Magnetic z-type photocatalyst and method for simultaneously producing heat by photocatalytic degradation of antibiotics in wastewater by combining the magnetic z-type photocatalyst with hydrodynamic cavitation

Abstract

This invention relates to a magnetic Z-type photocatalyst and a method for the combined hydrodynamic cavitation photocatalytic degradation of antibiotics in wastewater while simultaneously generating heat. The technical solution employed is: utilizing a hydrodynamic cavitation system and employing a magnetic Z-type BiFeO... 3 / Bi 2 Fe 4 O 9 Photocatalysts synergistically degrade antibiotics in wastewater, while the hydraulic cavitation system generates significant heat during wastewater treatment, substantially increasing the water temperature. Simultaneously, Z-type BiFeO... 3 / Bi 2 Fe 4 O 9 Photocatalysts are magnetic, easy to recover, and highly active, making them better suited for degrading antibiotics in wastewater. This invention combines two advanced oxidation technologies, enabling them to efficiently and synergistically degrade organic wastewater. This results in low treatment costs, no secondary pollution, and significant resource conservation. It provides valuable evidence for the future large-scale, industrial-scale treatment of organic wastewater and heat generation using hydrocavitation combined with advanced oxidation technology.

Description

Magnetic Z-type photocatalyst and its combined hydrodynamic cavitation photocatalytic degradation of antibiotics in wastewater with simultaneous heat generation Technical Field

[0001] This invention belongs to the field of hydraulic cavitation applications, specifically involving a method that uses a magnetic Z-type BiFeO3 / Bi2Fe4O9 photocatalyst as a composite photocatalyst, and combines hydraulic cavitation and photocatalysis technologies to degrade antibiotics and significantly increase water temperature by directly shining a laser into the cavitation zone. Background Technology

[0002] The production of chlortetracycline hydrochloride generates a large amount of pharmaceutical wastewater containing chlortetracycline hydrochloride. Due to the large volume of wastewater and the fact that chlortetracycline molecules readily form metal chelates with iron and calcium salts in water, making them difficult to degrade naturally, the direct discharge of this untreated wastewater can inhibit the growth of microorganisms in aquatic environments and affect the photosynthesis of aquatic plants, thus causing serious damage to the aquatic environment and ecological balance. Furthermore, chlortetracycline hydrochloride is highly accumulative in organisms; if not properly treated before discharge, it can coexist with bacteria in the natural environment for a long time, potentially leading to drug resistance in humans and posing a significant threat to human health. Therefore, it is necessary to research an efficient method for treating chlortetracycline hydrochloride pharmaceutical wastewater.

[0003] Traditional methods for treating antibiotic pharmaceutical wastewater include adsorption, membrane separation, Fenton / persulfate oxidation, sonochemical degradation, and activated sludge processes. However, these methods suffer from drawbacks such as long cycle times, high costs, small treatment volumes, low COD and TOC removal rates, and a tendency to generate secondary pollution, limiting their effectiveness in treating antibiotic pharmaceutical wastewater. In recent years, hydraulic cavitation technology, as an emerging advanced oxidation technology, has been widely applied to degrade antibiotics in wastewater due to its advantages, including no secondary pollution, low cost, high energy efficiency, and scalability.

