Methods and systems for electrothermal fluorination for lithium recovery

Abstract

Methods and systems of electrothermal fluorination, and more particularly, methods and systems of electrothermal fluorination for lithium recovery from brine salt. The electrothermal fluorination methods and systems to selectively fluorinate brine salts can use granular activated carbon (GAC)-sorbed aqueous film-forming foam (AFFF) as a fluorinating agent. During this process, GAC and PFAS in AFFF can be converted to graphene, while fluorine atoms can be effectively mineralized into metal fluorides. Followed by washing and flash distillation, lithium can be recovered from other alkali and alkaline earth metal cations in brine (Na+, Mg2+, K+, Ca2+) in the form of lithium fluoride, with a ~99% lithium purity and ~82% yield.

Description

Attorney Docket No.: 072174-07301METHODS AND SYSTEMS FOR ELECTROTHERMAL FLUORINATION FOR LITHIUM RECOVERY CROSS-REFERENCED TO RELATED PATENT APPLICATIONS

[0001] The application claims priority to U.S. Patent Appl. Serial No. 63 / 719,902, entitled “Methods And Systems For Electrothermal Fluorination For Lithium Recovery,” filed November 13, 2024, to James M. Tour, etal.

[0002] The application is related to PCT Patent Appl. Serial No. PCT / US24 / 50478, entitled “Methods For Remediation Of PFAS-Contaminated Soil By Rapid Electrothermal Mineralization,” filed October 9, 2024, to James M. Tour, etal. (" Tour ’478 PCT Application”), claiming priority to U.S. Patent Appl. Serial No. 63 / 589,489, entitled “Methods For Remediation Of PFAS-Contaminated Soil By Rapid Electrothermal Mineralization,” filed October 11, 2023, to James Mitchell Tour, et al..

[0003] The application is related to PCT Patent Appl. Serial No. PCT / US24 / 033209, entitled “Methods Of Flash Joule Heating Per- And Polyfluorinated Alkyl Substances And Compositions Thereof,” filed June 10, 2024, to James M. Tour, et al ((‘Tour ’209 PCT Application”), claiming priority to U.S. Patent Appl. Serial No. 63 / 507,045, entitled “Methods Of Flash Joule Heating Per- And Polyfluorinated Alkyl Substances And Compositions Thereof,” filed June 8, 2023, to James M. Tour, et al.

[0004] Each of these patent applications is commonly owned by the owner of the present invention and is incorporated herein by reference.TECHNICAL FIELD

[0005] The present invention relates to methods and systems of electrothermal fluorination, and more particularly, methods and systems of electrothermal fluorination for lithium recovery from brine salt.GOVERNMENT INTEREST

[0006] This invention was made with government support under Grant No. FA9550-22-1-Attorney Docket No.: 072174-07301 0526, awarded by the United States Air Force Office of Scientific Research, and Grant No. ERDC W912HZ-21-2-0050 and W912HZ-24-2-0027, awarded by the United States Engineer Research and Development Center for the United States Army Corp of Engineers. The United States government has certain rights in the invention.BACKGROUND

[0007] The worldwide pursuit of sustainable energy sources drives the urgent lithium demand for efficient and high-capacity energy storage. [Semieniuk 2021; Yu 2022; Baars 2021; Choubey 2016\. However, the lithium production rate was only -0.24 million tonnes in 2024, which lags far behind the rapidly growing demand, proj ected to be -3.5 million tonnes in 2035. Therefore, it is imperative to develop a promising method for sustainable lithium production and supply.

[0008] Traditional lithium supply from ore mining is energetically and chemically intensive, and faces the challenges of depleting reserves of lithium ores. [Kesler 2012,' Yang 2018}. Seawater contains more than three orders of magnitude lithium quantities than the lithium sources on land [Yang 2018], but the low lithium concentration (<0.2 ppm) renders it impractical for efficient extraction [Diallo 2015}. In contrast, brine, with high lithium concentrations (>1000 ppm), has emerged as an attractive alternative source for lithium extraction. [Choubey 2016,' Chen 2023,' Khalil 2022}.

[0009] During the lithium extraction from brine, the primary objective is to separate Li+from other coexisting cations, such as Na+, K+, Mg2+, and Ca2+. Currently, industrial lithium recovery from brine predominantly relies on an evaporation-precipitation process. [Amoatey 2021], This method is cost-effective using solar energy, but it often requires extensive land and takes years to complete multiple evaporation, concentration, precipitation, and filtration steps for lithium recovery. [Flexer 2018,' Swain 2017], Other methods, including adsorption [Zhang 2010,' Baird 2024], membrane sieving [Zhang Y 2024; ZhangS 2024; Song 2024], electrodialysis [Xu 2024;Attorney Docket No.: 072174-07301 Li 2024\, and solvent extraction [Shi 20 / 7 Zhang 2022], exhibit a much faster lithium recovery rate, even from low lithium-concentration sources. However, these methods are often limited by excessive solvent consumption, limited scalability, high costs, and / or secondary pollution. Furthermore, some methods are only applicable to separate Li+ from specific cations in brine, thereby rendering impure lithium products [Zhang 2022,' Sun 2021],

[0010] Considering the similar properties of different metal chlorides in brine salts, selectively exchanging chloride into other anions, like fluoride, is promising for lithium separation. Traditional fluorination metallurgical methods often rely on hydrogen fluoride (HF) as the fluorination agent [Guo 2027; Rosales 2017,' Rosales 2014], which is toxic and corrosive to the reactor. Additionally, the excessive emission of fluorine-containing gases can lead to secondary pollution. Per- and polyfluoroalkyl substances (PFAS) are a series of fluorine-containing persistent organic pollutants, which pose significant environmental concerns due to their bioaccumulation and toxicity. [Evich 2022,' Gltige 2020], It is estimated that ~0.3 million tonnes of PFAS are released into the environment globally every year [Evich 2022,' Ankley 2021], triggering an urgent demand for its management.

[0011] Granular activated carbon (GAC) is the most widely used sorbent for PFAS removal. In the United States alone, the annual generation of PFAS-laden spent GAC (PFAS / GAC) is estimated to be -0.2 million tonnes. [Jafarinejad 2025], Even though substantial efforts have been made to degrade PFAS over the past decades [Xiao 2020,' Alinezhad 2023,' Yang 2023,' Guan 2024], the effective defluorination of PFAS, especially the PFAS mixture in the complex organic matrices, like aqueous film-forming foam (AFFF), remains challenging.

[0012] Moreover, the potential for utilizing fluorine sources in PFAS has often been overlooked. Considering its unique structure with multiple fluorine atoms on its carbon chain and the abundant waste sources of PFAS / GAC, these PFAS wastes represent a promising opportunity to be repurposed as effective fluorination agents.Attorney Docket No.: 072174-07301SUMMARY OF THE INVENTION

[0013] The present invention relates to methods and systems of electrothermal fluorination, and more particularly, methods and systems of electrothermal fluorination for lithium recovery from brine salt.

[0014] The present invention can feature electrothermal fluorination methods and systems to selectively fluorinate brine salts that use granular activated carbon (GAC)-sorbed aqueous filmforming foam (AFFF) as a fluorinating agent. During this process, GAC and PF AS in AFFF can be converted to graphene, while fluorine atoms can be effectively mineralized into metal fluorides. Followed by washing and flash distillation, lithium can be recovered from other alkali and alkaline earth metal cations in brine (Na+, Mg2+, K+, Ca2+) in the form of lithium fluoride, with a -99% lithium purity and -82% yield.

[0015] In general, in one embodiment, the invention features a method that includes selecting a mixture including lithium-containing brine and a fluorination agent. The method further includes generating lithium fluoride from the mixture using electrothermal fluorination (ETF).

[0016] Implementations of the invention can include one or more of the following features:

[0017] The fluorination agent can be selected from the group consisting of ammonium fluoride, ammonium bifluoride, per- or polyfluorinated alkyl substances (PF AS), aqueous film forming foam (AFFF), polytetrafluoroethylene (PTFE), poly(vinylidene difluoride) (PVDF), fluorinated ethylene propylene (FEP), ethylene-tetrafluoroethylene (ETFE), polytrifluorochloroethylene (PCTFE), SFe, XeFe, hydrofluorocarbon (HFC) refrigerants, refrigerants comprising one or more fluorine atoms, and mixtures and combinations thereof.

