Conversion of fluorocarbons to inorganic fluoride and carbon dioxide and related compositions of matter

Abstract

Described herein is a method for chemically breaking down per- and polyfluoroalkyl substances (PFAs), whereby to convert the PFAs to products that are more friendly to the environment than are per- and polyfluoroalkyl substances. Also described are compositions containing PFAs and components that under the conditions described herein effect such breakdown, as well as an apparatus that can be used to effect the chemical transformation.

Description

[0001] CONVERSION OF FLUOROCARBONS TO INORGANIC FLUORIDE AND

[0002] CARBON DIOXIDE AND RELATED COMPOSITIONS OF MATTER

[0003] Related Applications

[0004] This Application claims priority under Paris Convention Article IV from, and the benefit under 35 U.S.C. 120 of, U.S. provisional patent application serial no. 63 / 638,785, filed 25 April, 2024 and U.S. provisional patent application serial no. 63 / 793,765, filed April 24, 2025. The contents of both of the aforesaid applications are incorporated herein by reference.

[0005] Background

[0006] Per- and poly-fluoroalkyl substances (PFAS) find broad use in automotive, semiconductor, manufacturing, and energy production industries. However, the large number of C-F bonds make PFAS highly resistant to natural degradation after discard, leading to their accumulation in the environment over time. Perfluorooctanoic acid, (PFOA), one of the most common PFAS, is of particular concern because of adverse human health effects. It is present at significant concentrations in both industrial and consumer products, including in nonstick cookware, firefighting foams, and textiles.

[0007] Concerns regarding this environmental stability have arisen as more extensive research has been conducted into PFAS toxicity. PFOA has been detected in up to 95% of the U.S. human population. Studies have generally linked PFOA exposure to liver, kidney, and testicular cancer, thyroid disease and related issues, decreases in fertility, and increased adipose tissue in children. Because of these potential health risks, and the massive global bioaccumulation occurring both within humans and the ambient environment, the development of ex situ PFOA degradation methods has significantly increased in recent years.

[0008] Harsh conditions are often necessary to destroy PFOA as a result of the strength of its many C-F bonds. Industrially, PFOA has been degraded using incineration at high temperature (650-1000°C) in the presence of hydrocarbons, producing primarily HF and CO2. However, incineration produces hazardous and volatile shorter-chain PFAS byproducts, and often does not even completely eliminate the initial PFOA. This can lead to environmental pollution through leachate and ash disposal. Non-incineration PFOA degradation methods have been developed recently, but these often employ complex organometallic photocatalysts and / or electrochemistry. At laboratory scale, various combinations of electrochemistry, advanced oxidation processes (including ozonation), and sonication have previously been employed to degrade PFOA, among other techniques. Common pitfalls of such methods include high costs, high energy input requirements and high temperatures, use of toxic metals, and production of smaller-chain PFAS byproducts. Photochemical methods are being introduced as milder alternatives to these processes.

[0009] Brief Statement of the Invention

[0010] There is provided, in accordance with an embodiment of the invention, a composition of matter comprising a mixture containing (a) at least one bromine-containing compound, and (b) at least one per- or polyfluoroalkyl substance (PFAS). In some embodiments, the composition of matter further comprises sulfuric acid (H2SO4) and manganese oxide (MnCh). In some embodiments, the weight ratio of MnCh to the total amount of carbon in the at least one perfluoroalkyl substance is at least 8 to 1.

[0011] In some embodiments, the at least one bromine-containing compound comprises elemental bromine (Bn). In some embodiments, the weight ratio of Bn to the at least one PFAS is at least 0.8: 1. In some embodiments, the weight ratio of Bn to said at least one PFAS is at least 1 : 1. In some embodiments, the weight ratio of Bn to said at least one PFAS is in the range of 1 : 1 to 5 : 1.

[0012] In some embodiments, the bromine-containing compound comprises NaBr. In some embodiments, the composition also comprises MnCh, and the weight ratio of the MnCh to said NaBr is at least 1 : 1. In some embodiments, the weight ratio of NaBr to the at least one PFAS is at least 1 : 1. In some embodiments, the weight ratio of NaBr to the at least one PFAS is in the range of 1 : 1 to 3 : 1.

[0013] In some embodiments, the composition comprises H2SO4, and the weight ratio of said H2SO4 to the other components of the composition is in the range of 1 : 1 to 100: 1. In some embodiments, the weight ratio of said H2SO4 to the other components of the composition is in the range of 5: 1 to 10: 1.

[0014] In some embodiments, the at least one PFAS comprises perfluorooctanoic acid (PFOA, C8F15O2H). In some embodiments, the at least one PFAS comprises polytetrafluoroethylene (PTFE, (-C2F4-)n). In some embodiments, the at least one PFAS comprises both PFOA and PTFE. There is also provided, in accordance with an embodiment of the invention, a composition of matter comprising sulfuric acid (H2SO4), manganese oxide (MnCh), at least one per- or polyfluoroalkyl substance (PFAS), and a substance that contains bromine atoms. In some embodiments, the weight ratio of MnCh to the total amount of carbon in said at least one perfluoroalkyl substance is at least 8 to 1. In some embodiments, the substance that contains bromine atoms is elemental bromine (Bn). In some embodiments, the weight ratio of Bn to the at least one PFAS is at least 0.8: 1. In some embodiments, the weight ratio of Bn to the at least one PFAS is at least 1 : 1. In some embodiments, the weight ratio of Bn to the at least one PF AS is in the range of 1 : 1 to 5 : 1. In some embodiments, the substance that contains bromine atoms is NaBr. In some embodiments, the weight ratio of the MnCh to the NaBr is at least 1 : 1. In some embodiments, the weight ratio of the NaBr to the at least one PFAS is at least 1 : 1. In some embodiments, the weight ratio of the NaBr to the at least one PFAS is in the range of 1 : 1 to 3 : 1. In some embodiments, the weight ratio of said H2SO4 to the other components of the composition is in the range of 1 : 1 to 100: 1. In some embodiments, the weight ratio of said H2SO4 to the other components of the composition is in the range of 5: 1 to 10: 1. In some embodiments, the at least one PFAS comprises perfluorooctanoic acid (PFOA, CsFisChH). In some embodiments, the at least one PFAS comprises poly-tetrafluoroethylene (PTFE). In some embodiments, the at least one PFAS substance comprises both PFOA and PTFE.

[0015] In accordance with some embodiments, the composition further comprises at least one of C3HF5 and C3H3F5. In some embodiments, the composition further comprises at least one of MnF4, MnF2Br2 and MnF3Br.

[0016] In accordance with some embodiments, the composition further comprises at least one of hexafluorosilicic acid (EESiFe) and hydrofluoric acid (HF).

