Continuous preparation method and application of high-flux and high-selectivity polyamide nanofiltration membrane

Abstract

The invention discloses a continuous preparation method and application of a high-flux and high-selectivity polyamide nanofiltration membrane, and belongs to the technical field of water treatment membranes.The method comprises the steps that a traction device is used for driving a carrier membrane to continuously move from a discharging mechanism to a collecting mechanism, in the moving process of the carrier membrane, water phase solution liquid drops are sprayed to the surface of the carrier membrane firstly, and then the carrier membrane is dried to obtain the high-flux and high-selectivity polyamide nanofiltration membrane. The preparation method comprises the following steps: preparing a carrier membrane, enabling the carrier membrane to be loaded with a water-phase monomer, spraying oil-phase solution droplets on the surface of the carrier membrane loaded with the water-phase monomer, enabling the oil-phase monomer and the water-phase monomer to be subjected to interfacial polymerization reaction, and enabling the membrane subjected to the interfacial polymerization reaction to pass through a heat treatment unit, so as to obtain the high-flux and high-selectivity polyamide nanofiltration membrane. Wherein the water-phase solution liquid drops and the oil-phase solution liquid drops are obtained in an ultrasonic atomization, electrostatic atomization or pneumatic atomization mode. According to the method disclosed by the invention, the nanofiltration membrane with high flux and high salt separation capacity can be prepared on the basis of realizing over 80 percent of solvent reduction.

Description

Technical Field

[0001] This invention relates to the field of water treatment membrane technology, specifically to a continuous preparation method and application of a high-flux, high-selectivity polyamide nanofiltration membrane. Background Technology

[0002] Membrane treatment is a commonly used technology in the field of water treatment, characterized by its simple operation, low cost, and high efficiency. Membrane materials are the core of membrane treatment technology, and their physicochemical properties directly determine separation efficiency, operational stability, and application range. Polyamide composite membranes prepared by interfacial polymerization exhibit good chemical stability, low operating pressure, and strong separation capabilities. However, current large-scale continuous preparation methods for polyamide composite membranes suffer from low raw material utilization and high solvent consumption, and the organic solvents are difficult to recover, posing certain safety hazards. To reduce solvent consumption, existing continuous preparation methods for polyamide composite membranes need to be optimized.

[0003] Chinese patent document CN119793221A discloses a continuous preparation method and system for nanofiltration membranes. The method includes: uniformly coating a polymer solution onto a moving carrier membrane to form a membrane layer of a predetermined thickness; filtering the membrane layer to remove the solvent, thereby forming a nanofiltration membrane with a predetermined pore structure; and finally drying and curling the nanofiltration membrane. This preparation method and system enable continuous automated production of nanofiltration membranes. Relevant parameters during the production process can be automatically adjusted based on real-time monitoring data, improving production efficiency, reducing production costs, and ensuring consistent product quality.

[0004] Chinese patent document CN117138607A discloses a high-throughput nanofiltration membrane, its mass production method, and its applications. This invention places a pretreated polyethersulfone (PES) membrane on a feeding mechanism and pulls it through a receiving mechanism, allowing the PES membrane to continuously pass through an aqueous phase unit, a first heat treatment unit, an oil phase unit, and a second heat treatment unit to obtain a high-flux nanofiltration membrane. In the aqueous phase unit, the PES membrane is in full contact with the aqueous monomer solution. In the oil phase unit, the aqueous monomers attached to the surface of the PES membrane contact the oil monomer solution and undergo interfacial polymerization to form the high-throughput nanofiltration membrane. The high-throughput nanofiltration membrane obtained by this invention has broad application prospects in fields such as concentrated fruit juice, drug separation, drinking water purification, wastewater treatment, and seawater desalination.

[0005] Most existing research, including the aforementioned technologies, focuses on adjusting various parameters of the interfacial polymerization process (including reactants, additives, reaction time, and thermosetting temperature) to prepare high-performance polyamide composite films. However, traditional impregnation methods for preparing polyamide composite films suffer from significant waste of oil-phase solvents, while coating methods exhibit poor uniformity, insufficient interfacial adhesion, and environmental concerns. Therefore, there is an urgent need to develop a method for the continuous, large-scale preparation of high-performance polyamide composite films with high raw material utilization and low solvent consumption. Summary of the Invention

[0006] To address the shortcomings of the existing technology, this invention provides a continuous preparation method for high-flux, high-selectivity polyamide nanofiltration membranes, which can prepare nanofiltration membranes with high flux and high salt separation capacity while achieving a solvent reduction of more than 80%.

