Preparation method and application of a bismuth-based photocatalytic porous ceramic material

Abstract

This invention provides a method for preparing a bismuth-based photocatalytic porous ceramic material, comprising preparing a Bi₂O₃ / Bi₂WO₆ heterojunction photocatalytic powder, adding it to a viscous solution to obtain a slurry, impregnating it with a porous polyurethane sponge, shaping and drying it, and then calcining it to prepare the bismuth-based photocatalytic porous ceramic material. An application is also provided: this bismuth-based photocatalytic porous ceramic material is used for the photocatalytic degradation of pollutants. The bismuth-based photocatalytic porous ceramic material of this invention can be recycled multiple times, has self-cleaning surface properties, can be excited by natural light, and is used for the photocatalytic degradation of pollutants.

Description

Technical Field

[0001] This invention belongs to the field of photocatalyst technology, specifically relating to a method for preparing and applying bismuth-based photocatalytic porous ceramic materials. Background Technology

[0002] In the field of photocatalysis, traditional suspended powder photocatalysts, with their advantages of large specific surface area and abundant active sites, can achieve photocatalytic reactions to a certain extent and have long been widely used in water treatment and other fields. However, in practical water treatment scenarios, traditional suspended powder photocatalysts face several challenging problems. Firstly, separation and recovery costs are high. Secondly, traditional suspended powder photocatalysts pose a high risk of secondary pollution. If they are not effectively recovered after the reaction, they may cause potential harm to aquatic organisms and ecosystems. To address these issues, recyclable photocatalysts have emerged.

[0003] Currently, there are two main methods for preparing recyclable photocatalytic materials: the first is to load photocatalytic powder onto a specific support to obtain a supported photocatalyst; the second is to directly prepare shaped recyclable photocatalysts (such as porous ceramics, microcrystalline glass, etc.) from powdered photocatalysts through sintering and other techniques. This allows the photocatalyst to maintain its photocatalytic activity while possessing higher recyclability, reducing its usage cost, and making it more suitable for practical wastewater treatment applications. However, supported photocatalysts inevitably face the problem of active component loss during long-term use. Due to the weak bonding between the support and the photocatalytic powder, it will gradually detach under mechanical action such as wind and water flow impact, making this approach unsuitable for long-term applications. The main problem with shaped photocatalysts is that the photocatalytic activity is difficult to retain during powder processing, resulting in a decrease in the photocatalytic degradation performance of the final product. For example, traditional TiO2-coated ceramics can hardly be excited by natural light when immersed in water. Therefore, the design of shaped photocatalytic materials should improve the utilization efficiency of natural light, while preserving photocatalytic performance as much as possible during the preparation process. Summary of the Invention

[0004] The technical problem to be solved by the present invention is to provide a method for preparing bismuth-based photocatalytic porous ceramic materials and their applications, which are in response to the shortcomings of the prior art. The bismuth-based photocatalytic porous ceramic materials can be recycled and reused multiple times, have self-cleaning properties, can be excited by natural light, and are used for photocatalytic degradation of pollutants.

[0005] To solve the above-mentioned technical problems, the technical solution adopted by the present invention is: a method for preparing bismuth-based photocatalytic porous ceramic materials, the method being as follows: Preparation of S1, Bi2O3 / Bi2WO6 heterojunction photocatalytic powder: S101, Preparation of precursor solution: Dissolve NaWO4·2H2O in ethylene glycol, then add Bi(NO3)·5H2O, and sonicate to dissolve to obtain solution A; Bi2O3 was added to ethanol and stirred to disperse, resulting in suspension B. The solution A is poured into the suspension B, and after ultrasonic stirring and mixing, a precursor solution is obtained. S102. The precursor solution obtained in S101 is subjected to a solvothermal reaction at a temperature of 160℃. After naturally cooling to room temperature, the supernatant is discarded. The precipitate is washed alternately with anhydrous ethanol and deionized water. The washed product is then dried to obtain Bi2O3 / Bi2WO6 heterojunction photocatalytic powder. S2. Disperse sodium carboxymethyl cellulose powder in a 12% (w / w) polyvinyl alcohol aqueous solution and stir magnetically at room temperature to obtain a viscous solution. S3. Add the Bi2O3 / Bi2WO6 heterojunction photocatalytic powder obtained in S102 to the viscous solution obtained in S2, stir evenly, and obtain a slurry; S4. After cleaning and drying the porous polyurethane sponge with deionized water, immerse it in the slurry obtained in S3, and repeatedly squeeze it to make the slurry penetrate and distribute inside the pores of the porous polyurethane sponge, thus obtaining the impregnated porous polyurethane sponge. S5. After shaping and drying the porous polyurethane sponge obtained in S4, heat it to 500℃ at a heating rate of 1℃ / min and hold it at that temperature for 2 hours. Then heat it to 770℃ at a heating rate of 2℃ / min and hold it at that temperature for 3 hours. Allow it to cool naturally to room temperature to obtain the Bi2O3 / Bi2WO6 porous ceramic photocatalyst, which is a bismuth-based photocatalytic porous ceramic material.

