Preparation method and application of two-dimensional graphene oxide intercalated one-dimensional encapsulated cobalt ferrite open carbon nanotube composite film

Abstract

The application relates to a preparation method and application of an open carbon nanotube composite film of two-dimensional graphene oxide intercalation one-dimensional encapsulated cobalt ferrite, and belongs to the technical field of two-dimensional material film preparation. The application aims to solve the problems that the catalytic effect of an existing catalytic film is easily interfered by natural organic matters and the selectivity for target pollutants is poor. The method comprises the following steps: one, preparation of open carbon nanotube encapsulated with cobalt ferrite; two, preparation of a composite film through two-dimensional graphene oxide intercalation. Application: used for removing organic pollutants in water. The application is used for the preparation and application of the open carbon nanotube composite film of two-dimensional graphene oxide intercalation one-dimensional encapsulated cobalt ferrite.

Description

Technical Field

[0001] This invention belongs to the field of two-dimensional material film preparation technology. Background Technology

[0002] Advanced oxidation processes (AOPs) are a highly efficient water treatment technology. However, the widespread presence of natural organic matter in actual water bodies competes with target pollutants for the free radicals generated during AOPs, resulting in low oxidant utilization and poor degradation efficiency of target pollutants. To improve the selectivity for target pollutants, effectively combining membranes with separation capabilities with catalysts can utilize membrane pore size for sieving, thereby retaining natural organic matter and improving selectivity. However, this approach is ineffective against natural organic matter that enters the membrane pores.

[0003] Therefore, reducing the interference of natural organic matter on catalytic membranes and developing catalytic membranes with selective catalytic oxidation capabilities are of significant environmental importance. Summary of the Invention

[0004] This invention aims to address the problems of existing catalytic membranes being susceptible to interference from natural organic matter and having poor selectivity for target pollutants. It provides a method for preparing and applying an open carbon nanotube composite membrane with two-dimensional graphene oxide intercalation and one-dimensional encapsulation of cobalt ferrite.

[0005] A method for preparing a two-dimensional graphene oxide intercalated one-dimensional encapsulated cobalt ferrite open carbon nanotube composite film, comprising the following steps:

[0006] I. Preparation of open carbon nanotubes encapsulating cobalt ferrite:

[0007] ① The carbon nanotubes were opened by reflux with concentrated nitric acid, and then centrifuged, purified, filtered and dried to obtain open carbon nanotubes.

[0008] ② Cobalt nitrate hexahydrate, ferric nitrate nonahydrate, open carbon nanotubes and methanol were ultrasonically and stirred until the methanol evaporated completely, and then dried. After drying, they were heat-treated, washed and dried in sequence to obtain CoFe@CNT.

[0009] II. Preparation of composite films by two-dimensional graphene oxide intercalation:

[0010] Graphene oxide and CoFe@CNT were added to deionized water and ultrasonically dispersed using an ultrasonic cell disruptor to obtain a dispersion. The dispersion was then vacuum filtered onto a hydrophilic polyvinylidene fluoride membrane and finally thermally fixed, thus completing the preparation method of a two-dimensional graphene oxide intercalated one-dimensional encapsulated cobalt ferrite open carbon nanotube composite membrane.

[0011] An application of a two-dimensional graphene oxide intercalated one-dimensional encapsulated cobalt ferrite open carbon nanotube composite membrane for the removal of organic pollutants from water.

[0012] The beneficial effects of this invention are:

[0013] This invention prepares a two-dimensional graphene oxide intercalated one-dimensional encapsulated cobalt ferrite open carbon nanotube composite film through vacuum-assisted self-assembly, which improves the problem of slow regeneration kinetics of low-cost cobalt metal when single cobalt metal catalyzes PMS. The internal cavity of the carbon nanotube prevents natural organic matter from entering the catalytic region. The oxygen vacancy defects rich in the catalyst mediate the electron transfer path, which greatly improves the utilization rate of the oxidant and enhances the selectivity for target pollutants.

[0014] (1) The present invention uses cobalt-iron synergistic catalysis to solve the problem of slow regeneration kinetics of divalent cobalt under single metal loading.

