Electrified filtering and extraction of PFAS using porous graphitic carbon

Abstract

A system for filtering per- and poly-fluoroalkyl substances (PFAS) from a sample includes at least one porous graphitic carbon (PGC) filter including porous graphitic carbon particles, wherein the at least one porous graphitic carbon particles includes a high specific surface area, and at least one working electrode configured to apply a positive and a negative electrical potential to the porous graphitic carbon particles.

Description

Atty. Docket No. U-8556T GEN013 FP306AWOELECTRIFIED FILTERING AND EXTRACTION OF PFAS USING POROUS GRAPHITIC CARBON CROSS-REFERENCE TO RELATED APPLICATION

[0001] This application claims priority to and the benefit under 35 U.S.C. § 119(e) of U.S. Provisional Application No. 63 / 730,150, filed on December 10, 2024, entitled "ELECTRIFIED FILTERING AND EXTRACTION OF PFAS USING POROUS GRAPHITIC CARBON" the disclosure of which is hereby incorporated herein by reference in its entirety.FIELD OF THE DISCLOSURE

[0002] The present disclosure generally relates to methods for filtering and extracting per- and polyfluoroalkyl substances (PFAS), and more particularly to electrified filtration and extraction methods for PFAS using porous graphitic carbon (PGC) filters, and the recycling of used filters via desorption of PFAS that can be expedited by applied electrical potential. The filter herein can be in the format of a membrane or column.BACKGROUND

[0003] Per- and poly-fluoroalkyl substances (PFAS), also known as "forever chemicals", are an emerging class of pollutants widely present in surface / ground waters and soils. These compounds have been used for over 60 years in hundreds of industrial applications and consumer products [e.g., carpet, apparel, upholstery, cookware, food wrappers, and aqueous fire-fighting foams (AFFFs)]. The term "forever chemicals" reflects the high chemical stability of PFAS, which renders them highly resistant to hydrolysis, biodegradation, metabolism, photolysis (sunlight), and other degradation processes. Due to the toxicity and tendency to bioaccumulate, the United States Environmental Protection Agency (EPA) has prioritized them as top unregulated contaminants. The chemical stability of PFAS compounds is owed to the stable carbon-fluorine bonds in their structure. The U.S. and European countries have begun to ban the manufacturing and use of many PFAS, but efforts to remediate the global spread of PFAS will likely take several decades.

[0004] More than 9,000 PFAS have been identified, with perfluorooctanesulfonic acid (PFOS) and perfluorooctanoic acid (PFOA) being the most prevalent pollutants in this chemical class owing to the extensive use in firefighting foams, surfactants, and repellents. The U.S. EPA has recently designated PFOS and PFOA as hazardous substances. Currently, the official health advisory level set by the U.S. EPA for PFOA and PFOS in drinking water is as low as 4 ppt. This value is defined as the maximum contaminant level (MCL), and is set by the U.S. EPA for a variety of other PFAS, perfluorohexanesulphonic acid (PFHxS) at 10ppt, perfluorononanoic acid (PFNA) at 10 ppt, and an ammonium salt of hexafluoropropylene oxide dimer acid (GenX™) at 10 ppt.

[0005] Current methods for removal of PFAS from aqueous solutions include adsorption by granular activated carbon (GAC). GAC sorption may be better only suited for removal of long-chain PFAS due to the molecules' hydrophobicity and low solubility in water. Meanwhile, short-chain PFAS, which possess increasing hydrophilicity and water solubility, undergo decreased efficiency in removal via adsorption using GAC filtering methods. Additionally, GACs filtration efficiency declines with prolonged use, which subsequently increases processing time for water treatment plants. Further methods for PFAS removal include using ion exchange resins (IXR). IXR systems can have adsorption efficiencies several times higher than those of GAC. However, these systems are not reusable as GAC, which incurs extra costs and waste. Although regenerable resins have been developed, it requires larger volumes and extended contact times at a given flow rate. Moreover, both adsorption efficiency and specificity for a variety of PFAS analogues remain unsatisfactory, and the additional regeneration step consumes more time and resources. Reverse osmosis (RO), nanofiltration (NF), and solid-phase extraction (SPE) are also used for PFAS removal as non-destructive treatments. RO / NF membranes filter PFAS through size exclusion, electrostatic, and hydrophobic interactions. Efficiency of PFAS removal also depends on membrane characteristics and external factors like temperature, pH, stirring speed and pressure. Current SPE methods are for PFAS detection and include varying performance across different sorbents and conditions, which makes current SPE methods less ideal for broad applications.SUMMARY OF THE DISCLOSURE

[0006] According to one aspect of the present disclosure, a system of filtering per- and poly-fluoroalky I substances (PFAS) from a sample includes a first aqueous solution containing a first concentration of PFAS, a first filter comprising porous graphitic carbon particles including a first porosity, at least one electrode, wherein the electrode is configured to apply a positive and a negative electrical potential to the first filter, a second aqueous solution containing the second concentration of PFAS, the first concentration of PFAS is larger than the second concentration of PFAS, the first filter is configured to reduce the first concentration of PFAS in the first aqueous solution to the second concentration of PFAS, a second filter comprising porous graphitic carbon particles including a secondporosity, the second porosity is less than the first porosity, and a third aqueous solution containing a third concentration of PFAS, the second concentration of PFAS is larger than the third concentration of PFAS, the second filter is configured to reduce the second concentration of PFAS in the second aqueous solution to the third concentration of PFAS.

[0007] According to another aspect of the present disclosure, a system for filtering per- and poly-fluoroalkyl substances (PFAS) from a sample includes at least one porous graphitic carbon (PGC) filter including porous graphitic carbon particles, the at least one porous graphitic carbon filter includes a specific surface area greater than 1000 m2 / g; and at least one working electrode configured to apply a positive and a negative electrical potential to the porous graphitic carbon particles.

[0008] According to yet another aspect of the present disclosure, a method of recycling a saturated filter with per- and poly-fluoroalkyl substances (PFAS) includes obtaining a porous graphitic carbon filter, the porous graphitic carbon filter is said saturated filter, applying a negative electrical potential to an electrode, the electrode is the porous graphitic carbon filter, flowing clean water through the porous graphitic carbon filter, and continuously collecting a permeate solution until the permeate solution has a concentration of PFAS below a maximum contaminant level defined by the Environmental Protection Agency.

[0009] According to another aspect of the present disclosure, a method of filtering per- and poly-fluoroalkyl substances (PFAS) from a sample includes preparing a porous graphitic carbon filter including an electrode, the porous graphitic carbon filter includes porous graphitic carbon particles, applying a positive electrical potential to the electrode, filtering the sample through the porous graphitic carbon filter, said sample has a first concentration of PFAS, collecting a permeated solution having a second concentration of PFAS, the second concentration of PFAS is lower than the first concentration of PFAS.

[0010] These and other features, advantages, and objects of the present disclosure will be further understood and appreciated by those skilled in the art by reference to the following specification, claims, and appended drawings.BRIEF DESCRIPTION OF THE DRAWINGS

[0011] In the drawings:

[0012] FIG. 1 is a schematic set up to filter PFAS particles from an aqueous solution using a porous graphitic carbon filter, according to aspects of the present disclosure;

[0013] FIG. 2A is a flowchart of a method of filtering PFAS using a series of electrified membranes or columns, according to aspects of the present disclosure;

[0014] FIG. 2B is a flow chart of a method of recycling a used filter facilitated by electrical potential for PFAS desorption, according to aspects of the present disclosure;

[0015] FIG. 3A is a scanning electron microscope image of porous graphitic carbon synthesized by pyrolysis of metal organic framework, according to aspects of the present disclosure;

[0016] FIG. 3B is a transmission electron microscope image of porous graphitic carbon particles, according to aspects of the present disclosure;

[0017] FIG. 3C is a Raman spectrum of porous graphitic carbon particles in a graphitic phase, according to aspects of the present disclosure;

[0018] FIG. 3D is a high-resolution transmission electron microscope image showing disordered graphitic phase with an interlayer spacing, according to aspects of the present disclosure;

[0019] FIG. 4 is a schematic of the porous graphitic carbon filter with varying electric potentials applied, according to aspects of the present disclosure;