[0006] This invention uses a sponge template to create holes, which can prevent breakage caused by significant shrinkage during the product firing process, while controlling the product to have a suitable pore size distribution.

[0007] Preferably, the molar ratio of NaWO4·2H2O, Bi(NO3)·5H2O and Bi2O3 in S101 is 3 mmol: 6 mmol: 0.3 mmol.

[0008] Preferably, the solvothermal reaction time in S102 is 12 hours, and the drying conditions are: drying at 60°C with forced air for 12 hours.

[0009] Preferably, the mass ratio of sodium carboxymethyl cellulose powder and 12% polyvinyl alcohol aqueous solution in S2 is 1:50.

[0010] Preferably, the mass ratio of the Bi2O3 / Bi2WO6 heterojunction photocatalytic powder to the viscous solution in S3 is 3.2:10.2.

[0011] Preferably, the porous polyurethane sponge in S4 has a pore density of 30 ppi and a thickness of 10 mm.

[0012] Preferably, the drying conditions described in S4 are: drying at 60°C with forced air for 12 hours.

[0013] Preferably, the bismuth-based photocatalytic porous ceramic material in S5 has an average specific surface area of ​​3.24 m². 2 / g, with an average pore size of 2.75μm.

[0014] The present invention also provides the application of the bismuth-based photocatalytic porous ceramic material prepared by the above preparation method, wherein the bismuth-based photocatalytic porous ceramic material is used for photocatalytic degradation of pollutants.

[0015] Preferably, the bismuth-based photocatalytic porous ceramic material degrades tetracycline in wastewater under sunlight.

[0016] Compared with the prior art, the present invention has the following advantages: This invention directly uses Bi₂O₃ / Bi₂WO₆ heterojunction photocatalytic powder to sinter porous ceramic materials with good photocatalytic activity. Using a sponge template for pore creation prevents breakage caused by significant shrinkage during sintering and controls the product's pore size distribution. By controlling the grain boundary fusion during powder sintering with appropriate sintering temperature and holding time, the loss of photocatalytic activity is prevented, ultimately yielding bismuth-based photocatalytic porous ceramic materials with excellent photocatalytic and mechanical properties. The prepared bismuth-based photocatalytic porous ceramic materials can be recycled multiple times, possess self-cleaning surface properties, and are suitable for photocatalytic degradation of pollutants. They are applicable to applications requiring low-cost, long-term self-purification of water and air, such as river purification products, aquarium decorations, and indoor air purifier components.

[0017] The present invention will now be described in further detail with reference to the accompanying drawings and embodiments. Attached Figure Description

[0018] Figure 1 This is a physical image of the Bi2O3 / Bi2WO6 porous ceramic photocatalyst sample prepared in Example 1 of the present invention.

[0019] Figure 2 These are SEM images of the Bi2O3 / Bi2WO6 porous ceramic photocatalysts prepared at different sintering temperatures in Example 1 of the present invention, wherein (a)-(d) sintering temperature is 720℃, (e)-(h) sintering temperature is 770℃, and (i)-(l) sintering temperature is 820℃.

