Preparation method and application of hydrophilic polytetrafluoroethylene microporous membrane

Abstract

The application discloses a preparation method and application of a hydrophilic polytetrafluoroethylene microporous membrane. The method comprises the following steps: soaking the polytetrafluoroethylene microporous membrane in a polyethylene imine water / isopropanol solution for infiltration, taking out the membrane, removing the surface solution, soaking the membrane in a dialdehyde carboxymethyl cellulose sodium aqueous solution for reaction, taking out the membrane, and performing heating treatment; soaking the membrane in a ferric chloride hexahydrate aqueous solution for heating reaction, taking out the membrane; soaking the membrane in a cobalt nitrate hexahydrate methanol solution for heating reaction, taking out the membrane; soaking the membrane in a dimethyl imidazole methanol solution for heating reaction, taking out the membrane; and washing and drying the membrane to obtain the hydrophilic polytetrafluoroethylene microporous membrane. The preparation method of the application not only further enhances the hydrophilicity of the membrane, but also endows the membrane with photocatalytic performance, and the membrane has a wide application prospect in complex system wastewater containing emulsified oil and dyes.

Description

TECHNICAL FIELD

[0001] The application relates to a preparation method of a microporous membrane, relates to the field of multifunctional hydrophilic separation membranes, and particularly relates to a preparation method and application of a hydrophilic polytetrafluoroethylene microporous membrane. BACKGROUND

[0002] The polytetrafluoroethylene microporous membrane has the advantages of high porosity, high mechanical strength and low price, and is widely used in the field of membrane separation. However, due to the small surface tension and poor surface wettability of the membrane, the membrane has strong hydrophobicity, and is prone to serious membrane pollution in the sewage treatment process, so that the membrane cannot effectively play a role in the water treatment process. In recent years, there are many reports on the hydrophilic modification of polytetrafluoroethylene membranes. Patent CN104998562A uses plasma to treat the polytetrafluoroethylene membrane under nitrogen conditions, then grafts acrylic acid, and then fixes titanium dioxide on the membrane surface through the coordination of carboxyl and Ti4+, so as to endow the membrane with hydrophilicity and photocatalytic properties. However, the plasma equipment is relatively expensive and the treatment is uneven, so it is difficult to produce industrially. Patent CN104353370A first blends hydrophilic nano inorganic particles into PTFE powder, then stretches to prepare a hydrophilic membrane, but the nano inorganic particles are not uniformly dispersed, resulting in uneven hydrophilicity of the membrane surface. Patent CN115414801A soaks the polytetrafluoroethylene membrane in an organic solvent containing hydrophilic non-polar particles, and then obtains a hydrophilic membrane after high-temperature treatment. However, the inorganic particles are not firmly combined with the membrane, and the hydrophilic effect will weaken with the extension of the use time. At the same time, the membranes prepared by these preparation methods have single performance. Actual industrial wastewater usually contains various complex pollutants, such as oil-containing wastewater containing dyes, and the application of separation membranes with only hydrophilic properties is limited. Therefore, it is urgent to develop multifunctional separation membrane materials that can separate insoluble oil and water-soluble dyes through special wettability. SUMMARY

[0003] In order to solve the problems in the background art, the application provides a preparation method and application of a hydrophilic polytetrafluoroethylene microporous membrane. The application uses polyethyleneimine and dialdehyde carboxymethyl cellulose sodium as raw materials, and endows the polytetrafluoroethylene microporous membrane with hydrophilic properties through a series of chemical reactions.

[0004] The technical scheme adopted by the application is:

[0005] I. A preparation method of a hydrophilic polytetrafluoroethylene microporous membrane, comprising:

[0006] 1) Soak the polytetrafluoroethylene microporous membrane in a polyethyleneimine water / isopropanol solution until it is completely soaked, and then take it out.

[0007] 2) The polytetrafluoroethylene microporous membrane is adsorbed with filter paper to remove the surface solution, then immersed in a dialdehyde carboxymethyl cellulose sodium aqueous solution for reaction, taken out, and then subjected to heat treatment.

