Preparation method of ultra-low-pressure anti-oxidation reverse osmosis membrane

Abstract

The invention discloses a preparation method of an extremely-low-pressure anti-oxidation reverse osmosis membrane. Comprising the following steps: carrying out pre-wetting and cleaning treatment on a porous support membrane to fully wet pore channels and remove residual solvents and soluble impurities; preparing a water-phase solution containing aromatic polyamine and a water-soluble antioxidant aid A, and impregnating the pretreated support membrane to obtain a water-phase saturated support membrane; preparing an organic phase solution containing aromatic polyacyl chloride and an organic phase additive B, enabling the water-phase saturated support membrane to be in contact with an organic phase to generate interfacial polymerization, and forming a polyamide separation layer containing an antioxidant structural unit on the surface of the support membrane; and sequentially carrying out heat treatment, alkali treatment, antioxidant treatment containing an antioxidant additive C, glycerol dipping and drying shaping on the obtained initial composite membrane to obtain the post-treated composite reverse osmosis membrane. The prepared reverse osmosis membrane has relatively high water flux and desalination rate under the condition that the water inlet pressure is 0.30-0.35 MPa, keeps relatively low performance degradation in a water body containing free chlorine, and is suitable for an extremely low-pressure water treatment system.

Description

Technical Field

[0001] This invention relates to the field of membrane separation and water treatment technology, specifically to a method for preparing an ultra-low pressure antioxidant reverse osmosis membrane. Background Technology

[0002] Aromatic polyamide composite reverse osmosis membranes are widely used in seawater desalination, brackish water desalination, and pure water production. The separation layer is typically prepared by interfacial polymerization of the aqueous and organic phases on a porous support membrane surface. Existing commercial reverse osmosis membranes mostly operate at feed water pressures above 0.8 MPa to ensure sufficient transmembrane pressure differential and water flux. Under medium and low pressure conditions, a significant decrease in water flux is common, limiting the widespread application of energy-efficient low-pressure water treatment systems. Furthermore, conventional aromatic polyamide separation layers are sensitive to oxidizing components such as free chlorine. In chlorine-containing environments, the polyamide chain structure is prone to breakage and degradation, leading to decreased desalination rate and shortened membrane life. While existing technologies can improve membrane mechanical and separation performance to some extent by adjusting monomer ratios and post-treatment conditions, there is still a lack of preparation processes that simultaneously maintain high water flux, high desalination rate, and good oxidation resistance under extremely low pressure conditions below 0.5 MPa. A systematic preparation and evaluation method specifically for extremely low-pressure operation is also lacking. Summary of the Invention

[0003] The purpose of this invention is to provide a method for preparing an ultra-low pressure antioxidant reverse osmosis membrane, which has the advantages of maintaining high water flux and desalination rate under feed water pressure below 0.5 MPa and being resistant to free chlorine oxidation. This solves the problems of insufficient flux and easy performance degradation of existing reverse osmosis membranes when operating at low pressure.

[0004] To achieve the above objectives, the present invention provides the following technical solution: A method for preparing an ultra-low pressure antioxidant reverse osmosis membrane includes the following steps:

[0005] S1. Support layer preparation and pretreatment: Obtain a porous support membrane, perform wetting and cleaning operations on the porous support membrane to remove residual solvent and soluble impurities in the membrane, and adjust the porous support membrane to a pretreatment state in which the pores are wetted and there is no obvious free liquid film residue on the surface.

[0006] S2. Aqueous phase preparation and membrane impregnation: Prepare an aqueous solution containing aromatic polyamines and antioxidant functional components. Immerse the pretreated porous support membrane in the aqueous solution. By controlling the immersion time and removal method, the aqueous solution penetrates and fills the surface and pores of the porous support membrane to obtain an aqueous saturated support membrane.

[0007] S3. Organic phase configuration and interface contact: Prepare an organic phase solution containing aromatic polyacrylamide chloride and organic phase additives, expose the aqueous phase saturated support membrane in the organic phase solution, and form a stable interface reaction layer on the surface of the porous support membrane by controlling the contact time and ambient temperature.

[0008] S4. Interfacial polymerization and separation layer film formation: Under preset temperature and contact time conditions, the aqueous phase and organic phase are kept in contact on the surface of the porous support membrane, so that the aromatic polyamine and aromatic polyacrylamide chloride undergo interfacial polymerization reaction in the interfacial reaction layer, and a polyamide separation layer containing antioxidant structural units is generated on the surface of the porous support membrane to obtain the initial composite reverse osmosis membrane.

[0009] S5. Post-treatment and structural stabilization: The initial composite reverse osmosis membrane is subjected to heat treatment, alkali treatment, antioxidant treatment, glycerol impregnation and drying operations in sequence. The process parameters are controlled within a predetermined range to stabilize the cross-linking structure and pore structure of the polyamide separation layer, and the post-treated composite reverse osmosis membrane is obtained.

[0010] S6. Performance Testing and Extremely Low Pressure Operation Limitation: Under extremely low pressure operation conditions with an inlet water pressure below 0.5 MPa, the post-treated composite reverse osmosis membrane is subjected to water flux and desalination rate tests, and an oxidation resistance test is conducted under conditions containing oxidizing components. When the test results meet the preset water flux, desalination rate, and oxidation resistance parameters, the post-treated composite reverse osmosis membrane is determined to be an extremely low pressure oxidation-resistant reverse osmosis membrane. When the test results do not meet the parameters, at least one process parameter in steps S1 to S5 is adjusted according to the performance deviation, and steps S1 to S6 are repeated.

[0011] Preferably, step S1, support layer preparation and preprocessing, includes the following sub-steps:

[0012] S1.1 Selection of porous support membrane: Select one of polysulfone ultrafiltration membrane, polyethersulfone ultrafiltration membrane or polyacrylonitrile ultrafiltration membrane as the porous support membrane, control the thickness of the porous support membrane to 80-200 μm, and control the porosity of the porous support membrane to 50-80%.

[0013] S1.2 Pre-wetting and cleaning operation: Immerse the porous support membrane selected in step S1.1 in deionized water or an aqueous solution containing a preservative, and control the immersion time to 1-30 min. The immersion operation dissolves the residual solvent and soluble impurities in the porous support membrane and fills the pores of the porous support membrane with the pretreatment solution.

[0014] S1.3 Removal of excess pretreatment liquid and conditioning: Take out the porous support membrane that has been pre-wetted and cleaned in step S1.2 from the pretreatment liquid, and remove the pretreatment liquid from the surface of the porous support membrane by at least one of gravity draining, roller pressing and squeezing or air knife blowing. Control the thickness of the residual liquid layer on the surface of the porous support membrane to a level where the continuous liquid film is difficult to observe with the naked eye, while keeping the internal pores of the porous support membrane in a wetted state to obtain a porous support membrane in a pretreated state.

