A polyamide composite reverse osmosis membrane with a vesicle structure, its preparation method and application

Abstract

The present invention belongs to the technical field of water treatment membrane, and discloses a polyamide composite reverse osmosis membrane with a vesicle structure, a preparation method and an application thereof. The polyamide composite reverse osmosis membrane comprises a porous support and a polyamide layer, and the polyamide layer is located on the porous support; the polyamide layer has a vesicle structure; the ratio of the projected area of the vesicle structure to the projected area of the polyamide layer is ≥50%, and the average diameter of the vesicle structure is between 10 - 500 nm; the average pore size of the polyamide layer. The polyamide composite reverse osmosis membrane of the present invention can simultaneously have a high water permeation flux and a high salt rejection rate. The rejection rate can reach more than 99.2%, and the permeation flux can reach 66.8 - 74.8 L·m<supgt;-2< / supgt>·h<supgt;-1< / supgt>, and it can be widely applied to the industrial water treatment technology field, especially seawater desalination.

Description

Technical Field

[0001] The present invention belongs to the technical field of water treatment membranes, and particularly relates to a polyamide composite reverse osmosis membrane with a vesicle structure, a preparation method thereof, and an application thereof. Background Art

[0002] Seawater desalination is one of the important means to solve the global water shortage. Existing seawater desalination technologies can be roughly divided into two categories according to technical principles: thermal methods (or distillation methods, evaporation methods) and membrane methods. Among them, membrane separation technology is widely used in the field of seawater desalination due to its excellent water-salt separation ability and low energy consumption characteristics, greatly alleviating the water resource crisis. Reverse osmosis technology is usually used as the last process of membrane method seawater desalination. Commonly used reverse osmosis membranes include asymmetric cellulose acetate membranes, polyester reverse osmosis membranes, and polyamide composite reverse osmosis membranes. Among them, polyamide composite reverse osmosis membranes (Polyamide reverse osmosis membranes) have become the core materials in the reverse osmosis membrane technology for seawater desalination due to their easy preparation and strong water-salt separation ability. Polyamide composite reverse osmosis membranes usually consist of a dense polyamide layer and a porous support. The fundamental reason why polyamide composite reverse osmosis membranes can be used for water purification treatment is based on their semi-permeable membrane characteristics, that is, they can allow water molecules to pass through while blocking larger molecules or ions from passing through.

[0003] Compared with other water treatment application scenarios, in seawater desalination, the high salt content in seawater significantly increases the difficulty of seawater desalination treatment. The main salt in seawater is sodium chloride. Compared with other common salts in seawater, such as sodium sulfate, magnesium chloride, magnesium sulfate, etc., its ionic forms in water - hydrated sodium ions and hydrated chloride ions have smaller hydrated ion radii, which requires higher performance of the polyamide composite reverse osmosis membrane and is thus more difficult to remove. The salt rejection rate or desalination rate mentioned hereinafter in this article refers to the sodium chloride rejection rate. On the one hand, the polyamide composite reverse osmosis membrane needs to withstand the influence of high operating pressure and high-salt-content water bodies. On the other hand, it needs to have sufficient water production while effectively separating high levels of salts, that is, it has both a high rejection rate (Rejection) and a high permeation flux (Flux) at the same time. On the one hand, the rejection rate refers to the ability of the membrane to prevent a certain component in the feed liquid from passing through or to retain a certain component therein. In seawater desalination, it refers to the ability to retain salts in seawater. The permeation flux refers to the volume of water passing through a unit membrane area per unit time under a unit pressure. It is well known in the industry that using a polyamide composite reverse osmosis membrane to treat seawater is the last process of seawater desalination, and the treated water needs to meet the requirements of drinking water. Therefore, the higher the rejection rate of the polyamide composite reverse osmosis membrane for salt components, the better. The higher the rejection rate, the better the seawater desalination effect. Currently, the salt rejection rate of seawater desalination in the industry must reach more than 99% to ensure effective salt removal and meet the safety requirements of drinking water. On the other hand, on the premise of ensuring that the salt rejection rate meets the requirements, the higher the water permeation flux, the better, which can greatly improve the water treatment efficiency and reduce energy consumption.

[0004] However, improving the rejection rate of existing polyamide composite reverse osmosis membranes often comes at the expense of the permeation flux. Therefore, there is a problem of low water permeation flux under the premise of achieving the required high rejection rate (CN116832626A). The high rejection rate described in the present invention means that the rejection rate reaches more than 99%. Only when such a rejection rate is met can the requirements of seawater desalination be satisfied. It is clearly reported in Chinese Patent CN104781001B that there is an antagonistic relationship between the desalination rate (also known as the rejection rate) and the permeation flux property. It is not feasible to prepare a water treatment membrane with excellent desalination rate and high permeation flux in practice. This is because the water treatment process of polyamide composite reverse osmosis membranes is based on the solution-diffusion theory. Water molecules and solute molecules diffuse through the dense polymer membrane independently, but the rejection of solutes is achieved through the competition between water transport and solute transport. Therefore, the improvement of the rejection rate often comes at the expense of the permeation flux (Yang Z, Guo H, Tang C Y. The upper bound of thin-film composite (TFC) polyamide membranes for desalination [J]. Journal of Membrane Science, 2019, 590: 117297.). In the separation performance test of polyamide reverse osmosis membranes, with a slight increase in the rejection rate, the permeation flux will decrease significantly. For example, for the polyamide reverse osmosis membrane disclosed in Chinese Patent CN114534491A, according to the data in Table 1, Example 2 and Example 3, its sodium chloride rejection rate increased from 98.8% to 99.1%, but its water flux decreased from 61.2 L·m -2 ·h -1 to 48.6 L·m -2 ·h -1 . The sodium chloride rejection rate only increased by 0.3%, but the water flux decreased by 12.6 L·m -2 ·h -1 . The reason is that a slight increase in the rejection rate will lead to a significant enhancement of the concentration polarization effect, resulting in a sharp increase in the loss of the effective driving force and a large decrease in the permeation flux. Therefore, when the rejection rate of existing polyamide reverse osmosis composite membranes reaches more than 99%, the permeation flux is poor. For example, Dow Chemical, a leading enterprise highly representative in the industry, its existing commercial polyamide composite reverse osmosis membranes for seawater desalination have a water permeation flux lower than 40 L·m -2 ·h -1 (FILMTECTM Reverse Osmosis and Nanofiltration Membrane Element Product and Technology Manual (2022 Edition), https: / / www.dow.com / )。In addition, for the reverse osmosis membrane for seawater desalination in Chinese Patent CN116832626A, according to the data recorded in Table 1 of this document, its salt rejection rate (also known as the retention rate) is above 99%, but its water permeation flux only reaches a maximum of 59.6 L·m -2 ·h -1 。

[0005] Therefore, in the application of existing polyamide composite reverse osmosis membranes in seawater desalination, the problem of low water permeation flux cannot be solved under the premise of meeting a high retention rate (that is, the retention rate reaches above 99%), that is, the performance of high retention rate and high permeation flux cannot be achieved simultaneously. Summary of the Invention

