Preparation method, product and application of polyaniline modified composite membrane

Abstract

This invention relates to the field of polymer materials technology, and in particular to a method for preparing a polyaniline-modified composite membrane, its product, and its application. The method for preparing the polyaniline-modified composite membrane includes the following steps: Step 1, activating and cleaning a polyvinylidene fluoride (PVDF) sheet, then immersing it in solution A with stirring; after stirring, removing the PVDF sheet and cleaning it to obtain a treated PVDF sheet; Step 2, mixing solution A with solution B and filtering to obtain a mixed solution; Step 3, immersing the treated PVDF sheet in the mixed solution; after immersion, removing it and drying it to obtain the polyaniline-modified composite membrane; Solution A is a SiO2 solution; Solution B is a mixed solution of polyaniline and polyvinylpyrrolidone. The preparation method of this invention is simple and easy to operate, which is beneficial for industrial production. The polyaniline-modified composite membrane has high oil / water separation efficiency.

Description

Technical Field

[0001] This invention relates to the field of polymer materials technology, and in particular to a method for preparing a polyaniline-modified composite film, the product, and its application. Background Technology

[0002] Mineral insulating oil, due to its excellent insulation and heat dissipation properties, is widely used in large power equipment such as transformers and reactors. To prevent pollution caused by oil spraying or leakage from large oil-filled electrical equipment such as main transformers and high-voltage reactors, substations are equipped with dedicated emergency oil pools. While storing leaked oil from electrical equipment and substation wastewater, these emergency oil pools also increase safety hazards and a series of environmental problems related to wastewater leakage. Transformer waste oil contains various toxic components, such as polycyclic aromatic hydrocarbons, biphenyls, and heavy metals. If this waste oil is not treated promptly and thoroughly, it will threaten the health of animals, plants, and humans. Therefore, adopting scientific and efficient oil-water separation methods and strengthening the treatment of oily wastewater at the discharge outlet of the emergency oil pool to ensure that wastewater discharge meets economic and environmental protection requirements has become a crucial issue in the current management of wastewater from substation emergency oil pools.

[0003] Polyaniline, as a conductive polymer, possesses excellent redox reversibility, conductivity, and stability, offering potential advantages for oil-water separation. Current oil-water separation technologies are only suitable for specific types of oil-water mixtures, showing poor separation performance for transformer oil-water mixtures. Furthermore, they may generate environmentally harmful byproducts or emissions and are difficult to maintain separation performance over extended periods. Therefore, enhancing the adaptability, environmental friendliness, and sustainability of membranes is a pressing technical challenge in developing new oil-water separation technologies. Summary of the Invention

[0004] In view of the above-mentioned shortcomings of the existing technology, the purpose of the present invention is to provide a method for preparing polyaniline modified composite membrane, product and application; the method of the present invention adopts a surface coating method to prepare polyaniline modified composite membrane with high separation efficiency, good water flux and long service life using polyvinylidene fluoride membrane as substrate.

[0005] To achieve the above objectives, the present invention provides the following solution:

[0006] One of the technical solutions of this invention is a method for preparing a polyaniline-modified composite film, comprising the following steps:

[0007] Step 1: Activate and clean the polyvinylidene fluoride sheet, then immerse it in solution A and stir. After stirring, remove the polyvinylidene fluoride sheet and clean it to obtain the treated polyvinylidene fluoride sheet.

[0008] Step 2: Mix solution A and solution B and then filter to obtain a mixture;

[0009] Step 3: Immerse the treated polyvinylidene fluoride sheet in the mixture, remove it after immersion and dry it to obtain the polyaniline modified composite film;

[0010] Solution A is a SiO2 solution;

[0011] Solution B is a mixed solution of polyaniline and polyvinylpyrrolidone.

[0012] The second technical solution of the present invention is a polyaniline modified composite film prepared according to the above preparation method.

[0013] The third technical solution of the present invention is the application of the above-mentioned polyaniline modified composite membrane in oil-water separation.

[0014] The present invention discloses the following technical effects:

[0015] The polyaniline-modified composite membrane provided by this invention has high membrane flux, good antifouling properties, and reusability. Using SiO2, polyaniline, and polyvinylpyrrolidone as the main materials, this polyaniline-modified composite membrane achieves high oil-floating separation efficiency, and exhibits good antifouling properties and reusability, effectively reducing the environmental harm of industrial wastewater and demonstrating good environmental performance.

[0016] The polyaniline-modified composite membrane of this invention has a membrane flux as high as 458.48 Lm. -2 h -1 The separation efficiency reached 98.73%. After multiple cycle tests, the total organic carbon content of the filtrate was measured to be 17.2 mg / L, which meets the national wastewater discharge standards.

[0017] The preparation method of this invention is simple and easy to operate, which is conducive to industrial production. Attached Figure Description

[0018] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0019] Figure 1 An optical photograph of the PANI@PVDF-3 composite film prepared in Example 3 of this invention.