[0015] Preferably, step S2, aqueous phase preparation and impregnation of the film, includes the following sub-steps:

[0016] S2.1 Preparation of aqueous solution: Aromatic polyamine is added to deionized water according to the mass-volume ratio and dissolved under stirring. The mass-volume concentration of aromatic polyamine is controlled at 1.0-5.0% to obtain an aqueous solution. The aromatic polyamine is one or a combination of two or more of m-phenylenediamine, p-phenylenediamine, and pyromellitic triamine.

[0017] S2.2 Addition and mixing of antioxidant auxiliaries: Add antioxidant auxiliaries A to the aqueous solution prepared in step S2.1, controlling the mass-volume fraction of antioxidant auxiliaries A to be 0.01-2.0%, and continue mixing under stirring until antioxidant auxiliaries A are completely dissolved or uniformly dispersed in the aqueous solution; wherein antioxidant auxiliaries A are hydrophilic organic compounds containing aromatic hydroxyl structures or nitrogen-containing heterocyclic structures;

[0018] S2.3, Aqueous Phase Impregnation and Removal of Excess Aqueous Phase: The pretreated porous support membrane obtained in step S1.3 is completely immersed in the aqueous solution containing antioxidant A obtained in step S2.2. The impregnation time is controlled to be 1 to 10 minutes, so that the aqueous solution enters the surface layer and pores of the porous support membrane through diffusion and permeation. After the set impregnation time is reached, the porous support membrane is removed from the aqueous solution and moved along the surface of the support membrane by roller pressing or air knife blowing to continuously remove the excess aqueous solution on the surface of the support membrane, so as to obtain an aqueous saturated support membrane.

[0019] Preferably, step S3, organic phase configuration and interface contact, includes the following sub-steps:

[0020] S3.1 Preparation of organic phase solution: Add aromatic polyacryl chloride to n-hexane, n-heptane or isoalkane solvent, dissolve under stirring, and control the mass-volume concentration of aromatic polyacryl chloride to be 0.05-0.30% to obtain organic phase solution; wherein the aromatic polyacryl chloride is one or a combination of two or more of trimesoyl chloride, isophthaloyl chloride, and terephthaloyl chloride;

[0021] S3.2 Addition and mixing of organic phase additive: Add organic phase additive B to the organic phase solution prepared in step S3.1, controlling the mass-volume fraction of organic phase additive B to be 0.01-3.0%, and continue mixing under stirring until organic phase additive B is uniformly distributed in the organic phase solution; the organic phase additive B is a polar amide or phosphate ester organic solvent, including one or more of dimethylimidazolium ketone, 1,3-dimethyl-3,4,5,6-tetrahydro-2(1H)-pyrimidinone, tributyl phosphate, and triethyl phosphate;

[0022] S3.3 Organic Phase Contact and Interface Formation: The aqueous phase saturated support membrane obtained in step S2.3 is placed in an environment of 15-40°C with the support membrane surface facing upwards. The organic phase solution containing organic phase additive B obtained in step S3.2 is applied to the surface of the aqueous phase saturated support membrane by spreading, pouring or spraying. The time for the organic phase solution to cover the support membrane surface is controlled to be 5-120s. A continuous interfacial reaction layer is formed on the support membrane surface through the contact between the organic phase and the aqueous phase.

[0023] Preferably, step S4, interfacial polymerization and separation layer film formation, includes the following sub-steps:

[0024] S4.1 Control of interfacial polymerization conditions: During the period when the organic phase solution covers the surface of the aqueous phase saturated support film in step S3.3, the aqueous phase saturated support film is kept in an environment of 15 to 40°C, and the organic phase contact time is controlled between 5 and 120 seconds. The reaction rate and degree of the interfacial polymerization reaction are limited by controlling the ambient temperature and contact time.

[0025] S4.2, Introduction of Interfacial Reaction and Antioxidant Structure: Within the organic phase contact time defined in step S4.1, aromatic polyamine molecules in the aqueous phase saturated support membrane of step S2.3 migrate to the interfacial reaction layer formed in step S3.3 and undergo a polycondensation reaction with aromatic polyacrylamide molecules in the organic phase, generating a polyamide separation layer on the surface of the porous support membrane; during the interfacial polymerization process, through the synergistic effect of antioxidant A added in step S2.2 and organic phase additive B added in step S3.2, antioxidant-related structural units or antioxidant microenvironment are introduced into the polyamide separation layer to obtain the initial composite reverse osmosis membrane.

[0026] Preferably, step S5, post-processing, and structural stabilization includes the following sub-steps:

[0027] S5.1 Heat treatment operation: Place the initial composite reverse osmosis membrane obtained in step S4.2 in an environment of 50-90℃ and control the heat treatment time to 1-15min. The heating operation promotes further cross-linking inside the polyamide separation layer and reduces the free volume fraction.

[0028] S5.2 Alkali treatment operation: Immerse the heat-treated composite reverse osmosis membrane in step S5.1 into a sodium hydroxide solution or carbonate solution with a mass-volume concentration of 0.01-2.0% and control the immersion time to 1-30 min. Alkali treatment changes the ionization state of functional groups on the surface and near the surface of the polyamide separation layer.

[0029] S5.3 Antioxidant Treatment Operation: The composite reverse osmosis membrane, which has been treated with alkali and washed with water in step S5.2 until the conductivity of the effluent is close to that of the influent, is immersed in an aqueous solution containing antioxidant C. The mass-volume concentration of antioxidant C is controlled at 0.01-1.0%, and the immersion time is controlled at 1-60 min, so that antioxidant C can fully contact the surface of the polyamide separation layer and the pore inlet area. The antioxidant C is an inorganic or organic salt containing reducing groups, including bisulfite, sulfite, and their complexes with polyols.

[0030] S5.4 Glycerin Impregnation and Drying: The composite reverse osmosis membrane, after antioxidant treatment and water washing in step S5.3, is immersed in a glycerin solution for 1-30 minutes to allow the glycerin to enter the polyamide separation layer and support layer pores. Subsequently, the composite reverse osmosis membrane is dried under controlled temperature conditions to gradually evaporate the water inside the membrane while retaining the glycerin, thereby limiting the shrinkage of the pore structure during the drying process, resulting in a post-treated composite reverse osmosis membrane.

[0031] Preferably, step S6, performance testing and ultra-low voltage operation limitation, includes the following sub-steps:

[0032] S6.1, Ultra-low pressure desalination performance test: Under 25℃ conditions, use a NaCl aqueous solution with a mass concentration of 250-500 mg / L as feed water, adjust the feed water pH to 6.5-7.5, load the post-treated composite reverse osmosis membrane obtained in step S5.4 into a pressure vessel or test device, control the operating pressure to 0.30-0.35 MPa, continuously supply water until the membrane flux reaches a stable state, record the permeate volume per unit membrane area, and calculate the corresponding water flux and desalination rate;

[0033] S6.2 Oxidation stability test: The composite reverse osmosis membrane that underwent the ultra-low pressure desalination performance test in step S6.1 was continuously immersed or operated online for more than 100 hours in a chlorinated aqueous solution containing 0.5-1.0 mg / L of free chlorine. The water flux and desalination rate were measured before and after the test according to the test conditions in S6.1, and the change rate of water flux and the change value of desalination rate were calculated.

