Preparation method and application of PTFE biomimetic membrane based on photocatalysis-filtration coupling mechanism

Abstract

The application discloses a preparation method and application of a PTFE biomimetic membrane based on a photocatalysis-filter coupling mechanism. The method comprises the following steps: firstly, blending polytetrafluoroethylene (PTFE) and a photocatalyst in a solvent; sequentially performing pushing, rolling, longitudinal stretching, transverse-longitudinal stretching and heat treatment operations on the blended slurry; and finally obtaining the PTFE biomimetic membrane with photocatalysis-filter functions. The PTFE biomimetic membrane can be used for air purification, atmospheric dust removal, industrial waste gas filtration and the like. The application adopts a photocatalysis free oxygen negative ion generation mechanism, orderly embeds isotactic photocatalysts and constructs a micro-rough surface to realize air purification efficiency improvement, pollutant screening and anti-pollution performance. In addition, the orderly arranged photocatalysts can greatly improve light scattering, and then improve the photocatalyst efficiency of the material.

Description

Technical Field

[0001] This invention belongs to the field of air purification, and in particular relates to a method for preparing and applying a PTFE biomimetic membrane based on a photocatalysis-filtration coupling mechanism. Background Technology

[0002] Public concern about air pollution is growing. Common air pollutants include toxic fumes, toxic volatile chemical gases, particulate matter, bacteria, and viruses. Wearing masks at home, in the office, and in hospitals has become routine. However, these passive protective measures cannot provide 24-hour protection. Therefore, developing comprehensive, thorough, and sustainable air purification technologies for various locations is an inevitable trend.

[0003] Polytetrafluoroethylene (PTFE) possesses unique properties such as fibrillation at its nodes, a smooth and flat surface, acid and alkali resistance, strong hydrophobicity, high airflow, high temperature resistance, flame retardancy, and non-toxicity. It is commonly used in the form of membranes for air purification. PTFE membrane manufacturing processes are well-established, highly controllable, and reusable. However, PTFE achieves air purification through a filtration mechanism. This mechanism has several drawbacks: 1) Low purification efficiency; all air in the space must pass through the PTFE membrane to achieve comprehensive air purification; 2) No sieving mechanism, making it unable to filter pollutants (viruses, etc.) smaller than the PTFE pore size; 3) Poor anti-fouling performance; after prolonged air purification, the PTFE surface is easily contaminated, significantly reducing the material's air purification performance, thus requiring regular cleaning. Summary of the Invention

[0004] To address the problems in the existing technology, this invention proposes a method for preparing and applying a biomimetic polytetrafluoroethylene (PTFE) membrane based on a photocatalysis-filtration coupling mechanism. The method of this invention uses a biaxial stretching process to composite an isotactic photocatalyst with PTFE, thereby designing and constructing an air purification membrane.

[0005] The technical solution of the present invention is as follows, including the following steps:

[0006] Step S1: Disperse the photocatalyst in an organic solvent and stir for 5 to 180 minutes at a temperature of 10 to 90°C to form a uniform dispersion; then immediately add polytetrafluoroethylene (PTFE) particles into the above dispersion and stir for 3 to 24 hours at a temperature of 15 to 105°C to obtain a uniform slurry.

[0007] Step S2: The slurry obtained in step S1 is injected into the roller press by pushing and rolled in the roller press. After the rolling process is completed, a rolled film is obtained.

[0008] Step S3: The roll-formed film is stretched longitudinally and transversely in sequence using a stretching machine to obtain a PTFE film;

[0009] Step S4: Heat-treat the PTFE film at a temperature of 100-320℃ for 2-8 hours, and then cool it to room temperature to obtain the PTFE biomimetic film.

[0010] In step S1, the photocatalyst is Co6-MOF, NH2-UiO-66, MIL-125, Ni 0.75 Mg 0.25 -One or more of MOF-74, HOF-66, PFC-42, HOF-1, TiO2, CdS, Ni-Co Prussian Blue, and Fe-Co Prussian Blue.

[0011] The photocatalyst uses a regular structure, such as hexahedron or sphere. The regular structure of the photocatalyst is conducive to the orderly micro-rough structure on the surface of the PTFE film, thereby improving the material's anti-fouling and light absorption rate.

[0012] In step S1, the PTFE particle size ranges from 10 to 85 μm.

