Carbon nanotube array modified graphene fiber and preparation method and use thereof

Abstract

The application provides a carbon nanotube array modified graphene fiber and a preparation method and application thereof, and belongs to the technical field of solid phase microextraction. The carbon nanotube array modified graphene fiber is prepared through an ionic liquid assisted wet spinning method, directional growth of a metal organic framework and pyrolysis. The carbon nanotube array modified graphene fiber has a stem structure, and ordered carbon nanotube arrays grow on the surface of the stem, is a graphene solid phase microextraction material based on a metal organic framework derived carbon nanotube array modification, and has high enrichment capacity for benzene series (including benzene, toluene, ethylbenzene, p-xylene and m-xylene). The carbon nanotube array modified graphene fiber has a detection linear range of 0.2-600 mu g / L, a minimum detection limit of 0.005-0.03 mg / L, and the like, and has the characteristics of high stability and strong extraction capacity.

Description

Technical Field

[0001] This invention relates to the field of solid-phase microextraction technology, and more particularly to graphene fibers modified with carbon nanotube arrays, their preparation methods, and applications. Background Technology

[0002] Oilfield extraction and refining processes generate large amounts of wastewater. In addition to conventional pollutants such as COD, BOD, and sulfides, this wastewater also contains highly polluting benzene compounds and polycyclic aromatic hydrocarbons (PAHs). Most benzene compounds are highly volatile and can enter the body through inhalation or even skin contact, causing chronic benzene poisoning. Therefore, establishing an accurate and rapid benzene compound analysis method is essential for benzene compound detection in oilfields.

[0003] Solid-phase microextraction (SPME) technology emerged in the 1990s and has received widespread attention. This technology eliminates the need for large amounts of organic solvents in the detection of benzene series compounds, is easy to operate, and has a simple process, making it a green and clean method for benzene series compound detection. SPME technology extracts benzene series compounds from wastewater by adsorbing them with solid-phase adsorbents. Its application in the oilfield industry demonstrates high treatment efficiency and low replacement costs. SPME materials are typically quartz fibers coated with a solid-phase extraction coating. Commonly used coatings include polyacrylate (PA), polydimethylsiloxane (PDMS), and polydimethylsiloxane / divinylbenzene (PDMS / DVB) coatings. However, these commercial coatings suffer from drawbacks such as instability, low operating temperatures, and coating peeling.

[0004] Therefore, in order to eliminate the defects of solid-phase microextraction fibers, graphene, metal oxide nanoparticles, metal-organic frameworks (MOFs), covalent organic frameworks (COFs), and polymeric ionic liquids have been used as coating materials for solid-phase microextraction fibers. Among them, the excellent physicochemical properties of carbon nanomaterials, including large specific surface area, high thermal stability, good mechanical properties, and low expansion cost, enable them to have stable extraction capabilities in harsh environments.

[0005] CN114471472A discloses a solid-phase microextraction fiber, its preparation method, and its application, relating to the field of materials science, to solve the technical problem of efficient and accurate extraction analysis of non-steroidal drugs in complex water bodies using existing technologies. The solid-phase microextraction fiber preparation method of this invention includes forming a metal oxide nanotube array on the surface of a metal fiber; carboxylating the metal oxide nanotube array to obtain a carboxylated nanotube array; silanizing the carboxylated nanotube array to obtain a silanized nanotube array; and coating the silanized nanotube array with MOFs material to obtain a solid-phase microextraction fiber; the metal fiber includes either Ti fiber or Al fiber. The fiber prepared by the solid-phase microextraction fiber preparation method provided by this invention is used for efficient and accurate extraction analysis of non-steroidal drugs. However, this invention utilizes metal fibers, resulting in a solid-phase microextraction fiber with a small specific surface area and lack of flexibility; the coating used is a polymer and is not heat-resistant.

[0006] CN108435138A discloses a solid-phase microextraction device and its application using an N-doped carbon nanotube coating synthesized with MOFs as a precursor. This invention first prepares N-doped carbon nanotubes with a ZIF-67 framework, then coats them onto a pretreated stainless steel wire. This stainless steel wire serves as the stainless steel fiber for solid-phase microextraction, further constructing the extraction device. The stainless steel fiber substrate used in this invention itself does not possess extraction capabilities, and the MOF-derived carbon material it supports is prone to detachment.

[0007] CN110681184A discloses a solid-phase microextraction column based on a multi-walled carbon nanotube / polyaniline composite coating and an online microextraction method. The multi-walled carbon nanotube / polyaniline composite coating solid-phase microextraction column comprises a stainless steel tube and a multi-walled carbon nanotube / polyaniline composite coating coated on the inner wall of the stainless steel tube. The multi-walled carbon nanotube / polyaniline composite coating is prepared in situ by synthesizing a multi-walled carbon nanotube / polyaniline solution on the inner wall of the stainless steel tube. This invention uses polyaniline as a binder and coating material, which is unstable, and the stainless steel material itself is not porous, resulting in weak overall extraction capacity.

[0008] CN111077254A discloses a thin-film solid-phase microextraction (SPME) coating material, its preparation method, and applications, as well as a high-throughput detection method for vomitoxin, belonging to the field of organic pollutant detection technology. This invention provides a thin-film SPME coating material, composed of polyacrylonitrile (PAC) and graphitized carboxyl-based multi-walled carbon nanotubes. The SPME coating material provided by this invention utilizes surface-bonded carboxyl groups on graphitized carboxyl-based multi-walled carbon nanotubes, and the combination of these two materials results in a thin-film SPME coating material. This invention uses commercially available carbon nanotubes and PAC as the coating; however, PAC lacks porosity, leading to poor thermal stability and weak extraction capacity in the SPME coating material.

