CN110586141A - Preparation method of Ag-Bi solid solution composite photocatalyst for treating oil field waste liquid - Google Patents

Abstract

The invention discloses a method for preparing an Ag-Bi solid solution composite photocatalyst for treating oil field waste liquid. The steps are as follows: S1. Dissolving a bismuth-containing compound in ethylene glycol to obtain solution A; Dissolve the chlorine compound in another part of ethylene glycol to obtain solution B; S2, add solution B dropwise to solution A, mix well, then raise the temperature of the mixed solution to 140-180°C, and react at constant temperature for 14-18 hours to obtain BiOCl _0.5 Br _0.5 ; S3, dissolving BiOCl _0.5 Br _0.5 in distilled water, then adding a silver-containing compound to obtain solution C; S4, dissolving another chlorine-containing compound and a bromine-containing compound in distilled water to obtain solution D, and dissolving solution D Add it into solution C, stir for 1-3 hours in the dark, centrifuge, and dry to obtain AgCl _0.5 Br _0.5 /BiOCl _0.5 Br _0.5 ; S5, dissolve AgCl _0.5 Br _0.5 /BiOCl _0.5 Br _0.5 in distilled water, and irradiate under full-wavelength xenon lamp 0.5-2h, to obtain Ag-AgCl _0.5 Br _0.5 /BiOCl _0.5 Br _0.5 composite photocatalyst. The catalyst of the invention has enhanced response to visible light, especially has high activity in photocatalytic degradation of acrylamide, and can be applied to the removal of acrylamide in oil fields.

Description

Preparation of a Ag-Bi solid solution composite photocatalyst for treating oilfield waste liquid method

technical field

The invention relates to the technical field of photocatalysis, in particular to a method for preparing an Ag-AgCl _0.5 Br _0.5 /BiOCl _0.5 Br _0.5 composite photocatalyst for visible light response of acrylamide in photocatalytic oxidation and fracturing flowback fluid.

Background technique

In the process of oilfield production, due to the heterogeneity of the bottom layer, water immersion problems often occur, and water plugging is required, that is, to change the seepage state of water in the formation, so as to reduce oilfield water production, maintain formation energy, and improve oilfield final production. yield purposes. The acrylamide chemical water shutoff agent has the selectivity of oil and water permeability, the maximum reduction of oil permeability can exceed 10%, and the reduction of water permeability can exceed 90%. While improving the benefit of the oil field, the treatment liquid discharged from the oil field also brings technical difficulties. The composition of fracturing flowback fluid is complex, containing a variety of organic additives, and has the characteristics of high COD value, high viscosity, high turbidity, high stability and so on. If the fracturing flowback fluid is directly discharged or reinjected into the formation, it will cause serious pollution to the underground environment and the natural environment, which runs counter to the green technology implemented in our country. In order to meet the requirements of green economy, an environmentally friendly technology for treating fracturing flowback fluid is the core technology for continuous oilfield production.

Photocatalytic oxidation is an advanced oxidation chemical method, which is an environmentally friendly treatment technology, which means that semiconductor photocatalysts can directly use solar energy to convert light energy into chemical energy to promote the degradation of compounds. Its mechanism of action is to generate extremely active active oxygen species under the action of light on the semiconductor catalyst, and the active oxygen species can almost non-selectively oxidize and degrade the refractory organic pollutants in the flowback liquid into non-toxic or low-toxic Small molecular substances are even directly mineralized into carbon dioxide, water and other small molecular carboxylic acids to achieve the purpose of harmlessness. This technology has the advantages of non-selectivity, strong oxidation ability, fast reaction speed, high treatment efficiency, and no secondary pollution. The unique advantages of photocatalytic technology make it have great application prospects in the treatment of shale gas fracturing flowback fluid, and photocatalyst is the hub of photocatalytic technology, and the development of new photocatalyst is the core technology of photocatalytic technology.

