Two-dimensional nanosheet self-assembled BiOCl microspheres as well as preparation method and application thereof in treatment of pharmaceutical wastewater

Abstract

The invention belongs to the technical field of material science and engineering, and particularly relates to a two-dimensional nanosheet self-assembled BiOCl microsphere, a preparation method thereof and application of the two-dimensional nanosheet self-assembled BiOCl microsphere in treatment of pharmaceutical wastewater. The preparation method comprises the following steps: S1, dissolving hexadecyl trimethyl ammonium bromide in water for ultrasonic dispersion to obtain a liquid crystal phase solution; s2, dissolving bismuth nitrate pentahydrate in a hydrochloric acid solution to obtain a precursor solution; s3, adding the liquid crystal phase solution into the BiOCl precursor solution to obtain a uniformly mixed solution; s4, transferring the mixed solution into a reaction kettle for constant-temperature reaction; cooling the reaction kettle to room temperature, centrifugally separating the product, and collecting the obtained precipitate to obtain a first BiOCl microsphere intermediate; s5, placing the first BiOCl microsphere intermediate in an N, N-dimethylformamide solvent for ultrasonic dispersion, and reacting to obtain a second BiOCl microsphere intermediate; and S6, sequentially dipping the second BiOCl microsphere intermediate into a polyethyleneimine aqueous solution and a polyacrylic acid aqueous solution, and carrying out vacuum drying at room temperature to obtain the BiOCl microsphere.

Description

Technical Field

[0001] The invention belongs to the field of material science and engineering technology, and specifically relates to a two-dimensional nanosheet self-assembled BiOCl microsphere and a preparation method thereof, and application thereof in treating pharmaceutical wastewater. Background Art

[0002] At present, pharmaceutical wastewater pollution, especially the residues of tetracycline antibiotics in water bodies, poses a huge threat to human health and the ecological environment. Traditional pharmaceutical wastewater treatment methods have limited removal effects on tetracycline antibiotics. Therefore, BiOCl materials with photocatalytic properties have attracted widespread attention, but they have problems such as small specific surface area and low photocatalytic efficiency. Although the performance of BiOCl can be improved by modification through doping, loading, and heterojunction construction, it has disadvantages such as complex preparation process and high cost.

[0003] In recent years, piezoelectric catalysis technology, as an emerging environmentally friendly catalytic technology, does not require light and can drive catalytic reactions using the piezoelectric effect of materials. It has great application potential. Modifying the material surface using layer-by-layer self-assembly technology can further improve the dispersion and stability of the material.

[0004] Therefore, there is an urgent need to develop a new material that can overcome the limitations of traditional BiOCl materials and have high-voltage electrocatalytic activity to effectively degrade tetracycline antibiotics in water. Summary of the invention

[0005] The present invention overcomes the deficiencies of the prior art and provides a two-dimensional nanosheet self-assembled BiOCl microsphere and a preparation method thereof, and application thereof in treating pharmaceutical wastewater.

[0006] To achieve the above object, the technical solution adopted by the present invention is: a method for preparing two-dimensional nanosheet self-assembled BiOCl microspheres, comprising the following steps:

[0007] S1. Dissolve hexadecyltrimethylammonium bromide in water, disperse by ultrasonication, stir by magnetic force until it is completely dissolved, and let stand to obtain a liquid crystal phase solution;

[0008] S2, dissolving bismuth nitrate pentahydrate in a hydrochloric acid solution, stirring with a magnetic force until it is completely dissolved, to obtain a precursor solution;

[0009] S3, adding the liquid crystal phase solution to the BiOCl precursor solution at a rate of 3-5 mL / min, and continuously stirring with magnetic force to obtain a uniform mixed solution;

[0010] S4, placing the mixed solution at 120-150° C. for constant temperature reaction for 8-12 hours; after cooling to room temperature, centrifuging and separating the product, collecting the obtained precipitate, washing and drying, to obtain the first BiOCl microsphere intermediate;

[0011] S5, placing the first BiOCl microsphere intermediate in N,N-dimethylformamide solvent for ultrasonic dispersion, and reflux reaction at 140-160° C. under nitrogen protection for 10-12 hours; after cooling to room temperature, centrifugally separating the product, collecting the obtained precipitate, washing and drying, to obtain a second BiOCl microsphere intermediate;

[0012] S6. The second BiOCl microsphere intermediate is sequentially immersed in a polyethyleneimine aqueous solution and a polyacrylic acid aqueous solution, and washed with water in between; after repeating the immersion process 3-5 times, the intermediate is dried to obtain BiOCl microspheres.

[0013] In a preferred embodiment of the present invention, the concentration of hexadecyltrimethylammonium bromide in the final solution in step S1 is 20-30 mM.

[0014] In a preferred embodiment of the present invention, step S1 further comprises: adjusting the pH of the liquid crystal phase solution to 7-8 at 25-30° C. using a 0.1-0.5 mol / L sodium hydroxide solution.

[0015] In a preferred embodiment of the present invention, the Bi of the precursor solution in step S2 is 3+ The concentration is

[0016] 0.9-1.1mmol / mL.

[0017] In a preferred embodiment of the present invention, in step S3, the volume ratio of the liquid crystal phase solution to the precursor solution is 1:1-1:2.

[0018] In a preferred embodiment of the present invention, step S3 further comprises: adjusting the pH value of the mixed solution to 7-8 with 4-6 mol / L sodium hydroxide solution, and stirring for 30-60 min.

[0019] In a preferred embodiment of the present invention, in step S5, the molar ratio of N,N-dimethylformamide to BiOCl is 2:1 to 4:1.

[0020] In a preferred embodiment of the present invention, in step S6, the concentration of the polyethyleneimine aqueous solution is 0.1-0.5 wt %, and the concentration of the polyacrylic acid aqueous solution is 0.1-0.5 wt %.

[0021] Another technical solution provided by the present invention is: a two-dimensional nanosheet self-assembled BiOCl microsphere made according to the above-mentioned method for preparing two-dimensional nanosheet self-assembled BiOCl microsphere.

[0022] Another technical solution provided by the present invention is the use of the above-mentioned two-dimensional nanosheet self-assembled BiOCl microspheres in treating pharmaceutical wastewater.

[0023] The present invention solves the defects existing in the background technology and has the following beneficial effects:

[0024] (1) The present invention dissolves hexadecyltrimethylammonium bromide in water, disperses it ultrasonically, and stirs it magnetically until it is completely dissolved; uses sodium hydroxide solution to adjust the pH to form a clear liquid crystal phase solution, which is used to guide the directional growth of BiOCl crystals to form a micron-sphere structure with a high crystallinity. Micron-spheres with high crystallinity have a more regular lattice structure and fewer crystal defects, which are beneficial to charge migration and separation of photogenerated electron-hole pairs. Compared with traditional BiOCl materials with low crystallinity and low charge migration efficiency, the present invention improves the charge migration efficiency of BiOCl materials and provides a good foundation for subsequent DMF reduction and polyelectrolyte coating.

[0025] (2) The present invention reduces the BiOCl microsphere surface part Bi by N, N-dimethylformamide solvent 3+ , forming a Bi-BiOCl heterojunction structure on the BiOCl surface. The Bi-BiOCl heterojunction structure can accelerate the separation of electron-hole pairs and improve the utilization efficiency of electrons, thereby improving the catalytic activity. Compared with the traditional BiOCl material lacking a heterojunction structure, the electron-hole pair separation efficiency is low, and the electron utilization efficiency is low. The present invention improves the electron migration efficiency and piezoelectric catalytic activity of the BiOCl material.

[0026] (3) The present invention forms a multi-layer polyelectrolyte layer on the surface of the material by sequentially immersing the second BiOCl microsphere intermediate in a polyethyleneimine aqueous solution and a polyacrylic acid aqueous solution. The polyelectrolyte layer can enhance the dispersibility and stability of the material, and can serve as an electron transfer bridge and adsorption carrier to further improve the catalytic efficiency. Compared with the traditional BiOCl material lacking a polyelectrolyte coating, the dispersibility, stability and electron transfer efficiency are low, and the present invention improves the dispersibility, stability and electron transfer efficiency of the BiOCl material.