[0009] In summary, graphene-coated metal solid-phase microextraction (SPE) materials are widely used in industry, utilizing the porosity of the graphene coating to extract contaminants. However, the metal material itself lacks porosity, thus limiting the extraction efficiency. Furthermore, the graphene coating on the metal surface tends to detach, resulting in poor stability and durability of graphene-coated metal SPE materials. Therefore, preparing SPE materials with high stability, large specific surface area, and strong extraction capability for benzene compounds is an urgent technical problem to be solved. Summary of the Invention

[0010] To address the above problems, this invention provides a graphene fiber modified with carbon nanotube arrays, its preparation method, and its applications. The graphene fiber modified with carbon nanotube arrays, as a solid-phase microextraction material, has high stability and a large specific surface area, significantly improving the sensing performance of benzene compounds, and is of great significance for pollution control in the oilfield ecological environment.

[0011] This invention provides a graphene fiber modified with a carbon nanotube array (GF@CNTAs). The graphene fiber has a "stem" structure with an orderly wrinkled morphology and a carbon nanotube array grown on its surface. The carbon nanotube array on the surface of the graphene fiber has an ordered 3D cross-linked structure. The graphene fiber has a diameter of 50-100 μm and a specific surface area of ​​320-330 m². 2 / g; In X-ray diffraction, the graphene fibers showed distinct characteristic peaks at 2θ of 44°±0.02° and 52°±0.02°.

[0012] This invention provides a method for preparing graphene fibers modified with carbon nanotube arrays, comprising the following steps:

[0013] Step 1: Oxidize expanded graphite powder to prepare graphene oxide (GO) solution;

[0014] Step 2: At room temperature, prepare an ionic liquid solution, and add the graphene oxide solution to the ionic liquid solution using a wet spinning method to obtain ionic liquid-modified graphene nascent fibers; wash the ionic liquid-modified graphene nascent fibers and vacuum dry them to obtain ionic liquid-modified graphene oxide fibers (IL-GOF).

[0015] Step 3: Prepare a 2-methylimidazolium cobalt (ZIF-67) mixed solution. Suspend the ionic liquid-modified graphene oxide fibers in the 2-methylimidazolium cobalt mixed solution, let it stand, take out the ionic liquid-modified graphene oxide fibers with 2-methylimidazolium cobalt growing on them, and vacuum dry them to obtain ionic liquid-modified graphene oxide fibers (IL-GOF@ZIF-67-NSs) with 2-methylimidazolium cobalt nanostructure arrays growing on them.

[0016] Step 4: The ionic liquid-modified graphene oxide fibers with the grown 2-methylimidazolium cobalt nanostructure array are placed together with a nitrogen-rich compound in a tube furnace for calcination to obtain metal-organic framework (MOF) graphene fibers; after acid washing, the MOF graphene fibers are washed with deionized water until the washing solution is neutral, cooled to room temperature, and vacuum dried to obtain carbon nanotube array-modified graphene fibers (GF@CNTAs).

[0017] Furthermore, the oxidation preparation process in step 1 involves adding an oxidant to expanded graphite powder, stirring at the reaction temperature to oxidize the expanded graphite powder into liquid graphene oxide, adjusting the pH value, and then filtering to obtain a graphene oxide solution.

[0018] Furthermore, the oxidant is composed of potassium nitrate, potassium permanganate, and 98% concentrated sulfuric acid.

[0019] Furthermore, the potassium nitrate and potassium permanganate are solid oxidants, and 98% concentrated sulfuric acid is a liquid oxidant.

[0020] Furthermore, the mass ratio of the expanded graphite powder, potassium nitrate, and potassium permanganate is 2:(1-1.25):(6-8), and the mass-to-volume ratio of the expanded graphite powder to 98% concentrated sulfuric acid is 0.04-0.05 g / mL.

[0021] Furthermore, the reaction temperature is 2-4℃, and the oxidation time is 2-3h.

[0022] Furthermore, the stirring speed is 100-200 r / min.

[0023] Furthermore, the pH value is adjusted within the range of 6-7.

[0024] Furthermore, the solvent used to adjust the pH value is deionized water.

[0025] Furthermore, the filtration method employs centrifugal filtration, with the centrifuge speed at 5000-6000 rpm and the centrifugation time at 10-15 minutes.

[0026] Furthermore, in step 1, the concentration of graphene oxide in the graphene oxide solution is 2-7 mg / mL.

[0027] Furthermore, the wet spinning method in step 2 involves placing a graphene oxide solution in a syringe and injecting it into an ionic liquid solution as a fine stream of graphene oxide using a micro-injection pump. Under the action of a dual diffusion mechanism, the graphene oxide fine stream solidifies in the ionic liquid solution to form ionic liquid-modified graphene nascent fibers.

[0028] Furthermore, the graphene oxide fine stream is extruded at a rate of 10-30 mL / h.

[0029] Further, in step 2, the ionic liquid solution is a 1-butyl-3-methylimidazolium tetrafluoroborate ([BMIM]BF4) solution, which is prepared by mixing 1-butyl-3-methylimidazolium tetrafluoroborate with deionized water, stirring and dissolving to prepare a 1-butyl-3-methylimidazolium tetrafluoroborate solution.

[0030] Furthermore, the concentration of 1-butyl-3-methylimidazolium tetrafluoroborate in the 1-butyl-3-methylimidazolium tetrafluoroborate solution is 2-5 mmol / L.

[0031] Furthermore, the stirring speed is 100-150 r / min, and the stirring time is 10-20 min.

[0032] Furthermore, in step 2, the volume ratio of the graphene oxide solution to the ionic liquid solution is (0.15:1)-(0.3:1).

[0033] Furthermore, the solvent used for washing in step 2 includes ethanol or water, and the washing is performed 3-5 times.

[0034] Furthermore, in step 2, the vacuum drying temperature is 50-60℃, the vacuum drying time is 2-3 hours, and the vacuum degree is 1000Pa.

