A method for preparing Ag / Bi2O3 photocatalyst and application of the photocatalyst in degrading new pollutants in water

Abstract

The present invention provides a method for preparing an Ag / Bi2O3 photocatalyst and its application in degrading new pollutants in water, comprising dissolving bismuth nitrate and silver nitrate in a mixed solution of dimethylformamide and water, stirring, adding trimesic acid, and mixing evenly, transferring the mixture to an autoclave for reaction at 150°C for 2 hours, washing, drying, and collecting the silver-based-bismuth-based precursor, grinding it, and placing it in a muffle furnace for calcination at 350°C for 2 hours to obtain an Ag / Bi2O3 photocatalyst. The benzoic acid substance used in the present invention contains C=O lone pairs of electrons that can compete with Bi(III) to generate holes for coordination, thereby improving the mobility of photogenerated electrons, and has low calcination and low energy consumption. The photocatalyst of the present invention can efficiently remove pollutants from sewage and sterilize and disinfect under dark and light conditions, and can be coupled with sulfate oxidation to synergistically remove organic pollutants in water.

Description

Technical Field

[0001] The present invention belongs to a water treatment material used as a photocatalyst, and in particular relates to the preparation and application of a bimetallic composite photocatalyst. Background Art

[0002] 17α-Ethinylestradiol (EE2) is considered a common, synthetic EDC with strong estrogenic activity and stable chemical properties. It seriously interferes with the endocrine system of organisms, such as neural development, reproduction and immune system. EE2 is enriched through the food chain and endangers the entire ecosystem. As a bismuth-based semiconductor with visible light excitation as a photocatalyst, simple binary bismuth oxide Bi2O3 has the characteristics of strong visible light response (Eg = 2.1-2.91 eV), good photochemical stability and unique electronic band structure. However, the low charge mobility of Bi2O3 and the easy recombination of photogenerated electrons and holes limit its application [see: S.Ashwini, SCPrashantha, Ramachandra Naik, et al.Journal of Science: Advanced Materials and Devices, 4(2019): 531-537; J.Divya, NJShivaramu, E.Coetsee, et al.Journal of Alloys and Compounds, 842(2020): 155641.]. Silver nanoparticles can establish an alternating internal electric field near metal nanoparticles through the surface plasmon resonance (SPR) effect, reducing electron and hole recombination and improving charge mobility, thereby fully utilizing visible light [see: Keliang Wu, Pengcheng Wu, Zhenyu Li, et al. Jom, 74(2022): 4441-4448; Fengting He, Shuaijun Wang, Hongfei Zhao, et al. Applied Surface Science, 2019, 485: 70-80.]. Muhammad Saeed, Atta ul Haq, Majid Muneer, et al. Physica Scripta, 96(2021):125707. Bismuth chloride was used to prepare a bismuth-based precursor, which was then calcined at high temperature to obtain Bi2O3. The Bi2O3 was then added to an ammonia solution containing silver nitrate, followed by glucose, to produce Ag-Bi2O3 via a silver mirror reaction. The calcination temperature required was 500°C and the time was 3 hours. This method achieved a photocatalytic degradation rate of 92% for the pollutant crystal violet in 120 minutes. In this method, Bi2O3 lacks C=O lone pairs that can compete with Bi(III) for holes. Holes are the main factor in increasing the charge mobility of photogenerated electrons under photocatalytic conditions and fully utilizing visible light. Furthermore, the preparation process requires two high-temperature calcinations, which consumes a lot of energy.

[0003] Sulfate-based advanced oxidation processes (S-AOPs) involve activating persulfate and peroxymonosulfate anions to produce SO4 with a higher oxidation potential. - (2.5-3.1eV). In special cases, SO4· - By reacting with organic compounds with aromatic π electrons or unsaturated bonds, electron transfer occurs. Aromatic π electrons are richer than ·OH, making SO4· - Has higher selectivity. In addition, SO4· - It has advantages such as a longer service life (40μs) and a wider pH range (2-8). However, the sulfate generation rate in persulfate is not high, and whether it is possible to use photocatalytic technology to activate persulfate and construct a persulfate-coupled advanced oxidation system to efficiently degrade organic pollutants in water has not yet been studied. Summary of the Invention

[0004] The purpose of the present invention is to prepare an Ag / Bi2O3 composite material photocatalytic water treatment agent by a hydrothermal-calcination method, and to construct a coupled advanced oxidation system by coupling with persulfate, so as to achieve effective removal of new organic pollutants EDCs while taking into account broad-spectrum antibacterial properties.

