized water for preservation to obtain a polyvinylidene fluoride mixed matrix membrane, denoted as M6 ultrafiltration membrane.

Example 7:

In this example, the SnO ₂ -Cu ₂ O nanocomposite material in Example 1 is used to further prepare a polyvinylidene fluoride mixed matrix film, and the specific preparation method is as follows:

1) Dissolve SnO ₂ -Cu ₂ O nanocomposite, PVP and PVDF in DMF at a mass ratio of 0.1:1:14, stir at 30°C for 8h until fully dissolved, and then stand for defoaming for 5h to obtain a cast film liquid;

2) Scratch the casting liquid on the glass plate, and the thickness of the scraped film is 100 μm;

3) Immerse the glass plate with the membrane liquid in a mixture of 14°C ethanol and deionized water in a volume ratio of 0.5:0.8 for phase separation;

4) Transfer the phase-separated membrane to deionized water for soaking to remove excess solvent, and then put it into clean deionized water for preservation to obtain a polyvinylidene fluoride mixed matrix membrane, which is recorded as an M7 ultrafiltration membrane.

Example 8:

In this example, the SnO ₂ -Cu ₂ O nanocomposite material in Example 1 is used to further prepare a polyvinylidene fluoride mixed matrix film, and the specific preparation method is as follows:

1) Dissolve SnO ₂ -Cu ₂ O nanocomposite, PVP and PVDF in DMF at a mass ratio of 1.6:1:20, stir at 80°C for 18h until fully dissolved, and then stand for defoaming for 12h to obtain a cast film liquid;

2) Scratch the casting liquid on the glass plate, and the thickness of the scraped film is 260 μm;

3) Immerse the glass plate with the membrane liquid in a mixture of ethanol and deionized water at a volume ratio of 1.5:1.3 at 30°C for phase separation;

4) Transfer the phase-separated membrane to deionized water for immersion to remove excess solvent, and then put it into clean deionized water for preservation to obtain a polyvinylidene fluoride mixed matrix membrane, which is recorded as an M8 ultrafiltration membrane.

Comparative ratio:

In this embodiment, the NIPS method is used to prepare the polyvinylidene fluoride flat film without SnO ₂ -Cu ₂ O nanocomposite material, and the specific preparation method is as follows:

1) Dissolve PVP and PVDF in DMF at a mass ratio of 1:15, stir at 60°C for 10 hours until fully dissolved, and then stand for deaeration for 6 hours to obtain a casting solution;

2) Scraping the casting liquid on the glass plate, the thickness of the scraping film is 250 μm;

3) Immerse the glass plate with the membrane liquid in a mixture of 15°C ethanol and deionized water in a volume ratio of 1.0:1.2 for phase separation;

4) Transfer the phase-separated membrane to deionized water for soaking to remove excess solvent, and then put it into clean deionized water for preservation to obtain an unmodified polyvinylidene fluoride flat membrane, which is recorded as M0 ultrafiltration membrane.

Example 9:

The present embodiment is used to test the water flux and pendimethalin rejection rate of the ultrafiltration membranes in Examples 4-8 and Comparative Examples, wherein the test method of water flux and pendimethalin rejection rate refers to literature: Y . Wang, Gui-E Chen, Hai-Ling Wu, Fabrication of GO-Ag/PVDF/F127 modified membrane IPA coagulation bath for catalytic reduction of 4-nitrophenol, Sep. Purif. Technol. 235(2020) 116143. The test results are shown in Figure 3 and Figure 4, respectively. It can be seen from the figures that each nanoparticle-added membrane exhibits superior permeability and better separation performance compared with the original PVDF membrane. The increase in permeability may be due to two main factors: 1) the addition of nanoparticles will render the membrane hydrophilic, thereby increasing the rate of water passing through the membrane; 2) the pore size and porosity of the modified membrane compared to the pristine membrane degree of expansion, which is undoubtedly conducive to permeability. The improvement of separation performance can be explained by the following three reasons: 1) the pore size of the membrane is smaller than the size of the pollutant; 2) the complex structure of the complete sponge pores formed by delayed phase separation can effectively intercept pendimethalin molecules; 3) Using the theory that the interfacial hydration layer enhances the hydrophilicity, the contact between the contaminants and the membrane surface is reduced, thereby preventing the contaminants from penetrating the modified membrane. At the same time, compared to simply washing the contaminated membrane with water, exposing the membrane to visible light can effectively catalyze the decomposition of pendimethalin attached to the membrane pores, resulting in a higher flux recovery rate.

