BiOCl photocatalyst as well as preparation method and application thereof

Abstract

The invention provides a BiOCl photocatalyst as well as a preparation method and application thereof, and relates to the technical field of photocatalytic materials. The preparation method comprises the following steps: mixing bismuth salt, chlorine salt and a solvent, and carrying out solvothermal reaction on the obtained mixed solution to obtain the BiOCl photocatalyst, the solvent is ethylene glycol, water or ethanol; when the solvent is ethylene glycol or water, the mixed solution further comprises glucose. The morphology and crystal face of BiOCl can be simply and conveniently regulated and controlled, the BiOCl photocatalyst with excellent photocatalytic performance is obtained, specifically, accurate morphology regulation and control are realized by regulating a reaction solvent, and crystal face regulation and control and carbon doping are realized by regulating and controlling glucose addition. In addition, according to the method, reaction raw materials are simple and easy to obtain, reaction conditions are mild, and addition of a surfactant is not needed. The BiOCl photocatalyst prepared by the invention has excellent performance of photocatalytic degradation of organic pollutants and photocatalytic reduction of heavy metal ions.

Description

Technical Field

[0001] The present invention relates to the technical field of photocatalytic materials, and in particular to a BiOCl photocatalyst and a preparation method and application thereof. Background Art

[0002] With the rapid development of industry, water pollution is becoming increasingly serious, especially heavy metal ions and organic pollutants in water, which pose a great threat to human production and life. Therefore, solving the water pollution problem is urgent. Photocatalysis utilizes inexhaustible solar energy and is a green and sustainable pollution treatment technology. As a common photocatalyst, bismuth oxychloride (BiOCl) has a [Bi2O2] 2+ BiOCl has a layered structure consisting of two interlaced layers of halogen atoms. The internal static electric field within this structure facilitates carrier separation and transport, making it a promising candidate for water pollution treatment. However, existing BiOCl has a narrow photoresponse range, resulting in poor photocatalytic performance and limiting its application in photocatalysis. Summary of the Invention

[0003] In view of this, the present invention aims to provide a BiOCl photocatalyst, its preparation method, and its application. The BiOCl photocatalyst prepared by the present invention has excellent photocatalytic performance and can be efficiently applied to the photocatalytic degradation of organic pollutants and the photocatalytic reduction of heavy metal ions.

[0004] In order to achieve the above-mentioned object of the invention, the present invention provides the following technical solutions:

[0005] The present invention provides a method for preparing a BiOCl photocatalyst, comprising the following steps:

[0006] Mixing a bismuth salt, a chloride salt, and a solvent, and subjecting the resulting mixture to a solvothermal reaction to obtain the BiOCl photocatalyst;

[0007] The molar ratio of the Bi element in the bismuth salt to the Cl element in the chloride salt is 1:1;

[0008] The solvent is ethylene glycol, water or ethanol; when the solvent is ethylene glycol or water, the mixed solution also includes glucose, and the molar ratio of the glucose to the Bi element in the bismuth salt is (0.5-5):1.

[0009] Preferably, the bismuth salt comprises bismuth nitrate.

[0010] Preferably, the chloride salt comprises sodium chloride and / or potassium chloride.

[0011] Preferably, the ratio of the bismuth salt to the solvent is 0.5-5 mmol:20-60 mL.

[0012] Preferably, the temperature of the solvent thermal reaction is 120-200° C., and the time is 1-10 h.

[0013] Preferably, after the solvothermal reaction is completed, the process further comprises sequentially subjecting the obtained reaction liquid to solid-liquid separation, solid phase washing and drying to obtain a powdered BiOCl photocatalyst.

[0014] The present invention provides a BiOCl photocatalyst prepared by the preparation method described in the above technical solution. The morphology of the BiOCl photocatalyst is flower-like or sheet-like, with the (110) crystal plane as the main exposed crystal plane.

[0015] The present invention provides the use of the BiOCl photocatalyst described in the above technical solution in the photocatalytic degradation of organic pollutants and / or the photocatalytic reduction of heavy metal ions.

[0016] Preferably, the organic pollutants include rhodamine B and / or tetracycline.

[0017] Preferably, the heavy metal ions include hexavalent chromium ions.

[0018] This invention provides a method for preparing a BiOCl photocatalyst. After mixing a bismuth salt and a chloride salt with a single-component solvent (ethylene glycol, water, or ethanol), the method uses a solvothermal reaction to initiate nucleation and crystal growth, resulting in a BiOCl photocatalyst with excellent crystallinity, uniform and controllable morphology, and good dispersibility. Compared with existing technologies, this invention has the following advantages:

[0019] The present invention uses different solvents to modify the material's morphology. The varying viscosities of different solvents affect the nucleus transfer and diffusion rates during the reaction, leading to significant differences in the morphology and crystallinity of the BiOCl materials obtained in different solvents. Furthermore, ethylene glycol, when used as a solvent, can act as a soft template, participating in the reaction and thus regulating the morphology. This manipulation of morphology and crystallinity can improve the photocatalytic performance of the catalyst.

