Magnetic bismuth-based visible light catalyst, preparation method and application

Abstract

The application belongs to the technical field of photocatalytic degradation, and relates to a magnetic bismuth-based visible light catalyst, a preparation method and application. The application prepares a magnetic bismuth-based photocatalyst Ni-NiO / Bi2O3 with a heterojunction structure through chemical nickel plating, physical combination and in-situ high-temperature decomposition. The photocatalytic material can mineralize antibiotics in wastewater into water and carbon dioxide under visible light irradiation, thereby eliminating the toxicity of pollutants from the source. Because the material itself has magnetism, it can be quickly separated and recovered with the aid of an external magnetic field, greatly reducing the risk of material residues in the water body after treatment. The photocatalytic reaction can be started directly by using sunlight without additional light source, thereby significantly reducing energy consumption cost; meanwhile, the material can be recycled and will not introduce secondary pollution, and has economic and environmental benefits.

Description

Technical Field

[0001] This invention belongs to the field of photocatalytic degradation technology, and relates to a magnetic bismuth-based visible light catalyst, its preparation method and application, and more specifically to a method for preparing a magnetic bismuth-based photocatalyst for efficiently degrading tetracycline antibiotics under visible light. Background Technology

[0002] Currently, photocatalysis technology has become a hot topic in antibiotic pollution control due to its advantages such as mild reaction conditions, utilization of solar energy, and thorough degradation. Its core principle is to utilize photogenerated electron-hole pairs produced by semiconductor materials (such as TiO2, ZnO, g-C3N4, etc.) under light irradiation, which generate •OH and •O2 through redox reactions. - Active free radicals are used to achieve the mineralization and decomposition of antibiotic molecules. For example, under ultraviolet light irradiation, the TiO2 photocatalytic system can increase the degradation rate of antibiotics such as levofloxacin and chloramphenicol to over 80%.

[0003] However, current mainstream semiconductor catalysts (such as TiO2 with a band gap of 3.2 eV) can only respond to ultraviolet light with wavelengths less than 387 nm (accounting for 5% of solar energy), while their utilization rates for visible light (400-760 nm), which accounts for 45%, and infrared light, which accounts for 49%, are extremely low. Although the photoresponse can be extended to the visible light region through elemental doping, defect engineering, and other means, the quantum efficiency of most catalysts is still below 10%. For example, although g-C3N4 can absorb visible light below 450 nm, its photogenerated electron-hole recombination rate is as high as 90% or more, which limits its actual degradation efficiency.

[0004] Furthermore, in practical applications, the safety of the catalyst itself is becoming increasingly apparent: nano-sized TiO2 is prone to agglomeration in water, forming aggregates with a particle size of 50-200 nm, which may be ingested and accumulated by aquatic organisms; some metal-doped catalysts (such as Ag / TiO2) release Ag under long-term light exposure. + The ions have an inhibitory effect on algae (EC50 = 0.8 mg / L). Summary of the Invention

[0005] In view of this, in order to overcome the limitations of single catalysts and prevent the pollution that catalysts may cause in practical applications, this invention discloses the preparation of a magnetic bismuth-based visible light catalyst. By constructing a heterojunction (Ni-NiO / Bi2O3), the light absorption capacity and carrier separation efficiency of the catalyst are significantly improved. Furthermore, by utilizing the inherent magnetism of the catalyst, after degradation, the catalyst is rapidly separated from the water body by an external magnetic field, thus preventing secondary pollution.

[0006] To achieve the above objectives, the present invention adopts the following technical solution:

[0007] The first technical objective of this invention is to provide a magnetic bismuth-based visible light photocatalyst, wherein the catalyst is a Ni-NiO / Bi2O3 heterojunction photocatalyst.

[0008] Furthermore, the catalyst uses micro / nano lignocellulose as its framework, with a Ni-NiO / Bi2O3 composite material on its surface, and has an overall hollow rod-like structure.

[0009] The second technical objective of this invention is to provide a method for preparing the magnetic bismuth-based visible light photocatalyst as described above. This method involves preparing a magnetic bismuth-based photocatalyst Ni-NiO / Bi2O3 with a heterojunction structure through chemical nickel plating, physical bonding, and in-situ high-temperature decomposition.

[0010] Metallized cellulose and basic bismuth nitrate were added to anhydrous ethanol, and the mixture was placed in a water bath until the ethanol was completely evaporated. The resulting grayish-white powder was then treated at high temperature.

