Preparation method and application of open carbon nanotube composite film with two-dimensional graphene oxide intercalation and one-dimensional cobalt ferrite encapsulation

Abstract

The invention discloses a preparation method and application of an open carbon nanotube composite film of two-dimensional graphene oxide intercalation one-dimensional packaged cobalt ferrite, and belongs to the technical field of preparation of two-dimensional material films. The invention aims to solve the problems that the catalytic effect of the existing catalytic membrane is easily interfered by natural organic matters and the selectivity on target pollutants is poor. The method comprises the following steps of: 1, preparing an open carbon nano tube for packaging cobalt ferrite; and 2, preparing the composite membrane by intercalating the two-dimensional graphene oxide. The method is used for removing organic pollutants in water. The preparation method is used for preparation and application of the open carbon nanotube composite film of the two-dimensional graphene oxide intercalation and one-dimensional packaging cobalt ferrite.

Description

Technical Field

[0001] The present invention belongs to the technical field of the preparation of two-dimensional material films. Background Art

[0002] Advanced oxidation processes (AOPs) are a kind of efficient water treatment technologies. However, natural organic matters widely existing in actual water bodies will compete with target pollutants to consume the free radicals generated in the advanced oxidation processes, resulting in low utilization rate of oxidants and poor degradation efficiency of target pollutants. In order to improve the selectivity for target pollutants, effectively combining a membrane with a separation function and a catalyst can utilize the membrane pore size for size screening to achieve the interception of natural organic matters and improve the selectivity for target pollutants. However, there is nothing to do with the natural organic matters that enter the membrane pores.

[0003] Therefore, how to reduce the interference of natural organic matters on the catalytic membrane and develop a catalytic membrane with selective catalytic oxidation ability has important environmental significance. Summary of the Invention

[0004] The present invention aims to solve the problems that the catalytic effect of the existing catalytic membrane is easily interfered by natural organic matters and the selectivity for target pollutants is poor, and further provides a preparation method and application of an open carbon nanotube composite membrane with two-dimensional graphene oxide intercalated with one-dimensional cobalt ferrite encapsulated.

[0005] A preparation method of an open carbon nanotube composite membrane with two-dimensional graphene oxide intercalated with one-dimensional cobalt ferrite encapsulated comprises the following steps:

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

[0007] ① Open the ports of carbon nanotubes by refluxing with concentrated nitric acid, and then carry out centrifugal purification and filtration drying in sequence to obtain open carbon nanotubes;

[0008] ② Ultrasonically mix cobalt nitrate hexahydrate, iron nitrate nonahydrate, open carbon nanotubes and methanol until the methanol volatilizes completely, and then dry. After drying, carry out heat treatment, washing and drying in sequence to obtain CoFe@CNT;

[0009] II. Preparation of a composite membrane by intercalating two-dimensional graphene oxide:

[0010] Add graphene oxide and CoFe@CNT to deionized water, disperse them ultrasonically with an ultrasonic cell disruptor to obtain a dispersion, vacuum filter the dispersion onto a hydrophilic polyvinylidene fluoride membrane, and finally thermally fix it, thus completing the preparation method of the open carbon nanotube composite membrane with two-dimensional graphene oxide intercalated with one-dimensional cobalt ferrite encapsulated.

[0011] An application of an open carbon nanotube composite membrane with two-dimensional graphene oxide intercalated with one-dimensional cobalt ferrite encapsulated is used for removing organic pollutants in water.

[0012] The beneficial effects of the present invention are as follows:

[0013] The present invention prepares a composite membrane of two-dimensional graphene oxide intercalated with one-dimensional cobalt ferrite encapsulated open carbon nanotubes by means of vacuum-assisted self-assembly, which improves the problem of slow regeneration kinetics of low-valent cobalt when a single metal cobalt catalyzes PMS. The internal cavity of the carbon nanotubes is used to prevent natural organic matter from entering the catalytic region, and the oxygen vacancy defects rich in the catalyst mediate the electron transfer path, greatly improving the utilization rate of the oxidant and the selectivity for target pollutants.

[0014] (1) The present invention solves the problem of slow regeneration kinetics of divalent cobalt when a single metal is loaded by means of cobalt-iron synergistic catalysis.

