Crown ether polyimide nanofiber membrane, method for preparing same, and use thereof

Abstract

The application provides a crown ether polyimide nanofiber membrane and a preparation method and application thereof, and belongs to the technical field of lithium ion selective adsorption. The crown ether polyimide nanofiber membrane is prepared by dissolving crown ether polyimide polymers with different masses in an organic solvent through an electrospinning technology; the diameter of the obtained crown ether polyimide nanofiber membrane ranges from 100 to 600 nm, and the specific surface area ranges from 17 to 41 m 2 g ‑1 The application utilizes the characteristics of the electrospinning technology that the fiber diameter is thin and the specific surface area is high, and the advantages of the crown ether polyimide that can selectively adsorb metal ions to prepare a high-efficiency lithium ion nanoadsorbent material, so that the problem that the crown ether adsorption sites are covered and cannot be fully utilized can be solved. Furthermore, the lithium ion adsorption capacity is improved, excellent lithium ion selective adsorption performance is exhibited, and lithium resources can be selectively recovered from waste lithium batteries and salt lake resources.

Description

TECHNICAL FIELD

[0001] The present application belongs to the technical field of lithium ion selective adsorption, and particularly relates to a crown ether polyimide nanofiber membrane as well as a preparation method and application thereof. BACKGROUND

[0002] In recent years, the field of new energy vehicles has developed rapidly, and the demand for lithium ion batteries has increased rapidly, resulting in a shortage of lithium resources. At the same time, lithium ion batteries have a limited lifespan, and a large number of waste lithium ion batteries are generated. How to recycle these lithium resources is of great significance to environmental protection. Therefore, it is necessary to develop efficient and green lithium ion selective adsorption separation technology to extract lithium ions from salt lake brine and recycle lithium ions from waste lithium batteries.

[0003] Pyrometallurgy and hydrometallurgy are two main technologies for metal ion recovery in research and industry. The extraction solution in hydrometallurgy needs to be separated and purified using different technologies to recover lithium resources, including precipitation, ion exchange, imprinted capacitive deionization, solvent extraction, and electrochemistry. However, these methods are either technically complex or economically unfeasible, requiring a large amount of reagents and energy input. Therefore, it is necessary to develop a green and efficient method for purifying and recycling lithium ions from a large number of waste lithium ion batteries.

[0004] The "adsorbent coupled membrane separation" method uses a substance with selective adsorption of ions combined with membrane separation to selectively separate lithium ions and other interfering ions by selectively adsorbing lithium ions and then desorbing them. In industry, inorganic lithium ion adsorbents are mainly used, including aluminum-based, manganese-based, and titanium-based lithium ion sieves, which are made into resins or membranes for fixation. However, this adsorbent has the problem of ion sieve dissolution during adsorption and desorption.

[0005] Therefore, researchers have developed an organic lithium ion adsorption medium coupled with membrane separation method. Among them, crown ether compounds are widely studied for selective extraction of lithium ions due to their special cavity size and chelation effect. Chinese patent application CN111253571A discloses a preparation method for a dibenzocrown ether polyimide polymer for selective extraction of lithium ions. The crown ether is introduced into the polymer main chain, effectively improving the uniformity of the crown ether adsorption site distribution, and is used for selective extraction of lithium ions, which shows a lithium ion adsorption capacity of 5.6 mg g -1 However, part of the crown ether adsorption sites are covered inside the polymer, which cannot be fully utilized, and the utilization rate of crown ether is only about 30%. Therefore, it is worth further studying to develop a method to improve the utilization rate of crown ether. SUMMARY

[0006] The application provides a crown ether polyimide nanofiber membrane and a preparation method and application thereof.

[0007] In order to achieve the above-mentioned purpose, the application provides a crown ether polyimide nanofiber membrane, wherein crown ether polyimide polymers with different masses are dissolved in an organic solvent, and the crown ether polyimide nanofiber membrane is prepared through an electrospinning technology.

[0008] The diameter of the obtained crown ether polyimide nanofiber membrane ranges from 100 nm to 600 nm, and the specific surface area ranges from 17 m 2 g -1 .

[0009] The saturated equilibrium adsorption capacity of the crown ether polyimide nanofiber membrane for lithium ions obtained through a dynamic cyclic adsorption experiment can reach 40.17 mg g -1 .

[0010] The crown ether polyimide is at least one of dibenzo 12-crown-4 polyimide, dibenzo 14-crown-4 polyimide, dibenzo 15-crown-5 polyimide and dibenzo 18-crown-6 polyimide. As a preferred embodiment, the crown ether polyimide is dibenzo 14-crown-4 polyimide. It can be understood that the application simulates the interaction force between dibenzo 14-crown-4 polyimide and Li + , Mn 2+ , Co 2+ and Ni 2+ based on the density functional theory calculation. Figure 4 The Gibbs free energy change value of the binding of dibenzo 14-crown-4 polyimide with Li + , Mn 2+ , Co 2+ and Ni 2+ is obtained through DFT theory calculation. The calculation software used in this part is Material Studio, and the Dmol3 module is used to model the structure of dibenzo 14-crown-4 polyimide, and the change of the coordination binding energy of the structure after optimization is simulated and calculated. In this process, the following formula (1) changes:

[0011]

[0012] wherein M represents Li + , Mn 2+ , Co 2+ , Ni 2+ , etc. The Gibbs free energy change is calculated by the following formula (2):

[0013]

[0014] The results show that the Gibbs free energy changes of the complexation of the dibenzo 14-crown-4 polyimide with Li + , Mn 2+ , Co 2+ , Ni 2+ are-113.99, -4.84, -19.86, -28.71 kcal mol -1 , respectively, which indicates that the binding capacity of the dibenzo 14-crown-4 polyimide nanofiber membrane to lithium ions is the largest, and thus the adsorption capacity to lithium ions is the best.

