A reverse osmosis membrane and a method for preparing a reverse osmosis membrane

Abstract

The application discloses a reverse osmosis membrane and a preparation method thereof, and relates to the technical field of reverse osmosis membranes. The preparation method comprises the following steps: preparing an organic layer on a flexible polymer substrate, and cross-linking and bonding the organic layer and the flexible polymer substrate; and preparing an inorganic oxide layer on the organic layer, and cross-linking and bonding the inorganic oxide layer and the organic layer. According to the application, the organic layer and the inorganic oxide layer are sequentially stacked on the flexible polymer substrate, and the flexible polymer substrate, the organic layer and the inorganic oxide layer are cross-linked and bonded with each other, so that a composite cross-linking type reverse osmosis membrane can be prepared, the technical problem that the bonding force between the membrane layers of the reverse osmosis membrane is weak is solved, the filtering capacity of the reverse osmosis membrane is improved, and the service life of the reverse osmosis membrane is prolonged.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of reverse osmosis membranes, in particular to a reverse osmosis membrane and a preparation method thereof. BACKGROUND

[0002] To improve the filtering capacity, the reverse osmosis membrane is usually a multi-layer structure. However, the membrane layers of the reverse osmosis membrane prepared by the existing method are usually formed by physical stacking, such as interfacial polymerization. The binding force between the membrane layers of such a reverse osmosis membrane structure is weak, and large gaps are easily formed between the membrane layers, causing inorganic suspended particles, hydrophobic oily organic matter and microorganisms to be retained therein, resulting in scale blockage, membrane pollution and other situations, which affect the service life and filtering effect of the reverse osmosis membrane. SUMMARY

[0003] In view of the above problems, the present application provides a reverse osmosis membrane and a preparation method thereof to improve the conditions of membrane pollution and membrane damage.

[0004] In a first aspect, the present application provides a preparation method of a reverse osmosis membrane, comprising:

[0005] An organic layer is prepared on a flexible polymer substrate, and the organic layer is cross-linked and bonded to the flexible polymer substrate;

[0006] An inorganic oxide layer is prepared on the organic layer, and the inorganic oxide layer is cross-linked and bonded to the organic layer.

[0007] In some embodiments, the organic layer is made by a molecular layer deposition process, the inorganic oxide layer is made 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 turn.

[0008] In some embodiments, after the inorganic oxide layer is prepared, the preparation method of the reverse osmosis membrane further comprises: heat treating the reverse osmosis membrane.

[0009] In some embodiments, the step of heat treating the reverse osmosis membrane comprises:

[0010] The reverse osmosis membrane is slowly heated to 50-200°C, and then cooled after a preset time.

[0011] In some embodiments, the preset time is 1-5 hours.

[0012] In some embodiments, the step of preparing the organic layer on the flexible polymer substrate, the step of preparing the inorganic oxide layer on the organic layer, and the step of heat treating the reverse osmosis membrane are carried out in the same reaction cavity.

[0013] In some embodiments, the organic layer is a polyamide material or a polyimide material, and the step of preparing the organic layer on the flexible polymer substrate comprises:

[0014] depositing an organic layer on a flexible polymer substrate using a first precursor and a second precursor, the first precursor being a precursor comprising an amino group, and the second precursor being a precursor comprising an acyl group.

[0015] In some embodiments, the step of depositing an organic layer on a flexible polymer substrate using a first precursor and a second precursor comprises:

[0016] pulsing the first precursor into the reaction chamber using a carrier gas, at a flow rate of 500-1500 sccm, for a duration of 1-3 s;

[0017] purging the reaction chamber using a purge gas, at a flow rate of 1000-1500 sccm, for a duration of 5-10 s;

[0018] pulsing the second precursor into the reaction chamber using a carrier gas, at a flow rate of 500-1500 sccm, for a duration of 1-3 s;

[0019] purging the reaction chamber using a purge gas, at a flow rate of 500-1500 sccm, for a duration of 5-10 s;

[0020] repeating the above steps 4000-10000 times to obtain the organic layer;

[0021] wherein the vacuum degree in the reaction chamber is 1-100 Pa, the reaction temperature is 100-200℃, and the temperature of the first precursor and the second precursor is 30-150℃.

[0022] In some embodiments, the step of preparing an inorganic oxide layer on the organic layer comprises: depositing an inorganic oxide layer on the organic layer using a third precursor and a fourth precursor, the inorganic oxide layer being a single oxide layer or a stacked oxide layer, the third precursor being one or more of a metal halide precursor, an organometallic precursor, and a silicon-containing precursor, and the fourth precursor being an oxygen source.

[0023] In some embodiments, the step of depositing an inorganic oxide layer on the organic layer comprises: alternately pulsing the third precursor and the fourth precursor into the reaction chamber using a carrier gas; and purging the reaction chamber using a purge gas before the third precursor and the fourth precursor are alternately pulsed.

[0024] 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 arranged in sequence, the flexible polymer substrate being cross-linked to the organic layer, and the organic layer being cross-linked to the inorganic oxide layer.

[0025] In some embodiments, the pore size of the flexible polymer substrate, the organic layer and the inorganic oxide layer decreases in turn.

[0026] In some embodiments, the pore size of the flexible polymer substrate is 0.1-1 mu m, and the pore size of the organic layer is 0.05-1 mu m.

[0027] In some embodiments, the pore size of the reverse osmosis membrane formed by the flexible polymer substrate, the organic layer and the inorganic oxide layer is 0.1-10 nm.

[0028] In some embodiments, the thickness of the flexible polymer substrate is 50-125 mu m, the thickness of the organic layer is 0.2-1 mu m, and the thickness of the inorganic oxide layer is 50-250 nm.

[0029] In some embodiments, the flexible polymer substrate is a polysulfone material, and the organic layer is a polyamide material or a polyimide material.

[0030] In some embodiments, the inorganic oxide layer comprises one or more of aluminum oxide, silicon oxide, titanium oxide and zinc oxide.

[0031] The beneficial effects of the present application are:

[0032] The present application can prepare a composite cross-linked reverse osmosis membrane by preparing an organic layer and an inorganic oxide layer which are sequentially stacked on a flexible polymer substrate, and the flexible polymer substrate, the organic layer and the inorganic oxide layer are cross-linked to each other. On the one hand, the combination between the layers of the reverse osmosis membrane can be improved, thereby improving the filtration capacity of the reverse osmosis membrane and prolonging the service life of the reverse osmosis membrane. On the other hand, the organic layer can be protected by the inorganic oxide layer, thereby reducing the possibility of corrosion of the organic layer by inorganic suspended particles, hydrophobic oily organic matter or microorganisms in the liquid, or reaction with active chlorine in the cleaning reagent, thereby further prolonging the service life of the reverse osmosis membrane.

