Carbon nitride modified carbon fiber composite material as well as preparation method and application thereof

Abstract

The invention relates to a carbon nitride modified carbon fiber composite material and a preparation method and application thereof, and the carbon nitride modified carbon fiber composite material is composed of phosphorus-doped tubular carbon nitride composite titanium dioxide and modified activated carbon fibers, the phosphorus-doped tubular carbon nitride composite titanium dioxide is uniformly distributed on the surface of the modified activated carbon fiber, the carbon nitride modified carbon fiber composite material shows characteristic peaks at positions with diffraction angles 2theta of 25.37 + / -0.20 degrees, 38.60 + / -0.20 degrees, 48.07 + / -0.20 degrees, 54.86 + / -0.20 degrees and 62.58 + / -0.20 degrees, and the characteristic peaks correspond to crystal faces (001), (101), (112), (200), (211) and (204), which indicate the high crystallization property of titanium dioxide, and the phosphorus-doped tubular carbon nitride composite titanium dioxide has the characteristic peaks corresponding to the crystal faces (001), (101), (112), (200), (211) and (204). The carbon nitride modified carbon fiber composite material is used for degrading n-hexane in VOCs, and the degradation rate is larger than or equal to 80.5%.

Description

Technical Field

[0001] The present invention relates to the technical field of environmental engineering, and in particular to a carbon nitride modified carbon fiber composite material, a preparation method thereof, and uses thereof. Background Art

[0002] As a pillar industry of the national economy, the petroleum and petrochemical industry provides the necessary petroleum energy and chemical products for social development, but at the same time, the environmental pollution problems it brings are becoming increasingly prominent. The exhaust gas emitted by the petroleum and petrochemical industry is complex in composition, with volatile organic compounds (VOCs) as the main component, including a variety of toxic and harmful gases, such as non-methane hydrocarbon pollutants, benzene series, halogenated hydrocarbons, alcohols... Among them, VOCs have carcinogenic and mutagenic hazards that seriously threaten the atmospheric environment and human health. For VOCs, the main treatment technologies are adsorption, condensation, incineration, catalytic combustion, photocatalysis, etc. However, the current single treatment technology can no longer achieve efficient removal of pollutants. Some scholars have combined adsorption with photocatalysis technology. A method for preparing an activated carbon fiber-loaded cerium and titanium dioxide catalytic material is a new type of photocatalytic material for adsorption-synergistic photocatalytic treatment of VOCs.

[0003] At present, the activated carbon fiber and titanium dioxide composite materials prepared by the current method, although they have achieved the combination of adsorption and photocatalysis, cannot achieve the effect of one plus one being greater than two. The main reason is that the titanium dioxide is loaded on the activated carbon fiber, which blocks the adsorption pores on the activated carbon fiber, reduces the specific surface area, and thus reduces the adsorption performance. Moreover, in the composite materials prepared by most researchers, the titanium dioxide is only loaded on the surface of the activated carbon fiber, with a low loading amount and low photocatalytic ability, and cannot achieve efficient treatment.

[0004] CN105176027A discloses a low-VOC environmentally friendly, high-quality automotive interior material, which is prepared from the following raw materials in parts by weight: polylactic acid 100-103, nano antimony trioxide 3.5-4, decabromodiphenyl ethane 10-11, SEBS 25-27, kenaf fiber 60-62, coconut shell activated carbon 6-7.2, acrylic copolymer emulsion 7-8.5, hydroxypropyl methylcellulose 5-6, porous silica 4-5, nano titanium dioxide 9-10.5, sodium dodecylbenzene sulfonate 2-3, and water in appropriate amounts. Although this material has a good adsorption effect and a certain photocatalytic effect, it can effectively degrade pollutants such as formaldehyde, benzene, toluene, and VOCs, but it can only achieve the effect of purifying the air inside the car. It cannot be widely used in the industrial field, especially in the petroleum and petrochemical fields.

[0005] CN104841369A discloses a honeycomb activated carbon filter air filter element and its preparation method. The raw materials of the honeycomb activated carbon filter air filter element include modified activated carbon, ordinary activated carbon, manganese compounds, activated alumina, and titanium dioxide spray in parts by weight. Similarly, this technical solution uses a combination of adsorption and oxidation to target common indoor pollutants such as formaldehyde and TVOC. The addition of potassium permanganate, a strong oxidant, enhances the ability to remove formaldehyde in a short period of time, but can only achieve the effect of purifying the air inside the vehicle. It is not widely applicable in the industrial field, especially in the petroleum and petrochemical fields.

[0006] Based on the above-mentioned existing technologies, there are technical problems in the existing technologies that need to be solved, such as low loading capacity after the composite of activated carbon and titanium dioxide, low photocatalytic ability, inability to achieve efficient treatment, and inability to effectively adsorb volatile organic compounds such as VOCs generated in the industrial field. Summary of the Invention

[0007] In order to solve the above technical problems, the present invention provides a carbon nitride modified carbon fiber composite material, wherein the carbon nitride modified carbon fiber composite material (PCN / TiO2 / Zn(CH3COO)2-ACF) is composed of phosphorus-doped tubular carbon nitride composite titanium dioxide (PCN / TiO2) and modified activated carbon fiber (Zn(CH3COO)2-ACF), wherein the phosphorus-doped tubular carbon nitride composite titanium dioxide is uniformly distributed on the surface of the modified activated carbon fiber, and the carbon nitride modified carbon fiber composite material has a diffraction angle 2θ of 25.37°±0.2 Characteristic peaks are shown at positions of 0°, 38.60°±0.20°, 48.07°±0.20°, 54.86°±0.20°, and 62.58°±0.20°, and the characteristic peaks correspond to the (001), (101), (112), (200), (211), and (204) crystal planes, indicating the high crystalline nature of titanium dioxide. The carbon nitride-modified carbon fiber composite material contains electron-hole pairs, and the characteristic peak with a diffraction angle 2θ of 25.37°±0.20° corresponds to both the (001) and (101) crystal planes.

[0008] Furthermore, the phosphorus-doped tubular carbon nitride composite titanium dioxide (PCN / TiO2) is composed of phosphorus-doped tubular carbon nitride (PCN) and titanium dioxide (TiO2), the phosphorus-doped tubular carbon nitride accounts for 2-8% by mass of the titanium dioxide, a heterojunction is formed between the phosphorus-doped tubular carbon nitride and the titanium dioxide, the structure of the phosphorus-doped tubular carbon nitride is a tubular structure, the tubular structure has a nanosheet structure layered along the length direction, and the band gap width of the phosphorus-doped tubular carbon nitride is 2.4-2.5 eV;

[0009] The phosphorus-doped tubular carbon nitride is composed of phosphorus element and carbon nitride, the phosphorus element is distributed on the surface of the carbon nitride, the phosphorus-doped tubular carbon nitride composite titanium dioxide shows a characteristic peak at a diffraction angle 2θ of 25.37°±0.20°, the characteristic peak corresponds to the heterojunction (001) crystal plane and the anatase phase (101) crystal plane, and the electron-hole pairs exist on the heterojunction (001) crystal plane and the anatase phase (101) crystal plane;

[0010] The titanium dioxide in the carbon nitride modified carbon fiber composite material is in anatase phase, has a band gap of 2.9-3.0 eV, and is dispersed between layers of the nanosheet layer.

[0011] Furthermore, the modified activated carbon fiber is composed of zinc acetate (Zn(CH3COO)2) and activated carbon fiber (ACF), and the activated carbon fiber is distributed in a bundle-like structure as a whole. Each activated carbon fiber has regular linear grooves on the surface, and the zinc acetate is loaded in the grooves, so that the modified activated carbon fiber has micropores and mesopores, the inner diameter of the micropores is less than 2nm, and the inner diameter of the mesopores is 2-50nm.

[0012] The present invention also provides a method for preparing a carbon nitride modified carbon fiber composite material, comprising the following steps:

[0013] Step 1: Preparation of phosphorus-doped tubular carbon nitride (PCN): Melamine (C3H6N6) and cyanuric acid (C3H3N3O3) are mixed and then reacted with phosphoric acid or phosphate to prepare phosphorus-doped tubular carbon nitride.

[0014] The phosphorus-doped tubular carbon nitride has a tubular structure due to phosphorus doping modification, that is, the phosphorus element affects the hydrogen bond self-assembly process of melamine and cyanuric acid in dimethyl sulfoxide, thereby forming a tubular structure;

[0015] Step 2: preparing a sol-gel solution (PCN / TiO2): adding the phosphorus-doped tubular carbon nitride prepared in step 1 to a tetrabutyl titanate solution to obtain a sol-gel solution;

[0016] Step 3, preparing modified activated carbon fiber (Zn(CH3COO)2-ACF): placing the pretreated activated carbon fiber (ACF) in a zinc acetate solution, ultrasonically stirring, vacuum impregnating, and drying to obtain modified activated carbon fiber;

[0017] Step 4: Preparation of carbon nitride modified carbon fiber composite material (PCN / TiO2 / Zn(CH3COO)2-ACF): Add the modified activated carbon fiber prepared in step 3 to the sol-gel solution prepared in step 2 for loading to obtain a carbon nitride modified carbon fiber composite material.

[0018] Furthermore, the phosphate in step 1 is sodium phosphate.

[0019] Furthermore, the step 1 specifically includes:

[0020] Step 1-1, dissolving melamine in dimethyl sulfoxide to obtain solution A;

[0021] Step 1-2, dissolving cyanuric acid in dimethyl sulfoxide to obtain solution B;

[0022] Step 1-3, mixing solution A and solution B at a mass ratio of (0.5-1):1 at room temperature, adding solution B dropwise to solution A, stirring after the addition, centrifuging, removing the supernatant to obtain a first precipitate, washing the first precipitate with a solvent, and centrifuging again to obtain a second precipitate;

[0023] Step 1-4, mixing the second precipitate and water, wherein the mass ratio of the second precipitate to water is (5-6):120, adding phosphoric acid or a phosphate and stirring to obtain a stirred mixture, wherein the mass ratio of the second precipitate to phosphoric acid or a phosphate is (5-6):(6-8), transferring the stirred mixture to a hydrothermal reactor for hydrothermal reaction to obtain a reaction mixture, centrifuging the reaction mixture, removing the supernatant, obtaining a precipitate, and drying the precipitate to obtain a precursor;

[0024] Step 1-5: The precursor is heated to a holding temperature under the protection of an inert gas and then kept at this temperature to obtain phosphorus-doped tubular carbon nitride.

[0025] Furthermore, in step 1-1, the concentration of melamine in solution A is 0.008-0.033 g / mL.

[0026] Furthermore, in step 1-2, the concentration of cyanuric acid in solution B is 0.02-0.04 g / mL.

[0027] Furthermore, in steps 1-3, the dropwise addition rate is 3-5 d / s, the stirring time is 2-3 h, the stirring temperature is room temperature, the centrifugal rate is 2000-2500 r / min, the centrifugal time is 10-20 min, the solvent is anhydrous ethanol or water, the number of washes is 3-6 times, the re-centrifugation rate is 2000-2500 r / min, and the re-centrifugation time is 10-20 min.

[0028] Furthermore, in steps 1-4, the stirring time is 2-3 hours, the stirring temperature is room temperature, the hydrothermal reaction temperature is 180-200°C, the hydrothermal reaction time is 8-10 hours, the centrifugal rate is 3000-4000 r / min, the centrifugal time is 10-20 minutes, and the drying temperature is 105-120°C and the time is 6-8 hours.

[0029] Furthermore, the inert gas in steps 1-5 is one or more of nitrogen and argon, the holding temperature is 520-550° C., the holding time is 4-5 h, and the heating rate of the programmed temperature is 2.5-5° C. / min.

[0030] Furthermore, the step 2 specifically includes:

[0031] Step 2-1, stirring tetrabutyl titanate, glacial acetic acid and anhydrous ethanol to obtain a solution C;

[0032] Step 2-2, stirring the phosphorus-doped tubular carbon nitride prepared in step 1 with anhydrous ethanol, water, and glacial acetic acid to obtain a solution D;

[0033] Step 2-3: Add solution D dropwise to solution C, continue stirring after the addition is completed at room temperature, and let it stand for aging to obtain a sol-gel solution.

[0034] Titanium dioxide is gradually generated during the process of dropwise addition to aging.

[0035] Furthermore, in step 2-1, the volume ratio of tetrabutyl titanate to glacial acetic acid and anhydrous ethanol is (10-20):(17-20):(30-34), the stirring time is 30-50 min, and the stirring speed is 200-800 r / min.

[0036] Furthermore, in step 2-2, the mass of phosphorus-doped tubular carbon nitride added is 2-8wt% of the mass of titanium dioxide generated in step 2, the volume ratio of anhydrous ethanol, water and glacial acetic acid is (1-10):(5-20):(2-10), the stirring time is 30-40min, and the stirring speed is 200-600r / min.

[0037] Furthermore, glacial acetic acid and anhydrous ethanol are used in both step 2-2 and step 2-1 because the same solvents are used, which facilitates the composite of phosphorus-doped tubular carbon nitride and titanium dioxide.

[0038] Furthermore, in step 2-3, the volume ratio of solution C to solution D is (48-62): (54-86), the dropwise addition rate is 3-5d / s, the stirring time is 2-3h, the stirring speed is 200-600r / min, and the standing time is 24-30h.