[0015] (2) Encapsulating the catalytic active center in the internal cavity of carbon nanotubes reduces the interference of natural organic matter and provides the possibility for nano-confined catalytic reactions.

[0016] (3) During the formation of cobalt ferrite, the cobalt-iron interface is unstable and easily generates oxygen vacancy defects. Oxygen vacancy mediates electron transfer, which significantly improves the selectivity for electron-rich target pollutants.

[0017] When the total thickness of the two-dimensional graphene oxide intercalated one-dimensional encapsulated cobalt ferrite open carbon nanotube composite film prepared by this invention is 7.4 μm, and the water flux is 120 L·m -2 ·h -1 When the water residence time inside the membrane is 222ms, continuous operation for 72 hours can remove more than 98% of organic pollutants. Attached Figure Description

[0018] Figure 1 SEM images of the surface and cross-section of the composite membranes prepared in Examples 1 to 3 and Comparative Examples 1 to 2;

[0019] Figure 2 The HAADF diagram and energy dispersive spectroscopy (EDS) of CoFe@CNT prepared in step one of Example 1 are shown below: (a) HAADF diagram, (b) oxygen element, (c) cobalt element, and (d) iron element.

[0020] Figure 3 The XRD patterns are of CoFe@CNT prepared in step one of Examples 1 to 3, Co@CNT prepared in step one of Comparative Example 1, and Fe@CNT prepared in step one of Comparative Example 2.

[0021] Figure 4 This is a fine spectrum of the O element in the CoFe@CNT prepared in step one of Example 1;

[0022] Figure 5The removal performance of the composite membranes prepared in Examples 1 to 3 and Comparative Examples 1 to 2 on the organic pollutant BPA;

[0023] Figure 6 The removal efficiency of CoFe@CNT-GO-Ⅰ prepared in Example 1 for organic pollutant BPA under 72-hour continuous flow conditions;

[0024] Figure 7 The removal efficiency of CoFe@CNT-GO-Ⅰ prepared in Example 1 for the organic pollutant BPA is shown in the presence of common natural organic matter. 1 is a solution containing BPA and PMS, 2 is a solution containing BPA, PMS and bovine serum albumin, and 3 is a solution containing BPA, PMS and humic acid. Detailed Implementation

[0025] Specific Implementation Method 1: This implementation method describes a method for preparing a two-dimensional graphene oxide intercalated one-dimensional encapsulated cobalt ferrite open carbon nanotube composite film, which is carried out according to the following steps:

[0026] I. Preparation of open carbon nanotubes encapsulating cobalt ferrite:

[0027] ① The carbon nanotubes were opened by reflux with concentrated nitric acid, and then centrifuged, purified, filtered and dried to obtain open carbon nanotubes.

[0028] ② Cobalt nitrate hexahydrate, ferric nitrate nonahydrate, open carbon nanotubes and methanol were ultrasonically and stirred until the methanol evaporated completely, and then dried. After drying, they were heat-treated, washed and dried in sequence to obtain CoFe@CNT.

[0029] II. Preparation of composite films by two-dimensional graphene oxide intercalation:

[0030] Graphene oxide and CoFe@CNT were added to deionized water and ultrasonically dispersed using an ultrasonic cell disruptor to obtain a dispersion. The dispersion was then vacuum filtered onto a hydrophilic polyvinylidene fluoride membrane and finally thermally fixed, thus completing the preparation method of a two-dimensional graphene oxide intercalated one-dimensional encapsulated cobalt ferrite open carbon nanotube composite membrane.

[0031] In this specific embodiment, cobalt ferrite nanoparticles are immobilized inside carbon nanotubes (10nm-20nm in diameter) as catalytic active centers. Two-dimensional graphene oxide is added to construct two-dimensional interlayer nanochannels within the membrane. Pollutants that can enter the catalytic region are sieved by the diameter of the carbon nanotubes. Natural organic matter, with its larger molecular weight, is less likely to enter the catalytic region, and the carbon nanotubes contain fewer hydrophilic functional groups, making it easier for pollutants rich in hydrophobic functional groups to enter. Secondly, during the synthesis of bimetallic materials, the Co-Fe interface is often unstable, easily forming oxygen vacancy defects. Oxygen vacancies can promote electron transfer via non-radical pathways, activating PMS and forming a catalyst-PMS complex (PMS*) with a low oxidation potential, achieving selective degradation of electron-rich pollutants. Therefore, by increasing the oxygen vacancy content and regulating the electron transfer pathway, selective degradation of target pollutants can be achieved, significantly increasing the utilization rate of the oxidant.

