CN116531974A

CN116531974A - Preparation method of nanofiber membrane loaded with modified activated carbon

Info

Publication number: CN116531974A
Application number: CN202310583836.8A
Authority: CN
Inventors: 郭俊毅; 余明; 焦顺; 施勇鹏; 高婷婷; 霍彦强; 郑军妹
Original assignee: Ningbo Fotile Kitchen Ware Co Ltd
Current assignee: Ningbo Fotile Kitchen Ware Co Ltd
Priority date: 2023-05-23
Filing date: 2023-05-23
Publication date: 2023-08-04

Abstract

The preparation method of the nanofiber membrane loaded with the modified activated carbon is characterized by comprising the following steps of: (1) uniformly mixing active carbon and acid substances, adding an initiator, and reacting to obtain a product; (2) adding Tween 80 into the product obtained in the step (1), adding weak acid, water bath, adding inorganic nonmetallic compound and ammonia water, and reacting to obtain modified activated carbon; (3) adding a solvent into modified activated carbon, adding dodecyldimethylamine oxide, adding polyurethane, completely dissolving, cooling, adding lithium salt, and uniformly stirring to prepare an electrostatic spinning precursor solution; (4) and (5) carrying out electrostatic spinning to obtain the nanofiber membrane. After the activated carbon is modified, the problem that the activated carbon is easy to agglomerate in the polymer can be effectively relieved, and the heavy metal removal capability of the nanofiber membrane is ensured to be stable.

Description

Preparation method of nanofiber membrane loaded with modified activated carbon

Technical Field

The invention relates to a preparation method of a nanofiber membrane, which can remove heavy metals in water.

Background

Along with the further acceleration of the industrialization process, the demands of various enterprises for heavy metals are increased day by day, and meanwhile, a large amount of composite pollutants, such as heavy metal ions Cd, are inevitably discharged to the environment ²⁺ 、Pb ²⁺ Etc. The heavy metal ions not only seriously pollute surface water and underground water and lead to the rapid decline of global available water resources, but also increase the heavy metal content in soil and endanger ecological environment and human health. In recent years, removal of composite pollutants in water has become a research hotspot in water environment treatment processes.

Currently, methods for heavy metal treatment mainly include precipitation, membrane separation, ion exchange and adsorption.

The precipitation method is to convert heavy metal ions in the wastewater solution into precipitate by using a certain mass of precipitant, but the sediment forming amount of the precipitate generated by the precipitation method is relatively high, the precipitate is required to be subjected to post-treatment, the influence of the PH value on the precipitate is also great, and the effect is unstable.

Membrane separation techniques, which generally use the action of an external force to cause a solution to pass through a selective semipermeable membrane to separate the solvent from the solution, mainly include: ultrafiltration, nanofiltration, reverse osmosis, microfiltration, etc., but the semipermeable membranes are expensive to manufacture, costly and have poor stability.

The ion exchange resin is an active group substance which is reacted with heavy metal and is arranged on the ion exchange resin, and the group can form chelation with the heavy metal ion, so that the aim of removing the heavy metal ion is fulfilled, but the ion exchange resin is expensive, a certain amount of wastewater is easy to generate during regeneration, and secondary pollution is easy to generate.

The adsorption method is a simple and efficient method which is attracting attention of students, and can deeply treat low-concentration heavy metal wastewater, and the treated effluent has high quality, strong operability and economy and effectiveness. However, the conventional adsorption materials such as zeolite, quartz sand, lignin, chitosan, cellulose and the like have the problems of poor selectivity, difficult regeneration, limited adsorption size of the adsorbent and the like. The activated carbon contains a large amount of hydroxyl groups in the molecule, can coordinate and adsorb heavy metal ions, and the adsorbed activated carbon material can be degraded by chemical and biological methods, so that the activated carbon material is a green heavy metal adsorption material, can be used for recycling heavy metals and purifying heavy metal industrial wastewater, and is considered as a green water treatment agent. However, the active carbon has the defects of easy agglomeration and the like, thereby affecting the stability of the composite material, so the modification research of the active carbon is an important method for improving the performance of the active carbon.

