Treatment method and device for degrading tetracycline antibiotics in wastewater based on solar energy

Abstract

The invention belongs to the technical field of sewage treatment, and particularly discloses a treatment method and device for degrading tetracycline antibiotics in wastewater based on solar energy. The photo-thermal continuous flow reactor comprises a copper heat exchanger, the surface of the copper heat exchanger is sequentially coated with a heat conduction material and a photo-thermal conversion material from inside to outside, and the copper heat exchanger is provided with a water inlet and a water outlet. The treatment method for degrading the tetracycline antibiotics in the wastewater utilizes a photo-thermal continuous flow reactor for treatment, and comprises the following steps: adding an oxidizing agent into the wastewater containing the tetracycline antibiotics, and then introducing the wastewater into a copper heat exchanger from a water inlet; the copper heat exchanger is illuminated for degradation treatment; finally, the degraded wastewater is discharged through a water outlet. According to the method, the tetracycline antibiotics are converted into copper complexes of the tetracycline antibiotics, so that not only is the dependence on temperature reduced, but also the degradation efficiency is improved, and the tetracycline antibiotics in the wastewater are degraded by continuous flow based on solar energy.

Description

Technical Field

[0001] The present invention belongs to the technical field of sewage treatment, and particularly relates to a treatment method and device for degrading tetracycline antibiotics in wastewater based on solar energy. Background Art

[0002] Tetracycline, as the first broad-spectrum antibiotic discovered by humans, has been widely used globally due to its excellent antibacterial efficacy, low side effects, and economic affordability (Environmental Pollution, 2017, 221, 1 - 14.). However, the absorption rate of tetracycline antibiotics in organisms is generally low, and the unmetabolized part often enters natural water bodies through sewage discharge, which not only disrupts the balance of the aquatic ecosystem but also induces the generation of bacterial drug resistance, posing a serious threat to public health (Antibiotics, 2023, 12, 440.). To address this issue, researchers have developed a series of technologies for degrading tetracycline antibiotics, mainly including physical methods, chemical methods, and biological methods. However, these methods all have certain limitations in practical applications. For example, traditional physical methods such as reverse osmosis generate a large amount of high-concentration wastewater during the treatment process, while sedimentation generates harmful sludge and it is difficult to achieve complete removal of the target. Although biological methods can achieve complete degradation by culturing specific microorganisms, they have high requirements for operation techniques, long treatment cycles, and poor stability, which limit their large-scale application. In contrast, advanced oxidation processes, as an efficient, simple, and widely applicable chemical treatment method, have been widely used in the field of water treatment. This method degrades pollutants into harmless substances by adding oxidants to wastewater and activating the generation of reactive oxygen species. Among them, the advanced oxidation process using sodium persulfate as an oxidant has attracted much attention due to its advantages such as easy storage, low cost, and excellent stability (Science of the Total Environment, 2022, 831, 154906.).

[0003] In the novel advanced oxidation process based on sodium persulfate, activating persulfate ions to generate reactive oxygen free radicals is a key step, which directly affects the applicability and economy of the method. Existing activation methods include physical methods such as heating, ultrasonic treatment, light irradiation, plasma activation, and chemical methods such as alkali activation, electrochemical activation, and catalytic activation (Science of the Total Environment, 2022, 831, 154906.). Among them, the thermal activation method has advantages due to its simple operation and high flexibility. Its principle is to break the oxygen-oxygen bond in persulfate ions by heating to generate strongly oxidizing sulfate radicals, which are then converted into more oxidizing hydroxyl radicals (Journal of Hazardous Materials, 2013, 254–255, 228–235.). However, since the activation energy of the oxygen-oxygen bond in sodium persulfate is as high as 140.16 kJ / mol, the system needs to be heated to 40 - 80 °C and maintained for 20 - 60 minutes to be effectively activated, which results in high energy consumption and is not conducive to continuous operation.

