Preparation method and application of oil-repellent hydroxyapatite nanowire / cellulose composite aerogel

Abstract

The application relates to a preparation method and application of an oil-resistant hydroxyapatite nanowire / cellulose composite aerogel, which comprises the following steps: drying and crushing leaves and stems of a baijao, adding a NaOH aqueous solution to stir, then washing with deionized water, then adding acetic acid and a NaClO solution to stir, and freeze-drying to obtain baijao cellulose; sequentially adding precursor solutions of alkali, calcium salt and phosphorus salt into a mixed solution of a fatty acid and anhydrous ethanol, uniformly mixing, and then placing into a reaction kettle to react, centrifugally separating the product to obtain hydroxyapatite nanowires; weighing sodium hydroxide and dissolving the sodium hydroxide in deionized water, pouring the baijao cellulose and the hydroxyapatite nanowires into the sodium hydroxide solution, stirring until uniformly dispersed; adding a crosslinking agent to perform freeze-drying to obtain the hydroxyapatite nanowire / cellulose composite aerogel. The material prepared by the application can separate various types of organic wastewater such as soluble, insoluble and emulsion.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of nanocomposite material preparation, and particularly relates to a preparation method and application of an oil-resistant hydroxyapatite nanowire / cellulose composite aerogel. BACKGROUND

[0002] Common wastewater usually contains various types of organic pollutants such as soluble, insoluble and complex emulsified oil. The existing common methods include gravity separation, adsorption, air flotation, biological treatment and the like. These methods usually have the disadvantages of high energy input, secondary pollution, complicated steps, low separation efficiency and the like, which seriously limit their practical application in the treatment of complex organic wastewater. Therefore, there is an urgent need for new treatment methods to treat oil-water emulsion and oil-water mixture.

[0003] In recent years, scientists have developed many materials based on the special wettability of the material surface, such as the currently popular membrane material. However, the inevitable decline in membrane flux leads to the problems of inability to be reused multiple times, inability to be widely used, low separation efficiency and disposal of the final waste membrane material. At the same time, aerogel materials have attracted attention due to their nanoscale pores, high specific surface area and high porosity, and have broad application prospects. However, the current aerogel preparation method is difficult, the pore size is not uniform, the mechanical properties are poor, the recycling ability is low, the function is single, and it is not environmentally friendly, which cannot meet the current demand.

[0004] The invention patent (application number 202310641187.2) discloses a preparation method of a super-hydrophilic / underwater super-oleophobic separation membrane. The preparation method is to use fabric as a substrate, dopamine as an adhesive, and Cu(OH)2 nanoparticles are fixed on the surface of the fabric to obtain a super-hydrophilic / underwater super-oleophobic separation membrane. Although it has a good separation rate, the separation flux of the membrane material decreases in subsequent separation, and the service life is short;

[0005] The invention patent (application number 202211676734.2) discloses a hydrophilic and oleophobic oil-water separation material and a preparation method thereof. The preparation method is to coat a porous sponge material with polydopamine, then load hydrophilic thorn-like particles on the sponge skeleton through the adhesion and high chemical reactivity of polydopamine, and finally load a fluorine-containing surfactant to form an oil-water separation material with hydrophilic and oleophobic properties. The material has good separation rate and recycling performance, but the material used contains fluorine, which pollutes the environment. SUMMARY

[0006] In order to overcome the above prior art problems, the purpose of the present application is to provide a preparation method and application of an oil-resistant hydroxyapatite nanowire / cellulose composite aerogel, which composites cellulose and hydroxyapatite nanowires, studies the influence of factors such as the ratio of the two materials and the hydrothermal time on the morphology of the product, realizes the controllable preparation, and obtains a material with high separation efficiency. In addition, the material can separate various types of organic wastewater such as soluble, insoluble and emulsion; compared with super-hydrophobic, the material has good anti-fouling performance and recycling times.