[0033] The above description is only a summary of the technical solutions of the present application. In order to more clearly understand the technical means of the present application, the specific embodiments of the present application can be implemented in accordance with the content of the description, and in order to make the above and other purposes, features and advantages of the present application more obvious and easy to understand, the following specific embodiments of the present application are described. BRIEF DESCRIPTION OF DRAWINGS

[0034] Various other advantages and benefits will become apparent to those of ordinary skill in the art upon reading the following detailed description of the preferred embodiments. The accompanying drawings are included to provide a better understanding of the preferred embodiments, and are not to be considered as limitations on the present application. Moreover, in all the drawings, like reference numerals refer to the same or similar components. In the drawings:

[0035] Figure 1 A structure diagram of a reverse osmosis membrane provided by some embodiments of the present application is shown in FIG. 1.

[0036] Figure 2 A structure diagram of an inorganic oxide layer provided by some embodiments of the present application is shown in FIG. 2.

[0037] Figure 3 A preparation flow diagram of a reverse osmosis membrane provided by some embodiments of the present application is shown in FIG. 3.

[0038] Figure 4 A preparation flow diagram of an organic layer provided by some embodiments of the present application is shown in FIG. 4.

[0039] Figure 5 A preparation flow diagram of an inorganic oxide layer provided by some embodiments of the present application is shown in FIG. 5.

[0040] Figure 6 A preparation flow diagram of an inorganic oxide layer provided by some embodiments of the present application is shown in FIG. 6.

[0041] Figure 7 A diagram showing the relationship between the number of ALD reaction cycles and the thickness of the inorganic oxide layer provided by some embodiments of the present application is shown in FIG. 7. DETAILED DESCRIPTION

[0042] The technical solutions in the embodiments of the present application will be clearly and completely described below with reference to the drawings in the embodiments of the present application. Obviously, the described embodiments are only some of the embodiments of the present application, but not all the embodiments of the present application. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without creative work fall within the scope of protection of the present application.

[0043] It should be noted that the terms "first", "second", etc. in the following are used only for the purpose of description, and cannot be understood as indicating or implying relative importance or implicitly indicating the number of the indicated technical features. Therefore, the features defined with "first", "second" can explicitly or implicitly include one or more of the features.

[0044] The words on the specification are used for the purpose of describing the embodiments of the present application, but are not intended to limit the present application. It should also be noted that, unless otherwise explicitly specified and limited, if the terms "provided", "connected", "connected" appear, they should be understood in a broad sense, for example, they can be fixedly connected, or detachably connected, or integrally connected; they can be mechanically connected, or directly connected, or indirectly connected through an intermediate medium, or the communication inside two elements. For those skilled in the art, the above can be specifically understood as the specific meaning in the present application.

[0045] Reference to“an embodiment” herein means that a particular feature, structure, or characteristic described in connection with the embodiment can be included in at least one embodiment of the application. The appearances of the phrase“in

[0046] The application provides a reverse osmosis membrane. Reverse osmosis is a technology for separating the solvent of a solution by using pressure difference as the driving force, and the reverse osmosis membrane is the core component of the reverse osmosis technology.

[0047] Please refer to Figure 1 , Figure 1 The structural schematic diagram of the reverse osmosis membrane provided for some embodiments of the application is shown in the following figure.

[0048] In some embodiments of the application, the reverse osmosis membrane 100 comprises a flexible polymer substrate 10, an organic layer 20 and an inorganic oxide layer 30 which are sequentially stacked. 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.

[0049] The flexible polymer substrate 10 is a flexible substrate formed of a polymer material, such as a flexible polyether sulfone substrate. Of course, the flexible polymer substrate 10 can also be formed of other polymer materials, such as but not limited to polyphenyl 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, and 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.

[0050] 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.

[0051] 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 can 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.

[0052] 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.

[0053] 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.

[0054] Optionally, the thicknesses of the flexible polymer substrate 10, the organic layer 20 and the inorganic oxide layer 30 decrease in turn, so that the composite cross-linked reverse osmosis membrane 100 has a gradient change trend from one side to the other side in terms of thickness from large to small.

[0055] Optionally, the thicknesses of the flexible polymer substrate 10, the organic layer 20 and the inorganic oxide layer 30 decrease in turn, so that the composite cross-linked reverse osmosis membrane 100 has a gradient change trend from one side to the other side in terms of thickness from large to small.

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

[0057] It can be understood that each layer of the reverse osmosis membrane 100 must have pores, and 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 great influence on its filtration performance. The reverse osmosis membrane 100 provided in the present application is improved in this regard, and for the sake of understanding, the size of the pore structure of the reverse osmosis membrane 100 is represented by "pore size" hereinafter.

[0058] In some embodiments, the pore size of the flexible polymer substrate 10 can 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.

[0059] The pore size of the organic layer 20 can 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.

[0060] It should be noted that, in the reverse osmosis membrane 100 provided by the embodiments of the present application, due to the gradient change of the pore diameters of different membrane layers, the pore diameter of the previous membrane layer is relatively small, and thus the overall pore diameter of the reverse osmosis membrane 100 gradually decreases, which meets the pore size requirements of various working conditions.

[0061] Therefore, the pore diameter of the membrane formed by laminating the flexible polymer substrate 10 and the organic layer 20 is much smaller than the pore diameter of any one of the flexible polymer substrate 10 and the organic layer 20. For example, after the flexible polymer substrate 10 with a pore diameter of 0.5 μm is prepared with the organic layer 20 with a thickness of 0.2 μm-0.5 μm, the pore diameter of the membrane formed by laminating the flexible polymer substrate 10 and the organic layer 20 can reach 30 nm-50 nm, such as 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.

[0062] The pore diameter 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 diameter of the reverse osmosis membrane 100 can be further reduced to 0.1 nm-10 nm, i.e. For example etc.

[0063] Alternatively, the pore diameters of the flexible polymer substrate 10, the organic layer 20 and the inorganic oxide layer 30 decrease in turn, so that the reverse osmosis membrane 100 has a gradient change trend from one side to the other side, i.e., the pore diameter gradually decreases from one side to the other side. The embodiments of the present application form a high-efficiency filtering channel through the gradual change of the pore diameter of the reverse osmosis membrane 100, which is beneficial to reduce the additional power consumption of the reverse osmosis membrane 100 in use.

