Polyamide reverse osmosis membrane and its preparation method

Abstract

This invention discloses a polyamide reverse osmosis membrane and its preparation method. The method includes: (1) providing a polysulfone-based membrane; (2) contacting the polysulfone-based membrane with a mixture containing polyamine monomers and polyacrylamide chloride monomers, and applying an electric field to form a polyamide desalination layer on at least a portion of the surface of the polysulfone-based membrane. The method for preparing the polyamide reverse osmosis membrane of this invention, by contacting the polysulfone-based membrane with a mixture containing polyamine monomers and polyacrylamide chloride monomers and applying an electric field, can increase the degree of polymerization of the polyamine monomers and polyacrylamide chloride monomers. This fundamentally optimizes the polyamide desalination layer, resulting in a dense porous network structure with high crosslinking degree, thereby improving the desalination and flux performance of the polyamide reverse osmosis membrane.

Description

Technical Field

[0001] This invention relates to the field of reverse osmosis membrane preparation technology, specifically to polyamide reverse osmosis membranes and their preparation methods. Background Technology

[0002] Polyamide reverse osmosis membranes are the most widely used membrane products in the field of membrane separation technology, and can be widely applied in drinking water purification, industrial pure water preparation, wastewater treatment and reuse, brackish water and seawater desalination, and other fields. Commercial polyamide reverse osmosis membranes are typically obtained by interfacial polymerization of m-phenylenediamine and trimesoyl chloride on a polysulfone porous support layer to generate a polyamide desalination layer. The ideal polyamide desalination layer structure should be a highly cross-linked, three-dimensional, dense porous network structure. However, current technologies for controlling the structure of polyamide desalination layers cannot more controllably and fundamentally optimize them to obtain a highly cross-linked, dense porous network structure.

[0003] Therefore, the current polyamide reverse osmosis membranes and their preparation methods still need improvement. Summary of the Invention

[0004] This invention aims to at least partially solve one of the technical problems in related technologies. Therefore, one object of this invention is to provide a polyamide reverse osmosis membrane and a method for preparing the same. The polyamide reverse osmosis membrane of this invention has a highly cross-linked polyamide desalination layer, exhibiting excellent desalination and flux performance.

[0005] In a first aspect, the present invention provides a method for preparing a polyamide reverse osmosis membrane. According to an embodiment of the present invention, the method comprises: (1) providing a polysulfone-based membrane; (2) contacting the polysulfone-based membrane with a mixture containing a polyamine monomer and a polyacrylamide chloride monomer, and applying an electric field to form a polyamide desalination layer on at least a portion of the surface of the polysulfone-based membrane.

[0006] According to the method for preparing polyamide reverse osmosis membranes described in the above embodiments of the present invention, by contacting the polysulfone-based membrane with a mixture containing polyamine monomers and polyacrylamide chloride monomers and applying an electric field, the polymerization degree of the polyamine monomers and polyacrylamide chloride monomers can be increased. This fundamentally optimizes the polyamide desalination layer, resulting in a dense porous network structure with high crosslinking degree, thereby improving the desalination and flux performance of the polyamide reverse osmosis membrane. Furthermore, this method is characterized by strong controllability, significant optimization effect, low cost, and simple operation, thus showing promising application prospects.

[0007] In addition, the method for preparing polyamide reverse osmosis membrane according to the above embodiments of the present invention may also have the following additional technical features:

[0008] In some embodiments of the present invention, the strength of the electric field is not less than 20 V / cm. This can improve the desalination and flux performance of the polyamide reverse osmosis membrane.

[0009] In some embodiments of the present invention, the polyamine monomer includes at least one of m-phenylenediamine, p-phenylenediamine, and m-phenylenediamine. This facilitates the formation of a polyamide desalination layer.

[0010] In some embodiments of the present invention, the polyacrylamide monomer includes at least one of pyromellitic methyl chloride, pyromellitic dimethyl chloride, phthaloyl chloride, and terephthaloyl chloride. This facilitates the formation of a polyamide desalination layer.

