A high-performance reverse osmosis membrane and its preparation method

Abstract

The present invention discloses a high-performance reverse osmosis membrane and a method for preparing the same. The reverse osmosis membrane comprises a polyester non-woven fabric layer, a polysulfone-based membrane, and a polyamide skin layer stacked in sequence. The polysulfone-based membrane has a micron-scale prism structure on the side away from the polyester non-woven fabric layer. The preparation method comprises coating the surface of the polyester non-woven fabric layer with the polysulfone-based membrane, and forming the micron-scale prism structure on the surface of the polysulfone-based membrane by cold pressing with a roller mold during the process of converting the polysulfone-based membrane from a liquid state to a solid state. The present invention improves the flux without affecting the desalination rate of the reverse osmosis membrane or sacrificing the thickness of the skin layer, thereby resolving the trade-off between flux and desalination in the current technology. At the same time, the micron-scale prism structure can be designed into different shapes according to performance requirements, thereby achieving precise control of the flux performance of the reverse osmosis membrane.

Description

Technical Field

[0001] The present invention relates to the technical field of reverse osmosis membranes, and in particular to a high-performance reverse osmosis membrane and a preparation method thereof. Background Art

[0002] Reverse osmosis (RO) is a highly efficient and energy-saving technology, a membrane separation and filtration technology that uses pressure difference as the driving force. That is, under a certain pressure, water molecules can pass through the RO membrane, while impurities such as inorganic salts, heavy metal ions, organic matter, colloids, bacteria, viruses, etc. in the raw water cannot pass through the RO membrane, thereby strictly distinguishing between the pure water that can pass through and the concentrated water that cannot pass through.

[0003] The current mainstream polyamide reverse osmosis membrane is mainly a composite membrane composed of a non-woven fabric base fabric, a polysulfone porous support layer, and a surface polyamide functional skin layer. The surface polyamide functional skin layer determines the performance of the reverse osmosis membrane. The existing technology is to form a functional layer of about 200nm on the polysulfone porous layer through interfacial polymerization reaction between the water phase and the oil phase. The surface functional layer is then subjected to certain post-treatment to achieve a certain balance between its flux and desalination. Flux refers to the mass of water passing through a unit area of ​​the membrane under a certain pressure. Generally speaking, a high-flux membrane can significantly reduce energy consumption in the system and achieve energy-saving purposes, but high flux is generally accompanied by a low desalination rate, resulting in poor water quality. Flux and desalination are a trade-off relationship, a kind of trade-off phenomenon (Parket al., Science, 2017, 356, 1137). How to improve flux while ensuring a high desalination rate has always been a problem that needs to be solved in the field of reverse osmosis membranes.

[0004] Defects and shortcomings of existing technology:

[0005] 1. Existing commercial reverse osmosis membranes can achieve high flux and high desalination by making a thin polyamide functional layer to reduce water resistance, but there is a limit to the flux improvement, and reducing the thickness of the polyamide functional layer will affect the service life of the membrane (the membrane will be cleaned during use, and cleaning will reduce the thickness of the polyamide functional layer. If the functional layer is too thin, the functional layer structure will be destroyed after multiple cleanings, thus affecting the service life).

[0006] 2. The patent "Method for preparing a high-flux composite reverse osmosis membrane and the reverse osmosis membrane prepared therefrom" (CN202010220110.4) mentions the use of other hydrophilic monomers added to the aqueous phase for copolymerization with TMC to reduce the crosslink density of the polyamide functional layer and increase its hydrophilicity to improve flux. While this method can increase flux, it reduces the crosslink density, which has a certain impact on the salt rejection rate. In other words, while increasing flux, it cannot meet the required salt rejection requirements.

[0007] 3. The patent "High-flux reverse osmosis membrane, preparation method, and use thereof" (CN201811566175.3) mentions increasing the microscopic surface area to increase flux without affecting desalination. However, the preparation process is complex and industrialization is difficult. Summary of the Invention

[0008] The present invention improves the flux without affecting the desalination rate of the reverse osmosis membrane and without sacrificing the thickness of the skin, thereby resolving the contradiction between flux and desalination in the current existing technology; at the same time, the micron-level prism structure can be designed into micron-level prism structures of different shapes according to performance requirements, thereby achieving precise regulation of the flux performance of the reverse osmosis membrane.