[0018] The fluorination agent can include ammonium fluoride.

[0019] The fluorination agent can be selected from the group consisting of per- or polyfluorinated alkyl substances (PF AS).

[0020] The fluorination agent can be an aqueous film-forming foam (AFFF).Attorney Docket No.: 072174-07301

[0021] The fluorination agent can include granular activated carbon (GAC) and the sorbed aqueous film-forming foam (AFFF).

[0022] The method can selectively recover the fluorine from non-fluorine alkali and earth metal cations in the form of lithium fluoride.

[0023] The selective recovery of the lithium fluoride can have at least an 80% lithium purity and at least a 60% yield.

[0024] The lithium fluoride can have at least 95% lithium purity and at least a 70% yield.

[0025] The method can further include, after the mixture is electrothermally fluorinated to form a fluorinated-brine salt mixture, washing the fluorinated-brine salt mixture to separate NaCl and KC1 from the fluorinated-brine salt mixture. The method can further include, after the step of washing, distilling the washed fluorinated-brine salt mixture to separate MgF2 and CaF2 from the washed fluorinated-brine salt mixture. The method can further include collecting the lithium fluoride from the distilled and washed fluorinated-brine salt mixture.

[0026] The step of distilling can further separate graphene and from the washed fluorinated-brine salt mixture.

[0027] The step of distilling further can separate carbon residues other than graphene from the washed fluorinated-brine salt mixture.

[0028] Flash Joule heating can be used in the step of distillation.

[0029] A first flash Joule heating can be used to electrothermally fluorinate the mixture.

[0030] A second flash Joule heating can be used in the step of distillation.

[0031] Flash Joule heating can be used to electrothermally fluorinate the mixture.

[0032] In general, in another embodiment, the invention features a method that includes selecting a mixture including an alkali metal and / or alkali earth metal cations-containing mixture and a fluorination agent. The method further includes separating the metal and / or alkali earth metal from the mixture using electrothermal fluorination (ETF).Attorney Docket No.: 072174-07301

[0033] Implementations of the invention can include one or more of the following features:

[0034] The alkali metal / alkali earth metal cations can be selected from the group consisting of Na, K, Mg, Ca, and Li.

[0035] The method can include that at least some of the alkali metal and / or alkali earth metal cations do not form a metal fluoride during the ETF.

[0036] The method can include, after the ETF, performing a washing step to separate the alkali-metal and / or alkali earth metal cations from fluorinated materials resulting from the ETF.

[0037] The ETF can form a metal fluoride including the alkali-metal and / or alkali earth metal cations separated from the mixture.

[0038] The method can include, after the ETF, performing a washing step to separate nonfluorinated materials resulting from the ETF. The method can include, after the washing step, performing a distilling step to separate at least some of the alkali and / or alkali earth-metal from the remaining fluorinated materials resulting from the ETF.

[0039] The distillation step can include a flash distillation process.

[0040] The separation can be integrated with a process selected from the group consisting of solvent extraction, ion exchange, adsorption, membrane filtration, cryogenic distillation, and thermal condensation to yield purified metals.

[0041] The mixture can be a waste stream selected from the group consisting of brine, industrial wastewater, geothermal brine, battery black mass, metallurgical slag, fly ash, clay minerals, tailings, electronic wastes, and combinations thereof.

[0042] The step of separating the metal and / or alkali earth metal from the mixture using ETF can separate a target metal species selected from the group consisting of Li, Na, K, Al, Mg, Ca, Ba, Sr, Mn, Co, Ni, Cu, Ga, Ge, Zr, Nb, Mo, Ag, Sn, Sb, rare earth elements, actinides, and combinations thereof.

[0043] The ETF can yield a fluorinated material selected from the group consisting of reactiveAttorney Docket No.: 072174-07301 fluorometallates (MxFy-), volatile metal fluorides, insoluble metal fluorides conducive to downstream separation, and combinations thereof.

[0044] The fluorinated material can include volatile metal fluorides selected from the group consisting of MFe, MF 4, MF3, and combinations thereof.

[0045] The fluorinated material can include insoluble metal fluorides selected from the group consisting of MF2, MFn, and combinations thereof.

[0046] In general, in another embodiment, the invention features a system to perform any of the above-described methods.

[0047] Implementations of the invention can include one or more of the following features:

[0048] The system can include a first source including a lithium-containing brine. The system can further include a second source including a fluorination agent. The system can further include a mixer operatively connected to the first source and second source and operable for mixing the lithium-containing brine and the fluorination agent to form a mixture. The system can further include an electrothermal fluorination (ETF) device that is operable to generate lithium fluoride from the mixture.

[0049] The electrothermal fluorination (ETF) device can be operable to form a fluorinated-brine salt mixture from the mixture.

[0050] The ETF device can be operable to perform a flash Joule heating process.

[0051] The system can further include a washer operatively connected to the ETF device. The washer can be operable to wash the fluorinated-brine salt mixture to separate NaCl and KC1 from the fluorinated-brine salt mixture.

[0052] The system can further include a distiller operatively connected to the washer. The distiller is operable to separate MgF2 and CaF2 from the washed fluorinated-brine salt mixture.

[0053] The distiller can be operable to perform a flash Joule heating process.

[0054] The system can further include a collector operatively connected to the distiller. TheAttorney Docket No.: 072174-07301 collector is operable for collecting the lithium fluoride from the distilled and washed fluorinated-brine salt mixture.BRIEF DESCRIPTION OF THE DRAWINGS

[0055] FIGS. 1A-1H show PF AS-assisted electrothermal fluorination of brine salt for Li recovery. FIG. 1A shows Gibbs free energy change (AG) of the conversion from each metal chloride to the corresponding metal fluoride with C2F6 under different temperatures. FIG. IB shows a protocol for the Li recovery from brine. FIG. 1C shows pictures of the sample before and during ETF. FIG. ID shows a real-time temperature curve recorded by an infrared thermometer with a detecting range of 200 °C to 1500 °C. FIG. IE shows relationship between electric heating peak temperature and input voltages. FIG. IF shows relative contents of total fluorine, mineralized fluorine ion, and organic fluorine in fluorinated products varied with input voltages. FIG. 1G shows removal efficiencies of different kinds of PF AS in AFFF after the fluorination under the input voltage of 100 V. FIG. 1H shows relative amount of generated volatile organic fluorinated compounds (VOF) with and without brine salts under the input voltage of 100 V. The error bars in FIGS. 1E-1G are the standard deviation (SD) of 3 parallel experiments (n = 3). Data are presented as mean values + / - SD.

[0056] FIGS.2A-2D show aqueous washing for lithium separation from NaCl in Li / Na binary salts. FIG. 2A shows water solubility of each salt component in the fluorinated brine salt at 25 °C. FIG.2B shows XRD patterns of fluorinated products of NaCl / LiCl with the Na / Li mole ratio of 20. FIG. 2C shows Li purity and yield using different washing agents with the Na / Li mole ratio of 20. FIG.2D shows Li yield versus input Na / Li mole ratio using different washing agents. The error bars in FIGS. 2C-2D are the standard deviation (SD) of 3 parallel experiments (n = 3). Data are presented as mean values + / - SD.

[0057] FIGS.3A-3F shows flash distillation for lithium separation from MgF2 in Li / Mg binary salts. FIG.3A shows vapor pressure-temperature relationship of different metal fluorides. FIG.Attorney Docket No.: 072174-07301 3B shows XRD patterns of fluorinated products of MgCh / LiCl with the Mg / Li mole ratio of 2.FIG. 3C shows distillation temperature under different current input settings. FIG. 3D shows Li purity and yield under different current input settings, and an inset picture of LiF obtained.FIG. 3E shows elemental content percentages in the precursors, fluorinated products, and the residue and volatile after distillation with a current input setting of 20 for 10 s. FIG. 3F shows Li purity and yield with different input ratios of Mg / Li. The error bars in FIGS.3C-3D and 3F are the standard deviation (SD) of 3 parallel experiments (n = 3). Data are presented as mean values + / - SD.