[0034] S6.3 Performance Judgment and Process Feedback: Based on the test results of steps S6.1 and S6.2, the water flux obtained under extremely low pressure test conditions is not less than 1.0 m³ / s. 3 / (m 2 ·d) When the desalination rate is not less than 98.0%, and the decrease in water flux after the oxidation stability test does not exceed 10.0% and the decrease in desalination rate does not exceed 1.0%, the post-treated composite reverse osmosis membrane obtained in step S5.4 is determined to be a reverse osmosis membrane that meets the requirements for ultra-low pressure oxidation resistance operation; when the test results do not meet any of the above determination conditions, at least one process parameter in steps S1 to S5 is adjusted according to the deviation of water flux and desalination rate, and steps S1 to S6 are re-executed accordingly.

[0035] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0036] 1. This invention introduces antioxidant A into the aqueous phase and adds organic phase additive B into the organic phase, thereby simultaneously constructing antioxidant-related structural units and an optimized micro-network structure in the polyamide separation layer during interfacial polymerization. This improves the chemical stability of the separation layer in the presence of free chlorine and reduces the decay rate of transmembrane water flux and desalination rate.

[0037] 2. This invention, by setting up a multi-stage post-treatment process including heat treatment, alkali treatment, and antioxidant treatment containing antioxidant agent C, can finely control the state of functional groups and the degree of crosslinking on the surface of the polyamide separation layer. This improves the desalination rate while suppressing performance drift during long-term continuous operation and enhancing the service life of the membrane element.

[0038] 3. This invention utilizes glycerol impregnation before drying to provide support for the membrane pore structure during the drying process, effectively inhibiting membrane pore shrinkage and structural collapse. This allows the resulting reverse osmosis membrane to achieve high water flux and stable operation even under extremely low pressure conditions of 0.30–0.35 MPa, thereby reducing the energy consumption of the water treatment system and the pressure rating requirements of supporting equipment.

[0039] 4. This invention establishes a combined evaluation method for water flux, desalination rate, and oxidation resistance stability under extremely low pressure conditions, and uses the evaluation results obtained in step S6 to adjust and optimize the preparation process parameters in steps S1 to S5. This enables the preparation method to have feedback-enabled process control capabilities, which facilitates the achievement of consistent and repeatable membrane performance in large-scale production and improves the engineering application value of the process. Attached Figure Description

[0040] Figure 1 This is a schematic diagram of the preparation process of the ultra-low pressure antioxidant reverse osmosis membrane of the present invention;

[0041] Figure 2 This is a schematic diagram of the composite reverse osmosis membrane structure of the present invention;

[0042] Figure 3 This is a schematic diagram of the post-processing and structural stabilization steps of the present invention;

[0043] Figure 4 This is a schematic diagram of the performance testing and ultra-low pressure operation limitation process of the present invention. Detailed Implementation

[0044] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of the present invention.

[0045] Please see Figures 1 to 4 This invention provides a technical solution: a method for preparing an ultra-low pressure antioxidant reverse osmosis membrane, which generally includes steps S1 to S6:

[0046] S1, Support layer preparation and pretreatment; S2, Aqueous phase preparation and impregnation film application; S3, Organic phase preparation and interfacial contact; S4, Interfacial polymerization and separation layer film formation; S5, Post-treatment and structural stabilization; S6, Performance testing and ultra-low pressure operation limits; Each main step S1 to S6 consists of several sub-steps, and sub-steps S1.1 to S6.3 correspond to specific operations in different process links, forming a complete technical closed loop from support layer preparation, separation layer film formation, post-treatment to performance evaluation and process feedback optimization under ultra-low pressure conditions.

[0047] (I) Step S1, preparation and pretreatment of the support layer. Step S1 consists of sub-steps S1.1 to S1.3. Its function is to obtain a porous support membrane with uniform wetting of pores and no obvious free liquid film on the surface, so as to provide a stable and repeatable substrate for subsequent interfacial polymerization.

[0048] In sub-step S1.1, a porous support membrane is selected from polysulfone ultrafiltration membranes, polyethersulfone ultrafiltration membranes, or polyacrylonitrile ultrafiltration membranes, and its thickness is controlled to be 80–200 μm, and its porosity is controlled to be 50–80%. When the thickness is less than 80 μm, the support layer is prone to deformation or damage under interfacial polymerization and operating pressure difference; when the thickness is greater than 200 μm, it will significantly increase the water flow resistance, which is not conducive to obtaining sufficient water flux under extremely low pressure conditions of 0.30–0.35 MPa. Controlling the porosity in the range of 50–80% can maintain sufficient skeleton strength while ensuring high permeability. In sub-step S1.2, the porous support membrane obtained in sub-step S1.1 is immersed in deionized water or an aqueous solution containing a protective agent, and the immersion time is controlled to be 1–30 min. When the soaking time is less than 1 minute, some pores inside the membrane may still be incompletely wetted, and residual solvent and soluble impurities may not dissolve sufficiently. When the soaking time is extended to 30 minutes, the pores can be basically wetted and impurities can be dissolved. Further extending the time has limited effect on improving the degree of wetting. In sub-step S1.3, the porous support membrane treated by soaking in sub-step S1.2 is taken out from the pretreatment solution. At least one of gravity draining, roller pressing, or air knife blowing is used to remove the pretreatment solution from the surface of the support membrane, reducing the surface residual liquid layer from a continuous liquid film visible to the naked eye to a continuous liquid film that is difficult to observe with the naked eye, while keeping the internal pores wetted. The "pretreated porous support membrane" obtained in this way ensures that during subsequent aqueous phase impregnation, the aqueous phase components mainly enter the pores and surface microstructure, and are not diluted by a large amount of surface free liquid, thereby improving the controllability and repeatability of interfacial polymerization.

[0049] (ii) Step S2, aqueous phase preparation and impregnation of the membrane. Step S2 consists of sub-steps S2.1 to S2.3. Its purpose is to prepare an aqueous solution containing aromatic polyamine and antioxidant A, and to make the aqueous phase uniformly distributed on the surface and pores of the pretreated support membrane to form an aqueous saturated support membrane.

[0050] In sub-step S2.1, aromatic polyamines are added to deionized water at a mass-to-volume ratio and dissolved under stirring. The mass-to-volume concentration of the aromatic polyamines is controlled at 1.0–5.0% to obtain an aqueous solution. When the concentration is below 1.0%, the number of amine groups available for reaction during interfacial polymerization is insufficient, easily leading to the formation of a polyamide separation layer that is too thin or has a low degree of crosslinking. When the concentration is above 5.0%, the interfacial polymerization rate is too fast, the separation layer is too thick, and the water flux is significantly reduced under extremely low pressure conditions. This invention maintains a reasonable balance between desalination performance and water flux by limiting the concentration to the range of 1.0–5.0%.