[0009] In order to solve the above technical problems, a technical solution adopted by the present invention is: the present invention provides a high-performance reverse osmosis membrane, comprising a polyester non-woven fabric layer, a polysulfone-based membrane and a polyamide skin layer stacked in sequence, and the side of the polysulfone-based membrane away from the polyester non-woven fabric layer has a micron-level prism structure.

[0010] Furthermore, the micron-scale prism structure is at least one of a regular tetrahedron, a regular square pyramid, and a regular triangular prism.

[0011] Furthermore, the thickness of the polyester non-woven fabric layer is 50-160 μm;

[0012] The thickness of the polysulfone-based membrane is 35-50 μm;

[0013] The thickness of the polyamide skin layer is 150-250 nm.

[0014] Preferably, the thickness of the polyester non-woven fabric layer is 80-160 μm;

[0015] The thickness of the polysulfone-based membrane is 42-44 μm;

[0016] The thickness of the polyamide skin layer is 200 nm.

[0017] The present invention also provides a method for preparing the high-performance reverse osmosis membrane, wherein a polysulfone-based membrane is coated on the surface of a polyester non-woven fabric layer, and in the process of converting the polysulfone-based membrane from liquid to solid, the micron-scale prism structure is formed on the surface of the polysulfone-based membrane by cold pressing with a roller mold.

[0018] Furthermore, the preparation method of the high performance reverse osmosis membrane comprises the following steps:

[0019] Step 1: Preparation of polysulfone-based membrane:

[0020] In a mixing kettle, polysulfone particles are mixed with the solvent DMF (N,N-dimethylformamide) and stirred until completely dissolved. A polysulfone solution is prepared and evenly coated on a polyester non-woven fabric layer. The non-woven fabric coated with the polysulfone solution then enters a gel tank. The organic solvent DMF (N,N-dimethylformamide) in the polysulfone solution dissolves in water, exchanges with the aqueous solution in the tank, and gradually escapes, causing the polysulfone to gradually solidify into a membrane with a porous surface structure.

[0021] Step 2: Forming a micron-scale prism structure on the surface of the polysulfone base membrane: Before the polysulfone has completely completed its phase transformation, it is soft and can be processed using a mold. After the polysulfone-coated base membrane enters the gel tank for gel reaction, the polysulfone base membrane becomes slightly hardened. It is then extruded through an underwater roller mold in the gel tank. The surface of the roller mold has a micron array structure. Through extrusion between the mold and the extrusion roller, a layer of tightly arranged micron-scale prism structure is formed on the surface of the polysulfone base membrane.

[0022] Step 3: Preparation of polyamide skin layer:

[0023] The polysulfone-based membrane is soaked in a water phase tank, and then passed through a squeeze roller to remove excess water. The membrane is then coated with an oil phase solution, and after reacting with the oil phase solution, an air knife is used to remove excess oil on the surface, and the membrane is placed in an oven for baking.

[0024] Step 4: Post-processing: first alkali washing, then pure water rinsing, then glycerin soaking, then spraying a protective layer, and finally drying and rolling.

[0025] Furthermore, in step 1: the polysulfone liquid has a solid content of 18 wt%, is filtered through a filter element, vacuum degassed to remove gas impurities, and the polysulfone liquid is transported to the coating head by a cylinder, and the coating head evenly coats the liquid on the polyester non-woven fabric layer.

[0026] Furthermore, after the base membrane coated with polysulfone enters the gel tank for a gel reaction of 1-10 seconds, the polysulfone layer becomes slightly hardened and is extruded into shape by an underwater roller mold in the gel tank. The roller mold has a speed of 2-20 m / min, a pressure of 0.5-5 MPa, and a tooth depth of 10-40 μm on the surface of the roller mold. Through extrusion between the mold and the extrusion roller, a layer of tightly arranged micron-sized prism structure is formed on the surface of the polysulfone base membrane. The polysulfone base membrane is then rinsed in a pure water rinsing tank (for example, 5 min) to clean the residual solvent in the membrane with water to obtain a polysulfone base membrane with a micron-sized prism structure on the surface.