[0020] Figure 2 FESEM images of the PVDF membrane (a) and the PANI@PVDF-3 composite membrane (b, c) prepared in Example 3 of this invention.

[0021] Figure 3AFM images of PVDF membranes (a, b) and PANI@PVDF-3 composite membranes (c, d).

[0022] Figure 4 The oil-water separation device used in the oil-water separation cycle test of this invention.

[0023] Figure 5 The figures show the experimental results of separating floating oil / aqueous solution using five types of PANI@PVDF composite membranes prepared in Examples 1 to 5 of this invention.

[0024] Figure 6 The graph shows the membrane flux and total organic carbon (TOC) content of the PANI@PVDF-3 composite membrane prepared in Example 3 of this invention during recycling. Detailed Implementation

[0025] Various exemplary embodiments of the present invention will now be described in detail. This detailed description should not be considered as a limitation of the present invention, but rather as a more detailed description of certain aspects, features, and embodiments of the present invention.

[0026] It should be understood that the terminology used in this invention is merely for describing particular embodiments and is not intended to limit the invention. Furthermore, with respect to numerical ranges in this invention, it should be understood that each intermediate value between the upper and lower limits of the range is also specifically disclosed. Any stated value or intermediate value within a stated range, as well as each smaller range between any other stated value or intermediate value within said range, is also included in this invention. The upper and lower limits of these smaller ranges may be independently included or excluded from the range.

[0027] Unless otherwise stated, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art. While only preferred methods and materials have been described herein, any methods and materials similar or equivalent to those described herein may be used in the implementation or testing of this invention. All references to this specification are incorporated by way of citation to disclose and describe methods and / or materials associated with those references. In the event of any conflict with any incorporated reference, the content of this specification shall prevail.

[0028] Various modifications and variations can be made to the specific embodiments described in this specification without departing from the scope or spirit of the invention, as will be apparent to those skilled in the art. Other embodiments derived from this specification will also be apparent to those skilled in the art. This specification and embodiments are merely exemplary.

[0029] The terms “include,” “including,” “have,” “contain,” etc., used in this article are all open-ended terms, meaning that they include but are not limited to.

[0030] The first aspect of this invention provides a method for preparing a polyaniline-modified composite film, comprising the following steps:

[0031] Step 1: Activate and clean the polyvinylidene fluoride sheet, then immerse it in solution A and stir. After stirring, remove the polyvinylidene fluoride sheet and clean it to obtain the treated polyvinylidene fluoride sheet.

[0032] Step 2: Mix solution A and solution B and then filter to obtain a mixture;

[0033] Step 3: Immerse the treated polyvinylidene fluoride sheet in the mixture, remove it after immersion and dry it to obtain the polyaniline modified composite film;

[0034] Solution A is a SiO2 solution;

[0035] Solution B is a mixed solution of polyaniline and polyvinylpyrrolidone.

[0036] In some embodiments of the present invention, the polyvinylidene fluoride sheet is activated by placing it in anhydrous ethanol for 0.5 to 3 hours.

[0037] The activation process simply requires standing; the main purpose of activating the membrane with anhydrous ethanol is to remove residual solvents and impurities from the membrane surface, clean the pores, improve the membrane's pore structure, and enhance porosity, thereby increasing the membrane's permeability and hydrophilicity. Furthermore, activation helps reduce membrane pore blockage, promotes uniform liquid penetration, and enhances membrane stability and subsequent performance. Through activation, the membrane's pore channels are optimized, laying a better foundation for oil-water separation or filtration processes.

[0038] In some embodiments of the present invention, the concentration of SiO2 in solution A is 2 to 10 g / L; the solvent of solution A is dimethylformamide; and the particle size of SiO2 in solution A is 5 nm to 50 nm.

[0039] The SiO2 concentration in solution A has a significant impact on the performance of the polyaniline-modified composite membrane. Excessive SiO2 concentration in solution A leads to decreased membrane porosity, reduced flux, and makes the membrane fragile and prone to breakage; conversely, insufficient concentration results in insufficient mechanical strength and reduced separation efficiency, particularly in treating high-oil-concentration wastewater. Therefore, the SiO2 concentration should be maintained within an appropriate range (2–10 g / L) to ensure membrane stability and good separation performance.

[0040] Meanwhile, the SiO2 particle size also plays a crucial role in membrane performance. If the SiO2 particle size is too large, the membrane's pore structure becomes too coarse, reducing separation precision and efficiency, and the membrane surface becomes rough, making it prone to fouling. Conversely, if the SiO2 particle size is too small, the membrane's pores become too fine, reducing flux and processing efficiency, and making it more susceptible to fouling and clogging. Therefore, the SiO2 particle size should be controlled between 5 nm and 50 nm to balance flux, separation efficiency, and membrane stability.

