Preparation method and application of hydrophilic / underwater oleophobic chitosan nanofiber membrane
By using electrospinning technology and modification treatment, the prepared chitosan nanofiber membrane solved the problems of flux and stability of nanofiber membranes in oil-water separation, and achieved efficient separation of water-in-oil emulsions with excellent flux and chemical stability.
Patent Information
- Application Number
- CN202311384148.5
- Authority / Receiving Office
- CN · China
- Patent Type
- Patents(China)
- Current Assignee / Owner
- Filing Date
- 2023-10-24
- Publication Date
- 2026-08-25
- Estimated Expiration
- 2043-10-24
AI Technical Summary
Existing nanofiber membranes are difficult to use for efficient separation of highly emulsified emulsions with stable surfactants in oil-water separation processes. Furthermore, the modification process is complex, leading to reduced porosity and flux, and making it difficult to guarantee chemical stability.
Chitosan nanofiber membranes were prepared by electrospinning. Polyvinyl alcohol was mixed with chitosan, and sodium methacrylate was added for modification. The microstructure and pore size of the membrane were adjusted to form a hydrophilic cross-linked network, thereby improving the hydrophilicity and mechanical stability of the membrane.
The prepared chitosan nanofiber membrane exhibits high throughput, low irreversible fouling rate, and long cleaning cycle during oil-water separation, with minimal throughput decay. It is suitable for efficient separation of oil-in-water emulsions and possesses excellent chemical stability and mechanical strength.
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Figure CN117323831B_ABST
Abstract
Description
Technical Field
[0001] This invention belongs to the field of oil-water separation technology, specifically relating to a method for preparing and applying a hydrophilic / underwater oleophobic chitosan nanofiber membrane. Background Technology
[0002] Traditional oil-water separation processes, such as gravity separation, centrifugal separation, electrostatic separation, and adsorption separation, suffer from low separation efficiency, high operating costs, and are prone to secondary pollution. They are gradually being replaced by emerging membrane separation technologies. Membrane separation technology is a rapidly developing oil-water separation technology in recent years. When the membrane possesses a unique pore structure and surface wettability, it can continuously separate trace amounts of water from emulsified oil, achieving rapid separation of oil-water mixtures. The key to membrane separation technology lies in the preparation of the separation membrane. High-efficiency oil-water separation membrane materials should possess advantages such as excellent oil-water selectivity, chemical stability, mechanical stability, and higher separation efficiency. Currently, nanofiber membranes have attracted widespread attention in the field of membrane separation due to their high porosity, small pore size, and ease of functionalization.
[0003] Electrospinning technology can be used to prepare nanofiber membranes with advantages such as high porosity and large specific surface area, and the operation is simple and controllable. The prepared nanofiber membranes exhibit high flux in oil-water separation processes, with small and more uniform fiber diameters, showing great application potential. Currently, most electrospinned nanofiber membranes face challenges in achieving stable separation of highly emulsified emulsions containing surfactants, and the modification process itself has drawbacks, such as complex modification processes leading to decreased porosity and consequently lower flux, and difficulty in ensuring the chemical stability of the modified membrane. This invention aims to achieve the wettability of the membrane surface through electrospinning, thereby enabling the effective separation of highly surfactant-emulsified oil-in-water emulsions. By designing multi-level structures at both the physical and chemical levels, the optimal spinning conditions and polymer ratios are sought to achieve superior superwetting, high flux, and sustained antifouling properties. Therefore, designing a hydrophilic electrospinned nanofiber membrane material for oil-water separation has significant application value. Summary of the Invention
[0004] In view of this, in order to solve the above-mentioned technical problems, the present invention provides a method for preparing and applying a hydrophilic / underwater oleophobic chitosan nanofiber membrane. The hydrophilic / underwater oleophobic chitosan nanofiber membrane prepared by the present invention has high flux and high fouling resistance, and has potential for application in oil-water separation processes.
[0005] The chitosan hydrophilic membrane (CS-PVA) prepared in this invention possesses hydrophilic and oleophobic properties. Research revealed that the microstructure of the membrane can be adjusted by controlling parameters such as the mass fraction of the CS-PVA spinning solution, voltage, and spinning time. The contact angle of the CS-PVA nanofiber membrane with water was measured using a contact angle meter. The oil content in the liquid before and after separation of oil-water mixtures composed of organic solvents and water, and oil-water emulsions, was determined, and the separation effect was tested using a UV-Vis spectrophotometer.