[0011] Specifically, the preparation method of the magnetic bismuth-based visible light catalyst includes the following steps:

[0012] (1) Weigh out the lignocellulose, dissolve it in deionized water, and stir evenly until a uniform suspension is formed;

[0013] (2) The lignocellulose solution was subjected to ultrasonic treatment;

[0014] (3) Preparation of activating solution A, activating solution B, primary electroless plating solution C, and secondary electroless plating solution D.

[0015] The activation solution A is a mixture of concentrated hydrochloric acid and nickel sulfate, with a concentration of 0.7-0.9 mL / g;

[0016] The activation solution B is a mixture of sodium hydroxide and sodium borohydride, with a mass ratio of 0.7-0.9:0.9-1.1.

[0017] The primary chemical plating solution C is prepared by adding 300 mL of distilled water, 9.9 g of nickel sulfate, 9.0 g of sodium citrate, 8.4 g of sodium hypophosphite, and 9.0 mg of thiourea, and finally adding ammonia water to adjust the pH of the plating solution to 9.0. The solution is stirred until completely dissolved.

[0018] The secondary chemical plating solution D is prepared by adding 300 mL of distilled water, 9.9 g of nickel sulfate, 9.0 g of sodium citrate, 8.4 g of sodium hypophosphite, and 9.0 mg of thiourea, and finally adding ammonia water to adjust the pH of the plating solution to 9.0. The solution is stirred until completely dissolved.

[0019] (4) Take the ultrasonically treated micro / nano lignocellulose in step (2) as a sample, put it into activation solution A for activation, filter it and take it out, put it into activation solution B for activation, after successful activation, take out the sample, put the sample into the first chemical plating solution C for nickel plating, and then put it into the second chemical plating solution D for nickel plating. After the two nickel plating treatments, filter it twice, dry the sample, and sieve the dried sample twice to obtain metallized cellulose with uniform appearance and morphology, and save the sample.

[0020] (5) Take 0.1 g of metallized cellulose and add it to 50 mL of anhydrous ethanol with 10 mg, 20 mg, 30 mg, 40 mg and 50 mg of basic bismuth nitrate respectively. After stirring evenly, place it in a 99 ℃ water bath to allow the ethanol to evaporate completely and scrape off the grayish-white powder. Finally, place it in a resistance furnace for high-temperature treatment to obtain Ni-NiO / Bi2O3 magnetic rod-shaped hollow composite material.

[0021] Optionally, the ultrasonic treatment in step (2) is as follows: using an ultrasonic signal generator to disperse lignocellulose; the dispersion time is 180 min, the power is 960 W, the ultrasonic water bath temperature is 30-40 ℃, and the temperature setting is affected by the climate environment.

[0022] Furthermore, the amplitude transformer of the ultrasonic signal generator is placed at half the height of the solution, with the amplitude transformer located at the center of the solution and away from the temperature control sensor of the ultrasonic signal generator. During the ultrasonic water bath process, the container containing dissolved lignocellulose is placed in a device containing ice, and the ice is continuously replaced at a frequency of once every 15 minutes in summer and once every 30 minutes in winter. The temperature of the ultrasonic water bath is 35°C.

[0023] Optionally, the preparation of the metallized cellulose specifically includes: taking the ultrasonically treated micro / nano lignocellulose of step (2) as a sample, activating it in activation solution A for 15 min, stirring it evenly, stirring once every 2 min, filtering it twice with a double-layer filter, taking out the sample until no liquid drips, activating it in activation solution B for 90 s, stirring it evenly, stirring once every 30 s, filtering it twice with a double-layer filter, filtering the sample by rolling a snowball back and forth, taking out the sample after successful activation, when no activation liquid drips from the surface, placing the sample in a primary chemical plating solution C, plating it with nickel for 25-35 min under the conditions of pH=9-9.5 and temperature of 60℃, the specific chemical plating time depending on the laboratory conditions, and then placing it in a secondary chemical plating solution D for continuous chemical nickel plating, after the two nickel plating treatments, filtering it twice with a double-layer filter, drying the sample, filtering the dried sample twice with a double-layer filter, shaking the filter evenly to obtain metallized cellulose with uniform appearance, and storing the sample.

[0024] Optionally, in step (3), the concentration of the activation solution A is 0.8 mL / g; the mass ratio of sodium hydroxide to sodium borohydride in the activation solution B is 0.8:1; and the mass ratio of nickel sulfate, sodium citrate, sodium hypophosphite, and thiourea in the primary electroless plating solution C is 9.9:9:8.4:0.01.