[0004] To solve the problem of high energy consumption in the traditional thermal activation method, researchers have explored converting solar energy, an economical and sustainable clean energy, into heat energy for the thermal activation process. Although solar energy has significant economic and environmental benefits, its low energy density and uneven distribution limit the heating efficiency. Currently, the advanced oxidation degradation scheme using solar energy to thermally activate sodium persulfate still requires heating for 4 hours to 65 °C and then maintaining for 2 hours to achieve 95% pollutant degradation efficiency (Solar Energy, 2020, 205, 372–379). Therefore, there are still major challenges in developing a mature scheme for continuously treating tetracycline antibiotic wastewater based on solar energy.

[0005] Therefore, developing new and efficient tetracycline antibiotic degradation technologies, especially innovative methods that combine solar energy utilization and chemical transformation, is of great significance for solving environmental pollution problems. Summary of the Invention

[0006] The present invention mainly aims at the technical problems of low efficiency and inability to operate continuously in the existing technology of using solar energy to treat tetracycline antibiotics in wastewater, and proposes a photothermal continuous flow reactor and a continuous flow treatment method for degrading tetracycline antibiotics in wastewater based on solar energy using the same.

[0007] The inventive concept of the present invention is: when tetracycline forms a complex with copper, due to the coordinated Cu 2+With strong electronegativity, the electron cloud density of the tetracycline copper complex is significantly increased compared to that of a single tetracycline molecule. This makes the copper complex more likely to react with electrophilic sulfate radicals or hydroxyl radicals, enabling effective degradation at relatively low temperatures. At the same time, the complex formed by tetracycline antibiotics and copper can further react to generate cuprous ions, promoting the cleavage of the oxidant to produce reactive oxygen species through the Fenton-like reaction, increasing the activation pathways of the oxidant and improving the degradation efficiency. Based on this, the present invention converts tetracycline antibiotics into copper complexes to reduce the required heating temperature and improve the degradation efficiency; and combines photothermal activation of sodium persulfate to achieve solar-driven efficient and continuous degradation of tetracycline antibiotics in wastewater.

[0008] First, solar energy is converted into heat energy by means of an excellent photothermal conversion material and transferred to the copper heat exchanger through a heat-conducting material to heat the wastewater. During this process, the thermally activated oxidant (such as sodium sulfate) generates reactive oxygen species, thereby initiating the degradation reaction with tetracycline antibiotics. At the same time, the tetracycline antibiotics form a copper complex with the divalent copper ions released from the copper heat exchanger, which is easily degraded by reactive oxygen species. The copper complex can be effectively degraded even at relatively low temperatures, significantly reducing the temperature requirement. At the same time, after the tetracycline antibiotics form a complex with copper, they can further react to generate cuprous ions, further enhancing the generation of reactive oxygen species of the oxidant through the Fenton-like reaction and broadening the activation pathways of the oxidant. Therefore, the present invention not only reduces the temperature dependence but also improves the degradation efficiency by converting tetracycline antibiotics into their copper complexes, achieving continuous flow degradation of tetracycline antibiotics in wastewater based on solar energy.

[0009] To solve the above technical problems, in the first aspect of the present invention, a photothermal continuous flow reactor is provided, which includes a copper heat exchanger. The surface of the copper heat exchanger is coated with a heat-conducting material and a photothermal conversion material in sequence from the inside to the outside, and the copper heat exchanger is provided with a water inlet and a water outlet.

[0010] In some embodiments of the present invention, the photothermal conversion material is selected from at least one of carbon black, activated carbon, graphite, and organic eutectic photothermal conversion materials.

[0011] In some embodiments of the present invention, the organic eutectic photothermal conversion material is formed by combining an electron donor and an electron acceptor. The electron donor is N,N,N',N'-tetramethylbenzidine, and the electron acceptor is tetracyanoquinodimethane. This organic eutectic photothermal conversion material exhibits good absorption performance in the wavelength range of 200 - 2500 nm and can efficiently convert solar energy into heat energy for activating the oxidant.

