Janus oil-water separation membrane as well as preparation method and application thereof

Abstract

The invention discloses a Janus oil-water separation membrane as well as a preparation method and application thereof, and belongs to the technical field of oil-water separation. The fabric is subjected to plasma activation and then sequentially subjected to hydrophobic modification and hydrophilic modification, so that the Janus oil-water separation membrane with asymmetric wettability is obtained, and the obtained Janus oil-water separation membrane can realize excellent one-way liquid transmission and has a good separation effect and hydraulic pressure resistance on an oil-water mixture; the separation rate of the oil-water mixture reaches 46000 L / m < 2 > * h, and the separation efficiency can reach 99% or above.

Description

Technical Field

[0001] The invention relates to the technical field of oil-water separation, and in particular to a Janus oil-water separation membrane and a preparation method and application thereof. Background Art

[0002] In today's era of rapid industrial development and increasingly abundant people's lives, the generation of waste oil water has become an issue that cannot be ignored. Waste oil water not only causes serious pollution to the environment, but also poses a great threat to the balance of the ecosystem. The oil substances in the waste oil water will form an oil film on the surface of the water body, preventing the oxygen in the air from dissolving into the water, causing aquatic organisms to die due to lack of oxygen. At the same time, the harmful substances in the waste oil water will also penetrate into the soil, pollute the groundwater, and pose a potential threat to human drinking water safety. In addition, the discharge of waste oil water will also affect the marine ecosystem, destroy the habitat of marine organisms, and have a serious impact on the survival and reproduction of marine organisms. Therefore, efficient oil-water separation technology has become an urgent need. Traditional oil-water separation methods mainly include gravity separation, centrifugal separation, chemical demulsification, etc. However, these methods often have problems such as low separation efficiency, high energy consumption, and complex operation. For example, the gravity separation method is only applicable to the case where the oil droplet size is large and the oil-water density difference is large, and the separation effect of tiny oil droplets and emulsified oil is poor; the centrifugal separation method has high equipment cost and limited effect on the treatment of high-viscosity oil and water; the chemical demulsification method may introduce new chemicals, causing secondary pollution.

[0003] In recent years, membrane separation has been considered the most promising technology in the field of gas and liquid separation due to its advantages such as simple operation, excellent separation effect, low production cost, strong flexibility and controllable environment. Using the difference in wettability between porous substrates for water and oily liquids, researchers have developed various types of porous substrate oil-water separation membranes. Common ones include polyvinylidene fluoride (PVDF) membranes, polytetrafluoroethylene (PTFE) membranes, polypropylene (PP) membranes, fabric membranes, metal mesh membranes, etc. Fabric substrates have attracted widespread attention due to their low cost, large-area preparation, and high separation rate. However, when too much liquid accumulates on the membrane surface and generates a large pressure, the porous membrane is easily penetrated by hydraulic pressure, causing non-wetting liquids to penetrate the micropores and causing the separation membrane to lose its oil-water separation ability. Researchers have found that Janus membrane materials with asymmetric wettability have more obvious advantages in oil-water separation. They use the difference in wettability of different surfaces on both sides of the membrane material to water and oil to achieve high separation efficiency and reusability. Therefore, they are known as "good candidate materials for oil / water separation." The Janus membrane, which is composed of a superhydrophilic / underwater superoleophobic layer and an oleophilic / superhydrophobic layer, can separate heavy oil / water and light oil / water mixtures. One side of the Janus membrane has superhydrophilic / underwater superoleophobic properties, and water can quickly penetrate and pass through the membrane on this side, while oil droplets will be repelled; the other side is oleophilic / hydrophobic, which has a good affinity for oil, allowing oil to selectively pass through this side, while preventing excessive water from being adsorbed on this side, achieving a higher permeability. However, although the current Janus membrane material has a relatively high oil-water separation efficiency and flux, it also faces the problem of being punctured under high hydraulic pressure and losing its oil-water separation ability. Summary of the invention

[0004] The purpose of the present invention is to overcome the deficiencies of the prior art and to provide a Janus oil-water separation membrane and a preparation method and application thereof.

