阅读说明：本技术 一种二元复合纳米催化剂及其制备方法和应用 (Binary composite nano catalyst and preparation method and application thereof ) 是由 杨磊 李志敏 雷倩 钟丹 于 2020-12-24 设计创作，主要内容包括：本申请提供了一种二元复合纳米催化剂及其制备方法和应用,涉及光催化水处理技术领域。该二元复合纳米催化剂为微球状的CQDs-BiOBr,微球状的CQDs-BiOBr的基底是BiOBr微球,CQDs纳米晶紧密负载在BiOBr微球表面,BiOBr微球由纳米板自组装而成BiOBr微球具有氧空位。本申请中在BiOBr中引入了氧空位和CQDs,氧空位和CQDs不仅拓宽了BiOBr催化剂对可见光的吸收范围,而且提高了BiOBr光生电子空穴对分离效率,显著增强了BiOBr光催化降解有机污染物的效率。本申请的CQDs-BiOBr二元复合纳米光催化剂还具有高化学稳定性,可回收重复利用,很好的体现了本材料的环境友好性。在可见光照射和过硫酸盐存在的条件下,CQDs-BiOBr对AAP具有很好光催化降解率,解决了传统光催化剂BiOBr光响应范围窄和光生电子空穴对复合效率高等缺点。(The application provides a binary composite nano catalyst and a preparation method and application thereof, relating to the technical field of photocatalytic water treatment. The binary composite nano catalyst is microspherical CQDs-BiOBr, the substrate of the microspherical CQDs-BiOBr is a BiOBr microsphere, CQDs nanocrystals are tightly loaded on the surface of the BiOBr microsphere, and the BiOBr microsphere is formed by self-assembling nano plates and has oxygen vacancies. Oxygen vacancies and CQDs are introduced into the BiOBr, so that the absorption range of the BiOBr catalyst to visible light is widened, the separation efficiency of the photo-generated electron hole pairs of the BiOBr is improved, and the efficiency of the BiOBr photocatalytic degradation of organic pollutants is obviously enhanced. The CQDs-BiOBr binary composite nano photocatalyst also has high chemical stability, can be recycled, and well embodies the environmental friendliness of the material. Under the conditions of visible light irradiation and persulfate, the CQDs-BiOBr has good photocatalytic degradation rate on AAP, and the defects of narrow light response range, high recombination efficiency of photo-generated electron hole pairs and the like of the traditional photocatalyst BiOBr are overcome.)

1. The binary composite nano catalyst is characterized by being microsphere-shaped CQDs-BiOBr, wherein the substrate of the microsphere-shaped CQDs-BiOBr is a BiOBr microsphere, CQDs nanocrystals are tightly loaded on the surface of the BiOBr microsphere, the BiOBr microsphere is formed by self-assembling of a nano plate, and the BiOBr microsphere is provided with oxygen vacancies.

2. The binary composite nanocatalyst of claim 1, wherein the diameter of the microsphere CQDs-BiOBr is 2.1 μm to 2.5 μm, and the thickness of the nanotube in the microsphere CQDs-BiOBr is 17nm to 23 nm.

3. A method for preparing a binary composite nanocatalyst, which is used for preparing the binary composite nanocatalyst of claim 1 or 2, and specifically comprises the following steps:

step 1, dissolving bismuth salt and a bromine-containing compound in alcohol according to a proportion, uniformly mixing, and reacting at 140-160 ℃ for 12-16h to obtain BiOBr suspension; cooling the BiOBr suspension to room temperature, and then carrying out centrifugal separation and drying treatment to obtain BiOBr;

step 2, dissolving citric acid and urea in water according to a proportion, uniformly mixing, and carrying out hydrothermal reaction at 150-180 ℃ for 8-10h to obtain CQDs suspension; cooling the CQDs suspension to room temperature, centrifuging, collecting supernatant, and vacuum freeze drying to obtain CQDs;

step 3, dissolving CQDs and BiOBr in an alcoholic solution according to a proportion, and heating until the alcoholic solution volatilizes to obtain mixed powder; calcining the mixed powder at 200-500 ℃ for 3-5h to prepare the binary composite nano catalyst.

