A double-interface conductive film and its preparation method and application

Abstract

The present invention relates to a double-interface conductive film and a preparation method and application thereof, wherein the preparation method comprises the following steps: (1) preparing a polyvinylidene fluoride film on one side of a film substrate; (2) preparing a conductive film SWCNT / GO; (3) preparing a SWCNT / PVDF casting solution, and applying the SWCNT / PVDF casting solution on the other side of the film substrate by a phase inversion method to obtain a SWCNT / PVDF film. The double-sided conductive film of the present invention prepares conductive films SWCNT / GO and SWCNT / PVDF on both sides of the polyvinylidene fluoride film, constructs an anode region and a cathode region, so that the conductive film of the double-interface layer undergoes orderly electro-reduction and electro-oxidation reactions in different regions during electrochemical membrane filtration, thereby improving the removal rate of antibiotics; under an applied voltage, the contaminants are separated and concentrated while degrading the contaminants, and the problems of membrane pollution are effectively suppressed.

Description

Technical Field

[0001] The invention relates to the field of membrane technology, and in particular to a double-interface conductive membrane and a preparation method and application thereof. Background Art

[0002] Antibiotics are introduced into the aquatic environment through aquaculture wastewater, animal husbandry, or widely used pharmaceuticals and personal care products, which poses a potential threat to the ecological environment and human health. In recent years, antibiotics have been removed mainly through traditional processes such as physical removal, chemical conversion or biological treatment, but these methods are inefficient. Membrane filtration is one of the most effective methods for removing small molecules, such as low-concentration antibiotics. The advantages of this method include good separation selectivity, no by-products or additional chemicals, recycling, and convenience for large-scale continuous operation. However, membrane filtration technology is a physical process that cannot degrade antibiotics, and the application of this technology is limited by the subsequent treatment of high-concentration liquids. Moreover, pollutants continue to accumulate on the membrane surface or in the pores during membrane filtration, resulting in membrane fouling, thereby reducing the performance of the membrane.

[0003] Electrochemical membrane filtration technology is a new membrane separation technology that combines membrane separation technology with electrochemical oxidation. The combination of membrane filtration technology and electrochemistry can degrade and remove pollutants while intercepting them, effectively alleviating membrane pollution. Compared with the traditional electrochemical oxidation mode, the mass transfer rate is significantly improved when the system operates in filtration mode. Compared with traditional membrane processes, electrochemical coupled membrane technology has a significant improvement effect on the removal of organic pollutants in wastewater and the anti-pollution performance of the membrane, and shows great application prospects in the field of large-scale water treatment.

[0004] Representative nanostructured carbon materials such as graphene and carbon nanotubes have become popular research materials for environmental applications due to their unique physical and chemical properties such as high specific surface area, thermal conductivity and mechanical strength. Hydroxyl radicals (·OH) and superoxide radicals (O2 ·- ) and oxidants such as hydrogen peroxide (H2O2) decompose organic pollutants. However, the traditional operation mode leads to a complex structure of the membrane device, so the double-interface electrocatalytic membrane may be a unique technology. In view of this, the present invention provides a double-interface conductive membrane and its preparation method and application. Summary of the invention

[0005] The technical problem to be solved by the present invention is to provide a double-interface conductive membrane and a preparation method and application thereof, with the purpose of solving the problem of complex membrane device structure caused by the operation mode of the existing electrochemical membrane filtration technology.

[0006] The technical solution of the present invention to solve the above technical problems is as follows:

[0007] In a first aspect, a method for preparing a conductive film with a double interface layer comprises the following steps:

[0008] (1) preparing a polyvinylidene fluoride (PVDF) membrane on one side of a membrane substrate;

[0009] (2) preparing a mixed solution of SWCNT dispersion and GO dispersion, and filtering the mixed solution onto the surface of the polyvinylidene fluoride membrane to obtain a conductive film SWCNT / GO;

[0010] (3) preparing a SWCNT / PVDF casting solution, and applying the SWCNT / PVDF casting solution to the other side of the membrane substrate by a phase inversion method to obtain a SWCNT / PVDF membrane, that is, a conductive membrane with a double interface layer.

[0011] The above-mentioned SWCNT is single-walled carbon nanotube, and GO is graphene oxide.