[0035] Furthermore, the preparation method of the 2-methylimidazolium cobalt solution in step 3 is to dissolve cobalt salt and 2-methylimidazolium in deionized water and stir to dissolve, wherein the cobalt metal ions in the cobalt salt coordinate with 2-methylimidazolium to obtain 2-methylimidazolium cobalt.

[0036] Further, the mass ratio of the cobalt salt to deionized water is (0.015-0.023):1, and the mass ratio of the 2-methylimidazole to deionized water is (0.002-0.004):1.

[0037] Furthermore, the cobalt salt is cobalt nitrate hexahydrate.

[0038] Furthermore, the stirring speed is 100-150 r / min, and the stirring time is 10-20 min.

[0039] Furthermore, in step 3, the ionic liquid-modified graphene oxide fibers must not contact the inner wall of the container during suspension and must be completely suspended to ensure the growth of 2-methylimidazolium cobalt on its surface.

[0040] Furthermore, the settling time in step 3 is 4-8 hours.

[0041] Furthermore, in step 3, the vacuum drying temperature is 50-60℃, the vacuum drying time is 6-8h, and the vacuum degree of vacuum drying is 1000Pa.

[0042] Furthermore, in step 4, the mass of the nitrogen-rich compound is 10-20 times the mass of the ionic liquid-modified graphene oxide fibers used to grow the 2-methylimidazolium cobalt nanostructure array.

[0043] Furthermore, the nitrogen-rich compound is melamine.

[0044] Furthermore, in step 4, the calcination temperature is 500-1000℃, the calcination time is 2-3h, and the calcination heating rate is 1-2℃ / min.

[0045] Furthermore, the calcination process in step 4 is carried out under inert gas conditions, wherein the inert gas is either nitrogen or argon, and the flow rate of the inert gas is 90-100 mL / min.

[0046] Furthermore, the acid solution used in the pickling process in step 4 is either nitric acid or hydrochloric acid, in order to remove impurities from the surface of the metal-organic framework graphene fiber.

[0047] Furthermore, the concentration of the acid solution is 3-5 mol / L, the acid washing temperature is 70-90℃, and the acid washing time is 3-5 h.

[0048] Furthermore, in step 4, the vacuum drying temperature is 100-200℃, the vacuum drying time is 1-2 hours, and the vacuum degree is 1000Pa.

[0049] The present invention also provides an application of graphene fibers modified with carbon nanotube arrays, wherein the graphene fibers modified with carbon nanotube arrays are used for rapid and effective detection of volatile organic compounds.

[0050] Furthermore, the volatile organic compounds are benzene compounds.

[0051] Furthermore, the carbon nanotube array-modified graphene fiber, as a solid-phase microextraction material, has a linear range of 0.2-600 μg / L for detecting volatile organic compounds, and a limit of detection of 0.005-0.03 mg / L.

[0052] Furthermore, the relative standard deviation of the graphene fiber modified with the carbon nanotube array for detecting volatile organic compounds is 3.2-5.5%, indicating high detection precision.

[0053] Furthermore, the graphene fibers modified with the carbon nanotube array are used to determine benzene compounds in wastewater, comprising the following steps:

[0054] Step 1: Activate the carbon nanotube array-modified graphene fibers to obtain activated carbon nanotube array-modified graphene fibers.

[0055] Step 2: Use the activated carbon nanotube array modified graphene fiber to extract wastewater containing benzene series compounds to obtain the extracted carbon nanotube array modified graphene fiber.

[0056] Step 3: Analyze the extracted carbon nanotube array-modified graphene fibers.

[0057] Furthermore, the carrier gas used for activation in step 1 is nitrogen, and the flow rate of the nitrogen is 1 mL / min.

[0058] Furthermore, the activation temperature in step 1 is 200-300℃, and the activation time is 1-2 hours.

[0059] Furthermore, the benzene compounds in the wastewater containing benzene compounds in step 2 include one or more of benzene, toluene, ethylbenzene, p-xylene, and m-xylene.

[0060] Further, in step 2, the extraction process involves placing wastewater containing benzene compounds into a sealed container, which includes the wastewater and air. Activated carbon nanotube array-modified graphene fibers are placed in the air within the sealed container without contacting the wastewater. The sealed container is then stirred and heated. The benzene compounds in the wastewater volatilize into the air within the sealed container, and the activated carbon nanotube array-modified graphene fibers adsorb the benzene compounds in the air, thereby performing extraction.

[0061] Furthermore, the volume ratio of the wastewater containing benzene compounds to air in the sealed container is (1:2)-(3:5).

[0062] Furthermore, the stirring speed is 2000-3000 r / min.

[0063] Furthermore, the heating temperature is 30-70℃, and the heating time is 30-60 minutes.

[0064] The beneficial effects of this invention are:

[0065] 1. The graphene fibers modified with carbon nanotube arrays in this invention have a porous and ordered folded morphology, which has a superior specific surface area and significantly improves the sensing performance of benzene series compounds in wastewater.

[0066] 2. The graphene fibers modified with carbon nanotube arrays in this invention are prepared under high-temperature pyrolysis conditions, with controllable morphology and stable structure, and have unique structural and mechanical properties.

[0067] 3. In this invention, the graphene fiber modified with carbon nanotube array has a "stem" structure. The surface of the "stem" is covered with an ordered carbon nanotube array structure, which increases the specific surface area of ​​the graphene fiber modified with carbon nanotube array, thereby improving the solid-phase microextraction capability.

[0068] 4. In this invention, the graphene fiber modified with carbon nanotube array is used as a solid-phase microextraction material. It does not need to be coated with other porous materials. Because of its high effective specific surface area, it can provide rich porous conditions during the extraction process and has high adsorption performance. Using it as a solid-phase microextraction material can greatly improve the extraction capacity.

[0069] 5. The graphene fibers modified with carbon nanotube arrays in this invention have high stability as solid-phase microextraction materials, and maintain excellent stability under any acidity, alkalinity and organic solvent conditions.