[0017] There is also provided, in accordance with an embodiment of the invention, a vessel having disposed therein a composition of matter as described above, wherein at least a portion the composition is disposed in a portion of said vessel that is transparent to light of wavelengths 300-800 nm. In some embodiments, the said portion of said vessel that is transparent to light of wavelengths 300-800 nm is transparent to sunlight. There is also provided, in accordance with an embodiment of the invention, a process for chemically decomposing per- and polyfluoroalkyl substances, comprising illuminating a mixture containing at least one per- or polyfluoroalkyl substance (PF AS) and Bn with light. In some embodiments, the light comprises focused sunlight. In some embodiments, the at least one PF AS includes perfluorooctanoic acid (PFOA, CsFisCEH). In some embodiments, the at least one PF AS includes poly-tetrafluoroethylene (PTFE). In some embodiments, the at least one PF AS includes both PFOA and PTFE. In some embodiments, the mixture further comprises sulfuric acid (H2SO4) and manganese oxide (Mn02). In some embodiments, the weight ratio of Mn02 to the total amount of carbon in said at least one perfluoroalkyl substance is at least 8 to 1. In some embodiments, the weight ratio of Bn to the at least one PFAS is at least 0.8: 1. In some embodiments, the weight ratio of Bn to said at least one PFAS is at least 1 : 1. In some embodiments, the weight ratio of Bn to said at least one PFAS is in the range of 1 : 1 to 5 : 1. In some embodiments, the Bn is generated in situ from a bromine-containing compound. In some embodiments, the bromine-containing compound is NaBr. In some embodiments, the weight ratio of said MnCh to said NaBr is at least 1 : 1. In some embodiments, the weight ratio of said NaBr to said at least one PFAS is at least 1 : 1. In some embodiments, the weight ratio of said NaBr to said at least one PFAS is in the range of 1 : 1 to 3 : 1. In some embodiments, the weight ratio of said H2SO4 to the other components of the composition is in the range of 1 : 1 to 100: 1. In some embodiments, the weight ratio of said H2SO4 to the other components of the composition is in the range of 5:1 to 10: 1.

[0018] There is also provided, in accordance with an embodiment of the invention, a process for photochemically converting a per- or polyfluoroalkyl substance (PFAS) and MnChto gaseous CO2 and a solution containing at least one of (1) hexafluorosilicic acid (EESiFe) and (2) hydrofluoric acid (HF) in liquid H2SO4, by illuminating a mixture containing said PFAS, sulfuric acid (H2SO4), said manganese oxide (MnCh), and sodium bromide (NaBr) in the presence of silica or a silica-based glass. In some embodiments, the illuminating is achieved by focusing sunlight on the mixture. In some embodiments, the PFAS comprises perfluorooctanoic acid (PFOA, C8F15O2H). In some embodiments, the PFAS comprises polytetrafluoroethylene (PTFE). In some embodiments, the PFAS comprises both PFOA and PTFE. In some embodiments, the weight ratio of Mn02 to the total amount of carbon in said at least one perfluoroalkyl substance is at least 8 to 1. In some embodiments, the weight ratio of the bromine atoms in said NaBr to the at least one PFAS is at least 0.8: 1. In some embodiments, the weight ratio of the bromine atoms in said NaBr to said at least one PFAS is at least 1 : 1. In some embodiments, the weight ratio of bromine atoms in said NaBr to said at least one PF AS is in the range of 1 : 1 to 5 : 1. In some embodiments, the weight ratio of said MnCh to said NaBr is at least 1 : 1. In some embodiments, the weight ratio of said NaBr to said at least one PFAS is at least 1 : 1. In some embodiments, the weight ratio of said NaBr to said at least one PFAS is in the range of 1 : 1 to 3 : 1. In some embodiments, the weight ratio of said H2SO4 to the other components of the composition is in the range of 1 : 1 to 100: 1. In some embodiments, the weight ratio of said H2SO4 to the other components of the composition is in the range of 5:1 to 10: 1.

[0019] In the context of the present patent application, we adopt the definition of “per- and polyfluoroalkyl substances” set forth by the U.S. Environmental Protection Agency in document no. 2022-23963 (87 FR 68060), published 14 November 2022, viz. herein the expression “per- or polyfluoroalkyl substance” (PFAS) refers to chemicals that contain at least one the following three structures:

[0020] (1) R-(CF2)-CF(R')R", where both the CF2 and CF moieties are saturated carbons, and none of the R groups can be hydrogen;

[0021] (2) R-CF2OCF2-R', where both the CF2 moieties are saturated carbons, and none of the R groups can be hydrogen.

[0022] (3) CF3C(CF3)RR', where all the carbons are saturated, and none of the R groups can be hydrogen.

[0023] Brief Description of the Drawings

[0024] Aspects of the invention will be explained below, and will be better understood, with reference to the drawings, in which:

[0025] Fig. 1 shows a photographic comparison of the appearance of two sample ampoules;

[0026] Fig. 2 shows19F NMR spectra, measured in deuterated chloroform (CDCI3), of unreacted PFOA (top) vs. the organic-soluble residue collected after a period of photoreaction (bottom); Fig. 3 shows FTIR spectra of the gases released upon breaking open the photoreaction ampoule shown in Fig. 1, and of 1, 2, and 4 mL injections of 100% CO2;

[0027] Fig. 4 shows an X-ray powder diffraction (XPRD) plot for a precipitate collected from a reaction ampoule;

[0028] Fig. 5 displays19F NMR spectra for water (D2O) extracts of the condensed phases from closed-ampoule photoreactions; Fig. 6 shows19F NMR spectra of two samples prepared for use as standards for comparison. Fig. 7 shows an apparatus for holding photoreaction ampoules at the focal point of an inexpensive solar concentrator;

[0029] Fig. 8shows one type of receiving apparatus for measuring the volume of gases evolved during the photoreaction; and

[0030] Fig. 8shows preliminary LC-MS analysis of the headspace gases collected from the gas trapping apparatus shown in Fig. 8.

[0031] It will be appreciated that despite the prevalence of color drawings and photographs in the scientific literature and the ease of presentation of such in electronic format, PCT rules remain mired in the 19th century and still do not permit the filing of color drawings or photographs. Therefore, although the present figures are being filed with this PCT application as color drawings, they are being converted by WIPO’s software to black and white drawings. However, the original drawings are in color and were filed as such in the aforesaid US provisional application serial number 63 / 793,765, filed April 24, 2025, which is incorporated herein by reference, and once the present application is published, that provisional application, including the color drawings therein, will be available via the USPTO. It will be noted that present Figs. 7, 8, 9 correspond respectively to Figs. S-l, S-2 and S-3 of the aforesaid US provisional application serial number 63 / 793,765. Additionally, to aid in making the color drawings publicly available, the plots or photographs shown in Figs. 1, 3, 4, 6, 7, 8 and 9 have been uploaded to a publicly-available picture sharing service, Shutterfly, and can be accessed over the internet by anyone using the link https: / / link.shutterfly.com / h5zzYBGUQSb; the link is being shared for the first time with the filing of this patent application, and the color photographs are incorporated herein by reference.

[0032] Detailed Discussion

[0033] We disclose herein a photochemical method of decomposing perfluoroalkyl substances (PFAS) using manganese dioxide (MnCh) as oxidant, sulfuric acid (H2SO4) as solvent, and bromine (either provided as Bn or generated in situ, e.g. from NaBr) as photocatalyst, for example inside transparent silica-based containers. We have found that this combination of reactants can degrade PFOA and even PTFE photolytically under focused solar irradiation. Substitution of less-hazardous NaBr for liquid Bn is possible because MnCh rapidly oxidizes Br" to Bn in situ in concentrated H2SO4. Without wishing to be bound by theory, it is hypothesized that Bn is reduced during perfluorocarbon degradation (oxidation), cyclically re-forming Bf.

[0034] The reagents and apparatus to carry out this degradation are inexpensive and readily obtained, especially because NaBr can be substituted for pure Bn as the sole source of bromine. Our results demonstrate the ability to degrade PFOAin a simple, controlled manner at lower temperatures than current industrial methods. The same products were obtained when polytetrafluoroethylene (PTFE) was substituted for PFOA as well, suggesting this process can potentially be used to degrade a wide range of PFAS.

