Supercritical fluids regeneration of PFAS-contaminated spent media and water treatment train

Abstract

A method of mitigation of persistent organic compounds absorbed on a sorbent, the method including extracting the persistent organic compounds from the sorbent with a supercritical carbon dioxide (scCO2) mixture comprising scCO2, a co-solvent, and an ion source, wherein a scCO2 to co-solvent ratio is between about 10,000:1 to 1:1, wherein a co-solvent to ion source ratio is between about 10:1 and about 1,000,000:1, and wherein the scCO2 mixture is at a pressure and a temperature, to provide an extractant containing the persistent organic compounds; and isolating the persistent organic compounds from the extractant for their reuse or end of life treatment. A composition for the mitigation of persistent organic compounds, the composition including a scCO2, an ion source, and a co-solvent, wherein a scCO2 to co-solvent ratio is between about 10,000:1 to 1:1, and wherein a co-solvent to ion source ratio is between about 10:1 and about 1,000,000:1.

Description

SUPERCRITICAL FLUIDS REGENERATION OF PF AS-CONTAMINATED SPENTMEDIA AND WATER TREATMENT TRAINCROSS-REFERENCE(S) TO RELATED APPLICATION S)

[0001] This application claims the benefit of and priority to U.S. Provisional Patent Application No. 63 / 651716, filed May 24, 2025, the contents of which are incorporated by reference herein in their entirety.STATEMENT OF GOVERNMENT LICENSE RIGHTS

[0002] This invention was made with Government support under U.S. EPA contract 68HERC20D0029 Task Order No. TO 68HERC25F0035. The Government has certain rights in the invention.BACKGROUND

[0003] Contamination of the environment by halocarbon and hydrocarbon organic materials is of serious concern. Granular activated carbon (GAC), ion exchange resin (IXR), and, to a lesser extent, novel sorbents, such as FluoroSorb (surface-modified organoclay), are commonly used sorbents for perfluoroalkyl and polyfluoroalkyl substance (PFAS) removal in water treatment. Contaminated water is passed through a bed of granules, where the contaminants adhere to the microporous carbon surfaces. Though it is considered a proven technology, the effectiveness of GAC varies depending on the specific PFAS, water chemistry, and other factors. Moreover, while widespread adoption of GAC offers a cost-effective solution, it also creates a pressing need for managing the accumulation of spent GAC. Sorbent regeneration unlocks the potential for sustainable, large-scale treatment of PF AS-contaminated streams. Thermal regeneration utilizes high temperatures, ranging from 600 to 1000°C, to desorb PFAS and other contaminants from spent GAC. Recent studies also show that thermal degradation yields the formation of volatile organo-fluorine (VOF) compounds that could re-enter the environment as gases or aerosols.

[0004] Though IXRs are widely used for water treatment, current research focuses on their modifications to enhance PFAS removal. Novel sorbents aim to enhance the efficiency and selectivity of PFAS removal from water. Polymeric adsorbents can be designed to have a high affinity for PFAS molecules, allowing for effective and selective removal. Metal-organic frameworks (MOFs) are crystalline materials with a high surface area and tunable properties. Certain MOFs have shown promise in adsorbing PFAScontaminants; however, MOF production has not been scaled up and is still considered an emerging technology. The practical implementation of the novel sorbents on a larger scale and their cost-effectiveness is a major consideration. Approaches that can desorb PF AS without forming VOFs while preserving GAC’s structural and adsorptive properties are highly desirable. Low-temperature methods rely on organic solvents or aqueous solutions. The application of these methods for the desorption of long-chain (C-8) PF AS is challenging due to their strong affinity to surfaces, and the large quantities of solvents required for GAC treatment hinder large-scale implementation. The disposal of spent sorbents is a significant challenge; PFAS desorption and regeneration present an opportunity to reuse sorbent media and facilitate effective end-of-life PFAS destruction.

[0005] Above its critical point (31°C, 7.4 MPa), carbon dioxide (CO2) becomes a supercritical fluid- a nonpolar solvent with low dielectric constant and negligible molecular dipole moment; scCCh is a nonpolar solvent due to the low dielectric constant and negligible molecular dipole moment. It is used in commercial applications, such as botanical extraction, cleaning nanostructures (e.g., carbon nanotubes, MOFs), surface sterilization, and food pasteurization. Supercritical fluid extraction (SFE) procedures for removing organic species from solid samples have been discussed in the literature for several decades. In analytical chemistry, the SFE enables quantitative recovery of polycyclic aromatic hydrocarbons (PAHs) from solid samples and sorbent traps at T = 45°C. Typical temperatures of scCCh extraction (T < 100°C) are insufficient for PFAS destruction; however, similar to PAHs, fluorinated organics can be dissolved in scCCh. Though most studies were limited to small molecules C1-C2, literature provides some evidence of PFOA solubility in scCCh. To optimize SFE for PF AS-contaminated matrices, the fundamental data on the solubility and desorption kinetics of PFAS are needed.

[0006] Recent advances in PFAS destruction led to the development of several technologies. Hydrothermal approaches, such as supercritical water oxidation (SCWO) and hydrothermal alkaline treatment (HALT), can be well-suited to destroy concentrated liquid waste. Due to the high heating value of the PFAS-containing solvent from the scCCh reactor (proposed here), SCWO could be a suitable option for end-of-life treatment. Solid matrix PFAS destruction, such as ball-milling (BM), was proposed to treat large (soil) volumes.SUMMARY

[0007] This summary is provided to introduce a selection of concepts in a simplified form that are further described below in the Detailed Description. This summary is not intended to identify key features of the claimed subject matter, nor is it intended to be used as an aid in determining the scope of the claimed subject matter.

[0008] In an aspect a method of mitigation of persistent organic compounds absorbed on a sorbent is presented, the method comprising: extracting the persistent organic compounds from the sorbent with a supercritical carbon dioxide (scCO2) mixture comprising scCO2, a co-solvent, and an ion source, wherein a scCO2to co-solvent ratio is between about 10,000: 1 to 1 : 1, wherein a co-solvent to ion source ratio is between about 10: 1 and about 1,000,000: 1, and wherein the scCO2mixture is at a pressure and a temperature, to provide an extractant containing the persistent organic compounds; and isolating the persistent organic compounds from the extractant for their reuse or end of life treatment.

[0009] In some embodiments, the scCO2to co-solvent ratio is between about 100: 1 and about 125: 1. In some embodiments, the scCO2to co-solvent ratio is about 125: 1.

[0010] In some embodiments, the co-solvent to ion source ratio is between about 40: 1 and about 100: 1.

[0011] In some embodiments, the ion source is a salt comprising a cation derived from a weak base and an anion derived from a strong acid. In some embodiments, the ion source is ammonium chloride, ammonium bromide, ammonium iodide, ammonium nitrate, ammonium sulfate, ammonium perchlorate, ammonium chlorate, pyridinium chloride, pyridinium bromide, pyridinium iodide, pyridinium nitrate, pyridinium sulfate, pyridinium perchlorate, pyridinium chlorate, ethylammonium chloride, ethylammonium bromide, ethylammonium iodide, ethylammonium nitrate, ethylammonium sulfate, ethylammonium perchlorate, and ethylammonium chlorate, or combinations thereof. In some embodiments, the ion source is ammonium chloride.

[0012] In some embodiments, the ion source is an acid. In some embodiments, the acid is a stronger acid than the persistent organic compound.

[0013] In some embodiments, the acid is sulfuric acid, methane sulfonic acid, p- toluene sulfonic acid, triflic acid, phosphoric acid, trichloroacetic acid, trifluoracetic acid, selenic acid, HF, HC1, formic acid, acetic acid, carbonic acid, or combinations thereof. In some embodiments, the acid is sulfuric acid. In some embodiments, the acid is HC1.

[0014] In some embodiments, the flow rate of scCO2is between about 10 mL / min and about 1,000,000 mL / min. In some embodiments, the flow rate of scCO2is between about 10 mL / min and about 1,000 mL / min. In some embodiments, the flow rate of scCO2is about 25 mL / min. In some embodiments, the flow rate is selected based on the size of a system containing persistent organic compounds. In some embodiments, the flow rate of scCO2 is selected so that a residence time in sorbent is between 1 minute and 100 minutes, between 1 minute and 80 minutes, between 1 minute and 60 minutes, between about 40 minutes and about 60 minutes, or about 60 minutes.

[0015] In some embodiments, the co-solvent is selected from the group consisting of ethanol, isopropanol, propanol, butanol, isobutanol, acetone, perfluorocarbon, hydrofluorocarbon, chlorofluorocarbon, hydrochlorofluorocarbon, or combinations thereof. In some embodiments, the co-solvent is methanol.

[0016] In some embodiments, the step of extracting the persistent organic compounds occurs at a temperature of 100 °C or less. In some embodiments, the step of extracting the persistent organic compounds occurs at a temperature of about 75 °C . In some embodiments, the step of extracting the persistent organic compounds occurs at a temperature of about 40 °C .

[0017] In some embodiments, the step of extracting the persistent organic compounds occurs at a pressure of about 10 MPa or less. In some embodiments, the step of extracting the persistent organic compounds occurs at a pressure of about 10 MPa.

[0018] In some embodiments, the step of extracting the persistent organic compounds occurs for a time of 1-60 minutes.

[0019] In some embodiments, the sorbent is ion exchange resin (IXR), granular activated carbon (GAC), textiles, PPE, MOFs, zeolites, contaminated soils, air filters, or combinations thereof.

[0020] In some embodiments, the mitigation involves capturing, concentrating, condensing, distilling, solidification, oxidizing, vitrification, mineralizing or any combination thereof the persistent organic compounds.

[0021] In some embodiments, the supercritical carbon dioxide, co-solvents, and sorbent are recycled.

[0022] In some embodiments, the method further comprises: concentration and solidification, wherein supercritical carbon dioxide is added to a supercritical carbon dioxide extractor with solvent mixture; wherein sorbent is added, wherein the supercriticalcarbon dioxide and solvent mixture are brought to an evaporator, wherein the persistent organic compounds or organic carbon are condensed into a solid or liquid, wherein the evaporated gaseous carbon dioxide is recycled; capturing, wherein the sorbent is regenerated and reused; end-of-life-treating, wherein the extracted persistent organic compounds, polyfluoroalkyl substances, or organic carbon are ball milled, processed by hydrothermal treatment, incinerated to achieve their destruction, vitrified, or immobilized in a solid matrix; wherein the solvents are recycled.

[0023] In some embodiments, the co-solvent to ion source ratio is adjusted based on a level of contamination.

[0024] In some embodiments, the co-solvent to ion source ratio is adjusted based on measurements selected from the group consisting of effluent measurements pH, ion donor depletion measurements, or real-time in-situ spectroscopic measurements.

[0025] In some embodiments, the real-time in-situ spectroscopic measurements are Raman or FTIR.

[0026] In some embodiments, the extractant containing the persistent organic compounds is in a single phase.

[0027] In some embodiments, the extractant containing the persistent organic compounds is in two phases.

[0028] In some embodiments, the method is used upon contaminated textiles, personal protective equipment (PPE), Department of Defense chemical warfare agents (CWA), chemical and oil spill cleanup, hazmat targets, or any combinations thereof.