[0027] Specifically, after the polysulfone-coated base film enters the gel tank for a gel reaction of 2-5 seconds, the roller mold has a speed of 8-15 m / min, a squeeze roller pressure of 0.5-2 MPa, and a tooth depth of 20-30 μm on the surface of the roller mold.

[0028] Furthermore, step three is specifically as follows: preparing an aqueous phase liquid, mixing m-phenylenediamine, camphorsulfonic acid and sodium hydroxide, filtering with a filter element, and preparing the aqueous phase liquid, wherein the mass concentration of m-phenylenediamine is 3wt%, the mass concentration of camphorsulfonic acid is 2wt%, and the mass concentration of sodium hydroxide is 0.5wt%;

[0029] The oil phase solution is prepared by adding trimesoyl chloride to cyclohexane, mixing evenly, filtering with a filter element and vacuum degassing to obtain the oil phase solution, wherein the mass concentration of trimesoyl chloride is 0.15wt%;

[0030] After the polysulfone-based membrane is soaked in the water phase tank for 10 seconds, excess water is removed by squeezing rollers, and then it is coated with oil phase. A layer of oil phase solution is coated on the surface. After the oil phase solution reacts for 30 seconds, the excess oil phase on the surface is removed with an air knife, and then it is placed in a 100°C oven for baking for 2 minutes.

[0031] Further, step four is specifically as follows: pass through a 60°C 2wt% sodium hydroxide alkaline washing tank for 3 minutes, remove excess liquid on the membrane surface with an air knife after exiting the alkaline washing tank, enter a 100°C pure water rinsing tank for 3 minutes, remove excess liquid on the membrane surface with an air knife after exiting the rinsing tank, enter a 60°C 5wt% glycerol tank for soaking for 5 minutes, remove excess liquid on the membrane surface with an air knife after exiting the glycerol tank, spray a layer of 0.1wt% PVA aqueous solution on the membrane surface as a protective layer, dry in an 80°C oven for 5 minutes, and roll up.

[0032] The beneficial effects of the present invention are:

[0033] The present invention provides a method for preparing a high-performance reverse osmosis membrane, which is different from traditional methods for improving flux. Traditional methods mainly involve: 1. thinning the surface cortex, but the flux improvement is accompanied by a decrease in desalination and a shortened service life; 2. introducing new hydrophilic groups. The increased hydrophilicity is beneficial to improving flux, but it will reduce the cross-linking density, causing a serious decrease in desalination rate and failing to meet water quality requirements; 3. The introduction of nanomaterials has the disadvantages of easy agglomeration and precipitation, and poor fixation in the desalination layer, making it impossible to effectively improve the flux of reverse osmosis membranes on a large-scale industrial scale.

[0034] The present invention starts with changing the macroscopic morphology of the polysulfone-based membrane. During the phase transformation process from liquid to solid, the polysulfone layer is transformed into a solid. The polysulfone has strong plasticity and is easy to process within a certain period of time. The polysulfone-based membrane that has not yet completed the phase transformation is cold-pressed by a roller mold underwater in a gel tank to impart a micron-level prism morphology to the surface of the polysulfone-based membrane, thereby greatly increasing the surface area of ​​the polysulfone-based membrane (for example, by imparting a regular tetrahedral morphology to the surface of the polysulfone-based membrane, the surface area S of the polysulfone support layer can be increased to 3S). At the same time, whether the reaction interface is flat or not has no effect on the thickness of the cortex (the polyamide cortex is formed on the surface of the polysulfone through the interface). Interfacial polymerization is the process of polymerization. Two highly reactive monomers react at the interface of two immiscible solvents. The aqueous monomers diffuse toward the oil phase interface, cross-linking to form a polymer layer. When the cross-linked polymer cortex grows to a certain thickness, the monomers can no longer penetrate the cortex and enter the oil phase, halting chain growth. This self-limiting reaction takes only a few seconds to complete, and the flatness of the interfacial polymerization reaction surface has no effect on the thickness of the cortex. By interfacial polymerization, a polyamide cortex is formed on the surface of the polysulfone micron-scale prism structure, resulting in a high-performance reverse osmosis membrane. This high-performance reverse osmosis membrane has a higher polyamide cortex area. This increase in polyamide cortex area increases the reverse osmosis membrane flux without affecting the salt rejection rate.

