Low-temperature plasma wastewater treatment method based on Venturi tube and Venturi tube discharge plasma device

Abstract

The invention belongs to the technical field of venturi tubes, 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, the venturi tube comprises an inlet section, the inlet section is connected with a throat, and the throat is connected with a diffusion section; the feed port is arranged at the inlet of the inlet section, the discharge port is arranged at the outlet of the diffusion section, and the negative pressure port is arranged at the joint of the inlet section and the throat; the venturi tube discharge plasma device further comprises an electrode which is connected with an excitation power supply. The method is applied to a device, gas and wastewater are mixed in the device, and after the device is started, plasma and microbubble mixed flow is used for treating the wastewater. The gas and the waste water are mixed in two modes in the device. The device and the method disclosed by the invention are high in practicability and high in removal efficiency of organic pollutants in sewage.

Description

Technical Field

[0001] The invention belongs to the technical field of venturi tubes, and in particular relates to a low-temperature plasma wastewater treatment method based on a venturi tube and a venturi tube discharge plasma device. Background Art

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

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

[0004] In view of the deficiencies in the prior art, the present invention provides a low-temperature plasma wastewater treatment method based on a venturi tube and a venturi tube discharge plasma device.

[0005] The technical solution of the present invention is as follows: In a first aspect, a venturi tube discharge plasma device includes a venturi tube, the venturi tube includes an inlet section, the inlet section is connected to a throat, and the throat is connected to a diffusion section; The feed port is located at the entrance of the inlet section, the discharge port is located at the outlet of the diffusion section, and the negative pressure port is located at the connection between the inlet section and the throat; The venturi discharge plasma device also includes an electrode, which is connected to an excitation power supply.

[0006] Preferably, the excitation power supply includes a high-voltage medium-frequency AC power supply, a high-voltage industrial-frequency AC power supply, and a nanosecond pulse power supply; When a high-voltage medium-frequency AC power supply generates plasma, the voltage is 10-50kV and the frequency is 1kHz-15kHz; when a high-voltage industrial-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.

[0007] Preferably, the electrode comprises a discharge electrode, the discharge electrode comprises a needle electrode, the needle electrode comprises 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 an excitation power supply; The electrode also includes a grounding needle electrode, one end of which is inserted into the venturi tube from the discharge port and stays in the throat, and the other end of the grounding needle electrode is connected to the ground wire.

[0008] Preferably, the distance between the tips of the high-voltage needle electrode and the grounding needle electrode is 10 mm-30 mm; the high-voltage needle electrode and the grounding needle electrode are made of white steel, tungsten, or titanium; and the diameters of the high-voltage needle electrode and the grounding needle electrode are both 1-5 mm.

[0009] Preferably, the electrode comprises a high-voltage electrode, the high-voltage electrode comprises a hollow metal tube needle electrode, an electrode air inlet 1 capable of ventilation is provided at the entrance of the hollow metal tube needle electrode, and the electrode air inlet 1 is connected to an external air source; The outlet of the hollow metal tube needle electrode is provided with an outlet port 1, and 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 source 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.

[0010] Preferably, the material of the hollow metal tube needle electrode includes white steel, titanium, copper or iron, and the diameter is 3-10 mm.

[0011] Preferably, the electrode includes a high-voltage electrode, and the high-voltage electrode includes a dielectric barrier high-voltage electrode, one end of the dielectric barrier high-voltage electrode is inserted into the dielectric tube, and the other end of the dielectric barrier high-voltage electrode is connected to the excitation power supply, and an electrode air inlet 2 is provided at the inlet of the dielectric tube, and an external air source is connected to the electrode air inlet 2, and an air outlet 2 is provided at the outlet of the dielectric tube, and one end where the air outlet 2 is located is inserted into the venturi tube from the feed port and stays in the throat; the throat of the venturi tube is connected to the ground wire.

[0012] Preferably, the material of the dielectric barrier high-voltage electrode includes titanium, copper, and iron, with a diameter of 1-20 mm; the wall thickness of the dielectric tube is 0.5-2 mm, and the material of the dielectric tube includes 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.