[0035] Experimental

[0036] Sample preparation. Samples were prepared in borosilicate glass ampoules and weighed accurately to 0.1 mg before and after addition of each reagent. After addition of the solid reagents, the ampoule was cooled to dry ice temperature, H2SO4 was added, the ampoule quickly re-weighed to ~10 mg accuracy, and then the ampoule was immediately recooled on dry ice to prevent the oxidation of Br" ions to Bn before the ampoule was sealed. The cold ampoule was quickly heat-sealed by using a blowtorch, then refrigerated. Upon warming to room temperature, orange Bn vapors began to form. When liquid Bn was used in place of NaBr, PFAS and MnCh were added first, followed by H2SO4, which was then cooled to dry ice temperature. Liquid Bn was added last, directly before flame sealing and refrigerating.

[0037] Solar illumination. Fig. 7 presents the apparatus used to hold the photoreaction ampoules at the focal point of an inexpensive solar concentrator. An inexpensive 15-cm diameter film-coated plastic paraboloid mirror from a scientific toy (Mirascope ™) with numerical aperture close to 0.5 was taped to a 15-cm diameter, 10 cm long piece of hard plastic drainpipe with a pre-drilled 1.5 cm hole in its side. To position the glass ampoule at the mirror’s focal point, the flame-sealed end of the photoreaction ampoule was inserted into a 15-cm length of Tygon tubing to create a snug fit. The photoreaction ampoule and the Tygon tubing were inserted through a hole in the side of the PVC pipe to help the experimenter hold the ampoule at the mirror’s focal point. As shown in Fig. 7, to aid in the rapid positioning of the ampoule at the mirror’s focal point, a piece of copper pipe extending close to the mirror’s focal point was inserted snugly into one side of the PVC drainpipe.

[0038] Solar illumination was performed under clear skies, ideally with the sun between 30- 80 degrees above the horizon, depending on the time of day and season. The seated experimenter, wearing protective sunglasses, generally used one hand and their lap to maintain the paraboloid-mirror apparatus pointed at the sun. The same hand was used to position a 2.5-cm-diameter inspection mirror at the edge of the paraboloid mirror below the sample, in order to optimize the alignment. The other hand manipulated the Tygon tubing to perform fine adjustment of the ampoule’s position at the mirror’s focal point. When the solar focus was well optimized at the ampoule surface or slightly within the sample itself, there was often a stream of tiny bubbles coming from that focal point. It was sometimes possible to hear a steady clicking noise, possibly associated with the formation of those bubbles. Another immediate sign of photoreaction was often the expulsion of orangish “smoke”, presumably some form of bromine aerosol, from the locus of solar illumination.

[0039] Periods of intense illumination would lead to rapid heating of the sample, with formation of orange / red Bn vapor and / or “smoke”. The contents of the ampoule were generally more liquid as the temperature rose during periods of illumination, and would then largely re-condense upon cooling in the ice water bath, with Bn and H2SO4 remaining as phase- separated liquids. As the sample cooled, residual PFOA formed a separate liquid, then solid phase, atop the sulfuric acid phase, as well as coated portions of the sides of the ampoule with a white film. Frequent vigorous re-mixing upon heating was necessary to resuspend these solids into the sulfuric acid liquid phase. After approximately three hours of solar illumination, no separate PFOA layer could be discerned in the ampoules (main paper Figure 1). This indicated its chemical consumption. PTFE in the absence of PFOA detergent tended to always float above the liquid phase (not shown), presumably due to a surfacetension phenomenon.

[0040] Trapping of evolved CO2 as a gas of defined volume and as calcium carbonate. In brief, the ampoule was attached via a piece of tight-fitting Tygon tubing to a Luer-lock syringe fitting, which was used to inject the gaseous products into a receiving apparatus, of two different types.

[0041] The first type of receiving apparatus used to measure the volume of gases evolved during the photoreaction was a glass syringe with a tight ground-glass seal on the plunger. The ampoule had been taken out of a dry ice bath and was allowed to warm only to 0°C after the ampoule neck was broken, in order to keep Bn from contributing significantly to the released-gas volume. Expulsion of the gas from the broken ampoule into this syringe allowed measurement of the released gas volume (at 1 bar and 25°C) to within ~5% accuracy. This accuracy was possible because the dead-volume of the ampoule, the connecting Tygon tubing, and the syringe fitting remained the same before and after breaking off the ampoule tip. Fig. 8 presents a photograph of this apparatus after collecting 6 mL of gas (0.26 mmol, subsequently determined with a gas-phase IR measurement to be predominantly CO2) trapped inside the sealed photoreaction ampoule after 12 h solar illumination of a sample, originally containing only 28 mg PFOA (0.07 mmol PFOA) as a source of carbon (0.54 mmol C).

[0042] The second type of receiving container used was a sealed 25 -mL Erlenmeyer flask containing 10.0 mL 0.02 M Ca(OH)2. This calcium hydroxide solution had been prepared in a 50-mL capped polypropylene centrifuge tube, purged with N2, centrifuged to remove any solids, and then the supernatant was poured carefully into the clean Erlenmeyer flask, which was then plugged with a tight-fitting rubber septum.

[0043] A 15-cm piece of fresh Tygon tubing was attached to a 12-gauge syringe needle by using a Luer-lock-to-hose-barb coupler, using a piece of twisted copper wire to seal the connection. A small piece of glass wool was then inserted through the open end of the tubing, reaching to within 1 cm of the hose barb. A2-cm long aluminum spacer was inserted ~8 cm into the Tygon tubing, using a few drops of water to lubricate the way. The flame-sealed end of the photoreaction ampoule was then inserted into the open end of the tubing to create a snug fit all the way over the narrowest part of the ampoule neck and down 1-2 mm over the ampoule body, Then, another piece of copper wire (or a hose clamp) was used to seal the Tygon tubing tightly around that ampoule neck.

[0044] The tight clamps on the ends of the Tygon tubing closed the system off from its surroundings, except through the syringe needle, which was then inserted through the septum into the Erlenmeyer flask containing the 0.2 M Ca(OH)2 to create a fully-closed system. The aluminum piece was then pushed back carefully through the tubing over the tip of the ampoule, and the aluminum piece and ampoule were bent against each other, causing the tip of the ampoule to be snapped off. This breakage typically produced a loud popping noise (the release of pressure), sometimes shattering the ampoule’s glass tip as well. The release of any condensed matter (solids or liquids) into the syringe needle was blocked by the glass wool plugs. The system was kept closed at room temperature for 24-48 h to allow complete diffusion and reaction of CO2 gases with the 0.02 M Ca(OH)2.

[0045] The white solid at the bottom of the flask was resuspended by swirling, poured into a fresh 50-mL polypropylene centrifuge tube, collected by centrifugation, and washed twice with water before drying and weighing.

[0046] Results

[0047] We carried out test reactions on a scale of 25-70 mg for several different sets of PFAS and reagents, in sealed 1-mL borosilicate ampoules. These ampoules were positioned in direct sunlight at the focal point of an inexpensive 15-cm-diameter paraboloid mirror for 0.5-2 min periods to keep the temperature below ~100°C, alternating with cooling in an ice bath. Total illumination times ranged from 1.5 to 12 h.

[0048] Visual detection of photoreaction. After sealing the prechilled ingredients in a glass ampoule and then allowing the ampoule to be heated by focused sunlight, the initial changes in visual appearance of the samples included the formation of orange Bn vapor and melting of the powdery PFOAto form a clear oily layer on top of the H2SO4. These changes can be attributed solely to heating, because similar changes could be obtained simply by heating the samples to 100°C, e.g. in a heating block.

