PANI modified PSS / PVDF semi-interpenetrating network structure ultrafiltration membrane and preparation method thereof
By modifying the PANI layer on the surface of the PSS/PVDF ultrafiltration membrane and constructing a PANI-modified PSS/PVDF semi-interpenetrating network structure, the problems of poor hydrophilicity and susceptibility to contamination of the PVDF ultrafiltration membrane were solved, and a significant improvement in high flux and anti-pollution performance was achieved, making it suitable for stable applications in extreme environments.
Patent Information
- Application Number
- CN202510847639.1
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2025-06-24
- Publication Date
- 2025-09-12
AI Technical Summary
Existing PVDF ultrafiltration membranes have problems such as poor hydrophilicity, susceptibility to contamination, and low flux, which limit their application range and service life.
The PANI layer was modified on the surface of the PSS/PVDF ultrafiltration membrane by a stepwise polymerization method or a synchronous polymerization method to construct a PANI-modified PSS/PVDF semi-interpenetrating network structure to improve the hydrophilicity and anti-fouling properties of the membrane.
The hydrophilicity and anti-fouling properties of the membrane were significantly improved, the pure water flux increased by 500%, the flux recovery rate increased to 95.59%, and excellent flux stability was maintained under extreme pH environments. The thermal decomposition temperature was increased by about 22°C, showing excellent engineering application potential.
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Figure CN120618282A_ABST
Abstract
Description
Technical Field
[0001] The invention belongs to the technical field of membrane materials, and particularly relates to a PANI-modified PSS / PVDF semi-interpenetrating network structure ultrafiltration membrane and a preparation method thereof. Background Art
[0002] Polyvinylidene fluoride (PVDF) occupies a key position in the field of separation membrane materials due to its outstanding physical and chemical properties. This polymer not only exhibits excellent chemical inertness and mechanical properties, but also possesses excellent anti-fouling properties and adaptability to thermally induced phase separation processing, making it the preferred substrate for ultrafiltration membrane systems. However, traditional PVDF ultrafiltration membranes still have some shortcomings, such as poor hydrophilicity, susceptibility to contamination, and low flux, which limit their further application. Among them, poor hydrophilicity can lead to decreased membrane flux and increased membrane fouling, susceptibility to contamination can shorten membrane life and increase operating costs, and low flux limits the scope of application of ultrafiltration technology.
[0003] To overcome these issues, existing technologies have used various modification methods to enhance the performance of PVDF ultrafiltration membranes. A semi-interpenetrating network structure can be achieved by introducing hydrophilic polymers into the PVDF matrix, forming an interpenetrating network structure, thereby improving the membrane's hydrophilicity and anti-fouling properties. Surface modification can also be achieved by introducing functional groups or polymers onto the membrane surface, imparting new properties such as antibacterial and catalytic properties. Summary of the Invention
[0004] In view of the shortcomings of existing PVDF ultrafiltration membranes in hydrophilicity, anti-fouling and separation performance, the present invention provides a PANI-modified PSS / PVDF semi-interpenetrating network structure ultrafiltration membrane and a preparation method.
[0005] The method includes: a method for preparing a PANI-modified PSS / PVDF semi-interpenetrating network structure ultrafiltration membrane, characterized in that: the method includes: step 1, preparing a PSS / PVDF ultrafiltration membrane; step 2, using the PSS / PVDF ultrafiltration membrane obtained in step 1 as the base membrane M1, and using a stepwise polymerization method or a synchronous polymerization method to modify a PANI layer on the surface of the PSS / PVDF ultrafiltration membrane.
