Visible-light-driven photocatalytic self-cleaning oil-water separation membrane, and preparation method and application thereof

Abstract

The application belongs to the field of membrane separation materials, and discloses a visible light catalytic self-cleaning oil-water separation membrane and a preparation method and application thereof, and comprises the following steps: 4-cyanopentanoic acid dithiobenzoate is used to prepare an alkyne functionalized RAFT reagent; the alkyne functionalized RAFT reagent is grafted on the polymerization chain of azidation polyether sulfone through a click chemistry reaction to obtain a RAFT reagent functionalized polyether sulfone polymer; based on the RAFT reagent functionalized polyether sulfone polymer, a PES / PES-CPPA membrane is prepared through a non-solvent induced phase separation method; a hydrophilic zwitterion PSBMA is modified on the surface of the PES / PES-CPPA membrane through a RAFT polymerization method to obtain a super-hydrophilic / underwater super-oleophobic membrane; Fe 3+ The super-hydrophilic / underwater super-oleophobic membrane is subjected to complex treatment to obtain the visible light catalytic self-cleaning oil-water separation membrane; and the application significantly improves the stability and effect of the membrane material in long-term use.

Description

Technical Field

[0001] This invention belongs to the field of membrane separation materials technology, and specifically relates to a visible light catalytic self-cleaning oil-water separation membrane, its preparation method, and its application. Background Technology

[0002] Polymer membrane materials have a wide range of applications in the field of filtration and separation, especially in the separation of complex media such as oil, biomolecules, and colloidal particles. Among them, polyethersulfone (PES) is a common polymer membrane material, which is often used in oil-water separation and other scenarios due to its specific physicochemical properties.

[0003] However, since polymer membrane materials such as PES membranes are generally hydrophobic, when they are used to filter and separate media containing substances such as oil, biomolecules, and colloidal particles, an adsorption layer is easily formed on the membrane surface. This phenomenon can lead to pore blockage and surface concentration polarization, thereby reducing filtration flux and severely affecting separation efficiency. In particular, for PES membranes, their relatively low hydrophilicity makes it easier for oily organic matter to form an adsorption layer on the membrane surface when used as an oil-water separation membrane, leading to membrane pore blockage and causing the performance of the membrane material to decline rapidly in practical applications.

[0004] Currently, to overcome the adverse effects of the hydrophobicity of PES membranes, improving their surface hydrophilicity is considered an important means to enhance their antifouling performance. Compared with blending modification, surface modification applied directly to the membrane surface can precisely adjust the chemical and physical properties of the membrane surface, constructing a more stable hydrophilic layer and enhancing the antifouling performance of PES membranes. Although hydrophilic modification technology significantly enhances the antifouling performance of PES membranes, under long-term exposure or in complex pollutant environments, pollutants may still form an adsorption layer on the membrane surface, leading to pore blockage. This causes the membrane flux and separation performance to gradually decline, affecting its long-term stability and effectiveness. Summary of the Invention

[0005] To address the technical problems existing in the prior art, this invention provides a visible light catalytic self-cleaning oil-water separation membrane, its preparation method, and its application. This solves the technical problem that even after hydrophilic modification, pollutants may still form an adsorption layer on the membrane surface under long-term action or in a complex pollutant environment, leading to pore blockage, which causes the membrane flux and separation performance to gradually decline, affecting its long-term stability and effectiveness.

[0006] To achieve the above objectives, the technical solution adopted by the present invention is as follows:

[0007] This invention provides a method for preparing a visible light catalytic self-cleaning oil-water separation membrane, comprising:

[0008] Alkyne-functionalized RAFT reagents were prepared using 4-cyanopentanoic acid dithiobenzoate RAFT reagents.

[0009] By using a click chemical reaction, alkynyl-functionalized RAFT reagents are grafted onto the polymer chain of azide-modified polyether sulfone to obtain RAFT reagent-functionalized polyether sulfone polymers.

[0010] PES / PES-CPPA membranes were prepared by functionalizing polyethersulfone polymers with RAFT reagents and then using a solvent-inducible phase separation method.

[0011] Using the RAFT polymerization method, hydrophilic zwitterionic PSBMA was modified on the surface of PES / PES-CPPA film to obtain a superhydrophilic / underwater superoleophobic film.

[0012] Use Fe 3+ Complexation treatment was performed on the superhydrophilic / underwater superoleophobic film to mineralize and form β-FeOOH nanoparticles on the surface of the superhydrophilic / underwater superoleophobic film, thereby obtaining a visible light catalytic self-cleaning oil-water separation membrane.

[0013] Furthermore, the preparation process of RAFT reagents based on 4-cyanopentanoic acid dithiobenzoate is as follows:

[0014] Sodium methoxide in methanol solution, elemental sulfur and anhydrous methanol were mixed, and benzyl chloride was added dropwise. The mixture was heated and stirred to react. After the reaction was completed, the mixture was cooled and filtered to remove salt and methanol, thus obtaining sodium dithiobenzoate solution.

[0015] An aqueous solution of potassium ferricyanide was added to a sodium dithiobenzoate solution, and the mixture was stirred and reacted at room temperature in the dark. After the reaction was completed, the mixture was filtered to obtain a dithiobenzoic acid dimer.

[0016] Dithiobenzoic acid dimer, 4,4′-azobis(4-cyanopentanoic acid) and ethyl acetate were mixed, heated and stirred to react, the solvent was removed after reaction, and purified by column chromatography to obtain RAFT reagents of 4-cyanopentanoic acid dithiobenzoic acid esters.

[0017] Furthermore, the process for preparing alkynyl-functionalized RAFT reagents using 4-cyanopentanoic acid dithiobenzoate RAFT reagents is as follows:

[0018] A RAFT reagent of 4-cyanopentanoic acid dithiobenzoate, propynyl alcohol and dichloromethane were mixed, a catalyst was added, and the mixture was heated and stirred. After the reaction, the solvent was removed and purified by column chromatography to obtain the alkynyl-functionalized RAFT reagent.

[0019] Furthermore, the process of grafting alkynyl-functionalized RAFT reagents onto the polymer chains of azide-modified polyethersulfones via click chemistry to obtain RAFT reagent-functionalized polyethersulfone polymers is as follows:

[0020] The polyethersulfone polymer was treated with a chloromethylating agent to obtain chloromethylated polyethersulfone;

[0021] Chloromethylated polyethersulfone was reacted with sodium azide to obtain azidolated polyethersulfone;

[0022] Alkyne-functionalized RAFT reagents were mixed with azide-modified polyethersulfones, and a RAFT reagent-functionalized polyethersulfone polymer was obtained through a click chemistry reaction.

[0023] Furthermore, the process of preparing PES / PES-CPPA membranes by functionalizing polyethersulfone polymers with RAFT reagents and then using a solvent-inducing phase separation method is as follows:

[0024] The polyethersulfone polymer, RAFT reagent-functionalized polyethersulfone polymer, polyethylene glycol 400 and N,N-dimethylformamide were mixed, heated and stirred until dissolved, and then allowed to stand to remove air bubbles to obtain the casting solution.

[0025] The casting solution was subjected to phase inversion to obtain a PES / PES-CPPA membrane.

[0026] Furthermore, the process of phase inversion of the casting solution to obtain a PES / PES-CPPA membrane is as follows:

[0027] The casting solution is uniformly coated onto a pre-designed substrate, then immersed in a coagulation bath for phase inversion. After removing residual solvent, the substrate is dried to obtain a PES / PES-CPPA membrane. The coagulation bath is a mixed solution of N,N-dimethylformamide and water.

[0028] Furthermore, the process of modifying the surface of the PES / PES-CPPA film with hydrophilic zwitterionic PSBMA using the RAFT polymerization method to obtain a superhydrophilic / underwater superoleophobic film is as follows:

[0029] PES / PES-CPPPA membrane and methacryloyl ethyl sulfobetaine were added to anhydrous methanol. After the methacryloyl ethyl sulfobetaine was fully dissolved, an initiator was added to carry out RAFT polymerization to obtain a PSBMA-modified separation membrane.