[0039] Furthermore, the step 3 specifically includes:

[0040] Step 3-1, pre-treating the activated carbon fiber (ACF): placing the activated carbon fiber in an ethanol solution with ultrasonic stirring, then boiling it in boiling water, and finally drying it to obtain pre-treated activated carbon fiber;

[0041] Step 3-2, preparing modified activated carbon fiber: placing the pretreated activated carbon fiber in a zinc acetate solution and ultrasonically stirring it, vacuum impregnating it after the ultrasonic stirring, and drying it after impregnation to obtain modified activated carbon fiber.

[0042] Furthermore, the amount of ethanol solution used in step 3-1 is sufficient to completely soak the activated carbon fiber, the volume fraction of ethanol in the ethanol solution is 2-15%, the solvent is water, the ultrasonic power is 100-200w, the ultrasonic stirring time is 30-40min, the number of ultrasonic stirring times is greater than or equal to 3 times, the stirring rate is 200-600r / min, the boiling water temperature is 100°C, the boiling time is 45-50min, the purpose is to remove impurities on the surface of the activated carbon fiber, and the drying temperature is 50-105°C.

[0043] Furthermore, the concentration of zinc acetate in the zinc acetate solution in step 3-2 is 0.01-0.1 mol / L, the solvent is water, the ultrasonic power is 100-200 w, the ultrasonic stirring time is 10-20 min, the stirring rate is 200-600 r / min, the immersion time is 10-20 min, the vacuum degree of vacuum impregnation is 0.06-0.08 MPa, and the drying temperature is 50-105° C.

[0044] Furthermore, the ultrasonic stirring to vacuum drying in step 3-2 is repeated at least 3 times.

[0045] Furthermore, the step 4 specifically includes:

[0046] Step 4-1, placing the modified activated carbon fiber into a sol-gel solution, performing ultrasound treatment, and then impregnating the solution after ultrasound treatment to obtain the impregnated modified activated carbon fiber;

[0047] Step 4-2, drying the impregnated modified activated carbon fiber at a constant temperature to complete the loading;

[0048] Step 4-3, placing all the modified activated carbon fibers loaded in step 4-2 back into the sol-gel solution prepared in step 2, repeating the operations of steps 4-1 and 4-2 to perform repeated loading, the number of repeated loading times being greater than or equal to 1, to obtain the final loaded modified activated carbon fibers;

[0049] Step 4-4: calcining the finally loaded modified activated carbon fiber under the protection of an inert gas at a programmed calcination temperature to obtain a carbon nitride modified carbon fiber composite material.

[0050] Furthermore, in step 4-1, the power of ultrasound is 100-300w, the time of ultrasound is 10-20min, and the time of immersion is 30-60min.

[0051] Furthermore, in step 4-2, the constant temperature drying temperature is 105-110° C., and the constant temperature drying time is 2-6 hours.

[0052] Furthermore, in step 4-4, the inert gas is nitrogen, the calcination temperature is 400-650° C., the heating rate of the programmed temperature is 2.5-5° C. / min, and the calcination time is 2-3 h.

[0053] The present invention also provides a use of a carbon nitride modified carbon fiber composite material, wherein the carbon nitride modified carbon fiber composite material is used for photocatalytic oxidation reaction.

[0054] Furthermore, the heterojunction (001) crystal plane and the anatase phase (101) crystal plane where the electron-hole pairs exist in the carbon nitride modified carbon fiber composite material participate in the photocatalytic oxidation reaction at the same time. At the same time, the electron-hole pairs have a strong adsorption ability on the heterojunction (001) crystal plane, resulting in high surface energy and high photocatalytic reaction efficiency.

[0055] Furthermore, the carbon nitride modified carbon fiber composite material is used to degrade VOCs.

[0056] Furthermore, the carbon nitride modified carbon fiber composite material is used to degrade n-hexane in VOCs, with a degradation rate of ≥80.5%.

[0057] Furthermore, after the carbon nitride modified carbon fiber composite material is deactivated, it is regenerated and can be recycled for ≥2 times, and the degradation rate of the regenerated carbon nitride modified carbon fiber composite material is ≥80%.

[0058] Furthermore, the regeneration treatment step is: heating at 450-500° C. for 2-3 hours in a programmed temperature tubular heating furnace to complete the regeneration treatment of the carbon nitride modified carbon fiber composite material.

[0059] The beneficial effects of the present invention are:

[0060] The carbon nitride-modified carbon fiber composite material prepared by the present invention is used to degrade n-hexane in VOCs, with a degradation rate of ≥80.5%. After the carbon nitride-modified carbon fiber composite material is deactivated, it is regenerated and can be recycled ≥2 times. The degradation rate of the regenerated carbon nitride-modified carbon fiber composite material is ≥80%. The preparation method is simple, and compared with the defects of the prior art in which the activated carbon and titanium dioxide are composited with low loading amount, low photocatalytic ability, and inability to achieve efficient treatment, the present invention has significantly improved the mass percentage of phosphorus-doped tubular carbon nitride in titanium dioxide to 2-8%. BRIEF DESCRIPTION OF THE DRAWINGS

[0061] Figure 1 This is a scanning electron microscope image of Test Example 1 of the present invention;

[0062] Figure 2 This is a transmission electron microscope image in Test Example 2 of the present invention;

[0063] Figure 3 This is the X-ray diffraction characterization diagram in Test Example 3 of the present invention;

[0064] Figure 4 This is a comparison chart of the removal effect of n-hexane by the composite material in Test Example 4 of the present invention;

[0065] Figure 5 This is a comparison chart showing the effects of different calcination temperatures on the removal of n-hexane from the composite material in Test Example 5 of the present invention;

[0066] Figure 6 This is a comparison chart showing the effect of the initial concentration of n-hexane on the removal of n-hexane from the composite material in Test Example 6 of the present invention;

[0067] Figure 7 This is a comparison chart of the effects of different space velocities on the removal of n-hexane from the composite material in Test Example 7 of the present invention;

[0068] Figure 8 This is a comparison chart of the effect of light intensity on the removal of n-hexane from the composite material in Test Example 8 of the present invention;

[0069] Figure 9 This is a graph showing the cyclic stability performance of the composite material in Test Example 9 of the present invention. DETAILED DESCRIPTION

[0070] Example 1 Sample 1

[0071] This embodiment provides a method for preparing a carbon nitride-modified carbon fiber composite material, comprising the following steps:

[0072] Step 1: Preparation of phosphorus-doped tubular carbon nitride (PCN): Melamine (C3H6N6) and cyanuric acid (C3H3N3O3) are mixed and reacted with sodium phosphate to prepare phosphorus-doped tubular carbon nitride. Specifically:

[0073] Step 1-1, dissolving 1.26 g of melamine in 60 mL of dimethyl sulfoxide to obtain solution A;

[0074] Step 1-2, dissolving 1.29 g of cyanuric acid in 50 mL of dimethyl sulfoxide to obtain solution B;

[0075] Step 1-3, solution B was added dropwise to solution A at a rate of 3 d / s. After the addition was completed, the mixture was stirred at room temperature for 2 h, centrifuged, and centrifuged in a desktop high-speed centrifuge at 2000 r / min for 10 min. After removing the supernatant, a first precipitate was obtained. The first precipitate was washed with anhydrous ethanol and deionized water in sequence, and care was taken to prevent the first precipitate from agglomerating. The mixture was centrifuged at a speed of 2000 r / min for 20 min each time, and 2.5 g of the second precipitate was obtained after removing the supernatant.

[0076] Step 1-4, the second precipitate was mixed with 60 mL of water, and then 3.92 g of sodium phosphate was added and stirred at room temperature on a magnetic stirrer for 2 h to obtain a stirred mixture, and the stirred mixture was transferred to a hydrothermal reactor for a hydrothermal reaction. The reaction mixture was subjected to a hydrothermal reaction at a temperature of 180 ° C. and a hydrothermal time of 8 h. The supernatant in the reaction mixture was removed and centrifuged at a speed of 3000 r / min for 10 min to obtain a precipitate, which was dried at a drying temperature of 105 ° C. for 6 h to obtain a precursor;

[0077] Step 1-5: heating the precursor to 520° C. for 4 h under nitrogen protection to obtain phosphorus-doped tubular carbon nitride;

[0078] Step 2: Preparation of sol-gel solution (PCN / TiO2): Add the phosphorus-doped tubular carbon nitride prepared in step 1 to a tetrabutyl titanate solution to obtain a sol-gel solution. Specifically:

[0079] Step 2-1, 20 mL of tetrabutyl titanate was stirred with 34 mL of glacial acetic acid and 68 mL of anhydrous ethanol for 30 min at a stirring speed of 200 rpm to obtain a solution C;

[0080] Step 2-2, stirring the phosphorus-doped tubular carbon nitride prepared in step 1 with 20 mL of anhydrous ethanol, 60 mL of water, and 24 mL of glacial acetic acid for 30 min at a stirring speed of 200 r / min to obtain a solution D;

[0081] Glacial acetic acid and anhydrous ethanol are used in both step 2-2 and step 2-1 because the same solvents are used to facilitate the composite of phosphorus-doped tubular carbon nitride and titanium dioxide;

[0082] Step 2-3: Add all the D solution to the C solution at a rate of 5 d / s. Continue stirring after the addition at room temperature. After the stirring is completed, let it stand for aging. The stirring time is 2 h, the stirring speed is 200 r / min, and the standing time is 24 h to obtain a sol-gel solution.

[0083] Titanium dioxide is gradually generated during the process of dropwise addition and aging. In this embodiment, the mass percentage of the phosphorus-doped tubular carbon nitride in the titanium dioxide is 2%;

[0084] Step 3, preparing modified activated carbon fiber (Zn(CH3COO)2-ACF): placing the pretreated activated carbon fiber (ACF) in a zinc acetate solution and ultrasonically stirring, vacuum impregnating after the ultrasonic stirring, and drying after impregnation to obtain modified activated carbon fiber, specifically:

[0085] Step 3-1, pretreating the activated carbon fiber (ACF): cutting the activated carbon fiber into 15 cm × 15 cm squares, placing the activated carbon fiber in an ethanol solution with a volume fraction of 10% ethanol, wherein the solvent in the ethanol solution is water, the ultrasonic power is 100 W, and the ultrasonic stirring time is 30 min. The ultrasonic stirring is repeated three times, and then the activated carbon fiber is placed in boiling water at 100°C for 45 minutes to remove impurities on the surface of the activated carbon fiber. Finally, the activated carbon fiber is dried in an oven at 105°C to obtain the pretreated activated carbon fiber;

[0086] Step 3-2, preparation of modified activated carbon fiber: the pretreated activated carbon fiber was placed in 1L of zinc acetate solution with a zinc acetate concentration of 0.05mol / L and ultrasonically stirred. The solvent in the zinc acetate solution was water. After the ultrasonic stirring, vacuum impregnation was performed. The ultrasonic power was 100w, the ultrasonic stirring time was 10min, the stirring rate was 200r / min, and the vacuum degree was controlled between 0.06-0.08Mpa. The above steps were repeated three times. After impregnation, the fiber was placed in an oven at 105°C for drying to obtain modified activated carbon fiber.

[0087] Step 4: Preparation of carbon nitride modified carbon fiber composite material: Add the modified activated carbon fiber prepared in step 3 to the sol-gel solution prepared in step 2 for loading to obtain a carbon nitride modified carbon fiber composite material. Specifically:

[0088] Step 4-1: Divide the sol-gel solution prepared in step 2 into three equal parts by volume, place all the modified activated carbon fibers prepared in step 3 into one of the sol-gel solutions, perform ultrasound at a power of 100 W for 10 min, and then immerse for 30 min to obtain the impregnated modified activated carbon fibers;

[0089] Step 4-2: Place the impregnated modified activated carbon fiber in a 105°C constant temperature drying oven for drying to complete the first loading;

[0090] Step 4-3, placing all the modified activated carbon fibers loaded in step 4-2 into the sol-gel solution prepared in step 2 again, repeating steps 4-1 and 4-2 twice to obtain the second loaded and final loaded modified activated carbon fibers, respectively;

[0091] Step 4-4: calcining the finally loaded modified activated carbon fiber at 400° C. for 2 h in a programmed temperature tubular heating furnace under the protection of nitrogen to obtain a carbon nitride modified carbon fiber composite material, namely, sample 1.

[0092] In this embodiment, the carbon nitride modified carbon fiber composite material is used to degrade n-hexane in VOCs.

[0093] Example 2 Sample 2

[0094] This embodiment provides a method for preparing a carbon nitride-modified carbon fiber composite material, comprising the following steps:

[0095] Step 1: Preparation of phosphorus-doped tubular carbon nitride (PCN): Melamine (C3H6N6) and cyanuric acid (C3H3N3O3) are mixed and reacted with sodium phosphate to prepare phosphorus-doped tubular carbon nitride. Specifically:

[0096] Step 1-1, dissolving 1.26 g of melamine in 60 mL of dimethyl sulfoxide to obtain solution A;

[0097] Step 1-2, dissolving 1.29 g of cyanuric acid in 50 mL of dimethyl sulfoxide to obtain solution B;

[0098] Step 1-3, solution B was added dropwise to solution A at a rate of 3 d / s. After the addition was completed, the mixture was stirred at room temperature for 2 h, centrifuged, and centrifuged in a desktop high-speed centrifuge at 2000 r / min for 10 min. After removing the supernatant, a first precipitate was obtained. The first precipitate was washed with anhydrous ethanol and deionized water in sequence, and care was taken to prevent the first precipitate from agglomerating. The mixture was centrifuged at a speed of 2000 r / min for 20 min each time, and 2.5 g of the second precipitate was obtained after removing the supernatant.