[0006] Furthermore, the step one includes: step one, pretreatment, drying the PVDF powder; step one two, preparation of the casting solution, accurately measuring dimethylformamide solution DMF, sodium p-styrene sulfonate SSS, PVDF, polyvinyl pyrrolidone PVP and potassium persulfate KPS, first placing sodium styrene sulfonate SSS in dimethylformamide solution DMF solution and stirring to dissolve, then sequentially adding PVDF, polyvinyl pyrrolidone PVP and dimethylformamide solution DMF solution to a round-bottom flask, stirring for 30 minutes under constant temperature, adding crosslinking agent DVB, continuing to stir for 30 minutes, then adding potassium persulfate KPS and stirring; step one three, standing and degassing; step one four, scraping: casting the casting solution on a glass plate, using a scraping knife to scrape the film at a uniform speed; step one five, phase conversion into film: waiting for 30 minutes after scraping S, place the glass plate containing the casting solution steadily in the deionized water of the coagulation bath, wait until the membrane is completely detached from the glass plate and the phase transformation membrane process is completed, then transfer the membrane to deionized water and continue to soak for 24 h.
[0007] Furthermore, the optimal preparation conditions of PSS / PVDF ultrafiltration membrane are: PVDF content is 15 wt. %, sodium styrene sulfonate content is 2 wt. % SSS, polyvinyl pyrrolidone content is 1.5 wt. %, reaction time was 7 h, and reaction temperature was 70℃.
[0008] Furthermore, the step 2 includes: a stepwise polymerization method of first soaking the base membrane M1 in a mixed solution of aniline and benzenesulfonic acid for 10 h, then placing it in an aqueous ammonium persulfate solution for reaction, and finally washing and soaking it in a 0.1 M hydrochloric acid solution to obtain a PANI-modified PSS / PVDF ultrafiltration membrane M2.
[0009] Furthermore, the concentration of aniline was 0.06 mol / L, the concentration of the mixed solution of aniline and benzenesulfonic acid was 0.18 mol / L, the concentration of ammonium persulfate was 0.1 mol / L, and the reaction time was 6 h.
[0010] Furthermore, the step 2 includes: the synchronous polymerization method is to place M1 in a homemade reactor with the membrane facing down, use an isolation device to compact the membrane, add an aqueous ammonium persulfate solution into the device, and then quickly assemble it with a beaker containing a mixed solution of aniline and P-TSA. After the reaction at room temperature, the membrane is taken out and rinsed and soaked with a 0.1 M hydrochloric acid solution to obtain a PANI-modified PSS / PVDF ultrafiltration membrane M3.
[0011] Furthermore, the concentration of aniline was 0.06 mol / L, the mixed concentration of the aniline and benzenesulfonic acid mixed solution was 0.18 mol / L, the concentration of ammonium persulfate was 0.1 mol / L, and the reaction time was 6 h.
[0012] A method for preparing a PANI-modified PSS / PVDF semi-interpenetrating network structure ultrafiltration membrane is disclosed. Beneficial effects
[0013] The invention prepares a PANI-modified PSS / PVDF semi-interpenetrating network structure ultrafiltration membrane through double modification. The PSS / PVDF ultrafiltration membrane has excellent hydrophilicity, high porosity and high flux as well as ideal anti-pollution performance and separation performance.
[0014] The constructed PSS / PVDF semi-interpenetrating network ultrafiltration membrane significantly reduced the membrane surface contact angle and increased pure water flux by 500%. After PANI modification, the modified membrane achieved a flux recovery rate of 95.59% in bovine serum albumin filtration experiments, a 41% increase compared to the original membrane. This simultaneously enhanced hydrophilicity, permeability, and selectivity. The membrane exhibited significantly improved resistance to typical membrane contaminants, such as proteins, dyes, and microorganisms, with a flux recovery rate exceeding 90%. The membrane maintained excellent flux stability even in extreme pH environments (pH = 2-12). Its thermal decomposition temperature (Td = 364°C) was approximately 22°C higher than that of the original PVDF membrane, demonstrating excellent potential for engineering applications.
