Bimodal atmospheric pressure plasma activated water generation system and method

Abstract

The present invention relates to a bimodal atmospheric pressure plasma activated water generation system and method, and belongs to the technical field of plasma activated water, the system comprises: a reaction container for accommodating a liquid to be activated; the medium assembly comprises an insulated medium pipe, the lower end of the medium pipe extends into and is suspended in the reaction container, an air inlet is formed in the side wall of the medium pipe, and a micropore is formed in the bottom end of the medium pipe; the discharging assembly comprises a high-voltage needle electrode, low-voltage electrodes and a power supply, the high-voltage needle electrode is inserted into the dielectric tube, the low-voltage electrodes comprise a first low-voltage electrode surrounding the periphery of the dielectric tube and a second low-voltage electrode fixedly connected to the bottom of the reaction container, and the high-voltage needle electrode is connected to the power supply through a high-voltage power line; and the second low-voltage electrode extends out of the reaction container and is connected to a power supply through a low-voltage power line. The preparation of plasma activated water with two properties can be realized on the same system through simple voltage regulation, and the application range and the use flexibility of equipment are greatly expanded.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of plasma-activated water, in particular to a bimodal atmospheric pressure plasma-activated water generation system and method thereof. BACKGROUND

[0002] Plasma-activated water is a new type of liquid rich in active substances, which has high bactericidal efficiency and no toxic effect, and is widely used in fields such as sterilization and disinfection, medicine, agriculture and food preservation. Plasma-activated water is mainly prepared by contacting active substances generated by discharge plasma with aqueous solution and undergoing a series of chemical reactions.

[0003] At present, there are many methods for preparing plasma-activated water, and different preparation methods have different discharge energies and products, resulting in different characteristics of plasma-activated water. The preparation methods of plasma-activated water mainly include dielectric barrier discharge (DBD), sliding arc discharge and jet discharge; according to the contact mode of plasma and water, it can be divided into gas phase discharge, gas-liquid mixed phase discharge and liquid phase discharge. However, the existing preparation methods have the following problems: first, the device function is single, it is difficult to take into account the advantages of different discharge modes, resulting in the performance of activated water being unadjustable; second, the structure is complex and the volume is large, which is difficult to adapt to small-sized and high-throughput application scenarios; third, the electrode is easy to be damaged in direct discharge, which affects the purity of activated water and the service life of the device; fourth, there is a lack of flexible process control means, which limits the ability of "on-demand customization" of active substance species.

[0004] Therefore, there is an urgent need in the art for a plasma-activated water preparation system with compact structure, long electrode service life and flexible discharge mode switching, to meet the diversified and refined research and application needs. SUMMARY

[0005] The present application aims to provide a bimodal atmospheric pressure plasma-activated water generation system and method thereof, to at least partially solve the technical problems mentioned in the background.

[0006] To achieve the above-mentioned purpose, the present application provides the following technical solutions: The first aspect of the present application provides a dual-mode atmospheric pressure plasma-activated water generating system, comprising a reaction vessel for containing liquid to be activated, a dielectric assembly, and a discharge assembly. The dielectric assembly comprises an insulating dielectric tube, the lower end of which extends into and hangs in the reaction vessel, the sidewall of the dielectric tube is provided with an air inlet and the bottom end is provided with a micropore. The discharge assembly comprises a high-voltage needle electrode, a low-voltage electrode, and a power supply. The high-voltage needle electrode is inserted into the dielectric tube. The low-voltage electrode comprises a first low-voltage electrode surrounding the outer periphery of the dielectric tube and a second low-voltage electrode fixedly connected to the bottom of the reaction vessel. The high-voltage needle electrode is connected to the power supply through a high-voltage power supply line. The second low-voltage electrode extends from the reaction vessel and is connected to the power supply through a low-voltage power supply line.

[0007] In a preferred embodiment, the reaction vessel comprises a reaction dish and a reaction dish cover that covers the reaction dish. The reaction dish cover is provided with an opening for mounting the dielectric tube and a vent hole.

[0008] In a preferred embodiment, the diameter of the micropore is 200 μm to 700 μm.

[0009] In a preferred embodiment, the wall thickness of the dielectric tube is 1.0 mm to 2.0 mm.

[0010] In a preferred embodiment, the high-voltage needle electrode has a needle shape or a rod shape with a sharp bottom end.

[0011] In a preferred embodiment, the tip of the high-voltage needle electrode is located near the micropore at the bottom of the dielectric tube.

[0012] In a preferred embodiment, the high-voltage needle electrode is fixed to the top opening of the dielectric tube by an elastic positioning plug.