[0058] FIGS. 4A-4I show Li recovery from brine salts. FIG. 4 A shows XRD patterns of fluorinated brine salt products. FIG. 4B shows elemental content percentages of brine salt, fluorinated brine salt, supernatant, and precipitate after dissolving, residue, and volatile after distillation. FIG. 4C shows elemental content percentages of concentrated brine salt (C-brine salt), fluorinated C-brine salt, supernatant, and precipitate after dissolving, residue, and volatile after distillation. FIG. 4D shows Li purity and yield with different concentration factors. FIG.4E shows comparison of Li recovery purity and yield using different fluorination agents. FIG.4F shows XPS full spectra of recovered LiF. FIG. 4G shows XRD patterns of recovered LiF FIG. 4H shows an SEM image of recovered LiF particle with cubic structure. FIG. 41 shows a high-resolution TEM image of recovered LiF after inverse fast Fourier transform (IFFT) processing. The error bars in FIGS. 4D-4E are the standard deviation (SD) of 3 experiments (n = 3). Data are presented as mean values + / - SD.

[0059] FIGS. 5A-5G show application of LiF in the electrolytes of LIBs. FIG. 5A shows pictures of electrolytes with different amounts of LiF after storage for 1 month at room temperature in the glovebox (~0.5 ppm oxygen content). FIG. 5B shows19F NMR spectra of different electrolytes. FIG. 5C shows voltage-time curves of Li||Li symmetrical cells at a cycling rate of 1 mA cm2using the electrolytes with 0.2 M LiF and without LiF. FIG. 5DAttorney Docket No.: 072174-07301 shows cycling stability of NMC532 half-cell at 0.2 C using the electrolyte with 0.2 M LiF and without LiF. FIG. 5E shows Nyquist plots of NMC532 half cells using the electrolytes with and without LiF. FIG.5F shows comparison of Li+diffusion coefficients ofNMC532 half-cell using electrolytes with and without LiF. FIG. 5G shows Li+diffusion coefficient of NMC532 half-cell using electrolytes with and without LiF by GITT.

[0060] FIGS. 6A-6B show morphology of the surface of Li chip in Li||Li symmetric cells after cycling for 100 cycles. FIG. 6A shows the surface using the electrolyte without LiF. FIG. 6B shows the surface after using the electrolyte with LiF.

[0061] FIGS. 7A-7E show LCA and TEA for 1 kg Li recovery from brine. FIG. 7A shows cumulative energy demand (CED) distribution. FIG. 7B shows global warming potential (GWP) in CO2 equivalent distribution for different scenarios. FIG. 7C shows water resource depletion (WRD) distribution. FIGS.7D-7E show, respectively, (D) profit comparison and (E) comprehensive comparisons between different lithium recovery methods.

[0062] FIGS. 8A-8C show elemental content percentages of during flash fluorination separation process. FIG.8A shows R410a as the fluorination agent. FIG. 8B shows CF4 as the fluorination agent. FIG. 8C shows Li purity and yield using different fluorination agent.DETAILED DESCRIPTION

[0063] The present invention relates to methods and systems of electrothermal fluorination, and more particularly, methods and systems of electrothermal fluorination for lithium recovery from brine salt.

[0064] Considering its unique structure with multiple fluorine atoms on its carbon chain, PF AS presents a promising opportunity to be used as an effective fluorination agent. Electrothermal heating has emerged as an advanced method for waste management [Cheng 12024,' Dong 2023,' Cui 202T, Chen 2024,' Cheng 2025] and environmental remediations \Cheng II 2024,' Yu 2023,' Sun 2023,' Scotland 2025] offering ultrafast heating and cooling, rapid processing, high energyAttorney Docket No.: 072174-07301 efficiency, and precise temperature control [Chen 20 / 6 Dong 2022,' Jiang 2027],

[0065] Compared with other PFAS / GAC management technologies such as incineration and regeneration [Gagliano 202J, Abou-Khalil 2024}, electrothermal heating lowers energy demand by 5-50 times, and decreases greenhouse gas emissions by 5-27%. [Scotland 2025}.

[0066] When coupled with fluorination using metal cations, the organic fluorine can be mineralized into non-toxic fluoride ions with negligible formation of secondary organic fluorinated pollutants. [Scotland 2025}.

[0067] Electrothermal fluorination (ETF) methods and systems of the present invention have been discovered to recover lithium from brine salts using granular activated carbon absorbed AFFF (AFFF / GAC) as a fluorinating agent, i.e., embodiments of the present invention can simultaneously degrade waste field-collected AFFF pollutants and recover lithium from brine salts. By employing GAC-sorbed AFFF (AFFF / GAC) as the fluorinating agent, nearly all organofluorine atoms in AFFF can be mineralized into nontoxic metal fluorides in a sealed system after ETF. By virtue of the strong C-F bonds in PFAS and the precise temperature control during the ETF process, specific metal cations in brine salts, such as Li+, Mg2+, and Ca2+, have been selectively fluorinated, whereas Na+and K+remained in their chloride forms. Subsequent washing and flash distillation enables the rapid recovery of lithium fluoride (LiF) with both high purity and yield. The recovered LiF was an effective additive to mitigate electrolyte acidification and solid electrolyte interphase (SEI) degradation in lithium-ion batteries (LIBs), thereby enhancing battery performance. Thus, the ETF methods and systems not only upcycles persistent PFAS contaminants into value-added fluoride materials but also enables selective lithium extraction from complex brine resources, which offers a sustainable way to integrate environmental remediation with resource circularity.Electrothermal fluorination (ETF) By Waste AFFF

[0068] Thermodynamic calculations can be for the fluorination reactions of each componentAttorney Docket No.: 072174-07301 in brine salts. C2F6 was selected as the computational fluorination agent, serving as a representative fragment for high-temperature PF AS decomposition products. [Wang 2015, Xiao 2O2O]50’51. The fluorination reaction was calculated based on Equation (1).MClx + X / 6C2F6 = MFx + X / 2C12+ x / 3 C ( 1 )

[0069] Thermodynamic analysis indicated a broad temperature range, from 200 °C to 1600 °C, where Li, Mg, and Ca can be selectively fluorinated while Na and K remain as metal chlorides.FIG. 1A (with plots 101-105, for LiCl, NaCl, MgCh, KC1, and CaCh, respectively, with horizontal dashed line 106 denoting AG = 0 kJ mol'1).

[0070] Subsequently, the differences in physical properties among each component in fluorinated brine salts (F-brine salt) enable the separation of LiF through additional aqueous washing and a flash distillation process. As shown in FIG. IB, the whole process includes three steps: fluorination 113, washing 116, and distillation 120. During the fluorination process 113 (a flash fluorination process utilizing brine salt 111 and granular activated carbon absorbed AFFF (AFFF / GAC 112) as a fluorinating agent) produces F-brine salt 114 having Li+, Mg2+, and Ca2+are fluorinated, while Na+and K+remain in chloride forms. F-brine salt denotes the fluorinated brine salt, which consists of LiF, MgF2, CaF2, NaCl, and KC1. After washing 116 (which removes NaCl 117 and KC1 118) such as by using a solution 115 of 0.2 M NFLF, the insoluble fluorides (MgF2122, CaF2123, and LiF 124 with graphene 121 from the flash process) are collected and the target product, LiF, is then separated by electric distillation (such as by a flash distillation). “Gr” in FIG. IB denotes graphene.

[0071] For example, PF AS was sorbed from field-collected AFFF pollutants using GAC, where the concentrations of each PF AS in the field-collected AFFF are listed in TABLE I.Attorney Docket No.: 072174-07301TABLE IConcentrations of Different PEAS in the Field Collected AFFF Used HereinPF AS concentrations were tested using liquid chromatography-mass spectrometry (LC-MS) utilizing an Agilent 1290 Infinity II LC system coupled to an Agilent 6495C triple quadrupole mass spectrometer operated in negative electrospray ionization mode with multiple reaction monitoring.

