Preparation method of Ag2O-Bi4O5I2 broadband absorption heterojunction photocatalyst and its application in microreactors
By constructing an Ag2O-Bi4O5I2 heterojunction photocatalyst, the problems of easy recombination of photogenerated carriers and narrow absorption spectrum of bismuth iodide photocatalyst were solved, achieving efficient degradation of tetracycline, which is suitable for wastewater treatment.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Patents(China)
- Current Assignee / Owner
- CHANGZHOU UNIV
- Filing Date
- 2023-12-20
- Publication Date
- 2026-06-30
Smart Images
Figure HDA0004618087730000011 
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Abstract
Description
Technical Field
[0001] This invention relates to a method for preparing Ag2O-Bi4O5I2 broadband absorption heterojunction photocatalyst, belonging to the field of photocatalyst preparation. Background Technology
[0002] Since the discovery of penicillin, antibiotics have played an increasingly important role in human society. However, antibiotics are being overused on a large scale, especially in the pharmaceutical and aquaculture industries, leading to a continuous increase in antibiotic concentrations in wastewater. Tetracycline is a broad-spectrum antibiotic that easily induces drug resistance in organisms. Due to its high antibacterial properties and stability, traditional methods such as biodegradation are ineffective. Therefore, finding an efficient method to remove tetracycline from water is particularly important.
[0003] Over the past half-century, photocatalysis technology has flourished, gaining widespread application in wastewater treatment due to its clean and efficient characteristics. Bismuth oxyiodide (BiOI), as a highly efficient photocatalyst, has attracted considerable attention; however, its photogenerated carriers are prone to recombination, and its thermal stability is poor. Heating and sintering can transform BiOI into Bi4O5I2, which has a higher bismuth content and better thermal stability. However, Bi4O5I2 has a large band gap, failing to absorb the visible and near-infrared light that constitute a large portion of the solar spectrum, resulting in significant waste of solar energy. Constructing heterojunctions is a common method in photocatalysis to address the recombination problem of photogenerated carriers. By combining two materials with different valence band positions, photogenerated electrons and holes can accumulate on different materials, achieving carrier separation. Furthermore, broadening the absorption spectrum of BiOI-based photocatalysts to utilize visible and even near-infrared light is another breakthrough point for enhancing their photocatalytic performance. BiOI-based photocatalysts generally exhibit a nanosheet structure with a relatively small specific surface area; increasing the number of surface active sites is another direction for improvement.
[0004] Therefore, it is of great significance to seek a method for constructing heterojunctions to optimize iodine-oxybismuth photocatalysts, suppress the recombination of photogenerated carriers, broaden the absorption spectrum, and increase the surface active sites so that they can play an effective role in the degradation of tetracycline in wastewater. Summary of the Invention
[0005] This invention provides a method for preparing an Ag₂O-Bi₄O₅I₂ broadband absorption heterojunction photocatalyst. The method involves heat treatment to convert the BiOI precursor into Bi₄O₅I₂, followed by chemical precipitation to support broadband-absorbing Ag₂O on the surface of Bi₄O₅I₂ nanosheets, thus constructing a heterojunction to achieve the separation of photogenerated carriers. The resulting composite material exhibits good performance in the photocatalytic degradation of tetracycline.
[0006] The technical solution adopted in this invention includes the following steps:
[0007] Step 1: Dissolve bismuth nitrate pentahydrate in ethanol and stir at room temperature; slowly add potassium iodide and continue stirring; add sodium hydroxide solution dropwise to make pH=7; carry out water bath reaction; wash and dry to obtain BiOI sample.
[0008] Step 2: Place the BiOI powder into a muffle furnace and calcine it in air at a temperature of 400-500℃ for 2-6 hours. After grinding, obtain the Bi4O5I2 sample.
[0009] Step 3: Disperse Bi4O5I2 powder in water, add silver nitrate and stir; add sodium hydroxide solution dropwise to make pH=13, and continue stirring; after washing and drying, obtain Ag2O-Bi4O5I2 sample.
[0010] Step 4: Disperse Ag2O-Bi4O5I2 powder in a 5% Nafion solution and coat it onto a glass surface to obtain Ag2O-Bi4O5I2-supported glass. Using this glass as the lower layer and another glass without photocatalyst as the upper layer, construct a microreactor with a pore height of 100-300 μm in parallel.