[0006] To achieve the above-mentioned objectives, the present invention provides the following technical solution:
[0007] A method for preparing a hydrophilic / underwater oleophobic chitosan nanofiber membrane, specifically comprising the following steps:
[0008] I. Preparation of chitosan solution and polyvinyl alcohol solution:
[0009] ① Dissolve chitosan in an 80% (v / v) acetic acid solution to obtain a chitosan solution;
[0010] ② Dissolve polyvinyl alcohol in water to obtain a polyvinyl alcohol solution;
[0011] II. Preparation of the modified solution:
[0012] Chitosan solution and polyvinyl alcohol solution were mixed and stirred at room temperature for a period of time to obtain casting solution; hydrophilic modifying monomer and initiator were added to casting solution and stirred at room temperature to obtain modified solution;
[0013] 3. The modified solution prepared in step 2 is electrospun to obtain a hydrophilic modified nanofiber membrane; the prepared hydrophilic modified nanofiber membrane is hot-pressed to obtain a hydrophilic / underwater oleophobic chitosan nanofiber membrane.
[0014] Application of hydrophilic / underwater oleophobic chitosan nanofiber membranes in oil-water separation.
[0015] The principle of this invention:
[0016] Hydrophilic surfaces exhibit excellent affinity for water and opposite wettability towards oil and aqueous phases, thus effectively removing oil droplets from oil-in-water emulsions. Chitosan, a polymer containing numerous hydroxyl and amino groups, possesses high hydration capacity. It boasts advantages such as low cost, ease of modification, controllable molecular weight, easy biodegradability, and significant commercial-scale potential. It can prevent crude oil adhesion, making it suitable for use in oil-water separation. However, due to the polycationic nature of chitosan, electrospinning pure chitosan (CS) is extremely difficult due to its low chain flexibility, poor solubility, high viscosity, and low mechanical properties. Therefore, adding polyvinyl alcohol (PVA) to chitosan for blending mitigates the internal interactions of chitosan caused by H bonds, thereby increasing the spinnability of the solution.
[0017] Compared with the prior art, the present invention has the following beneficial effects:
[0018] I. In this invention, after preparing the original chitosan hydrophilic membrane, sodium methacrylate is added to modify the chitosan hydrophilic membrane. During the oil-water separation process, it can play a demulsifying role and increase the oil removal rate.
[0019] Furthermore, this invention utilizes acetic acid as a solvent to adjust its evaporation rate, thereby preparing a chitosan hydrophilic membrane with a hydrophilic structure and abundant pore size. The chitosan hydrophilic membrane prepared by this invention exhibits excellent stability, high permeability, low permeability decay over long-term operation, and long cleaning cycle.
[0020] II. The hydrophilic / underwater oleophobic chitosan nanofiber membrane prepared by this invention exhibits excellent hydrophilicity, high flux and separation efficiency for oil-water emulsions, a contact angle of 37.69°, complete wetting within 0.6 s, and fluxes of 21101 L·m for water-coated toluene and n-octane emulsions, respectively. -2 ·h -1 ·bar -1 and 24822 L·m -2 ·h -1 ·bar -1 With a retention rate of over 98%, the flux reduction rate of its water-in-octane emulsion after 5 hours is approximately 6%, the flux recovery rate is over 94%, the irreversible fouling rate is less than 3%, the flux reduction after 30 days is less than 10%, the cleaning cycle can reach 7 days, and the strength is all above 20 MPa. It has broad application prospects in the field of oil-water separation. Attached Figure Description
[0021] Figure 1 This is a microscopic morphology diagram of the hydrophilic modified nanofiber membrane prepared in step two of Example 1. Detailed Implementation
[0022] Specific Implementation Method 1: This implementation method describes a method for preparing a hydrophilic / underwater oleophobic chitosan nanofiber membrane, which is specifically completed according to the following steps:
[0023] I. Preparation of chitosan solution and polyvinyl alcohol solution:
[0024] ① Dissolve chitosan in an 80% (v / v) acetic acid solution to obtain a chitosan solution;
[0025] ② Dissolve polyvinyl alcohol in water to obtain a polyvinyl alcohol solution;
[0026] II. Preparation of the modified solution:
[0027] Chitosan solution and polyvinyl alcohol solution were mixed and stirred at room temperature for a period of time to obtain casting solution; hydrophilic modifying monomer and initiator were added to casting solution and stirred at room temperature to obtain modified solution;
[0028] 3. The modified solution prepared in step 2 is electrospun to obtain a hydrophilic modified nanofiber membrane; the prepared hydrophilic modified nanofiber membrane is hot-pressed to obtain a hydrophilic / underwater oleophobic chitosan nanofiber membrane.
