PFAS treatment method and calcium fluoride manufacturing method

Abstract

PFAS can be efficiently treated using methods that have a low environmental impact. [Solution] In one embodiment, the method for treating PFAS involves stirring PFAS contaminants into water to produce PFAS-containing water, adding activated carbon with a positive zeta potential to the PFAS-containing water to adsorb the PFAS in the PFAS-containing water onto the surface of the activated carbon, adding an acidic or alkaline solution to the PFAS adsorbed on the activated carbon to desorb and concentrate the PFAS from the activated carbon, adding hydrogen peroxide to the PFAS desorbed from the activated carbon to generate nanobubbles in the hydrogen peroxide, and adjusting the hydrogen peroxide to a pH that destroys the nanobubbles to decompose the PFAS into hydrofluoric acid.

Description

[Technical Field]

[0001] The present disclosure relates to methods for treating PFAS and methods for producing calcium fluoride. [Background technology]

[0002] PFAS are persistent and highly bioaccumulative, which has led to a problem of adverse environmental impacts, and there is an urgent need to establish a technology to remove them from PFAS-contaminated soil or PFAS-contaminated water, etc. For example, the technology described in Non-Patent Document 1 involves dry treatment in which activated carbon that has adsorbed PFAS from PFAS-contaminated water is incinerated.

[0003] For relatively high concentrations of PFAS, methods have been adopted, such as capturing PFAS with a porous carbon membrane (Non-Patent Document 2), decomposing PFAS using radicals such as plasma or photocatalysis (Non-Patent Documents 3 and 4), distillation (Non-Patent Document 5), and electrode methods (Non-Patent Document 6). A decomposition method using bubbles generated by cavitation (Non-Patent Document 7) has also been reported. [Prior art documents] [Non-patent literature]

[0004] [Non-Patent Document 1] Kakamigahara City Waterworks Division, Gifu Prefecture, "PFAS Countermeasures for Tap Water - Aiming for Safe and Secure Tap Water," Kakamigahara Public Relations, February 1, 2025, Kakamigahara City, Gifu Prefecture, February 1, 2025, p. 2-3 [Non-patent document 2] Toshihiro Isobe et al., "Tokyo University of Science Develops Membrane Distillation System that Can Remove PFAS to Below Environmental Standards," [Online], [Text], January 20, 2025, University Journal Online Editorial Department, [Accessed June 18, 2025], Retrieved from<https: / / univ-journal.jp / 251075 / ?cn-reloaded=1> [Non-patent document 3] Yasuoka, Koichi, "Complete decomposition of organic fluorine compounds and fluorine recovery using inline underwater plasma," FY2012 Comprehensive Research Report for the Research Project Supported by the Environmental Research Promotion Fund, March 2013 [Non-patent document 4] Yuzo Arima and 4 others “Multiphoton-driven Photocatalytic Defluorination of Persistent Perfluoroalkyl Substances and Polymers by Visible Light”, Angewandte Chemie International Edition,German, German Chemical Society,October 14,2024,Volume 63, Issue 42 [Non-patent document 5] Masashi Oyama, "Development of PFAS Decomposition Treatment Technology Using Hydrogen Combustion High-Temperature Superheated Steam," Journal of the Japan Society of Material Cycles and Waste Management, Vol. 35, No. 4, pp. 271-280, 2024 [Non-patent document 6] Shi Lifeng, et al., “A review of electrooxidation systems treatment of poly-fluoroalkyl substances (PFAS): electrooxidation degradation mechanisms and electrode materials”, Environmental Science and Pollution Research International, Springer Nature, 20 Jun 2024, 31(30) ,pp. 42593-42613 [Non-Patent Document 7] Masaru Oyama, Takashi Matsuo, Takuo Nakajima, and Toshihiro Hirao, "Development of Treatment Technology for PFOS / PFOA, etc. (PFASs) in Environmental Water - Decomposition Treatment by Cavitation and Adsorption Treatment by Powdered Activated Carbon," Konoike Technical Research Report, 2023, pp. 9-20. Summary of the Invention [Problem to be solved by the invention]

[0005] However, the methods described in Non-Patent Documents 1 to 6 all require enormous energy costs. Furthermore, PFASs are often present in dilute forms in the soil and water sources to be decontaminated, and the challenge is how to concentrate such dilute PFASs. The techniques described in Non-Patent Documents 2 to 6 have difficulty in solving the above-mentioned problems.

