Plasma water treatment

Abstract

To provide an apparatus and a method for treating water with plasma, plasma-treated water, and a method for using the plasma-treated water.SOLUTION: An apparatus for treating a liquid with plasma includes one or two dielectric barriers, in which the dielectric barriers and a high-voltage electrode define a discharge region between them. The high-voltage electrode may be electrically insulated from the discharge region by an internal dielectric barrier. In this apparatus, an external dielectric barrier is gas-permeable, and the discharge region is configured to accommodate a gas flow therethrough.SELECTED DRAWING: Figure 7

Description

[Technical Field]

[0001] The present invention relates to an apparatus and method for treating water with plasma, plasma-treated water, and methods for using plasma-treated water.

[0002] The present invention has been developed primarily for use in water treatment and will be described hereinafter with reference to this application, although it will be understood that the invention is not limited to this particular field of use. [Background technology]

[0003] Reactive species produced by plasma are known to be effective in the decomposition of certain biological and chemical compounds that may be present in water. Water exposed to plasma-derived reactive species can be "activated" by introducing a range of reactive metastable species into the water. This plasma-activated water (PAW) can be used to treat materials exposed to the water and decontaminate products containing microorganisms, fungi, viruses, and chemicals. PAW may also be used as a fertilizer or as a fuel. Plasma and plasma-water reactions generate a variety of reactive species through various pathways, including hydroxyl radicals, hydroperoxyl radicals, hydrogen peroxide, ozone, excited molecules, and excited atoms. One of the key factors in sterilization is the presence of reactive species generated in the plasma during the process. These reactive species can be broadly classified into two types: primary reactive species, such as charged particles, photons, and certain radicals (·H, ·O, ·OH, ·NO), and secondary reactive species (H2O2, NOx, O3, HNOx, ONOOH). When high voltage is applied to atmospheric gases, primary reactive species are generated. Hydroxyl radicals are the core component in advanced oxidation processes because they react almost instantaneously and nonselectively with pollutants such as persistent and volatile organic compounds. Therefore, the generation of OH radicals is essential for the efficiency of plasma-based water treatment. However, OH radicals have a short lifespan due to their high reactivity. This is often due to their dimerization to form a secondary reactive species, hydrogen peroxide, which has been used for disinfection and sterilization in water treatment processes. Hydrogen peroxide is preferred over chlorination because it does not produce toxic by-products in the oxidation reaction. Much of the work on water treatment reactions has focused on the generation of ozone (O3), a secondary reactive species. O3 is used to decompose organic contaminants in water treatment by selectively attacking unsaturated bonds and partially decomposing organic compounds. O3 is typically generated by discharging an electric discharge through air in a discharge channel, and the liquid to be treated is received in the discharge channel, thereby directly exposing it to the generated O3. O3 disinfection systems aim to maximize the solubility of O3 in wastewater, since disinfection relies on the transfer of O3 into the wastewater. In conventional ozone generators, DBDs are separated from the water, and ozone is diffused into the water through a tube. The dispersed high-energy electrons increase the production of reactive species, particularly UV radiation, O, and O3. However, the production of OH radicals and H2O2 by DBD reactors has not shown competitive results compared to other gas discharge methods. O3 generators / reactors have many drawbacks, including: Low concentrations may not effectively inactivate some viruses, spores, and cysts. Ozonation is a more complex technology than chlorine or ultraviolet disinfection, requiring complex equipment and efficient contact systems. O3 is highly reactive and corrosive, requiring corrosion-resistant materials such as stainless steel. · Ozonation is not economical for wastewaters with high concentrations of suspended solids (SS), biochemical oxygen demand (BOD), chemical oxygen demand, or total organic carbon. O3 is highly irritating and potentially toxic, so the gases evolved from the contactor must be destroyed to prevent worker exposure.

[0004] Plasma can be interfaced with water via direct discharge on the water surface, underwater discharge, discharge within bubbles in water, or via introduction of reactive gas species as bubbles into the water bulk. How gas-phase generated plasma is interfaced with water, such as in existing bubbles, on the liquid surface, or when the water is in the form of droplets or splashes, greatly influences the chemical makeup of the species produced due to the different decomposition strengths in the gas phase and in solution, respectively.

[0005] It is desirable to provide a reactor means for generating the primary reactive OH radicals and allowing an effective reaction time between the generated OH radicals and the treatment solution. In addition to the above, scaling atmospheric plasma technology has proven difficult due to the need to effectively introduce short-lived reactive species from the gas plasma into the water. It is a further object of the present invention to provide an apparatus that overcomes or substantially ameliorates at least some of the deficiencies of the prior art, or at least provides an alternative.

[0006] Where any prior art information is referenced herein, it should be understood that such reference does not constitute an admission that that information forms part of the common general knowledge in the art in Australia or any other country. Summary of the Invention

[0007] According to a first aspect, there is provided an apparatus for treating a liquid with a plasma, the apparatus comprising a first dielectric barrier and a second dielectric barrier defining a discharge region therebetween, and a high voltage electrode electrically insulated from the discharge region by the first dielectric barrier, wherein the second dielectric barrier is gas permeable and the discharge region is configured to receive a gas flow therethrough.

[0008] The following options may be used individually or in any suitable combination in conjunction with the first aspect.

[0009] The apparatus may further include a ground electrode. The ground electrode may be separated from the discharge area by at least a second dielectric barrier. The ground electrode and the discharge area may be on opposite sides of the second dielectric barrier.

[0010] The apparatus may further comprise a container for containing a liquid. During use, the liquid in the container may contact a second dielectric barrier. The liquid may be separated from the discharge area by the second dielectric barrier. As used herein, the term "separated from by," e.g., "A is separated from B by C," indicates that at least a portion of C is disposed between A and B such that A does not contact B. This does not imply that C is the only integral entity between A and B, although in some cases it may be.

