Reverse osmosis membrane and preparation method therefor

Abstract

A reverse osmosis membrane and a preparation method therefor. The preparation method for the reverse osmosis membrane comprises: preparing an organic layer (20) on a flexible polymer substrate (10), the organic layer (20) being cross-linked and bonded with the flexible polymer substrate (10); and preparing an inorganic oxide layer (30) on the organic layer (20), the inorganic oxide layer (30) being cross-linked and bonded to the organic layer (20).

Description

[Corrected 07.02.2025 according to Rule 26] A reverse osmosis membrane and a method for preparing a reverse osmosis membrane

[0001] This application claims priority to the Chinese patent application filed with the Patent Office of China on February 5, 2024, with application number 202410167530.9 and invention name “A reverse osmosis membrane and a method for preparing a reverse osmosis membrane”, and incorporates its entire contents into this application by reference.

Technical field

[0002] The present application relates to the field of reverse osmosis membranes, and in particular to a reverse osmosis membrane and a method for preparing the reverse osmosis membrane. [Background Technology]

[0003] To improve filtration capacity, reverse osmosis membranes are typically multilayered. However, existing methods for producing reverse osmosis membranes typically involve physically stacking the membrane layers, such as through interfacial polymerization. This weak bonding between the layers of these membrane structures can lead to large gaps between the layers, trapping inorganic suspended particles, hydrophobic oily organic matter, and microorganisms. This can lead to scale clogging and membrane fouling, impacting the lifespan and filtration performance of the reverse osmosis membrane. [Summary of the invention]

[0004] In view of the above problems, the present application provides a reverse osmosis membrane and a preparation method thereof to improve the situation of membrane fouling and membrane damage.

[0005] In a first aspect, the present application provides a method for preparing a reverse osmosis membrane, comprising:

[0006] preparing an organic layer on a flexible polymer substrate, wherein the organic layer is cross-linked and bonded to the flexible polymer substrate;

[0007] An inorganic oxide layer is prepared on the organic layer, and the inorganic oxide layer is cross-linked and bonded with the organic layer.

[0008] In some embodiments, the organic layer is formed by a molecular layer deposition process, and the inorganic oxide layer is formed by an atomic layer deposition process, and the pore sizes of the flexible polymer substrate, the organic layer, and the inorganic oxide layer decrease in sequence.

[0009] In some embodiments, after preparing the inorganic oxide layer, the method for preparing the reverse osmosis membrane further comprises: heat-treating the reverse osmosis membrane.

[0010] In some embodiments, the step of heat treating the reverse osmosis membrane comprises:

[0011] The reverse osmosis membrane is slowly heated to 50°C-200°C and cooled after a preset time.

[0012] In some embodiments, the preset time is 1 hour to 5 hours.

[0013] In some embodiments, the steps of preparing an organic layer on the flexible polymer substrate, preparing an inorganic oxide layer on the organic layer, and heat-treating the reverse osmosis membrane are performed in the same reaction chamber.

[0014] In some embodiments, the organic layer is a polyamide material or a polyimide material, and the steps of preparing the organic layer on the flexible polymer substrate include:

[0015] An organic layer is deposited on a flexible polymer substrate by using a first precursor and a second precursor, wherein the first precursor is a precursor containing an amino group, and the second precursor is a precursor containing an acyl group.

[0016] In some embodiments, the step of depositing an organic layer on a flexible polymer substrate using a first precursor and a second precursor includes:

[0017] The first precursor is introduced into the reaction chamber in a pulsed manner using a source-carrying gas at a flow rate of 500 sccm-1500 sccm for a duration of 1 s-3 s;

[0018] Purge gas is introduced into the reaction chamber for purging, with a purge flow rate of 1000 sccm-1500 sccm and a purge time of 5s-10s;

[0019] The second precursor is introduced into the reaction chamber in a pulsed manner using a source-carrying gas at a flow rate of 500 sccm-1500 sccm for a duration of 1 s-3 s.

[0020] Purge gas is introduced into the reaction chamber for purging, with a purge flow rate of 500 sccm-1500 sccm and a purge time of 5s-10s;

[0021] Repeat the above steps 4000-10000 times to obtain an organic layer;

[0022] The vacuum degree in the reaction chamber is 1Pa-100Pa, the reaction temperature is 100°C-200°C, and the temperature of the first precursor and the second precursor is 30°C-150°C.

[0023] In some embodiments, the step of preparing an inorganic oxide layer on the organic layer includes: using a third precursor and a fourth precursor to deposit an inorganic oxide layer on the organic layer, the inorganic oxide layer is a single oxide layer or a stacked oxide layer, the third precursor is one or more of a metal halide precursor, an organometallic precursor and a silicon-containing precursor, and the fourth precursor is an oxygen source.

[0024] In some embodiments, the step of depositing an inorganic oxide layer on the organic layer includes: using a source-carrying gas to alternately introduce a third precursor and a fourth precursor into a reaction chamber; before the third precursor and the fourth precursor are alternately introduced, using a purge gas to purge the reaction chamber.

[0025] In a second aspect, the present application provides a reverse osmosis membrane comprising a flexible polymer substrate, an organic layer and an inorganic oxide layer stacked in sequence, wherein the flexible polymer substrate is cross-linked and bonded to the organic layer, and the organic layer is cross-linked and bonded to the inorganic oxide layer.

[0026] In some embodiments, the pore sizes of the flexible polymer substrate, the organic layer, and the inorganic oxide layer decrease in sequence.

[0027] In some embodiments, the pore size of the flexible polymer substrate is 0.1 μm-1 μm, and the pore size of the organic layer is 0.05 μm-1 μm.

[0028] In some embodiments, the reverse osmosis membrane formed by the flexible polymer substrate, the organic layer, and the inorganic oxide layer has a pore size of 0.1 nm to 10 nm.

[0029] In some embodiments, the thickness of the flexible polymer substrate is 50 μm-125 μm, the thickness of the organic layer is 0.2 μm-1 μm, and the thickness of the inorganic oxide layer is 50 nm-250 nm.

[0030] In some embodiments, the flexible polymer substrate is a polysulfone material, and the organic layer is a polyamide material or a polyimide material.

[0031] In some embodiments, the inorganic oxide layer includes one or more of aluminum oxide, silicon oxide, titanium oxide, and zinc oxide.

[0032] The beneficial effects of this application are:

[0033] The present application prepares an organic layer and an inorganic oxide layer stacked in sequence on a flexible polymer substrate, and the flexible polymer substrate, the organic layer and the inorganic oxide layer are cross-linked and bonded to each other, thereby producing a composite cross-linked reverse osmosis membrane. On the one hand, the bonding force between the membrane layers of the reverse osmosis membrane can be improved, thereby improving the filtration capacity of the reverse osmosis membrane and extending the service life of the reverse osmosis membrane. On the other hand, the inorganic oxide layer can be used to protect the organic layer, thereby reducing the possibility of the organic layer being corroded by inorganic suspended particles, hydrophobic oily organic matter or microorganisms in the liquid during the process of the reverse osmosis membrane filtering the liquid, or reacting with active chlorine in the cleaning reagent to cause damage to the membrane structure, thereby further extending the service life of the reverse osmosis membrane.

[0034] The above description is only an overview of the technical solution of the present application. In order to more clearly understand the technical means of the present application, it can be implemented in accordance with the contents of the specification. In order to make the above and other purposes, features and advantages of the present application more obvious and easy to understand, the specific implementation methods of the present application are listed below.