[0013] In a second aspect, a low-temperature plasma wastewater treatment method based on a venturi tube is applied in the venturi tube discharge plasma device. The gas and wastewater are mixed in the Venturi discharge plasma device. After the Venturi discharge plasma device is turned on, plasma is generated in situ in the micro-bubble mixed flow at the throat to treat the wastewater. There are two ways to mix gas and wastewater in a venturi discharge plasma device: The first type is to introduce wastewater into the feed port and gas into the negative pressure port. After the gas and wastewater are mixed in the throat, they are discharged from the discharge port. The gas is introduced by the negative pressure suction of the Venturi tube; The second method is to introduce gas into the feed port and wastewater into the negative pressure port. After the gas and wastewater are mixed in the throat, they are discharged from the discharge port. The gas is introduced into the Venturi tube through pumping or positive pressure from a high-pressure gas cylinder.

[0014] Preferably, a catalyst is added to the wastewater, and the method for preparing the catalyst comprises the following steps: TiO2 powder and anhydrous ethanol were mixed, ultrasonically dispersed, PVP was added, stirred at room temperature, centrifuged, and the modified TiO2 was collected, washed, and dried; Prepare tetrachloroauric acid solution and sodium borohydride solution respectively, disperse the modified TiO2 in water, ultrasonicate, then drop the tetrachloroauric acid solution, stir, then add the sodium borohydride solution, continue stirring to obtain a loaded solution; centrifuge the loaded solution, wash, and dry to obtain a catalyst.

[0015] Compared with the prior art, the present invention has the following beneficial effects: 1. The present invention makes full use of the gas-liquid two-phase flow formed by the hydraulic cavitation of the Venturi tube to perform gas-liquid discharge and dielectric barrier discharge.

[0016] 2. The present invention makes full use of high-energy electrons, ultraviolet light, hydrodynamic cavitation and other effects in plasma to remove pollutants in water.

[0017] 3. The present invention produces high-concentration hydroxyl radicals and other strong oxidizing active particles that directly act on organic wastewater. Long-life active species such as ozone and hydrogen peroxide have high mass transfer efficiency in the gas-liquid mixed flow and can produce hydroxyl radicals.

[0018] 4. The plasma excitation modes of the present invention include high-voltage medium-frequency AC power supply, high-voltage industrial-frequency AC power supply, and nanosecond pulse power supply. The excitation voltage is 10-50 kV. High voltage excitation is adopted, the injected energy is large, and the removal efficiency of organic pollutants in sewage is high.

[0019] 5. Using Venturi tube plasma water treatment technology, it occupies a small area, is easy to operate and has high removal efficiency.

[0020] 6. The self-priming and pumping through the Venturi tube or the positive pressure of the high-pressure gas cylinder provides air and oxygen to form a gas-liquid mixed flow, and the discharge gas flow rate is larger.

[0021] 7. The device of the present invention can also use multiple Venturi plasma water treatment devices in series and in parallel, which is highly practical and has high efficiency in removing organic pollutants in sewage.

[0022] 8. The present invention has further developed a new catalyst suitable for the device of the present invention, and the combined device exerts a synergistic effect to further improve the wastewater treatment effect.

[0023] The remaining more specific mechanisms are explained in detail in the examples. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] The accompanying drawings are used to provide further understanding of the present invention and constitute a part of the specification. They are used to explain the present invention together with the embodiments of the present invention and do not constitute a limitation of the present invention.

[0025] In the attached picture: Figure 1 It 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 the electrical connection devices related to the electrodes are omitted.

[0026] Figure 2 It is a schematic diagram of the needle-needle gas-liquid discharge structure of the present invention; Figure 3 It is a schematic diagram of the needle-water gas-liquid discharge structure of the present invention; Figure 4 It is a schematic diagram of the dielectric barrier gas-liquid discharge structure of the present invention.

[0027] The markings in the figure are: 1. inlet section; 2. throat; 3. diffusion section; 4. feed port; 5. discharge port; 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 wire; 15. dielectric barrier high-voltage electrode; 16. dielectric tube; 17. air outlet two; 18. electrode air inlet two. DETAILED DESCRIPTION

[0028] In order to make the purpose, technical scheme and advantages of the present invention more clearly understood, the present invention is further described in detail below in conjunction with the embodiments and the accompanying drawings. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not intended to limit the present invention. The experimental methods used below are conventional methods unless otherwise specified, and the materials, reagents, parts, etc. used, unless otherwise specified, can all be obtained from commercial sources.