[0006] An object of one embodiment is to provide a method for treating PFAS and a method for producing calcium fluoride that can efficiently treat PFAS using a method that imposes little burden on the environment. [Means for solving the problem]

[0007] In the embodiment, the PFAS treatment method comprises mixing PFAS contaminants in water. death to produce PFAS-containing water, In neutral to acidic aqueous solutions Activated carbon having a positive zeta potential is added to the PFAS-containing water, and the PFAS in the PFAS-containing water is adsorbed onto the surface of the activated carbon. An acidic or alkaline solution is added to the PFAS adsorbed on the activated carbon, and the PFAS is desorbed from the activated carbon and concentrated. Hydrogen peroxide is added to the PFAS desorbed from the activated carbon, and the hydrogen peroxide is added to the hydrogen peroxide. , having a diameter of 100 nm or more and 1000 nm or less Nanobubbles are generated, and the hydrogen peroxide solution is dissolved in the nanobubbles. 3.0 or more and less than 6.0 The pH is adjusted to decompose the PFAS into hydrofluoric acid. [Effects of the Invention]

[0008] According to the PFAS treatment method and calcium fluoride production method of the embodiment, PFAS can be efficiently treated using a method that places little burden on the environment. [Brief explanation of the drawings]

[0009] [Figure 1] FIG. 1 is a schematic diagram illustrating an example of the configuration of a processing apparatus according to an embodiment. [Figure 2]FIG. 2 is a schematic diagram showing an example of a method for producing activated carbon according to an embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0010] (overview) The PFAS treatment method and calcium fluoride production method of the embodiment are intended to treat all perfluoroalkyl compounds (PFAS: Per- and poly-Fluoro-Alkyl Substances), which are organic fluorine compounds with fluorinated carbon chains. PFAS to be treated may include perfluorooctanoic acid (PFOA) and perfluorooctanesulfonic acid (PFOS).

[0011] In the PFAS treatment method and calcium fluoride manufacturing method of the present embodiment, PFAS in PFAS contaminants are first adsorbed onto activated carbon using a wet chemical treatment method, and then the PFAS is concentrated by desorbing it using ion exchange. Activated carbon is obtained by heating organic waste with nitrates and other substances at several hundred degrees in an inert gas atmosphere. At this time, the surface of the activated carbon takes on a positive zeta (ζ) potential, making it more susceptible to PFAS adsorption.

[0012] The concentrated PFAS is decomposed into hydrofluoric acid by the destruction of nanobubbles and hydrogen peroxide, and then recovered as calcium fluoride by adding calcium salt. When using hydrogen peroxide, nanobubbles are generated in the hydrogen peroxide solution to promote the PFAS decomposition reaction. The calcium fluoride obtained as a by-product can be reused as a useful industrial substance, such as a raw material for hydrofluoric acid.

[0013] (Example of processing device configuration) 1 is a schematic diagram showing an example of the configuration of a treatment device 1 according to an embodiment. The treatment device 1 according to the embodiment is configured to treat PFAS contaminants, such as contaminated soil or water, and decompose them into hydrofluoric acid, and further produce calcium fluoride. The treatment device 1 according to the embodiment also produces activated carbon that adsorbs PFAS.

[0014] 1, the processing apparatus 1 includes processing vessels 10, 20, and 30. These processing vessels 10, 20, and 30 are interconnected by connection lines 25g and 35p through which, for example, a processing object or the like is supplied from the upstream processing vessel 10 through the processing vessel 20 to the downstream processing vessel 30.

