Preparation method of electrostatic spinning composite fiber membrane for separating surfactant-stabilized oil-in-water emulsion
By introducing PAN and LDH onto the surface of PLA fiber membranes, PLA@PAN/LDH composite fiber membranes were prepared, which solved the problems of low flux and poor antifouling performance of PLA fiber membranes in the separation of surfactant-stable oil-in-water emulsions, and achieved high flux, high separation efficiency and self-cleaning capability.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- PETROCHINA CO LTD
- Filing Date
- 2024-11-21
- Publication Date
- 2026-05-22
AI Technical Summary
Existing PLA fiber membranes have low flux and poor antifouling performance in separating surfactant-stable oil-in-water emulsions, and are prone to scaling over time.
By introducing polyacrylonitrile (PAN) and layered double hydroxide (LDH) onto the surface of PLA fiber membranes through electrospinning, surface hydrophilic modification is carried out to prepare PLA@PAN/LDH composite fiber membranes, thereby improving the hydrophilicity and antifouling properties of the membranes.
It achieves high-throughput and high-efficiency separation of oil-in-water emulsions, has good antifouling properties and self-cleaning ability, and its performance does not decline significantly after 30 cycles of use.
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Figure CN122071835A_ABST
Abstract
Description
Technical fields:
[0001] This invention relates to the field of polymer material preparation technology, and in particular to a method for preparing an electrospun composite fiber membrane for separating surfactant-stabilized oil-in-water emulsions. Background technology:
[0002] Currently, superwetting membranes mainly include physically or chemically treated metal meshes, polymer-based membranes, and graphite-based membranes. Although these superwetting membranes show great promise in oil-water emulsion separation, most of their raw materials are non-renewable, non-degradable, and expensive, which has adverse effects on the environment and practical applications.
[0003] Polylactic acid (PLA) fiber membranes, as a green, biodegradable, and inexpensive nanofiber material, possess great potential for developing sustainable functional composite materials due to their attractive porous structure and unique chemical composition. Electrospun nanofiber materials offer advantages such as high permeability, high separation efficiency, large specific surface area, tunable hydrophilicity, simple preparation process, low cost, highly interconnected pore structure, high porosity, and tunable surface structure stability.
[0004] PLA fiber membranes are widely used for the efficient separation of oil-water mixtures and emulsions. However, over time, the strong hydrophobic interaction between fouling and the PLA fiber membrane surface often leads to severe fouling and poor antifouling performance. Furthermore, PLA fiber membranes exhibit low flux in separating surfactant-stabilized oil-in-water emulsions. Therefore, modification of PLA fiber membranes is necessary to address these issues. Summary of the Invention:
[0005] The technical problem to be solved by the present invention is to provide a method for preparing an electrospun composite fiber membrane for separating oil-in-water emulsions stabilized by surfactants. The electrospun composite fiber membrane prepared by this method achieves high throughput and high separation efficiency of oil-in-water emulsions stabilized by different surfactants, and has good antifouling performance and self-cleaning ability.
[0006] The technical solution adopted in this invention is: a method for preparing an electrospun composite fiber membrane for separating surfactant-stabilized oil-in-water emulsions, the steps of which are as follows:
[0007] Step 1: Preparation of polylactic acid fiber membrane: Polylactic acid, polyvinylpyrrolidone, N,N-dimethylformamide, and dichloromethane are mixed to form a mixed solution. The volume ratio of N,N-dimethylformamide to dichloromethane is 3:7. The concentration of polylactic acid in the mixed solution is 8 wt%, and the mass fraction of polyvinylpyrrolidone is 0 wt%-3.3 wt%. The solution is heated and stirred at 35°C, and then allowed to stand at room temperature until no bubbles are present. The resulting solution is then electrospun to obtain a polylactic acid fiber membrane.
[0008] Step 2: Preparation of polyacrylonitrile / layered double hydroxide electrospinning solution: Polyacrylonitrile and layered double hydroxide are mixed with solvent N,N-dimethylformamide to form a mixed solution. The mass fraction of polyacrylonitrile in the mixed solution is 3.2wt%-6.3wt%, and the mass fraction of layered double hydroxide is 0.04wt%-0.17wt%. The mixed solution is stirred to prepare the electrospinning solution.
