An oil-water separation membrane, a preparation method and application thereof
By preparing a superhydrophilic/underwater oleophobic oil-water separation membrane, the problems of low permeation flux and easy fouling and clogging of existing oil-water separation membranes were solved, achieving a highly efficient oil-water separation effect.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Patents(China)
- Current Assignee / Owner
- SHAANXI UNIV OF SCI & TECH
- Filing Date
- 2024-05-31
- Publication Date
- 2026-05-29
AI Technical Summary
Existing oil-water separation membranes have low permeation flux and are prone to surface fouling and pore blockage, resulting in low separation efficiency.
Using CDB as a chain transfer agent, Macro-GMA was prepared by RAFT polymerization with GMA as the monomer. Combined with PVDF and EDA crosslinking, zwitterionic pSBMA was modified on the membrane substrate surface by RAFT polymerization to prepare a superhydrophilic/underwater oleophobic oil-water separation membrane.
It improves the permeation flux and separation efficiency of oil-water separation membranes, reduces membrane surface fouling and pore blockage, and achieves efficient separation of different oil-in-water emulsions.
Smart Images
Figure CN118594273B_ABST
Abstract
Description
Technical Field
[0001] This invention belongs to the field of membrane separation materials technology, and specifically relates to an oil-water separation membrane, its preparation method, and its application. Background Technology
[0002] Industrial wastewater discharge and crude oil spills have caused serious harm to ecosystems and humans, becoming one of the most serious forms of environmental pollution. With the rapid development of the social economy, industries such as textiles, steel, food, leather, and petrochemicals generate a large amount of stable oily wastewater containing emulsifiers during the production process. Among these, the effective separation of surfactant-stabilized oily wastewater has become a crucial issue in oily wastewater treatment and an environmental problem that urgently needs to be solved.
[0003] Currently, membrane separation is commonly used to treat oily wastewater that is stabilized by surfactants. However, during the separation process using existing oil-water separation membranes, the membrane surface is prone to fouling and pore blockage due to the low permeation flux, resulting in a decrease in permeation flux and thus a low separation efficiency. Summary of the Invention
[0004] In view of the technical problems existing in the prior art, the present invention provides an oil-water separation membrane, its preparation method and application, to solve the technical problem that the existing oil-water separation membrane has a low permeation flux, is prone to membrane surface fouling and membrane pore blockage, resulting in a decrease in permeation flux and a low separation efficiency.
[0005] To achieve the above objectives, the technical solution adopted by the present invention is as follows:
[0006] This invention provides a method for preparing an oil-water separation membrane, comprising:
[0007] Macro-GMA was obtained by RAFT polymerization using CDB as a chain transfer agent and GMA as a monomer.
[0008] Polyvinylidene fluoride, Macro-GMA, NMP and ammonia are mixed and heated and stirred to obtain a casting solution;
[0009] A membrane substrate was prepared using the casting solution;
[0010] The epoxy groups of GMA in the membrane substrate were crosslinked using EDA to obtain a crosslinked substrate;
[0011] The oil-water separation membrane was obtained by modifying the cross-linked substrate surface with zwitterionic pSBMA using the RAFT polymerization method.
[0012] Furthermore, the synthesis process of the CDB is as follows:
[0013] 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 to react. After the reaction was completed, the mixture was cooled and filtered to remove salt and methanol to obtain the reaction product.
[0014] The reaction product was purified to obtain dithiobenzoic acid;
[0015] The dithiobenzoic acid, α-methylstyrene, and carbon tetrachloride were mixed, heated and stirred to react, the solvent was removed after the reaction, and the CDB was obtained by column chromatography purification.
[0016] Furthermore, the process of obtaining Macro-GMA via RAFT polymerization using CDB as a chain transfer agent and GMA as a monomer is as follows:
[0017] GMA, azobisisobutyronitrile and CDB were mixed to obtain a purple-red mixed solution;
[0018] The operation of removing dissolved oxygen from the purple-red mixed solution yields a deoxygenated mixed solution;
[0019] The deoxygenated mixed solution was heated and stirred to react, and after the reaction was completed, it was cooled to obtain the reaction product.
[0020] The product after the reaction was purified by repeated precipitation and dissolution in tetrahydrofuran and cold methanol, and then dried to obtain the Macro-GMA.
[0021] Furthermore, the process of mixing polyvinylidene fluoride, Macro-GMA, NMP, and ammonia, and heating and stirring to obtain the casting solution is as follows:
[0022] Polyvinylidene fluoride was completely dissolved in NMP to obtain a homogeneous and transparent solution; Macro-GMA was completely dissolved in NMP to obtain a Macro-GMA solution.
[0023] After the homogeneous and transparent solution is mixed evenly with the Macro-GMA solution, ammonia water is added, and the mixture is heated and stirred to obtain the casting solution.
