Self-cleaning composite piezoelectric ceramic film and preparation method and application thereof

Abstract

The application discloses a self-cleaning composite piezoelectric ceramic membrane and a preparation method and application thereof, and belongs to the field of composite ceramic membranes. The application aims to solve the technical problem of poor anti-biofilm pollution effect of existing ceramic membrane separation technology. The application first prepares a barium titanate ceramic membrane as a base film, and then loads copper oxide one-dimensional nano structures on the piezoelectric ceramic substrate. Since the base film has a large membrane surface area, more catalysts can be combined, thereby providing more active sites for catalytic reaction. The composite membrane significantly improves the hydrophilicity, anti-pollution performance and piezoelectric catalytic self-cleaning performance of the membrane, can quickly and effectively separate pollutants in water, and thereby improves the flux and anti-pollution performance of the membrane.

Description

Technical Field

[0001] This invention belongs to the field of composite ceramic membranes, specifically, it relates to a self-cleaning composite piezoelectric ceramic membrane, its preparation method, and its application. Background Technology

[0002] Membrane separation technology, due to its high separation accuracy and stable effluent quality, has become a core process unit in modern water treatment, especially in the field of advanced wastewater treatment and reuse. However, membrane fouling, particularly biofouling, severely restricts the widespread application and long-term stable operation of this technology. Biofouling begins with the initial adhesion of microorganisms to the membrane surface, followed by their proliferation and secretion of extracellular polymeric substances (EPS), forming a dense and difficult-to-remove biofilm. Biofilms not only clog membrane pores, leading to decreased permeate flux and increased operating energy consumption, but can also cause irreversible damage to membrane materials, shortening membrane life.

[0003] Currently, water treatment primarily relies on physical and chemical cleaning to control membrane fouling. Physical cleaning has limited effectiveness against firmly attached biofilms; while chemical cleaning (such as using sodium hypochlorite, acids, and alkalis) can effectively remove contaminants, it also brings a series of problems: the cleaning process is complex and costly, chemical agents can accelerate membrane material aging, and cleaning wastewater may cause secondary pollution. Therefore, developing functionalized membrane materials with active antibacterial and antifouling functions that can control biofilm formation at the source is key to achieving long-term, green, and low-energy operation of membrane systems.

[0004] Against this backdrop, coupling advanced oxidation technologies (AOPs) with membrane separation processes to construct self-cleaning catalytic membranes has become a research hotspot. These membranes can generate strong oxidizing species in situ during filtration, degrading pollutants and biofilm matrix on the membrane surface, thereby mitigating contamination. Although various functionalized membranes have been reported, they generally still suffer from the following technical bottlenecks: Catalytic processes require the continuous addition of chemical reagents or rely on external energy sources such as light and electricity, which not only results in high operating costs but may also lead to secondary pollution. The catalyst layer is mostly loaded by physical coating or deposition, which results in insufficient bonding strength with the base film. It is prone to detachment under long-term water impact, affecting stability. Existing technologies mostly rely on a single physical or chemical mechanism, making it difficult to address complex and highly adhesive biofilm pollution in a coordinated manner.

[0005] Therefore, the industry urgently needs to develop a new type of self-cleaning membrane that can operate stably without relying on external chemicals and utilizing the system's own energy, with a strong bond between the functional layer and the substrate, and possessing a multi-mechanism synergistic anti-fouling capability. If high-performance piezoelectric materials can be used to make filter membranes and a composite interface capable of synergistically employing multiple anti-fouling mechanisms can be constructed, it is hoped that the hydraulic fluctuations during the filtration process can be directly used as a driving force to achieve in-situ self-cleaning of the membrane surface, thereby fundamentally overcoming the technical limitations of existing membrane fouling control. Summary of the Invention