[0012] The beneficial effects of the present invention are as follows: the double-sided conductive membrane of the present invention prepares conductive membranes SWCNT / GO and SWCNT / PVDF membranes on both sides of the PVDF membrane to construct the anode region and the cathode region, so that the conductive membrane of the double interface layer undergoes orderly electro-reduction and electro-oxidation reactions in different regions during the electrochemical membrane filtration process, thereby improving the removal rate of antibiotics; and the good conductive properties of the membrane itself, on the basis of an applied voltage, enable it to separate and concentrate pollutants while degrading pollutants, and effectively inhibit problems such as membrane pollution.

[0013] Based on the above technical solution, the present invention can also be improved as follows.

[0014] Furthermore, the film substrate is a non-woven fabric.

[0015] The beneficial effect of adopting the above further scheme is that the present invention uses non-woven fabric with good mechanical properties, excellent hydrophilicity and low cost as the membrane substrate, providing a good carrier for preparing stable and efficient conductive membrane. The preparation method of double-sided conductive membrane is simple, low cost and can be promoted and utilized on a large scale.

[0016] Furthermore, step (1) includes the following specific steps: adding polyvinylidene fluoride and polyvinyl pyrrolidone (e.g., polyvinyl pyrrolidone K30, PVP) to N,N-dimethylacetamide (DMAC), mixing and then standing to exhaust gas to obtain a polyvinylidene fluoride casting solution; scraping the polyvinylidene fluoride casting solution onto one side of the film substrate to obtain a polyvinylidene fluoride film; the polyvinylidene fluoride film has a thickness of 60 to 100 μm.

[0017] The beneficial effect of adopting the above further solution is that the polyvinylidene fluoride film of the present invention provides an insulating layer for the double-sided film to avoid short circuit when power is applied.

[0018] Furthermore, the mass ratio of the N,N-dimethylacetamide, the polyvinylidene fluoride and the polyvinyl pyrrolidone is 12-15:1-2:84-86.

[0019] The beneficial effect of adopting the above further solution is that the present invention enables the PVDF membrane to have a more suitable pore size.

[0020] Further, step (2) includes the following specific steps:

[0021] (2-1) uniformly dispersing the active agent and SWCNT in an aqueous solvent, centrifuging the SWCNT dispersion at 5000-15000 rpm for 30 minutes to improve the degree of dispersion, and collecting the supernatant dispersion to obtain a SWCNT dispersion, wherein the concentration of SWCNT powder in the SWCNT dispersion is 0.1-0.5 mg / mL;

[0022] (2-2) preparing GO by a modified Hummers method, uniformly dispersing GO in an aqueous solvent to obtain a GO dispersion, wherein the concentration of GO in the GO dispersion is 0.04 to 0.1 mg / mL;

[0023] (2-3) The SWCNT dispersion and the GO dispersion are uniformly mixed, wherein the volume ratio of the SWCNT dispersion to the GO dispersion is 4:1; and then filtered onto the surface of the polyvinylidene fluoride membrane to obtain a conductive film SWCNT / GO.

[0024] The beneficial effect of adopting the above further scheme is that the present invention can prepare a stable conductive interface, wherein the addition of GO increases the hydrophilicity.

[0025] Further, the concentration of SWCNT powder in the SWCNT dispersion is 0.1 mg / mL; the concentration of GO in the GO dispersion is 0.05 mg / mL;

[0026] The active agent is sodium dodecylbenzene sulfonate.

[0027] The beneficial effect of adopting the above further scheme is that the sodium dodecylbenzene sulfonate of the present invention makes SWCNT more stably and evenly dispersed in water, which is conducive to preparing a more uniform membrane material.

[0028] Further, step (3) includes the following specific steps: mixing SWCNT powder, polyvinyl pyrrolidone, N,N-dimethylacetamide and polyvinylidene fluoride, standing to exhaust, ultrasonicating for 2 hours, then adding PVDF and stirring for 4 hours, standing to exhaust for one day to obtain SWCNT / PVDF casting solution, and evenly scraping the SWCNT / PVDF casting solution on the other side of the membrane substrate, then evaporating at room temperature for 30-90 seconds, and then immersing in deionized water to obtain a SWCNT / PVDF membrane; the thickness of the SWCNT / PVDF membrane is 80-150 μm.

