A multifunctional aerogel membrane based on charge demulsification, its preparation method and application

Abstract

This invention belongs to the field of environmental functional materials and water treatment technology, specifically relating to a multifunctional aerogel membrane based on charge-induced demulsification, its preparation method, and its applications. The oil-water separation aerogel membrane prepared by this invention uses quaternized chitosan as the backbone and agricultural waste corn cobs as the filler material, prepared through a directional freeze-drying composite process. This aerogel membrane combines multiple functions including oil-water separation, emulsion demulsification, and dye adsorption. For oil-water mixtures, after 10 cycles of recycling, the separation flux can maintain more than 85% of the initial flux, with a separation efficiency of up to 99%. The separation efficiency for different types of oil-in-water emulsions can reach over 97%. Furthermore, the raw materials are renewable, and the preparation process is green and environmentally friendly, solving the problems of weak demulsification ability, single function, and poor environmental friendliness of traditional oil-water separation materials. It can be widely used in oily wastewater treatment, industrial wastewater treatment, and other fields.

Description

Technical Field

[0001] This invention belongs to the field of environmental functional materials and water treatment technology, specifically relating to a multifunctional aerogel membrane based on charge demulsification, its preparation method, and its application. Background Technology

[0002] The information disclosed in the background section of this invention is intended only to enhance the understanding of the overall background of the invention and is not necessarily to be construed as an admission or in any way implying that such information constitutes prior art known to those skilled in the art.

[0003] Oily wastewater is widely found in industrial production processes such as petrochemicals, machining, textile printing and dyeing, and food processing. In these processes, a large number of oil droplets form stable emulsion systems under the action of surfactants. The oil droplets in these emulsions are small in size and have stable interfacial charges, making them difficult to remove effectively using traditional separation techniques (gravity sedimentation, centrifugation, adsorption, etc.). Furthermore, actual industrial wastewater often contains dye pollutants, further increasing the difficulty of treatment.

[0004] Existing separation materials mostly possess only a single oil-water separation function, failing to achieve multi-functional synergistic processing. Furthermore, some materials are prepared using non-renewable raw materials, resulting in pollution during the preparation process. Currently, aerogel materials, due to their high specific surface area and porous structure, show promising application prospects in the field of oil-water separation. However, existing technologies face the following unresolved challenges:

[0005] (1) Weak demulsification ability: It relies on physical sieving or surface wettability separation (hydrophobic and oleophilic or hydrophilic and oleophobic), which cannot neutralize the surface charge of the emulsion oil droplets, resulting in low efficiency of stable emulsion separation.

[0006] (2) Functional limitation: Most aerogels are designed only for oil-water separation and cannot simultaneously treat complex pollutants such as dyes. They require multi-stage treatment equipment, which increases costs.

[0007] (3) Insufficient stability: Non-crosslinked aerogels have poor mechanical strength and are difficult to withstand the pressure generated by the solution above during filtration or the structure collapses after repeated use.

[0008] Therefore, those skilled in the art urgently need to develop separation materials that are multifunctional, environmentally friendly, highly efficient, and stable, combining demulsification, separation, and adsorption capabilities, in order to solve the above problems. Summary of the Invention

[0009] To address the needs of existing technologies, the purpose of this invention is to provide a multifunctional aerogel membrane based on charge-induced demulsification, its preparation method, and its applications. This invention achieves multifunctional integration of efficient demulsification of oil-containing emulsions, oil-water separation, and dye adsorption through the synergistic effect of the charge properties of quaternized chitosan and the porous structure of corn cobs, while simultaneously ensuring the material's environmental friendliness and recyclability.

[0010] Specifically, the present invention provides the following technical solution:

[0011] In a first aspect, the present invention provides a multifunctional aerogel membrane based on charge demulsification, comprising, by mass concentration, the following raw materials: 1% to 5% corn cob powder, 2% quaternized chitosan, 2% crosslinking agent, and the balance being deionized water.

[0012] Preferably, the multifunctional aerogel membrane comprises, by mass concentration, the following raw materials: 2% corn cob powder, 2% quaternized chitosan, 2% crosslinking agent, and the balance being deionized water.

[0013] Preferably, the degree of substitution of the quaternized chitosan is 90% to 95%.

