Preparation method of silver and oxygen vacancy modified bismuth oxybromide photocatalyst for removing antibiotics

Abstract

The invention relates to a preparation method of a silver and oxygen vacancy modified bismuth oxybromide photocatalyst for removing antibiotics. Aiming at the problems that the treatment difficulty of antibiotic pollution in industrial wastewater is relatively high, the photocatalytic activity of bismuth oxybromide is not high and the like, a proper amount of silver ions and polyvinylpyrrolidone are introduced to obtain the high-activity bismuth oxybromide photocatalyst. The bismuth oxybromide photocatalyst which has excellent photocatalytic antibiotic removal activity and is synergistically modified by silver and oxygen vacancies is successfully prepared by optimizing the technological process. Silver ions are introduced to adjust the energy band structure of the material, and polyvinylpyrrolidone can be used as a surfactant to regulate the particle size of the material, so that the catalytic performance and stability of the material are improved. The preparation method is simple and convenient to operate and low in cost, the activity of the prepared photocatalyst is obviously improved, and harmless treatment of antibiotics in industrial wastewater can be realized.

Description

Technical Field

[0001] The invention relates to a method for preparing a silver and oxygen vacancy modified bismuth oxybromide photocatalyst for removing antibiotics, and belongs to the technical field of semiconductor photocatalysis preparation. Background Art

[0002] With the vigorous development of modern industry, the proper treatment of industrial wastewater has become a thorny problem in the field of environmental protection today. Among them, organic antibiotic pollution is extremely prominent. Due to its wide use in many fields such as medical treatment and animal husbandry, a large number of incompletely metabolized antibiotics are discharged with wastewater. They are both biologically toxic and difficult to degrade naturally. They are easy to accumulate in water bodies and soil, posing a potential threat to the ecological environment and human health. Traditional wastewater treatment methods, such as biodegradation, physical adsorption and chemical precipitation, generally have many limitations in the treatment of organic antibiotics, such as high treatment costs, low efficiency, and easy to cause secondary pollution. It is often difficult to effectively remove these organic antibiotics. Therefore, it is urgent to seek efficient, green and sustainable wastewater treatment technologies.

[0003] In recent years, semiconductor photocatalysis technology has attracted much attention as a green and sustainable environmental purification technology. It is driven by solar energy and can deeply mineralize organic pollutants under mild conditions. Among many semiconductor photocatalysts, bismuth oxybromide has shown application potential in the field of photocatalysis due to its unique layered structure and suitable bandgap width. However, pure bismuth oxybromide has certain limitations. Its photogenerated carrier recombination rate is fast and its photocatalytic efficiency is low, which cannot meet the actual needs of industrial wastewater treatment.

[0004] The study found that silver doping has unique advantages in adjusting the band structure of materials. The redox potential of silver ions is appropriate. When doped into the bismuth oxybromide lattice, it can not only adjust the band structure to broaden the light absorption range, but also promote the rearrangement of the electron cloud, reduce the low energy of the conduction band, and narrow the band gap, laying a solid foundation for improving the performance of photocatalysts. At the same time, polyvinyl pyrrolidone, as a surfactant, can regulate the morphology and particle size of the material, expose more active crystal faces, and improve the dispersion and stability of the photocatalyst.

[0005] Based on this, the present invention provides a method for preparing a bismuth oxybromide modified microsphere photocatalyst synergistically modified with silver and oxygen vacancies. This material can fully absorb visible light during photocatalytic removal of organic antibiotics, and efficiently decompose organic antibiotic molecules under mild conditions. Thanks to the modification of silver and polyvinyl pyrrolidone, its microsphere structure has a large specific surface area, strong ability to adsorb pollutants, and provides abundant active sites. By optimizing the process flow and overcoming the deficiencies of the prior art, the preparation method is simple, low-cost, and easy to mass-produce and apply, and has broad application prospects in actual industrial wastewater treatment antibiotic scenarios. Summary of the invention

[0006] Problem to be solved

[0007] In view of the problems existing in existing bismuth oxybromide photocatalysts, such as the low photocatalytic activity, the present invention introduces silver ions and polyvinyl pyrrolidone to coordinate oxygen vacancies, effectively improves the structure of bismuth oxybromide microspheres, and significantly improves their photocatalytic activity in removing pollutants.

[0008] Furthermore, the present invention also provides a method for preparing a silver and oxygen vacancy modified bismuth oxybromide photocatalyst for removing antibiotics. The preparation method has a convenient process, and the raw materials are easy to obtain, which is conducive to large-scale production.