[0012] In some embodiments of the present invention, the organic eutectic photothermal conversion material is prepared by a solvent method, which includes the following steps: First, dissolve N,N,N',N'-tetramethylbenzidine powder in an organic solvent, then add tetracyanoquinodimethane powder. After ultrasonic-assisted dissolution, it is allowed to stand, separated, and dried to obtain the product.

[0013] In some embodiments of the present invention, the molar ratio of N,N,N',N'-tetramethylbenzidine to tetracyanoquinodimethane is (1-2):1.

[0014] In some embodiments of the present invention, the organic solvent includes acetone.

[0015] In some embodiments of the present invention, the standing time is 10-20 minutes. During the standing period, two kinds of molecules, N,N,N',N'-tetramethylbenzidine and tetracyanoquinodimethane in the solution, form an organic eutectic and precipitate from the solution through non-covalent bond-driven self-assembly.

[0016] In some embodiments of the present invention, the heat-conducting material is selected from at least one of heat-conducting silicone cloth, heat-conducting silicone grease, and heat-conducting paste.

[0017] In some embodiments of the present invention, the inner lining or pipeline material of the copper heat exchanger is metallic copper. Metallic copper is an ideal choice for heat exchanger materials due to its excellent thermal conductivity, low price, and easy processability. In addition, tetracycline antibiotics can form copper complexes with divalent copper ions released by metallic copper. Since the Cu 2+ with relatively strong electronegativity makes the electron cloud of the copper complex of tetracycline denser than that of tetracycline, and thus it is more likely to react with electrophilic sulfate radicals or hydroxyl radicals. This can not only achieve effective degradation at a lower temperature but also promote the generation of cuprous ions through the Fenton-like reaction, further enhancing the generation path of reactive oxygen radicals of the oxidant and improving the degradation efficiency.

[0018] In some embodiments of the present invention, the copper heat exchanger is a plate heat exchanger or a tube heat exchanger.

[0019] The second aspect of the present invention provides a continuous flow treatment method for degrading tetracycline antibiotics in wastewater, which is treated by using the above-mentioned photothermal continuous flow reactor, and includes the following steps:

[0020] (1) Add an oxidant to the wastewater containing tetracycline antibiotics to obtain mixed wastewater; then introduce the mixed wastewater into the copper heat exchanger from the inlet.

[0021] (2) Irradiate the copper heat exchanger for degradation treatment, and then discharge the degraded wastewater through the outlet.

[0022] In some embodiments of the present invention, the tetracycline antibiotics include one or more of tetracycline, oxytetracycline, and chlortetracycline.

[0023] In some embodiments of the present invention, the oxidant includes sodium persulfate. In the mixed wastewater, the molar amount of sodium persulfate is 4 - 24 times that of the tetracycline antibiotics, preferably 8 - 20 times.

[0024] In some embodiments of the present invention, the illumination is continuous irradiation using sunlight.

[0025] The above technical solution of the present invention has at least the following technical effects or advantages compared with the prior art:

[0026] (1) The present invention adopts the advanced oxidation technology. By adding and activating the oxidant in the wastewater containing tetracycline antibiotics, the tetracycline antibiotics in the wastewater are effectively degraded. Compared with physical methods such as reverse osmosis, ion exchange, and sedimentation, the advanced oxidation method not only achieves the full - effect degradation of tetracycline antibiotics but also avoids the generation of high - concentration wastewater and toxic sludge; compared with the biological method of constructing a bioreactor and chemical methods such as electrocatalysis and photocatalysis, the advanced oxidation method has significant advantages in its convenient operation, high efficiency, and wide applicability; different from the methods relying on electrical activation and photo - activation, the present invention does not require the configuration of an electrolytic cell or an artificial ultraviolet light source, the operation process is more simplified, and compared with alkali activation and catalytic activation technologies, the present invention does not require the introduction of foreign chemical reagents or materials, thus eliminating the risk of secondary pollution.

