A method for preparing a protein-induced polyamide nanofiltration membrane
By regulating the interfacial polymerization process through protein, a high-flux polyamide nanofiltration membrane was prepared, solving the problem of pore size control and achieving efficient water treatment and wastewater treatment.
Patent Information
- Application Number
- CN202411091639.5
- Authority / Receiving Office
- CN · China
- Patent Type
- Patents(China)
- Current Assignee / Owner
- Filing Date
- 2024-08-09
- Publication Date
- 2026-01-06
- Estimated Expiration
- 2044-08-09
AI Technical Summary
Existing technologies make it difficult to achieve precise control of pore size and polyamide membrane formation, which makes it difficult to prepare high-water-flux polyamide composite nanofiltration membranes.
The process employs protein-regulated interfacial polymerization. By adding protein to the aqueous phase to form hydrogen bonds with piperazine, the release of piperazine is slowed down, resulting in a thinner, defect-free polyamide film. Combined with the condensation reaction of protein and trimesoyl chloride, a hierarchical porous structure is formed.
Without altering the existing interfacial polymerization process, the water flux was increased to 32.13 L m⁻²h⁻¹bar⁻¹, while maintaining a high salt rejection rate, and the preparation process was simple and easy to operate.
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Figure CN118925519B_ABST
Abstract
Description
Technical Field
[0001] This invention belongs to the field of drinking water purification and wastewater pollution control, and specifically relates to a method for preparing a protein-induced polyamide nanofiltration membrane. Background Technology
[0002] Compared to other technologies, membrane separation technology is a relatively energy-efficient water treatment technology. Currently, membrane elements on the market can be broadly categorized into microfiltration (MF), ultrafiltration (UF), nanofiltration (NF), and reverse osmosis (RO). Among these, nanofiltration membranes are important materials widely used in advanced water treatment, hard water softening, and brackish water treatment. They can remove specific organic matter, pigments, and salts from water and are a type of separation membrane with a pore size between porous ultrafiltration membranes and dense reverse osmosis membranes. Due to their advantages such as lower operating pressure, higher water flux, and effective removal of dissolved organic matter and hardness from water, they are widely used in drinking water purification and wastewater pollution control. Polyamide composite membranes prepared using porous base membranes are currently the most widely used nanofiltration membranes. Interfacial polymerization is currently the most widely used polyamide membrane preparation technology, featuring controllable pore size and molecular sieving, simple operation, and customizability.
[0003] However, interfacial polymerization has some limitations, making it difficult to precisely control pore size and polyamide membrane formation. The physical structure and chemical properties of the polyamide separation layer determine the separation performance of the composite membrane. Optimizing the physicochemical properties of the polyamide layer by regulating the interfacial polymerization process can improve the separation performance of the composite membrane. Therefore, how to regulate the interfacial polymerization process for polyamide layer formation is a current research focus. Summary of the Invention
[0004] The purpose of this invention is to solve the problem that existing methods are difficult to achieve precise control of pore size and polyamide membrane formation, and thus cannot prepare high-flux polyamide composite nanofiltration membranes. In this invention, a method for preparing protein-induced polyamide nanofiltration membranes is provided.
[0005] This invention utilizes protein-regulated interfacial polymerization to achieve precise control of interfacial polymerization, thereby preparing a polyamide composite nanofiltration membrane that ensures high separation rate while achieving high water flux. Proteins have abundant functional groups and high affinity for water and amine molecules, making them a highly promising material that has not yet been developed for interfacial polymerization regulation.
[0006] A method for preparing a protein-induced polyamide nanofiltration membrane is carried out according to the following steps:
[0007] I. Pretreatment of ultrafiltration membranes:
[0008] The ultrafiltration membrane was rinsed multiple times with deionized water and then soaked in anhydrous ethanol for a period of time. Before use, the ultrafiltration membrane was removed from the anhydrous ethanol and then rinsed with deionized water to remove the anhydrous ethanol from the surface of the ultrafiltration membrane, thus obtaining the pretreated ultrafiltration membrane.
