Composite photocatalyst and its preparation method and application

Abstract

The present invention relates to the field of photocatalysts, and more particularly to a composite photocatalyst, its preparation method, and application. The present invention provides a method for preparing a composite photocatalyst, comprising the steps of: mixing a bromine source, a bismuth source, and a solvent, adding carbon-coated Ti3C2 and bentonite for a hydrothermal reaction, and obtaining the composite photocatalyst. The present invention prepares the composite catalyst by mixing a bromine source, a bismuth source, and a solvent, and then adding carbon-coated Ti3C2 and bentonite for a hydrothermal reaction. Each step cooperates with each other to prepare the composite catalyst. This unprecedented strategy of utilizing carbon-coated Ti3C2 and bentonite to jointly enhance the activity and stability of BiOBr enables the composite photocatalyst provided by the present invention to have a wider light absorption range and better photocatalytic performance.

Description

Technical Field

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

[0002] Organic pollutants in wastewater have significant toxic effects, impacting people's production and daily lives. Residual organic pollutants in wastewater are low in concentration, complex in structure, slow to decompose, and difficult to biodegrade. Traditional water treatment technologies are far from ideal for their removal. Photocatalysis directly utilizes solar energy to excite semiconductor photocatalysts to generate photogenerated electrons and holes, inducing oxidation-reduction reactions that rapidly decompose organic pollutants accumulated on the catalyst surface into carbon dioxide, water, and other substances. This makes the wastewater treatment process simple, green, and rapid. The core of photocatalysis is the photocatalyst. Among various photocatalysts, bismuth (Bi)-based materials represent a new class of photocatalytic materials with narrow band gaps and a wide visible light response range, demonstrating stable chemical properties and excellent visible light responsiveness. BiOBr, a semiconductor material with a tetragonal magnesite crystal structure, possesses an appropriate band gap, is green and non-toxic, and is a stable visible light-responsive photocatalyst. However, single-component BiOBr still suffers from issues such as a small specific surface area, a limited number of adsorption and active sites, easy recombination of photogenerated carriers, and insufficient visible light catalytic activity, limiting its effectiveness in removing organic pollutants from water. In summary, the BiOBr materials in the prior art have a narrow light absorption range and poor photocatalytic performance. Summary of the Invention

[0003] Therefore, the technical problem to be solved by the present invention is to overcome the defects of the BiOBr material in the prior art, such as the narrow light absorption range and poor photocatalytic performance, thereby providing a photocatalyst and its preparation method and application.

[0004] The present invention provides a method for preparing a composite photocatalyst, comprising the following steps: mixing a bromine source, a bismuth source and a solvent, adding carbon-coated Ti3C2 and bentonite to carry out a hydrothermal reaction to obtain the composite photocatalyst.

[0005] Preferably, the hydrothermal reaction is followed by filtering and drying steps.

[0006] Preferably, the hydrothermal reaction further comprises a step of stirring the reactants uniformly before the hydrothermal reaction;

[0007] Optionally, the step of uniformly stirring is ultrasonic stirring; the temperature of the ultrasonic stirring is 20-40° C., and the ultrasonic stirring power is 70%-90%;

[0008] Preferably, the mass ratio of the bismuth source, the bromine source, the carbon-coated Ti3C2 and the bentonite is (0.5~2): (0.2~0.4): (0.05~0.20): (0.05~0.20); the addition ratio of the bismuth source and the solvent is (0.5~2): (50~200), and the ratio unit is g:mL.

[0009] Preferably, the temperature of the hydrothermal reaction is 100-200° C., and the time of the hydrothermal reaction is 12-36 h.

[0010] Preferably, the bromine source is at least one selected from potassium bromide, sodium bromide, cetyltrimethylammonium bromide, and cetylpyridinium bromide;

[0011] The bismuth source is selected from at least one of bismuth nitrate and sodium bismuthate;

[0012] The solvent is selected from at least one of acetic acid, ethylene glycol, isopropanol, ethanol, glycerol, and water; preferably, the solvent is an acetic acid aqueous solution, wherein the acetic acid concentration is 10-30wt%;

[0013] Preferably, the bromine source comprises sodium bromide;

[0014] Preferably, the bismuth source comprises bismuth nitrate;

[0015] Preferably, the bismuth nitrate is Bi(NO3)3•5H2O.