[0015] Activated carbon is produced in the processing vessel 10. The processing vessel 10 is made of, for example, stainless steel. A tape heater 11 is wrapped around the outer wall of the processing vessel 10, and the temperature inside the processing vessel 10 can be raised to approximately 1000°C. A thermocouple-type temperature sensor (not shown) or the like that can measure the temperature of the processing vessel 10 may be provided near the tape heater 11 on the outer wall of the processing vessel 10.

[0016] Supply lines 15g, 16, 17, 18, and 19a are connected to the top of the treatment vessel 10. Supply line 15g is a line that supplies organic waste, which is a raw material for activated carbon, into the treatment vessel 10. Supply line 16 is a line that supplies nitrates such as HNO3 into the treatment vessel 10. In addition to nitrates, chitin and chitosan may also be supplied from supply line 16 into the treatment vessel 10. Supply line 18 is a line that supplies an inert gas such as N2 into the treatment vessel 10. Supply line 19a is a spare supply line and does not necessarily have to be provided in the treatment vessel 10.

[0017] A connection line 25g and a discharge line 19b are connected to the bottom of the treatment vessel 10. The connection line 25g connects the treatment vessel 10 and the treatment vessel 20, and is a line that supplies activated carbon produced in the treatment vessel 10 to the treatment vessel 20. The discharge line 19b is a spare discharge line that can be used to discharge reaction residues from various reactions and used activated carbon from the treatment vessel 10, etc.

[0018] Desorption of PFAS onto activated carbon is carried out in the treatment vessel 20. The treatment vessel 20 is made of, for example, stainless steel or Teflon (registered trademark).

[0019] In addition to the above-mentioned connection line 25g, supply lines 25p, 26, 27, and 29a are connected to the top of treatment vessel 20. Supply line 25p is a line that supplies PFAS-containing water obtained from PFAS-contaminated materials into treatment vessel 20. Supply line 26 is a line that supplies hydrochloric acid into treatment vessel 20. Supply line 27 is a line that supplies sodium hydroxide into treatment vessel 20. Supply line 29a is a spare supply line and does not necessarily need to be provided in treatment vessel 20.

[0020] A connection line 35p and a discharge line 29b are connected to the bottom of treatment vessel 20. Connection line 35p connects treatment vessel 20 and treatment vessel 30, and is a line that supplies PFAS-containing water that has been concentrated by desorption onto activated carbon within treatment vessel 20 to treatment vessel 30. Discharge line 29b is a spare discharge line that can be used, for example, to discharge reaction residues from various reactions from treatment vessel 20.

[0021] In the processing vessel 30, the PFAS in the concentrated PFAS-containing water is decomposed into hydrofluoric acid, and calcium fluoride is further produced. The processing vessel 20 is made of, for example, Monel, an alloy of nickel and copper, and nickel is sprayed onto the inner wall. This makes the processing vessel 30 corrosion-resistant against hydrofluoric acid generated during processing. However, other materials, such as vinyl chloride, may also be used for the processing vessel 30 as long as they are resistant to hydrofluoric acid. The processing vessel 30 is also provided with an outlet 31 through which the generated calcium fluoride can be removed.

[0022] An ultrasonic oscillator 32 coated with, for example, Teflon is provided inside the processing vessel 30. A power supply line 32s for supplying power to the ultrasonic oscillator 32 is drawn from the ultrasonic oscillator 32 to the outside of the processing vessel 30.

[0023] In addition to the connection line 35g, supply lines 36 and 37 are connected to the top of the processing vessel 30. The supply line 36 is a line that supplies hydrogen peroxide solution into the processing vessel 30. The supply line 37 is a line that supplies calcium salt such as CaCl2 into the processing vessel 30.

[0024] The processing vessel 30 is further housed in a glove box 33. The glove box 33 can be airtightly filled with an inert gas and has an opening 33t to which a glove 33g is attached. A supply line 33n for supplying an inert gas to the glove box 33 and an exhaust line 33e for exhausting the atmosphere inside the glove box 33 are connected to the glove box 33. The exhaust line 33e is connected to, for example, an exhaust gas treatment device (not shown), and the atmosphere inside the glove box 33 is rendered harmless by the exhaust gas treatment device and exhausted to the outside air.

