Preparation method and application of dual self-cleaning polytetrafluoroethylene microporous membrane

Abstract

The invention provides a preparation method and application of a dual-cleaning polytetrafluoroethylene microporous membrane, and the preparation method comprises the following steps: 1) heating polyethyleneimine and 1, 3-propane sultone in one step to form a polyion liquid, and dissolving the polyion liquid and dopamine in a Tris aqueous alkali to obtain a buffer reaction liquid; 2) soaking a polytetrafluoroethylene microporous membrane in a buffer reaction solution, heating and reacting, and then taking out to obtain a first microporous membrane; 3) soaking the first microporous membrane in a ferric chloride hexahydrate aqueous solution for heating reaction, and then taking out the first microporous membrane to obtain a second microporous membrane; 4) soaking the second microporous membrane in a copper acetate methanol solution for heating reaction, and then taking out to obtain a third microporous membrane; 5) soaking the third microporous membrane in a methanol solution of 2, 5-dihydroxy terephthalic acid, heating and reacting, and then taking out to obtain a fourth microporous membrane; and 6) washing and drying the fourth microporous membrane to obtain the dual self-cleaning polytetrafluoroethylene microporous membrane. The dual self-cleaning polytetrafluoroethylene microporous membrane is high in separation efficiency, high in flux recovery rate and low in pollution rate in treatment of high-viscosity emulsified oil-containing wastewater.

Description

Technical Field

[0001] The invention relates to the field of multifunctional hydrophilic separation microporous membranes, and in particular to a preparation method and application of a double-cleaning polytetrafluoroethylene microporous membrane. Background Art

[0002] Polytetrafluoroethylene microporous membrane is a filter membrane made of polytetrafluoroethylene material. It has excellent physical and chemical properties such as high temperature, corrosion resistance, high pressure, and high filtration accuracy, and is widely used in the field of membrane separation. However, due to the small surface tension and poor surface wettability of the membrane, it has strong hydrophobicity, which also makes the membrane very easy to produce serious membrane pollution during sewage treatment, making it difficult to play an effective role in the water treatment process.

[0003] In recent years, there are many reports on the hydrophilic modification of polytetrafluoroethylene membranes. Patent CN117771960A soaks the polytetrafluoroethylene membrane in a hydrophilic PVA mixed solution, places the soaked polytetrafluoroethylene membrane in a crosslinking agent aqueous solution, and heats the reaction and then dries to obtain a pre-modified polytetrafluoroethylene membrane; the pre-modified polytetrafluoroethylene membrane is placed in a γ-glycidyloxypropyltrimethoxysilane aqueous solution, and heats the reaction and then dries to obtain a hydrophilic modified polytetrafluoroethylene membrane, but the hydrophilic membrane is easily contaminated when filtering high-viscosity oily wastewater, resulting in a decrease in hydrophilic function. Patent CN116920634B completely dissolves di(methacryloyloxyethyl) phosphate, methacrylamide, photoinitiator, adhesive and antioxidant in a solvent, uses an applicator to evenly coat the solution on a polytetrafluoroethylene microporous membrane, and obtains a polytetrafluoroethylene microporous hydrophilic membrane after photocuring with ultraviolet light for a period of time, but its process is complicated and time-consuming. Patent CN 117046326A first modifies the polytetrafluoroethylene membrane with polyethyleneimine and sodium dialdehyde carboxymethylcellulose, and then deposits iron oxyhydroxide, cobalt oxyhydroxide and dimethyl imidazole cobalt micro-nano particles in situ to give the membrane photocatalytic function to solve the membrane pollution problem, but it is only used for low-viscosity oily wastewater treatment, and the application scope is limited. In addition, during the continuous separation process of membrane separation, the "amphiphilic" surfactant in the emulsion system can have a strong surface-interface interaction with the membrane surface to change the membrane surface wettability, causing the membrane flux to decay rapidly. In the later membrane cleaning process, the surfactant and oil stains adhering to the membrane surface are often difficult to remove.

[0004] In summary, there is an urgent need on the market for a hydrophilic modification method for a polytetrafluoroethylene microporous membrane that has good hydrophilic modification effect and photocatalytic self-cleaning ability. Summary of the invention

[0005] The purpose of the present invention is to provide a preparation method and application of a double-cleaning polytetrafluoroethylene microporous membrane, introduce hydrophilic groups and photocatalytic particles, so that the double-cleaning polytetrafluoroethylene microporous membrane has both super-hydrophilic self-cleaning and photocatalytic self-cleaning capabilities, and has high separation efficiency, high flux recovery rate and low pollution rate in the treatment of high-viscosity emulsified oil-containing wastewater.