[0015] The organic solvent is at least one of N,N-dimethylformamide, N,N-dimethylacetamide and N-methylpyrrolidone. It can be understood that the boiling point and volatility of the selected organic solvent have an influence on the uniformity and compatibility of the spinning solution system and the morphology of the fibers in the obtained crown ether polyimide nanofiber membrane, and not all or similar organic solvents can be applicable. In the present scheme, although the above-mentioned solvents can be used, the effect of the latter two is inferior to that of N,N-dimethylformamide.

[0016] The mass ratio of the crown ether polyimide to the organic solvent is 12wt.% to 20wt.%. It can be understood that when the concentration of the spinning solution is lower than 12wt.%, the viscosity of the spinning solution is low, and the fibers with good morphology cannot be formed, and a large amount of beaded structures appear; when the concentration of the spinning solution is higher than 20wt.%, the viscosity of the spinning solution is large, and the spinning needle is easily blocked, and the continuous spinning process cannot be carried out.

[0017] The present application also provides a preparation method of the crown ether polyimide nanofiber membrane according to any one of the above technical solutions, which comprises the following steps:

[0018] The spinning solution is configured: the crown ether polyimide and the organic solvent are configured according to different mass ratios, and then added to a reaction container with magnetic stirring, heated to 50-70℃, stirred for 2-4 hours, and then left to remove the bubbles generated in the stirring process;

[0019] Electrospinning: the obtained spinning solution is loaded into a syringe, the syringe is clamped on a push injection pump, and then a conductive clamp is clamped on a stainless steel needle (20G) at the other end of the syringe, non-woven fabric for collecting fibers is fixed on a roller, and the fibers fall on the non-woven fabric on the roller, and after spinning for 6-8 hours, the crown ether polyimide nanofiber membrane with a certain thickness (100-190μm) is formed, and after natural air drying, peeling is carried out to obtain the crown ether polyimide nanofiber membrane.

[0020] As preferred, in the electrospinning, the spinning voltage is 10-30 kV. It can be understood that when the spinning voltage is lower than 10 kV, it is easy to produce beads and droplets, and the nanofiber with good morphology cannot be formed, because the electric field force is insufficient to stretch the jet; and when the spinning voltage is higher than 30 kV, the needle is blocked because the spinning solution flows out of the nozzle due to the excessive electric field force, the jet is not formed, and the spinning cannot be carried out smoothly.

[0021] As preferred, in the electrospinning, the extrusion rate of the spinning solution is 0.8-1.6 mL h -1 . It can be understood that when the extrusion rate of the spinning solution is greater than 1.6 mL h -1 , the jet cannot be fully stretched in the electric field, the solvent is not fully volatilized, the fibers are adhered to each other, and the needle is blocked to cause the spinning to be interrupted; and when the extrusion rate of the spinning solution is less than 0.8 mL h -1 , the jet is unstable, the spinning process is unstable, and the continuous spinning cannot be carried out.

[0022] As preferred, in the electrospinning, the distance between the stainless steel needle and the drum is 10-20 cm. It can be understood that when the distance between the stainless steel needle and the drum is less than 10 cm, the solvent cannot be fully volatilized to cause the fibers to be adhered to each other, and the nanofiber membrane with good morphology cannot be obtained; and when the distance between the stainless steel needle and the drum is greater than 20 cm, the jet is unstable to cause the fibers to be unable to be deposited and collected on the drum, because the distance is too large and the electric field strength is reduced.

[0023] The application also provides application of the crown ether polyimide nanofiber membrane according to any one of the above technical solutions in selective recovery of lithium ions from waste lithium resources.

[0024] As preferred, the adsorption amount of the crown ether polyimide nanofiber membrane to Li + , Na + , K + , Mn 2+ , Co 2+ , Ni 2+ is respectively 34.2, 2.1, 3.4, 5.0, 6.7, 8.1 mg g -1 , and the separation factor selectivity of Li + to Na + , K + , Mn 2+ , Co 2+ , Ni 2+ in the simulated waste battery extraction solution is respectively 52.3, 54.9, 48.8, 41.1, 35.1.

[0025] It can be understood that in the above lithium ion selective adsorption separation application, the experimental environment is a simulated wet waste battery extraction solution: the salt solution solute is LiCl, NaCl, KCl, MnCl2, CoCl2, NiCl2, the ion salt solution concentration is Li + 200mg L -1 , Na + , K + , Mn 2+ , Co 2+ , Ni 2+ 400mg L -1 . The adsorption temperature is 25 DEG C, and the adsorption time is 0-4h.

[0026] Compared with the prior art, the application has the advantages and positive effects that:

[0027] The crown ether polyimide nanofiber membrane disclosed by the application has the advantages of simple and efficient preparation method, high specific surface area, high crown ether loading capacity and high lithium ion adsorption capacity, and has a better selective separation effect on lithium ions. BRIEF DESCRIPTION OF DRAWINGS

[0028] Figure 1 is a scanning electron microscope test diagram of the electrospun dibenzo 14-crown-4 polyimide nanofiber membrane prepared in Example 1 of the application;

[0029] Figure 2 is a scanning electron microscope test diagram of the electrospun dibenzo 14-crown-4 polyimide nanofiber membrane prepared in Example 7 of the application;

[0030] Figure 3 is a specific surface area comparison diagram of the electrospun dibenzo 14-crown-4 polyimide nanofiber membranes and the dibenzo 14-crown-4 polyimide porous membranes prepared in Examples 4-7 of the application at different concentrations;

[0031] Figure 4 is a selective adsorption performance of the electrospun dibenzo 14-crown-4 polyimide nanofiber membrane prepared in Example 7 of the application on Li + , Na + , K + , Mn 2+ , Co 2+ , Ni 2+ ;

[0032] Figure 5 is a Gibbs free energy change value of the dibenzo 14-crown-4 polyimide combined with lithium, manganese, cobalt and nickel ions obtained by DFT theory calculation. DETAILED DESCRIPTION

[0033] The technical solutions in the embodiments of the present application will be clearly and completely described below. Obviously, the described embodiments are only some of the embodiments of the present application, rather than all the embodiments. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without creative work fall within the protection scope of the present application.

