Bionic on-demand emulsion separation membrane and preparation method thereof

Abstract

The invention belongs to the technical field of chemical separation, and relates to a bionic on-demand emulsion separation membrane which is formed by compounding a normal beetle wettability fiber layer and an anti-beetle wettability fiber layer, and the two layers form a stable laminated structure through mechanical entanglement of fibers, the thickness of the normal beetle wettability fiber layer and the thickness of the anti-beetle wettability fiber layer are both 0.2-500 micrometers, and the thickness ratio of the normal beetle wettability fiber layer to the anti-beetle wettability fiber layer is 1: 0.2-5. The invention also discloses a preparation method of the bionic on-demand emulsion separation membrane. According to the invention, bionic design and asymmetric wettability technology are utilized to realize high-efficiency treatment of oil-containing wastewater. The method has the advantages that the separation effect is improved by a bionic synergistic demulsification mechanism; multiple types of emulsions are efficiently separated, energy consumption is low, and external stimulation is not needed; the bionic synergistic demulsification mechanism based on positive beetle wettability and anti-beetle wettability is achieved, the separation effect is remarkably improved, the advantage of performance integration is achieved, and efficient on-demand separation of water-in-oil emulsion and oil-in-water emulsion through a single membrane material is achieved.

Description

Technical Field

[0001] The invention belongs to the technical field of chemical separation, relates to a separation membrane, and in particular to a bionic on-demand emulsion separation membrane and a preparation method thereof. Background Art

[0002] Industrialization has led to serious problems with oil spills and oily wastewater discharge, damaging the ecology and threatening biological and human health. The oily wastewater system is complex, containing floating oil / water, heavy oil / water mixtures and emulsions, which require effective separation. Inspired by the superwetting behavior of organisms, special wettability materials have been developed for the treatment of oily wastewater. Separation materials are divided into "water removal" (superhydrophilic / superoleophobic) and "oil removal" (superhydrophobic / superoleophilic), which achieve separation through interfacial effects. However, traditional single wettability materials are unable to separate complex oily wastewater, so the development of switchable wettability surfaces to separate oil-water mixtures and emulsions on demand has become a research hotspot.

[0003] Wettability-smart responsive membrane separation materials can switch wettability through external stimuli, offering advantages such as controllable separation and remote operation, and are widely used in fields such as biomedicine, sensing, and oil-water separation. However, existing materials have a single response factor and require external energy to maintain stimulation, resulting in high energy consumption. Separation membrane materials with asymmetric wettability can effectively avoid the above-mentioned defects and achieve wettability switching by flipping over, showing industrial application potential in oily wastewater treatment. Manually switched wettability separation membranes utilize the diametrically opposite wettability for water and oil and the screening effect of the membrane pore size being smaller than the emulsion particle size to achieve efficient separation of free oil / water mixtures (such as floating oil and dispersed oil), but are not very effective in separating stable water-in-oil (W / O) or oil-in-water (O / W) emulsions.

[0004] In recent years, research on biomimetic superwetting materials has provided a new direction for addressing these issues. The back of a desert beetle is composed of a hydrophobic carapace and hydrophilic protrusions, creating heterogeneous wettability that can capture water droplets from fog in the dry desert environment. This paper draws on the desert beetle's excellent droplet-capturing ability to construct a separation membrane with both beetle-like and asymmetric wettability. The membrane's positive beetle-wetting fiber layer, with the same wettability as the beetle's back, captures water droplets from the emulsion, enabling demulsification of water-in-oil emulsions. The membrane's anti-beetle-wetting fiber layer, with opposite wettability to the beetle's back, captures oil droplets from the emulsion, enabling separation of oil-in-water emulsions. The "positive beetle-wetting" refers to heterogeneous wettability that mimics the wettability structure of the desert beetle's back (i.e., hydrophilic protrusions distributed on a hydrophobic substrate), while the "anti-beetle-wetting" refers to heterogeneous wettability that is the opposite of the wettability structure of the desert beetle's back (i.e., hydrophobic protrusions distributed on a hydrophilic substrate). Summary of the Invention

[0005] The purpose of the present invention is to provide a biomimetic on-demand emulsion separation membrane for high-efficiency demulsification and separation of multiple types of emulsions and a preparation method thereof, so as to solve the problems existing in the above-mentioned background technology.