[0064] In an application scenario, the flexible polymer substrate 10 forms the liquid inlet side of the reverse osmosis membrane 100, the inorganic oxide layer 30 forms the liquid outlet side of the reverse osmosis membrane 100, and the flexible polymer substrate 10, the organic layer 20 and the inorganic oxide layer 30 can cooperate to filter the liquid.

[0065] It should be noted that the existing reverse osmosis membrane is mainly prepared by a coating process or an interfacial polymerization reaction, i.e., an organic functional layer is formed on the surface of a porous substrate by spraying or interfacial polymerization. On the one hand, the obtained reverse osmosis membrane has a physical stacking structure between the membrane layers, the bonding force between the membrane layers is weak, and large gaps are easily formed between the membrane layers, so that inorganic suspended particles, hydrophobic oily organic matter and microorganisms are retained in the gaps, resulting in situations such as scale blocking, membrane fouling, etc., which affect the service life and filtering 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 stability of the membrane, thereby reducing the service life of the reverse osmosis membrane.

[0066] The application improves the binding force between the membrane layers of the reverse osmosis membrane 100, thereby improving the filtering performance and prolonging the service life, and also protects the organic layer 20 by the inorganic oxide layer 30, reduces the possibility of corrosion of the organic layer 20 by inorganic suspended particles, hydrophobic oily organic matter and microorganisms and the like or the reaction with active chlorine in the cleaning reagent to cause the membrane structure to be damaged, improves the interception rate of bacteria of the reverse osmosis membrane 100, increases the water flux of the reverse osmosis membrane 100, enhances the resistance of the reverse osmosis membrane 100 to active chlorine, and further prolongs the service life of the reverse osmosis membrane 100.

[0067] Further, the application also designs the reverse osmosis membrane 100 to have the above-mentioned gradient change from large to small, so that the pre-membrane pressure of the reverse osmosis membrane 100 during filtering can be greatly reduced, the water permeation of the reverse osmosis membrane 100 is further increased, the time of clogging of the reverse osmosis membrane 100 can be effectively and significantly delayed, the negative effects caused by the membrane fouling problem are reduced, thereby improving the service life of the reverse osmosis membrane 100, and the power consumption of the reverse osmosis system is also reduced.

[0068] In some embodiments, the inorganic oxide layer 30 can be formed by one oxide of aluminum oxide, silicon oxide, titanium oxide and zinc oxide, which can be selected according to the application scenario of the reverse osmosis membrane 100. For example, titanium oxide has the property of resisting alkali corrosion, so the reverse osmosis membrane 100 applied to the filtering treatment of alkaline waste liquid can 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 of neutral (6 < pH < 8) liquid. For still another example, silicon oxide has good resistance to general acid and alkali corrosion, so it is suitable for many application scenarios.

[0069] In other embodiments, the inorganic oxide layer 30 can be formed by two or more oxides of aluminum oxide, silicon oxide, titanium oxide and zinc oxide, and the different oxides are alternately and sequentially arranged. Please refer to Figure 2 , Figure 2 is a structure diagram of the inorganic oxide layer provided in some embodiments of the application.

[0070] 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, the second oxide layer 32 is selected from another one of aluminum oxide, silicon oxide, titanium oxide and zinc oxide, and the first oxide layer 31 and the second oxide layer 32 are alternately and sequentially arranged.

[0071] By designing the inorganic oxide layer 30 as an alternating layer structure of multiple oxides, the protection 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 be formed of three or more oxides, for example, three different oxides respectively form different oxide layers and are arranged in an alternating manner. When the number of oxides forming the oxide layer 30 is greater than 2, there can be multiple alternating ways, for example, ABCABC, ABACABAC, ABCBCABCBC, and the like, where A, B, and C represent one oxide, and more alternating ways can be similarly derived, which are not listed one by one.

[0072] It should be noted that "multiple" mentioned herein represents "two or more", and other quantity terms involving "multiple" are the same.

[0073] The reverse osmosis membrane 100 provided by the embodiments of the present application can further improve the problem of contamination of the reverse osmosis membrane 100 by pollutants and corrosion and damage of the reverse osmosis membrane 100 by microorganisms and chemical reagents by the acid, alkali, corrosion resistance, and other properties of inorganic oxide materials such as TiO2 and SiO2, thereby improving the service life. The inorganic oxide material can also increase the hydrophilicity of the membrane surface, improve the interception rate of hydrophobic organic pollutants, and increase the water flow rate.

[0074] The present application further provides a preparation method of a reverse osmosis membrane. The reverse osmosis membrane 100 described above can be prepared by the preparation method of the reverse osmosis membrane provided by the present application. The reverse osmosis membrane obtained by the embodiments of the present application is a three-layer organic and inorganic composite membrane, and the membrane layers are cross-linked and bonded to form an integral reverse osmosis membrane.

[0075] Please refer to Figure 3 , Figure 3 is a preparation flowchart of the reverse osmosis membrane provided by some embodiments of the present application.

[0076] In some embodiments, the preparation method of the reverse osmosis membrane comprises the following steps:

[0077] S11, preparing an organic layer on a flexible polymer substrate.

[0078] The polymer material used for the flexible polymer substrate can be polyether sulfone. Polyether sulfone has excellent heat resistance, physical and mechanical properties, insulation properties, and the like, and has outstanding advantages such as continuous use at high temperatures and stable performance in environments with rapid temperature changes, and is widely used in electronic-grade films, water permeable membranes, hemodialysis membranes, and special environmental materials.

[0079] The organic layer can be made of a polyamide material or a polyimide material. The organic layer prepared on the flexible polymer substrate cooperates with the flexible polymer substrate to form a laminated film structure, which has good filtering performance.

[0080] In the embodiments of the present application, the organic layer can be prepared by molecular layer deposition (MLD).

[0081] Molecular layer deposition is an advanced organic polymer thin film and organic-inorganic hybrid film preparation technology, which can deposit one molecular layer per cycle and accurately control the thickness. Compared with the traditional organic polymer thin film deposition process (spin coating, thermal evaporation), MLD has accurate controllable film thickness (control cycle number), more uniform thickness, better step coverage and shape retention, and more reliable repeatability. By alternately introducing two reaction gases (or vapors) in the form of gas pulses into the reactor, the film is generated by reaction with adsorbed molecules (such as hydroxyl or amino) on the substrate surface. Since the reactants involved in the reaction each time are limited to the molecules chemisorbed on the substrate surface, MLD has the self-limiting growth feature.

[0082] S12, preparing an inorganic oxide layer on the organic layer.