[0035] This invention improves flux without compromising the reverse osmosis membrane's salt rejection rate or sacrificing membrane skin thickness, resolving the trade-off between flux and salt removal in existing technologies. Furthermore, the micron-scale prism structure can be designed into various shapes based on performance requirements, enabling precise control of the reverse osmosis membrane's flux performance. Operation requires only the replacement of the roller mold.

[0036] During the process of rolling a reverse osmosis membrane into a reverse osmosis membrane element, the membrane skin contacts the brine grid. The brine grid has protrusions at the intersection of its warp and weft threads. These protrusions contact the membrane skin, causing friction during the rolling process and damaging the membrane surface. This, in turn, reduces the desalination rate of the entire element to a certain extent. Generally, the desalination rate decreases by approximately 0.1-0.2% after the membrane is rolled. The reverse osmosis membrane produced by the present invention has a micron-scale prismatic protrusion structure on its surface. During the contact process with the brine grid, the actual contact area between the membrane surface and the brine grid is reduced, effectively reducing the area of ​​scratches on the membrane by the brine grid, thereby improving the desalination rate of the rolled membrane.

[0037] At the same time, the preparation method is easy to operate and relatively simple to industrialize.

[0038] The above description is only an overview of the technical solution of the present invention. In order to more clearly understand the technical means of the present invention and implement it according to the contents of the specification, the following is a detailed description of the preferred embodiments of the present invention with reference to the accompanying drawings. BRIEF DESCRIPTION OF THE DRAWINGS

[0039] Figure 1 is a cross-sectional view of a reverse osmosis membrane of the present invention;

[0040] Figure 2 This is a cross-sectional view of the reverse osmosis membrane and the concentrated water grid of the present invention;

[0041] Figure 3 Schematic diagram of the structure of a micron-sized regular tetrahedron on the surface of the roller mold of Example 1 of the present invention;

[0042] Figure 4 Schematic diagram of the structure of a single tetrahedron on the surface of the roller mold of Example 1 of the present invention;

[0043] Figure 5 Schematic diagram of the structure of a single quadrangular pyramid on the surface of the roller mold of Example 2 of the present invention;

[0044] Figure 6 Schematic diagram of the structure of a single regular triangular prism on the surface of the roller mold of Example 3 of the present invention;

[0045] The reference numerals are as follows:

[0046] Polyester non-woven fabric layer 10 , polysulfone base membrane 20 , polyamide skin layer 30 , concentrated water grid 40 . DETAILED DESCRIPTION

[0047] The following describes the specific embodiments of the present invention through specific examples. Those skilled in the art will readily understand the advantages and benefits of the present invention from the disclosure herein. The present invention may also be implemented in various other forms, i.e., various modifications and variations are possible without departing from the scope of the present invention.

[0048] Example: A high performance reverse osmosis membrane, such as Figure 1 and Figure 2 As shown, it comprises a polyester non-woven fabric layer 10, a polysulfone base film 20 and a polyamide skin layer 30 stacked in sequence, wherein the side of the polysulfone base film away from the polyester non-woven fabric layer has a micron-scale prism structure.

[0049] The micron-scale prism structure is at least one of a regular tetrahedron, a regular square pyramid, and a regular triangular prism, but is not limited thereto.

[0050] In this embodiment, the thickness of the polyester non-woven fabric layer is 50-160 μm; the thickness of the polysulfone-based membrane is 35-50 μm; and the thickness of the polyamide skin layer is 150-250 nm.

[0051] Preferably, the thickness of the polyester non-woven fabric layer is 50-160 μm; the thickness of the polysulfone-based membrane is 42-44 μm; and the thickness of the polyamide skin layer is 200 nm.

[0052] like Figure 1 and Figure 2 As shown, the reverse osmosis membrane manufactured by the present invention has a micron-level prismatic protrusion structure on its surface, which can reduce the actual contact area between the membrane surface and the concentrated water grid 40 during the contact process with the concentrated water grid, effectively reducing the area of ​​scratches on the reverse osmosis membrane by the concentrated water grid, thereby improving the desalination rate of the membrane roll.

