A high-flux reverse osmosis membrane and a method for preparing the same

Abstract

The application discloses a high-flux reverse osmosis membrane and a preparation method thereof. The preparation method comprises the following steps: obtaining a base film, preparing an agar solution, a water-phase solution and an oil-phase solution, pretreating the base film by using the agar solution at a first temperature, fully contacting the base film with the agar solution, cooling the base film soaked with the agar solution to a second temperature after removing the excess agar solution, obtaining a precursor base film, fully immersing the precursor base film in the water-phase solution, taking out the precursor base film from the water-phase solution, removing the excess water-phase solution, immersing the precursor base film in the oil-phase solution again, obtaining a precursor reverse osmosis membrane after sufficient reaction, and performing a heat treatment operation on the precursor reverse osmosis membrane to obtain a target high-flux reverse osmosis membrane. The second temperature is lower than the first temperature. The preparation method is simple, the cost of the materials used is low, the materials are environment-friendly and non-toxic, the high-flux reverse osmosis membrane prepared has good rejection rate, high flux and good desalination performance.

Description

Technical Field

[0001] This invention relates to the fields of membrane separation and water treatment, and in particular to a high-flux reverse osmosis membrane and its preparation method. Background Technology

[0002] Reverse osmosis technology, as one of the most important water treatment technologies, has demonstrated excellent performance characteristics in seawater desalination, pure water production, and reclaimed water reuse. The reverse osmosis membrane is the core of this technology. Currently, the mainstream reverse osmosis membrane on the market is the aromatic polyamide membrane, which is highly favored due to its excellent permeation selectivity and stability. However, the industrialization of reverse osmosis membranes faces challenges such as high manufacturing costs and relatively low permeation performance. Current research shows that existing technologies offer limited improvements in membrane performance, and the industrial feasibility of membrane fabrication processes is low.

[0003] The performance of reverse osmosis composite membranes is the result of the synergistic effect of the performance of the nonwoven support layer, the porous ultrafiltration support layer, and the ultrathin functional layer. The performance of the base membrane and various factors in the interfacial polymerization process will affect the final membrane performance.

[0004] Currently, the mainstream reverse osmosis membrane is the aromatic polyamide thin-layer composite reverse osmosis membrane prepared by interfacial polymerization process.

[0005] Heat treatment is a crucial step in the fabrication process of aromatic polyamide thin-film composite reverse osmosis membranes. Heat treatment removes residual organic solvents from the membrane and promotes additional cross-linking through the reaction of amine and carboxylic acid residues, thereby improving the desalination rate. Furthermore, it helps to solidify the polyamide layer formed after the interfacial polymerization reaction, thus stabilizing the membrane structure.

[0006] However, high heat treatment temperatures or long curing times can also damage the microporous skin layer of the supporting membrane. When reverse osmosis membranes are heat-treated, the moisture inside the organic ultrafiltration membrane evaporates rapidly, causing the membrane pores to shrink, reducing the water passage channels, and thus decreasing the water flux. This negative impact is often irreversible; even if the membrane is re-wetted during post-treatment, it is difficult to restore it to its initial state.

[0007] In existing reverse osmosis membrane preparation technologies, most attention is focused on controlling the temperature and reaction time during the interfacial polymerization stage, while the pore-preserving treatment of the substrate membrane during the heat treatment stage is almost entirely neglected.

[0008] In summary, there is an urgent need for a method that can protect the membrane pores during the heat treatment and drying process of reverse osmosis membranes, thereby enabling the preparation of high-flux reverse osmosis membranes. Summary of the Invention

[0009] The technical problem to be solved by the embodiments of the present invention is to provide a high-flux reverse osmosis membrane and a method for preparing the same, which can protect the membrane pores during the heat treatment and drying process of the reverse osmosis membrane, thereby obtaining a high-flux reverse osmosis membrane.

[0010] To address the aforementioned technical problems, this invention provides a method for preparing a high-flux reverse osmosis membrane. The method includes the following steps: obtaining a base membrane; preparing an agar solution, an aqueous solution, and an oil solution; pretreating the base membrane with the agar solution at a first temperature; fully contacting the base membrane with the agar solution; removing excess agar solution; cooling the agar-soaked base membrane to a second temperature to obtain a precursor base membrane; fully immersing the precursor base membrane in the aqueous solution; removing it from the aqueous solution; removing excess aqueous solution; immersing it in the oil solution; allowing it to react fully to obtain a precursor reverse osmosis membrane; and performing a heat treatment operation on the precursor reverse osmosis membrane to obtain the target high-flux reverse osmosis membrane; wherein the second temperature is lower than the first temperature.

[0011] In one feasible implementation, the first temperature is 70℃-100℃, and the second temperature is 0-40℃.

[0012] In one feasible implementation, the mass concentration of the agar solution is 0.1%-10%.

[0013] In one feasible implementation, the operation of pretreating the base film with an agar solution at a first temperature is selected from one of immersion, single-sided spraying, double-sided spraying, and brushing.

[0014] In one feasible implementation, the precursor base film is immersed in the oil phase solution for 10s-120s.