[0051] In sub-step S2.2, antioxidant A is added to the aqueous solution from sub-step S2.1, with the mass-volume fraction of antioxidant A controlled at 0.01–2.0%. When the mass-volume fraction is close to 0.01%, it can provide basic antioxidant components for the interfacial region without significantly altering the viscosity and diffusion characteristics of the aqueous phase. When the mass-volume fraction is close to 2.0%, it can significantly enhance the antioxidant environment inside the separation layer, but further increasing the concentration can easily lead to decreased solution stability or precipitation risk; therefore, it is limited to the range of 0.01–2.0%. Through this control, antioxidant A can enter the interfacial region along with aromatic polyamines during subsequent interfacial polymerization.

[0052] In sub-step S2.3, the pretreated porous support membrane obtained in sub-step S1.3 is completely immersed in an aqueous solution containing 1.0–5.0% aromatic polyamine and 0.01–2.0% antioxidant A in sub-step S2.2, with the immersion time controlled to be 1–10 min. When the immersion time is less than 1 min, the aqueous phase and antioxidant A are difficult to diffuse sufficiently into the pores of the support membrane; when the immersion time exceeds 10 min, the diffusion depth is not significantly improved. After immersion, excess aqueous solution on the surface is removed by rolling or air-knife blowing along the support membrane surface, while keeping the pores filled with aqueous phase containing the above-mentioned concentration range, resulting in an aqueous-saturated support membrane, providing a stable aqueous substrate for subsequent organic phase contact and interfacial polymerization.

[0053] (III) Step S3, Organic Phase Configuration and Interface Contact: Step S3 consists of sub-steps S3.1 to S3.3. Its purpose is to prepare an organic phase solution containing aromatic polyacrylamide chloride and organic phase additive B, and to contact it with an aqueous saturated support film to form a stable interface reaction layer.

[0054] In sub-step S3.1, aromatic polyacrylamide chlorides are added to hexane, heptane, or isoalkanes and dissolved under stirring conditions, with the mass-volume concentration of the aromatic polyacrylamide chlorides controlled at 0.05–0.30%. When the concentration is below 0.05%, the supply of acrylamide monomers at the interface is insufficient, which can easily lead to insufficient crosslinking of the separation layer and a decrease in pressure resistance and oxidation resistance. When the concentration is above 0.30%, the interfacial polymerization reaction is too fast, the internal stress of the separation layer is large, and microcracks or local defects are easily formed, thus affecting long-term operational stability.

[0055] In sub-step S3.2, organic phase additive B is added to the organic phase solution from sub-step S3.1, and the mass-volume fraction of organic phase additive B is controlled between 0.01% and 3.0%. When the mass-volume fraction is below 0.01%, its effect on regulating the polarity, viscosity, and interfacial polymerization behavior of the organic phase is limited; when the mass-volume fraction is above 3.0%, it may lead to increased miscibility between the organic phase and the aqueous phase and interfacial instability. This invention limits the organic phase additive B to the range of 0.01% to 3.0%, allowing it to exert an effective but not excessive influence in regulating the density and pore structure of the polyamide layer and its synergistic effect with antioxidant A.

[0056] In sub-step S3.3, the aqueous-saturated support membrane obtained in sub-step S2.3 is placed in an environment of 15–40°C with the aqueous side of the support membrane facing upwards. The organic phase solution obtained in sub-step S3.2 is uniformly applied to the surface of the support membrane by spreading, pouring, or spraying, ensuring that the organic phase completely covers the surface of the aqueous-saturated support membrane. The covering time is controlled to be 5–120 s. Below 15°C, the interfacial polycondensation reaction rate is too low, and the polyamide layer may be too thin or insufficiently cross-linked. Above 40°C, the organic phase evaporates too quickly and reacts violently, easily leading to interfacial instability. When the contact time is less than 5 s, the polyamide layer has not yet formed a continuous structure; when the contact time is longer than 120 s, the increase in the separation layer thickness is limited and may exacerbate stress accumulation. Through the above temperature and time control, a uniform, continuous aqueous / organic phase interfacial reaction layer with a suitable reaction time window can be formed on the surface of the support membrane.

[0057] (iv) Step S4, Interfacial Polymerization and Separation Layer Formation: Step S4 consists of sub-steps S4.1 to S4.2. Its function is to generate a dense polyamide separation layer containing antioxidant structural units at the aqueous / organic phase interface formed in step S3. In sub-step S4.1, the state of the organic phase covering the surface of the aqueous phase saturated support membrane as in sub-step S3.3 is maintained, and the contact time of the organic phase is controlled within 5–120 s, while the ambient temperature is maintained within 15–40 °C. By controlling the contact time and temperature, the aromatic polyamine and aromatic polyacrylamide chloride undergo condensation polymerization at the interface at an appropriate rate, forming a polyamide layer of moderate thickness and suitable crosslinking degree. If the contact time is near the lower limit of the range, a relatively thin separation layer with high flux can be obtained; when the contact time is close to the upper limit of the range, the separation layer is thicker, the desalination rate is higher, and the flux is relatively lower. In sub-step S4.2, aromatic polyamine molecules with a mass-volume concentration of 1.0–5.0% and antioxidant A with a mass-volume concentration of 0.01–2.0% in the aqueous saturated supported membrane obtained in sub-step S2.3 diffuse from the aqueous phase side to the interface. These molecules, along with aromatic polyacrylamide chloride molecules with a mass-volume concentration of 0.05–0.30% and organic phase additive B with a mass-volume concentration of 0.01–3.0% in the organic phase solution of sub-step S3.2, contact and undergo a condensation reaction within the interfacial reaction layer, generating a polyamide separation layer with an amide bond backbone in situ on the supported membrane surface. The presence of antioxidant A in the interfacial region and the regulation of the reaction environment by organic phase additive B cause the formation of antioxidant-related structural units or microenvironments within the polyamide separation layer, thereby obtaining an initial composite reverse osmosis membrane with antioxidant potential.

[0058] (V) Step S5, post-treatment and structural stabilization. Step S5 consists of sub-steps S5.1 to S5.4, which are used to further adjust the cross-linking structure, surface functional group state and pore structure stability of the polyamide separation layer based on the initial composite reverse osmosis membrane, so as to obtain the post-treated composite reverse osmosis membrane.

