Piezoelectric-conductive composite ultrafiltration membrane, preparation method and application thereof
By combining piezoelectric and conductive materials to form a heterojunction structure and operating under pulsed hydraulic conditions, the membrane fouling problem of ultrafiltration membranes is solved, achieving a high-efficiency, low-energy-consumption self-cleaning effect and significantly improving the membrane's anti-fouling performance.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- BEIJING FORESTRY UNIVERSITY
- Filing Date
- 2026-04-08
- Publication Date
- 2026-06-05
AI Technical Summary
Existing ultrafiltration membranes suffer from membrane fouling during the treatment process, leading to decreased flux and increased operating costs. Existing modification strategies, such as CNT modification and piezoelectric nanomaterial modification, have problems with high energy consumption or low efficiency, and have not yet effectively combined the piezoelectric-conductive synergistic effect of composite materials.
By combining piezoelectric and conductive materials to form a heterojunction structure and operating under pulsed hydraulic conditions, the electronic transport and adsorption properties of the conductive materials are combined with the piezoelectric effect to achieve in-situ degradation of pollutants accumulated on the membrane surface.
It significantly improves the antifouling performance of ultrafiltration membranes, reduces energy consumption and operational complexity, extends membrane lifespan, reduces maintenance costs, and has good antifouling effects against different types of organic pollutants.
Smart Images
Figure CN122141497A_ABST
Abstract
Description
Technical Field
[0001] This invention relates to the field of membrane separation technology, and in particular to a piezoelectric-conductive composite ultrafiltration membrane, its preparation method, and its application. Background Technology
[0002] Membrane separation technology, especially ultrafiltration technology, has been widely used in water treatment, food processing, and biomedicine due to its high efficiency and low energy consumption. However, membrane fouling is a key bottleneck restricting the development of ultrafiltration membrane technology. During the filtration process, organic matter, colloids, microorganisms, and other substances in the feed liquid can be adsorbed and deposited on the membrane surface, leading to a decrease in membrane flux, deterioration of product water quality, increased operating costs, and a significant shortening of membrane lifespan.
[0003] To alleviate membrane fouling, researchers have conducted various modification studies on membrane materials. A common strategy is to modify membranes using carbon nanotubes (CNTs). CNT-modified membranes possess both adsorption and conductivity. On the one hand, the adsorption of CNTs can retain some pollutants, improving effluent quality. However, this adsorption itself leads to a large accumulation of pollutants on the membrane surface, which in turn exacerbates membrane fouling. On the other hand, utilizing the conductivity of CNTs, pollutants accumulated on the membrane surface can be electrochemically removed by applying a negative voltage to the membrane, thereby mitigating fouling. However, this method requires a continuous external electric field during filtration, increasing the system's energy consumption and operational complexity.
[0004] Another strategy is to modify the membrane with piezoelectric nanomaterials (such as barium titanate BaTiO3, molybdenum disulfide MoS2, etc.). These modified membranes, when subjected to external mechanical stress, can generate a piezoelectric effect, exciting the generation of electron-hole pairs. This allows them to utilize piezoelectric catalysis to degrade contaminants on the membrane surface, achieving a self-cleaning function without an external power source. However, the efficiency of piezoelectric catalysis is highly dependent on the effective migration of electron-hole pairs to the contaminant surface and their participation in the reaction. In practical applications, the electrons and holes generated by piezoelectricity are easily deactivated due to recombination within the material or during migration, resulting in a limited number of effective charges reaching the contaminant surface, thus restricting the degradation efficiency of piezoelectric catalysis for contaminants.
[0005] To address the aforementioned issues, some researchers in this field have attempted to combine conductive and piezoelectric materials to leverage the superior electron transport properties of conductive materials to accelerate electron-hole separation and improve piezoelectric catalytic efficiency. However, existing research largely focuses on characterizing the properties of the materials themselves and has not yet developed a technical solution that organically combines the synergistic piezoelectric and conductive effects of composite materials with the actual operating conditions of ultrafiltration membrane filtration processes to achieve high efficiency, low energy consumption, and pollution resistance.
