Reverse osmosis membrane, manufacturing method therefor, and water treatment method using same

Abstract

The present invention relates to a method for manufacturing a reverse osmosis membrane, the method comprising the steps of: (a) preparing a hydrophilic porous polymer support layer; (b) forming, on the support layer, a polyamide selective layer having a two-dimensional covalent organic framework-like (COF-like) structure through layer-by-layer self-assembly of organic monomers of a polyfunctional organic monomer; and (c) forming the same or a different polyamide selective layer on the polyamide selective layer to form a stacked polyamide selective layer in which a plurality of polyamide selective layers are chemically connected to each other through a hydrogen bond or a covalent bond.

Description

Reverse osmosis membrane, method of manufacturing the same, and water treatment method using the same

[0001] The present invention relates to a reverse osmosis membrane, a method for manufacturing the same, and a water treatment method using the same. More specifically, it relates to a reverse osmosis membrane with improved polyamide selective layer structure and surface characteristics to effectively remove neutral contaminants present in trace amounts in water, a method for manufacturing the same, and a water treatment method using the same.

[0002]

[0003] Reverse osmosis membranes are a core technology widely used to remove dissolved salts and ionic contaminants in seawater desalination, industrial water treatment, and water purification systems. A typical reverse osmosis membrane has a thin-film composite (TFC) structure with an ultra-thin polyamide (PA) selective layer formed on a porous support layer, and operates by using a pressure gradient to allow water molecules to pass through while filtering out solutes. Conventional PA-based reverse osmosis membranes exhibit excellent removal rates of over 99% for monovalent and divalent ions, and this outstanding salt removal performance is attributed to the high cross-linking density of the polyamide selective layer and the electrical repulsion effect caused by negative charges (e.g., carboxyl groups) remaining on the surface.

[0004] However, there is a problem in that the removal efficiency of existing RO membranes is insufficient for small-sized neutral molecular contaminants. For example, it has been reported that it is difficult to remove fine neutral molecules, such as urea, to potable water levels using conventional RO. In fact, trace neutral contaminants such as N-nitrosodimethylamine (NDMA), hydrophobic residual pharmaceuticals, endocrine disruptors, and boron can be detected in the permeate of wastewater reuse or drinking water purification processes. Since these substances do not carry an electric charge, the electrostatic rejection mechanism at the membrane does not operate, allowing a significant portion to pass through if they are small in size. Although these neutral contaminants are present in trace amounts, they can be harmful to human health or affect the ecosystem, so it is necessary to minimize their presence in the treated water.

[0005] The low removal rate of neutral contaminants is attributed to membrane-solute interactions and membrane structural factors. The separation mechanism of RO membranes is fundamentally determined by the size exclusion effect (molecular sieve filtration). Since neutral molecules do not have charge interactions with the membrane, their behavior is determined solely by the micropore size of the selective layer and the membrane affinity of the molecules themselves. Many organic trace contaminants can easily dissolve and diffuse into the membrane by forming interactions such as hydrogen bonds with the polyamide selective layer, which leads to a reduction in the rejection rate.

[0006] Meanwhile, PA selective layers formed by a general interface polymerization method do not have a completely homogeneous structure but rather a heterogeneous network structure, which may result in the localized existence of relatively large free volume spaces (pores). Although these microdefects or relatively large pores do not pose a problem for normal salt removal, it is known that small neutral molecules with a molecular weight of 200 g / mol or less can partially permeate through these gaps. In short, conventional reverse osmosis membranes have had limitations in completely removing specific neutral contaminants due to structural limitations and chemical interactions between the selective layer and contaminants.

[0007] Various existing technological attempts have been made to address these issues. Studies have been reported on creating denser selective layers by increasing monomer concentration or adjusting reaction conditions to enhance the density of the polyamide layer during the membrane manufacturing stage; however, these methods present a problem involving trade-offs, such as increased membrane thickness and reduced permeation flux.

[0008] As another approach, methods have been proposed to alter the structure or surface properties of the selective layer by applying post-treatment modifications after polyamide formation. For example, there have been attempts to reduce the permeation of small neutral molecules by attaching diamine-based crosslinking agents to the residual carboxyl groups of the polyamide membrane to fill micropores and densify the selective layer; additionally, there are cases where performance has been improved by stabilizing the structure of the polyamide surface through carbodiimide chemistry or heat treatment.

