A cellulose-based nanofiber material, and a method of preparing and using the same

Abstract

The application provides a cellulose-based nanofiber material and a preparation method and application thereof, and the preparation method is as follows: a cellulose raw material is dissolved in an ionic liquid, an aprotic solvent is added, and an electrospinning solution is obtained; the electrospinning solution comprises, in percentage by mass, 4-6% of cellulose, 10-76% of ionic liquid, 20-84% of aprotic solvent, 0.2-1.5% of soluble ferric salt, 0.4-3% of soluble ferrous salt, and a cellulose polymerization degree of 100-1200; spinning is performed by using the electrospinning solution under ambient humidity of 50-80%, the product is immersed in a NaOH solution, and then cleaned with water to obtain cellulose nanofibers; the cellulose nanofibers are immersed in a mixed solution of N-isopropyl acrylamide, a crosslinking agent and an initiator for 12-24 hours, and then immersed in a tetramethylethylenediamine liquid for 12-24 hours to obtain the cellulose-based nanofiber material. The cellulose-based nanofiber material has high oil-water separation efficiency, good recycling performance, and can realize automatic oil-water separation on demand.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of nanofiber material manufacturing, and particularly relates to a cellulose-based nanofiber material and a preparation method and application thereof. BACKGROUND

[0002] The global oil spill accidents and the massive discharge of industrial and domestic oil-containing wastewater have caused disastrous damage to the ecosystem and human health, and effective separation of oil-water mixture is an urgent problem to be solved. Compared with traditional separation methods such as gravity method, centrifugal method and air floatation method, adsorption method and membrane separation method have attracted widespread attention due to low energy consumption, convenient operation and small secondary pollution. The porosity and wettability of the material are important parameters for controlling the oil-water separation efficiency. Usually, the "oil-removing" and "water-removing" porous materials with superhydrophobic or superhydrophilic properties can selectively separate one liquid from the oil-water mixture, but hinder the penetration of the liquid with opposite polarity. The existing phase separation materials, porous modified materials and one-dimensional / two-dimensional nanomaterials are generally processed from fluorine-containing petrochemical raw materials, which causes environmental pollution and waste of resources in the preparation process, cannot meet the current national development requirements for health, ecology, environmental protection and the like, and the materials themselves have defects such as low porosity, poor pore connectivity and high cost.

[0003] In recent years, the electrospinning method for preparing oil-water separation materials has attracted widespread attention from researchers. The nanofiber material is very suitable for oil-water separation due to its small fiber diameter, small pore size, high porosity and good pore connectivity. Cellulose is the most abundant natural renewable and naturally degradable green organic polymer on earth, and its homogeneous solution has spinnability. However, the existing cellulose dissolution technology can only realize electrospinning when N-methylmorpholine-N-oxide (NMMO), LiCl / N, N-dimethylacetamide (DMAc) or 1-butyl-3-methylimidazolium chloride (BmimCl) is used as the solvent, and the prepared nanofiber is seriously adhered and the morphology is difficult to control. In addition, the currently prepared electrospun nanofiber separation materials are mostly single-functional wettability materials. For example, it is reported that polyvinyl alcohol (PVA), polyacrylonitrile (PAN) and polymethyl methacrylate (PMMA) nanofiber membranes are prepared by electrospinning technology, the fiber membranes are modified by modifying PVA hydrogel, and the cross-linked PVA hydrogel is coated on the fiber surface to form an oil-water separation material with hydrophilic and oleophobic properties through freezing and thawing steps. It is also reported that the prepared cellulose nitrate electrospun nanofiber membrane is immersed in amino silicone oil solution and fumed particle solution for 20-50 minutes and then dried to obtain an electrospun superhydrophobic membrane for oil-water separation. These materials have low oil-water separation efficiency, poor recycling performance and are easily contaminated on the membrane surface, which lacks flexibility and controllability in actual operation, limiting their application in on-demand automated oil-water separation. SUMMARY

[0004] The main object of the present application is to provide a cellulose-based nanofiber material, its preparation method and application, and to solve the technical problem of making the cellulose-based nanofiber material with high oil-water separation efficiency, good recycling performance, and automatic oil-water separation on demand, thereby being more suitable for practical use.

[0005] The object and the technical problem of the present application are solved by the following technical solution. The present application provides a preparation method of a cellulose-based nanofiber material, comprising the following steps:

[0006] S1 dissolving cellulose raw material in ionic liquid, then adding aprotic solvent to obtain electrospinning solution; the electrospinning solution comprises, by mass percentage, 4-6% cellulose, 10-76% ionic liquid, and 20-84% aprotic solvent; the cellulose has a polymerization degree of 100-1200;

[0007] S2 spinning using the electrospinning solution, the spinning environment has a humidity of 50-80%, to obtain cellulose nanofiber;

[0008] S3 immersing the cellulose nanofiber in a mixed solution of N-isopropyl acrylamide, crosslinking agent and initiator for 12-24 hours, then taking out the immersed cellulose nanofiber and immersing it in tetramethyl ethylenediamine liquid for 12-24 hours for reaction, to obtain cellulose-based nanofiber material.

[0009] The object and the technical problem of the present application can also be further realized by the following technical measures.

[0010] Preferably, after the spinning in step S2, it further comprises the following steps: immersing the spinning product in coagulation liquid to regenerate cellulose; the coagulation liquid comprises water and / or alcohol.

[0011] Preferably, in step S1, the electrospinning solution further comprises 0.2-1.5% soluble ferric salt and 0.4-3% soluble ferrous salt; and,

[0012] After the spinning in step S2, it further comprises the following steps: immersing the spinning product in sodium hydroxide solution, so that the soluble ferric salt and the soluble ferrous salt react with sodium hydroxide to generate nano-magnetic iron oxide, and then washing with water to remove residual sodium hydroxide.

[0013] Preferably, the concentration of the sodium hydroxide solution is 0.05-0.2 mol / L, the immersion time in the sodium hydroxide solution is 3-6 hours, and the washing time is 30-40 minutes.

[0014] Preferably, after the reaction in step S3, it further comprises the following steps: immersing the reaction product into a solution of amino silane coupling agent with a mass percentage concentration of 10% to 20% for 5 to 12 hours, taking out and air-drying, and then reacting at 100 to 120 degrees Celsius for 1 to 3 hours.

[0015] Preferably, the aforementioned ambient humidity is 70% to 80%.

[0016] Preferably, the aforementioned ionic liquid is a methyl imidazole salt, a 1,8-diazabicyclo[5.4.0]undec-7-ene acid salt, or a 1,5-diazabicyclo[4.3.0]non-5-ene acid salt.