[0020] Figure 3The figures show the photocatalytic performance of Bi2O3 / Bi2WO6 porous ceramics prepared at different sintering temperatures in Example 1 of this invention. (a) is the photocatalytic degradation efficiency curve, and (b) is a bar chart of the photocatalytic degradation efficiency and a curve showing the degradation rate k-value.

[0021] Figure 4 The image shows the mercury intrusion porosimetry pore size distribution curves of Bi2O3 / Bi2WO6 photocatalytic ceramics at different sintering temperatures (720℃, 770℃, 820℃) in Example 1 of this invention.

[0022] Figure 5 This is a photocatalytic effect diagram of the Bi2O3 / Bi2WO6 porous ceramic photocatalyst (sintering temperature 770℃) prepared in Example 1 of the present invention under sunlight self-cleaning comparison test.

[0023] Figure 6 This is a cycle test diagram of the Bi2O3 / Bi2WO6 porous ceramic photocatalyst (sintering temperature 770℃) prepared in Example 1 of the present invention.

[0024] Figure 7 The EPR spectra of the Bi2O3 / Bi2WO6 heterojunction photocatalytic powder (a) prepared in step S102 and the Bi2O3 / Bi2WO6 porous ceramic photocatalyst (b) prepared in step S5 of Example 1 of the present invention are the DMPO-OH adduct formed after the spin trapping agent DMPO captures hydroxyl radicals. Detailed Implementation

[0025] Example 1

[0026] The method for preparing the bismuth-based photocatalytic porous ceramic material in this embodiment is as follows: Preparation of S1, Bi2O3 / Bi2WO6 heterojunction photocatalytic powder: S101, Preparation of precursor solution: Dissolve 3 mmol NaWO4·2H2O (0.989 g) in 34 mL of ethylene glycol, then add 6 mmol Bi(NO3)·5H2O (2.91 g), and sonicate to dissolve to obtain solution A; 0.3 mmol Bi2O3 (0.1398 g) was added to 86 mL of ethanol and stirred for 30 min to obtain suspension B; The solution A was poured into the suspension B and ultrasonically stirred for 30 minutes to obtain the precursor solution. S102. The precursor solution obtained in S101 was transferred to a 150 mL polytetrafluoroethylene liner, sealed in a stainless steel high-pressure reactor, and placed in a vacuum drying oven. A solvothermal reaction was carried out at 160℃ for 12 h. After natural cooling to room temperature, the supernatant was discarded. The precipitate was washed alternately with anhydrous ethanol and deionized water. The washed product was then dried for 12 h to obtain Bi2O3 / Bi2WO6 heterojunction photocatalytic powder. The molar ratio of Bi2O3 to Bi2WO6 in the Bi2O3 / Bi2WO6 heterojunction photocatalytic powder was 1:10. S2. Disperse 0.2g of sodium carboxymethyl cellulose (CMC) powder in 10g of a 12% (w / w) aqueous solution of polyvinyl alcohol. Stir magnetically at room temperature to obtain a uniform and transparent viscous solution. S3. Add 3.2 g of Bi2O3 / Bi2WO6 heterojunction photocatalytic powder obtained in S102 to 10.2 g of viscous solution obtained in S2, stir evenly to obtain slurry; S4. After ultrasonic cleaning with deionized water and drying at 60°C for 12 hours, the porous polyurethane sponge (pore density of 30ppi, thickness of 10mm, φ61.2mm) is immersed in the slurry obtained in S3 and repeatedly squeezed to allow the slurry to fully penetrate and evenly distribute inside the pores of the porous polyurethane sponge, thus obtaining the impregnated porous polyurethane sponge. S5. After shaping and drying the porous polyurethane sponge obtained in S4, heat it to 500℃ at a heating rate of 1℃ / min and hold it at that temperature for 2 hours to complete the full decomposition of the organic components. Then, heat it to 770℃ at a heating rate of 2℃ / min and hold it at that temperature for 3 hours to promote the sintering of heterojunction particles and the improvement of the framework crystal form. Finally, cool it naturally to room temperature to obtain the Bi2O3 / Bi2WO6 porous ceramic photocatalyst, which is a bismuth-based photocatalytic porous ceramic material. Figure 1 The bismuth-based photocatalytic porous ceramic material has an average specific surface area of ​​3.24 m². 2 / g, with an average pore size of 2.75μm.

