Transition metal modified carbon fiber loaded titanium dioxide photocatalyst as well as preparation method and application thereof

Abstract

The invention discloses a transition metal modified carbon fiber loaded titanium dioxide photocatalyst as well as a preparation method and application thereof. The preparation method comprises the following steps: dispersing a first transition metal salt, a second transition metal salt, a coupling agent and biomass cellulose in a solvent for hydrothermal reaction to obtain transition metal modified composite biomass cellulose; then dispersing the transition metal modified composite biomass cellulose, titanium salt and urea in a solvent for a coupling reaction to obtain a titanium dioxide photocatalyst precursor; finally, the titanium dioxide photocatalyst precursor is sequentially subjected to pyrolysis treatment and lower activation treatment, and the titanium dioxide photocatalyst is obtained. According to the preparation method provided by the invention, a mode of first loading and then pore forming is adopted, so that the prepared titanium dioxide photocatalyst has excellent photocatalytic performance and stability.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of photocatalysts, in particular to a transition metal modified carbon fiber loaded titanium dioxide photocatalyst and a preparation method and application thereof. BACKGROUND

[0002] Volatile organic compounds (VOCs) and pathogenic microorganisms in the air are important air pollutants. Uncontrolled emission of these pollutants not only directly pollutes the atmospheric environment, but more importantly, long-term exposure of humans to these pollutants has been proven to significantly increase the risk of respiratory diseases and other health risks. Therefore, it is of urgent practical significance to develop efficient and green treatment technologies.

[0003] Photocatalytic technology is a promising air purification strategy because it can completely eliminate VOCs and pathogenic microorganisms using light energy, perfectly fitting the green environmental protection concept. Among them, nano titanium dioxide (TiO2) photocatalyst, with its unique physical and chemical properties such as small size effect, surface effect, quantum size effect, and macroscopic quantum tunneling effect, has been considered as one of the ideal photocatalytic materials.

[0004] In order to solve the problem of recycling of nano titanium dioxide, it is generally loaded on a certain carrier. In the past technology, the carrier materials used have been metal wire mesh, metal foam wire mesh or inorganic minerals, etc. Due to the small specific surface area of these carrier materials, the efficiency of catalytic reaction is not high. Carbon fiber not only provides high specific surface area and optimized pore structure, significantly enhancing the ability to capture pollutants, but also effectively promotes the separation and transport of photo-generated carriers due to its excellent optical effect and unique "electron reservoir" effect, inhibiting their recombination, thereby significantly improving the overall photocatalytic activity and stability, making it an excellent choice for titanium dioxide carrier.

[0005] Chinese patent CN103100378A discloses a preparation method of activated carbon fiber loaded titanium dioxide photocatalyst. The titanium dioxide / activated carbon fiber photocatalyst is prepared by adopting the technology of oxidation modification and uniform precipitation, and the main steps are as follows: the activated carbon fiber is soaked in hydrogen peroxide for 1 hour, then taken out, washed with deionized water, dried in an oven for 4 hours, and then taken out for use; a mixed solution of titanium salt and urea is prepared in a certain molar ratio, and stirred uniformly for 3 hours for use; the treated activated carbon fiber is placed in the mixed solution of titanium salt and urea, stirred at 80℃ for 5 hours, and then the activated carbon fiber is taken out and dried in a 100℃ oven after the reaction is completed; the dried activated carbon fiber is calcined at 500℃ for 2 hours under nitrogen protection, and the titanium dioxide / activated carbon fiber photocatalyst is obtained. Although the method uses carbon fiber as the carrier and loads titanium dioxide, it adopts a post-loading preparation method, i.e. a "pore-making and then loading" method, which specifically includes: first, soaking the activated carbon fiber in hydrogen peroxide, i.e. making pores first, and then mixing with titanium salt and urea, i.e. post-loading. This method is prone to cause the titanium dioxide to block the carrier pores and lead to uneven loading, thereby reducing the photocatalytic performance of the titanium dioxide photocatalyst. In addition, this loading method is prone to cause the titanium dioxide to fall off, thereby affecting the stability of the titanium dioxide photocatalyst.

[0006] Therefore, a new preparation method of titanium dioxide photocatalyst is developed to solve the problems existing in the existing post-loading method. SUMMARY

[0007] The purpose of the present application is to overcome the deficiencies or shortcomings of the existing preparation method of titanium dioxide photocatalyst, and to provide a preparation method of titanium dioxide photocatalyst.

[0008] Another purpose of the present application is to provide a titanium dioxide photocatalyst prepared by the above preparation method.

[0009] Still another purpose of the present application is to provide the application of the above titanium dioxide photocatalyst in purifying indoor air pollutants.