4. The method for preparing the binary composite nano-catalyst according to claim 3, wherein in the step 1, the molar ratio of the bismuth salt to the alcohol is 1 (100-150);

the molar ratio of the bismuth salt to the bromine-containing compound is 1: 1;

the alcohol comprises ethylene glycol;

the bromine-containing compound comprises KBr;

the bismuth salt comprises Bi (NO)₃)₃·5H₂O；

The centrifugation times are 6-10 times;

the drying temperature is 60-80 ℃, and the drying time is 5-10 h.

5. The preparation method of the binary composite nano catalyst according to claim 3, wherein in the step 2, the mass ratio of the citric acid to the urea is (2-3): 1.

6. The method for preparing the binary composite nano-catalyst according to claim 3, wherein in the step 3, the mass ratio of the CQDs to the BiOBr is 1 (9-50).

7. The method for preparing the binary composite nanocatalyst according to claim 3, wherein in the step 3, the heating temperature is 60 ℃ to 80 ℃;

the calcination is vacuum calcination, and the heating rate is 1-5 ℃/min in the calcination process.

8. Use of the binary composite nanocatalyst of claim 1 or 2 for the catalytic degradation of organic pollutants in a body of water.

9. The use of claim 8, wherein the organic contaminants in the body of water comprise one or more of acetaminophen, bisphenol-A, phenol, caffeine, and organic dyes.

10. The use of claim 9, wherein the binary composite nanocatalyst activates persulfate degradation of acetaminophen in a body of water;

in the water body, the initial concentration of the acetaminophen is 0.5 mg/L-20 mg/L;

the persulfate comprises potassium persulfate, and the concentration of the persulfate is 0.05 mol/L-0.2 mol/L;

the pH value of the water body is 5-9.

Technical Field

The invention relates to the technical field of photocatalytic water treatment, in particular to a binary composite nano catalyst and a preparation method and application thereof.

Background

Acetaminophen (AAP), a commonly used antipyretic analgesic, has become a typical personal drug and care product (PPCPs) that is detected in water. Generally, most of the non-metabolized AAP molecules in the human body are discharged out of the body through excreta and then released into the aquatic environment, even detected in surface water, sewage treatment plants, and drinking water. Since AAP has a resistant molecular structure and is difficult to fully degrade through a traditional wastewater treatment process, a novel advanced oxidation process attracts researchers' attention, and a photocatalytic technology is a green environment-friendly advanced oxidation technology, can fully utilize solar energy, has the advantages of low cost, no pollution and the like, and a photocatalyst is widely paid attention as a key thereof.

Bismuth oxyhalide (X ═ F, Cl, Br, I) is an important PbFCl-type layered tetragonal semiconductor material, and is a novel photocatalyst due to its unique energy band position and layered structure. Wherein BiOBr has a unique structure and a suitable visible light response band gap, and the band gap of BiOBr is measured to be 2.76eV, so that the BiOBr is a novel photocatalytic semiconductor material with great potential. However, BiOBr still has some non-negligible disadvantages, such as that the narrow light absorption edge of BiOBr prevents BiOBr from maximizing the advantages of solar energy converted into chemical energy. In addition, due to the bare surface, the active centers are rare, resulting in slow surface reaction kinetics, further resulting in severe recombination of photo-generated electron-hole pairs.

Disclosure of Invention

The application provides a binary composite nano catalyst and a preparation method and application thereof, and aims to solve the problems of narrow BiOBr light absorption edge and high recombination rate of photo-generated electron-hole pairs.

In a first aspect, the application discloses a binary composite nano catalyst, which is microspherical CQDs-BiOBr, wherein the substrate of the microspherical CQDs-BiOBr is a BiOBr microsphere, CQDs nanocrystals are tightly loaded on the surface of the BiOBr microsphere, and the BiOBr microsphere is formed by self-assembling nano plates and has oxygen vacancies.

In one embodiment, the diameter of the microsphere CQDs-BiOBr is 2.1 μm to 2.5 μm, and the thickness of the nano-plate in the microsphere CQDs-BiOBr is 17nm to 23 nm.