[0032] The beneficial effects of this embodiment are:

[0033] This embodiment prepares a two-dimensional graphene oxide intercalated one-dimensional encapsulated cobalt ferrite open carbon nanotube composite film through vacuum-assisted self-assembly, which improves the problem of slow regeneration kinetics of low-cost cobalt metal when single cobalt metal catalyzes PMS. The internal cavity of the carbon nanotube prevents natural organic matter from entering the catalytic region. The oxygen vacancy defects rich in the catalyst mediate the electron transfer path, which greatly improves the utilization rate of the oxidant and enhances the selectivity for the target pollutant.

[0034] (1) This embodiment uses cobalt-iron synergistic catalysis to solve the problem of slow regeneration kinetics of divalent cobalt under single metal loading.

[0035] (2) Encapsulating the catalytic active center in the internal cavity of carbon nanotubes reduces the interference of natural organic matter and provides the possibility for nano-confined catalytic reactions.

[0036] (3) During the formation of cobalt ferrite, the cobalt-iron interface is unstable and easily generates oxygen vacancy defects. Oxygen vacancy mediates electron transfer, which significantly improves the selectivity for electron-rich target pollutants.

[0037] When the total thickness of the two-dimensional graphene oxide intercalated one-dimensional encapsulated cobalt ferrite open carbon nanotube composite film prepared in this embodiment is 7.4 μm, and the water flux is 120 L·m -2 ·h -1 When the water residence time inside the membrane is 222ms, continuous operation for 72 hours can remove more than 98% of organic pollutants.

[0038] Specific Implementation Method Two: This implementation method differs from Specific Implementation Method One in that: Step 1①, opening the ports of the carbon nanotubes by reflux with concentrated nitric acid, is specifically carried out as follows: The multi-walled carbon nanotubes are placed in concentrated nitric acid with a mass percentage of 65%–68%, and then refluxed at a temperature of 125℃–130℃ for 13–14 hours. After reflux, they are washed with deionized water until neutral, and finally freeze-dried at a temperature of -50℃–-55℃ for 46–48 hours to obtain the crude product. The outer diameter of the multi-walled carbon nanotubes is 10 nm–20 nm, and the length is 10 μm–30 μm. Everything else is the same as in Specific Implementation Method One.

[0039] Specific Implementation Method Three: This implementation method differs from Specific Implementation Method One or Two in that the centrifugal purification and filtration drying described in step one ① are specifically carried out as follows: The crude product is added to deionized water, and ultrasonically dispersed for 28-30 minutes using an ultrasonic cell disruptor at a power of 250W-300W. Then, it is centrifuged for 15-20 minutes at a speed of 2800-3000 rpm. The supernatant is collected, vacuum filtered, and finally dried at 55℃-60℃ for 10-12 hours. The mass ratio of the crude product to the volume of deionized water is 1 g:(4000-5000) mL. Everything else is the same as in Specific Implementation Method One or Two.

[0040] Specific Implementation Method Four: This implementation method differs from Specific Implementation Methods One to Three in that: the mass ratio of open carbon nanotubes to cobalt nitrate hexahydrate in step one ② is 200:(13-27); the molar ratio of cobalt nitrate hexahydrate to ferric nitrate nonahydrate in step one ② is 1:(0.5-2); and the mass ratio of open carbon nanotubes to methanol in step one ② is 200 mg:(15-20) mL. Everything else is the same as in Specific Implementation Method Three.

[0041] Specific Implementation Method Five: This implementation method differs from Specific Implementation Methods One to Four in that: in step one ②, cobalt nitrate hexahydrate, ferric nitrate nonahydrate, open carbon nanotubes, and methanol are ultrasonically and stirred until the methanol evaporates completely, and then dried. Specifically, the following steps are performed: cobalt nitrate hexahydrate, ferric nitrate nonahydrate, and methanol are mixed and ultrasonicated at a power of 250W to 300W for 0.8h to 1h. Then, open carbon nanotubes are added, and ultrasonicated at a power of 250W to 300W for 0.8h to 1h. Finally, the mixture is stirred at a speed of 200rpm to 300rpm until the methanol evaporates completely. Everything else is the same as in Specific Implementation Methods One to Four.