[0009] In addition, studies have been conducted to inhibit the adsorption and diffusion of contaminants by forming a hydrophilic coating layer (e.g., polycomposites, graphene oxide, etc.) on the surface of the separation membrane, or to modify the characteristics of the PA layer into a mixed matrix membrane (MMM) structure through nanoparticle filling.

[0010] However, these individual technologies have been limited to showing only a certain level of improvement or have faced limitations in practical application due to manufacturing process complexity and stability issues. Therefore, there is a high demand for new membrane manufacturing technologies that can fundamentally improve the removal performance of trace neutral contaminants without significantly degrading permeability.

[0011]

[0012] The objective of the present invention is to provide a reverse osmosis membrane capable of effectively removing trace neutral contaminants that were difficult to remove with conventional reverse osmosis membranes, and a method for manufacturing the same.

[0013] In addition, the invention provides a method for manufacturing a reverse osmosis membrane that can minimize problems such as reduced water permeability, decreased durability of the selective layer, and deterioration of manufacturing stability, which are generally associated with the process of improving the performance of removing neutral contaminants.

[0014] Furthermore, the invention provides a reverse osmosis membrane capable of improving exclusion performance for neutral contaminants while maintaining a high flux by uniformly controlling the microstructure of the polyamide selective layer and precisely tuning the membrane-solute interaction characteristics on the surface.

[0015] Meanwhile, other unspecified objectives of the present invention will be further considered to the extent that they can be easily inferred from the following detailed description and effects.

[0016]

[0017] According to an embodiment of the present invention, a method for manufacturing a reverse osmosis membrane is provided, comprising: (a) preparing a hydrophilic porous polymer support layer; (b) forming a polyamide selective layer having a two-dimensional covalent-like organic framework (COF-like) structure on the support layer through organic monomer layer-by-layer self-assembly of a polyfunctional organic monomer; and (c) forming the same or different polyamide selective layer on the polyamide selective layer to form a stacked polyamide selective layer in which a plurality of polyamide selective layers are chemically connected to each other through hydrogen bonding or covalent bonding.

[0018] The above-mentioned laminated polyamide selective layer can be formed by repeating steps (b) and (c) two or more times.

[0019] In step (a) above, the hydrophilic porous polymer support layer can be prepared by casting a polyacrylonitrile (PAN) solution and then hydrolyzing the surface of the porous membrane formed by a phase transition with an alkaline solution.

[0020] In step (b) above, the polyfunctional organic monomer may be one or more of an aromatic amine-based monomer having three or more functional groups and an aromatic acid halogenate monomer.

[0021] The above aromatic amine monomer is benzene-1,3,5-triamine, 1,3,5-triazine-2,4,6-triamine, 1,2,4,5-benzenetetracarboxylic acid, or a salt thereof, and the above aromatic acid halide monomer may be 1,3,5-benzenetricarbonyl trichloride or 1,2,4,5-benzenetetraamine tetrahydrochloride.

[0022] The stacked polyamide selective layer formed in step (c) above can be formed by sequentially reacting two or more monomers to form a two-dimensional COF-like planar network, and then connecting them through interlayer covalent bonds via additional monomers.

[0023] The stacked polyamide selective layer formed in step (c) above can be formed by a stacking process in which one or more of 2,4,6-trihydroxybenzene-1,3,5-tricarbaldehyde (Tp), terephthaloyl chloride (TCL), and 2-aminobenzene-1,3,5-tricarboxylic acid (ABTCA) are condensed to form a two-dimensional COF-like planar network, and one or more of p-phenylenediamine (PPD) and m-phenylenediamine (MPD) are added to interlayer connect the residual -CHO groups and PPD by imine bonding.

[0024] According to another embodiment of the present invention, a reverse osmosis membrane is provided, comprising: a hydrophilic porous polymer support layer prepared by the method for preparing the reverse osmosis membrane; and a laminated polyamide selective layer.

[0025] The above-mentioned stacked polyamide selective layer may have a two-dimensional network structure formed by a multifunctional monomer and may be a stacked structure in which a plurality of polyamide selective layers are connected by interlayer hydrogen bonds or covalent bonds.