[0008] 3) The polytetrafluoroethylene microporous membrane is immersed in a ferric chloride hexahydrate aqueous solution for heat reaction, and then taken out.

[0009] 4) The polytetrafluoroethylene microporous membrane is immersed in a cobalt nitrate hexahydrate methanol solution for heat reaction, and then taken out.

[0010] 5) The polytetrafluoroethylene microporous membrane is immersed in a dimethylimidazole methanol solution for heat reaction, and then taken out.

[0011] 6) The polytetrafluoroethylene microporous membrane is washed and dried to obtain a hydrophilic polytetrafluoroethylene microporous membrane.

[0012] In the step 1), the polytetrafluoroethylene microporous membrane is specifically a polytetrafluoroethylene flat microporous membrane or a polytetrafluoroethylene hollow microporous membrane; the polyethyleneimine in the water / isopropyl alcohol solution has a molecular weight of 600, a polyethyleneimine concentration of 1-10 g / L, and a mass ratio of water to isopropyl alcohol of 6:4.

[0013] In the step 2), the dialdehyde carboxymethyl cellulose sodium aqueous solution has a dialdehyde carboxymethyl cellulose sodium concentration of 1-10 g / L, and the polytetrafluoroethylene microporous membrane is immersed in the dialdehyde carboxymethyl cellulose sodium aqueous solution for 30 min.

[0014] In the step 2), the heat treatment is specifically heating at a temperature of 50-80 ℃ for 0.5-3 h.

[0015] In the step 3), the ferric chloride hexahydrate aqueous solution has a ferric chloride hexahydrate concentration of 5-20 g / L, and the pH of the ferric chloride hexahydrate aqueous solution is 3; the heat reaction is specifically carried out at 40-80 ℃ for 8-24 h.

[0016] In the step 4), the cobalt nitrate hexahydrate methanol solution has a cobalt nitrate hexahydrate concentration of 5-20 g / L, and the heat reaction is specifically carried out at 25 ℃ for 6-12 h.

[0017] In the step 5), the dimethylimidazole methanol solution has a dimethylimidazole concentration of 5-20 g / L, and the heat reaction is specifically carried out at 25 ℃ for 6-12 h.

[0018] In the step 6), the solvent for washing is anhydrous ethanol; and the drying temperature is 60 ℃.

[0019] II. A method for preparing the hydrophilic polytetrafluoroethylene microporous membrane.

[0020] III. The preparation method of the hydrophilic polytetrafluoroethylene microporous membrane The application of the prepared hydrophilic polytetrafluoroethylene microporous membrane

[0021] The application of the hydrophilic polytetrafluoroethylene microporous membrane in the degradation of complex system wastewater containing emulsified oil and dyes.

[0022] The polytetrafluoroethylene membrane has good hydrophilic property and photocatalytic property.

[0023] The beneficial effects of the present application are:

[0024] 1) The polyethyleneimine and dialdehyde carboxymethyl cellulose sodium form a three-dimensional network structure layer on the surface of the polytetrafluoroethylene microporous membrane through Schiff base reaction, a large number of carboxyl ions and amines are formed on the surface of the polytetrafluoroethylene microporous membrane, so that the hydrophilicity of the membrane obtained by the present application is greatly improved.

[0025] 2) The hydroxyl ferric oxide, hydroxyl cobalt oxide and dimethyl imidazole cobalt microparticles on the surface of the membrane are connected to the three-dimensional network structure layer on the surface of the membrane through chemical bonds, which not only further enhances the hydrophilicity of the membrane, but also endows the membrane with photocatalytic property, and can be applied in the fields of oil-containing wastewater and printing and dyeing wastewater treatment. BRIEF DESCRIPTION OF DRAWINGS

[0026] Figure 1 The 0s static water contact angle diagram of the membrane in the present application comparative example 1;

[0027] Figure 2 The 0s static water contact angle diagram of the membrane obtained in the present application example 1;

[0028] Figure 3 The 0s static water contact angle diagram of the membrane obtained in the present application comparative example 5;

[0029] Figure 4 The effect diagram of the membrane obtained in the present application example 1 for continuous 10 times photocatalytic degradation of rhodamine B. DETAILED DESCRIPTION

[0030] The present application will be further described in detail below in combination with the drawings and specific examples.