[0006] Technical Solution

[0007] A bionic on-demand emulsion separation membrane is composited by a positive beetle-wettable fiber layer and an anti-beetle-wettable fiber layer. The two layers form a stable laminated structure through mechanical entanglement of the fibers. The thickness of the positive beetle-wettable fiber layer and the anti-beetle-wettable fiber layer are both 0.2 to 500 μm, and the thickness ratio between the two is 1:0.2 to 5.

[0008] In a preferred disclosed example of the present invention, the beetle wettability fiber layer is based on a hydrophobic polyethylene terephthalate fiber membrane and hydrophilic graded porous alumina microspheres as protrusions, forming heterogeneous wettability with hydrophilic microspheres alternating on the hydrophobic surface, the fiber membrane pore size is 0.1 to 5 μm, the fiber diameter is 10 to 400 nm, and the fiber aspect ratio is 100 to 10,000.

[0009] In a preferred disclosed example of the present invention, the anti-beetle wettability fiber layer is based on a hydrophilic cellulose acetate membrane and hydrophobic graded porous alumina microspheres as protrusions, forming heterogeneous wettability with hydrophobic microspheres alternating on the hydrophilic surface. The pore size of the cellulose membrane is 0.1 to 5 μm, the diameter of the cellulose is 20 to 400 nm, and the fiber aspect ratio is 100 to 10,000.

[0010] In a preferred embodiment of the present invention, the hierarchical porous alumina microspheres are assembled from alumina nanosheets and have a spherical or ellipsoidal morphology. They are commercially available or homemade, and a preparation method is disclosed herein: 2-20 mmol, preferably 10 mmol, of aluminum nitrate and 2-8 mmol, preferably 4 mmol, of hexadecyltrimethylammonium bromide are added to every 100 mL of water, followed by hydrothermal treatment at 120-200°C for 5-20 hours, preferably at 180°C for 10 hours, followed by washing 2-3 times with deionized water and drying at room temperature, and finally calcining in air at 400-600°C for 0.5-3 hours, preferably at 500°C for 2 hours, to obtain hierarchical porous alumina microspheres.

[0011] In a preferred disclosed embodiment of the present invention, the hydrophobic graded porous alumina microspheres are obtained by surface chemically modifying the graded porous alumina microspheres with a hydrophobic modifier, wherein the hydrophobic modifier is a mixture of one or more of KH-550, KH-560, and A-151, preferably KH-550; the surface chemical modification process is as follows: mixing the graded porous alumina microspheres with the hydrophobic modifier in a molar ratio of 1:0.001 to 0.02, preferably 1:0.01, reacting at 20 to 120°C for 0.5 to 24 hours, preferably at 90°C for 12 hours, and then washing alternately with deionized water and ethanol to remove impurities.

[0012] The second object of the present invention is to disclose a method for preparing the above-mentioned biomimetic on-demand emulsion separation membrane.

[0013] A method for preparing a biomimetic on-demand emulsion separation membrane comprises the following steps:

[0014] a) adding polyethylene terephthalate to a mixture of trifluoroacetic acid and dichloromethane in a mass ratio of 1:0 to 3, and continuously stirring to uniformly prepare a 1 to 8 wt % solution, preferably 3 wt %, and preparing a polyethylene terephthalate fiber membrane by an electrospinning method;

[0015] b) adding cellulose acetate to a mixture of trifluoroacetic acid and acetone in a mass ratio of 1:0 to 5, stirring continuously to obtain a 1 to 10 wt % solution, preferably 5 wt %, and further depositing a cellulose acetate layer on the surface of the polyethylene terephthalate fiber membrane by electrospinning to obtain a laminated fiber membrane;

[0016] c) chemically modifying the surface of the hierarchical porous alumina microspheres with a hydrophobic modifier;

[0017] d) preparing a 0.2-5 g / L aqueous suspension of hierarchical porous alumina microspheres, preferably 2 g / L; and preparing a 0.2-5 g / L ethanol suspension of hydrophobic hierarchical porous alumina microspheres, preferably 2 g / L;