Disclosure of Invention

The technical problem to be solved by the invention is to provide a preparation method of a nanofiber membrane loaded with modified activated carbon and stable in adsorption capacity aiming at the state of the art

The technical scheme adopted for solving the technical problems is as follows: the preparation of the nanofiber membrane loaded with the modified activated carbon comprises the following steps:

(1) 0.1g-0.3g of active carbon is weighed into a round bottom flask, 80ml-150ml of ethanol and 45ml-60ml of ultrapure water are added, and active carbon-ethanol suspension is obtained. Adding 20ml-30ml of solvent and 3g-4g of acid substance into the suspension, continuously stirring for 20-30min at room temperature, slowly adding 10ml-15ml of initiator after uniformly mixing, and reacting for 1h to obtain the product. The diameter of the unmodified active carbon is 0.18-0.45 mm.

(2) Weighing 0.5g-1.5g of Tween 80 in a round-bottomed flask, adding 50ml-60ml of ultrapure water, continuously stirring for 30-40min, weighing 4g-5g of the product prepared in the step (1) in the same round-bottomed flask, adding 100ml-120ml of weak acid, and heating to 80-90 ℃ in a water bath. Rapidly adding 1-2g inorganic nonmetallic compound and 5ml-10ml ammonia water, and stirring for 1.5-2h under the condition of keeping 80-90 ℃. Then stopping heating and cooling to room temperature, and cleaning the material to be neutral by using ultrapure water to obtain the modified activated carbon.

(3) Adding solvent (N, N-dimethylformamide, N-dimethylacetamide, tetrahydrofuran and 1, 4-dioxane) and modified active carbon into a round bottom flask, stirring for 50-60min at 30-40 ℃ to form a homogeneous solution, adding dodecyldimethylamine oxide, continuously stirring for 20-30min at the constant temperature, adding polyurethane, continuously stirring for 10-20min at 60-70 ℃ to completely dissolve the polyurethane, adding lithium salt after completely dissolving and cooling, and uniformly stirring for 25-35min to prepare the electrostatic spinning precursor solution.

(4) Placing the electrostatic spinning precursor liquid into a liquid storage tank of electrostatic spinning equipment, taking non-woven fabrics as receiving base materials, and starting spinning after power is turned on to prepare the nanofiber membrane.

(5) Preparation and performance test of the filter element: the spun nanofiber membrane is rolled into a filter core with the length of 2.5 meters by a central tube and a diversion cloth, 26g of standard solution of cadmium ions and lead ions are respectively weighed in a water bucket with the length of 1000 liters to prepare the standard solution with the concentration of 26ug/L, the pH value of the standard solution is regulated by sodium hydroxide, the standard solution containing the heavy metal ions passes through the filter core through a lapped waterway, the adsorbed water sample is taken every other hour, diluted and stored by 0.2% dilute nitric acid, and the solubility of residual heavy metal in the sample is measured by an atomic absorption spectrophotometer.

Preferably, the solvent in the step (1) is any one of cyclohexane, oleic acid, methyl acetate or ethyl acetate; the acid substance is any one of humic acid, tannic acid or cysteine; the initiator is any one of potassium persulfate or azodiisobutyronitrile or tert-butyl hydroperoxide. The weak acid in the step (2) is any one of acetic acid, trifluoroacetic acid or trichloroacetic acid; the inorganic nonmetallic compound is any one of boron nitride or boron carbide or silicon nitride or silicon boride.