[0013] The second aspect of the present application provides a method for generating plasma-activated water according to the system, comprising the steps of: adding liquid to be activated into the reaction vessel; continuously introducing working gas into the dielectric assembly; turning on the high-voltage high-frequency alternating current power supply, adjusting its output voltage to a first voltage range to make the system work in a dielectric barrier discharge mode to generate a first type of plasma-activated water, or adjusting its output voltage to a second voltage range higher than the first voltage range to make the system work in a liquid-electric discharge mode to generate a second type of plasma-activated water.

[0014] In a preferred embodiment, the critical breakdown voltage between the first voltage range and the second voltage range depends on the wall thickness of the dielectric tube, the shape of the tip of the high-voltage needle electrode, and the type of working gas.

[0015] In a preferred embodiment, the medium barrier discharge mode activation and the liquid-electric discharge mode activation are sequentially performed, or the liquid-electric discharge mode activation and the medium barrier discharge mode activation are sequentially performed.

[0016] Compared with the prior art, the present application has the following advantages: 1. The present application innovatively proposes a switchable dual-mode plasma discharge mechanism, which can selectively excite a DBD discharge mode or a gas-liquid mixed phase discharge mode according to needs through a single power supply and an electrode system. On the one hand, the present application solves the problems of single function and unadjustable performance. Users can prepare plasma activated water (PAW) with different physicochemical properties on the same system by adjusting a simple parameter, i.e., the voltage of the power supply. The DBD mode is suitable for scenarios that need to be rich in specific RNS (active nitrogen) and have no high requirements for pH value, while the liquid-electric discharge mode can obtain PAW with more complex components and relatively high pH value, which greatly expands the application spectrum of the system. On the other hand, the present application realizes programmable activated water customization, which provides an unprecedented flexible tool for studying the synergistic effect of different active components and exploring the optimal preparation process of PAW in different fields (such as inhibiting a specific pathogen or promoting the growth of a specific plant).

[0017] 2. The present application adopts a highly integrated one-piece structure design, in which the discharge assembly and the medium assembly are integrated in a micro reaction container. On the one hand, the present application overcomes the defects of complex structure and poor scale adaptability. The system has a compact structure and a small size, saves valuable laboratory space, and reduces equipment cost, which is particularly suitable for high-throughput screening experiments, micro-sample processing, and use as a portable or embedded device module. On the other hand, the present application is easy to operate, and users do not need to switch between multiple devices. Comparative experiments can be carried out on the same platform, which ensures the consistency of experimental conditions and greatly improves the research efficiency.

[0018] 3. The present application designs a high-voltage electrode structure with dielectric potential barrier protection, i.e., a tungsten needle high-voltage needle electrode is covered with a quartz glass dielectric tube, which acts as a dielectric layer in the DBD mode and becomes a breakable barrier in the liquid-electric discharge mode. This scheme fundamentally solves the problems of electrode wear and pollution. In the DBD mode, the dielectric tube completely isolates the electrode from the liquid, avoiding electrochemical corrosion. Even in the severe liquid-electric discharge mode, the breakdown only occurs at the micropore at the bottom end of the dielectric tube, and the electrode erosion is minimized. At the same time, this scheme also ensures the purity of the activated water and the reproducibility of the experimental results, significantly prolongs the service life of the electrode and the system, and ensures the stability of the discharge process, so that the prepared PAW has consistent composition, reliable experimental data, and excellent reproducibility.

[0019] 4. The present application also introduces a multifunctional electrode assembly integrated with a gas channel, which supplies gas to the liquid below the liquid surface through a medium tube, and combines the external copper ring electrode (first low-voltage electrode) with the gas channel, greatly enhancing the flexibility of process control. On the one hand, the gas (such as O2, N2, Air, Ar) not only serves as the working gas for generating plasma, but also as the reaction raw material for generating specific active species (such as ozone, hydrogen peroxide, nitrous acid). By selecting different gases and combining them with two discharge modes, a matrix-type, extremely rich PAW formula library can be formed, truly realizing the "fine control" of the chemical properties of PAW. On the other hand, the activation efficiency can also be improved. After the gas is released from the micro-holes at the bottom of the medium tube, it will pass through the DBD activation area near the copper ring electrode. The bubbles themselves may be further plasmaized, increasing the contact area and efficiency of the gas-liquid two-phase reaction. BRIEF DESCRIPTION OF DRAWINGS

[0020] Figure 1 Figure 1 is a schematic diagram of the overall structure of the dual-mode atmospheric pressure plasma-activated water generation system in the embodiments of the present application. Figure 2 Figure 2 is a sectional view of the dual-mode atmospheric pressure plasma-activated water generation system in the embodiments of the present application. Figure 3 Figure 3 is a discharge waveform diagram of the DBD activation mode in Example 1 of the present application. Figure 4 Figure 4 is a hydroxyl radical ERP spectrum diagram during the activation process of the DBD activation mode in Example 1 of the present application. Figure 5 Figure 5 is a discharge waveform diagram of the liquid-electric discharge activation mode in Example 2 of the present application. Figure 6 Figure 6 is a pH value trend graph of the plasma-activated water of the embodiments and the control group of the present application. Figure 7 Figure 7 is a total nitrogen oxide trend graph of the plasma-activated water of the embodiments and the control group of the present application. Figure 8 Figure 8 is a H2O2 trend graph of the plasma-activated water of the embodiments and the control group of the present application. Figure 9 Figure 9 is an antibacterial effect control graph of the plasma-activated water of the embodiments and the control group of the present application.