[0031] The specific embodiments of the present application are as follows:

[0032] The application takes polyethyleneimine and sodium dialdehyde carboxymethyl cellulose as raw materials, forms carboxyl ion, amino and other hydrophilic groups on the surface of polytetrafluoroethylene microporous membrane through Schiff base reaction, and then deposits hydroxyl iron oxide and dimethyl imidazole cobalt micro-nano particles on the membrane surface in sequence through in-situ deposition method, so that the polytetrafluoroethylene membrane has good hydrophilic performance and photocatalytic performance, has high efficiency and flux recovery rate for oil-water emulsion separation, and has high degradation rate for dyes.

[0033] Example 1

[0034] The polytetrafluoroethylene flat microporous membrane with an average pore size of 0.2 μm is soaked in a polyethyleneimine water / isopropanol solution with a concentration of 5 g / L until completely soaked, the polyethyleneimine in the polyethyleneimine water / isopropanol solution has a molecular weight of 600, and the mass ratio of water to isopropanol is 6:4; the membrane is adsorbed to remove the surface solution using filter paper, then soaked in a sodium dialdehyde carboxymethyl cellulose aqueous solution with a concentration of 5 g / L for reaction for 30 min, then taken out after heating treatment at a heating temperature of 70 ℃ for 1 h; the membrane is soaked in a ferric chloride hexahydrate aqueous solution with a concentration of 10 g / L and pH = 3, heated at 60 ℃ for reaction for 8 h, then taken out; the membrane is soaked in a cobalt nitrate hexahydrate methanol solution with a concentration of 10 g / L, heated at 25 ℃ for reaction for 6 h, then taken out; the membrane is soaked in a dimethyl imidazole methanol solution with a concentration of 10 g / L, heated at 25 ℃ for reaction for 12 h, then taken out; the membrane is washed using anhydrous ethanol, then dried at 60 ℃ to obtain a hydrophilic polytetrafluoroethylene microporous membrane.

[0035] Example 2

[0036] The polytetrafluoroethylene flat microporous membrane with an average pore size of 0.45 μm is soaked in a polyethyleneimine water / isopropanol solution with a concentration of 3 g / L until completely soaked, the polyethyleneimine in the polyethyleneimine water / isopropanol solution has a molecular weight of 600, and the mass ratio of water to isopropanol is 6:4; the membrane is adsorbed to remove the surface solution using filter paper, then soaked in a sodium dialdehyde carboxymethyl cellulose aqueous solution with a concentration of 6 g / L for reaction for 30 min, then taken out after heating treatment at a heating temperature of 80 ℃ for 0.5 h; the membrane is soaked in a ferric chloride hexahydrate aqueous solution with a concentration of 5 g / L and pH = 3, heated at 60 ℃ for reaction for 12 h, then taken out; the membrane is soaked in a cobalt nitrate hexahydrate methanol solution with a concentration of 15 g / L, heated at 25 ℃ for reaction for 10 h, then taken out; the membrane is soaked in a dimethyl imidazole methanol solution with a concentration of 15 g / L, heated at 25 ℃ for reaction for 10 h, then taken out; the membrane is washed using anhydrous ethanol, then dried at 60 ℃ to obtain a hydrophilic polytetrafluoroethylene microporous membrane.

