High permeability anti-fouling reverse osmosis membrane based on secondary interface polymerization and preparation method thereof

Abstract

This invention provides a high-permeability, antifouling reverse osmosis membrane based on secondary interfacial polymerization and its preparation method, belonging to the field of reverse osmosis membrane preparation technology. The method involves dissolving m-phenylenediamine in deionized water to obtain an aqueous phase solution; dissolving trimesoyl chloride in n-hexane to obtain an organic phase solution; coating the aqueous phase solution onto a polysulfone-based membrane, allowing it to stand, and then coating it with the organic phase solution again, resulting in an interfacial polymerization reaction to form a polyamide layer, thus obtaining reverse osmosis membrane I; coating the surface of reverse osmosis membrane I with an aqueous solution of a linear aliphatic aminosulfonic acid compound, allowing it to undergo a secondary interfacial polymerization reaction with residual acyl chloride groups, and allowing it to stand to obtain a secondary interfacially polymerized reverse osmosis membrane II; and placing reverse osmosis membrane II in an oven for heat treatment to obtain a high-permeability, antifouling reverse osmosis membrane. This invention not only significantly improves the water flux of the reverse osmosis membrane but also effectively inhibits organic and inorganic fouling.

Description

Technical Field

[0001] This invention belongs to the field of reverse osmosis membrane preparation technology, and particularly relates to a high-permeability, antifouling reverse osmosis membrane based on secondary interfacial polymerization and its preparation method. Background Technology

[0002] As an advanced water treatment technology, reverse osmosis has become a leading technology for solving freshwater supply shortages and is widely used in seawater desalination and industrial wastewater treatment. As the core of reverse osmosis technology, the performance of the reverse osmosis membrane directly affects the economy and feasibility of the desalination process; therefore, developing high-performance reverse osmosis membranes is crucial.

[0003] Polyamide reverse osmosis membranes are the most commonly used reverse osmosis membranes due to their excellent selectivity, good stability, and high mechanical strength. Their core performance is mainly determined by the polyamide separation layer. The permeability of a reverse osmosis membrane refers to its ability to allow water molecules to pass through the membrane under driving forces, and is a key indicator for measuring water treatment efficiency and operating costs. Improving the permeability of a reverse osmosis membrane helps to obtain higher permeate flow rates at lower operating pressures, thereby reducing energy consumption. However, the inherent dense polyamide separation layer and relatively hydrophobic and rough ridge-like surface structure of reverse osmosis membranes lead to serious membrane fouling problems in practical applications. This results in a continuous decrease in water flux during practical use, increasing system operating and maintenance costs, and requiring improvement in long-term operational stability. This further highlights the "dual requirement" of high permeability and high fouling resistance for reverse osmosis membranes.

[0004] In practical applications, due to the complexity of feed water, reverse osmosis membranes typically face various types of membrane fouling, including organic fouling, inorganic fouling, biological fouling, colloidal fouling, and complex fouling, significantly reducing membrane performance and lifespan. The process and extent of membrane fouling depend on the interaction between the membrane surface and contaminants, and this interaction is closely related to the surface properties of the reverse osmosis membrane. Therefore, by adjusting the surface characteristics of the reverse osmosis membrane, such as increasing surface hydrophilicity, reducing roughness, and introducing an antifouling functional layer, the adhesion of contaminants to the reverse osmosis membrane surface can be significantly weakened, effectively alleviating membrane fouling problems. Specifically, a hydrophilic membrane surface can form a hydration layer, effectively repelling organic contaminants (such as proteins and lipids), significantly reducing the adsorption of organic contaminants on the membrane surface. On the other hand, a hydrophilic membrane surface can distribute water molecules more evenly, reducing local salt concentration and thus lowering the risk of inorganic salt crystallization and deposition. In addition, a smooth membrane surface has fewer uneven structures, which helps reduce the adsorption sites of contaminants on the membrane surface, thereby alleviating contaminant retention and aggregation. At the same time, a smooth membrane surface makes it easier to restore membrane performance through simple physical or chemical cleaning methods, which is of great significance for extending membrane life and improving water treatment efficiency.

[0005] To reduce the direct interaction between contaminants and the reverse osmosis membrane surface, membrane surface modification has become a direct and effective method to alleviate reverse osmosis membrane fouling. By forming a thin and uniform antifouling layer on the modified membrane surface, direct contact between contaminants and the membrane can be prevented. Currently, most methods involve coating the membrane with hydrophilic polymer coatings (such as PVA and polydopamine coatings) or grafting hydrophilic macromolecules to improve the hydrophilicity of the membrane surface, thereby resisting the adhesion of contaminants. However, the introduction of coatings often increases additional transmission resistance, leading to a decrease in membrane permeability. Furthermore, there is a risk of coating material loss and leakage during long-term operation of the reverse osmosis membrane, which not only compromises its antifouling performance but also easily causes secondary pollution to the water body.