[0024] Furthermore, the process of preparing the membrane substrate using the casting solution is as follows:
[0025] Remove air bubbles from the casting solution to obtain a uniform casting solution;
[0026] The uniform casting solution is evenly coated onto a glass plate to obtain a liquid film;
[0027] A glass plate with a liquid film is transferred to a coagulation bath for phase transformation, and then the residual solvent is removed to obtain the film substrate.
[0028] Furthermore, the process of crosslinking the epoxy groups of GMA in the membrane substrate using EDA to obtain the crosslinked substrate is as follows:
[0029] The membrane substrate is placed in an aqueous solution of EDA to undergo a crosslinking reaction, thereby obtaining the crosslinked substrate.
[0030] Furthermore, the process of modifying the cross-linked substrate surface with zwitterionic pSBMA using the RAFT polymerization method to obtain the oil-water separation membrane is as follows:
[0031] SBMA was added to anhydrous methanol, and after the SBMA was fully dissolved, an initiator was added to carry out RAFT polymerization to obtain a pSBMA-modified separation membrane.
[0032] The pSBMA-modified separation membrane was washed with ethanol and deionized water to obtain the oil-water separation membrane.
[0033] Furthermore, the initiator is AIBN.
[0034] The present invention also provides an oil-water separation membrane, which is prepared by the method described above.
[0035] The present invention also provides an application of an oil-water separation membrane, which is used to separate oil from oily wastewater.
[0036] Compared with the prior art, the beneficial effects of the present invention are as follows:
[0037] The oil-water separation membrane and its preparation method provided by this invention contain a macromolecular reversible addition-fragmentation chain transfer agent, which can be grafted onto the membrane surface via RAFT polymerization with zwitterionic pSBMA exhibiting excellent hydrophilicity. During the oil-water separation process, a hydration layer can be formed on the membrane surface, resulting in a high permeate flux, excellent oil-water separation efficiency, and excellent separation performance for different oil-in-water emulsions, effectively reducing membrane surface fouling and pore blockage. Specifically, a macromolecular chain transfer agent, Macro-GMA, is prepared via reversible RAFT polymerization using CDB as the chain transfer agent and GMA as the monomer. Subsequently, a casting solution is prepared using polyvinylidene fluoride, Macro-GMA, NMP, and ammonia. Next, the Macro-GMA in the membrane substrate prepared using the casting solution is crosslinked using EDA. Finally, the surface of the membrane substrate is modified with hydrophilic zwitterionic pSBMA using RAFT polymerization, thereby preparing an oil-water separation membrane with superhydrophilic / underwater oleophobic properties.
[0038] Furthermore, using PVDF as the substrate for the separation membrane, GMA as a macromolecular chain transfer agent present in the membrane substrate, pSBMA as a hydrophilic polymer brush, and AIBN as an initiator, a superhydrophilic underwater oleophobic membrane was prepared. The resulting superhydrophilic / underwater oleophobic membrane can separate different oil-in-water emulsions, providing a new idea and method for the preparation of oil-water separation membranes and the prevention of membrane surface fouling and pore blockage. Attached Figure Description
[0039] Figure 1 The NMR spectrum of CDB in Example 1;
[0040] Figure 2 The NMR spectrum of the Macro-GMA in Example 1;
[0041] Figure 3 The images show SEM images of the oil-water separation membrane M1 in Example 1 at different magnifications; where, Figure 3 a is a SEM image of oil-water separation membrane M1 at a magnification of 1K; Figure 3 b is a SEM image of oil-water separation membrane M1 at a magnification of 10K; Figure 3 c is a SEM image of oil-water separation membrane M1 at a magnification of 5K; Figure 3 d is the SEM image of oil-water separation membrane M1 at a magnification of 5K;
[0042] Figure 4 The images show the AFM diagrams of oil-water separation membranes M1-M5 in Examples 1-5; where, Figure 4 a is the AFM image of the oil-water separation membrane M1 prepared in Example 1; Figure 4 b is the AFM image of the oil-water separation membrane M2 prepared in Example 2; Figure 4 c is the AFM image of the oil-water separation membrane M3 prepared in Example 3; Figure 4 d is the AFM image of the oil-water separation membrane M4 prepared in Example 4; Figure 4 e is the AFM image of the oil-water separation membrane M5 prepared in Example 5;
[0043] Figure 5 The images show the infrared spectra of oil-water separation membranes M1-M5 in Examples 1-5; where curve a is the infrared spectrum of oil-water separation membrane M1 prepared in Example 1; curve b is the infrared spectrum of oil-water separation membrane M2 prepared in Example 2; curve c is the infrared spectrum of oil-water separation membrane M3 prepared in Example 3; curve d is the infrared spectrum of oil-water separation membrane M4 prepared in Example 4; and curve e is the infrared spectrum of oil-water separation membrane M5 prepared in Example 5.
[0044] Figure 6Figure 1 shows the water contact angle of the oil-water separation membranes M1-M5 in Examples 1-5; wherein, Figure M1 is the water contact angle of the oil-water separation membrane M1 prepared in Example 1; Figure M2 is the water contact angle of the oil-water separation membrane M2 prepared in Example 2; Figure M3 is the water contact angle of the oil-water separation membrane M3 prepared in Example 3; Figure M4 is the water contact angle of the oil-water separation membrane M4 prepared in Example 4; and Figure M5 is the water contact angle of the oil-water separation membrane M5 prepared in Example 5.