[0009] Step 3: Preparation of polylactic acid@polyacrylonitrile / layered double hydroxide fiber membrane: Using the polylactic acid fiber membrane obtained in Step 1 as a substrate, the electrospinning solution prepared in Step 2 is spun onto the polylactic acid fiber membrane to obtain the polylactic acid@polyacrylonitrile / layered double hydroxide fiber membrane.
[0010] Furthermore, in step one, the mass fraction of polyvinylpyrrolidone in the mixed solution is 1.7 wt%.
[0011] Furthermore, in step one, the mixed solution is heated and stirred at 35°C for 24 hours.
[0012] Furthermore, in step one, the spinning settings are as follows: voltage 13KV, needle diameter 20, distance between needle and collector 15cm, and syringe advance speed 0.251mm / min.
[0013] Furthermore, in step two, the mass fraction of polyacrylonitrile in the mixed solution is 4.2 wt%.
[0014] Furthermore, in step two, the mass fraction of the layered double hydroxide in the mixed solution is 0.13 wt%.
[0015] Furthermore, in step two, the mixed solution is stirred for 6 hours.
[0016] Furthermore, in step three, the spinning parameters are: voltage 13KV, needle diameter 20, distance between needle and collector 16cm, and syringe advance speed 0.125mm / min.
[0017] Furthermore, the polylactic acid@polyacrylonitrile / layered double hydroxide fiber membrane obtained in step three is used to separate surfactant-stabilized oil-in-water emulsions.
[0018] Furthermore, the oil-in-water emulsion is a hexane oil-in-water emulsion, a soybean oil oil-in-water emulsion, a xylene oil-in-water emulsion, a petroleum ether oil-in-water emulsion, or an n-octane oil-in-water emulsion, and the surfactant is sodium dodecyl sulfate.
[0019] The beneficial effects of this invention are:
[0020] 1. PAN is introduced onto the PLA surface through electrospinning to modify the surface of PLA fiber membranes to be hydrophilic.
[0021] 2. After the introduction of LDH, LDH has superhydrophilicity due to the large number of hydroxyl groups on its surface. Its composition can be adjusted and it is suitable for various substrates. In addition, because LDH has a flower-like structure, it can increase the surface roughness of the membrane, improve the hydrophilicity and underwater oleophobicity of the membrane, and have antifouling properties and self-cleaning ability.
[0022] 3. The electrospun composite fiber membrane prepared by this invention achieves high throughput and high separation efficiency of water-in-oil emulsions with different surfactants. After 30 cycles, the throughput and separation efficiency do not decrease significantly. Moreover, after degradation and recycling, the composite fiber membrane is re-prepared, and the throughput and separation efficiency do not decrease significantly. Attached image description:
[0023] The present invention will now be described in further detail with reference to the accompanying drawings and specific embodiments.
[0024] Figure 1 The infrared spectra of the PLA@PAN / LDH composite fiber membrane, PLA@PAN fiber membrane, and PLA fiber membrane prepared in Example 1 are shown.
[0025] Figure 2 The surface morphology of the PLA fiber membrane prepared in Example 1 is shown in the scanning electron microscope image.
[0026] Figure 3 The surface morphology of the PLA@PAN / LDH composite fiber membrane prepared in Example 1 is shown in the scanning electron microscope image.
[0027] Figure 4 This is a schematic diagram illustrating the effect of adding different amounts of polyvinylpyrrolidone on membrane separation performance in Example 2.
[0028] Figure 5 This is a schematic diagram illustrating the effect of adding different amounts of LDH on membrane separation performance in Example 2.
[0029] Figure 6 This is a schematic diagram illustrating the effect of adding different amounts of PAN on membrane separation performance in Example 2.
[0030] Figure 7 This is a schematic diagram of the separation performance test of the PLA@PAN / LDH composite fiber membrane prepared in Example 1.
