Self-cleaning piezoelectric hybrid ceramic membrane, preparation method and application thereof

Abstract

The application discloses a kind of self-cleaning piezoelectric hybrid ceramic membranes, its preparation method and application, belong to ceramic membrane separation technical field.The technical scheme includes a kind of self-cleaning piezoelectric hybrid ceramic membranes, including piezoelectric ceramic membrane, silane coupling agent connected to the surface of piezoelectric ceramic membrane with Si-O-M covalent bond and the negative electric charge nanobrush grafted to the other end of silane coupling agent;Negative electric charge nanobrush is grafted with hydrophilic polymer containing carboxyl group to the other end of silane coupling agent, and carboxyl is converted into negative electric charge carboxylate with alkaline solution and obtains.The application is applied to water organic pollutant treatment aspect, solves the modification layer of existing piezoelectric hybrid ceramic membrane surface and easily falls off, catalytic structure is easily covered and poor anti irreversible pollution performance and other limitations, so that membrane is difficult to maintain long-term operation stability when processing complex organic pollution water body, with the characteristics of pulse pressure response and self-cleaning characteristics.

Description

Technical Field

[0001] This invention belongs to the field of ceramic membrane separation technology, and particularly relates to a self-cleaning piezoelectric hybrid ceramic membrane, its preparation method and application. Background Technology

[0002] Organic micropollutants (such as drug residues, microplastics, and natural macromolecular humic acids) are widely present in water bodies, posing a serious threat to ecosystems and public health due to their complex molecular structures and high chemical stability. Among traditional advanced water purification technologies, membrane separation technology has attracted much attention due to its advantages such as high separation precision and stable effluent quality. Although polymer separation membranes are widely used, they are prone to irreversible fouling during long-term operation, have short service lives, and are susceptible to structural collapse during backwashing. In contrast, inorganic ceramic membranes, with their high mechanical strength, excellent stability, and lack of microplastic and perfluorinated compound (PFAS) release risks, demonstrate irreplaceable application potential in water purification. However, the inherent porous structure of ceramic membranes makes them highly susceptible to adsorbing organic pollutants, leading to pore blockage and irreversible fouling. This results in a significant increase in transmembrane pressure and a sharp decline in permeate flux, which has become a key factor limiting the large-scale application of ceramic membranes.

[0003] Currently, methods to improve the resistance of ceramic membranes to organic fouling mainly focus on enhancing the hydrophilicity of the membrane surface or increasing its charge density, constructing a hydration layer on the membrane surface, or using electrostatic repulsion to hinder pollutant adhesion. Since typical organic pollutants such as humic acid are usually negatively charged in water, surface modification strategies can increase the surface charge density to effectively inhibit pollutant adsorption and deposition through electrostatic repulsion. However, this traditional surface chemical modification strategy can only delay, not prevent, the development of membrane fouling, and it easily leads to membrane pore blockage, causing a continuous increase in transmembrane pressure and thus reducing membrane permeability. More importantly, the steric hindrance effect of the polymers used in surface modification greatly limits their grafting density on the membrane surface, making it difficult to further increase the surface charge density after it reaches its peak.

[0004] To overcome the limitations of peak surface charge density in surface chemical modifications, piezoelectric materials offer a novel approach to dynamically enhancing membrane surface charge density. In pressure-driven membrane processes (as seen in ceramic membranes for water treatment), pulsed pressure can excite a continuous piezoelectric effect, converting water flow pressure into transient surface charge, thereby increasing the membrane surface charge density. However, piezoelectricity alone is insufficient for achieving long-term resistance to organic fouling in ceramic membranes. This is primarily because the inherent hydrophobicity of piezoelectric materials hinders the formation of a hydration layer on the membrane surface, leading to irreversible fouling.

[0005] To overcome the hydrophobicity of piezoelectric materials and improve the antifouling ability of ceramic membranes, researchers have focused on surface modification and functionalization of piezoelectric ceramic membranes in recent years. For example, Chinese patent CN120325099A discloses a method for preparing zwitterionic modified piezoelectric ceramic membranes. This method uses piezoelectric ceramic as a support, coats its surface with a membrane layer with small pores, and sinterstensibly at high temperature to obtain a composite membrane. Subsequently, grafting is performed sequentially using a polydopamine / polyethyleneimine mixture and a haloethyl sulfonate solution, ultimately forming a modified piezoelectric ceramic membrane with sulfonamide-type zwitterions on its surface. However, the zwitterions grafted onto the membrane surface are easily detached under long-term water erosion, making it difficult to maintain a long-term and stable antifouling effect. Chinese patent CN11992... Patent 6195A discloses a method for preparing a piezoelectric photocatalytic self-cleaning hollow fiber ceramic membrane. This method first immobilizes non-metallic doped titanium dioxide nanotubes onto the surface of a hollow fiber ceramic substrate membrane using a vacuum-assisted dip-coating method and a low-temperature sintering method. Then, a calcium-doped barium titanate piezoelectric photocatalyst is grown in situ using a hydrothermal method, resulting in a composite membrane with synergistic self-cleaning functions of photocatalysis and piezoelectric effect. However, high-turbidity wastewater severely hinders the efficiency of the photocatalytic reaction, and its weak piezoelectric catalytic ability is insufficient to remove the already formed dense fouling layer, resulting in limited antifouling ability of the membrane; Chinese Patent C N121446323A discloses a method for preparing a self-cleaning composite piezoelectric ceramic membrane. This method involves dry pressing barium titanate piezoelectric ceramic powder into shape, followed by high-temperature sintering and polarization treatment to obtain a porous ceramic substrate membrane. Then, a copper oxide nanowire array is grown in situ on the membrane surface using a hydrothermal method to obtain a composite membrane with piezoelectric and antibacterial functions. However, contaminants easily accumulate rapidly on the membrane surface and cover the copper oxide nanostructure, hindering the piezoelectric catalysis of the membrane to generate active oxygen, resulting in poor overall antifouling effect and instability. Chinese patent CN120860... 842A discloses a method for preparing an antifouling piezoelectric ceramic membrane. This method uses porous ceramic as a support and spin-coates a membrane-forming solution containing piezoelectric crystal material and pore-forming agent onto the inner wall of the through-hole. Combined with low-temperature calcination and high-pressure polarization processes, a piezoelectric ceramic separation layer is obtained. The membrane layer is driven to generate ultrasonic vibration by the induced current generated by the medium flowing through the built-in coil to achieve self-cleaning. However, the ultrasonic vibration energy distribution of the built-in components of the membrane is uneven, resulting in significant differences in the antifouling ability of the membrane surface. Moreover, single physical vibration is difficult to remove high-viscosity organic matter, making the membrane's antifouling ability poor.