[0029] The beneficial effect of adopting the above further solution is that the present invention can construct a stable conductive interface.

[0030] Furthermore, the concentration of SWCNT powder in the SWCNT / PVDF casting solution is 0.1-0.5 mg / mL, the concentration of polyvinyl pyrrolidone in the SWCNT / PVDF casting solution is 0.005-0.01 g / mL, and the concentration of polyvinylidene fluoride in the SWCNT / PVDF casting solution is 0.12-0.15 g / mL. The amount of N,N-dimethylacetamide used can meet the needs.

[0031] The beneficial effect of adopting the above further solution is that the present invention constructs a suitable pore size and has good conductivity.

[0032] In a second aspect, a conductive film with a double interface layer is prepared by the preparation method.

[0033] In a third aspect, a double-interface conductive film is used, wherein the double-interface conductive film prepared by the preparation method is used for removing antibiotics.

[0034] The beneficial effect of adopting the above scheme is that the construction mode of the conductive membrane of the double interface layer of the present invention adopts the SWCNT / PVDF membrane surface facing upward as the cathode and the SWCNT / GO surface facing downward as the anode, which improves the removal rate of antibiotics, and the membrane itself has good conductive properties. On the basis of an applied voltage, it separates and concentrates pollutants while degrading pollutants, and effectively inhibits problems such as membrane pollution.

[0035] Furthermore, the conductive film SWCNT / GO of the conductive film of the double interface layer is the anode region, and the conductive film SWCNT / PVDF of the conductive film of the double interface layer is the cathode region. BRIEF DESCRIPTION OF THE DRAWINGS

[0036] Figure 1 The SEM image of the SWCNT / PVDF film of the double-interface conductive film prepared in Example 1;

[0037] Figure 2The SEM image of the SWCNT / GO conductive film of the double interface layer prepared in Example 1;

[0038] Figure 3 This is an XPS graph of the conductive film of the double interface layer prepared in Example 1;

[0039] Figure 4 This is a comparison chart of the removal rate of tetracycline by the conductive films of the double interface layer with different GO contents prepared in Examples 1-3;

[0040] Figure 5 This is a comparison chart of the removal rate of tetracycline when different voltages are applied to the conductive film of the double interface layer prepared in Example 1;

[0041] Figure 6 This is a comparison chart of the removal rates of tetracycline by conductive films with different double interface layers prepared in Examples 1, 4-5;

[0042] Figure 7 Flux comparison chart of different construction modes;

[0043] Figure 8 Removal rate of tetracycline by different construction modes. DETAILED DESCRIPTION

[0044] The principles and features of the present invention are described below, and the examples are only used to explain the present invention and are not used to limit the scope of the present invention. If no specific technology or conditions are specified in the embodiments, the technology or conditions described in the literature in this field or the product instructions are used. If the manufacturer of the reagents or instruments used is not specified, they are all conventional products that can be purchased through regular channels.

[0045] The sources of the materials and reagents in the following examples are as follows:

[0046] Polyvinylidene fluoride (Shanghai Aladdin Biochemical Technology Co., Ltd.); N,N-dimethylacetamide (Shanghai Aladdin Biochemical Technology Co., Ltd.); Polyvinylpyrrolidone K30 (Shanghai Aladdin Biochemical Technology Co., Ltd.); SWCNT powder (Nanjing Pioneer Nanomaterials Technology Co., Ltd.); Flake graphite (Shanghai Aladdin Biochemical Technology Co., Ltd.).

[0047] Example 1

[0048] This embodiment relates to a method for preparing a conductive film with a double interface layer, comprising the following steps:

[0049] (1) preparing a polyvinylidene fluoride (PVDF) membrane on one side of a membrane substrate;

[0050] The specific steps for preparing the polyvinylidene fluoride membrane are as follows: first, prepare a PVDF casting solution (mass ratio of PVDF:PVP:DMAC=15:1:84), heat and stir in a 70°C water bath magnetic stirrer for 4 hours, let stand at room temperature for 24 hours, and then scrape a PVDF membrane with a thickness of 100 μm on a non-woven fabric material to prepare a polyvinylidene fluoride membrane;

[0051] (2) preparing a mixed solution of SWCNT and GO, and filtering the mixed solution of SWCNT and GO onto the surface of the polyvinylidene fluoride membrane to obtain a conductive film SWCNT / GO;

