A low-temperature plasma wastewater treatment method based on a venturi and a venturi discharge plasma device

Abstract

The present application belongs to the technical field of Venturi tube, and particularly relates to a low-temperature plasma wastewater treatment method based on a Venturi tube and a Venturi tube discharge plasma device. The device comprises a Venturi tube, which comprises an inlet section, a throat connected to the inlet section, and a diffusion section connected to the throat. A feed inlet is arranged at the inlet of the inlet section, a discharge outlet is arranged at the outlet of the diffusion section, and a negative pressure port is arranged at the connection between the inlet section and the throat. The Venturi tube discharge plasma device further comprises an electrode connected to an excitation power source. The method is applied in the device, gas and wastewater are mixed in the device, and wastewater is treated by a plasma and micro-bubble mixed flow after the device is turned on. The mixing mode of the gas and the wastewater in the device has two modes. The device and the method have high practicability and high removal efficiency for organic pollutants in wastewater.

Description

Technical Field

[0001] This invention belongs to the field of Venturi tube technology, specifically relating to a low-temperature plasma wastewater treatment method based on Venturi tubes and a Venturi tube discharge plasma device. Background Technology

[0002] Venturi tube low-temperature discharge plasma water treatment technology is a green and environmentally friendly water treatment technology. This technology generates hydraulic cavitation within a Venturi tube to form a gas-liquid two-phase flow. Within the two-phase flow, high-voltage discharge is used to generate high-concentration active particles, strong oxidizing free radicals, and ultraviolet light. High-energy electrons, ultraviolet light, hydroxyl free radicals, oxygen atoms, ozone, hydrogen peroxide, etc. are used to efficiently remove recalcitrant organic matter from wastewater.

[0003] The existing technology has the following problems: (1) By generating plasma through discharge in the gas and then transferring active species such as ozone to the liquid phase, the mass transfer efficiency is low; (2) The high-energy electrons, ultraviolet light, hydroxyl radicals, oxygen atoms and other components in the gas phase discharge plasma fail to directly interact with the recalcitrant organic matter in the wastewater. Summary of the Invention

[0004] To address the shortcomings of existing technologies, this invention provides a low-temperature plasma wastewater treatment method and a Venturi tube discharge plasma device based on a Venturi tube.

[0005] The technical solution of this invention is as follows:

[0006] Firstly, a Venturi tube discharge plasma device includes a Venturi tube, which includes an inlet section connected to a throat, and the throat connected to a diffusion section.

[0007] The feed inlet is located at the inlet of the inlet section, the discharge outlet is located at the outlet of the diffuser section, and the negative pressure outlet is located at the connection between the inlet section and the throat.

[0008] The Venturi tube discharge plasma device also includes electrodes, which are connected to an excitation power source.

[0009] Preferably, the excitation power supply includes a high-voltage intermediate frequency AC power supply, a high-voltage power frequency AC power supply, and a nanosecond pulse power supply;

[0010] When a high-voltage intermediate-frequency AC power supply generates plasma, the voltage is 10-50kV and the frequency is 1kHz-15kHz; when a high-voltage power frequency AC power supply generates plasma, the voltage is 10-50kV and the frequency is 0-50Hz; when a nanosecond pulse power supply generates plasma, the peak voltage is 10-50kV and the frequency is 0-1000Hz.

[0011] Preferably, the electrode includes a discharge electrode, the discharge electrode includes a needle electrode, the needle electrode includes a high-voltage needle electrode, one end of the high-voltage needle electrode is inserted into the venturi tube from the feed port and stays in the throat, and the other end of the high-voltage needle electrode is connected to the excitation power supply.

[0012] The electrode also includes a grounding needle electrode. One end of the grounding needle electrode is inserted into the venturi tube from the discharge port and stays in the throat. The other end of the grounding needle electrode is connected to the ground wire.

[0013] Preferably, the distance between the tips of the high-voltage needle electrode and the grounding needle electrode is 10mm-30mm; the high-voltage needle electrode and the grounding needle electrode are made of stainless steel, tungsten, or titanium; and the diameter of both the high-voltage needle electrode and the grounding needle electrode is 1-5mm.