[0009] In order to achieve the above object, the technical solution adopted by the present invention is:

[0010] [1] First, a 0.1 mol / L bismuth nitrate pentahydrate solution was prepared, that is, 4 mmol of bismuth nitrate pentahydrate was dissolved in a mixed solution of 20 mL of ethylene glycol and 20 mL of deionized water, and a certain amount of silver acetate monohydrate was added thereto, and the molar ratio of silver ion to bismuth ion was 0.5%, 1%, 2%, 3%, 4% and 5%, respectively, to obtain a solution S1;

[0011] [2] Secondly, a 0.1 mol / L hexadecyltrimethylammonium bromide solution was prepared, that is, 4 mmol of hexadecyltrimethylammonium bromide was dissolved in a mixed solution of 20 mL of ethylene glycol and 20 mL of deionized water to obtain a solution S2;

[0012] [3] Subsequently, solutions S1 and S2 were placed on a magnetic stirrer and stirred continuously for 30 min until they were uniformly dissolved, and then solution S2 was slowly added to solution S1 to form a transparent mixed solution. Then, 6.95 mmol of polyvinyl pyrrolidone was added to the mixed solution under vigorous stirring and continued to stir for 30 min to form a uniform mixed solution S3;

[0013] [4] Finally, the solution S3 was transferred to a 100 mL polytetrafluoroethylene-lined stainless steel autoclave and maintained at 160°C for 12 h. After cooling naturally to room temperature, the product was centrifuged and washed several times with deionized water and anhydrous ethanol, then dried at 80°C for 10 h, and the dried sample was ground in a mortar to obtain the final product, the antibiotic-removed silver and oxygen vacancy-modified bismuth oxybromide photocatalytic composite powder.

[0014] [5] A silver and oxygen vacancy modified bismuth oxybromide photocatalyst product for removing antibiotics, characterized in that the silver and oxygen vacancy modified bismuth oxybromide photocatalyst product for removing antibiotics prepared by the preparation method described in [1-4] above has high photocatalytic properties. Effects of the Invention

[0015] First, the present invention adds silver acetate monohydrate to bismuth oxybromide, which can effectively improve the problem of low photocatalytic efficiency of pure bismuth oxybromide, and the specific effects are as follows:

[0016] (1) By Figure 1 Comparison of the X-ray diffraction results of Example 1 and Comparative Example 1 shows that the addition of silver ions can weaken the characteristic diffraction peak intensity of Vo-BiOBr to a certain extent, confirming that the addition of silver acetate monohydrate can assist in the construction of oxygen vacancies.

[0017] (2) The addition of silver ions can improve the photocatalytic removal ability of photocatalysts for antibiotics in industrial wastewater, making it more efficient in decomposing organic antibiotics under mild conditions and reducing treatment time and cost.

[0018] (3) Through Figure 3 Comparison of the removal test efficiency results of Example 1 and Comparative Examples 1-6 confirms that doping a certain amount of silver can significantly improve the photocatalytic efficiency of the catalyst, confirming the above theoretical basis.

[0019] (4) Through Figure 4 The solid ultraviolet band gap spectrum shows that silver ions have a suitable redox potential. Doping them into the bismuth oxybromide lattice can adjust its band structure, broaden the light absorption range, and improve the efficiency of the photocatalytic reaction.

[0020] In addition, polyvinyl pyrrolidone is added to the bismuth oxybromide modified microsphere photocatalyst of the present invention, and the specific effects are as follows:

[0021] (1) Polyvinyl pyrrolidone is a commonly used surfactant. During preparation, it can inhibit the growth direction of low-activity crystal faces through selective adsorption, promote the exposure of more high-activity crystal faces, thereby increasing the surface oxygen vacancy density, making the structure of the photocatalyst more suitable, increasing the contact opportunity with pollutants, and improving the photocatalytic performance. When treating organic antibiotics in industrial wastewater, it has stronger adsorption and photocatalytic removal capabilities for pollutants.

[0022] (2) Adding polyvinyl pyrrolidone can improve the stability of the photocatalyst, so that it can maintain good photocatalytic performance during long-term use, and to a certain extent reduce the problem of decreased treatment effect caused by attenuation of photocatalyst performance.

