Conductive Janus membrane, preparation method thereof, and application thereof in treating surfactant-containing brine by electric field-assisted membrane distillation

Abstract

The present invention provides a conductive Janus membrane, a preparation method thereof, and its application in electric field-assisted membrane distillation to treat surfactant-containing brine. Modified materials Zr-MOF, graphene oxide, and nanosilver are fixed to a PTFE hydrophobic base membrane via a crosslinking agent, thereby preparing a novel conductive Janus membrane that resists membrane wetting and exhibits excellent anti-wetting properties. The membrane was tested using a sodium chloride feed solution containing a high concentration of anionic surfactant. During operation, direct current was intermittently passed to negatively charge the membrane surface. Under long-term operation conditions of 48 hours, a desalination rate of up to 99.9% was still achieved, and the flux was maintained at 21.2 L / (m 2 h), the conductivity on the permeate side was kept below 5.0 μS / cm.

Description

Technical Field

[0001] The present invention belongs to the technical field of water treatment, and particularly relates to a novel Janus membrane prepared from a composite material of UiO-66-NH2, GO and nanosilver, a preparation method thereof, and an application thereof in treating brine containing a high concentration of surfactant by electric field-assisted membrane distillation. Background Art

[0002] Membrane distillation (MD) is an emerging water treatment process that has attracted widespread attention because of its ability to use clean, low-grade thermal energy and its high desalination rate (theoretically up to 100%).

[0003] Surfactants are among the most common contaminants in wastewater from the cosmetics, pharmaceutical, food, and oil and gas industries. The presence of surfactants reduces the surface tension of the solution, allowing their hydrophobic tails to adhere to hydrophobic membranes and penetrate into the pores, exposing their hydrophilic heads. This disrupts the membrane's hydrophobicity, reduces the liquid entry pressure (LEP), and ultimately renders the pores hydrophilic, leading to irreversible wetting. Consequently, recent MD research has focused on modifying membrane surfaces with novel materials to delay membrane wetting.

[0004] Graphene oxide (GO) exhibits various attractive properties due to its abundant oxygen-containing functional groups, such as excellent mechanical stability, a two-dimensional structure, a negatively charged surface, good compatibility with polymers, and hydrophilicity. It has been demonstrated to be an effective antifouling material and a promising modifier for use in mechanical dynamics (MD). However, when GO, with its two-dimensional layered structure, is used as the sole modifying material, a narrow interlayer spacing between GO nanosheets often results, resulting in a reduced flux of pure water.

[0005] Among various MOFs, UiO-66-NH2 is considered an ideal material for increasing the interlayer spacing of GO because it is built on a zirconium terephthalate framework, forming a strong Zr-O coordination bond. This helps improve stability under chemical, hydrous, and thermal conditions. However, relying solely on a membrane surface coating can only improve the membrane's anti-wetting effect in a short period of time, but it cannot ensure long-term operation. Summary of the Invention

[0006] The present invention aims to provide a conductive Janus membrane and a preparation method thereof. The modified materials Zr-MOF (UiO-66-NH2), graphene oxide (GO) and nanosilver are fixed on a polytetrafluoroethylene (PTFE) hydrophobic base membrane through a crosslinking agent, thereby preparing a novel GO / UiO-66-NH2 / Silver Janus film that resists membrane wetting, referred to as GUS Janus membrane or Janus membrane.

[0007] Another object of the present invention is to provide the application of a conductive Janus membrane in electric field-assisted membrane distillation to treat brine containing surfactants. The hydrophobic membrane has good anti-wetting properties. By applying an external voltage, the electrostatic repulsion of the membrane is increased, and it is easier to maintain stable performance over a long period of time. It is used to treat wastewater containing high concentrations of surfactants.

[0008] The specific technical solutions of the present invention are as follows:

[0009] A method for preparing a conductive Janus film comprises the following steps:

[0010] 1) Preparation of Zr-MOF materials;

[0011] 2) Preparation of a conductive Janus membrane: Zr-MOF material was weighed and ultrasonically dispersed in anhydrous ethanol. After mixing, a polydopamine solution was added. After stirring, a graphene oxide solution and a polyvinyl alcohol solution were added and ultrasonically treated. Finally, a nanosilver solution was added. After ultrasonic stirring, the mixed solution was added to a vacuum filtration device fixed with a PTFE membrane and vacuum filtered. After drying, a conductive GO / UiO-66-NH2 / Silver Janus film was obtained, hereinafter referred to as a conductive GUS Janus membrane or a conductive Janus membrane.

