Systems, methods, and devices for destruction of per- and polyfluoroalkyl substances (PFAS) and for reactivating spent activated carbon

Abstract

Embodiments disclosed herein relate to a systems, methods, and apparatus for the destruction of per- and polyfluoroalkyl substances (PFAS). These embodiments may be applied to spent activated carbon or biosolids containing PFAS. Embodiments disclosed herein involve destruction of PFAS using a microwave generated plasma, including propagating microwaves through a microwave plasma apparatus, the microwaves generated using a microwave generator to generate a microwave plasma; introducing the PFAS into the microwave plasma apparatus; and contacting the PFAS with the microwave plasma, wherein contacting the PFAS with the microwave plasma initiates a chemical reaction that destroys the PFAS. Embodiments disclosed herein also involve reactivating spent activated carbon using a microwave generated plasma. Spent activated carbon can include activated carbon and adsorbates adsorbed onto the activated carbon. Contacting the spent activated carbon with the microwave plasma can reactivate the spent activated carbon by, for example, removing the adsorbates from the activated carbon.

Description

SYSTEMS, METHODS, AND DEVICES FOR DESTRUCTION OF PER- AND POLYFLUOROALKYL SUBSTANCES (PFAS) AND FOR REACTIVATING SPENT ACTIVATED CARBONINCORPORATION BY REFERENCE TO ANY PRIORITY APPLICATIONS

[0001] This application claims the benefit of U.S. Provisional Application Numbers 63 / 536,040 and 63 / 680,541, filed August 31, 2023 and August 7, 2024, respectively, the entireties of which are hereby incorporated by reference. All publications, patents, and patent applications mentioned in this specification are herein incorporated by reference to the same extent as if each individual publication, patent, or patent application was specifically and individually indicated to be incorporated by reference.BACKGROUNDField

[0002] The present disclosure is generally directed to systems, methods, and devices for destruction of Per- and Polyfluoroalkyl Substances (PFAS). The present disclosure is also directed to systems, methods, and devices for reactivating spent activated carbon.Description

[0003] PFAS are a group of human-made chemicals that are widely used in various industrial and consumer products. These chemicals are known for their water- and greaseresistant properties, which make them useful in applications such as non-stick cookware, waterproof clothing, food packaging, and firefighting foams. One of the concerning aspects of PFAS is their persistence in the environment and their potential to accumulate in the bodies of humans and animals. They are often referred to as "forever chemicals" because they do not break down easily in the environment and can remain present for significant periods of time. Some studies suggest that human exposure to high levels of certain PFAS may lead to adverse health effects, including developmental issues in children, thyroid disruption, and an increased risk of certain cancers. Additionally, PFAS can contaminate water sources and soil, leading to potential harm to aquatic life and ecosystems. These compounds can also accumulate in thebodies of humans and animals over time, potentially reaching higher concentrations as they move up the food chain. Due to these concerns, there has been increasing attention on regulating and reducing the use of PFAS in various products and / or researching new methods of destroying PFAS before it enters the environment.

[0004] However, destroying PFAS is a complex process due to the strong carbonfluorine bonds in the chemical structure of PFAS. PFAS are highly resistant to traditional degradation methods. There are several methods that have been explored for PFAS destruction or conversion into less harmful forms.

[0005] Heating PFAS to high temperatures (typically above 1,000° C) in specialized incinerators or thermal treatment systems can break down the chemical bonds and result in the destruction of PFAS. However, this method can generate potentially hazardous byproducts and requires careful control to prevent the release of harmful gases or particles into the environment. Alternatively, advanced oxidation processes (AOPs) involve using chemical reactions to generate highly reactive species, such as hydroxyl radicals, which are capable of breaking down PFAS molecules. Methods such as UV photolysis, ozonation, and Fenton's reagent have been explored for PFAS degradation. While effective for some PFAS, these processes are not effective for all types of PFAS compounds. Similarly, electrochemical degradation methods, which involve applying an electrical current to PFAS-containing solutions leading to the breakdown of the chemical bonds in PFAS, are only effective for certain PFAS compounds under limited conditions. Some microorganisms have also shown the ability to partially degrade PFAS. However, these methods have not been shown to lead to complete destruction of PFAS molecules.

[0006] Thus, there is a need for systems, methods, and devices for PFAS destruction that are non-hazardous, applicable to a wide range of PFAS, and lead to complete destruction of PFAS.

[0007] Activated carbon treatment, such as granulated activated carbon (GAC) filters, have been used for contaminant removal such as PFAS removal. For example, activated carbon filters may be used to remove PFAS from drinking water, wherein PFAS adsorb to the carbon causing the activated carbon to be spent. There is also a need for improved systems, devices and methods for removing PFAS from activated carbon in order to reuse the activated carbon.SUMMARY

[0008] For purposes of this summary, certain aspects, advantages, and novel features of the invention are described herein. It is to be understood that not all such advantages necessarily may be achieved in accordance with any particular embodiment of the invention. Thus, for example, those skilled in the art will recognize that the invention may be embodied or carried out in a manner that achieves one advantage or group of advantages as taught herein without necessarily achieving other advantages as may be taught or suggested herein.

[0009] Some embodiments herein are directed to a method for destruction of per- and polyfluoroalkyl substances (PFAS) using a microwave generated plasma, the method comprising: propagating microwaves through a microwave plasma apparatus, the microwaves generated using a microwave generator to generate a microwave plasma; introducing the PFAS into the microwave plasma apparatus; and contacting the PFAS with the microwave plasma, wherein contacting the PFAS with the microwave plasma initiates a chemical reaction that destroys the PFAS.

[0010] In some embodiments, the chemical reaction comprises a thermal degradation reaction. In some embodiments, the thermal degradation reaction occurs at a temperature between 1000 °C and about 1200 °C. In some embodiments, the PFAS is thermally degraded in about 1 second to about 2 seconds. In some embodiments, the chemical reaction comprises at least one radical reaction. In some embodiments, the at least one radical reaction converts molecules of the PFAS to HF and at least one carbon-containing molecule. In some embodiments, the at least one carbon-containing molecule comprises CO2 or CH4.

[0011] In some embodiments, the microwave generated plasma generates ultraviolet (UV) light. In some embodiments, the UV light generates one or more radicals, and wherein the chemical reaction comprises a radical reaction involving the one or more radicals generated by the UV light. In some embodiments, the radical reaction converts molecules of the PFAS to HF and at least one carbon-containing molecule. In some embodiments, the at least one carbon-containing molecule comprises CO2 or CH4.

[0012] In some embodiments, the PFAS comprises at least one of the following: Perfluorooctanoic Acid (PFOA), Perfluorooctane Sulfonate (PFOS), Perfluorononanoic Acid (PFNA), Perfluorohexane Sulfonic Acid (PFHxS), Perfluorobutane Sulfonic Acid (PFBS), Perfluorodecanoic Acid (PFDA), Perfluoroundecanoic Acid (PFUnDA),PerfluorododecanoicAcid (PFDoDA), Perfluorotetradecanoic Acid (PFTeDA), Perfluorohexanoic Acid (PFHxA), Pcrfluoropcntanoic Acid (PFPcA), Pcrfluorobutanoic Acid (PFBA), Pcrfluoropcntanc Sulfonic Acid (PFPeS), Perfluorohexane Sulfonamide (PFHxSA), Perfluorooctane Sulfonamide (PFOSA), Perfluoroheptanoic Acid (PFHpA), Perfluorohexadecanoic Acid (PFHxDA), Perfluorooctadecanoic Acid (PFOcDA), Perfluorotridecanoic Acid (PFTrDA), Perfluoroheptadecanoic Acid (PFHpDA), Perfluorononadecanoic Acid (PFNDA), Perfluorotetradecanoic Acid (PFTDA), Perfluorooctane Sulfonamide Ethanol (FOSE), Perfluorodecane Sulfonic Acid (PFDS), Perfluoroundecane Sulfonic Acid (PFUnDS), Perfluorododecane Sulfonic Acid (PFDoDS), Perfluorotetradecane Sulfonic Acid (PFTeDS), Perfluorohexadecane Sulfonic Acid (PFHxDS), Perfluorooctadecane Sulfonic Acid (PFOcDS), Perfluorobutane Sulfonamide (PFBSA), Perfluorobutanesulfonamide Ethanol (FBSA), Perfluorohexanesulfonamide (PFHxSA), Perfluorooctanesulfonamide Ethanol (FOSEA), Perfluorohexyl Iodide (PFHI), N-Ethyl Perfluorooctanesulfonamide (NEtFOSA), N-Methyl Perfluorooctanesulfonamide (NMeFOSA), N-Ethyl Perfluorooctane Sulfonamidoacetate (NEtFOSAA), N-Methyl Perfluorooctane Sulfonamidoacetate (NMeFOSAA), N-Ethyl Perfluorooctane Sulfonamidoacetic Acid (NEtFOSAAc), N-Methyl Perfluorooctane Sulfonamidoacetic Acid (NMeFOSAAc), N-Ethyl Perfluorooctane Sulfonamidoethanol (NEtFOSEA), N-Methyl Perfluorooctane Sulfonamidoethanol (NMeFOSEA), N-Ethyl Perfluorooctane Sulfonamide Ethyl Ester (NEtFOSE), N-Methyl Perfluorooctane Sulfonamide Ethyl Ester (NMeFOSE), N-Ethyl Perfluorooctane Sulfonamide Ethanol (NEtFOSEA), N-Methyl Perfluorooctane Sulfonamide Ethanol (NMeFOSEA), N- Ethyl Perfluorooctane Sulfonamide Acetate (NEtFOSAAc), N-Methyl Perfluorooctane Sulfonamide Acetate (NMeFOSAAc), N-Ethyl Perfluorooctane Sulfonamide Ethyl Acetate (NEtFOSEAc), and N-Methyl Perfluorooctane Sulfonamide Ethyl Acetate (NMeFOSEAc).