[0023] Finally, the present invention effectively improves the activity of silver-doped bismuth oxybromide microsphere photocatalyst in removing pollutants by controlling the appropriate heating rate and setting the appropriate reaction and drying temperature and time. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] Figure 1 The X-ray diffraction patterns of Example 1 and Comparative Examples 1-6 of the present invention are shown in FIG.

[0025] Figure 2This is a transmission electron micrograph of the silver and oxygen vacancy modified bismuth oxybromide photocatalyst for removing antibiotics prepared in Example 1 of the present invention.

[0026] Figure 3 It is a performance diagram of removing tetracycline by Example 1 of the present invention and Comparative Examples 1-6.

[0027] Figure 4 The solid ultraviolet images of Example 1 of the present invention and Comparative Examples 1-6 are shown.

[0028] Figure 5 The solid ultraviolet band gap diagram of Example 1 of the present invention and Comparative Examples 1-6. DETAILED DESCRIPTION

[0029] The content of the present invention will be described in detail. The description of the technical features described below is based on representative embodiments of the present invention, but the present invention is not limited to these embodiments. Example

[0030] The embodiments of the present invention will be described in detail below in conjunction with the examples, but those skilled in the art will appreciate that the following examples are only used to illustrate the present invention and should not be considered to limit the scope of the present invention. If no specific conditions are specified in the examples, they are carried out according to conventional conditions or conditions recommended by the manufacturer. If the manufacturer of the reagents or instruments used is not specified, they are all conventional products that can be obtained commercially.

[0031] The performance testing methods of Example 1 and Comparative Examples 1-6 of the present invention are as follows:

[0032] Photocatalytic performance and removal rate: The photocatalytic performance of the bismuth oxybromide composite powder was tested using a liquid ultraviolet tester, and the removal rate was calculated according to a pseudo-first-order kinetic model. Example 1

[0033] The method for removing antibiotic silver and oxygen vacancy modified bismuth oxybromide photocatalyst described in Example 1 comprises the following steps:

[0034] First, a 0.1 mol / L bismuth nitrate pentahydrate solution was prepared, that is, 4 mmol of bismuth nitrate pentahydrate was dissolved in a mixed solution of 20 mL of ethylene glycol and 20 mL of deionized water, and a certain amount of silver acetate monohydrate was added thereto, and the molar ratio of silver ions to bismuth ions was 4%, to obtain a solution S1;

[0035] Secondly, a hexadecyltrimethylammonium bromide solution with a concentration of 0.1 mol / L is prepared, that is, 4 mmol of hexadecyltrimethylammonium bromide is dissolved in a mixed solution of 20 mL of ethylene glycol and 20 mL of deionized water to obtain a solution S2;

[0036] Subsequently, solutions S1 and S2 were placed on a magnetic stirrer and stirred continuously for 30 min until uniformly dissolved, and then solution S2 was slowly added to solution S1 to form a transparent mixed solution. Then, 6.95 mmol of polyvinyl pyrrolidone was added to the mixed solution under vigorous stirring and continued to stir for 30 min to form a uniform mixed solution S3;

[0037] Finally, solution S3 was transferred to a 100 mL polytetrafluoroethylene-lined stainless steel autoclave and maintained at 160°C for 12 h. After cooling naturally to room temperature, the product was centrifuged and washed several times with deionized water and anhydrous ethanol, then dried at 80°C for 10 h, and the dried sample was ground in a mortar to obtain the final product, a composite powder of antibiotic-removed silver and oxygen vacancy-modified bismuth oxybromide.

[0038] The silver and oxygen vacancy modified bismuth oxybromide photocatalyst product for removing antibiotics was tested. For 10 mg / L tetracycline, the removal rate was 76.60% when the LED illumination time was 60 minutes. Comparative Example 1

[0039] Comparative Example 1 does not add polyvinyl pyrrolidone, and the preparation method of the silver and oxygen vacancy modified bismuth oxybromide photocatalyst for removing antibiotics comprises the following steps:

[0040] First, a 0.1 mol / L bismuth nitrate pentahydrate solution was prepared, that is, 4 mmol of bismuth nitrate pentahydrate was dissolved in a mixed solution of 20 mL of ethylene glycol and 20 mL of deionized water, and a certain amount of silver acetate monohydrate was added thereto, and the molar ratio of silver ions to bismuth ions was 4%, to obtain a solution S1;