[0004] The principle of hydraulic cavitation technology can be explained by Bernoulli's principle. During liquid flow, when the liquid encounters a throttling device (such as a Venturi tube or orifice plate), the liquid velocity increases, and the internal pressure decreases. When the internal pressure falls below the saturated vapor pressure, hydraulic cavitation occurs. The hydraulic cavitation process can be divided into three stages: cavitation bubble generation, growth, and collapse. Cavitation bubble collapse is a crucial process. When cavitation bubbles collapse, a series of physicochemical effects are generated within the hydraulic cavitation system, including "hot spots," shear forces, and shock waves. The instantaneous temperature of these "hot spots" can reach 5000-10000 K, and the pressure can reach 500-1000 atm. Under these extreme conditions, water molecules break down to generate highly oxidizing ·OH, which can effectively oxidize and degrade antibiotics in pharmaceutical wastewater. However, using hydraulic cavitation alone to treat antibiotic pharmaceutical wastewater has problems such as poor single-treatment effect and long treatment cycles, resulting in limited degradation efficiency. Combining hydraulic cavitation with other advanced oxidation technologies (AOPs) is an excellent way to improve the degradation efficiency of antibiotics by hydraulic cavitation. Photocatalytic degradation is another green and efficient advanced oxidation technology for treating antibiotic pharmaceutical wastewater. Therefore, to further improve wastewater treatment efficiency, combining hydraulic cavitation with photocatalysis can achieve large-scale wastewater treatment while simultaneously enhancing degradation efficiency. Furthermore, the hydraulic cavitation effect releases a large amount of heat, raising the liquid temperature. This high-temperature heat source can meet certain societal needs (such as heating), which is of great significance for energy conservation. Summary of the Invention

[0005] To achieve large-scale treatment of antibiotic pharmaceutical wastewater while simultaneously generating heat, this invention provides a method for the combined hydrocavitation and photocatalytic degradation of antibiotics in wastewater while generating heat.

[0006] The technical solution adopted in this invention is: a magnetic Z-type photocatalyst, wherein the magnetic Z-type photocatalyst is a BiFeO3 / Bi2Fe4O9 photocatalyst, and the preparation method includes the following steps: adding an appropriate amount of Bi(NO3)3·5H2O to a nitric acid solution, stirring magnetically until completely dissolved, adding an appropriate amount of Fe(NO3)3·9H2O, stirring magnetically until completely dissolved, heating the resulting mixed solution to 100℃, evaporating the liquid to obtain a solid, grinding the obtained solid into powder, transferring it to an 80℃ vacuum oven for drying, and finally placing the dried product in a muffle furnace and calcining it at 600℃ for 3.0h, cooling and grinding thoroughly to obtain the magnetic Z-type BiFeO3 / Bi2Fe4O9 photocatalyst.

[0007] Furthermore, the molar ratio of Bi(NO3)3·5H2O and Fe(NO3)3·9H2O is 1:1.0 to 1:1.5.

[0008] This invention provides the application of a magnetic Z-type photocatalyst combined with hydrocavitation in the photocatalytic degradation of antibiotics in wastewater while simultaneously generating heat.

[0009] A method for the simultaneous heat generation of antibiotics in wastewater by combining a magnetic Z-type photocatalyst with hydrodynamic cavitation photocatalysis utilizes a hydrodynamic cavitation system and employs the aforementioned magnetic Z-type BiFeO3 / Bi2Fe4O9 photocatalyst. The method includes the following steps: placing antibiotic-containing wastewater in a reaction tank, adding the magnetic Z-type BiFeO3 / Bi2Fe4O9 photocatalyst, mixing thoroughly, turning on a laser lamp to directly illuminate the cavitation zone, and simultaneously turning on a self-priming pump to draw the mixed solution of antibiotic wastewater and BiFeO3 / Bi2Fe4O9 photocatalyst from the reaction tank into a water pipe, which then enters the main pipeline. After passing through a porous plate on the main pipeline, the solution returns to the reaction tank through an outlet pipeline. The mixed solution of antibiotic wastewater and BiFeO3 / Bi2Fe4O9 photocatalyst continuously circulates between the reaction tank and the porous plate illuminated by the laser lamp for 60 minutes. A secondary pipeline is used to regulate the pressure at the inlet end of the porous plate.

[0010] Furthermore, the initial concentration of the antibiotic was adjusted to 5–15 mg / L.

[0011] Furthermore, the amount of the magnetic Z-type BiFeO3 / Bi2Fe4O9 photocatalyst added is 0.5–1.5 g / L.

[0012] Furthermore, the inlet pressure at the inlet end of the porous plate is adjusted to 2.0–4.0 bar.

[0013] Furthermore, the thickness of the porous plate is 4.0 to 5.0 mm, and the number of through holes on the porous plate is 3, with the diameter of each through hole being 2.0 to 3.0 mm.

