Preparation method and application of BiOBr / black TiO2 / tourmaline composite photocatalyst

Abstract

The application discloses a preparation method and application of a BiOBr / black TiO2 / tourmaline composite photocatalyst. The method comprises the following steps: mixing, stirring and obtaining a first suspension liquid by using tetrabutyl titanate, isopropyl alcohol and tourmaline; adding a manganese acetate solution into the first suspension liquid to obtain a first emulsion; transferring the first emulsion into a reaction kettle, sealing and reacting at 160-180 DEG C for 6-10 hours to obtain black TiO2 / tourmaline; adding TiO2 / tourmaline into a bismuth nitrate solution, stirring to obtain a second suspension liquid, then adding a potassium bromide solution drop by drop into the second suspension liquid to obtain a second emulsion; transferring the second emulsion into a reaction kettle, sealing and reacting at 100-140 DEG C for 4-8 hours to obtain the BiOBr / black TiO2 / tourmaline composite photocatalyst. The composite photocatalyst has high visible light utilization rate and good degradation performance, and is used for degrading residual tetracycline hydrochloride in wastewater, and the effect is remarkable.

Description

Technical Field

[0001] The present invention belongs to the technical field of inorganic photocatalytic materials, and in particular relates to a preparation method and application of a BiOBr / black TiO2 / tourmaline composite photocatalyst. Background Art

[0002] In 2011, Chen et al. (Science, 2011, 331: 746) first reported that black TiO2 was prepared by using white TiO2 as raw material and hydrogenation under heating conditions of 200 ° C. By comparing its spectral absorbance, it was found that black TiO2 has the potential to absorb full-spectrum sunlight, so it is more suitable for use as a photocatalyst than white TiO2. Since TiO2 itself has a wide band gap (about 3.2eV), the visible light utilization rate is low, and the photogenerated carriers are easy to recombine, it is often necessary to compound, dope or construct a heterojunction of TiO2 in practical applications to broaden its spectral response range and improve the separation efficiency of its photogenerated electron / hole pairs. Black TiO2 is precisely the result of the introduction of Ti in the synthesis process of TiO2. 3+ Color change caused by self-doping. In order to further improve the visible light utilization rate of black TiO2, compounding or constructing heterojunction is still a relatively effective treatment method.

[0003] Tourmaline, a general term for the tourmaline family of minerals, has a complex chemical composition and is a ring-shaped silicate mineral characterized by boron content. It possesses unique properties such as spontaneous polarization, pyroelectricity, far-infrared radiation, and negative ion emission. Fe-rich tourmaline appears black and is also known as black tourmaline (Schorl). Research has shown that combining tourmaline with TiO2 not only enhances the photocatalytic activity of TiO2 but also combines the advantages of both materials. The ferrous and ferric ions contained in tourmaline make it a Fenton-like catalyst. Furthermore, tourmaline's far-infrared emission reduces water molecule clustering and increases the concentration of reactive species such as hydroxyl radicals (·OH) in the solution. Furthermore, the electric field of tourmaline reduces the recombination probability of photogenerated electron / hole pairs, thereby improving quantum efficiency. For example, Chinese patent CN107774241B discloses a TiO2 / tourmaline composite photocatalyst and TiO2 / tourmaline gauze, which can purify and remove indoor formaldehyde gas and provide a method for fixing the photocatalyst. However, the composite photocatalyst needs to be excited by ultraviolet light with higher energy to exert its degradation performance. Chinese patent CN102836728A prepares TiO2 / black tourmaline / rare earth ion (Nd 3+ , Gd 3+) composite photocatalytic material, by adding black tourmaline, tetrabutyl titanate and rare earth oxide (Nd2O3), and using concentrated nitric acid as a hydrolysis inhibitor, TiO2 / black tourmaline / rare earth ion composite photocatalytic material was prepared by sol-gel method, and used for the catalytic degradation of methyl orange in printing and dyeing wastewater, but the light response activity needs to be further improved, and the degradation performance of the composite photocatalytic material for tetracycline hydrochloride has not been studied. Summary of the Invention