[0041] Secondly, a hexadecyltrimethylammonium bromide solution with a concentration of 0.1 mol / L is prepared, that is, 4 mmol of hexadecyltrimethylammonium bromide is dissolved in a mixed solution of 20 mL of ethylene glycol and 20 mL of deionized water to obtain a solution S2;

[0042] Subsequently, solutions S1 and S2 were placed on a magnetic stirrer and stirred continuously for 30 min to be uniformly dissolved, and then solution S2 was slowly added to solution S1 to form a transparent mixed solution S3;

[0043] Finally, solution S3 was transferred to a 100 mL polytetrafluoroethylene-lined stainless steel autoclave and maintained at 160°C for 12 h. After cooling naturally to room temperature, the product was centrifuged and washed several times with deionized water and anhydrous ethanol, then dried at 80°C for 10 h, and the dried sample was ground in a mortar to obtain the final product, the antibiotic-free silver and oxygen vacancy-modified bismuth oxybromide complex powder.

[0044] The silver and oxygen vacancy modified bismuth oxybromide photocatalyst product for removing antibiotics was tested. For 10 mg / L of tetracycline, the removal rate was 42.44% when the LED illumination time was 60 minutes. Comparative Example 2

[0045] Comparative Example 2 does not add polyvinyl pyrrolidone and silver acetate monohydrate, and the method for preparing bismuth oxybromide monomer photocatalyst includes the following steps:

[0046] First, a bismuth nitrate pentahydrate solution with a concentration of 0.1 mol / L was prepared, that is, 4 mmol of bismuth nitrate pentahydrate was dissolved in a mixed solution of 20 mL of ethylene glycol and 20 mL of deionized water to obtain a solution S1;

[0047] Secondly, a hexadecyltrimethylammonium bromide solution with a concentration of 0.1 mol / L is prepared, that is, 4 mmol of hexadecyltrimethylammonium bromide is dissolved in a mixed solution of 20 mL of ethylene glycol and 20 mL of deionized water to obtain a solution S2;

[0048] Subsequently, solutions S1 and S2 were placed on a magnetic stirrer and stirred continuously for 30 min to be uniformly dissolved, and then solution S2 was slowly added to solution S1 to form a transparent mixed solution S3;

[0049] Finally, solution S3 was transferred to a 100 mL polytetrafluoroethylene-lined stainless steel autoclave and maintained at 160 ° C for 12 h. After naturally cooling to room temperature, the product was centrifuged and washed several times with deionized water and anhydrous ethanol, then dried at 80 ° C for 10 h, and the dried sample was ground in a mortar to obtain the final product, bismuth oxybromide monomer photocatalytic powder.

[0050] The bismuth oxybromide monomer photocatalyst product was tested. For 10 mg / L of tetracycline, the removal rate was 51.95% when the LED illumination time was 60 minutes.

[0051] Since silver ions are not doped and polyvinyl pyrrolidone is not added to construct oxygen vacancies, the distance between the oxygen ion free radicals and the adsorbed pollutant molecules is far, which reduces the rate of the decomposition reaction. In addition, due to the lack of silver, the light absorption range is smaller and the catalytic efficiency is lower. Comparative Example 3, Example 4, Example 5, Example 6

[0052] Comparative Examples 3, 4, 5, and 6 change the doping amount of silver ions. The preparation method of the silver- and oxygen-vacancy-modified bismuth oxybromide photocatalyst for removing antibiotics is basically the same as the steps described in Example 1, except that the molar ratio of silver ions to bismuth ions is adjusted to 0.5%, 1%, 2%, and 5%, respectively.

[0053] Testing the photocatalytic activity of silver and oxygen vacancy modified bismuth oxybromide for the removal of antibiotics:

[0054] Comparative Example 3: For 10 mg / L tetracycline, when the LED illumination duration is 60 min, the removal rate is 67.27%.

[0055] Comparative Example 4: For 10 mg / L tetracycline, when the LED illumination duration is 60 min, the removal rate is 53.58%.

[0056] Comparative Example 5: For 10 mg / L tetracycline, when the LED illumination duration is 60 min, the removal rate is 52.43%.

[0057] Comparative Example 6: For 10 mg / L tetracycline, when the LED illumination duration is 60 min, the removal rate is 74.33%.

[0058] Doping with excessive silver ions reduces the photocatalytic removal efficiency because too many metallic silver ions form particles with large grain size, which reduces the specific surface area of ​​the material, causes an imbalance in the energy band structure, reduces the efficiency of light absorption, and makes it difficult for photogenerated holes to migrate to the surface of the material, affecting the catalytic activity.