[0027] This embodiment uses a sponge template to create holes, which can prevent breakage caused by significant shrinkage during the product firing process, while also controlling the product to have a suitable pore size distribution.

[0028] In this embodiment, the sintering temperature of 770℃ in step S5 was further optimized, and experiments were conducted to prepare Bi2O3 / Bi2WO6 porous ceramic photocatalysts at different sintering temperatures of 720℃, 745℃, 770℃, 795℃, 820℃, and 870℃.

[0029] SEM images of Bi₂O₃ / Bi₂WO₆ porous ceramic photocatalysts sintered at 720℃, 770℃, and 820℃ are shown below. Figure 2 As shown, by respectively testing at 720℃ ( Figure 2 (ad), 770℃ ( Figure 2 (e.g., 820℃) Figure 2 The porous Bi2O3 / Bi2WO6 ceramics under medium-sized substrates were characterized by SEM. Figure 2 Comparison of microstructures of the same row at the same sintering temperature but different dimensions. Figure 2 (a), (e), (i) and Figure 2 (b), (f), and (j) show that the higher the sintering temperature, the smoother the ceramic surface. At 720 ℃, porous ceramics contain a large number of pores. Figure 2 (c) The distribution is relatively uniform, and the ceramic particles undergo polymerization and cross-linking to form a three-dimensional network structure. With increasing sintering temperature, the accumulation between the porous ceramic particles gradually becomes denser, leading to a gradual decrease in the number of pores. Meanwhile, compared to... Figure 2 (d), (h), and (l) revealed that the crystallinity of the porous ceramic continuously increased, the ceramic sample became denser, and the average grain size of the porous ceramic also continuously increased with increasing temperature. At 720℃, the grains were not fully developed, the grain size was small, and the photocatalytic activity was insufficient. When the temperature increased to 770℃, the crystallinity increased, the number and size of pores decreased, the grains gradually grew and developed to a complete equilibrium, and the photocatalytic activity reached its maximum value. When the temperature continued to increase to 820℃, abnormal grain growth occurred, the porous ceramic structure became too dense, and the photocatalytic activity decreased sharply. This is consistent with the photocatalytic experiment results, jointly confirming that the optimal sintering temperature for preparing Bi2O3 / Bi2WO6 porous ceramics is 770℃.

[0030] The sintering temperatures were 720℃, 745℃, 770℃, 795℃, 820℃, and 870℃, respectively, and the resulting Bi2O3 / Bi2WO6 porous ceramic photocatalysts were denoted as BO-BWO 720℃, BO-BWO 745℃, BO-BWO 770℃, BO-BWO 795℃, BO-BWO 820℃, and BO-BWO 870℃, respectively.

[0031] Figure 3 The photocatalytic degradation efficiency curves of tetracycline by Bi2O3 / Bi2WO6 photocatalytic ceramics are shown respectively. Figure 3 (a) and its corresponding bar graph and the curve of the light reaction rate constant k ( Figure 3(b) By comparing the photocatalytic degradation efficiency curves at different sintering temperatures, it can be found that the degradation efficiency of tetracycline by the Bi2O3 / Bi2WO6 porous ceramic photocatalyst prepared at different sintering temperatures varies significantly. With increasing sintering temperature, the photocatalytic degradation effect of the porous ceramic on tetracycline generally shows a trend of first increasing and then decreasing, and the reaction rate constant k also exhibits a consistent pattern. The porous ceramic prepared at 770℃ showed the highest degradation efficiency, at 65.97%. At this temperature, the active sites are fully exposed, and the photogenerated carrier separation efficiency and stability reach a balance, thus exhibiting the optimal photocatalytic degradation efficiency. Simultaneously, its reaction rate constant k also reaches a peak value of 0.0042 min. -1 When the sintering temperature reaches or exceeds 820℃, the photocatalytic effect decreases sharply, and the photoreaction rate also drops drastically. Therefore, the optimal sintering temperature for the prepared Bi₂O₃ / Bi₂WO₆ porous ceramic photocatalyst is 770℃.

