Wettability switchable separation membrane and preparation method thereof, and method for achieving membrane cleaning based on electric field switching wettability

Abstract

The present invention relates to the technical field of sewage treatment, and discloses a wettability switchable separation membrane, a preparation method thereof, and a method for achieving membrane cleaning based on electric field-switched wettability. The method comprises the following steps: (1) contacting and mixing a conductive polymer monomer, a dopant, and a phosphate buffer solution to obtain a mixture I; (2) heating the membrane at 30-60°C and 1-2 mA / cm 2 Under a constant current density of , a metal mesh is used as an anode, a graphite plate is used as a cathode, and Ag / AgCl is used as a working electrode to perform electrochemical deposition in the mixture I to obtain a deposited film; and (3) the deposited film is sequentially rinsed and dried to obtain a wettability-switchable separation membrane. The wettability-switchable separation membrane provided by the present invention has a simple and environmentally friendly preparation process, and the method for achieving membrane cleaning based on electric field-switching wettability using the wettability-switchable separation membrane can achieve simple and effective separation of various types of pollutants, and the membrane cleaning process can be successfully completed in a short time.

Description

Technical Field

[0001] The present invention relates to the technical field of sewage treatment, and in particular to a wettability switchable separation membrane and a preparation method thereof, and a method for achieving membrane cleaning based on electric field switching wettability. Background Art

[0002] In recent years, membrane separation technology has garnered widespread attention in the wastewater separation field due to its advantages, including high separation efficiency, zero secondary pollution, low energy consumption, and small footprint. However, after treating wastewater, traditional membranes are prone to adsorbing pollutants on the membrane surface and / or within the membrane pores, causing pore blockage and significantly reducing filtration flux. This also shortens the membrane's lifespan and increases operating costs. Therefore, membrane fouling cleaning technology is key to improving membrane separation performance and promoting its application in wastewater separation.

[0003] Conventional physical cleaning methods require high instrumentation, generate high energy consumption, are difficult to remove irreversible contamination, and may cause mechanical damage to the membrane material. Chemical cleaning methods can address irreversible contamination, but the cleaning agents may affect the membrane structure and performance, and also face problems such as high cleaning agent costs and secondary contamination. Smart responsive membranes, on the other hand, can achieve self-cleaning properties by modifying their surface properties. This process is highly adjustable and flexible, allowing for multiple membrane reuse.

[0004] The temperature-sensitive intelligent response membrane disclosed in CN117339398A can achieve efficient cleaning and regeneration of the membrane through changes in ambient temperature, but the cleaning process requires repeated alternation of high-temperature water and low-temperature water, resulting in high energy consumption.

[0005] CN115920664A discloses an emulsion separation membrane with self-cleaning and controllable wettability, but it needs to be soaked in multiple chemical agents to achieve hydrophilicity and hydrophobicity switching, and self-cleaning also requires irradiation with a 500W mercury lamp for 60 minutes. Not only does it introduce additional chemical reagents, but it also exhibits higher energy consumption and longer processing time during the self-cleaning process.

[0006] Based on this, it is of great significance to provide a separation membrane that is simple to prepare, has easy switching conditions, rapid switching, is environmentally friendly and energy-saving, and can achieve membrane cleaning through wettability switching. Summary of the Invention

[0007] The purpose of the present invention is to overcome the problems of complex operation, high energy consumption, environmental pollution and limited separation effect in the prior art in preparing smart responsive membranes.

[0008] In order to achieve the above object, the first aspect of the present invention provides a method for preparing a wettability switchable separation membrane, the method comprising the following steps:

[0009] (1) contacting and mixing a conductive polymer monomer, a dopant, and a phosphate buffer solution to obtain a mixture I;

[0010] (2) At 30-60°C and 1-2 mA / cm 2 Under a constant current density of , a metal mesh is used as an anode, a graphite plate is used as a cathode, and Ag / AgCl is used as a working electrode, and electrochemical deposition is performed in the mixture I to obtain a deposited film;

[0011] (3) The deposited film is rinsed and dried in sequence to obtain a wettability-switchable separation membrane.

