Activated carbon-carbon nanotube modified TiO2 composite material and its preparation method and application

Abstract

The present invention discloses an activated carbon-carbon nanotube-modified TiO2 composite material, its preparation method, and application. The activated carbon-carbon nanotube-modified TiO2 composite material is formed from activated carbon and a carbon nanotube-doped TiO2 material; the mass ratio of the activated carbon to the carbon nanotube-doped TiO2 material is 1:7-11; the carbon nanotube-doped TiO2 material is prepared from raw materials including titanate and carbon nanotubes; the mass ratio of the titanate to the carbon nanotubes, calculated as TiO2, is 100:0.08-0.12. The activated carbon-carbon nanotube-modified TiO2 composite material of the present invention exhibits good photocatalytic activity and high formaldehyde treatment efficiency.

Description

Technical Field

[0001] The invention relates to an activated carbon-carbon nanotube modified TiO2 composite material and a preparation method and application thereof. Background Art

[0002] It is widely known that residual formaldehyde after interior decoration poses a significant threat to the human body. Formaldehyde removal has become a major research topic, and low-concentration residual formaldehyde indoors is particularly challenging to treat. Photocatalytic degradation of formaldehyde using photocatalytic materials is an effective approach. Currently, titanium dioxide (TiO2) offers excellent catalytic activity, is non-toxic, low-cost, and pollution-free for formaldehyde treatment. However, TiO2 inherently suffers from the disadvantage of readily recombinating photogenerated electrons and holes, and its photocatalytic degradation rate remains to be improved.

[0003] So far, the main methods for improving the photocatalytic performance of TiO2 include: non-metallic doping, metal doping, non-multi-element co-doping, structural heterojunction, etc. Among them, the most common doping method is non-metallic doping, such as doping with C, N, B, etc.

[0004] Literature has reported that nanomaterials composited with carbon nanotubes and TiO2 can degrade phenol under ultraviolet light at a rate 2.6 times that of pure TiO2.

[0005] CN101723313B discloses a method for preparing a nano-titanium dioxide-carbon nanotube composite material, comprising adding an inorganic titanium salt, an alkali metal carbonate, carbon nanotubes and deionized water to a ball mill, and subjecting the mixture to thorough mixing and reaction by ball milling in the ball mill; annealing the product after the mixed reaction at 450-700° C. under inert gas protection for at least 1 hour, washing and filtering the annealed powder, drying and grinding the powder to obtain a nano-titanium dioxide / carbon nanotube composite material. The composite material can be used as a catalyst, but the degradation effect of formaldehyde is not mentioned.

[0006] CN101053845A discloses a sol-gel method for preparing an activated carbon-titanium dioxide composite photocatalyst and its application. The preparation method comprises first mixing a certain amount of butyl titanate with anhydrous ethanol under constant stirring, then dropwise adding a catalyst composed of water, acetic acid, and anhydrous ethanol while stirring, and continuing to stir to obtain a TiO2 sol. Activated carbon is then added during the sol formation process at a mass ratio of butyl titanate to carbon of 0.1:1. After thorough stirring, the mixture is shaken, vacuum filtered, dried, and heat treated to obtain the activated carbon-titanium dioxide composite photocatalyst. The formaldehyde degradation efficiency of this composite photocatalyst still needs to be further improved.

[0007] CN110394155A discloses a modified activated carbon adsorbent modified with carbon nanotubes and its preparation method. The preparation method comprises: 1) reacting diatomaceous earth and titanium dioxide to form a diatomaceous earth / titanium dioxide composite; 2) calcining montmorillonite; 3) preparing carbon nanotubes; 4) mixing the calcined product with carbon nanotubes, activated carbon, coal tar, and an appropriate amount of water to form a slurry, grinding, and drying; 5) spraying an aqueous solution of methylcellulose on the surface of the product to enhance its activity, and drying to obtain a modified activated carbon adsorbent modified with carbon nanotubes. This patent document also incorporates diatomaceous earth, montmorillonite, methylcellulose, and other components, resulting in a relatively large number of components. Furthermore, the patent document only mentions that the resulting adsorbent has a good adsorption effect but does not mention the specific treatment targets. Summary of the Invention

[0008] In view of this, one object of the present invention is to provide an activated carbon-carbon nanotube-modified TiO2 composite material. Another object of the present invention is to provide a method for preparing the activated carbon-carbon nanotube-modified TiO2 composite material. Yet another object of the present invention is to provide a use of the activated carbon-carbon nanotube-modified TiO2 composite material for removing formaldehyde.

