Activated carbon, adsorption filter including same, water purifier, and method for producing activated carbon

Abstract

One aspect of the present invention relates to activated carbon which has a BET specific surface area of 500 m2 / g or larger and which, in a solid 19F-NMR examination, shows a 19F-derived peak at between -100 ppm and -120 ppm.

Description

Activated carbon, adsorption filter and water purifier using the same, and method for manufacturing activated carbon

[0001] The present invention relates to activated carbon, an adsorption filter and a water purifier using the same, and a method for producing activated carbon. In particular, the present invention relates to activated carbon used in water treatment to remove perfluoroalkyl compounds and polyfluoroalkyl compounds contained in water.

[0002] Fluorine-containing organic compounds have unique properties that cannot be achieved with other substances (excellent heat and chemical resistance, usable even under harsh conditions, no light absorption, etc.), and so have been used in a variety of applications, including surfactants, emulsifiers, water repellents, fire extinguishing agents, waxes, carpet cleaning agents, coating agents, etc. Recently, they have also been increasingly used as functional materials, such as surface treatment agents for semiconductors and fuel cell constituent materials.

[0003] However, in recent years, researchers in the United States and Canada have begun to report that some fluorine-containing organic compounds accumulate in environmental water and in the bodies of wildlife. A typical example is perfluorooctanoic acid (PFOA). ７ F １５ COOH) and perfluorooctanesulfonic acid (PFOS:C ８ F １７ SO ３ These are perfluorosulfonic acids, represented by PFCs (Perfluorooctafluorocarbons (PFCs)). Subsequently, European and Japanese researchers also began to participate in environmental analysis research, and it became clear that these compounds exist in the environment on a global scale, including in Japan. In response to this situation, efforts have begun to reduce the environmental risks posed by fluorine-containing organic compounds (PFCs).

[0004] Patent Document 1 discloses a method for recovering PFOA using granular activated carbon. Note that perfluoroalkyl compounds have a completely fluorinated straight-chain alkyl group, and examples include perfluorooctanoic acid (PFOA) (IUPAC name: 2,2,3,3,4,4,5,5,6,6,7,7,8,8,8-pentadecafluorooctanoic acid) and perfluorooctanesulfonic acid (PFOS), as shown in the following chemical formula:

[0005]

[0006] However, although the method of using activated carbon in treating PFOA and the like as in Patent Document 1 has a great economic advantage, the treatment efficiency of the conventional technology has not been satisfactory.

[0007] Therefore, in view of the above-mentioned current situation, a main object of the present invention is to provide activated carbon capable of efficiently removing fluorine-containing organic compounds, and an adsorption filter and a water purifier using the same for treating water containing fluorine-containing organic compounds.

[0008] US Patent Application Publication No. 2005 / 0000904

[0009] As a result of intensive investigations to solve the above problems, the present inventors have found that the above problems can be solved by activated carbon having the following composition, and have completed the present invention through further investigations based on this finding.

[0010] That is, the activated carbon according to the first aspect of the present invention has a BET specific surface area of ​​500 m ２ / g or more, and solid １９ In F-NMR measurements １９ It is characterized in that a peak due to F is observed between -100 and -120 ppm.

[0011] FIG. 1 shows the activated carbon obtained in the example. １９ Figure 2 shows the results of F-NMR measurements. Figure 2 is a comparative graph showing the perfluorooctanoic acid (PFOA) removal effect of the activated carbons of Example 1, Example 3, and Comparative Example 1. Figure 3 is a comparative graph showing the perfluorooctanoic acid (PFOA) removal effect of the activated carbons of Example 2 and Comparative Example 2.

[0012] Hereinafter, embodiments of the present invention will be specifically described, but the present invention is not limited to these.

[0013] (Activated carbon) The activated carbon of this embodiment has a BET specific surface area of ​​500 m ２ / g or more, and solid １９ In F-NMR measurements １９It is characterized in that a peak due to F is observed between -100 and -120 ppm.

[0014] According to the above configuration, it is possible to provide activated carbon that can efficiently remove fluorine-containing organic compounds, and an adsorption filter and a water purifier that use the same for treating water that contains fluorine-containing organic compounds.