[0014] Preferably, the crosslinking agent is selected from one or more of glutaraldehyde, epichlorohydrin, and ethylene glycol diglycidyl ether, and the crosslinking agent is an aqueous solution with a concentration of 25%.

[0015] Preferably, after the multifunctional aerogel membrane is recycled 10 times, the separation flux of the oil-water mixture is maintained at more than 85% of the initial flux, and the separation efficiency is ≥99%.

[0016] Preferably, the multifunctional aerogel membrane has an adsorption rate of ≥96% for anionic dyes, including toluidine blue, orthocyanin, Nile red, and Congo red.

[0017] A second aspect of the present invention provides a method for preparing the above-mentioned multifunctional aerogel membrane based on charge demulsification, comprising the following steps:

[0018] S1. Add the pretreated corn cob powder and quaternized chitosan to deionized water, stir at room temperature until uniformly dispersed, then add the crosslinking agent, heat and stir at a constant temperature to obtain a viscous mixed solution.

[0019] S2. The mixed solution is quantitatively injected into the mold, and directional freezing is performed by mixing liquid nitrogen with ethanol to form a frozen preform with a gradient pore structure.

[0020] S3. Vacuum dry the frozen preform to remove moisture until constant weight is achieved.

[0021] Preferably, in step S1, the pretreatment includes crushing the corn cob, passing it through a 300-mesh sieve, ultrasonically cleaning it with deionized water for 10-20 minutes to remove surface impurities and soluble components, and then drying it to constant weight at 80-100°C.

[0022] Preferably, in step S1, the room temperature stirring rate is 300~500 r / min and the time is 2~4 h; the constant temperature stirring temperature is 40~50℃ and the time is 2~4 h.

[0023] Preferably, in step S2, the mold is a copper-based polycarbonate mold.

[0024] Preferably, in step S2, the directional freezing temperature is -150~-120℃ and the time is 25~35 min.

[0025] Preferably, in step S2, the pore size range of the gradient pore structure is 37~112 μm, and the pore size is gradually reduced from top to bottom by adjusting the concentration of corn cob powder.

[0026] Preferably, in step S3, the vacuum drying process involves a vacuum degree ≤ 50 Pa, a temperature of -50 to -60°C, and a time of 24 to 48 hours.

[0027] A third aspect of the present invention provides an application of the multifunctional aerogel membrane based on charge demulsification described in the first aspect in the treatment of oily wastewater, oil-in-water emulsions, and / or dye wastewater.

[0028] Preferably, the oil phase in the oil-in-water emulsion is PAO4 olefin lubricating oil, petroleum ether, diesel oil, or vacuum pump oil, and the surfactant is sodium dodecyl sulfate.

[0029] The beneficial effects achieved by one or more of the above technical solutions of the present invention are as follows:

[0030] (1) This invention utilizes the synergistic effect of quaternized chitosan and corn cob, combined with a directional freeze-freeze drying process, to construct an aerogel membrane with a gradient pore size structure and positive surface charge characteristics. Specifically:

[0031] By utilizing quaternized chitosan to impart a positive charge to the surface of the aerogel membrane, the stability of oil-in-water emulsions is rapidly disrupted through charge neutralization, achieving a demulsification rate of over 98%. This overcomes the technical bottleneck of traditional aerogel materials that rely on physical sieving or surface wettability separation, resulting in poor performance in treating stable emulsions. Simultaneously, the gradient pore structure generates capillary gradient forces during separation, accelerating the oil-water separation process. The separation efficiency for different types of oil-in-water emulsions reaches over 90%, significantly superior to existing materials.

[0032] (2) By adjusting the concentration of corn cob powder (1%~5%), this invention enables precise control of the aerogel membrane pore size within the range of 37~112 μm. Large-pore membranes are suitable for separating oil-water mixtures, achieving a separation efficiency of ≥99% while significantly increasing the separation flux; small-pore membranes are suitable for treating oil-in-water emulsions and dye wastewater, improving separation efficiency. This structure can flexibly match different treatment requirements, balancing separation efficiency and flux.

[0033] (3) The aerogel membrane prepared by the present invention not only has efficient oil-water separation and emulsion demulsification functions, but also can remove dye pollutants through electrostatic adsorption and natural adsorption of corn cob. The adsorption rate of anionic dyes (such as toluidine blue, Congo red, etc.) can reach more than 96%, realizing one-stop treatment of oil and dye composite wastewater without the need for multi-stage equipment, significantly reducing treatment costs and system complexity.

