Piezoelectric filter membrane with constant hydraulic response, self-cleaning anti-membrane fouling method and wastewater treatment method

Abstract

The application discloses a piezoelectric filter membrane with constant hydraulic pressure response, a self-cleaning anti-membrane pollution method and a sewage treatment method. A micro-nano three-dimensional structure is constructed on the membrane surface, so that local turbulent flow or other hydraulic transient disturbance is continuously generated on the membrane surface during constant pressure flow of fluid. The disturbance can stimulate the piezoelectric filter membrane to generate a positive piezoelectric effect, convert mechanical energy generated by local fluctuating hydraulic pressure into electric energy in situ, and realize integration of the membrane separation and the anti-membrane pollution process. The technical scheme of the application has the advantages of existing piezoelectric membrane pollution control, can generate multiple anti-pollution effects such as in-situ generation of oxidative free radicals, electrostatic repulsion and dielectrophoresis force, breaks through the limitation that traditional positive piezoelectric technology needs external pulse hydraulic driving, can trigger piezoelectric response only under constant hydraulic pressure, is more suitable for constant pressure operation conditions of an industrialized membrane system, realizes self-cleaning anti-pollution and sewage treatment of the piezoelectric membrane under conventional constant pressure conditions, has good process compatibility, and has a wide application prospect.

Description

Technical Field

[0001] This invention belongs to the field of water treatment membrane technology, specifically a piezoelectric filter membrane with constant hydraulic response, a self-cleaning anti-membrane fouling method, and a wastewater treatment method. Background Technology

[0002] Faced with the widespread challenge of membrane fouling in water treatment membrane technology, existing projects mostly employ traditional methods such as physical flushing, chemical cleaning, and periodic regeneration to maintain membrane flux and operational stability. Although these methods have formed relatively mature process systems in practical applications, their main mechanism of action remains focused on removing the fouling layer already formed on the membrane surface, representing a typical reactive control mode. Such strategies often only become effective after fouling accumulation leads to flux decline. This not only results in frequent cleaning, high chemical and energy consumption, but also fails to inhibit the initial deposition of pollutants on the membrane surface, thus making it difficult to provide real-time active antifouling capabilities during membrane separation. With increasingly complex wastewater qualities, the limitations of this passive control mode in terms of stable operation and long-term antifouling are becoming increasingly apparent.

[0003] In recent years, piezoelectric water treatment membranes capable of simultaneous self-cleaning and regeneration during membrane filtration have attracted widespread attention and are considered an important technological direction for overcoming traditional passive membrane fouling control. These membrane materials can generate surface charges under stress through the positive piezoelectric effect, which can further induce multiple effects such as interfacial oxidation, electrostatic repulsion, and dielectric adhesion, thereby achieving self-cleaning and anti-fouling during operation. Existing research and technical practices show that the self-cleaning effect of piezoelectric membranes based on the positive piezoelectric effect usually relies on periodically changing transmembrane pressure differences or pulsed hydraulic drives, such as the technical solution disclosed in Chinese Invention Patent Application Publication No. CN 114849485 A, and related recently reported work (…). J. Am. Chem. Soc. 2024, 146, 13306−13316 All of these technologies employ pulsed hydraulic triggering for positive piezoelectric response. However, these pulsed or periodic pressure conditions differ significantly from the constant hydraulic operating mode commonly used in industrial membrane systems. This imposes additional operational burdens on actual water treatment membrane processes, such as pressure-changing equipment, making direct large-scale application difficult and thus limiting the promotion of positive piezoelectric antifouling membrane technology in practical water treatment scenarios.

[0004] Therefore, there is an urgent need to invent a piezoelectric filter membrane with constant hydraulic response, a self-cleaning anti-membrane fouling method, and a wastewater treatment method. The aim is to overcome the problem that existing piezoelectric membranes rely on pulsed hydraulic drive and are difficult to adapt to constant pressure operation in industrial water treatment membrane processes, while achieving self-cleaning and anti-membrane fouling in the membrane separation process. Summary of the Invention

[0005] Objectives of the Invention: The first objective of this invention is to provide a self-cleaning piezoelectric filter membrane with constant hydraulic response; the second objective of this invention is to provide a self-cleaning anti-fouling method with constant hydraulic response; and the third objective of this invention is to provide a wastewater treatment method utilizing a self-cleaning piezoelectric filter membrane with constant hydraulic response.