[0041] In some embodiments of the present invention, solution A is prepared by dispersing SiO2 powder with a particle size of 5 nm to 50 nm in dimethylformamide and stirring for 1 to 3 hours.

[0042] Dimethylformamide is a polar solvent with good dispersibility for SiO2, which helps to form a uniform dispersion system, improves its flowability and formability in subsequent processing, and reduces the difficulty of preparing thin films.

[0043] Replacing dimethylformamide (DMF) with other polar solvents such as ethyl acetate, ethanol, acetone, tetrahydrofuran, or dimethyl sulfoxide will adversely affect the performance of polyaniline-modified composite membranes. First, ethyl acetate and ethanol have poor dispersibility, leading to uneven dispersion of SiO2 particles, which in turn affects the membrane's uniformity and mechanical strength. While acetone has strong solubility, it is unsuitable for dispersing SiO2 and evaporates quickly, affecting the membrane's formability and surface smoothness. Tetrahydrofuran (THF) disperses SiO2 well, but it interacts with polyaniline, affecting the membrane's electrical properties and mechanical strength. Furthermore, THF's rapid volatility leads to uneven membrane formation. Dimethyl sulfoxide (DMSO) has strong dispersibility, but its high polarity affects the membrane's hydrophilicity, reduces oil-water separation efficiency, and negatively impacts polyaniline.

[0044] In summary, although these solvents have some ability to disperse SiO2, compared with dimethylformamide, they lead to uneven SiO2 dispersion, difficulty in film formation, poor film stability, and negative impacts on polyaniline. Therefore, dimethylformamide is a more suitable choice.

[0045] In some embodiments of the present invention, the concentration of polyaniline in solution B is 5–15 g / L, specifically, for example, 5 g / L, 10 g / L, or 15 g / L; the concentration of polyvinylpyrrolidone in solution B is 2–10 g / L, specifically, for example, 2 g / L, 3 g / L, 4 g / L, 5 g / L, 8 g / L, or 10 g / L; and the solvent of solution B is 0.5–1.5 mol·L⁻¹. -1 A hydrochloric acid solution.

[0046] In some embodiments of the present invention, polyaniline (PANI) and polyvinylpyrrolidone are dissolved in a solution with a concentration of 1 mol·L⁻¹. -1 In hydrochloric acid solution, under acidic conditions, the amino group (-NH) of polyaniline reacts with hydrogen ions (H+). + PANI + HCl → PANI + +Cl - This process forms protonated polyaniline, increasing its solubility in acidic environments. Simultaneously, polyvinylpyrrolidone, as a water-soluble polymer, can form complexes or blends with polyaniline, improving its dispersibility and uniformity. This blending enhances the electrical conductivity and mechanical properties of the polyaniline-modified composite film, while also improving its physical and chemical stability.

[0047] If the concentrations of polyaniline (PANI) and polyvinylpyrrolidone (PVP) in solution B exceed the ranges specified above, it will adversely affect the performance of the composite membrane, as follows:

[0048] Excessive polyaniline concentration can increase membrane brittleness, decrease mechanical strength, and make it prone to cracking or rupture. Furthermore, excessively high polyaniline concentration can lead to excessive conductivity, affecting its application performance and reducing flux. Conversely, insufficient polyaniline concentration results in inadequate electrical properties, weak mechanical strength, and compromised membrane stability.

[0049] Excessive polyvinylpyrrolidone (PVP) concentration may increase membrane swelling, affecting membrane stability and structure, and increasing surface roughness, thus reducing membrane separation efficiency. Conversely, excessively low concentration may lead to poor membrane stability and insufficient hydrophilicity, affecting membrane wettability and separation performance, especially in water treatment applications.

[0050] In some embodiments of the present invention, in step 1, the stirring parameters are set as follows: stirring at a temperature of 35–75°C and a speed of 400–600 r / min for 1–3 hours.

[0051] The stirring parameters in step 1 (such as stirring speed and time) are crucial for ensuring the homogeneity of the solution and the performance of the membrane.

[0052] If the stirring speed is too high, air bubbles will be introduced, affecting the surface quality of the membrane. Furthermore, high shear forces will lead to uneven particle dispersion, thus impacting the membrane's mechanical and electrical properties. Conversely, if the stirring speed is too low, the particles will not disperse sufficiently, resulting in uneven composition in the solution and affecting the membrane's stability and separation efficiency.

[0053] Excessive stirring time can cause the solution temperature to rise, affecting the membrane's formability and even leading to material degradation or over-polymerization. Conversely, insufficient stirring time results in incomplete mixing of the solution, uneven dispersion of polyaniline and PVP, which in turn affects the membrane's mechanical strength and properties.

[0054] Therefore, the stirring speed and time should be controlled within an appropriate range to ensure the homogeneity of the solution and avoid adverse effects on the membrane performance.