[0006] In summary, although the aforementioned surface modification and composite strategies have mitigated the formation of fouling layers on the piezoelectric ceramic membrane surface to some extent, their actual self-cleaning effect is not significant. Furthermore, limitations such as the ease with which the modified layer can detach, the catalytic structure can be easily covered, and poor resistance to irreversible fouling make it difficult for the membrane to maintain long-term operational stability when treating complex organically polluted water bodies. Therefore, preparing a piezoelectric ceramic membrane that combines excellent resistance to organic fouling with long-term dynamic self-cleaning capabilities has become crucial for solving the membrane fouling problem and overcoming its limitations in practical applications. Summary of the Invention

[0007] In view of the shortcomings of the existing technology, the technical problem to be solved by the present invention is that the modified layer on the surface of the existing piezoelectric hybrid ceramic membrane is easy to fall off, the catalytic structure is easily covered, and the resistance to irreversible pollution is poor. This makes it difficult for the membrane to maintain long-term operational stability when treating complex organic polluted water bodies. The present invention proposes a self-cleaning piezoelectric hybrid ceramic membrane with pulse pressure response and self-cleaning characteristics, its preparation method and application.

[0008] To solve the aforementioned technical problem, the technical solution adopted by the present invention is as follows: This invention provides a self-cleaning piezoelectric hybrid ceramic membrane, comprising a piezoelectric ceramic membrane, a silane coupling agent covalently bonded to the surface of the piezoelectric ceramic membrane via Si-OM bonds, and a negatively charged nanobrush grafted to the other end of the silane coupling agent. Specifically, using a self-made or commercially available piezoelectric ceramic membrane as a base membrane, the silane coupling agent is firmly grafted to the surface of the base membrane via Si-OM bonds. Subsequently, a hydrophilic polymer containing carboxyl groups is grafted to the other end of the silane coupling agent. After deprotonation using an alkaline solution, a negatively charged nanobrush is formed, thereby obtaining a self-cleaning piezoelectric hybrid ceramic membrane. The negatively charged nanobrush is obtained by grafting a hydrophilic polymer containing carboxyl groups to the other end of the silane coupling agent and converting the carboxyl groups into negatively charged carboxylate groups using an alkaline solution. During pulse filtration, periodic negative charges can be generated on the surface of the piezoelectric hybrid ceramic membrane, which electrostatically repel the negatively charged nanobrushes. This causes the negatively charged nanobrushes to undergo periodic curling (without electrostatic repulsion) – stretching (with electrostatic repulsion) dynamic oscillations, which loosen the organic pollutants deposited on the membrane surface and remove them with the shear force of the water flow, thereby achieving self-cleaning of the membrane.

[0009] In some embodiments, the silane coupling agent is selected from γ-aminopropyltriethoxysilane, γ-methacryloxypropyltrimethoxysilane, N-(2-aminoethyl)-3-aminopropyltrimethoxysilane, and polyethylene glycol trimethoxysilylpropyl ether; the hydrophilic polymer containing carboxyl groups is selected from maleic acid-acrylic acid copolymer, polymethacrylic acid, polymaleic acid, polyglutamic acid, and polyacrylic acid containing multiple carboxyl groups; and the alkaline solution is selected from sodium carbonate solution, potassium carbonate solution, sodium hydroxide solution, and potassium hydroxide solution.

[0010] In some embodiments, the molecular weight of the hydrophilic polymer containing carboxyl groups is selected from any value in the range of 2000-6000 g / mol; the pore size of the piezoelectric ceramic film is selected from any value in the range of 20-500 nm; and the piezoelectric constant is selected from any value in the range of 10-200 pC / N.

[0011] Another aspect of the present invention provides a method for preparing a self-cleaning piezoelectric hybrid ceramic membrane according to any of the above technical solutions, comprising: grafting a silane coupling agent onto the surface of the piezoelectric ceramic membrane; utilizing the silanol groups generated by the hydrolysis of the silane coupling agent to undergo dehydration condensation with the hydroxyl groups on the surface of the piezoelectric ceramic membrane; covalently linking the silane coupling agent to the surface of the piezoelectric ceramic membrane with Si-OM; subsequently grafting a hydrophilic polymer containing carboxyl groups onto the other end of the silane coupling agent; and finally converting the carboxyl groups into negatively charged carboxylate groups using an alkaline solution to obtain a self-cleaning piezoelectric hybrid ceramic membrane.

[0012] In some embodiments, including: S1. Prepare ethanol solutions of silane coupling agent and hydrophilic polymers containing carboxyl groups, respectively. S2. Immerse the piezoelectric ceramic membrane in an ethanol solution of silane coupling agent and react at 50-85℃ for 8-14 hours to obtain a piezoelectric ceramic membrane with silane coupling agent grafted on its surface. S3. After reacting an ethanol solution of a piezoelectric ceramic film grafted with a silane coupling agent with a hydrophilic polymer containing carboxyl groups at 25-45°C for 15-24 hours, the hydrophilic polymer containing carboxyl groups is treated with an alkaline solution to deprotonate it and form negatively charged groups, thereby obtaining a self-cleaning piezoelectric hybrid ceramic film.

[0013] In some embodiments, the ethanol used in S1 is an aqueous solution of ethanol with a mass fraction of 80-98%, the concentration of the silane coupling agent in the ethanol solution of the silane coupling agent is 1-50 mL / L, the concentration of the hydrophilic polymer containing carboxyl groups in the ethanol solution of the hydrophilic polymer containing carboxyl groups is 10-50 mL / L, and the concentration of the alkaline solution is 1-100 mmol / L.

[0014] In some embodiments, the piezoelectric ceramic film is a self-made or commercially available piezoelectric ceramic film, and the material is one of potassium sodium niobate, lead zirconate titanate, zinc oxide, potassium niobate, lithium tantalate, and barium titanate.