[0025] The pH value of the primary electroless plating solution C is 9-9.5. Before adjusting the pH of the primary electroless plating solution C and the secondary electroless plating solution D, the pH value is measured with a pH meter. The normal range is 5.2-5.8. If the pH is not within the range of 5.2-5.8, the plating solution should be re-prepared or the pH meter should be calibrated. The pH meter should be calibrated first with deionized water and then with an alkaline solution with pH=9.15. After calibration, the pH meter should be rinsed with clean water, and the pH value of the solution should be readjusted to be within the normal range. Then, the pH value of the plating solution should be adjusted to 9-9.5 with ammonia. The final pH value of the plating solution is determined based on the initial pH value of the prepared plating solution, and the pH value of the plating solution should be adjusted within the range of 9 to 9.5.

[0026] Optionally, the sign of successful activation in step (4) is that the sample surface turns black and bubbles are released between the gaps. If the sample does not show the sign of successful activation, the sample is immediately reactivated until the sign of successful activation appears.

[0027] Optionally, in step (5), a mechanical stirrer is used at a speed of 450 r / min to mix metallized cellulose, anhydrous ethanol and basic bismuth nitrate. The stirring time is 25-30 min, and the container is shaken every 2-5 min. Then, the well-stirred mixture is placed in a water bath at 99°C to react and obtain a grayish-white powder material.

[0028] Further, in step (5), the resistance furnace used in the high-temperature preparation process is model SX2-4-10N; the resistance furnace setting program is to heat up to 300℃-500℃, keep it at 3-5h and then cool it down to room temperature, preferably 400℃ for 4h, and then cool it down to room temperature, finally obtaining Ni-NiO / Bi2O3 magnetic rod hollow composite material.

[0029] It should be noted that this invention prepares a magnetic bismuth-based photocatalyst Ni-NiO / Bi2O3 with a heterojunction structure through chemical nickel plating, physical bonding, and in-situ high-temperature decomposition. Under visible light irradiation, this photocatalytic material can mineralize antibiotics in wastewater into water and carbon dioxide, eliminating pollutant toxicity at the source. Because the material itself is magnetic, it can be rapidly separated and recovered using an external magnetic field, greatly reducing the risk of residual material in the treated water. It requires no additional light source for excitation; the photocatalytic reaction can be initiated directly using sunlight, significantly reducing energy costs. Furthermore, the material is recyclable and does not introduce secondary pollution, thus offering both economic and environmental benefits.

[0030] The third technical objective of this invention is to provide an application of the magnetic bismuth-based visible light catalyst described above in the degradation of antibiotics.

[0031] Furthermore, the magnetic bismuth-based visible light catalyst is used in the degradation of tetracycline antibiotics.

[0032] Specifically, the magnetic bismuth-based visible light catalyst achieved degradation rates of up to 85.89% and 62.5% for 50 mL of tetracycline hydrochloride solution and oxytetracycline hydrochloride solution with a concentration of 100 mg / L, respectively, over 60 min.

[0033] Compared with the prior art, the beneficial effects of the present invention are:

[0034] 1. Hollow magnetic materials are prepared by selecting natural materials such as sand willow and wood, or various biomass wastes, and using micro / nano lignocellulose extracted from them as a framework. The raw materials used in this invention are readily available, making full use of natural resources and waste materials; the preparation process is simple and efficient, requiring no complex equipment or processes, and has strong operability and promotional value.

[0035] 2. By employing two electroless nickel plating processes, metallized cellulose and basic bismuth nitrate are prepared at high temperature in an electric resistance furnace according to a specific mass ratio, thus obtaining a photocatalyst with excellent magnetic rod-shaped hollow structure.

[0036] 3. During the high-temperature preparation process, basic bismuth nitrate decomposition and nickel oxidation are simultaneously achieved, realizing the one-step formation of Ni-NiO / Bi2O3 heterojunction structure, which has responsive performance under visible light;

[0037] 4. The magnetic bismuth-based photocatalyst prepared by the method of the present invention can rapidly and efficiently degrade high concentrations of antibiotics (tetracycline hydrochloride and oxytetracycline hydrochloride) under visible light. It can achieve degradation rates of up to 85.89% and 62.5% for 50 mL of tetracycline hydrochloride solution and oxytetracycline hydrochloride solution with a concentration of 100 mg / L, respectively, in just 60 min.