[0070] 6. The graphene fibers modified with carbon nanotube arrays in this invention have high reproducibility as solid-phase microextraction materials, with a relative standard deviation of 3.2%-5.5% after 6 reuses, indicating high precision in reuse.

[0071] 7. The carbon nanotube array-modified graphene fibers of this invention have a wide detection linear range for benzene compounds, with a detection linear range of 0.2-600 μg / L and a minimum detection limit of 0.005-0.03 mg / L, and have extremely high commercial value.

[0072] 8. The graphene fibers modified with carbon nanotube arrays in this invention are not only suitable for the detection of benzene compounds, but can also be applied to the detection of other volatile organic compounds. Attached Figure Description

[0073] Figure 1 This is a scanning electron microscope image of the ionic liquid-modified graphene oxide fiber in Example 1 of the present invention;

[0074] Figure 2 This is a scanning electron microscope image of the graphene fibers modified with carbon nanotube arrays in Example 1 of the present invention;

[0075] Figure 3 This is a scanning electron microscope image of the carbon nanotube array on the surface of the graphene fiber modified with carbon nanotube array in Example 1 of the present invention.

[0076] Figure 4 X-ray diffraction patterns of graphene fibers modified with carbon nanotube arrays (GF@CNTAs), graphene oxide fibers modified with ionic liquids growing 2-methylimidazolium cobalt (IL-GOF@ZIF-67-NSs), and graphene oxide fibers modified with ionic liquids (IL-GOF) in Example 1 of this invention.

[0077] Figure 5 The extraction temperature optimization diagram is obtained by gas chromatography-mass spectrometry analysis of the graphene fibers modified with carbon nanotube arrays in Example 1 of the present invention.

[0078] Figure 6 This is a graph showing the optimized extraction time of the carbon nanotube array-modified graphene fibers in Example 1 of the present invention, analyzed by gas chromatography-mass spectrometry.

[0079] Figure 7 The desorption temperature optimization diagram of the carbon nanotube array modified graphene fiber in Example 1 of the present invention is obtained by gas chromatography-mass spectrometry analysis.

[0080] Figure 8 The image shows the optimized desorption time of the carbon nanotube array-modified graphene fibers in Example 1 of this invention, analyzed by gas chromatography-mass spectrometry.

[0081] Figure 9 In Example 2 of this invention, the graphene fibers modified with carbon nanotube arrays were repeatedly extracted six times to obtain a relative standard deviation diagram for different benzene compounds.

[0082] Figure 10 This is a comparison of the chromatographic peak areas of the graphene fibers (GF@CNTAs) modified with carbon nanotube arrays in Example 1 of the present invention and the extraction material (PDMS fibers) modified with commercial PDMS coating in Comparative Example 1, when solid microextraction experiments were performed on benzene series compounds under the same conditions. Detailed Implementation

[0083] The invention will be described in detail below with reference to the embodiments:

[0084] This invention provides a carbon nanotube array-modified graphene fiber, its preparation method, and its applications. The method employs a simple and controllable preparation method to produce a solid-phase microextraction fiber material with high stability, good adsorption, and high extraction capacity, which greatly improves the accuracy and detection capability of benzene series compounds in oilfield wastewater.

[0085] Example 1

[0086] This embodiment provides a method for preparing graphene fibers modified with carbon nanotube arrays, including the following steps:

[0087] Step 1: Add 5g KNO3, 30g KMnO4 and 230mL 98% concentrated sulfuric acid to 10g expanded graphite powder. Stir at 2℃ and 200r / min for 2h to oxidize the expanded graphite powder into liquid graphene oxide. Adjust the pH to 6 with ultrapure water and centrifuge at 5000rpm for 10min to remove the carbon black generated during the oxidation process, and obtain graphene oxide solution.

[0088] Step 2: At room temperature, 45 mg of 1-butyl-3-methylimidazolium tetrafluoroborate was mixed with 100 mL of deionized water and stirred at 100 r / min for 10 min to prepare a 2 mmol / L 1-butyl-3-methylimidazolium tetrafluoroborate solution. 3 mL of the graphene oxide solution was loaded into a 5 mL plastic syringe and injected into the 1-butyl-3-methylimidazolium tetrafluoroborate solution as a fine stream of graphene oxide using a micro-injection pump at a rate of 30 mL / h. Under the action of a double diffusion mechanism, the graphene oxide fine stream solidified into nascent graphene oxide fibers in the 1-butyl-3-methylimidazolium tetrafluoroborate solution. The ionic liquid-modified nascent graphene fibers in the 1-butyl-3-methylimidazolium tetrafluoroborate solution were taken out, washed three times with ethanol and water, and dried in a vacuum drying oven at 60 °C and a vacuum degree of 1000 Pa for 2 h to obtain ionic liquid-modified graphene oxide fibers.

[0089] Step 3: At room temperature, 1.465 g of cobalt salt and 0.246 g of 2-methylimidazole are dissolved in 100 mL of deionized water and stirred at 100 r / min for 1 min to dissolve them. Cobalt metal ions coordinate with 2-methylimidazole to obtain a 2-methylimidazole cobalt mixed solution. The ionic liquid-modified graphene oxide fiber is suspended in the 2-methylimidazole cobalt mixed solution without contacting the inner wall of the container and left to stand for 4 h to obtain ionic liquid-modified graphene oxide fiber with 2-methylimidazole cobalt grown on it. The ionic liquid-modified graphene oxide fiber with 2-methylimidazole cobalt grown on it is taken out and vacuum dried at 60 °C and 1000 Pa for 6 h to obtain ionic liquid-modified graphene oxide fiber with 2-methylimidazole cobalt nanostructure array grown on it.