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

[0016] (3) During the formation of cobalt ferrite, the cobalt-iron interface is unstable and prone to oxygen vacancy defects. The oxygen vacancies mediate electron transfer, significantly improving the selectivity for electron-rich target pollutants.

[0017] When the total thickness of the composite membrane of two-dimensional graphene oxide intercalated with one-dimensional cobalt ferrite encapsulated open carbon nanotubes prepared by the present invention is 7.4 μm and the water flux is 120 L·m -2 ·h -1 (the residence time of water in the membrane is 222 ms), after continuous operation for 72 h, more than 98% of organic pollutants can be removed. Description of the Drawings

[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 HAADF image of CoFe@CNT prepared in Step 1 of Example 1 and energy spectrum diagrams of cobalt, iron, and oxygen elements, (a) HAADF image, (b) oxygen element, (c) cobalt element, (d) iron element;

[0020] Figure 3 XRD patterns of CoFe@CNT prepared in Step 1 of Examples 1 to 3, Co@CNT prepared in Step 1 of Comparative Example 1, and Fe@CNT prepared in Step 1 of Comparative Example 2;

[0021] Figure 4 Fine spectrum diagram of O element in CoFe@CNT prepared in Step 1 of Example 1;

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

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

[0024] Figure 7 Removal efficiency of CoFe@CNT-GO-I prepared in Example 1 for the organic pollutant BPA in the presence of common natural organic matters. 1 is the solution containing BPA and PMS, 2 is the solution containing BPA, PMS and bovine serum albumin, and 3 is the solution containing BPA, PMS and humic acid. Specific implementation manners

[0025] Specific implementation manner 1: A preparation method of a two-dimensional graphene oxide intercalated one-dimensional cobalt ferrite encapsulated open carbon nanotube composite membrane. The method is carried out according to the following steps:

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

[0027] ① Open the ports of carbon nanotubes by refluxing with concentrated nitric acid, and then successively carry out centrifugal purification, filtration and drying to obtain open carbon nanotubes;

[0028] ② Ultrasonically mix cobalt nitrate hexahydrate, iron nitrate nonahydrate, open carbon nanotubes and methanol until the methanol volatilizes completely, and then dry. After drying, successively carry out heat treatment, washing and drying to obtain CoFe@CNT;

[0029] II. Preparation of a composite membrane by intercalating two-dimensional graphene oxide:

[0030] Add graphene oxide and CoFe@CNT into deionized water, and disperse them by ultrasonic cell crusher to obtain a dispersion liquid. Vacuum filter the dispersion liquid onto a hydrophilic polyvinylidene fluoride membrane, and finally heat-fix it to complete the preparation method of the two-dimensional graphene oxide intercalated one-dimensional cobalt ferrite encapsulated open carbon nanotube composite membrane.

[0031] In this specific embodiment, cobalt ferrite nanoparticles are fixed inside carbon nanotubes (with a diameter of 10 nm to 20 nm) as catalytic active centers, and two-dimensional graphene oxide is added to construct two-dimensional interlayer nanochannels in the membrane. Pollutants that can enter the catalytic region are screened by the carbon nanotube diameter. Natural organic matter has a large molecular weight and is not easily able to enter the catalytic region, and there are fewer hydrophilic functional groups inside the carbon nanotubes, so pollutants with rich hydrophobic functional groups are more likely to enter. Secondly, during the synthesis of the bimetallic material, the Co-Fe interface is often unstable and prone to the formation of oxygen vacancy defects. Oxygen vacancies can promote the transfer of electrons through a non-radical pathway, activate PMS, and form a catalyst-PMS complex (PMS*) with a lower oxidation potential, achieving the selective degradation of electron-rich pollutants. Therefore, by increasing the content of oxygen vacancies and regulating the electron transfer path, the selective degradation of target pollutants is realized, significantly increasing the utilization rate of the oxidant.

[0032] The beneficial effects of this embodiment are:

[0033] In this embodiment, an open carbon nanotube composite membrane with two-dimensional graphene oxide intercalated and one-dimensional cobalt ferrite encapsulated is prepared by vacuum-assisted self-assembly, which improves the problem of slow regeneration kinetics of low-valent cobalt when a single metal cobalt catalyzes PMS. The internal cavity of the carbon nanotube is used to prevent natural organic matter from entering the catalytic region, and the oxygen vacancy defects rich in the catalyst mediate the electron transfer path, greatly improving the utilization rate of the oxidant and the selectivity for target pollutants.