[0014] Furthermore, the laser lamp has a power of 300–1000 mW and a wavelength of 300–500 nm.

[0015] Furthermore, the antibiotic is chlortetracycline hydrochloride.

[0016] Furthermore, when the temperature of the wastewater in the reaction tank is ≥60℃, the high-temperature wastewater is discharged through the drainage pipe.

[0017] The beneficial effects of this invention are:

[0018] This invention addresses the limitations of low efficiency in treating antibiotic wastewater using hydraulic cavitation alone and the inability of photocatalysis to treat antibiotic wastewater on a large scale. By combining these two methods, it achieves large-scale degradation of organic pollutants in wastewater while simultaneously improving degradation efficiency. Firstly, building upon the standalone use of hydraulic cavitation to treat antibiotic-containing wastewater, photocatalysis is effectively integrated into the hydraulic cavitation system to further enhance degradation. Specifically, the outlet pipe at the rear of the orifice plate is replaced with a colorless and transparent water pipe, allowing the laser to penetrate the transparent pipe and directly strike the cavitation zone, stimulating the photocatalyst in the wastewater to undergo photocatalytic oxidation degradation. By activating the self-priming pump, the antibiotic wastewater in the reaction tank circulates within the hydraulic cavitation degradation system, allowing the hydraulic cavitation and photocatalytic degradation of antibiotics in the wastewater to occur simultaneously. Compared to using hydraulic cavitation alone to degrade antibiotics in wastewater, this combined device significantly improves degradation efficiency. Secondly, compared to using photocatalysis alone, this combined device enables large-scale treatment of antibiotic wastewater, improves degradation efficiency, and shortens treatment time.

[0019] The composite photocatalyst used in this invention is a Z-type BiFeO3 / Bi2Fe4O9 photocatalyst. Since Bi2Fe4O9 in the BiFeO3 / Bi2Fe4O9 photocatalyst is generated through the direct conversion of BiFeO3, the composite structure of the Z-type BiFeO3 / Bi2Fe4O9 photocatalyst is more stable than the composite structures of other Z-type photocatalysts formed through coating and loading. This allows the Z-type BiFeO3 / Bi2Fe4O9 photocatalyst to maintain its Z-type composite structure even under extreme physical and chemical conditions caused by hydrocavitation, thus preventing damage to its antibiotic degradation effect. This ensures that the Z-type BiFeO3 / Bi2Fe4O9 photocatalyst can be continuously used to degrade antibiotics, thereby significantly reducing wastewater treatment costs. Simultaneously, the Z-type BiFeO3 / Bi2Fe4O9 photocatalyst is magnetic, easy to recover, and highly active, making it better suited for treating antibiotic wastewater.

[0020] This invention offers low-cost treatment with no secondary pollution, effectively purifying antibiotic pharmaceutical wastewater while simultaneously yielding a large quantity of high-temperature hot water. This hot water can be used by heating companies or utilized as needed, significantly conserving resources and providing invaluable evidence for the application of hydraulic cavitation combined with photocatalysis in large-scale, industrial wastewater treatment and heating projects. Attached Figure Description

[0021] Figure 1 shows the X-ray powder diffraction (XRD) patterns of the BFO-1:1.0(a), BFO-1:1.5(b), and BFO-1:2.0(c) samples prepared in Example 1.

[0022] Figure 2 is a schematic diagram of the hydraulic cavitation degradation system in Example 2.

[0023] Figure 3 shows the effect of different degradation systems on the degradation of chlortetracycline hydrochloride in Example 2.

[0024] Figure 4 shows the effect of photocatalysts prepared under different molar ratios in Example 2 on the degradation (a) and heat generation (b) of chlortetracycline hydrochloride.

[0025] Figure 5 shows the effect of different inlet pressures on the degradation (a) and heat generation (b) of chlortetracycline hydrochloride in Example 2.

[0026] Figure 6 shows the effect of different initial concentrations on the degradation (a) and heat generation (b) of chlortetracycline hydrochloride in Example 2.

[0027] Figure 7 shows the effect of different catalyst dosages on the degradation (a) and heat generation (b) of chlortetracycline hydrochloride in Example 2.