[0017] The aforementioned aprotic solvent is one or more of dimethyl sulfoxide, N,N-dimethylformamide, 1,3-dimethyl-2-imidazolidinone, or N,N-dimethylacetamide.

[0018] The purposes of the present application and the technical problems thereof can also be achieved by the following technical solutions. The present application provides a cellulose-based nanofiber material, which comprises cellulose nanofibers and poly-N-isopropyl acrylamide.

[0019] The aforementioned cellulose nanofibers are obtained by electrospinning a solution, and the ambient humidity during the electrospinning is 50% to 80%; the aforementioned electrospinning solution comprises, in terms of mass percentage, 4% to 6% of cellulose, 10% to 76% of ionic liquid, and 20% to 84% of aprotic solvent; and the aforementioned cellulose has a degree of polymerization of 100 to 1200.

[0020] The aforementioned cellulose nanofibers form an interpenetrating polymer network with the poly-N-isopropyl acrylamide.

[0021] The purposes of the present application and the technical problems thereof can also be achieved by the following technical solutions.

[0022] Preferably, the aforementioned cellulose-based nanofiber material is prepared by any of the aforementioned preparation methods.

[0023] The purposes of the present application and the technical problems thereof can also be achieved by the following technical solutions. The present application provides an application of the aforementioned cellulose-based nanofiber material in the field of oil-water separation.

[0024] By means of the above technical solutions, the present application provides a cellulose-based nanofiber material, a preparation method thereof, and an application thereof, which at least have the following advantages:

[0025] According to the cellulose-based nanofiber material preparation method proposed in the present application, firstly, in the process of spinning the cellulose-based nanofiber material, a pre-coagulation device is added to humidify the environment, and the humidity of the spinning environment is controlled to be 50% to 80%. Under this humidity, the dissolved cellulose in the electrospinning solution is regenerated, and the electrospinning solution is coagulated, so that the cellulose nanofiber prepared has high porosity, connected voids, and the fiber filaments are not easy to adhere to each other, so that the oil-water separation rate and separation efficiency of the cellulose-based nanofiber material prepared subsequently are improved. Secondly, the temperature-responsive polymer poly-N-isopropyl acrylamide is penetrated into the cellulose nanofiber network in the form of a network by using the interpenetrating polymer network structure method, so that the material has excellent mechanical properties, stability and recyclability. Thirdly, the material has the characteristics of temperature-responsive oil-water separation, and by controlling the temperature, the material can realize the conversion of hydrophilicity or lipophilicity, realize automatic oil-water separation on demand, and be more suitable for practical use.

[0026] Further, by the method of in-situ embedding, nano-ferroferric oxide is embedded into cellulose nanofiber to make it a stable photothermal conversion medium, so that the temperature response is changed into a photothermal response, and the material has the characteristics of photothermal response oil-water separation. At the same time, the material has more excellent mechanical properties, stability and recyclability.

[0027] Further, the surface of the temperature-responsive or photothermal-responsive cellulose-based nanofiber material is chemically grafted with amino groups, so that the charge density of each region is differentiated, and the pH-controllable oil-water separation characteristics are realized through protonation and deprotonation effects. When the temperature-pH or photothermal-pH is simultaneously responsive, the oil-water separation rate and oil-water separation efficiency can be further improved. At the same time, the material modified by amino groups has high antibacterial property, and the sterilization rate is close to 100%, which prolongs the service life of the material.

[0028] The above description is only a summary of the technical solutions of the present application. In order to more clearly understand the technical means of the present application, and to implement the content of the description, the following will be described in detail with the preferred embodiments of the present application and with the help of the accompanying drawings. BRIEF DESCRIPTION OF DRAWINGS

[0029] Figure 1 The scanning electron microscope image of the cellulose-based nanofiber material prepared in Example 1 is shown in FIG. 1.

[0030] Figure 2 The scanning electron microscope image of the cellulose-based nanofiber material prepared in Comparative Example 1 is shown in FIG. 2.

[0031] Figure 3 The scanning electron microscope image of the cellulose-based nanofiber material prepared in Comparative Example 2 is shown in FIG. 3.

[0032] Figure 4 The X-ray diffraction patterns of the cellulose raw material, the cellulose-based nanofiber material prepared in Example 1 and Comparative Example 1 are shown in FIG. 4.

[0033] Figure 5 are infrared thermography images of the cellulose-based nanofiber material prepared in Example 1 and Example 6 after light exposure. DETAILED DESCRIPTION

[0034] To further clarify the technical means and effects taken by the present application to achieve the predetermined object of the application, the following describes in detail the specific embodiments, structures, features and effects of the cellulose-based nanofiber material, the preparation method thereof and the application thereof according to the present application, combined with the accompanying drawings and preferred embodiments. In the following description, different "an embodiment" or "embodiments" do not necessarily refer to the same embodiment. In addition, the specific features, structures or characteristics in one or more embodiments can be combined in any suitable form.

[0035] The present application provides a preparation method of a cellulose-based nanofiber material, comprising the following steps:

[0036] S1 dissolving a cellulose raw material in an ionic liquid, then adding a non-protic solvent thereto to obtain an electrospinning solution; the electrospinning solution comprises, in terms of mass percentage: cellulose 4% to 6%, ionic liquid 10% to 76%, and non-protic solvent 20% to 84%; the aforementioned cellulose has a degree of polymerization of 100 to 1200;

[0037] S2 using the aforementioned electrospinning solution to perform spinning, the environmental humidity during spinning being 50% to 80% to obtain cellulose nanofiber;

[0038] S3 immersing the aforementioned cellulose nanofiber in a mixed solution of N-isopropyl acrylamide, a crosslinking agent and an initiator for 12h to 24h, then taking out the immersed cellulose nanofiber and immersing it in a tetramethyl ethylenediamine liquid for 12h to 24h to perform reaction, thereby obtaining a cellulose-based nanofiber material.

[0039] Specifically, in step S1, when the cellulose is dissolved, the dissolution temperature is 70-90°C, and the dissolution time is 1-4 hours, so that the obtained cellulose solution is transparent and uniform. The cellulose concentration is 4-6%, which is too low to be spun into a film; the concentration is too high, the solution viscosity increases, and the spinning cannot be extruded, which is easy to damage the instrument; the cellulose dissolution temperature is 70-90°C, and the dissolution time is 1-4 hours, which is too low or too short, and the cellulose cannot be dissolved; the temperature is too high or the time is too long, and the cellulose is easily degraded into glucose, which affects the performance of the subsequent material. The concentration of the ionic liquid is 10-76%, which can dissolve the cellulose, reduce the solution viscosity, and improve the conductivity, which is beneficial to spinning. The concentration is too low, and the cellulose cannot be dissolved; the concentration is too high, and the solution is difficult to solidify, and cannot be spun. The concentration of the aprotic solvent is 20-84%, which can effectively reduce the viscosity and surface tension of the spinning solution and improve its conductivity, and promote the formation of a stable Taylor cone. The cellulose polymerization degree is 100-1200, including microcrystalline cellulose, cotton linters, wood dissolving pulp, etc. The cellulose has poor mechanical and thermal stability, which affects the subsequent use; the polymerization degree is too high, and the cellulose is difficult to dissolve in the solvent, and the solution viscosity is too large, which cannot be spun.