[0009] The present invention adopts the following technical solutions to achieve the above-mentioned purpose.

[0010] In one aspect, the present invention provides an activated carbon-carbon nanotube modified TiO2 composite material, which is formed by activated carbon and carbon nanotube doped TiO2 material;

[0011] Wherein, the mass ratio of the activated carbon to the carbon nanotube-doped TiO2 material is 1:7-11;

[0012] The carbon nanotube-doped TiO2 material is prepared from raw materials including titanate and carbon nanotubes; wherein the mass ratio of titanate to carbon nanotubes calculated as TiO2 is 100:0.08-0.12.

[0013] According to the composite material of the present invention, preferably, the carbon nanotubes are multi-walled carbon nanotubes; and the titanate is selected from one or more of ethyl titanate, isopropyl titanate and n-butyl titanate.

[0014] On the other hand, the present invention also provides a method for preparing the activated carbon-carbon nanotube modified TiO2 composite material as described above, comprising the following steps:

[0015] (1) mixing titanate with a first alcohol solvent and a C1-C4 organic carboxylic acid to obtain a titanium element-containing solution; mixing carbon nanotubes with a second alcohol solvent and water to obtain a carbon nanotube solution;

[0016] (2) adding the carbon nanotube solution to a titanium-containing solution for reaction, aging until a colloidal state is formed, and drying to obtain a carbon nanotube-doped TiO2 material; wherein the mass ratio of the titanate calculated as TiO2 to the mass of the carbon nanotube is 100:0.08-0.12;

[0017] (3) The carbon nanotube-doped TiO2 material and activated carbon are mixed, ground, and calcined to obtain an activated carbon-carbon nanotube-modified TiO2 composite material; wherein the mass ratio of the activated carbon to the carbon nanotube-doped TiO2 material is 1:7-11.

[0018] According to the preparation method of the present invention, preferably, in step (1), the titanate is selected from one or more of ethyl titanate, isopropyl titanate and n-butyl titanate; and the volume proportion of the titanate in the titanium element solution is 13-25%.

[0019] According to the preparation method of the present invention, preferably, in step (1), the first alcohol solvent is selected from one or more of methanol, ethanol, isopropanol and n-butanol; the C1-C4 organic carboxylic acid is selected from one or more of formic acid, acetic acid, n-propionic acid and n-butyric acid; and the second alcohol solvent is selected from one or more of methanol, ethanol, isopropanol and n-butanol.

[0020] According to the preparation method of the present invention, preferably, in step (1), the mass concentration of carbon nanotubes in the carbon nanotube solution is 1.0 to 1.8 g / L.

[0021] According to the preparation method of the present invention, preferably, in step (2), the carbon nanotube solution is added dropwise to the titanium element-containing solution to react for 1 to 4 hours, allowed to stand and age until it becomes colloidal, and dried at 70 to 110° C. for 1.5 to 4.5 hours to obtain the carbon nanotube-doped TiO2 material.

[0022] According to the preparation method of the present invention, preferably, in step (3), the carbon nanotube-doped TiO2 material is mixed with activated carbon, ground, and calcined to obtain an activated carbon-carbon nanotube-modified TiO2 composite material; wherein the calcination temperature is 450-550°C and the calcination time is 1.5-5h.

[0023] According to the preparation method of the present invention, preferably, no surfactant or dispersant is added in steps (1) to (3).

[0024] In another aspect, the present invention further provides a use of the activated carbon-carbon nanotube modified TiO2 composite material as described above in removing harmful gases and treating sewage.

[0025] The activated carbon-carbon nanotube-modified TiO2 composite material of the present invention comprises activated carbon, carbon nanotubes, and TiO2 in a specific ratio, resulting in enhanced photocatalytic activity. Furthermore, compared with pure activated carbon, pure titanium dioxide, and carbon nanotube-doped TiO2 materials, the activated carbon-carbon nanotube-modified TiO2 composite material of the present invention exhibits significantly improved formaldehyde treatment efficiency, particularly at relatively low formaldehyde concentrations. The preparation method of the present invention is simple to operate and exhibits excellent process stability. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] Figure 1 This is a scanning electron microscope image of the activated carbon-carbon nanotube modified TiO2 composite material obtained in Example 1, magnified 50,000 times.

[0027] Figure 2 This is a scanning electron microscope image of the activated carbon-carbon nanotube modified TiO2 composite material obtained in Example 1 at a magnification of 100,000 times.