[0020] When the solvent is ethylene glycol or water, glucose is added to the mixed solution in the present invention. The addition of glucose can regulate the growth trend of BiOCl during the solvent thermal reaction process, adjust the exposure degree of the crystal plane of the BiOCl material, and reduce the exposure degree of the (001) plane. At the same time, glucose can also be used as a carbon source to achieve carbon doping. Carbon doping can significantly increase the light absorption range of the BiOCl material, improve the light absorption performance of the catalyst, and induce the generation of oxygen vacancies during the photoreaction process.

[0021] The preparation method provided by the present invention is simple to operate, energy-efficient, efficient, and environmentally friendly. The crystal surface exposure and morphology of the BiOCl material can be adjusted by a simple method. The reaction raw materials are simple and easily available, the reaction conditions are mild, and no surfactant addition is required.

[0022] The present invention provides a BiOCl photocatalyst prepared by the preparation method described in the above technical solution. The morphology of the BiOCl photocatalyst is flower-like or sheet-like, with the (110) crystal plane as the main exposed crystal plane.

[0023] The present invention provides the use of the BiOCl photocatalyst described in the above technical solution for the photocatalytic degradation of organic pollutants and / or the photocatalytic reduction of heavy metal ions. Example results demonstrate that the BiOCl photocatalyst provided by the present invention exhibits excellent photocatalytic degradation performance, achieving a degradation efficiency of over 98% for rhodamine B within 10 minutes. The BiOCl photocatalyst prepared using water as the solvent and the addition of glucose exhibits optimal photocatalytic performance, achieving 100% photodegradation efficiency for rhodamine B within 6 minutes, achieving complete removal of pollutants. Furthermore, the reduction efficiency for hexavalent chromium reaches 100% within 30 minutes at a pH of 3. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] Figure 1 X-ray diffraction spectra of the BiOCl photocatalysts prepared in Examples 1 to 3 of the present invention and Comparative Examples 1 to 3;

[0025] Figure 2 This is a transmission electron microscope image of the BiOCl photocatalyst prepared in Comparative Example 1;

[0026] Figure 3 This is a transmission electron microscopy image of the BiOCl photocatalyst prepared in Example 1;

[0027] Figure 4 This is a transmission electron microscopy image of the BiOCl photocatalyst prepared in Example 2;

[0028] Figure 5 This is a transmission electron microscopy image of the BiOCl photocatalyst prepared in Comparative Example 2;

[0029] Figure 6 This is a transmission electron microscopy image of the BiOCl photocatalyst prepared in Comparative Example 3;

[0030] Figure 7 This is a transmission electron microscopy image of the BiOCl photocatalyst prepared in Example 3;

[0031] Figure 8 UV-visible diffuse reflectance spectra of the BiOCl photocatalysts prepared in Examples 1 to 3 and Comparative Examples 1 to 3;

[0032] Figure 9 The degradation efficiency curves of Rhodamine B by the BiOCl photocatalysts prepared in Examples 1 to 3 and Comparative Examples 1 to 3 are shown;

[0033] Figure 10 The degradation efficiency curve of the BiOCl photocatalyst prepared in Example 3 for reducing hexavalent chromium ions and the degradation efficiency curve of tetracycline for reducing hexavalent chromium ions when the two catalysts coexist are shown;

[0034] Figure 11 This is the X-ray diffraction spectrum of the BiOCl photocatalyst prepared in Comparative Example 4;

[0035] Figure 12 This is a SEM image of the BiOCl photocatalyst prepared in Comparative Example 4;

[0036] Figure 13 This is a SEM image of the BiOCl photocatalyst obtained by replacing the ethylene glycol and deionized water in Comparative Example 4 with ethylene glycol;

[0037] Figure 14 This is the degradation efficiency curve of Rhodamine B by the BiOCl photocatalyst prepared in Comparative Example 4;

[0038] Figure 15 Degradation curves of tetracycline by BiOCl photocatalysts prepared with different glucose addition amounts in Examples 3 and 4;

[0039] Figure 16 This is a bar chart showing the degradation efficiency of tetracycline by BiOCl photocatalysts prepared with different glucose addition amounts in Example 3 and Example 4. DETAILED DESCRIPTION

[0040] The present invention provides a method for preparing a BiOCl photocatalyst, comprising the following steps:

[0041] Mixing a bismuth salt, a chloride salt, and a solvent, and subjecting the resulting mixture to a solvothermal reaction to obtain the BiOCl photocatalyst;

[0042] The molar ratio of the Bi element in the bismuth salt to the Cl element in the chloride salt is 1:1;

[0043] The solvent is ethylene glycol, water or ethanol; when the solvent is ethylene glycol or water, the mixed solution also includes glucose, and the molar ratio of the glucose to the Bi element in the bismuth salt is (0.5-5):1.

[0044] In the present invention, unless otherwise specified, all raw materials involved are commercially available products well known in the art.

