A reverse osmosis membrane material, a preparation method thereof and a water purification reverse osmosis membrane

Abstract

This invention discloses a reverse osmosis membrane material, its preparation method, and a water purification reverse osmosis membrane, relating to the field of water purification and separation. The preparation method includes the following steps: S1, immersing an ultrafiltration base membrane in a pretreatment solution for reaction, followed by washing and drying to obtain a hydrophilic base membrane; S2, sequentially contacting the hydrophilic base membrane with an aqueous solution containing amine monomers and zwitterionic monomers, and an organic solution containing acyl chloride monomers, to carry out interfacial polymerization; S3, subjecting the polymerized base membrane to heat treatment to obtain the reverse osmosis membrane material. By covalently anchoring zwitterionic monomers to the interfacial polymerization system on the base membrane, compared to the problem of easy adsorption and clogging inside traditional polyamide reverse osmosis membranes, the reverse osmosis membrane of this invention can maintain stable high-flux operation even when facing highly polluted water sources for a long time, thereby greatly delaying the performance degradation caused by pollution and significantly improving the membrane's durability and reliability.

Description

Technical Field

[0001] This invention relates to the field of water purification and separation technology, and in particular to separation membrane materials, specifically a reverse osmosis membrane material, its preparation method, and a water purification reverse osmosis membrane. Background Technology

[0002] Reverse osmosis technology, as a highly efficient water purification and desalination technology, has been widely used in seawater desalination, municipal wastewater resource utilization, and landfill leachate treatment. Its performance largely depends on its core component, the reverse osmosis membrane. Currently, polyamide composite reverse osmosis membranes prepared by interfacial polymerization have become the mainstream reverse osmosis membrane material due to their high desalination rate, good mechanical strength, and chemical stability.

[0003] However, in real-world water bodies with complex compositions, especially in specific application scenarios with high organic matter and high microbial loads such as municipal wastewater reuse and landfill leachate treatment, the abundant natural organic matter, proteins, polysaccharides, and microorganisms in the water readily adsorb and deposit on the surface of traditional polyamide membranes through non-covalent interactions such as hydrophobic interactions and hydrogen bonds. This initial adsorption not only directly clogs membrane pores and increases mass transfer resistance, but also provides a nutrient-rich environment for subsequent microbial attachment and colonization, thereby inducing and accelerating the formation of biofilms. Once a dense biofilm forms, it leads to a sharp and often irreversible decrease in membrane flux, forcing the system to undergo frequent high-intensity chemical cleaning. This not only significantly increases operating energy consumption and maintenance costs but also severely damages the membrane material itself, shortening its service life.

[0004] Therefore, how to effectively improve the antifouling ability of reverse osmosis membranes in harsh polluted environments, especially to resist both initial adsorption of organic matter and bioadhesion of microorganisms, and to ensure long-term operational stability, has become a technical bottleneck that urgently needs to be overcome in this field. Summary of the Invention

[0005] This invention overcomes the shortcomings of the prior art and provides a reverse osmosis membrane material, its preparation method, and a water purification reverse osmosis membrane.

[0006] To achieve the above objectives, the technical solution adopted by the present invention is as follows: Firstly, the present invention provides a method for preparing a reverse osmosis membrane material, comprising the following steps:

[0007] S1. Immerse the ultrafiltration membrane in the pretreatment solution for reaction, then wash and dry to obtain a hydrophilic membrane;

[0008] S2. The hydrophilic base film is sequentially immersed in an aqueous solution containing amine monomers and zwitterionic monomers, and an organic solution containing acyl chloride monomers to carry out interfacial polymerization reaction.

[0009] S3. Heat-treat the base membrane after polymerization to obtain the reverse osmosis membrane material;

[0010] The aqueous phase solution comprises, by mass percentage: 1.2-1.5% amine monomer, 0.2-0.5% zwitterionic monomer, 0.1-0.4% piperazine, and the balance being water; the organic phase solution comprises, by mass percentage: 0.08-0.12% acyl chloride monomer, and the balance being n-hexane.

[0011] In a preferred embodiment of the present invention, in step S1, the pretreatment solution comprises Tris-HCl buffer, dopamine hydrochloride, and polyethylene glycol diacrylate; the concentration of the Tris-HCl buffer is 8-12 mM, and the pH value is 8-9; the concentration of the dopamine hydrochloride is 1.5-3 wt%; and the concentration of the polyethylene glycol diacrylate is 0.3-0.8 wt%.

[0012] In a preferred embodiment of the present invention, in step S1, the reaction is carried out at 20-30 °C and a rotation speed of 100-150 rpm for 2-4 h; the drying temperature is 38-45 °C and the time is 1-3 h.

[0013] In a preferred embodiment of the present invention, in step S2, the amine monomer is m-phenylenediamine, the zwitterionic monomer is sulfobetaine methacrylate, and the acyl chloride monomer is pyromellitic trimethylolpropionate chloride.

[0014] In a preferred embodiment of the present invention, in step S2, the immersion contact time between the hydrophilic base film and the aqueous solution is 24-37 s, and the immersion contact time between the hydrophilic base film and the organic solution is 20-30 s.