[0090] Step 4: The ionic liquid-modified graphene oxide fibers with the 2-methylimidazolium cobalt nanostructure array grown thereon are placed together with 10g of melamine in a tube furnace. Under nitrogen gas conditions of 90-100mL / min, the temperature is increased to 800℃ for 2h at a heating rate of 2℃ / min to obtain metal-organic framework graphene fibers. The metal-organic framework graphene fibers are then soaked in 5mol / L nitric acid solution at 70℃ for 3h to remove impurities on the surface of the metal-organic framework graphene fibers. After cooling to room temperature, they are vacuum dried at 100℃ and a vacuum degree of 1000Pa for 2h to obtain carbon nanotube array-modified graphene fibers.

[0091] like Figure 1 The image shown is a scanning electron microscope image of the ionic liquid-modified graphene oxide fiber in this embodiment. The ionic liquid-modified graphene oxide fiber has an ordered folded morphology and a diameter of 80 μm.

[0092] like Figure 2 The image shown is a scanning electron microscope image of the graphene fiber modified with carbon nanotube array in this embodiment. The graphene fiber modified with carbon nanotube array has a "stem" structure with orderly wrinkles and a carbon nanotube array growing on its surface.

[0093] like Figure 3 The image shown is a scanning electron microscope image of the carbon nanotube array on the surface of the graphene fiber modified with carbon nanotube array in this embodiment. The carbon nanotube array on the surface of the graphene fiber modified with carbon nanotube array in the image has an ordered 3D cross-linked structure.

[0094] like Figure 4 The image shows the X-ray diffraction patterns of the graphene fibers modified with carbon nanotube arrays (GF@CNTAs), the graphene oxide fibers modified with ionic liquids growing 2-methylimidazolium cobalt (IL-GOF@ZIF-67-NSs), and the graphene oxide fibers modified with ionic liquids (IL-GOF) in this embodiment. By comparison, the graphene oxide fibers modified with ionic liquids show a characteristic peak corresponding to graphite at 2θ = 26°, the graphene oxide fibers modified with ionic liquids growing 2-methylimidazolium cobalt show a characteristic peak corresponding to 2-methylimidazolium cobalt in the range of 2θ = 5°-30°, and the carbon nanotube array solid-phase microextraction fibers show characteristic peaks corresponding to the (111) and (002) crystal planes of Co nanoparticles at 2θ = 44° and 52°. This indicates that the growth of metal-organic framework materials enriches the adsorption active sites of the extraction materials.

[0095] This embodiment also provides an application of carbon nanotube array-modified graphene fibers, which are used to determine benzene series compounds in wastewater, including the following steps:

[0096] Step 1: Pass one side of the carbon nanotube array-modified graphene fiber through the needle of a 1 mL syringe, and connect the other side to the syringe plunger to assemble a simple, retractable solid-phase microextraction device for carbon nanotube array-modified graphene fiber. Insert the syringe needle of the simple solid-phase microextraction device into the gas chromatograph-mass spectrometer's gas chromatograph-mass spectrometer's gas chromatograph-mass spectrometer. Push the syringe plunger to push the carbon nanotube array-modified graphene fiber out of the syringe needle. Activate the carbon nanotube array-modified graphene fiber at 280℃ for 1 h under nitrogen conditions of 1 mL / min to obtain activated carbon nanotube array-modified graphene fiber. Pull the syringe plunger of the simple solid-phase microextraction device to retract the activated carbon nanotube array-modified graphene fiber back into the syringe needle, thus obtaining the activated simple solid-phase microextraction device.

[0097] Step 2: 10 mL of wastewater containing benzene compounds is placed into a 20 mL sealed sample bottle. The bottle opening is sealed with a 3 cm × 3 cm PTFE silicone membrane. The sealed sample bottle contains 10 mL of wastewater containing benzene compounds and air. The syringe needle of the activated simple solid-phase microextraction device is used to pierce the PTFE silicone membrane, and the syringe plunger of the simple solid-phase microextraction device is pushed to push the activated carbon nanotube array-modified graphene fiber out of the syringe needle. The activated carbon nanotube array-modified graphene fiber is placed in the... In a sealed sample bottle, the activated carbon nanotube array-modified graphene fiber does not come into contact with the wastewater containing benzene compounds. The sealed sample bottle is placed under a stirring condition of 2000 r / min and heated to 70°C. The benzene compounds in the wastewater containing benzene compounds volatilize into the air of the sealed sample bottle. The activated carbon nanotube array-modified graphene fiber is used to adsorb the benzene compounds in the air of the sealed sample bottle for 50 min. Extraction is then performed to obtain the extracted carbon nanotube array-modified graphene fiber.

[0098] Step 3: Pull the syringe plunger of the simple solid-phase microextraction device to retract the extracted carbon nanotube array-modified graphene fiber into the syringe needle of the simple solid-phase microextraction device, and remove the syringe needle of the simple solid-phase microextraction device containing the extracted carbon nanotube array-modified graphene fiber, and insert it into the injection port of the gas chromatography-mass spectrometry instrument for analysis.

[0099] like Figure 5-8 As shown, the optimal pretreatment conditions for the carbon nanotube array-modified graphene fibers (GF@CNTAs) described in this embodiment were obtained by gas chromatography-mass spectrometry analysis of the optimized extraction temperature, extraction time, desorption temperature, desorption time, solution pH, and ion intensity. The optimal extraction temperature was 70℃, the optimal extraction time was 50 min, the optimal desorption temperature was 310℃, and the optimal desorption time was 5 min.

[0100] In this embodiment, the gas chromatograph used is a TRACE 1610; the capillary column used in the gas chromatography is a DB-5MS fused capillary column with dimensions of 60m × 0.25mm × 0.25μm; the carrier gas in the gas chromatography is helium with a purity of 99.999% and a flow rate of 1mL / min; the injection method used in the gas chromatography is splitless injection, and the temperature of the injection port is 250℃; the temperature program set for the gas chromatography is as follows: 40℃ held for 6min, then increased to 60℃ at 10℃ / min, held for 1min, then increased to 100℃ at 2.5℃ / min, then increased to 250℃ at 10℃ / min, held for 3min, then increased to 310℃ at 20℃ / min, held for 5min.