[0034] (4) The present invention constructs a stable three-dimensional network structure through crosslinking agent. Combined with the capillary force enhancement effect brought about by gradient pore size, the aerogel membrane still maintains a separation efficiency of more than 99.9% and a separation flux of more than 85% of the initial value after 10 cycles of use, showing excellent mechanical stability and pollution resistance, and meeting the requirements for long-term material performance in practical applications.

[0035] (5) This invention uses agricultural waste corn cobs as one of the main raw materials to realize the high-value utilization of biomass resources; the preparation process uses water as the dispersion medium and does not use toxic organic solvents, which has good environmental friendliness and industrialization prospects. Attached Figure Description

[0036] The accompanying drawings, which form part of this invention, are used to provide a further understanding of the invention. The illustrative embodiments of the invention and their descriptions are used to explain the invention and do not constitute an improper limitation of the invention.

[0037] Figure 1 This is a schematic diagram of the preparation process of the multifunctional aerogel membrane prepared according to the present invention;

[0038] Figure 2 The images shown are cross-sectional scanning electron microscope (SEM) images of the aerogel membranes prepared in Examples 1-5 and Comparative Example 1 of this invention. Specifically, a is a cross-sectional SEM image of the aerogel membrane prepared in Comparative Example 1, b is a cross-sectional SEM image of the multifunctional aerogel membrane prepared in Example 2, c is a cross-sectional SEM image of the multifunctional aerogel membrane prepared in Example 1, d is a cross-sectional SEM image of the multifunctional aerogel membrane prepared in Example 3, e is a cross-sectional SEM image of the multifunctional aerogel membrane prepared in Example 4, and f is a cross-sectional SEM image of the multifunctional aerogel membrane prepared in Example 5.

[0039] Figure 3 This is a schematic diagram of the capillary force principle when the aerogel membrane prepared in the embodiment of the present invention is placed in the forward and reverse directions, where a is the capillary force principle diagram when placed in the forward direction and b is the capillary force principle diagram when placed in the reverse direction.

[0040] Figure 4 The graph shows the separation efficiency and separation flux of the aerogel membrane prepared in Example 1 of this invention after 10 cycles of cyclic separation of oil-water mixture.

[0041] Figure 5These are photographs of the aerogel membranes prepared in Example 1 and Comparative Example 1 of the present invention after adsorbing different dyes. In example a, the aerogel membrane prepared in Example 1 is photographed after adsorbing toluidine blue (1), orthocyanin (2), Nile red (3), and Congo red (4), respectively. In example b, the aerogel membrane prepared in Comparative Example 1 is photographed after adsorbing toluidine blue (1), orthocyanin (2), Nile red (3), and Congo red (4), respectively. Detailed Implementation

[0042] It should be noted that the following detailed descriptions are exemplary and intended to provide further illustration of the invention. Unless otherwise specified, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains.

[0043] As mentioned above, existing aerogel materials mostly rely on surface wettability (hydrophobic / oleophilic or hydrophilic / oleophobic) for separation, which suffers from problems such as weak demulsification ability, limited functionality, and poor cycle stability. Furthermore, industrial wastewater often contains complex pollutants such as dyes, necessitating the development of separation materials that are multifunctional, environmentally friendly, and highly efficient and stable, combining demulsification, separation, and adsorption capabilities. Therefore, this invention provides a multifunctional aerogel membrane based on charge-induced demulsification, using quaternized chitosan as the framework and corn cob as the filler material, prepared through a directional freeze-drying process. It possesses gradient pore size and positive surface charge characteristics, achieving integrated multifunctionality for oil-water separation, emulsion demulsification, and dye adsorption.

[0044] The first typical embodiment of the present invention provides a multifunctional aerogel membrane based on charge demulsification, which, by mass concentration, comprises the following raw materials: 1%~5% corn cob powder, 2% quaternized chitosan, 2% crosslinking agent, and the balance being deionized water.

[0045] In one or more embodiments of this implementation, the multifunctional aerogel membrane comprises, by mass concentration, the following raw materials: 2% corn cob powder, 2% quaternized chitosan, 2% crosslinking agent, and the balance being deionized water.