[0021] The meanings of the various reference numbers in the figures are as follows: 1, reaction vessel; 11, reaction dish; 12, reaction dish cover; 13, air hole; 2, medium assembly; 21, medium tube; 22, gas inlet; 23, micro-hole; 3, discharge assembly; 31, high-voltage needle electrode; 32, low-voltage electrode; 321, first low-voltage electrode; 322, second low-voltage electrode; 33, power supply; 34, elastic positioning plug; 35, high-voltage power supply line; 36, low-voltage power supply line. DETAILED DESCRIPTION

[0022] The technical solutions in the embodiments of the present application will be apparently and completely described below with reference to the drawings in the embodiments of the present application. Obviously, the described embodiments are only part of the embodiments of the present application, rather than all the embodiments. Based on the embodiments in the present application, all other embodiments obtained by a person of ordinary skill in the art without creative work fall within the protection scope of the present application.

[0023] In the description of the present application, it should be understood that the orientation or positional relationship indicated by the terms "center", "longitudinal", "lateral", "length", "width", "thickness", "upper", "lower", "front", "rear", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer" and the like is based on the orientation or positional relationship shown in the drawings, and is only for the convenience of describing the present application and simplifying the description, and therefore cannot be understood as indicating or implying that the device or element referred to must have a particular orientation, be constructed and operated in a particular orientation, and therefore cannot be understood as a limitation on the present application.

[0024] Referring to Figures 1-2 The first aspect of the present application discloses a dual-mode atmospheric pressure plasma activated water generation system, comprising a reaction container 1, a medium assembly 2 connected with the reaction container 1, and a discharge assembly 3, the discharge assembly 3 and the medium assembly 2 are integrated in the reaction container 1, through the cooperation of the three, the system can selectively be in two completely different plasma discharge operation modes according to the application requirements, so as to realize the accurate and flexible control of the physicochemical properties of the finally generated plasma activated water.

[0025] Specifically, the reaction container 1 is used for containing the liquid to be activated, and constitutes the reaction cavity of the whole system, including a reaction dish 11 and a reaction dish cover 12 covering the reaction dish 11. In this embodiment, the reaction dish 11 adopts an open cup structure, and the reaction dish cover 12 is used to seal the reaction dish 11 and is tightly covered thereon by interference fit, threaded connection or clamping, etc. to ensure the stability of the reaction process. Considering the strong oxidizing substances that may be generated in the plasma activation process and the high pressure that may exist inside the system, in this embodiment, the material of the reaction dish 11 should have certain chemical inertness, insulation and mechanical strength, and is preferably glass material (such as borosilicate glass), quartz, ceramic or polytetrafluoroethylene, etc. The volume of the reaction dish 11 can be flexibly designed according to the specific application requirements. The material of the reaction dish cover 12 can be the same as or different from that of the reaction dish 11, and is preferably a material with high insulation and high mechanical strength, and the reaction dish cover 12 is provided with an opening for mounting the medium assembly 2 and a vent hole 13, and a sealing structure is provided at the opening to ensure the sealing of the system.

[0026] The medium assembly 2 is configured as the airflow channel and dielectric barrier of the system, which comprises a medium tube 21 fixedly connected to the opening of the reaction dish cover 12, with the lower end of the medium tube 21 extending into and hanging in the reaction dish 11 and the bottom end close to the bottom of the reaction dish 11 when the reaction dish cover 12 is covered on the reaction dish 11. In the embodiment, the medium tube 21 is made of tubular insulating material, preferably quartz glass tube, which has excellent dielectric properties, high temperature resistance and chemical stability and can withstand the high temperature and high pressure environment generated by plasma discharge.