[0006] In addition, although the modification of the membrane surface with some hydrophilic substances with rigid structures can improve the hydrophilicity of the membrane surface, the rigid structure embedded in the polyamide separation layer network structure will hinder the construction of water permeation channels, which is often not conducive to improving water permeability. Summary of the Invention

[0007] The technical problem to be solved by the present invention is to provide a high-permeability, antifouling reverse osmosis membrane based on secondary interfacial polymerization and its preparation method.

[0008] To solve the above-mentioned technical problems, the technical solution adopted by the present invention is: a method for preparing a high-permeability, antifouling reverse osmosis membrane based on secondary interfacial polymerization, comprising the following steps:

[0009] S1. Dissolve m-phenylenediamine in deionized water and mix thoroughly to obtain an aqueous solution. Dissolve pyromellitic chloride in n-hexane to obtain an organic solution.

[0010] S2. The aqueous solution from step S1 is coated onto the polysulfone-based membrane. After standing, the residual aqueous solution on the surface is removed to obtain membrane I. Then, the organic solution from step S1 is coated onto membrane I. After interfacial polymerization, a polyamide layer is formed to obtain reverse osmosis membrane I.

[0011] S3. Rinse the surface of reverse osmosis membrane I with n-hexane to remove unreacted trimesoyl chloride and residual impurities;

[0012] S4. Dissolve the linear aliphatic aminosulfonic acid compound and a small amount of surfactant in deionized water to obtain an aqueous solution of the linear aliphatic aminosulfonic acid compound. Then, uniformly coat the surface of the reverse osmosis membrane I obtained in step S3 with the aqueous solution of the linear aliphatic aminosulfonic acid compound to allow it to undergo a secondary interfacial polymerization reaction with the acyl chloride groups remaining on the surface of the reverse osmosis membrane I. After standing, remove the residual aqueous solution on the surface to obtain the reverse osmosis membrane II after secondary interfacial polymerization.

[0013] S5. Place the reverse osmosis membrane II in an oven for heat treatment, and after repeated rinsing, obtain a high-permeability, anti-fouling reverse osmosis membrane.

[0014] Furthermore, in step S1, camphor sulfonic acid and triethylamine are added to the aqueous solution.

[0015] Further, in step S1, the mass fraction of m-phenylenediamine in the aqueous solution is 1.5–2.0 wt.%; the mass fraction of camphor sulfonic acid in the aqueous solution is 1.8 wt.%; the mass fraction of triethylamine in the aqueous solution is 1.6 wt.%; and the mass fraction of trimesoyl chloride in n-hexane is 0.1–0.15 wt.%.

[0016] Further, in step S2, the standing time of the aqueous phase solution coated on the polysulfone-based membrane is 30-60 s; the reaction time of the organic phase solution coated on membrane I for interfacial polymerization is 10-30 s.

[0017] Furthermore, in step S3, the time for rinsing the membrane surface with n-hexane is 30 seconds;

[0018] Further, in step S4, the surfactant is sodium dodecyl sulfate with a concentration of 0.01 wt.%.

[0019] Further, in step S4, the linear aliphatic aminosulfonic acid compound is one or more of the following: sodium 2-[(2-aminoethyl)amino]ethanesulfonate, 2-aminoethanol hydrogen sulfate, N-carbamoylmethyl ethanesulfonic acid, sodium aminosulfonate, taurine, and 3-aminopropanesulfonic acid.

[0020] Further, in step S4, the linear aliphatic aminosulfonic acid compound is sodium 2-[(2-aminoethyl)amino]ethanesulfonate.

[0021] Further, in step S4, the mass fraction of the sodium 2-[(2-aminoethyl)amino]ethanesulfonate aqueous solution is 0.05-0.5 wt.%; the sodium 2-[(2-aminoethyl)amino]ethanesulfonate aqueous solution is coated on the surface of reverse osmosis membrane I, and the standing reaction time is 2-20 min.

[0022] Furthermore, in step S5, the heat treatment time in the oven is 5 to 10 minutes; the temperature is 80 to 100°C.

[0023] Another objective of this application is to provide a method for preparing a high-permeability antifouling reverse osmosis membrane based on secondary interfacial polymerization.

[0024] The high-permeability antifouling reverse osmosis membrane exhibits a flux recovery rate of 80.6%–91.3% for organic fouling (SDS) and 89.3%–96.9% for inorganic fouling (CaSO4).

[0025] The beneficial effects of this invention are as follows:

[0026] This invention addresses the issue of insufficient improvement in the water flux and antifouling properties of reverse osmosis membranes by providing a high-permeability, antifouling reverse osmosis membrane based on secondary interfacial polymerization and its preparation method.