[0027] (4) In the two-dimensional nanosheet self-assembled BiOCl microspheres prepared by the present invention, Bi 0 As an efficient electron acceptor, it quickly captures the electrons generated by the piezoelectric effect and transfers them to the polyelectrolyte coating; the polyelectrolyte coating acts as an electron transfer bridge and adsorption carrier, selectively enriching tetracycline molecules on Bi 0 and stabilize its conformation. 0The catalysis generates active oxygen species, and the polyelectrolyte coating further activates these active oxygen species, forming a multi-pathway synergistic catalytic system, forming an overall structure with synergistic effects, optimizing the electron transfer path, enhancing adsorption selectivity, and improving catalytic activity, thus achieving efficient degradation of tetracycline antibiotics. The effect of this synergistic effect far exceeds the effect of a single feature, making the invention have excellent catalytic performance and application prospects. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art are briefly introduced below. Obviously, the drawings described below are only some embodiments recorded in the present invention. For those of ordinary skill in the art, other drawings can be obtained based on these drawings without creative work.

[0029] Figure 1 The present invention is a flow chart of a method for preparing BiOCl microspheres by self-assembly of two-dimensional nanosheets. DETAILED DESCRIPTION

[0030] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0031] In the following description, many specific details are set forth to facilitate a full understanding of the present invention, but the present invention may also be implemented in other ways different from those described herein. Therefore, the protection scope of the present invention is not limited to the specific embodiments disclosed below.

[0032] In the description of the present application, it should be understood that the terms "center", "longitudinal", "lateral", "up", "down", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inside", "outside", etc., indicating the orientation or positional relationship, are based on the orientation or positional relationship shown in the drawings, and are only for the convenience of describing the present application and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore cannot be understood as limiting the scope of protection of the present application. In addition, the terms "first", "second", etc. are only used for descriptive purposes, and cannot be understood as indicating or implying relative importance or implicitly indicating the number of technical features indicated. Therefore, features defined as "first", "second", etc. may explicitly or implicitly include one or more of the features. In the description of the invention, unless otherwise specified, "multiple" means two or more.

[0033] In the description of this application, it should be noted that, unless otherwise clearly specified and limited, the terms "installed", "connected", and "connected" should be understood in a broad sense, for example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be directly connected or indirectly connected through an intermediate medium, and it can be the internal communication of two components. For ordinary technicians in this field, the specific meanings of the above terms in this application can be understood by specific circumstances.

[0034] Application Overview:

[0035] The piezoelectric degradation process combines the conversion of mechanical energy (provided by stirring vibration) into electrical energy (piezoelectric effect), which in turn triggers a chemical reaction (catalytic degradation). Here is a detailed explanation:

[0036] Piezoelectric effect: When mechanical stress (such as vibrations generated during stirring) is applied to a material with piezoelectric properties (such as BiOCl microspheres), charge separation occurs within the material. This is because when piezoelectric materials are mechanically deformed, their lattice structure changes, causing the positive and negative charge centers to no longer coincide, resulting in charge accumulation on the surface of the material. These charges caused by mechanical stress can move on the surface of the material and in the surrounding environment. For semiconductor materials such as BiOCl, electrons jump from the valence band to the conduction band, leaving holes in the valence band. These charge carriers (electrons and holes) can migrate to the surface of the material and participate in redox reactions.

[0037] Catalytic degradation: On the surface of BiOCl microspheres, the electron-hole pairs generated by the piezoelectric effect can be used to catalytically degrade organic pollutants, such as tetracycline. Holes have strong oxidizing properties and can directly oxidize tetracycline molecules adsorbed on the catalyst surface; while electrons can reduce dissolved oxygen in the solution to generate superoxide radicals, which also have strong oxidizing ability and can further oxidize tetracycline.

[0038] Exemplary methods:

[0039] like Figure 1 As shown, a method for preparing BiOCl microspheres self-assembled from two-dimensional nanosheets comprises the following steps:

[0040] S1. Dissolve hexadecyltrimethylammonium bromide (CTAB) in water, disperse it by ultrasonication at 25-30°C for 5-15 minutes, and stir it by magnetic stirring for 30-60 minutes until it is completely dissolved; adjust the pH to 7-8 with 0.1-0.5 mol / L NaOH solution at 25-30°C, and let it stand for 10-30 minutes to form a clear liquid crystal phase solution. The CTAB concentration of the final solution is 20-30 mM.

[0041] S2, bismuth nitrate pentahydrate (Bi(NO 3 ) 3 ·5H 2 O) was dissolved in 0.08-0.12 mol / L hydrochloric acid (HCl) solution and stirred magnetically for 30-60 min until it was completely dissolved to obtain Bi 3+ A BiOCl precursor solution with a concentration of 0.9-1.1 mmol / mL.

[0042] S3. Add the liquid crystal phase solution to the BiOCl precursor solution at a rate of 3-5mL / min, and continue magnetic stirring; adjust the pH value of the mixed solution to 7-8 with 4-6mol / L sodium hydroxide (NaOH) solution, and stir for 30-60min to obtain a uniform mixed solution; wherein the volume ratio of the liquid crystal phase solution to the precursor solution is 1:1-1:2. By slowly adding the BiOCl precursor solution to the liquid crystal phase solution and controlling the pH value of the mixed solution at 7-8, it is ensured that the BiOCl crystals are uniformly nucleated and grown in the CTAB liquid crystal. The precursor solution is added slowly to avoid excessive local concentrations that lead to rapid precipitation of BiOCl, affecting the morphology of the final product, and ensuring its uniform nucleation in the liquid crystal.

[0043] S4. Transfer the mixed solution to a stainless steel autoclave lined with polytetrafluoroethylene, and react at a constant temperature of 120-150° C. for 8-12 hours, with a filling rate of the autoclave being 20-40%; after cooling the autoclave to room temperature, centrifuge the product at 8000-10000 rpm for 5-10 minutes, and collect the resulting precipitate; wash the product alternately with water and anhydrous ethanol, and dry the washed product in an oven at 60-70° C. for 6-10 hours; obtain the first BiOCl microsphere intermediate by removing unreacted raw materials, by-products and residual solvents.

[0044] S5, ultrasonically dispersing the first BiOCl microsphere intermediate in N,N-dimethylformamide solvent (DMF), reflux reacting in a reactor at 140-160°C under nitrogen protection for 10-12 hours, cooling the reactor to room temperature and taking out the product; centrifuging the product in a high-speed centrifuge at 5000-8000 rpm for 3-5 minutes, collecting the resulting precipitate; washing the resulting precipitate with water and anhydrous ethanol by centrifugation for 3-5 times, drying it in an oven at 60-70°C for 12-24 hours, and obtaining the second BiOCl microsphere intermediate; wherein the molar ratio of N,N-dimethylformamide to BiOCl is 2:1 to 4:1. Reducing the surface BiOCl microspheres by DMF 3+ , a Bi-BiOCl composite material is obtained, forming a Bi-BiOCl heterojunction.

[0045] S6, the second BiOCl microsphere intermediate is sequentially immersed in a 0.1-0.5wt% polyethyleneimine (PEI) aqueous solution and a 0.1-0.5wt% polyacrylic acid (PAA) aqueous solution, each immersion time is 30-60min, and the intermediate is fully washed with water, and the immersion process is repeated 3-5 times, and then vacuum dried at room temperature for 12-24h to obtain BiOCl microspheres. PEI and PAA are alternately adsorbed on the surface of the second BiOCl microsphere intermediate through electrostatic interaction, modifying the surface of the second BiOCl microsphere intermediate to form a multilayer polyelectrolyte layer.