[0099] Step 1-4, the second precipitate was mixed with 60 mL of water, and then 3.92 g of sodium phosphate was added and stirred at room temperature on a magnetic stirrer for 2 h to obtain a stirred mixture, and the stirred mixture was transferred to a hydrothermal reactor for a hydrothermal reaction. The reaction mixture was subjected to a hydrothermal reaction at a temperature of 180 ° C. and a hydrothermal time of 8 h. The supernatant in the reaction mixture was removed and centrifuged at a speed of 3000 r / min for 10 min to obtain a precipitate, which was dried at a drying temperature of 105 ° C. for 6 h to obtain a precursor;

[0100] Step 1-5: heating the precursor to 520° C. for 4 h under nitrogen protection to obtain phosphorus-doped tubular carbon nitride;

[0101] Step 2: Preparation of sol-gel solution (PCN / TiO2): Add the phosphorus-doped tubular carbon nitride prepared in step 1 to a tetrabutyl titanate solution to obtain a sol-gel solution. Specifically:

[0102] Step 2-1, 20 mL of tetrabutyl titanate was stirred with 34 mL of glacial acetic acid and 68 mL of anhydrous ethanol for 30 min at a stirring speed of 200 rpm to obtain a solution C;

[0103] Step 2-2, stirring the phosphorus-doped tubular carbon nitride prepared in step 1 with 20 mL of anhydrous ethanol, 60 mL of water, and 24 mL of glacial acetic acid for 30 min at a stirring speed of 200 r / min to obtain a solution D;

[0104] Glacial acetic acid and anhydrous ethanol are used in both step 2-2 and step 2-1 because the same solvents are used to facilitate the composite of phosphorus-doped tubular carbon nitride and titanium dioxide;

[0105] Step 2-3: Add all the D solution to the C solution at a rate of 5 d / s. Continue stirring after the addition at room temperature. After the stirring is completed, let it stand for aging. The stirring time is 2 h, the stirring speed is 200 r / min, and the standing time is 24 h to obtain a sol-gel solution.

[0106] Titanium dioxide is gradually generated during the process of dropwise addition and aging. In this embodiment, the mass percentage of the phosphorus-doped tubular carbon nitride in the titanium dioxide is 2%;

[0107] Step 3, preparing modified activated carbon fiber (Zn(CH3COO)2-ACF): placing the pretreated activated carbon fiber (ACF) in a zinc acetate solution and ultrasonically stirring, vacuum impregnating after the ultrasonic stirring, and drying after impregnation to obtain modified activated carbon fiber, specifically:

[0108] Step 3-1, pretreating the activated carbon fiber (ACF): cutting the activated carbon fiber into 15 cm × 15 cm squares, placing the activated carbon fiber in an ethanol solution with a volume fraction of 10% ethanol, wherein the solvent in the ethanol solution is water, the ultrasonic power is 100 W, and the ultrasonic stirring time is 30 min. The ultrasonic stirring is repeated three times, and then the activated carbon fiber is placed in boiling water at 100°C for 45 minutes to remove impurities on the surface of the activated carbon fiber. Finally, the activated carbon fiber is dried in an oven at 105°C to obtain the pretreated activated carbon fiber;

[0109] Step 3-2, preparation of modified activated carbon fiber: the pretreated activated carbon fiber was placed in 1L of zinc acetate solution with a zinc acetate concentration of 0.05mol / L and ultrasonically stirred. The solvent in the zinc acetate solution was water. After the ultrasonic stirring, vacuum impregnation was performed. The ultrasonic power was 100w, the ultrasonic stirring time was 10min, the stirring rate was 200r / min, and the vacuum degree was controlled between 0.06-0.08Mpa. The above steps were repeated three times. After impregnation, the fiber was placed in an oven at 105°C for drying to obtain modified activated carbon fiber.

[0110] Step 4: Preparation of carbon nitride modified carbon fiber composite material: Add the modified activated carbon fiber prepared in step 3 to the sol-gel solution prepared in step 2 for loading to obtain a carbon nitride modified carbon fiber composite material. Specifically:

[0111] Step 4-1: Divide the sol-gel solution prepared in step 2 into three equal parts by volume, place all the modified activated carbon fibers prepared in step 3 into one of the sol-gel solutions, perform ultrasound at a power of 100 W for 10 min, and then immerse for 30 min to obtain the impregnated modified activated carbon fibers;

[0112] Step 4-2: Place the impregnated modified activated carbon fiber in a 105°C constant temperature drying oven for drying to complete the first loading;

[0113] Step 4-3, placing all the modified activated carbon fibers loaded in step 4-2 into the sol-gel solution prepared in step 2 again, repeating steps 4-1 and 4-2 twice to obtain the second loaded and final loaded modified activated carbon fibers, respectively;

[0114] Step 4-4: calcining the finally loaded modified activated carbon fiber at 450° C. for 2 h in a programmed temperature tubular heating furnace under the protection of nitrogen to obtain a carbon nitride modified carbon fiber composite material, namely, Sample 2.

[0115] In this embodiment, the carbon nitride modified carbon fiber composite material is used to degrade n-hexane in VOCs.

[0116] Example 3 Sample 3

[0117] This embodiment provides a method for preparing a carbon nitride-modified carbon fiber composite material, comprising the following steps:

[0118] Step 1: Preparation of phosphorus-doped tubular carbon nitride (PCN): Melamine (C3H6N6) and cyanuric acid (C3H3N3O3) are mixed and reacted with sodium phosphate to prepare phosphorus-doped tubular carbon nitride. Specifically:

[0119] Step 1-1, dissolving 1.26 g of melamine in 60 mL of dimethyl sulfoxide to obtain solution A;

[0120] Step 1-2, dissolving 1.29 g of cyanuric acid in 50 mL of dimethyl sulfoxide to obtain solution B;

[0121] Step 1-3, solution B was added dropwise to solution A at a rate of 3 d / s. After the addition was completed, the mixture was stirred at room temperature for 2 h, centrifuged, and centrifuged in a desktop high-speed centrifuge at 2000 r / min for 10 min. After removing the supernatant, a first precipitate was obtained. The first precipitate was washed with anhydrous ethanol and deionized water in sequence, and care was taken to prevent the first precipitate from agglomerating. The mixture was centrifuged at a speed of 2000 r / min for 20 min each time, and 2.5 g of the second precipitate was obtained after removing the supernatant.

[0122] Step 1-4, the second precipitate was mixed with 60 mL of water, and then 3.92 g of sodium phosphate was added and stirred at room temperature on a magnetic stirrer for 2 h to obtain a stirred mixture, and the stirred mixture was transferred to a hydrothermal reactor for a hydrothermal reaction. The reaction mixture was subjected to a hydrothermal reaction at a temperature of 180 ° C. and a hydrothermal time of 8 h. The supernatant in the reaction mixture was removed and centrifuged at a speed of 3000 r / min for 10 min to obtain a precipitate, which was dried at a drying temperature of 105 ° C. for 6 h to obtain a precursor;

[0123] Step 1-5: heating the precursor to 520° C. for 4 h under nitrogen protection to obtain phosphorus-doped tubular carbon nitride;

[0124] Step 2: Preparation of sol-gel solution (PCN / TiO2): Add the phosphorus-doped tubular carbon nitride prepared in step 1 to a tetrabutyl titanate solution to obtain a sol-gel solution. Specifically:

[0125] Step 2-1, 20 mL of tetrabutyl titanate was stirred with 34 mL of glacial acetic acid and 68 mL of anhydrous ethanol for 30 min at a stirring speed of 200 rpm to obtain a solution C;

[0126] Step 2-2, stirring the phosphorus-doped tubular carbon nitride prepared in step 1 with 20 mL of anhydrous ethanol, 60 mL of water, and 24 mL of glacial acetic acid for 30 min at a stirring speed of 200 r / min to obtain a solution D;

[0127] Glacial acetic acid and anhydrous ethanol are used in both step 2-2 and step 2-1 because the same solvents are used to facilitate the composite of phosphorus-doped tubular carbon nitride and titanium dioxide;

[0128] Step 2-3: Add all the D solution to the C solution at a rate of 5 d / s. Continue stirring after the addition at room temperature. After the stirring is completed, let it stand for aging. The stirring time is 2 h, the stirring speed is 200 r / min, and the standing time is 24 h to obtain a sol-gel solution.

[0129] Titanium dioxide is gradually generated during the process of dropwise addition and aging. In this embodiment, the mass percentage of the phosphorus-doped tubular carbon nitride in the titanium dioxide is 2%;

[0130] Step 3, preparing modified activated carbon fiber (Zn(CH3COO)2-ACF): placing the pretreated activated carbon fiber (ACF) in a zinc acetate solution and ultrasonically stirring, vacuum impregnating after the ultrasonic stirring, and drying after impregnation to obtain modified activated carbon fiber, specifically:

[0131] Step 3-1, pretreating the activated carbon fiber (ACF): cutting the activated carbon fiber into 15 cm × 15 cm squares, placing the activated carbon fiber in an ethanol solution with a volume fraction of 10% ethanol, wherein the solvent in the ethanol solution is water, the ultrasonic power is 100 W, and the ultrasonic stirring time is 30 min. The ultrasonic stirring is repeated three times, and then the activated carbon fiber is placed in boiling water at 100°C for 45 minutes to remove impurities on the surface of the activated carbon fiber. Finally, the activated carbon fiber is dried in an oven at 105°C to obtain the pretreated activated carbon fiber;

[0132] Step 3-2, preparation of modified activated carbon fiber: the pretreated activated carbon fiber was placed in 1L of zinc acetate solution with a zinc acetate concentration of 0.05mol / L and ultrasonically stirred. The solvent in the zinc acetate solution was water. After the ultrasonic stirring, vacuum impregnation was performed. The ultrasonic power was 100w, the ultrasonic stirring time was 10min, the stirring rate was 200r / min, and the vacuum degree was controlled between 0.06-0.08Mpa. The above steps were repeated three times. After impregnation, the fiber was placed in an oven at 105°C for drying to obtain modified activated carbon fiber.

[0133] Step 4: Preparation of carbon nitride modified carbon fiber composite material: Add the modified activated carbon fiber prepared in step 3 to the sol-gel solution prepared in step 2 for loading to obtain a carbon nitride modified carbon fiber composite material. Specifically:

[0134] Step 4-1: Divide the sol-gel solution prepared in step 2 into three equal parts by volume, place all the modified activated carbon fibers prepared in step 3 into one of the sol-gel solutions, perform ultrasound at a power of 100 W for 10 min, and then immerse for 30 min to obtain the impregnated modified activated carbon fibers;

[0135] Step 4-2: Place the impregnated modified activated carbon fiber in a 105°C constant temperature drying oven for drying to complete the first loading;

[0136] Step 4-3, placing all the modified activated carbon fibers loaded in step 4-2 into the sol-gel solution prepared in step 2 again, repeating steps 4-1 and 4-2 twice to obtain the second loaded and final loaded modified activated carbon fibers, respectively;

[0137] Step 4-4: calcining the finally loaded modified activated carbon fiber at 500° C. for 2 h in a programmed temperature tubular heating furnace under the protection of nitrogen to obtain a carbon nitride modified carbon fiber composite material, namely, sample three.

[0138] In this embodiment, the carbon nitride modified carbon fiber composite material is used to degrade n-hexane in VOCs.

[0139] Example 4 Sample 4

[0140] This embodiment provides a method for preparing a carbon nitride-modified carbon fiber composite material, comprising the following steps:

[0141] Step 1: Preparation of phosphorus-doped tubular carbon nitride (PCN): Melamine (C3H6N6) and cyanuric acid (C3H3N3O3) are mixed and reacted with sodium phosphate to prepare phosphorus-doped tubular carbon nitride. Specifically:

[0142] Step 1-1, dissolving 1.26 g of melamine in 60 mL of dimethyl sulfoxide to obtain solution A;

[0143] Step 1-2, dissolving 1.29 g of cyanuric acid in 50 mL of dimethyl sulfoxide to obtain solution B;

[0144] Step 1-3, solution B was added dropwise to solution A at a rate of 3 d / s. After the addition was completed, the mixture was stirred at room temperature for 2 h, centrifuged, and centrifuged in a desktop high-speed centrifuge at 2000 r / min for 10 min. After removing the supernatant, a first precipitate was obtained. The first precipitate was washed with anhydrous ethanol and deionized water in sequence, and care was taken to prevent the first precipitate from agglomerating. The mixture was centrifuged at a speed of 2000 r / min for 20 min each time, and 2.5 g of the second precipitate was obtained after removing the supernatant.