[0028] Figure 3 This is the Fourier transform infrared (FTIR) image of the activated carbon-carbon nanotube modified TiO2 composite material obtained in Example 1.

[0029] Figure 4 This is the differential thermal analysis - thermogravimetric (DTA-TG) of the activated carbon-carbon nanotube modified TiO2 composite material obtained in Example 1.

[0030] Figure 5 This is the X-ray diffraction (XRD) pattern of the activated carbon-carbon nanotube modified TiO2 composite material obtained in Example 1. DETAILED DESCRIPTION

[0031] The present invention will be further described below with reference to specific embodiments, but the protection scope of the present invention is not limited thereto.

[0032] As mentioned above, while there are reports on activated carbon doping with titanium dioxide (TiO2) and carbon nanotube doping with titanium dioxide (TiO2), to date, there have been no reports on the combined modification of titanium dioxide (TiO2) using a small amount of activated carbon and a very small amount of carbon nanotubes. This is not a conventional option.

[0033] <Activated carbon-carbon nanotube modified TiO2 composite material>

[0034] The activated carbon-carbon nanotube modified TiO2 composite material of the present invention is formed from activated carbon and carbon nanotube-doped TiO2 materials. This can significantly improve the composite material's treatment efficiency for formaldehyde gas, that is, significantly improve the formaldehyde degradation efficiency.

[0035] The mass ratio of activated carbon to carbon nanotube-doped TiO2 material is 1:7-11, preferably 1:8-11, and more preferably 1:8.5-10.5, such as 1:9, 1:9.5, or 1:10. The present invention has found that controlling the ratio of the two within the above range is beneficial for improving the formaldehyde treatment efficiency. However, further increasing the amount of carbon nanotube-doped TiO2 material reduces the formaldehyde treatment efficiency. This may be due to the increased absorption of the photocatalyst, which slows the photon transmission rate and causes the composite material to perform poorly.

[0036] In the present invention, the carbon nanotubes are preferably multi-walled carbon nanotubes. The source of the multi-walled carbon nanotubes is not particularly limited, and they can be purchased from, for example, Shenzhen Nanoport Co., Ltd.

[0037] In the present invention, the carbon nanotube-doped TiO2 material is prepared from raw materials including titanate and carbon nanotubes. The ratio of the mass of titanate calculated as TiO2 to the mass of carbon nanotubes can be 100:0.08-0.12, preferably 100:0.09-0.11, and more preferably 100:0.1-0.11. The present invention has found that controlling the carbon nanotubes within the above range can improve the treatment efficiency of formaldehyde. This may be because the doping of carbon nanotubes within a specific range can suppress the recombination rate of electron-hole pairs, improve the utilization rate of light sources, and enhance the ability of photocatalytic degradation. When the doping amount of carbon nanotubes is too large, the probability of electron collision will increase, which in turn increases the recombination rate of electron-hole pairs, reduces the utilization rate of light sources, and weakens the photocatalytic degradation ability.

[0038] The detailed preparation methods of carbon nanotube-doped TiO2 materials and activated carbon-carbon nanotube-modified TiO2 composite materials are described below.

[0039] Preparation method

[0040] The present invention provides a method for preparing an activated carbon-carbon nanotube-modified TiO2 composite material, comprising: (1) preparing a titanium-containing solution; (2) preparing a carbon nanotube solution; (3) preparing a carbon nanotube-doped TiO2 material; and (4) preparing an activated carbon-carbon nanotube-modified TiO2 composite material. This method is described in detail below.

[0041] Preparation of titanium-containing solution

[0042] Titanate is mixed with the first alcohol solvent and C1-C4 organic carboxylic acid to obtain a titanium element-containing solution, which is beneficial to the doping of carbon nanotubes.

[0043] In certain embodiments, a first alcohol solvent and a C1-C4 organic carboxylic acid are mixed to obtain a mixed solution; and titanate is added to the mixed solution and mixed to obtain a titanium element-containing solution.

[0044] In the present invention, the titanate may be selected from one or more of ethyl titanate, isopropyl titanate, and n-butyl titanate. Preferably, the titanate is selected from one of ethyl titanate, isopropyl titanate, and n-butyl titanate. More preferably, the titanate is selected from isopropyl titanate or n-butyl titanate.