[0016] Preferably, the preparation process of the carbon-coated Ti3C2 comprises the following steps:

[0017] Chemically etching Ti3AlC2 to obtain Ti3C2 with a multilayer structure; coating the Ti3C2 with a multilayer structure with organic carbon to obtain the carbon-coated Ti3C2;

[0018] Preferably, the chemical etching process comprises the following steps: mixing Ti3AlC2 with hydrofluoric acid at 20-30°C for 12-36h, and then filtering and drying to obtain Ti3C2 with a multilayer structure;

[0019] Preferably, the concentration of the hydrofluoric acid is 30-50wt%; the addition ratio of the hydrofluoric acid to Ti3AlC2 is (30-150): (1-5), and the ratio unit is mL:g mass ratio;

[0020] Preferably, the organic carbon coating process comprises the following steps: placing the Ti3C2 having a multilayer structure and glucose in water, stirring them uniformly with ultrasound, and then performing a hydrothermal reaction at 100-200°C for 12-36 hours; then filtering, washing, and drying, and then performing a heat treatment at 350-600°C for 2-4 hours under a nitrogen atmosphere to obtain the carbon-coated Ti3C2;

[0021] Preferably, the mass ratio of the Ti3C2 with a multilayer structure, glucose, and water is (1-5): (3-15): (100-500).

[0022] Optionally, the pH value of the supernatant after washing is 6-7.

[0023] Preferably, the Ti3AlC2 has a MAX phase.

[0024] Preferably, the bentonite is exfoliated bentonite.

[0025] Preferably, the preparation process of the exfoliated bentonite comprises the following steps: mixing 1-5 g of bentonite with 300-800 g of water, ultrasonically exfoliating the mixture at 25-50° C. with an ultrasonic intensity of 90-135 W for 2-3 h, then filtering and drying to obtain the exfoliated bentonite.

[0026] Optionally, a standing step is included after ultrasonic stripping and before filtration, and the standing time is 1-2 hours.

[0027] Optionally, the water used in the preparation process of the exfoliated bentonite is ultrapure water.

[0028] Optionally, in the present invention, after filtration and before drying, the process further includes washing the filtrate, wherein the washing step is to wash the filtrate 3-5 times with ultrapure water.

[0029] Optionally, in the present invention, drying is vacuum freeze drying, and the drying time is 12-24 hours.

[0030] The present invention provides a composite photocatalyst. The composite photocatalyst uses carbon-coated Ti3C2 as a substrate, and BiOBr and bentonite are loaded on the surface of the carbon-coated Ti3C2.

[0031] Preferably, the carbon-coated Ti3C2 has a multilayer structure; the BiOBr has a nano-flower-spherical structure; and the bentonite has a flaky structure.

[0032] Preferably, the composite photocatalyst is prepared by the preparation method described above.

[0033] The present invention provides an application of a photocatalyst prepared by the above-mentioned preparation method or the above-mentioned composite photocatalyst in photocatalytic degradation of organic pollutants.

[0034] The organic pollutants include: moxifloxacin, ofloxacin, tetracycline, rhodamine B, ciprofloxacin, lomefloxacin hydrochloride, and norfloxacin.

[0035] The technical solution of the present invention has the following advantages:

[0036] The present invention provides a composite photocatalyst, comprising: carbon-coated Ti3C2, bentonite, and BiOBr; the Ti3C2 has a multilayer structure; and the BiOBr and bentonite are uniformly distributed on the surface of the carbon-coated Ti3C2.

[0037] The single component BiOBr has a small specific surface area, few adsorption and active sites, and easy recombination of photogenerated carriers, resulting in low visible light catalytic activity and limited removal effect on organic pollutants. Although the composite of Ti3C2 and BiOBr can improve its catalytic activity to a certain extent, Ti3C2 itself is easily oxidized, thereby affecting the catalytic activity. The present invention adds carbon-coated Ti3C2 and exfoliated bentonite to a mixture of bromine source, bismuth source and solvent for hydrothermal reaction. During the hydrothermal reaction, the surface of the carbon-coated Ti3C2 will be A mixed layer of bentonite and BiOBr is formed. The carbon-coated Ti3C2 composite photocatalyst obtained by this method has high temperature resistance, photocorrosion, acid and alkali resistance, thereby avoiding the oxidation of Ti3C2. At the same time, due to the carbon coating on the Ti3C2 surface, the aggregation of single BiOBr can be effectively inhibited, more reaction catalytic active sites can be provided, the separation and transfer of photogenerated carriers can be enhanced, and the photocatalytic effect can be improved. If only carbon is used to coat Ti3C2, the carbon layer has a rich microporous structure with low density and hydrophobicity. Characteristics, easy to aggregate and float in the water surface, which is not conducive to the loading of active components and sufficient solid-liquid contact during the catalytic process; the present invention adds bentonite to the hydrothermal reaction, so that an active layer co-doped with bentonite and BiOBr is formed on the surface of the carbon-coated Ti3C2 during the reaction, and the hydrophilicity and binding force of the hydroxyl groups on the surface of the bentonite are utilized to avoid the agglomeration and floating of the carbon-coated Ti3C2 on the one hand, and on the other hand; the bentonite is utilized to preferentially adsorb oxygen on Ti3C2, further reducing the contact between Ti3C2 and oxygen and improving the stability of Ti3C2. Thirdly, the introduction of bentonite can promote the functionalization of the terminal oxygen group on the surface of Ti3C2, regulate the effect of the metal-semiconductor junction type between Ti3C2 and BiOBr, broaden the light absorption range of the photocatalyst while improving its activity. In summary, the present invention mixes a bromine source, a bismuth source and a solvent, and then adds carbon-coated Ti3C2 and bentonite for hydrothermal reaction. The various steps cooperate with each other to prepare a composite catalyst, adopting this unprecedented strategy of using carbon-coated Ti3C2 and bentonite to jointly enhance the activity and stability of BiOBr. The composite photocatalyst provided by the present invention has a wider light absorption range and better photocatalytic performance.