[0006] To achieve the primary objective, the technical solution of the piezoelectric filter membrane adopted in this invention is as follows: The present invention provides a piezoelectric filter membrane, comprising a body and a plurality of three-dimensional structures distributed on the body, wherein the three-dimensional structures are used to generate hydraulic transient disturbances under constant pressure water inlet conditions to excite the positive piezoelectric response of the piezoelectric filter membrane.

[0007] As a further improvement of the present invention, the material of the piezoelectric filter membrane includes at least one of inorganic piezoelectric materials, organic piezoelectric materials, and inorganic-organic composite piezoelectric materials; the structure of the piezoelectric filter membrane is a pure piezoelectric membrane or a piezoelectric membrane-substrate integrated structure.

[0008] As a further improvement of the present invention, the inorganic piezoelectric material is selected from: barium titanate, lead titanate, lead zirconate titanate, lead metaniobate, lithium lead barium niobate, lithium gallium oxide, lithium germanate, titanium germanate, lithium niobate, lithium tantalate, potassium niobate, sodium potassium niobate, bismuth ferrite, tungsten diselenide, molybdenum disulfide, tungsten disulfide, zinc oxide, quartz, and their modified doped film materials; the organic piezoelectric material is selected from: polyvinylidene fluoride, polytetrafluoroethylene, polyamide, polypropylene, and their modified doped film materials.

[0009] As a further improvement of the present invention, the piezoelectric filter membrane is a microfiltration membrane, an ultrafiltration membrane, a nanofiltration membrane, or a reverse osmosis membrane.

[0010] As a further improvement of the present invention, the micro-three-dimensional structure is selected from one or more of the following: protrusions, pits, prisms, frustums, stripes, rib structures, microporous structures, honeycomb structures, periodic array structures, and random rough structures.

[0011] To achieve the second objective, the technical solution of the self-cleaning anti-fouling method adopted in this invention is as follows: This invention provides a self-cleaning anti-fouling method with constant hydraulic response. The method employs a piezoelectric filter membrane with a micro / nano-scale three-dimensional structure on its surface. Under constant pressure influent conditions, wastewater flows over the surface of the piezoelectric filter membrane. The three-dimensional structure on the membrane surface generates transient hydraulic disturbances under the influence of fluid flow. These transient disturbances excite the positive piezoelectric response of the filter membrane, achieving self-cleaning and anti-fouling. Specifically, the transient hydraulic disturbances are localized turbulence or other mechanical forces generated by the fluid in the micro / nano-scale three-dimensional structure regions.

[0012] As a further improvement of the present invention, the water inlet method adopted is a dead-end or cross-flow filtration operation with constant hydraulic pressure, and the target pressure range is 1 Pa-10000 kPa.

[0013] As a further improvement of the present invention, the piezoelectric filter membrane is used for membrane fouling control in the membrane separation process of organic wastewater, inorganic wastewater, microbial wastewater, saline wastewater or heavy metal wastewater.

[0014] To achieve the third objective, the technical solution of the wastewater treatment method adopted in this invention is as follows: This invention provides a wastewater treatment method using the above-mentioned piezoelectric filter membrane, which treats wastewater through membrane separation.

[0015] As a further improvement of the present invention, the wastewater is organic wastewater, inorganic wastewater, microbial wastewater, saline wastewater, or heavy metal wastewater.