[0029] In another aspect, the present disclosure relates to a composition for the mitigation of persistent organic compounds, the composition including: a supercritical carbon dioxide (SCCO2); an ion source; and a co-solvent, wherein a SCCO2 to co-solvent ratio is between about 10,000: 1 to 1 : 1, and wherein a co-solvent to ion source ratio is between about 10: 1 and about 1,000,000: 1.

[0030] In some embodiments, the composition for the mitigation of persistent organic compounds is configured to be used in the method for of mitigation of persistent organic compounds adsorbed on a sorbent.

[0031] In some embodiments, the scCO2to co-solvent ratio is about 125: 1.

[0032] In some embodiments, the co-solvent to ion source ratio is between about40: 1 and about 100: 1.

[0033] In some embodiments, the co-solvent is methanol, ethanol, isopropanol, propanol, butanol, isobutanol, acetone, perfluorocarbon, hydrofluorocarbon, chlorofluorocarbon, hydrochlorofluorocarbon, or combinations thereof.

[0034] In some embodiments, the mitigation of persistent organic compounds of claim 31, wherein the ion source is sulfuric acid, methane sulfonic acid, p-toluene sulfonic acid, triflic acid, phosphoric acid, trichloroacetic acid, trifluoracetic acid, selenic acid, HF, HC1, formic acid, acetic acid, carbonic acid, ammonium chloride, ammonium bromide, ammonium iodide, ammonium nitrate, ammonium sulfate, ammonium perchlorate, ammonium chlorate, pyridinium chloride, pyridinium bromide, pyridinium iodide, pyridinium nitrate, pyridinium sulfate, pyridinium perchlorate, pyridinium chlorate, ethylammonium chloride, ethylammonium bromide, ethylammonium iodide, ethylammonium nitrate, ethylammonium sulfate, ethylammonium perchlorate, and ethylammonium chlorate, or combination thereof.DESCRIPTION OF THE DRAWINGS

[0035] The foregoing aspects and many of the attendant advantages of this disclosure will become more readily appreciated as the same become better understood by reference to the following detailed description, when taken in conjunction with the accompanying drawings, wherein:

[0036] FIGURE 1 is a diagram of a treatment train according to an aspect of the present disclosure, including trapping pollutants on sorbent, extract! on / solidificati on step, and end-of-life treatment;

[0037] FIGURE 2 is a flow diagram of the bench scale SFE setup according to an aspect of the present disclosure;

[0038] FIGURE 3A depicts a process flow diagram of the University of Washington (UW) SCWO system with flow control, in-situ monitoring, and effluent and gas sample collection according to an aspect of the present disclosure. Thermocouple 1 (TCI) TCI and thermocouple 2 (TC2) monitor inlet temperatures; thermocouple 3 (TC3), thermocouple 4 (TC4), and thermocouple 5 (TC5) — reactor fluid temperature; thermocouple 6 (TC6) and thermocouple 7 (TC7) — effluent before and after the heat exchanger; thermocouple 8 (TC8), thermocouple 9 (TC9), and thermocouple 10 (TC10) — wall temperatures. BPR = back-pressure regulator;

[0039] FIGURE 3B depicts a schematic of the reactor and location of thermocouples according to an aspect of the present disclosure;

[0040] FIGURE 3C depicts CFD simulations (T contours) showing reactor zone: pilot fuel and air injection, oxidation zone, and process quenching with an alkaline solution for HF neutralization;

[0041] FIGURE 4 depicts a diagram of CF-HALT reactor according to an aspect of the present disclosure. Thermocouples 1 and 2 (TCI and TC2) control heater temperatures, thermocouples 3 and 4 (TC3 and TC4) monitor reactor wall temperature, and thermocouple 5 (TC5) monitors effluent temperature;

[0042] FIGURE 5 depicts a schematic of monitoring and sampling for gaseous species in SCWO according to an aspect of the present disclosure;

[0043] FIGURE 6 depicts the extraction efficiency of PFOA-laden GAC for different co-solvents and flow rates according to an aspect of the present disclosure;

[0044] FIGURE 7 depicts PFOA recovery from GAC — scCO2 / co-solvent experiments in a small column reactor;

[0045] FIGURE 8 depicts an SFE process flow diagram and thermocouple (TC) locations according to an aspect of the present disclosure. A gas cylinder supplies CO2, which is condensed to the liquid phase in a cold bath (TCI), pumped, and heated before entering the mixing section (TC2) and mixed with MeOH. The fluid is cooled to ~40 °C before entering the back pressure regulator (BPR) placed in a warm water bath to avoid rapid throttling and diaphragm damage. After exiting the BPR, the effluent was collected in a flask while gaseous CO2separated naturally;

[0046] FIGURE 9 depicts PFOA desorption from GAC using only scCO2, scCO2+ MeOH, and scCO2+ MeOH / H2SO4. Experimental conditions are 110 °C, 10 MPa, and an exposure time of 60 min. The second cycle of desorption in CO2was not conducted. Error bars are standard deviations from triplicated experiments;

[0047] FIGURE 10 depicts PFOA desorption routes from GAC, blue - porous water, green - scCO2, according to an aspect of the present disclosure. Route I - in pure scCO2, high dielectric permittivity and subsequent proton association lead to partial PFOA protonation; Route II - in pure scCO2, bicarbonate ions formed from CO2interaction with retained water compete with PFOA for adsorption sites; Route III - in scCO2 / MeOH / H2SO4(i) competition of the sulfate ion for GAC active site and (ii) PFOA protonation; and

[0048] FIGURE 11 depicts desorption efficiency of PFOA-laden GAC for varying the flow rate of the co-solvent (MeOH + 2.3% v / v H2SO4) and constant flow rateof scCO2at 25 mL / min. The value of the flow rate of the co-solvent determines the molar fraction of methanol (XMeOH) in the mixture and affects its state in the supercritical or sub critical condition.DETAILED DESCRIPTION

[0049] Disclosed is a low-temperature method for treating sorbents, filtration media, textiles and solids contaminated by persistent organic pollutants, volatile and gaseous pollutants, and hazardous substances. Adsorbed compounds such as polyfluoroalkyl substances (PF AS), fluorinated and chlorinated gases, microplastics, and chemical waste are extracted from ion exchange resin (IXR) granular activated carbon (GAC) sorbent media or other filtration media by utilizing the antisolvent properties of supercritical CO2 (scCCh) and presents a cost-effective treatment train for the complete mineralization of persistent organic compounds and other harmful pollutants and hazardous substances.

[0050] In an aspect a method of mitigation of persistent organic compounds absorbed on a sorbent includes extracting the persistent organic compounds from the sorbent with a supercritical carbon dioxide (scCO2) mixture comprising scCO2, a cosolvent, and an ion source, wherein a scCO2to co-solvent ratio is between about 10,000: 1 to 1 : 1, wherein a co-solvent to ion source ratio is between about 10: 1 and about 1,000,000: 1, and wherein the scCO2mixture is at a pressure and a temperature, to provide an extractant containing the persistent organic compounds; and isolating the persistent organic compounds from the extractant for their reuse or end of life treatment.

[0051] As used herein, “supercritical carbon dioxide” refers to carbon dioxide where the pressure and temperature conditions are above the critical point of the carbon dioxide.

[0052] As used herein, “ion source” refers to a chemical composition and / or compound that, when placed in contact with a solvent, provides a cation and an anion. In some embodiments, an ion source may be a salt, an acid, a base, or a combination thereof.

[0053] As used herein, “strong acid” and “strong base” refer to acidic or basic chemical compositions and / or compounds that substantively completely dissociate into their component ions.

[0054] As used herein, “weak acid” and “weak base” refers to acidic or basic chemical compositions and / or compounds that at least partially dissociate into their component ions, but do not completely dissociate.

[0055] Persistent organic compounds include, but are not limited to, aldrin, chlordane, dichlorodiphenyl trichloroethane (DDT), dieldrin, endrin, heptachlor, hexachlorobenzene, mirex, toxaphene, polychlorinated biphenyls (PCBs), polychlorinated dibenzo-p-dioxins (dioxins), polychlorinated dibenzofurans, per-and polyfluoroalkyl substances, perfluorooctanoic acid (PFOA), perfluorooctanesulfonic acid (PFOS), perfluorobutanesulfonic acid (PFBS), hexafluoropropylene oxide-dimer acid (HFPO-DA or GenX), perfluorononanoic acid (PFNA), perfluorohexanesulfonic acid (PFHxS), perfluorodecanoic acid (PFDA), perfluorohexanoic acid (PFHxA), and perfluorobutanoic acid (PFBA, volatile organic compounds (VOC), aromatics, benzene, toluene, mesitylene, esters, ethyl acetate, butyl acetate, amyl acetate, chlorinated organics, dichloromethane, chloroform, chlorobenzene, di chlorobenzene, volatile organic fluorinated compounds (VOF), tetrafluoromethane, hexafluoroethane, octafluoropropane trifluoromethane, trifluoroethane, tetrafluoropopene, refrigerants, chlorofluorocarbon (CFC), hydrochlorofluorocarbon (HCFC), or hydrofluorocarbon (HFC), Rl l, R12, R22, R123, R134a, R407A, R407C, R404A, R410A, R514A, hydrocarbons, propane, isobutane, chemical warfare agents, GD, VX, sarin, chlorine, hydrogen cyanide, cyanogen chloride, blistering agents, blood agents, chocking agents, nerve agents, micro and nano plastics, polyethylene, polypropylene, acrylics, styrenics, polyesters, PET, melamine, nylon, polyolefin, polyurethane, and the like.

[0056] Disclosed is an investigation into low-temperature PF AS and persistent organic compound extraction from sorbent media by utilizing the antisolvent properties of supercritical CO2. In the present disclosure, a cost-effective treatment train is described for a variety of PFAS, resulting in the complete mineralization of PF AS and regenerating sorbent media for future reuse. The disclosure focuses on providing low-cost solutions by leveraging existing technologies and developing and optimizing new processes.

[0057] FIGURE 1 depicts a conceptual diagram that utilizes high technology readiness level (TRL) hardware. The spent sorbents are regenerated by exposure to SCCO2 (or scCO2 / organic solvent) mixture extraction followed by end-of-life treatment of concentrated slurries (in solvent), sludges, or solid residues. The effort consists of first-in- kind demonstrations of supercritical fluid extraction (SFE) of PFAS and co-contaminants and regeneration of spent granular activated carbon (GAC) and ion exchange resins (IXRs); bench-scale optimization waste stream recovery for end of life treatment; the evaluation of end-of-life treatment approaches for solid residues and concentrated effluent; an evaluationof process scale-up using commercial off-the-shelf (COTS) technologies; and techno- economic analysis (TEA). FIGURE 1 shows a conceptual diagram of the sorbent regeneration using SCCO2 / co-solvent extraction. BM or vitrification can be a suitable treatment for small, concentrated volumes of solid residue from the SCCO2 sorbent regeneration train (FIGURE 1).