[0145] Step 1-4, the second precipitate was mixed with 60 mL of water, and then 3.92 g of sodium phosphate was added and stirred at room temperature on a magnetic stirrer for 2 h to obtain a stirred mixture, and the stirred mixture was transferred to a hydrothermal reactor for a hydrothermal reaction. The reaction mixture was subjected to a hydrothermal reaction at a temperature of 180 ° C. and a hydrothermal time of 8 h. The supernatant in the reaction mixture was removed and centrifuged at a speed of 3000 r / min for 10 min to obtain a precipitate, which was dried at a drying temperature of 105 ° C. for 6 h to obtain a precursor;

[0146] Step 1-5: heating the precursor to 520° C. for 4 h under nitrogen protection to obtain phosphorus-doped tubular carbon nitride;

[0147] Step 2: Preparation of sol-gel solution (PCN / TiO2): Add the phosphorus-doped tubular carbon nitride prepared in step 1 to a tetrabutyl titanate solution to obtain a sol-gel solution. Specifically:

[0148] Step 2-1, 20 mL of tetrabutyl titanate was stirred with 34 mL of glacial acetic acid and 68 mL of anhydrous ethanol for 30 min at a stirring speed of 200 rpm to obtain a solution C;

[0149] Step 2-2, stirring the phosphorus-doped tubular carbon nitride prepared in step 1 with 20 mL of anhydrous ethanol, 60 mL of water, and 24 mL of glacial acetic acid for 30 min at a stirring speed of 200 r / min to obtain a solution D;

[0150] Glacial acetic acid and anhydrous ethanol are used in both step 2-2 and step 2-1 because the same solvents are used to facilitate the composite of phosphorus-doped tubular carbon nitride and titanium dioxide;

[0151] Step 2-3: Add all the D solution to the C solution at a rate of 5 d / s. Continue stirring after the addition at room temperature. After the stirring is completed, let it stand for aging. The stirring time is 2 h, the stirring speed is 200 r / min, and the standing time is 24 h to obtain a sol-gel solution.

[0152] Titanium dioxide is gradually generated during the process of dropwise addition and aging. In this embodiment, the mass percentage of the phosphorus-doped tubular carbon nitride in the titanium dioxide is 2%;

[0153] Step 3, preparing modified activated carbon fiber (Zn(CH3COO)2-ACF): placing the pretreated activated carbon fiber (ACF) in a zinc acetate solution and ultrasonically stirring, vacuum impregnating after the ultrasonic stirring, and drying after impregnation to obtain modified activated carbon fiber, specifically:

[0154] Step 3-1, pretreating the activated carbon fiber (ACF): cutting the activated carbon fiber into 15 cm × 15 cm squares, placing the activated carbon fiber in an ethanol solution with a volume fraction of 10% ethanol, wherein the solvent in the ethanol solution is water, the ultrasonic power is 100 W, and the ultrasonic stirring time is 30 min. The ultrasonic stirring is repeated three times, and then the activated carbon fiber is placed in boiling water at 100°C for 45 minutes to remove impurities on the surface of the activated carbon fiber. Finally, the activated carbon fiber is dried in an oven at 105°C to obtain the pretreated activated carbon fiber;

[0155] Step 3-2, preparation of modified activated carbon fiber: the pretreated activated carbon fiber was placed in 1L of zinc acetate solution with a zinc acetate concentration of 0.05mol / L and ultrasonically stirred. The solvent in the zinc acetate solution was water. After the ultrasonic stirring, vacuum impregnation was performed. The ultrasonic power was 100w, the ultrasonic stirring time was 10min, the stirring rate was 200r / min, and the vacuum degree was controlled between 0.06-0.08Mpa. The above steps were repeated three times. After impregnation, the fiber was placed in an oven at 105°C for drying to obtain modified activated carbon fiber.

[0156] Step 4: Preparation of carbon nitride modified carbon fiber composite material: Add the modified activated carbon fiber prepared in step 3 to the sol-gel solution prepared in step 2 for loading to obtain a carbon nitride modified carbon fiber composite material. Specifically:

[0157] Step 4-1: Divide the sol-gel solution prepared in step 2 into three equal parts by volume, place all the modified activated carbon fibers prepared in step 3 into one of the sol-gel solutions, perform ultrasound at a power of 100 W for 10 min, and then immerse for 30 min to obtain the impregnated modified activated carbon fibers;

[0158] Step 4-2: Place the impregnated modified activated carbon fiber in a 105°C constant temperature drying oven for drying to complete the first loading;

[0159] Step 4-3, placing all the modified activated carbon fibers loaded in step 4-2 into the sol-gel solution prepared in step 2 again, repeating steps 4-1 and 4-2 twice to obtain the second loaded and final loaded modified activated carbon fibers, respectively;

[0160] Step 4-4: calcining the finally loaded modified activated carbon fiber at 550° C. for 2 h in a programmed temperature tubular heating furnace under the protection of nitrogen to obtain a carbon nitride-modified carbon fiber composite material, namely, Sample 4.

[0161] In this embodiment, the carbon nitride modified carbon fiber composite material is used to degrade n-hexane in VOCs.

[0162] Example 5 Sample 5

[0163] This embodiment provides a method for preparing a carbon nitride-modified carbon fiber composite material, comprising the following steps:

[0164] Step 1: Preparation of phosphorus-doped tubular carbon nitride (PCN): Melamine (C3H6N6) and cyanuric acid (C3H3N3O3) are mixed and reacted with sodium phosphate to prepare phosphorus-doped tubular carbon nitride. Specifically:

[0165] Step 1-1, dissolving 1.26 g of melamine in 60 mL of dimethyl sulfoxide to obtain solution A;

[0166] Step 1-2, dissolving 1.29 g of cyanuric acid in 50 mL of dimethyl sulfoxide to obtain solution B;

[0167] Step 1-3, solution B was added dropwise to solution A at a rate of 3 d / s. After the addition was completed, the mixture was stirred at room temperature for 2 h, centrifuged, and centrifuged in a desktop high-speed centrifuge at 2000 r / min for 10 min. After removing the supernatant, a first precipitate was obtained. The first precipitate was washed with anhydrous ethanol and deionized water in sequence, and care was taken to prevent the first precipitate from agglomerating. The mixture was centrifuged at a speed of 2000 r / min for 20 min each time, and 2.5 g of the second precipitate was obtained after removing the supernatant.

[0168] Step 1-4, the second precipitate was mixed with 60 mL of water, and then 3.92 g of sodium phosphate was added and stirred at room temperature on a magnetic stirrer for 2 h to obtain a stirred mixture, and the stirred mixture was transferred to a hydrothermal reactor for a hydrothermal reaction. The reaction mixture was subjected to a hydrothermal reaction at a temperature of 180 ° C. and a hydrothermal time of 8 h. The supernatant in the reaction mixture was removed and centrifuged at a speed of 3000 r / min for 10 min to obtain a precipitate, which was dried at a drying temperature of 105 ° C. for 6 h to obtain a precursor;

[0169] Step 1-5: heating the precursor to 520° C. for 4 h under nitrogen protection to obtain phosphorus-doped tubular carbon nitride;

[0170] Step 2: Preparation of sol-gel solution (PCN / TiO2): Add the phosphorus-doped tubular carbon nitride prepared in step 1 to a tetrabutyl titanate solution to obtain a sol-gel solution. Specifically:

[0171] Step 2-1, 20 mL of tetrabutyl titanate was stirred with 34 mL of glacial acetic acid and 68 mL of anhydrous ethanol for 30 min at a stirring speed of 200 rpm to obtain a solution C;

[0172] Step 2-2, stirring the phosphorus-doped tubular carbon nitride prepared in step 1 with 20 mL of anhydrous ethanol, 60 mL of water, and 24 mL of glacial acetic acid for 30 min at a stirring speed of 200 r / min to obtain a solution D;

[0173] Glacial acetic acid and anhydrous ethanol are used in both step 2-2 and step 2-1 because the same solvents are used to facilitate the composite of phosphorus-doped tubular carbon nitride and titanium dioxide;

[0174] Step 2-3: Add all the D solution to the C solution at a rate of 5 d / s. Continue stirring after the addition at room temperature. After the stirring is completed, let it stand for aging. The stirring time is 2 h, the stirring speed is 200 r / min, and the standing time is 24 h to obtain a sol-gel solution.

[0175] Titanium dioxide is gradually generated during the process of dropwise addition and aging. In this embodiment, the mass percentage of the phosphorus-doped tubular carbon nitride in titanium dioxide is 4%.

[0176] Step 3, preparing modified activated carbon fiber (Zn(CH3COO)2-ACF): placing the pretreated activated carbon fiber (ACF) in a zinc acetate solution and ultrasonically stirring, vacuum impregnating after the ultrasonic stirring, and drying after impregnation to obtain modified activated carbon fiber, specifically:

[0177] Step 3-1, pretreating the activated carbon fiber (ACF): cutting the activated carbon fiber into 15 cm × 15 cm squares, placing the activated carbon fiber in an ethanol solution with a volume fraction of 10% ethanol, wherein the solvent in the ethanol solution is water, the ultrasonic power is 100 W, and the ultrasonic stirring time is 30 min. The ultrasonic stirring is repeated three times, and then the activated carbon fiber is placed in boiling water at 100°C for 45 minutes to remove impurities on the surface of the activated carbon fiber. Finally, the activated carbon fiber is dried in an oven at 105°C to obtain the pretreated activated carbon fiber;

[0178] Step 3-2, preparation of modified activated carbon fiber: the pretreated activated carbon fiber was placed in 1L of zinc acetate solution with a zinc acetate concentration of 0.05mol / L and ultrasonically stirred. The solvent in the zinc acetate solution was water. After the ultrasonic stirring, vacuum impregnation was performed. The ultrasonic power was 100w, the ultrasonic stirring time was 10min, the stirring rate was 200r / min, and the vacuum degree was controlled between 0.06-0.08Mpa. The above steps were repeated three times. After impregnation, the fiber was placed in an oven at 105°C for drying to obtain modified activated carbon fiber.

[0179] Step 4: Preparation of carbon nitride modified carbon fiber composite material: Add the modified activated carbon fiber prepared in step 3 to the sol-gel solution prepared in step 2 for loading to obtain a carbon nitride modified carbon fiber composite material. Specifically:

[0180] Step 4-1: Divide the sol-gel solution prepared in step 2 into three equal parts by volume, place all the modified activated carbon fibers prepared in step 3 into one of the sol-gel solutions, perform ultrasound at a power of 100 W for 10 min, and then immerse for 30 min to obtain the impregnated modified activated carbon fibers;

[0181] Step 4-2: Place the impregnated modified activated carbon fiber in a 105°C constant temperature drying oven for drying to complete the first loading;

[0182] Step 4-3, placing all the modified activated carbon fibers loaded in step 4-2 into the sol-gel solution prepared in step 2 again, repeating steps 4-1 and 4-2 twice to obtain the second loaded and final loaded modified activated carbon fibers, respectively;

[0183] Step 4-4: calcining the finally loaded modified activated carbon fiber at 400° C. for 2 h in a programmed temperature tubular heating furnace under the protection of nitrogen to obtain a carbon nitride modified carbon fiber composite material, namely, Sample 5.

[0184] In this embodiment, the carbon nitride modified carbon fiber composite material is used to degrade n-hexane in VOCs.

[0185] Example 6 Sample 6

[0186] This embodiment provides a method for preparing a carbon nitride-modified carbon fiber composite material, comprising the following steps:

[0187] Step 1: Preparation of phosphorus-doped tubular carbon nitride (PCN): Melamine (C3H6N6) and cyanuric acid (C3H3N3O3) are mixed and reacted with sodium phosphate to prepare phosphorus-doped tubular carbon nitride. Specifically:

[0188] Step 1-1, dissolving 1.26 g of melamine in 60 mL of dimethyl sulfoxide to obtain solution A;

[0189] Step 1-2, dissolving 1.29 g of cyanuric acid in 50 mL of dimethyl sulfoxide to obtain solution B;

[0190] Step 1-3, solution B was added dropwise to solution A at a rate of 3 d / s. After the addition was completed, the mixture was stirred at room temperature for 2 h, centrifuged, and centrifuged in a desktop high-speed centrifuge at 2000 r / min for 10 min. After removing the supernatant, a first precipitate was obtained. The first precipitate was washed with anhydrous ethanol and deionized water in sequence, and care was taken to prevent the first precipitate from agglomerating. The mixture was centrifuged at a speed of 2000 r / min for 20 min each time, and 2.5 g of the second precipitate was obtained after removing the supernatant.