[0005] To achieve the above purpose, the specific approach of the present invention is:

[0006] The synthesis method of the Ag / Bi2O3 composite photocatalyst disclosed in the present invention comprises the following specific steps:

[0007] (1) Preparation method of silver / bismuth oxide composite photocatalyst

[0008] The following steps are involved:

[0009] (1) Dissolving bismuth nitrate and silver nitrate in a mixed solution of dimethylformamide and deionized water in 100 mL and stirring magnetically at room temperature for 30 min; the dimethylformamide and deionized water in the 100 mL mixed solution are in a volume ratio of 1:1;

[0010] (2) 36 mmol of trimesic acid was added to the above solution, and the mixture was stirred for 1 h before being transferred to a reaction kettle. The mixture was placed in an oven and reacted at 150°C for 2 h to obtain a brown solid, which was then washed and dried to obtain a silver-bismuth-based precursor.

[0011] (3) Grind the silver-based-bismuth-based precursor, place the precursor powder in a muffle furnace, and calcine it at 350°C for 2 hours to obtain a gray-blue solid, which is a silver / bismuth oxide composite photocatalyst. The structure of the composite photocatalyst is a nanosheet with small pores and Ag nanoparticles loaded on the surface of Bi2O3.

[0012] Preferably, the total dosage of silver nitrate and bismuth nitrate in step (1) is 6 mmol.

[0013] (2) Application of silver / bismuth oxide composite photocatalyst

[0014] The silver / bismuth oxide composite photocatalyst removes new pollutants and harmful microorganisms in sewage.

[0015] Preferably, the silver / bismuth oxide composite photocatalyst efficiently and quickly removes the new pollutant EE2 in water.

[0016] Preferably, the silver / bismuth oxide composite photocatalyst efficiently removes Escherichia coli and Staphylococcus aureus in darkness and light.

[0017] (3) Application of silver / bismuth oxide composite photocatalyst

[0018] The silver / bismuth oxide composite photocatalyst of the present invention is coupled with sulfate advanced oxidation to synergistically remove new pollutants in water, wherein the persulfate is one of sodium persulfate, ammonium persulfate and potassium persulfate.

[0019] Preferably, the persulfate is sodium persulfate, and the dosage is 0.1-0.5 g / L.

[0020] The above organic pollutants E2 is 17β-estradiol; BPA is bisphenol A, E1 is estrone; RhB is rhodamine B; MO is methyl orange; MB is methylene blue; GR is Congo red; EE2 is 17α-ethynyl estradiol.

[0021] The beneficial effects and improvements of the present invention are:

[0022] (1) The catalyst prepared by the present invention adopts solvent thermal-calcination method

[0023] The catalyst preparation method of the present invention uses bismuth nitrate and silver nitrate as raw materials, dimethylformamide as a reducing solvent, and a benzoic acid-based substance as an additive to synthesize a silver-containing bismuth-based precursor through a one-step solvothermal reaction. The benzoic acid-based substance contains a C=O lone pair of electrons that can compete with Bi(III) for coordination. The reaction rate of the bismuth-based precursor can be controlled by regulating the ratio of Ag and Bi metal salts in water in the reaction system (the actual Bi / Ag ratios of the Ag / Bi2O3 composite photocatalyst are 5:1, 4:2, 3:3, 2:4, and 1:5, as shown in Examples 1 and Examples 3-6).

[0024] This method shortens the solvent thermal reaction temperature and time, which are 150° C. and 12 h respectively, and the precursor calcination temperature and time are 350° C. and 2 h, and the energy consumption required for the reaction is low.

[0025] The XRD pattern of the Ag / Bi2O3 composite photocatalyst synthesized by the present invention (such as Figure 1 ) Characteristic diffraction peaks of Ag and Bi2O3 can be observed, and no other impurity peaks are observed;

[0026] SEM and TEM images of the Ag / Bi2O3 composite photocatalyst synthesized by the present invention ( Figure 2 (cd), Figure 3 ) It can be observed that the surface of the small-pore nanosheet Bi2O3 is loaded with a layer of Ag nanoparticles to form a porous nanosheet composite material Ag / Bi2O3.