[0058] Organic molecules are potentially miscible in SCCO2. In this disclosure PF AS and persistent organic compound extraction are optimized for GAC and IXR and other sorbents. Contaminants are mitigated by varying operating parameters, such as temperature, exposure time, and the addition of co-solvent or co-solvents. Long-chain PF AS, persistent organic compounds and other polar co-contaminants may require elevated temperatures (T ~100 — 150 °C), which may potentially lead to perfluoro-carboxylic acids (PFCAs), thermal degradation, and the formation of gaseous compounds, e.g., 1H- perfluoroalkanes. As such, this disclosure reveals a system framework that adapts to not only PDAS and persistent organic compounds, but also their degradation daughter molecules. Real-world spent solvents contain a high level of organic contaminants, and the techniques of this disclosure are applicable to organic solvents and the contaminants found in organic solvents. Exposure to elevated temperatures and co-solvents may lead to the deterioration of resins; however, the operational envelope of the disclosed SFE process prevents such deterioration and maintains the sorbent capacity for repeated use.

[0059] Highly concentrated PF AS (or persistent organic compounds) / Organic Carbon (OC) / Solvent slurries and sludges are to be produced by the disclosed supercritical CO2 process and transported to the end-of-life treatment process. The disclosed PF AS and persistent organic compound recovery (and transport to the end-of-life treatment stage) depends on the system design and the operating conditions, i.e., co-solvent / CO2 ratio. Ballmilling is an effective method for the treatment of complex slurries which can be achieved by the slurries being concentrated by distillation before BM treatment. Another process is by hydrothermal methods, i.e., supercritical water oxidation (SCWO) and hydrothermal alkaline treatment (HALT) of slurries.

[0060] The disclosed supercritical extraction process, scCCh extractors and other ancillary components are readily available as they are commercially produced and can be utilized in the construction of the scale-up treatment plant.

[0061] In addition to scCO2, cosolvent mixtures of scCO2are also disclosed. The cosolvent mixture of SCCO2 / organic solvent with an acidic or alkaline modifier improvessorbent regeneration. PFAS has strong hydrophobic interactions with carbon-based structures, as well as electrostatic interactions due to the strong electronegativity of the fluorine atoms and the Lewis acid properties of carbon dioxide. Although dipolar organic solvents such as methanol and ethanol can disrupt the hydrophobic interaction between PFAS molecules and GAC surfaces, this process is slow which this disclosure solves by the addition of a catalyst / pH adjuster. The use of a solvent / base mixture was reported for GAC regeneration, but the mechanism remains unclear. ScCC^ / MeOH / acid mixture is shown in this disclosure to extract PFOA, PFOS and persistent organic compounds as well as persistent organics from sorbent materials and is applicable in a wide range of applications extending to textiles and other matrices. Data shown in this disclosure demonstrates that adding acid (1%, v / v) increases PFOA extraction efficiency, reaching -99% in 30 min of GAC exposure.

[0062] In some embodiments, GAC (Filtrasorb 400) GAG was loaded with PFOA by placing GAC in the PFOA / water mixture overnight. The spent GAC was placed into an % inch stainless steel tube (SS 316) with 149-micron filters at both ends (FIGURE 2 shows the system flow diagram). The flow rate of scCO2was held constant while the cosolvent and amendment were varied for the methanol and acid cosolvent experiments. The exposure time was held constant at 60 min. The liquid effluent was collected and analyzed by LC-MS / MS. A high extraction of PFOA was observed at the high flow rate of methanol and using acid (Table 1). These data demonstrate a proof-of-concept for GAC regeneration using a scCO2 / solvent mixture.Table 1: PFOA extraction from spent GAC using scCC^ / co-solvent mixtures.GAC 1 25 MeOH + 1% 6.8 120-135 276.53 v / v H2SO4GAC 2 25 MeOH + 1% 0.2 120-180 14.84 v / v H2SO4GAC 3 25 EtOH+ 0.5% 0.2 110-175 12.24 v / v NH4OHGAC 4 25 MeOH 0.2 80-55 17.1

[0063] Mitigation of PFAS and persistent organic compounds involves chemically changing or sequestering the compounds after extraction. The present disclosure advances PFAS and persistent organic compound sequestering and destruction involving several technologies. Hydrothermal approaches, such as supercritical water oxidation (SCWO) and hydrothermal alkaline treatment (HALT) are part of this disclosure to destroy concentrated liquid waste. Due to the high heating value of the PF AS-containing solvent from the scCCh reactor (proposed here), SCWO could be a suitable option for end- of-life treatment. Solid matrix PFAS destruction, such as ball-milling (BM), is disclosed in this application to treat large (soil) volumes. BM or vitrification is disclosed for treatment for small, concentrated volumes of solid residue from the SCCO2 sorbent regeneration train (FIGURE 1). The specific operational scenarios, the residue properties, and the treatment train’s techno-economic analysis (TEA) will inform the final selection.

[0064] Above its critical point (374 °C, 22.1 MPa), water becomes an excellent solvent for organic compounds with excellent mass transfer properties for oxidative reactions to occur rapidly. The oxidation chemistry is driven by free radical reaction mechanisms involving OH», O», and H», ultimately terminating as stable products of CO2, H2O, acids, and salts. The disclosed system operated for > 2000+ hours and was tested at the DoD’s chemical and biological center (Edgewood, MD), demonstrating single-step chemical warfare agent (CWA) destruction (DRE > 99.99%). This disclosure demonstratesa DRE > 99.99% for neat C2-C8 PF AS, AFFF, persistent organic compound, and PFAS- contaminated landfill leachate. FIGURE 3A shows four influent streams introducing the reagents: ethanol-water solution, compressed air-water mixture, PFAS(or persistent organic compound)-water solution, and liquid water injection (with NaOH for HF neutralizing) at the reactor exit. A Ti liner is placed within a stainless steel (SS316) pipe to mitigate corrosion associated with an aggressive SCWO environment. The co-fuel (ethanol / water solution) and air / SCW mixture are injected through a co-axial nozzle at the top of the reactor, providing a heating value for reactor operation. The PFAS-laden stream is injected through two ports at the reactor’s dome. Water injection forces transition to the subcritical phase within the reactor. Control of each stream allows for precise operating conditions, enabling kinetic studies.

[0065] The disclosed mitigations have several Benefits of SCWO Technology for PF AS Treatment: (i) the treated waste stream is contained within the reactor, avoiding the emissions of VOF; (ii) the disclosed system, autogenetic operation (internal heating) enables reaching high fluid temperature (T ~ 700°C) while maintaining the wall temperatures within the materials’ limit. The precise temperature and stoichiometry control by pilot fuel flow is essential when processing energetic feedstocks; and (iii) organic cocontaminants and gases can be treated. For example, several industries emit CF4 and other GHGs that are challenging to process via thermal oxidation. These steps are shown in FIGURE 5

[0066] Another aspect of this disclosure is the continuous HALT reactor shown in FIGURE 4. The feedstock is selected by a ball valve upstream of a high-pressure metering pump (Teledyne, LS-Class). The reactor is fabricated by coiling the tubing and placing it in a heated sand bath. All the reactors were made from 12’ of seamless Inconel 600 tubing. The heaters are controlled by a PID controller. Two thermocouples were added to the reactor wall at the bottom and top of the coil to monitor the reactor temperature. The reactor effluent was then cooled to room temperature and depressurized in the BPR. Our team has demonstrated the treatment of PFCA, persistent organic compounds, and PFSA in CF-HALT in under 10 min residence time.

[0067] With BM primarily focusing on the treatment of dry and semi-dry extract, the slurry or liquid extracted products unsuitable for the BM process are treated by hydrothermal processes. Hydrothermal processes, such as SCWO and HALT, each have their benefits and drawbacks. For the purposes of this disclosure, it is defined that thematerial limiting solvent injection rates and control strategy for the safe operation of the SCWO reactor that enables complete oxidation of persistent organic compounds, PF AS and OC constituents without the release of VOF or product of incomplete oxidation. The steps for treatment are: (i) characterize the SCWO and CF-HALT process for PFAS- contaminated slurries, compared to similar reactions of neat PF AS to identify matrixdependent performance; and (ii) HALT reduce caustic concentration (low corrosion) and maintain the high DRE and %DeF.

[0068] SCWO is a wet waste treatment process that oxidizes all organic pollutants into benign, non-toxic minerals. SCWO relies on the high-density, high- temperature, free radical environment at supercritical water conditions to facilitate fast destruction reactions, capable of achieving log 6 PF AS destruction efficiencies (below the LOD of the available analytical methods). High temperatures and excess air availability (air-rich oxidation) are used to ensure that all compounds were fully mineralized and to avoid the production of VOFs. For example, T < 600 °C yielded short-chain PF AS such as trifluoroacetic acid (TFA) and volatile organo-fluorine (VOF) compounds as intermediate compounds, indicating that high processing temperatures are required to avoid the production of unwanted byproducts. In a hydrothermal environment, TFA and other PFCAs undergo a decarboxylation process yielding IH-perfluoalkanes (e.g., CHF3 in the case of TFA); these gases could be stable in the environment with low oxidizer content (low air / fuel ratio, AFR). FIGURE 3A shows a process flow diagram (PFD) of the SCWO system, FIGURE 3B shows a reactor vessel, including reagent and co-fuel injection at the top of the downflow vessel, and FIGURE 3C shows computational fluid dynamic (CFD) simulations of the reactor operating with ethanol as a pilot fuel. Specific to the SCWO system, autogenetic operation (internal heating) enables reaching high fluid temperature (T ~ 700°C) while maintaining the reactor wall temperatures within the materials’ limit with precise temperature and stoichiometry control by pilot fuel flow. In some embodiments, FIGURES 3 A-3C are examples of the process flow diagram, reactor vessel, and computational fluid dynamic simulations described further in co-pending U.S. Patent Application No. 18 / 034583, which is incorporated herein by reference.

[0069] The temperature and stoichiometry control are considered when processing energetic feedstocks and / or non-uniform feedstock, such as slurries and viscous liquids. The process will be controlled by adjusting the air-fuel ratio (AFR), T, and residence time required for the complete mineralization of PFAS while avoiding emissionsof liquid and gaseous byproducts. Real-time close loop control relies on real-time gas exhaust and temperature measurement. Access Oxygen and CO measurement inform the availability of oxidizer and its presence in incomplete products of oxidation. Independent control of feedstock injection rate, pilot fuel, and oxidizer flows allows reaction media homogeneity and control oxidizer availability. Locally fuel / PFAS-rich zones will occur when operating with energetic liquid feedstock such as AFFF, solvent / PFAS mixtures, or with heterogeneous feedstock like biosolids, spent resin, GAC, etc. The diffusion of heat or oxidizer will likely limit the reaction to fuel or PF AS. Operation with limited oxidizer concentration can result in a buildup of a potentially combustible mixture of free radical species and a local transition to much hotter hydrothermal flames that should be avoided for safe reactor operation.

[0070] As part of this disclosure, several operational parameters are monitored in addition to temperatures and effluent composition as the real-world persistent organic compound or PF AS contaminated stream affects the operation of the SCWO system; among the concerns addressed by this disclosure are: (i) reactor stability — ignition and extinction of the heating releasing reaction can lead to harmonic oscillations, and the onset of resonance modes the can affect the pressure in the reactor leading to unwanted wear in the system and dropping the pressure below the supercritical point, (ii) temperature distribution — local heat release can lead to rapid local heating with temperature spike beyond the material limits which is detrimental the operational safety.