[0007] The specific technical solution adopted is as follows: A continuous preparation method for a high-flux, high-selectivity polyamide nanofiltration membrane includes the following steps: The carrier membrane is continuously moved from the feeding mechanism to the receiving mechanism by a traction device. During the movement of the carrier membrane, the aqueous solution droplets are first sprayed onto the surface of the carrier membrane to load the aqueous monomers on the carrier membrane. Then, the oil solution droplets are sprayed onto the surface of the carrier membrane loaded with aqueous monomers to cause the oil monomers and aqueous monomers to undergo interfacial polymerization. The membrane that has undergone interfacial polymerization is then passed through a heat treatment unit to obtain the high-flux, high-selectivity polyamide nanofiltration membrane. Specifically, an atomization system atomizes the aqueous and oil phase solutions into droplets, with the atomizing nozzle perpendicular to the carrier film surface. Both the aqueous and oil phase droplets have a particle size of 10-200 μm and a specific surface area of ​​3 × 10⁻⁶. 4 -6×10 5 m 2 / m 3 .

[0008] This invention addresses the shortcomings of traditional interfacial polymerization methods for preparing polyamide separation membranes, such as low raw material utilization, high solvent consumption, and large separation layer thickness. By introducing a microdroplet reaction system and changing the contact mode between the carrier membrane and the water-oil two-phase system, the interfacial polymerization reaction is enhanced, resulting in a surge in the density of the water-oil two-phase interface, improving monomer utilization, and reducing diffusion inhibition. This leads to the preparation of nanofiltration membranes with high flux and high salt separation capacity, while significantly reducing waste liquid production and making it environmentally friendly.

[0009] Preferably, during the movement of the carrier membrane, the traction force of the traction device is adjusted according to the tension of the carrier membrane, so that the moving speed of the carrier membrane is 10-1000 cm / min.

[0010] Specifically, the carrier membrane is one of polyester ultrafiltration membrane, polyethersulfone ultrafiltration membrane, polysulfone ultrafiltration membrane, polyacrylonitrile ultrafiltration membrane, polypropylene ultrafiltration membrane, polyvinylidene fluoride ultrafiltration membrane, and polytetrafluoroethylene ultrafiltration membrane, and is more preferably a hydrophilic polyethersulfone ultrafiltration membrane, polysulfone ultrafiltration membrane, or polyacrylonitrile ultrafiltration membrane.

[0011] Specifically, the atomization system atomizes an aqueous solution with a concentration of 0.1-5 wt% (preferably 0.5-2 wt%) and an oil solution with a concentration of 0.01-1 wt% (preferably 0.05-0.5 wt%) into aqueous solution droplets and oil solution droplets by means of ultrasonic atomization, electrostatic atomization or pneumatic atomization.

[0012] Preferably, during ultrasonic atomization, the ultrasonic power is 0.1-10 W (more preferably 1-5 W), the flow rate of the solution to be sprayed is 0.1-15 mL / h (more preferably 0.1-5 mL / h), the carrier gas pressure is 0.01-2 MPa (more preferably 0.1-0.5 MPa), the spraying environment temperature is 10-70 ℃ (more preferably 20-50 ℃), and the relative humidity of the spraying environment is 10%-80% (more preferably 20%-80%).

[0013] Preferably, during electrostatic atomization, the voltage applied to the atomizing nozzle is 1-15 kV (more preferably 3-10 kV), the propulsion flow rate of the solution to be sprayed is 0.1-15 mL / h (more preferably 0.1-5 mL / h), the spraying ambient temperature is 10-70 ℃ (more preferably 20-50 ℃), and the relative humidity of the spraying ambient is 10%-80% (more preferably 20%-80%).

[0014] Preferably, during the pneumatic atomization process, the spraying air pressure is 0.01-2 MPa (more preferably 0.01-0.5 MPa), the propulsion flow rate of the solution to be sprayed is 0.1-15 mL / h (more preferably 0.1-5 mL / h), the spraying ambient temperature is 10-70 ℃ (more preferably 20-50 ℃), and the relative humidity of the spraying ambient is 10%-80% (more preferably 20%-80%).