[0072] After adsorption by GAC, the concentration of each PF AS in AFFF was reduced by >99.5%, the solution pH approached neutrality, and the total dissolved organic carbon (TOC) decreased by >99.8%. Total F loading content on GAC was -10.5 wt% tested by combustion ion chromatography (CIC). The mass percentages of cations in the brine used here are listed in TABLE II, with 1.18 wt% Li, 72.11 wt% Na, 18.83 wt% K, 7.55 wt% Mg, and 0.33 wt% Ca.TABLE IIMass Percentage Of Different Cations In Salar de Atacama Brine Source In Chile And Artificial Brine SaltsThe cation ratios in Salar de Atacama brine source were obtained from An 2012. Mass % of different cations in brine salts and the concentrated brine salts were tested by ICP-OES.Attorney Docket No.: 072174-07301

[0073] The electrothermal fluorination (ETF) process was then applied to fluorinate the brine salt after mixing it with AFFF / GAC. GAC served as the AFFF sorbent and conductive additive, while AFFF acted as the fluorination agent. The entire process was carried out in an O-ring sealed system to prevent Li evaporation loss and ensure complete use of the F sources. See FIG. 1C (shows pictures 131-132 of the sample before and during ETF, respectively). The two O-rings on each side were used to avoid the emission of fluorocarbon gas and facilitate PFAS mineralization. A spring coiled around the quartz tube was used to increase the mechanical integrity of the tube reactor.

[0074] The ETF system that was used was similar to systems as described in the Tour ’478 PCT Application and the Tour ’09 PCT Application). Five metal chloride salts (LiCl, NaCl, KC1, MgCh, and CaCh) were selectively mixed with the required ratios and the ground using a planetary ball miller (MSE Supplies, PMV1-0.4L) for 2 h to ensure uniform mixing. The salts were then mixed with fluorination regents with 10% mole F excess and ground by mortar and pestle for 30 min. The F content in AFFF / GAC was determined by CIC, and metal cations in the brine salts were quantified by ICP-OES. TABLE II. For the electrothermal fluorination, 100 mg metallurgical coke (metcoke) was added to the 200 mg brine salts and solid -state fluorination agents, such as PTFE, PVDF, NFLF, to ensure the required conductivity, which was then loaded into a quartz tube with an inner diameter (ID) of 8 mm and outer diameter (OD) of 12 mm. For the AFFF / GAC as the fluorination agent, metal salts were directly mixed with AFFF / GAC with 10% mole excess F and a total mass of 300 mg per batch.

[0075] During the reaction, two graphite rods were fixed on each side of the quartz tube as the separators to avoid contamination from the metal electrodes. The tube was mounted on a homemade reaction jig and connected to the external ETF power system. The two brass electrodes with double O-rings on each side were applied to compress and seal the sample inside the tube to minimize the evaporation loss of Li precursors and ensure a completeAttorney Docket No.: 072174-07301mineralization of all F-contained compounds. A spring coiled around the surface of the tube was used to enhance the tube mechanical integrity and prevent pressure-induced breakage during electric heating.

[0076] During the fluorination process, the jig was placed in a vacuum desiccator under the ~10 mm Hg vacuum and then connected to the power system. The capacitor bank (60 mF) was charged by an AC supply and output a DC pulse. The maximal voltage of the capacitor bank can reach 400 V. The relay with programmable delay time with millisecond controllability was applied to control the discharging time. The input voltage was modulated from 0 to 150 V, and the discharging time was regularly set as 1 s. The reaction temperature was recorded using two infrared thermometers. A low-temperature thermometer (Micro-Epsilon, CTM-3SF75H2-C3) was used to measure temperature in the range of 200-1500 °C. A high-temperature thermometer (Micro-Epsilon, CTRM-1H1SF100-C3) was used to measure the temperature in the range of 1000-3000 °C. The energy consumption during the electrothermal process was measured by a power meter (Atorch AC Wattmeter, Amazon). The thermometers are connected to Lab VIEW using a Multifunction I / O (NI USB-6009) for real-time temperature recording with a time resolution of 0.1 ms. After fluorination, the samples rapidly cooled to room temperature and were collected for further analysis. The detailed conditions are listed in TABLE III TABLE IIIReaction Conditions For The Electrothermal FluorinationAttorney Docket No.: 072174-07301

[0077] Note: *Mass 1 is the input mass of precursor salts. **Mass 2 is the input mass of the fluorination agent. ***C-Brine salt is the concentrated brine salt. ****For the sample using PTFE or NH4F as the fluorinated regent, 100 mg metcoke was added as the conductive additive. *****AFF / GAC is the AFFF-loaded granular activated carbon.

[0078] For the larger sample, a mixture of brine salt (~3.5 g) and AFFF / GAC (~8.5 g) was loaded into a quartz tube with ID of 1.6 cm and OD of 2.0 cm. A programmable power supply (TDK Lambda GENESYS 125-80), with a rated power of 10 kW, was used as the power source, where the threshold voltage and current were set as 125 V and 80 A, respectively. The fluorination duration time was set to 20 s. For the further enlarged sample, a mixture of brine salts (~17 g) and AFFF / GAC (~43 g) was loaded into a quartz tube with ID of 50 mm and OD of 55 mm. Fluorination was conducted by the same system with a duration time of 20 s. The concentration of each cation content was measured before and after the fluorination process.

[0079] During ETF, a high-voltage pulse applied in 1 s rapidly heated the sample mixture toAttorney Docket No.: 072174-07301 temperatures of >1000 °C, with ultrafast heating (~104°C s'1) and cooling rates (~103°C s'1).FIG. ID. By regulating the input voltage, the heating temperature was precisely modulated within a wide range from 400 °C to 2000 °C (FIG. IE), which can meet the temperature requirement for PFAS mineralization and metal fluorination (FIG. 1A).

[0080] To show the feasibility and ability of AFFF for selective fluorination, different types of metal chloride were separately mixed with AFFF / GAC. After ETF treatment, LiCl, MgCh, and CaCh were selectively fluorinated with an input voltage of 100 V. Then, brine salts were mixed with AFFF / GAC with 10% mole excess F and proceeded with fluorination. With the increase of input voltage, the organofluorine concentration progressively decreased with an increased F' concentration due to higher reaction temperatures. FIG. IF (with plots 151-152 for total F, F ion, and organic F, respectively). The F content was normalized to the initial total F content in the mixed precursor. The total F content was tested by CIC, and F' content was tested by IC.

[0081] The removal efficiency of >99.9% was achieved using AFFF with a total F mineralization ratio of 91%. FIGS. 1F-1G.19F nuclear magnetic resonance (NMR) spectra revealed that multiple PFAS peaks turned into a single peak at -128 ppm, corresponding to hydrated fluoride ions. [Camdzic 2021], Besides, during the fluorination process, PFAS-degraded gaseous fluorocarbon species were reduced by >99.9%, compared to directly heating AFFF / GAC without any brine salts. FIG. 1H (showing brine salts provide >99.9% fluoride mineralization.).

[0082] This indicated that the cations in brine salts facilitated PFAS mineralization, minimizing the emission of secondary pollutant gases. The simultaneous PFAS degradation and selective salt fluorination were further confirmed by X-ray diffraction (XRD) patterns and X-ray photoelectron spectroscopy (XPS) spectra. Meanwhile, amorphous GAC was converted into crystalline and more valuable turbostratic graphene with distinct TSi and TS2 peaks in Raman spectra. The specific surface area of GAC decreased substantially by >90% after theAttorney Docket No.: 072174-07301electrothermal treatment, leading to a reduced capacity to re-adsorb PF AS. Aside from AFFF, other fluorine-contained compounds, such as polytetrafluoroethylene (PTFE) and ammonia fluoride (NFUF), can also serve as the fluorination agents during the ETF process, selectively fluorinating Li, Mg, and Ca in brine salts.Aqueous Washing For Li / Na Binary Salt Separation

[0083] After fluorination (flash fluorination step 113 as shown in FIG. IB), the main components of F-brine salt can be divided into two categories: fluorinated salts, including LiF, MgF2, and CaF2, and non-fluorinated metal chlorides, including NaCl and KC1. The latter have much higher water solubility than the fluorinated salts (FIG. 2A; TABLE IV), enabling the removal of Na and K impurities through a simple water washing step.TABLE IVSolubility And Solubility Product Constant ( sp) OfThese data were collected from HSC Chemistry 10 software.