[0034] Embodiment 1

[0035] Preparation method of electrospun dibenzo 14-crown-4 polyimide nanofiber membrane: 1 g of dibenzo 14-crown-4 polyimide polymer was dissolved in 4 g of N, N-dimethylformamide (polymer solid content 20 wt. %), which was added to a three-necked round-bottom flask equipped with a magnetic spindle, heated to 70 ℃, stirred for 2 hours, and then left to remove the bubbles generated during stirring. The obtained spinning solution was loaded into a 5 mL syringe, the syringe was clamped on a push pump, and then a conductive clamp was clamped on the stainless steel needle (20G) at the other end of the syringe. The spinning voltage was 20 kV, the collection distance between the stainless steel needle and the drum was 20 cm, and the solution extrusion rate was set to 1.6 mL h -1 The non-woven fabric for collecting fibers was fixed on the drum, the fibers fell on the non-woven fabric of the drum, and after spinning for 8 h, a certain thickness of dibenzo 14-crown-4 polyimide nanofiber membrane was formed. After natural air drying, the membrane was peeled off to obtain a dibenzo 14-crown-4 polyimide nanofiber membrane, the thickness of which was 175 μm, and the specific surface area was 17.12 m 2 g -1 As shown in the figure, the fiber morphology is good, indicating that N, N-dimethylformamide is a good spinning solvent for crown ether polyimide materials. Figure 1

[0036] The fiber diameter of the prepared dibenzo 14-crown-4 polyimide nanofiber membrane was 546 nm, and the maximum adsorption capacity of lithium ions was 21.4 mg g -1 .

[0037] It can be understood that the purpose of the dynamic cycle experiment is to study the adsorption performance of the membrane rather than the retention performance. Li + The solution penetrates the membrane from top to bottom, and then Li + is selectively complexed by the crown ether in the polymer and stays on the surface and pores of the membrane. At the same time, the dynamic cycle adsorption keeps the Li + concentration in the feed almost unchanged during the adsorption process, thereby maintaining consistent operation.

[0038] The specific test method is as follows: the membrane is placed in a membrane cell with an effective diameter of 30 mm, 200 mL of a solution with a concentration of 400 mg L​-1 Lithium chloride solution was added to the screw bottle, and the adsorption performance of the membrane to Li + was studied for 4h operation time respectively. The equilibrium adsorption capacity of lithium ion was obtained by measuring the concentration of Li + solution after adsorption time through ICP-OES.

[0039] Example 2

[0040] Preparation method of electrospun dibenzo 14-crown-4 polyimide nanofiber membrane: 1g of dibenzo 14-crown-4 polyimide polymer was dissolved in 4g of N,N-dimethylformamide (polymer solid content 20wt.%), which was added to a three-necked round-bottom flask equipped with a magnet, heated to 70℃, stirred for 2 hours, and then left to remove the bubbles generated during stirring. The obtained spinning solution was loaded into a 5mL syringe, which was clamped on a push injection pump. Then, a conductive clamp was clamped on the stainless steel needle (20G) at the other end of the syringe. The spinning voltage was 30kV, the collection distance between the stainless steel needle and the drum was 20cm, and the solution extrusion rate was set to 1.6mL h -1 The non-woven fabric for collecting fibers was fixed on the drum, and the fibers fell on the non-woven fabric of the drum. After spinning for 8h, a certain thickness of dibenzo 14-crown-4 polyimide nanofiber membrane was formed, which was naturally dried and then peeled off to obtain the dibenzo 14-crown-4 polyimide nanofiber membrane. The membrane thickness was 172μm, and the specific surface area was 17.38m 2 g -1 .

[0041] The fiber diameter of the prepared dibenzo 14-crown-4 polyimide nanofiber membrane was 478nm, and the equilibrium adsorption capacity of lithium ion was 23.7mg g -1 .

[0042] Example 3

[0043] Preparation method of electrospun dibenzo 14-crown-4 polyimide nanofiber membrane: 1g of dibenzo 14-crown-4 polyimide polymer was dissolved in 4g of N,N-dimethylformamide (polymer solid content 20wt.%), which was added to a three-necked round-bottom flask equipped with a magnet, heated to 70℃, stirred for 2 hours, and then left to remove the bubbles generated during stirring. The obtained spinning solution was loaded into a 5mL syringe, which was clamped on a push injection pump. Then, a conductive clamp was clamped on the stainless steel needle (20G) at the other end of the syringe. The spinning voltage was 30kV, the collection distance between the stainless steel needle and the drum was 20cm, and the solution extrusion rate was set to 1.6mL h -1The non-woven fabric for collecting fibers is fixed on the roller, the fibers fall on the non-woven fabric of the roller, and a certain thickness of the dibenzo 14-crown-4 polyimide nanofiber membrane is formed after spinning for 8 hours. After natural drying, the dibenzo 14-crown-4 polyimide nanofiber membrane is obtained by peeling, the film thickness is 134 μm, the specific surface area is 17.37 m 2 g -1 .

[0044] The fiber diameter of the prepared dibenzo 14-crown 4 polyimide nanofiber membrane is 451 nm by scanning electron microscopy, and the equilibrium adsorption capacity of lithium ions is 23.9 mg g -1 .