[0014] Preferably, the electrode includes a high-voltage electrode, which includes a hollow metal needle electrode. The hollow metal needle electrode has an electrode air inlet that allows air to pass through, and the electrode air inlet is connected to an external air source.

[0015] The hollow metal tube needle electrode has an outlet port 1 at its outlet. One end of the outlet port 1 is inserted into the venturi tube from the feed port and stays in the throat. The excitation power supply is connected to the outside of the other end of the hollow metal tube needle electrode.

[0016] The throat of the venturi tube is connected to the ground wire.

[0017] Preferably, the hollow metal tube electrode is made of stainless steel, titanium, copper, or iron, with a diameter of 3-10 mm.

[0018] Preferably, the electrode includes a high-voltage electrode, which includes a dielectric barrier high-voltage electrode. One end of the dielectric barrier high-voltage electrode is inserted into a dielectric tube, and the other end of the dielectric barrier high-voltage electrode is connected to an excitation power supply. The dielectric tube has an electrode air inlet two at its inlet, and an external air source is connected to the electrode air inlet two. The dielectric tube has an air outlet two at its outlet, and the end of the air outlet two is inserted into a venturi tube from the feed inlet and stays in the throat. The throat of the venturi tube is connected to a ground wire.

[0019] Preferably, the dielectric barrier high-voltage electrode is made of titanium, copper, or iron, with a diameter of 1-20 mm; the dielectric tube has a wall thickness of 0.5-2 mm, and the dielectric tube is made of aluminum oxide or silica quartz tube; the gap between the inner wall of the dielectric tube and the outer wall of the dielectric barrier high-voltage electrode is 0.5-2 mm.

[0020] Secondly, a low-temperature plasma wastewater treatment method based on a Venturi tube is applied in the aforementioned Venturi tube discharge plasma device.

[0021] Gas and wastewater are mixed in a venturi tube discharge plasma device. After the venturi tube discharge plasma device is turned on, plasma is generated in situ in the microbubble mixing flow at the throat to treat the wastewater.

[0022] There are two ways in which gases and wastewater are mixed in a Venturi tube discharge plasma device:

[0023] The first method involves introducing wastewater into the feed inlet and introducing gas into the negative pressure outlet. After the gas and wastewater are mixed in the throat, they are discharged from the outlet. The gas is introduced by negative pressure suction through a venturi tube.

[0024] The second method involves introducing gas into the feed inlet and wastewater into the negative pressure outlet. After the gas and wastewater are mixed in the throat, they are discharged from the outlet. The gas is introduced by pumping or by positive pressure from a high-pressure gas cylinder into the venturi tube.

[0025] Preferably, a catalyst is added to the wastewater, and the catalyst preparation method includes the following steps:

[0026] TiO2 powder and anhydrous ethanol were mixed, ultrasonically dispersed, PVP was added, stirred at room temperature, centrifuged, the modified TiO2 was collected, washed, and dried.

[0027] Tetrachloroauric acid solution and sodium borohydride solution were prepared separately. Modified TiO2 was dispersed in water and sonicated. Then, tetrachloroauric acid solution was added dropwise and stirred. Then, sodium borohydride solution was added and stirred continuously to obtain a loaded solution. The loaded solution was centrifuged, washed, and dried to obtain the catalyst.

[0028] Compared with the prior art, the beneficial effects of the present invention are:

[0029] 1. This invention fully utilizes the gas-liquid two-phase flow formed by hydraulic cavitation in a Venturi tube to perform gas-liquid discharge and dielectric barrier discharge.

[0030] 2. This invention fully utilizes the effects of high-energy electrons, ultraviolet light, and hydraulic cavitation in plasma to remove pollutants from water.

[0031] 3. This invention generates highly concentrated hydroxyl radicals and other strongly oxidizing active particles that directly act on organic wastewater. Ozone, hydrogen peroxide, and other long-lived active species have high mass transfer efficiency in gas-liquid mixed flow and can generate hydroxyl radicals.

[0032] 4. The plasma excitation methods of the present invention include high-voltage medium-frequency AC power supply, high-voltage power frequency AC power supply, and nanosecond pulse power supply. The excitation voltage is 10-50 kV. High voltage excitation is used, the injected energy is large, and the removal efficiency of organic pollutants in wastewater is high.