[0027] The wall thickness of the medium tube 21 can affect the critical breakdown voltage value of the system, and the greater the wall thickness, the stronger the dielectric barrier effect and the higher the required breakdown voltage. In the embodiment, the wall thickness of the medium tube 21 is set to be between 1.0 mm and 2.0 mm to balance the insulation strength and discharge efficiency. The wall thickness not less than 1.0 mm can ensure sufficient dielectric strength to prevent accidental breakdown in the DBD mode and provide necessary mechanical stability; the wall thickness not greater than 2.0 mm can prevent the DBD discharge efficiency from being reduced due to excessive decay of the electric field and avoid the breakdown voltage of the liquid-electric discharge mode being too high. Preferably, the wall thickness is set to be 1.0 mm, which can achieve higher discharge activity and reasonable breakdown voltage requirement under the premise of ensuring insulation safety.

[0028] An air inlet 22 is arranged at the upper end of the side wall of the medium tube 21, which is connected with an external gas source through a pipeline and used to deliver working gas to the internal cavity of the medium tube 21. A micropore 23 is arranged at the bottom end of the medium tube 21, which is configured as a gas outlet to guide the working gas in the medium tube 21 into the liquid in the reaction dish 11 and as a current channel under high pressure to form a plasma breakdown path under a specific voltage. The diameter of the micropore 23 is set to be between 200 μm and 700 μm, which is set to optimize the gas dispersion effect and breakdown characteristics: the diameter not less than 200 μm can effectively prevent the airflow from being blocked and the pressure from being unstable due to the surface tension of the liquid, ensuring the continuous generation of gas bubbles and the stability of the breakdown voltage; the diameter not greater than 700 μm can generate small and uniformly distributed gas bubbles, increase the gas-liquid reaction area, and at the same time, concentrate the energy of the liquid-electric discharge in the micropore 23 channel to avoid the discharge from spreading to protect the electrode. Preferably, the diameter of the micropore 23 is set to be 500 μm, which can achieve the best balance among the bubble dispersion quality, controllability of the breakdown characteristics and processing reliability, and achieve good bubble dispersion effect and controllable breakdown characteristics.

[0029] The discharge assembly 3 provides energy source for the whole system and establishes the discharge electric field, which comprises a high-voltage needle electrode 31, a low-voltage electrode 32 and a high-voltage high-frequency alternating current power supply 33.

[0030] The high-voltage needle electrode 31 is used to apply high voltage to excite plasma, which is coaxially installed in the inside of the dielectric tube 21. Specifically, the high-voltage needle electrode 31 is inserted into the dielectric tube 21, and the insertion end is fixed to the top opening of the dielectric tube 21 by an elastic positioning plug 34. For example, the elastic positioning plug 34 is a silica gel positioning plug or a rubber positioning plug, which can not only stably fix the high-voltage needle electrode 31 in the dielectric tube 21, but also ensure the sealing of the dielectric tube 21 to prevent gas leakage. Further, the high-voltage needle electrode 31 is preferably made of a material with good electrical conductivity, high temperature resistance, and plasma erosion resistance, such as tungsten, platinum, stainless steel, or corrosion-resistant alloy. The shape of the high-voltage needle electrode 31 is preferably needle-shaped or rod-shaped with a sharp bottom end, and the tip is located near the micropore 23 at the bottom of the dielectric tube 21, aiming to use the tip effect to highly concentrate the electric field, thereby reducing the threshold voltage required for gas breakdown. In this embodiment, the other end of the high-voltage needle electrode 31 is connected to the high-voltage output end of the high-voltage high-frequency alternating current power supply 33 through a high-voltage power supply 33 line.

[0031] The low-voltage electrode 32 cooperates with the high-voltage needle electrode 31 to form a complete discharge circuit in the reaction container 1, which includes a first low-voltage electrode 321 surrounding the outer periphery of the dielectric tube 21 and a second low-voltage electrode 322 fixedly connected to the bottom of the reaction dish 11. Specifically, the first low-voltage electrode 321 is preferably a copper ring that surrounds the outer periphery of the dielectric tube 21 and can form a capacitive discharge structure with the high-voltage needle electrode 31 inside the dielectric tube 21, which is blocked by the wall of the dielectric tube 21, forming a uniform and stable electric field in the gas phase, especially suitable for dielectric barrier discharge mode. The second low-voltage electrode 322 is arranged at the bottom of the cavity of the reaction dish 11 and is configured in a plate or mesh structure, and has a connection end extending from the bottom of the reaction dish 11, which is used to provide a grounding return path for the plasma current broken out from the micropore 23, and the connection end is connected to the ground end of the high-voltage high-frequency alternating current power supply 33 through a low-voltage power supply 33 line, especially suitable for liquid discharge mode.

[0032] The high-voltage high-frequency alternating current power supply 33 provides energy input for the system, and by precisely adjusting the output voltage of the power supply 33, the system can be flexibly switched between dielectric barrier discharge mode and liquid discharge mode.