[0046] Exemplary microspheres:

[0047] The two-dimensional nanosheet self-assembled BiOCl microspheres are prepared according to the above-mentioned method for preparing two-dimensional nanosheet self-assembled BiOCl microspheres, and the particle size is 1-5 μm.

[0048] Example applications:

[0049] An application of the above-mentioned two-dimensional nanosheet self-assembled BiOCl microspheres in treating pharmaceutical wastewater, wherein the main components of the pharmaceutical wastewater include one or more of tetracycline, norfloxacin, amoxicillin, ciprofloxacin, levofloxacin, acetaminophen and metronidazole.

[0050] In a specific embodiment, the piezoelectric catalytic degradation of tetracycline using two-dimensional nanosheet self-assembled BiOCl microspheres was performed. 0.05 g of BiOCl microspheres were added to 15 mL of 0.4 mmol / L tetracycline solution; the mixture was stirred continuously at 500-5000 rpm at 25°C, and samples were taken at 0 min, 10 min, 20 min, 30 min, 40 min and 50 min, and the supernatant was separated, and the absorbance value was measured to obtain the degradation rate.

[0051] Example 1

[0052] A method for preparing two-dimensional nanosheet self-assembled BiOCl microspheres, comprising the following steps:

[0053] S1. Dissolve hexadecyltrimethylammonium bromide (CTAB) in water, disperse it ultrasonically at 25°C for 5 minutes, and stir it magnetically for 30 minutes until it is completely dissolved; use 0.1 mol / L NaOH solution to adjust the pH to 8 at 25°C, let it stand for 15 minutes, and form a clear liquid crystal phase solution; wherein the CTAB concentration of the final solution is 20 mM.

[0054] S2, bismuth nitrate pentahydrate (Bi(NO 3 ) 3 ·5H 2 O) was dissolved in 0.10 mol / L hydrochloric acid (HCl) solution and stirred magnetically for 30 min until it was completely dissolved to obtain Bi 3+ BiOCl precursor solution with a concentration of 1.0 mmol / mL.

[0055] S3, adding the liquid crystal phase solution to the BiOCl precursor solution at a rate of 5 mL / min, continuously stirring with magnetic force; adjusting the pH value of the mixed solution to 8 with 5 mol / L sodium hydroxide (NaOH) solution, stirring for 30 min, and obtaining a uniform mixed solution. The volume ratio of the liquid crystal phase solution to the precursor solution is 1:2.

[0056] S4. The mixed solution is transferred to a stainless steel high-pressure reactor lined with polytetrafluoroethylene, and the reaction is carried out at a constant temperature of 120°C for 12 hours, and the filling rate of the reactor is 30%; after the reactor is cooled to room temperature, the product is placed in a high-speed centrifuge and centrifuged at 8000 rpm for 5 minutes to separate the product, and the resulting precipitate is collected; after the reaction, the reactor is cooled to room temperature and the product is taken out; the product is centrifuged and washed three times with water and anhydrous ethanol respectively, and placed in a 60°C oven for drying for 12 hours to obtain the first BiOCl microsphere intermediate.

[0057] S5, the first BiOCl microsphere intermediate was placed in DMF for ultrasonic dispersion, and refluxed for 12 hours in a reactor under nitrogen protection at 160°C, and the product was taken out after the reactor was cooled to room temperature; the product was placed in a high-speed centrifuge and centrifuged at 8000 rpm for 3 minutes, and the obtained precipitate was collected; the obtained precipitate was washed three times by centrifugation with water and anhydrous ethanol, and dried in a 70°C oven for 12 hours to obtain the second BiOCl microsphere intermediate. The molar ratio of N,N-dimethylformamide to BiOCl is 2:1.

[0058] S6. The second BiOCl microsphere intermediate was immersed in 0.20wt% PEI aqueous solution and 0.20wt% PAA aqueous solution in sequence, each immersion time was 30min, and it was fully washed with water in the middle, and the immersion process was repeated 3 times; the coated product was vacuum dried at room temperature for 12h to obtain BiOCl microspheres.

[0059] Example 2

[0060] A method for preparing two-dimensional nanosheet self-assembled BiOCl microspheres, comprising the following steps:

[0061] S1. Dissolve hexadecyltrimethylammonium bromide (CTAB) in water, disperse it ultrasonically at 25°C for 5 minutes, and stir it magnetically for 30 minutes until it is completely dissolved; use 0.1 mol / L NaOH solution to adjust the pH to 8 at 25°C, let it stand for 15 minutes, and form a clear liquid crystal phase solution; wherein the CTAB concentration of the final solution is 20 mM.

[0062] S2, bismuth nitrate pentahydrate (Bi(NO 3 ) 3 ·5H 2 O) was dissolved in 0.10 mol / L hydrochloric acid (HCl) solution and stirred magnetically for 30 min until it was completely dissolved to obtain Bi 3+ BiOCl precursor solution with a concentration of 1.0 mmol / mL.

[0063] S3, adding the liquid crystal phase solution to the BiOCl precursor solution at a rate of 5 mL / min, continuously stirring with magnetic force; adjusting the pH value of the mixed solution to 8 with 5 mol / L sodium hydroxide (NaOH) solution, stirring for 30 min, and obtaining a uniform mixed solution. The volume ratio of the liquid crystal phase solution to the precursor solution is 1:2.

[0064] S4. The mixed solution is transferred to a stainless steel high-pressure reactor lined with polytetrafluoroethylene, and the reaction is carried out at a constant temperature of 120°C for 12 hours, and the filling rate of the reactor is 30%; after the reactor is cooled to room temperature, the product is placed in a high-speed centrifuge and centrifuged at 8000 rpm for 5 minutes to separate the product, and the resulting precipitate is collected; after the reaction, the reactor is cooled to room temperature and the product is taken out; the product is centrifuged and washed three times with water and anhydrous ethanol respectively, and placed in a 60°C oven for drying for 12 hours to obtain the first BiOCl microsphere intermediate.

[0065] S5, the first BiOCl microsphere intermediate was placed in DMF for ultrasonic dispersion, and refluxed for 12 hours in a reactor under nitrogen protection at 160°C, and the product was taken out after the reactor was cooled to room temperature; the product was placed in a high-speed centrifuge and centrifuged at 8000 rpm for 3 minutes, and the obtained precipitate was collected; the obtained precipitate was washed three times by centrifugation with water and anhydrous ethanol, and dried in a 70°C oven for 12 hours to obtain the second BiOCl microsphere intermediate. The molar ratio of N,N-dimethylformamide to BiOCl is 2:1.

[0066] S6. The second BiOCl microsphere intermediate was immersed in 0.25wt% PEI aqueous solution and 0.25wt% PAA aqueous solution in sequence, each immersion time was 30min, and it was fully washed with water in the middle, and the immersion process was repeated 3 times; the coated product was vacuum dried at room temperature for 12h to obtain BiOCl microspheres.

[0067] Example 3

[0068] A method for preparing two-dimensional nanosheet self-assembled BiOCl microspheres, comprising the following steps:

[0069] S1. Dissolve hexadecyltrimethylammonium bromide (CTAB) in water, disperse it ultrasonically at 25°C for 5 minutes, and stir it magnetically for 30 minutes until it is completely dissolved; use 0.1 mol / L NaOH solution to adjust the pH to 8 at 25°C, let it stand for 15 minutes, and form a clear liquid crystal phase solution; wherein the CTAB concentration of the final solution is 20 mM.

[0070] S2, bismuth nitrate pentahydrate (Bi(NO 3 ) 3 ·5H 2 O) was dissolved in 0.10 mol / L hydrochloric acid (HCl) solution and stirred magnetically for 30 min until it was completely dissolved to obtain Bi 3+ BiOCl precursor solution with a concentration of 1.0 mmol / mL.

[0071] S3, adding the liquid crystal phase solution to the BiOCl precursor solution at a rate of 5 mL / min, continuously stirring with magnetic force; adjusting the pH value of the mixed solution to 8 with 5 mol / L sodium hydroxide (NaOH) solution, stirring for 30 min, and obtaining a uniform mixed solution. The volume ratio of the liquid crystal phase solution to the precursor solution is 1:2.