[0011] In one option, the container comprises a dielectric material, and the device comprises a ground electrode in contact with the dielectric material. The ground electrode may be positioned such that, in use, the dielectric material separates the liquid in the container from the ground electrode. Thus, the ground electrode may be positioned outside the container. In this example, in use, the liquid would be contained inside the container.

[0012] In another option, the device includes a ground electrode positioned such that, in use, the ground electrode is in electrical contact with the liquid in the container. In one form, the container is electrically conductive and includes or forms the ground electrode. In yet another option, a separate metallic ground electrode is positioned within the liquid in the container, optionally on an interior surface of the container.

[0013] The high voltage electrode may be disposed within a first dielectric barrier. The electrode may be surrounded, enclosed, or encased in the first dielectric barrier. In one configuration, the high voltage electrode, first dielectric barrier, discharge area, and second dielectric barrier are concentric. The high voltage electrode may be surrounded by the first dielectric barrier, which is surrounded by the discharge area, which is in turn surrounded by the second dielectric barrier.

[0014] The first dielectric barrier may be gas impermeable, may be impermeable to the gas used in the discharge area, or may be impermeable to liquids.

[0015] The second dielectric barrier may be porous; microporous; permeable to any one or more of the gas in the discharge region, the plasma species, and the discharge itself; hydrophobic; or hydrophilic. If at least a portion of the region is porous and / or gas permeable, the barrier may have non-porous and / or gas impermeable regions.

[0016] The apparatus may include a gas inlet, which allows a gas or gas mixture to enter the discharge region. In some instances, the discharge region has a gas outlet, while in other instances, a second (gas-permeable) dielectric barrier serves as the only gas outlet. The apparatus may include a gas propulsion device, e.g., a pump, that passes the gas from the gas inlet into the discharge region. In some instances, all of the gas entering the discharge region exits the discharge region through the outer dielectric barrier.

[0017] The apparatus may include a high-voltage generator capable of applying a voltage to the high-voltage electrode sufficient to generate a plasma in the gas within the discharge region. The voltage may be between about 1 kV RMS (root mean square) and about 150 kV RMS. The high-voltage generator may be electrically coupled to and / or in electrical contact with the high-voltage electrode.

[0018] In an embodiment, an apparatus for treating a liquid with a plasma is provided, the apparatus comprising: a gas-impermeable first dielectric barrier and a porous second dielectric barrier defining a discharge region therebetween; and a high-voltage electrode electrically insulated from the discharge region by the first dielectric barrier. In this embodiment, the discharge region is configured to receive a gas flow therethrough.

[0019] In another embodiment, an apparatus for treating a liquid with a plasma is provided, the apparatus comprising: a gas-impermeable first dielectric barrier and a porous second dielectric barrier defining a discharge region therebetween; a high-voltage electrode contained within and electrically insulated from the discharge region by the first dielectric barrier; and a high-voltage generator capable of applying a voltage to the high-voltage electrode sufficient to generate a plasma in a gas within the discharge region, the voltage typically being between about 1 kV RMS and about 150 kV RMS.

[0020] In this embodiment, the discharge region is configured to receive a gas flow therethrough.

[0021] In a second aspect, there is provided a method of treating a liquid with a plasma, the method comprising providing an apparatus according to the first aspect, passing a gas through a discharge region to expose the side of the second dielectric barrier remote from the discharge region to the liquid, and applying a voltage to the high voltage electrode sufficient to generate a plasma in the gas in the discharge region.

[0022] The following options may be used in connection with the second aspect, either individually or in any suitable combination.

[0023] The gas may be any one of air, nitrogen, oxygen, carbon dioxide, helium, neon, argon, xenon, or a mixture of any two or more of these. For example, the gas may be air.

[0024] The liquid may be an aqueous liquid, such as water.

[0025] The pressure differential across the second dielectric barrier may be sufficient to cause the gas to pass from the discharge area into the liquid.

[0026] The voltage may be between about 1 kV RMS and about 150 kV RMS.

[0027] The liquid may contain one or more contaminants. In this case, the method may at least partially remove and / or destroy the contaminants. The contaminants may be microorganisms, viruses, or chemical contaminants, and the water may contain any two or more of viruses, microorganisms, and chemical contaminants. In a specific example, the contaminants include PFAS (perfluoroalkyl and / or polyfluoroalkyl compounds). In another example, the contaminants include one or more of pharmaceuticals, endocrine disruptors, and PFAS.

[0028] In one embodiment, the method provides an apparatus for treating a liquid with plasma, the apparatus comprising: a first dielectric barrier and a second dielectric barrier defining a discharge region therebetween; and a high-voltage electrode electrically insulated from the discharge region by the first dielectric barrier, the second dielectric barrier being gas permeable, the discharge region being configured to receive a gas flow therethrough, the method including passing the gas through the discharge region to expose a side of the second dielectric barrier remote from the discharge region to the liquid; and applying a voltage to the high-voltage electrode sufficient to generate a plasma in the gas in the discharge region.

[0029] In another embodiment, the method treats water containing microbial and / or chemical contaminants, the method providing an apparatus for treating water with plasma, the apparatus comprising: a gas-impermeable first dielectric barrier and a porous second dielectric barrier defining a discharge region therebetween; and a high-voltage electrode electrically insulated from the discharge region by the first dielectric barrier, the discharge region configured to receive a gas flow therethrough, the method including passing the gas through the discharge region and the second dielectric barrier and exposing a side of the second dielectric barrier remote from the discharge region to the water; and applying a voltage of between about 1 and about 150 kV RMS to the high-voltage electrode.

[0030] In another embodiment, the method provides an apparatus for treating a liquid with plasma, the apparatus comprising: a first dielectric barrier and a second dielectric barrier defining a discharge region therebetween; and a high-voltage electrode electrically insulated from the discharge region by the first dielectric barrier, the second dielectric barrier being gas permeable, the discharge region being configured to receive a gas flow therethrough; passing the gas through the discharge region and exposing a side of the second dielectric barrier remote from the discharge region to the liquid; and applying a voltage to the high-voltage electrode sufficient to generate a plasma in the gas in the discharge region, wherein a pressure differential across the second dielectric barrier is sufficient to pass the gas from the discharge region into the liquid.