[0005] To achieve the above objectives, the technical solution adopted by the present disclosure is as follows: In a first aspect, the present invention provides a method for preparing a Janus oil-water separation membrane, comprising the following steps:

[0006] After first activating the first fabric with plasma, placing the first fabric in a silane coupling agent solution and reacting at 50-70° C. to obtain a second fabric with ethoxy end-capping;

[0007] placing the second fabric in a hydroxy-terminated polydimethylsiloxane solution until the surface of the second fabric is completely wetted by the polydimethylsiloxane solution, taking it out, removing the organic solvent, and heating and curing it to obtain a hydrophobically modified fabric;

[0008] The first surface of the hydrophobic modified fabric is second activated by plasma, and then a hydrophilic coating is coated on the first surface after the second activation to obtain a Janus oil-water separation membrane; wherein the hydrophilic coating comprises nano-silica particles and tetraethyl orthosilicate.

[0009] The present invention uses plasma to activate the first fabric, which can form irregular nano-scale and micron-scale pits and protrusions on the surface of the first fabric, with obvious rough texture and undulations. On the one hand, the micro-nano structure increases the roughness of the surface of the first fabric, which is beneficial to the subsequent hydrophobic treatment; on the other hand, due to the presence of the micro-nano structure, when water droplets contact the hydrophobically modified surface, the air stored in the grooves of the rough surface prevents the water droplets from completely infiltrating, thereby improving the hydrophobic properties of the surface.

[0010] The present invention performs hydrophobic modification on the first fabric after the first activation, and forms a liquid-like super-slippery coating on the surface of the first fabric. The solid-liquid interface of the liquid-like super-slippery coating has highly mobile polymer chains, thereby providing excellent dynamic liquid repellency; the smooth liquid-like super-slippery coating can reduce the flow resistance of the liquid on the surface of the Janus oil-water separation membrane, so that water can pass through the Janus oil-water separation membrane more quickly, thereby increasing the separation flux of the Janus oil-water separation membrane; at the same time, the liquid-like properties of the liquid-like super-slippery coating reduce the interfacial tension between oil and water on the surface of the Janus oil-water separation membrane, making the separation between oil and water easier.

[0011] The present invention activates one of the surfaces of the hydrophobically modified fabric obtained after hydrophobic modification and grafts hydrophilic nanoparticles to obtain a Janus oil-water separation membrane with asymmetric wettability. The obtained Janus oil-water separation membrane can achieve excellent unidirectional liquid transmission and has a good separation effect on oil-water mixtures, with a separation rate of 46000L / m 2 *h and the separation efficiency can reach more than 99%; the hydrophilic nanoparticle layer on the surface of the Janus oil-water separation membrane can hinder the penetration of oily liquid in the micropores of the Janus oil-water separation membrane under high hydraulic pressure, thereby improving the hydraulic resistance of the Janus oil-water separation membrane.

[0012] There are a large number of silanol groups in the silanol groups generated by the hydrolysis of ethyl orthosilicate and in the silicon-oxygen network structure finally formed. These silanol groups can undergo condensation reactions with active functional groups such as hydroxyl groups generated on the surface after plasma treatment to form covalent bonds. The formation of such covalent bonds greatly enhances the chemical bonding force between the nanoparticles and the plasma-treated surface, allowing the nanoparticles to be firmly attached to the surface and not easily fall off, thereby achieving a stable hydrophilic modification effect.

[0013] In some embodiments, in the hydrophilic solution, the mass concentration of the nano-silica particles is 1-3 g / mL, and the mass concentration of the tetraethyl orthosilicate is 3-5 g / mL.

[0014] For example, in different embodiments, the mass concentration of the nano-silicon dioxide particles may be, but is not limited to, 1 g / mL, 1.2 g / mL, 1.5 g / mL, 1.7 g / mL, 2 g / mL, 2.3 g / mL, 2.5 g / mL, 2.8 g / mL, 3 g / mL;

[0015] For example, in different embodiments, the mass concentration of the tetraethyl orthosilicate can be but is not limited to 3 g / mL, 3.2 g / mL, 3.5 g / mL, 3.7 g / mL, 4 g / mL, 4.3 g / mL, 4.5 g / mL, 4.8 g / mL, and 5 g / mL.

