Preparation method of bentonite-based multi-stage photocatalytic composite particles

Abstract

The application belongs to the field of photocatalytic materials, and particularly relates to a preparation method of a photocatalytic composite material. The method comprises the following steps: placing a bentonite carrier in a bismuth salt solution, adding hydrochloric acid to etch the bentonite after ultrasonic dispersion, further adding sodium iodide and polyvinylpyrrolidone to mix uniformly, adjusting the pH of the solution to form an aluminum hydroxide gel porous network on the surface of the bentonite, continuously stirring the suspension to obtain a BiOI@Al(OH)3 / MMT photocatalytic composite nanomaterial coated with a gel porous network, mixing the photocatalytic composite nanomaterial with bentonite, and performing disc granulation to obtain the photocatalytic composite material. The photocatalytic composite material has very excellent effects of photocatalytic adsorption and degradation of pollutants and sterilization, is stable in performance, can long-acting maintain the performance, and has a simple and efficient preparation process and can be used under acid and alkali conditions.

Description

Technical Field

[0001] This invention belongs to the field of photocatalytic materials, and particularly relates to a method for preparing bentonite-based multi-level photocatalytic composite particles. Background Technology

[0002] In this field, pollutants are often decomposed using free radicals with oxidizing capabilities generated by semiconductor materials. With further research, an increasing number of photocatalytic materials have emerged. Among them, bismuth-based photocatalytic materials possess excellent visible light absorption and superior stability. Furthermore, BiOX (X = I, Br, Cl) materials have halogen atomic layers and [Bi₂O₂]. 2+ The unique layered structure, composed of alternating layers, creates a strong built-in electric field, promoting the separation of photogenerated electron-hole pairs. BiOI is a compound with photocatalytic bactericidal activity, naturally activating O2 and OH- through photocatalysis. - It forms highly reactive free radicals to kill bacteria and pathogens, while the slow release of iodine ions from BiOI provides a long-lasting and broad-spectrum bactericidal effect, achieving efficient, durable, safe, and broad-spectrum antibacterial disinfection. However, BiOI prepared by existing processes is prone to aggregation, which not only hinders the release of iodine ions but also reduces photocatalytic efficiency, thereby reducing the actual antibacterial disinfection effect of BiOI. Summary of the Invention

[0003] To address the aforementioned issues and fully leverage the superior bactericidal properties of BiOI, this invention provides a method for preparing bentonite-based multi-level photocatalytic composite particles. During the preparation process, by controlling the system conditions, the gel network formed with Al elements is generated synchronously with BiOI, ensuring that BiOI particles are tightly and orderly anchored between and on the surface of the bentonite layers, significantly enhancing the load's strength and stability. Furthermore, due to the good hygroscopic properties of bentonite, the gel structure is further strengthened after absorbing moisture. This dynamic gel network can control the release of the loaded BiOI. When applied to water treatment or antibacterial applications, this bentonite composite material loaded with BiOI gradually releases BiOI upon contact with moisture, maintaining a long-term effective concentration of BiOI while ensuring its highly efficient bactericidal ability. Therefore, it achieves a highly efficient and long-lasting bactericidal effect of BiOI in practical applications. This design not only improves the utilization rate of BiOI nanomaterials but also expands its application potential in environmental governance and public health safety.

[0004] Specifically, the present invention adopts the following technical solution: a method for preparing bentonite-based multi-level photocatalytic composite particles, comprising:

[0005] (1) The bentonite (MMT) carrier is placed in a bismuth salt solution and ultrasonically dispersed and mixed evenly; the bismuth salt solution is an alcoholic solution of soluble bismuth salt; the concentration of bismuth ions in the bismuth salt solution is 0.16-0.25 mol / L; the bismuth salt solution is used at a ratio of 0.3-0.7 mL / g bentonite carrier;

[0006] (2) Add hydrochloric acid to etch bentonite; the concentration of the hydrochloric acid solution is 0.1M, and the amount used is 0.03 to 0.07 ml / g of bentonite in step 1.

[0007] (3) Add sodium iodide or potassium iodide, surfactant, and adjust the pH of the solution to form an aluminum hydroxide gel porous network on the surface of bentonite; continue stirring to form BiOI nanoparticles on the surface of bentonite, and obtain BiOI@MMT photocatalytic composite nanomaterials coated with gel porous network.