[0026] According to another embodiment of the present invention, a water treatment method is provided that removes trace neutral contaminants using the reverse osmosis membrane as a filtration means.

[0027]

[0028] The reverse osmosis membrane according to the present invention provides the effect of significantly improving the removal rate of neutral trace contaminants, which was difficult to achieve with existing technology. In particular, it can achieve a high removal rate of over 90%, and under certain conditions over 95%, for contaminants that have small molecular sizes and do not carry an electric charge, such as NDMA and urea.

[0029] This performance improvement is attributed to the homogenization of effective pore size and pore distribution through a COF-like dense polyamide selective layer formed based on multifunctional monomers, and the structural stabilization of permeation pathways by a COF-like-PA stacked structure.

[0030] Furthermore, the membrane of the present invention minimizes or even increases the decrease in water permeability despite improved selectivity, and possesses the advantage of improved structural stability, heat resistance, and chemical resistance during long-term operation. Accordingly, process stability and energy efficiency can be simultaneously improved in high-quality water treatment fields such as advanced water purification, water reuse treatment, and ultrapure water production.

[0031] Meanwhile, it should be added that even if an effect is not explicitly mentioned here, the effects described in the following specification and the provisional effects expected by the technical features of the present invention are treated as described in the specification of the present invention.

[0032]

[0033] FIG. 1 is a flowchart illustrating a method for manufacturing a reverse osmosis separation membrane according to one embodiment of the present invention.

[0034] FIG. 2 is a conceptual diagram schematically illustrating the planar and cross-sectional structures of a polyamide dense selective layer based on a polyfunctional monomer according to one embodiment of the present invention.

[0035] FIG. 3 is a conceptual cross-sectional view of a reverse osmosis membrane having a COF-like-PA stacked structure according to one embodiment of the present invention.

[0036] It should be noted that the attached drawings are provided as examples for reference to help understand the technical concept of the present invention, and the scope of the rights of the present invention is not limited by them.

[0037]

[0038] In describing the present invention, detailed descriptions of related known functions are omitted if they are deemed obvious to a person skilled in the art and could unnecessarily obscure the essence of the invention.

[0039] The terms used in this application are used merely to describe specific embodiments and are not intended to limit the invention. The singular expression includes the plural expression unless the context clearly indicates otherwise. In this application, terms such as "comprising" or "having" are intended to specify the presence of the features, numbers, steps, actions, components, parts, or combinations thereof described in the specification, and should be understood as not precluding the existence or addition of one or more other features, numbers, steps, actions, components, parts, or combinations thereof.

[0040] Hereinafter, embodiments of a reverse osmosis membrane according to the present invention, a method for manufacturing the same, and a water treatment method using the same will be described in detail with reference to the accompanying drawings. In describing with reference to the accompanying drawings, identical or corresponding components are given the same reference numerals, and redundant descriptions thereof will be omitted.

[0041] FIG. 1 is a flowchart illustrating a method for manufacturing a reverse osmosis membrane according to an embodiment of the present invention. FIG. 2 is a conceptual diagram schematically illustrating the planar and cross-sectional structures of a polyamide dense selective layer based on a polyfunctional monomer according to an embodiment of the present invention. FIG. 3 is a conceptual cross-sectional diagram of a reverse osmosis membrane having a COF-like-PA laminated structure according to an embodiment of the present invention.

[0042] Referring to FIG. 1, a method for manufacturing a reverse osmosis membrane according to an embodiment of the present invention comprises: (a) a step of preparing a hydrophilic porous polymer support layer (S100); (b) a step of forming a polyamide selective layer having a two-dimensional covalent-like organic framework (COF-like) structure on the support layer through organic monomer layer-by-layer self-assembly of a polyfunctional organic monomer (S200); and (c) a step of forming the same or different polyamide selective layer on the polyamide selective layer to form a stacked polyamide selective layer in which a plurality of polyamide selective layers are chemically connected to each other through hydrogen bonds or covalent bonds (S300).

[0043] The manufacturing method according to the present invention can simultaneously improve the removal performance of neutral trace contaminants and water permeability performance by forming a polyfunctional group-based two-dimensional Covalent Organic Framework-like (COF-like) structure and controlling membrane-solute interactions through the stacking of COF-like-based selective layers. Each step is described in detail below.