[0101] In this embodiment, the ion source of the mass spectrometer used is an electron impact ion source (EI), the temperature of the ion source is 230°C, and the electron capability of the ion source is 70 eV; the acquisition mode of the mass spectrometer is selective ion detection (SIM), the temperature of the quadrupole in the mass spectrometer is 150°C, the temperature of the transfer line is 280°C, and the solvent delay time in the mass spectrometer is set to 6 min.

[0102] Example 2

[0103] This embodiment provides a method for preparing graphene fibers modified with carbon nanotube arrays, including the following steps:

[0104] Step 1: Add 5g KNO3, 30g KMnO4 and 230mL 98% concentrated sulfuric acid to 10g expanded graphite powder. Stir at 2℃ and 200r / min for 2h to oxidize the expanded graphite powder into liquid graphene oxide. Adjust the pH to 6 with ultrapure water and centrifuge at 5000rpm for 10min to remove the carbon black generated during the oxidation process, and obtain graphene oxide solution.

[0105] Step 2: At room temperature, 45 mg of 1-butyl-3-methylimidazolium tetrafluoroborate was mixed with 100 mL of deionized water and stirred at 100 r / min for 10 min to prepare a 2 mmol / L 1-butyl-3-methylimidazolium tetrafluoroborate solution. 3 mL of the graphene oxide solution was loaded into a 5 mL plastic syringe and injected into the 1-butyl-3-methylimidazolium tetrafluoroborate solution as a fine stream of graphene oxide using a micro-injection pump at a rate of 30 mL / h. Under the action of a double diffusion mechanism, the graphene oxide fine stream solidified into nascent graphene oxide fibers in the 1-butyl-3-methylimidazolium tetrafluoroborate solution. The ionic liquid-modified nascent graphene fibers in the 1-butyl-3-methylimidazolium tetrafluoroborate solution were taken out, washed three times with ethanol and water, and dried in a vacuum drying oven at 60 °C and a vacuum degree of 1000 Pa for 2 h to obtain ionic liquid-modified graphene oxide fibers.

[0106] Step 3: At room temperature, dissolve 2.9 g of cobalt salt and 0.5 g of 2-methylimidazole in 100 mL of deionized water and stir at 100 r / min for 10 min to dissolve. Cobalt metal ions coordinate with 2-methylimidazole to obtain a 2-methylimidazole cobalt mixed solution. Suspend the ionic liquid-modified graphene oxide fiber in the 2-methylimidazole cobalt mixed solution without contacting the inner wall of the container and let it stand for 4 h to obtain ionic liquid-modified graphene oxide fiber with 2-methylimidazole cobalt grown on it. Take out the ionic liquid-modified graphene oxide fiber with 2-methylimidazole cobalt grown on it and vacuum dry it at 60 °C and a vacuum degree of 1000 Pa for 6 h to obtain ionic liquid-modified graphene oxide fiber with 2-methylimidazole cobalt nanostructure array grown on it.

[0107] Step 4: The ionic liquid-modified graphene oxide fibers with the 2-methylimidazolium cobalt nanostructure array grown thereon are placed together with 10g of melamine in a tube furnace. Under nitrogen gas conditions of 90-100mL / min, the temperature is increased to 800℃ for 2h at a heating rate of 2℃ / min to obtain metal-organic framework graphene fibers. The metal-organic framework graphene fibers are then soaked in 5mol / L nitric acid solution at 70℃ for 3h to remove impurities on the surface of the metal-organic framework graphene fibers. After cooling to room temperature, they are vacuum dried at 100℃ and a vacuum degree of 1000Pa for 2h to obtain carbon nanotube array-modified graphene fibers.

[0108] This embodiment also provides an application of carbon nanotube array-modified graphene fibers, which are used to determine benzene series compounds in wastewater, including the following steps:

[0109] Step 1: Pass one side of the carbon nanotube array-modified graphene fiber through the needle of a 1 mL syringe, and connect the other side to the syringe plunger to assemble a simple, retractable solid-phase microextraction device for carbon nanotube array-modified graphene fiber. Insert the syringe needle of the simple solid-phase microextraction device into the gas chromatograph-mass spectrometer's gas chromatograph-mass spectrometer's gas chromatograph-mass spectrometer. Push the syringe plunger to push the carbon nanotube array-modified graphene fiber out of the syringe needle. Activate the carbon nanotube array-modified graphene fiber at 280℃ for 1 h under nitrogen conditions of 1 mL / min to obtain activated carbon nanotube array-modified graphene fiber. Pull the syringe plunger of the simple solid-phase microextraction device to retract the activated carbon nanotube array-modified graphene fiber back into the syringe needle, thus obtaining the activated simple solid-phase microextraction device.

[0110] Step 2: 10 mL of wastewater containing benzene compounds is placed into a 20 mL sealed sample bottle. The bottle opening is sealed with a 3 cm × 3 cm PTFE silicone membrane. The sealed sample bottle contains 10 mL of wastewater containing benzene compounds and air. The syringe needle of the activated simple solid-phase microextraction device is used to pierce the PTFE silicone membrane, and the syringe plunger of the simple solid-phase microextraction device is pushed to push the activated carbon nanotube array-modified graphene fiber out of the syringe needle. The activated carbon nanotube array-modified graphene fiber is placed in the... In a sealed sample bottle, the activated carbon nanotube array-modified graphene fiber does not come into contact with the wastewater containing benzene compounds. The sealed sample bottle is placed under a stirring condition of 2000 r / min and heated to 70°C. The benzene compounds in the wastewater containing benzene compounds volatilize into the air of the sealed sample bottle. The activated carbon nanotube array-modified graphene fiber is used to adsorb the benzene compounds in the air of the sealed sample bottle for 50 min. Extraction is then performed to obtain the extracted carbon nanotube array-modified graphene fiber.