[0016] The piezoelectric filter membrane with constant hydraulic response, the self-cleaning anti-fouling method, and the wastewater treatment method proposed in this invention, under constant pressure influent conditions, achieve self-cleaning and anti-fouling by constructing micro-nano-scale three-dimensional structures on the membrane surface to generate local turbulence or other transient hydraulic disturbances through the synergistic effect of the three-dimensional structure and fluid flow. This excites the positive piezoelectric response of the piezoelectric membrane material without the need for pulsed hydraulic pressure, thus overcoming the requirement of periodic transmembrane pressure difference or pulsed hydraulic pressure for existing piezoelectric membranes to generate positive piezoelectric anti-fouling effects. This method is more compatible with the constant hydraulic operation mode commonly used in current industrial membrane systems. Therefore, compared to traditional passive membrane fouling control methods and existing self-cleaning methods that rely on pulsed hydraulic pressure to excite the positive piezoelectric effect, the constant hydraulic response self-cleaning anti-fouling method has significant advantages in terms of adaptability to industrial membrane systems, operational stability, and engineering feasibility, demonstrating important practical application value and broad prospects for promotion.

[0017] Beneficial effects: Compared with the prior art, the present invention has the following significant advantages: (1) Highly compatible with industrial operating conditions: Industrial membrane systems generally adopt a constant hydraulic operating mode, while this invention does not require external pulse hydraulic pressure or periodic pressure modulation. It can stably trigger the positive piezoelectric response of the piezoelectric membrane by relying solely on conventional constant pressure. Therefore, it can be directly applied to existing equipment without changing the existing process conditions, and has strong adaptability.

[0018] (2) Self-cleaning and anti-fouling effect: The micro-nano-scale three-dimensional structure on the membrane surface induces local turbulence or disturbance flow field, continuously generating local pressure fluctuations under constant pressure, thereby stimulating the piezoelectric membrane to generate a positive piezoelectric effect to resist membrane fouling. This positive piezoelectric effect can further drive the generation of oxidative free radicals, electrostatic repulsion and dielectric force, etc., to achieve multiple anti-fouling effects, enabling the membrane to have a continuous self-cleaning effect during filtration. Attached Figure Description

[0019] Figure 1 The diagram depicts a piezoelectric filter membrane with a micro-nano-scale three-dimensional structure on its surface. Detailed Implementation

[0020] The present invention will be further explained below with reference to the embodiments. The following embodiments are for illustrative purposes only and are not intended to limit the scope of the invention.

[0021] This invention provides a piezoelectric filter membrane with constant hydraulic pressure response, a self-cleaning anti-membrane fouling method, and a wastewater treatment method. Under constant pressure influent conditions, a piezoelectric filter membrane with a micro-nano-scale three-dimensional structure on its surface is used. By forming turbulent or other disturbed flow fields in the micro-three-dimensional structure region on the membrane surface, the positive piezoelectric response of the membrane is excited, thereby achieving self-cleaning and anti-membrane fouling effects.

[0022] In this embodiment of the invention, the water inlet method is a constant hydraulic pressure dead-end or cross-flow filtration operation, with a target pressure range of 1 Pa-10000 kPa. The piezoelectric filter membrane includes at least one of inorganic piezoelectric materials, organic piezoelectric materials, and inorganic-organic composite piezoelectric materials; the structure of the piezoelectric filter membrane is a pure piezoelectric membrane or a piezoelectric membrane-substrate integrated structure. The inorganic piezoelectric materials include barium titanate, lead titanate, lead zirconate titanate, lead metaniobate, lithium lead barium niobate, lithium gallium oxide, lithium germanate, titanium germanate, lithium niobate, lithium tantalate, potassium niobate, sodium potassium niobate, bismuth ferrite, tungsten diselenide, molybdenum disulfide, tungsten disulfide, zinc oxide, quartz, and their modified doped membrane materials. The organic piezoelectric materials include polyvinylidene fluoride, polytetrafluoroethylene, polyamide, polypropylene, and their modified doped membrane materials. The micro-three-dimensional structure includes: protrusions, pits, prisms, frustums, stripes, rib structures, microporous structures, honeycomb structures, periodic array structures, random rough structures, or combinations thereof. The piezoelectric filter membrane is a microfiltration membrane, ultrafiltration membrane, nanofiltration membrane, or reverse osmosis membrane. This piezoelectric filter membrane is used for membrane fouling control in membrane separation processes of organic wastewater, inorganic wastewater, microbial wastewater, saline wastewater, or heavy metal wastewater.