[0006] Therefore, how to provide an ultrafiltration membrane and its operation method that can effectively alleviate organic pollution and achieve low-energy self-cleaning remains a technical problem that urgently needs to be solved in this field. Summary of the Invention
[0007] The purpose of this invention is to address the problems existing in the prior art by providing a piezoelectric-conductive composite ultrafiltration membrane, its preparation method, and its application. By combining piezoelectric and conductive materials to form a heterojunction structure and operating under pulsed hydraulic conditions, a synergistic effect of piezoelectric catalysis and membrane separation is achieved, significantly improving the antifouling performance of the ultrafiltration membrane.
[0008] To achieve the above objectives, the present invention provides a piezoelectric-conductive composite ultrafiltration membrane, comprising: An ultrafiltration membrane substrate, and a functional layer loaded on the surface of the ultrafiltration membrane substrate; The functional layer comprises a heterojunction composite material formed of piezoelectric and conductive materials; The piezoelectric-conductive composite ultrafiltration membrane is used to filter water containing organic pollutants under pulsed hydraulic conditions to excite the piezoelectric material to generate a piezoelectric effect, thereby degrading the organic pollutants on the membrane surface.
[0009] This invention combines piezoelectric and conductive materials to form a heterojunction structure. On one hand, the excellent electron transport properties of the conductive material accelerate the separation and transport of electron-hole pairs generated by the piezoelectric material, effectively suppressing electron-hole recombination and deactivation, thereby improving piezoelectric catalytic efficiency. On the other hand, the conductive material (carbon nanotubes) has good adsorption properties, enabling it to adsorb and enrich organic pollutants in water onto the surface of the composite material. This significantly shortens the migration path of electrons and holes generated by the piezoelectric material to the pollutants, reducing electron-hole recombination losses during migration and achieving efficient utilization of electrons and holes. Furthermore, this composite material is loaded onto the surface of an ultrafiltration membrane substrate to form a functional layer. During the filtration process, pulsed hydraulic operation is employed. The periodic changes in pressure repeatedly excite the piezoelectric material to generate a piezoelectric effect, achieving in-situ degradation of organic pollutants accumulated on the membrane surface, achieving self-cleaning, and effectively alleviating membrane fouling.
[0010] In one optional embodiment, the piezoelectric material is barium titanate, the conductive material is carbon nanotube, and the heterojunction composite material is a barium titanate@carbon nanotube composite material.
[0011] Barium titanate has excellent piezoelectric properties, while carbon nanotubes have good electrical conductivity and one-dimensional nanostructure. The heterojunction structure formed by the combination of the two can give full play to the synergistic effect.
[0012] In an alternative embodiment, the functional layer is formed by filtration of a suspension containing the heterojunction composite material onto the surface of the ultrafiltration membrane substrate.
[0013] This invention also provides a method for preparing a piezoelectric-conductive composite ultrafiltration membrane, comprising the following steps: S1. Provides a heterojunction composite material composed of piezoelectric and conductive materials; S2. Disperse the heterojunction composite material in a solvent to form a suspension; S3. Load the suspension onto the surface of the ultrafiltration membrane substrate to obtain a piezoelectric-conductive composite ultrafiltration membrane.
[0014] In an optional embodiment, in S1, the heterojunction composite material is a barium titanate@carbon nanotube composite material.
[0015] In an optional embodiment, the preparation method of the barium titanate@carbon nanotube composite material includes the following steps: mixing carbon nanotubes, surfactants, solvents, and barium titanate, followed by solvent removal, washing, drying, annealing, and grinding to obtain the barium titanate@carbon nanotube composite material.
[0016] In one optional embodiment, the carbon nanotubes have a diameter of 5-20 nm and a length of 10-30 μm; the surfactant is selected from hexadecyltrimethylammonium bromide; the solvent is selected from ethanol; the average particle size of the barium titanate is 40-60 nm; and the mass-to-volume ratio of the carbon nanotubes, surfactant, solvent, and barium titanate is (0.05-0.15) g : (0.01-0.03) g : (80-120) mL : (0.8-1.2) g.
[0017] In one optional embodiment, the solvent removal is performed by heating at a temperature of 55-65°C; the washing reagent is selected from isopropanol, and the surfactant is removed by washing; the drying temperature is 55-65°C for 8-12 hours, and the washing reagent (isopropanol) is removed by drying; the annealing temperature is 550-650°C for 1.5-2.5 hours.