[0038] Furthermore, the composite photocatalyst provided by the present invention has better photogenerated electron separation efficiency and stronger corrosion resistance and oxidation resistance, thereby making the composite photocatalyst have better stability.

[0039] Furthermore, the composite photocatalyst provided by the present invention can treat a variety of organic pollutants. BRIEF DESCRIPTION OF THE DRAWINGS

[0040] In order to more clearly illustrate the specific embodiments of the present invention or the technical solutions in the prior art, the following briefly introduces the drawings required for use in the specific embodiments or the description of the prior art. Obviously, the drawings described below are some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative work.

[0041] Figure 1 This is a SEM structural diagram of Ti3C2 with a multilayer structure obtained during the preparation process of Example 1 of the present invention;

[0042] Figure 2 SEM structure of the exfoliated bentonite obtained during the preparation process of Example 1 of the present invention;

[0043] Figure 3 is a SEM structure diagram of carbon-coated Ti3C2 obtained in the preparation process of Example 1 of the present invention;

[0044] Figure 4 This is a TEM structure diagram of carbon-coated Ti3C2 obtained during the preparation process of Example 1 of the present invention;

[0045] Figure 5 SEM structure of the composite photocatalyst prepared in Example 1 of the present invention;

[0046] Figure 6 XRD test results of the composite photocatalysts prepared in Example 1, Comparative Example 1, Comparative Example 2, and Comparative Example 3 of the present invention;

[0047] Figure 7 UV-vis test results of the composite photocatalysts prepared in Example 1, Comparative Example 1, Comparative Example 2, and Comparative Example 3 of the present invention;

[0048] Figure 8 PL test results of the composite photocatalysts prepared in Example 1, Comparative Example 1, Comparative Example 2, and Comparative Example 3 of the present invention;

[0049] Figure 9 A graph showing the relationship between the removal rate of moxifloxacin and time of the composite photocatalysts prepared in Example 1, Example 2, Example 3, Comparative Example 1, Comparative Example 2, and Comparative Example 3 of the present invention;

[0050] Figure 10 A graph showing the relationship between the removal rate of moxifloxacin and time of the composite photocatalysts prepared in Example 1, Example 2, Example 3, Comparative Example 1, Comparative Example 2, and Comparative Example 3 of the present invention;

[0051] Figure 11Removal rate of different organic matter by the composite photocatalyst prepared in Example 1 of the present invention;

[0052] Figure 12 The removal performance of the composite photocatalyst prepared in Example 1 of the present invention for 5 cycles of moxifloxacin degradation. DETAILED DESCRIPTION

[0053] The following examples are provided for a better understanding of the present invention and are not intended to limit the best mode of implementation. They do not limit the content and scope of protection of the present invention. Any product identical or similar to the present invention obtained by anyone under the guidance of the present invention or by combining the features of the present invention with other prior arts shall fall within the scope of protection of the present invention.

[0054] If no specific experimental steps or conditions are specified in the examples, the conventional experimental steps or conditions described in the literature in this field can be used. If the manufacturer of the reagents or instruments is not specified, they are all commercially available conventional reagents.

[0055] The bentonite used in the examples and comparative examples of the present invention was purchased from Tianjin Bailunsi Biotechnology Co., Ltd.

[0056] Ultraviolet-visible spectrophotometry test of the photocatalysts of the present invention and the comparative example The absorbance (UV-vis) test of the substances was tested using UV-3600plus (Shimadzu Corporation, Japan);

[0057] The fluorescence spectra (PL) of the photocatalysts of the embodiments of the present invention and the comparative examples were tested using an FL3C-111 TCSPC (HORIBA, Japan) device.