[0011] In some embodiments of the present invention, step (2) includes the following steps: (2-1) contacting the polysulfone-based membrane with an aqueous solution containing polyamine monomers; (2-2) contacting the polysulfone-based membrane after contact with the aqueous solution with an organic solution containing polyacrylamide chloride monomers under an applied electric field; (2-3) subjecting the polysulfone-based membrane after contact with the organic solution to heat treatment and post-treatment. Thus, a dense porous network structure with high crosslinking degree can be obtained, thereby improving the desalination and flux performance of the polyamide reverse osmosis membrane.

[0012] In some embodiments of the present invention, the concentration of the polyamine monomer in the aqueous solution is 0.5 wt% to 5 wt%.

[0013] In some embodiments of the present invention, the concentration of the polyamine monomer in the aqueous solution is 1 wt% to 4 wt%.

[0014] In some embodiments of the present invention, the concentration of polyacrylamide chloride monomer in the organic phase solution is 0.01 wt% to 0.5 wt%.

[0015] In some embodiments of the present invention, the concentration of polyacrylamide chloride monomer in the organic phase solution is 0.1 wt% to 0.3 wt%.

[0016] In some embodiments of the present invention, the post-treatment includes pickling, washing with water, soaking in glycerin, and drying.

[0017] In some embodiments of the present invention, the pickling temperature is 10°C to 100°C.

[0018] In some embodiments of the present invention, the acid includes at least one of citric acid, oxalic acid, hydrochloric acid, sulfuric acid, and phosphoric acid.

[0019] In some embodiments of the present invention, the concentration of the acid is 1 wt% to 30 wt%.

[0020] In some embodiments of the present invention, the polysulfone-based membrane is prepared using a casting solution comprising polysulfone, a pore-forming agent, and an organic solvent.

[0021] In some embodiments of the present invention, the concentration of polysulfone in the casting solution is 14 wt% to 30 wt%.

[0022] In some embodiments of the present invention, the concentration of the pore-forming agent in the casting solution is 1 wt% to 20 wt%.

[0023] In a second aspect, the present invention provides a polyamide reverse osmosis membrane. According to an embodiment of the present invention, the polyamide reverse osmosis membrane is prepared using the method described above. Thus, the polyamide reverse osmosis membrane has a highly cross-linked polyamide desalination layer, exhibiting excellent desalination and flux performance.

[0024] Additional aspects and advantages of the invention will be set forth in part in the description which follows, and in part will be obvious from the description, or may be learned by practice of the invention. Attached Figure Description

[0025] The above and / or additional aspects and advantages of the present invention will become apparent and readily understood from the description of the embodiments taken in conjunction with the following drawings, in which:

[0026] Figure 1 This is a schematic flowchart of a method for preparing a polyamide reverse osmosis membrane according to an embodiment of the present invention;

[0027] Figure 2 This is a scanning electron microscope image of the polyamide reverse osmosis membrane obtained according to Comparative Example 1 of the present invention;

[0028] Figure 3 This is a scanning electron microscope image of the polyamide reverse osmosis membrane obtained according to Example 1 of the present invention. Detailed Implementation

[0029] Embodiments of the present invention are described in detail below, examples of which are illustrated in the accompanying drawings, wherein the same or similar reference numerals denote the same or similar elements or elements having the same or similar functions throughout. The embodiments described below with reference to the accompanying drawings are exemplary and intended to explain the present invention, and should not be construed as limiting the present invention.

[0030] The technical solution of this invention was developed by the inventors based on the following discoveries:

[0031] Currently, there are three main technologies for controlling the structure of polyamide desalination layers: first, in the membrane preparation process, the morphology of the upper polyamide desalination layer is affected by optimizing the polysulfone support layer; second, the structure of the polyamide desalination layer is controlled by optimizing the polymerization reaction process through reactive phase additives; and third, the performance of membrane products is improved by reshaping the polyamide desalination layer structure through post-treatment.

