Preparation method and application of porous nanofiber aerogel

Abstract

The invention discloses a preparation method and application of porous nanofiber aerogel, SiO2 fiber aerogel is used as a carrier, the aperture of the SiO2 fiber aerogel is modified by CuBTC, and more sites are provided for growth of CuFC; and finally, synthesizing the carboxylated CuFC / CuBTC / SiO2 fiber aerogel by using an in-situ synthesis method. The CuFC / CuBTC / SiO2 fiber aerogel can be clamped by tweezers as an integral material, and centrifugal operation is not needed, so that the operation steps are effectively simplified, and the separation time is saved. The operation technology is simple and convenient, energy consumption is greatly reduced, meanwhile, the device can be recycled, and the concept of energy conservation, carbon reduction and environmental protection is achieved. The method overcomes the vulnerability of SiO2 aerogel, enhances the activation efficiency of SiO2 fiber aerogel, solves the problems that Prussian blue analogues are easy to colloid in water and are not easy to separate and recover, and further improves the adsorption selectivity and separation capacity of the fiber aerogel to radionuclide cesium.

Description

Technical Field

[0001] The present invention belongs to the fields of new materials and energy conservation and environmental protection, and particularly relates to a preparation method and application of a porous nanofiber aerogel. Background Art

[0002] The rapid development of the nuclear power industry has caused a large amount of radioactive wastewater to be discharged into the water environment, threatening the environment and human health. As the main component of radioactive wastewater, cesium ions with high solubility can quickly migrate in the environment, causing pollution of the water body and soil. In addition, radioactive nuclide cesium can enter the human body through the food chain and other ways, inducing various diseases and threatening human health. The research on methods for separating cesium from radioactive wastewater at home and abroad mainly focuses on: precipitation method, solvent extraction method, electrochemistry method, adsorption method, etc. Among them, the adsorption method for treating radioactive wastewater has the advantages of simple process, high removal rate, low cost, and high decontamination factor.

[0003] Prussian blue analogs (PBAs) are a kind of face-centered cubic lattice inorganic materials, which are composed of octahedrons with high-spin Fe 3+ connecting six nitrogen atoms and low-spin Fe 2+ connecting six cyanide carbon atoms, showing good chemical and radiation stability. Transition metal ions cover Cu 2+ Co 2+ Ni 2+ Fe 3+ and other several substances. The structure of PBAs includes narrow channels of about , which is similar to the hydrated ion radius of cesium , but smaller than the channels of Na + Ca 2+ and Mg 2+ . Therefore, Prussian blue analogs have high ion sieving function and adsorption selectivity for cesium ions, which are considered to be a relatively superior cesium ion adsorbent. However, due to its easy colloidization in water and difficult separation from the solution, its industrial application is severely restricted. To solve this problem, it is extremely important to select a suitable carrier.

[0004] SiO 2 aerogel, although having extremely low thermal conductivity, high temperature resistance, and porosity as high as 80% - 99.8%, and its properties are stable even after multiple adsorption / desorption cycles, with extremely low efficiency loss and easy recovery, can be used as a carrier for Prussian blue analogs; but SiO 2 aerogel has poor strength and insufficient toughness, and is easily broken under stress, making it difficult to implement the next application.

[0005] Therefore, developing an adsorbent material that can efficiently remove cesium ions from radioactive wastewater and is easy to enrich and recycle is a quite challenging problem. Summary of the Invention

[0006] Aiming at the problem that the adsorbent materials in the prior art cannot both efficiently remove cesium ions and be easily enriched and recycled, the present invention provides a preparation method and application of a porous nanofiber aerogel. Using SiO 2 fiber aerogel as a carrier, modifying its pore size by CuBTC to provide more sites for the growth of CuFC; finally, synthesizing carboxylated CuFC / CuBTC / SiO 2 fiber aerogel by in-situ synthesis method. Since the CuFC / CuBTC / SiO 2 fiber aerogel as a whole material can be picked up with tweezers without centrifugation operation, effectively simplifying the operation steps and saving separation time. The operation technology is simple and convenient, greatly reducing energy consumption, and at the same time can be recycled, realizing the concept of energy conservation, carbon reduction and environmental protection. And the adsorbent can effectively remove radioactive nuclide cesium in wastewater, overcome the fragility of SiO 2 aerogel, improve the activation efficiency of SiO 2 fiber aerogel at the same time, and solve the problem that it is difficult to separate Prussian blue analogues from the solution.