[0045] Example 4

[0046] The preparation method of the electrospun dibenzo 14-crown 4 polyimide nanofiber membrane: 1 g of dibenzo 14-crown-4 polyimide polymer is dissolved in 4 g of N, N-dimethylformamide (polymer solid content 20 wt. %), which is added to a three-necked round-bottom flask equipped with a magnet, heated to 70°C, stirred for 2 hours, and then placed to remove the bubbles generated during stirring. The obtained spinning solution is loaded into a 5 mL syringe, the syringe is clamped on the push injection pump, and then the conductive clamp is clamped on the stainless steel needle (20G) at the other end of the syringe. The spinning voltage is 30 kV, the collection distance between the stainless steel needle and the roller is 10 cm, and the solution extrusion rate is set to 1 mL h -1 The non-woven fabric for collecting fibers is fixed on the roller, the fibers fall on the non-woven fabric of the roller, and a certain thickness of the dibenzo 14-crown-4 polyimide nanofiber membrane is formed after spinning for 8 hours. After natural drying, the dibenzo 14-crown-4 polyimide nanofiber membrane is obtained by peeling, the film thickness is 121 μm, the specific surface area is 17.44 m 2 g -1 .

[0047] The fiber diameter of the prepared dibenzo 14-crown 4 polyimide nanofiber membrane is 353.2 nm by scanning electron microscopy, and the equilibrium adsorption capacity of lithium ions is 24.6 mg g -1 .

[0048] Example 5

[0049] Preparation method of electrospun dibenzo 14-crown 4 polyimide nanofiber membrane: 1 g of dibenzo 14-crown-4 polyimide polymer was dissolved in 5.25 g of N, N-dimethylformamide (polymer solid content 16 wt.%), which was added to a three-necked round-bottom flask equipped with a magnetor, heated to 70 °C, stirred for 2 hours, and then left to remove the bubbles generated during stirring. The obtained spinning solution was loaded into a 5 mL syringe, which was clamped on a push pump, and then a conductive clamp was clamped on the stainless steel needle (20G) at the other end of the syringe. The spinning voltage was 30 kV, the collection distance between the stainless steel needle and the drum was 10 cm, and the solution extrusion rate was set to 1 mL h -1 The non-woven fabric for collecting fibers was fixed on the drum, the fibers fell on the non-woven fabric of the drum, and after spinning for 8 h, a certain thickness of dibenzo 14-crown-4 polyimide nanofiber membrane was formed. After natural drying, the membrane was peeled off to obtain the dibenzo 14-crown-4 polyimide nanofiber membrane. The membrane thickness was 149 μm, and the specific surface area was 20.87 m 2 g -1 .

[0050] The fiber diameter of the prepared dibenzo 14-crown 4 polyimide nanofiber membrane was 195.8 nm, and the equilibrium adsorption capacity of lithium ion was 31.7 mg g -1 .

[0051] Example 6

[0052] Preparation method of electrospun dibenzo 14-crown 4 polyimide nanofiber membrane: 1 g of dibenzo 14-crown-4 polyimide polymer was dissolved in 5.25 g of N, N-dimethylformamide (polymer solid content 16 wt.%), which was added to a three-necked round-bottom flask equipped with a magnetor, heated to 70 °C, stirred for 2 hours, and then left to remove the bubbles generated during stirring. The obtained spinning solution was loaded into a 5 mL syringe, which was clamped on a push pump, and then a conductive clamp was clamped on the stainless steel needle (20G) at the other end of the syringe. The spinning voltage was 30 kV, the collection distance between the stainless steel needle and the drum was 10 cm, and the solution extrusion rate was set to 1 mL h -1 The non-woven fabric for collecting fibers was fixed on the drum, the fibers fell on the non-woven fabric of the drum, and after spinning for 8 h, a certain thickness of dibenzo 14-crown-4 polyimide nanofiber membrane was formed. After natural drying, the membrane was peeled off to obtain the dibenzo 14-crown-4 polyimide nanofiber membrane. The membrane thickness was 149 μm, and the specific surface area was 20.87 m 2 g -1 .

[0053] The fiber diameter of the prepared dibenzo 14-crown 4 polyimide nanofiber membrane was 169.9 nm, and the equilibrium adsorption capacity of lithium ions was 35.8 mg g -1 .

[0054] Example 7

[0055] The preparation method of the electrospun dibenzo 14-crown 4 polyimide nanofiber membrane: 1 g of dibenzo 14-crown-4 polyimide polymer was dissolved in 7.33 g of N,N-dimethylformamide (polymer solid content 12 wt.%), which was added to a three-necked round-bottom flask equipped with a magnet, heated to 70°C, and stirred for 2 hours. After standing to remove the bubbles generated during stirring, the obtained spinning solution was loaded into a 5 mL syringe, which was clamped on a push pump, and then a conductive clamp was clamped on the stainless steel needle (20G) at the other end of the syringe. The spinning voltage was 30 kV, the collection distance between the stainless steel needle and the drum was 10 cm, and the solution extrusion rate was set to 1 mL h -1 The non-woven fabric for collecting fibers was fixed on the drum, and the fibers fell on the non-woven fabric on the drum. After spinning for 8 hours, a certain thickness of dibenzo 14-crown-4 polyimide nanofiber membrane was formed, which was naturally dried and then peeled off to obtain the dibenzo 14-crown-4 polyimide nanofiber membrane. The membrane thickness was 115 μm, and the specific surface area was 41.21 m 2 g -1 , and its structural formula is shown below.

[0056]

[0057] As Figure 2 shown, the fiber diameter of the prepared dibenzo 14-crown 4 polyimide nanofiber membrane was 122.7 nm, and the equilibrium adsorption capacity of lithium ions was 40.17 mg g -1 . The dibenzo 14-crown 4 polyimide nanofiber membrane prepared in this example showed excellent lithium ion adsorption capacity and crown ether utilization rate, and the crown ether utilization rate reached 70%, and the calculation formula is shown as (3):

[0058]

[0059] where EAR represents the crown ether utilization rate, Qe represents the equilibrium adsorption capacity of the nanofiber membrane, M Li is the molar mass of the LiCl salt solution, I A is the crown ether content of the nanofiber membrane (1.38 mmol g -1 ).