[0006] Aiming at the problems of the prior art, the present invention provides a polyamide composite reverse osmosis membrane with a vesicle structure, its preparation method and application, and unexpectedly obtains a polyamide composite reverse osmosis membrane with a specific morphological structure, mainly characterized by a vesicle structure, precisely controlling the size and projected area of the vesicle structure, overcoming the technical prejudice in the prior art that a polyamide composite reverse osmosis membrane with a fully developed leaf structure is required to have a high permeation flux. Specifically, the polyamide composite reverse osmosis membrane has a high proportion of vesicle structures. Through the synergistic effect of the specific projected area, specific diameter of the polyamide vesicle structure, and the average pore size of the specific polyamide layer, on the one hand, the compactness of the polyamide composite reverse osmosis membrane is greatly improved and the salt rejection rate is significantly increased, and on the other hand, it has a relatively high effective permeation area and the water permeation flux is increased, so that the polyamide composite reverse osmosis membrane of the present invention can simultaneously have a high water permeation flux and a high salt rejection rate. The retention rate of the polyamide composite reverse osmosis membrane can reach above 99.2%, and the permeation flux can reach 66.8 - 74.8 L·m -2 ·h -1 , which can greatly improve the water treatment efficiency and reduce energy consumption, and can be widely applied to the industrial water treatment technology field, especially seawater desalination. The vesicle structure of the polyamide in the present invention refers to a spherical or spherical-like structure formed on the surface of the polyamide membrane, and this structure can be detected by a scanning electron microscope (SEM). Among them, the spherical-like structure refers to a geometric shape that is close to a sphere but not a perfect sphere, such as an ellipsoid; the precise quantitative method for the vesicle structure is: in the two-dimensional planar projection, the ratio of the difference between the maximum and minimum Feret diameters to the minimum Feret diameter ≤ 20%, and the structure that meets this condition is the vesicle structure. The leaf structure in the present invention refers to a leaf-like protrusion structure with irregular or wavy edges formed on the surface of the polyamide membrane, and the quantitative method for the leaf structure is: in the two-dimensional planar projection, the ratio of the difference between the maximum and minimum Feret diameters to the minimum Feret diameter > 20%.

[0007] The technical solution of the present invention is as follows:

[0008] The present invention provides a polyamide composite reverse osmosis membrane with a vesicle structure. The polyamide composite reverse osmosis membrane includes a porous support and a polyamide layer, and the polyamide layer is located on the porous support; the polyamide layer has a vesicle structure; the ratio of the projected area of the vesicle structure to the projected area of the polyamide layer is ≥ 50%, and the average diameter of the vesicle structure is between 10 - 500 nm; the average pore size of the polyamide layer is ≤

[0009] The intrinsic structure of the polyamide layer develops from polyamide clusters to small vesicles, then to large vesicles, and finally to a fully developed leaf structure as the reaction progresses. The prior art believes that: the leaf-like structure is beneficial to increasing the effective surface area for water transport, thereby contributing to enhancing the membrane flux (It is believed that the leaf-like structure can increase the effective surface area for water transport and thus contribute to the enhancement of membrane flux. Shi M, Yan W, Zhou Y, et al. Combining tannic acid-modified support and a green co-solvent for high performance reverse osmosis membranes [J]. Journal of Membrane Science, 2020, 595: 117474.). Therefore, in order to obtain a polyamide composite reverse osmosis membrane with a high permeation flux, the prior art takes the growth of a complete leaf structure as the main structural feature.

[0010] The present invention unexpectedly overcomes the technical prejudice in the prior art that a polyamide composite reverse osmosis membrane needs to have a fully developed leaf structure as the main feature to have a high permeation flux. The polyamide composite reverse osmosis membrane of the present invention unexpectedly has a vesicle structure as the main structure. By precisely controlling the morphological structure of the membrane to have a specific projected area, specific diameter of the vesicle structure, and specific average pore size of the polyamide layer, the multiple features work together. Compared with the large-area growth of a complete leaf structure in the prior art, the polyamide composite reverse osmosis membrane of the present invention has both a higher effective permeation area and denseness, enabling the polyamide composite reverse osmosis membrane of the present invention to have a high water permeation flux while maintaining a high salt rejection rate.

[0011] Preferably, the ratio of the projected area of the vesicle structure to the projected area of the polyamide layer is ≥ 70%; preferably, the ratio of the projected area of the vesicle structure to the projected area of the polyamide layer is ≥ 80%; more preferably, the ratio of the projected area of the vesicle structure to the projected area of the polyamide layer is ≥ 85%.

[0012] Preferably, the average diameter of the vesicle structure is between 50 - 300 nm; preferably, the average diameter of the vesicle structure is between 100 - 200 nm; more preferably, the average diameter of the vesicle structure is between 100 - 150 nm.

[0013] Preferably, the average pore size of the polyamide layer is ≤

[0014] Preferably, the porous support is selected from any one of polysulfone ultrafiltration membrane, polyethersulfone ultrafiltration membrane, polyacrylonitrile ultrafiltration membrane, polyvinylidene fluoride ultrafiltration membrane, polypropylene ultrafiltration membrane, polyethylene ultrafiltration membrane, polystyrene ultrafiltration membrane or polyimide ultrafiltration membrane.

[0015] Preferably, the surface pore size of the porous support is between 1 - 200 nm, and the cut-off molecular weight is between 1,000 - 500,000 Daltons.

[0016] The present invention also provides a method for preparing the polyamide composite reverse osmosis membrane as described above, and the method includes the following steps:

[0017] (1) Immerse the porous support in an aqueous solution of polyamine to obtain a wetted porous support;

[0018] (2) Place the wetted porous support in an organic solution of polyacyl chloride for a rapid primary interfacial polymerization reaction, the time of the rapid primary interfacial polymerization reaction is within 20 s, and immediately carry out a quenching reaction to obtain a primary reaction nascent polyamide composite reverse osmosis membrane; the primary reaction nascent polyamide composite reverse osmosis membrane has a vesicle structure; the ratio of the projected area of the vesicle structure to the projected area of the polyamide layer is ≥ 50%, and the average diameter of the vesicle structure is between 50 - 200 nm;

[0019] (3) Place the primary reaction nascent polyamide composite reverse osmosis membrane in an organic solution of polyacyl chloride for a secondary reaction in the organic phase to obtain a secondary reaction nascent polyamide composite reverse osmosis membrane;

[0020] (4) Heat-treat the secondary reaction nascent polyamide composite reverse osmosis membrane to obtain the polyamide composite reverse osmosis membrane;

[0021] It is well-known to those skilled in the art that in the case where the desolvation temperature is not explicitly mentioned, it is defaulted that the temperature of the rinsing solvent during the desolvation process after the interfacial polymerization reaction is the same as the temperature of the polymerization reaction, usually room temperature, and room temperature is understood as 25±5°C. The polyamide composite reverse osmosis membrane prepared in this way has been fully developed for a long time and is mainly characterized by a complete leaf structure.