[0044] First, the hydrophilic porous polymer support layer used in step (a) (S100) above functions as a mechanical support for the reverse osmosis membrane and simultaneously enables the uniform formation of the polyamide selective layer formed on top.

[0045] In one embodiment, the support layer can be manufactured by casting a polyacrylonitrile (PAN) solution onto a support, forming a porous membrane in a phase transition manner, and then hydrolyzing the surface with an alkaline solution.

[0046] Through such hydrolysis treatment, hydrophilic functional groups (e.g., -COOH, -CONH2, etc.) are introduced to the surface of the support layer, which improves the uniform distribution of aqueous monomers and adhesion to the selective layer during the subsequent organic monomer layer-by-layer self-assembly method. As a result, defects in the selective layer are reduced, and the overall durability and long-term stability of the membrane are improved.

[0047] In step (b) (S200) above, a polyamide selective layer having a two-dimensional organic framework (COF-like) structure is formed through an organic monomer layer-by-layer self-assembly method using a polyfunctional organic monomer. Here, the polyfunctional organic monomer includes an aromatic amine-based monomer or an aromatic acid halide monomer having three or more reactive functional groups, and one or more of these may be used.

[0048] Specifically, when the selective layer is formed, monomers with three or more functions, such as aromatic triamines or polyfunctional acid halides, are used to form a polyamide layer composed of a covalent-based two-dimensional organic framework (COF-like) structure. At this time, the reaction between the monomers induces periodic and repetitive bonding in the planar direction, forming a regular porous lattice structure on a two-dimensional plane. This 2D COF-like polyamide network enables precise control of pore size at the molecular level and can effectively block non-selective pathways through which neutral micro-contaminants can pass through due to its dense structure. At the same time, the planar structure formed by covalent bonds provides excellent thermal and mechanical stability, ensuring both selectivity and durability.

[0049] In one embodiment, the aromatic amine monomer may be benzene-1,3,5-triamine, 1,3,5-triazine-2,4,6-triamine, 1,2,4,5-benzenetetracarboxylic acid, or a salt thereof, and the aromatic acid halide monomer may be 1,3,5-benzenetricarbonyl trichloride or 1,2,4,5-benzenetetraamine tetrahydrochloride. By using such polyfunctional monomers, a two-dimensional network structure regularly connected by covalent bonds, rather than a simple amorphous polyamide structure, can be formed within the selected layer.

[0050] Accordingly, the effective pore size of the selective layer is reduced and the pore distribution is homogenized, effectively blocking non-selective pathways through which neutral contaminants can pass. At the same time, the degree of cross-linking can be improved without an excessive increase in thickness, thereby minimizing the degradation of water permeability performance.

[0051] In step (c) (S300) above, a structure in which multiple selective layers are stacked is formed by additionally forming a polyamide selective layer of the same or different composition on the polyamide selective layer formed in step (b). At this time, each selective layer is chemically connected by hydrogen bonding or covalent bonding, thereby improving structural stability.

[0052] According to one embodiment, by repeating steps (b) and (c) two or more times, a multilayer COF-like based polyamide selective layer can be formed. This repeating stacked structure increases the length of the permeation path compared to a single selective layer and further normalizes the pore distribution, thereby significantly reducing the possibility of diffusion of neutral contaminants.

[0053] In another embodiment, two or more monomers are reacted sequentially to form a two-dimensional COF-like planar network, and then additional monomers are introduced using a residual reactor to connect the layers by covalent bonds. That is, a two-dimensional pseudo-organic framework (COF-like) polyamide layer is formed in advance on a membrane support layer, and then a COF-like-PA layer is formed again through monomers to chemically bond the layers together.

[0054] For example, a structure can be formed by fabricating a nanoporous COF-like selective layer on a support layer and then closely connecting the COF-like selective layers using hydrogen bonding between them, or by polymerizing a linking monomer with residual reactive functional groups (e.g., -OH or -NH2) of the COF-like layer to form a structure through covalent bonding between the COF-like selective layers. In this process, each layer has a stable stacked structure as chemical bonding is formed. This COF-like-PA stacked structure can control the micropores of the PA layer and impart structural regularity and precision, thereby increasing the removal performance for neutral contaminants and improving the mechanical and thermal stability of the membrane.

