Preparation method of multi-scale titanium dioxide fiber / carbon nanotube film composite photocatalyst

Abstract

The present invention belongs to the field of photocatalytic degradation of polluted wastewater and relates to a method for preparing a multi-scale titanium dioxide fiber / carbon nanotube film composite photocatalyst. The method comprises the following steps: while drawing a carbon nanotube array, preparing TiO2 fibers on its surface by microemulsion electrospinning to obtain the multi-scale TiO2 fiber / carbon nanotube film. The multi-scale TiO2 fiber / carbon nanotube film provided by the present invention not only solves the problem of poor mechanical properties of carbon nanotube (CNTs) membranes prepared by methods such as filtration by drawing multi-walled carbon nanotubes (MWCNTs), but also overcomes the problems of TiO2 fibers being brittle and difficult to recycle by loading TiO2 fibers on the CNTs membrane. In addition, the method of preparing TiO2 fibers by electrospinning replaces the method of depositing TiO2 particles on the CNTs membrane, solving the problems of easy shedding of TiO2 particles, high preparation cost, and complex process.

Description

Technical Field

[0001] The invention belongs to the field of photocatalytic degradation of polluted wastewater and relates to a method for preparing a multi-scale titanium dioxide fiber / carbon nanotube film composite photocatalyst. Background Art

[0002] TiO2 is a semiconductor material with numerous advantageous properties, including low price, non-toxicity, high photocatalytic activity, and excellent stability. Due to its outstanding photoelectric properties, TiO2 has garnered significant attention in the field of photocatalysis. However, TiO2 not only has a wide bandgap (electron transitions can only occur upon absorption of ultraviolet light), but also exhibits a high recombination rate of photogenerated electrons and holes in nano-TiO2. Furthermore, TiO2 fibers suffer from poor mechanical properties and fragility, hindering their widespread application in photocatalysis.

[0003] Carbon nanotubes (CNTs) are hollow tubes formed by curling together single or multiple layers of graphite. They possess a unique hollow structure, a large specific surface area, excellent mechanical properties, and good stability. They can serve as TiO2 carriers and form complexes with TiO2, rapidly conducting away photogenerated electrons and inhibiting the recombination of photogenerated electrons and holes. Therefore, prior research has sought to enhance the performance of TiO2 as a photocatalyst by preparing TiO2 / CNTs composite photocatalysts. However, existing TiO2 / CNTs composite photocatalysts suffer from technical issues such as small specific surface area, poor mechanical properties, and easy shedding of TiO2 particles, which also affect their performance. Therefore, the preparation of flexible TiO2 fiber / CNT film composite photocatalysts with excellent mechanical properties, a large specific surface area, and resistance to TiO2 shedding has become increasingly important. Summary of the Invention

[0004] The present invention aims to provide a method for preparing a multi-scale titanium dioxide fiber / carbon nanotube film composite photocatalyst to address the problems of existing TiO2 / CNTs composite photocatalysts, such as small specific surface area, poor mechanical properties, easy shedding of TiO2 particles, and high cost.

[0005] One of the technical solutions of the present invention is a method for preparing a multi-scale TiO2 fiber / carbon nanotube film (TiO2 / CNTs composite film), which includes the following steps: using a roller to stretch a carbon nanotube array, and preparing TiO2 fibers on its surface by microemulsion electrospinning to obtain the multi-scale TiO2 fiber / carbon nanotube film.

[0006] Further, the following steps are included:

[0007] Step 1: Prepare vertically aligned carbon nanotube arrays by chemical vapor deposition; prepare TiO2 precursor emulsion;

[0008] Step 2: A small amount of carbon nanotubes is taken from the edge of the carbon nanotube array and stretched to form a carbon nanotube film. One end of the stretched carbon nanotube array is fixed on a roller. While the roller is rotating, the TiO2 precursor emulsion is electrospun onto the surface of the stretched carbon nanotube film to obtain a composite film composed of carbon nanotube film and TiO2 fibers.

[0009] Step 3: calcining the composite membrane at high temperature to obtain the multi-scale TiO2 fiber / carbon nanotube membrane.