[0072] S4. The mixed solution is transferred to a stainless steel high-pressure reactor lined with polytetrafluoroethylene, and the reaction is carried out at a constant temperature of 120°C for 12 hours, and the filling rate of the reactor is 30%; after the reactor is cooled to room temperature, the product is placed in a high-speed centrifuge and centrifuged at 8000 rpm for 5 minutes to separate the product, and the resulting precipitate is collected; after the reaction, the reactor is cooled to room temperature and the product is taken out; the product is centrifuged and washed three times with water and anhydrous ethanol respectively, and placed in a 60°C oven for drying for 12 hours to obtain the first BiOCl microsphere intermediate.

[0073] S5, the first BiOCl microsphere intermediate was placed in DMF for ultrasonic dispersion, and refluxed for 12 hours in a reactor under nitrogen protection at 160°C, and the product was taken out after the reactor was cooled to room temperature; the product was placed in a high-speed centrifuge and centrifuged at 8000 rpm for 3 minutes, and the obtained precipitate was collected; the obtained precipitate was washed three times by centrifugation with water and anhydrous ethanol, and dried in a 70°C oven for 12 hours to obtain the second BiOCl microsphere intermediate. The molar ratio of N,N-dimethylformamide to BiOCl is 2:1.

[0074] S6. The second BiOCl microsphere intermediate was immersed in 0.30wt% PEI aqueous solution and 0.30wt% PAA aqueous solution in sequence, each immersion time was 30min, and it was fully washed with water in the middle, and the immersion process was repeated 3 times; the coated product was vacuum dried at room temperature for 12h to obtain BiOCl microspheres.

[0075] Example 4

[0076] A method for preparing two-dimensional nanosheet self-assembled BiOCl microspheres, comprising the following steps:

[0077] S1. Dissolve hexadecyltrimethylammonium bromide (CTAB) in water, disperse it ultrasonically at 25°C for 5 minutes, and stir it magnetically for 30 minutes until it is completely dissolved; use 0.1 mol / L NaOH solution to adjust the pH to 8 at 25°C, let it stand for 15 minutes, and form a clear liquid crystal phase solution; wherein the CTAB concentration of the final solution is 20 mM.

[0078] S2, bismuth nitrate pentahydrate (Bi(NO 3 ) 3 ·5H 2O) was dissolved in 0.10 mol / L hydrochloric acid (HCl) solution and stirred magnetically for 30 min until it was completely dissolved to obtain Bi 3+ BiOCl precursor solution with a concentration of 1.0 mmol / mL.

[0079] S3, adding the liquid crystal phase solution to the BiOCl precursor solution at a rate of 5 mL / min, continuously stirring with magnetic force; adjusting the pH value of the mixed solution to 8 with 5 mol / L sodium hydroxide (NaOH) solution, stirring for 30 min, and obtaining a uniform mixed solution. The volume ratio of the liquid crystal phase solution to the precursor solution is 1:2.

[0080] S4. The mixed solution is transferred to a stainless steel high-pressure reactor lined with polytetrafluoroethylene, and the reaction is carried out at a constant temperature of 120°C for 12 hours, and the filling rate of the reactor is 30%; after the reactor is cooled to room temperature, the product is placed in a high-speed centrifuge and centrifuged at 8000 rpm for 5 minutes to separate the product, and the resulting precipitate is collected; after the reaction, the reactor is cooled to room temperature and the product is taken out; the product is centrifuged and washed three times with water and anhydrous ethanol respectively, and placed in a 60°C oven for drying for 12 hours to obtain the first BiOCl microsphere intermediate.

[0081] S5, the first BiOCl microsphere intermediate was placed in DMF for ultrasonic dispersion, and refluxed in a reactor at 160°C under nitrogen protection for 12 hours. After the reaction, the reactor was cooled to room temperature and the product was taken out; the product was placed in a high-speed centrifuge and centrifuged at 8000 rpm for 3 minutes, and the obtained precipitate was collected; the obtained precipitate was washed three times by centrifugation with water and anhydrous ethanol, and dried in a 70°C oven for 12 hours to obtain the second BiOCl microsphere intermediate. The molar ratio of N,N-dimethylformamide to BiOCl is 3:1.

[0082] S6. The second BiOCl microsphere intermediate was immersed in 0.20wt% PEI aqueous solution and 0.20wt% PAA aqueous solution in sequence, each immersion time was 30min, and it was fully washed with water in the middle, and the immersion process was repeated 3 times; the coated product was vacuum dried at room temperature for 12h to obtain BiOCl microspheres.

[0083] Example 5

[0084] A method for preparing two-dimensional nanosheet self-assembled BiOCl microspheres, comprising the following steps:

[0085] S1. Dissolve hexadecyltrimethylammonium bromide (CTAB) in water, disperse it ultrasonically at 25°C for 5 minutes, and stir it magnetically for 30 minutes until it is completely dissolved; use 0.1 mol / L NaOH solution to adjust the pH to 8 at 25°C, let it stand for 15 minutes, and form a clear liquid crystal phase solution; wherein the CTAB concentration of the final solution is 20 mM.

[0086] S2, bismuth nitrate pentahydrate (Bi(NO 3 ) 3 ·5H 2 O) was dissolved in 0.10 mol / L hydrochloric acid (HCl) solution and stirred magnetically for 30 min until it was completely dissolved to obtain Bi 3+ BiOCl precursor solution with a concentration of 1.0 mmol / mL.

[0087] S3, adding the liquid crystal phase solution to the BiOCl precursor solution at a rate of 5 mL / min, continuously stirring with magnetic force; adjusting the pH value of the mixed solution to 8 with 5 mol / L sodium hydroxide (NaOH) solution, stirring for 30 min, and obtaining a uniform mixed solution. The volume ratio of the liquid crystal phase solution to the precursor solution is 1:2.

[0088] S4. The mixed solution is transferred to a stainless steel high-pressure reactor lined with polytetrafluoroethylene, and the reaction is carried out at a constant temperature of 120°C for 12 hours, and the filling rate of the reactor is 30%; after the reactor is cooled to room temperature, the product is placed in a high-speed centrifuge and centrifuged at 8000 rpm for 5 minutes to separate the product, and the resulting precipitate is collected; after the reaction, the reactor is cooled to room temperature and the product is taken out; the product is centrifuged and washed three times with water and anhydrous ethanol respectively, and placed in a 60°C oven for drying for 12 hours to obtain the first BiOCl microsphere intermediate.

[0089] S5, the first BiOCl microsphere intermediate was placed in DMF for ultrasonic dispersion, and refluxed in a reactor at 160°C under nitrogen protection for 12 hours. After the reaction, the reactor was cooled to room temperature and the product was taken out; the product was placed in a high-speed centrifuge and centrifuged at 8000 rpm for 3 minutes, and the obtained precipitate was collected; the obtained precipitate was washed three times by centrifugation with water and anhydrous ethanol, and dried in a 70°C oven for 12 hours to obtain the second BiOCl microsphere intermediate. The molar ratio of N,N-dimethylformamide to BiOCl is 3:1.

[0090] S6. The second BiOCl microsphere intermediate was immersed in 0.25wt% PEI aqueous solution and 0.25wt% PAA aqueous solution in sequence, each immersion time was 30min, and it was fully washed with water in the middle, and the immersion process was repeated 3 times; the coated product was vacuum dried at room temperature for 12h to obtain BiOCl microspheres.

[0091] Example 6

[0092] A method for preparing two-dimensional nanosheet self-assembled BiOCl microspheres, comprising the following steps:

[0093] S1. Dissolve hexadecyltrimethylammonium bromide (CTAB) in water, disperse it ultrasonically at 25°C for 5 minutes, and stir it magnetically for 30 minutes until it is completely dissolved; use 0.1 mol / L NaOH solution to adjust the pH to 8 at 25°C, let it stand for 15 minutes, and form a clear liquid crystal phase solution; wherein the CTAB concentration of the final solution is 20 mM.