[0040] In the process of electrospinning of the cellulose solution, a pre-coagulation device is added to adjust the humidity of the spinning environment, so that the humidity of the spinning environment is 50-80%. Under this humidity range, the dissolved cellulose in the electrospinning solution is regenerated, the electrospinning solution is coagulated, and the prepared cellulose nanofiber has uniform voids and less adhesion between the fibers. The method for spinning using the electrospinning solution is: moving the electrospinning solution into a syringe with a needle diameter of 1.4-1.8 mm, adjusting the distance between the needle and the drum receiver to 8-18 mm, adjusting the feeding rate to 0.0010-0.0040 mm / s, the rotating speed of the drum receiver is 100-2000 rpm, and a voltage of 10-20 kV is applied for spinning.

[0041] In the mixed solution, N-isopropyl acrylamide (NIPAAm) is used as monomer, N-N'methylene bisacrylamide (MBA) is used as crosslinking agent, ammonium persulfate (APS) is used as initiator, the concentration of NIPAAm is 2% to 6%, the concentration of MBA is 0.1% to 0.3%, and the concentration of APS is 0.5% to 2%. The cellulose nanofiber is immersed in the mixed solution for 12 to 24 hours to make it swell sufficiently. Then, the surface moisture is wiped dry with filter paper, and the product is immersed in tetramethyl ethylenediamine (TEMED) for 12 to 24 hours for reaction. After drying at room temperature or freeze-drying, the temperature-responsive cellulose-based nanofiber material is obtained. In the process, TEMED initiates the decomposition of ammonium persulfate to generate free radicals to promote the polymerization of NIPAAm, and a temperature-sensitive substance, poly-N-isopropyl acrylamide (PNIPAAm), is generated. The cellulose nanofiber and PNIPAAm form an interpenetrating polymer network.

[0042] The preparation method of the cellulose-based nanofiber material has at least the following advantages. Firstly, during the spinning process of the cellulose-based nanofiber material, the humidity of the spinning environment is controlled to be 50% to 80%. Under this humidity, the dissolved cellulose in the electrospinning solution is regenerated, and the electrospinning solution is coagulated. The prepared cellulose nanofiber has high porosity, connected voids, and is not easy to adhere between the fiber filaments. This improves the oil-water separation rate and separation efficiency of the subsequently prepared cellulose-based nanofiber material. Secondly, the temperature-responsive polymer poly-N-isopropyl acrylamide is interpenetrated into the cellulose nanofiber network in the form of a network by using the interpenetrating polymer network structure method. This makes the material have excellent mechanical properties, stability, and recyclability. Thirdly, the material has the characteristics of temperature-responsive oil-water separation. By controlling the temperature, the material can realize the transformation from hydrophilic to oleophilic, realize automatic oil-water separation on demand, and be more suitable for practical use.

[0043] Further, after the spinning in step S2, the product obtained by spinning is immersed in a coagulation liquid to regenerate cellulose. The coagulation liquid includes water and / or alcohol. During the spinning process, most of the cellulose in the electrospinning solution is regenerated under the action of the humidity of the pre-coagulation device, and the electrospinning solution is coagulated. However, a small amount of cellulose is still in a dissolved state, and a small amount of electrospinning solution is not coagulated on the nanofiber. Immersing the product obtained by spinning in a coagulation liquid can regenerate the cellulose and remove excess ionic liquid. Water and / or alcohol are used as the coagulation liquid because the double diffusion between the cellulose solution and water or alcohol is relatively mild, which is beneficial to form fibers with high overall orientation and perfect crystallization, thereby improving the mechanical properties, stability, and recyclability of the material.

[0044] Further, in step S1, the electrospinning solution further comprises: 0.2% to 1.5% of soluble ferric salt and 0.4% to 3% of soluble ferrous salt; and after the spinning in step S2, the method further comprises the following steps: immersing the spinning product into a sodium hydroxide solution, so that the soluble ferric salt and the soluble ferrous salt react with the sodium hydroxide to generate nano-magnetic ferrite, and then washing with water to remove residual sodium hydroxide.

[0045] Specifically, the nano-magnetic ferrite is embedded into the cellulose nanofiber by an in-situ embedding method, so as to become a stable photo-thermal conversion medium. Then, the temperature-responsive polymer poly-N-isopropyl acrylamide is penetrated into the cellulose nanofiber network in a network form by an interpenetrating polymer network structure method, and the poly-N-isopropyl acrylamide is combined with the nano-magnetic ferrite, so that the temperature response is changed into a photo-thermal response, the material has the photo-thermal response oil-water separation characteristic, and the material has more excellent mechanical properties, stability and recycling performance.

[0046] Further, the concentration of the sodium hydroxide solution is 0.05 mol / L to 0.2 mol / L, the immersion time in the sodium hydroxide solution is 3 h to 6 h, and the washing time is 30 min to 40 min.

[0047] Specifically, by adjusting the concentration of sodium hydroxide, the nano-magnetic ferrite particles are controllably loaded on the electrospun nanofiber, and the material changes from white before treatment to black, which indicates that the loading is successful. When the penetration percentage of the ferrite nano-particles in the material is greater than 30 wt% and the size is small, the photo-thermal conversion efficiency of the material is higher.

[0048] Further, after the reaction in step S3, the method further comprises the following steps: immersing the reaction product into a 10% to 20% amino silane coupling agent solution for 5 h to 12 h, taking out and air-drying, and then placing at 100°C to 120°C for 1 h to 3 h.

[0049] Specifically, the amino silane coupling agent is one or more of 3-aminopropyl trimethoxysilane, 3-aminopropyl triethoxysilane, 3-aminopropyl methyl dimethoxysilane, 3-aminopropyl(diethoxyl)methylsilane, 3-[2-(2-aminoethylamino)ethylamino]propyl-trimethoxysilane, 3-(2-aminoethylamino)propyl methyl dimethoxysilane, N-aminoethyl-3-aminopropyl triethoxysilane, or N-(2-aminoethyl)-3-aminopropyl trimethoxysilane.