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

[0035] (2) The catalytic active center is encapsulated in the internal cavity of the carbon nanotube, reducing the interference of natural organic matter and providing the possibility for the occurrence of nanoconfined catalytic reactions.

[0036] (3) During the formation of cobalt ferrite, the Co-Fe interface is unstable and prone to the generation of oxygen vacancy defects. Oxygen vacancies mediate electron transfer and significantly improve the selectivity for electron-rich target pollutants.

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

[0038] Embodiment 2: The difference between this embodiment and Embodiment 1 is as follows: The specific steps for opening the ports of carbon nanotubes by refluxing with concentrated nitric acid in Step ① are as follows: Place multi-walled carbon nanotubes in concentrated nitric acid with a mass percentage of 65% - 68%, then reflux for 13h - 14h under the condition of a temperature of 125°C - 130°C. After refluxing, wash with deionized water until neutral, and finally freeze-dry for 46h - 48h under the condition of a temperature of -50°C - -55°C to obtain a crude product; the outer diameter of the multi-walled carbon nanotubes is 10nm - 20nm, and the length is 10μm - 30μm. Others are the same as in Embodiment 1.

[0039] Embodiment 3: The difference between this embodiment and either Embodiment 1 or Embodiment 2 is as follows: The specific steps for centrifugal purification, filtration, and drying in Step ① are as follows: Add the crude product to deionized water, use an ultrasonic cell disruptor to ultrasonically disperse for 28min - 30min under the condition of a power of 250W - 300W, then centrifuge for 15min - 20min under the condition of a rotation speed of 2800rpm - 3000rpm, take the supernatant, vacuum filter the supernatant, and finally dry for 10h - 12h under the condition of a temperature of 55°C - 60°C; the mass ratio of the crude product to the volume of deionized water is 1g:(4000 - 5000)mL. Others are the same as in either Embodiment 1 or Embodiment 2.

[0040] Embodiment 4: The difference between this embodiment and any one of Embodiments 1 to 3 is as follows: The mass ratio of the opened carbon nanotubes to cobalt nitrate hexahydrate in Step ② is 200:(13 - 27); the molar ratio of cobalt nitrate hexahydrate to iron nitrate nonahydrate in Step ② is 1:(0.5 - 2); the mass ratio of the opened carbon nanotubes to the volume of methanol in Step ② is 200mg:(15 - 20)mL. Others are the same as in Embodiment 3.

[0041] Embodiment 5: The difference between this embodiment and any one of Embodiments 1 to 4 is as follows: The specific steps for ultrasonically stirring and mixing cobalt nitrate hexahydrate, iron nitrate nonahydrate, opened carbon nanotubes, and methanol until the methanol volatilizes completely and then drying in Step ② are as follows: Mix cobalt nitrate hexahydrate, iron nitrate nonahydrate, and methanol, ultrasonically for 0.8h - 1h under the condition of an ultrasonic power of 250W - 300W, then add the opened carbon nanotubes and ultrasonically for 0.8h - 1h under the condition of an ultrasonic power of 250W - 300W, and then stir and mix at a rotation speed of 200rpm - 300rpm until the methanol volatilizes completely. Others are the same as in Embodiments 1 to 4.

[0042] Specific Embodiment Six: The difference between this embodiment and any one of Specific Embodiments One to Five is as follows: The heat treatment described in step 1② is specifically carried out according to the following steps: Heat up to 390°C - 410°C at a rate of 3°C / min - 5°C / min, and maintain for 1.8 h - 2 h at a temperature of 390°C - 410°C, and then cool to room temperature; The drying described in step 1② is specifically carried out under vacuum at a temperature of 55°C - 60°C for 11 h - 12 h; The washing described in step 1② is specifically carried out by washing 5 - 6 times with ultrapure water. Others are the same as Specific Embodiments One to Five.

[0043] Specific Embodiment Seven: The difference between this embodiment and any one of Specific Embodiments One to Six is as follows: The mass ratio of graphene oxide to CoFe@CNT described in step 2 is 1:(3.8 - 4); The mass ratio of the total mass of graphene oxide and CoFe@CNT to deionized water is 1:(95000 - 100000). Others are the same as Specific Embodiments One to Six.