[0071] Liquid effluent and gas analysis is part of this disclosure. Disclosed analysis of mitigated streams includes (i) quantification of residual parent compounds via LC-MS / MS to quantify destruction and removal efficiency (%DRE), (ii) identification and quantification of liquid intermediates via high-resolution LC-MS / MS, (iii) identification and quantification (if possible) of gaseous intermediates via GC-MS / MS and FTIR, and (iv) quantification of fluoride in the liquid product to quantify defluorination efficiency (%FE) via IC or ISE. The %DRE and %deF are defined as:[PFAS]in- [PFAS]effDRE = x 100% ,[PFAS]in

[0072] where [PFAS]jnis the PFAS concentration (mg / L) after mixing all influents, and [PFAS]eff is the residual PFAS concentration in the effluents as measured byLC-MS / MS. The defluorination efficiency is the percent of fluorine atoms in PFAS molecules transformed into fluoride ions:

[0073] where the CF- is the effluent’ s fluoride ion concentration (mg / L) measured by IC and the Corganic.p is the concentration of organic fluorine in (mg / L) after mixing all four influent lines. What has been developed is a standard operation procedure (SOP) for PFAS analyses.

[0074] The disclosed treatments avoid the formation of VOFs. The development of gas sample collection and analytical methods to identify and quantify intermediate byproducts will support the closure of F-balances. Thus, robust sampling methods are needed to effectively capture the reactor’s gaseous exhaust. At the exit of the SCWO reactor, the cooled effluent is separated into liquid and gas streams; see FIGURE 5. The gas / liquid separator allows for the simultaneous collection and conditioning (fine droplets and water vapor removal) of gas samples. The liquid stream is collected into the container. The gases consisting of N2, excess O2, CO2, and products of incomplete PFAS are passed through a combustion analyzer to monitor (O2, CO, CO2) characterizing oxidation conditions in real-time. In parallel, the gas can be collected in Tedlar bags, XAD resin and / or carbon trap filters, and Summa canisters, as per EPA method OTM-45 or OTM-50 when available. To enable these analyses, low-vacuum pumps will draw air through a series of XAD resin and / or carbon trap filters to trap volatile PFASs for analysis by GC-MS or FTIR using a long-path gas cell. A Brucker Tensor 27 instrument is used with a folded path gas cell design that provides an extended path length. The PFAS will be identified based on published libraries.

[0075] The disclosed HALT technologies show the ability to destroy PFAS compounds in a variety of matrices, including AFFF, groundwater, spent GAC, and fire training pit water. In some embodiments, the HALT technologies are examples of the perfluoroalkyl or polyfluoroalkyl substance destruction technologies disclosed in U.S. Patent Application Nos. 17 / 998,459 and 18 / 261,618, each of which is incorporated herein by reference. The disclosed Continuous Flow (CF) -HALT process is shown to be more efficient than traditional batch reactors. The feedstock is introduced as a high-pressuremetering pump. The reactor is fabricated by coiling the tubing and placing it in a heated sand bath. The laminar flow reactors are made from 1 ’ ’ seamless Inconel 600 tubing. A PID controller controls two heaters. The reactor effluent is cooled to room temperature and depressurized in the BPR.EXPERIMENTAL

[0076] Example 1

[0077] The development of gas sample collection and analytical methods to identify and quantify intermediate byproducts will support the closure of F-balances. These VOFs are expected to exhibit various vapor pressures and polarities. Thus, robust sampling methods are needed to capture the reactor’s gaseous exhaust effectively. In our previous work are collected and identified VOF byproducts from SCWO and continuous flow HALT systems. The effluent is separated into liquid and gas streams; see FIGURE 4.

[0078] The liquid separator allows for the collection and conditioning (fine droplets and water vapor removal) of gas samples simultaneously. The gas stream consisting of N2, excess O2, CO2, and products of incomplete persistent organic compounds, PF AS and fuel oxidation are passed through a combustion gas analyzer to monitor (O2, CO, combustible gases, and AFR) characterizing oxidation conditions in realtime. In parallel, the gas can be collected in Tedlar bags, XAD resin and / or carbon trap filters, Summa canisters or using cryogenic impinging stages, as per EPA method OTM- 45. To enable these analyses, low-vacuum pumps will be used to draw air through a series of XAD resin and / or carbon trap filters to trap volatile persistent organic compounds or PFASs for analysis with either LC-MS or GC-MS. XAD cartridges will be solvent extracted and analyzed for both target and non-target PFASs using suspect screening with LC-HRMS and GC-MS / MS.

[0079] FTIR analysis can be challenging due to the high dilution of the VOF in the gas sample with N2, CO2, and excess O2. The best chances of detecting persistent organic compound or PFAS decomposition by-products will be at lower operational temperatures using a long-path gas cell. A Brucker Tensor 27 instrument is used with folded path gas cell design providing an extended path length (available as University of Washington (UW) TOAC). The PFAS is identified based on the recently published libraries; when possible quantitative calibration was performed for available standards (e.g., Fluoroform, 1H- Perfluoroheptane). Identifying VOF allows for establishing the decomposition routes, while quantification would allow fully closing the F-balance.

[0080] In this disclosure the SFE setup to perform quantitative extraction, sorbent recovery, and regeneration studies involves scCO2and co-solvent injection and heating techniques with precise flow and temperature controls. The reactor has an operating pressure to 30 MPa with CO2injection. The apparatus has liquid effluent / gas separator, as shown in FIGURE 3A. The separator is designed and operated in the PF AS thermal degradation study, which demonstrated the onset of TFA breakdown and formation of gaseous byproducts fluoroform at temperatures as low as ~150°C.

[0081] The current setup (FIGURE 2) has been operated up to 15 MPa and 150°C. CO2 is first cooled to a liquid state and then pumped into a coil around a cartridge heater. The reactor was designed for MOF synthesis and can provide temperature residence time control for synthesis in single (supercritical) or two-phase (vapor / liquid) environments.

[0082] The organic solvent is pumped through a separate line and mixed with the heated scCCh before entering the reactor section. The mixture of CO2 and solvent postmixing is supercritical if the flow rate of the organic solvent does not exceed its solubility limit in the scCCh. In the case of high flow rates, a part of the fluid is supercritical, while a portion of the fluid persists as liquid (droplets or bubble regimes). In regeneration studies, the reactor section for the GAC placement is a 3.5-inch long, ID=l / 4-inch stainless steel tube with 149-micron frits on both sides to hold the sorbent in place. In the future the sorbent volume will be increased by employing a larger reactor size (e.g., Parr high- pressure high-temperature vessels can operate at temperatures up to 500 °C and pressures up to 20MPa, the capacity of the reactor vessel can be varied. In some embodiments, a reactor may be used with an internal volume of -100-500 mL, such as series 4760).

[0083] It is shown in this disclosure that scCCh / MeOH is an effective in PFOA and PFOS extraction from nonporous materials (e.g., GAC, IXR, paper, fabrics, and sand) with excellent extraction efficiency at P=20 MPa. The CO2 from the gas cylinder is condensed to the liquid phase before entering the HPLC pump. A calcium chloride cold bath is used to provide sufficient cooling (-10 to -5 °C) to ensure that liquid CO2 enters the pump. This approach is limited to the flow rate of the HPLC pump (~20mL / min) and often leads to pump failures and vapor lock in the system at lower flow rates as the CO2 transitions to the vapor phase. For the laboratory reactor, in some embodiments, COTS high-pressure cryogenic pumps, e.g., syringe pump - SyriXus 500x (Teledyne ISCO pump)- up to 200 mL / min, P=34 MPa and a Chiller / Pre-chiller (Julabo FL1201) which are often used in supercritical liquid chromatography may be used.

[0084] The extraction (desorption) efficiency is tested in the modified setup. The extraction efficiency (%EE is) is quantified as:

[0085] where [PFAS]ss is the PF AS loading (mg / g) in the spent sorbent, and [PFAS]Rg is the residual concentration in the regenerated sorbent. The %EE can be calculated using the following procedure:

[0086] [PFAS]ss: Sorbent is loaded with a quantifiable amount of PFAS by soaking it in the known concentration of PFAS solution. For example, for the currently used reactor size, sorbent is first weighed to ~1 grams (to fill in the column) and then soaked in PFAS-water solution for ~48 hours. The liquid PFAS levels are analyzed pre- and postexposure to determine the amount of PFAS adsorbed to GAC.

[0087] [PFAS]RS: The PFAS-laden sorbent is loaded into the reactor and exposed to controlled conditions, Table 2. Post-treatment, the GAC is dried in an oven overnight and then the regenerated sorbent is soaked in a solution of ethanol and 0.5% ammonium hydroxide for 12 hours to extract any adsorbed PFAS on GAC post-regeneration. This extraction protocol is used in a series of experiments with PFBA, PFOA, and PFBS, FIGURE 6. Varied temperatures, co-solvent composition, and flow rates (Table 2) indicates that the extraction is very effective.Table 2: Conditions for PFOA extraction from GAC from the preliminary experiments.

[0088] Extraction into scCCh / MeOH at elevated temperatures yielded -20% and -50% for MeOH / alkaline mixture after 30 minutes of exposure in a continuous flow reactor, indicating that long polar PFOA molecules are somewhat soluble in the scCCh or CCh / MeOH mixtures due to non-polar nature of scCO2.

[0089] It was found that better extraction occurred in acid-modified SFE cases with (MeOH with 1% vol H2SO4) cosolvent, approaching %EE - 95 - 99% at 30 min exposure. Since PF AS with charged groups (-COO-, -SO3-) have limited solubility in a scCCh / alcohol mixture, adding strong acids forces the PFOA and PFOS to remain in their protonated states (i.e., -COOH, -SO3H), increasing their solubility and, consequently, their extraction efficiency.

[0090] Interestingly, the concentration of acid-modified co-solvent in SCCO2 did not significantly affect the extraction. While the CO2flow rate was held constant (25 mL / min), the co-solvent flow rate was varied from 0.2 to 6.8 mL / min, suggesting that the process may yield a very concentrated effluent, reducing consumption of co-solvent and reducing the volume of effluent that need to be treated in the end-of-life destruction step.

[0091] Example 2:

[0092] Further changes to the process parameters may combine the batch loading of PFAS on the sorbents (as in preliminary experiments), rapid small-scale column tests (RSSCTs), and SFE study with several modifiers and process conditions (outlined above) for GAC and IX resins (Table 3). F-balance is determined using the targeted LC / MS-MS(compatible with EPA method 1633), combustion ion chromatography (CIC), IC, and Raman analyses of recovered residue and the regenerated sorbent. Analysis of gaseous samples and potential VOF emissions is performed by FTIR and GC / MS.

[0093] The disclosed experimental procedure examines the extract! on / recovery and regeneration efficiencies of the CCh / co-solvent mixture. Ethanol or methanol cosolvents are added to the CO2 stream to aid the collection of PF AS in a small liquid volume (concentrated slurries can be produced by evaporating the solvent). Acid and base modifiers may or may not be added as a control. Depending on their mixture fraction, in some embodiments, organic solvents may be dissolved in scCCh, forming a single-phase medium that enhances mass transfer. The solvent fraction is varied (0.1-10% within their solubility limits in scCCh), ensuring a single-phase mixture in the reactor. Screening is performed by loading GAC and IXRs with known PFAS concentrations. Many experiments performed include several common sorbents (coal-based vs. lignite-based GACs; gel-based vs. microporous single-use IXRs; and the surface-modified organoclay (Fluororsorb FS200).Table 3: Experimental matrix for supercritical CO2 extraction of PFAS.