[0049] Subsequent changes in appearance were gradual but eventually striking, and could not be induced perceptibly simply by incubating the sample at 100°C for many days. Fig. 1 shows a photographic comparison of the appearance of two sample ampoules: one without illumination, the other after 8 total h of focused illumination and then after 12 total h of focused illumination. Both ampoules initially contained PFOA, MnCh, H2SO4, and NaBr as the sole initial source of bromine. One ampoule (shown on the left in Fig. 1) was a control that had never been illuminated but rather remained refrigerated for 8 weeks. This limited the oxidation of the NaBr to form orange colored Bn, and also prevented the destruction of the PFOA, which is still visible as a clear / white residue on some areas on the inside glass surface. A different ampoule containing the same quantities of starting materials (show in the center in Fig. 1) had been illuminated cumulatively 8 h in the 3 days prior to taking this photograph, and was then refrigerated. It shows no evidence of remaining solid PFOA, but still shows a significant quantity of orange colored Bn. Another image of the same ampoule after a further 4 h of illumination (shown on the right in Fig. 1) shows the formation of a distinctly blue photoproduct, particularly at the site of the most recent focusing of the sunlight for a 1-min interval. Additional blue-gray solid formed during prior illuminations is also clearly visible at the bottom of the H2SO4 layer. This sample was photographed immediately after a period of 1 min of focused solar illumination, and was too hot to touch. It was therefore left in the piece of Tygon tubing used to hold it.

[0050] Spectroscopic detection of partially-degraded fluorocarbons and CC - Fig. 2 shows19F NMR spectra, measured in deuterated chloroform (CDCh), of unreacted PFOA (top) vs. the organic-soluble residue collected after 1 h of photoreaction (bottom). For the latter, the solid residue after photoreaction was first extracted with water, and then the remaining waterinsoluble solid residue was extracted into ~1 mL CDCh and transferred into an NMR tube. The unreacted PFOA (Figure 1, top) shows a number of peaks (a-g) with complex splitting patterns due to the many perfluorinated carbons in its chain, matching previously published PFOA spectra.26Additional peaks in the bottom spectrum (a, P, y) were detected after several hours of solar illumination, clearly demonstrating the presence of partially decomposed fluorocarbon intermediates formed by the Bn-sensitized photoreaction. Peak assignments a-g in Fig. 2 are based on previous work. Neat PFOA (top):19F NMR (CDCh, 400 MHz) 5 -81.27 (tt, 3F, J = 10.4, 0.4 Hz), -119.39 (tt, 2F, J = 13.1, 2.0 Hz), -122.09 (s, 2F), -122.50 (s, 2F), -123.19 (m, 4F), -126.61 (m, 2F). PFOA after photoreaction (bottom):19F NMR (CDCh, 400 MHz) 5 -64.12 (tt, IF, J = 15.2, 2.7 Hz) -81.27 (m, 3F), -117.80 (tt, IF, J = 16.4, 3.2 Hz), -119.58 (tt, 2F, J = 13.4, 2.8 Hz), -121.55 (m, IF), -122.14 (s, 2F), -122.48 (s, 3F), -123.24 (m, 5F), -126.61 (m, 3F).

[0051] Fig. 3 shows an FTIR spectrum of the gases released upon breaking open the photoreaction ampoule shown in Fig. 1 (green trace), along with spectra of 1, 2, and 4 mL injections of 100% CO2 (black traces). For the headspace sample (green trace), 3 mL out of the 4 mL total volume released upon breaking open the refrigerated photoreaction ampoule into a glass syringe was injected into (and thus diluted in) an Ar-filled gas cell. This gas cell had a 100-mm path length, and internal volume ~50 mL, was made of borosilicate glass, and was fitted with BaF2 windows and PTFE seals. The spectrum was measured using a Thermo Magna series FTIR instrument, (2 cm'1resolution, 500 scans, 20 min), immediately following an otherwise-identical Ar-only background spectrum from the same gas cell. For the standard spectra of 100% CO2 shown in black, the indicated cumulative volumes of 100% CO2 were injected after obtaining a background spectrum with 100% Ar. The green trace for the 3-mL injection of headspace gas coincidentally matched nearly perfectly with the black spectrum measured for the first (1-mL) injection of CO2. The inset in Fig. 3 shows the absorbance value at 2360 cm'1(A2360) vs injected volume of CO2, taken from the green 3-mL headspace spectrum and the spectra of 1, 2, and 4 mL injections of 100% CO2 (black points). Additional A2360 values are also plotted here for 8- and 16-mL injections of 100% CO2 (black), as well as for a 1-mL aliquot from a different 6-mL headspace volume, from a 12-h-photoreacted ampoule similar to that shown in Figure 1 (green).

[0052] Fig. 9 shows preliminary LC-MS analysis of the headspace gases collected from the gas trapping apparatus shown in Fig. 8, and correspond to the green IR spectrum in Fig. 3. To each vial containing 0.25 mL injected gas (headspace gas MSB1 and N2-only control MSB3), 200 pL LCMS grade methanol was added via syringe through the septum. Both samples then sat for a minimum of 5 days prior to this analysis for the possible diffusion of gaseous compounds into the methanol. For analysis, 25 uL of sample was injected into the LCMS. A C18, 2.1 x 100 mm column was used with 2.0 pm particle size. A solvent gradient was used, from 10 mM ammonium acetate in water (A) to 10 mM ammonium acetate in 80% methanol, 20% acetonitrile (B). Panel Ain Fig. 9 shows chromatogram traces for total ion current (m / z 50-200), with the trace for the headspace-gas sample shown in the upper box and the trace for the control shown in the lower box. Panel B of Fig. 9 shows chromatogram traces showing just the extracted ion channel with m / z range of 125-135, again with the trace for the headspace sample in the upper box and the trace for the control in the lower box. The arrow at 0.22 minutes shows the one peak clearly observable in the headspace sample that was not present in the control. None of other 14 extracted 10-amu m / z ranges from 50-200 showed a peak above the noise when plotted over the time course of the measurement. Panels C parts 1 and 2 in Fig. 9 show mass spectra collected from 0.20-25 min after sample injection, for headspace-gas sample in panel C part 1 and for the control in panel C part 2. The vertical scale represents the ion current percentage at that m / z value, relative to the largest peak at m / z=59. The latter is a background peak present in both sample and control, and at almost all time points during the chromatograph. This was also true of nearly all of the peaks observable in these spectra. That is, the only ion observed in the sample spectrum (part 1) that stood out both as a compact temporal peak and as different from the control was the labeled peak at m / z=131.

[0053] When photoreaction ampoules were broken open after even ~12 h of illumination, room-temperature IR spectra of the gases released (Fig. 3, green trace) showed clear evidence of IR absorption due to C-F stretching vibrations near 1250 cm'1, in addition to somewhat larger CO2 bands near 2200-2400 cm'1. This spectrum corresponded to a nearly 50-fold dilution of the headspace gases in the pressurized ampoule, as there was a ~4-fold expansion of the ~l-mL headspace upon breaking open the ampoule, then only ~3 mL of the resulting expanded gases were injected into an IR gas cell already containing ~50 mL argon.

[0054] The green spectral trace in Fig. 3, obtained after injection of 3 mL of reaction headspace gas, shows CO2 absorption bands that nearly match those of a control injection of 1 mL of 100% CO2 (nearly-superimposable black trace). The relative volume measurements are imprecise, especially for the 1-mL volume, because of dead space in the connection tubing between the glass syringe and the gas cell. Propagating this uncertainty, we can conclude that the headspace gas contained 25%-35% CO2 by volume. In the 4 mL of total recovered volume, this corresponded to 1-1.5 mL or 0.04-0.06 mmol or 2-3 mg CO2, i.e. 0.5- 0.7 mg C. This in turn corresponds to 8-12% conversion to CO2 of the original -5 mg C in the 23-mg (0.055 mmol) PFOA sample. The sample that produced the other green data point in the Fig. 3 inset generated 6 mL of headspace gas (see Fig. 8), containing 25-35% CO2, or 0.8-1.2 mg C, from an original sample of 28 mg PFOA containing 6.5 mg C, corresponding to a carbon recovery of 12-18%.