[0059] In sub-step S5.1, the initial composite reverse osmosis membrane obtained in sub-step S4.2 is placed in an environment of 50–90°C, and the heat treatment time is controlled to be 1–15 min. Temperatures below 50°C have limited promoting effect on residual reactions and are unlikely to significantly improve the degree of crosslinking; temperatures above 90°C may cause local thermal degradation or stress concentration of polyamide segments. A treatment time shorter than 1 min results in insufficient heat treatment, while a time exceeding 15 min provides limited performance improvement and increases energy consumption. This invention controls this range to ensure sufficient but not excessive crosslinking reaction within the separation layer. In sub-step S5.2, the heat-treated composite reverse osmosis membrane is immersed in a sodium hydroxide solution or carbonate solution with a mass-volume concentration of 0.01–2.0%, and the immersion time is controlled to be 1–30 min. When the alkali concentration is below 0.01%, the regulatory effect on the ionization state of functional groups on the surface and near-surface of the separation layer is weak; when the concentration is above 2.0%, there is a risk of excessive hydrolysis of amide bonds. Soaking time shorter than 1 minute is insufficient for adjustment, while soaking time exceeding 30 minutes may adversely corrode the surface structure. This step adjusts the surface charge and hydrophilicity of the separation layer, helping to improve water flux and antifouling ability under extremely low pressure conditions. In sub-step S5.3, the composite reverse osmosis membrane, after alkali treatment and thorough water washing, is immersed in an aqueous solution containing antioxidant C. The mass-volume concentration of antioxidant C is controlled at 0.01–1.0%, and the soaking time is controlled at 1–60 minutes. An antioxidant protective layer formed at a concentration below 0.01% is weak; at a concentration above 1.0%, solubility deteriorates or precipitation occurs easily. Soaking time shorter than 1 minute makes it difficult for antioxidant C to be fully adsorbed onto the separation layer surface and pore inlet area, while soaking time exceeding 60 minutes has limited effect on increasing adsorption capacity. This step forms a protective layer with reducing or active chlorine-capturing capabilities on the surface of the separation layer and in the pore inlet area. This, combined with the aforementioned internal antioxidant structure formed by antioxidant A and organic phase additive B, improves the membrane's oxidation resistance in environments containing free chlorine. In sub-step S5.4, the antioxidant-treated and water-washed composite reverse osmosis membrane is immersed in a glycerol solution for 1–30 minutes, allowing glycerol to enter the pores of the polyamide separation layer and support layer. Subsequently, drying is performed under controlled temperature conditions, gradually evaporating the water within the membrane while partially retaining the glycerol. This inhibits pore structure shrinkage and membrane warping during drying, maintaining the stability of the pore structure and geometry of the separation layer and support layer, ultimately yielding a post-treated composite reverse osmosis membrane.

[0060] (VI) Step S6, Performance Testing and Extremely Low Pressure Operation Limitations: Step S6 consists of sub-steps S6.1 to S6.3, used to evaluate the separation performance and oxidation resistance of the post-treated composite reverse osmosis membrane under extremely low pressure and free chlorine-containing conditions. The evaluation results are fed back to the process parameter adjustments in steps S1 to S5, achieving closed-loop optimization of the preparation method. In sub-step S6.1, at 25°C, using a NaCl aqueous solution with a mass concentration of 250–500 mg / L as feed water, the post-treated composite reverse osmosis membrane obtained in sub-step S5.4 is loaded into the test device. The feed water pH is adjusted to 6.5–7.5, and the operating pressure is controlled at 0.30–0.35 MPa. This pressure range is below 0.5 MPa, which falls under the extremely low pressure operating conditions as defined in this invention. After stable operation for a period of time, the permeate volume per unit membrane area is recorded, the water flux is calculated, and the desalination rate is calculated by measuring the conductivity of the feed water and permeate. The results are used to characterize the initial separation performance of the membrane under extremely low pressure conditions.

[0061] In sub-step S6.2, the same membrane is placed in an aqueous chlorination solution containing 0.5–1.0 mg / L of free chlorine and continuously operated or immersed at 25°C and an operating pressure of 0.30–0.35 MPa for at least 100 hours. Before and after the test, the test conditions of sub-step S6.1 are repeated to measure the water flux and desalination rate, and the flux change rate and desalination rate change value are calculated to evaluate the membrane's oxidation resistance stability in an environment containing free chlorine.

[0062] In sub-step S6.3, based on the test results of sub-steps S6.1 and S6.2, the water flux obtained under extremely low pressure conditions of 0.30–0.35 MPa is not less than 1.0 m³ / s. 3 / (m 2 •d) If the desalination rate is not less than 98.0%, and after continuous operation for more than 100 hours under conditions containing 0.5–1.0 mg / L of free chlorine, the decrease in water flux does not exceed 10.0%, and the decrease in desalination rate does not exceed 1.0%, then the composite reverse osmosis membrane obtained in sub-step S5.4 is determined to meet the requirements for ultra-low pressure anti-oxidation operation. If any indicator fails to meet the above limits, then according to the direction and magnitude of the deviation in water flux and desalination rate, at least one process parameter in steps S1–S5 is adjusted. For example, the concentration of aromatic polyamine is finely adjusted in the range of 1.0–5.0%, the concentration of aromatic polyacrylamide chloride is finely adjusted in the range of 0.05–0.30%, the heat treatment temperature is adjusted in the range of 50–90℃, or the alkali treatment concentration is adjusted in the range of 0.01–2.0%. Steps S1–S6 are then re-executed accordingly to achieve iterative optimization of membrane structure and performance and consistency control in batch production.

[0063] (VII) Principles for Selecting and Optimizing Process Parameters: In practical implementation, the concentration, temperature, time, and pressure ranges defined in this invention constitute an adjustable process window. Parameter combinations near the midpoint of the range typically balance separation layer density, water flux, and oxidation resistance. For example, the concentration of aromatic polyamines can preferably be selected within the range of 2.0–3.5%; the concentration of aromatic polyacrylamide chlorides can preferably be selected within the range of 0.10–0.20%; and the heat treatment temperature can preferably be selected within the range of 60–80℃. Specifically, within the above ranges, a set of initial parameter combinations that balance water flux and desalination rate can be determined through small-scale testing. Then, based on the results of the ultra-low pressure operation and oxidation resistance test in step S6, single or a few process parameters can be fine-tuned, thereby achieving process optimization for different water qualities or application scenarios within the established range.

[0064] (VIII) Explanation of the Relationship between Membrane Structure and Performance: The composite reverse osmosis membrane formed through steps S1 to S5 above exhibits a "three-layer structure": a porous support layer, a transition layer, and a dense polyamide separation layer. The combination of parameters—80–200 μm thickness and 50–80% porosity—ensures that the support layer provides mechanical support while controlling its contribution to overall hydraulic resistance at a reasonable level. The polyamide separation layer, formed by interfacial polymerization, is generated under contact times of 5–120 s and temperatures of 15–40 °C. With moderate thickness and cross-linking degree, it can achieve a thickness of not less than 1.0 m under extremely low pressure conditions of 0.30–0.35 MPa. 3 A water flux of / (m2·d) and a desalination rate of not less than 98.0%.