[0038] 5. The unique cavity structure of magnetic rod-shaped hollow materials provides an ideal physical space for antibiotic adsorption. This structural characteristic lays a solid theoretical foundation for developing materials that integrate adsorption and photocatalysis functions and utilize visible light to degrade antibiotics.

[0039] 6. After the magnetic bismuth-based photocatalyst has been used, it can be quickly separated and recovered from the solution using an external magnetic field. This recovery method is efficient and convenient, avoiding the risk of secondary pollution caused by catalyst residue in the water, and ensuring the safety and cleanliness of the aquatic environment. Attached Figure Description

[0040] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on the provided drawings without creative effort.

[0041] Figure 1 This is a schematic diagram of the composite material preparation process of the present invention;

[0042] Figure 2 SEM and EDS images of the magnetic bismuth-based photocatalyst; where: Figure 2 a, Figure 2 b is a SEM image of the magnetic bismuth-based photocatalyst. Figure 2 c. Figure 2 d is the EDS diagram of the magnetic bismuth-based photocatalyst;

[0043] Figure 3 The image shows the XRD pattern of a magnetic bismuth-based photocatalyst.

[0044] Figure 4 XPS images of magnetic bismuth-based photocatalysts; where: Figure 4 a is the XPS full spectrum of the magnetic bismuth-based photocatalyst. Figure 4 b、 Figure 4 c. Figure 4 d is the fine XPS spectrum of the magnetic bismuth-based photocatalyst;

[0045] Figure 5 Isothermal adsorption curves of magnetic bismuth-based photocatalysts;

[0046] Figure 6 This is a pore size distribution diagram of a magnetic bismuth-based photocatalyst.

[0047] Figure 7 The magnetic bismuth-based photocatalyst and its UV-Vis diffuse reflectance absorption spectrum;

[0048] Figure 8 The band gap spectrum of a magnetic bismuth-based photocatalyst;

[0049] Figure 9 Electrochemical impedance spectroscopy for magnetic bismuth-based photocatalysts;

[0050] Figure 10 Transient photocurrent plot of magnetic bismuth-based photocatalyst;

[0051] Figure 11 The fluorescence spectrum of the magnetic bismuth-based photocatalyst is shown.

[0052] Figure 12 a is a line graph of tetracycline hydrochloride degradation time-concentration. Figure 12b is a bar chart showing the degradation concentration-degradation amount of tetracycline hydrochloride; Figure 12 c is a line graph of oxytetracycline hydrochloride degradation time versus concentration; Figure 12 d is a bar chart showing the degradation concentration of oxytetracycline hydrochloride versus the amount of degradation.

[0053] Figure 13 A schematic diagram of the mechanism of tetracycline hydrochloride degradation by a magnetic bismuth-based photocatalyst;

[0054] Figure 14 A schematic diagram of the mechanism of degradation of oxytetracycline hydrochloride by a magnetic bismuth-based photocatalyst;

[0055] Figure 15 Toxicity analysis diagram of intermediate products for the degradation of tetracycline hydrochloride and oxytetracycline hydrochloride by magnetic bismuth-based photocatalyst; Figure 15 a, Figure 15 b, Figure 15 c is a toxicity analysis diagram of intermediate products from three pathways for the degradation of tetracycline hydrochloride by magnetic bismuth-based photocatalysts. Figure 15 d, Figure 15 e, Figure 15 f is a toxicity analysis diagram of intermediate products in the three pathways for the degradation of oxytetracycline hydrochloride by magnetic bismuth-based photocatalysts. Detailed Implementation

[0056] The technical solutions in the embodiments of the present invention will be clearly and completely described below. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of the present invention.

[0057] The term "embodiment" used herein, as an example, is not necessarily to be construed as superior to or better than other embodiments. Performance testing in the embodiments of this application, unless otherwise specified, employs conventional testing methods in the art. It should be understood that the terminology used in this application is merely for describing particular implementations and is not intended to limit the scope of this disclosure.

[0058] Unless otherwise stated, the technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application pertains; other experimental methods and technical means not specifically mentioned herein refer to experimental methods and technical means commonly used by one of ordinary skill in the art.

[0059] To better illustrate the content of this application, numerous specific details are provided in the following detailed embodiments. Those skilled in the art should understand that this application can be implemented even without certain specific details. In the embodiments, some methods, means, instruments, and devices well-known to those skilled in the art are not described in detail in order to highlight the main points of this application.