[0045] In the present invention, the bismuth salt preferably comprises bismuth nitrate. In an embodiment of the present invention, the bismuth nitrate is added in the form of bismuth nitrate pentahydrate. The chloride salt preferably comprises sodium chloride and / or potassium chloride. The molar ratio of the Bi element in the bismuth salt to the Cl element in the chloride salt is 1:1. In the present invention, the molar ratio of the Bi element in the bismuth salt to the Cl element in the chloride salt is controlled to 1:1. When the molar ratio is less than 1:1, bismuth vacancies will be generated. When the molar ratio is greater than 1:1, impurities (such as bismuth oxide) or bismuth-rich materials will be generated, which will adversely affect catalyst performance.

[0046] In the present invention, the solvent is ethylene glycol, water or ethanol; the ratio of the bismuth salt to the solvent is preferably 0.5-5 mmol:20-60 mL, preferably 1-2 mmol:20 mL; the ratio of the bismuth salt to the solvent will have a certain impact on the growth size of the material. The present invention regulates the morphology of the BiOCl material through different reaction solvents. Due to the different viscosities of different solvents, the crystal nucleus transfer rate and diffusion rate are affected to a certain extent during the reaction process, and the morphology of the BiOCl material obtained by reaction in different solvents is very different; when ethylene glycol is used as a solvent, it can also act as a soft template, participating in the reaction process and thus playing a role in regulating the morphology. In the present invention, the morphology of the BiOCl photocatalyst prepared with ethylene glycol as the solvent is a nanoflower assembled from nanosheets. This three-dimensional structure has a large specific surface area, which is conducive to the adsorption of pollutants, thereby improving the photocatalytic performance; the morphology of the BiOCl photocatalyst prepared with ethanol as the solvent is an aggregated nanosheet with a low degree of aggregation; the morphology of the BiOCl photocatalyst prepared with water as the solvent is nanosheet-shaped. In addition, different solvents also play different surface modification roles, affecting the crystallinity of the material. For example, when water is used as the solvent, the crystal growth is not constrained by the solvent and grows into a flake structure. Although the specific surface area of ​​the material is small, its crystallinity is optimal, which is also beneficial to improving the catalytic performance of the BiOCl photocatalyst.

[0047] In the present invention, the method for mixing the bismuth salt, chloride salt and solvent is preferably: adding the bismuth salt and chloride salt to the solvent and stirring at room temperature; the present invention has no special requirements for the stirring time, as long as the raw materials are mixed evenly, which can be 30 minutes.

[0048] In the present invention, when the solvent is ethylene glycol or water, the mixed solution also includes glucose (when the solvent is ethanol, the crystallinity of the material decreases significantly after adding glucose, resulting in a decrease in the catalytic degradation efficiency of the catalyst; and when the solvent is ethylene glycol or water, adding glucose plays a positive role, and the crystallinity also decreases but not significantly); the glucose is conventional dextrorotatory glucose. In the present invention, the molar ratio of the glucose to the Bi element in the bismuth salt is (0.5-5):1, which can be 0.5:1, 1:1, 2:1, 3:1, 4:1 or 5:1, preferably 2:1. The present invention preferably mixes the bismuth salt, chloride salt and solvent evenly, then adds glucose thereto, and stirs at room temperature; the stirring time can be 10-60 minutes, depending on the mixing uniformity. The present invention adjusts the exposure degree of the crystal plane of the BiOCl material (reduces the exposure degree of the (001) plane) by adding glucose; and the glucose, as a carbon source, can achieve carbon doping of the BiOCl material (the addition of glucose has no significant effect on the material morphology). An appropriate amount of carbon doping improves the light absorption performance by introducing defect energy levels in the energy band. At the same time, the charge imbalance caused by the alivalent doping generates color centers, inducing the generation of oxygen vacancies in the photoreaction, thereby improving the photocatalytic activity.

[0049] In the present invention, the temperature of the solvent thermal reaction is preferably 120 to 200°C, and may be 130, 140, 150, 160, 170, 180 or 190°C, and the time is preferably 1 to 10 hours, and may be 2, 3, 4, 5, 6, 7, 8 or 9 hours. The present invention preferably transfers the mixed solution to a high-pressure reactor, and then places it in an oven for heating to carry out the solvent thermal reaction. During the solvent thermal reaction, the coordination and viscosity of the solvent play a crucial role in the reaction rate and diffusion movement of the reactants, thereby leading to differences in crystal growth. Specifically: (1) When the solvent is ethylene glycol (EG), the metal ions may coordinate with ethylene glycol to form alcohol oxides (Bi 3+ -EG), which is weakened during the solvothermal reaction to form BiO +Through the above process, the nucleation rate can be adjusted to generate a sheet structure. The resulting thin sheets gradually aggregate through electrostatic interaction. Ethylene glycol can also serve as a soft template, eventually forming a nanoflower structure. In addition, ethylene glycol can also modify the hydroxyl groups on the crystal surface and reduce the crystallinity. (2) When the solvent is ethanol, the guiding effect of ethanol on self-assembly is too weak to fully form a hierarchical structure. Therefore, the morphology of the formed BOC-E (E represents ethanol) is a loosely arranged thin sheet aggregation. (3) When the solvent is water, due to the low viscosity of water, the reactants have the highest diffusion rate and supersaturation during the hydrothermal process. Through the classic Ostwald ripening, tiny nuclei are gradually generated; small crystals dissolve to form smooth large thin sheets. During the reaction, glucose plays a role in regulating viscosity through its hydroxyl groups and provides greater spatial resistance for crystal growth, regulating the crystal plane and crystallinity. In addition, glucose also serves as a carbon source to achieve carbon doping.