[0050] The temperature-responsive or photo-thermal-responsive nanofiber is immersed into the amino silane coupling agent solution, taken out and air-dried, and then subjected to a thermal reaction, so as to graft the amino groups on the surface of the cellulose, and the grafting rate is greater than 1.5 mg / cm 2The amino group is protonated under acidic conditions to form a positively charged amino group, and the protonated fragment changes to a stretched conformation and extends, and the material has a higher affinity for water; in a neutral or alkaline environment, the protons are removed by hydroxide ions in the solution, and the segments of the molecular chain exhibit a collapsed conformation, and the exposed hydrophobic chains dominate the surface wettability, at this time, the material exhibits hydrophobicity and lipophilicity. When temperature and pH are simultaneously responsive, the oil-water separation efficiency can be further improved. In addition, the protonated amino group, as a polycation, interacts with the negatively charged surface of bacteria, can destroy the cell wall of bacteria, leading to bacterial cell lysis and death, making the material have excellent antibacterial performance.

[0051] Further, the aforementioned environmental humidity is 70% to 80%. The cellulose nanofiber prepared at this humidity has high porosity, interconnected voids, and is not prone to adhesion between fiber filaments, which improves the oil-water separation rate and oil-water separation efficiency of the subsequently prepared cellulose-based nanofiber material.

[0052] Further, the ionic liquid is a methyl imidazole salt, a 1,8-diazabicyclo[5.4.0]undec-7-ene acid salt, or a 1,5-diazabicyclo[4.3.0]non-5-ene acid salt. Among the aforementioned ionic liquids, the cellulose has good solubility, the cellulose solution is uniform, and the linear viscoelasticity is excellent, which is more conducive to spinning.

[0053] Further, the ionic liquid is a 1-allyl-3-methylimidazolium chloride (AmimCl), a 1,8-diazabicyclo[5.4.0]undec-7-ene acetate ([DBUH][CH3COO]), a 1,8-diazabicyclo[5.4.0]undec-7-ene methoxyacetate ([DBUH][CH3OCH2COO]), a 1,8-diazabicyclo[5.4.0]undec-7-ene ethoxyacetate ([DBUH][CH3CH2OCH2COO]), a 1,5-diazabicyclo[4.3.0]non-5-ene acetate ([DBNH][CH3COO]), a 1,5-diazabicyclo[4.3.0]non-5-ene methoxyacetate ([DBNH][CH3OCH2COO]), or a 1,5-diazabicyclo[4.3.0]non-5-ene ethoxyacetate ([DBNH][CH3CH2OCH2COO]). Among the aforementioned ionic liquids, the cellulose has good solubility, the cellulose solution is uniform, and the linear viscoelasticity is excellent, which is more conducive to spinning.

[0054] Further, the aprotic solvent is one or more of dimethyl sulfoxide (DMSO), N,N-dimethylformamide (DMF), 1,3-dimethyl-2-imidazolidinone (DMI) or N,N-dimethylacetamide (DMAc). The addition of the aforementioned aprotic solvent has no effect on the cellulose solubility, and reduces the viscosity and surface tension of the cellulose solution, and increases the conductivity, which is more conducive to spinning.

[0055] Further, the aprotic solvent is dimethyl sulfoxide (DMSO) and / or N,N-dimethylacetamide (DMAc). The addition of the aforementioned aprotic solvent has no effect on the cellulose solubility, and reduces the viscosity and surface tension of the cellulose solution, and increases the conductivity, which is more conducive to spinning.

[0056] The cellulose-based nanofiber material according to the present application comprises cellulose nanofibers and poly-N-isopropyl acrylamide;

[0057] The aforementioned cellulose nanofibers are obtained by electrospinning a solution, and the electrospinning solution comprises, in percentage by mass: 4-6% cellulose, 10-76% ionic liquid and 20-84% aprotic solvent; the aforementioned cellulose has a degree of polymerization of 100-1200;

[0058] The aforementioned cellulose nanofibers form an interpenetrating polymer network with the poly-N-isopropyl acrylamide.

[0059] Further, the aforementioned cellulose-based nanofiber material is prepared by any of the aforementioned preparation methods.

[0060] The present application provides the use of any of the aforementioned cellulose-based nanofiber materials in the field of oil-water separation, which can provide technical support for the treatment of offshore oil spill accidents and industrial and domestic oil-containing wastewater.

[0061] The present application will be further described in conjunction with specific examples, but it should not be understood as limiting the scope of protection of the present application. Some non-essential improvements and adjustments made by those skilled in the art based on the content of the present application still fall within the scope of protection of the present application.

[0062] Unless otherwise specified, the materials, reagents and the like involved in the following are commercially available goods well known to those skilled in the art; unless otherwise specified, the methods described are well-known methods in the art. Unless otherwise defined, the technical terms or scientific terms used should be the usual meaning understood by those skilled in the art in the field to which the present application belongs.

[0063] In the following examples and comparative examples:

[0064] The cellulose raw material used is dissolving pulp, which has a cellulose content of >90%.

[0065] Photo-thermal conversion performance detection method: Xenon lamp (CEL-HXUV300) was used to simulate sunlight (300 mW·cm -2 ), which was placed at a linear distance of 10 cm from the film. The temperature change of the film under light conditions was recorded by an infrared thermal imager (Fluke Ti27) to evaluate its heat transfer behavior.

[0066] Water contact angle detection method: KINOSL200KS instrument equipped with a high-speed camera was used to test the water contact angle of the film. The film was placed on the measurement platform, the viewing angle was adjusted, and 5 μL of water droplets (pH = 2, pH = 7, pH = 11) were added to the film surface. Young's formula was used to fit the profile image when the water droplet just contacted the film, and the water contact angle was calculated.

[0067] Oil-water separation test method: Different organic solvents (1 mL, toluene, diesel, hexadecane or hexane) were added to 100 mL aqueous solution containing surfactant sodium dodecyl sulfate (pH = 2, pH = 7, pH = 11), and 1000 rpm high-speed stirring was carried out for 12 h to obtain stable emulsion. All emulsions had no obvious demulsification or precipitation within 24 h. 30 mL of emulsion was poured into a separation device for gravity separation, and the xenon lamp was placed at a distance of 10 cm from the filter module. The formula Flux = V / (S x t) was used to calculate the separation flux, where V (L) was the emulsion volume, S (m 2 ) was the effective area of the filter material, and t (h) represented the separation time. In addition, COD removal rate was used as an indicator to evaluate the separation efficiency, and the formula SE (%) = (COD1-COD2) / COD1 x 100% was used, where SE represented the separation efficiency, and COD1 and COD2 were the COD values of the feed emulsion and the filtrate, respectively. The same film material was used multiple times for oil-water separation to explore its recycling performance.