[0028] Among them, 1-reaction tank; 2-self-priming pump; 3-flow meter; 4-1-pressure gauge I; 4-2-pressure gauge II; 5-1-cavitation front-end thermometer; 5-2-cavitation rear-end thermometer; 5-3-thermometer; 6-perforated plate; 7-laser lamp; 8-butterfly switch; 9-water inlet pipe; 10-main line pipe; 11-sub-line pipe; 12-water outlet pipe; 13-regulating switch; 14-drainage pipe. Detailed Implementation

[0029] Example 1 Preparation of magnetic Z-type BiFeO3 / Bi2Fe4O9 photocatalyst (I) The preparation method is as follows:

[0030] Three 30 mL portions of nitric acid solution (2.0 mol / L) were measured and placed into 100 mL beakers labeled K, L, and M, respectively. Three portions of Bi(NO3)3·5H2O, each weighing 2.91 g, were added to the respective beakers, and the mixture was stirred using a magnetic stirrer until the Bi(NO3)3·5H2O was completely dissolved in the nitric acid solution. Then, 2.42 g, 3.64 g, and 4.85 g portions of Fe(NO3)3·9H2O were added to the nitric acid solutions containing the dissolved Bi(NO3)3·5H2O, respectively. The Fe(NO3)3·9H2O was then completely dissolved in the nitric acid solution using a magnetic stirrer, resulting in a completely dispersed solution. At this point, the molar ratios of Bi(NO3)3·5H2O to Fe(NO3)3·9H2O in the beakers labeled K, L, and M were 1:1.0, 1:1.5, and 1:2.0, respectively. The temperature of the obtained solution was heated to 100℃ using a magnetic stirrer heater, and all liquid was evaporated to obtain a brown solid. The brown solid was ground into powder and then transferred to an 80℃ vacuum oven to dry for 30 min. Finally, the dried brown powder was placed in a muffle furnace and calcined at 600℃ for 3.0 h. After cooling, it was thoroughly ground to obtain magnetic Z-type BiFeO3 / Bi2Fe4O9 photocatalysts prepared under different molar ratios of Bi(NO3)3·5H2O and Fe(NO3)3·9H2O, labeled as BFO-1:1.0, BFO-1:1.5, and BFO-1:2.0.

[0031] (II) Testing

[0032] To determine the crystal structure and phase composition of the catalyst, X-ray powder diffraction (XRD) analysis was performed. Figure 1 shows the XRD patterns of BFO-1:1.0 (a), BFO-1:1.5 (b), and BFO-1:2.0 (c), respectively.

[0033] As shown in Figures 1(a) and (b), all the characteristic diffraction peaks of the prepared BFO-1:1.0 and BFO-1:1.5 samples correspond well to the characteristic diffraction peaks of BiFeO3 (JCPDS No. 20-0169) and Bi2Fe4O9 (JCPDS No. 25-0090) standard cards, respectively. This result indicates that the BiFeO3 / Bi2Fe4O9 photocatalyst can be successfully synthesized. However, the intensity of the Bi2Fe4O9 characteristic diffraction peak of the BFO-1:1.0 sample is lower than that of the BFO-1:1.5 sample. This indicates that the Bi2Fe4O9 content in the prepared samples gradually increases with the increase of Fe(NO3)3·9H2O content. As can be seen from Figure 1(c), only the diffraction peaks of the Bi2Fe4O9 monomer are shown in the BFO-1:2.0 sample, which indicates that the Bi2Fe4O9 monomer was prepared under the condition that the molar ratio of Bi(NO3)3·5H2O and Fe(NO3)3·9H2O is 1:2.0.

[0034] Example 2: A method for the combined thermal degradation of antibiotics in wastewater by a magnetic Z-type BiFeO3 / Bi2Fe4O9 photocatalyst and hydrodynamic cavitation photocatalytic process, while simultaneously generating heat.