[0018] In an optional embodiment, in S2, the solvent is selected from water; the mass-to-volume ratio of the heterojunction composite material to the solvent is (0.3-0.7) g: (450-550) mL; the dispersion is carried out by ultrasonic treatment for a duration of 0.5-1.5 h.
[0019] In an optional embodiment, in S3, the material of the ultrafiltration membrane substrate is selected from polyacrylonitrile; before loading operation, the ultrafiltration membrane substrate is pretreated; the pretreatment includes: treating the ultrafiltration membrane substrate with an ethanol solution with a mass fraction of 60-70% for 10-20 minutes, and then washing it with water 2-4 times.
[0020] The present invention also provides an application of a piezoelectric-conductive composite ultrafiltration membrane in treating water containing organic pollutants under pulsed hydraulic conditions.
[0021] The present invention also provides a method for membrane separation using a piezoelectric-conductive composite ultrafiltration membrane. In the process of filtering water containing organic pollutants, a pulsed hydraulic pressure is applied to the ultrafiltration membrane to excite the piezoelectric material in the functional layer to generate a piezoelectric effect, thereby performing piezoelectric catalytic degradation of organic pollutants on the membrane surface.
[0022] In an optional embodiment, the organic pollutant includes at least one of sodium alginate and bovine serum albumin.
[0023] In one alternative implementation, the pressure of the pulsed hydraulic pressure varies periodically between 0 and 0.1 MPa.
[0024] In one alternative implementation, one cycle of the pulsed hydraulic pressure includes: the pressure increasing from 0 to 0.1 MPa, maintaining a stable pressure at 0.1 MPa, and then decreasing from 0.1 MPa to 0.
[0025] Compared with the prior art, the present invention has the following beneficial effects: (1) This invention combines piezoelectric materials with conductive materials to form a heterojunction structure. On the one hand, the conductive material has excellent electron transport performance, which can accelerate the separation and migration of electron-hole pairs generated by the piezoelectric material under mechanical stress, and effectively suppress the recombination and deactivation of electron-hole pairs. On the other hand, the conductive material has good adsorption performance, which can adsorb and enrich organic pollutants in water onto the surface of the composite material, significantly shortening the migration path of electrons and holes generated by the piezoelectric material to the pollutants, and reducing the recombination loss of electrons and holes during migration. This synergistic mechanism of "adsorption and enrichment - shortened path - efficient transport" enables the electrons and holes generated by the piezoelectric material to act more effectively on the pollutants, significantly improving the degradation efficiency of organic pollutants.
[0026] (2) This invention employs pulsed hydraulic operation during the filtration process. The periodic changes in pressure repeatedly excite the piezoelectric material in the functional layer to generate a piezoelectric effect, achieving in-situ degradation of organic pollutants accumulated on the membrane surface. Compared to traditional electrochemical antifouling technologies that require an external electric field, this invention eliminates the need for an additional electric field, relying solely on the inherent pulsed hydraulic pressure during the filtration process to excite the piezoelectric effect, significantly reducing system energy consumption and operational complexity. Compared to traditional chemical cleaning methods, this invention achieves in-situ self-cleaning during the filtration process without interrupting the filtration process to add chemical agents, saving on agent costs and avoiding secondary environmental pollution from chemical cleaning agents.
[0027] (3) This invention effectively reduces the accumulation of pollutants on the membrane surface through the synergistic effect of piezoelectric catalytic degradation and membrane pore size retention. During the filtration process, the piezoelectric effect excited by pulsed hydraulic pressure can continuously degrade organic pollutants attached to the membrane surface, preventing them from forming a dense fouling layer; at the same time, the adsorption effect of conductive materials enriches pollutants on the material surface, improving degradation efficiency. This "filtration and degradation simultaneously" working mode significantly suppresses membrane flux decay and reduces membrane fouling resistance, especially irreversible fouling resistance. The reduction of irreversible fouling means that the service life of the membrane can be extended, and the cleaning frequency and intensity can be reduced, thereby reducing membrane maintenance costs and replacement frequency.