[0045] Figure 7 The bar chart shows the underwater oil 1,2-dichloroethane contact angle of oil-water separation membranes M1-M5 in Examples 1-5;
[0046] Figure 8 The bar chart shows the separation flux of oil-water separation membranes M1-M5 in Examples 1-5; wherein, Figure 8 a is a bar chart showing the separation flux of pure water by the oil-water separation membranes M1-M5 prepared in Examples 1-5; Figure 8 b is a bar chart showing the separation flux of the oil-water separation membranes M1-M5 prepared in Examples 1-5 for the 1,2-dichloroethane emulsion in water. Figure 8 c is a bar chart showing the separation flux of the oil-water separation membranes M1-M5 prepared in Examples 1-5 for petroleum ether emulsions in water; Figure 8 d is a bar chart showing the separation flux of the oil-water separation membranes M1-M5 prepared in Examples 1-5 for the n-hexane-in-water emulsion; Figure 8 e is a bar chart showing the separation flux of the oil-water separation membranes M1-M5 prepared in Examples 1-5 to the water-in-toluene emulsion;
[0047] Figure 9 The bar chart shows the separation efficiency of oil-water separation membranes M1-M5 in Examples 1-5; where, Figure 9 a is a bar chart showing the separation efficiency of the oil-water separation membranes M1-M5 prepared in Examples 1-5 for the water-encapsulated 1,2-dichloroethane emulsion; Figure 9 b is a bar chart showing the separation efficiency of the oil-water separation membranes M1-M5 prepared in Examples 1-5 for petroleum ether emulsions in water; Figure 9 c is a bar chart showing the separation efficiency of the oil-water separation membranes M1-M5 prepared in Examples 1-5 for the water-in-hexane emulsion; Figure 9 d is a bar chart showing the separation efficiency of the oil-water separation membranes M1-M5 prepared in Examples 1-5 for water-in-toluene emulsions;
[0048] Figure 10 The image shows the DLS curves of the oil-water separation membrane M3 in Example 3 before and after emulsion separation; where, Figure 10 DLS curve of 1,2-dichloroethane emulsion (a) Figure 10 a1 is the DLS curve of the filtrate of 1,2-dichloroethane; Figure 10 b is the DLS curve of the petroleum ether emulsion; Figure 10 b1 is the DLS curve of petroleum ether filtrate; Figure 10 c is the DLS curve of the n-hexane emulsion; Figure 10 c1 is the DLS curve of the n-hexane filtrate; Figure 10 d represents the DLS curve of the toluene emulsion; Figure 10 d1 is the DLS curve of the toluene filtrate. Detailed Implementation
[0049] To make the technical problems solved by the present invention, the technical solutions, and the beneficial effects clearer, the following specific embodiments provide a further detailed description of the present invention. It should be understood that the specific embodiments described herein are merely illustrative and are not intended to limit the scope of the invention.
[0050] This invention provides a method for preparing an oil-water separation membrane, comprising the following steps:
[0051] Step 1: Preparation of 2-phenylpropyl-2-dithiobenzoic acid (CDB); wherein, CDB serves as a small-molecule chain transfer agent; the synthesis process of CDB is as follows:
[0052] A methanol solution of sodium methoxide, elemental sulfur, and anhydrous methanol were added to a three-necked round-bottom flask, and then benzyl chloride was added dropwise to obtain a mixed solution. The mixed solution was heated and stirred to react, and after the reaction was completed, the entire reaction system was cooled. The reaction system was then filtered to remove the salts generated during the reaction. Then, methanol removal was performed to obtain the reaction product. The reaction product was then repeatedly extracted and purified using diethyl ether to obtain dithiobenzoic acid. Dithiobenzoic acid, α-methylstyrene, and carbon tetrachloride were added to a three-necked flask and mixed, and the mixture was heated and stirred to react. After the reaction, the solvent was removed to obtain a crude product. The crude product was purified by column chromatography to obtain CDB.
[0053] Step 2: Using CDB as a chain transfer agent and glycidyl methacrylate (GMA) as a monomer, Macro-GMA is obtained by reversible addition-fragmentation chain transfer radical polymerization (RAFT); wherein, the Macro-GMA serves as a large-molecule chain transfer agent; the preparation process of the Macro-GMA is as follows:
[0054] GMA, AIBN, and CDB were added to a Schlenk tube to obtain a purple-red mixed solution. The purple-red mixed solution was purged with dry nitrogen to remove dissolved oxygen, resulting in a deoxygenated mixed solution. The deoxygenated mixed solution was heated and stirred, and after the reaction was completed, it was rapidly cooled to room temperature to obtain the product. The product was purified by repeated precipitation and dissolution in tetrahydrofuran and cold methanol, and then dried to obtain Macro-GMA.