In a second aspect, the present application discloses a method for preparing a binary composite nano catalyst, which is characterized in that the method for preparing the binary composite nano catalyst of the first aspect specifically comprises the following steps:

step 1, dissolving bismuth salt and a bromine-containing compound in alcohol according to a proportion, uniformly mixing, and reacting at 140-160 ℃ for 12-16h to obtain BiOBr suspension; cooling the BiOBr suspension to room temperature, and then carrying out centrifugal separation and drying treatment to prepare BiOBr;

step 2, dissolving citric acid and urea in water according to a proportion, uniformly mixing, and carrying out hydrothermal reaction at 150-180 ℃ for 8-10h to obtain CQDs suspension; cooling the CQDs suspension to room temperature, centrifuging, collecting supernatant, and vacuum freeze drying to obtain CQDs;

step 3, dissolving CQDs and BiOBr in an alcoholic solution according to a proportion, and heating until the alcoholic solution volatilizes to obtain mixed powder; calcining the mixed powder at 200-500 ℃ for 3-5h to prepare the binary composite nano catalyst.

In a specific embodiment, in the step 1, the molar ratio of the bismuth salt to the alcohol is 1 (100-150);

the molar ratio of the bismuth salt to the bromine-containing compound is 1: 1;

the alcohol comprises ethylene glycol;

bromine-containing compounds include KBr;

the bismuth salt comprises Bi (NO)₃)₃·5H₂O；

Centrifuging for 6-10 times;

the drying temperature is 60-80 ℃ and the drying time is 5-10 h.

In one embodiment, in the step 2, the mass ratio of citric acid to urea is (2-3): 1.

In one embodiment, in step 3, the mass ratio of CQDs to BiOBr is 1 (9-50).

In one embodiment, in step 3, the heating temperature is 60 ℃ to 80 ℃;

the calcination is vacuum calcination, and the heating rate is 1-5 ℃/min in the calcination process.

In a third aspect, the application provides an application of the binary composite nano-catalyst of the first aspect in catalytic degradation of organic pollutants in a water body.

In a particular embodiment, the organic contaminants in the body of water include one or more of acetaminophen, bisphenol a, phenol, caffeine, and organic dyes.

In a specific embodiment, the binary composite nano catalyst activates persulfate to degrade acetaminophen in the water body; in the water body, the initial concentration of the acetaminophen is 0.5 mg/L-20 mg/L; the persulfate comprises potassium persulfate, and the concentration of the persulfate is 0.05 mol/L-0.2 mol/L;

the pH value of the water body is 5-9.

Compared with the prior art, the method has the following advantages:

the application provides a microspherical CQDs-BiOBr binary composite nano catalyst, wherein a base in the microspherical CQDs-BiOBr is a BiOBr microsphere, CQDs nanocrystals are tightly loaded on the surface of the BiOBr microsphere, the BiOBr microsphere is formed by self-assembling a nano plate, and the BiOBr microsphere has an oxygen vacancy. Oxygen vacancy and CQDs are introduced into BiOBr, the absorption range of the BiOBr catalyst to visible light can be widened by the oxygen vacancy and the CQDs, and the CQDs have good electron transfer capacity, so that photo-generated electrons can move rapidly, photo-generated electron hole pair recombination is inhibited, and BiOBr photocatalysis efficiency is obviously enhanced. The CQDs-BiOBr binary composite nano catalyst has the degradation efficiency of more than 99% on AAP, and has high chemical stability and can be recycled.

The application provides an application of a binary composite nano-catalyst in photocatalytic degradation of organic pollutants, wherein in the presence of Persulfate (PS), visible light is irradiated to enable the CQDs-BiOBr binary composite nano-catalyst to generate electrons to activate the PS and degrade the organic pollutants in a water body.

Drawings

FIG. 1 is SEM images of example 1 of the present invention and a comparative example; (a) (b) is an SEM image of bibbr at different magnifications; (c) (d) is SEM picture of CQDs-BiOBr under different magnification;

FIG. 2 is electron paramagnetic resonance spectra of example 1 of the present invention and a comparative example;

FIG. 3 is a UV-visible diffuse reflectance spectrum of example 1 of the present invention and a comparative example;

FIG. 4 is a Fourier transform infrared spectrum of example 1 of the present invention and a comparative example;

FIG. 5 is a graph comparing the performance of the present invention in Experimental example 1, example 2, example 3, and comparative example 1 with that of photocatalytic degradation of AAP under pure illumination;

FIG. 6 is a graph comparing the performance of example 1 of the present invention in catalytically degrading RhB and BPA;

FIG. 7 shows the stability study of photocatalytic degradation of AAP in Experimental example 1 of the present invention.

Detailed Description

In order to make the aforementioned objects, features and advantages of the present application more comprehensible, the present application is described in further detail with reference to the accompanying drawings and the detailed description.