[0007] In order to achieve the above purpose, the technical scheme adopted by the present application is:

[0008] A preparation method of an oil-resistant hydroxyapatite nanowire / cellulose composite aerogel, comprising the following steps:

[0009] (1) Preparation of cellulose: dry and crush the stem and leaf of the banana, add NaOH (16.6 g / L) aqueous solution, stir at 70 DEG C for 7 h, then wash with deionized water to wash away the excess NaOH, then add acetic acid (20 g / L) and NaClO (20 g / L) solution at 70 DEG C for 7 h, wash to neutral, freeze-dry, and obtain the required banana cellulose for the experiment;

[0010] (2) Preparation of hydroxyapatite nanowires: sequentially add the precursor solutions of alkali, calcium salt and phosphorus salt to the mixed solution of fatty acid and anhydrous ethanol, mix uniformly, then put into a reaction kettle for a period of time, centrifuge the product to obtain hydroxyapatite nanowires;

[0011] (3) Preparation of hydroxyapatite nanowire / cellulose composite aerogel: a certain amount of sodium hydroxide is dissolved in deionized water, the banana cellulose and hydroxyapatite nanowires are poured into the sodium hydroxide solution, stirred until uniformly dispersed; a certain amount of crosslinking agent is added and stirred again until the crosslinking agent is completely dissolved; after being put into a refrigerator and frozen, it is put into a freeze-drying machine for freeze-drying to obtain the hydroxyapatite nanowire / cellulose composite aerogel.

[0012] The present application is further improved in step (2), wherein the amount of fatty acid is 0-10 g, and the mass ratio of anhydrous ethanol to fatty acid is 1:1

[0013] The application further improves that in step (2), the base is one of sodium hydroxide and potassium hydroxide, the concentration is 1-2 mol / L, the calcium salt is one of calcium chloride and calcium nitrate, the concentration is 0.1-0.5 mol / L, and the phosphate is one of sodium dihydrogen phosphate and disodium hydrogen phosphate, the concentration is 0.1-0.5 mol / L; the above-mentioned solutions are all aqueous solutions, 10 mL of the aqueous solution is added in the reaction process, and the dropping speed of the aqueous solution is 1-5 mL / min.

[0014] The application further improves that in step (2), the stirring time is 20-40 min in the hydrothermal kettle reaction process, the reaction temperature is 100-150 DEG C, and the reaction time is 20-48 h.

[0015] The application further improves that in step (3), the banana cellulose content is 0.1-1 g, and the hydroxyapatite nanowire accounts for 10-70% of the cellulose complex mass.

[0016] The application further improves that in step (3), the concentration of the sodium hydroxide solution is 2 mol / L, and the volume is 20 mL.

[0017] The application further improves that in step (3), the crosslinking agent is one or more of epoxy chloropropane and glutaraldehyde, the amount of the crosslinking agent is 1-5 mL, and the stirring time is 10-60 min.

[0018] The application further improves that in step (3), the freeze-drying time is 30-60 h.

[0019] The hydroxyapatite nanowire / cellulose composite aerogel has a much smaller pore diameter than that of pure cellulose, the pure banana cellulose aerogel has a three-dimensional network porous structure, and is mostly a large pore (the pore diameter can reach 500 mu m); after being combined with the hydroxyapatite nanowire, the pore diameter is obviously reduced, the hydroxyapatite nanowire is embedded in the inside of the crosslinked cellulose skeleton; on the surface of the cellulose skeleton, there are exposed hydroxyapatite nanowires in a winding state, which are used as connecting bridges between the cellulose skeletons.

[0020] The hydroxyapatite nanowire / cellulose composite aerogel is applied to the separation of insoluble oil and water mixtures, especially the efficient separation of oil-in-water solutions. The separation efficiency of the aerogel in dichloromethane emulsion, pump oil emulsion, toluene emulsion and n-hexane emulsion is 99.2%, 98.2%, 98.8% and 98.9% respectively, which shows that the aerogel has high demulsification separation efficiency. The efficient separation mechanism of the aerogel lies in the irreversible adsorption of the multi-stage pore structure of the aerogel to the surfactant and the aggregation demulsification of the emulsion droplets.