[0028] (4) The preparation method of the piezoelectric-conductive composite ultrafiltration membrane provided by this invention is simple and easy to operate. The loading of the functional layer can be carried out by conventional processes such as vacuum filtration at room temperature and pressure, without the need for complex equipment, and is easy to scale up for production. The pretreatment of the ultrafiltration membrane substrate only requires ethanol solution treatment and water washing, without the need for special reagents and conditions. At the same time, the pulse hydraulic operation can be realized through a conventional pump and valve control system, without the need for large-scale modification of the existing ultrafiltration system, and is easy to promote and apply in existing water treatment facilities. The entire preparation and operation process is low in cost and highly operable, and has good application prospects.
[0029] (5) The piezoelectric-conductive composite ultrafiltration membrane prepared by this invention has good anti-fouling effects on different types of organic pollutants. Sodium alginate and bovine serum albumin represent typical organic pollutant types such as polysaccharide pollutants and protein pollutants, respectively. The technical solution of this invention can effectively play a role in these different types of pollutants, indicating that it has broad-spectrum anti-fouling performance and can be widely used in the treatment of complex water bodies containing a variety of organic pollutants, such as municipal sewage treatment, industrial wastewater treatment, drinking water purification and other fields.
[0030] In summary, this invention achieves synergistic effects of piezoelectric catalysis and membrane separation by forming a heterojunction structure by combining piezoelectric and conductive materials and operating under pulsed hydraulic conditions, thereby significantly improving the antifouling performance of ultrafiltration membranes. Attached Figure Description
[0031] Figure 1 This is a normalized flux variation graph of the piezoelectric-conductive composite ultrafiltration membrane in SA solution at different filtration stages in Example 1 of this invention; Figure 2 This is a comparison chart of the flux decrease rate and recovery rate of the piezoelectric-conductive composite ultrafiltration membrane in SA solution in Example 1 of this invention; Figure 3 This is a normalized flux variation graph of the piezoelectric-conductive composite ultrafiltration membrane in BSA solution at different filtration stages in Example 1 of this invention; Figure 4This is a comparison chart of the flux decrease rate and recovery rate of the piezoelectric-conductive composite ultrafiltration membrane in BSA solution in Example 1 of this invention; Figure 5 This is a SEM characterization image of the barium titanate@carbon nanotube composite material in Example 1 of this invention; Figure 6 These are XRD analysis images of BaTiO3, CNTs, and BaTiO3@CNTs in Example 1 of this invention; Figure 7 This is a SEM characterization image of the piezoelectric-conductive composite ultrafiltration membrane in Example 1 of this invention; Figure 8 This is a piezoelectric response performance diagram of the polyacrylonitrile ultrafiltration membrane in Example 1 of this invention; Figure 9 This is a piezoelectric response performance diagram of the piezoelectric-conductive composite ultrafiltration membrane in Example 1 of this invention. Detailed Implementation
[0032] The following embodiments are provided to better understand the present invention and are not limited to the described embodiments. They do not constitute a limitation on the content and scope of protection of the present invention. Any product that is the same as or similar to the present invention, derived by any person under the guidance of the present invention or by combining the features of the present invention with other prior art, falls within the protection scope of the present invention.
[0033] For experiments not specifically described in the examples, the procedures or conditions should be followed according to the conventional experimental procedures described in the literature in this field. Reagents or instruments whose manufacturers are not specified are all commercially available products.
[0034] Example 1 This embodiment provides a method for preparing a piezoelectric-conductive composite ultrafiltration membrane, including the following steps: 0.1 g of carbon nanotubes (5-20 nm in diameter and 10-30 μm in length) and 0.02 g of cetyltrimethylammonium bromide (CTAB) were added to 100 mL of ethanol and ultrasonically dispersed until uniform. 1 g of barium titanate nanoparticles (average particle size 50 nm) were added and stirred at 60 °C until the ethanol evaporated. CTAB was removed by washing with isopropanol, and then vacuum dried at 60 °C for 10 h to remove isopropanol. Finally, the mixture was annealed at 600 °C for 2 h, naturally cooled, and then thoroughly ground to obtain the barium titanate@carbon nanotube composite material.
[0035] Weigh 0.5g of barium titanate@carbon nanotube composite material, add it to 500mL of ultrapure water, and sonicate for 1h to uniformly disperse the composite material and obtain a suspension.