[0027] Grafting compounds rich in hydrophilic sulfonic acid groups (–SO3H) and possessing linear flexible segments onto the surface of a polyamide separation layer has several advantages. First, the linear segments containing hydrophilic groups can form a rigid-flexible interpenetrating network with the rigid benzene ring structure in the polyamide layer, thereby constructing continuous water channels, reducing the diffusion resistance of water molecules through the interface, and significantly improving the membrane's permeability. Second, the strong hydrophilicity and electrostatic repulsion of the sulfonic acid groups significantly enhance the hydration capacity and antifouling ability of the membrane surface.

[0028] Therefore, after traditional interfacial polymerization, a secondary interfacial polymerization reaction introduces hydrophilic and charged flexible segments, forming a flexible layer on the membrane surface. This improves both hydrophilicity and charge properties while reshaping the reverse osmosis membrane surface structure, resulting in a highly permeable, fouling-resistant reverse osmosis membrane. Through the "structure-chemistry synergistic effect" introduced at the molecular level, not only is the water flux of the reverse osmosis membrane significantly increased, but it also effectively inhibits both organic and inorganic fouling. Furthermore, this preparation method requires fewer materials and has a simpler process, providing a new strategy for designing highly permeable, fouling-resistant reverse osmosis membranes.

[0029] Specifically, in this invention, a grafting strategy involving secondary interfacial polymerization is employed. The amino groups in sodium 2-[(2-aminoethyl)amino]ethanesulfonate react with the acyl chloride groups remaining on the reverse osmosis membrane surface, introducing a flexible segmental structure to the membrane surface. This increases the free volume and transport pathways within the polyamide layer, facilitating rapid water molecule permeation. Simultaneously, the grafting process reshapes the membrane's surface structure, forming a smoother and thinner selective layer. Furthermore, the hydrophilic and charged sulfonic acid groups, firmly grafted onto the membrane surface via covalent bonds, help regulate the membrane's surface chemical properties. The synergistic effect of these two factors results in a reverse osmosis membrane that, while possessing high permeability, significantly improves its antifouling performance against both organic and inorganic contaminants. Compared with traditional reverse osmosis membranes, the reverse osmosis membrane prepared by this invention optimizes the network structure of the polyamide layer and forms a smooth, hydrophilic, and charged membrane surface, which significantly improves the water permeability of the reverse osmosis membrane (water flux can be increased by up to 183.3%) and enhances the membrane's dual resistance to organic and inorganic fouling. Under the conditions of typical organic pollutant sodium alkyl sulfate (SDS) and typical inorganic pollutant calcium sulfate (CaSO4) fouling, the flux recovery rates reached 91.3% and 96.9%, respectively, demonstrating good application value and promising prospects for promotion.

[0030] In summary, the surface properties of the reverse osmosis membrane were optimized through a secondary interfacial polymerization reaction between a flexible segmental structure containing reactive amine and hydrophilic sulfonic acid groups and unreacted acyl chloride groups on the membrane surface. This effectively avoided the additional resistance caused by surface coatings and the complex process of grafting reactions. The introduction of the flexible segmental structure reshapes the surface structure of the reverse osmosis membrane, making the membrane surface smoother and thinner. It also increases the free volume and diffusion path within the membrane separation layer, facilitating rapid water molecule permeation and significantly improving the permeate flux of the reverse osmosis membrane. Furthermore, the introduced sodium sulfonate groups (–SO3H) and amine groups (–NH2) possess strong hydrophilicity, enabling them to adsorb and stabilize a layer of water molecules on the membrane surface, forming a hydration barrier layer. Simultaneously, the sulfonic acid groups have strong electronegativity, which reduces the adsorption of contaminants on the membrane surface through the hydration barrier layer and electrostatic interactions. The flexible segmental structure also provides a dynamic buffer layer on the membrane surface, further reducing contaminant accumulation.

[0031] The preparation method of this invention is simple and easy to control, and can effectively regulate the hydrophilicity and charge density of the membrane surface while reshaping the microstructure and polyamide layer network structure of the reverse osmosis membrane. Through the synergistic effect of surface structure and chemical properties, the permeate flux of the reverse osmosis membrane is effectively improved, while reducing the deposition of pollutants on the membrane surface, thus enhancing the reverse osmosis membrane's resistance to organic and inorganic fouling. Attached Figure Description

[0032] The present invention will be described in detail below with reference to the accompanying drawings and examples. The advantages and implementation methods of the present invention will become more apparent from this description. The accompanying drawings are for illustrative purposes only and do not constitute any limitation on the present invention. In the accompanying drawings:

[0033] Figure 1 This is a scanning electron microscope image of the cross-section of the reverse osmosis membrane prepared in the comparative example of this invention.

[0034] Figure 2 This is a scanning electron microscope image of the cross-section of the high-permeability, anti-fouling reverse osmosis membrane prepared in Example 1 of the present invention.

[0035] Figure 3 This is a scanning electron microscope image of the surface of the reverse osmosis membrane prepared in the comparative example of this invention.

[0036] Figure 4 This is a surface roughness diagram of the reverse osmosis membrane prepared in the comparative example of this invention.