[0055] In some embodiments of the present invention, step 2, before mixing solution B with solution A, further includes stirring solution B at 75°C and a rotation speed of 400-600 r / min for 3-5 hours.

[0056] The purpose of stirring solution B within the aforementioned temperature range for a certain period is to ensure that all components in the solution are uniformly dispersed and fully dissolved, preventing particle aggregation and guaranteeing the uniformity and stability of the membrane. During stirring, controlling the temperature and time helps optimize the membrane's mechanical properties, conductivity, and separation efficiency, while also promoting uniform reaction and ensuring the final quality and performance of the membrane.

[0057] In some embodiments of the present invention, in step 2, the volume ratio of solution A to solution B is 1:1.

[0058] In some embodiments of the present invention, in step 3, the soaking is specifically: vertical soaking for 8 to 12 hours; the drying parameters are set to: drying at 80 to 120°C for 15 to 30 minutes.

[0059] The purpose of vertical immersion is to ensure sufficient contact between the membrane material and the solution, thereby forming a uniform membrane layer and optimizing its structure and performance. Immersion time exceeding the above-mentioned parameter range leads to excessive adsorption or deposition on the membrane surface, resulting in uneven membrane layer, inconsistent thickness, and even affecting the membrane's mechanical strength and separation efficiency. Simultaneously, changes in solution composition can also cause adverse alterations to the membrane's chemical structure, thus affecting its functionality.

[0060] In this invention, the drying parameters are adjusted based on the material properties of the membrane. Different membrane materials have different sensitivities to temperature and time; appropriate drying conditions help optimize the membrane's microstructure and improve its mechanical strength, porosity, and separation performance. Furthermore, the specific drying parameters (temperature and time) mentioned above can prevent the membrane from becoming brittle, collapsing, or exhibiting uneven pore size distribution during the drying process, ensuring the membrane's stability and functionality.

[0061] A second aspect of the present invention provides a polyaniline-modified composite film prepared according to the above-described preparation method.

[0062] The third aspect of this invention provides the application of the above-mentioned polyaniline modified composite membrane in oil-water separation.

[0063] The polyaniline-modified composite membrane of the present invention can effectively filter transformer floating oil aqueous solution, and is suitable for various types of oil-water mixtures, showing good adaptability.

[0064] Unless otherwise specified, the technical solutions described in this invention are all conventional solutions in the field, and the reagents or raw materials used are all purchased from commercial channels or are publicly available unless otherwise specified.

[0065] The pore size range of the polyvinylidene fluoride (PVDF) substrate used in the embodiments of the present invention is 0.1 to 0.5 μm; commercially available polyvinylidene fluoride (PVDF) substrates with a pore size range of 0.1 to 0.5 μm are also suitable for the present invention.

[0066] The average particle size of the SiO2 powder used in this embodiment of the invention is 25 nm.

[0067] The testing methods involved in the embodiments of the present invention are as follows:

[0068] Micromorphological analysis

[0069] To investigate the effect of polyaniline on film roughness and its influence on film wettability, scanning electron microscopy (SEM) and atomic force microscopy (AFM) were used to analyze the effect of polyaniline on film roughness. Field emission scanning electron microscopy (FEM) was used to observe the microstructure of different materials. The prepared samples were subjected to gold sputtering treatment at a voltage of 10 kV for 90 s, with an accelerating voltage of 5 kV during the test.

[0070] Surface chemical composition analysis

[0071] The chemical composition of PVDF films before and after PANI modification was investigated using ATR-FTIR and XPS methods. Fourier transform infrared spectroscopy was used to analyze the functional groups in the samples. The samples were dried before testing, and the scanning range was 500–4000 cm⁻¹. -1 .

[0072] X-ray photoelectron spectroscopy was used to perform solid surface analysis on the samples, including the chemical composition of the fiber membrane surface. The energy analysis range was 0–1500 eV to cover the binding energies of electrons of all possible elements.

[0073] The phase structure was analyzed using an X-ray diffractometer, with a test range of 5–80° and a scanning rate of 5° / min.

[0074] Mechanical performance analysis

[0075] The samples were cut into rectangular films of a certain area, and the clamping distance was set to 2 cm. The fracture strength, Young's modulus, and fracture growth rate of each sample were tested using a texture analyzer, and each test was performed in triplicate, and the average value was taken.

[0076] Formula for calculating separation efficiency

[0077] The oil content in the original solution and filtrate was determined by infrared spectrophotometry. The separation efficiency R (%) of the prepared membrane was calculated using the following equation (1):

[0078]

[0079] Wherein, C0 and C1 represent the oil content in the original emulsion and the filtrate after filtration, respectively.

[0080] Membrane flux J (Lm) -2 h -1 Its calculation equation is as shown in equation (2):

[0081]

[0082] Where V represents the volume of the filtrate (L), and A (m³) represents the volume of the filtrate. 2 ) represents the effective area of ​​the membrane, and T represents the separation time (h).

