Reverse osmosis membrane structure using 3D printing

Abstract

The present invention relates to a reverse osmosis membrane structure comprising a membrane support in which the pore diameter, arrangement regularity, porosity, and thickness are precisely controlled, and the reverse osmosis membrane structure of the present invention comprises: a membrane support comprising a plurality of pores, wherein each the plurality of pores has a diameter of 100 μm or less, and the membrane support has a porosity of 20-80% and a thickness of 5-500 μm; and an active layer formed on one surface of the membrane support.

Description

Reverse osmosis membrane structure using 3D printing

[0001] Cross-reference regarding related applications

[0002] The present application claims the benefit of priority to Korean Patent Application No. 2025-0184420 filed on December 12, 2024 and Korean Patent Application No. 2025-0119766 filed on August 27, 2025, the full contents of said patent applications incorporated by reference herein.

[0003] The present invention relates to a reverse osmosis membrane structure utilizing 3D printing.

[0004] Reverse osmosis membranes (RO membranes) are an essential technology used in various fields, such as seawater desalination, water purification, and the production of industrial ultrapure water. Conventional reverse osmosis membranes generally consist of a thin film composite (TFC) structure in which an ultrathin polyamide active layer is formed on a porous support such as polysulfone or polyethersulfone.

[0005] However, these conventional supports suffer from problems such as non-uniformity in pore size distribution, disorder in arrangement, and limitations in mechanical strength, which consequently restrict permeability performance and durability. Furthermore, traditional manufacturing processes (solution casting, phase transition methods, etc.) present challenges due to difficult process control, low manufacturing yields, and significant material loss.

[0006] Therefore, there is a need to develop a new support that has a precisely controlled pore structure, excellent raw material utilization efficiency, and ensures the mechanical stability of the reverse osmosis membrane structure, as well as a reverse osmosis membrane using the same.

[0007] The present invention is a research supported by a national research and development project and has the following information.

[0008] [Assignment No.] 20264539

[0009] [Ministry Name] Ministry of SMEs and Startups

[0010] [Name of Project Management (Specialized) Agency] Korea Institute of Startup & Entrepreneurship Promotion

[0011] [Research Project Name] '24 Public-Private Joint Startup Discovery and Incubation Program Startups

[0012] [Project Title] World's First Polymer-based Homogeneous Porous Membrane Using 3D Nanoprinting Technology

[0013] [Name of Project Performing Organization] 3DMEM Co., Ltd.

[0014] [Research Period] 2024-11-01 ~ 2025-08-31

[0015]

[0016] [Assignment No.] 20264530

[0017] [Ministry Name] Ministry of SMEs and Startups

[0018] [Name of Project Management (Specialized) Agency] Korea Institute of Startup & Entrepreneurship Promotion

[0019] [Research Project Name] 2024 Public-Private Joint Startup Discovery and Incubation Program Startups

[0020] [Project Title] World's First Polymer-based Homogeneous Porous Membrane Using 3D Nanoprinting Technology

[0021] [Name of Project Performing Organization] 3DMEM Co., Ltd.

[0022] [Research Period] 2024-11-01 ~ 2025-08-31

[0023] The objective of the present invention is to provide a reverse osmosis membrane structure comprising a membrane support in which the pore diameter, arrangement regularity, porosity, and thickness are precisely controlled.

[0024] In addition, another objective of the present invention is to improve raw material utilization efficiency by reducing manufacturing loss to 10% or less using a 3D printing process, and at the same time, to secure mechanical stability and durability by realizing a reverse osmosis membrane structure with a tensile strength of 5 MPa or more.

[0025] The present invention aims to realize a high-performance reverse osmosis membrane applicable to advanced water purification processes such as seawater desalination, water purification, and ultrapure water production by providing a reverse osmosis membrane structure that simultaneously satisfies permeability performance and selectivity by forming an active layer on a membrane support.

[0026] The present invention is a reverse osmosis membrane structure comprising: a membrane support having a plurality of pores, wherein the diameter of the plurality of pores is 100 μm or less, the porosity is 20 to 80%, and the thickness is 5 to 500 μm; and an active layer formed on one surface of the membrane support.

[0027] In the present invention, the total number of pores in the image measured by the following measurement method may be -5 to 5% of the total average number of pores.

[0028] [measurement method]

[0029] Determining magnification based on pore size: Magnification [x] = 500 / pore diameter (um)

[0030] Total number of pores in the image at the corresponding magnification: After generating a total of 20 images, the total number of pores was measured using Image J.