[0020] FIG. 5 is a bar graph showing retention ratios of a concentration of PFOS dependent on voltage potential fora porous graphitic carbon filter, according to aspects of the present disclosure;

[0021] FIG. 6 is a bar graph showing retention ratios of PFOS dependent on voltage potential applied to a porous graphitic carbon filter tested using several initial porous graphitic carbon amounts on the filter, according to aspects of the present disclosure;

[0022] FIG. 7 is a line graph showing retention ratios of a concentration of PFOS for a porous graphitic carbon (PGC) filter compared with different initial PGC mass at different applied voltage potentials across the filter, according to aspects of the present disclosure;

[0023] FIG. 8 is a bar graph showing retention ratios of a concentration of PFOS for a porous graphitic carbon filter compared with different applied voltage potentials across the filter, according to aspects of the present disclosure;

[0024] FIG. 9 is a line graph illustrating long-term filtration performance of a porous graphitic carbon (PGC) filter over time, according to aspects of the present disclosure;

[0025] FIG. 10A is a line graph illustrating results of a stability test for a porous graphitic carbon (PGC) filter by cycling a voltage potential from +1V to -IV, according to aspects of the present disclosure;

[0026] FIG. 10B is a line graph illustrating results of a stability test for a porous graphitic carbon (PGC) filter by cycling a voltage potential from OV to +1V, according to aspects of the present disclosure;

[0027] FIG. IOC is a line graph illustrating results of a stability test for a porous graphitic carbon (PGC) membrane by cycling a voltage potential from OV to -IV, according to aspects of the present disclosure

[0028] FIG. 11 is a schematic set up to filter PFAS particles from an aqueous solution using a porous graphitic carbon column, according to aspects of the present disclosure;

[0029] FIG. 12 is a bar graph showing PFOS uptake and retention ratios of a porous graphitic carbon column, according to aspects of the present disclosure;

[0030] FIG. 13A is a line graph showing PFOS desorption ratios using a porous graphitic carbon column at a voltage potential of 0V and -IV against volume, according to aspects of the present disclosure;

[0031] FIG. 13B is a line graph showing PFOS desorption ratios using a porous graphitic carbon column at a voltage potential of 0V and -IV against column flow rate, according to aspects of the present disclosure;

[0032] FIG. 14A is a line graph showing stability testing of a porous graphitic carbon column by measuring PFOS uptake through voltage cycling according to aspects of the present disclosure;

[0033] FIG. 14B is a line graph showing stability testing of a porous graphitic carbon column by measuring PFOS desorption from column through voltage cycling, according to aspects of the present disclosure; and

[0034] FIG. 15 is a bar graph showing a comparative study using a porous graphitic carbon column and a granular activated carbon column for evaluation of PFOS removal, according to aspects of the present disclosure.DETAILED DESCRIPTION

[0035] The present illustrated embodiments reside primarily in combinations of method steps and apparatus components related to porous graphitic carbon (PGC) membranes for filtering and extracting per- and poly-fluoroalkyl substances (PFAS) in a sample,strengthened by applying positive potential, and recycling of used PGC membranes and columns via desorption of PFOS expedited by applying negative potential. Accordingly, the apparatus components and method steps have been represented, where appropriate, by conventional symbols in the drawings, showing only those specific details that are pertinent to understanding the embodiments of the present disclosure so as not to obscure the disclosure with details that will be readily apparent to those of ordinary skill in the art having the benefit of the description herein. Further, like numerals in the description and drawings represent like elements.

[0036] For purposes of description herein, the terms "upper," "lower," "right," "left," "rear," "front," "vertical," "horizontal," and derivatives thereof, shall relate to the disclosure as oriented in FIG. 1. Unless stated otherwise, the term "front" shall refer to the surface of the device closer to an intended viewer of the device, and the term "rear" shall refer to the surface of the device further from the intended viewer of the device. However, it is to be understood that the disclosure may assume various alternative orientations, except where expressly specified to the contrary. It is also to be understood that the specific devices and processes illustrated in the attached drawings, and described in the following specification are simply exemplary embodiments of the inventive concepts defined in the appended claims. Hence, specific dimensions and other physical characteristics relating to the embodiments disclosed herein are not to be considered as limiting, unless the claims expressly state otherwise.

[0037] The terms "including," "comprises," "comprising," or any other variation thereof, are intended to cover a non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements does not include only those elements but may include other elements not expressly listed or inherent to such process, method, article, or apparatus. An element preceded by "comprises a . . ." does not, without more constraints, preclude the existence of additional identical elements in the process, method, article, or apparatus that comprises the element.

[0038] Referring to FIG. 1, a schematic set up to filter PFAS particles from an aqueous solution using a porous graphitic carbon (PGC) filter system 10 is illustrated. According to methods of the present disclosure, modulating the surface potential of PGC is realized via electrochemical method by using a PGC filter 14 and a working electrode 18. Adjusting the electrode 18 potential costs minimal electricity, thus consuming minimal energy,significantly less than traditional PFAS removal methods, which usually consume significant amount of chemicals, energy and labor. In some implementations, PFAS filtration is conducted by modulating an electrostatic potential on the porous graphitic carbon (PGC) filter 14. The PGC filter 14 may be formed by depositing conductive PGC particles 22 onto a supporting substrate 26, which may include a porous polymer (e.g., nylon film), but is not limited to such. In other implementations, the PGC filter 14 may be in the form of a column made from PGC particles in the form of a powder. The surface electrostatic potential of the PGC filter 14 can be adjusted via an electrochemical approach to facilitate PFAS adsorption and desorption on the PGC filter 14. In this way, adjusting the electric potential between positive and negative via the electrode 18 allows the PGC filter 14 to alternate between efficiently adsorbing and desorbing PFAS. In specific implementations, a conductive material, such as a metal (e.g., copper or platinum) ring 30 may be used to provide a uniform electric field across the PGC filter 14 when a voltage potential is applied. The PGC filter 14 may be pre-saturated with a feed solution including a concentration of PFAS to eliminate a fluctuation effect due to the adsorption of PFAS onto the PGC filter 14. The feed solution may include a concentrations of PFAS in a range of approximately, greater than approximately 0-20 pM, greater than approximately 0-15 pM, greater than approximately 5-15 pM. In specific examples, the feed solution used for pre-saturation of the PGC filter 14 may include a concentration of PFAS of approximately 10 pM. The pre-saturation of the PGC filter 14 with the PFAS feed solution can improve the reproducibility of the PGC filter's 14 response.

[0039] According to aspects of the present disclosure, the use of the PGC filter 14 for PFAS filtration can further include successive cycling through the electrical potential without degradation or a decrease in efficiency for at least 30 cycles. The long-term filtration performance of the PGC filters 14 of the present disclosure allow for multiple cycles through adjusting an applied electrical potential. After a multitude of cycles, there is still material stability for reusability of the system.

[0040] Advantageously, the electro-modulated PGC filters 14 of the present disclosure are not only suitable as membrane filters for filtering PFAS from aqueous samples, but also may be used for applications in solid-phase extraction (SPE) materials. For application as SPE, the PGC particles 22 may be fabricated into membrane or column format in some examples.

[0041] Definitions of specific method techniques and chemical terms are described in more detail below.

[0042] The term adsorption, as used herein, refers to the process of a molecule of a gas, a liquid, or solute dissolved in the gas or the liquid which may include atoms, ions, or molecules, that adhere to a solid surface. Further, the term desorption, as used herein, means the process of the release of an adsorbed substance from the solid surface.

[0043] The term metal organic framework (MOF), as used herein, refers to porous polymers including metal clusters that can supramolecularly coordinate to organic ligands to form multi-dimensional structures. In other words, MOF structures are three dimensional porous structures made of metal ions or clusters linked by organic molecules. In some aspects, the metal clusters or ions can include copper, aluminum, zirconium, zinc, hafnium, but are not limited to such.

[0044] The term porous graphitic carbon (PGC), as used herein, refers to materials composed of graphite sheets with a network of interconnected pores. These materials may be made up of sheets of carbon atoms that are hexagonally arranged and linked by conjugated bonds. The structure provides a high surface area.