[0013] In some embodiments, the PFAS comprises at least one of ultra short-chain PF AS, short-chain PFAS, medium-chain PFAS, and long-chain PFAS. In some embodiments, the PFAS comprise one or more of the following functional groups; carboxylic acid (-COOH), sulfonic acid (-SO3H), phosphonic acid (-PO3H2), ester (-COOR), amide (-CONH2 or - CONHR’), ether (-O-), alkyl (-R), and heterocyclic ring.

[0014] In some embodiments, the chemical reaction comprises at least one of the following: fluorination, defluorination, fragmentation, cross-coupling, and polymerization. Insome embodiments, the PFAS is introduced into a plume or exhaust of the microwave generated plasma. In some embodiments, the chemical reaction comprises breaking a carbonfluorine bond in the PFAS.

[0015] In some embodiments, introducing the PFAS into the microwave plasma apparatus comprises introducing a PFAS-containing medium into the microwave plasma apparatus. In some embodiments, the PFAS-containing medium is spent activated carbon. In some embodiments, the PFAS-containing medium is biosolids.

[0016] In some embodiments, a method of reactivating spent activated carbon using a microwave generated plasma is provided. The method comprises propagating microwaves through a microwave plasma apparatus, the microwaves generated using a microwave generator to generate a microwave plasma; introducing spent activated carbon into the microwave plasma apparatus, wherein the spent activated carbon comprises activated carbon and adsorbates adsorbed onto the activated carbon; contacting the spent activated carbon with the microwave plasma, wherein contacting the spent activated carbon with the microwave plasma removes the adsorbates from the activated carbon.

[0017] In some embodiments, the activated carbon comprises granulated activated carbon. In some embodiments, the adsorbate comprises per- and polyfluoroalkyl substances (PFAS). In some embodiments, contacting the spent activated carbon with microwave plasma removes and destroys all or substantially all of the adsorbates from the activated carbon. In some embodiments, contacting the spent activated carbon with microwave plasma reactivates the spent activated carbon. In some embodiments, the reactivated spent activated carbon has an adsorption capacity substantially similar to an adsorption capacity of the activated carbon with no adsorbates adsorbed thereto.

[0018] In some embodiments, a method of converting biosolids to activated carbon is provided. The method comprises propagating microwaves through a microwave plasma apparatus, the microwaves generated using a microwave generator to generate a microwave plasma; introducing biosolids into the microwave plasma apparatus, wherein the biosolids include per-and polyfluoroalkyl substances (PFAS); and contacting the biosolids with the microwave plasma, wherein contacting the biosolids with the microwave plasma removes the PFAS from the biosolids to produce biosolids-derived carbon. In some embodiments, the bio solids -derived carbon includes biosolids-based activated carbon.BRIEF DESCRIPTION OF THE DRAWINGS

[0019] The drawings are provided to illustrate example embodiments and are not intended to limit the scope of the disclosure. A better understanding of the systems and methods described herein will be appreciated upon reference to the following description in conjunction with the accompanying drawings, wherein:

[0020] FIG. 1 illustrates an example microwave plasma torch that can be used in the destruction of PFAS according to some embodiments herein.

[0021] FIG. 2 illustrates another example microwave plasma torch that can be used in the destruction of PFAS according to some embodiments herein.

[0022] FIGS. 3A-B illustrate an exemplary micro wave plasma torch that includes a side feeding hopper, thus allowing for downstream feeding, according to some embodiments herein.

[0023] FIG 4 illustrates another exemplary microwave plasma torch that can be used in the destruction of PFAS according to some embodiments herein.DETAILED DESCRIPTION

[0024] Although certain preferred embodiments and examples are disclosed below, inventive subject matter extends beyond the specifically disclosed embodiments to other alternative embodiments and / or uses and to modifications and equivalents thereof. Thus, the scope of the claims appended hereto is not limited by any of the particular embodiments described below. For example, in any method or process disclosed herein, the acts or operations of the method or process may be performed in any suitable sequence and are not necessarily limited to any particular disclosed sequence. Various operations may be described as multiple discrete operations in turn, in a manner that may be helpful in understanding certain embodiments; however, the order of description should not be construed to imply that these operations are order dependent. Additionally, the structures, systems, and / or devices described herein may be embodied as integrated components or as separate components. For purposes of comparing various embodiments, certain aspects and advantages of these embodiments are described. Not necessarily all such aspects or advantages are achieved by any particular embodiment. Thus, for example, various embodiments may be carried out in a manner thatachieves or optimizes one advantage or group of advantages as taught herein without necessarily achieving other aspects or advantages as may also be taught or suggested herein.

[0025] Certain exemplary embodiments will now be described to provide an overall understanding of the principles of the structure, function, manufacture, and use of the devices and methods disclosed herein. One or more examples of these embodiments are illustrated in the accompanying drawings. Those skilled in the art will understand that the devices and methods specifically described herein and illustrated in the accompanying drawings are non-limiting exemplary embodiments and that the scope of the invention is defined solely by the claims. The features illustrated or described in connection with one exemplary embodiment may be combined with the features of other embodiments. Such modifications and variations are intended to be included within the scope of the present technology.

[0026] In some embodiments, microwave plasma systems, methods, and devices for destruction of PFAS are provided herein. As used herein, PFAS refers to any per- and polyfluoroalkyl substance. Perfluoroalkyl substances have fully fluorinated carbon chains while polyfluoroalkyl substances have partially fluorinated carbon chains. These substances include, for example, Perfluorooctanoic Acid (PFOA), Perfluorooctane Sulfonate (PFOS), Perfluorononanoic Acid (PFNA), Perfluorohexane Sulfonic Acid (PFHxS), Perfluorobutane Sulfonic Acid (PFBS), Perfluorodecanoic Acid (PFDA), Perfluoroundecanoic Acid (PFUnDA),Perfluorododecanoic Acid (PFDoDA), Perfluorotetradecanoic Acid (PFTeDA), Perfluorohexanoic Acid (PFHxA), Perfluoropentanoic Acid (PFPeA), Perfluorobutanoic Acid (PFBA), Perfluoropentane Sulfonic Acid (PFPeS), Perfluorohexane Sulfonamide (PFHxSA), Perfluorooctane Sulfonamide (PFOSA), Perfluoroheptanoic Acid (PFHpA), Perfluorohexadecanoic Acid (PFHxDA), Perfluorooctadecanoic Acid (PFOcDA),Perfluorotridecanoic Acid (PFTrDA), Perfluoroheptadecanoic Acid (PFHpDA), Perfluorononadecanoic Acid (PFNDA), Perfluoro tetradecanoic Acid (PFTDA),Perfluorooctane Sulfonamide Ethanol (FOSE), Perfluorodecane Sulfonic Acid (PFDS), Perfluoroundecane Sulfonic Acid (PFUnDS), Perfluorododecane Sulfonic Acid (PFDoDS), Perfluorotetradecane Sulfonic Acid (PFTeDS), Perfluorohexadec ane Sulfonic Acid (PFHxDS), Perfluorooctadecane Sulfonic Acid (PFOcDS), Perfluorobutane Sulfonamide (PFBSA), Perfluorobutanesulfonamide Ethanol (FBSA), Perfluorohexanesulfonamide(PFHxSA), Perfluorooctanesulfonamide Ethanol (FOSEA), Perfluorohexyl Iodide (PFHI), N- Ethyl Pcrfluorooctancsulfonamidc (NEtFOSA), N-Mcthyl Pcrfluorooctancsulfonamidc (NMeFOSA), N-Ethyl Perfluorooctane Sulfonamidoacetate (NEtFOSAA), N-Methyl Perfluorooctane Sulfonamidoacetate (NMeFOSAA), N-Ethyl Perfluorooctane Sulfonamidoacetic Acid (NEtFOSAAc), N-Methyl Perfluorooctane Sulfonamidoacetic Acid (NMeFOSAAc), N-Ethyl Perfluorooctane Sulfonamidoethanol (NEtFOSEA), N-Methyl Perfluorooctane Sulfonamidoethanol (NMeFOSEA), N-Ethyl Perfluorooctane Sulfonamide Ethyl Ester (NEtFOSE), N-Methyl Perfluorooctane Sulfonamide Ethyl Ester (NMeFOSE), N- Ethyl Perfluorooctane Sulfonamide Ethanol (NEtFOSEA), N-Methyl Perfluorooctane Sulfonamide Ethanol (NMeFOSEA), N-Ethyl Perfluorooctane Sulfonamide Acetate (NEtFOSAAc), N-Methyl Perfluorooctane Sulfonamide Acetate (NMeFOSAAc), N-Ethyl Perfluorooctane Sulfonamide Ethyl Acetate (NEtFOSEAc), and N-Methyl Perfluorooctane Sulfonamide Ethyl Acetate (NMeFOSEAc) among others. However, the above is a non- exhaustive list as there are thousands of PFAS chemicals, both known and potentially unknown, to which the systems, methods, and devices herein are applicable.