[0031] Figure 8 This is a schematic diagram showing the effect of the PLA@PAN / LDH composite fiber membrane prepared in Example 1 on the separation of n-hexane oil-in-water emulsion before and after separation.
[0032] Figure 9This is a schematic diagram of the cyclic separation performance test of the PLA@PAN / LDH composite fiber membrane prepared in Example 1.
[0033] Figure 10 This is a schematic diagram of the self-cleaning ability of PLA fiber membranes tested with a hexane solution stained with oil red.
[0034] Figure 11 This is a schematic diagram of the self-cleaning ability of PLA@PAN fiber membranes tested with a hexane solution stained with oil red.
[0035] Figure 12 This is a schematic diagram of the self-cleaning ability of PLA@PAN / LDH composite fiber membranes tested with an oil red-stained hexane solution. Detailed implementation method:
[0036] Example 1: Preparation of electrospun composite fiber membrane
[0037] 1. Preparation of PLA fiber membrane: PLA, polyvinylpyrrolidone, N,N-dimethylformamide, and dichloromethane were mixed, with a volume ratio of N,N-dimethylformamide to dichloromethane of 3:7. The PLA concentration in the mixed solution was 8 wt%, and the mass fraction of polyvinylpyrrolidone was 1.7 wt%. The mixture was heated and stirred at 35°C for 24 h, then allowed to stand at room temperature until no bubbles were present. The resulting solution was then electrospun to obtain the PLA fiber membrane. The spinning parameters were: voltage 13 kV, needle diameter 20 mm, distance between the needle and the collector 15 cm, and syringe advance speed 0.251 mm / min.
[0038] 2. Preparation of PLA@PAN composite fiber membrane: Using PLA fiber membrane as a substrate, the prepared PAN electrospinning solution was spun onto the PLA fiber membrane to obtain PLA@PAN composite fiber membrane. The spinning parameters were: voltage 13KV, needle diameter 20mm, distance between needle and collector 16cm, and syringe advance speed 0.125mm / min. 4.2wt% PAN was mixed with solvent N,N-dimethylformamide and stirred for 6h to prepare the electrospinning solution.
[0039] 3. Preparation of PAN electrospinning solution: 4.2 wt% PAN was mixed with solvent N,N-dimethylformamide and stirred for 6 h to prepare electrospinning solution;
[0040] 4. Preparation of PAN / LDH electrospinning solution: 4.2 wt% PAN and 0.13 wt% LDH were mixed with solvent N,N-dimethylformamide and stirred for 6 h to prepare electrospinning solution;
[0041] 5. Preparation of PLA@PAN / LDH composite fiber membrane: Using PLA fiber membrane as a substrate, the prepared PAN / LDH electrospinning solution was spun onto the PLA fiber membrane to obtain the electrospun composite fiber membrane, namely PLA@PAN / LDH composite fiber membrane. The spinning parameters were: voltage 13KV, needle diameter 20mm, distance between needle and collector 16cm, and syringe advance speed 0.125mm / min.
[0042] like Figure 1 As shown, PLA fiber membrane: at 1749cm -1 The peaks at 1182 and 1086 cm⁻¹ are related to the stretching of the C=O structure of PLA. -1 The COC bending vibration peak of PLA was observed nearby; PLA@PAN fiber membrane: peak at 2932 cm⁻¹ -1 For the CH tensile vibration of PAN, at 2244cm -1 The peak value of tensile vibration of C≡N in PAN was observed nearby, at 1661 cm⁻¹. -1 The peak value generated at 1447 cm is a tensile vibration of C=C. -1 The peak value generated at this point is due to the bending vibration of CH; PLA@PAN / LDH fiber membrane: peak value at 3462 cm⁻¹ -1 The OH stretching vibration of LDH exhibits a broad peak. For example... Figure 2 , Figure 3 As shown in the figure, LDH nanoflowers have been successfully spun onto the membrane surface.
