Preparation method of strontium and graphite co-assisted titanium dioxide nanofiber photocatalyst

Abstract

The application provides a preparation method of a strontium and graphite double-assisted titanium dioxide nanofiber photocatalyst, and comprises the following steps: strontium acetate is put into anhydrous ethanol and glacial acetic acid solvents, and stirred to make it completely dissolved; then butyl titanate is poured in, and stirred uniformly to form a clear solution; polyvinylpyrrolidone is slowly added, and continuously stirred until a light yellow transparent viscous electrospinning precursor solution is generated; the precursor solution is electrospun at room temperature; the collected nanofiber felt is put into air for calcination to form strontium-doped titanium dioxide nanofiber; the titanium dioxide nanofiber is subjected to hydrothermal treatment by using dimethylformamide and ammonia water, the precipitate is washed with water, and the strontium-doped titanium dioxide nanofiber is calcined in a protective gas, so that the graphite is attached to the surface of the titanium dioxide nanofiber without adhesive. The strontium and graphite double assistance improves the photocatalytic efficiency of the titanium dioxide, and the nanoscale titanium dioxide is easy to recycle.

Description

Technical Field

[0001] This invention relates to a method for preparing a photocatalyst, and more particularly to a method for preparing a strontium and graphite duo-assisted titanium dioxide nanofiber photocatalyst. Background Technology

[0002] The information disclosed in this background section is intended only to enhance understanding of the overall background of the invention and is not necessarily to be construed as an admission or in any way implying that such information constitutes prior art known to those skilled in the art.

[0003] With rapid industrial and economic development, environmental pollution, especially water pollution, has become a global environmental problem. The increasing discharge of organic wastewater causes numerous environmental issues, such as hindering photosynthesis in aquatic plants and exhibiting biotoxicity, posing potential threats to ecosystems and human health. Various methods, including biodegradation, adsorption, and chemical degradation, have been developed to remove organic pollutants from wastewater. However, for some organic pollutants that lack self-degradation capabilities, traditional wastewater treatment methods suffer from low efficiency, high energy consumption, and a tendency to cause secondary pollution. Therefore, finding a highly efficient and environmentally friendly method for removing organic pollutants is crucial.

[0004] Photocatalytic degradation is a green technology for removing pollutants from water. Its use of solar energy, low energy consumption, and high degradation efficiency have attracted significant interest in scientific and engineering fields. Among various photocatalysts, titanium dioxide is considered one of the most promising photocatalysts for wastewater treatment due to its good stability, low energy consumption, suitable band structure, relatively low cost, and non-toxicity. Currently, there are already well-developed products, such as titanium dioxide P25 (nanoparticles of a mixed phase of anatase and rutile crystals with an average particle size of 25 nm). However, photogenerated electrons and holes in titanium dioxide are easily recombinated, resulting in low utilization of photogenerated carriers. Therefore, maximizing the generation of photogenerated electron-hole pairs under sunlight and extending carrier lifetime by promoting electron and hole transfer is key to improving the photocatalytic efficiency of titanium dioxide. Combining photocatalysts with highly conductive materials is a common and effective method to limit the recombination of photogenerated electrons and holes. Highly conductive materials provide a transport channel for photogenerated electrons from the conduction band to the catalyst surface, which can greatly reduce the recombination of photogenerated electrons and holes, thereby improving photocatalytic efficiency. Therefore, selecting appropriate materials and finding a reasonable preparation process are key to improving the photocatalytic performance of titanium dioxide. Furthermore, titanium dioxide P25 is a nanoscale material with a very large specific surface area, which is beneficial for photocatalytic reactions. However, due to its small particle size, it is prone to agglomeration when treating water pollution, affecting the photocatalytic effect. Moreover, nanoparticles are difficult to collect and easily drift with the water, causing secondary pollution. Summary of the Invention

[0005] To address the shortcomings of existing technologies, this invention provides a method for preparing a strontium and graphite-coated titanium dioxide nanofiber photocatalyst. The first objective of this invention is to provide the strontium and graphite-coated titanium dioxide nanofiber photocatalyst to improve the photocatalytic efficiency of titanium dioxide. The second objective of this invention is to provide a method for preparing the strontium and graphite-coated titanium dioxide nanofiber photocatalyst, aiming to prepare a photocatalyst with excellent performance.