[0027] For example, PFAS encompasses a wide range of compounds with varying chain lengths, functional groups, and properties. PFAS compounds can have different carbon chain lengths. For instance, PFAS can be categorized into “ultra short-chain” PFAS, which comprise very short carbon chains, usually only one or two carbon atoms, “short-chain” PFAS, which generally comprise about four to six carbon atoms (e.g., perfluorobutane sulfonate (PFBS) and perfluorohexane sulfonate (PFHxS)), “medium-chain” PFAS, which generally comprise about seven to nine carbon atoms, and “long-chain” PFAS, which generally comprise eight or more carbon atoms (e.g., perfluorooctanoic acid (PFOA) and perfluorooctane sulfonate (PFOS)). Furthermore, PFAS compounds may comprise varying functional groups, including for example, carboxylic acids (-COOH), sulfonic acids (-SO3H), phosphonic acids (-PO3H2), esters (-COOR), amides (-CONH2 or -CONHR’), ethers (-O-), alkyls (-R), or heterocyclic rings, among others. In addition, PFAS compounds may have widely varying properties including hydrophobicity, oleophobicity, environmental persistence, bioaccumulation, and potential adverse health impacts, among others.

[0028] As used herein, “destruction” of PFAS refers to the degradation, breakdown, removal, or conversion of PFAS through chemical or physical reactions (e.g.,pyrolysis, oxidation, reduction, etc.). Generally, destruction of PFAS results in conversion of PF AS into less harmful substances, such as non-toxic and environmentally benign substances.

[0029] Previous efforts of destroying PFAS using plasma have been conducted using cold plasma technology. Cold plasma, sometimes referred to as non-thermal plasma, is a partially ionized gas that contains a mix of ions, electrons, and neutral particles. It is generated by applying a high voltage to a gas, causing it to become ionized. This ionization process creates a mixture of reactive species, such as ions, electrons, free radicals, and excited molecules, which can have strong oxidizing and reducing properties. Cold plasma can be utilized to break down the complex chemical bonds in PFAS molecules, as the reactive species present in the cold plasma can interact with the PFAS molecules and cause various chemical reactions that lead to their breakdown. However, cold plasma applications have not been established to provide the necessary selectivity and efficiency to target PFAS compounds without formation of harmful intermediate byproducts or transformation products. Furthermore, there are additional challenges such as scale-up, material compatibility, regulatory considering, operating complexity, and environmental impact that remain barriers to wide-scale use of cold plasma for destruction of PFAS.

[0030] The embodiments herein are directed to alternative systems, methods, and devices for destruction of PFAS utilizing microwave plasma. Microwave plasma is a thermal plasma, which uses microwaves to generate high-temperature plasmas that can reach temperatures of several thousand degrees Celsius. According to some embodiments herein, microwave plasma can achieve extremely high temperatures, which is crucial for breaking the strong carbon-fluorine bonds in PFAS molecules. Furthermore, the high temperatures and reactivity of the microwave plasma lead to rapid and efficient degradation of PFAS compounds. In some embodiments, the high-energy environment of the plasma may selectively break down carbon-fluorine bonds without necessarily resulting in the complete combustion of the entire molecule, minimizing the formation of harmful byproducts, which is a significant problem with the use of cold plasma and incineration technologies.

[0031] In some embodiments herein, microwave energy is used to generate plasma. In some embodiments, the plasma is contacted with a PFAS-containing medium. In some embodiments, the energy from the microwaves causes the molecules in the PFAS, PFAS- containing medium, and / or a plasma gas to become ionized and dissociate into reactive species.In some embodiments, the plasma gas may comprise a hydrogen containing gas such as, for example, H2, H2O, etc. a UV generating gas such as, for example, Xc, Ar, etc., and / or an oxidizing gas such as, for example, O2, CO2. In some embodiments, the high-energy environment of the microwave plasma is conducive to breaking the strong carbon-fluorine bonds present in PFAS molecules. These bonds are particularly difficult to break using traditional methods, but the high temperature and reactivity of the microwave plasma may enable the cleavage of these bonds. In some embodiments, the reactive species generated within the microwave plasma interact with PFAS molecules, resulting in a series of chemical reactions that destroy the PFAS molecules. In some embodiments, these reactions can result in the degradation of the PFAS compounds into smaller non-toxic molecules. In some embodiments, various intermediate byproducts may be formed as PFAS molecules break down. These intermediate byproducts may also undergo further reactions within the plasma. In some embodiments, the nature and extent of byproduct formation depend on factors such as plasma temperature, gas composition, and treatment time. In some embodiments, after the PF AS-containing medium passes through the microwave plasma zone, the PF AS-containing medium may undergo cooling to bring the temperature back to a suitable range for further processing, collection, and / or discharge. In some embodiments, residual reactive species or byproducts may be captured.

[0032] In some embodiments, PFAS may be provided to the microwave plasma within one or more PFAS-containing mediums. PFAS can be present in these mediums either as intentional ingredients or as contaminants. For example, PFAS-containing mediums include, for example, water (e.g., wastewater, groundwater, surface water, drinking water), soil, sediments, air or other gasses, pellets, consumer products, food, leachate, building materials, biosolids, consumer waste, medical products, granulated activated carbon, textiles, fabrics, coatings, cleaning products, firefighting foam, electronics, semiconductors, adhesives, sealants, leather, packaging materials, and lubricants, among others.

[0033] In some embodiments, exposing the PFAS to microwave plasma may initiate one or more concurrent or sequential physical and / or chemical reactions, resulting in destruction of PFAS. For example, in some embodiments, PFAS may be destroyed through thermal decomposition at high temperatures. For example, the PFAS may undergo a thermal breakdown and / or various radical reactions. In some embodiments, a microwave plasma maybe maintained at about 1 ,000 °C to about 1 ,200 °C, and exposed PFAS may undergo thermal decomposition in about 1 second to about 2 seconds. For example, in some embodiments, PFAS may be destroyed through thermal decomposition at high temperatures. In some embodiments, a microwave plasma may be maintained at about 1,000 °C to about 6,000 °C, and exposed PFAS may undergo thermal decomposition in about 1 second to about 1 minute, for example in about 1 second to 2 seconds. Thermal decomposition may occur when the carbon-fluorine bonds in PFAS molecules break, resulting in the formation of simpler organic fragments, including carbon dioxide (CO2), hydrogen fluoride (HF), and other gaseous byproducts.

[0034] In some embodiments, dehydrofluorination reactions may occur, in which fluorine atoms are removed from PFAS, resulting in HF as a byproduct. In some embodiments, the high-energy environment of the microwave plasma may generate reactive species such as free radicals, which may initiate a variety of radical reactions. For instance, radicals can attack the carbon-fluorine bonds in PFAS molecules, leading to chain scission and the formation of smaller fragments, which eventually can lead to formation of HF, CO2, and smaller carbon chains such as methane, among others. Other reactions such as fluorination, defluorination, fragmentation, cross-coupling, and polymerization may also occur, which can form various smaller or larger compounds. The specific chemical reactions that occur may depend on specific plasma conditions, PFAS-containing-medium, cooling parameters, and other variables within the microwave plasma system.

[0035] In some embodiments, microwave plasma may generate or be used in conjunction with ultraviolet (UV) light to initiate chemical reactions resulting in the destruction of PFAS. In some embodiments, UV light is capable of initiating photodissociation reactions in PFAS. For example, when high-energy UV photons interact with PFAS molecules, the photons can break certain chemical bonds, including carbon-fluorine bonds. Furthermore, UV light can create reactive radicals, such as hydroxyl radicals (+OH) that initiate chain scission reactions, leading to the degradation of PFAS compounds into, for example, HF, CO2, CH4, and H2S, among others, depending on the specific PFAS being processed.

[0036] In some embodiments, the PFAS-containing medium may be granulated activated carbon (GAC) or any other embodiment of activated carbon, such as biosolids-basedactivated carbon (BBAC, further discussed below). In some embodiments, activated carbon may be used for filtration. Activated carbon, c.g., GAC and BBAC, has adsorption capacity. Adsorbates can adsorb onto the activated carbon. In some embodiments, adsorbates that can adsorb onto the activated carbon can include, for example, impurities, PFAS, ions in solution, metal ions, metal atoms, water impurities, drinking water impurities, or metal catalyst. In some embodiments, when adsorbates adsorb onto activated carbon, the adsorption capacity of the activated carbon is reduced. Activated carbon with a reduced adsorption capacity can be referred to as spent activated carbon. In some embodiments, spent activated carbon includes activated carbon with an adsorption capacity, with adsorbates adsorbed onto the activated carbon.

[0037] It can be beneficial to be able to reuse activated carbon. In some embodiments, once activated carbon is spent, it can be beneficial to remove the adsorbates from the activated carbon, thereby at least partially restoring the adsorption capacity of the activated carbon. Two different processes for removing adsorbates from activated carbon are regeneration and reactivation. Regeneration is a process that partially restores the adsorption capacity of the activated carbon to a fraction of the original adsorption capacity. Regeneration can include a thermal, chemical, or biological process. Unlike regeneration, reactivation beneficially removes all or substantially all of the adsorbates from spent activated carbon. Reactivation is a process that fully or substantially fully restores the adsorption capacity of the activated carbon to the original adsorption capacity.