[0010] In order to achieve the above purposes, the present application realizes the following technical solutions: A preparation method of titanium dioxide photocatalyst, comprising the following steps: S1. Stir and disperse a first transition metal salt, a second transition metal salt, a coupling agent and biomass cellulose in a solvent, stir and mix to form a uniform dispersion liquid, and perform a hydrothermal reaction to obtain a transition metal modified composite biomass cellulose; S2. Disperse the transition metal modified composite biomass cellulose, urea and titanium salt in a solvent, stir and mix, and perform a coupling reaction by heating to obtain a titanium dioxide photocatalyst precursor; S3. The titanium dioxide photocatalyst precursor is subjected to pyrolysis treatment and activation treatment in sequence, to obtain the titanium dioxide photocatalyst. The coupling agent in step S1 includes a soluble saccharide and a nitrogen-containing organic compound.

[0011] The present application first disperses the first transition metal salt, the second transition metal salt, the coupling agent and the biomass cellulose in a solvent by stirring, mixes and forms a uniform dispersion, and then performs a hydrothermal reaction to obtain a transition metal modified composite biomass cellulose. The uniform dispersion system is conducive to the mutual contact of the first transition metal salt, the second transition metal salt, the coupling agent and the biomass cellulose, and provides a good reaction basis for the subsequent hydrothermal reaction, and then the first transition metal salt, the second transition metal salt and the coupling agent are uniformly deposited on the surface of the biomass cellulose. Then the transition metal modified composite biomass cellulose, urea and titanium salt are dispersed in a solvent, stirred and mixed, and heated to perform a coupling reaction to obtain a titanium dioxide photocatalyst precursor. The coupling agent is deposited on the surface of the biomass cellulose, which optimizes the nanocrystallization generation process of titanium dioxide, and at the same time enhances the steric hindrance effect of the biomass cellulose, effectively inhibits the aggregation of titanium dioxide in the loading process, and promotes its uniform distribution. In addition, the coupling agent enhances the binding energy between titanium dioxide and biomass cellulose, and realizes stable loading. Secondly, the slow provision of alkaline hydrolysis environment by urea enables the metal oxide generated by the hydrolysis of transition metal salt to be uniformly deposited on the surface of biomass cellulose, and at the same time promotes the more uniform deposition of titanium salt on the surface of biomass cellulose. Finally, the titanium dioxide photocatalyst precursor is subjected to pyrolysis treatment and activation treatment in sequence under an inert gas atmosphere and under a carbon dioxide atmosphere, to obtain a titanium dioxide photocatalyst. The metal oxide is reduced to a metal element in the pyrolysis process, and effectively promotes the conversion of biomass cellulose from amorphous carbon to graphite carbon and improves the graphitization degree, and optimizes the pore structure of biomass cellulose.

[0012] The preparation method provided by the present application adopts the mode of "loading first and then forming pores", which makes titanium dioxide more uniformly and stably loaded on biomass cellulose, and then converts the biomass cellulose into carbon fiber with high graphitization and high specific surface area porosity. Thanks to the above characteristics, the problem of titanium dioxide blocking the carrier pore channel is effectively solved, the carrier separation and VOCs adsorption-reaction-mass transfer resistance in the photocatalysis process are effectively reduced, the adsorption and capture capacity of VOCs is effectively improved, thereby the photocatalytic performance of the titanium dioxide photocatalyst is improved, and the rapid deactivation of the photocatalyst caused by the accumulation of intermediate products is effectively avoided, so that the photocatalyst has excellent stability.

[0013] Preferably, the soluble saccharide in the coupling agent in step S1 is one or more of glucose, sucrose or fructose.

[0014] Preferably, the nitrogen-containing organic compound in the coupling agent in step S1 is one or more of melamine, polyvinylpyrrolidone, or polyaniline.

[0015] As is known to those skilled in the art, biomass cellulose refers to cellulose extracted or biosynthesized from renewable biomass such as plants or microorganisms. Preferably, the biomass cellulose is one or both of plant cellulose and bacterial cellulose. More preferably, the biomass cellulose is bacterial cellulose. Even more preferably, the plant cellulose is one or more of cotton cellulose, wood pulp cellulose, or straw cellulose.

[0016] Preferably, the mass ratio of the soluble sugar to the nitrogen-containing organic compound is 0.1~1:0.1~1.

[0017] Preferably, the mass ratio of biomass cellulose to coupling agent in step S1 is 1:2.5~50.

[0018] More preferably, the mass ratio of biomass cellulose to coupling agent in step S1 is 1:10~40.

[0019] Preferably, in step S1, the ratio of the added biomass cellulose to the total molar amount of transition metal ions is 1g:1.5~3mmol.

[0020] Preferably, the first transition metal ion accounts for 10-90% of the total molar amount of transition metal ions in the system.

[0021] More preferably, the first transition metal ion accounts for 50-70% of the total molar amount of transition metal ions in the system.

[0022] Preferably, in step S1, the first transition metal salt is one of iron salt, cobalt salt, or nickel salt; the second transition metal salt is one of iron salt, cobalt salt, or nickel salt, and the second transition metal and the first transition metal are different types of metals.

[0023] Specifically, the iron salt is one or more of ferric chloride, ferric acetate, ferric nitrate, or ferric sulfate; the cobalt salt is one or more of cobalt nitrate, cobalt acetate, or cobalt chloride; and the nickel salt is one or more of nickel sulfate, nickel nitrate, nickel chloride, or nickel acetate.