[0015] Activated carbon has a small amount of functional groups relative to its specific surface area and is generally known as a hydrophobic substance in water. On the other hand, perfluoroalkyl compounds and polyfluoroalkyl compounds have amphiphilic properties, having hydrophobic groups derived from C—F bonds and hydrophilic groups such as carboxylic acids and sulfonic acids. Activated carbon, which is a hydrophobic substance, is said to adsorb perfluoroalkyl compounds and / or polyfluoroalkyl compounds into its pores, and the cause of this adsorption is thought to be hydrophobic interaction.

[0016] The activated carbon of this embodiment has a viscosity of at least 500 m ２ The specific surface area is determined by the pores formed in activated carbon for adsorbing substances, and is 500 m ２ / g or more, a sufficient area for adsorption of substances can be secured. On the other hand, there is no particular upper limit on the specific surface area, but an excessively large specific surface area is not preferred because it reduces the mechanical strength of the activated carbon. From the viewpoint of more effectively thermally decomposing the adsorbed perfluoroalkyl compound and / or polyfluoroalkyl compound and suppressing a decrease in mechanical strength, a specific surface area of ​​600 to 3500 m ２ / g, and 750 to 2500m ２ More preferably, it is 500 m / g. ２ / g, 750m ２ / g, 1000m ２ / g, 1250m ２ / g, 1500m ２ / g, 1750m ２ / g, 2000m ２ / g, 2250m ２ / g, 2500m ２ / g, 2750m ２ / g, 3000m ２ / g, 3250m ２ / g, 3500m ２ / g, etc.

[0017] In this embodiment, the BET specific surface area refers to the specific surface area calculated by the nitrogen adsorption method, and is a value measured by the method described in the examples below.

[0018] In addition to the specific surface area, the present inventors have considered that the affinity for perfluoroalkyl compounds and / or polyfluoroalkyl compounds having C-F bonds can be improved by adding fluorine derived from the C-F bonds to activated carbon, which will promote more effective adsorption. Based on this finding, the adsorption of perfluoroalkyl compounds and / or polyfluoroalkyl compounds by activated carbon will be described.

[0019] The activated carbon of this embodiment is a solid １９ In F-NMR measurements １９ A peak due to F is observed between -100 and -120 ppm. １９ The F-NMR measurement can be performed using any NMR device that can obtain an NMR spectrum of a solid sample by nuclear magnetic resonance (NMR) without any particular limitation. For example, the measurement can be performed using a device such as that used in the examples described below.

[0020] The activated carbon for which the above peaks are observed contains fluorine and is therefore considered to have a high affinity with perfluoroalkyl compounds and / or polyfluoroalkyl compounds.

[0021] The solid １９ In F-NMR measurement, １９ The peak derived from F is preferably a peak derived from fluorine bonded to the activated carbon. As a result, the presence of fluorine derived from the C—F bond in the activated carbon further enhances the affinity with perfluoroalkyl compounds and / or polyfluoroalkyl compounds having C—F bonds, which is thought to promote more efficient adsorption of the perfluoroalkyl compounds and / or polyfluoroalkyl compounds to the activated carbon of this embodiment.

[0022] In this embodiment, the fluorine content relative to 100% by weight of activated carbon is preferably 0.0001% by weight or more. A trace amount of fluorination of activated carbon can improve adsorption function. The preferred fluorine content relative to 100% by weight of activated carbon may be 0.0001 to 5% by weight, 0.0001 to 3% by weight, 0.0001 to 2% by weight, 0.001 to 1.5% by weight, 0.001 to 1% by weight, 0.001 to 0.2% by weight, 0.005 to 0.15% by weight, or 0.01 to 0.1% by weight. Specifically, the fluorine content may be 0.0001% by weight, 0.0005% by weight, 0.001% by weight, 0.002% by weight, 0.005% by weight, 0.01% by weight, 0.05% by weight, 0.1% by weight, 0.5% by weight, 1% by weight, 1.5% by weight, 2% by weight, or the like.