[0018] e) The laminated fiber membrane obtained in step b) is treated with 0.5-10 mL of the aqueous suspension of graded porous alumina microspheres obtained in step d) per square centimeter, preferably 5 mL / cm 2 , using vacuum filtration to deposit the hierarchical porous alumina microspheres on the surface of the polyethylene terephthalate fiber layer of the laminated fiber membrane; using 0.5 to 10 mL of the hydrophobic hierarchical porous alumina microsphere ethanol suspension obtained in step d) per square centimeter, preferably 5 mL / cm 2 The hydrophobic graded porous alumina microspheres are deposited on the surface of the cellulose acetate layer of the laminated fiber membrane by vacuum filtration, and dried at 60-80° C. for 8-20 h, preferably at 70° C. for 10 h.

[0019] According to a preferred embodiment of the present invention, in step a), the trifluoroacetic acid and dichloromethane mixture is mixed in a mass ratio of 1:1.5.

[0020] In a preferred embodiment of the present invention, in step a), the process parameters of the electrospinning method are: the solution flow rate is 10 to 200 μL / min, preferably 50 μL / min, the voltage is 8 to 20 kV, preferably 10 kV, the distance between the needle and the roller is 6 to 20 cm, preferably 10 cm, and the rotation speed of the roller is 50 to 400 r / min, preferably 150 r / min.

[0021] According to a preferred embodiment of the present invention, in step b), the mixture of trifluoroacetic acid and acetone is mixed in a mass ratio of 1:2.

[0022] In a preferred embodiment of the present invention, in step b), the process parameters of the electrospinning method are: the solution flow rate is 10 to 200 μL / min, preferably 80 μL / min, the voltage is 10 to 25 kV, preferably 15 kV, the distance between the needle and the roller is 5 to 20 cm, preferably 10 cm, and the rotation speed of the roller is 50 to 400 r / min, preferably 180 r / min.

[0023] In a preferred embodiment of the present invention, in step c), the surface chemical modification is carried out by mixing the hierarchical porous alumina microspheres with a hydrophobic modifier in a molar ratio of 1:0.001 to 0.02, preferably 1:0.01, reacting at 20 to 120°C for 0.5 to 24 hours, preferably at 90°C for 12 hours, and then washing alternately with deionized water and ethanol to remove impurities.

[0024] Beneficial effects

[0025] This invention utilizes biomimetic design and asymmetric wettability technology to achieve efficient treatment of oily wastewater. Its advantages include: a biomimetic synergistic demulsification mechanism improves separation efficiency; highly efficient separation of multiple emulsion types, low energy consumption, and the absence of external stimulation; and a biomimetic synergistic demulsification mechanism based on "positive beetle wettability" and "anti-beetle wettability" significantly improves separation efficiency. This has the advantage of integrated performance, enabling efficient, on-demand separation of both water-in-oil (W / O) and oil-in-water (O / W) emulsions using a single membrane material, with a separation efficiency exceeding 98.6%. DETAILED DESCRIPTION

[0026] The present invention will be described in detail below with reference to the following examples so that those skilled in the art can better understand the present invention. However, the present invention is not limited to the following examples.

[0027] Example 1

[0028] A method for preparing a biomimetic on-demand emulsion separation membrane comprises the following steps:

[0029] a) adding polyethylene terephthalate to a mixture of trifluoroacetic acid and dichloromethane in a mass ratio of 1:1.5, and continuously stirring to obtain a 3 wt % solution, and preparing a polyethylene terephthalate fiber membrane by electrospinning, wherein the electrospinning process parameters are: solution flow rate of 100 μL / min, voltage of 10 kV, distance between needle and roller of 10 cm, and roller speed of 150 rpm;

[0030] b) adding cellulose acetate to a mixture of trifluoroacetic acid and acetone in a mass ratio of 1:2, and continuously stirring to obtain a 5 wt % solution; and further depositing a cellulose acetate layer on the surface of the polyethylene terephthalate fiber membrane prepared in step a by electrospinning to obtain a laminated fiber membrane, wherein the electrospinning process parameters are: solution flow rate of 80 μL / min, voltage of 15 kV, distance between needle and roller of 10 cm, and roller speed of 180 rpm;

[0031] c) chemically modifying the surface of the hierarchical porous alumina microspheres using KH-550. The chemical modification process comprises mixing the hierarchical porous alumina microspheres with the modifier at a molar ratio of 1:0.01, reacting for 12 hours at a temperature of 90° C., and washing three times alternately with deionized water and ethanol.