[0191] Step 1-4, the second precipitate was mixed with 60 mL of water, and then 3.92 g of sodium phosphate was added and stirred at room temperature on a magnetic stirrer for 2 h to obtain a stirred mixture, and the stirred mixture was transferred to a hydrothermal reactor for a hydrothermal reaction. The reaction mixture was subjected to a hydrothermal reaction at a temperature of 180 ° C. and a hydrothermal time of 8 h. The supernatant in the reaction mixture was removed and centrifuged at a speed of 3000 r / min for 10 min to obtain a precipitate, which was dried at a drying temperature of 105 ° C. for 6 h to obtain a precursor;

[0192] Step 1-5: heating the precursor to 520° C. for 4 h under nitrogen protection to obtain phosphorus-doped tubular carbon nitride;

[0193] Step 2: Preparation of sol-gel solution (PCN / TiO2): Add the phosphorus-doped tubular carbon nitride prepared in step 1 to a tetrabutyl titanate solution to obtain a sol-gel solution. Specifically:

[0194] Step 2-1, 20 mL of tetrabutyl titanate was stirred with 34 mL of glacial acetic acid and 68 mL of anhydrous ethanol for 30 min at a stirring speed of 200 rpm to obtain a solution C;

[0195] Step 2-2, stirring the phosphorus-doped tubular carbon nitride prepared in step 1 with 20 mL of anhydrous ethanol, 60 mL of water, and 24 mL of glacial acetic acid for 30 min at a stirring speed of 200 r / min to obtain a solution D;

[0196] Glacial acetic acid and anhydrous ethanol are used in both step 2-2 and step 2-1 because the same solvents are used to facilitate the composite of phosphorus-doped tubular carbon nitride and titanium dioxide;

[0197] Step 2-3: Add all the D solution to the C solution at a rate of 5 d / s. Continue stirring after the addition at room temperature. After the stirring is completed, let it stand for aging. The stirring time is 2 h, the stirring speed is 200 r / min, and the standing time is 24 h to obtain a sol-gel solution.

[0198] Titanium dioxide is gradually generated during the process of dropwise addition and aging. In this embodiment, the mass percentage of the phosphorus-doped tubular carbon nitride in the titanium dioxide is 6%;

[0199] Step 3, preparing modified activated carbon fiber (Zn(CH3COO)2-ACF): placing the pretreated activated carbon fiber (ACF) in a zinc acetate solution and ultrasonically stirring, vacuum impregnating after the ultrasonic stirring, and drying after impregnation to obtain modified activated carbon fiber, specifically:

[0200] Step 3-1, pretreating the activated carbon fiber (ACF): cutting the activated carbon fiber into 15 cm × 15 cm squares, placing the activated carbon fiber in an ethanol solution with a volume fraction of 10% ethanol, wherein the solvent in the ethanol solution is water, the ultrasonic power is 100 W, and the ultrasonic stirring time is 30 min. The ultrasonic stirring is repeated three times, and then the activated carbon fiber is placed in boiling water at 100°C for 45 minutes to remove impurities on the surface of the activated carbon fiber. Finally, the activated carbon fiber is dried in an oven at 105°C to obtain the pretreated activated carbon fiber;

[0201] Step 3-2, preparation of modified activated carbon fiber: the pretreated activated carbon fiber was placed in 1L of zinc acetate solution with a zinc acetate concentration of 0.05mol / L and ultrasonically stirred. The solvent in the zinc acetate solution was water. After the ultrasonic stirring, vacuum impregnation was performed. The ultrasonic power was 100w, the ultrasonic stirring time was 10min, the stirring rate was 200r / min, and the vacuum degree was controlled between 0.06-0.08Mpa. The above steps were repeated three times. After impregnation, the fiber was placed in an oven at 105°C for drying to obtain modified activated carbon fiber.

[0202] Step 4: Preparation of carbon nitride modified carbon fiber composite material: Add the modified activated carbon fiber prepared in step 3 to the sol-gel solution prepared in step 2 for loading to obtain a carbon nitride modified carbon fiber composite material. Specifically:

[0203] Step 4-1: Divide the sol-gel solution prepared in step 2 into three equal parts by volume, place all the modified activated carbon fibers prepared in step 3 into one of the sol-gel solutions, perform ultrasound at a power of 100 W for 10 min, and then immerse for 30 min to obtain the impregnated modified activated carbon fibers;

[0204] Step 4-2: Place the impregnated modified activated carbon fiber in a 105°C constant temperature drying oven for drying to complete the first loading;

[0205] Step 4-3, placing all the modified activated carbon fibers loaded in step 4-2 into the sol-gel solution prepared in step 2 again, repeating steps 4-1 and 4-2 twice to obtain the second loaded and final loaded modified activated carbon fibers, respectively;

[0206] Step 4-4: calcining the finally loaded modified activated carbon fiber at 400° C. for 2 h in a programmed temperature tubular heating furnace under the protection of nitrogen to obtain a carbon nitride-modified carbon fiber composite material, namely, sample six.

[0207] In this embodiment, the carbon nitride modified carbon fiber composite material is used to degrade n-hexane in VOCs.

[0208] Example 7 Sample 7

[0209] This embodiment provides a method for preparing a carbon nitride-modified carbon fiber composite material, comprising the following steps:

[0210] Step 1: Preparation of phosphorus-doped tubular carbon nitride (PCN): Melamine (C3H6N6) and cyanuric acid (C3H3N3O3) are mixed and reacted with sodium phosphate to prepare phosphorus-doped tubular carbon nitride. Specifically:

[0211] Step 1-1, dissolving 1.26 g of melamine in 60 mL of dimethyl sulfoxide to obtain solution A;

[0212] Step 1-2, dissolving 1.29 g of cyanuric acid in 50 mL of dimethyl sulfoxide to obtain solution B;

[0213] Step 1-3, solution B was added dropwise to solution A at a rate of 3 d / s. After the addition was completed, the mixture was stirred at room temperature for 2 h, centrifuged, and centrifuged in a desktop high-speed centrifuge at 2000 r / min for 10 min. After removing the supernatant, a first precipitate was obtained. The first precipitate was washed with anhydrous ethanol and deionized water in sequence, and care was taken to prevent the first precipitate from agglomerating. The mixture was centrifuged at a speed of 2000 r / min for 20 min each time, and 2.5 g of the second precipitate was obtained after removing the supernatant.

[0214] Step 1-4, the second precipitate was mixed with 60 mL of water, and then 3.92 g of sodium phosphate was added and stirred at room temperature on a magnetic stirrer for 2 h to obtain a stirred mixture, and the stirred mixture was transferred to a hydrothermal reactor for a hydrothermal reaction. The reaction mixture was subjected to a hydrothermal reaction at a temperature of 180 ° C. and a hydrothermal time of 8 h. The supernatant in the reaction mixture was removed and centrifuged at a speed of 3000 r / min for 10 min to obtain a precipitate, which was dried at a drying temperature of 105 ° C. for 6 h to obtain a precursor;

[0215] Step 1-5: heating the precursor to 520° C. for 4 h under nitrogen protection to obtain phosphorus-doped tubular carbon nitride;

[0216] Step 2: Preparation of sol-gel solution (PCN / TiO2): Add the phosphorus-doped tubular carbon nitride prepared in step 1 to a tetrabutyl titanate solution to obtain a sol-gel solution. Specifically:

[0217] Step 2-1, 20 mL of tetrabutyl titanate was stirred with 34 mL of glacial acetic acid and 68 mL of anhydrous ethanol for 30 min at a stirring speed of 200 rpm to obtain a solution C;

[0218] Step 2-2, stirring the phosphorus-doped tubular carbon nitride prepared in step 1 with 20 mL of anhydrous ethanol, 60 mL of water, and 24 mL of glacial acetic acid for 30 min at a stirring speed of 200 r / min to obtain a solution D;

[0219] Glacial acetic acid and anhydrous ethanol are used in both step 2-2 and step 2-1 because the same solvents are used to facilitate the composite of phosphorus-doped tubular carbon nitride and titanium dioxide;

[0220] Step 2-3: Add all the D solution to the C solution at a rate of 5 d / s. Continue stirring after the addition at room temperature. After the stirring is completed, let it stand for aging. The stirring time is 2 h, the stirring speed is 200 r / min, and the standing time is 24 h to obtain a sol-gel solution.

[0221] Titanium dioxide is gradually generated during the process of dropwise addition and aging. In this embodiment, the mass percentage of the phosphorus-doped tubular carbon nitride in the titanium dioxide is 8%;

[0222] Step 3, preparing modified activated carbon fiber (Zn(CH3COO)2-ACF): placing the pretreated activated carbon fiber (ACF) in a zinc acetate solution and ultrasonically stirring, vacuum impregnating after the ultrasonic stirring, and drying after impregnation to obtain modified activated carbon fiber, specifically:

[0223] Step 3-1, pretreating the activated carbon fiber (ACF): cutting the activated carbon fiber into 15 cm × 15 cm squares, placing the activated carbon fiber in an ethanol solution with a volume fraction of 10% ethanol, wherein the solvent in the ethanol solution is water, the ultrasonic power is 100 W, and the ultrasonic stirring time is 30 min. The ultrasonic stirring is repeated three times, and then the activated carbon fiber is placed in boiling water at 100°C for 45 minutes to remove impurities on the surface of the activated carbon fiber. Finally, the activated carbon fiber is dried in an oven at 105°C to obtain the pretreated activated carbon fiber;

[0224] Step 3-2, preparation of modified activated carbon fiber: the pretreated activated carbon fiber was placed in 1L of zinc acetate solution with a zinc acetate concentration of 0.05mol / L and ultrasonically stirred. The solvent in the zinc acetate solution was water. After the ultrasonic stirring, vacuum impregnation was performed. The ultrasonic power was 100w, the ultrasonic stirring time was 10min, the stirring rate was 200r / min, and the vacuum degree was controlled between 0.06-0.08Mpa. The above steps were repeated three times. After impregnation, the fiber was placed in an oven at 105°C for drying to obtain modified activated carbon fiber.

[0225] Step 4: Preparation of carbon nitride modified carbon fiber composite material: Add the modified activated carbon fiber prepared in step 3 to the sol-gel solution prepared in step 2 for loading to obtain a carbon nitride modified carbon fiber composite material. Specifically:

[0226] Step 4-1: Divide the sol-gel solution prepared in step 2 into three equal parts by volume, place all the modified activated carbon fibers prepared in step 3 into one of the sol-gel solutions, perform ultrasound at a power of 100 W for 10 min, and then immerse for 30 min to obtain the impregnated modified activated carbon fibers;

[0227] Step 4-2: Place the impregnated modified activated carbon fiber in a 105°C constant temperature drying oven for drying to complete the first loading;

[0228] Step 4-3, placing all the modified activated carbon fibers loaded in step 4-2 into the sol-gel solution prepared in step 2 again, repeating steps 4-1 and 4-2 twice to obtain the second loaded and final loaded modified activated carbon fibers, respectively;

[0229] Step 4-4: calcining the finally loaded modified activated carbon fiber at 400° C. for 2 h in a programmed temperature tubular heating furnace under the protection of nitrogen to obtain a carbon nitride modified carbon fiber composite material, namely, sample seven.

[0230] In this embodiment, the carbon nitride modified carbon fiber composite material is used to degrade n-hexane in VOCs.

[0231] Example 8 Sample 8

[0232] This embodiment provides a method for preparing a carbon nitride-modified carbon fiber composite material, comprising the following steps:

[0233] Step 1: Preparation of phosphorus-doped tubular carbon nitride (PCN): Melamine (C3H6N6) and cyanuric acid (C3H3N3O3) are mixed and reacted with sodium phosphate to prepare phosphorus-doped tubular carbon nitride. Specifically:

[0234] Step 1-1, dissolving 1.26 g of melamine in 60 mL of dimethyl sulfoxide to obtain solution A;

[0235] Step 1-2, dissolving 1.29 g of cyanuric acid in 50 mL of dimethyl sulfoxide to obtain solution B;

[0236] Step 1-3, solution B was added dropwise to solution A at a rate of 3 d / s. After the addition was completed, the mixture was stirred at room temperature for 2 h, centrifuged, and centrifuged in a desktop high-speed centrifuge at 2000 r / min for 10 min. After removing the supernatant, a first precipitate was obtained. The first precipitate was washed with anhydrous ethanol and deionized water in sequence, and care was taken to prevent the first precipitate from agglomerating. The mixture was centrifuged at a speed of 2000 r / min for 20 min each time, and 2.5 g of the second precipitate was obtained after removing the supernatant.

[0237] Step 1-4, the second precipitate was mixed with 60 mL of water, and then 3.92 g of sodium phosphate was added and stirred at room temperature on a magnetic stirrer for 2 h to obtain a stirred mixture, and the stirred mixture was transferred to a hydrothermal reactor for a hydrothermal reaction. The reaction mixture was subjected to a hydrothermal reaction at a temperature of 180 ° C. and a hydrothermal time of 8 h. The supernatant in the reaction mixture was removed and centrifuged at a speed of 3000 r / min for 10 min to obtain a precipitate, which was dried at a drying temperature of 105 ° C. for 6 h to obtain a precursor;

[0238] Step 1-5: heating the precursor to 520° C. for 4 h under nitrogen protection to obtain phosphorus-doped tubular carbon nitride;

[0239] Step 2: Preparation of sol-gel solution (PCN / TiO2): Add the phosphorus-doped tubular carbon nitride prepared in step 1 to a tetrabutyl titanate solution to obtain a sol-gel solution. Specifically:

[0240] Step 2-1, 20 mL of tetrabutyl titanate was stirred with 34 mL of glacial acetic acid and 68 mL of anhydrous ethanol for 30 min at a stirring speed of 200 rpm to obtain a solution C;

[0241] Step 2-2, stirring the phosphorus-doped tubular carbon nitride prepared in step 1 with 20 mL of anhydrous ethanol, 60 mL of water, and 24 mL of glacial acetic acid for 30 min at a stirring speed of 200 r / min to obtain a solution D;

[0242] Glacial acetic acid and anhydrous ethanol are used in both step 2-2 and step 2-1 because the same solvents are used to facilitate the composite of phosphorus-doped tubular carbon nitride and titanium dioxide;

[0243] Step 2-3: Add all the D solution to the C solution at a rate of 5 d / s. Continue stirring after the addition at room temperature. After the stirring is completed, let it stand for aging. The stirring time is 2 h, the stirring speed is 200 r / min, and the standing time is 24 h to obtain a sol-gel solution.