[0023] Example 1

[0024] This embodiment provides a piezoelectric filter membrane, which includes a barium titanate ceramic membrane body and barium titanate nanowires grown in situ on the body.

[0025] The piezoelectric filter membrane was prepared by immersing the compressed barium titanate ceramic membrane in an aqueous solution of barium titanate precursor and titanium dioxide for 10 h, followed by a hydrothermal reaction to achieve in-situ growth of barium titanate nanowires on the barium titanate ceramic membrane. The prepared membrane was then subjected to electric field polarization treatment to prepare a piezoelectric microfiltration ceramic membrane for water treatment with a surface structure of micron-scale protrusions (average pore size of approximately 0.5 μm).

[0026] This embodiment provides a wastewater treatment method and a self-cleaning anti-membrane fouling method: The aforementioned piezoelectric microfiltration ceramic membrane is used to complete the dead-end membrane separation process with a constant transmembrane pressure difference of 20 kPa; this membrane separation operation is applied to the treatment of medical pathogenic wastewater. The membrane can utilize its micro-three-dimensional structure to generate hydraulic fluctuations, producing an in-situ positive piezoelectric effect. This generates free radicals to oxidize and remove pathogenic membrane contaminants, and employs multiple mechanisms such as electrostatic repulsion and dielectric adhesion to control membrane fouling. Membrane flux decays slowly, only decreasing to 68% of the initial stable flux after 2 hours, resulting in good control of membrane fouling.

[0027] Comparative Example 1 The difference between this comparative example and Example 1 is that the piezoelectric filter membrane is a barium titanate microfiltration ceramic membrane with a smooth surface. Specifically, barium titanate tablets are subjected to electrodeization treatment to prepare a barium titanate microfiltration ceramic membrane with a smooth surface (average pore size of approximately 0.5 μm) as a water treatment piezoelectric filter membrane. Dead-end membrane separation is completed with a constant transmembrane pressure difference of 20 kPa. This membrane separation operation is applied to the treatment of medical pathogenic wastewater. This membrane cannot generate an effective positive piezoelectric effect, the piezoelectric potential and oxidative free radicals formed in situ are limited, the electrostatic repulsion and dielectric force are weak, the membrane flux decays rapidly, and the flux decays to 30% of the initial stable flux in 0.5 h, indicating severe membrane fouling.

[0028] Example 2

[0029] This embodiment provides a piezoelectric filter membrane, which includes a polyvinylidene fluoride body and a nanoscale stripe structure disposed on the polyvinylidene fluoride body.

[0030] The piezoelectric filter membrane is prepared by spreading polyvinylidene fluoride casting liquid on the surface of a template with a preset nanoscale stripe structure. The stripe width is 50-500 nm, the stripe spacing is 100-1000 nm, the stripe height is 50-800 nm, and the stripes are regularly arranged along the intersecting directions to form anisotropic surface geometric features.

[0031] This embodiment provides a wastewater treatment method and a self-cleaning anti-membrane fouling method: a polyvinylidene fluoride (PVDF) ultrafiltration piezoelectric membrane with a nanoscale striped structure on its surface (average pore size approximately 50 nm) is prepared using a template-induced phase inversion method. Using this PVDF ultrafiltration piezoelectric membrane, a cross-flow membrane separation process is completed with a constant transmembrane pressure difference of 100 kPa. This membrane separation operation is applied to the treatment of oil emulsion wastewater. The membrane can utilize the nanoscale striped structure to generate hydraulic fluctuations, producing an in-situ positive piezoelectric effect. This, along with multiple mechanisms such as generating free radical oxide film oil droplets, electrostatic repulsion, and dielectric adhesion, controls membrane fouling. Membrane flux decays slowly, only decreasing to 64% of the initial stable flux after 2 hours, indicating good control of membrane fouling.