[0045] With reference to FIG. 2A, a method 100 of filtering per- and poly-fluoroalkyl substances (PFAS) from a sample includes an initial step 110 of preparing a PFAS contaminated water sample. Next, a step 120 of applying a positive electrical potential to a first porous graphitic carbon (PGC) filter, is conducted. Another step in the method 100 includes a step 130, filtering the PFAS contaminated water sample through the first PGC filter. The first PGC filter may be in the form of a column or a membrane. Then, step 140 of collecting a first permeated solution from the first PGC filter is conducted. The first permeated solution of step 140 may have a lower concentration of PFAS than the contaminated water sample of step 110. Next, step 150 of applying a positive electrical potential to a second PGC filter, is conducted. Then, step 160 of filtering the first permeated solution through the second PGC filter. The second PGC filter may be in the form of a column or a membrane. Another step in the method 100 includes step 170 of collecting a second permeated solution from the second PGC filter. The second permeated solution of step 170 may have a lower concentration of PFAS than the first permeated solution of step 140. Another step in the method 100 includes step 180, if the second permeated solution is of PFAS concentration greater than a maximum contaminant level(MCL) defined by the U.S. EPA then the solution will continue to subsequent PGC filters. Each subsequent PGC filter may have a positive electrical potential applied to the PGC filter before the sample is filtered through. The last step in method 100 includes step 190, collecting a clean water sample with PFAS concentration below the EPA MCL.

[0046] In other implementations, an aqueous sample includes PFAS contaminated water sample. First, a positive electrical potential is applied to a porous graphitic carbon (PGC) filter according to the present disclosure. The PGC filter may be in the form of a column or a membrane. Next, the PFAS contaminated water sample is passed through the PGC filter. Then, a first permeated solution is collected from the PGC filter. The first permeated solution may have a lower concentration of PFAS than the contaminated water sample. Next, a negative electrical potential is applied to the PGC filter, and a wash solution is passed through the filter. The wash solution is then collected as a waste solution. The waste solution may have a higher PFAS concentration than the wash solution. Optionally, the first permeated solution is again passed through the PGC filter and a second permeated solution is collected.

[0047] The EPA MCL is an official health advisory level set by the U.S. EPA for PFAS in drinking water. For perfluorooctanesulfonic acid (PFOS) and perfluorooctanoic acid (PFOA) the MCL is 4 ppt. For perfluorohexanesulphonic acid (PFHxS) the MCL is 10 ppt. For perfluorononanoic acid (PFNA) the MCL is 10 ppt. For an ammonium salt of hexafluoropropylene oxide dimer acid (GenX™) the MCL 10 ppt. While method 100 of FIG. 2A preferably includes reducing the concentration of PFAS in a PFAS contaminated water sample, method 100 may not be exclusively applied to PFAS with a MCL set by the EPA, and rather may include more types of PFAS molecules. In one aspect, method 100 includes PFAS molecules with negatively charged moieties.

[0048] Referring now to FIG. 2B, a method of cleaning PGC filters saturated with PFAS molecules includes step 210 of rinsing the PGC filter saturated with PFAS molecules with clean water. A permeated waste solution may result from the rinsing of the PGC filter. The PGC filter may be in the form of a column or a membrane. Step 220 of method 200 includes applying a negative electrical potential to the PGC filter. Next, step 230 of method 200 includes the continuous rinsing of the PGC filter until the permeated waste solution has a concentration of PFAS that is around 0. In some examples, method 100 may be followed by method 200. In further examples, the method 100 may be repeated until the permeatedsolution has the same PFAS concentration as the concentration in the feed solution before it is followed by method 200. If the PFAS concentration in the permeate solution equals the PFAS concentration in the feed solution, this may indicate the filter is saturated with PFAS and reaches a kinetic equilibrium. In still some further examples, the combination of method 100 followed by method 200 may be repeated up to around 30 times or more.

[0049] Again, the present disclosure utilizes the conductive PGC particles 22 to filter a variety of PFAS analogues from samples that may or may not be aqueous. The PGC particles 22 provide greater adsorption capacity than conventional granular activated carbon (GAC) materials as the PGC particles 22 include a high specific surface area and porous structure. A specific area of the PGC particles 22 may be in a range of approximately 1,000 m2 / g to approximately 2,500 m2 / g, or approximately 2,000 m2 / g.

[0050] FIG. 3A shows a scanning electron microscope (SEM) image of example PGC particles 22 synthesized by pyrolysis of metal organic framework (MOF) compounds. Synthesizing the PGC particles 22 using MOF compounds advantageously allows for a tunable structure with respect to pore size, geometry, and distribution in order to target the variety of PFAS analogues (e.g., PFAS with varying chain lengths). GAC materials cannot effectively filter short-chain PFAS, which do not experience agglomeration in the GAC pores and, therefore, desorb too readily. The SEM image of FIG. 3A shows the structure of the overall PGC particles 22 and the porous surface. FIG. 3B shows a transmission electron microscope (TEM) image that more clearly illustrates the high porosity of the surface of the example PGC particles 22. FIG. 3C shows a Raman spectrum of the example PGC particles 22, including a G-band, indicating the graphitic phase, which is desirable for electrified filtration. FIG. 3D shows a high-resolution transmission electron microscope (HR-TEM) image of the example PGC particles 22, showing interlayer spacing therebetween. The HR-TEM image of FIG. 3D shows a disordered graphitic phase with an interlayer spacing of 0.34nm. The interlayer spacing of the example PGC particles 22 is comparable to that of graphite at 0.33 nm. In some examples, the PGC particles 22 may include a specific area in a range of approximately 1,000 m2 / g to approximately 2,500 m2 / g, or approximately 1,500 m2 / g to approximately 2,000 m2 / g.

[0051] Conventional PFAS filtering methods include graphite having a nonporous structure, which does not allow for a flow-through filtration process nor tunable pore size to target various PFAS analogues. Pyrolysis of the MOF materials of the present disclosureproduces PGC particles 22 in a tunable structure with respect to pore size, geometry, and distribution. The tunable structure of the MOF material is due to the selection of different metals or metal clusters and / or the selection of different organic ligands in MOF synthesis. However, the PGC particles 22 may be synthesized from MOF materials according to other techniques. These tunable characteristics of the PGC particles 22 pore structure allow the PGC particles 22 to be effective and selective at removal of PFAS of different chain lengths, such as, but not limited to perfluorooctane sulfonic acid, perfluorohexanesulfonic acid, perfluorooctanoic acid, and perfluorobutane sulfonate. Further, the graphitic structure of the PGC particles 22 enhances electrical conductivity, enabling efficient responses to changes in voltage potential. Adjusting the voltage potentials across the PGC filter 14 is simple and rapid, which allows the PGC filter 14 to quickly absorb and desorb PFAS. This rapid adsorption and desorption of the PFAS solutes to and from the PGC filter 14 eliminates the need for labor-intensive filter cleaning and replacement. Current methods for PFAS removal, including ion exchange resins, may require large columns and extended contact times at a given flow rate for proper reuse of the resin. The cycling of electrical potential of the PGC filter 14 speeds up both adsorption and desorption without requiring elution processes, facilitating membrane reuse and waste solution recycling. Further, the in-situ applied potential across the PGC filter 14 accelerating the adsorption and desorption is also a favorable trait compared to purely physical diffusion-based adsorption methods.