[0008] (4) Take bentonite separately, mix it with photocatalytic composite nanomaterials, and then granulate it in a disc and dry it to obtain photocatalytic composite particles.

[0009] Bentonite (MMT) possesses a hierarchical porous structure, a large specific surface area, and high porosity. By employing acid etching and pH adjustment, an Al(OH)3 gel porous network can be formed on the bentonite surface. The specific preparation method of this invention enables the photocatalyst BiOI to be highly dispersed and loaded within the Al(OH)3 porous network, thereby improving the adsorption-photocatalytic performance of the BiOI@Al(OH)3 / MMT composite material. The rich pore structure also promotes the adsorption of bacteria and viruses by the material, enhancing inactivation efficiency.

[0010] During the loading process, the porous network of MMT-Al(OH)3 gel adsorbs iodide ions, achieving a high concentration of iodide ions while simultaneously coating BiOI. This results in the prepared photocatalytic nanomaterial having strong and long-lasting bactericidal effects. On the other hand, MMT-Al(OH)3 promotes the dispersion of BiOI, avoiding the performance degradation caused by BiOI aggregation, and is beneficial for the photocatalytic formation of hydroxyl radicals and superoxide radicals by BiOI.

[0011] This invention modifies MMT by adjusting pH. Hydrochloric acid is used to etch the MMT surface, exposing the active sites and dissolving a large number of aluminum ions. After further adjusting the pH to alkaline, an Al(OH)3 gel porous network is formed in situ on the MMT surface. This results in the inorganic nanocomposite material having stronger surface positive charge, smaller diameter, and larger specific surface area. This not only makes the inorganic nanocomposite material more dispersed but also enhances its adsorption capacity for ammonia pollutants.

[0012] BiOI was in situ self-assembled into the pores and porous network of Al(OH)3 / MMT, resulting in an MMT-based BiOI-supported adsorption-photocatalytic composite material (BiOI@Al(OH)3 / MMT). The hierarchical pore structure of Al(OH)3 / MMT, with its large specific surface area and high porosity, facilitates the dispersion and loading of the photocatalyst BiOI on the gel porous network and pore surface of Al(OH)3 / MMT, ensuring the light absorption of BiOI while preventing the blockage of the MMT's hierarchical pores, thus improving the adsorption-photocatalytic performance of the BiOI@Al(OH)3 / MMT composite material. BiOI is a compound with photocatalytic bactericidal activity, capable of releasing active species through photoexcitation to kill bacteria and pathogens. By combining the hierarchical pore structure of Al(OH)3 / MMT with photocatalytic bactericidal BiOI, more efficient adsorption performance, deodorization effect, and disinfection and sterilization capability can be achieved. Meanwhile, the slow-release iodine ions in BiOI can exert a long-lasting and broad-spectrum bactericidal effect, providing a lasting hygienic effect.

[0013] Furthermore, after hydrochloric acid etching, a zinc salt solution with a zinc ion concentration of 0.35–0.70 mol / L is added along with sodium iodide or potassium iodide and a surfactant; the zinc salt solution is used at a ratio of 0.1–0.3 mL / g bentonite carrier. The addition of a metal salt solution in this invention, through the action of metal cations, promotes the separation of photogenerated electron-hole pairs in BiOI, resulting in higher photocatalytic efficiency and improved photoelectron transport efficiency. However, not all metal cations can have a positive promoting effect. For example, iron and copper ions, while also promoting the separation of photogenerated electron-hole pairs, also lead to partial site occupancy, thus limiting the actual catalytic threshold. Therefore, the rational selection of metal cations provided by the metal salt solution has a very significant effect on improving the actual application effect of photocatalytic composite nanomaterials.

[0014] Furthermore, the presence of metal cations other than BiOI can enhance the MMT adsorption capacity of the BiOI@Al(OH)3 / MMT photocatalytic composite material under acidic conditions. H2S adsorption and complexation are achieved through the complexation of metal cations, thereby enabling the adsorption of acidic pollutants. Under these combined effects, the photocatalytic composite material of this invention exhibits excellent performance when used as an additive in cat litter.

[0015] Furthermore, the surfactant in step 3 is polyvinylpyrrolidone, and its dosage is 0.03-0.07 g / g of bentonite in step 1.