[0068] Antibacterial detection method: 5 cm 2 of the film was immersed in 10 mL of bacterial suspension (Escherichia coli or Staphylococcus aureus) with a concentration of 1 x 10 6 CFU / mL, and incubated at 120 rpm in a 37°C shaking incubator for 6 h. The OD value of the solution at 600 nm was measured, and the formula antibacterial rate (%) = (OD control-OD experiment) / OD control x 100% was used to calculate the antibacterial rate.

[0069] Example 1

[0070] The experimental data of Example 1 is summarized in Table 1, and the test data is summarized in Table 2. The formulation of the electrospinning solution is: 10 g of ionic liquid [DBUH][CH3CH2OCH2COO], 1 g of dissolving pulp (cellulose degree of polymerization is 550), 0.05 g of ferric chloride hexahydrate, 0.1 g of ferrous chloride tetrahydrate, and 10 g of DMSO.

[0071] The preparation method of the electrospinning solution is: weigh the ionic liquid in a beaker, preheat to 80°C. Under 100 rpm magnetic stirring, add ferric chloride hexahydrate and ferrous chloride tetrahydrate, and then add dissolving pulp after complete transparency. Heat at 90°C for 1.5 h until the cellulose is completely dissolved. Then slowly add DMSO under stirring at room temperature to obtain the electrospinning solution.

[0072] Transfer the electrospinning solution to a syringe, the diameter of the needle is 1.8 mm, the distance between the needle and the receiver is 12 mm, control the local humidity at 80%, and the micro pump pushes the cellulose solution to the needle tip at a rate of 0.0020 mm / s. Apply a high voltage of 15 kv for spinning, and set the rotating speed of the drum receiver to 500 r / min. Then, immerse the fibers collected on the drum in 0.1 mol / L sodium hydroxide solution for 4 h, and wash with deionized water for 5 times to obtain cellulose nanofibers.

[0073] Mix 600 mg of NIPAAM, 30 mg of MBA, 4 mL of 5.0% APS solution, and 10 mL of water uniformly to prepare a mixed solution. Immerse the cellulose nanofibers in it for 24 h, then wipe off the surface moisture with filter paper, immerse in 800 μL of TEMED liquid again for 12 h, and dry at room temperature to obtain photo-thermal responsive nanofibers.

[0074] Immerse the photo-thermal responsive nanofibers in a 3-aminopropyltrimethoxysilane acetone solution with a mass percentage concentration of 12% for 8 h, dry at room temperature, and then heat in a 110°C oven for 2 h to obtain photo-thermal-pH responsive cellulose-based nanofiber materials.

[0075] The water contact angle test shows that the material has a contact angle >102° in the absence of light, has a hydrophobic surface, and corresponds to an oil removal mode. When irradiated for 20 min, as shown in Figure 5 , the material temperature reaches 137°C, and the contact angle is <28°, showing superhydrophilicity and water permeability, so the material has photo-thermal responsive wettability.

[0076] Under neutral or alkaline conditions, the contact angle of the material is >120°, and the material has a hydrophobic surface. When the pH is 2 or lower, the contact angle of the material is <30°, showing superhydrophilicity, and the material has pH responsive wettability.

[0077] The oil-water separation test shows that when the emulsion is neutral or alkaline, the membrane flux is 0; when the emulsion pH = 2, the membrane flux > 80 L / (m 2 h), the oil-water separation efficiency > 90%; on this basis, the light irradiation time is 20 min, the membrane flux reaches 90 L / (m 2 h), the oil-water separation efficiency > 99%, and the oil-water separation efficiency can still reach 90% after 20 cycles.

[0078] The antibacterial test shows that the antibacterial rates of the material on Escherichia coli and Staphylococcus aureus are 97.57% and 99.79% respectively, and the antibacterial performance is excellent.

[0079] The SEM-EDS scanning electron microscope detection shows that, as shown in Figure 1 , the material voids are reduced, uniformly distributed and interconnected, and the porosity is high, and elements such as iron and nitrogen are found. The X-ray diffraction detection shows that, as shown in Figure 4 , the cellulose crystal form is changed from cellulose I to cellulose II, and the crystal face peak containing ferroferric oxide is found. The infrared thermal imager detection shows that, as shown in Figure 5 , the surface temperature of the material gradually rises with the extension of the xenon lamp irradiation time, and the membrane surface temperature can rise by more than 100℃ after 20 min of irradiation.

[0080] Example 2

[0081] The experimental data of Example 2 is summarized in Table 1, and the test data is summarized in Table 2. The difference between Example 2 and Example 1 is:

[0082] The formula of the electrospinning solution is: 10 g of ionic liquid [DBNH][CH3CH2OCH2COO], 1 g of dissolved pulp (cellulose degree of polymerization is 550), 0.1 g of ferric chloride hexahydrate, 0.2 g of ferrous chloride tetrahydrate, and 10 g of DMAc; when the cellulose solution is electrospun, the local humidity is controlled at 70%;

[0083] The fibers collected on the roller are immersed in sodium hydroxide solution for 6 h;

[0084] The photo-thermal responsive nanofiber is immersed in a 3-aminopropyltrimethoxysilane acetone solution with a mass percentage concentration of 10% for 12 h, dried at room temperature, and then placed in a 100℃ oven for heating for 3 h.

[0085] The rest of the experimental conditions remain unchanged.

[0086] Example 3

[0087] The experimental data of Example 3 is summarized in Table 1, and the test data is summarized in Table 2. The difference between Example 3 and Example 1 is that the electrospinning solution is formulated as follows: 10 g of ionic liquid [DBUH][CH3OCH2COO], 1 g of dissolved pulp (cellulose degree of polymerization is 550), 0.2 g of ferric chloride hexahydrate, 0.4 g of ferrous chloride tetrahydrate, and 10 g of DMF; when the cellulose solution is electrospun, the local humidity is controlled at 60%;

[0088] The fibers collected on the drum are immersed in a sodium hydroxide solution for 8 h.

[0089] The photo-thermal responsive nanofibers are immersed in a 3-aminopropyltrimethoxysilane acetone solution with a mass percentage concentration of 15% for 8 h.

[0090] The remaining experimental conditions remain unchanged.

[0091] Example 4

[0092] The experimental data of Example 4 is summarized in Table 1, and the test data is summarized in Table 2. The difference between Example 4 and Example 1 is that the electrospinning solution is formulated as follows: 10 g of ionic liquid [DBNH][CH3COO], 1 g of dissolved pulp (cellulose degree of polymerization is 550), 0.3 g of ferric chloride hexahydrate, 0.6 g of ferrous chloride tetrahydrate, and 10 g of DMSO; when the cellulose solution is electrospun, the local humidity is controlled at 50%;

[0093] The fibers collected on the drum are immersed in a 0.05 mol / L sodium hydroxide solution for 12 h.