[0043] Example 2: Investigation of Optimal Separation Conditions
[0044] Based on Example 1, different membranes were prepared by varying the amount of polyvinylpyrrolidone (PVP) added under the same conditions. The effects of PPVP addition on membrane separation performance were investigated using mass fractions of 0 wt%, 0.8 wt%, 1.7 wt%, 2.5 wt%, and 3.3 wt%. Based on Example 1, the effects of LDH addition on membrane separation performance were investigated using mass fractions of 0 wt%, 0.04 wt%, 0.08 wt%, 0.13 wt%, and 0.17 wt%. Based on Example 1, the effects of PAN addition on membrane separation performance were investigated using mass fractions of 3.2 wt%, 4.2 wt%, 5.3 wt%, and 6.3 wt%. Figure 4 As shown, 1.7 wt% polyvinylpyrrolidone is the optimal addition amount. Polyvinylpyrrolidone dissolves in water, increasing the specific surface area, which helps increase pore space and leads to increased flux. It is worth noting that high polyvinylpyrrolidone content in the membrane may cause swelling, leading to water blockage on the membrane. Figure 5 As shown, 0.13wt% LDH is the optimal content; without LDH, there is no performance and the antifouling performance is poor; too much LDH makes the membrane too dense, causing some degree of pore blockage and affecting the separation flux. Figure 6 As shown, the optimal PAN content is 4.2 wt%. The increase in flux is due to the hydrophilic nature of PAN; as the PAN content increases, the surface becomes more hydrophilic, thus increasing the separation flux. However, with increasing PAN content, the viscosity of the solution also increases. High concentrations may cause adhesion on the fibers, thereby clogging the pores and reducing flux.
[0045] Example 3: Separation Performance Test
[0046] Using a vacuum filtration apparatus, the separation performance of the PLA@PAN / LDH composite fiber membrane prepared in Example 1 was measured at a pressure of 1 bar using different oil-in-water emulsions stabilized by surfactants as feed.
[0047] like Figure 7 As shown, flux changes of different oil-in-water emulsions stabilized by surfactants were tested, including n-hexane oil-in-water emulsion, soybean oil oil-in-water emulsion, petroleum ether oil-in-water emulsion, n-octane oil-in-water emulsion, and xylene oil-in-water emulsion.
[0048] from Figure 8 As can be seen, the PLA@PAN / LDH composite fiber membrane can demulsify different oil-in-water emulsions through its pore size and superwetting properties, allowing clean water to pass through the membrane while the oil is trapped on the membrane.
[0049] Example 4: Stability Test
[0050] The electrospun composite fiber membrane prepared in Example 1 was subjected to a cycle stability test, and rinsed with water after the test. The membrane stability was determined by calculating the change in flux in each cycle.
[0051] like Figure 9 As shown, from Figure 9 As can be seen from the example of separating n-hexane oil-in-water emulsion, after 30 cycles, the flux did not decrease significantly, which is attributed to the rough, flower-like structure of LDH, as well as the membrane's superhydrophilicity and underwater superoleophobicity. This demonstrates that the PLA@PAN / LDH composite fiber membrane exhibits good stability.
[0052] Example 5: Self-cleaning performance test
[0053] The PLA fiber membrane, PLA@PAN fiber membrane, and PLA@PAN / LDH composite fiber membrane prepared in Example 1 were respectively attached to a glass plate and placed underwater. An appropriate amount of hexane stained with oil red was drawn up with a syringe and injected into the membrane from underwater. The membrane's ability to self-clean was determined by observing whether it repelled the hexane solution.
[0054] like Figure 10 , Figure 11 , Figure 12 As shown, PLA fiber membranes and PLA@PAN fiber membranes adhered to a large number of oil droplets, while the PLA@PAN / LDH composite fiber membrane, due to the addition of LDH, exhibited a rougher surface structure, improving its hydrophilicity and underwater oleophobicity. This indicates that the PLA@PAN / LDH composite fiber membrane possesses excellent antifouling properties and self-cleaning effects.
[0055] It is understood that the above specific description of the present invention is only for illustrating the present invention and is not limited to the technical solutions described in the embodiments of the present invention. Those skilled in the art should understand that modifications or equivalent substitutions can still be made to the present invention to achieve the same technical effect; as long as the use needs are met, they are all within the protection scope of the present invention.