[0055] For example, a stacked structure can be realized by condensing 2,4,6-trihydroxybenzene-1,3,5-tricarbaldehydride (Tp) and terephthaloyl chloride (TCL) to form a COF-like planar network, and then adding p-phenylenediamine (PPD) to form imine bonds with the remaining -CHO groups.

[0056] This stacked selective layer structure improves the structural durability and long-term operational stability of the selective layer, while simultaneously providing the effect of structurally suppressing the diffusion path of neutral pollutants.

[0057] The reverse osmosis membrane manufactured by the above-described manufacturing method comprises a hydrophilic porous polymer support layer and a stacked polyamide selective layer formed thereon. The selective layer has a two-dimensional network structure formed by a polyfunctional monomer, and a plurality of selective layers form a stacked structure connected by hydrogen bonds or covalent bonds.

[0058] A membrane manufactured by the method for manufacturing a reverse osmosis membrane according to one embodiment of the present invention provides the effect of significantly improving the removal performance of neutral contaminants, which was difficult to secure with conventional technology. In particular, for neutral contaminants such as N-nitrosodimethylamine (NDMA) and urea, which have small molecular sizes and do not carry a charge and easily diffuse through the amorphous gaps of a general reverse osmosis membrane, the removal rate, which previously remained at about 50 to 80%, can be improved to 90% or more, and in one embodiment, it was confirmed that a removal rate of 95% or more can be achieved through the optimization of operating conditions.

[0059] This performance improvement can be understood not merely as a temporary effect, but as the result of the continuous combination of precise control of the pore size and distribution of the selective layer, structural stabilization of the diffusion pathway, and thermodynamic and kinetic control of membrane-solute interactions. Accordingly, the removal performance of neutral inorganic contaminants (e.g., boron), which were difficult to treat in existing RO systems, is also significantly increased, making it easier to meet the strict quality standards required in high-quality water treatment fields such as advanced water purification, ultrapure water for semiconductors, and recycled water.

[0060] The separation membrane according to the present invention has the advantage of minimizing or even improving the reduction in water permeability or structural durability that typically accompanies the process of improving selectivity. This performance improvement is attributed to (i) a reduction in effective pore size and homogenization of pore distribution (blocking of non-selective pathways) resulting from the formation of a COF-like dense polyamide selective layer based on multifunctional monomers, and (ii) an increase in permeation path length and normalization of distribution (structural stabilization) due to a COF-like-PA stacked structure.

[0061] In addition, the manufacturing method of the present invention has the advantage of optimally achieving a balance between water permeability performance and separation performance. Forming a PA layer using polyfunctional monomers allows for increased cross-linking without making the membrane excessively thick, thereby improving selectivity while minimizing the reduction in water permeability at the same thickness. In the case of a PA structure incorporating COF-like elements, an increase in water permeability can be expected due to the improved surface hydrophilicity and the formation of continuous water channels resulting from the introduction of the COF-like structure. For example, the TFC-COF-like-PA membrane of the present invention can maintain a salt removal rate of over 99% while exhibiting an increase in water flux of approximately 20–30% or more compared to conventional PA membranes under the same conditions. Therefore, the present invention is advantageous not only for improving the performance of removing neutral contaminants but also in terms of energy efficiency in water treatment processes.

[0062] Additionally, the membrane according to the present invention has improved effects in terms of durability and stability. The polyamide selective layer is structurally stable due to polyfunctional crosslinking, and thermal and chemical resistance is improved due to COF-like-PA bonding. For example, the COF-like-PA structure enables long-term operation without performance degradation even in high-temperature environments (e.g., 60-70°C), and the polyfunctional PA has the effect of improving resistance to oxidizing agents such as chlorine due to the reduction of residual amine groups.

[0063] In summary, the serial combination of the COF-like dense PA selective layer and the COF-PA stacked structure of the present invention simultaneously achieves a high rejection rate for neutral trace contaminants, high water permeability, and excellent anti-fouling properties, thereby significantly improving the process stability and energy efficiency of high-quality purified water production and complex water reuse treatment processes.