[0015] Optionally, the aqueous monomer is at least one selected from piperazine, 2-methylpiperazine, 2,5-dimethylpiperazine, 2,6-dimethylpiperazine, 1,2-diaminocyclohexane, 1,4-diaminocyclohexane, ethylenediamine, N,N-bis(2-aminoethyl)ethylenediamine, divinyltriamine, and polyethyleneimine.

[0016] Optionally, the oil phase monomer is at least one of pyromellitic methyl methacrylate (PMMA), terephthaloyl chloride (TBMA), phthaloyl chloride (ODM), pyromellitic methyl methacrylate (TMM), malonyl chloride (MDM), glutaryl chloride (GMA), and fumarate chloride (FMA); the solvent of the oil phase solution includes n-hexane, cyclohexane, n-heptane, toluene, benzene, isopar G, isopar E, isopar H, isopar L, or isopar M.

[0017] Furthermore, the atomization system is connected to the raw material solution (aqueous phase solution, oil phase solution) supply system, and the raw material solution supply system adjusts the supply speed of the raw material solution in real time according to the target spray volume.

[0018] The number of atomizing nozzles in the atomization system is 2-100, and the spraying height is 2-20 cm (further 5-10 cm).

[0019] Preferably, the heat treatment unit has a treatment temperature of 40-100 ℃ (more preferably 50-80 ℃) and a heat treatment time of 3-20 min (more preferably 5-10 min).

[0020] Preferably, the high-flux, high-selectivity polyamide nanofiltration membrane has a water flux ≥18 LMH / bar, a separation factor for monovalent and polyvalent salts ≥100, and the separated monovalent and polyvalent salts are monovalent anions and divalent anions.

[0021] The present invention also provides the application of the continuous preparation method of the high-flux, high-selectivity polyamide nanofiltration membrane in the field of water treatment.

[0022] Compared with the prior art, the beneficial effects of the present invention are as follows: (1) The continuous preparation method of high-flux and high-selectivity polyamide nanofiltration membrane provided by the present invention can realize the continuous automated production of high-performance polyamide composite membrane, improve production efficiency, reduce production costs, reduce solvent consumption and waste liquid generation, and ensure product quality consistency.

[0023] (2) This invention utilizes continuously moving carrier membranes, aqueous solution droplets, and oil solution droplets to prepare high-performance polyamide nanofiltration membranes. The organic solvent required per square meter of product separation membrane is less than 100 mL, the solvent reduction exceeds 80%, and the performance surpasses that of commonly mass-produced polyamide separation membranes. The water flux reaches a maximum of 25.2 LMH / bar, and the separation factor for monovalent and polyvalent salts reaches a maximum of 375.65. The method of this invention is green and environmentally friendly and has great industrialization potential. Attached Figure Description

[0024] Figure 1 This is a schematic diagram of the continuous preparation method of the high-flux, high-selectivity polyamide nanofiltration membrane.

[0025] Figure 2 This is a SEM image of the high-flux, high-selectivity polyamide nanofiltration membrane prepared in Example 3. Detailed Implementation

[0026] To make the objectives, features, and advantages of this invention more apparent and understandable, a detailed description is provided below through specific embodiments. Many specific details are set forth in the following description to provide a thorough understanding of the invention. However, the invention can be practiced in many other ways different from those described herein, and those skilled in the art can make similar modifications without departing from the spirit of the invention. Therefore, the invention is not limited to the specific embodiments disclosed below. Technical features in various embodiments of the invention can be combined appropriately without mutual conflict.

[0027] Unless otherwise specified, the operating methods in the following examples are generally performed under conventional conditions or as recommended by the manufacturer. Contents not described in detail in this specification are prior art known to those skilled in the art. Unless otherwise specified, the experimental materials used in the examples below can be purchased from conventional biochemical reagent companies.