[0006] This invention addresses the technical problem of poor anti-biofilm fouling performance in existing ceramic membrane separation technologies by providing a self-cleaning composite piezoelectric ceramic membrane and its preparation method. This invention improves the self-cleaning performance of the ceramic membrane by immobilizing a catalyst on it. Specifically, this invention uses a prepared barium titanate ceramic membrane as the base membrane, and then loads a copper-containing one-dimensional nanostructure onto the piezoelectric ceramic substrate. Because the base membrane has a large surface area, it can bind more catalyst, thus providing more active sites for the catalytic reaction. This composite membrane significantly improves the membrane's hydrophilicity, anti-fouling performance, and piezoelectric catalytic self-cleaning performance, enabling rapid and effective separation of pollutants in water, thereby increasing membrane flux and anti-fouling performance.

[0007] To address the aforementioned technical problems, the present invention adopts the following technical solution: The purpose of this invention is to provide a method for preparing a self-cleaning composite piezoelectric ceramic film, characterized by comprising the following steps: Step 1: Mix piezoelectric ceramic powder and an aqueous solution of organic binder, grind thoroughly, dry, grind and sieve, press into a blank through a molding process, sinter at high temperature and polarize to obtain a porous ceramic substrate film; Step 2: Add the copper salt precursor to deionized water and stir until completely dissolved. Then add urea and stir until completely dissolved. Add ammonium fluoride and stir until homogeneous to obtain the precursor solution. Step 3: Completely immerse the porous ceramic substrate membrane in the precursor solution, seal it, and carry out a hydrothermal reaction at a constant temperature. After the reaction is completed, immediately remove the composite membrane, ultrasonically clean it with a large amount of deionized water, and dry it; this completes the process.

[0008] Step 1 prepares a substrate material with both excellent piezoelectric properties and suitable pore structure. The substrate material is then pressed into a ceramic film preform with a predetermined shape and size using a molding process. The high-temperature sintering involves placing the ceramic film preform in a high-temperature tube furnace and performing solid-state sintering under a specific atmosphere and temperature program to remove organic binders and densify the ceramic powder, forming a porous ceramic substrate film with interconnected pore structures. The polarization treatment involves polarizing the sintered porous ceramic substrate film to preferentially align the randomly oriented ferroelectric domains along the electric field direction, thereby endowing the substrate film with macroscopic piezoelectric properties, resulting in the final porous piezoelectric ceramic substrate film.

[0009] Further specifying, in step 1, the piezoelectric ceramic powder includes a perovskite structure or a perovskite-like structure piezoelectric material, specifically, the piezoelectric ceramic powder is one or more of barium titanate (BaTiO3), bismuth ferrite (BiFeO3), and potassium sodium niobate (KNN); The organic binder is one or more of polyvinyl alcohol (PVA), polyethylene glycol (PEG), and methylcellulose (MC).

[0010] Further specifying, in step 1, the aqueous solution of the organic binder has a mass concentration of 5%-15%.

[0011] Further specifying, in step 1, the mass ratio of organic binder to piezoelectric ceramic powder is (1-3):100.

[0012] Further specifying, the molding process is dry pressing, the pressing pressure is 20MPa-50MPa, the holding time is 30 seconds-90 seconds, and the diameter of the resulting ceramic film preform is 2 cm-4 cm and the thickness is 1 mm-3 mm.

[0013] Further specifying, in step 1, the sintering gas atmosphere is air or oxygen, the heating rate is 2℃-6℃ / min, the sintering temperature is 750℃-1250℃, and the holding time is 2 hours-6 hours.

[0014] Further specifying, in step 1, the specific operation of polarization treatment is as follows: immerse the ceramic substrate film coated with silver paste as an electrode into insulating silicone oil at 80℃-120℃, apply a DC electric field of 1 kV / mm-5 kV / mm, and maintain it for 20 minutes-40 minutes.