[0058] Example 1

[0059] This embodiment provides a method for preparing a composite photocatalyst, comprising the following steps:

[0060] (1) Add 60 mL of hydrofluoric acid (the concentration of hydrofluoric acid is 40 wt%) to a polyethylene beaker, add 2 g of Ti3AlC2 (having MAX phase) in small amounts and in multiple times while stirring, continue stirring at room temperature for 24 h, and then filter. After filtration, wash the filtrate with ultrapure water three times (the pH value of the supernatant after the last washing is 6), and dry the washed product by vacuum freeze drying for 12 h to obtain Ti3C2 with a multilayer structure. Figure 1 is a SEM structure diagram of the Ti3C2 having a multilayer structure;

[0061] (2) Take 2g of bentonite and place it in a beaker, add 500ml of ultrapure water, stir evenly, and then place it in an ultrasonic crusher at room temperature with an ultrasonic intensity of 120W for ultrasonic peeling for 2h. After the ultrasonic is finished, let it stand for 1h. After filtering and washing, use vacuum freeze drying to dry the washed product for 12h to obtain peeled bentonite. Figure 2 This is the SEM structure of exfoliated bentonite;

[0062] (3) Take 200 mg of the multilayered Ti3C2 obtained in step (1) and 600 mg of glucose and dissolve them in 50 ml of ultrapure water. After ultrasonic stirring, perform hydrothermal reaction at 160 °C for 24 h. After filtering, washing and drying, place the product in a tube furnace and heat treat it at 500 °C in N2 atmosphere for 2 h to obtain carbon-coated Ti3C2. Figure 3 and Figure 4 SEM and TEM structures of carbon-coated Ti3C2;

[0063] (4) 0.97 g of Bi(NO3)3•5H2O was dissolved in 50 mL of 20% acetic acid aqueous solution, 0.206 g of NaBr was added to form a BiOBr precursor, and 55 mg of the exfoliated bentonite prepared in step (2) and 91.5 mg of the carbon-coated Ti3C2 prepared in step (3) were added in sequence under ultrasonic stirring. After continuous ultrasonic stirring for 3 h at room temperature, the mixture was hydrothermally reacted at 160 °C for 24 h. After filtering and washing, the washed product was dried by vacuum freeze drying for 12 h to obtain the composite photocatalyst. Figure 5 is a SEM structure diagram of the photocatalyst;

[0064] from Figure 5 It can be seen that the composite photocatalyst prepared by the present invention is based on a multilayer carbon-coated Ti3C2 substrate, with nano-flower-shaped BiOBr and sheet-like bentonite loaded on the surface of the carbon-coated Ti3C2.

[0065] The XRD test results of the photocatalyst are as follows Figure 6 As shown;

[0066] The UV-vis test results of the photocatalyst are as follows Figure 7 As shown;

[0067] The PL test results of the photocatalyst are as follows Figure 8 As shown;

[0068] The photocatalyst obtained in this example was used to test the removal of moxifloxacin under visible light. The specific steps of the test included:

[0069] Step 1: Prepare a 10 mg / L moxifloxacin solution for use. Weigh 25 mg of the photocatalyst prepared in this example and place it in a photocatalytic tube. Then add 50 mL of the above moxifloxacin solution, disperse it evenly with ultrasound, and stir it in the dark for 30 minutes.

[0070] Step 2: Use a xenon lamp as a visible light source, place the photocatalytic tube in step 1 under the light source to react, take samples every 30 minutes, use a UV spectrophotometer to test its absorbance and calculate the relationship between the removal rate of moxifloxacin and time. The results are as follows: Figure 9 As shown in the figure, the relationship between the removal rate of moxifloxacin and time is shown in the figure Figure 10 As shown, where C t / C0 is the ratio of the concentration of moxifloxacin in the sample to the initial concentration, and the removal rate or removal efficiency corresponding to time “0” is the removal rate or removal efficiency after stirring in the dark for 30 minutes.

[0071] Example 2

[0072] This embodiment provides a method for preparing a composite photocatalyst. The preparation method is similar to the preparation method in Example 1, except that in step (4) of the preparation method, the amount of exfoliated bentonite is 85 mg and the amount of carbon-coated Ti3C2 is 150 mg.

[0073] The composite photocatalyst obtained in this example was used to test the removal of moxifloxacin under visible light. The test method was the same as that in Example 1. The relationship between the removal rate of moxifloxacin and time was as follows: Figure 9 As shown in the figure, the relationship between the removal rate of moxifloxacin and time is shown in the figure Figure 10 As shown, where C t / C0 is the ratio of the concentration of moxifloxacin in the sample to the initial concentration, and the removal rate or removal efficiency corresponding to time “0” is the removal rate or removal efficiency after stirring in the dark for 30 minutes.