[0029] The invention provides a low-temperature plasma wastewater treatment method based on a venturi tube, and the method is applied in a venturi tube discharge plasma device.

[0030] The venturi tube discharge plasma device includes a venturi tube, which includes an inlet section 1, a throat 2, and a diffusion section 3. The basic structure and principle of the venturi tube are well known, so they are not described in detail. Figure 1 , from left to right, the inlet section 1 is connected to the throat 2, and the throat 2 is connected to the diffuser 3. The introduction of "left" and "right" is to combine Figure 1 Clearly describe the structure without limiting the actual specific direction.

[0031] The feed port 4 is arranged at the entrance of the inlet section 1 , the discharge port 5 is arranged at the exit of the diffusion section 3 , and the negative pressure port 6 is arranged at the connection between the inlet section 1 and the throat 2 .

[0032] There are two ways to mix gas and wastewater in the Venturi discharge plasma device: The first type: wastewater is introduced into the feed port 4, and gas is introduced into the negative pressure port 6. After the gas and wastewater are mixed in the throat 2, they are discharged from the discharge port 5. The gas is introduced by the negative pressure suction of the venturi tube.

[0033] The second type: gas is introduced into the feed port 4, and wastewater is introduced into the negative pressure port 6. After the gas and wastewater are mixed in the throat 2, they are discharged from the discharge port 5. The gas is introduced by pumping or positive pressure feeding of high-pressure gas cylinders, and the amount of gas introduced is larger.

[0034] The wastewater is high-COD and high-salt wastewater, and the water quality characteristics include: COD: 30-200000mg / L, salt 5%-10%. Gases include air and oxygen.

[0035] The venturi discharge plasma device may include one or more venturi tubes connected in series or in parallel, and may be connected to a pipeline, a tank, a water pump, or a container through threads or flanges.

[0036] For example, it can be connected to a pipe or container through threads, or it can be connected to a pipe or container through flanges.

[0037] The venturi discharge plasma device also includes electrodes. There are many ways to set the electrodes, which are specifically described in Examples 1-3.

[0038] The electrodes are electrically connected to an excitation power supply 8, which includes a high-voltage medium-frequency AC power supply, a high-voltage industrial-frequency AC power supply, and a nanosecond pulse power supply.

[0039] When the high voltage medium frequency AC power supply generates plasma, the voltage is 10-50kV and the frequency is 1kHz-15kHz.

[0040] When the high voltage industrial frequency AC power supply generates plasma, the voltage is 10-50kV and the frequency is 0-50Hz.

[0041] When the nanosecond pulse power supply generates plasma, the peak voltage is 10-50kV and the frequency is 0-1000Hz.

[0042] It should be noted that the present invention passes wastewater into a venturi tube to form a large number of microbubble mixed flows at the throat 2, and uses high-voltage discharge in the gas-liquid mixed flow to generate high-concentration hydroxyl radicals and other strong oxidizing free radicals and various active particles to treat difficult-to-degrade organic pollutants in the sewage.

[0043] Example 1 Reference Figure 2When needle-needle discharge is used to generate plasma, 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 inlet 4 and stays in the throat 2, and the other end of the high-voltage needle electrode 7 is connected to the excitation power supply 2.

[0044] 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 , and the other end of the grounding needle electrode 9 is electrically connected to the ground wire 10 .

[0045] Inside the venturi tube, the distance d1 between the tips of the high-voltage needle electrode 1 and the ground needle electrode 4 is 10 mm to 30 mm.

[0046] The high voltage needle electrode 7 and the ground needle electrode 9 are made of white steel, tungsten or titanium.

[0047] The diameters of the high voltage needle electrode 7 and the ground needle electrode 9 are both 1-5 mm.

[0048] Example 2 Reference Figure 3 When the needle-water electrode discharge is used to generate plasma, the high voltage electrode is a hollow metal tube needle electrode 11. A hollow metal tube needle electrode 11 is arranged in a venturi tube.

[0049] The hollow metal tube needle electrode 11 is a metal and hollow needle electrode, that is, the hollow metal tube needle electrode 11 is a hollow electrode with ventilation function, and the entrance of the hollow metal tube needle electrode 11 has an electrode air inlet 12 for ventilation. The exit of the hollow metal tube needle electrode 11 has an air outlet 13. The electrode air inlet 12 and the air outlet 13 are respectively at the two ends of the hollow metal tube needle electrode 11.