[0031] In a third aspect of the invention there is provided the use of water treated for human consumption using the apparatus of the first aspect or the method of the second aspect.

[0032] In a fourth aspect of the present invention there is provided a process for producing drinking water comprising applying the method of the second aspect to contaminated water.

[0033] In a fifth aspect of the invention there is provided the use of water treated using the apparatus of the first aspect or treated using the method of the second aspect to irrigate seeds, crops or other plants, or to make chemicals to be used as fuels.

[0034] In a sixth aspect of the present invention there is provided a method of irrigating seeds, crops or other plants comprising treating water using the apparatus of the first aspect, or treating water using the method of the second aspect, and applying the water so treated to the seeds, crops or other plants, or to the soil in which the seeds, crops or other plants are located or growing.

[0035] In the fifth and sixth aspects of the invention, the gas may be a nitrogen-containing gas or may be nitrogen itself, thereby causing the method of the second aspect to produce nitrogen species in the water that are beneficial to plant growth. In these aspects, plant growth nutrients and / or hormones and / or essential minerals may be added to the treated water after applying the method of the second aspect to further enhance the beneficial properties of the water.

[0036] The present invention is also broadly said to consist of the parts, elements and features referred to or shown in the specification of this application, individually or collectively, and any or all combinations of any two or more of said parts, elements or features, where specific wholes having equivalents known in the art to which the invention pertains are referred to herein and such known equivalents are deemed to be incorporated herein as if individually set forth.

[0037] Other aspects of the invention are also disclosed.

[0038] Notwithstanding any other forms that may fall within the scope of the present invention, embodiments of the present invention will now be described, by way of example only, with reference to the accompanying drawings in which: [Brief explanation of the drawings]

[0039] [Figure 1] 1 is an apparatus according to one embodiment of the present invention. [Figure 2] 1 is an apparatus according to another embodiment of the present invention. [Figure 3] 1 is a graph showing the production of reactive oxygen species (OH·, HO, O) produced using the method of the present invention. The data curves show the production [mg / L] of hydrogen peroxide (HO) [○], ozone (O) [◆], and hydroxyl radical (OH·) [■] over time. The gas used is air. The liquid is water. [Figure 4](a) Graphs of nitrite production as a function of gas flow rate (SLM: standard liters per minute) using the design of Figure 1 directly grounded (i.e., ground electrode [IN]) in 20°C water and (b) the effect of water temperature on nitrite production under the conditions of (a) at a gas flow rate of 0.5 SLM. [Figure 5] An example of a plasma gas excitation spectrum for air in a reactor is shown, demonstrating the presence of excited nitrogen and oxygen species. The discharge is dominated by excited nitrogen molecules, and the first negative N2+ transition induced by collisions of energetic electrons with O2 and N2 molecules. Hydroxyl and atomic oxygen radicals are also evident. [Figure 6] Photograph showing the device in operation using CO2 as the feed gas, where the plasma discharge can be seen in the bubbles formed upon exiting the reactor. The setup consists of two reactors with 12 microholes of 200 μm diameter. [Figure 7] 1 is a photograph showing a plasma discharge within a forming bubble exiting a porous reactor, in this case the gas is argon. [Figure 8] 1 is an apparatus according to yet another embodiment of the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0040] An apparatus and method for producing non-equilibrium atmospheric plasma in water are described. A range of gases and gas mixtures can be used in this approach, including air, nitrogen, oxygen, helium, neon, argon, carbon dioxide, and mixtures of any two or more of these in any combination. It is understood that the species generated from plasma derived from these different gases are different and therefore may be used for different applications. Using common knowledge and routine trial and error, one of ordinary skill in the art can readily determine a gas or gas combination suitable for a particular application. For example, a gas or mixture suitable for destroying viruses may be different from one suitable for destroying PFAS or other chemical contaminants. Similarly, it is understood that different operating parameters may be appropriate for different gases used in the apparatus, and these can also be easily determined by one of ordinary skill in the art using common knowledge and / or routine trial and error and the guidance provided herein. Operating parameters that may need to be adjusted include gas flow rate, pressure across the second dielectric barrier, voltage supplied to the high-voltage electrode, and whether the ground electrode is in electrical contact with or electrically isolated from the liquid. Some or all of these parameters can also be adjusted to accommodate different scales of the apparatus. For example, a device according to the present invention designed to process 1 L / min of water may be used for 1 m 3 A device designed to treat 1000 sq. m. / min. of water may require different operating parameters (voltage, gas flow rate, etc.) than a device designed to treat 1000 sq. m. / min. of water. Also, as will be appreciated, the dimensions of these two devices will be different. Appropriate sizing can be readily determined without the input of the present invention.

[0041] In the context of the present invention, the term "dielectric barrier" refers to an entity that electrically separates two regions, i.e., divides one region from another, and has high electrical resistivity. It may be physically permeable, physically impermeable, or physically selectively permeable.