The foregoing description of the embodiments is provided to facilitate understanding and use of the invention by those of ordinary skill in the art. It will be apparent to those skilled in the art that various modifications to these embodiments can be readily made, and the generic principles described herein can be applied to other embodiments without inventive step. Therefore, the present invention is not limited to the above-mentioned embodiments, and improvements and modifications made by those skilled in the art according to the disclosure of the present invention without departing from the scope of the present invention should all fall within the protection scope of the present invention.

Claims (10)

1. a preparation method of a polyvinylidene fluoride mixed matrix film with photocatalytic self-cleaning performance is characterized in that, the method comprises: mixing SnO ₂ -Cu ₂ O nanocomposite material with polyvinylidene fluoride and preparing to obtain cast membrane liquid, and then a polyvinylidene fluoride mixed matrix membrane was prepared by a non-solvent-induced phase separation method. 2 . The preparation method of the polyvinylidene fluoride mixed matrix film with photocatalytic self-cleaning performance according to claim 1 , wherein the preparation method of the SnO ₂ -Cu ₂ O nanocomposite comprises: the copper Salt, tin salt and hydrochloric acid are prepared into a mixed solution, and the pH is adjusted to 7-12, then a reducing agent is added and the reaction is carried out at room temperature. ₂ -Cu ₂ O nanocomposite. 3. the preparation method of the polyvinylidene fluoride mixed matrix film with photocatalytic self-cleaning performance according to claim 2, is characterized in that, described copper salt comprises cuprous chloride, and described tin salt comprises chloride tin; The mol ratio of described copper salt and tin salt is (1-4): (0.1-2); The addition of described hydrochloric acid is 10-30mL/mol Cu, and the concentration of hydrochloric acid is 30-40mol/L; The preparation method of the mixed solution includes: adding copper salt, tin salt and hydrochloric acid into deionized water, and ultrasonicating for 15-45min; The reducing agent includes hydrazine hydrate, and the addition of the hydrazine hydrate is 10-30 mL/mol Cu; In the reduction reaction, the reaction time is 1-4h. 4. the preparation method of the polyvinylidene fluoride mixed matrix film with photocatalytic self-cleaning performance according to claim 2, is characterized in that, in the described washing process, the detergent is ethanol; The drying process includes vacuum drying at 40-80°C; In the calcination process, the calcination atmosphere includes argon gas, the calcination temperature is 100-400° C., and the calcination time is 1-4 hours. 5. The preparation method of the polyvinylidene fluoride mixed matrix film with photocatalytic self-cleaning performance according to claim 1, wherein the preparation method of the film casting solution comprises: SnO ₂ -Cu ₂ O nanometer The composite material, the porogen and the polyvinylidene fluoride are added to the N,N-dimethylformamide and stirred evenly, and the casting liquid is obtained after standing for defoaming. 6. The preparation method of the polyvinylidene fluoride mixed matrix film with photocatalytic self-cleaning performance according to claim 5, wherein the porogen comprises polyvinylpyrrolidone; The mass ratio of the SnO ₂ -Cu ₂ O nanocomposite material, porogen and polyvinylidene fluoride is (0.1-1.6):1:(14-20); During the stirring process, the stirring temperature is 30-80 °C, and the stirring time is 8-18 h. 7. The preparation method of the polyvinylidene fluoride mixed matrix film with photocatalytic self-cleaning performance according to claim 1, wherein the non-solvent-induced phase separation method comprises: scraping the casting liquid on the substrate and placed in a gel bath for phase separation to obtain the polyvinylidene fluoride mixed matrix membrane. 8. The method for preparing a polyvinylidene fluoride mixed matrix film with photocatalytic self-cleaning performance according to claim 7, wherein the thickness of the scraped film is 100-260 μm; The gel bath includes a mixed solution of ethanol and water in a volume ratio of (0.5-1.5):(0.8-1.3), and the temperature of the gel bath is 14-30°C. 9 . A polyvinylidene fluoride mixed matrix film with photocatalytic self-cleaning performance, characterized in that, it is prepared by the method according to any one of claims 1 to 8 . 10. An application of the polyvinylidene fluoride mixed matrix membrane as claimed in claim 9 in resisting organic pollutants.

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