[0050] The end of the hollow metal tube needle electrode 11 where the gas outlet 13 is located is inserted into the venturi tube from the feed port 7 and stays in the throat 2. The excitation power supply 8 is connected to the high-voltage line 14, and the high-voltage line 14 is connected to the outside of the other end of the hollow metal tube needle electrode 11. The external gas source is connected to the electrode gas inlet 12. The external gas source is air or oxygen. The external gas source is sprayed into the venturi tube from the gas outlet 13 to form a gas-liquid mixed flow.

[0051] The ground wire 10 is electrically connected to the throat 2 of the venturi tube and is connected to the water in the throat 2 .

[0052] The hollow metal tube needle electrode 11 is made of white steel, titanium, copper or iron, and has a diameter of 3-10 mm.

[0053] Working process: The hollow metal tube needle electrode 11 is inserted into the feed port 4 of the venturi tube to provide a channel for gas to flow in. External gas flows into the hollow metal tube needle electrode 11, enters the hollow metal tube needle electrode 11 through the electrode gas inlet 12, and then reacts with wastewater in the venturi tube.

[0054] The excitation power source 8 is connected to the hollow metal tube needle electrode 11 through the high voltage line 14, and the ground wire 10 is connected to the throat 2 of the venturi tube to form a discharge circuit through grounding.

[0055] 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, forming charged particles and free electrons, thereby generating plasma. The excitation power supply 8 applies voltage between the hollow metal tube needle electrode 11 and the ground wire 10, so that the gas molecules are ionized and reactive particles such as electrons, ions, and free radicals are generated. These reactive particles (especially hydroxyl radicals) play an important role in wastewater treatment and can effectively degrade organic pollutants.

[0056] It can also be said that 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, free radicals), thereby degrading and treating organic pollutants in the wastewater.

[0057] In general, the mixed flow of wastewater and gas in the Venturi tube produces high concentrations of active oxygen species such as hydroxyl radicals in the discharge zone.

[0058] Example 3 Reference Figure 4 When the dielectric barrier discharge is used to generate plasma, the dielectric barrier high-voltage electrode 15 is a high-voltage electrode. A dielectric barrier high-voltage electrode 15 is arranged in a venturi tube.

[0059] The inlet of the medium tube 16 is provided with an electrode air inlet 18, and an external air source is connected to the electrode air inlet 18. The external air source is air or oxygen. The outlet of the medium tube 16 is provided with an air outlet 17. The external air source is sprayed into the venturi tube from the air outlet 17 to form a gas-liquid mixed flow. The electrode air inlet 18 and the air outlet 17 are respectively at the two ends of the dielectric barrier high-voltage electrode 15.

[0060] One end of the medium tube 16 where the gas outlet 17 is located is inserted into the Venturi tube from the feed port 4 and stays in the throat 2. One end of the dielectric barrier high-voltage electrode 15 is inserted into the medium tube 16, and the other end of the dielectric barrier high-voltage electrode 15 is electrically connected to the excitation power supply 8.

[0061] The dielectric barrier high voltage electrode 15 is made of titanium, copper, iron or copper, with a diameter of 1-20 mm. The wall thickness of the dielectric tube 16 is 0.5-2 mm, and the material of the dielectric tube 16 is alumina or silicon dioxide 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.

[0062] The ground wire 10 is electrically connected to the throat 2 of the venturi tube and is connected to the water in the throat 2 .

[0063] It should be noted that the working processes of Examples 1 and 3 can refer to Example 2, and the gas and wastewater mixing method of the Venturi discharge plasma device and the mechanism of the device of the present invention have also been explained above.

[0064] Example 4 The specific steps for preparing the new catalyst are as follows: 1. Raw materials Tetrachloroauric acid (HAuCl4·4H2O): 99% purity; TiO2 powder: titanium dioxide P25, 99% purity; Sodium borohydride (NaBH4): 99% purity, available from Nanjing Reagent; PVP (polyvinyl pyrrolidone): PVP-K30, 99% purity; Deionized water; Anhydrous ethanol: 99% purity.

