Method for improving water flux and anti-pollution capacity of polyamide reverse osmosis membrane and application of method

Abstract

The invention discloses a method for improving water flux and anti-pollution capacity of a polyamide reverse osmosis membrane and application of the method, and belongs to the technical field of water treatment membranes.The method comprises the steps that a water-phase solution containing polyamine monomers and an oil-phase solution containing polyacyl chloride monomers are respectively subjected to droplet formation into a water-phase solution containing polyamine monomers and an oil-phase solution containing polyacyl chloride monomers through a droplet generator, and the water-phase solution containing polyamine monomers and the oil-phase solution containing polyacyl chloride monomers have the particle size of 10-200 microns; water phase solution droplets and oil phase solution droplets with the specific surface area of 3 * 10 < 4 >-6 * 10 < 5 > m < 2 > / m < 3 > are sequentially sprayed on the ultrafiltration substrate membrane through a moving spray head system, so that the water phase solution droplets and the oil phase solution droplets are fully contacted to generate an interfacial polymerization reaction, and after the spraying process is finished, heat treatment is performed to obtain the polyamide reverse osmosis membrane. According to the method disclosed by the invention, the traditional interfacial polymerization method is improved, a new additive is not introduced, and the water flux and the anti-pollution capacity of the polyamide reverse osmosis membrane are further improved on the basis of reducing the solvent dosage.

Description

Technical Field

[0001] This invention relates to the field of water treatment membrane technology, specifically to a method and its application for improving the water flux and antifouling ability of polyamide reverse osmosis membranes. Background Technology

[0002] Membrane-based water treatment technology, as a highly efficient and green separation technology, has been widely used in industrial wastewater treatment, seawater desalination, drinking water purification, and biopharmaceuticals due to its advantages such as low energy consumption, simple operation, and ease of industrial scale-up. Polyamide reverse osmosis membranes are currently the most widely used and advanced type of reverse osmosis membrane on the market. Under pressure, water molecules can overcome the osmotic pressure difference of the reverse osmosis membrane and preferentially permeate through the dense polyamide active layer, while pollutants such as ions, organic matter, microorganisms, and colloids dissolved in the water are selectively retained on one side of the reverse osmosis membrane (the concentrate side). Currently, the mainstream method for preparing polyamide reverse osmosis membranes is interfacial polymerization, but this method suffers from low raw material utilization and high organic solvent consumption. Furthermore, polyamide reverse osmosis membranes also exhibit poor antifouling performance.

[0003] Chinese patent document CN112957915A discloses a method and apparatus for preparing a high-flux, low-pressure reverse osmosis membrane. The method includes: coating a casting solution onto a nonwoven fabric support, followed by gel treatment with an aqueous monomer and N,N-dimethylformamide to obtain a base membrane; then coating an oil-phase monomer solution to undergo an interfacial reaction to prepare a polyamide membrane; and finally drying and post-treating the polyamide membrane to obtain a high-flux, low-pressure reverse osmosis membrane. This invention can be used to prepare high-performance, low-pressure, high-flux reverse osmosis membranes, achieving stable and continuous production. However, it may suffer from poor uniformity, and the introduced N,N-dimethylformamide may also affect the interfacial polymerization process.

[0004] Chinese patent document CN113457459A discloses a continuous preparation method for polyamide functional composite membranes. The method includes: (1) uniformly coating a polyamine solution onto the surface of a conveying mechanism using a scraper to form a polyamine liquid film; (2) spraying a polyacrylamide chloride solution onto the polyamine liquid film using a spraying mechanism, whereby the polyamine and polyacrylamide undergo interfacial polymerization to generate a polyamide self-supporting membrane; (3) immersing the conveying mechanism with the polyamide self-supporting membrane attached in a washing tank, whereby the polyamide self-supporting membrane detaches from the conveying mechanism and enters a drying mechanism for drying and heat treatment; and (4) combining the dried and heat-treated polyamide self-supporting membrane with a porous support material to obtain a polyamide functional composite membrane. This invention can continuously prepare polyamide functional composite membranes with uniform structure and stable performance over a large area. However, this polyamide functional composite membrane may have a problem of weak bonding between the polyamide functional layer and the support layer.