[0010] Furthermore, in step 1, preparing the vertically aligned carbon nanotube array by chemical vapor deposition specifically includes:

[0011] The catalyst and substrate are placed in a chemical vapor deposition apparatus, which is sealed and evacuated, and then heated to raise the chamber temperature to 700-800°C. Acetylene, argon, and chlorine are introduced to react and obtain a 1-5 mm carbon nanotube array.

[0012] Furthermore, the catalyst is FeCl2; the amount of the catalyst added is 0.1-5.0g;

[0013] Furthermore, the vacuuming is to reduce the gas pressure to below 10 mTorr; the acetylene flow rate is 500-700 mL / min; the argon flow rate is 350-450 mL / min; the chlorine flow rate is 4-6 mL / min; and the reaction time is 10-30 min.

[0014] The role of argon is to ensure an inert gas environment in the chamber to prevent oxidation of the generated CNTs, while chlorine plays a mediating role in the formation of carbon nanotubes.

[0015] Furthermore, in step 1, preparing the TiO2 precursor emulsion specifically includes:

[0016] The high molecular weight polymer and surfactant are added to the mixed solution of the organic solvent and the catalyst and mixed evenly. The TiO2 precursor is added dropwise, stirred for reaction, and then the dispersed phase is added and stirred and dispersed to obtain a TiO2 precursor emulsion.

[0017] Furthermore, the high molecular polymer is polyvinylpyrrolidone (PVP), the surfactant is cetyltrimethylammonium bromide (CTAB), the organic solvent is anhydrous ethanol, the catalyst is acetic acid, the TiO2 precursor is tetrabutyl titanate (TBT), and the dispersed phase is liquid paraffin or soybean oil;

[0018] Furthermore, the mass ratio of the polymer and the surfactant is 0.3-0.5:0.05-0.25; the mass ratio of the organic solvent and the catalyst is 6.5-8.35:0.3-0.5; the mass ratio of the polymer and the organic solvent is 0.3-0.5:6.5-8.35; the mass ratio of the TiO2 precursor and the organic solvent is 1.0-3.0:6.5-8.35; the mass ratio of the dispersed phase and the organic solvent is 0.5-2.0:6.5-8.35; the stirring reaction time is 1-5h; and the stirring dispersion time is 2-8h.

[0019] Furthermore, in step 2, the drum speed is 10 to 180 s / rev (i.e., the time for CNTs to wrap around the drum is 10 to 180 s); the electrospinning parameters are: spinning voltage is 10 to 25 kV, flow rate is 0.5 to 3.0 mL / h, and the distance from the spinning needle to the drum is 10 to 20 cm; the number of times the multi-scale TiO2 fiber / carbon nanotube film is wrapped around the drum is 3 to 100;

[0020] The setting of the above parameters will affect the electrospinning process. If the parameters change, the internal structure of the prepared TiO2 fiber will change, thereby affecting the performance of the multi-scale TiO2 fiber / carbon nanotube.

[0021] By changing the drum speed from 10 to 180 s / rpm, fiber membranes with different CNTs ratios were obtained.

[0022] Furthermore, in step 3: high temperature calcination conditions: heating to 500-900°C at a rate of 1-5°C / min and keeping the temperature for 2-5h, and then cooling naturally.

[0023] The role of high-temperature calcination is, on the one hand, to remove the organic polymer polyvinyl pyrrolidone in the electrospinning process, and on the other hand, to degrade the TiO2 precursor into TiO2.

[0024] The second technical solution of the present invention is the multi-scale TiO2 fiber / carbon nanotube film prepared by the above preparation method.

[0025] The third technical solution of the present invention is the application of the above-mentioned multi-scale TiO2 fiber / carbon nanotube film in the photocatalytic degradation of dye wastewater.

[0026] Furthermore, the multi-scale TiO2 fiber / carbon nanotube film is used as a photocatalyst when used for photocatalytic degradation of dye wastewater.