[0011] Preferably, in step 1, the mass ratio of bismuth nitrate pentahydrate to potassium iodide is 0.485:0.166-0.332; the mass of bismuth nitrate pentahydrate accounts for 0.6-1% of the mass of anhydrous ethanol; the stirring time is 30-60 min; and the concentration of sodium hydroxide solution is 1 mol / L.
[0012] Preferably, the water bath reaction temperature in step 1 is 70–85°C, and the reaction time is 3–6 hours.
[0013] Preferably, in step 1, the washing solvent is a mixture of water and ethanol in a volume ratio of 1:1, and the washing is performed 3 to 6 times. The drying temperature is 50 to 70°C, and the drying time is 12 to 24 hours.
[0014] Preferably, in step 3, the mass ratio of Bi4O5I2 to silver nitrate is 2:0.06-1.47; the mass of Bi4O5I2 accounts for 0.3-0.5% of the mass of water; the stirring time is 30-60 min; and the stirring time continues for 3-6 h after adding sodium hydroxide.
[0015] Preferably, in step 3, the washing solvent is a mixture of water and ethanol in a volume ratio of 1:1, and the washing is performed 3 to 6 times. The drying temperature is 50 to 70°C, and the drying time is 12 to 24 hours.
[0016] Preferably, in the Ag2O-Bi4O5I2 sample prepared in step 3, Ag2O accounts for 5-50% of the mass of Bi4O5I2; more preferably, Ag2O accounts for 20% of the mass of Bi4O5I2.
[0017] Preferably, the mass concentration of the Nafion solution in step 4 is 5%; the amount of Ag₂O-Bi₄O₅I₂ powder in the Nafion solution is 0.1–0.3 g / mL. The glass has an area of 40*25 mm, and each cm²... 2 The amount of catalyst coated on the glass is approximately 0.5-1.5 mg.
[0018] Preferably, the pore height of the microreactor in step 4 is 200 μm.
[0019] The beneficial effects of this invention are as follows:
[0020] 1. This invention prepares BiOI via a simple water bath method and then heat-treats it to prepare a Bi4O5I2 photocatalyst with better thermal stability. The problem of easy recombination of photogenerated carriers is solved by constructing a heterojunction. The auxiliary catalyst Ag2O used exhibits good light absorption in the visible to near-infrared range, and the prepared composite material also shows excellent broad-spectrum absorption. The composite Ag2O exhibits a nanoparticle morphology, increasing the reactive sites on the Bi4O5I2 nanosheets and further enhancing its photocatalytic performance.
[0021] 2. This invention does not use any toxic solvents throughout the entire process, the solution is simple and environmentally friendly, does not produce any toxic or harmful byproducts, the raw materials are readily available, and it is suitable for large-scale industrial production.
[0022] 3. This invention proposes the application of Ag2O-Bi4O5I2 photocatalyst in the treatment of tetracycline in wastewater. The synthesized composite photocatalyst significantly improves the degradation rate of tetracycline, which helps to solve the current problem of excessive levels of antibiotics that are difficult to degrade in wastewater.
[0023] 4. This invention constructs a flat-plate microreactor, utilizing the thermal localization effect of the microreactor to prevent heat loss into the solution, further enhancing the photothermal effect of Ag2O-Bi4O5I2. Compared with traditional reactors, its photocatalytic reaction efficiency is significantly improved. Attached Figure Description
[0024] Figure 1 The image shows the XRD pattern of the Ag2O-Bi4O5I2 sample prepared in Example 3.
[0025] Figure 2 Scanning electron microscope image of the Ag2O-Bi4O5I2 sample prepared in Example 3.
[0026] Figure 3 The image shows the UV-Vis-NIR absorption spectrum of the Ag2O-Bi4O5I2 sample.
[0027] Figure 4 Digital photograph of the Ag2O-Bi4O5I2 sample.
[0028] Figure 5 The image shows the photocatalytic performance of the Ag2O-Bi4O5I2 sample. Detailed Implementation
[0029] To further understand the present invention, the present invention will be described below with reference to embodiments. These descriptions are only for further explaining the features and advantages of the present invention and are not intended to limit the claims of the present invention.