[0015] The present invention also provides the application of self-cleaning piezoelectric hybrid ceramic membranes of any of the above technical solutions in the treatment of organic pollutants in water.

[0016] In some embodiments, under the action of pulsed water flow pressure of the feed liquid, periodic negative charges can be generated on the surface of the piezoelectric hybrid ceramic membrane, which generate electrostatic repulsion with the negatively charged nanobrush, causing the hydrophilic polymerization to undergo periodic curling (without electrostatic repulsion) - stretching (with electrostatic repulsion) dynamic oscillation, which loosens the organic pollutants deposited on the surface of the piezoelectric ceramic membrane and removes them with the shear force of the incoming water flow.

[0017] In some embodiments, the pressure of the feed liquid pulse water flow is 5-10 bar.

[0018] Compared with the prior art, the beneficial effects of the present invention are as follows: This invention provides a self-cleaning piezoelectric hybrid ceramic membrane. This membrane achieves high resistance to organic fouling through the synergistic effect of self-cleaning and the physical barrier effect of the hydration layer. When a pulse pressure is applied to the pressure-driven membrane, periodic negative charges are generated on the surface of the piezoelectric hybrid ceramic membrane. These charges electrostatically repel the negatively charged nanobrushes, causing the nanobrushes to undergo periodic curling (without electrostatic repulsion) – stretching (with electrostatic repulsion) dynamic oscillations. Under pulse pressure, the negatively charged nanobrushes undergo periodic "peristaltic-like" dynamic oscillations (i.e., the polyacrylate conformation periodically generates negative charges on the membrane surface, resulting in periodic curling (without electrostatic repulsion) and stretching (with electrostatic repulsion) changes). This loosens the organic pollutants deposited on the membrane surface and causes them to detach due to the shear force of the incoming water flow, ultimately achieving the membrane's in-situ self-cleaning function and high resistance to organic fouling. Meanwhile, the negatively charged nanobrushes grafted onto the membrane surface contain abundant hydrophilic groups, which can tightly bind with water molecules through hydrogen bonds to form a dense hydration layer. This hydration layer acts as a physical barrier, effectively blocking the contact between organic pollutants and the membrane surface, and significantly preventing their adsorption and deposition. Attached Figure Description

[0019] Figure 1 This is a schematic diagram illustrating the periodic "creep-like" dynamic oscillation principle of a self-cleaning piezoelectric hybrid ceramic membrane under pulsed pressure filtration using a negatively charged nanobrush, as provided in an embodiment of the present invention. Detailed Implementation

[0020] The technical solutions in specific embodiments of the present invention will be described in detail and completely below. Obviously, the described embodiments are only some specific implementations of the overall technical solution of the present invention, and not all implementations. Based on the overall concept of the present invention, all other embodiments obtained by those skilled in the art fall within the protection scope of the present invention.

[0021] One aspect of this invention provides a self-cleaning piezoelectric hybrid ceramic membrane, comprising a piezoelectric ceramic membrane, a silane coupling agent covalently bonded to the surface of the piezoelectric ceramic membrane via Si-OM bonds, and a negatively charged nanobrush grafted to the other end of the silane coupling agent; the negatively charged nanobrush is obtained by grafting a hydrophilic polymer containing carboxyl groups to the other end of the silane coupling agent, and converting the carboxyl groups into negatively charged carboxylate groups using an alkaline solution.

[0022] The above technical solution first grafts a silane coupling agent onto the surface of a self-made or commercially available piezoelectric ceramic membrane. The silanol groups (Si-OH) generated by the hydrolysis of the silane coupling agent undergo dehydration condensation with the hydroxyl groups (M-OH) on the surface of the ceramic membrane, and the coupling agent is stably introduced into the membrane surface by Si-OM covalent bonds. Then, a hydrophilic polymer containing carboxyl groups is grafted onto the other end of the silane coupling agent. Finally, an alkaline solution is used to convert the carboxyl groups into negatively charged carboxylate groups, thereby obtaining a negatively charged nanobrush smart piezoelectric hybrid ceramic membrane with pulse pressure response and self-cleaning properties.

[0023] Specifically, such as Figure 1 As shown, under the pressure of the pulsed water flow of the feed liquid, the surface of the piezoelectric ceramic hybrid membrane can generate periodic negative charges, which generate periodic electrostatic repulsion between the carboxyl groups of the negatively charged nanobrushes. This causes the negatively charged nanobrushes to undergo periodic "peristalsis-like" dynamic oscillations (i.e., the polyacrylate conformation periodically generates negative charges on the membrane surface, resulting in periodic curling (without electrostatic repulsion) and stretching (with electrostatic repulsion) changes). This promotes the loosening of organic pollutants deposited on the membrane surface and their removal by the shear force of the feed water flow, ultimately achieving the membrane's in-situ self-cleaning function and high resistance to organic fouling.

[0024] The aforementioned self-cleaning piezoelectric hybrid ceramic membrane achieves high resistance to organic fouling through the synergistic effect of self-cleaning and the physical barrier of the hydration layer. When pulse pressure is applied to the pressure-driven membrane, periodic negative charges are generated on the surface of the piezoelectric hybrid ceramic membrane, causing electrostatic repulsion between the negatively charged nanobrushes and the nanobrushes to undergo periodic curling (without electrostatic repulsion) – stretching (with electrostatic repulsion) dynamic oscillations. Under pulse pressure, the negatively charged nanobrushes undergo periodic "peristaltic-like" dynamic oscillations (i.e., the polyacrylate conformation periodically generates negative charges on the membrane surface, resulting in periodic curling (without electrostatic repulsion) and stretching (with electrostatic repulsion) changes), which loosens the organic pollutants deposited on the membrane surface and causes them to fall off with the shear force of the influent water flow, ultimately achieving the membrane's in-situ self-cleaning function and high resistance to organic fouling. At the same time, the negatively charged nanobrushes grafted on the membrane surface contain abundant hydrophilic groups, which can tightly bind with water molecules through hydrogen bonds to form a dense hydration layer. This hydration layer acts as a physical barrier, effectively blocking the contact between organic pollutants and the membrane surface, significantly preventing their adsorption and deposition. In summary, the synergistic effect of the "peristaltic" dynamic oscillation of the negatively charged nanobrush on the surface of the self-cleaning piezoelectric ceramic membrane and the static barrier of the hydration layer enables the membrane to achieve excellent resistance to organic fouling.