[0027] (2) The Ag / Bi2O3 of the present invention can efficiently and rapidly photocatalytically degrade EE2 in water.

[0028] For an initial concentration of 3 mg / L EE2, the dosage of the photocatalyst is 25 mg / L. After 40 minutes of visible light irradiation, the degradation rate of EE2 can reach 99.88%, and the degradation efficiency is 0.0177 min -1 , which is 6.81 times that of Bi2O3.

[0029] (III) Ag / Bi2O3 activated persulfate photocatalytic degradation of EE2 in water

[0030] Under the conditions of an initial concentration of 3 mg / L EE2, a photocatalyst dosage of 25 mg / L, and an addition amount of 0.1 g / L of sodium persulfate, an EE2 degradation rate of 99.63% was achieved after 2 minutes of illumination, and the degradation rate was 1.8816 min -1 This photocatalytic reaction system, which activates persulfate, can achieve efficient and rapid degradation of EE2, further improving the photocatalytic performance of the material. Furthermore, this system also exhibits excellent degradation effects on rhodamine B (RhB), methyl orange (MO), methylene blue (MB), and Congo red (GR).

[0031] (IV) Evaluation of the cytotoxicity of materials and water before and after photocatalytic treatment by MTT test

[0032] First, according to the cell survival rate (%) = (OD 570 / Blank group OD 570 )×100% to evaluate cytotoxicity. 3 When 20 μL of 200 μg / mL Ag / Bi2O3 was added to the culture medium inoculated with Hela cells, the Hela cell survival rate was 85.60±2.8%, which was much higher than the cell survival rate (43.7±8.1%) in Bi2O3 culture medium under the same conditions.

[0033] Secondly, we conducted cytotoxicity experiments on water samples after photocatalytic treatment. For EE2 water samples treated for 2 and 5 minutes, the cell viability was 97.2±4.2% and 98.7±4.5%, respectively, which was much higher than the biological activity of EE2 solution (72.1±2.8%).

[0034] The above two experiments show that Ag / Bi2O3, as a water pollution remover, not only has low biological toxicity, but also has excellent detoxification performance. It can safely and efficiently reduce the toxic effects of pollutants on animals and plants in water bodies.

[0035] (5) The photocatalyst of the present invention has a removal rate of more than 99.99% for Escherichia coli or Staphylococcus aureus

[0036] According to the control antibacterial test, the invented Ag / Bi2O3 composite photocatalyst was added to a suspension containing Escherichia coli or Staphylococcus aureus. The removal rate of Escherichia coli and Staphylococcus aureus by the photocatalyst under dark and light conditions exceeded 99.99%, achieving efficient sterilization.

[0037] (VI) Comparison of the Ag / Bi2O3 photocatalyst prepared by the present invention with that recorded in the literature is shown in Table 1 below:

[0038]

[0039]

[0040] Literature description: [1] Min Ma, Shenglan Wu, Jie Liu, et al. ChemistrySelect, 6 (2021), 45: 12590-12603.; [2] Xinhe Liu, Yong Kang, Yi Wang, Chemical Physics Letters, 790 (2022): 139347.; [3] Phyu Phyu Tun, Junting Wang, Thinn Thinn Khaing, et al. Journal of Alloys and Compounds, 818 (2020): 152836.; [4] Muhammad Saeed, Atta ul Haq, Majid Muneer, et al. Physica Scripta, 96 (2021): 125707.

[0041] As shown in Table 1, the solvent thermal-calcination method used in the present invention to prepare the Ag / Bi2O3 photocatalyst has a simplified reaction system, shorter synthesis temperature and time, and reduced preparation cost; the photocatalyst of the present invention has excellent performance in catalysis, antibacterial, and detoxification of specific new pollutants, as well as pollutants of this spectrum and bacteria after coupling photocatalysis and S-AOPs, and is expected to become a green, safe, and multifunctional water treatment agent that can simultaneously remove organic pollutants and kill bacteria.

[0042] The present invention will be further described below with reference to the accompanying drawings and specific embodiments. BRIEF DESCRIPTION OF THE DRAWINGS

[0043] Figure 1 The X-ray diffraction (XRD) patterns of pure Bi2O3, Ag and the Ag / Bi2O3 composite photocatalyst prepared by the present invention.