[0032] d) adding 2 g of graded porous alumina microspheres per liter of water and mechanically stirring to obtain a graded porous alumina microsphere water suspension; adding 2 g of hydrophobically modified graded porous alumina microspheres per liter of ethanol and mechanically stirring to obtain a hydrophobic graded porous alumina microsphere ethanol suspension;

[0033] e) The laminated fiber membrane obtained in step b) was deposited on the surface of the polyethylene terephthalate fiber layer of the laminated fiber membrane by vacuum filtration using 5 mL / cm2 of the aqueous suspension of graded porous alumina microspheres obtained in step d. The hydrophobic graded porous alumina microspheres were deposited on the surface of the cellulose acetate layer of the laminated fiber membrane by vacuum filtration using 5 mL / cm2 of the ethanol suspension of hydrophobic graded porous alumina microspheres obtained in step d. The membrane was dried at 70°C for 10 h.

[0034] As a comparative example, an emulsion separation membrane lacking a biomimetic structure was prepared: a polyethylene terephthalate electrospun membrane (hydrophobic layer) and a cellulose acetate electrospun membrane (hydrophilic layer) identical to those in this example but not modified with alumina microspheres were taken and subjected to the same emulsion separation test. The results are shown in Table 1.

[0035] Table 1. Summary of emulsion separation efficiency of Example 1

[0036]

[0037] Example 2

[0038] A method for preparing a biomimetic on-demand emulsion separation membrane comprises the following steps:

[0039] a) adding polyethylene terephthalate to a mixture of trifluoroacetic acid and dichloromethane in a mass ratio of 1:3, and continuously stirring to obtain a 1 wt % solution, and preparing a polyethylene terephthalate fiber membrane by electrospinning, wherein the electrospinning process parameters are: solution flow rate of 200 μL / min, voltage of 8 kV, distance between needle and roller of 15 cm, and roller speed of 300 rpm;

[0040] b) adding cellulose acetate to a mixture of trifluoroacetic acid and acetone in a mass ratio of 1:5, and continuously stirring to obtain a 2 wt % solution; and further depositing a cellulose acetate layer on the surface of the polyethylene terephthalate fiber membrane prepared in step a by electrospinning to obtain a laminated fiber membrane, wherein the electrospinning process parameters are: solution flow rate of 180 μL / min, voltage of 20 kV, distance between needle and roller of 15 cm, and roller speed of 300 rpm;

[0041] c) chemically modifying the surface of the hierarchical porous alumina microspheres using KH-560. The chemical modification process comprises mixing the hierarchical porous alumina microspheres with the modifier at a molar ratio of 1:0.001, reacting for 24 hours at a temperature of 120° C., and washing three times alternately with deionized water and ethanol.

[0042] d) adding 5 g of graded porous alumina microspheres per liter of water and mechanically stirring to obtain a graded porous alumina microsphere water suspension; adding 5 g of hydrophobically modified graded porous alumina microspheres per liter of ethanol and mechanically stirring to obtain a hydrophobic graded porous alumina microsphere ethanol suspension;

[0043] e) The laminated fiber membrane obtained in step b) was deposited on the surface of the polyethylene terephthalate fiber layer of the laminated fiber membrane by vacuum filtration using 0.5 mL / cm2 of the aqueous suspension of graded porous alumina microspheres obtained in step d. The hydrophobic graded porous alumina microspheres were deposited on the surface of the cellulose acetate layer of the laminated fiber membrane by vacuum filtration using 0.5 mL / cm2 of the ethanol suspension of hydrophobic graded porous alumina microspheres obtained in step d. The membrane was dried at 80°C for 8 h.

[0044] As a comparative example, an emulsion separation membrane lacking a biomimetic structure was prepared: a polyethylene terephthalate electrospun membrane (hydrophobic layer) and a cellulose acetate electrospun membrane (hydrophilic layer) identical to those in this example but not modified with alumina microspheres were taken and subjected to the same emulsion separation test. The results are shown in Table 2.