Preferably, the activated carbon is modified by the acid substance in the step (1), because the acid substance such as humic acid contains a large amount of carboxyl groups, phenolic hydroxyl groups and quinones, the functional groups have strong capability of complexing heavy metals, and meanwhile, the functional groups can act with the activated carbon, so that the humic acid can be covalently bonded to the surface of the activated carbon, and the activated carbon is endowed with excellent capability of absorbing the heavy metals; after the Tween 80 in the step (2) modifies the active carbon, the compatibility between the modified Tween 80 and the polymer can be improved, and the phenomenon that the active carbon is agglomerated in the polymer can be effectively prevented; in addition, the introduction of inorganic nonmetal improves the mechanical properties of the porous structure. The modified material is microsphere with porous structure and large specific surface area and diameter of 0.6-1.0 mm.

Preferably, the lithium salt in the step (3) is one or a combination of lithium chloride, lithium acetate and lithium formate; the molecular weight of the polyurethane is 60000-120000, and the viscosity of the electrostatic spinning precursor solution is 200-2000 mPa.s.

Preferably, the spinning voltage is 70-95kv, the distance between the electrode thread and the collector is 15-25cm, the liquid supply speed is 5-200ml/h, the collector speed is 0.01-0.05m/min, the spinning temperature is 20-40 ℃, and the humidity is 20% -40%.

Preferably, the mass ratio of solvent to polyurethane is from 70:8 to 70:20, preferably from 70:10 to 70:15, for example 70:12; the mass ratio of the solvent to the modified activated carbon is 70:1-70: 9, preferably 70:3.5 to 70:6.6, for example 70:5; the mass ratio of the solvent to the lithium salt is 70:1-70:4, preferably 70:2-70:3, for example 70:2.5; the mass ratio of the solvent to the dodecyldimethylamine oxide is 70:4-70:8, preferably 70:4.5-70:6, for example 70:5.

Preferably, the specific surface area of the prepared nanofiber membrane loaded with the modified activated carbon is 600-760m ² And/g, wherein the porosity is 70-80%, and the fiber diameter is 50-150nm.

Preferably, modified activated carbon and dodecyl dimethyl amine oxide are added in the process of electrostatic spinning of polyurethane, so that the heavy metal adsorption capacity can be improved, and the modified activated carbon and dodecyl dimethyl amine oxide can be widely applied to the field of liquid filtration.

Compared with the prior art, the invention has the advantages that: the activated carbon contains a large amount of hydroxyl groups in the molecule, can coordinate and adsorb heavy metal ions, and the adsorbed activated carbon material can be degraded by chemical and biological methods, so that the activated carbon material is a green heavy metal adsorption material, can be used for recycling heavy metals and purifying heavy metal industrial wastewater, and is considered as a green water treatment agent. Humic acid contains a large amount of carboxyl, phenolic hydroxyl and quinone, and the functional groups have strong capability of complexing heavy metals, so that after the humic acid is used for modifying active carbon, the surface activity of the material is effectively improved, and meanwhile, the excellent capability of absorbing heavy metals is endowed, and the adsorption capacity is improved. Tween 80 is a hydrophilic surfactant, can improve the compatibility between the surfactant and the polymer, and can effectively relieve the problem that activated carbon is easy to agglomerate in the polymer after being modified by the surfactant. The introduction of inorganic nonmetallic compounds improves the mechanical properties and enriches the pore structure. The dodecyl dimethyl amine has good chemical stability, can effectively solve the problems of uniform pore diameter and size control, improves the porosity and pore permeability, and can effectively adsorb even under the condition of low heavy metal concentration. In addition, the introduction of the dodecyl dimethyl amine can provide a water channel, can combine a large number of water molecules, improves the hydrophilicity of the surface of the membrane, forms a hydration layer on the surface of the membrane, and can effectively improve the flux.

The electrostatic spinning method has the advantages of wide raw material source range, good controllability of fiber structure, strong expansibility of preparation process and the like, the diameter of the fiber obtained by electrostatic spinning is hundreds of nanometers, and the material piled by the fiber has the characteristics of small pore diameter, high porosity, good fiber continuity, controllable stacking density and the like, and has wide application prospect in the fields of electronic information, environmental management, energy, safety protection, tissue engineering and the like.