[0031] In the present invention, the membrane support may have a pore diameter within an image measured by the following measurement method that is -5 to 5% of the average pore diameter.

[0032] [measurement method]

[0033] Determining magnification based on pore size: Magnification [x] = 500 / pore diameter (um)

[0034] Pore ​​diameter in the image at the corresponding magnification: After generating a total of 20 images, the pore diameter was measured using Image J.

[0035] In the present invention, the membrane support may have a plurality of pores arranged regularly.

[0036] In the present invention, the active layer may comprise a polyamide, a polyimide, or a polyamide-polyimide copolymer.

[0037] In the present invention, the thickness of the active layer may be 50 to 300 nm.

[0038] In the present invention, the reverse osmosis membrane structure may have a Loss(%) value of 10% or less as measured by the following measurement method.

[0039] [measurement method]

[0040] Loss(%) = {(W0-W1) / W0} X 100

[0041] W0 above represents the total weight (g) of the input raw materials used in manufacturing, and W1 represents the dry weight (g) of the manufactured reverse osmosis membrane structure.

[0042] In the present invention, the reverse osmosis membrane structure may have a tensile strength of 5 MPa as measured by the ASTM D882 method.

[0043] According to the present invention, by using a membrane support manufactured by a 3D printing process, a precise pore structure is realized in which the pore diameter is 100 μm or less and the pore arrangement regularity and pore diameter distribution are each controlled within ±5%, thereby simultaneously improving the permeation flow rate and salt removal rate.

[0044] In addition, the reverse osmosis membrane structure of the present invention has a manufacturing loss of 10% or less, which improves raw material utilization efficiency and ensures the economic feasibility of the manufacturing process.

[0045] Furthermore, since the reverse osmosis membrane structure of the present invention has a tensile strength of 5 MPa or more, it can be operated stably even under high pressure conditions and can exhibit superior mechanical stability compared to conventional support-based reverse osmosis membranes.

[0046] Hereinafter, embodiments of the present invention will be described in detail with reference to the attached drawings so that those skilled in the art can easily implement the present invention. However, the present invention may be embodied in various different forms and is not limited to the embodiments described herein. Throughout the specification, similar parts are denoted by the same reference numerals.

[0047]

[0048] In the present invention, pores can be formed and arranged in various forms.

[0049] The present invention is a reverse osmosis membrane structure comprising: a membrane support having a plurality of pores, wherein the diameter of the plurality of pores is 100 μm or less, the porosity is 20 to 80%, and the thickness is 5 to 500 μm; and an active layer formed on one surface of the membrane support.

[0050] Preferably, the membrane support may have a porosity of 50 to 80% and a thickness of 10 to 100 μm.

[0051] Here, when the porosity is less than 20%, the pore fraction of the support is excessively low, which increases the resistance to water permeation, and thus there is a problem in that the permeate flux of the reverse osmosis membrane is significantly reduced.

[0052] On the other hand, if the porosity exceeds 80%, the mechanical strength of the support decreases, making it difficult to ensure structural stability under high pressure conditions, and the interfacial adhesion with the active layer weakens.

[0053] In addition, if the thickness of the support is less than 5㎛, the support is excessively thin, increasing the risk of damage due to external pressure and making it difficult to form stably during the manufacturing process.

[0054] On the other hand, if the thickness exceeds 500㎛, the permeation resistance increases, reducing the efficiency of water treatment, and there is a problem that the overall manufacturing cost increases due to the unnecessarily thick structure.

[0055] Therefore, the porosity and thickness ranges presented in the present invention can be considered optimal conditions for simultaneously satisfying permeability performance and mechanical stability.

[0056] In the present invention, the total number of pores in the image measured by the following measurement method of the membrane support may be -5 to 5% of the total average number of pores, and preferably -3 to 3%.

[0057] [measurement method]

[0058] Determining magnification based on pore size: Magnification [x] = 500 / pore diameter (um)

[0059] Total number of pores in the image at the corresponding magnification: After generating a total of 20 images, the total number of pores was measured using Image J.

[0060] Since the total number of pores in the image measured by the above measurement method can exhibit uniform filtration performance, etc., when it is between -5% and 5% of the total average number of pores, the above range is desirable.

[0061] In addition, in the present invention, the membrane support may have a pore diameter in an image measured by the following measurement method that is -5 to 5% of the average pore diameter, and preferably -3 to 3%.