[0038] Beneficially, reactivation of spent activated carbon can allow for the activated carbon to be recycled and / or reused. In some embodiments, during a reactivation process, the adsorbates are fully or substantially fully removed from the activated carbon. In some embodiments, removed adsorbates that are volatile are devolatilized during the reactivation process. In some embodiments, the removed adsorbates are destroyed or otherwise separated from the reactivated carbon. In some embodiments, a reactivation process can include a high-temperature thermal process. In some embodiments, the reactivation process can include temperatures above, for example, 1000 °C. In some embodiments, the reactivation process can include plasma processing. In some embodiments, spent activated carbon can be injected into a plasma. In some embodiments, the plasma can include superheated nitrogen, oxygen, and / or other gases. In some embodiments, spent activated carbon canbe reactivated by being injected into the microwave plasma apparatus described below. In some embodiments, the plasma can pyrolyzc the adsorbates adsorbed to the carbon and remove the adsorbates from the carbon. Removing the adsorbates from the carbon allows the reactivated carbon to regain its adsorptive capacity. In some embodiments, all or substantially all removed adsorbates are destroyed by the plasma to the mineral components. In some embodiments, in which PFAS are adsorbed onto activated carbon (e.g., GAC and biosolids- based activated carbon (BBAC)), a single reactivation process using plasma can destroy the PFAS and reactivate the spent activated carbon. In some embodiments, the reactivation process using plasma can occur in seconds, for example, within about 15 seconds, within about 30 seconds, within about 60 seconds, within about 2 minutes, within about 5 minutes, within about 10 minutes, or within about 15 minutes. Beneficially, the reactivation process using plasma can be a safe and cost effective recycling process that is energy efficient and time efficient, with no or at least reduced emissions and requiring a small footprint.

[0039] In some embodiments, the PFAS-containing medium may be biosolids. Biosolids can be produced by the wastewater treatment of solid waste. The wastewater treatment of such solid waste can include physical and / or chemical treatment, producing biosolids. Biosolids can be semisolid and can be nutrient-rich. The terms “biosolids” and “sewage sludge” can be used interchangeably. Biosolids are re-used in various ways, including as fertilizer and as land filler at reclamation sites (e.g., at mining sites). PFAS-containing biosolids may have stalled out as PFAS-containing solid waste, which was processed in a wastewater treatment procedure that did not remove the PFAS.

[0040] Removing PFAS from biosolids can have various benefits. Removing PFAS from biosolids can, first, improve the quality of biosolids for its current uses, and second, introduce new applications for biosolids.

[0041] First, removing PFAS from biosolids can improve the quality or usability of biosolids for its current uses. Biosolids are currently used, for example, as fertilizer and as land filler at reclamation sites. For such uses, it is often preferable to use biosolids that a e free or substantially free of contaminants like PFAS. Moreover, PFAS-containing biosolids may be considered too contaminated to use, and so might be disposed of without use. Biosolids are classified by the Environmental Protection Agency (EPA) according to, for example, contamination levels, which includes pollutants and pathogens. One pollutant that may affectthe classification - and so the usability - of biosolids may include PFAS. At least for this reason, removing PFAS can increase the usability of biosolids. In this way, removing PFAS from biosolids is similar to removing PFAS from other PFAS-containing mediums (e.g., drinking water): the removal of the PFAS allows for the medium (e.g., drinking water) to be used conventionally, and in a healthier or otherwise less-contaminated way.

[0042] Second, removing PFAS from biosolids can introduce new applications for biosolids. For example, the process described herein for removing PFAS from PFAS- containing mediums like biosolids can produce biosolids-derived carbon. Biosolids-derived carbon is a general term that applies to lower quality carbon, such as biochar, and to higher quality carbon, such as activated carbon. A skilled artisan will understand that biosolids- derived carbon (e.g., biochar and activated carbon) can serve many functions, such as filtration. Activated carbon produced from biosolids can be referred to as biosolids-based activated carbon (BBAC) or sludge-based activated carbon (SBAC). In some embodiments, biosolids- derived carbon (e.g., BBAC) can have applications similar to those of GAC, e.g., filtration, disclosed above. In some embodiments, biosolids-derived carbon (e.g., BBAC) can be used to filter out contaminants from contaminated mediums, such as water. In some embodiments, biosolids-derived carbon (e.g., BBAC) that has already been used (e.g., spent BBAC) can be reactivated using a process similar to the process disclosed above for reactivating spent activated carbon.

[0043] Converting biosolids to biosolids-derived carbon (e.g., BBAC) has various beneficial applications. Other activated carbon, such as GAC, has various applications, but resources of activated carbon, such as virgin GAC, are limited. Introducing biosolids-derived carbon (e.g., BBAC) to the supply of activated carbon can, for example, increase applicability of activated carbon, reduce the cost of activated carbon, and / or slow the consumption of limited resources such as virgin GAC. Additionally, because much of today’s biosolids are disposed of in landfills (either directly or after being incinerated), converting biosolids to biosolids- derived carbon (e.g., BBAC) for commercial use can also save tons of waste from being deposited in landfills, even as ash.Microwave Plasma Apparatus

[0044] A microwave plasma at atmospheric pressure is generally considered a thermal plasma, i.e., electrons and ions have energy at the same level due to high collision frequency. However, in some embodiments, the degree of ionization may not be exceedingly high, only about 10% of gas particles becoming ionized. While the ion energies in micro wave plasmas are lower than those of higher potential direct-current (DC) arc systems, the electron energies are quite high. In some embodiments, this property allows for microwave plasma to form radicals which can be used to enhance or even initiate certain chemical steps which would otherwise not occur at certain pressures and temperatures. The chemical species present in radio frequency (RF) plasma at higher powers compared to that of lower power microwave plasma show that a higher intensity and degree of radicals are present in the micro wave plasma over the RF.

[0045] Thermal plasma torches generate and provide high temperature directed flows of plasma for a variety of purposes. The two main types of plasma torches are induction plasma torches and microwave plasma torches. Generally, inductive plasmas suffer from plasma non-uniformity. This non-uniformity leads to limitations on the ability of inductive plasmas to process certain materials. Furthermore, significant differences exist between the micro wave plasma apparatuses and other plasma generation torches, such as induction plasma. For example, microwave plasma is hotter on the interior of the plasma plume, while induction is hotter on the outside of the plumes. In particular, the outer region of an induction plasma can reach about 10,000 K while the inside processing region may only reach about 1,000 K. This large temperature difference leads to material processing and feeding problems. Furthermore, induction plasma apparatuses are unable to process feedstocks at low enough temperatures to avoid melting of certain feed materials without extinguishing the plasma.

[0046] Unlike other plasma systems driven by high voltage potentials (e.g., DC arc), in some embodiments, micro wave plasmas are primarily driven by the avalanche effect with an initial seed of free electrons required to begin the plasma. In some embodiments, joule heating of the gas follows as the ionized gases couple the microwave energy and continue to heat the surrounding gases. An example microwave plasma torch setup according to some embodiments is shown in FIG. 1. In some embodiments, the PFAS, PFAS-containing medium, and / or plasma gas is injected into a quartz tube, which directs the PFAS, PFAS-containingmedium, and / or plasma gas toward a reaction chamber. Prior to entering the reaction chamber, the PFAS, PFAS-containing medium, and / or plasma gas is exposed to a microwave, which propagates to the quartz tube through a waveguide where it is applied to the PFAS, PFAS- containing medium, and / or plasma gas. The ionized gas is then exhausted into the reaction chamber where mixing and recombination of the ionized species may occur. In some embodiments, one or more swirl gases may be applied to protect the apparatus from the ionized gas and / or to direct the gas to the reaction chamber.

[0047] FIG. 2 illustrates a microwave plasma apparatus 200 for destruction of PFAS. In some embodiments, the microwave plasma apparatus 200 may operate under atmospheric pressure. In some embodiments, the microwave plasma apparatus 200 may comprise one or more feed / inj ection ports 202 for the injection of a gas, solid, or liquid, such as a PFAS-containing medium.

[0048] In some embodiments, after introduction of the PFAS-containing medium to the tube 204 or into a liner of the tube 204, microwaves may be propagated through waveguide 206. In some embodiments, the microwaves energize and ionize the PFAS- containing medium. In some embodiments, in processing region 216, heating and decomposition of the PFAS may occur. As discussed above, PFAS may be ionized and / or heated in processing region 216 to create lower molecular weight radicals that are highly reactive. In some embodiments, the PFAS molecules proceed through the apparatus to a reaction chamber 210. In some embodiments, a UV light source and / or catalyst may be provided within the tube 204 and / or the reaction chamber 210.

[0049] Advantageously, in some embodiments, the tube 204 and / or the reaction chamber 210 may be provided with a catalyzing composition to facilitate the destruction of PFAS. In various embodiments, only portions of a substrate or module may comprise catalyzing sections or the entire substrate or module may contain a catalyzing surface. In various embodiments, the catalyst may comprise transition metals. In some embodiments, the catalyzing material may be W, Ta, Fe, Mo, Co, Cu, Cr, Ru, Co, Ag, Pt, Pd, Au, Ni, Ti, or alloys and mixtures thereof. In some embodiments the catalyzing material may be comprise organic layer doped with transition metals. In some embodiments, the catalyst may comprise a single transition metal catalyzing element. In other embodiments, the catalyst may have a bimetallicor trimetallic composition. In other embodiments, the catalyst may comprise a mixture or alloy of metallic elements.

[0050] In some embodiments, the walls of the chamber 210 may be coated or lined with a material that prevents deposition or synthesis of the chemical byproducts or intermediates. In some embodiments, the coating may be a substantially inert or non-reactive material or metal. In some embodiments, the coating or lining may be engineered to withstand the high temperatures of the plasma process. In some embodiments, the coating may be a metallic coating, a glass coating, a ceramic coating, a thermoplastic or plastic coating, a selfassembled monolayer or coating, or a metallic alloy coating.