[0028] Example 1 Polyethersulfone ultrafiltration membrane was selected as the carrier membrane. A traction device was used to continuously move the carrier membrane from the feeding mechanism to the receiving mechanism at a speed of 20 cm / min. During the movement of the carrier membrane, droplets of the aqueous solution (particle size 10-50 μm, specific surface area 1.2 × 10⁻⁶) were first introduced. 5 -6×10 5 m 2 / m 3 The aqueous monomer is sprayed onto the surface of the carrier membrane, thus loading the carrier membrane with aqueous monomers. Then, droplets of the oil phase solution (particle size 10-50 μm, specific surface area 1.2×10⁻⁶) are added. 5 -6×10 5 m 2 / m 3 The oil phase monomer is sprayed onto the surface of a carrier membrane loaded with aqueous monomers, so that the oil phase monomers and aqueous monomers undergo interfacial polymerization. The membrane that has undergone interfacial polymerization is then heat-treated at 80°C for 5 min by a heat treatment unit to obtain a high-flux, high-selectivity polyamide nanofiltration membrane. The atomization system atomizes a 1.0 wt% piperazine aqueous solution and a 0.1 wt% trimesoyl chloride solution (solvent isopar G) into aqueous and oil phase solution droplets using ultrasonic atomization. The ultrasonic power is 1 W, the carrier gas pressure is 0.1 MPa, the flow rate of the solution to be sprayed is 5 mL / min, the spraying height is 5 cm, the spraying ambient temperature is 20 ℃, the spraying ambient relative humidity is 20%, the ultrasonic atomizing nozzle is perpendicular to the surface of the carrier film, and there are 5 ultrasonic atomizing nozzles for the aqueous phase and 5 for the oil phase.

[0029] Example 2 Polyethersulfone ultrafiltration membrane was selected as the carrier membrane. A traction device was used to continuously move the carrier membrane from the feeding mechanism to the receiving mechanism at a speed of 200 cm / min. During the movement of the carrier membrane, droplets of the aqueous solution (particle size 50-100 μm, specific surface area 6 × 10⁻⁶) were first introduced. 4 -1.2×10 5 m 2 / m 3 The aqueous monomer is sprayed onto the surface of the carrier membrane, thus loading the carrier membrane with aqueous monomers. Then, droplets of the oil phase solution (particle size 50-100 μm, specific surface area 6×10⁻⁶) are added. 4 -1.2×10 5 m 2 / m 3 The oil phase monomer is sprayed onto the surface of a carrier membrane loaded with aqueous monomers, so that the oil phase monomers and aqueous monomers undergo interfacial polymerization. The membrane that has undergone interfacial polymerization is then heat-treated at 60°C for 10 min by a heat treatment unit to obtain a high-flux, high-selectivity polyamide nanofiltration membrane. The atomization system atomizes a 2.0 wt% piperazine aqueous solution and a 0.2 wt% trimesoyl chloride solution (solvent isopar G) into aqueous and oil phase solution droplets using ultrasonic atomization. The ultrasonic power is 5 W, the carrier gas pressure is 0.3 MPa, the flow rate of the solution to be sprayed is 1 mL / min, the spraying height is 5 cm, the spraying ambient temperature is 25 ℃, the relative humidity of the spraying ambient is 40%, the ultrasonic atomizing nozzle is perpendicular to the surface of the carrier film, and there are 20 ultrasonic atomizing nozzles for the aqueous phase and 20 for the oil phase.

[0030] Example 3 Polyethersulfone ultrafiltration membrane was selected as the carrier membrane. A traction device was used to continuously move the carrier membrane from the feeding mechanism to the receiving mechanism at a speed of 1000 cm / min. During the movement of the carrier membrane, droplets of the aqueous solution (particle size 100-200 μm, specific surface area 3×10⁻⁶) were first introduced. 4 -6×10 4 m 2 / m3 The aqueous monomer is sprayed onto the surface of the carrier membrane, thus loading the carrier membrane with aqueous monomers. Then, droplets of the oil phase solution (particle size 100-200 μm, specific surface area 3×10⁻⁶) are added. 4 -6×10 4 m 2 / m 3 The oil phase monomer is sprayed onto the surface of a carrier membrane loaded with aqueous monomers, so that the oil phase monomers and aqueous monomers undergo interfacial polymerization. The membrane that has undergone interfacial polymerization is then heat-treated at 90°C for 5 min by a heat treatment unit to obtain a high-flux, high-selectivity polyamide nanofiltration membrane. The atomization system atomizes a 0.5 wt% piperazine aqueous solution and a 0.1 wt% trimesoyl chloride solution (solvent isopar G) into aqueous and oil phase solution droplets using ultrasonic atomization. The ultrasonic power is 10 W, the carrier gas pressure is 0.5 MPa, the flow rate of the solution to be sprayed is 0.1 mL / min, the spraying height is 5 cm, the spraying ambient temperature is 30 ℃, the relative humidity of the spraying ambient is 60%, the ultrasonic atomizing nozzle is perpendicular to the surface of the carrier film, and there are 100 ultrasonic atomizing nozzles for the aqueous phase and 100 for the oil phase.