[0094] S2, bismuth nitrate pentahydrate (Bi(NO 3 ) 3 ·5H 2 O) was dissolved in 0.10 mol / L hydrochloric acid (HCl) solution and stirred magnetically for 30 min until it was completely dissolved to obtain Bi 3+ BiOCl precursor solution with a concentration of 1.0 mmol / mL.

[0095] S3, adding the liquid crystal phase solution to the BiOCl precursor solution at a rate of 5 mL / min, continuously stirring with magnetic force; adjusting the pH value of the mixed solution to 8 with 5 mol / L sodium hydroxide (NaOH) solution, stirring for 30 min, and obtaining a uniform mixed solution. The volume ratio of the liquid crystal phase solution to the precursor solution is 1:2.

[0096] S4. The mixed solution is transferred to a stainless steel high-pressure reactor lined with polytetrafluoroethylene, and the reaction is carried out at a constant temperature of 120°C for 12 hours, and the filling rate of the reactor is 30%; after the reactor is cooled to room temperature, the product is placed in a high-speed centrifuge and centrifuged at 8000 rpm for 5 minutes to separate the product, and the resulting precipitate is collected; after the reaction, the reactor is cooled to room temperature and the product is taken out; the product is centrifuged and washed three times with water and anhydrous ethanol respectively, and placed in a 60°C oven for drying for 12 hours to obtain the first BiOCl microsphere intermediate.

[0097] S5, the first BiOCl microsphere intermediate was placed in DMF for ultrasonic dispersion, and refluxed in a reactor at 160°C under nitrogen protection for 12 hours. After the reaction, the reactor was cooled to room temperature and the product was taken out; the product was placed in a high-speed centrifuge and centrifuged at 8000 rpm for 3 minutes, and the obtained precipitate was collected; the obtained precipitate was washed three times by centrifugation with water and anhydrous ethanol, and dried in a 70°C oven for 12 hours to obtain the second BiOCl microsphere intermediate. The molar ratio of N,N-dimethylformamide to BiOCl is 3:1.

[0098] S6. The second BiOCl microsphere intermediate was immersed in 0.30wt% PEI aqueous solution and 0.30wt% PAA aqueous solution in sequence, each immersion time was 30min, and it was fully washed with water in the middle, and the immersion process was repeated 3 times; the coated product was vacuum dried at room temperature for 12h to obtain BiOCl microspheres.

[0099] Example 7

[0100] A method for preparing two-dimensional nanosheet self-assembled BiOCl microspheres, comprising the following steps:

[0101] S1. Dissolve hexadecyltrimethylammonium bromide (CTAB) in water, disperse it ultrasonically at 25°C for 5 minutes, and stir it magnetically for 30 minutes until it is completely dissolved; use 0.1 mol / L NaOH solution to adjust the pH to 8 at 25°C, let it stand for 15 minutes, and form a clear liquid crystal phase solution; wherein the CTAB concentration of the final solution is 20 mM.

[0102] S2, bismuth nitrate pentahydrate (Bi(NO 3 ) 3 ·5H 2 O) was dissolved in 0.10 mol / L hydrochloric acid (HCl) solution and stirred magnetically for 30 min until it was completely dissolved to obtain Bi 3+ BiOCl precursor solution with a concentration of 1.0 mmol / mL.

[0103] S3, adding the liquid crystal phase solution to the BiOCl precursor solution at a rate of 5 mL / min, continuously stirring with magnetic force; adjusting the pH value of the mixed solution to 8 with 5 mol / L sodium hydroxide (NaOH) solution, stirring for 30 min, and obtaining a uniform mixed solution. The volume ratio of the liquid crystal phase solution to the precursor solution is 1:2.

[0104] S4. The mixed solution is transferred to a stainless steel high-pressure reactor lined with polytetrafluoroethylene, and the reaction is carried out at a constant temperature of 120°C for 12 hours, and the filling rate of the reactor is 30%; after the reactor is cooled to room temperature, the product is placed in a high-speed centrifuge and centrifuged at 8000 rpm for 5 minutes to separate the product, and the resulting precipitate is collected; after the reaction, the reactor is cooled to room temperature and the product is taken out; the product is centrifuged and washed three times with water and anhydrous ethanol respectively, and placed in a 60°C oven for drying for 12 hours to obtain the first BiOCl microsphere intermediate.

[0105] S5, the first BiOCl microsphere intermediate was placed in DMF for ultrasonic dispersion, and refluxed in a reactor at 160°C under nitrogen protection for 12 hours. After the reaction, the reactor was cooled to room temperature and the product was taken out; the product was placed in a high-speed centrifuge and centrifuged at 8000 rpm for 3 minutes, and the obtained precipitate was collected; the obtained precipitate was washed three times by centrifugation with water and anhydrous ethanol, and dried in a 70°C oven for 12 hours to obtain the second BiOCl microsphere intermediate. The molar ratio of N,N-dimethylformamide to BiOCl is 4:1.

[0106] S6. The second BiOCl microsphere intermediate was immersed in 0.20wt% PEI aqueous solution and 0.20wt% PAA aqueous solution in sequence, each immersion time was 30min, and it was fully washed with water in the middle, and the immersion process was repeated 3 times; the coated product was vacuum dried at room temperature for 12h to obtain BiOCl microspheres.

[0107] Example 8

[0108] A method for preparing two-dimensional nanosheet self-assembled BiOCl microspheres, comprising the following steps:

[0109] S1. Dissolve hexadecyltrimethylammonium bromide (CTAB) in water, disperse it ultrasonically at 25°C for 5 minutes, and stir it magnetically for 30 minutes until it is completely dissolved; use 0.1 mol / L NaOH solution to adjust the pH to 8 at 25°C, let it stand for 15 minutes, and form a clear liquid crystal phase solution; wherein the CTAB concentration of the final solution is 20 mM.

[0110] S2, bismuth nitrate pentahydrate (Bi(NO 3 ) 3 ·5H 2 O) was dissolved in 0.10 mol / L hydrochloric acid (HCl) solution and stirred magnetically for 30 min until it was completely dissolved to obtain Bi 3+ BiOCl precursor solution with a concentration of 1.0 mmol / mL.

[0111] S3, adding the liquid crystal phase solution to the BiOCl precursor solution at a rate of 5 mL / min, continuously stirring with magnetic force; adjusting the pH value of the mixed solution to 8 with 5 mol / L sodium hydroxide (NaOH) solution, stirring for 30 min, and obtaining a uniform mixed solution. The volume ratio of the liquid crystal phase solution to the precursor solution is 1:2.

[0112] S4. The mixed solution is transferred to a stainless steel high-pressure reactor lined with polytetrafluoroethylene, and the reaction is carried out at a constant temperature of 120°C for 12 hours, and the filling rate of the reactor is 30%; after the reactor is cooled to room temperature, the product is placed in a high-speed centrifuge and centrifuged at 8000 rpm for 5 minutes to separate the product, and the resulting precipitate is collected; after the reaction, the reactor is cooled to room temperature and the product is taken out; the product is centrifuged and washed three times with water and anhydrous ethanol respectively, and placed in a 60°C oven for drying for 12 hours to obtain the first BiOCl microsphere intermediate.

[0113] S5, the first BiOCl microsphere intermediate was placed in DMF for ultrasonic dispersion, and refluxed in a reactor at 160°C under nitrogen protection for 12 hours. After the reaction, the reactor was cooled to room temperature and the product was taken out; the product was placed in a high-speed centrifuge and centrifuged at 8000 rpm for 3 minutes, and the obtained precipitate was collected; the obtained precipitate was washed three times by centrifugation with water and anhydrous ethanol, and dried in a 70°C oven for 12 hours to obtain the second BiOCl microsphere intermediate. The molar ratio of N,N-dimethylformamide to BiOCl is 4:1.