[0084] For example, for aqueous washing, -500 mg of fluorinated product was washed in the washing agent (water or NFLF solution) 3 times. Each time, 1 mL washing solution was added to the samples with an ultrasonic treatment (DUC- 1002-00, CREWORKS) for 10 min to ensure the complete dissolution of NaCl and / or KC1. The precipitate, including the metal fluoride (LiF, MgF2, and CaF2) and residue carbon, was filtrated and dried in the oven at 100 °C for 2 h.

[0085] To simulate the conditions in brine, NaCl and LiCl was mixed with a mole ratio of 20: 1, respectively. Following the ETF process, Li was selectively fluorinated into LiF, while NaClAttorney Docket No.: 072174-07301 remained. FIG.2B (with powder diffraction files for (i) graphene 211 (denoted as Gr) 00-056-0159, (ii) NaCl 212, 00-005-0628, and (iii) LiF 213, 01-088-2298). Then, the fluorinated salt mixture was washed with water.

[0086] To balance the Li yield and purity, the water-to-salt ratio was kept at 5. Even though -96% of Li purity was achieved, the Li yield was only -66% (FIG. 2C with bars 221-222 for purity and yield, respectively), which indicated a substantial amount of Li dissolution loss during the washing process.

[0087] Based on Le Chatelier ’s principle, introducing F’ into washing agents can reduce the dissolution loss of LiF. (According to Ze Chatelier ’s principle, introducing F’ into the washing agent decreases the dissolution of LiF while ensuring the complete dissolution of NaCl; however, a high concentration of F’ may lead to the precipitation of NaF prior to NaCl, since Ksp(NaF) is much lower than Ksp(NaCl)). Experimentally, 0.2 M NFLF was used to replace water as the washing agent, resulting in an increase in Li yield to 86% with a purity of 99%.FIG. 2C. After drying the washing supernatants, and calcinating the dried salts to remove NH4F, the main component was NaCl with no LiF signals, indicating negligible LiF loss during the washing step.

[0088] It was demonstrated that introducing NFLF in the washing agent consistently improved Li yield compared to using only water with the input Na / Li mole ratios from 1 to 50. FIG. 2D (with plots 231-233 for water, 0.1 M F’, and 0.2 M F’, respectively).

[0089] Similarly, for the Li / K separation, KC1 and LiCl were initially mixed with a mole ratio of 10:1, respectively. After ETF, Li was converted into LiF, while KC1 remained unchanged. To ensure the Li recovery yield, 0.2 M NFLF solution was also applied as the washing agent, increasing the Li recovery to 99% purity and 87% yield, compared to the results by water washing (99% purity but 68% yield). This indicated that the aqueous washing process can effectively separate LiF from both NaCl and KC1 in the Li / Na and Li / K binary system after theAttorney Docket No.: 072174-07301 selective fluorination.Flash Distillation For Li / Mg Binary Salt Separation

[0090] After removing Na and K compounds (washing step 116 as shown in FIG. IB), the next step is to separate LiF from MgF2 and CaF2 (flash distillation step 120 as shown in FIG. IB). Considering that the boiling points of MgF2 (2260 °C) and CaF2 (2533 °C) are much higher than that of LiF (1676 °C), LiF can be distilled from MgF2 and CaF2 in a wide temperature range of -600 °C (1676 °C to 2260 °C). FIG.3A (with plots 301-305 for Lif, NaF, MgF2, KF, and CaF2, respectively, and horizontal dash line 306 denoting atmospheric pressure of -105Pa).

[0091] For the Li / Mg separation, MgCh and LiCl were mixed with a mole ratio of 2:1, respectively, similar to the Mg / Li ratio in brine. After fluorination, both Mg and Li were converted into fluorides. FIG.3B (with powder diffraction files for (i) graphene 311 (denoted as Gr) 00-056-0159, (ii) MgF2312, 01-072-2231, and (iii) LiF 313, 01-088-2298). Benefitting from previous experience with metal separation by high-temperature evaporation [Deng 202 Deng 2024], a flash distillation setup was built to separate LiF from MgF2 and CaF2 based on their boiling points differences. During the process, the precipitate mixture from the previous washing step was heated through a current input, whereupon, LiF evaporated, transported, and finally condensed in a collection tube. A commercial arc welder was used as the power source to provide a constant current input. The current profile was measured with different input settings during the flash process by a Hall effect sensor (Tamura L34S1T2D15) through a custom Lab VIEW program. With the current setting from 10 to 30, the measured current remained stable throughout the 10 sec output duration, with minimal fluctuation (<10%). A linear calibration curve was established between the setting value and the actual output current, described by the equation (2):Attorney Docket No.: 072174-07301 / = 0.83x+ 5.82 (2)where I is the measured current, and x is the current setting.

[0092] The high correlation coefficient (R2= 0.999) confirmed excellent linearity, demonstrating that the arc welder system provided predictable and consistent current levels across the tested range. The output current was recorded with the current settings changed from 10 to 30, remaining stable throughout the 10-second duration with minimal fluctuation (<10%). With a continuous current input, a steady temperature was maintained for 10 sec with a low temperature variation of ~5%. By adjusting the input current setting from 10 to 30, the temperature can be modulated from -1400 to -2500 °C (FIG. 3C, line 321), which can meet the requirements for LiF distillation. In FIG. 3C, horizontal dash lines from 322-324 denote the boiling points of LiF, MgF2, and CaF2, respectively. The shaded region 325 (between horizontal dash lines 322-323 represents the desirable distillation temperature for LiF evaporation.

[0093] The impact of current input on Li purity and yield was investigated by modulating the input current setting from 15 to 30. Generally, increasing the current improved the Li recovery yield due to the more complete distillation under the elevated temperature. However, the Li purity decreased when the current setting exceeded 20, which can be ascribed to the concomitant distillation of MgF2. FIG. 3D (with plots 331-332 for purity and yield, respectively; the current input setting was determined by reading the setting displayed on the screen of the arc welder). Inset 333 of FIG.3D is a picture of the LiF obtained. The optimized result exhibited 99% purity and 90% yield of Li in the volatiles with the current input setting of 20 and a short heating time of -10 sec. FIG. 3E (with bars 341-342 for Mg and Li, respectively).

[0094] XRD patterns and XPS spectra confirmed the residues consisted of graphene and MgF2, without any LiF signals, which indicated the complete distillation of LiF. When increasing theAttorney Docket No.: 072174-07301 input Mg / Li mole ratio up to 10:1 and conducting the fluorination and distillation, 97% purity and 79% yield of Li recovery was also achieved. FIG. 3F (with plots 351-352 for purity and yield, respectively). Constructions with more plates can enable a more effective separation.

[0095] Using the same process, Li / Ca separation was conducted with an initial Li / Ca mole ratio of 1. After fluorination, LiF was distilled from the fluorinated compounds under different current inputs. Even though a higher Li yield of -95% was achieved under the current setting of 25, an input current setting of 20 was selected to meet the optimal parameters for Li / Mg separation, leading to 97% purity and 93% yield of Li. Even when increasing the input Ca / Li mole ratio to 10, 93% purity and 83% yield of Li were achieved. This demonstrated that LiF was efficiently separated from MgF2 and CaF2 through a simple distillation step.