[0062] [measurement method]

[0063] Determining magnification based on pore size: Magnification [x] = 500 / pore diameter (um)

[0064] Pore ​​diameter in the image at the corresponding magnification: After generating a total of 20 images, the pore diameter was measured using Image J.

[0065] Since the pore diameter within the image measured by the above measurement method can exhibit uniform filtration performance, etc., at -5 to 5% relative to the average pore diameter, the above range is desirable.

[0066] In the present invention, the membrane support may have a plurality of pores arranged regularly, and in the present invention, the term "regular" means that a plurality of pores are arranged according to a certain rule.

[0067] In addition, in the present invention, regular may mean that the distance between the closest pores is the same, or that there is a difference of -5 to 5% in the average distance.

[0068] In the present invention, the membrane support can be made of polymer materials such as polysulfone, polyethersulfone, polyvinylidene fluoride (PVDF), nylon, polyethylene, polypropylene, nitrocellulose, cellulose acetate, and polytetrafluoroethylene (PTFE), as well as ceramics, metals, carbon isomers, etc.

[0069] In the present invention, the active layer is a layer that selectively permeates only water molecules while blocking solutes such as solute salts, heavy metals, and microorganisms, and can be formed on a membrane support.

[0070] The active layer may comprise a polyamide, a polyimide, or a polyamide-polyimide copolymer, and preferably may comprise an aromatic polyamide. Additionally, if necessary, it may be formed as a nanocomposite in which inorganic nanoparticles (TiO2, SiO₂, ZrO₂, etc.), carbon nanotubes, graphene oxide, nanocellulose, etc. are dispersed.

[0071] The thickness of the active layer may be 50 to 300 nm, and preferably 100 to 200 nm.

[0072] If the thickness of the active layer is less than 50 nm, the layer becomes excessively thin, increasing the likelihood of defects and potentially degrading salt removal performance.

[0073] On the other hand, if it exceeds 300 nm, the transmission resistance increases, which can cause a problem where the water flow rate decreases rapidly.

[0074] The density of the active layer may be 0.8 to 1.5 g / cm³, and preferably 1.0 to 1.2 g / cm³. If the density is excessively low, the active layer is not dense, which reduces selectivity, and conversely, if the density is excessively high, the permeation flow rate may decrease.

[0075] In addition, the active layer can be formed on a membrane support by interfacial polymerization, spray coating, dip-coating, layer-by-layer self-assembly, etc.

[0076] In the present invention, the reverse osmosis membrane structure may have a Loss (%) value of 10% or less measured by the following measurement method, and preferably 1 to 5%.

[0077] [measurement method]

[0078] Loss(%) = {(W0-W1) / W0} X 100

[0079] W0 above represents the total weight (g) of the input raw materials used in manufacturing, and W1 represents the dry weight (g) of the manufactured reverse osmosis membrane structure.

[0080] If the above Loss(%) exceeds 10%, the loss of raw materials increases, which lowers the economic efficiency of the manufacturing process and increases the manufacturing unit cost during mass production. On the other hand, if the Loss(%) is less than 1%, there is a concern that permeability performance may be reduced because sufficient porosity is not secured during the pore formation process.

[0081] In addition, the reverse osmosis membrane structure may have a tensile strength of 5 MPa as measured by the ASTM D882 method, and preferably 5.5 to 8 MPa. If the tensile strength is 5 MPa or less, problems may occur such as the structure breaking or the active layer peeling off from the support during high-pressure operation. On the other hand, if the tensile strength exceeds 8 MPa, there is a problem in which the water permeation velocity is significantly reduced due to the increased permeation resistance caused by the support becoming excessively densified.

[0082] Therefore, the range of Loss (%) and tensile strength presented in the present invention can be considered the optimal conditions for simultaneously satisfying manufacturing efficiency, transmission performance, and mechanical stability.

[0083] Another aspect of the present invention is a method for manufacturing a reverse osmosis membrane structure comprising: a) forming a plurality of pore structures on a substrate; b) applying a membrane-forming solution between the plurality of pore structures and heat-treating; c) removing the plurality of pore structures; and d) applying and curing an active layer-forming solution.

[0084] In the present invention, step a) is a step of forming a plurality of pore structures on a substrate using 3D printing. The formation of the pore structures can be achieved by 3D printing produced by pulling borosilicate capillaries with a Sutter device.

[0085] Specifically, a pillar can be formed by the principle in which support ink is ejected from a nano nozzle, and the solvent evaporates upon ejection, leaving only the remaining support material. At this time, the concentration of the solid content of the ejected support ink may be 0.1 to 10 weight%, but is not limited thereto, and the diameter of the pore structure can be easily adjusted according to the application.