[0015] In one feasible implementation, the aqueous phase solution contains an amine monomer selected from at least one of N,N-dimethyl-m-phenylenediamine, triethanolamine, m-phenylenediamine, mesitylenetriamine, p-phenylenediamine, 3-aminopiperazine, n-hexylamine, and decylamine;

[0016] In one feasible implementation, the solute in the oil phase solution is an acyl chloride monomer selected from at least one of biphenyl dicarboxylate chloride, pyromellitic tricarboxylate chloride, benzoyl chloride, terephthaloyl chloride, isophthaloyl chloride, o-phthaloyl chloride, oxaloyl chloride, and benzene disulfonyl chloride.

[0017] In one feasible implementation, the concentration of the amine monomer is from 1.0 wt% to 8.0 wt%.

[0018] In one feasible implementation, the concentration of acyl chloride monomers in the oil phase solution is from 0.01 wt% to 5 wt%.

[0019] In one feasible implementation, the solvent of the oil phase solution is one or more of n-hexane, heptane, isoalkanes, cyclohexane, ethylcyclohexane, propylcyclohexane, n-butylcyclohexane, isobutylcyclohexane, tert-butylcyclohexane, and isopropylcyclohexane.

[0020] In one feasible implementation, the heat treatment operation of the precursor reverse osmosis membrane includes the following steps: placing the precursor reverse osmosis membrane in an oven for heat treatment, and then thoroughly cleaning it with deionized water; the temperature of the oven is 60℃-100℃; the heat treatment time is 2min-10min.

[0021] Accordingly, the present invention also provides a high-flux reverse osmosis membrane, prepared by any of the above-described reverse osmosis membrane preparation methods.

[0022] Implementing this invention has the following beneficial effects:

[0023] In the method for preparing the high-flux reverse osmosis membrane provided in this application, the base membrane is pretreated with an agar solution. The high-temperature liquid agar solution fills the micropores in the organic membrane, so that the bottom membrane pore structure remains intact during the heat treatment of membrane formation. This agar-embedded structure not only prevents the water flux of the composite membrane from being lost due to pore shrinkage, but also reduces the stress generated by the shrinkage of the bottom membrane pore structure on the polyamide separation functional layer structure, reduces the generation of defects, and thus optimizes the desalination performance of the functional layer. The high-flux reverse osmosis membrane prepared has good rejection rate, high flux, and good desalination performance.

[0024] The preparation process is simple, the materials used are low-cost, and the process is environmentally friendly and non-toxic. It is easy to carry out large-scale industrial production and has good application prospects in brackish water desalination and seawater desalination. Attached Figure Description

[0025] Figure 1 This is a flowchart of a method for preparing a high-flux reverse osmosis membrane according to an embodiment of the present invention;

[0026] Figure 2 These are physical images of the base film and precursor base film shown in some embodiments of the present invention;

[0027] Figure 3 These are scanning electron microscope (SEM) images of the base film and precursor base film shown in some embodiments of the present invention.

[0028] Figure 4 These are scanning electron microscope (SEM) images of the base film after it has been filled with agar and then washed with hot water, as shown in some embodiments of the present invention. Detailed Implementation

[0029] To make the above-mentioned objects, features, and advantages of the present invention more apparent and understandable, specific embodiments of the present invention will be described in detail below with reference to the accompanying drawings. Many specific details are set forth in the following description to provide a thorough understanding of the present invention. However, the present invention can be practiced in many other ways different from those described herein, and those skilled in the art can make similar modifications without departing from the spirit of the present invention. Therefore, the present invention is not limited to the specific embodiments disclosed below.

[0030] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains. The terminology used herein in the description of the invention is for the purpose of describing particular embodiments only and is not intended to be limiting of the invention. The term "and / or" as used herein includes any and all combinations of one or more of the associated listed items.

[0031] Please refer to Figure 1 This application provides a method for preparing a high-flux reverse osmosis membrane, the method comprising the following steps:

[0032] S110, Obtain the base film.

[0033] The base membrane referred to here is a porous support membrane. In one feasible implementation, the base membrane can be selected from polysulfone-based membranes, polyethersulfone-based membranes, polyacrylonitrile-based membranes, polyvinylidene fluoride membranes, polytetrafluoroethylene membranes, polyimide-based membranes, polyvinyl chloride membranes, polyethylene-based membranes, or polypropylene-based membranes. Optionally or preferably, the base membrane is a polysulfone-based membrane or a polyethersulfone-based membrane. Optionally or preferably, the base membrane is a polysulfone-based membrane. Polysulfone has good mechanical properties, including high strength and toughness, which allows it to withstand stretching and other treatments during manufacturing and resist certain pressures and physical damage in practical applications. Polysulfone exhibits excellent resistance to a variety of chemicals, such as acids, alkalis, and some organic solvents, which is important for applications that need to be exposed to various water qualities or chemical environments. This material can maintain its physical properties over a wide temperature range, making it suitable for high-temperature water treatment or other applications that require exposure to temperature changes. Polysulfone materials are generally considered bioinert and do not react with living organisms, making them ideal for industries with strict hygiene requirements, such as pharmaceuticals and food processing. Polysulfone can be processed into desired shapes and sizes through various methods such as injection molding and extrusion, facilitating the production of products with complex structures, such as hollow fiber membranes. By adjusting the preparation conditions, the pore size distribution and surface properties of polysulfone membranes can be controlled to meet the needs of specific separation tasks.