[0004] The purpose of the present invention is to address the problem of low visible light utilization rate faced by single TiO2 nanomaterials as photocatalysts, and to provide a preparation method for BiOBr / black TiO2 / tourmaline composite photocatalysts. The method prepares black TiO2 by solvent thermal method and constructs BiOBr / black TiO2 heterojunction by hydrothermal method, that is, introduces Ti into TiO2 by self-doping method. 3+ This method produces black TiO2 that absorbs the entire spectrum. On this basis, tourmaline minerals and the light-sensitive semiconductor BiOBr are introduced as co-catalysts. The resulting composite photocatalyst exhibits high visible light utilization and excellent degradation performance, and is highly effective in degrading residual tetracycline hydrochloride in wastewater.

[0005] To achieve the above object, the technical solution of the present invention is as follows:

[0006] A method for preparing a BiOBr / black TiO2 / tourmaline composite photocatalyst, the method comprising the following steps:

[0007] (1) Tetrabutyl titanate, isopropyl alcohol, and tourmaline are mixed and stirred to obtain a first suspension; then, manganese acetate solution is added dropwise to the first suspension and stirred for 20 to 40 minutes to obtain a first emulsion;

[0008] Wherein, 20-30 mL of isopropyl alcohol, 0.01-0.08 g of tourmaline, and 0.06-0.13 g of manganese acetate are added to every 2.0-4.0 g of tetrabutyl titanate;

[0009] The concentration of the manganese acetate solution is 0.01-0.02 mol / L;

[0010] (2) transferring the first emulsion into a reaction kettle, sealing it, reacting it at 160-180° C. for 6-10 hours, and then washing and drying it to obtain black TiO2 / tourmaline;

[0011] (3) adding TiO2 / tourmaline to the bismuth nitrate solution and stirring to obtain a second suspension, then adding potassium bromide solution dropwise to the second suspension and stirring for 20 to 40 minutes to obtain a second emulsion;

[0012] The mass ratio of bismuth nitrate to TiO2 / tourmaline is 1:2-3:2, and the mass ratio of bismuth nitrate to potassium bromide is 4:1-5:1.

[0013] The concentration of potassium bromide solution is 0.013-0.038 mol / L; the concentration of bismuth nitrate solution is 0.005-0.015 mol / L;

[0014] (4) transferring the second emulsion into a reaction kettle, sealing it, and reacting it at 100-140° C. for 4-8 hours. After the reaction, washing and drying are performed to obtain a BiOBr / black TiO2 / tourmaline composite photocatalyst;

[0015] The BiOBr / black TiO2 / tourmaline composite photocatalyst prepared by the method is used to degrade residual tetracycline hydrochloride in wastewater.

[0016] Add BiOBr / black TiO2 / tourmaline composite material to tetracycline hydrochloride solution, irradiate with visible light power of 300-400W for 30-180min to complete the degradation of tetracycline hydrochloride;

[0017] Wherein, 10 to 30 mg of BiOBr / black TiO2 / tourmaline composite material is added to every 50 mL of tetracycline hydrochloride solution;

[0018] The treatment concentration of tetracycline hydrochloride solution is 10-50 mg / L.

[0019] In the above-mentioned preparation method of the BiOBr / black TiO2 / tourmaline composite photocatalyst, the raw materials, reagents and equipment other than tourmaline involved are all obtained through well-known routes, and the operation process is within the skill of those skilled in the art.