[0064] Meanwhile, such reverse osmosis membranes can be used as a filtration means to remove trace neutral contaminants and can be applied to various water treatment processes, such as advanced water purification, wastewater reuse, and the production of ultrapure water for semiconductor processes. When using the membrane of the present invention, excellent water permeability performance and long-term operational stability can be simultaneously secured while maintaining a high removal rate for neutral contaminants.

[0065] Hereinafter, an example of the method for manufacturing a reverse osmosis separation membrane according to the present invention will be described in detail.

[0066]

[0067] <Example 1: Preparation of a dense polyamide layer having a polyfunctional group-based two-dimensional organic framework (COF-like) structure>

[0068] (1) Manufacturing of support layer and surface pretreatment

[0069] Polyacrylonitrile (PAN) polymer was used as the support layer. PAN was dissolved in N-methyl-2-pyrrolidone (NMP) solvent to prepare a dope solution of a certain viscosity, which was then cast onto a flat glass substrate. The cast film was immersed in a bath of pure water and solidified at room temperature for about 30 minutes via a non-solvent-induced phase transition. The PAN porous support film obtained in this way was thoroughly washed with distilled water and stored in a wet state for use.

[0070] The above support layer is a thick, asymmetric porous membrane with high water permeability, but since the surface pore size is relatively large, surface pretreatment was performed to improve the uniformity of the selective layer to be formed thereafter.

[0071] Specifically, the support layer was immersed in a 1.0 M aqueous sodium hydroxide (NaOH) solution for 1 hour to hydrolyze the surface cyano groups (-CN) of the PAN chains, converting them into carboxyl groups (-COOH). Afterward, the hydrolyzed support layer was removed, thoroughly washed with water, and then immersed in pure water for at least 12 hours to remove any remaining NaOH and byproducts.

[0072] The support layer that has undergone such a surface hydrolysis process acquires hydrophilic negative charge characteristics on its surface, which can improve interaction with the selective layer or intermediate layer formed in subsequent steps.

[0073]

[0074] (2) Formation of a polyfunctional monomer-based COF-like PA selective layer

[0075] A polyfunctional monomer-based polyamide (PA) selective layer was formed in a lamination manner on the above-mentioned pre-treated support layer. A monomer with an aromatic trifunctional group and a triacid halide monomer were used to form the selective layer.

[0076] Specifically, 1,3,5-benzenetriamine (tris(4-aminophenyl)amine, TAP) monomer was used as the aromatic trifunctional amine monomer, and 1,3,5-benzenetricarbonyl trichloride (trimethoyl chloride, TMC) monomer was used as the acid halide monomer.

[0077] In the examples, TAP and TMC monomers were prepared by dissolving each in the corresponding solvent to a concentration in the range of about 0.5 to 20 wt%. It is preferable to dissolve the TAP monomer in a mixed solvent of acetone, ethanol, or methanol, and to dissolve the TMC monomer in toluene, hexane, or Isopar G.

[0078] After mounting the pretreated support layer onto the membrane holder, it was placed in a TAP monomer solution and reacted for 5 minutes. At this stage, the polyfunctional -NH2 groups of TAP form hydrogen bonds or partially covalent bonds with the -COOH groups on the surface of the support layer, forming a single organic layer.

[0079] Subsequently, the support layer was transferred to a TMC monomer solution and reacted for 5 minutes, and the triple -COCl groups of TMC rapidly reacted with the -NH2 groups of the previously attached TAP monomer to form -CONH- bonds (polyamide bonds).

[0080] After the reaction, the solution was removed to form a selective layer on the membrane, and the remaining TMC and by-products were removed by washing with toluene or hexane.

[0081] The above TAP and TMC steps were defined as one cycle, and this [TAP / TMC] stacking cycle was repeated a total of once. The number of cycles can be optimized by considering the target thickness and density of the selected layer, and in this embodiment, sufficient shielding performance and high transmission characteristics could be obtained with a single stacking.

[0082] The laminated separator was heat-treated at 80°C for 10 minutes to further firmly fix the structure of the formed PA layer.

