High-flux reverse osmosis membrane and preparation method thereof

Abstract

The preparation method comprises the following steps: obtaining a base membrane, preparing an agar solution, a water phase solution and an oil phase solution, pretreating the base membrane by using the agar solution at a first temperature, enabling the base membrane to be in full contact with the agar solution, removing the redundant agar solution, and obtaining the high-flux reverse osmosis membrane. Cooling the base membrane immersed with the agar solution to a second temperature to obtain a precursor base membrane, fully immersing the precursor base membrane in the aqueous phase solution, taking out the precursor base membrane from the aqueous phase solution, removing the redundant aqueous phase solution, immersing the precursor base membrane in the oil phase solution, and fully reacting to obtain a precursor reverse osmosis membrane, and carrying out 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. According to the method, the preparation process is simple, the used materials are low in cost, environment-friendly and non-toxic, and the prepared high-flux reverse osmosis membrane is good in rejection rate, high in flux and good in desalting performance.

Description

Technical Field

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

[0002] As one of the important technologies in current water treatment technology, reverse osmosis technology has demonstrated its excellent performance characteristics in the fields of seawater desalination, pure water preparation and reclaimed water reuse. Among them, reverse osmosis membrane is the core of reverse osmosis technology. At present, the mainstream reverse osmosis membrane on the market is aromatic polyamide membrane, which is favored for its excellent permeation selectivity and stability. In the process of industrialization, reverse osmosis membrane has problems such as high production cost and relatively low permeability. In current research, the existing technology has limited improvement in membrane performance, and the feasibility of industrial implementation of membrane manufacturing process is low.

[0003] The performance of the reverse osmosis composite membrane is the result of the synergistic effect of the performance of the non-woven support layer, the porous ultrafiltration support layer, and the ultra-thin functional layer. The base membrane performance and various factors in the interfacial polymerization reaction process will affect the final membrane performance.

[0004] The current mainstream reverse osmosis membrane is an aromatic polyamide thin-layer composite reverse osmosis membrane prepared by interfacial polymerization technology.

[0005] Heat treatment is a key step in the preparation process of aromatic polyamide thin-layer composite reverse osmosis membranes. Heat treatment can remove residual organic solvents in the film and promote additional cross-linking through the reaction of amine and carboxylic acid residues, thereby improving the salt rejection rate. It also helps to solidify the polyamide layer formed after the interfacial polymerization reaction, thereby stabilizing the membrane structure.

[0006] However, higher heat treatment temperatures or longer curing times can also damage the microporous epidermis of the supporting membrane. When the reverse osmosis membrane is heat treated, the water in the organic ultrafiltration base membrane evaporates rapidly, causing the pores of the membrane to shrink, reducing the water passage channel and thus reducing the water flux. This negative impact is often irreversible, and even if the membrane is re-wetted after post-treatment, it is difficult to restore to its original state.

[0007] In the existing reverse osmosis membrane preparation technology, most of the focus is on controlling the temperature and reaction time in the interfacial polymerization reaction stage, while the pore preservation treatment of the bottom membrane in the heat treatment stage is almost not involved.

[0008] In summary, there is an urgent need for a method for preparing a high-flux reverse osmosis membrane by protecting the membrane pores during the heat treatment and drying process of the reverse osmosis membrane. 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 preparation method thereof, 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] In order to solve the above technical problems, the present invention provides a method for preparing a high-flux reverse osmosis membrane, which comprises the following steps: obtaining a basement membrane, preparing an agar solution, an aqueous solution and an oil phase solution, pretreating the basement membrane with the agar solution at a first temperature, fully contacting the basement membrane with the agar solution, removing excess agar solution, cooling the basement membrane soaked with the agar solution to a second temperature, obtaining a precursor basement membrane, fully immersing the precursor basement membrane in an aqueous solution, taking it out of the aqueous solution, removing excess aqueous solution, and then immersing it in an oil phase solution, 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; wherein the second temperature is lower than the first temperature.

[0011] In a feasible implementation, the first temperature is 70°C-100°C, and the second temperature is 0-40°C.

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

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

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

[0015] In a feasible implementation, the aqueous phase solution contains an amine monomer, and the amine monomer is selected from at least one of N,N-dimethyl-m-phenylenediamine, triethanolamine, m-phenylenediamine, mesitylenetriamine, p-phenylenediamine, 3-aminopiperazine, n-hexylamine and decylamine; In a feasible implementation, the solute in the oil phase solution is an acyl chloride monomer, and the acyl chloride monomer is selected from at least one of biphenyl dichloride, trimesoyl chloride, benzoyl chloride, terephthaloyl chloride, isophthaloyl chloride, phthaloyl chloride, oxalyl chloride, and benzene disulfonyl chloride.