[0032] The effect of optimizing the polysulfone support layer to regulate the structure of the polyamide desalination layer is mainly focused on improving the integrity and defect-free nature of the polyamide desalination layer and enhancing the bonding strength between the polysulfone support layer and the polyamide desalination layer. However, its effect on improving the crosslinking degree of the polyamide desalination layer itself is limited. For example, patent CN112844078A improves the uniform distribution of aqueous reactive monomers in the polysulfone layer by increasing the hydrophilicity of the polysulfone layer, thereby reducing film surface defects. Patent CN112823855A incorporates a poly-2-oxazoline block copolymer into the polysulfone support layer. This copolymer can form an interpenetrating network structure with the polyamide as an anchor to fix the polyamide between the through-pores of the polysulfone substrate, thereby improving the bonding strength between the two.

[0033] The most widespread application of controlling the polymerization process through reactive phase additives is as follows: For example, patent CN107617346A adds polyether-modified polydimethylsiloxane with low surface tension and long flexible side chains to the aqueous phase, making it easier for the aqueous phase monomers to diffuse into the oil phase reaction zone, increasing the degree of interfacial polymerization of polyamide, and making the polyamide active layer more dense. Patent CN110773004A adds water-soluble B vitamins to the aqueous phase, which can act as end-capping agents to react with the acyl halide groups of polyacyl halides, reducing the degree of crosslinking of the polyamide layer and increasing membrane flux. Controlling the polymerization process through reactive phase additives is basically achieved by increasing or decreasing the amount of reactive monomers. However, the reaction process has poor controllability. Increasing the amount of reactive monomers can improve the degree of crosslinking to some extent, but it also easily forms a large number of low molecular weight copolymers, which not only fail to contribute to desalination performance but also increase membrane permeation resistance. Furthermore, the use of additives also increases the difficulty of treating wastewater in later stages of production.

[0034] Post-treatment to reshape the desalination layer structure involves adjusting the desalination layer after it has already formed and solidified using physicochemical methods. For example, patent CN1163793A uses a chlorine oxidant to contact the desalination layer; chlorine addition to the aromatic ring of the amine increases the bulk density of the polymer itself. This method mostly uses chemical agents to destroy the polyamide structure, reducing its density and increasing membrane flux, rather than optimizing the highly cross-linked, three-dimensional multi-network structure of the polyamide layer itself.

[0035] An electric field is a special kind of matter that objectively exists in the space surrounding electric charges and changing magnetic fields, possessing the objective properties of force and energy inherent in ordinary matter. In recent years, researchers have introduced external electric fields into practical research and production in multiple fields, confirming that external electric fields do indeed affect the diffusion and reaction processes of some substances. For some physicochemical processes or reactions that are difficult to achieve under ordinary conditions, the application of an external electric field can excite and activate some electrons, thereby activating reactants, improving reaction efficiency, or achieving the desired reaction result. Compared with other physicochemical methods that affect chemical reaction processes, such as magnetic fields, ultrasound, temperature control, and the addition of chemical catalysts, external electric fields have the advantages of wide availability, low energy consumption, low cost, and simple and convenient operation, making them highly valuable and practical.

[0036] Therefore, in a first aspect, the present invention provides a method for preparing a polyamide reverse osmosis membrane. According to embodiments of the present invention, reference is made to... Figure 1 The method includes the following steps:

[0037] S100: Provides polysulfone-based films

[0038] In this step, the polysulfone-based membrane can be prepared by an immersion phase inversion process using a casting solution comprising polysulfone, a pore-forming agent, and an organic solvent. In some embodiments of the present invention, the preparation method of the polysulfone-based membrane may include: dissolving a certain proportion of polysulfone and a pore-forming agent in an organic solvent to prepare a casting solution; coating the casting solution onto a polyester nonwoven fabric by scraping or slit extrusion; immersing the nonwoven fabric coated with the casting solution in a pure water coagulation bath to solidify it into a membrane; and washing the polysulfone-based membrane after phase inversion with pure water to remove excess organic solvent from the membrane. It should be noted that the pore size of the polysulfone-based membrane is not particularly limited, and those skilled in the art can select it according to actual needs, for example, it can be 10 nm to 100 nm.