[0055] Step 3: Mix polyvinylidene fluoride (PVDF), Macro-GMA, N-methylpyrrolidone (NMP), and ammonia water, and heat and stir to obtain a casting solution; wherein, the process for preparing the casting solution is as follows:
[0056] PVDF was added to a three-necked flask containing NMP, and the mixture was heated and stirred to fully dissolve the PVDF, resulting in a homogeneous and transparent solution. Macro-GMA was completely dissolved in NMP to obtain a Macro-GMA solution. The homogeneous and transparent solution and the Macro-GMA solution were mixed and stirred thoroughly. Ammonia was then added, and the mixture was heated and stirred continuously to obtain the casting solution.
[0057] Step 4: Prepare the membrane substrate using the casting solution; the process of obtaining the membrane substrate is as follows:
[0058] Remove air bubbles from the casting solution to obtain a homogeneous casting solution; pour the homogeneous casting solution onto a glass plate and use a doctor blade to evenly coat it to obtain a liquid film on the glass plate; then, transfer the glass plate with the liquid film to a coagulation bath for phase inversion to obtain a solid film; wherein, the coagulation bath is a mixed solution of water and ethanol; transfer the glass plate with the solid film to deionized water to remove residual volume, thereby obtaining a PVDF oil-water separation membrane substrate, i.e., the membrane substrate.
[0059] Step 5: Crosslink the epoxy groups of GMA in the membrane substrate using ethylenediamine (EDA) to obtain a crosslinked substrate. The specific process is as follows: EDA is added to deionized water to obtain an aqueous solution of EDA; the membrane substrate is placed in the aqueous solution of EDA to carry out a crosslinking reaction, so as to crosslink Macro-GMA in the membrane substrate using EDA to obtain a crosslinked substrate.
[0060] Step 6: Using sulfobetaine methacrylate (SBMA) as a monomer, zwitterionic pSBMA is modified on the surface of the crosslinked substrate by RAFT polymerization to obtain an oil-water separation membrane; the specific process is as follows:
[0061] SBMA, an initiator, and anhydrous methanol were added to a three-necked separable round-bottom flask. Then, SBMA was added to anhydrous methanol, and after the SBMA was fully dissolved, the initiator was added to carry out RAFT polymerization to obtain a pSBMA-modified separation membrane. The initiator was AIBN. The pSBMA-modified separation membrane was washed with ethanol and deionized water to obtain the oil-water separation membrane.
[0062] Preparation principle:
[0063] The method for preparing the oil-water separation membrane of the present invention firstly synthesizes 2-phenylpropyl-2-yl dithiobenzoic acid (CDB); using the synthesized CDB as a small-molecule chain transfer agent, a macro-molecule chain transfer agent Macro-GMA is prepared by reversible addition-fragmentation chain transfer radical polymerization (RAFT) using glycidyl methacrylate (GMA) as a monomer; then, a casting solution is prepared using PVDF, Macro-GMA, NMP, and ammonia; the casting solution is coated onto a glass plate using a blade coating process and, after phase inversion, a membrane substrate is obtained; next, the Macro-GMA in the membrane substrate is crosslinked using ethylenediamine (EDA); finally, the crosslinked substrate surface is treated with RAFT polymerization. This invention modifies hydrophilic zwitterionic methacrylate sulfobetaine (pSBMA) to prepare an oil-water separation membrane with superhydrophilic underwater oleophobic properties. In this invention, Macro-GMA is introduced into the PVDF membrane substrate, and then the epoxy end groups of GMA are crosslinked using EDA, improving the hydrophilicity of the PVDF membrane substrate. Simultaneously, the effective modification of the hydrophilic polymer brushes on the membrane surface is ensured. Since one SBMA molecule can bind eight water molecules, the pSBMA modified on the membrane surface via RAFT polymerization significantly improves the membrane's hydrophilicity. Furthermore, the polymer brushes on the membrane surface and the crosslinked GMA on the substrate enhance membrane wettability, thereby increasing membrane flux and separation efficiency.
[0064] In this invention, when the prepared oil-water separation membrane is used to separate oil-containing wastewater, a hydration layer can be formed on the membrane surface, so that the oil-water separation membrane has high permeation flux, excellent oil-water separation efficiency and separation performance for different oil-in-water emulsions, effectively reducing membrane surface fouling and membrane pore blockage problems.
[0065] Example 1
[0066] This embodiment 1 provides a method for preparing an oil-water separation membrane, including the following steps:
[0067] Step 1: Add a methanol solution of sodium methoxide, 8.00 g of elemental sulfur, and 160.00 mL of anhydrous methanol to a 500 mL three-necked round-bottom flask. Then, add 15.75 g of benzyl chloride dropwise at room temperature to obtain a mixed solution. The mass concentration of the methanol solution of sodium methoxide is greater than 50%. Heat the mixed solution to 70 °C and stir for 18 h. After the reaction is complete, cool the entire reaction system to 5 °C. Then, filter the reaction system to remove the salts generated during the reaction. Finally, remove methanol to obtain the reaction product.