[0016] In a feasible implementation, the concentration of the amine monomer is 1.0 wt % to 8.0 wt %; In a feasible implementation, the concentration of the acyl chloride monomer in the oil phase solution is 0.01 wt % to 5 wt %.

[0017] In a feasible implementation, the solvent of the oil phase solution is one or more of n-hexane, heptane, isoparaffin, cyclohexane, ethylcyclohexane, propylcyclohexane, n-butylcyclohexane, isobutylcyclohexane, tert-butylcyclohexane, and isopropylcyclohexane.

[0018] In a feasible implementation, the heat treatment operation on the precursor reverse osmosis membrane includes the following steps: placing the precursor reverse osmosis membrane in an oven for heat treatment, and then washing it thoroughly with deionized water; the temperature of the oven is 60°C-100°C; and the heat treatment time is 2min-10min.

[0019] Correspondingly, the present invention also provides a high-flux reverse osmosis membrane, which is prepared by any of the above-mentioned methods for preparing the reverse osmosis membrane.

[0020] The implementation of the present invention has the following beneficial effects: In the preparation method of the high-flux reverse osmosis membrane provided in the present application, the base membrane is pretreated with an agar solution, and the high-temperature liquid agar solution fills the micropores in the organic membrane, so that the bottom membrane pore structure of the composite membrane remains intact during the heat treatment process of film formation. This agar mosaic structure not only prevents the water flux of the composite membrane from being lost due to the shrinkage of the pores, but also reduces the destructive effect of the stress generated by the shrinkage of the bottom membrane pore structure on the structure of the polyamide separation functional layer, reduces the generation of defects, and thus optimizes the desalination performance of the functional layer. The prepared high-flux reverse osmosis membrane has a good retention rate, high flux, and good desalination performance.

[0021] The method has a simple preparation process, low material cost, and is environmentally friendly and non-toxic; it is easy to industrialize on a large scale and has good application prospects in brackish water desalination, seawater desalination, etc. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] Figure 1 is a flow chart of a method for preparing a high-flux reverse osmosis membrane according to one embodiment of the present invention; Figure 2 is a physical picture of a base film and a precursor base film shown in some embodiments of the present invention; Figure 3 is a scanning electron microscope (SEM) image of a base film and a precursor base film shown in some embodiments of the present invention; Figure 4 It is a scanning electron microscope (SEM) image of the basement membrane after being filled with agar and then washed with hot water as shown in some embodiments of the present invention. DETAILED DESCRIPTION

[0023] In order to make the above-mentioned objects, features and advantages of the present invention more obvious and easy to understand, the specific embodiments of the present invention are described in detail below in conjunction with the accompanying drawings. In the following description, many specific details are set forth to facilitate a full understanding of the present invention. However, the present invention can be implemented in many other ways different from those described herein, and those skilled in the art can make similar improvements without violating the connotation of the present invention, so the present invention is not limited by the specific embodiments disclosed below.

[0024] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as those commonly understood by those skilled in the art to which the present invention belongs. The terms used herein in the specification of the present invention are only for the purpose of describing specific embodiments and are not intended to limit the present invention. The term "and / or" used herein includes any and all combinations of one or more of the related listed items.

[0025] Please refer to Figure 1 The present invention provides a method for preparing a high-flux reverse osmosis membrane, the method comprising the following steps: S110, obtaining a basement membrane.

[0026] The base membrane mentioned here is a porous support base membrane. In a feasible implementation, the base membrane can be selected from a polysulfone base membrane, a polyethersulfone base membrane, a polyacrylonitrile base membrane, a polyvinylidene fluoride base membrane, a polytetrafluoroethylene base membrane, a polyimide base membrane, a polyvinyl chloride base membrane, a polyethylene base membrane or a polypropylene base membrane. Optionally or preferably, the base membrane is a polysulfone base membrane or a polyethersulfone base membrane. Optionally or preferably, the base membrane is a polysulfone base membrane. Polysulfone has good mechanical properties, including high strength and toughness, which enables it to withstand stretching and other treatments during the manufacturing process, and can also resist certain pressures and physical damage in practical applications. Polysulfone shows excellent tolerance to a variety of chemical substances, for example, it is resistant to acids, alkalis and some organic solvents, which is very important for applications that need to contact various different water qualities or chemical environments. This material can keep its physical properties unchanged over a wide temperature range, and is suitable for high temperature water treatment or other application scenarios that need to withstand temperature changes. Polysulfone materials are generally considered to be biologically inert and will not react with organisms, so they are very suitable for industries such as medicine and food processing that have strict requirements on sanitary conditions. Polysulfone can be processed into the desired shape and size by injection molding, extrusion and other methods, which is convenient for producing complex structure products such as hollow fiber membranes. By adjusting the preparation conditions, the pore size distribution of polysulfone membranes and their surface characteristics can be controlled to meet the needs of specific separation tasks.

[0027] S120, preparing an agar solution, an aqueous phase solution and an oil phase solution.