[0039] According to embodiments of the present invention, the concentration of polysulfone in the casting solution can be 14 wt% to 30 wt%, such as 14 wt%, 16 wt%, 18 wt%, 20 wt%, 22 wt%, 24 wt%, 26 wt%, 28 wt%, and 30 wt%, and the concentration of the porogen in the casting solution can be 1 wt% to 20 wt%, such as 1 wt%, 2 wt%, 4 wt%, 6 wt%, 8 wt%, 10 wt%, 12 wt%, 14 wt%, 16 wt%, 18 wt%, and 20 wt%. The inventors have found that if the concentration of polysulfone is too high or too low, a polysulfone-based membrane with suitable pore size cannot be obtained. Similarly, if the concentration of the porogen in the casting solution is too high or too low, a polysulfone-based membrane with suitable porosity cannot be obtained. The present invention obtains a polysulfone-based membrane with suitable pore size and porosity by controlling the concentration of polysulfone and the concentration of the porogen within the above-mentioned ranges.

[0040] It should be noted that the specific composition of the pore-forming agent and organic solvent in the casting solution is not particularly limited, and those skilled in the art can select them according to actual needs. For example, the pore-forming agent in the casting solution may include at least one of polyethylene glycol, polyvinylpyrrolidone, ethylene glycol monomethyl ether and ethylene glycol dimethyl ether, and the organic solvent in the casting solution may include at least one of N,N-dimethylformamide, N,N-dimethylacetamide and dimethyl sulfoxide.

[0041] S200: A polysulfone-based film is contacted with a mixture containing polyamine monomers and polyacrylamide chloride monomers, and an electric field is applied.

[0042] In this step, by contacting the polysulfone-based membrane with a mixture containing polyamine monomers and polyacrylamide monomers, the polyamine monomers and polyacrylamide monomers can undergo interfacial polymerization on at least a portion of the surface of the polysulfone-based membrane to generate a polyamide desalination layer. Applying an electric field can increase the degree of polymerization of the polyamine monomers and polyacrylamide monomers, thereby fundamentally optimizing the formed polyamide desalination layer, giving it a dense porous network structure with a high degree of crosslinking, and thus improving the desalination and flux performance of the polyamide reverse osmosis membrane.

[0043] According to an embodiment of the present invention, step S200 includes the following steps:

[0044] S201: Contact the polysulfone-based film with an aqueous solution containing polyamine monomers.

[0045] In this step, the polysulfone-based membrane is contacted with an aqueous solution containing polyamine monomers, allowing the polyamine monomers to adhere to the surface of the polysulfone-based membrane. Subsequently, during contact with an organic solution containing polyacrylamide chloride monomers, the polyacrylamide chloride monomers undergo interfacial polymerization with the polyamine monomers to form a polyamide desalination layer. It should be noted that the method of contacting the polysulfone-based membrane with the aqueous solution containing polyamine monomers is not particularly limited; those skilled in the art can choose the appropriate method as needed, such as dip coating or slot extrusion.

[0046] According to embodiments of the present invention, the concentration of polyamine monomer in the aqueous solution can be 0.5 wt% to 5 wt%, for example, 0.5 wt%, 1 wt%, 2 wt%, 3 wt%, 4 wt%, or 5 wt%.