[0015] When the PVDF content is 15 wt. %, SSS content is 2 wt. %, PVP content is 1.5 wt. %, stirring time was 7 h, stirring temperature was 70 ℃, under these conditions, the water flux of the ultrafiltration membrane was 737.21 L / m 2 h, the retention rate is 86.83%; When prepared by adsorption post-polymerization method, the concentration of aniline was 0.06 mol / L, the concentration of p-toluenesulfonic acid (P-TSA) was 0.18 mol / L, the concentration of ammonium persulfate (APS) was 0.1 mol / L, and the stirring time was 6 h. Under these conditions, the pure water flux was 265.39 L / m 2 h, the retention rate was 96.33%; When prepared by synchronous polymerization, the concentration of aniline was 0.06 mol / L, the concentration of p-toluenesulfonic acid (P-TSA) was 0.18 mol / L, the concentration of ammonium persulfate (APS) was 0.1 mol / L, and the stirring time was 6 h. Under these conditions, the water flux was 401.03 L / m 2 ·h, the retention rate is 99.02%.
[0016] The PANI-modified PSS / PVDF ultrafiltration membrane has an average pore size of 0.022 μm and a porosity of 62.8%. The membrane surface roughness Ra is 65.85 nm and the membrane surface potential is -15 mV. The PANI-modified PSS / PVDF ultrafiltration membrane has a water contact angle of 42.9° and a water flux of 401.03 L / m 2 h, with a retention rate of 99.02% and a thermal decomposition temperature of 480°C. After 28 days of immersion in strong acid and strong base solutions, the BSA retention rate of the PANI-modified PSS / PVDF ultrafiltration membrane remained above 80%. After three simulated pollutant filtration cycle tests, the FRR of the PANI-modified PSS / PVDF ultrafiltration membrane reached 95.59%, while that of the PVDF ultrafiltration membrane was only 54.30%. The static adsorption capacity of BSA on the PANI-modified PSS / PVDF ultrafiltration membrane was only 6.18 g / cm 3 The inhibition rates of Escherichia coli and Staphylococcus aureus were both greater than 80%; the water flux of the PANI-modified PSS / PVDF ultrafiltration membrane for MB and CR aqueous solutions were 274.43 L / m²·h and 231.18 L / m²·h, respectively, and the retention rate remained above 99%; in the circulation test, a relatively high stable water flux could be maintained, and the flux recovery rate could reach 97%. BRIEF DESCRIPTION OF THE DRAWINGS
[0017] Figure 1 Schematic diagram of the operation of the step-by-step aggregation (a) and synchronous aggregation (b) methods; Figure 2 This is a diagram of the formation process of PSS / PVDF polymer with semi-interpenetrating network structure; Figure 3 This is a schematic diagram of the polymerization and anchoring principle of the PANI modified layer on the PSS / PVDF ultrafiltration membrane; Figure 4 This is a diagram of the formation process of PSS / PVDF ultrafiltration membrane and PANI modification layer; Figure 5 These are photos of the appearance of different ultrafiltration membranes; Figure 6 is the EDS spectrum image of M1; Figure 7 SEM images of the surface (a) and cross-section (b) of different ultrafiltration membranes; Figure 8 It is the three-dimensional morphology and plane diagram of the surface of different ultrafiltration membranes; Figure 9 is the water contact angle of different ultrafiltration membranes ( , n=3); Figure 10 is the pure water flux and rejection rate of different ultrafiltration membranes ( , n = 3) histogram; Figure 11It is the thermogravimetric analysis graph of different ultrafiltration membranes; Figure 12 This is the pure water flux diagram of different ultrafiltration membranes after soaking in NaOH solution for different time periods; Figure 13 This is the pure water flux diagram of different ultrafiltration membranes after soaking in HCl solution for different time periods; Figure 14 The results of BSA cyclic filtration experiments on different ultrafiltration membranes (a), the flux recovery rate (FRR), the proportion of total fouling (Rt), the proportion of irreversible fouling (Rir), and the proportion of reversible fouling (Rr) on different ultrafiltration membranes after three cycles of filtration (b), and the bar graph of the static adsorption capacity of BSA on different ultrafiltration membranes (c); Figure 15 This is a graph showing the antibacterial effects of