[0005] Therefore, it is necessary to develop novel methods for preparing polyamide reverse osmosis membranes to improve the problems of low raw material utilization, high organic solvent consumption, poor uniformity, and weak interfacial bonding in existing preparation processes, while further improving the fouling resistance of polyamide reverse osmosis membranes. Summary of the Invention

[0006] This invention provides a method for improving the water flux and antifouling ability of polyamide reverse osmosis membranes. This method improves upon the traditional interfacial polymerization method without introducing new additives, and further improves the water flux and antifouling ability of polyamide reverse osmosis membranes while reducing solvent usage.

[0007] The specific technical solution adopted is as follows: A method for improving the water flux and antifouling ability of polyamide reverse osmosis membranes includes the following steps: Using a droplet generator, aqueous solutions containing polyamine monomers and oil solutions containing polyacrylamide chloride monomers were respectively dropletized into particles with a diameter of 10-200 μm and a specific surface area of ​​3×10⁻⁶. 4 -6×10 5 m 2 / m 3 Aqueous and oil phase solution droplets are sequentially sprayed onto the ultrafiltration substrate membrane via a moving nozzle system, allowing the two phases to come into full contact and undergo interfacial polymerization. After the spraying process, heat treatment is performed to obtain a polyamide reverse osmosis membrane (the water flux and antifouling ability of the obtained polyamide reverse osmosis membrane are enhanced through microdroplet reaction). The aforementioned anti-contamination capabilities include resistance to protein contamination; The polyamide reverse osmosis membrane has a water flux of ≥3.0 LMH / bar and a flux recovery rate of ≥99.0% after filtering protein solution and washing.

[0008] This invention introduces a microdroplet reaction system. Through extensive experimental research, the inventors discovered that using a particle size of 10-200 μm and a specific surface area of ​​3×10⁻⁶... 4 -6×10 5 m 2 / m 3 The microdroplet interfacial polymerization reaction between aqueous and oil phase solution droplets can cause a surge in the density of the water-oil two-phase interface, weaken diffusion inhibition, enhance the reaction, improve monomer utilization, significantly reduce waste liquid production, and reduce the generation of defects in the separation layer. This results in a polyamide separation layer with a smooth surface and low roughness, thereby reducing the physical retention sites of pollutants during filtration, making it less likely to form an "anchoring" effect, and providing strong anti-pollution capability.

[0009] Optionally, the polyamine monomer is at least one selected from m-phenylenediamine, o-phenylenediamine, 1,3,5-triaminobenzene, 1,2,4-triaminobenzene, 3,5-diaminobenzoic acid, 2,4-diaminotoluene, 2,6-diaminotoluene, xylenediamine, ethylenediamine, propylenediamine, tris(2-aminoethyl)amine, 1,3-diaminocyclohexane, 1,2-diaminocyclohexane, and 1,4-diaminocyclohexane.

[0010] Optionally, the polyacrylamide chloride monomer is at least one of pyromellitic methyl methacrylate (PMMA), terephthaloyl chloride (TBMA), phthaloyl chloride (DMA), 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.

[0011] Preferably, the concentration of polyamine monomer in the aqueous solution is 0.1-5 wt%; the concentration of polyacrylamide monomer in the oil solution is 0.01-1 wt%; the aqueous solution and the oil solution are stored in an aqueous supply system and an oil supply system, respectively, and the aqueous supply system and the oil supply system are connected to the droplet generator.

[0012] More preferably, the concentration of the polyamine monomer in the aqueous phase solution is 0.5-2 wt%; and the concentration of the polyacrylamide chloride monomer in the oil phase solution is 0.05-0.5 wt%.