[0027] Compared with the prior art, the present invention has the following beneficial effects:

[0028] Microemulsion electrospinning is a simple and versatile method for producing multi-scale TiO2 fibers. By varying the ratio of the continuous phase to the dispersed phase in the precursor emulsion, the internal structure of the fibers can be flexibly transformed from a multi-channel, hollow structure to a mesoporous structure, effectively increasing the specific surface area of ​​the TiO2 fibers and enhancing their photocatalytic properties. The carbon nanotubes prepared by chemical vapor deposition in this invention are oriented longitudinally. After stretching, the carbon nanotube film is oriented horizontally. The uniform orientation of the carbon nanotubes and the strong van der Waals forces between the carbon nanotubes give the stretched carbon nanotubes excellent mechanical properties. The CNTs membrane obtained by stretching is used to load TiO2 fibers. The preparation process is that each layer of CNTs membrane stretched onto the roller is used as a carrier to receive the electrospun fibers. The electrospun fibers and the CNTs fibers are cross-arranged. As the stretching proceeds, the number of layers of CNTs membrane on the roller increases, and each layer of CNTs membrane loaded with TiO2 fibers will be covered with a layer of CNTs membrane loaded with TiO2 fibers. Finally, the CNTs membrane loaded with TiO2 fibers is a whole membrane. Even after high-temperature calcination, the TiO2 fibers will not fall off because the whole membrane is covered layer by layer and the TiO2 fibers and CNTs fibers are randomly cross-arranged.

[0029] The multi-scale TiO2 fiber / carbon nanotube membrane provided by the present invention not only solves the problem of poor mechanical properties of carbon nanotube (CNTs) membranes prepared by methods such as filtration through multi-walled carbon nanotubes (MWCNTs) drawing, but also overcomes the problems of brittleness and difficulty in recycling of TiO2 fibers by loading TiO2 fibers on CNTs membranes. In addition, the method of preparing TiO2 fibers by electrospinning replaces the CNTs membrane to deposit TiO2 particles, solving the problems of easy shedding of TiO2 particles, high preparation cost and complex process. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] Figure 1 This is a photo of the TiO2 fiber / carbon nanotube film composite photocatalyst prepared in Example 1;

[0031] Figure 2 This is a scanning electron microscope image of the TiO2 fiber / carbon nanotube film composite photocatalyst prepared in Example 1;

[0032] Figure 3 This is a scanning electron micrograph of a cross section of the TiO2 fiber / carbon nanotube film composite photocatalyst prepared in Example 1;

[0033] Figure 4 This is a comparison of the photocatalytic performance of the TiO2 fiber / carbon nanotube film composite photocatalysts prepared in Examples 1-3;

[0034] Figure 5This is a comparison chart of the photocatalytic performance results of the TiO2 fiber / carbon nanotube film composite photocatalyst prepared in Example 3 after three cycles of use;

[0035] Figure 6 This is a photo of the simultaneous electrospinning process to prepare TiO2 composite fibers and CNTs drawing process according to an embodiment of the present invention. DETAILED DESCRIPTION

[0036] Various exemplary embodiments of the present invention will now be described in detail. This detailed description should not be considered as limiting the present invention, but rather as a more detailed description of certain aspects, features, and embodiments of the present invention.

[0037] It should be understood that the terms described herein are intended only to describe particular embodiments and are not intended to limit the present invention. In addition, for numerical ranges herein, it should be understood that each intermediate value between the upper and lower limits of the range is also specifically disclosed. Each smaller range between any intermediate value within a stated value or stated range and any other stated value or intermediate value within the stated range is also encompassed by the present invention. The upper and lower limits of these smaller ranges may be independently included or excluded within the scope.

[0038] Unless otherwise indicated, all technical and scientific terms used herein have the same meaning as commonly understood by those skilled in the art. Although only preferred methods and materials are described herein, any methods and materials similar or equivalent to those described herein may also be used in the practice or testing of the present invention. All documents mentioned in this specification are incorporated by reference to disclose and describe the methods and / or materials associated with the documents. In the event of any conflict with any incorporated document, the contents of this specification shall prevail.

[0039] It will be apparent to those skilled in the art that various modifications and variations may be made to the specific embodiments described herein without departing from the scope or spirit of the invention. Other embodiments will be apparent to those skilled in the art from the description of the invention. The description and examples are intended to be illustrative only.