[0024] Preferably, the solvent in step S1 is a mixture of alcohol and water.

[0025] More preferably, the mass concentration of alcohol in the solvent is 1-50%. Specifically, it can be any value from 1-50%, such as 1%, 2%, 4%, 6%, 8%, 10%, 20%, 24%, 26%, 28%, 30%, 32%, 34%, 36%, 38%, 40%, 42%, 44%, 46%, 48%, 50%, etc.

[0026] More preferably, the alcohol is one or more of methanol, ethanol, ethylene glycol or glycerol.

[0027] Preferably, the temperature of the hydrothermal reaction in step S1 is 140~200℃.

[0028] More preferably, the temperature of the hydrothermal reaction in step S1 is 170~200°C.

[0029] Preferably, the hydrothermal reaction time in step S1 is 4 to 20 hours.

[0030] More preferably, the hydrothermal reaction time in step S1 is 6 to 12 hours.

[0031] Preferably, after the reaction in step S1 is completed, a washing step is also included.

[0032] The inventors discovered that by utilizing urea to slowly provide an alkaline environment during heating, the metal oxides generated from transition metal salts are deposited more uniformly on the surface of biomass cellulose, providing a good catalyst for subsequent pyrolysis. This simultaneously avoids rapid hydrolysis of titanium salts in the system, which could lead to particle agglomeration and uneven adhesion. Preferably, the temperature of the coupling reaction in step S2 is 40~90℃. More preferably, the temperature of the coupling reaction in step S2 is 70~90℃.

[0033] Preferably, the coupling reaction in step S2 takes 1 to 24 hours.

[0034] More preferably, the coupling reaction in step S2 takes 6 to 12 hours.

[0035] Preferably, the titanium salt in step S2 is one or more of titanium oxysulfate, titanium tetrachloride, or tetrabutyl titanate.

[0036] Preferably, the mass ratio of the titanium salt to the transition metal modified composite biomass cellulose in step S2 is 1:1 to 10.

[0037] More preferably, the mass ratio of the titanium salt to the transition metal modified composite biomass cellulose in step S2 is 1:1~5.

[0038] Preferably, the molar ratio of titanium ions in the titanium salt to amino groups in the urea in step S2 is 1:2.5~10.

[0039] More preferably, the molar ratio of titanium ions in the titanium salt to amino groups in the urea in step S2 is 1:5~8.

[0040] Preferably, the solvent in step S2 is a mixture of alcohol and water.

[0041] More preferably, the mass concentration of alcohol in the solvent is 1-50%. Specifically, it can be any value from 1-50%, such as 1%, 2%, 4%, 6%, 8%, 10%, 20%, 24%, 26%, 28%, 30%, 32%, 34%, 36%, 38%, 40%, 42%, 44%, 46%, 48%, 50%, etc.

[0042] More preferably, the alcohol is one or more of methanol, ethanol, ethylene glycol or glycerol.

[0043] Preferably, the stirring speed in step S2 is 800~1200 rpm.

[0044] Preferably, the stirring time in step S2 is 10~60 min.

[0045] Preferably, the stirring temperature in step S2 is 20~25℃.

[0046] As those skilled in the art will know, biomass cellulose needs to be pyrolyzed in an inert gas atmosphere to prevent oxidation. The inert gas can be at least one of those commonly used in the art, such as argon, nitrogen, or helium.

[0047] Preferably, the temperature of the pyrolysis treatment in step S3 is 400~900℃.

[0048] More preferably, the temperature of the pyrolysis treatment in step S3 is 600~800℃.

[0049] The inventors discovered that as the pyrolysis temperature increases, the amorphous carbon in the titanium dioxide photocatalyst undergoes pyrolysis and volatilization, leading to shrinkage of the porous carbon volume, thinning of the biomass cellulose diameter, and uniform fragmentation of the porous carbon particles. In particular, when the pyrolysis temperature exceeds 750°C, TiO2 crystals gradually become exposed and aggregate, thereby affecting the photocatalytic performance of the titanium dioxide photocatalyst.

[0050] Preferably, the pyrolysis treatment in step S3 takes 2 to 12 hours.

[0051] More preferably, the pyrolysis treatment in step S3 takes 4 to 10 hours.

[0052] Preferably, the heating rate of the pyrolysis treatment in step S3 is 1~10℃ / min.

[0053] The inventors discovered that activating titanium dioxide photocatalysts after pyrolysis treatment can further improve their photocatalytic performance.

[0054] Preferably, the activation temperature in step S3 is 150~500℃.

[0055] More preferably, the activation treatment temperature in step S3 is 300~500°C.

[0056] Preferably, the heating rate of the activation treatment in step S3 is 0.1~10℃ / min.

[0057] More preferably, the heating rate of the activation treatment in step S3 is 2~10℃ / min.

[0058] Preferably, the activation treatment time in step S3 is 0.1~10h.

[0059] More preferably, the activation treatment in step S3 takes 1 to 6 hours.