[0037] Figure 5 This is a scanning electron microscope image of the surface of the high-permeability, anti-fouling reverse osmosis membrane prepared in Example 1 of the present invention.

[0038] Figure 6 This is a surface roughness diagram of the high-permeability, anti-fouling reverse osmosis membrane prepared in Example 1 of the present invention.

[0039] Figure 7 This is a scanning electron microscope image of the surface of the high-permeability, anti-fouling reverse osmosis membrane prepared in Example 6 of the present invention.

[0040] Figure 8 This is a surface roughness diagram of the high-permeability, anti-fouling reverse osmosis membrane prepared in Example 6 of the present invention. Detailed Implementation

[0041] To enable those skilled in the art to better understand the technical solution of the present invention, the present invention will be further described in detail below with reference to the preferred embodiments.

[0042] The preparation method of a high-permeability, antifouling reverse osmosis membrane based on secondary interfacial polymerization includes the following steps:

[0043] S1. Dissolve m-phenylenediamine, camphor sulfonic acid and triethylamine in deionized water and mix well to obtain an aqueous solution. Dissolve pyromellitic acid chloride in n-hexane to obtain an organic solution.

[0044] S2. The aqueous solution from step S1 is coated onto the polysulfone-based membrane. After standing, the residual aqueous solution on the surface is removed to obtain membrane I. Then, the organic solution from step S1 is coated onto membrane I. After interfacial polymerization, a polyamide layer is formed to obtain reverse osmosis membrane I.

[0045] S3. Rinse the surface of reverse osmosis membrane I with n-hexane to remove unreacted trimesoyl chloride and residual impurities (because a trimesoyl chloride monomer has three acyl chloride groups, this step removes monomers in which none of the three groups have reacted).

[0046] S4. Dissolve sodium 2-[(2-aminoethyl)amino]ethanesulfonate and a small amount of sodium dodecyl sulfate (concentration of 0.01 wt.%) in deionized water to obtain an aqueous solution of sodium 2-[(2-aminoethyl)amino]ethanesulfonate. Then, uniformly coat the surface of the reverse osmosis membrane I obtained in step S3 with the aqueous solution of sodium 2-[(2-aminoethyl)amino]ethanesulfonate to allow it to undergo a secondary interfacial polymerization reaction with the acyl chloride groups remaining on the surface of reverse osmosis membrane I. After standing, remove the residual aqueous solution on the surface to obtain the reverse osmosis membrane II after secondary interfacial polymerization.

[0047] S5. Place the reverse osmosis membrane II in an oven for heat treatment, and after repeated rinsing, obtain a high-permeability, anti-fouling reverse osmosis membrane.

[0048] In step S1, the mass fraction of m-phenylenediamine in the aqueous solution is 1.5 to 2.0 wt.%, preferably 1.5 wt.%; and the mass fraction of trimesoyl chloride in n-hexane is 0.1 to 0.15 wt.%, preferably 0.1 wt.%.

[0049] In step S1, camphor sulfonic acid and triethylamine are added to the aqueous solution as acid acceptors, wherein the mass fraction of camphor sulfonic acid in the aqueous solution is 1.8 wt.% and the mass fraction of triethylamine in the aqueous solution is 1.6 wt.%.

[0050] In step S2, the aqueous solution coated on the polysulfone-based film is left to stand for 30 to 60 seconds, preferably 30 seconds.

[0051] In step S2, the reaction time for the organic phase solution coated on membrane I to undergo interfacial polymerization is 10 to 30 seconds, preferably 30 seconds.

[0052] In step S3, the hexane rinsing time on the membrane surface is 30 seconds;

[0053] In step S4, the mass fraction of the sodium 2-[(2-aminoethyl)amino]ethanesulfonate aqueous solution is 0.05-0.5 wt.%; the sodium 2-[(2-aminoethyl)amino]ethanesulfonate aqueous solution is coated on the surface of reverse osmosis membrane I, and the reaction time is 2-20 min.

[0054] Preferably, the mass fraction of the sodium 2-[(2-aminoethyl)amino]ethanesulfonate aqueous solution is 0.05-0.2 wt.%; the sodium 2-[(2-aminoethyl)amino]ethanesulfonate aqueous solution is coated on the surface of reverse osmosis membrane I, and the reaction time is 5-15 min.

[0055] In step S5, the heat treatment time in the oven is 5 to 10 minutes, preferably 8 minutes; the temperature is 80 to 100°C.

[0056] Another objective of this application is to provide a method for preparing a high-permeability antifouling reverse osmosis membrane based on secondary interfacial polymerization.

[0057] The obtained high-permeability antifouling reverse osmosis membranes showed a flux recovery rate of 80.6%–91.3% for organic fouling (SDS) and 89.3%–96.9% for inorganic fouling (CaSO4).