[0065] Furthermore, the synergistic effect of antioxidants A and C, along with organic phase additive B, within and on the surface of the separation layer reduces the amide bond breaking rate and inhibits the formation of microscopic defects during long-term operation at a free chlorine concentration of 0.5–1.0 mg / L. Consequently, even after more than 100 hours of continuous operation, the changes in water flux and desalination rate remain within a relatively small range, demonstrating good oxidation resistance and stability. This structure-performance relationship can be further verified through specific test data in the examples section.

[0066] To facilitate understanding and implementation of the present invention by those skilled in the art, the preparation method and performance of the ultra-low pressure antioxidant reverse osmosis membrane of the present invention are described below with reference to specific embodiments. Those skilled in the art should understand that, without departing from the aforementioned process flow and working principle, adjustments, substitutions, and equivalent modifications to the parameters in steps S1 to S6 can all form other embodiments of the present invention.

[0067] The following embodiments are all based on the process flow described in steps S1 to S6. Unless otherwise specified, all embodiments are performed according to the conditions described in the "I. Process Flow and Working Principle" section above. Except for specifically indicated variables, the reagents, equipment, and operating conditions are the same or similar between the embodiments, and are used only to illustrate the present invention and do not constitute a limitation on the scope of protection.

[0068] I. General Experimental Conditions and Performance Evaluation Methods

[0069] 1. Porous Support Membrane and Storage Conditions: The porous support membranes used in the following examples were all commercial polysulfone ultrafiltration membranes with a molecular weight cutoff of approximately 50,000 Da. The interval between the production date and the experimental date of the polysulfone membrane did not exceed 30 days, and it was stored in a 1.5% (w / v) sodium bisulfite aqueous solution during this period. Before preparing the composite membrane, the porous support membrane was pretreated according to step S1, with a pre-wetting time of no less than 60 minutes.

[0070] Table 1. Basic parameters and storage conditions of porous support membranes

[0071]

[0072]

[0073] Note: Unless otherwise specified, the support layer parameters in the embodiments are selected from the ranges shown in Table 1 above and the parameter ranges given in "I. Process Flow and Working Principle".

[0074] 2. Performance testing conditions and evaluation indicators: The performance evaluation of the obtained polyamide reverse osmosis composite membrane mainly includes the desalination rate of sodium chloride solution and the permeate flow rate. When examining oxidation resistance, free chlorine was further added to the feed water, and a long-term operating test was conducted. Table 2: Reverse osmosis performance testing conditions:

[0075] project Parameters / conditions Test device Flat sheet membrane high voltage testing device Influent solute NaCl aqueous solution NaCl concentration 250~500mg / L Inlet water pressure 0.30~0.35MPa Concentrate flow rate Approximately 1.0 L / min Ambient temperature 25℃ Inlet water pH 6.5～7.5 Operating mode Constant pressure continuous operation Free chlorine concentration (if used) 0.5~1.0mg / L Oxidation resistance test duration ≥100h

[0076] The definitions of desalination rate and water production are as follows: Table 3 Definition of performance evaluation indicators

[0077]

[0078] Each data point can be obtained by averaging the test results of multiple parallel membrane samples.

[0079] II. Comparative Example 1: Reverse osmosis composite membrane without the introduction of organic phase additive B and without antioxidant treatment. This comparative example is used as a reference sample to illustrate the performance level of the traditional reverse osmosis composite membrane under the condition of no introduction of organic phase additive B and no antioxidant treatment.

[0080] 1. Preparation conditions: In this comparative example, the aqueous phase contains only aromatic polyamine monomers and does not contain antioxidant A; the organic phase contains only aromatic polyacrylamide monomers and does not contain organic phase additive B; the post-treatment does not include antioxidant C treatment, and other steps are performed in accordance with the aforementioned process flow.

[0081] Table 4 Comparative Preparation Conditions of Example 1

[0082]

[0083] A traditional polyamide reverse osmosis composite membrane was prepared under the above conditions.

[0084] 2. Performance test results: Under the test conditions described in Table 2, the water flux and desalination rate of this comparative example were measured, and the results are as follows: Table 5 Performance results of Comparative Example 1

[0085]

[0086] This comparative example shows that, under the conventional process without the addition of organic phase additive B and antioxidant auxiliaries, although the desalination rate is high, the water production is relatively low, and the oxidation resistance is not optimized.

[0087] III. Example 1: Typical preparation method and performance of ultra-low pressure antioxidant reverse osmosis composite membrane

[0088] This embodiment provides a typical combination of process parameters that meets the requirements of ultra-low pressure and oxidation resistance of the present invention, and fully involves steps S1 to S6.

[0089] 1. Preparation conditions: Based on general conditions, the specific components and parameters are selected as follows:

[0090] Table 6. Preparation conditions for Example 1 (corresponding to steps S1-S5)

[0091]

[0092] The post-treated composite reverse osmosis membrane was prepared under the above conditions, which is the ultra-low pressure antioxidant reverse osmosis membrane described in this embodiment.

[0093] 2. Separation performance under extremely low pressure conditions: The membrane of this embodiment was tested under the test conditions listed in Table 2 (25℃, NaCl 250~500mg / L, pH 6.5~7.5, 0.30~0.35MPa), and the water flux and desalination rate were obtained as follows: Table 7 Separation performance of Example 1 under extremely low pressure conditions

[0094]

[0095] It can be seen that under extremely low pressure conditions of 0.30 to 0.35 MPa, which is far lower than the operating pressure of conventional spiral wound reverse osmosis systems, the membrane in this embodiment still maintains a high desalination rate and a water flux that is significantly higher than that of Comparative Example 1.

[0096] 3. Oxidation resistance under free chlorine conditions: Based on the above-mentioned extremely low pressure conditions, the free chlorine concentration in the influent was adjusted to 0.8 mg / L, and the system was continuously operated for 120 h at 25℃ and 0.30 MPa. The water flux and desalination rate before and after the test were measured respectively. The results are as follows: Table 8 Comparison of oxidation resistance performance before and after Example 1.

[0097]

[0098] This embodiment shows that after long-term operation in water containing free chlorine, the water flux of the membrane of the present invention decreases by less than 10%, and the desalination rate decreases by less than 1%, thus meeting the aforementioned requirements for ultra-low pressure antioxidant performance.

[0099] IV. Examples 2-9: Effects of the type and concentration of organic phase additive B on membrane performance

[0100] This set of examples mainly investigates the effects of different types and mass / volume fractions of organic phase additive B on the water flux and desalination rate of the reverse osmosis membrane. The preparation steps are generally the same as those in Comparative Example 1, except that different types and concentrations of additive B are added to the organic phase, while the other conditions remain the same. The setting of antioxidants and the oxidation resistance test can be carried out in accordance with Example 1. This set of examples focuses on demonstrating the changes in water flux and desalination rate under the conditions of 0.30 MPa and 25°C.