[0035] (I) Hydraulic cavitation degradation system

[0036] Figure 2 shows a hydrocavitation degradation system, the structure of which is as follows:

[0037] A reaction tank (1) for holding organic wastewater is wrapped with a layer of polyester insulation cotton. The inlet end of the inlet pipe (9) extends into the reaction tank (1), and the other end is connected to a self-priming pump (2). After passing through the self-priming pump (2), the inlet pipe (9) is connected to the main pipeline (10). A flow meter (3), pressure gauge I (4-1), cavitation front-end thermometer (5-1), perforated plate (6), and cavitation rear-end thermometer (5-2) are installed sequentially on the main pipeline (10), and then connected to the outlet pipe (12). The outlet end of the outlet pipe (12) extends into the reaction tank (1). A laser lamp (7) is set at one end of the perforated plate (6) for direct illumination of the cavitation zone. The starting end of the secondary pipeline (11) is located between the self-priming pump (2) and the flow meter (3), and the ending end is located on the outlet pipeline (12). Pressure gauge II (4-2) and butterfly switch (8) are installed on the secondary pipeline (11). The secondary pipeline (11) is used to regulate the pressure of organic wastewater before it enters the porous plate (6). A drainage pipeline (14) is provided at the lower end of the reaction tank (1). A thermometer (5-3) and regulating switch (13) are installed on the drainage pipeline (14).

[0038] As a preferred option, the water outlet pipe (12) is made of a colorless and transparent material.

[0039] (II) Methods for Degrading Antibiotics and Generating Heat

[0040] The method is as follows: Wastewater containing antibiotics is placed in a reaction tank (1), and a magnetic Z-type BiFeO3 / Bi2Fe4O9 photocatalyst is added and mixed evenly. The mixed solution of antibiotic wastewater and photocatalyst BiFeO3 / Bi2Fe4O9 is drawn into the water pipe (9) by a self-priming pump (2) and then enters the main pipeline (10). It passes through the flow meter (3), pressure gauge I (4-1), cavitation front-end thermometer (5-1), porous plate (6) and cavitation rear-end thermometer on the main pipeline (10) in sequence. After the temperature meter (5-2), the water flows back to the reaction tank (1) through the outlet pipe (12) for a circulation time of 60 minutes. The laser lamp (7) is set at one end of the porous plate (6) to directly irradiate the cavitation zone. The auxiliary pipeline (11) is used to adjust the pressure of the antibiotic wastewater entering the inlet end of the porous plate (6). Under the action of the self-priming pump (2), the mixed solution of antibiotic wastewater and photocatalyst BiFeO3 / Bi2Fe4O9 circulates between the reaction tank (1) and the porous plate (6) irradiated by the laser lamp (7).

[0041] Furthermore, the initial concentration of the antibiotic was adjusted to 5–15 mg / L.

[0042] Furthermore, the addition amount of Z-type BiFeO3 / Bi2Fe4O9 photocatalyst is 0.5–1.5 g / L.

[0043] Furthermore, the inlet pressure at the inlet end of the perforated plate (6) is adjusted to 2.0 to 4.0 bar by the butterfly switch (8) on the secondary pipeline (11).

[0044] Furthermore, the thickness of the perforated plate (6) is 4.0 to 5.0 mm, and the perforated plate is provided with 3 through holes, each with a diameter of 2.0 to 3.0 mm.

[0045] Furthermore, when the temperature of the wastewater in the reaction tank (1) is ≥60℃, the high-temperature wastewater is discharged through the drainage pipe (14).

[0046] Furthermore, the initial solution temperature of the chlortetracycline hydrochloride solution should be maintained at 10–20°C.

[0047] This example uses chlortetracycline hydrochloride for illustration.

[0048] Due to the hydraulic cavitation effect generated by the porous plate (6), the high temperature, high pressure, high jet, and strong shock wave generated by the rupture of cavitation bubbles form high-temperature hot spots and strong oxidizing free radicals such as hydroxyl radicals and superoxide radicals, which decompose the antibiotics in the wastewater into CO2, H2O, and inorganic substances, thereby degrading the antibiotics in the wastewater and obtaining high-temperature hot water. The obtained high-temperature hot water can be used by heating companies or utilized according to demand, which greatly saves resources.