[0030] The PSBMA-modified separation membrane was washed and dried to obtain a superhydrophilic / underwater superoleophobic membrane.

[0031] Furthermore, utilizing Fe 3+ The process of complexing a superhydrophilic / underwater superoleophobic film to mineralize β-FeOOH nanoparticles on its surface and obtain a visible-light-catalyzed self-cleaning oil-water separation membrane is as follows:

[0032] A superhydrophilic / underwater superoleophobic membrane was immersed in FeCl3·6H2O solution for mineralization to obtain a self-cleaning oil-water separation membrane loaded with β-FeOOH nanoparticles.

[0033] A self-cleaning oil-water separation membrane loaded with β-FeOOH nanoparticles was washed and dried to obtain a visible light catalytic self-cleaning oil-water separation membrane.

[0034] The present invention also provides a visible light catalytic self-cleaning oil-water separation membrane, which is prepared by the method described above.

[0035] The present invention also provides an application of a visible light catalytic self-cleaning oil-water separation membrane, which is used in the oil-water separation process of emulsified oily wastewater.

[0036] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0037] The present invention provides a method for preparing a visible light catalytic self-cleaning oil-water separation membrane. A PES / PES-CPPA membrane is prepared using a solvent-inducible phase separation method. Then, hydrophilic zwitterionic PSBMA is grafted onto the membrane using RAFT polymerization to obtain a superhydrophilic / underwater superoleophobic membrane, achieving the goal of enhancing the antifouling properties of the membrane material through surface modification. Secondly, Fe... 3+ Complexation treatment of superhydrophilic / underwater superoleophobic films using Fe 3+ -SO3 on PSBMA - Group complexation is used to mineralize β-FeOOH nanoparticles on the surface of a superhydrophilic / underwater superoleophobic membrane. Based on the photocatalytic self-cleaning effect of β-FeOOH nanoparticles, the membrane material exhibits excellent antifouling ability when facing fouling and can maintain surface cleanliness and performance stability through a self-cleaning mechanism, effectively improving the separation flux and oil-water separation efficiency of the membrane material, thereby significantly improving the long-term stability and effectiveness of the membrane material. In particular, the β-FeOOH nanoparticles loaded on the membrane surface combine catalytic degradation function with membrane separation technology to form a dynamic self-cleaning mechanism. This dynamic self-cleaning mechanism continuously decomposes pollutant molecules through surface catalytic reactions, not only maintaining the integrity of the membrane structure, but also effectively reducing the negative impact of fouling on separation performance, providing an efficient solution for the long-term treatment of complex wastewater. The visible light photocatalytic self-cleaning oil-water separation membrane prepared by this invention has high separation flux and excellent oil-water separation efficiency. It can be used in the treatment of emulsified oily wastewater and meets the separation performance requirements of different oil-in-water emulsions. Its preparation process is simple and has low process difficulty.

[0038] The visible light catalytic self-cleaning oil-water separation membrane and its application provided by this invention possess all the advantages of the aforementioned methods for preparing visible light catalytic self-cleaning oil-water separation membranes. Attached Figure Description

[0039] To more clearly illustrate the technical solutions in the embodiments of this application 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 of this application. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0040] Figure 1 A flowchart illustrating the preparation method of the visible light catalytic self-cleaning oil-water separation membrane provided by the present invention;

[0041] Figure 2 The RAFT reagent of 4-cyanopentanoic acid dithiobenzoate prepared in Example 3 1 H-NMR spectrum;

[0042] Figure 3 The alkynyl-functionalized RAFT reagent prepared in Example 3 1 H-NMR spectrum;

[0043] Figure 4 The ATR-FTIR spectra of PES (a), PES-CH2Cl (b), PES-CH2N3 (c) and PES-CPPA (d) in Example 3 are shown.

[0044] Figure 5 PES (a), PES / PES-CPPA membrane (b), and PES / PSBMA in Example 3 12 ATR-FTIR spectra of membrane (c) and the visible light catalytic self-cleaning oil-water separation membrane (d) prepared in Example 7;

[0045] Figure 6 This includes existing pure PES membranes and the PES / PES-CPPA membrane and PES / PSBMA membranes in Example 3. 12 SEM images of the membrane and the visible light photocatalytic self-cleaning oil-water separation membrane prepared in Example 7; wherein, Figure 6 a1 is a surface SEM image of a pure PES film. Figure 6 a2 is a cross-sectional SEM image of a pure PES membrane; Figure 6 b1 is a surface SEM image of the PES / PES-CPPA membrane in Example 3. Figure 6 b2 is a cross-sectional SEM image of the PES / PES-CPPA membrane in Example 3; Figure 6 c1 is the PES / PSBMA in Example 312 SEM image of the membrane surface. Figure 6 c2 is the PES / PSBMA in Example 3. 12 SEM image of the membrane cross section; Figure 6 d1 is a surface SEM image of the visible light catalytic self-cleaning oil-water separation membrane prepared in Example 7. Figure 6 d2 is a cross-sectional SEM image of the visible light catalytic self-cleaning oil-water separation membrane prepared in Example 7;

[0046] Figure 7 The graph shows the WCA variation over time for the superhydrophilic / underwater superoleophobic films prepared in Examples 1-6.

[0047] Figure 8 PES / PSBMA prepared in Example 3 for different oils 12 UWOCA diagram on the membrane;

[0048] Figure 9 The bar chart shows the separation flux of pure water by the PES / PSBMA0 / β-FeOOH0 membrane prepared in Comparative Example 1 and the superhydrophilic / underwater superoleophobic membranes prepared in Examples 1-6.

[0049] Figure 10 The graph shows the flux and separation efficiency of the PES / PSBMA0 / β-FeOOH0 membrane prepared in Comparative Example 1 and the superhydrophilic / underwater superoleophobic membranes prepared in Examples 1-6 for the hexane-in-water emulsion.

[0050] Figure 11 PES / PSBMA in Example 3 12 Graphs showing the flux and separation efficiency of membranes for different types of emulsions;

[0051] Figure 12 PES / PSBMA in Example 3 12 DLS curves of the membrane before and after separation of different types of emulsions; among them, Figure 12 a1 is the DLS curve of the toluene emulsion; Figure 12 a2 is the DLS curve of the toluene filtrate; Figure 12 b1 is the DLS curve of the 1,2-dichloroethane emulsion; Figure 12 b2 is the DLS curve of the filtrate of 1,2-dichloroethane; Figure 12 c1 is the DLS curve of the n-hexane emulsion; Figure 12 c2 is the DLS curve of the n-hexane filtrate; Figure 12 d1 is the DLS curve of the petroleum ether emulsion; Figure 12 d2 is the DLS curve of petroleum ether filtrate;

[0052] Figure 13PES / PSBMA prepared in Comparative Example 2 12 The effect of the β-FeOOHO membrane on permeation flux and MB degradation rate compared to the visible light photocatalytic self-cleaning oil-water separation membranes prepared in Examples 3 and 7-9 is shown in the figure; Figure 13 a represents the PES / PSBMA prepared in Comparative Example 2. 12 The effect of the β-FeOOHO membrane on the permeation flux compared to the visible light catalytic self-cleaning oil-water separation membranes prepared in Examples 3 and 7-9; Figure 13 b represents the PES / PSBMA prepared in Comparative Example 2. 12 The effect of the / β-FeOOHO membrane and the visible light catalytic self-cleaning oil-water separation membrane prepared in Examples 3 and 7-9 on the degradation rate of MB is shown in the figure.