[0045] The first alcohol solvent is selected from one or more of methanol, ethanol, isopropanol and n-butanol. Preferably, the first alcohol solvent is selected from one of methanol, ethanol, isopropanol and n-butanol. More preferably, the first alcohol solvent is selected from ethanol or isopropanol.

[0046] The C1-C4 organic carboxylic acid is selected from one or more of formic acid, acetic acid, n-propionic acid, and n-butyric acid. Preferably, the C1-C4 organic carboxylic acid is selected from one of formic acid, acetic acid, and n-propionic acid. More preferably, the C1-C4 organic carboxylic acid is selected from formic acid or acetic acid.

[0047] In the present invention, the volume ratio of the first alcohol solvent to the C1-C4 organic carboxylic acid is 1.8-3:1, preferably 2-2.6:1, and more preferably 2.3-2.5:1.

[0048] The volume fraction of the titanate in the titanium-containing solution is 13-25%, preferably 15-25%, and more preferably 18-22%, for example 19%, 20%, or 21%. "Volume fraction" refers to the ratio of the volume of the added titanate to the total volume of the titanium-containing solution. This facilitates the doping of carbon nanotubes, resulting in a modified composite material with higher catalytic activity.

[0049] Preparation of carbon nanotube solution

[0050] The carbon nanotubes are mixed with the second alcohol solvent and water to obtain a carbon nanotube solution, which is conducive to doping the carbon nanotubes with titanium dioxide.

[0051] The second alcohol solvent is selected from one or more of methanol, ethanol, isopropanol and n-butanol. Preferably, the second alcohol solvent is selected from one of methanol, ethanol, isopropanol and n-butanol. More preferably, the second alcohol solvent is selected from ethanol or isopropanol.

[0052] In a preferred embodiment, the first alcohol solvent and the second alcohol solvent are the same.

[0053] The volume ratio of the second alcohol solvent to water may be 0.55 to 1.1:1, preferably 0.6 to 1.0:1, and more preferably 0.7 to 0.8:1.

[0054] In certain embodiments, the carbon nanotubes are mixed with a second alcohol solvent and water, and ultrasonicated to completely dissolve the carbon nanotubes to obtain a carbon nanotube solution.

[0055] The mass concentration of carbon nanotubes in the carbon nanotube solution can be 1.0-1.8 g / L, preferably 1.1-1.6 g / L, more preferably 1.25-1.45 g / L, such as 1.3 g / L, 1.38 g / L, and 1.4 g / L, which is beneficial to the uniformity of carbon nanotube-doped titanium dioxide.

[0056] Preparation of Carbon Nanotube-Doped TiO2 Materials

[0057] The carbon nanotube solution is added into a titanium element-containing solution for reaction, aged to a colloidal state, and dried to obtain a carbon nanotube-doped TiO2 material.

[0058] In a preferred embodiment, the carbon nanotube solution is added dropwise to a titanium element-containing solution for reaction, allowed to stand and age until it becomes colloidal, and dried to obtain a carbon nanotube-doped TiO2 material.

[0059] The ratio of the mass of titanate, calculated as TiO2, to the mass of carbon nanotubes is 100:0.08-0.12, preferably 100:0.09-0.11, and more preferably 100:0.1-0.11. The present invention has discovered that controlling the carbon nanotube content within this range can improve formaldehyde treatment efficiency. This is likely because the covalent bonds formed between the carbon nanotubes and the photocatalyst TiO2 effectively separate photogenerated electrons and holes, significantly improving interfacial charge transfer efficiency.

[0060] In the present invention, the temperature of the titanium element-containing solution during dropwise addition may be 15 to 40° C., preferably 20 to 35° C. The reaction time may be 1 to 4 hours, preferably 1.5 to 3 hours, more preferably 2 to 3 hours.

[0061] The drying temperature may be 70 to 110° C., preferably 80 to 100° C., more preferably 85 to 100° C. The drying time may be 1.5 to 4.5 hours, preferably 2 to 4 hours, more preferably 2 to 3.5 hours.

[0062] The aging time may be 24 to 56 hours, preferably 36 to 50 hours, and more preferably 48 to 50 hours.

[0063] According to one embodiment of the present invention, a method for preparing a carbon nanotube-doped TiO2 material is as follows: (1) mixing a titanate with a first alcohol solvent and a C1-C4 organic carboxylic acid to obtain a titanium element-containing solution; mixing carbon nanotubes with a second alcohol solvent and water to obtain a carbon nanotube solution; (2) adding the carbon nanotube solution to the titanium element-containing solution to react, aging to a colloidal state, and drying to obtain a carbon nanotube-doped TiO2 material.