[0020] The essential features of the present invention are:

[0021] In the preparation of Ti by solvothermal method 3+ In the process of doping TiO2, tourmaline is first introduced. On the one hand, it can inhibit the large-scale agglomeration of black TiO2 nanoparticles. On the other hand, the spontaneous polarization, far-infrared emission and surface electric field properties of tourmaline can reduce the recombination probability of photogenerated electron / hole pairs in the composite photocatalyst and generate more reactive substances; then the photosensitive semiconductor BiOBr is synthesized in situ and composited with black TiO2 to construct a heterojunction, further improving the visible light response ability of black TiO2, so that the prepared BiOBr / black TiO2 / tourmaline composite photocatalyst can achieve rapid and effective degradation of tetracycline hydrochloride under visible light conditions.

[0022] The beneficial effects of the present invention are as follows: Compared with the prior art, the present invention has the following outstanding substantive features and significant improvements:

[0023] (1) The introduction of tourmaline during the synthesis of black TiO2 suppresses the probability of photogenerated electron / hole recombination under light conditions, making good use of the unique advantages of tourmaline minerals themselves.

[0024] (2) The photosensitive semiconductor BiOBr nanosheets were synthesized by hydrothermal method and then composited with black TiO2 to construct heterojunction, which further enhanced the visible light response ability of black TiO2.

[0025] (3) The present invention utilizes solvent thermal and hydrothermal methods to prepare BiOBr / black TiO2 / tourmaline composite photocatalysts. The preparation process is relatively simple and has high tolerance to experimental parameters.

[0026] (4) The degradation rate of the composite photocatalyst disclosed in the present application for 50 mg / L tetracycline hydrochloride is 86.5%, which is significantly better than the degradation rate of the sample in the comparative example for tetracycline hydrochloride under the same conditions.

[0027] (5) The pollutants oxidized and degraded by the composite photocatalyst disclosed in this application are not limited to tetracycline hydrochloride. It can be used to remove other organic pollutants in wastewater, providing a new material for the catalytic purification of residual pollutants in wastewater.

[0028] The present invention provides a preparation method and application of BiOBr / black TiO2 / tourmaline composite photocatalyst, which utilizes solvent thermal method to prepare TiO2. 3+ Tourmaline is introduced during the doping process of TiO2, and then BiOBr is synthesized to construct a heterojunction with black TiO2. The prepared composite photocatalyst can significantly expand the visible light response range of black TiO2 and improve its visible light utilization rate. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] Figure 1 This is the XRD pattern of the BiOBr / black TiO2 / tourmaline composite material prepared in Example 1.

[0030] Figure 2 This is a SEM photo of the BiOBr / black TiO2 / tourmaline composite material prepared in Example 1, wherein: Figure 2 (a) is a low-magnification SEM image of BiOBr / black TiO2 / tourmaline composite material. Figure 2 (b) High magnification SEM image of BiOBr / black TiO2 / tourmaline composite material.

[0031] Figure 3 This is a detailed spectrum of Bi, Br, Ti, Si, Fe and O elements in the BiOBr / black TiO2 / tourmaline composite material prepared in Example 1; wherein, Figure 3 (a) is the fine spectrum of Bi element, Figure 3 (b) is the fine spectrum of Br element; Figure 3 (c) is the fine spectrum of Ti element, Figure 3 (d) is the fine spectrum of Si element; Figure 3 (e) is the fine spectrum of Fe element, Figure 3 (f) is the fine spectrum of O element.

[0032] Figure 4 The degradation rate curves and degradation kinetic fitting lines of BiOBr, black TiO2, BiOBr / black TiO2, BiOBr / tourmaline, black TiO2 / tourmaline prepared in Comparative Examples 1-5 and BiOBr / black TiO2 / tourmaline prepared in Example 1 for tetracycline hydrochloride; wherein, Figure 4 (a) is the degradation rate curve of tetracycline hydrochloride by different samples. Figure 4 (b) is the fitting line diagram of the degradation kinetics of tetracycline hydrochloride by different samples.

[0033] Figure 5 This is the absorbance change curve of the BiOBr / black TiO2 / tourmaline composite material prepared in Example 1 for the immediate degradation of tetracycline hydrochloride. DETAILED DESCRIPTION

[0034] The present invention will be described below with reference to specific embodiments, but the protection scope of the present invention is not limited to these embodiments.