[0036] A polyacrylonitrile ultrafiltration membrane (molecular weight cutoff of 50 kDa) was used as the substrate membrane. It was treated with a 66.7% ethanol solution for 15 min, then washed three times with pure water. The pretreated polyacrylonitrile ultrafiltration membrane was then fixed in a vacuum filtration apparatus. The suspension was filtered onto the membrane surface, ensuring the composite material was uniformly loaded onto the substrate membrane surface, resulting in a piezoelectric-conductive composite ultrafiltration membrane (effective area of 28.7 cm²). 2 The loading mass of the composite material on the piezoelectric-conductive composite ultrafiltration membrane is 0.5g.
[0037] Example 2 This embodiment provides a method for preparing a piezoelectric-conductive composite ultrafiltration membrane, including the following steps: 0.05 g of carbon nanotubes (5-20 nm in diameter and 10-30 μm in length) and 0.03 g of cetyltrimethylammonium bromide (CTAB) were added to 80 mL of ethanol and ultrasonically dispersed until uniform. Then, 0.8 g of barium titanate nanoparticles (average particle size of 40 nm) were added and stirred at 55 °C until the ethanol evaporated. The CTAB was removed by washing with isopropanol, and then the mixture was vacuum dried at 55 °C for 12 h to remove isopropanol. Finally, the mixture was annealed at 550 °C for 2.5 h, allowed to cool naturally, and then ground thoroughly to obtain the barium titanate@carbon nanotube composite material.
[0038] Weigh 0.3g of barium titanate@carbon nanotube composite material, add it to 450mL of ultrapure water, and sonicate for 1.5h to uniformly disperse the composite material and obtain a suspension.
[0039] A polyacrylonitrile ultrafiltration membrane (molecular weight cutoff of 50 kDa) was used as the substrate membrane. It was treated with a 60% ethanol solution for 20 min, then washed twice with pure water. The pretreated polyacrylonitrile ultrafiltration membrane was then fixed in a vacuum filtration apparatus. The suspension was filtered onto the membrane surface, ensuring the composite material was uniformly loaded onto the substrate membrane surface, resulting in a piezoelectric-conductive composite ultrafiltration membrane (effective area of 28.7 cm²). 2 The loading mass of the composite material on the piezoelectric-conductive composite ultrafiltration membrane is 0.5g.
[0040] Example 3 This embodiment provides a method for preparing a piezoelectric-conductive composite ultrafiltration membrane, including the following steps: 0.15 g of carbon nanotubes (5-20 nm in diameter and 10-30 μm in length) and 0.02 g of cetyltrimethylammonium bromide (CTAB) were added to 120 mL of ethanol and ultrasonically dispersed until uniform. Then, 1.2 g of barium titanate nanoparticles (average particle size of 60 nm) were added and stirred at 65 °C until the ethanol evaporated. The CTAB was removed by washing with isopropanol, and then the mixture was vacuum dried at 65 °C for 8 h to remove isopropanol. Finally, the mixture was annealed at 650 °C for 1.5 h, allowed to cool naturally, and then thoroughly ground to obtain the barium titanate@carbon nanotube composite material.
[0041] Weigh 0.7g of barium titanate@carbon nanotube composite material, add it to 550mL of ultrapure water, and sonicate for 0.5h to uniformly disperse the composite material and obtain a suspension.
[0042] A polyacrylonitrile ultrafiltration membrane (molecular weight cutoff of 50 kDa) was used as the substrate membrane. It was treated with a 70% ethanol solution for 10 min, then washed four times with pure water. The pretreated polyacrylonitrile ultrafiltration membrane was then fixed in a vacuum filtration apparatus. The suspension was filtered onto the membrane surface, ensuring the composite material was uniformly loaded onto the substrate membrane surface, resulting in a piezoelectric-conductive composite ultrafiltration membrane (effective area of 28.7 cm²). 2 The loading mass of the composite material on the piezoelectric-conductive composite ultrafiltration membrane is 0.5g.
[0043] Application Example 1 The piezoelectric-conductive composite ultrafiltration membrane prepared in Example 1 was applied to treat water containing organic pollutants. Specifically, a sodium alginate (SA) solution with a concentration of 10 mg / L was used as a model pollutant to investigate its antifouling performance in constant pressure mode and pulsed hydraulic pressure mode.