[0064] Preparation of Activated Carbon-Carbon Nanotube Modified TiO2 Composites

[0065] The carbon nanotube-doped TiO2 material is mixed with activated carbon, ground, and calcined to obtain an activated carbon-carbon nanotube-modified TiO2 composite material.

[0066] The mass ratio of activated carbon to carbon nanotube-doped TiO2 material is 1:7-11, preferably 1:8-11, more preferably 1:8.5-10.5, for example 1:9, 1:9.5, 1:10. The present invention has found that controlling the usage ratio of the two within the above range is beneficial to improving the treatment efficiency of formaldehyde.

[0067] In certain preferred embodiments, the carbon nanotube-doped TiO2 material is mixed with activated carbon and ground, and then calcined to obtain an activated carbon-carbon nanotube-modified TiO2 composite material.

[0068] The calcination temperature can be 450-550°C, preferably 470-530°C, more preferably 490-510°C, for example 500°C or 505°C. The calcination time can be 1.5-5 hours, preferably 2-4.5 hours, more preferably 2-3.5 hours. This helps improve the formaldehyde treatment efficiency of the resulting composite material.

[0069] In the present invention, no additional surfactant or dispersant is added.

[0070] Application

[0071] The present invention also provides an application of an activated carbon-carbon nanotube modified TiO2 composite material in removing harmful gases and treating sewage. The harmful gases include formaldehyde.

[0072] The activated carbon-carbon nanotube modified TiO2 composite material of the present invention has potential application prospects in the fields of indoor formaldehyde treatment, sewage treatment, environmental protection and manufacturing of new functional materials.

[0073] The composite material obtained by the present invention has a high formaldehyde treatment efficiency, that is, a high formaldehyde degradation efficiency, especially a high treatment efficiency for lower concentrations of formaldehyde. The formaldehyde concentration can be below 10 ppm, preferably below 8 ppm, and more preferably below 5 ppm.

[0074] The activated carbon-carbon nanotube-modified TiO2 composite material obtained by the present invention achieves a formaldehyde treatment efficiency of over 90%, preferably 90.26%, when treating 5 ppm of formaldehyde gas (i.e., a formaldehyde degradation efficiency). Compared to pure nano-titanium dioxide, the composite material obtained by the present invention improves formaldehyde treatment efficiency by over 40%. Compared to pure activated carbon, the improvement is over 70%. Therefore, the composite material obtained by the present invention still has a good degradation effect on lower concentrations of formaldehyde.

[0075] <Analysis Method>

[0076] Scanning electron microscopy (SEM) characterization: A NOVANANO 230FEG field emission scanning electron microscope (FEI) was used.

[0077] Fourier transform infrared (FTIR) characterization: Shimadzu Instruments Co., Ltd. IRPrestige-21 infrared spectrometer was used.

[0078] Differential thermal analysis-thermogravimetric (DTA-TG) was performed using a HCT-2 differential thermal analysis-thermogravimetric instrument from Beijing Hengjiu Scientific Instruments.

[0079] X-ray diffraction (XRD) characterization: A TD-3000 X-ray diffractometer from Liaoning Dandong Tongda Instrument Factory was used.

[0080] <Methods for treating formaldehyde>

[0081] Specific steps: Weigh 40 mg of the material to be evaluated and place it in formaldehyde gas with a concentration of 5 ppm. Under xenon lamp irradiation for 120 minutes, treat the formaldehyde with a treatment device, pass it through a formaldehyde detection system, and calculate the formaldehyde treatment effect to obtain the formaldehyde degradation efficiency. The materials to be evaluated include the activated carbon-carbon nanotube-modified TiO2 composite material of Example 1, the activated carbon-carbon nanotube-modified TiO2 composite material of the comparative example, as well as activated carbon, titanium dioxide, etc. The formaldehyde treatment efficiency is calculated as follows: (initial formaldehyde concentration V0 - final formaldehyde concentration V1) / initial formaldehyde concentration V0 × 100%.

[0082] The raw materials used in the examples and comparative examples are described below:

[0083] Tetrabutyl titanate: purchased from Tianjin Chemical Reagent Supply and Marketing Company, analytical grade.

[0084] Activated carbon: purchased from Fuchen (Tianjin) Chemical Reagent Co., Ltd., analytical grade.

[0085] Carbon nanotubes were purchased from Shenzhen Nanoport Co., Ltd.