[0060] Without conflict, the technical features disclosed in the embodiments of this application can be combined arbitrarily, and the resulting technical solution belongs to the content disclosed in the embodiments of this application.

[0061] To better understand the present invention, the following embodiments are provided for further detailed description of the present invention, but they should not be construed as limiting the present invention. Any non-essential improvements and adjustments made by those skilled in the art based on the above-described invention are also considered to fall within the protection scope of the present invention.

[0062] In this invention, the lignocellulose type is a conventional type.

[0063] Examples 1-5

[0064] This embodiment provides a method for preparing a photocatalyst for the efficient degradation of tetracycline antibiotics under visible light. The catalyst has a micro / nano lignocellulose as the framework, a Ni-NiO / Bi2O3 composite material on the surface, and an overall hollow rod-shaped structure.

[0065] Includes the following steps:

[0066] (1) Weigh 0.6g of lignocellulose, dissolve it in 200 mL of deionized water, and stir evenly until a uniform suspension is formed;

[0067] (2) Disperse lignocellulose using an ultrasonic signal generator; the dispersion time is 180 min, the power is 960 W, the ultrasonic water bath temperature is 40 ℃, and the temperature setting is affected by the climate environment; the amplitude rod of the ultrasonic signal generator is placed at half the height of the solution, the amplitude rod is located at the center of the solution, and the amplitude rod is far away from the temperature control sensor of the ultrasonic signal generator; during the ultrasonic water bath, the container containing dissolved lignocellulose is placed in a device containing ice, and the ice is replaced continuously during the process. The ice replacement frequency is: once every 15 min in summer and once every 30 min in winter; the ultrasonic water bath temperature is 35 ℃.

[0068] (3) Prepare activation solution A, activation solution B, primary chemical plating solution C, and secondary chemical plating solution D. The activation solution A is a mixture of concentrated hydrochloric acid and nickel sulfate with a concentration of 0.9 mL / g.

[0069] The activation solution B is a mixture of sodium hydroxide and sodium borohydride in a mass ratio of 0.9:1.1.

[0070] The primary chemical plating solution C is prepared by adding 300 mL of distilled water, 9.9 g of nickel sulfate, 9.0 g of sodium citrate, 8.4 g of sodium hypophosphite, and 9.0 mg of thiourea, and finally adding ammonia water to adjust the pH of the plating solution to 9.0. The solution is stirred until completely dissolved.

[0071] The secondary chemical plating solution D is prepared by adding 300 mL of distilled water, 9.9 g of nickel sulfate, 9.0 g of sodium citrate, 8.4 g of sodium hypophosphite, and 9.0 mg of thiourea, and finally adding ammonia water to adjust the pH of the plating solution to 9.0. The solution is stirred until completely dissolved.

[0072] (4) Take the micro / nano lignocellulose prepared in step (2) as a sample, put it into activation solution A for 15 min, stir evenly, stir once every 2 min, filter twice with double-layer filter screen, take out the sample until no liquid drips, put it into activation solution B for activating for 90 s, stir evenly, stir once every 30 s, filter twice with double-layer filter screen, filter out the sample by rolling a snowball back and forth, take out the sample after successful activation, when no activation liquid drips on the surface, put the sample into the first chemical plating solution C, and plate nickel for 25-35 min under the conditions of pH=9-9.5 and temperature of 60℃. The specific chemical plating time depends on the laboratory conditions. Then put it into the second chemical plating solution D for continuous chemical plating. After the two nickel plating treatments, filter twice with double-layer filter screen, dry the sample, filter twice with double-layer filter screen after drying, shake the filter screen evenly to obtain metallized cellulose with uniform appearance and morphology, and save the sample.

[0073] The signs of successful activation are: the sample surface turns black and bubbles are released from the gaps. If the sample does not show signs of successful activation, it should be reactivated immediately until the signs of successful activation appear.

[0074] (5) The metallized cellulose prepared in step (4) and basic bismuth nitrate were arranged in the following mass ratios: 10:1, 10:2, 10:3, 10:4, and 10:5, respectively, as in Examples 1-5. That is, 0.1 g of metallized cellulose was added to 50 mL of anhydrous ethanol with 10 mg, 20 mg, 30 mg, 40 mg, and 50 mg of basic bismuth nitrate, respectively. The mixture of metallized cellulose, ethanol, and basic bismuth nitrate was stirred for 25-30 min using a mechanical stirrer at a speed of 450 r / min. The container was shaken every 2-5 min. The mixed solution was then placed in a water bath at 99°C to react and obtain a grayish-white powder material. Finally, it was placed in a resistance furnace for high-temperature treatment. The model number was SX2-4-10N. The resistance furnace was set to heat to 300°C, hold at 300°C for 4 h, and then cool to room temperature to obtain Ni-NiO / Bi2O3 magnetic rod-shaped hollow composite material.