[0111] Step 3: Pull the syringe plunger of the simple solid-phase microextraction device to retract the extracted carbon nanotube array-modified graphene fiber into the syringe needle of the simple solid-phase microextraction device, and remove the syringe needle of the simple solid-phase microextraction device containing the extracted carbon nanotube array-modified graphene fiber, and insert it into the injection port of the gas chromatography-mass spectrometry instrument for analysis.

[0112] As shown in Table 1, the extraction capacity of the carbon nanotube array-modified graphene fiber in this embodiment for different benzene compounds in wastewater containing benzene compounds at pH 1 and pH 14 after heating at 350℃ for 15 min is compared. The extraction capacity did not change significantly.

[0113]

[0114] like Figure 9As shown, the graph shows the relative standard deviation of the graphene fibers modified with carbon nanotube arrays in this embodiment after six repeated extractions for different benzene compounds. As can be seen from the graph, the relative standard deviation of the graphene fibers modified with carbon nanotube arrays is 3.2%-5.5%, indicating that the graphene fibers modified with carbon nanotube arrays in this embodiment have high precision and good stability.

[0115] In this embodiment, the gas chromatograph used is a TRACE 1610; the capillary column used in the gas chromatography is a DB-5MS fused capillary column with dimensions of 60m × 0.25mm × 0.25μm; the carrier gas in the gas chromatography is helium with a purity of 99.999% and a flow rate of 1mL / min; the injection method used in the gas chromatography is splitless injection, and the temperature of the injection port is 250℃; the temperature program set for the gas chromatography is as follows: 40℃ held for 6min, then increased to 60℃ at 10℃ / min, held for 1min, then increased to 100℃ at 2.5℃ / min, then increased to 250℃ at 10℃ / min, held for 3min, then increased to 310℃ at 20℃ / min, held for 5min.

[0116] In this embodiment, the ion source of the mass spectrometer used is an electron impact ion source (EI), the temperature of the ion source is 230°C, and the electron capability of the ion source is 70 eV; the acquisition mode of the mass spectrometer is selective ion detection (SIM), the temperature of the quadrupole in the mass spectrometer is 150°C, the temperature of the transfer line is 280°C, and the solvent delay time in the mass spectrometer is set to 6 min.

[0117] Comparative Example 1

[0118] This comparative example provides the use of a commercially available PDMS-coated extractable material, comprising the following steps:

[0119] Step 1: Insert the commercial PDMS-coated modified extraction material into the gas chromatograph-mass spectrometer's ...

[0120] Step 2: 10 mL of wastewater containing benzene compounds is placed into a 20 mL sealed sample bottle. The bottle opening is sealed with a 3 cm × 3 cm PTFE silicone membrane. The sealed sample bottle contains 10 mL of wastewater containing benzene compounds and air. The activated commercial PDMS-coated extraction material is used to puncture the PTFE silicone membrane. The activated commercial PDMS-coated extraction material is placed in the air of the sealed sample bottle, ensuring that it does not come into contact with the wastewater containing benzene compounds. The sealed sample bottle is stirred at 2000 r / min and heated to 70°C. The benzene compounds in the wastewater volatilize into the air of the sealed sample bottle. The activated commercial PDMS-coated extraction material is used to adsorb the benzene compounds in the air of the sealed sample bottle for 50 min, thereby performing extraction to obtain the extracted commercial PDMS-coated extraction material.

[0121] Step 3: Insert the extracted material modified with commercial PDMS coating into the injection port of the gas chromatograph-mass spectrometer for analysis.

[0122] In this comparative example, the gas chromatograph used was a TRACE 1610; the capillary column used in the gas chromatography was a DB-5MS fused capillary column with dimensions of 60m × 0.25mm × 0.25μm; the carrier gas in the gas chromatography was helium with a purity of 99.999% and a flow rate of 1mL / min; the injection method used in the gas chromatography was splitless injection, and the temperature of the injection port was 250℃; the temperature program set for the gas chromatography was as follows: 40℃ held for 6 min, then increased to 60℃ at 10℃ / min, held for 1 min, then increased to 100℃ at 2.5℃ / min, then increased to 250℃ at 10℃ / min, held for 3 min, and then increased to 310℃ at 20℃ / min, held for 5 min.

[0123] In this comparative example, the ion source of the mass spectrometer used was an electron impact ion source (EI), with a temperature of 230℃ and an electron capability of 70 eV; the acquisition mode of the mass spectrometer was selective ion detection (SIM), with the temperature of the quadrupole in the mass spectrometer being 150℃ and the temperature of the transfer line being 280℃; the solvent delay time in the mass spectrometer was set to 6 min.

[0124] The diameter of the extraction material modified with the commercial PDMS coating described in this comparative example is 100 μm.

[0125] like Figure 10The figure shows a comparison of the chromatographic peak areas of the graphene fibers modified with carbon nanotube arrays (GF@CNTAs) in Example 1 and the extraction material modified with commercial PDMS coating (PDMS fibers) in Comparative Example 1, under the same conditions, in a solid microextraction experiment on benzene compounds. The comparison shows that the graphene fibers modified with carbon nanotube arrays have a 5-10 times higher extraction capacity for wastewater containing benzene compounds than the extraction material modified with commercial PDMS coating. This is because the graphene fibers modified with carbon nanotube arrays have a large specific surface area, active sites, and π-π stacking interaction between carbon nanotubes and benzene rings in benzene compounds.

[0126] As can be seen from the above, the carbon nanotube array solid-phase microextraction fiber of the present invention has extremely high extraction capacity and stability, and has a wide range of applications. Therefore, it can replace some solid-phase microextraction materials and has extremely high market prospects.