[0050] After the solvothermal reaction is complete, the present invention preferably further includes sequentially subjecting the resulting reaction solution to solid-liquid separation, solid-phase washing, and drying to obtain a powdered BiOCl photocatalyst. The present invention does not particularly require the solid-liquid separation method; any solid-liquid separation method familiar to those skilled in the art, such as centrifugation, can be employed. The washing agent used for the solid-phase washing is preferably anhydrous ethanol, and the number of washes is preferably five. The drying temperature is preferably 60°C, and the drying time is preferably 12 hours.

[0051] The preparation method provided by this invention enables simple manipulation of BiOCl morphology and crystal planes, yielding a BiOCl photocatalyst with excellent photocatalytic degradation performance. Specifically, precise morphology control is achieved by simply adjusting the reaction solvent, while crystal plane manipulation and carbon doping are achieved by regulating the addition of glucose. Furthermore, the preparation method provided by this invention utilizes readily available raw materials, operates under mild reaction conditions, and does not require the addition of surfactants.

[0052] The present invention provides a BiOCl photocatalyst prepared by the preparation method described in the above technical solution, wherein the morphology of the BiOCl photocatalyst is flower-shaped or sheet-shaped, with the (110) crystal plane being the main exposed crystal plane. The present invention can optimize the physicochemical properties of the catalyst, including specific surface area, pore size distribution, and active site distribution, by precisely designing the morphology of the BiOCl photocatalyst, thereby improving the photocatalytic performance. In an embodiment of the present invention, the morphology of the BiOCl photocatalyst prepared using ethylene glycol as a solvent is a nanoflower assembled from nanosheets; the morphology of the BiOCl photocatalyst prepared using ethanol as a solvent is an aggregated nanosheet with a low degree of aggregation; and the morphology of the BiOCl photocatalyst prepared using water as a solvent is a nanosheet. The BiOCl material prepared by the prior art mainly exposes the (001) crystal plane. The (001) crystal plane intensity of the BiOCl photocatalyst prepared by the present invention is significantly reduced, and the highest peak of the XRD intensity corresponds to the (110) crystal plane. The (110) crystal plane is a high-energy crystal plane that can provide more active sites and is conducive to the degradation of pollutants. In the present invention, when glucose is added during the preparation process, the prepared BiOCl photocatalyst also includes carbon doping, which can significantly increase the light absorption range of the BiOCl material, improve the light absorption performance of the catalyst, and induce the generation of oxygen vacancies during the photoreaction.

[0053] The present invention provides the use of the BiOCl photocatalyst described in the above technical solution in the photocatalytic degradation of organic pollutants and / or the photocatalytic reduction of heavy metal ions.

[0054] In the present invention, the organic pollutants preferably include rhodamine B and / or tetracycline; the heavy metal ions preferably include hexavalent chromium ions. The BiOCl photocatalyst provided by the present invention exhibits excellent photodegradation performance against organic pollutants. Appropriate carbon doping lowers the material's conduction band position, increases the reduction potential of photogenerated electrons, and improves the utilization rate of their reduction reactions, thereby promoting the reduction of high-valent metal ions. This results in the BiOCl photocatalyst exhibiting excellent photocatalytic reduction performance against high-valent metal ions. In the examples of the present invention, the synergistic treatment of tetracycline and hexavalent chromium ions by the BiOCl photocatalyst was tested, demonstrating similarly excellent photocatalytic performance.

[0055] To further illustrate the present invention, the BiOCl photocatalyst provided by the present invention, its preparation method and application are described in detail below with reference to examples, but they should not be construed as limiting the scope of protection of the present invention.

[0056] Comparative Example 1

[0057] (1) Add 0.485 g of bismuth nitrate pentahydrate and 0.058 g of sodium chloride to a beaker containing 20 mL of ethylene glycol and stir at room temperature for 30 min.

[0058] (2) The mixed solution was transferred to an autoclave and then placed in an oven for reaction at 160°C for 3 h. The product was then separated by centrifugation, washed five times with anhydrous ethanol, and dried at 60°C for 12 h to obtain a BiOCl photocatalyst powder with a mass of 0.5139 g. The BiOCl photocatalyst obtained in Comparative Example 1 was designated BOC-EG.