[0042] Specific Implementation Method Six: This implementation method differs from Specific Implementation Methods One to Five in that: the heat treatment described in step one to two is specifically carried out as follows: the temperature is increased to 390°C to 410°C at a rate of 3°C / min to 5°C / min, and maintained at 390°C to 410°C for 1.8h to 2h, and then cooled to room temperature; the drying described in step one to two is specifically carried out under vacuum at a temperature of 55°C to 60°C for 11h to 12h; the washing described in step one to two is specifically carried out by washing 5 to 6 times with ultrapure water. The rest is the same as in Specific Implementation Methods One to Five.

[0043] Specific Implementation Method Seven: This implementation method differs from Specific Implementation Methods One to Six in that: the mass ratio of graphene oxide to CoFe@CNT in step two is 1:(3.8-4); the mass ratio of the total mass of graphene oxide and CoFe@CNT to deionized water in step two is 1:(95000-100000). Everything else is the same as in Specific Implementation Methods One to Six.

[0044] Specific Implementation Method Eight: This implementation method differs from Specific Implementation Methods One to Seven in that: in step two, graphene oxide and CoFe@CNT are added to deionized water, and ultrasonically dispersed for 4 to 5 minutes using an ultrasonic cell disruptor at a power of 250W to 300W to obtain a dispersion. The dispersion is then vacuum filtered onto a hydrophilic polyvinylidene fluoride membrane at a vacuum filtration pressure of 0.09MPa to 0.1MPa. Finally, it is heat-fixed at a temperature of 55℃ to 60℃ for 25 to 30 minutes. The pore size of the hydrophilic polyvinylidene fluoride membrane is 0.20μm to 0.22μm. Everything else is the same as in Specific Implementation Methods One to Seven.

[0045] Specific Implementation Method Nine: This implementation method describes the application of a two-dimensional graphene oxide intercalated one-dimensional encapsulated cobalt ferrite open carbon nanotube composite membrane, which is used to remove organic pollutants from water.

[0046] Specific Implementation Method Ten: This implementation method differs from Specific Implementation Method Nine in that, under the condition of a liquid column driven by its own weight to an applied pressure of 0.1 MPa, a two-dimensional graphene oxide intercalated with a one-dimensionally encapsulated cobalt ferrite open carbon nanotube composite membrane removes organic pollutants from water. Everything else is the same as in Specific Implementation Method Nine.

[0047] The beneficial effects of the present invention are verified using the following embodiments:

[0048] Example 1:

[0049] A method for preparing a two-dimensional graphene oxide intercalated one-dimensional encapsulated cobalt ferrite open carbon nanotube composite film, comprising the following steps:

[0050] I. Preparation of open carbon nanotubes encapsulating cobalt ferrite:

[0051] ① Multi-walled carbon nanotubes were placed in concentrated nitric acid with a mass percentage of 68%, and then refluxed at 130℃ for 14 hours. After reflux, they were washed with deionized water until neutral, and finally freeze-dried at -50℃ for 48 hours to obtain crude product. The crude product was added to deionized water and ultrasonically dispersed for 30 minutes using an ultrasonic cell disruptor at a power of 300W. Then, it was centrifuged at 3000 rpm for 20 minutes, and the supernatant was collected. The supernatant was vacuum filtered and finally dried at 60℃ for 12 hours to obtain open carbon nanotubes.

[0052] The multi-walled carbon nanotubes have an outer diameter of 10 nm to 20 nm and a length of 10 μm to 30 μm; the mass ratio of the crude product to the volume of deionized water is 1 g: 5000 mL.