[0009] II. Preparation of aqueous solution:
[0010] The protein was dissolved in a buffer solution with a specific pH value, then allowed to stand for a period of time in a refrigerator at 3℃~4℃, and then piperazine was added to obtain an aqueous solution containing protein and piperazine.
[0011] III. Preparation of organic phase solutions:
[0012] Pyrimethanil chloride was dissolved in an organic solvent, stirred until homogeneous, and allowed to stand for a period of time to obtain an organic phase solution for interfacial polymerization.
[0013] IV. Immobilizing the ultrafiltration membrane:
[0014] Cut the pretreated ultrafiltration membrane to the same size as the glass plate, then place the pretreated ultrafiltration membrane on the glass plate to avoid the formation of air bubbles. Then place the silicone pad and polytetrafluoroethylene frame on the edge of the glass plate in sequence and fix them with dovetail clips.
[0015] V. Enrichment of aqueous solution in membrane pores:
[0016] A certain volume of aqueous solution containing protein and piperazine is poured onto the pretreated ultrafiltration membrane, left to stand for a certain time, and then the aqueous solution containing protein and piperazine is poured off. The excess aqueous solution visible to the naked eye on the surface is removed by using an N2 purge gun to obtain an ultrafiltration membrane enriched with aqueous solution.
[0017] VI. Interface Aggregation:
[0018] The ultrafiltration membrane enriched with aqueous solution was laid flat and allowed to stand for a period of time. Then, a certain volume of organic phase solution for interfacial polymerization was poured onto the ultrafiltration membrane enriched with aqueous solution. After crosslinking at room temperature for a period of time, the organic phase solution was poured off. Then, the unreacted organic phase solution was washed off with an organic solvent. Finally, it was placed in an oven for thermal crosslinking for a period of time to obtain a protein-induced polyamide nanofiltration membrane.
[0019] The principle of this invention:
[0020] 1. When preparing polyamide membranes using interfacial polymerization, there is a problem that the reaction rate is relatively fast, making it difficult to control the interfacial polymerization process from a kinetic perspective. Currently, there is a lot of research on the regulation of polyamide layers, such as methods for preparing sacrificial layers of cadmium hydroxide nanowires and preparing hydrophilic interlayers. However, this invention uses the addition of proteins to the aqueous phase to regulate the interfacial polymerization process. This regulation principle is based on the fact that proteins and piperazine in the aqueous phase are attracted by hydrogen bonds, which slows down the release of piperazine and forms a thinner, defect-free polyamide membrane, thereby improving water flux and salt rejection rate.
[0021] 2. This invention demonstrates that proteins themselves can undergo a condensation reaction with trimesoyl chloride (TMC) in the organic phase to form a film. Therefore, proteins in the aqueous phase form their own films. Since the pores formed by the reaction of proteins with TMC are relatively large, the dense pores formed by the reaction with piperazine (PIP) and TMC form a hierarchical pore structure, thereby forming a nanofiltration membrane with special structure and function.
[0022] 3. The membrane structure prepared by this invention has obvious striped Turing structure and special coffee ring structure, which greatly increases the specific surface area of the membrane. The two special structures provide additional water passage channels for the membrane, which greatly improves the water flux of the membrane while ensuring the salt rejection rate.
[0023] The advantages of this invention are:
[0024] 1. The method used in this invention can be implemented without changing the existing interfacial polymerization process, making it highly applicable and capable of increasing the water flux from 15.46 L / m³ while maintaining a high salt rejection rate. -2 h -1 bar -1 Increased to 32.13L m -2 h -1 bar -1 ;
[0025] 2. Compared with membranes formed by conventional interfacial polymerization, the polyamide layer of the membrane prepared by this invention has a striped Turing structure and a coffee ring structure, while the nanofiltration membrane prepared by conventional interfacial polymerization has a typical nodular structure. These two special morphologies greatly increase the specific surface area of the polyamide layer, providing additional water channels for the membrane, thereby greatly improving the water flux of the membrane.