[0021] The application has the following beneficial effects:

[0022] (1) The hydroxyapatite nanowire prepared by the hydrothermal method has high purity, uniform particle size and single morphology.

[0023] (2) The hydroxyapatite nanowire / cellulose prepared by the chemical crosslinking method has small pore size and high porosity, can effectively separate oil-water emulsion and oil-water mixture, and exhibits good antifouling performance and mechanical performance.

[0024] (3) The hydroxyapatite nanowire / cellulose composite material has simple preparation method, mild conditions, can separate various types of organic wastewater, has excellent oleophobicity and oil-water separation, and has high application prospect. BRIEF DESCRIPTION OF DRAWINGS

[0025] Figure 1 is the SEM diagram of the hydroxyapatite nanowire / cellulose composite aerogel prepared by the present application.

[0026] Figure 2 is the infrared spectrum diagram of the hydroxyapatite nanowire / cellulose composite aerogel prepared by the present application.

[0027] Figure 3 are the underwater contact angle tests of pump oil, toluene, n-hexane, trichloromethane and dichloromethane on the hydroxyapatite nanowire / cellulose composite aerogel prepared by the present application.

[0028] Figure 4 is the optical micrograph of the solution before and after separation of the hydroxyapatite nanowire / cellulose composite aerogel prepared by the present application.

[0029] Figure 5 is the oil droplet drop test diagram of the hydroxyapatite nanowire / cellulose composite aerogel prepared by the present application on toluene and pump oil.

[0030] Figure 6 is the mechanical elasticity test of the hydroxyapatite nanowire / cellulose composite aerogel prepared by the present application. DETAILED DESCRIPTION

[0031] The present application will be further described in detail below in combination with the drawings.

[0032] Example 1:

[0033] (1) Preparation of cellulose: Dry and crush the stem and leaf of the banana, add NaOH (16.6 g / L) aqueous solution, stir at 70°C for 7 h, then wash with deionized water to wash away the remaining NaOH. Add the washed cellulose to acetic acid (20 g / L) and NaClO (20 g / L) solution, stir at 70°C for 7 h, then wash again. Dry the washed cellulose, and finally freeze-dry to obtain the required banana cellulose for the experiment.

[0034] (2) Preparation of hydroxyapatite nanowires: Add 1.25 mol / L sodium hydroxide, 0.30 mol / L calcium nitrate, and 0.20 mol / L sodium dihydrogen phosphate solution to a mixed solution of fatty acid and anhydrous ethanol in sequence, with a dropwise addition rate of 2 mL / min, where the mass of fatty acid is 8 g and the amount of anhydrous ethanol is 8 g. After stirring for 30 min, pour into a reaction kettle and react at 150°C for 24 h. Centrifuge the white product and freeze-dry in a refrigerator to obtain hydroxyapatite nanowires.

[0035] (3) Preparation of hydroxyapatite nanowires / cellulose: Take 20 mL of 2 mol / L sodium hydroxide solution, weigh 0.5 g of banana cellulose and 0.2 g of hydroxyapatite nanowires, and pour them into the above solution. Stir to disperse uniformly; add 1 mL of crosslinking agent epichlorohydrin and stir for about 15 min to make the crosslinking agent completely dissolved; then, place in a refrigerator and freeze for 48 h, and then place in a freeze-drying machine for freeze-drying to obtain a hydroxyapatite nanowire / cellulose composite aerogel material.

[0036] Case 2:

[0037] (1) Preparation of cellulose: Dry and crush the stem and leaf of the banana, add NaOH (16.6 g / L) aqueous solution, stir at 70°C for 7 h, then wash with deionized water to wash away the remaining NaOH. Add the washed cellulose to acetic acid (20 g / L) and NaClO (20 g / L) solution, stir at 70°C for 7 h, then wash again. Dry the washed cellulose, and finally freeze-dry to obtain the required banana cellulose for the experiment.