[0046] In one or more embodiments of this implementation, the degree of substitution of the quaternized chitosan is 90% to 95%. The higher the degree of substitution, the more quaternary ammonium groups on the chitosan molecule, and the more sites that can be crosslinked with the crosslinking agent, thereby improving the strength of the sample.

[0047] In one or more embodiments of this implementation, the crosslinking agent is selected from one or more of glutaraldehyde, epichlorohydrin, and ethylene glycol diglycidyl ether, and the crosslinking agent is a 25% aqueous solution. The crosslinking agent enables corn cob and quaternized chitosan to form a stable crosslinked network, improving the mechanical stability and water resistance of the material.

[0048] Deionized water is used as a dispersion medium to ensure the directional growth of ice crystals during freezing, forming a gradient porous structure.

[0049] In one or more embodiments of this implementation, after the multifunctional aerogel membrane is recycled 10 times, the separation flux of the oil-water mixture is maintained at more than 85% of the initial flux, and the separation efficiency is ≥99%.

[0050] In one or more embodiments of this implementation, the multifunctional aerogel membrane has an adsorption rate of ≥96% for anionic dyes, including toluidine blue, carmine, Nile red, and Congo red.

[0051] A second typical embodiment of the present invention provides a method for preparing the above-mentioned multifunctional aerogel membrane based on charge demulsification, comprising the following steps:

[0052] S1. Add the pretreated corn cob powder and quaternized chitosan to deionized water, stir at room temperature until uniformly dispersed, then add the crosslinking agent, heat and stir at a constant temperature to obtain a viscous mixed solution.

[0053] S2. The mixed solution is quantitatively injected into the mold, and directional freezing is performed by mixing liquid nitrogen with ethanol to form a frozen preform with a gradient pore structure.

[0054] S3. Vacuum dry the frozen preform to remove moisture until constant weight is achieved.

[0055] In one or more embodiments of this implementation, in step S1, the pretreatment includes crushing the corn cob, passing it through a 300-mesh sieve, ultrasonically cleaning it with deionized water for 10-20 minutes to remove surface impurities and soluble components, and then drying it to constant weight at 80-100°C.

[0056] In one or more embodiments of this implementation, in step S1, the stirring rate at room temperature is 300~500 r / min and the time is 2~4 h; the temperature of the constant temperature stirring is 40~50℃ and the time is 2~4 h.

[0057] In one or more embodiments of this implementation, in step S2, the mold is a copper-base polycarbonate mold.

[0058] In this invention, the copper-base polycarbonate mold specifically refers to: using AB glue to attach a PC tube to a 1 mm thick copper plate, ensuring no gaps between the copper plate and the PC tube; quantitatively adding the cross-linked solution into the PC tube; and quickly placing it into a liquid nitrogen tank (ensuring that the corn cob powder in the solution does not precipitate); ensuring that the copper plate just contacts the liquid nitrogen while the PC tube does not contact the liquid nitrogen; thus, through conduction by the copper plate, the solution in the PC tube freezes from bottom to top.

[0059] In one or more embodiments of this implementation, in step S2, the directional freezing temperature is -150 to -120°C, and the time is 25 to 35 minutes. Directional freezing is used to cause ice crystals to grow in a directional manner along the cooling direction, forming a frozen blank with a gradient pore size.

[0060] In one or more embodiments of this implementation, in step S2, the pore size range of the gradient pore structure is 37~112 μm, and the pore size is gradually reduced from top to bottom by adjusting the concentration of corn cob powder.

[0061] In one or more embodiments of this implementation, in step S3, the vacuum drying process involves a vacuum degree ≤ 50 Pa, a temperature of -50 to -60°C, and a time of 24 to 48 hours. Vacuum drying is used to directly sublimate and remove ice crystals while preserving the gradient porous structure to obtain an aerogel membrane.

[0062] A third typical embodiment of the present invention provides an application of the multifunctional aerogel membrane based on charge demulsification as described in the first aspect in the treatment of oily wastewater, oil-in-water emulsions, and / or dye wastewater.

[0063] In one or more embodiments of this implementation, the oil phase in the oil-in-water emulsion is PAO4 olefin lubricating oil, petroleum ether, diesel oil, or vacuum pump oil, and the surfactant is sodium dodecyl sulfate.

[0064] To enable those skilled in the art to better understand the technical solution of the present invention, the technical solution of the present invention will be described in detail below with reference to specific embodiments.