[0034] S120. Prepare agar solution, aqueous solution and oil solution.

[0035] The agar can gradually dissolve upon heating at low temperatures and then form a gel upon cooling. A hysteresis phenomenon exists during the solid-liquid transition of agar, which is the main reason for its two temperature ranges. This hysteresis manifests as a discrepancy between the melting temperature and solidification temperature of agar during state transitions. For example, agar begins to melt at 85°C but begins to solidify from 32 to 40°C. This means that once agar melts at 85°C, it remains liquid until the temperature drops to around 40°C before beginning to solidify. Therefore, between 40 and 85°C, agar can exist in either a solid or liquid state, depending on its previous state. This hysteresis phenomenon has unique implications for the applications of agar. During heating, agar transitions from a solid to a liquid state; it begins to melt when the temperature rises to 85°C, but does not immediately and completely transform into a liquid state. It only fully transforms into a liquid state when the temperature continues to rise. Similarly, during cooling, when the temperature drops to 32 to 40°C, agar begins to solidify until it becomes completely solid.

[0036] In one feasible implementation, the mass concentration of agar in the agar solution is 0.1%-10%. This invention utilizes the different properties exhibited by agar at different concentrations during solidification and melting. The concentration of agar affects its solidification effect; within a certain concentration range, agar can form a stable gel structure. When the agar concentration is low, the solidification point decreases. Regarding the melting point, under normal circumstances, when using a 1%-2% agar solution, the agar begins to melt at approximately 45 degrees Celsius. For example, if it is desired that the agar begins to melt at temperatures above 45 degrees Celsius, such as 50 or 55 degrees Celsius, the agar content in the solution can be increased; the specific ratio needs to be adjusted according to the actual situation. Thus, using an agar solution to pretreat the base membrane allows the liquid agar to penetrate the membrane pores, and the cooled agar solidifies and fills the pores. This not only effectively avoids pore leakage during interfacial polymerization but also reduces membrane pore shrinkage and collapse during membrane heat treatment, thus preserving pores and significantly reducing membrane flux loss. After the drying step, a hot water rinse is sufficient to remove the agar from the membrane pores, without negatively impacting the reverse osmosis membrane. Optionally or preferably, the agar concentration in the agar solution of this application is 0.1%-9%. Optionally or preferably, the agar concentration in the agar solution of this application is 0.2%-9%. Optionally or preferably, the agar concentration in the agar solution of this application is 0.5%-9%. Optionally or preferably, the agar concentration in the agar solution of this application is 0.5%-5%. In this way, the agar fills the micropores in the organic membrane, ensuring the integrity of the bottom membrane pore structure during the heat treatment of membrane formation. This agar-embedded structure not only prevents the water flux of the composite membrane from being lost due to pore shrinkage, but also reduces the stress generated by the shrinkage of the bottom membrane pore structure on the polyamide separation functional layer structure, reducing defects and thus optimizing the desalination performance of the functional layer.

[0037] The agar solution can be prepared by first weighing the target amount of agar powder and deionized water, adding the agar powder to the deionized water to obtain an agar suspension, and then heating the agar suspension until the agar powder is completely dissolved. The heating method can be water bath heating, high-temperature sterilizer heating, or microwave heating, etc.

[0038] In one feasible implementation, the aqueous phase solution contains an amine monomer. The amine monomer is selected from at least one of N,N-dimethyl-m-phenylenediamine, triethanolamine, m-phenylenediamine, pyromellitic triamine, p-phenylenediamine, 3-aminopiperazine, n-hexylamine, and decylamine. Optionally or preferably, the amine monomer is m-phenylenediamine. Further, the concentration of the amine monomer in the aqueous phase solution is 1.0 wt% to 8.0 wt%. Optionally or preferably, the concentration of the amine monomer is 2 wt% to 5 wt%. Reverse osmosis membranes prepared with such an aqueous phase solution further facilitate pore protection during the heat treatment and drying process of the reverse osmosis membrane, thereby obtaining high-flux reverse osmosis membranes.

[0039] In one feasible implementation, the aqueous solution further includes additives. Additives may include catalysts, such as triethylamine. Triethylamine acts as a catalyst, promoting the interfacial polymerization reaction between amine monomers and acyl chloride monomers, while neutralizing the HCl generated in the reaction, maintaining the stability of the reaction environment. Additives may also include pH adjusters, such as camphor sulfonic acid. By adjusting the pH of the aqueous solution, the reaction is ensured to proceed under suitable conditions, and may affect the surface charge and hydrophilicity of the membrane. Additives may also be surfactants, such as sodium dodecyl sulfate. Sodium dodecyl sulfate acts as a surfactant, reducing surface tension, promoting uniform monomer distribution, and improving the surface morphology and properties of the membrane.