[0059] The X-ray diffraction spectrum of the BiOCl photocatalyst obtained in Comparative Example 1 is shown in FIG. Figure 1 . Figure 2 The transmission electron microscope image of the BiOCl photocatalyst prepared in Comparative Example 1 shows that the product morphology of Comparative Example 1 is a nanoflower assembled from nanosheets. The UV-visible diffuse reflectance spectrum of the BiOCl photocatalyst obtained in Comparative Example 1 is shown in FIG. Figure 8 .

[0060] Generally speaking, the (001) crystal plane is the preferred orientation plane. However, when ethylene glycol is used as a solvent, the main crystal plane becomes the (110) crystal plane, indicating that ethylene glycol restricts the growth of the (001) plane. When ethylene glycol is used as a solvent, it can act as a soft template to induce the formation of hierarchical nanostructures. The viscosity of the solvent can affect the transfer and diffusion rates of ions. Therefore, the growth of the crystal nucleus plays a significant role in the morphology and size of the final nanostructure. Due to the high viscosity of ethylene glycol, the raw materials grow into nanoflowers composed of aggregated nanosheets through the Ostwald ripening process during the reaction. It is precisely because of the formation of the flower-like structure that the material has a large specific surface area, which facilitates the adsorption of pollutants and thus improves the photocatalytic activity.

[0061] The BiOCl photocatalyst prepared in Comparative Example 1 was tested for its photocatalytic degradation of organic pollutants. The testing method was as follows:

[0062] 20 mg of the photocatalyst was dispersed in 30 mL of a 10 mg / L rhodamine B (RhB) solution and stirred in the dark for 30 minutes to achieve adsorption / desorption equilibrium between the pollutant and the photocatalyst. The solution was then irradiated under a 400 W xenon lamp (simulating sunlight). Every 2 minutes, 3 mL of the solution was collected and filtered through a 0.22 μm filter. The RhB concentration was determined by measuring the absorbance at 553 nm using a UV-visible spectrophotometer.

[0063] The calculation formula for degradation efficiency is: Degradation efficiency (%) = (C0-C) / (C0)×100%, where C0 is the initial concentration of the pollutant and C is the concentration of the pollutant when the photocatalytic reaction reaches a certain time.

[0064] Test results: Within 6 minutes, the degradation efficiency of Rhodamine B reached 85.37% (see Figure 9 ).

[0065] Example 1

[0066] (1) Add 0.485 g of bismuth nitrate pentahydrate and 0.058 g of sodium chloride to a beaker containing 20 mL of ethylene glycol. Add 0.36 g of glucose to the above solution and stir at room temperature for 30 min.

[0067] (2) The mixed solution was transferred to an autoclave and then placed in an oven for reaction at 160°C for 3 h. The product was then separated by centrifugation, washed five times with anhydrous ethanol, and dried at 60°C for 12 h to obtain a BiOCl photocatalyst powder with a mass of 0.4986 g. The BiOCl photocatalyst obtained in Example 1 was designated BOC-EG-G.

[0068] The X-ray diffraction spectrum of the BiOCl photocatalyst obtained in Example 1 is shown in FIG. Figure 1 . Figure 3 The transmission electron microscope image of the BiOCl photocatalyst obtained in Example 1 shows that the product morphology of Example 1 is nanoflowers assembled from nanosheets. The UV-visible diffuse reflectance spectrum of the BiOCl photocatalyst obtained in Example 1 is shown in FIG. Figure 8 .

[0069] After adding glucose to ethylene glycol as a solvent, the exposure of the (001) crystal plane decreased significantly, as did the crystallinity. Because glucose acts as both a carbon source and a chelating agent during the reaction, it restricts molecular motion, altering the formation of bismuth oxychloride and inducing the formation of small nanosheets that aggregate into flower-like shapes. UV-visible diffuse reflectance spectroscopy also reveals that carbon doping enhances light absorption, thereby improving photocatalytic activity.

[0070] The performance of photocatalytic degradation of organic pollutants of the BiOCl photocatalyst prepared in Example 1 was tested according to the method of Comparative Example 1. The test results showed that the degradation efficiency of Rhodamine B by the BiOCl photocatalyst obtained in Example 1 reached 99.88% within 6 minutes (see Figure 9 ), it can be seen that the photocatalytic performance is greatly improved after BiOCl is modified with glucose as the carbon source.

[0071] Example 2

[0072] (1) Add 0.485 g of bismuth nitrate pentahydrate and 0.058 g of sodium chloride to a beaker containing 20 mL of ethanol and stir at room temperature for 30 min.

[0073] (2) The mixed solution was transferred to an autoclave and then placed in an oven for reaction at 160°C for 3 h. The product was then separated by centrifugation, washed five times with anhydrous ethanol, and dried at 60°C for 12 h to obtain BiOCl powder with a mass of 0.4787 g. The BiOCl photocatalyst obtained in Example 2 was designated BOC-E.

[0074] The X-ray diffraction spectrum of the BiOCl photocatalyst obtained in Example 2 is shown in FIG. Figure 1 . Figure 4 The transmission electron microscope image of the BiOCl photocatalyst obtained in Example 2 shows that the product morphology of Example 2 is aggregated nanosheets. The UV-visible diffuse reflectance spectrum of the BiOCl photocatalyst obtained in Example 2 is shown in FIG. Figure 8 .