[0083] TOC content was determined by a total organic carbon analyzer using the non-dispersive infrared absorption method.

[0084] The technical solutions provided by the present invention will be described in detail below with reference to the embodiments, but they should not be construed as limiting the scope of protection of the present invention.

[0085] This invention provides a method for preparing a polyaniline (PANI) modified composite film, the steps of which are as follows:

[0086] S1. Activate the polyvinylidene fluoride (PVDF) substrate for 0.5–3 hours;

[0087] S2. Disperse SiO2 powder in 50 mL of polar organic solution and stir for 1 to 3 hours, denoted as solution A; the concentration of SiO2 in solution A is 2 to 10 g / L;

[0088] S3. Dissolve PANI and polyvinylpyrrolidone (PVP) in 50 mL of acidic solution, denoted as solution B; the concentration of PANI in solution B is 5–15 g / L, and the concentration of PVP is 2–10 g / L;

[0089] S4. Clean the activated PVDF substrate with deionized water and immerse it in solution A. Stir at 35-75°C for 1-3 hours at a speed of 400-600 r / min. After stirring, remove the PVDF substrate and clean it again with deionized water.

[0090] S5. Place solution B in a constant temperature water bath at 75℃ and stir for 3-5 hours at a speed of 400-600 r / min;

[0091] S6. Mix solution A after stirring in step S4 and solution B after stirring in step S5 at a volume ratio of 1:1, filter the mixture to remove the precipitate, and then vertically place the PVDF substrate cleaned in step S4 into the filtered mixture and soak for 8-12 hours.

[0092] S7. Remove the soaked PVDF substrate and place it in a drying oven to dry. The drying temperature is 80-120℃ and the drying time is 15-30 minutes. This will produce a PANI-modified composite film, denoted as PANI@PVDF.

[0093] Example 1

[0094] A PANI-modified composite membrane, denoted as PANI@PVDF-1, is prepared by the following steps:

[0095] S1. Activate the PVDF substrate in anhydrous ethanol for 2 hours;

[0096] S2. Disperse SiO2 powder in 50 mL of dimethylformamide (DMF) solution and stir for 2 h. This solution is denoted as solution A. The concentration of SiO2 in solution A is 2 g / L.

[0097] S3. Dissolve PANI and PVP in 50 mL of 1 mol·L⁻¹ solution. -1 In the hydrochloric acid solution, let's call it solution B; the concentration of PANI in solution B is 10 g / L, and the concentration of PVP is 2 g / L.

[0098] S4. Clean the PVDF substrate activated in step S1 with deionized water, immerse it in solution A, stir at 75°C for 2 hours at a speed of 500 r / min, remove the PVDF substrate after stirring, and clean it again with deionized water.

[0099] S5. Place solution B in a constant temperature water bath at 75℃ and stir for 4 hours at a speed of 500 r / min;

[0100] S6. Mix solution A after stirring in step S4 and solution B after stirring in step S5 at a volume ratio of 1:1, filter the mixture to remove the precipitate, and then vertically place the PVDF substrate cleaned in step S4 into the filtered mixture and soak for 10 hours.

[0101] S7. Remove the soaked PVDF substrate and place it in a drying oven to dry at 100℃ for 20 minutes to obtain the PANI@PVDF-1 composite film.

[0102] The PANI@PVDF-1 composite membrane prepared in this embodiment was tested and found to have a tensile strength of 30.1 MPa, a Young's modulus of 2.4 MPa, an elongation at break of 29.8%, and a membrane flux of 441.50 μm. -2 h -1 The oil / water solution separation efficiency reached 98.5%.

[0103] Example 2

[0104] A PANI-modified composite membrane, denoted as PANI@PVDF-2, is prepared by the following steps:

[0105] S1. Activate the PVDF substrate in anhydrous ethanol for 2 hours;

[0106] S2. Disperse SiO2 powder in 50 mL of DMF solution and stir for 2 h, denoted as solution A; the concentration of SiO2 in solution A is 6 g / L;

[0107] S3. Dissolve polyaniline and PVP in 50 mL of 1 mol·L⁻¹ solution. -1 In the hydrochloric acid solution, let's call it solution B; the concentration of PANI in solution B is 10 g / L, and the concentration of PVP is 6 g / L.

[0108] S4. Clean the PVDF substrate activated in step S1 with deionized water, immerse it in solution A, stir at 75°C for 2 hours at a speed of 500 r / min, remove the PVDF substrate after stirring, and clean it again with deionized water.

[0109] S5. Place solution B in a constant temperature water bath at 75℃ and stir for 4 hours at a speed of 500 r / min;

[0110] S6. Mix solution A after stirring in step S4 and solution B after stirring in step S5 at a volume ratio of 1:1, filter the mixture to remove the precipitate, and then vertically place the PVDF substrate cleaned in step S4 into the filtered mixture and soak for 10 hours.