[0053] Example 1:

[0054] Step 1: Preparation of polysulfone-based membrane:

[0055] In a mixing kettle, polysulfone particles are mixed with DMF (N,N-dimethylformamide) solvent and stirred until completely dissolved to prepare a polysulfone liquid with a solid content of 18 wt%. The liquid is filtered through a filter element and vacuum degassed to remove gas impurities. The polysulfone liquid is then transported to a coating head using an air cylinder, which evenly coats the liquid on a 120 μm polyester non-woven fabric layer.

[0056] Step 2: Forming a micron-scale prism structure on the surface of the polysulfone base membrane:

[0057] Then the non-woven fabric coated with polysulfone liquid enters the gel tank. After the membrane enters the gel tank and gels for 2 seconds, the polysulfone layer becomes slightly hardened and is extruded through an underwater roller mold in the gel tank. The roller mold has a speed of 8m / min and a pressure of 0.5Mpa. The roller mold has an array structure composed of precise micron-level regular tetrahedrons on its surface. Figure 3 As shown, a single regular tetrahedron is Figure 4 As shown, it is a closed spatial figure surrounded by four congruent equilateral triangles, all of which have equal edge lengths. The height of the regular tetrahedron, i.e., the tooth depth h, is 20 μm, and the edge length is 24.5 μm. Through extrusion by the mold and the extrusion roller, the polysulfone layer on the surface of the membrane forms a layer of tightly arranged regular tetrahedral micron-level prism structure. The surface area of ​​the polysulfone-based membrane increases from the original S to 3S. The polysulfone-based membrane is then rinsed in a pure water rinsing tank for 5 minutes to clean the residual solvent in the membrane with water to obtain a polysulfone-based membrane with a micron-level prism structure on the surface. The thickness of the polysulfone-based membrane is 42-44 μm.

[0058] Step 3: Preparation of polyamide skin layer:

[0059] The aqueous phase liquid is prepared by uniformly mixing m-phenylenediamine, camphorsulfonic acid and sodium hydroxide, filtering with a filter element, and preparing the aqueous phase liquid, wherein the mass concentration of m-phenylenediamine is 3wt%, the mass concentration of camphorsulfonic acid is 2wt%, and the mass concentration of sodium hydroxide is 0.5wt%;

[0060] The oil phase solution is prepared by adding trimesoyl chloride to cyclohexane, mixing evenly, filtering with a filter element and vacuum degassing to obtain the oil phase solution, wherein the mass concentration of trimesoyl chloride is 0.15 wt %.

[0061] After the polysulfone-based membrane is soaked in the water phase tank for 10 seconds, excess water is removed by squeezing rollers, and then the membrane is coated with an oil phase solution. After the oil phase solution reacts for 30 seconds, excess oil phase on the surface is removed with an air knife, and the membrane is baked in an oven A at 100°C for 2 minutes.

[0062] Step 4: Post-processing:

[0063] After the membrane comes out of oven A, it passes through a 60℃ 2wt% sodium hydroxide alkaline washing tank for 3 minutes. After leaving the alkaline washing tank, excess liquid on the membrane surface is removed with an air knife. It enters a 100℃ pure water rinsing tank for 3 minutes. After leaving the rinsing tank, excess liquid on the membrane surface is removed with an air knife. It enters a 60℃ 5wt% glycerol tank for soaking for 5 minutes. After leaving the glycerol tank, excess liquid on the membrane surface is removed with an air knife. A layer of 0.1wt% PVA aqueous solution is sprayed on the membrane surface as a protective layer. It is dried in oven B at 80℃ for 5 minutes and rolled into a high-performance reverse osmosis membrane.

[0064] Example 2:

[0065] Step 1: Preparation of polysulfone-based membrane:

[0066] In a mixing kettle, polysulfone particles are mixed with solvent DMF (N,N-dimethylformamide) and stirred until completely dissolved to prepare a polysulfone liquid with a solid content of 18wt%. The liquid is filtered through a filter element and vacuum degassed to remove gas impurities. The polysulfone liquid is transported to a coating head using an air cylinder, and the coating head evenly coats the liquid on a 120μm polyester non-woven fabric layer.