[0015] Step 2: First, one or more soluble copper salt precursors are dissolved in a solvent, and a pH adjuster and morphology control agent are added to prepare a homogeneous hydrothermal reaction solution. The polarized porous piezoelectric ceramic substrate film prepared in the previous step is immersed in the hydrothermal reaction solution and subjected to hydrothermal treatment at a specific temperature under sealed conditions, so that one-dimensional copper oxide (CuO) nanostructures are nucleated and grown in situ on the surface and in the pores of the piezoelectric ceramic substrate film to form a functional layer. The hydrothermally treated composite film is taken out, thoroughly washed with deionized water to remove residual reactants on the surface, and then dried to obtain the self-cleaning composite piezoelectric ceramic film.

[0016] Further specifying, in step 2, the copper salt precursor is one or more of copper nitrate, copper sulfate, copper acetate, and copper chloride.

[0017] Further specifying, in step 2, the molar ratio of copper salt precursor, urea and ammonium fluoride is (5-15):(10-30):(15-45).

[0018] To further specify, in step 2, the pH adjuster is urea.

[0019] To further specify, in step 2, the morphology control agent is ammonium fluoride.

[0020] Further specifying, in step 2, the molar ratio of copper salt precursor, pH adjuster and morphology control agent is (5-15):(10-30):(15-45).

[0021] Further specifying, in step 2, the hydrothermal reaction is carried out at 80-120℃ for 6-12 hours.

[0022] Another object of the present invention is to provide a self-cleaning composite piezoelectric ceramic membrane prepared by any of the above methods.

[0023] Further, a one-dimensional copper oxide nanowire array is nucleated and grown in situ on the surface and within the pores of the piezoelectric ceramic substrate film.

[0024] Another objective of this invention is to provide an application of the aforementioned self-cleaning composite piezoelectric ceramic membrane in anti-fouling water treatment. By applying the self-cleaning composite piezoelectric ceramic membrane to a filtration device, during the water filtration process, the mechanical energy generated by the water treatment system itself, i.e., the water flow pulse, is used as an excitation source to activate the piezoelectric effect and surface nanostructure of the composite membrane, thereby synergistically achieving the dual functions of antibacterial and anti-fouling, thereby achieving the purpose of inhibiting biofilm formation, alleviating membrane fouling, and extending the operating cycle.

[0025] Further specifying, the mechanical energy is the periodic pressure pulse generated in the filtration system by pump start-up and shutdown, valve switching or fluid turbulence, with the pulse pressure fluctuation range being 0.01 MPa-0.3 MPa.

[0026] Further, the antibacterial efficacy is verified by inhibiting or killing one or more microorganisms among the common Gram-negative bacteria in water, such as Escherichia coli and Pseudomonas aeruginosa, and among the Gram-positive bacteria, such as Staphylococcus aureus and Staphylococcus epidermidis.

[0027] Furthermore, the anti-fouling treatment targets one or more of the following pollutants in the water: microorganisms, proteins, natural organic matter, and colloidal particles, and can effectively inhibit the formation of biofilms.

[0028] Compared with the prior art, the present invention has the following beneficial effects: The self-cleaning composite piezoelectric ceramic membrane prepared by this invention has its functional layer chemically bonded to the piezoelectric substrate via an in-situ hydrothermal method, resulting in an integrated and firmly bonded structure that solves the problem of easy detachment in physical loading methods. It also exhibits strong chemical stability. The preparation method is simple and inexpensive, and requires no external chemicals or energy during operation, achieving self-sufficiency in energy. This represents a green and sustainable membrane fouling control technology.

[0029] The self-cleaning composite piezoelectric ceramic membrane prepared by this invention can synergistically activate multiple antibacterial and antifouling mechanisms, including physical puncture, dynamic electroporation, chemical oxidation, and dielectric electrophoretic physical repulsion, under the drive of hydraulic mechanical energy. This synergistic effect enables broad-spectrum and efficient degradation and inhibition of various pollutants such as bacteria and organic matter, exhibiting excellent antifouling performance in wastewater treatment, with a slow decline in membrane flux and effective reduction in membrane fouling.