[0012] The Zr-MOF material in step 1) is preferably UiO-66-NH2;

[0013] Step 1) specifically comprises: mixing an amino-functionalized organic ligand, a zirconium salt and an organic acid in a solvent, heating the mixture for reaction, and preparing UiO-66-NH2.

[0014] The molar ratio of the amino-functionalized organic ligand, the zirconium salt and the organic acid is 1:1:100;

[0015] The concentration of the amino-functionalized organic ligand in the solvent is 0.02M;

[0016] The amino-functionalized organic ligand is selected from 2-aminoterephthalic acid;

[0017] The zirconium salt is selected from zirconium chloride;

[0018] The organic acid is selected from glacial acetic acid;

[0019] The solvent is selected from N,N-dimethylformamide.

[0020] The heating reaction conditions are: reaction at 120°C for 24h;

[0021] In step 1), after heating reaction, the obtained crude product was washed with N,N-dimethylformamide and ethanol, collected and dried in vacuo at 70° C. for 12 h.

[0022] In step 2), the mass ratio of the Zr-MOF material, the graphene oxide in the graphene oxide solution, and the nanosilver in the nanosilver solution is 1:1:2;

[0023] The dosage ratio of the Zr-MOF material and the polydopamine solution is: 0.025-0.05:1 mg / mL;

[0024] The dosage ratio of the Zr-MOF material and the polyvinyl alcohol solution is: 0.025-0.05:0.5 mg / mL;

[0025] The concentration of the polydopamine solution is 1 g / L, and the preparation method thereof is as follows: dopamine and Tris solution are dissolved in deionized water and mixed uniformly.

[0026] The graphene oxide solution has a concentration of 0.1 g / L and is a purchased graphene oxide solution;

[0027] The concentration of the polyvinyl alcohol solution is 0.1 g / L, and the preparation method is as follows: weigh the required amount of polyvinyl alcohol solid, add pure water, and stir and heat at 95-98° C. to melt the solid to form a polyvinyl alcohol solution;

[0028] The concentration of the nanosilver solution was 5 mg / mL and was purchased from a commercial manufacturer.

[0029] The ultrasonic dispersion and mixing in step 2) refers to ultrasonic dispersion for 15 minutes;

[0030] The ultrasonic treatment refers to ultrasonic treatment for 15 minutes;

[0031] The drying refers to drying at room temperature for 2 hours;

[0032] In step 2), the vacuum filtration is performed using a PTFE membrane as filter paper. The liquid in the mixed solution is filtered out through the filter membrane, and the substances in the mixed solution are loaded on the PTFE membrane to achieve its modification.

[0033] The present invention provides a conductive Janus film, which is prepared by adopting the above method.

[0034] The conductive Janus membrane provided by the present invention is used in the electric field assisted membrane distillation treatment of brine containing surfactants. The specific application method is as follows:

[0035] A direct contact membrane distillation device is used, equipped with a DC power supply, with a titanium sheet as a conductor and a conductive Janus membrane as the negative electrode of the power supply to treat brine containing surfactant.

[0036] The surfactant-containing saline is a saline containing 1 M sodium chloride and 1 mM sodium lauryl sulfate.

[0037] The conductive Janus membrane can still maintain a 99.9% desalination rate after 48 hours of operation, making the permeate side conductivity below 15.0 μS / cm and the permeate flux maintained at 21.2 L / (m 2 ·h).

[0038] Compared with the prior art, the technical solution of the present invention has the following beneficial technical effects: the amount of material used for hydrophobic membrane modification is very small, only 0.05 mg / cm 2 , significantly reducing material input. The conductive GUS Janus membrane provided by the present invention exhibits excellent anti-wetting properties and can be used as a potential modification method for wastewater containing high concentrations of surfactants. The novel conductive Janus membrane prepared by the present invention and the electric field-assisted membrane distillation process can become a very promising resource-based treatment method for surfactant-containing wastewater, replacing the MD process, which plays an important role in promoting its application. BRIEF DESCRIPTION OF THE DRAWINGS

[0039] Figure 1 The X-ray powder diffraction patterns of Zr-MOF (UiO-66-NH2), PTFE, GO, nanosilver and conductive Janus film prepared in the practice of the present invention are shown;