[0038] (2) Preparation of hydroxyapatite nanowires: Add 1.25 mol / L sodium hydroxide, 0.30 mol / L calcium chloride, and 0.20 mol / L sodium dihydrogen phosphate solution to a mixed solution of fatty acid and anhydrous ethanol in sequence, with a dropwise addition rate of 2 mL / min, where the mass of fatty acid is 9 g and the amount of anhydrous ethanol is 9 g. After stirring for 30 min, pour into a reaction kettle and react at 140°C for 24 h. Centrifuge the white product and freeze-dry in a refrigerator to obtain hydroxyapatite nanowires.

[0039] (3) Preparation of hydroxyapatite nanowires / cellulose: 20 mL of 0.62 mol / L g of sodium hydroxide solution was dissolved in 10 mL of deionized water, 0.5 g of banana cellulose and 0.3 g of hydroxyapatite nanowires were weighed into the above solution, and stirred to disperse uniformly; 1 mL of crosslinking agent glutaraldehyde was added after stirring for 15 min, so that the crosslinking agent was completely dissolved; then, it was put into the refrigerator and frozen for 48 h, and then put into the freeze dryer for freeze drying, to obtain hydroxyapatite nanowire / cellulose composite aerogel material.

[0040] Case 3:

[0041] (1) Preparation of cellulose: dry and crush the stems and leaves of banana, add NaOH (16.6 g / L) aqueous solution, stir at 70°C for 7 h, then wash with deionized water to wash away the remaining NaOH. The washed cellulose is added to acetic acid (20 g / L) and NaClO (20 g / L) solution and stirred at 70°C for 7 h, then washed again. The washed cellulose is dehydrated and finally freeze-dried to obtain the experimental required banana cellulose.

[0042] (2) Preparation of hydroxyapatite nanowires: 1.25 mol / L of barium hydroxide, 0.30 mol / L of potassium chloride, and 0.20 mol / L of sodium dihydrogen phosphate solution were added to a mixed solution of fatty acid and anhydrous ethanol in sequence, with a dropwise addition rate of 2 mL / min, wherein the mass of fatty acid was 8.5 g and the amount of anhydrous ethanol was 8.5 g. After stirring for 30 min, it was poured into a reaction kettle and reacted at 130°C for 24 h. The white product was centrifuged and then freeze-dried in a refrigerator to obtain hydroxyapatite nanowires.

[0043] (3) Preparation of hydroxyapatite nanowires / cellulose: 20 mL of 2 mol / L sodium hydroxide solution was weighed into 0.5 g of banana cellulose and 0.6 g of hydroxyapatite nanowires, and stirred to disperse uniformly; 1 mL of crosslinking agent epichlorohydrin was added after stirring for 5 min, so that the crosslinking agent was completely dissolved; then, it was put into the refrigerator and frozen for 48 h, and then put into the freeze dryer for freeze drying, to obtain hydroxyapatite nanowire / cellulose composite aerogel material.

[0044] Case 4:

[0045] (1) Preparation of cellulose: dry and crush the stems and leaves of banana, add NaOH (16.6 g / L) aqueous solution, stir at 70°C for 7 h, then wash with deionized water to wash away the remaining NaOH. The washed cellulose is added to acetic acid (20 g / L) and NaClO (20 g / L) solution and stirred at 70°C for 7 h, then washed again. The washed cellulose is dehydrated and finally freeze-dried to obtain the experimental required banana cellulose.

[0046] (2) Preparation of hydroxyapatite nanowires: 1.5 mol / L sodium hydroxide, 0.40 mol / L calcium chloride, and 0.50 mol / L sodium dihydrogen phosphate solution were sequentially added dropwise to a mixed solution of fatty acid and anhydrous ethanol at a dropwise addition rate of 2 mL / min, where the mass of the fatty acid was 8 g and the amount of anhydrous ethanol was 8 g. After stirring for 30 min, the mixture was poured into a reaction kettle and reacted at 150°C for 24 h. The white product was centrifugally separated and then placed in a refrigerator for freeze-drying to obtain hydroxyapatite nanowires.