[0030] The self-cleaning composite piezoelectric ceramic membrane prepared in this invention loads a one-dimensional copper oxide nanostructure onto a piezoelectric ceramic substrate. This structure not only achieves physical antibacterial properties through its sharp morphology, but its p-type semiconductor characteristics also allow it to form a pn heterojunction with the n-type piezoelectric substrate. This structure enhances the separation efficiency of piezoelectric charges and increases the yield of reactive oxygen species (ROS), thereby strengthening the chemical self-cleaning capability. This ensures both the flux of the composite membrane and the mitigation of membrane fouling.

[0031] For a deeper understanding of the features and technical content of this invention, please refer to the accompanying detailed description and drawings. It should be noted that the drawings are provided for illustrative purposes only and are not intended to limit the scope of the invention. Attached Figure Description

[0032] Figure 1 This is a schematic diagram of the composite piezoelectric ceramic film of the present invention; Figure 2 This is a flowchart illustrating the preparation method of the composite piezoelectric ceramic film of the present invention. Figure 3 The macroscopic morphology of the piezoelectric ceramic substrate film and composite film prepared in this invention is as follows: (a) A photograph of the piezoelectric ceramic substrate film prepared in Example 1; (b) Macroscopic morphology of the composite piezoelectric ceramic film (CuO-NWs / BTO) prepared in Example 2; Figure 4 The microstructure and elemental composition of the piezoelectric ceramic substrate film and composite film prepared in this invention are as follows: (a) SEM and EDS images of the piezoelectric ceramic substrate film prepared in Example 1; (b) SEM and EDS images of the composite piezoelectric ceramic film (CuO-NWs / BTO) prepared in Example 2; Figure 5 Comparison of the crystal structures of the piezoelectric ceramic substrate film and the composite film prepared in this invention: (a) XRD pattern of the piezoelectric ceramic substrate film prepared in Example 1; (b) XRD pattern of the surface layer of the composite piezoelectric ceramic film (CuO-NWs / BTO) prepared in Example 2; Figure 6 XPS image of the composite piezoelectric ceramic film (CuO-NWs / BTO) prepared in Example 2; Figure 7 This is a diagram of a piezoelectric ceramic membrane filtration device. Figure 8 This is a comparison chart of the antibacterial efficacy of different membranes in Example 3; Figure 9 This is a comparison chart of the broad-spectrum antifouling performance of different membranes in Example 4; Figure 10 This is a quantitative comparison chart of the long-term operation of different membranes in Example 4; Figure 11 This is a PFM diagram of a composite piezoelectric ceramic film. Detailed Implementation

[0033] The present invention will be described in detail below with reference to specific embodiments. These embodiments will help those skilled in the art to further understand the present invention, but should not be considered as limiting the present invention. It should be noted that those skilled in the art can make several modifications and improvements without departing from the concept of the present invention. These all fall within the protection scope of the present invention.

[0034] Example 1: Preparation of piezoelectric ceramic substrate film: Step 1: Grind 40.0 g of tetragonal barium titanate powder and 6.0 g of 10% polyvinyl alcohol aqueous solution thoroughly in an agate mortar. Dry the mixture in an oven at 80°C for 12 hours. Step 2: Grind the dried lumps and sieve them through 160-mesh and 200-mesh sieves respectively to obtain granulated powder with good flowability; Step 3: Weigh 5g of granulated powder and spread it evenly in a circular cemented carbide steel mold with a diameter of 3cm. Use a hydraulic press to dry press the powder under a pressure of 40 MPa for 1 minute. After slowly releasing the pressure, remove the powder to obtain a circular ceramic film preform with a thickness of about 2 mm.