[0052] The conductive film SWCNT / GO includes the following specific steps:

[0053] (2-1) Preparation of SWCNT (single-wall carbon nanotube) dispersion: 1 g / L sodium dodecylbenzene sulfonate and 0.05 g SWCNT powder were added to 100 mL water, and ultrasonic treatment was performed using an ultrasonic machine for 5 hours to prepare a SWCNT dispersion; in order to improve the degree of dispersion, the SWCNT dispersion was centrifuged at 10,000 rpm for 30 minutes, and the supernatant dispersion was collected; the final concentration of SWCNT in the SWCNT dispersion was 0.1 mg / mL;

[0054] (2-2) Preparation of GO (graphene oxide) dispersion: GO was prepared by a modified Hummers method, specifically: First, 2.5 g of flake graphite was weighed using an analytical balance and added to a 250 mL beaker, followed by the addition of 60 mL of concentrated sulfuric acid to form a suspension. Under stirring conditions in an ice-water bath, 8 g of potassium permanganate was slowly added, and then stirred at a constant temperature for 2 h at 35 °C. After stirring, 30 wt% H2O2 solution and deionized water were slowly added to the suspension in an ice-water bath, and stirred in an ice-water bath until no bubbles were generated. It was then collected in a centrifuge tube and centrifuged at 8000 rpm for 8 min. The centrifuged product was washed with 5% dilute hydrochloric acid until the supernatant was free of sulfate (barium chloride solution detection), and then the precipitate was washed with deionized water to remove metal ions and residual acid until the pH value of the supernatant reached above 4. The centrifuged product was transferred to a culture dish and freeze-dried, and ground to obtain a brown-yellow GO powder. GO was added to 100 ml of water and ultrasonicated for 30 min to obtain a 0.05 mg / mL GO dispersion;

[0055] (2-3) The SWCNT dispersion and the GO dispersion are uniformly mixed by ultrasonication for 10 minutes, wherein the volume ratio of the SWCNT dispersion to the GO dispersion is 4:1; and then the mixture is filtered onto the surface of the polyvinylidene fluoride membrane to obtain a conductive film SWCNT / GO.

[0056] (3) preparing a SWCNT / PVDF casting solution, and applying the SWCNT / PVDF casting solution to the other side of the membrane substrate by a phase inversion method to obtain a SWCNT / PVDF membrane, that is, a conductive membrane with a double interface layer.

[0057] Preparation of SWCNT / PVDF membrane: SWCNT and PVP powders were dissolved in DMAC and ultrasonicated for 2 hours, then PVDF was added to make the concentration of SWCNT powder 0.3 mg / mL, the concentration of polyvinyl pyrrolidone 0.01 g / mL, and the concentration of polyvinylidene fluoride 0.15 g / mL, stirred for 4 hours, and then allowed to stand for one day to exhaust gas to obtain SWCNT / PVDF casting solution; the SWCNT / PVDF casting solution was scraped on the back of the conductive film SWCNT / GO to make it evenly covered with a thickness of 100 μm. After scraping, it was evaporated at room temperature for 60 seconds, and then slowly immersed in deionized water for storage.

[0058] The SEM image of the conductive film of the double interface layer prepared in this embodiment is as follows: Figure 1 , Figure 2 As shown in the XPS diagram Figure 3 As shown. Figure 1-3 It can be seen that SWCNT, GO and PVDF are successfully attached to the nonwoven fabric.

[0059] This embodiment also involves the application of the double-interface conductive membrane: the double-interface conductive membrane is placed in an existing wastewater treatment system, different direct currents are applied to the double-interface conductive membrane, and samples are taken at the outlet to measure the antibiotic content in the wastewater. Figure 6 As shown, when a voltage of -2.0 V was applied, the removal efficiency of tetracycline was the best.

[0060] Example 2: Comparative Example

[0061] The difference between the method for preparing the conductive film of the double interface layer described in this embodiment and the method in embodiment 1 is that:

[0062] In step (2), no GO is added, and a conductive film with a double interface layer (film 2) is obtained.

[0063] Example 3

[0064] The difference between the method for preparing the conductive film of the double interface layer described in this embodiment and the method in embodiment 1 is that:

[0065] In step (2), the concentration of GO is 0.1 mg / mL, and a conductive film (film 3) with a double interface layer is obtained.