[0086] Example 1

[0087] 30 mL of anhydrous ethanol and 12 mL of glacial acetic acid were mixed to obtain a mixed solution, and 10 mL of tetrabutyl titanate was slowly added dropwise to the mixed solution and mixed uniformly to obtain a titanium-containing solution.

[0088] 0.0023475 g of carbon nanotubes, 7 mL of anhydrous ethanol, and 10 mL of distilled water were mixed, and ultrasonicated to completely dissolve the carbon nanotubes to obtain a carbon nanotube solution.

[0089] The carbon nanotube solution was slowly added dropwise to the titanium element solution. After the addition was completed, stirring was continued for 2 hours. The solution was allowed to stand and aged until it became colloidal. The solution was dried at 100° C. for 2 hours to obtain a carbon nanotube-doped TiO 2 material.

[0090] 0.108 g of the carbon nanotube-doped TiO2 material prepared above and 0.012 g of activated carbon were mixed and ground, and then calcined in a muffle furnace at 500° C. for 2 h to obtain an activated carbon-carbon nanotube-modified TiO2 composite material.

[0091] The activated carbon-carbon nanotube modified TiO2 composite material obtained in Example 1 was characterized.

[0092] Scanning electron microscopy (SEM) characterization Figure 1 and Figure 2 . Figure 1 This is a scanning electron microscope image magnified 50,000 times. Figure 2 This is a scanning electron microscope image magnified 100,000 times. Figure 1 and Figure 2 It can be seen that the obtained activated carbon-carbon nanotube modified TiO2 composite material is spherical and has an obvious pore structure.

[0093] Fourier transform infrared (FTIR) characterization see Figure 3 .Depend on Figure 3 It can be seen that at 3429.43cm -1 The broad peak near 2920.23cm is the characteristic absorption peak of -OH bonded to TiO2 surface or free -OH or -OH on activated carbon surface; -1 、2854.65cm -1 (-CH) symmetric and asymmetric stretching vibration peaks appear at 2357.01cm -1 Caused by the vibration of C=C skeleton in carbon nanotubes; 1543.05cm -1 The absorption peak at 1450.47 cm is caused by the vibration of C=C skeleton or C=O in activated carbon; -1 The absorption peak of -OH in the acid is at 1033.85cm -1 The absorption peak at 833.25cm is the stretching vibration peak of Ti-OC; -1 It is caused by the stretching vibration of the Ti-O bond in the [TiO6] octahedral ligand, indicating the presence of TiO6 groups; 474.49~655.78cm -1 The absorption peak at is the characteristic stretching vibration peak of the Ti-O-Ti skeleton.

[0094] Differential thermal-thermogravimetric (DTA-TG) analysis Figure 4 .Depend on Figure 4The results show an endothermic peak around 80°C, caused by the catalyst removing water and adsorbed ethanol; an exothermic peak around 350°C is due to the conversion of titanium dioxide from amorphous to anatase; the weight loss in the thermogravimetric curve around 380°C is due to the decomposition of carbon nanotubes; and the exothermic peak around 480°C is caused by the conversion of titanium dioxide from anatase to rutile. The weight loss from room temperature to 100°C represents the loss of organic solvent and water remaining in the composite; the weight loss from 100°C to 350°C is due to the conversion of titanium dioxide from amorphous to rutile; the plateau at 350°C represents the weight loss of carbon nanotubes; and the weight loss after 450°C is due to the decomposition of activated carbon in the composite. Differential thermal-thermogravimetric analysis indicates that the resulting composite is successfully doped with carbon nanotubes and exhibits good thermal stability.

[0095] X-ray diffraction (XRD) characterization results are shown in Figure 5 .Depend on Figure 5 It can be seen that the region between 5° and 15° is the amorphous characteristic peak region of activated carbon. The characteristic diffraction peaks at 25.8°, 46.56°, 58.92°, 63.08°, and 66.68° correspond to the (101), (200), (213), (204), and (116) crystal planes of anatase titanium dioxide, respectively. It can be inferred that the crystal form of titanium dioxide in the composite material is mainly anatase, and the characteristic diffraction peak of rutile titanium dioxide is not obvious. The diffraction peak of carbon nanotubes should appear at 25.8°, so there are two possibilities: (1) the diffraction peak of carbon nanotubes at 25.8° is covered by titanium dioxide; (2) since the doped carbon nanotubes are only 0.1%, the content is very small, so no peak appears.