[0044] Figure 2 This is a scanning electron microscope (SEM) image of the Ag / Bi2O3 composite photocatalyst prepared by the present invention; wherein, Figure 2 (a) is the scanning image of Ag; Figure 2 (b) is a scanning image of Bi2O3; Figure 2 (c) and Figure 2 (d) is the scanning image of Ag / Bi2O3.

[0045] Figure 3 This is a transmission electron microscope (TEM) image of the Ag / Bi2O3 composite photocatalyst prepared by the present invention; wherein, Figure 3 (a) and Figure 3 (b) TEM image of Ag / Bi2O3; Figure 3 (c) and Figure 3 (d) is the HRTEM image of Ag / Bi2O3.

[0046] Figure 4 This is the Ag / Bi2O3 energy spectrum prepared by the present invention; wherein, Figure 4 (a) is the energy spectrum of Ag / Bi2O3; Figure 4 (b) is the basic mapping image of Ag / Bi2O3; Figure 4 (ce) are the basic mapping images of Ag, Bi and O elements in Ag / Bi2O3 materials, respectively.

[0047] Figure 5 This is a comparison chart of the photocatalytic degradation of EE2 in water by the Ag / Bi2O3 composite photocatalyst prepared by the present invention. The vertical axis is the residual concentration fraction of EE2, and the horizontal axis is the reaction time (min). Figure 5 (a) Photodegradation of other typical new pollutants by Bi2O3 and Ag / Bi2O3; Figure 5(b) Photodegradation kinetics of EE2 by Bi2O3 and Ag / Bi2O3; Figure 5 (c) Photodegradation of BPA, RhB, MO and MB by Ag / Bi2O3 activated sodium persulfate.

[0048] Figure 6 The cytotoxicity test of Bi2O3 and Ag / Bi2O3 and their liquids before and after photocatalysis was conducted using the MTT method. Figure 6 (a) Cell viability of HeLa cells at various concentrations of Ag / Bi2O3 and Bi2O3 (0-200 μg / mL); Figure 6 (b) shows the growth of Hela cells in EE2 solution, EE2 solution treated with the Ag / Bi2O3 composite photocatalyst prepared in the present invention, and pure water (blank control).

[0049] Figure 7 This is a diagram showing the removal effect of the Ag / Bi2O3 composite photocatalyst prepared by the present invention on Escherichia coli.

[0050] Figure 8 This is a diagram showing the removal effect of Staphylococcus aureus by the Ag / Bi2O3 composite photocatalyst prepared by the present invention. DETAILED DESCRIPTION

[0051] Example 1

[0052] (1) Dissolve 4 mmol of bismuth nitrate and 2 mmol of silver nitrate in 100 mL of a 1:1 mixture of dimethylformamide and deionized water and stir magnetically at room temperature for 30 min.

[0053] (2) 36 mmol of trimesic acid was added to the above solution, and the mixture was stirred for 1 h before being transferred to a reactor. The mixture was placed in an oven and reacted at 150°C for 12 h. After the reaction was completed, a brown solid was obtained, which was the silver-bismuth-based precursor.

[0054] (3) The solid was washed three times with deionized water and three times with anhydrous ethanol, centrifuged, and dried at 60°C. The dried precursor solid was taken out and ground using an agate mortar to obtain a dry bismuth-based precursor powder. The precursor powder was placed in a muffle furnace and calcined at 350°C for 2 h to obtain a gray-blue solid, which was the Ag / Bi2O3 composite photocatalyst.

[0055] 25 mg of the Ag / Bi2O3 composite photocatalyst was added to 50 mL of a 3 mg / L EE2 solution. After a 30-minute dark reaction, the system was subjected to photocatalytic degradation under visible light (500W xenon lamp with a 420nm filter). After 30 minutes of visible light irradiation, the degradation rate of EE2 reached 99.88%. Furthermore, 0.1 g / L of sodium persulfate was added after the dark reaction and the persulfate was activated under visible light under 500W xenon lamp irradiation, enhancing the photocatalytic activity. This system achieved a 99.63% degradation rate of EE2 after 2 minutes of photocatalysis.