[0015] In a preferred embodiment of the present invention, in step S2, after the hydrophilic base film comes into contact with the aqueous solution, inert gas is used to purge and remove droplets from the film surface.

[0016] In a preferred embodiment of the present invention, in step S3, the heat treatment is performed at 70-85 °C for 8-15 min.

[0017] Secondly, the present invention provides a reverse osmosis membrane material, which is prepared by any of the preparation methods described above.

[0018] In a preferred embodiment of the present invention, the reverse osmosis membrane material includes a base membrane and a polyamide separation layer formed thereon. The polyamide separation layer is a copolymer network generated by the reaction of amine monomers, zwitterionic monomers and acyl chloride monomers. The surface of the polyamide separation layer has a peak-valley rough structure, with an average surface roughness Ra≤20 nm and a peak-valley height difference Rz≤90 nm.

[0019] Thirdly, the present invention provides a water purification reverse osmosis membrane comprising the reverse osmosis membrane material described in any one of the above descriptions.

[0020] This invention addresses the shortcomings of the prior art and has the following beneficial effects:

[0021] (1) This invention provides a reverse osmosis membrane material, its preparation method, and a water purification reverse osmosis membrane. By anchoring zwitterionic monomers to the interfacial polymerization system on the base membrane, the amine groups and acyl chloride monomers undergo a condensation reaction, and the entire molecule is chemically anchored in the polyamide network. It can form a dense hydration layer with water molecules through ion dipole interaction, and bind water molecules through strong ion dipole interaction, forming a stable energy barrier. It can effectively block the adsorption of organic matter and the adhesion of microorganisms. Compared with the problem of easy adsorption and clogging inside the traditional polyamide reverse osmosis membrane, the reverse osmosis membrane of this invention can still maintain stable operation with high flux even when facing highly polluted water sources for a long time, thereby greatly delaying the performance degradation caused by pollution and significantly improving the durability and reliability of the membrane.

[0022] (2) In this invention, by controlling the interfacial polymerization process, a smooth separation layer rich in zwitterions is constructed using MPD and TMC. By using a specific low concentration of acyl chloride monomer and an extremely short reaction time, the rapid, heterogeneous polymerization process controlled by diffusion can be suppressed, forcing the polymer network to grow more gently and orderly at the interface, thereby forming a smooth polyamide thin layer with low surface roughness and small peak-valley height difference. Compared with the polyamide separation layer generated by traditional interfacial polymerization, which has a peak-valley rough structure, is prone to becoming a fouling trap and has uneven zwitterion loading, the proposed method can avoid the accumulation of pollutants in the rough area, thereby improving the antifouling performance of the membrane and achieving high flux recoverability.

[0023] (3) In this invention, the base membrane is pretreated by co-deposition of dopamine and PEGDA, which can build a stable interpenetrating network hydrophilic layer on the inner wall and surface of the base membrane pores. This can change the interfacial characteristics of the pores, transforming the originally hydrophobic inner wall of the pores into a surface rich in hydrophilic segments. This allows water molecules to pass through quickly with lower resistance, while organic molecules are difficult to retain due to the weakening of hydrophobicity. This improves the transport efficiency of water molecules and reduces the concentration polarization phenomenon inside the pores, thereby improving the transport dynamics of water molecules, reducing the tendency of fouling inside the pores, and effectively extending the service life of the membrane. Attached Figure Description

[0024] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments recorded in the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0025] Figure 1 This is a flowchart of a preferred embodiment of the present invention for preparing a reverse osmosis membrane material;

[0026] Figure 2 This is a schematic diagram of the structure of the reverse osmosis membrane material according to a preferred embodiment of the present invention;

[0027] In the diagram: 1. Base membrane; 2. Polyamide separation layer. Detailed Implementation

[0028] 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 skilled in the art without creative effort are within the scope of protection of the present invention.

[0029] Many specific details are set forth in the following description in order to provide a full understanding of the invention. However, the invention may also be practiced in other ways different from those described herein. Therefore, the scope of protection of the invention is not limited to the specific embodiments disclosed below.

[0030] Application Overview:

[0031] The applicant discovered that zwitterionic materials have shown excellent anti-adhesion properties in the field of specific protein adsorption. For example, Chinese invention patent CN120939307A discloses a biomimetic antithrombotic PMP gas exchange membrane based on zwitterionic gradient grafting and its preparation method. By gradient grafting zwitterionic ions onto the surface of poly-4-methyl-1-pentene (PMP) membrane, the protein adsorption rate is significantly reduced. This kind of research provides theoretical inspiration for improving antifouling performance through surface hydrophilic modification, and theoretically it can be applied to water treatment membranes across fields.

[0032] However, when zwitterionic layers are directly loaded onto ultrafiltration membranes, it is difficult to form a stable, uniform thin layer, which is easily detached or destroyed under the impact of high-pressure water flow, resulting in unstable antifouling effects. To address this issue, existing technologies involve first forming a cross-linked backbone network on the membrane surface and then loading the zwitterionic layer. The applicant's research has shown that using m-phenylenediamine (MPD) as an amine monomer in combination with trimesoyl chloride (TMC) can rapidly cross-link to form a polyamide backbone, subsequently or simultaneously covalently bonding zwitterions into it. However, since the interfacial polymerization of MPD and TMC is a rapid, heterogeneous process controlled by reactant diffusion, the resulting polyamide separation layer typically exhibits a typical peak-valley rough structure. While this rough structure objectively increases the specific surface area, the valley regions easily become hiding places and accumulation areas for organic pollutants and microorganisms, potentially weakening or even offsetting the antifouling gains from surface chemical modification, leading to irreversible flux decline.