[0053] Figure 14 The PES / PSBMA prepared in Example 3 12 The membrane and the visible light photocatalytic self-cleaning oil-water separation membrane prepared in Example 7 were tested for cyclic separation; wherein, Figure 14 a is PES / PSBMA 12 Graph showing the membrane flux and separation efficiency for n-hexane-water emulsion in 5 cycles; Figure 14 b is a graph showing the flux and separation efficiency of the visible light catalytic self-cleaning oil-water separation membrane prepared in Example 7 for n-hexane-water emulsion in 5 cycles. Figure 14 c represents the PES / PSBMA prepared in Example 3. 12 Flux recovery rate of membrane in 5 cycles (F) rr Total pollution rate (R) t Reversible pollution rate (R) r ) and irreversible pollution rate (R i r) diagram; Figure 14 d represents the flux recovery rate (F) of the visible light catalytic self-cleaning oil-water separation membrane prepared in Example 7 after 5 cycles. rr Total pollution rate (R) t Reversible pollution rate (R) r ) and irreversible pollution rate (R i r) diagram. Detailed Implementation

[0054] To make the technical problems, technical solutions, and beneficial effects solved by this application clearer, the technical solutions in the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only a part of the embodiments of this application, and not all of them. All other embodiments obtained by those skilled in the art based on the embodiments of this application without creative effort are within the scope of protection of this application.

[0055] As attached Figure 1 As shown, this invention provides a method for preparing a visible light catalytic self-cleaning oil-water separation membrane, comprising the following steps:

[0056] Step 100: Prepare alkynyl-functionalized RAFT reagents using 4-cyanopentanoic acid dithiobenzoate RAFT reagents.

[0057] The preparation process of RAFT reagents of 4-cyanopentanoic acid dithiobenzoate is as follows;

[0058] A methanol solution of sodium methoxide, elemental sulfur, and anhydrous methanol were mixed, and benzyl chloride was added dropwise. The mixture was heated and stirred. After the reaction was completed, the mixture was cooled, and excess methanol was removed by filtration and vacuum distillation to obtain a wine-red and viscous crude product. Deionized water was then added to the wine-red and viscous crude product, and extraction was performed using diethyl ether. During the third extraction, concentrated hydrochloric acid was added until the upper layer turned purple-red, at which point the upper layer was retained. Sodium hydroxide solution was added to the retained upper layer to obtain a sodium dithiobenzoate solution. Potassium ferricyanide aqueous solution was slowly added dropwise to the sodium dithiobenzoate solution, and the mixture was stirred at room temperature in the dark. After the reaction was completed, the mixture was filtered to obtain a dithiobenzoic acid dimer. The dithiobenzoic acid dimer, 4,4′-azobis(4-cyanopentanoic acid), and ethyl acetate were mixed, heated, and stirred. After the reaction, the solvent was removed, and the mixture was purified by column chromatography to obtain a RAFT reagent (CPPA) for 4-cyanopentanoic acid dithiobenzoate.

[0059] Specifically, the process for preparing alkynyl-functionalized RAFT reagents is as follows:

[0060] CPPA, propynyl alcohol, and dichloromethane were mixed, and 4-dimethylaminopyridine and 1-ethyl-(3-dimethylaminopropyl)carbodiimide hydrochloride were added as catalysts. The mixture was heated and stirred to react. After the reaction, the solvent was removed by rotary evaporation and purified by column chromatography to obtain (4-cyanopentyl propynyl ester)-dithiobenzoate, which is the alkynyl-functionalized RAFT reagent.

[0061] Step 200: Through click chemistry, an alkyne-functionalized RAFT reagent is grafted onto the polymer chain of azide-modified polyethersulfone to obtain a RAFT reagent-functionalized polyethersulfone polymer. Specifically, the polyethersulfone polymer is treated with a chloromethylating agent to obtain chloromethylated polyethersulfone (PES-CH2Cl); the chloromethylated polyethersulfone is reacted with sodium azide (NaN3) to obtain azide-modified polyethersulfone (PES-CH2N3); the alkyne-functionalized RAFT reagent is mixed with the azide-modified polyethersulfone, and a click chemistry reaction is performed to obtain a RAFT reagent-functionalized polyethersulfone polymer (PES-CPPA).

[0062] More specifically, it includes the following processes:

[0063] Under ice bath conditions, polyethersulfone polymer was added to concentrated sulfuric acid and mechanically stirred until completely dissolved. Chloromethyl ethyl ether was then added dropwise to initiate the reaction. After the reaction was complete, the mixture was transferred to ice water until a white flocculent precipitate formed. The white flocculent precipitate was filtered, washed with water, and dried to obtain PES-CH2Cl. PES-CH2Cl and NaN3 were dispersed in N,N-dimethylformamide (DMF) and reacted under magnetic stirring. After the reaction system cooled, a mixture of methanol and water was added to precipitate the precipitate. The precipitate was then collected using a Buchner funnel to obtain PES-CH2Cl. 2N3; PES-CH2N3 was mixed and dissolved with DMF, and after deoxygenation, cuprous bromide (CuBr) and 2,2'-bipyridine were added, followed by another deoxygenation treatment; then the mixture was heated and stirred to react, and after the reaction was completed and cooled, it was poured into a mixture of methanol and water for precipitation treatment. Ammonia water was added and stirred with a glass rod. After a large amount of pink flocculent polymer precipitate was formed, it was filtered using a Buchner funnel to obtain the polymer precipitate; the polymer precipitate was repeatedly washed with distilled water and dried to obtain PES-CPPA.

[0064] Step 300: Based on the RAFT reagent, functionalize the polyethersulfone polymer and prepare a PES / PES-CPPA membrane by a solvent-inducible phase separation method. Specifically, mix the polyethersulfone polymer, PES-CPPA, DMF, and polyethylene glycol 400 (PEG 400), heat and stir until dissolved, then place in a vacuum oven to remove air bubbles, obtaining a casting solution; perform a phase inversion on the casting solution to obtain the PES / PES-CPPA membrane; wherein, the process of performing a phase inversion on the casting solution to obtain the PES / PES-CPPA membrane includes: uniformly coating the casting solution onto a preset substrate, then immersing it in a coagulation bath for phase inversion, removing residual solvent, and drying to obtain the PES / PES-CPPA membrane; preferably, the coagulation bath is a mixed solution of N,N-dimethylformamide and water.

[0065] Step 400: Using the RAFT polymerization method, hydrophilic zwitterionic PSBMA is modified on the surface of the PES / PES-CPPA membrane to obtain a superhydrophilic / underwater superoleophobic membrane.

[0066] Specifically, the process is as follows:

[0067] PES / PES-CPPPA membrane and methacryloyl ethyl sulfobetaine (SBMA) were added to anhydrous methanol. After the SBMA was fully dissolved, an initiator was added to carry out RAFT polymerization to obtain a PSBMA-modified separation membrane. The RAFT polymerization reaction time was 4-24 h. The PSBMA-modified separation membrane was washed and dried to obtain a superhydrophilic / underwater superoleophobic membrane (PES / PSBMA membrane).

[0068] Step 500, using Fe 3+ Complexation treatment was performed on the superhydrophilic / underwater superoleophobic film to mineralize and form β-FeOOH nanoparticles on the surface of the superhydrophilic / underwater superoleophobic film, thereby obtaining a visible light catalytic self-cleaning oil-water separation membrane.

[0069] Specifically, the process is as follows:

[0070] The PES / PSBMA membrane was rinsed with deionized water, dried, and then immersed in FeCl3·6H2O solution for mineralization at 60°C to allow Fe to pass through. 3+ -SO3 on PSBMA - Group complexation occurs, and β-FeOOH is mineralized on the membrane surface to form β-FeOOH, resulting in a self-cleaning oil-water separation membrane loaded with β-FeOOH nanoparticles; wherein the concentration of FeCl3·6H2O solution is 2-8 mg / mL. -1 The self-cleaning oil-water separation membrane loaded with β-FeOOH nanoparticles was washed and dried to obtain a visible light catalytic self-cleaning oil-water separation membrane (PES / PSBMA / β-FeOOH).

[0071] Preparation principle:

[0072] The present invention provides a method for preparing a visible light catalytic self-cleaning oil-water separation membrane. This method involves functionalizing a 4-cyanopentanoic acid dithiobenzoate-based RAFT reagent with an alkynyl group, and then grafting the alkynyl-functionalized RAFT reagent onto the polymer chain of azide-modified polyethersulfone via click chemistry. Subsequently, a PES / PES-CPPA membrane is prepared using a solvent-inducible phase separation method. Then, a hydrophilic zwitterionic polysulfobetaine methacrylate (PSBMA) is grafted onto the PES / PES-CPPA membrane using RAFT polymerization to obtain a superhydrophilic / underwater superoleophobic membrane (PES / PSBMA membrane), thus achieving the goal of enhancing the antifouling properties of the membrane material through surface modification.