[0028] Among them, the agar can be gradually dissolved after heating at a low temperature, and then form a gel after cooling. There is a hysteresis phenomenon in the solid-liquid conversion process of agar, which is the main reason for its two temperatures. The hysteresis phenomenon is reflected in the fact that the melting temperature of agar is inconsistent with the solidification temperature when the state is converted. For example, agar begins to melt at 85°C and solidifies from 32 to 40°C. This means that once agar melts at 85°C, it will remain liquid until the temperature drops to about 40°C before it begins to solidify. Therefore, between 40 and 85°C, agar can appear in a solid or liquid state, depending on its previous state. This hysteresis phenomenon has a unique impact on the application of agar. During the heating process, agar changes from a solidified state to a liquid state, and when the temperature rises to 85°C, it begins to melt, but does not immediately completely change to a liquid state. It will not completely change to a liquid state until the temperature continues to rise. Similarly, during the cooling process, when the temperature drops to 32 to 40 degrees Celsius, agar begins to solidify until it becomes completely solid.

[0029] In a feasible implementation, the mass concentration of agar in the agar solution is 0.1%-10%. The present invention utilizes different concentrations of agar to exhibit different characteristics during solidification and melting. The concentration of agar affects its solidification effect, and agar can form a stable gel structure within a certain concentration range. When the agar concentration is low, the solidification point will decrease. For the melting point, under normal circumstances, when 1%-2% agar is used, the temperature reaches about 45 degrees and the agar begins to melt. For example: If you want the agar to melt at a temperature higher than 45°C, such as 50°C or 55°C, you can consider increasing the content of agar in the agar solution, and the specific proportion needs to be adjusted according to the actual situation. In this way, the basement membrane is pretreated with an agar solution, and the liquid agar infiltrates the membrane pores of the basement membrane. The cooled agar solidifies and fills the membrane pores, which can not only effectively avoid the pore permeation phenomenon during the interfacial polymerization process, but also reduce the shrinkage and collapse of the membrane pores during the membrane heat treatment process, play a pore-preserving role, and greatly reduce the loss of membrane flux. After the drying step, only hot water washing treatment is required to wash away the agar in the membrane pores, which will not have a negative impact on the reverse osmosis membrane. Optionally or preferably, the mass concentration of agar in the agar solution of the present application is 0.1%-9%. Optionally or preferably, the mass concentration of agar in the agar solution of the present application is 0.2%-9%. Optionally or preferably, the mass concentration of agar in the agar solution of the present application is 0.5%-9%. Optionally or preferably, the mass concentration of agar in the agar solution of the present application is 0.5%-5%. In this way, agar plays a role in filling the micropores in the organic membrane, so that the bottom membrane pore structure of the composite membrane remains intact during the thermal treatment of the film formation. This agar mosaic structure not only prevents the water flux of the composite membrane from being lost due to the shrinkage of the pores, but also reduces the stress generated by the shrinkage of the bottom membrane pore structure. The destructive effect on the structure of the polyamide separation functional layer reduces the generation of defects and optimizes the desalination performance of the functional layer.

[0030] The preparation method of the agar solution can be to first weigh a target amount of agar powder and deionized water, add the agar powder to the deionized water to obtain an agar suspension, and then heat the agar suspension until the agar powder is completely dissolved. The heating method mentioned here can be water bath heating, high temperature sterilizer heating or microwave heating.

[0031] In a feasible implementation, the aqueous phase solution contains amine monomers. The amine monomers are selected from at least one of N,N-dimethyl-m-phenylenediamine, triethanolamine, m-phenylenediamine, s-phenylenediamine, 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 1.0wt% to 8.0wt%. Optionally or preferably, the concentration of the amine monomer is 2wt% to 5wt%. The reverse osmosis membrane prepared from such an aqueous phase solution can further facilitate the protection of the membrane pores during the heat treatment and drying process of the reverse osmosis membrane, thereby obtaining a high-flux reverse osmosis membrane.

[0032] In a feasible implementation, the aqueous phase solution also includes additives. The additives may include catalysts, such as triethylamine. Triethylamine acts as a catalyst to promote the interfacial polymerization reaction of amine monomers and acyl chloride monomers, while neutralizing the HCl generated by the reaction to maintain the stability of the reaction environment. The additives may also include pH regulators. For example, camphorsulfonic acid. By adjusting the pH value of the aqueous phase solution, it is ensured that the reaction is carried out under suitable conditions, and the surface charge and hydrophilicity of the membrane may be affected. The additive may also be a surfactant, such as sodium dodecyl sulfate. Sodium dodecyl sulfate acts as a surfactant to reduce surface tension, promote uniform distribution of monomers, and improve the surface morphology and performance of the membrane.