[0075] Although the (110) plane is the primary crystal face when ethanol is used as the solvent, the exposure of the (102) plane is significantly reduced compared to ethylene glycol, and the crystallinity is also significantly reduced. Ethanol can effectively reduce the rate of the hydrolysis process, thereby slowing the growth rate of BiOCl and facilitating the formation of uniform BiOCl nanoplates, but it also leads to a decrease in crystallinity.

[0076] The performance of photocatalytic degradation of organic pollutants of the BiOCl photocatalyst prepared in Example 2 was tested according to the method of Comparative Example 1. The test results showed that the degradation efficiency of Rhodamine B by the BiOCl photocatalyst obtained in Example 2 reached 99.41% within 6 minutes (see Figure 9 ).

[0077] Comparative Example 2

[0078] (1) Add 0.485 g of bismuth nitrate pentahydrate and 0.058 g of sodium chloride to a beaker containing 20 mL of ethanol. Add 0.36 g of glucose to the above solution and stir at room temperature for 30 min.

[0079] (2) The mixed solution was transferred to an autoclave and then placed in an oven for reaction at 160°C for 3 h. The product was then separated by centrifugation, washed five times with anhydrous ethanol, and dried at 60°C for 12 h to obtain BiOCl powder with a mass of 0.4457 g. The BiOCl photocatalyst obtained in Comparative Example 2 was designated BOC-EG.

[0080] The X-ray diffraction spectrum of the BiOCl photocatalyst obtained in Comparative Example 2 is shown in FIG. Figure 1 . Figure 5 The transmission electron microscope image of the BiOCl photocatalyst obtained in comparative example 2 shows that the product morphology of comparative example 2 is small-sized nanosheets. The UV-visible diffuse reflectance spectrum of the BiOCl photocatalyst obtained in comparative example 2 is shown in FIG. Figure 8 .

[0081] The catalytic performance of the material prepared using ethanol as the solvent decreased significantly after the addition of glucose. This is because the crystallinity of the material decreases significantly after carbon doping, which seriously affects the photocatalytic performance. The addition of glucose induces the formation of small nanosheets, resulting in the small-sized nanosheets in the morphology of this comparative example.

[0082] The BiOCl photocatalyst prepared in Comparative Example 2 was tested for its photocatalytic degradation of organic pollutants according to the method of Comparative Example 1. The test results showed that the BiOCl photocatalyst obtained in Comparative Example 2 had a degradation efficiency of 81.76% for Rhodamine B within 6 minutes (see Figure 9 ).

[0083] Comparative Example 3

[0084] (1) Add 0.485 g of bismuth nitrate pentahydrate and 0.058 g of sodium chloride to a beaker containing 20 mL of deionized water and stir at room temperature for 30 min.

[0085] (2) The mixed solution was transferred to an autoclave and then placed in an oven for reaction at 160°C for 3 h. The product was then separated by centrifugation, washed five times with anhydrous ethanol, and dried at 60°C for 12 h to obtain BiOCl powder with a mass of 0.2980 g. The BiOCl photocatalyst obtained in Comparative Example 3 was designated BOC-W.

[0086] The X-ray diffraction spectrum of the BiOCl photocatalyst obtained in Comparative Example 3 is shown in FIG. Figure 1 . Figure 6 The transmission electron microscope image of the BiOCl photocatalyst obtained in comparative example 3 is shown in FIG. The product of comparative example 3 has a nano-sheet morphology, with the (001) crystal plane being the main crystal plane. The UV-visible diffuse reflectance spectrum of the BiOCl photocatalyst obtained in comparative example 3 is shown in FIG. Figure 8 .

[0087] When water is used as the solvent, the viscosity of the system is low and the crystal growth during the reaction process is less restricted. Therefore, the (001) crystal plane is preferentially oriented as the main crystal plane, and the material has a high degree of crystallinity, which is beneficial to improving the photocatalytic performance. However, due to its flaky morphology, its specific surface area is lower than that of the assembled flower-like structure, so the adsorption performance is slightly lower than that of the materials prepared in Examples 1 to 2 and Comparative Example 1.

[0088] The BiOCl photocatalyst prepared in Comparative Example 3 was tested for its photocatalytic degradation of organic pollutants according to the method of Comparative Example 1. The test results showed that the degradation efficiency of the material for Rhodamine B was 91.36% within 6 minutes (see Figure 9 ), which is the result of multiple factors such as high crystallinity, exposure of high-energy crystal planes and small specific surface area.

[0089] Example 3

[0090] (1) 0.485 g of bismuth nitrate pentahydrate and 0.058 g of sodium chloride were added to a beaker containing 20 mL of water. 0.36 g of glucose (2 mmol) was added to the above solution and stirred at room temperature for 30 min.