[0073] In this invention, to further improve the hydrophilicity of the membrane material and impart self-cleaning properties, Fe... 3+ -SO3 on hydrophilic zwitterionic PSBMA in superhydrophilic / submarine superoleophobic films -Group complexation further mineralizes β-FeOOH nanoparticles on the membrane surface, resulting in a PES / PSBMA / β-FeOOH membrane with excellent hydrophilicity and self-cleaning properties. Among them, the photocatalytic self-cleaning effect based on β-FeOOH nanoparticles enables the membrane material to exhibit excellent antifouling ability when facing fouling, and maintains surface cleanliness and performance stability through the self-cleaning mechanism, effectively improving the separation flux and oil-water separation efficiency of the membrane material, thereby significantly improving the long-term stability and effectiveness of the membrane material.

[0074] The visible light catalytic self-cleaning oil-water separation membrane prepared in this invention exhibits high separation flux, excellent oil-water separation efficiency, and separation performance for various oil-in-water emulsions. The PES / CPPA membrane contains a large amount of CPPA, providing ample reaction sites. Grafting a zwitterionic polymer brush with excellent hydrophilicity via RAFT significantly improves membrane wettability, thereby increasing the membrane material flux and separation efficiency. Furthermore, the β-FeOOH nanoparticles loaded on the membrane surface combine catalytic degradation with membrane separation technology, forming a dynamic self-cleaning mechanism. This mechanism continuously decomposes pollutant molecules through surface catalytic reactions, maintaining the integrity of the membrane structure and effectively mitigating the negative impact of contamination on separation performance, providing an efficient solution for complex wastewater treatment.

[0075] The following specific embodiments further explain the preparation method of the visible light catalytic self-cleaning oil-water separation membrane provided by the present invention:

[0076] Example 1

[0077] This embodiment 1 provides a method for preparing a visible light catalytic self-cleaning oil-water separation membrane, including the following steps:

[0078] Step 1: Under nitrogen protection, 10.5 g of sodium methoxide and 6.7 g of sublimed sulfur were first added to a three-necked round-bottom flask, followed by 100 mL of methanol. The mixture was stirred magnetically to ensure uniform dispersion. The reaction mixture was gradually heated to 80°C, and then 11.45 mL of benzyl chloride was slowly added dropwise. The reaction was continued at 80°C for 10 h. After the reaction was complete, the reaction mixture was allowed to cool naturally to room temperature, then filtered, and excess methanol was removed by vacuum distillation to obtain a wine-red, viscous crude product. Next, 100 mL of deionized water was added to the wine-red, viscous crude product, and extraction was performed using diethyl ether (50 mL × 3). During the third extraction, 30 mL of 36% hydrochloric acid was added until the upper layer turned purple-red, at which point the upper layer was retained. Then, 140 mL of 1 mol / L sodium hydroxide solution was added to the retained upper layer to finally obtain a sodium dithiobenzoate solution. Weigh 13.24 g of K3[Fe(CN)6] and dissolve it in 200 mL of distilled water, stirring thoroughly to ensure complete dissolution, to obtain a K3[Fe(CN)6] solution. Then, transfer a pre-prepared sodium dithiobenzoate solution to a three-necked flask. At room temperature, add the K3[Fe(CN)6] solution dropwise to the three-necked flask, stirring vigorously to ensure thorough mixing. React strictly in the dark for 8 h. After the reaction is complete, filter and wash repeatedly with water until the washings are colorless, indicating that impurities have been largely removed, yielding a solid product. Finally, place the obtained solid product in a vacuum drying oven at 45 °C to remove residual moisture. After complete drying, recrystallize the product using ethanol to obtain a pure pink product, namely the dithiobenzoic acid dimer. Under nitrogen protection, 2.36 g of dithiobenzoic acid dimer and 3.25 g of 4,4′-azobis(4-cyanopentanoic acid) were uniformly dispersed in 40 mL of anhydrous ethyl acetate. The mixture was then heated to 70 °C and maintained at this temperature for 18 h. After the reaction was complete, the solvent was removed by vacuum distillation, and then separated by column chromatography (ethyl acetate / petroleum ether = 3:7) to finally obtain 4-cyanopentanoic acid dithiobenzoate RAFT reagent (CPPA). Under nitrogen protection, 0.5 g of CPPA and 0.299 g of propynyl alcohol were added to 15 mL of anhydrous dichloromethane and stirred in an ice bath. 0.043 g of 4-dimethylaminopyridine was added, and 1.02 g of 1-ethyl-(3-dimethylaminopropyl)carbodiimide hydrochloride was dispersed in 10 mL of anhydrous dichloromethane and added to the CPPA solution. The mixture was stirred in an ice bath for 2 h and then reacted at room temperature for 18 h.After the reaction was completed, the reaction mixture was washed with deionized water (3 × 50 mL), dried with anhydrous MgSO4, filtered, and the solvent was removed by rotary evaporation. Finally, the mixture was purified by column chromatography (petroleum ether / ethyl acetate = 4 / 1) to obtain the alkynyl-functionalized RAFT reagent ((4-cyanopentyl propargyl)-dithiobenzoate).

[0079] Step 2: Under ice bath conditions, 1.675 g of polyethersulfone polymer was added to a three-necked flask containing 67 mL of concentrated sulfuric acid and mechanically stirred until completely dissolved. Then, 0.632 mL of chloromethyl ethyl ether was slowly added dropwise. After reacting for 2 h, the mixture was slowly transferred to ice water with a glass rod and stirred, resulting in the precipitation of white flocculent matter. The white flocculent matter was filtered, washed with water until the washings were neutral, and dried under vacuum at 40 °C for 24 h to obtain PES-CH2Cl. Under nitrogen protection, 1.8 g of PES-CH2Cl and 1.32 g of NaN3 were dispersed in 168 mL of DMF and reacted at 60 °C for 24 h under magnetic stirring. After the reaction mixture cooled to room temperature, a mixture of methanol and water was added for precipitation, resulting in the precipitation of a large amount of white flocculent matter; the volume ratio of methanol to distilled water in the methanol-water mixture was 4:1. The white flocculent matter was collected by filtration using a Buchner funnel. After washing 4-5 times with distilled water, PES-CH2N3 was obtained by vacuum drying at 40°C for 24 hours. Then, the alkynyl-functionalized RAFT reagent was mixed with azide-modified polyethersulfone and the RAFT reagent-functionalized polyethersulfone polymer (PES-CPPA) was obtained through click chemistry reaction.

[0080] The specific steps for synthesizing PES-CPPA via click chemistry are as follows: First, 0.2 g of PES-CH2N3 and 12 mL of DMF are placed in a 25 mL vacuum tube and immersed in a 60°C oil bath. Stirring is continued for 5-10 minutes to ensure complete dissolution. Then, the vacuum tube is removed and allowed to cool to room temperature. An alkyne-functionalized RAFT reagent is added, causing the solution to turn red. Stirring continues until homogeneous. Next, the solution in the vacuum tube is deoxygenated. After deoxygenation, 7 mg of cuprous bromide (CuBr) and 16 mg of 2,2'-bipyridine are added for further deoxygenation. Under nitrogen protection, the vacuum tube is returned to the 60°C oil bath, and the reaction continues for 24 h, at which point the solution turns brownish-yellow. After the reaction is complete, the solution is cooled to room temperature and poured into a methanol-water mixture (volume ratio of methanol:distilled water = 9:1) for precipitation. Ammonia is added to neutralize excess copper ions from the reaction. Under the guidance and stirring of a glass rod, after a large amount of pink flocculent polymer precipitate is formed, it is filtered using a Buchner funnel to obtain the polymer precipitate. The polymer precipitate is repeatedly washed with distilled water and then dried in a vacuum drying oven at 40°C for 24 h until the weight is constant, thus obtaining PES-CPPA. PES-CPPA is stored in a sealed container for later use.