[0067] Step 2: Forming a micron-scale prism structure on the surface of the polysulfone base membrane:

[0068] Then the non-woven fabric coated with polysulfone liquid enters the gel tank. After the membrane enters the gel tank and gels for 3 seconds, it is extruded by the underwater roller mold in the gel tank. The roller mold has a speed of 12m / min and a pressure of 1Mpa. The surface of the roller mold has a precision micron-level equilateral tetrahedron. The regular tetrahedron is as follows: Figure 5 As shown, the bottom surface is a square, all the edges are equal in length, the height of the regular tetrahedron, that is, the depth of the mold tooth h is 25μm, and the edge length is 35.4μm. Through the extrusion of the mold and the extrusion roller, the polysulfone layer on the surface of the membrane forms a layer of closely arranged regular tetrahedrons with a micron-level prism structure. The surface area of ​​the polysulfone-based membrane increases from the original S to 1.73S. The polysulfone-based membrane is then rinsed in a pure water rinsing tank for 5 minutes to clean the residual solvent in the membrane with water to obtain a polysulfone-based membrane with a micron-level prism structure on the surface. The thickness of the polysulfone-based membrane is 42-44μm.

[0069] Step 3: Preparation of polyamide skin layer:

[0070] The aqueous phase liquid is prepared by uniformly mixing m-phenylenediamine, camphorsulfonic acid and sodium hydroxide, filtering with a filter element, and preparing the aqueous phase liquid, wherein the mass concentration of m-phenylenediamine is 3wt%, the mass concentration of camphorsulfonic acid is 2wt%, and the mass concentration of sodium hydroxide is 0.5wt%;

[0071] The oil phase solution is prepared by adding trimesoyl chloride to cyclohexane, mixing evenly, filtering with a filter element and vacuum degassing to obtain the oil phase solution, wherein the mass concentration of trimesoyl chloride is 0.15 wt %.

[0072] After the polysulfone-based membrane is soaked in the water phase tank for 10 seconds, excess water is removed by squeezing rollers, and then the membrane is coated with an oil phase solution. After the oil phase solution reacts for 30 seconds, excess oil phase on the surface is removed with an air knife, and the membrane is baked in an oven A at 100°C for 2 minutes.

[0073] Step 4: Post-processing:

[0074] After the membrane comes out of oven A, it passes through a 60℃ 2wt% sodium hydroxide alkaline washing tank for 3 minutes. After leaving the alkaline washing tank, excess liquid on the membrane surface is removed with an air knife. It enters a 100℃ pure water rinsing tank for 3 minutes. After leaving the rinsing tank, excess liquid on the membrane surface is removed with an air knife. It enters a 60℃ 5wt% glycerol tank for soaking for 5 minutes. After leaving the glycerol tank, excess liquid on the membrane surface is removed with an air knife. A layer of 0.1wt% PVA aqueous solution is sprayed on the membrane surface as a protective layer. It is dried in oven B at 80℃ for 5 minutes and rolled into a high-performance reverse osmosis membrane.

[0075] Example 3:

[0076] Step 1: Preparation of polysulfone-based membrane:

[0077] In a mixing kettle, polysulfone particles are mixed with solvent DMF (N,N-dimethylformamide) and stirred until completely dissolved to prepare a polysulfone liquid with a solid content of 18wt%. The liquid is filtered through a filter element and vacuum degassed to remove gas impurities. The polysulfone liquid is transported to a coating head using an air cylinder, and the coating head evenly coats the liquid on a 120μm polyester non-woven fabric layer.

[0078] Step 2: Forming a micron-scale prism structure on the surface of the polysulfone base membrane:

[0079] Then the non-woven fabric coated with polysulfone liquid enters the gel tank. After the membrane enters the gel tank and gels for 4 seconds, it is extruded by the underwater roller mold in the gel tank. The roller mold has a speed of 15m / min and a pressure of 2Mpa. The surface of the roller mold has regular triangular prisms of the same size as the micron level. Figure 6As shown, the base of the regular triangular prism is a rectangle, and the two ends are regular triangles. The height of the regular triangular prism, that is, the mold tooth depth h is 30μm, and the edge length is 34.64μm. Through the extrusion of the mold and the extrusion roller, the polysulfone layer on the surface of the membrane forms a layer of tightly arranged triangular prisms with micron-level prism morphology. The surface area of ​​the polysulfone-based membrane increases from the original S to 2S. The polysulfone-based membrane is then rinsed in a rinsing tank for 5 minutes to clean the residual solvent in the membrane with water to obtain a polysulfone-based membrane with a micron-level prism structure on the surface. The thickness of the polysulfone-based membrane is 42-44μm.