[0111] S7. Remove the soaked PVDF substrate and place it in a drying oven to dry at 100℃ for 20 minutes to obtain the PANI@PVDF-2 composite film.

[0112] The PANI@PVDF-2 composite membrane prepared in this embodiment was tested and found to have a tensile strength of 55.2 MPa, a Young's modulus of 3.3 MPa, an elongation at break of 23.5%, and a membrane flux of 475.46 Lm. -2 h -1 The oil / water solution separation efficiency is 90%.

[0113] Example 3

[0114] A PANI-modified composite membrane, denoted as PANI@PVDF-3, is prepared by the following steps:

[0115] S1. Activate the PVDF substrate in anhydrous ethanol for 2 hours;

[0116] S2. Disperse SiO2 powder in 50 mL of DMF solution and stir for 2 h, denoted as solution A; the concentration of SiO2 in solution A is 10 g / L;

[0117] S3. Dissolve polyaniline and PVP in 1 mol·L⁻¹ -1 In the hydrochloric acid solution, let's call it solution B; the concentration of PANI in solution B is 10 g / L, and the concentration of PVP is 10 g / L.

[0118] S4. Clean the PVDF substrate activated in step S1 with deionized water, immerse it in solution A, stir at 75°C for 2 hours at a speed of 500 r / min, remove the PVDF substrate after stirring, and clean it again with deionized water.

[0119] S5. Place solution B in a constant temperature water bath at 75℃ and stir for 4 hours at a speed of 500 r / min;

[0120] S6. Mix solution A after stirring in step S4 and solution B after stirring in step S5 at a volume ratio of 1:1, filter the mixture to remove the precipitate, and then vertically place the PVDF substrate cleaned in step S4 into the filtered mixture and soak for 10 hours.

[0121] S7. Remove the soaked PVDF substrate and place it in a drying oven to dry at 100℃ for 20 minutes to obtain the PANI@PVDF-3 composite film.

[0122] The PANI@PVDF-3 composite membrane prepared in this embodiment was tested and found to have a tensile strength of 60.9 MPa, a Young's modulus of 3.1 MPa, an elongation at break of 19.9%, and a membrane flux of 458.48 Lm. -2 h -1 The oil / water solution separation efficiency was 98.73%, indicating the most thorough separation. An optical photograph of the PANI@PVDF-3 composite membrane prepared in this embodiment is shown below. Figure 1 As shown, the FESEM image is as follows Figure 2 As shown, by Figure 2 It can be seen that, compared with the unmodified PVDF membrane, the PANI@PVDF-3 composite membrane has a rougher surface and a denser structure, indicating that the polymerization of polyaniline increases the roughness of the fibers, and that PANI and PVDF have good compatibility. Meanwhile, from... Figure 2 It can be seen that the PANI@PVDF-3 membrane has a dense porous structure, and this compact structure gives it better mechanical properties.

[0123] Surface roughness analysis of the film was performed using atomic force microscopy (AFM). Figure 3 As shown, the base film surface exhibits a uniform uneven structure due to its uniform pores. In contrast, the PANI@PVDF surface displays an uneven uneven structure due to varying degrees of adsorption and aggregation of polyaniline nanofibers in different locations. Atomic force microscopy was used to precisely measure the surface roughness of the PVDF film and the PANI@PVDF-3 composite film. The average roughness of the PVDF film was 8.9 nm, indicating a relatively smooth surface. In contrast, the average roughness of the PANI@PVDF composite film increased significantly to 95.39 nm, which is related to the adsorption and aggregation of polyaniline nanowires on the film surface.

[0124] Multiple oil-water separation cycle tests were conducted using the PANI@PVDF-3 composite membrane, such as... Figure 6 As shown in the figure, the total organic carbon content of the filtrate was 17.2 mg / L, which meets the national wastewater discharge standards, indicating that the PANI@PVDF-3 composite membrane prepared in this invention has good antifouling properties and reusability.

[0125] The test method for oil-water separation circulation test is as follows:

[0126] 1. Experimental setup

[0127] Membrane material: Five different PANI@PVDF composite membranes were used, among which PANI@PVDF-3 composite membrane was the best choice, with the best separation effect.

[0128] Filtration device: The membrane is fixed with an inner diameter of 5cm and an effective separation area of ​​19.63cm². 2In the sand core filter device. The oil-water separation device used in the experiment is shown in the figure ( Figure 4 ).

[0129] 2. Preparation of floating oil / aqueous solution

[0130] Mix deionized water with an organic solvent (transformer surface oil) in a ratio of V. 去离子水 / V 有机溶剂 =100 / 1. After mixing, pour into the upper glass tube for oil-water separation.

[0131] The mixture was filtered under a pressure of 0.07 MPa to obtain a stock solution and filtrate containing an oil-water mixture.