[0052] Referring now to FIG. 4, a schematic of the porous graphitic carbon filter 14 with varying electric potentials applied is illustrated. The PGC filter 14 is shown at a pristine surface potential 200, a negative surface potential 210, and a positive surface potential 220. In the pristine state 200, when no electrical potential is applied, an aqueous feed solution of PFAS containing negative moieties is run through the PGC filter 14 and a kinetic equilibrium is maintained. As a result of the maintained kinetic equilibrium, the solution following the filter (e.g., permeated solution) may have a similar final concentration to the initial, feed solution. When a negative electrical potential 210 is applied to the PGC filter 14, the PFAS anions adsorbed (e.g., saturated) on the PGC filter 14 are repelled. The negative potential state 210 may result in an increased concentration of PFAS in the permeated or collected solution. When a positive electrical potential 220 is applied to the PGC filter 14, the PFAS anions in the feed solution are attracted on the PGC filter 14,restraining the PFAS anions on the PGC filter 14 through electrostatic interactions. The positive potential state 220 may result in a decreased concentration of PFAS in the permeated solution (e.g., providing a purified solution). Therefore, during a purification process, the positive electrical potential 220 can be applied to purify the sample by restraining the PFAS on the PGC filter 14. Once the filter is saturated with the PFAS, the negative electrical potential 210 can be applied to the PGC filter 14 to rinse the filter and collect the concentrated, waste permeated solution for further treatment. When the concentration of PFAS in the permeated solution reaches around 0 M, the filter may be considered to be recycled. A recycled filter may then have a second positive potential applied to process the PFAS contaminated solution. In some examples, washing the PGC filter 14 with an elution solution may facilitate desorption of the captured PFAS material. The washing or rinsing may be performed with organic solvents such as methanol, ethanol, or dimethyl sulfoxide as a rinsing solvent leveraging the good solubility of PFAS in these solvents. In some examples, the washing may be performed with clean water as the rinsing solvent.

[0053] Accordingly, the PGC filter 14, may use the switch between the positive electrical potential 220 and negative electrical potential 210 to switch between adsorption and desorption of solutes containing the PFAS with negative moieties. Again, when no electrical potential is applied to the PGC filter 14, a kinetic equilibrium is reached for a solute of PFAS with negative moieties adsorbing and desorbing onto the PGC filter 14. When the PGC filter 14 starts in a pristine state 200 and then a negative electrical potential 210 is applied, a shift in the kinetic equilibrium occurs, which can result in less of the PFAS solute being associated with the surface of the PGC filter 14. When the PGC filter 14 starts in a pristine state 200 and then a positive electrical potential 220 is applied, a shift in the kinetic equilibrium can occur, which results in more of the PFAS solute being associated with, or captured by, the surface of the PGC filter 14. The shift from adsorption to desorption on the PGC membrane may be achieved by switching the electric potential of the electrode 18 from positive to negative. For example, if the PGC filter 14 is in the positive potential state 220, with more solute molecules associated with the PGC filter 14, then switched to the negative potential state 210, the PFAS solute molecules desorb from the PGC filter 14 resulting in less PFAS solute molecules associated with the PGC filter 14 (e.g., the PFAS material may be released from the filter 14). The ability to switch from a positivepotential state 220 to a negative potential state 210, as well as from a negative potential state 210 to a positive potential state 220 allows the PGC filter 14 to cycle through adsorption and desorption of a negatively charged solute (e.g., PFAS) over many cycles for much re-use of the same PGC filter 14. The cycle is ultimately timesaving, as it may eliminate the need to replace the PGC filter 14 or to conduct extensive cleaning after use for filtration.

[0054] To assess the efficacy of the filtration system, the retention ratio, or retention rate, may be calculated. The retention ratio, R(%) is defined using equation (I):wherein R(%) is the retention ratio, Cpis the concentration of the permeate, the solution collected after filtration, and Cf is the concentration of the feed solution. The higher the retention ratio the more effective the membrane is at filtering out the solute. Retention ratios of negative values may be possible when using a pre-saturated membrane. A negative retention ratio may indicate a higher rate of desorption from the pre-saturated membrane by the solute.EXAMPLES

[0055] Example 1: Synthesis of Porous Graphitic Carbon (PGC) Particles

[0056] The synthesis of porous graphitic carbon (PGC) included two parts: (1) the synthesis of the MOF and (2) the synthesis of PGC from the MOF. The MOF may be composed of inorganic nodes, referred to as secondary building units, which can include a variety of metal ions suitable for MOF synthesis. Examples of metals ions include, but are not limited to, zirconium, hafnium, copper, zinc, and aluminum. Additionally, any organic ligand containing an aromatic ring can be used as an organic linker, such as terephthalic acid (1,4- benzenedicarboxylate), 4,4'-biphenyl dicarboxylic acid, or 4,4',4",4"'-(pyrene-l,3,6,8- tetrayl)tetrabenzoic acid. Zirconium tetrachloride (ZrCU, 50 mg), terephthalic acid (35.7 mg), and benzoic acid (786 mg) were placed in a sealed tube. Dimethylformamide (DMF, 3 mL) was added to the mixture and sonicated until all the benzoic acid dissolved. The mixture was heated at 120°C for 24 hours. The resulting UiO-66 MOF powder was filtered and washed with acetone and dried in an air oven. UiO-66 MOF (100 mg) was pyrolyzed at 900 °C. The ramp rate of the pyrolysis was 5 °C / min with 1 hour hold time under an argon gas (Ar) flow. The resulting black powder was allowed to cool to room temperature. Thepowder was dispersed in hydrofluoric acid (20% (v / v) aqueous solution of HF) and heated at 80°C for 12 hours. The mixture was washed with methanol and water (v / v=l:4) three times, filtered, and dried in an air oven.

[0057] FIG. 3B shows a TEM image of the PGC particles 22 synthesized according to Example 1. The TEM showed a high porosity, which is consistent with the specific surface area of 1,805 m2 / g measured by BET methods. Depending on the MOF precursors used, PGC particles may have a specific surface area in a range of about 50 to about 7,000 m2 / g, about 75 to about 6,000 m2 / g, about 100 to about 5,000 m2 / g. FIG. 3D shows a high- resolution transmission electron microscope (HR-TEM) image of the PGC particles 22 synthesized according to Example 1. The HR-TEM image shows a disordered graphitic phase with interlayer spacing at 0.34 nm. The interlay spacing of the PGC particles 22 is comparable to the interlayer spacing of graphite (~0.33 nm).

[0058] Example 2: Preparation of Porous Graphitic Carbon (PGC) Membrane Filters

[0059] A nylon membrane with a pore size of 0.8 pm and a diameter of 25 mm was obtained. A copper ring (outer diameter: 25 mm, inner diameter: 16 mm) was affixed onto the membrane's surface. Coppertape (32.5 mm in length and 6 mm in width) was attached to the copper ring to connect the system to a CHI 660E electrochemical workstation instrument. PGC particles 22 (1.0 mg) were dispersed in 30 mL deionized (DI) water. The suspension was sonicated for one hour. The water solution with PGC particles 22 dispersed therein were added to a glass funnel to deposit the PGC particles 22 onto the nylon membrane via vacuum filtration at a pump rate of 0.2 LPM. The membrane was allowed to air-dry overnight at room temperature before any experiments were conducted. As shown schematically in FIG. 1, the copper tape in contact with the PGC filter 14 acted as the working electrode 18 (WE) connected to the CHI 660E electrochemical workstation. A platinum wire functioned as the counter electrode (CE), while an Ag / AgCI electrode in 1 M KCI served as the reference electrode (RE). The electrodes were immersed in a PFAS solution within the glass funnel. Perfluorooctanesulfonic acid (PFOS), as a potassium salt, was used as a representation of the PFAS to test the performance of the electrified PGC filter 14. For each test, 5 mL of a 10 pM PFOS stock solution was added, and vacuum filtration was maintained at a pump rate of 0.2 LPM. This process was repeated until the concentration of the permeated solution matched that of the feed solution, such that the nylon membrane was fully saturated with PGC particles 22.

[0060] Example 3: Evaluation of Porous Graphitic Carbon (PGC) Membrane Studies

[0061] Referring to FIG. 5, the efficacy of the filtration system of Example 2 was calculated using the retention ratio as defined herein as equation (I). FIG. 5 shows retention ratios of a concentration of PFOS dependent on voltage potential with 1.0 mg porous graphitic carbon on the filter. The retention ratios were calculated to evaluate the effect of voltage potential when the PGC membrane was set to -IV, 0V, and IV (vs. Ag / AgCI). When the PGC filter 14 was set to IV, more PFOS was adsorbed onto the PGC filter 14, yielding a positive value of retention ratio. The retention ratio for PFOS adsorption to the PGC filter 14 was approximately 29%. The PGC filter 14 then desorbed when the potential was set to -IV, yielding a negative value of retention ratio. The retention ratio for PFOS desorption to the PGC filter 14 was approximately -49%.