[0047] According to embodiments of the present invention, the polyamine monomer may include at least one of m-phenylenediamine, p-phenylenediamine, and m-phenylenediamine, preferably m-phenylenediamine. Thus, the polyamine monomer can subsequently undergo interfacial polymerization with a polyacrylamide chloride monomer in an organic phase solution to generate a polyamide desalination layer.

[0048] S202: The polysulfone-based film, after being in contact with an aqueous solution, is then contacted with an organic phase solution containing polyacrylamide chloride monomers under an applied electric field.

[0049] In this step, the polysulfone-based membrane, after contact with the aqueous solution, is brought into contact with an organic phase solution containing polyacrylamide chloride monomers under an applied electric field. This allows the polyacrylamide chloride monomers to undergo interfacial polymerization with the polyamine monomers attached to the surface of the polysulfone-based membrane, generating a polyamide desalination layer. The applied electric field enhances the polymerization reaction of the polyamine and polyacrylamide monomers, thereby fundamentally optimizing the polyamide desalination layer and resulting in a dense, porous network structure with high crosslinking degree, thus improving the desalination and flux performance of the polyamide reverse osmosis membrane. The method of contacting the polysulfone-based membrane with the organic phase solution containing polyacrylamide chloride monomers is not particularly limited; those skilled in the art can choose according to their needs, for example, by dip coating or slot extrusion.

[0050] According to embodiments of the present invention, the strength of the electric field is not less than 20 V / cm. The inventors have found that when the applied electric field strength is less than 20 V / cm, the polymerization degree of the polyamine monomers and polyacrylamide chloride monomers is not significantly improved, and the effect of improving the crosslinking degree of the polyamide desalination layer cannot be achieved. In this invention, by controlling the applied electric field strength within the above-mentioned range, the polymerization degree of the polyamine monomers and polyacrylamide chloride monomers can be significantly improved, thereby giving the polyamide desalination layer a dense porous network structure with a high degree of crosslinking, thus improving the desalination and flux performance of the polyamide reverse osmosis membrane.

[0051] According to embodiments of the present invention, the concentration of polyacrylamide chloride monomer in the organic phase solution is 0.01 wt% to 0.5 wt%, for example, it can be 0.01 wt%, 0.05 wt%, 0.1 wt%, 0.2 wt%, 0.3 wt%, 0.4 wt%, or 0.5 wt%.

[0052] According to embodiments of the present invention, the polyacrylamide chloride monomer includes at least one of pyromellitic chloride, pyromellitic dimethyl chloride, phthaloyl chloride, and terephthaloyl chloride, preferably pyromellitic chloride. Thus, the polyacrylamide chloride monomer can undergo interfacial polymerization with the polyamine monomer attached to the surface of the polysulfone-based film to generate a polyamide desalination layer.

[0053] According to embodiments of the present invention, the solvent in the organic phase solution includes at least one of n-hexane, ethylcyclohexane, cyclohexane, and isoalkanes, thereby enabling better dissolution of polyacrylamide chloride monomers.

[0054] S203: Heat treatment and post-treatment of polysulfone-based films after contact with organic phase solutions.

[0055] In this step, the polysulfone-based membrane after contact with the organic phase solution is subjected to heat treatment and post-treatment to allow the polyacrylamide monomers and polyamine monomers attached to the surface of the polysulfone-based membrane to undergo a full interfacial polymerization reaction, and unreacted monomers are removed through post-treatment.

[0056] According to an embodiment of the present invention, the heat treatment temperature can be 40°C to 100°C, for example, 40°C, 50°C, 60°C, 70°C, 80°C, 90°C, or 100°C, which can facilitate the full interfacial polymerization reaction between polyacrylamide monomers and polyamine monomers.