With the development of photocatalytic technology, following the most classic titanium dioxide catalyst, a series of new photocatalysts based on bismuth, silver and phosphorus have been reported. In the process of catalyst development, solid solution catalysts are the focus of researchers. A solid solution is a substance similar to a solution that can form a homogeneous, variable composition of crystals with the same quality. Solid solution is an effective method to change the electronic structure and energy band structure of semiconductors. It is formed by two semiconductors with similar radii, the same crystal structure, and different wide and narrow band gaps. When these two substances form a solid solution, the structure of the semiconductor material does not change, but the electronic structure of the semiconductor changes due to changes in the constituent elements. Bismuth oxyhalide is a new type of bismuth-based semiconductor material, which has the characteristics of non-toxic, cheap, strong redox ability, stable chemical properties and anti-light corrosion. Silver halide-based photocatalyst is also a new type of semiconductor material with high activity, and simple silver has efficient plasmonic effect. Based on the advantages of bismuth oxyhalide-based and silver halide-based photocatalysis, and the halogen atoms in these two types of photocatalysts meet the conditions for forming solid solutions, a series of solid-solution bismuth oxyhalide-based and solid-solution silver halide catalysts have been developed. Bismuth oxyhalide solid solution catalysts and silver halide solid solution catalysts reported in the existing literature have stronger performance than monomers, but their utilization of solar energy is not ideal, and the catalytic performance needs to be improved, so they need to be further modified. Research.

Contents of the invention

The object of the present invention is to provide a preparation method of Ag-Bi solid solution composite photocatalyst Ag-AgCl _0.5 Br _0.5 /BiOCl _0.5 Br _0.5 for treating oil field waste liquid.

The preparation method of the Ag-AgCl _0.5 Br _0.5 /BiOCl _0.5 Br _0.5 composite solid-solution photocatalyst provided by the present invention has the following steps:

S1. Dissolving the bismuth-containing compound in ethylene glycol to obtain solution A; dissolving the bromine-containing compound and chlorine-containing compound in another part of ethylene glycol according to the molar ratio Br:Cl=1:1 to obtain solution B; wherein , the amounts of bromine-containing compounds, chlorine-containing compounds and bismuth-containing compounds are equal; in solution A, the concentration of bismuth-containing compounds is 0.07～0.2mol/L; in solution B, the concentrations of bromine-containing compounds and chlorine-containing compounds are the same, The value range is 0.08-0.2mol/L.

S2. Add solution B to solution A drop by drop, stir for 20-100 minutes, mix well, then raise the temperature of the mixture to 140-180°C, react at constant temperature for 14-18 hours, wash the product with absolute ethanol, and heat it at 60-80°C Dry for 5-24 hours to obtain BiOCl _0.5 Br _0.5 .

S3. Add BiOCl _0.5 Br _0.5 into distilled water, stir for 30 minutes to dissolve completely, then add the silver-containing compound, stir at room temperature for 20-100 minutes, the molar ratio of BiOCl _0.5 Br _0.5 to the silver-containing compound is 2:1, and obtain solution C; In solution C, the concentration of BiOCl _0.5 Br _0.5 is 0.04-0.1 mol/L, and the concentration of the silver-containing compound is 0.02-0.05 mol/L. The silver-containing compound is preferably silver nitrate.

S4, another chlorine-containing compound and a bromine-containing compound are dissolved in distilled water to obtain a solution D, wherein the molar ratio of the chlorine-containing compound to the silver-containing compound is 1:1, the molar ratio of the bromine-containing compound to the silver-containing compound is 0.5:1, and solution D The concentration of chlorine-containing compounds in the medium is 0.02-0.05mol/L; the concentration of bromine-containing compounds is 0.01-0.025mol/L. Add solution D into solution C, stir for 1-3 hours in the dark, centrifuge, dry at a temperature of 50-70°C, and dry for 8-16 hours to obtain AgCl _0.5 Br _0.5 /BiOCl _0.5 Br _0.5 ;

S5. Dissolving AgCl _0.5 Br _0.5 /BiOCl _0.5 Br _0.5 in distilled water, irradiating under full-wavelength xenon lamp for 0.5-2h, centrifuging and drying to obtain Ag-AgCl _0.5 Br _0.5 /BiOCl _0.5 Br _0.5 composite photocatalyst.

Preferably, the bismuth-containing compound is bismuth nitrate pentahydrate; the bromine-containing compound is potassium bromide or sodium bromide; and the chlorine-containing compound is potassium chloride or sodium chloride.

Preferably, the step S5 can be carried out as follows: 0.2-0.5 g of AgCl _0.5 Br _0.5 /BiOCl _0.5 Br _0.5 is dissolved in 20-50 mL of distilled water, irradiated under a full-wavelength xenon lamp for 0.5-2 h, centrifuged, and Dry at 50-70°C for 8-16 hours to obtain Ag-AgCl _0.5 Br _0.5 /BiOCl _0.5 Br _0.5 composite photocatalyst.