[0040] The terms “include,” “including,” “have,” “contain,” etc. used in the present invention are open-ended terms, meaning including but not limited to.

[0041] Example 1

[0042] Step 1: Synthesis of MWCNTs: First, FeCl2 and a substrate are placed in an inner quartz tube (the substrate is a quartz substrate, and the FeCl2 catalyst is placed in a ceramic boat at the bottom of the substrate. The amount of FeCl2 added is 3.0g). This inner tube is then placed in a horizontal outer quartz tube. The quartz tube is sealed and the pressure is reduced to below 10mTorr before being heated to 760°C. When the chamber temperature reaches 760°C, acetylene (600mL / min), argon (395mL / min), and chlorine (5mL / min) are introduced. The reaction continues for 20 minutes, after which the reaction returns to its initial state. The height of the prepared CNT array is approximately 1mm.

[0043] Step 2: Preparation of the TiO2 / PVP spinning solution: 0.5g of polyvinylpyrrolidone (PVP) and 0.25g of cetyltrimethylammonium bromide (CTAB) were weighed separately and added to a mixture of 6.5g of anhydrous ethanol and 0.5g of glacial acetic acid, stirring thoroughly. 1.5g of tetrabutyl titanate (TBT) was then added dropwise and stirred for 2h. Afterwards, 1.0g of liquid paraffin was added and stirred for 4h to obtain a uniform microemulsion.

[0044] Step 3: Preparation of TiO2 / CNTs composite film: The prepared precursor microemulsion is poured into a 10mL syringe for electrospinning. The spinning voltage is 15kV, the flow rate is 1.0mL / h, the distance from the spinning needle to the roller is 15cm, and a layer of aluminum foil is wrapped on the roller. At the same time, the prepared CNTs array with a substrate is fixed on an iron stand about 10cm away from the roller, and a blade is used to take a small amount from the edge of the CNTs array prepared by CVD and stretch it. One end of the stretched CNTs is fixed on the roller, and electrospinning and CNTs stretching are carried out simultaneously. The time for the CNTs to wrap around the roller is set to 12s, and the spinning is completed when it is wrapped 30 times. The TiO2 / PVP / CNTs composite fiber membrane was calcined at high temperature in a muffle furnace. The temperature of the muffle furnace was raised from room temperature to 500°C at a rate of 1°C / min and kept at that temperature for 2 hours, and then naturally cooled to obtain a TiO2 / CNTs composite photocatalyst.

[0045] Figure 1 This is a photo of the TiO2 fiber / carbon nanotube film composite photocatalyst prepared in Example 1;

[0046] Figure 2 This is a scanning electron microscope image of the TiO2 fiber / carbon nanotube film composite photocatalyst prepared in Example 1;

[0047] Figure 3 This is a scanning electron microscope image of the cross section of the TiO2 fiber / carbon nanotube film composite photocatalyst prepared in Example 1.

[0048] Depend on Figure 1 It can be seen that the present invention prepares a TiO2 fiber / carbon nanotube membrane. Compared with the current situation where the CNTs membrane prepared by traditional methods such as filtration is just a pile of powder and has no mechanical properties, the TiO2 fiber / carbon nanotube membrane of the present invention has better mechanical properties.

[0049] Depend on Figure 2 and Figure 3 It can be concluded that the TiO2 fiber / carbon nanotube membrane prepared has a diameter of 200-800nm, a pore structure with a composite of macropores and mesopores, and a multi-scale state, which is a multi-scale TiO2 fiber / carbon nanotube membrane. Figure 2 It can be seen that TiO2 fibers are deposited on each layer of CNTs membrane and cross-arranged with the CNTs fibers to a certain extent. At the same time, each layer of TiO2 / CNTs composite fibers will be covered by the next layer of TiO2 / CNTs fibers wound on the roller, eventually forming a whole membrane. Therefore, the TiO2 fibers are firmly bonded to the CNTs membrane.