[0027] (2) The present invention utilizes solar energy for photothermal conversion to provide the thermal energy required for activating the oxidant to degrade tetracycline antibiotics. As a clean and renewable energy source, the application of solar energy significantly reduces energy consumption and costs compared with traditional heating methods relying on electrical energy or chemical energy, while improving the environmental protection benefits.

[0028] (3) The present invention uses a copper heat exchanger to introduce free divalent copper ions, which form easily degradable copper complexes with tetracycline antibiotics, thus effectively reducing the reaction temperature requirement. At the same time, this treatment method also expands the generation path of reactive oxygen free radicals, further improving the degradation efficiency. Compared with other advanced oxidation schemes relying on photo - thermal activation of persulfate, the present invention has made a significant breakthrough in degradation efficiency. The single - pass degradation rate of tetracycline antibiotics can be stably above 99.47%, up to 99.82%, and it can achieve continuous - flow operation relying on solar energy with a lower energy density, opening up a broad application prospect for the effective control and degradation of tetracycline - antibiotic wastewater. Description of the Drawings

[0029] Figure 1 It is a physical diagram of the copper heat exchanger;

[0030] Figure 2 Schematic diagram of the structure (a) and preparation process flow diagram (b) of the photothermal continuous flow reactor;

[0031] Figure 3 Absorption spectrum of the organic eutectic photothermal conversion material formed by N,N,N',N'-tetramethylbenzidine and tetracyano-p-benzoquinone dimethane;

[0032] Figure 4 Schematic diagram of the treatment process for degrading tetracycline antibiotics in wastewater;

[0033] Figure 5 Physical picture of the device for degrading tetracycline antibiotics in wastewater;

[0034] Figure 6 Experimental results of degrading tetracycline in wastewater in Example 1;

[0035] Figure 7 Surface temperature distribution diagram (a) and outlet water temperature (b) of the photothermal continuous flow reactor in Example 1;

[0036] Figure 8 Experimental results (a) and outlet water temperature (b) of degrading tetracycline in wastewater in Example 2;

[0037] Figure 9 Experimental results of degrading oxytetracycline in wastewater in Example 3;

[0038] Figure 10 Absorption spectra of the tetracycline stock solution, copper complex of tetracycline, and the water sample after flowing through the photothermal continuous flow reactor (a), and absorption spectra of the tetracycline stock solution, the water sample after flowing through the photothermal continuous flow reactor, and after adding the cuprous ion scavenger (b);

[0039] Figure 11 Electron spin resonance spectrum of adding DMPO to capture reactive oxygen free radicals. Detailed implementation mode

[0040] The following describes the present invention in detail in conjunction with the embodiments, so as to facilitate the understanding of the present invention by those skilled in the art. It is necessary to specifically point out here that the embodiments are only used to further illustrate the present invention and cannot be understood as limiting the protection scope of the present invention. Those skilled in the art, based on the above-mentioned invention content, make non-essential improvements and adjustments to the present invention, which should still fall within the protection scope of the present invention. At the same time, for the raw materials not specifically described below, they are all commercially available products; for the process steps or preparation methods not specifically mentioned, they are all process steps or preparation methods known to those skilled in the art.

[0041] The copper heat exchanger and photothermal continuous flow reactor used in the following embodiments of the present invention are asFigure 1-2 As shown in the figure, where: Figure 1 Figure Figure 1 is a physical diagram of a copper heat exchanger, which is a tubular copper heat exchanger. It uses a hollow copper metal coil with a diameter of 2 mm and an inner diameter of 1 mm as the heat exchanger. The coil diameter is 7.5 cm, the coil length is 1.8 m, and the heat exchanger volume is 1.5 mL.