[0094] The cellulose nanofibers are immersed in the mixed solution for 12 h, and in the TEMED liquid for 24 h.

[0095] The photo-thermal responsive nanofibers are immersed in a 3-aminopropyltrimethoxysilane acetone solution with a mass percentage concentration of 20% for 5 h, and then dried at room temperature and placed in a 120°C oven for 1 h.

[0096] The remaining experimental conditions remain unchanged.

[0097] Table 1 Summary of experimental data of Examples 1-4

[0098]

[0099]

[0100] Table 2 Summary of test data of Examples 1-4

[0101]

[0102] Example 5

[0103] The experimental data of Example 5 are summarized in Table 3. The formulation of the electrospinning solution is: 10 g of ionic liquid AmimCl, 1 g of dissolving pulp (cellulose degree of polymerization is 550), 0.1 g of ferric chloride hexahydrate, 0.2 g of ferrous chloride tetrahydrate, and 10 g of DMSO.

[0104] The preparation method of the electrospinning solution is: weigh the ionic liquid in a beaker, preheat to 80°C. Under 100 rpm magnetic stirring, add ferric chloride hexahydrate and ferrous chloride tetrahydrate, and then add dissolving pulp after complete transparency. Heat at 90°C for 1.5 h until the cellulose is completely dissolved. Then slowly add DMSO under stirring at room temperature to obtain the electrospinning solution.

[0105] Transfer the electrospinning solution to a syringe, the diameter of the needle is 1.8 mm, the distance between the needle and the receiver is 15 mm, control the local humidity at 80%, and the micro pump pushes the cellulose solution to the needle tip at a rate of 0.0010 mm / s. Set the rotating speed of the drum receiver to 1000 r / min, and apply a high voltage of 18 kv for spinning. Then, immerse the fibers collected on the drum in 0.2 mol / L sodium hydroxide solution for 4 h, and wash with deionized water for 5 times to obtain cellulose nanofibers.

[0106] Mix 600 mg of NIPAAM, 45 mg of MBA, 4 mL of 5.0% APS solution, and 10 mL of water uniformly to prepare a mixed solution. Immerse the cellulose nanofibers in the mixed solution for 24 h, then wipe off the surface moisture with filter paper, and immerse in 800 μL of TEMED liquid again for 12 h to form an interpenetrating polymer network of cellulose nanofibers and temperature-sensitive substances. After air drying or freeze drying at room temperature, a cellulose-based nanofiber material with photothermal response is obtained.

[0107] The water contact angle test shows that the material has a hydrophobic surface with a contact angle >101° in the absence of light, and can open the oil removal mode. After 20 min of light irradiation, the material temperature reaches 128°C, and the contact angle is <28°, showing superhydrophilicity and water permeability. Therefore, the material has a photothermal response of wettability. The oil-water separation test shows that after 20 min of light irradiation, the membrane flux reaches 70 L / (m 2 h), and the oil-water separation efficiency is >93.1%. After 15 cycles of use, the oil-water separation efficiency is 85%.

[0108] Example 6

[0109] The experimental data of Example 6 are summarized in Table 3. The formulation of the electrospinning solution is: 10 g of ionic liquid AmimCl, 1 g of dissolving pulp (cellulose degree of polymerization is 550), 0.1 g of ferric chloride hexahydrate, 0.2 g of ferrous chloride tetrahydrate, and 10 g of DMSO.

[0110] The preparation method of the electrospinning solution is as follows: Weigh the ionic liquid into a beaker and preheat it to 80°C. Add the dissolving slurry while stirring magnetically at 100 rpm, and heat at 90°C for 1.5 h until the cellulose is completely dissolved. Then, slowly add DMSO while stirring at room temperature to obtain the electrospinning solution.

[0111] The electrospinning solution was transferred into a syringe with a needle diameter of 1.6 mm and a distance of 12 mm between the needle and the receiver. The local humidity was controlled at 80%. A micro-pump propelled the cellulose solution to the needle tip at a rate of 0.0020 mm / s. A high voltage of 20 kV was applied for spinning, and the roller receiver rotation speed was set to 1000 r / min. Subsequently, the fibers collected on the roller were immersed in deionized water for 30 min to obtain cellulose nanofibers.

[0112] A transparent solution was prepared by thoroughly mixing 600 mg NIPAAM, 30 mg MBA, 4 mL of 5.0% APS solution, and 10 mL of water. The nanofiber gel was then immersed in this solution for 24 hours, followed by wiping the surface dry with filter paper. The gel was then immersed again in 800 μL of TEMED solution for 12 hours to form an interpenetrating polymer network of regenerated cellulose nanofibers and a temperature-sensitive substance. After air-drying or freeze-drying at room temperature, a temperature-responsive nanofiber material was obtained.

[0113] The nanofibers were immersed in a 10% (w / w) solution of 3-aminopropyltrimethoxysilane-acetone for 8 hours, air-dried at room temperature, and then heated in an oven at 110°C for 2 hours to obtain temperature-pH responsive cellulose-based nanofibers. Experimental data are summarized in Table 3.

[0114] Water contact angle testing showed that the material had a contact angle >100° in the absence of light, indicating a hydrophobic surface that could activate the degreasing mode; after 20 minutes of light exposure, as... Figure 5 As shown, at a material temperature of 21.6℃, the contact angle remains >100°; however, when heated to 70℃, the contact angle is <30°, exhibiting superhydrophilicity. Therefore, the material possesses temperature-responsive wettability. Furthermore, the material exhibits pH-responsive wettability. Under neutral or alkaline conditions, the contact angle is >123°, indicating a hydrophobic surface; when pH=2 or lower, the contact angle is <29°, again exhibiting superhydrophilicity. Oil-water separation tests show that when the emulsion is neutral or alkaline, the membrane flux is 0; when the emulsion pH=2, the membrane flux is >79 L / (m²). 2 h), the oil-water separation efficiency is >88%, and it still reaches 83% after 18 cycles of use. Antibacterial tests show that the material has antibacterial rates of 96.76% and 99.58% against Escherichia coli and Staphylococcus aureus, respectively, demonstrating excellent antibacterial properties.

[0115] Example 7

[0116] Example 7 differs from Example 6 in that the electrospinning solution of Example 7 has the following formulation: 18.5 g of ionic liquid [DBUH][CH3CH2OCH2COO], 1 g of dissolved pulp (cellulose degree of polymerization is 100), and 5 g of DMSO. The rest of the experimental conditions remain unchanged.