The Ag-AgCl _0.5 Br _0.5 /BiOCl _0.5 Br _0.5 composite photocatalyst prepared by the above method is used for catalytic oxidation of acrylamide in fracturing flowback fluid under visible light.

Compared with the prior art, the benefits of the present invention are:

First, the catalytic activity of the Ag-AgCl _0.5 Br _0.5 /BiOCl _0.5 Br _0.5 composite solid solution photocatalyst prepared by the present invention is better than that of Ag-AgCl _0.5 Br _0.5 and BiOCl _0.5 Br _0.5 monomers. The prepared photocatalyst can excite more photogenerated electrons under visible light, the electron-hole recombination rate is reduced, and the photocatalytic activity is significantly improved, especially the acrylamide oxide has a high activity, and the preparation method is simple and the conditions are mild, reaching The purpose of reducing cost and simplifying production process can be applied to oxidize acrylamide in fracturing flowback fluid.

Second, the present invention uses non-toxic components, which reduces the harm to human health and the ecological environment, optimizes the preparation process of this type of photocatalyst, and achieves the purpose of reducing costs and simplifying the production process. The photocatalyst prepared by the invention does not need to add other chemical reagents and other post-preparation treatments, and the method is simple.

Other advantages, objectives and features of the present invention will partly be embodied through the following descriptions, and partly will be understood by those skilled in the art through the study and practice of the present invention.

Description of drawings

Figure 1 is the XRD spectrum of the Ag-AgCl _0.5 Br _0.5/ BiOCl _0.5 Br _0.5 composite solid solution photocatalyst, Ag-AgCl _0.5 Br _0.5 and BiOCl _0.5 Br _0.5 prepared in Example 1, and b is a partial enlarged view of Figure a.

Fig. 2 is the TEM spectrum of the Ag-AgCl _0.5 Br _0.5 /BiOCl _0.5 Br _0.5 composite solid solution photocatalyst prepared in Example 1.

Figure 3 is a diagram of the degradation efficiency of Ag-AgCl _0.5 Br _0.5 /BiOCl _0.5 Br _0.5 composite solid solution photocatalyst, Ag-AgCl _0.5 Br _0.5 and BiOCl _0.5 Br _0.5 prepared in Example 1 for degrading acrylamide.

Detailed ways

The preferred embodiments of the present invention will be described below in conjunction with the accompanying drawings. It should be understood that the preferred embodiments described here are only used to illustrate and explain the present invention, and are not intended to limit the present invention.

Example 1

A preparation method of Ag-AgCl _0.5 Br _0.5 /BiOCl _0.5 Br _0.5 composite photocatalyst for treatment of oil field waste liquid, the steps are as follows:

S1. Dissolve 1.9402g of bismuth nitrate pentahydrate in 20mL of ethylene glycol with an analytical balance to obtain solution A; then dissolve 0.2982g of potassium chloride and 0.4760g of potassium bromide in 60mL of ethylene glycol to obtain solution B ;

S2. Add solution B to solution A, stir and react for 30 minutes; transfer the mixed solution to a reaction kettle for 16 hours at 160° C., wash with absolute ethanol, and dry at 60° C. for 12 hours to obtain BiOCl _0.5 Br _0.5 .

S3. Dissolve 2 mmol of BiOCl _0.5 Br _0.5 in distilled water, stir for 30 min, and then add 1 mmol of silver nitrate to obtain solution C.

S4. Dissolve 1mmol of potassium bromide and 0.5mmo of potassium chloride in 30mL of distilled water to obtain solution D; then add solution D to solution C, and stir for 2 hours in the dark; wash with distilled water for centrifugation, and dry at 60°C for 12 hours This gives AgCl _0.5 Br _0.5 /BiOCl _0.5 Br _0.5 .

S5. Dissolve 0.4 g of AgCl _0.5 Br _0.5 /BiOCl _0.5 Br _0.5 in 30 mL of distilled water, stir and react for 1 h under a 300-w xenon lamp, centrifuge and dry at 60° C. for 12 h to obtain Ag-AgCl _0.5 Br _0.5 /BiOCl _0.5 Br _0.5 .