Brief Description of the Drawings

[0035] Various other advantages and benefits will become apparent to those skilled in the art upon reading the detailed description of the preferred embodiment below. The accompanying drawings are for illustration purposes only and are not to be considered as limiting the present application. The same reference numerals are used throughout the drawings to represent the same components. In the drawings:

[0036] FIG1 is a schematic diagram of the structure of a reverse osmosis membrane provided in some embodiments of the present application;

[0037] FIG2 is a schematic structural diagram of an inorganic oxide layer provided in some embodiments of the present application;

[0038] FIG3 is a schematic diagram of a preparation process of a reverse osmosis membrane provided in some embodiments of the present application;

[0039] FIG4 is a schematic diagram of the preparation process of the organic layer provided in some embodiments of the present application;

[0040] FIG5 is a schematic diagram of the preparation process of an inorganic oxide layer provided in some embodiments of the present application;

[0041] FIG6 is a schematic diagram of the preparation process of an inorganic oxide layer provided in other embodiments of the present application;

[0042] FIG. 7 is a schematic diagram showing the relationship between the number of ALD reaction cycles and the thickness of the inorganic oxide layer provided in one embodiment of the present application. [Specific implementation method]

[0043] The following will be combined with the drawings in the embodiments of this application to clearly and completely describe the technical solutions in the embodiments of this application. Obviously, the embodiments described are only part of the embodiments of this application, not all of the embodiments. Based on the embodiments in this application, all other embodiments obtained by ordinary technicians in this field without making creative efforts are within the scope of protection of this application.

[0044] It should be noted that the terms "first," "second," etc., used hereinafter are for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the quantity of the technical features being referred to. Therefore, features designated as "first" or "second" may explicitly or implicitly include one or more of the aforementioned features.

[0045] The terms used in this specification are intended to illustrate the embodiments of the present invention and are not intended to limit the present invention. It should also be noted that, unless otherwise expressly specified or limited, the terms "disposed," "connected," and "connected" should be understood in a broad sense. For example, they can refer to fixed connections, detachable connections, or integral connections; they can refer to mechanical connections, direct connections, indirect connections through an intermediate medium, or internal connections between two components. Those skilled in the art will have a clear understanding of the specific meanings of the above terms in the present invention.

[0046] References herein to "embodiments" mean that a particular feature, structure, or characteristic described in connection with the embodiments may be included in at least one embodiment of the present application. The appearance of this phrase in various places in the specification does not necessarily refer to the same embodiment, nor does it constitute an independent or alternative embodiment that is mutually exclusive of other embodiments. It is understood, both explicitly and implicitly, by those skilled in the art that the embodiments described herein may be combined with other embodiments.

[0047] The present application provides a reverse osmosis membrane. Reverse osmosis is a technology that uses pressure difference as a driving force to separate the solvent in a solution, and the reverse osmosis membrane is the core component of reverse osmosis technology.

[0048] Please refer to FIG. 1 , which is a schematic structural diagram of a reverse osmosis membrane provided in some embodiments of the present application.

[0049] In some embodiments of the present application, the reverse osmosis membrane 100 includes a flexible polymer substrate 10, an organic layer 20, and an inorganic oxide layer 30 stacked in sequence. The organic layer 20 is cross-linked and bonded to the flexible polymer substrate 10, and the inorganic oxide layer 30 is cross-linked and bonded to the organic layer 20.

[0050] The flexible polymer substrate 10 is a flexible substrate formed of a polymer material, such as a flexible polyethersulfone substrate. Of course, the flexible polymer substrate 10 can also be formed of other polymer materials, such as, but not limited to, polyphenylene ether, polycarbonate, etc. The organic layer 20 is formed of an organic material, such as a polyamide material or a polyimide material. The inorganic oxide layer 30 is a film layer formed of an inorganic oxide material. The inorganic oxide material used to form the inorganic oxide layer 30 can include, but is not limited to, aluminum oxide (Al2O3), silicon oxide (SiO2), titanium oxide (TiO2), zinc oxide (ZnO), etc.

[0051] In some embodiments, the thickness of the flexible polymer substrate 10 is 50 μm-125 μm. For example, the thickness of the flexible polymer substrate 10 can be: 50 μm, 55.2 μm, 60.15 μm, 70 μm, 75 μm, 80 μm, 85 μm, 90.3 μm, 95 μm, 100 μm, 105 μm, 110 μm, 115.2 μm, 120 μm, 125 μm, etc.

[0052] In some embodiments, the thickness of the organic layer 20 is 0.2 μm-1 μm. For example, the thickness of the organic layer 20 may be 0.2 μm, 0.25 μm, 0.3 μm, 0.4 μm, 0.5 μm, 0.6 μm, 0.7 μm, 0.8 μm, 0.85 μm, 0.9 μm, 1 μm, etc.

[0053] In some embodiments, the thickness of the inorganic oxide layer 30 is 50 nm-250 nm. For example, the thickness of the inorganic oxide layer 30 can be 50 nm, 50.5 nm, 60 nm, 70 nm, 80 nm, 90 nm, 100 nm, 100.55 nm, 110 nm, 120 nm, 130 nm, 140 nm, 150 nm, 155.5 nm, 160 nm, 170 nm, 180 nm, 190 nm, 195.5 nm, 200 nm, 220 nm, 240 nm, etc.

[0054] It can be understood that the thickness of the reverse osmosis membrane 100 is the sum of the thicknesses of the flexible polymer substrate 10 , the organic layer 20 and the inorganic oxide layer 30 .

[0055] The composite cross-linked reverse osmosis membrane 100 may have a gradient change from large to small in the direction in which the flexible polymer substrate 10 , the organic layer 20 , and the inorganic oxide layer 30 are sequentially arranged.

[0056] Optionally, the thicknesses of the flexible polymer substrate 10 , the organic layer 20 and the inorganic oxide layer 30 decrease in sequence, so that the composite cross-linked reverse osmosis membrane 100 has a gradient thickness change trend from large to small from one side to the other.

[0057] Optionally, the particle diameters of the flexible polymer substrate 10 , the organic layer 20 and the inorganic oxide layer 30 decrease in sequence, so that the composite cross-linked reverse osmosis membrane 100 has a gradient change trend from large to small particle diameters from one side to the other.

[0058] It is understood that each layer of the reverse osmosis membrane 100 necessarily has pores. When the reverse osmosis membrane 100 is used for filtration, liquid can pass through the pores of the reverse osmosis membrane 100, while impurities are intercepted by the reverse osmosis membrane 100. Therefore, the pore structure of the reverse osmosis membrane 100 has a significant impact on its filtration performance. The reverse osmosis membrane 100 provided in this application has improved this. For ease of understanding, the pore structure size of the reverse osmosis membrane 100 will be referred to as "pore size" below.

[0059] In some embodiments, the pore size of the flexible polymer substrate 10 may be 0.1 μm-1 μm, for example, 0.1 μm, 0.2 μm, 0.3 μm, 0.4 μm, 0.5 μm, 0.6 μm, 0.7 μm, 0.8 μm, 0.9 μm, 1 μm, etc.

[0060] The pore size of the organic layer 20 may be 0.05 μm-1 μm, for example, 0.05 μm, 0.07 μm, 0.1 μm, 0.2 μm, 0.3 μm, 0.4 μm, 0.5 μm, 0.6 μm, 0.7 μm, 0.8 μm, 0.9 μm, 1 μm, etc.

[0061] It should be noted that in the reverse osmosis membrane 100 provided in the embodiment of the present application, due to the gradient change of the pore size of different membrane layers, the pore size of the upper membrane layer becomes relatively smaller, and then the overall pore size of the reverse osmosis membrane 100 gradually becomes smaller, meeting the filtration requirements required by various working conditions.

[0062] As a result, the pore size of the film formed by laminating the flexible polymer substrate 10 and the organic layer 20 is much smaller than the pore size of either the flexible polymer substrate 10 or the organic layer 20. For example, after preparing an organic layer 20 having a thickness of 0.2 μm to 0.5 μm on a flexible polymer substrate 10 having a pore size of 0.5 μm, the pore size of the film formed by laminating the flexible polymer substrate 10 and the organic layer 20 can reach 30 nm to 50 nm, for example, 30 nm, 31.5 nm, 33 nm, 35 nm, 37 nm, 39.5 nm, 40 nm, 42.55 nm, 45 nm, 46 nm, 47.5 nm, 49 nm, 49.5 nm, 50 nm, etc.