[0101] 1. Overview of Preparation Conditions: Based on Comparative Example 1, the aqueous phase used was a 2.0% m-phenylenediamine aqueous solution, and the organic phase used was 0.1% trimesoyl chloride dissolved in n-hexane. The interfacial contact time was 10–30 s, and the post-treatment conditions were the same as in Table 4. Based on this, different types and concentrations of organic phase additive B were replaced or added, while the remaining operating steps remained unchanged. 2. Effects of Different Additives B on Performance: According to the disclosed experimental data, the types and concentrations of different organic phase additives B had the following effects on the water flux and desalination rate of the membrane (test conditions: 25℃, 0.30 MPa, NaCl 250 mg / L, pH 6.5–7.5): Table 9: Effects of Different Additives B in the Organic Phase on Membrane Performance

[0102]

[0103] Note: DMI is 1,3-dimethylimidazolium ketone, DMPU is N,N'-dimethylacrylamide urea, TBP is tributyl phosphate, and TEP is triethyl phosphate, all of which are specific examples of the organic phase additive B described in this invention.

[0104] As shown in Table 9, compared to the comparative example without organic phase additive B, the water flux of the membrane generally increased after adding appropriate amounts of polar amide or phosphate ester additives, with significant increases under certain concentration conditions, while the desalination rate only slightly decreased or remained at a high level. By combining this with the antioxidant data from Example 1, we can further optimize the types and concentration combinations of organic phase additive B that can both improve ultra-low pressure flux and maintain antioxidant stability.

[0105] Although embodiments of the invention have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of the invention, the scope of which is defined by the appended claims and their equivalents.

Claims

1. A method for preparing an ultra-low pressure antioxidant reverse osmosis membrane, characterized in that, Includes the following steps: S1. Support layer preparation and pretreatment: Obtain a porous support membrane, perform wetting and cleaning operations on the porous support membrane to remove residual solvent and soluble impurities in the membrane, and adjust the porous support membrane to a pretreatment state where the pores are wetted and there is no obvious free liquid film residue on the surface. S2. Aqueous phase preparation and membrane impregnation: Prepare an aqueous solution containing aromatic polyamines and antioxidant functional components. Immerse the pretreated porous support membrane in the aqueous solution. By controlling the immersion time and removal method, the aqueous solution penetrates and fills the surface and pores of the porous support membrane to obtain an aqueous saturated support membrane. S3. Organic phase configuration and interface contact: Prepare an organic phase solution containing aromatic polyacrylamide chloride and organic phase additives, expose the aqueous phase saturated support membrane in the organic phase solution, and form a stable interface reaction layer on the surface of the porous support membrane by controlling the contact time and ambient temperature. S4. Interfacial polymerization and separation layer film formation: Under preset temperature and contact time conditions, the aqueous phase and organic phase are kept in contact on the surface of the porous support membrane, so that the aromatic polyamine and aromatic polyacrylamide chloride undergo interfacial polymerization reaction in the interfacial reaction layer, and a polyamide separation layer containing antioxidant structural units is generated on the surface of the porous support membrane to obtain the initial composite reverse osmosis membrane. S5. Post-treatment and structural stabilization: The initial composite reverse osmosis membrane is subjected to heat treatment, alkali treatment, antioxidant treatment, glycerol impregnation and drying operations in sequence. The process parameters are controlled within a predetermined range to stabilize the cross-linking structure and pore structure of the polyamide separation layer, and the post-treated composite reverse osmosis membrane is obtained. S6. Performance Testing and Extremely Low Pressure Operation Limitation: Under extremely low pressure operation conditions with an inlet water pressure below 0.5 MPa, the post-treated composite reverse osmosis membrane is subjected to water flux and desalination rate tests, and an oxidation resistance test is conducted under conditions containing oxidizing components. When the test results meet the preset water flux, desalination rate, and oxidation resistance parameters, the post-treated composite reverse osmosis membrane is determined to be an extremely low pressure oxidation-resistant reverse osmosis membrane. When the test results do not meet the parameters, at least one process parameter in steps S1 to S5 is adjusted according to the performance deviation, and steps S1 to S6 are repeated.

2. The method for preparing an ultra-low pressure antioxidant reverse osmosis membrane according to claim 1, characterized in that, Step S1, Support Layer Preparation and Preprocessing, includes the following sub-steps: S1.1 Selection of porous support membrane: Select one of polysulfone ultrafiltration membrane, polyethersulfone ultrafiltration membrane or polyacrylonitrile ultrafiltration membrane as the porous support membrane, control the thickness of the porous support membrane to 80-200 μm, and control the porosity of the porous support membrane to 50-80%. S1.2 Pre-wetting and cleaning operation: Immerse the porous support membrane selected in step S1.1 in deionized water or an aqueous solution containing a preservative, and control the immersion time to 1-30 min. The immersion operation dissolves the residual solvent and soluble impurities in the porous support membrane and fills the pores of the porous support membrane with the pretreatment solution. S1.3 Removal of excess pretreatment liquid and conditioning: Take out the porous support membrane that has been pre-wetted and cleaned in step S1.2 from the pretreatment liquid, and remove the pretreatment liquid from the surface of the porous support membrane by at least one of gravity draining, roller pressing and squeezing or air knife blowing. Control the thickness of the residual liquid layer on the surface of the porous support membrane to a level where the continuous liquid film is difficult to observe with the naked eye, while keeping the internal pores of the porous support membrane in a wetted state to obtain a porous support membrane in a pretreated state.

3. The method for preparing an ultra-low pressure antioxidant reverse osmosis membrane according to claim 2, characterized in that, Step S2, aqueous phase preparation and impregnation of the membrane, includes the following sub-steps: S2.1 Preparation of aqueous solution: Aromatic polyamine is added to deionized water according to the mass-volume ratio and dissolved under stirring. The mass-volume concentration of aromatic polyamine is controlled at 1.0-5.0% to obtain an aqueous solution. The aromatic polyamine is one or a combination of two or more of m-phenylenediamine, p-phenylenediamine, and pyromellitic triamine. S2.2 Addition and mixing of antioxidant auxiliaries: Add antioxidant auxiliaries A to the aqueous solution prepared in step S2.1, controlling the mass-volume fraction of antioxidant auxiliaries A to be 0.01-2.0%, and continue mixing under stirring until antioxidant auxiliaries A are completely dissolved or uniformly dispersed in the aqueous solution; wherein antioxidant auxiliaries A are hydrophilic organic compounds containing aromatic hydroxyl structures or nitrogen-containing heterocyclic structures; S2.3, Aqueous Phase Impregnation and Removal of Excess Aqueous Phase: The pretreated porous support membrane obtained in step S1.3 is completely immersed in the aqueous solution containing antioxidant A obtained in step S2.