Materials, reagents and the like used in the following examples are commercially available unless otherwise specified.

In a first aspect, the application provides a binary composite nano catalyst, which is microspherical CQDs-BiOBr, wherein the substrate of the microspherical CQDs-BiOBr is a BiOBr microsphere, CQDs nanocrystals are tightly loaded on the surface of the BiOBr microsphere, and the BiOBr microsphere is formed by self-assembling nano plates and has oxygen vacancies. The diameter of the CQDs-BiOBr microsphere is 2.1-2.5 μm, and the thickness of the nano-plate in the CQDs-BiOBr microsphere is 17-23 nm.

In the application, oxygen vacancy and CQDs are introduced into BiOBr to obtain the binary composite nano catalyst. The oxygen vacancies promote the separation of photo-generated electron-hole pairs in the optimization of the photocatalytic performance, and expand the light absorption range of BiOBr. The CQDs not only broadens the absorption range of the BiOBr to visible light, but also the CQDs-BiOBr binary composite nano photocatalyst has high photo-generated electron hole pair separation efficiency, and the efficiency of degrading AAP by photocatalysis is obviously enhanced. Experiments prove that the CQDs-BiOBr degrades the AAP with the initial concentration of 10mg/L and the initial pH of 7 under the conditions of visible light irradiation and the existence of Persulfate (PS), and the degradation rate of the AAP can reach more than 99 percent after 20 minutes. In addition, the CQDs-BiOBr binary composite nano catalyst also has high chemical stability, can be recycled and is environment-friendly.

In a second aspect, the application provides a preparation method of a binary composite visible light catalytic nano material, comprising the following steps:

step 1: a certain amount of Bi (NO)₃)₃·5H₂Completely dissolving O in ethylene glycol to obtain a uniform solution A, completely dissolving a certain amount of KBr in the ethylene glycol to obtain a uniform solution B, dripping the solution B into the solution A by magnetic stirring at room temperature, stirring for 30 minutes, sealing the suspension into a high-pressure reaction kettle, and heating for 12-16 hours at the temperature of 140-; and after the reaction is finished, cooling the product to room temperature, centrifugally washing for 6-10 times, and finally drying in an oven at the temperature of 60-80 ℃ for 5-10 hours to obtain the BiOBr. Wherein, Bi (NO)₃)₃·5H₂The molar ratio of O to glycol is 1 (100-150); bi (NO)₃)₃·5H₂The molar ratio of O to KBr was controlled at 1: 1.

The Bi-based oxygen-containing compound prepared by the method contains a large amount of Bi-O bonds, so that O atoms are easily lost to form oxygen vacancies. In general, BiOBr has a layered structure, but in the present application, the alcohol is used as a solvent, and thus the alcohol can bend the layered structure of BiOBr to form microspherical BiOBr.

Step 2: dissolving citric acid and urea in deionized water according to the mass ratio of (2-3) to (1), sealing the mixture in a high-pressure reaction kettle, and heating at the temperature of 150 ℃ and 180 ℃ for 8-10 h; after the reaction is finished, centrifuging at high speed, and freeze-drying the supernatant to obtain CQDs.

And step 3: and (3) dissolving the CQDs solid particles obtained in the step (2) in absolute ethyl alcohol, adding the BiOBr obtained in the step (1), continuously heating at 60-80 ℃, stirring until the absolute ethyl alcohol is completely volatilized, and calcining the obtained powder at 200-500 ℃ in vacuum for 3-5 hours to obtain CQDs-BiOBr. Wherein the mass ratio of CQDs to BiOBr is 1 (9-50), and the heating rate in the calcining process is 1-5 ℃/min.

In a third aspect, the application provides an application of a binary composite nano catalyst CQDs-BiOBr in photocatalytic degradation of organic pollutants. The contaminants include, but are not limited to, AAP, bisphenol a, phenol, caffeine, dye-based contaminants, and the like, preferably AAP.

CQDs-BiOBr can activate persulfate to degrade AAP in water. In the presence of visible light, CQDs-BiOBr generate photo-generated electrons which activate PS to generate active substance SO with strong oxidizing property^- ₄And OH; SO^- ₄Further OH can be formed; produced SO^- ₄OH decomposes the AAP in solution by means of organic functional groups or chemical bonds, and finally mineralizes to form CO₂And H₂And small molecular inorganic substances such as O and the like. When the CQDs-BiOBr activates persulfate to degrade AAP in water, the degradation rate can reach 99 percent after 20 min.