[0035] Step 4: Carefully transfer the pressed mold blank into a high-precision tube furnace for sintering in an air atmosphere. The sintering program is set as follows: heat from room temperature to 500℃ at a heating rate of 2℃ / min, hold at that temperature for 2 hours to completely burn out the polyvinyl alcohol binder; then continue heating at a rate of 5℃ / min to the target temperature of 1100℃, and hold at that temperature for 4 hours; finally, remove it after natural cooling to room temperature to obtain a porous ceramic substrate film.

[0036] Step 5: Apply conductive silver paste evenly to both sides of the sintered ceramic film as electrodes, and cure at 80°C.

[0037] Step 6: Immerse the electrode-coated sample in insulating silicone oil at 110℃, apply a DC electric field of 2.5kV / mm, and maintain for 60 minutes for polarization treatment. Then, while maintaining the electric field, slowly cool to below 60℃. Finally, remove the electric field and clean the sample surface with ethanol to remove any remaining silicone oil, thus obtaining the desired sample. Figure 3 (a) shows the porous piezoelectric ceramic substrate film.

[0038] Example 2: Preparation of a self-cleaning composite piezoelectric ceramic film, comprising the following steps: Step 1: Add 0.1208 g of copper nitrate trihydrate to 100 mL of deionized water and stir on a magnetic stirrer for 5 minutes until completely dissolved.

[0039] Step 2: Add 0.12012 g of urea to the above solution and continue to stir magnetically for 5 minutes until the urea is completely dissolved.

[0040] Step 3: Add 0.1111 g of ammonium fluoride to the above mixed solution and stir magnetically for 20 minutes to ensure that all components are mixed evenly, and finally prepare a hydrothermal reaction solution.

[0041] Step 4: Place the optimal BTO substrate membrane prepared in Example 1 and subjected to polarization treatment onto a polytetrafluoroethylene (PTFE) support, and then place it in a 150 mL capacity PTFE-lined stainless steel high-pressure reactor. Slowly transfer the precursor solution prepared in Step 1 into the reactor, ensuring that the substrate membrane is completely submerged.

[0042] Step 5: After sealing the reactor, place the entire vessel in a precisely temperature-controlled oven, raise the temperature to 90°C, and maintain this temperature for 10 hours.

[0043] Step 6: After the reaction is complete, carefully open the reaction vessel and immediately rinse it several times with a large amount of deionized water in an ultrasonic cleaner to thoroughly remove the physically adsorbed, unbonded nanostructures and residual reactants on the membrane surface.

[0044] Step 7: Dry the cleaned composite membrane in an oven at 60°C for 4 hours to obtain the final self-cleaning composite piezoelectric ceramic membrane with a one-dimensional copper oxide nanowire structure as the functional layer.

[0045] Example 3: Evaluation of the synergistic antibacterial properties of self-cleaning composite piezoelectric ceramic membranes Using the pure BTO substrate film prepared in Example 1 and the self-cleaning composite piezoelectric ceramic film prepared in Example 2, in Figure 7 The device was operated in the dead-end filtration unit shown to evaluate its synergistic antimicrobial efficacy against Gram-negative Escherichia coli, Gram-positive Staphylococcus aureus, and a mixture of both.

[0046] Comparative Example 1: The membrane used in Example 1 that was not treated in steps 5 and 6, i.e., the pure BTO substrate membrane that was not polarized, was used.

[0047] Comparative Example 2: The membrane prepared in its entirety in Example 1 is used, namely, the pure BTO substrate membrane after polarization treatment.

[0048] Comparative Example 3: The self-cleaning composite piezoelectric ceramic membrane was prepared in its entirety in Example 2.

[0049] Aseptic Escherichia coli and Staphylococcus aureus were inoculated separately into 50 mL of LB liquid medium and cultured in a shaker at 37°C and 180 rpm until the logarithmic growth phase. The bacterial cells were collected, washed three times by centrifugation with sterile phosphate-buffered saline (PBS, pH 7.4), and then resuspended in PBS to prepare bacterial cultures with a concentration of approximately 10⁻⁶. 7 A single bacterial suspension with CFU / mL, and a suspension containing two different bacteria at 0.5 × 10⁻⁶ CFU / mL each. 7 A mixed bacterial suspension of CFU / mL.