[0006] To achieve the above objectives, the present technical solution provides a method for preparing a double-cleaning polytetrafluoroethylene microporous membrane, comprising the following steps:

[0007] 1) heating polyethyleneimine and 1,3-propanesultone in one step to form a polyionic liquid, and dissolving the polyionic liquid and dopamine in a Tris base solution to obtain a buffered reaction solution;

[0008] 2) immersing the polytetrafluoroethylene microporous membrane in a buffered reaction solution, heating the solution for reaction, and then taking the solution out to obtain a first microporous membrane;

[0009] 3) immersing the first microporous membrane in an aqueous solution of ferric chloride hexahydrate, heating it for reaction, and then taking it out to obtain a second microporous membrane;

[0010] 4) immersing the second microporous membrane in a copper acetate methanol solution, heating it for reaction, and then taking it out to obtain a third microporous membrane;

[0011] 5) soaking the third microporous membrane in a methanol solution of 2,5-dihydroxyterephthalic acid, heating it for reaction, and then taking it out to obtain a fourth microporous membrane;

[0012] 6) The fourth microporous membrane is washed and then dried to obtain a double self-cleaning polytetrafluoroethylene microporous membrane.

[0013] This scheme first uses polyethyleneimine and 1,3-propane sultone to synthesize a polyionic liquid containing sulfonic acid groups and amino groups. The polyionic liquid reacts with dopamine in one step on the surface of a polytetrafluoroethylene microporous membrane to form hydrophilic groups such as sulfonic acid groups and amino groups. Subsequently, iron sulfonate nanoparticles and 2,5-dihydroxycopper terephthalate nanoparticles are deposited on the surface of the polytetrafluoroethylene microporous membrane in sequence by an in-situ deposition method, thereby making the polytetrafluoroethylene membrane have superhydrophilicity and photocatalytic properties, and having high efficiency and flux recovery rate for the separation of high-viscosity oil-water emulsions.

[0014] In other words, this scheme is to modify the polytetrafluoroethylene microporous membrane using a polyionic liquid containing sulfonic acid groups and amino groups, and subsequently to directionally grow a catalyst with catalytic function on the surface of the polytetrafluoroethylene microporous membrane through a coordination chemical reaction, thereby giving the polytetrafluoroethylene microporous membrane dual self-cleaning properties, which can effectively solve the problem of membrane pollution in high-viscosity oily wastewater.

[0015] Specifically, in step 1), polyethyleneimine and 1,3-propane sultone are subjected to a one-step heating reaction to obtain a polyionic liquid, wherein the polyethyleneimine contains multiple amino groups, and the 1,3-propane sultone contains a sultone ring structure. The amino groups in the polyethyleneimine attack the sultone ring of 1,3-propane sultone to undergo a ring-opening reaction to obtain a polyionic liquid, wherein the polyionic liquid contains sulfonic acid groups and amino groups.

[0016] In some embodiments, polyethyleneimine is prepared as a polyethyleneimine solution, and the polyethyleneimine solution is mixed with 1,3-propane sultone and then heated to react to obtain a polyionic liquid.

[0017] In some embodiments, the molecular weight of polyethyleneimine is 500-700, and preferably, the molecular weight of polyethyleneimine is 600.

[0018] In some embodiments, the concentration of polyethyleneimine in the polyethyleneimine solution is 1-10 g / L, and preferably, the concentration of polyethyleneimine is 4 g / L.

[0019] In some embodiments, the concentration of 1,3-propane sultone is 2 to 10 g / L, and preferably, the concentration of 1,3-propane sultone is 8 g / L.

[0020] In some embodiments, the heating temperature for the one-step heating reaction of polyethyleneimine and 1,3-propane sultone is 45-55° C., and the reaction time is 3-5 hours. Preferably, the heating temperature for the one-step heating reaction of polyethyleneimine and 1,3-propane sultone is 50° C., and the reaction time is 4 hours.

[0021] In some embodiments, the polyionic liquid is washed and dried and then dissolved with dopamine in a Tris base solution to obtain a buffered reaction solution.

[0022] In some embodiments, the polyionic liquid is washed with anhydrous ethanol and dried at 70°C.

[0023] In some embodiments, the polyionic liquid and dopamine are dissolved in a Tris base solution to obtain a buffered reaction solution, the concentration of the polyionic liquid is 1 to 10 g / L, and the mass ratio of the polyionic liquid to dopamine is 5:1.

[0024] In some embodiments, the Tris base solution at pH 8.5 has a tris content of 50 mM.