[0042] The method may be employed to treat water or to create plasma activated water (PAW) for material decontamination, sterilization, and plant growth promotion. The reactor (i.e., the portion of the apparatus consisting of the first and second dielectric barriers, the discharge area therebetween, and the high-voltage electrode) is designed to be at least partially immersed in the liquid to be treated. This liquid may act as a ground, or a separate ground electrode may be provided. The separate ground electrode, if present, may be in electrical contact with the liquid or electrically insulated from the liquid by a dielectric material, either in the form of a discrete electrode in electrical contact with the liquid or in the form of a grounded vessel in which the liquid is contained. In the present invention, the term "dielectric" is used to mean a dielectric constant between 0.01 and 10 15 It may also be considered to refer to a material having an electrical resistivity between about 0.01 and about 10 Ω.m. Suitable dielectrics for any or all of the first dielectric barrier, second dielectric barrier, and dielectric material (if present) include ceramics, glass, and polymeric materials, such as glass, quartz, silica, aluminosilicates, polyolefins, fluoropolymers, polyamides, polyimides, and the like. Any of the dielectrics used in the present invention may independently have a resistivity between about 0.01 and about 10 15 Ω.m, or approximately 1 to 10 15 , 10 3 ~10 15 , 10 7 ~10 15 , 10 10 ~10 15 , 0.01 to 10 10 , 0.01 to 10 5 , 0.01~10, 0.01~1, 1~10 10 , 10 5 ~10 10 , or 100 to 10 7 Ω.m, e.g., approximately 0.01, 0.1, 1, 10, 100, 1000, 10 4 , 10 5 , 10 6 , 10 7 , 10 8 , 10 9 , 10 10 , 10 11 , 10 12 , 10 13 , 1014 or 10 15 It may have a resistivity of Ω.m.

[0043] The second dielectric barrier is permeable to the gas and / or plasma discharge. It may be porous. It may have controlled porosity to promote contact and interaction of the liquid with both the plasma discharge and the plasma afterglow. The second dielectric barrier may be hydrophobic to prevent or inhibit penetration of aqueous liquid therethrough into the discharge region and / or to promote passage of gas from the discharge region through the second dielectric barrier. Alternatively, it may be hydrophilic. If the second dielectric barrier is porous, the pore size may be such that it prevents or inhibits leakage of liquid into the discharge region. Suitable gas pressure in the discharge region may also play a role in inhibiting such leakage. Suitable pore sizes are about 0.1 to about 2000 microns, or about 0.1 to 1000, 0.1 to 500, 0.1 to 100, 0.1 to 50, 0.1 to 10, 1 to 2000, 10 to 2000, 100 to 2000, 500 to 2000, 500 to 1000, 1 to 1000, 1 to 100, 10 to 1000, 10 to 100, or 10 to 500 microns, for example, about 0.1, 0 0.5, 1, 2, 5, 10, 15, 20, 25, 30, 35, 40, 45, 50, 60, 70, 80, 90, 100, 150, 200, 250, 300, 350, 400, 450, 500, 600, 700, 800, 900, 1000, 1100, 1200, 1300, 1400, 1500, 1600, 1700, 1800, 1900 or 2000 microns. These may independently be maximum or average pore sizes. A suitable pressure differential across the second dielectric barrier is at least about 10 kPa, or at least about 20, 30, 40, 50, 60, 70, 80, 90, or 100 kPa, or about 10 to about 100 kPa, or about 10 to 50, 10 to 20, 20 to 100, 50 to 100, or 20 to 50 kPa, e.g., about 10, 15, 20, 25, 30, 34, 40, 45, 50, 60, 70, 80, 90, or 100 kPa. This pressure can be created by adjusting the flow rate of gas through the discharge region and / or by narrowing the exit port (if any) from the discharge region. In some instances, there is no exit port from the discharge region other than through the porous second dielectric barrier.In this case, all gas passing through the discharge region exits through the second dielectric barrier, capturing the plasma and / or by-products from the plasma. Therefore, in one embodiment of the present invention, the pressure difference across the second dielectric barrier is sufficient to pass the gas and / or plasma from the discharge region into the liquid. This causes bubbles to form in the liquid. The plasma and / or plasma by-products can then pass across the gas-liquid barrier into the liquid to treat the liquid. Generally, the smaller the pore size of the second dielectric barrier, the smaller the bubbles that form in the liquid, and therefore the larger the gas-liquid interfacial area. Increasing the interfacial area increases the transfer rate and therefore the more efficient the treatment. However, as the pore size decreases, the flow rate through the second dielectric barrier also decreases for a given pressure across the second dielectric barrier. Therefore, a suitable combination of pore size and pressure must be used to achieve the desired level of treatment efficiency. This combination can be easily determined through routine experimentation. If gas bubbles form within the liquid surrounding the second dielectric barrier, it is preferred that the liquid be in contact or connected with the outside atmosphere to prevent a build-up of pressure within the liquid.

[0044] A range of plasma control parameters, including discharge gap (i.e., thickness of the discharge area), discharge volume (i.e., volume of the discharge area), voltage, and frequency, may be controlled within the apparatus to produce controlled plasma reactive species in the water. A suitable discharge gap is about 1 to about 50 mm, or about 1 to 40, 1 to 30, 1 to 20, 1 to 10, 10 to 50, 20 to 50, 30 to 50, 40 to 50, 10 to 30, or 20 to 40 mm, for example, about 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 15, 20, 25, 30, 35, 40, 45, or 50 mm. The discharge volume depends on the discharge gap and the length of the discharge area. Generally, the size of the discharge area depends on the desired throughput of the liquid being treated. A suitable discharge volume is about 10 -2 ~about 10 5 cm 3 , or about 10 -2 ~10 2 , 10 -2 ~1, 1~10 5, 10 2 ~10 5 , 10 -2 ~2*10 4 , 1 to 10 3 or 10 -1 ~10cm 3 , for example, about 10 -2 , 5*10 -2 ,0.1,0.5,1,5,10,50,100,500,1000,5000,10 4 , 2*10 4 , 5*10 4 or 10 5 cm 3 Suitable discharge voltages are about 1 to about 150 kV, or about 1 to 100, 1 to 50, 1 to 10, 10 to 150, 50 to 150, 100 to 150, or 50 to 100 kV, for example, about 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 20, 30, 40, 50, 60, 70, 80, 90, 100, 110, 120, 130, 140, or 150 kV. The smaller the discharge gap, the lower the voltage required to generate plasma. The applied voltage can be AC, DC, or rectified AC. 12 Between Hz, or about 1 and 10 10 , 1 to 10 8 , 1 to 10 6 , 1 to 10 4 , 1 to 10 2 , 10 2 ~10 12 , 10 4 ~10 12 , 10 6 ~10 12 , 10 8 ~10 12 , 10 10 ~10 12 , 10 2 ~10 6 , 10 6 ~10 10 or 10 4 ~10 8The frequency may be, for example, about 1, 10 or 100 Hz, 1, 10 or 100 kHz, 1, 10 or 100 MHz, 1, 10 or 100 GHz or 1 THz. The method of the present invention may be used for microbial or chemical decontamination of water, wastewater, food, medical devices, or other objects that benefit from treatment with reactive water or liquids.