different ultrafiltration membranes on Escherichia coli and Staphylococcus aureus; Figure 16 This is a bar graph showing the antibacterial activity of different ultrafiltration membranes against Escherichia coli and Staphylococcus aureus; Figure 17 It is a bar graph of the static adsorption capacity of MB (a) and CR (b) by different ultrafiltration membranes; Figure 18 This is a diagram showing the treatment effects of two dye aqueous solutions using different ultrafiltration membranes; Figure 19 This is a graph showing the water flux and rejection rate of CR solution treated with different ultrafiltration membranes; Figure 20 This is a graph showing the water flux and rejection rate of MB solution treated with different ultrafiltration membranes; Figure 21 This is the principle diagram of the interception of CR dye aqueous solution by M2 and M3; Figure 22 This is the principle diagram of the interception of MB dye aqueous solution by M2 and M3; Figure 23 It is the cyclic filtering diagram of M2 and M3 on CR (a) and MB (b). DETAILED DESCRIPTION
[0018] Specific embodiment 1: A method for preparing a PANI-modified PSS / PVDF semi-interpenetrating network structure ultrafiltration membrane, the method comprising: step 1, preparing a PSS / PVDF ultrafiltration membrane; The step one comprises: step one, pretreatment, placing the PVDF powder in a vacuum drying oven, and continuously drying it at a constant temperature of 75±1°C for 4 hours; step one two, preparing a casting solution, accurately measuring dimethylformamide solution DMF, sodium p-styrene sulfonate SSS, PVDF, polyvinyl pyrrolidone PVP and potassium persulfate KPS, first placing sodium styrene sulfonate SSS in dimethylformamide solution DMF solution and stirring to dissolve, then sequentially adding PVDF, polyvinyl pyrrolidone PVP and dimethylformamide solution DMF solution to a round-bottom flask, stirring at a constant temperature for 30 minutes, adding a cross-linking agent DVB, wherein DVB is 1 / 10 of the SSS content, continuing to stir for 30 minutes, and then adding potassium persulfate KPS and stirring, wherein KPS is 1 / 10 of the SSS content; step one three, standing and degassing: the round-bottom flask is sealed and placed at room temperature for 12 h; Step 14, scraping: take a glass plate with a flat surface and pretreat it before use to keep it clean and dry; cast the casting liquid on the glass plate and use a scraping knife with a specification of 200 μm to scrape the film at a constant speed; Step 15, phase transformation into film: wait 30 seconds after scraping, place the glass plate containing the casting liquid steadily in a coagulation bath (deionized water), wait until the film is completely detached from the glass plate, and the phase transformation into film process is completed. In order to remove the residual solvent, initiator and cross-linking agent in the film, transfer the membrane to deionized water and continue soaking for 24 hours.
[0019] The optimal preparation conditions of PSS / PVDF ultrafiltration membrane are: PVDF content of 15 wt.%, sodium styrene sulfonate content of 2 wt.%, polyvinylpyrrolidone content of 1.5 wt.%, reaction time of 7 h, and reaction temperature of 70 ℃.
[0020] In step 2, the PSS / PVDF ultrafiltration membrane obtained in step 1 is used as base membrane M1. A PANI layer is then modified on the surface of the PSS / PVDF ultrafiltration membrane using a stepwise polymerization method. The stepwise polymerization method involves first soaking the base membrane M1 in a mixed solution of aniline and benzenesulfonic acid (P-TSA) for 10 hours, then reacting it in an aqueous solution of ammonium persulfate (APS). Finally, the membrane is rinsed and soaked in a 0.1 M hydrochloric acid solution to remove monomers and oxidants attached to the membrane surface, resulting in the PANI-modified PSS / PVDF ultrafiltration membrane M2.
[0021] The concentration of aniline was 0.06 mol / L, the concentration of the mixed solution of aniline and benzenesulfonic acid was 0.18 mol / L, the concentration of ammonium persulfate was 0.1 mol / L, and the reaction time was 6 h.
[0022] Under these conditions, the pure water flux of the PANI-modified PSS / PVDF ultrafiltration membrane was 265.39 L / m 2 ·h, and the retention rate was 96.33%.