[0066] Example 4: Comparative Example

[0067] The difference between the method for preparing the conductive film of the double interface layer described in this embodiment and the method in embodiment 1 is that:

[0068] A conductive film (film 4) having a SWCNT / GO double interface layer prepared in step (2) on both the front and back sides.

[0069] Example 5: Comparative Example

[0070] The difference between the method for preparing the conductive film of the double interface layer described in this embodiment and the method in embodiment 1 is that:

[0071] A conductive film (film 5) having a SWCNT / PVDF double interface layer prepared in step (3) on both the front and back sides.

[0072] Example 6: Comparative Example

[0073] The difference between the method for preparing the conductive film of the double interface layer described in this embodiment and the method in embodiment 1 is that:

[0074] SWCNT / GO single-sided film (film 6) prepared only by steps (1) and (2).

[0075] Example 7: Comparative Example

[0076] The difference between the method for preparing the conductive film of the double interface layer described in this embodiment and the method in embodiment 1 is that:

[0077] SWCNT / PVDF single-sided film (film 7) prepared only by step (3).

[0078] Example 8: Comparative Example

[0079] The difference between the method for preparing the conductive film of the double interface layer described in this embodiment and the method in embodiment 1 is that:

[0080] In the application of the double interface layer conductive film, the position of the double interface layer conductive film is swapped, the conductive film SWCNT / GO surface is facing upward as the cathode, and a voltage of -2.0V is applied.

[0081] Example 9: Comparative Example

[0082] The difference between the method for preparing the conductive film of the double interface layer described in this embodiment and the method in embodiment 1 is that:

[0083] In the application of the double-interface conductive film, the single-sided SWCNT / PVDF film is used as the cathode, and the titanium mesh is used as the counter electrode.

[0084] Example 10: Comparative Example

[0085] The difference between the method for preparing the conductive film of the double interface layer described in this embodiment and the method in embodiment 1 is that:

[0086] In the application of the double-interface conductive film, the single-sided SWCNT / GO film is used as the anode and the titanium mesh is used as the counter electrode.

[0087] Experimental example

[0088] The flux and removal rate of antibiotics of different membranes and construction methods in Examples 1-10 were tested.

[0089] Removal rate of antibiotics: The conductive membrane with double interface layer is placed in the existing wastewater treatment system, and simulated antibiotic wastewater is introduced into the system. The concentration of tetracycline in the wastewater is 20mg / L. Through different construction modes, samples are taken at the outlet to measure the antibiotic content in the wastewater and calculate the removal rate of antibiotics. Figure 4 and Figure 5 As shown, when the GO content is 0.05 mg / mL, and the conductive film SWCNT / GO of the double interface layer is used as the anode area and SWCNT / PVDF is used as the cathode area, a higher removal rate of antibiotics is achieved.

[0090] Mode I is a double-interface conductive membrane filtration method, with SWCNT / PVDF facing up as the cathode; Mode ⅠⅠ is a double-interface conductive membrane filtration method, with SWCNT / GO facing up as the cathode; Mode ⅠⅠⅠ is a single-sided SWCNT / PVDF membrane filtration method, with SWCNT / PVDF as the cathode and a titanium mesh as the counter electrode; Mode ⅠⅤ is a single-sided SWCNT / GO membrane filtration method, with SWCNT / GO as the anode and a titanium mesh as the counter electrode; Mode V is a double-interface conductive membrane filtration method without power. The flux results of different construction methods are shown in Figure 1. Figure 7 As shown in Figure 2, the removal rates of antibiotics by different construction methods are as follows: Figure 8 As shown in Figure 2, different construction modes show that only when the electrochemical membrane filtration system is constructed in mode I, the removal rate of tetracycline is the highest and the flux is the largest.

[0091] In summary, the double-sided conductive membrane of the present invention prepares conductive membranes SWCNT / GO and SWCNT / PVDF membranes on both sides of the PVDF membrane to construct the anode region and the cathode region, so that the conductive membrane of the double interface layer undergoes orderly electro-reduction and electro-oxidation reactions in different regions during the electrochemical membrane filtration process, thereby improving the removal rate of antibiotics; and the good conductive properties of the membrane itself, on the basis of an applied voltage, enable it to separate and concentrate pollutants while degrading pollutants, and effectively inhibit problems such as membrane pollution.