[0037] Example 3

[0038] A polytetrafluoroethylene hollow microporous membrane having an average pore diameter of 0.45 μm was immersed in a polyethyleneimine water / isopropanol solution having a concentration of 8 g / L until it was completely infiltrated, and then taken out. The polyethyleneimine water / isopropanol solution had a polyethyleneimine molecular weight of 600, and a water / isopropanol mass ratio of 6:4. The membrane was adsorbed using filter paper to remove the surface solution, and then immersed in a dialdehyde carboxymethyl cellulose sodium aqueous solution having a concentration of 4 g / L for 30 min, and then taken out. The membrane was then subjected to heat treatment by heating at a temperature of 60°C for 2 h. The membrane was immersed in an aqueous solution of ferric chloride hexahydrate having a concentration of 15 g / L and a pH of 3, and then taken out after being heated at 40°C for 16 h. The membrane was immersed in a methanol solution of cobalt nitrate hexahydrate having a concentration of 10 g / L, and then taken out after being heated at 25°C for 8 h. The membrane was immersed in a methanol solution of dimethylimidazole having a concentration of 10 g / L, and then taken out after being heated at 25°C for 12 h. The membrane was washed using anhydrous ethanol, and then dried at 60°C to obtain a hydrophilic polytetrafluoroethylene microporous membrane.

[0039] Example 4:

[0040] A polytetrafluoroethylene hollow microporous membrane having an average pore diameter of 1 μm was immersed in a polyethyleneimine water / isopropanol solution having a concentration of 5 g / L until it was completely infiltrated, and then taken out. The polyethyleneimine water / isopropanol solution had a polyethyleneimine molecular weight of 600, and a water / isopropanol mass ratio of 6:4. The membrane was adsorbed using filter paper to remove the surface solution, and then immersed in a dialdehyde carboxymethyl cellulose sodium aqueous solution having a concentration of 5 g / L for 30 min, and then taken out. The membrane was then subjected to heat treatment by heating at a temperature of 80°C for 0.5 h. The membrane was immersed in an aqueous solution of ferric chloride hexahydrate having a concentration of 5 g / L and a pH of 3, and then taken out after being heated at 50°C for 12 h. The membrane was immersed in a methanol solution of cobalt nitrate hexahydrate having a concentration of 10 g / L, and then taken out after being heated at 25°C for 6 h. The membrane was immersed in a methanol solution of dimethylimidazole having a concentration of 10 g / L, and then taken out after being heated at 25°C for 10 h. The membrane was washed using anhydrous ethanol, and then dried at 60°C to obtain a hydrophilic polytetrafluoroethylene microporous membrane.

[0041] Comparative Example 1:

[0042] A polytetrafluoroethylene flat microporous membrane having an average pore diameter of 0.20 μm was used without treatment.

[0043] Comparative Example 2:

[0044] A polytetrafluoroethylene flat microporous membrane having an average pore diameter of 0.45 μm was used without treatment.

[0045] Comparative Example 3:

[0046] A polytetrafluoroethylene hollow microporous membrane having an average pore diameter of 0.45 μm was used without treatment.

[0047] Comparative Example 4:

[0048] Untreated polytetrafluoroethylene hollow microporous membrane with an average pore size of 1.0 μm.

[0049] Comparative Example 5:

[0050] A polytetrafluoroethylene flat microporous membrane with an average pore size of 0.2 μm was taken out after being completely immersed in a polyethyleneimine water / isopropanol solution with a concentration of 5 g / L, the polyethyleneimine in the polyethyleneimine water / isopropanol solution had a molecular weight of 600, and the mass ratio of water to isopropanol was 6:4; the membrane was then adsorbed using filter paper to remove the surface solution, and then immersed in a dialdehyde carboxymethyl cellulose sodium aqueous solution with a concentration of 5 g / L for 30 min, and then heated at a heating temperature of 70°C for 1 h for heating treatment; finally, the membrane was washed using deionized water and dried at a temperature of 60°C to obtain a first polytetrafluoroethylene microporous membrane.

[0051] Comparative Example 6:

[0052] A polytetrafluoroethylene hollow microporous membrane with an average pore size of 0.45 μm was taken out after being completely immersed in a polyethyleneimine water / isopropanol solution with a concentration of 8 g / L, the polyethyleneimine in the polyethyleneimine water / isopropanol solution had a molecular weight of 600, and the mass ratio of water to isopropanol was 6:4; the membrane was then adsorbed using filter paper to remove the surface solution, and then immersed in a dialdehyde carboxymethyl cellulose sodium aqueous solution with a concentration of 4 g / L for 30 min, and then heated at a heating temperature of 60°C for 2 h; finally, the membrane was washed using deionized water and dried at a temperature of 60°C to obtain a second polytetrafluoroethylene microporous membrane.