[0025] In step 2), the polytetrafluoroethylene microporous membrane is first soaked with ethanol and then immersed in a buffered reaction solution for heating reaction and then taken out to obtain a first microporous membrane, wherein the heating reaction temperature is 35-40° C. and the heating time is 8-24 hours.

[0026] In this step 2), the polytetrafluoroethylene microporous membrane is first soaked with ethanol and then immersed in a buffered reaction solution containing a polyionic liquid and dopamine for heating reaction, so as to modify the surface of the polytetrafluoroethylene microporous membrane, and the purpose is to allow dopamine to undergo oxidative polymerization reaction, and to work together with the polyionic liquid to form a coating with special functions on the surface of the polytetrafluoroethylene microporous membrane. Specifically, the polytetrafluoroethylene fiber membrane is completely soaked with an ethanol solution so that ethanol can penetrate into the pore structure of the polytetrafluoroethylene fiber membrane, so as to fully wet the surface and interior of the polytetrafluoroethylene fiber membrane, and to help the reaction solution to soak the inside of the membrane pores. In the alkaline Tris base buffer environment, dopamine will undergo oxidative self-polymerization reaction to form polydopamine, which has excellent adhesion properties and can be firmly attached to the surface of the polytetrafluoroethylene microporous membrane. At the same time, groups such as amino and sulfonic acid groups in the polyionic liquid can interact with polydopamine, such as hydrogen bonding and electrostatic interaction, so that the polyionic liquid is also fixed on the membrane surface. In this way, a coating rich in hydrophilic groups such as amino and sulfonic acid groups is formed on the membrane surface, which gives the membrane good hydrophilicity and enables it to have super hydrophilic self-cleaning ability. At the same time, it also provides favorable surface conditions for the subsequent loading of photocatalytic particles.

[0027] The heating reaction temperature is set at 35-40°C. This temperature range has been optimized. If the temperature is too low, the rate of dopamine oxidative polymerization reaction will be too slow, resulting in incomplete coating formation on the membrane surface and affecting hydrophilicity; if the temperature is too high, the reaction may be too intense, resulting in uneven coating and reducing the performance stability of the membrane.

[0028] The heating reaction time is set to 8 to 24 hours. A shorter reaction time (such as 8 hours) results in a thinner coating on the membrane surface, and relatively weaker hydrophilicity and self-cleaning ability; a longer reaction time (such as 24 hours) can fully polymerize dopamine to form a thicker and more uniform coating, enhancing the hydrophilicity and self-cleaning properties of the membrane, but will increase the reaction cost and time.

[0029] In some embodiments, the polytetrafluoroethylene microporous membrane of the present embodiment is specifically a polytetrafluoroethylene flat microporous membrane or a polytetrafluoroethylene hollow microporous membrane.

[0030] In step 3), the concentration of the ferric chloride hexahydrate aqueous solution is 5-20 mmol / L, and the pH is 3.

[0031] Furthermore, the first microporous membrane is immersed in an aqueous solution of ferric chloride hexahydrate and heated at a temperature of 40 to 80° C. and a reaction time of 8 to 24 hours. After the reaction is completed, the first microporous membrane is taken out to obtain a second microporous membrane.

[0032] Step 3 of this scheme is to soak the first microporous membrane in an aqueous solution of ferric chloride hexahydrate of a specific concentration and pH value, and react under appropriate temperature and time conditions, so that the iron ions can coordinate or otherwise interact with the amino groups, sulfonic acid groups, and other groups existing on the membrane surface, thereby forming iron sulfonate nanoparticles on the membrane surface. These nanoparticles give the membrane photocatalytic self-cleaning properties, which, combined with the super-hydrophilic self-cleaning ability previously given to the membrane, achieve a dual self-cleaning effect, thereby improving the performance and service life of the membrane in applications such as sewage treatment.

[0033] In step 4), the concentration of the copper acetate methanol solution is 5 to 20 g / L.

[0034] Furthermore, the second microporous membrane is immersed in a copper acetate methanol solution and heated at a temperature of 20 to 30° C. for a reaction time of 6 to 12 hours, and after the reaction is completed, the third microporous membrane is taken out. Preferably, the heating temperature is 25° C. for a reaction time of 6 to 12 hours.

[0035] Step 4 of this scheme is to immerse the second microporous membrane in a copper acetate methanol solution of a specific concentration and control the heating conditions, introduce 2,5-dihydroxy copper terephthalate micro-nano particles on the membrane surface, further enhance the hydrophilicity and photocatalytic self-cleaning properties of the membrane, and the copper ions in the copper acetate will react with the existing groups on the membrane surface to form a stable 2,5-dihydroxy copper terephthalate micro-nano particle coating on the membrane surface. These particles can not only further improve the hydrophilicity of the membrane, but also synergize with the previously loaded iron sulfonate nanoparticles to enhance the photocatalytic activity of the membrane, making it perform better in applications such as degrading high-viscosity emulsified oil wastewater.