[0060] Preferably, the activation treatment in step S3 is carried out in a carbon dioxide atmosphere.

[0061] The titanium dioxide photocatalyst prepared by the above method is also within the scope of protection of this invention.

[0062] The application of the aforementioned titanium dioxide photocatalyst in purifying indoor air pollutants is also within the scope of protection of this invention.

[0063] Compared with the prior art, the beneficial effects of the present invention include: This invention provides a novel method for preparing titanium dioxide photocatalysts. First, a first transition metal salt, a second transition metal salt, a coupling agent, and biomass cellulose are dispersed in a solvent and stirred to form a colloidal dispersion. A hydrothermal reaction is then carried out to obtain transition metal-modified composite biomass cellulose. Next, the transition metal-modified composite biomass cellulose, urea, and titanium salt are dispersed in a solvent, stirred, and heated to carry out a coupling reaction, yielding a titanium dioxide photocatalyst precursor. Finally, the titanium dioxide photocatalyst precursor is subjected to pyrolysis and activation treatments sequentially to obtain the titanium dioxide photocatalyst. This invention optimizes the crystallization and loading processes of titanium dioxide by introducing a coupling agent, and promotes the graphitization process of biomass cellulose and optimizes the pore-forming process during pyrolysis by introducing transition metals and urea. The preparation method provided by this invention adopts a "loading before pore-forming" approach, first enabling titanium dioxide to be more uniformly and stably loaded onto biomass cellulose, and then converting the biomass cellulose into carbon fibers with high graphitization and high specific surface area porosity. Based on the above characteristics, the titanium dioxide photocatalyst prepared by this invention has excellent photocatalytic performance and stability. Attached Figure Description

[0064] Figure 1 This is a scanning electron microscope image of the titanium dioxide photocatalyst prepared in Example 1 of the present invention.

[0065] Figure 2 The image shows the nitrogen adsorption-desorption isotherm of the titanium dioxide photocatalyst prepared in Example 1 of this invention.

[0066] Figure 3 This is a pore size distribution diagram of the titanium dioxide photocatalyst prepared in Example 1 of the present invention.

[0067] Figure 4 The image shows the XRD pattern of the titanium dioxide photocatalyst prepared in Example 1 of this invention.

[0068] Figure 5 The stability test results are shown for the titanium dioxide photocatalysts prepared in Example 1 and Comparative Example 7 of this invention. Detailed Implementation

[0069] The present invention will be further described below with reference to embodiments and comparative examples. These embodiments are merely typical descriptions of the present invention, but the present invention is not limited thereto. Unless otherwise specified, the test methods used in the following embodiments and comparative examples are conventional methods, and the raw materials and reagents used are commercially available from conventional commercial sources.

[0070] Raw materials and reagents used in this embodiment and comparative example: Bacterial cellulose, model: BC, purchased from Guilin Qihong Technology Co., Ltd. Cotton cellulose, type: CNF, purchased from Guilin Qihong Technology Co., Ltd.; Wood pulp cellulose, model: MFC, purchased from Guilin Qihong Technology Co., Ltd.

[0071] Example 1 This embodiment provides a method for preparing a titanium dioxide photocatalyst, specifically including the following steps: S1. Based on a total molar amount of 3 mmol of transition metal ions in the system, with the first transition metal ion accounting for 66%, weigh 1.98 mmol of ferric acetate (0.46 g) and 1.02 mmol of nickel acetate (0.17 g) and mix them to form a complex transition metal salt. S2. Weigh 4g of melamine, 4g of sucrose and 0.2g of bacterial cellulose into a beaker, add the composite transition metal salt obtained in step S1, add 10mL of ethanol and 75mL of deionized water, stir and mix to form a colloidal dispersion, and transfer it to a polytetrafluoroethylene reactor. Heat the mixture to 175℃ at 10℃ / min and maintain it for 6h. Finally, filter and wash the reaction product twice with anhydrous ethanol and deionized water respectively to obtain transition metal modified composite cellulose. S3. Weigh 2g of transition metal modified composite cellulose and place it in a reaction flask. Add 60mL of ethanol aqueous solution (volume fraction of 50%) and 10mL of urea aqueous solution (10mL of water contains 3g of urea). Stir and mix. Add 3.15mL of TiCl4 ethanol solution (concentration of 2mol / L) while stirring at 1000rpm. Then heat to 70℃ and stir for 6h. Finally, filter and wash the reaction product with anhydrous ethanol and freeze dry to obtain the titanium dioxide photocatalyst precursor. S4. The titanium dioxide photocatalyst precursor is placed in a tube furnace and subjected to pyrolysis under an argon atmosphere and activation under a carbon dioxide atmosphere in sequence to obtain the titanium dioxide photocatalyst.

[0072] The pyrolysis treatment conditions were as follows: heating to 600℃ at a heating rate of 10℃ / min and holding for 6 hours; the activation treatment conditions were as follows: heating to 400℃ at a heating rate of 10℃ / min and holding for 1 hour.