[0056] Example 2

[0057] (1) Dissolve 4 mmol of bismuth nitrate and 2 mmol of silver nitrate in 100 mL of dimethylformamide and stir magnetically at room temperature for 30 min.

[0058] (2) 36 mmol of trimesic acid was added to the above solution, and the mixture was stirred for 1 h before being transferred to a reactor. The mixture was placed in an oven and reacted at 150°C for 12 h. After the reaction was completed, a brown solid was obtained, which was the silver-bismuth-based precursor.

[0059] (3) washing the solid with deionized water and anhydrous ethanol three times each, centrifuging and drying at 60°C; taking out the dried precursor solid and grinding it with an agate mortar to obtain a dry bismuth-based precursor powder; placing the precursor powder in a muffle furnace, placing the silver-based-bismuth-based precursor powder in step (3) in a crucible, and covering the crucible with a lid, calcining the crucible at 350°C for 2 hours in the muffle furnace to obtain a gray solid, which is the Ag / Bi2O3 composite photocatalyst. The crucible can not only promote the complete calcination of the precursor and improve the mass transfer rate of the material, but also prevent the oxidation of Ag to generate silver oxide during the calcination process, and form a porous structure during the calcination process, which affects the catalytic performance.

[0060] 25 mg of Ag / Bi2O3 composite photocatalyst was added to 50 mL of a 3 mg / L EE2 solution. After a 30-minute dark reaction, the system was subjected to photocatalytic degradation under visible light (500W xenon lamp with 420nm filter). After 30 minutes of visible light irradiation, the degradation rate of EE2 reached 93.24%. Furthermore, 0.1 g / L of sodium persulfate was added after the dark reaction, and the persulfate was activated by visible light under 500W xenon lamp irradiation to enhance the photocatalytic activity. This system achieved a 97.13% degradation rate of EE2 after 2 minutes of photocatalysis.

[0061] Example 3

[0062] (1) Dissolve 5 mmol of bismuth nitrate and 1 mmol of silver nitrate in 100 mL of a mixed solution of water and dimethylformamide (volume ratio of 1:1) and stir magnetically at room temperature for 30 min.

[0063] (2) 36 mmol of trimesic acid was added to the above solution, and the mixture was stirred for 1 h before being transferred to a reactor. The mixture was placed in an oven and reacted at 150°C for 12 h. After the reaction was completed, a brown solid was obtained, which was the silver-bismuth-based precursor.

[0064] (3) The solid was washed three times with deionized water and three times with anhydrous ethanol, centrifuged, and dried at 60°C. The dried precursor solid was taken out and ground using an agate mortar to obtain a dry bismuth-based precursor powder. The precursor powder was placed in a muffle furnace and calcined at 350°C for 2 h to obtain a gray solid, which was the Ag / Bi2O3 composite photocatalyst.

[0065] 25 mg of the Ag / Bi2O3 composite photocatalyst was added to 50 mL of a 3 mg / L EE2 solution. After a 30-minute dark reaction, the system was subjected to photocatalytic degradation under visible light (500W xenon lamp with a 420nm filter). After 30 minutes of visible light irradiation, the degradation rate of EE2 reached 93.05%. Furthermore, 0.1 g / L of sodium persulfate was added after the dark reaction, and the persulfate was activated by visible light under 500W xenon lamp irradiation to enhance the photocatalytic activity. This system achieved a 98.52% degradation rate of EE2 after 2 minutes of photocatalysis.

[0066] Example 4

[0067] (1) Dissolve 3 mmol of bismuth nitrate and 3 mmol of silver nitrate in 100 mL of a mixed solution of water and dimethylformamide (volume ratio of 1:1) and stir magnetically at room temperature for 30 min.

[0068] (2) 36 mmol of trimesic acid was added to the above solution, and the mixture was stirred for 1 h before being transferred to a reactor. The mixture was placed in an oven and reacted at 150°C for 12 h. After the reaction was completed, a brown solid was obtained, which was the silver-bismuth-based precursor.

[0069] (3) The solid was washed three times with deionized water and three times with anhydrous ethanol, centrifuged, and dried at 60°C. The dried precursor solid was taken out and ground using an agate mortar to obtain a dry bismuth-based precursor powder. The precursor powder was placed in a muffle furnace and calcined at 350°C for 2 h to obtain a gray solid, which was the Ag / Bi2O3 composite photocatalyst.