[0012] The second aspect of the present invention provides a wettability switchable separation membrane prepared by the method described in the first aspect.

[0013] A third aspect of the present invention provides a method for membrane cleaning based on electric field-switching wettability, the method being performed using the wettability-switching separation membrane described in the second aspect, comprising the following steps:

[0014] S1. Performing membrane separation on the sewage using a wettability switching separation membrane, and stopping the membrane separation when the membrane flux attenuation rate of the wettability switching separation membrane reaches 10-20%;

[0015] S2. Applying a positive voltage of 0.2 to 0.8 V to the wettability switchable separation membrane after the membrane separation in a cleaning solution to disturb the pollutants;

[0016] S3. Apply a negative voltage of -1.2 to -2.0 V to desorb pollutants from the wettability switching separation membrane disturbed by the pollutants in step S2, so as to complete membrane cleaning based on electric field switching wettability.

[0017] Compared with the prior art, the method provided by the present invention has at least the following beneficial effects:

[0018] (1) The wettability-switchable separation membrane and the membrane cleaning method based on electric field-switching wettability provided by the present invention solve the problems of high energy consumption, incomplete cleaning effect, membrane structure damage, or the use of chemical reagents in traditional cleaning methods, providing an economical and environmentally friendly solution with good cleaning effect. The method has a simple step to switch the membrane wettability, requiring only changing the direction of the electric field, and the membrane cleaning can be completed in a short time.

[0019] (2) The wettability switching separation membrane provided by the present invention can not only process various oil types, emulsions stabilized by various surfactants, and pollutants such as diatomaceous earth, but also maintains good membrane performance after multiple cleaning cycles, with a flux recovery rate of over 90%, which can effectively achieve membrane surface cleaning. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] Figure 1 This is a schematic diagram of a system for applying a preferred method for membrane cleaning based on electric field switching wettability provided by the present invention;

[0021] Figure 2 This is a SEM image of a preferred wettability switchable separation membrane provided by the present invention;

[0022] Figure 3 This is a multi-cycle wettability switching performance diagram of a preferred wettability switchable separation membrane provided by the present invention;

[0023] Figure 4 The preferred method for achieving membrane cleaning based on electric field switching wettability provided by the present invention and the flux recovery rate of the separation membrane after each cycle of operation of the comparative example;

[0024] Figure 5 This is a diagram of the reversible fouling resistance of the separation membrane in each cycle of the preferred method for membrane cleaning based on electric field switching wettability provided by the present invention and the comparative example;

[0025] Figure 6 This is a preferred method for achieving membrane cleaning based on electric field switching wettability provided by the present invention and a graph of irreversible fouling resistance of the separation membrane in each cycle of the comparative example.

[0026] Description of Reference Numerals

[0027] 1. Reaction chamber; 2. Water inlet valve;

[0028] 3. Outlet valve; 4. Sewage return valve;

[0029] 5. Cleaning fluid inlet valve; 6. Cleaning fluid return valve;

[0030] 7. First peristaltic pump; 8. Second peristaltic pump;

[0031] 9. Wettability-switchable separation membrane; 10. Counter electrode. DETAILED DESCRIPTION

[0032] The endpoints of the ranges and any values ​​disclosed herein are not limited to the precise ranges or values, and these ranges or values ​​should be understood to include values ​​close to these ranges or values. For numerical ranges, the endpoints of each range, the endpoints of each range and individual point values, and the individual point values ​​can be combined with each other to obtain one or more new numerical ranges, which should be considered to be specifically disclosed herein.

[0033] As mentioned above, the first aspect of the present invention provides a method for preparing a wettability-switchable separation membrane, the method comprising the following steps:

[0034] (1) contacting and mixing a conductive polymer monomer, a dopant, and a phosphate buffer solution to obtain a mixture I;

[0035] (2) At 30-60°C and 1-2 mA / cm 2 Under a constant current density of , a metal mesh is used as an anode, a graphite plate is used as a cathode, and Ag / AgCl is used as a working electrode, and electrochemical deposition is performed in the mixture I to obtain a deposited film;

[0036] (3) The deposited film is rinsed and dried in sequence to obtain a wettability-switchable separation membrane.