[0127] It should be understood that the present invention is not limited to what has been described above and shown in the accompanying drawings, and various modifications and changes can be made without departing from its scope. The scope of the invention is limited only by the appended claims.

Claims

1. A graphene fiber modified with a carbon nanotube array, characterized in that, The graphene fiber has a "stem" structure with orderly wrinkles and an array of carbon nanotubes grown on its surface; the carbon nanotube array on the surface of the graphene fiber has an ordered 3D cross-linked structure; the graphene fiber has a diameter of 50-100 μm and a specific surface area of ​​320-330 m². 2 / g; In X-ray diffraction, the graphene fibers showed distinct characteristic peaks at 2θ of 44°±0.02° and 52°±0.02°; The method for preparing the carbon nanotube array-modified graphene fiber includes the following steps: Step 1: Oxidize expanded graphite powder to prepare graphene oxide solution; Step 2: At room temperature, prepare an ionic liquid solution, and add the graphene oxide solution to the ionic liquid solution using a wet spinning method to obtain ionic liquid-modified graphene nascent fibers; wash the ionic liquid-modified graphene nascent fibers and then vacuum dry them to obtain ionic liquid-modified graphene oxide fibers. In step 2, the ionic liquid solution is a 1-butyl-3-methylimidazolium tetrafluoroborate solution. The preparation process involves mixing 1-butyl-3-methylimidazolium tetrafluoroborate with deionized water, stirring and dissolving to prepare a 1-butyl-3-methylimidazolium tetrafluoroborate solution. Step 3: Prepare a 2-methylimidazolium cobalt mixed solution. Suspend the ionic liquid-modified graphene oxide fibers in the 2-methylimidazolium cobalt mixed solution, let it stand, take out the ionic liquid-modified graphene oxide fibers with 2-methylimidazolium cobalt growing on them, and vacuum dry them to obtain ionic liquid-modified graphene oxide fibers with 2-methylimidazolium cobalt nanostructure arrays. Step 4: Place the ionic liquid-modified graphene oxide fibers with the 2-methylimidazolium cobalt nanostructure array grown therein and nitrogen-rich compounds together in a tube furnace for calcination to obtain metal-organic framework graphene fibers; after acid washing, wash the metal-organic framework graphene fibers with deionized water until the washing solution is neutral, cool to room temperature, and vacuum dry to obtain carbon nanotube array-modified graphene fibers.

2. A method for preparing graphene fibers modified with carbon nanotube arrays as described in claim 1, characterized in that, Includes the following steps: Step 1: Oxidize expanded graphite powder to prepare graphene oxide solution; Step 2: At room temperature, prepare an ionic liquid solution, and add the graphene oxide solution to the ionic liquid solution using a wet spinning method to obtain ionic liquid-modified graphene nascent fibers; wash the ionic liquid-modified graphene nascent fibers and then vacuum dry them to obtain ionic liquid-modified graphene oxide fibers. Step 3: Prepare a 2-methylimidazolium cobalt mixed solution. Suspend the ionic liquid-modified graphene oxide fibers in the 2-methylimidazolium cobalt mixed solution, let it stand, take out the ionic liquid-modified graphene oxide fibers with 2-methylimidazolium cobalt growing on them, and vacuum dry them to obtain ionic liquid-modified graphene oxide fibers with 2-methylimidazolium cobalt nanostructure arrays. Step 4: Place the ionic liquid-modified graphene oxide fibers with the 2-methylimidazolium cobalt nanostructure array grown therein and nitrogen-rich compounds together in a tube furnace for calcination to obtain metal-organic framework graphene fibers; after acid washing, wash the metal-organic framework graphene fibers with deionized water until the washing solution is neutral, cool to room temperature, and vacuum dry to obtain carbon nanotube array-modified graphene fibers.

3. The method for preparing carbon nanotube array-modified graphene fibers according to claim 2, characterized in that, The oxidation preparation process in step 1 involves adding an oxidant to expanded graphite powder, stirring at the reaction temperature to oxidize the expanded graphite powder into liquid graphene oxide, adjusting the pH value, and then filtering to obtain a graphene oxide solution.

4. The method for preparing carbon nanotube array-modified graphene fibers according to claim 3, characterized in that, The oxidizing agents include potassium nitrate, potassium permanganate, and 98% concentrated sulfuric acid.

5. The method for preparing carbon nanotube array-modified graphene fibers according to claim 3, characterized in that, The pH value is adjusted to a range of 6-7.

6. The method for preparing carbon nanotube array-modified graphene fibers according to claim 2, characterized in that, The wet spinning method in step 2 involves placing a graphene oxide solution in a syringe and injecting it into an ionic liquid solution as a fine stream of graphene oxide using a micro-injection pump. Under the action of a dual diffusion mechanism, the graphene oxide fine stream solidifies in the ionic liquid solution to form ionic liquid-modified graphene nascent fibers.

7. The method for preparing carbon nanotube array-modified graphene fibers according to claim 2, characterized in that, In step 3, the ionic liquid-modified graphene oxide fibers must not come into contact with the inner wall of the container during the suspension process and must be completely suspended to ensure that ZIF-67 grows on its surface.

8. The use of the carbon nanotube array-modified graphene fiber according to claim 1, characterized in that, The graphene fibers modified with carbon nanotube arrays are used for rapid and effective detection of volatile organic compounds.

9. The use of the carbon nanotube array-modified graphene fiber according to claim 8, characterized in that, The carbon nanotube array-modified graphene fibers are used to determine benzene compounds in wastewater, including the following steps: Step 1: Activate the carbon nanotube array-modified graphene fibers to obtain activated carbon nanotube array-modified graphene fibers. Step 2: Use the activated carbon nanotube array modified graphene fiber to extract wastewater containing benzene series compounds to obtain the extracted carbon nanotube array modified graphene fiber. Step 3: Analyze the extracted carbon nanotube array-modified graphene fibers.

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