[0059] It should be noted that, although the technical solution of the present invention is introduced with specific examples, those skilled in the art will appreciate that the present invention should not be limited thereto.

[0060] The embodiments of the present invention have been described above, and the above description is exemplary, not exhaustive, and is not limited to the disclosed embodiments. Many modifications and variations will be apparent to those of ordinary skill in the art without departing from the scope and spirit of the described embodiments. The selection of terms used herein is intended to best explain the principles of the embodiments, practical applications, or technical improvements in the market, or to enable other persons of ordinary skill in the art to understand the embodiments disclosed herein.

Claims

1. A method for preparing a silver and oxygen vacancy modified bismuth oxybromide photocatalyst for removing antibiotics, characterized in that: (1) Raw material preparation: weigh a certain amount of bismuth nitrate pentahydrate, hexadecyltrimethylammonium bromide, polyvinyl pyrrolidone, and silver acetate monohydrate; (2) Solution preparation: Mix equal proportions of silver acetate monohydrate, a certain amount of ethylene glycol and deionized water to obtain solution S1; (3) Stirring and dissolving: Add the weighed raw materials into solution S1 in sequence and stir until fully dissolved to obtain uniform solutions S2, S3, and S4; (4) Reaction process: The final solution S4 is transferred to a stainless steel autoclave for high temperature reaction for a period of time to obtain the product; (5) Centrifugal washing: The obtained product is centrifuged and washed several times with deionized water and anhydrous ethanol to obtain a precipitate; (6) Drying: Drying the precipitate at a suitable temperature for a period of time; (7) Grinding the finished product: Grinding the dried sample to obtain a final product, which is silver-doped bismuth oxybromide composite powder containing oxygen vacancies.

2. The method for preparing the silver and oxygen vacancy modified bismuth oxybromide photocatalyst for removing antibiotics according to claim 1, characterized in that: The raw materials and amounts of step (1) are: 4.00 mmol bismuth nitrate pentahydrate, 4.00 mmol hexadecyltrimethylammonium bromide, 6.95 mmol polyvinylpyrrolidone, and an equal proportion of silver acetate monohydrate.

3. According to the equal proportion of silver acetate monohydrate in claim 2, the molar ratios of silver acetate monohydrate and bismuth nitrate pentahydrate are 0.5%, 1%, 2%, 3%, 4% and 5% respectively.

4. The method for preparing the silver and oxygen vacancy modified bismuth oxybromide photocatalyst for removing antibiotics according to claim 1, characterized in that: The certain amount of ethylene glycol and deionized water in step (2) are both 20 mL.

5. The method for preparing the silver and oxygen vacancy modified bismuth oxybromide photocatalyst for removing antibiotics according to claim 1, characterized in that: The stirring and dissolving in step (3) is divided into three steps: In the first step, 4 mmol of bismuth nitrate pentahydrate was added to 40 mL of the mixed solution S1 and stirred continuously for 30 min to obtain a uniform solution S2; In the second step, 4.00 mmol of hexadecyltrimethylammonium bromide was added to 40 mL of the mixed solution S1 and stirred continuously for 30 min to obtain a uniform solution S3; In the third step, solution S3 was slowly added to solution S2, and 6.95 mmol polyvinyl pyrrolidone was added to the mixed solution of S2 and S3, and stirred vigorously for 30 min to form a transparent mixed solution S4.

6. The method for preparing the silver and oxygen vacancy modified bismuth oxybromide photocatalyst for removing antibiotics according to claim 1, characterized in that: The stainless steel autoclave in step (4) is lined with polytetrafluoroethylene, has a capacity of 100 mL, a reaction temperature of 160 °C, and a reaction time of 12 h.

7. The method for preparing the silver and oxygen vacancy modified bismuth oxybromide photocatalyst for removing antibiotics according to claim 1, characterized in that: The washing method in step (5) is to wash alternately with anhydrous ethanol and deionized water for 3 times to obtain a precipitate.

8. The method for preparing the silver and oxygen vacancy modified bismuth oxybromide photocatalyst for removing antibiotics according to claim 1, characterized in that: In step (7), more than 90% of the powder samples have a particle size of 150-250 mesh.

9. The method for preparing the silver and oxygen vacancy modified bismuth oxybromide photocatalyst for removing antibiotics according to claim 1, characterized in that: In step (7), more than 90% of the powder samples have a particle size of 150-250 mesh.

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