[0058] By employing a secondary interfacial polymerization technique, linear aliphatic aminosulfonic acid compounds with reactive amino and hydrophilic sulfonic acid groups are grafted onto the surface of reverse osmosis membranes. This effectively improves the membrane's hydrophilicity, charge properties, flux stability, and antifouling ability, thereby enhancing water purification efficiency. It has broad application value in the preparation of reverse osmosis membranes for seawater and brackish water desalination, industrial wastewater treatment, and ultrapure water production.

[0059] The main raw materials used in the following examples and comparative examples are as follows:

[0060] Polysulfone-based membrane, purchased from Jiangsu Qicheng Purification Technology Co., Ltd.;

[0061] m-Phenylenediamine (MPD), 99%, purchased from Shanghai Aladdin Biochemical Technology Co., Ltd.

[0062] Trimethylbenzene chloride (TMC), 98%, purchased from Shanghai Aladdin Biochemical Technology Co., Ltd.

[0063] n-Hexane, >98%, purchased from Marine Aladdin Biochemical Technology Co., Ltd.

[0064] Sodium dodecyl sulfate (SDS), 98%, purchased from Shanghai Aladdin Biochemical Technology Co., Ltd.

[0065] Camphor sulfonic acid (CSA), >98%, purchased from TCI (Shanghai) Chemical Industry Development Co., Ltd.

[0066] Sodium chloride (NaCl), analytical grade, purchased from Tianjin Kemeo Chemical Reagent Co., Ltd.

[0067] Sodium sulfate (Na2SO4), analytical grade, purchased from Tianjin Kemeo Chemical Reagent Co., Ltd.

[0068] Calcium chloride (CaCl2), analytical grade, purchased from Tianjin Kemeo Chemical Reagent Co., Ltd.;

[0069] Triethylamine (TEA), 99%, purchased from Tianjin Kemeo Chemical Reagent Co., Ltd.

[0070] Sodium 2-[(2-aminoethyl)amino]ethanesulfonate (AAS), 50% aqueous solution, was purchased from Shanghai E. En Chemical Technology Co., Ltd.

[0071] The main equipment used in the following embodiments and comparative examples is as follows:

[0072] The medium-pressure cross-flow test apparatus for evaluating the performance of reverse osmosis membranes was purchased from Hangzhou Saifei Membrane Separation Technology Co., Ltd.

[0073] Conductivity meter, DDSJ-307F, purchased from Shanghai Oster Industrial Co., Ltd.

[0074] Atomic force microscope, Icon, Bruker, USA;

[0075] Fully automatic contact angle measuring instrument, DSA30S, KRUSS, Germany;

[0076] Solid surface zeta potential meter, SURPASS-3, Anton Paar, Austria;

[0077] Thermal field emission scanning electron microscope, GeminiSEM 500, Carl Zeiss, UK.

[0078] The reverse osmosis membrane performance testing methods are as follows:

[0079] (1) Reverse osmosis membrane water flux and desalination rate:

[0080] The permeability and selectivity of the reverse osmosis membrane were evaluated using water flux and desalination rate (sodium chloride). The feed solution used was a 2 g / L NaCl aqueous solution, the test pressure was 1.55 MPa, and the cross-flow rate was 80 L·m³. -2 ·h -1 The temperature is 25℃; water flux (J) refers to the volume of osmotic fluid passing through a unit area per unit time, as shown in the following formula:

[0081]

[0082] In the formula, J represents the water flux (L·m³). -2 ·h -1 V is the osmotic volume of pure water (L), and A is the effective osmotic area (m²). 2 ), where △t is the infiltration time (h).

[0083] Under the same conditions as above, the desalination rate (R) is calculated using the following formula:

[0084]

[0085] In the formula, C f and C p (μS / cm) represents the conductivity of the influent and the product water, respectively.

[0086] (2) Antifouling performance of reverse osmosis membranes:

[0087] Sodium dodecyl sulfate (SDS) and calcium sulfate (CaSO4) were used as typical organic and inorganic contaminants to test the flux decay rate and flux recovery rate of reverse osmosis membranes, evaluating the antifouling performance and its changes. In the organic contamination test, an aqueous solution containing 2 g / L NaCl and 0.2 g / L SDS was used as the feed solution, pH = 7.0 ± 0.5; in the inorganic contamination test, an aqueous solution containing 2 g / L NaCl, 20 mM Na2SO4, and 20 mM CaCl2 was used as the feed solution, pH = 6.5 ± 0.5. The fouling operation time was 8 h. The flux decay rate was expressed as the ratio of the difference between the initial equilibrium flux (J0) and the instantaneous flux (J) of the reverse osmosis membrane at 25℃ and 1.55 MPa to the initial equilibrium flux (J0) ((J0-J) / J0).

[0088] After the fouling process is completed, the feed solution is replaced with clean water, and the reverse osmosis membrane is cleaned in situ for 0.5 hours. The permeation flux of the reverse osmosis membrane is measured again to obtain the recovery flux (J1). The flux recovery rate is expressed as the ratio (J1 / J0) of the recovery flux after cleaning to the initial equilibrium flux (J0).