[0050] The specific surface area of ​​the TiO2 fiber / carbon nanotube film prepared in Example 1 was 215.43 m 2 / g, showing a large specific surface area.

[0051] Example 2

[0052] Step 1: The synthesis process of MWCNTs is as described in Example 1.

[0053] Step 2: Prepare the TiO2 / PVP spinning solution: Add 0.5g PVP and 0.25g CTAB to 6.5g anhydrous ethanol and 0.5g glacial acetic acid, respectively, and stir thoroughly. Once completely dissolved, add 3.75g TBT dropwise. Stir for 2 hours, then add 2.0g liquid paraffin and stir thoroughly to obtain a uniform microemulsion.

[0054] Step 3: Preparation of TiO2 / CNTs composite film: The prepared precursor emulsion is loaded into a disposable syringe, and a layer of aluminum foil is covered on the roller. The spinning voltage is 15kV, the distance from the needle to the roller is 15cm, and the flow rate is 2.0mL / h. The position of the MWCNTs array is the same as in Example 1. The time for the CNTs to wrap around the roller is set to 60s, and the spinning is completed when the CNTs are wrapped 30 times. The TiO2 / PVP / CNTs composite fiber membrane is calcined at high temperature in a muffle furnace. The muffle furnace is heated from room temperature to 500℃ at a rate of 1℃ / min and kept warm for 2h, and then cooled naturally to obtain a TiO2 / CNTs composite photocatalyst.

[0055] Example 3

[0056] Step 1: The synthesis process of MWCNTs is as described in Example 1.

[0057] Step 2: Prepare the TiO2 / PVP spinning solution: Add 0.5g PVP and 0.25g CTAB to 6.5g anhydrous ethanol and 0.5g glacial acetic acid, respectively, and mix thoroughly. Once completely dissolved, add 3.0g TBT dropwise. Stir for 2 hours, then add 1.0g liquid paraffin and stir thoroughly to obtain a uniform microemulsion.

[0058] Step 3: The prepared precursor emulsion is loaded into a disposable syringe, and a layer of aluminum foil is covered on the roller. The spinning voltage is 15kV, the distance from the needle to the roller is 15cm, and the flow rate is 2.0mL / h. The position of the MWCNTs array is the same as in Example 1. The time for the CNTs to wrap around the roller is set to 180s, and the spinning is completed after 30 turns. The TiO2 / PVP / CNTs composite fiber membrane is calcined at high temperature in a muffle furnace. The muffle furnace is heated from room temperature to 500℃ at a rate of 1℃ / min and kept warm for 2h, and then cooled naturally to obtain a TiO2 / CNTs composite photocatalyst.

[0059] Comparative Example 1

[0060] Carbon nanotubes were added to anhydrous ethanol and dispersed by ultrasonication to form a uniform suspension, which was then filtered to form a carbon nanotube film. 1.2 g of PVP was dissolved in 15 mL of anhydrous ethanol and stirred to obtain solution A. 3 mL of anhydrous ethanol, 3 mL of glacial acetic acid, and 3 mL of tetra-n-butyl titanate were mixed and stirred to obtain solution B. Solution B was poured into solution A and stirred for 2 hours to obtain a PVP / TiO2 precursor solution. The solution was added to a 10 mL syringe and electrospun using a voltage of 15 kV, a spinning flow rate of 2 mL / h, and a receiving distance of 10 cm. PVP / TiO2 composite fibers were deposited on the filtered CNT film by electrospinning. The film was then hot-pressed at 200°C and placed in a muffle furnace. The temperature was increased at a rate of 10°C / min to 500°C and maintained for 6 hours. The resulting TiO2 / CNTs composite photocatalyst was then obtained after natural cooling.

