An oil-resistant core-shell nanofiber membrane and its preparation method

Abstract

The present invention relates to an anti-oil pollution core-shell nanofiber membrane and a preparation method thereof. First, a core layer polymer solution is prepared, and then a mixed solution of sodium alginate and a water-soluble polymer in the shell layer is prepared; finally, the core layer and shell layer spinning solutions are passed through a coaxial electrospinning device to prepare core-shell structured nanofibers with a polymer as the core and a water-soluble polymer and sodium alginate as the shell; the sodium alginate in the shell layer of the prepared nanofiber membrane is crosslinked, and then the water-soluble polymer is removed by washing with water, so that the shell layer of the obtained core-shell structured nanofibers is a homogeneous component of sodium alginate. The method of the present invention is simple and easy to implement, and the obtained fiber membrane has superhydrophilic properties and can be applied to the field of anti-pollution membranes for oil-water separation.

Description

Technical Field

[0001] The present invention belongs to the technical field of fiber materials, and relates to an anti-oil pollution core-shell nanofiber membrane material and a preparation method thereof. Background Art

[0002] Sodium alginate (SA) is a natural polysaccharide with rich sources, good biocompatibility, non-toxicity and hydrophilicity. The molecular chain of SA is rich in hydroxyl and carboxyl groups, which endows SA with super hydrophilic properties and has potential application value in the field of membrane anti-fouling. Electrospun nanofibers have structural advantages such as high porosity, good pore connectivity and adjustable thickness, and are widely used in the research of oil-water filtration field. The public literature [PVDF-CaAlg nanofiltration membranes with dual thin-film-composite (TFC) structure and high permeation flux for dye removal] realizes anti-fouling by impregnating an electrospun PVDF substrate membrane with a sodium alginate solution, but the membrane structure coated with sodium alginate is severely damaged and the porosity is reduced. Since SA is a low molecular polymer, it is not easy to electrospin. The public patent literature (CN 105586716 A) provides a preparation method of a two-component nanofiber rich in sodium alginate, which blends sodium alginate with polyethylene oxide (or polyvinyl alcohol), but the surface of the prepared nanofiber is a two-component, not a homogeneous component of sodium alginate, which has a certain influence on the wettability of the nanofiber membrane. Summary of the Invention

[0003] In the existing research, the structure of the fiber membrane is severely damaged by sodium alginate impregnation coating, and the preparation of a two-component nanofiber membrane containing sodium alginate by electrospinning method limits the improvement of its wettability. The purpose of the present invention is to solve the above problems existing in the prior art and provide an anti-oil pollution core-shell nanofiber membrane material. The shell layer of the core-shell nanofiber membrane material is a homogeneous component of sodium alginate nanofiber and has super hydrophilic properties. When performing oil-water separation, the presence of sodium alginate forms a hydration layer on the membrane surface, preventing oil droplets from contacting the fiber membrane, thereby achieving an anti-fouling effect.

[0004] To achieve the above object, the technical solution adopted by the present invention is as follows:

[0005] A method for preparing an oil-resistant core-shell nanofiber membrane, characterized in that: first, a polymer is dissolved in a solvent to obtain a solution for preparing a core layer structure; then, a water-soluble polymer is dissolved in a mixed solvent of water and ethanol to obtain a first solution, and sodium alginate is dissolved in water to obtain a second solution. Then, the two are mixed in a certain proportion to obtain a solution for preparing a shell layer structure; subsequently, coaxial electrospinning is used to obtain core-shell structured nanofibers with the polymer as the core and the water-soluble polymer and sodium alginate as the shell; the sodium alginate in the shell layer of the prepared nanofiber membrane is crosslinked, and then the water-soluble polymer is removed by washing with water to obtain an oil-resistant core-shell nanofiber membrane with sodium alginate as the shell.

[0006] The reasons for preparing the oil-resistant nanofibers with core-shell structure by coaxial electrospinning in the present invention are as follows: (1) The high porosity and interconnected pore structure of the electrospun fiber membrane are beneficial to the practical application of oil-water separation; (2) The polymer nanofibers in the core layer of the core-shell structure can enhance the mechanical properties of the nanofiber membrane, and the nanofiber shell layer of the core-shell structure is a single component and has super-hydrophilic sodium alginate nanofibers.

[0007] As a preferred technical solution:

[0008] For the method for preparing an oil-resistant core-shell nanofiber membrane as described above, the polymers in the core layer structure include but are not limited to polyacrylonitrile, polyvinylidene fluoride, polyurethane, polyethersulfone, etc.; the water-soluble polymers in the shell layer structure include but are not limited to polyethylene oxide, polyvinyl alcohol, etc.; the concentration of the polymer solution in the core layer is 10-20 wt%.

[0009] For the method for preparing an oil-resistant core-shell nanofiber membrane as described above, the mixing ratio of ethanol and water in the mixing ratio of the water-soluble polymer is 1:9-3:7.