[0074] Example 3

[0075] This embodiment provides a method for preparing a composite photocatalyst. The preparation method is similar to the preparation method in Example 1, except that in step (4) of the preparation method: the amount of exfoliated bentonite is 50 mg, and the amount of carbon-coated Ti3C2 is 50 mg.

[0076] The composite photocatalyst obtained in this example was used to test the removal of moxifloxacin under visible light. The test method was the same as that in Example 1. The relationship between the removal rate of moxifloxacin and time was as follows: Figure 9 As shown in the figure, the relationship between the removal rate of moxifloxacin and time is shown in the figure Figure 10 As shown, where C t / C0 is the ratio of the concentration of moxifloxacin in the sample to the initial concentration, and the removal rate or removal efficiency corresponding to time “0” is the removal rate or removal efficiency after stirring in the dark for 30 minutes.

[0077] Comparative Example 1

[0078] This comparative example provides a photocatalyst, and the preparation method includes the following steps: taking 0.97 g of Bi(NO3)3•5H2O and dissolving it in 50 mL of 20% acetic acid aqueous solution, adding 0.206 g of NaBr to form a BiOBr precursor, stirring it ultrasonically at room temperature for 3 hours, and then hydrothermally reacting it at 160°C for 24 hours. After filtering and washing, the washed product is dried by vacuum freeze drying for 12 hours to obtain the composite photocatalyst;

[0079] The XRD test structure of the composite photocatalyst is as follows Figure 6 As shown;

[0080] The UV-vis test results of the composite photocatalyst are as follows Figure 7 As shown;

[0081] The PL test results of the composite photocatalyst are as follows Figure 8 shown.

[0082] The composite photocatalyst obtained in this comparative example was used to test the removal of moxifloxacin under visible light. The test method was the same as that in Example 1. The relationship between the removal rate of moxifloxacin and time was as follows: Figure 9 As shown in the figure, the relationship between the removal rate of moxifloxacin and time is shown in the figure Figure 10 As shown, where C t / C0 is the ratio of the concentration of moxifloxacin in the sample to the initial concentration, and the removal rate or removal efficiency corresponding to time “0” is the removal rate or removal efficiency after stirring in the dark for 30 minutes.

[0083] Comparative Example 2

[0084] This comparative example provides a method for preparing a composite photocatalyst, comprising the following steps:

[0085] (1) Add 60 mL of hydrofluoric acid (the concentration of hydrofluoric acid is 40 wt%) to a polyethylene beaker, add 2 g of Ti3AlC2 (having MAX phase) in small amounts and in multiple times while stirring, continue stirring at room temperature for 24 h, and then filter. After filtration, wash the filtrate with ultrapure water three times (the pH value of the supernatant after the last washing is 6), and dry the washed product by vacuum freeze drying for 12 h to obtain Ti3C2 with a multilayer structure. Figure 1 is a SEM structure diagram of the Ti3C2 having a multilayer structure;

[0086] (2) Take 200 mg of the multilayered Ti3C2 obtained in step (1) and 600 mg of glucose and dissolve them in 50 ml of ultrapure water. After ultrasonic stirring, perform hydrothermal reaction at 160 °C for 24 h. After filtering, washing and drying, place the product in a tube furnace and heat treat it at 500 °C in N2 atmosphere for 2 h to obtain carbon-coated Ti3C2. Figure 3 and Figure 4 SEM and TEM structures of carbon-coated Ti3C2;

[0087] (3) 0.97 g of Bi(NO3)3•5H2O was dissolved in 50 mL of 20% acetic acid aqueous solution, 0.206 g of NaBr was added to form a BiOBr precursor, and 91.5 mg of the carbon-coated Ti3C2 prepared in step (2) was added under ultrasonic stirring. The mixture was subjected to continuous ultrasonic stirring at room temperature for 3 h and then hydrothermally reacted at 160 °C for 24 h. After filtering and washing, the washed product was dried by vacuum freeze drying for 12 h to obtain the composite photocatalyst.

[0088] The XRD test structure of the composite photocatalyst is as follows Figure 6 As shown;

[0089] The UV-vis test results of the composite photocatalyst are as follows Figure 7 As shown;

[0090] The PL test results of the composite photocatalyst are as follows Figure 8 shown.