[0040] Figure 2 This is the infrared spectrum of Zr-MOF (UiO-66-NH2), PTFE, GO, nanosilver and conductive Janus film prepared in the practice of the present invention;

[0041] Figure 3 1 is a SEM image of UiO-66-NH2, PTFE, nanosilver and conductive Janus membrane prepared in the practice of the present invention;

[0042] Figure 4 It is a schematic diagram of the operation flow of the membrane distillation device of the present invention;

[0043] Figure 5 The conductivity and flux diagrams of the conductive Janus membrane under electric field assistance, the conductive Janus membrane without electric field assistance, and the original PTFE membrane are shown in FIG. PTFE in the figure is the original PTFE membrane, G2M2 refers to the conductive Janus membrane without electric field assistance, and GUS refers to the conductive Janus membrane with electric field assistance.

[0044] Figure 6 is the interaction energy distribution between 1 mM SDS salt solution and different membranes;

[0045] Figure 7Schematic diagram of the anti-wetting mechanism, a is a schematic diagram of the wetting mechanism of the original unmodified PTFE when treating a brine containing a surfactant, b is a schematic diagram of the anti-wetting mechanism of the modified conductive Janus membrane of the present invention when treating a brine containing a surfactant;

[0046] Figure 8 A schematic diagram of the preparation of the present invention;

[0047] Figure 9 The comparison of four membranes in the comparative experiment is shown in Figure 2. DETAILED DESCRIPTION

[0048] Example 1

[0049] A method for preparing a conductive Janus film comprises the following steps:

[0050] 1) Preparation of Zr-MOF Material: First, a mixed solution of zirconium chloride:2-aminoterephthalic acid:glacial acetic acid at a molar ratio of 1:1:100 was prepared: zirconium chloride (233.0 mg, 1 mmol) and 2-aminoterephthalic acid (181.2 mg, 1 mmol) were dissolved in N,N-dimethylformamide (50 mL). Then, 6.0 g of glacial acetic acid (100 mmol) was added to the solution. The mixed solution was homogenized with the aid of ultrasonication for 30 minutes and then stirred at room temperature for 2 hours. The clear mixed solution, free of solid residue, was then transferred to a 100 mL PTFE-lined reactor and reacted at 120°C for 24 hours. The solid and liquid were separated by centrifugation and washed three times with N,N-dimethylformamide and anhydrous ethanol, respectively, to completely remove any unreacted solids. Finally, the product obtained after washing was dried in a vacuum drying oven at 70°C for 24 hours to obtain the final product Zr-MOF material (UiO-66-NH2).

[0051] 2) Preparation of a conductive Janus membrane: 0.2 g dopamine and 25 μL Tris solution were dissolved in 200 mL deionized water to prepare a polydopamine solution with a concentration of 1 g / L; 100 mL of anhydrous ethanol solution of Zr-MOF material was ultrasonically dispersed for 15 min, containing 0.05 mg Zr-MOF material, added to 1 mL of polydopamine solution, and ultrasonically dispersed and mixed evenly for 15 minutes to obtain a suspension. Then, a graphene oxide solution containing 0.05 mg of graphene oxide and a concentration of 0.1 g / L and 0.5 mL of a polyvinyl alcohol solution with a concentration of 0.1 g / L were added to the above-mentioned polydopamine-modified Zr-MOF material suspension and ultrasonically treated for 15 minutes, and then a nanosilver solution containing 0.1 mg of nanosilver and a concentration of 5 mg / mL was added and ultrasonically stirred for 15 minutes. The mixed solution was added to a vacuum filtration device for fixing a PTFE membrane, vacuum filtered, and dried to obtain a conductive Janus membrane. The prepared membrane was dried at room temperature for 2 hours before use.

[0052] Figure 1 The XRD patterns of the prepared conductive Janus membrane, nanosilver, GO and Zr-MOF materials, and the original PTFE membrane are shown. Two diffraction peaks of the Zr-MOF material UiO-66-NH2 can be seen at 2θ = 7.32° and 8.46°, corresponding to the (111) and (200) crystal planes, respectively. This is consistent with the results of existing research reports, indicating that the synthesis of UiO-66-NH2 has been successfully achieved. The characteristic diffraction peak of PTFE appears at 2θ = 18.1°, which is consistent with the standard pattern PDF#54-1595. The diffraction peaks in the range of 2θ = 20-30° are related to the cellulose in the PTFE membrane support layer. In the conductive Janus membrane, only a weak diffraction peak of UiO-66-NH2 can be seen at 2θ = 7.32°. The reason for this weak diffraction peak is that a very small amount of modified material is used.