[0063] The pore size of the inorganic oxide layer 30 is related to the selected oxide material. After the inorganic oxide layer 30 is prepared on the organic layer 20, the overall pore size of the reverse osmosis membrane 100 can be further reduced to 0.1nm-10nm, i.e. For example wait.

[0064] Optionally, the pore sizes of the flexible polymer substrate 10, the organic layer 20, and the inorganic oxide layer 30 decrease sequentially, so that the reverse osmosis membrane 100 exhibits a gradient pore size change from large to small from one side to the other. In this embodiment of the present application, the gradual change in pore size of the reverse osmosis membrane 100 forms a high-efficiency filtration channel, which helps reduce excess power consumption during use of the reverse osmosis membrane 100.

[0065] In one application scenario, the flexible polymer substrate 10 forms the liquid inlet side of the reverse osmosis membrane 100, and the inorganic oxide layer 30 forms the liquid outlet side of the reverse osmosis membrane 100. The flexible polymer substrate 10, the organic layer 20 and the inorganic oxide layer 30 can cooperate to filter the liquid.

[0066] It should be noted that the existing reverse osmosis membranes are mainly prepared by coating process or interfacial polymerization reaction, that is, spraying or interfacial polymerization is performed on the surface of a porous substrate to form an organic functional layer. On the one hand, not only is the obtained reverse osmosis membrane a physical stacking structure between the membrane layers, the bonding force between the membrane layers is weak, but also large gaps are easily formed between the membrane layers, resulting in inorganic suspended particles, hydrophobic oily organic matter and microorganisms being retained there, causing scale blockage, membrane pollution, etc., affecting the service life and filtration effect of the reverse osmosis membrane. On the other hand, the film forming quality of the existing preparation process is poor, and the interfacial polymerization reaction is also prone to organic group residues, which affects the membrane stability and thus reduces the service life of the reverse osmosis membrane.

[0067] The present application designs the reverse osmosis membrane 100 as a structure in which a flexible polymer substrate 10, an organic layer 20 and an inorganic oxide layer 30 are stacked in sequence and cross-linked with each other. On the one hand, the bonding force between the membrane layers of the reverse osmosis membrane 100 is improved, thereby improving the filtration performance and extending the service life. On the other hand, the inorganic oxide layer 30 is used to protect the organic layer 20, reducing the possibility of the organic layer 20 being corroded by inorganic suspended particles, hydrophobic oily organic matter and microorganisms or reacting with active chlorine in the cleaning reagent to cause damage to the membrane structure. The reverse osmosis membrane 100 intercepts bacteria, increases the clean water flux of the reverse osmosis membrane 100, enhances the tolerance of the reverse osmosis membrane 100 to active chlorine, and further extends the service life of the reverse osmosis membrane 100.

[0068] Furthermore, the present application also designs the reverse osmosis membrane 100 to have the above-mentioned gradient change structure from large to small, so that the membrane front pressure of the reverse osmosis membrane 100 during filtration can be greatly reduced, while further increasing the water permeability of the reverse osmosis membrane 100, which can effectively and significantly delay the clogging time of the reverse osmosis membrane 100 and reduce the negative impact caused by the membrane scale clogging problem, thereby increasing the service life of the reverse osmosis membrane 100 and helping to reduce the power consumption of the reverse osmosis system.

[0069] In some embodiments, the inorganic oxide layer 30 may be formed of one oxide selected from aluminum oxide, silicon oxide, titanium oxide, and zinc oxide, and may be specifically selected according to the application scenario of the reverse osmosis membrane 100. For example, titanium oxide has the property of being resistant to alkali corrosion. Therefore, the reverse osmosis membrane 100 used for filtering and treating alkaline waste liquid may use titanium oxide to make the inorganic oxide layer 30. For another example, aluminum oxide, zinc oxide, and titanium oxide are not resistant to strong acid (pH < 2) corrosion, so they are suitable for the recycling and reuse of neutral (6 < pH < 8) liquids. For still another example, silicon oxide has good tolerance to general acid and alkali corrosion, and thus is suitable for many application scenarios.

[0070] In other embodiments, the inorganic oxide layer 30 may be formed of two or more oxides selected from aluminum oxide, silicon oxide, titanium oxide, and zinc oxide, and different oxides are alternately stacked. Please refer to FIG. 2, which is a schematic structural diagram of the inorganic oxide layer provided by some embodiments of the present application.

[0071] Optionally, the inorganic oxide layer 30 at least includes a first oxide layer 31 and a second oxide layer 32. The first oxide layer 31 is selected from one of aluminum oxide, silicon oxide, titanium oxide, and zinc oxide, and the second oxide layer 32 is selected from another of aluminum oxide, silicon oxide, titanium oxide, and zinc oxide. The first oxide layer 31 and the second oxide layer 32 are alternately stacked.

[0072] By designing the inorganic oxide layer 30 as a multi-oxide alternately stacked structure, the protective effect of the inorganic oxide layer 30 can be further enhanced. It can be understood that the inorganic oxide layer 30 can be formed of a single oxide, can be formed of a double oxide, and can also be formed of three or more oxides. For example, three different oxides respectively form different oxide layers and are alternately stacked with each other. When the number of oxides forming the oxide layer 30 is greater than 2, there may be various alternating methods, such as ABCABC, ABACABAC, ABCBCABCBC, etc., where A, B, and C respectively represent an oxide, and more alternating methods can be analogously deduced therefrom, which are not listed one by one here.

[0073] It should be noted that the "multiple" mentioned herein represents "two or more", and the same applies to other quantity terms involving "multiple" such as "multiple".

[0074] The reverse osmosis membrane 100 provided by the embodiments of the present application can further improve the problems of the reverse osmosis membrane 100 being contaminated by pollutants and being corroded and damaged by microorganisms and chemical reagents through the acid and alkali resistance and corrosion prevention properties of inorganic oxide materials such as TiO2 and SiO2, improve the service life, and the inorganic oxide materials can also increase the hydrophilicity of the membrane surface, improve the interception rate of hydrophobic organic pollutants, and the purified water flow rate.

[0075] This application further provides a method for preparing a reverse osmosis membrane. The aforementioned reverse osmosis membrane 100 can be prepared using the method provided herein. The reverse osmosis membrane obtained in the embodiments of this application is a three-layer organic and inorganic composite membrane, with each layer cross-linked to form a monolithic reverse osmosis membrane.

[0076] Please refer to FIG3 , which is a schematic diagram of the preparation process of the reverse osmosis membrane provided in some embodiments of the present application.

[0077] In some embodiments, the method for preparing a reverse osmosis membrane comprises the following steps:

[0078] S11. Preparing an organic layer on a flexible polymer substrate.

[0079] Among them, the polymer material selected for the flexible polymer substrate can be polyethersulfone, which has excellent heat resistance, physical and mechanical properties, insulation properties, etc., especially the outstanding advantages of being able to be used continuously at high temperatures and maintaining stable performance in environments with rapid temperature changes. It is widely used in electronic-grade films, water-permeable membranes, blood-permeable membranes, special environmental materials, etc.

[0080] The organic layer can be made of polyamide or polyimide materials. The organic layer prepared on the flexible polymer substrate cooperates with the flexible polymer substrate to form a laminated membrane structure with good filtration performance.

[0081] In the embodiment of the present application, the organic layer can be prepared by molecular layer deposition (MLD).

[0082] Molecular layer deposition (MLD) is an advanced technology for preparing organic polymer thin films and organic-inorganic hybrid films. It can deposit one molecular layer per cycle, precisely controlling thickness. Compared to traditional organic polymer thin film deposition processes (spin coating and thermal evaporation), MLD offers precise control over film thickness (by controlling the number of cycles), more uniform thickness, better step coverage and conformality, and more reliable repeatability. The film is generated by alternately introducing two reactant gases (or vapors) into the reactor in the form of gas pulses, reacting with adsorbed molecules (such as hydroxyl or amino groups) remaining on the substrate surface. Because the reactants involved in each reaction are limited to molecules chemically adsorbed on the substrate surface, MLD exhibits self-limiting growth characteristics.