[0023] In this embodiment, the activated carbon may be any one selected from powdered activated carbon, fibrous activated carbon, granular activated carbon, and pelleted activated carbon. Fibrous activated carbon is activated carbon obtained by carbonizing and activating appropriate fibers, such as phenolic resin-based, acrylic resin-based, cellulose-based, and coal pitch-based activated carbon. The fiber length, cross-sectional diameter, and the like are appropriate.

[0024] Raw materials for granular activated carbon include wood (waste wood, thinned wood, sawdust), coffee grounds, rice husks, coconut shells, bark, and fruit kernels. These naturally derived raw materials are more likely to develop pores when carbonized and activated. Furthermore, because they are secondary waste materials, they can be procured inexpensively. Other materials that can be used include burned materials derived from tires, petroleum pitch, urethane resin, phenolic resin, and other synthetic resins, as well as coal.

[0025] In particular, the activated carbon of the present embodiment is preferably activated carbon in the form of powder, granules, or pellets.

[0026] Powdered activated carbon and pelleted activated carbon can be produced by pulverizing or molding the above-mentioned fibrous or granular activated carbon.

[0027] (Method for Producing Activated Carbon) The activated carbon of the present embodiment can be obtained, for example, by activating the activated carbon raw material as described above, allowing a fluorine-containing compound to be adsorbed onto the activated activated carbon raw material (base activated carbon), and then heat-treating the fluorine-containing compound-impregnated activated carbon at a temperature equal to or higher than the decomposition starting temperature of the fluorine-containing compound.

[0028] The activated carbon raw material is heated and carbonized as needed in a temperature range of 200° C. to 600° C., whereby carbon fixation proceeds and micropores are formed. When carbonization is required, it is usually carried out in a state where oxygen or air is blocked.

[0029] Next, the activated carbon raw material is exposed to water vapor, carbon dioxide gas, or a mixture of these gases in the temperature range of 600°C to 1200°C for activation treatment. As a result, activated carbon with various types of developed pores is obtained. In consideration of safety and reactivity, it is preferable to use a water vapor-containing gas containing 10 to 40 volume % water vapor as the activation gas. The activation time and temperature rise rate are not particularly limited and can be selected appropriately depending on the type, shape, and size of the selected carbonaceous material. In addition to the gas activation method, chemical activation (chemical activation) methods such as adding potassium hydroxide or zinc chloride and performing heat treatment may also be used for activation, or gas activation and chemical activation may be combined. Sequential washing is also performed.

[0030] In this embodiment, the solid １９ In F-NMR measurements １９ The method for obtaining activated carbon in which a peak derived from F is observed between −100 and −120 ppm is not particularly limited, and the activated carbon can be produced by activating a fluorine-containing resin (activated carbon raw material), or by adding a fluorine compound to the activated carbon obtained as a base after activating the activated carbon raw material, allowing the base activated carbon to adsorb, and then reacting the fluorine compound with the activated carbon.

[0031] In this embodiment, examples of usable fluorine-containing resins include polytetrafluoroethylene, perfluoroalkoxyalkane, ethylene-tetrafluoroethylene copolymer, perfluoroethylene-propene copolymer, polyvinylidene fluoride, polychlorotrifluoroethylene, and ethylene-chlorotrifluoroethylene copolymer.

[0032] In a preferred embodiment, the fluorine-containing compound-impregnated activated carbon is produced by adding and adsorbing a fluorine compound to a base activated carbon obtained by activating an activated carbon raw material, and then reacting the base activated carbon with the fluorine compound. The method for reacting the base activated carbon with the fluorine compound is not particularly limited, and examples include a method in which hydrogen in the base activated carbon is replaced with a metal and then reacted with the fluorine compound, a method in which the base activated carbon is heated together with the base activated carbon and fluorinated by thermally generated radicals, and a method in which the base activated carbon is directly reacted with hydrogen fluoride. In consideration of the versatility of the method, the method in which the fluorine compound is heated together with the base activated carbon is preferred.