[0050] The membranes of Comparative Examples 1, 2, and 3 were aseptically installed as follows: Figure 7In each of the filtration devices shown, 10 mL of the prepared bacterial suspension was added. All comparative examples were operated under the same hydraulic pulse conditions: periodic pressure changes were achieved via a peristaltic pump connected to a programmable logic controller (PLC). A typical pressure cycling pattern was as follows: the pressure was first increased to 0.2 MPa within 7 seconds, then maintained at a constant operating pressure of 0.2 MPa for 70 seconds, and then rapidly decreased to 0 MPa within 2 seconds, repeating the cycle. All devices were continuously operated in a 37°C incubator for 4 hours. After the experiment, bacteria on the membrane surface were washed with 10 mL of sterile PBS. The eluent was serially diluted tenfold, and 100 μL was spread onto LB agar medium and incubated at 37°C for 24 hours. Colony counting was then performed to calculate the bacterial inactivation rate. Simultaneously, the membrane surface was fluorescently stained after the operation, and the bacterial density on the membrane surface was analyzed and calculated using a confocal laser scanning microscope (CLSM). The results are shown in Table 1.

[0051] Results Analysis: Table 1 shows that under the same hydraulic pulse conditions, Comparative Example 1 had virtually no bactericidal effect on either single or mixed bacterial populations. Comparative Example 2 exhibited certain antibacterial activity, demonstrating that the piezoelectric effect driven by the hydraulic pulse itself has bactericidal capabilities. The antibacterial effect of Comparative Example 3 was superior to that of Comparative Example 2, which is attributed to the static physical penetration and chemical contact bactericidal effect of the one-dimensional copper oxide nanowire structure.

[0052] Most importantly, Comparative Example 3 exhibited significantly higher antibacterial efficiency than any single comparative example, with removal rates exceeding 85% for both single bacterial species and mixed bacterial communities. Its logarithmic kill value was not only significantly higher than each comparative example, but the effect was not a simple linear additive, demonstrating a strong synergistic enhancement effect between the piezoelectric effect driven by the hydraulic pulse and the antibacterial activity of the one-dimensional copper oxide nanowire structure. These results also indicate that the composite membrane of this invention possesses highly efficient broad-spectrum bactericidal capabilities against both Gram-negative and Gram-positive bacteria, and maintains excellent antibacterial performance even in more complex mixed bacterial environments.

[0053] Table 1

[0054] Example 4: Antifouling performance and long-term operation evaluation of self-cleaning composite piezoelectric ceramic membranes Using the membranes of Comparative Example 1, Comparative Example 2, and Comparative Example 3, in Figure 7 The dead-end filter shown was operated under the same periodic hydraulic pulse conditions (pulse mode as in Example 3) and a constant pressure of 0.2 MPa to evaluate its broad-spectrum antifouling performance and long-term operating capability.

[0055] Broad-spectrum antifouling performance was evaluated using oil-water emulsion (2500 ppm), protein (BSA, 50 ppm), bacteria (E. coli, 107 CFU / mL), positively charged colloid (Al2O3, 0.5 g / L), negatively charged colloid (SiO2, 0.5 g / L), a mixture of the above pollutants, and domestic sewage as feed liquids in filtration experiments. Flux changes during the filtration process were continuously monitored, and the final flux reduction rate was calculated to evaluate the membrane's broad-spectrum antifouling performance. The results are shown in Table 2.

[0056] Table 2

[0057] Results Analysis: Table 2 shows that under the same pulsed hydraulic conditions, Comparative Example 1 (unpolarized BTO membrane) experienced rapid clogging when filtering all types of contaminants, indicating its extremely weak antifouling ability. Comparative Example 2 (polarized BTO membrane) showed significantly improved antifouling performance, with a significant reduction in flux decline rates for all types of contaminants, proving that the piezoelectric effect plays a crucial and broad-spectrum role in mitigating membrane fouling.