[0083] S12. Preparing an inorganic oxide layer on the organic layer.

[0084] The inorganic oxide layer is formed of an inorganic oxide prepared on the organic layer, such as silicon oxide, titanium oxide, zinc oxide, aluminum oxide, etc. In the embodiment of the present application, the inorganic oxide layer can be prepared by atomic layer deposition (ALD).

[0085] Atomic layer deposition (ALD), also known as atomic layer epitaxy (ALE), is a method for depositing a material onto a substrate layer by layer in the form of a single atomic film. ALD shares similarities with conventional chemical deposition. However, during ALD, the chemical reaction of each new layer is directly linked to the previous one, resulting in only one atomic layer being deposited per reaction. ALD forms a film by alternately introducing pulses of vaporous precursors into a reactor, where they chemically adsorb and react on the substrate. When the precursors reach the substrate surface, they chemically adsorb and react. The ALD reactor must be purged with an inert gas between precursor pulses. Therefore, whether the deposition precursor can chemically adsorb on the surface of the substrate is crucial for achieving ALD. The surface adsorption characteristics of vaporous substances on substrate materials indicate that any vaporous substance can physically adsorb on a material surface. However, chemical adsorption on the surface requires a certain activation energy, making the selection of appropriate precursors crucial for achieving ALD. In a self-limiting deposition process involving chemical adsorption, the first precursor is introduced to the substrate surface and held there by chemical adsorption (saturated adsorption). When a second precursor is introduced into the reactor, it reacts with the first precursor adsorbed on the substrate surface. A displacement reaction occurs between the two precursors, producing corresponding byproducts. This process continues until the first precursor on the surface is completely consumed, at which point the reaction automatically ceases and the desired atomic layer is formed. This is a self-limiting process, and the reaction is repeated over and over to form a thin film.

[0086] Atomic layer deposition includes thermal atomic layer deposition (TALD) and plasma enhanced atomic layer deposition (PEALD). Among them, thermal atomic layer deposition relies on thermal energy to stimulate two or more precursors to undergo chemical reactions. In order to provide sufficient reaction activation energy, the general operating temperature range of thermal atomic layer deposition equipment is 200-500°C. Plasma enhanced atomic layer deposition is to generate a large number of active free radicals by introducing plasma, thereby enhancing the reactivity of the precursor material, thereby expanding the selection range and application requirements of ALD for the precursor source, shortening the reaction cycle time, and also reducing the requirements for the sample deposition temperature, and can achieve low temperature or even room temperature deposition, which is particularly suitable for thin film deposition on temperature-sensitive materials and flexible materials. In addition, the introduction of plasma can further remove impurities in the thin film, and can obtain lower resistivity and higher film density. In addition, plasma can also clean the reaction chamber and perform surface activation treatment on the substrate. The inorganic oxide layer in the embodiment of the present application can be prepared by TALD or PEALD.

[0087] It should be noted that TALD and PEALD can also be used in combination. For example, based on thermal atomic layer deposition equipment, plasma can be introduced into the process chamber. This can effectively reduce the process temperature, meet the process requirements of low thermal budget, and also has advantages in improving film density and reducing film impurity content. The inorganic oxide layer in the embodiment of the present application can be prepared by TALD and PEALD.

[0088] By depositing and growing organic layers of molecular structures and inorganic layers of atomic structures, not only does the reverse osmosis membrane microscopic membrane layer gradually change from a micron-level large-pore base and a micron-level small-pore organic layer to a nanometer-level micropore inorganic layer, which can effectively alleviate the impact of membrane front pressure and prevent the membrane front pressure from damaging the separation functional layer, but also the membrane layers are cross-linked through chemical bonds, the bonding force is enhanced, and the stability of the reverse osmosis membrane is improved. The molecular and atomic structures can also reduce the gap between the membrane layers, avoid the retention of inorganic suspended particles, hydrophobic oily organic matter and microorganisms, prevent scale blockage, membrane pollution, etc., reduce the possibility of membrane pollution such as microbial corrosion, improve the filtration effect, and extend the service life.

[0089] The embodiment of the present application prepares an inorganic oxide layer on the organic layer, which can form a reverse osmosis membrane into a stacked membrane structure in which a flexible polymer substrate, an organic layer and an inorganic oxide layer are stacked in sequence and cross-linked and bonded to each other, which is beneficial to improving the chemical stability and microstructural stability of the reverse osmosis membrane. For example, an inorganic oxide layer formed by an acid-resistant oxide such as silicon oxide can protect the organic layer from hydrogen chloride corrosion in an acidic environment that is corrosive to the multi-membrane body, such as an acidic environment containing chlorides. The material that can be used for the inorganic oxide layer can be selected according to the application scenario of the reverse osmosis membrane, which has been recorded above and will not be repeated here.

[0090] Compared with the existing reverse osmosis membranes prepared by coating process or interfacial polymerization reaction, the preparation method provided in this application uses atomic layer deposition and molecular layer deposition methods, and utilizes the unique saturated adsorption reaction principle to prepare organic layer and inorganic oxide layer films, which can effectively reduce the residual chemical groups inside the film.

[0091] The organic layer and inorganic oxide layer provided in this application can be made using chemical vapor deposition technology. The organic layer and inorganic oxide layer are grown in situ on a flexible polymer substrate by the chemical vapor deposition method. The film layer is uniform and the film quality is good. It can also avoid residual organic groups that affect the stability of the reverse osmosis membrane and improve the service life of the reverse osmosis membrane.

[0092] By chemical vapor deposition of organic layers and different inorganic oxide layers, not only can the organic groups be avoided from remaining in the membrane and the performance of the membrane be improved, but also the specific pore size of the membrane material can be precisely controlled to regulate the pressure required before the reverse osmosis membrane, while simplifying the composite membrane structure of the reverse osmosis membrane and achieving By controlling the pore size at the angstrom level, reverse osmosis membranes with varying pore sizes can be applied to a wide range of water treatment conditions, including drinking water purification, seawater desalination, and wastewater treatment. Depositing inorganic oxides on the membrane surface also increases the membrane's surface hydrophilicity, thereby improving the membrane's interception rate for hydrophobic organic pollutants and increasing the membrane's clean water flow rate.

[0093] S13, performing heat treatment on the reverse osmosis membrane.

[0094] After preparing the inorganic oxide layer, the reverse osmosis membrane is heat-treated. It should be noted that the reverse osmosis membrane heat-treated in this step is a laminated structure comprising a composite cross-linked flexible polymer substrate, an organic layer, and an inorganic oxide layer, obtained through the aforementioned steps. This laminated structure is distinct from the reverse osmosis membrane obtained after this step. Step S13 specifically involves slowly heating the reverse osmosis membrane to a certain temperature, maintaining it for a sufficient time, and then slowly cooling it to remove impurities from the membrane surface and improve the filtration efficiency of the reverse osmosis membrane.

[0095] Optionally, in the heat treatment step, the reverse osmosis membrane is heated to 50°C-200°C, such as 80°C, 100°C, 120°C, 150°C, 180°C, etc., and low-temperature annealing can effectively remove impurities on the membrane surface and improve the filtering effect of the reverse osmosis membrane.

[0096] Optionally, the heat treatment step includes: slowly heating the reverse osmosis membrane to 50°C-200°C and slowly cooling it after a preset time, which can be 1 hour-5 hours, such as 1.5 hours, 2 hours, 2.5 hours, 3 hours, 3.5 hours, 4 hours, 4.5 hours, etc.

[0097] Optionally, the steps of preparing an organic layer on the flexible polymer substrate, preparing an inorganic oxide layer on the organic layer, and heat-treating the reverse osmosis membrane are performed in the same reaction chamber to improve the preparation efficiency of the reverse osmosis membrane.

[0098] It should be noted that the heat treatment step may be performed after the preparation of the organic layer, or after the preparation of the inorganic oxide layer, or may be performed after the preparation of the organic layer and after the preparation of the inorganic oxide layer respectively.