[0013] PTFE particles within this size range are not only advantageous for processing and molding, but also result in PTFE membranes with smaller pore sizes, enabling them to filter large particulate pollutants such as dust from the air. Furthermore, PTFE particles within this size range are beneficial for the distribution of photocatalysts.

[0014] In step S1, the organic solvent is one or more of chloroform, carbon tetrachloride, dichloroethane, and toluene;

[0015] In step S1, the concentration ratio of PTFE particles to photocatalyst is 5-240 g / L: 10 g / mL.

[0016] In step S2, the pushing rate during the rolling process is 0.1 to 1.2 m / min, and the rolling pressure is 1 to 4 MPa.

[0017] In step S3, the tensile force is in the range of 0.1 to 1.3 MPa.

[0018] The thickness of the stretched PTFE film is in the range of 150 to 350 nm.

[0019] The PTFE biomimetic membrane is used for air purification, atmospheric dust removal, industrial waste gas filtration, sterilization and disinfection, and odor degradation.

[0020] This invention is based on a biaxially oriented PTFE membrane manufacturing process. First, a photocatalyst and PTFE particles are blended in an organic solvent to form a homogeneous slurry. Then, the slurry is injected into a rolling mill for rolling. After rolling, it is sequentially stretched longitudinally and then laterally. Finally, heat treatment yields a PTFE air purification membrane with both photocatalytic and filtration functions. The air purification performance and antifouling properties of the material are optimized by controlling the type of isotactic photocatalyst, PTFE particle size, the concentration ratio of PTFE to isotactic photocatalyst, light intensity, and cycle number.

[0021] This invention stretches the rolled film so that the thickness of the PTFE film is smaller than the size of a single photocatalyst. This exposes the photocatalyst over a large area, and since only one layer of photocatalyst exists in the PTFE film, it greatly increases the possibility of the photocatalyst being arranged in an orderly manner.

[0022] Heat treatment is a routine operation in the PTFE membrane preparation process, mainly serving to rapidly form the PTFE film. The PTFE biomimetic membrane obtained in this invention differs from ordinary PTFE filter membranes. Ordinary PTFE filter membranes are primarily used for passively filtering air impurities, while the PTFE biomimetic membrane of this invention can actively purify the air. When the PTFE biomimetic membrane is placed in the air, the photocatalyst within it absorbs sunlight and generates photo-generated electrons. These photo-generated electrons spontaneously react with oxygen to generate small-particle free oxygen negative ions. Due to electrostatic interactions, these oxygen negative ions continuously adhere to positively charged pollutants, causing them to settle from the air. Furthermore, the free oxygen negative ions can automatically capture bacteria and viruses in the air; their own electrons can destroy the protein structure of bacteria, viruses, and other microorganisms, causing protein denaturation and ultimately achieving a bactericidal and disinfecting effect. In addition, after the oxygen negative ions are absorbed, the membrane potential of blood cells increases. Under electrostatic repulsion, red blood cells maintain a healthy distance, and toxins, cholesterol, lipids, and other harmful substances on the surface of red blood cells are removed and eliminated from the body.

[0023] The beneficial effects of this invention are as follows:

[0024] 1. This invention generates small-particle free negative oxygen ions through a photocatalytic reaction. These ions not only sterilize and remove suspended particles, but can also be absorbed by the human body, promoting the absorption of oxygen and nutrients by the lungs and blood vessels, accelerating metabolism, and benefiting human health. More importantly, compared to traditional air filtration membranes, these free negative oxygen ions can float throughout the space to regulate the ion balance in the air, thus achieving comprehensive and thorough air purification.

[0025] 2. Because PTFE is biaxially stretched to achieve a very small thickness, the exposed area of ​​the photocatalyst is large. The nanopores within the photocatalyst itself act as a sieve, effectively filtering small pollutants such as viruses.

[0026] 3. The photocatalyst is arranged in an orderly manner on the PTFE surface, forming a micro-rough surface, which greatly reduces the surface energy between pollutants and PTFE, reduces the adhesion ability of pollutants to PTFE, and enables PTFE to achieve excellent anti-fouling performance.

[0027] 4. The ordered micro-rough surface enhances light scattering, improves the photocatalyst efficiency, accelerates the production of oxygen negative ions, and further improves air purification performance. Attached Figure Description

[0028] Figure 1 This is a schematic diagram of the air filtration process of the PTFE biomimetic membrane based on the photocatalyst-filtration coupling effect of the present invention;

[0029] Figure 2 The bar chart shows the air filtration performance of the PTFE biomimetic membranes based on photocatalyst-filtration coupling prepared in Examples 2-12.