[0025] It should be noted that the above-mentioned self-cleaning piezoelectric hybrid ceramic membrane has the following characteristics: (1) It has excellent long-term operational stability. The negatively charged nanobrush is introduced into the membrane surface in the form of covalent bonds, which ensures that the membrane can maintain a long-term and stable chemical structure and separation performance; (2) It can achieve in-situ dynamic self-cleaning. During the pulse pressure filtration process, the negatively charged nanobrush on the surface of the hybrid membrane generates a "peristaltic" dynamic oscillation, which loosens and removes the pollutants; The aforementioned self-cleaning piezoelectric hybrid ceramic membrane exhibits significantly enhanced resistance to organic fouling, effectively addressing numerous limitations encountered during ceramic membrane operation, such as the need for backwashing, poor resistance to organic fouling, and weak modified layer. This method is also applicable to various piezoelectric ceramic membrane configurations, including flat, tubular, and multi-channel types.

[0026] In some embodiments, the silane coupling agent is selected from γ-aminopropyltriethoxysilane, γ-methacryloxypropyltrimethoxysilane, N-(2-aminoethyl)-3-aminopropyltrimethoxysilane, and polyethylene glycol trimethoxysilylpropyl ether; the hydrophilic polymer containing carboxyl groups is selected from maleic acid-acrylic acid copolymer, polymethacrylic acid, polymaleic acid, polyglutamic acid, and polyacrylic acid containing multiple carboxyl groups; and the alkaline solution is selected from sodium carbonate solution, potassium carbonate solution, sodium hydroxide solution, and potassium hydroxide solution.

[0027] In some embodiments, the molecular weight of the hydrophilic polymer containing carboxyl groups is selected from any value in the range of 2000-6000 g / mol; the pore size of the piezoelectric ceramic film is selected from any value in the range of 20-500 nm; and the piezoelectric constant is selected from any value in the range of 10-200 pC / N.

[0028] Understandably, the molecular weight of the hydrophilic polymer containing carboxyl groups can be any value within the range of 2500 g / mol, 3000 g / mol, 3500 g / mol, 4000 g / mol, 4500 g / mol, 5000 g / mol, 5500 g / mol, and so on. The pore size of the piezoelectric ceramic film can also be any value within the range of 50 nm, 100 nm, 150 nm, 200 nm, 250 nm, 300 nm, 350 nm, 400 nm, 450 nm, and so on. The piezoelectric constant can also be any value within the range of 20 pC / N, 40 pC / N, 60 pC / N, 80 pC / N, 100 pC / N, 120 pC / N, 140 pC / N, 160 pC / N, 180 pC / N, and so on.

[0029] Another aspect of the present invention provides a method for preparing a self-cleaning piezoelectric hybrid ceramic membrane according to any of the above technical solutions, comprising: grafting a silane coupling agent onto the surface of the piezoelectric ceramic membrane; utilizing the silanol groups generated by the hydrolysis of the silane coupling agent to undergo dehydration condensation with the hydroxyl groups on the surface of the piezoelectric ceramic membrane; covalently linking the silane coupling agent to the surface of the piezoelectric ceramic membrane with Si-OM; subsequently grafting a hydrophilic polymer containing carboxyl groups onto the other end of the silane coupling agent; and finally converting the carboxyl groups into negatively charged carboxylate groups using an alkaline solution to obtain a self-cleaning piezoelectric hybrid ceramic membrane.

[0030] The preparation method is simple and easy to scale up. The resulting hybrid membrane has excellent antifouling performance, exhibits high flux retention, and has excellent retention and antifouling performance for typical organic pollutants such as humic acid in water, significantly improving the long-term operational stability of the membrane.

[0031] In some embodiments, including: S1. Prepare ethanol solutions of silane coupling agent and hydrophilic polymers containing carboxyl groups, respectively. S2. Immerse the piezoelectric ceramic membrane in an ethanol solution of silane coupling agent and react it at 50-85℃ (this temperature can also be any value within the range of 55℃, 60℃, 65℃, 70℃, 75℃, 80℃) for 8-14 hours (this time can also be any value within the range of 9h, 10h, 11h, 12h, 13h) to obtain a piezoelectric ceramic membrane with silane coupling agent grafted on its surface. S3. The piezoelectric ceramic film grafted with silane coupling agent on its surface is reacted with an ethanol solution of a hydrophilic polymer containing carboxyl groups at 25-45℃ (this temperature can also be any value within the range of 30℃, 35℃, 40℃) for 15-24h (this time can also be any value within the range of 16h, 17h, 18h, 19h, 20h, 21h, 22h, 23h) and then the hydrophilic polymer containing carboxyl groups is treated with an alkaline solution to deprotonate and form negatively charged groups, thereby obtaining a self-cleaning piezoelectric hybrid ceramic film.

[0032] The above technical solution uses a silane coupling agent as a grafting intermediate to graft hydrophilic polymers onto the membrane surface via covalent bonds. Under long-term operating conditions, the hydrophilic polymer exhibits excellent adhesion to the membrane surface. This surface modification strategy is highly technically feasible; however, the temperature and time need to be optimized during the grafting reaction to stably introduce the hydrophilic polymer onto the membrane surface via covalent bonds.

[0033] In some embodiments, the ethanol used in S1 is an aqueous solution of ethanol with a mass fraction of 80-98%, and the concentration of the silane coupling agent in the ethanol solution is 1-50 mL / L (this concentration can also be any value within the range of 5 mL / L, 10 mL / L, 15 mL / L, 20 mL / L, 25 mL / L, 30 mL / L, 35 mL / L, 40 mL / L, 45 mL / L), and the concentration of the hydrophilic polymer containing carboxyl groups in the ethanol solution is 1. The concentration of alkaline solutions is 0-50 mL / L (this concentration can also be 15 mL / L, 20 mL / L, 25 mL / L, 30 mL / L, 35 mL / L, 40 mL / L, 45 mL / L and any point value within the range); the concentration of alkaline solutions is 1-100 mmol / L (this concentration can also be 10 mL / L, 20 mL / L, 30 mL / L, 40 mL / L, 50 mL / L, 60 mL / L, 70 mL / L, 80 mL / L, 90 mL / L and any point value within the range).