[0091] The composite photocatalyst obtained in this comparative example was used to test the removal of moxifloxacin under visible light. The test method was the same as that in Example 1. The relationship between the removal rate of moxifloxacin and time was as follows: Figure 9 As shown in the figure, the relationship between the removal rate of moxifloxacin and time is shown in the figure Figure 10 As shown, where C t / C0 is the ratio of the concentration of moxifloxacin in the sample to the initial concentration, and the removal rate or removal efficiency corresponding to time “0” is the removal rate or removal efficiency after stirring in the dark for 30 minutes.

[0092] Comparative Example 3

[0093] This comparative example provides a method for preparing a composite photocatalyst, comprising the following steps:

[0094] (1) Add 60 mL of hydrofluoric acid (hydrofluoric acid concentration is 40 wt%) to a polyethylene beaker, add 2 g of Ti3AlC2 (having MAX phase) in small amounts and several times while stirring, continue stirring at room temperature for 24 h, filter, and wash the filtrate with ultrapure water three times (the pH value of the supernatant after the last wash is 6). Dry the washed product by vacuum freeze drying for 12 h to obtain Ti3C2 with a multilayer structure.

[0095] (2) Take 2g of bentonite and place it in a beaker, add 500ml of ultrapure water, stir evenly, and then place it in an ultrasonic crusher at room temperature with an ultrasonic intensity of 120W for ultrasonic peeling for 2h. After the ultrasonic is finished, let it stand for 1h. After filtering and washing, use vacuum freeze drying to dry the washed product for 12h to obtain peeled bentonite. Figure 2 This is the SEM structure of exfoliated bentonite;

[0096] (3) 0.97 g of Bi(NO3)3•5H2O was dissolved in 50 mL of 20% acetic acid aqueous solution, 0.206 g of NaBr was added to form a BiOBr precursor, and 55 mg of the exfoliated bentonite prepared in step (2) and 91.5 mg of the multilayered Ti3C2 prepared in step (1) were added in sequence under ultrasonic stirring. After continuous ultrasonic stirring for 3 h at room temperature, the mixture was hydrothermally reacted at 160 °C for 24 h. After filtering and washing, the washed product was dried by vacuum freeze drying for 12 h to obtain the composite photocatalyst.

[0097] The XRD test structure of the composite photocatalyst is as follows Figure 6 As shown;

[0098] The UV-vis test results of the composite photocatalyst are as follows Figure 7 As shown;

[0099] The PL test results of the composite photocatalyst are as follows Figure 8 shown.

[0100] The composite photocatalyst obtained in this comparative example was used to test the removal of moxifloxacin under visible light. The test method was the same as that in Example 1. The relationship between the removal rate of moxifloxacin and time was as follows: Figure 9 As shown in the figure, the relationship between the removal rate of moxifloxacin and time is shown in the figure Figure 10 As shown, where C t / C0 is the ratio of the concentration of moxifloxacin in the sample to the initial concentration, and the removal rate or removal efficiency corresponding to time “0” is the removal rate or removal efficiency after stirring in the dark for 30 minutes.

[0101] Application Example 1

[0102] The composite photocatalyst obtained in Example 1 was used to remove organic pollutants, wherein the organic pollutants were ofloxacin, tetracycline, rhodamine B, ciprofloxacin, lomefloxacin hydrochloride, and norfloxacin.

[0103] Application method:

[0104] Step 1: Prepare a 10 mg / L organic pollutant solution for use. Weigh 25 mg of the composite photocatalyst prepared in Example 1 into a photocatalytic tube, add 50 mL of the organic pollutant solution, disperse evenly by ultrasonication, and stir in the dark for 30 min.

[0105] Step 2: Use a xenon lamp as a visible light source, place the photocatalytic tube in step 1 under the light source for 120 minutes, use an ultraviolet spectrophotometer to test its absorbance and calculate the removal rate of organic pollutants. The results are as follows: Figure 11 shown.

[0106] Application Example 2

[0107] The composite photocatalyst obtained in Example 1 was used to remove moxifloxacin and was recycled 5 times to explore the stability of the material.

[0108] Application method:

[0109] Step 1: Prepare a 10 mg / L moxifloxacin solution for use. Weigh 25 mg of the composite photocatalyst prepared in Example 1 into a photocatalytic tube, add 50 mL of the above solution, disperse evenly by ultrasonication, and stir in the dark for 30 minutes.

[0110] Step 2: Using a xenon lamp as a visible light source, place the photocatalytic tube in step 1 under the light source to react for 120 minutes, test its absorbance using an ultraviolet spectrophotometer, and calculate the removal rate of moxifloxacin.

[0111] Step 3: The used composite photocatalyst was obtained by centrifugal washing and further reused for the photocatalytic degradation of moxifloxacin. Steps 1 and 2 were repeated 5 times to evaluate the stability of the material. The results are as follows: Figure 12 shown.