[0007] The preparation method of the porous nanofiber aerogel of the present invention includes the following steps:

[0008] S1. Mix the SiO 2 fiber membrane with deionized water and stir into a sol state, then place it in a reaction container, add a cross-linking agent and stir and react overnight. After the reaction is completed, centrifuge and wash, then add glutaric anhydride and stir evenly. Finally, perform centrifugation, washing and freeze-drying treatments in sequence to obtain carboxylated SiO 2 fiber aerogel;

[0009] S2. Add the carboxylated SiO 2 fiber aerogel obtained in step S1 to the copper acetate ethanol solution, ultrasonically mix evenly, then centrifuge and wash, and add it to the trimesic acid ethanol solution for ultrasonic reaction. After the reaction is completed, perform centrifugation, washing and drying treatments in sequence to obtain carboxylated CuBTC / SiO 2 fiber aerogel crude product;

[0010] S3. Using the carboxylated CuBTC / SiO 2 fiber aerogel crude product in step S2 as a raw material, repeat the operation of step S2 multiple times to obtain a fully grown carboxylated CuBTC / SiO 2 fiber aerogel;

[0011] S4. Add the carboxylated CuBTC / SiO 2 fiber aerogel obtained in step S3 into the copper chloride-citric acid solution. After stirring and mixing evenly, perform ultrasonic treatment and centrifugal washing in sequence to obtain a composite material. After continuing to perform ultrasonic treatment on the composite material in the copper chloride-citric acid solution, add a potassium ferrocyanide-citric acid solution dropwise for reaction. After the reaction is completed, obtain a liquid carboxylated CuFC / CuBTC / SiO 2 fiber aerogel;

[0012] S5. Use the liquid carboxylated CuFC / CuBTC / SiO 2 fiber aerogel as a raw material to repeat step S4, and then obtain the target product after freeze-drying treatment. The purpose of the cyclic operation in steps S3 and S5 is to ensure that the generated MOF and Prussian blue analogues can be fully complexed and grown, and further improve the ability of the generated adsorbent material to remove radioactive nuclide cesium in water.

[0013] In the said step S1, the mass ratio of the SiO 2 fiber membrane to deionized water is 1:80; the mass ratio of the SiO 2 fiber membrane to the cross-linking agent is 1:1.5 - 2.5; the mass ratio of the SiO 2 fiber membrane to glutaric anhydride is 1:2 - 3.

[0014] In the said step S1, the cross-linking agent is 3-aminopropyltriethoxysilane (APTES) or methyltriethoxysilane; the stirring time is 3 - 5 h; the temperature inside the reaction vessel is 80 - 90 °C, the stirring speed is 800 - 1500 rpm, and the overnight reaction time is 12 - 18 h; the freeze-drying temperature is -50 - -60 °C, and the freeze-drying time is 48 - 72 h.

[0015] In the said step S2, the molar ratio of acetic acid to trimesic acid is 1:5; the molar ratio of copper acetate to ethanol in the copper acetate-ethanol solution is 1:0.5 - 1.8, and the molar ratio of trimesic acid to ethanol in the trimesic acid-ethanol solution is 1:0.1 - 0.4; the ultrasonic mixing time is 10 - 20 min, and the ultrasonic reaction time is 20 - 60 min.

[0016] In the said step S4, the molar ratio of copper chloride to potassium ferrocyanide is 1:1; the molar ratio of copper chloride to citric acid in the copper chloride-citric acid solution is 20:1, and the molar ratio of potassium ferrocyanide to citric acid in the potassium ferrocyanide-citric acid solution is 20:1; the stirring time is 3 - 5 h; the ultrasonic treatment time is 20 - 60 min.

[0017] In the said step S5, the freeze-drying temperature is -50 - -60 °C, and the freeze-drying time is 48 - 72 h.

[0018] Another object of the present invention is to provide an application of the porous nanofiber aerogel prepared by the above preparation method in removing radioactive nuclide cesium in water.

[0019] The present invention has the following beneficial effects:

[0020] (1) The present invention overcomes the fragility of SiO 2 aerogel by fiber-reinforcing or crosslinking polymers.