[0023] Specific embodiment 2: A method for preparing a PANI-modified PSS / PVDF semi-interpenetrating network structure ultrafiltration membrane, the method comprising: step 1, preparing a PSS / PVDF ultrafiltration membrane; The step one comprises: step one, pretreatment, placing the PVDF powder in a vacuum drying oven, and continuously drying it at a constant temperature of 75±1°C for 4 hours; step one two, preparing a casting solution, accurately measuring dimethylformamide solution DMF, sodium p-styrene sulfonate SSS, PVDF, polyvinyl pyrrolidone PVP and potassium persulfate KPS, first placing sodium styrene sulfonate SSS in dimethylformamide solution DMF solution and stirring to dissolve, then sequentially adding PVDF, polyvinyl pyrrolidone PVP and dimethylformamide solution DMF solution to a round-bottom flask, stirring at a constant temperature for 30 minutes, adding a crosslinking agent DVB, continuing to stir for 30 minutes, and then adding potassium persulfate KPS and stirring; step one three, standing and degassing: sealing the round-bottom flask and placing it at room temperature for 12 hours; step one four, scraping the film: taking a glass plate with a smooth surface, pretreating it before use to keep it clean and dry; casting the casting solution on the glass plate, using a specification of 200 The film was scraped at a constant speed with a scraping knife of 0.01 μm; Step 15, phase transformation film formation: wait 30 seconds after scraping the film, place the glass plate containing the casting solution steadily in a coagulation bath (deionized water), wait until the film is completely detached from the glass plate, and the phase transformation film formation process is completed. In order to remove the residual solvent, initiator and cross-linking agent in the film, transfer the membrane to deionized water and continue soaking for 24 hours.
[0024] The optimal preparation conditions of PSS / PVDF ultrafiltration membrane are: PVDF content is 15 wt. %, sodium styrene sulfonate content is 2 wt. %, polyvinyl pyrrolidone content is 1.5 wt. %, reaction time was 7 h, and reaction temperature was 70 ℃.
[0025] In step 2, the PSS / PVDF ultrafiltration membrane obtained in step 1 was used as the base membrane M1. A PANI layer was then modified on the surface of the PSS / PVDF ultrafiltration membrane using a synchronous polymerization method. The synchronous polymerization method involved placing M1 in a homemade reactor with the membrane facing downward. The membrane was compacted using an isolation device. After adding an aqueous ammonium persulfate (APS) solution to the reactor, the membrane was quickly assembled with a beaker containing a mixed solution of aniline and P-TSA. After the reaction was completed at room temperature, the membrane was removed and rinsed and soaked in 0.1 M hydrochloric acid to remove monomers and oxidants attached to the membrane surface, resulting in the PANI-modified PSS / PVDF ultrafiltration membrane M3.
[0026] The concentration of aniline was 0.06 mol / L, the concentration of the mixed solution of aniline and benzenesulfonic acid was 0.18 mol / L, the concentration of ammonium persulfate was 0.1 mol / L, and the reaction time was 6 h.
[0027] Under these conditions, the pure water flux of the PANI-modified PSS / PVDF ultrafiltration membrane was 401.03 L / m 2 ·h, the retention rate is 99.02%.
[0028] Experimental data: Ultrafiltration membranes were prepared according to the preparation methods of implementation mode one and implementation mode two, and the contact angles of the membranes were measured using a static contact angle tester. The water contact angles of PSS / PVDF ultrafiltration membrane M1, PANI-modified PSS / PVDF ultrafiltration membranes M2 and M3 were 63.3°, 52.8° and 42.9°, respectively. Compared with the water contact angle of 81.3° of PVDF ultrafiltration membrane M0, they decreased by 18°, 28.5° and 38.4°, respectively, confirming that the double modification improved the hydrophilicity of the PVDF ultrafiltration membrane.
[0029] The membrane permeability and separation effect were evaluated by measuring the pure water flux and BSA rejection rate. Compared with the PVDF ultrafiltration membrane (M0), the pure water flux of the PSS / PVDF ultrafiltration membrane (M1) and the PANI-modified PSS / PVDF ultrafiltration membrane (M2, M3) increased by 595.67 L / m 2 h, 123.85 L / m 2 h and 259.49 L / m 2 h. The retention rate of PANI-modified PSS / PVDF ultrafiltration membrane was higher than 95%, confirming that dual modification can improve the filtration performance of PVDF ultrafiltration membrane.