[0045] The devices and / or methods of the invention may operate at temperatures of between about 10 and about 90°C, or between about 20 and 90, 30 and 90, 40 and 90, 50 and 90, 60 and 90, 70 and 90, 80 and 90, 10 and 80, 10 and 70, 10 and 60, 10 and 50, 10 and 40, 10 and 30, 10 and 20, 20 and 50, 50 and 80, or 20 and 40°C, e.g., about 10, 15, 20, 25, 30, 35, 40, 45, 50, 55, 60, 65, 70, 75, 80, 85, or 90°C.

[0046] The reactive species created in the plasma are hydrogen peroxide (H2O2), ozone (O3), and nitrates (NO 3- ) and nitrite (NO 2- ), and other long-lived species such as hydroxyl radical (OH·), nitric oxide (NO·), atomic oxygen (O), and peroxynitrite (OONO 2- ) and peroxynitrite (ONOO - The amount of reactive oxygen and nitrogen species (RONS) produced using the method of the present invention may also include reactive oxygen and nitrogen species (RONS), which typically include (relatively) short-lived species such as NO₁₀, HO₂, and O₃. An example of data on reactive oxygen species (OH₁₀, HO₂, and O₃) produced using the method of the present invention is shown in Figure 3. NO₁₀ as a function of gas flow rate and water 2-An example of this generation is shown in Figure 4. Figure 5 shows an example of a gas excitation spectrum relative to air, showing nitrogen and oxygen species excited in situ within the reactor discharge gap. These species can result in a decrease in the pH of the liquid. PAW can be used as an antibacterial agent against bacteria, biofilms, fungi, amoeba, and viruses. Similarly, it can degrade chemical contaminants such as pesticides, antibiotics, pharmaceuticals, and perfluoroalkyl and polyfluoroalkyl substances (PFAS). It can also be used as a plant fertilizer by producing nitrates and other nitrogen species, which are then applied to plants or cells. The decrease in pH may require adjusting the pH of the liquid after treatment and before use. Neutralizing the liquid may be necessary.

[0047] An atmospheric non-thermal plasma reactor is presented herein as a means for treating water and / or generating PAW. Because the reactor and associated equipment are readily scalable, the device can be sized to process large volumes of liquid and / or have high liquid throughput. Thus, the device may be readily adapted to process any of the following volumes: between about 1 and about 10,000 L / hour or more, or about 1-1000, 1-100, 1-10, 10-10,000, 100-10,000, 1000-10,000, or 500-5000 L / hour, e.g., about 1, 5, 10, 20, 50, 100, 200, 500, 1000, 2000, 5000, or 10,000 L / hour, or volumes greater than 10,000 L / hour. Parameters that may be adjusted to regulate throughput include the diameter of the discharge area, the discharge gap, the length of the discharge area, the gas flow rate, the volume of the vessel containing the liquid, etc. In some instances, more than one reactor, e.g., 2, 3, 4, 5, 6, 7, 8, 9, or 10 or more reactors (a reactor, as discussed above, is an assembly of a high-voltage electrode, first and second dielectric barriers, and a discharge area between these barriers) may be immersed in the same body of liquid to increase the processing rate of the liquid. They may have the same dimensions and operate at the same voltage, or may be different dimensions and / or operate at different voltages.

[0048] In some embodiments, the liquid is treated in batches. In other embodiments, the liquid is treated continuously. In such embodiments, the flow rate of the liquid through the device can be controlled to provide effective treatment. If the flow rate is too high, insufficient plasma / plasma byproducts will come into contact with the water to provide effective treatment.

[0049] In one form, the reactor includes a high-voltage electrode and a plasma discharge region in the form of a dielectric barrier discharge (DBD) with a gas inlet to the discharge region. The DBD thus comprises (or consists of) first and second dielectric barriers and a discharge region therebetween. The first, typically inner, dielectric barrier that covers or surrounds the high-voltage electrode for the DBD may be made of quartz, glass, ceramic, or a polymeric material. The second, typically outer, dielectric barrier surrounds the first dielectric barrier and defines a discharge region between the first and second dielectric barriers. In one example of a DBD in use, the reactor is immersed in water, and the water acts as a ground electrode, either directly grounded by an immersion electrode or a conductive water container, or indirectly grounded outside a non-conductive water container. Inserting bare metal directly into the water changes the resulting chemistry of the reactor, acting as an electrochemical electrode. A second, generally outer, dielectric barrier is porous to the flowing conductor gas, which acts as a gas outlet and a mechanism for introducing plasma species into the water.

[0050] According to one aspect of the present invention, water is part of the device and acts as a ground electrode for the DBD. The means by which this circuit is completed is important to the resulting chemistry. At least two options are possible. The first option is to use a remote electrode, immersed in the water, to complete the electrical circuit relative to the DBD. The second option is to complete the circuit by grounding the wall of a non-metallic water container. In the first approach, the electrochemical reaction can occur at the electrode, which is controlled by its construction material and surface area.