[0045] Table 2. Summary of emulsion separation efficiency of Example 2

[0046]

[0047] Example 3

[0048] A method for preparing a biomimetic on-demand emulsion separation membrane comprises the following steps:

[0049] a) adding polyethylene terephthalate to a mixture of trifluoroacetic acid and dichloromethane in a mass ratio of 1:2, and continuously stirring to obtain a 2 wt % solution, and preparing a polyethylene terephthalate fiber membrane by electrospinning, wherein the electrospinning process parameters are: solution flow rate of 150 μL / min, voltage of 15 kV, distance between needle and roller of 15 cm, and roller speed of 300 rpm;

[0050] b) adding cellulose acetate to a mixture of trifluoroacetic acid and acetone in a mass ratio of 1:3, and continuously stirring to obtain a 4 wt % solution; and further depositing a cellulose acetate layer on the surface of the polyethylene terephthalate fiber membrane prepared in step a by electrospinning to obtain a laminated fiber membrane, wherein the electrospinning process parameters are: solution flow rate of 150 μL / min, voltage of 20 kV, distance between needle and roller of 20 cm, and roller speed of 400 rpm;

[0051] c) chemically modifying the surface of the hierarchical porous alumina microspheres using KH-550. The chemical modification process comprises mixing the hierarchical porous alumina microspheres with the modifier at a molar ratio of 1:0.02, reacting for 1 hour at a temperature of 120° C., and washing the microspheres alternately with deionized water and ethanol three times.

[0052] d) adding 4 g of graded porous alumina microspheres per liter of water and mechanically stirring to obtain a graded porous alumina microsphere water suspension; adding 4 g of hydrophobically modified graded porous alumina microspheres per liter of ethanol and mechanically stirring to obtain a hydrophobic graded porous alumina microsphere ethanol suspension;

[0053] e) The laminated fiber membrane obtained in step b) was deposited on the surface of the polyethylene terephthalate fiber layer of the laminated fiber membrane by vacuum filtration using 8 mL / cm2 of the aqueous suspension of graded porous alumina microspheres obtained in step d. The hydrophobic graded porous alumina microspheres were deposited on the surface of the cellulose acetate layer of the laminated fiber membrane by vacuum filtration using 8 mL / cm2 of the ethanol suspension of hydrophobic graded porous alumina microspheres obtained in step d. The membrane was dried at 60°C for 15 h.

[0054] As a comparative example, an emulsion separation membrane lacking a biomimetic structure was prepared: a polyethylene terephthalate electrospun membrane (hydrophobic layer) and a cellulose acetate electrospun membrane (hydrophilic layer) identical to those in this example but not modified with alumina microspheres were taken and subjected to the same emulsion separation test. The results are shown in Table 3.

[0055] Table 3. Summary of emulsion separation efficiency of Example 3

[0056]

[0057] Example 4

[0058] A method for preparing a biomimetic on-demand emulsion separation membrane comprises the following steps:

[0059] a) adding polyethylene terephthalate to trifluoroacetic acid and continuously stirring to obtain an 8 wt % solution, and preparing a polyethylene terephthalate fiber membrane by electrospinning, wherein the electrospinning process parameters are: solution flow rate of 50 μL / min, voltage of 20 kV, distance between needle and roller of 6 cm, and roller speed of 100 rpm;

[0060] b) adding cellulose acetate to a mixture of trifluoroacetic acid and acetone in a mass ratio of 1:1, and continuously stirring to obtain an 8 wt % solution; and further depositing a cellulose acetate layer on the surface of the polyethylene terephthalate fiber membrane prepared in step a by electrospinning to obtain a laminated fiber membrane, wherein the electrospinning process parameters are: solution flow rate of 50 μL / min, voltage of 20 kV, distance between needle and roller of 8 cm, and roller speed of 150 rpm;

[0061] c) chemically modifying the surface of hierarchical porous alumina microspheres using A-151, wherein the hierarchical porous alumina microspheres and the modifier are mixed at a molar ratio of 1:0.005, reacted at 90°C for 20 hours, and washed alternately with deionized water and ethanol three times;