[0114] S6. The second BiOCl microsphere intermediate was immersed in 0.25wt% PEI aqueous solution and 0.25wt% PAA aqueous solution in sequence, each immersion time was 30min, and it was fully washed with water in the middle, and the immersion process was repeated 3 times; the coated product was vacuum dried at room temperature for 12h to obtain BiOCl microspheres.

[0115] Example 9

[0116] A method for preparing two-dimensional nanosheet self-assembled BiOCl microspheres, comprising the following steps:

[0117] S1. Dissolve hexadecyltrimethylammonium bromide (CTAB) in water, disperse it ultrasonically at 25°C for 5 minutes, and stir it magnetically for 30 minutes until it is completely dissolved; use 0.1 mol / L NaOH solution to adjust the pH to 8 at 25°C, let it stand for 15 minutes, and form a clear liquid crystal phase solution; wherein the CTAB concentration of the final solution is 20 mM.

[0118] S2, bismuth nitrate pentahydrate (Bi(NO 3 ) 3 ·5H 2 O) was dissolved in 0.10 mol / L hydrochloric acid (HCl) solution and stirred magnetically for 30 min until it was completely dissolved to obtain Bi 3+ BiOCl precursor solution with a concentration of 1.0 mmol / mL.

[0119] S3, adding the liquid crystal phase solution to the BiOCl precursor solution at a rate of 5 mL / min, continuously stirring with magnetic force; adjusting the pH value of the mixed solution to 8 with 5 mol / L sodium hydroxide (NaOH) solution, stirring for 30 min, and obtaining a uniform mixed solution. The volume ratio of the liquid crystal phase solution to the precursor solution is 1:2.

[0120] S4. The mixed solution is transferred to a stainless steel high-pressure reactor lined with polytetrafluoroethylene, and the reaction is carried out at a constant temperature of 120°C for 12 hours, and the filling rate of the reactor is 30%; after the reactor is cooled to room temperature, the product is placed in a high-speed centrifuge and centrifuged at 8000 rpm for 5 minutes to separate the product, and the resulting precipitate is collected; after the reaction, the reactor is cooled to room temperature and the product is taken out; the product is centrifuged and washed three times with water and anhydrous ethanol respectively, and placed in a 60°C oven for drying for 12 hours to obtain the first BiOCl microsphere intermediate.

[0121] S5, the first BiOCl microsphere intermediate was placed in DMF for ultrasonic dispersion, and refluxed in a reactor at 160°C under nitrogen protection for 12 hours. After the reaction, the reactor was cooled to room temperature and the product was taken out; the product was placed in a high-speed centrifuge and centrifuged at 8000 rpm for 3 minutes, and the obtained precipitate was collected; the obtained precipitate was washed three times by centrifugation with water and anhydrous ethanol, and dried in a 70°C oven for 12 hours to obtain the second BiOCl microsphere intermediate. The molar ratio of N,N-dimethylformamide to BiOCl is 4:1.

[0122] S6. The second BiOCl microsphere intermediate was immersed in 0.30wt% PEI aqueous solution and 0.30wt% PAA aqueous solution in sequence, each immersion time was 30min, and it was fully washed with water in the middle, and the immersion process was repeated 3 times; the coated product was vacuum dried at room temperature for 12h to obtain BiOCl microspheres.

[0123] Comparative Example 1

[0124] A method for preparing two-dimensional nanosheet self-assembled BiOCl microspheres, comprising the following steps:

[0125] S1. Bismuth nitrate pentahydrate (Bi(NO 3 ) 3 ·5H 2 O) was dissolved in 0.10 mol / L hydrochloric acid (HCl) solution and stirred magnetically for 30 min until it was completely dissolved to obtain Bi 3+ BiOCl precursor solution with a concentration of 1.0 mmol / mL.

[0126] S2. The precursor solution is transferred to a stainless steel high-pressure reactor lined with polytetrafluoroethylene, and the reaction is carried out at a constant temperature of 120°C for 12 hours, and the filling rate of the reactor is 30%; after the reactor is cooled to room temperature, the product is placed in a high-speed centrifuge and centrifuged at 8000 rpm for 5 minutes to separate the product, and the resulting precipitate is collected; after the reaction, the reactor is cooled to room temperature and the product is taken out; the product is centrifuged and washed three times with water and anhydrous ethanol respectively, and placed in a 60°C oven for drying for 12 hours to obtain the first BiOCl microsphere intermediate.

[0127] S3, the first BiOCl microsphere intermediate was placed in DMF for ultrasonic dispersion, and refluxed in a reactor at 160°C under nitrogen protection for 12 hours. After the reaction, the reactor was cooled to room temperature and the product was taken out; the product was placed in a high-speed centrifuge and centrifuged at 8000 rpm for 3 minutes, and the obtained precipitate was collected; the obtained precipitate was washed three times by centrifugation with water and anhydrous ethanol, and dried in a 70°C oven for 12 hours to obtain the second BiOCl microsphere intermediate. The molar ratio of N,N-dimethylformamide to BiOCl is 3:1.

[0128] S5. The second BiOCl microsphere intermediate is immersed in 0.25wt% PEI aqueous solution and 0.25wt% PAA aqueous solution in sequence, each immersion time is 30min, and it is fully washed with water in the middle, and the immersion process is repeated 3 times; the coated product is vacuum dried at room temperature for 12h to obtain BiOCl microspheres.

[0129] Comparative Example 2

[0130] A method for preparing two-dimensional nanosheet self-assembled BiOCl microspheres, comprising the following steps:

[0131] S1. Dissolve hexadecyltrimethylammonium bromide (CTAB) in water, disperse it ultrasonically at 25°C for 5 minutes, and stir it magnetically for 30 minutes until it is completely dissolved; use 0.1 mol / L NaOH solution to adjust the pH to 8 at 25°C, let it stand for 15 minutes, and form a clear liquid crystal phase solution; wherein the CTAB concentration of the final solution is 20 mM.

[0132] S2, bismuth nitrate pentahydrate (Bi(NO 3 ) 3 ·5H 2 O) was dissolved in 0.10 mol / L hydrochloric acid (HCl) solution and stirred magnetically for 30 min until it was completely dissolved to obtain Bi 3+ BiOCl precursor solution with a concentration of 1.0 mmol / mL.

[0133] S3, adding the liquid crystal phase solution to the BiOCl precursor solution at a rate of 5 mL / min, continuously stirring with magnetic force; adjusting the pH value of the mixed solution to 8 with 5 mol / L sodium hydroxide (NaOH) solution, stirring for 30 min, and obtaining a uniform mixed solution. The volume ratio of the liquid crystal phase solution to the precursor solution is 1:2.

[0134] S4. The mixed solution is transferred to a stainless steel high-pressure reactor lined with polytetrafluoroethylene, and the reaction is carried out at a constant temperature of 120°C for 12 hours, and the filling rate of the reactor is 30%; after the reactor is cooled to room temperature, the product is placed in a high-speed centrifuge and centrifuged at 8000 rpm for 5 minutes to separate the product, and the resulting precipitate is collected; after the reaction, the reactor is cooled to room temperature and the product is taken out; the product is centrifuged and washed three times with water and anhydrous ethanol respectively, and placed in a 60°C oven for drying for 12 hours to obtain the first BiOCl microsphere intermediate.

[0135] S5, the first BiOCl microsphere intermediate is placed in DMF for ultrasonic dispersion, and refluxed in a reactor at 160°C under nitrogen protection for 12 hours. After the reaction, the reactor is cooled to room temperature and the product is taken out; the product is placed in a high-speed centrifuge and centrifuged at 8000 rpm for 3 minutes, and the resulting precipitate is collected; the resulting precipitate is washed three times by centrifugation with water and anhydrous ethanol, and dried in a 70°C oven for 12 hours to obtain BiOCl microspheres. The molar ratio of N,N-dimethylformamide to BiOCl is 3:1.