[0051] The DBD's external barrier not only acts as an outer wall of the discharge region, maintaining the gas gap and the dielectric layer that promotes stable plasma discharge, but also as a means of contacting the plasma with the water. The controlled porosity of the second dielectric barrier allows gas plasma species to exit the DBD reactor. The pore size is designed to be small enough to prevent water from entering the discharge gap. Pore size is also important in controlling the size distribution of bubbles that form. The porous DBD design minimizes the time it takes to introduce reactive species formed in the liquid. However, this design allows for more than simply introducing reactive gas species (plasma afterglow) that form in the discharge region. Once the conducting gas passes through the pores, the plasma itself can exit and contact the surrounding water. This approach not only increases the possibility of introducing short-lived species into the water, but also potentially introduces solvated electrons into the water. UV light can also pass through the external dielectric barrier from the discharge region if it is constructed from a UV-transparent material such as quartz. UV light may be generated by the plasma. This can be useful in destroying contaminants in the water, particularly microorganisms and viruses.

[0052] DBD designs can be tailored by using concentric tubes, where the annular gap of the discharge region is determined by the gas input and discharge voltage. However, the discharge volume per unit length can be increased by employing larger diameter inner and outer dielectric barriers for DBDs while maintaining the same gap between these barriers. Thus, the discharge gap can be kept constant as the radii of both the inner and outer tubes increase as well. This design facilitates large-volume gas decomposition without increasing the discharge gap, i.e., the distance between the two dielectric barriers.

[0053] By submerging the DBD reactor in water, the device has an effective heat sink that uses natural forced convection to remove the potential for thermal energy accumulation. This can be enhanced if the device is used in continuous mode, i.e., the water flows past a second dielectric barrier, thereby removing heat from the entire system. The use of mixer elements can be used to increase convective heat transfer, but also control the amount of metastable and / or unstable species from the plasma in the bulk solution through mixing of the species with the bulk fluid. Suitable mixer elements may be present in the liquid and include active elements such as powered mixer blades and passive elements such as baffles. In some instances, there may be a cooler in contact with the liquid to facilitate heat removal. This may be a simple heat exchanger, a jacketed vessel, or any other suitable form of cooler.

[0054] The apparatus may include a gas flow controller that controls the amount of gas introduced into the discharge region, the residence time of the gas in the discharge region, the partial pressure in the discharge region, and the size of bubbles that form in the liquid. If a mixture of gases is supplied to the discharge region, there may be a gas mixer to mix the gases in the desired ratio. This may be located before the gas inlet so that the gases are mixed before entering the discharge region. Alternatively, a supply of suitably mixed gases may be used.

[0055] The device may be powered by a pulsed AC voltage, a positive or negative DC voltage, or a pulsed radio frequency voltage.

[0056] The second dielectric barrier, which contacts the gas and liquid, may be actively vibrated via ultrasound, for example, at frequencies between about 20 kHz and about 1 MHz (or about 20-500, 20-100, 20-50, 50-1000, 100-1000, 500-1000, 100-500, or 200-700 kHz, e.g., about 20, 30, 40, 50, 60, 70, 80, 90, 100, 150, 200, 250, 300, 350, 400, 450, 500, 600, 700, 800, 900, or 1000 kHz), to produce controlled bubbles in the nanometer or micrometer range. Smaller bubbles are known to be more stable than larger bubbles and offer a larger interfacial surface area. This may therefore facilitate the transfer of plasma and / or plasma byproducts into the liquid.

[0057] In certain embodiments of the present invention, the first dielectric barrier is not present. In such embodiments, the discharge region is defined between the high-voltage electrode and the second dielectric barrier. Thus, the high-voltage electrode contacts and / or passes through the gas in the discharge region.

[0058] In certain embodiments, the second dielectric barrier is non-porous and / or impermeable to gases in and / or passing through the discharge region. In such embodiments, the outlet from the discharge region is generally in contact with, but distinct from, the second dielectric barrier. The outlet is positioned and designed to allow gases and / or discharge products to pass from the discharge region into the liquid. This can therefore result in treatment of the liquid with the gases and / or discharge products.

[0059] The above-described embodiments (absence of a first dielectric barrier and a non-porous second dielectric barrier) may be used separately or in combination.

[0060] Thus, the present invention provides a system for optionally treating or activating large volumes of water or liquid, comprising an apparatus configured to create atmospheric plasma while being introduced into the water. The apparatus typically includes a high-voltage electrode, an inner dielectric barrier surrounding the high-voltage electrode, a discharge area for gas flow, and a gas-permeable, generally porous, outer dielectric barrier that contacts the plasma and water. The bulk water may act as a ground electrode. Additionally or alternatively, it may act as a heat sink. Thus, a discharge gap may be maintained between the non-porous and porous dielectric barriers. The working gas may be air or may include at least two gases selected from air, nitrogen, oxygen, carbon dioxide, and a noble gas. The plasma discharge may directly contact the water through the porous outer dielectric barrier. The plasma-inducing reactive gas species may directly contact the water through a porous second dielectric barrier. The voltage applied to the high-voltage electrode may be at least about 1 kV RMS and up to about 150 kV RMS.

[0061] The present invention also provides a method for disinfecting or decomposing contaminants in water, which comprises immersing the device described hereinabove in a volume of water to be treated, flowing a working gas or gases into the discharge area of ​​the device, and inducing a plasma in the working gas using a high voltage difference between a high voltage electrode and the grounded water.

[0062] The present invention further provides a method for producing plasma activated water (PAW) comprising immersing a device in a volume of water to be treated, flowing a working gas or gases into the discharge area of ​​the device, and inducing a plasma in the working gas using a high voltage differential between a high voltage electrode and grounded water.

[0063] Embodiment 1 and 2 show schematic representations of the apparatus of the present invention. A high-voltage generator (not shown) is connected to a high-voltage metallic electrode 10. A first dielectric barrier 20 surrounds the high-voltage electrode 10 to form a covering electrode. The effect of the dielectric barrier 20 is to limit the current flow between the electrode 10 and ground and prevent the formation of an arc. The dielectric barrier 20 also physically separates the high-voltage electrode 10 from the discharge region 30 surrounding it, preventing contact between the high-voltage electrode 10 and water that might enter the discharge region 30 due to insufficient pressure within the discharge region 30. The discharge region 30 is maintained between the outer surface of the inner dielectric barrier 20 and the inner surface of the outer dielectric barrier 40. The gap distance between the inner and outer dielectric barriers 20 and 40 (i.e., the thickness of the discharge region 30) determines the breakdown voltage required for a particular gas. The outer dielectric barrier 40 is porous to allow gas and / or plasma to pass from the discharge region 30, where the plasma is generated, to the water in contact with the outer dielectric barrier 40. In FIG. 1, the water in contact with the outer dielectric barrier 40 is grounded by a metallic ground connection 50, whereas in FIG. 2, the ground connection 50 is coupled to a non-metallic container 60 containing the water.