[0083] The inorganic oxide layer is formed of inorganic oxides prepared on the organic layer, such as silicon oxide, titanium oxide, zinc oxide, aluminum oxide, etc. In the embodiments of the present application, the inorganic oxide layer can be prepared by atomic layer deposition (ALD).

[0084] Atomic layer deposition, also known as atomic layer epitaxy, is a method that can deposit material on the surface of a substrate in the form of a monolayer film. Atomic layer deposition has similarities with ordinary chemical deposition. However, in the process of atomic layer deposition, the chemical reaction of a new layer of atomic film is directly associated with the previous layer, which makes each reaction deposit only one layer of atoms; atomic layer deposition is a method of forming a deposition film by alternately introducing gas phase precursors into a reactor and chemisorbing and reacting on the deposition substrate. When the precursors reach the surface of the deposition substrate, they will chemisorb on the surface and undergo surface reaction. The atomic layer deposition reactor needs to be cleaned with inert gas between precursor pulses. Therefore, whether the deposition reaction precursor substance can be chemisorbed on the surface of the deposited material is the key to realizing atomic layer deposition. The adsorption characteristics of gas phase substances on the surface of the substrate material show that any gas phase substance can be physically adsorbed on the surface of the material, but chemical adsorption on the surface of the material must have a certain activation energy. Therefore, it is important to select appropriate reaction precursors to realize atomic layer deposition. In the self-limiting deposition process, the first reaction precursor is input to the surface of the substrate material and maintained on the surface by chemical adsorption (saturated adsorption). When the second precursor is introduced into the reactor, it will react with the first precursor that has been adsorbed on the surface of the substrate material. A displacement reaction occurs between the two precursors and produces corresponding by-products, until the first precursor on the surface is completely consumed, the reaction will automatically stop and form the required atomic layer. Therefore, this is a self-limiting process, and the reaction is repeated to form a thin film.

[0085] 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 excite two or more precursors to react. In order to provide sufficient reaction activation energy, the general working temperature range of the thermal atomic layer deposition equipment is 200-500°C. Plasma enhanced atomic layer deposition is to introduce plasma to generate a large number of active free radicals, enhance the reactivity of the precursor substance, thereby expand the selection range of ALD precursors and application requirements, shorten the reaction period of time, and also reduce the requirements for the deposition temperature of the sample. Low-temperature or even room-temperature deposition can be achieved, which is especially 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, obtain lower resistivity and higher thin film density, etc. In addition, the plasma can also clean the reaction chamber and perform surface activation treatment on the substrate, etc. The inorganic oxide layer in the embodiments of the present application can be prepared by TALD or PEALD.

[0086] It should be noted that TALD and PEALD can also be used in combination, for example, on the basis of a thermal atomic layer deposition device, a plasma is introduced into the process chamber, so that the process temperature can be effectively reduced to meet the process requirements of low heat budget, and advantages are also obtained in improving the densification of the thin film and reducing the impurity content of the thin film. The inorganic oxide layer in the embodiments of the present application can be prepared by TALD and PEALD.

[0087] By depositing the organic layer of the molecular structure and the inorganic layer of the atomic structure, the micro membrane layer of the reverse osmosis membrane gradually changes from the micron-sized large-pore base, the micron-sized small-pore organic layer to the nanometer-sized microporous inorganic layer, which can effectively alleviate the impact of the pre-membrane pressure and prevent the pre-membrane pressure from damaging the separation function layer. Moreover, the membrane layers are cross-linked by chemical bonds, the bonding force is enhanced, 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 organic matter and microorganisms, prevent scale blockage and membrane pollution, reduce the possibility of microbial corrosion and other membrane pollution, and improve the filtration effect and prolong the service life.

[0088] The embodiments of the present application can make the reverse osmosis membrane form a laminated membrane body structure in which the flexible polymer base, the organic layer and the inorganic oxide layer are sequentially stacked and cross-linked to each other by preparing the inorganic oxide layer on the organic layer, which is conducive to improving the chemical stability and microstructure stability of the reverse osmosis membrane. For example, the inorganic oxide layer formed by silicon oxide and other acid-resistant oxides can protect the organic layer from corrosion by hydrogen chloride 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 described above and will not be repeated here.

[0089] Compared with the existing reverse osmosis membranes prepared by coating process or interfacial polymerization reaction, the preparation method provided by the present application uses the unique saturated adsorption reaction principle to prepare the organic layer and the inorganic oxide layer thin film by atomic layer deposition and molecular layer deposition method, which can effectively reduce the residual of chemical groups in the thin film.

[0090] The organic layer and the inorganic oxide layer provided by the present application can be made by chemical vapor deposition technology. The organic layer and the inorganic oxide layer are grown in situ on the flexible polymer base by chemical vapor deposition method, the membrane layer is uniform, the film quality is good, and the residual of organic groups can be avoided, which affects the stability of the reverse osmosis membrane and improves the service life of the reverse osmosis membrane.

[0091] By chemical vapor deposition of organic layer and different kinds of inorganic oxide layer, not only the organic group can be avoided to remain in the membrane, the performance of the membrane can be improved, but also the specific pore size of the membrane material can be accurately controlled to regulate the required pressure before the reverse osmosis membrane, at the same time, the composite membrane structure of the reverse osmosis membrane can be simplified, and the control of the pore size of the (Angstrom) level can be realized, so that the reverse osmosis membranes with different pore sizes can be obtained, thereby the reverse osmosis membranes can be applied to water treatment in different working conditions such as direct drinking water purification, seawater desalination and wastewater treatment, and the application range is wide. By depositing inorganic oxide to form the membrane body surface, the surface hydrophilicity of the reverse osmosis membrane can be increased, so that the interception rate of the reverse osmosis membrane to hydrophobic organic pollutants can be improved, and the water flow of the reverse osmosis membrane can be increased.

[0092] S13, heat treating the reverse osmosis membrane.

[0093] After the inorganic oxide layer is prepared, the reverse osmosis membrane is heat treated. It should be noted that the reverse osmosis membrane heat treated in this step is the laminated membrane structure including the composite crosslinked flexible polymer substrate, the organic layer and the inorganic oxide layer prepared by the above steps, which is different from the reverse osmosis membrane obtained after this step. The step S13 can be specifically that the reverse osmosis membrane is slowly heated to a certain temperature, kept for a sufficient time, and then slowly cooled to remove impurities on the membrane surface and improve the filtration effect of the reverse osmosis membrane.