The preparation method has the advantages of simple process, mild and easily controlled conditions, and the adopted raw materials are nontoxic or low-toxicity raw materials, so that the raw materials are consumed less in the reaction process, the cost is lower, toxic byproducts are not generated, and the preparation method belongs to an environment-friendly synthesis method. The fiber has higher content of functional groups, keeps good shape and strength, and has wide application prospect in aspects of functional textiles, water and air purification, chemical substance separation and extraction and the like.

Detailed Description

The present invention is described in further detail below with reference to examples.

Example 1

(1) 0.1g of activated carbon was weighed into a round-bottomed flask, and 80ml of ethanol and 45ml of ultrapure water were added to obtain an activated carbon-ethanol suspension. And adding 20ml of solvent cyclohexane and 3g of humic acid into the suspension, continuously stirring at room temperature for 20min, slowly adding 10ml of potassium persulfate after uniformly mixing, and reacting for 1h to obtain the product.

(2) Weighing 0.5g of Tween 80 into a round-bottomed flask, adding 50ml of ultrapure water, continuously stirring for 30min, weighing 4g of the product prepared in the step (1) into the same round-bottomed flask, adding 100ml of acetic acid, and heating to 80 ℃ in a water bath. 1g of boron nitride and 5ml of ammonia water were rapidly added, and stirred for 1.5 hours at 80 ℃. Then stopping heating and cooling to room temperature, and cleaning the material to be neutral by using ultrapure water to obtain the modified activated carbon.

(3) 700g of N, N-dimethylformamide solvent and 50g of modified activated carbon are added into a round-bottom flask, the mixture is stirred at 30 ℃ for 50min to form a homogeneous solution, 50g of dodecyl dimethyl amine oxide is added, the mixture is kept at the constant temperature and is continuously stirred for 20min, 120g of polyurethane with the molecular weight of 60000 is added, the polyurethane is continuously stirred at 60 ℃ to be completely dissolved, 25g of lithium chloride is added after the polyurethane is completely dissolved and cooled to 0 ℃, and the mixture is stirred for 10min to uniformly prepare an electrostatic spinning precursor solution, wherein the viscosity of the spinning solution is 300 mPa.s.

(4) And placing the electrostatic spinning precursor liquid prepared in the steps in a liquid storage device of electrostatic spinning equipment, connecting the device with a spinning needle head, and switching on a power supply to spin. The voltage during electrostatic spinning was set at 70kv, the distance between the electrode screw and the collector was 15cm, the liquid supply speed was 5ml/h, the collector speed was 0.01m/min, the spinning temperature was 20℃and the humidity was 20%, and the spun nanofiber membrane was collected with a nonwoven fabric.

Example 2

(1) 0.2g of activated carbon was weighed into a round-bottomed flask, and 100ml of ethanol and 50ml of ultrapure water were added to obtain an activated carbon-ethanol suspension. 25ml of cyclohexane solvent and 3.5g of humic acid are added into the suspension, the mixture is continuously stirred for 25min at room temperature, 13ml of potassium persulfate is slowly added after the mixture is uniformly mixed, and the product is obtained after the reaction for 1 h.

(2) 1.0g of Tween 80 was weighed into a round-bottomed flask, 55ml of ultrapure water was added and stirred for 35 minutes, 4.5g of the product prepared in step (1) was weighed into the same round-bottomed flask, 110ml of acetic acid was added, and the mixture was heated to 80℃in a water bath. 1.5g of boron nitride and 7ml of ammonia water were rapidly added, and stirred at 80℃for 1.7 hours. Then stopping heating and cooling to room temperature, and cleaning the material to be neutral by using ultrapure water to obtain the modified activated carbon.