[0099] It can be understood that the heat treatment step is an optional preparation step for further improving the filtration performance of the reverse osmosis membrane, and the preparation method of the reverse osmosis membrane provided in this application is not limited to including this step.

[0100] Please refer to FIG4 , which is a schematic diagram of the preparation process of the organic layer provided in some embodiments of the present application.

[0101] In some embodiments, the organic layer can be formed by depositing a first precursor and a second precursor on a flexible polymer substrate. The first precursor is a precursor containing an amino group (-NH2), such as m-phenylenediamine, aniline, p-phenylenediamine, o-phenylenediamine, and ethylmethylamine; the second precursor is a precursor containing an acyl group (-COX, where X is a halogen atom, such as chlorine, bromine, or iodine), such as trimesoyl chloride, trimesoyl iodide, or trimesoyl; and the first and second precursors can react to form a polyamide or polyimide.

[0102] Optionally, the method for preparing the organic layer comprises the following steps:

[0103] S21, introducing the first precursor into the reaction chamber.

[0104] The first precursor can be carried into the reaction chamber by a source-carrying gas introduced into the reaction chamber. The source-carrying gas can be nitrogen or other gases that will not react during the preparation of the reverse osmosis layer.

[0105] Optionally, the first precursor is introduced into the reaction chamber in a pulsed manner. The source-carrying gas may have an introduction rate of 500 sccm-1500 sccm, such as 600 sccm, 700 sccm, 800 sccm, 900 sccm, 1000 sccm, 1050 sccm, 1100 sccm, 1150 sccm, 1200 sccm, 1250 sccm, 1300 sccm, 1350 sccm, 1400 sccm, 1450 sccm, 1500 sccm, etc. The source-carrying gas may be introduced for a duration of 1 s-3 s, such as 1 s, 1.5 s, 2 s, 2.5 s, 3 s, etc.

[0106] S22, introducing a purge gas into the reaction chamber for purge.

[0107] After depositing the first precursor, a purge gas is introduced to purge excess precursor or impurities from the reaction chamber. The purge gas can be nitrogen or another gas that does not react during the preparation of the reverse osmosis layer. It is understood that the purge gas and the source-carrying gas can be the same gas, such as nitrogen, to improve preparation efficiency. This also applies to the source-carrying gas and purge gas mentioned below.

[0108] Optionally, the purge flow rate of the purge gas is a nitrogen source flow rate of 500sccm-1500sccm, for example, 600sccm, 700sccm, 800sccm, 900sccm, 1000sccm, 1050sccm, 1100sccm, 1150sccm, 1200sccm, 1250sccm, 1300sccm, 1350sccm, 1400sccm, 1450sccm, 1500sccm, etc.; the purge time is 5s-10s, for example, 5s, 5.5s, 6s, 6.5s, 7s, 7.5s, 8s, 8.5s, 9s, 9.5s, etc.

[0109] S23, introducing the second precursor into the reaction chamber.

[0110] After the purging is completed, the second precursor is introduced to react with the first precursor in the reaction chamber to generate polyamide or polyimide.

[0111] The second precursor may be introduced into the reaction chamber in a pulsed form by a source-carrying gas, and the flow rate may be 500 sccm-1500 sccm, for example, 600 sccm, 700 sccm, 800 sccm, 900 sccm, 1000 sccm, 1050 sccm, 1100 sccm, 1150 sccm, 1200 sccm, 1250 sccm, 1300 sccm, 1350 sccm, 1400 sccm, 1450 sccm, 1500 sccm, etc. The source-carrying gas may be introduced for a duration of 1 s-3 s, for example, 1 s, 1.5 s, 2 s, 2.5 s, 3 s, etc.

[0112] S24, introducing a purge gas into the reaction chamber for purge.

[0113] A purge gas is introduced into the reaction chamber for purging. The purge flow rate can be 500 sccm-1500 sccm, for example, 600 sccm, 700 sccm, 800 sccm, 900 sccm, 1000 sccm, 1050 sccm, 1100 sccm, 1150 sccm, 1200 sccm, 1250 sccm, 1300 sccm, 1350 sccm, 1400 sccm, 1450 sccm, 1500 sccm, etc.; the purge time is 5s-10s, for example, 5s, 5.5s, 6s, 6.5s, 7s, 7.5s, 8s, 8.5s, 9s, 9.5s, etc.

[0114] S25. Repeat the above steps 4000-10000 times.

[0115] By repeatedly cycling through the steps of introducing a first precursor, purging, introducing a second precursor, and purging, an organic layer is gradually grown on the flexible polymer substrate. Research has found that when the number of repetitions ranges from 4,000 to 10,000, such as 4,000, 5,000, 6,000, 7,000, 8,000, 9,000, and 10,000, an organic layer with suitable thickness and porosity can be grown.

[0116] Alternatively, the organic layer can be formed by molecular layer deposition.

[0117] In some embodiments, the preparation conditions of the organic layer include:

[0118] The vacuum degree in the reaction chamber is 1Pa-100Pa, for example, 3Pa, 5Pa, 8Pa, 10Pa, 15.5Pa, 20Pa, 30Pa, 40Pa, 50Pa, 55.5Pa, 60Pa, 65.5Pa, 70Pa, 75Pa, 80Pa, 85Pa, 90Pa, 95.5Pa, 100Pa, etc.

[0119] The reaction temperature is 100°C-200°C, for example, 100°C, 110°C, 112.5°C, 120°C, 130°C, 135.5°C, 140°C, 150°C, 155.3°C, 160°C, 170°C, 180°C, 190°C, 195.3°C, 200°C, etc.

[0120] The temperature of the first precursor and the second precursor is 30℃-150℃, for example, 30℃, 31.5℃, 33℃, 35℃, 37.5℃, 39℃, 40℃, 41.5℃, 42℃, 43℃, 44℃, 45.5℃, 47℃, 48.5℃, 49℃, 49.5℃, 50℃, 60℃, 80℃, 100℃, 120℃, 140℃, etc.

[0121] Please refer to FIG5 , which is a schematic diagram of the preparation process of the inorganic oxide layer provided in some embodiments of the present application.

[0122] In some embodiments, the inorganic oxide layer can be formed by depositing a third precursor and a fourth precursor on the organic layer. The third precursor is one of a metal halide precursor, an organometallic precursor, and a silicon-containing precursor, such as titanium tetrachloride, isopropyl titanate, trimethylaluminum, dimethylzinc, diethylzinc, diisopropylaminosilane, bis(diethylamino)silane, etc.; the fourth precursor is an oxygen source, such as oxygen, ozone, water, etc.; and the third precursor and the fourth precursor can react to form the inorganic oxide.

[0123] The step of depositing the inorganic oxide layer on the organic layer may include: using a source-carrying gas to alternately introduce a third precursor and a fourth precursor into the reaction chamber; before the latter precursor is introduced, using a purge gas to purge the reaction chamber.

[0124] Optionally, the step of depositing an inorganic oxide layer on the organic layer comprises the following steps:

[0125] S31, introducing the third precursor into the reaction chamber.

[0126] The third precursor can be carried into the reaction chamber by the source-carrying gas introduced into the reaction chamber.

[0127] Optionally, the third precursor is introduced into the reaction chamber in a pulsed form. The flow rate of the source-carrying gas can be 500 sccm-1500 sccm, for example, 600 sccm, 700 sccm, 800 sccm, 900 sccm, 1000 sccm, 1050 sccm, 1100 sccm, 1150 sccm, 1200 sccm, 1250 sccm, 1300 sccm, 1350 sccm, 1400 sccm, 1450 sccm, 1500 sccm, etc. The duration of the source-carrying gas introduction can be 0.1 s-2 s, for example, 0.1 s, 0.2 s, 0.3 s, 0.4 s, 0.5 s, 0.6 s, 0.7 s, 0.8 s, 0.9 s, 1 s, 1.2 s, 1.4 s, 1.6 s, 1.8 s, etc.

[0128] S32, introducing a purge gas into the reaction chamber for purge.