[0047] (3) Preparation of hydroxyapatite nanowires / cellulose: 20 mL of 2 mol / L sodium hydroxide solution was prepared, and 0.5 g of banana cellulose and 0.3 g of hydroxyapatite nanowires were weighed into the solution and stirred to disperse uniformly. After 2 mL of crosslinking agent epichlorohydrin was added and stirred for 20 min to completely dissolve the crosslinking agent, the mixture was placed in a refrigerator for freezing for 48 h and then placed in a freeze-drying machine for freeze-drying to obtain a hydroxyapatite nanowire / cellulose composite aerogel material.

[0048] Case 5:

[0049] (1) Preparation of cellulose: The stems and leaves of the banana were dried and crushed, and then added to an aqueous NaOH solution (16.6 g / L) and stirred at 70°C for 7 h. The remaining NaOH was then washed away with deionized water. The washed cellulose was added to a solution of acetic acid (20 g / L) and NaClO (20 g / L) and stirred at 70°C for 7 h, and then washed again with water. The washed cellulose was dehydrated and then freeze-dried to obtain the desired banana cellulose.

[0050] (2) Preparation of hydroxyapatite nanowires: 1.5 mol / L sodium hydroxide, 0.40 mol / L calcium chloride, and 0.50 mol / L sodium dihydrogen phosphate solution were sequentially added dropwise to a mixed solution of fatty acid and anhydrous ethanol at a dropwise addition rate of 2 mL / min, where the mass of the fatty acid was 8 g and the amount of anhydrous ethanol was 8 g. After stirring for 30 min, the mixture was poured into a reaction kettle and reacted at 150°C for 24 h. The white product was centrifugally separated and then placed in a refrigerator for freeze-drying to obtain hydroxyapatite nanowires.

[0051] (3) Preparation of hydroxyapatite nanowires / cellulose: 20 mL of 2 mol / L sodium hydroxide solution was prepared, and 0.5 g of banana cellulose and 0.3 g of hydroxyapatite nanowires were weighed into the solution and stirred to disperse uniformly. After 2 mL of crosslinking agent epichlorohydrin was added and stirred for 20 min to completely dissolve the crosslinking agent, the mixture was placed in a refrigerator for freezing for 48 h and then placed in a freeze-drying machine for freeze-drying to obtain a hydroxyapatite nanowire / cellulose composite aerogel material.

[0052] Please refer toFigure 1 SEM (lower) of the hydroxyapatite nanowires / cellulose composite aerogel material prepared by the method example 1 of the present application and SEM (upper) of pure cellulose. It can be seen from the figure that the pure banana cellulose aerogel has a three-dimensional network porous structure, mostly macroporous (pore size up to 500 μm), and the surface of the skeleton is smooth. After being combined with hydroxyapatite nanowires, the pore size is obviously reduced, and the hydroxyapatite nanowires are embedded in the interior of the crosslinked cellulose skeleton. In addition to the embedded hydroxyapatite nanowires, exposed hydroxyapatite nanowires are obviously observed on the surface of the cellulose skeleton, and are in a twisted state, serving as a connecting bridge between the cellulose skeletons. This indicates that the HAP nanowires are uniformly distributed in the cellulose skeleton, and the pore structure is changed from single microporous to micro-nano multi-level pores, which is extremely important for the mechanical strength of the aerogel and size sieving demulsification in the oil-water emulsion separation process. Figure 1 Please refer to