[0026] 3. The protein-induced polyamide nanofiltration membrane prepared by this invention has fewer defects in the polyamide layer, a smaller thickness, and a significantly increased roughness.
[0027] 4. The protein-induced polyamide nanofiltration membrane prepared by this invention greatly improves the water flux of the nanofiltration membrane while ensuring a high salt rejection rate. The preparation process is simple, easy to operate, short in cycle, and does not require changes to the existing interfacial polymerization process, making it suitable for large-scale nanofiltration membrane preparation. Attached Figure Description
[0028] Figure 1 The figures show the morphology of a conventional nanofiltration membrane and a protein-induced polyamide nanofiltration membrane prepared using the present invention. In the figures, 1 and 2 are the surface morphology of the nanofiltration membrane prepared by the conventional interfacial polymerization method in Example 6, where 1 is a low-magnification image and 2 is a high-magnification image. 3 and 4 are the surface morphology of the protein-induced polyamide nanofiltration membrane in Example 3, where 3 is a low-magnification image and 4 is a high-magnification image. 5 and 6 are the surface morphology of the protein-induced polyamide nanofiltration membrane in Example 5, where 5 is a low-magnification image and 6 is a high-magnification image.
[0029] Figure 2 FTIR spectra of the membranes and protein powders prepared in Examples 1 to 6;
[0030] Figure 3 The images are atomic force microscopy images of the membranes prepared in Examples 3 and 6. In the images, 2 is the PA-L1 membrane prepared in Example 1, and 1 is the PA-L0 membrane prepared in Example 6 for comparison. The upper image is a 2D image, the lower image is a 3D image, and the inset shows the height change along the scribbled lines.
[0031] Figure 4 To test the water flux and salt rejection rate of the membranes prepared in Examples 1 to 6, the water flux was measured at 0.4 MPa after pre-pressurization at 0.5 MPa for 1 h, and the salt rejection rate was measured using a 1000 ppm sodium sulfate solution.
[0032] Figure 5 The salt rejection rate and water flux of the membranes prepared in Examples 3 and 6 are compared. The bar graph shows the salt rejection rate of several salts, including sodium sulfate, magnesium sulfate, magnesium chloride, calcium chloride and sodium chloride, and the line graph shows the water flux. The concentration of the solutions used in the salt rejection rate test was 1000 ppm. Detailed Implementation
[0033] The following embodiments further illustrate the content of the present invention, but should not be construed as limiting the present invention. Any modifications and substitutions made to the methods, steps, or conditions of the present invention without departing from the essence of the invention are within the scope of the present invention.
[0034] Specific Implementation Method 1: This implementation method describes a method for preparing a protein-induced polyamide nanofiltration membrane, which is completed according to the following steps:
[0035] I. Pretreatment of ultrafiltration membranes:
[0036] The ultrafiltration membrane was rinsed multiple times with deionized water and then soaked in anhydrous ethanol for a period of time. Before use, the ultrafiltration membrane was removed from the anhydrous ethanol and then rinsed with deionized water to remove the anhydrous ethanol from the surface of the ultrafiltration membrane, thus obtaining the pretreated ultrafiltration membrane.
[0037] II. Preparation of aqueous solution:
[0038] The protein was dissolved in a buffer solution with a specific pH value, then allowed to stand in a refrigerator at 3℃~4℃ for a period of time, and then piperazine was added to obtain an aqueous solution containing protein and piperazine.
[0039] III. Preparation of organic phase solutions:
[0040] Pyrimethanil chloride was dissolved in an organic solvent, stirred until homogeneous, and allowed to stand for a period of time to obtain an organic phase solution for interfacial polymerization.