[0053] Oil-water separation performance test:

[0054] An oil-water emulsion was prepared using 0.1% (M 大豆油 / M 水 ) soybean oil and 20% Tween-80 (M T-80 / M 大豆油 ) as an emulsifier. Then the oil-water emulsion was stirred at 10,000 rpm for 0.5 h, and the permeation and separation performance of the membrane was studied using dead-end filtration at a transmembrane pressure of 0.1 MPa; the oil content in the water was determined using a UV-vis spectrophotometer, and the oil-water separation efficiency was calculated using formula (2).

[0055]

[0056] wherein J is the permeation flux, V is the permeation volume, A is the effective area, and Δt is the test time.

[0057]

[0058] wherein R1 is the retention rate during oil-water emulsion separation, Cp C is the concentration of the filtrate oil f C0 is the original oil-water emulsion concentration.

[0059] Dye degradation performance test:

[0060] Each of the membranes prepared in the application was placed in a methyl blue solution with a concentration of 5 mg / L and a rhodamine B solution with a concentration of 5 mg / L, respectively, and after adsorption equilibrium in the dark environment, the solution containing the membrane was placed under a xenon lamp for irradiation treatment, and the dye concentration in the solution before and after degradation was determined by UV-vis spectrophotometry. The degradation efficiency (R2) of the dye was calculated according to formula (3).

[0061]

[0062] Wherein, R2 is the degradation efficiency of the dye, C1 is the concentration of the dye after degradation, and C0 is the original dye concentration.

[0063] Table 1 Performance of polytetrafluoroethylene microporous membrane

[0064]

[0065] As can be seen from Table 1, the hydrophilic polytetrafluoroethylene microporous membrane obtained by the method of the application has good hydrophilic performance, not only has high separation efficiency and anti-pollution performance for oil-water emulsion, but also has extremely high degradation efficiency for dyes in wastewater.

[0066] As Figure 1 The 0s static water contact angle diagram of the membrane in the comparative example 1 of the application is shown in FIG. 1, and the 0s static water contact angle diagram of the membrane obtained in the example 1 of the application is shown in FIG. 2. Figure 2 The 0s static water contact angle diagram of the membrane in the comparative example 1 of the application is shown in FIG. 1, and the 0s static water contact angle diagram of the membrane obtained in the example 1 of the application is shown in FIG. 2. Figure 3 The 0s static water contact angle diagram of the membrane obtained in the comparative example 5 of the application is shown in FIG. 3. The hydrophilic polytetrafluoroethylene microporous membrane obtained by the application has a greatly reduced water contact angle on the membrane surface and greatly increased hydrophilicity of the membrane compared with the original polytetrafluoroethylene microporous membrane. Figure 4 The effect diagram of the continuous 10 times photocatalytic degradation of rhodamine B of the membrane obtained in the example 1 of the application is shown in FIG. 4. Since the hydroxyl iron oxide, hydroxyl cobalt oxide and dimethyl imidazole cobalt on the surface of the membrane are connected to the three-dimensional network structure layer on the surface through chemical bonds, the membrane has good stability.

[0067] The method of the present application uses polyethyleneimine and sodium dialdehyde carboxymethyl cellulose as raw materials, forms carboxyl ion, amino and other hydrophilic groups on the surface of polytetrafluoroethylene microporous membrane through Schiff base reaction, and then deposits hydroxyl iron oxide, hydroxyl cobalt oxide and dimethyl imidazole cobalt micro-nano particles on the membrane surface in sequence through in-situ deposition method, so that the polytetrafluoroethylene membrane has good hydrophilic performance and photocatalytic performance. The oil-water emulsion separation efficiency is more than 99.85%, the flux recovery rate is more than 99.98%, and the degradation rates of rhodamine B and methyl blue are both 100%.