[0068] Step 2: Add the reaction product to 100 mL of deionized water and wash three times with diethyl ether. Then, add a predetermined amount of diethyl ether and 250 mL of 1.0 M hydrochloric acid to extract dithiobenzoic acid from the reaction product into the ether layer, and wash the ether layer three times with deionized water. Next, add 200 mL of deionized water and 250 mL of 1.0 M NaOH solution to react and obtain sodium dithiobenzoate. Then, extract sodium dithiobenzoate into the aqueous layer and wash the aqueous layer three times with diethyl ether. Next, add a predetermined amount of diethyl ether and 250 mL of 1.0 M hydrochloric acid to extract dithiobenzoic acid into the ether layer, wash the ether layer three times with deionized water, and dry with anhydrous Na2SO4. Finally, remove the solvent by rotary evaporation to obtain an oily product; wherein the oily product is dithiobenzoic acid.
[0069] Step 3: Weigh 10.59 g of dithiobenzoic acid and 10.0 g of α-methylstyrene, and measure 40 mL of carbon tetrachloride; add dithiobenzoic acid, α-methylstyrene and carbon tetrachloride into a three-necked flask, heat to 70 °C under a nitrogen atmosphere, react for 6 h and then remove the solvent to obtain the crude product; using n-hexane as the eluent, obtain a dark purple oily 2-phenylpropyl-2-yl dithiobenzoic acid (CDB) by column chromatography.
[0070] Step 4: 4.3 g of GMA, 24.6 mg of AIBN, 0.2 g of CDB, and a magnetic particle were added to a Schlenk tube to obtain a purple-red mixed solution. The purple-red mixed solution was purged with dry nitrogen and subjected to three freeze-dissolve cycles to remove dissolved oxygen, resulting in a deoxygenated mixed solution. The Schlenk tube containing the deoxygenated mixed solution was sealed under vacuum and immersed in an oil bath at 65°C. After 6 hours, the reaction was stopped, and the reaction tube was rapidly cooled to room temperature with cold water to obtain the reaction product. The reaction product was purified by repeated precipitation and dissolution three times in tetrahydrofuran (THF) and cold methanol, and then vacuum dried at room temperature to obtain a red powder of Macro-GMA.
[0071] Step 5: Add 1g of PVDF to a three-necked flask containing 13mL of NMP, heat and stir at 65℃ for 8h to fully dissolve the PVDF and obtain a homogeneous and transparent solution; completely dissolve 0.1g of Macro-GMA in 2mL of NMP to obtain a Macro-GMA solution; mix the homogeneous and transparent solution with the Macro-GMA solution, stir thoroughly, add 200μL of ammonia water, and continue heating and stirring to obtain the casting solution.
[0072] Step 6: Remove air bubbles from the casting solution using vacuum to obtain a uniform casting solution; pour the uniform casting solution onto a glass plate and uniformly coat it with a 400μm thick scraper to obtain a liquid film on the glass plate; then, transfer the glass plate with the liquid film to a coagulation bath for phase transformation to obtain a solid phase film; wherein, the coagulation bath is water; after the glass plate with the solid phase film has been left in the coagulation bath for 24 hours, it is transferred to deionized water to remove residual volume, thus obtaining the PVDF oil-water separation membrane substrate, i.e., the membrane substrate.
[0073] Step 5: Add 4 mL of EDA to 100 mL of deionized water to obtain an aqueous solution of EDA; place the membrane substrate in the aqueous solution of EDA and stir at 25°C for 24 h to carry out a crosslinking reaction, so as to crosslink the Macro-GMA in the membrane substrate using EDA to obtain the crosslinked substrate.
[0074] Step 6: Add 2.4 g of SBMA, 30.0 mg of AIBN, and 200 mL of anhydrous methanol to a three-necked separable round-bottom flask; then, add SBMA to the anhydrous methanol, and after the SBMA is fully dissolved, add AIBN. After 300 min under nitrogen protection, start RAFT polymerization to obtain a pSBMA-modified separation membrane; the entire reaction is carried out at 65 °C under nitrogen atmosphere and stirring for 24 h; then, wash the pSBMA-modified separation membrane three times with ethanol and deionized water to obtain the oil-water separation membrane, which is labeled as oil-water separation membrane M1; the oil-water separation membrane is stored in deionized water for later use.
[0075] Example 2
[0076] The preparation method of the oil-water separation membrane provided in Example 2 is basically the same as the preparation method of the oil-water separation membrane described in Example 1 above in terms of process and principle; the difference is that: in step 6 of Example 2, the coagulation bath is a mixed solution of water and ethanol; wherein, the volume fraction of ethanol is 5%; and the oil-water separation membrane prepared in Example 2 is marked as oil-water separation membrane M2.