[0042] Figure 2 Figure is a schematic diagram of the structure and preparation process flow of a photothermal continuous flow reactor. As shown in Figure 2 (a), this photothermal continuous flow reactor includes a copper heat exchanger, and the surface of the copper heat exchanger is coated with a heat-conducting material and a photothermal (conversion) material in sequence from the inside to the outside. Its preparation process is as shown in Figure 2 (b): First, evenly cover the heat-conducting material on the surface of the copper heat exchanger, and then evenly apply the powdered photothermal material to obtain the photothermal continuous flow reactor.

[0043] Among them: The heat-conducting material is a heat-conducting double-sided tape made of 0.15-mm-thick acrylic polymer and organic silicone; the photothermal material is an organic eutectic photothermal conversion material formed by N,N,N',N'-tetramethylbenzidine and tetracyanoquinodimethane, with a mass of 150 mg.

[0044] The preparation process of the organic eutectic photothermal conversion material includes the following steps:

[0045] (1) Weigh 84.12 mg of N,N,N',N'-tetramethylbenzidine powder and dissolve it in 15 mL of acetone solution;

[0046] (2) Weigh 71.47 mg of tetracyanoquinodimethane powder and add it to the acetone solution of N,N,N',N'-tetramethylbenzidine prepared in step (1). Completely dissolve it under ultrasonic assistance to obtain a mixed solution;

[0047] (3) Let the mixed solution prepared in step (2) stand for 10 - 20 min. During this period, the two molecules in the solution form an organic eutectic through non-covalent bond-driven self-assembly and precipitate from the solution. Subsequently, filter the precipitate under reduced pressure to separate the precipitated organic eutectic from the solution;

[0048] (4) Collect the filtered organic eutectic powder and let it stand until the acetone completely evaporates to obtain the dry organic eutectic photothermal conversion material formed by N,N,N',N'-tetramethylbenzidine and tetracyanoquinodimethane. This organic eutectic photothermal conversion material can effectively absorb light with a wavelength of 200 - 2500 nm (see Figure 3 , where the horizontal and vertical coordinates Wavelength represent the wavelength, and the vertical coordinate Absorbance represents the absorption rate), and the photothermal conversion efficiency under sunlight can reach 90%.

[0049] In the following embodiments of the present invention, the treatment process for the degradation of tetracycline antibiotics in wastewater using the above-mentioned photothermal continuous flow reactor is as follows: Figure 4 As shown, it includes the following steps: First, the wastewater containing tetracycline antibiotics and an oxidant is pumped into the water inlet of the copper heat exchanger of the photothermal continuous flow reactor, and then the photothermal continuous flow reactor is continuously irradiated by sunlight for degradation; the degraded wastewater flows out from the water outlet. The physical device for degrading tetracycline antibiotics in the above wastewater is as follows: Figure 5 As shown.

[0050] Example 1

[0051] Using the device shown in Figure 5 to treat tetracycline antibiotics in wastewater. In this example, the tetracycline antibiotic in the wastewater is tetracycline, with a concentration of 0.125 mmol / L (56 mg / L), and the concentration of the added oxidant sodium persulfate is 2 mmol / L, which is 16 equivalents of tetracycline.

[0052] In this example, a syringe pump with a controllable flow rate is used to transport the raw water containing tetracycline and sodium persulfate at the above concentrations to the photothermal continuous flow reactor, with a flow rate of 1 mL / min. When conducting experimental exploration, an ultra-fine thermocouple is additionally used to measure the temperature of the treated water sample at the water outlet of the device. The photothermal continuous flow reactor is placed in the sun for illumination, and the power meter measures that the solar power density during the experiment is about 127 mW / cm 2 . The residence time of the raw water in the photothermal continuous flow reactor is 1.5 min. The treated water samples flowing out from the photothermal continuous flow reactor are collected every 5 min, the concentration of tetracycline in the treated water samples is detected, and the degradation rate is calculated. The results are as follows: Figure 6 As shown. It can be seen from Figure 6 that in the treated water sample taken at the 5th minute, 87.96% of the tetracycline has been degraded. After a short equilibrium, the single-pass degradation rate of the device for tetracycline is stable above 99.47%, and the highest can reach 99.82%. According to the 1.5-min residence time, the pseudo-first-order reaction kinetic constant k for degrading tetracycline in water using this device under this operating condition can be calculated as k = 3.070 min -1 .