[0036] In step 5), the concentration of the methanol solution of 2,5-dihydroxyterephthalic acid is 5 to 20 g / L.

[0037] Further, the third microporous membrane is immersed in a methanol solution of 2,5-dihydroxyterephthalic acid and heated at a temperature of 20 to 30°C for a reaction time of 6 to 12 hours, and after the reaction is completed, the fourth microporous membrane is taken out. Preferably, the heating temperature is 25°C and the reaction time is 6 to 12 hours.

[0038] Step 5 of this scheme is to further optimize the surface structure and performance of the membrane by soaking the third microporous membrane in a methanol solution of 2,5-dihydroxyterephthalic acid under specific conditions, so that 2,5-dihydroxyterephthalic acid reacts chemically or interacts with the existing groups on the membrane surface. In this process, 2,5-dihydroxyterephthalic acid will form a more stable micro-nano particle coating on the membrane surface or synergize with other loaded substances to enhance the hydrophilicity and photocatalytic self-cleaning properties of the membrane. Specifically, it can further reduce the surface energy of the membrane and improve the hydrophilicity of the membrane. At the same time, its own structural characteristics also participate in the photocatalytic reaction, and work together with the previously loaded iron sulfonate nanoparticles and 2,5-dihydroxyterephthalate copper micro-nano particles to improve the efficiency of photocatalytic degradation of pollutants, so that the final prepared membrane performs better in treating complex systems such as high-viscosity emulsified oil wastewater.

[0039] In step 6), the fourth microporous membrane is washed with anhydrous ethanol and then dried at 60° C. to obtain a polytetrafluoroethylene microporous membrane with dual self-cleaning properties.

[0040] In the second aspect, the present invention provides a double-cleaning polytetrafluoroethylene microporous membrane, which is prepared according to the above-mentioned preparation method of the double-cleaning polytetrafluoroethylene microporous membrane. The double-cleaning polytetrafluoroethylene microporous membrane comprises:

[0041] A polytetrafluoroethylene microporous membrane and iron sulfonate nanoparticles and 2,5-dihydroxy terephthalate copper nanoparticles grown on the polytetrafluoroethylene microporous membrane, wherein sulfonic acid groups and amino groups are formed on the surface of the polytetrafluoroethylene microporous membrane, and the iron sulfonate nanoparticles are chemically bonded to the sulfonic acid groups and amino groups.

[0042] In other words, the present invention uses a buffered reaction solution to form a hydrophilic layer rich in sulfonic acid groups and amino groups on the surface of a polytetrafluoroethylene microporous membrane, and then immerses the membrane in an aqueous solution of ferric chloride hexahydrate to react and in situ grow iron sulfonate nanoparticles, and then immerses the membrane in a methanol solution of copper acetate and a methanol solution of 2,5-dihydroxyterephthalic acid to react and in situ grow a 2,5-dihydroxyterephthalic acid copper micro-nano particle layer. Since the dual-cleaning polytetrafluoroethylene microporous membrane of the present invention has both iron sulfonate nanoparticles and 2,5-dihydroxyterephthalic acid copper micro-nano particles, there is a synergistic effect between the 2,5-dihydroxyterephthalic acid copper micro-nano particles and the iron sulfonate nanoparticles, which can improve the photocatalytic efficiency, jointly promote the degradation of organic pollutants on the membrane surface, and enhance the photocatalytic self-cleaning performance of the membrane.

[0043] The double-cleaning polytetrafluoroethylene microporous membrane prepared in this scheme is used to degrade high-viscosity wastewater containing emulsified oil.

[0044] Compared with the prior art, this technical solution has the following characteristics and beneficial effects:

[0045] The present invention first uses polyethyleneimine and 1,3-propanesultone as raw materials, synthesizes a polyionic liquid PSIL containing sulfonic acid groups and amino groups through a series of chemical reactions, and then reacts with dopamine to give the polytetrafluoroethylene microporous membrane superhydrophilic self-cleaning ability; finally, iron sulfonate and 2,5-dihydroxycopper terephthalate are grown in situ through coordination chemistry to give the separation membrane photocatalytic self-cleaning ability.