[0065] Example 1: This example provides a multifunctional aerogel membrane based on charge demulsification and its preparation method.

[0066] The multifunctional superhydrophilic / underwater superoleophobic oil-water separation aerogel membrane based on charge demulsification comprises the following raw materials by mass concentration: 2% corn cob powder, 2% quaternized chitosan, 2% crosslinking agent, and the balance being deionized water.

[0067] The degree of substitution of the quaternized chitosan is 95%, and the crosslinking agent is a 25% aqueous solution of glutaraldehyde.

[0068] The specific preparation process is as follows:

[0069] (1) Corn cob powder pretreatment process: crush the corn cob, pass it through a 300-mesh sieve, ultrasonically clean it with deionized water for 15 minutes to remove surface impurities and soluble components, and then dry it at 80℃ to constant weight;

[0070] (2) According to the above mass concentration setting, the pretreated corn cob powder and quaternized chitosan were added to deionized water and stirred at 500 r / min for 3 h at room temperature until uniformly dispersed. Then, a crosslinking agent was added, the temperature was raised to 40℃, and the mixture was stirred at a constant temperature for 3 h to obtain a viscous mixed slurry. The mixed slurry was quantitatively injected into a copper-bottom polycarbonate mold and directionally frozen at -130℃ for 30 min using liquid nitrogen mixed with ethanol to allow ice crystals to grow directionally along the cooling direction, forming a frozen preform with gradient pore size. The frozen preform was placed in a freeze dryer and dried at a vacuum degree ≤50 Pa and a temperature of -50℃ for 24 h to allow the ice crystals to be directly sublimated and removed, retaining the gradient pore structure, thus obtaining an aerogel membrane. The preparation process is shown in the figure. Figure 1 As shown.

[0071] Example 2: This example provides a multifunctional aerogel membrane based on charge demulsification.

[0072] The difference between this embodiment and Embodiment 1 is that the mass concentration of corn cob powder is 1%, while the content of other components and the preparation method are the same as in Embodiment 1.

[0073] Example 3: This example provides a multifunctional aerogel membrane based on charge demulsification.

[0074] The difference between this embodiment and Embodiment 1 is that the mass concentration of corn cob powder is 3%, while the content of other components and the preparation method are the same as in Embodiment 1.

[0075] Example 4: This example provides a multifunctional aerogel membrane based on charge demulsification.

[0076] The difference between this embodiment and Embodiment 1 is that the mass concentration of corn cob powder is 4%, while the content of other components and the preparation method are the same as in Embodiment 1.

[0077] Example 5: This example provides a multifunctional aerogel membrane based on charge demulsification.

[0078] The difference between this embodiment and Embodiment 1 is that the mass concentration of corn cob powder is 5%, while the content of other components and the preparation method are the same as in Embodiment 1.

[0079] Comparative Example 1: This comparative example provides an aerogel membrane.

[0080] The difference between this comparative example and Example 1 is that the mass concentration of corn cob powder is 0%, while the content of other components and the preparation method are the same as in Example 1.

[0081] Comparative Example 2:

[0082] The difference between this comparative example and Example 1 is that the mass concentration of quaternized chitosan is 0%, while the content of other components and the preparation method are the same as in Example 1.

[0083] Comparative Example 3: This comparative example provides an aerogel membrane.

[0084] The difference between this comparative example and Example 1 is that the mass concentration of quaternized chitosan is 1%, while the content of other components and the preparation method are the same as in Example 1.

[0085] Comparative Example 4:

[0086] The difference between this comparative example and Example 1 is that the mass concentration of quaternized chitosan is 4%, while the content of other components and the preparation method are the same as in Example 1.

[0087] Comparative Example 5: This comparative example provides an aerogel membrane.

[0088] The difference between this comparative example and Example 1 is that in step (2), the mixed slurry is injected into the mold and then placed in a refrigerator for freezing (the temperature is set to -15℃). The content of other components and the preparation method are the same as in Example 1.

[0089] Experimental Example 1: This experimental example involves structural determination of the samples prepared in Examples 1-5 and Comparative Examples 1-5.

[0090] like Figure 2 As shown in the cross-sectional scanning electron microscope images of the aerogel membranes prepared in Examples 1-5, the pore size of the aerogel membrane gradually decreases as the corn cob concentration increases. Thus, the pore size can be adjusted within the range of 37-112 μm by adjusting the corn cob concentration.