[0033] In a feasible implementation, the solute in the oil phase solution is an acyl chloride monomer. In this way, the aqueous phase solution containing amine monomers can form a polyamide chain with the acyl chloride monomer in the oil phase. Since the reaction occurs at the interface of the two phases, the formed polyamide layer is very thin, usually only a few hundred nanometers thick, but very dense and uniform, so it has good reverse osmosis. Optionally or preferably, the acyl chloride monomer is selected from at least one of biphenyl dicarboxylic acid chloride, trimesoyl chloride, benzoyl chloride, terephthaloyl chloride, isophthaloyl chloride, phthaloyl chloride, oxalyl chloride, and benzene disulfonyl chloride. Optionally or preferably, the acyl chloride monomer is trimesoyl chloride (TMC). TMC has three acyl chloride functional groups and can 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 in a few seconds, ensuring the rapidity and economy of the production process. Due to the multifunctional nature of TMC, it is able to produce multiple cross-links with diamine monomers at the interface, thereby generating a very thin but extremely dense polyamide active layer. This not only helps to improve the selectivity and desalination efficiency of the membrane, but also reduces concentration polarization and increases water flux. The polyamide layer formed by TMC usually has good mechanical strength and flexibility, which is essential for maintaining the structural stability and service life of the reverse osmosis membrane under high-pressure operating conditions. Polyamide membranes synthesized by TMC exhibit excellent chemical resistance, especially for pH changes, oxidants and other harmful substances. They have good resistance, which makes them suitable for use in a wide range of water treatment environments, including seawater desalination and industrial wastewater treatment. The use of TMC can adjust the surface properties of the membrane, such as hydrophilicity or hydrophobicity, and control porosity, all of which have an important influence on the final performance of the membrane. In addition, TMC can be used in combination with other monomers to further customize the functional properties of the membrane to meet the needs of specific applications.

[0034] In a feasible implementation, the concentration of the acyl chloride monomer in the oil phase solution is 0.01wt% to 5wt%. More preferably, the concentration of the acyl chloride monomer is 0.1% to 0.5%. When the concentration of the acyl chloride monomer is lower than 0.01wt%, the flux of the prepared composite membrane is high and the desalination rate is low; when the concentration of the acyl chloride monomer is higher than 5wt%, the prepared composite membrane has a high desalination rate and a low flux. In this way, a solute concentration of 0.1% ensures a moderate interfacial polymerization reaction rate, which helps to form a uniform and thin polyamide layer, which is usually the key to obtaining efficient separation performance. A lower solute concentration can prevent excessive cross-linking from occurring, thereby avoiding the formation of an overly dense or thick membrane layer, which may 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 very important for increasing the water flux of the membrane while maintaining a good desalination rate. A thinner and more uniform membrane layer helps mitigate the concentration polarization effect, allowing the membrane to achieve efficient separation at a lower operating pressure. At the appropriate concentration, the formed polyamide layer is not only dense enough to provide good separation performance, but also maintains sufficient flexibility and mechanical strength, which is critical for the long-term stable operation of the membrane. The optimized membrane structure can better resist the erosion of chemicals and extend the service life of the membrane.

[0035] In a feasible implementation, the solvent of the oil phase solution is one or more of n-hexane, heptane, isoparaffin, cyclohexane, ethylcyclohexane, propylcyclohexane, n-butylcyclohexane, isobutylcyclohexane, tert-butylcyclohexane, and isopropylcyclohexane. The selection of solvent for the oil phase solution is crucial. The 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 interface between the two phases. In addition, the solvent should also have low toxicity, good chemical stability, and easy handling and recycling. 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 non-polar solvent that has good solubility for TMC and is relatively cheap. It has high volatility and is therefore easy to remove after the reaction. Alternatively, cyclohexane may be used: cyclohexane is also an excellent non-polar solvent, and its boiling point is slightly higher than that of n-hexane, which helps to reduce volatile losses, and also has good solubility for TMC. Optionally or preferably, the solvent of the oil phase solution may be n-hexane.

[0036] S130, pretreating the base film with the agar solution at a first temperature, bringing the base film into full contact with the agar solution, removing excess agar solution, and cooling the base film soaked in the agar solution to a second temperature to obtain a precursor base film, wherein the second temperature is lower than the first temperature.

[0037] In this way, agar fills the micropores in the organic membrane so that the bottom membrane pore structure of the composite membrane remains intact during the heat treatment process of film formation. This agar mosaic structure not only prevents the water flux of the composite membrane from being lost due to the shrinkage of the pores, but also reduces the stress generated by the shrinkage of the bottom membrane pore structure. The destructive effect on the structure of the polyamide separation functional layer, reduces the generation of defects, and thus optimizes the desalination performance of the functional layer.