[0041] IV. Immobilizing the ultrafiltration membrane:
[0042] Cut the pretreated ultrafiltration membrane to the same size as the glass plate, then place the pretreated ultrafiltration membrane on the glass plate to avoid the formation of air bubbles. Then place the silicone pad and polytetrafluoroethylene frame on the edge of the glass plate in sequence and fix them with dovetail clips.
[0043] V. Enrichment of aqueous solution in membrane pores:
[0044] A certain volume of aqueous solution containing protein and piperazine is poured onto the pretreated ultrafiltration membrane, left to stand for a certain time, and then the aqueous solution containing protein and piperazine is poured off. The excess aqueous solution visible to the naked eye on the surface is removed by using an N2 purge gun to obtain an ultrafiltration membrane enriched with aqueous solution.
[0045] VI. Interface Aggregation:
[0046] The ultrafiltration membrane enriched with aqueous solution was laid flat and allowed to stand for a period of time. Then, a certain volume of organic phase solution for interfacial polymerization was poured onto the ultrafiltration membrane enriched with aqueous solution. After crosslinking at room temperature for a period of time, the organic phase solution was poured off. Then, the unreacted organic phase solution was washed off with an organic solvent. Finally, it was placed in an oven for thermal crosslinking for a period of time to obtain a protein-induced polyamide nanofiltration membrane.
[0047] Specific Implementation Method Two: This implementation method differs from Specific Implementation Method One in that: in step one, the ultrafiltration membrane is rinsed with deionized water 3 to 5 times, and then the ultrafiltration membrane is soaked in anhydrous ethanol for more than 24 hours. The other steps are the same as in Specific Implementation Method One.
[0048] Specific Implementation Method Three: This implementation method differs from Specific Implementation Method One or Two in that the ultrafiltration membrane in step one is a polyethersulfone membrane, polytetrafluoroethylene membrane, polyvinylidene fluoride membrane, polyvinylidene fluoride membrane, or cellulose acetate membrane. The other steps are the same as in Specific Implementation Method One or Two.
[0049] Specific Implementation Method Four: This implementation method differs from Specific Implementation Methods One to Three in that the protein mentioned in step two is one or a mixture of several of lysozyme, bovine serum albumin, β-lactoglobulin, and pepsin. The other steps are the same as in Specific Implementation Methods One to Three.
[0050] Specific Implementation Method 5: The difference between this implementation method and Specific Implementation Methods 1 to 4 is that: the buffer solution mentioned in step 2 is HEPES buffer solution or Tris-HCl buffer solution; the concentration of the buffer solution mentioned in step 2 is 10 mmol / L, and the pH value is 7.0 to 8.5; the standing time mentioned in step 2 is 8h to 12h.
[0051] The other steps are the same as those in specific implementation methods one to four.
[0052] Specific Implementation Method Six: This implementation method differs from Specific Implementation Methods One to Five in that: the mass fraction of protein in the aqueous solution containing protein and piperazine in step two is 0.05wt% to 0.8wt%; the mass fraction of piperazine in the aqueous solution containing protein and piperazine in step two is 0.1wt% to 0.5wt%. The other steps are the same as in Specific Implementation Methods One to Five.
[0053] Specific Implementation Method Seven: This implementation method differs from Specific Implementation Methods One through Six in that: the mass fraction of pyromellitic methyl chloride in the organic phase solution used for interfacial polymerization in step three is 0.05wt% to 0.2wt%; the organic solvent in step three is n-hexane or ISOPAR-G; and the standing time in step three is 1h to 2h. Other steps are the same as in Specific Implementation Methods One through Six.
[0054] Specific Implementation Method Eight: The difference between this implementation method and Specific Implementation Methods One to Seven is that: the size of the glass plate mentioned in step four is 14cm × 10cm; in step five, 20mL of aqueous solution containing protein and piperazine is poured onto the pretreated ultrafiltration membrane; the standing time mentioned in step five is 10min to 20min.
[0055] The other steps are the same as those in Specific Implementation Methods 1 to 7.