[0073] Sample characterization 1. Scanning electron microscopy characterization The titanium dioxide photocatalyst prepared in this embodiment was characterized by scanning electron microscopy, and the results are as follows: Figure 1 As shown.

[0074] Depend on Figure 1 As can be seen, the titanium dioxide photocatalyst prepared in this embodiment has an interwoven network structure, surrounded by abundant transition metal-modified porous carbon fibers and uniformly wrapped with TiO2 nanoshells. This indicates that titanium dioxide is uniformly loaded onto carbon fibers.

[0075] 2. Characterization of channel structure The pore structure of the titanium dioxide photocatalyst prepared in this embodiment was characterized by testing, and the results are as follows: Figure 2 and Figure 3 As shown.

[0076] from Figure 2 It can be seen that the adsorption curve of the titanium dioxide photocatalyst prepared in this embodiment is derived from... The isotherms are composed of a combination of type I and type IV isotherms. This type of hysteresis loop is a typical curve containing narrow pores. This indicates that the titanium dioxide photocatalyst prepared in this example has a microporous and mesoporous composite structure.

[0077] from Figure 3 As can be seen, the titanium dioxide catalyst prepared in this embodiment possesses a rich mesoporous structure, with pore sizes mainly distributed in the range of 2-20 nm. This indicates that the pore-forming process of the catalyst during pyrolysis was optimized under the combined catalytic action of the two transition metal salts, resulting in excellent specific surface area and pore structure. This structure effectively reduces the mass transfer resistance of contaminants on the catalyst surface and improves interfacial electron transfer, while providing sufficient active sites for the catalytic reaction.

[0078] 3. XRD spectral characterization The titanium dioxide photocatalyst prepared in this embodiment was characterized by XRD patterns, and the results are as follows: Figure 4 As shown.

[0079] from Figure 4 It can be seen that the titanium dioxide photocatalyst prepared in this embodiment has obvious anatase peaks, such as 2θ=25.3, 37.9, 48.1, 75.3, indicating that the TiO2 crystallinity in the material is good under the conditions.

[0080] Examples 2-15 Examples 2-15 provide different methods for preparing titanium dioxide photocatalysts. The difference from Example 1 lies in the type or amount of raw materials used in the preparation. The specific differences are shown in Table 1 below: Table 1. List of raw materials for the preparation of Examples 1-15

[0081] Sample characterization 1. Scanning electron microscopy characterization: The scanning electron micrographs of Examples 2-15 are similar to those of Example 1.

[0082] 2. Characterization of pore structure: The nitrogen adsorption-desorption isotherms and pore size distribution diagrams of Examples 2-15 are similar to those of Example 1.

[0083] 3. XRD pattern characterization: The XRD patterns of Examples 2-15 are similar to those of Example 1.

[0084] Examples 16-26 Examples 16-26 provide different methods for preparing titanium dioxide photocatalysts. The difference from Example 1 lies in the different preparation processes, as shown in Table 2 below.

[0085] Table 2. Detailed preparation process of Examples 1, 16-26

[0086] Sample characterization 1. Scanning electron microscopy characterization: The scanning electron micrographs of Examples 16-26 are similar to those of Example 1.

[0087] 2. Characterization of pore structure: The nitrogen adsorption-desorption isotherms and pore size distribution diagrams of Examples 16-26 are similar to those of Example 1.

[0088] 3. XRD pattern characterization: The XRD patterns of Examples 16-26 are similar to those of Example 1.

[0089] Comparative Example 1 This comparative example provides a method for preparing a titanium dioxide photocatalyst, which differs from Example 1 only in that it does not require the compounding of transition metal salts, i.e., only one transition metal salt is used. The specific steps include: S1. Weigh 4g of melamine, 4g of sucrose and 0.2g of bacterial cellulose into a beaker, add 3mmol of ferric acetate (0.69g), 10mL of ethanol and 75mL of deionized water, stir and mix to form a colloidal dispersion, and transfer it to a polytetrafluoroethylene reactor. Heat to 175℃ at 10℃ / min and maintain for 6h. Finally, filter and wash the reaction product twice with anhydrous ethanol and deionized water respectively to obtain transition metal modified composite cellulose. S2. Weigh 2g of transition metal modified composite cellulose and place it in a reaction flask. Add 60mL of ethanol aqueous solution (volume fraction of 50%) and 10mL of urea aqueous solution (10mL of water contains 3g of urea). Stir and mix. Add 3.15mL of TiCl4 ethanol solution (concentration of 2mol / L) while stirring at 1000rpm. Then heat to 70℃ and stir for 6h. Finally, filter and wash the reaction product with anhydrous ethanol and freeze dry to obtain the titanium dioxide photocatalyst precursor. S3. The titanium dioxide photocatalyst precursor is placed in a tube furnace and subjected to pyrolysis under an argon atmosphere and activation under a carbon dioxide atmosphere in sequence to obtain the titanium dioxide photocatalyst.

[0090] The pyrolysis treatment conditions were as follows: heating to 600℃ at a heating rate of 10℃ / min and holding for 6 hours; the activation treatment conditions were as follows: heating to 400℃ at a heating rate of 10℃ / min and holding for 1 hour.