[0086] In addition, when 3D printing a porous structure, support ink may be applied as a thin film to the bottom surface to eliminate the risk of clogging of the pores, and various methods to prevent clogging of the pores may be applied, such as printing the height of the pore columns on the top surface opposite the bottom surface higher than the film thickness.

[0087] In step a), the shape of the pore structure can be various, such as a cylinder, a triangular prism, or a rectangular prism, and a membrane can be manufactured in which pore channels of the separation membrane can be formed in the shape of the prism by forming intaglio or embossed protrusions on the surface of the prism.

[0088] In step a), the pore structure may be a 3D printing support material that is easily soluble in water, such as polyvinyl alcohol (PVA), or a material that is soluble in an acidic solution, such as vanadium oxide, but is not limited thereto; any material that can be easily dissolved by a solvent that does not dissolve the material of the nanomembrane structure may be used without limitation.

[0089] In the present invention, step b) is a step of applying a membrane-forming solution between a plurality of porous structures and heat-treating.

[0090] The above membrane-forming solution may include polymer materials such as polysulfone, polyethersulfone, polyvinylidene fluoride (PVDF), nylon, polyethylene, polypropylene, nitrocellulose, cellulose acetate, and polytetrafluoroethylene (PTFE), as well as ceramics, metals, carbon isomers, etc.

[0091] In the present invention, in step b), the solid content of the membrane forming solution may be 1 to 30 weight%, and the viscosity of the solution may be 1 to 1,000 mPa·s at 20°C.

[0092] The content of the solids and the viscosity of the solution may vary depending on the diameter of the pore structure being manufactured, the nano nozzle, etc., but the above range is preferred because it facilitates discharge and the formation of the pore structure within the above range.

[0093] Applying the membrane solution between the pore structures in step c) above may be performed inside the 3D printer, or it may be performed in a separate device after removing the pore structures from the 3D printer.

[0094] If carried out in a separate device, the porous structure can be transferred from the 3D printer to the separate device via an automated process, and this can be done using conventional technology.

[0095] In addition, the process of applying a membrane solution between pore structures can be used without limitation as long as it is a method widely known in the art. For example, a nano-membrane solution can be injected outside the pore structures and applied by the flow of the solution over time due to the difference in height, and to make this more precise, a dip coating device or a spin coating device may be used.

[0096] In addition, when manufacturing a thin membrane, a vacuum suction plate can be used as a substrate, and after forming a pore structure on the vacuum suction plate, a membrane solution can be applied. In this case, potential problems such as wrinkling of the membrane can be prevented.

[0097] In step b) above, the heat treatment can be carried out at 60 to 200°C and can be appropriately selected depending on the components contained in the membrane solution, and the heat treatment device can be integrated with the device for applying the membrane solution or can be kept separate from the device.

[0098] In the present invention, step c) is a step of removing a pore structure, and the solution used to remove the pore structure may be used without limitation as long as it does not dissolve the membrane structure and dissolves the pore structure, but preferably, water or an acidic solution may be applied to remove it.

[0099] In the present invention, step d) is a step of forming an active layer by applying an active layer forming solution to one surface of a membrane support and curing it. The active layer is a functional layer that selectively allows water molecules to pass through in a reverse osmosis membrane structure while blocking impurities such as salts, heavy metal ions, and organic matter, and is a layer that determines the core performance of the reverse osmosis membrane structure.

[0100] The above active layer forming solution may include monomers capable of forming polyamide, polyimide, or polyamide-polyimide copolymers, and may further include inorganic nanoparticles, carbon-based materials, hydrophilic additives, etc. as needed. The formation of the active layer can generally be performed by interfacial polymerization, which induces a polymerization reaction at the interface by sequentially applying an aqueous solution and an organic phase solution, but it may also be performed by various coating processes known in the art, such as spray coating, dip coating, and spin coating.

[0101] The above curing process can be performed by methods such as heat treatment or ultraviolet (UV) irradiation, and can typically be carried out for 1 second to 10 minutes at a temperature range of 30 to 150°C. This curing process has the effect of increasing the density of the active layer to ensure selective permeability and simultaneously improving durability.

[0102] Accordingly, by step d), an active layer with a thickness of 50 to 300 nm, preferably 100 to 200 nm, can be formed on one side of the membrane support, and this active layer can simultaneously achieve high permeability and high salt removal rate.

[0103]

[0104] Hereinafter, specific embodiments according to the present invention will be described.