[0064] In operation, the conductor gas enters the discharge region 30 through the inlet valve and exits through the porous outer dielectric barrier 40. The porous dielectric barrier 40 serves both to maintain the gap in the discharge region 30 and to allow the plasma discharge and its reactive species to contact the surrounding water. When a suitable high voltage is applied to the high-voltage electrode 10, a plasma is formed in the conductor gas flowing through the discharge region 30. As the conductor gas passes into the water surrounding the outer dielectric barrier 40, it carries with it the plasma and / or plasma byproducts that treat the water. These can kill microorganisms in the water and / or destroy or decompose harmful chemicals in the water. They can also be used as chemicals, such as fertilizers and fuels. Figure 6 shows the device in operation using CO2 as a feed gas, with the plasma discharge visible within the bubbles formed as they emerge from the microholes in the reactor. Figure 7 shows the plasma discharge within the bubbles formed as they emerge from the porous reactor.

[0065] FIG. 8 shows a schematic representation of an apparatus according to another embodiment of the present invention. The apparatus 100 shown in FIG. 8 includes a high-voltage electrode 110 and a dielectric barrier 120, defining a discharge region 130 therebetween. The dielectric barrier 120 is porous and gas-permeable. The discharge region 130 is fitted with a gas inlet 140 connected to a gas propulsion device (e.g., a pump) 150, which drives gas into and through the discharge region 130. The apparatus 100 also includes a container 160 for containing a liquid during operation of the apparatus. Also located within the container 160 is a ground electrode 170 that is in electrical and physical contact with the liquid in the container 160 during operation. In some embodiments of the present invention, the ground electrode 170 is separated from the liquid by a dielectric barrier. The high-voltage electrode 110, which is in contact with the gas in the discharge region 130 during operation, is electrically connected to a high-voltage generator 180, which provides the necessary high voltage to the electrode 110.

[0066] According to the apparatus shown in Figure 8, in operation, the apparatus 100 separates a gas in the discharge region 130 from a liquid phase on either side of the dielectric barrier 120. A gas propulsion device 150 forces gas into the discharge region 130 through the gas inlet 140. A high voltage is generated by a high voltage generator 180 and applied to the high voltage electrode 110. The gas passes through the insulating barrier 120 and flows into the liquid in the vessel 160, forming gas bubbles in the liquid. A spark discharge is generated within these gas bubbles due to the high voltage between the electrode 110 and the ground electrode 170. The products of this discharge flow into the liquid and treat it.

[0067] interpretation Markush group Furthermore, when features or aspects of the invention are described in terms of a Markush group, those skilled in the art will recognize that the invention is also thereby described in terms of any individual member or subgroup of members of the Markush group.

[0068] Time series For purposes of this specification, when method steps are described in a sequence, the sequence does not necessarily imply that the steps are performed chronologically in that order unless there is another logical way to interpret the sequence.

[0069] Embodiment References throughout this specification to "one embodiment" or "an embodiment" mean that a particular feature, structure, or characteristic described in connection with an embodiment is included in at least one embodiment of the present invention. Thus, the appearances of the phrase "in one embodiment" or "in an embodiment" in various places throughout this specification may, but do not necessarily all refer to the same embodiment. Furthermore, the particular features, structures, or characteristics may be combined in any suitable manner in one or more embodiments, as would be apparent to one of ordinary skill in the art from this disclosure.

[0070] Similarly, in the foregoing description of exemplary embodiments of the invention, it should be understood that various features of the invention may be grouped together in a single embodiment, figure, or description thereof for the purpose of streamlining the disclosure and facilitating understanding of one or more of the various inventive aspects. This method of disclosure, however, should not be interpreted as reflecting an intention that the claimed invention requires more features than are expressly recited in each claim. Rather, as the following claims reflect, inventive aspects lie in less than all features of a single foregoing disclosed embodiment. Accordingly, the claims following the Detailed Description are hereby expressly incorporated into this Detailed Description, with each claim standing on its own as a separate embodiment of the invention.

[0071] Furthermore, as will be understood by those skilled in the art, some embodiments described herein may include some features but not others included in other embodiments, meaning that combinations of features from different embodiments are within the scope of the present invention and form different embodiments. For example, in the following claims, any of the claimed embodiments may be used in any combination.

[0072] Different instances of the object As used herein, unless otherwise specified, the use of ordinal adjectives "first," "second," "third," etc., is intended merely to indicate that different instances of similar objects are being referenced to describe a common object, and is not intended to imply that the objects so described must be in a given order, either in time, space, ranking, or in any other manner.

[0073] Specific details In the description provided herein, numerous specific details are set forth. However, it should be understood that embodiments of the present invention may be practiced without these specific details. In other instances, well-known methods, structures, and techniques have not been shown in detail in order not to obscure an understanding of this description.

[0074] term In describing the preferred embodiments of the present invention illustrated in the drawings, certain terms will be rearranged for clarity. However, it is understood that the present invention is not intended to be limited to the specific terms so selected, and each specific term includes all technical equivalents that operate in a similar manner to achieve a similar technical purpose.

[0075] For the purposes of this specification, the term "plastic" is taken to refer generically to a wide range of synthetic or semi-synthetic polymerization products, generally consisting of hydrocarbon-based polymers.

[0076] As used herein, the term "and / or" means "and," or "or," or both.