[0038] Wherein, the first temperature is 70-100°C. Optionally or preferably, the first temperature is 75-95°C. Optionally or preferably, the first temperature is 80-95°C. The second temperature is 0-40°C. Optionally or preferably, the second temperature is 5-35°C. Optionally or preferably, the second temperature is 10-30°C. Optionally or preferably, the second temperature is 20-30°C. In this way, at the first temperature, the agar solution is in a liquid state and can fully penetrate into the micropores of the basement membrane, and at the same time, it will not melt during heat treatment. At the second temperature, the agar is completely solidified, fully supporting the micropores, avoiding shrinkage or collapse of the pores of the membrane, thereby improving or ensuring high flux.

[0039] In a feasible implementation, the operation of pre-treating the base film with the agar solution at the first temperature is selected from one of soaking, single-sided spraying, double-sided spraying, and brushing. Optionally or preferably, the operation of pre-treating the base film with the agar solution at the first temperature is soaking. Specifically, the base film can be fully soaked in the agar solution for 5 min-10 min.

[0040] Please refer to Figures 2 to 4 , Figure 2 is a physical picture of a base film and a precursor base film shown in some embodiments of the present invention; Figure 3 is a scanning electron microscope (SEM) image of a base film and a precursor base film shown in some embodiments of the present invention; Figure 4 is a scanning electron microscope (SEM) image of the basement membrane after being filled with agar and then washed with hot water as shown in some embodiments of the present invention. Figure 2 a in is the basement membrane, Figure 2 b in the figure is the basement membrane after agar immersion treatment, i.e. the precursor basement membrane; Figure 3 a in the figure is the basement membrane before agar pretreatment. Figure 3 b in the figure is the basement membrane after agar immersion. Figure 3It can be seen that agar is filled into the pores of the basement membrane. Agar has good solubility in hot water, so it can be cleaned by hot water washing, and will not cause negative effects such as clogging the pores and aggravating pollution in the later stage. Figure 4 It can be seen that hot water can effectively remove the agar in the membrane pores without causing any residue to clog the membrane pores.

[0041] S140, fully immersing the precursor base membrane in an aqueous solution, then taking it out from the aqueous solution, removing excess aqueous solution, and then immersing it in an oil solution again, and after sufficient reaction, obtaining a precursor reverse osmosis membrane.

[0042] In this way, a layer of aqueous solution containing meta-phenylenediamine (MPD) or other aromatic diamines is first formed on the surface of the precursor base 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 covered on 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 water to the oil phase and undergoes a rapid condensation reaction with TMC to form polyamide. Since the reaction occurs at the interface of the two phases, the polyamide layer formed is very thin, usually only a few hundred nanometers thick, but it is very dense and uniform. It should be noted that the oil phase or water phase solute is not limited here, but is only used as an optional or preferred example.

[0043] In a feasible implementation, the precursor base membrane is immersed in the oil phase solution for 10-120 seconds. Optionally or preferably, the precursor base membrane is immersed in the oil phase solution for 30-60 seconds. A short immersion time will cause incomplete interfacial polymerization and defects, and the reverse osmosis membrane has a low desalination rate; a longer time will result in a thicker desalination layer of the reverse osmosis membrane, which will cause a decrease in flux. In this way, uniform interfacial polymerization can be ensured, and the immersion time of 30-60 seconds is sufficient to allow the metaphenylenediamine (MPD) in the water phase to fully contact the trimesoyl chloride (TMC) in the oil phase, and a rapid and uniform interfacial polymerization reaction occurs at the interface between the two phases. The immersion time of 30-60 seconds can avoid the problem of excessive cross-linking or excessive thickness of the membrane layer caused by too long a reaction time, thereby ensuring that the generated polyamide layer is both dense and not too thick. The immersion time of 30-60 seconds helps to form an ideal membrane thickness, usually several hundred nanometers, which can provide efficient separation performance without sacrificing water flux. Moderate reaction time can promote the formation of uniform pore structure, which is very important for improving membrane selectivity and reducing concentration polarization. It can also optimize the rejection rate and water flux: by precisely controlling the immersion time, good water flux can be achieved while maintaining high rejection rate, which is a key performance indicator in reverse osmosis membrane applications. Enhance mechanical strength: The appropriate reaction time can ensure that the generated polyamide layer has sufficient mechanical strength to cope with the high pressure conditions in actual operation. In addition, 30-60s is a relatively short time period, which makes the process very suitable for large-scale continuous production processes, improving production efficiency and reducing costs. Compared with longer immersion, 30-60s can significantly shorten each production cycle, allowing the entire process from base membrane processing to final product packaging to be completed faster. The short and fixed immersion time facilitates operators to conduct precise time management and is easy to realize automated control to ensure product consistency for each batch. Fixed time parameters reduce variables in the process that may affect membrane performance, which is conducive to maintaining stable production quality and performance.

[0044] S150, performing a heat treatment operation on the precursor reverse osmosis membrane to obtain a target high-flux reverse osmosis membrane.