[0032] Comparative Example 2 The difference between this comparative example and Example 2 is that the piezoelectric filter membrane is a polyvinylidene fluoride (PVDF) membrane with a smooth surface. Specifically, PVDF casting solution is spread on a smooth template surface, and a PVDF ultrafiltration piezoelectric filter membrane (average pore size of approximately 50 nm) with a smooth surface is prepared by template-induced phase inversion. The cross-flow membrane separation process is completed with a constant transmembrane pressure difference of 100 kPa. This membrane separation operation is applied to the treatment of oil emulsion wastewater. This membrane cannot generate an effective positive piezoelectric effect, the piezoelectric potential and oxidative free radicals formed in situ are limited, the electrostatic repulsion and dielectric force are weak, the membrane flux decays rapidly, and the flux decays to 25% of the initial stable flux in 0.5 h, indicating severe membrane fouling.

[0033] Example 3

[0034] This embodiment provides a piezoelectric filter membrane, which includes a polyvinylidene fluoride / molybdenum disulfide membrane body and molybdenum disulfide nanosheets grown in situ on the polyvinylidene fluoride / molybdenum disulfide membrane body.

[0035] The piezoelectric filter membrane is prepared by immersing a polyvinylidene fluoride / molybdenum disulfide membrane prepared by electrospinning in an aqueous solution of sodium molybdate and thiourea for 10 h, followed by a hydrothermal reaction to achieve additional in-situ growth of molybdenum disulfide nanosheets on the surface of the polyvinylidene fluoride / molybdenum disulfide membrane, thereby preparing a polyvinylidene fluoride / molybdenum disulfide nanofiltration composite piezoelectric filter membrane for water treatment with a micron-scale protrusion structure on the surface (average pore size of about 1 nm).

[0036] This embodiment provides a wastewater treatment method and a self-cleaning anti-membrane fouling method: a polyvinylidene fluoride / molybdenum disulfide nanofiltration composite piezoelectric filter membrane is used to complete the cross-flow membrane separation process with a constant transmembrane pressure difference of 1000 kPa. This membrane separation operation is applied to the treatment of bovine serum albumin wastewater containing nano-alumina particles. The membrane can utilize its micron-level protrusion structure to form hydraulic fluctuations, generating a positive piezoelectric effect in situ. This effect controls membrane fouling through multiple mechanisms, including the generation of free radicals to oxidize bovine serum albumin membrane contaminants, electrostatic repulsion, and dielectric force. The membrane flux decays slowly, only decreasing to 72% of the initial stable flux after 1 hour, resulting in good control of membrane fouling.

[0037] Comparative Example 3 The difference between this comparative example and Example 3 is that the piezoelectric filter membrane is a polyvinylidene fluoride / molybdenum disulfide nanofiltration composite membrane with a smooth surface. Specifically, a polyvinylidene fluoride / molybdenum disulfide nanofiltration composite membrane (average pore size of approximately 1 nm) with a smooth surface, prepared by electrospinning, was used as the piezoelectric filter membrane for water treatment. Cross-flow membrane separation was performed using a constant transmembrane pressure difference of 1000 kPa. This membrane separation operation was applied to the treatment of bovine serum albumin wastewater containing nano-alumina particles. The membrane could not generate an effective positive piezoelectric effect; the piezoelectric potential and free radicals formed in situ were limited; the membrane flux decayed rapidly, decreasing to 21% of the initial stable flux in just 0.5 h; and membrane fouling was severe.

[0038] Example 4

[0039] This embodiment provides a piezoelectric filter membrane, which includes a polyvinylidene fluoride / barium titanate membrane body and a plurality of micro-pit structures provided on the polyvinylidene fluoride / barium titanate membrane body.

[0040] The piezoelectric filter membrane is prepared by immersing the prepared polyvinylidene fluoride / barium titanate membrane in hydrochloric acid at pH=3 for 8 hours for surface etching, thereby obtaining a polyvinylidene fluoride / barium titanate nanofiltration composite water treatment piezoelectric filter membrane with micron-scale irregular micro-pit structure on the surface (average pore size of about 0.1 nm).