[0022] Surprisingly, the present invention is different from the prior art. By using a specific low-temperature oil-phase pure solvent, precisely controlling the contact time and quenching the interfacial polymerization reaction once, the development degree of the polyamide surface morphology is precisely controlled unexpectedly, so that it stops at the stage with the vesicle structure as the main characteristic morphology, having a specific vesicle structure projection area and size. The present invention rapidly rinses the nascent polyamide composite reverse osmosis membrane once with a low-temperature oil-phase pure solvent. The low temperature can rapidly reduce the activity of the reaction monomers, and rinsing enables the unreacted monomers to be quickly removed from the membrane surface in time, thereby intercepting the reaction process and making the morphology of the polyamide composite reverse osmosis membrane stay in the vesicle stage, thus providing conditions for obtaining the polyamide composite reverse osmosis membrane with high permeation flux. Due to the precise control of the interfacial polymerization for a very short time once and the secondary reaction in the oil phase, together with the original low-temperature quenching reaction technology, the polyamide composite reverse osmosis membrane of the present invention finally has a vesicle structure with precisely controlled projection area and diameter and an average pore size of the polyamide layer within a specific range. The effective permeation area is much larger than that of the polyamide composite reverse osmosis membrane with a leaf structure, having a high water permeation flux, and at the same time greatly improving the densification degree of the polyamide composite reverse osmosis membrane. Through the overall synergistic effect of the above characteristics, a polyamide composite reverse osmosis membrane with a high water permeation flux and a greatly improved rejection rate is obtained.

[0023] It should be emphasized that the present invention precisely controls the reaction time of the present invention through a low-temperature oil-phase pure solvent, which is equivalent to the actual reaction time of the interfacial polymerization of the present invention. This is because the use of a specific low-temperature oil-phase pure solvent for rinsing can simultaneously and rapidly reduce the monomer reaction activity and remove unreacted monomers, achieving the purpose of stopping the interfacial polymerization reaction. In the traditional interfacial polymerization methods of the prior art, the interfacial polymerization reaction cannot be effectively stopped midway. Therefore, the polymerization time, reaction time, or immersion time recorded in the reaction steps is not equivalent to the actual reaction time. The means commonly used in the prior art to stop the interfacial polymerization reaction is desolvation treatment. The desolvation treatment refers to taking out the bottom film in the reaction from the acyl chloride organic monomer solution to stop the reaction, or pouring out the solution containing the acyl chloride monomer, and then using a solvent to clean the film surface to stop the interfacial polymerization reaction. However, in the prior art, the residual monomers on the bottom film after taking out will continue to react, or the solvent cleaning used is a normal-temperature solvent. In fact, during the desolvation process, the film will further grow, and the film will experience a process from an underdeveloped PA film to a fully developed PA film, and the morphological structure of the film will change accordingly; that is to say, in the existing desolvation process, the polyamide composite reverse osmosis membrane does not stop growing, and the interfacial polymerization reaction does not really stop. Therefore, there are obvious differences between the polymerization time, reaction time, and immersion time recorded in the reaction steps of the prior art and the reaction time of the present invention. For example, the polymerization time recorded in the prior art is 30 s. When rinsing with a normal-temperature solvent, the polymerization reaction does not really stop, and its actual polymerization reaction time is much longer than 30 s (see Comparative Examples 1-4 of the present invention).

[0024] Preferably, in step (1), the porous support is cleaned with deionized water.

[0025] Preferably, in step (1), the polyamine is at least one of ethylenediamine, m-phenylenediamine, and diethylenetriamine.

[0026] Preferably, in step (1), the concentration of the polyamine in the aqueous solution is 1.0-10.0 wt%.

[0027] Preferably, in step (1), the soaking time is 10 s-30 min.

[0028] Preferably, in step (2), the temperature of the quenching reaction is low temperature, and the low temperature is ≤ 10 °C; more preferably, the method of immediately performing the quenching reaction is to immediately remove the polyacyl chloride oil phase solution and rinse it with a low-temperature oil phase pure solvent to stop the reaction. The low-temperature oil phase pure solvent is an oil phase pure solvent with a temperature ≤ 10 °C, immiscible with water, and capable of dissolving polyacyl chloride monomers; more preferably, the temperature of the low-temperature oil phase pure solvent is -30 to 10 °C; more preferably, the temperature of the low-temperature oil phase pure solvent is -5 °C; more preferably, the time for rinsing with the low-temperature oil phase pure solvent is 30 s - 5 min;

[0029] Preferably, in step (2), the reaction time is 2 - 20 s; more preferably, the reaction time is 5 - 20 s; more preferably, the reaction time is 5 - 10 s;

[0030] Preferably, in steps (2) and (3), the polyacyl chloride is at least one of trimellitic acid trichloride, terephthaloyl chloride, and isophthaloyl chloride;

[0031] Preferably, in steps (2) and (3), the concentration of polyacyl chloride in the oil phase solution is 0.01 - 10.0 wt%;

[0032] Preferably, in steps (2) and (3), the oil phase solvent is at least one of n-hexane, cyclohexane, n-heptane, toluene, benzene, Isopar G, Isopar E, Isopar H, Isopar L, and Isopar M;

[0033] Preferably, in step (2), the temperature of the first interfacial polymerization reaction is room temperature; more preferably, the temperature of the first interfacial polymerization reaction is 25 ± 5 °C;

[0034] Preferably, in step (3), the oil phase secondary reaction uses the low-temperature oil phase pure solvent to stop the reaction; more preferably, the temperature of the low-temperature oil phase pure solvent is -30 to 10 °C; more preferably, the temperature of the low-temperature oil phase pure solvent is -5 °C;

[0035] Preferably, in step (3), the temperature of the oil phase secondary reaction is room temperature; more preferably, the temperature of the oil phase secondary reaction is 25 ± 5 °C;

[0036] Preferably, in step (3), the reaction time of the oil phase secondary reaction is 5 s - 10 min; more preferably, the reaction time of the oil phase secondary reaction is 5 s - 2 min;

[0037] Preferably, in step (4), the method of heat treatment is heating in a water bath or an oven; more preferably, the temperature of the heat treatment is 30 - 120 °C, and the time of the heat treatment is 2 - 20 min.

[0038] The present invention also provides a membrane module, wherein the membrane module comprises the polyamide composite reverse osmosis membrane as described above or the polyamide composite reverse osmosis membrane prepared by the preparation method as described above.

[0039] The present invention also provides a water treatment device, wherein the water treatment device comprises the membrane module as described above.

[0040] Applications of the polyamide composite reverse osmosis membrane as described above, the polyamide composite reverse osmosis membrane prepared by the preparation method as described above, the membrane module as described above, and the water treatment device as described above in the water treatment process; preferably, the water treatment is seawater desalination.