[0016] Specifically, the preparation method of the hydrophilic solution is: adding nano silicon dioxide particles and tetraethyl orthosilicate into ethanol, stirring evenly, to obtain the hydrophilic solution.

[0017] In the present invention, the contents of nano-silica particles and ethyl orthosilicate have a great influence on the oil-water separation efficiency and hydraulic resistance of the Janus oil-water separation membrane. If the contents of nano-silica particles and / or ethyl orthosilicate are too little, the oil-water separation efficiency will be reduced, because insufficient nano-silica cannot form an effective separation structure, insufficient ethyl orthosilicate makes the membrane hydrophilicity uneven, and the hydraulic resistance is reduced, too little nano-silica cannot enhance the membrane structure, and too little ethyl orthosilicate makes the network support weak; if the contents of nano-silica particles and ethyl orthosilicate are too high, the water separation efficiency will be reduced, nano-silica will agglomerate to block the channel, too much ethyl orthosilicate will cause an imbalance in hydrophilicity and hydrophobicity, and the hydraulic resistance will be reduced, nano-silica will agglomerate into stress points, and ethyl orthosilicate will make the structure too dense and easy to break.

[0018] In some embodiments, the average particle size of the nano-silica particles is 20-50 nm, for example, but not limited to, 20 nm, 25 nm, 30 nm, 35 nm, 40 nm, 45 nm, and 50 nm.

[0019] Specifically, the preparation method of the hydroxy-terminated polydimethylsiloxane solution is: adding hydroxy-terminated polydimethylsiloxane (HO-PDMS) into an organic solvent, stirring evenly, to obtain a hydroxy-terminated polydimethylsiloxane solution; wherein the organic solvent is at least one of n-hexane, n-heptane, toluene, and petroleum ether.

[0020] In some embodiments, in the hydroxyl-terminated polydimethylsiloxane solution, the mass concentration of the hydroxyl-terminated polydimethylsiloxane is 1-10 g / mL, for example, but not limited to 1 g / mL, 2 g / mL, 3 g / mL, 4 g / mL, 5 g / mL, 6 g / mL, 7 g / mL, 8 g / mL, 9 g / mL, and 10 g / mL.

[0021] In some embodiments, the heating curing is performed at a temperature of 70-100° C. and a time of 1-3 hours.

[0022] For example, in different embodiments, the temperature of the heating and curing may be, but is not limited to, 70°C, 75°C, 80°C, 85°C, 90°C, 95°C, or 100°C; and the time of the heating and curing may be 1 hour, 2 hours, or 3 hours.

[0023] In some embodiments, the silane coupling agent is 3-aminopropyltriethoxysilane (APTES) and / or vinyltrimethoxysilane (VTMS).

[0024] Specifically, the preparation method of the silane coupling agent solution is: adding the silane coupling agent into ethanol and stirring evenly to obtain the silane coupling agent solution.

[0025] Specifically, in the silane coupling agent solution, the mass of the silane coupling agent is 3-8 g / mL, for example, but not limited to 3 g / mL, 4 g / mL, 5 g / mL, 6 g / mL, 7 g / mL, and 8 g / mL.

[0026] In some embodiments, the activation parameters of the first activation and the second activation are independently: plasma voltage is 500-900V, gas flow rate is 1-10 sccm, and power duty cycle is 60-100%.

[0027] As in different embodiments, the plasma voltage may be, but is not limited to, 500V, 600V, 700V, 800V, 900V;

[0028] For example, in different embodiments, the gas flow rate may be, but is not limited to, 1 sccm, 2 sccm, 3 sccm, 4 sccm, 5 sccm, 6 sccm, 7 sccm, 8 sccm, 9 sccm, 10 sccm;

[0029] For example, in different implementations, the power duty cycle may be, but is not limited to, 60%, 70%, 80%, 90%, or 100%.