[0030] A universal material testing machine was used to test the tensile strength of the membrane and evaluate its elasticity. Compared with the PVDF ultrafiltration membrane (M0), the tensile strength and elongation at break of the PANI-modified PSS / PVDF ultrafiltration membranes (M2 and M3) were improved, indicating that the dual modification strategy can improve the mechanical properties of the PVDF ultrafiltration membrane.
[0031] Standard liquid permeation tests were used to determine the porosity and separation efficiency of the membranes, and the measured data were recorded. Non-isothermal decomposition experiments were conducted on the ultrafiltration membranes using a thermogravimetric analyzer (NETZSCH STA 449F3) under nitrogen protection. The thermal properties of the membranes were analyzed by thermogravimetric analysis. The PSS / PVDF ultrafiltration membrane (M1) and the PANI-modified PSS / PVDF ultrafiltration membranes (M2 and M3) exhibited large-scale weight loss temperatures around 480°C, while the PVDF ultrafiltration membrane (M0) exhibited a large-scale weight loss temperature of 450°C. Furthermore, the PANI-modified PSS / PVDF ultrafiltration membrane exhibited an initial decomposition temperature exceeding 300°C, confirming that the dual modification effectively improved the thermal stability of the PVDF ultrafiltration membrane.
[0032] Corrosion resistance was tested by measuring the change in pure water flux after the ultrafiltration membranes were immersed in NaOH and HCl solutions for different periods of time. The PANI-modified PSS / PVDF ultrafiltration membranes (M2 and M3) exhibited excellent corrosion resistance. In particular, M3 exhibited minimal flux growth after immersion in strong acid and alkali solutions for a certain period of time, while maintaining a BSA retention rate above 80%.
[0033] Bovine serum albumin (BSA) was used as a model pollutant to evaluate the membrane's anti-fouling performance through static adsorption experiments. After a long period of cyclic filtration, the reversible fouling ratio of M3 was 4.41%, the flux recovery rate reached 95.59%, and the static BSA adsorption capacity was only 6.18 g / cm 3 , which confirmed that M3 can effectively resist BSA contamination, and the obtained M3 has better anti-pollution ability than the PVDF-based ultrafiltration membrane studied by the research group in the early stage and by others.
[0034] Gram-positive bacteria (Staphylococcus aureus) and Gram-negative bacteria (Escherichia coli) were used as experimental test strains to determine the anti-biofouling performance of the ultrafiltration membrane. The classic plate count method was used to quantify the antibacterial performance of the ultrafiltration membrane. The antibacterial performance test results showed that the PANI-modified PSS / PVDF ultrafiltration membrane had excellent antibacterial and anti-biofouling properties, with a certain inhibitory effect on both Escherichia coli and Staphylococcus aureus. The inhibition rate of M3 against both bacteria was greater than 80%. PSS / PVDF ultrafiltration membranes, PANI-modified PSS / PVDF ultrafiltration membranes, and PVDF ultrafiltration membranes prepared according to specific embodiments were used to treat methylene blue (MB) and Congo red (CR) dye solutions. The separation performance of the different ultrafiltration membranes was evaluated by systematically measuring water flux and retention rate. Static dye adsorption experiments were also conducted on each membrane, and long-term operational stability testing of the PANI-modified PSS / PVDF ultrafiltration membrane was conducted to comprehensively evaluate its practical application potential. The results are as follows: Dye solution filtration tests revealed that the PSS / PVDF ultrafiltration membrane M1 exhibited excellent retention of MB dye aqueous solution, while the PANI-modified PSS / PVDF membranes M2 and M3 exhibited excellent retention of MB and CR dye aqueous solutions. These membranes maintained retention rates above 99% while exhibiting high water flux. The PANI-modified PSS / PVDF ultrafiltration membranes obtained through dual modification demonstrated excellent performance in dye wastewater treatment.