[0021] (2) The present invention utilizes the characteristics of CuBTC having high crystallinity, porosity and excellent thermal stability to provide more sites for the growth of CuFC Prussian blue analogues; due to the firm growth of CuFC on the surface of the fiber aerogel, there will be no phenomenon of gelation in water and it will be recovered together while separating and recycling the fiber aerogel, effectively improving the recovery problem of Prussian blue analogues, with simple and convenient operation technology, greatly reducing energy consumption, and realizing the concept of energy conservation, carbon reduction and environmental protection.

[0022] (3) Compared with the prior art, the carboxylated CuFC / CuBTC / SiO 2 fiber aerogel prepared by the present invention uses less amount and has a larger cesium adsorption amount when used as an adsorbent, further reducing the cost.

[0023] (4) The carboxylated CuFC / CuBTC / SiO 2 fiber aerogel prepared by the present invention can effectively enrich and recover cesium ions in water. In a cesium ion solution with a concentration of 64 mg / L and a pH of 6, the carboxylated CuFC / CuBTC / SiO 2 fiber aerogel reaches the adsorption equilibrium within 128 min, and the maximum cesium adsorption amount is 97.88 mg / g. After five repeated cycles of use, it can still reach 82.68% of the initial cesium adsorption amount. Description of the Drawings

[0024] Figure 1 SEM image of the CuFC / CuBTC / SiO 2 fiber aerogel in Example 1;

[0025] Figure 2 XRD pattern of the CuFC / CuBTC / SiO 2 fiber aerogel in Example 1;

[0026] Figure 3 FI-IR spectrum of the CuFC / CuBTC / SiO 2 fiber aerogel in Example 1;

[0027] Figure 4 For the CuFC / CuBTC / SiO in Example 1 2UV-vis diagram of the fibrous aerogel;

[0028] Figure 5 For CuFC / CuBTC / SiO in Example 1 2 Adsorption effect diagrams of the fibrous aerogel under different initial concentration conditions;

[0029] Figure 6 For CuFC / CuBTC / SiO in Example 1 2 Adsorption effect diagrams of the fibrous aerogel under different time conditions;

[0030] Figure 7 For CuFC / CuBTC / SiO in Example 1 2 Adsorption effect diagram of the fibrous aerogel after being reused 5 times. Detailed implementation manners

[0031] The present invention will be further described below with reference to the accompanying drawings. The following examples are only used to more clearly illustrate the technical solution of the present invention and cannot be used to limit the protection scope of the present invention.

[0032] Example 1:

[0033] S1. Weigh 1 g of SiO 2 fiber membrane and cut it into pieces, then add 80 mL of deionized water and mix at a stirring speed of 800 rpm for 3 h at room temperature. Stir the SiO 2 fiber membrane solution into a sol state, then place it in an oil bath pot controlled by magnetic heating, set the oil bath temperature to 80 °C, the rotation speed to 800 rpm, and add 2 mL of 3-aminopropyltriethoxysilane (APTES) and react overnight for 12 h; centrifuge the reacted turbid liquid and wash it 3 times with ethanol, then add 3.0 g of glutaric anhydride, stir slowly, react at room temperature for 3 h, then centrifuge and wash it 3 times with deionized water, and then transfer it to a freeze-drying oven and freeze-dry at -55 °C for 48 h to obtain carboxylated SiO 2 fibrous aerogel;

[0034] S2. Prepare 10 mmol / L copper acetate and 50 mmol / L trimesic acid ethanol (250 mL) solutions respectively for standby; Disperse 50 mg of SiO 2 fibrous aerogel modified with carboxyl functional groups in an ethanol solution containing 10 mL of pre-prepared copper acetate, and ultrasonically disperse the SiO 2 fibrous aerogel evenly. After reacting for 10 min, centrifuge and wash it 2 times with ethanol; then disperse the above-obtained precipitate solid in 10 mL of the pre-prepared trimesic acid ethanol solution, ultrasonically react for 20 min, then centrifuge and wash it 2 times with ethanol. Repeat the above steps three times, and dry the obtained composite material and seal it for storage;

[0035] S3. Prepare 1 mmol / L copper chloride and 1 mmol / L potassium ferrocyanide trihydrate citric acid solutions for later use; weigh 1 g of carboxylated CuBTC / SiO 2 Fiber aerogel and disperse it in 200 mL of the pre-prepared copper chloride citric acid solution, and stir for 3 h. Then, ultrasonically treat for 20 min, centrifuge and wash twice with deionized water; disperse the obtained solid in 50 mL of the pre-prepared copper chloride citric acid solution, ultrasonically react for 20 min, add an equal volume of potassium ferrocyanide citric acid solution, and react for 30 min. Repeat the above steps three times, pour into a circular mold, and transfer to a freeze-drying oven for freeze-drying at -55 °C for 48 h to obtain carboxylated CuFC / CuBTC / SiO 2 Fiber aerogel.