[0033] 5. Utilizing Venturi plasma water treatment technology, it has a small footprint, is simple to operate, and has high removal efficiency.

[0034] 6. By using a venturi tube for self-priming and pumping or by providing air and oxygen under positive pressure from a high-pressure gas cylinder to form a gas-liquid mixture flow, the discharge gas flow rate is greater.

[0035] 7. The device of the present invention can also be used in series and in parallel with multiple Venturi plasma water treatment devices, which is highly practical and has a high efficiency in removing organic pollutants from sewage.

[0036] 8. The present invention further developed a novel catalyst suitable for the device of the present invention, which, together with the device, exerts a synergistic effect to further improve the wastewater treatment effect.

[0037] The other more specific mechanisms are described in detail in the embodiments. Attached Figure Description

[0038] The accompanying drawings are provided to further illustrate the invention and form part of the specification. They are used together with the embodiments of the invention to explain the invention and do not constitute a limitation thereof.

[0039] In the attached diagram:

[0040] Figure 1 This is a schematic diagram of the structure of the Venturi tube discharge plasma device of the present invention; it should be noted that the electrodes and electrode-related electrical connection devices are omitted.

[0041] Figure 2 This is a schematic diagram of the needle-needle gas-liquid discharge structure of the present invention;

[0042] Figure 3 This is a schematic diagram of the needle-water gas-liquid discharge structure of the present invention;

[0043] Figure 4 This is a schematic diagram of the dielectric barrier gas-liquid discharge structure of the present invention.

[0044] The markings in the diagram are as follows: 1. Inlet section; 2. Throat; 3. Diffusion section; 4. Feed inlet; 5. Discharge outlet; 6. Negative pressure port; 7. High-voltage needle electrode; 8. Excitation power supply; 9. Grounding needle electrode; 10. Ground wire; 11. Hollow metal tube needle electrode; 12. Electrode air inlet one; 13. Air outlet one; 14. High-voltage line; 15. Medium barrier high-voltage electrode; 16. Medium tube; 17. Air outlet two; 18. Electrode air inlet two. Detailed Implementation

[0045] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to embodiments and accompanying drawings. It should be understood that the specific embodiments described herein are merely illustrative of the invention and are not intended to limit the invention. Unless otherwise specified, the experimental methods used below are conventional methods, and the materials, reagents, components, etc., used are commercially available.

[0046] This invention provides a method for treating wastewater using a low-temperature plasma based on a Venturi tube, which is applied in a Venturi tube discharge plasma device.

[0047] A Venturi tube discharge plasma device includes a Venturi tube, which comprises an inlet section 1, a throat 2, and a diffuser section 3. The basic structure and principle of the Venturi tube are well-known and will not be elaborated upon further. (Refer to...) Figure 1 From left to right, the segments are: inlet segment 1 connecting to throat segment 2, and throat segment 2 connecting to diffuser segment 3. The terms "left" and "right" are introduced to combine... Figure 1 Clearly describe the structure, without limiting the actual specific direction.

[0048] The feed inlet 4 is located at the inlet of the inlet section 1, the discharge outlet 5 is located at the outlet of the diffuser section 3, and the negative pressure outlet 6 is located at the connection between the inlet section 1 and the throat 2.

[0049] There are two methods for mixing gas and wastewater in a Venturi tube discharge plasma device:

[0050] The first method involves introducing wastewater through inlet 4 and gas through negative pressure outlet 6. The gas and wastewater mix in throat 2 and are then discharged from outlet 5. The gas is introduced through a venturi tube under negative pressure.

[0051] The second method involves introducing gas through inlet 4 and wastewater through negative pressure outlet 6. The gas and wastewater mix in throat 2 and are then discharged from outlet 5. The gas is introduced via pumping or positive pressure from a high-pressure gas cylinder, allowing for a larger gas flow rate.

[0052] The wastewater is high in COD and high in salinity, with the following characteristics: COD: 30-200,000 mg / L, salinity 5%-10%. The gases include air and oxygen.

[0053] A venturi tube discharge plasma device may consist of one or more venturi tubes connected in series or parallel. In use, it can be connected to pipes, tanks, pumps, or containers via threads or flanges.

[0054] For example, it can be connected to pipes or containers via threads, or via flanges.