[0032] Figure 4 The mercury intrusion porosimetry (MIP) pore size distribution curves of Bi₂O₃ / Bi₂WO₆ photocatalytic ceramics at different sintering temperatures (720℃, 770℃, and 820℃) are presented. The 720℃ sample (720℃ BO-BWO Ceramic) exhibits a sharp single-peak distribution, with most probable pore sizes of approximately 150-200 nm and a differential pore volume as high as 0.95 × 10⁻⁶. -4 The sample has a pore size uniformity of mL / g·nm, but the pores are too fine. The main peak of the 770°C sample (770℃ BO-BWO Ceramic) broadens and shifts to 200-300 nm, forming a continuous distribution within the 100-1000 nm range, with moderate peak intensity. Test results show that the average pore size is 2.75 μm. The significant difference between the average pore size and the most probable pore size (i.e., the pore size with the highest probability of occurrence) is due to the presence of a small number of interconnected macropores in addition to numerous mesopores in the ceramic structure, and the average pore size is significantly affected by these macropores. Simultaneously, tests... The porosity of the photocatalytic ceramic was 61.86%; the pore structure of the 820°C sample (820℃ BO-BWO Ceramic) was severely degraded, and the characteristic peaks disappeared. Combined with the photocatalytic activity test results, The sintered sample exhibited the best photocatalytic performance, which indicates that the photocatalytic activity of photocatalytic ceramics does not depend solely on pore volume or porosity, but is the result of the synergistic effect of pore size distribution, pore connectivity and specific surface area. Although the sample has the highest pore volume, the small pore size (<200nm) may lead to increased mass transfer resistance, enhanced light scattering, and reduced accessibility of active sites; The moderate pore size distribution (200-1000nm) of the sample maintains a certain porosity while optimizing the reactant diffusion path and photogenerated carrier separation efficiency, achieving the best match between pore structure parameters and photocatalytic performance; The sample suffered from pore collapse due to excessive sintering, resulting in a sharp decrease in active sites and a significant decline in performance.

[0033] The optimal BO-BWO at 770℃ (i.e., the Bi2O3 / Bi2WO6 porous ceramic photocatalyst prepared in this embodiment, denoted as BO-BWO Ceramics) was subjected to a solar self-purification test. A 500 mL solution of tetracycline with a concentration of 10 mg / L was used as simulated target wastewater and placed under sunlight to maintain solar conditions. A blank sample (simulated wastewater) and a powdered Bi2O3 / Bi2WO6 sample (i.e., the Bi2O3 / Bi2WO6 heterojunction photocatalytic powder prepared in step S1, denoted as BO-BWO Powder) were placed as control groups. The photocatalytic effect is as follows: Figure 5 As shown, the photocatalytic curve of the blank sample remained almost horizontal, proving that tetracycline hardly degraded without the addition of a catalyst. The powdered Bi2O3 / Bi2WO6 sample (BO-BWO Powder) exhibited high degradation efficiency for tetracycline, reaching a degradation rate of 99.99% within one day. The Bi2O3 / Bi2WO6 porous ceramic photocatalyst (BO-BWO Ceramics) showed high degradation efficiency in the first 4 days, and the degradation efficiency reached 74.57% within 8 days, with a pollutant residue rate of 25.43%. The data show that the catalytic efficiency of the ceramic sample (BO-BWO Ceramics) decreased compared to the powdered catalyst (BO-BWO Powder), which is mainly due to the high catalytic activity brought about by the high specific surface area and nanoscale size of the powdered catalyst. Although the microscale size increased after sintering due to grain boundary fusion, which reduced the specific surface area and increased the electron-hole recombination probability, it could still maintain a degradation performance of more than 60%, which improved its practical application value as a photocatalytic material.