(3) 700g of N, N-dimethylformamide solvent and 50g of modified activated carbon are added into a round bottom flask, the mixture is stirred at 35 ℃ for 55min to form a homogeneous solution, 50g of dodecyl dimethyl amine oxide is added, the mixture is kept at the constant temperature and is continuously stirred for 25min, 120g of polyurethane with molecular weight of 90000 is added, the polyurethane is continuously stirred at 60 ℃ to be completely dissolved, 50g of lithium chloride is added after the polyurethane is completely dissolved and cooled to 3 ℃, and the mixture is stirred for 15min to uniformly prepare an electrostatic spinning precursor solution, and the viscosity of the spinning solution is 700 mPa.s.

(4) And placing the electrostatic spinning precursor liquid prepared in the steps in a liquid storage device of electrostatic spinning equipment, connecting the device with a spinning needle head, and switching on a power supply to spin. The voltage during electrostatic spinning was set at 80kv, the distance between the electrode screw thread and the collector was 20cm, the liquid feeding speed was 50ml/h, the collector speed was 0.03m/min, the spinning temperature was 30℃and the humidity was 30%, and the spun nanofiber membrane was collected with a nonwoven fabric.

Example 3

(1) 0.3g of activated carbon was weighed into a round-bottomed flask, and 150ml of ethanol and 60ml of ultrapure water were added to obtain an activated carbon-ethanol suspension. 30ml of cyclohexane solvent and 4g of humic acid are added into the suspension, the mixture is stirred for 30min at room temperature, 15ml of potassium persulfate is slowly added after the mixture is uniformly mixed, and the product is obtained after the reaction for 1 h.

(2) 1.5g of Tween 80 was weighed into a round-bottomed flask, 60ml of ultrapure water was added and stirred continuously for 40 minutes, 5g of the product prepared in step (1) was weighed into the same round-bottomed flask, 120ml of acetic acid was added, and the mixture was heated to 80℃in a water bath. 2g of boron nitride and 10ml of ammonia water were rapidly added and stirred for 1.2 hours at 80 ℃. Then stopping heating and cooling to room temperature, and cleaning the material to be neutral by using ultrapure water to obtain the modified activated carbon.

(3) 700g of N, N-dimethylformamide solvent and 50g of modified activated carbon are added into a round bottom flask, the mixture is stirred at 40 ℃ for 60min to form a homogeneous solution, 50g of dodecyl dimethyl amine oxide is added, the mixture is kept at the constant temperature and is continuously stirred for 30min, 120g of polyurethane with the molecular weight of 120000 is added, the polyurethane is continuously stirred at 60 ℃ to be completely dissolved, 50g of lithium chloride is added after the polyurethane is completely dissolved and cooled to 5 ℃, and the mixture is stirred for 20min to uniformly prepare an electrostatic spinning precursor solution, wherein the viscosity of the spinning solution is 1500 mPa.s.

(4) And placing the electrostatic spinning precursor liquid prepared in the steps in a liquid storage device of electrostatic spinning equipment, connecting the device with a spinning needle head, and switching on a power supply to spin. The voltage during electrostatic spinning was 95kv, the distance between the electrode screw thread and the collector was 25cm, the liquid feeding speed was 150ml/h, the collector speed was 0.05m/min, the spinning temperature was 40℃and the humidity was 40%, and the spun nanofiber membrane was collected with a nonwoven fabric.

Comparative example 1 activated carbon modified without Tween 80

(2) 5g of the product prepared in step (1) are weighed into a round-bottomed flask, 120ml of acetic acid are added, and the mixture is heated to 80℃in a water bath. 2g of boron nitride and 10ml of ammonia water were rapidly added and stirred for 1.2 hours at 80 ℃. Then stopping heating and cooling to room temperature, and cleaning the material to be neutral by using ultrapure water to obtain the modified activated carbon.