[0057] According to embodiments of the present invention, post-treatment may include acid washing, water washing, glycerol soaking, and drying. Specifically, acid washing can remove unreacted polyamine monomers. According to some specific embodiments of the present invention, the acid washing temperature can be between 10°C and 100°C, for example, 10°C, 20°C, 30°C, 40°C, 50°C, 60°C, 70°C, 80°C, 90°C, and 100°C. The inventors have found that when the temperature is below 10°C, the acid has low reactivity with the polyamine monomers, making it difficult to achieve a good neutralization reaction; when the temperature is above 100°C, it easily damages the nascent polyamide reverse osmosis membrane. The present invention, by controlling the acid washing temperature within the above-mentioned range, not only facilitates the effective removal of unreacted polyamine monomers but also avoids damage to the nascent polyamide reverse osmosis membrane. According to some specific embodiments of the present invention, the specific composition of the acid used in acid washing is not particularly limited; for example, the acid used may include at least one of citric acid, oxalic acid, hydrochloric acid, sulfuric acid, and phosphoric acid, preferably sulfuric acid.

[0058] Furthermore, the acid concentration can be from 1 wt% to 30 wt%, for example, 1 wt%, 5 wt%, 10 wt%, 15 wt%, 20 wt%, 25 wt%, and 30 wt%. The inventors have found that when the acid concentration is below 1%, the reactivity with the polyamine monomer is poor, resulting in poor amine washing effect; when the acid concentration is above 30%, the acidity is too strong, easily damaging the nascent polyamide reverse osmosis membrane. This invention, by controlling the acid concentration within the above-mentioned range, not only further facilitates obtaining a better amine washing effect but also avoids damage to the nascent polyamide reverse osmosis membrane. It should be noted that the specific methods of water washing, glycerol soaking, and drying are not particularly limited, and those skilled in the art can choose according to their needs.

[0059] Therefore, by contacting the polysulfone-based membrane with a mixture containing polyamine monomers and polyacrylamide monomers and applying an electric field, the polyamide desalination layer can be fundamentally optimized to obtain a dense porous network structure with high crosslinking degree, thereby improving the desalination and flux performance of the polyamide reverse osmosis membrane. In addition, this method has the characteristics of strong controllability, obvious optimization effect, low cost and simple operation, thus having good application prospects.

[0060] In a second aspect, the present invention provides a polyamide reverse osmosis membrane. According to an embodiment of the invention, the polyamide reverse osmosis membrane is prepared using the method described above. Thus, the polyamide reverse osmosis membrane has a highly cross-linked polyamide desalination layer, exhibiting excellent desalination and flux performance.

[0061] The present invention will now be described with reference to specific embodiments. It should be noted that these embodiments are merely descriptive and do not limit the present invention in any way.

[0062] Comparative Example 1

[0063] (1) Preparation of polysulfone-based films

[0064] 18 wt% polysulfone, 8 wt% polyethylene glycol 200, and 74 wt% N,N-dimethylformamide were mixed and heated with stirring to obtain a completely dissolved casting solution. The casting solution was coated onto a polyester nonwoven fabric by slit extrusion and then immersed in a pure water coagulation bath at 18°C ​​for phase inversion and curing to form a film. Finally, the film was washed successively with pure water at 40°C and 60°C to obtain a polysulfone-based film.

[0065] (2) Preparation of polyamide desalination layer

[0066] 1) Dissolve appropriate amounts of m-phenylenediamine and triethylamine hydrochloride in pure water, and adjust the pH of the aqueous phase to approximately 11 with NaOH. Dissolve appropriate amounts of trimesoyl chloride in ethylcyclohexane solution to prepare an organic phase solution.

[0067] 2) Contact the polysulfone-based membrane with the aqueous solution for 20 seconds to remove excess droplets from the surface of the polysulfone-based membrane.

[0068] 3) Contact the membrane obtained in step 2) with the organic phase solution for 15 seconds to remove excess organic phase from the surface.

[0069] 4) Place the membrane obtained in step 3) into an oven at 50°C for 3 minutes to obtain a nascent polyamide reverse osmosis membrane.

[0070] 5) Soak the nascent polyamide reverse osmosis membrane in a 25°C, 1wt% sulfuric acid solution for 3 minutes, then rinse with pure water for later use.