[0060] Figure 4 The electrospun dibenzo-14-crown-4 polyimide nanofiber membrane prepared in Example 7 is effective against Li + Na + K + Mn 2+ Co 2+ Ni 2+ The adsorption performance was selected; the experimental environment was a simulated wet-process waste battery extraction solution: the salt solution solutes were LiCl, NaCl, KCl, MnCl2, CoCl2, NiCl2, and the ion salt solution concentration was Li + 200mg L -1 Na + K + Mn 2+ Co 2+ Ni 2+ 400mg L -1 The adsorption temperature was 25℃, and the adsorption time was 0–4 h. The resulting crown ether polyimide nanofiber membrane exhibited good adhesion to Li. + Na + K + Mn 2+ Co 2+ Ni 2+ The adsorption capacities were 34.2, 2.1, 3.4, 5.0, 6.7, and 8.1 mg g, respectively. -1 In simulated waste battery extract, Li + To Na + K + Mn 2+ Co 2+ Ni 2+ The separation factor selectivity was 52.3, 54.9, 48.8, 41.1, and 35.1, respectively.

[0061] Figure 3 This is a comparison of the specific surface area of ​​electrospun dibenzo-14-crown-4 polyimide nanofiber membranes and dibenzo-14-crown-4 polyimide porous membranes at different concentrations prepared in Examples 4-7 of this invention (data obtained using BET nitrogen isotherm adsorption curves). Figure 3 As shown, 14C4PI-M represents a dibenzo-14-crown-4 polyimide porous membrane prepared by a solvent-free phase inversion method, with a specific surface area of ​​9.65 m². 2 g -1 14C4PI-12, 14C4PI-14, 14C4PI-16, and 14C4PI-20 represent spinning solutions with concentrations of 12 wt.%, 14 wt.%, 16 wt.%, and 20 wt.%, respectively, and spinning parameters of 30 kV and 1 mL h. -1The specific surface area of the dibenzo 14-crown-4 polyimide nanofiber membrane prepared under the condition of 10 cm was 41.21, 33.39, 20.87, 17.44 m 2 g -1 , respectively, indicating that the specific surface area of the membrane can be effectively controlled by adjusting the concentration of the spinning solution.

[0062] Example 8

[0063] The preparation method of the electrospun dibenzo 12-crown 4 polyimide nanofiber membrane was as follows: 1 g of dibenzo 12-crown-4 polyimide polymer was dissolved in 7.33 g of N,N-dimethylformamide (polymer solid content 12 wt.%), which was added to a three-necked round-bottom flask equipped with a magnetic stirrer, heated to 70°C, stirred for 2 hours, and then left to remove the bubbles generated during stirring. The obtained spinning solution was loaded into a 5 mL syringe, which was clamped on a syringe pump, and then a conductive clamp was clamped on the stainless steel needle (20G) at the other end of the syringe. The spinning voltage was 30 kV, the collection distance between the stainless steel needle and the drum was 10 cm, and the solution extrusion rate was set to 1 mL h -1 . The non-woven fabric for collecting fibers was fixed on the drum, and the fibers fell on the non-woven fabric of the drum. After spinning for 8 hours, a certain thickness of dibenzo 12-crown 4 polyimide nanofiber membrane was formed, which was naturally dried and then peeled off to obtain the dibenzo 12-crown 4 polyimide nanofiber membrane. The membrane thickness was 137 μm, and its structural formula was as shown below.

[0064]

[0065] Through the dynamic cyclic adsorption experiment, the equilibrium adsorption capacity of lithium ions was 15.8 mg g -1 .

[0066] Example 9

[0067] The preparation method of the electrospun dibenzo 15-crown-5 polyimide nanofiber membrane was as follows: 1 g of dibenzo 15-crown-5 polyimide polymer was dissolved in 7.33 g of N,N-dimethylformamide (polymer solid content 20 wt.%), which was added to a three-necked round-bottom flask equipped with a magnetic stirrer, heated to 70°C, stirred for 2 hours, and then left to remove the bubbles generated during stirring. The obtained spinning solution was loaded into a 5 mL syringe, which was clamped on a syringe pump, and then a conductive clamp was clamped on the stainless steel needle (20G) at the other end of the syringe. The spinning voltage was 30 kV, the collection distance between the stainless steel needle and the drum was 10 cm, and the solution extrusion rate was set to 1 mL h -1The non-woven fabric for collecting fibers is fixed on the roller, the fibers fall on the non-woven fabric of the roller, and after spinning for 8h, a certain thickness of the dibenzo 15-crown-5 polyimide nanofiber membrane is formed. After natural drying, the dibenzo 15-crown-5 polyimide nanofiber membrane is obtained by peeling. The membrane thickness is 154μm, and the structural formula is as shown below.

[0068]

[0069] The equilibrium adsorption capacity of lithium ions is 11.7mg g -1 .

[0070] Example 10

[0071] The preparation method of the electrospun dibenzo 18-crown-6 polyimide nanofiber membrane is as follows: 1g of dibenzo 18-crown-6 polyimide polymer is dissolved in 7.33g of N,N-dimethylformamide (polymer solid content 12wt.%), which is added to a three-necked round-bottom flask equipped with a magnetor, heated to 70℃, stirred for 2h, and then placed to remove the bubbles generated during stirring. The obtained spinning solution is loaded into a 5mL syringe, the syringe is clamped on the syringe pump, and then the conductive clamp is clamped on the stainless steel needle (20G) at the other end of the syringe. The spinning voltage is 30kV, the collection distance between the stainless steel needle and the roller is 10cm, and the solution extrusion rate is set to 1mL h -1 The non-woven fabric for collecting fibers is fixed on the roller, the fibers fall on the non-woven fabric of the roller, and after spinning for 8h, a certain thickness of the dibenzo 18-crown-6 polyimide nanofiber membrane is formed. After natural drying, the dibenzo 18-crown-6 polyimide nanofiber membrane is obtained by peeling. The membrane thickness is 187μm, and the structural formula is as shown below.