[0034] In some embodiments, the piezoelectric ceramic film is a self-made or commercially available piezoelectric ceramic film, and the material is one of potassium sodium niobate, lead zirconate titanate, zinc oxide, potassium niobate, lithium tantalate, and barium titanate.

[0035] The present invention also provides the application of self-cleaning piezoelectric hybrid ceramic membranes of any of the above technical solutions in the treatment of organic pollutants in water.

[0036] In some embodiments, under the action of pulsed water flow pressure of the feed liquid, periodic negative charges are generated on the surface of the piezoelectric ceramic membrane, which generate periodic electrostatic repulsion with the negatively charged nanobrush, causing the negatively charged nanobrush to undergo periodic peristaltic dynamic oscillation, loosening the organic pollutants deposited on the surface of the piezoelectric ceramic membrane and causing them to fall off with the shear force of the incoming water flow.

[0037] Under pulsed pressure, the piezoelectric ceramic substrate membrane generates periodic negative charges due to the piezoelectric effect, which then electrostatically interact with the negatively charged nanobrushes. Specifically, when pulsed pressure is applied to the pressure-driven membrane, periodic negative charges are generated on the surface of the piezoelectric hybrid ceramic membrane, causing electrostatic repulsion between the negatively charged nanobrushes and resulting in a periodic curling (without electrostatic repulsion) – stretching (with electrostatic repulsion) dynamic oscillation of the negatively charged nanobrushes. Therefore, as long as the piezoelectric ceramic substrate membrane maintains stable piezoelectric properties under pulsed pressure, the periodic "peristaltic-like" oscillation of the negatively charged nanobrushes can be effectively induced. However, this process presents certain technical challenges. This invention has found that the applied pressure for generating the periodic "peristaltic-like" oscillation of the negatively charged nanobrushes is limited; that is, the applied pressure cannot be lower than 5 bar. Otherwise, sufficient voltage and surface charge density cannot be generated in the water to provide sufficient repulsive force between the brushes. In some embodiments, the pressure of the pulsed water flow of the feed liquid is 5-10 bar.

[0038] Based on the excellent mechanical strength of the piezoelectric ceramic film, the piezoelectric ceramic film of the present invention can generate periodic surface negative charges in a wide range of pulsed water flow pressure (5-10 bar).

[0039] The pulsed water flow pressure was set to 0→X bar with a pressurization time of 0.5 s and X→0 bar with a depressurization time of 0.5 s, where X is 5-10 bar. The filtration mode was cross-flow filtration. Without water flow pressure, the charge centers of positive and negative ions inside the crystal coincide, and their microscopic dipole moments cancel each other out. Therefore, the membrane material is macroscopically neutral. When water flow pressure is applied to the membrane surface, the crystal lattice inside the material undergoes asymmetric deformation, generating a directional macroscopic dipole moment along a specific crystal axis. This dipole moment forms a polarized electric field at the macroscopic interface of the membrane, ultimately resulting in a negative polarized charge on the membrane surface. When the water flow pressure is removed, the internal crystal lattice structure returns to its initial symmetrical equilibrium state, the positive and negative charge centers re-coincide, and the macroscopic dipole moment becomes zero. This causes the polarized negative charges that were originally concentrated on the membrane surface to rapidly dissipate or be neutralized by the environment, and the membrane surface regains its electrical neutrality.

[0040] It should be noted that this invention limits the grafting of negatively charged nanobrushes onto the surface of a piezoelectric ceramic membrane. This is because, to generate a strong repulsive force between the nanobrushes and induce a conformational change, the feed liquid pulse pressure needs to be no less than 5 bar. Existing polymer membranes, such as the polyvinylidene fluoride membrane disclosed in Chinese patent CN121623598A, cannot withstand this pulse pressure due to their limited mechanical strength. This is because polymer microfiltration or ultrafiltration membranes have limited pulse pressure resistance, and the inorganic nanoparticles in the polymer membrane are simply introduced into the PVDF through doping, resulting in a significant interface between the two. This interface is essentially a defect and will rupture under even a small amount of external force, especially under higher impact pressures (such as 5 bar), leading to the detachment of the inorganic nanoparticles. Furthermore, the aforementioned patent directly grafts polyacrylic acid onto the polyvinylidene fluoride surface. If the polyvinylidene fluoride at the grafting site degrades after alkali treatment, it will directly cause the grafted polypropylene to detach from the membrane surface.

[0041] This invention specifies the use of a piezoelectric ceramic membrane with excellent piezoelectric response as the base membrane. Under a pulsed water flow pressure of 5-10 bar, the membrane can generate sufficient surface charge density to drive the negatively charged nanobrushes grafted onto the membrane surface to produce periodic "creep-like" oscillations. Furthermore, the piezoelectric ceramic base membrane selected in this invention (material selected from sodium potassium niobate, lead zirconate titanate, zinc oxide, potassium niobate, lithium tantalate, and barium titanate) all possess excellent piezoelectric response capabilities, thereby generating sufficient surface charge density under pulsed pressure to maintain the periodic "creep-like" oscillations of the negatively charged nanobrushes.

[0042] To provide a clearer and more detailed description of the self-cleaning piezoelectric hybrid ceramic membrane, its preparation method, and its applications provided by the embodiments of the present invention, the following description will be based on specific embodiments.