[0081] Step 3: Dissolve 0.587 g of PES, 0.08 g of PES-CPPA, and 1.11 g of PEG-400 in 4 mol of DMF. Stir at 60°C for 12 h to ensure complete dissolution, obtaining a homogeneous and transparent red casting solution. Then, place the solution in a vacuum oven and let it stand for 1 h to remove air bubbles. Afterward, use a 250 μm doctor blade to evenly coat the degassed casting solution onto a glass plate. After exposure to air for a predetermined time, immerse the membrane in a coagulation bath at 35°C containing a 2% DMF and water solution for phase inversion. After 1 h, transfer the membrane to water and soak for 24 h to remove residual solvent. Dry at room temperature for 24 h to obtain the PES / PES-CPPA membrane for later use.

[0082] Step 4: Weigh 2.4 g of SBMA and add 200 mL of anhydrous methanol to a three-necked separable round-bottom flask. After the SBMA is fully dissolved, add 30.0 mg of AIBN as an initiator. After nitrogen protection for 30 min, start heating. The entire reaction is carried out at 65℃ under N2 atmosphere with magnetic stirring for 4 h. Then, wash three times with ethanol and deionized water respectively to prepare a superhydrophilic / underwater superoleophobic membrane, which is designated as PES / PSBMA4 membrane. The PES / PSBMA4 membrane is stored in deionized water for later use.

[0083] Step 5: Rinse the PES / PSBMA4 membrane with deionized water and dry at room temperature for 24 h; then immerse it in 2 mg mL of water. -1 The membrane was soaked in FeCl3·6H2O solution for 30 min, mineralized at 60℃ for 24 h, rinsed with deionized water, and dried to obtain a visible light catalytic self-cleaning oil-water separation membrane, denoted as PES / PSBMA4 / β-FeOOH2 membrane.

[0084] Example 2

[0085] The method for preparing a visible light catalytic self-cleaning oil-water separation membrane provided in Example 2 is basically the same in process and principle as the method for preparing a visible light catalytic self-cleaning oil-water separation membrane described in Example 1 above, except that:

[0086] In step 4, the reaction was carried out under magnetic stirring for 8 hours, and the superhydrophilic / underwater superoleophobic film obtained in step 4 was designated as PES / PSBMA8 film.

[0087] The remaining steps are the same and will not be repeated here; the visible light catalytic self-cleaning oil-water separation membrane finally prepared in Example 2 is denoted as PES / PSBMA8 / β-FeOOH2 membrane.

[0088] Example 3

[0089] The method for preparing a visible light catalytic self-cleaning oil-water separation membrane provided in Example 3 is basically the same in process and principle as the method for preparing a visible light catalytic self-cleaning oil-water separation membrane described in Example 1 above, except that:

[0090] In step 4, the reaction was carried out under magnetic stirring for 12 h, and the superhydrophilic / underwater superoleophobic film obtained in step 4 was designated as PES / PSBMA. 12 membrane.

[0091] The remaining steps are the same and will not be repeated here; the visible light catalytic self-cleaning oil-water separation membrane finally prepared in Example 3 is denoted as PES / PSBMA. 12 / β-FeOOH2 membrane.

[0092] Example 4

[0093] The method for preparing a visible light catalytic self-cleaning oil-water separation membrane provided in Example 4 is basically the same in process and principle as the method for preparing a visible light catalytic self-cleaning oil-water separation membrane described in Example 1 above, except that:

[0094] In step 4, the reaction was carried out under magnetic stirring for 16 h, and the superhydrophilic / underwater superoleophobic film obtained in step 4 was designated as PES / PSBMA. 16membrane.

[0095] The remaining steps are the same and will not be repeated here; the visible light catalytic self-cleaning oil-water separation membrane finally prepared in Example 4 is denoted as PES / PSBMA. 16 / β-FeOOH2 membrane.

[0096] Example 5

[0097] The method for preparing a visible light catalytic self-cleaning oil-water separation membrane provided in Example 5 is basically the same in process and principle as the method for preparing a visible light catalytic self-cleaning oil-water separation membrane described in Example 1 above, except that:

[0098] In step 4, the reaction was carried out under magnetic stirring for 20 h, and the superhydrophilic / underwater superoleophobic film obtained in step 4 was denoted as PES / PSBMA. 20 membrane.

[0099] The remaining steps are the same and will not be repeated here; the visible light catalytic self-cleaning oil-water separation membrane finally prepared in Example 5 is denoted as PES / PSBMA. 20 / β-FeOOH2 membrane.

[0100] Example 6

[0101] The method for preparing a visible light catalytic self-cleaning oil-water separation membrane provided in Example 6 is basically the same in process and principle as the method for preparing a visible light catalytic self-cleaning oil-water separation membrane described in Example 1 above, except that:

[0102] In step 4, the reaction was carried out under magnetic stirring for 24 h, and the superhydrophilic / underwater superoleophobic film obtained in step 4 was designated as PES / PSBMA. 24 membrane.

[0103] The remaining steps are the same and will not be repeated here; the visible light catalytic self-cleaning oil-water separation membrane finally prepared in Example 6 is denoted as PES / PSBMA. 24 / β-FeOOH2 membrane.

[0104] Example 7

[0105] The method for preparing a visible light catalytic self-cleaning oil-water separation membrane provided in Example 7 is basically the same in process and principle as the method for preparing a visible light catalytic self-cleaning oil-water separation membrane described in Example 3 above, except that:

[0106] In step 5, the concentration of the FeCl3·6H2O solution is 4 mg / mL. -1 .

[0107] The remaining steps are the same and will not be repeated here; the visible light catalytic self-cleaning oil-water separation membrane finally prepared in Example 7 is denoted as PES / PSBMA. 12 / β-FeOOH4 membrane.

[0108] Example 8

[0109] The method for preparing a visible light catalytic self-cleaning oil-water separation membrane provided in Example 8 is basically the same in process and principle as the method for preparing a visible light catalytic self-cleaning oil-water separation membrane described in Example 3 above, except that:

[0110] In step 5, the concentration of the FeCl3·6H2O solution is 6 mg / mL. -1 .

[0111] The remaining steps are the same and will not be repeated here; the visible light catalytic self-cleaning oil-water separation membrane finally prepared in Example 8 is denoted as PES / PSBMA. 12 / β-FeOOH6 membrane.

[0112] Example 9

[0113] The method for preparing a visible light catalytic self-cleaning oil-water separation membrane provided in Example 9 is basically the same in process and principle as the method for preparing a visible light catalytic self-cleaning oil-water separation membrane described in Example 3 above, except that:

[0114] In step 5, the concentration of the FeCl3·6H2O solution is 8 mg / mL. -1 .

[0115] The remaining steps are the same and will not be repeated here; the visible light catalytic self-cleaning oil-water separation membrane finally prepared in Example 9 is denoted as PES / PSBMA. 12 / β-FeOOH8 membrane.

[0116] Comparative Example 1

[0117] The method for preparing an oil-water separation membrane provided in Comparative Example 1 is basically the same as the method for preparing a visible light catalytic self-cleaning oil-water separation membrane described in Example 3 above, except that:

[0118] In step 4, the reaction was carried out under magnetic stirring for 0 h, that is, in Comparative Example 1, the surface of the PES / PES-CPPA membrane was not modified with hydrophilic zwitterionic PSBMA; the membrane material obtained in step 4 is referred to as PES / PSBMA0 membrane.

[0119] The remaining steps are the same and will not be repeated here; the oil-water separation membrane finally prepared in Comparative Example 1 is denoted as PES / PSBMA0 / β-FeOOH0 membrane.

[0120] It should be noted that, since the PES / PSBMA0 membrane is not actually grafted with zwitterionic PSBMA, the Fe... 3+ After treating the PES / PSBMA0 membrane, it will be impossible to mineralize and form β-FeOOH nanoparticles on the surface of the PES / PSBMA0 membrane; therefore, the oil-water separation membrane finally prepared in Comparative Example 1 can be referred to as the PES / PSBMA0 / β-FeOOH0 membrane.