[0053] ② Mix 27 mg cobalt nitrate hexahydrate (0.093 mol), 19 mg ferric nitrate nonahydrate (0.047 mol), and 20 mL methanol. Sonicate for 1 h at 300 W. Then add 200 mg open carbon nanotubes and sonicate for 1 h at 300 W. Stir at 200 rpm until the methanol evaporates. Vacuum dry at 60 °C for 12 h. After drying, raise the temperature to 400 °C at a rate of 3 °C / min and maintain at 400 °C for 2 h. Cool to room temperature, wash 6 times with ultrapure water, and vacuum dry at 60 °C for 12 h to obtain CoFe@CNT.

[0054] II. Preparation of composite films by two-dimensional graphene oxide intercalation:

[0055] 2 mg of graphene oxide and 8 mg of CoFe@CNT were added to 1000 g of deionized water. The mixture was ultrasonically dispersed for 5 min using an ultrasonic cell disruptor at a power of 300 W to obtain a dispersion. The dispersion was then vacuum filtered onto a hydrophilic polyvinylidene fluoride membrane at a vacuum filtration pressure of 0.1 MPa. Finally, the membrane was heat-fixed at a temperature of 60 °C for 30 min to obtain a two-dimensional graphene oxide intercalated one-dimensional cobalt ferrite encapsulated open carbon nanotube composite membrane, named CoFe@CNT-GO-Ⅰ.

[0056] The hydrophilic polyvinylidene fluoride membrane has a pore size of 0.22 μm and a diameter of 5 cm.

[0057] Example 2: This example differs from Example 1 in that the amount of cobalt nitrate hexahydrate added in step 1② is 20 mg (0.069 mol), and the amount of ferric nitrate nonahydrate added is 28 mg (0.069 mol). Everything else is the same as in Example 1.

[0058] The two-dimensional graphene oxide intercalated one-dimensional encapsulated cobalt ferrite open carbon nanotube composite film prepared in Example 2 is named CoFe@CNT-GO-Ⅱ.

[0059] Example 3: This example differs from Example 1 in that the amount of cobalt nitrate hexahydrate added in step 1② is 13 mg (0.045 mol), and the amount of ferric nitrate nonahydrate added is 37 mg (0.092 mol). Everything else is the same as in Example 1.

[0060] The two-dimensional graphene oxide intercalated one-dimensional encapsulated cobalt ferrite open carbon nanotube composite film prepared in Example 3 is named CoFe@CNT-GO-Ⅲ.

[0061] Comparative Example 1: This comparative experiment differs from Example 1 in that the amount of cobalt nitrate hexahydrate added in step 1② is 40 mg, and the amount of ferric nitrate nonahydrate added is 0 mg. Everything else is the same as in Example 1.

[0062] Comparative Example 1 yielded a two-dimensional graphene oxide intercalated one-dimensional encapsulated cobalt tetroxide open carbon nanotube composite film, named Co@CNT-GO.

[0063] Comparative Example 2: This comparative experiment differs from Example 1 in that the amount of cobalt nitrate hexahydrate added in step 1② is 0 mg, and the amount of ferric nitrate nonahydrate added is 56 mg. Everything else is the same as in Example 1.

[0064] Comparative Example 2 yielded a two-dimensional graphene oxide intercalated one-dimensional encapsulated iron oxide open carbon nanotube composite film, named Fe@CNT-GO.

[0065] Figure 1 The images show SEM images of the surface and cross-section of the composite films prepared in Examples 1 to 3 and Comparative Examples 1 to 2. As can be seen from the images, carbon nanotubes and graphene oxide have good compatibility. The thickness of Co@CNT-GO on the hydrophilic polyvinylidene fluoride film in Comparative Example 1 is approximately 7.1 μm. The thickness of CoFe@CNT-GO-Ⅰ on the hydrophilic polyvinylidene fluoride film in Example 1 is approximately 7.4 μm. The thickness of CoFe@CNT-GO-Ⅱ on the hydrophilic polyvinylidene fluoride film in Example 2 is approximately 6.5 μm. The thickness of CoFe@CNT-GO-Ⅲ on the hydrophilic polyvinylidene fluoride film in Example 3 is approximately 7.5 μm. The thickness of Fe@CNT-GO on the hydrophilic polyvinylidene fluoride film in Comparative Example 2 is approximately 7.5 μm.