[0046] 1) Polyethyleneimine and 1,3-propane sultone react in one step to form a polyionic liquid PSIL containing sulfonic acid groups and amino groups, which reacts with dopamine on the surface of a polytetrafluoroethylene microporous membrane to give the polytetrafluoroethylene microporous membrane a large number of sulfonic acid groups and amino groups. The hydrophilic groups have a strong binding ability with water molecules, so that the hydrophilicity of the membrane obtained by the present invention is greatly improved, and the membrane is given super-hydrophilic self-cleaning ability.

[0047] 2) The present invention grows iron sulfonate nanoparticles and 2,5-dihydroxy terephthalate copper micro-nanoparticles on the membrane surface through coordination chemistry and connects to the hydrophilic groups on the membrane surface through chemical bonds, which not only further enhances the hydrophilicity of the membrane, but also gives the membrane photocatalytic self-cleaning properties. At the same time, the synergistic effect between iron and copper further improves the catalytic performance of the membrane. BRIEF DESCRIPTION OF THE DRAWINGS

[0048] Figure 1 It is a chemical reaction flow chart of the present invention;

[0049] Figure 2 This is a SEM image of the membrane surface in Comparative Example 1 of the present invention;

[0050] Figure 3 This is a SEM image of the membrane surface in Comparative Example 5 of the present invention;

[0051] Figure 4 This is a SEM image of the membrane surface obtained in Example 1 of the present invention;

[0052] Figure 5 0s static water contact angle diagram of the membrane in Comparative Example 1 of the present invention;

[0053] Figure 6 This is a 0s static water contact angle diagram of the film obtained in Example 1 of the present invention;

[0054] Figure 7 This is the 0s static water contact angle diagram of the film obtained in Comparative Example 5 of the present invention. DETAILED DESCRIPTION

[0055] The following will be combined with the accompanying drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field belong to the scope of protection of the present invention.

[0056] The invention uses polyethyleneimine and 1,3-propane sultone as raw materials to prepare a polyionic liquid, which is then mixed with dopamine in a Tris base solution to obtain a buffered reaction liquid, and a polytetrafluoroethylene microporous membrane is immersed in the buffered reaction liquid to form hydrophilic groups such as sulfonic acid ions and amino groups on the surface of the polytetrafluoroethylene microporous membrane by a one-step reaction, and then iron sulfonate nanoparticles and 2,5-dihydroxy terephthalate copper nanoparticles are sequentially deposited on the membrane surface by an in-situ deposition method, so that the polytetrafluoroethylene membrane has superhydrophilicity and photocatalytic performance, and has high efficiency and flux recovery rate for separation of high-viscosity oil-water emulsions.

[0057] Embodiment 1:

[0058] Prepare a polyethyleneimine ethanol solution with a concentration of 4 g / L, add 1,3-propane sultone and control its concentration to 8 g / L, heat to 50°C, react for 4 hours, filter, wash with ethanol and dry at 70°C. A polytetrafluoroethylene flat microporous membrane with an average pore size of 0.2 μm was heated to 37°C in a buffered reaction solution of a polyion liquid with a concentration of 5 g / L, reacted for 8 hours, taken out, and the surface solution was removed by adsorption of filter paper on the membrane; the membrane was immersed in a 10 g / L, pH=3, ferric chloride hexahydrate aqueous solution, heated at 60°C for 4 hours, and then taken out; the membrane was immersed in a 10 g / L copper acetate methanol solution, heated at 25°C for 12 hours, and then taken out; the membrane was immersed in a 10 g / L 2,5-dihydroxyterephthalic acid methanol solution, heated at 25°C for 12 hours, and then taken out; the membrane was washed with anhydrous ethanol and dried at 60°C to obtain a hydrophilic polytetrafluoroethylene microporous membrane with photocatalytic function.

[0059] Embodiment 2:

[0060] Prepare a polyethyleneimine ethanol solution with a concentration of 4 g / L, add 1,3-propane sultone and control its concentration to 8 g / L, heat to 50°C, react for 4 hours, filter, wash with ethanol and dry at 70°C. A polytetrafluoroethylene flat microporous membrane with an average pore size of 0.45 μm was heated to 37°C in a buffered reaction solution of a polyion liquid with a concentration of 3 g / L, and was taken out after the reaction for 16 hours. The surface solution of the membrane was removed by adsorption using filter paper. The membrane was immersed in a ferric chloride hexahydrate aqueous solution with a concentration of 5 g / L and a pH of 3, and was heated at 60°C for reaction for 6 hours, and then taken out; the membrane was immersed in a copper acetate methanol solution with a concentration of 15 g / L, and was heated at 25°C for reaction for 6 hours, and then taken out; the membrane was immersed in a 2,5-dihydroxyterephthalic acid methanol solution with a concentration of 15 g / L, and was heated at 25°C for reaction for 12 hours, and then taken out; the membrane was washed with anhydrous ethanol and then dried at 60°C to obtain a polytetrafluoroethylene microporous membrane with double self-cleaning properties.