[0055] The relatively large magnitude of the strong C-F absorptions in this room-temperature spectrum (Fig. 3), and the absence of any H-F rotation-vibration absorption bands near 4000 cm'1,27is most consistent with almost all of the -70% of the gas in the reaction headspace that is not CO2 being low-molecular-weight fluorocarb on(s). Such a high fluorocarbon vapor pressure is inconsistent with them being due to unreacted starting material. PFOA has insufficient vapor pressure at room temperature to give rise to these IR bands, as confirmed by a control measurement with solid PFOA equilibrated inside the gas cell, for which the gasphase C-F absorption bands at room temperature were below the level of detection (0.01 absorbance unit; data not shown). The IR results in Fig. 3 thus indicate that the partially decomposed condensed-phase fluorocarbons detected after -4 h of photoreaction (Fig. 2) likely give rise to further-decomposed small volatile fluorocarbons after 8 h additional illumination.

[0056] With an aim of identifying the decomposed fluorocarbons in the headspace giving rise to the C-F stretch vibrations in Fig. 3, we allowed 0.25 mL of the headspace gas to equilibrate with methanol, and then performed a liquid-chromatography-mass-spectrometry (LCMS) analysis. This resulted in only 1 identifiable solute peak from the liquid chromatogram, with two clearly identifiable M / Z peaks at 131 and 133 (see Supplementary Information). These masses match most closely the values expected for CsFs" and CsFsFb’, respectively

[0057] When the glass photoreaction ampoules were broken open after 8 h of illumination, it was possible to confirm of the presence of CO2 in 5-10 mL of the released gases by trapping them with a 10 mL of 0.02 M Ca(OH)2 solution, collecting a powdery white precipitate by centrifugation and drying, and measuring the powder X-ray diffraction spectrum of the precipitate (Fig. 4). The measured 1-2 mg mass of the recovered dry sample, containing 0.1- 0.2 mg C, represented -1% recovery of carbon from the original -50 mg sample of PFOA, which contained 12 mg C. The XRD indicated no significant presence of crystalline CaF2 or CaSO4 within the sample, as these would have shown significant additional diffraction peaks. From this we conclude that, while HF is formed during the photoreaction (see Fig. 5), HF remains in condensed phase so that no significant amount of gaseous HF is released when the ampoules are broken open. Detection of HF as a terminal photoproduct in the condensed phase. Fig. 5 displays19F NMR spectra for water (D2O) extracts of the condensed phases from closed-ampoule photoreactions. Trifluoroacetic acid (TFA) was used as a chemical shift standard that gives a sharp resonance at -76.55 ppm. In Fig. 5, spectrum A shows photoproducts from PFOA + PTFE / MnCF / NaBr; spectrum B shows photoproducts from PFOA / MnCh / NaBr; spectrum C shows photoproducts from PTFE / MnCh / NaBr; spectrum D shows photoproducts from PFOA / MnCh / Bn; and spectrum D shows a NaF standard (2 mg / mL) added to 10% H2SO4 in D2O. As an internal standard, TFA (-76.55 ppm) was added to each sample to give a concentration of 0.2%. The peaks observable between -120 and -175 ppm for the photoproduct samples (Fig. 5, spectra A-D) are generally indicative of inorganic fluoride compounds, indicating C-F bonds in PFOA have been broken and the fluorine has been converted to inorganic compounds such as HF (more specifically,2HF).

[0058] Apeak with identical shape and chemical shift of -167.1 ppm is observed in all these photoproduct samples (spectra A-D in Fig. 5), as well as when a standard NaF sample is dissolved in 10% H2SO4 in D2O to give a similar acidity to our samples (spectrum E in Fig. 5) and measured in an NMR tube with a PTFE insert. This -167.1 ppm19F chemical shift is within the range of values previously published for aqueous HF / DF.28These were noted to be strongly dependent on pH, and somewhat less dependent on level of deuteration and HF concentration.

[0059] Fig. 6 shows19F NMR spectra for samples prepared for use as standards for comparison by first preparing a solution of 90: 10 (w:w) D2O / H2SO4, then adding trifluoroacetic acid (TFA) to a concentration of 0.2%. A quantity of 1-2 mg of NaF or Na2SiFe (respectively) was added to each of 2 separate freshly opened PTFE NMR tube inserts. Then 0.5 mL of the 10% sulfuric acid solution was added to each, with gentle mixing, allowing 1 h for each sample to dissolve before making the NMR measurements. Our observed chemical shift of -167.1 ppm (Fig. 5) is well upfield from the value of -130 ppm previously observed for a pH 3 solution of Na2SiFe. The latter value, however, matches the value that we observed for a solution of Na2SiFe in 10% H2SO4 in D2O (Fig. 6, lower plot, which has peaks labeled at -130.030, -150.936 and -167.091 ppm, in contrast to the upper plot in Fig. 6, which has a single peak labeled for NaF in 10% H2SO4 in D2O). We conclude that the chemical shift value of -167.1 ppm that we observe for our photoproduct samples (Fig. 5) is due to HF rather than either SiFe' or HSiFe, despite the presence of silica in both our reaction vessels and our NMR tubes. Somewhat surprisingly, we did not see visual evidence of etching of the photoreaction ampoules, in the form of frosting or other optical perturbation, even after many days in contact with the HF-containing photoproducts in the presence of concentrated H2SO4. This could hypothetically be due to very strong HF-H2SO4 hydrogen-bonding interactions that render the HF unusually unreactive towards silica (see discussion below).

[0060] When we used borosilicate NMR tubes without PTFE inserts to measure NMR spectra of the D2O-diluted photoproduct samples, we saw peaks in the 140-160 ppm range that could be attributable to fluoroborate compounds (Fig. 5). However, these fluoroborate lines were not observed alongside the -167.1 ppm HF line, when we were careful to keep the HF photoproduct away from borosilicate glass as the H2SO4 was diluted (data not shown).

[0061] By comparison to the known amounts of fluorine in the TFA standard as well as in the acidified NaF standard (Fig. 5, spectrum E), we estimate that these inorganic19F signals from the photolyzed samples (Figure 5, spectra A-D) represent a 2-4% recovery of the 30-40 mg of fluorine present in the original 50-60 mg samples of PFOA, after 4-5 h worth of focused solar illumination with our 15-cm-dia mirror. The recovery from a sample made with PTFE (Fig. 5 panel C) was a factor of ~10 lower than from the best PFOA sample.

[0062] Estimate of maximum likely mass of inorganic fluoride in the residual photoproduct solid. It is likely, but not proven, that inorganic fluoride is also present in the residual inorganic solid phase obtained after it was washed, first with ethanol (to remove residual fluorocarbons and excess H2SO4, and to chemically reduce residual Mn02 to MnSO4) and subsequently with water (to remove Na+, Br", and SO42'). The final aqueous supernatant after these washes typically had a pH value near 4.5, suggesting that it might be buffered by fluoride. After drying the solid residue, up to ~5 mg of grey-black powdery solids was recovered. However, the color was too dark to be pure MnF2. This dark color is most consistent with partial reformation of MnCh from the predominantly blue and / or white solids that were visible in the unbroken sample ampoule after extensive illumination (Fig. 1). However, the chemistry involved in such putative MnCh re-formation is unclear, and IR and X-ray powder diffraction measurements have not yet given interpretable results for us to identify any components in the powdery solid.