[0043] Example 1 S1. Prepare a γ-aminopropyltriethoxysilane solution with a concentration of 50 ml / L using a 98% (v / v) aqueous ethanol solution; prepare a maleic acid-acrylic acid copolymer solution with a molecular weight of 5000 g / mol and a concentration of 40 ml / L using an 85% (v / v) aqueous ethanol solution. S2. Immerse a 500 nm pore size potassium sodium niobate piezoelectric ceramic membrane in a γ-aminopropyltriethoxysilane solution and react at 85 °C for 8 h. The silane coupling agent hydrolyzes to generate Si-OH, which undergoes dehydration condensation with M-OH on the surface of the piezoelectric ceramic, making it stably grafted onto the surface of the piezoelectric ceramic membrane. After cleaning, immerse it in deionized water for later use. S3. The piezoelectric ceramic membrane with a silane coupling agent on its surface is reacted with a maleic acid-acrylic acid copolymer solution at 25°C for 24 hours. The hydrophilic polymer reacts with the other end of the silane coupling agent to introduce the hydrophilic polymer on the membrane surface. Then, the hydrophilic polymer is treated with a 1 mmol / L sodium hydroxide solution to deprotonate and form negatively charged groups, thereby obtaining the desired negatively charged nanobrush smart piezoelectric hybrid ceramic membrane with pulse pressure response and self-cleaning properties.

[0044] A pulsed pressure cyclic mode was used to treat humic acid solution wastewater with an initial concentration of C0=1000ppm: a dynamic filtration system was constructed by periodic pulses (pressure application time of 0.5s from 0 to 5 bar, pressure release time of 0.5s from 5 to 0 bar), and the retention performance of the negatively charged nanobrush smart piezoelectric hybrid ceramic membrane was quantitatively detected by combining the changes in TOC before and after filtration.

[0045] Measurements showed that the zeta potential (pH=7) of the undeprotonated piezoelectric hybrid ceramic membrane was -37 mV, and under pulsed pressure operation, the TOC removal rate was 54.5%, with a membrane flux retention rate of 61.4% after 168 hours of operation. In contrast, the zeta potential (pH=7) of the negatively charged nanobrush smart piezoelectric hybrid ceramic membrane was -83 mV, and under pulsed pressure operation, the TOC removal rate was 95.1%, with a membrane flux retention rate of 92.2% after 168 hours of operation.

[0046] Example 2 S1. Prepare a γ-methacryloxypropyltrimethoxysilane solution with a concentration of 40 ml / L using a 96% (v / v) aqueous ethanol solution; prepare a polymethacrylic acid solution with a molecular weight of 5000 g / mol and a concentration of 50 ml / L using an 80% (v / v) aqueous ethanol solution. S2. The lead zirconate titanate piezoelectric ceramic membrane with a pore size of 100 nm was immersed in a γ-methacryloxypropyltrimethoxysilane solution and reacted at 85 °C for 8 h. The silane coupling agent was hydrolyzed to generate Si-OH, which underwent dehydration condensation with M-OH on the surface of the piezoelectric ceramic, making it firmly grafted onto the surface of the piezoelectric ceramic membrane. After cleaning, it was immersed in deionized water for later use. S3. The piezoelectric ceramic membrane with silane coupling agent on its surface is reacted with polymethyl methacrylate solution at 35°C for 20 h. The hydrophilic polymer reacts with the other end of the silane coupling agent to introduce the hydrophilic polymer on the membrane surface. Then, the hydrophilic polymer is treated with 10 mmol / L sodium carbonate solution to deprotonate and form negatively charged groups, thereby obtaining the desired negatively charged nanobrush smart piezoelectric hybrid ceramic membrane with pulse pressure response and self-cleaning properties.

[0047] The pulse pressure circulation mode of Example 1 was used to treat humic acid solution wastewater with an initial concentration of C0=1000ppm.

[0048] Measurements showed that the zeta potential (pH=7) of the undeprotonated piezoelectric hybrid ceramic membrane was -21 mV, and under pulsed pressure operation, the TOC removal rate was 75.9%, with a membrane flux retention rate of 68.7% after 168 hours of operation. In contrast, the zeta potential (pH=7) of the negatively charged nanobrush intelligent piezoelectric hybrid ceramic membrane was -38 mV, with a TOC removal rate of 96.5%, and a membrane flux retention rate of 92.8% after 168 hours of operation.

[0049] Example 3 S1. Prepare an N-(2-aminoethyl)-3-aminopropyltrimethoxysilane solution with a concentration of 30 ml / L using a 98% (v / v) aqueous ethanol solution; prepare a polymethacrylic acid solution with a molecular weight of 3000 g / mol and a concentration of 40 ml / L using an 87% (v / v) aqueous ethanol solution. S2. Immerse a self-made or commercial zinc oxide piezoelectric ceramic membrane with a pore size of 300 nm in an N-(2-aminoethyl)-3-aminopropyltrimethoxysilane solution and react at 75°C for 9 h. The silane coupling agent hydrolyzes to generate Si-OH, which undergoes dehydration condensation with M-OH on the surface of the piezoelectric ceramic, making it stably grafted onto the surface of the piezoelectric ceramic membrane. After cleaning, immerse it in deionized water for later use. S3. The piezoelectric ceramic membrane with silane coupling agent on its surface is reacted with polymethyl methacrylate solution at 40°C for 18 hours. The hydrophilic polymer reacts with the other end of the silane coupling agent to introduce the hydrophilic polymer on the membrane surface. Then, the hydrophilic polymer is treated with 100 mmol / L potassium carbonate solution to deprotonate and form negatively charged groups, thereby obtaining the desired negatively charged nanobrush smart piezoelectric hybrid ceramic membrane with pulse pressure response and self-cleaning properties.

[0050] The pulse pressure circulation mode of Example 1 was used to treat humic acid solution wastewater with an initial concentration of C0=1000ppm.

[0051] Measurements showed that the zeta potential (pH=7) of the undeprotonated piezoelectric hybrid ceramic membrane was -38 mV, and under pulsed pressure operation, the TOC removal rate was 68.2%, with a membrane flux retention rate of 51.4% after 168 hours of operation. In contrast, the zeta potential (pH=7) of the negatively charged nanobrush intelligent piezoelectric hybrid ceramic membrane was -55 mV, with a TOC removal rate of 97.1%, and a membrane flux retention rate of 93.6% after 168 hours of operation.