[0033] To address the aforementioned problems, this invention provides a reverse osmosis membrane material, its preparation method, and a water purification reverse osmosis membrane. The method involves constructing internal hydrophilic channels through a base membrane hydrophilization pretreatment, improving water molecule transport and reducing organic matter retention within the channels. Furthermore, through an optimized functionalized interface polymerization process, the growth kinetics of the polyamide separation layer are precisely controlled, suppressing excessive and disordered peak-valley structure development and constructing a smooth, zwitterionic-rich, anti-adhesion surface. This effectively solves problems such as fouling traps, uneven functional layers, and cleaning difficulties caused by the rough structure of the cross-linked polyamide membrane. The membrane simultaneously possesses high separation performance and long-term anti-fouling capability, thereby significantly reducing flux decay and improving cleaning recovery rate.

[0034] It should be noted that the raw materials, equipment and reagents used in this invention can all be purchased from the market or obtained through existing preparation methods.

[0035] like Figure 1 As shown, a method for preparing a reverse osmosis membrane material includes the following steps:

[0036] S1. Immerse the ultrafiltration membrane in the pretreatment solution for reaction, then wash and dry to obtain a hydrophilic membrane;

[0037] S2. The hydrophilic base film is sequentially immersed in an aqueous solution containing amine monomers and zwitterionic monomers, and an organic solution containing acyl chloride monomers to carry out interfacial polymerization reaction.

[0038] S3. Heat-treat the base membrane after polymerization to obtain the reverse osmosis membrane material;

[0039] The aqueous phase solution contains, by mass percentage: 1.2-1.5% amine monomer, 0.2-0.5% zwitterionic monomer, 0.1-0.4% piperazine, and the balance being water; the organic phase solution contains, by mass percentage: 0.08-0.12% acyl chloride monomer, and the balance being n-hexane.

[0040] In some specific embodiments, in step S1, the pretreatment solution comprises Tris-HCl buffer, dopamine hydrochloride, and polyethylene glycol diacrylate (PEGDA); the concentration of the Tris-HCl buffer is 8-12 mM and the pH value is 8-9; the concentration of dopamine hydrochloride is 1.5-3 wt%; and the concentration of polyethylene glycol diacrylate is 0.3-0.8 wt%.

[0041] In some specific embodiments, in step S1, the reaction is carried out at 20-30 °C and a rotation speed of 100-150 rpm for 2-4 h; the drying temperature is 38-45 °C and the drying time is 1-3 h.

[0042] In some specific embodiments, in step S2, the amine monomer is m-phenylenediamine (MPD), the zwitterionic monomer is sulfobetaine methacrylate (SBMA), and the acyl chloride monomer is trimesoyl chloride (TMC).

[0043] It should be noted that through the polymerization reaction, because SBMA molecules simultaneously possess quaternary ammonium cations and sulfonate anions, their methacrylate groups are relatively stable in the aqueous phase. However, in the high-energy reaction region of the organic-aqueous interface in contact with TMC, the -NH2 group in the SBMA molecule can undergo an amidation reaction with the -COCl group of TMC, thereby chemically anchoring the entire SBMA molecule covalently to the generated polyamide network. The anchored SBMA molecule then sets its zwitterionic end group, i.e., -N... + (CH3)2-CH2-CH2-CH2-SO3 - It extends onto the membrane surface. One end group has an extremely strong hydration capacity. Its positive and negative charge centers can form a strong and directional bond with surrounding water molecules through ion-dipole interactions, thereby forming a dense hydration layer.

[0044] In some specific embodiments, in step S2, the immersion contact time between the hydrophilic base film and the aqueous solution is 24-37 s, and the immersion contact time between the hydrophilic base film and the organic solution is 20-30 s.

[0045] In some specific embodiments, in step S2, after the hydrophilic base membrane comes into contact with the aqueous solution, inert gas is used to purge and remove droplets from the membrane surface.

[0046] In some specific implementations, in step S3, the heat treatment is carried out at 70-85 °C for 8-15 min.

[0047] This invention provides a reverse osmosis membrane material, which is prepared by any of the above-mentioned preparation methods.

[0048] In some specific implementation methods, such as Figure 2 As shown, the reverse osmosis membrane material includes a base membrane 1 and a polyamide separation layer 2 formed thereon. The polyamide separation layer is a copolymer network formed by the reaction of amine monomers, zwitterionic monomers and acyl chloride monomers. The surface of the polyamide separation layer 2 has a peak-valley rough structure, with an average surface roughness Ra≤20 nm and a peak-valley height difference Rz≤90 nm.

[0049] The present invention provides a water purification reverse osmosis membrane comprising any one of the reverse osmosis membrane materials described above.

[0050] To further simplify and make the present invention achieve its objectives and effects, the present invention will be further described in conjunction with the following specific embodiments, but the present invention is not limited to the scope of the embodiments described herein.