[0053] Figure 2 shows the infrared spectrum of the hydroxyapatite nanowire / cellulose composite aerogel material prepared by the method example 1 of the present application. For pure cellulose, (012) and (040) crystal planes can be observed, which are the inherent diffraction peaks of banana cellulose; for the hydroxyapatite nanowire / cellulose porous composite aerogel, the characteristic peaks of banana cellulose and hydroxyapatite nanowires can still be clearly observed, indicating the successful combination of hydroxyapatite nanowires and banana cellulose. Figure 2 Please refer to

[0054] Figure 3 shows the underwater oil droplet contact angle test of the hydroxyapatite nanowire / cellulose composite aerogel material prepared by the method example 2 of the present application. It can be clearly seen from the figure that the underwater contact angles of the oil droplets in pump oil, toluene, n-hexane, chloroform, and dichloromethane are 168°, 159°, 156°, 152°, and 170°, respectively, and the material exhibits good oleophobicity. Figure 3 Figure 3 Please refer to Figure 4 shows the separation performance test of the hydroxyapatite nanowire / cellulose composite aerogel material prepared by the method example 3 of the present application. It can be seen from the figure that the oil droplets disappear after separation, proving that the composite aerogel can well perform oil-water emulsion separation.

[0055] Figure 4 Please refer to Figure 4 Figure 5 shows the antifouling performance test of the hydroxyapatite nanowire / cellulose composite aerogel material prepared by the method example 4 of the present application. It can be seen from the figure that when the composite aerogel material is just immersed underwater, the dyed oil droplets will immediately detach, and the surface still remains white, proving that the antifouling performance of the aerogel is very excellent.

[0056] Please refer to Figure 5 Figure 6 shows the antifouling performance test of the hydroxyapatite nanowire / cellulose composite aerogel material prepared by the method example 4 of the present application. It can be seen from the figure that when the composite aerogel material is just immersed underwater, the dyed oil droplets will immediately detach, and the surface still remains white, proving that the antifouling performance of the aerogel is very excellent. Figure 5 ​​

[0057] Referring to Figure 6 Figure 5 shows the mechanical performance test of the hydroxyapatite nanowire / cellulose composite aerogel material prepared by the method example 5 of the present application. In order to obtain aerogel with high service life, the mechanical performance test was carried out Figure 6 A volume of 10 cm 3 The aqueous aerogel was placed on two glass slides to ensure uniform stress on the aerogel. The height of the aqueous aerogel before extrusion was 1 cm, and after compression to a height of only 5 mm, the height of the aerogel rebounded to 1 cm, showing excellent resilience.

[0058] The method prepares hydroxyapatite nanowires by hydrothermal method, and then composites with cellulose, and prepares hydroxyapatite nanowire / cellulose composite aerogel by adding chemical crosslinking and freeze-drying, so as to realize the controllable preparation of hydroxyapatite / cellulose porous composite material. On the one hand, the aerogel has nanoscale pores, has a multi-level pore structure and hydrophilic active sites, and shows excellent underwater super-oil-repellent performance; on the other hand, cellulose shows hydrophilicity, and hydroxyapatite has good compatibility with biology. Cellulose and hydroxyapatite are both biomass-based materials, non-toxic and harmless, biodegradable, and have good biocompatibility, and can be exchanged with other anions and cations, and have good practicability for oil-water emulsion separation,

[0059] In addition, the material not only has good anti-fouling performance, but also has good mechanical strength. It has a wide application prospect in oil-water treatment.

[0060] In summary, the composite aerogel material for oil-water separation of the present application is a relatively new type of separation material with excellent separation performance, no secondary pollution, and recycling use. The material can be used under a relatively large pressure of 21 kPa, and can be applied to the treatment and purification of actual oil-containing wastewater, and has a good prospect in the field of wastewater treatment.