[0013] Optionally, the movement of the nozzle system is achieved via a guide rail, wherein the moving speed of the nozzle is 1-2000 cm / min, the stepping distance of the nozzle is 0.1-20 cm, the nozzle is sprayed perpendicular to the ultrafiltration base membrane, and the distance between the nozzle and the ultrafiltration base membrane is 2-20 cm.

[0014] Preferably, the ultrafiltration substrate membrane is a hydrophilic polymer ultrafiltration membrane, including a polyethersulfone ultrafiltration membrane, a polysulfone ultrafiltration membrane, or a polyacrylonitrile ultrafiltration membrane.

[0015] During the interfacial polymerization reaction, the volumes of the aqueous and oil phase solutions participating in the reaction per unit area are 1-100 mL / m². 2 The volume ratio of the aqueous phase solution to the oil phase solution is 1:10-10:1, and more preferably 1:1.

[0016] Preferably, the interfacial polymerization reaction temperature is 15-30 ℃ and the interfacial polymerization reaction time is 1-15 min.

[0017] Preferably, the heat treatment conditions are 40-100 °C for 3-20 min, and the heat treatment also includes a step of winding the film into a membrane assembly.

[0018] This invention also provides the application of the method for improving the water flux and antifouling ability of polyamide reverse osmosis membranes in the field of water treatment.

[0019] Compared with the prior art, the beneficial effects of the present invention are as follows: (1) The present invention introduces a microdroplet reaction system, which uses aqueous solution droplets and oil solution droplets to carry out interfacial polymerization reaction. The organic solvent consumption per square meter of separation membrane is less than 100 mL, the solvent reduction is more than 80%, and the performance is superior to that of polyamide reverse osmosis membranes prepared by traditional methods. In particular, the water flux and antifouling ability are significantly improved. The method of the present invention is green and environmentally friendly and has great industrialization potential.

[0020] (2) The method of the present invention can realize the continuous automated production of high-performance polyamide reverse osmosis membranes in industry. The relevant parameters in the production process can be automatically adjusted according to the real-time detection data, which improves production efficiency, reduces production costs, and ensures product quality consistency.

[0021] (3) The present invention introduces a microdroplet reaction system, which utilizes the microdroplet interfacial polymerization reaction of aqueous solution droplets and oil solution droplets under specific parameters to increase the density of the water-oil two-phase contact interface, weaken diffusion inhibition, and achieve reaction enhancement. This can reduce the generation of defects in the separation layer and prepare a polyamide separation layer with high water flux, smooth surface and low roughness. Thus, during the filtration process, the physical retention sites of pollutants are reduced, and it is not easy to form an "anchoring" effect, providing strong filtration capacity and anti-pollution capacity. Attached Figure Description

[0022] Figure 1 This is a surface SEM image of the polyamide reverse osmosis membrane prepared in Example 1.

[0023] Figure 2 This is an atomic force microscope (AFM) image of the polyamide reverse osmosis membrane prepared in Example 1. Detailed Implementation

[0024] 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.

[0025] 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.

[0026] Comparative Example 1 A commercial polyethersulfone ultrafiltration membrane was fixed with a plate and frame. An aqueous solution containing 1.0 wt% m-phenylenediamine (m-phenylenediamine aqueous solution) was poured onto the surface of the polyethersulfone ultrafiltration membrane. After standing for 1 min, excess liquid on the surface was removed. Then, an oil solution containing 0.1 wt% trimesoyl chloride (isopar G) was poured onto the membrane surface. The m-phenylenediamine monomer and trimesoyl chloride monomer came into contact and underwent interfacial polymerization at 25 °C for 2 min. Excess liquid on the membrane surface was then removed. The membrane was removed and heat-treated at 80 °C for 5 min to obtain a conventional polyamide reverse osmosis membrane.