[0030] Example 1
[0031] (1) Dissolve 0.485 g of bismuth nitrate pentahydrate in 60 mL of ethanol and stir at room temperature for 30 min; slowly add 0.166 g of potassium iodide and continue stirring for 30 min; add 1 mol / L sodium hydroxide solution to make pH = 7; react in a water bath at 80 °C for 5 h; wash three times with a mixed solvent of water and ethanol in a volume ratio of 1:1, and dry at 60 °C for 12 h to obtain BiOI sample.
[0032] (2) The BiOI powder was placed in a muffle furnace and calcined in air at 420°C for 3 hours. After grinding, Bi4O5I2 sample was obtained.
[0033] (3) Disperse 0.200g Bi4O5I2 powder into 50mL of water, add 0.015g silver nitrate, stir for 30min; add 1mol / L sodium hydroxide solution dropwise to make pH=13, continue stirring for 4h; wash 3 times with a mixed solvent of water and ethanol in a volume ratio of 1:1, and dry at 60℃ for 12h to obtain 5% Ag2O-Bi4O5I2 sample.
[0034] Example 2
[0035] (1) Dissolve 0.485 g of bismuth nitrate pentahydrate in 60 mL of ethanol and stir at room temperature for 30 min; slowly add 0.166 g of potassium iodide and continue stirring for 30 min; add 1 mol / L sodium hydroxide solution to make the pH = 7; perform water bath reaction at 80 °C for 5 h; wash 3 times with a mixed solvent of water and ethanol in a volume ratio of 1:1, and dry at 60 °C for 12 h to obtain BiOI sample.
[0036] (2) The BiOI powder was placed in a muffle furnace and calcined in air at 420°C for 3 hours. After grinding, Bi4O5I2 sample was obtained.
[0037] (3) Disperse 0.200g Bi4O5I2 powder into 50mL of water, add 0.029g silver nitrate, stir for 30min; add 1mol / L sodium hydroxide solution dropwise to make pH=13, continue stirring for 4h; wash 3 times with a mixed solvent of water and ethanol in a volume ratio of 1:1, and dry at 60℃ for 12h to obtain 10% Ag2O-Bi4O5I2 sample.
[0038] Example 3
[0039] (1) Dissolve 0.485 g of bismuth nitrate pentahydrate in 60 mL of ethanol and stir at room temperature for 30 min; slowly add 0.166 g of potassium iodide and continue stirring for 30 min; add 1 mol / L sodium hydroxide solution to make the pH = 7; perform water bath reaction at 80 °C for 5 h; wash 3 times with a mixed solvent of water and ethanol in a volume ratio of 1:1, and dry at 60 °C for 12 h to obtain BiOI sample.
[0040] (2) The BiOI powder was placed in a muffle furnace and calcined in air at 420°C for 3 hours. After grinding, Bi4O5I2 sample was obtained.
[0041] (3) Disperse 0.200g Bi4O5I2 powder into 50mL of water, add 0.058g silver nitrate, stir for 30min; add 1mol / L sodium hydroxide solution dropwise to make pH=13, continue stirring for 4h; wash 3 times with a mixed solvent of water and ethanol in a volume ratio of 1:1, and dry at 60℃ for 12h to obtain 20% Ag2O-Bi4O5I2 sample.
[0042] Example 4
[0043] (1) Dissolve 0.485 g of bismuth nitrate pentahydrate in 60 mL of ethanol and stir at room temperature for 30 min; slowly add 0.166 g of potassium iodide and continue stirring for 30 min; add 1 mol / L sodium hydroxide solution to make the pH = 7; perform water bath reaction at 80 °C for 5 h; wash 3 times with a mixed solvent of water and ethanol in a volume ratio of 1:1, and dry at 60 °C for 12 h to obtain BiOI sample.
[0044] (2) The BiOI powder was placed in a muffle furnace and calcined in air at 420°C for 3 hours. After grinding, Bi4O5I2 sample was obtained.
[0045] (3) Disperse 0.200g Bi4O5I2 powder into 50mL of water, add 0.147g silver nitrate, stir for 30min; add 1mol / L sodium hydroxide solution dropwise to make pH=13, continue stirring for 4h; wash 3 times with a mixed solvent of water and ethanol in a volume ratio of 1:1, and dry at 60℃ for 12h to obtain 50% Ag2O-Bi4O5I2 sample.