[0070] 25 mg of Ag / Bi2O3 composite photocatalyst was added to 50 mL of a 3 mg / L EE2 solution. After a 30-minute dark reaction, the system was subjected to photocatalytic degradation under visible light (500W xenon lamp with 420nm filter). After 30 minutes of visible light irradiation, the degradation rate of EE2 reached 89.17%. Furthermore, 0.1 g / L of sodium persulfate was added after the dark reaction and the persulfate was activated under visible light under 500W xenon lamp irradiation, enhancing the photocatalytic activity. This system achieved a 95.53% degradation rate of EE2 after 2 minutes of photocatalysis.

[0071] Example 5

[0072] (1) Dissolve 5 mmol of bismuth nitrate and 1 mmol of silver nitrate in 100 mL of a mixed solution of water and dimethylformamide (volume ratio of 1:1) and stir magnetically at room temperature for 30 min.

[0073] (2) 36 mmol of trimesic acid was added to the above solution, and the mixture was stirred for 1 h before being transferred to a reactor. The mixture was placed in an oven and reacted at 150°C for 12 h. After the reaction was completed, a brown solid was obtained, which was the silver-bismuth-based precursor.

[0074] (3) The solid was washed three times with deionized water and three times with anhydrous ethanol, centrifuged, and dried at 60°C. The dried precursor solid was taken out and ground using an agate mortar to obtain a dry bismuth-based precursor powder. The precursor powder was placed in a muffle furnace and calcined at 350°C for 2 h to obtain a gray solid, which was the Ag / Bi2O3 composite photocatalyst.

[0075] 25 mg of Ag / Bi2O3 composite photocatalyst was added to 50 mL of a 3 mg / L EE2 solution. After a 30-minute dark reaction, the system was subjected to photocatalytic degradation under visible light (500W xenon lamp with 420nm filter). After 30 minutes of visible light irradiation, the degradation rate of EE2 reached 84.75%. Furthermore, 0.1 g / L of sodium persulfate was added after the dark reaction and the persulfate was activated under visible light under 500W xenon lamp irradiation, enhancing the photocatalytic activity. This system achieved a 94.14% degradation rate of EE2 after 2 minutes of photocatalysis.

[0076] Example 6

[0077] (1) Dissolve 5 mmol of bismuth nitrate and 1 mmol of silver nitrate in 100 mL of a mixed solution of water and dimethylformamide (volume ratio of 1:1) and stir magnetically at room temperature for 30 min.

[0078] (2) 36 mmol of trimesic acid was added to the above solution, and the mixture was stirred for 1 h before being transferred to a reactor. The mixture was placed in an oven and reacted at 150°C for 12 h. After the reaction was completed, a brown solid was obtained, which was the silver-bismuth-based precursor.

[0079] (3) The solid was washed three times with deionized water and three times with anhydrous ethanol, centrifuged, and dried at 60°C. The dried precursor solid was taken out and ground using an agate mortar to obtain a dry bismuth-based precursor powder. The precursor powder was placed in a muffle furnace and calcined at 350°C for 2 h to obtain a gray solid, which was the Ag / Bi2O3 composite photocatalyst.

[0080] 25 mg of the Ag / Bi2O3 composite photocatalyst was added to 50 mL of a 3 mg / L EE2 solution. After a 30-minute dark reaction, the system was subjected to photocatalytic degradation under visible light (500W xenon lamp with a 420nm filter). After 30 minutes of visible light irradiation, the degradation rate of EE2 reached 73.59%. Furthermore, 0.1 g / L of sodium persulfate was added after the dark reaction, and the persulfate was activated by visible light under 500W xenon lamp irradiation to enhance the photocatalytic activity. This system achieved an EE2 degradation rate of 89.18% after 2 minutes of photocatalysis.

[0081] Example 7

[0082] (1) Dissolve 4 mmol of bismuth nitrate and 2 mmol of silver nitrate in 100 mL of a mixed solution of water and dimethylformamide (volume ratio of 1:1) and stir magnetically at room temperature for 30 min.

[0083] (2) 36 mmol of trimesic acid was added to the above solution, and the mixture was stirred for 1 h before being transferred to a reactor. The mixture was placed in an oven and reacted at 90°C for 12 h. After the reaction was completed, a brown solid was obtained, which was the silver-bismuth-based precursor.