[0037] Preferably, in step (1), the conductive polymer monomer is pyrrole. This preferred embodiment facilitates the preparation of a membrane with reversible wettability switching performance at a relatively low voltage, while also improving the safety of the prepared membrane when used in water treatment.

[0038] Preferably, in step (1), the dopant is an amphiphilic molecule.

[0039] Preferably, the dopant is sodium dodecylbenzenesulfonate and / or β-naphthalenesulfonic acid. This preferred embodiment enhances the wettability-switchable membrane's ability to reversibly switch between hydrophilic and hydrophobic states, making it more suitable for specific applications such as oil-water separation, protein purification, and sensors. It also improves the membrane's stability and mechanical properties.

[0040] According to a preferred embodiment, in step (1), the amount of the conductive polymer monomer is controlled so that the concentration of the conductive polymer monomer in the mixture I is 0.1-0.5M.

[0041] Preferably, in step (1), the molar ratio of the dopant to the conductive polymer monomer is 1-5: 100. This preferred embodiment can modify the surface of the conductive polymer monomer while facilitating more effective insertion of the dopant into the polymer chain, thereby improving charge transfer efficiency.

[0042] Preferably, in step (2), the average pore size of the metal mesh is 5-30 μm.

[0043] Preferably, in step (2), the electrochemical deposition conditions at least meet the following requirements: temperature of 30-40° C. and time of 10-120 min. Studies have found that under this preferred condition, the wettability switching effect of the prepared separation membrane is better.

[0044] Preferably, in step (3), the rinsing is performed using deionized water.

[0045] As mentioned above, the second aspect of the present invention provides a wettability switchable separation membrane prepared by the method described in the first aspect.

[0046] Preferably, the wettability switchable separation membrane has a water contact angle of 120°-140° in a hydrophobic state and a water contact angle of 0°-15° in a hydrophilic state.

[0047] Preferably, the average pore size of the wettability-switchable separation membrane is 2.0-6.0 μm.

[0048] As mentioned above, the third aspect of the present invention further provides a method for membrane cleaning based on electric field switching wettability, which is performed using the wettability switching separation membrane described in the second aspect and comprises the following steps:

[0049] S1. Performing membrane separation on the sewage using a wettability switching separation membrane, and stopping the membrane separation when the membrane flux attenuation rate of the wettability switching separation membrane reaches 10-20%;

[0050] S2. Applying a positive voltage of 0.2 to 0.8 V to the wettability switchable separation membrane after the membrane separation in a cleaning solution to disturb the pollutants;

[0051] S3. Apply a negative voltage of -1.2 to -2.0 V to desorb pollutants from the wettability switching separation membrane disturbed by the pollutants in step S2, so as to complete membrane cleaning based on electric field switching wettability.

[0052] It should be noted that, in the present invention, the operation of membrane separation of sewage does not include the membrane cleaning step after conventional membrane separation of sewage.

[0053] According to a preferred embodiment, in step S1, the sewage is selected from at least one of crude oil wastewater, wastewater containing suspended particles, mechanical processing wastewater, and kitchen wastewater.

[0054] More preferably, the pollutant is selected from at least one of crude oil, soybean oil, paraffin, diatomaceous earth, cationic surfactants, anionic surfactants, and nonionic surfactants.

[0055] Preferably, in step S2, the cleaning solution is a phosphate buffer solution containing 0.01-0.05M dopant.

[0056] Preferably, the dopant is selected from at least one of sodium dodecylbenzenesulfonate and / or β-naphthalenesulfonic acid.

[0057] Preferably, in step S2, the positive voltage is applied for 2-5 minutes.

[0058] Preferably, in step S3, the negative voltage is applied for 2-5 minutes.

[0059] According to a preferred embodiment, the method for achieving membrane cleaning based on electric field switching wettability is Figure 1 The system is performed as shown and includes the following steps:

[0060] S1. In a reaction chamber 1, membrane separation is performed on sewage using a wettability switching separation membrane 9. When the membrane flux attenuation rate of the wettability switching separation membrane 9 reaches 10-20%, the membrane separation is stopped.