[0041] Furthermore, the method of the application is: testing the permeation flux and rejection rate of the polyamide composite reverse osmosis membrane under the conditions of a temperature of 25 °C, a feed liquid of 32000 ppm sodium chloride solution, and a pressure of 55.2 bar; more preferably, the permeation flux of the polyamide composite reverse osmosis membrane is 66.8 - 74.8 L·m -2 ·h -1 , and the rejection rate is more than 99.2%.

[0042] Furthermore, the water treatment component or device can be any component or device installed with the polyamide composite reverse osmosis membrane of the present invention that can be applied to the water treatment process. Preferably, the component can be, for example, a spiral wound membrane module, a tubular membrane module, a flat sheet membrane module, etc. The device can be, for example, a household / commercial reverse osmosis water purifier, an industrial boiler feed water reverse osmosis pure water device, an industrial intermediate water reuse reverse osmosis device, and a seawater desalination device, etc.

[0043] Furthermore, the water treatment component is a spiral wound reverse osmosis membrane element, which includes a central pipe, reverse osmosis membrane sheets, a feed water diversion net, and a pure water diversion net. The reverse osmosis membrane sheets include the polyamide composite reverse osmosis membrane as described above in the present invention or the polyamide composite reverse osmosis membrane prepared by the preparation method as described above. Specifically, the spiral wound reverse osmosis membrane element is formed by winding a water purification membrane sheet group composed of superposed reverse osmosis membrane sheets, a feed water diversion net, and a pure water diversion net around a central water production pipe. Among them, the reverse osmosis membrane sheets are folded, the feed water diversion net is located in the feed water flow channel formed between the inner surfaces after folding of the reverse osmosis membrane sheets, the pure water diversion net is located in the product water flow channel formed between the outer surfaces after folding of the reverse osmosis membrane sheets, and the spiral wound reverse osmosis membrane element glues the two side edges of the end face of the product water flow channel and the side edge far from the central water production pipe with glue so that the product water flow channel has an opening facing the central water production pipe. After the water purification membrane sheet group is wound around the central water production pipe, the entire outer surface is wrapped and sealed with an outer tape. The working process of the spiral wound reverse osmosis element is as follows: the feed liquid flows into the feed water flow channel from one end face of the element, a part of the water is filtered by the reverse osmosis membrane sheets to form pure water and flows into the central water production pipe along the pure water diversion net, and the remaining concentrated water that is not filtered flows out from the other end face of the element along the feed water diversion net in the feed water flow channel.

[0044] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0045] (1) For the polyamide composite reverse osmosis membrane described in the present invention, a polyamide composite reverse osmosis membrane with a specific morphological structure is unexpectedly obtained, which is mainly characterized by a vesicle structure, and the size and projected area of the vesicle structure are precisely controlled, overcoming the technical prejudice in the prior art that a polyamide composite reverse osmosis membrane needs to be mainly characterized by a fully developed leaf structure to have a high permeation flux. Specifically, the polyamide composite reverse osmosis membrane has a high proportion of vesicle structures. Through the synergistic effect of the specific projected area, specific diameter of the vesicle structure, and the average pore size of the polyamide layer, on the one hand, the compactness of the polyamide composite reverse osmosis membrane is greatly improved and the salt rejection rate is significantly increased, and on the other hand, it has a relatively high effective permeation area and the water permeation flux is increased, so that the polyamide composite reverse osmosis membrane of the present invention can simultaneously have a high water permeation flux and a high salt rejection rate. The rejection rate of the polyamide composite reverse osmosis membrane is above 99.2%, and the permeation flux is 66.8 - 74.8 L·m -2 ·h -1 , which can greatly improve the water treatment efficiency and reduce energy consumption, and can be widely applied to the industrial water treatment technology field, especially seawater desalination.

[0046] (2) Due to the precise control of the interfacial polymerization in an extremely short time and the secondary reaction in the oil phase, combined with the original low-temperature quenching reaction technology, the present invention unexpectedly and precisely regulates the development degree of the polyamide surface morphology, making it stop at the stage where the vesicle structure is the main characteristic morphology. The vesicle structure has a specific projected area and size. Finally, the polyamide composite reverse osmosis membrane of the present invention has vesicles with precisely regulated projected area and diameter and an average pore size of the polyamide layer within a specific range. The effective permeation area is much larger than that of the polyamide composite reverse osmosis membrane with a leaf structure, and it has a high water permeation flux. At the same time, the compactness of the polyamide composite reverse osmosis membrane is greatly improved. Through the overall synergistic effect of the above characteristics, a polyamide composite reverse osmosis membrane with a high water permeation flux and a greatly improved rejection rate is obtained. The method of the present invention has low equipment requirements, a simple and easy process flow, and is convenient for improvement on the basis of the traditional polyamide composite reverse osmosis membrane preparation process to realize large-scale production. Description of the Drawings

[0047] Figure 1 Schematic diagram of the experimental operation process for Examples 1 - 8.

[0048] Figure 2 Schematic diagram of the experimental operation process for Comparative Example 1.

[0049] Figure 3 SEM surface morphology diagram of the polyamide composite reverse osmosis membrane in Example 1.

[0050] Figure 4 SEM surface morphology diagram of the polyamide composite reverse osmosis membrane in Comparative Example 1.

[0051] Figure 5 SEM surface morphology diagram of the polyamide composite reverse osmosis membrane in Comparative Example 2.

[0052] Figure 6 SEM surface morphology diagram of the polyamide composite reverse osmosis membrane in Comparative Example 3.

[0053] Figure 7 Glancing incidence wide-angle X-ray scattering diagram of Example 1 and Comparative Example 1. Detailed Description of the Invention

[0054] In the description of the present invention, it should be noted that the orientation or positional relationship indicated by the terms "upper", "lower", "left", "right", "vertical", "parallel", "inner", "outer", "front", "rear", etc. is based on the orientation or positional relationship shown in the drawings. It is only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation. Therefore, it should not be construed as a limitation to the present invention. The present invention will be further illustrated below in conjunction with the drawings and embodiments. It should be understood that these embodiments are only used to illustrate the present invention and not to limit the scope of the present invention.

[0055] All water purification treatment processes, such as ultrapure water preparation, brackish water desalination, and seawater desalination, essentially utilize the intrinsic structure of the membrane. Based on its semi-permeable membrane characteristics, water molecules are allowed to pass through while larger molecules or ions are blocked. The commonly used indicators in the industry to characterize the water purification treatment ability of polyamide composite reverse osmosis membranes are the permeation flux and the rejection rate. These two indicators are precisely determined by the intrinsic structure of the polyamide layer. Specifically, the effective permeation area on the surface of the polyamide layer determines the water permeation flux of the polyamide composite reverse osmosis membrane, and the internal compactness of the polyamide layer affects the salt rejection rate of the polyamide composite reverse osmosis membrane. The polyamide composite reverse osmosis membrane described in the present invention includes a porous support and a specific polyamide layer. The polyamide layer has a high proportion of vesicle structures. Through the synergistic effect of precisely controlling the specific projected area, specific diameter of the vesicle structure, and the average pore size of the specific polyamide layer, the polyamide composite reverse osmosis membrane of the present invention, on the one hand, has a relatively high effective permeation area, thus improving the water permeation flux, and on the other hand, greatly improving the compactness of the polyamide composite reverse osmosis membrane, thus significantly improving the salt rejection rate. Therefore, the polyamide composite reverse osmosis membrane of the present invention is applicable to all water purification treatment processes.