[0091] Comparative Example 2 This comparative example provides a method for preparing a titanium dioxide photocatalyst, which differs from Example 1 only in the type of coupling agent added in step S2. Specifically, it includes the following steps: S1. Based on a total molar amount of 3 mmol of transition metal ions in the system, with the first transition metal ion accounting for 66%, weigh 1.98 mmol of ferric acetate (0.46 g) and 1.02 mmol of nickel acetate (0.17 g) and mix them to form a complex transition metal salt. S2. Weigh 8g of sucrose and 0.2g of bacterial cellulose into a beaker, add the compound transition metal salt obtained in step S1, add 10mL of ethanol and 75mL of deionized water, stir and mix to form a colloidal dispersion, and transfer it to a polytetrafluoroethylene reactor. Heat the mixture to 175℃ at 10℃ / min and maintain it for 6h. Finally, filter and wash the reaction product twice with anhydrous ethanol and deionized water respectively to obtain transition metal modified composite cellulose. S3. Weigh 2g of transition metal modified composite cellulose and place it in a reaction flask. Add 60mL of ethanol aqueous solution (volume fraction of 50%) and 10mL of urea aqueous solution (10mL of water contains 3g of urea). Stir and mix. Add 3.15mL of TiCl4 ethanol solution (concentration of 2mol / L) while stirring at 1000rpm. Then heat to 70℃ and stir for 6h. Finally, filter and wash the reaction product with anhydrous ethanol and freeze dry to obtain the titanium dioxide photocatalyst precursor. S4. The titanium dioxide photocatalyst precursor is placed in a tube furnace and subjected to pyrolysis under an argon atmosphere and activation under a carbon dioxide atmosphere in sequence to obtain the titanium dioxide photocatalyst.

[0092] The pyrolysis treatment conditions were as follows: heating to 600℃ at a heating rate of 10℃ / min and holding for 6 hours; the activation treatment conditions were as follows: heating to 400℃ at a heating rate of 10℃ / min and holding for 1 hour.

[0093] Comparative Example 3 This comparative example provides a method for preparing a titanium dioxide photocatalyst, which differs from Example 1 only in the type of coupling agent added in step S2. Specifically, it includes the following steps: S1. Based on a total molar amount of 3 mmol of transition metal ions in the system, with the first transition metal ion accounting for 66%, weigh 1.98 mmol of ferric acetate (0.46 g) and 1.02 mmol of nickel acetate (0.17 g) and mix them to form a complex transition metal salt. S2. Weigh 8g of melamine and 0.2g of bacterial cellulose into a beaker, add the composite transition metal salt obtained in step S1, add 10mL of ethanol and 75mL of deionized water, stir and mix to form a colloidal dispersion, and transfer it to a polytetrafluoroethylene reactor. Heat the mixture to 175℃ at 10℃ / min and maintain the temperature for 6h. Finally, filter and wash the reaction product twice with anhydrous ethanol and deionized water respectively to obtain the transition metal modified composite cellulose. S3. Weigh 2g of transition metal modified composite cellulose and place it in a reaction flask. Add 60mL of ethanol aqueous solution (volume fraction of 50%) and 10mL of urea aqueous solution (10mL of water contains 3g of urea). Stir and mix. Add 3.15mL of TiCl4 ethanol solution (concentration of 2mol / L) while stirring at 1000rpm. Then heat to 70℃ and stir for 6h. Finally, filter and wash the reaction product with anhydrous ethanol and freeze dry to obtain the titanium dioxide photocatalyst precursor. S4. The titanium dioxide photocatalyst precursor is placed in a tube furnace and subjected to pyrolysis under an argon atmosphere and activation under a carbon dioxide atmosphere in sequence to obtain the titanium dioxide photocatalyst.

[0094] The pyrolysis treatment conditions were as follows: heating to 600℃ at a heating rate of 10℃ / min and holding for 6 hours; the activation treatment conditions were as follows: heating to 400℃ at a heating rate of 10℃ / min and holding for 1 hour.

[0095] Comparative Example 4 This comparative example provides a method for preparing a titanium dioxide photocatalyst. The only difference from Example 1 is the type of substance that provides the alkaline hydrolysis environment in step S3. Specifically, the urea aqueous solution is replaced with a sodium bicarbonate aqueous solution (3g of sodium bicarbonate in 10mL of water).