[0112] first, Figure 1 This is an SEM image of the multilayered structure Ti3C2 obtained in step (1) of Example 1. The accordion-shaped multilayer structure in the figure proves that the chemical etching of the Al layer in the MAX phase Ti3AlC2 is successful. Figure 2 This is an SEM image of the bentonite obtained in step (2) of Example 1. The image shows that the bentonite after peeling is in the form of thin flakes. This structure with a large specific surface area can provide more active sites, which is beneficial to improving the performance of the material. Figure 3This is the SEM image of the carbon-coated Ti3C2 obtained in step (3) of Example 1. The surface of the Ti3C2 coated with organic carbon shows an obvious carbon layer structure. Figure 4 The TEM images show that the carbon layer coating thickness of carbon-coated Ti3C2 is at the nanometer level (the carbon layer thickness is 7.5nm). The nano-carbon layer coating can effectively inhibit the oxidation of Ti3C2, expand the specific surface area, and promote charge transfer. Figure 5 This is the SEM structure of the composite photocatalyst obtained in step (4) of Example 1. It can be seen from the figure that BiOBr forms a typical nano-flower ball and is loaded on the carbon-coated Ti3C2, and the exfoliated bentonite is evenly covered on the surface of the carbon-coated Ti3C2, proving that the composite photocatalyst is a composite material. Figure 6 The XRD patterns of the composite photocatalyst in Example 1, the composite photocatalyst in Comparative Example 2, the composite photocatalyst in Comparative Example 3, and the BiOBr photocatalyst in Comparative Example 1 are shown. The characteristic diffraction peaks of BiOBr fully match those of the tetragonal BiOBr phase (JCPDS Card 09-0393), and the high and sharp diffraction peaks confirm the crystal structure of BiOBr. The composite photocatalyst in Example 1 has a peak shape similar to that of pure BiOBr, demonstrating that the introduction of a small amount of carbon-coated Ti3C2 and exfoliated bentonite has no effect on the crystal form of BiOBr. Figure 7 The UV-vis spectra of the composite photocatalyst in Example 1, the composite photocatalyst in Comparative Example 2, the composite photocatalyst in Comparative Example 3, and the BiOBr photocatalyst in Comparative Example 1 show that, compared with pure BiOBr, after coupling carbon-coated Ti3C2 and exfoliated bentonite, the light absorption capacity of the composite material is significantly enhanced, especially in the visible light range, the light absorption edge of the composite photocatalyst red-shifts to 518 nm. Figure 8 The following are PL spectra of the composite photocatalyst in Example 1, the composite photocatalyst in Comparative Example 2, the composite photocatalyst in Comparative Example 3, and the BiOBr photocatalyst in Comparative Example 1. The PL spectra reveal the recombination of photoexcited charge carriers. The order of PL intensity is: BiOBr composite photocatalyst in Comparative Example 1 > composite photocatalyst in Comparative Example 3 > composite photocatalyst in Comparative Example 2 > composite photocatalyst in Example 1, demonstrating that the composite photocatalyst in Example 1 effectively separates photogenerated electrons and holes, extending the lifetime of photogenerated charge carriers. Figure 9 This is a graph showing the photocatalytic degradation performance of the composite photocatalyst in Example 1 for moxifloxacin. The composite photocatalyst in Example 1 can achieve a moxifloxacin removal rate of 93.35% under visible light conditions, which is better than the composite photocatalyst in Comparative Example 2 (removal rate of 69.35%), the composite photocatalyst in Comparative Example 3 (removal rate of 79.67%), and the BiOBr photocatalyst in Comparative Example 1 (removal rate of 67.32%). Figure 10It can be seen that the removal rate of moxifloxacin by the composite photocatalyst in Example 1 is 2.5 times that of the composite photocatalyst in Example 2, 1.8 times that of the composite photocatalyst in Example 3, and 2.7 times that of the BiOBr photocatalyst in Example 1. Figure 11 3 is a performance diagram of the composite photocatalyst in Example 1 for degrading different organic pollutants. It can be seen from the figure that the removal rate of the composite photocatalyst in Example 1 for moxifloxacin, ofloxacin, tetracycline, rhodamine B, ciprofloxacin, lomefloxacin hydrochloride and norfloxacin under visible light can reach more than 90%, proving that the composite photocatalyst in Example 1 is suitable for a variety of organic pollutant treatment scenarios. Figure 12 This is a performance diagram of the composite photocatalyst in Example 1 for degrading moxifloxacin after five cycles. As shown in the figure, after five cycles, the dark adsorption removal rate of the material decreased from 31.52% to 21.89%. This is because some adsorption sites of the recycled material were occupied by organic pollutants. The material's removal rate for moxifloxacin only decreased from 93.35% to 89.29%, demonstrating that the composite material has good cyclic stability.