[0031] Example 4 Polyethersulfone ultrafiltration membrane was selected as the carrier membrane. A traction device was used to continuously move the carrier membrane from the feeding mechanism to the receiving mechanism at a speed of 20 cm / min. During the movement of the carrier membrane, droplets of the aqueous solution (particle size 10-50 μm, specific surface area 1.2 × 10⁻⁶) were first introduced. 5 -6×10 5 m 2 / m 3 The aqueous monomer is sprayed onto the surface of the carrier membrane, thus loading the carrier membrane with aqueous monomers. Then, droplets of the oil phase solution (particle size 10-50 μm, specific surface area 1.2×10⁻⁶) are added. 5 -6×10 5 m 2 / m 3 The oil phase monomer is sprayed onto the surface of a carrier membrane loaded with aqueous monomers, so that the oil phase monomers and aqueous monomers undergo interfacial polymerization. The membrane that has undergone interfacial polymerization is then heat-treated at 80°C for 5 min by a heat treatment unit to obtain a high-flux, high-selectivity polyamide nanofiltration membrane. The atomization system electrostatically atomizes a 1.0 wt% piperazine aqueous solution and a 0.1 wt% trimesoyl chloride solution (solvent isopar G) into aqueous and oil phase droplets. The voltage applied to the atomizing nozzle is 5 kV, the raw material solution supply rate during electrostatic atomization is 5 mL / min, the spraying height is 5 cm, the spraying ambient temperature is 20 ℃, the relative humidity of the spraying environment is 20%, the electrostatic atomizing nozzle is perpendicular to the carrier film surface, and there are 5 aqueous phase atomizing nozzles and 5 oil phase atomizing nozzles.

[0032] Example 5 Polyethersulfone ultrafiltration membrane was selected as the carrier membrane. A traction device was used to continuously move the carrier membrane from the feeding mechanism to the receiving mechanism at a speed of 200 cm / min. During the movement of the carrier membrane, droplets of the aqueous solution (particle size 50-100 μm, specific surface area 6 × 10⁻⁶) were first introduced. 4 -1.2×10 5 m 2 / m 3 The aqueous monomer is sprayed onto the surface of the carrier membrane, thus loading the carrier membrane with aqueous monomers. Then, droplets of the oil phase solution (particle size 50-100 μm, specific surface area 6×10⁻⁶) are added. 4 -1.2×10 5 m 2 / m 3 The oil phase monomer is sprayed onto the surface of a carrier membrane loaded with aqueous monomers, so that the oil phase monomers and aqueous monomers undergo interfacial polymerization. The membrane that has undergone interfacial polymerization is then heat-treated at 60°C for 10 min by a heat treatment unit to obtain a high-flux, high-selectivity polyamide nanofiltration membrane. The atomization system electrostatically atomizes a 2.0 wt% piperazine aqueous solution and a 0.2 wt% trimesoyl chloride solution (solvent isopar G) into aqueous and oil phase droplets. The voltage applied to the atomizing nozzle is 10 kV, the raw material solution supply rate during electrostatic atomization is 1 mL / min, the spraying height is 5 cm, the spraying ambient temperature is 25 ℃, the relative humidity of the spraying environment is 40%, the electrostatic atomizing nozzle is perpendicular to the carrier film surface, and there are 20 aqueous phase atomizing nozzles and 20 oil phase atomizing nozzles.