[0044] Specific Embodiment Eight: The difference between this embodiment and any one of Specific Embodiments One to Seven is as follows: Add graphene oxide and CoFe@CNT to deionized water, and use an ultrasonic cell disruptor to ultrasonically disperse for 4 min - 5 min under the condition of a power of 250 W - 300 W to obtain a dispersion liquid. Under the condition of a vacuum filtration pressure of 0.09 MPa - 0.1 MPa, vacuum filter the dispersion liquid onto a hydrophilic polyvinylidene fluoride membrane, and finally thermally fix for 25 min - 30 min under the condition of a thermal fixation temperature of 55°C - 60°C; The pore size of the hydrophilic polyvinylidene fluoride membrane is 0.20 μm - 0.22 μm. Others are the same as Specific Embodiments One to Seven.

[0045] Specific Embodiment Nine: The application of a two-dimensional graphene oxide intercalated one-dimensional cobalt ferrite encapsulated open carbon nanotube composite membrane, which is used to remove organic pollutants in water.

[0046] Specific Embodiment Ten: The difference between this embodiment and Specific Embodiment Nine is as follows: Under the condition of driving by the self-weight of the liquid column to an external pressure of 0.1 MPa, the two-dimensional graphene oxide intercalated one-dimensional cobalt ferrite encapsulated open carbon nanotube composite membrane removes organic pollutants in water. Others are the same as Specific Embodiment Nine.

[0047] The following examples are used to verify the beneficial effects of the present invention:

[0048] Example 1:

[0049] A preparation method of a two-dimensional graphene oxide intercalated one-dimensional cobalt ferrite encapsulated open carbon nanotube composite membrane, which is carried out according to the following steps:

[0050] I. Preparation of Open Carbon Nanotubes Encapsulating Cobalt Ferrite:

[0051] ① Place multi-walled carbon nanotubes in concentrated nitric acid with a mass percentage of 68%, then reflux at 130 °C for 14 h. After reflux, wash with deionized water until neutral, and finally freeze-dry at -50 °C for 48 h to obtain a crude product. Add the crude product to deionized water, use an ultrasonic cell disruptor to ultrasonically disperse for 30 min at a power of 300 W, then centrifuge at 3000 rpm for 20 min, take the supernatant, vacuum filter the supernatant, and finally dry at 60 °C for 12 h to obtain open carbon nanotubes;

[0052] The outer diameter of the multi-walled carbon nanotubes is 10 nm - 20 nm, and the length is 10 μm - 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 of cobalt nitrate hexahydrate (0.093 mol), 19 mg of iron nitrate nonahydrate (0.047 mol) and 20 mL of methanol, ultrasonically treat for 1 h at an ultrasonic power of 300 W, then add 200 mg of open carbon nanotubes, ultrasonically treat for 1 h at an ultrasonic power of 300 W, then stir and mix at 200 rpm until the methanol volatilizes completely, then vacuum dry at 60 °C for 12 h. After drying, heat up to 400 °C at a rate of 3 °C / min and hold 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;

[0054] II. Preparation of Composite Membrane by Intercalation of Two-Dimensional Graphene Oxide:

[0055] Add 2 mg of graphene oxide and 8 mg of CoFe@CNT to 1000 g of deionized water, use an ultrasonic cell disruptor to ultrasonically disperse for 5 min at a power of 300 W to obtain a dispersion. Under the condition of a vacuum filtration pressure of 0.1 MPa, vacuum filter the dispersion onto a hydrophilic polyvinylidene fluoride membrane, and finally thermally fix at 60 °C for 30 min to obtain a two-dimensional graphene oxide intercalated one-dimensional open carbon nanotube composite membrane encapsulating cobalt ferrite, named CoFe@CNT-GO-I;

[0056] The pore size of the hydrophilic polyvinylidene fluoride membrane is 0.22 μm, and the diameter is 5 cm.

[0057] Example 2: The difference between this example and Example 1 is that in step ①②, the addition amount of cobalt nitrate hexahydrate is 20 mg (0.069 mol), and the addition amount of iron nitrate nonahydrate is 28 mg (0.069 mol). Others are the same as in Example 1.