[0136] Comparative Example 3

[0137] A method for preparing two-dimensional nanosheet self-assembled BiOCl microspheres, comprising the following steps:

[0138] S1. Dissolve hexadecyltrimethylammonium bromide (CTAB) in water, disperse it ultrasonically at 25°C for 5 minutes, and stir it magnetically for 30 minutes until it is completely dissolved; use 0.1 mol / L NaOH solution to adjust the pH to 8 at 25°C, let it stand for 15 minutes, and form a clear liquid crystal phase solution; wherein the CTAB concentration of the final solution is 20 mM.

[0139] S2, bismuth nitrate pentahydrate (Bi(NO 3 ) 3 ·5H 2 O) was dissolved in 0.10 mol / L hydrochloric acid (HCl) solution and stirred magnetically for 30 min until it was completely dissolved to obtain Bi 3+ BiOCl precursor solution with a concentration of 1.0 mmol / mL.

[0140] S3, adding the liquid crystal phase solution to the BiOCl precursor solution at a rate of 5 mL / min, continuously stirring with magnetic force; adjusting the pH value of the mixed solution to 8 with 5 mol / L sodium hydroxide (NaOH) solution, stirring for 30 min, and obtaining a uniform mixed solution. The volume ratio of the liquid crystal phase solution to the precursor solution is 1:2.

[0141] S4. The mixed solution is transferred to a stainless steel high-pressure reactor lined with polytetrafluoroethylene, and the reaction is carried out at a constant temperature of 120°C for 12 hours, and the filling rate of the reactor is 30%; after the reactor is cooled to room temperature, the product is placed in a high-speed centrifuge and centrifuged at 8000 rpm for 5 minutes to separate the product, and the resulting precipitate is collected; after the reaction, the reactor is cooled to room temperature and the product is taken out; the product is centrifuged and washed three times with water and anhydrous ethanol respectively, and placed in a 60°C oven for drying for 12 hours to obtain the first BiOCl microsphere intermediate.

[0142] S5. The product obtained in step S5 is immersed in 0.25wt% PEI aqueous solution and 0.25wt% PAA aqueous solution in sequence, each immersion time is 30min, and the mixture is fully washed with water in the middle, and the immersion process is repeated 3 times; the coated product is vacuum dried at room temperature for 12h to obtain BiOCl microspheres.

[0143] Comparative Example 4

[0144] S1. Dissolve hexadecyltrimethylammonium bromide (CTAB) in water, disperse it ultrasonically at 25°C for 5 minutes, and stir it magnetically for 30 minutes until it is completely dissolved; use 0.1 mol / L NaOH solution to adjust the pH to 8 at 25°C, let it stand for 15 minutes, and form a clear liquid crystal phase solution; wherein the CTAB concentration of the final solution is 20 mM.

[0145] S2, bismuth nitrate pentahydrate (Bi(NO 3 ) 3 ·5H 2 O) was dissolved in 0.10 mol / L hydrochloric acid (HCl) solution and stirred magnetically for 30 min until it was completely dissolved to obtain Bi 3+ BiOCl precursor solution with a concentration of 1.0 mmol / mL.

[0146] S3, adding the liquid crystal phase solution to the BiOCl precursor solution at a rate of 5 mL / min, continuously stirring with magnetic force; adjusting the pH value of the mixed solution to 8 with 5 mol / L sodium hydroxide (NaOH) solution, stirring for 30 min, and obtaining a uniform mixed solution. The volume ratio of the liquid crystal phase solution to the precursor solution is 1:2.

[0147] S4. The mixed solution was transferred to a stainless steel high-pressure reactor lined with polytetrafluoroethylene, and the reaction was carried out at a constant temperature of 120°C for 12 hours, and the filling rate of the reactor was 30%; after the reactor was cooled to room temperature, the product was placed in a high-speed centrifuge and centrifuged at 8000 rpm for 5 minutes to separate the product, and the resulting precipitate was collected; after the reaction, the reactor was cooled to room temperature and the product was taken out; the product was centrifuged and washed three times with water and anhydrous ethanol respectively, and dried in an oven at 60°C for 12 hours to obtain BiOCl microspheres.

[0148] Experimental Example 1

[0149] (1) Catalyst preparation: According to Examples 1-9 and Comparative Examples 1-4, corresponding BiOCl catalysts were prepared respectively;

[0150] (2) Preparation of tetracycline: Prepare 0.4 mmol / L tetracycline solution;

[0151] (3) Weighing catalyst: prepare a group of test tubes numbered corresponding to Examples 1-9 and Comparative Examples 1-4; weigh 0.05 g of different BiOCl catalyst powders and place them in corresponding test tubes (the same mass of catalyst, i.e., 0.05 g, is used in each test tube);

[0152] (4) Add tetracycline solution: Use a pipette to add 15 mL of 0.4 mmol / L tetracycline solution to each test tube (make sure the volume of tetracycline solution added to each test tube is the same);

[0153] (5) Add rotors: Add two rotors to each test tube (make sure the rotors are of the same size and shape);

[0154] (6) Stirring and vibrating: Place the test tube on a magnetic stirrer and set the stirring speed to 500 rpm; set the stirring time to 50 min, and take samples at 10, 20, 30, 40, and 50 min respectively;

[0155] (7) Sampling: At each set time point, take a small amount of solution (2 mL) from each test tube and record the test tube number corresponding to each time point;

[0156] (8) Centrifugation: Place the removed solution into a centrifuge, set the centrifugal speed and time (5000 rpm, 5 min), and centrifuge to precipitate the solid catalyst;

[0157] (9) Absorbance measurement: Use a pipette to transfer the supernatant after centrifugation into a cuvette; use a spectrophotometer to measure the absorbance value A of the supernatant at the maximum absorption wavelength of tetracycline;

[0158] (10) Blank control: Following the same procedure, take 15 mL of 0.4 mmol / L tetracycline solution without adding any catalyst as a blank control and test its absorbance value A at different times. 0 ;

[0159] (11) Data recording and calculation: Record the absorbance values ​​(A and A) at each time point. 0 ); According to the formula, the tetracycline degradation rate D under different catalysts at each time point is calculated; the calculation formula is: Where D is the degradation rate, A is the absorbance of tetracycline after degradation, A0 is the absorbance of tetracycline without catalyst, C is the concentration of tetracycline after degradation, and C 0 is the concentration of tetracycline when no catalyst is added.

[0160] The experimental results are shown in Tables 1 and 2 below:

[0161] Table 1 Tetracycline degradation rate of Examples 1-9

[0162]

[0163] Table 2 Comparative Examples 1-4 Tetracycline Degradation Rate

[0164] Comparative Example Comparative Example 1 Comparative Example 2 Comparative Example 3 Comparative Example 4 10min 27.6 27.3 25.1 20.9 20min 46.0 45.6 41.9 34.8 30min 57.5 57.0 52.3 43.5 40min 71.9 71.2 65.4 54.4 50min 79.9 79.1 72.7 60.4

[0165] According to Table 1 and Table 2, Example 5 is significantly better than Comparative Example 1. This is because Example 5 uses a CTAB liquid crystal template with a hexagonal phase structure to guide the directional growth of BiOCl crystals to form a micron-sphere structure with a higher crystallinity. A higher crystallinity can provide a more regular lattice structure, reduce crystal defects, thereby improving charge transfer efficiency and enhancing catalytic activity.

[0166] According to Table 1 and Table 2, Example 5 is better than Comparative Example 2. This is because, in the piezoelectric catalytic process, the single Bi particles act as efficient electron acceptors and quickly capture the electrons generated by the piezoelectric effect of BiOCl. This allows the charges generated by the piezoelectric effect to be quickly separated, avoiding the recombination of electron-hole pairs, thereby increasing the utilization efficiency of electrons.