[0036] Take 10 mg of the carboxylated CuFC / CuBTC / SiO 2 Fiber aerogel prepared in Example 1 and place it in a solution with a system of 20 mL and an initial cesium ion concentration of 1 mg / L. The reaction temperature is 25 °C, the pH is 6, and react in a shaker at 200 rpm for 12 h. The removal rate of cesium ions in water reaches 97.43%. The adsorbed carboxylated CuFC / CuBTC / SiO 2 Fiber aerogel is effectively enriched and recovered to achieve the purpose of removing cesium ions from water.

[0037] Example 2:

[0038] S1. Weigh 2 g of SiO 2 Fiber membrane and cut it into pieces, then add 160 mL of deionized water and mix at a stirring speed of 1000 rpm at room temperature for 4 h. Stir the SiO 2 Fiber membrane solution into a sol state, then place it in an oil bath controlled by magnetic heating, set the oil bath temperature to 85 °C, the rotation speed to 1000 rpm, and add 3 mL of methyltriethoxysilane and react overnight for 15 h; centrifuge the reaction turbid liquid and wash 3 times with ethanol, then add 5.0 g of glutaric anhydride, stir slowly, react at room temperature for 4 h, then centrifuge and wash 3 times with deionized water, and then transfer to a freeze-drying oven for freeze-drying at -50 °C for 60 h to obtain carboxylated SiO 2 Fiber aerogel;

[0039] S2. Prepare 20 mmol / L copper acetate and 100 mmol / L trimesic acid ethanol (300 mL) solutions for later use; disperse 50 mg of the SiO 2 Fiber aerogel modified with carboxyl functional groups in 10 mL of the pre-prepared copper acetate ethanol solution, and ultrasonically treat the SiO 2The fibrous aerogel was evenly dispersed. After reacting for 15 min, it was centrifuged and washed three times with ethanol. Then, the obtained precipitate solid was dispersed in 10 mL of a pre-prepared ethanol solution of trimesic acid. After ultrasonic reaction for 40 min, it was centrifuged and washed three times with ethanol. The above steps were repeated three times. The obtained composite material was dried and stored in a sealed manner.

[0040] S3. Citric acid solutions of 3 mmol / L copper chloride and 3 mmol / L potassium ferrocyanide trihydrate were respectively prepared for standby. 1 g of carboxylated CuBTC / SiO was weighed. 2 The fibrous aerogel was dispersed in 200 mL of a pre-prepared citric acid solution of copper chloride and stirred for 4 h. Subsequently, it was ultrasonically treated for 20 min, centrifuged and washed twice with deionized water. The obtained solid was dispersed in 50 mL of a pre-prepared citric acid solution of copper chloride. After ultrasonic reaction for 20 min, an equal volume of a citric acid solution of potassium ferrocyanide was added dropwise, and the reaction was carried out for 30 min. The above steps were repeated three times, and then it was poured into a round mold and transferred to a freeze-drying oven for freeze-drying at -50 °C for 60 h to obtain carboxylated CuFC / CuBTC / SiO 2 fibrous aerogel.

[0041] 10 mg of the carboxylated CuFC / CuBTC / SiO prepared in Example 2 was taken 2 and placed in a solution with a system of 20 mL and an initial cesium ion concentration of 1 mg / L. The reaction temperature was 25 °C, the pH was 6, and the reaction was carried out in a shaker at 200 rpm for 12 h. The removal rate of cesium ions in water reached 97.03%. The adsorbed carboxylated CuFC / CuBTC / SiO 2 fibrous aerogel was effectively enriched and recovered to achieve the purpose of removing cesium ions from water.