[0016] Furthermore, the iodine content in the sodium iodide in step 3 is 0.9–2.4 mmol / g of the bentonite in step 1.

[0017] Furthermore, in step 3, the pH of the solution is adjusted to 7-10.

[0018] Furthermore, step 3 is stirring at room temperature, specifically: stirring continuously at a speed of 1000-5000 rpm for 30-60 minutes at room temperature.

[0019] Furthermore, the bentonite and photocatalytic composite nanomaterials taken in step 4 are in a mass ratio of 95:5.

[0020] Furthermore, after granulation and drying, the granules are sieved to control the cat litter particle size to 2-6mm.

[0021] The beneficial effects of this invention are: the photocatalytic composite material of this invention has excellent photocatalytic adsorption and degradation of pollutants and sterilization effects, and its performance is stable and can maintain its performance for a long time. At the same time, the preparation process is simple and efficient. Attached Figure Description

[0022] Figure 1 The image shows the SEM characterization of the BiOI@Al(OH)3 / MMT photocatalytic composite material prepared in Example 1 of this invention.

[0023] Figure 2 SEM characterization of BiOI particles in photocatalytic composite materials.

[0024] Figure 3 The image shows the antibacterial test results of the BiOI@Al(OH)3 / MMT photocatalytic composite material prepared in Example 1 of this invention.

[0025] Figure 4 This is a photograph of the novel bentonite cat litter made from the photocatalytic composite material prepared in Example 1 of the present invention.

[0026] Figure 5 The figure shows the characterization results of the adsorption and degradation performance of the novel bentonite cat litter using the photocatalytic composite material prepared in Example 1 of this invention.

[0027] Figure 6 The figure shows the characterization results of the adsorption and degradation performance of commercially available bentonite cat litter.

[0028] Figure 7 The figure shows the characterization results of the adsorption and degradation performance of the novel bentonite cat litter with different BiOI content composite materials prepared in Example 1 of this invention.

[0029] Figure 8 The figure shows the characterization results of the adsorption and degradation performance of the novel bentonite cat litter with different BiOI content composite materials prepared in Example 1 of this invention.

[0030] Figure 9The figure shows the characterization results of the adsorption and degradation performance of the novel bentonite cat litter with different metal contents prepared in Example 1 of the present invention. Detailed Implementation

[0031] The present invention will be further described clearly and in detail below with reference to specific embodiments and the accompanying drawings. Those skilled in the art will be able to implement the present invention based on these descriptions. Furthermore, the embodiments of the present invention described below are generally only some, not all, of the embodiments of the present invention. Therefore, all other embodiments obtained by those skilled in the art based on the embodiments of the present invention without inventive effort should fall within the scope of protection of the present invention.

[0032] Unless otherwise specified, all raw materials used in the embodiments of the present invention are commercially available or obtainable by those skilled in the art; unless otherwise specified, all methods used in the embodiments of the present invention are methods mastered by those skilled in the art.

[0033] Example 1

[0034] A photocatalytic composite material, the preparation process of which is as follows:

[0035] Bentonite carrier was placed in a 0.20 mol / L bismuth nitrate ethylene glycol solution at a ratio of 10 g: 5 mL and ultrasonically dispersed. Then, 0.1 M hydrochloric acid was added at a ratio of 0.05 mL / g bentonite. Potassium iodide was then added at a ratio of 1.5 mmol / g bentonite, and polyvinylpyrrolidone was added at a ratio of 0.05 g / g bentonite. The mixture was thoroughly mixed, and the pH was adjusted to 9. The suspension was continuously stirred at room temperature to obtain the photocatalytic composite nanomaterial. Bentonite and the photocatalytic composite nanomaterial were added to a pulverizer at a mass ratio of 95:5 for pre-mixing and pulverizing to obtain a mixed powder, which was then granulated using a disc granulator. After granulation and drying, the particles were sieved to control the particle size to 2-6 mm.

[0036] The obtained photocatalytic composite material was characterized by SEM, and the characterization results are as follows: Figure 1 As shown. From Figure 1 It can be clearly seen that the Al(OH)3 / MMT surface is coated with a rich layered nanosheet structure, which has a large specific surface area. At the same time, it effectively preserves the pore structure of Al(OH)3 / MMT and does not block the pore structure of the Al(OH)3 / MMT support, thus maintaining its adsorption capacity.