[0091] (2) The mixed solution was transferred to an autoclave and then placed in an oven for reaction at 160°C for 3 h. The product was then separated by centrifugation, washed five times with anhydrous ethanol, and dried at 60°C for 12 h to obtain BiOCl powder with a mass of 0.3584 g. The BiOCl photocatalyst obtained in Example 3 was designated BOC-WG.

[0092] The X-ray diffraction spectrum of the BiOCl photocatalyst obtained in Example 3 is shown in FIG. Figure 1 . Figure 7 The transmission electron microscope image of the BiOCl photocatalyst obtained in Example 3 is shown in FIG. The product morphology of Example 3 is nanosheet-like, and the exposure degree of the (001) crystal plane is significantly reduced. The UV-visible diffuse reflectance spectrum of the BiOCl photocatalyst obtained in Example 3 is shown in FIG. Figure 8 . Figure 8 In the results, the absorption edges of all samples are located around 380nm. For samples prepared only with solvent, BOC-EG has a wider light adsorption range than BOC-E and BOC-W. With the doping of carbon, the adsorption edge shows an obvious red shift and the light absorption range is significantly broadened, which is caused by the introduction of impurity levels by carbon doping.

[0093] After adding glucose with water as solvent, the exposure degree of the (001) crystal plane was significantly reduced, indicating that glucose has a significant effect on inhibiting the growth of the (001) crystal plane. The addition of glucose also slightly decreased the crystallinity.

[0094] The performance of photocatalytic degradation of organic pollutants of the BiOCl photocatalyst prepared in Example 3 was tested according to the method of Comparative Example 1. The test results are shown in Table 1. Figure 9 : The degradation efficiency of the material for rhodamine B reached 100% within 6 minutes, and the material changed color significantly before and after the photoreaction. The carbon doping induced the generation of oxygen vacancies in the photoreaction, which promoted the photocatalytic reaction.

[0095] The performance of the BiOCl photocatalyst prepared in Example 3 in photocatalytic reduction of heavy metal ions was tested. The test method was as follows: 20 mg of the photocatalyst was dispersed in 30 mL of Cr 6+ Solution (Cr 6+ The solution was placed under a 400W xenon lamp and irradiated with about 3 mL of solution every 2 minutes. The solution was filtered with a 0.22 μm membrane filter and the absorbance at 352 nm was measured using a UV-visible spectrophotometer to determine the Cr 6+ The test results are shown in Figure 10 ( Figure 10 pH = 9Cr 6+ and pH = 3Cr 6+):At pH=3, the removal efficiency of hexavalent chromium ions by the catalyst reached 100% within 30 minutes. At pH=9, the removal efficiency remained at a high level of 89.9% within 30 minutes.

[0096] The BiOCl photocatalyst prepared in Example 3 was tested for its synergistic treatment effect on tetracycline and hexavalent chromium ions. The test method was as follows: 20 mg of the photocatalyst was dispersed in 30 mL of a solution containing tetracycline (TC) and Cr. 6+ The test solution (tetracycline concentration is 10 mg / L, Cr 6+ The solution was stirred in the dark for 30 minutes to reach the adsorption / desorption equilibrium between the pollutant and the photocatalyst. The solution was then placed under a 400W xenon lamp. 3 mL of the solution was collected every 2 minutes, filtered through a 0.22 μm membrane filter, and the absorbance at 352 nm was measured to determine the Cr 6+ The test results are shown in Figure 10 ( Figure 10 pH = 9Cr 6+ +TC), compared with only Cr 6+ In the case of tetracycline and Cr 6+ When the two coexist 6+ The degradation rate of Cr 6+ When the catalyst has a 6+ The degradation efficiency reached 65.26% within 20 min, and the degradation rate constant was 0.064 min -1 When coexisting with tetracycline, the catalyst has a strong effect on Cr 6+ The degradation efficiency reached 97.15% within 20 min, and the degradation rate constant was 0.11 min -1 , compared with the presence of only Cr 6+ The rate increased by 1.7 times, indicating that the BiOCl photocatalyst prepared by the present invention can achieve the synergistic treatment of tetracycline and hexavalent chromium ions.

[0097] The above test results show that the prepared BiOCl photocatalytic material has excellent effects in both photocatalytic oxidation and reduction reactions, and can be used to remove a variety of pollutants in water.

[0098] The synthesis conditions of Examples 1 to 3 and Comparative Examples 1 to 3, as well as the morphology, crystal surface and degradation effect of the obtained products on Rhodamine B are listed in Table 1.

[0099] Table 1 Synthesis conditions of Examples 1 to 3 and Comparative Examples 1 to 3 and product morphology, crystal surface, and degradation effect

[0100]

[0101] Comparative Example 4

[0102] (1) Add 0.485 g of bismuth nitrate pentahydrate and 0.058 g of sodium chloride to a beaker containing 15 mL of ethylene glycol and 5 mL of deionized water and stir at room temperature for 30 min.

[0103] (2) The mixed solution was transferred to a high-pressure reactor, placed in an oven, and reacted at 160°C for 3 h. The product was then separated by centrifugation, washed five times with anhydrous ethanol, and dried at 60°C for 12 h to obtain BiOCl powder.