[0034] Cyclic testing was conducted on the optimal BO-BWO at 770℃ (i.e., the Bi2O3 / Bi2WO6 porous ceramic photocatalyst prepared in this embodiment), and it was found that, as Figure 6 As shown, the photocatalytic degradation efficiency was 74.57% after the first cycle and decreased to 69.08% after the fifth cycle. This indicates that the photocatalytic degradation efficiency of the porous ceramic photocatalyst decreased by only about 5% after five cycles. The main reason for the 5% decrease in degradation rate with the number of cycles is the weakening of the adsorption and removal of pollutants after multiple uses of the material. However, the photocatalytic performance remained basically stable, indicating that it has excellent stability.

[0035] This embodiment also provides the application of the bismuth-based photocatalytic porous ceramic material (BO-BWO 770℃) prepared by the above preparation method. The bismuth-based photocatalytic porous ceramic material is used for photocatalytic degradation of pollutants, including tetracycline.

[0036] The bismuth-based photocatalytic porous ceramic material prepared in this embodiment was used to degrade tetracycline in wastewater under sunlight, achieving a photocatalytic efficiency of 74.57% within 8 days.

[0037] The bismuth-based photocatalytic porous ceramic material prepared in this embodiment belongs to the category of photocatalytic molding products. Compared with commercially available photocatalytic products with similar functions, such as antibacterial ceramic tiles and self-cleaning glass, this product focuses more on improving the performance of photocatalytic degradation of pollutants. Because this product uses bismuth-based materials that can be excited by visible light as ceramic powder, and controls the sintering process to fully preserve the photocatalytic ability of the powder material, the final bismuth-based photocatalytic porous ceramic material, when immersed in water, can achieve approximately 60% of the removal performance of dyes, antibiotics, and other common organic pollutants in wastewater compared to an equivalent mass of suspended powder. Electron paramagnetic resonance (EPR) test results support this conclusion (e.g., ...). Figure 7 The efficiency of degrading pollutants under natural sunlight is significantly better than that of traditional TiO2 coating products. The photocatalytic effect is not significantly reduced within a immersion depth of 200 mm. At the same time, the compressive strength test shows that the compressive strength is 2.15 MPa.

[0038] The EPR diagrams of the Bi2O3 / Bi2WO6 heterojunction photocatalytic powder (a) prepared in step S102 and the Bi2O3 / Bi2WO6 porous ceramic photocatalyst (b) prepared in step S5 in this embodiment are shown below. Figure 7 As shown.

[0039] Figure 7 The Bi2O3 / Bi2WO6 heterojunction powder photocatalyst prepared in step S102 is shown respectively. Figure 7 The Bi2O3 / Bi2WO6 photocatalytic ceramics prepared in step S5 (a) and step S5) Figure 7(b) EPR spectra of the DMPO-OH adduct (denoted as DMPO-OH) formed after the spin trapping agent DMPO captures hydroxyl radicals (·OH). Both sets of spectra show typical DMPO-OH adduct quartets with peak intensities of 1:2:2:1 from left to right, a clear characteristic of ·OH radicals. No signal was observed under dark conditions, confirming that ·OH originates from a photocatalytic process rather than thermal catalysis or spontaneous oxidation. With prolonged illumination, the signal intensity significantly increased, indicating that ·OH was continuously generated and had not reached steady-state equilibrium. Quantitative comparison under 10-minute illumination showed that the ·OH yield of the powder sample was approximately 5.7 times that of the ceramic sample, while the powder photocatalyst exhibited narrower peaks and better symmetry. This may be because the powder photocatalyst maintains more complete interfacial contact, promoting electron-hole pair separation, while the porous structure of the photocatalytic ceramic may hinder the contact between DMPO and ·OH, affecting O2 / H2O diffusion.

[0040] The bismuth-based photocatalytic porous ceramic material prepared in this embodiment can be recycled and reused multiple times. It has self-cleaning properties and is suitable for occasions that require low-cost long-term self-purification of water and air, such as river purification products, aquarium decorations, and indoor air purifier components.

[0041] The above description is merely a preferred embodiment of the present invention and is not intended to limit the invention in any way. Any simple modifications, alterations, and equivalent changes made to the above embodiments based on the inventive essence shall still fall within the protection scope of the present invention.