[0105]

[0106] Examples

[0107] Multiple porous structures were formed on a substrate using polyvinyl alcohol (PVA) by utilizing 3D printing with a nano nozzle fabricated by pulling borosilicate capillaries with a Sutter device. Subsequently, a membrane-forming solution containing 20 wt% polyvinylidene fluoride (PVDF) and having a viscosity of 500 mPa·s at 20°C was applied to the substrate with the multiple porous structures to fill the spaces between the multiple porous structures. Then, a heat treatment was performed at 120°C for 30 minutes. Afterward, the multiple porous structures were removed using water to produce a membrane support with a thickness of approximately 51 μm and a porosity of 70%.

[0108] Next, an active layer was formed on one surface of the membrane support. Specifically, a 2 wt% solution of m-phenylenediamine (MPD) was applied as an aqueous solution to one surface of the membrane support, followed by the application of a 0.1 wt% hexane solution of trimesoyl chloride (TMC) as an organic phase solution to induce interfacial polymerization at the interface. As a result, a polyamide-based ultrathin film layer with a thickness of 150 nm was formed on the surface of the support.

[0109] The formed active layer was stabilized by curing it at 80°C for 5 minutes, thereby producing a reverse osmosis membrane structure having a finally stable active layer.

[0110]

[0111] Comparative Example 1

[0112] A reverse osmosis membrane was manufactured according to a known method. Specifically, 15 wt% polysulfone and 3 wt% PVP were dissolved in an NMP solvent and cast, and then a support with a thickness of approximately 51 μm was formed through a phase transition method. This support was a porous membrane with a porosity of 70% and a heterogeneous pore structure.

[0113] Subsequently, a 2 wt% aqueous solution of m-phenylenediamine (MPD) was applied as an aqueous solution to one surface of the support, followed by the application of a 0.1 wt% hexane solution of trimethoyl chloride (TMC) as an organic phase solution to perform interface polymerization. As a result, a polyamide-based active layer was formed on the surface of the support.

[0114] A reverse osmosis membrane structure was prepared by curing the formed active layer by heat treating it at 80°C for 5 minutes.

[0115]

[0116] Comparative Example 2

[0117] Multiple porous structures were formed on a substrate using polyvinyl alcohol (PVA) by utilizing 3D printing with a nano nozzle fabricated by pulling borosilicate capillaries with a Sutter device. Subsequently, a membrane-forming solution containing 20 wt% polyvinylidene fluoride (PVDF) and having a viscosity of 500 mPa·s at 20°C was applied to the substrate with the multiple porous structures to fill the spaces between the multiple porous structures. Then, a heat treatment was performed at 120°C for 30 minutes. Afterward, the multiple porous structures were removed using water to produce a membrane support with a thickness of approximately 51 μm and a porosity of 70%.

[0118]

[0119] Experimental Example 1

[0120] Using the membrane supports prepared in the standard example and comparative example 1, the average number of pores error and the average pore diameter error were measured using the following measurement method, and the results are shown in Tables 1 and 2 below.

[0121] [measurement method]

[0122] Determining magnification based on pore size: Magnification [x] = 500 / pore diameter (um)

[0123] Total number of pores in the image at the corresponding magnification: After generating a total of 20 images, the total number of pores was measured using Image J.

[0124] Pore ​​diameter in the image at the corresponding magnification: After generating a total of 20 images, the pore diameter was measured using Image J.

[0125]

[0126] Classification Preliminary Comparison Example 1 Error %±3±50

[0127] Classification Preliminary Comparison Example 1 Error %±3±25

[0128] Referring to Tables 1 and 2 above, it can be seen that the membrane support according to the present invention has an average pore count error and an average pore diameter error of -3 to 3%.

[0129]

[0130] Experimental Example 2

[0131] The weight loss rate in the manufacturing process, which is the Loss (%) of the reverse osmosis membrane structure according to the above examples and comparative example 1, was calculated using the following measurement method, and the results are shown in Table 3.

[0132] [measurement method]

[0133] Loss(%) = {(W0-W1) / W0} X 100

[0134] W0 above represents the total weight (g) of the input raw materials used in manufacturing, and W1 represents the dry weight (g) of the manufactured reverse osmosis membrane structure.

[0135]

[0136] Classification Preliminary Comparison Example 1 Loss(%) 420

[0137] Referring to Table 3 above, it can be seen that the Loss (%) of the reverse osmosis membrane structure according to the present invention is significantly lower than that of Comparative Example 1.