[0040] In one feasible implementation, the solute in the oil phase solution is an acyl chloride monomer. Thus, the aqueous phase solution containing the amine monomer can form polyamide chains with the acyl chloride monomer in the oil phase. Because the reaction occurs at the interface between the two phases, the resulting polyamide layer is very thin, typically only a few hundred nanometers thick, but very dense and uniform, thus exhibiting good reverse osmosis properties. Optionally or preferably, the acyl chloride monomer is selected from at least one of biphenyl dichloroisocyanurate, trimesoyl pyromellitic acid, benzoyl chloride, terephthaloyl chloride, isophthaloyl chloride, phthaloyl chloride, oxaloyl chloride, and benzene disulfonyl chloride. Optionally or preferably, the acyl chloride monomer is trimesoyl pyromellitic acid (TMC). TMC possesses three acyl chloride functional groups, enabling it to react rapidly with amine monomers (such as m-phenylenediamine) in the aqueous phase to form a highly cross-linked polyamide network. This efficient interfacial polymerization reaction can be completed within seconds, ensuring the speed and economy of the production process. Due to its multifunctional properties, TMC can form multiple crosslinks with diamine monomers at the interface, resulting in a very thin but extremely dense polyamide active layer. This not only helps improve membrane selectivity and desalination efficiency but also reduces concentration polarization and increases water flux. The polyamide layer formed by TMC typically possesses good mechanical strength and flexibility, which is crucial for maintaining the structural stability and service life of reverse osmosis membranes under high-pressure operating conditions. Polyamide membranes synthesized from TMC exhibit excellent chemical resistance, especially against pH changes, oxidants, and other harmful substances, making them suitable for a wide range of water treatment environments, including seawater desalination and industrial wastewater treatment. Using TMC allows for the adjustment of membrane surface properties, such as hydrophilicity or hydrophobicity, and control of porosity, all of which significantly impact the final membrane performance. Furthermore, TMC can be combined with other monomers to further customize the membrane's functional properties to meet the needs of specific applications.

[0041] In one feasible implementation, the concentration of the acyl chloride monomer in the oil phase solution is from 0.01 wt% to 5 wt%. More preferably, the concentration of the acyl chloride monomer is from 0.1% to 0.5%. When the concentration of the acyl chloride monomer is below 0.01 wt%, the resulting composite membrane has a high flux but a low desalination rate; when the concentration of the acyl chloride monomer is above 5 wt%, the resulting composite membrane has a high desalination rate but a low flux. Thus, a solute concentration of 0.1% ensures a moderate interfacial polymerization rate, which helps to form a uniform and thin polyamide layer, often key to achieving high separation performance. A lower solute concentration prevents excessive crosslinking, thus avoiding the formation of overly dense or thick membrane layers, which could reduce water flux and increase operating pressure. An appropriate concentration of TMC helps to form a polyamide layer with a suitable pore size distribution, which is important for improving the membrane's water flux while maintaining a good desalination rate. A thinner and more uniform membrane layer helps mitigate concentration polarization, enabling the membrane to achieve efficient separation at lower operating pressures. At appropriate concentrations, the resulting polyamide layer is not only dense enough to provide good separation performance but also maintains sufficient flexibility and mechanical strength, which is crucial for the long-term stable operation of the membrane. An optimized membrane structure better resists chemical attack, extending the membrane's lifespan.

[0042] In one feasible implementation, the solvent of the oil phase solution is one or more of n-hexane, heptane, isoalkanes, cyclohexane, ethylcyclohexane, propylcyclohexane, n-butylcyclohexane, isobutylcyclohexane, tert-butylcyclohexane, and isopropylcyclohexane. The choice of solvent for the oil phase solution is crucial. An ideal solvent should be able to dissolve acyl chloride monomers such as trimesoyl chloride (TMC) and be immiscible with the aqueous phase to ensure that the interfacial polymerization reaction can occur at the two-phase interface. Furthermore, the solvent should have low toxicity, good chemical stability, and be easy to handle and recycle. The oil phase solution can be selected from alkane solvents, aromatic hydrocarbon solvents, chlorinated hydrocarbon solvents, ester solvents, and other solvents. Among them, the alkane solvent can be n-hexane: n-hexane is a common nonpolar solvent with good solubility for TMC and is relatively inexpensive. Its high volatility makes it easy to remove after the reaction. Cyclohexane can also be used: cyclohexane is also an excellent nonpolar solvent, with a boiling point slightly higher than n-hexane, which helps reduce evaporation losses, while also having good solubility for TMC. Optionally or preferably, the solvent for the oil phase solution can be n-hexane.

[0043] S130. The base film is pretreated with the agar solution at a first temperature. The base film is brought into full contact with the agar solution. After removing excess agar solution, the base film immersed in the agar solution is cooled to a second temperature to obtain a precursor base film, wherein the second temperature is lower than the first temperature.

[0044] In this way, agar fills the micropores in the organic membrane, so that the bottom membrane pore structure remains intact during the heat treatment of membrane formation. This agar-embedded structure not only prevents the water flux of the composite membrane from being lost due to pore shrinkage, but also reduces the stress generated by the shrinkage of the bottom membrane pore structure on the polyamide separation functional layer structure, reduces the generation of defects, and thus optimizes the desalination performance of the functional layer.