[0080] Step 3: Preparation of polyamide skin layer:

[0081] The aqueous phase liquid is prepared by uniformly mixing m-phenylenediamine, camphorsulfonic acid and sodium hydroxide, filtering with a filter element, and preparing the aqueous phase liquid, wherein the mass concentration of m-phenylenediamine is 3wt%, the mass concentration of camphorsulfonic acid is 2wt%, and the mass concentration of sodium hydroxide is 0.5wt%;

[0082] The oil phase solution is prepared by adding trimesoyl chloride to cyclohexane, mixing evenly, filtering with a filter element and vacuum degassing to obtain the oil phase solution, wherein the mass concentration of trimesoyl chloride is 0.15 wt %.

[0083] After the polysulfone-based membrane is soaked in the water phase tank for 10 seconds, excess water is removed by squeezing rollers, and then the membrane is coated with an oil phase solution. After the oil phase solution reacts for 30 seconds, excess oil phase on the surface is removed with an air knife, and the membrane is baked in an oven A at 100°C for 2 minutes.

[0084] Step 4: Post-processing:

[0085] After the membrane comes out of oven A, it passes through a 60℃ 2wt% sodium hydroxide alkaline washing tank for 3 minutes. After leaving the alkaline washing tank, excess liquid on the membrane surface is removed with an air knife. It enters a 100℃ pure water rinsing tank for 3 minutes. After leaving the rinsing tank, excess liquid on the membrane surface is removed with an air knife. It enters a 60℃ 5wt% glycerol tank for soaking for 5 minutes. After leaving the glycerol tank, excess liquid on the membrane surface is removed with an air knife. A layer of 0.1wt% PVA aqueous solution is sprayed on the membrane surface as a protective layer. It is dried in oven B at 80℃ for 5 minutes and rolled into a high-performance reverse osmosis membrane.

[0086] Note: The comparative example uses an ordinary polysulfone-based membrane with a thickness of 45 μm and no micron-level prism structure on the surface. The subsequent process conditions are the same as those in the embodiment.

[0087] Performance test results of the reverse osmosis membranes of the embodiments and comparative examples:

[0088] Test conditions:

[0089] The membrane test conditions are 2000ppm NaCl aqueous solution, operating pressure 225psi, temperature 25℃, pH value 7, and concentrate flow rate 4 / min.

[0090] The membrane element test conditions were 2000 ppm NaCl aqueous solution, operating pressure 225 psi, temperature 25°C, pH 7, and recovery rate 15%.

[0091] The test results of Examples 1-3 and Comparative Examples are shown in Table 1:

[0092]

[0093] As can be seen from the table, reverse osmosis membranes fabricated with polysulfone-based membranes incorporating micron-scale prism structures exhibit improved flux, but this improvement is not simply exponential. For example, in Example 1, the surface area of ​​the base membrane increased from s to 3s, but the corresponding flux did not increase proportionally, only increasing by 2.2 times. Similarly, in Example 3, the surface area of ​​the base membrane increased from s to 2s, but the corresponding flux did not increase proportionally, only increasing by 1.48 times. This is due to the partial compaction of surface pores during the cold pressing process in the gel tank, which reduces the flux. Regarding the salt rejection of membrane elements, the control group using conventional polysulfone-based membranes experienced a 0.2% loss in salt rejection when the membrane sheets were rolled into elements. However, the reverse osmosis membranes fabricated with polysulfone-based membranes incorporating micron-scale prism structures experienced a reduced loss in salt rejection, only 0.1%, demonstrating that the micron-scale prism structure effectively reduces the loss in salt rejection during membrane roll-up.

[0094] The above descriptions are merely embodiments of the present invention and are not intended to limit the patent scope of the present invention. Any equivalent structures made using the contents of the present invention's description and drawings, or directly or indirectly applied in other related technical fields, are also included in the patent protection scope of the present invention.