(4) And placing the electrostatic spinning precursor liquid prepared in the steps in a liquid storage device of electrostatic spinning equipment, connecting the device with a spinning needle head, and switching on a power supply to spin. The voltage during electrostatic spinning was 95kv, the distance between the electrode screw thread and the collector was 25cm, the liquid feeding speed was 150ml/h, the collector speed was 0.05m/min, the spinning temperature was 40℃and the humidity was 40%, and the spun nanofiber membrane was collected with a nonwoven fabric

Comparative example 2 modification of activated carbon with inorganic nonmetallic Compounds

(2) 1.5g of Tween 80 was weighed into a round-bottomed flask, 60ml of ultrapure water was added and stirred continuously for 40 minutes, 5g of the product prepared in step (1) was weighed into the same round-bottomed flask, 120ml of acetic acid was added, and the mixture was heated to 80℃in a water bath. Then stopping heating and cooling to room temperature, and cleaning the material to be neutral by using ultrapure water to obtain the modified activated carbon.

(4) Placing the electrostatic spinning precursor liquid prepared by the steps in a liquid storage device of electrostatic spinning equipment, connecting the device with a spinning needle head, and connecting

Spinning by a power supply. The voltage during electrostatic spinning was 95kv, the distance between the electrode screw thread and the collector was 25cm, the liquid feeding speed was 150ml/h, the collector speed was 0.05m/min, the spinning temperature was 40℃and the humidity was 40%, and the spun nanofiber membrane was collected with a nonwoven fabric

(5) Preparation and performance test of the filter element: the spun nanofiber membrane is rolled into a filter core with the length of 2.5 meters by a central tube and a diversion cloth, which are respectively called as

And (3) taking 26g of standard solution of cadmium ions and lead ions in a water bucket of 1000 liters to prepare a standard solution with the concentration of 26ug/L, regulating the pH value of the standard solution by using sodium hydroxide, allowing the standard solution containing heavy metal ions to pass through a filter element through a lapped waterway, taking the adsorbed water sample every other hour, diluting and preserving the water sample by using 0.2% dilute nitric acid, and measuring the solubility of residual heavy metal in the sample by using an atomic absorption spectrophotometer.

Comparative example 3 spinning dope without dodecyldimethylamine oxide

(3) 700g of N, N-dimethylformamide solvent and 50g of modified activated carbon are added into a round-bottom flask, the mixture is stirred at 40 ℃ for 60min to form a homogeneous solution, 120g of polyurethane with molecular weight of 120000 is added, the mixture is continuously stirred at 60 ℃ to enable the polyurethane to be completely dissolved, 50g of lithium chloride is added after the polyurethane is completely dissolved and cooled to 5 ℃, and the mixture is stirred for 20min to uniformly prepare an electrostatic spinning precursor solution, wherein the viscosity of the spinning solution is 1500 mPa.s.

The results of the heavy metal adsorption experiments performed on the cartridges made of nanofibers of examples 1-3 and comparative examples 1-3 are shown in table 1:

according to the previous description, 26g of standard solution of cadmium ions and lead ions is weighed into a 1000 liter bucket to prepare standard solution with the concentration of 26ug/L, the PH value of the standard solution is regulated by sodium hydroxide, the standard solution containing heavy metal ions passes through a filter core through a lapped waterway, the adsorbed water sample is taken every other hour, the water sample is taken for 10 hours, the water sample is diluted and stored by 0.2% dilute nitric acid, and the solubility of the residual heavy metal in the sample is measured by an atomic absorption spectrophotometer.

TABLE 1

From table 1, it is clear that the nanofiber membrane prepared by the modification method of the present invention has a good adsorption effect on heavy metals.

To further confirm that the addition of dodecyldimethylamine oxide contributes to the improvement of porosity and permeability of the fibrous membrane, relevant tests were performed, the test results being shown in Table 2

The flux test method is as follows: the pipeline is lapped, water passes through the filter element, the reading of the pressure gauge is stabilized at 0.1MPa by controlling the switch of the return pipeline, after the water outlet is stabilized, water is received from the water outlet pipeline container, after one minute of timing, water receiving is stopped, and the mass of the water is converted into volume

TABLE 2

From table 2, it can be seen that the addition of dodecyldimethylamine can increase the specific surface area and porosity of the fibrous membrane, thereby increasing the flux of the filter element.