Claims

1. A method for preparing an oil-resistant hydroxyapatite nanowire / cellulose composite aerogel, characterized in that, Includes the following steps; (1) Preparation of cellulose: The banana stems and leaves were dried and crushed, and 16.6 g / L NaOH aqueous solution was added and stirred at 70 °C for 7 h. Then, the banana cellulose was washed with deionized water to remove excess NaOH. Then, 20 g / L acetic acid and 20 g / L NaClO solution were added and stirred at 70 °C for 7 h. The mixture was washed with water until neutral and then freeze-dried to obtain the banana cellulose required for the experiment. (2) Preparation of hydroxyapatite nanowires: The precursor solutions of alkali, calcium salt and phosphate salt were added dropwise to a mixed solution of fatty acid and anhydrous ethanol. After mixing evenly, the mixture was placed in a reaction vessel and reacted for a period of time. The product was then centrifuged to obtain hydroxyapatite nanowires. (3) Preparation of hydroxyapatite nanowire / cellulose composite aerogel: Weigh a certain amount of sodium hydroxide and dissolve it in deionized water. Take the banana cellulose and hydroxyapatite nanowires and pour them into the sodium hydroxide solution in the above solution. Stir until they are evenly dispersed. Add a certain amount of crosslinking agent and stir again until the crosslinking agent is completely dissolved. After freezing in a refrigerator, freeze dry in a freeze dryer to obtain hydroxyapatite nanowire / cellulose composite aerogel.

2. The preparation method of the oil-resistant hydroxyapatite nanowire / cellulose composite aerogel according to claim 1, characterized in that, In step (2), the amount of fatty acid used is 8-10 g, and the mass ratio of anhydrous ethanol to fatty acid is 1:

1.

3. The preparation method of the oil-resistant hydroxyapatite nanowire / cellulose composite aerogel according to claim 1, characterized in that, In step (2), the alkali is either sodium hydroxide or potassium hydroxide, with a concentration of 1-2 mol / L; the calcium salt is either calcium chloride or calcium nitrate, with a concentration of 0.1-0.5 mol / L; and the phosphate is either sodium dihydrogen phosphate or disodium hydrogen phosphate, with a concentration of 0.1-0.5 mol / L. All of the above solutions are aqueous solutions, and the volume added during the reaction is 10 mL, with the aqueous solution being added at a rate of 1-5 mL / min.

4. The preparation method of the oil-resistant hydroxyapatite nanowire / cellulose composite aerogel according to claim 1, characterized in that, In step (2), during the reaction in the reactor, the stirring time is 20-40 min, the reaction temperature is 100-150 ℃, and the reaction time is 20-48 h.

5. The preparation method of the oil-resistant hydroxyapatite nanowire / cellulose composite aerogel according to claim 1, characterized in that, In step (3), the banana cellulose content is 0.1-1 g, and the hydroxyapatite nanowires account for 10-70% of the cellulose complex mass.

6. The method for preparing an oil-resistant hydroxyapatite nanowire / cellulose composite aerogel according to claim 1, characterized in that, In step (3), the concentration of the sodium hydroxide solution is 2 mol / L and the volume is 20 mL; In step (3), the crosslinking agent is epichlorohydrin or glutaraldehyde, wherein the crosslinking agent is one or more of them, the amount is 1-5 mL, and the stirring time is 10-60 min; In step (3), the freeze-drying time is 30-60 h.

7. A hydroxyapatite nanowire / cellulose composite aerogel prepared by the method according to any one of claims 1-6, characterized in that, Banana cellulose aerogel has a three-dimensional network porous structure with a pore size of up to 500 μm and a smooth skeleton surface. After being combined with hydroxyapatite nanowires, the pore size is significantly reduced, and the hydroxyapatite nanowires are embedded inside the cross-linked cellulose skeleton. On the surface of the cellulose skeleton, there are exposed hydroxyapatite nanowires in an entangled state, which serve as connecting bridges between the cellulose skeletons.

8. The application of a hydroxyapatite nanowire / cellulose composite aerogel prepared by the method according to any one of claims 1-6, characterized in that, It is used for the separation of insoluble oil-water mixtures.

9. The application of the hydroxyapatite nanowire / cellulose composite aerogel according to claim 8, characterized in that, It is used for the efficient separation of oil-in-water solutions.

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