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

[0059] Example 3: The difference between this example and Example 1 is that in step ①②, the addition amount of cobalt nitrate hexahydrate is 13 mg (0.045 mol), and the addition amount of iron nitrate nonahydrate is 37 mg (0.092 mol). Others are the same as in Example 1.

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

[0061] Comparative Example 1: The difference between this comparative experiment and Example 1 is that in step ①②, the addition amount of cobalt nitrate hexahydrate is 40 mg, and the addition amount of iron nitrate nonahydrate is 0 mg. Others are the same as in Example 1.

[0062] The open carbon nanotube composite film of two-dimensional graphene oxide intercalated with one-dimensional encapsulated cobalt ferrite obtained in Comparative Example 1 is named Co@CNT-GO.

[0063] Comparative Example 2: The difference between this comparative experiment and Example 1 is that in step ①②, the addition amount of cobalt nitrate hexahydrate is 0 mg, and the addition amount of iron nitrate nonahydrate is 56 mg. Others are the same as in Example 1.

[0064] The open carbon nanotube composite film of two-dimensional graphene oxide intercalated with one-dimensional encapsulated iron oxide obtained in Comparative Example 2 is named Fe@CNT-GO.

[0065] Figure 1 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 figure, the carbon nanotubes and graphene oxide have good compatibility. The thickness of Co@CNT-GO on the hydrophilic polyvinylidene fluoride membrane in Comparative Example 1 is about 7.1 μm. The thickness of CoFe@CNT-GO-I on the hydrophilic polyvinylidene fluoride membrane in Example 1 is about 7.4 μm. The thickness of CoFe@CNT-GO-II on the hydrophilic polyvinylidene fluoride membrane in Example 2 is about 6.5 μm. The thickness of CoFe@CNT-GO-III on the hydrophilic polyvinylidene fluoride membrane in Example 3 is about 7.5 μm. The thickness of Fe@CNT-GO on the hydrophilic polyvinylidene fluoride membrane in Comparative Example 2 is about 7.5 μm.

[0066] Figure 2HAADF images of CoFe@CNT prepared in Step 1 of Example 1 and energy spectrum diagrams of cobalt, iron, and oxygen elements. (a) HAADF image, (b) oxygen element, (c) cobalt element, (d) iron element. It can be seen that cobalt ferrite nanoparticles (statistical average particle size of 9 nm) are successfully encapsulated within the carbon nanotubes, and the nanoparticles are evenly distributed within the cavities of the carbon nanotubes. The positions where cobalt and iron aggregate are highly consistent, laying a good foundation for the synergistic effect of the cobalt-iron bimetallic center.

[0067] Figure 3 XRD patterns of CoFe@CNT prepared in Step 1 of Examples 1 to 3, Co@CNT prepared in Step 1 of Comparative Example 1, and Fe@CNT prepared in Step 1 of Comparative Example 2. The spectra show that cobalt tetroxide is loaded within the cavities of the carbon nanotubes in Comparative Example 1, iron tetroxide is loaded within the cavities of the carbon nanotubes in Comparative Example 2, and CoFe is loaded within the cavities of the carbon nanotubes in Examples 1 to 3. 2 O 4 。

[0068] Figure 4 Fine spectrum of the O element in CoFe@CNT prepared in Step 1 of Example 1. It can be seen from the figure that 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), the membrane filtration experiment adopted a dead-end filtration method. The effective filtration area of the composite membrane was 10 cm 2 , and 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 the oxidant potassium peroxymonosulfate PMS (pH = 7) was placed in the buffer bottle, with the concentration of BPA being 5 mg / L and the concentration of the oxidant potassium peroxymonosulfate PMS being 0.5 mM.

[0070] Figure 5 Removal performance of the composite membranes prepared in Examples 1 to 3 and Comparative Examples 1 to 2 for the organic pollutant BPA. In Comparative Example 1, 78% of BPA could be removed within 60 min at a water flux of 90 L·m -2 ·h -1 . In Example 1, the removal rate of BPA was 97% at 60 min at a water flux of 90 L·m -2 ·h -1 , indicating that the cobalt-iron bimetal can effectively improve the problem of slow regeneration kinetics of low-valent cobalt. In Example 2, the removal rate of BPA was 82% at 60 min at a water flux of 90 L·m -2 ·h -1 . In Example 3, the removal rate of BPA was 82% at 60 min at a water flux of 90 L·m -2 ·h -1At a water flux rate, the removal rate of BPA was 70% at 60 min. Comparative Example 2 had a water flux rate of 90 L·m -2 ·h -1 At this water flux rate, the removal rate of BPA was 52% at 60 min.