[0068] The applicant declares that the above is only a specific embodiment of the present application, but the protection scope of the present application is not limited thereto. It should be understood by those skilled in the art that any changes or replacements within the technical scope disclosed by the present application can be easily thought of by any person skilled in the art, and all fall within the protection scope and disclosure scope of the present application.

Claims

1. A method for producing a hydrophilic polytetrafluoroethylene microporous membrane, characterized by, The preparation method comprises the following steps: 1) soaking the polytetrafluoroethylene microporous membrane in a polyethyleneimine water-isopropanol solution to completely soak the polytetrafluoroethylene microporous membrane, and then taking out the polytetrafluoroethylene microporous membrane; 2) removing the surface solution of the polytetrafluoroethylene microporous membrane, then soaking the polytetrafluoroethylene microporous membrane in a dialdehyde carboxymethyl cellulose sodium aqueous solution to react, then taking out the polytetrafluoroethylene microporous membrane, and then performing a heating treatment; 3) soaking the polytetrafluoroethylene microporous membrane in a ferric chloride hexahydrate aqueous solution to react under heating, and then taking out the polytetrafluoroethylene microporous membrane; 4) soaking the polytetrafluoroethylene microporous membrane in a cobalt nitrate hexahydrate methanol solution to react under heating, and then taking out the polytetrafluoroethylene microporous membrane; 5) soaking the polytetrafluoroethylene microporous membrane in a dimethylimidazole methanol solution to react under heating, and then taking out the polytetrafluoroethylene microporous membrane; 6) washing the polytetrafluoroethylene microporous membrane, and then drying the polytetrafluoroethylene microporous membrane to obtain a hydrophilic polytetrafluoroethylene microporous membrane.

2. The method of claim 1, wherein: In the step 1), the polytetrafluoroethylene microporous membrane is specifically a polytetrafluoroethylene flat microporous membrane or a polytetrafluoroethylene hollow microporous membrane; the polyethyleneimine in the polyethyleneimine water-isopropanol solution has a molecular weight of 600, the polyethyleneimine has a concentration of 1-10 g / L, and the mass ratio of water to isopropanol is 6:

4.

3. The method of claim 1, wherein: In the step 2), the dialdehyde carboxymethyl cellulose sodium in the dialdehyde carboxymethyl cellulose sodium aqueous solution has a concentration of 1-10 g / L, and the polytetrafluoroethylene microporous membrane is soaked in the dialdehyde carboxymethyl cellulose sodium aqueous solution for 30 min.

4. The method of claim 1, wherein: In the step 2), the heating treatment is specifically heating at a heating temperature of 50-80 ℃ for 0.5-3 h.

5. The method of claim 1, wherein: In the step 3), the ferric chloride hexahydrate in the ferric chloride hexahydrate aqueous solution has a concentration of 5-20 g / L, and the pH of the ferric chloride hexahydrate aqueous solution is 3; the heating reaction is specifically a reaction at 40-80 ℃ for 8-24 h.

6. The method of claim 1, wherein: In the step 4), the cobalt nitrate hexahydrate in the cobalt nitrate hexahydrate methanol solution has a concentration of 5-20 g / L, and the heating reaction is specifically a reaction at 25 ℃ for 6-12 h.

7. The method of claim 1, wherein: In the step 5), the dimethylimidazole in the dimethylimidazole methanol solution has a concentration of 5-20 g / L, and the heating reaction is specifically a reaction at 25 ℃ for 6-12 h.

8. The method of claim 1, wherein: In the step 6), the solvent used for washing is anhydrous ethanol, and the drying temperature is 60 ℃.

9. The hydrophilic polytetrafluoroethylene microporous membrane obtained by the preparation method of any one of claims 1-8.

10. Use of the hydrophilic polytetrafluoroethylene microporous membrane obtained by the production process according to any one of claims 1-8, characterized in that: The hydrophilic polytetrafluoroethylene microporous membrane is used for degrading complex system wastewater containing emulsified oil and dyes.

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