[0051] In some embodiments, any remaining solids or liquids produced according to methods herein may be removed from the bottom of the chamber or from the side of the chamber. Similarly, gasses or gaseous byproducts may be removed from the chamber 210 through one or more ports. In some embodiments, the one or more ports may contain a filter to prevent the removal of unwanted solid particles though the ports. In some embodiments, the removal of gases may be driven by a pneumatic pump. In some embodiments, the gasses sent through the one or more ports may be separated in a gas separator, although a gas separator is not required.

[0052] FIG. 2 generally depicts a plasma apparatus 200 that may be configured to operate under atmospheric pressure. In some embodiments, a catalyst is not provided in the reaction chamber 210 of the plasma apparatus 200. In some embodiments, one or more of the walls of the reaction chamber 210 may be coated or lined with a catalyst to facilitate the PFAS destruction reactions. In some embodiments, a portion of the one or more walls is coated with the catalyst material, but in various other embodiments 1 / 8, 1 / 4, 1 / 3, 1 / 2, 3 / 4, or the entirety of the reaction chamber may be coated with the catalyst material. In some embodiments, the walls may be lined with an anti-stick or anti-deposition coating that prevents the deposition or sticking of any solid or liquid materials thereon.

[0053] Any of the embodiments provided herein may be provided with sensors to monitor, adjust, and provide feedback for the microwave process. In some embodiments the microwave apparatus may be provided with one or more Thermo-Couples (TC), one or more Optical Emission Spectroscopy (OES) sensors, or one or more Residual Gas Analyzers (RGA). These sensors may provide a non-intrusive mechanism to measure the reaction parameters.For example, the one or more optical emission spectroscopy sensors may provide a nonintrusive, qualitative measure of plasma / gas composition, such as in the active plasma region. The one or more Thermo-Couples may provide a quantitative measure of the temperature. In some embodiments, the one or more residual gas analyzers may provide a quantitative measure of gas composition. In some embodiments, the RGA is provided close to a chamber exit of the reaction chamber. In some embodiments, the TC or OES sensors may be provided to measure through a window of one of the walls of the reaction chamber such that the sensor may non-intrusively measure the parameters of the reaction chamber. In other embodiments, the sensors or a portion of the sensors may be provided in the reaction chamber, and the sensors may be lined with a material that prevents deposition of solids on the sensors. In some embodiments the reaction chamber is provided with a pressure sensor for the regulation of gas pressures in the reaction chamber.

[0054] In some embodiments the sensors are provided in an open loop or closed feedback loop to automatically adjust parameters in the apparatus. For example, the sensors may be in communication with the ports for the injection of PFAS to increase or decrease PF AS injection or in communication with the microwave plasma propagator or waveguide. In this manner the sensors and control mechanisms may automatically adjust the parameters of the process, such as temperature, pressure, gas flow, gas composition, etc. The temperature of the plasma and the reaction chamber may be monitored to optimize the destruction of PFAS.

[0055] In some embodiments, the microwave plasma apparatus may comprise a microwave generator for generating microwaves at a frequency between 300 MHz and 300 GHz. In some embodiments, the microwave plasma apparatus may comprise a gas mixing panel, plasma torch with quartz liner, water-cooled stainless-steel reactor, water cooled exhaust and water separation particle filter. In some embodiments, monitoring instrumentation may be provided, including a machine vision camera, one or more thermocouples, one or more inspection ports, such as at the liner exit, mass spectrometer, and in the exhaust.

[0056] In some embodiments, an extension tube may be provided. The extension tube may comprise a graphite tube or a tube lined with a material to prevent deposition of materials thereon. In some embodiments, the extension tube extends downward into a reaction chamber of the microwave plasma apparatus, the extension tube confining and directing the microwave plasma to extend its length. In some embodiments, the extension tube mayconcentrate the energy and power provided by a microwave power source, in order to form a longer microwave plasma within the apparatus. The methods and apparatuses described herein may utilize an extension tube, which extends downward from a core plasma tube into the reaction chamber. In some embodiments, the extension tube may concentrate energy from the microwave power source into a smaller volume, extending and directing the plasma at a greater length than would be possible using a conventional microwave plasma apparatus. In some embodiments, a length of a plasma may be tuned or altered by configuring one or more of the following parameters: power, plasma gas flow, type of gas, extension tube material, level of insulation of the reactor chamber or the extension tube, level of coating of extension tube, and geometry of the extension tube (e.g., tapered / stepped).

[0057] Furthermore, in some embodiments, a lining, an agitator, vibrator, or other device may be provided to prevent sticking and / or to remove particles from surfaces of the extension tube. In some embodiments, providing an extension tube with a specific shape may facilitate prevention of material accumulation on one or more surfaces of the microwave plasma torch. For example, a conical extension tube may prevent buildup on surfaces of the extension tube.

[0058] In some embodiments, an extension tube as described herein may extend downward into the reaction chamber of a microwave plasma apparatus. In some embodiments, the extension tube may extend downward at a length of at least 5%, at least 10%, at least 15%, at least 20%, at least 25%, at least 30%, at least 35%, at least 40%, at least 45%, at least 50%, at least 55%, at least 60%, at least 65%, at least 70%, at least 75%, at least 80%, at least 85%, at least 90%, at least 95%, or at least 100% of the reaction chamber length, or any value between the aforementioned values.

[0059] Various parameters of the microwave plasma may be adjusted manually or automatically in order to achieve a desired reaction and / or products. These parameters may include, for example, power, plasma gas flow rates, type of plasma gas, presence of an extension tube, extension tube material, level of insulation of the reactor chamber or the extension tube, level of coating of the extension tube, geometry of the extension tube (e.g. tapered / stepped), feed material size, feed material insertion rate, feed material inlet location, feed material inlet orientation, number of feed material inlets, plasma temperature, residence time and cooling rates. The resulting material may exit the plasma into a sealed chamber wherethe material is quenched then collected. In some embodiments, the extension tube may comprise isomoldcd graphite and be held up by, for example, a stainless sheet scaffold. In some embodiments, the top edge of the extension tube may be machined to fit over the quartz liner to create a seamless extension of the plasma containment.

[0060] In some embodiments, the microwave plasma apparatus may be operated at atmospheric pressure (760 Torr). In some embodiments, before running, the chamber may be purged to below 100 ppm oxygen using argon gas before striking plasma. In some embodiments, after processing and once the chamber temperature has fallen below 50 °C, compressed dry air (CDA) may be slowly added in 5 vol% increments with Argon until 100 vol% CDA fills the chamber.

[0061] As noted above, FIG. 2 illustrates an embodiment of a microwave plasma torch 200 that can be used in the destruction of PF AS according to some embodiments herein. In some embodiments, a feedstock, such as a PFAS-containing medium can be introduced, via one or more feedstock inlets 202, into a microwave plasma 216. In some embodiments, an entrainment gas flow and / or a sheath flow may be injected into the microwave plasma torch 200 to create flow conditions within the plasma torch prior to ignition of the plasma 216 via micro wave radiation source 206. In some embodiments, the entrainment flow and sheath flow are both axis-symmetric and laminar, while in other embodiments the gas flows are swirling. In some embodiments, the feedstock may be introduced into the microwave plasma torch 200, where the feedstock may be entrained by a gas flow that directs the materials toward the plasma 216.

[0062] The gas flows can comprise a noble gas column of the periodic table, such as helium, neon, argon, etc. Although the gases described above may be used, it is to be understood that a variety of gases can be used depending on the desired material and processing conditions, or no gas can be used in combination with the PFAS-containing medium. In some embodiments, within the microwave plasma 216, the feedstock may undergo a physical and / or chemical transformation. Inlets 202 can be used to introduce process gases to entrain and accelerate the feedstock towards plasma 216. In some embodiments, a second gas flow can be created to provide sheathing for the inside wall of a core gas tube or liner 204 and a reaction chamber 210 to protect those structures from melting due to heat radiation from plasma 216.

[0063] Various parameters of the microwave plasma 216 may be adjusted manually or automatically in order to achieve desired reactions and / or products. These parameters may include, for example, power, plasma gas flow rates, type of plasma gas, presence of an extension tube, extension tube material, level of insulation of the reactor chamber or the extension tube, level of coating of the extension tube, geometry of the extension tube (e.g. tapered / stepped), feed material size, feed material insertion rate, feed material inlet location, feed material inlet orientation, number of feed material inlets, plasma temperature, residence time and cooling rates. The resulting material may exit the plasma into a sealed chamber 212 where the material is quenched then collected.

[0064] In some embodiments, the feedstock is injected after the microwave plasma torch applicator for processing in the “plume” or “exhaust” of the microwave plasma torch. Thus, the plasma of the micro wave plasma torch is engaged at the exit end of the plasma torch core tube 204, or further downstream. In some embodiments, adjustable downstream feeding allows engaging the feedstock or catalytic particles with the plasma plume downstream at a temperature suitable for optimal process control of feedstock through precise targeting of temperature level and residence time. Adjusting the inlet location and plasma characteristics may allow for further customization of product / byproduct and reaction characteristics. Furthermore, in some embodiments, by adjusting power, gas flow rates, pressure, and equipment configuration (e.g., introducing an extension tube), the length of the plasma plume may be adjusted.