[0061] Embodiment 3:

[0062] Prepare a polyethyleneimine ethanol solution with a concentration of 4 g / L, add 1,3-propane sultone and control its concentration to 8 g / L, heat to 50°C, react for 4 hours, filter, wash with ethanol and dry at 70°C. A polytetrafluoroethylene hollow microporous membrane with an average pore size of 0.45 μm was heated to 37°C in a buffered reaction solution of 8 g / L polyion liquid, and the membrane was taken out after reacting for 24 hours; the surface solution of the membrane was removed by adsorption using filter paper, and the membrane was immersed in a 15 g / L, pH=3, ferric chloride hexahydrate aqueous solution, and the membrane was heated at 40°C for reaction for 6 hours, and then taken out; the membrane was immersed in a 10 g / L copper acetate methanol solution, and the membrane was heated at 25°C for reaction for 6 hours, and then taken out; the membrane was immersed in a 10 g / L 2,5-dihydroxyterephthalic acid methanol solution, and the membrane was heated at 25°C for reaction for 12 hours, and then taken out; the membrane was washed with anhydrous ethanol and dried at 60°C to obtain a polytetrafluoroethylene microporous membrane with double self-cleaning properties.

[0063] Embodiment 4:

[0064] Prepare a 4g / L polyethyleneimine ethanol solution, add 1,3-propane sultone and control its concentration to 8g / L, heat to 50℃, react for 4h, filter, wash with ethanol and dry at 70℃. Heat a polytetrafluoroethylene hollow microporous membrane with an average pore size of 1μm in a buffered reaction solution with a concentration of 5g / L polyion liquid at 37℃, react for 20h, remove the membrane by adsorption with filter paper to remove the surface solution, soak the membrane in a 5g / L, pH=3 hexahydrate ferric chloride aqueous solution, heat at 50℃ for 6h and remove it; soak the membrane in a 10g / L copper acetate methanol solution, heat at 25℃ for 6h and remove it; soak the membrane in a 10g / L 2,5-dihydroxyterephthalic acid methanol solution, heat at 25℃ for 10h and remove it; wash the membrane with anhydrous ethanol and dry it at 60℃ to obtain a double self-cleaning polytetrafluoroethylene microporous membrane.

[0065] Comparative Example 1:

[0066] Untreated polytetrafluoroethylene flat microporous membrane with an average pore size of 0.20 μm.

[0067] Comparative Example 2:

[0068] Untreated polytetrafluoroethylene flat microporous membrane with an average pore size of 0.45 μm.

[0069] Comparative Example 3:

[0070] Untreated polytetrafluoroethylene hollow microporous membrane with an average pore size of 0.45 μm.

[0071] Comparative Example 4:

[0072] Untreated polytetrafluoroethylene hollow microporous membrane with an average pore size of 1.0 μm.

[0073] Comparative Example 5:

[0074] Prepare a 4g / L polyethyleneimine ethanol solution, add 1,3-propanesulfonic acid lactone and control its concentration to 8g / L, heat to 50°C, react for 4h, filter, wash with ethanol and dry at 70°C. Heat a polytetrafluoroethylene flat microporous membrane with an average pore size of 0.2μm in a buffered reaction solution with a concentration of 5g / L polyionic liquid at 37°C, take it out after reacting for 8h, use filter paper to absorb the surface solution, and finally wash the membrane with deionized water and dry it at 60°C to obtain a hydrophilic polytetrafluoroethylene microporous membrane.

[0075] Comparative Example 6:

[0076] Prepare a 4g / L polyethyleneimine ethanol solution, add 1,3-propanesulfonic acid lactone and control its concentration to 8g / L, heat to 50℃, react for 4h, filter, wash with ethanol and dry at 70℃. Heat a polytetrafluoroethylene hollow microporous membrane with an average pore size of 0.45μm to 37℃ in a buffered reaction solution with a concentration of 8g / L polyionic liquid, take it out after reacting for 24h; use filter paper to adsorb the membrane to remove the surface solution, and finally wash the membrane with deionized water and dry it at 60℃ to obtain a hydrophilic polytetrafluoroethylene microporous membrane.