[0056] The detection method of the present invention is as follows:

[0057] The method for determining the vesicle structure and detecting and calculating the ratio of the projected area of the vesicle structure to the projected area of the polyamide layer is as follows: Take a scanning electron microscope morphology image of the surface of the obtained polyamide composite reverse osmosis membrane sample. First, observe the spherical or quasi-spherical structures formed on the membrane surface, and then use the Image Pro Plus software to automatically track the contour of the object of study in the image to extract the target object. The ratio of the difference between the maximum and minimum Feret diameters of the target object to the minimum Feret diameter ≤ 20% is identified as the vesicle structure; Count the identified vesicle structures in the obtained morphology image, calculate the ratio of the projected area of the vesicle structure to the projected area of the polyamide layer, and count the average diameter of the vesicle structures. The test parameters of the scanning electron microscope of the present invention are: the acceleration voltage is 2 - 15 kV, the emission current is 5 - 15 μA, and the working distance is 3 - 15 mm.

[0058] The detection and calculation method of the average pore size is as follows: the peak position (Q) of the diffraction signal of the polyamide layer is obtained by a grazing incidence wide-angle X-ray scattering instrument, and the average pore size of the polyamide layer is calculated by the Bragg equation.

[0059] The detection method for the surface pore size of the porous support is as follows: the surface pore size of the porous support is obtained by taking a scanning electron microscope image of the surface of the porous support.

[0060] The detection method for the cut-off molecular weight is as follows: a series of standard solutes with known molecular weights are used to test the rejection ability of the porous support for these solutes, and the cut-off molecular weight of the porous support is obtained.

[0061] The detection method for the permeation flux and rejection rate:

[0062] Test with sodium chloride salt. Under the conditions of a temperature of 25 °C, a feed solution of 32000 ppm sodium chloride solution, and a pressure of 55.2 bar, the permeation flux and rejection rate of the polyamide composite reverse osmosis membrane are tested.

[0063] Example 1

[0064] Using a commercial polysulfone ultrafiltration membrane as the porous support membrane, pour an aqueous solution containing 2 wt% m-phenylenediamine onto the surface of the reactive support membrane. After contacting and standing for 10 min, pour out the excess solution and remove the residual liquid on the surface. Subsequently, pour an Isopar G solution containing 0.1 wt% trimesoyl chloride onto the membrane surface for an interfacial polymerization reaction. After reacting for 10 seconds, pour out the excess solution and use a 0 °C low-temperature pure Isopar G solution to rinse the membrane surface for 3 min to remove the residual liquid on the surface to terminate the reaction, obtaining a primary reaction nascent polyamide composite reverse osmosis membrane; then pour an Isopar G solution containing 0.1 wt% trimesoyl chloride onto the surface of the above primary reaction nascent polyamide composite reverse osmosis membrane for a secondary oil-phase reaction. After reacting for 50 seconds, pour out the excess solution and use a 0 °C low-temperature pure Isopar G solution to rinse the membrane surface for 3 min to remove the residual liquid on the surface to terminate the reaction, obtaining a secondary reaction nascent polyamide composite reverse osmosis membrane; then heat-treat the secondary reaction nascent polyamide composite reverse osmosis membrane in an oven at 80 °C for 10 min to obtain the polyamide composite reverse osmosis membrane. For the schematic diagram of the preparation method steps, see Figure 1 Take a scanning electron microscope morphology image of the surface of the obtained polyamide composite reverse osmosis membrane sample, as shown in Figure 3As shown, it can be seen that the surface of Example 1 is basically covered by vesicle structures. Representative vesicle structures have been circled in the figure, where the red color represents the vesicle structures and the blue color represents the leaf structures. In the morphological map obtained by statistical analysis using Image Pro Plus software, the ratio of the projected area of the vesicle structures to the projected area of the polyamide layer is 83.2%, and the average diameter of the vesicle structures is 111.4 nm. Using a grazing incidence wide-angle X-ray scattering instrument, the polyamide composite reverse osmosis membrane shows a scattering peak near (as shown in Figure 7 ), and the average pore size of the corresponding polyamide nano-separation layer is

[0065] The polyamide composite reverse osmosis membrane prepared in Example 1 was tested for its permeability and salt rejection rate under the conditions of a temperature of 25 °C, a feed solution of 32,000 ppm sodium chloride solution, and a pressure of 55.2 bar. The results show that the water permeation flux is 72.6 L·m -2 ·h -1 , and the sodium chloride rejection rate is 99.5%.

[0066] Example 2

[0067] Example 2 referred to the preparation method and detection method of Example 1, except that the first interfacial polymerization reaction was stopped by rinsing with a low-temperature oil-phase pure solvent after reacting for 2 s; for the polyamide composite reverse osmosis membrane obtained in Example 2, the ratio of the projected area of the vesicle structures to the projected area of the polyamide layer is 86.6%, the average diameter of the vesicle structures is 73.4 nm, and the average pore size of the polyamide nano-separation layer is Testing the permeability and salt rejection rate of the polyamide composite reverse osmosis membrane of this example, the results show that the water permeation flux is 68.2 L·m -2 ·h -1 , and the sodium chloride rejection rate is 99.7%.

[0068] Example 3

[0069] Example 3 referred to the preparation method and detection method of Example 1, except that the first interfacial polymerization reaction was stopped by rinsing with a low-temperature oil-phase pure solvent after reacting for 20 s; for the polyamide composite reverse osmosis membrane obtained in Example 3, the ratio of the projected area of the vesicle structures to the projected area of the polyamide layer is 52.1%, the average diameter of the vesicle structures is 142.5 nm, and the average pore size of the polyamide nano-separation layer is Testing the permeability and salt rejection rate of the polyamide composite reverse osmosis membrane of this example, the results show that the water permeation flux is 74.8 L·m -2 ·h -1 , and the sodium chloride rejection rate is 99.3%.

[0070] Example 4

[0071] Example 4 Referring to the preparation method and detection method of Example 1, the difference is that the low-temperature oil-phase pure solvent used is n-hexane at 1°C. The ratio of the projected area of the vesicle structure of the polyamide composite reverse osmosis membrane obtained in Example 4 to the projected area of the polyamide layer is 80.8%, the average diameter of the vesicle structure is 113.8 nm, and the average pore size of the polyamide nano-separation layer is The permeability and salt rejection rate of the polyamide composite reverse osmosis membrane of this example were tested. The results showed that the water permeation flux was 70.4 L·m -2 ·h -1 , and the sodium chloride rejection rate was 99.6%.