[0091] like Figure 3 As shown, the aerogel membrane prepared in this invention has a gradient pore size structure, characterized by a gradual decrease in pore size from top to bottom (forward). During forward filtration, water is not only subjected to dynamic forces during the filtration process, but also experiences a gradient capillary force due to capillary action, which accelerates the water through the pores to complete filtration. However, during reverse filtration, the generated gradient capillary force acts in the opposite direction to gravity, slowing down the separation process and reducing the separation flux. Therefore, when filtering in different directions, the separation flux in the forward direction is 2 to 5 times higher than that in the reverse direction (in the figure, F). G For gravity, F L (This refers to capillary gradient force).

[0092] Quaternized chitosan acts as a framework in aerogel membranes. While the pore size can be adjusted by changing the concentration of quaternized chitosan at the same corn cob concentration, the adjustment range is limited. Under the premise of ensuring sample usability, the adjustment is only possible within 2-3%, and the pore size decreases as the concentration of quaternized chitosan increases. Specifically, when the mass concentration of quaternized chitosan is 0% (Comparative Example 2), only the corn cob crumbles easily after freeze-drying; at a concentration of 1% (Comparative Example 3), the sample wrinkles during freeze-drying and cannot maintain its original shape; at a concentration of 4% (Comparative Example 4), the addition of glutaraldehyde crosslinking causes a gelation reaction, forming a hydrogel, making further directional freezing and subsequent steps impossible.

[0093] The aerogel membrane prepared in Comparative Example 5 was made by slow freezing at low temperature in a refrigerator. Due to gravity, most of the corn cob powder settled to the bottom, and only a very small amount of corn cob was present in the middle and upper parts. This caused the same problem as in Comparative Example 3 during filtration. The membrane could not withstand the pressure generated by the solution above, and gaps would be formed between it and the separation device, making it impossible to separate the oil-water mixture.

[0094] Experimental Example 1: This experimental example tests the performance of the aerogel membranes prepared in Examples 1-5 and Comparative Examples 1-5.

[0095] (1) Separation of oil-water mixture

[0096] The specific test data is shown in Table 1:

[0097] Table 1

[0098]

[0099] (2) Separation of oil-in-water emulsions, including separation of PAO4 oil-in-water emulsions and separation of petroleum ether / diesel / vacuum pump oil-in-water emulsions.

[0100] The specific test data is shown in Table 2:

[0101] Table 2

[0102]

[0103] Analysis of the data in Tables 1 and 2 shows that:

[0104] When separating oil-water mixtures, Comparative Example 1 exhibits a higher separation flux because its pores are not filled with corn cob particles and have a larger pore size, thus resulting in a higher separation flux. Comparative Example 5, on the other hand, has a more disordered pore size formed by its refrigerator, and the separation process relies solely on gravity without the assistance of capillary gradient forces.

[0105] When separating oil-in-water emulsions, the separation efficiency of the examples was significantly higher than that of the comparative examples. This is attributed to the fact that the corn cob particles reduced the pore size, making it easier for the oil-in-water emulsion particles to contact the pore walls and improving the efficiency of demulsification and separation. In contrast, Comparative Example 1, lacking the corn cob filling in its internal pores, allowed the oil-in-water emulsion particles to easily pass through the aerogel membrane without contacting the pore walls, resulting in low separation efficiency. Comparative Example 5, compared to the examples, exhibited a slow freezing process and no temperature gradient during freezing, resulting in disordered internal pores and significant corn cob sedimentation. After freeze-drying, the aerogel membrane sample showed obvious stratification, meaning that although corn cob particles were added, they failed to provide adequate filling, thus not significantly improving the separation efficiency of the oil-in-water emulsion. By adjusting the corn cob particle content and testing the separation efficiency of the emulsions in each group of examples, it was found that Example 1 had the best separation effect.

[0106] In addition, such as Figure 4 As shown, after the aerogel membrane prepared in Example 1 is used 10 times to separate oil-water mixtures, the separation flux still maintains more than 85% of the initial flux, and the separation efficiency is ≥99.9%.