[0055] The Venturi tube discharge plasma device also includes electrodes, and there are various ways to arrange the electrodes, which are described in specific examples 1-3.

[0056] The electrodes are electrically connected to the excitation power supply 8, which includes a high-voltage intermediate frequency AC power supply, a high-voltage power frequency AC power supply, and a nanosecond pulse power supply.

[0057] When a high-voltage intermediate-frequency AC power supply generates plasma, the voltage is between 10-50kV and the frequency is between 1kHz-15kHz.

[0058] When a high-voltage power frequency AC power supply generates plasma, the voltage is between 10-50kV and the frequency is between 0-50Hz.

[0059] When a nanosecond pulse power supply generates plasma, the peak voltage is between 10-50kV and the frequency is between 0-1000Hz.

[0060] It should be noted that in this invention, wastewater is introduced into a venturi tube, forming a large number of microbubbles mixed flow at the throat 2. In the gas-liquid mixed flow, high-voltage discharge is used to generate high concentrations of strong oxidizing free radicals such as hydroxyl radicals and various active particles to treat recalcitrant organic pollutants in wastewater.

[0061] Example 1

[0062] Reference Figure 2 When plasma is generated by needle-needle discharge, the discharge electrode is a needle-shaped electrode. Specifically, one end of the high-voltage needle electrode 7 is inserted into the venturi tube from the feed port 4 and stays in the throat 2. The other end of the high-voltage needle electrode 7 is connected to the excitation power supply 2.

[0063] One end of the grounding needle electrode 9 is inserted into the venturi tube from the discharge port 5 and stays in the throat 2. The other end of the grounding needle electrode 9 is electrically connected to the ground wire 10.

[0064] Inside the venturi tube, the distance d1 between the tips of the high-voltage needle electrode 1 and the grounding needle electrode 4 is 10mm-30mm.

[0065] The high-voltage needle electrode 7 and the grounding needle electrode 9 are made of stainless steel, tungsten, and titanium.

[0066] The diameters of both the high-voltage needle electrode 7 and the grounding needle electrode 9 are 1-5 mm.

[0067] Example 2

[0068] Reference Figure 3 When plasma is generated using a needle-water electrode discharge, the high-voltage electrode is a hollow metal tube needle electrode 11. One hollow metal tube needle electrode 11 is installed inside a Venturi tube.

[0069] The hollow metal needle electrode 11 is a metal and hollow needle electrode, meaning it is a hollow electrode with ventilation capabilities. The hollow metal needle electrode 11 has an electrode air inlet 12 at its inlet for ventilation. The hollow metal needle electrode 11 also has an air outlet 13 at its outlet. The electrode air inlet 12 and air outlet 13 are located at opposite ends of the hollow metal needle electrode 11.

[0070] One end of the hollow metal needle electrode 11, where the outlet 13 is located, is inserted into the venturi tube through the feed inlet 7 and remains in the throat 2. The excitation power supply 8 is connected to the high-voltage line 14, which is connected to the outside of the other end of the hollow metal needle electrode 11. An external gas source is connected to the electrode inlet 12. The external gas source is air or oxygen. The external gas source is injected into the venturi tube from the outlet 13 to form a gas-liquid mixture.

[0071] Ground wire 10 is electrically connected to the throat 2 of the venturi tube and is connected to the water in the throat 2.

[0072] The hollow metal tube electrode 11 is made of stainless steel, titanium, copper or iron, and has a diameter of 3-10mm.

[0073] Work process:

[0074] The hollow metal needle electrode 11 is inserted into the feed inlet 4 of the venturi tube, providing a channel for gas inflow. External gas flows into the hollow metal needle electrode 11, enters the interior of the hollow metal needle electrode 11 through the electrode gas inlet 12, and then reacts with wastewater in the venturi tube.

[0075] The excitation power supply 8 is connected to the hollow metal tube needle electrode 11 through the high voltage line 14, and the ground line 10 is connected to the throat 2 of the venturi tube to form a discharge circuit through grounding.