[0062] FIG. 6 shows the effect of using varying amounts of PGC particles 22 deposited on the nylon membrane against the efficacy of the resulting membrane system in adsorption and desorption quantity. The PGC filter 14, was prepared by depositing 0.5, 1.0, 1.5, and 2.5 mg of PGC particles 22 onto the nylon membrane. Retention ratios were measured with varying amounts of PGC particles 22 on the PGC filter 14 at different potentials. The adsorption and desorption improved as the amount of PGC particles 22 in the membrane increased. However, beyond 1.0 mg, the retention ratio performance began to stabilize around 40% for adsorption and around -50% for desorption, and the standard deviation started to increase, suggesting that 1.0 mg of PGC particles 22 was sufficient to saturate the nylon membrane used in these experiments. As the amount is increased above 1.0 mg, PGC particles 22 detached from the membrane and were suspended in the feed solution, indicating that the amount of PGC on the surface of the nylon membrane had reached its maximum. The retention ratio shown in FIG. 6, as a bar graph, was dependent on the electrical potential applied across the PGC filter 14 for the different amounts of PGC particles added to the membrane. The retention ratio as shown in the line graph of FIG. 7, was dependent on the mass of PGC particles added to the nylon membrane for the different electrical potentials applied across the PGC filter 14.

[0063] FIG. 8 shows the filtration performance of PGC filter 14 being evaluated under varying external electrical potential conditions ranging from -1.0V to +1.0V using a PFOS feed solution. As the potential increased from the pristine, 0V, state to positive values, the PGC filter 14 attracted the anionic PFOS molecules. Increasing the potential to higherpositive values resulted in adsorption being increased. The stronger adsorption increased the retention ratio. Conversely, when the potential changed from the pristine state to negative values, the negative potential repelled the anionic PFOS molecules, initiating desorption and desorbing PFOS from the PGC filter 14. Larger negative potentials enhanced desorption and increased the retention ratio in the negative direction by removing more PFOS from the PGC filter 14.

[0064] The long-term filtration performance of PGC membranes for PFOS was assessed at - IV, 0V, and +1V by continuous flowing through of PFOS (10 pM) solution. As shown in FIG. 9, each data point indicates 5 mL of solution passed through the PGC filter 14. When a neutral potential of 0V was applied to the pre-saturated PGC membrane 14 for 50 minutes, neither adsorption nor desorption was observed due to the kinetic equilibrium between the feed PFOS solution and the saturated PGC filter 14. When a positive potential of IV was applied to the same PGC filter 14, high values of positive retention ratios were obtained initially, which consistently decreased as more PFOS was adsorbed onto the membrane, eventually reaching saturation of adsorption at +1V. Similarly, when a negative potential of -IV was applied, high values of negative retention ratios were obtained initially, which consistently decreased as more PFOS was desorbed from the membrane, eventually reaching an equilibrium state of adsorption at -IV.

[0065] FIG. 10 shows a stability test of the PGC filter 14 by cycling through potential values for when the potential was directly switched from +1V to -IV (FIG. 10A), from 0V to +1.0V (FIG. 10B), and from 0V to -1.0V (FIG. 10C). Each test point was conducted after the PGC filter 14 had been restored to its pre-saturated state. Switching the potential directly from +1V to -IV, as seen in FIG. 10A, caused the PFOS pre-adsorbed on the PGC filter 14 to desorb at -IV, increasing the concentration of PFOS in the permeate solution, resulting in a switch of retention ratio from a positive to a negative value. FIG. 10B shows the PGC filter 14 adsorbing PFOS for each cycle as the electrical potential was increased to +1.0V resulting in increased retention ratios. FIG. 10C shows the PGC filter 14 desorbing PFOS for each cycle as the electrical potential was decreased to -1.0V resulting in larger negative retention ratios. For the three different cycling tests, FIGS. 10A-C, the five cycles performance repeatable retention ratios for adsorption and desorption, indicating that the PGC filter 14 maintains excellent stability for reusability and recyclability when used for processing the PFOS solution.

[0066] Example 4: Preparation of Porous Graphitic Carbon (PGC) Column

[0067] Referring now to FIG. 11, a porous graphitic carbon (PGC) column system 40 was fabricated using a glass pipette 44 with an inner diameter of approximately 0.5 cm as the column body. First, a 25 mg plug of a first glass wool 48 was positioned at the bottom of the pipette 44 to serve as mechanical support for a PGC packing. Subsequently, 5.0 mg of PGC powder was dispersed in 10 mL of deionized water and ultrasonicated for one hour to obtain a uniform suspension. The resulting suspension was poured into the column 46, allowing the PGC particles to deposit onto the first glass wool 48 layer by gravity-assisted filtration, forming a conductive PGC particle bed 52. A platinum (Pt) first wire 56 was coiled and inserted into the PGC column 46 to function the column 46 as a working electrode. The first wire 56 was encapsulated within a glass capillary tube with a 0.5 mm diameter. The glass capillary tube was completely filled with a polyvinyl chloride (PVC) polymer to ensure electrical insulation and mechanical stability of the first wire. An additional 25 mg of a second glass wool 60 was placed above the PGC particle bed 52 to form a compact upper seal. A second Pt wire 64, insulated within a PVC-filled glass capillary tube in the same manner as the first wire, was positioned above the upper glass wool layer 60 to serve as a counter electrode. Glass beads 68 with a 1 mm diameter were then added to the top of the upper second glass wool 60 layer, with a 1 cm layer to facilitate stabilization of the multilayer column structure. Both Pt electrodes, the first and second wires 56, 64 were connected to an external power supply to regulate an applied potential across the PGC particle bed 52 during subsequent tests.

[0068] Still referring to FIG. 11, the first and second wires are shown positioned at both ends of the PGC bed 52 to provide a uniform electric field across the column 46 when a voltage potential is applied. As shown, the first wire 56 is coupled with the working electrode and the second wire 64 is coupled to the counter electrode. In a pristine state (e.g., no potential is applied), a feed solution 72 containing a concentration of PFOS (e.g., a concentration of approximately 570 pM) is permeated through, or flows through, the PGC column 46 by way of gravity. Optionally, the feed solution 72 may pass through the PGC column 46 using a pressure-driven flow. During this process of adsorption, the PFOS molecules can reach a dynamic adsorption-desorption equilibrium with the surface of the PGC particles, resulting in a permeate solution concentration approximately equal to that of the feed solution. When a positive potential is applied to the PGC bed 52, the surfacebecomes electrostatically attractive toward PFOS as PFOS is an anionic compound. Consequently, the PFOS molecules can be adsorbed and retained within the PGC particle bed 52 through electrostatic interactions. Thus, a permeate 76 of the feed solution 72 during application of a positive potential includes a decreased PFOS concentration relative to a permeate of the feed solution from flow through in the pristine state, where no potential is applied to the PGC particle bed 52. Conversely, when a negative potential is applied to the PGC particle bed 52, the PGC surface repels PFOS anions due to electrostatic repulsion, thereby reducing adsorption affinity. Therefore, permeate solution 76 from the PGC particle bed 52 during application of a negative potential results in a relative increase in the PFOS concentration compared to a PFOS concentration of the permeate 76 of the same feed solution 72 when the PGC particle bed 52 is in the pristine state (e.g., no potential applied). This reversible control of adsorption and desorption of PFOS through electrical potential modulation facilitates switching between a state of PFOS retention and a state of PFOS release by alternating the applied potential from positive to negative.

[0069] The ability to release, or clean, PFOS from the column 46 (e.g., regenerate the column 46) by way of electrical potential application eliminates the need for column replacement or solvent-based cleaning, thereby enhancing operational efficiency, reusability, and long-term recyclability of the PGC column 46. Example 4 as shown and described herein represents a rapid small-scale column test (RSSCTs), which proves the technical feasibility to scale up the PCG column 46 of the present disclosure for field applications to effectively remove PFAS from large bodies of water. Thus, using an electrified PGC column 46 according to aspects of the present disclosure provides for effective adsorption capacity of PFAS and expedites the desorption process for recycling the sorbents (e.g., the PGC particle bed 52).