[0030] Figure 3 The bar chart shows the air filtration performance of the PTFE air filter membranes based on the photocatalyst mechanism prepared in Examples 13-18.

[0031] Figure 4 The bar chart shows the air filtration performance of the PTFE air filter membranes based on the photocatalyst mechanism prepared in Examples 19-23.

[0032] Figure 5 The bar chart shows the air filtration performance of the PTFE air filter membranes based on the photocatalyst mechanism prepared in Examples 24-28.

[0033] Figure 6 The bar chart shows the air filtration performance of the PTFE air filter membranes based on the photocatalyst mechanism prepared in Examples 29-38. Detailed Implementation

[0034] The present invention will be further described in detail below with reference to the accompanying drawings and embodiments. It should be noted that the embodiments described below are intended to facilitate the understanding of the present invention and do not limit it in any way.

[0035] Example 1

[0036] Step S1: Select Co6-MOF as the desired photocatalyst, disperse 10g of Co6-MOF in 1L of dichloroethane solvent, and stir continuously at 25℃ for 3h; finally, add 80g of PTFE particles (particle size: 40μm), and stir vigorously at 65℃ for 24h to finally form a homogeneous slurry;

[0037] Step S2: The slurry is injected into the roller press at a pushing rate of 0.5 m / min and the roller press pressure is 2 MPa. After the roller press is completed, the roller film is obtained.

[0038] Step S3: The rolled film is stretched longitudinally and transversely with a tensile force of 0.6 MPa to obtain a PTFE film;

[0039] Step S4: Heat-treat the PTFE film at 200℃ for 4 hours to obtain a PTFE biomimetic membrane with both photocatalytic and filtration functions, such as... Figure 1 As shown.

[0040] Step S5: Conduct an air purification experiment on the PTFE biomimetic membrane; experimental conditions are: in an experimental space (30m... 3 A certain concentration of large-sized pollutants (500nm) and bacteria are injected into the membrane; a PTFE biomimetic membrane (size: 1m) 2 Under illumination conditions (illuminance: 1kW / m²) 2 The air was continuously purified for 24 hours. The experimental results showed a 99.9999% removal rate of large-sized pollutants and a 99.99% sterilization rate.

[0041] It can be seen that the PTFE biomimetic membrane obtained by this invention has excellent air purification performance.

[0042] Examples 2-12

[0043] Air purification experiments were conducted using PTFE air biomimetic membranes with different photocatalysts, with other conditions the same as in Example 1.

[0044] The types of photocatalysts used in Examples 2-12 are shown in Table 1. The air purification performance of the PTFE biomimetic membranes prepared in Examples 2-12 was tested using the method described in Example 1, and the results are shown in Table 1. Figure 2 As shown.

[0045] Table 1

[0046]

[0047]

[0048] It can be seen that PTFE biomimetic membranes containing different photocatalysts all have excellent air purification performance.

[0049] Examples 13-18

[0050] Examples 13-18 selected PTFE particles with sizes of 10μm, 20μm, 40μm, 60μm, 70μm and 85μm respectively, and the other conditions were the same as in Example 1.

[0051] The PTFE particle sizes described in Examples 13-18 are shown in Table 2. The air purification performance of the PTFE biomimetic membranes prepared in Examples 13-18 was tested using the method described in Example 1, and the results are shown in Table 2. Figure 3 As shown.

[0052] Table 2

[0053]

[0054] It can be seen that PTFE biomimetic membranes with different particle sizes all have excellent air purification performance.

[0055] Examples 19-23

[0056] In Examples 19-23, air purification experiments were conducted using PTFE biomimetic membranes with different concentration ratios of PTFE particles to photocatalysts, with the other conditions being the same as in Example 1.

[0057] The air purification performance of the PTFE biomimetic membranes prepared in Examples 19-23 was tested using the method described in Example 1. The results are shown in Table 3. Figure 4 As shown.

[0058] Table 3

[0059]

[0060]

[0061] It can be seen that PTFE biomimetic membranes with different PTFE to photocatalyst concentration ratios all have excellent air purification performance.