[0056] Specific Implementation Method Nine: This implementation method differs from Specific Implementation Methods One to Eight in that: the volume ratio of the organic phase solution used for interfacial polymerization in step six to the aqueous phase solution containing protein and piperazine in step five is 1:1; the crosslinking time at room temperature in step six is 30s to 120s. Other steps are the same as in Specific Implementation Methods One to Eight.
[0057] Specific Implementation Method Ten: This implementation method differs from Specific Implementation Methods One to Nine in the following ways: In step six, the ultrafiltration membrane enriched with the aqueous phase solution is laid flat and allowed to stand for 30 to 120 seconds; the organic solvent mentioned in step six is n-hexane or ISOPAR-G; the temperature of the oven mentioned in step six is 60°C to 80°C, and the thermal crosslinking time is 10 to 20 minutes. Other steps are the same as in Specific Implementation Methods One to Nine.
[0058] The beneficial effects of the present invention are verified using the following embodiments:
[0059] Example 1: A method for preparing a protein-induced polyamide nanofiltration membrane, which is carried out according to the following steps:
[0060] I. Pretreatment of ultrafiltration membranes:
[0061] The ultrafiltration membrane was rinsed three times with deionized water and then soaked in anhydrous ethanol for 24 hours. Before use, the ultrafiltration membrane was removed from the anhydrous ethanol and rinsed with deionized water to remove the anhydrous ethanol from the surface of the ultrafiltration membrane, thus obtaining the pretreated ultrafiltration membrane.
[0062] In step one, the ultrafiltration membrane is a polyethersulfone membrane, model GC-UF0202;
[0063] II. Preparation of aqueous solution:
[0064] The protein was dissolved in a buffer solution with a specific pH value, then allowed to stand in a refrigerator at 4°C for 8 hours, and then piperazine was added to obtain an aqueous solution containing protein and piperazine.
[0065] The protein mentioned in step two is lysozyme;
[0066] The buffer solution mentioned in step two is Tris-HCl buffer; the concentration of the buffer solution mentioned in step two is 10 mmol / L and the pH value is 7.4;
[0067] The protein mass fraction in the aqueous solution containing protein and piperazine described in step two is 0.05 wt%.
[0068] The aqueous solution containing protein and piperazine described in step two has a piperazine mass fraction of 0.1 wt%.
[0069] III. Preparation of organic phase solutions:
[0070] Trimethylbenzene chloride was dissolved in an organic solvent and stirred at a stirring speed of 600 r / min for 6 h, and then allowed to stand for 1 h to obtain an organic phase solution for interfacial polymerization.
[0071] The organic phase solution used for interfacial polymerization in step three contains 0.1 wt% trimesoyl chloride.
[0072] The organic solvent mentioned in step three is ISOPAR-G;
[0073] IV. Immobilizing the ultrafiltration membrane:
[0074] Cut the pretreated ultrafiltration membrane to the same size as the glass plate, then place the pretreated ultrafiltration membrane on the glass plate to avoid the formation of air bubbles. Then place the silicone pad and polytetrafluoroethylene frame on the edge of the glass plate in sequence and fix them with dovetail clips.
[0075] The glass plate mentioned in step four has dimensions of 14cm × 10cm;
[0076] V. Enrichment of aqueous solution in membrane pores:
[0077] Pour 20 mL of an aqueous solution containing protein and piperazine onto the pretreated ultrafiltration membrane, let it stand for 10 min, then pour off the aqueous solution containing protein and piperazine, and use an N2 purge gun to remove the excess aqueous solution visible to the naked eye on the surface to obtain an ultrafiltration membrane enriched with aqueous solution.
[0078] VI. Interface Aggregation:
[0079] The ultrafiltration membrane enriched with aqueous solution was laid flat and allowed to stand for 2 minutes. Then, 20 mL of organic phase solution for interfacial polymerization was poured onto the ultrafiltration membrane enriched with aqueous solution. After crosslinking at room temperature for 1 minute, the organic phase solution was poured off. Unreacted organic phase solution was then washed off with an organic solvent. Finally, the membrane was placed in an oven at 60°C for thermal crosslinking for 10 minutes to obtain a protein-induced polyamide nanofiltration membrane (named PA-L1).