[0094] Optionally, the reverse osmosis membrane is heated to 50-200℃, for example, 80℃, 100℃, 120℃, 150℃, 180℃, etc. in the heat treatment step, and the impurities on the membrane surface can be effectively removed by low-temperature annealing to improve the filtration effect of the reverse osmosis membrane.

[0095] Optionally, the heat treatment step includes that the reverse osmosis membrane is slowly heated to 50-200℃, and slowly cooled after a preset time, and the preset time can be 1-5 hours, for example, 1.5 hours, 2 hours, 2.5 hours, 3 hours, 3.5 hours, 4 hours, 4.5 hours, etc.

[0096] Optionally, the steps of preparing the organic layer on the flexible polymer substrate, preparing the inorganic oxide layer on the organic layer and heat treating the reverse osmosis membrane are carried out in the same reaction cavity to improve the preparation efficiency of the reverse osmosis membrane.

[0097] It should be noted that the above heat treatment step can be carried out after the organic layer is prepared, or after the inorganic oxide layer is prepared, or after the organic layer is prepared and after the inorganic oxide layer is prepared, respectively.

[0098] ​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 the present application does not necessarily include this step.

[0099] Please refer to Figure 4 , Figure 4 is a schematic diagram of the preparation process of the organic layer provided in some embodiments of the present application.

[0100] In some embodiments, the organic layer can be formed by depositing the first precursor and the second precursor on the flexible polymer substrate. The first precursor is a precursor containing an amino group (-NH2), such as m-phenylenediamine, aniline, p-phenylenediamine, o-phenylenediamine, and methyl ethylamine, etc. The second precursor is a precursor containing an acyl group (-COX, X is a halogen atom, such as chlorine atom, bromine atom, iodine atom, etc.), such as trimesoyl chloride, trimesoyl iodine, and trimesoyl, etc. The first precursor and the second precursor can react to form a polyamide or a polyimide.

[0101] Optionally, the preparation method of the organic layer comprises the following steps:

[0102] S21, introducing the first precursor into the reaction cavity.

[0103] The first precursor can be carried into the reaction cavity by a carrier gas introduced into the reaction cavity. The carrier gas can be nitrogen or other gases that do not react in the preparation of the reverse osmosis layer.

[0104] Optionally, the first precursor is introduced into the reaction cavity in the form of pulses. The flow rate of the carrier gas can be 500-1500sccm, such as 600sccm, 700sccm, 800sccm, 900sccm, 1000sccm, 1050sccm, 1100sccm, 1150sccm, 1200sccm, 1250sccm, 1300sccm, 1350sccm, 1400sccm, 1450sccm, 1500sccm, etc. The duration of the carrier gas can be 1-3s, such as 1s, 1.5s, 2s, 2.5s, 3s, etc.

[0105] S22, introducing a purge gas into the reaction cavity for purging.

[0106] After depositing the first precursor, the purge gas is introduced to purge the excess precursor or impurities in the reaction cavity. The purge gas can be nitrogen or other gases that do not react in the preparation of the reverse osmosis layer. It can be understood that the purge gas and the carrier gas can use the same gas, such as nitrogen, to improve the preparation efficiency. The same applies to the carrier gas and the purge gas mentioned below.

[0107] Optionally, the purge flow of the purge gas is 500-1500 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 duration is 5-10 s, for example, 5 s, 5.5 s, 6 s, 6.5 s, 7 s, 7.5 s, 8 s, 8.5 s, 9 s, 9.5 s, etc.

[0108] S23, introducing the second precursor into the reaction cavity.

[0109] After the purge is completed, the second precursor is introduced to react with the first precursor in the reaction cavity to generate polyamide or polyimide.

[0110] Optionally, the second precursor can be introduced into the reaction cavity in the form of pulses by the carrier gas, and the flow rate can be 500-1500 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 carrier gas introduction can be 1-3 s, for example, 1 s, 1.5 s, 2 s, 2.5 s, 3 s, etc.

[0111] S24, introducing the purge gas into the reaction cavity for purging.

[0112] The purge gas is introduced into the reaction cavity for purging, and the purge flow can be 500-1500 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 duration is 5-10 s, for example, 5 s, 5.5 s, 6 s, 6.5 s, 7 s, 7.5 s, 8 s, 8.5 s, 9 s, 9.5 s, etc.

[0113] S25, repeating the above steps 4000-10000 times.

[0114] The organic layer is gradually grown on the flexible polymer substrate by repeatedly performing the steps of introducing the first precursor, purging, introducing the second precursor, and purging. Research has found that when the number of repeated steps is 4000-10000, such as 4000, 5000, 6000, 7000, 8000, 9000, or 10000, an organic layer with a suitable thickness and porosity can be grown.

[0115] Optionally, the organic layer can be prepared by a molecular layer deposition method.

[0116] In some embodiments, the preparation conditions of the organic layer include:

[0117] The vacuum degree in the reaction cavity is 1 Pa-100 Pa, such as 3 Pa, 5 Pa, 8 Pa, 10 Pa, 15.5 Pa, 20 Pa, 30 Pa, 40 Pa, 50 Pa, 55.5 Pa, 60 Pa, 65.5 Pa, 70 Pa, 75 Pa, 80 Pa, 85 Pa, 90 Pa, 95.5 Pa, 100 Pa, etc.

[0118] The reaction temperature is 100°C-200°C, such as 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.

[0119] The temperature of the first precursor and the second precursor is 30°C-150°C, such as 30°C, 31.5°C, 33°C, 35°C, 37.5°C, 39°C, 40°C, 41.5°C, 42°C, 43°C, 44°C, 45.5°C, 47°C, 48.5°C, 49°C, 49.5°C, 50°C, 60°C, 80°C, 100°C, 120°C, 140°C, etc.

[0120] Please refer to Figure 5 , Figure 5 is a preparation process schematic diagram of the inorganic oxide layer provided in some embodiments of the present application.

[0121] 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 organic metal 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.; the third precursor and the fourth precursor can react to form an inorganic oxide.

[0122] The step of depositing the inorganic oxide layer on the organic layer can comprise: alternately introducing a third precursor and a fourth precursor into the reaction cavity by using a carrier gas; and purging the reaction cavity by using a purge gas before introducing the latter precursor.

[0123] Optionally, the step of depositing the inorganic oxide layer on the organic layer comprises the following steps:

[0124] S31, introducing the third precursor into the reaction cavity.

[0125] The third precursor can be carried into the reaction cavity by the carrier gas introduced into the reaction cavity.

[0126] Optionally, the third precursor is introduced into the reaction cavity in a pulse form. The flow rate of the carrier gas can be 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 duration of the carrier gas can be 0.1 s-2 s, such as 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.