[0045] The first temperature is 70-100℃. Optionally or preferably, the first temperature is 75-95℃. Optionally or preferably, the first temperature is 80-95℃. The second temperature is 0-40℃. Optionally or preferably, the second temperature is 5-35℃. Optionally or preferably, the second temperature is 10-30℃. Optionally or preferably, the second temperature is 20-30℃. Thus, at the first temperature, the agar solution is in a liquid state, allowing it to fully penetrate the micropores of the base membrane without melting during heat treatment. At the second temperature, the agar completely solidifies, fully supporting the micropores and preventing membrane pore shrinkage or collapse, thereby improving or ensuring high throughput.

[0046] In one feasible implementation, the pretreatment of the base film with the agar solution at the first temperature is selected from one of immersion, single-sided spraying, double-sided spraying, and brushing. Optionally or preferably, the pretreatment of the base film with the agar solution at the first temperature is an immersion treatment. Specifically, the base film can be fully immersed in the agar solution for 5-10 minutes.

[0047] Please refer to Figures 2 to 4 , Figure 2 These are physical images of the base film and precursor base film shown in some embodiments of the present invention; Figure 3 These are scanning electron microscope (SEM) images of the base film and precursor base film shown in some embodiments of the present invention. Figure 4 These are scanning electron microscope (SEM) images of the base membrane after agar filling and hot water washing, as shown in some embodiments of the present invention. Figure 2 In this context, 'a' represents the base film. Figure 2 In this context, 'b' refers to the base film after agar impregnation treatment, i.e., the precursor base film. Figure 3 In this context, 'a' represents the base film before agar pretreatment. Figure 3 In this context, 'b' represents the base film after agar impregnation treatment. From... Figure 3As can be seen, agar has filled the pores of the base membrane. Agar has good solubility in hot water, so it can be thoroughly cleaned with hot water, preventing subsequent pore blockage and increased contamination. From Figure 4 As can be seen, hot water can effectively remove agar from the membrane pores without leaving any residue that could cause pore blockage.

[0048] S140. The precursor membrane is fully immersed in an aqueous solution, then removed from the aqueous solution, and after removing excess aqueous solution, it is immersed in an oil solution. After sufficient reaction, a precursor reverse osmosis membrane is obtained.

[0049] In this process, an aqueous solution containing m-phenylenediamine (MPD) or other aromatic diamines is first formed on the surface of the precursor film. MPD, as an amine monomer, will participate in the formation of polyamide chains in subsequent reactions. Subsequently, an organic solvent (such as hexane or cyclohexane) containing trimesoyl chloride (TMC) or other acyl chlorides is applied over the aqueous solution. TMC, as an oil-phase monomer, will react with MPD at the interface. When the two phases come into contact, MPD diffuses from the water into the oil phase and undergoes a rapid condensation reaction with TMC to form polyamide. Because the reaction occurs at the interface between the two phases, the resulting polyamide layer is very thin, typically only a few hundred nanometers thick, but very dense and uniform. It should be noted that the use of either an oil-phase or aqueous-phase solute is not limited here, but is merely an example of an optional or preferred method.

[0050] In one feasible implementation, the precursor membrane is immersed in the oil phase solution for 10-120 seconds. Optionally or preferably, the immersion time is 30-60 seconds. Short immersion times result in incomplete interfacial polymerization and defects, leading to low desalination rates in the reverse osmosis membrane; longer immersion times result in a thicker desalination layer, causing a decrease in flux. This ensures uniform interfacial polymerization; the 30-60 second immersion time allows sufficient contact between m-phenylenediamine (MPD) in the aqueous phase and trimesoyl chloride (TMC) in the oil phase, resulting in a rapid and uniform interfacial polymerization reaction at the two-phase interface. The 30-60 second immersion time avoids excessive cross-linking or excessive membrane thickness caused by excessively long reaction times, ensuring that the resulting polyamide layer is both dense and not excessively thick. The 30-60 second immersion time helps to form an ideal membrane thickness, typically several hundred nanometers, which provides efficient separation performance without sacrificing water flux. A suitable reaction time promotes the formation of a uniform pore structure, which is crucial for improving membrane selectivity and reducing concentration polarization. It also optimizes desalination rate and water flux: by precisely controlling the immersion time, good water flux can be achieved while maintaining a high desalination rate, a key performance indicator in reverse osmosis membrane applications. Enhanced mechanical strength: An appropriate reaction time ensures that the resulting polyamide layer possesses sufficient mechanical strength to withstand the high-pressure conditions of actual operation. Furthermore, 30-60 seconds is a relatively short timeframe, making this process ideal for large-scale continuous production, improving production efficiency and reducing costs. Compared to longer immersion times, 30-60 seconds significantly shortens each production cycle, allowing for faster completion of the entire process from base membrane treatment to final product packaging. The shorter and fixed immersion time facilitates precise time management by operators and is easily automated, ensuring batch consistency. The fixed time parameter reduces variables that may affect membrane performance, contributing to maintaining stable production quality and performance.

[0051] S150. Perform heat treatment on the precursor reverse osmosis membrane to obtain the target high-flux reverse osmosis membrane.