[0030] The present invention adjusts the micro-nano structure and roughness of the first fabric surface by controlling the activation parameters of the first activation, such as plasma voltage, gas flow rate and power duty cycle. The first activation is performed within the above activation parameter range, which can effectively improve the oil-water separation efficiency of the Janus oil-water separation membrane.

[0031] The present invention increases the surface active groups on one side of the hydrophobically modified fabric by controlling the activation parameters of the second activation, such as plasma voltage, gas flow rate and power duty cycle, which is beneficial to the subsequent grafting of hydrophilic nano-silica particles.

[0032] In order to avoid the influence of impurities on the fabric on the first activation, the fabric needs to be cleaned before the first activation. The specific steps are: ultrasonically clean the fabric with ethanol and deionized water in turn, then wash it with distilled water, and dry it to obtain the first fabric.

[0033] The first fabric herein refers to the fabric that has been subjected to the above cleaning treatment.

[0034] In order to prevent the second activation from affecting the hydrophobic modified layer on one surface of the hydrophobic modified fabric, the hydrophobic modified fabric needs to be single-sided protected before the second activation. The steps of single-sided protection and second activation are: one side of the hydrophobic modified fabric is attached to plastic or cardboard, and the other side is exposed to a plasma reaction chamber for the second activation.

[0035] In some embodiments, the organic solvent is at least one of n-hexane, n-heptane, toluene, and petroleum ether.

[0036] In some embodiments, the first fabric is at least one of a cotton fabric and a linen fabric.

[0037] In a second aspect, a Janus oil-water separation membrane is provided. The Janus oil-water separation membrane is prepared by the preparation method of the Janus oil-water separation membrane.

[0038] In a third aspect, the application of the Janus oil-water separation membrane in oil recovery is provided.

[0039] Compared with the prior art, the beneficial effects of the present invention are as follows: the present invention performs hydrophobic modification and hydrophilic modification in sequence after plasma activation on the first fabric, thereby obtaining a Janus oil-water separation membrane with asymmetric wettability. The obtained Janus oil-water separation membrane can achieve excellent unidirectional liquid transmission and has a good separation effect on oil-water mixture, with a separation rate of 46000L / m 2*h and the separation efficiency can reach more than 99%; the hydrophilic nanoparticle layer on the surface of the Janus oil-water separation membrane can hinder the penetration of oily liquid in the micropores of the Janus oil-water separation membrane under high hydraulic pressure, thereby improving the hydraulic resistance of the Janus oil-water separation membrane. BRIEF DESCRIPTION OF THE DRAWINGS

[0040] Figure 1 is a SEM image of the first cotton fabric in Example 1;

[0041] Figure 2 This is a SEM image of the first activated cotton fabric in Example 1 magnified 6000 times;

[0042] Figure 3 This is a SEM image of the first activated cotton fabric in Example 1 magnified 10,000 times;

[0043] Figure 4 This is a water contact angle diagram of the front side of the Janus oil-water separation membrane obtained in Example 1;

[0044] Figure 5 This is a water contact angle diagram of the reverse side of the Janus oil-water separation membrane obtained in Example 1;

[0045] Figure 6 This is the underwater oil contact angle diagram of the front side of the Janus oil-water separation membrane obtained in Example 1. DETAILED DESCRIPTION

[0046] In order to facilitate understanding of the present disclosure, the present disclosure will be described more fully below. However, the present disclosure can be implemented in many different forms and is not limited to the embodiments described herein. On the contrary, the purpose of providing these embodiments is to make the understanding of the disclosure of the present disclosure more thorough and comprehensive.

[0047] In order to further illustrate the present invention, the Janus oil-water separation membrane provided by the present invention and its preparation method and application are described in detail below in conjunction with the accompanying drawings and examples, but they should not be construed as limiting the scope of protection of the present invention.