[0035] Example 1

[0036] 3.4 g of tetrabutyl titanate was placed in a beaker, 25 mL of isopropanol and 0.01 g of tourmaline were added and stirred for 10 min, and the obtained suspension was recorded as A1; 0.1226 g (i.e., 0.5 mmol) of manganese acetate tetrahydrate was dissolved in 25 mL of deionized water, and the obtained solution was recorded as B1. Solution B1 was added dropwise to suspension A1 and stirred for 30 min to obtain emulsion C1; emulsion C1 was transferred to a 100 mL closed reactor for solvent thermal reaction at a reaction temperature of 180 ° C and a reaction time of 8 h. After the reaction, the obtained black TiO2 / tourmaline composite material was washed and dried; 0.375 g of Bismuth nitrate pentahydrate was dissolved in 50 mL of deionized water, and 0.24 g of black TiO2 / tourmaline was added. The resulting suspension, labeled A2, was stirred for 20 minutes. 0.09 g (0.75 mmol) of potassium bromide was dissolved in 20 mL of deionized water and stirred for 10 minutes. The resulting solution, labeled B2, was added dropwise to suspension A2 and stirred for 20 minutes to obtain emulsion C2. Emulsion C2 was transferred to a 100 mL sealed reactor for a hydrothermal reaction at 120°C for 6 hours. The resulting BiOBr / black TiO2 / tourmaline composite was washed, dried, and set aside. The photoresponsiveness of the composite can be further enhanced by modifying the black TiO2 surface with the photosensitive semiconductor BiOBr to create a BiOBr / black TiO2 heterojunction.

[0037] Example 2

[0038] The other steps are the same as those in Example 1, except that “3.4 g of tetrabutyl titanate” is replaced by “2.55 g of tetrabutyl titanate”, “0.375 g of bismuth nitrate pentahydrate” is replaced by “0.25 g of bismuth nitrate pentahydrate”, and “0.09 g of potassium bromide” is replaced by “0.06 g of potassium bromide”. The obtained composite photocatalyst still exhibits good degradation performance for tetracycline hydrochloride.

[0039] Example 3

[0040] The other steps are the same as those in Example 1, except that “3.4 g of tetrabutyl titanate” is replaced by “1.7 g of tetrabutyl titanate”, “0.375 g of bismuth nitrate pentahydrate” is replaced by “0.125 g of bismuth nitrate pentahydrate”, and “0.09 g of potassium bromide” is replaced by “0.03 g of potassium bromide”. The obtained composite photocatalyst still exhibits good degradation performance for tetracycline hydrochloride.

[0041] Comparative Example 1

[0042] 0.25 g of bismuth nitrate pentahydrate was dissolved in 50 mL of deionized water and stirred for 20 min, resulting in a solution designated A1. 0.06 g of potassium bromide was dissolved in 20 mL of deionized water and stirred for 10 min, resulting in a solution designated B1. Solution B1 was added dropwise to solution A1 and stirred for 20 min to obtain solution C1. Solution C1 was transferred to a 100 mL reactor for a hydrothermal reaction. After the reaction, the obtained BiOBr nanosheets were washed and dried for later use.

[0043] Comparative Example 2

[0044] 3.4 g of tetrabutyl titanate was placed in a beaker, 25 mL of isopropanol was added and the mixture was stirred for 10 minutes. The obtained solution was recorded as A1. 0.1226 g of manganese acetate tetrahydrate was dissolved in 25 mL of deionized water. The obtained solution was recorded as B1. Solution B1 was added dropwise to solution A1 and stirred for 30 minutes to obtain emulsion C1. Emulsion C1 was transferred to a 100 mL reactor for solvothermal reaction. After the reaction, the obtained black TiO2 nanoparticles were washed and dried for later use.