[0049] The concentration of chlortetracycline hydrochloride solution at 60 min was determined using a UV-Vis spectrophotometer operating at wavelengths of K = 200-800 nm. A linear relationship between concentration and absorbance was determined by measuring a standard curve of concentration versus absorbance.

[0050] Degradation rate (%) = [C0 - C t ] / C0×100%

[0051] Where C0 is the initial concentration of the chlortetracycline hydrochloride solution, C t It is the instantaneous concentration after a certain time (t) of the cyclic reaction.

[0052] 1. The effect of different degradation systems on the degradation of chlortetracycline hydrochloride in wastewater

[0053] Method: 5.0 L of chlortetracycline hydrochloride solution was added to the reaction tank (1). The initial concentration of the chlortetracycline hydrochloride solution was adjusted to 10 mg / L and the solution temperature was controlled at 20 °C. The laser lamp (7) and the self-priming pump (2) were turned on to circulate the chlortetracycline hydrochloride solution between the reaction tank (1) and the porous plate (6) irradiated by the laser lamp (7) for 60 min. The inlet pressure at the inlet end of the porous plate (6) was controlled at 3.0 bar.

[0054] Hydraulic cavitation (HC), photocatalysis (Light+BFO), and a combination of hydraulic cavitation and photocatalysis (HC+Light+BFO) systems were selected for the degradation of antibiotics in wastewater. The composite photocatalyst used in the reactions involving the addition of a photocatalyst was a magnetic Z-type photocatalyst, BFO-1:1.5, added at a concentration of 1.0 g / L.

[0055] The degradation effects of different degradation systems on chlortetracycline hydrochloride are shown in Figure 3. As can be seen from Figure 3, within a 60-minute cycle, the degradation rates of chlortetracycline hydrochloride were ranked as follows: hydraulic cavitation + photocatalysis (HC + Light + BFO) > photocatalysis (Light + BFO) > hydraulic cavitation (HC). The hydraulic cavitation + photocatalysis (HC + Light + BFO) system of this invention exhibited the highest efficiency in degrading chlortetracycline hydrochloride in wastewater, reaching 50.08%.

[0056] 2. Effects of BiFeO3 / Bi2Fe4O9 photocatalysts prepared under different molar ratios on the combined hydrocavitation and photocatalytic degradation of chlortetracycline hydrochloride in wastewater and heat generation.

[0057] Method: 5.0 L of chlortetracycline hydrochloride solution was added to the reaction tank (1). The initial concentration of the chlortetracycline hydrochloride solution was adjusted to 10 mg / L and the solution temperature was controlled at 20 °C. The laser lamp (7) and the self-priming pump (2) were turned on to circulate the chlortetracycline hydrochloride solution between the reaction tank (1) and the porous plate (6) irradiated by the laser lamp (7) for 60 min. The inlet pressure at the inlet end of the porous plate (6) was controlled at 3.0 bar. The hydrocavitation + photocatalysis (HC + Light + BFO) degradation system was used for the experiment, and the catalyst addition was 1.0 g / L.

[0058] The catalysts used were magnetic photocatalysts BFO-1:1.0, BFO-1:1.5, and BFO-1:2.0, respectively.

[0059] The degradation and heat generation effects of BiFeO3 / Bi2Fe4O9 photocatalysts prepared under different molar ratios on chlortetracycline hydrochloride are shown in Figure 4. As shown in Figure 4(a), within a 60-min cycle, BFO-1:1.5 exhibited the highest degradation rate of chlortetracycline hydrochloride, reaching 50.08%. As shown in Figure 4(b), at 15 and 30 min, BFO-1:1.5 resulted in a faster temperature rise in the chlortetracycline hydrochloride solution, with a maximum heat generation efficiency of 45.97%, enabling the temperature of 5.0 L of chlortetracycline hydrochloride solution to rise from 20 °C to 65.80 °C within 60 min.