In order to better illustrate the scheme provided by the embodiment of the present invention, correspondingly, the present invention also provides a specific example of a preparation method of the above CQDs-BiOBr binary composite nano-photocatalyst, as shown below.

Example 1

Step 1, add 8mmol of Bi (NO)₃)₃·5H₂Dissolving O in 50mL of ethylene glycol completely to obtain a uniform solution A, dissolving 8mmol of KBr in 50mL of ethylene glycol completely to obtain a uniform solution B, dripping the solution B into the solution A by magnetic stirring at room temperature, continuously stirring for 30min to obtain a stable solution, transferring the solution into a 100-mL reaction kettle with a polytetrafluoroethylene lining, keeping the reaction kettle at 160 ℃ for 16 hours, cooling to room temperature after the reaction is completed, washing the suspension with absolute ethyl alcohol and ultrapure water for 6 times, collecting precipitates, and drying the precipitates for 10 hours at 80 ℃ by using an oven to obtain the BiOBr.

Step 2, accurately weighing 2.0g of citric acid and 0.5g of urea, dissolving in 10ml of deionized water, transferring the solution into a reaction kettle with a 100 ml of polytetrafluoroethylene lining, and reacting for 8 hours at 180 ℃; after cooling to room temperature, the mixture was transferred to a centrifuge tube, centrifuged at high speed for 30min, and the supernatant was freeze-dried to give CQDs.

Step 3, accurately weighing 25mg of CQDs obtained in the step 2, dissolving the CQDs in 20ml of absolute ethyl alcohol, then adding 475mg of BiOBr obtained in the step 1, and placing the mixture in a magnetic stirrer to continuously stir at the temperature of 80 ℃ until the absolute ethyl alcohol is completely volatilized; then calcining the obtained powder at 300 ℃ for 3 hours to obtain the 5 percent CQDs-BiOBr binary composite nano catalyst.

Example 2

Step 1, add 8mmol of Bi (NO)₃)₃·5H₂Dissolving O in 50mL of ethylene glycol completely to obtain a uniform solution A, dissolving 8mmol of KBr in 50mL of ethylene glycol completely to obtain a uniform solution B, dripping the solution B into the solution A by magnetic stirring at room temperature, continuously stirring for 30min to obtain a stable solution, transferring the solution into a 100-mL reaction kettle with a polytetrafluoroethylene lining, keeping the reaction kettle at 160 ℃ for 16 hours, cooling to room temperature after the reaction is completed, washing the suspension with absolute ethyl alcohol and ultrapure water for 6 times, collecting precipitates, and drying the precipitates for 10 hours at 80 ℃ by using an oven to obtain the BiOBr.

Step 2, accurately weighing 2.0g of citric acid and 0.5g of urea, dissolving in 10ml of deionized water, transferring the solution into a reaction kettle with a 100 ml of polytetrafluoroethylene lining, and reacting for 8 hours at 180 ℃; after cooling to room temperature, the mixture was transferred to a centrifuge tube, centrifuged at high speed for 30min, and the supernatant was freeze-dried to give CQDs.

Step 3, accurately weighing 5mg of CQDs obtained in the step 2, dissolving the CQDs in 20ml of absolute ethyl alcohol, then adding 495mg of BiOBr obtained in the step 1, and placing the mixture in a magnetic stirrer to continuously stir at 80 ℃ until the absolute ethyl alcohol is completely volatilized; then calcining the obtained powder at 300 ℃ for 3 hours to obtain the 1 percent CQDs-BiOBr binary composite nano catalyst.

Example 3

Step 1, add 8mmol of Bi (NO)₃)₃·5H₂O was completely dissolved in 50mL of ethylene glycol to obtain a homogeneous solutionA, completely dissolving 8mmol of KBr in 50mL of ethylene glycol to obtain a uniform solution B, dripping the solution B into the solution A by magnetic stirring at room temperature, continuously stirring for 30min to obtain a stable solution, transferring the solution into a 100 mL of reaction kettle with a polytetrafluoroethylene lining, keeping the reaction kettle at 160 ℃ for 16 hours, cooling to room temperature after the reaction is completed, washing the suspension with absolute ethyl alcohol and ultrapure water for 6 times, collecting precipitates, and drying the precipitates for 10 hours at 80 ℃ by using an oven to obtain the BiOBr.