[0051] It should be noted that the raw materials used in the examples and comparative examples are as follows: Polysulfone ultrafiltration membrane: molecular weight cutoff 50,000 Da, porosity 85%; SBMA: CAS number 3637-26-1, molecular weight 279.4, purity >98%, purchased from Wuhan Jihechang New Materials; MPD: molecular weight 108.1411, density 1.15 g / cm³. 3 Purchased from Jinan Yuno Chemical; TMC: molecular weight 736.7817, density 1.487 g / mL, purchased from Jiangsu Pulesi Biotechnology; Dopamine hydrochloride: catalog number ZA6356, purity ≥99%, purchased from Shanghai Zheyan Biotechnology; PEGDA: molecular weight 170.163, density 1.1 g / cm³. 3 The purity is ≥99%, purchased from Hubei Watson Chemical Co., Ltd.; piperazine: molecular weight 86.136, density 1.1 g / cm³. 3 Purchased from Changzhou Hongyu Chemical Co., Ltd.; n-Hexane: density 0.659 g / cm³ 3 Purity ≥ 99%, purchased from Jinan Shanhai Chemical Co., Ltd.

[0052] Example 1:

[0053] A method for preparing a reverse osmosis membrane material includes the following steps:

[0054] S1. The polysulfone ultrafiltration membrane was immersed in a pretreatment solution containing Tris-HCl buffer, dopamine hydrochloride, and PEGDA. The reaction was carried out at 25 °C and 120 rpm for 3 h. After the reaction, the membrane was rinsed with water to remove unreacted substances, and then dried at 40 °C for 2 h to obtain the hydrophilic membrane. The pretreatment solution contained 10 mM Tris-HCl buffer at pH 8.5, 2 wt% dopamine hydrochloride, and 0.5 wt% PEGDA.

[0055] S2. Immerse the hydrophilic base membrane in the aqueous solution for 30 s, then purge with a 0.3 MPa high-intensity nitrogen knife for 5 s to form an ultrathin, uniform amine adsorption layer without flowing water. Immediately immerse the membrane in the organic solution for 24 s to carry out interfacial polymerization reaction and form a metastable thin layer. The aqueous solution contains, by mass percentage: 1.3% MPD, 0.3% SBMA, 0.1% piperazine, and the balance being water; the organic solution contains, by mass percentage: 0.1% TMC and the balance being n-hexane.

[0056] S3. Heat-treat the polymerized base membrane at 80 °C for 10 min to obtain the reverse osmosis membrane material.

[0057] Example 2:

[0058] This embodiment is basically the same as Embodiment 1, except that the raw material content of the aqueous solution is different. Specifically, the aqueous solution contains, by mass percentage: 1.5% MPD, 0.3% SBMA, 0.1% piperazine, and the balance water.

[0059] Example 3:

[0060] This embodiment is basically the same as Embodiment 1, except that the raw material content of the aqueous solution is different. Specifically, the aqueous solution contains, by mass percentage: 1.8% MPD, 0.3% SBMA, 0.1% piperazine, and the balance water.

[0061] Example 4:

[0062] This embodiment is basically the same as Embodiment 1, except that the raw material content of the aqueous solution is different. Specifically, the aqueous solution contains, by mass percentage: 1.2% MPD, 0.3% SBMA, 0.1% piperazine, and the balance water.

[0063] Example 5:

[0064] This embodiment is basically the same as Embodiment 1, except that the raw material content of the aqueous solution is different. Specifically, the aqueous solution contains, by mass percentage: 1.0% MPD, 0.3% SBMA, 0.1% piperazine, and the balance water.

[0065] Example 6:

[0066] This embodiment is basically the same as Example 1, except that the raw material content of the organic phase solution is different. Specifically, the organic phase solution contains 0.12% TMC and the balance n-hexane by mass percentage.

[0067] Example 7:

[0068] This embodiment is basically the same as Example 1, except that the raw material content of the organic phase solution is different. Specifically, the organic phase solution contains 0.15% TMC and the balance n-hexane by mass percentage.

[0069] Example 8:

[0070] This embodiment is basically the same as Example 1, except that the raw material content of the organic phase solution is different. Specifically, the organic phase solution contains 0.08% TMC and the balance n-hexane by mass percentage.

[0071] Example 9:

[0072] This embodiment is basically the same as Example 1, except that the raw material content of the organic phase solution is different. Specifically, the organic phase solution contains 0.05% TMC and the balance n-hexane by mass percentage.

[0073] Performance testing: The average surface roughness Ra and average peak-to-valley height difference Rz of the polyamide separation layer of the reverse osmosis membrane materials prepared in Examples 1-9 were statistically recorded. The reverse osmosis membrane materials were subjected to performance tests of flux attenuation rate, flux recovery rate and surface bacterial adhesion amount, respectively. The results are shown in Table 1.