[0096] Generally, for the above-described flash distillation, 500 mg of precipitate after the dissolving step were loaded into a quartz tube with an ID of 8 mm and an OD of 12 mm. Copper wool was used as the porous electrode on one side to facilitate the gas diffusion, while a graphite rod served as the electrode on the other side of the quartz tube. The tube was loaded on a homemade reaction jig, and two brass electrodes with two O-rings on each side were applied to compress the samples. One hollow electrode was connected to the copper wool side, and the other solid electrode was connected to the graphite side. A glass vessel with a diameter of 1 inch and a volume of -40 mL was used as the cold trap. A mechanical pump was employed to evacuate the vessel. During the electric distillation, a commercial arc welder (DEKOPRO, 110 / 220 V) was used as the power source. The current input setting was determined by reading the setting displayed on the screen of the arc welder. The current profile with different input settings during the process was recorded by a Hall effect sensor (Tamura L34S1T2D15) through a custom Lab VIEW program. The heating temperature was controlled by modulating the input voltage and was measured using the high-temperature infrared thermometer (MicroEpsilon, CTRM-1H1SF100-C3) with a detecting range of 1000-3000 °C. The energyAttorney Docket No.: 072174-07301consumption during the electrothermal process was measured by a power meter (Atorch AC Wattmeter, Amazon). After the distillation, the apparatus was allowed to cool to room temperature, and the total volatiles and residues were collected for further digestion and ICP measurement. The detailed conditions are listed in TABLE V.TABLE VReaction Conditions Of The Electrothermal Distillation For Li Recovery

[0097] Note: * The precursor salts in this step include LiF, MgF2, and CaF2 after the former treatments. **t-metcoke is the treated metcoke. t-GAC is the treated GAC. The salt / t-metcoke contains 35.5 wt% of salts, while the salt / t-GAC sample contains 22.8 wt% of salt. ***The Li yield is only considered in this step.Li Recovery From Brine Salts

[0098] After successfully showing Li separation from individual binary salt mixtures containing alkali or alkaline-earth metal cations, the process for lithium recovery was extended from complex brine salt mixtures. This involved sequential steps of fluorination, aqueous washing, and distillation. FIG. 4A (with powder diffraction files for (i) LiF 401, 01-088-2298, (ii) KCL 402, 00-001-0786, (iii) NaCl 403, 00-005-0628, (iv) CaF2404, 01-086-2987, and (iii) MgF2405, 01-072-2231). This allowed for the recovery of Li products from brine with a 96% purity. FIG. 4B (with bars 411-415 for Ca, K, Mg, Na, and Li, respectively). However, since Li constitutes only 1.18 wt% of the brine, a significant Li loss occurred during the processes,Attorney Docket No.: 072174-07301 leading to a low yield of 55%. FIG. 4B.

[0099] In view of the results of the industrial Li extraction process, a similar concentration step for Li concentration was adopted. Experimentally, the brine salts were dissolved in a small amount of water, where LiCl completely dissolved due to its low proportion, while some of NaCl, MgCh, and KC1 remained undissolved. After removing the precipitates by filtration, and drying, the concentrated salt (termed as “C-brine salt”) was obtained. By modulating the salt-to-water mass ratio (defined as concentration factor), it was determined that an optimal Li concentration of 11% can be obtained in the C-brine salts with a concentration factor of 5.TABLE II

[0100] C-brine salt was then used as the precursor, followed by the same fluorination, washing, and distillation steps. With a concentration factor of 5, 82% yield and 99% Li purity were achieved. FIG. 4C (with bars 421-425 for Ca, K, Mg, Na, and Li, respectively). Increasing the concentration factor improved both Li recovery yield and purity, owing to a higher Li concentration in the C-brine salts. FIG. 4D (with plots 431-432 for purity and yield, respectively). For FIG. 4D, the concentration factor ( ) was calculated by the mass ratio of brine salts and water, where Cf = 0 indicates the original brine salts without concentrating in water.

[0101] Other fluorination agents, such as NFLF and PTFE, were tried for the Li recovery from C-brine salt. Both facilitated a >98% purity and >75% yield of Li (FIG. 4E, with bars 441-442 for purity and yield, respectively), which provides feasible alternatives for Li recovery through fluorination.

[0102] During the fluorination process, the capacitor-based electrothermal system was more energy-efficient. However, for the distillation process, the arc welder system was more effective for LiF evaporation, as it could maintain more stable heating conditions over longer periods of time.Attorney Docket No.: 072174-07301

[0103] Further characterizations were conducted to assess the purity of the recovered LiF. XPS and ion chromatography (IC) data revealed that the anion changed from CF to F’ during the recovery process, with no Cl signals detected in the final volatile product, confirming the fluorination efficiency of Li. FIG. 4F. XRD patterns revealed the only phase of LiF without other impurities. FIG. 4G (with powder diffraction files LiF, 01-088-2298). The cubic structure (FIG. 4H) and the periodical atomic arrangement (FIG. 41) confirmed the high crystallinity of the recovered LiF particle.

[0104] The ETF process also demonstrated good scalability. Using a programmable power supply as the second-generation fluorination power source, 12 g of precursors was reacted per batch using a 16-mm diameter reactor. Following subsequent washing and distillation steps, a 77% yield and 98% purity of Li was achieved. Scaling up to a 50-mm diameter reactor, 60 g of mixed brine salt and AFFF / GAC precursors were processed per batch. Following washing and distillation, lithium was recovered from brine salt with 95% purity and 74% yield under unoptimized conditions. Further theoretical analysis indicated that scaling up can be further achieved by increasing the reactor size and input energy, while the energy consumption required to recover 1 kg of Li can be simultaneously reduced. TABLES VI- VII.TABLE VIEnergy Consumption In The Fluorination Step At Different Scales* Sample mass includes the mass of brine salts and the mass fluorination agents (AFFF / GAC).TABLE VIIEnergy Consumption In The Fluorination Step At Different Scales* Sample mass includes the mass of brine salts and the mass fluorination agents (AFFF / GAC).Attorney Docket No.: 072174-07301

[0105] Moreover, this electrothermal process has been scaled up for graphene synthesis to > 1 tonne day'1in a pilot facility. This capability can be readily adapted for large-scale Li recovery.Application Of Recovered Lif In The Battery Electrolytes

[0106] LiF, with its high Li+diffusion efficiency, electrical insulation, and mechanical properties, can be a significant component for forming a robust and fast-ion-transport SEI in LIBs to prevent Li dendrite formation and facilitate Li migration. [Fan 2024,' Ramasubramanian 2019], Here, recovered LiF was incorporated into the electrolyte. After one month in the glove box, the blank electrolyte without LiF turned dark red. FIG. 5A (pictures of electrolytes 501-504 with 0, 0.05 M, 0.1 M, and 0.2 M, of LiF, respectively, after storage for 1 month at room temperature in the glovebox (~0.5 ppm oxygen content).

[0107] 19F and31P NMR spectra showed the formation of phosphorus oxide, which was attributed to the LiPFe decomposition. FIG. 5B (spectra 511-514 for 0, 0.05 M, 0.1 M, and 0.2 M, of LiF, respectively, with F2P2O2' peaks 515 shown for spectra 511).

[0108] However, the recovered LiF reduced the electrolyte contrast change with a decreased amount of degraded F2P2O2' FIGS. 5A-5B. This occurs because LiF shifts the following equilibrium (equation 3) toward the left and mitigates electrolyte acidification.LiPFe LiF + PFs (3)

[0109] Considering the limited solubility of LiF in the electrolyte, the LiF concentration was kept at 0.2 M. Higher concentrations led to undissolved LiF. The contrast of electrolyte remained unchanged, and negligible F2P2O2' signals in NMR spectra were detected after one month. FIGS. 5A-5B.

[0110] To evaluate the electrolyte performance, Li||Li symmetrical cells were assembled using electrolytes with and without LiF. The Li||Li symmetric cell was assembled in coin cells (CR2032) inside the glove box. Two lithium chips (D = 16 mm, t = 0.6 mm, 99.9 wt%, MTIAttorney Docket No.: 072174-07301 Corporation) were used as the electrodes with a polypropylene separator with AI2O3 coating (~26 pm, SH416W14, SENIOR Inc.). The electrolyte volume in each coin cell was set as 50 pL to fully wet the electrode and separator. Each symmetric cell was cycled using a battery testing station (CT2001A, LANHE Corporation, China) at 0.1, 0.2, and 0.5 mA cm2for 3, 3, and 4 cycles, respectively, before cycling at 1.0 mA cm2for another 100 cycles.

[0111] The increase of LiF concentration in electrolyte afforded lower impendence, improved long-term cyclability (-300 h), and a reduced overpotential (-60 mV) of the cell at 1 mA cm2, especially when compared to the blank electrolyte. FIG. 5C (with plots 521-522 with and without LiF, respectively).

[0112] After cycling, Li dendrites were observed on the surface of Li electrode without LiF additive, while the Li electrode with LiF exhibited a more compact and nearly dendrite-free SEI film, highlighting the benefits of recovered LiF in SEI formation. FIGS. 6A-6B. Dashed circles 601-603 in FIG. 6A show the formed lithium dendrites after cycling.