[0052] Example 4 S1. Prepare a polyethylene glycol trimethoxysilyl propyl ether solution with a concentration of 20 ml / L using a 92% (v / v) ethanol aqueous solution; prepare a polyglutamic acid solution with a molecular weight of 3000 g / mol and a concentration of 40 ml / L using a 94% (v / v) ethanol aqueous solution. S2. Immerse a self-made or commercial zinc oxide piezoelectric ceramic membrane with a pore size of 400nm in a polyethylene glycol trimethoxysilylpropyl ether solution and react at 60℃ for 10h. The silane coupling agent hydrolyzes to generate Si-OH, which undergoes dehydration condensation with M-OH on the surface of the piezoelectric ceramic, making it stably grafted onto the surface of the piezoelectric ceramic membrane. After cleaning, immerse it in deionized water for later use. S3. The piezoelectric ceramic membrane with silane coupling agent on its surface is reacted with polyglutamic acid solution at 45°C for 15 h. The hydrophilic polymer reacts with the other end of the silane coupling agent to introduce the hydrophilic polymer on the membrane surface. Then, the hydrophilic polymer is treated with 20 mmol / L potassium hydroxide solution to deprotonate and form negatively charged groups, thereby obtaining the desired negatively charged nanobrush smart piezoelectric hybrid ceramic membrane with pulse pressure response and self-cleaning properties.

[0053] The pulse pressure circulation mode of Example 1 was used to treat humic acid solution wastewater with an initial concentration of C0=1000ppm.

[0054] Measurements showed that the zeta potential (pH=7) of the undeprotonated piezoelectric hybrid ceramic membrane was -27 mV, and under pulsed pressure operation, the TOC removal rate was 69.7%, with a membrane flux retention rate of 54.7% after 168 hours of operation. In contrast, the zeta potential (pH=7) of the negatively charged nanobrush intelligent piezoelectric hybrid ceramic membrane was -48 mV, with a TOC removal rate of 97.5%, and a membrane flux retention rate of 93.8% after 168 hours of operation.

[0055] Example 5 S1. Prepare a γ-methacryloxypropyltrimethoxysilane solution with a concentration of 10 ml / L using a 90% (v / v) aqueous ethanol solution; prepare a polyacrylic acid solution with a molecular weight of 2000 g / mol and a concentration of 30 ml / L using an 85% (v / v) aqueous ethanol solution. S2. Immerse a self-made or commercial zinc oxide piezoelectric ceramic membrane with a pore size of 200nm in a polyethylene glycol trimethoxysilylpropyl ether solution and react at 65℃ for 11h. The silane coupling agent hydrolyzes to generate Si-OH, which undergoes dehydration condensation with M-OH on the surface of the piezoelectric ceramic, making it stably grafted onto the surface of the piezoelectric ceramic membrane. After cleaning, immerse it in deionized water for later use. S3. The piezoelectric ceramic membrane with silane coupling agent on its surface is reacted with polyglutamic acid solution at 30°C for 20 h. The hydrophilic polymer reacts with the other end of the silane coupling agent to introduce the hydrophilic polymer on the membrane surface. Then, the hydrophilic polymer is treated with 90 mmol / L potassium carbonate solution to deprotonate and form negatively charged groups, thereby obtaining the desired negatively charged nanobrush smart piezoelectric hybrid ceramic membrane with pulse pressure response and self-cleaning properties.

[0056] The pulse pressure circulation mode of Example 1 was used to treat humic acid solution wastewater with an initial concentration of C0=1000ppm.

[0057] Measurements showed that the zeta potential (pH=7) of the undeprotonated piezoelectric hybrid ceramic membrane was -36 mV, with a TOC removal rate of 71.5% under pulsed pressure operation and a membrane flux retention rate of 63.2% after 168 hours of operation. In contrast, the zeta potential (pH=7) of the negatively charged nanobrush intelligent piezoelectric hybrid ceramic membrane was -59 mV, with a TOC removal rate of 97.7% and a membrane flux retention rate of 94.3% after 168 hours of operation.

[0058] Example 6 S1. Prepare a γ-methacryloxypropyltrimethoxysilane solution with a concentration of 1 ml / L using a 92% (v / v) aqueous ethanol solution; prepare a polymaleic acid solution with a molecular weight of 2000 g / mol and a concentration of 50 ml / L using a 98% (v / v) aqueous ethanol solution. S2. Immerse a self-made or commercial zinc oxide piezoelectric ceramic membrane with a pore size of 50 nm in a γ-methacryloxypropyltrimethoxysilane solution and react at 60 °C for 13 h. The silane coupling agent hydrolyzes to generate Si-OH, which undergoes dehydration condensation with M-OH on the surface of the piezoelectric ceramic, making it stably grafted onto the surface of the piezoelectric ceramic membrane. After cleaning, immerse it in deionized water for later use. S3. The piezoelectric ceramic membrane with silane coupling agent on its surface is reacted with polymaleic acid solution at 28°C for 22 hours. The hydrophilic polymer reacts with the other end of the silane coupling agent to introduce the hydrophilic polymer on the membrane surface. Then, the hydrophilic polymer is treated with 70 mmol / L potassium hydroxide solution to deprotonate and form negatively charged groups, thereby obtaining the desired negatively charged nanobrush smart piezoelectric hybrid ceramic membrane with pulse pressure response and self-cleaning properties.

[0059] The pulse pressure circulation mode of Example 1 was used to treat humic acid solution wastewater with an initial concentration of C0=1000ppm.

[0060] Measurements showed that the zeta potential (pH=7) of the undeprotonated piezoelectric hybrid ceramic membrane was -24 mV, and under pulsed pressure operation, the TOC removal rate was 72.3%, with a membrane flux retention rate of 65.7% after 168 hours of operation. In contrast, the zeta potential (pH=7) of the negatively charged nanobrush intelligent piezoelectric hybrid ceramic membrane was -32 mV, with a TOC removal rate of 99.5%, and a membrane flux retention rate of 94.9% after 168 hours of operation.

[0061] Example 7 S1. Prepare a γ-aminopropyltriethoxysilane solution with a concentration of 40 ml / L using an 85% (v / v) aqueous ethanol solution; prepare a polymethacrylic acid solution with a molecular weight of 4000 g / mol and a concentration of 30 ml / L using an 80% (v / v) aqueous ethanol solution. S2. Immerse a self-made or commercial zinc oxide piezoelectric ceramic membrane with a pore size of 20nm in a γ-aminopropyltriethoxysilane solution and react at 80℃ for 8h. The silane coupling agent hydrolyzes to generate Si-OH, which undergoes dehydration condensation with M-OH on the surface of the piezoelectric ceramic, making it stably grafted onto the surface of the piezoelectric ceramic membrane. After cleaning, immerse it in deionized water for later use. S3. The piezoelectric ceramic membrane with silane coupling agent on its surface is reacted with polymethyl methacrylate solution at 35°C for 20 h. The hydrophilic polymer reacts with the other end of the silane coupling agent to introduce the hydrophilic polymer on the membrane surface. Then, the hydrophilic polymer is treated with 80 mmol / L potassium carbonate solution to deprotonate and form negatively charged groups, thereby obtaining the desired negatively charged nanobrush smart piezoelectric hybrid ceramic membrane with pulse pressure response and self-cleaning properties.