[0071] Figure 6 Figure 8 shows the removal efficiency of the organic pollutant BPA by CoFe@CNT-GO-I prepared in Example 1 under continuous flow conditions for 72 hours; when the flux was 120 L·m -2 ·h -1 (the residence time of water in the membrane was 222 ms), the degradation efficiency was stable between 98% and 99%, indicating that the cobalt ferrite nanoparticles encapsulated in the carbon nanotubes were very stable and there was no sign of shedding.

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

[0073] Figure 7 Figure 25 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 is the solution containing BPA and PMS, 2 is the solution containing BPA, PMS and bovine serum albumin, and 3 is the solution containing BPA, PMS and humic acid; as can be seen from the figure, compared with the case without adding natural organic matter, the removal rate was only reduced by about 15%, indicating that the carbon nanotubes can effectively block the entry of natural organic matter into the interior of the carbon nanotubes to compete for catalytic active sites with the target pollutant and consume the oxidant, achieving selective removal of the target pollutant BPA.

[0074] In summary, the two-dimensional graphene oxide intercalated one-dimensional encapsulated cobalt ferrite open carbon nanotube composite membrane prepared in the examples has a high transmembrane flux, and cobalt and iron cooperate to remove BPA, effectively improving the problem of slow regeneration kinetics of a single low-valent metal. When the molar ratio of cobalt to iron is 2:1 during the raw material addition process in Example 1, the membrane catalytic performance is the best. Encapsulating cobalt ferrite in carbon nanotubes can effectively prevent natural organic matter from entering the carbon nanotube cavity to compete for catalytic active sites with target pollutants, significantly reducing the consumption of oxidants and having a high selectivity for target pollutants.

Claims

1. A method for preparing a two-dimensional graphene oxide intercalated one-dimensionally encapsulated open carbon nanotube composite film of cobalt ferrite, characterized in that It is carried out in the following steps:

1. Preparation of open carbon nanotubes encapsulating cobalt ferrite: ① The carbon nanotubes are refluxed with concentrated nitric acid to open the ports, and then centrifuged, purified, filtered and dried in sequence to obtain open carbon nanotubes; ② The cobalt nitrate hexahydrate, the iron nitrate nonahydrate, the open carbon nanotubes and methanol are ultrasonically mixed and stirred until the methanol is completely volatilized, and then dried. After drying, heat treatment, washing and drying are performed in sequence to obtain CoFe@CNT; 2. Preparation of composite membrane by two-dimensional graphene oxide intercalation: Graphene oxide and CoFe@CNT are added to deionized water, ultrasonically dispersed by an ultrasonic cell disruptor to obtain a dispersion, the dispersion is vacuum filtered onto a hydrophilic polyvinylidene fluoride membrane, and finally thermally fixed to complete the preparation method of a two-dimensional graphene oxide intercalated one-dimensional cobalt ferrite encapsulated open carbon nanotube composite membrane.

2. The method for preparing a two-dimensional graphene oxide intercalated one-dimensionally encapsulated open carbon nanotube composite film of cobalt ferrite according to claim 1, characterized in that In step 1①, opening the port by refluxing the carbon nanotubes through concentrated nitric acid is specifically carried out according to the following steps: placing the multi-walled carbon nanotubes in 65% to 68% concentrated nitric acid by mass, and then refluxing for 13h to 14h at a temperature of 125°C to 130°C, washing with deionized water to neutrality after refluxing, and finally freeze-drying for 46h to 48h at a temperature of -50°C to -55°C to obtain a crude product; the outer diameter of the multi-walled carbon nanotubes is 10nm to 20nm, and the length is 10μm to 30μm.