[0080] The organic solvent mentioned in step six is ISOPAR-G.
[0081] Example 2: The difference between this example and Example 1 is that the protein mass fraction in the aqueous solution containing protein and piperazine in step two is 0.1 wt%; the resulting protein-induced polyamide nanofiltration membrane is named PA-L2. All other steps and parameters are the same as in Example 1.
[0082] Example 3: The difference between this example and Example 1 is that the mass fraction of protein in the aqueous solution containing protein and piperazine in step two is 0.3 wt%; the protein-induced polyamide nanofiltration membrane obtained is named PA-L3. All other steps and parameters are the same as in Example 1.
[0083] Example 4: The difference between this example and Example 1 is that the mass fraction of protein in the aqueous solution containing protein and piperazine in step two is 0.5 wt%; the protein-induced polyamide nanofiltration membrane obtained is named PA-L4. All other steps and parameters are the same as in Example 1.
[0084] Example 5: The difference between this example and Example 1 is that the mass fraction of protein in the aqueous solution containing protein and piperazine in step two is 0.8 wt%; the protein-induced polyamide nanofiltration membrane obtained is named PA-L5. All other steps and parameters are the same as in Example 1.
[0085] Example 6: The difference between this example and Example 1 is that the mass fraction of protein in the aqueous solution containing protein and piperazine in step two is 0 wt%; the mass fraction of piperazine in the aqueous solution containing protein and piperazine in step two is 0.1 wt%; the aqueous solution is pure water, and the final membrane is named PA-L0. All other steps and parameters are the same as in Example 1.
[0086] The membranes PA-L1-5 prepared in Examples 1-5 were mainly used to investigate the effect of different lysozyme concentrations on a protein-induced polyamide nanofiltration membrane. Example 6 is a polyamide nanofiltration membrane (PA-L0) prepared without protein induction, which was mainly used to compare with the protein-induced polyamide nanofiltration membrane.
[0087] Figure 1 The figures show the morphology of a conventional nanofiltration membrane and a protein-induced polyamide nanofiltration membrane prepared using the present invention. In the figures, 1 and 2 are the surface morphology of the nanofiltration membrane prepared by the conventional interfacial polymerization method in Example 6, where 1 is a low-magnification image and 2 is a high-magnification image. 3 and 4 are the surface morphology of the protein-induced polyamide nanofiltration membrane in Example 3, where 3 is a low-magnification image and 4 is a high-magnification image. 5 and 6 are the surface morphology of the protein-induced polyamide nanofiltration membrane in Example 5, where 5 is a low-magnification image and 6 is a high-magnification image.
[0088] Depend on Figure 1 It can be seen that ordinary nanofiltration membranes exhibit a typical nodular morphology, while the protein-induced polyamide nanofiltration membrane of the present invention exhibits two special morphologies on its surface. These are the special coffee ring structure shown in the SEM images (3 and 4) of the membrane prepared in Example 3 and the striped Turing structure shown in the SEM image of the membrane prepared in Example 5. Both special structures provide special water passage channels for the polyamide membrane, which explains why the water flux of the present invention is greatly improved in subsequent tests.
[0089] Figure 2 FTIR spectra of the membranes and protein powders prepared in Examples 1 to 6;
[0090] Figure 2 The infrared spectrum of LYZ lysozyme powder is shown in the image for comparison; (The image is from...) Figure 2 It can be seen that: in the range of 1500-1800cm -1Successful immobilization and post-crosslinking integrity of lysozyme were confirmed in the fingerprint region, involving carbonyl and amide bands; 1650 cm -1 The peak intensity at 2960 cm⁻¹ gradually increases with increasing lysozyme concentration, which is due to the C=O stretching vibration of peptide bonds in the protein; -1 The peak at 1540 cm⁻¹ may be related to the aliphatic portion of the protein; -1 The peak at 3300 cm⁻¹ is caused by peptide bonds (NH bending and CN stretching vibrations) in the protein; a peak at 3300 cm⁻¹ was observed in all lysozyme membranes. -1 The central broadband and several at 3000cm -1 The smaller peak centered on this involves the stretching vibrations of N-H and -COOH formed during interfacial polymerization, which overlap with other groups (such as O-H groups) in the lysozyme layer.