[0046] Comparative Example 1
[0047] (1) Dissolve 0.485 g of bismuth nitrate pentahydrate in 60 mL of ethanol and stir at room temperature for 30 min; slowly add 0.166 g of potassium iodide and continue stirring for 30 min; add 1 mol / L sodium hydroxide solution to make the pH = 7; perform water bath reaction at 80 °C for 5 h; wash 3 times with a mixed solvent of water and ethanol in a volume ratio of 1:1, and dry at 60 °C for 12 h to obtain BiOI sample.
[0048] (2) The BiOI powder was placed in a muffle furnace and calcined in air at 420°C for 3 hours. After grinding, Bi4O5I2 sample was obtained.
[0049] Comparative Example 2
[0050] Add 0.200 g of silver nitrate to 50 mL of water and stir for 30 min; add 1 mol / L sodium hydroxide solution dropwise to make pH = 13, and continue stirring for 4 h; wash three times with a mixed solvent of water and ethanol in a volume ratio of 1:1, and dry at 60 °C for 12 h to obtain the Ag2O sample.
[0051] The photocatalytic test conditions are as follows:
[0052] 10 mg of catalyst was added to a 60 mL beaker, followed by 50 mL of tetracycline solution (20 mg / L). Simultaneously, a 300 W full-spectrum xenon lamp was used to simulate sunlight, and the reaction was continued for 1 h. The solution was then collected, and the degradation rate of tetracycline was measured.
[0053] The degradation rates of 5% Ag2O-Bi4O5I2, 10% Ag2O-Bi4O5I2, 20% Ag2O-Bi4O5I2, and 50% Ag2O-Bi4O5I2 in Examples 1-4 were 76.1%, 85.2%, 97.8%, and 75.4%, respectively.
[0054] After 60 min of degradation, Bi4O5I2 in Comparative Example 1 degraded 69.3% of tetracycline; Ag2O in Comparative Example 2 degraded 58.7%; and the performance of the composite samples was improved to varying degrees, with the best performance achieved by 20% Ag2O-Bi4O5I2, which degraded 97.8%.
[0055] The degradation rate of 20% Ag2O-Bi4O5I2 is 3.82. The reaction rate constant of 20% Ag2O-Bi4O5I2 is 3.01 times that of Bi4O5I2 and 4.16 times that of Ag2O.
[0056] Example 5
[0057] 10 mg of 20% Ag₂O-Bi₄O₅I₂ powder was dispersed in 0.5 mL of 5% Nafion solution and coated onto a glass surface (40 mm * 25 mm) to obtain a glass supported on 20% Ag₂O-Bi₄O₅I₂. Using this glass as the lower layer and another unsupported glass as the upper layer, a microreactor with a pore height of 200 μm, a length of 40 mm, and a width of 25 mm was constructed in parallel. Both sides were sealed with adhesive, and this was designated as the 20% AO-MR sample.
[0058] Take 20 mL of tetracycline solution (concentration 20 mg / L) and flow it through the sample with the aid of a syringe pump. The flow rate is 20 mL / h, and the sample is simultaneously irradiated with a 300 W full-spectrum xenon lamp for 60 min.
[0059] Example 6
[0060] 10 mg of Bi4O5I2 powder was dispersed in 0.5 mL of 5% Nafion solution and coated onto a glass surface to obtain a Bi4O5I2-supported glass. Using this glass as the lower layer and another unsupported glass as the upper layer, a microreactor with a pore height of 200 μm, a length of 40 mm, and a width of 25 mm was constructed in parallel. The two sides were sealed with glue, and this was designated as the BOI-MR sample.
[0061] Take 20 mL of tetracycline solution (concentration 20 mg / L) and flow it through the sample with the help of a syringe pump (flow rate 20 mL / h), while irradiating it with a 300 W full-spectrum xenon lamp for 60 min.
[0062] Example 7
[0063] 10 mg of Ag₂O powder was dispersed in 0.5 mL of 5% Nafion solution and coated onto a glass surface to obtain Ag₂O-supported glass. Using this glass as the lower layer and another unsupported glass as the upper layer, a microreactor with a pore height of 200 μm, a length of 40 mm, and a width of 25 mm was constructed in parallel. The two sides were sealed with glue, and this was designated as the AO-MR sample.