[0033] The fluorine compound to be adsorbed on the base activated carbon is not particularly limited, and examples thereof include inorganic fluorides such as sodium fluoride, potassium fluoride, lithium fluoride, calcium fluoride, magnesium fluoride, iron fluoride, copper fluoride, and nickel fluoride, perfluorobutane, perfluoropentane, perfluorohexane, perfluoroheptane, perfluorooctane, perfluorononane, perfluorodecane, perfluoroundecane, perfluorododecane, perfluorotridecane, perfluorotetradecane, perfluorobutanoic acid, and perfluoroisopropyl fluoride. perfluoropentanoic acid, perfluorohexanoic acid, perfluoroheptanoic acid, perfluorooctanoic acid, perfluorononanoic acid, perfluorodecanoic acid, perfluoroundecanoic acid, perfluorododecanoic acid, perfluorotridecanoic acid, perfluorotetradecanoic acid, perfluorobutanesulfonate, perfluoropentanesulfonate, perfluorohexanesulfonate, perfluoroheptanesulfonate, perfluorooctane sulfonate, perfluorononanesulfonate, perfluorodecanesulfonate, 1H,1H,2H,2H-perfluorooctanoic acid, perfluorohexanesulfonic acid, 1H,1H,2H,2H-perfluorooctane sulfonic acid, 1H,1H,2H,2H-perfluorodecanesulfonic acid, perfluorooctane sulfonamide, N-methylperfluorooctane sulfonamide, N-ethylperfluorooctane sulfonamide, N-methylperfluorooctane sulfonamide acetic acid, N-ethylperfluorooctane sulfonamide acetic acid, N-methylperfluorooctane sulfonamide ethanol, N-ethylperfluorooctane sulfonamide ethanol, hexafluoropropylene oxide perfluorooctanoic acid, 4,8-dioxa-3H-perfluorononanoic acid, perfluoro-3-methoxypropanoic acid, perfluoro-4-methoxybutanoic acid, nonafluoro-3,6-dioxaheptanoic acid, 9-chlorohexadecafluoro-3-oxanonane-1-sulfonic acid, 11-chloroeicosafluoro-3-oxaundecane-1-sulfonic acid, perfluoro(2-ethoxyethane)sulfonic acid, 3-perfluoropropylpropanoic acid, 2H,2H,3H,3H-perfluorooctanoic acid, 3-perfluoroheptylpropanoic acid, bis(1H,1H,2H,2H-perfluorodecyl) and derivatives thereof such as salts thereof. These may be used alone or in combination.

[0034] Furthermore, a fluorine-containing polymer can also be used. The polymer to be used is not particularly limited, and examples thereof include polytetrafluoroethylene, perfluoroalkoxyalkane, ethylene-tetrafluoroethylene copolymer, perfluoroethylene-propene copolymer, polyvinylidene fluoride, polychlorotrifluoroethylene, and ethylene-chlorotrifluoroethylene copolymer. These may be used alone or in combination.

[0035] The amount of fluorine compound added to the base activated carbon is not particularly limited, but since the amount of fluorination varies depending on the amount of fluorine compound added, a somewhat larger amount is preferable because it allows for more efficient fluorination. On the other hand, an excessively large amount is not preferred because it volatilizes without being used for fluorination, and there is a risk of highly reactive fluorine leaking out of the system. Therefore, the amount added to the activated carbon is in the range of 0.01 ppm to 100 wt%, more preferably 0.1 ppm to 10 wt%, and even more preferably 0.2 ppm to 8 wt%, relative to 100 wt% of the base activated carbon used.

[0036] In the production method of this embodiment, the fluorination conditions are not particularly limited, and a thermal or radical decomposition method can be used as long as the conditions are such that the fluorine-containing compound added to the activated carbon is decomposed to generate fluorine anions and fluorine radicals. That is, it is preferable to use a method in which the activated carbon together with the fluorine-containing compound is heated to the decomposition temperature of the fluorine-containing compound, or a method in which ultraviolet light, an electron beam, or the like is irradiated. In consideration of not requiring special equipment, it is preferable to use a thermal method, i.e., heat treatment.