[0072] Example 5

[0073] Example 5 Referring to the preparation method and detection method of Example 1, the difference is that the low-temperature oil-phase pure solvent used is Isopr E solvent at 1°C. The ratio of the projected area of the vesicle structure of the polyamide composite reverse osmosis membrane obtained in Example 5 to the projected area of the polyamide layer is 83.5%, the average diameter of the vesicle structure is 112.3 nm, and the average pore size of the polyamide nano-separation layer is The permeability and salt rejection rate of the polyamide composite reverse osmosis membrane of this example were tested. The results showed that the water permeation flux was 73.8 L·m -2 ·h -1 , and the sodium chloride rejection rate was 99.5%.

[0074] Example 6

[0075] Example 6 Referring to the preparation method and detection method of Example 1, the difference is that the low-temperature oil-phase pure solvent used is Isopr G solvent at -30°C. The ratio of the projected area of the vesicle structure of the polyamide composite reverse osmosis membrane obtained in Example 6 to the projected area of the polyamide layer is 88.2%, the average diameter of the vesicle structure is 60.6 nm, and the average pore size of the polyamide nano-separation layer is The permeability and salt rejection rate of the polyamide composite reverse osmosis membrane of this example were tested. The results showed that the water permeation flux was 74.2 L·m -2 ·h -1 , and the sodium chloride rejection rate was 99.2%.

[0076] Example 7

[0077] Example 7 Referring to the preparation method and detection method of Example 1, the difference is that the low-temperature oil-phase pure solvent used is Isopr G solvent at 10°C. The ratio of the projected area of the vesicle structure of the polyamide composite reverse osmosis membrane obtained in Example 7 to the projected area of the polyamide layer is 50.3%, the average diameter of the vesicle structure is 100.2 nm, and the average pore size of the polyamide nano-separation layer is The permeability and salt rejection rate of the polyamide composite reverse osmosis membrane of this example were tested. The results showed that the water permeation flux was 70.1 L·m -2 ·h -1 , and the sodium chloride rejection rate was 99.6%.

[0078] Example 8

[0079] Example 8 referred to the preparation method and detection method of Example 1. The difference was that the oil phase solution used was an Isopar G solution of 0.5 wt% trimellitic acid chloride. The ratio of the projected area of the vesicle structure of the polyamide composite reverse osmosis membrane obtained in Example 8 to the projected area of the polyamide layer was 66.7%, the average diameter of the vesicle structure was 83.9 nm, and the average pore size of the polyamide nano-separation layer was The permeability and salt rejection rate of the polyamide composite reverse osmosis membrane of this example were tested. The results showed that the water permeation flux was 66.8 L·m -2 ·h -1 , and the sodium chloride rejection rate was 99.7%.

[0080] Comparative Example 1

[0081] Comparative Example 1 referred to the preparation method and detection method of Example 1. The only difference was that the step of using the Isopar G solution of 0.1 wt% trimellitic acid chloride for the second oil phase secondary reaction and the step of rinsing the membrane surface with the 0°C low-temperature pure Isopar G solution for the second time were omitted. See the schematic diagram of the preparation method steps in Figure 2 . A scanning electron microscope morphology image was taken of the surface of the obtained polyamide composite reverse osmosis membrane sample. As Figure 4 shown, it can be seen that the surface of Comparative Example 1 was basically covered by the vesicle structure, which was due to the termination reaction of Comparative Example 1 when the vesicle was the main morphology. The ratio of the projected area of the vesicle structure of the polyamide composite reverse osmosis membrane obtained in Comparative Example 1 to the projected area of the polyamide layer was 85.1%, the average diameter of the vesicle structure was 103.8 nm, and the average pore size of the polyamide nano-separation layer was The permeability and salt rejection rate of the polyamide composite reverse osmosis membrane of this comparative example were tested. The results showed that the water permeation flux was 80.5 L·m -2 ·h -1 , and the sodium chloride rejection rate was 96.8%.

[0082] Comparative Example 2

[0083] Comparative Example 2 referred to the preparation method and detection method of Example 1. The differences were that the contact time of the first interfacial polymerization reaction was 60 s and the step of using the Isopar G solution of 0.1 wt% trimellitic acid chloride for the second oil phase secondary reaction was omitted. A scanning electron microscope morphology image was taken of the surface of the obtained polyamide composite reverse osmosis membrane sample. As Figure 5As shown, it can be seen that the surface of Comparative Example 2 is basically covered by the leaf structure. The ratio of the projected area of the vesicle structure of the polyamide composite reverse osmosis membrane obtained in Comparative Example 2 to the projected area of the polyamide layer is 22.4%, the average diameter of the vesicle structure is 71.8 nm, and the average pore size of the polyamide nano-separation layer is The permeability and salt rejection rate of the polyamide composite reverse osmosis membrane of this comparative example were tested. The results showed that the water permeation flux was 73.4 L·m -2 ·h -1 , and the sodium chloride rejection rate was 98.2%.

[0084] Comparative Example 3

[0085] Comparative Example 3 referred to the preparation method and detection method of Example 1. The only difference was that the first interfacial polymerization reaction was stopped by rinsing with a low-temperature oil-phase pure solvent at 0 °C when the contact time was 30 s. A scanning electron microscope morphology image of the surface of the obtained polyamide composite reverse osmosis membrane sample was taken, as Figure 6 shown. It can be seen that the surface of Comparative Example 3 is basically covered by the leaf structure. The ratio of the projected area of the vesicle structure of the polyamide composite reverse osmosis membrane obtained in Comparative Example 3 to the projected area of the polyamide layer is 35.2%, the average diameter of the vesicle structure is 72.3 nm, and the average pore size of the polyamide nano-separation layer is The permeability and salt rejection rate of the polyamide composite reverse osmosis membrane of this comparative example were tested. The results showed that the water permeation flux was 75.5 L·m -2 ·h -1 , and the sodium chloride rejection rate was 97.9%. From the comparison of the SEM surface morphology image of the polyamide composite reverse osmosis membrane of Comparative Example 3 ( Figure 6 ) and the SEM surface morphology image of the polyamide composite reverse osmosis membrane of Example 1 ( Figure 3 ), it can be seen that the interfacial polymerization reaction time of Comparative Example 3 is long, and the surface morphology of the obtained polyamide composite reverse osmosis membrane is mainly leaf structure, while the surface morphology of Example 1 is mainly vesicle structure.

[0086] Comparative Example 4

[0087] Comparative Example 4 referred to the preparation method and detection method of Example 1. The only difference was that after 10 s of the first interfacial polymerization reaction, it was rinsed with 25 °C Isopar G solvent to stop the first interfacial polymerization reaction; due to the fact that the solvent at room temperature could not effectively stop the polymerization reaction in Comparative Example 4, the actual reaction time was prolonged. The ratio of the projected area of the vesicle structure of the obtained polyamide composite reverse osmosis membrane to the projected area of the polyamide layer was 25.4%, the average diameter of the vesicle structure was 92.3 nm, and the average pore size of the polyamide nano-separation layer was The permeability and salt rejection rate of the polyamide composite reverse osmosis membrane of this comparative example were tested. The results showed that the water permeation flux was 38.2 L·m -2 ·h-1 , the sodium chloride rejection rate is 99.4%.