[0037] The BiOI particles of the obtained photocatalytic composite material were characterized by SEM, and the characterization results are as follows: Figure 2 As shown. From Figure 2It can be clearly seen that the surface of Al(OH)3 / MMT is coated with BiOI particles, which are highly dispersed and uniform in size.

[0038] Based on the above, the performance of the photocatalytic composite material prepared in this example was also characterized.

[0039] Antibacterial performance characterization:

[0040] Microbiological testing was performed on the composite particles obtained in this case. Four common feline pathogens, namely Yersinia enterocolitica, Shigella dysenteriae, Staphylococcus aureus, and Escherichia coli, were transferred into ordinary nutrient agar medium using sterile pipettes and incubated at 37°C for 24 hours. Four typical colonies from the incubated nutrient agar plates were picked with sterile cotton swabs and placed into sterile LB broth medium. The mixture was thoroughly mixed and incubated at 37°C and 200 rpm for 24 hours. The bacterial cells were centrifuged and then prepared with sterile MH broth to make 10 3 Take 2g of the composite particles from this example and add them to 20mL of the prepared bacterial suspension (the experimental group without photocatalytic composite nanomaterials is used as the control experimental group). Incubate at 37℃ for 24h. Take 1.0mL of the culture medium after the culture is completed and dilute it 100 times. Quantitatively (50μL) spread it on MH agar plates and count the total number of colonies.

[0041] The cultivation results are as follows Figure 3 As shown. Figure 3 The left image shows the control group, and the right image shows the experimental results of the composite particles in this example. The experimental results demonstrate that the photocatalytic composite material prepared in this example exhibits excellent antibacterial properties.

[0042] The adsorption and degradation performance of the obtained composite particles was characterized, and the actual images are shown below. Figure 4 As shown:

[0043] Prepare a 1wt% saline solution. Adjust the pH of the saline solution to 5.5 with hydrogen sulfide as an acidic test solution and adjust the pH to 8.0 with ammonia as an alkaline test solution. Place equal amounts of the composite particles prepared in this example into different sealed containers. Add acidic and alkaline test solutions to the composite particles in the sealed containers at a ratio of 25 mL / 10 g composite particles (experimental group). Then, use sealed containers with equal amounts of acidic and alkaline test solutions (without photocatalytic composite nanomaterials) as blank controls. Characterize and record the hydrogen sulfide gas content and ammonia content in the sealed containers every 3 minutes. Calculate the adsorption and degradation rates of hydrogen sulfide gas content (ΔH2S) and ammonia content (ΔNH3) of the experimental groups (acidic experimental group with acidic test solution and alkaline experimental group with alkaline test solution) compared to the blank control group. The experiment was conducted in a dark room for the first 15 minutes and under incandescent light for the last 15 minutes.

[0044] The formula for calculating the adsorption degradation rate ΔOG is as follows:

[0045]

[0046] In the formula: OG represents NH3 or H2S, c c OG represents the OG content of the blank control group, c t OG represents the OG content in the experimental group.

[0047] The calculation results above are plotted in a table, as follows: Figure 5 As shown in the figure, it is clear that the composite particles of this invention maintain the good adsorption properties of the original MMT carrier. However, it can also be seen that, due to the excessive addition of both acidic and alkaline test solutions, the adsorption degradation rate initially increases and then decreases in the first 15 minutes under adsorption-only conditions. This indicates that it does not possess good catalytic degradation ability under dark chamber conditions, resulting in a rapid increase in the hydrogen sulfide and ammonia content in the container after MMT adsorption saturation. In particular, the adsorption capacity of MMT itself is significantly inhibited under acidic conditions, with a more significant decrease, and the adsorption degradation rate is even only about 20% in the short term. However, after the application of light, the adsorption degradation rate increases rapidly and maintains a relatively stable upward trend, indicating that the composite particles of this invention have good and long-lasting stable photocatalytic degradation ability, can rapidly degrade hydrogen sulfide and ammonia in the container, and exhibit good photocatalytic activity.

[0048] Comparative Example 1

[0049] The adsorption and degradation performance of commercially available MMT (bentonite, i.e. the same bentonite carrier used in Example 1) and BiOI particles physically mixed at a mass ratio of 550:1 was characterized in the same way as in Example 1.