Step 2, accurately weighing 2.0g of citric acid and 0.5g of urea, dissolving in 10ml of deionized water, transferring the solution into a reaction kettle with a 100 ml of polytetrafluoroethylene lining, and reacting for 8 hours at 180 ℃; after cooling to room temperature, the mixture was transferred to a centrifuge tube, centrifuged at high speed for 30min, and the supernatant was freeze-dried to give CQDs.

Step 3, accurately weighing 50mg of CQDs obtained in the step 2, dissolving the CQDs in 20ml of absolute ethyl alcohol, then adding 450mg of BiOBr obtained in the step 1, and placing the mixture in a magnetic stirrer to continuously stir at 80 ℃ until the absolute ethyl alcohol is completely volatilized; then calcining the obtained powder at 300 ℃ for 3 hours to obtain the 10 percent CQDs-BiOBr binary composite nano catalyst.

Comparative example

Step 1, add 8mmol of Bi (NO)₃)₃·5H₂Dissolving O in 50mL of ethylene glycol completely to obtain a uniform solution A, dissolving 8mmol of KBr in 50mL of ethylene glycol completely to obtain a uniform solution B, dripping the solution B into the solution A by magnetic stirring at room temperature, continuously stirring for 30min to obtain a stable solution, transferring the solution into a 100-mL reaction kettle with a polytetrafluoroethylene lining, keeping the reaction kettle at 160 ℃ for 16 hours, cooling to room temperature after the reaction is completed, washing the suspension with absolute ethyl alcohol and ultrapure water for 6 times, collecting precipitates, and drying the precipitates for 10 hours at 80 ℃ by using an oven to obtain the BiOBr.

FIG. 1 is SEM images of example 1 of the present invention and a comparative example; (a) (b) is an SEM image of bibbr at different magnifications; (c) (d) is SEM image of CQDs-BiOBr at different magnifications. As can be seen from fig. (a) and (b), the obtained BiOBr had a microspherical shape, and the microspherical BiOBr was assembled from the nano-plates. As can be seen from the graphs (c) and (d), the obtained CQDs-BiOBr shows a tiny spherical shape, the diameter of the CQDs-BiOBr sphere is 2.1-2.5 μm, and the CQDs-BiOBr sphere is formed by assembling nano plates with the thickness of 17-23 nm; it is suggested that CQDs did not affect the microscopic morphology of BiOBr, probably because CQDs were added in a lesser amount and entered the lattice of BiOBr in a doping manner.

Further observation shows that BiOBr grows preferentially in the (110) direction, and the structure is favorable for separating CQDs-BiOBr photoproduction electron-hole pairs and improves the photocatalytic activity of the CQDs-BiOBr.

In order to verify the existence of oxygen vacancies in the BiOBr and CQDs-BiOBr binary composite nano-catalyst prepared by the patent, an Electron Paramagnetic Resonance (EPR) spectrum test is carried out, and the result is shown in FIG. 2. As can be seen from the graph, BiOBr and 5% CQDs-BiOBr both showed typical EPR signals, and showed stronger EPR signals of oxygen vacancies after introduction of CQDs, confirming that BiOBr and 5% CQDs-BiOBr successfully introduced oxygen vacancies.

Fig. 3 is a uv-visible diffuse reflectance spectrum of example 1 of the present invention and a comparative example. As can be seen from the figure, the light absorption edge of the BiOBr photocatalyst is about 450nm, and the CQDs-BiOBr light absorption expands to the full visible spectrum light, and the CQDs-BiOBr can be excited to generate photo-generated electron-hole pairs within the range of visible light (400-800nm), so that the photo-generated electron-hole pairs have strong absorptivity. Further, the introduction of CQDs plays a crucial role in shifting the light absorption edge of CQDs-BiOBr to the visible light direction.