[0063] Discussion

[0064] The main conclusion from our results is that at least some fluorocarbons, such as PFOA and PTFE, can be broken down with Mn02 serving as an oxidant in H2SO4 solvent, and using photocatalytic Bn and concentrated sunlight to initiate the reaction that did not proceed to any observable extent in the presence of unfocused direct sunlight. The requirement for very high intensity suggests that multiple photons are required for the initial stage of photodecomposition of the PFOA.

[0065] One reason for investigating the reaction with PTFE was to determine whether the fluorocarbon degradation mechanism requires an oxygen-containing functionality, or might also involve direct attack on C-F bonds by photoactivated Bn. The detection of HF as a photoproduct of PTFE / MnO2 / Br2 (Fig. 5C), even in the absence of any added surfactant, suggests the latter. However, the low yield of F' gives some pause, as small amounts of fluorocarbon surfactants such as PFOA and GenX (hexafluoropropylene oxide dimer acid) have generally been used in the commercial synthesis of PTFE, and we have no way to assay whether a residual amount of this in our sample might account for the very small yield of HF (-0.2% of the original F' in the PTFE sample).

[0066] For PFOA, the photocatalytic processes form progressively smaller stable fluorocarbon products that can be detected in both condensed and gaseous phases with19F NMR and IR spectroscopic measurements (Figs. 2 and 3). If these intermediates remain confined in a borosilicate reaction ampoule, they are ultimately broken down to form CO2 as detected by IR and XRD measurements, and inorganic fluoride (as HF) as detected by19F NMR measurements (Fig. 3-5).

[0067] As mentioned above, fluorocarbons can be thermally oxidized in incinerators. The high temperature of incinerators generally precludes confinement, and therefore leads to continual escape of incompletely-oxidized intermediates.6Furthermore, incineration requires the additional presence of hydrocarbons to yield HF. In the absence of such a source of hydrogen, thermodynamics predict that fluorocarbons are stable to reaction with O2.

[0068] For example, the PTFE combustion process e.g. 02(g) +1 / 2(-C2F4-)(S) —> F2(g) + CO2(g) is computed to have a positive AH° = +20.32 kJ mol'1, using an enthalpy of formation of PTFE, (-C2F4-)(s), from published work.30No thermodynamic help can be obtained by further oxidation of the F2 product by O2. In simplified terms, C-F bonds are more stable than C-0 bonds, so it is not easy to replace the former with the latter.

[0069] Why then can the carbon in PFAS be converted into CO2 photocatalytically using the process described in the current work? The answer to this question becomes clearer if the overall reaction 1,

[0070] MnO2(S) +1A(-C2F4-)(s) MnF2(S) + CO2(g) (1) is written as the sum of the combustion process 2 with additional reactions 3 and 4: 1

[0071] Reactions 2 and 3 are both endothermic. However, reaction 4 is highly exothermic, with a negative AH° large enough to overcome the combined positive values of the other reactions. This is partly due to the enormous crystal energy stabilization of solid MnF2.

[0072] However, even when the MnF2 product is partially dissolved in H2SO4, it appears that the solution enthalpies of Mn2+and HF are sufficiently favorable (exergonic; actual values do not appear in the literature) that coupling PFAS oxidation to their release into H2SO4 can still thermodynamically drive the otherwise unfavorable formation of C-0 bonds from C-F bonds.

[0073] Unusually strong H-bonding interactions of HF with H2SO4 solvent would be consistent with several qualitative observations from our experiments. First, despite the measurable presence of up to ~1 mg of HF product in multiple solutions prepared in these borosilicate glass photoreaction ampoules, even over the course of many hours at intermittently elevated temperatures, we have seen no sign of etching of the glass, nor the formation of fluorosilicate products that would be expected to give rise to19F NMR signals near -130 ppm (see Fig. 5,6). Second, no odor of HF is detected from these opened ampoules, despite the boiling point of pure HF being just below room temperature. Third, when the pressure in these photoproduct vials is released and allowed to mix for many hours with Ca(OH)2, there is no sign of CaF2 formation. Fourth, there is no sign of HF absorption bands in the gas-phase IR spectrum (spectral region 3500-4000 cm'1in Fig. 3). Together these observations support the idea that even at HF concentrations measurable with19F NMR, strong H-bonding interactions with concentrated H2SO4 greatly suppress the HF chemical activity, probably in a similar way that they suppress the activity of H2O, whose activity coefficient approaches 10'9when dissolved at low concentrations in H2SO4.31

[0074] Reaction 1 between mixed-powder samples of perfluorocarbons (specifically PTFE) and MnCh has been determined experimentally32to initiate thermally at a temperature near 570°C, which is above the temperature at which PFAS generally depolymerize and / or evaporate to form gases. That determination therefore used milligram quantities of the reagents in a thermogravimetric differential scanning calorimeter designed to quickly remove evolved heat and gas. It would be impossible with any current technology to remove so quickly the evolved heat and gas from million-fold greater quantities of these reagents and products confined in an industrial-scale reactor. Using the known heat capacities of the products CO2 and MnF2, thermally triggering reaction 1 above 570°C on a macroscopic quantity in a closed vessel could lead to a near-instantaneous runaway completion of the reaction, with a temperature increase of over 2000 K and a concomitant explosion potential from the evolved CO2.

[0075] In contrast, our photocatalytic approach allows the highly exothermic reaction 1 to be carried out at temperatures in the range 0-100°C, in the presence of a thermally modulating solvent (H2SO4), thereby preventing runaway reaction. The reaction rate can be easily reduced to near zero at any time, simply by discontinuing illumination. Nevertheless, our spectroscopic results detecting HF and CO2 photoproducts from PF AS or PTFE using MnCh, NaBr, and sunlight, and the thermodynamic analysis above, suggest that our brominephotocatalyzed reaction should go to completion with sufficient photoreaction time.

[0076] The exact mechanistic role of Bn in the photocatalytic process is not yet clear. It may be investigated in the future with other methods, mainly time-resolved spectroscopy with pulsed-laser light sources. Such sources are unlikely to be superior to sunlight as the most inexpensive source of intense illumination for this process.

[0077] Without wishing to be bound by theory, we speculate that the mechanism is most likely to involve as a first step the photolysis of Bn to Br atoms by blue and ultraviolet light, which is known to occur in response to light absorption throughout the main electronic absorption band of Bn (A,max = 405 nm). It may be possible that the resulting Br atoms can then attack C-F bonds, in a manner similar to the well-established free-radical mechanism for photolytic substitution of halogen atoms (Cl,Br) for H in alkanes. Once a fluorocarbon is brominated, it is then likely to be susceptible to nucleophilic substitution, e.g. by water, to form alcohols which can then be oxidized to aldehydes or ketones by Mn02, and then further oxidized by Bn to form carboxylic acids. If such bromination / hydroxylation / oxidation reactions occur at both a terminal carbon and a carbon down the chain to form a P-keto carboxylic acids, this could likely lead to spontaneous decarboxylation and chain shortening. Repetition of this process could ultimately lead to complete breakdown of the starting fluorocarbon While such an overall mechanism is speculative, the individual steps in it (other than Br attack at a C-F bond) are all well-known organic chemical reactions.

[0078] Our results so far support the release of up to -10-15% of the original carbon in the PFOA as CO2 after -12 h total of focused solar illumination, and a likely conversion of most of the original remaining carbon as to shorter-chain fluorocarbons. These fluorocarbon intermediates can be detected after various periods of photoreactions, either by extraction into organic phase and19F NMR measurement (Fig. 2), or by collection of the gaseous photoproducts and measurement of their IR absorption spectrum (Fig. 3) and preliminary LC- MS analysis. Such measurements have allowed only a general identification, but not a full speciation of the fluorocarbon intermediates produced by the photoreaction.