[0094] Next, the organic carbon extraction and the effect of co-contaminants on PFAS extraction were evaluated. The presence of organic carbon (OC) in the sorbent media may influence the extraction of PFAS. Thus, the extraction efficiencies for OC contaminants and evaluation of their effect on the PFAS extraction are determined. This was done on two types of samples:

[0095] (1) Spent media from various ongoing RSSCTs conducted for high- (surface water) versus low-(groundwater) TOC waters. Spent media extracted fromRSSCTs conducted to assess the applicability of GACs, IXRs, and novel sorbents in removing PF AS present in high (greater than 1 mg / L) TOC surface water and low (> 1 mg / L) TOC groundwater.

[0096] (2) Field samples of spent sorbents from current installations. DoD facilities where pilot- / full-scale water treatment systems using adsorptive media are used to address PF AS impacts [e.g., Travis Air Force Base (CA), Wurtsmith AFB (MI), Willow Grove Naval Air Station (PA)]. Samples of spent media are collected in conjunction with available site-specific data (PF AS composition and concentration, treatment throughput, media life, etc.)

[0097] PF AS recoveries for various sorbents and feedstocks are optimized. Transport of PF AS and OC to the end-of-life treatment is an essential step in optimizing the overall treatment train. The PFAS losses to the internal surfaces are generally lower in solvent-based slurries compared to water-based solutions. In some embodiments, effluent recovery and reactor cleaning strategies compatible with the scale-up system may be used. The small column reactor used for data collection is efficient at performing rapid studies to optimize the extraction parameters; however, due to the high surface-to-volume ratio (leading to wall losses) and low over-PFAS loading (~1 gram of sorbent), the approach is somewhat limited for (i) evaluating PF AS-containing recovery strategies for scale-up system or (ii) producing sufficient PFAS effluent for the end-of-life analysis. Parr high- pressure high-temperature vessels can operate at temperatures up to 500°C and pressures up to 20 MPa; the capacity of the reactor vessel can vary. In some embodiments, a reactor with an internal volume of -100-500 ml, such as Parr reactor vessels series 4760, with multiple ports for flow connection and fluid temperature control, may be used. Pressure is controlled by a back pressure regulator, see FIGURE 2. The pressure vessel is configured in the flow-through configuration, similar to the small columns that have been used. In the experiments, the spent sorbents was loaded into the reactor vessel and subjected to the flow of scCCh / co-solvent mixture. The fraction of co-solvent and amendments have been shown to achieve the best recoveries of PFAS. The experimental matrix includes both neat PFAS and PFAS / OC mixture from spent GAC and IXR sorbents from field pilot studies. The data from the small column reactor, FIGURE 7, shows that the recovery improves with the higher co-solvent fraction; the conditions are shown in Table 2. The Recovery efficiency (%Recovery) may be quantified as follows:

[0098] where [PFAS]Eff is the PFAS loading (mg / g) in the captured effluent. F’ balance is determined using the targeted LC / MS-MS (compatible with EPA method 1633) and Raman analysis of recovered residue and the regenerated sorbent.

[0099] Another aspect of the disclosure is introducing cleaning cycles for PFAS or persistent organic compounds trapped on the internal surfaces as a semi-batch process. The recovery of PFAS or persistent organic compounds from exposed equipment (fire trucks, fire suppression systems, etc.) has been investigated in the context of fire trucks and other unfractured cleanings.

[0100] Another aspect of the disclosure is to add an alternative Alkaline Hydrolysis step for the in-situ treatment of PFAS deposited on the reactor’s internal surfaces and downstream components. This strategy can be beneficial as the reactor vessel and components are high-pressure rated, and implementation of HALT would not require significant modifications. However, the addition of an alkaline agent may lead to corrosion and pressure losses in the system.

[0101] The gaseous and liquid effluents from the reactor are analyzed using FTIR / GC-MS and LC-MS, respectively. This analysis allows for the calculation of recovery efficiency and PFAS losses to the gas phase (evaporation of formation of gas intermediate byproducts). Extraction temperature, CO2 flow rate, and exposure time are varied. In some embodiments, (i) A low flow rate of co-solvent may lead to PFAS and OC deposition on the internal reactor surfaces - an additional cleaning cycle can be added to flush the PFAS and OC components, (ii) The gaseous products may include VOF products of incomplete PFAS thermal degradation, the vapor of high-vapor-pressure compounds (ultrashort PFAS, e.g., TFA), and volatile organic compounds, including VOCs and other high-vapor-pressure pollutants, that could have been retained by IXR sorbents. It has been found that operating the reactor at T<100 °C is likely to avoid this issue.

[0102] In this disclosure, all the end-of-life treatment-related samples are analyzed. The analytical approaches and QA / QC control are applied to the samples generated in this disclosure. A combination of targeted PFAS analysis and non-targeted screening is used; samples are also analyzed for ion composition (by ion chromatography,IC), total organic carbon (by TOC analyzer), and total fluorine (by combustion ion chromatography).

[0103] Example 3:

[0104] Unlike traditional solvent-based or aqueous desorption methods, scCO2 regeneration operates at relatively low temperatures, which not only reduces energy consumption but also minimizes the risk of sorbent degradation. Furthermore, this technique prevents the formation of VOFs typically associated with high-temperature thermal regeneration, offering a safer and more sustainable alternative for PF AS treatment. This example describes low-temperature spent GAC regeneration using scCCh extraction with the addition of co-solvents and acid modifiers. Perfluorooctanoic acid (PFOA) was chosen for this example due to its environmental persistence and high adsorption affinity, yet the modified SFE approach yielded >99% desorption after 1 hour of GAC treatment.

[0105] Materials and Methods

[0106] Granular activated carbon (Filtrasorb-400) for experiments was obtained from Calgon Carbon (Pittsburgh, PA). All chemicals and solvents used in this study are described as follows: PFOA (> 95%, Sigma Aldrich, China) and deionized (DI) water (p = 18.2 MQ-cm) from ELGA PURELAB® Option-Q (Woodridge, IL, USA) lab water purification system was used for preparing solutions for adsorption. CO2 (99.5%, Linde, Danbury, CT, USA), ACS reagent grade methanol (99.8%, Thermo Fisher Scientific, Waltham, MA, USA), H2SO4 (95.0-98.0%, Avantor Performance Material LLC, Radnor, PA, USA), ethanol (200 Proof, Decon Labs, Inc., King of Prussia, PA, USA), and NH4OH (28-30%, Millipore Sigma, Darmstadt, Germany) were used for sorbent treatment. LC / MS grade methanol (>99.9%, Thermo Fisher Scientific, Waltham, MA, USA) and HPLC grade ammonium acetate (>98%, Thermo Fisher Scientific, Waltham, MA, USA) were used for LC-MS / MS samples. Granular activated carbon (Filtrasorb-400) was obtained from Calgon Carbon (Pittsburgh, PA).

[0107] The analytical methods for PF AS analysis are described as follows: The quantitative analysis of PFOA in all the liquid samples was performed by Quattro Micro quadrupole tandem mass spectrometer, 2795 Alliance HT LC system (Waters Corporation, Milford, MA, USA) equipped with a Kinetex-C18 column (4.6 x 50 mm, 2.6 pm, Phenom enex, Torrance, CA, USA).

[0108] Before each analysis, the samples were diluted with LC-MS grade methanol and water in a volumetric ratio of 60:40. The calibration curves in the 0.1 - 50p.g / L range for each PF AS were obtained using PFAC30PAR standard solutions. The mobile phase for LC consisted of: (A) 10 mM ammonium acetate in Optima® HPLC grade water and (B) 10 mM ammonium acetate in Optima® HPLC grade methanol. The eluent flow rate was 0.20 mL / min, and the gradient timetable contained 5 entries: 0 min (50 % A, 50 % B), 5 min (5 % A, 95 % B), 7 min (5 % A, 95 % B), 7.5 min (50 % A, 50 % B), and 13 min (50 % A, 50 % B). MS protocols were previously reported. [1] The analytical detection limit for PFOA in LC-MS / MS analysis is 0.05 pg / L. The GAC’s surface areas and pore size distributions were determined using nitrogen adsorption at 77 K with a Micromeritics 3Flex analyzer, following the Brunauer-Emmett-Teller (BET) analysis of surface area and pore sizes.

[0109] Sorption conditions

[0110] After 5 days, the GAC was removed, and the liquid analyzed using LC- MS / MS. The GAC pellets were dried in an oven at 70 °C for 12 hours. Sub-samples were extracted into 20 mL of ethanol (EtOH) + 0.15% NH4OH solution to determine the amount of PFOA sorbed onto GAC. The PFOA loading on virgin GAC was 0.52 ± 0.02 mg / g under the described conditions. After 24 hours, the GAC was removed by centrifugation, and the liquid analyzed using LC-MS / MS.

[0111] Regeneration in supercritical CO 2 conditions

[0112] The diagram of the laboratory SFE setup is shown in FIGURE 8. The CO2 from the gas cylinder is condensed to the liquid phase in a calcium chloride cold bath (- 10 to -5°C) before entering the HPLC pump. CO2 is pumped at 25 mL / min. The co-solvent (methanol (MeOH), or MeOH + 2.3% v / v H2SO4) is injected at 1 mL / min at ~20°C through a separate line and mixed with the heated scCCh before entering the reactor section. The CO2 and solvent post-mixing become a supercritical single-phase fluid if the flow rate of the organic solvent does not exceed its solubility limit in the scCCh. Critical points for a two-phase system depend on mixture fraction and the type of organic co-solvent. These critical transition points can be obtained experimentally, but the data are limited to only a few solvents. The operational parameters for these experiments were chosen as P = 10.0 MPa and T = 110-120°C to ensure single-phase conditions, with an extraction time of t = 60 min.

[0113] The reactor has a volume of 1.29 mL, a length of 63.5 mm, and consists of a stainless steel tube with an inner diameter of 5.1 mm and an outer diameter of 6.35 mm, fitted with 149-micron frits on both ends to contain the sorbent. After performing SFEfor 60 minutes, the column contents were dried in an oven at 70°C for 24 hours. The sample was divided into two sub-samples: one was subjected to extraction by soaking in ethanol and ammonium hydroxide, followed by LC-MS / MS, and the other underwent a second regeneration cycle. The regenerated GAC sample set aside for the second regeneration cycle was loaded with PFOA again. Each experiment was performed in triplicates. The desorption efficiency (DE) was calculated as:

[0114] where [PFAS in spent GAC] is the PFAS loading (mg / g) in the spent sorbent, and [PFAS in GAC after regeneration] is the residual PFAS concentration (mg / g) in the regenerated sorbent.

[0115] Results and Discussion

[0116] Modified scCC method for GAC regeneration

[0117] Without wishing to be bound by theory, PFOA exhibits strong adsorption onto GAC due to hydrophobic and electrostatic interactions, which present challenges for conventional techniques. The modified SCCO2 extraction yielded near complete desorption of PFOA (FIGURE 9) by counteracting both forces. First, the method takes advantage of the transition from a polar aqueous to a nonpolar SCCO2 environment, which weakens / eliminates hydrophobic interactions. Once in SCCO2, PFOA miscibility decreases compared to the shorter fluorinated molecules. Due to the high polarity of the perfluorooctanoate ion, C8FISO2', electrostatic interactions become the dominant force; therefore, in pure SCCO2, desorption efficiency was limited to < 30% (FIGURE 9).