[0042] Example 3:

[0043] S1. 3 g of SiO 2 fiber membrane was weighed and cut into pieces, and then 240 mL of deionized water was added and mixed at a stirring speed of 1500 rpm at room temperature for 5 h to stir the SiO 2 fiber membrane solution into a sol state. Then, it was placed in an oil bath pot controlled by magnetic heating, the oil bath temperature was set at 90 °C, the rotation speed was 1500 rpm, and 7.5 mL of 3-aminopropyltriethoxysilane (APTES) was added and reacted overnight for 18 h. The reaction turbid liquid was centrifuged and washed three times with ethanol. Then, 6.0 g of glutaric anhydride was added, and it was slowly stirred and reacted at room temperature for 3 h, then centrifuged and washed three times with deionized water, and then transferred to a freeze-drying oven for freeze-drying at -60 °C for 72 h to obtain carboxylated SiO 2 fibrous aerogel;

[0044] S2. Prepare 30 mmol / L copper acetate and 150 mmol / L trimesic acid ethanol (400 mL) solutions for later use; Disperse 50 mg of SiO fiber aerogel surface-modified with carboxyl functional groups in an ethanol solution containing 10 mL of pre-prepared copper acetate, and ultrasonically disperse the SiO fiber aerogel evenly. After reacting for 20 min, centrifuge and wash with ethanol 5 times; Then disperse the above-obtained precipitated solid in 10 mL of the pre-prepared trimesic acid ethanol solution, ultrasonically react for 60 min, centrifuge and wash with ethanol 5 times. Repeat the above steps three times, dry the obtained composite material and store it sealed; 2 Fiber aerogel is dispersed in an ethanol solution containing 10 mL of pre-prepared copper acetate, and ultrasonically disperse the SiO 2 Fiber aerogel evenly. After reacting for 20 min, centrifuge and wash with ethanol 5 times; Then disperse the above-obtained precipitated solid in 10 mL of the pre-prepared trimesic acid ethanol solution, ultrasonically react for 60 min, centrifuge and wash with ethanol 5 times. Repeat the above steps three times, dry the obtained composite material and store it sealed;

[0045] S3. Prepare 5 mmol / L copper chloride and 5 mmol / L potassium ferrocyanide trihydrate citric acid solutions for later use; Weigh 1 g of carboxylated CuBTC / SiO 2 Fiber aerogel is dispersed in 200 mL of the pre-prepared copper chloride citric acid solution and stirred for 5 h. Then ultrasonically treat for 60 min, centrifuge and wash with deionized water 2 times; Disperse the above-obtained solid in 50 mL of the pre-prepared copper chloride citric acid solution, ultrasonically react for 60 min, add an equal volume of potassium ferrocyanide citric acid solution dropwise, and react for 30 min. Repeat the above steps three times, pour into a round mold, and transfer to a freeze-drying oven at -60 °C for freeze-drying for 72 h to obtain carboxylated CuFC / CuBTC / SiO 2 Fiber aerogel.

[0046] Take 10 mg of the carboxylated CuFC / CuBTC / SiO 2 Fiber aerogel prepared in Example 3, place it in a solution with a system of 20 mL and an initial cesium ion concentration of 1 mg / L, the reaction temperature is 25 °C, the pH is 6, and react in a shaker at 200 rpm for 12 h. The removal rate of cesium ions in water reaches 98.12%. The adsorbed carboxylated CuFC / CuBTC / SiO 2 Fiber aerogel is effectively enriched and recovered to achieve the purpose of removing cesium ions from water.

[0047] Comparative Example 1:

[0048] Weigh 1 g of SiO 2 Fiber membrane and cut it into pieces, then add 80 mL of deionized water and mix at a stirring speed of 800 rpm at room temperature for 3 h to stir the SiO 2 Fiber membrane solution into a sol state; Weigh 20 g of tert-butanol, 1 g of 3-aminopropyltriethoxysilane (APTES) and 0.2 g of oxalic acid, mix them and add them to the sol, stir for 2 min and then pour into a round silica gel mold, and then transfer to a freeze-drying oven at -55 °C for freeze-drying for 48 h to prepare SiO 2Fiber aerogel.

[0049] Take 10 mg of the SiO fiber aerogel prepared in Comparative Example 1 and place it in a solution with a system volume of 20 mL and an initial cesium ion concentration of 1 mg / L. The reaction temperature is 25 °C, the pH is 6, and the reaction is carried out in a shaker at 200 rpm for 12 h. The removal rate of cesium ions in water is 32%. 2 Take 10 mg of the SiO fiber aerogel prepared in Comparative Example 1 and place it in a solution with a system volume of 20 mL and an initial cesium ion concentration of 1 mg / L. The reaction temperature is 25 °C, the pH is 6, and the reaction is carried out in a shaker at 200 rpm for 12 h. The removal rate of cesium ions in water is 32%.