2. The impregnation time is controlled to be 1 to 10 minutes, so that the aqueous solution enters the surface layer and pores of the porous support membrane through diffusion and permeation. After the set impregnation time is reached, the porous support membrane is removed from the aqueous solution and moved along the surface of the support membrane by roller pressing or air knife blowing to continuously remove the excess aqueous solution on the surface of the support membrane, so as to obtain an aqueous saturated support membrane.

4. The method for preparing an ultra-low pressure antioxidant reverse osmosis membrane according to claim 3, characterized in that, Step S3, Organic Phase Configuration and Interface Contact, includes the following sub-steps: S3.1 Preparation of organic phase solution: Add aromatic polyacryl chloride to n-hexane, n-heptane or isoalkane solvent, dissolve under stirring, and control the mass-volume concentration of aromatic polyacryl chloride to be 0.05-0.30% to obtain organic phase solution; wherein the aromatic polyacryl chloride is one or a combination of two or more of trimesoyl chloride, isophthaloyl chloride, and terephthaloyl chloride; S3.2 Addition and mixing of organic phase additive: Add organic phase additive B to the organic phase solution prepared in step S3.1, controlling the mass-volume fraction of organic phase additive B to be 0.01-3.0%, and continue mixing under stirring until organic phase additive B is uniformly distributed in the organic phase solution; the organic phase additive B is a polar amide or phosphate ester organic solvent, including one or more of dimethylimidazolium ketone, 1,3-dimethyl-3,4,5,6-tetrahydro-2(1H)-pyrimidinone, tributyl phosphate, and triethyl phosphate; S3.3 Organic Phase Contact and Interface Formation: The aqueous phase saturated support membrane obtained in step S2.3 is placed in an environment of 15-40°C with the support membrane surface facing upwards. The organic phase solution containing organic phase additive B obtained in step S3.2 is applied to the surface of the aqueous phase saturated support membrane by spreading, pouring or spraying. The time for the organic phase solution to cover the support membrane surface is controlled to be 5-120s. A continuous interfacial reaction layer is formed on the support membrane surface through the contact between the organic phase and the aqueous phase.

5. The method for preparing an ultra-low pressure antioxidant reverse osmosis membrane according to claim 4, characterized in that, Step S4, interfacial polymerization and separation layer film formation, includes the following sub-steps: S4.1 Control of interfacial polymerization conditions: During the period when the organic phase solution covers the surface of the aqueous phase saturated support film in step S3.3, the aqueous phase saturated support film is kept in an environment of 15 to 40°C, and the organic phase contact time is controlled between 5 and 120 seconds. The reaction rate and degree of the interfacial polymerization reaction are limited by controlling the ambient temperature and contact time. S4.2 Introduction of interfacial reaction and antioxidant structure: During the organic phase contact time defined in step S4.1, the aromatic polyamine molecules in the aqueous phase saturated support membrane in step S2.3 migrate to the interfacial reaction layer formed in step S3.3 and undergo a polycondensation reaction with the aromatic polyacrylamide molecules in the organic phase, thereby generating a polyamide separation layer on the surface of the porous support membrane. During the interfacial polymerization process, the antioxidant A added in step S2.2 and the organic phase additive B added in step S3.2 work synergistically to introduce antioxidant-related structural units or antioxidant microenvironments into the polyamide separation layer, thereby obtaining the initial composite reverse osmosis membrane.

6. The method for preparing an ultra-low pressure antioxidant reverse osmosis membrane according to claim 5, characterized in that, Step S5, post-processing and structural stabilization, includes the following sub-steps: S5.1 Heat treatment operation: Place the initial composite reverse osmosis membrane obtained in step S4.2 in an environment of 50-90℃ and control the heat treatment time to 1-15min. The heating operation promotes further cross-linking inside the polyamide separation layer and reduces the free volume fraction. S5.2 Alkali treatment operation: Immerse the heat-treated composite reverse osmosis membrane in step S5.1 into a sodium hydroxide solution or carbonate solution with a mass-volume concentration of 0.01-2.0% and control the immersion time to 1-30 min. Alkali treatment changes the ionization state of functional groups on the surface and near the surface of the polyamide separation layer. S5.3 Antioxidant Treatment Operation: The composite reverse osmosis membrane, which has been treated with alkali and washed with water in step S5.2 until the conductivity of the effluent is close to that of the influent, is immersed in an aqueous solution containing antioxidant C. The mass-volume concentration of antioxidant C is controlled at 0.01-1.0%, and the immersion time is controlled at 1-60 min, so that antioxidant C can fully contact the surface of the polyamide separation layer and the pore inlet area. The antioxidant C is an inorganic or organic salt containing reducing groups, including bisulfite, sulfite, and their complexes with polyols. S5.4 Glycerin Impregnation and Drying: The composite reverse osmosis membrane, after antioxidant treatment and water washing in step S5.3, is immersed in a glycerin solution for 1-30 minutes to allow the glycerin to enter the polyamide separation layer and support layer pores. Subsequently, the composite reverse osmosis membrane is dried under controlled temperature conditions to gradually evaporate the water inside the membrane while retaining the glycerin, thereby limiting the shrinkage of the pore structure during the drying process, resulting in a post-treated composite reverse osmosis membrane.

7. The method for preparing an ultra-low pressure antioxidant reverse osmosis membrane according to claim 6, characterized in that, Step S6, Performance Testing and Extremely Low Voltage Operation Limitations, includes the following sub-steps: S6.1, Ultra-low pressure desalination performance test: Under 25℃ conditions, use a NaCl aqueous solution with a mass concentration of 250-500 mg / L as feed water, adjust the feed water pH to 6.5-7.5, load the post-treated composite reverse osmosis membrane obtained in step S5.4 into a pressure vessel or test device, control the operating pressure to 0.30-0.35 MPa, continuously supply water until the membrane flux reaches a stable state, record the permeate volume per unit membrane area, and calculate the corresponding water flux and desalination rate; S6.2 Oxidation stability test: The composite reverse osmosis membrane that underwent the ultra-low pressure desalination performance test in step S6.1 was continuously immersed or operated online for more than 100 hours in a chlorinated aqueous solution containing 0.5-1.0 mg / L of free chlorine. The water flux and desalination rate were measured before and after the test according to the test conditions in S6.1, and the change rate of water flux and the change value of desalination rate were calculated. S6.3 Performance Judgment and Process Feedback: Based on the test results of steps S6.1 and S6.2, the water flux obtained under extremely low pressure test conditions is not less than 1.0 m³ / s. 3 / (m 2 ·d) When the desalination rate is not less than 98.0%, and the decrease in water flux after the oxidation stability test does not exceed 10.0% and the decrease in desalination rate does not exceed 1.0%, the post-treated composite reverse osmosis membrane obtained in step S5.4 is determined to be a reverse osmosis membrane that meets the requirements for ultra-low pressure oxidation resistance operation; when the test results do not meet any of the above determination conditions, at least one process parameter in steps S1 to S5 is adjusted according to the deviation of water flux and desalination rate, and steps S1 to S6 are re-executed accordingly.

Images