[0050] Characterization results as follows Figure 6 As shown in the figure. Characterization results show that the physical mixed particles have a slightly stronger adsorption performance for ammonia than the composite particles prepared in Example 1, while their adsorption capacity for hydrogen sulfide is slightly lower than that of the composite particles prepared in Example 1. However, they do not have degradation capacity, and the adsorption degradation rate continues to decrease after light irradiation until ammonia and hydrogen sulfide reach volatilization equilibrium.

[0051] Compared with Example 1, it can be found that the composite particles of the present invention have obviously and effectively achieved the loading of BiOI and effectively verified their performance in photodegrading odor pollutants (hydrogen sulfide and ammonia).

[0052] Example 2

[0053] A photocatalytic composite material, the preparation process of which is as follows:

[0054] Bentonite carrier was placed in a 0.20 mol / L bismuth nitrate ethylene glycol solution at a ratio of 10 g: 3 mL and ultrasonically dispersed. Then, 0.1 M hydrochloric acid was added at a ratio of 0.05 mL / g bentonite. Potassium iodide was then added at a ratio of 0.9 mmol / g bentonite, and polyvinylpyrrolidone was added at a ratio of 0.03 g / g bentonite. The mixture was thoroughly mixed, and the pH was adjusted to 9. The suspension was continuously stirred at room temperature to obtain the photocatalytic composite nanomaterial. Bentonite and the photocatalytic composite nanomaterial were added to a pulverizer at a ratio of 95:5 for pre-mixing and pulverizing to obtain a mixed powder, which was then granulated using a disc granulator. After granulation and drying, the powder was sieved to control the particle size to 2-6 mm.

[0055] Example 3

[0056] A novel bentonite cat litter made from photocatalytic composite nanomaterials is prepared as follows:

[0057] Bentonite carrier was placed in a 0.16 mol / L bismuth nitrate ethylene glycol solution at a ratio of 10 g: 7 mL, and ultrasonically dispersed. Then, 0.1 M hydrochloric acid was added at a ratio of 0.03 mL / g bentonite. Potassium iodide was then added at a ratio of 2.4 mmol / g bentonite, and polyvinylpyrrolidone was added at a ratio of 0.07 g / g bentonite. The mixture was thoroughly mixed, and the pH was adjusted to 7. The suspension was continuously stirred at room temperature to obtain the photocatalytic composite nanomaterial. Bentonite and the photocatalytic composite nanomaterial were added to a pulverizer at a ratio of 95:5 for pre-mixing and pulverizing to obtain a mixed powder, which was then granulated using a disc granulator. After granulation and drying, the powder was sieved to control the particle size to 2-6 mm.

[0058] The photocatalytic composite nanomaterials prepared in this example were characterized for adsorption and degradation performance in the same manner as in Example 1.

[0059] The characterization results of Examples 2 and 3 above are as follows: Figure 7 and Figure 8 As shown. From Figure 6 and Figure 7It is evident that as the relative proportion of BiOI increases, the tendency of the composite material to aggregate reduces its adsorption performance, leading to a significant decrease in its adsorption degradation rate under light-free conditions. Upon illumination, the limited adsorption capacity of the composite material also hinders a rapid increase in the catalytic degradation rate. At lower BiOI proportions, the ammonia adsorption performance of the photocatalytic composite nanomaterial increases while the sulfur adsorption performance decreases, highlighting the inherent weakness of Al(OH)3 / MMT in its adsorption of acidic reagents. The addition of BiOI can mitigate this issue to some extent. Furthermore, at lower BiOI content, the degradation capacity is significantly weaker than in Examples 1 and 3, indicating that the degradation capacity is primarily provided by BiOI. However, the overall adsorption and degradation capacity is not directly proportional to the BiOI content; rather, a performance peak appears within a certain content range. This peak is based on balancing the adsorption and degradation performance of the photocatalytic composite nanomaterial.