[0045] In a 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 fully washing it with deionized water. Further, the temperature of the oven is 60-100°C; the heat treatment time is 2-10min. Optionally or preferably, the temperature of the oven is 70-90°C; the heat treatment time is 3-6min. Optionally or preferably, the temperature of the oven is 80°C; the heat treatment time is 5min. In this way, the drying heat treatment temperature is lower than the first temperature of the agar solution, so that the solidified agar in the precursor reverse osmosis membrane will not melt during the heat treatment process, thereby avoiding the shrinkage or collapse of the pores of the membrane, thereby improving or ensuring the water flux of the reverse osmosis membrane. At the same time, agar can also reduce the destructive effect of the stress generated by the shrinkage of the bottom membrane pore structure on the structure of the polyamide separation functional layer, reduce the generation of defects, and thus optimize the desalination performance of the functional layer.

[0046] Furthermore, after the drying step, the agar in the membrane pores can be cleaned out by only hot water cleaning, without having a negative impact on the reverse osmosis membrane.

[0047] In the method of the present invention, the agar solution mainly plays the role of filling the micropores in the organic membrane, so that the bottom membrane pore structure of the composite membrane remains intact during the heat treatment process of film formation. This agar mosaic structure not only prevents the water flux of the composite membrane from being lost due to the shrinkage of the pores, but also reduces the destructive effect of the stress generated by the shrinkage of the bottom membrane pore structure on the structure of the polyamide separation functional layer, reduces the generation of defects, and thus optimizes the desalination performance of the functional layer.

[0048] The method has a simple preparation process, low material cost, and is environmentally friendly and non-toxic; it is easy to industrialize on a large scale and has good application prospects in brackish water desalination, seawater desalination, and the like.

[0049] Correspondingly, the present application also provides a high-flux reverse osmosis membrane, which is prepared by any of the above-mentioned methods for preparing reverse osmosis membranes. The high-flux reverse osmosis membrane provided by the present application is prepared by immersing the base membrane in a hot agar solution, the agar solution infiltrates and fills the membrane pores, and then removing the excess solution on the surface, and then cooling, and the agar solidifies. Then, the steps of water phase coating, oil phase coating, and heat treatment are performed. In this way, not only can the pore permeation phenomenon during interfacial polymerization be effectively avoided, but also the shrinkage and collapse of the membrane pores can be reduced during the membrane drying process, which plays a role in preserving pores and greatly reduces the loss of membrane flux.

[0050] With reference to the above implementation contents, in order to make the technical solution of the present application more specific, clear and easy to understand, the technical solution of the present application is now exemplified. However, it should be noted that the contents to be protected by the present application are not limited to the following embodiments.

[0051] Example 1 The 15 cm × 20 cm polysulfone ultrafiltration base membrane was soaked in deionized water for thorough washing, then immersed in a 1% agar solution at 90 ° C for 5 minutes, and then the agar solution on the membrane surface was removed with a scraper; then cooled to 25 ° C and waited for the agar to solidify. Then the surface was soaked in an aqueous phase solution containing 1.1% triethylamine, 2.1% camphorsulfonic acid, 0.1% sodium dodecyl sulfate and 2% m-phenylenediamine for 2 minutes to allow the support membrane to be fully soaked in the aqueous phase solution. Then the solution was poured out. Then the residual droplets on the membrane surface were removed with an air knife, and the membrane surface was soaked in a hexane oil phase solution containing 0.1% trimesoyl chloride to initiate interfacial polymerization for 30 seconds. Finally, the membrane was placed in an oven at 80 ° C for heat treatment for 5 minutes to obtain an aromatic polyamide composite reverse osmosis membrane, and immediately washed thoroughly with 90 ° C deionized water, and then stored in deionized water for testing.

[0052] Example 2 The method is basically the same as Example 1, except that the polysulfone ultrafiltration base membrane is immersed in a 0.1% agar solution at 70°C for 5 minutes, and the heat treatment temperature is 70°C.

[0053] Example 3 The method is basically the same as 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.

[0054] Example 4 The method is substantially the same as Example 1, except that the aqueous phase solution includes 1.1% triethylamine, 2.1% camphorsulfonic acid, 0.1% sodium lauryl sulfate and 5% m-phenylenediamine; Example 5 The method is basically the same as Example 1, except that the oil phase solution is a hexane solution of trimesoyl chloride with a concentration of 0.5%; Comparative Example 1 The 15 cm × 20 cm polysulfone ultrafiltration support membrane was soaked in deionized water for thorough washing, and then the surface was soaked in an aqueous solution containing 1.1% triethylamine, 2.1% camphorsulfonic acid, 0.1% sodium dodecyl sulfate and 2% m-phenylenediamine for 2 minutes to allow the support membrane to be fully soaked in the aqueous solution. The solution was then poured off. The residual droplets on the membrane surface were then removed with an air knife, and the membrane surface was soaked in a hexane oil phase solution containing 0.1% trimesoyl chloride to initiate interfacial polymerization for 30 seconds. Finally, the membrane was placed in an oven at 80°C for heat treatment for 5 minutes to obtain an aromatic polyamide composite reverse osmosis membrane, which was immediately washed thoroughly with deionized water and then stored in deionized water for testing.