Example 2

A preparation method of Ag-AgCl _0.5 Br _0.5 /BiOCl _0.5 Br _0.5 composite photocatalyst for treatment of oil field waste liquid, the steps are as follows:

S1. Dissolve 4 mmol of bismuth nitrate pentahydrate in 40 mL of ethylene glycol to obtain solution A, and dissolve 4 mmol of sodium bromide and 4 mmol of sodium chloride in 40 mL of ethylene glycol to obtain solution B.

S2. Add solution B to solution A and stir for 30 minutes; transfer the mixed solution to a reaction kettle at 140°C for 18 hours, wash with absolute ethanol, and dry at 70°C for 10 hours to obtain BiOCl _0.5 Br _0.5 .

S3. Dissolve 2 mmol of BiOCl _0.5 Br _0.5 in distilled water, stir for 30 min, and then add 1 mmol of silver nitrate to obtain solution C.

S4. Dissolve 1mmol of sodium bromide and 0.5mmo of sodium chloride in 30mL of distilled water to obtain solution D; then add solution D to solution C, and stir for 1h in the dark; wash with distilled water for centrifugation, and dry at 50°C for 16h This gives AgCl _0.5 Br _0.5 /BiOCl _0.5 Br _0.5 .

S5. Dissolve 0.4g of AgCl _0.5 Br _0.5 /BiOCl _0.5 Br _0.5 in 20mL of distilled water, stir and react for 0.5h under a 300w xenon light, and dry at 50°C for 16h after centrifugation to obtain Ag-AgCl _0.5 Br _0.5 /BiOCl _0.5 Br _0.5 .

Example 3

A preparation method of Ag-AgCl _0.5 Br _0.5 /BiOCl _0.5 Br _0.5 composite photocatalyst for treatment of oil field waste liquid, the steps are as follows:

S1. Dissolve 1.9402g of bismuth nitrate pentahydrate in 20mL of ethylene glycol with an analytical balance to obtain solution A; then dissolve 0.2982g of potassium chloride and 0.4760g of potassium bromide in 60mL of ethylene glycol to obtain solution B ;

S2. Add solution B to solution A, stir and react for 30 minutes; transfer the mixed solution to a reaction kettle for 14 hours at 180°C, wash with absolute ethanol, and dry at 80°C for 5 hours to obtain BiOCl _0.5 Br _0.5 .

S3. Dissolve 2 mmol of BiOCl _0.5 Br _0.5 in distilled water, stir for 30 min, and then add 1 mmol of silver nitrate to obtain solution C.

S4. Dissolve 1 mmol of potassium bromide and 0.5 mmol of potassium chloride in 30 mL of distilled water to obtain solution D; then add solution D to solution C, and stir for 3 hours in the dark; wash with distilled water for centrifugation, and dry at 70°C for 8 hours , to obtain AgCl _0.5 Br _0.5 /BiOCl _0.5 Br _0.5 .

S5. Dissolve 0.4 g of AgCl _0.5 Br _0.5 /BiOCl _0.5 Br _0.5 in 50 mL of distilled water, stir and react under a 300w xenon lamp for 2 hours, centrifuge and dry at 70°C for 8 hours to obtain Ag-AgCl _0.5 Br _0.5 /BiOCl _0.5 Br _0.5 .

Performance Characterization:

The Ag-AgCl _0.5 Br _0.5 /BiOCl _0.5 Br _0.5 prepared in Example 1 was tested by XRD, and compared with the XRD patterns of Ag-AgCl _0.5 Br _0.5 and BiOCl _0.5 Br _0.5 , the results are shown in Figure 1. It can be seen from the figure that the diffraction peaks of Ag-AgCl _0.5 Br _0.5 /BiOCl _0.5 Br _0.5 prepared in Example 1 correspond to crystal planes 102 and 200, which are BiOCl _0.5 Br _0.5 monomer catalysts, and the diffraction peaks that appear correspond to crystal planes 200, 200, 220 and 111 are Ag-AgCl _0.5 Br _0.5 monomer catalysts, and the crystal planes of the XRD pattern diffraction peaks of the composite catalyst contain crystal planes of two monomer diffraction peaks at the same time, indicating that Ag-AgCl _0.5 Br _0.5 /BiOCl _0.5 has been successfully prepared Br _0.5 composite photocatalyst.