[0084] (3) The solid was washed three times with deionized water and three times with anhydrous ethanol, centrifuged, and dried at 60°C. The dried precursor solid was taken out and ground using an agate mortar to obtain a dry bismuth-based precursor powder. The precursor powder was placed in a muffle furnace and calcined at 350°C for 2 h to obtain a light blue solid, which was the Ag / Bi2O3 composite photocatalyst.

[0085] 25 mg of the Ag / Bi2O3 composite photocatalyst was added to 50 mL of a 3 mg / L EE2 solution. After a 30-minute dark reaction, the system was subjected to photocatalytic degradation under visible light (500W xenon lamp with a 420 nm filter). After 30 minutes of visible light irradiation, the degradation rate of EE2 reached 92.19%. Furthermore, 0.1 g / L of sodium persulfate was added after the dark reaction to activate the persulfate with visible light, enhancing the photocatalytic activity. This system achieved a 95.73% degradation rate of EE2 after 2 minutes of photocatalysis.

[0086] The main technical features of Examples 1 to 7 and the EE2 degradation rates of the two systems are summarized as follows:

[0087]

[0088] Example 8:

[0089] Under visible light irradiation conditions, as in Example 1, the obtained Ag / Bi2O3 composite photocatalyst was used to photocatalytically degrade the organic pollutant EE2 in water. During the photocatalytic process, a 300W xenon lamp was used as the light source, and a filter (λ>420nm) was used to filter the ultraviolet light; the initial concentration of EE2 was 3mg / L, the dosage of the photocatalyst was 25mg, and the dark reaction was carried out for 30 minutes to achieve adsorption equilibrium, after which the light source was turned on to irradiate the sample. The Ag / Bi2O3 composite photocatalyst synthesized by the present invention was compared with the photocatalytic degradation of EE2. Figure 4 As shown in the figure, the Ag / Bi2O3 composite photocatalyst prepared by the present invention exhibits excellent photocatalytic activity against the pollutant EE2. After 40 minutes of visible light irradiation, the degradation rate of EE2 can reach 99.88%, and the degradation efficiency is 0.0177min -1 , which is 6.81 times that of Bi2O3. It can achieve efficient and rapid degradation of target pollutants.

[0090] Example 9:

[0091] Adding an appropriate amount of persulfate to the above-mentioned photocatalytic reaction can achieve efficient and rapid degradation of target pollutants. Figure 4 As shown in Figure 2, when the addition amount of sodium persulfate is 0.1 g / L, the visible light activated persulfate system can achieve an EE2 degradation rate of 99.63% after 2 minutes of illumination, and the degradation rate is 1.8816 min -1 In addition, the system still has a good degradation effect on rhodamine B (RhB), methyl orange (MO), methylene blue (MB) and Congo red (GR).

[0092] Example 10:

[0093] The cytotoxicity of the materials and water before and after photocatalytic treatment was evaluated by MTT test, specifically:

[0094] 8×10 3 Hela cells were seeded on a 96-well plate containing 10% PBS and 100 CFU / mL penicillin in DMEM / glucose medium and incubated at 37°C and 5% CO2 for 24 hours. When the cells can be spread as a single layer on the bottom of the 96-well flat-bottom plate, the culture medium is replaced with 0.1 mL of fresh culture medium containing various concentrations of photocatalytic materials (0-200 μg / mL) or EE2 (un)degraded water, and incubated for 24 hours. The supernatant was removed, 50 μL of 1 mg / mL thiazolyl blue (MTT) solution was added, and the plate was incubated at 37°C and 5% CO2 for 3 hours. The supernatant culture medium was removed, 50 μL of DMSO solution was added, and the plate was gently shaken for 10-30 minutes. The absorbance (OD value) of each well at 570 nm was detected using a multifunctional microplate reader to evaluate cytotoxicity. Cell survival rate (%) = (OD value of experimental group) 570 / Blank group OD 570 )×100%. Figure 6 As shown in (a), when the culture medium contained 200 μg / mL Ag / Bi2O3, the HeLa cell viability was 85.60±2.8%, which was much higher than the cell viability (43.7±8.1%) in Bi2O3 culture medium under the same conditions. This indicates that the Ag / Bi2O3 sample is non-toxic and safe.