[0075] In this embodiment, the pH value of the primary electroless plating solution C is 9-9.5. Before adjusting the pH of the primary electroless plating solution C and the secondary electroless plating solution D, the pH value is measured with an acidity meter. The normal range is 5.2-5.8. If the pH is not within the range of 5.2-5.8, the plating solution is reconfigured or the acidity meter is calibrated. The acidity meter is calibrated first with deionized water and then with an alkaline solution of pH=9.15. After calibration, the acidity meter is rinsed with clean water, and the pH value of the solution is readjusted to be within the normal range. Then, the pH value of the plating solution is adjusted to 9-9.5 with ammonia. The final acidity value of the plating solution is determined based on the initial pH value of the plating solution. The pH value of the plating solution is adjusted within the range of 9 to 9.5.

[0076] Examples 6-9

[0077] Based on catalytic effects, such as Figure 12 As shown, under visible light, the magnetic bismuth-based photocatalyst can efficiently and rapidly degrade tetracycline hydrochloride and oxytetracycline hydrochloride solutions. Furthermore, when the amount of basic bismuth nitrate added is 40 mg, the degradation effect on high concentrations of tetracycline hydrochloride and oxytetracycline hydrochloride solutions is even better, with degradation rates as high as 85.89% and 62.5% for 100 mg / L tetracycline hydrochloride and oxytetracycline hydrochloride solutions, respectively. Therefore, the optimal dosage of basic bismuth nitrate added in Examples 1-5 is determined to be 40 mg. Based on this, the high-temperature preparation temperature was changed, with 300 °C set to 350 °C, 400 °C, 450 °C, and 500 °C respectively, while other conditions remained unchanged, resulting in Examples 6-9.

[0078] To further demonstrate the beneficial effects of the present invention and to better understand it, the following experiments are conducted to further clarify the technical features disclosed in the present invention, but these should not be construed as limiting the invention. Other improvements made by those skilled in the art based on the above description of the invention, without inventive effort, are also considered to fall within the protection scope of the present invention.

[0079] Effect Experiment

[0080] Visible light degrades antibiotics (targeting tetracycline hydrochloride and oxytetracycline hydrochloride).

[0081] Antibiotic solution preparation

[0082] Preparation of tetracycline hydrochloride solution: Weigh 100 mg of tetracycline hydrochloride, put it into a 1 L volumetric flask, add distilled water to make up to volume, shake well, and a 100 mg / L tetracycline hydrochloride solution can be prepared.

[0083] Preparation of oxytetracycline hydrochloride solution: Weigh 100 mg of oxytetracycline hydrochloride, put it into a 1 L volumetric flask, add distilled water to make up to volume, shake well, and you can prepare a 100 mg / L oxytetracycline hydrochloride solution.

[0084] Photocatalysis experiment

[0085] Multiple groups of 50 mg magnetic bismuth-based photocatalysts were placed in 50 mL of tetracycline hydrochloride solution and oxytetracycline hydrochloride solution with concentrations of 100 mg / L, respectively, and reacted in a photocatalytic reaction apparatus for 1 h. After the experiment, the photocatalysts were recovered using an external magnetic field. The concentration of the solution after the photocatalytic reaction was measured using an ultraviolet absorption spectrophotometer. The catalytic amount and catalytic rate were calculated using formulas.

[0086] (1)

[0087] - Catalytic efficiency, c0 - initial concentration, c1 - concentration after photocatalysis

[0088] (2)

[0089] β represents the catalytic amount, c0 is the initial concentration, c1 is the concentration after photocatalysis, V represents the solution volume, and m0 represents the mass of the catalyst.

[0090] The photocatalytic reaction apparatus in the photocatalysis experiment used a 300W xenon lamp as the visible light source; the ultraviolet spectrophotometer was model L9.

[0091] Tests and experiments have shown that, as Figure 1 The diagram shows a schematic of the preparation process for a magnetic bismuth-based photocatalyst.