[0048] Example 1

[0049] This embodiment provides a method for preparing a Janus oil-water separation membrane, comprising the following steps:

[0050] S1: The first cotton fabric is suspended and fixed in a plasma chamber, and when the vacuum is evacuated to 5 Pa, 5 sccm of O2 is introduced, the plasma power is 800 V, the power duty cycle is 90%, and the first activated cotton fabric is taken out after reacting for 10 minutes;

[0051] S2: The first activated cotton fabric was immersed in an APTES ethanol solution with a mass concentration of 5 g / mL and reacted at a temperature of 60° C. for 2 h. The fabric obtained by the reaction was rinsed with ethanol and dried under a nitrogen atmosphere to obtain a second cotton fabric.

[0052] S3: The second cotton fabric was immersed in a HO-PDMS n-hexane solution with a mass concentration of 1 g / mL for 2 min, and then the completely soaked fabric was taken out and naturally dried. The obtained fabric was cured in an oven at a temperature of 80°C for 2 h to obtain a hydrophobically modified cotton fabric;

[0053] S4; After the hydrophobic modified fabric is protected on one side, it is placed in a plasma chamber, and when the vacuum is evacuated to 5Pa, 7sccm of O2 is introduced, the plasma power is 600V, the power duty cycle is 90%, and the reaction is taken out after 10min to obtain a second activated cotton fabric;

[0054] S5: Spray the hydrophilic solution on the activated surface of the second activated cotton fabric, let it stand for 2 hours, then wash with deionized water, and then dry in an oven at 40°C for 30 minutes to obtain a Janus oil-water separation membrane; in the hydrophilic solution, the mass concentration of nano-silica particles is 1.5 g / mL, the average particle size of the nano-silica particles is 25 nm, and the mass concentration of tetraethyl orthosilicate is 5 g / mL.

[0055] Example 2

[0056] This embodiment provides a method for preparing a Janus oil-water separation membrane, comprising the following steps:

[0057] S1: The first fabric is suspended and fixed in a plasma chamber, and when the vacuum is evacuated to 5 Pa, 1 sccm of O2 is introduced, the plasma power is 800 V, the power duty cycle is 90%, and the fabric is taken out after reacting for 15 minutes to obtain a first activated fabric;

[0058] S2: The first activated fabric was immersed in an APTES ethanol solution with a mass concentration of 6 g / mL and reacted at a temperature of 50° C. for 3 h. The fabric obtained by the reaction was rinsed with ethanol and dried under a nitrogen atmosphere to obtain a second fabric.

[0059] S3: The second fabric was immersed in a HO-PDMS n-hexane solution with a mass concentration of 10 g / mL for 2 min, and then the completely immersed fabric was taken out and naturally dried. The obtained fabric was cured in an oven at a temperature of 100° C. for 2 h to obtain a hydrophobic modified fabric;

[0060] S4; After the hydrophobic modified fabric is protected on one side, it is placed in a plasma chamber, and when the vacuum is evacuated to 5Pa, 10sccm of O2 is introduced, the plasma power is 800V, the power duty cycle is 60%, and the reaction is taken out after 10min to obtain a second activated fabric;

[0061] S5: Spray the hydrophilic solution on the activated surface of the second activated fabric, let it stand for 2 hours, then wash with deionized water, and then dry in an oven at a temperature of 40°C for 30 minutes to obtain a Janus oil-water separation membrane; in the hydrophilic solution, the mass concentration of nano-silica particles is 3 g / mL, the average particle size of the nano-silica particles is 40 nm, and the mass concentration of tetraethyl orthosilicate is 5 g / mL.

[0062] Example 3

[0063] This embodiment provides a method for preparing a Janus oil-water separation membrane, comprising the following steps:

[0064] S1: The first fabric is suspended and fixed in a plasma chamber, and when the vacuum is evacuated to 5 Pa, 10 sccm of O2 is introduced, the plasma power is 500 V, the power duty cycle is 90%, and the fabric is taken out after reacting for 10 minutes to obtain a first activated fabric;

[0065] S2: The first activated fabric was immersed in an APTES ethanol solution with a mass concentration of 5 g / mL and reacted at a temperature of 70° C. for 1 h. The fabric obtained by the reaction was rinsed with ethanol and dried under a nitrogen atmosphere to obtain a second fabric.