[0025] The above-mentioned connection line 35g and supply lines 36 and 37 connected to the processing vessel 30, and the power supply line 32s drawn out from the processing vessel 30, pass through the top of the glove box 33 and extend to the outside of the glove box 33.

[0026] By wearing a glove 33g attached to the glove box 33 while the glove box 33 is filled with an inert gas, it is possible to safely extract products such as calcium fluoride from the outlet 31 of the processing vessel 30 in an environment inside the processing vessel 30 that involves the generation of hydrofluoric acid.

[0027] (Activated carbon production method) Next, a method for producing activated carbon in the processing vessel 10 included in the processing apparatus 1 of the embodiment will be described with reference to Fig. 2. Fig. 2 is a schematic diagram showing an example of a method for producing activated carbon according to the embodiment.

[0028] As shown in Figure 2(a), organic waste OW is prepared. The organic waste OW contains various organic materials, including food waste. The organic waste OW is washed with tap water, then washed with deionized water, and dried by heating in an oven or the like at a temperature of about 80°C for 24 hours.

[0029] As shown in FIG. 2(b), the organic waste OW is crushed into an organic powder OWp having an average particle size of, for example, several hundred μm or less, more preferably, less than 150 μm.

[0030] 2(c), organic powder OWp is introduced into the treatment vessel 10 through a supply line 15g, and a nitrate such as HNO3 is supplied to the treatment vessel 10 through a supply line 16. At this time, chitin and chitosan may also be supplied to the treatment vessel 10 through the supply line 16.

[0031] An inert gas atmosphere such as N2 is supplied from a supply line 18 to create an inert gas atmosphere inside the processing vessel 10. The tape heater 11 on the outer wall of the processing vessel 10 is then operated to heat the inside of the processing vessel 10 at a temperature of, for example, 400°C to 500°C for about an hour.

[0032] In this way, by adding nitrate and heating under an inert gas atmosphere, activated carbon with N groups attached to the surface is produced, and as a result, the surface potential of the activated carbon, more specifically, the zeta potential, which is the potential difference generated between the surface of the activated carbon dispersed in a liquid such as a treatment solution and the surrounding liquid, can be made positive.

[0033] In addition, chitin, which has an amide group (-CO-NH2), and chitosan, which has an amino group (-NH2), have a positive zeta potential in near-neutral or acidic conditions. Therefore, by adding these, chitin and chitosan can work together with the activated carbon produced to contribute to the concentration of PFAS, which dissociates into anions as described below.

[0034] As shown in Figure 2(d), Ni is further supplied to the treatment vessel 10 via a supply line 17 and heated at a temperature between 400°C and 800°C, preferably between 400°C and 600°C, for several hours. This results in activated carbon nanoparticles with Ni attached to their surfaces. The Ni attached to the surface of the activated carbon functions as a catalyst in the adsorption reaction with organic substances such as PFAS.

[0035] It has been confirmed that the above method can produce activated carbon with a positive zeta potential on the surface, using discarded pomelo peels.

[0036] (PFAS concentration method) Next, a method for concentrating PFAS in the processing vessel 20 included in the processing apparatus 1 of the embodiment will be described.

[0037] First, PFAS-contaminated materials such as contaminated soil or water are collected from a PFAS contamination source, and the PFAS-contaminated materials are mixed with water to produce PFAS-containing water.

[0038] If readily degradable organic matter is present in the PFAS-containing water, it must be removed in advance. Unlike persistent PFAS, readily degradable organic matter is easily decomposed by microorganisms, for example.

[0039] Easily degradable organic matter in PFAS-containing water can be removed using aeration methods, such as pumping air into the water to activate aerobic microorganisms and promote the decomposition of easily degradable organic matter in the PFAS-containing water.