Claims

1. A method for preparing a bismuth-based photocatalytic porous ceramic material, characterized in that, The method is as follows: Preparation of S1, Bi2O3 / Bi2WO6 heterojunction photocatalytic powder: S101, Preparation of precursor solution: Dissolve NaWO4·2H2O in ethylene glycol, then add Bi(NO3)·5H2O, and sonicate to dissolve to obtain solution A; Bi2O3 was added to ethanol and stirred to disperse, resulting in suspension B. The solution A is poured into the suspension B, and after ultrasonic stirring and mixing, a precursor solution is obtained. S102. The precursor solution obtained in S101 is subjected to a solvothermal reaction at a temperature of 160℃. After naturally cooling to room temperature, the supernatant is discarded. The precipitate is washed alternately with anhydrous ethanol and deionized water. The washed product is then dried to obtain Bi2O3 / Bi2WO6 heterojunction photocatalytic powder. S2. Disperse sodium carboxymethyl cellulose powder in a 12% (w / w) polyvinyl alcohol aqueous solution and stir magnetically at room temperature to obtain a viscous solution. S3. Add the Bi2O3 / Bi2WO6 heterojunction photocatalytic powder obtained in S102 to the viscous solution obtained in S2, stir evenly, and obtain a slurry; S4. After cleaning and drying the porous polyurethane sponge with deionized water, immerse it in the slurry obtained in S3, and repeatedly squeeze it to make the slurry penetrate and distribute inside the pores of the porous polyurethane sponge, thus obtaining the impregnated porous polyurethane sponge. S5. After shaping and drying the porous polyurethane sponge obtained in S4, heat it to 500℃ at a heating rate of 1℃ / min and hold it at that temperature for 2 hours. Then heat it to 770℃ at a heating rate of 2℃ / min and hold it at that temperature for 3 hours. Allow it to cool naturally to room temperature to obtain the Bi2O3 / Bi2WO6 porous ceramic photocatalyst, which is a bismuth-based photocatalytic porous ceramic material.

2. The method for preparing a bismuth-based photocatalytic porous ceramic material according to claim 1, characterized in that, The molar ratio of NaWO4·2H2O, Bi(NO3)·5H2O and Bi2O3 in S101 is 3 mmol: 6 mmol: 0.3 mmol.

3. The method for preparing a bismuth-based photocatalytic porous ceramic material according to claim 1, characterized in that, The solvothermal reaction time in S102 is 12 hours, and the drying conditions are: drying at 60℃ with forced air for 12 hours.

4. The method for preparing a bismuth-based photocatalytic porous ceramic material according to claim 1, characterized in that, The mass ratio of sodium carboxymethyl cellulose powder and a 12% polyvinyl alcohol aqueous solution in S2 is 1:

50.

5. The method for preparing a bismuth-based photocatalytic porous ceramic material according to claim 1, characterized in that, The mass ratio of the Bi2O3 / Bi2WO6 heterojunction photocatalytic powder to the viscous solution in S3 is 3.2:10.

2.

6. The method for preparing a bismuth-based photocatalytic porous ceramic material according to claim 1, characterized in that, The porous polyurethane sponge described in S4 has a pore density of 30 ppi and a thickness of 10 mm.

7. The method for preparing a bismuth-based photocatalytic porous ceramic material according to claim 1, characterized in that, The drying conditions described in S4 are: drying at 60°C with forced air for 12 hours.

8. The method for preparing a bismuth-based photocatalytic porous ceramic material according to claim 1, characterized in that, The average specific surface area of ​​the bismuth-based photocatalytic porous ceramic material described in S5 is 3.24 m². 2 / g, with an average pore size of 2.75μm.

9. An application of a bismuth-based photocatalytic porous ceramic material prepared by the preparation method according to any one of claims 1-8, characterized in that, The bismuth-based photocatalytic porous ceramic material is used for photocatalytic degradation of pollutants.

10. The application according to claim 9, characterized in that, The bismuth-based photocatalytic porous ceramic material is used to degrade tetracycline in wastewater under sunlight.

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