[0062] The pulse pressure circulation mode of Example 1 was used to treat humic acid solution wastewater with an initial concentration of C0=1000ppm.

[0063] Measurements showed that the zeta potential (pH=7) of the undeprotonated piezoelectric hybrid ceramic membrane was -39 mV, and under pulsed pressure operation, the TOC removal rate was 79.4%, with a membrane flux retention rate of 72.7% after 168 hours of operation. In contrast, the negatively charged nanobrush smart piezoelectric hybrid ceramic membrane had a surface potential of -64 mV, a TOC removal rate of 99.9%, and a membrane flux retention rate of 95.2% after 168 hours of operation.

[0064] In the above embodiments, the unprotonated piezoelectric hybrid ceramic film refers to a piezoelectric hybrid ceramic film obtained by firmly grafting a silane coupling agent onto the surface of a base film with Si-OM covalent bonds, and then grafting a hydrophilic polymer containing a carboxyl group onto the other end of the silane coupling agent, but without deprotonating it with an alkaline solution.

Claims

1. A self-cleaning piezoelectric hybrid ceramic membrane, characterized in that, The invention includes a piezoelectric ceramic film, a silane coupling agent covalently bonded to the surface of the piezoelectric ceramic film via Si-OM bonds, and a negatively charged nanobrush grafted to the other end of the silane coupling agent. The negatively charged nanobrush is obtained by grafting a hydrophilic polymer containing carboxyl groups to the other end of the silane coupling agent and converting the carboxyl groups into negatively charged carboxylate groups using an alkaline solution.

2. The self-cleaning piezoelectric hybrid ceramic membrane according to claim 1, characterized in that, The silane coupling agent is selected from γ-aminopropyltriethoxysilane, γ-methacryloxypropyltrimethoxysilane, N-(2-aminoethyl)-3-aminopropyltrimethoxysilane, and polyethylene glycol trimethoxysilyl ether; the hydrophilic polymer containing carboxyl groups is selected from maleic acid-acrylic acid copolymer, polymethacrylic acid, polymaleic acid, polyglutamic acid, and polyacrylic acid containing multiple carboxyl groups; the alkaline solution is selected from sodium carbonate solution, potassium carbonate solution, sodium hydroxide solution, and potassium hydroxide solution.

3. The self-cleaning piezoelectric hybrid ceramic membrane according to claim 2, characterized in that, The molecular weight of the hydrophilic polymer containing carboxyl groups is selected from any value in the range of 2000-6000 g / mol; the pore size of the piezoelectric ceramic film is selected from any value in the range of 20-500 nm, and the piezoelectric constant is selected from any value in the range of 10-200 pC / N.

4. The method for preparing a self-cleaning piezoelectric hybrid ceramic film according to any one of claims 1-3, characterized in that, include: A silane coupling agent is grafted onto the surface of a piezoelectric ceramic membrane. The silanol groups generated by the hydrolysis of the silane coupling agent undergo dehydration condensation with the hydroxyl groups on the surface of the piezoelectric ceramic membrane, thereby covalently linking the silane coupling agent to the surface of the piezoelectric ceramic membrane with Si-OM. Subsequently, a hydrophilic polymer containing carboxyl groups is grafted onto the other end of the silane coupling agent. Finally, the carboxyl groups are converted into negatively charged carboxylate groups using an alkaline solution to obtain the self-cleaning piezoelectric hybrid ceramic membrane.

5. The preparation method according to claim 4, characterized in that, include: S1. Prepare ethanol solutions of silane coupling agent and hydrophilic polymers containing carboxyl groups, respectively. S2. Immerse the piezoelectric ceramic membrane in an ethanol solution of the silane coupling agent and react at 50-85°C for 8-14 hours to obtain a piezoelectric ceramic membrane with silane coupling agent grafted on its surface. S3. After reacting the piezoelectric ceramic film grafted with silane coupling agent on its surface with an ethanol solution of the hydrophilic polymer containing carboxyl groups at 25-45°C for 15-24 hours, the hydrophilic polymer containing carboxyl groups is treated with an alkaline solution to deprotonate it and form negatively charged groups, thereby obtaining the self-cleaning piezoelectric hybrid ceramic film.

6. The preparation method according to claim 5, characterized in that, The ethanol used in S1 is an aqueous solution of ethanol with a mass fraction of 80-98%, the concentration of silane coupling agent in the ethanol solution is 1-50 mL / L, the concentration of hydrophilic polymer containing carboxyl groups in the ethanol solution is 10-50 mL / L, and the concentration of alkaline solution is 1-100 mmol / L.

7. The preparation method according to claim 5, characterized in that, The piezoelectric ceramic membrane is a self-made or commercially available piezoelectric ceramic membrane, and the material is one of potassium sodium niobate, lead zirconate titanate, zinc oxide, potassium niobate, lithium tantalate, and barium titanate.

8. The application of the self-cleaning piezoelectric hybrid ceramic membrane according to any one of claims 1-3 in the treatment of organic pollutants in water.

9. The application according to claim 8, characterized in that, Under the pressure of the pulsed water flow of the raw material liquid, periodic negative charges are generated on the surface of the piezoelectric ceramic membrane, which generate periodic electrostatic repulsion with the negatively charged nanobrush. This causes the negatively charged nanobrush to undergo periodic peristaltic dynamic oscillation, which loosens the organic pollutants deposited on the surface of the piezoelectric ceramic membrane and causes them to fall off with the shear force of the incoming water flow.

10. The application according to claim 9, characterized in that, The pressure of the feed liquid pulse water flow is 5-10 bar.

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