[0060] Example 4

[0061] A photocatalytic composite material, the preparation process of which is as follows:

[0062] Bentonite carrier was placed in a 0.25 mol / L bismuth nitrate ethylene glycol solution at a ratio of 10 g: 5 mL and ultrasonically dispersed. Then, 0.1 M hydrochloric acid was added at a ratio of 0.07 mL / g bentonite. Potassium iodide was added at a ratio of 1.5 mmol / g bentonite, and polyvinylpyrrolidone was added at a ratio of 0.05 g / g bentonite; the mixture was then thoroughly mixed. A metal salt solution was added at a ratio of 0.2 mL / g bentonite, and the metal cation concentration in the solution was 0.50 mol / L. The pH was adjusted to 10, and the suspension was continuously stirred at room temperature to obtain the photocatalytic composite nanomaterial. Bentonite and the photocatalytic composite nanomaterial were then pre-mixed and pulverized in a pulverizer at a ratio of 95:5 to obtain a mixed powder, which was then granulated using a disc granulator. After granulation and drying, the powder was sieved to control the particle size to 2-6 mm.

[0063] This example uses different complexed metal salt solutions for the experiment, and the corresponding metal cations contained therein are shown in the table below.

[0064]

[0065] The above experimental groups were characterized for adsorption and degradation performance in the same manner as in Example 1, with only the characterization results of the acidic test solution being recorded. Figure 9 As shown.

[0066] from Figure 9It is evident that using zinc and iron ions as coordinating ions effectively enhances the adsorption and fixation of sulfur in acidic reagents by the original BiOI@Al(OH)3 / MMT photocatalytic composite nanomaterial under light-free conditions. However, zinc ions significantly improve the degradation capacity of the photocatalytic composite nanomaterial under light irradiation, while iron ions, although enhancing early sulfur adsorption, do not significantly improve catalytic degradation. Copper and silver ions fail to effectively enhance either adsorption or catalytic degradation performance, but their peak catalytic degradation performance is advanced after light irradiation. This indicates that different metal ion combinations produce different technical effects, and overall, the effect of zinc ions alone in combination is significantly better than that of other metal ions.

Claims

1. A method for preparing bentonite-based multi-level photocatalytic composite particles, characterized in that, include: (1) Place the bentonite (MMT) carrier in a bismuth salt solution and ultrasonically disperse and mix it evenly; The bismuth salt solution is an alcoholic solution of soluble bismuth salt; the bismuth ion concentration in the bismuth salt solution is 0.16–0.25 mol / L; the bismuth salt solution is used at a ratio of 0.3–0.7 mL / g bentonite carrier; (2) Add hydrochloric acid to etch bentonite; the concentration of the hydrochloric acid solution is 0.1 M, and the amount used is 0.03 to 0.07 ml / g of bentonite in step 1; (3) Add sodium iodide or potassium iodide, add polyvinylpyrrolidone, and adjust the pH of the solution to form an aluminum hydroxide gel porous network on the surface of bentonite; continue stirring to form BiOI nanoparticles on the surface of bentonite, and obtain BiOI@MMT photocatalytic composite nanomaterials coated with gel porous network. (4) Take bentonite separately, mix it with photocatalytic composite nanomaterials, and then granulate it in a disc and dry it to obtain photocatalytic composite particles.

2. The preparation method according to claim 1, characterized in that, In step (3), the amount of polyvinylpyrrolidone used is 0.03 to 0.07 g / g of bentonite in step (1).

3. The preparation method according to claim 1, characterized in that, In step (3), the iodine content in sodium iodide is 0.9–2.4 mmol / g of the bentonite in step 1.

4. The preparation method according to claim 1, characterized in that, In step (3), the pH of the solution is adjusted to 7-10.

5. The preparation method according to claim 1, characterized in that, After etching with hydrochloric acid, a zinc salt solution with a zinc ion concentration of 0.35–0.70 mol / L is added along with sodium iodide or potassium iodide and polyvinylpyrrolidone; the zinc salt solution is used at a ratio of 0.1–0.3 mL / g bentonite carrier.

6. The preparation method according to claim 1, characterized in that, Step (3) is stirring at room temperature, specifically: stirring continuously at 1000-5000 rpm for 30-60 min at room temperature.

7. The preparation method according to claim 1, characterized in that, The bentonite and photocatalytic composite material taken in step (4) are mixed in a mass ratio of 95:

5.

8. The preparation method according to claim 1, characterized in that, After granulation and drying, the granules are sieved to control the cat litter particle size to 2-6 mm.

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