[0045] Comparative Example 3

[0046] The other steps are the same as those in Example 1, except that the preparation process of BiOBr is removed. After the reaction, the obtained black TiO2 / tourmaline composite material is washed and dried for use.

[0047] Comparative Example 4

[0048] 0.25 g of bismuth nitrate pentahydrate was dissolved in 50 mL of deionized water, stirred for 10 minutes, and then 0.24 g of tourmaline was added and stirred for another 10 minutes. The resulting suspension was recorded as A1. 0.06 g of potassium bromide was dissolved in 20 mL of deionized water and stirred for 10 minutes. The resulting solution was recorded as B1. The B1 solution was added dropwise to the suspension A1 and stirred for 20 minutes to obtain a suspension C1. The suspension C1 was transferred to a 100 mL reactor for a hydrothermal reaction. After the reaction, the obtained BiOBr / tourmaline composite material was washed and dried for later use.

[0049] Comparative Example 5

[0050] The other steps are the same as those in Example 1, except that “add 25 mL of isopropanol and 0.01 g of tourmaline and mix and stir for 10 min” is replaced by “add 25 mL of isopropanol and mix and stir for 10 min”, and “add 0.24 g of black TiO2 / tourmaline” is replaced by “add 0.24 g of black TiO2”. After the reaction, the obtained BiOBr / black TiO2 composite material is washed and dried for use.

[0051] From the attached Figure 1Obvious characteristic diffraction peaks of tourmaline, black TiO2 and BiOBr can be seen, confirming the successful preparation of BiOBr / black TiO2 / tourmaline ternary composite photocatalytic material.

[0052] From the attached Figure 2 (a) Low magnification SEM image of BiOBr / TiO2 / tourmaline composite material shows that BiOBr nanosheets and black TiO2 nanoparticles are evenly distributed in the composite material; Figure 2 (b) A high-magnification SEM image of the BiOBr / TiO2 / tourmaline composite shows that the BiOBr nanosheets range in size from 0.2 to 1.0 μm and in thickness from 40 to 60 nm, while the black TiO2 nanoparticles range in size from 20 to 40 nm. The black TiO2 nanoparticles adhere to the BiOBr surface, facilitating the formation of a BiOBr / black TiO2 heterojunction.

[0053] From the attached Figure 3 The chemical valence and bonding of Bi, Br, Ti, Si, Fe and O elements in the BiOBr / TiO2 / tourmaline ternary composite photocatalytic material can be seen, indicating that the components in the composite photocatalytic material are tightly bound by chemical bonds. Figure 3 The binding energies at 164.7 eV and 159.3 eV in (a) correspond to Bi 3+ 4f 5 / 2 and 4f 7 / 2 track; Figure 3 The binding energies at 69.5 eV and 68.6 eV in (b) correspond to Bi -1 3D 3 / 2 and 3D 5 / 2 track; Figure 3 The binding energies at 466.2 eV, 464.5 eV, 458.6 eV, and 456.4 eV in (c) correspond to the Ti 4+ 2p 1 / 2 、Ti 3+ 2p 1 / 2 、Ti 4+ 2p 3 / 2 and Ti 3+ 2p 3 / 2 orbit, indicating that Ti in black TiO2 3+ The successful introduction of Figure 3 The binding energies at 101.8 eV and 99.3 eV in (d) correspond to Si-O-Si and Si-OH bonds, respectively; Figure 3 The binding energies at 725.4 eV, 722.5 eV, 712.4 eV, and 710.1 eV in (e) correspond to the Fe 3+ 2p 1 / 2、Fe 2+ 2p 1 / 2 、Fe 3+ 2p 3 / 2 and Fe 2+ 2p 3 / 2 tracks, indicating the presence of black tourmaline in the composite; Figure 3 The binding energies at 531.0 eV, 530.1 eV, and 528.6 eV in (f) correspond to Si-O, Ti-O, and OH bonds, respectively.