[0010] For the method for preparing an oil-resistant core-shell nanofiber membrane as described above, the ratio of the water-soluble polymer solution to the sodium alginate solution is 1:9-5:5; the total mass fraction of the mixed solution is 3-5 wt%.

[0011] For the method for preparing an oil-resistant core-shell nanofiber membrane as described above, the perfusion speed of the polymer solution in the shell layer during the coaxial electrospinning process is 1-1.5 times that of the polymer solution in the core layer.

[0012] For the method for preparing an oil-resistant core-shell nanofiber membrane as described above, the crosslinking agent is one of CaCl2, FeCl3, AlCl3, ZnCl2, BaCl2, etc., and the concentration of the crosslinking agent is 0.5-5 wt%.

[0013] According to the second aspect of the present invention, the present invention provides an anti-oil pollution core-shell nanofiber membrane, which is prepared by any of the above preparation methods. The water contact angle of the prepared anti-oil pollution core-shell nanofiber membrane is 0-10°; the underwater oil contact angle is 150-160°; the underwater oil rolling angle is 5-10°.

[0014] Advantages of the present invention:

[0015] (1) For the nanofiber membrane with a core-shell structure of the present invention, the core layer polymer in the core-shell structure enhances the mechanical strength of the nanofiber membrane, and the shell layer is a homogeneous component of sodium alginate nanofibers, thus having both good mechanical properties and wetting properties.

[0016] (2) Compared with the existing sodium alginate / polymer two-component nanofibers, the shell layer of the nanofiber membrane with a core-shell structure of the present invention is a single-component sodium alginate. Due to the super-hydrophilic property of sodium alginate, it is widely used in the field of oil-water separation anti-pollution membranes. Description of the drawings

[0017] Figure 1 It is a schematic diagram of the core-shell structure nanofibers prepared by the present invention. Embodiments

[0018] The present invention will be further described below in conjunction with specific embodiments. It should be understood that these embodiments are only used to illustrate the present invention and not to limit the scope of the present invention. In addition, it should be understood that after reading the content taught by the present invention, those skilled in the art can make various changes or modifications to the present invention, and these equivalent forms also fall within the scope defined by the appended claims of this application. Examples

[0019] A preparation method of an anti-oil pollution core-shell nanofiber membrane. First, a polyacrylonitrile solution with a concentration of 10 wt% is prepared as the core layer solution; a 5 wt% sodium alginate solution and a 3 wt% polyethylene oxide (water: ethanol = 9:1) are respectively prepared, and then the sodium alginate solution and the polyethylene oxide solution are mixed at a ratio of 9:1 to obtain a total mass fraction of the polymer of 4.8 wt% as the shell layer solution; the core layer solution and the shell layer solution are respectively put into the syringes of the core liquid and the sheath liquid of a coaxial electrospinning device, and electrospinning is carried out to obtain core-shell structure nanofibers with the polymer as the core and polyethylene oxide and sodium alginate as the shell. Subsequently, the obtained core-shell structure nanofiber material is put into a 2 wt% CaCl2 solution for cross-linking, and then polyethylene oxide is removed by washing with water to obtain an anti-oil pollution core-shell nanofiber membrane with a single-component sodium alginate in the shell layer.

[0020] The surface of the finally prepared electrospun core-shell structured nanofiber membrane is sodium alginate, which has certain oil resistance properties. The water contact angle of the oil-resistant core-shell nanofiber membrane is 0-10°; the underwater oil contact angle is 150-160°; the underwater oil rolling angle is 5-10°.

[0021] Figure 1 The core-shell structured nanofiber is illustrated, where the reference numeral 1 in the attached figure is the sodium alginate nanofiber of the shell layer, and the reference numeral 2 is the polymer nanofiber located in the core layer. Example

[0022] A preparation method of an oil-resistant core-shell nanofiber membrane. First, a polyvinylidene fluoride solution with a concentration of 18 wt% is prepared as the core layer solution; a 4 wt% sodium alginate solution and a 4 wt% polyvinyl alcohol solution (water:ethanol = 8:2) are respectively prepared, and then the sodium alginate solution and the polyvinyl alcohol solution are mixed at a ratio of 8:2 to obtain a total polymer mass fraction of 4 wt% as the shell layer solution; the core layer solution and the shell layer solution are respectively put into the syringes of the core liquid and the sheath liquid of a coaxial electrospinning device, and electrospinning is carried out to obtain core-shell structured nanofibers with the polymer as the core and polyvinyl alcohol and sodium alginate as the shell. Subsequently, the obtained core-shell structured nanofiber material is put into a 1 wt% FeCl3 solution for crosslinking, and then polyvinyl alcohol is removed by washing with water to obtain an oil-resistant core-shell nanofiber membrane with sodium alginate as a single-component shell layer.