[0089] Example 1:

[0090] The preparation method of a high-permeability, antifouling reverse osmosis membrane based on secondary interfacial polymerization includes the following steps:

[0091] S1. Using interfacial polymerization, m-phenylenediamine, camphor sulfonic acid, and triethylamine are dissolved in deionized water and mixed evenly to obtain an aqueous solution containing 1.5 wt.% m-phenylenediamine, 1.8 wt.% camphor sulfonic acid, and 1.6 wt.% triethylamine. Tristylacetyl chloride is dissolved in n-hexane to obtain an organic solution containing 0.1 wt.% tristylacetyl chloride.

[0092] S2. The aqueous solution from step S1 is coated onto the polysulfone-based membrane. After standing for 30 seconds, nitrogen gas is used to purge the surface to completely remove the residual aqueous solution, resulting in membrane I. The organic solution from step S1 is then coated onto membrane I. After standing for 30 seconds, it is removed. An interfacial polymerization reaction occurs to form a polyamide layer, resulting in reverse osmosis membrane I.

[0093] S3. Rinse the membrane surface with n-hexane for 30 seconds to remove unreacted trimesoyl chloride and residual impurities;

[0094] S4. Dissolve 0.1 wt.% sodium 2-[(2-aminoethyl)amino]ethanesulfonate and 0.01 wt.% sodium dodecyl sulfate completely in deionized water to obtain an aqueous solution of sodium 2-[(2-aminoethyl)amino]ethanesulfonate. Then, uniformly coat the surface of the reverse osmosis membrane I obtained in step S2 with the aqueous solution of sodium 2-[(2-aminoethyl)amino]ethanesulfonate to allow it to undergo a secondary interfacial polymerization reaction with the acyl chloride groups remaining on the surface of reverse osmosis membrane I. After standing for 10 minutes, remove the residual aqueous solution on the surface to obtain the reverse osmosis membrane II after secondary interfacial polymerization.

[0095] S5. Place the reverse osmosis membrane II in an oven at 100℃ for heat treatment for 8 minutes, and then rinse it repeatedly with pure water to obtain a high-permeability, anti-fouling reverse osmosis membrane.

[0096] Example 2:

[0097] The only difference from Example 1 is that in step S4, the settling time for the secondary interfacial polymerization reaction is 15 minutes, while the other conditions remain unchanged.

[0098] Example 3:

[0099] The only difference from Example 2 is that in step S4, the mass concentration of the sodium 2-[(2-aminoethyl)amino]ethanesulfonate aqueous solution is 0.05 wt.%, while the other conditions remain unchanged.

[0100] Example 4:

[0101] The only difference from Example 2 is that in step S4, the mass concentration of the sodium 2-[(2-aminoethyl)amino]ethanesulfonate aqueous solution is 0.2 wt.%, while the other conditions remain unchanged.

[0102] Example 5:

[0103] The only difference from Example 4 is that in step S4, the settling time for the secondary interfacial polymerization reaction is 5 minutes, while the other conditions remain unchanged.

[0104] Example 6:

[0105] The only difference from Example 4 is that in step S4, the settling time for the secondary interfacial polymerization reaction is 10 minutes, while the other conditions remain unchanged.

[0106] Example 7:

[0107] The only difference from Example 3 is that in step S4, the settling time for the secondary interfacial polymerization reaction is 5 minutes, while the other conditions remain unchanged.

[0108] Example 8:

[0109] The only difference from Example 3 is that in step S4, the settling time for the secondary interfacial polymerization reaction is 10 minutes, while the other conditions remain unchanged.

[0110] Example 9:

[0111] The only difference from Example 1 is that in step S4, the settling time for the secondary interfacial polymerization reaction is 5 minutes, while the other conditions remain unchanged.

[0112] Example 10:

[0113] The only difference from Example 1 is that in step S1, the mass concentration of m-phenylenediamine is 2.0 wt.%, while the other conditions remain unchanged.

[0114] Comparative example:

[0115] The only difference from Example 1 is that steps S3 and S4 are omitted, and after obtaining reverse osmosis membrane I in step S2, reverse osmosis membrane I is placed in an oven at 100°C for 8 minutes for heat treatment, and then repeatedly washed with pure water to obtain the reverse osmosis membrane.

[0116] The amounts of reactants and reaction times in Examples 1 to 10 and the comparative examples are shown in Table 1.

[0117] Table 1 shows the amount of reactants added and the reaction time for each example and comparative example.

[0118]

[0119] The performance of the high-permeability antifouling reverse osmosis membranes prepared in Examples 1 to 10 and the reverse osmosis membranes prepared in the comparative examples were tested, and the results are shown in Table 2.