[0076] The excitation power supply 8 establishes a strong electric field between the electrodes by providing sufficient voltage. This electric field accelerates the molecules or atoms in the gas, causing them to lose some electrons and form charged particles and free electrons, thus generating plasma. The excitation power supply 8 applies a voltage between the hollow metal needle electrode 11 and the ground wire 10, causing the gas molecules to be ionized and generating reactive particles such as electrons, ions, and free radicals. These reactive particles (especially hydroxyl radicals) play an important role in wastewater treatment and can effectively degrade organic pollutants.

[0077] In other words, the core function of the excitation power supply 8 is to provide the required voltage and energy for plasma discharge, so that the gas is ionized under the action of the electric field to generate active particles (such as electrons, ions, and free radicals), thereby degrading and treating organic pollutants in wastewater.

[0078] In general, the mixed flow of wastewater and gas inside the Venturi tube generates a high concentration of reactive oxides such as hydroxyl radicals in the discharge zone.

[0079] Example 3

[0080] Reference Figure 4 When plasma is generated using dielectric barrier discharge, the dielectric barrier high-voltage electrode 15 serves as the high-voltage electrode. One dielectric barrier high-voltage electrode 15 is installed inside a venturi tube.

[0081] The dielectric tube 16 has an electrode inlet 2 18 at its inlet, and an external gas source is connected to the electrode inlet 2 18. The external gas source is air or oxygen. The dielectric tube 16 has an outlet 2 17 at its outlet. The external gas source is injected into the Venturi tube from the outlet 2 17 to form a gas-liquid mixture. The electrode inlet 2 18 and outlet 2 17 are located at opposite ends of the dielectric-blocking high-voltage electrode 15.

[0082] One end of the medium tube 16, where the outlet 2 17 is located, is inserted into the venturi tube from the feed inlet 4 and stays in the throat 2. One end of the medium blocking high voltage electrode 15 is inserted into the medium tube 16, and the other end of the medium blocking high voltage electrode 15 is electrically connected to the excitation power supply 8.

[0083] The dielectric barrier high-voltage electrode 15 is made of titanium, copper, iron, or copper, with a diameter of 1-20 mm. The dielectric tube 16 has a wall thickness of 0.5-2 mm and is made of aluminum oxide or silica quartz tube. The gap between the inner wall of the dielectric tube 16 and the outer wall of the dielectric barrier high-voltage electrode 15 is 0.5-2 mm.

[0084] Ground wire 10 is electrically connected to the throat 2 of the venturi tube and is connected to the water in the throat 2.

[0085] It should be noted that the working process of Examples 1 and 3 can be referred to Example 2. The gas and wastewater mixing method of the Venturi tube discharge plasma device and the mechanism of the device of the present invention have also been explained above.

[0086] Example 4

[0087] The specific steps for preparing the novel catalyst are as follows:

[0088] 1. Raw materials

[0089] Tetrachloroauric acid (HAuCl4·4H2O): 99% purity;

[0090] TiO2 powder: Titanium dioxide P25, 99% purity;

[0091] Sodium borohydride (NaBH4): 99% purity, available at Nanjing Reagent Shop;

[0092] PVP (polyvinylpyrrolidone): PVP-K30, 99% purity;

[0093] Deionized water;

[0094] Anhydrous ethanol: 99% purity.

[0095] 2. Preparation:

[0096] TiO2 surface modification: Weigh 1g of TiO2 powder, add 100mL of anhydrous ethanol, ultrasonically disperse for 30min, add 0.5g of PVP, stir at room temperature for 2h, centrifuge, collect the modified TiO2, wash 3 times with ethanol, and vacuum dry at 40℃ for 4h.

[0097] Au nanoparticle loading:

[0098] Prepare 50 mL of 0.01 M tetrachloroauric acid solution. Prepare 20 mL of fresh 0.1 M sodium borohydride solution. Disperse the modified TiO2 in 200 mL of water, sonicate for 15 min, then add tetrachloroauric acid solution dropwise at 2 mL / min, stir at 400 rpm for 30 min, then quickly add sodium borohydride solution, and continue stirring for 1 h to obtain the loaded solution.

[0099] Post-processing:

[0100] The loaded solution was centrifuged at 8000 rpm for 10 min, washed 5 times with deionized water and 2 times with ethanol, dried under vacuum at 40℃, and stored for later use to obtain a novel catalyst.