[0096] The prepared activated carbon-carbon nanotube modified TiO2 composite material was used to treat formaldehyde using the method described above (method for treating formaldehyde). The results are shown in Table 1.

[0097] Comparative Examples 1 to 7

[0098] The only difference from Example 1 is that the mass ratio of activated carbon to carbon nanotube-doped TiO2 material is different, as shown in Table 1. Formaldehyde was treated using the above method, and the results are shown in Table 1.

[0099] Table 1

[0100]

[0101] As shown in Table 1, the formaldehyde treatment effect increases with the increase in the amount of carbon nanotube-doped TiO2 material, but decreases as the composite ratio exceeds 1:9. This may be due to the increased absorption of the photocatalyst, which slows down the photon transmission speed and causes the composite material to perform poorly.

[0102] Comparative Examples 8 to 11

[0103] The only difference from Example 1 is that the doping amount of carbon nanotubes is different, as shown in Table 2. Formaldehyde was treated using the above method, and the results are shown in Table 2.

[0104] Table 2

[0105] serial number Carbon nanotube doping amount% Treatment efficiency of formaldehyde % Example 1 0.1 90.26 Comparative Example 8 0.05 59.02 Comparative Example 9 0.13 64.23 Comparative Example 10 0.15 61.58 Comparative Example 11 0.18 57.96

[0106] As can be seen from Table 2, Example 1 of the present invention has the best effect on formaldehyde treatment. The reasons for this phenomenon may be: first, the photocatalytic properties of carbon nanotubes themselves, that is, the generation of electron-hole pairs with catalytic oxidizing and reducing properties under light conditions. Second, the doping of carbon nanotubes with titanium dioxide greatly suppresses the recombination rate of electron-hole pairs, improves the utilization rate of light sources, and enhances the ability of photocatalytic degradation. However, the higher the doping ratio of carbon nanotubes, the better. When the doping ratio of carbon nanotubes is too large, the probability of electron collisions will increase, which in turn increases the recombination rate of electron-hole pairs, reduces the utilization rate of light sources, and weakens the photocatalytic degradation ability.

[0107] Comparative Examples 12 to 16

[0108] The only difference from Example 1 is the calcination temperature. See Table 3 below. Formaldehyde was treated using the above method, and the results are shown in Table 3.

[0109] Table 3

[0110] serial number Calcination temperature / ℃ Treatment efficiency of formaldehyde % Example 1 500 90.26 Comparative Example 12 200 15.64 Comparative Example 13 300 23.45 Comparative Example 14 400 41.2 Comparative Example 15 600 46.78 Comparative Example 16 700 26.31

[0111] Table 3 shows that the formaldehyde treatment effect increases with increasing calcination temperature, but decreases above 500°C. This may be because at this temperature, titanium dioxide forms a mixed phase of anatase and rutile. Furthermore, carbon nanotube-doped TiO2 crystals calcined at 500°C reach their optimal state, improving the defects of the crystal facets and achieving maximum formaldehyde treatment. However, calcination at excessively high temperatures causes the anatase phase to transform into the rutile phase, affecting photocatalytic activity and reducing degradation performance.

[0112] Comparative Examples 17 to 19

[0113] Comparative Example 17 used activated carbon alone to treat formaldehyde. Comparative Example 18 used titanium dioxide alone to treat formaldehyde. Comparative Example 19 used the carbon nanotube-doped TiO2 material obtained in Example 1 alone to treat formaldehyde. The results are shown in Table 4 below.

[0114] Table 4

[0115] serial number Materials used Treatment efficiency of formaldehyde % Example 1 <![CDATA[Activated carbon-carbon nanotube modified TiO2 composite material]]> 90.26 Comparative Example 17 Pure activated carbon 12.90 Comparative Example 18 Pure titanium dioxide 51.04 Comparative Example 19 <![CDATA[Carbon nanotube doped TiO2 material]]> 72.74

[0116] As can be seen from Table 4, regarding the treatment effect of formaldehyde gas, the activated carbon-carbon nanotube-modified TiO2 composite material obtained in Example 1 of the present invention has a formaldehyde treatment effect that is about 40% higher than that of nano-titanium dioxide, about 20% higher than that of carbon nanotube-doped TiO2 material, and about 70% higher than that of activated carbon, and the photocatalytic performance is greatly improved.

[0117] The present invention is not limited to the above-mentioned embodiments. Any modification, improvement, or substitution that can be conceived by those skilled in the art without departing from the essential content of the present invention shall fall within the scope of the present invention.