[0113] Afterward, these two electrolytes were paired with a LiNi0.5Mn0.3Co0.2 (NMC532) cathode. For the NMC532||Li cell, commercial NMC532 (Xiamen Aot Electronics Technology Co., Ltd., China), conductive carbon black (MSE PRO super P, MSE Supplies) and poly(vinyl difluoride) (PVDF, MTI Corporation) were mixed and ground with a mass ratio of 8: 1 : 1, while l-methyl-2-pyrrolidinone (NMP, 99.5 wt%, Millipore-Sigma) with -2.5 times of total mass was added to prepare a homogeneous slurry. The slurry was coated onto an 18-pm-thick carbon-coated aluminum (Al / C) foil by a doctor blade with blade spacing of 250 pm, and dried by a built-in heating cover at 65 °C for 2 h, followed by drying in a vacuum oven at 70 °C under vacuum (-10 mmHg) overnight. During battery assembly, a lithium chip was used as the counter electrode with a polypropylene separator with AI2O3 coating (-26 pm, SH416W14, SENIOR Inc.). The cathode area was -1.54 cm2, and the average areal mass loading of the active materials was -7 mg cm’2(1 C = 1.6 mAh). The added volume of each electrolyte wasAttorney Docket No.: 072174-07301 set as 50 pL. Each cell was cycled in the potential range between 3.0 to 4.3 V at 0.05 C and 0.1 C for 5 cycles, respectively, before cycling at 0.2 C for stability tests.

[0114] After 300 cycles at 0.2 C, the LiF-added NMC532 cell showed higher capacity retention (127 mAh g'1) in the potential range of 3.0 V to 4.3 V, compared to the blank cell (82 mAh g’1.FIG. 5D with plots 531-532 for specific capacity with LiF and without LiF, respectively, and with plots 533-534 for coulombic efficiency with LiF and without LiF, respectively). (Each half cell was cycled at 0.05 C and 0.1 C for 5 cycles, respectively, before cycling at 0.2 C.)

[0115] When increasing the cycling rate, the LiF-added cell maintained a higher capacity of 99 mAh g'1than the blank cell (87 mAh g'1) at 2 C. After returning the cycling rate to 0.2 C, the capacity of the LiF-added cell remained at 144 mAh g’1, whereas the capacity of the blank cell decayed to 129 mAh g’1. The Li electrode showed a higher LiF signal in F 15 XPS spectra compared to the blank after cycling, demonstrating the incorporation of LiF into the SEI. Thus, a lower impendence was observed in the LiF-added cell by electrochemical impedance spectroscopy (EIS), indicating an improved charge transfer after introducing LiF. FIG. 5E (with plots 541-542 for with LiF and without LiF, respectively).

[0116] Meanwhile, the Li+diffusion coefficient was improved, as confirmed by cyclic voltammetry (CV, FIG. 5F with plots 551-552 for with LiF and without LiF, respectively) and the galvanostatic intermittent titration technique (GITT, FIG. 5G with plots 541-542 for with LiF and without LiF, respectively) results. These findings revealed that fluorinated-recovered LiF is a promising additive to stabilize electrolytes and improve LIB performance.Life-Cycle Assessment And Techno-Economic Analysis

[0117] A comparative cradle-to-gate life cycle assessment (LCA) was conducted to evaluate the environmental impacts and energy demand of the ETF process, where two different fluorination agents, AFFF / GAC and NFLF, were considered. Industrial evaporation followed by precipitation process, and membrane sorption process were chosen as representatives LiAttorney Docket No.: 072174-07301 recovery processes for the comparison. The functional unit was defined as the selective recovery of 1 kg of Li-contained products. Monte Carlo simulations were used for sensitivity analysis.

[0118] The cumulative energy demand (CED) for ETF using AFFF / GAC was calculated to be -460 MJ kg'1of Li, which is 53% and 72% lower than commercial sorption and precipitation methods, respectively. FIG.7A (with plots 701-704 for ETF by AFFF, ETF by NFLF, sorption, and precipitation, respectively). The global warming potential (GWP) of ETF using AFFF / GAC was estimated to be -37 kg of CO2 equivalent per kg of Li, which are 20% and 72% lower than sorption and precipitation methods, respectively. FIG.7B (with plots 711-714 for ETF by AFFF, ETF by NFLF, sorption, and precipitation, respectively). Furthermore, the ETF process demonstrated much lower water resource depletion (WRD) by nearly 100* compared to other methods. FIG. 7C (with plots 721-724 for ETF by AFFF, ETF by NFLF, sorption, and precipitation, respectively). Compared to using NFLF as the fluorination agent, using AFFF / GAC for the ETF process showed much lower environmental impacts, offering a more sustainable option for Li recovery.

[0119] To assess the economic feasibility, a techno-economic analysis (TEA) was conducted to compare the cost and profitability of these processes. (The weight of Li recovery was only for Li and does not include the weight of the counterions). The ETF process using AFFF / GAC was projected to have a low operating cost of $3.50 kg'1of Li, exhibiting 87-89% reduction compared to sorption and precipitation processes. Considering that LiF has a 2* higher market value than lithium carbonate, and GAC was converted into more valuable graphene during the process, ETF can realize a higher profit of -$582 kg'1of Li products, which is nearly 5 times higher than other processes. FIG. 7D (with plots 731-734 for ETF by AFFF, ETF by NH4F, sorption, and precipitation, respectively).

[0120] Benefitting from the low environmental impact, reduced costs, and shorter processingAttorney Docket No.: 072174-07301 time (FIG.7E, with areas 741-744 for ETF by AFFF, ETF by NFUF, sorption, and precipitation, respectively), the ETF process shows promise for a sustainable Li recovery for a low-carbon-footprint industry, while using the toxic waste materials, PF AS, as the active component for fluorination.Further Fluorinating Agents and Processes

[0121] Alternative to PFAS, other F-contained compounds, such as gaseous hydrofluorocarbon (HFC) refrigerant can be used as the fluorination agents. For example, R-410a refrigerant and pure CF4 gas were used as the fluorinating agent. See FIG. 8A (for 410a refrigerant with bars 801-805 for Ca, K, Mg, Na, and Li, respectively); FIG. 8B (for pure CF4 with bars 811-815 for Ca, K, Mg, Na, and Li, respectively). Both realized lithium recovery ratio of >75% and purity of >96%. FIG. 8C (with bars 821-822 for purity and yield, respectively).

[0122] Thus, the flash fluorination methods and systems described herein can use different fluorination sources, such as waste PFAS, PTFE, PVDF, inorganics (such as NFLF, NH4HF2), gaseous (CF4, SFe, CH2F2, hydrofluorocarbon (HFC) refrigerant).

[0123] Moreover, the flash fluorination methods and systems described herein can not only separate lithium from brine but can also extend to other metal separations.Advantages and Usage

[0124] For the lithium recovery from brine salts by electrothermal fluorination (ETF) method, advantages and uses include: (i) per- and poly-fluoroalkyl substances (PFAS) pollutants can be effectively used as the fluorination agent, which can be mineralized into nontoxic metal fluorides during the process, mitigating its environmental impacts; (ii) the temperature in these processes can be precisely modulated, where certain metal compounds can be selectively fluorinated; (iii) different kinds F’ containing compounds can be used in these processes, including organic fluorine compounds, inorganic fluoride salts, and absorbed PFAS pollutant;Attorney Docket No.: 072174-07301 and (iv) ETF treatment is time- and energy-saving for lithium extraction from brine, especially compared with the traditional evaporation-precipitation process, which needs extensive land and lasts for years.

[0125] While embodiments of the invention have been shown and described, modifications thereof can be made by one skilled in the art without departing from the spirit and teachings of the invention. The embodiments described and the examples provided herein are exemplary only, and are not intended to be limiting. Many variations and modifications of the invention disclosed herein are possible and are within the scope of the invention. The scope of protection is not limited by the description set out above, but is only limited by the claims which follow, that scope including all equivalents of the subject matter of the claims.

[0126] The disclosures of all patents, patent applications, and publications cited herein are hereby incorporated herein by reference in their entirety, to the extent that they provide exemplary, procedural, or other details supplementary to those set forth herein.