[0104] Figure 11 is the X-ray diffraction spectrum of the BiOCl photocatalyst prepared in Comparative Example 4, Figure 12 This is the SEM image of the BiOCl photocatalyst prepared in Comparative Example 4. Figure 13 This is an SEM image of the BiOCl photocatalyst obtained by replacing 15 mL of ethylene glycol and 5 mL of deionized water in Comparative Example 4 with 20 mL of ethylene glycol.

[0105] The BiOCl material obtained in Comparative Example 4 is a pure phase, with (101) crystal plane as the main crystal plane, and its morphology is a spherical shape aggregated from flakes. Compared with the single ethylene glycol solvent ( Figure 12 and Figure 13 In contrast), its sheet structure is smaller in size and thicker in thickness.

[0106] The BiOCl photocatalyst prepared in Comparative Example 4 was tested for its photocatalytic degradation of organic pollutants according to the method of Comparative Example 1. The test results showed that the degradation efficiency of the BiOCl material obtained in Comparative Example 4 for pollutant degradation was 88.9% for Rhodamine B in 10 minutes (see Figure 14 ), the degradation efficiency decreased compared with the single ethylene glycol solvent system.

[0107] Example 4

[0108] The addition amount of glucose in Example 3 was changed to 0.5 mmol, 1 mmol, 3 mmol, 4 mmol, and 5 mmol, respectively. The rest was the same as in Example 3.

[0109] The performance of BiOCl photocatalysts prepared by adding different amounts of glucose in Example 3 and Example 4 for photocatalytic degradation of tetracycline was tested. The test method was as follows: 20 mg of photocatalyst was dispersed in 30 mL of tetracycline solution (concentration 20 mg / L), stirred in the dark for 30 minutes to reach adsorption / desorption equilibrium between the pollutant and the photocatalyst; the solution was then placed under a 400W xenon lamp (simulating sunlight), 2.5 mL of solution was collected every 2 minutes, filtered with a 0.22 μm membrane filter, and the absorbance at 357 nm was measured using a UV-visible spectrophotometer to determine the concentration of tetracycline. The test results are shown in Figure 2. Figure 15 and Figure 16 shown.

[0110] Depend on Figure 15 and Figure 16 It can be seen that the degradation efficiency shows a volcanic correlation with the amount of glucose added, with 2 mmol being the optimal glucose addition amount. As the addition amount increases from 0 to 2 mmol, it can be seen that the material's adsorption performance for pollutants gradually improves within 30 minutes of dark state adsorption, thereby enhancing degradation performance. However, as the addition amount continues to increase from 2 mmol, the degradation performance begins to decline, which can be attributed to the excessive carbon nanoclusters formed on the surface of the catalyst, which accumulate and cover the surface active sites.

[0111] The above description is merely a preferred embodiment of the present invention and does not constitute any limitation thereto. It should be noted that those skilled in the art may make various improvements and modifications without departing from the principles of the present invention, and such improvements and modifications shall also be considered within the scope of protection of the present invention.

Claims

1. A method for preparing a BiOCl photocatalyst, characterized in that: The following steps are involved: Mixing a bismuth salt, a chloride salt, and a solvent, and subjecting the resulting mixture to a solvothermal reaction to obtain the BiOCl photocatalyst; The molar ratio of the Bi element in the bismuth salt to the Cl element in the chloride salt is 1:1; The solvent is ethylene glycol, water or ethanol; when the solvent is ethylene glycol or water, the mixed solution also includes glucose, and the molar ratio of the glucose to the Bi element in the bismuth salt is (0.5-5):

1.

2. The preparation method according to claim 1, characterized in that The bismuth salt includes bismuth nitrate.

3. The preparation method according to claim 1, characterized in that The chloride salts include sodium chloride and / or potassium chloride.

4. The preparation method according to claim 1 or 2, characterized in that The usage ratio of the bismuth salt to the solvent is 0.5-5 mmol:20-60 mL.

5. The preparation method according to claim 1, characterized in that The temperature of the solvent thermal reaction is 120-200° C., and the time is 1-10 hours.

6. The preparation method according to claim 1 or 5, characterized in that After the solvothermal reaction is completed, the obtained reaction liquid is sequentially subjected to solid-liquid separation, solid phase washing and drying to obtain a powdered BiOCl photocatalyst.

7. The BiOCl photocatalyst prepared by the preparation method according to any one of claims 1 to 6, wherein the BiOCl photocatalyst has a flower-like or flake-like morphology, with the (110) crystal plane being the main exposed crystal plane.

8. Use of the BiOCl photocatalyst according to claim 7 in the photocatalytic degradation of organic pollutants and / or the photocatalytic reduction of heavy metal ions.

9. The use according to claim 8, characterized in that The organic pollutants include rhodamine B and / or tetracycline.

10. The use according to claim 8, characterized in that The heavy metal ions include hexavalent chromium ions.

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