[0071] 6) Immerse the membrane obtained in step 5) in 8wt% glycerol solution for 1 min, and finally dry it in an oven at 60℃ for 5 min to obtain a dry membrane sample.

[0072] Comparative Example 2

[0073] The polysulfone casting solution in Comparative Example 1 was changed to 16 wt% polysulfone, 8 wt% polyethylene glycol 200, and 76 wt% N,N-dimethylformamide, with the rest remaining unchanged.

[0074] Comparative Example 3

[0075] The polysulfone casting solution in Comparative Example 1 was changed to 17 wt% polysulfone, 8 wt% polyethylene glycol 200, and 75 wt% N,N-dimethylformamide, with the rest remaining unchanged.

[0076] Example 1

[0077] Compared with Comparative Example 1, an external electrostatic field of 20V / cm was applied during the 15s contact in step 3), while the rest remained unchanged.

[0078] Example 2

[0079] Compared with Comparative Example 1, an external electrostatic field of 30V / cm was applied during the 15s contact process in step 3), while the rest remained unchanged.

[0080] Example 3

[0081] Compared with Comparative Example 1, an external electrostatic field of 40V / cm was applied during the 15s contact in step 3), while the rest remained unchanged.

[0082] Example 4

[0083] Compared with Example 2, the polysulfone casting solution ratio was changed to 16 wt% polysulfone, 8 wt% polyethylene glycol 200, and 76 wt% N,N-dimethylformamide, while the rest remained unchanged.

[0084] Example 5

[0085] Compared with Example 2, the polysulfone casting solution ratio was changed to 17 wt% polysulfone, 8 wt% polyethylene glycol 200, and 75 wt% N,N-dimethylformamide, while the rest remained unchanged.

[0086] Characterization of the polyamide desalination layer structure of polyamide reverse osmosis membrane

[0087] The polyamide reverse osmosis membrane sample tested was 100 cm². 2 The microstructure of the reverse osmosis membrane polyamide desalination layer obtained in Comparative Example 1 and Example 1 was characterized by scanning electron microscopy (S-3400N, Hitachi, Japan).

[0088] Flux and rejection rate testing of polyamide reverse osmosis membranes

[0089] Cut the membrane sheet to the shape and size specified for the test plate and place it in the testing equipment. Prepare a 250 ppm sodium chloride test solution. The test conditions are: test pressure 0.48 MPa, test water temperature 25℃, and test recovery rate 15%. Calculate the water flux by measuring the permeate flow rate per unit time and per unit membrane area using an electronic balance. Calculate the rejection rate (also known as desalination rate for salt solutions) by measuring the conductivity of the permeate and feed water using a conductivity meter. Refer to GB / T 32373-2015, "Reverse Osmosis Membrane Test Methods," for specific methods.

[0090]

[0091]

[0092] The microstructures of the polyamide reverse osmosis membranes obtained in Comparative Example 1 and Example 1 are as follows: Figure 2-3 As shown, by Figure 2 and Figure 3 It can be seen that, compared with Comparative Example 1, the polyamide desalination layer structure of the polyamide reverse osmosis membrane obtained in Example 1 is more three-dimensional, the blade size is larger, and the degree of polymerization is higher. Therefore, it is beneficial to improve the desalination and flux performance of the polyamide reverse osmosis membrane.

[0093] The flux rejection performance of the polyamide reverse osmosis membranes obtained in Comparative Examples 1-3 and Examples 1-5 is shown in Table 1:

[0094] Table 1

[0095] Comparative Example 1 18 1 none 35 98.1 Comparative Example 2 16 1 none 30 98.5 Comparative Example 3 17 1 none 32 98.3 Example 1 18 1 20 38 98.5 Example 2 18 1 30 45 98.7 Example 3 18 1 40 46 98.7 Example 4 16 1 30 41 99.2 Example 5 17 1 30 42 98.9

[0096] As shown in Table 1, corresponding to the polyamide layer structure in the microstructure of the polyamide reverse osmosis membrane, the flux and retention performance of the prepared polyamide reverse osmosis membrane are improved to a certain extent in the presence of an applied electric field. According to Examples 1-5, when the applied electric field strength is greater than 20 V / cm, it has an improving effect on the flux retention performance of the polyamide reverse osmosis membrane.