FIG. 4 is a Fourier transform infrared spectrum of example 1 of the present invention and a comparative example. As can be seen from the figure, BiOBr and CQDs-BiOBr are both 520cm^-1The characteristic peak of Bi-O bond appears, and then combined with the visual observation of the color of the binary composite nano photocatalyst, the CQDs and the BiOBr can be preliminarily deduced to be successfully compounded. Secondly, 878cm^-1Corresponds to sp of CQDs³C-OH bond of orbital, and 1390cm^-1、1620cm^-1And 3000cm^-1The characteristic absorption peaks of (A) correspond to the stretching vibration peaks of-COO, C ═ O and O-H, respectively, thereby showing that hydrophilic hydroxyl and carboxyl organic functional groups and hydrophilic carboxyl organic functional groups exist on the surfaces of CQDs/BiOBrThe organic functional group can react with hydroxyl ions to generate water, so that the water is favorable for adsorbing the hydroxyl ions, and the function of hydroxyl free radicals (. OH) in subsequent trapping agent experiments can be well corresponded.

The degradation performance of the CQDs-BiOBr binary composite nano-catalyst prepared by the method on AAP is verified below.

The photocatalytic oxidation of AAP is carried out in a cylindrical double-layer quartz container, a 300W xenon lamp with a filter (400nm) is horizontally placed outside the reactor as a visible light source, and the average light intensity of the surface of the reaction solution in the reaction solution is 200mW/cm measured by a photon densitometer²I.e. 2 standard solar intensities (AM 3G). To maintain a constant reaction temperature, a cooling water circulation system was applied around the reactor and the experiment was performed with slow magnetic stirring.

Firstly, 50mLAAP aqueous solution is added into a reactor in a cylindrical double-layer quartz container, the initial AAP concentration is 10mg/L, the pH value is controlled to be 7 through 0.1MHCl or NaOH, the adding amount of the catalyst is 0.5g/L, and before visible light irradiation, a dark adsorption experiment is carried out in the dark for 30 minutes to ensure that the adsorption and desorption balance between the catalyst and the AAP is achieved. Subsequently, 2mM PS was added. Carrying out photocatalytic reaction under the irradiation of a visible light source (lambda is more than or equal to 400nm), taking out liquid samples at intervals, and measuring the concentration change of the AAP in the samples by an ultra-high performance liquid chromatograph through a filter membrane of 0.22 mu m so as to calculate the degradation rate of the AAP.

The experimental results show that: under the irradiation of 2 standard sunlight intensity visible lights (lambda is more than 400nm), the catalyst dosage is 0.5g/L, the PS dosage is 2mM, the AAP initial concentration is 10mg/L, and the initial pH is 7, the degradation efficiency of the CQDs-BiOBr photocatalysis nano material to AAP after 10 minutes is as high as 100%.

FIG. 5 is a graph comparing the performance of the present invention in Experimental example 1, example 2, example 3, and comparative example 1 with that of photocatalytic degradation of AAP under pure illumination. As can be seen from the figure, after 20min of illumination, AAP under pure illumination is hardly degraded; BiOBr can only remove about 48%, however, the degradation efficiency of the CQDs-BiOBr binary composite nano catalyst on AAP reaches 100%. The compounding of CQDs and BOB is more beneficial to activating PS, thereby improving the photocatalytic effect of the system. In addition, when the ratio of CQDs is increased from 1% to 10%, the removal rates of AAP reach 45.1%, 100% and 80.8%, respectively. As CQDs increase from 5% to 10%, the efficiency of CQDs-BiOBr/PS degradation decreases significantly because excess CQDs compete with BiOBr for photon adsorption and provide recombination sites for photogenerated electron-hole pairs.

FIG. 6 is a graph comparing the performance of example 1 of the present invention in catalytically degrading RhB and BPA. As can be seen from the figure, the degradation rate of 5% CQDs-BiOBr on RhB within 10min is 99%, and the degradation rate on BPA within 20min is 97%. Therefore, the CQDs-BiOBr binary composite nano photocatalyst not only has good degradation performance on AAP, but also has good degradation performance on other organic matters such as BPA and RhB.

Fig. 7 shows the stability of the visible light catalytic degradation AAP of the CQDs-BiOBr binary composite nano-catalyst in example 1 of the present invention, and the degradation efficiency of the AAP in three consecutive degradation experiments is basically consistent and is maintained above 90%, which indicates that the photocatalytic activity of the CQDs-BiOBr binary composite nano-catalyst is still good after three cycles of the AAP degradation experiments, so that the material of the present invention can be repeatedly recycled in the experiments of photocatalytic degradation of organic matters.

Although particular embodiments of the invention have been described above, it will be apparent to those skilled in the art that many additional modifications or improvements to these embodiments are possible in light of the above teaching. Accordingly, such modifications and improvements are intended to be within the scope of the invention as claimed.