[0052] In one feasible implementation, the heat treatment operation of the precursor reverse osmosis membrane includes the following steps: placing the precursor reverse osmosis membrane in an oven for heat treatment, and then thoroughly rinsing it with deionized water. Further, the temperature of the oven is 60-100℃; the heat treatment time is 2-10 minutes. Optionally or preferably, the temperature of the oven is 70-90℃; the heat treatment time is 3-6 minutes. Optionally or preferably, the temperature of the oven is 80℃; the heat treatment time is 5 minutes. In this way, the drying heat treatment temperature is lower than the first temperature of the agar solution, ensuring that the solidified agar in the precursor reverse osmosis membrane does not melt during the heat treatment process, thereby preventing membrane pore shrinkage or collapse, thus improving or ensuring the water flux of the reverse osmosis membrane. Simultaneously, the agar can also reduce the stress caused by the shrinkage of the bottom membrane pore structure on the destructive effect on the polyamide separation functional layer structure, reducing the generation of defects and thus optimizing the desalination performance of the functional layer.

[0053] Furthermore, after the drying step, a hot water rinse is sufficient to remove the agar from the membrane pores, which will not have a negative impact on the reverse osmosis membrane.

[0054] In the method of this invention, the agar solution mainly serves to fill the micropores in the organic membrane, so that the bottom membrane pore structure remains intact during the heat treatment of membrane formation. This agar-embedded structure not only prevents the water flux of the composite membrane from being lost due to pore shrinkage, but also reduces the stress generated by the shrinkage of the bottom membrane pore structure on the polyamide separation functional layer structure, thereby reducing the generation of defects and optimizing the desalination performance of the functional layer.

[0055] The preparation process is simple, the materials used are low-cost, and the process is environmentally friendly and non-toxic. It is easy to carry out large-scale industrial production and has good application prospects in brackish water desalination and seawater desalination.

[0056] Accordingly, this application also provides a high-flux reverse osmosis membrane, prepared by any of the above-described reverse osmosis membrane preparation methods. The high-flux reverse osmosis membrane provided by this application is prepared by immersing a base membrane in a hot agar solution, allowing the agar solution to penetrate and fill the membrane pores, removing excess solution from the surface, and then cooling to solidify the agar. Subsequent steps include aqueous phase coating, oil phase coating, and heat treatment. This not only effectively avoids pore leakage during interfacial polymerization but also reduces membrane pore shrinkage and collapse during membrane drying, thus preserving pores and significantly reducing membrane flux loss.

[0057] Referring to the above implementation details, in order to make the technical solution of this application more specific, clear, and easy to understand, examples of the technical solution of this application are given below. However, it should be noted that the content to be protected by this application is not limited to the following embodiments.

[0058] Example 1

[0059] A 15cm × 20cm polysulfone ultrafiltration membrane was thoroughly washed in deionized water, then immersed in a 1% agar solution at 90°C for 5 minutes. The agar solution was then removed from the membrane surface using a scraper. The membrane was subsequently cooled to 25°C to allow the agar to solidify. The surface was then immersed in an aqueous solution containing 1.1% triethylamine, 2.1% camphor sulfonic acid, 0.1% sodium dodecyl sulfate, and 2% m-phenylenediamine for 2 minutes to ensure the supporting membrane was fully wetted. The solution was then discarded. Residual droplets on the membrane surface were removed using an air knife, and the membrane surface was immersed in a hexane oil solution containing 0.1% trimesoyl chloride to initiate interfacial polymerization for 30 seconds. Finally, the membrane was heat-treated in an oven at 80°C for 5 minutes to obtain an aromatic polyamide composite reverse osmosis membrane. This membrane was immediately thoroughly washed in deionized water at 90°C and then stored in deionized water for testing.

[0060] Example 2

[0061] The process is basically the same as in Example 1, except that the polysulfone ultrafiltration membrane is immersed in a 0.1% agar solution at 70°C for 5 minutes, and the heat treatment temperature is 70°C.

[0062] Example 3

[0063] The procedure is basically the same as in Example 1, except that the polysulfone ultrafiltration membrane is immersed in a 10% agar solution at 100°C for 5 minutes, and the heat treatment temperature is 90°C.

[0064] Example 4

[0065] The method is basically the same as in Example 1, except that the aqueous solution includes 1.1% triethylamine, 2.1% camphor sulfonic acid, 0.1% sodium dodecyl sulfate and 5% m-phenylenediamine.

[0066] Example 5

[0067] The method is basically the same as in Example 1, except that the oil phase solution is a hexane solution with a concentration of 0.5% pyromellitic chlorohydrin.

[0068] Comparative Example 1

[0069] A 15cm × 20cm polysulfone ultrafiltration support membrane was thoroughly washed by immersing it in deionized water. Then, its surface was immersed in an aqueous solution containing 1.1% triethylamine, 2.1% camphor sulfonic acid, 0.1% sodium dodecyl sulfate, and 2% m-phenylenediamine for 2 minutes to ensure complete wetting. The solution was then discarded. Residual droplets on the membrane surface were removed using an air knife, and the membrane surface was immersed in a hexane oil solution containing 0.1% trimesoyl chloride to initiate interfacial polymerization for 30 seconds. Finally, the membrane was heat-treated in an oven at 80°C for 5 minutes to obtain an aromatic polyamide composite reverse osmosis membrane. This membrane was immediately and thoroughly washed with deionized water and then stored in deionized water for testing.