[0088] The water permeation flux and salt (sodium chloride) rejection rate of the polyamide composite reverse osmosis membranes obtained in Examples 1-8 and Comparative Examples 1-4 were tested under the conditions of a temperature of 25 °C, a feed liquid of a sodium chloride solution at 32000 ppm, and a pressure of 55.2 bar, and are shown in Table 1.

[0089] Table 1 Summary of experimental results of the structural characteristics and separation performance of polyamide composite reverse osmosis membranes

[0090]

[0091] According to the above results, it can be seen that Examples 1-8 have a relatively high permeation flux, and their permeation flux is above 66.8 L·m -2 ·h -1 or more, and more preferably up to 74.8 L·m -2 ·h -1 , and the rejection rate is above 99.2%, meeting the requirement that the rejection rate of polyamide reverse osmosis membranes for seawater desalination needs to be above 99%. Although Comparative Examples 1-3 have a relatively high permeation flux, the rejection rate of the polyamide reverse osmosis membranes is lower than 99%. In addition, it should be emphasized that although the permeation fluxes of Comparative Examples 2 and 3 are relatively high and the rejection rate seems to be not much different from 99%, due to the antagonistic relationship between the rejection rate and the permeation flux properties, a small increase in the rejection rate will cause a large decrease in the permeation flux. Therefore, a small numerical difference in the rejection rate actually has a great impact (see the reason explanation in the background technology); although the rejection rate of Comparative Example 4 is above 99%, the permeation flux is significantly low.

[0092] From the water permeation flux and salt rejection rate data of Example 1 and Comparative Example 1 in Table 1 and Figure 3 , Figure 4 it can be seen that compared with Comparative Example 1, the polyamide composite reverse osmosis membrane after the oil-phase secondary reaction in Example 1 has a vesicular surface morphology similar to that of the polyamide composite reverse osmosis membrane with a shorter time of the primary interfacial polymerization reaction. Therefore, the difference in their permeation fluxes is not significant. However, the sodium chloride rejection rate of Example 1 is significantly higher than that of Comparative Example 1. This is because the oil-phase secondary reaction regulates the later reaction process of interfacial polymerization, resulting in a significant increase in the crosslinking degree of the polyamide composite reverse osmosis membrane after the oil-phase secondary reaction. The increase in the crosslinking degree restricts the movement and swelling of molecular chain segments, reduces the free volume between polyamide molecular chains, and thus increases the density of the polyamide nanofilm.

[0093] From the water permeation flux and salt rejection rate data of Example 1 and Comparative Example 2 in Table 1 and Figure 3 , Figure 5It can be seen that, compared with Comparative Example 2, Example 1 can further significantly improve the salt rejection rate on the premise that the permeation flux is maintained at a high level.

[0094] It can be seen from Comparative Example 3 that the time of the first interfacial polymerization needs to be precisely controlled. Even if the time of the first interfacial polymerization exceeds 20 s, a fully developed leaf structure has been formed in the interfacial polymerization reaction, and thus a polyamide composite reverse osmosis membrane with both high permeation flux and high rejection rate cannot be prepared.

[0095] It can be seen from Comparative Example 4 that if the normal temperature oil-phase pure solvent is used instead of the low temperature oil-phase pure solvent to rinse and quench the reaction, the first interfacial polymerization reaction cannot be effectively stopped even if other conditions remain unchanged, and thus a polyamide composite reverse osmosis membrane with both high permeation flux and high rejection rate cannot be prepared.

[0096] Based on the data of the above examples and comparative examples, it can be seen that in the present invention, due to the precise control of the first interfacial polymerization for a very short time and the oil-phase secondary reaction, combined with the unique low-temperature quenching reaction technology, the development degree of the polyamide surface morphology is unexpectedly and precisely regulated, so that it stops at the stage with the vesicle structure as the main characteristic morphology. The vesicle structure has a specific projected area and size. Finally, the polyamide composite reverse osmosis membrane of the present invention has vesicles with precisely regulated projected area and diameter and an average pore size of the polyamide layer within a specific range. The effective permeation area is much larger than that of the polyamide composite reverse osmosis membrane with a leaf structure, and it has a high water permeation flux. At the same time, the compactness of the polyamide composite reverse osmosis membrane is greatly improved. In the method of the present invention, the low temperature oil-phase pure solvent, the time of the first interfacial polymerization reaction, and the characteristic parameters of the oil-phase secondary reaction step act as an overall synergistic effect, and none of the above characteristics can be missing. Only when the above parameters are simultaneously satisfied can a polyamide composite reverse osmosis membrane with both high permeation flux and high rejection rate be achieved, which is applicable to all water purification processes, especially seawater desalination.

[0097] The above examples are intended to clarify the design concept and technical characteristics of the present invention, so that those skilled in the relevant fields can fully understand the specific content of the present invention and implement it accordingly. It should be emphasized that these specific examples should not be construed as limiting the protection scope of the present invention. The protection scope of the present invention should be subject to the scope defined by the claims. Any technical solution obtained by equivalent changes or modifications based on the disclosed design concept and technical solution of the present invention should be regarded as belonging to the scope of protection required by the present invention as long as it does not substantially deviate from the purpose of the present invention.

Claims

1. A polyamide composite reverse osmosis membrane with a vesicle structure, characterized in that: The polyamide composite reverse osmosis membrane comprises a porous carrier and a polyamide layer, wherein the polyamide layer is located on the porous carrier; the polyamide layer has a vesicle structure; the ratio of the projected area of ​​the vesicle structure to the projected area of ​​the polyamide layer is ≥50%, and the average diameter of the vesicle structure is between 10-500nm; and the average pore size of the polyamide layer is ≤4.1 Å.

2. The polyamide composite reverse osmosis membrane according to claim 1, characterized in that: The ratio of the projected area of ​​the vesicle structure to the projected area of ​​the polyamide layer is ≥70%.

3. The polyamide composite reverse osmosis membrane according to claim 1, characterized in that: The ratio of the projected area of ​​the vesicle structure to the projected area of ​​the polyamide layer is ≥80%.

4. The polyamide composite reverse osmosis membrane according to claim 1, characterized in that: The ratio of the projected area of ​​the vesicle structure to the projected area of ​​the polyamide layer is ≥85%.

5. The polyamide composite reverse osmosis membrane according to claim 1, characterized in that: The average diameter of the vesicle structure is between 50-300 nm.

6. The polyamide composite reverse osmosis membrane according to claim 1, characterized in that: The average diameter of the vesicle structure is between 100-200 nm.

7. The polyamide composite reverse osmosis membrane according to claim 1, characterized in that: The average diameter of the vesicle structure is between 100-150 nm.

8. The polyamide composite reverse osmosis membrane according to claim 1, characterized in that: The average pore size of the polyamide layer is ≤4 Å.

9. The polyamide composite reverse osmosis membrane according to claim 1, characterized in that: The surface pore size of the porous carrier is between 1-200 nm, and the cut-off molecular weight is between 1,000-500,000 Daltons.