[0050] Comparative Example 2:

[0051] Weigh 1 g of the SiO fiber membrane and cut it into pieces. Then add 80 mL of deionized water and mix at a stirring speed of 800 rpm at room temperature for 3 h. Stir the SiO fiber membrane solution into a sol state, and then place it in an oil bath controlled by magnetic heating. Set the oil bath temperature to 80 °C, the rotation speed to 800 rpm, and add 2 mL of 3-aminopropyltriethoxysilane (APTES) and react overnight for 12 h; centrifuge the reaction turbid liquid and wash it 3 times with ethanol. Then add 3.0 g of glutaric anhydride, stir slowly, react at room temperature for 3 h, then centrifuge and wash it 3 times with deionized water. Then transfer it to a freeze-drying oven and freeze-dry at -55 °C for 48 h to obtain carboxylated SiO fiber aerogel. 2 Weigh 1 g of the SiO fiber membrane and cut it into pieces. Then add 80 mL of deionized water and mix at a stirring speed of 800 rpm at room temperature for 3 h. Stir the SiO fiber membrane solution into a sol state, and then place it in an oil bath controlled by magnetic heating. Set the oil bath temperature to 80 °C, the rotation speed to 800 rpm, and add 2 mL of 3-aminopropyltriethoxysilane (APTES) and react overnight for 12 h; centrifuge the reaction turbid liquid and wash it 3 times with ethanol. Then add 3.0 g of glutaric anhydride, stir slowly, react at room temperature for 3 h, then centrifuge and wash it 3 times with deionized water. Then transfer it to a freeze-drying oven and freeze-dry at -55 °C for 48 h to obtain carboxylated SiO fiber aerogel. 2 Weigh 1 g of the SiO fiber membrane and cut it into pieces. Then add 80 mL of deionized water and mix at a stirring speed of 800 rpm at room temperature for 3 h. Stir the SiO fiber membrane solution into a sol state, and then place it in an oil bath controlled by magnetic heating. Set the oil bath temperature to 80 °C, the rotation speed to 800 rpm, and add 2 mL of 3-aminopropyltriethoxysilane (APTES) and react overnight for 12 h; centrifuge the reaction turbid liquid and wash it 3 times with ethanol. Then add 3.0 g of glutaric anhydride, stir slowly, react at room temperature for 3 h, then centrifuge and wash it 3 times with deionized water. Then transfer it to a freeze-drying oven and freeze-dry at -55 °C for 48 h to obtain carboxylated SiO fiber aerogel. 2 Fiber aerogel.

[0052] Take 10 mg of the carboxylated SiO fiber aerogel prepared in Comparative Example 2 and place it in a solution with a system volume of 20 mL and an initial cesium ion concentration of 1 mg / L. The reaction temperature is 25 °C, the pH is 6, and the reaction is carried out in a shaker at 200 rpm for 12 h. The removal rate of cesium ions in water is 65%. 2 Take 10 mg of the carboxylated SiO fiber aerogel prepared in Comparative Example 2 and place it in a solution with a system volume of 20 mL and an initial cesium ion concentration of 1 mg / L. The reaction temperature is 25 °C, the pH is 6, and the reaction is carried out in a shaker at 200 rpm for 12 h. The removal rate of cesium ions in water is 65%.

[0053] Table 1 Evaluation Table of Adsorption Effect

[0054]

[0055]

[0056] According to the results in Table 1, it can be seen that the removal rate of cesium by the porous nanofiber aerogel prepared in the present invention reaches more than 97%, the maximum cesium adsorption capacity is 97.88 mg / g, and after five repeated cycles of use, it can still reach 82.68% of the initial cesium adsorption capacity, greatly reducing energy consumption and realizing the concept of energy conservation, carbon reduction and environmental protection; compared with the prior art, the porous nanofiber aerogel prepared in the present invention has less dosage and a larger cesium adsorption capacity when used as an adsorbent, further reducing the cost.