Claims

1. A high-performance reverse osmosis membrane, characterized in that: The invention comprises a polyester non-woven fabric layer, a polysulfone base film and a polyamide skin layer stacked in sequence, wherein the side of the polysulfone base film away from the polyester non-woven fabric layer has a micron-scale prism structure; The micron-scale prism structure is at least one of a regular tetrahedron, a regular square pyramid, and a regular triangular prism; The preparation method of the polysulfone-based membrane comprises the following steps: Step 1: In a mixing kettle, polysulfone particles are mixed with the solvent DMF and stirred until completely dissolved. A polysulfone solution is prepared and the polysulfone solution is evenly coated on a polyester non-woven fabric layer. The non-woven fabric coated with the polysulfone solution then enters a gel tank. The organic solvent DMF in the polysulfone solution dissolves in water, exchanges with the aqueous solution in the tank and gradually escapes, causing the polysulfone to gradually solidify into a membrane with a porous surface structure. Step 2: The polyester non-woven fabric layer coated with polysulfone enters the gel tank for gel reaction for 1-10 seconds, and the polysulfone layer becomes slightly hardened. It is then extruded into shape by an underwater roller mold in the gel tank. The roller mold has a speed of 2-20m / min and a pressure of 0.5-5Mpa. The tooth depth of the roller mold surface is 10-40μm. Through extrusion between the mold and the extrusion roller, a layer of tightly arranged micron-level prism structure is formed on the surface of the polysulfone-based membrane. The polysulfone-based membrane is then rinsed in a pure water rinsing tank to clean the residual solvent in the membrane with water to obtain a polysulfone-based membrane with a micron-level prism structure on the surface.

2. The high performance reverse osmosis membrane according to claim 1, characterized in that: The thickness of the polyester non-woven fabric layer is 50-160 μm; The thickness of the polysulfone-based membrane is 35-50 μm; The thickness of the polyamide skin layer is 150-250 nm.

3. The high performance reverse osmosis membrane according to claim 1, characterized in that: In step 1, the polysulfone liquid has a solid content of 18 wt%, is filtered through a filter element, vacuum degassed to remove gas impurities, and transported to a coating head using a cylinder. The coating head evenly coats the liquid on the polyester non-woven fabric layer.

4. The high performance reverse osmosis membrane according to claim 1, characterized in that: After the polyester non-woven fabric layer coated with polysulfone enters the gel tank for gel reaction for 2-5 seconds, the roller mold speed is 8-15m / min, the squeeze roller pressure is 0.5-2Mpa, and the tooth depth of the roller mold surface is 20-30μm.

5. A method for preparing a high-performance reverse osmosis membrane according to claim 1, characterized in that: The process includes the following steps: Step 1: In a mixing kettle, polysulfone particles are mixed with the solvent DMF and stirred until completely dissolved. A polysulfone solution is prepared and the polysulfone solution is evenly coated on a polyester non-woven fabric layer. The non-woven fabric coated with the polysulfone solution then enters a gel tank. The organic solvent DMF in the polysulfone solution dissolves in water, exchanges with the aqueous solution in the tank and gradually escapes, causing the polysulfone to gradually solidify into a membrane with a porous surface structure. Step 2: The polyester non-woven fabric layer coated with polysulfone enters the gel tank for a gel reaction of 1-10 seconds, and the polysulfone layer becomes slightly hardened. It is then extruded through an underwater roller mold in the gel tank at a speed of 2-20 m / min and a pressure of 0.5-5 MPa. The tooth depth of the roller mold surface is 10-40 μm. Through the extrusion of the mold and the extrusion roller, a layer of tightly arranged micron-sized prism structure is formed on the surface of the polysulfone-based membrane. The polysulfone-based membrane is then rinsed in a pure water rinsing tank to clean the residual solvent in the membrane with water, thereby obtaining a polysulfone-based membrane with a micron-sized prism structure on the surface; Step 3: Preparation of polyamide skin layer: The polysulfone-based membrane is soaked in a water phase tank, and then passed through a squeeze roller to remove excess water. The membrane is then coated with an oil phase solution, and after reacting with the oil phase solution, an air knife is used to remove excess oil on the surface, and the membrane is placed in an oven for baking. Step 4: Post-processing: first alkali washing, then pure water rinsing, then glycerin soaking, then spraying a protective layer, and finally drying and rolling.

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