[0107] (3) Adsorption of dyes

[0108] like Figure 5 As shown, the adsorption effects of Example 1 and Comparative Example 1 on various dyes were tested. The results showed that the adsorption effect of Example 1 was significantly better than that of the Comparative Example. Figure 5 Figure b shows optical photographs of the dye wastewater before and after adsorption in Comparative Example 1. It can be seen that Comparative Example 1 has almost no adsorption effect on the dye. In subsequent test examples, it was found that the adsorption effect of the aerogel membrane on the dye mainly comes from the added corn cob particles. The test results of Example 1 also illustrate this point. Figure 5 As can be seen from Figure a, Example 1 has a significant adsorption effect on a variety of dyes, and its separation efficiency can reach more than 96%.

[0109] The above description is merely a preferred embodiment of the present invention and is not intended to limit the invention. Various modifications and variations can be made to the present invention by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A multifunctional aerogel membrane based on charge-induced demulsification, characterized in that, Based on mass concentration, the following raw materials are included: Corn cob powder 1%~5%, quaternized chitosan 2%, cross-linking agent 2%, and the balance is deionized water; The method for preparing the multifunctional aerogel membrane based on charge demulsification includes the following steps: Pretreated corn cob powder and quaternized chitosan were added to deionized water and stirred at room temperature until uniformly dispersed. Then, a crosslinking agent was added, and the mixture was heated and stirred at a constant temperature to obtain a viscous mixed solution. The mixed solution was quantitatively injected into a mold and directionally frozen using liquid nitrogen mixed with ethanol to form a frozen preform with a gradient pore size structure. The frozen preform was vacuum dried to remove moisture until constant weight, and the final product was obtained.

2. The multifunctional aerogel membrane as described in claim 1, characterized in that, The multifunctional aerogel membrane comprises, by mass concentration, the following raw materials: 2% corn cob powder, 2% quaternized chitosan, 2% crosslinking agent, and the balance being deionized water.

3. The multifunctional aerogel membrane as described in claim 1, characterized in that, The degree of substitution of the quaternized chitosan is 90%~95%; The crosslinking agent is glutaraldehyde, and the crosslinking agent is an aqueous solution with a concentration of 25%.

4. The multifunctional aerogel membrane as described in claim 1, characterized in that, After being recycled 10 times, the multifunctional aerogel membrane maintains more than 85% of the initial flux for separating oil-water mixtures, with a separation efficiency of ≥99%. The multifunctional aerogel membrane has an adsorption rate of ≥96% for anionic dyes, wherein the dyes are toluidine blue, carmine, Nile red, or Congo red.

5. A method for preparing a multifunctional aerogel membrane based on charge demulsification as described in any one of claims 1 to 4, characterized in that, Includes the following steps: Pretreated corn cob powder and quaternized chitosan were added to deionized water and stirred at room temperature until uniformly dispersed. Then, a crosslinking agent was added, and the mixture was heated and stirred at a constant temperature to obtain a viscous mixed solution. The mixed solution was quantitatively injected into a mold and directionally frozen using liquid nitrogen mixed with ethanol to form a frozen preform with a gradient pore size structure. The frozen preform was vacuum dried to remove moisture until constant weight, and the final product was obtained.

6. The preparation method according to claim 5, characterized in that, The pretreatment includes crushing the corn cobs, passing them through a 300-mesh sieve, ultrasonically cleaning them with deionized water for 10-20 minutes to remove surface impurities and soluble components, and then drying them at 80-100°C to constant weight. The room temperature stirring rate is 300~500 r / min, and the time is 2~4 h; the constant temperature stirring temperature is 40~50℃, and the time is 2~4 h.

7. The preparation method according to claim 5, characterized in that, The mold is a copper-base polycarbonate mold; The directional freezing temperature is -150~-120℃, and the time is 25~35 min; The pore size range of the gradient pore structure is 37~112 μm, and the pore size is gradually reduced from top to bottom by adjusting the concentration of corn cob powder.

8. The preparation method according to claim 5, characterized in that, The vacuum drying process involves a vacuum degree ≤ 50 Pa, a temperature of -50 to -60°C, and a time of 24 to 48 hours.

9. The application of the multifunctional aerogel membrane based on charge demulsification as described in any one of claims 1 to 4 in the treatment of oily wastewater, oil-in-water emulsions, or dye wastewater.

10. The application as described in claim 9, characterized in that, The oil phase in the oil-in-water emulsion is PAO4 olefin lubricating oil, petroleum ether, diesel oil, or vacuum pump oil, and the surfactant is sodium dodecyl sulfate.

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