[0040] In addition, PFAS contaminants often contain only small amounts of PFAS, in which case the PFAS concentration in the PFAS-containing water obtained as described above will also be low. For example, the PFAS concentration in PFAS-containing water at this stage can vary widely, from very low concentrations of several hundred ng / L to tens of thousands of ng / L, more typically from several hundred ng / L to several thousand ng / L, ranging from very high concentrations of PFAS.

[0041] Therefore, in the treatment vessel 20 provided in the treatment device 1 described above, the dilute PFAS in the PFAS-containing water is desorbed onto the activated carbon obtained as described above and concentrated.

[0042] The activated carbon produced in the treatment vessel 10 described above is supplied into the treatment vessel 20 via a connection line 25g. In addition, PFAS-containing water is supplied into the treatment vessel 20 from a supply line 25p.

[0043] As shown in the chemical formula below, PFOA ionizes into an anion in PFAS-containing water.

[0044] [ka]

[0045] As shown in the chemical formula below, PFOS also ionizes in PFAS-containing water to become an anion.

[0046] [ka]

[0047] Therefore, PFASs including PFOA and PFOS can be adsorbed onto the surface of activated carbon having the above-mentioned positive zeta potential. Furthermore, the PFASs adsorbed onto the surface of the activated carbon and bound to the activated carbon can be desorbed from the surface of the activated carbon by acidifying or alkaline the PFAS-containing water in the treatment vessel 20.

[0048] To make the PFAS-containing water acidic, hydrochloric acid can be introduced into treatment vessel 20 via supply line 26. To make the PFAS-containing water alkaline, sodium hydroxide can be introduced into treatment vessel 20 via supply line 27. This causes the PFAS to be desorbed from the activated carbon surface by ion exchange.

[0049] By repeatedly passing hydrochloric acid and sodium hydroxide through the PFAS-containing water, the pH of the water can be changed from acidic to neutral and then from neutral to alkaline, allowing the PFAS to be repeatedly desorbed onto the activated carbon. This allows the PFAS to be gradually concentrated, resulting in concentrated PFAS-containing water.

[0050] Although it depends on the initial concentration of the PFAS-containing water immediately after collection, it is preferable that the PFAS concentration in the PFAS-containing water after desorption onto activated carbon and concentration is at least several thousand ng / L or more.

[0051] In addition, used activated carbon can be recycled after the adsorbed PFASs are finally desorbed.

[0052] (PFAS decomposition method) Next, a method for decomposing PFAS and a method for producing calcium fluoride in the processing vessel 30 included in the processing apparatus 1 of the embodiment will be described.

[0053] The PFAS-containing water concentrated in the above-described treatment vessel 20 is supplied into treatment vessel 30 via connection line 35p. Hydrogen peroxide solution is also supplied into treatment vessel 30 from supply line 36. This fills treatment vessel 30 with hydrogen peroxide solution, and ultrasonic oscillator 32 in treatment vessel 30 is immersed in the hydrogen peroxide solution. The upper part of treatment vessel 30 is filled with a gas such as nitrogen or air to be used as the nanobubble gas.

[0054] In this state, when the ultrasonic oscillator 32 is operated, the ultrasonic vibrations cause the gas in the upper part of the processing vessel 30 to become nanobubbles, which are then generated and dispersed in the liquid. If the processing vessel 30 contains hydrogen peroxide solution, the ultrasonic vibrations generate nanobubbles containing the gas in the upper part of the processing vessel 30 in the hydrogen peroxide solution. The diameter of the nanobubbles is, for example, 100 nm or more and 1000 nm or less, and more preferably 100 nm or more and 200 nm or less.

[0055] In this case, if the pH of the hydrogen peroxide solution is maintained at a weak acidity of 3.0 or more and less than 6.0, for example, at about pH 4.5, nanobubbles containing air, for example, will become unstable without having a surface potential and will burst and disappear. More specifically, by appropriately adjusting the pH of the hydrogen peroxide solution, the zeta potential of the nanobubbles can be made close to zero, causing the nanobubbles to burst and disappear.