[0072]

[0073] The equilibrium adsorption capacity of lithium ions is 9.6mg g -1 .

[0074] Example 11

[0075] Preparation method of electrospun dibenzo 14-crown-4 polyimide nanofiber membrane: 1 g of dibenzo 14-crown-4 polyimide polymer was dissolved in 4 g of N,N-dimethylacetamide (polymer solid content 20 wt.%), which was added to a three-necked round-bottom flask equipped with a magnetic bar, heated to 70°C, stirred for 2 hours, and then left to remove the bubbles generated during stirring. The obtained spinning solution was loaded into a 5 mL syringe, which was clamped on a push injection pump. Then, a conductive clamp was clamped on the stainless steel needle (20G) at the other end of the syringe. The spinning voltage was 20 kV, the collection distance between the stainless steel needle and the drum was 20 cm, and the solution extrusion rate was set to 1.6 mL h -1 The non-woven fabric for collecting fibers was fixed on the drum, and the fibers fell on the non-woven fabric of the drum. After spinning for 8 h, a certain thickness of dibenzo 14-crown-4 polyimide nanofiber membrane was formed. After natural drying, the crown ether polyimide nanofiber membrane was peeled off. The fibers were adhered to each other, indicating that N,N-dimethylacetamide was not suitable for use as a spinning solvent for crown ether polyimide materials. Through dynamic cyclic adsorption experiments, the maximum adsorption capacity of lithium ions was 14.7 mg g -1 .

[0076] Example 12

[0077] Preparation method of electrospun dibenzo 14-crown-4 polyimide nanofiber membrane: 1 g of dibenzo 14-crown-4 polyimide polymer was dissolved in 4 g of N-methyl pyrrolidone (polymer solid content 20 wt.%), which was added to a three-necked round-bottom flask equipped with a magnetic bar, heated to 70°C, stirred for 2 hours, and then left to remove the bubbles generated during stirring. The obtained spinning solution was loaded into a 5 mL syringe, which was clamped on a push injection pump. Then, a conductive clamp was clamped on the stainless steel needle (20G) at the other end of the syringe. The spinning voltage was 20 kV, the collection distance between the stainless steel needle and the drum was 20 cm, and the solution extrusion rate was set to 1.6 mL h -1 The non-woven fabric for collecting fibers was fixed on the drum, and the fibers fell on the non-woven fabric of the drum. After spinning for 8 h, a certain thickness of dibenzo 14-crown-4 polyimide nanofiber membrane was formed. After natural drying, the crown ether polyimide nanofiber membrane was peeled off. The fibers were adhered to each other, indicating that N-methyl pyrrolidone was not suitable for use as a spinning solvent for crown ether polyimide materials. Through dynamic cyclic adsorption experiments, the maximum adsorption capacity of lithium ions was 14.3 mg g -1 .

[0078] Comparative Example 1

[0079] Preparation method of electrospun dibenzo 14-crown 4 polyimide nanofiber membrane: 1 g of dibenzo 14-crown-4 polyimide polymer was dissolved in 11.5 g of N,N-dimethylformamide (polymer solid content 8 wt.%), which was added to a three-necked round-bottom flask equipped with a magnet, heated to 70°C, stirred for 2 hours, and then left to remove the bubbles generated during stirring. The obtained spinning solution was loaded into a 5 mL syringe, which was clamped on a push injection pump, and then a conductive clamp was clamped on the stainless steel needle (20G) at the other end of the syringe. The spinning voltage was 30 kV, the collection distance between the stainless steel needle and the drum was 10 cm, and the solution extrusion rate was set to 1 mL h -1 The non-woven fabric for collecting fibers was fixed on the drum, the fibers fell on the non-woven fabric of the drum, and after spinning for 8 h, a certain thickness of dibenzo 14-crown-4 polyimide nanofiber membrane was formed. After natural drying, the membrane was peeled off to obtain the dibenzo 14-crown-4 polyimide nanofiber membrane. The scanning electron microscopy characterization results showed that at a concentration of 8 wt.%, the fibers could not form a good morphology, and a large number of beaded structures appeared.

[0080] Comparative example 2

[0081] Preparation method of electrospun dibenzo 14-crown 4 polyimide nanofiber membrane: 1 g of dibenzo 14-crown-4 polyimide polymer was dissolved in 11.5 g of N,N-dimethylformamide (polymer solid content 8 wt.%), which was added to a three-necked round-bottom flask equipped with a magnet, heated to 70°C, stirred for 2 hours, and then left to remove the bubbles generated during stirring. The obtained spinning solution was loaded into a 5 mL syringe, which was clamped on a push injection pump, and then a conductive clamp was clamped on the stainless steel needle (20G) at the other end of the syringe. The spinning voltage was 30 kV, the collection distance between the stainless steel needle and the drum was 10 cm, and the solution extrusion rate was set to 1 mL h -1 The non-woven fabric for collecting fibers was fixed on the drum, the fibers fell on the non-woven fabric of the drum, and after spinning for 8 h, a certain thickness of dibenzo 14-crown-4 polyimide nanofiber membrane was formed. After natural drying, the membrane was peeled off to obtain the dibenzo 14-crown-4 polyimide nanofiber membrane. The scanning electron microscopy characterization results showed that at a concentration of 8 wt.%, the fibers could not form a good morphology, and a large number of beaded structures appeared.