[0129] After depositing the third precursor, a purge gas is introduced to purge excess precursor or impurities in the reaction chamber.

[0130] Optionally, the purge flow rate of the purge gas is a nitrogen source flow rate of 500sccm-1500sccm, for example, 600sccm, 700sccm, 800sccm, 900sccm, 1000sccm, 1050sccm, 1100sccm, 1150sccm, 1200sccm, 1250sccm, 1300sccm, 1350sccm, 1400sccm, 1450sccm, 1500sccm, etc.; the purge time is 2s-8s, for example, 2s, 2.5s, 3s, 3.5s, 4s, 4.5s, 5s, 5.5s, 6s, 6.5s, 7s, 7.5s, etc.

[0131] S33, introducing the fourth precursor into the reaction chamber.

[0132] After the purging is completed, the fourth precursor is introduced to oxidize the third precursor in the reaction chamber to generate inorganic oxides.

[0133] Among them, the fourth precursor can be introduced into the reaction chamber in a pulsed form by carrying the source gas, and the introduction flow rate can be 500sccm-1500sccm, for example, 600sccm, 700sccm, 800sccm, 900sccm, 1000sccm, 1050sccm, 1100sccm, 1150sccm, 1200sccm, 1250sccm, 1300sccm, 1350sccm, 1400sccm, 1450sccm, 1500sccm, etc.; the introduction time can be 0.1s-2s, for example, 0.1s, 0.2s, 0.3s, 0.4s, 0.5s, 0.6s, 0.7s, 0.8s, 0.9s, 1s, 1.2s, 1.4s, 1.6s, 1.8s, etc.

[0134] S34, introducing a purge gas into the reaction chamber for purge.

[0135] A purge gas is introduced into the reaction chamber for purging. The purge flow rate can be 500 sccm-1500 sccm, for example, 600 sccm, 700 sccm, 800 sccm, 900 sccm, 1000 sccm, 1050 sccm, 1100 sccm, 1150 sccm, 1200 sccm, 1250 sccm, 1300 sccm, 1350 sccm, 1400 sccm, 1450 sccm, 1500 sccm, etc.; the purge time can be 2s-8s, for example, 2s, 2.5s, 3s, 3.5s, 4s, 4.5s, 5s, 5.5s, 6s, 6.5s, 7s, 7.5s, etc.

[0136] S35. Repeat the above steps 1-500 times.

[0137] The inorganic oxide layer is gradually grown on the organic layer by repeatedly introducing the third precursor, purging, introducing the fourth precursor, and purging. The number of repetitions can be 1-500 times, for example, 50 times, 100 times, 150 times, 200 times, 250 times, 300 times, 350 times, 400 times, 450 times, 500 times, etc.

[0138] Specifically, the third precursor and the fourth precursor are pulsed alternately into the reaction chamber to chemically adsorb and react on the organic layer to form an oxide. The third precursor initially introduced into the reaction chamber is adsorbed on the surface of the organic layer. When the fourth precursor is introduced into the reaction chamber, it reacts with the third precursor adsorbed on the surface of the organic layer. A replacement reaction occurs between the two precursors and corresponding by-products are produced until the third precursor on the surface is completely consumed. The reaction automatically stops and the required film layer is formed. When a new third precursor is further introduced, the new third precursor will be adsorbed on the oxide. By repeating this process multiple times, an inorganic oxide layer can be formed. The formation of the organic layer is similar to this.

[0139] In some embodiments, the preparation conditions of the inorganic oxide layer include:

[0140] The vacuum degree in the reaction chamber is 1Pa-100Pa, for example, 3Pa, 5Pa, 8Pa, 10Pa, 15.5Pa, 20Pa, 30Pa, 40Pa, 50Pa, 55.5Pa, 60Pa, 65.5Pa, 70Pa, 75Pa, 80Pa, 85Pa, 90Pa, 95.5Pa, 100Pa, etc.

[0141] The reaction temperature is 100°C-200°C, for example, 100°C, 110°C, 112.5°C, 120°C, 130°C, 135.5°C, 140°C, 150°C, 155.3°C, 160°C, 170°C, 180°C, 190°C, 195.3°C, 200°C, etc.

[0142] The temperature of the third precursor and the fourth precursor is 20°C-40°C, for example, 20°C, 23°C, 25°C, 28°C, 30°C, 31.5°C, 33°C, 35°C, 37.5°C, 39°C, 40°C, etc.

[0143] Optionally, the organic layer and the inorganic oxide layer are prepared in the same reaction chamber, at the same pressure and at the same temperature. For example, the MLD and ALD deposition reactions and the heat treatment are also completed in the same chamber, at the same pressure and at the same temperature. This can avoid the transfer of reverse osmosis membrane intermediates between the various treatment steps, effectively improve production efficiency, reduce production costs, and ensure the performance and quality of the reverse osmosis membrane, which is conducive to the mass production of roll-type reverse osmosis membranes.

[0144] This application prepares the organic layer through the molecular layer deposition process and the inorganic oxide layer through the atomic layer deposition process, and can accurately control the thickness and pore size of the prepared organic layer and inorganic oxide layer, so that the reverse osmosis membrane can be prepared according to the needs of different application scenarios, so that the prepared reverse osmosis membrane can be suitable for various required application fields, including but not limited to direct drinking water purification, seawater desalination, wastewater treatment, etc.

[0145] For example, when the reverse osmosis membrane needs to be used for direct drinking water purification, an organic layer of 0.2μm-0.5μm polyimide material can be prepared on a flexible polymer substrate with a pore size of 0.5μm. At this time, the pore size of the flexible polymer-polyimide overall membrane can reach 30nm-50nm; after further growing an inorganic oxide layer (TiO2+SiO2)×(160-200 cycles) on the surface of the polyimide film, the pore size of the flexible polymer-polyimide-TiO2+SiO2 laminated oxide overall membrane, that is, the reverse osmosis membrane, can reach

[0146] The present application can also utilize the characteristics of MLD to prepare a dense membrane layer and ALD to prepare a dense membrane layer, so that the prepared reverse osmosis membrane has a gradient pore size change, reducing the pre-membrane pressure of the influent water and reducing the power consumption of the reverse osmosis system.

[0147] Among them, the pore size of the inorganic oxide layer can be controlled by the following methods: first, controlling the reaction temperature of ALD. Different ALD reaction temperatures will result in different densities of the prepared oxide films, so the pore size of the inorganic oxide layer will be different; second, controlling the thickness of the inorganic oxide layer prepared by ALD. Different thicknesses of the inorganic oxide layer will result in different pore sizes of the inorganic oxide layer; third, adjusting the generation of different types of inorganic oxide layers. The microscopic atomic sizes of the oxides prepared by ALD will be different, and the pore sizes of the inorganic oxide layers will be different.

[0148] It should be noted that the inorganic oxide layer provided in the present application can be formed of a single oxide or a plurality of oxides. The latter can form an inorganic oxide layer in which a plurality of oxides are alternately stacked.

[0149] Please refer to FIG6 , which is a schematic diagram of the preparation process of the inorganic oxide layer provided in other embodiments of the present application.

[0150] In some embodiments, the step of preparing the inorganic oxide layer on the organic layer further includes: depositing the inorganic oxide layer using a fifth precursor and a sixth precursor.

[0151] The fifth precursor is one of a metal halide precursor, an organometallic precursor, and a silicon-containing precursor, and is different from the third precursor. For example, the third precursor may be a precursor of silicon oxide, and the fifth precursor may be a precursor of titanium oxide, zinc oxide, or aluminum oxide. It will be appreciated that the inorganic oxide layer may also be formed from oxides other than titanium oxide, silicon oxide, zinc oxide, and aluminum oxide.

[0152] The sixth precursor is an oxygen source, such as oxygen, water, or ozone. The fifth and sixth precursors react to form an inorganic oxide, which, in combination with the third and fourth precursors, forms an inorganic oxide layer having alternating first and second oxide layers. Specifically, the third and fourth precursors can be used to form the first oxide layer, while the fifth and sixth precursors can be used to form the second oxide layer. The first and second oxide layers are grown in an alternating and repeated manner.