[0077] As used herein, "(s)" following a noun refers to the plural and / or singular form of the noun. The use of a singular noun herein is not intended to exclude the presence of a plurality of the specified integer unless the context indicates such limitation.

[0078] "Comprises" and "includes" In the claims that follow the preceding description of the invention, and in the preceding description, unless otherwise required by context, clear language, or necessary implication, the word "comprises" or variations such as "comprises" or "comprising" are used in the inclusive sense, i.e., to specify the presence of stated features, but do not exclude the presence or addition of further features in various embodiments of the invention. These terms should not be construed to mean any minimum percentage of the stated whole.

[0079] As used herein, any one of the terms including, including, or includes is also open, meaning to include at least the element / feature that follows the term, but not to exclude others. Thus, including is synonymous with and means to comprise.

[0080] Scope of the invention Thus, while what are believed to be preferred embodiments of the present invention have been described, those skilled in the art will recognize that other and further modifications may be made thereto without departing from the spirit of the invention, and it is intended that all such changes and modifications be claimed as falling within the scope of the present invention. Steps may be added or deleted to the methods described within the scope of the present invention.

[0081] Although the present invention has been described with reference to specific embodiments, those skilled in the art will appreciate that the present invention can be embodied in many other forms.

[0082] Industrial Applicability From the above, it is clear that the described arrangements are applicable to the water purification and agricultural industries.

Claims

1. 1. An apparatus for treating a liquid with plasma, comprising: a high voltage electrode and a dielectric barrier disposed to define a discharge region therebetween; a high voltage generator configured to supply a voltage of about 1 kV root mean square (RMS) to about 150 kV RMS to the high voltage electrode; a container for containing the liquid to be treated; the dielectric barrier is gas permeable and has a pore size of 0.1 to 2000 microns; the discharge region is configured to receive a gas flow therethrough, the gas flow in the discharge region creating a pressure differential across the gas-permeable dielectric barrier sufficient to cause gas to diffuse through the dielectric barrier; the high voltage electrode is in contact with the gas in the discharge region and / or the gas passing through the discharge region; the liquid in the container is in use in contact with the gas-permeable dielectric barrier and is separated from the discharge area by the gas-permeable dielectric barrier; gas diffusing from the discharge area through the gas-permeable dielectric barrier appears in the liquid in the form of gas bubbles at the interface between the liquid and the gas-permeable dielectric barrier; When a sufficient voltage is generated by the high voltage electrode, a spark is generated within a gas bubble formed at or near the interface between the gas-permeable dielectric barrier and the liquid; The spark generates a discharge in the gas phase within the formed gas bubbles, creating H ２ O ２ and generating highly reactive primary plasma intermediates including H radicals, OH radicals, and O radicals, and enabling direct reaction of the highly reactive primary plasma intermediates with the liquid at the interface between the gas and the liquid in the vessel.

2. 10. The apparatus of claim 1, further comprising a ground electrode, said ground electrode separated from said discharge region by said gas-permeable dielectric barrier.

3. 10. The apparatus of claim 1, wherein the container comprises a dielectric material and the apparatus comprises a ground electrode in contact with the dielectric material, the ground electrode being positioned such that, in use, the dielectric material separates the liquid from the ground electrode.

4. 10. The apparatus of claim 1, comprising a ground electrode arranged such that, in use, the ground electrode is in electrical contact with the liquid in the container.

5. 5. The apparatus of claim 1, wherein the high voltage electrode, the discharge area, and the gas-permeable dielectric barrier are concentric.

6. 6. The device of claim 1, wherein the gas-permeable dielectric barrier is hydrophobic.

7. 1. A method for treating a liquid with plasma, comprising: providing an apparatus comprising a high voltage electrode and a gas permeable barrier disposed to define a discharge region therebetween; passing a gas through the discharge area; exposing a side of the gas-permeable barrier remote from the discharge area to the liquid; applying a voltage to the high voltage electrode sufficient to generate a spark; providing a device comprising the high voltage electrode and the gas permeable barrier, the gas permeable barrier has a pore size of 0.1 to 2000 microns, and the pressure differential across the gas permeable barrier is sufficient to cause gas to pass from the discharge area into the liquid and to cause gas microbubbles to appear at the interface between the liquid and the gas permeable barrier; the discharge region is configured to receive a gas flow therethrough; the high voltage electrode is in contact with the gas in the discharge region and / or the gas passing through the discharge region; providing a high voltage generator configured to supply a voltage of about 1 kV root mean square (RMS) to about 150 kV RMS to the high voltage electrode; providing a container for containing said liquid, said liquid in said container being in contact with said gas permeable barrier in use and being separated from said discharge area by said gas permeable barrier; wherein in the step of passing a gas through the discharge area, the pressure differential across the gas permeable barrier is sufficient to pass gas from the discharge area through the gas permeable barrier interfacing with the liquid in the form of gas microbubbles at the interface between the liquid and the gas permeable barrier; In the step of applying a voltage to the high voltage electrode sufficient to generate a spark, the spark generates a discharge in the gas microbubbles, and H ２ O ２ generating a highly reactive plasma intermediate including H radicals, OH radicals, and O radicals, and allowing the highly reactive plasma intermediate to react directly with the liquid at the interface between the gas and the liquid in the container; method.

8. 8. The method of claim 7, wherein the gas is selected from the group consisting of air, nitrogen, oxygen, carbon dioxide, helium, neon, argon, xenon, and mixtures of any two or more thereof.

9. The method of claim 7 wherein the gas is air.

10. The method of claim 7 , wherein the liquid is an aqueous liquid.

11. The method of claim 7 , wherein the liquid includes a contaminant, and the method at least partially removes and / or destroys the contaminant.

12. 12. The method of claim 11, wherein the contaminants are selected from the group consisting of microbial and chemical contaminants.

13. 13. The method of claim 12, wherein the contaminants include one or more of pharmaceuticals, endocrine disruptors, and PFAS.

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