[0079] We tentatively conclude that the observed ion M / Z values of 131 and 133 in headspace gas mass spectral analysis after ~12 h photoreaction correspond to deprotonated ions of C3HF5 and C3H3F5, respectively. These are known molecules, some of whose isomers have been considered as substitutes for traditional fluorocarbon refrigerants because they are equally nontoxic but degrade more easily under low-atmosphere conditions.33For such reasons, these might be considered acceptable end products for PF AS degradation, to be released without further treatment into the atmosphere.

[0080] Determining whether C3HF5 and C3H3F5 are indeed the principal species in the residual headspace gas after extensive photolysis will probably require mass spectrometry with high-resolution and the ability to analyze ionization fragments with M / Z <50. However, further speciation by IR and NMR spectroscopy will likely be required, because C3HF5 is expected to have 7 stable isomers (pentafluorocyclopropane as well as cis and trans versions of 1,1,3,3,3-pentafluoropropene; 1,2, 3, 3, 3 pentafluoropropene; and 1, 1,2, 3,3- pentafluoropropene) while C3H3F5 is expected to have 4 stable isomers (1 , 1, 1,2,2- pentafluoropropane; 1,1,2,2,3-pentafluoropropane; 1,1,2,3,3-pentafluoropropane; and 1,1,1,3,3-pentafluoropropane). Where data exists, the NIST Chem Webbook indicates that these species generally have boiling points at or below room temperature, making them reasonable candidates for headspace gases. However, gas-phase IR spectra of only a few of them have been published, for example cis- and trans- , 1,3,3,3-pentafluoropropane.33. Each of these two isomers shows distinctive strong absorptions due to C-F stretches in the range 1030-1260. Vibrations in this range are seen in our headspace IR spectrum (Fig. 3), but these frequencies are not perfect matches for the published data.33In summary, while clear identification of all the residual fluorocarbon species in our reaction products will require additional work, such identification is not necessary in the context of the presently claimed invention.

[0081] After 12 h photoreaction, the combined volume of gas released as CO2 and 3 -carbon fluorocarbons can possibly account for nearly 100% of the original carbon in the PFOA. That is, as stated above, 10% of that carbon is accounted for as 0.04-0.06 mmol CO2 making up 25% of the volume of the headspace gas. To account for the other 75% of the volume of released headspace gas, there must be 0.12-0.18 mmol of such non-CCh gas. If all of such non-CO2 gas(es) have molecular formulas with 3 carbons, as suggested by the mass spectrometry, then these other headspace gases contain 0.4-0.6 mmol C. The total amount of C in the headspace gases can therefore easily be as high as 0.5-0.75 mmol, which is enough to account for essentially all the original 0.055 mmol C in the 23-mg PFOA starting material.

[0082] Therefore, our results indicate that there need not be significant amounts of fluorocarbons remaining in the condensed-phase (liquid and solid) residue in order to account for all of the original C from the PFOA sample. Detecting any such residual condensed-phase fluorocarbon could possibly be accomplished by some kind of organic-solvent extraction from the corrosive and reactive condensed phase, followed by LC-MS. However, the simple chloroform extraction method suitable for19F NMR (Fig. 2) is not adequate to prepare samples for nondestructive injection onto an expensive liquid chromatography column. Thus identifying any residual condensed-phase species in the final reaction mixture will likely require extensive studies to find suitable extraction procedures, followed by more sophisticated MS methods were available to us hitherto.

[0083] In contrast to carbon, accounting for what has happened to all the fluorine in our original PFOA sample is more problematic. Using19F NMR, which is approximately quantitative, inorganic fluoride (HF) dissolved in the H2SO4 phase can account for only up to -4% of the original F from PFOA, which is significantly less than the C released as CO2. There is no sign of the “missing” inorganic fluoride in the headspace gas phase, which should give very strong HF rotation-vibration absorptions in the IR spectra.32We tentatively conclude that the solids remaining after photoreaction must contain a significant fraction of the -10% of the original fluoride to match the -10% of inorganic carbon released as CO2. Our attempts to use XRD analysis to identify such stable fluoride-containing end-product solids have not yet yielded any identifiable compounds.

[0084] In addition, further spectroscopic and / or XRD analysis will also be required to identify the transient bluish photoproduct seen after long periods of illumination (Fig. 1). Although its several-h lifetime at room temperature was too brief to analyze spectroscopically as yet, this was the clearest direct visual evidence of a photochemical process occurring over the course of -12 h of illumination. Few Mn compounds with the six other elements present in our samples (C,O,S,Na,Br,H) are blue. We speculate that it could be the known stable aquamarine-colored compound MnF4, or possibly one of its unreported analogs MnF2Br2 or MnFsBr.

[0085] Not only is the sunlight-focusing apparatus required for further lab oratory -scale optimization and analysis of this photoreaction extremely inexpensive, but so too are the reagents. These reagents are also abundant in the natural environment, easily transported, and even available at reagent-grade purity as consumer products: MnCF as a ceramic glaze colorant (US$2 / kg), concentrated H2SO4 as a drain cleaner (US$20 / kg), and NaBr as a hot tub disinfectant (US$50 / kg). Upon dilution with water, the products of the reaction (carried to completion) are also relatively benign for the environment. By contrast, other commercially available compounds being investigated for PFOA photocatalytic destruction are at least 5-10 fold more expensive, e.g. boron nitride is typically US$250 / kg and indium oxide is US$1500 / kg.

[0086] To summarize, both PFOA and PTFE were degraded using a combination of Mn02, H2SO4, either liquid Bn or NaBr, and focused sunlight, at temperatures of 0-100°C. Compared to most other PF AS degradation methods being developed, this process is less expensive, depends exclusively on the sun as an energy source, and does not require dangerously high temperatures or persistently toxic metals.

Claims

AMENDED CLAIMS received by the International Bureau on 17 November 2025 (17.11.2025)1. A composition of matter comprising a mixture containing (a) at least one brominecontaining compound, and (b) at least one per- or polyfluoroalkyl substance (PF AS), the composition of matter further comprising sulfuric acid (H2SO4) and manganese oxide (MnO2).

2. The composition of matter according to claim 1, wherein the weight ratio of MnO2to the total amount of carbon in said at least one perfluoroalkyl substance is at least 8 to 1.

3. The composition of claim 1 or claim 2, wherein the at least one bromine-containing compound comprises elemental bromine (Br2).

4. The composition of claim 3, wherein the weight ratio of Br2to the at least one PF AS is at least 0.8: 1.

5. The composition of claim 4, wherein the weight ratio of Br2to said at least one PF AS is at least 1 : 1.

6. The composition of claim 4, wherein the weight ratio of Br2to said at least one PF AS is in the range of 1 : 1 to 5 : 1.

7. The composition of any one of claims 1 to 6, wherein the bromine-containing compound comprises NaBr.

8. The composition according to claim 7, wherein the weight ratio of said MnO2to said NaBr is at least 1 : 1.

9. The composition according to claim 7 or 8, wherein the weight ratio of NaBr to said at least one PF AS is at least 1 : 1.

10. The composition according to claim 9, wherein the weight ratio of NaBr to said at least one PF AS is in the range of 1 : 1 to 3 : 1.2911. The composition according to any one of claims 1 to 10, wherein the composition comprises H2SO4, and the weight ratio of said H2SO4 to the other components of the composition is in the range of 1 : 1 to 100: 1.