[0070] The composite reverse osmosis membrane was tested at 15.5 bar and 25 °C by filtering a 2000 ppm NaCl aqueous solution, and the permeation flux and desalination rate were found to be 36 LMH and 98.8%, respectively.

[0071] Comparative Example 2

[0072] A 15cm × 20cm polysulfone ultrafiltration support membrane was thoroughly washed by immersing it in deionized water. Then, its surface was immersed in an aqueous solution containing 1.1% triethylamine, 2.1% camphor sulfonic acid, 0.1% sodium dodecyl sulfate, and 2% m-phenylenediamine for 2 minutes to ensure complete wetting. The solution was then discarded. Residual droplets on the membrane surface were removed using an air knife, and the membrane surface was immersed in a hexane oil solution containing 0.5% trimesoyl chloride to initiate interfacial polymerization for 30 seconds. Finally, the membrane was heat-treated in an oven at 80°C for 5 minutes to obtain an aromatic polyamide composite reverse osmosis membrane. This membrane was immediately and thoroughly washed with deionized water and then stored in deionized water for testing.

[0073] The composite reverse osmosis membrane was tested at 15.5 bar and 25 °C by filtering a 2000 ppm NaCl aqueous solution, and the permeation flux and desalination rate were found to be 36 LMH and 98.8%, respectively.

[0074] Performance testing

[0075] Permeation flux and desalination rate detection

[0076] A 2000 ppm NaCl aqueous solution was filtered at 15.5 bar and 25 °C, and the permeation flux and desalination rate of the reverse osmosis membranes prepared in the corresponding examples and comparative examples were tested.

[0077] Desalination rate and permeate flux are two important parameters for evaluating the separation performance of reverse osmosis membranes. This invention evaluates the separation performance of reverse osmosis membranes according to GB / T32373-2015 "Test Methods for Reverse Osmosis Membranes".

[0078] Desalination rate (R) is defined as: under certain operating conditions, the salt concentration (C) of the feed solution...f ) and the salt concentration in the permeate (C p The difference between the two is then divided by the feed solution salt concentration (C). f ), as shown in the following formula.

[0079]

[0080] Permeation flux is defined as the volume of water that permeates through a unit membrane area per unit time under certain operating conditions, and its unit is L / (m²). 2 ·h), abbreviated as LMH.

[0081] The operating conditions used for the reverse osmosis membrane performance determination in this invention are as follows: the feed solution is a 2000ppm sodium chloride aqueous solution, the solution pH is 7.0±0.5, the operating pressure is 15.5 bar, and the operating temperature is 25℃.

[0082] The test results are shown in the table below.

[0083]

[0084] The test results above show that the high-flux reverse osmosis membranes prepared by the methods provided in Examples 1-5 of this application all have higher membrane fluxes than the reverse osmosis membrane provided in Comparative Example 1, and also exhibit good rejection rates. Among them, the high-flux reverse osmosis membrane prepared in Example 1 has the highest membrane flux of 54 LMH and a relatively high rejection rate. It is evident that in the preparation method of the high-flux reverse osmosis membrane provided in this application, the agar solution mainly serves to fill the micropores in the organic membrane, ensuring that the bottom membrane pore structure remains intact during the heat treatment process of membrane formation. This agar-embedded structure not only prevents the water flux of the composite membrane from being lost due to pore shrinkage, but also reduces the stress generated by the shrinkage of the bottom membrane pore structure on the polyamide separation functional layer structure, reducing defects and thus optimizing the desalination performance of the functional layer.

[0085] The basic concepts have been described above. Obviously, for those skilled in the art, the detailed disclosure above is merely illustrative and does not constitute a limitation of this specification. Although not explicitly stated herein, those skilled in the art may make various modifications, improvements, and corrections to this specification. Such modifications, improvements, and corrections are suggested in this specification and therefore remain within the spirit and scope of the exemplary embodiments described herein.

[0086] Furthermore, this specification uses specific terms to describe embodiments thereof. For example, "an embodiment," "one embodiment," and / or "some embodiments" refer to a particular feature, structure, or characteristic associated with at least one embodiment of this specification. Therefore, it should be emphasized and noted that references to "an embodiment," "one embodiment," or "an alternative embodiment" in different locations throughout this specification do not necessarily refer to the same embodiment. Moreover, certain features, structures, or characteristics in one or more embodiments of this specification can be appropriately combined.

[0087] Furthermore, unless expressly stated in the claims, the order of processing elements and sequences, the use of numbers and letters, or other names described in this specification are not intended to limit the order of the processes and methods described herein. Although some inventive embodiments that are currently considered useful have been discussed by way of various examples in the foregoing disclosure, it should be understood that such details are for illustrative purposes only, and the appended claims are not limited to the disclosed embodiments. Rather, the claims are intended to cover all modifications and equivalent combinations that conform to the substance and scope of the embodiments described herein.