[0061] Comparative Example 2

[0062] FeC 32 N8H 16FePc (FePc) as a metal catalyst and carbon source was placed on a quartz glass plate. This was then placed in a quartz glass tube flowing with Ar / H2 gas and heated to 1000°C for high-temperature calcination, resulting in the deposition of an aligned carbon nanotube layer on the quartz glass plate. The prepared carbon nanotube film served as the positive electrode, and a graphite rod served as the negative electrode. Both electrodes were immersed in a sol-gel solution prepared by dissolving 10 mL of tetraisopropyl titanate in 30 mL of ethanol containing 12 wt.% glacial acetic acid, followed by the addition of 0.6 mL of a pH 2 hydrochloric acid-deionized water solution, and magnetically stirring for 1 hour. A voltage of 1 V was then applied between the two electrodes for several minutes, causing electrophoretic deposition of positively charged protonated TiO2 onto the carbon nanotube film. After electrophoretic deposition, the sample was dried at 80°C for 1 hour, resulting in a TiO2-CNTs composite photocatalyst with a TiO2 coating on the surface.

[0063] Effect Verification Example 1

[0064] The photocatalytic degradation performance of the TiO2 / CNTs composite photocatalysts prepared in Examples 1-3 and Comparative Examples 1-2 was tested: a 15 mg / L reactive red solution was prepared, 20 ml of the reactive red solution was measured and placed in a test tube, 7.5 mg of the TiO2 / CNTs composite photocatalyst was cut with scissors, the composite photocatalyst was placed in a test tube, a stirrer was placed in the test tube, and the test tube was placed in a photochemical reactor. The mixture was allowed to stand for 1 hour in the dark, and after adsorption saturation, the photochemical reactor was turned on. Every 20 minutes, a certain amount of solution was measured with a pipette and placed in a glass cuvette. The absorbance at a wavelength of 542 nm was tested on a UV-visible spectrophotometer. The UV spectrophotometer was calibrated with deionized water before testing.

[0065] The experimental results of Examples 1-3 are shown in Figure 4 , Figure 4 In the equation, A0 represents the initial absorbance value, and A represents the absorbance value after a certain period of photocatalytic degradation. Figure 4 It can be concluded that as the degradation time increases, the concentration of reactive red in the solution gradually decreases, and the degradation of reactive red can be basically completed in about 200 minutes.

[0066] After the above-mentioned 200-min photocatalytic degradation experiment, the TiO2 / CNTs composite photocatalyst prepared in Example 1-3 was taken out, and the product morphology was observed to find that the TiO2 / CNTs film remained intact. Scanning electron microscopy showed that its TiO2 fibers did not undergo significant changes and were still cross-arranged with the CNTs. After photocatalytic degradation, the TiO2 / CNTs composite photocatalysts of Example 1-3 showed good stability both macroscopically and microscopically. The reason is that the present invention stretches the carbon nanotube array by roller winding, and simultaneously electrospins titanium dioxide fibers on its surface, so that the titanium dioxide fibers are deposited in the single-layer carbon nanotube film formed by stretching and cross-arranged with the CNTs. The single-layer carbon nanotube film deposited with titanium dioxide fibers will be covered by the next layer of stretched single-layer carbon nanotube film, thereby obtaining a multi-layer carbon nanotube film, which is equivalent to doping titanium dioxide inside the carbon nanotube film, thereby avoiding the shedding of titanium dioxide during the photocatalytic degradation process. Since the TiO2 / CNTs composite photocatalysts prepared in Examples 1-3 did not have technical problems such as film rupture and TiO2 shedding after the 200-min photocatalytic degradation experiment, the TiO2 / CNTs composite photocatalysts prepared in the examples of the present invention can be recycled after being treated with light and deionized water. The TiO2 fiber / carbon nanotube film composite photocatalyst prepared in Example 3 of the present invention was used again for photocatalytic degradation experiment verification under the same conditions (effect verification example 1), and the results are shown in FIG. Figure 5 , Figure 5 The comparison chart of the photocatalytic performance of the TiO2 fiber / carbon nanotube film composite photocatalyst prepared in Example 3 after three cycles of use is shown in FIG. Figure 5 It can be concluded that the catalytic effect of the product prepared by the present invention remains essentially unchanged after three cycles of use, and it has extremely high stability. While the composite films prepared by Comparative Examples 1 and 2 have the same good photocatalytic performance and degradation rate as the product of the present invention, after one photocatalytic degradation experiment, the composite films were removed and found to have varying degrees of cracking. This is because the CNTs in the carbon nanotube film formed by filtration in Comparative Example 1 are oriented in a disordered manner, the van der Waals forces between the CNTs are weak, and the mechanical properties of the carbon nanotube film are poor due to the lack of stretching. In Comparative Example 2, titanium dioxide is vapor-deposited on the surface of the carbon nanotube layer prepared by chemical vapor deposition. Because the titanium dioxide is deposited on the surface of the carbon nanotube layer and has a weak bonding force with the carbon nanotubes, it is easily detached during use, resulting in severe titanium dioxide loss and inability to be recycled.