[0029] Specific Implementation Method Two: This implementation method differs from Specific Implementation Method One in that the mass fraction of the chitosan solution mentioned in step one ① is 1%~10%. The other steps are the same as in Specific Implementation Method One.
[0030] Specific Implementation Method 3: This implementation method differs from Specific Implementation Method 1 or 2 in that the mass fraction of the polyvinyl alcohol solution mentioned in step 1 ② is 5%~15%. The other steps are the same as in Specific Implementation Method 1 or 2.
[0031] Specific Implementation Method Four: This implementation method differs from Specific Implementation Methods One to Three in that: the volume ratio of chitosan solution to polyvinyl alcohol solution in the casting solution in step two is (1~5):(5~9); the chitosan solution and polyvinyl alcohol solution are mixed in step two and stirred at room temperature for 10 to 12 hours. Other steps are the same as in Specific Implementation Methods One to Three.
[0032] Specific Implementation Method Five: This implementation method differs from Specific Implementation Methods One to Four in that: the mass fraction of the hydrophilic modifying monomer in the modified solution described in step two is 1% to 5%; the mass fraction of the initiator in the modified solution described in step two is 0.1% to 1%. The other steps are the same as in Specific Implementation Methods One to Four.
[0033] Specific Implementation Method Six: This implementation method differs from Specific Implementation Methods One to Five in that the hydrophilic modifying monomer mentioned in step two is one or a mixture of several of sodium methacrylate, acrylamide, and ethyl acrylate. The other steps are the same as in Specific Implementation Methods One to Five.
[0034] Specific Implementation Method Seven: This implementation method differs from Specific Implementation Methods One to Six in that: the initiator mentioned in step two is ammonium persulfate; in step two, hydrophilic modified monomers and initiators are added to the casting solution, and the stirring time at room temperature is 3 to 4 hours. Other steps are the same as in Specific Implementation Methods One to Six.
[0035] Specific Implementation Method Eight: This implementation method differs from Specific Implementation Methods One through Seven in that the electrospinning process parameters in step three are: voltage of 10kV to 20kV, injection rate of 0.0001mm / s to 0.01mm / s, roller speed of 100r / min to 400r / min; and spinning distance of 20cm to 30cm. Other steps are the same as in Specific Implementation Methods One through Seven.
[0036] Specific Implementation Method Nine: This implementation method differs from Specific Implementation Methods One to Eight in that the hot-pressing temperature in step three is 50℃~100℃, and the hot-pressing time is 0.5h~3h. The other steps are the same as in Specific Implementation Methods One to Eight.
[0037] Specific Implementation Method 10: This implementation method is the application of hydrophilic / underwater oleophobic chitosan nanofiber membranes in oil-water separation.
[0038] The beneficial effects of the present invention are verified using the following embodiments:
[0039] Example 1: A method for preparing a hydrophilic / underwater oleophobic chitosan nanofiber membrane, specifically carried out according to the following steps:
[0040] I. Preparation of chitosan solution and polyvinyl alcohol solution:
[0041] ① Dissolve chitosan in an acetic acid solution with a volume fraction of 80% to obtain a chitosan solution with a mass fraction of 3%;
[0042] ② Dissolve polyvinyl alcohol in water to obtain a polyvinyl alcohol solution with a mass fraction of 8%;
[0043] II. Preparation of the modified solution:
[0044] A 3% (w / w) chitosan solution and an 8% (w / w) polyvinyl alcohol solution were mixed evenly at a volume ratio of 3:7 and stirred at room temperature for 12 hours to obtain a casting solution. Sodium methacrylate and ammonium persulfate were added to the casting solution to introduce a hydrophilic cross-linking network and increase the solvent resistance and hydrophilicity of the chitosan membrane material. The mixture was stirred at room temperature for 3 hours to obtain a modified solution.
[0045] The modified solution described in step two contains 2.6% sodium methacrylate by mass; the modified solution described in step two contains 0.2% ammonium persulfate by mass.