[0088] Similarly, it should be noted that, in order to simplify the description disclosed herein and thus aid in the understanding of one or more embodiments of the invention, the foregoing description of embodiments in this specification may sometimes combine multiple features into a single embodiment, drawing, or description thereof. However, this method of disclosure does not imply that the subject matter of this specification requires more features than those mentioned in the claims. In fact, the embodiments contain fewer features than all the features of a single embodiment disclosed above.

[0089] In some embodiments, numbers describing the quantity of components and attributes are used. It should be understood that such numbers used in the description of embodiments are modified in some examples with the terms "approximately," "approximately," or "generally." Unless otherwise stated, "approximately," "approximately," or "generally" indicates that the numbers are allowed to vary by ±20%. Accordingly, in some embodiments, the numerical parameters used in the specification and claims are approximate values, which may be changed depending on the characteristics required by individual embodiments. In some embodiments, numerical parameters should take into account specified significant digits and employ a general method of digit reservation. Although the numerical ranges and parameters used to confirm their breadth of range in some embodiments of this specification are approximate values, in specific embodiments, such values ​​are set as precisely as feasible.

[0090] For each patent, patent application, patent application publication, and other material such as articles, books, specifications, publications, and documents referenced in this specification, the entire contents of which are incorporated herein by reference. This excludes historical application documents that are inconsistent with or conflict with the content of this specification, as well as documents that limit the broadest scope of the claims in this specification (currently or subsequently appended to this specification). It should be noted that in the event of any inconsistency or conflict between the descriptions, definitions, and / or terminology used in the supplementary materials to this specification and the content of this specification, the descriptions, definitions, and / or terminology used in this specification shall prevail.

[0091] Finally, it should be understood that the embodiments described in this specification are merely illustrative of the principles of the embodiments described herein. Other variations may also fall within the scope of this specification. Therefore, alternative configurations of the embodiments described herein are intended to be illustrative rather than limiting, and should be considered consistent with the teachings of this specification. Accordingly, the embodiments described herein are not limited to those explicitly introduced and described herein.

Claims

1. A method for preparing a high-flux reverse osmosis membrane, characterized in that, The preparation method includes the following steps: Obtain the base film. Preparation of agar solutions, aqueous solutions and oil solutions, The base film is pretreated with the agar solution at a first temperature, and the base film is brought into full contact with the agar solution. After removing excess agar solution, the base film immersed in the agar solution is cooled to a second temperature to obtain the precursor base film. The precursor membrane is fully immersed in an aqueous solution, then removed from the aqueous solution. After removing excess aqueous solution, it is immersed in an oil solution. After sufficient reaction, a precursor reverse osmosis membrane is obtained. The precursor reverse osmosis membrane is subjected to heat treatment to obtain the target high-flux reverse osmosis membrane; in, The first temperature is 70℃-100℃, and the second temperature is 0-40℃; the mass concentration of the agar solution is 0.1%-10%; at the first temperature, the agar solution is in a liquid state; at the second temperature, the agar solidifies. The heat treatment operation of the precursor reverse osmosis membrane includes the following steps: placing the precursor reverse osmosis membrane in an oven for heat treatment, and then thoroughly washing it with hot water to remove the agar in the membrane pores; The heat treatment temperature of the heat treatment operation is lower than the first temperature.

2. The method for preparing a high-flux reverse osmosis membrane according to claim 1, characterized in that, The operation of pretreating the base film with an agar solution at a first temperature is selected from one of immersion, single-sided spraying, double-sided spraying, and brushing.

3. The method for preparing a high-flux reverse osmosis membrane according to claim 1, characterized in that, The precursor base film is immersed in the oil phase solution for 10s-120s.

4. The method for preparing a high-flux reverse osmosis membrane according to claim 1, characterized in that, The aqueous solution contains an amine monomer, which is selected from at least one of N,N-dimethyl-m-phenylenediamine, triethanolamine, m-phenylenediamine, pyromellitic triamine, p-phenylenediamine, and 3-aminopiperazine; The solute in the oil phase solution is an acyl chloride monomer, which is selected from at least one of biphenyl dicarboxylate chloride, pyromellitic tricarboxylate chloride, terephthaloyl chloride, isophthaloyl chloride, and phthaloyl chloride.

5. The method for preparing a high-flux reverse osmosis membrane according to claim 4, characterized in that, The concentration of the amine monomer is from 1.0 wt% to 8.0 wt%. The concentration of acyl chloride monomers in the oil phase solution is from 0.01 wt% to 5 wt%.

6. The method for preparing a high-flux reverse osmosis membrane according to claim 1, characterized in that, The solvent of the oil phase solution is one or more of n-hexane, heptane, isoalkanes, cyclohexane, ethylcyclohexane, propylcyclohexane, n-butylcyclohexane, isobutylcyclohexane, tert-butylcyclohexane, and isopropylcyclohexane.

7. The method for preparing a high-flux reverse osmosis membrane according to claim 1, characterized in that, The heat treatment time is 2 min to 10 min.

8. A high-flux reverse osmosis membrane, characterized in that, Prepared by the method for preparing the reverse osmosis membrane according to any one of claims 1 to 7.

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