[0091] The membranes prepared in Examples 3 and 6 were tested using atomic force microscopy, and the results are shown in the figure. Figure 3 ;
[0092] Figure 3 The images are atomic force microscopy images of the membranes prepared in Examples 3 and 6. In the images, 2 is the PA-L1 membrane prepared in Example 1, and 1 is the PA-L0 membrane prepared in Example 6 for comparison. The upper image is a 2D image, the lower image is a 3D image, and the inset shows the height change along the scribbled lines.
[0093] Depend on Figure 3 It can be seen that the polyamide nanofiltration membrane prepared by protein-induced interfacial polymerization has a special striped Turing structure with a height of about 15 nm. Compared with the ordinary polyamide nanofiltration membrane prepared in Example 6, the roughness increases from 3.45±0.45 to 5.09±0.30.
[0094] Figure 4 To test the water flux and salt rejection rate of the membranes prepared in Examples 1 to 6, the water flux was measured at 0.4 MPa after pre-pressurization at 0.5 MPa for 1 h, and the salt rejection rate was measured using a 1000 ppm sodium sulfate solution.
[0095] from Figure 4 It can be seen that as the concentration of lysozyme increases, the water flux first increases and then decreases, while the salt rejection rate first decreases, then increases and then decreases again. Combining the water flux and salt rejection rate, PA-L2 and PA-L3 are determined to be suitable concentrations, because at this time the water flux is significantly improved compared with the normally prepared polyamide membrane, while ensuring a high salt rejection rate.
[0096] Figure 5The salt rejection rate and water flux of the membranes prepared in Examples 3 and 6 are compared. The bar graph shows the salt rejection rate of several salts, including sodium sulfate, magnesium sulfate, magnesium chloride, calcium chloride and sodium chloride, and the line graph shows the water flux. The concentration of the solutions used in the salt rejection rate test was 1000 ppm.
[0097] from Figure 5 It can be seen that the membrane prepared using the protein-induced polyamide layer method can maintain a high salt rejection rate while increasing the water flux from 15.46 L / m². -2 h -1 bar -1 Increased to 32.13L m -2 h -1 bar -1 The reasons for this are twofold: firstly, the addition of proteins slows down the release of piperazine in the aqueous phase, forming special structures of stripes and coffee rings, providing additional water channels and greatly increasing water flux; secondly, protein-induced interfacial polymerization effectively controls interfacial polymerization, resulting in thinner polyamide layers with fewer defects.