[0060] 3. Effects of different inlet pressures on the combined hydrocavitation and photocatalytic degradation of chlortetracycline hydrochloride and heat generation in wastewater

[0061] Method: 5.0 L of chlortetracycline hydrochloride solution was added to the reaction tank (1). The initial concentration of the chlortetracycline hydrochloride solution was adjusted to 10 mg / L, and the solution temperature was controlled at 20 °C. The laser lamp (7) and the self-priming pump (2) were turned on to circulate the chlortetracycline hydrochloride solution between the reaction tank (1) and the porous plate (6) irradiated by the laser lamp (7) for 60 min. The experiment was conducted using a hydrocavitation + photocatalysis (HC + Light + BFO) degradation system. The composite photocatalyst used was a magnetic Z-type photocatalyst BFO-1:1.5, with an addition amount of 1.0 g / L.

[0062] The inlet pressure of the perforated plate (6) on the main pipeline (10) is adjusted to 2.0 bar, 3.0 bar and 4.0 bar respectively through the secondary pipeline (11).

[0063] The effects of different inlet pressures on the degradation and heat generation of chlortetracycline hydrochloride are shown in Figure 5. As shown in Figure 5(a), the degradation rate of chlortetracycline hydrochloride was highest (50.08%) within a 60-minute cycle time when the inlet pressure was 3.0 bar. As shown in Figure 5(b), at 15 and 30 minutes, the system with an inlet pressure of 4.0 bar resulted in a faster temperature rise rate for the chlortetracycline hydrochloride solution compared to the other two inlet pressure systems, achieving a maximum heat generation efficiency of 53.25%. This allowed 5.0 L of chlortetracycline hydrochloride solution to rise from 20°C to 69.83°C within 60 minutes.

[0064] 4. Effects of different initial concentrations on the hydrochloric acid chlortetracycline hydrochloride degradation and heat generation in wastewater treated by combined hydrocavitation and photocatalytic degradation

[0065] Method: 5.0 L of chlortetracycline hydrochloride solution was added to the reaction tank (1), and the solution temperature was controlled at 20 °C. The laser lamp (7) and the self-priming pump (2) were turned on to circulate the chlortetracycline hydrochloride solution between the reaction tank (1) and the porous plate (6) irradiated by the laser lamp (7) for 60 min. The experiment was conducted using a hydrocavitation + photocatalysis (HC + Light + BFO) degradation system. The composite photocatalyst used was a magnetic Z-type photocatalyst BFO-1:1.5, with an addition amount of 1.0 g / L.

[0066] The initial concentrations of chlortetracycline hydrochloride solution were adjusted to 5 mg / L, 10 mg / L, and 15 mg / L, respectively.

[0067] The effects of different initial concentrations on the degradation and heat generation of chlortetracycline hydrochloride are shown in Figure 6. As shown in Figure 6(a), within a 60-minute cycle, the degradation rate of chlortetracycline hydrochloride was highest at an initial concentration of 10 mg / L, reaching 50.08%. As shown in Figure 6(b), at 15 and 30 minutes, the temperature rise rate of the chlortetracycline hydrochloride solution at an initial concentration of 15 mg / L was faster than that at initial concentrations of 5 mg / L and 10 mg / L, with a maximum heat generation efficiency of 46.93%, enabling the temperature of a 5.0 L chlortetracycline hydrochloride solution to rise from 20 °C to 66.23 °C within 60 minutes.

[0068] 5. Effects of different catalyst dosages on the combined hydrocavitation and photocatalytic degradation of chlortetracycline hydrochloride in wastewater and heat generation.

[0069] Method: 5.0 L of chlortetracycline hydrochloride solution was added to the reaction tank (1). The initial concentration of the chlortetracycline hydrochloride solution was adjusted to 10 mg / L, and the solution temperature was controlled at 20 °C. The laser lamp (7) and the self-priming pump (2) were turned on to circulate the chlortetracycline hydrochloride solution between the reaction tank (1) and the porous plate (6) irradiated by the laser lamp (7) for 60 min. The experiment was conducted using a hydrocavitation + photocatalysis (HC + Light + BFO) degradation system. The composite photocatalyst used was a magnetic Z-type photocatalyst BFO-1:1.5.