[0044] 1. Constant pressure mode: (1) Initial flux determination: The piezoelectric-conductive composite ultrafiltration membrane was installed in the ultrafiltration cup, 100 mL of pure water was added, and the membrane was pre-pressurized to a constant pressure of 0.1 MPa until the flux stabilized. The pure water flux at this time was recorded as the initial flux J0.
[0045] (2) First contamination stage: Replace the pure water in the ultrafiltration cup with 200 mL of SA solution with a concentration of 10 mg / L, and filter under constant pressure of 0.1 MPa. Start timing from the beginning of filtration and continuously record the change data of the cumulative permeate volume over time until all 200 mL of solution is filtered. Add 100 mL of pure water and pre-pressurize under constant pressure of 0.1 MPa until the flux stabilizes. Record the pure water flux at this time, which is recorded as the flux after the first contamination J1.
[0046] (3) First cleaning and flux recovery measurement: Pour out the remaining pure water in the ultrafiltration cup, then take the membrane out of the ultrafiltration cup and gently rinse the membrane surface with pure water for 2-3 minutes to remove loosely attached contaminants on the membrane surface. After cleaning, reinstall the membrane into the ultrafiltration cup, pour in 100 mL of pure water again, and pre-pressurize it under a constant pressure of 0.1 MPa until the flux stabilizes. Record the pure water flux at this time as the flux after the first cleaning J2.
[0047] (4) Second pollution stage: Replace the pure water in the ultrafiltration cup with 200 mL of SA solution with a concentration of 10 mg / L, filter under constant pressure of 0.1 MPa, and continuously record the change data of the cumulative permeate volume over time until all 200 mL of solution is filtered. Add 100 mL of pure water, pre-pressurize under constant pressure of 0.1 MPa until the flux is stable, and record the pure water flux at this time, which is recorded as the flux after the second pollution J3.
[0048] (5) Second cleaning and flux recovery measurement: Repeat step (3) to obtain the flux J4 after the second cleaning.
[0049] (6) Third stage of contamination: Replace the pure water in the ultrafiltration cup with 200 mL of SA solution with a concentration of 10 mg / L, filter under constant pressure of 0.1 MPa, and continuously record the change data of the cumulative permeate volume over time until all 200 mL of solution is filtered.
[0050] 2. Pulse hydraulic mode: The operating procedure is exactly the same as the constant pressure mode. The only difference is that during the contamination stage (i.e., the stage of filtering SA solution in the first, second, and third contamination), the pressure condition is changed from a constant pressure of 0.1 MPa to a pulse hydraulic mode. The parameters for the pulse hydraulic mode are set as follows: the pressure linearly increases from 0 to 0.1 MPa within 8 seconds, remains stable at 0.1 MPa for 70 seconds, and then linearly decreases from 0.1 MPa to 0 within 3 seconds. This constitutes one cycle, and the cycle is repeated until 200 mL of SA solution is filtered.
[0051] 3. Data Acquisition and Processing: (1) During the fouling stage, based on the continuously recorded cumulative permeate volume change data over time, the instantaneous flux at each time point is calculated using the following formula: J = ΔV / (A × Δt). Where ΔV is the increase in permeate volume (L) within Δt, and A is the effective membrane area (m²). 2Δt represents the time interval (h). To eliminate inter-membrane differences, each instantaneous flux value is divided by the initial flux J0 to obtain the normalized flux. The cumulative filtered SA solution volume (mL) is plotted on the x-axis, ranging from 0 to 600 mL, corresponding to the first contamination (0-200 mL, labeled "first cycle"), the second contamination (200-400 mL, labeled "second cycle"), and the third contamination (400-600 mL, labeled "third cycle"); the normalized flux is plotted on the y-axis. The normalized flux variation graph of the piezoelectric-conductive composite ultrafiltration membrane in SA solution at different filtration stages in Example 1 is obtained, as shown below. Figure 1 As shown.
[0052] (2) The flux recovery rate FRR = (J2 / J0) × 100% was calculated based on the following formulas: reversible flux decline rate DRR = (J2-J1) / J0 × 100%; flux decline rate DRt = (1-J1 / J0) × 100%; irreversible flux decline rate DRir = (1-J2 / J0) × 100%. A comparison chart of flux decline rate and recovery rate of the piezoelectric-conductive composite ultrafiltration membrane in SA solution in Example 1 was obtained, as shown below. Figure 2 As shown.