[0053] Figure 7 is the surface temperature of the photothermal continuous flow reactor photographed by a thermal imaging camera and the temperature of the treated water sample at the water outlet of the device monitored by an ultra-fine thermocouple under the operating conditions of Example 1. It can be seen from Figure 7 that at a power density of about 127 mW / cm 2Under sunlight irradiation, the surface temperature of the stable photothermal continuous flow reactor can reach 71.4 °C. At the outlet of the device, the temperature of the treated water sample can be stabilized at about 64 °C. This shows that the organic eutectic photothermal conversion material formed by N,N,N',N'-tetramethylbenzidine and tetracyano-p-benzoquinodimethane can effectively capture sunlight and efficiently convert it into heat energy. At the same time, the heat energy converted by the photothermal material can be conducted to the tetracycline water sample in the heat exchanger through the thermally conductive double-sided tape and the tubular copper heat exchanger, and can effectively heat it to about 64 °C.

[0054] Example 2

[0055] Degrade tetracycline antibiotics in water according to the conditions of Example 1, except that due to cloudy weather, the measured sunlight power density during the experiment was about 60.8 - 73.6 mW / cm 2 . Figure 8 are the experimental results of degrading tetracycline in water under the conditions of Example 2 and the temperature of the treated water sample at the outlet of the device. From Figure 8 it can be seen that under cloudy weather, in the treated water sample taken at the 5th minute, 60.51% of tetracycline has been degraded. After this short equilibrium, the single-pass degradation rate of the device for tetracycline is stable above 81.66%, and the highest can reach 85.75%. At the outlet of the device, the temperature of the treated water sample can be stabilized at about 43 °C. According to the retention time of 1.5 minutes, the pseudo-first-order reaction kinetic constant k for degrading tetracycline in water using this device under these operating conditions can be calculated as k = 1.299 min -1 . The above results show that even under the condition of poor solar irradiance density, the treatment method of the present invention can still efficiently degrade tetracycline.

[0056] Example 3

[0057] Degrade tetracycline antibiotics in water according to the conditions of Example 1, except that during the experiment, the measured sunlight power density was about 102 mW / cm 2 , and the tetracycline antibiotic was oxytetracycline, and the concentration was 0.125 mmol / L (57.5 mg / L). The degradation results are as Figure 9 shown. The single-pass degradation rate of the device for tetracycline is stable above 76.03%, and the highest can reach 76.41%. According to the retention time of 1.5 minutes, the pseudo-first-order reaction kinetic constant k for degrading tetracycline in water using this device under these operating conditions can be calculated as k = 0.963 min -1 . The above results show that the treatment method of the present invention can efficiently degrade oxytetracycline, one of the tetracycline antibiotics.

[0058] Comparative Examples 1 - 7

[0059] The pseudo-first-order reaction kinetic constants k for treating tetracycline antibiotics in wastewater using the treatment methods of Examples 1-3 were 3.070, 1.299, and 0.963 min -1 (the larger the value, the faster the degradation). Comparative Examples 1-7 respectively used existing technical solutions to treat tetracycline antibiotics in wastewater, and their pseudo-first-order reaction kinetic constants k are shown in Table 1.