[0082] Comparative example 3

[0083] Preparation method of electrospun dibenzo 14-crown 4 polyimide nanofiber membrane: 1 g of dibenzo 14-crown-4 polyimide polymer was dissolved in 7.33 g of N,N-dimethylformamide (polymer solid content 12 wt.%), which was added to a three-necked round-bottom flask equipped with a magnet, heated to 70°C, stirred for 2 hours, and then left to remove the bubbles generated during stirring. The obtained spinning solution was loaded into a 5 mL syringe, which was clamped on a push injection pump. A conductive clamp was clamped on the stainless steel needle (20G) at the other end of the syringe. The spinning voltage was 8 kV, the collection distance between the stainless steel needle and the drum was 10 cm, and the solution extrusion rate was set to 1 mL h -1 The non-woven fabric for collecting fibers was fixed on the drum, and the fibers fell on the non-woven fabric of the drum. After spinning for 8 h, a certain thickness of dibenzo 14-crown-4 polyimide nanofiber membrane was formed, which was naturally dried and then peeled off to obtain the dibenzo 14-crown-4 polyimide nanofiber membrane. The scanning electron microscopy characterization results showed that when the spinning voltage was lower than 10 kV, beaded and droplet were generated, and nanofibers with good morphology could not be formed. The reason was that the electric field force was not enough to stretch the jet.

[0084] Comparative example 4

[0085] Preparation method of electrospun dibenzo 14-crown 4 polyimide nanofiber membrane: 1 g of dibenzo 14-crown-4 polyimide polymer was dissolved in 7.33 g of N,N-dimethylformamide (polymer solid content 12 wt.%), which was added to a three-necked round-bottom flask equipped with a magnet, heated to 70°C, stirred for 2 hours, and then left to remove the bubbles generated during stirring. The obtained spinning solution was loaded into a 5 mL syringe, which was clamped on a push injection pump. A conductive clamp was clamped on the stainless steel needle (20G) at the other end of the syringe. The spinning voltage was 8 kV, the collection distance between the stainless steel needle and the drum was 10 cm, and the solution extrusion rate was set to 1 mL h -1 The non-woven fabric for collecting fibers was fixed on the drum, and the fibers fell on the non-woven fabric of the drum. After spinning for 8 h, a certain thickness of dibenzo 14-crown-4 polyimide nanofiber membrane was formed, which was naturally dried and then peeled off to obtain the dibenzo 14-crown-4 polyimide nanofiber membrane. The spinning solution was not formed into a jet from the nozzle, resulting in unsuccessful spinning.

[0086] Comparative example 5

[0087] The preparation method of the electrospun dibenzo 14-crown 4 polyimide nanofiber membrane is as follows: 1 g of dibenzo 14-crown 4 polyimide polymer is dissolved in 7.33 g of N,N-dimethylformamide (polymer solid content 12 wt.%), which is added to a three-necked round-bottom flask with a magnet, heated to 70°C, stirred for 2 hours, and then left to remove the bubbles generated during stirring. The obtained spinning solution is loaded into a 5 mL syringe, which is clamped on a push injection pump, and then a conductive clamp is clamped on the stainless steel needle (20G) at the other end of the syringe. The spinning voltage is 30 kV, the collection distance between the stainless steel needle and the drum is 10 cm, and the solution extrusion rate is set to 0.6 mL h -1 The non-woven fabric for collecting fibers is fixed on the drum, the fibers fall on the non-woven fabric of the drum, and a certain thickness of dibenzo 14-crown 4 polyimide nanofiber membrane is formed after spinning for 8 hours. After natural drying, the dibenzo 14-crown 4 polyimide nanofiber membrane is obtained by peeling. The results show that when the extrusion rate is too low, the jet unstable spinning process is easily interrupted, and continuous spinning cannot be carried out.

[0088] Comparative Example 6

[0089] The preparation method of the electrospun dibenzo 14-crown 4 polyimide nanofiber membrane is as follows: 1 g of dibenzo 14-crown 4 polyimide polymer is dissolved in 7.33 g of N,N-dimethylformamide (polymer solid content 12 wt.%), which is added to a three-necked round-bottom flask with a magnet, heated to 70°C, stirred for 2 hours, and then left to remove the bubbles generated during stirring. The obtained spinning solution is loaded into a 5 mL syringe, which is clamped on a push injection pump, and then a conductive clamp is clamped on the stainless steel needle (20G) at the other end of the syringe. The spinning voltage is 30 kV, the collection distance between the stainless steel needle and the drum is 10 cm, and the solution extrusion rate is set to 1.8 mL h -1 The non-woven fabric for collecting fibers is fixed on the drum, the fibers fall on the non-woven fabric of the drum, and a certain thickness of dibenzo 14-crown 4 polyimide nanofiber membrane is formed after spinning for 8 hours. After natural drying, the dibenzo 14-crown 4 polyimide nanofiber membrane is obtained by peeling. The results show that when the extrusion rate is too low, the jet unstable spinning process is easily interrupted, and continuous spinning cannot be carried out. -1 The non-woven fabric for collecting fibers is fixed on the drum, the fibers fall on the non-woven fabric of the drum, and a certain thickness of dibenzo 14-crown 4 polyimide nanofiber membrane is formed after spinning for 8 hours. After natural drying, the dibenzo 14-crown 4 polyimide nanofiber membrane is obtained by peeling. The results show that when the extrusion rate is too low, the jet unstable spinning process is easily interrupted, and continuous spinning cannot be carried out.