[0118] The addition of organic co-solvents can enhance PFAS solubility in SCCO2. scCCh / MeOH mixtures are effective in extracting PFOA and PFOS from nonporous materials. Table 4 shows that organic solvent-based extraction (MeOH, EtOH, acetone) in the batch GAC / C-8 PFAS systems reach the DE ~ 40-95% after 12-24 hours.Table 4. Comparison of modified supercritical CO2 extraction and existing technologies for regeneration PFAS-laden granular activated carbon

[0119] MeOH extraction showed the best results. The GAC Filtrasorb 400 comparative example utilized a column flow reactor and MeOH, reporting DE = 67% desorption of PFOA from GAC 400 after 24 hours of treatment. The solubility of PF AS in alcohols generally decreases for longer PFAS molecules and longer carbon chain lengths of alcohol. For example, the solubility of PFOS in MeOH is ~ 37 g / L; it is ~ 5 times higher than in EtOH (~ 7 g / L). The solubility of PFOA in MeOH is 37.1 g / L, similar to PFOS’s. Thus, in this example, MeOH is used as a co-solvent.

[0120] In this example, adding MeOH alone did not significantly affect PFOA desorption (FIGURE 9), indicating that scCO2is an effective agent for disrupting the hydrophobic interaction. A slight increase in desorption efficiency from 18.7% to 26.3%in the second cycle might be attributed to carryover from the previous cycle. While dipolar organic solvents can disrupt hydrophobic interactions, they are unlikely to affect the electrostatic interactions between PFAS molecules and GAC surfaces. Without wishing to be bound by theory, lacking hydrophobic PFOA / GAC interaction in scCCh and scCCh / MeOH mixtures, the low desorption is contributed to electrostatic interactions, which can be weakened by introducing an ionic agent. In this manner, adding sulfuric acid (1% vol in MeOH) increased the desorption efficiency to >97%.

[0121] The modified SFE regeneration method yielded significantly faster and more efficient PFAS removal compared to conventional solvent-based techniques (Table 4). Treatment time was 1 hour, compared to 5-24 hours for traditional methods, yielding >97% PFAS removal (max DE~99.9%). Notably, solvent consumption was decreased to ~ 4% of other reported solvent-based methods, presenting an environmentally friendly and cost-effective approach for GAC regeneration. Thus, the synergistic result of combining scCCh, a co-solvent, and an acid modifier achieves remarkable desorption results and complete restoration of GAC properties (Table 5), all while surprisingly decreasing total treatment time and decreasing material component costs.Table 5: Characteristics of the porous structure of virgin GAC, PFOA-laden GAC, and regenerated GAC

[0122] Proposed mechanisms for modified supercritical CO 2 GAC regeneration

[0123] PFOA / GAC interaction is governed by two forces, which must be effectively counteracted. Specifically, the Filtrasorb 400 GAC has a point of zero charge (pHpzc) of 8.65, characteristic of activated carbons with low oxygen content. The low oxygen content is reflected in the measured concentration of oxygen-containing groups(phenolic, carboxylic, lactonic) of 0.21 mmol / g. The measured pH during adsorption in this study (~ 4.8) was below the pHpzc. Under such conditions, the surface of the activated carbon becomes positively charged due to the protonation of surface groups, enhancing electrostatic interactions with negatively charged PF AS anions. The shift to the scCCh environment weakened hydrophobic interactions, leading to a change from a predominantly surface-aligned orientation to a perpendicular orientation. This reorientation, consistent with the classical work of Zisman and colleagues, minimizes the contribution of hydrophobic forces, leaving electrostatic interactions as the dominant force between the monovalent PFOA anion and the GAC surface in the scCCh environment.

[0124] Without wishing to be bound by theory, Route I is enabled by the high dielectric permittivity of scCCh, facilitating proton availability from PFOA dissociation. This can lead to the association of PFOA molecules (FIGURE 10, Route I) and subsequent desorption in its protonated form. However, this route exhibits limited efficacy for PFOA, DE < 30% (FIGURE 9). The effectiveness of this route may vary in other systems.

[0125] Route / / involves the interaction of CO2 molecules with water retained in the GAC pores, leading to the formation of bicarbonate ions. While the bicarbonate ion is typically a weak competitor for PF AS on GAC under normal conditions, the high concentration of CO2 and small pore volume may enhance the effect (FIGURE 10, Route II). However, the presence of water within the pores can also promote hydrophobic interactions, potentially hindering the efficacy of Route II.

[0126] Route Ill is based on disrupting the electrostatic forces between GAC and PF AS. The scCCh or methanol cannot effectively weaken the electrostatic interaction between GAC and PFOA. FIGURE 9 shows no significant change in desorption efficiency from SCCO2 to SCCO2 / MeOH experiments. On the other hand, adding the MeOH / acid mixture yields significant improvement in the PFOA desorption. The MeOH assists in introducing sulfuric acid to a single-phase supercritical mixture and ultimately inside the sorbent’s pores. Mechanistically, a divalent sulfate ion exhibits a stronger affinity to the active sites on the GAC surface, causing the release of a weaker PFOA monovalent perfluorooctanoate ion, C8FisO2' (FIGURE 10, Route III). Moreover, sulfuric acid (pKa = -3) can protonate PFOA (pKa = - 0.2 - +3.8). The long-chain PF AS may form micelles / hemi-micelles in an aqueous environment that can interact with the GAC surface during sorption; however, it is unclear if these structures interact in a scCO2 / organic cosolvent environment in the absence of liquid water. It is expected that micelle formation isnegligible in a nonpolar solvent and does not significantly affect the proposed mechanism of hydrophobic and electrostatic forces disruption in the scCCh environment. Though beyond the scope of the current report and the subject of ongoing work, we suspect that Route III should also hold for other PF AS.

[0127] Impacts of co-solvent concentration on regeneration efficiency

[0128] Increasing the concentration of acid-modified co-solvent in scCCh yielded the highest desorption efficiency of 99.9% (FIGURE 11). In these experiments, the CO2 flow rate was constant (25 mL / min), and the co-solvent flow rate varied from 0.2 to 6.8 mL / min. The results showed only marginal improvement for high MeOH flow rates. This corroborates that the hydrophobic interaction does not play a significant role in the scCCh environment, and the disruption of electrostatic attraction by the pH surface modifier is the dominant mechanism.

[0129] From a practical perspective, these observations suggest that, advantageously, the process can yield a very concentrated effluent, reducing consumption of co-solvent and, in turn, reducing the volume of effluent that needs to be treated in the end-of-life destruction step. In a binary CO2 / solvent system, the pressure, temperature, and mole fractions of each solvent determine the phase of the overall fluid mixture. Based on data extrapolation from Reighard et al. (“Determination of methanol / CO2 and acetonitrile / CO2 vapor-liquid phase equilibria using a variable-volume view cell:, Fluid Phase Equilibria, 1996. 123(1-2)), at XMe0H= 0.1792 and 10 MPa, the dew point of the CCh / MeOH mixture is at ~ 110°C. Assuming that a trace concentration of sulfuric acid does not affect the solubility of MeOH in CO2, a lower XMe0Hwould lead to a single-phase supercritical gas-like mixture of MeOH completely dissolved in CO2, while a higher XM6OH would lead to a two-phase mixture due to the excess liquid MeOH that doesn’t dissolve into SCCO2. Adjusting the flow rates controls MeOH concentration and mixture phase during regeneration. Though limiting the concentration of MeOH produces more concentrated effluent, the presence of a liquid interface at the GAC surface may surprisingly improve the desorption and regeneration efficiency, as seen in the experiment at 6.8 mL / min, where the increased amount of MeOH shifts the dew point to below experimental conditions.

[0130] Assessment of GAC properties after regeneration

[0131] A sustainable PFAS regeneration approach must not only produce a concentrated PFAS effluent and prevent the formation of VOFs but also maintain GAC’sstructural integrity and adsorption capacity after regeneration. Table 5 presents the BET surface area of virgin GAC, PFOA-loaded GAC, and regenerated GAC with the modified scCCh extraction. It is shown that BET surface area and micropore volume of spent GAC decreased (971 to 922 m2 / g), indicating the occupation of active sorption sites and pore blockage by PFOA molecules. After the regeneration step, the BET surface area and micropore volume slightly increased (971 to 1012 m2 / g) compared to the virgin GAC. Though it is unclear what fraction of PFOA molecules resided within the micropores or on the surface, the modified SFE could desorb PFOA from all active sites, preserving the GAC porous structure for subsequent use. This was further verified by testing the adsorption capacity and confirming no changes compared to the virgin GAC at 0.52 ± 0.02 mg / g. This suggests that sulfate ions, which compete with the CsFisO?' ion during desorption in the scCO2 environment, are transferred to the aqueous phase during the next adsorption cycle, allowing the regenerated GAC to function effectively.

[0132] The scCCh-based sorbent regeneration method of the present disclosure provides significant surprising advantages for mitigating the environmental impact of PFAS contamination, offering a sustainable alternative to traditional practices. This method operates under mild temperature conditions, minimizing energy consumption and reducing the risk of sorbent degradation. Furthermore, the absence of water in the scCCh environment effectively eliminates hydrophobic interactions between the sorbent and the adsorbate, facilitating the release of PFOA molecules. While SCCO2 alone proves effective in disrupting hydrophobic interactions, achieving complete PFOA desorption requires additional strategies.

[0133] To overcome the electrostatic barrier, sulfuric acid modifiers are introduced, which plays a dual role: it protonates the PFOA anion (C8FisO2'), reducing its electrostatic attraction to the GAC surface, and the divalent sulfate ion exhibits a stronger affinity for the active sorption sites on the GAC surface, effectively competing with the PFOA anion and displacing it from the sorbent. This synergistic approach, combining SCCO2, a co-solvent, and an acid modifier, achieves remarkable results, yielding a desorption efficiency of 99.9% while fully restoring the GAC’s adsorption capacity.

[0134] The modified SFE process offers significant environmental benefits. By regenerating the GAC, the need for disposal is minimized, reducing landfill waste and associated environmental risks. The reusable GAC reduces the demand for new materials, promoting resource conservation and minimizing the environmental impact of production.Furthermore, the process produces a concentrated PFAS effluent, facilitating efficient and cost-effective downstream destruction technologies such as supercritical water oxidation hydrothermal alkaline treatment and ball milling.

[0135] Example 4:

[0136] The regeneration and recovery efficiency of 592E IXR sorbent filters was compared at different solvent temperatures, as shown in Table 6. The experimental procedure was similar to Example 3. The spent IXR was loaded into the reactor and exposed to the flow through scCO2 / co / solvent and ion donor (HC1 wt.0.02% in ethanol). The flow rate of co-solvent was set to 1 / mL / min while the flow rate of liquid CO2at the pump was set to 25 mL / min. After 30 min of exposure, the IXR was removed; both IXR and the effluent collected in the cold trap were analyzed for the presence of PFAS. Sorbent regeneration and recovery into the solvent were calculated based on the LC-MS analysis.Table 6: Regeneration and Recovery Efficiencies on 592E Resin at Different Temperatures; Cosolvent ethanol with 0.02 wt.% of HC1. Exposure time - 30mins

[0137] Very high regeneration efficiencies and recovery efficiencies were achieved at both 75 °C and 40 °C. However, the consistency of regeneration and recovery efficiency was higher when the extraction was performed at 75 °C than at 40 °C, and the regeneration efficiency at 75 °C had a small but statistically significant improvement over the extraction performed at 40 °C. On the other hand, very high regeneration efficiencies and recovery efficiencies were achieved in the 40 °C case, despite significant differences in the operational energy requirements of this lower temperature case. To achieve higherregeneration efficiencies, longer residence times may be employed to improve the consistency of regeneration efficiency at lower temperatures.