[0127] S32, purging the reaction cavity by introducing a purge gas.

[0128] After depositing the third precursor, the purge gas is introduced to purge the excess precursor or impurities in the reaction cavity.

[0129] Optionally, the purge flow rate of the purge gas is 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 purge duration is 2 s-8 s, such as 2 s, 2.5 s, 3 s, 3.5 s, 4 s, 4.5 s, 5 s, 5.5 s, 6 s, 6.5 s, 7 s, 7.5 s, etc.

[0130] S33, introducing the fourth precursor into the reaction cavity.

[0131] After purging, the fourth precursor is introduced into the reaction cavity to oxidize the third precursor in the reaction cavity to form inorganic oxide.

[0132] The fourth precursor can be introduced into the reaction cavity in a pulse form by carrying the source gas, and the flow rate can be 500-1500 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 duration of introduction can be 0.1-2 s, such as 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.

[0133] S34, introducing a purge gas into the reaction cavity for purging.

[0134] The purge gas is introduced into the reaction cavity for purging, and the flow rate can be 500-1500 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 duration of purging can be 2-8 s, such as 2 s, 2.5 s, 3 s, 3.5 s, 4 s, 4.5 s, 5 s, 5.5 s, 6 s, 6.5 s, 7 s, 7.5 s, etc.

[0135] S35, repeating the above steps 1-500 times.

[0136] The steps of introducing the third precursor, purging, introducing the fourth precursor, and purging are repeated to gradually grow the inorganic oxide layer on the organic layer. The number of repetitions can be 1-500 times, such as 50 times, 100 times, 150 times, 200 times, 250 times, 300 times, 350 times, 400 times, 450 times, 500 times, etc.

[0137] Specifically, the third precursor and the fourth precursor are alternately introduced into the reaction cavity to form an oxide by chemisorption and reaction on the organic layer. The third precursor initially introduced into the reaction cavity is adsorbed on the surface of the organic layer, and when the fourth precursor is introduced into the reaction cavity, it reacts with the third precursor adsorbed on the surface of the organic layer. A displacement reaction occurs between the two precursors and a corresponding byproduct is generated. When the surface of the third precursor is completely consumed, the reaction stops automatically and the desired film layer is formed. When new third precursors are introduced, the new third precursors are adsorbed on the oxide. By repeating the process multiple times, an inorganic oxide layer is formed. The formation of the organic layer is similar.

[0138] In some embodiments, the preparation conditions of the inorganic oxide layer include:

[0139] The vacuum degree in the reaction cavity is 1 Pa-100 Pa, such as 3 Pa, 5 Pa, 8 Pa, 10 Pa, 15.5 Pa, 20 Pa, 30 Pa, 40 Pa, 50 Pa, 55.5 Pa, 60 Pa, 65.5 Pa, 70 Pa, 75 Pa, 80 Pa, 85 Pa, 90 Pa, 95.5 Pa, 100 Pa, etc.

[0140] The reaction temperature is 100°C-200°C, such as 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.

[0141] The temperature of the third precursor and the fourth precursor is 20°C-40°C, such as 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.

[0142] Optionally, the organic layer and the inorganic oxide layer are prepared in the same reaction cavity under the same pressure and the same temperature. For example, the MLD and ALD deposition reactions and the heat treatment are also completed in the same chamber under the same pressure and the same temperature. This avoids the transfer of the reverse osmosis membrane intermediate between the various processing procedures, effectively improves the production efficiency and reduces the production cost, and ensures the performance and quality of the reverse osmosis membrane, which is beneficial to the batch production of the roll-type reverse osmosis membrane.

[0143] The present application prepares an organic layer by a molecular layer deposition process and an inorganic oxide layer by an atomic layer deposition process, which can accurately control the thickness and pore size of the prepared organic layer and inorganic oxide layer. Therefore, the reverse osmosis membrane can be prepared according to the requirements of different application scenarios, so that the prepared reverse osmosis membrane can be applied to various application fields, including but not limited to direct drinking water purification, seawater desalination, wastewater treatment, etc.

[0144] For example, when the reverse osmosis membrane needs to be applied to direct drinking water purification, an organic layer of 0.2-0.5 pm polyimide material can be prepared on a flexible polymer substrate with a pore size of 0.5 pm, and the pore size of the flexible polymer-polyimide integrated membrane can reach 30-50 nm; after growing a (TiO2+SiO2) x (160-200 cycles) inorganic oxide layer on the surface of the polyimide film, the pore size of the flexible polymer-polyimide-TiO2+SiO2 laminated oxide integrated membrane, i.e., the reverse osmosis membrane, can reach 10-20 nm.

[0145] The application can also take advantage of the characteristics of MLD for preparing dense and sparse membrane layers and ALD for preparing dense membrane layers, so that the prepared reverse osmosis membrane has a gradient change in pore size, reduces the pre-membrane pressure of the incoming water, and reduces the power consumption of the reverse osmosis system.

[0146] The pore size of the inorganic oxide layer can be controlled by the following methods: first, controlling the reaction temperature of ALD, different reaction temperatures of ALD result in different densities of the oxide film, so the pore size of the inorganic oxide layer is different; second, controlling the thickness of the inorganic oxide layer prepared by ALD, different thicknesses of the inorganic oxide layer result in different pore sizes of the inorganic oxide layer; third, adjusting the generation of different types of inorganic oxide layers, different micro-atomic sizes of the oxide prepared by ALD result in different pore sizes of the inorganic oxide layer.

[0147] It should be noted that the inorganic oxide layer provided by the application can be formed by a single oxide or a plurality of oxides, and the latter can form an inorganic oxide layer with a plurality of alternating oxide layers.

[0148] Please refer to Figure 6 , Figure 6 is a preparation flowchart of the inorganic oxide layer provided by some other embodiments of the application.

[0149] In some embodiments, the step of preparing the inorganic oxide layer on the organic layer further comprises: depositing the inorganic oxide layer by using a fifth precursor and a sixth precursor.

[0150] The fifth precursor is one of a metal halide precursor, an organic metal precursor, and a silicon-containing precursor, and is different from the third precursor. For example, the third precursor can be a precursor of silicon oxide, and the fifth precursor can be a precursor of any one of titanium oxide, zinc oxide, and aluminum oxide. It can be understood that the inorganic oxide layer can also be formed by oxides other than titanium oxide, silicon oxide, zinc oxide, and aluminum oxide.