[0065] In some embodiments, feeding configurations may include one or more individual feeding nozzles surrounding the plasma plume. The feedstock may enter the plasma from any direction and can be fed in 360° around the plasma depending on the placement and orientation of the inlets 202. Furthermore, the feedstock may enter the plasma at a specific position along the length of the plasma 216 by adjusting placement of the inlets 202, where a specific temperature has been measured and a residence time estimated for providing the desirable characteristics of the resulting products.

[0066] In some embodiments, the angle of the inlets 202 relative to the plasma 216 may be adjusted, such that the feedstock can be injected at any angle relative to the plasma 216. For example, the inlets 202 may be adjusted, such that the feedstock may be injected into the plasma at an angle of about 0 degrees, about 5 degrees, about 10 degrees, about 15 degrees,about 20 degrees, about 25 degrees, about 30 degrees, about 35 degrees, about 40 degrees, about 45 degrees, about 50 degrees, about 55 degrees, about 60 degrees, about 65 degrees, about 70 degrees, about 75 degrees, about 80 degrees, about 85 degrees, or about 90 degrees relative to the direction of the plasma 216, or between any of the aforementioned values.

[0067] In some embodiments, implementation of the downstream injection method may use a downstream swirl or quenching. A downstream swirl refers to an additional swirl component that can be introduced downstream from the plasma torch to keep the powder from the walls of the core tube 204, the reactor chamber 210, and / or an extension tube 214.

[0068] In some embodiments, the extension tube may extend into the reaction chamber of a micro wave plasma apparatus. In some embodiments, the extension tube may comprise a stepped shape, such that the tube comprises one or more cylindrical volumes extending downward in the reaction chamber, wherein each successive cylindrical volume comprises a larger diameter than each previous cylindrical volume as the tube extends downward in the reaction chamber. In some embodiments, the extension tube may have a conical shape, tapering radially outwards as it extends downward into the reaction chamber. In some embodiments, the extension tube may comprise a single cylindrical volume.

[0069] In some embodiments, the extension tube may have a dual conical shape, where the first conical shape tapers radially outwards as it extends downward into the rection chamber, and the second conical shape is an inverted asymmetrical shape to the first conical shape and is connected to the end of the first conical shape and tapers radially inwards as it extends downward into the reaction chamber. In some embodiments, the extension tube may comprise a dual conical shape, where the widest portion of the first conical shape is connected to the widest portion of the second conical shape. In some embodiments, the length of the first conical shape is greater than the length of the second conical shape.

[0070] In some embodiments, the extension tube may have a dual conical shape, where the first conical shape tapers radially outwards as it extends downward into the reaction chamber and the second conical shape is an inverted symmetrical shape to the first conical shape and is connected to the end of the first conical shape and tapers radially inwards as it extends downward into the reaction chamber. In some embodiments, the widest portion of the first conical shape is connected to the widest portion of the second conical shape. In some embodiments, the length of the first conical shape is equal to the length of the second conicalshape. In some embodiments, the length of the second conical shape is greater than the length of the first conical shape. In some embodiments, the feed material inlets may insert feedstock within the extension tube.

[0071] In some embodiments, the extension tube may comprise a length of about 1 foot. In some embodiments, the extension tube may comprise a length of about 1 inch, about 2 inches, about 3 inches, about 4 inches, about 5 inches, about 6 inches, about 7 inches, about 8 inches, about 9 inches, about 10 inches, about 11 inches, about 1 foot, about 2 feet, about 3 feet, about 4 feet, about 5 feet, about 6 feet, about 7 feet, about 8 feet, about 9 feet, about 10 feet, about 11 feet, about 12 feet, about 13 feet, about 14 feet, about 15 feet, about 16 feet, about 17 feet, about 18 feet, about 19 feet, about 20 feet, about 21 feet, about 22 feet, about 23 feet, about 24 feet, about 25 feet, about 26 feet, about 27 feet, about 28 feet, about 29 feet, or about 30 feet, or any value between the aforementioned values.

[0072] In some embodiments, the length of a reaction chamber 210 of a microwave plasma apparatus may be about 1 foot, about 2 feet, about 3 feet, about 4 feet, about 5 feet, about 6 feet, about 7 feet, about 8 feet, about 9 feet, about 10 feet, about 11 feet, about 12 feet, about 13 feet, about 14 feet, about 15 feet, about 16 feet, about 17 feet, about 18 feet, about 19 feet, about 20 feet, about 21 feet, about 22 feet, about 23 feet, about 24 feet, about 25 feet, about 26 feet, about 27 feet, about 28 feet, about 29 feet, or about 30 feet, or any value between the aforementioned values.

[0073] In some embodiments, the length of the plasma 216, which may be extended by adjusting various processing conditions and equipment configurations, may be about 1 foot, about 2 feet, about 3 feet, about 4 feet, about 5 feet, about 6 feet, about 7 feet, about 8 feet, about 9 feet, about 10 feet, about 11 feet, about 12 feet, about 13 feet, about 14 feet, about 15 feet, about 16 feet, about 17 feet, about 18 feet, about 19 feet, about 20 feet, about 21 feet, about 22 feet, about 23 feet, about 24 feet, about 25 feet, about 26 feet, about 27 feet, about 28 feet, about 29 feet, or about 30 feet, or any value between the aforementioned values.

[0074] In some embodiments, the entrainment flow and sheath flow are both axis- symmetric and laminar, while in other embodiments the gas flows are swirling. The feed materials may be introduced axially into the micro wave plasma torch, where they are entrained by a gas flow that directs the materials toward the plasma. Inlets can be used to introduce process gases to entrain and accelerate particles towards the plasma. In some embodiments,particles are accelerated by entrainment using a core laminar gas flow created through an annular gap within the plasma torch. A second laminar flow can be created through a second annular gap to provide laminar sheathing for the inside wall of dielectric torch to protect the wall from melting due to heat radiation from plasma. In some embodiments, the laminar flows direct particles toward the plasma along a path as close as possible to a central axis of the plasma, exposing the particles to a substantially uniform temperature within the plasma.

[0075] In some embodiments, suitable flow conditions are present to keep particles from reaching the inner wall of the plasma torch where plasma attachment could take place. In some embodiments, particles are guided by the gas flows towards the microwave plasma, where each particle undergoes homogeneous thermal treatment. Various parameters of the microwave generated plasma, as well as particle parameters, may be adjusted in order to achieve desired results. These parameters may include micro wave power, feed material size, feed material insertion rate, gas flow rates, plasma temperature, residence time and cooling rates. In some embodiments, the cooling or quenching rate is not less than 10+3degrees C / sec upon exiting the plasma. As discussed above, in some embodiments, the gas flows are laminar; however, in alternative embodiments, swirl flows or turbulent flows may be used to direct the feed materials toward the plasma.

[0076] FIGS. 3A-B illustrate an exemplary micro wave plasma torch that includes a side feeding hopper, thus allowing for downstream feeding. Thus, in this implementation the feedstock is injected after the microwave plasma torch applicator for processing in the “plume” or “exhaust” of the microwave plasma torch. Thus, the plasma of the microwave plasma torch is engaged at the exit end of the plasma torch to allow downstream feeding of the feedstock. This downstream feeding can advantageously extend the lifetime of the torch as the hot zone is preserved indefinitely from any material deposits on the walls of the hot zone liner. Furthermore, it allows engaging the plasma plume downstream at temperature suitable for optimal processing of powders through precise targeting of temperature level and residence time. For example, there is the ability to dial the length of the plume using microwave powder, gas flows, and pressure in the quenching vessel that contains the plasma plume.

[0077] Other feeding configurations may include one or several individual feeding nozzles surrounding the plasma plume. The feedstock can enter the plasma at a point from any direction and can be fed in from any direction, 360° around the plasma, into the point withinthe plasma. The feedstock can enter the plasma at a specific position along the length of the plasma plume where a specific temperature has been measured and a residence time estimated for desired reactions / products. In some embodiments, the particles exit the plasma into a sealed chamber where they are quenched then collected.

[0078] The feed materials 314 can be introduced into a microwave plasma torch 302. A hopper or other apparatus 306 can be used to store the feed material 314 before feeding the feed material 314 into the microwave plasma torch 302, plume, or exhaust. The feed material 314 can be injected at any angle to the longitudinal direction of the plasma torch 302, such as at 5, 10, 15, 20, 25, 30, 35, 40, 45, 50, 55 degrees, or any value between the aforementioned values. In some embodiments, the feedstock can be injected an angle of greater than 5, 10, 15, 20, 25, 30, 35, 40, 45, 50, or 55 degrees. In some embodiments, the feedstock can be injected an angle of less than 5, 10, 15, 20, 25, 30, 35, 40, 45, 50, or 55 degrees. In alternative embodiments, the feedstock can be injected along the longitudinal axis of the plasma torch.

[0079] The microwave radiation can be brought into the plasma torch through a waveguide 304. The feed material 314 may be fed into a plasma chamber 310 and may be placed into contact with the plasma generated by the plasma torch 302. When in contact with the plasma, plasma plume, or plasma exhaust, the feed material may undergo physical and / or chemical reactions. While still in the plasma chamber 310, the processed material 314 may cool before being collected into a container 312. Alternatively, the feed material 314 can exit the plasma chamber 310 while still in a gaseous phase. In some embodiments, a quenching chamber may be used, which may or may not use positive pressure. While described separately from FIG. 2, the embodiments of FIGS. 3 A and 3B are understood to use similar features and conditions to the embodiment of FIG. 2.