[0061] S2, close the water inlet valve 2 and the water outlet valve 3, open the sewage return valve 4, pump the untreated sewage back to the sewage bucket, close the sewage return valve 4 and the first peristaltic pump 7, open the cleaning liquid inlet valve 5 and the second peristaltic pump 8, allow the cleaning liquid to enter the reaction chamber 1, control the distance between the counter electrode 10 and the wettability switch separation membrane 9 to be 2-5 mm, connect a DC power supply to the counter electrode 10 and the wettability switch separation membrane 9 respectively, apply a positive voltage of 0.2-0.8V for 2-5 minutes, and convert the membrane into a hydrophobic membrane to perform pollutant disturbance;

[0062] S3. Apply a negative voltage of -1.2 to -2.0 V for 2-5 minutes to convert the membrane into a hydrophilic membrane, desorb the pollutants, and then open the cleaning liquid return valve 6 to pump the cleaning liquid in the reaction chamber 1 into the cleaning liquid barrel to complete the membrane cleaning process based on electric field switching wettability.

[0063] It should be noted that in the present invention, after completing the membrane cleaning based on electric field switching wettability, the cleaning liquid inlet valve 5, the cleaning liquid return valve 6 and the second peristaltic pump 8 can be closed, and the inlet valve 2, the outlet valve 3 and the first peristaltic pump 7 can be opened to carry out the next cycle of membrane separation process.

[0064] The present invention is described in detail below by way of examples. Unless otherwise specified, the raw materials used are all common commercially available products.

[0065] Conductive polymer monomer: pyrrole;

[0066] Dopant:

[0067] Dopant I: sodium dodecylbenzenesulfonate;

[0068] Dopant II: sodium di(2-ethylhexyl)sulfosuccinate;

[0069] Phosphate buffer solution: The concentration of phosphate is 0.5 M and the pH is 6.8;

[0070] Metal mesh: average pore size is 8μm;

[0071] Cleaning solution: phosphate buffer solution containing 0.01M dopant;

[0072] Sewage:

[0073] Wastewater I: It is an emulsion stabilized by the surfactant SDBS (sodium dodecylbenzenesulfonate), wherein the oil phase is liquid paraffin with a concentration of 5000ppm and the concentration of sodium dodecylbenzenesulfonate is 100ppm;

[0074] Wastewater II: diatomaceous earth wastewater, the concentration of diatomaceous earth is 500ppm;

[0075] Wastewater III: an emulsion stabilized by the surfactant SDBS (sodium dodecylbenzenesulfonate), wherein the oil phase is soybean oil with a concentration of 5000 ppm and the concentration of sodium dodecylbenzenesulfonate is 100 ppm;

[0076] Wastewater IV: crude oil wastewater with an oil concentration of 4200ppm;

[0077] Wastewater V: an emulsion stabilized by the surfactant CTAB (cetyltrimethylammonium bromide), wherein the oil phase is liquid paraffin with a concentration of 5000 ppm and the concentration of cetyltrimethylammonium bromide is 100 ppm;

[0078] Wastewater VI: It is an emulsion stabilized by the surfactant Tween 80, in which the oil phase is liquid paraffin with a concentration of 5000 ppm; the concentration of Tween 80 is 100 ppm.

[0079] It should be noted that the surfactant-stabilized emulsion is a mixture of an oil phase and a surfactant.

[0080] The calculation method of flux recovery rate (FRR) after running n cycles is:

[0081] After running for n cycles

[0082] Where, J n The wettability switching separation membrane or the filtration flux of the separation membrane to the sewage in the nth cycle;

[0083] J n-1 The wettability switching separation membrane or the filtration flux of the separation membrane to the sewage in the n-1th cycle.