[0113] Obviously, the above embodiments are merely examples for clarity of explanation and are not intended to limit the implementation methods. Those skilled in the art will readily appreciate that other variations or modifications based on the above descriptions are possible. It is not necessary and impossible to enumerate all implementation methods here. Obvious variations or modifications arising therefrom remain within the scope of protection of the present invention.

Claims

1. A method for preparing a composite photocatalyst, characterized in that: The method comprises the following steps: mixing a bromine source, a bismuth source and a solvent, adding carbon-coated Ti3C2 and bentonite to carry out a hydrothermal reaction, and then filtering, washing and drying to obtain the composite photocatalyst; The bentonite is an exfoliated bentonite; The mass ratio of the bismuth source, bromine source, carbon-coated Ti3C2 and bentonite is (0.5-2): (0.2-0.4): (0.05-0.20): (0.05-0.20); the addition ratio of the bismuth source to the solvent is 0.5-2 g: 50-200 ml; The bromine source is selected from at least one of potassium bromide, sodium bromide, cetyltrimethylammonium bromide, and cetylpyridinium bromide; The bismuth source is selected from at least one of bismuth nitrate and sodium bismuthate; The composite photocatalyst uses carbon-coated Ti3C2 as a substrate, and BiOBr and bentonite are loaded on the surface of the carbon-coated Ti3C2.

2. The preparation method according to claim 1, characterized in that The temperature of the hydrothermal reaction is 100-200° C., and the time of the hydrothermal reaction is 12-36 h.

3. The preparation method according to claim 1, characterized in that The solvent is selected from at least one of acetic acid, ethylene glycol, isopropyl alcohol, ethanol, glycerol and water.

4. The preparation method according to claim 1, characterized in that The solvent is an acetic acid aqueous solution, wherein the acetic acid concentration is 10-30 wt%.

5. The preparation method according to claim 1, characterized in that The bromine source includes sodium bromide.

6. The preparation method according to claim 1, characterized in that The bismuth source includes bismuth nitrate.

7. The preparation method according to claim 1, characterized in that The bismuth nitrate is Bi(NO3)3•5H2O.

8. The preparation method according to claim 1, characterized in that The preparation process of the carbon-coated Ti3C2 comprises the following steps: Ti3AlC2 is chemically etched to obtain Ti3C2 with a multilayer structure; and the Ti3C2 with a multilayer structure is organic carbon-coated to obtain the carbon-coated Ti3C2.

9. The preparation method according to claim 8, characterized in that The chemical etching process includes the following steps: mixing Ti3AlC2 and hydrofluoric acid at 20-30°C and stirring for 12-36 hours, and then filtering and drying to obtain Ti3C2 with a multilayer structure.

10. The preparation method according to claim 9, characterized in that The concentration of the hydrofluoric acid is 30-50wt%; the addition ratio of the hydrofluoric acid to Ti3AlC2 is 30-150mL:1-5g.

11. The preparation method according to claim 8, characterized in that The organic carbon coating process includes the following steps: placing the Ti3C2 with a multilayer structure and glucose in water, ultrasonically stirring them until uniform, and then performing a hydrothermal reaction at 100-200°C for 12-36 hours; then filtering, washing, and drying, and then performing a heat treatment at 350-600°C for 2-4 hours under a nitrogen atmosphere to obtain the carbon-coated Ti3C2.

12. The preparation method according to claim 11, characterized in that The mass ratio of the Ti3C2 with a multilayer structure, glucose, and water is (1-5): (3-15): (100-500).

13. The preparation method according to claim 1, characterized in that The preparation process of the exfoliated bentonite comprises the following steps: mixing 1-5 g of bentonite with 300-800 g of water, performing ultrasonic exfoliation at 25-50° C. and an ultrasonic intensity of 90-135 W for 2-3 hours, and then filtering and drying to obtain the exfoliated bentonite.

14. A composite photocatalyst, characterized in that The composite photocatalyst is prepared by the method according to any one of claims 1 to 13. The composite photocatalyst uses carbon-coated Ti3C2 as a substrate, and BiOBr and bentonite are loaded on the surface of the carbon-coated Ti3C2.

15. The composite photocatalyst according to claim 14, characterized in that The carbon-coated Ti3C2 has a multilayer structure; the BiOBr has a nano-flower-spherical structure; and the bentonite has a flaky structure.

16. Use of the photocatalyst prepared by the preparation method according to any one of claims 1 to 13 or the composite photocatalyst according to claim 14 or 15 in photocatalytic degradation of organic pollutants.

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