Claims

1. An activated carbon-carbon nanotube modified TiO2 composite material for degrading formaldehyde, characterized in that: It is formed by activated carbon and carbon nanotube-doped TiO2 material; the carbon nanotube-doped TiO2 material is prepared from raw materials including titanate and carbon nanotubes; The activated carbon-carbon nanotube modified TiO2 composite material is prepared by a preparation method comprising the following steps: (1) mixing titanate with a first alcohol solvent and a C1-C4 organic carboxylic acid to obtain a titanium element-containing solution; mixing carbon nanotubes with a second alcohol solvent and water to obtain a carbon nanotube solution; (2) adding the carbon nanotube solution to a titanium-containing solution for reaction, aging until a colloidal state is formed, and drying to obtain a carbon nanotube-doped TiO2 material; wherein the mass ratio of the titanate calculated as TiO2 to the mass of the carbon nanotube is 100:0.08-0.12; (3) mixing and grinding the carbon nanotube-doped TiO2 material and activated carbon, and calcining them at 490-505°C for 1.5-5h to obtain an activated carbon-carbon nanotube-modified TiO2 composite material; wherein the mass ratio of activated carbon to carbon nanotube-doped TiO2 material is 1:7-11; Wherein, the titanate ester is selected from one or more of ethyl titanate, isopropyl titanate and n-butyl titanate; the first alcohol solvent is selected from one or more of methanol, ethanol, isopropanol and n-butanol; the C1-C4 organic carboxylic acid is selected from one or more of formic acid, acetic acid, n-propionic acid and n-butyric acid; the second alcohol solvent is selected from one or more of methanol, ethanol, isopropanol and n-butanol.

2. The composite material according to claim 1, characterized in that The carbon nanotubes are multi-walled carbon nanotubes; and the titanate is selected from one of ethyl titanate, isopropyl titanate and n-butyl titanate.

3. The method for preparing the activated carbon-carbon nanotube modified TiO2 composite material according to claim 1 or 2, characterized in that: The steps include: (1) mixing titanate with a first alcohol solvent and a C1-C4 organic carboxylic acid to obtain a titanium element-containing solution; mixing carbon nanotubes with a second alcohol solvent and water to obtain a carbon nanotube solution; (2) adding the carbon nanotube solution to a titanium-containing solution for reaction, aging until a colloidal state is formed, and drying to obtain a carbon nanotube-doped TiO2 material; wherein the mass ratio of the titanate calculated as TiO2 to the mass of the carbon nanotube is 100:0.08-0.12; (3) mixing and grinding the carbon nanotube-doped TiO2 material and activated carbon, and calcining them at 490-505°C for 1.5-5h to obtain an activated carbon-carbon nanotube-modified TiO2 composite material; wherein the mass ratio of activated carbon to carbon nanotube-doped TiO2 material is 1:7-11; Among them, the titanate ester is selected from one or more of ethyl titanate, isopropyl titanate and n-butyl titanate; the first alcohol solvent is selected from one or more of methanol, ethanol, isopropanol and n-butanol; the C1-C4 organic carboxylic acid is selected from one or more of formic acid, acetic acid, n-propionic acid and n-butyric acid; the second alcohol solvent is selected from one or more of methanol, ethanol, isopropanol and n-butanol.

4. The preparation method according to claim 3, characterized in that In step (1), the titanate is selected from one of ethyl titanate, isopropyl titanate and n-butyl titanate; and the volume proportion of the titanate in the titanium element-containing solution is 13 to 25%.

5. The preparation method according to claim 3, characterized in that In step (1), the mass concentration of carbon nanotubes in the carbon nanotube solution is 1.0 to 1.8 g / L.

6. The preparation method according to claim 3, characterized in that In step (2), the carbon nanotube solution is added dropwise to the titanium element solution to react for 1 to 4 hours, allowed to stand and age until it becomes colloidal, and dried at 70 to 110° C. for 1.5 to 4.5 hours to obtain a carbon nanotube-doped TiO 2 material.

7. The preparation method according to any one of claims 3 to 6, characterized in that: In steps (1) to (3), no surfactant or dispersant is added.

8. Use of the activated carbon-carbon nanotube modified TiO2 composite material according to any one of claims 1 to 2 or the activated carbon-carbon nanotube modified TiO2 composite material prepared according to the preparation method according to any one of claims 3 to 7 in removing harmful gas formaldehyde.

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