[0054] From the attached Figure 4 In (a), it can be seen that the degradation rate of tetracycline hydrochloride by the BiOBr / black TiO2 / tourmaline composite material is better than that of the materials prepared in Comparative Examples 1-5; Figure 4 (b) shows that the degradation process of tetracycline hydrochloride by all samples follows pseudo-first-order kinetics, and the BiOBr / black TiO2 / tourmaline composite material exhibits the best degradation rate. The degradation rate of the BiOBr nanosheets prepared in Comparative Example 1 for tetracycline hydrochloride with an initial concentration of 50 mg / L is 53.7%. This may be because the higher surface energy of the BiOBr nanosheets causes them to stack with each other, reducing the number of photoreaction active sites and thus affecting their photocatalytic degradation rate; the degradation rate of the black TiO2 nanoparticles prepared in Comparative Example 2 for tetracycline hydrochloride with an initial concentration of 50 mg / L is 80.7%, slightly lower than the degradation rate of the BiOBr / TiO2 / tourmaline composite material for tetracycline hydrochloride under the same conditions. This is mainly because the black TiO2 nanoparticles with higher surface energy are easy to agglomerate with each other, reducing the number of exposed active sites and thus affecting its photocatalytic degradation rate. This result also directly proves that black TiO2 exhibits excellent photocatalytic performance under visible light conditions; the degradation rate of the black TiO2 / tourmaline composite material prepared in Comparative Example 3 for tetracycline hydrochloride with an initial concentration of 50 mg / L is 74.7%. Since the black TiO2 / tourmaline composite material does not construct a BiOBr / black TiO2 heterojunction, its photocatalytic performance is significantly lower than that of the BiOBr / black TiO2 / tourmaline composite material ternary composite material; the degradation rate of the BiOBr / tourmaline composite material prepared in Comparative Example 4 for tetracycline hydrochloride with an initial concentration of 50 mg / L is only 30.6%, which may be because the BiOBr nanosheets do not form a stable chemical bond with the tourmaline particles; the degradation rate of the BiOBr / black TiO2 composite material prepared in Comparative Example 5 for tetracycline hydrochloride with an initial concentration of 50 mg / L is 80.5%, which is slightly lower than the degradation rate of the BiOBr / TiO2 / tourmaline composite material for tetracycline hydrochloride under the same conditions. This is mainly because the BiOBr / black TiO2 composite material does not introduce tourmaline that can improve the separation efficiency of photogenerated electron / hole pairs, so its photocatalytic performance is reduced.

[0055] The photodegradation of tetracycline hydrochloride was conducted using a PL-03 dual-rotational motion ventilation photochemical reactor. The absorbance of tetracycline hydrochloride at a wavelength of 357 nm was measured using a UV1901PC UV-visible spectrophotometer. The degradation rate (D) of tetracycline hydrochloride by the BiOBr / black TiO2 / tourmaline composite was calculated using the Lambert-Beer law. The calculation formula is as follows:

[0056]

[0057] Where C0 and C represent the initial concentration of SIPX and the concentration after adsorption or degradation, respectively; A0 and A represent the initial absorbance of SIPX at the characteristic absorption wavelength of 357 nm and the absorbance after degradation, respectively. The degradation rate of tetracycline hydrochloride can be expressed by the following pseudo-first-order kinetic model:

[0058] In(C0 / C)=kt

[0059] Where k is the reaction kinetic constant and t is the illumination time.

[0060] The specific test steps are as follows: First, a dark adsorption test is conducted in the dark. 10-30 mg of the photocatalyst is added to 50 mL of a tetracycline hydrochloride solution with an initial concentration of 10-50 mg / L to begin the dark adsorption test. The dark adsorption duration is set to 30 minutes. After the dark adsorption reaction has essentially reached equilibrium, the light source is turned on to begin the photocatalytic degradation test. The power of the xenon lamp is 300-400 W. The illumination interval is set to 30 minutes, and the sampling time for a single group of samples is set to 5 minutes. After sampling, the sample is filtered using a 0.22 μm water filter membrane, and the filtrate is taken to test its absorbance value at a wavelength of 357 nm.