[0077] Example 3
[0078] The preparation method of the oil-water separation membrane provided in Example 3 is basically the same as the preparation method of the oil-water separation membrane described in Example 1 above in terms of process and principle; the difference is that: in step 6 of Example 3, the coagulation bath is a mixed solution of water and ethanol; wherein, the volume fraction of ethanol is 10%; and the oil-water separation membrane prepared in Example 3 is marked as oil-water separation membrane M3.
[0079] Example 4
[0080] The preparation method of the oil-water separation membrane provided in Example 4 is basically the same as the preparation method of the oil-water separation membrane described in Example 1 above in terms of process and principle; the difference is that: in step 6 of Example 4, the coagulation bath is a mixed solution of water and ethanol; wherein, the volume fraction of ethanol is 15%; and the oil-water separation membrane prepared in Example 4 is marked as oil-water separation membrane M4.
[0081] Example 5
[0082] The preparation method of the oil-water separation membrane provided in Example 5 is basically the same as the preparation method of the oil-water separation membrane described in Example 1 above in terms of process and principle; the difference is that: in step 6 of Example 5, the coagulation bath is a mixed solution of water and ethanol; wherein, the volume fraction of ethanol is 20%; and the oil-water separation membrane prepared in Example 5 is marked as oil-water separation membrane M5.
[0083] Performance testing:
[0084] The structure and performance of the oil-water separation membranes M1-M5 prepared in Examples 1-5 above were tested and analyzed, and the specific results are as follows:
[0085] As attached Figure 1-2 As shown, attached Figure 1 The NMR spectrum of CDB in Example 1 is shown in the attached figure. Figure 2 The attached diagram shows the Macro-GMA NMR spectrum of Example 1; from the appendix... Figure 1-2 As can be seen from the attached Figure 1 and attached Figure 2 Each proton on CDB and Macro-GMA is represented by 1 The chemical shifts in the H NMR spectrum, where each hydrogen atom is assigned, indicate that the organic compounds were successfully synthesized.
[0086] As attached Figure 3 As shown, attached Figure 3 The paper presents SEM images of the oil-water separation membrane M1 in Example 1 at different magnifications; among them, Figure 3 a is a SEM image of oil-water separation membrane M1 at a magnification of 1K; Figure 3 b is a SEM image of oil-water separation membrane M1 at a magnification of 10K; Figure 3 c is a SEM image of oil-water separation membrane M1 at a magnification of 5K; Figure 3 d is a SEM image of oil-water separation membrane M1 at a magnification of 5K; from the attached... Figure 3 As can be seen, the surface of the oil-water separation membrane M1 has a rich and relatively uniform pore structure, and the membrane surface obviously exhibits a rough structure.
[0087] As attached Figure 4 As shown, attached Figure 4 The AFM diagrams of oil-water separation membranes M1-M5 in Examples 1-5 are given; among them, Figure 4 a is the AFM image of the oil-water separation membrane M1 prepared in Example 1; Figure 4 b is the AFM image of the oil-water separation membrane M2 prepared in Example 2; Figure 4 c is the AFM image of the oil-water separation membrane M3 prepared in Example 3; Figure 4 d is the AFM image of the oil-water separation membrane M4 prepared in Example 4; Figure 4 e is the AFM image of the oil-water separation membrane M5 prepared in Example 5; from the attached... Figure 4 As can be seen, the surface roughness of oil-water separation membranes M1-M5 are 190.9 nm, 131 nm, 90.4 nm, 62.59 nm, and 72.31 nm, respectively. Comparison reveals that as the ethanol content in the coagulation bath increases, the surface roughness of oil-water separation membranes M1-M5 shows a trend of first decreasing and then increasing. When PVDF membranes are hydrophilically modified and used for the separation of oil-in-water emulsions, because the density of water is greater than that of most oil, it combines with the rough structure of the membrane surface to form a hydration layer, blocking the oil above the membrane and protecting the membrane pores and surface from clogging and contamination by oil droplets.
[0088] As attached Figure 5 As shown, attached Figure 5 The infrared spectra of oil-water separation membranes M1-M5 in Examples 1-5 are given below; where, curve a is the infrared spectrum of oil-water separation membrane M1 prepared in Example 1; curve b is the infrared spectrum of oil-water separation membrane M2 prepared in Example 2; curve c is the infrared spectrum of oil-water separation membrane M3 prepared in Example 3; curve d is the infrared spectrum of oil-water separation membrane M4 prepared in Example 4; and curve e is the infrared spectrum of oil-water separation membrane M5 prepared in Example 5. Figure 5 It can be seen from this that 1038cm -1 The infrared absorption peak can be attributed to the characteristic absorption peak of C=S in Macro-GMA; 3670 cm⁻¹ -1 And 3775cm -1 The absorption peak at -NH2 indicates that the epoxy groups in GMA were successfully crosslinked by EDA; 1180 cm⁻¹-1 The peak at 1721 cm⁻¹ can be attributed to the S=O absorption peak in pSBMA. -1 The infrared absorption peaks at the point are attributed to the C=O absorption peaks in Macro-GMA and pSBMA, confirming that Macro-GMA was successfully introduced into the membrane matrix and that pSBMA was successfully modified onto the membrane surface.