[0033] Based on the above-mentioned dual-mode atmospheric pressure plasma activated water generation system, the second aspect of the present application provides a dual-mode atmospheric pressure plasma activated water generation method, which comprises the following steps: Step one, adding the liquid to be activated: adding a predetermined volume of liquid to be activated into the reaction dish 11, and the liquid level of the liquid to be activated needs to ensure that it can immerse the first low-voltage electrode 321 arranged around the outer periphery of the dielectric tube 21; Step 2, gas feeding: continuously feed selected working gas into the dielectric tube 21 through the gas inlet 22, and adjust the gas flow to a set value (e.g. 0.5 L / min), exemplary working gas can be air, oxygen or inert gas, selected according to the performance requirement of the activated liquid; Step 3, select discharge mode, start activation: turn on the high-voltage high-frequency AC power supply 33, and select one of the following two modes or switch them in sequence by adjusting the output voltage, i.e. adjust the output voltage to a set value to start the DBD activation mode, and continue to increase the voltage to be higher than the critical breakdown voltage of the system to adjust to the liquid-electric discharge activation mode: 1) DBD activation mode: adjust the output voltage of the high-voltage high-frequency AC power supply 33 to be lower than the critical breakdown voltage of the system, at which the system works in dielectric barrier discharge mode to generate the first type of plasma activated water; 2) Liquid-electric discharge activation mode: adjust the output voltage of the high-voltage high-frequency AC power supply 33 to be higher than the critical breakdown voltage of the system, at which the system works in liquid-electric discharge mode to generate the second type of plasma activated water.

[0034] Step 4, collect activated liquid: after a predetermined activation time, turn off the high-voltage high-frequency AC power supply 33 and the gas source, and collect the prepared plasma activated water from the reaction dish 11.

[0035] Wherein, the critical breakdown voltage depends on the wall thickness of the dielectric tube 21, the tip curvature radius of the high-voltage needle electrode 31 and the type of working gas fed, the critical breakdown voltage V critical , can be estimated by the following formula: V critical ≈K*E gas *d eff Wherein: V critical is the critical breakdown voltage (unit: V , peak value); K is the field enhancement factor, which is greater than 1, determined by the geometry of the tip of the high-voltage needle electrode 31 (especially the curvature radius), the sharper the tip, K the greater the value; E gas is the breakdown field strength of the specific working gas at the operating pressure (unit: V / m ); for example, in normal pressure air, E gasTypical values are 3 x 10 6 V / m ; d eff Effective breakdown distance (unit: m) m , which is mainly determined by the wall thickness of the dielectric tube 21 at the micro-hole 23.

[0036] For example, to prepare a system with a critical breakdown voltage of about 10 kV, the following design can be made: normal pressure air is selected as the working gas (the breakdown voltage of air is about 30 kV) E gas = 3 x 10 6 V / m , the wall thickness of the dielectric tube 21 at the micro-hole 23 d eff is designed to be 1 mm, and a high-voltage needle electrode 31 with a small tip curvature radius is used (assuming that the corresponding breakdown voltage is about 3.33 kV) K ≈ 3.33). Substituting into the formula: V critical ≈ 3.33 x (3 x 10 6 V / m ) x (0.001 m ) ≈ 10 kV It should be noted that this formula is a theoretical estimate and can be used as a reference for voltage regulation in actual applications. The actual critical breakdown voltage needs to be determined through experiments, i.e., gradually increasing the output voltage and observing the moment when the discharge pattern changes from DBD halo discharge to liquid electric spark discharge.

[0037] For ease of understanding, the principles of the two operation modes involved in the above method are introduced as follows: 1) In the DBD activation mode, the high-voltage high-frequency AC power supply 33 applies high-frequency AC high voltage to the high-voltage needle electrode 31 through the high-voltage power line 35. At this time, the voltage is not enough to break down the gas-liquid medium at the micro-hole 23 at the bottom of the dielectric tube 21. The strong electric field is mainly distributed between the high-voltage needle electrode 31 and the first low-voltage electrode 321, and is blocked by the dielectric tube 21 wall. The dielectric tube 21 wall acts as a dielectric barrier, preventing direct current flow and promoting high concentration of electric field in the local area around the first low-voltage electrode 321.

[0038] When the electric field strength exceeds the breakdown field strength of the surrounding gas, the gas between the high-voltage needle electrode 31 and the first low-voltage electrode 321 is ionized to form a diffuse gas-phase plasma discharge zone (usually manifested as a blue halo-shaped light-emitting layer), generating plasma rich in high-energy electrons, ions, ultraviolet photons, and various active species (such as ozone O3, excited-state oxygen atoms O, nitrogen oxides NOx, hydroxyl radicals •OH, etc.). The incoming gas will directly pass through this plasma zone during the formation of the gas bubble rising, and will be highly activated and decomposed. The activated active species will then dissolve in the liquid in the reaction dish 11 and react with the liquid through the gas-liquid interface to generate long-lived active substances such as hydrogen peroxide (H2O2), nitrite (NO2⁻), and nitrate (NO3⁻), thereby preparing a plasma-activated liquid.