[0084] Example A-1

[0085] This example is used to illustrate the method for preparing a wettability switchable separation membrane provided by the present invention, which is performed by the following steps:

[0086] (1) contacting and mixing a conductive polymer monomer, a dopant (dopant I) and a phosphate buffer solution to obtain a mixture I; controlling the amount of the conductive polymer monomer so that the concentration of the conductive polymer monomer in the mixture I is 0.2 M; and the molar ratio of the dopant to the conductive polymer monomer is 5:100;

[0087] (2) At 30°C and 2 mA / cm 2 Under a constant current density of , a metal mesh was used as an anode, a graphite plate was used as a cathode, and Ag / AgCl was used as a working electrode to perform electrochemical deposition in the mixture I to obtain a deposited film for 30 min;

[0088] (3) The deposited film was rinsed with deionized water and then dried to obtain a wettability-switchable separation membrane, named P1, with an average pore size of 5.66 μm;

[0089] Figure 2 The SEM image (scanning electron microscope image) of P1 is shown. Figure 2 The conventional metal mesh surface on the left side is obviously different from the Figure 2 The surface of P1 on the middle right side is a rough structure, in which polypyrrole is uniformly wrapped on the metal wire in a granular form.

[0090] Example A-2

[0091] This example is carried out using a method similar to that of Example A-1, except that in step (2), the dopant used is dopant II;

[0092] Finally, a wettability-switchable separation membrane was obtained, named P2.

[0093] Comparative Example B-1

[0094] This comparative example was carried out using a method similar to that of Example A-1, except that in step (2), the temperature of electrochemical deposition was 25°C;

[0095] Finally, the separation membrane was obtained and named DP1.

[0096] Comparative Example B-2

[0097] This comparative example was carried out in a similar manner to Example A-1, except that in step (2), the constant current density of the electrochemical deposition was 0.5 mA / cm 2 ;

[0098] Finally, the separation membrane was obtained and named DP2.

[0099] Test Case C-1

[0100] The wettability switchable separation membrane and the separation membrane prepared in the above example were tested for contact angle hydrophilicity-hydrophobicity switching performance, including:

[0101] First, a voltage of -1.6 V was applied to perform a reduction reaction, and the water contact angle of each separation membrane in this state was measured, which was recorded as the water contact angle in reduction state 1 (hydrophilic state);

[0102] A voltage of 0.5 V was then applied to carry out the oxidation reaction, and the water contact angle of each separation membrane in this state was measured and recorded as the water contact angle in the oxidation state (hydrophobic state);

[0103] Then, a voltage of -1.6 V was applied to perform the reduction reaction again, and the water contact angle of each separation membrane in this state was measured, which was recorded as the water contact angle in the reduction state 2 (hydrophilic state). The oxidation reaction-reduction reaction was performed alternately in this way;

[0104] The results are shown in Table 1;

[0105] Figure 3 The water contact angles of the wettability switchable separation membrane in the hydrophobic and hydrophilic states during the alternating oxidation-reduction reaction of P1 are shown, with the hydrophobic state being designated as "oxygen" and the hydrophilic state being designated as "reduction". Figure 3 It can be seen that the wettability of P1 did not change significantly during the whole process, indicating that the separation membrane has the ability to achieve membrane cleaning in multi-cycle filtration by utilizing wettability switching.

[0106] Table 1

[0107] Performance indicators P1 P2 DP1 DP2 Water contact angle in reduced state 1 (°) 9.48 11.09 8.33 11.00 Water contact angle in oxidized state (°) 126.04 98.46 74.66 75.05 Water contact angle in reduced state 2 (°) 11.51 10.08 10.92 9.08

[0108] Example D-1

[0109] This example is used to illustrate the method for membrane cleaning based on electric field switching wettability provided by the present invention. Figure 1 The system is performed as shown and includes the following steps:

[0110] S1. In a reaction chamber 1, membrane separation is performed on sewage (sewage I) using a wettability switching separation membrane. When the membrane flux attenuation rate of the wettability switching separation membrane reaches 15%, the membrane separation is stopped.

[0111] S2. Close the water inlet valve 2 and the water outlet valve 3, open the sewage return valve 4, pump the untreated sewage back to the sewage bucket, close the sewage return valve 4 and the first peristaltic pump 7, open the cleaning liquid inlet valve 5 and the second peristaltic pump 8, allow the cleaning liquid to enter the reaction chamber 1, control the distance between the counter electrode 10 and the wettability switching separation membrane 9 to be 5 mm, connect a DC power supply to the counter electrode 10 and the wettability switching separation membrane 9 respectively, apply a positive voltage of 0.5 V for 5 minutes, and convert the membrane into a hydrophobic membrane to perform pollutant disturbance;

[0112] S3. Apply a negative voltage of -1.6 V for 5 minutes to convert the membrane into a hydrophilic membrane, desorbing the pollutants. Then open the cleaning liquid return valve 6 and pump the cleaning liquid in the reaction chamber 1 into the cleaning liquid barrel to complete the membrane cleaning based on the electric field switching wettability.