[0055] The composite reverse osmosis membrane was tested by filtering a 2000 ppm NaCl aqueous solution at 15.5 bar and 25° C. and the permeation flux and desalination rate were 36 LMH and 98.8% respectively.

[0056] Comparative Example 2 The 15 cm × 20 cm polysulfone ultrafiltration support membrane was soaked in deionized water for thorough washing, and then the surface was soaked in an aqueous solution containing 1.1% triethylamine, 2.1% camphorsulfonic acid, 0.1% sodium dodecyl sulfate and 2% m-phenylenediamine for 2 minutes to allow the support membrane to be fully soaked in the aqueous solution. The solution was then poured off. The residual droplets on the membrane surface were then removed with an air knife, and the membrane surface was soaked in a hexane oil phase solution containing 0.5% trimesoyl chloride to initiate interfacial polymerization for 30 seconds. Finally, the membrane was placed in an oven at 80 ° C for heat treatment for 5 minutes to obtain an aromatic polyamide composite reverse osmosis membrane, which was immediately washed thoroughly with deionized water and then stored in deionized water for testing.

[0057] The composite reverse osmosis membrane was tested by filtering a 2000 ppm NaCl aqueous solution at 15.5 bar and 25° C. and the permeation flux and desalination rate were 36 LMH and 98.8% respectively.

[0058] Performance Testing Permeate flux and salt rejection rate test A 2000 ppm NaCl aqueous solution was filtered at 15.5 bar and 25° C., and the permeation flux and salt rejection rate of the reverse osmosis membranes prepared in the corresponding examples and comparative examples were measured.

[0059] Salt rejection rate and permeation flux are two important parameters for evaluating the separation performance of reverse osmosis membranes. The present invention evaluates the separation performance of reverse osmosis membranes according to GB / T32373-2015 "Test Method for Reverse Osmosis Membrane".

[0060] The desalination rate (R) is defined as: under certain operating conditions, the salt concentration of the feed solution (C f ) and the salt concentration in the permeate (C p ) and then divided by the feed solution salt concentration (C f ), as shown below.

[0061] Permeation flux is defined as the volume of water that passes through a unit membrane area per unit time under certain operating conditions, and its unit is L / (m 2 ·h), abbreviated as LMH.

[0062] The operating conditions used in the reverse osmosis membrane performance measurement in the present invention are: the feed liquid is a 2000 ppm 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°C.

[0063] The test results are shown in the following table It can be seen from the above test results that the membrane flux of the high-flux reverse osmosis membrane prepared by the preparation method provided in Examples 1-5 of the present application is higher than the membrane flux of the reverse osmosis membrane provided in Comparative Example 1 and the retention rate is good. Among them, the membrane flux of the high-flux reverse osmosis membrane prepared in Example 1 is 54LMH, with the highest membrane flux and a high retention rate. It can be seen that in the preparation method of the high-flux reverse osmosis membrane provided in the present application, the agar solution mainly plays the role of filling the micropores in the organic membrane, so that the bottom membrane pore structure of the composite membrane remains intact during the heat treatment process of film formation. This agar mosaic structure can not only prevent the water flux of the composite membrane from being lost due to the shrinkage of the pores, but also reduce the stress generated by the shrinkage of the bottom membrane pore structure. The destructive effect on the structure of the polyamide separation functional layer, reduce the generation of defects, and thus optimize the desalination performance of the functional layer.

[0064] The basic concepts have been described above. Obviously, for those skilled in the art, the above detailed disclosure is only for example and does not constitute a limitation of this specification. Although not explicitly stated here, 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, so such modifications, improvements and corrections still belong to the spirit and scope of the exemplary embodiments of this specification.

[0065] At the same time, this specification uses specific words to describe the embodiments of this specification. For example, "one embodiment", "an embodiment", and / or "some embodiments" refer to a certain feature, structure or characteristic related to at least one embodiment of this specification. Therefore, it should be emphasized and noted that "one embodiment" or "an embodiment" or "an alternative embodiment" mentioned twice or more in different positions in this specification does not necessarily refer to the same embodiment. In addition, certain features, structures or characteristics in one or more embodiments of this specification can be appropriately combined.

[0066] In addition, unless explicitly stated in the claims, the order of the processing elements and sequences described in this specification, the use of alphanumeric characters, or the use of other names are not intended to limit the order of the processes and methods of this specification. Although the above disclosure discusses some invention embodiments that are currently considered useful through various examples, it should be understood that such details are only for illustrative purposes, and the attached claims are not limited to the disclosed embodiments. On the contrary, the claims are intended to cover all modifications and equivalent combinations that are consistent with the essence and scope of the embodiments of this specification.