[0074] Flux decay rate and flux recovery rate: The reverse osmosis membrane to be tested was cut into pieces with an effective area of ​​10 cm². 2 The membrane was soaked in water for 24 hours to ensure it was fully wetted. The wetted membrane was then installed in the cross-flow filtration device, with the operating pressure set to 1.5 MPa, temperature 25 ℃, and cross-flow velocity 0.2 m / s. Pre-filtration with water was performed for 30 min, and the initial flux J0 was recorded after the flux stabilized. Subsequently, the feed was switched to simulated wastewater containing 50 ppm humic acid and 10... 6 CFU / mL E. coli suspension was continuously run under the same operating conditions for 72 h, with real-time throughput recorded every 6 h. tThe test was repeated 3 times, and the result was obtained by using the formula (J0-J). t The flux decline rate is calculated using the formula J1 / J0×100%. After the operation is completed, the feed is stopped, the membrane surface is rinsed with water for 10 min, and then circulated and cleaned with 200 ppm sodium hypochlorite solution at 25 ℃ for 1 h. After cleaning, the membrane is rinsed with water until neutral, and the deionized water flux J1 is tested again. The cycle test is repeated 3 times, and the flux recovery rate is calculated using the formula J1 / J0×100%.

[0075] Surface bacterial adhesion amount: Take an effective area of ​​5cm² 2 The test membrane was cut under sterile conditions and then immersed in sterile deionized water for 1 hour. The membrane was then transferred to a solution containing 10... 6 In sterile culture dishes containing a CFU / mL *E. coli* suspension, ensure the membrane is completely submerged and incubate at 25 °C for 24 h. After incubation, gently rinse the membrane three times with sterile phosphate-buffered saline to remove any unadhered airborne bacteria. Place the rinsed membrane into a centrifuge tube containing 10 mL of sterile physiological saline and vortex for 10 min to detach any adhering bacteria. Perform serial dilutions using 1 mL of the vortex buffer. Spread 0.1 mL of the appropriately diluted bacterial suspension onto LB agar plates and incubate at 37 °C for 24 h. Count the colonies and calculate the bacterial adhesion density (CFU / cm²) per unit area based on the dilution factor and membrane area. 2 .

[0076] Table 1:

[0077] project Ra (nm) Rz (nm) Flux decay rate (%) Flux recovery rate (%) <![CDATA[Bacterial adhesion amount (CFU / cm 2 )]]> Example 1 13 76 38.4 97.9 <![CDATA[8.4×10 3 ]]> Example 2 17 80 40.1 97.2 <![CDATA[9.1×10 3 ]]> Example 3 32 143 55.3 89.4 <![CDATA[2.1×10 4 ]]> Example 4 15 89 39.2 95.6 <![CDATA[8.8×10 3 ]]> Example 5 29 158 45.6 83.4 <![CDATA[1.2×10 5 ]]> Example 6 18 82 41.3 97.0 <![CDATA[9.2×10 3 ]]> Example 7 42 165 60.5 85.3 <![CDATA[7.5×10 4 ]]> Example 8 20 90 40.2 96.8 <![CDATA[9.7×10 3 ]]> Example 9 31 155 50.8 90.3 <![CDATA[3.5×10 4 ]]>

[0078] As shown in Table 1:

[0079] A comparison of Examples 1-9 shows that the present invention successfully achieved effective regulation of interfacial polymerization kinetics by precisely controlling the MPD concentration in the aqueous phase and the TMC concentration in the organic phase, thereby preparing a reverse osmosis membrane with a smooth surface and excellent antifouling performance.

[0080] Specifically, the interfacial polymerization process is essentially a reaction in which amine monomers diffuse from the aqueous phase into the organic phase, where they undergo rapid condensation polymerization with acyl chloride monomers at the interface. A suitable low concentration of MPD allows for reasonable control of its diffusion flux into the organic phase, matching the extremely low concentration of TMC, thus shifting the polymerization reaction from diffusion-controlled to reactant-supply-controlled. This controlled reaction kinetics forces the polyamide network to grow smoothly and orderly at the interface, effectively suppressing secondary growth and coarse particles caused by excessively rapid reactions and localized over-crosslinking. This results in a thin layer with an average surface roughness Ra ≤ 20 nm and a peak-to-valley height difference Rz ≤ 90 nm. Its smooth surface reduces hydrodynamic dead zones, preventing the formation of contamination traps and allowing zwitterionic SBMA to be grafted more uniformly and its hydration end groups exposed. Therefore, it exhibits a low flux decay rate, an extremely high flux recovery rate, and an extremely low bacterial adhesion.

[0081] Furthermore, in Example 3, when the MPD concentration was too high, the amine monomer in the aqueous phase was excessive, leading to a sharp increase in its diffusion flux to the organic phase. Although the TMC concentration remained within a suitable range, the excess MPD reacted violently and heterogeneously with the TMC, instantly generating a large number of polyamide particles that stacked, resulting in a significant development of peak-valley structures. The rough surface provided hiding spaces for organic matter and microorganisms, and may also affect the uniform anchoring of SBMA, leading to weak points in the antifouling hydration layer. Consequently, the flux decay rate increased to 55.3%, the recovery rate decreased to 89.4%, and the bacterial adhesion increased to 10. 4 Level. Furthermore, in Example 5, when the MPD concentration is too low, the supply of amine monomers is insufficient, making it difficult to form a complete and dense cross-linked network with TMC. The separation layer may exhibit localized weakness or discontinuity. Although the roughness is slightly improved compared to excessively high concentrations, it is still above the suitable range. Moreover, the mechanical integrity and density of the separation layer decrease, affecting the basic desalination performance and the stability of the antifouling layer, leading to a decline in overall performance.