[0092] Although the embodiments of the present invention have been shown and described above, it is to be understood that the above embodiments are exemplary and are not to be construed as limitations of the present invention. A person skilled in the art may change, modify, replace and vary the above embodiments within the scope of the present invention.

Claims

1. A method for preparing a conductive film with a double interface layer, characterized in that: The steps include: (1) preparing a polyvinylidene fluoride film on one side of a film substrate; (2) preparing a mixed solution of SWCNT dispersion and GO dispersion, and filtering the mixed solution onto the surface of the polyvinylidene fluoride membrane to obtain a conductive film SWCNT / GO; (3) preparing a SWCNT / PVDF casting solution, and applying the SWCNT / PVDF casting solution to the other side of the membrane substrate by a phase inversion method to obtain a SWCNT / PVDF membrane, that is, a conductive membrane with a double interface layer; Step (2) includes the following specific steps: (2-1) uniformly dispersing the active agent and SWCNT in an aqueous solvent to obtain a SWCNT dispersion, wherein the concentration of SWCNT powder in the SWCNT dispersion is 0.1-0.5 mg / mL; (2-2) preparing GO by a modified Hummers method, uniformly dispersing GO in an aqueous solvent to obtain a GO dispersion, wherein the concentration of GO in the GO dispersion is 0.04-0.1 mg / mL; (2-3) uniformly mixing the SWCNT dispersion and the GO dispersion, wherein the volume ratio of the SWCNT dispersion to the GO dispersion is 4:1; and then filtering onto the surface of the polyvinylidene fluoride membrane to obtain a conductive film SWCNT / GO; The active agent is sodium dodecylbenzene sulfonate; The concentration of SWCNT powder in the SWCNT / PVDF casting solution is 0.1-0.5 mg / mL, the concentration of polyvinyl pyrrolidone in the SWCNT / PVDF casting solution is 0.005-0.01 g / mL, and the concentration of polyvinylidene fluoride in the SWCNT / PVDF casting solution is 0.12-0.15 g / mL.

2. The method for preparing a double-interface conductive film according to claim 1, characterized in that: Step (1) comprises the following specific steps: adding polyvinylidene fluoride and polyvinyl pyrrolidone into N,N-dimethylacetamide, mixing and then standing to exhaust gas, thereby obtaining a polyvinylidene fluoride casting liquid; applying the polyvinylidene fluoride casting liquid on one side of a film substrate, thereby obtaining a polyvinylidene fluoride film; and the polyvinylidene fluoride film has a thickness of 60 to 100 μm.

3. The method for preparing a double-interface conductive film according to claim 2, characterized in that: The mass ratio of the N,N-dimethylacetamide, the polyvinylidene fluoride and the polyvinyl pyrrolidone is 12-15:1-2:84-86.

4. The method for preparing a double-interface conductive film according to claim 1, characterized in that: The concentration of SWCNT powder in the SWCNT dispersion is 0.1 mg / mL; the concentration of GO in the GO dispersion is 0.05 mg / mL.

5. The method for preparing a double-interface conductive film according to claim 1, characterized in that: Step (3) comprises the following specific steps: mixing SWCNT powder, polyvinyl pyrrolidone, N,N-dimethylacetamide and polyvinylidene fluoride and then standing to exhaust gas to obtain SWCNT / PVDF casting solution, evenly scraping the SWCNT / PVDF casting solution on the other side of the membrane substrate, then evaporating at room temperature for 30-90 seconds, and then immersing in deionized water to obtain a SWCNT / PVDF membrane; the thickness of the SWCNT / PVDF membrane is 80-150 μm.

6. A conductive film with a double interface layer, characterized in that: Prepared by the preparation method according to any one of claims 1 to 5.

7. Application of a double-interface conductive film, characterized in that: Using the conductive film of the double interface layer prepared by the preparation method according to any one of claims 1 to 5 or the conductive film of the double interface layer according to claim 6 for removing antibiotics; The conductive film SWCNT / GO of the conductive film of the double interface layer is the anode region, and the conductive film SWCNT / PVDF of the conductive film of the double interface layer is the cathode region.

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