[0097] In the description of this specification, the references to terms such as "one embodiment," "some embodiments," "example," "specific example," or "some examples," etc., indicate that a specific feature, structure, material, or characteristic described in connection with that embodiment or example is included in at least one embodiment or example of the present invention. In this specification, the illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments or examples. Moreover, without contradiction, those skilled in the art can combine and integrate the different embodiments or examples described in this specification, as well as the features of different embodiments or examples.

[0098] Although embodiments of the present invention have been shown and described above, it is understood that the above embodiments are exemplary and should not be construed as limiting the present invention. Those skilled in the art can make changes, modifications, substitutions and variations to the above embodiments within the scope of the present invention.

Claims

1. A method for preparing a polyamide reverse osmosis membrane, characterized in that, include: (1) Provide polysulfone-based films; (2) Dissolve the polyamine monomer in water to prepare an aqueous solution, dissolve the polyacrylamide chloride monomer in an organic solvent to prepare an organic solution, then contact the polysulfone membrane with the aqueous solution, and then contact the polysulfone membrane after contact with the aqueous solution with the organic solution under an external electric field, so that the polyacrylamide chloride monomer and the polyamine monomer attached to the surface of the polysulfone membrane undergo an interfacial polymerization reaction under an external electric field to generate a polyamide desalination layer. Finally, the polysulfone membrane after contact with the organic solution is subjected to heat treatment and post-treatment to obtain the polyamide reverse osmosis membrane. The strength of the electric field is 20V / cm to 40V / cm.

2. The method according to claim 1, characterized in that, The polyamine monomer includes at least one of m-phenylenediamine, p-phenylenediamine, and m-phenylenediamine.

3. The method according to claim 1, characterized in that, The polyacryl chloride monomer includes at least one of pyromellitic trimethylol chloride, pyromellitic dimethylol chloride, phthaloyl chloride, and terephthaloyl chloride.

4. The method according to claim 1, characterized in that, The concentration of polyamine monomer in the aqueous solution is 0.5wt%~5wt%.

5. The method according to claim 4, characterized in that, The concentration of polyamine monomers in the aqueous solution is 1wt%~4wt%.

6. The method according to claim 1, characterized in that, The concentration of polyacrylamide chloride monomer in the organic phase solution is 0.01wt%~0.5wt%.

7. The method according to claim 6, characterized in that, The concentration of polyacrylamide chloride monomer in the organic phase solution is 0.1wt%~0.3wt%.

8. The method according to claim 1, characterized in that, The post-processing includes pickling, washing, glycerin soaking, and drying.

9. The method according to claim 8, characterized in that, The pickling temperature is 10℃~100℃.

10. The method according to claim 8, characterized in that, The acid includes at least one of citric acid, oxalic acid, hydrochloric acid, sulfuric acid, and phosphoric acid.

11. The method according to claim 8, characterized in that, The concentration of the acid is 1wt% to 30wt%.

12. The method according to claim 1, characterized in that, The polysulfone-based membrane is prepared using a casting solution comprising polysulfone, a pore-forming agent, and an organic solvent.

13. The method according to claim 12, characterized in that, The concentration of polysulfone in the casting solution is 14wt%~30wt%.

14. The method according to claim 12, characterized in that, The concentration of the pore-forming agent in the casting solution is 1wt%~20wt%.

15. A polyamide reverse osmosis membrane, characterized in that, It is prepared by any one of claims 1-14.

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