[0006] This invention has found that using strontium and graphite as co-catalysts can effectively improve the photocatalytic performance of titanium dioxide.

[0007] In this invention, the synergistic effect of strontium doping and graphite surface modification is key to improving the photocatalytic performance of titanium dioxide.

[0008] The study also found that the nanofiber structure can effectively avoid aggregation, and the photocatalyst can be easily recovered through precipitation, exhibiting stability and reusability.

[0009] To achieve the above objectives, the present invention is implemented through the following technical solution:

[0010] The preparation method of strontium and graphite dual-auxiliary titanium dioxide nanofiber photocatalyst includes the following steps:

[0011] Step (1): Strontium acetate is placed in anhydrous ethanol and glacial acetic acid solvent and stirred until completely dissolved. Then, tetrabutyl titanate is added and stirred evenly to form a clear solution.

[0012] Step (2): Slowly add polyvinylpyrrolidone, cover the container, and stir continuously at room temperature until a light yellow, transparent, viscous electrospinning precursor solution is generated. Electrospin the above precursor solution and place the collected nanofiber felt in the air to calcine to form strontium-doped titanium dioxide nanofibers.

[0013] Step (3) involves hydrothermal treatment of titanium dioxide nanofibers with dimethylformamide and ammonia. After the precipitate is washed with water, it is calcined in a protective gas to allow graphite to adhere to the surface of the titanium dioxide nanofibers without binder.

[0014] Preferably, the volume ratio of tetrabutyl titanate to strontium acetate is 100 ml: (0.2-0.8) g.

[0015] Preferably, the volume ratio of tetrabutyl titanate to the mass ratio of polyvinylpyrrolidone is 100 ml: (120-200) g.

[0016] Preferably, the electrospinning voltage is 20–40 kV.

[0017] Preferably, the maximum calcination temperature in air is 450–550°C, and the heating rate is 20–40°C / h.

[0018] Preferably, the volume ratio of dimethylformamide, titanium dioxide nanofibers, and ammonia (25%) is 100 ml: (0.4-1) g: (10-20) ml.

[0019] Preferably, the hydrothermal reaction temperature is 150–250℃ and the hydrothermal time is 10–40 h.

[0020] Preferably, the roasting temperature is 350–450℃ and the roasting time is 1–3 hours.

[0021] This invention has found that the phase composition and the degree of graphitization can affect the photocatalytic performance of titanium dioxide.

[0022] This invention has found that, under the combined control of the preparation process, composition, and material ratio, a synergistic effect can be effectively achieved, which can significantly improve the photocatalytic performance of the prepared titanium dioxide nanofibers.

[0023] The present invention also provides a photocatalyst prepared by the aforementioned method.

[0024] The preferred application of this invention is as a photocatalyst for the photocatalytic degradation of organic pollutants in water.

[0025] The beneficial effects of this invention are:

[0026] 1. The preparation method of the strontium and graphite dual-auxiliary titanium dioxide nanofiber photocatalyst provided by the present invention is simple, easy to implement, low in cost, and has low equipment requirements.

[0027] 2. The strontium and graphite dual-aided titanium dioxide nanofiber photocatalyst provided by this invention utilizes strontium doping to reduce the grain size of titanium dioxide and increase the dislocation density. Through reasonable doping, the lattice distortion can be controlled, promoting the separation of photogenerated electron-hole pairs. By constructing a semiconductor heterojunction with titanium dioxide through high-conductivity zero-level semiconductor graphite, the band gap structure of titanium dioxide is changed, providing a transfer channel for photogenerated carriers. Under the synergistic effect of the two effects, the photocatalytic performance of titanium dioxide is improved.