[0132] 3. Separation process and data recording

[0133] After each filtration, the oil content in the original solution and filtrate was determined by infrared spectrophotometry to calculate the separation efficiency R (%).

[0134] Membrane flux (J) is determined by calculating the volume of filtrate (V), the effective area of ​​the membrane (A), and the separation time (T).

[0135] 4. Cyclic test procedure

[0136] In each cycle of the experiment, the PANI@PVDF-3 composite membrane was simply rinsed with water to restore the membrane flux.

[0137] The experiment will be repeated multiple times, and the membrane flux and TOC content will be checked after each experiment.

[0138] TOC Analysis: The TOC content in the filtrate was tested using a total organic carbon analyzer and non-dispersive infrared absorption spectrometry to assess the durability of the oil-water separation effect.

[0139] 5. Results of the cyclic experiment

[0140] After 5 cycles, the membrane flux decreased slightly, but it could be restored to near its original value by simple rinsing.

[0141] After the fifth cycle, the TOC content in the filtrate was 17.2 mg / L, which meets the national wastewater discharge standards.

[0142] Experimental results show that the PANI@PVDF-3 composite membrane has good antifouling properties and reusability, making it suitable for multiple uses while maintaining good separation performance.

[0143] 6. Summary

[0144] Cyclic testing was conducted to evaluate the performance of the composite membrane after multiple uses. The membrane flux decreased slightly after repeated filtration, but recovered with simple rinsing. The TOC content met environmental standards, demonstrating the membrane's good antifouling properties and reusability.

[0145] Example 4

[0146] The only difference from Example 3 is that in step S4, the stirring is carried out at a temperature of 35°C. All other steps and parameters are the same as in Example 3. The obtained PANI modified composite film is denoted as PANI@PVDF-4.

[0147] The membrane flux of the PANI@PVDF-4 composite membrane prepared in this embodiment was tested to be 339.62 Lm. -2 h -1 The oil / water solution separation efficiency is 95.5%.

[0148] Example 5

[0149] The only difference from Example 3 is that in step S4, the stirring is carried out at a temperature of 55°C. All other steps and parameters are the same as in Example 3. The obtained PANI modified composite film is denoted as PANI@PVDF-5.

[0150] The membrane flux of the PANI@PVDF-5 composite membrane prepared in this embodiment was tested to be 407.54 Lm. -2 h -1 The oil / water solution separation efficiency was 98.5%.

[0151] Figure 5 The figures show the experimental results of separating floating oil / aqueous solutions using five types of PANI@PVDF composite membranes prepared in Examples 1 to 5 of this invention. In the figures, bottles A, B, C, and D correspond to PANI@PVDF-2, PANI@PVDF-4, PANI@PVDF-1, and PANI@PVDF-5 composite membranes, respectively, while bottle E uses a PANI@PVDF-3 composite membrane. Figure 5 It can be seen that the oil content gradually decreases after separation. Bottle A shows obvious oil droplets, indicating incomplete oil-water separation. Bottles B, C, and D have a small amount of oil droplets, also indicating incomplete separation. Bottle E has virtually no visible oil droplets, indicating near-complete oil-water separation. Bottle E's oil-water separation was performed using a PANI@PVDF-3 composite membrane, demonstrating that the membrane achieves optimal separation performance when the heating temperature is 75℃ and the concentration ratio of SiO2, PVP, and polyaniline is 1:1:1. The original membrane flux was 390.5 L / m³. -2 h -1 The separation efficiency is 53.2%.

[0152] Further verification was conducted by increasing the stirring temperature in step S4 to 80°C, 85°C, and 90°C, based on Example 3 (i.e., the only difference from Example 3 is that stirring in step S4 is performed at temperatures of 80°C, 85°C, and 90°C, respectively; all other steps and parameters are the same as in Example 3). The results showed that as the stirring temperature in step S4 gradually increased from 35°C to 90°C, the membrane flux initially increased because higher temperatures help improve solution fluidity, reduce membrane resistance, and thus accelerate the separation process. However, excessively high temperatures can cause changes in the membrane structure, especially deformation of the membrane's pore structure due to thermal expansion or contraction, thereby affecting the membrane's mechanical strength and stability. High temperatures can also cause degradation or detachment of the membrane surface coating or modified materials (such as SiO2 and polyaniline), which affects the membrane's hydrophilicity and wettability, leading to a decrease in separation efficiency. Furthermore, prolonged stirring under excessively high temperatures reduces membrane durability, decreases membrane reusability, and makes the membrane surface more susceptible to fouling, affecting its cleaning effect. Therefore, the temperature should be kept within a suitable range to ensure the long-term stability of the membrane and the best separation effect.