[0151] The sixth precursor is an oxygen source, such as oxygen, water, ozone, etc. The fifth precursor and the sixth precursor can react to form an inorganic oxide, and cooperate with the third precursor and the fourth precursor to form an inorganic oxide layer having first oxide layers and second oxide layers arranged in an alternating stack. Specifically, the third precursor and the fourth precursor can be used to prepare the first oxide layers, the fifth precursor and the sixth precursor can be used to prepare the second oxide layers, and the first oxide layers and the growing second oxide layers are alternately repeated.

[0152] Optionally, the preparation of the inorganic oxide layer comprises the following steps:

[0153] S41, introducing the third precursor into the reaction cavity.

[0154] Optionally, the third precursor is introduced into the reaction cavity in a pulse form by using a carrier gas, the flow rate is 500-1500 sccm, and the introduction time is 0.1-2 s.

[0155] S42, introducing a purge gas into the reaction cavity for purging.

[0156] Optionally, the purge gas is introduced into the reaction cavity for purging, the flow rate is 500-1500 sccm, and the introduction time is 2-8 s.

[0157] S43, introducing the fourth precursor into the reaction cavity.

[0158] Optionally, the fourth precursor is introduced into the reaction cavity in a pulse form by using a carrier gas, the flow rate is 500-1500 sccm, and the introduction time is 0.1-2 s.

[0159] S44, introducing a purge gas into the reaction cavity for purging.

[0160] Optionally, the purge gas is introduced into the reaction cavity for purging, the flow rate is 500-1500 sccm, and the introduction time is 2-8 s.

[0161] S45, repeating steps S41-S44 for 1-500 times.

[0162] Steps S41-S45 are similar to the preparation steps of the inorganic oxide layer described above, and will not be repeated here. The main difference is that steps S41-S45 are used to prepare the first oxide layers, and the number of repeated steps can be adjusted according to factors such as the thickness difference between the inorganic oxide layer and the first oxide layer.

[0163] S46, introducing the fifth precursor into the reaction cavity.

[0164] Optionally, the fifth precursor is introduced into the reaction cavity in a pulse form by using the carrier gas, the flow rate is 500-1500 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., and the duration is 0.1-2 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.

[0165] S47, the purge gas is introduced into the reaction cavity for purging.

[0166] Optionally, the purge gas is introduced into the reaction cavity for purging, the flow rate is 500-1500 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., and the duration is 2-8 s, for example, 2 s, 2.5 s, 3 s, 3.5 s, 4 s, 4.5 s, 5 s, 5.5 s, 6 s, 6.5 s, 7 s, 7.5 s, etc.

[0167] S48, the sixth precursor is introduced into the reaction cavity.

[0168] Optionally, the fourth precursor is introduced into the reaction cavity in a pulse form by using the carrier gas, the flow rate is 500-1500 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., and the duration is 0.1-2 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.

[0169] S49, the purge gas is introduced into the reaction cavity for purging.

[0170] Optionally, the purge gas is introduced into the reaction cavity for purging, and the purging flow rate is 500-1500 seem, for example, 600 seem, 700 seem, 800 seem, 900 seem, 1000 seem, 1050 seem, 1100 seem, 1150 seem, 1200 seem, 1250 seem, 1300 seem, 1350 seem, 1400 seem, 1450 seem, 1500 seem, etc.; the introduction time is 2-8 s, for example, 2 s, 2.5 s, 3 s, 3.5 s, 4 s, 4.5 s, 5 s, 5.5 s, 6 s, 6.5 s, 7 s, 7.5 s, etc.

[0171] S410, repeating steps S46-S49 1-1000 times.

[0172] The first oxide layer gradually grows into the second oxide layer by repeatedly performing the step cycle of introducing the fifth precursor, purging, introducing the sixth precursor, and purging. The number of repeated steps can be 1-500, for example, 50, 100, 150, 200, 250, 300, 350, 400, 450, 500, 600, 700, 800, 900, etc.

[0173] S411, repeating steps S41-S410 1-1000 times.

[0174] The first oxide layer and the second oxide layer are alternately and repeatedly grown by repeatedly performing the above steps to obtain the inorganic oxide layer having the first oxide layer and the second oxide layer alternately and stacked. Optionally, the number of repetitions of the above steps is 1-500, for example, 50, 100, 150, 200, 250, 300, 350, 400, 450, 500, 600, 700, 800, 900, etc.

[0175] Optionally, the preparation conditions of the inorganic oxide layer having the first oxide layer and the second oxide layer alternately and stacked include:

[0176] The vacuum degree in the reaction cavity is 1-100 Pa, for example, 3 Pa, 5 Pa, 8 Pa, 10 Pa, 15.5 Pa, 20 Pa, 30 Pa, 40 Pa, 50 Pa, 55.5 Pa, 60 Pa, 65.5 Pa, 70 Pa, 75 Pa, 80 Pa, 85 Pa, 90 Pa, 95.5 Pa, 100 Pa, etc.

[0177] The reaction temperature is 100-200℃, for example, 100℃, 110℃, 112.5℃, 120℃, 130℃, 135.5℃, 140℃, 150℃, 155.3℃, 160℃, 170℃, 180℃, 190℃, 195.3℃, 200℃, etc.

[0178] The temperature of the third precursor, the fourth precursor, the fifth precursor and the sixth precursor is 20-40℃, for example, 20℃, 23℃, 25℃, 28℃, 30℃, 31.5℃, 33℃, 35℃, 37.5℃, 39℃, 40℃, etc.

[0179] It can be understood that the inorganic oxide layer provided by the embodiments of the present application can be a single oxide layer or a multi-oxide layer. The 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. The multi-oxide layer can be prepared by the above steps S41-S411, and the corresponding inorganic oxide layer is a multi-oxide film layer cross-linked and bonded with the organic layer. In other embodiments, the preparation of the multi-oxide layer can also be obtained by more precursor reactions, in other words, the multi-oxide layer can also have a third oxide layer alternately stacked with the first oxide layer and the second oxide layer, and even more oxide layers.

[0180] The present application can obtain the inorganic oxide layer formed by the multi-layer different oxide layers alternately stacked by 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.

[0181] Please refer to Figure 7 , Figure 7 is a schematic diagram of the relationship between the number of ALD reaction cycles and the thickness of the inorganic oxide layer provided by an embodiment of the present application.

[0182] In some embodiments, the thickness of each inorganic oxide layer film grown by the ALD method or the polyimide layer grown by the MLD method is taken as the ordinate, and the number of reaction cycles (repetition times) is taken as the abscissa to plot a graph, 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 per ALD or MLD reaction cycle.