[0065] 2. Preparation: TiO2 surface modification: Weigh 1 g of TiO2 powder, add 100 mL of anhydrous ethanol, ultrasonically disperse for 30 min, add 0.5 g of PVP, stir at room temperature for 2 h, centrifuge, collect the modified TiO2, wash with ethanol three times, and vacuum dry at 40 °C for 4 h.

[0066] Au nanoparticle loading: 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, ultrasonicate for 15 min, then drop the tetrachloroauric acid solution at 2 mL / min, stir at 400 rpm for 30 min, then quickly add the sodium borohydride solution, continue stirring for 1 h to obtain the loaded solution.

[0067] Post-processing: The loaded solution was centrifuged at 8000 rpm for 10 min, washed with deionized water 5 times, washed with ethanol 2 times, dried under vacuum at 40° C., and stored for later use to obtain a novel catalyst.

[0068] Example 5 The novel catalyst prepared in Example 4 is applied in a venturi discharge plasma device, specifically, when treating wastewater, the novel catalyst is added into the wastewater.

[0069] It should be noted that for the new catalyst, Au nanoparticles are evenly dispersed on the TiO2 surface, PVP modification provides good dispersibility to prevent agglomeration, Au and TiO2 form a metal-semiconductor heterojunction interface, and the TiO2 carrier provides a large specific surface area.

[0070] The new catalyst combined with the Venturi discharge plasma device can produce multiple synergistic effects: Plasma synergy: In the Venturi plasma system, plasma can excite TiO2 to produce electron-hole pairs, and the high-energy electrons interact with Au nanoparticles, and the generation efficiency of active species will be enhanced.

[0071] Catalytic enhancement effect: Au nanoparticles can capture electrons, inhibit electron-hole recombination, and provide additional active sites.

[0072] Physical synergy: The microbubbles produced by the Venturi tube increase the contact area of ​​the catalyst, the turbulence can enhance the mass transfer process, and the cavitation effect can promote the decomposition of pollutants in the wastewater.

[0073] In addition, the use of the new catalyst does not require high-temperature activation, has good stability, can be recycled many times, and the microbubbles, catalysis and plasma form a multiphase reaction system.

[0074] Detection: (1) Control group 1: The venturi discharge plasma apparatus of Example 1 was used, but the novel catalyst of Example 4 was not added.

[0075] (2) Control group 2: The Venturi discharge plasma apparatus of Example 1 was used, and 0.5 g / L of TiO2 powder (titanium dioxide P25) was added.

[0076] (2) Experimental group: The Venturi discharge plasma apparatus of Example 1 was used, and 0.5 g / L of the novel catalyst of Example 4 was added.

[0077] Simulated wastewater: add 20 mg / L methyl orange solution to 10L of water; Processing time: 60min; Sampling interval: 0, 15, 30, 45, 60min; Operating temperature: 25±2℃; Water inlet flow: 2L / min; Gas: air; Detection of COD removal rate, methyl orange concentration (UV-Vis spectrophotometry), TOC removal rate: (1) Methyl orange concentration: Instrument: UV-Vis spectrophotometer, wavelength: 464 nm, sampling: 10 mL each time, filtered through a 0.45 μm filter membrane.

[0078] (2) COD detection: Method: potassium dichromate method, Instrument: COD digester, Sampling: 10 mL each time.

[0079] (3) TOC detection: Instrument: TOC analyzer, sampling: 20 mL each time, filtration.

[0080] The results are shown in Tables 1 to 4.

[0081] Table 1 Comparison of treatment effects of different treatment methods on methyl orange wastewater

[0082] Table 2 Comparison of COD removal effects of different treatment methods

[0083] Table 3 Comparison of TOC removal effects of different treatment methods

[0084] Table 4 Comparison of removal rates of different treatment methods

[0085] From the above, it can be seen that 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%.

[0086] It can be seen that the degradation rate of the new catalyst combined with the Venturi discharge plasma device is faster, and the wastewater degradation effect is better under the same energy consumption conditions. The addition of the new catalyst can further improve the wastewater treatment effect of the device of the present invention.

[0087] Finally, it should be noted that the above content is only used to illustrate the technical solution of the present invention, rather than to limit the scope of protection of the present invention. Simple modifications or equivalent substitutions of the technical solution of the present invention by ordinary technicians in this field do not deviate from the essence and scope of the technical solution of the present invention.