[0046] 3. The modified solution prepared in step 2 was electrospun in a 10mL syringe. The spinning conditions were: feed rate 0.0007mm / s, spinning distance 25cm, positive voltage 18KV, negative voltage 2000V, roller speed 285rpm, and spinneret diameter 0.9mm. The casting solution was electrospun to obtain a hydrophilic modified nanofiber membrane. The prepared hydrophilic modified nanofiber membrane was hot-pressed at a temperature of 60℃ for 2h to obtain a hydrophilic / underwater oleophobic chitosan nanofiber membrane.
[0047] The hydrophilic / underwater oleophobic chitosan nanofiber membrane prepared in this embodiment has the characteristics of forming a hydrophilic cross-linked network structure, high hydrophilicity, high porosity, and high mechanical strength, and is suitable for the field of oil-in-water emulsion separation.
[0048] Example 2: A method for preparing a hydrophilic / underwater oleophobic chitosan nanofiber membrane, specifically carried out according to the following steps:
[0049] I. Preparation of chitosan solution and polyvinyl alcohol solution:
[0050] ① Dissolve chitosan in an acetic acid solution with a volume fraction of 80% to obtain a chitosan solution with a mass fraction of 4%;
[0051] ② Dissolve polyvinyl alcohol in water to obtain a polyvinyl alcohol solution with a mass fraction of 8%;
[0052] II. Preparation of the modified solution:
[0053] A 4% (w / w) chitosan solution and an 8% (w / w) polyvinyl alcohol solution were mixed evenly at a volume ratio of 4:6 and stirred at room temperature for 12 hours to obtain a casting solution. Sodium methacrylate and ammonium persulfate were added to the casting solution to introduce a hydrophilic cross-linking network and increase the solvent resistance and hydrophilicity of the chitosan membrane material. The mixture was stirred at room temperature for 3 hours to obtain a modified solution.
[0054] The modified solution described in step two contains 2.6% sodium methacrylate by mass; the modified solution described in step two contains 0.2% ammonium persulfate by mass.
[0055] 3. The modified solution prepared in step 2 was electrospun in a 10mL syringe. The spinning conditions were: feed rate 0.0007mm / s, spinning distance 25cm, positive voltage 18KV, negative voltage 2000V, roller speed 285rpm, and spinneret diameter 0.9mm. The casting solution was electrospun to obtain a hydrophilic modified nanofiber membrane. The prepared hydrophilic modified nanofiber membrane was hot-pressed at a temperature of 60℃ for 2h to obtain a hydrophilic / underwater oleophobic chitosan nanofiber membrane.
[0056] Example 3: The difference between this example and Example 1 is that the voltage for electrospinning in step three is 25kV, the injection rate is 0.0005mm / s, and the roller speed is 300r / min. All other steps and parameters are the same as in Example 1.
[0057] Example 4: The difference between this example and Example 1 is that the mass fraction of sodium methacrylate in the modified solution in step two is 4.8%; the mass fraction of ammonium persulfate in the modified solution in step two is 0.4%. All other steps and parameters are the same as in Example 1.
[0058] Comparative Example 1: The preparation of the chitosan hydrophilic membrane was carried out according to the following steps:
[0059] I. Preparation of chitosan solution and polyvinyl alcohol solution:
[0060] ① Dissolve chitosan in an acetic acid solution with a volume fraction of 80% to obtain a chitosan solution with a mass fraction of 3%;
[0061] ② Dissolve polyvinyl alcohol in water to obtain a polyvinyl alcohol solution with a mass fraction of 8%;
[0062] II. Preparation of the modified solution:
[0063] A 3% (w / w) chitosan solution and an 8% (w / w) polyvinyl alcohol solution were mixed evenly at a volume ratio of 3:7 and stirred at room temperature for 12 hours to obtain a casting solution. The casting solution was then electrospun in a 10 mL syringe under the following conditions: feed rate 0.0007 mm / s, spinning distance 25 cm, positive voltage 18 KV, negative voltage 2000 V, roller speed 285 rpm, and spinneret diameter 0.9 mm. The casting solution was electrospun to obtain a chitosan hydrophilic membrane.
[0064] Comparative Example 2: The difference between this example and Example 1 is that the sodium methacrylate modifier is replaced with acrylamide. All other steps and parameters are the same as in Example 1.