[0053] Figure 2 The FTIR spectra of the conductive Janus film, nanosilver, GO and Zr-MOF materials UiO-66-NH2 and the original PTFE membrane are shown. Since the ligand of UiO-66-NH2 contains both carboxylic acid and aromatic groups, the FTIR spectrum at 1574 cm -1 The peaks observed at 1505 cm are associated with symmetric and asymmetric CO stretching bonds. -1 The weak absorption peaks at 1378 and 1100 cm-1 are considered to be typical vibrations of C=C stretching in the benzene ring of BDC ligand. -1 The peaks found at 769 and 718 cm correspond to the C=OH group and C-O-C stretching vibration of GO, respectively. -1 The band is believed to be a mixture of OH and CH bending vibration modes, with the Zr-O mode at a low frequency.

[0054] Figure 3 1 is a SEM image of UiO-66-NH2, PTFE, nanosilver and conductive Janus membrane prepared in the practice of the present invention; Figure 3 Figure a clearly shows the SEM image of UiO-66-NH2, in which a very regular octahedral structure can be observed, with a uniform size between 100-150 nm. Figure 3 Middle bc shows that the PTFE membrane itself is filamentous and has a large micron-scale pore structure. Figure 3 In the middle (d), the linear structure of the nanosilver material can be clearly seen, and the cross section is about 50nm. Figure 3 Figure ef (center) shows an SEM image of a conductive Janus film. It shows the uniform distribution of UiO-66-NH2 and GO, which improves the overall performance of the film. The interpenetration of silver nanoparticles increases the overall conductivity. Because GO encapsulates the UiO-66-NH2 crystals, combined with the cross-sectional image, it can be seen that UiO-66-NH2 is well embedded in the GO layers, increasing the interlayer spacing between the GO layers.

[0055] Example 2

[0056] Application of a conductive Janus membrane in electric field assisted membrane distillation to treat brine containing surfactant, specifically:

[0057] The schematic diagram of the laboratory-scale direct contact membrane distillation (DCMD) apparatus used is shown in Figure 4 . The system consists of a DCMD membrane assembly, a water bath, a feed liquid tank, a liquid storage tank, two peristaltic pumps, a condensation tank, a balance, a conductivity meter and a computer. When powered on, a 1-3V external voltage is connected. The titanium sheet at the upper end and the titanium sheet on the membrane surface form positive and negative electrodes, and an electrical circuit is formed through the ions in the solution. The membrane assembly part from the feed side to the permeation side can be divided into: feed side membrane assembly, titanium sheet (connected to the positive electrode), feed side water flow, grid, titanium sheet (connected to the negative electrode), modified membrane (including the modified material of the present invention and PTFE membrane), permeation side water flow, permeation side membrane assembly. The effective membrane area of ​​the membrane surface in the membrane assembly is approximately 4cm 2(2×2cm). The feed solution and permeate were circulated simultaneously in the membrane module at a speed of 50mm / s. In each experiment, the temperature of the feed side was maintained at 60℃ and the permeate side was maintained at 10℃. The feed solution was prepared by adding 1mol sodium chloride and 1mmol sodium dodecyl sulfate to 1L of pure water. A layer of titanium sheet was added to each of the feed and permeate sides. A positive current was connected to the feed side and a negative current was connected to the permeate side. The power was applied for 5 minutes every two hours, and the voltage was controlled at 0.5-2V. The optimal voltage was 1V. During the experiment, the permeate conductivity and flux were recorded every 10 minutes. Initially, 100mL of deionized water was added to the beaker on the permeate side. The conductivity of the solution therein was measured with a conductivity meter to monitor the wetting of the membrane pores. At the same time, the beaker was placed on a digital balance connected to a computer to record the flow changes on the permeate side.

[0058] like Figure 5 As shown in the figure, the Janus membrane prepared in Example 1 without electric field assistance (G2M2 in the figure) began to partially wet around the 11th hour of operation, and the conductivity began to rise and gradually became completely wetted. After 24 hours, the conductivity rose to 2589 μS / cm, and the sieving performance of the membrane was almost lost. Due to complete wetting, the flux increased from the original 21.2 L / (m 2 ·h) increased to 29.6L / (m 2 ·h). The conductive GUS Janus membrane prepared in Example 1 maintained a conductivity of less than 5.0 μS / cm within 48 h under the assistance of the electric field, and the flux also tended to be stable without large fluctuations, maintaining at 20.2 L / (m 2 ·h), it can be said that it has good moisture resistance.