[0066] S3: The second fabric was immersed in a HO-PDMS n-hexane solution with a mass concentration of 5 g / mL for 2 min, and then the completely immersed fabric was taken out and naturally dried. The obtained fabric was cured in an oven at a temperature of 80°C for 2 h to obtain a hydrophobic modified fabric;

[0067] S4; After the hydrophobic modified fabric is protected on one side, it is placed in a plasma chamber, and when the vacuum is evacuated to 5Pa, 7sccm of O2 is introduced, the plasma power is 600V, the power duty cycle is 90%, and the reaction is removed after 10min to obtain a second activated fabric;

[0068] S5: Spray the hydrophilic solution on the activated surface of the second activated fabric, let it stand for 2 hours, then wash with deionized water, and then dry in an oven at 40°C for 30 minutes to obtain a Janus oil-water separation membrane; in the hydrophilic solution, the mass concentration of nano-silica particles is 1 g / mL, the average particle size of the nano-silica particles is 50 nm, and the mass concentration of tetraethyl orthosilicate is 3 g / mL.

[0069] Comparative Example 1

[0070] This comparative example provides a method for preparing a Janus oil-water separation membrane. The difference between the method for preparing a Janus oil-water separation membrane in this comparative example and that in Example 1 is that step S1 is not performed, and the remaining steps and parameters are exactly the same.

[0071] Comparative Example 2

[0072] This comparative example provides a method for preparing a Janus oil-water separation membrane. The difference between the method for preparing a Janus oil-water separation membrane in this comparative example and that in Example 1 is that steps S2 and S3 are not performed, and the remaining steps and parameters are exactly the same.

[0073] Comparative Example 3

[0074] This comparative example provides a method for preparing a Janus oil-water separation membrane. The difference between the method for preparing a Janus oil-water separation membrane in this comparative example and that in Example 1 is that steps S4 and S5 are not performed, and the remaining steps and parameters are exactly the same.

[0075] Comparative Example 4

[0076] This comparative example provides a method for preparing a Janus oil-water separation membrane. The difference between the method for preparing a Janus oil-water separation membrane in this comparative example and that in Example 1 is that step S5 is not performed, and the remaining steps and parameters are exactly the same.

[0077] Comparative Example 5

[0078] This comparative example provides a method for preparing a Janus oil-water separation membrane. The difference between the method for preparing a Janus oil-water separation membrane in this comparative example and that in Example 1 is that the hydrophilic solution in step S5 does not contain ethyl orthosilicate, and the remaining steps and parameters are exactly the same.

[0079] Performance Testing

[0080] The Janus oil-water separation membranes obtained in the examples and comparative examples were tested for performance, and the testing method was as follows:

[0081] (1) Water contact angle: The static contact angle of the sample was tested using a contact angle meter, and the drop size used was 5 μl;

[0082] (2) Underwater oil contact angle: The underwater oil contact angle of the sample was tested using a contact angle meter. The sample was placed in a deionized water environment, and then a 5 μl oil droplet was dropped on the sample surface;

[0083] (3) Oil-water separation efficiency: The separation efficiency is calculated based on the change in the weight of the oil phase and the water phase before and after the oil-water mixture passes through the separation membrane;

[0084] (4) Hydraulic breakdown height: Oil-water mixture is continuously added to a rectangular container with a separation membrane fixed in the middle, and the height of the liquid at which the separation membrane is broken down is recorded; the higher the hydraulic breakdown height, the better the hydraulic resistance of the oil-water separation membrane.

[0085] Test results such as Figure 1-6 And as shown in Table 1.

[0086] Table 1

[0087]

[0088] Note: The front side in Table 1 refers to the hydrophilic side of the nano-silica particles of the Janus oil-water separation membrane, and the back side refers to the hydrophobic modified side of the Janus oil-water separation membrane.