[0095] Example 11:

[0096] Cytotoxicity tests were conducted on water samples after photocatalytic treatment, and the results are as follows: Figure 6 (b) EE2 exhibited surprisingly low toxicity in water after 2 and 5 minutes of photocatalytic treatment, with cell viabilities of 97.2±4.2% and 98.7±4.5%, respectively. This activity was significantly higher than the biological activity of the EE2 solution (72.1±2.8%). This demonstrates the strong detoxification capacity of Ag / Bi2O3 for EE2 water.

[0097] Example 12:

[0098] The photocatalysts were evaluated by removing Escherichia coli and Staphylococcus aureus under dark and light conditions. Specifically:

[0099] Introduce the bacteria containing Escherichia coli or Staphylococcus aureus into fresh LB medium and shake and culture at 37℃ until the OD value of the bacterial solution is 600 =0.5 for the experiment. 180 μL Ag / Bi2O3 material was mixed with 20 μL bacterial suspension (10 7CFU / mL) were mixed to make the final material concentration 500μg / mL. Incubate in the dark for 30 minutes, and some samples were irradiated with white light for 5min to compare the antibacterial properties of the materials under dark and light conditions. 100μL of bacterial solution diluted with PBS was spread on LB agar plates, and the number of colonies was recorded by plate counting method after incubation at 37°C for 24h. All bacterial activity experiments were carried out in 3 replicates. A blank control group without material was used for control antibacterial test. The antibacterial effect of the Ag / Bi2O3 composite photocatalyst synthesized by the present invention is as follows: Figure 7 and Figure 8 As shown, the photocatalyst of the present invention has a removal rate of more than 99.99% for Escherichia coli and Staphylococcus aureus under both dark and light conditions.

Claims

1. A method for preparing an Ag / Bi2O3 photocatalyst, comprising the following steps: (1) Dissolve 5-1 mmol of bismuth nitrate and 1-5 mmol of silver nitrate in 100 mL of a mixed solution of dimethylformamide and deionized water, and stir magnetically at room temperature for 30 min; the dimethylformamide and deionized water in the 100 mL mixed solution are composed of a volume ratio of 1:1; (2) Add 36 mmol of trimesic acid to the above solution, continue stirring for 1 h, then transfer to a reactor and place in an oven at 150 °C for 2 h to obtain a brown solid, which is then washed, dried, and the silver-bismuth-based precursor is collected; (3) Grind the silver-based-bismuth-based precursor and place the precursor powder in a muffle furnace and calcine it at 350 °C for 2 h. The gray-blue solid obtained is the Ag / Bi2O3 composite photocatalyst, which has a structure of nanosheets with small pores and Ag nanoparticles loaded on the surface of Bi2O3.

2. The method for preparing the Ag / Bi2O3 photocatalyst according to claim 1, wherein: Bismuth nitrate and silver nitrate were dissolved in a mixed solution of 100 mL of dimethylformamide and deionized water at a total dosage of 6 mmol, wherein the dimethylformamide and deionized water were prepared in a volume ratio of 1:

1.

3. Use of the Ag / Bi2O3 photocatalyst obtained by the method according to claim 1 or 2, characterized in that: The silver / bismuth oxide composite photocatalyst removes pollutants E2, BPA, E1, RhB, MO, MB, GR and EE2 in sewage.

4. The use of the Ag / Bi2O3 photocatalyst according to claim 3, characterized in that: The silver / bismuth oxide composite photocatalyst removes the pollutant EE2 in water and achieves a disinfection effect.

5. The use of the Ag / Bi2O3 photocatalyst according to claim 4, characterized in that: The silver / bismuth oxide composite photocatalyst removes Escherichia coli and Staphylococcus aureus in the dark and light conditions.

6. Use of the Ag / Bi2O3 photocatalyst prepared by the method according to claim 1 or 2, characterized in that: The silver / bismuth oxide composite photocatalyst is coupled with the persulfate advanced oxidation to synergistically remove the pollutant EE2 in water, and the persulfate is one of sodium persulfate, ammonium persulfate, and potassium persulfate.

7. The use of the Ag / Bi2O3 photocatalyst according to claim 6, characterized in that: The persulfate is sodium persulfate, and the dosage is 0.1-0.5 g / L.

Images