[0089] As attached Figure 6-7 As shown, attached Figure 6 The diagram shows the water contact angles of the oil-water separation membranes M1-M5 in Examples 1-5. Figure 6 The appendix provides underwater contact angle histograms of oil-water separation membranes M1-M5 prepared in Examples 1-5 with 1,2-dichloroethane. Specifically, Figure M1 shows the water contact angle of oil-water separation membrane M1 prepared in Example 1; Figure M2 shows the water contact angle of oil-water separation membrane M2 prepared in Example 2; Figure M3 shows the water contact angle of oil-water separation membrane M3 prepared in Example 3; Figure M4 shows the water contact angle of oil-water separation membrane M4 prepared in Example 4; and Figure M5 shows the water contact angle of oil-water separation membrane M5 prepared in Example 5. Figure 6-7 As can be seen, the oil-water separation membranes M1-M5 exhibit excellent wetting properties in air. The water droplets spread completely immediately upon exiting the syringe needle, and the water vapor affinity (WCA) becomes 0. This is mainly because pSBMA has excellent hydrophilic properties; one SBMA molecule can bind eight water molecules. The UWOCA of 1,2-dichloroethane in the oil-water separation membranes M1-M5 are 127°, 131°, 132°, 116°, and 118°, respectively. The results indicate that the prepared oil-water separation membranes possess excellent hydrophilic properties and underwater oleophobic properties.
[0090] As attached Figure 8 As shown, attached Figure 8 The figure shows bar charts of the separation flux of oil-water separation membranes M1-M5 in Examples 1-5; wherein, Figure 8 a is a bar chart showing the separation flux of pure water by the oil-water separation membranes M1-M5 prepared in Examples 1-5; Figure 8 b is a bar chart showing the separation flux of the oil-water separation membranes M1-M5 prepared in Examples 1-5 for the 1,2-dichloroethane emulsion in water. Figure 8 c is a bar chart showing the separation flux of the oil-water separation membranes M1-M5 prepared in Examples 1-5 for petroleum ether emulsions in water; Figure 8 d is a bar chart showing the separation flux of the oil-water separation membranes M1-M5 prepared in Examples 1-5 for the n-hexane-in-water emulsion; Figure 8 e is a bar chart showing the separation flux of the oil-water separation membranes M1-M5 prepared in Examples 1-5 for water-in-toluene emulsions; from the appendix Figure 8As can be seen, all membranes exhibit high permeation flux for pure water, with the oil-water separation membrane M2 showing the highest permeation flux at 1707.2 L / m². -2 h -1 Comparative analysis revealed that, under gravity-driven conditions only, the M3 oil-water separation membrane exhibited high separation flux and efficiency for the four types of oil-in-water emulsions, with separation fluxes reaching 198.5 Lm. -2 h -1 258.2Lm -2 h -1 169.8Lm -2 h -1 162.5Lm -2 h -1 .
[0091] As attached Figure 9 As shown, attached Figure 9 The figure shows bar charts of the separation efficiency of oil-water separation membranes M1-M5 in Examples 1-5; wherein, Figure 9 a is a bar chart showing the separation efficiency of the oil-water separation membranes M1-M5 prepared in Examples 1-5 for the water-encapsulated 1,2-dichloroethane emulsion; Figure 9 b is a bar chart showing the separation efficiency of the oil-water separation membranes M1-M5 prepared in Examples 1-5 for petroleum ether emulsions in water;
[0092] Figure 9 c is a bar chart showing the separation efficiency of the oil-water separation membranes M1-M5 prepared in Examples 1-5 for the water-in-hexane emulsion; Figure 9 d is a bar chart showing the separation efficiency of oil-water separation membranes M1-M5 prepared in Examples 1-5 for water-in-toluene emulsions; from the appendix Figure 9 The separation efficiencies of oil-water separation membranes M1-M5 for four different oil-in-water emulsions are presented; among them, the separation efficiencies of oil-water separation membrane M3 for the four emulsions are 71.0%, 92.7%, 96.3%, and 88.9%, respectively.
[0093] As attached Figure 10 As shown, attached Figure 10 The following are examples: DLS curves of oil-water separation membrane M3 before and after emulsion separation; DLS curves of oil-water separation membrane M3 before and after emulsion separation in Example 3; wherein... Figure 10 DLS curve of 1,2-dichloroethane emulsion (a) Figure 10 a1 is the DLS curve of the filtrate of 1,2-dichloroethane; Figure 10 b is the DLS curve of the petroleum ether emulsion; Figure 10 b1 is the DLS curve of petroleum ether filtrate; Figure 10 c is the DLS curve of the n-hexane emulsion; Figure 10 c1 is the DLS curve of the n-hexane filtrate; Figure 10d represents the DLS curve of the toluene emulsion; Figure 10 d1 is the DLS curve of the toluene filtrate; from the attached... Figure 10 As can be seen, after all the emulsions were separated by the oil-water separation membrane M3, the oil droplet size distribution became significantly smaller, indicating that larger oil droplets were retained after passing through the oil-water separation membrane M3.