[0037] In the present embodiment, when heat treatment is performed, it is preferable to perform the heat treatment at a temperature equal to or higher than the temperature at which the fluorine-containing compound decomposes, as described above. The heating temperature is preferably 200 to 2000°C, more preferably 300 to 1800°C, and even more preferably 400 to 1500°C. If the temperature exceeds 2000°C, the generated reactive fluorine compound may not easily react with the activated carbon.

[0038] In this embodiment, it is preferable to perform the heat treatment under conditions in which carbon is not burned or consumed. That is, it is preferable to perform the heat treatment in the absence of oxygen. "In the absence of oxygen" refers to an atmosphere in which carbon is not substantially oxidized by oxygen, burned, or consumed. Therefore, "in the absence of oxygen" in this specification may refer to an environment substituted with an inert gas such as nitrogen, or an environment in which decomposition products produced during heating react with oxygen to create a substantially oxygen-free state.

[0039] The reaction time of the heat treatment in this embodiment is not particularly limited as long as the fluorination proceeds, and is, for example, in the range of 1 to 720 minutes, more preferably in the range of 2 to 360 minutes, and even more preferably in the range of 5 to 180 minutes.

[0040] In this embodiment, the activated carbon that has been subjected to the heat treatment can be taken out by cooling it to an inert temperature, typically to 200° C. or less.

[0041] In addition to the above steps, it is known that reducing the surface oxide concentration is also effective in further improving the hydrophobicity of activated carbon. Known methods such as heat treatment under an inert gas atmosphere can be used to reduce the surface oxide concentration of activated carbon, which can reduce acidic functional groups such as phenolic hydroxyl groups and carboxyl groups on the surface of activated carbon.

[0042] The fluorinated activated carbon obtained as described above has a BET specific surface area of ​​500 m ２ / g or more, and solid １９ In F-NMR measurements １９This activated carbon exhibits a peak derived from F observed between −100 and −120 ppm, and by using this activated carbon, fluorine-containing organic compounds can be efficiently removed.

[0043] Furthermore, in the production method of this embodiment, activated carbon that has been used to remove perfluoroalkyl compounds and / or polyfluoroalkyl compounds can also be used as the activated carbon raw material. In this case, the used activated carbon may be ordinary activated carbon (activated carbon that has not adsorbed fluorine-containing compounds after activation) that has been used to remove perfluoroalkyl compounds and / or polyfluoroalkyl compounds.

[0044] That is, first, non-fluorinated activated carbon is used to remove perfluoroalkyl and / or polyfluoroalkyl compounds, thereby obtaining activated carbon with adsorbed perfluoroalkyl and / or polyfluoroalkyl compounds. By subjecting the used activated carbon to the heat treatment described above, activated carbon with fluorine bonded thereto can be obtained. By heat treating the activated carbon used for such removal, it is possible to obtain activated carbon with stronger hydrophobicity, and the fluorine introduced into the activated carbon (fluorine bonded to the activated carbon) has the advantage of making it easier to adsorb perfluoroalkyl and / or polyfluoroalkyl compounds.

[0045] (Adsorption filter) This embodiment includes an adsorption filter comprising the above-described activated carbon. The adsorption filter of this embodiment is not particularly limited as long as it comprises the above-described activated carbon, but for example, it includes the activated carbon and a fibrous binder.

[0046] The fibrous binder used in the adsorption filter of this embodiment is not particularly limited as long as it can be entangled with the activated carbon and shaped, and a wide range of synthetic and natural binders can be used. Examples of such binders include acrylic fibers, polyethylene fibers, polypropylene fibers, polyacrylonitrile fibers, cellulose fibers, nylon fibers, aramid fibers, and pulp. The fiber length of the fibrous binder is preferably 4 mm or less.

[0047] These fibrous binders may be used in combination of two or more. It is particularly preferred to use polyacrylonitrile fibers or cellulose fibers as the binder. This can further increase the density and strength of the molded product and suppress performance degradation.

[0048] In this embodiment, the water permeability of the fibrous polymer binder is preferably about 10 to 150 mL in terms of CSF value. More preferably, it is about 20 to 110 mL. In this embodiment, the CSF value is a value measured in accordance with JIS P8121 (2012) "Testing Method for Freeness of Pulp," a Canadian Standard Freeness Method. The CSF value can be adjusted, for example, by fibrillating the binder.