[0027] Example 1 A commercial polyethersulfone ultrafiltration membrane was immobilized on a receiving platform. A 1.0 wt% aqueous solution of m-phenylenediamine was stored in the aqueous phase supply system, and a 0.1 wt% isopar G oil phase solution of trimesoyl chloride was stored in the oil phase supply system. Both systems were connected to a droplet generator. The droplet generator atomized the aqueous and oil phase solutions into droplets with a particle size of 10–50 μm and a specific surface area of ​​1.2 × 10⁻⁶ m². 5 -6×10 5 m 2 / m 3 Aqueous and oil phase solution droplets were sprayed onto the polyethersulfone ultrafiltration membrane first via a moving nozzle system. After standing for 1 minute, oil phase solution droplets were then sprayed onto the polyethersulfone ultrafiltration membrane via the same moving nozzle system, thus ensuring sufficient contact between the two phases and initiating an interfacial polymerization reaction. (The nozzle movement was achieved via a guide rail; during spraying, the nozzle moving speed was 360 cm / min, the nozzle step distance was 0.5 cm, the nozzle was perpendicular to the ultrafiltration substrate membrane, and the distance between the nozzle and the ultrafiltration substrate membrane was 5 cm.) The interfacial polymerization reaction temperature was 25℃, and the reaction time was 2 minutes. During the interfacial polymerization reaction, the volume of both the aqueous and oil phase solutions participating in the reaction per unit area was 40 mL / m². 2 The volume ratio of the aqueous solution to the oil solution was 1:1. After the reaction was completed, the resulting membrane was heat-treated at 80 °C for 5 min to obtain a polyamide reverse osmosis membrane.

[0028] Example 2 A commercial polyethersulfone ultrafiltration membrane was immobilized on a receiving platform. A 1.0 wt% aqueous solution of m-phenylenediamine was stored in the aqueous phase supply system, and a 0.1 wt% isopar G oil phase solution of trimesoyl chloride was stored in the oil phase supply system. Both systems were connected to a droplet generator. The droplet generator atomized the aqueous and oil phase solutions into droplets with a particle size of 50-100 μm and a specific surface area of ​​6 × 10⁻⁶. 4 -1.2×10 5 m 2 / m 3 Aqueous and oil phase solution droplets were sprayed onto the polyethersulfone ultrafiltration membrane first via a moving nozzle system. After standing for 5 minutes, oil phase solution droplets were then sprayed onto the polyethersulfone ultrafiltration membrane via the same moving nozzle system, thus ensuring sufficient contact between the two phases and initiating an interfacial polymerization reaction. (The nozzle movement was achieved via a guide rail; during spraying, the nozzle moving speed was 360 cm / min, the nozzle step distance was 0.5 cm, the nozzle was perpendicular to the ultrafiltration substrate membrane, and the distance between the nozzle and the ultrafiltration substrate membrane was 5 cm.) The interfacial polymerization reaction temperature was 20℃, and the reaction time was 2 minutes. During the interfacial polymerization reaction, the volume of both the aqueous and oil phase solutions participating in the reaction per unit area was 60 mL / m². 2 The volume ratio of the aqueous solution to the oil solution was 1:1. After the reaction was completed, the resulting membrane was subjected to heat treatment at 65 °C for 10 min to obtain a polyamide reverse osmosis membrane.