[0094] The oil-water separation membrane, its preparation method, and its application described in this invention utilize synthesized CDB as a chain transfer agent and glycidyl methacrylate (GMA) as a monomer to prepare a macromolecular chain transfer agent, Macro-GMA, via reversible addition-fragmentation chain transfer radical polymerization (RAFT). Ethylenediamine (EDA) is used to crosslink the macromolecular RAFT agent of Macro-GMA in the prepared membrane substrate. Hydrophilic zwitterionic sulfobetaine methacrylate (pSBMA) is then modified onto the surface of the membrane substrate using RAFT polymerization to prepare the oil-water separation membrane. This invention introduces the macromolecular RAFT reagent Macro-GMA into the membrane matrix, enabling multiple surface hydrophilic modifications during membrane post-modification. The pSBMA polymer brush prepared by RAFT polymerization on the membrane surface significantly improves the membrane's hydrophilicity, resulting in high separation flux and efficiency for different oil-in-water emulsions. Specifically, combining Macro-GMA with polymethacryloylethyl sulfobetaine (pSBMA) not only improves the membrane surface's hydrophilicity but also allows for subsequent hydrophilic modification of the membrane through RAFT polymerization of Macro-GMA.
[0095] 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 an oil-water separation membrane, characterized in that, include: Macro-GMA was obtained by RAFT polymerization using CDB as a chain transfer agent and GMA as a monomer. Polyvinylidene fluoride, Macro-GMA, NMP and ammonia are mixed and heated and stirred to obtain a casting solution; A membrane substrate was prepared using the casting solution; The epoxy groups of GMA in the membrane substrate were crosslinked using EDA to obtain a crosslinked substrate; The oil-water separation membrane was obtained by modifying the cross-linked substrate surface with zwitterionic pSBMA using the RAFT polymerization method. The process of obtaining Macro-GMA via RAFT polymerization using CDB as a chain transfer agent and GMA as a monomer is as follows: GMA, azobisisobutyronitrile and CDB were mixed to obtain a purple-red mixed solution; The operation of removing dissolved oxygen from the purple-red mixed solution yields a deoxygenated mixed solution; The deoxygenated mixed solution was heated and stirred to react, and after the reaction was completed, it was cooled to obtain the reaction product. The product after the reaction was purified by repeated precipitation and dissolution in tetrahydrofuran and cold methanol, and then dried to obtain the Macro-GMA. The process of modifying the cross-linked substrate surface with zwitterionic pSBMA using the RAFT polymerization method to obtain the oil-water separation membrane is as follows: SBMA was added to anhydrous methanol, and after the SBMA 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 with ethanol and deionized water to obtain the oil-water separation membrane.
2. The method for preparing an oil-water separation membrane according to claim 1, characterized in that, The synthesis process of CDB is as follows: 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 to react. After the reaction was completed, the mixture was cooled and filtered to remove salt and methanol to obtain the reaction product. The reaction product was purified to obtain dithiobenzoic acid; Dithiobenzoic acid, α-methylstyrene, and carbon tetrachloride were mixed, heated, and stirred to react. After the reaction, the solvent was removed, and the mixture was purified by column chromatography to obtain the CDB.
3. The method for preparing an oil-water separation membrane according to claim 1, characterized in that, The process of mixing polyvinylidene fluoride, Macro-GMA, NMP, and ammonia, and then heating and stirring to obtain the casting solution is as follows: Polyvinylidene fluoride was completely dissolved in NMP to obtain a homogeneous and transparent solution; Macro-GMA was completely dissolved in NMP to obtain a Macro-GMA solution. After the homogeneous and transparent solution is mixed evenly with the Macro-GMA solution, ammonia water is added, and the mixture is heated and stirred to obtain the casting solution.
4. The method for preparing an oil-water separation membrane according to claim 1, characterized in that, The process of preparing the membrane substrate using the casting solution is as follows: Remove air bubbles from the casting solution to obtain a uniform casting solution; The uniform casting solution is evenly coated onto a glass plate to obtain a liquid film; A glass plate with a liquid film is transferred to a coagulation bath for phase transformation, and then the residual solvent is removed to obtain the film substrate.
5. The method for preparing an oil-water separation membrane according to claim 1, characterized in that, The process of crosslinking the epoxy groups of GMA in the membrane substrate using EDA to obtain the crosslinked substrate is as follows: The membrane substrate is placed in an aqueous solution of EDA to undergo a crosslinking reaction, thereby obtaining the crosslinked substrate.
6. The method for preparing an oil-water separation membrane according to claim 1, characterized in that, The initiator is AIBN.
7. An oil-water separation membrane, characterized in that, The oil-water separation membrane is prepared using the oil-water separation membrane preparation method as described in any one of claims 1-6.
8. The application of the oil-water separation membrane as described in claim 7, characterized in that, The oil-water separation membrane is used to separate oil from oily wastewater.