[0153] Optionally, the preparation of the inorganic oxide layer comprises the following steps:

[0154] S41, introducing the third precursor into the reaction chamber.

[0155] Optionally, the third precursor is introduced into the reaction chamber in a pulsed manner using a source-carrying gas, with an introduction flow rate of 500 sccm-1500 sccm and an introduction time of 0.1 s-2 s.

[0156] S42, introducing a purge gas into the reaction chamber for purge.

[0157] Optionally, a purge gas is introduced into the reaction chamber for purge, with a purge flow rate of 500 sccm-1500 sccm and an introduction time of 2s-8s.

[0158] S43, introducing the fourth precursor into the reaction chamber.

[0159] Optionally, the fourth precursor is introduced into the reaction chamber in a pulsed manner using a source-carrying gas, with an introduction flow rate of 500 sccm-1500 sccm and an introduction time of 0.1 s-2 s.

[0160] S44, introducing a purge gas into the reaction chamber for purge.

[0161] Optionally, a purge gas is introduced into the reaction chamber for purge, with a purge flow rate of 500 sccm-1500 sccm and an introduction time of 2s-8s.

[0162] S45. Repeat steps S41-S44 1-500 times.

[0163] Steps S41-45 are similar to the steps for preparing the inorganic oxide layer described above and are not described in detail here. The main difference is that steps S41-S45 are used to prepare the first oxide layer, and the number of repetitions can be adjusted based on factors such as the thickness difference between the inorganic oxide layer and the first oxide layer.

[0164] S46, introducing the fifth precursor into the reaction chamber.

[0165] Optionally, the fifth precursor is introduced into the reaction chamber in a pulsed form using a source-carrying gas, with an introduction flow rate of 500sccm-1500sccm, for example, 600sccm, 700sccm, 800sccm, 900sccm, 1000sccm, 1050sccm, 1100sccm, 1150sccm, 1200sccm, 1250sccm, 1300sccm, 1350sccm, 1400sccm, 1450sccm, 1500sccm, etc.; the introduction time is 0.1s-2s, for example, 0.1s, 0.2s, 0.3s, 0.4s, 0.5s, 0.6s, 0.7s, 0.8s, 0.9s, 1s, 1.2s, 1.4s, 1.6s, 1.8s, etc.

[0166] S47, introducing a purge gas into the reaction chamber for purge.

[0167] Optionally, a purge gas is introduced into the reaction chamber for purging, and the purge flow rate is 500sccm-1500sccm, for example, 600sccm, 700sccm, 800sccm, 900sccm, 1000sccm, 1050sccm, 1100sccm, 1150sccm, 1200sccm, 1250sccm, 1300sccm, 1350sccm, 1400sccm, 1450sccm, 1500sccm, etc.; the introduction time is 2s-8s, for example, 2s, 2.5s, 3s, 3.5s, 4s, 4.5s, 5s, 5.5s, 6s, 6.5s, 7s, 7.5s, etc.

[0168] S48, introducing the sixth precursor into the reaction chamber.

[0169] Optionally, the fourth precursor is introduced into the reaction chamber in a pulsed form using a source-carrying gas, with an introduction flow rate of 500sccm-1500sccm, for example, 600sccm, 700sccm, 800sccm, 900sccm, 1000sccm, 1050sccm, 1100sccm, 1150sccm, 1200sccm, 1250sccm, 1300sccm, 1350sccm, 1400sccm, 1450sccm, 1500sccm, etc.; the introduction time is 0.1s-2s, for example, 0.1s, 0.2s, 0.3s, 0.4s, 0.5s, 0.6s, 0.7s, 0.8s, 0.9s, 1s, 1.2s, 1.4s, 1.6s, 1.8s, etc.

[0170] S49, introducing a purge gas into the reaction chamber for purge.

[0171] Optionally, a purge gas is introduced into the reaction chamber for purging, and the purge flow rate is 500sccm-1500sccm, for example, 600sccm, 700sccm, 800sccm, 900sccm, 1000sccm, 1050sccm, 1100sccm, 1150sccm, 1200sccm, 1250sccm, 1300sccm, 1350sccm, 1400sccm, 1450sccm, 1500sccm, etc.; the introduction time is 2s-8s, for example, 2s, 2.5s, 3s, 3.5s, 4s, 4.5s, 5s, 5.5s, 6s, 6.5s, 7s, 7.5s, etc.

[0172] S410, repeat steps S46-S49 1-1000 times.

[0173] The second oxide layer is gradually grown from the first oxide layer by repeatedly introducing the fifth precursor, purging, introducing the sixth precursor, and purging. The number of repetitions can be 1-500 times, for example, 50 times, 100 times, 150 times, 200 times, 250 times, 300 times, 350 times, 400 times, 450 times, 500 times, 600 times, 700 times, 800 times, 900 times, etc.

[0174] S411. Repeat steps S41-S410 1-1000 times.

[0175] The above steps are repeated to alternately grow the first oxide layer and the second oxide layer, thereby producing an inorganic oxide layer having the first oxide layer and the second oxide layer alternately stacked. Optionally, the above steps are repeated 1-500 times, for example, 50 times, 100 times, 150 times, 200 times, 250 times, 300 times, 350 times, 400 times, 450 times, 500 times, 600 times, 700 times, 800 times, 900 times, etc.

[0176] Optionally, the preparation conditions of the inorganic oxide layer having the first oxide layer and the second oxide layer alternately stacked include:

[0177] The vacuum degree in the reaction chamber is 1Pa-100Pa, for example, 3Pa, 5Pa, 8Pa, 10Pa, 15.5Pa, 20Pa, 30Pa, 40Pa, 50Pa, 55.5Pa, 60Pa, 65.5Pa, 70Pa, 75Pa, 80Pa, 85Pa, 90Pa, 95.5Pa, 100Pa, etc.

[0178] The reaction temperature is 100°C-200°C, for example, 100°C, 110°C, 112.5°C, 120°C, 130°C, 135.5°C, 140°C, 150°C, 155.3°C, 160°C, 170°C, 180°C, 190°C, 195.3°C, 200°C, etc.

[0179] The temperature of the third precursor, the fourth precursor, the fifth precursor and the sixth precursor is 20°C-40°C, for example, 20°C, 23°C, 25°C, 28°C, 30°C, 31.5°C, 33°C, 35°C, 37.5°C, 39°C, 40°C, etc.

[0180] It is understood that the inorganic oxide layer provided in the embodiment of the present application may be a single oxide layer or a multiple oxide layer. A single oxide layer can be prepared by the above steps S31-S35, and the corresponding inorganic oxide layer is a single oxide film layer cross-linked and bonded with the organic layer. A multiple oxide layer can be prepared by the above steps S41-S411, and the corresponding inorganic oxide layer is a multiple oxide film layer cross-linked and bonded with the organic layer. In other embodiments, the preparation of the multiple oxide layer can also be obtained by more precursor reactions. In other words, the multiple oxide layer can also have a third oxide layer alternately stacked with the first oxide layer and the second oxide layer, or even more oxide layers.

[0181] The present application can obtain an inorganic oxide layer formed by alternating multiple different oxide layers through the above method, which is beneficial to further improve the performance of the inorganic oxide layer and expand the application range of the reverse osmosis membrane.

[0182] Please refer to FIG. 7 , which is a schematic diagram showing the relationship between the number of ALD reaction cycles and the thickness of the inorganic oxide layer according to an embodiment of the present application.

[0183] In some embodiments, a graph is plotted with the thickness of each inorganic oxide layer grown using the ALD method or the polyimide layer grown using the MLD method as the vertical axis and the number of reaction cycles (number of repetitions) as the horizontal axis, and the growth rate of each thin film material is determined by the slope of the linear relationship, that is, the thickness of the thin film grown in each ALD or MLD reaction cycle.