[0049] The adsorption filter of the embodiment may also contain functional components other than those described above, as long as the effects of the present invention are not impaired. For example, any amount of adsorbent containing silver ions and / or silver compounds to impart antibacterial properties, zeolite such as silica or titanosilicate to remove metals such as lead and copper, or molded diatomaceous earth may be added, and in such cases, the amount is typically 0.1 to 30 parts by mass relative to the entire adsorption filter.

[0050] In terms of adsorption effect, moldability, and the like, the mixing ratio of each component in the adsorption filter of this embodiment is preferably about 3 to 8 parts by mass of the fibrous binder per 100 parts by mass of the activated carbon or the mixture of the activated carbon and the functional component. If the amount of fibrous binder is less than 3 parts by mass, sufficient strength may not be obtained and a molded body may not be able to be formed. Furthermore, if the amount of fibrous binder exceeds 8 parts by mass, adsorption performance may be reduced. More preferably, it is desirable to blend 3.5 to 6 parts by mass of the fibrous binder.

[0051] The adsorption filter of this embodiment may be a cylindrical filter containing a core in addition to the activated carbon and the fibrous binder. The cylindrical shape reduces water flow resistance and, when used as a cartridge by filling a housing as described below, simplifies the loading and replacement of the cartridge into a water purifier.

[0052] The core that can be used in this embodiment is not particularly limited as long as it can be inserted into the hollow part of the cylindrical filter and can reinforce the cylindrical filter, but for example, a toric pipe, a netron pipe, or a ceramic filter is preferable. Furthermore, a nonwoven fabric or the like can be wrapped around the outer periphery of the core.

[0053] (Uses of the adsorption filter) The adsorption filter of this embodiment is used, for example, as a filter for a water purifier, a simple water purification filter, an air purification filter, etc. When used as a filter for a water purifier, for example, the adsorption filter of this embodiment can be obtained by shaping, drying, and then cutting to a desired size and shape. Furthermore, if necessary, a cap may be attached to the tip portion, or a nonwoven fabric may be attached to the surface.

[0054] The adsorption filter of this embodiment can be packed into a housing and used as a water purification cartridge. The cartridge is loaded into a water purifier and used to pass water, and the water passing method can be a total filtration method in which the entire amount of raw water is filtered or a circulating filtration method. Therefore, this embodiment also includes a water purifier that uses the adsorption filter.

[0055] In this embodiment, the cartridge loaded into the water purifier may be, for example, a water purification filter filled into the housing, but it may also be used in combination with known nonwoven fabric filters, various adsorbents, mineral additives, ceramic filtering materials, etc.

[0056] As described above, this specification discloses various aspects of the technology, but the main technologies among them are summarized below.

[0057] The activated carbon according to the first aspect of the present invention has a BET specific surface area of ​​500 m ２ / g or more, and solid １９ In F-NMR measurements １９ It is characterized in that a peak due to F is observed between -100 and -120 ppm.

[0058] The activated carbon according to the second aspect of the present invention is the activated carbon according to the first aspect, wherein the solid １９ In F-NMR measurement, １９ The peak due to F is due to fluorine bonded to activated carbon.

[0059] The activated carbon according to the third aspect of the present invention is the activated carbon according to the first or second aspect, in which the fluorine content relative to 100% by weight of the activated carbon is 0.0001% by weight or more.

[0060] The activated carbon according to the fourth aspect of the present invention is the activated carbon according to any one of the first to third aspects, which is in the form of powder, granules or pellets.

[0061] The activated carbon according to the fifth aspect of the present invention is the activated carbon according to any one of the first to fourth aspects, which is used to remove perfluoroalkyl compounds and polyfluoroalkyl compounds.

[0062] An adsorption filter according to a sixth aspect of the present invention is an adsorption filter comprising the activated carbon of any one of the first to fifth aspects.

[0063] A water purifier according to a seventh aspect of the present invention includes the adsorption filter according to the sixth aspect.