[0064] Take 20 mL of tetracycline solution (concentration 20 mg / L) and flow it through the sample with the help of a syringe pump (flow rate 20 mL / h), while irradiating it with a 300 W full-spectrum xenon lamp for 60 min.
[0065] Comparative Example 3
[0066] 10 mg of 20% Ag₂O-Bi₄O₅I₂ powder was dispersed in 0.5 mL of 5% Nafion solution and coated onto a glass surface to obtain glass loaded with 20% Ag₂O-Bi₄O₅I₂. This glass was placed at the bottom of a reactor of equal area, i.e., a conventional biaxial reactor, with a bottom the size of the glass (40 mm * 25 mm) and a height of 10 cm, and was designated as the 20% AO-BR sample.
[0067] Take 20 mL of tetracycline solution (concentration 20 mg / L), add it to the reactor, and simultaneously irradiate it with a 300 W full-spectrum xenon lamp for 60 min.
[0068] Comparative Example 4
[0069] 10 mg of Bi4O5I2 powder was dispersed in 0.5 mL of 5% Nafion solution and coated onto a glass surface to obtain Bi4O5I2-supported glass. This glass was placed at the bottom of a reactor of equal area, i.e., a conventional two-dimensional reactor, with a bottom the size of the glass (40 mm * 25 mm) and a height of 10 cm, and was designated as the BOI-BR sample.
[0070] Take 20 mL of tetracycline solution (concentration 20 mg / L), add it to the reactor, and simultaneously irradiate it with a 300 W full-spectrum xenon lamp for 60 min.
[0071] Comparative Example 5
[0072] 10 mg of Ag₂O powder was dispersed in 0.5 mL of 5% Nafion solution and coated onto a glass surface to obtain Ag₂O-supported glass. This glass was placed at the bottom of a reactor of equal area, i.e., a conventional biaxial reactor, with a bottom the size of the glass (40 mm * 25 mm) and a height of 10 cm, and was designated as the AO-BR sample.
[0073] Take 20 mL of tetracycline solution (concentration 20 mg / L), add it to the reactor, and simultaneously irradiate it with a 300 W full-spectrum xenon lamp for 60 min.
[0074] After the photocatalytic reaction was completed, the solution concentration was measured. The degradation rate of the 20% AO-MR sample in Example 5 reached 95.2%, while that of Comparative Example 3 was only 14.7%. The degradation rate of BOI-MR in Example 6 was 41.5%, while that of Comparative Example 4 was 5.2%. The degradation rate of AO-MR in Example 7 using Ag2O as a catalyst was 49.8%, while that of Comparative Example 5 was 4.3%.
[0075] The reaction rate constant of Example 5 is 3.04, and the reaction rate constant of Comparative Example 3 is 0.16.
[0076] The reaction rate constant of Example 5 is 19.2 times higher than that of Comparative Example 3. The main reason is that Ag2O-Bi4O5I2 powder, as a catalyst that can absorb near-infrared light, has excellent thermal effects. By rapidly preparing a simple microreactor, the thermal localization effect can be greatly enhanced, accelerating the transport of photogenerated carriers and achieving more efficient photocatalysis.
[0077] The reaction rate constant of Example 6 was 0.54, and the reaction rate constant of Comparative Example 4 was 0.05. The reaction rate constant of Example 6 was 10.8 times that of Comparative Example 4. The reaction rate constant of Example 7 was 0.69, and the reaction rate constant of Comparative Example 5 was 0.04. The reaction rate constant of Example 7 was 15.7 times that of Comparative Example 5.
[0078] It can be seen that the efficiency improvement of Bi4O5I2 without photothermal effect is relatively small, while the performance improvement of Ag2O with photothermal effect is relatively high, but not as good as Ag2O-Bi4O5I2 composite material. This is because the heterojunction of Ag2O-Bi4O5I2 composite material further improves the separation of photogenerated carriers.