[0062] Examples 24-28

[0063] Examples 24-28 use the PTFE biomimetic membrane from Example 1.

[0064] Examples 24-28 were performed under a light intensity of 0.1 kW / m². 2 0.2kW / m 2 0.4kW / m 2 0.8kW / m 2 and 1kW / m 2 An air purification experiment was conducted under the same conditions as in Example 1, and the results are shown in Table 4. Figure 5 As shown.

[0065] Table 4

[0066]

[0067] It can be seen that the PTFE biomimetic membrane has excellent air purification performance under different light intensities.

[0068] Examples 29-38

[0069] Examples 29-38 used the PTFE biomimetic membrane from Example 1 for 10 air purification experiments, with all other conditions the same as in Example 1. The results are shown in Table 5. Figure 6 As shown.

[0070] Table 5

[0071]

[0072]

[0073] It can be seen that after ten cycles of use, the PTFE air biomimetic membrane still maintains excellent air purification performance.

[0074] As can be seen from Examples 1-38, the PTFE biomimetic membranes in each example possess excellent air optimization performance. The PTFE biomimetic membranes prepared using the method of this invention exhibit excellent air optimization performance at a depth of 30m. 3 Within the air purifier's enclosure, the pollutant removal rate reaches 99.99%, and the sterilization rate reaches 99%. While ordinary PTFE air filter membranes can achieve similar performance, their air purification process is time-consuming and the purified area is limited. This is because, under light conditions, this invention can generate a large number of free oxygen negative ions, quickly achieving all-round, dead-angle-free air purification.

Claims

1. A method for preparing a PTFE biomimetic membrane based on a photocatalysis-filtration coupling mechanism, characterized in that, Includes the following steps: Step S1: Disperse the photocatalyst in an organic solvent and stir for 5 to 180 min at a temperature of 10 to 90 °C to form a uniform dispersion; then immediately add polytetrafluoroethylene (PTFE) particles into the above dispersion and stir for 3 to 24 h at a temperature of 15 to 105 °C to obtain a uniform slurry. In step S1, the photocatalyst is Co6-MOF, NH2-UiO-66, MIL-125, or Ni. 0.75 Mg 0.25 -One or more of MOF-74, HOF-66, PFC-42, HOF-1, TiO2, CdS, Ni-Co Prussian Blue, and Fe-Co Prussian Blue; Step S2: The slurry obtained in step S1 is injected into the roller press by pushing and rolled in the roller press. After the rolling process is completed, a rolled film is obtained. Step S3: The roll-formed film is stretched longitudinally and transversely in sequence using a stretching machine to obtain a PTFE film; The thickness of the stretched PTFE film is in the range of 150~350 nm, which makes the thickness of the stretched PTFE film smaller than the size of a single photocatalyst. Step S4: Heat-treat the PTFE film at a temperature of 100~320 ℃ for 2~8 h, and then cool it at room temperature to obtain the PTFE biomimetic film.

2. The method for preparing a PTFE biomimetic membrane based on a photocatalysis-filtration coupling mechanism according to claim 1, characterized in that: In step S1, the PTFE particle size ranges from 10 to 85 μm.

3. The method for preparing a PTFE biomimetic membrane based on a photocatalysis-filtration coupling mechanism according to claim 1, characterized in that: In step S1, the organic solvent is one or more of chloroform, carbon tetrachloride, dichloroethane, and toluene.

4. The method for preparing a PTFE biomimetic membrane based on a photocatalysis-filtration coupling mechanism according to claim 1, characterized in that: In step S1, the concentration ratio of PTFE particles to photocatalyst is 5~240 g / L:10 g / mL.

5. The method for preparing a PTFE biomimetic membrane based on a photocatalysis-filtration coupling mechanism according to claim 1, characterized in that: In step S2, the pushing rate during the rolling process is 0.1~1.2 m / min, and the rolling pressure is 1~4 MPa.

6. The method for preparing a PTFE biomimetic membrane based on a photocatalysis-filtration coupling mechanism according to claim 1, characterized in that: In step S3, the tensile force is in the range of 0.1~1.3 MPa.

7. The application of the PTFE biomimetic membrane obtained by the preparation method according to any one of claims 1-6, characterized in that: The PTFE biomimetic membrane is used for air purification, atmospheric dust removal, industrial waste gas filtration, sterilization and disinfection, and odor degradation.

Images