[0070] The addition amounts of the magnetic Z-type photocatalyst BFO-1:1.5 were adjusted to 0.5 g / L, 1.0 g / L, and 1.5 g / L, respectively.

[0071] The effects of different catalyst dosages on the degradation and heat generation of chlortetracycline hydrochloride are shown in Figure 7. As shown in Figure 7(a), within a 60-minute cycle, the degradation rate of chlortetracycline hydrochloride was highest, reaching 50.08%, when the catalyst dosage was 1.0 g / L. As shown in Figure 7(b), at 15 and 30 minutes, the temperature rise rate of the chlortetracycline hydrochloride solution under the catalyst dosage of 1.0 g / L was faster than that under the other two catalyst dosage conditions, with the highest heat generation efficiency reaching 45.97%, enabling the temperature of 5.0 L of chlortetracycline hydrochloride solution to rise from 20 °C to 65.80 °C within 60 minutes.

Claims

1. A method for the simultaneous thermal generation of a magnetic Z-type photocatalyst combined with hydrodynamic cavitation photocatalytic degradation of antibiotics in wastewater, characterized in that, Using a hydrocavitation system and employing a magnetic Z-type BiFeO3 / Bi2Fe4O9 photocatalyst, the method includes the following steps: placing antibiotic-containing wastewater in a reaction tank (1), adding the magnetic Z-type BiFeO3 / Bi2Fe4O9 photocatalyst, mixing evenly, and turning on a laser lamp (7), wherein the laser lamp (7) has a power of 300–1000 mW and a wavelength of 300–500 nm. nm, so that the laser directly hits the cavitation zone, and at the same time the self-priming pump (2) is turned on, so that the mixed solution of antibiotic wastewater and photocatalyst BiFeO3 / Bi2Fe4O9 in the reaction tank (1) is sucked into the water pipe (9) by the self-priming pump (2) and then into the main pipeline (10). After passing through the porous plate (6) on the main pipeline (10), it returns to the reaction tank (1) through the outlet pipe (12). The mixed solution of antibiotic wastewater and photocatalyst BiFeO3 / Bi2Fe4O9 continuously circulates between the reaction tank (1) and the porous plate (6) irradiated by the laser lamp (7) for 60 minutes. min; the secondary line pipe (11) is used to adjust the pressure at the inlet end of the porous plate (6); the magnetic Z-type photocatalyst is a BiFeO3 / Bi2Fe4O9 photocatalyst, and the preparation method includes the following steps: add an appropriate amount of Bi(NO3)3•5H2O to the nitric acid solution, stir magnetically until completely dissolved, add an appropriate amount of Fe(NO3)3•9H2O, stir magnetically until completely dissolved, heat the resulting mixed solution to 100 ℃, evaporate the liquid to obtain a solid, grind the obtained solid into powder, transfer it to an 80 ℃ vacuum oven for drying, and finally place the dried product in a muffle furnace, calcine at 600 ℃ for 3.0 h, cool and grind thoroughly to obtain the magnetic Z-type BiFeO3 / Bi2Fe4O9 photocatalyst.

2. The method according to claim 1, characterized in that, The initial concentration of antibiotics should be adjusted to 5–15 mg / L.

3. The method according to claim 1, characterized in that, The amount of magnetic Z-type BiFeO3 / Bi2Fe4O9 photocatalyst added is 0.5–1.5 g / L.

4. The method according to claim 1, characterized in that, Adjust the inlet pressure at the inlet end of the perforated plate (6) to 2.0 to 4.0 bar.

5. The method according to claim 1, characterized in that, The thickness of the porous plate (6) is 4.0 to 5.0 mm, and the number of through holes on the porous plate (6) is 3, with the diameter of each through hole being 2.0 to 3.0 mm.

6. The method according to any one of claims 1-5, characterized in that, The antibiotic in question is chlortetracycline hydrochloride.

7. The method according to any one of claims 1-5, characterized in that, When the temperature of the wastewater in the reaction tank (1) is ≥60 ℃, the high-temperature wastewater is discharged through the drainage pipe (14).

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