Fig. 2 is the TEM spectrum of the Ag-AgCl _0.5 Br _0.5 /BiOCl _0.5 Br _0.5 composite solid solution photocatalyst prepared in Example 1. It can be drawn from the figure that the crystal distance of the BiOCl _0.5 Br _0.5 crystal plane (102) is 0.277nm, the crystal distance of the Ag-AgCl _0.5 Br _0.5 crystal plane (220) is 0.194nm, and the Ag-AgCl _0.5 Br _0.5 crystal plane (200 ) is 0.272nm, and the Ag ⁰ crystal plane (111) is 0.230nm. The TEM electron microscope projection image of Ag-AgCl _0.5 Br _0.5 /BiOCl _0.5 Br _0.5 contains crystal planes of BiOCl _0.5 Br _0.5 , Ag-AgCl _0.5 Br _0.5 , and Ag ⁰ at the same time, indicating that Ag-AgCl _0.5 Br _0.5 / BiOCl _0.5 Br _0.5 complex catalyst.

In addition, the bandgap energies of Ag-AgCl _0.5 Br _0.5 /BiOCl _0.5 Br _0.5 , BiOCl _0.5 Br _0.5 and Ag-AgCl _0.5 Br _0.5 are 2.90eV and 2.62eV respectively, while Ag-AgCl _0.5 Br _0.5 /BiOCl _0.5 Br _0.5 composite The bandgap energy of the bulk is 2.71eV.

Ag-AgCl _0.5 Br _0.5 /BiOCl _0.5 Br _0.5 and Ag-AgCl _0.5 Br _0.5 , BiOCl _0.5 Br _0.5 prepared in Example 1 were subjected to a test experiment of visible light catalytic degradation of acrylamide. The photocatalytic activity test is characterized by oxidizing and removing oilfield acrylamide under visible light. A 500W xenon lamp is used as the light source, and visible light in the range of 420-780nm is obtained after passing through a filter. The absorbance after catalytic oxidation was measured with a UV-Vis spectrophotometer (model UV-1600PC), and the sampling volume was 2 mL. The obtained experimental results are shown in Fig. 3. It can be seen that the Ag-AgCl _0.5 Br _0.5 /BiOCl _0.5 Br _0.5 composite photocatalyst has significantly better degradation effect on acrylamide than Ag-AgCl _0.5 Br _0.5 and BiOCl _0.5 Br _0.5 . The removal rate of acrylamide at 4h was 34.8% for BiOCl _0.5 Br _0.5 , 36.9% for Ag-AgCl _0.5 Br _0.5 , and 40.1% for Ag-AgCl _0.5 Br _0.5 /BiOCl _0.5 Br _0.5 composite photocatalyst. The efficiency of Ag-AgCl _0.5 Br _0.5 /BiOCl _0.5 Br _0.5 composite solid solution photocatalyst to remove acrylamide under visible light is 1.2 times that of Ag-AgCl _0.5 Br _0.5 and BiOCl _0.5 Br _0.5 . It is further concluded that the catalytic activity of Ag-AgCl _0.5 Br _0.5 /BiOCl _0.5 Br _0.5 composite photocatalyst is higher than that of Ag-AgCl _0.5 Br _0.5 and BiOCl _0.5 Br _0.5 .

In summary, the present invention provides a method for preparing Ag-AgCl _0.5 Br _0.5 /BiOCl _0.5 Br _0.5 composite photocatalyst, the preparation method of the catalyst reduces the production cost and simplifies the production process. Compared with the existing Ag-AgCl _0.5 Br _0.5 and BiOCl _0.5 Br _0.5 solid solution photocatalysts, the catalyst has better performance, and can catalyze and oxidize acrylamide in fracturing flowback fluid under visible light.

The above description is only a preferred embodiment of the present invention, and does not limit the present invention in any form. Although the present invention has been disclosed as above with preferred embodiments, it is not intended to limit the present invention. Anyone familiar with this field Those skilled in the art, without departing from the scope of the technical solution of the present invention, can use the technical content disclosed above to make some changes or modify equivalent embodiments with equivalent changes, but all the content that does not depart from the technical solution of the present invention, according to the present invention Any simple modifications, equivalent changes and modifications made to the above embodiments by the technical essence still belong to the scope of the technical solutions of the present invention.