[0083] The finally obtained separation membrane comprises a dense PA selective layer in which polyfunctional aromatic monomers are polymerized into a two-dimensional planar lattice structure on a porous support layer, and this selective layer has a periodic network structure based on benzene rings, which is evaluated to have a uniform pore size compared to a general PA layer and to form a very fine pore network of about 0.3 to 0.5 nm even as a single layer.

[0084] Meanwhile, variations using other tetrafunctional monomer combinations instead of TAP and TMC can also be considered. For example, a dense COF-like structure can be formed by using melamine or 1,2,4,5-benzenetetracarboxylic acid (BTCA) instead of TAP monomer and 1,2,4,5-benzenetetraamine tetrahydrochloride (BTATCL) instead of TMC. In this case, a stronger and denser structure can be achieved by forming cross-links on the plane between the -COCl of BTCA and the -NH2 group of BTATCL.

[0085] All such variations are included within the technical scope of the present invention. The membrane of this embodiment was stored in distilled water after manufacturing in preparation for subsequent characteristic evaluation.

[0086]

[0087] <Example 2: Preparation of a Separator with a COF-like-PA Stacked Structure>

[0088] (1) Formation of planar COF-like layers and stacking

[0089] A COF-like structure selective layer can be formed by sequentially reacting two or more monomers on a PAN support film in the same manner as in Example 1, but in this example, an additional chemical linkage structure was introduced to improve the bonding strength between layers.

[0090] To this end, solutions of 2,4,6-trihydroxybenzene-1,3,5-tricarbaldehyde (Tp) monomer, p-phenylenediamine (PPD) monomer, and terephthaloyl chloride (TCL) monomer were prepared, respectively.

[0091] Tp monomer was dissolved in acetone, ethanol, or methanol as a molecule having three polyaldehyde (-CHO) groups, PPD monomer was dissolved in a mixed solvent of acetone, ethanol, or methanol as an aromatic diamine, and TCL monomer was dissolved in toluene or hexane as a dioxide halide.

[0092] After mounting the pretreated membrane onto a membrane holder, a TCl solution was added and reacted for 3 minutes. Subsequently, the membrane was immersed in a Tp monomer solution for 5 minutes and reacted, followed by washing with acetone, ethanol, or methanol. At this stage, the triple -CHO groups of Tp react with the active groups attached in the previous step (or the -NH2 groups of the support layer / intermediate layer, etc.) to form Schiff-based imine bonds (-C=N-), thereby forming a two-dimensional planar COF-like structure.

[0093] Next, the layers were immersed in a PPD monomer solution and reacted for 5 minutes, after which they were washed with acetone, ethanol, or methanol. The two -NH2 groups of PPD reacted further with the remaining -CHO groups of Tp, causing the layers to act as bridges to the covalent chains, and vertical imine bonds were formed.

[0094] The three-step reaction of (TCL → Tp → PPD) was defined as a single stacking cycle, and in this example, this was repeated five times. After five stacking cycles, the interlayer bonding was strengthened through heat treatment at 60°C for 3 minutes. Finally, the heat-treated membrane was stored in pure water (DI).

[0095]

[0096] (2) Characteristics of the stacked structure

[0097] The separator according to Examples 1 and 2 forms a two-dimensional COF-like network composed of amide or ester bonds, and is also closely bonded in the vertical direction (interlayer) of each planar COF-like layer through aromatic π-π interactions and NH…O hydrogen bonds, thereby forming an integrated multilayer thin film selective layer.

[0098] In addition, the stability of the stacked structure was improved by creating bridges through covalent bonding between layers and introducing chemical bonding between layers through the addition of monomers such as PPD.

[0099] Referring to FIG. 2, the process of forming a two-dimensional COF-like polyamide network by the polycondensation reaction of a polyfunctional amine and a polyfunctional acid halide on a porous support layer is illustrated. The uniform subnanopore distribution resulting from periodic bonding in the planar direction and the pore distribution resulting from high crosslinking are schematically shown. (Examples include the reaction scheme and planar lattice structure representation of the 1,2,4,5-Benzenetetracarboxylic acid (89-05-4) - 1,2,4,5-Benzenetetramine tetrahydrochloride (4506-66-5) monomer.)

[0100] Referring to FIG. 3, a plurality of COF-like polyamide planar layers formed on a support layer are connected to each other through interlayer hydrogen bonding and covalent bonding (bridge bonding) through additional monomers to form an integral laminated selective layer.