[0060] Table 1: Comparison table of k values for treating tetracycline antibiotics in wastewater between Examples 1-3 and Comparative Examples 1-7

[0061]

[0062]

[0063] It can be seen from Table 1 that the pseudo-first-order reaction kinetic constant k for treating tetracycline antibiotics in wastewater using the method of the present invention is significantly greater than the k values of other existing technical solutions in the literatures of Comparative Examples 1-7 for treating tetracycline antibiotics in wastewater, that is, the efficiency of treating tetracycline antibiotics in wastewater using the method of the present invention is extremely high.

[0064] Verification experiment

[0065] The method of the present invention shows extremely high efficiency in treating tetracycline antibiotics in wastewater. This excellent performance is mainly attributed to two key factors: First, the photothermal conversion material used can efficiently capture solar energy and convert it into heat energy; Second, tetracycline antibiotics can form copper complexes with divalent copper ions released from the metal copper heat exchanger. This copper complex not only reacts more easily with reactive oxygen free radicals, thereby reducing the heating temperature required for degradation, but also further reacts to generate cuprous ions. These cuprous ions further promote the production of reactive oxygen free radicals by the oxidant through the Fenton-like reaction, thereby increasing the pathways for activating the oxidant and improving the degradation efficiency. Therefore, these mechanisms work together to greatly improve the efficiency of degrading tetracycline antibiotics.

[0066] 1. Formation of copper complex and its effect on reducing degradation temperature

[0067] In this example, the mechanism of the method of the present invention for treating tetracycline antibiotics in wastewater was verified through experiments. The experiments were carried out under the conditions of Example 1, and the only difference was that the photothermal continuous flow reactor was not irradiated, so the degradation effect of tetracycline was not significant. By collecting the water samples at the outlet of the reactor and measuring their ultraviolet absorption spectra, they were compared with the absorption spectra of the tetracycline stock solution and the copper complex of tetracycline. As Figure 10As shown in a, after flowing through the photothermal continuous flow reactor, the absorption spectrum of the water sample changed significantly compared to the original tetracycline solution. Its characteristic absorption peak significantly red-shifted from 357 nm to 374 nm, which was very similar to the absorption spectrum of the copper-tetracycline complex. This indicates that after flowing through the heat exchanger made of metallic copper, tetracycline reacted with the divalent copper ions released from the copper heat exchanger to form a copper-tetracycline complex. Since the Cu 2+ with strong electronegativity, the electron cloud of the copper complex of tetracycline is denser than that of tetracycline itself. Therefore, the copper complex of tetracycline is more likely to react with electrophilic sulfate radicals or hydroxyl radicals, enabling it to be effectively degraded at a relatively low temperature, thereby reducing the temperature requirement.

[0068] 2. Generation of cuprous ions and their role in improving the degradation efficiency

[0069] Meanwhile, according to the method reported in the literature (Journal of Hazardous Materials, 2022, 421, 126673), 2,9-dimethyl-1,10-phenanthroline was used to generate a yellow complex with cuprous ions (with a characteristic absorption at 457 nm) to confirm the generation of cuprous ions. The methanol solution of 2,9-dimethyl-1,10-phenanthroline was added to the water sample flowing through the photothermal continuous flow reactor, and its ultraviolet absorption spectrum was measured. The results are as Figure 10 shown in b. After adding the methanol solution of 2,9-dimethyl-1,10-phenanthroline, a new absorption peak appeared at 457 nm, which confirmed the generation of cuprous ions. It shows that tetracycline first forms a copper-tetracycline complex after flowing through the photothermal continuous flow reactor, and then further reacts to generate cuprous ions. These cuprous ions catalyze the cleavage of the oxygen-oxygen bond in the persulfate ion through the Fenton-like reaction to generate sulfate radicals for degrading tetracycline antibiotics in wastewater, thereby improving the degradation efficiency.