3. The method for preparing a two-dimensional graphene oxide intercalated one-dimensionally encapsulated open carbon nanotube composite film of cobalt ferrite according to claim 2, characterized in that The centrifugal purification and filtration and drying described in step 1① are specifically carried out according to the following steps: the crude product is added to deionized water, ultrasonically dispersed for 28min to 30min at a power of 250W to 300W using an ultrasonic cell disruptor, and then centrifuged for 15min to 20min at a speed of 2800rpm to 3000rpm, the supernatant is taken, and the supernatant is vacuum filtered, and finally dried for 10h to 12h at a temperature of 55°C to 60°C; the mass ratio of the crude product to the volume of deionized water is 1g: (4000~5000)mL.

4. The method for preparing a two-dimensional graphene oxide intercalated one-dimensionally encapsulated open carbon nanotube composite film of cobalt ferrite according to claim 1, characterized in that The mass ratio of the open carbon nanotubes described in step 1② to cobalt nitrate hexahydrate is 200:(13-27); the molar ratio of cobalt nitrate hexahydrate described in step 1② to ferric nitrate nonahydrate is 1:(0.5-2); the mass ratio of the open carbon nanotubes described in step 1② to the volume ratio of methanol is 200mg:(15-20)mL.

5. The method for preparing a two-dimensional graphene oxide intercalated one-dimensionally encapsulated open carbon nanotube composite film of cobalt ferrite according to claim 1, characterized in that In step 1②, cobalt nitrate hexahydrate, ferric nitrate nonahydrate, open carbon nanotubes and methanol are ultrasonically mixed and stirred until the methanol is completely volatilized, and then dried. Specifically, the following steps are performed: cobalt nitrate hexahydrate, ferric nitrate nonahydrate and methanol are mixed, ultrasonically mixed for 0.8h to 1h under the condition of ultrasonic power of 250W to 300W, and then the open carbon nanotubes are added, ultrasonically mixed for 0.8h to 1h under the condition of ultrasonic power of 250W to 300W, and then stirred and mixed at a rotation speed of 200rpm to 300rpm until the methanol is completely volatilized.

6. The method for preparing a two-dimensional graphene oxide intercalated one-dimensionally encapsulated open carbon nanotube composite film of cobalt ferrite according to claim 1, characterized in that The heat treatment described in step 1 ② is specifically carried out according to the following steps: heating to 390 ℃ ~ 410 ℃ at a rate of 3 ℃ / min ~ 5 ℃ / min, and maintaining at a temperature of 390 ℃ ~ 410 ℃ for 1.8h ~ 2h, and then cooling to room temperature; the drying described in step 1 ② is specifically carried out at a temperature of 55 ℃ ~ 60 ℃, vacuum drying for 11h ~ 12h; the washing described in step 1 ② is specifically carried out using ultrapure water for 5 to 6 times.

7. The method for preparing a two-dimensional graphene oxide intercalated one-dimensionally encapsulated open carbon nanotube composite film of cobalt ferrite according to claim 1, characterized in that The mass ratio of the graphene oxide and CoFe@CNT described in step 2 is 1:(3.8-4); the mass ratio of the total mass of the graphene oxide and CoFe@CNT described in step 2 to deionized water is 1:(95000-100000).

8. The method for preparing a two-dimensional graphene oxide intercalated one-dimensional cobalt ferrite encapsulated open carbon nanotube composite film according to claim 1, characterized in that In step 2, graphene oxide and CoFe@CNT are added to deionized water, and ultrasonic cell disruptor is used to ultrasonically disperse for 4min to 5min at a power of 250W to 300W to obtain a dispersion. The dispersion is vacuum filtered onto a hydrophilic polyvinylidene fluoride membrane at a vacuum filtration pressure of 0.09MPa to 0.1MPa, and finally heat fixed at a heat fixing temperature of 55°C to 60°C for 25min to 30min; the pore size of the hydrophilic polyvinylidene fluoride membrane is 0.20μm to 0.22μm.

9. The use of an open carbon nanotube composite film of two-dimensional graphene oxide intercalated with one-dimensional encapsulated cobalt ferrite prepared as claimed in claim 1, characterized in that It is used to remove organic pollutants from water.

10. The use of a two-dimensional graphene oxide intercalated one-dimensional open carbon nanotube composite film of cobalt ferrite according to claim 9, characterized in that Under the condition of an external pressure of 0.1 MPa driven by the deadweight of the liquid column, an open carbon nanotube composite membrane of two-dimensional graphene oxide intercalated with one-dimensional cobalt ferrite was used to remove organic pollutants from water.

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