[0092] like Figure 2 As shown, Figure 2 a, Figure 2 b is a SEM image of the magnetic bismuth-based photocatalyst. Figure 2 c. Figure 2 d is the EDS image of the magnetic bismuth-based photocatalyst. The cross-section and side surface of the magnetic bismuth-based photocatalyst exhibit regular morphology, and Ni, Bi and O elements are uniformly distributed on the sample surface with roughly the same element content. It also forms a hollow rod-like structure, which proves that it has been successfully prepared.

[0093] like Figure 3 and Figure 4 , Figure 6 , Figure 7 , Figure 8 , Figure 9 , Figure 10 and Figure 11 As shown, Figure 4 a is the XPS full spectrum of the magnetic bismuth-based photocatalyst. Figure 4 b、 Figure 4 c. Figure 4Image d shows the fine XPS spectrum of the magnetic bismuth-based photocatalyst. XPS, XRD, UV-Vis, and electrochemical performance analyses revealed that the prepared photocatalyst contains Ni, NiO, and Bi₂O₃, and a heterojunction structure was successfully formed.

[0094] like Figure 5 As shown, the magnetic bismuth-based photocatalyst forms a large number of micro / nanoporous structures. The hollow rod-like structure and the large number of micro / nanopores provide the photocatalyst with strong adsorption performance, which helps to improve the photocatalytic performance.

[0095] like Figure 6 and Figure 7 As shown, the magnetic bismuth-based photocatalyst exhibits strong absorption of both ultraviolet and visible light, enabling it to catalyze under visible light; moreover, it has a small band gap of 1.81 eV.

[0096] like Figure 8 , Figure 9 , Figure 10 and Figure 11 As shown, the magnetic bismuth-based photocatalyst exhibits a strong transient photocurrent response, a relatively small Nyquist arc radius, and low fluorescence intensity. This demonstrates its low resistance, fast interfacial carrier migration rate, strong separation capability of photogenerated carriers, and excellent photocatalytic performance.

[0097] like Figure 12 As shown, under visible light, the magnetic bismuth-based photocatalyst can efficiently and rapidly degrade tetracycline hydrochloride and oxytetracycline hydrochloride solutions. When the amount of basic bismuth nitrate added is 40 mg, the degradation effect on high concentrations of tetracycline hydrochloride and oxytetracycline hydrochloride solutions is even better, with degradation rates of up to 85.89% and 62.5% for 100 mg / L tetracycline hydrochloride and oxytetracycline hydrochloride solutions, respectively.

[0098] like Figure 13 As shown, the main degradation products of tetracycline hydrochloride were analyzed using liquid chromatography-mass spectrometry (LC-MS), and a total of 14 possible intermediate products were detected. Three possible pathways for tetracycline degradation were proposed. (1) In •O2 - and h + Under the influence of , tetracycline molecules are converted into P1 (m / z = 477) and P4 (m / z = 461) through hydroxylation reaction (2) in •O2 - Under the oxidation of O2, tetracycline decomposes into P7 (m / z = 417) through the loss of methyl groups. (3) In O2 -Under the attack of the catalyst, P2 (m / z = 403), P5 (m / z = 459), and P8 (m / z = 373) are mainly generated through deamination. With increasing reaction time, intermediates P3, P6, and P9 (m / z = 352, 397, and 357) appear. Finally, the small molecule intermediates are degraded into water and carbon dioxide on the photocatalyst.

[0099] like Figure 14 As shown, the main degradation products of oxytetracycline hydrochloride were analyzed using liquid chromatography-mass spectrometry (LC-MS), and 19 possible intermediate products were detected. Three possible pathways for oxytetracycline degradation were proposed. OTC is converted to P1 (m / z = 446) via demethylation. P1 can be converted to P2 (m / z = 414) by removing N-methyl and hydroxyl groups. Subsequently, P2 is further decomposed into P3 (m / z = 371) via decarboxylamide. P4 (m / z = 353) can be generated from P3 via dehydration, while P5 (m / z = 338) is obtained from P4 via deamination. Subsequently, reactive oxygen species (•OH and •O−2) attack the double bond on P5, generating P6 (m / z = 312) and P7 (m / z = 302) through ring-opening reactions. In addition, P1 can be cleaved to form P8 (m / z = 358) by removing amide, N-methyl, carboxamide, and hydroxyl groups. Subsequently, P8 undergoes a ring-opening reaction to generate P9 (m / z=320), and P9 can be decomposed into P10 (m / z=246) through demethylation, dehydration, and decarboxylation reactions. Furthermore, OTC (m / z=462) is converted to P11 (m / z=364) through dehydroxylation, dehydration, deamidation, and N-methyl removal. The removal of P11 through hydrogenation and ring-opening reactions generates P12 (m / z=279). The removal of P12 through dehydration, hydrogenation, and ring-opening reactions generates P13 (m / z=233). P13 is then further oxidized to generate P14 (m / z=192), and the hydroxyl group loss of P15 (m / z=165) is formed from P14. Finally, some intermediates (P11, P12, and P13) decompose into small organic or inorganic molecules.