[0079] Figure 1 The XRD pattern of the Ag2O-Bi4O5I2 sample in Example 3 is shown. It can be seen that both Bi4O5I2 and Ag2O exhibit good crystallinity, and the peak positions correspond to those on the standard card. In the Ag2O-Bi4O5I2 composite sample, isomorphic crystal planes (-411) and (402) of Bi4O5I2 and (111) of Ag2O can be observed, indicating that Bi4O5I2 and Ag2O have achieved good composite formation.
[0080] Figure 2 This is a scanning electron microscope image of the Ag2O-Bi4O5I2 sample from Example 3. It can be seen that Bi4O5I2 exhibits a nanosheet morphology of 200–400 nm, while Ag2O is attached to its surface in the form of nanoparticles, exposing more reactive sites on its surface.
[0081] Figure 3 The image shows the UV-Vis-NIR absorption spectra of the Ag₂O-Bi₄O₅I₂ sample. Pure Bi₄O₅I₂ exhibits absorption only below 500 nm, while pure Ag₂O demonstrates excellent absorption across the entire spectral range, particularly below 800 nm. The composite photocatalyst sample inherits the advantages of both, exhibiting good absorption across the UV-Vis-NIR spectrum.
[0082] Figure 4This is a digital photograph of the Ag2O-Bi4O5I2 sample. It can be seen that pure Bi4O5I2 is lighter in color, while Ag2O is darker. In the complex, the color gradually deepens with increasing Ag2O content, indicating that it can absorb more light, consistent with the spectral data.
[0083] Figure 5 The image shows the photocatalytic performance of the Ag2O-Bi4O5I2 sample. After 60 min, Bi4O5I2 degraded 69.3% of tetracycline, while Ag2O degraded 58.7%. The performance of the composite samples was improved to varying degrees, with the best performance from the 20% Ag2O-Bi4O5I2 sample, which degraded 97.8%. Its reaction rate constant was 3.01 times that of Bi4O5I2 and 4.16 times that of Ag2O.
[0084] Examples 1-4 all used powders, while Examples 5-7 used thin films, making direct comparisons between them impossible. However, the above embodiments of the present invention demonstrate the advantages of composite materials and microreactors.
Claims
1. A method for preparing a microreactor based on an Ag₂O-Bi₄O₅I₂ broadband absorption heterojunction photocatalyst, characterized in that: (1) Disperse Bi4O5I2 powder in water, add silver nitrate and stir; add sodium hydroxide solution dropwise to make pH=13, and continue stirring; wash and dry to obtain Ag2O-Bi4O5I2 broadband absorption heterojunction photocatalyst; Ag2O accounts for 5~50% of the mass of Bi4O5I2 in Ag2O-Bi4O5I2; (2) The prepared Ag2O-Bi4O5I2 powder was dispersed in Nafion solution and coated onto the glass surface to obtain Ag2O-Bi4O5I2-supported glass. The glass coated with photocatalyst was used as the lower layer and another glass without photocatalyst was used as the upper layer. The two layers were constructed in parallel to form a microreactor with a pore height of 100~300μm.
2. The method for preparing the microreactor based on the Ag2O-Bi4O5I2 broadband absorption heterojunction photocatalyst according to claim 1, characterized in that, In step (1), the mass ratio of Bi4O5I2 to silver nitrate is 2:0.06~1.
47.
3. The method for preparing the microreactor based on the Ag2O-Bi4O5I2 broadband absorption heterojunction photocatalyst according to claim 1, characterized in that, Step (1) After adding sodium hydroxide solution, continue stirring for 3-6 hours; the drying temperature is 50-70℃ and the drying time is 12-24 hours.
4. The method for preparing the microreactor based on the Ag2O-Bi4O5I2 broadband absorption heterojunction photocatalyst according to claim 1, characterized in that, Step (1) Ag2O accounts for 20% of the mass of Bi4O5I2.
5. The method for preparing a microreactor based on a broad-spectrum absorption heterojunction photocatalyst of Ag2O-Bi4O5I2 according to claim 1, wherein the mass concentration of the Nafion solution is 5%; and the amount of Ag2O-Bi4O5I2 powder in the Nafion solution is 0.1~0.3 g / mL.
6. The method for preparing the microreactor based on the Ag2O-Bi4O5I2 broadband absorption heterojunction photocatalyst according to claim 1, characterized in that: Every cm on the glass 2 The mass of the coated photocatalyst is 0.5-1.5 mg.