[0244] Titanium dioxide is gradually generated during the process of dropwise addition and aging. In this embodiment, the mass percentage of the phosphorus-doped tubular carbon nitride in the titanium dioxide is 6%;

[0245] Step 3, preparing modified activated carbon fiber (Zn(CH3COO)2-ACF): placing the pretreated activated carbon fiber (ACF) in a zinc acetate solution and ultrasonically stirring, vacuum impregnating after the ultrasonic stirring, and drying after impregnation to obtain modified activated carbon fiber, specifically:

[0246] Step 3-1, pretreating the activated carbon fiber (ACF): cutting the activated carbon fiber into 15 cm × 15 cm squares, placing the activated carbon fiber in an ethanol solution with a volume fraction of 10% ethanol, wherein the solvent in the ethanol solution is water, the ultrasonic power is 100 W, and the ultrasonic stirring time is 30 min. The ultrasonic stirring is repeated three times, and then the activated carbon fiber is placed in boiling water at 100°C for 45 minutes to remove impurities on the surface of the activated carbon fiber. Finally, the activated carbon fiber is dried in an oven at 105°C to obtain the pretreated activated carbon fiber;

[0247] Step 3-2, preparation of modified activated carbon fiber: the pretreated activated carbon fiber was placed in 1L of zinc acetate solution with a zinc acetate concentration of 0.05mol / L and ultrasonically stirred. The solvent in the zinc acetate solution was water. After the ultrasonic stirring, vacuum impregnation was performed. The ultrasonic power was 100w, the ultrasonic stirring time was 10min, the stirring rate was 200r / min, and the vacuum degree was controlled between 0.06-0.08Mpa. The above steps were repeated three times. After impregnation, the fiber was placed in an oven at 105°C for drying to obtain modified activated carbon fiber.

[0248] Step 4: Preparation of carbon nitride modified carbon fiber composite material: Add the modified activated carbon fiber prepared in step 3 to the sol-gel solution prepared in step 2 for loading to obtain a carbon nitride modified carbon fiber composite material. Specifically:

[0249] Step 4-1: Divide the sol-gel solution prepared in step 2 into three equal parts by volume, place all the modified activated carbon fibers prepared in step 3 into one of the sol-gel solutions, perform ultrasound at a power of 100 W for 10 min, and then immerse for 30 min to obtain the impregnated modified activated carbon fibers;

[0250] Step 4-2: Place the impregnated modified activated carbon fiber in a 105°C constant temperature drying oven for drying to complete the first loading;

[0251] Step 4-3, placing all the modified activated carbon fibers loaded in step 4-2 into the sol-gel solution prepared in step 2 again, repeating steps 4-1 and 4-2 twice to obtain the second loaded and final loaded modified activated carbon fibers, respectively;

[0252] Step 4-4: calcining the finally loaded modified activated carbon fiber at 450° C. for 2 h in a programmed temperature tubular heating furnace under the protection of nitrogen to obtain a carbon nitride-modified carbon fiber composite material, namely, Sample 8.

[0253] In this embodiment, the carbon nitride modified carbon fiber composite material is used to degrade n-hexane in VOCs.

[0254] Example 9 Sample 9

[0255] This embodiment provides a method for preparing a carbon nitride-modified carbon fiber composite material, comprising the following steps:

[0256] Step 1: Preparation of phosphorus-doped tubular carbon nitride (PCN): Melamine (C3H6N6) and cyanuric acid (C3H3N3O3) are mixed and reacted with sodium phosphate to prepare phosphorus-doped tubular carbon nitride. Specifically:

[0257] Step 1-1, dissolving 1.26 g of melamine in 60 mL of dimethyl sulfoxide to obtain solution A;

[0258] Step 1-2, dissolving 1.29 g of cyanuric acid in 50 mL of dimethyl sulfoxide to obtain solution B;

[0259] Step 1-3, solution B was added dropwise to solution A at a rate of 3 d / s. After the addition was completed, the mixture was stirred at room temperature for 2 h, centrifuged, and centrifuged in a desktop high-speed centrifuge at 2000 r / min for 10 min. After removing the supernatant, a first precipitate was obtained. The first precipitate was washed with anhydrous ethanol and deionized water in sequence, and care was taken to prevent the first precipitate from agglomerating. The mixture was centrifuged at a speed of 2000 r / min for 20 min each time, and 2.5 g of the second precipitate was obtained after removing the supernatant.

[0260] Step 1-4, the second precipitate was mixed with 60 mL of water, and then 3.92 g of sodium phosphate was added and stirred at room temperature on a magnetic stirrer for 2 h to obtain a stirred mixture, and the stirred mixture was transferred to a hydrothermal reactor for a hydrothermal reaction. The reaction mixture was subjected to a hydrothermal reaction at a temperature of 180 ° C. and a hydrothermal time of 8 h. The supernatant in the reaction mixture was removed and centrifuged at a speed of 3000 r / min for 10 min to obtain a precipitate, which was dried at a drying temperature of 105 ° C. for 6 h to obtain a precursor;

[0261] Step 1-5: heating the precursor to 520° C. for 4 h under nitrogen protection to obtain phosphorus-doped tubular carbon nitride;

[0262] Step 2: Preparation of sol-gel solution (PCN / TiO2): Add the phosphorus-doped tubular carbon nitride prepared in step 1 to a tetrabutyl titanate solution to obtain a sol-gel solution. Specifically:

[0263] Step 2-1, 20 mL of tetrabutyl titanate was stirred with 34 mL of glacial acetic acid and 68 mL of anhydrous ethanol for 30 min at a stirring speed of 200 rpm to obtain a solution C;

[0264] Step 2-2, stirring the phosphorus-doped tubular carbon nitride prepared in step 1 with 20 mL of anhydrous ethanol, 60 mL of water, and 24 mL of glacial acetic acid for 30 min at a stirring speed of 200 r / min to obtain a solution D;

[0265] Glacial acetic acid and anhydrous ethanol are used in both step 2-2 and step 2-1 because the same solvents are used to facilitate the composite of phosphorus-doped tubular carbon nitride and titanium dioxide;

[0266] Step 2-3: Add all the D solution to the C solution at a rate of 5 d / s. Continue stirring after the addition at room temperature. After the stirring is completed, let it stand for aging. The stirring time is 2 h, the stirring speed is 200 r / min, and the standing time is 24 h to obtain a sol-gel solution.

[0267] Titanium dioxide is gradually generated during the process of dropwise addition and aging. In this embodiment, the mass percentage of the phosphorus-doped tubular carbon nitride in the titanium dioxide is 6%;

[0268] Step 3, preparing modified activated carbon fiber (Zn(CH3COO)2-ACF): placing the pretreated activated carbon fiber (ACF) in a zinc acetate solution and ultrasonically stirring, vacuum impregnating after the ultrasonic stirring, and drying after impregnation to obtain modified activated carbon fiber, specifically:

[0269] Step 3-1, pretreating the activated carbon fiber (ACF): cutting the activated carbon fiber into 15 cm × 15 cm squares, placing the activated carbon fiber in an ethanol solution with a volume fraction of 10% ethanol, wherein the solvent in the ethanol solution is water, the ultrasonic power is 100 W, and the ultrasonic stirring time is 30 min. The ultrasonic stirring is repeated three times, and then the activated carbon fiber is placed in boiling water at 100°C for 45 minutes to remove impurities on the surface of the activated carbon fiber. Finally, the activated carbon fiber is dried in an oven at 105°C to obtain the pretreated activated carbon fiber;

[0270] Step 3-2, preparation of modified activated carbon fiber: the pretreated activated carbon fiber was placed in 1L of zinc acetate solution with a zinc acetate concentration of 0.05mol / L and ultrasonically stirred. The solvent in the zinc acetate solution was water. After the ultrasonic stirring, vacuum impregnation was performed. The ultrasonic power was 100w, the ultrasonic stirring time was 10min, the stirring rate was 200r / min, and the vacuum degree was controlled between 0.06-0.08Mpa. The above steps were repeated three times. After impregnation, the fiber was placed in an oven at 105°C for drying to obtain modified activated carbon fiber.

[0271] Step 4: Preparation of carbon nitride modified carbon fiber composite material: Add the modified activated carbon fiber prepared in step 3 to the sol-gel solution prepared in step 2 for loading to obtain a carbon nitride modified carbon fiber composite material. Specifically:

[0272] Step 4-1: Divide the sol-gel solution prepared in step 2 into three equal parts by volume, place all the modified activated carbon fibers prepared in step 3 into one of the sol-gel solutions, perform ultrasound at a power of 100 W for 10 min, and then immerse for 30 min to obtain the impregnated modified activated carbon fibers;

[0273] Step 4-2: Place the impregnated modified activated carbon fiber in a 105°C constant temperature drying oven for drying to complete the first loading;

[0274] Step 4-3, placing all the modified activated carbon fibers loaded in step 4-2 into the sol-gel solution prepared in step 2 again, repeating steps 4-1 and 4-2 twice to obtain the second loaded and final loaded modified activated carbon fibers, respectively;

[0275] Step 4-4: calcining the finally loaded modified activated carbon fiber at 500° C. for 2 h in a programmed temperature tubular heating furnace under the protection of nitrogen to obtain a carbon nitride modified carbon fiber composite material, namely, Sample 9.

[0276] In this embodiment, the carbon nitride modified carbon fiber composite material is used to degrade n-hexane in VOCs.

[0277] Comparative Example 1 Sample 10

[0278] In this comparative example 1, the phosphorus-doped tubular carbon nitride (PCN) in Example 1 was replaced with phosphorus-doped tubular carbon nitride (TCN), and the other conditions remained unchanged to prepare the phosphorus-doped TCN composite material of this comparative example 1, namely, sample 10.

[0279] Comparative Example 2 Sample 11

[0280] In this comparative example 2, titanium dioxide replaces the sol-gel solution (PCN / TiO2) in Example 1 and is directly loaded on the modified activated carbon fiber (Zn(CH3COO)2-ACF). The remaining conditions are the same as those in Example 1, and the titanium dioxide composite material (TiO2 / Zn(CH3COO)2-ACF) of this comparative example 2, namely sample 11, is prepared.

[0281] Test Example 1

[0282] The pretreated activated carbon fiber (ACF), modified activated carbon fiber (Zn(CH3COO)2-ACF), phosphorus-doped tubular carbon nitride (PCN), sol-gel solution (PCN / TiO2), and carbon nitride-modified carbon fiber composite material (PCN / TiO2 / Zn(CH3COO)2-ACF) in Example 1 were subjected to scanning electron microscopy (SEM) testing, and the test results are shown in FIG. Figure 1 .

[0283] like Figure 1 As shown in (a) and (b), (b) is a partial enlarged view of (a): the surface of the activated carbon fiber (ACF) is basically free of particle impurities after pretreatment, which indicates that ethanol and boiling water washing can remove impurities on the surface of the activated carbon fiber. Figure 1 The activated carbon fiber shown in (a) is distributed in a bundle structure. Figure 1 As shown in (b), each activated carbon fiber has regular linear grooves on its surface. These grooves provide a larger contact and sintering surface area for the photocatalyst, which also facilitates photocatalysis and electron adsorption mass transfer. Large gaps exist between the activated carbon fibers. This spatial structure makes it easier for VOCs in the experimental device to contact the active sites on the activated carbon fiber surface, which also facilitates electron mass transfer and reduces pressure drop, thereby increasing the flow space and residence time of n-hexane gas in the activated carbon fibers.

[0284] like Figure 1 As shown in (c) and (d), (d) is a partial enlargement of (c): Compared with the pretreated activated carbon fiber (a), it can be clearly observed that white particles are attached to the modified activated carbon fiber (Zn(CH3COO)2-ACF), indicating that Zn(CH3COO)2 is successfully attached to the activated carbon fiber and the modified activated carbon fiber is successfully prepared. This is because the modification of Zn(CH3COO)2 increases the number of micropores and mesopores and the attachment sites of the modified activated carbon fiber, thereby increasing the adsorption of n-hexane gas and the contact area between the carbon nitride-modified carbon fiber composite material and n-hexane gas, which is beneficial to improving the photocatalytic reaction.

[0285] like Figure 1 As shown in (e): it can be seen that the phosphorus-doped tubular carbon nitride monomer presents a tubular structure, and white spots can be seen on the surface of the phosphorus-doped tubular carbon nitride, proving that the phosphorus element has been successfully doped during the high-temperature firing process.

[0286] like Figure 1 As shown in (f): The sol-gel solution (PCN / TiO2) is prepared by the sol-gel method and is fully mixed during the stirring and aging process to finally form an agglomerated mixture.

[0287] like Figure 1As shown in (g) and (h), (h) is a local enlarged view of (g): It can be clearly observed that the surface of the modified activated carbon fiber (Zn(CH3COO)2-ACF) is successfully loaded with the sol-gel liquid (PCN / TiO2), and the surface of the activated carbon fiber (ACF) has been covered by the sol-gel liquid (PCN / TiO2). The surface of the activated carbon fiber (ACF) remains smooth, but some raised parts can still be seen. This is caused by the agglomeration of the sol-gel liquid (PCN / TiO2) and uneven loading during the ultrasonic stirring and vacuum impregnation process of the material prepared by the sol-gel method.