[0080] FIG. 4 illustrates an exemplary microwave plasma torch that can be used in the destruction of PFAS, according to embodiments of the present disclosure. Feed materials, such as PFAS-containing medium 9, 10 can be introduced into a microwave plasma torch 2 in an introduction zone 3, the torch sustaining a microwave-generated plasma 11. In one example embodiment, an entrainment gas flow, and a sheath flow (downward arrows) may be injected through inlets 5 to create flow conditions within the plasma torch 2 prior to ignition of the plasma 11 via microwave radiation source 1.

[0081] In some embodiments, the entrainment flow and sheath flow are both axisymmctric and laminar, while in other embodiments the gas flows arc swirling. The feed materials 9 may be introduced axially into the microwave plasma torch 2, where they are entrained by a gas flow that directs the materials toward the plasma hot zone 6. Within the microwave-generated plasma, the feed materials may undergo various physical and / or chemical reactions, as described above. Inlets 5 can be used to introduce process gases to entrain and accelerate material or particles 9, 10 along axis 12 towards plasma 11. First, in some embodiments, particles 9 are accelerated by entrainment using a core laminar gas flow (upper set of arrows) created through an annular gap within the plasma torch. A second laminar flow (lower set of arrows) can be created through a second annular gap to provide laminar sheathing for the inside wall of dielectric torch to protect it from melting due to heat radiation from plasma 11. In exemplary embodiments, the laminar flows direct particles 9, 10 toward the plasma 11 along a path as close as possible to axis 12, exposing them to a substantially uniform temperature within the plasma.

[0082] In some embodiments, suitable flow conditions are present to keep particles 10 from reaching the inner wall of the plasma torch 2 where plasma attachment could take place. Particles 9, 10 may be guided by the gas flows towards microwave plasma 11 were each undergoes homogeneous thermal treatment. Various parameters of the microwave-generated plasma, as well as particle parameters, may be adjusted in order to achieve desired results. These parameters may include microwave power, feed material size, feed material insertion rate, gas flow rates, plasma temperature, residence time and cooling rates. In some embodiments, the cooling or quenching rate is not less than 10+3degrees C / sec upon exiting plasma 11. As discussed above, in this particular embodiment, the gas flows are laminar; however, in alternative embodiments, swirl flows or turbulent flows may be used to direct the feed materials toward the plasma.Microwave Plasma Processing

[0083] In a microwave plasma process, the feedstock may be entrained in an inert and / or reducing gas environment and injected into the microwave plasma, the microwave plasma plume, or the microwave plasma exhaust. Upon injection into a hot plasma (or plasma plume or exhaust), the feedstock may undergo a physical and / or chemical transformation.After processing, the resulting material may be released into a chamber filled with an inert gas and directed into hermetically sealed drums where is it stored. This process can be carried out at atmospheric pressure, in a partial vacuum, or at a slightly higher pressure than atmospheric pressure.

[0084] In alternative embodiments, the process can be carried out in a low, medium, or high vacuum environment. The process can run in batches or continuously, with the drums being replaced as they fill up with processed material. By controlling the process parameters, such as cooling gas flow rate, residence time, plasma conditions, cooling gas composition, various product characteristics can be controlled.

[0085] Residence time of the particles or gases within a hot zone of the plasma can also be adjusted to provide control over the resulting product characteristics. That is, the length of time the particles are exposed to the plasma determines the extent of processing of the feedstock particles. Residence time can be adjusted by adjusting such operating variables of particle injection rate and flow rate (and conditions, such as laminar flow or turbulent flow) within the hot zone. Equipment changes can also be used to adjust residence time. For example, residence time can be adjusted by changing the cross-sectional area of the plasma, by, for example, extending the plasma. In some embodiments, extending the plasma may comprise incorporating an extension tube into the micro wave plasma apparatus.

[0086] In some embodiments, the extension tube may comprise a stepped shape, such that the tube comprises one or more cylindrical volumes extending downward in the reaction chamber, wherein each successive cylindrical volume comprises a larger diameter than each previous cylindrical volume as the tube extends downward in the reaction chamber. In some embodiments, the extension tube may have a conical shape, tapering radially outwards as it extends downward into the reaction chamber. In some embodiments, the extension tube may comprise a single cylindrical volume4. In some embodiments, the feed material inlets may insert feedstock within the extension tube.

[0087] In some embodiments, the extension tube may comprise a length of about 1 foot. In some embodiments, the extension tube may comprise a length of about 1 inch, about 2 inches, about 3 inches, about 4 inches, about 5 inches, about 6 inches, about 7 inches, about 8 inches, about 9 inches, about 10 inches, about 11 inches, about 1 foot, about 2 feet, about 3 feet, about 4 feet, about 5 feet, about 6 feet, about 7 feet, about 8 feet, about 9 feet, about 10feet, about 1 1 feet, about 12 feet, about 13 feet, about 14 feet, about 15 feet, about 16 feet, about 17 feet, about 18 feet, about 19 feet, about 20 feet, about 21 feet, about 22 feet, about 23 feet, about 24 feet, about 25 feet, about 26 feet, about 27 feet, about 28 feet, about 29 feet, or about 30 feet, or any value between the aforementioned values.Additional Embodiments

[0088] In the foregoing specification, the invention has been described with reference to specific embodiments thereof. It will, however, be evident that various modifications and changes may be made thereto without departing from the broader spirit and scope of the invention. The specification and drawings are, accordingly, to be regarded in an illustrative rather than restrictive sense.

[0089] Indeed, although this invention has been disclosed in the context of certain embodiments and examples, it will be understood by those skilled in the art that the invention extends beyond the specifically disclosed embodiments to other alternative embodiments and / or uses of the invention and obvious modifications and equivalents thereof. In addition, while several variations of the embodiments of the invention have been shown and described in detail, other modifications, which are within the scope of this invention, will be readily apparent to those of skill in the art based upon this disclosure. It is also contemplated that various combinations or sub-combinations of the specific features and aspects of the embodiments may be made and still fall within the scope of the invention. It should be understood that various features and aspects of the disclosed embodiments can be combined with, or substituted for, one another in order to form varying modes of the embodiments of the disclosed invention. Any methods disclosed herein need not be performed in the order recited. Thus, it is intended that the scope of the invention herein disclosed should not be limited by the particular embodiments described above.

[0090] It will be appreciated that the systems and methods of the disclosure each have several innovative aspects, no single one of which is solely responsible or required for the desirable attributes disclosed herein. The various features and processes described above may be used independently of one another or may be combined in various ways. All possible combinations and subcombinations are intended to fall within the scope of this disclosure.

[0091] Certain features that are described in this specification in the context of separate embodiments also may be implemented in combination in a single embodiment. Conversely, various features that are described in the context of a single embodiment also may be implemented in multiple embodiments separately or in any suitable subcombination. Moreover, although features may be described above as acting in certain combinations and even initially claimed as such, one or more features from a claimed combination may in some cases be excised from the combination, and the claimed combination may be directed to a subcombination or variation of a subcombination. No single feature or group of features is necessary or indispensable to each and every embodiment.

[0092] It will also be appreciated that conditional language used herein, such as, among others, “can,” “could,” “might,” “may,” “e.g.,” and the like, unless specifically stated otherwise, or otherwise understood within the context as used, is generally intended to convey that certain embodiments include, while other embodiments do not include, certain features, elements and / or steps. Thus, such conditional language is not generally intended to imply that features, elements and / or steps are in any way required for one or more embodiments or that one or more embodiments necessarily include logic for deciding, with or without author input or prompting, whether these features, elements and / or steps are included or are to be performed in any particular embodiment. The terms “comprising,” “including,” “having,” and the like are synonymous and are used inclusively, in an open- ended fashion, and do not exclude additional elements, features, acts, operations, and so forth. In addition, the term “or” is used in its inclusive sense (and not in its exclusive sense) so that when used, for example, to connect a list of elements, the term “or” means one, some, or all of the elements in the list. In addition, the articles “a,” “an,” and “the” as used in this application and the appended claims are to be construed to mean “one or more” or “at least one” unless specified otherwise. Similarly, while operations may be depicted in the drawings in a particular order, it is to be recognized that such operations need not be performed in the particular order shown or in sequential order, or that all illustrated operations be performed, to achieve desirable results. Further, the drawings may schematically depict one more example processes in the form of a flowchart. However, other operations that are not depicted may be incorporated in the example methods and processes that are schematically illustrated. For example, one or more additional operations may be performed before, after, simultaneously, or between any of the illustrated operations.Additionally, the operations may be rearranged or reordered in other embodiments. In certain circumstances, multitasking and parallel processing may be advantageous. Moreover, the separation of various system components in the embodiments described above should not be understood as requiring such separation in all embodiments, and it should be understood that the described program components and systems may generally be integrated together in a single software product or packaged into multiple software products. Additionally, other embodiments are within the scope of the following claims. In some cases, the actions recited in the claims may be performed in a different order and still achieve desirable results.