[0064] A production method according to an eighth aspect of the present invention is the production method of activated carbon according to any one of the first to fifth aspects, characterized in that it includes activating a raw material for activated carbon, allowing the activated raw material for activated carbon to adsorb a fluorine-containing compound, and heat-treating the fluorine-containing compound-impregnated activated carbon at a temperature equal to or higher than the decomposition starting temperature of the fluorine-containing compound.

[0065] The present invention will be explained in more detail below with reference to examples, but the present invention is not limited to these examples in any way.

[0066] First, the test methods for evaluating the properties in the present example will be described.

[0067] [BET Specific Surface Area Measurement] The specific surface area was determined by the BET method, which measures the nitrogen adsorption isotherm of a sample, using a nitrogen adsorption amount measuring device "BELSORP-MAX" manufactured by Microtrac-Bel.

[0068] [solid １９ F-NMR measurement] Solid １９ F-NMR was measured using the following apparatus. Apparatus: Nuclear Magnetic Resonance Apparatus "ECZ-500R" manufactured by JEOL Ltd. Conditions: Resonance frequency: 19F 470 MHz / Probe: 3.2 mm Measurement mode: MAS (Relaxation Delay = 10 s) Rotation speed: 14 kHz Measurement temperature: Room temperature BF: 20 Hz

[0069] [Fluorine Content] The fluorine content in the activated carbon was calculated by automatic combustion ion chromatography.

[0070] (Combustion device) Device: Automatic sample combustion device "AQF-2100H" manufactured by Mitsubishi Chemical Analytech Co., Ltd. Combustion temperature: 1000°C Absorption liquid: Ion-exchanged water

[0071] (Ion Chromatography) Apparatus: Ion Chromatograph "ICS-2100" manufactured by Thermo Fisher Scientific Separation column: "IonPac AS20" manufactured by Thermo Fisher Scientific Eluent: KOH aqueous solution Column temperature: 35°C

[0072] [Activated Carbon Adsorbent Used] The activated carbon raw material (base activated carbon) used in the following examples (production examples) is as follows: Granular activated carbon: "F400" manufactured by Calgon Carbon Corporation (specific surface area: 1200 m) ２ / g) Granular activated carbon "PGW" manufactured by Kuraray Co., Ltd. (specific surface area: 1400 m ２ / g)

[0073] Example 1: 200 ml of methanol, 2 g of perfluorooctanoic acid, and 100 g of activated carbon "F400" manufactured by Calgon Carbon Corporation were placed in a 500 ml round-bottom flask and stirred by shaking for 1 hour. The mixture was then heated and depressurized at 60°C and 14 Torr for 5 minutes three times to distill off the methanol. The activated carbon thus obtained, on which 2% by weight of perfluorooctanoic acid had been adsorbed, was further vacuum-dried at 80°C for 2 hours to produce perfluorooctanoic acid-adsorbed activated carbon.

[0074] 20 g of the obtained activated carbon was placed in a crucible and calcined in a quartz tubular calciner by heating to 900°C at a rate of 10°C / min under a nitrogen gas flow (1 L / min), followed by heat treatment at 900°C for 1 hour, and then cooled to room temperature by natural cooling. The obtained fluorinated activated carbon weighed 19.6 g and had a specific surface area of ​​1210 m ２ / g.

[0075] The obtained activated carbon was subjected to the above-mentioned method. １９ F-NMR was measured and it was confirmed that there was a peak at a predetermined chemical shift. １９ The results of F-NMR are shown in Figure 1. The fluorine content of the activated carbon measured by the above-mentioned method was 0.07% by weight.

[0076] Example 2 An experiment was carried out in the same manner as in Example 1, except that "PGW" manufactured by Kuraray Co., Ltd. was used as the raw material instead of the "F400," to obtain a fluorinated activated carbon. The obtained activated carbon was subjected to the above-mentioned method. １９ F-NMR was measured and it was confirmed that there was a peak at a predetermined chemical shift. １９ The results of F-NMR are shown in Figure 1. The fluorine content of the activated carbon measured by the above method was 0.002 wt % and the specific surface area was 1380 m ２ / g.