[0117] The water contact angle test shows that the material has a contact angle > 100° in the absence of light, has a hydrophobic surface, and can open the oil removal mode; after 20 min of light, the material still has a contact angle > 100°; if the material is heated to 70°C, the contact angle is < 30°, showing superhydrophilicity, so the material has temperature-responsive wettability. In addition, the material has pH-responsive wettability, and under neutral or alkaline conditions, the material has a contact angle > 123°, has a hydrophobic surface; when the pH is 2 or lower, the material has a contact angle < 29°, showing superhydrophilicity. The oil-water separation test shows that when the emulsion is neutral or alkaline, the membrane flux is 0; when the emulsion pH is 2, the membrane flux is > 76 L / (m 2 h), the oil-water separation efficiency is > 87%, and after 18 cycles of use, the oil-water separation efficiency can still reach 80%. The antibacterial test shows that the antibacterial rates of the material against E. coli and S. aureus are 96.74% and 99.89%, respectively, and the antibacterial performance is excellent.

[0118] Example 8

[0119] The experimental data of Example 8 are summarized in Table 3. The electrospinning solution has the following formulation: 10 g of ionic liquid [DBUH][CH3CH2OCH2COO], 1.3 g of dissolved pulp (cellulose degree of polymerization is 550), and 10 g of DMSO.

[0120] The preparation method of the electrospinning solution is as follows: weigh the ionic liquid into a beaker and preheat to 80°C. Add the dissolved pulp under 100 rpm magnetic stirring, heat at 90°C for 1.5 h until the cellulose is completely dissolved. Then slowly add DMSO under stirring at room temperature to obtain the electrospinning solution.

[0121] Transfer the electrospinning solution to a syringe, the diameter of the needle is 1.6 mm, the distance between the needle and the receiver is 12 mm, control the local humidity at 80%, the micro pump pushes the cellulose solution to the needle tip at a rate of 0.0020 mm / s, set the rotating drum receiver speed to 1000 r / min, apply a high voltage of 20 kv for spinning to obtain cellulose nanofiber.

[0122] A mixture solution was prepared by mixing 600 mg NIPAAM, 30 mg MBA, 4 mL 5.0% APS solution and 10 mL water thoroughly. The cellulose nanofiber was immersed in the mixture solution for 24 h, then wiped the surface water with filter paper, and immersed in 800 μL TEMED liquid for 12 h to form the interpenetrating polymer network of cellulose nanofiber and temperature sensitive substance PNIPAAM. The temperature responsive cellulose based nanofiber material was obtained after air drying or freeze drying at room temperature.

[0123] The water contact angle test showed that the material had a contact angle > 100° in the absence of light, had a hydrophobic surface, and could start the oil removal mode. After 20 min of light, the material still had a contact angle > 100°. If the material was heated to 70°C, the contact angle was < 35°, showing hydrophilicity, so the material had temperature responsive wettability. The oil-water separation test showed that when the local temperature was 70°C, the membrane flux reached 65 L / (m 2 h), the oil-water separation efficiency was > 80%, and the oil-water separation efficiency reached 74% after 10 cycles.

[0124] Example 9

[0125] Example 9 is different from Example 8 in that the electrospinning solution of Example 9 has the following formulation: 2.5 g of ionic liquid [DBUH][CH3CH2OCH2COO], 1 g of dissolved pulp (cellulose degree of polymerization is 1200), and 17.5 g of DMSO. The rest of the experimental conditions remain unchanged.

[0126] The water contact angle test showed that the material had a contact angle > 100° in the absence of light, had a hydrophobic surface, and could start the oil removal mode. After 20 min of light, the material still had a contact angle > 100°. If the material was heated to 70°C, the contact angle was < 35°, showing hydrophilicity, so the material had temperature responsive wettability. The oil-water separation test showed that when the local temperature was 70°C, the membrane flux reached 63 L / (m 2 h), the oil-water separation efficiency was > 79%, and the oil-water separation efficiency reached 71% after 10 cycles.

[0127] Table 3 Summary of experimental data of Examples 5, 6 and 8

[0128]

[0129] Comparative Example 1

[0130] The electrospinning solution has the following formulation: 10 g of ionic liquid [DBUH][CH3CH2OCH2COO], 1 g of dissolved pulp, and 10 g of DMSO.

[0131] The preparation method of the electrospinning solution is as follows: the ionic liquid is weighed in a beaker and preheated to 80°C. The dissolving pulp is added under magnetic stirring at 100 rpm, and heating is carried out at 90°C for 1.5 h until the cellulose is completely dissolved. Then, DMSO is slowly added while stirring at room temperature to obtain the electrospinning solution.

[0132] The electrospinning solution is transferred to a syringe, the diameter of the needle is 1.8 mm, the distance between the needle and the receiver is 12 mm, the local humidity is controlled at 80%, the micro pump pushes the cellulose solution to the needle tip at a rate of 0.0020 mm / s, the high voltage of 15 kv is applied for spinning, and the rotating speed of the drum receiver is set to 500 r / min. Then, the fibers collected on the drum are immersed in deionized water for 4 h, washed 5 times, and dried at room temperature or freeze-dried to obtain the cellulose-based nanofiber material.

[0133] The SEM-EDS scanning electron microscope detection shows that the material has uniform and interconnected voids and high porosity, as shown in FIG. 1. Figure 2 The X-ray diffraction detection shows that the cellulose crystal form is changed from cellulose I to cellulose II. The water contact angle test shows that the contact angle of the material under different pH and temperature conditions is about 38°, and the material has hydrophilicity. The oil-water separation test shows that the membrane flux is only 15 L / (m 2 h), the oil-water separation efficiency is 64%, and the membrane is damaged after 5 cycles.

[0134] Comparative Example 2

[0135] The difference between Comparative Example 2 and Example 1 is that the local humidity is controlled at 40% when the cellulose solution is electrospun, and the rest of the experimental conditions remain unchanged.

[0136] The SEM-EDS scanning electron microscope detection shows that the material has almost no pores and serious fiber adhesion, and elements such as iron and nitrogen are found, as shown in FIG. 2. Figure 3 The X-ray diffraction detection shows that the cellulose crystal form is changed from cellulose I to cellulose II, and the crystal face peak of ferroferric oxide is contained. The infrared thermal imager detection shows that the surface temperature of the material gradually rises with the extension of the xenon lamp irradiation time, and the surface temperature of the membrane can rise by more than 100°C after 20 min of irradiation.

[0137] The water contact angle test shows that the contact angle of the material is >113° in the absence of light, and the material has a hydrophobic surface; after 20 min of light irradiation, the material temperature reaches 142°C, and the contact angle is <28°, showing superhydrophilicity. In neutral or alkaline conditions, the contact angle of the material is >124°, and the material has a hydrophobic surface; when the pH is 2 or lower, the contact angle of the material is <30°, showing superhydrophilicity.