[0066] Figure 2The images show the HAADF diagram and energy dispersive spectroscopy (EDS) spectra of CoFe@CNTs prepared in step one of Example 1: (a) HAADF diagram, (b) oxygen element, (c) cobalt element, and (d) iron element. It can be seen that the cobalt ferrite nanoparticles (statistically averaged particle size of 9 nm) were successfully encapsulated in carbon nanotubes. The nanoparticles are uniformly distributed within the carbon nanotube cavities, and the cobalt and iron aggregates are highly consistent, laying a good foundation for the synergistic effect of the cobalt-iron bimetallic center.

[0067] Figure 3 The XRD patterns are of CoFe@CNT prepared in step one of Examples 1 to 3, Co@CNT prepared in step one of Comparative Example 1, and Fe@CNT prepared in step one of Comparative Example 2. The spectra show that the carbon nanotubes in Comparative Example 1 are loaded with cobalt tetroxide, the carbon nanotubes in Comparative Example 2 are loaded with iron tetroxide, and the carbon nanotubes in Examples 1 to 3 are loaded with CoFe2O4.

[0068] Figure 4 The figure shows a detailed spectrum of the O element in the CoFe@CNT prepared in step one of Example 1. As can be seen from the figure, the content of oxygen vacancies in CoFe@CNT accounts for 26.77% of the total oxygen.

[0069] To test the removal performance of the composite membrane for the organic pollutant bisphenol A (BPA), a dead-end filtration method was used in the membrane filtration experiment, and the effective filtration area of ​​the composite membrane was 10 cm². 2 The water flux of each membrane was kept constant under a pressure of 0.01 MPa to 0.1 MPa. A solution containing BPA and potassium persulfate PMS oxidant (pH=7) was placed in the buffer bottle, with the concentration of BPA being 5 mg / L and the concentration of potassium persulfate PMS oxidant being 0.5 mM.

[0070] Figure 5 The removal performance of the composite membranes prepared in Examples 1 to 3 and Comparative Examples 1 to 2 on the organic pollutant BPA was evaluated; Comparative Example 1 was tested at 90 L·m⁻¹. -2 ·h -1 At a flow rate of 90 L·m, 78% of BPA can be removed within 60 minutes. Example 1 shows this at a flow rate of 90 L·m. -2 ·h -1 At a flow rate of 90 L·m⁻¹, the removal rate of BPA was 97% after 60 min, indicating that cobalt-iron bimetallic compounds can effectively improve the slow regeneration kinetics of low-cost cobalt. Example 2: At a flow rate of 90 L·m⁻¹... -2 ·h -1 At a flow rate of [value missing], the removal rate of BPA was 82% after 60 min. Example 3: At a flow rate of 90 L·m [value missing] -2 ·h -1 At a flow rate of [value missing], the removal rate of BPA was 70% after 60 min. Comparative Example 2, at a flow rate of 90 L·m [value missing], [value missing]... -2·h -1 At the specified flow rate, the removal rate of BPA was 52% after 60 minutes.

[0071] Figure 6 The removal efficiency of CoFe@CNT-GO-Ⅰ prepared in Example 1 for the organic pollutant BPA under 72-hour continuous flow conditions; when the flux is 120 L·m -2 ·h -1 When the water residence time inside the membrane is 222ms, the degradation efficiency is stable between 98% and 99%, indicating that the cobalt ferrite nanoparticles encapsulated in the carbon nanotubes are very stable and show no signs of detachment.

[0072] To test the selectivity of the composite membrane for the organic pollutant bisphenol A (BPA), the membrane filtration experiment employed dead-end filtration, with the effective filtration area of ​​the composite membrane being 10 cm². 2 The water flow rate was maintained at 90 L·m under a pressure of 0.01 MPa to 0.1 MPa. -2 ·h -1 The solutions to be treated were: a solution containing BPA and PMS (pH=7), a solution containing BPA, PMS and bovine serum albumin (10 mg / L) (pH=7), and a solution containing BPA, PMS and humic acid (10 mg / L) (pH=7). The concentration of BPA in all three solutions was 5 mg / L, and the concentration of PMS was 0.5 mM.