Claims
1. A method for preparing a protein-induced polyamide nanofiltration membrane, characterized by The preparation method is completed according to the following steps: I. Pretreatment of ultrafiltration membrane: The ultrafiltration membrane is washed with deionized water for several times, then the ultrafiltration membrane is soaked in anhydrous ethanol for a period of time, the ultrafiltration membrane is taken out from the anhydrous ethanol before use, the surface of the ultrafiltration membrane is washed with deionized water to remove the anhydrous ethanol, and the pretreated ultrafiltration membrane is obtained; II. Preparation of aqueous solution: The protein is dissolved in a buffer solution with a certain pH value, then the solution is placed in a refrigerator at 3-4 DEG C for a period of time, and then piperazine is added to obtain an aqueous solution containing protein and piperazine; The protein in step II is one or a mixture of several of lysozyme, bovine serum albumin, beta-lactoglobulin and pepsin; The mass fraction of the protein in the aqueous solution containing protein and piperazine in step II is 0.3wt%-0.8wt%; the mass fraction of piperazine in the aqueous solution containing protein and piperazine in step II is 0.1wt%-0.5wt%; III. Preparation of organic phase solution: Trimesoyl chloride is dissolved in an organic solvent, stirred uniformly, and then placed for a period of time to obtain an organic phase solution for interfacial polymerization; IV. Fixing of ultrafiltration membrane: The pretreated ultrafiltration membrane is cut into the same size as the glass plate, then the pretreated ultrafiltration membrane is placed on the glass plate to avoid the generation of air bubbles, then a silica gel pad and a polytetrafluoroethylene frame are sequentially placed at the edge of the glass plate, and a dovetail clamp is used for fixing; V. Enrichment of aqueous solution in membrane pores: A certain volume of the aqueous solution containing protein and piperazine is poured on the pretreated ultrafiltration membrane, and then placed for a period of time, the aqueous solution containing protein and piperazine is poured out, and the excess aqueous solution is removed from the surface by using a N2 blowing gun, and the ultrafiltration membrane enriched with the aqueous solution is obtained; VI. Interfacial polymerization: The ultrafiltration membrane enriched with the aqueous solution is placed horizontally for a period of time, then a certain volume of the organic phase solution for interfacial polymerization is poured on the ultrafiltration membrane, and then crosslinked at room temperature for a period of time, the organic phase solution is poured out, the unreacted organic phase solution is washed away by using an organic solvent, and finally the ultrafiltration membrane is placed in an oven for thermal crosslinking for a period of time, and a protein-induced polyamide nanofiltration membrane is obtained.
2. The method for preparing a protein-induced polyamide nanofiltration membrane according to claim 1, characterized in that In step I, the ultrafiltration membrane is washed with deionized water for 3-5 times, and then soaked in anhydrous ethanol for more than 24 hours.
3. The method for preparing a protein-induced polyamide nanofiltration membrane according to claim 1, characterized in that... In step I, the ultrafiltration membrane is polyether sulfone membrane, polytetrafluoroethylene membrane, polyvinylidene fluoride membrane, polyvinylidene fluoride membrane or cellulose acetate membrane.
4. The method for preparing a protein-induced polyamide nanofiltration membrane according to claim 1, 2 or 3, characterized in that In step II, the buffer solution is HEPES buffer solution or Tris-HCl buffer solution; the concentration of the buffer solution in step II is 10mmol / L, and the pH value is 7.0-8.5; the time for standing in step II is 8-12 hours.
5. A method for preparing a protein-induced polyamide nanofiltration membrane according to claim 1, 2, or 3, characterized in that... In step III, the mass fraction of trimesoyl chloride in the organic phase solution for interfacial polymerization is 0.05wt%-0.2wt%; the organic solvent in step III is n-hexane or ISOPAR-G; the time for standing in step III is 1-2 hours.
6. A method for preparing a protein-induced polyamide nanofiltration membrane according to claim 1, 2, or 3, characterized in that... The size of the glass plate in step four is 14 cm x 10 cm; 20 mL of the aqueous phase solution containing proteins and piperazine is poured on the pretreated ultrafiltration membrane in step five; the standing time in step five is 10 min to 20 min.
7. A method for preparing a protein-induced polyamide nanofiltration membrane according to claim 1, 2, or 3, characterized in that... The volume ratio of the organic phase solution for interfacial polymerization to the aqueous phase solution containing proteins and piperazine in step five in step six is 1:1; the crosslinking time at room temperature in step six is 30 s to 120 s.
8. A method for preparing a protein-induced polyamide nanofiltration membrane according to claim 1, 2 or 3, characterized in that... The ultrafiltration membrane enriched with the aqueous phase solution is laid flat and stood for 30 s to 120 s in step six; the organic solvent in step six is n-hexane or ISOPAR-G; the temperature of the oven in step six is 60 DEG C to 80 DEG C, and the heat crosslinking time is 10 min to 20 min.