[0138] Example 5:

[0139] Different modifiers beyond strong acids were examined for their effect on regeneration and recovery efficiencies. Supercritical CO2 was used to extract PFOA from 592E type resin sorbent filters, at a regeneration temperature of 75 °C and a regeneration time of 60 minutes. Two cosolvent-ion combinations were methanol and ammonium chloride mixture, and the other an ethanol hydrochloric acid mixture. The results of this experiment are depicted in Table 7.Table 7: Regeneration and Recovery Efficiencies on 592E Resin, with extraction at 75 °C for 60 minutes

[0140] Surprisingly, the modifier combination of methanol with ammonium chloride provided a high percentage of regeneration and recovery of PFOA, comparable to the ethanol and hydrochloric acid modifier, at a comparable total flow rate.

[0141] The detailed description set forth above in connection with the appended drawings, where like numerals reference like elements, are intended as a description of various embodiments of the present disclosure and are not intended to represent the only embodiments. Each embodiment described in this disclosure is provided as a representativeexample or illustration and should not be construed as preferred or advantageous over other embodiments. The representative examples provided herein are not intended to be exhaustive or to limit the disclosure to the precise forms disclosed. Similarly, any steps described herein may be interchangeable with other steps, or combinations of steps, in order to achieve the same or substantially similar result. Generally, the embodiments disclosed herein are non-limiting, and it is contemplated that other embodiments within the scope of this disclosure may include structures and functionalities from more than one specific embodiment shown in the figures and described in the specification. That is, the present disclosure includes embodiments that combine features from different embodiments.

[0142] In the foregoing description, specific details are set forth to provide a thorough understanding of exemplary embodiments of the present disclosure. It will be apparent to one skilled in the art, however, that the embodiments disclosed herein may be practiced without embodying all the specific details. In some instances, well-known process steps have not been described in detail in order not to unnecessarily obscure various aspects of the present disclosure. Further, it will be appreciated that embodiments of the present disclosure may employ any combination of features described herein.

[0143] In the detailed description herein, references to “one embodiment”, “an embodiment”, “an example embodiment”, “one or more embodiments”, “some embodiments”, etc., indicate that the embodiment described may include a particular feature, structure, or characteristic, but every embodiment may not necessarily include the particular feature, structure, or characteristic. Moreover, such phrases are not necessarily referring to the same embodiment. In addition, when a particular feature, structure, or characteristic is described in connection with an embodiment, it is submitted that it is within the knowledge of one skilled in the art to affect such feature, structure, or characteristic in connection with other embodiments whether or not explicitly described. After reading the description, it will be apparent to one skilled in the relevant art(s) how to implement the disclosure in alternative embodiments. Thus, it will be appreciated that embodiments of the present disclosure may employ any combination of features described herein. All such combinations or sub-combinations of features are within the scope of the present disclosure.

[0144] Throughout this specification, terms of art may be used. These terms are to take on their ordinary meaning in the art from which they come, unless specifically defined herein or the context of their use would clearly suggest otherwise.

[0145] The drawings in the FIGURES are not to scale. Similar elements are generally denoted by similar references in the FIGURES. For the purposes of this disclosure, the same or similar elements may bear the same references. Furthermore, the presence of reference numbers or letters in the drawings cannot be considered limiting, even when such numbers or letters are indicated in the claims.

[0146] In the claims and for purposes of the present disclosure, the terms “a”, “an”, “the”, and the like, refer to the singular and the plural forms of the object or element referenced.

[0147] The present application may include references to directions, such as “vertical,” “horizontal,” “front,” “rear,” “left,” “right,” “top,” and “bottom,” etc. These references, and other similar references in the present application, are intended to assist in helping describe and understand the particular embodiment (such as when the embodiment is positioned for use) and are not intended to limit the present disclosure to these directions or locations.

[0148] The present application may also reference quantities and numbers. Unless specifically stated, such quantities and numbers are not to be considered restrictive, but exemplary of the possible quantities or numbers associated with the present application. Also in this regard, the present application may use the term “plurality” to reference a quantity or number. In this regard, the term “plurality” is meant to be any number that is more than one, for example, two, three, four, five, etc. The term “about,” “approximately,” etc., means plus or minus 5% of the stated value. The term “about” as used in relation to the number 0 in a range means within 5% of the stated value at the other end of the recited range. For example, for the range “0 to 100”, “about 0” means “between 0 and 5”. The term “based upon” means “based at least partially upon.”

[0149] The principles, representative embodiments, and modes of operation of the present disclosure have been described in the foregoing description. However, aspects of the present disclosure, which are intended to be protected, are not to be construed as limited to the particular embodiments disclosed. Further, the embodiments described herein are to be regarded as illustrative rather than restrictive. It will be appreciated that variations and changes may be made by others, and equivalents employed, without departing from the spirit of the present disclosure. Accordingly, it is expressly intended that all such variations, changes, and equivalents fall within the spirit and scope of the present disclosure as claimed.

[0150] While illustrative embodiments have been illustrated and described, it will be appreciated that various changes can be made therein without departing from the spirit and scope of the disclosure.EMBODIMENTSBy example and without limitation, embodiments are described according to the following examples:1. A method of mitigation of persistent organic compounds absorbed on a sorbent, the method comprising: extracting the persistent organic compounds from the sorbent with a supercritical carbon dioxide (scCO2) mixture comprising scCO2, a co-solvent, and an ion source, wherein a scCO2to co-solvent ratio is between about 10,000: 1 to 1 : 1, wherein a co-solvent to ion source ratio is between about 10: 1 and about 1,000,000: 1, and wherein the scCO2mixture is at a pressure and a temperature, to provide an extractant containing the persistent organic compounds; and isolating the persistent organic compounds from the extractant for their reuse or end of life treatment.2. The method of mitigation of persistent organic compounds of Embodiment 1, wherein the scCO2to co-solvent ratio is between about 100: 1 and about 125: 1.3. The method of mitigation of persistent organic compounds of any of the proceeding embodiments, wherein the scCO2to co-solvent ratio is about 125: 1.4. The method of mitigation of persistent organic compounds of any of the proceeding embodiments, wherein the co-solvent to ion source ratio is between about 40: 1 and about 100: 1.5. The method of mitigation of persistent organic compounds of any of the proceeding embodiments, wherein the ion source is a salt comprising a cation derived from a weak base and an anion derived from a strong acid.6. The method of mitigation of persistent organic compounds of any of the proceeding embodiments, wherein the ion source is selected from the group consisting of ammonium chloride, ammonium bromide, ammonium iodide, ammonium nitrate,ammonium sulfate, ammonium perchlorate, ammonium chlorate, pyridinium chloride, pyridinium bromide, pyridinium iodide, pyridinium nitrate, pyridinium sulfate, pyridinium perchlorate, pyridinium chlorate, ethylammonium chloride, ethylammonium bromide, ethylammonium iodide, ethylammonium nitrate, ethylammonium sulfate, ethylammonium perchlorate, and ethylammonium chlorate, or combinations thereof.7. The method of mitigation of persistent organic compounds of any of the proceeding embodiments, wherein the ion source is an acid.8. The method of mitigation of persistent organic compounds of any of the proceeding embodiments, wherein the acid is a stronger acid than the persistent organic compound.9. The method of mitigation of persistent organic compounds of any of the proceeding embodiments, wherein the flow rate of scCO2is between about 10 mL / min and about 1,000,000 mL / min.10. The method of mitigation of persistent organic compounds of any of the proceeding embodiments, wherein the flow rate of scCO2is between about 10 mL / min and about 1,000 mL / min.11. The method of mitigation of persistent organic compounds of any of the proceeding embodiments, wherein the flow rate of scCO2is about 25 mL / min.12. The method of mitigation of persistent organic compounds of any of the proceeding embodiments, wherein the co-solvent is selected from the group consisting of ethanol, isopropanol, propanol, butanol, isobutanol, acetone, perfluorocarbon, hydrofluorocarbon, chlorofluorocarbon, hydrochlorofluorocarbon, or combinations thereof.13. The method of mitigation of persistent organic compounds of any of the proceeding embodiments, wherein the co-solvent is methanol.14. The method of mitigation of persistent organic compounds of any of the proceeding embodiments, wherein the acid is sulfuric acid, methane sulfonic acid, p-toluene sulfonic acid, triflic acid, phosphoric acid, trichloroacetic acid, trifluoracetic acid, selenic acid, HF, HC1, formic acid, acetic acid, carbonic acid, or combinations thereof.15. The method of mitigation of persistent organic compounds of any of the proceeding embodiments, wherein the acid is sulfuric acid.16. The method of mitigation of persistent organic compounds of any of the proceeding embodiments, wherein the step of extracting the persistent organic compounds occurs at a temperature of 100 °C or less.17. The method of mitigation of persistent organic compounds of any of the proceeding embodiments, wherein the step of extracting the persistent organic compounds occurs at a temperature of about 40 °C .18. The method of mitigation of persistent organic compounds of any of the proceeding embodiments, wherein the step of extracting the persistent organic compounds occurs at a pressure of about 10 MPa or less.19. The method of mitigation of persistent organic compounds of any of the proceeding embodiments, wherein the step of extracting the persistent organic compounds occurs at a pressure of about 10 MPa.20. The method of mitigation of persistent organic compounds of any of the proceeding embodiments, wherein the step of extracting the persistent organic compounds occurs for a time of 1-60 minutes.21. The method of mitigation of persistent organic compounds of any of the proceeding embodiments, wherein the sorbent is ion exchange resin (IXR), granular activated carbon (GAC), textiles, PPE, MOFs, zeolites, contaminated soils, air filters, or combinations thereof.22. The method of mitigation of persistent organic compounds of any of the proceeding embodiments, wherein the mitigation involves capturing, concentrating, condensing, distilling, solidification, oxidizing, vitrification, mineralizing or any combination thereof the persistent organic compounds.23. The method of mitigation of persistent organic compounds of any of the proceeding embodiments, wherein the supercritical carbon dioxide, co-solvents, and sorbent are recycled.24. The method of mitigation of persistent organic compounds of any of the proceeding embodiments, wherein the method further comprises: concentration and solidification, wherein supercritical carbon dioxide is added to a supercritical carbon dioxide extractor with solvent mixture; wherein sorbent is added, wherein the supercritical carbon dioxide and solvent mixture are brought to an evaporator, wherein the persistent organic compounds or organic carbon are condensed into a solid or liquid, wherein the evaporated gaseous carbon dioxide is recycled; capturing, wherein the sorbent is regenerated and reused; end-of-life-treating, wherein the extracted persistent organic compounds, polyfluoroalkyl substances, or organic carbon are ball milled, processed by hydrothermal treatment, incinerated to achieve their destruction, vitrified, or immobilized in a solid matrix; and wherein the solvents are recycled.25. The method of mitigation of persistent organic compounds of any of the proceeding embodiments, wherein the co-solvent to ion source ratio is adjusted based on a level of contamination.26. The method of mitigation of persistent organic compounds of any of the proceeding embodiments, wherein the co-solvent to ion source ratio is adjusted based on measurements selected from the group consisting of effluent measurements pH, ion donor depletion measurements, or real-time in-situ spectroscopic measurements.27. The method of mitigation of persistent organic compounds of any of the proceeding embodiments, wherein the real-time in-situ spectroscopic measurements are Raman or FTIR.28. The method of mitigation of persistent organic compounds of any of the proceeding embodiments, wherein the extractant containing the persistent organic compounds is in a single phase.29. The method of mitigation of persistent organic compounds of any of the proceeding embodiments, wherein the extractant containing the persistent organic compounds is in two phases.30. The method of mitigation of persistent organic compounds of any of the proceeding embodiments, wherein the method is used upon contaminated textiles, personal protective equipment (PPE), Department of Defense chemical warfare agents (CWA), chemical and oil spill cleanup, hazmat targets, or any combinations thereof.31. A composition for the mitigation of persistent organic compounds, the composition comprising: a supercritical carbon dioxide (scCO2); an ion source; and a co- solvent, wherein a scCO2to co-solvent ratio is between about 10,000: 1 to 1 : 1, and wherein a co-solvent to ion source ratio is between about 10: 1 and about 1,000,000: 1.32. The composition for the mitigation of persistent organic compounds of Embodiment 31, wherein the scCO2to co-solvent ratio is about 125: 1.33. The composition for the mitigation of persistent organic compounds of any of Embodiments 31 or 32, wherein the co-solvent to ion source ratio is between about 40: 1 and about 100: 1.34. The composition for the mitigation of persistent organic compounds of any of Embodiments 31-33, wherein the co-solvent is methanol, ethanol, isopropanol, propanol, butanol, isobutanol, acetone, perfluorocarbon, hydrofluorocarbon, chlorofluorocarbon, hydrochlorofluorocarbon, or combinations thereof.35. The composition for the mitigation of persistent organic compounds of any of Embodiments 31-34, wherein the ion source is sulfuric acid, methane sulfonic acid, p- toluene sulfonic acid, triflic acid, phosphoric acid, trichloroacetic acid, trifluoracetic acid, selenic acid, HF, HC1, formic acid, acetic acid, carbonic acid, ammonium chloride, ammonium bromide, ammonium iodide, ammonium nitrate, ammonium sulfate, ammonium perchlorate, ammonium chlorate, pyridinium chloride, pyridinium bromide,pyridinium iodide, pyridinium nitrate, pyridinium sulfate, pyridinium perchlorate, pyridinium chlorate, ethylammonium chloride, ethylammonium bromide, ethylammonium iodide, ethylammonium nitrate, ethylammonium sulfate, ethylammonium perchlorate, and ethylammonium chlorate or combination thereof.