[0093] Further, while the methods and devices described herein may be susceptible to various modifications and alternative forms, specific examples thereof have been shown in the drawings and are herein described in detail. It should be understood, however, that the invention is not to be limited to the particular forms or methods disclosed, but, to the contrary, the invention is to cover all modifications, equivalents, and alternatives falling within the spirit and scope of the various implementations described and the appended claims. Further, the disclosure herein of any particular feature, aspect, method, property, characteristic, quality, attribute, element, or the like in connection with an implementation or embodiment can be used in all other implementations or embodiments set forth herein. Any methods disclosed herein need not be performed in the order recited. The methods disclosed herein may include certain actions taken by a practitioner; however, the methods can also include any third-party instruction of those actions, either expressly or by implication. The ranges disclosed herein also encompass any and all overlap, sub-ranges, and combinations thereof. Language such as “up to,” “at least,” “greater than,” “less than,” “between,” and the like includes the number recited. Numbers preceded by a term such as “about” or “approximately” include the recited numbers and should be interpreted based on the circumstances (e.g., as accurate as reasonably possible under the circumstances, for example ±5%, ±10%, ±15%, etc.). For example, “about 3.5 mm” includes “3.5 mm.” Phrases preceded by a term such as “substantially” include the recited phrase and should be interpreted based on the circumstances (e.g., as much as reasonably possible under the circumstances). For example, “substantially constant” includes “constant.” Unless stated otherwise, all measurements are at standard conditions including temperature and pressure.

[0094] As used herein, a phrase referring to “at least one of’ a list of items refers to any combination of those items, including single members. As an example, “at least one of: A, B, or C” is intended to cover: A, B, C, A and B, A and C, B and C, and A, B, and C. Conjunctive language such as the phrase “at least one of X, Y and Z,” unless specifically stated otherwise, is otherwise understood with the context as used in general to convey that an item, term, etc. may be at least one of X, Y or Z. Thus, such conjunctive language is not generally intended to imply that certain embodiments require at least one of X, at least one of Y, and at least one of Z to each be present. The headings provided herein, if any, are for convenience only and do not necessarily affect the scope or meaning of the devices and methods disclosed herein.

[0095] Accordingly, the claims are not intended to be limited to the embodiments shown herein but are to be accorded the widest scope consistent with this disclosure, the principles and the novel features disclosed herein.

Claims

WHAT TS CLAIMED TS:

1. A method for destruction of per- and polyfluoroalkyl substances (PFAS) using a microwave generated plasma, the method comprising: propagating microwaves through a microwave plasma apparatus, the microwaves generated using a microwave generator to generate a microwave plasma; introducing the PFAS into the microwave plasma apparatus; and contacting the PFAS with the microwave plasma, wherein contacting the PFAS with the microwave plasma initiates a chemical reaction that destroys the PFAS.

2. The method of Claim 1, wherein the chemical reaction comprises a thermal degradation reaction.

3. The method of Claim 2, wherein the thermal degradation reaction occurs at a temperature between 1000 °C and about 1200 °C.

4. The method of Claim 3, wherein the PFAS is thermally degraded in about 1 second to about 2 seconds.

5. The method of Claim 1, wherein the chemical reaction comprises at least one radical reaction.

6. The method of Claim 5, wherein the at least one radical reaction converts molecules of the PFAS to HF and at least one carbon-containing molecule.

7. The method of Claim 6, wherein the at least one carbon-containing molecule comprises CO2 or CH4.

8. The method of Claim 1, wherein the microwave generated plasma generates ultraviolet (UV) light.

9. The method of Claim 8, wherein the UV light generates one or more radicals, and wherein the chemical reaction comprises a radical reaction involving the one or more radicals generated by the UV light.

10. The method of Claim 9, wherein the radical reaction converts molecules of the PFAS to HF and at least one carbon-containing molecule.

11. The method of Claim 10, wherein the at least one carbon-containing molecule comprises CO2 or CH4.

12. The method of Claim 1, wherein the PFAS comprises at least one of the following: Perfluorooctanoic Acid (PFOA), Perfluorooctane Sulfonate (PFOS), Perfluorononanoic Acid(PFNA), Perfluorohexane Sulfonic Acid (PFHxS), Perfluorobutane Sulfonic Acid (PFBS), Pcrfluorodccanoic Acid (PFDA), Pcrfluoroundccanoic Acid (PFUnDA),Pcrfluorododccanoic Acid (PFDoDA), Perfluorotetradecanoic Acid (PFTeDA), Perfluorohexanoic Acid (PFHxA), Perfluoropentanoic Acid (PFPeA), Perfluorobutanoic Acid (PFBA), Perfluoropentane Sulfonic Acid (PFPeS), Perfluorohexane Sulfonamide (PFHxSA), Perfluorooctane Sulfonamide (PFOSA), Perfluoroheptanoic Acid (PFHpA), Perfluorohexadecanoic Acid (PFHxDA), Perfluorooctadecanoic Acid (PFOcDA), Perfluorotridecanoic Acid (PFTrDA), Perfluoroheptadecanoic Acid (PFHpDA), Perfluorononadecanoic Acid (PFNDA), Perfluorotetradecanoic Acid (PFTDA), Perfluorooctane Sulfonamide Ethanol (FOSE), Perfluorodecane Sulfonic Acid (PFDS), Perfluoroundecane Sulfonic Acid (PFUnDS), Perfluorododecane Sulfonic Acid (PFDoDS), Perfluorotetradecane Sulfonic Acid (PFTeDS), Perfluorohexadecane Sulfonic Acid (PFHxDS), Perfluorooctadecane Sulfonic Acid (PFOcDS), Perfluorobutane Sulfonamide (PFBSA), Perfluorobutanesulfonamide Ethanol (FBSA), Perfluorohexanesulfonamide (PFHxSA), Perfluorooctanesulfonamide Ethanol (FOSEA), Perfluorohexyl Iodide (PFHI), N-Ethyl Perfluorooctanesulfonamide (NEtFOSA), N-Methyl Perfluorooctanesulfonamide (NMeFOSA), N-Ethyl Perfluorooctane Sulfonamidoacetate (NEtFOSAA), N-Methyl Perfluorooctane Sulfonamidoacetate (NMeFOSAA), N-Ethyl Perfluorooctane Sulfonamidoacetic Acid (NEtFOSAAc), N-Methyl Perfluorooctane Sulfonamidoacetic Acid (NMeFOSAAc), N-Ethyl Pcrlluorooctanc Sulfonamidoethanol (NEtFOSEA), N-Methyl Perfluorooctane Sulfonamidoethanol (NMeFOSEA), N-Ethyl Perfluorooctane Sulfonamide Ethyl Ester (NEtFOSE), N-Methyl Perfluorooctane Sulfonamide Ethyl Ester (NMeFOSE), N-Ethyl Perfluorooctane Sulfonamide Ethanol (NEtFOSEA), N-Methyl Perfluorooctane Sulfonamide Ethanol (NMeFOSEA), N- Ethyl Perfluorooctane Sulfonamide Acetate (NEtFOSAAc), N-Methyl Perfluorooctane Sulfonamide Acetate (NMeFOSAAc), N-Ethyl Perfluorooctane Sulfonamide Ethyl Acetate (NEtFOSEAc), and N-Methyl Perfluorooctane Sulfonamide Ethyl Acetate (NMeFOSEAc).

13. The method of Claim 1, wherein the PFAS comprises at least one of ultra shortchain PFAS, short-chain PFAS, medium-chain PFAS, and long-chain PFAS.

14. The method of Claim 1, wherein the PFAS comprise one or more of the following functional groups: carboxylic acid (-COOH), sulfonic acid (-SO3H), phosphonic acid (-PO3H2), ester (-COOR), amide (-CONH2or -CONHR’), ether (-O-), alkyl (-R), and heterocyclic ring.

15. The method of Claim 1, wherein the chemical reaction comprises at least one of the following: fluorination, defluorination, fragmentation, cross-coupling, and polymerization.

16. The method of Claim 1, wherein the PFAS is introduced into a plume or exhaust of the microwave generated plasma.

17. The method of Claim 1, wherein the chemical reaction comprises breaking a carbon-fluorine bond in the PFAS.

18. The method of Claim 1, wherein introducing the PFAS into the micro wave plasma apparatus comprises introducing a PFAS-containing medium into the microwave plasma apparatus.

19. The method of Claim 18, wherein the PFAS-containing medium is spent activated carbon.

20. The method of Claim 18, wherein the PFAS-containing medium comprises biosolids.

21. A method of reactivating spent activated carbon using a micro wave generated plasma, the method comprising: propagating microwaves through a microwave plasma apparatus, the microwaves generated using a microwave generator to generate a microwave plasma; introducing spent activated carbon into the microwave plasma apparatus, wherein the spent activated carbon comprises activated carbon and adsorbates adsorbed onto the activated carbon; contacting the spent activated carbon with the microwave plasma, wherein contacting the spent activated carbon with the microwave plasma removes the adsorbates from the activated carbon.

22. The method of Claim 20, wherein the activated carbon comprises granulated activated carbon.

23. The method of Claim 20, wherein the adsorbate comprises per- and polyfluoroalkyl substances (PFAS).

24. The method of Claim 20, wherein contacting the spent activated carbon with microwave plasma removes and destroys all or substantially all of the adsorbates from the activated carbon.

25. The method of Claim 20, wherein contacting the spent activated carbon with microwave plasma reactivates the spent activated carbon.

26. The method of Claim 24, wherein the reactivated spent activated carbon has an adsorption capacity substantially similar to an adsorption capacity of the activated carbon with no adsorbates adsorbed thereto.

27. A method of converting biosolids to activated carbon, the method comprising: propagating microwaves through a microwave plasma apparatus, the microwaves generated using a microwave generator to generate a microwave plasma; introducing biosolids into the microwave plasma apparatus, wherein the biosolids comprise per- and polyfluoroalkyl substances (PFAS); and contacting the biosolids with the microwave plasma, wherein contacting the biosolids with the microwave plasma removes the PFAS from the biosolids to produce bio solids -derived carbon.

28. The method of Claim 27, wherein the biosolids-derived carbon comprises biosolids-based activated carbon.

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