[0090] Comparative Example 7

[0091] Preparation method of electrospun dibenzo 14-crown 4 polyimide nanofiber membrane: 1 g of dibenzo 14-crown-4 polyimide polymer was dissolved in 7.33 g of N,N-dimethylformamide (polymer solid content 12 wt.%), which was added to a three-necked round-bottom flask equipped with a magnet, heated to 70°C, stirred for 2 hours, and then left to remove the bubbles generated during stirring. The obtained spinning solution was loaded into a 5 mL syringe, which was clamped on a push injection pump. A conductive clamp was clamped on the stainless steel needle (20G) at the other end of the syringe. The spinning voltage was 30 kV, the collection distance between the stainless steel needle and the drum was 8 cm, and the solution extrusion rate was set to 1 mL h -1 The non-woven fabric for collecting fibers was fixed on the drum, and the fibers fell on the non-woven fabric of the drum. After spinning for 8 hours, a certain thickness of dibenzo 14-crown-4 polyimide nanofiber membrane was formed. After natural drying, the membrane was peeled off to obtain the dibenzo 14-crown-4 polyimide nanofiber membrane. The scanning electron microscope showed that the fibers were adhered to each other and could not form a good fiber structure. The reason was that the collection distance between the stainless steel needle and the drum was too small, and the solvent could not completely volatilize, so the jet was deposited on the collection drum.

[0092] Comparative example 8

[0093] Preparation method of electrospun dibenzo 14-crown 4 polyimide nanofiber membrane: 1 g of dibenzo 14-crown-4 polyimide polymer was dissolved in 7.33 g of N,N-dimethylformamide (polymer solid content 12 wt.%), which was added to a three-necked round-bottom flask equipped with a magnet, heated to 70°C, stirred for 2 hours, and then left to remove the bubbles generated during stirring. The obtained spinning solution was loaded into a 5 mL syringe, which was clamped on a push injection pump. A conductive clamp was clamped on the stainless steel needle (20G) at the other end of the syringe. The spinning voltage was 30 kV, the collection distance between the stainless steel needle and the drum was 22 cm, and the solution extrusion rate was set to 1 mL h -1 The non-woven fabric for collecting fibers was fixed on the drum, and the fibers fell on the non-woven fabric of the drum. After spinning for 8 hours, a certain thickness of dibenzo 14-crown-4 polyimide nanofiber membrane was formed. After natural drying, the membrane was peeled off to obtain the dibenzo 14-crown-4 polyimide nanofiber membrane. The scanning electron microscope showed that the fibers were adhered to each other and could not form a good fiber structure. The reason was that the collection distance between the stainless steel needle and the drum was too small, and the solvent could not completely volatilize, so the jet was deposited on the collection drum.

[0094] Comparative example 9

[0095] Preparation method of electrospun polyimide nanofiber membrane: 1 g of polyimide polymer was dissolved in 4 g of N,N-dimethylformamide (polymer solid content 22 wt.%), which was added to a three-necked round-bottom flask equipped with a magnetic stirrer, heated to 70 °C, and stirred for 2 h. After standing to remove the bubbles generated during stirring, the obtained spinning solution was loaded into a 5 mL syringe, which was clamped on a push injection pump. A conductive clamp was clamped on the stainless steel needle (20G) at the other end of the syringe. The spinning voltage was 20 kV, the collection distance between the stainless steel needle and the drum was 20 cm, and the solution extrusion rate was set to 1.6 mL h -1 The non-woven fabric for collecting fibers was fixed on the drum, and the fibers fell on the non-woven fabric of the drum. During the spinning process, due to the high polymer concentration (22 wt.%) and the large viscosity of the spinning solution, the spinning needle was constantly blocked, which prevented the continuous spinning process.

Claims

1. The application of crown ether polyimide nanofiber membranes in the selective recovery of lithium ions from waste lithium battery resources, characterized in that, The crown ether polyimide nanofiber membrane is prepared by dissolving crown ether polyimide polymers of different masses in an organic solvent and then electrospinning. The obtained crown ether polyimide nanofiber membranes have diameters ranging from 100 to 600 nm and specific surface areas ranging from 17 to 41 m². 2 g -1 ; The crown ether polyimide is dibenzo-14-crown-4 polyimide; The mass ratio of the crown ether polyimide to the organic solvent is 12 wt.%~20 wt.%; Crown ether polyimide nanofiber membrane for Li + Na + K + Mn 2+ Co 2+ Ni 2+ The adsorption capacities were 34.2, 2.1, 3.4, 5.0, 6.7, and 8.1 mg g, respectively. -1 In Li + The concentration is 200 mg / L -1 Other competing ion concentrations were 400 mg / L. -1 In the simulated waste battery extract, Li + To Na + K + Mn 2+ Co 2+ Ni 2+ The separation factor selectivity was 52.3, 54.9, 48.8, 41.1, and 35.1, respectively.

2. The application according to claim 1, characterized in that, The organic solvent is at least one of N,N-dimethylformamide, N,N-dimethylacetamide, and N-methylpyrrolidone.

3. The application according to claim 1 or 2, characterized in that, The preparation method of the crown ether polyimide nanofiber membrane includes the following steps: Preparation of spinning solution: Prepare crown ether polyimide and organic solvent according to different masses, then add them to a reaction vessel with magnetic stirring, heat to 50~70℃, stir for 2~4 hours, and let stand to remove bubbles generated during stirring; Electrospinning: The spinning solution obtained above is loaded into a syringe, the syringe is clamped on a push pump, and then a conductive clip is clamped on the stainless steel needle at the other end of the syringe. The nonwoven fabric for collecting fibers is fixed on a roller, and the fibers fall onto the nonwoven fabric of the roller. After spinning for 6-8 hours, a crown ether polyimide nanofiber membrane with a certain thickness is formed. After being left to stand and air-dried, it is peeled off to obtain the crown ether polyimide nanofiber membrane.

4. The application according to claim 3, characterized in that, In electrospinning, the spinning voltage is 10~30 kV.

5. The application according to claim 3, characterized in that, In electrospinning, the extrusion rate of the spinning solution is 0.8~1.6 mL / h. -1 .

6. The application according to claim 3, characterized in that, In electrospinning, the distance between the stainless steel needle and the roller is 10~20 cm.

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