[0056] This impact can generate hydroxyl radicals (·OH) from hydrogen peroxide, as shown in the chemical formula below.

[0057] H2O2+N2→2·OH+N2 H2O2+O2→2·OH+O2 (2H2O+H2→·O2 - +3H2 → 2·OH+H2)

[0058] In addition, PFAS in concentrated PFAS-containing water can be decomposed into hydrofluoric acid by the hydroxyl radicals generated by generating and bursting nanobubbles in hydrogen peroxide. The following chemical formula shows how PFOA in PFAS-containing water is decomposed.

[0059] [ka]

[0060] As shown in the chemical formula above, the hydroxyl radical generated from hydrogen peroxide reacts with the carboxyl group (-COO) at the end of the PFAS anion. - ) and so on, it acts in order from the most vulnerable parts, cleaving the fluorine in PFOA one by one and breaking it down into hydrofluoric acid.

[0061] As mentioned above, PFOS in PFAS-containing water is also anionized and, like PFOA, is subsequently decomposed into hydrofluoric acid.

[0062] After the reaction between the PFAS and the hydroxyl group has progressed sufficiently and the PFAS has been largely decomposed into hydrofluoric acid, a calcium salt such as CaCl2 is supplied into the treatment vessel 30 from the supply line 37. This causes the hydrofluoric acid and the calcium salt to react, resulting in the precipitation of calcium fluoride (CaF2).

[0063] However, care must be taken when adding calcium salts before the reaction between PFAS and hydroxyl groups has progressed sufficiently, as this will inhibit the production of nanovalves in hydrogen peroxide.

[0064] As described above, calcium fluoride precipitated in the processing vessel 30 is recovered from the outlet 31 provided in the processing vessel 30 by using, for example, the glove 33g of the glove box 33 in which the processing vessel 30 is accommodated.

[0065] This completes the treatment of PFAS and produces calcium fluoride from PFAS.

[0066] Thus, the PFAS treatment method of the embodiment includes a method for producing calcium fluoride, which can be recycled as a raw material for hydrofluoric acid, for example.

[0067] (Overview) According to the PFAS treatment method of the embodiment, activated carbon with a positive zeta potential is added to PFAS-containing water to adsorb the PFAS in the PFAS-containing water onto the surface of the activated carbon, and an acidic or alkaline solution is added to the PFAS adsorbed on the activated carbon to desorb and concentrate the PFAS from the activated carbon.

[0068] The positive zeta potential of activated carbon makes it possible to obtain activated carbon that easily adsorbs PFASs that are anionic in PFAS-containing water. Furthermore, desorption onto such activated carbon increases the concentration of PFASs in PFAS-containing water, resulting in concentrated PFAS-containing water.

[0069] According to the PFAS treatment method of the embodiment, hydrogen peroxide solution is added to the PFAS desorbed from activated carbon, nanobubbles are generated in the hydrogen peroxide solution, and the pH of the hydrogen peroxide solution is adjusted to a level at which the nanobubbles are destroyed, thereby decomposing the PFAS into hydrofluoric acid.

[0070] In this way, by utilizing the impact of nanobubbles bursting, hydroxyl radicals can be generated from hydrogen peroxide solution, increasing its reactivity with PFAS, thereby decomposing PFAS into hydrofluoric acid.

[0071] Conventionally, methods for generating hydroxyl radicals from hydrogen peroxide solution have been known, such as ultraviolet irradiation. However, it is difficult to irradiate ultraviolet rays evenly over a wide area, for example, in a large-capacity processing vessel. It is also difficult to irradiate ultraviolet rays in an environment inside the processing vessel that involves the generation of hydrofluoric acid.

[0072] The PFAS treatment method of the embodiment is advantageous because it can generate nanobubbles throughout the hydrogen peroxide solution, thereby promoting the generation of hydroxyl radicals.

[0073] As described above, according to the PFAS treatment method of the embodiment, PFAS can be efficiently treated by a method that uses a chemical wet method and has a low environmental impact.