[0153] Comparative Example 1

[0154] A PANI-modified composite membrane, denoted as PANI@PVDF-D1, is prepared by the following steps:

[0155] S1. Activate the PVDF substrate in anhydrous ethanol for 2 hours;

[0156] S2. Disperse SiO2 powder in 50 mL of DMF solution and stir for 2 h, denoted as solution A; the concentration of SiO2 in solution A is 10 g / L;

[0157] S3. Dissolve polyaniline and PVP in 50 mL of 1 mol·L⁻¹ solution. -1 In the hydrochloric acid solution, let's call it solution B; the concentration of PANI in solution B is 10 g / L, and the concentration of PVP is 10 g / L.

[0158] S4. Stir solution A at 75°C for 2 hours at a speed of 500 r / min;

[0159] S5. Place solution B in a constant temperature water bath at 75℃ and stir for 4 hours at a speed of 500 r / min;

[0160] S6. Mix solution A after stirring in step S4 and solution B after stirring in step S5 at a volume ratio of 1:1, filter the mixture to remove the precipitate, then wash the PVDF substrate activated in step S1 with deionized water, and vertically place it into the filtered mixture for 10 hours.

[0161] S7. Remove the soaked PVDF substrate and place it in a drying oven to dry at 100°C for 20 minutes to obtain the PANI@PVDF-D1 composite film. (That is, the only difference from Example 3 is that the step of immersing the PVDF substrate in solution A is omitted.)

[0162] The PANI@PVDF-D1 prepared in this comparative example was subjected to the same performance verification as in Example 3. The results showed that PANI@PVDF-D1 had a tensile strength of 40.3 MPa, a Young's modulus of 2.0 MPa, an elongation at break of 28.7%, and a membrane flux of 382.5 Lm. -2 h -1 Oil / water solution separation efficiency: 83%.

[0163] Comparing Comparative Example 1 and Example 3, it can be seen that omitting the step of immersing the PVDF substrate in solution A significantly reduces the performance of the composite membrane. Specifically, mechanical properties deteriorate, such as reduced tensile strength and Young's modulus; insufficient surface roughness leads to decreased hydrophilicity and wettability, resulting in significantly lower separation efficiency and membrane flux compared to Example 3. Furthermore, due to the lack of SiO2 coating modification on the membrane surface, the filtrate after oil-water separation has a high oil content, making it difficult to meet environmental emission standards.

[0164] The embodiments described above are merely preferred embodiments of the present invention and are not intended to limit the scope of the present invention. Various modifications and improvements made by those skilled in the art to the technical solutions of the present invention without departing from the spirit of the present invention should fall within the protection scope defined by the claims of the present invention.

Claims

1. A method for preparing a polyaniline-modified composite film, characterized in that, Includes the following steps: Step 1: Activate and clean the polyvinylidene fluoride sheet, then immerse it in solution A and stir. After stirring, remove the polyvinylidene fluoride sheet and clean it to obtain the treated polyvinylidene fluoride sheet. Step 2: Mix solution A and solution B and then filter to obtain a mixture; Step 3: Immerse the treated polyvinylidene fluoride sheet in the mixture, remove it after immersion and dry it to obtain the polyaniline modified composite film; Solution A is a SiO2 solution; Solution B is a mixed solution of polyaniline and polyvinylpyrrolidone.

2. The method for preparing the polyaniline-modified composite film according to claim 1, characterized in that, The polyvinylidene fluoride sheet was activated by placing it in anhydrous ethanol for 0.5 to 3 hours.

3. The method for preparing the polyaniline-modified composite film according to claim 1, characterized in that, The concentration of SiO2 in solution A is 2–10 g / L; the solvent of solution A is dimethylformamide; and the particle size of SiO2 in solution A is 5 nm–50 nm.

4. The method for preparing the polyaniline-modified composite film according to claim 1, characterized in that, The concentration of polyaniline in solution B is 5–15 g / L, and the concentration of polyvinylpyrrolidone is 2–10 g / L; the solvent of solution B is 0.5–1.5 mol·L⁻¹. -1 A hydrochloric acid solution.

5. The method for preparing the polyaniline-modified composite film according to claim 1, characterized in that, In step 1, the stirring parameters are set as follows: stirring at 400-600 r / min for 1-3 hours at a temperature of 35-75℃.

6. The method for preparing the polyaniline-modified composite film according to claim 1, characterized in that, In step 2, before mixing solution B with solution A, the process also includes stirring solution B at 75°C and a speed of 400-600 r / min for 3-5 hours.

7. The method for preparing the polyaniline-modified composite film according to claim 1, characterized in that, In step 2, the volume ratio of solution A to solution B is 1:

1.

8. The method for preparing the polyaniline-modified composite film according to claim 1, characterized in that, In step 3, the soaking is specifically: vertical soaking for 8 to 12 hours; the drying parameters are set to: drying at 80 to 120°C for 15 to 30 minutes.

9. The polyaniline-modified composite film prepared by the preparation method according to any one of claims 1 to 8.

10. The application of the polyaniline-modified composite membrane as described in claim 9 in oil-water separation.

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