12. The composition according to claim 11, wherein the weight ratio of said H2SO4 to the other components of the composition is in the range of 5: 1 to 10: 1.

13. The composition of matter according to any one of claims 1 to 12, wherein said at least one PF AS comprises perfluorooctanoic acid (PFOA, CsFisCEH).

14. The composition of matter according to any one of claims 1 to 12, wherein said at least one PF AS comprises poly-tetrafluoroethylene (PTFE, (-C2F4-)n).

15. The composition of matter according to any one of claims 1 to 14, wherein said at least one PF AS comprises both PFOA and PTFE.

16. A composition of matter comprising sulfuric acid (H2SO4), manganese oxide (Mn02), at least one per- or polyfluoroalkyl substance (PF AS), and a substance that contains bromine atoms.

17. The composition of matter according to claim 16, wherein the weight ratio of Mn02 to the total amount of carbon in said at least one perfluoroalkyl substance is at least 8 to 1.

18. The composition of matter according to claim 16 or 17, wherein the substance that contains bromine atoms is elemental bromine (Bn).

19. The composition of claim 18, wherein the weight ratio of Bn to the at least one PF AS is at least 0.8: 1.

20. The composition of claim 19, wherein the weight ratio of Bn to said at least one PF AS is at least 1 : 1.

21. The composition of claim 19, wherein the weight ratio of Bn to said at least one PF AS is in the range of 1 : 1 to 5 : 1.3022. The composition of matter according to claim 16 or 17, wherein the substance that contains bromine atoms is NaBr.

23. The composition according to claim 22, wherein the weight ratio of said MnCh to said NaBr is at least 1 : 1.

24. The composition according to claim 22 or 23, wherein the weight ratio of said NaBr to said at least one PFAS is at least 1 : 1.

25. The composition according to claim 24, wherein the weight ratio of said NaBr to said at least one PFAS is in the range of 1 : 1 to 3 : 1.

26. The composition according to any one of claims 16 to 25, wherein the weight ratio of said H2SO4 to the other components of the composition is in the range of 1 : 1 to 100: 1.

27. The composition according to claim 26, wherein the weight ratio of said H2SO4 to the other components of the composition is in the range of 5: 1 to 10: 1.

28. The composition of matter according to any one of claims 16 to 27, wherein the at least one PFAS comprises perfluorooctanoic acid (PFOA, CsFisChH).

29. The composition of matter according to any one of claims 16 to 28, wherein the at least one PFAS comprises poly-tetrafluoroethylene (PTFE).

30. The composition of matter according to any one of claims 16 to 29, wherein the at least one PFAS substance comprises both PFOA and PTFE.

31. The composition of matter according to any one of claims 1 to 30, wherein the composition further comprises at least one of C3HF5 and C3H3F5.

32. The composition of matter according to any one of claims 1 to 31, wherein the composition further comprises at least one of MnF4, MnF2Br2 and MnF3Br.

33. The composition of matter according to any one of claims 1 to 32, wherein the composition further comprises at least one of hexafluorosilicic acid (JLSiFe) and hydrofluoric acid (HF).

34. A vessel having disposed therein a composition of matter according to any one of claims 1 to 33, wherein at least a portion said composition is disposed in a portion of said vessel that is transparent to light of wavelengths 300-800 nm.

35. The vessel of claim 34, wherein the said portion of said vessel that is transparent to light of wavelengths 300-800 nm is transparent to sunlight.

36. A process for chemically decomposing per- and poly fluoroalkyl substances, comprising illuminating a mixture containing at least one per- or polyfluoroalkyl substance (PF AS) and Bn with light.

37. The process according to claim 36, wherein said light comprises focused sunlight.

38. The process according to claim 36 or 37, wherein said at least one PF AS includes perfluorooctanoic acid (PFOA, CsFisCEH).

39. The process according to any one of claims 36 to 38, wherein said at least one PF AS includes poly-tetrafluoroethylene (PTFE).

40. The process according to any one of claims 36 to 39, wherein said at least one PF AS includes both PFOA and PTFE.

41. The process of any one of claims 36 to 40, wherein the mixture further comprises sulfuric acid (H2SO4) and manganese oxide (Mn02).

42. The process of claim 41, wherein the weight ratio of Mn02 to the total amount of carbon in said at least one perfluoroalkyl substance is at least 8 to 1.

43. The process of any one of claims 36 to 42, wherein the weight ratio of Bn to the at least one PF AS is at least 0.8: 1.

44. The process of claim 43, wherein the weight ratio of Bn to said at least one PFAS is at least 1 : 1.

45. The process of claim 43, wherein the weight ratio of Bn to said at least one PFAS is in the range of 1 : 1 to 5 : 1.

46. The process of any one of claims 36 to 45, wherein the Bn is generated in situ from a bromine-containing compound.

47. The process of claim 46, wherein the bromine-containing compound is NaBr.

48. The process of claim 47, wherein the weight ratio of said MnCh to said NaBr is at least 1 : 1.

49. The process of claim 47 or 48, wherein the weight ratio of said NaBr to said at least one PFAS is at least 1 : 1.

50. The process according to claim 49, wherein the weight ratio of said NaBr to said at least one PFAS is in the range of 1 : 1 to 3 : 1.

51. The process of any one of claims 41 to 50, wherein the weight ratio of said H2SO4 to the other components of the composition is in the range of 1 : 1 to 100: 1.

52. The composition according to claim 51, wherein the weight ratio of said H2SO4 to the other components of the composition is in the range of 5: 1 to 10: 1.

53. A process for photochemically converting a per- or polyfluoroalkyl substance (PFAS) and MnCh to gaseous CO2 and a solution containing at least one of (1) hexafluorosilicic acid (FFSiFe) and (2) hydrofluoric acid (HF) in liquid H2SO4, by illuminating a mixture containing at least one PFAS, sulfuric acid (H2SO4), said manganese oxide (MnCh), and sodium bromide (NaBr) in the presence of silica or a silica-based glass.3354. The process according to claim 53, wherein said illuminating is achieved by focusing sunlight on said mixture.

55. The process according to claim 53 or claim 54, wherein said PF AS comprises perfluorooctanoic acid (PFOA, CsFisCEH).

56. The process according to any one of claims 53-55, wherein said PFAS comprises polytetrafluoroethylene (PTFE).

57. The process according to any one of claims 53-56, wherein said PFAS comprises both PFOA and PTFE.

58. The process of any one of claims 53 to 57, wherein the weight ratio of Mn02 to the total amount of carbon in said at least one perfluoroalkyl substance is at least 8 to 1.

59. The process of any one of claims 53 to 58, wherein the weight ratio of the bromine atoms in said NaBr to the at least one PFAS is at least 0.8:1.

60. The process of claim 59, wherein the weight ratio of the bromine atoms in said NaBr to said at least one PFAS is at least 1 : 1.

61. The process of claim 60, wherein the weight ratio of bromine atoms in said NaBr to said at least one PFAS is in the range of 1 : 1 to 5 : 1.

62. The process of any one of claims 53 to 61, wherein the weight ratio of said MnCh to said NaBr is at least 1 : 1.

63. The process of any one of claims 53 to 62, wherein the weight ratio of said NaBr to said at least one PFAS is at least 1 : 1.

64. The process according to claim 63, wherein the weight ratio of said NaBr to said at least one PFAS is in the range of 1 : 1 to 3 : 1.3465. The process of any one of claims 53 to 64, wherein the weight ratio of said H2SO4 to the other components of the composition is in the range of 1 : 1 to 100: 1.

66. The composition according to claim 65, wherein the weight ratio of said H2SO4 to the other components of the composition is in the range of 5: 1 to 10: 1.35