Claims (8)

1. a kind of preparation method of the Ag-Bi solid solution composite photocatalyst that is used to process oil field waste liquid, is characterized in that, comprises the steps: S1. Dissolving the bismuth-containing compound in ethylene glycol to obtain solution A; dissolving the bromine-containing compound and the chlorine-containing compound in an equimolar amount to the bismuth-containing compound in another part of ethylene glycol to obtain solution B; S2. Add solution B to solution A dropwise, mix evenly, then raise the temperature of the mixed solution to 140-180° C., and react at constant temperature for 14-18 hours to obtain BiOCl _0.5 Br _0.5 ; S3. Dissolve BiOCl _0.5 Br _0.5 in distilled water, then add a silver-containing compound, stir at room temperature for 20-100 min, the molar ratio of BiOCl _0.5 Br _0.5 to the silver-containing compound is 2:1, and obtain solution C; S4, another chlorine-containing compound and a bromine-containing compound are dissolved in distilled water to obtain a solution D, wherein the molar ratio of the chlorine-containing compound to the silver-containing compound is 1:1, and the molar ratio of the bromine-containing compound to the silver-containing compound is 0.5:1. D was added to solution C, stirred for 1-3 hours in the dark, centrifuged, and dried to obtain AgCl _0.5 Br _0.5 /BiOCl _0.5 Br _0.5 ; S5. Dissolving AgCl _0.5 Br _0.5 /BiOCl _0.5 Br _0.5 in distilled water, irradiating under full-wavelength xenon lamp for 0.5-2h, centrifuging and drying to obtain Ag-AgCl _0.5 Br _0.5 /BiOCl _0.5 Br _0.5 composite photocatalyst. 2. the preparation method of the Ag-Bi solid solution composite photocatalyst that is used to process oil field waste liquid as claimed in claim 1 is characterized in that, in solution A, the concentration of bismuth-containing compound is 0.07～0.2mol/L; Solution B In , the concentration of bromine-containing compounds and chlorine-containing compounds is the same, and the value range is 0.08-0.2mol/L. 3. the preparation method of the Ag-Bi solid solution composite photocatalyst that is used to process oil field waste liquid as claimed in claim 2 is characterized in that, described bismuth-containing compound is bismuth nitrate pentahydrate; Bromine-containing compound is potassium bromide or Sodium Bromide; Chlorine Compounds are Potassium Chloride or Sodium Chloride. 4. the preparation method of the Ag-Bi solid solution composite photocatalyst that is used to process oil field waste liquid as claimed in claim 1, is characterized in that, described step S2 is specifically: solution B is added dropwise in solution A, stirs After 20-100 min, the temperature of the mixture was raised to 160°C, and the reaction was carried out at a constant temperature for 16 hours. The product was washed with absolute ethanol and dried at 60-80°C for 5-24 hours to obtain BiOCl _0.5 Br _0.5 . 5. the preparation method of the Ag-Bi solid solution composite photocatalyst that is used to process oil field waste liquid as claimed in claim 4 is characterized in that, described step S3 is specifically: BiOCl _0.5 Br _0.5 is added in distilled water, stirs 30min to make It dissolves completely, then add silver-containing compound, stir at room temperature for 60min, the molar ratio of BiOCl _0.5 Br _0.5 to silver-containing compound is 2:1, and obtain solution C; in solution C, the concentration of BiOCl _0.5 Br _0.5 is 0.04-0.1mol/L , the concentration of the silver-containing compound is 0.02-0.05mol/L. 6. The preparation method of Ag-Bi solid solution composite photocatalyst for treating oilfield waste liquid as claimed in claim 5, characterized in that, in step S4, the concentration of chlorine-containing compounds in solution D is 0.02～0.05mol/L ; The concentration of bromine-containing compounds is 0.01-0.025mol/L; the drying temperature is 50-70°C, and the drying time is 8-16h. 7. The preparation method of Ag-Bi solid solution composite photocatalyst for treating oil field waste liquid as claimed in claim 1, characterized in that, the step S5 is specifically: adding 0.2-0.5g of AgCl _0.5 Br _0.5 /BiOCl _0.5 Br _0.5 was dissolved in 20-50mL of distilled water, irradiated under full-wavelength xenon lamp for 0.5-2h, centrifuged, and then dried at 50-70°C for 8-16h to obtain Ag-AgCl _0.5 Br _0.5 /BiOCl _0.5 Br _0.5 composite photocatalyst. 8. The preparation method of the composite photocatalyst according to any one of claims 1-7, characterized in that the prepared Ag-AgCl _0.5 Br _0.5 /BiOCl _0.5 Br _0.5 composite photocatalyst is used to catalyze oxidation fracturing under visible light Acrylamide in the drain.