Claims

1. The preparation method of the nanofiber membrane loaded with the modified activated carbon is characterized by comprising the following steps of:

(1) adding ethanol and ultrapure water into activated carbon to obtain an activated carbon ethanol suspension, adding a solvent and an acid substance into the activated carbon ethanol suspension, stirring at room temperature, adding an initiator after uniformly mixing, and reacting to obtain a product;

(2) adding Tween 80 into ultrapure water, stirring, adding the product obtained in the step (1), adding weak acid, heating to 80-90 ℃ in a water bath, adding an inorganic nonmetallic compound and ammonia water, stirring, cooling to room temperature, and cleaning to neutrality to obtain modified activated carbon;

(3) adding a solvent into modified activated carbon, stirring at 30-40 ℃ to form a homogeneous solution, adding dodecyldimethylamine oxide, continuously stirring, adding polyurethane, stirring at 60-70 ℃ to completely dissolve the polyurethane, cooling after completely dissolving, adding lithium salt, and stirring uniformly to prepare an electrostatic spinning precursor solution;

(4) and placing the electrostatic spinning precursor liquid into electrostatic spinning equipment, and carrying out electrostatic spinning by using non-woven fabrics as receiving base materials to prepare the nanofiber membrane.

2. The preparation method of claim 1, wherein the weight ratio of the activated carbon to the acid substances in the step (1) is 0.1-0.3:3-4, and the volume ratio of the activated carbon to the initiator satisfies the following conditions: 0.1-0.3 g active carbon and 10-15 ml initiator.

3. The process according to claim 1, wherein the solvent in the step (1) is at least one of cyclohexane, oleic acid, methyl acetate and ethyl acetate.

4. The method according to claim 1, wherein the acid in the step (1) is at least one of humic acid, tannic acid and cysteine.

5. The process according to claim 1, wherein the initiator in the step (1) is at least one of potassium persulfate, azobisisobutyronitrile, t-butyl hydroperoxide.

6. The method according to claim 1, wherein the weak acid in step (2) is at least one of acetic acid, trifluoroacetic acid or trichloroacetic acid.

7. The method according to claim 1, wherein the inorganic nonmetallic compound in step (2) is at least one of boron nitride, boron carbide, silicon nitride, or silicon boride.

8. The preparation method according to claim 1, wherein the diameter of the unmodified activated carbon in the step (1) is 0.18-0.45 mm; the diameter of the modified activated carbon in the step (2) is 0.6-1.0 mm.

9. The method according to claim 1, wherein the lithium salt in the step (3) is at least one of lithium chloride, lithium acetate and lithium formate.

10. The process according to claim 1, wherein the polyurethane in the step (3) has a molecular weight of 60000 to 120000.

11. The method according to claim 1, wherein the viscosity of the electrospinning precursor liquid in the step (3) is 200 to 2000 mpa.s.

12. The process according to claim 1, wherein the solvent in the step (3) is at least one of N, N-dimethylformamide, N-dimethylacetamide, tetrahydrofuran, and 1, 4-dioxane.

13. The preparation method according to claim 1, wherein the mass ratio of the solvent to the polyurethane in the step (3) is 70:8 to 70:20; the mass ratio of the solvent to the modified activated carbon is 70:1 to 70:9, a step of performing the process; the mass ratio of the solvent to the lithium salt is 70:1-70:4; the mass ratio of the solvent to the dodecyl dimethyl amine oxide is 70:4-70:8.

14. The method according to claim 1, wherein the electrospinning conditions in the step (4) are as follows: the spinning voltage is 70-95kv, the distance between the electrode thread and the collector is 15-25cm, the liquid supply speed is 5-200ml/h, the collector speed is 0.01-0.05m/min, the spinning temperature is 20-40 ℃, and the humidity is 20-40%.

15. The method according to claim 1, wherein the specific surface area of the nanofiber membrane in the step (4) is 600 to 760m ² And/g, wherein the porosity is 70-80%, and the fiber diameter is 50-150nm.