[0082] Furthermore, in Example 7, when the TMC concentration was too high, the excess of acyl chloride monomers in the organic phase led to an extremely rapid and uncontrollable crosslinking reaction with the amine monomers diffused to the interface. This explosive polymerization rapidly consumed the amine monomers and formed a highly crosslinked, unevenly thick, and rough polymer layer with large surface undulations near the interface, deteriorating the surface morphology. In Example 9, when the TMC concentration was too low, there was a severe shortage of acyl chloride monomers, especially the MPD involved in the construction of the main network, which could not complete a sufficient crosslinking reaction with the amine monomers. This may result in insufficient crosslinking of the generated polyamide network, a thin and non-dense layer, and an inability to form a smooth and robust separation layer. Consequently, its separation performance and long-term stability were not robust, and the anti-fouling modification effect was difficult to fully realize.

[0083] To further illustrate the present invention, the preferred embodiment 1 is used as the basis for comparison.

[0084] Comparative Example 1:

[0085] The commercially available reverse osmosis membrane, model 8040, has a desalination rate of 99.5%, an operating pressure of 1-1.5 MPa, and is made of polysulfone resin. It was purchased from Hangzhou Youli Technology.

[0086] Comparative Example 2:

[0087] This comparative example is basically the same as Example 1, except that the immersion contact between the hydrophilic base film and the organic phase solution is different. The specific steps of S2 are as follows: the hydrophilic base film is immersed in the aqueous phase solution for 30 seconds, and then purged with a 0.3 MPa high-intensity nitrogen knife for 5 seconds to form an ultrathin and uniform amine liquid adsorption layer without flowing water. The film is then immediately immersed in the organic phase solution for 30 seconds to carry out interfacial polymerization reaction and form a metastable thin layer. The aqueous phase solution contains, by mass percentage: 1.3% MPD, 0.3% SBMA, 0.1% piperazine, and the balance being water; the organic phase solution contains, by mass percentage: 0.1% TMC and the balance being n-hexane.

[0088] Comparative Example 3:

[0089] This comparative example is basically the same as Example 1, except that the immersion contact between the hydrophilic base film and the organic phase solution is different. The specific steps of S2 are as follows: the hydrophilic base film is immersed in the aqueous phase solution for 30 seconds, and then purged with a 0.3 MPa high-intensity nitrogen knife for 5 seconds to form an ultrathin and uniform amine liquid adsorption layer without flowing water. The film is then immediately immersed in the organic phase solution for 35 seconds to carry out interfacial polymerization reaction and form a metastable thin layer. The aqueous phase solution contains, by mass percentage: 1.3% MPD, 0.3% SBMA, 0.1% piperazine, and the balance being water; the organic phase solution contains, by mass percentage: 0.1% TMC and the balance being n-hexane.

[0090] Comparative Example 4:

[0091] This comparative example is basically the same as Example 1, except that the immersion contact between the hydrophilic base film and the organic phase solution is different. The specific steps of S2 are as follows: the hydrophilic base film is immersed in the aqueous phase solution for 30 seconds, and then purged with a 0.3 MPa high-intensity nitrogen knife for 5 seconds to form an ultrathin and uniform amine liquid adsorption layer without flowing water. The film is then immediately immersed in the organic phase solution for 20 seconds to carry out interfacial polymerization reaction and form a metastable thin layer. The aqueous phase solution contains, by mass percentage: 1.3% MPD, 0.3% SBMA, 0.1% piperazine, and the balance being water; the organic phase solution contains, by mass percentage: 0.1% TMC and the balance being n-hexane.

[0092] Comparative Example 5:

[0093] This comparative example is basically the same as Example 1, except that the immersion contact between the hydrophilic base film and the organic phase solution is different. The specific steps of S2 are as follows: the hydrophilic base film is immersed in the aqueous phase solution for 30 s, and then purged with a 0.3 MPa high-intensity nitrogen knife for 5 s to form an ultrathin and uniform amine liquid adsorption layer without flowing water. The film is then immediately immersed in the organic phase solution for 15 s to carry out the interfacial polymerization reaction and form a metastable thin layer. The aqueous phase solution contains, by mass percentage: 1.3% MPD, 0.3% SBMA, 0.1% piperazine, and the balance being water; the organic phase solution contains, by mass percentage: 0.1% TMC and the balance being n-hexane.

[0094] Comparative Example 6:

[0095] This comparative example is basically the same as Example 1, except that the raw material content of the aqueous solution is different. Specifically, the aqueous solution contains, by mass percentage: 1.3% MPD, 0.5% SBMA, 0.1% piperazine, and the balance water.

[0096] Comparative Example 7:

[0097] This comparative example is basically the same as Example 1, except that the raw material content of the aqueous solution is different. Specifically, the aqueous solution contains, by mass percentage: 1.3% MPD, 0.7% SBMA, 0.1% piperazine, and the balance water.

[0098] Comparative Example 8:

[0099] This comparative example is basically the same as Example 1, except that the raw material content of the aqueous solution is different. Specifically, the aqueous solution contains, by mass percentage: 1.3% MPD, 0.2% SBMA, 0.1% piperazine, and the balance water.