[0077] Oil-water separation performance test:

[0078] At 0.1% (M 机油 / M 水 ) of motor oil and 20% Tween-80 (M T-80 / M 机油 ) was used as an emulsifier to prepare an oil-water emulsion. The oil-water emulsion was then stirred at 10,000 rpm for 0.5 h, and the membrane permeation and separation performance were studied by cross-flow filtration experiments at a transmembrane pressure of 0.1 MPa. The membrane flux was calculated by formula (1); the oil content before and after filtration was measured by an infrared oil meter, and the oil-water separation efficiency was calculated by formula (2).

[0079]

[0080] Where J is the permeation flux, V is the permeation volume, A is the effective area, and Δt is the test time.

[0081]

[0082] Among them, R1 is the retention rate when the oil-water emulsion is separated, C p is the concentration of filtrate oil, C f is the original oil-water emulsion concentration.

[0083] Self-cleaning performance test:

[0084] The flux change of the water-in-oil emulsion during the filtration process was used to evaluate the antifouling and self-cleaning ability of the composite membrane. First, the membrane was pre-wetted with deionized water and fixed in the cross-flow filtration device. After the flow rate was stabilized with deionized water, the pressure was set to 0.1 MPa and the flow rate (J) was recorded once every 5 min. 0 ), the process lasted for 20 min; after that, the deionized water was replaced by the previously prepared oil / water emulsion, and the flow rate (J) was recorded every 5 min. 1 ), the process lasts for 20 minutes; after emulsion separation, the filter membrane is cleaned with deionized water and then filtered with pure water, and the flow rate is recorded every 5 minutes, and the process lasts for 20 minutes; then the filter membrane is cleaned with a PMS aqueous solution, and after irradiation with a xenon lamp to simulate natural light, the membrane is used to filter pure water, and the flow rate is recorded every 5 minutes (J F), the process lasts for 20 minutes. All the above processes are one cycle. After repeating three times, the flux recovery rate (FRR) and total fouling rate (Rt) of the composite membrane are calculated using the following formula:

[0085]

[0086] Among them J 0 is the pure water flux of the membrane, J 1 is the permeation flux of the oil-water emulsion. F is the pure water flux after the persulfate advanced oxidation process.

[0087] The performance of each polytetrafluoroethylene microporous membrane obtained by performing performance tests on Examples 1 to 4 and Comparative Examples 1 to 6 is shown in Table 1 below:

[0088] Table 1 Performance of polytetrafluoroethylene microporous membrane

[0089]

[0090]

[0091] It can be seen from Table 1 that the dual self-cleaning polytetrafluoroethylene microporous membrane obtained by the method of the present invention has a higher permeation flux, has a higher separation efficiency for high-viscosity oil-water emulsion, and exhibits strong self-cleaning properties.

[0092] like Figure 2 This is a SEM image of the membrane surface in Comparative Example 1 of the present invention. Figure 3 This is a SEM image of the membrane surface in Comparative Example 5 of the present invention. Figure 4 This is a SEM image of the membrane surface obtained in Example 1 of the present invention, as shown Figure 5 The 0s static water contact angle diagram of the film in Comparative Example 1 of the present invention is shown as follows: Figure 6 The 0s static water contact angle diagram of the film obtained in Example 1 of the present invention is shown as follows: Figure 7 The figure shows the 0s static water contact angle diagram of the membrane obtained in comparative example 5 of the present invention. Compared with the original polytetrafluoroethylene microporous membrane, the hydrophilic polytetrafluoroethylene microporous membrane with photocatalytic function obtained by the present invention is not only wrapped by a layer of hydrophilic substance, but also has a large number of micro-nano particles. The water contact angle of the membrane surface is greatly reduced, and the hydrophilicity of the membrane is greatly increased.

[0093] The method of the present invention uses polyethyleneimine polymer as a raw material to react with 1,3-propane sultone to obtain PSIL precipitation, forms hydrophilic groups such as sulfonic acid ions and amino groups on the surface of the polytetrafluoroethylene microporous membrane, and then deposits iron sulfonate nanoparticles and 2,5-dihydroxy terephthalate copper micro-nanoparticles on the membrane surface in sequence through an in-situ deposition method, thereby making the polytetrafluoroethylene membrane have good hydrophilic properties and photocatalytic self-cleaning properties. The oil-water emulsion separation efficiency is above 99.85%, and the flux recovery rate is above 99.98%.

[0094] Those skilled in the art should understand that the technical features of the above embodiments may be arbitrarily combined. To make the description concise, not all possible combinations of the technical features in the above embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0095] The above embodiments only express several implementation methods of the present application, and the descriptions thereof are relatively specific and detailed, but they cannot be understood as limiting the scope of the present application. It should be pointed out that, for a person of ordinary skill in the art, several variations and improvements can be made without departing from the concept of the present application, and these all belong to the protection scope of the present application. Therefore, the protection scope of the present application shall be subject to the attached claims.