[0029] Example 3 A commercial polyethersulfone ultrafiltration membrane was immobilized on a receiving platform. A 1.0 wt% aqueous solution of m-phenylenediamine was stored in the aqueous phase supply system, and a 0.1 wt% isopar G oil phase solution of trimesoyl chloride was stored in the oil phase supply system. Both systems were connected to a droplet generator. The droplet generator atomized the aqueous and oil phase solutions into droplets with a particle size of 100-200 μm and a specific surface area of ​​3 × 10⁻⁶ m². 4 -6×10 4 m 2 / m 3Aqueous and oil phase solution droplets were sprayed onto the polyethersulfone ultrafiltration membrane first via a moving nozzle system. After standing for 3 minutes, oil phase solution droplets were then sprayed onto the polyethersulfone ultrafiltration membrane via the same moving nozzle system, thus ensuring sufficient contact between the two phases and initiating an interfacial polymerization reaction. (The nozzle movement was achieved via a guide rail; during spraying, the nozzle moving speed was 360 cm / min, the nozzle step distance was 0.5 cm, the nozzle was perpendicular to the ultrafiltration substrate membrane, and the distance between the nozzle and the ultrafiltration substrate membrane was 5 cm.) The interfacial polymerization reaction temperature was 30℃, and the reaction time was 1 minute. During the interfacial polymerization reaction, the volume of both the aqueous and oil phase solutions participating in the reaction per unit area was 20 mL / m². 2 The volume ratio of the aqueous solution to the oil solution was 1:1. After the reaction was completed, the resulting membrane was subjected to heat treatment at 65 °C for 10 min to obtain a polyamide reverse osmosis membrane.

[0030] Comparative Example 2 A commercial polyethersulfone ultrafiltration membrane was immobilized on a receiving platform. A 1.0 wt% aqueous solution of m-phenylenediamine was stored in the aqueous phase supply system, and a 0.1 wt% isopar G oil phase solution of trimesoyl chloride was stored in the oil phase supply system. Both systems were connected to a droplet generator. The droplet generator atomized the aqueous and oil phase solutions into droplets with a particle size of 200-300 μm and a specific surface area of ​​2 × 10⁻⁶ m². 4 -3×10 4 m 2 / m 3 Aqueous and oil phase solution droplets were applied to the polyethersulfone ultrafiltration membrane via a moving nozzle system. The aqueous phase solution droplets were first sprayed onto the membrane via the moving nozzle system. After standing for 3 minutes, the oil phase solution droplets were then sprayed onto the membrane via the same system, ensuring sufficient contact between the two phases and initiating interfacial polymerization. (The nozzle movement was achieved via a guide rail; during spraying, the nozzle speed was 360 cm / min, the nozzle step distance was 0.5 cm, the nozzle was perpendicular to the ultrafiltration substrate membrane, and the distance between the nozzle and the substrate membrane was 5 cm.) The interfacial polymerization reaction was carried out at 30℃ for 2 minutes. During the reaction, the volume of both the aqueous and oil phase solutions participating in the reaction per unit area was 80 mL / m². 2 The volume ratio of the aqueous solution to the oil solution was 1:1. After the reaction was completed, the resulting membrane was subjected to heat treatment at 60 °C for 8 min to obtain a polyamide reverse osmosis membrane.

[0031] Sample Analysis The water flux of the polyamide reverse osmosis membranes prepared in Examples 1-3 and Comparative Examples 1-2 was tested at room temperature using a cross-flow flat sheet membrane performance evaluation device. A 1 g / L bovine serum albumin (BSA) solution was used as a simulated fouling aqueous solution and the system was run continuously for 8 hours to test the water flux after membrane fouling. The membranes were kept in the membrane tank without being removed, and the fouling solution in the test system was completely drained. The membranes were then rinsed with a 2000 mg / L sodium chloride aqueous solution for 30 min. The water flux of the membranes after rinsing was tested using a 2000 ppm NaCl aqueous solution, and the flux recovery rate was calculated. The results are shown in Table 1.

[0032] Table 1. Test data of polyamide reverse osmosis membrane

[0033] Down Figure 1 , 2 The characterization results of the polyamide reverse osmosis membrane prepared in Example 1 show that its surface is smooth and has low roughness (Rq=2.90 nm, Ra=2.20 nm), while the polyamide reverse osmosis membrane prepared in Comparative Example 1 has Rq=59.3 nm and Ra=61.2 nm. The lower the roughness, the fewer physical retention sites for pollutants, making it less likely to form an "anchoring" effect and providing stronger anti-fouling ability.