[0070] Example 5: Evaluation of Porous Graphitic Carbon (PGC) Column Studies

[0071] Referring now to FIG. 12, adsorption uptake and retention ratios of PFOS were determined to evaluate influence of applied surface potential on the PGC column 46. Measurements were conducted under applied voltages of +1 V, 0 V, and -1 V to assess the effect on PFOS adsorption performance. PFOS uptake is calculated as amount of PFOS adsorbed (in unit of mg) per gram of PGC according to equation (II):where CPermeateis the concentration of the permeated solution collected after filtration, CFeed isthe concentration of the feed solution, mPGCis the mass of the PGC used in the column 46, and V is the total volume of solution used for adsorption. In Example 5, the CFeed is570 pM and V is 30 mL. When a positive potential of +1 V was applied to the PGC column 46, increased adsorption of PFOS occurred on the PGC surface, resulting in a positive retention ratio. In contrast, when a negative potential of -1 V was applied, electrostatic repulsion between the negatively charged PGC surface and PFOS anions leads to reduced adsorption, corresponding to a negative retention ratio.

[0072] Referring now to FIG. 13A, desorption performance evaluated as a function of eluent volume using deionized (DI) water is illustrated. The flow rate of the DI waters was fixed at a rate of 9.23 mL-h“1under 0 V and -1 V. For each potential, the PFOS desorption ratio decreased with increasing Dl-water volume, with negative bias yielding higher desorption relative to zero bias, which is indicative of electrified regeneration of the column 46.

[0073] Turning now to FIG. 13 B, the effect of flow rate on regeneration efficiency is illustrated. The regeneration efficiency was assessed at -1 V using a fixed 20 mL Dl-water rinse. Prior to regeneration, each 3 mg PGC column was saturated by passing 30 mL of 570 pM PFOS to establish a loaded state. As shown, at -1 V, the desorption ratio increased with flow rate, consistent with reduced mass-transfer limitations and suppression of readsorption during elution. The use of a 20 mL regenerant volume achieved near-complete recovery, demonstrating low regenerant consumption and a potential for reusability for the PGC column 46.

[0074] The PFOS desorption ratio is calculated using equation (III):where mPermeate soiutton 'sthe mass of PFOS in the permeate solution and msaturated column 'sthe mass of the PFOS retained in the pre-saturated column 46 prior to experiment. The application of a negative potential (-1 V) during regeneration increases the desorption ratio relative to no applied potential; showing electrostatic repulsion- assisted release of PFOS from the PGC particles. Without wishing to be bound by theory, increasing the flow rate at a fixed eluent volume further improves regeneration efficiency by decreasing boundary-layer resistance, thus limiting re-adsorption.

[0075] Referring to FIGS. 14A and 14B, stability testing of the PGC column 46 under cyclic potential switching conditions is illustrated. Potential was switched between 0 V and +1.0 V as shown in FIG. 14A, and between 0 V and -1.0 V as shown in FIG. 14B. Each measurement point was recorded afterthe column 46 had been fully regenerated to a presaturated state to ensure consistent initial conditions. In both positive and negative potential switching tests, the PGC column 46 exhibited highly repeatable adsorption and desorption performance over five consecutive cycles, as reflected by stable or consistent retention ratios. These results may confirm that the PGC column 46 possesses electrochemical and structural stability, maintaining reusability and recyclability during repeated electro-modulated adsorption-desorption operations, even when treating high- concentration PFOS solutions.

[0076] Turning now to FIG. 15, results of a comparative study evaluating adsorption performance of the PGC column 46 and a commercial granular activated carbon (GAC) column for low-concentration PFOS removal is illustrated. The feed solution for the PGC column 46 and the GAC column included 500 mL of deionized (DI) water having a concentration of 50 ppt PFOS. The columns were packed with 1 mg of the corresponding sorbent material (GAC or PGC). A blank control column (no sorbent material) was also tested under identical conditions to account for background adsorption by the system components. The flow rate through the PGC and GAC columns was controlled and maintained at comparable rates, 4.83 mL-min“1for PGC, and 5.45 mL-min“1for GAC. A PFOS removal efficiency was calculated using equation (IV):where CPermeate soiutionis PFOS concentration in the permeate solution and CFeed soiutionis PFOS concentration in the feed solution. The PGC column according to the preset disclosure exhibited a significantly higher PFOS removal efficiency (%) compared to the GAC column under equivalent experimental conditions. The PGC column showed approximately a 96% efficiency at PFOS removal, while the GAC column showed approximately a 53% efficiency at PFOS removal. As shown by the comparison between the PGC and GAC in FIG. 15, the PGC column had a greater PFOS removal efficiency.

[0077] According to one aspect of the present disclosure, a method of filtering per- and poly-fluoroalky I substances (PFAS) from a sample includes preparing a porous graphiticcarbon filter including an electrode, the porous graphitic carbon filter includes porous graphitic carbon particles, applying a positive electrical potential to the electrode, filtering the sample through the porous graphitic carbon filter, the sample has a first concentration of PFAS, collecting a permeated solution having a second concentration of PFAS, the second concentration of PFAS is lower than the first concentration of PFAS, filtering the sample through a second porous graphic carbon filter, the second porous graphitic carbon filter includes porous graphitic carbon particles, collecting a second permeated solution having a third concentration of PFAS, the third concentration of PFAS is lower than the second concentration of PFAS, repeating filtering the sample through a plurality of porous graphitic carbon filters until the permeated solution is below a maximum contaminant level defined by the Environmental Protection Agency.

[0078] According to another aspect of the present disclosure, the porous graphitic carbon filter includes a membrane or column.

[0079] According to yet another aspect of the present disclosure, the membrane includes a polymer membrane substrate and the porous graphitic carbon particles, the porous graphitic carbon particles are dispersed on the polymer membrane substrate.

[0080] According to another aspect of the present disclosure, the membrane includes a self-standing membrane including the porous graphitic carbon particles and a polymer binder, the porous graphitic carbon particles are blended with the polymer binder.

[0081] According to yet another aspect of the present disclosure, the column is filled with the porous graphitic carbon particles.

[0082] According to another aspect of the present disclosure, the porous graphitic carbon particles are synthesized from a metal organic framework material.

[0083] According to yet another aspect of the present disclosure, the metal organic framework material includes copper, aluminum, zirconium, zinc, hafnium, or others as metal nodes and molecules containing aromatic carbon rings, such as terephthalic acid (1,4-benzenedicarboxylate), 4,4'-biphenyl dicarboxylic acid, or 4,4',4",4"'-(pyrene-l,3,6,8- tetrayl)tetra benzoic acid as the ligands.

[0084] According to another aspect of the present disclosure, the porous graphitic carbon particles are produced from the metal organic framework material through a process including pyrolyzing in an inert gas phase at temperatures in a range of 500 - 1000 °C,rinsing with one or more acids, and obtaining a pure carbon material in a graphitic phase, the graphitic phase enables high electrical conductivity.

[0085] According to yet another aspect of the present disclosure, the porous graphitic carbon particles have a high porosity and a large specific surface area above 500 m2 / g.

[0086] According to another aspect of the present disclosure, the porous graphitic carbon particles have a high porosity and a large specific surface above 1500 m2 / g.

[0087] According to yet another aspect of the present disclosure, the large specific surface area is approximately 1,805 m2 / g.

[0088] According to another aspect of the present disclosure, the positive electrical potential is between 0 and +1.0 V.

[0089] According to yet another aspect of the present disclosure, a retention ratio during the step of filtering the sample is up to 100%.

[0090] According to another aspect of the present disclosure, the method includes a multistage filtration system incorporating multiple porous graphitic carbon filters, the porous graphitic carbon particles contain pore sizes that are in the range of 0.5-5 nm, the pore sizes get progressively smaller on each subsequent porous graphitic carbon filter.

[0091] According to yet another aspect of the present disclosure, a method of recycling a saturated filter with per- and poly-fluoroalkyl substances (PFAS) includes obtaining a porous graphitic carbon filter, the porous graphitic carbon filter is said saturated filter, applying a negative electrical potential to an electrode, the electrode is the porous graphitic carbon filter, flowing clean water through the porous graphitic carbon filter, and continuously collecting a permeate solution until the permeate solution has a concentration of PFAS around 0 M or below a maximum contaminant level defined by the Environmental Protection Agency.

[0092] According to another aspect of the present disclosure, the negative electrical potential is in a range between 0 and -1.0 V.