[0113] The operation from step S1 to step S3 is regarded as one cycle, and the above cycle is repeated 10 times. The flux recovery rate of the separation membrane after each cycle is recorded. The results are shown in Figure 4 The wettability switching group is shown in the figure. It can be seen that the flux recovery rate in this method remains at 100% after ten consecutive cycles. The average flux recovery rate of the separation membrane over ten cycles is calculated to be 100%.

[0114] Figure 5 The wettability switching group shows the reversible fouling resistance of the separation membrane in ten cycles. It can be seen from the figure that the reversible fouling resistance of the separation membrane is only 8.75nm after ten cycles. -1 ;

[0115] Figure 6 The wettability switching group shows the irreversible fouling resistance of the separation membrane in ten cycles. It can be seen from the figure that the irreversible fouling resistance of the separation membrane after ten cycles is only 0.41nm -1 ;

[0116] It can be seen that this method has a good cleaning effect on the separation membrane and can maintain the continuous operation of the membrane for multiple cycles.

[0117] Example D-2

[0118] This example was carried out using a method similar to that of Example D-1, except that in step S1, the sewage used was sewage II;

[0119] The final calculated ten-cycle average flux recovery rate of the separation membrane was 95.99%.

[0120] Example D-3

[0121] This example was carried out using a method similar to that of Example D-1, except that in step S1, the sewage used was sewage III;

[0122] The final calculated ten-cycle average flux recovery rate of the separation membrane was 95.00%.

[0123] Example D-4

[0124] This example was carried out using a method similar to that of Example D-1, except that in step S1, the sewage used was sewage IV;

[0125] The final calculated ten-cycle average flux recovery rate of the separation membrane was 94.93%.

[0126] Example D-5

[0127] This example is carried out using a method similar to that of Example D-1, except that in step S1, the sewage used is sewage V;

[0128] The final calculated ten-cycle average flux recovery rate of the separation membrane was 95.86%.

[0129] Example D-6

[0130] This example is carried out using a method similar to that of Example D-1, except that in step S1, the sewage used is sewage VI;

[0131] The final calculated ten-cycle average flux recovery rate of the separation membrane was 96.48%.

[0132] Comparative Example E-1

[0133] In this comparative example, the membrane cleaning was performed using conventional hydraulic flushing instead of wettability switching. The membrane was cleaned for 10 minutes on the wettability switching separation membrane after membrane separation in step S1 of Example D-1, including:

[0134] SS1. In reaction chamber 1, membrane separation is performed on sewage (sewage I) using a wettability switching separation membrane. When the membrane flux attenuation rate of the wettability switching separation membrane reaches 15%, the membrane separation is stopped.

[0135] SS2, using conventional hydraulic flushing method to clean the wettability switching separation membrane for 10 min;

[0136] The operations of step SS1 and step SS2 are regarded as one cycle, and the cycle is repeated for 10 cycles;

[0137] Starting from the second cycle, the flux recovery rate of the separation membrane after each cycle is recorded. The results are shown in Figure 4 (hydraulic flushing group), where the flux recovery rate dropped to 41.67% after six consecutive cycles;

[0138] Record the reversible fouling resistance of the separation membrane during each cycle. The results are shown in Figure 5 (Hydraulic flushing group), where the reversible contamination resistance increased to 425.44 nm after six cycles -1 ;

[0139] Record the irreversible fouling resistance of the separation membrane during each cycle. The results are shown in Figure 6 (Hydraulic flushing group), where the irreversible contamination resistance increased to 18.92nm after six cycles -1 ;

[0140] This indicates that the cleaning effect of this method is poor and it is impossible to maintain the continuous operation of the membrane for multiple cycles.