[0034] 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 method for improving the water flux and antifouling ability of a polyamide reverse osmosis membrane, characterized in that, Includes the following steps: Using a droplet generator, aqueous solutions containing polyamine monomers and oil solutions containing polyacrylamide chloride monomers were respectively dropletized into particles with a diameter of 10-200 μm and a specific surface area of ​​3×10⁻⁶. 4 -6×10 5 m 2 / m 3 Aqueous solution droplets and oil solution droplets are sequentially sprayed onto the ultrafiltration substrate membrane via a moving nozzle system, thereby enabling the two phases to fully contact and undergo interfacial polymerization. After the spraying process is completed, heat treatment is performed to obtain a polyamide reverse osmosis membrane. The aforementioned anti-contamination capabilities include resistance to protein contamination; The polyamide reverse osmosis membrane has a water flux of ≥3.0 LMH / bar and a flux recovery rate of ≥99.0% after filtering protein solution and washing.

2. The method for improving the water flux and antifouling ability of polyamide reverse osmosis membranes according to claim 1, characterized in that, The polyamine monomer is at least one selected from m-phenylenediamine, o-phenylenediamine, 1,3,5-triaminobenzene, 1,2,4-triaminobenzene, 3,5-diaminobenzoic acid, 2,4-diaminotoluene, 2,6-diaminotoluene, xylenediamine, ethylenediamine, propylenediamine, tris(2-aminoethyl)amine, 1,3-diaminocyclohexane, 1,2-diaminocyclohexane, and 1,4-diaminocyclohexane.

3. The method for improving the water flux and antifouling ability of polyamide reverse osmosis membranes according to claim 1, characterized in that, The polyacryl chloride monomer is at least one of pyromellitic tricarboxylic acid chloride, terephthaloyl chloride, phthaloyl chloride, pyromellitic tetracarboxylic acid chloride, malonyl chloride, glutaryl chloride, and fumaric acid chloride; 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.

4. The method for improving the water flux and antifouling ability of polyamide reverse osmosis membranes according to claim 1, characterized in that, In the aqueous solution, the concentration of polyamine monomers is 0.1-5 wt%; in the oil solution, the concentration of polyacrylamide chloride monomers is 0.01-1 wt%; the aqueous and oil solutions are stored in an aqueous supply system and an oil supply system, respectively, and the aqueous and oil supply systems are connected to a droplet generator.

5. The method for improving the water flux and antifouling ability of polyamide reverse osmosis membranes according to claim 1, characterized in that, The movement of the nozzle system is achieved through guide rails, with the nozzle moving at a speed of 1-2000 cm / min, the nozzle stepping distance being 0.1-20 cm, the nozzle spraying perpendicular to the ultrafiltration base membrane, and the distance between the nozzle and the ultrafiltration base membrane being 2-20 cm.

6. The method for improving the water flux and antifouling ability of polyamide reverse osmosis membranes according to claim 1, characterized in that, The ultrafiltration substrate membrane is a hydrophilic polymer ultrafiltration membrane, including polyethersulfone ultrafiltration membrane, polysulfone ultrafiltration membrane, or polyacrylonitrile ultrafiltration membrane.

7. The method for improving the water flux and antifouling ability of polyamide reverse osmosis membranes according to claim 1, characterized in that, During the interfacial polymerization reaction, the volumes of the aqueous and oil phase solutions participating in the reaction per unit area are 1-100 mL / m². 2 The volume ratio of the aqueous phase solution to the oil phase solution is 1:10-10:1; the interfacial polymerization reaction temperature is 15-30 ℃, and the interfacial polymerization reaction time is 1-15 min.

8. The method for improving the water flux and antifouling ability of polyamide reverse osmosis membranes according to claim 1, characterized in that, The heat treatment conditions are 40-100 ℃ for 3-20 min, and the heat treatment also includes the step of winding to form a membrane module.

9. The application of the method for improving the water flux and antifouling ability of polyamide reverse osmosis membranes according to any one of claims 1-8 in the field of water treatment.

Images