[0288] Test Example 2

[0289] The phosphorus-doped tubular carbon nitride (PCN) and the sol-gel solution (PCN / TiO2) in Example 1 were subjected to transmission electron microscopy (TEM) testing. The test results are shown in FIG. Figure 2 .

[0290] like Figure 2 As shown in (a) and (b), (b) is a partial magnification of (a): This is an image of phosphorus-doped tubular carbon nitride (PCN). It can be clearly observed that the PCN has a regularly densely distributed thin tubular structure and exhibits lateral stratification. This structure greatly increases the specific surface area of ​​the material. The nanoscale tubular structure of PCN is due to the large atomic radius of phosphorus, which hinders the binding of melamine and cyanuric acid molecules. The smaller PCN tube diameter is more conducive to the multiple reflection and refraction of visible light within the tube, enhancing absorbance and facilitating the transmission of electron-hole pairs. In addition, the smaller tube diameter can increase the specific surface area, increasing the number of active sites for contact with n-hexane gas and photocatalytic reaction.

[0291] like Figure 2 As shown in (c) and (d), (d) is a partial magnification of (c): It can be observed that the sol-gel solution (PCN / TiO2) is composed of black granular titanium dioxide and gray thin-layered PCN. This phenomenon also proves that the titanium dioxide particles are well distributed in the tubular nanosheets of PCN. In the figure, the corresponding heterojunction (001) lattice and TiO2 anatase (101) lattice can be obtained by calculating the lattice spacing and consulting the lattice spacing PDF card. Electron-hole pairs exist on the (001) and (101) crystal planes of the anatase TiO2 heterojunction. At the same time, the surface energy of the bisecting heterojunction lattice (001) is high, the adsorption capacity is strong, and the photocatalytic reaction efficiency is high. At the same time, the two lattices participate in the photocatalytic oxidation reaction. The PCN lattice was not measured in this transmission electron microscope image. This is because PCN is a semiconductor, which is why the PCN lattice was not detected. There is a certain cross-over phenomenon at the intersection of PCN / TiO2 lattices, which may be a new chemical interaction generated during the process of ultrasonic stirring and high-temperature calcination.

[0292] Test Example 3

[0293] The phosphorus-doped TCN in Comparative Example 1, the phosphorus-doped tubular carbon nitride (PCN) in Example 1, and the carbon nitride-modified carbon fiber composites (PCN / TiO2 / Zn(CH3COO)2-ACF) prepared in Examples 1-4, i.e., samples 1 to 4, were subjected to X-ray diffraction characterization. The characterization results are shown in FIG. Figure 3 As shown:

[0294] According to the standard card JCPDS no. 21-1272, the XRD patterns of the carbon nitride modified carbon fiber composite material calcined at 400°C, 450°C, 500°C and 550°C showed characteristic peaks at 25.37°±0.20°, 38.60°±0.20°, 48.07°±0.20°, 54.86°±0.20° and 62.58°±0.20°, which correspond to the (001), (101), (112), (200), (211) and (204) crystal planes, respectively, indicating the high crystalline nature of titanium dioxide. The carbon nitride modified carbon fiber composite material contains electron-hole pairs, wherein the characteristic peak with a diffraction angle 2θ of 25.37°±0.20° corresponds to both the (001) and (101) crystal planes. The phosphorus-doped TCN prepared in Comparative Example 1 and the phosphorus-doped tubular carbon nitride (PCN) prepared in Example 1 exhibit two independent diffraction peaks, attributable to the interplanar spacing of the (002) crystal plane (2θ = 27.3°) and the in-plane structural repeating unit tris-s-triazine of the (100) crystal plane (2θ = 13.2°). These two diffraction peaks are highly consistent with previous reports and match the standard card JCPDS No: 87e1526. As the temperature increases, no rutile phase of TiO2 is observed in the graph, so the characteristic peaks indicate that the TiO2 exists in the anatase phase. Furthermore, the characteristic peaks at 450°C, 500°C, and 550°C are all stronger than those of the carbon nitride-modified carbon fiber composite prepared at 400°C. Furthermore, the intensity of the characteristic peaks increases slowly with increasing temperature. This suggests that increasing temperature can increase the grain size of the composite material and enhance the crystallinity of the TiO2. The characteristic peak of phosphorus-doped tubular carbon nitride (PCN) at 2θ = 27.3° (002 crystal plane) is much stronger than that of TCN, indicating that phosphorus doping has a high degree of crystallinity. After doping modification, the characteristic peaks at both locations still exist and do not shift, indicating that doping modification does not affect the structural morphology of the crystal, and neither the interlayer spacing nor the interlayer pore spacing is changed. Compared with the characteristic peak of carbon nitride-modified carbon fiber composites, the carbon nitride-modified carbon fiber composite shows a small shift at 2θ = 25.37° (101 crystal plane), which also indicates that the phosphorus-doped tubular carbon nitride (PCN) has been loaded onto the carbon nitride-modified carbon fiber composites.

[0295] Test Example 4

[0296] The composite materials prepared in Example 1, Example 5, Example 6, Example 7 and Comparative Example 2 were used to degrade n-hexane in VOCs.

[0297] Figure 4 (a) Effect of PCN mass fraction on the removal of n-hexane by PCN / TiO2 / Zn(CH3COO)2-ACF composite materials, (b) Relationship between ln(C / C0) of the removal efficiency of PCN / TiO2 / Zn(CH3COO)2-ACF composite materials with different mass fractions and illumination time.

[0298] At the initial n-hexane concentration of 200 mg / m 3 , light intensity 24W, air speed 1000h -1 Under the condition of light intensity of 24W, the effect of the mass percentage of phosphorus-doped tubular carbon nitride in titanium dioxide on the efficiency of photocatalytic removal of n-hexane gas by carbon nitride modified carbon fiber composites was studied. Figure 4As shown in (a). When PCN is doped with different mass fractions, the degradation rate of n-hexane by the carbon nitride modified carbon fiber composite material (PCN / TiO2 / Zn(CH3COO)2-ACF) under the irradiation of a 24W high-pressure mercury lamp is higher than that of the titanium dioxide composite material (TiO2 / Zn(CH3COO)2-ACF) in Comparative Example 2. When the mass fraction of PCN doping is 6%, the degradation rate of n-hexane by PCN / TiO2 / Zn(CH3COO)2-ACF is as high as 90.2%. The degradation rate of n-hexane by the TCN / TiO2 / Zn(CH3COO)2-ACF composite material is 87.9%. This also shows that the photocatalytic effect of the TiO2 / Zn(CH3COO)2-ACF composite material doped with PCN is stronger than that of the TCN / TiO2 / Zn(CH3COO)2-ACF composite material. This is because the doping of PCN causes defects in the crystal lattice of the composite material, resulting in more active sites, thereby achieving the effect of improving the photocatalytic activity. With the continuous increase of the doping content of PCN, the photocatalytic efficiency is the best when the doping amount is 6%. The photocatalytic efficiency of composite materials with other doping amounts has decreased, but they are all higher than the removal efficiency of TiO2 / Zn(CH3COO)2-ACF composite materials. This is because the doping ratio of PCN is too low, and the number of photogenerated carriers generated per unit time is too small to improve the photocatalytic effect. On the contrary, when the doping ratio of PCN is too high, the number of photogenerated carriers increases, resulting in the transfer of photoelectrons on the surface of TiO2 photocatalyst. The effective component of photogenerated electrons-holes is weakened, resulting in an increase in the electron-hole recombination rate, which in turn inhibits the photocatalytic effect, and the photocurrent density does not increase with the increase of the doping ratio. Only when the PCN doping ratio is appropriate can the photocurrent density be maximized, the electron-hole recombination rate be reduced, and the transfer of photogenerated electrons can be facilitated, thereby improving the photocatalytic strength of the composite material. Figure 4 The LH model shown in (b) is a linear relationship, indicating that the adsorption process of n-hexane on PCN / TiO2 / Zn(CH3COO)2-ACF composite material can be described by the LH model.

[0299] Test Example 5

[0300] The composite materials prepared in Example 6, Example 8, and Example 9 were used to degrade n-hexane in VOCs.

[0301] The effects of different calcination temperatures (400℃, 450℃, 550℃) on the removal efficiency of n-hexane gas from PCN / TiO2 / Zn(CH3COO)2-ACF composite materials were investigated. Figure 5As shown in the figure, the PCN / TiO2 / Zn(CH3COO)2-ACF composite material showed the highest n-hexane degradation efficiency at a calcination temperature of 450°C. The degradation efficiency of the composite material decreased at calcination temperatures of 400°C and 550°C. The photocatalytic degradation efficiency of n-hexane for the PCN / TiO2 / Zn(CH3COO)2-ACF composite material at 400°C, 450°C, and 550°C was 84.5%, 90.2%, and 80.5%, respectively. The highest removal efficiency for the TCN / TiO2 / Zn(CH3COO)2-ACF composite material was 87.9%. Figure 4 The TiO2 / Zn(CH3COO)2-ACF composite calcined at 450°C achieved a n-hexane removal efficiency of 65.8%. The PCN-doped TiO2 / Zn(CH3COO)2-ACF composite also exhibited higher n-hexane degradation efficiencies than the TiO2 / Zn(CH3COO)2-ACF composite at various calcination temperatures. Furthermore, the TiO2 material exhibited the best photocatalytic performance at 450°C. XRD patterns indicate that as the temperature increases, some of the anatase phase of TiO2 transforms into the rutile phase. The anatase TiO2 content is highest at 450°C. Defect dislocations in the anatase TiO2 lattice doped with PCN generate more vacancies, enhancing photocatalytic performance. BET analysis indicates that the pore size and specific surface area of ​​the composite decrease with increasing calcination temperature. Increasing calcination temperature facilitates the loading of TiO2 onto PCN, thereby enhancing photocatalytic activity. Under high temperature conditions, TiO2 grains tend to grow larger due to sintering, which also leads to a reduction in photocatalytic effect. At the same time, high-temperature calcination will change the number and structure of oxygen-containing functional groups in the PCN / TiO2 / Zn(CH3COO)2-ACF composite material, which will hinder and weaken the transfer of photoelectrons, resulting in enhanced photocatalytic ability. Of course, PCN / TiO2 / Zn(CH3COO)2-ACF has a stronger photocatalytic effect than TCN / TiO2 / Zn(CH3COO)2-ACF because the doping of P element reduces the photocatalytic band gap and effectively inhibits the recombination of electron-hole pairs.

[0302] Test Example 6

[0303] The sample prepared in Example 8 was used to investigate the catalytic degradation of n-hexane at different concentrations.

[0304] At a light intensity of 24W and an air speed of 1000h -1 Under the conditions of calcination temperature of 450℃ and PCN doping ratio of 6%, the initial concentration of n-hexane was 100mg / m 3 , 200mg / m 3 , 500mg / m 3 , 1000mg / m 3The efficiency of removing n-hexane gas by PCN / TiO2 / Zn(CH3COO)2-ACF composite material was studied. Figure 6 As shown in Figure 2, the removal efficiency of n-hexane by PCN / TiO2 / Zn(CH3COO)2-ACF composite material decreases with the increase of the initial concentration of n-hexane. When the initial concentration of n-hexane is 100 mg / m 3 When the n-hexane concentration is 200 mg / m 3 , 500mg / m 3 , 1000mg / m 3 The degradation efficiency of n-hexane is 90.2%, 81.25% and 59.48% respectively, and the initial concentration of n-hexane is 1000 mg / m 3 The reason why the n-hexane removal efficiency of the PCN / TiO2 / Zn(CH3COO)2-ACF composite material is reduced is that the number of photogenerated carriers and free radicals generated per unit time is limited. The photocatalytic degradation reaction of n-hexane relies on the hydroxyl radicals of the photocatalyst. In the early stage of the experimental reaction, there are not many n-hexane molecules attached to the PCN / TiO2 / Zn(CH3COO)2-ACF composite material, and the photocatalytic active sites on the ACF surface are sufficient to degrade n-hexane gas. Increasing the concentration of n-hexane gas will reduce the n-hexane removal efficiency of the PCN / TiO2 / Zn(CH3COO)2-ACF composite material. When the n-hexane gas concentration is too high, the number of photogenerated electrons generated per unit time is constant, and the number of n-hexane molecules per unit time in the reaction system exceeds the number of photogenerated electrons and hydroxyl radicals required for the reaction. This will result in the n-hexane gas not being completely degraded and discharged into the environment. The high concentration of n-hexane gas in the initial stage of the reaction can maintain a very high degradation efficiency. On the one hand, it is due to the photocatalytic effect of the photocatalyst. On the other hand, there are certain adsorption sites on ACF. The adsorption-coupled photocatalysis synergistically degrades n-hexane gas. A large amount of n-hexane gas adheres to the surface of ACF. In this process, the photocatalytic effect continuously produces intermediate products. These intermediate products compete with n-hexane gas for the active sites and adsorption sites of the PCN / TiO2 / Zn(CH3COO)2-ACF composite material, which is also an important factor in the reduction of photocatalytic efficiency and one of the reasons for the reduction of catalyst life.