[0100] Comparative Example 9:

[0101] This comparative example is basically the same as Example 1, except that the aqueous solution does not contain zwitterionic monomers. Specifically, the aqueous solution contains, by mass percentage: 1.3% MPD, 0.1% piperazine, and the balance water.

[0102] Comparative Example 10:

[0103] This comparative example is basically the same as Example 1, except that the base film was not subjected to hydrophilic pretreatment, specifically, step S1 was omitted.

[0104] Performance testing: The reverse osmosis membrane materials prepared in Comparative Examples 1-10 were subjected to performance tests of flux attenuation rate, flux recovery rate and surface bacterial adhesion amount, respectively, and compared with those in Example 1. The results are shown in Table 2.

[0105] Table 2:

[0106] project Flux decay rate (%) Flux recovery rate (%) <![CDATA[Bacterial adhesion amount (CFU / cm 2 )]]> Example 1 38.4 97.9 <![CDATA[8.4×10 3 ]]> Comparative Example 1 68.5 70.3 <![CDATA[5.2×10 5 ]]> Comparative Example 2 41.3 97.1 <![CDATA[8.8×10 3 ]]> Comparative Example 3 50.1 92.2 <![CDATA[5.8×10 4 ]]> Comparative Example 4 39.2 96.9 <![CDATA[8.7×10 3 ]]> Comparative Example 5 46.3 93.4 <![CDATA[1.3×10 4 ]]> Comparative Example 6 39.7 95.8 <![CDATA[9.4×10 3 ]]> Comparative Example 7 44.7 92.8 <![CDATA[1.1×10 4 ]]> Comparative Example 8 40.1 96.9 <![CDATA[9.8×10 3 ]]> Comparative Example 9 60.1 80.2 <![CDATA[3.8×10 5 ]]> Comparative Example 10 58.9 89.3 <![CDATA[2.5×10 5 ]]>

[0107] As shown in Table 2:

[0108] A comparison between Example 1 and Comparative Example 1 reveals that: Comparative Example 1 uses a commercially available traditional polyamide reverse osmosis membrane, which often has a rough separation layer and lacks an amphoteric hydration layer, resulting in a lack of a dense hydration barrier. This leads to hydrophobic adsorption of organic matter and colonization of microorganisms, resulting in a flux attenuation rate of 68.5% and a recovery rate of only 70.3%. The amount of bacteria adhering to the membrane remains high, and its antifouling properties are far lower than those of Example 1.

[0109] A comparison of Example 1 with Comparative Examples 2-5 reveals that in Examples 1, 2, and 4, the immersion contact time between the hydrophilic base film and the organic phase was controlled within a short range of 20-30 seconds, matching the extremely low TMC concentration. This ensures sufficient but not excessive cross-linking reaction between the amine monomer and the acyl chloride monomer at the interface, terminating the main reaction before the rough structure fully develops, forming a metastable, smooth thin layer, thus achieving excellent antifouling performance. Conversely, in Comparative Example 3, when the immersion contact time was too long, the TMC concentration was low, and the prolonged reaction time provided opportunities for secondary reactions between residual amine monomers and TMC, or further rearrangement and stacking of already formed polymer chains. This could lead to localized overpolymerization or polymer particle growth, slightly disrupting surface uniformity and weakening the antifouling effect, resulting in an increase in flux decay rate to 50.1% and a decrease in flux recovery rate to 92.2%. In Comparative Example 5, when the immersion contact time is too short, the reaction time is insufficient, which may lead to incomplete polycondensation reaction between the amine monomer and TMC, resulting in insufficient crosslinking or incomplete coverage of the generated polyamide network. This structure may lead to microscopic defects or uneven density in the separation layer, which not only affects the desalination performance but may also cause uneven distribution of the subsequently anchored SBMA, affecting the continuity of the hydration layer and ultimately leading to a decline in the overall performance of the membrane.

[0110] A comparison of Example 1 with Comparative Examples 6-9 shows that in Example 1, Comparative Examples 6 and 8, the amount of SBMA used is within the suitable range of 0.2-0.5 wt%. SBMA molecules can effectively participate in interfacial polymerization through their amino groups, and are uniformly and stably covalently anchored to the surface and near-surface regions of the polyamide network. Their exposed zwitterionic end groups can form a dense, continuous molecular-level hydration layer, effectively blocking contaminants without excessively interfering with the highly cross-linked, highly selective polyamide backbone formed by MPD and TMC. However, in Comparative Example 7, when the amount of SBMA was too high, excessive SBMA monomers participated in the reaction. The steric hindrance and molecular structure of SBMA may compete with MPD for reaction sites, disrupting the process of MPD and TMC forming a regular, dense cross-linked network to some extent, potentially leading to a loose microstructure or increased defects in the separation layer. Therefore, although its antifouling performance is still better than the membrane without SBMA, it is lower than the suitable amount. In Comparative Example 9, when SBMA was completely absent, the membrane surface consisted only of traditional polyamide chemistry. Although a relatively smooth surface could be obtained through process optimization, it completely lacked the strong hydration barrier constructed by zwitterionic groups. Therefore, the membrane surface mainly relied on physical smoothness to reduce fouling retention, and could not actively repel pollutants through a chemical hydration layer. In polluted water sources, the flux attenuation rate increased to 60.1%, and the bacterial adhesion increased sharply to 3.8 × 10⁻⁶. 5 CFU / cm 2 level.