[0039] This mode is a non-contact discharge, and the plasma does not directly act on the water body, with extremely low electrode loss. The activated water produced is usually strongly acidic (low pH value) and rich in acidic components derived from nitrogen oxides, making it suitable for use in fields such as surface disinfection that are not sensitive to strongly acidic environments.

[0040] 2) In the liquid-electric discharge activation mode, the voltage value applied by the high-voltage high-frequency alternating current power supply 33 is higher than the aforementioned critical breakdown voltage. Higher voltage causes the electric field strength at the tip of the high-voltage needle electrode 31 to increase sharply and concentrate at the micro-hole 23 at the bottom of the dielectric tube 21, causing the gas and liquid medium present at this location to be instantaneously electrically broken down, forming a conductive path. Strong current is directly emitted from the tip of the high-voltage needle electrode 31, enters the liquid in the reaction dish 11 through the micro-hole 23, and ultimately flows to the second low-voltage electrode 322 connected to ground, forming a strong liquid-phase plasma discharge channel (usually manifested as bright filamentous or beam-shaped discharge, accompanied by a popping sound).

[0041] The temperature in the discharge channel is extremely high, creating a local high-temperature and high-pressure area, accompanied by strong ultraviolet radiation and shock waves. Water molecules are directly dissociated, generating a large number of active groups such as hydroxyl radicals •OH and hydrogen radicals •H. At the same time, the incoming gas (such as O2) is efficiently converted into active oxygen species (ROS) in the discharge channel. This direct liquid-phase discharge has extremely high energy injection efficiency, and can generate extremely rich active substances in situ within the water body, with significant differences in species and concentration compared to the DBD mode. The shock wave effect also promotes the mixing and mass transfer of substances, preventing the accumulation of active substances around the electrodes.

[0042] The mode is direct contact discharge, energy is directly deposited in water, activation efficiency is high, generated activated water active substance spectrum is more complex, may contain more short-lived free radicals generated by direct water cracking, and pH drop is generally less than DBD mode. However, although the discharge is violent, due to the protection of the medium tube 21, the discharge only occurs in a small area of the micropore 23, which greatly limits the loss of the high-voltage needle electrode 31, solves the key problem of short service life of the traditional liquid-electric discharge electrode, and at the same time ensures the purity of the activated water and avoids the pollution of the electrode material.

[0043] The following further combines embodiments to explain the dual-mode atmospheric pressure plasma activated water generation method provided by the present application in detail. It should also be understood that the following embodiments are only used to further illustrate the present application and cannot be understood as limiting the protection scope of the present application. Some non-essential improvements and adjustments made by those skilled in the art according to the above content of the present application all belong to the protection scope of the present application. The specific process parameters in the following examples are only one example in the appropriate range, that is, those skilled in the art can select within the appropriate range through the description herein, and are not limited to the specific values of the following examples.

[0044] Embodiment 1

[0045] In this embodiment, the dual-mode atmospheric pressure plasma activated water generation method comprises the following steps: Step one, add the liquid to be activated: 30ml of ultrapure water is added to the reaction dish 11, and the liquid level of the liquid to be activated needs to be ensured to be able to immerse the first low-voltage electrode 321 arranged on the outer periphery of the medium tube 21; In this embodiment, the wall thickness of the medium tube 21 is 1mm, the diameter of the micropore 23 is 500μm, and the tip curvature radius of the high-voltage needle electrode 31 is 3.33; Step two, gas inlet: continuously inlet normal pressure air into the medium tube 21 through the gas inlet 22, and adjust the gas flow to stabilize to the set value 0.5 L / min; Step three, select the discharge mode and start activation: turn on the high-voltage high-frequency alternating current power supply 33, estimate the critical voltage value V critical ≈ 3.33×(3×10 6 V / m )×(0.001 m ) ≈ 10 kV , the accurate critical voltage value determined by experiment is 10.8kV, the output voltage is adjusted to 10.7kV, the DBD activation mode is started, the first type of plasma activated water is generated, Figure 3The discharge waveform diagram showing this activation mode is shown in the figure, in which the blue voltage waveform is a high-frequency alternating voltage signal with a peak value of about 10.8 kV, and this high voltage is the fundamental driving force for generating and maintaining the two plasma discharge modes; the red current waveform presents a large number of continuous, dense and low-amplitude current spikes, each of which represents the formation of a short-lived micro-discharge filament in the air gap, which is a typical DBD discharge feature.

[0046] Step four, collect the activated liquid: after 10 minutes of activation treatment, turn off the high-voltage high-frequency alternating power supply and the gas source, and collect the prepared plasma-activated water from the reaction dish 11.