[0074] According to the PFAS treatment method of the embodiment, chitin and chitosan are added when nitrate is added to activated carbon. This allows chitin and chitosan, which are acidic and have a positive zeta potential, to work together with activated carbon to further promote PFAS adsorption, enabling efficient concentration of PFAS-containing water.

[0075] According to the PFAS treatment method of the embodiment, activated carbon is produced by heating organic waste in an inert gas atmosphere at a temperature of 400°C to 500°C, adding nickel to the organic waste, and further heating it at a temperature of 400°C to 800°C. This produces high-quality activated carbon.

[0076] According to the embodiment of the PFAS treatment method and calcium fluoride production method, calcium fluoride is produced by adding calcium salt to hydrofluoric acid in which PFAS has been decomposed. This not only decomposes PFAS contaminants but also converts PFAS into a useful industrial resource. This can help establish a material flow that ensures a stable supply of calcium fluoride in Japan.

[0077] In the above-described embodiment, the treatment device 1 has, for example, only one treatment container 20 for concentrating PFAS. However, the treatment containers for concentrating PFAS may be configured in multiple stages. This allows PFAS to be desorbed onto activated carbon efficiently and repeatedly, and concentrated PFAS-containing water can be obtained in a shorter treatment time.

[0078] In the above-described embodiment, nanobubbles are introduced into hydrogen peroxide by ultrasonic vibration. However, the method for generating nanobubbles is not limited to this. Nanobubbles can also be generated by, for example, a method of stirring hydrogen peroxide at high speed, a method using a porous membrane, a pressurized method, or the like. [Explanation of symbols]

[0079] 1 Processing equipment 10, 20, 30 Treatment container 15g, 16, 17, 25p, 26, 27, 36, 37...supply lines 25g, 35p...connection line 32...Ultrasonic oscillator 32s...power line 33...Glove box

Claims

1. agitating the PFAS contaminant into water to produce PFAS-containing water; adding activated carbon having a positive zeta potential in a neutral to acidic aqueous solution to the PFAS-containing water, and adsorbing the PFAS in the PFAS-containing water onto the surface of the activated carbon; adding an acidic or alkaline solution to the PFAS adsorbed on the activated carbon to desorb the PFAS from the activated carbon and concentrate it; adding hydrogen peroxide water to the PFAS desorbed from the activated carbon, generating nanobubbles having a diameter of 100 nm or more and 1000 nm or less in the hydrogen peroxide water, and adjusting the pH of the hydrogen peroxide water to 3.0 or more and less than 6.0 at which the nanobubbles are destroyed, thereby decomposing the PFAS into hydrofluoric acid; Methods for treating PFAS.

2. The nanobubbles are generated by at least one of an ultrasonic method, a stirring method, a porous membrane permeation method, and a pressure method. The method for treating PFAS according to claim 1.

3. The diameter of the nanobubbles is 50 nm or more and 900 nm or less on average. The method for treating PFAS according to claim 1.

4. The diameter of the nanobubbles is 200 nm or less on average. The method for treating PFAS according to claim 3.

5. adding a calcium salt to the hydrofluoric acid to produce calcium fluoride; The method for treating PFAS according to claim 1.

6. agitating the PFAS contaminant into water to produce PFAS-containing water; adding activated carbon having a positive zeta potential in a neutral to acidic aqueous solution to the PFAS-containing water, and adsorbing the PFAS in the PFAS-containing water onto the surface of the activated carbon; adding an acidic or alkaline solution to the PFAS adsorbed on the activated carbon to desorb the PFAS from the activated carbon and concentrate it; adding hydrogen peroxide water to the PFAS desorbed from the activated carbon to generate nanobubbles having a diameter of 100 nm or more and 1000 nm or less in the hydrogen peroxide water; adjusting the pH of the hydrogen peroxide water to 3.0 or more and less than 6.0 at which the nanobubbles are destroyed; and decomposing the PFAS into hydrofluoric acid; adding a calcium salt to the hydrofluoric acid to produce calcium fluoride; How calcium fluoride is produced.

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