[0073] Figure 7 The figure shows the removal efficiency of CoFe@CNT-GO-Ⅰ prepared in Example 1 for the organic pollutant BPA in the presence of common natural organic matter. 1 represents a solution containing BPA and PMS, 2 represents a solution containing BPA, PMS and bovine serum albumin, and 3 represents a solution containing BPA, PMS and humic acid. As shown in the figure, compared with no addition of natural organic matter, the removal rate is reduced by only about 15%, indicating that carbon nanotubes can effectively block natural organic matter from entering the interior of carbon nanotubes and competing with the target pollutant for catalytic active sites and consuming oxidants, thus achieving selective removal of the target pollutant BPA.

[0074] In summary, the two-dimensional graphene oxide intercalated with one-dimensionally encapsulated cobalt ferrite open carbon nanotube composite membrane prepared in the examples exhibits high transmembrane flux and synergistic removal of BPA by cobalt and iron, effectively improving the slow regeneration kinetics of low-valence metals. The membrane catalytic performance is optimal when the molar ratio of cobalt to iron during the feedstock addition process in Example 1 is 2:1. Encapsulating cobalt ferrite in carbon nanotubes effectively prevents natural organic matter from entering the carbon nanotube cavity and competing with the target pollutant for catalytic active sites, significantly reducing oxidant consumption and demonstrating high selectivity for the target pollutant.

Claims

1. A method for preparing a two-dimensional graphene oxide intercalated one-dimensional encapsulated cobalt ferrite open carbon nanotube composite film, characterized in that, It is done in the following steps: I. Preparation of open carbon nanotubes encapsulating cobalt ferrite: ① Multi-walled carbon nanotubes were placed in concentrated nitric acid (68% by mass) and refluxed at 130℃ for 14 hours. After reflux, they were washed with deionized water until neutral and then freeze-dried at -50℃ for 48 hours to obtain crude product. The crude product was added to deionized water and ultrasonically dispersed for 30 minutes using an ultrasonic cell disruptor at 300W. Then, it was centrifuged at 3000rpm for 20 minutes, and the supernatant was collected. The supernatant was vacuum filtered and dried at 60℃ for 12 hours to obtain open carbon nanotubes. The multi-walled carbon nanotubes have an outer diameter of 10 nm to 20 nm and a length of 10 μm to 30 μm; the mass ratio of the crude product to the volume of deionized water is 1 g: 5000 mL. ② Mix 0.093 mol cobalt nitrate hexahydrate, 0.047 mol ferric nitrate nonahydrate, and 20 mL methanol. Sonicate for 1 h at an ultrasonic power of 300 W. Then add 200 mg of open carbon nanotubes and sonicate for 1 h at an ultrasonic power of 300 W. Stir at 200 rpm until the methanol evaporates. Vacuum dry at 60 °C for 12 h. After drying, raise the temperature to 400 °C at a rate of 3 °C / min and maintain at 400 °C for 2 h. Then cool to room temperature, wash 6 times with ultrapure water, and vacuum dry at 60 °C for 12 h to obtain CoFe@CNT. II. Preparation of composite films by two-dimensional graphene oxide intercalation: 2 mg of graphene oxide and 8 mg of CoFe@CNT were added to 1000 g of deionized water. The mixture was ultrasonically dispersed for 5 min using an ultrasonic cell disruptor at a power of 300 W to obtain a dispersion. The dispersion was then vacuum filtered onto a hydrophilic polyvinylidene fluoride membrane at a vacuum filtration pressure of 0.1 MPa. Finally, the membrane was heat-fixed at a temperature of 60 °C for 30 min to obtain a two-dimensional graphene oxide intercalated one-dimensional cobalt ferrite encapsulated open carbon nanotube composite membrane. The hydrophilic polyvinylidene fluoride membrane has a pore size of 0.22 μm and a diameter of 5 cm. The oxygen vacancy content in the CoFe@CNT mentioned in step one accounts for 26.77% of the total oxygen, and the CoFe@CNT is a cobalt ferrite catalyst with an average particle size of 9 nm encapsulated inside an open carbon nanotube. The two-dimensional graphene oxide intercalated one-dimensional encapsulated cobalt ferrite open carbon nanotube composite membrane prepared in step two showed a BPA degradation efficiency of 98%~99% over 72 hours when water residence time in the membrane was 222ms, and effectively blocked natural organic matter from entering the interior of the carbon nanotubes.

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