[0059] The XDLVO model shows that in the absence of additional voltage, the interaction forces between the pollutant and the membrane include van der Waals force (LW), hydrophobic force (AB) and electrostatic force (EL). The sum of these three forces (TOTal) determines the interaction force between SDS and the membrane. The zeta potential of the original membrane is a minimum of -20mV. With the addition of modified materials, the zeta potential of the modified membrane increases, and the conductive GUS Janus membrane can be increased to -10mV. The interaction energy was further calculated using the XDLVO model, as shown in Figure 2. Figure 6As shown in Figure 2 . Unlike the hydrophobic PTFE membrane, the surface of the conductive GUS Janus membrane is hydrophilic, so variations in AB interactions are expected, highly dependent on the degree of surface hydrophobicity or hydrophilicity. The addition of GO significantly alters the surface characteristics, rendering the membrane hydrophilic. When the distance between the modified membrane and SDS is above 5 nm, all forces are relatively small, with the AB and LW forces being quite close. As the distance increases, the AB force becomes dominant, reaching nearly four times the LW force at a distance of 3 nm. Furthermore, the AB repulsive force increases with increasing distance. Notably, the hydrophilic nature of the membrane creates a significant repulsive force with the hydrophobic tail of SDS. Although SDS has a hydrophilic sulfate head, the hydrophobic long dodecyl chain makes the hydrophilic attraction significantly smaller than the hydrophobic repulsion. Therefore, the interaction between the conductive GUS Janus membrane and SDS is repulsive, significantly mitigating membrane fouling.

[0060] The conductive Janus membrane was tested in a mixed solution of 1 mM sodium dodecyl sulfate anionic surfactant and 1 M sodium chloride at 60°C on the hot water side. It was found that the best effect was found when the amount of UiO-66-NH2 and GO was 0.05 mg each and the amount of nanosilver was 0.1 mg.

[0061] Figure 7The anti-wetting mechanism of the conductive GUS Janus membrane is elucidated. From the perspective of the Janus membrane itself, the following is explained: The UiO-66-NH2, GO, and nanosilver composite is loaded onto the PTFE surface using PVA and PDA as crosslinkers to form a hydrophilic layer. PDA crosslinks the Zr-MOF and GO; PVA crosslinks the hybrid material and the PTFE membrane. The present invention alters the original hydrophobic structure, resulting in an asymmetric Janus membrane. The heat transfer effect of membrane distillation inevitably causes SDS to flow toward the PTFE membrane. Due to the hydrophilic effect, the hydrophilic heads of SDS tend to contact the hydrophilic surface of the Janus membrane. Because the long hydrophobic chains of SDS account for the majority of the SDS mass, the repulsive force between the hydrophilic and hydrophobic regions persists when it approaches the hydrophilic membrane, effectively preventing direct contact between the SDS and the PTFE membrane. Furthermore, two-dimensional nanotransmission channels exist within the GO. The interlayer spacing between adjacent GO sheets can separate molecules of a certain size, preventing particles larger than the interlayer spacing from passing through. Given the confined space within GO, only water molecules can pass through the hydrophilic layer to the hydrophobic layer, indicating that the LEP of the hydrophobic membrane pores remains unchanged, thus preserving membrane wetting. The addition of silver nanoparticles also enhances conductivity. Furthermore, under these conditions, the resistance to water molecule passage increases, leading to an overall increase in salt rejection but a corresponding decrease in water flux. This size-based separation mechanism makes interlayer spacing a crucial factor influencing GO membrane performance. Graphene oxide nanosheets are inherently flexible, and their curvature influences their interlayer spacing. The addition of UiO-66-NH2 allows GO to encapsulate the embedded UiO-66-NH2 nanoparticles, thereby expanding the interlayer spacing of GO. Furthermore, due to the uneven molecular surface and random orientation of the embedded UiO-66-NH2 nanoparticles, an interfacial gap exists between the GO nanosheets and the UiO-66-NH2 nanoparticles, resulting in wrinkles in the GO surrounding the UiO-66-NH2 nanoparticles. This increased interstitial space may serve as an additional water transport channel, thereby promoting the increase in water permeability, but still intercepting SDS outside the GO layer, preventing the ingress of contaminants.