[0028] 3. The nanofiber structure of the present invention has the advantages of large specific surface area of ​​nanomaterials, and is not easy to agglomerate, making it easy to recycle and avoiding secondary pollution to water bodies. Attached Figure Description

[0029] The accompanying drawings, which form part of this specification, are used to provide a further understanding of the invention. The illustrative embodiments of the invention and their descriptions are used to explain the invention and do not constitute an improper limitation of the invention.

[0030] Appendix Figure 1 These are scanning electron microscope images of embodiments of the present invention and Comparative Example 2;

[0031] Appendix Figure 2 These are transmission electron microscope images of embodiments of the present invention;

[0032] Appendix Figure 3 These are the X-ray diffraction patterns of embodiments and comparative examples of the present invention;

[0033] Appendix Figure 4 These are the Raman spectra of embodiments and comparative examples of the present invention;

[0034] Appendix Figure 5 These are fluorescence spectra of embodiments and comparative examples of the present invention. Detailed Implementation

[0035] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are some embodiments of the present invention, but not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0036] This invention provides a method for preparing a strontium and graphite dual-auxiliary titanium dioxide nanofiber photocatalyst, wherein the titanium dioxide nanofiber has anatase crystal structure.

[0037] This invention describes the experimental steps and data processing methods for the degradation of organic pollutants in wastewater:

[0038] Rhodamine B, methylene blue, methyl orange, and malachite green were used as representative organic pollutants in the photocatalysts, and their photocatalytic activity was determined. 40 mg of the photocatalyst was added to 50 ml of organic pollutant (concentration 10 mg / L), stirred in the dark for 20 min, and then irradiated with a 350 W xenon lamp to carry out the photocatalytic reaction. Samples were taken at regular intervals. After separating the photocatalyst, the degradation efficiency was measured using a UV-Vis spectrophotometer. The degradation efficiency η can be calculated using the residual concentration C and the initial concentration C0, and the calculation formula is as follows:

[0039] η = (1 - C / C0) × 100%.

[0040] To further understand the invention's content, features, and advantages, the following embodiments and comparative examples will be used to further illustrate these points.

[0041] Example

[0042] This invention provides a method for preparing a strontium and graphite-coated titanium dioxide nanofiber photocatalyst, comprising the following steps:

[0043] Step (1): Strontium acetate is placed in anhydrous ethanol and glacial acetic acid solvent and stirred until completely dissolved. Then, tetrabutyl titanate is added and stirred evenly to form a clear solution.

[0044] According to the preferred method, 0.022g of strontium acetate is placed in 50ml of anhydrous ethanol and 4ml of glacial acetic acid solvent, stirred until completely dissolved, and then 5ml of tetrabutyl titanate is added and stirred evenly to form a clear solution.

[0045] Step (2): Slowly add polyvinylpyrrolidone, cover the container, and stir continuously at room temperature until a light yellow, transparent, viscous electrospinning precursor solution is generated. Electrospin the above precursor solution and place the collected nanofiber felt in the air to calcine to form strontium-doped titanium dioxide nanofibers.

[0046] According to the preferred scheme, 4g of polyvinylpyrrolidone was added to prepare an electrospinning precursor solution;

[0047] According to the preferred scheme, the electrospinning voltage is 20kV;

[0048] According to the preferred scheme, the calcination heating rate is 20℃ / h, and the maximum calcination temperature is 500℃.

[0049] Step (3) involves hydrothermal treatment of titanium dioxide nanofibers with dimethylformamide and ammonia. After the precipitate is washed with water, it is calcined in a protective gas to allow graphite to adhere to the surface of the titanium dioxide nanofibers without binder.

[0050] According to the preferred method, 15 ml of dimethylformamide and 2 ml of ammonia water were used for hydrothermal treatment for 24 hours at a hydrothermal temperature of 150°C. After washing with water, the mixture was calcined in a nitrogen protective gas for 2 hours at a calcination temperature of 400°C.