[0065] Comparative Example 3: The difference between this example and Example 1 is that the hot pressing process in step three is not performed. All other steps and parameters are the same as in Example 1.
[0066] The membranes of Examples 1-4 and Comparative Examples 1-3 were subjected to performance tests, and the results are shown in Table 1.
[0067] Table 1. Data on the membranes of Examples 1-4 and Comparative Examples 1-3.
[0068]
[0069] Table 1 shows that the hydrophilic / underwater oleophobic chitosan nanofiber membrane prepared in the embodiments of the present invention exhibits excellent hydrophilicity, with a contact angle of 37.69°, complete wetting within 0.6 s, and fluxes of water-coated toluene (99:1 volume ratio) and water-coated n-octane emulsion fiber membranes (99:1 volume ratio) are 21101 L·m⁻¹, respectively. -2 ·h -1 ·bar -1 and 24822 L·m -2 ·h -1 ·bar -1 With a retention rate of over 98%, the flux reduction rate of its filtered water-encapsulated n-octane emulsion is about 6%, the flux recovery rate is as high as 94%, and the irreversible fouling rate is less than 3%, it has broad application potential in oil-water separation.
Claims
1. A method for preparing a hydrophilic / underwater oleophobic chitosan nanofiber membrane, characterized in that... The preparation method is specifically carried out according to the following steps: I. Preparation of chitosan solution and polyvinyl alcohol solution: ① Dissolve chitosan in an 80% (v / v) acetic acid solution to obtain a chitosan solution; ② Dissolve polyvinyl alcohol in water to obtain a polyvinyl alcohol solution; II. Preparation of the modified solution: Chitosan solution and polyvinyl alcohol solution are mixed and stirred at room temperature for a period of time to obtain casting solution; hydrophilic modifying monomer and initiator are added to casting solution and stirred at room temperature for 3-4 hours to obtain modified solution; The hydrophilic modifying monomer mentioned in step two is one or a mixture of several of sodium methacrylate, acrylamide and ethyl acrylate; The initiator mentioned in step two is ammonium persulfate; 3. The modified solution prepared in step 2 is electrospun to obtain a hydrophilic modified nanofiber membrane; the prepared hydrophilic modified nanofiber membrane is hot-pressed to obtain a hydrophilic / underwater oleophobic chitosan nanofiber membrane.
2. The method for preparing a hydrophilic / underwater oleophobic chitosan nanofiber membrane according to claim 1, characterized in that... The mass fraction of the chitosan solution mentioned in step 1① is 1%~10%.
3. The method for preparing a hydrophilic / underwater oleophobic chitosan nanofiber membrane according to claim 1, characterized in that... The mass fraction of the polyvinyl alcohol solution mentioned in step 1② is 5%~15%.
4. The method for preparing a hydrophilic / underwater oleophobic chitosan nanofiber membrane according to claim 1, characterized in that... In step two, the volume ratio of chitosan solution to polyvinyl alcohol solution in the casting solution is (1~5):(5~9); in step two, the chitosan solution and polyvinyl alcohol solution are mixed and stirred at room temperature for 10h~12h.
5. The method for preparing a hydrophilic / underwater oleophobic chitosan nanofiber membrane according to claim 1, characterized in that... The mass fraction of the hydrophilic modifying monomer in the modified solution described in step two is 1% to 5%; the mass fraction of the initiator in the modified solution described in step two is 0.1% to 1%.
6. The method for preparing a hydrophilic / underwater oleophobic chitosan nanofiber membrane according to claim 1, characterized in that... The electrospinning process parameters described in step three are as follows: voltage 10kV ~ 20kV, injection rate 0.0001mm / s ~ 0.01mm / s, roller speed 100r / min ~ 400r / min; spinning distance 20cm ~ 30cm.
7. The method for preparing a hydrophilic / underwater oleophobic chitosan nanofiber membrane according to claim 1, characterized in that... The hot pressing temperature in step three is 50℃~100℃, and the hot pressing time is 0.5h~3h.
8. The application of the hydrophilic / underwater oleophobic chitosan nanofiber membrane prepared by the preparation method according to claims 1-7, characterized in that... Application of hydrophilic / underwater oleophobic chitosan nanofiber membranes in oil-water separation.
Citation Information
Patent Citations
Preparation method of nanofiber oil-water separation membrane, and nanofiber oil-water separation membrane
CN113663533A