[0057] The above are only the preferred embodiments of the present invention, and do not impose any form of limitation on the present invention. Although the present invention has been shown above with the preferred embodiments, it is not intended to limit the present invention. Any person skilled in the art can make some changes or modifications to equivalent embodiments by using the disclosed technical content within the scope of the technical solution of the present invention. However, as long as it does not depart from the technical solution of the present invention, any simple modification, equivalent change and modification made to the above embodiments based on the technical essence of the present invention still fall within the scope of the technical solution of the present invention.

Claims

1. A method for preparing a porous nanofiber aerogel, characterized in that: The steps are as follows: S1, mixing the SiO2 fiber membrane with deionized water and stirring into a sol state, then placing it in a reaction container, adding a cross-linking agent, stirring and reacting overnight, after the reaction is completed, centrifugally washing, adding glutaric anhydride and stirring and mixing, and finally centrifugally washing and freeze-drying in sequence to obtain a carboxylated SiO2 fiber aerogel; S2, adding the carboxylated SiO2 fiber aerogel obtained in step S1 to the copper acetate ethanol solution, mixing by ultrasonication, washing by centrifugation, and adding to a trimesic acid ethanol solution for ultrasonic reaction, after the reaction is completed, centrifugation washing and drying are performed in sequence to obtain a crude carboxylated CuBTC / SiO2 fiber aerogel; S3, using the crude carboxylated CuBTC / SiO2 fiber aerogel product in step S2 as a raw material and repeating step S2 to obtain a fully grown carboxylated CuBTC / SiO2 fiber aerogel; S4, adding the carboxylated CuBTC / SiO2 fiber aerogel obtained in step S3 to the copper chloride citric acid solution, stirring and mixing, and then successively subjecting to ultrasonic treatment and centrifugal washing to obtain a composite material, placing the composite material in the copper chloride citric acid solution for ultrasonic treatment, and then dropping potassium ferrocyanide citric acid solution to react, and obtaining liquid carboxylated CuFC / CuBTC / SiO2 fiber aerogel after the reaction is completed; S5. Using the liquid carboxylated CuFC / CuBTC / SiO2 fiber aerogel in step S4 as a raw material, repeat step S4 and then freeze-dry to obtain the target product.

2. The preparation method according to claim 1, characterized in that: In the step S1, the mass ratio of SiO2 fiber membrane to deionized water is 1:80; the mass ratio of SiO2 fiber membrane to cross-linking agent is 1:1.5-2.5; the mass ratio of SiO2 fiber membrane to glutaric anhydride is 1:2-3.

3. The preparation method according to claim 1, characterized in that: In step S1, the crosslinking agent is 3-aminopropyltriethoxysilane or methyltriethoxysilane.

4. The preparation method according to claim 1, characterized in that: In the step S1, the stirring time is 3 to 5 hours; the temperature in the reaction container is 80 to 100° C., the stirring speed is 800 to 1500 rpm, and the overnight reaction time is 12 to 18 hours; the freeze-drying temperature is -50 to -60° C., and the freeze-drying time is 48 to 72 hours.

5. The preparation method according to claim 1, characterized in that: The molar ratio of copper acetate to trimesic acid in step S2 is 1:5; the molar ratio of copper acetate to ethanol in the copper acetate ethanol solution is 1:0.5-1.8, and the molar ratio of trimesic acid to ethanol in the trimesic acid ethanol solution is 1:0.1-0.

4.

6. The preparation method according to claim 1, characterized in that: In step S2, the ultrasonic mixing time is 10 to 20 minutes, and the ultrasonic reaction time is 20 to 60 minutes.

7. The preparation method according to claim 1, characterized in that: In step S4, the molar ratio of cupric chloride to potassium ferrocyanide is 1:1; the molar ratio of cupric chloride to citric acid in the cupric chloride citric acid solution is 20:1, and the molar ratio of potassium ferrocyanide to citric acid in the potassium ferrocyanide citric acid solution is 20:

1.

8. The preparation method according to claim 1, characterized in that: In step S4, the stirring time is 3 to 5 hours; and the ultrasonic treatment time is 20 to 60 minutes.

9. The preparation method according to claim 1, characterized in that: In step S5, the freeze-drying temperature is -50 to -60°C, and the freeze-drying time is 48 to 72 hours.

10. Use of the porous nanofiber aerogel prepared by the preparation method according to any one of claims 1 to 9 in removing radioactive cesium from water.

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