[0093] According to yet another aspect of the present disclosure, the porous graphitic carbon filter is in the form of a membrane or a column.

[0094] According to another aspect of the present disclosure, a system for filtering per- and poly-fluoroalkyl substances (PFAS) from a sample, the system including at least one porous graphitic carbon (PGC) filter including porous graphitic carbon particles, the at least one porous graphitic carbon filter includes a specific surface area greater than 1000 m2 / g,and at least one working electrode configured to apply a positive and a negative electrical potential to the porous graphitic carbon particles.

[0095] According to yet another aspect of the present disclosure, the at least one porous graphitic carbon filter comprises a first porous graphitic carbon filter and a second porous graphitic carbon filter and the at least one working electrode comprises a first working electrode in electrical communication with first porous graphitic carbon particles of the first porous graphitic carbon filter and a second working electrode in electrical communication with second porous graphitic carbon particles of the second porous graphitic carbon filter.

[0096] According to another aspect of the present disclosure, the system further including a counter electrode in electrical communication with the porous graphitic carbon filter.

[0097] According to yet another aspect of the present disclosure, the first porous graphitic carbon particles include a first porosity and the second porous graphitic carbon particles include a second porosity, the second porosity is less than the first porosity.

[0098] According to another aspect of the present disclosure, the membrane comprises a polymer membrane substrate and the porous graphitic carbon particles, the porous graphitic carbon particles are dispersed on the polymer membrane substrate.

[0099] According to yet another aspect of the present disclosure, the at least one porous graphitic carbon filter is in the form of a self-standing membrane including the porous graphitic carbon particles and a polymer binder, wherein the porous graphitic carbon particles are blended with the polymer binder.

[0100] According to another aspect of the present disclosure, the at least one porous graphitic carbon filter is in the form of a column including a column body that is filled with the porous graphitic carbon particles and includes a mechanical support configured to retain the porous graphitic carbon particles within the column body.

[0101] According to yet another aspect of the present disclosure, the porous graphitic carbon particles are in the form of a powder.

[0102] According to another aspect of the present disclosure, the porous graphitic carbon particles are synthesized from a metal organic framework material.

[0103] According to yet another aspect of the present disclosure, the metal organic framework material includes at least one of copper, aluminum, zirconium, zinc, hafniumor a combination thereof as metal nodes and at least one molecule containing an aromatic carbon ring.

[0104] According to another aspect of the present disclosure, the metal organic framework material includes at least one of terephthalic acid (1,4-benzenedicarboxylate), 4,4'-biphenyl dicarboxylic acid, or 4,4',4",4"'-(pyrene-l,3,6,8-tetrayl)tetrabenzoic acid as the ligands.According to yet another aspect of the present disclosure, the porous graphitic carbon particles include a specific surface area greater than 1400 m2 / g.

[0105] According to another aspect of the present disclosure, the specific surface area is approximately 1,800 m2 / g.

[0106] According to yet another aspect of the present disclosure, the electrical potential is in a range of greater than -1.0 and +1.0 V.

[0107] It will be understood by one having ordinary skill in the art that construction of the described disclosure and other components is not limited to any specific material. Other exemplary embodiments of the disclosure disclosed herein may be formed from a wide variety of materials, unless described otherwise herein.

[0108] For purposes of this disclosure, the term "coupled" (in all of its forms, couple, coupling, coupled, etc.) generally means the joining of two components (electrical or mechanical) directly or indirectly to one another. Such joining may be stationary in nature or movable in nature. Such joining may be achieved with the two components (electrical or mechanical) and any additional intermediate members being integrally formed as a single unitary body with one another or with the two components. Such joining may be permanent in nature or may be removable or releasable in nature unless otherwise stated.

[0109] It is also important to note that the construction and arrangement of the elements of the disclosure, as shown in the exemplary embodiments, is illustrative only. Although only a few embodiments of the present innovations have been described in detail in this disclosure, those skilled in the art who review this disclosure will readily appreciate that many modifications are possible (e.g., variations in sizes, dimensions, structures, shapes and proportions of the various elements, values of parameters, mounting arrangements, use of materials, colors, orientations, etc.) without materially departing from the novel teachings and advantages of the subject matter recited. For example, elements shown as integrally formed may be constructed of multiple parts, or elements shown as multipleparts may be integrally formed, the operation of the interfaces may be reversed or otherwise varied, the length or width of the structures and / or members or connector or other elements of the system may be varied, the nature or number of adjustment positions provided between the elements may be varied. It should be noted that the elements and / or assemblies of the system may be constructed from any of a wide variety of materials that provide sufficient strength or durability, in any of a wide variety of colors, textures, and combinations. Accordingly, all such modifications are intended to be included within the scope of the present innovations. Other substitutions, modifications, changes, and omissions may be made in the design, operating conditions, and arrangement of the desired and other exemplary embodiments without departing from the spirit of the present innovations.

[0110] It will be understood that any described processes or steps within described processes may be combined with other disclosed processes or steps to form structures within the scope of the present disclosure. The exemplary structures and processes disclosed herein are for illustrative purposes and are not to be construed as limiting.

[0111] It is also to be understood that variations and modifications can be made on the aforementioned structures and methods without departing from the concepts of the present disclosure, and further it is to be understood that such concepts are intended to be covered by the following claims unless these claims by their language expressly state otherwise.

Claims

What is claimed is:

1. A system of filtering per- and poly-fluoroalkyl substances (PFAS) from a sample, the system comprising: a first aqueous solution containing a first concentration of PFAS; a first filter comprising porous graphitic carbon particles including a first porosity; at least one electrode, wherein the electrode is configured to apply a positive and a negative electrical potential to the first filter; a second aqueous solution containing a second concentration of PFAS, wherein the first concentration of PFAS is larger than the second concentration of PFAS, wherein the first filter is configured to reduce the first concentration of PFAS in the first aqueous solution to the second concentration of PFAS a second filter comprising porous graphitic carbon particles including a second porosity, wherein the second porosity is less than the first porosity; and a third aqueous solution containing a third concentration of PFAS, wherein the second concentration of PFAS is larger than the third concentration of PFAS, wherein the second filter is configured to reduce the second concentration of PFAS in the second aqueous solution to the third concentration of PFAS.

2. The system of filtering PFAS from a sample of claim 1, wherein the first and second filters are configured to have a greater affinity to said PFAS with a positive potential applied to the filter compared to no electrical potential applied to the filter, wherein the filter has a retention ratio for PFOS larger than 20% when the positive potential is applied.

3. The system of filtering PFAS from a sample of claim 1, wherein the first and second filters are a column.

4. The system of filtering PFAS from a sample of claim 3, wherein the first and second filters further comprise a packed bed of porous graphitic carbon particles.

5. The system of filtering PFAS from a sample of claim 4, wherein the porous graphitic carbon particles are in powder form.

6. The system of filtering PFAS from a sample of any one of claims 1-5, wherein the electrode comprises a platinum wire.

7. The system of filtering PFAS from a sample of claim 1, wherein the first and second filters are a membrane.

8. The system of filtering PFAS from a sample of claim 7, wherein the membrane comprises a self-standing membrane comprising the porous graphitic carbon particles and a polymer binder.

9. The system of filtering PFAS from a sample of any one of claims 1-8, wherein the porous graphitic carbon particles are synthesized from a metal organic framework material.

10. The system of filtering PFAS from a sample of any one of claims 1-9, wherein the first and second filters are configured to desorb said PFAS at a greater rate when the negative electrical potential is applied to the first and second filters compared to no electrical potential, wherein the first and second filters have a retention ratio larger than - 20% to PFOS when the negative electrical potential is applied.

11. A system for filtering per- and poly-fluoroalkyl substances (PFAS) from a sample, the system comprising: at least one porous graphitic carbon (PGC) filter including porous graphitic carbon particles, wherein the porous graphitic carbon particles include a specific surface area greater than 1000 m2 / g; and at least one working electrode configured to apply a positive and a negative electrical potential to the porous graphitic carbon particles.