Claims

1. A Venturi discharge plasma device, characterized in that: The venturi tube includes an inlet section, the inlet section is connected to the throat, and the throat is connected to the diffusion section; The feed port is located at the entrance of the inlet section, the discharge port is located at the outlet of the diffusion section, and the negative pressure port is located at the connection between the inlet section and the throat; The venturi discharge plasma device also includes an electrode, which is connected to an excitation power supply.

2. The Venturi discharge plasma device according to claim 1, characterized in that: The excitation power supply includes a high-voltage medium-frequency AC power supply, a high-voltage industrial-frequency AC power supply, and a nanosecond pulse power supply; When a high-voltage medium-frequency AC power supply generates plasma, the voltage is 10-50kV and the frequency is 1kHz-15kHz; when a high-voltage industrial-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 according to claim 1, characterized in that: 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 an excitation power supply; The electrode also includes a grounding needle electrode, one end of which is inserted into the venturi tube from the discharge port and stays in the throat, and the other end of the grounding needle electrode is connected to the ground wire.

4. The Venturi discharge plasma device according to claim 3, characterized in that: The tip distance between the high-voltage needle electrode and the ground needle electrode is 10mm-30mm; the high-voltage needle electrode and the ground needle electrode are made of white steel, tungsten, and titanium; the diameters of the high-voltage needle electrode and the ground needle electrode are both 1-5mm.

5. The Venturi discharge plasma device according to claim 1, characterized in that: The electrode comprises a high-voltage electrode, and the high-voltage electrode comprises a hollow metal tube needle electrode, and an electrode air inlet 1 capable of ventilation is provided at the entrance of the hollow metal tube needle electrode, and the electrode air inlet 1 is connected to an external air source; The outlet of the hollow metal tube needle electrode is provided with an outlet port 1, and 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 source 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.

6. The Venturi discharge plasma device according to claim 5, characterized in that: The materials of the hollow metal tube needle electrode include stainless steel, titanium, copper or iron, with a diameter of 3-10 mm.

7. The Venturi discharge plasma device according to claim 1, characterized in that: 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. An electrode air inlet 2 is provided at the inlet of the dielectric tube, and an external air source is connected to the electrode air inlet 2. An air outlet 2 is provided at the outlet of the dielectric tube, and one end of the air outlet 2 is inserted into the venturi tube from the feed port and stays in the throat; the throat of the venturi tube is connected to the ground wire.

8. The Venturi discharge plasma device according to claim 7, characterized in that: The materials of the dielectric barrier high-voltage electrode include titanium, copper, and iron, with a diameter of 1-20mm; the wall thickness of the dielectric tube is 0.5-2mm, and the materials of the dielectric tube include 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 0.5-2mm.

9. A low-temperature plasma wastewater treatment method based on a venturi tube is applied to the venturi tube discharge plasma device according to any one of claims 1 to 8, characterized in that: The gas and wastewater are mixed in the Venturi discharge plasma device. After the Venturi discharge plasma device is turned on, plasma is generated in situ in the micro-bubble mixed flow at the throat to treat the wastewater. There are two ways to mix gas and wastewater in a venturi discharge plasma device: The first type is to introduce wastewater into the feed port and gas into the negative pressure port. After the gas and wastewater are mixed in the throat, they are discharged from the discharge port. The gas is introduced by the negative pressure suction of the Venturi tube; The second method is to introduce gas into the feed port and wastewater into the negative pressure port. After the gas and wastewater are mixed in the throat, they are discharged from the discharge port. The gas is introduced into the Venturi tube through pumping or positive pressure from a high-pressure gas cylinder.

10. The low-temperature plasma wastewater treatment method based on a venturi tube according to claim 9, characterized in that: A catalyst is added to the wastewater. The preparation method of the catalyst comprises the following steps: TiO2 powder and anhydrous ethanol were mixed, ultrasonically dispersed, PVP was added, stirred at room temperature, centrifuged, and the modified TiO2 was collected, washed, and dried; Prepare tetrachloroauric acid solution and sodium borohydride solution respectively, disperse the modified TiO2 in water, ultrasonicate, then drop the tetrachloroauric acid solution, stir, then add the sodium borohydride solution, continue stirring, and obtain a loaded solution; The loaded solution is centrifuged, washed, and dried to obtain a catalyst.

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