[0047] To prove the existence of high-activity short-lived free radicals in the plasma-activated water generated by the system of this embodiment, this embodiment uses electron paramagnetic resonance (EPR) spectroscopy and uses DMPO (5,5-dimethyl-1-pyrroline-N-oxide) as a spin trapping agent to analyze the water sample. The obtained EPR spectrum (as shown in Figure 4 The characteristic four-peak (with an intensity ratio of about 1:2:2:1) is shown.

[0048] The appearance of this characteristic peak provides direct and conclusive evidence that hydroxyl radicals (·OH) are successfully captured and stably present in the water sample after treatment in this embodiment. Figure 4 The hydroxyl ERP spectrum during the activation of this mode is shown.

[0049] Embodiment 2

[0050] Step one, add the liquid to be activated: add 30 ml of ultrapure water to the reaction dish 11, and the liquid level of the liquid to be activated should be ensured to be able to immerse the first low-voltage electrode 321 around the outer periphery of the dielectric tube 21; In this embodiment, the dielectric tube 21 has a wall thickness of 1 mm, the micro-holes 23 have a diameter of 500 μm, and the high-voltage needle electrode 31 has a tip curvature radius of 3.33; Step two, gas inlet: continuously introduce normal pressure air into the dielectric tube 21 through the gas inlet 22, and adjust the gas flow to stabilize to the set value of 0.5 L / min; Step three, select the discharge mode and start activation: turn on the high-voltage high-frequency alternating power supply 33, estimate the critical voltage value V critical ≈ 3.33×(3×10 6 V / m )×(0.001 m ) ≈ 10 kV, the output voltage is regulated to 11kV, the liquid discharge activation mode is started, and the second type of plasma activated water is generated, Figure 5 The discharge waveform diagram of the activation mode is shown. The blue voltage waveform shown in the diagram is a unique non-standard sinusoidal form with a transient drop spike with a peak value of about 11kV, which is an inherent characteristic of high-intensity high-energy pulse liquid discharge; the red current waveform presents sparse current spikes, each current spike corresponds to a voltage waveform spike, and the amplitude of a single spike is significantly larger than that of DBD discharge, and such high-amplitude high-energy pulses indicate that the plasma channel has successfully broken through the micropores and formed a strong conductive wire in the water. Each such pulse is accompanied by a high-energy liquid discharge, which directly injects energy into the water and produces strong physical and chemical effects (such as shock waves, ultraviolet radiation).

[0051] Step four, collecting the activated liquid: after 10 minutes of activation treatment, the high-voltage high-frequency alternating current power supply and the gas source are turned off, and the prepared plasma activated water is collected from the reaction dish 11.

[0052] The physicochemical properties of the first type of plasma activated water prepared in Example 1 and the second type of plasma activated water prepared in Example 2 are determined, and an equal amount of ultrapure water without any treatment is used as a control group, Figures 6-8 The pH value change trend, total nitrogen oxide change trend and H2O2 change trend of each example and the control group are shown respectively: The first type of plasma activated water: its pH is low, showing strong acidity, and is rich in acidic components derived from nitrogen oxide, generating a lower content of hydrogen peroxide (H2O2), and is suitable for surface disinfection in environments that are not sensitive to strong acidity; The second type of plasma activated water: its pH value is in the range of 5.0 to 7.0, closer to neutral or weakly acidic, unlike the first type of plasma activated water, the second type of plasma is rich in reactive oxygen species (ROS), especially long-lived active oxygen-hydrogen peroxide (H2O2) with a higher concentration, and the concentration of nitrogen oxide species is relatively low, and is suitable for wound disinfection and food preservation in environments sensitive to pH.

[0053] The present application further verifies the broad-spectrum antibacterial effect of the plasma activated water prepared by the examples: To prove that the two types of plasma activated water (PAW) prepared by the examples of the present application have excellent and broad-spectrum antibacterial properties, the present application selects Escherichia coli (E. coil) as a representative of gram-negative bacteria and Staphylococcus aureus (S. aureus) as a representative of gram-positive bacteria as experimental objects, and comprehensively uses colony plating method, scanning electron microscope (SEM) observation and bacterial live and dead staining three methods for systematic evaluation.

[0054] Referring toFigure 9 Compared with the negative control group treated with PBS, the number of bacteria on the plate of the experimental group treated with the two types of PAW was significantly reduced by 8 orders of magnitude, and the scanning electron microscope showed that the bacteria in the control group were full, complete and smooth in surface, and the two PAW treatment groups were observed to have severe and irreversible physical damage such as cell wall shrinkage and dryness; the bacterial fluorescence staining results showed that most of the bacteria in the control group emitted green fluorescence, indicating that the bacteria were alive, while the PAW treatment group showed a large area of dense red fluorescence, and the green fluorescence was significantly weakened, with a mortality rate of 100%. The results directly prove that the first type of plasma activated water and the second type of plasma activated water prepared by the embodiment of the application have strong and direct killing effect on E. coli and S. aureus.