[0141] Comparative Example E-2

[0142] In this comparative example, the wettability switching separation membrane obtained in step S1 of Example D-1 was cleaned for 10 minutes using a conventional backwashing method instead of using wettability switching for membrane cleaning, including:

[0143] A1. In a reaction chamber 1, membrane separation is performed on the sewage (sewage I) using a wettability switching separation membrane. When the membrane flux attenuation rate of the wettability switching separation membrane reaches 15%, the membrane separation is stopped.

[0144] A2. Use conventional backwashing method to clean the wettability switching separation membrane for 10 minutes;

[0145] Consider the operations of A1 and A2 as one cycle and repeat for 10 cycles;

[0146] Starting from the second cycle, the flux recovery rate of the separation membrane after each cycle is recorded. The results are shown in Figure 4 (Backwash group) Among them, the flux recovery rate dropped to 80.77% after six consecutive cycles;

[0147] Record the reversible fouling resistance of the separation membrane during each cycle. The results are shown in Figure 5 (Backwash group), where the reversible contamination resistance increased to 18.54 nm after six cycles -1 ;

[0148] Record the irreversible fouling resistance of the separation membrane during each cycle. The results are shown in Figure 6 (Backwash group), where the irreversible contamination resistance increased to 7.62nm after six cycles -1 ;

[0149] This indicates that the cleaning effect of this method is poor and it is impossible to maintain the continuous operation of the membrane for multiple cycles.

[0150] Comparative Example E-3

[0151] This comparative example was carried out using a method similar to that of Example D-1, except that a 0.01 mol / L HCl solution was used instead of the cleaning solution to clean the membrane without applying voltage, including:

[0152] S1. In a reaction chamber, performing membrane separation on sewage (sewage I) using a wettability switching separation membrane, and stopping the membrane separation when the membrane flux attenuation rate of the wettability switching separation membrane reaches 15%;

[0153] S2. Close the water inlet valve and the water outlet valve, open the sewage return valve, pump the untreated sewage back to the sewage bucket, close the sewage return valve and the first peristaltic pump, open the HCl solution inlet valve, the peristaltic pump and the return valve, allow the HCl solution to enter the reaction chamber, and continue to flow in the inlet and return flow paths to complete the membrane cleaning.

[0154] The operation from step S1 to step S2 is regarded as one cycle, and six cycles are repeated.

[0155] Starting from the second cycle, the flux recovery rate of the separation membrane after each cycle is recorded. The results are shown in Figure 4 (acid washing group), the flux recovery rate after six cycles decreased to 58.06% after six consecutive cycles;

[0156] Record the reversible fouling resistance of the separation membrane during each cycle. The results are shown in Figure 5 (Acid washing group), where the reversible contamination resistance increased to 225.58nm after six cycles -1 ;

[0157] Record the irreversible fouling resistance of the separation membrane during each cycle. The results are shown in Figure 6 (Acid washing group), where the irreversible contamination resistance increased to 21.17nm after six cycles -1 ;

[0158] This indicates that the cleaning effect of this method is poor and it is impossible to maintain the continuous operation of the membrane for multiple cycles.

[0159] Comparative Example E-4

[0160] This comparative example was carried out using a method similar to that of Example D-1, except that a 0.01 mol / L NaOH solution was used instead of the cleaning solution to clean the membrane without applying voltage, including:

[0161] S1. In a reaction chamber 1, membrane separation is performed on sewage (sewage I) using a wettability switching separation membrane. When the membrane flux attenuation rate of the wettability switching separation membrane reaches 15%, the membrane separation is stopped.

[0162] S2. Close the water inlet valve and the water outlet valve, open the sewage return valve, pump the untreated sewage back to the sewage bucket, close the sewage return valve and the first peristaltic pump, open the NaOH solution inlet valve, peristaltic pump and return valve, allow the NaOH solution to enter the reaction chamber, and continue to flow in the inlet and return flow paths to complete membrane cleaning.

[0163] The operation from step S1 to step S2 is regarded as one cycle, and six cycles are repeated.