[0053] comprehensive Figure 1 and Figure 2 The results show that the piezoelectric-conductive composite ultrafiltration membrane prepared by this invention can effectively excite the piezoelectric effect of barium titanate under pulsed hydraulic conditions, thereby degrading sodium alginate pollutants in situ, significantly reducing irreversible pollution resistance, improving flux recovery rate, and thus achieving excellent antifouling performance.
[0054] Application Example 2 Using the same operating procedures and test conditions as in Application Example 1, the piezoelectric-conductive composite ultrafiltration membrane prepared in Example 1 was applied to treat a bovine serum albumin (BSA) solution with a concentration of 10 mg / L, and its antifouling performance in constant pressure mode and pulsed hydraulic pressure mode was investigated.
[0055] The normalized flux variation of the piezoelectric-conductive composite ultrafiltration membrane in BSA solution at different filtration stages in Example 1 is shown in the figure below. Figure 3 As shown in the figure. The graph compares the flux decrease and recovery rate of the piezoelectric-conductive composite ultrafiltration membrane in BSA solution in Example 1. Figure 4 As shown.
[0056] comprehensive Figure 3 and Figure 4 The results show that the piezoelectric-conductive composite ultrafiltration membrane prepared by this invention can effectively excite the piezoelectric effect of barium titanate under pulsed hydraulic conditions, thereby degrading bovine serum albumin contaminants in situ, significantly reducing irreversible contamination resistance, improving flux recovery rate, and thus achieving excellent anti-fouling performance.
[0057] Experimental Example 1 The barium titanate@carbon nanotube composite material in Example 1 was characterized by scanning electron microscopy (SEM), and the SEM characterization image of the barium titanate@carbon nanotube composite material in Example 1 was obtained, as shown below. Figure 5 As shown. From Figure 5 It can be seen that pure barium titanate exhibits a dense agglomeration of nanoparticles, while carbon nanotubes display a network morphology of interwoven slender tubular structures. In the barium titanate@carbon nanotube composite material, barium titanate nanoparticles are uniformly anchored to the surface of carbon nanotubes, forming a heterogeneous hierarchical structure composed of one-dimensional carbon nanotubes and zero-dimensional barium titanate particles, confirming the successful composite of the two materials.
[0058] The barium titanate (BaTiO3), carbon nanotubes (CNTs), and barium titanate@carbon nanotube composites (BaTiO3@CNTs) from Example 1 were analyzed by X-ray diffraction (XRD). The XRD patterns of BaTiO3, CNTs, and BaTiO3@CNTs from Example 1 are shown below. Figure 6 As shown. From Figure 6 It can be seen that both pure BaTiO3 and BaTiO3@CNTs samples exhibit sharp characteristic diffraction peaks of tetragonal BaTiO3, especially with obvious peak splitting observed at approximately 45°, indicating that the tetragonal crystal structure with excellent piezoelectric activity is completely preserved after composite formation. The CNTs samples only show characteristic broad peaks in the low-angle region. The BaTiO3@CNTs composite material retains all diffraction signals of tetragonal BaTiO3 and the characteristic broad peaks of CNTs, further confirming the successful composite formation of piezoelectric BaTiO3 and conductive CNTs without disrupting the crystal structure, providing structural assurance for its excellent piezoelectric catalytic performance.
[0059] Experimental Example 2 The piezoelectric-conductive composite ultrafiltration membrane in Example 1 was characterized by scanning electron microscopy (SEM), and the SEM image of the piezoelectric-conductive composite ultrafiltration membrane in Example 1 was obtained, as shown below. Figure 7 As shown. From Figure 7 As can be seen, granular barium titanate and tubular carbon nanotubes are uniformly distributed on the membrane surface, interwoven to form a relatively uniform composite layer. This indicates that the BaTiO3@CNTs composite material has been successfully loaded onto the surface of the ultrafiltration membrane substrate, providing a structural basis for subsequent piezoelectric catalytic performance.