[0055] The verification results show that the first type of activated water (strong acid, high RNS) and the second type of activated water (near neutral, high ROS) can achieve the same high efficiency of broad-spectrum sterilization by different active ingredient dominations, which exactly reflects the great advantages and flexibility of the "double mode" design of the application in application, and users can select the most suitable mode to prepare the high-efficiency disinfectant with specific preference according to the characteristics (such as whether acid-resistant) of the object to be treated.

[0056] The double-mode atmospheric pressure plasma activated water generation system provided by the application can realize the preparation of two types of plasma activated water on the same system through simple voltage adjustment, greatly expanding the application range and use flexibility of the equipment, and the system structure is compact and easy to operate, providing a powerful tool for scientific research and industrial application.

[0057] The basic principles, main features and advantages of the application are shown and described above. Those skilled in the art should understand that the application is not limited by the above examples, and the above examples and descriptions in the specification are only preferred examples of the application and are not intended to limit the application. Without departing from the spirit and scope of the application, various changes and improvements can be made to the application, and these changes and improvements all fall within the scope of the claimed application. The scope of protection of the application is defined by the appended claims and their equivalents.

Claims

1. A dual-mode atmospheric pressure plasma-activated water generation system, characterized by, The application relates to a plasma activated water generator. The application comprises: a reaction container (1) for containing liquid to be activated; a medium assembly (2) comprising an insulated medium tube (21), the lower end of the medium tube (21) extending into and hanging in the reaction container (1), the side wall of the medium tube (21) being provided with an air inlet (22) and the bottom end being provided with a micropore (23); 2. The dual-mode atmospheric-pressure plasma-activated water generation system of claim 1, wherein, a discharge assembly (3) comprising a high-voltage needle electrode (31), a low-voltage electrode (32) and a power supply (33), the high-voltage needle electrode (31) being inserted into the medium tube (21), the low-voltage electrode (32) comprising a first low-voltage electrode (321) surrounding the outer periphery of the medium tube (21) and a second low-voltage electrode (322) fixedly connected to the bottom of the reaction container (1), the high-voltage needle electrode (31) being connected to the power supply (33) through a high-voltage power supply line (35), and the second low-voltage electrode (322) extending out of the reaction container (1) and being connected to the power supply (33) through a low-voltage power supply line (36).

3. The dual-mode atmospheric pressure plasma-activated water generation system of claim 1, wherein, The reaction container (1) comprises a reaction dish (11) and a reaction dish cover (12) covering the reaction dish (11), the reaction dish cover (12) being provided with an opening for mounting the medium tube (21) and a vent hole (13).

4. The dual-mode atmospheric-pressure plasma-activated water generation system of claim 1, wherein, The diameter of the micropore (23) is 200-700 microns.

5. The dual-mode atmospheric-pressure plasma-activated water generation system of claim 1, wherein, The wall thickness of the medium tube (21) is 1.0-2.0 mm.

6. The dual -mode atmospheric -pressure plasma-activated water generation system of claim 1, wherein, The high-voltage needle electrode (31) is needle-shaped or rod-shaped with a sharp bottom end.

7. The dual -mode atmospheric -pressure plasma-activated water generation system of claim 1, wherein, The tip of the high-voltage needle electrode (31) is located near the micropore (23) at the bottom of the medium tube (21).

8. A method of generating plasma activated water using the system of any one of claims 1-7, characterized in that, The high-voltage needle electrode (31) is fixed to the top opening of the medium tube (21) through an elastic positioning plug (34). The application comprises the following steps: adding liquid to be activated into the reaction container (1); continuously feeding working gas into the medium assembly (2); 9. The method of claim 8, wherein, turning on the high-voltage high-frequency alternating current power supply (33), adjusting the output voltage to a first voltage range to make the system work in a dielectric barrier discharge mode to generate first type of plasma activated water, or adjusting the output voltage to a second voltage range higher than the first voltage range to make the system work in a liquid-electric discharge mode to generate second type of plasma activated water.

10. The method of claim 8, wherein, The critical breakdown voltage between the first voltage range and the second voltage range depends on the wall thickness of the medium tube (21), the shape of the tip of the high-voltage needle electrode (31) and the type of the working gas. The application also comprises sequentially performing dielectric barrier discharge mode activation and liquid-electric discharge mode activation, or sequentially performing liquid-electric discharge mode activation and dielectric barrier discharge mode activation.

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