[0033] Example 6 Polyethersulfone ultrafiltration membrane was selected as the carrier membrane. A traction device was used to continuously move the carrier membrane from the feeding mechanism to the receiving mechanism at a speed of 1000 cm / min. During the movement of the carrier membrane, droplets of the aqueous solution (particle size 100-200 μm, specific surface area 3×10⁻⁶) were first introduced. 4 -6×10 4 m 2 / m3 The aqueous monomer is sprayed onto the surface of the carrier membrane, thus loading the carrier membrane with aqueous monomers. Then, droplets of the oil phase solution (particle size 100-200 μm, specific surface area 3×10⁻⁶) are added. 4 -6×10 4 m 2 / m 3 The oil phase monomer is sprayed onto the surface of a carrier membrane loaded with aqueous monomers, so that the oil phase monomers and aqueous monomers undergo interfacial polymerization. The membrane that has undergone interfacial polymerization is then heat-treated at 90°C for 5 min by a heat treatment unit to obtain a high-flux, high-selectivity polyamide nanofiltration membrane. The atomization system electrostatically atomizes a 0.5 wt% piperazine aqueous solution and a 0.1 wt% trimesoyl chloride solution (solvent isopar G) into aqueous and oil phase droplets. The voltage applied to the atomizing nozzle is 15 kV, the raw material solution supply rate during electrostatic atomization is 0.1 mL / min, the spraying height is 5 cm, the spraying ambient temperature is 30 ℃, the relative humidity of the spraying environment is 60%, the electrostatic atomizing nozzle is perpendicular to the carrier film surface, and there are 100 aqueous phase atomizing nozzles and 100 oil phase atomizing nozzles.

[0034] Example 7 Polyethersulfone ultrafiltration membrane was selected as the carrier membrane. A traction device was used to continuously move the carrier membrane from the feeding mechanism to the receiving mechanism at a speed of 20 cm / min. During the movement of the carrier membrane, droplets of the aqueous solution (particle size 10-50 μm, specific surface area 1.2 × 10⁻⁶) were first introduced. 5 -6×10 5 m 2 / m 3 The aqueous monomer is sprayed onto the surface of the carrier membrane, thus loading the carrier membrane with aqueous monomers. Then, droplets of the oil phase solution (particle size 10-50 μm, specific surface area 1.2×10⁻⁶) are added. 5 -6×10 5 m 2 / m 3 The oil phase monomer is sprayed onto the surface of a carrier membrane loaded with aqueous monomers, so that the oil phase monomers and aqueous monomers undergo interfacial polymerization. The membrane that has undergone interfacial polymerization is then heat-treated at 80°C for 5 min by a heat treatment unit to obtain a high-flux, high-selectivity polyamide nanofiltration membrane. The atomization system atomizes a 1.0 wt% piperazine aqueous solution and a 0.1 wt% trimesoyl chloride solution (solvent isopar G) into aqueous and oil phase solution droplets using pneumatic atomization. The spraying pressure is 0.01 MPa, the flow rate of the solution to be sprayed is 5 mL / h, the spraying height is 5 cm, the spraying ambient temperature is 20 ℃, and the relative humidity of the spraying ambient is 20%. The pneumatic atomizing nozzles are perpendicular to the surface of the carrier film, and there are 5 pneumatic atomizing nozzles for the aqueous phase and 5 for the oil phase.

[0035] Example 8 Polyethersulfone ultrafiltration membrane was selected as the carrier membrane. A traction device was used to continuously move the carrier membrane from the feeding mechanism to the receiving mechanism at a speed of 200 cm / min. During the movement of the carrier membrane, droplets of the aqueous solution (particle size 50-100 μm, specific surface area 6 × 10⁻⁶) were first introduced. 4 -1.2×10 5 m 2 / m 3 The aqueous monomer is sprayed onto the surface of the carrier membrane, thus loading the carrier membrane with aqueous monomers. Then, droplets of the oil phase solution (particle size 50-100 μm, specific surface area 6×10⁻⁶) are added. 4 -1.2×10 5 m 2 / m 3 The oil phase monomer is sprayed onto the surface of a carrier membrane loaded with aqueous monomers, so that the oil phase monomers and aqueous monomers undergo interfacial polymerization. The membrane that has undergone interfacial polymerization is then heat-treated at 60°C for 10 min by a heat treatment unit to obtain a high-flux, high-selectivity polyamide nanofiltration membrane. The atomization system atomizes a 2.0 wt% piperazine aqueous solution and a 0.2 wt% trimesoyl chloride solution (solvent isopar G) into aqueous and oil phase droplets using pneumatic atomization. The spraying pressure is 0.1 MPa, the flow rate of the solution to be sprayed is 1 mL / h, the spraying height is 5 cm, the spraying ambient temperature is 25 ℃, and the relative humidity of the spraying environment is 40%. The pneumatic atomizing nozzles are perpendicular to the surface of the carrier film, and there are 20 aqueous phase atomizing nozzles and 20 oil phase atomizing nozzles.