10. A method for preparing a polyamide composite reverse osmosis membrane as claimed in claim 1, characterized in that: The method comprises the following steps: (1) soaking the porous carrier in a polyamine aqueous solution to obtain an impregnated porous carrier; (2) placing the impregnated porous carrier in a polyacyl chloride oil phase solution to carry out a rapid primary interfacial polymerization reaction, wherein the time of the rapid primary interfacial polymerization reaction is within 20 seconds, and immediately carrying out a quenching reaction to obtain a primary reaction primary polyamide composite reverse osmosis membrane, wherein the temperature of the quenching reaction is a low temperature, and the low temperature is ≤10°C; (3) placing the primary reaction nascent polyamide composite reverse osmosis membrane in a polyacid chloride oil phase solution to perform an oil phase secondary reaction to obtain a secondary reaction nascent polyamide composite reverse osmosis membrane; (4) heat-treating the secondary reaction primary polyamide composite reverse osmosis membrane to obtain the polyamide composite reverse osmosis membrane.

11. The method for preparing a polyamide composite reverse osmosis membrane according to claim 10, characterized in that: In step (2), the method for immediately quenching the reaction is to immediately remove the polyacyl chloride oil phase solution and rinse it with a low-temperature oil phase pure solvent to stop the reaction. The low-temperature oil phase pure solvent is an oil phase pure solvent with a temperature of ≤10°C, which is immiscible with water and can dissolve the polyacyl chloride monomer.

12. The method for preparing a polyamide composite reverse osmosis membrane according to claim 11, characterized in that: The temperature of the low-temperature oil phase pure solvent is -30 to 10°C.

13. The method for preparing a polyamide composite reverse osmosis membrane according to claim 11, characterized in that: The temperature of the low-temperature oil phase pure solvent is -5°C.

14. The method for preparing a polyamide composite reverse osmosis membrane according to claim 11, characterized in that: The time for flushing with low-temperature oil phase pure solvent is 30s-5min.

15. The method for preparing a polyamide composite reverse osmosis membrane according to claim 10, characterized in that: In step (1), the soaking time is 10s-30min.

16. The method for preparing a polyamide composite reverse osmosis membrane according to claim 10, characterized in that: In step (1), the concentration of the polyamine in the aqueous phase solution is 1.0-10.0 wt %.

17. The method for preparing a polyamide composite reverse osmosis membrane according to claim 10, characterized in that: In step (1), the polyamine is at least one of ethylenediamine, m-phenylenediamine and diethylenetriamine.

18. The method for preparing a polyamide composite reverse osmosis membrane according to claim 10, characterized in that: In step (2), the reaction time is 2-20s.

19. The method for preparing a polyamide composite reverse osmosis membrane according to claim 10, characterized in that: In step (2), the reaction time is 5-20s.

20. The method for preparing a polyamide composite reverse osmosis membrane according to claim 10, characterized in that: In step (2), the reaction time is 5-10s.

21. The method for preparing a polyamide composite reverse osmosis membrane according to claim 10, characterized in that: In steps (2) and (3), the polyacyl chloride is at least one of trimesoyl chloride, terephthaloyl chloride and isophthaloyl chloride.

22. The method for preparing a polyamide composite reverse osmosis membrane according to claim 10, characterized in that: In steps (2) and (3), the concentration of the polyacyl chloride in the oil phase solution is 0.01-10.0 wt %.

23. The method for preparing a polyamide composite reverse osmosis membrane according to claim 10, characterized in that: In steps (2) and (3), the oil phase solvent is at least one of n-hexane, cyclohexane, n-heptane, toluene, benzene, Isopar G, Isopar E, Isopar H, Isopar L and Isopar M.

24. The method for preparing a polyamide composite reverse osmosis membrane according to claim 10, characterized in that: In step (2), the temperature of the primary interfacial polymerization reaction is room temperature.

25. The method for preparing a polyamide composite reverse osmosis membrane according to claim 10, characterized in that: In step (2), the temperature of the primary interfacial polymerization reaction is 25±5°C.

26. The method for preparing a polyamide composite reverse osmosis membrane according to claim 10, characterized in that: In step (3), the oil phase secondary reaction uses a low temperature oil phase pure solvent to stop the reaction.

27. The method for preparing a polyamide composite reverse osmosis membrane according to claim 26, characterized in that: In step (3), the temperature of the low-temperature oil phase pure solvent is -30 to 10°C.

28. The method for preparing a polyamide composite reverse osmosis membrane according to claim 26, characterized in that: In step (2), the temperature of the low-temperature oil phase pure solvent is -5°C.

29. The method for preparing a polyamide composite reverse osmosis membrane according to claim 10, characterized in that: In step (3), the oil phase secondary reaction temperature is room temperature.

30. The method for preparing a polyamide composite reverse osmosis membrane according to claim 10, characterized in that: In step (3), the oil phase secondary reaction temperature is 25±5°C.

31. The method for preparing a polyamide composite reverse osmosis membrane according to claim 10, characterized in that: In step (3), the reaction time of the oil phase secondary reaction is 5s-10min.

32. The method for preparing a polyamide composite reverse osmosis membrane according to claim 10, characterized in that: In step (3), the reaction time of the oil phase secondary reaction is 5s-2min.

33. The method for preparing a polyamide composite reverse osmosis membrane according to claim 10, characterized in that: In step (4), the heat treatment method is water bath or oven heating.

34. The method for preparing a polyamide composite reverse osmosis membrane according to claim 10, characterized in that: In step (4), the heat treatment temperature is 30-120° C., and the heat treatment time is 2-20 min.

35. A membrane module, wherein: The membrane assembly comprises the polyamide composite reverse osmosis membrane described in any one of claims 1 to 9 or the polyamide composite reverse osmosis membrane prepared by the preparation method described in any one of claims 10 to 34.

36. The membrane assembly according to claim 35, wherein the membrane assembly is a rolled reverse osmosis membrane element, comprising a central tube, a reverse osmosis membrane, an inlet water guide net and a pure water guide net.

37. A water treatment device, wherein: The water treatment device comprises the membrane module according to claim 35.

38. Use of the polyamide composite reverse osmosis membrane described in any one of claims 1 to 9, the polyamide composite reverse osmosis membrane prepared by the preparation method described in any one of claims 10 to 34, the membrane assembly described in claim 35 or 36, and the water treatment device described in claim 37 in a water treatment process.

39. The use according to claim 38, characterized in that The water treatment is seawater desalination.

40. The use according to claim 38, characterized in that The application method is: testing the permeation flux and retention rate of the polyamide composite reverse osmosis membrane under the conditions of a temperature of 25°C, a feed liquid of 32000 ppm sodium chloride solution, and a pressure of 55.2 bar.

41. The use according to claim 40, characterized in that The permeation flux of the polyamide composite reverse osmosis membrane is 66.8-74.8 L·m -2 ·h -1 , the interception rate is over 99.2%.

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