[0183] In some embodiments, at 200℃ and a reaction cavity vacuum degree of 80Pa, the precursor of aluminum oxide and ozone are used as the precursors of the stacked aluminum oxide, and the linear relationship between the thickness of the aluminum oxide film prepared by different ALD cycles is obtained by experiments as shown in the figure, and the y-x equation is obtained by fitting the linear curve, y=0.0946x+0.7779, R 2= 0.9964, wherein y represents the thickness of the aluminum oxide film, x represents the number of ALD reaction cycles, and the slope represents the growth rate of the aluminum oxide film under the process conditions, so that ALD aluminum oxide thin film materials of different thicknesses can be prepared in the embodiments of the present application. Thus, in the embodiments of the present application, inorganic oxide layers of different thicknesses can be generated to meet the needs of different application scenarios, and reverse osmosis membranes of different thicknesses can be produced.

[0184] In the above embodiments, a reverse osmosis membrane is formed by sequentially stacking a flexible polymer substrate, an organic layer, and an inorganic oxide layer, which can improve the filtration effect of the reverse osmosis membrane, prolong the service life of the reverse osmosis membrane, simplify the preparation process of the reverse osmosis membrane, and also allow the preparation of corresponding reverse osmosis membranes according to the use requirements of various application scenarios, thereby expanding the application range thereof.

[0185] Reverse osmosis membrane corrosion resistance test:

[0186] In this test, the composite cross-linked reverse osmosis membrane prepared by the above method is soaked in Mocoledon artificial seawater with a pH value of 8-8.5 and a total salt content of 35,000 mg / L for 24-72 h under the conditions of a temperature of 25-30°C and a humidity of 50%±5%, and the water permeability of the composite cross-linked reverse osmosis membrane before and after soaking is tested to characterize the corrosion resistance of the membrane in the simulated seawater experiment. The test results are as follows:

[0187]

[0188] The sample used in this test is a reverse osmosis membrane prepared by the above method, the flexible polymer substrate of the reverse osmosis membrane is polyether sulfone, the organic layer is polyimide, and the inorganic oxide layer is an alternating stack film of silicon dioxide and titanium dioxide.

[0189] As can be seen from the water vapor permeability results of the reverse osmosis membrane before and after soaking, the microstructure of the reverse osmosis membrane of the present application does not collapse significantly during the soaking process in the simulated seawater experiment, and thus the water permeability remains substantially consistent at the order of magnitude of E-4. It can be seen that the reverse osmosis membrane prepared in the present application has good stability, corrosion resistance, and can effectively prolong the service life.

[0190] In the description of the present specification, the description of the terms "one embodiment", "another embodiment", and the like means that the specific features, structures, materials, or characteristics described in connection with the embodiment or example are included in at least one embodiment or example of the present application. In the present specification, the illustrative description of the above terms does not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials, or characteristics described can be combined in any one or more embodiments or examples in a suitable manner.

[0191] The above merely describes the embodiments of the present application, and does not limit the patent scope of the present application. Any equivalent structure or equivalent process transformation, or direct or indirect application in other related technical fields, which is made by using the content of the present application specification and drawings, is also included in the patent protection scope of the present application.

Claims

1. A method for producing a reverse osmosis membrane, characterized by, The method comprises the following steps: preparing an organic layer on a flexible polymer substrate, the organic layer being cross-linked to the flexible polymer substrate; preparing an inorganic oxide layer on the organic layer, the inorganic oxide layer being cross-linked to the organic layer; the organic layer is prepared by a molecular layer deposition process, and the inorganic oxide layer is prepared by an atomic layer deposition process.

2. The method for producing a reverse osmosis membrane according to claim 1, wherein The pore size of the flexible polymer substrate, the organic layer and the inorganic oxide layer decreases in turn.

3. The method for producing a reverse osmosis membrane according to claim 1, wherein After the inorganic oxide layer is prepared, the method further comprises the step of: performing a heat treatment on the reverse osmosis membrane.

4. The method for producing a reverse osmosis membrane according to claim 3, wherein The step of performing a heat treatment on the reverse osmosis membrane comprises the steps of: slowly heating the reverse osmosis membrane to 50-200℃, and cooling after a preset time.

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

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

7. The method for producing 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 comprises the step of: depositing the organic layer on the flexible polymer substrate by using a first precursor and a second precursor, the first precursor being a precursor containing an amino group, and the second precursor being a precursor containing an acyl group.

8. The method for producing a reverse osmosis membrane according to claim 7, wherein The step of depositing the organic layer on the flexible polymer substrate by using the first precursor and the second precursor comprises the steps of: introducing the first precursor into the reaction chamber in a pulse form by using a carrier gas, the flow rate being 500-1500sccm, and the time being 1-3s; purging the reaction chamber by introducing a purge gas, the flow rate being 1000-1500sccm, and the time being 5-10s; depositing the second precursor in the reaction chamber in a pulse form by using the carrier gas, the flow rate being 500-1500sccm, and the time being 1-3s; purging the reaction chamber by introducing a purge gas, the flow rate being 500-1500sccm, and the time being 5-10s; repeating the above steps 4000-10000 times to obtain the organic layer; wherein the vacuum degree in the reaction chamber is 1-100Pa, the reaction temperature is 100-200℃, and the temperature of the first precursor and the second precursor is 30-150℃.

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

10. The method for producing a reverse osmosis membrane according to claim 9, wherein The step of depositing the inorganic oxide layer on the organic layer comprises the step of: alternately introducing the third precursor and the fourth precursor into the reaction chamber by using a carrier gas. The third precursor and the fourth precursor are alternately introduced into the reaction cavity, and a purge gas is introduced into the reaction cavity for purging.

11. A reverse osmosis membrane, characterized by, The flexible polymer substrate, the organic layer and the inorganic oxide layer are sequentially stacked, the flexible polymer substrate is cross-linked with the organic layer, and the organic layer is cross-linked with the inorganic oxide layer; wherein the organic layer is made by a molecular layer deposition process, and the inorganic oxide layer is made by an atomic layer deposition process.

12. The reverse osmosis membrane of claim 11, wherein, The pore size of the flexible polymer substrate, the organic layer and the inorganic oxide layer is sequentially reduced.

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

14. The reverse osmosis membrane of claim 12, wherein, The pore size of the reverse osmosis membrane formed by the flexible polymer substrate, the organic layer and the inorganic oxide layer is 0.1-10 nanometers.

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

16. The reverse osmosis membrane of 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 of claim 11, wherein The inorganic oxide layer comprises one or more of aluminum oxide, silicon oxide, titanium oxide and zinc oxide.

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