[0120] Table 2. Test results of high-permeability, anti-fouling reverse osmosis membrane and reverse osmosis membrane structure and performance.

[0121]

[0122] Sodium 2-[(2-aminoethyl)amino]ethanesulfonate is an aliphatic hydrophilic linear small molecule compound possessing both polyamine functional groups and sodium sulfonate groups. It can be introduced onto the membrane surface through covalent bonding of its terminal amine groups to the polyamide layer. The introduction of flexible segment structures can reshape the surface structure of reverse osmosis membranes, making the membrane surface smoother and thinner, while increasing the free volume and diffusion paths within the membrane separation layer, facilitating rapid water molecule permeation. Furthermore, the sulfonic acid groups in this molecular structure effectively enhance the hydrophilicity and negative charge of the membrane surface, strengthening its antifouling performance. Simultaneously, the flexible segments help construct water channel structures with steric repulsion effects, making it an ideal building block for achieving synergistic rigid-flexible antifouling modification.

[0123] As shown in Table 2, the water flux of the modified high-permeability, antifouling reverse osmosis membrane was significantly improved by secondary interfacial polymerization of sodium 2-[(2-aminoethyl)amino]ethanesulfonate on the surface of reverse osmosis membrane I. This improvement was compared to the water flux of the comparative example (49.2 L·m⁻¹). -2 ·h -1 In Examples 1 to 10, the water flux was increased to 69.6–90.2 L·m⁻². -2 ·h -1 The presence of sodium 2-[(2-aminoethyl)amino]ethanesulfonate indicates that it exhibits a significant advantage in improving the water permeability of reverse osmosis membranes.

[0124] Furthermore, a smaller membrane flux decline rate or a larger flux recovery rate after the fouling experiment indicates better antifouling performance of the reverse osmosis membrane. The reverse osmosis membranes modified by the secondary interfacial polymerization grafting of sodium 2-[(2-aminoethyl)amino]ethanesulfonate according to this invention all exhibited excellent antifouling capabilities. In the organic fouling experiment, the flux decline rates after fouling in Examples 1 to 10 were 19.8%–36.3%, significantly lower than the initial reverse osmosis membrane (42.7%) in the comparative example without secondary interfacial polymerization. This indicates that the high-permeability antifouling reverse osmosis membrane prepared according to this invention can effectively reduce the interaction between the membrane surface and contaminants, thereby reducing the adsorption and deposition of contaminants on its surface. In addition, after cleaning, the flux recovery rates of Examples 1 to 10 reached 80.6%–91.3%, while the flux recovery rate of the comparative example was only 72.9%. The high membrane flux recovery rate indicates that the modified membrane is easier to clean after fouling, which is beneficial for the recovery of membrane performance. Similar to the results above, in the inorganic fouling experiment, the flux decline rate of Examples 1 to 10 decreased from 33.3% (comparative example) to 20.0%-29.1%, while the flux recovery rate after cleaning increased from 89.0% (comparative example) to 89.3%-96.9%. These results indicate that the modification method combining the rigid-flexible structure and chemical properties of the present invention can significantly improve the resistance of reverse osmosis membranes to organic and inorganic fouling while constructing highly permeable reverse osmosis membranes.

[0125] The above changes can be explained as follows: As shown in Table 2, the water contact angle of the membrane surface significantly decreased after secondary interfacial polymerization, indicating a significant improvement in the hydrophilicity of the membrane surface. Furthermore, as... Figure 1 and Figure 2 As shown, compared with the comparative example, the membrane thickness of Example 1 is significantly reduced, and the smoothness is significantly improved. This indicates that the polyamide layer modified by the linear aliphatic structure has a lower membrane thickness and a smoother surface. The synergistic effect of surface hydrophilicity and membrane thickness can effectively reduce water transport resistance. At the same time, the constructed rigid-flexible interpenetrating structure can show a significant advantage in improving water flux, ultimately resulting in a substantial increase in flux.

[0126] As shown in Table 2, the comparative sample exhibits lower hydrophilicity and charge properties, as well as higher surface roughness, making the membrane highly susceptible to organic and inorganic fouling. Figures 3 to 6 As shown, compared with the comparative example, the morphology of the high-permeability antifouling reverse osmosis membrane prepared in Example 1 changed significantly. The secondary interfacial polymerization reaction initiated by sodium 2-[(2-aminoethyl)amino]ethanesulfonate can significantly reduce the roughness of the membrane surface, and the smooth membrane surface constructed can greatly reduce the deposition of pollutants on the membrane surface. At the same time, due to the introduction of sulfonic acid groups, the hydrophilicity and negative charge density of the reverse osmosis membrane are significantly enhanced. The resulting hydration layer barrier and electrostatic repulsion synergistic effect effectively improve the reverse osmosis membrane's ability to resist organic and inorganic fouling.