[0184] In some embodiments, at 200°C and a reaction chamber vacuum of 80 Pa, an aluminum oxide precursor and ozone are used as precursors for laminated aluminum oxide. The linear relationship between the thickness of the aluminum oxide film prepared with different ALD cycle numbers is shown in the figure. The linear curve is fitted to obtain the yx equation, y = 0.0946x + 0.7779, R 2= 0.9964, where y represents the thickness of the aluminum oxide film, x represents the number of ALD reaction cycles, and the slope represents the aluminum oxide film growth rate under the process conditions. Therefore, in the present embodiment, ALD aluminum oxide thin films of varying thicknesses can be produced. Thus, in the present embodiment, inorganic oxide layers of varying thicknesses can be precisely tailored to the needs of different application scenarios, thereby producing reverse osmosis membranes of varying thicknesses.

[0185] In the above embodiment, a reverse osmosis membrane is formed by stacking a flexible polymer substrate, an organic layer and an inorganic oxide layer in sequence, which can improve the filtration effect of the reverse osmosis membrane, extend the service life of the reverse osmosis membrane, simplify the preparation process of the reverse osmosis membrane, and prepare corresponding reverse osmosis membranes according to the usage requirements of various application scenarios, thereby expanding its application range.

[0186] Reverse osmosis membrane anti-corrosion performance test:

[0187] This test used Mocoledon artificial seawater with a pH of 8-8.5 and a total salt content of 35,000 mg / L. The composite cross-linked reverse osmosis membrane prepared by the above method was immersed in this solution for 24-72 hours. The water permeability of the composite cross-linked reverse osmosis membrane was measured before and after immersion at a temperature of 25-30°C and a humidity of 50% ± 5%. This test characterizes the corrosion resistance of the membrane in the simulated seawater experiment. The test results are as follows:

[0188] The test sample is a reverse osmosis membrane prepared by the above method. The flexible polymer substrate of the reverse osmosis membrane is made of polyethersulfone, the organic layer is made of polyimide, and the inorganic oxide layer is an alternating laminated membrane of silicon dioxide and titanium dioxide.

[0189] As shown in the table, the water vapor transmission rate of the reverse osmosis membrane before and after immersion in simulated seawater demonstrates that the reverse osmosis membrane of this patent exhibits no significant microstructural collapse during immersion in simulated seawater, maintaining a substantially consistent water transmission rate (E-4). This demonstrates the excellent stability and corrosion resistance of the reverse osmosis membrane prepared in this application, effectively extending its service life.

[0190] Throughout this specification, terms such as "one embodiment" and "another embodiment" mean that the specific features, structures, materials, or characteristics described in conjunction with that embodiment or example are included in at least one embodiment or example of the present application. In this specification, schematic representations of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in any one or more embodiments or examples.

[0191] The above is only an implementation method of the present application and does not limit the patent scope of the present application. Any equivalent structure or equivalent process transformation made using the contents of the description and drawings of this application, or directly or indirectly applied in other related technical fields, are also included in the patent protection scope of the present application.

Claims

1. A method for preparing a reverse osmosis membrane, characterized in that: include: preparing an organic layer on a flexible polymer substrate, wherein the organic layer is cross-linked and bonded to the flexible polymer substrate; An inorganic oxide layer is prepared on the organic layer, and the inorganic oxide layer is cross-linked and bonded with the organic layer.

2. The method for preparing a reverse osmosis membrane according to claim 1, wherein The organic layer is formed by a molecular layer deposition process, and the inorganic oxide layer is formed by an atomic layer deposition process. The pore sizes of the flexible polymer substrate, the organic layer, and the inorganic oxide layer decrease in sequence.

3. The method for preparing a reverse osmosis membrane according to claim 1, wherein After preparing the inorganic oxide layer, the method for preparing the reverse osmosis membrane further comprises: heat-treating the reverse osmosis membrane.

4. The method for preparing a reverse osmosis membrane according to claim 3, wherein The step of heat treating the reverse osmosis membrane comprises: The reverse osmosis membrane is slowly heated to 50° C.-200° C. and cooled after a preset time.

5. The method for preparing a reverse osmosis membrane according to claim 4, wherein The preset time is 1 hour to 5 hours.

6. The method for preparing a reverse osmosis membrane according to claim 3, wherein The steps of preparing an organic layer on the flexible polymer substrate, preparing an inorganic oxide layer on the organic layer, and heat-treating the reverse osmosis membrane are performed in the same reaction chamber.

7. The method for preparing a reverse osmosis membrane according to claim 1, wherein The organic layer is a polyamide material or a polyimide material, and the step of preparing the organic layer on the flexible polymer substrate includes: The organic layer is deposited on the flexible polymer substrate using a first precursor and a second precursor, wherein the first precursor is a precursor containing an amino group, and the second precursor is a precursor containing an acyl group.

8. The method for preparing a reverse osmosis membrane according to claim 7, wherein The step of depositing the organic layer on the flexible polymer substrate using the first precursor and the second precursor comprises: The first precursor is introduced into the reaction chamber in a pulsed manner using a source-carrying gas at a flow rate of 500 sccm-1500 sccm for a duration of 1 s-3 s; Passing a purge gas into the reaction chamber for purging, with a purge flow rate of 1000 sccm-1500 sccm and a purge time of 5s-10s; The second precursor is introduced into the reaction chamber in a pulsed manner using the source-carrying gas, with an introduction flow rate of 500 sccm-1500 sccm and an introduction time of 1 s-3 s; Passing a purge gas into the reaction chamber for purging, with a purge flow rate of 500 sccm-1500 sccm and a purge time of 5s-10s; Repeat the above steps 4000-10000 times to obtain the organic layer; The vacuum degree in the reaction chamber is 1 Pa-100 Pa, the reaction temperature is 100° C.-200° C., and the temperature of the first precursor and the second precursor is 30° C.-150° C.

9. The method for preparing a reverse osmosis membrane according to claim 1, wherein The step of preparing an inorganic oxide layer on the organic layer includes: using a third precursor and a fourth precursor to deposit the inorganic oxide layer on the organic layer, the inorganic oxide layer is a single oxide layer or a stacked oxide layer, the third precursor is one or more of a metal halide precursor, an organometallic precursor and a silicon-containing precursor, and the fourth precursor is an oxygen source.

10. The method for preparing a reverse osmosis membrane according to claim 9, wherein The step of depositing the inorganic oxide layer on the organic layer includes: using a source-carrying gas to alternately introduce the third precursor and the fourth precursor into a reaction chamber; before the third precursor and the fourth precursor are alternately introduced, using a purge gas to purge the reaction chamber.

11. A reverse osmosis membrane, characterized in that: The invention comprises a flexible polymer substrate, an organic layer and an inorganic oxide layer which are sequentially stacked. The flexible polymer substrate is cross-linked and bonded to the organic layer, and the organic layer is cross-linked and bonded to the inorganic oxide layer.

12. The reverse osmosis membrane according to claim 11, wherein The pore sizes of the flexible polymer substrate, the organic layer, and the inorganic oxide layer decrease in sequence.

13. The reverse osmosis membrane according to claim 12, wherein The pore size of the flexible polymer substrate is 0.1 μm-1 μm, and the pore size of the organic layer is 0.05 μm-1 μm.

14. The reverse osmosis membrane according to claim 12, wherein The reverse osmosis membrane formed by the flexible polymer substrate, the organic layer and the inorganic oxide layer has a pore size of 0.1 nm to 10 nm.

15. The reverse osmosis membrane according to claim 11, wherein The thickness of the flexible polymer substrate is 50 μm-125 μm, the thickness of the organic layer is 0.2 μm-1 μm, and the thickness of the inorganic oxide layer is 50 nm-250 nm.

16. The reverse osmosis membrane according to claim 11, wherein The flexible polymer substrate is a polysulfone material, and the organic layer is a polyamide material or a polyimide material.

17. The reverse osmosis membrane according to claim 11, wherein The inorganic oxide layer includes one or more of aluminum oxide, silicon oxide, titanium oxide, and zinc oxide.

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