[0096] Comparative Example 5 This comparative example provides a method for preparing a titanium dioxide photocatalyst, which differs from Example 1 only in that activation treatment is not performed in step S4. Specifically, it includes the following steps: S1. Based on a total molar amount of 3 mmol of transition metal ions in the system, with the first transition metal ion accounting for 66%, weigh 1.98 mmol of ferric acetate (0.46 g) and 1.02 mmol of nickel acetate (0.17 g) and mix them to form a complex transition metal salt. S2. Weigh 4g of melamine, 4g of sucrose and 0.2g of bacterial cellulose into a beaker, add the composite transition metal salt obtained in step S1, add 10mL of ethanol and 75mL of deionized water, stir and mix to form a colloidal dispersion, and transfer it to a polytetrafluoroethylene reactor. Heat the mixture to 175℃ at 10℃ / min and maintain it for 6h. Finally, filter and wash the reaction product twice with anhydrous ethanol and deionized water respectively to obtain transition metal modified composite cellulose. S3. Weigh 2g of transition metal modified composite cellulose and place it in a reaction flask. Add 60mL of ethanol aqueous solution (volume fraction of 50%) and 10mL of urea aqueous solution (10mL of water contains 3g of urea). Stir and mix. Add 3.15mL of TiCl4 ethanol solution (concentration of 2mol / L) while stirring at 1000rpm. Then heat to 70℃ and stir for 6h. Finally, filter and wash the reaction product with anhydrous ethanol and freeze dry to obtain the titanium dioxide photocatalyst precursor. S4. Place the titanium dioxide photocatalyst precursor in a tube furnace and perform pyrolysis treatment under an argon atmosphere to obtain the titanium dioxide photocatalyst.

[0097] The pyrolysis treatment conditions were as follows: the temperature was increased to 600℃ at a heating rate of 10℃ / min, and held for 6 hours.

[0098] Comparative Example 6 This comparative example provides a method for preparing a titanium dioxide photocatalyst, which differs from Example 1 in the order of steps S3 and S4, and specifically includes the following steps: S1. Based on a total molar amount of 3 mmol of transition metal ions in the system, with the first transition metal ion accounting for 66%, weigh 1.98 mmol of ferric acetate (0.46 g) and 1.02 mmol of nickel acetate (0.17 g) and mix them to form a complex transition metal salt. S2. Weigh 4g of melamine, 4g of sucrose and 0.2g of bacterial cellulose into a beaker, add the composite transition metal salt obtained in step S1, add 10mL of ethanol and 75mL of deionized water, stir and mix to form a colloidal dispersion, and transfer it to a polytetrafluoroethylene reactor. Heat the mixture to 175℃ at 10℃ / min and maintain it for 6h. Finally, filter and wash the reaction product twice with anhydrous ethanol and deionized water respectively to obtain transition metal modified composite cellulose. S3. Weigh 2g of transition metal modified composite cellulose and place it in a tube furnace. Then, perform pyrolysis treatment under an argon atmosphere and activation treatment under a carbon dioxide atmosphere to obtain transition metal modified composite carbon fiber. The pyrolysis treatment conditions are as follows: heating to 600℃ at a heating rate of 10℃ / min and holding for 6 hours; the activation treatment conditions are as follows: heating to 400℃ at a heating rate of 10℃ / min and holding for 1 hour. S4. Place the transition metal modified composite carbon fiber in a reaction flask, add 60 mL of ethanol aqueous solution (volume fraction of 50%) and 10 mL of urea aqueous solution (10 mL of water contains 3 g of urea), stir and mix, and add 3.15 mL of TiCl4 ethanol solution (concentration of 2 mol / L) under the condition of stirring speed of 1000 rpm, then heat to 70℃ and stir for 6 h, finally filter and wash the reaction product with anhydrous ethanol, freeze dry, and obtain titanium dioxide photocatalyst.

[0099] Comparative Example 7 This comparative example provides a commercially available titanium dioxide photocatalyst, model P25, purchased from Aladdin Reagents.

[0100] Performance testing 1. Photocatalytic performance The photocatalytic performance of the titanium dioxide photocatalysts prepared in each example and comparative example was tested, and the results are shown in Table 3 below. The continuous phase photocatalytic testing and evaluation method was used, and the specific testing method is as follows: S1. Take 40 mg of titanium dioxide photocatalyst and fill it into a quartz tube. Pre-treat it at 120 °C and under vacuum (2~5 Pa) for 1 h. S2. After pretreatment, cool to room temperature, backfill with nitrogen to atmospheric pressure, and transfer the quartz tube to a fixed-bed reactor; S3. In continuous flow mode, toluene was introduced into a fixed-bed reactor for dynamic adsorption testing. The residual toluene concentration in the reaction system was measured every 5 minutes. The photocatalytic performance was characterized by calculating the degradation efficiency and degradation rate. The test parameters were: toluene concentration 40 ppm, toluene flow rate 30 mL / min, and test time 600 min.

[0101] Degradation efficiency and degradation rate are calculated using the following formula: ; in, The equilibrium concentration of toluene in the system before the reaction; This represents the remaining concentration of toluene in the system after the reaction.

[0102] ; in, The total amount of toluene in the reaction system within time t; The total amount of undegraded toluene in the reaction system within time t; t is the test time.

[0103] Table 3. Photocatalytic performance test results of the titanium dioxide photocatalysts prepared in each example and comparative example.