[0305] Test Example 7

[0306] The sample prepared in Example 8 was used to investigate the catalytic degradation of n-hexane at different space velocities.

[0307] At a light intensity of 24W and an initial concentration of n-hexane of 200mg / m 3Under the conditions of calcination temperature of 450℃ and PCN doping ratio of 6%, the composite material (2cm×2cm) was placed in the reactor, and n-hexane gas was continuously introduced. The space velocity of n-hexane gas was adjusted by flow meter. The results of the experiments were carried out under different n-hexane gas space velocity (1000h -1 , 2000h -1 , 4000h -1 , 6000h -1 ) studied the efficiency of removing n-hexane gas by PCN / TiO2 / Zn(CH3COO)2-ACF composite materials, such as Figure 7 As shown. When the space velocity of n-hexane gas is 1000h -1 When the space velocity of n-hexane gas is 2000h -1 , 4000h -1 , 6000h -1 The n-hexane removal efficiencies of the PCN / TiO2 / Zn(CH3COO)2-ACF composites were 84.6%, 77.25%, and 66.15%, respectively. The data indicate that a higher n-hexane gas space velocity shortens its residence time in the PCN / TiO2 / Zn(CH3COO)2-ACF composite, which hinders its adsorption and degradation by photogenerated electrons, leading to a decrease in the n-hexane removal efficiency. As the space velocity increases, the time it takes for n-hexane to penetrate the PCN / TiO2 / Zn(CH3COO)2-ACF composite decreases, resulting in a decrease in the n-hexane removal efficiency. Lowering the space velocity increases the time it takes for n-hexane to penetrate the composite, increasing the energy gained per unit time and the number of active free radicals, thereby improving the n-hexane removal efficiency of the PCN / TiO2 / Zn(CH3COO)2-ACF composite.

[0308] Test Example 8

[0309] The sample prepared in Example 8 was used to investigate the effect of light intensity on the catalytic degradation of n-hexane.

[0310] At an initial concentration of 200 mg / m 3 , airspeed 1000h -1 The material was calcined at 450℃ and the PCN doping ratio was 6%. The composite material (2cm×2cm) was placed in a reactor and n-hexane gas was continuously introduced. The effect of different light intensities (8W, 16W, 24W) on the removal efficiency of n-hexane gas from PCN / TiO2 / Zn(CH3COO)2-ACF composite material was studied. Figure 8As shown in the figure, the photocatalytic removal efficiency of n-hexane gas by the PCN / TiO2 / Zn(CH3COO)2-ACF composite material was not significantly affected by different light intensities at the beginning of the experimental reaction. However, as time went on, the n-hexane removal efficiency of the PCN / TiO2 / Zn(CH3COO)2-ACF composite material reached a maximum of 90.2% after 6 hours of reaction under irradiation with a 24W high-pressure mercury lamp. Under irradiation with an 8W high-pressure mercury lamp, the composite material achieved a n-hexane removal efficiency of 76.3%. The photocatalytic removal efficiency of n-hexane gas by the PCN / TiO2 / Zn(CH3COO)2-ACF composite material increased significantly with increasing light intensity. Stronger light intensity increases the number of electrons and holes generated per unit time, leading to a greater number of superoxide radicals produced, thus enhancing the photocatalytic activity of the photocatalyst. As light intensity increases, the number of electrons and holes generated per unit time and the recombination rate also increase. This contributes to the relatively small change in n-hexane removal efficiency at light intensities of 24 W and 16 W. Increasing light intensity also enhances the thermal effect of the reaction. The thermal effect on the surface of the PCN / TiO2 / Zn(CH3COO)2-ACF composite is far lower than the composite's adsorption-coupled photocatalytic activity. This results in a disproportionate relationship between light intensity and n-hexane removal efficiency. At a certain wavelength, changes in light intensity during the initial reaction period have little effect on the degradation rate, which can be attributed to the inherent adsorption properties of the PCN / TiO2 / Zn(CH3COO)2-ACF composite. However, as time goes by, on the one hand, the adsorption sites are occupied by n-hexane molecules and some intermediates, and the temperature in the reactor tends to stabilize, and the heat provided by the thermal effect is not conducive to adsorption. On the other hand, the increase in light intensity leads to an increase in the number of electron-hole pairs, which promotes the removal of n-hexane. Of course, the light intensity cannot be increased indefinitely, because the thermal effect will also increase with the increase in light intensity, which will greatly weaken the adsorption of the composite material and create certain safety hazards. In actual industrial production processes, the light intensity that best suits the actual needs should be selected.

[0311] Test Example 9

[0312] In order to explore the cyclic stability of PCN / TiO2 / Zn(CH3COO)2-ACF composite materials in the n-hexane removal experiment, the composite materials were recycled three times, and the n-hexane removal efficiency of the composite materials was compared each time. Figure 9As shown in the figure, during the experimental reaction, n-hexane gas molecules and some intermediate products of gas degradation occupied the adsorption and photocatalytic active sites of the PCN / TiO2 / Zn(CH3COO)2-ACF composite, causing the photocatalyst to lose activity. Therefore, regeneration was performed after each reaction. The PCN / TiO2 / Zn(CH3COO)2-ACF composite was heated at 450°C for 2 hours in a temperature-programmed tubular furnace. After three repeated cycles, the regenerated composite showed a slight decrease in n-hexane removal, but the decrease was not significant. In the first run, the composite achieved an n-hexane removal efficiency of 89.9%. In the second and third runs, the regenerated composite achieved an n-hexane removal efficiency of 84.4% and 83.2%, respectively. This demonstrates the excellent cyclic performance of the PCN / TiO2 / Zn(CH3COO)2-ACF composite and demonstrates its promising application in alkane gas removal.

[0313] It should be understood that the present invention is not limited to what has been described above and shown in the accompanying drawings, and that various modifications and changes may be made without departing from the scope thereof. The scope of the present invention is limited only by the appended claims.

Claims

1. A carbon nitride modified carbon fiber composite material, characterized in that: The carbon nitride modified carbon fiber composite material is composed of phosphorus-doped tubular carbon nitride composite titanium dioxide and modified activated carbon fiber, wherein the phosphorus-doped tubular carbon nitride composite titanium dioxide is uniformly distributed on the surface of the modified activated carbon fiber, and the carbon nitride modified carbon fiber composite material shows characteristic peaks at diffraction angles 2θ of 25.37°±0.20°, 38.60°±0.20°, 48.07°±0.20°, 54.86°±0.20°, and 62.58°±0.20°, and these characteristic peaks correspond to (001), (101), (112), (200), (211), and (204) crystal planes, respectively. The carbon nitride modified carbon fiber composite material contains electron-hole pairs, wherein the characteristic peak at a diffraction angle 2θ of 25.37°±0.20° corresponds to both (001) and (101) crystal planes.

2. The carbon nitride modified carbon fiber composite material according to claim 1, characterized in that: The phosphorus-doped tubular carbon nitride composite titanium dioxide is composed of phosphorus-doped tubular carbon nitride and titanium dioxide, wherein the mass percentage of the phosphorus-doped tubular carbon nitride to the titanium dioxide is 2-8%, and a heterojunction is formed between the phosphorus-doped tubular carbon nitride and the titanium dioxide. The structure of the phosphorus-doped tubular carbon nitride is a tubular structure, and the tubular structure has a nanosheet structure layered along the length direction. The band gap width of the phosphorus-doped tubular carbon nitride is 2.4-2.5 eV; The phosphorus-doped tubular carbon nitride is composed of phosphorus element and carbon nitride, the phosphorus element is distributed on the surface of the carbon nitride, and the phosphorus-doped tubular carbon nitride composite titanium dioxide shows characteristic peaks at a diffraction angle 2θ of 25.37°±0.20°, and these characteristic peaks correspond to the heterojunction (001) crystal plane and the anatase phase (101) crystal plane, respectively. The electron-hole pairs exist on the heterojunction (001) crystal plane and the anatase phase (101) crystal plane; The titanium dioxide in the carbon nitride modified carbon fiber composite material is in anatase phase, has a band gap of 2.9-3.0 eV, and is dispersed between layers of the nanosheet layer.

3. The carbon nitride modified carbon fiber composite material according to claim 2, characterized in that: The modified activated carbon fiber is composed of zinc acetate and activated carbon fiber. The activated carbon fiber is distributed in a bundle structure as a whole. The surface of each activated carbon fiber has regular linear grooves. The zinc acetate is loaded in the grooves, so that the modified activated carbon fiber has micropores and mesopores. The inner diameter of the micropores is less than 2nm, and the inner diameter of the mesopores is 2-50nm.

4. A method for preparing the carbon nitride modified carbon fiber composite material according to any one of claims 1 to 3, characterized in that: The steps include: Step 1, preparing phosphorus-doped tubular carbon nitride: mixing melamine and cyanuric acid and reacting the mixture with phosphoric acid or phosphate to prepare phosphorus-doped tubular carbon nitride; Step 2: preparing a sol-gel solution: adding the phosphorus-doped tubular carbon nitride prepared in step 1 to a tetrabutyl titanate solution to obtain a sol-gel solution; Step 3, preparing modified activated carbon fiber: placing the pretreated activated carbon fiber in a zinc acetate solution, ultrasonically stirring, vacuum impregnating, and drying to obtain modified activated carbon fiber; Step 4: preparing a carbon nitride modified carbon fiber composite material: adding the modified activated carbon fiber prepared in step 3 to the sol-gel solution prepared in step 2 for loading to obtain a carbon nitride modified carbon fiber composite material.

5. The method for preparing the carbon nitride modified carbon fiber composite material according to claim 4, characterized in that: The step 1 specifically includes: Step 1-1, dissolving melamine in dimethyl sulfoxide to obtain solution A; Step 1-2, dissolving cyanuric acid in dimethyl sulfoxide to obtain solution B; Step 1-3, mixing solution A and solution B at a mass ratio of (0.5-1):1 at room temperature, adding solution B dropwise to solution A, stirring after the addition, centrifuging, removing the supernatant to obtain a first precipitate, washing the first precipitate with a solvent, and centrifuging again to obtain a second precipitate; Step 1-4, mixing the second precipitate and water, wherein the mass ratio of the second precipitate to water is (5-6):120, adding phosphoric acid or a phosphate and stirring to obtain a stirred mixture, wherein the mass ratio of the second precipitate to phosphoric acid or a phosphate is (5-6):(6-8), transferring the stirred mixture to a hydrothermal reactor for hydrothermal reaction to obtain a reaction mixture, centrifuging the reaction mixture, removing the supernatant, obtaining a precipitate, and drying the precipitate to obtain a precursor; Step 1-5: The precursor is heated to a holding temperature under the protection of an inert gas and then kept at this temperature to obtain phosphorus-doped tubular carbon nitride.

6. The method for preparing the carbon nitride modified carbon fiber composite material according to claim 4, characterized in that: The step 2 specifically includes: Step 2-1, stirring tetrabutyl titanate, glacial acetic acid and anhydrous ethanol to obtain a solution C; Step 2-2, stirring the phosphorus-doped tubular carbon nitride prepared in step 1 with anhydrous ethanol, water, and glacial acetic acid to obtain a solution D; Step 2-3: add solution D dropwise to solution C, continue stirring after the addition is completed at room temperature, and let it stand for aging to obtain a sol-gel solution.

7. The method for preparing a carbon nitride modified carbon fiber composite material according to claim 4, characterized in that: The step 3 specifically includes: Step 3-1, pre-treating the activated carbon fiber: placing the activated carbon fiber in an ethanol solution with ultrasonic stirring, then boiling it in boiling water, and finally drying it to obtain pre-treated activated carbon fiber; Step 3-2, preparing modified activated carbon fiber: placing the pretreated activated carbon fiber in a zinc acetate solution and ultrasonically stirring it, vacuum impregnating it after the ultrasonic stirring, and drying it after impregnation to obtain modified activated carbon fiber.

8. The method for preparing a carbon nitride modified carbon fiber composite material according to claim 4, characterized in that: The step 4 specifically includes: Step 4-1, placing the modified activated carbon fiber into a sol-gel solution, performing ultrasound treatment, and then impregnating the solution after ultrasound treatment to obtain the impregnated modified activated carbon fiber; Step 4-2, drying the impregnated modified activated carbon fiber at a constant temperature to complete the loading; Step 4-3, placing all the modified activated carbon fibers loaded in step 4-2 back into the sol-gel solution prepared in step 2, repeating the operations of steps 4-1 and 4-2 to perform repeated loading, the number of repeated loading times being greater than or equal to 1, to obtain the final loaded modified activated carbon fibers; Step 4-4: calcining the finally loaded modified activated carbon fiber under the protection of an inert gas at a programmed calcination temperature to obtain a carbon nitride modified carbon fiber composite material.

9. Use of the carbon nitride modified carbon fiber composite material according to any one of claims 1 to 3, characterized in that: The carbon nitride modified carbon fiber composite material is used for photocatalytic oxidation reaction.

10. The use of the carbon nitride modified carbon fiber composite material according to claim 4, characterized in that: The carbon nitride modified carbon fiber composite material is used for degrading n-hexane in VOCs, with a degradation rate of ≥80.5%.

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