[0051] Comparative Example 1

[0052] Step (1): Strontium acetate is placed in anhydrous ethanol and glacial acetic acid solvent and stirred until completely dissolved. Then, tetrabutyl titanate is added and stirred evenly to form a clear solution.

[0053] According to the preferred method, 0.022g of strontium acetate is placed in 50ml of anhydrous ethanol and 4ml of glacial acetic acid solvent, stirred until completely dissolved, and then 5ml of tetrabutyl titanate is added and stirred evenly to form a clear solution.

[0054] Step (2): Slowly add polyvinylpyrrolidone, cover the container, and stir continuously at room temperature until a light yellow, transparent, viscous electrospinning precursor solution is generated. Electrospin the above precursor solution and place the collected nanofiber felt in the air to calcine to form strontium-doped titanium dioxide nanofibers.

[0055] According to the preferred scheme, 4g of polyvinylpyrrolidone was added to prepare an electrospinning precursor solution;

[0056] According to the preferred scheme, the electrospinning voltage is 20kV;

[0057] According to the preferred scheme, the calcination heating rate is 20℃ / h, and the maximum calcination temperature is 500℃.

[0058] Comparative Example 2

[0059] Step (1): Tetrabutyl titanate is placed in anhydrous ethanol and glacial acetic acid solvent and stirred until it is completely dissolved to form a clear solution;

[0060] According to the preferred method, 5 ml of tetrabutyl titanate is placed in 50 ml of anhydrous ethanol and 4 ml of glacial acetic acid solvent;

[0061] Step (2): Slowly add polyvinylpyrrolidone, cover the container, and stir continuously at room temperature until a light yellow, transparent, viscous electrospinning precursor solution is generated. Electrospin the above precursor solution and place the collected nanofiber felt in the air to calcine to form strontium-doped titanium dioxide nanofibers.

[0062] According to the preferred scheme, 4g of polyvinylpyrrolidone was added to prepare an electrospinning precursor solution;

[0063] According to the preferred scheme, the electrospinning voltage is 20kV;

[0064] According to the preferred scheme, the calcination heating rate is 20℃ / h, and the maximum calcination temperature is 500℃.

[0065] Characterization and evaluation of the photocatalyst:

[0066] The photocatalysts prepared in the above examples and comparative examples were characterized by scanning electron microscopy, transmission electron microscopy, X-ray diffraction, Raman spectroscopy, and fluorescence spectroscopy, and their photocatalytic performance was tested.

[0067] Figure 1These are scanning electron microscope (SEM) images of the embodiments and Comparative Example 1. The SEM images show the morphology of the photocatalysts, which are composed of short nanofibers with diameters ranging from 150 to 250 nm. These short nanofibers are formed by the growth of titanium dioxide along the nanofibers during crystallization. The cross-sections of the broken nanofibers after calcination can be seen. In Comparative Example 1, there is no surface modification with graphite, so the surfaces of these short nanofibers are smooth and not interconnected. In the embodiments, the graphite adheres to the surface of the nanofibers, forming granules that are uniformly distributed without aggregation. The connections between the graphite and the titanium dioxide nanofibers are clearly visible, indicating the locations of the semiconductor heterojunctions. Due to the limited magnification, the morphology of the graphite cannot be clearly observed.

[0068] Figure 2 The transmission electron microscope (TEM) image of the embodiment is further magnified to make the morphology of graphite clearer, forming a nanorod structure. The high-resolution image shows the crystal structure of graphite and titanium dioxide. The (003) crystal plane of graphite and the (101), (200), and (103) crystal planes of the anatase phase of titanium dioxide are observed, indicating the phase structure of graphite and titanium dioxide.