[0167] According to Table 1 and Table 2, Example 5 is better than Comparative Example 3. This is because the polyelectrolyte coating in Example 5 has a large number of polar groups, such as amino groups in PEI and carboxyl groups in PAA, which can serve as bridges for electron transfer, effectively transferring the electrons captured by elemental Bi to the surface, and finally transferring them to tetracycline molecules or dissolved oxygen in the solution, avoiding the loss of electrons during the transfer process and improving the efficiency of the reaction.

[0168] According to Table 1, at the same PEI / PAA concentration, as the molar ratio of N,N-dimethylformamide to BiOCl increases from 2:1 to 4:1, the degradation rate increases first and then decreases, and the optimal molar ratio of N,N-dimethylformamide to BiOCl is 3:1. This is because when the molar ratio of N,N-dimethylformamide to BiOCl increases from 2:1 to 3:1, Bi 0The amount of BiOCl formed increases and can be well dispersed on the BiOCl surface to form an effective Bi-BiOCl heterojunction, thereby improving the separation efficiency of electron-hole pairs and the efficiency of electron transfer, thereby enhancing the catalytic degradation ability. However, when the molar ratio of N,N-dimethylformamide to BiOCl continues to increase to 4:1, Bi 0 The excessive reduction and agglomeration of Bi-BiOCl reduce the number of active sites in the Bi-BiOCl heterojunction and form larger metal particles covering the BiOCl surface, which in turn hinders the catalytic reaction and reduces the degradation rate. Therefore, there is an optimal molar ratio of N,N-dimethylformamide to BiOCl. The lower the molar ratio of N,N-dimethylformamide to BiOCl, the better the degradation rate. 0 Insufficient production and a higher DMF molar ratio lead to Bi 0 Agglomeration is not conducive to catalytic performance. A DMF molar ratio of 3:1 can form more active Bi 0 , and maintain its good dispersibility.

[0169] According to Table 1, under the same molar ratio of N,N-dimethylformamide to BiOCl, as the PEI / PAA concentration increases from 0.20wt% to 0.30wt%, the degradation rate also increases first and then decreases, and the optimal PEI / PAA concentration is 0.25wt%. This is because when the PEI / PAA concentration increases from 0.20wt% to 0.25wt%, the polyelectrolyte layer can provide more adsorption sites, improve the adsorption capacity of tetracycline molecules, and the formed electrolyte layer can assist electron transfer, thereby improving the catalytic degradation efficiency. However, when the PEI / PAA concentration continues to increase to 0.30wt%, the polyelectrolyte layer becomes too thick, which will hinder the diffusion of tetracycline molecules to the catalytic active sites, and also hinder the diffusion of intermediates produced by the catalytic reaction, reducing the overall catalytic efficiency. In addition, an overly thick polyelectrolyte layer may also affect the transmission of electrons and reduce charge separation and utilization efficiency. Therefore, there is an optimal value for the PEI / PAA concentration. Too low a concentration cannot provide sufficient adsorption sites and charge transfer, and too high a concentration hinders the transfer of substances and charges. A concentration of 0.25 wt% provides the best balance.

[0170] According to Table 1 and Table 2, all examples are significantly better than Comparative Example 4. This is because, in the process of piezoelectric catalytic degradation of tetracycline, the single Bi particles and the polyelectrolyte coating exhibit a strong synergistic effect: Bi 0 As an efficient electron acceptor, it quickly captures the electrons generated by the piezoelectric effect and transfers them to the polyelectrolyte coating, which acts as an electron transfer bridge and adsorption carrier to selectively enrich tetracycline molecules on Bi 0 and stabilize its conformation. 0The catalytic generation of active oxygen species, and the polyelectrolyte coating further activates these active oxygen species, forming a multi-pathway synergistic catalytic system, and ultimately efficiently degrading tetracycline molecules. This synergistic effect not only optimizes the electron transfer pathway, but also enhances the adsorption selectivity and catalytic activity, thereby significantly improving the degradation efficiency.

[0171] In summary, the molar ratio of N,N-dimethylformamide to BiOCl and the concentration of PEI / PAA in Example 5 are optimally balanced, and the synergistic effect is most obvious at this time. The electron capture ability of elemental Bi and the electron transfer ability of the polyelectrolyte have reached a balance point, so that electrons can be quickly and efficiently transferred to tetracycline molecules, thereby rapidly degrading them.

[0172] The above is based on the ideal embodiment of the present invention. Through the above description, relevant personnel can make various changes and modifications without departing from the technical concept of the present invention. The technical scope of the present invention is not limited to the content in the specification, and the technical scope must be determined according to the scope of the claims.

Claims

1. A method for preparing BiOCl microspheres self-assembled from two-dimensional nanosheets, characterized in that: The following steps are involved: S1. Dissolve hexadecyltrimethylammonium bromide in water, disperse by ultrasonication, stir by magnetic force until completely dissolved, and let stand to obtain a liquid crystal phase solution; S2, dissolving bismuth nitrate pentahydrate in a hydrochloric acid solution, stirring with a magnetic force until it is completely dissolved, to obtain a precursor solution; S3, adding the liquid crystal phase solution to the BiOCl precursor solution at a rate of 3-5 mL / min, and continuously stirring with magnetic force to obtain a uniform mixed solution; S4, placing the mixed solution at 120-150° C. for constant temperature reaction for 8-12 hours; after cooling to room temperature, centrifuging and separating the product, collecting the obtained precipitate, washing and drying, to obtain the first BiOCl microsphere intermediate; S5, placing the first BiOCl microsphere intermediate in N,N-dimethylformamide solvent for ultrasonic dispersion, and reflux reaction at 140-160° C. under nitrogen protection for 10-12 hours; after cooling to room temperature, centrifugally separating the product, collecting the obtained precipitate, washing and drying, to obtain a second BiOCl microsphere intermediate; S6, immersing the second BiOCl microsphere intermediate in a polyethyleneimine aqueous solution and a polyacrylic acid aqueous solution in sequence, and washing with water in between; After repeating the impregnation process 3-5 times, BiOCl microspheres were obtained by drying.

2. The method for preparing BiOCl microspheres self-assembled from two-dimensional nanosheets according to claim 1, characterized in that: The concentration of hexadecyltrimethylammonium bromide in the final solution in step S1 is 20-30 mM.

3. The method for preparing BiOCl microspheres self-assembled from two-dimensional nanosheets according to claim 2, characterized in that: Step S1 further includes: adjusting the pH of the liquid crystal phase solution to 7-8 using a 0.1-0.5 mol / L sodium hydroxide solution at 25-30° C.

4. The method for preparing BiOCl microspheres self-assembled from two-dimensional nanosheets according to claim 1, characterized in that: Bi in the precursor solution in step S2 3+ The concentration is 0.9-1.1mmol / mL.

5. The method for preparing BiOCl microspheres self-assembled from two-dimensional nanosheets according to claim 1, characterized in that: In step S3, the volume ratio of the liquid crystal phase solution to the precursor solution is 1:1-1:

2.

6. The method for preparing two-dimensional nanosheet self-assembled BiOCl microspheres according to claim 5, characterized in that: Step S3 also includes: adjusting the pH value of the mixed solution to 7-8 with a 4-6 mol / L sodium hydroxide solution, and stirring for 30-60 minutes.

7. The method for preparing BiOCl microspheres self-assembled from two-dimensional nanosheets according to claim 1, characterized in that: In step S5, the molar ratio of N,N-dimethylformamide to BiOCl is 2:1 to 4:

1.

8. The method for preparing two-dimensional nanosheet self-assembled BiOCl microspheres according to claim 1, characterized in that: In step S6, the concentration of the polyethyleneimine aqueous solution is 0.1-0.5 wt %, and the concentration of the polyacrylic acid aqueous solution is 0.1-0.5 wt %.

9. A two-dimensional nanosheet self-assembled BiOCl microsphere made according to the method for preparing two-dimensional nanosheet self-assembled BiOCl microsphere according to any one of claims 1 to 8.

10. Use of the two-dimensional nanosheet self-assembled BiOCl microspheres according to claim 9 in treating pharmaceutical wastewater.

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