[0062] Comparative experiment:

[0063] The preparation was carried out according to Example 1, except that the amounts of Zr-MOF, graphene oxide and nanosilver were changed. As shown in Table 1, the four membranes prepared were named G1M2, G2M1, GUS1 and GUS2.

[0064] Table 1 Comparative experiment of the amount of raw materials used in the membrane

[0065]

[0066] The membrane prepared above was tested and the results were as follows:

[0067] like Figure 9 As shown in the figure, in the preliminary experiment, MD experiments were carried out on four membranes. The prepared Janus membrane (G1M2 in the figure) began to show partial wetting around the 4th hour of operation under the assistance of the electric field. The conductivity began to rise and gradually became completely wetted. The flux increased from the original 23.0L / (m 2 ·h) increased to 23.9L / (m 2 ·h); G2M1 also showed signs of wetting after 8 hours under the assistance of electric field, and the flux increased from the original 20.5L / (m 2 ·h) rose to 21.1L / (m 2 ·h); With the addition of electric field, GUS1 has poor conductivity due to the low loading of nanosilver under the assistance of electric field. Although it can delay the occurrence of membrane wetting, it still shows signs of membrane wetting after 15h; while GUS2 has excessive loading of nanosilver under the assistance of electric field, which blocks the membrane pores and reduces the membrane flux. Although it has good anti-wetting property, the flux is only maintained at 19.3L / (m 2 h) or so.

[0068] From the perspective of applying an electric field: Although the Janus membrane itself has a certain ability to prevent direct contact between SDS and the membrane surface through its hydrophilicity and hydrophobicity, this is only effective for a long time in the presence of low concentrations of SDS. As the concentration increases, SDS will accumulate, thereby breaking the hydrophilicity of the membrane surface, causing partial wetting and then complete wetting, leading to a decline in membrane performance. In contrast, the conductive GUS Janus membrane with electrical repulsion exhibits stable MD operation even at very high contaminant concentrations. Before SDS accumulates, it negatively charges the membrane surface, thereby increasing the electrostatic repulsion between the membrane surface and the contaminants, removing the SDS that has accumulated on the membrane surface and restoring the properties of the Janus membrane, thereby ensuring no decrease in flux and repulsion.

Claims

1. A method for preparing a conductive Janus film, characterized in that: The method for preparing the conductive Janus film comprises the following steps: 1) Preparation of Zr-MOF materials; 2) Preparation of a conductive Janus membrane: Zr-MOF material was weighed and ultrasonically dispersed in anhydrous ethanol. After mixing, a polydopamine solution was added. After stirring, a graphene oxide solution and a polyvinyl alcohol solution were added and ultrasonically treated. Finally, a nanosilver solution was added. After ultrasonic stirring, the mixed solution was added to a vacuum filtration device with a PTFE membrane fixed thereon, vacuum filtered, and dried to obtain a conductive Janus film.

2. The preparation method according to claim 1, characterized in that Step 1) specifically comprises: mixing an amino-functionalized organic ligand, a zirconium salt and an organic acid in a solvent, heating and reacting the mixture to prepare a Zr-MOF material.

3. The preparation method according to claim 2, characterized in that The molar ratio of the amino-functionalized organic ligand, the zirconium salt and the organic acid is 1:1:

100.

4. The preparation method according to claim 2 or 3, characterized in that The heating reaction conditions are: 120° C. for 24 hours.

5. The preparation method according to claim 1, characterized in that In step 2), the mass ratio of the Zr-MOF material, the graphene oxide in the graphene oxide solution, and the nanosilver in the nanosilver solution is 1:1:

2.

6. The preparation method according to claim 1 or 5, characterized in that The dosage ratio of the Zr-MOF material and the polydopamine solution is: 0.025-0.05:1 mg / mL.

7. The preparation method according to claim 1 or 5, characterized in that The mass ratio of the Zr-MOF material to the polyvinyl alcohol solution is: 0.025-0.05:0.5 mg / mL.

8. A conductive Janus film prepared by the preparation method according to any one of claims 1 to 7.

9. Use of a conductive Janus membrane prepared by the preparation method according to any one of claims 1 to 7 in treating brine containing surfactant by electric field-assisted membrane distillation.

10. The use according to claim 9, characterized in that A direct contact membrane distillation device is used, equipped with a DC power supply, with a titanium sheet as a conductor and a conductive Janus membrane as the negative electrode of the power supply to treat brine containing surfactant.

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