[0100] like Figure 15 As shown, we evaluated the aquatic toxicity of tetracycline hydrochloride, oxytetracycline hydrochloride, and intermediates using the ECOSAR procedure in the EPI suite software. Figure 15 a, Figure 15 b, Figure 15 c is a toxicity analysis diagram of intermediate products from three pathways for the degradation of tetracycline hydrochloride by magnetic bismuth-based photocatalysts. Figure 15 d, Figure 15 e, Figure 15 f is a toxicity analysis diagram of intermediate products in the three pathways for the degradation of oxytetracycline hydrochloride by magnetic bismuth-based photocatalysts. Figure 15 The acute and chronic toxicities of tetracycline hydrochloride, oxytetracycline hydrochloride, and their intermediates to fish, water fleas, and green algae were analyzed. The results showed that these intermediates were ultimately converted into harmless products in the presence of active free radicals. Therefore, magnetic bismuth-based photocatalysts can effectively degrade tetracycline hydrochloride and oxytetracycline hydrochloride, reducing their toxicity to aquatic organisms.

[0101] The above description of the disclosed embodiments enables those skilled in the art to make or use the invention. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of the invention. Therefore, the invention is not to be limited to the embodiments shown herein, but is to be accorded the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. A magnetic bismuth-based visible light photocatalyst, characterized in that, The catalyst is a Ni-NiO / Bi2O3 heterojunction photocatalyst; the catalyst has micro / nano lignocellulose as the framework, the surface is Ni-NiO / Bi2O3 composite material, and the whole is a hollow rod structure. The magnetic bismuth-based visible light photocatalyst is prepared by chemical nickel plating, physical bonding, and in-situ high-temperature decomposition to prepare a magnetic bismuth-based photocatalyst Ni-NiO / Bi2O3 with a heterojunction structure; wherein... Metallized cellulose and basic bismuth nitrate were added to anhydrous ethanol, and the mixture was placed in a water bath until the ethanol was completely evaporated. The resulting grayish-white powder was then treated at high temperature. The high-temperature treatment operation is as follows: The temperature was raised to 300℃-500℃, held for 3-5 hours, and then cooled to room temperature to finally obtain Ni-NiO / Bi2O3 magnetic rod-shaped hollow composite material; The mass ratio of metallized cellulose to basic bismuth nitrate is 10:1-5; The metallized cellulose is prepared as follows: first, micro / nano lignocellulose is ultrasonically treated, activated, and then subjected to secondary chemical nickel plating. The first electroless plating solution consists of 300 mL distilled water, 9.9 g nickel sulfate, 9.0 g sodium citrate, 8.4 g sodium hypophosphite, and 9.0 mg thiourea. Ammonia is added dropwise to adjust the pH of the plating solution to 9.

0. The solutions are added sequentially and stirred until completely dissolved. The second electroless plating solution consists of 300 mL distilled water, 9.9 g nickel sulfate, 9.0 g sodium citrate, 8.4 g sodium hypophosphite, and 9.0 mg thiourea. Ammonia is added dropwise to adjust the pH of the plating solution to 9.

0. The solutions are added sequentially and stirred until completely dissolved.

2. The application of a magnetic bismuth-based visible light catalyst as described in claim 1 in the degradation of antibiotics.

3. The application according to claim 2, characterized in that, Application of the magnetic bismuth-based visible light catalyst in the degradation of tetracycline antibiotics.

4. The application according to claim 3, characterized in that, Taking 50 mg of the magnetic bismuth-based visible light photocatalyst and exposing it to 50 mL of 100 mg / L tetracycline hydrochloride solution for 60 min resulted in degradation rates as high as 85.89% and 62.5%, respectively. After the reaction is complete, an external magnetic field is used to separate the photocatalyst from the solution to prevent secondary pollution.

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