[0067] Experimental verification revealed that, in Example 1, by adjusting the parameters of step 1 (acetylene flow rate of 500-700 mL / min, argon flow rate of 350-450 mL / min, chlorine flow rate of 4-6 mL / min, and reaction time of 10-30 minutes) to achieve a CNT array height of 1-5 mm, the TiO2 / CNT composite film prepared in step 3 can be prepared without significantly affecting the photocatalytic performance of the final product. However, if the CNT array height exceeds the range specified in the present invention, it may affect the number of layers formed on the roller during CNT drawing, hindering the preparation of the final product.

[0068] Through experimental verification, it was found that the TiO2 spinning solution prepared by adjusting the parameters of step 2 in Example 1 (the mass ratio of the polymer and the surfactant is 0.3-0.5:0.05-0.25; the mass ratio of the organic solvent and the catalyst is 6.5-8.35:0.3-0.5; the mass ratio of the polymer and the organic solvent is 0.3-0.5:6.5-8.35; the mass ratio of the TiO2 precursor and the organic solvent is 1.0-3.0:6.5-8.35; the mass ratio of the dispersed phase and the organic solvent is 0.5-2.0:6.5-8.35; the stirring reaction time is 1-5h; the stirring and dispersion time is 2-8h) can meet the preparation of the TiO2 / CNTs composite film in step 3 and has little effect on the photocatalytic performance of the final product. However, when the above parameters exceed the range defined in the present invention, the complete TiO2 fiber structure cannot be formed during the electrospinning process due to the excessive concentration of the prepared microemulsion, thereby affecting the photocatalytic performance of the final product.

[0069] Through experimental verification, it was found that by adjusting the parameters of step 3 in Example 1 (drum speed 10-180s / rpm; electrospinning parameters: spinning voltage 10-25kV, flow rate 0.5-3.0mL / h, distance from spinning needle to drum 10-20cm; number of windings of the multi-scale TiO2 fiber / carbon nanotube film on the drum 3-100 times; calcination conditions: heating to 500-900℃ at a rate of 1-5℃ / min and keeping warm for 2-5h), the preparation of TiO2 / CNTs composite film can be achieved, and the photocatalytic performance of the final product is not greatly affected. However, when the above parameters exceed the range defined by the present invention, a complete TiO2 fiber / carbon nanotube film cannot be formed or the prepared film is too thick, which affects the formation of TiO2 fibers during the high-temperature calcination process and thus affects the photocatalytic performance of the final product.

[0070] The above are merely preferred embodiments of the present invention, but the scope of protection of the present invention is not limited thereto. Any changes or substitutions that can be easily conceived by a person skilled in the art within the technical scope disclosed in this application should be included in the scope of protection of the present invention. Therefore, the scope of protection of the present invention should be based on the scope of protection of the claims.

Claims

1. A method for preparing a multi-scale TiO2 fiber / carbon nanotube film, characterized in that: The following steps are involved: While the carbon nanotube array is stretched using a roller, TiO2 fibers are prepared on its surface by microemulsion electrospinning to obtain the multi-scale TiO2 fiber / carbon nanotube membrane; the multi-scale TiO2 fiber / carbon nanotube membrane is wound around the roller 3-100 times; each layer of CNTs membrane loaded with TiO2 fibers will be covered with a layer of CNTs membrane loaded with TiO2 fibers, and finally the CNTs membrane loaded with TiO2 fibers is a whole membrane.