[0138] The oil-water separation test shows that when the emulsion is neutral or alkaline, the membrane flux is 0; when the emulsion pH is 2, the membrane flux is >50 L / (m 2h), oil-water separation efficiency >62%, under the basis of light for 20 min, the membrane flux reached 68 L / (m 2 h), oil-water separation efficiency >70%, after 20 times of recycling, the oil-water separation efficiency reached 69%. The antibacterial test showed that the antibacterial rates of the material on escherichia coli and staphylococcus aureus were 95.81% and 99.26% respectively, and the antibacterial performance was excellent.

[0139] Comparative example 3

[0140] The formula of the electrospinning solution is: 10 g of ionic liquid [DBUH][CH3CH2OCH2COO], 1 g of dissolving pulp, 0.05 g of ferric chloride hexahydrate, 0.1 g of ferrous chloride tetrahydrate, and 10 g of DMSO.

[0141] The preparation method of the electrospinning solution is: weigh the ionic liquid in a beaker, preheat to 80 DEG C. Under the condition of 100 rpm magnetic stirring, add ferric chloride hexahydrate and ferrous chloride tetrahydrate, and then add dissolving pulp after completely transparent, heat at 90 DEG C for 1.5 h until the cellulose is completely dissolved. Then slowly add DMSO under stirring at room temperature, and obtain the electrospinning solution.

[0142] Transfer the electrospinning solution to a syringe, the diameter of the needle is 1.8 mm, the distance between the needle and the receiver is 12 mm, the local humidity is controlled at 90%, and the micro pump is used to push the cellulose solution to the needle tip at a speed of 0.0020 mm / s, and the high voltage of 15 kv is applied for spinning, and the rotating speed of the drum receiver is set to 500 r / min. Under this condition, the silk cannot be shaped, the needle tip quickly forms large droplets and sprays on the drum collector, so the subsequent operation cannot be carried out.

[0143] According to the experimental data of examples 1-9 and comparative examples 1-3, by controlling the humidity of the spinning environment, the preparation of cellulose nanofiber with high porosity and void communication is realized, the nano four-iron oxide / cellulose nanofiber is prepared by in-situ embedding method, the temperature and pH stimuli-responsive substance with reversible water / oil wettability is introduced into the nanofiber by the combination of interpenetrating polymer network structure method and chemical grafting means, and the intelligent material with switchable wettability between water and oil is prepared. The material has high oil-water separation efficiency, good antibacterial performance, excellent stability and recycling performance, has the characteristics of photo-thermal and pH dual response of oil-water separation, can realize automatic oil-water separation on demand, widens the application field of cellulose-based nanofiber material, and has wide application prospect in the field of oil-water separation.

[0144] The technical features in the claims and / or description of the application can be combined, and the combination manner is not limited to the combination obtained by reference relationship in the claims. The technical solutions obtained by combining the technical features in the claims and / or description are also within the protection scope of the application.

[0145] The above merely describes the preferred embodiments of the present application, and is not intended to limit the present application in any form. Any simple modification, equivalent change and modification made to the above embodiments according to the technical essence of the present application are still within the scope of the technical solutions of the present application.

Claims

1. A method for preparing cellulose-based nanofiber materials, characterized in that, The steps include: S1 dissolves cellulose raw material in an ionic liquid, and then adds an aprotic solvent to obtain an electrospinning solution; by mass percentage, the electrospinning solution comprises: 4%–6% cellulose, 10%–76% ionic liquid, and 20%–84% aprotic solvent; the degree of polymerization of the cellulose is 100–1200. S2 uses the electrospinning solution to spin fibers, and the ambient humidity during spinning is 50% to 80%, to obtain cellulose nanofibers. S3. The cellulose nanofibers are immersed in a mixed solution of N-isopropylacrylamide, crosslinking agent and initiator for 12h to 24h. Then the immersed cellulose nanofibers are taken out and immersed in tetramethylethylenediamine liquid for 12h to 24h to react, so as to obtain cellulose-based nanofiber material. In step S1, the electrospinning solution further includes: 0.2%–1.5% soluble iron salt and 0.4%–3% soluble ferrous salt; and, After spinning as described in step S2, the process further includes the following steps: immersing the spun product in a sodium hydroxide solution to allow soluble iron salts and soluble ferrous salts to react with sodium hydroxide to generate nano-iron tetroxide, followed by washing with water to remove residual sodium hydroxide.

2. The preparation method according to claim 1, characterized in that, After spinning as described in step S2, the process further includes the following step: immersing the spun product in a coagulation solution to regenerate the cellulose; the coagulation solution includes water and / or alcohol.

3. The preparation method according to claim 1, characterized in that, The concentration of the sodium hydroxide solution is 0.05 mol / L to 0.2 mol / L, the immersion time in the sodium hydroxide solution is 3 h to 6 h, and the cleaning time is 30 min to 40 min.

4. The preparation method according to any one of claims 1 to 3, characterized in that, After the reaction described in step S3, the process further includes the following steps: immersing the reaction product in an aminosilane coupling agent solution with a mass percentage concentration of 10% to 20% for 5 to 12 hours, removing it and drying it, and then reacting it at 100°C to 120°C for 1 to 3 hours.

5. The preparation method according to claim 1, characterized in that, The ambient humidity is 70%–80%.

6. The preparation method according to claim 1, characterized in that, The ionic liquid is a methylimidazolium salt, 1,8-diazabicyclo[5.4.0]undec-7-enoate, or 1,5-diazabicyclo[4.3.0]non-5-enoate; The aprotic solvent is one or more of dimethyl sulfoxide, N,N-dimethylformamide, 1,3-dimethyl-2-imidazolinone, or N,N-dimethylacetamide.

7. A cellulose-based nanofiber material, characterized in that, The cellulose-based nanofiber material is prepared by the preparation method according to any one of claims 1-6; The cellulose-based nanofiber material includes cellulose nanofibers and poly(N-isopropylacrylamide); The cellulose nanofibers were obtained by electrospinning solution spinning, with the spinning environment humidity being 50%–80%. The electrospinning solution comprises, by mass percentage: 4%–6% cellulose, 10%–76% ionic liquid, and 20%–84% aprotic solvent; The degree of polymerization of the cellulose is 100–1200; The cellulose nanofibers form an interpenetrating polymer network with poly(N-isopropylacrylamide); The electrospinning solution includes 0.2%–1.5% soluble iron salt and 0.4%–3% soluble ferrous salt. After spinning, the spun product is immersed in a sodium hydroxide solution, whereby the soluble iron salt and soluble ferrous salt react with sodium hydroxide to generate nano-iron tetroxide. Subsequently, the product is washed with water to remove residual sodium hydroxide.

8. An application of the cellulose-based nanofiber material according to claim 7 in the field of oil-water separation.

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