[0067] Similarly, it should be noted that in order to simplify the description disclosed in this specification and thus help understand one or more embodiments of the invention, in the above description of the embodiments of this specification, multiple features are sometimes combined into one embodiment, figure or description thereof. However, this disclosure method does not mean that the features required by the subject matter of this specification are more than the features mentioned in the claims. In fact, the features of the embodiments are less than all the features of the single embodiment disclosed above.

[0068] In some embodiments, numbers describing the number of components and attributes are used. It should be understood that such numbers used in the description of the embodiments are modified by the modifiers "about", "approximately" or "substantially" in some examples. Unless otherwise specified, "about", "approximately" or "substantially" indicate 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 change according to the required features of individual embodiments. In some embodiments, the numerical parameters should take into account the specified significant digits and adopt the general method of retaining the digits. Although the numerical domains and parameters used to confirm the breadth of the range in some embodiments of this specification are approximate values, in specific embodiments, the setting of such numerical values ​​is as accurate as possible within the feasible range.

[0069] Each patent, patent application, patent application publication, and other materials, such as articles, books, specifications, publications, documents, etc., cited in this specification is hereby incorporated by reference in its entirety. Except for application history documents that are inconsistent with or conflicting with the contents of this specification, documents that limit the broadest scope of the claims of this specification (currently or later attached to this specification) are also excluded. It should be noted that if the descriptions, definitions, and / or use of terms in the materials attached to this specification are inconsistent or conflicting with the contents described in this specification, the descriptions, definitions, and / or use of terms in this specification shall prevail.

[0070] Finally, it should be understood that the embodiments described in this specification are only used to illustrate the principles of the embodiments of this specification. Other variations may also fall within the scope of this specification. Therefore, as an example and not a limitation, alternative configurations of the embodiments of this specification may be considered consistent with the teachings of this specification. Accordingly, the embodiments of this specification are not limited to the embodiments explicitly introduced and described in this specification.

Claims

1. A method for preparing a high-flux reverse osmosis membrane, characterized in that: The preparation method comprises the following steps: Get the basement membrane, Prepare agar solution, aqueous solution and oil phase solution, The base film is pretreated with the agar solution at a first temperature, the base film is fully contacted with the agar solution, and after removing excess agar solution, the base film soaked with the agar solution is cooled to a second temperature to obtain a precursor base film. The precursor base film is fully immersed in the aqueous solution, then taken out from the aqueous solution, and after removing the excess aqueous solution, it is immersed in the oil solution again, and after sufficient reaction, a precursor reverse osmosis membrane is obtained. Performing a heat treatment operation on the precursor reverse osmosis membrane to obtain a target high-flux reverse osmosis membrane; Wherein, the second temperature 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 first temperature is 70°C-100°C, and the second temperature is 0-40°C.

3. The method for preparing a high-flux reverse osmosis membrane according to claim 1, characterized in that: The mass concentration of the agar solution is 0.1%-10%.

4. 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 the agar solution at the first temperature is selected from one of soaking, single-sided spraying, double-sided spraying, and brushing.

5. 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.

6. The method for preparing a high-flux reverse osmosis membrane according to claim 1, characterized in that: The aqueous phase solution contains an amine monomer, and the amine monomer is selected from at least one of N,N-dimethyl-m-phenylenediamine, triethanolamine, m-phenylenediamine, mesitylenetriamine, p-phenylenediamine, 3-aminopiperazine, n-hexylamine and decylamine; The solute in the oil phase solution is an acyl chloride monomer, and the acyl chloride monomer is selected from at least one of biphenyl dichloride, trimesoyl chloride, benzoyl chloride, terephthaloyl chloride, isophthaloyl chloride, phthaloyl chloride, oxalyl chloride, and benzene disulfonyl chloride.

7. The method for preparing a high-flux reverse osmosis membrane according to claim 6, characterized in that: The concentration of the amine monomer is 1.0wt% to 8.0wt%; The concentration of the acyl chloride monomer in the oil phase solution is 0.01 wt % to 5 wt %.

8. 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, isoparaffin, cyclohexane, ethylcyclohexane, propylcyclohexane, n-butylcyclohexane, isobutylcyclohexane, tert-butylcyclohexane, and isopropylcyclohexane.

9. The method for preparing a high-flux reverse osmosis membrane according to claim 1, characterized in that: The heat treatment operation of the precursor reverse osmosis membrane comprises the following steps: The precursor reverse osmosis membrane is placed in an oven for heat treatment, and then fully washed with deionized water; the temperature of the oven is 60° C.-100° C.; and the heat treatment time is 2 min-10 min.

10. A high flux reverse osmosis membrane, characterized in that: Prepared by the method for preparing a reverse osmosis membrane according to any one of claims 1 to 9.

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