[0127] Furthermore, the surface properties and membrane performance of the obtained membrane are closely related to the concentration of the grafted material and the grafting time. Table 2 shows that with increasing concentration of sodium 2-[(2-aminoethyl)amino]ethanesulfonate, the surface hydrophilicity and negative charge density continuously increase. However, as... Figure 7 and Figure 8 As shown, when the grafting concentration is greater than 0.2 wt.% or the reaction time is greater than 20 min, the relatively vigorous secondary polymerization reaction will lead to a decrease in structural uniformity, resulting in a reduction in desalination rate. Therefore, within a certain concentration and time range, the secondary interfacial polymerization reaction of sodium 2-[(2-aminoethyl)amino]ethanesulfonate can not only significantly increase membrane flux, but also simultaneously enhance the membrane's resistance to both organic and inorganic contamination.

[0128] The sodium 2-[(2-aminoethyl)amino]ethanesulfonate salt in all the above embodiments and comparative examples can be replaced with 2-aminoethanol hydrogen sulfate, N-carbamoylmethylethanesulfonic acid, sodium aminosulfonate, taurine, or 3-aminopropanesulfonic acid, all of which can achieve the above results. This invention is only illustrated using sodium 2-[(2-aminoethyl)amino]ethanesulfonate salt as an example.

[0129] The embodiments of the present invention have been described in detail above, but the content described is only a preferred embodiment of the present invention and should not be considered as limiting the scope of the present invention. All equivalent changes and improvements made within the scope of the present invention should still fall within the scope of the present invention.

Claims

1. A method for preparing a high-permeability, antifouling reverse osmosis membrane based on secondary interfacial polymerization, characterized in that: Includes the following steps: S1. Dissolve m-phenylenediamine in deionized water and mix thoroughly to obtain an aqueous solution. Dissolve pyromellitic chloride in n-hexane to obtain an organic solution. S2. The aqueous solution from step S1 is coated onto the polysulfone-based membrane. After standing, the residual aqueous solution on the surface is removed to obtain membrane I. Then, the organic solution from step S1 is coated onto membrane I. After interfacial polymerization, a polyamide layer is formed to obtain reverse osmosis membrane I. S3. Rinse the surface of reverse osmosis membrane I with n-hexane to remove unreacted trimesoyl chloride and residual impurities; S4. A linear aliphatic aminosulfonic acid compound and a surfactant are dissolved in deionized water to obtain an aqueous solution of the linear aliphatic aminosulfonic acid compound. This aqueous solution is then uniformly coated onto the surface of the reverse osmosis membrane I obtained in step S3, causing a secondary interfacial polymerization reaction with the residual acyl chloride groups on the surface of reverse osmosis membrane I. After standing, the residual aqueous solution is removed to obtain the reverse osmosis membrane II after secondary interfacial polymerization. The linear aliphatic aminosulfonic acid compound is sodium 2-[(2-aminoethyl)amino]ethanesulfonate; the mass fraction of the aqueous solution of sodium 2-[(2-aminoethyl)amino]ethanesulfonate is 0.05~0.2 wt.%; the sodium 2-[(2-aminoethyl)amino]ethanesulfonate aqueous solution is coated onto the surface of reverse osmosis membrane I, and the standing reaction time is 2~20 min. S5. Place the reverse osmosis membrane II in an oven for heat treatment, and after repeated rinsing, obtain a high-permeability, anti-fouling reverse osmosis membrane.

2. The method for preparing a high-permeability, antifouling reverse osmosis membrane based on secondary interfacial polymerization according to claim 1, characterized in that: In step S1, camphor sulfonic acid and triethylamine are also added to the aqueous solution.

3. The method for preparing a high-permeability, antifouling reverse osmosis membrane based on secondary interfacial polymerization according to claim 1, characterized in that: In step S1, the mass fraction of m-phenylenediamine in the aqueous solution is 1.5~2.0 wt.%; and the mass fraction of trimesoyl chloride in n-hexane is 0.1~0.15 wt.%.

4. The method for preparing a high-permeability, antifouling reverse osmosis membrane based on secondary interfacial polymerization according to claim 1, characterized in that: In step S2, the standing time of the aqueous solution coated on the polysulfone-based membrane is 30-60 s; the reaction time of the organic solution coated on membrane I for interfacial polymerization is 10-30 s.

5. The method for preparing a high-permeability, antifouling reverse osmosis membrane based on secondary interfacial polymerization according to claim 1, characterized in that: In step S5, the heat treatment time in the oven is 5-10 minutes; the temperature is 80-100℃.

6. A high-permeability, anti-fouling reverse osmosis membrane, characterized in that: It is prepared by the method for preparing a high-permeability antifouling reverse osmosis membrane based on secondary interfacial polymerization as described in any one of claims 1 to 5.

7. The high-permeability, anti-fouling reverse osmosis membrane according to claim 6, characterized in that: The flux recovery rate for organic pollution was 80.6%–91.3%, and the flux recovery rate for inorganic pollution was 89.3%–96.9%.

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