[0089] It can be seen from Table 1 that the Janus oil-water separation membrane of the present invention has a high oil-water separation efficiency and hydraulic breakdown height.

[0090] from Figure 1 is a SEM image of the first cotton fabric in the present invention; Figure 2 This is a SEM image of the first activated cotton fabric in Example 1 magnified 6000 times, Figure 3 This is a SEM image of the first activated cotton fabric in Example 1 magnified 10,000 times;

[0091] from Figure 1-3 It can be seen that the surface of the first cotton fabric is relatively flat and smooth, with a texture formed by natural interweaving of fibers, and the fibers appear to be arranged relatively regularly; the first activated cotton fabric forms irregular nano- and micro-scale pits and protrusions, with obvious rough texture and undulations.

[0092] Figure 4 This is a water contact angle diagram of the front side of the Janus oil-water separation membrane obtained in Example 1; Figure 5 This is a water contact angle diagram of the reverse side of the Janus oil-water separation membrane obtained in Example 1; Figure 6 This is the underwater oil contact angle diagram of the front side of the Janus oil-water separation membrane obtained in Example 1. Figure 4-6 It can be seen that the Janus oil-water separation membrane of the present invention has obvious asymmetric wettability.

[0093] Finally, it should be noted that the above embodiments are used to illustrate the technical solution of the present disclosure rather than to limit the protection scope of the present disclosure. Although the present disclosure has been described in detail with reference to the preferred embodiments, those skilled in the art should understand that the technical solution of the present disclosure can be modified or replaced by equivalents without departing from the essence and scope of the technical solution of the present disclosure.

Claims

1. A method for preparing a Janus oil-water separation membrane, characterized in that: The following steps are involved: The first fabric is first activated by plasma, and then placed in a silane coupling agent solution to react at 50-70° C. to obtain a second fabric; placing the second fabric in a hydroxy-terminated polydimethylsiloxane solution until the surface of the second fabric is completely wetted by the polydimethylsiloxane solution, taking it out, removing the organic solvent, and heating and curing it to obtain a hydrophobically modified fabric; The first surface of the hydrophobic modified fabric is second activated by plasma, and then a hydrophilic coating is coated on the first surface after the second activation to obtain a Janus oil-water separation membrane; wherein the hydrophilic coating comprises nano-silica particles and tetraethyl orthosilicate.

2. The method for preparing a Janus oil-water separation membrane according to claim 1, wherein: In the hydrophilic solution, the mass concentration of the nano-silicon dioxide particles is 1-3 g / mL, and the mass concentration of the tetraethyl orthosilicate is 3-5 g / mL.

3. The method for preparing the Janus oil-water separation membrane according to claim 1, characterized in that: The average particle size of the nano silicon dioxide particles is 20-50 nm.

4. The method for preparing a Janus oil-water separation membrane according to claim 1, wherein: In the hydroxy-terminated polydimethylsiloxane solution, the mass concentration of the hydroxy-terminated polydimethylsiloxane is 1-10 g / mL.

5. The method for preparing the Janus oil-water separation membrane according to claim 1, characterized in that: The temperature of the heating curing is 70-100° C. and the time is 1-3 hours.

6. The method for preparing a Janus oil-water separation membrane according to claim 1, wherein: The silane coupling agent is 3-aminopropyltriethoxysilane and / or vinyltrimethoxysilane.

7. The method for preparing a Janus oil-water separation membrane according to claim 1, characterized in that: The activation parameters of the first activation and the second activation are independent of each other: the plasma voltage is 500-900V, the gas flow rate is 1-10sccm, and the power duty cycle is 60-100%.

8. The method for preparing a Janus oil-water separation membrane according to claim 1, characterized in that: The organic solvent is at least one of n-hexane, n-heptane, toluene and petroleum ether.

9. A Janus oil-water separation membrane, characterized in that: The Janus oil-water separation membrane is prepared by the preparation method of the Janus oil-water separation membrane according to any one of claims 1 to 8.

10. Use of the Janus oil-water separation membrane as claimed in claim 9 in oil product recovery.

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