Claims
1. A method for preparing an electrospun composite fiber membrane for separating surfactant-stabilized oil-in-water emulsions, characterized in that: The steps of this method are as follows: Step 1: Preparation of polylactic acid fiber membrane: Polylactic acid, polyvinylpyrrolidone, N,N-dimethylformamide, and dichloromethane are mixed to form a mixed solution. The volume ratio of N,N-dimethylformamide to dichloromethane is 3:
7. The concentration of polylactic acid in the mixed solution is 8 wt%, and the mass fraction of polyvinylpyrrolidone is 0 wt%-3.3 wt%. The solution is heated and stirred at 35°C, and then allowed to stand at room temperature until no bubbles are present. The resulting solution is then electrospun to obtain a polylactic acid fiber membrane. Step 2, Preparation of polyacrylonitrile / layered double hydroxide electrospinning solution: Polyacrylonitrile and layered double hydroxide are mixed with solvent N,N-dimethylformamide to form a mixed solution. The mass fraction of polyacrylonitrile in the above mixed solution is 3.2wt%-6.3wt%, and the mass fraction of layered double hydroxide is 0.04wt%-0.17wt%. Stir the mixed solution to prepare the electrospinning solution; Step 3: Preparation of polylactic acid@polyacrylonitrile / layered double hydroxide fiber membrane: Using the polylactic acid fiber membrane obtained in Step 1 as a substrate, the electrospinning solution prepared in Step 2 is spun onto the polylactic acid fiber membrane to obtain the polylactic acid@polyacrylonitrile / layered double hydroxide fiber membrane.
2. The method for preparing an electrospun composite fiber membrane for separating surfactant-stabilized oil-in-water emulsions according to claim 1, characterized in that: In step one, the mass fraction of polyvinylpyrrolidone in the mixed solution is 1.7 wt%.
3. The method for preparing an electrospun composite fiber membrane for separating surfactant-stabilized oil-in-water emulsions according to claim 1, characterized in that: In step one, the mixed solution is heated and stirred at 35°C for 24 hours.
4. The method for preparing an electrospun composite fiber membrane for separating surfactant-stabilized oil-in-water emulsions according to claim 1, characterized in that: In step one, the spinning parameters are: voltage 13KV, needle diameter 20, distance between needle and collector 15cm, and syringe advance speed 0.251mm / min.
5. The method for preparing an electrospun composite fiber membrane for separating surfactant-stabilized oil-in-water emulsions according to claim 1, characterized in that: In step two, the mass fraction of polyacrylonitrile in the mixed solution is 4.2 wt%.
6. The method for preparing an electrospun composite fiber membrane for separating surfactant-stabilized oil-in-water emulsions according to claim 1, characterized in that: In step two, the mass fraction of the layered double hydroxide in the mixed solution is 0.13 wt%.
7. The method for preparing an electrospun composite fiber membrane for separating surfactant-stabilized oil-in-water emulsions according to claim 1, characterized in that: In step two, the mixed solution is stirred for 6 hours.
8. The method for preparing an electrospun composite fiber membrane for separating surfactant-stabilized oil-in-water emulsions according to claim 1, characterized in that: In step three, the spinning parameters are: voltage 13KV, needle diameter 20, distance between needle and collector 16cm, and syringe advance speed 0.125mm / min.
9. The method for preparing an electrospun composite fiber membrane for separating surfactant-stabilized oil-in-water emulsions according to claim 1, characterized in that: The polylactic acid@polyacrylonitrile / layered double hydroxide fiber membrane obtained in step three is used to separate surfactant-stabilized oil-in-water emulsions.
10. The method for preparing an electrospun composite fiber membrane for separating surfactant-stabilized oil-in-water emulsions according to claim 9, characterized in that: The oil-in-water emulsion is an oil-in-water emulsion of n-hexane, an oil-in-water emulsion of soybean oil, an oil-in-water emulsion of xylene, an oil-in-water emulsion of petroleum ether, or an oil-in-water emulsion of n-octane, and the surfactant is sodium dodecyl sulfate.