[0062] d) adding 0.2 g of graded porous alumina microspheres per liter of water and mechanically stirring to obtain a graded porous alumina microsphere water suspension, and adding 0.2 g of hydrophobically modified graded porous alumina microspheres per liter of ethanol and mechanically stirring to obtain a hydrophobic graded porous alumina microsphere ethanol suspension;

[0063] e) The laminated fiber membrane obtained in step b) was deposited on the surface of the polyethylene terephthalate fiber layer of the laminated fiber membrane by vacuum filtration using 8 mL / cm2 of the aqueous suspension of the graded porous alumina microspheres obtained in step d. The hydrophobic graded porous alumina microspheres were deposited on the surface of the cellulose acetate layer of the laminated fiber membrane by vacuum filtration using 8 mL / cm2 of the ethanol suspension of the hydrophobic graded porous alumina microspheres obtained in step d. The membrane was dried at 60°C for 10 h.

[0064] As a comparative example, an emulsion separation membrane lacking a biomimetic structure was prepared: a polyethylene terephthalate electrospun membrane (hydrophobic layer) and a cellulose acetate electrospun membrane (hydrophilic layer) identical to those in this example but not modified with alumina microspheres were taken and subjected to the same emulsion separation test. The results are shown in Table 4.

[0065] Table 4. Summary of emulsion separation efficiency of Example 4

[0066]

[0067] Example 5

[0068] A method for preparing a biomimetic on-demand emulsion separation membrane comprises the following steps:

[0069] a) adding polyethylene terephthalate to a mixture of trifluoroacetic acid and dichloromethane in a mass ratio of 1:1, and continuously stirring to obtain a 5 wt % solution, and preparing a polyethylene terephthalate fiber membrane by electrospinning, wherein the electrospinning process parameters are: solution flow rate of 100 μL / min, voltage of 15 kV, distance between needle and roller of 16 cm, and roller speed of 80 rpm;

[0070] b) adding cellulose acetate to trifluoroacetic acid and continuously stirring to obtain a 10 wt % solution, and further depositing a cellulose acetate layer on the surface of the polyethylene terephthalate fiber membrane prepared in step a by electrospinning to obtain a laminated fiber membrane, wherein the electrospinning process parameters are: solution flow rate of 50 μL / min, voltage of 25 kV, distance between needle and roller of 8 cm, and roller speed of 50 rpm;

[0071] c) chemically modifying the surface of the hierarchical porous alumina microspheres using KH-550, wherein the hierarchical porous alumina microspheres and the modifier are mixed at a molar ratio of 1:0.02, reacted at 100°C for 2 hours, and washed three times alternately with deionized water and ethanol;

[0072] d) adding 5 g of graded porous alumina microspheres per liter of water and mechanically stirring to obtain a graded porous alumina microsphere water suspension; adding 5 g of hydrophobically modified graded porous alumina microspheres per liter of ethanol and mechanically stirring to obtain a hydrophobic graded porous alumina microsphere ethanol suspension;

[0073] e) The laminated fiber membrane obtained in step b) is deposited on the surface of the polyethylene terephthalate fiber layer of the laminated fiber membrane by vacuum filtration using 3 mL / cm2 of the aqueous suspension of the graded porous alumina microspheres obtained in step d. The hydrophobic graded porous alumina microspheres obtained in step d are deposited on the surface of the cellulose acetate layer of the laminated fiber membrane by vacuum filtration using 3 mL / cm2 of the ethanol suspension of the hydrophobic graded porous alumina microspheres obtained in step d. The membrane is then dried at 80°C for 10 h.

[0074] As a comparative example, an emulsion separation membrane lacking a biomimetic structure was prepared: a polyethylene terephthalate electrospun membrane (hydrophobic layer) and a cellulose acetate electrospun membrane (hydrophilic layer) identical to those in this example but not modified with alumina microspheres were taken and subjected to the same emulsion separation test. The results are shown in Table 5.