[0138]

[0139] Experimental Example 3

[0140] The tensile strength of the reverse osmosis membrane structures prepared in Example 1 and Comparative Example 1 was measured according to ASTM D882, and the results are shown in Table 4 below. ASTM D882 is an international standard test method for evaluating the tensile properties of plastic films and sheets, and in this invention, this standard was applied to quantitatively evaluate the mechanical stability of the prepared reverse osmosis membrane structures. The test was performed under standard conditions (23±2℃, relative humidity 50±5%), and the test specimens were cut to a constant width and length, mounted on a tensile testing machine, and then subjected to tensile testing at a tensile speed of 50 mm / min until fracture.

[0141]

[0142] Classification Preliminary Comparative Example 1 Tensile Strength (MPa) 65

[0143] Referring to Table 4 above, it can be seen that the tensile strength of the reverse osmosis membrane structure according to the present invention is higher than that of Comparative Example 1.

[0144]

[0145] Experimental Example 4

[0146] For the reverse osmosis membrane structures prepared in Example 1, Comparative Example 1, and Comparative Example 2, the salt removal rate and permeability flux of the reverse osmosis membranes were evaluated, and the results are shown in Table 5 below. To this end, a test was performed at 25°C under a pressure condition of 225 psi (approx. 1.55 MPa) using a 2,000 ppm NaCl aqueous solution as the feed water. The effective area of ​​the test specimen was set to 40 cm².

[0147] Salt Rejection (%) was calculated according to the following formula by measuring the salt concentration in the permeate and feed.

[0148]

[0149] Here, C p is the salt concentration in the permeate (ppm), C f is the salt concentration (ppm) in the supply water.

[0150] Water Permeation Flux (L / m²) 2 h) was calculated according to the following formula.

[0151]

[0152] Here, V is the volume of permeable water (L), A is the effective area of ​​the membrane (m²), and t is the permeation time (h).

[0153]

[0154] Classification Preliminary Comparative Example 1 Comparative Example 2 Salt Removal Rate (%) 95 88 85 Permeability Flux (L / m² 2 h)201514

[0155] Referring to Table 5 above, it can be seen that the reverse osmosis membrane structure according to the embodiment of the present invention exhibits a significantly higher salt removal rate and permeability flux compared to Comparative Example 1 and Comparative Example 2.

[0156]

[0157] The present invention can provide a reverse osmosis membrane structure comprising a membrane support in which the pore diameter, arrangement regularity, porosity, and thickness are precisely controlled.

Claims

1. A membrane support comprising a plurality of pores, wherein the diameter of the plurality of pores is 100 μm or less, the porosity is 20 to 80%, and the thickness is 5 to 500 μm; and An active layer formed on one surface of the above membrane support; A reverse osmosis membrane structure including 2. In Paragraph 1, The above membrane support is a reverse osmosis membrane structure in which the total number of pores in an image measured by the following measurement method is -5 to 5% of the total average number of pores. [measurement method] Determining magnification based on pore size: Magnification [x] = 500 / pore diameter (um) Total number of pores in the image at the corresponding magnification: After generating a total of 20 images, the total number of pores was measured using Image J.

3. In Paragraph 1, The above membrane support is a reverse osmosis membrane structure in which the pore diameter in the image measured by the following measurement method is -5 to 5% relative to the average pore diameter. [measurement method] Determining magnification based on pore size: Magnification [x] = 500 / pore diameter (um) Pore ​​diameter in the image at the corresponding magnification: After generating a total of 20 images, the pore diameter was measured using Image J.

4. In Paragraph 1, The above membrane support is a reverse osmosis membrane structure having a plurality of pores arranged regularly.

5. In Paragraph 1, A reverse osmosis membrane structure in which the active layer comprises a polyamide, a polyimide, or a polyamide-polyimide copolymer.

6. In Paragraph 1, A reverse osmosis membrane structure having an active layer thickness of 50 to 300 nm.

7. In Paragraph 1, The above reverse osmosis membrane structure is a reverse osmosis membrane structure having a Loss(%) value of 10% or less as measured by the following measurement method: [measurement method] Loss(%) = {(W0-W1) / W0} X 100 W0 above represents the total weight (g) of the input raw materials used in manufacturing, and W1 represents the dry weight (g) of the manufactured reverse osmosis membrane structure.

8. In Paragraph 1, The above reverse osmosis membrane structure is a reverse osmosis membrane structure having a tensile strength exceeding 5 MPa as measured by the ASTM D882 method.

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