[0077] Example 3 The same procedure as in Example 1 was carried out except that the firing temperature was 700°C and the firing time was 3 hours. ２ / g.

[0078] The obtained activated carbon was subjected to the above-mentioned method. １９F-NMR was measured and it was confirmed that there was a peak at a predetermined chemical shift (between -100 and -120 ppm). The fluorine content of the activated carbon was measured by the above-mentioned method and was found to be 0.11 wt %.

[0079] Comparative Example 1 Non-fluorinated "F400" was used.

[0080] Comparative Example 2 Non-fluorinated "PGW" was used.

[0081] In Comparative Examples 1 and 2, １９ Fluorine was not detected by F-NMR measurement or combustion ion chromatography. １９ The results of F-NMR measurement are shown in Figure 1. The addition of PFOA to Comparative Example 1 alone did not produce the same results as in the present embodiment. １９ No fluorine peak is observed in F-NMR.

[0082] <Evaluation Method> The activated carbons of Examples 1-3 and Comparative Examples 1-2 were evaluated for their effectiveness in removing perfluorooctanoic acid (PFOA). Five columns consisting solely of the activated carbons of Examples 1-3 and Comparative Examples 1-2 were prepared according to ASTM D 6586. Testing was performed using the Rapid Small Scale Column Test (RSSCT) prepared as described above, in accordance with EPA Method 537, Version 1.1, "Methodology," for measuring the adsorption of pollutants onto granular activated carbon in aqueous systems. Feedwater was passed through the column, and the concentration of perfluorooctanoic acid at the outlet was measured at specified intervals to evaluate the compound's removal ability. To normalize for bed size, the results were expressed as "bed volume," calculated by dividing the volume of water passing through the activated carbon bed by the volume of the bed itself. The results of Examples 1 and 3 and Comparative Example 1 are shown in Figure 2, and the results of Examples 2 and Comparative Example 2 are shown in Figure 3.

[0083] 2 and 3, the fluorinated activated carbon of the Example had a lower concentration of perfluorooctanoic acid at the outlet than the untreated activated carbon of the Comparative Example, demonstrating superior removal ability of the compound. Furthermore, it was found that the activated carbon of the Example was able to maintain its superior removal ability for a longer period of time than the activated carbon of the Comparative Example.

[0084] This application is based on Japanese Patent Application No. 2023-193657 filed on November 14, 2023, the contents of which are incorporated herein by reference.

[0085] In order to express the present invention, the present invention has been properly and sufficiently described above through embodiments with reference to specific examples, etc. However, it should be recognized that those skilled in the art can easily change and / or improve the above-described embodiments. Therefore, unless changes or improvements made by those skilled in the art deviate from the scope of the claims set forth in the claims, such changes or improvements are construed as being encompassed within the scope of the claims.

[0086] INDUSTRIAL APPLICABILITY The present invention has wide industrial applicability in technical fields relating to activated carbon, its manufacturing method, and adsorption filters and water purification using activated carbon.

Claims

1. BET specific surface area is 500m ２ / g or more, and solid １９ In F-NMR measurement １９ Activated carbon in which a peak due to F is observed between -100 and -120 ppm.

2. The solid １９ In F-NMR measurement, １９ 2. The activated carbon according to claim 1, wherein the peak due to F is due to fluorine bonded to the activated carbon.

3. The activated carbon according to claim 1, having a fluorine content of 0.0001% by weight or more based on 100% by weight of the activated carbon.

4. The activated carbon of claim 1, which is in powder, granular or pellet form.

5. The activated carbon according to claim 1, which is used for removing perfluoroalkyl and polyfluoroalkyl compounds.

6. An adsorption filter comprising the activated carbon according to any one of claims 1 to 5.

7. A water purifier using the adsorption filter according to claim 6.

8. A method for producing activated carbon according to any one of claims 1 to 5, comprising: activating a raw material for activated carbon; allowing the activated raw material for activated carbon to adsorb a fluorine-containing compound; and heat-treating the fluorine-containing compound-impregnated activated carbon at a temperature equal to or higher than the decomposition starting temperature of the fluorine-containing compound.

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