Claims

1. CLAIMSThe embodiments of the invention in which an exclusive property or privilege is claimed are defined as follows:

1. A method of mitigation of persistent organic compounds absorbed on a sorbent, the method comprising: extracting the persistent organic compounds from the sorbent with a supercritical carbon dioxide (SCCO2) mixture comprising SCCO2, a co-solvent, and an ion source, wherein a scCO2to co-solvent ratio is between about 10,000: 1 to 1 : 1, wherein a co-solvent to ion source ratio is between about 10: 1 and about 1,000,000: 1, and wherein the SCCO2 mixture is at a pressure and a temperature, to provide an extractant containing the persistent organic compounds; and isolating the persistent organic compounds from the extractant for their reuse or end of life treatment.

2. The method of mitigation of persistent organic compounds of claim 1, wherein the scCO2to co-solvent ratio is between about 100: 1 and about 125: 1.

3. The method of mitigation of persistent organic compounds of claim 2, wherein the scCO2to co-solvent ratio is about 125: 1.

4. The method of mitigation of persistent organic compounds of claim 1, wherein the co-solvent to ion source ratio is between about 40: 1 and about 100: 1.

5. The method of mitigation of persistent organic compounds of claim 1, wherein the ion source is a salt comprising a cation derived from a weak base and an anion derived from a strong acid.

6. The method of mitigation of persistent organic compounds of claim 5, wherein the ion source is selected from the group consisting of ammonium chloride, ammonium bromide, ammonium iodide, ammonium nitrate, ammonium sulfate, ammonium perchlorate, ammonium chlorate, pyridinium chloride, pyridinium bromide, pyridinium iodide, pyridinium nitrate, pyridinium sulfate, pyridinium perchlorate, pyridinium chlorate, ethylammonium chloride, ethylammonium bromide, ethylammoniumiodide, ethylammonium nitrate, ethylammonium sulfate, ethylammonium perchlorate, and ethylammonium chlorate, or combinations thereof.

7. The method of mitigation of persistent organic compounds of claim 1, wherein the ion source is an acid.

8. The method of mitigation of persistent organic compounds of claim 7, wherein the acid is a stronger acid than the persistent organic compound.

9. The method of mitigation of persistent organic compounds of claim 7, wherein the acid is sulfuric acid, methane sulfonic acid, p-toluene sulfonic acid, triflic acid, phosphoric acid, trichloroacetic acid, trifluoracetic acid, selenic acid, HF, HC1, formic acid, acetic acid, carbonic acid, or combinations thereof.

10. The method of mitigation of persistent organic compounds of claim 7, wherein the acid is sulfuric acid.

11. The method of mitigation of persistent organic compounds of claim 1, wherein the flow rate of SCCO2 is between about 10 mL / min and about 1,000,000 mL / min.

12. The method of mitigation of persistent organic compounds of claim 11, wherein the flow rate of SCCO2 is between about 10 mL / min and about 1,000 mL / min.

13. The method of mitigation of persistent organic compounds of claim 11, wherein the flow rate of SCCO2 is about 25 mL / min.

14. The method of mitigation of persistent organic compounds of claim 1, wherein the co-solvent is selected from the group consisting of ethanol, isopropanol, propanol, butanol, isobutanol, acetone, perfluorocarbon, hydrofluorocarbon, chlorofluorocarbon, hydrochlorofluorocarbon, or combinations thereof.

15. The method of mitigation of persistent organic compounds of claim 14, wherein the co-solvent is methanol.

16. The method of mitigation of persistent organic compounds of claim 1, wherein the step of extracting the persistent organic compounds occurs at a temperature of 100 °C or less.

17. The method of mitigation of persistent organic compounds of claim 1, wherein the step of extracting the persistent organic compounds occurs at a temperature of about 40 °C .

18. The method of mitigation of persistent organic compounds of claim 1, wherein the step of extracting the persistent organic compounds occurs at a pressure of about 10 MPa or less.

19. The method of mitigation of persistent organic compounds of claim 18, wherein the step of extracting the persistent organic compounds occurs at a pressure of about 10 MPa.

20. The method of mitigation of persistent organic compounds of claim 1, wherein the step of extracting the persistent organic compounds occurs for a time of 1-60 minutes.

21. The method of mitigation of persistent organic compounds of claim 1, wherein the sorbent is ion exchange resin (IXR), granular activated carbon (GAC), textiles, PPE, MOFs, zeolites, contaminated soils, air filters, or combinations thereof.

22. The method of mitigation of persistent organic compounds of claim 1, wherein the mitigation involves capturing, concentrating, condensing, distilling, solidification, oxidizing, vitrification, mineralizing or any combination thereof the persistent organic compounds.

23. The method of mitigation of persistent organic compounds of claim 1, wherein the supercritical carbon dioxide, co-solvents, and sorbent are recycled.

24. The method of mitigation of persistent organic compounds of claim 1, wherein the method further comprises: concentration and solidification, wherein supercritical carbon dioxide is added to a supercritical carbon dioxide extractor with solvent mixture; wherein sorbent is added, wherein the supercritical carbon dioxide and solvent mixture are brought to an evaporator, wherein the persistent organic compounds or organic carbon are condensed into a solid or liquid, wherein the evaporated gaseous carbon dioxide is recycled; capturing, wherein the sorbent is regenerated and reused;end-of-life-treating, wherein the extracted persistent organic compounds, polyfluoroalkyl substances, or organic carbon are ball milled, processed by hydrothermal treatment, incinerated to achieve their destruction, vitrified, or immobilized in a solid matrix; and wherein the solvents are recycled.

25. The method of mitigation of persistent organic compounds of claim 1, wherein the co-solvent to ion source ratio is adjusted based on a level of contamination.

26. The method of mitigation of persistent organic compounds of claim 1, wherein the co-solvent to ion source ratio is adjusted based on measurements selected from the group consisting of effluent measurements pH, ion donor depletion measurements, or real-time in-situ spectroscopic measurements.

27. The method of mitigation of persistent organic compounds of claim 1, wherein the real-time in-situ spectroscopic measurements are Raman or FTIR.

28. The method of mitigation of persistent organic compounds of claim 1, wherein the extractant containing the persistent organic compounds is in a single phase.

29. The method of mitigation of persistent organic compounds of claim 1, wherein the extractant containing the persistent organic compounds is in two phases.

30. The method of mitigation of persistent organic compounds of claim 1, wherein the method is used upon contaminated textiles, personal protective equipment (PPE), Department of Defense chemical warfare agents (CWA), chemical and oil spill cleanup, hazmat targets, or any combinations thereof.

31. A composition for the mitigation of persistent organic compounds, the composition comprising: a supercritical carbon dioxide (SCCO2); an ion source; and a co- solvent, wherein a SCCO2 to co-solvent ratio is between about 10,000: 1 to 1 : 1, and wherein a co-solvent to ion source ratio is between about 10: 1 and about 1,000,000: 1.

32. The composition for the mitigation of persistent organic compounds of claim 31, wherein the scCO2to co-solvent ratio is about 125: 1.

33. The composition for the mitigation of persistent organic compounds of claim 31, wherein the co-solvent to ion source ratio is between about 40: 1 and about 100: 1.

34. The composition for the mitigation of persistent organic compounds of claim 31, wherein the co-solvent is methanol, ethanol, isopropanol, propanol, butanol, isobutanol, acetone, perfluorocarbon, hydrofluorocarbon, chlorofluorocarbon, hydrochlorofluorocarbon, or combinations thereof.

35. The composition for the mitigation of persistent organic compounds of claim 31, wherein the ion source is sulfuric acid, methane sulfonic acid, p-toluene sulfonic acid, triflic acid, phosphoric acid, trichloroacetic acid, trifluoracetic acid, selenic acid, HF, HC1, formic acid, acetic acid, carbonic acid, ammonium chloride, ammonium bromide, ammonium iodide, ammonium nitrate, ammonium sulfate, ammonium perchlorate, ammonium chlorate, pyridinium chloride, pyridinium bromide, pyridinium iodide, pyridinium nitrate, pyridinium sulfate, pyridinium perchlorate, pyridinium chlorate, ethylammonium chloride, ethylammonium bromide, ethylammonium iodide, ethylammonium nitrate, ethylammonium sulfate, ethylammonium perchlorate, and ethylammonium chlorate or combination thereof.

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