[0058] In comparison, Comparative Example 3 (composite membrane) exhibited the best antifouling performance, with the lowest flux decline rate under all test conditions. This fully demonstrates that the introduction of the composite functional layer significantly improves the overall antifouling performance of the membrane through synergistic physical antibacterial (inhibition of biofilm formation) and enhanced chemical degradation capabilities, enabling it to demonstrate the strongest stability in the face of complex water quality conditions, including oil, proteins, bacteria, colloids, and even real wastewater.

[0059] The specific embodiments of the present invention have been described in detail above. It should be noted that the present invention is not limited to the specific embodiments described above. Various modifications or alterations can be made by those skilled in the art without departing from the scope of protection defined by the claims, and all such modifications or alterations fall within the scope of the present invention.

Claims

1. A method for preparing a self-cleaning composite piezoelectric ceramic film, characterized in that, Includes the following steps: Step 1: Mix piezoelectric ceramic powder and an aqueous solution of organic binder, grind thoroughly, dry, grind and sieve, press into a blank through a molding process, sinter at high temperature and polarize to obtain a porous ceramic substrate film; Step 2: Add the copper salt precursor to deionized water and stir until completely dissolved. Then add the pH adjuster and stir until completely dissolved. Add the morphology control agent and stir until homogeneous to obtain the precursor solution. Step 3: Completely immerse the porous ceramic substrate membrane in the precursor solution, seal it, and carry out a hydrothermal reaction at a constant temperature. After the reaction is completed, immediately remove the composite membrane, ultrasonically clean it with a large amount of deionized water, and dry it; this completes the process. The piezoelectric ceramic powder is one or more of barium titanate, bismuth ferrite, and potassium sodium niobate; the copper salt precursor is one or more of copper nitrate, copper sulfate, copper acetate, and copper chloride.

2. The method according to claim 1, characterized in that, The organic binder is one or more of polyvinyl alcohol, polyethylene glycol, and methylcellulose.

3. The method according to claim 1, characterized in that, The aqueous solution of the organic binder has a mass concentration of 5%-15%; the mass ratio of the organic binder to the piezoelectric ceramic powder is (1-3):

100.

4. The method according to claim 1, characterized in that, The molding process is dry pressing, with a pressing pressure of 20MPa-50MPa and a holding time of 30-90 seconds. The resulting ceramic film preform has a diameter of 2 cm-4 cm and a thickness of 1 mm-3 mm.

5. The method according to claim 1, characterized in that, The sintering atmosphere is air or oxygen, the heating rate is 2℃ / min-6℃ / min, the sintering temperature is 750℃-1250℃, and the holding time is 2h-6h.

6. The method according to claim 1, characterized in that, The specific operation of polarization treatment is as follows: immerse the ceramic substrate film coated with silver paste as an electrode into insulating silicone oil at 80℃-120℃, apply a DC electric field of 1kV / mm-5 kV / mm, and maintain it for 20min-40min.

7. The method according to claim 1, characterized in that, The pH adjuster is urea, the morphology control agent is ammonium fluoride, and the molar ratio of copper salt precursor, pH adjuster and morphology control agent is (5-15):(10-30):(15-45). The reaction is carried out under hydrothermal conditions at 80℃-120℃.

8. A self-cleaning composite piezoelectric ceramic membrane prepared by the method of any one of claims 1-7.

9. The composite piezoelectric ceramic film according to claim 8, characterized in that, One-dimensional copper oxide nanowire arrays were nucleated and grown in situ on the surface and within the pores of the piezoelectric ceramic substrate film.

10. The application of a self-cleaning composite piezoelectric ceramic membrane prepared by the method of any one of claims 1-7 in anti-pollution water treatment.

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