[0127] Amounts and other numerical data may be presented herein in a range format. It is to be understood that such range format is used merely for convenience and brevity and should be interpreted flexibly to include not only the numerical values explicitly recited as the limits of the range, but also to include all the individual numerical values or sub-ranges encompassed within that range as if each numerical value and sub-range is explicitly recited. For example, a numerical range of approximately 1 to approximately 4.5 should be interpreted to include not only the explicitly recited limits of 1 to approximately 4.5, but also to include individual numerals such as 2, 3, 4, and sub-ranges such as 1 to 3, 2 to 4, etc. The same principle applies to ranges reciting only one numerical value, such as “less than approximately 4.5,” which should be interpreted to include all of the above-recited values and ranges. Further, such an interpretation should apply regardless of the breadth of the range or the characteristic being described.Attorney Docket No.: 072174-07301

[0128] Unless defined otherwise, all technical and scientific terms used herein have the same meaning as commonly understood to one of ordinary skill in the art to which the presently disclosed subject matter belongs. Although any methods, devices, and materials similar or equivalent to those described herein can be used in the practice or testing of the presently disclosed subject matter, representative methods, devices, and materials are now described.

[0129] Following long-standing patent law convention, the terms “a” and “an” mean “one or more” when used in this application, including the claims.

[0130] Unless otherwise indicated, all numbers expressing quantities of ingredients, reaction conditions, and so forth used in the specification and claims are to be understood as being modified in all instances by the term “about.” Accordingly, unless indicated to the contrary, the numerical parameters set forth in this specification and attached claims are approximations that can vary depending upon the desired properties sought to be obtained by the presently disclosed subject matter.

[0131] As used herein, the term “about” and “substantially” when referring to a value or to an amount of mass, weight, time, volume, concentration or percentage is meant to encompass variations of in some embodiments ±20%, in some embodiments ±10%, in some embodiments ±5%, in some embodiments ±1%, in some embodiments ±0.5%, and in some embodiments ±0.1% from the specified amount, as such variations are appropriate to perform the disclosed method.

[0132] As used herein, the term “substantially perpendicular” and “substantially parallel” is meant to encompass variations of in some embodiments within ±10° of the perpendicular and parallel directions, respectively, in some embodiments within ±5° of the perpendicular and parallel directions, respectively, in some embodiments within ±1° of the perpendicular and parallel directions, respectively, and in some embodiments within ±0.5° of the perpendicular and parallel directions, respectively.Attorney Docket No.: 072174-07301

[0133] As used herein, the term “and / or” when used in the context of a listing of entities, refers to the entities being present singly or in combination. Thus, for example, the phrase “A, B, C, and / or D” includes A, B, C, and D individually, but also includes any and all combinations and subcombinations of A, B, C, and D.REFERENCES

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[0135] Alinezhad, A., et al., “Mechanistic investigations of thermal decomposition of perfluoroalkyl ether carboxylic acids and short-chain perfluoroalkyl carboxylic acids,” Environ. Sci. Technol., 2023, 57, 8796- 8807 (‘Alinezhad 2023”).

[0136] Amoatey, P., etal., “A critical review of environmental and public health impacts from the activities of evaporation ponds,” Sci. Total Environ. , 2021, 796, 149065 (' Amoatey 202 T" ).

[0137] An, J. W ., etal., “Recovery of lithium from Uyuni salar brine,” Hydrometallurgy, 2012, 117, 64-70 (‘An 2012”).

[0138] Ankley, G. T., et al., “Assessing the ecological risks of per- and polyfluoroalkyl substances: Current state-of-the science and a proposed path forward,” Environ. Toxicol. Chem., 2021, 40, 564-605 (‘Ankley 2021”).

[0139] Baars, J., et aL, “Circular economy strategies for electric vehicle batteries reduce reliance on raw materials,” Nat. Sustain., 2021, 4, 71-79 (‘Baars 2021”).

[0140] Baird, M. A., et al., “Microporous Polymer Sorbents for Direct Lithium Extraction,” ACS Energy Lett., 2014, 9, 4361-4368 (‘Baird 2024”).

[0141] Camdzic, D., et al., “Total and class-specific analysis of per-and polyfluoroalkyl substances in environmental samples using nuclear magnetic resonance spectroscopy,” J. Hazard. Mater. Lett., 2021, 2, 100023 (‘Camdzic 2021”).Attorney Docket No.: 072174-07301

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Claims

Attorney Docket No.: 072174-07301 WHAT IS CLAIMED IS:

1. A method compri sing :(a) selecting a mixture comprising lithium-containing brine and a fluorination agent;(b) generating lithium fluoride from the mixture using electrothermal fluorination (ETF).

2. The method of Claim 1, wherein the fluorination agent is selected from the group consisting of ammonium fluoride, ammonium bifluoride, per- or polyfluorinated alkyl substances (PF AS), aqueous film forming foam (AFFF), polytetrafluoroethylene (PTFE), poly(vinylidene difluoride) (PVDF), fluorinated ethylene propylene (FEP), ethylene-tetrafluoroethylene (ETFE), polytrifluorochloroethylene (PCTFE), SFe, XeFe, hydrofluorocarbon (HFC) refrigerants, refrigerants comprising one or more fluorine atoms, and mixtures and combinations thereof.

3. The method of Claim 1, wherein the fluorination agent comprises ammonium fluoride.

4. The method of Claim 1, wherein the fluorination agent is selected from the group consisting of per- or polyfluorinated alkyl substances (PFAS).

5. The method of Claim 2, wherein the fluorination agent is an aqueous film-forming foam (AFFF).

6. The method of Claim 4, wherein the fluorination agent comprises granular activatedAttorney Docket No.: 072174-07301 carbon (GAC) and the sorbed aqueous film-forming foam (AFFF).

7. The method of Claim 1, wherein the method selectively recovers the fluorine from nonfluorine alkali and earth metal cations in the form of lithium fluoride.

8. The method of Claim 7, wherein the selective recovery of the lithium fluoride has at least an 80% lithium purity and at least a 60% yield.

9. The method of Claim 1, wherein the method further comprises:(a) after the mixture is electrothermally fluorinated to form a fluorinated-brine salt mixture, washing the fluorinated-brine salt mixture to separate NaCl and KC1 from the fluorinated-brine salt mixture;(b) after the step of washing, distilling the washed fluorinated-brine salt mixture to separate MgF? and CaF2 from the washed fluorinated-brine salt mixture; and (c) collecting the lithium fluoride from the distilled and washed fluorinated-brine salt mixture.

10. The method of Claim 10, wherein flash Joule heating is used in the step of distillation.

11. The method of Claim 10, wherein a first flash Joule heating is used to electrothermally fluorinate the mixture.

12. The method of Claim 1, wherein flash Joule heating is used to electrothermally fluorinate the mixture.Attorney Docket No.: 072174-07301 13. A method compri sing :(a) selecting a mixture comprising an alkali metal and / or alkali earth metal cations- containing mixture and a fluorination agent;(b) separating the metal and / or alkali earth metal from the mixture using electrothermal fluorination (ETF).

14. The method of Claim 13, wherein the alkali metal / alkali earth metal cations are selected from the group consisting of Na, K, Mg, Ca, and Li.

15. The method of Claim 13, wherein the ETF forms a metal fluoride comprising the alkali-metal and / or alkali earth metal cations separated from the mixture.

16. The method of Claim 13, separation is integrated with a process selected from the group consisting of solvent extraction, ion exchange, adsorption, membrane filtration, cryogenic distillation, and thermal condensation to yield purified metals.

17. The method of Claim 13, wherein the mixture is a waste stream selected from the group consisting of brine, industrial wastewater, geothermal brine, battery black mass, metallurgical slag, fly ash, clay minerals, tailings, electronic wastes, and combinations thereof.

18. The method of Claim 13, wherein the step of separating the metal and / or alkali earth metal from the mixture using ETF separates a target metal species selected from the group consisting of Li, Na, K, Al, Mg, Ca, Ba, Sr, Mn, Co, Ni, Cu, Ga, Ge, Zr, Nb, Mo, Ag, Sn, Sb, rare earth elements, actinides, and combinations thereof.Attorney Docket No.: 072174-07301 19. The method of Claim 13, wherein the ETF yields a fluorinated material selected from the group consisting of reactive fluorometallates (MxFy-), volatile metal fluorides, insoluble metal fluorides conducive to downstream separation, and combinations thereof.

20. A system that performs the method of Claim 1.

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