[0069] Figure 3 The images show the X-ray diffraction patterns of Examples 1, 2, and 3. It can be seen that the peaks in Examples 1, 2, and 3 are all relatively sharp, indicating good crystallinity. Furthermore, all three are anatase phase, without the presence of the rutile phase, which has low photocatalytic efficiency. The highest peak is magnified, and the magnified image shows that the entry of strontium into the titanium dioxide lattice caused a shift in the peak positions of Examples 1 and 3, indicating that the entry of strontium led to lattice distortion. Simultaneously, Examples 1 and 3 showed a significant broadening of the peak, indicating a smaller grain size, increased dislocation density, and more crystal defects.

[0070] Figure 4 These are the Raman spectra of Examples 1, 2, and 3. In Examples 1, D and G bands formed by graphite are visible, indicating that this method can effectively load graphite onto titanium dioxide nanofibers, where it exists as the graphite phase. The higher G peak indicates a high degree of graphitization. In the magnified image of the highest peak, a significant shift in the peak position is observed in Examples 1 and 2, indicating that the entry of strontium into the titanium dioxide lattice leads to changes in the Raman vibrations of the chemical bonds.

[0071] Figure 5 The following are fluorescence spectra of Examples, Comparative Example 1, and Comparative Example 2. Although Examples, Comparative Example 1, and Comparative Example 2 show similar peak shapes, their luminescence intensity is significantly reduced, with Examples showing the lowest intensity. This indicates that the synergistic effect of the heterojunction structure formed by graphite and strontium doping alters the optical properties and bandgap structure of titanium dioxide. The reduction in luminescence intensity implies a higher separation rate of photogenerated electron-hole pairs, which is beneficial for the photocatalytic reaction.

[0072] Photocatalytic tests showed that within 120 min, the degradation efficiencies of Example 1, Comparative Example 2, and Comparative Example 3 for Rhodamine B were 91.94%, 84.66%, and 61.70%, respectively; within 90 min, the degradation efficiencies for methylene blue were 97.10%, 86.70%, and 65.41%, respectively; within 105 min, the degradation efficiencies for methyl orange were 92.51%, 83.16%, and 58.56%, respectively; and within 50 min, the degradation efficiencies for malachite green were 97.89%, 92.99%, and 64.36%, respectively.

[0073] The photocatalysts prepared in the examples showed significantly higher photocatalytic efficiency for the four simulated pollutants than those in Comparative Example 1 and Comparative Example 2.

[0074] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and not to limit them; although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some of the technical features; and these modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. A method for preparing a strontium and graphite dual-auxiliary titanium dioxide nanofiber photocatalyst, characterized in that, Includes the following steps: Step (1): Strontium acetate is placed in anhydrous ethanol and glacial acetic acid solvent and stirred until completely dissolved. Then, tetrabutyl titanate is added and stirred evenly to form a clear solution. Step (2): Slowly add polyvinylpyrrolidone, cover the container, and stir continuously at room temperature until a light yellow, transparent, viscous electrospinning precursor solution is generated. Electrospin the above precursor solution and place the collected nanofiber felt in the air to calcine to form strontium-doped titanium dioxide nanofibers. Step (3) involves hydrothermal treatment of titanium dioxide nanofibers with dimethylformamide and ammonia. After the precipitate is washed with water, it is calcined in a protective gas to allow graphite to adhere to the surface of the titanium dioxide nanofibers without binder.

2. The preparation method of the strontium and graphite dual-auxiliary titanium dioxide nanofiber photocatalyst according to claim 1, characterized in that: In step (1), the volume ratio of tetrabutyl titanate to strontium acetate is 100 mL : (0.2-0.8) g.

3. The preparation method of the strontium and graphite dual-auxiliary titanium dioxide nanofiber photocatalyst according to claim 1, characterized in that: In step (2), the volume ratio of tetrabutyl titanate to the mass ratio of polyvinylpyrrolidone is 100 mL : (120-200) g.

4. The preparation method of the strontium and graphite dual-auxiliary titanium dioxide nanofiber photocatalyst according to claim 1, characterized in that: In step (3), the volume ratio of dimethylformamide, titanium dioxide nanofibers, and 25% ammonia is 100mL:(0.4-1)g:(10-20)ml.

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