[0035] The static adsorption test showed that the static adsorption capacity of MB by the four ultrafiltration membranes was greater than that of CR. The size of the static adsorption capacity was related to factors such as the charge type of the pollutant, the charge type of the membrane surface and the membrane surface roughness.
[0036] Long-term stability tests have shown that the PANI-modified PSS / PVDF ultrafiltration membrane M3 can maintain a relatively high stable water flux in long-term tests, and the flux recovery rate can reach 97% after flushing, showing excellent anti-pollution effect.
Claims
1. A method for preparing a PANI-modified PSS / PVDF semi-interpenetrating network structure ultrafiltration membrane, characterized in that: The method comprises: step 1, preparing a PSS / PVDF ultrafiltration membrane; step 2, using the PSS / PVDF ultrafiltration membrane obtained in step 1 as a base membrane M1, and modifying a PANI layer on the surface of the PSS / PVDF ultrafiltration membrane by a stepwise polymerization method or a synchronous polymerization method.
2. The preparation method according to claim 1, wherein: The step one comprises: Step 11, pretreatment, drying the PVDF powder; Step 12, preparation of casting solution, accurately measuring dimethylformamide solution DMF, sodium p-styrene sulfonate SSS, PVDF, polyvinyl pyrrolidone PVP and potassium persulfate KPS, first placing sodium styrene sulfonate SSS in dimethylformamide solution DMF solution and stirring to dissolve, then adding PVDF, polyvinyl pyrrolidone PVP, dimethylformamide solution DMF solution in turn to the round-bottom flask, stirring at a constant temperature for 30 minutes, adding cross-linking agent DVB, continuing to stir for 30 minutes, and then adding potassium persulfate KPS and stirring; Step 13, standing and degassing; Step 14, scraping: casting the casting solution on a glass plate, using a scraping knife to scrape the film at a constant speed; Step 15, phase transformation into film: wait 30 seconds after scraping, place the glass plate containing the casting solution steadily in the deionized water in the coagulation bath, wait until the film completely falls off the glass plate, completing the phase transformation into film process, and then transfer the membrane to deionized water and continue soaking for 24 hours.
3. The preparation method according to claim 2, wherein: The optimal preparation conditions of PSS / PVDF ultrafiltration membrane are: PVDF content is 15 wt. %, sodium styrene sulfonate content is 2 wt. % SSS, polyvinyl pyrrolidone content is 1.5 wt. %, reaction time was 7 h, and reaction temperature was 70 ℃.
4. The preparation method according to claim 1, wherein: The step 2 includes: the base membrane M1 is first placed in a mixed solution of aniline and benzenesulfonic acid and soaked for 10 hours by a step polymerization method, then placed in an aqueous ammonium persulfate solution for reaction, and finally rinsed and soaked in a 0.1 M hydrochloric acid solution to obtain a PANI-modified PSS / PVDF ultrafiltration membrane M2.
5. The preparation method according to claim 4, characterized in that: The concentration of aniline was 0.06 mol / L, the concentration of the mixed solution of aniline and benzenesulfonic acid was 0.18 mol / L, the concentration of ammonium persulfate was 0.1 mol / L, and the reaction time was 6 h.
6. The preparation method according to claim 1, wherein: The second step includes: the synchronous polymerization method is to place M1 in a homemade reactor with the membrane facing down, use an isolation device to compact the membrane, add an aqueous ammonium persulfate solution into the device, and then quickly assemble it with a beaker containing a mixed solution of aniline and P-TSA. After the reaction at room temperature, the membrane is taken out and rinsed and soaked with a 0.1 M hydrochloric acid solution to obtain a PANI-modified PSS / PVDF ultrafiltration membrane M3.
7. The preparation method according to claim 6, characterized in that: The concentration of aniline was 0.06 mol / L, the concentration of the mixed solution of aniline and benzenesulfonic acid was 0.18 mol / L, the concentration of ammonium persulfate was 0.1 mol / L, and the reaction time was 6 h.
8. An ultrafiltration membrane prepared by the method for preparing the PANI-modified PSS / PVDF semi-interpenetrating network structure ultrafiltration membrane according to claim 1.