[0036] Example 9 Polyethersulfone ultrafiltration membrane was selected as the carrier membrane. A traction device was used to continuously move the carrier membrane from the feeding mechanism to the receiving mechanism at a speed of 1000 cm / min. During the movement of the carrier membrane, droplets of the aqueous solution (particle size 100-200 μm, specific surface area 3×10⁻⁶) were first introduced. 4 -6×10 4 m 2 / m 3The aqueous monomer is sprayed onto the surface of the carrier membrane, thus loading the carrier membrane with aqueous monomers. Then, droplets of the oil phase solution (particle size 100-200 μm, specific surface area 3×10⁻⁶) are added. 4 -6×10 4 m 2 / m 3 The oil phase monomer is sprayed onto the surface of a carrier membrane loaded with aqueous monomers, so that the oil phase monomers and aqueous monomers undergo interfacial polymerization. The membrane that has undergone interfacial polymerization is then heat-treated at 90°C for 5 min by a heat treatment unit to obtain a high-flux, high-selectivity polyamide nanofiltration membrane. The atomization system atomizes a 0.5 wt% piperazine aqueous solution and a 0.1 wt% trimesoyl chloride solution (solvent isopar G) into aqueous and oil phase droplets using pneumatic atomization. The spraying pressure is 0.5 MPa, the flow rate of the solution to be sprayed is 0.1 mL / h, the spraying height is 5 cm, the spraying ambient temperature is 30 ℃, and the relative humidity is 60%. The pneumatic atomizing nozzles are perpendicular to the surface of the carrier film, and there are 100 aqueous phase atomizing nozzles and 100 oil phase atomizing nozzles.

[0037] Comparative Example 1 Using a commercial polyethersulfone ultrafiltration membrane as a porous support membrane, an aqueous solution containing 1.0 wt% piperazine was poured onto the surface of the porous support membrane. After contact and standing for 1 min, excess liquid on the membrane surface was removed. Subsequently, an Isopar G solution containing 0.1 wt% trimesoyl chloride was poured onto the membrane surface. After contact and standing for 0.5 min, excess liquid on the membrane surface was removed. Finally, the membrane was heat-treated at 80 °C for 5 min to obtain a polyamide nanofiltration membrane based on conventional interfacial polymerization.

[0038] Sample Analysis A schematic diagram of the continuous preparation method of this high-flux, high-selectivity polyamide nanofiltration membrane is shown below. Figure 1 As shown, the atomizing nozzle is perpendicular to the surface of the carrier film. Figure 1 For illustrative purposes only, the SEM image of the high-flux, high-selectivity polyamide nanofiltration membrane prepared in the representative Example 3 is shown below. Figure 2 As shown.

[0039] The performance of the nanofiltration membranes prepared in Examples 1-9 and Comparative Example 1 was tested at room temperature using a cross-flow flat sheet membrane performance evaluation device. The pure water flux, the rejection rate of 2000 ppm Na2SO4 aqueous solution, and the rejection rate of 2000 ppm NaCl aqueous solution were tested respectively (test temperature: 25 ℃, pressure: 5 bar). The results are shown in Table 1.

[0040] Table 1. Detection data of polyamide nanofiltration membrane As can be seen from the data in the table above, when preparing polyamide nanofiltration membranes using the method of this invention, the smaller the microdroplet size, the higher the water flux and monovalent / polyvalent salt separation factor of the corresponding product membrane.

[0041] The embodiments described above provide a detailed explanation of the technical solutions of the present invention. It should be understood that the above descriptions are merely specific embodiments of the present invention and are not intended to limit the present invention. Any modifications, additions, or similar substitutions made within the scope of the principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A continuous preparation method for a high-flux, high-selectivity polyamide nanofiltration membrane, characterized in that, Includes the following steps: The carrier membrane is continuously moved from the feeding mechanism to the receiving mechanism by a traction device. During the movement of the carrier membrane, the aqueous solution droplets are first sprayed onto the surface of the carrier membrane to load the aqueous monomers onto the carrier membrane. Then, the oil solution droplets are sprayed onto the surface of the carrier membrane loaded with aqueous monomers to allow the oil monomers and aqueous monomers to undergo interfacial polymerization. The membrane that has undergone interfacial polymerization is then passed through a heat treatment unit to obtain the high-flux, high-selectivity polyamide nanofiltration membrane. The aqueous and oil phase solutions are atomized into droplets by the atomization system, with the atomizing nozzle perpendicular to the surface of the carrier film. The droplet sizes of both the aqueous and oil phase solutions were 10-200 μm, and their specific surface areas were both 3 × 10⁻⁶. 4 -6×10 5 m 2 / m 3 .