[0023] The surface of the finally prepared electrospun core-shell structured nanofiber membrane is sodium alginate, which has certain oil resistance properties. The water contact angle of the oil-resistant core-shell nanofiber membrane is 0-10°; the underwater oil contact angle is 150-160°; the underwater oil rolling angle is 5-10°. Example

[0024] A preparation method of an oil-resistant core-shell nanofiber membrane. First, a polyethersulfone solution with a concentration of 26 wt% is prepared as the core layer solution; a 3 wt% sodium alginate solution and a 3 wt% polyethylene oxide solution (water:ethanol = 8:2) are respectively prepared, and then the sodium alginate solution and the polyethylene oxide solution are mixed at a ratio of 7:3 to obtain a total polymer mass fraction of 3 wt% as the shell layer solution; the core layer solution and the shell layer solution are respectively put into the syringes of the core liquid and the sheath liquid of a coaxial electrospinning device, and electrospinning is carried out to obtain core-shell structured nanofibers with the polymer as the core and polyethylene oxide and sodium alginate as the shell. Subsequently, the obtained core-shell structured nanofiber material is put into a 3 wt% ZnCl2 solution for crosslinking, and then polyethylene oxide is removed by washing with water to obtain an oil-resistant core-shell nanofiber membrane with sodium alginate as a single-component shell layer.

[0025] The surface of the finally obtained electrospun core-shell structured nanofiber membrane is sodium alginate, which has certain oil resistance properties. The water contact angle of the oil-resistant core-shell nanofiber membrane is 0-10°; the underwater oil contact angle is 150-160°; the underwater oil rolling angle is 5-10°. Example

[0026] A preparation method of an oil-resistant core-shell nanofiber membrane. First, prepare a polyurethane solution with a concentration of 15 wt% as the core layer solution; separately prepare a 5 wt% sodium alginate solution and a 5 wt% polyvinyl alcohol solution (water:ethanol = 7:3), and then mix the sodium alginate solution and the polyvinyl alcohol solution in a ratio of 5:5 to obtain a total polymer mass fraction of 5 wt% as the shell layer solution; put the core layer solution and the shell layer solution into the syringes of the core liquid and the sheath liquid of a coaxial electrospinning device respectively, and electrospin to obtain core-shell structured nanofibers with the polymer as the core and polyvinyl alcohol and sodium alginate as the shell. Subsequently, put the obtained core-shell structured nanofiber material into a 2 wt% BaCl2 solution for crosslinking, and then wash with water to remove polyvinyl alcohol to obtain an oil-resistant core-shell nanofiber membrane with sodium alginate as a single-component shell layer.

[0027] The surface of the finally obtained electrospun core-shell structured nanofiber membrane is sodium alginate, which has certain oil resistance properties. The water contact angle of the oil-resistant core-shell nanofiber membrane is 0-10°; the underwater oil contact angle is 150-160°; the underwater oil rolling angle is 5-10°.

Claims

1. A preparation method of an oil-resistant core-shell nanofiber membrane, characterized in that: First, dissolve the polymer in a solvent to obtain a solution for preparing the core layer structure. The polymer is polyacrylonitrile, polyvinylidene fluoride, polyurethane or polyethersulfone. Then, dissolve the water-soluble polymer in a mixed solvent of water and ethanol to obtain a first solution, dissolve sodium alginate in water to obtain a second solution, and then mix the two in proportion to obtain a solution for preparing the shell layer structure. The water-soluble polymer is polyethylene oxide or polyvinyl alcohol. The ratio of ethanol to water in the used mixed solvent is 1:9 to 3:

7. The ratio of the water-soluble polymer solution to the sodium alginate solution is 1:9 to 5:

5. The total mass fraction of the mixed solution is 3 to 5 wt%. Subsequently, coaxial electrospinning is used to obtain core-shell structured nanofibers with the polymer as the core and the water-soluble polymer and sodium alginate as the shell. Crosslink the sodium alginate in the shell layer of the prepared nanofiber membrane, and then wash away the water-soluble polymer through water washing to obtain an oil-resistant core-shell nanofiber membrane.

2. The preparation method of the oil-resistant core-shell nanofiber membrane according to claim 1, characterized in that, The concentration of the polymer solution is 10 to 20 wt%.

3. The preparation method of the oil-resistant core-shell nanofiber membrane according to claim 1, characterized in that, During the coaxial electrospinning process, the perfusion speed of the polymer solution in the shell layer is 1 to 1.5 times that of the polymer solution in the core layer.

4. The preparation method of the anti-oil pollution core-shell nanofiber membrane according to claim 1, characterized in that, The crosslinking agent used is one of CaCl2, FeCl3, AlCl 3、 ZnCl2, BaCl2, and the concentration of the crosslinking agent is 0.5 - 5 wt%.

5. The anti-oil fouling core-shell nanofiber membrane is characterized in that Prepared by any one of the preparation methods of claims 1, 2, 3 or 4, the water contact angle of the oil-resistant core-shell nanofiber membrane is 0 to 10°; the underwater oil contact angle is 150 to 160°; the underwater oil rolling angle is 5 to 10°.

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