[0104] As shown in Table 3, the titanium dioxide photocatalyst provided by this invention achieves a degradation rate of 94.64% to 99.99%, exhibiting excellent photocatalytic performance. Examples 22-24 demonstrate that controlling the pyrolysis temperature effectively reduces the pyrolysis and volatilization of amorphous carbon in the titanium dioxide photocatalyst, helping to maintain the structural stability and pore size distribution of biomass cellulose, thereby improving the photocatalytic performance of the titanium dioxide photocatalyst.

[0105] As can be seen from Comparative Example 1, when only one transition metal salt is used, the degree of transformation of biomass cellulose from amorphous carbon to graphitic carbon decreases, and the pore structure of biomass cellulose cannot be effectively optimized, resulting in a decrease in the photocatalytic performance of the prepared titanium dioxide photocatalyst.

[0106] As shown in Examples 1 and Comparative Examples 2-3, soluble sugars and nitrogen-containing organic compounds exhibit a synergistic effect. Together, they act on the surface of biocellulose, optimizing the formation process of titanium dioxide nanocrystals. Simultaneously, they enhance the steric hindrance effect of biocellulose, effectively inhibiting the aggregation of titanium dioxide during loading and promoting its uniform distribution. However, when only one of these substances is used as a coupling agent, the lack of synergistic effect leads to a decrease in the photocatalytic performance of the prepared titanium dioxide photocatalyst.

[0107] As shown in Example 1 and Comparative Example 4, urea can slowly release alkalinity, providing a mild hydrolysis environment for the system. This promotes the uniform deposition of metal oxides generated from the hydrolysis of transition metal salts on the surface of biomass cellulose, and also helps titanium salts to be deposited more uniformly on the biomass cellulose surface. When other weakly alkaline substances are chosen, such as sodium bicarbonate, their strong alkalinity causes rapid hydrolysis of titanium salts, leading to agglomeration and uneven adhesion of titanium dioxide, ultimately reducing the photocatalytic performance of the prepared titanium dioxide photocatalyst.

[0108] Comparative Example 5 shows that activating the titanium dioxide photocatalyst precursor helps to further improve the photocatalytic performance of the titanium dioxide photocatalyst.

[0109] As can be seen from Comparative Example 6, compared with the "first create pores then load" method, the present invention further improves the adsorption and capture capacity of titanium dioxide photocatalyst for VOCs by adopting the "first load then create pores" method, so that the prepared titanium dioxide photocatalyst has excellent photocatalytic performance.

[0110] 2. Stability The stability of the titanium dioxide photocatalysts provided in Example 1 and Comparative Example 7 was tested, and the results are as follows: Figure 5 As shown. The results were obtained using the continuous phase photocatalysis testing and evaluation method.

[0111] from Figure 5It can be seen that the titanium dioxide photocatalyst provided by the present invention maintains excellent degradation efficiency within 700 min, indicating that it has excellent stability.

[0112] The specific embodiments of the present invention have been described above. It should be understood that the present invention is not limited to the specific embodiments described above, and those skilled in the art can make various modifications or variations within the scope of the claims, which do not affect the essence of the present invention.

Claims

1. A method for preparing a titanium dioxide photocatalyst, characterized in that, Includes the following steps: S1. The first transition metal salt, the second transition metal salt, the coupling agent and biomass cellulose are stirred and dispersed in a solvent, and a uniform dispersion is formed by stirring and mixing. A hydrothermal reaction is then carried out to obtain the transition metal modified composite biomass cellulose. S2. Disperse transition metal modified composite biomass cellulose, urea and titanium salt in a solvent, stir and mix, and heat to carry out a coupling reaction to obtain titanium dioxide photocatalyst precursor; S3. The titanium dioxide photocatalyst precursor is subjected to pyrolysis and activation treatment in sequence to obtain the titanium dioxide photocatalyst; The coupling agent mentioned in step S1 includes soluble sugars and nitrogen-containing organic compounds.

2. The preparation method according to claim 1, characterized in that, In step S1, the first transition metal salt is one of iron salt, cobalt salt, or nickel salt; the second transition metal salt is one of iron salt, cobalt salt, or nickel salt, and the second transition metal and the first transition metal are different types of metals.

3. The preparation method according to claim 1, characterized in that, In step S1, the ratio of the added biomass cellulose to the total molar amount of transition metal ions is 1g:1.5~3mmol.

4. The preparation method according to claim 1, characterized in that, The mass ratio of biomass cellulose to coupling agent in step S1 is 1:2.5~50.

5. The preparation method according to claim 1, characterized in that, The temperature of the coupling reaction in step S2 is 40~90℃.

6. The preparation method according to claim 1, characterized in that, The mass ratio of titanium salt to transition metal modified composite biomass cellulose in step S2 is 1:1~10.

7. The preparation method according to claim 1, characterized in that, In step S2, the molar ratio of titanium ions in the titanium salt to amino groups in the urea is 1:2.5~10.

8. The preparation method according to claim 1, characterized in that, The activation temperature in step S3 is 150~500℃.

9. The titanium dioxide photocatalyst prepared by any of the preparation methods described in claims 1 to 8.

10. The application of the titanium dioxide photocatalyst according to claim 9 in purifying indoor air pollutants.

Images