[0101] In the laminated structure manufactured in this way, even a COF-like network, which has relatively high porosity when formed as a single layer, becomes multilayered as the pore paths narrow, so the effective pore size of the entire selected layer decreases.

[0102] In another embodiment, a variation using a different combination of trifunctional monomers instead of Tp and PPD can also be considered. For example, a COF-like stacked structure can be formed by using 2-aminobenzene-1,3,5-tricarboxylic acid (ABTCA) instead of the Tp monomer and m-phenylenediamine (MPD) instead of PPD. In this case, the -NH2 group of ABTCA and the -COCl group of TCl form interlayer crosslinks, thereby enabling a strong stacked structure.

[0103] All of these variations are included within the technical scope of the present invention.

[0104] The scope of protection of the present invention is not limited to the description and expression of the embodiments explicitly described above. Furthermore, it is added once again that the scope of protection of the present invention cannot be limited by obvious changes or substitutions in the technical field to which the present invention belongs.

Claims

1. (a) A step of preparing a hydrophilic porous polymer support layer; (b) forming a polyamide selective layer having a two-dimensional covalent-like organic framework (COF-like) structure on the support layer through organic monomer layer-by-layer self-assembly of a polyfunctional organic monomer; and (c) a step comprising forming identical or different polyamide selective layers on the polyamide selective layer to form a stacked polyamide selective layer in which a plurality of polyamide selective layers are chemically connected to each other through hydrogen bonds or covalent bonds, Method for manufacturing a reverse osmosis membrane.

2. In Paragraph 1, The above-mentioned laminated polyamide selective layer is, Formed by repeating steps (b) and (c) above two or more times, Method for manufacturing a reverse osmosis membrane.

3. In Paragraph 1, In step (a) above, the hydrophilic porous polymer support layer is, A porous membrane formed by casting a polyacrylonitrile (PAN) solution and then hydrolyzing the surface of the membrane formed by a phase transition with an alkaline solution, Method for manufacturing a reverse osmosis membrane.

4. In Paragraph 1, In step (b) above, the polyfunctional organic monomer is, One or more of an aromatic amine monomer having three or more functional groups and an aromatic acid halogenate monomer, Method for manufacturing a reverse osmosis membrane.

5. In Paragraph 4, The above aromatic amine monomer is benzene-1,3,5-triamine, 1,3,5-triazine-2,4,6-triamine, 1,2,4,5-benzenetetracarboxylic acid, or a salt thereof, and The above aromatic acid halide monomer is 1,3,5-benzenetricarbonyl trichloride or 1,2,4,5-benzenetetraamine tetrahydrochloride, Method for manufacturing a reverse osmosis membrane.

6. In Paragraph 1, The laminated polyamide selective layer formed in step (c) above is, A structure formed by sequentially reacting two or more monomers to form a two-dimensional COF-like planar network, and then connecting them via interlayer covalent bonds through additional monomers. Method for manufacturing a reverse osmosis membrane.

7. In Paragraph 6, The laminated polyamide selective layer formed in step (c) above is, One or more of 2,4,6-trihydroxybenzene-1,3,5-tricarbaldehyde (Tp), terephthaloyl chloride (TCL), and 2-aminobenzene-1,3,5-tricarboxylic acid (ABTCA) are condensed to form a two-dimensional COF-like planar network, and A stacked polyamide selective layer is formed by a stacking process that adds one or more of p-phenylenediamine (PPD) and m-phenylenediamine (MPD) to interlayer connect residual -CHO groups and PPD by imine bonding. Method for manufacturing a reverse osmosis membrane.

8. Manufactured by the method of manufacturing the reverse osmosis membrane of paragraph 1, hydrophilic porous polymer support layer; and including a laminated polyamide selective layer, Reverse osmosis membrane.

9. In Paragraph 8, The above-mentioned laminated polyamide selective layer is, It has a two-dimensional network structure formed by polyfunctional monomers, and A stacked structure in which a plurality of polyamide selective layers are connected by interlayer hydrogen bonds or covalent bonds, Reverse osmosis membrane.

10. A water treatment method for removing trace neutral contaminants using the reverse osmosis membrane of claim 8 as a filtration means.

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