[0164] Starting from the second cycle, the flux recovery rate of the separation membrane after each cycle is recorded. The results are shown in Figure 4 (alkaline washing group), the flux recovery rate after six cycles decreased to 78.49% after six consecutive cycles;

[0165] Record the reversible fouling resistance of the separation membrane during each cycle. The results are shown in Figure 5 (Alkaline washing group), where the reversible contamination resistance increased to 48.77nm after six cycles -1 ;

[0166] Record the irreversible fouling resistance of the separation membrane during each cycle. The results are shown in Figure 6 (Alkaline washing group), where the irreversible contamination resistance increased to 11.86nm after six cycles -1 .

[0167] This indicates that the cleaning effect of this method is poor and it is impossible to maintain the continuous operation of the membrane for multiple cycles.

[0168] It can be seen from the above results that the preparation process of the wettability switching separation membrane provided by the present invention is simple and environmentally friendly, and the method for achieving membrane cleaning based on electric field switching wettability utilizes the cleaning effect of the wettability switching separation membrane on various pollutants to make the average flux recovery rate of multiple cycles above 90%, which can achieve simple and effective separation of various types of pollutants and can successfully complete the membrane cleaning process in a short time.

[0169] The preferred embodiments of the present invention have been described in detail above, but the present invention is not limited thereto. Within the technical concept of the present invention, various simple variations of the technical solution of the present invention may be made, including combining the various technical features in any other appropriate manner. These simple variations and combinations should also be regarded as disclosed in the present invention and fall within the scope of protection of the present invention.

Claims

1. A method for preparing a wettability-switchable separation membrane, characterized in that: The method comprises the following steps: (1) contacting and mixing a conductive polymer monomer, a dopant, and a phosphate buffer solution to obtain a mixture I; wherein the conductive polymer monomer is pyrrole; and the dopant is an amphiphilic molecule; (2) At 30-60°C and 1-2 mA / cm 2 Under a constant current density of , a metal mesh is used as an anode, a graphite plate is used as a cathode, and Ag / AgCl is used as a working electrode, and electrochemical deposition is performed in the mixture I to obtain a deposited film; (3) sequentially rinsing and drying the deposited film to obtain a wettability-switchable separation membrane; The wettability switching separation membrane has the following functions: when a positive voltage of 0.2-0.8 V is applied for 2-5 minutes, the wettability switching separation membrane can be converted into a hydrophobic membrane to disturb the pollutants; when a negative voltage of -1.2 to -2.0 V is applied for 2-5 minutes, the wettability switching separation membrane can be converted into a hydrophilic membrane to desorb the pollutants.

2. The method according to claim 1, wherein In step (1), the amount of the conductive polymer monomer is controlled so that the concentration of the conductive polymer monomer in the mixture I is 0.1-0.5M.

3. The method according to claim 1, wherein In step (1), the molar ratio of the dopant to the conductive polymer monomer is 1-5:

100.

4. A wettability-switchable separation membrane prepared by the method according to any one of claims 1 to 3.

5. The wettability-switchable separation membrane according to claim 4, wherein The wettability switchable separation membrane has a water contact angle of 120°-140° in a hydrophobic state and a water contact angle of 0°-15° in a hydrophilic state.

6. A method for membrane cleaning based on electric field switching wettability, characterized in that: The method is carried out using the wettability switchable separation membrane according to claim 4 or 5, and comprises the following steps: S1. Performing membrane separation on the sewage using a wettability switching separation membrane, and stopping the membrane separation when the membrane flux attenuation rate of the wettability switching separation membrane reaches 10-20%; S2. Applying a positive voltage of 0.2 to 0.8 V to the wettability switchable separation membrane after the membrane separation in a cleaning solution to disturb the pollutants; S3. Apply a negative voltage of -1.2 to -2.0 V to desorb pollutants from the wettability switching separation membrane disturbed by the pollutants in step S2, so as to complete membrane cleaning based on electric field switching wettability.

7. The method according to claim 6, wherein: In step S2, the cleaning solution is a phosphate buffer solution containing 0.01-0.05 M dopant.

8. The method according to claim 6 or 7, wherein: In step S2, the positive charge is applied for 2-5 minutes; and / or In step S3, the negative charge is applied for 2-5 minutes.

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