[0101] Example 5

[0102] The novel catalyst prepared in Example 4 was applied in a Venturi tube discharge plasma device, specifically by adding the novel catalyst into the wastewater during wastewater treatment.

[0103] It should be noted that for the novel catalyst, Au nanoparticles are uniformly dispersed on the TiO2 surface. PVP modification provides good dispersibility and prevents agglomeration. Au and TiO2 form a metal-semiconductor heterojunction interface, and the TiO2 support provides a large specific surface area.

[0104] The novel catalyst, combined with a Venturi tube discharge plasma device, can produce a variety of synergistic effects:

[0105] Plasma synergy: In a venturi plasma system, plasma can excite TiO2 to generate electron-hole pairs. The high-energy electrons interact with Au nanoparticles, which enhances the generation efficiency of active species.

[0106] Catalytic enhancement effect: Au nanoparticles can capture electrons, inhibit electron-hole recombination, and provide additional active sites.

[0107] Physical synergy: The microbubbles generated by the Venturi tube increase the catalyst contact area, turbulence can enhance the mass transfer process, and the cavitation effect can promote the decomposition of pollutants in wastewater.

[0108] In addition, the new catalyst does not require high-temperature activation, has good stability, can be recycled many times, and forms a multiphase reaction system with microbubbles, catalysis, and plasma.

[0109] Detection:

[0110] (1) Control group 1: The Venturi tube discharge plasma device of Example 1 was used without the novel catalyst of Example 4.

[0111] (2) Control group 2: The Venturi tube discharge plasma device of Example 1 was used, and 0.5 g / L of TiO2 powder (titanium dioxide P25) was added.

[0112] (2) Experimental group: The Venturi tube discharge plasma device of Example 1 was used, and 0.5 g / L of the novel catalyst of Example 4 was added.

[0113] Simulated wastewater: Add 20 mg / L methyl orange solution to 10 L of water;

[0114] Processing time: 60 minutes;

[0115] Sampling intervals: 0, 15, 30, 45, 60 min;

[0116] Operating temperature: 25±2℃;

[0117] Inlet flow rate: 2L / min;

[0118] Gas: Air;

[0119] The following parameters were measured: COD removal rate, methyl orange concentration (UV-Vis spectrophotometry), and TOC removal rate.

[0120] (1) Methyl orange concentration: Instrument: UV-Vis spectrophotometer, wavelength: 464nm, sampling: 10mL each time, filtered through a 0.45μm filter membrane.

[0121] (2) COD detection: Method: potassium dichromate method, instrument: COD digester, sampling: 10 mL each time.

[0122] (3) TOC detection: Instrument: TOC analyzer, sampling: 20mL each time, filtered.

[0123] The results are shown in Tables 1-4.

[0124] Table 1. Comparison of treatment effects of different treatment methods on methyl orange wastewater

[0125]

[0126] Table 2 Comparison of COD removal effects of different treatment methods

[0127]

[0128] Table 3 Comparison of TOC removal effects of different treatment methods

[0129]

[0130] Table 4. Comparison of removal rates of different treatment methods

[0131]

[0132] As can be seen from the above, compared with control group 1 and control group 2, the methyl orange removal rate of the experimental group increased by 16-28%, the COD removal rate increased by 16-30%, and the TOC removal rate increased by 17-30%.

[0133] Therefore, it can be seen that the novel catalyst combined with the Venturi tube discharge plasma device results in a faster degradation rate and better wastewater degradation effect under the same energy consumption conditions. The addition of the novel catalyst can further improve the wastewater treatment effect of the device of this invention.

[0134] Finally, it should be noted that the above content is only used to illustrate the technical solution of the present invention, and is not intended to limit the scope of protection of the present invention. Simple modifications or equivalent substitutions made by those skilled in the art to the technical solution of the present invention do not depart from the essence and scope of the technical solution of the present invention.

Claims

1. A venturi discharge plasma device, characterized by, This includes a venturi tube, which includes an inlet section that connects to a throat, and a diffuser section that connects to a diffuser section. The feed inlet is located at the inlet of the inlet section, the discharge outlet is located at the outlet of the diffuser section, and the negative pressure outlet is located at the connection between the inlet section and the throat. The venturi discharge plasma device also includes electrodes, which are connected to an excitation power supply; The electrode includes a high-voltage electrode, which includes a hollow metal tube needle electrode. The hollow metal tube needle electrode has an electrode air inlet that allows air to pass through, and the electrode air inlet is connected to an external air source. The hollow metal tube needle electrode has an air outlet at its outlet. The end with the air outlet is inserted into the venturi tube from the feed inlet and stays in the throat. The excitation power supply is connected to the outside of the other end of the hollow metal tube needle electrode; The throat of the venturi tube is connected to the ground wire.