[0121] Comparative Example 2

[0122] The method for preparing an oil-water separation membrane provided in Comparative Example 2 is basically the same as the method for preparing a visible light catalytic self-cleaning oil-water separation membrane described in Example 3 above, except that:

[0123] In step 5, the concentration of the FeCl3·6H2O solution is 0 mg / mL. -1 That is, in Comparative Example 2, Fe was not utilized. 3+ Complexation treatment was performed on the superhydrophilic / underwater superoleophobic film, with a loading of 0 for β-FeOOH nanoparticles.

[0124] The remaining steps are the same and will not be repeated here; the oil-water separation membrane finally prepared in Comparative Example 2 is denoted as PES / PSBMA. 12 / β-FeOOH0 membrane.

[0125] Performance test results analysis and explanation:

[0126] As attached Figure 2 As shown, attached Figure 2 The RAFT reagent of 4-cyanopentanoic acid dithiobenzoate prepared in Example 3 is given in the example. 1 H-NMR spectrum; from the attached Figure 2 As can be seen from the spectrum, each proton has its corresponding chemical shift, indicating that each hydrogen atom in the spectrum has been accurately assigned; thus, it can be confirmed that the RAFT reagent of 4-cyanopentanoic acid dithiobenzoate has been successfully synthesized.

[0127] As attached Figure 3 As shown, attached Figure 3 The preparation of the alkyne-functionalized RAFT reagent in Example 3 is described in [the document / reference]. 1 H-NMR spectrum; from the attached Figure 3 As can be seen, each proton signal exhibits a specific chemical shift, and each proton has its corresponding chemical shift, which fully demonstrates that the alkynyl-functionalized RAFT reagent, namely (4-cyanopentyl propargyl)-dithiobenzoate, was successfully synthesized.

[0128] As attached Figure 4 As shown, attached Figure 4 The ATR-FTIR spectra of PES (a), PES-CH2Cl (b), PES-CH2N3 (c), and PES-CPPA (d) in Example 3 are given to characterize the surface functional groups of unmodified PES, PES-CH2Cl, PES-CH2N3, and PES-CPPA by ATR-FTIR; from the appendix Figure 4 As can be seen from this, PES-CH2Cl at 750 cm -1 The presence of an absorption peak at 2100 cm⁻¹, attributed to the stretching vibration of -C-Cl, indicates the successful chloromethylation reaction of PES; PES-CH₂N₃ at 2100 cm⁻¹ -1 The presence of absorption peaks at 1737 and 1043 cm⁻¹, attributed to the stretching vibration of -N₃, indicates a successful azide reaction; the spectrum shows absorption peaks at 1737 and 1043 cm⁻¹. -1 Absorption peaks were observed at the locations, which were attributed to the stretching vibration of -C=O and the symmetric stretching vibration of -C≡N, respectively. Furthermore, the stretching vibration peak of -N3 was weakened, indicating that the copper-catalyzed azido-alkynyl cyclization addition reaction was successful. The infrared spectroscopy results confirmed the successful preparation of PES-CPPA.

[0129] As attached Figure 5 As shown, attached Figure 5 The text describes PES (a), PES / PES-CPPA membrane (b), and PES / PSBMA in Example 3. 12 ATR-FTIR spectra of membrane (c) and the visible light photocatalytic self-cleaning oil-water separation membrane (d) prepared in Example 7; from the attached... Figure 5 As can be seen from this, the PES membrane at 1316 cm⁻¹... -1 and 1240 cm -1 Characteristic peaks appear at [values ​​missing], attributed to stretching vibrations of -CO and O=S=O bonds; compared to the PES film, peaks at 1726 and 1038 cm⁻¹ appear in the spectrum. -1 Absorption peaks were observed at the locations, attributed to the stretching vibrations of -C=O and the symmetric stretching vibrations of O=S=O, respectively, indicating that the hydrophilic polymer brush PSBMA was successfully grafted onto the membrane surface. During the subsequent in-situ surface mineralization process, FeCl3 hydrolyzed to form β-FeOOH nanorods, generating an 844 cm⁻¹ peak. -1 and 790 cm -1 The new peak is attributed to the tensile vibration of Fe-O; furthermore, at 3500 cm⁻¹ -1 and 3100 cm -1 The broad peaks observed correspond to the stretching vibrations of the -OH groups in O-Fe-OH, further verifying the successful preparation of a visible light catalytic self-cleaning oil-water separation membrane.

[0130] As attached Figure 6 As shown, attached Figure 6 The text presents existing pure PES membranes and the PES / PES-CPPA and PES / PSBMA membranes in Example 3. 12 SEM images of the membrane and the visible light photocatalytic self-cleaning oil-water separation membrane prepared in Example 7; from the attached... Figure 6 As can be seen from the scanning electron microscope observations, the PES / PES-CPPA membrane and PES / PSBMA in Example 3... 12 The membrane and the visible light catalytic self-cleaning oil-water separation membrane prepared in Example 7 exhibit a unique asymmetric structure; specifically, the above membrane material consists of a dense top layer and a porous sublayer, and its structure is mainly due to the transient phase separation phenomenon that occurred in the casting solution during the preparation process; among which, from the attached Figure 6 a1, Appendix Figure 6 b1 and appendix Figure 6 As can be clearly seen in c1, the membrane surface is covered with a large number of nanoscale porous structures, and the pores are uniformly distributed. After the addition of PES-CPPA, the surface structure and morphology of the membrane are hardly affected, as shown in the attached figure. Figure 6 As shown in b1; furthermore, after grafting PSBMA chains, the pores of the PES / PSBMA membrane were partially blocked by the grafted PSBMA layer, resulting in a significant decrease in membrane pore size. Figure 6 As shown in c1; additionally, from the appendix Figure 6 As can be seen in d1, the surface of the visible light catalytic self-cleaning oil-water separation membrane prepared in Example 7 is uniformly distributed with rod-shaped β-FeOOHNPs; furthermore, through the attachment Figure 6 a2, Appendix Figure 6 b2, Appendix Figure 6 c2 and appendix Figure 6 Cross-sectional scanning electron microscope images shown in d2 reveal that the PES / PES-CPPA membrane and PES / PSBMA in Example 3... 12 The membrane and the visible light catalytic self-cleaning oil-water separation membrane prepared in Example 7 both exhibit very similar asymmetric structures in their cross-sections, which contain large and wide finger-shaped pores. It is worth noting that after PSBMA grafting, the internal structure of the PES membrane was not significantly affected, indicating that the grafting process can maintain the basic internal structural integrity of the membrane well.

[0131] As attached Figure 7 As shown, attached Figure 7 The figure shows the WCA variation curves over time for the superhydrophilic / underwater superoleophobic films prepared in Examples 1-6; from the appendix Figure 7As can be seen from the figures, the WCA of the superhydrophilic / underwater superoleophobic films prepared in Examples 1-6 exhibits time variability. The initial WCA of the PES film is 78.2°, which gradually decreases to about 72.6° after 80 s. Compared with the PES film, the initial WCA of the PES / CPPA film is 76.3°, which gradually decreases to about 70.1° after 80 s, showing a slight improvement in hydrophilicity. After introducing the hydrophilic zwitterionic polymer brush PSBMA, the figure shows the degree of decrease in the initial WCA of the PES / PSBMA film at different SBMA grafting times. When the grafting time is 12 h, it decreases to 0° within 80 s. The composite film with a grafting time of 24 h reaches 0° in a very short time (30 s), achieving a completely wetted state. This fully demonstrates the excellent effect of the zwitterionic polymer brush in improving the surface energy and enhancing hydrophilicity of the film, and that the degree of improvement in hydrophilicity becomes more obvious with the extension of grafting time.

[0132] As attached Figure 8 As shown, attached Figure 8 The paper presents PES / PSBMA prepared in Example 3 using different oils. 12 UWOCA diagram on the membrane; from the attached Figure 8 As can be seen from the data, the PES / PSBMA prepared in Example 3... 12 The membrane exhibits excellent underwater oleophobic properties, with underwater contact angles of 1,2-dichloroethane, petroleum ether, n-hexane, and toluene at 130°, 167°, 165°, and 155°, respectively, all at a high level. These results indicate that the PES / PSBMA membrane not only has good hydrophilic properties but also exhibits excellent underwater oleophobicity.