[0111] A comparison of Example 1 and Comparative Example 10 reveals that Comparative Example 10 lacked the base membrane hydrophilication pretreatment step, directly using an unmodified hydrophobic polysulfone ultrafiltration base membrane for interfacial polymerization. Its pore inner walls are inherently hydrophobic. During reverse osmosis operation, water molecule transport resistance is high, and hydrophobic organic pollutants readily adsorb and accumulate on the pore inner walls through hydrophobic interactions, exacerbating concentration polarization and membrane fouling. Even if a smooth polyamide separation layer containing SBMA is formed on the surface through interfacial polymerization, the hydrophobic adsorption trap characteristics of the underlying base membrane pores remain unchanged. Pollutants may first accumulate inside the base membrane pores, gradually spreading upwards and affecting the separation layer, potentially even blocking the pore inlet. Flux attenuation rate was 58.9%, recovery rate was 89.3%, and bacterial adhesion was 2.5 × 10⁻⁶. 5 CFU / cm 2 Its resistance to pollution has decreased significantly.

[0112] The above description is based on the preferred embodiments of the present invention. It will be apparent to those skilled in the art that the present invention is not limited to the details of the exemplary embodiments described above, and that the invention can be implemented in other specific forms without departing from its spirit or essential characteristics. Therefore, the embodiments should be considered exemplary and non-limiting in all respects. The scope of the invention is defined by the appended claims rather than the foregoing description, and all variations falling within the meaning and scope of equivalents of the claims are intended to be included within the present invention. No reference numerals in the claims should be construed as limiting the scope of the claims.

[0113] Furthermore, it should be understood that although this specification describes embodiments, not every embodiment contains only one independent technical solution. This narrative style is merely for clarity. Those skilled in the art should consider the specification as a whole, and the technical solutions in each embodiment can also be appropriately combined to form other embodiments that can be understood by those skilled in the art.

Claims

1. A method for preparing a reverse osmosis membrane material, characterized in that, Includes the following steps: S1. Immerse the ultrafiltration membrane in the pretreatment solution for reaction, then wash and dry to obtain a hydrophilic membrane; S2. The hydrophilic base film is sequentially immersed in an aqueous solution containing amine monomers and zwitterionic monomers, and an organic solution containing acyl chloride monomers to carry out interfacial polymerization reaction. S3. Heat-treat the base membrane after polymerization to obtain the reverse osmosis membrane material; The aqueous phase solution comprises, by mass percentage: 1.2-1.5% amine monomer, 0.2-0.5% zwitterionic monomer, 0.1-0.4% piperazine, and the balance being water; the organic phase solution comprises, by mass percentage: 0.08-0.12% acyl chloride monomer, and the balance being n-hexane.

2. The method for preparing a reverse osmosis membrane material according to claim 1, characterized in that: In step S1, the pretreatment solution comprises Tris-HCl buffer, dopamine hydrochloride, and polyethylene glycol diacrylate; the concentration of the Tris-HCl buffer is 8-12 mM and the pH value is 8-9; the concentration of the dopamine hydrochloride is 1.5-3 wt%; and the concentration of the polyethylene glycol diacrylate is 0.3-0.8 wt%.

3. The method for preparing a reverse osmosis membrane material according to claim 1, characterized in that: In step S1, the reaction is carried out at 20-30 °C at a rotation speed of 100-150 rpm for 2-4 h; the drying temperature is 38-45 °C and the time is 1-3 h.

4. The method for preparing a reverse osmosis membrane material according to claim 1, characterized in that: In step S2, the amine monomer is m-phenylenediamine, the zwitterionic monomer is sulfobetaine methacrylate, and the acyl chloride monomer is pyromellitic trimethylolpropionate chloride.

5. The method for preparing a reverse osmosis membrane material according to claim 1, characterized in that: In step S2, the immersion contact time between the hydrophilic base membrane and the aqueous solution is 24-37 s, and the immersion contact time between the hydrophilic base membrane and the organic solution is 20-30 s.

6. The method for preparing a reverse osmosis membrane material according to claim 1, characterized in that: In step S2, after the hydrophilic base membrane comes into contact with the aqueous solution, inert gas is used to purge and remove droplets from the membrane surface.

7. The method for preparing a reverse osmosis membrane material according to claim 1, characterized in that: In step S3, the heat treatment is performed at 70-85 °C for 8-15 min.

8. A reverse osmosis membrane material, characterized in that, It is prepared by any of the preparation methods described in claims 1-7.

9. A reverse osmosis membrane material according to claim 8, characterized in that: The reverse osmosis membrane material includes a base membrane and a polyamide separation layer formed thereon. The polyamide separation layer is a copolymer network formed by the reaction of amine monomers, zwitterionic monomers and acyl chloride monomers. The surface of the polyamide separation layer has a peak-valley rough structure with an average surface roughness Ra≤20 nm and a peak-valley height difference Rz≤90 nm.

10. A reverse osmosis membrane for water purification, characterized in that, The reverse osmosis membrane material comprising any one of claims 8-9.

Images