2. The continuous preparation method of the high-flux, high-selectivity polyamide nanofiltration membrane according to claim 1, characterized in that, During the movement of the carrier membrane, the traction force of the traction device is adjusted according to the tension of the carrier membrane to make the moving speed of the carrier membrane 10-1000 cm / min.

3. The continuous preparation method of the high-flux, high-selectivity polyamide nanofiltration membrane according to claim 1, characterized in that, The carrier membrane is one of the following: polyester ultrafiltration membrane, polyethersulfone ultrafiltration membrane, polysulfone ultrafiltration membrane, polyacrylonitrile ultrafiltration membrane, polypropylene ultrafiltration membrane, polyvinylidene fluoride ultrafiltration membrane, and polytetrafluoroethylene ultrafiltration membrane.

4. The continuous preparation method of the high-flux, high-selectivity polyamide nanofiltration membrane according to claim 1, characterized in that, The atomization system atomizes aqueous solutions with a concentration of 0.1-5 wt% and oil solutions with a concentration of 0.01-1 wt% into droplets of aqueous solution and oil solution, respectively, through ultrasonic atomization, electrostatic atomization, or pneumatic atomization.

5. The continuous preparation method of the high-flux, high-selectivity polyamide nanofiltration membrane according to claim 4, characterized in that, During ultrasonic atomization, the ultrasonic power is 0.1-10 W, the flow rate of the solution to be sprayed is 0.1-15 mL / h, the carrier gas pressure is 0.01-2 MPa, the spraying environment temperature is 10-70 ℃, and the relative humidity of the spraying environment is 10%-80%. During electrostatic atomization, the voltage applied to the atomizing nozzle is 1-15 kV, the flow rate of the solution to be sprayed is 0.1-15 mL / h, the ambient temperature is 10-70 ℃, and the relative humidity is 10%-80%. During the pneumatic atomization process, the spraying air pressure is 0.01-2 MPa, the propulsion flow rate of the solution to be sprayed is 0.1-15 mL / h, the spraying ambient temperature is 10-70 ℃, and the relative humidity of the spraying ambient is 10%-80%.

6. The continuous preparation method of the high-flux, high-selectivity polyamide nanofiltration membrane according to claim 1, characterized in that, The aqueous monomer is at least one of piperazine, 2-methylpiperazine, 2,5-dimethylpiperazine, 2,6-dimethylpiperazine, 1,2-diaminocyclohexane, 1,4-diaminocyclohexane, ethylenediamine, N,N-bis(2-aminoethyl)ethylenediamine, divinyltriamine, and polyethyleneimine.

7. The continuous preparation method of the high-flux, high-selectivity polyamide nanofiltration membrane according to claim 1, characterized in that, The oil phase monomer is at least one of pyromellitic methyl methacrylate (PMMA), terephthaloyl chloride (TBMA), phthaloyl chloride (ODMA), pyromellitic methyl methacrylate (PMMA), malonyl chloride (MDMA), glutaryl chloride (GMA), and fumarate chloride (FMA); the solvent of the oil phase solution includes n-hexane, cyclohexane, n-heptane, toluene, benzene, isopar G, isopar E, isopar H, isopar L, or isopar M.

8. The continuous preparation method of the high-flux, high-selectivity polyamide nanofiltration membrane according to claim 1, characterized in that, The heat treatment unit has a treatment temperature of 40-100 ℃ and a heat treatment time of 3-20 min.

9. The continuous preparation method of the high-flux, high-selectivity polyamide nanofiltration membrane according to claim 1, characterized in that, The high-flux, high-selectivity polyamide nanofiltration membrane has a water flux ≥18 LMH / bar and a separation factor ≥100 for monovalent and polyvalent salts, separating monovalent and polyvalent salts as monovalent anions and divalent anions.

10. The application of the continuous preparation method of high-flux, high-selectivity polyamide nanofiltration membrane according to any one of claims 1-9 in the field of water treatment.

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