2. The method for preparing a multi-scale TiO2 fiber / carbon nanotube film according to claim 1, characterized in that: The following steps are involved: Step 1: Prepare vertically aligned carbon nanotube arrays by chemical vapor deposition; preparing TiO2 precursor emulsion; Step 2: A small amount of carbon nanotubes is taken from the edge of the carbon nanotube array and stretched to form a carbon nanotube film. One end of the stretched carbon nanotube array is fixed on a roller. While the roller is rotating, the TiO2 precursor emulsion is electrospun onto the surface of the stretched carbon nanotube film to obtain a composite film composed of carbon nanotube film and TiO2 fibers. Step 3: calcining the composite membrane at high temperature to obtain the multi-scale TiO2 fiber / carbon nanotube membrane.

3. The method for preparing the multi-scale TiO2 fiber / carbon nanotube film according to claim 2, characterized in that: In step 1, preparing a vertically aligned carbon nanotube array by chemical vapor deposition specifically includes: The catalyst and substrate are placed in a chemical vapor deposition device, which is sealed and evacuated, then heated to raise the chamber temperature to 700-800°C. Acetylene, argon, and chlorine are introduced to react and obtain a 1-5 mm carbon nanotube array.

4. The method for preparing the multi-scale TiO2 fiber / carbon nanotube film according to claim 3, characterized in that: The catalyst is FeCl2; the amount of the catalyst added is 0.1-5.0g; the vacuuming is to reduce the air pressure to below 10 mTorr; the acetylene flow rate is 500-700 mL / min; the argon flow rate is 350-450 mL / min; the chlorine flow rate is 4-6 mL / min; and the reaction time is 10-30 min.

5. The method for preparing the multi-scale TiO2 fiber / carbon nanotube film according to claim 2, characterized in that: In the step 1, preparing the TiO2 precursor emulsion specifically includes: The high molecular weight polymer and surfactant are added to the mixed solution of the organic solvent and the catalyst and mixed evenly. The TiO2 precursor is added dropwise, stirred for reaction, and then the dispersed phase is added and stirred and dispersed to obtain a TiO2 precursor emulsion.

6. The method for preparing the multi-scale TiO2 fiber / carbon nanotube film according to claim 5, characterized in that: The high molecular polymer is polyvinyl pyrrolidone, the surfactant is cetyltrimethylammonium bromide, the organic solvent is anhydrous ethanol, the catalyst is acetic acid, the TiO2 precursor is tetra-n-butyl titanate, and the dispersed phase is liquid paraffin or soybean oil; The mass ratio of the polymer and the surfactant is 0.3-0.5:0.05-0.25; the mass ratio of the organic solvent and the catalyst is 6.5-8.35:0.3-0.5; the mass ratio of the polymer and the organic solvent is 0.3-0.5:6.5-8.35; the mass ratio of the TiO2 precursor and the organic solvent is 1.0-3.0:6.5-8.35; the mass ratio of the dispersed phase and the organic solvent is 0.5-2.0:6.5-8.35; the stirring reaction time is 1-5h; and the stirring dispersion time is 2-8h.

7. The method for preparing a multi-scale TiO2 fiber / carbon nanotube film according to claim 2, wherein: In step 2, the drum speed is 10-180 s / rev; the electrospinning parameters are: spinning voltage is 10-25 kV, flow rate is 0.5-3.0 mL / h, and the distance from the spinning needle to the drum is 10-20 cm; the number of turns of the multi-scale TiO2 fiber / carbon nanotube film on the drum is 3-100; In step 3: high temperature calcination conditions: heating to 500-900°C at a rate of 1-5°C / min and keeping the temperature for 2-5h, and then cooling naturally.

8. A multi-scale TiO2 fiber / carbon nanotube film prepared according to the preparation method according to any one of claims 1 to 7.

9. Use of the multi-scale TiO2 fiber / carbon nanotube film according to claim 8 in photocatalytic degradation of dye wastewater.

10. Use of the multi-scale TiO2 fiber / carbon nanotube film in photocatalytic degradation of dye wastewater according to claim 9, characterized in that: The multi-scale TiO2 fiber / carbon nanotube film serves as a photocatalyst to photocatalytically degrade dye wastewater.

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