[0075] Table 5. Summary of emulsion separation efficiency of Example 5

[0076]

[0077] Example 6

[0078] A method for preparing a biomimetic on-demand emulsion separation membrane comprises the following steps:

[0079] a) adding polyethylene terephthalate to a mixture of trifluoroacetic acid and dichloromethane in a mass ratio of 1:1.5, and continuously stirring to obtain a 3 wt % solution, and preparing a polyethylene terephthalate fiber membrane by electrospinning, wherein the electrospinning process parameters are: solution flow rate of 100 μL / min, voltage of 10 kV, distance between needle and roller of 10 cm, and roller speed of 150 rpm;

[0080] b) adding cellulose acetate to a mixture of trifluoroacetic acid and acetone in a mass ratio of 1:1, and continuously stirring to obtain an 8 wt % solution; and further depositing a cellulose acetate layer on the surface of the polyethylene terephthalate fiber membrane prepared in step a by electrospinning to obtain a laminated fiber membrane, wherein the electrospinning process parameters are: solution flow rate of 100 μL / min, voltage of 25 kV, distance between needle and roller of 5 cm, and roller speed of 100 rpm;

[0081] c) chemically modifying the surface of the hierarchical porous alumina microspheres using KH-560. The chemical modification process comprises mixing the hierarchical porous alumina microspheres with the modifier at a molar ratio of 1:0.005, reacting for 15 hours at a temperature of 50° C., and washing three times alternately with deionized water and ethanol.

[0082] d) adding 2 g of graded porous alumina microspheres per liter of water and mechanically stirring to obtain a graded porous alumina microsphere water suspension; adding 2 g of hydrophobically modified graded porous alumina microspheres per liter of ethanol and mechanically stirring to obtain a hydrophobic graded porous alumina microsphere ethanol suspension;

[0083] e) The laminated fiber membrane obtained in step b) is deposited on the surface of the polyethylene terephthalate fiber layer of the laminated fiber membrane by vacuum filtration using 10 mL / cm2 of the aqueous suspension of graded porous alumina microspheres obtained in step d. The hydrophobic graded porous alumina microspheres obtained in step d are deposited on the surface of the cellulose acetate layer of the laminated fiber membrane by vacuum filtration using 10 mL / cm2 of the ethanol suspension of hydrophobic graded porous alumina microspheres obtained in step d. The membrane is then dried at 80°C for 8 h.

[0084] As a comparative example, an emulsion separation membrane lacking a biomimetic structure was prepared: a polyethylene terephthalate electrospun membrane (hydrophobic layer) and a cellulose acetate electrospun membrane (hydrophilic layer) identical to those in this example but not modified with alumina microspheres were taken and subjected to the same emulsion separation test. The results are shown in Table 6.

[0085] Table 6. Summary of emulsion separation efficiency of Example 6

[0086]

[0087] The above-described embodiments are merely implementation methods of the present invention and are not intended to limit the patent scope of the present invention. Any equivalent structure or equivalent process transformation made using the description of the present invention, or directly or indirectly applied in other related technical fields, are also included in the patent protection scope of the present invention.

Claims

1. A biomimetic on-demand emulsion separation membrane, comprising a composite of a positive beetle-wettable fiber layer and an anti-beetle-wettable fiber layer, wherein the two layers are mechanically entangled to form a stable laminated structure, characterized by: The thickness of the positive beetle wettability fiber layer and the anti-beetle wettability fiber layer are both 0.2-500 μm, and the thickness ratio between the two is 1:0.2-5.

2. The biomimetic on-demand emulsion separation membrane according to claim 1, characterized in that: The beetle wettability fiber layer is based on a hydrophobic polyethylene terephthalate fiber membrane and hydrophilic graded porous alumina microspheres as protrusions, forming heterogeneous wettability with hydrophilic microspheres alternating on the hydrophobic surface. The fiber membrane pore size is 0.1 to 5 μm, the fiber diameter is 10 to 400 nm, and the fiber aspect ratio is 100 to 10,000.

3. The biomimetic on-demand emulsion separation membrane according to claim 1, characterized in that: The anti-beetle wettability fiber layer is based on a hydrophilic cellulose acetate membrane and has hydrophobic graded porous alumina microspheres as protrusions, forming heterogeneous wettability with hydrophobic microspheres alternating on the hydrophilic surface. The pore size of the cellulose membrane is 0.1 to 5 μm, the diameter of the cellulose is 20 to 400 nm, and the fiber aspect ratio is 100 to 10,000.