Claims

1. A method for preparing a double-cleaning polytetrafluoroethylene microporous membrane, characterized in that: The following steps are involved: 1) heating polyethyleneimine and 1,3-propane sultone in one step to form a polyionic liquid, and dissolving the polyionic liquid and dopamine in a Tris base solution to obtain a buffered reaction solution; 2) immersing the polytetrafluoroethylene microporous membrane in a buffered reaction solution, heating the solution for reaction, and then taking the solution out to obtain a first microporous membrane; 3) immersing the first microporous membrane in an aqueous solution of ferric chloride hexahydrate, heating it for reaction, and then taking it out to obtain a second microporous membrane; 4) immersing the second microporous membrane in a copper acetate methanol solution, heating it for reaction, and then taking it out to obtain a third microporous membrane; 5) soaking the third microporous membrane in a methanol solution of 2,5-dihydroxyterephthalic acid, heating it for reaction, and then taking it out to obtain a fourth microporous membrane; 6) The fourth microporous membrane is washed and then dried to obtain a double self-cleaning polytetrafluoroethylene microporous membrane.

2. The method for preparing a double-cleaning polytetrafluoroethylene microporous membrane according to claim 1, characterized in that: The polyethyleneimine is configured as a polyethyleneimine ethanol solution, and the polyethyleneimine ethanol solution is mixed with 1,3-propane sultone and then heated to react to obtain a polyionic liquid, wherein the polyethyleneimine concentration in the polyethyleneimine solution is 1-10 g / L, and the concentration of 1,3-propane sultone is 2-10 g / L.

3. The method for preparing a double-cleaning polytetrafluoroethylene microporous membrane according to claim 1, characterized in that: The heating temperature for the one-step heating reaction of polyethyleneimine and 1,3-propanesultone is 45-55° C., and the reaction time is 3-5 hours.

4. The method for preparing a double-cleaning polytetrafluoroethylene microporous membrane according to claim 1, characterized in that: The polytetrafluoroethylene microporous membrane is first soaked with ethanol and then immersed in a buffered reaction solution for heating reaction and then taken out to obtain a first microporous membrane, wherein the heating reaction temperature is 35-40° C. and the heating time is 8-24 hours.

5. The method for preparing a double-cleaning polytetrafluoroethylene microporous membrane according to claim 1, characterized in that: The concentration of the ferric chloride hexahydrate aqueous solution is 5-20 mmol / L, and the pH is 3. The first microporous membrane is immersed in the ferric chloride hexahydrate aqueous solution and heated at a temperature of 40-80° C., and the reaction time is 8-24 hours.

6. The method for preparing a double-cleaning polytetrafluoroethylene microporous membrane according to claim 1, characterized in that: The concentration of the copper acetate methanol solution is 5-20 g / L. The second microporous membrane is immersed in the copper acetate methanol solution and heated at a temperature of 20-30° C. The reaction time is 6-12 hours. After the reaction is completed, the third microporous membrane is taken out to obtain.

7. The method for preparing a double-cleaning polytetrafluoroethylene microporous membrane according to claim 1, characterized in that: The concentration of the methanol solution of 2,5-dihydroxyterephthalic acid is 5-20 g / L, the heating temperature of immersing the third microporous membrane in the methanol solution of 2,5-dihydroxyterephthalic acid is 20-30° C., and the reaction time is 6-12 hours.

8. The method for preparing a double-cleaning polytetrafluoroethylene microporous membrane according to claim 1, characterized in that: The fourth microporous membrane was washed with anhydrous ethanol and then dried at 60° C. to obtain a polytetrafluoroethylene microporous membrane with dual self-cleaning properties.

9. A double-cleaning polytetrafluoroethylene microporous membrane, characterized in that: The method for preparing a double-cleaning polytetrafluoroethylene microporous membrane according to any one of claims 1 to 8 comprises: A polytetrafluoroethylene microporous membrane and iron sulfonate nanoparticles and 2,5-dihydroxy terephthalate copper nanoparticles grown on the polytetrafluoroethylene microporous membrane, wherein sulfonic acid groups and amino groups are formed on the surface of the polytetrafluoroethylene microporous membrane, and the iron sulfonate nanoparticles are chemically bonded to the sulfonic acid groups and amino groups.

10. The double-cleaning polytetrafluoroethylene microporous membrane according to claim 9, characterized in that: Applied to the degradation of high-viscosity wastewater containing emulsified oil.

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