[0070] 3. Copper is beneficial to promoting the formation of reactive oxygen species and improving the degradation efficiency

[0071] According to the method reported in the literature (Chemical Engineering Journal, 2023, 474, 145510), 5,5-dimethyl-1-pyrroline-N-oxide (DMPO) and electron paramagnetic resonance spectroscopy (EPR) were used to capture the reactive oxygen species generated in the system respectively. During the experiment, the aqueous solution of the copper-tetracycline complex and sodium persulfate was heated in a water bath at 50 °C to simulate the situation in the photothermal continuous flow reactor. At the same time, a control group containing only tetracycline and sodium persulfate was set up. The experimental results are as Figure 11As shown, in the figure, the horizontal and vertical coordinates "Magnet Field" represent the magnetic field, and the vertical coordinate "Intensity" represents the intensity. When there is no copper in the system (as shown in Figure 11 a), only with tetracycline and sodium persulfate, no obvious EPR signal was observed after heating at 50 °C for 15 minutes; while when copper was introduced into the system (as shown in Figure 11 b), obvious signals of DMPO-OH· and DMPO-SO 4 ·- could be detected after heating at 50 °C for only 3 minutes. This indicates that the introduction of copper significantly promotes the formation of reactive oxygen free radicals, thus significantly improving the efficiency of degrading tetracycline antibiotics in wastewater.

[0072] For those of ordinary skill in the art to which the present invention pertains, without departing from the concept of the present invention, several simple deductions or substitutions can be made without the need for creative labor. Therefore, simple improvements made by those skilled in the art based on the disclosure of the present invention should fall within the protection scope of the present invention. The above embodiments are the preferred embodiments of the present invention, and all processes similar to the present invention and equivalent changes made thereto shall fall within the protection scope of the present invention.

Claims

1. A photothermal continuous flow reactor, characterized in that: It comprises a copper heat exchanger, the surface of which is coated with a heat-conducting material and a light-to-heat conversion material in sequence from the inside to the outside, and the copper heat exchanger is provided with a water inlet and a water outlet.

2. The photothermal continuous flow reactor according to claim 1, characterized in that: The photothermal conversion material is selected from at least one of carbon black, activated carbon, graphite, and organic eutectic photothermal conversion materials.

3. The photothermal continuous flow reactor according to claim 2, characterized in that: The organic eutectic light-to-heat conversion material is formed by combining an electron donor and an electron acceptor, wherein the electron donor is N,N,N',N'-tetramethylbenzidine, and the electron acceptor is tetracyanoquinodimethane.

4. The photothermal continuous flow reactor according to claim 1, characterized in that: The thermally conductive material is selected from at least one of thermally conductive silicone cloth, thermally conductive silicone grease, and thermally conductive paste.

5. The photothermal continuous flow reactor according to claim 1, characterized in that: The material of the inner lining or pipe of the copper heat exchanger is metallic copper.

6. The photothermal continuous flow reactor according to claim 1 or 5, characterized in that: The copper heat exchanger is a plate radiator or a tube radiator.

7. A method for degrading tetracycline antibiotics in wastewater, characterized in that: The process using the photothermal continuous flow reactor according to any one of claims 1 to 6 comprises the following steps: (1) adding an oxidant to wastewater containing tetracycline antibiotics to obtain mixed wastewater; and then introducing the mixed wastewater into a copper heat exchanger from a water inlet; (2) The copper heat exchanger is exposed to light to perform degradation treatment, and then the degraded wastewater is discharged through an outlet.

8. The method for treating tetracycline antibiotics in degraded wastewater according to claim 7, characterized in that: The tetracycline antibiotics include one or more of tetracycline, oxytetracycline and chlortetracycline.

9. The method for treating tetracycline antibiotics in degraded wastewater according to claim 7, characterized in that: The oxidant comprises sodium persulfate, and in the mixed wastewater, the molar number of the sodium persulfate is 4-24 times that of the tetracycline antibiotics.

10. The method for treating tetracycline antibiotics in degraded wastewater according to claim 7, characterized in that: The illumination is continuous illumination using sunlight.

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