[0133] As attached Figure 9 As shown, attached Figure 9 The figure shows bar charts of the separation flux of pure water for the PES / PSBMA0 / β-FeOOH0 membrane prepared in Comparative Example 1 and the superhydrophilic / underwater superoleophobic membranes prepared in Examples 1-6; from the appendix Figure 9 As can be seen, with the extension of grafting time, the water flux of the membrane material decreases stepwise at grafting times of 0, 4, 8, 12, 16, 20, and 24 h, respectively, to 5960, 4529, 3774, 3145, 2156, 1728, and 1372 L / m. -2 h -1 bar -1 This indicates that grafting zwitterionic PSBMA onto the membrane reduces the membrane pore size, thereby decreasing the membrane flux.

[0134] To analyze the wettability, permeate flux, and separation efficiency of membrane materials, membranes with different PSBMA grafting times were selected for separation experiments of water-in-hexane emulsions. The results of the separation experiments are attached. Figure 10 As shown; Appendix Figure 10 The figure shows the flux and separation efficiency of the PES / PSBMA0 / β-FeOOH0 membrane prepared in Comparative Example 1 and the superhydrophilic / underwater superoleophobic membranes prepared in Examples 1-6 for the hexane-in-water emulsion; from the appendix Figure 10 As can be seen, when the grafting time is 0, 4, 8, 12, 16, 20, and 24 h, the emulsion flux shows a certain decreasing trend, which is 415, 441, 306, 220, 195, 172, and 149 L / m, respectively. -2 h -1 bar -1 After 12 hours of grafting, the emulsion separation efficiency of the PES / PSBMA membrane remained largely unchanged.

[0135] As attached Figure 11 As shown, attached Figure 11 The PES / PSBMA in Example 3 is given in the example. 12 Graphs showing membrane flux and separation efficiency for different types of emulsions; from the attached... Figure 11 As can be seen from this, PES / PSBMA 12 The membrane achieved rapid separation of four different oil-in-water emulsions, with permeate fluxes of 152, 218, 220, and 207.4 L / m², respectively. -2 h -1 bar -1 The corresponding separation efficiencies are 94.79%, 88.47%, 94.77%, and 95.65%. It is worth noting that the separation flux of the membrane is also affected by the physicochemical properties of the separated oil, such as the polarity and viscosity of the oil.

[0136] As attached Figure 12 As shown, attached Figure 12 The PES / PSBMA in Example 3 is given in the example. 12 DLS curves of the membrane before and after separation of different types of emulsions; from the attached... Figure 12 As can be seen, the particle size of the oil droplets in the prepared emulsified oil wastewater is several hundred nanometers and several micrometers; at the same time, although PES / PSBMA 12 The membrane exhibits good performance and high efficiency in the separation of surfactant-stabilized emulsified oil wastewater due to its irregular pore size, which allows for the permeation of small oil droplets. It is suitable for low-viscosity and viscous emulsions.

[0137] As attached Figure 13 As shown, attached Figure 13 The PES / PSBMA prepared in Comparative Example 2 is given. 12 The effect of the β-FeOOHO membrane on permeation flux and MD degradation rate compared to the visible light photocatalytic self-cleaning oil-water separation membranes prepared in Examples 3 and 7-9; (See attached figure) Figure 13As can be seen from Figure a, as the loading of β-FeOOH nanoparticles gradually increased from 0 to 8.0 mg / mL... -1 The permeation flux of the visible light photocatalytic self-cleaning oil-water separation membrane showed a significant decreasing trend. This phenomenon is mainly attributed to the over-packing of magnetic nanoparticles in the membrane matrix, which blocked the mass transfer channels, thus leading to a reduction in permeation flux. Figure 13 As can be seen from b, within the same reaction time, the greater the amount of β-FeOOH nanoparticles loaded on the membrane, the higher the degradation rate of MB. This fully demonstrates that with the increase of β-FeOOH nanoparticle content, the density of active sites on the membrane surface is significantly increased, thereby promoting the decomposition of H2O2, generating more free radicals, and thus accelerating the degradation process of MB. The loading of β-FeOOH nanoparticles combines catalytic degradation function with membrane separation technology to form a dynamic self-cleaning mechanism.

[0138] As attached Figure 14 As shown, attached Figure 14 The PES / PSBMA prepared in Example 3 is given in the example. 12 Cyclic separation tests were conducted on the membrane and the visible light photocatalytic self-cleaning oil-water separation membrane prepared in Example 7; among them, the PES / PSBMA was further investigated through five-cycle separation experiments using a water-in-hexane emulsion. 12 and PES / PSBMA 12 Stability of the β-FeOOH4 membrane.

[0139] From the appendix Figure 14 As can be seen from a, PES / PSBMA 12 After each cycle of soaking in 10% H2O2, the membrane could basically recover its initial flux, but after five cycles, the flux decreased by 30.14%, while the rejection rate stabilized above 90.76%. In contrast, from the attached... Figure 14 As can be seen in b, PES / PSBMA 12 The β-FeOOH4 membrane exhibited superior stability under the same cleaning conditions. After five cycles, the flux decreased slightly, but the rejection rate remained at 96.75%, demonstrating that the introduction of β-FeOOH nanoparticles effectively improved the stability of the membrane material. Furthermore, comparative analysis of the PES / PSBMA prepared in Example 3... 12 The self-cleaning ability of the membrane material was evaluated by the flux changes during filtration and cleaning of the membrane and the visible light catalytic self-cleaning oil-water separation membrane prepared in Example 7; from the attached... Figure 14 c. Appendix Figure 14 As can be seen in d, in multiple loops, PES / PSBMA 12 Flux recovery rate of β-FeOOH4 membrane (F rrThe percentage of pollutants remained consistently above 96.8%, while the rate of irreversible pollution (R) remained relatively low. ir The content remained below 4%, significantly better than the PES / PSBMA prepared in Example 3. 12 The membrane benefits from PES / PSBMA. 12 The synergistic effect of the hydrophilic polymer brush and β-FeOOH nanoparticles on the β-FeOOH4 membrane surface enhances the interaction between the membrane and water molecules, thereby forming a hydration layer. Notably, when oil droplets come into contact with the pre-wetted membrane surface, the hydrophilic membrane surface in air exhibits oleophobicity underwater due to the higher surface tension of water compared to oil. The oil droplets cannot penetrate this underwater oleophobic surface, which only allows water to pass through, thus forming a dynamic physical barrier on the membrane surface that effectively resists oil droplet adsorption. Furthermore, during the cleaning process, the hydroxyl radicals (·OH) generated by β-FeOOH catalyzing H2O2 can oxidize and decompose contaminants on the membrane surface, achieving a dual effect of chemical cleaning and physical rinsing. This "defense-removal" synergistic mechanism endows PES / PSBMA with these properties. 12 / β-FeOOH membranes offer efficient, long-lasting, and stable oil-water separation performance.

[0140] The method for preparing a visible light catalytic self-cleaning oil-water separation membrane according to the present invention involves grafting the RAFT reagent CPPA onto a polyethersulfone molecular chain via click chemistry, preparing an oil-water separation membrane substrate using a non-solvent induced phase separation (NIPS) method, and then grafting a hydrophilic zwitterionic polysulfobetaine methacrylate (PSBMA) onto the PES membrane using RAFT polymerization to obtain a superhydrophilic / underwater superoleophobic membrane (PES / PSBMA membrane). To further improve the membrane's hydrophilicity and impart self-cleaning properties, Fe... 3+ -SO3 on PSBMA - Group complexation further mineralizes β-FeOOH nanoparticles on the membrane surface, resulting in a PES / PSBMA / β-FeOOH membrane with excellent hydrophilicity and self-cleaning properties. The photocatalytic self-cleaning effect of β-FeOOH nanoparticles enables the membrane to exhibit excellent anti-fouling ability when facing pollution, and maintains surface cleanliness and performance stability through a self-cleaning mechanism.