[0061] From the attached Figure 5 It can be seen that as the illumination time increases, the characteristic absorption peak intensity of tetracycline hydrochloride (TCH) gradually weakens, indicating that it is gradually degraded.

[0062] Through the above examples and comparative examples, it can be seen that the present invention can self-dope TiO2 3+ The process of preparing black TiO2 begins by introducing a small amount of tourmaline. The spontaneous polarization and surface electric field of tourmaline are used to control the crystal defects of the black TiO2 particles, increasing their surface activity. A photosensitive semiconductor, BiOBr, is then prepared to form a heterojunction with the black TiO2, further enhancing the black TiO2's visible light response. This invention utilizes a simple preparation process, and the resulting tourmaline-black TiO2-BiOBr ternary composite photocatalyst system leverages the advantages of each component to achieve efficient degradation of tetracycline hydrochloride under visible light conditions.

[0063] The above description shows the basic principles and main features of the present invention, as well as the advantages of the present invention. It should be understood by those skilled in the art that the present invention is not limited to the above embodiments. The above embodiments and descriptions are merely illustrative of the principles of the present invention. Various changes and modifications may be made to the present invention without departing from the spirit and scope of the present invention. Such changes and modifications are intended to fall within the scope of the present invention. The scope of protection claimed in the present invention is defined by the appended claims and their equivalents.

[0064] Matters not covered by the present invention are known technologies.

Claims

1. A method for preparing a BiOBr / black TiO2 / tourmaline composite photocatalyst, characterized by The method comprises the following steps: (1) Tetrabutyl titanate, isopropyl alcohol and tourmaline are mixed and stirred to obtain a first suspension; then manganese acetate solution is added dropwise to the first suspension and stirred for 20 to 40 minutes to obtain a first emulsion; For every 2.0-4.0 g of tetrabutyl titanate, add 20-30 mL of isopropyl alcohol, 0.01-0.08 g of tourmaline, and 0.06-0.13 g of manganese acetate. (2) The first emulsion is transferred to a reactor, sealed and reacted at 160-180°C for 6-10 hours, and then washed and dried to obtain black TiO2 / tourmaline; (3) Add black TiO2 / tourmaline to the bismuth nitrate solution and stir to obtain a second suspension. Then, add potassium bromide solution dropwise to the second suspension and stir for 20-40 minutes to obtain a second emulsion. The mass ratio of bismuth nitrate to black TiO2 / tourmaline is 1:2~3:2, and the mass ratio of bismuth nitrate to potassium bromide is 4:1~5:1; (4) The second emulsion was transferred to a reactor, sealed, and reacted at 100-140°C for 4-8 h. After the reaction, it was washed and dried to obtain a BiOBr / black TiO2 / tourmaline composite photocatalyst.

2. The method for preparing the BiOBr / black TiO2 / tourmaline composite photocatalyst according to claim 1, characterized in that The concentration of the manganese acetate solution in step (1) is 0.01 to 0.02 mol / L; the concentration of the potassium bromide solution in step (3) is 0.013 to 0.038 mol / L; and the concentration of the bismuth nitrate solution in step (3) is 0.005 to 0.015 mol / L.

3. Use of the BiOBr / black TiO2 / tourmaline composite photocatalyst prepared by the method of claim 1, characterized in that it is used to degrade residual tetracycline hydrochloride in wastewater.

4. The method according to claim 3, comprising the steps of: A BiOBr / black TiO2 / tourmaline composite photocatalyst was added to a tetracycline hydrochloride solution and irradiated with visible light power of 300-400 W for 30-180 min to degrade tetracycline hydrochloride. in, Add 10-30 mg of BiOBr / black TiO2 / tourmaline composite photocatalyst to every 50 mL of tetracycline hydrochloride solution; The treatment concentration of tetracycline hydrochloride solution is 10~50 mg / L.

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