2. The venturi discharge plasma device of claim 1, wherein, Excitation power supplies include high-voltage medium-frequency AC power supplies, high-voltage power-frequency AC power supplies, and nanosecond pulse power supplies; When a high-voltage intermediate-frequency AC power supply generates plasma, the voltage is 10-50kV and the frequency is 1kHz-15kHz; when a high-voltage power frequency AC power supply generates plasma, the voltage is 10-50kV and the frequency is 0-50Hz; when a nanosecond pulse power supply generates plasma, the peak voltage is 10-50kV and the frequency is 0-1000Hz.

3. The venturi discharge plasma device of claim 1, wherein, The materials for hollow metal tube electrodes include stainless steel, titanium, copper, or iron, with a diameter of 3-10mm.

4. A venturi discharge plasma device characterized by, This includes a venturi tube, which includes an inlet section that connects to a throat, and a diffuser section that connects to a diffuser section. The feed inlet is located at the inlet of the inlet section, the discharge outlet is located at the outlet of the diffuser section, and the negative pressure outlet is located at the connection between the inlet section and the throat. The venturi discharge plasma device also includes electrodes, which are connected to an excitation power supply; The electrode includes a high-voltage electrode, which includes a dielectric barrier high-voltage electrode. One end of the dielectric barrier high-voltage electrode is inserted into a dielectric tube, and the other end is connected to an excitation power supply. There is an electrode air inlet two at the inlet of the dielectric tube, and an external air source is connected to the electrode air inlet two. There is an air outlet two at the outlet of the dielectric tube. The end of the air outlet two is inserted into a venturi tube from the feed inlet and stays in the throat. The throat of the venturi tube is connected to the ground wire.

5. The venturi discharge plasma device of claim 4, wherein, The dielectric barrier high-voltage electrode is made of materials including titanium, copper, and iron, with a diameter of 1-20 mm; the dielectric tube has a wall thickness of 0.5-2 mm, and the dielectric tube is made of materials including aluminum oxide and silicon dioxide quartz tube; the gap between the inner wall of the dielectric tube and the outer wall of the dielectric barrier high-voltage electrode is 0.5-2 mm.

6. A method for treating wastewater using a venturi tube-based low-temperature plasma system, applied in the venturi tube discharge plasma device according to any one of claims 1-5, characterized in that, Gas and wastewater are mixed in a venturi tube discharge plasma device. After the venturi tube discharge plasma device is turned on, plasma is generated in situ in the microbubble mixing flow at the throat to treat the wastewater. There are two ways in which gases and wastewater are mixed in a Venturi tube discharge plasma device: The first method involves introducing wastewater into the feed inlet and introducing gas into the negative pressure outlet. After the gas and wastewater are mixed in the throat, they are discharged from the outlet. The gas is introduced by negative pressure suction through a venturi tube. The second method involves introducing gas into the feed inlet and wastewater into the negative pressure outlet. After the gas and wastewater are mixed in the throat, they are discharged from the outlet. The gas is introduced by pumping or by positive pressure from a high-pressure gas cylinder into the venturi tube.

7. A method of treating wastewater with low temperature plasma based on a Venturi according to claim 6, characterized in that, A catalyst is added to the wastewater. The catalyst preparation method includes the following steps: TiO2 powder and anhydrous ethanol were mixed, ultrasonically dispersed, PVP was added, stirred at room temperature, centrifuged, the modified TiO2 was collected, washed, and dried. Tetrachloroauric acid solution and sodium borohydride solution were prepared separately. Modified TiO2 was dispersed in water and sonicated. Then, tetrachloroauric acid solution was added dropwise and stirred. Then, sodium borohydride solution was added and stirred continuously to obtain the loaded solution. The loaded solution was centrifuged, washed, and dried to obtain the catalyst.

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