12. The system for filtering per- and poly-fluoroalkyl substances (PFAS) from a sample of claim 11, wherein the at least one porous graphitic carbon filter comprises a first porous graphitic carbon filter and a second porous graphitic carbon filter and the at least oneworking electrode comprises a first working electrode in electrical communication with first porous graphitic carbon particles of the first porous graphitic carbon filter and a second working electrode in electrical communication with second porous graphitic carbon particles of the second porous graphitic carbon filter.

13. The system for filtering per-and poly-fluoroalky I substances (PFAS) from a sample of either one of claims 11 or 12, the system further comprising: a counter electrode in electrical communication with the at least one porous graphitic carbon filter.

14. The system for filtering per- and poly-fluoroalkyl substances (PFAS) from a sample of claim 12, wherein the first porous graphitic carbon particles include a first porosity and the second porous graphitic carbon particles include a second porosity, wherein the second porosity is less than the first porosity.

15. The system for filtering per- and poly-fluoroalkyl substances (PFAS) from a sample of claim 14, wherein the at least one porous graphitic carbon filter is a membrane, wherein the membrane comprises a polymer membrane substrate and the porous graphitic carbon particles, wherein the porous graphitic carbon particles are dispersed on the polymer membrane substrate.

16. The system for filtering per- and poly-fluoroalkyl substances (PFAS) from a sample of claim 11, wherein the at least one porous graphitic carbon filter is in the form of a selfstanding membrane including the porous graphitic carbon particles and a polymer binder, wherein the porous graphitic carbon particles are blended with the polymer binder.

17. The system for filtering per- and poly-fluoroalkyl substances (PFAS) from a sample of claim 11, wherein the at least one porous graphitic carbon filter is in the form of a column including a column body that is filled with the porous graphitic carbon particles and includes a mechanical support configured to retain the porous graphitic carbon particles within the column body.

18. The system for filtering per- and poly-fluoroalkyl substances (PFAS) from a sample of claim 11, wherein the porous graphitic carbon particles are in the form of a powder.

19. The system for filtering per- and poly-fluoroalkyl substances (PFAS) from a sample of claim 11, wherein the porous graphitic carbon particles are synthesized from a metal organic framework material.

20. The system for filtering per- and poly-fluoroalkyl substances (PFAS) from a sample of claim 19, wherein the metal organic framework material includes at least one of copper, aluminum, zirconium, zinc, hafnium or a combination thereof as metal nodes and at least one molecule containing an aromatic carbon ring.

21. The system for filtering per- and poly-fluoroalkyl substances (PFAS) from a sample of claim 20, wherein the metal organic framework material includes at least one of terephthalic acid (1,4-benzenedicarboxylate), 4,4'-biphenyl dicarboxylic acid, or 4,4' ,4", 4"'- (pyrene-l,3,6,8-tetrayl)tetrabenzoic acid as ligands.

22. The system for filtering per- and poly-fluoroalkyl substances (PFAS) from a sample of claim 11, wherein the porous graphitic carbon particles include a specific surface area greater than 1400 m2 / g.

23. The system for filtering per- and poly-fluoroalkyl substances (PFAS) from a sample of claim 22, wherein the specific surface area is approximately 1,800 m2 / g.

24. The system for filtering per- and poly-fluoroalkyl substances (PFAS) from a sample of any one of claims 11-23, wherein the positive and negative electrical potentials are in a range of greater than -1.0 and +1.0 V.

25. A method of filtering per- and poly-fluoroalkyl substances (PFAS) from a sample, the method comprising: preparing a porous graphitic carbon filter including an electrode, wherein the porous graphitic carbon filter includes porous graphitic carbon particles;applying a positive electrical potential to the electrode; filtering said sample through the porous graphitic carbon filter, wherein said sample has a first concentration of PFAS; and collecting a first permeated solution having a second concentration of PFAS, wherein the second concentration of PFAS is lower than the first concentration of PFAS.

26. The method of filtering of per- and poly-fluoroalky I substances (PFAS) from a sample of claim 25, wherein the method further comprises: filtering the same through a second porous graphitic carbon filter, wherein the second porous graphitic carbon filter includes porous graphitic carbon particles; collecting a second permeated solution having a third concentration of PFAS, wherein the third concentration of PFAS is lower than the second concentration of PFAS; and repeating filtering the sample through a plurality of porous graphitic carbon filters until the permeated solution is below a maximum contaminant level defined by the Environmental Protection Agency.

27. The method of filtering of per- and poly-fluoroalky I substances (PFAS) from a sample of claim 25, wherein the porous graphitic carbon filter is in the form of a membrane or a column.

28. The method of filtering of per- and poly-fluoroalky I substances (PFAS) from a sample of claim 27, wherein the membrane comprises a polymer membrane substrate and the porous graphitic carbon particles, wherein the porous graphitic carbon particles are dispersed on the polymer membrane substrate.

29. The method of filtering of per- and poly-fluoroalky I substances (PFAS) from a sample of claim 27, wherein the membrane comprises a self-standing membrane including the porous graphitic carbon particles and a polymer binder, wherein the porous graphitic carbon particles are blended with the polymer binder.

30. The method of filtering of per- and poly-fluoroalky I substances (PFAS) from a sample of claim 27, wherein the porous graphitic carbon filter is a column that is filled with the porous graphitic carbon particles.

31. The method of filtering of per- and poly-fluoroalky I substances (PFAS) from a sample of claim 30, wherein the porous graphitic carbon particles are in the form of a powder.

32. The method of filtering of per- and poly-fluoroalky I substances (PFAS) from a sample of claim 31, wherein the porous graphitic carbon particles are synthesized from a metal organic framework material.

33. The method of filtering of per- and poly-fluoroalky I substances (PFAS) from a sample of claim 32, wherein the metal organic framework material includes at least one of copper, aluminum, zirconium, zinc, hafnium or a combination thereof as metal nodes and at least one molecule containing an aromatic carbon ring.

34. The method of filtering of per- and poly-fluoroalky I substances (PFAS) from a sample of claim 33, wherein the metal organic framework material includes at least one of terephthalic acid (1,4-benzenedicarboxylate), 4,4'-biphenyl dicarboxylic acid, or 4,4' ,4", 4"'- (pyrene-l,3,6,8-tetrayl)tetrabenzoic acid as ligands.

35. The method of filtering of per- and poly-fluoroalky I substances (PFAS) from a sample of claim 34, wherein the porous graphitic carbon particles are produced from the metal organic framework material through a process comprising: pyrolyzing in an inert gas phase at temperatures in a range of 500 - 1000 °C to form a carbon powder; rinsing the carbon powder with one or more acids; and obtaining a pure carbon material in a graphitic phase.

36. The method of filtering of per- and poly-fluoroalky I substances (PFAS) from a sample of claim 25, wherein the porous graphitic carbon particles include a specific surface area greater than 500 m2 / g.

37. The method of filtering of per- and poly-fluoroalky I substances (PFAS) from a sample of claim 36, wherein the porous graphitic carbon particles include the specific surface area greater than 1400 m2 / g.

38. The method of filtering of per- and poly-fluoroalky I substances (PFAS) from a sample of claim 36, wherein the specific surface area is approximately 1,800 m2 / g.

39. The method of filtering of per- and poly-fluoroalky I substances (PFAS) from a sample of any one of claims 25-38, wherein the positive electrical potential is in a range of greater than 0 and +1.0 V.

40. The method of filtering of per- and poly-fluoroalky I substances (PFAS) from a sample of any one of claims 25-39, wherein a retention ratio during a step of filtering the sample is greater than 40%.

41. A method of recycling a filter saturated with per- and poly-fluoroalkyl substances (PFAS), the method comprising: obtaining a porous graphitic carbon filter saturated with PFAS; applying a negative electrical potential to an electrode, wherein the electrode is coupled to the porous graphitic carbon filter; flowing clean water through the porous graphitic carbon filter; and continuously collecting a permeate solution until the permeate solution has a concentration of PFAS below 10 ppt.

42. The method of recycling a saturated filter with per- and poly-fluoroalkyl substances (PFAS) of claim 41, wherein the negative electrical potential is in a range of less than 0 and-1.0 V.

43. The method of recycling a saturated filter with per- and poly-fluoroalkyl substances (PFAS) of claim 42, wherein the porous graphitic carbon filter is in the form of a membrane or a column.

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