[0041] This embodiment provides a wastewater treatment method and a self-cleaning anti-membrane fouling method: a dead-end membrane separation process is completed using a constant transmembrane pressure difference of 10000 kPa. This membrane separation operation is applied to the treatment of sodium chloride wastewater. The membrane can utilize its micron-level stripe structure to form hydraulic fluctuations, generating an in-situ positive piezoelectric effect, thus combating membrane fouling through multiple mechanisms. Membrane flux decays slowly, only decreasing to 60% of the initial stable flux after 1 hour, resulting in good control of membrane fouling.

[0042] Comparative Example 4 The difference between this comparative example and Example 4 is that the piezoelectric filter membrane is a polyvinylidene fluoride / barium titanate composite reverse osmosis ceramic membrane with a smooth surface. Specifically, a polyvinylidene fluoride / barium titanate composite reverse osmosis ceramic membrane (with an average pore size of approximately 0.1 nm) with a smooth surface was used as the piezoelectric filter membrane for water treatment, and the dead-end membrane separation process was completed with a constant transmembrane pressure difference of 10000 kPa. This membrane separation operation was applied to the treatment of sodium chloride wastewater. This membrane could not generate an effective positive piezoelectric effect, and the membrane flux decayed rapidly, decreasing to 16% of the initial stable flux in just 0.4 h, indicating severe membrane fouling.

Claims

1. A piezoelectric filter membrane, characterized in that: The piezoelectric filter membrane includes a body and several three-dimensional structures distributed on the body. The three-dimensional structures are used to generate hydraulic transient disturbances under constant pressure water inlet conditions to excite the positive piezoelectric response of the piezoelectric filter membrane.

2. The piezoelectric filter membrane according to claim 1, characterized in that: The material of the piezoelectric filter membrane includes at least one of inorganic piezoelectric materials, organic piezoelectric materials, and inorganic-organic composite piezoelectric materials; the structure of the piezoelectric filter membrane is a pure piezoelectric membrane or a piezoelectric membrane-substrate integrated structure.

3. The piezoelectric filter membrane according to claim 1, characterized in that: The inorganic piezoelectric material is selected from: barium titanate, lead titanate, lead zirconate titanate, lead metaniobate, lithium lead barium niobate, lithium gallium oxide, lithium germanate, titanium germanate, lithium niobate, lithium tantalate, potassium niobate, sodium potassium niobate, bismuth ferrite, tungsten diselenide, molybdenum disulfide, tungsten disulfide, zinc oxide, and quartz; the organic piezoelectric material is selected from: polyvinylidene fluoride, polytetrafluoroethylene, polyamide, and polypropylene.

4. The piezoelectric filter membrane according to claim 1, characterized in that: The piezoelectric filter membrane is a microfiltration membrane, ultrafiltration membrane, nanofiltration membrane, or reverse osmosis membrane.

5. The piezoelectric filter membrane according to claim 1, characterized in that: The three-dimensional structure is selected from any one or more of the following: protrusions, pits, prisms, frustums, stripes, ribs, microporous structures, honeycomb structures, periodic array structures, and random rough structures.

6. A self-cleaning anti-fouling method, characterized in that: Under constant pressure influent conditions, wastewater flows on the surface of the piezoelectric filter membrane. The three-dimensional structure on the surface of the piezoelectric filter membrane generates hydraulic transient disturbances under the action of fluid flow. The hydraulic transient disturbances excite the positive piezoelectric response of the piezoelectric filter membrane, achieving self-cleaning and anti-fouling.

7. The self-cleaning anti-fouling method according to claim 6, characterized in that: The water inlet method adopted is a constant hydraulic dead-end or cross-flow filtration operation, with a target pressure range of 1 Pa to 10000 kPa.

8. The self-cleaning anti-fouling method according to claim 6, characterized in that: This piezoelectric filter membrane is used for membrane fouling control in membrane separation processes of organic wastewater, inorganic wastewater, microbial wastewater, saline wastewater, or heavy metal wastewater.

9. A wastewater treatment method using the piezoelectric filter membrane according to any one of claims 1-5.

10. The wastewater treatment method using a piezoelectric filter membrane according to claim 9, characterized in that: Wastewater can be organic wastewater, inorganic wastewater, microbial wastewater, saline wastewater, or heavy metal wastewater.

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