[0141] The superhydrophilic oil-water separation membrane prepared in this invention exhibits high separation flux, excellent oil-water separation efficiency, and excellent separation performance for various oil-in-water emulsions. The superhydrophilic oil-water separation membrane is grafted with a zwitterionic polymer brush possessing excellent hydrophilicity via RAFT grafting, forming a hydration layer on the membrane surface, which significantly reduces pollutant adsorption and deposition. To further enhance the membrane's hydrophilicity and impart self-cleaning properties, Fe... 3+ -SO3 on PSBMA -Group complexation further mineralizes β-FeOOH nanoparticles on the membrane surface, resulting in a PES / PSBMA / β-FeOOH membrane with excellent hydrophilicity and self-cleaning properties. The photocatalytic self-cleaning effect of β-FeOOH nanoparticles enables the membrane to exhibit excellent antifouling ability when facing pollution, and the self-cleaning performance of the membrane provides a new approach and an effective solution.

[0142] In this invention, by controlling the RAFT polymerization time and adjusting the PSBMA grafting rate on the membrane surface, the membrane achieves superhydrophilicity without significant changes to its surface and internal structure. A hydration layer forms on the membrane surface, greatly reducing pollutant adsorption and deposition; it exhibits high separation flux, excellent oil-water separation efficiency, and good separation performance for various oil-in-water emulsions. Further, through Fe... 3+ -SO3 on PSBMA - Group complexation mineralizes β-FeOOH nanoparticles on the membrane surface, resulting in a PES / PSBMA / β-FeOOH membrane with excellent hydrophilicity and self-cleaning properties. The photocatalytic self-cleaning effect of β-FeOOH nanoparticles enables the membrane to exhibit excellent anti-fouling ability when facing pollution, and maintains surface cleanliness and performance stability through a self-cleaning mechanism.

[0143] The above embodiments are merely one of the implementation methods for achieving the technical solution of the present invention. The scope of protection claimed by the present invention is not limited to this embodiment, but also includes any variations, substitutions and other implementation methods that can be easily conceived by those skilled in the art within the scope of the technology disclosed in the present invention.

Claims

1. A method for preparing a visible light photocatalytic self-cleaning oil-water separation membrane, characterized in that, include: Alkyne-functionalized RAFT reagents were prepared using 4-cyanopentanoic acid dithiobenzoate RAFT reagents. By using a click chemical reaction, alkynyl-functionalized RAFT reagents are grafted onto the polymer chain of azide-modified polyether sulfone to obtain RAFT reagent-functionalized polyether sulfone polymers. PES / PES-CPPA membranes were prepared by functionalizing polyethersulfone polymers with RAFT reagents and then using a solvent-inducible phase separation method. Using the RAFT polymerization method, hydrophilic zwitterionic PSBMA was modified on the surface of PES / PES-CPPA film to obtain a superhydrophilic / underwater superoleophobic film. Use Fe 3+ Complexation treatment was performed on the superhydrophilic / underwater superoleophobic film to mineralize and form β-FeOOH nanoparticles on the surface of the superhydrophilic / underwater superoleophobic film, thereby obtaining a visible light catalytic self-cleaning oil-water separation membrane; The preparation process of RAFT reagents based on 4-cyanopentanoic acid dithiobenzoate is as follows: Sodium methoxide in methanol solution, elemental sulfur and anhydrous methanol were mixed, and benzyl chloride was added dropwise. The mixture was heated and stirred to react. After the reaction was completed, the mixture was cooled and filtered to remove salt and methanol, thus obtaining sodium dithiobenzoate solution. An aqueous solution of potassium ferricyanide was added to a sodium dithiobenzoate solution, and the mixture was stirred and reacted at room temperature in the dark. After the reaction was completed, the mixture was filtered to obtain a dithiobenzoic acid dimer. Dithiobenzoic acid dimer, 4,4′-azobis(4-cyanopentanoic acid) and ethyl acetate were mixed, heated and stirred to react, the solvent was removed after reaction, and purified by column chromatography to obtain RAFT reagents of 4-cyanopentanoic acid dithiobenzoic acid esters. The process of grafting alkynyl-functionalized RAFT reagents onto the polymer chains of azide-modified polyethersulfones via click chemical reactions to obtain RAFT reagent-functionalized polyethersulfone polymers is as follows: The polyethersulfone polymer was treated with a chloromethylating agent to obtain chloromethylated polyethersulfone; Chloromethylated polyethersulfone was reacted with sodium azide to obtain azidolated polyethersulfone; Alkyne-functionalized RAFT reagents were mixed with azide-modified polyethersulfones, and RAFT reagent-functionalized polyethersulfone polymers were obtained through click chemistry. Use Fe 3+ The process of complexing a superhydrophilic / underwater superoleophobic film to mineralize β-FeOOH nanoparticles on its surface and obtain a visible-light-catalyzed self-cleaning oil-water separation membrane is as follows: A superhydrophilic / underwater superoleophobic membrane was immersed in FeCl3·6H2O solution for mineralization to obtain a self-cleaning oil-water separation membrane loaded with β-FeOOH nanoparticles. A self-cleaning oil-water separation membrane loaded with β-FeOOH nanoparticles was washed and dried to obtain a visible light catalytic self-cleaning oil-water separation membrane.

2. The method for preparing a visible light catalytic self-cleaning oil-water separation membrane according to claim 1, characterized in that, The process for preparing alkynyl-functionalized RAFT reagents using 4-cyanopentanoic acid dithiobenzoate RAFT reagents is as follows: A RAFT reagent of 4-cyanopentanoic acid dithiobenzoate, propynyl alcohol and dichloromethane were mixed, a catalyst was added, and the mixture was heated and stirred. After the reaction, the solvent was removed and purified by column chromatography to obtain the alkynyl-functionalized RAFT reagent.

3. The method for preparing a visible light catalytic self-cleaning oil-water separation membrane according to claim 1, characterized in that, The process of preparing PES / PES-CPPA membranes by functionalizing polyethersulfone polymers with RAFT reagents and then using a solvent-inducing phase separation method is as follows: The polyethersulfone polymer, RAFT reagent-functionalized polyethersulfone polymer, polyethylene glycol 400 and N,N-dimethylformamide were mixed, heated and stirred until dissolved, and then allowed to stand to remove air bubbles to obtain the casting solution. The casting solution was subjected to phase inversion to obtain a PES / PES-CPPA membrane.

4. The method for preparing a visible light catalytic self-cleaning oil-water separation membrane according to claim 3, characterized in that, The process of phase inversion of the casting solution to obtain a PES / PES-CPPA membrane is as follows: The casting solution is uniformly coated onto a pre-designed substrate, then immersed in a coagulation bath for phase inversion. After removing residual solvent, the substrate is dried to obtain a PES / PES-CPPA membrane. The coagulation bath is a mixed solution of N,N-dimethylformamide and water.

5. The method for preparing a visible light catalytic self-cleaning oil-water separation membrane according to claim 1, characterized in that, The process of modifying the surface of a PES / PES-CPPA film with hydrophilic zwitterionic PSBMA using the RAFT polymerization method to obtain a superhydrophilic / underwater superoleophobic film is as follows: PES / PES-CPPPA membrane and methacryloyl ethyl sulfobetaine were added to anhydrous methanol. After the methacryloyl ethyl sulfobetaine was fully dissolved, an initiator was added to carry out RAFT polymerization to obtain a PSBMA-modified separation membrane. The PSBMA-modified separation membrane was washed and dried to obtain a superhydrophilic / underwater superoleophobic membrane.

6. A visible light photocatalytic self-cleaning oil-water separation membrane, characterized in that, The visible light catalytic self-cleaning oil-water separation membrane is prepared using the method described in any one of claims 1-5.

7. The application of the visible light photocatalytic self-cleaning oil-water separation membrane as described in claim 6, characterized in that, The visible light catalytic self-cleaning oil-water separation membrane is used in the oil-water separation process of emulsified oily wastewater.

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