4. The biomimetic on-demand emulsion separation membrane according to claim 1, characterized in that: The hydrophobic graded porous alumina microspheres are obtained by surface chemically modifying the graded porous alumina microspheres with a hydrophobic modifier, wherein the hydrophobic modifier is a mixture of one or more of KH-550, KH-560, and A-151, preferably KH-550. The surface chemical modification process comprises mixing the graded porous alumina microspheres with the hydrophobic modifier in a molar ratio of 1:0.001 to 0.02, preferably 1:0.01, reacting at 20 to 120° C. for 0.5 to 24 hours, preferably at 90° C. for 12 hours, and then washing alternately with deionized water and ethanol to remove impurities.

5. A method for preparing the biomimetic on-demand emulsion separation membrane according to any one of claims 1 to 4, characterized in that: The steps include: a) adding polyethylene terephthalate to a mixture of trifluoroacetic acid and dichloromethane in a mass ratio of 1:0 to 3, and continuously stirring to uniformly prepare a 1 to 8 wt % solution, preferably 3 wt %, and preparing a polyethylene terephthalate fiber membrane by an electrospinning method; b) adding cellulose acetate to a mixture of trifluoroacetic acid and acetone in a mass ratio of 1:0 to 5, stirring continuously to obtain a 1 to 10 wt % solution, preferably 5 wt %, and further depositing a cellulose acetate layer on the surface of the polyethylene terephthalate fiber membrane by electrospinning to obtain a laminated fiber membrane; c) chemically modifying the surface of the hierarchical porous alumina microspheres with a hydrophobic modifier; d) preparing a 0.2-5 g / L aqueous suspension of hierarchical porous alumina microspheres, preferably 2 g / L; and preparing a 0.2-5 g / L ethanol suspension of hydrophobic hierarchical porous alumina microspheres, preferably 2 g / L; e) The laminated fiber membrane obtained in step b) is treated with 0.5-10 mL of the aqueous suspension of graded porous alumina microspheres obtained in step d) per square centimeter, preferably 5 mL / cm 2 , using vacuum filtration to deposit the hierarchical porous alumina microspheres on the surface of the polyethylene terephthalate fiber layer of the laminated fiber membrane; using 0.5 to 10 mL of the hydrophobic hierarchical porous alumina microsphere ethanol suspension obtained in step d) per square centimeter, preferably 5 mL / cm 2 The hydrophobic graded porous alumina microspheres are deposited on the surface of the cellulose acetate layer of the laminated fiber membrane by vacuum filtration, and dried at 60-80° C. for 8-20 h, preferably at 70° C. for 10 h.

6. The method for preparing the biomimetic on-demand emulsion separation membrane according to claim 5, wherein: In step a), the trifluoroacetic acid and dichloromethane mixture is mixed in a mass ratio of 1:1.

5.

7. The method for preparing the biomimetic on-demand emulsion separation membrane according to claim 5, wherein: In step a), the process parameters of the electrospinning method are: solution flow rate of 10-200 μL / min, voltage of 8-20 kV, distance between the needle and the roller of 6-20 cm, and roller speed of 50-400 rpm.

8. The method for preparing the biomimetic on-demand emulsion separation membrane according to claim 7, wherein: In step a), the process parameters of the electrospinning method are: solution flow rate of 50 μL / min, voltage of 10 kV, distance between the needle and the roller of 10 cm, and rotation speed of the roller of 150 rpm.

9. The method for preparing the biomimetic on-demand emulsion separation membrane according to claim 5, characterized in that: In step b), the mixture of trifluoroacetic acid and acetone is mixed in a mass ratio of 1:

2.

10. The method for preparing the biomimetic on-demand emulsion separation membrane according to claim 5, characterized in that: In step b), the process parameters of the electrospinning method are: solution flow rate of 10 to 200 μL / min, preferably 80 μL / min, voltage of 10 to 25 kV, preferably 15 kV, the distance between the needle and the roller is 5 to 20 cm, preferably 10 cm, and the roller speed is 50 to 400 rpm, preferably 180 rpm.

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