[0060] Experimental Example 3 The piezoelectric response performance of the polyacrylonitrile ultrafiltration membrane and the piezoelectric-conductive composite ultrafiltration membrane in Example 1 were tested. The test method was as follows: under finger pressure, the voltage change signal of the membrane was captured using an oscilloscope. The piezoelectric response performance diagram of the polyacrylonitrile ultrafiltration membrane in Example 1 was obtained, as shown below. Figure 8 As shown; the piezoelectric response performance diagram of the piezoelectric-conductive composite ultrafiltration membrane in Example 1 is as follows. Figure 9 As shown. From Figure 8 and 9 As can be seen, the polyacrylonitrile ultrafiltration membrane shows no obvious piezoelectric response signal, and its amplitude curve is flat. In contrast, the piezoelectric-conductive composite ultrafiltration membrane exhibits a significant piezoelectric response, proving that the functional layer of the loading successfully endows the ultrafiltration membrane with piezoelectric properties. This provides performance assurance for stimulating the piezoelectric effect under pulsed hydraulic conditions and achieving in-situ degradation of pollutants.
[0061] In summary, this invention utilizes the aforementioned piezoelectric-conductive composite ultrafiltration membrane, its preparation method, and its application. By combining piezoelectric and conductive materials to form a heterojunction structure and operating under pulsed hydraulic conditions, it achieves synergistic enhancement of piezoelectric catalysis and membrane separation, significantly improving the antifouling performance of the ultrafiltration membrane.
[0062] Finally, it should be noted that the above embodiments are merely illustrative examples for clear explanation and are not intended to limit the implementation. Those skilled in the art will recognize that other variations or modifications can be made based on the above description. It is neither necessary nor possible to exhaustively list all possible implementations here. However, obvious variations or modifications derived therefrom are still within the scope of protection of this invention.
Claims
1. A piezoelectric-conductive composite ultrafiltration membrane, characterized in that, include: An ultrafiltration membrane substrate, and a functional layer loaded on the surface of the ultrafiltration membrane substrate; The functional layer comprises a heterojunction composite material formed of piezoelectric and conductive materials; The piezoelectric-conductive composite ultrafiltration membrane is used to filter water containing organic pollutants under pulsed hydraulic conditions to excite the piezoelectric material to generate a piezoelectric effect, thereby degrading the organic pollutants on the membrane surface.
2. The piezoelectric-conductive composite ultrafiltration membrane according to claim 1, characterized in that, The piezoelectric material is barium titanate, the conductive material is carbon nanotube, and the heterojunction composite material is a barium titanate@carbon nanotube composite material.
3. The piezoelectric-conductive composite ultrafiltration membrane according to claim 1 or 2, characterized in that, The functional layer is formed by filtration of a suspension containing the heterojunction composite material onto the surface of the ultrafiltration membrane substrate.
4. A method for preparing a piezoelectric-conductive composite ultrafiltration membrane as described in any one of claims 1-3, characterized in that, Includes the following steps: S1. Provides a heterojunction composite material composed of piezoelectric and conductive materials; S2. Disperse the heterojunction composite material in a solvent to form a suspension; S3. Load the suspension onto the surface of the ultrafiltration membrane substrate to obtain a piezoelectric-conductive composite ultrafiltration membrane.
5. The method according to claim 4, characterized in that, In S1, the heterojunction composite material is a barium titanate@carbon nanotube composite material.
6. The application of a piezoelectric-conductive composite ultrafiltration membrane as described in any one of claims 1-3 in the treatment of water containing organic pollutants under pulsed hydraulic conditions.
7. A method for membrane separation using a piezoelectric-conductive composite ultrafiltration membrane as described in any one of claims 1-3, characterized in that, During the filtration of water containing organic pollutants, pulsed hydraulic pressure is applied to the ultrafiltration membrane to excite the piezoelectric material in the functional layer to generate a piezoelectric effect, thereby performing piezoelectric catalytic degradation of organic pollutants on the membrane surface.
8. The method according to claim 7, characterized in that, The organic pollutants include at least one of sodium alginate and bovine serum albumin.
9. The method according to claim 7 or 8, characterized in that, The pressure of the pulsed hydraulic pressure varies periodically between 0 and 0.1 MPa.
10. The method according to claim 9, characterized in that, One cycle of the pulsed hydraulic pressure includes: the pressure rising from 0 to 0.1 MPa, maintaining a stable pressure at 0.1 MPa, and then decreasing from 0.1 MPa to 0.