Activated carbon fibers

Abstract

In activated carbon fibers of this invention, the content of a functional group derived from a carboxylic acid and / or a carboxylic acid metal salt is 0.60 mmol / g or more and the average fiber length is 10-180 μm. The activated carbon fibers have excellent metal removal performance with minimized entanglement between fibers.

Description

activated carbon fiber

[0001] The present invention relates to activated carbon fibers.

[0002] Activated carbon has excellent adsorption capacity for various pollutants, malodorous and harmful substances, particularly malodorous and harmful substances in the air and trace substances in water, and has been used as an adsorbent in various fields, both for domestic and industrial use. In recent years, there has been a demand for delicious water without chlorine odors, mold odors, etc., in water purification applications, and various water purifiers using activated carbon have been proposed to meet this demand. On the other hand, there has been an increasing interest in safety and hygiene regarding water quality, such as trihalomethanes, environmental hormones, and heavy metals. To meet these demands, activated carbon alone is insufficient, and it has been necessary to use an adsorbent with unique adsorption capacity in combination.

[0003] In particular, in water purification applications, lead ions, among heavy metals, are suspected of having endocrine disrupting effects. The lead ion concentration in drinking water was limited to 10 ppb or less in 2003, and water purifiers are often required to be able to remove soluble lead, making it essential to develop effective water purification materials.

[0004] Metal-removing activated carbon for use in water purifiers is expected to be in granular, powdered, or fibrous forms, but considering that water purifiers require both high metal removal performance and low pressure loss, it is preferable to use fibrous metal-removing activated carbon fiber.

[0005] Under these circumstances, activated carbon with introduced functional groups is generally known as activated carbon with improved metal removal ability. For example, Patent Document 1 describes activated carbon to which a predetermined amount of acidic functional groups such as carboxylic acid has been introduced to impart metal removal ability. Meanwhile, Patent Document 2 successfully improves chloramine removal performance by using activated carbon to which specific amounts of acidic functional groups and basic functional groups have been introduced, and similar effects are achieved with activated carbon fibers.

[0006] JP 2004-315243 A International Publication No. 2021 / 106364

[0007] However, in water purifier applications, activated carbon fibers for metal removal alone often cannot sufficiently remove trihalomethanes, free residual chlorine, 2-methylisoborneol (2-MIB), etc., and are therefore often used in combination with other materials, such as coconut shell activated carbon (granular activated carbon) or other activated carbon fibers. In this case, activated carbon fibers for metal removal are mixed with coconut shell activated carbon (granular activated carbon) and a binder, and then molded in a mold or the like to form a molded body. Because activated carbon fibers for metal removal in molded bodies are expensive and have low density, which leads to large deposits in water purifiers, metal removal is typically required at a low blending ratio of several percent to several tens of percent by mass. Therefore, if activated carbon fibers for metal removal are not uniformly dispersed in the molded body, the metals to be removed will not come into sufficient contact with the activated carbon fibers for metal removal when water is passed through them, and the original metal removal performance will not be achieved. When activated carbon fibers for metal removal are long, they tend to become entangled with each other, and therefore are not uniformly dispersed when mixed with other components. Since the activated carbon fibers for metal removal are not uniformly dispersed within the molded body, the metal removal performance is not fully exhibited. In this regard, Patent Document 1 is not specialized for activated carbon fibers, and it is unclear whether it can also be applied to activated carbon fibers. Patent Document 2 is specialized for the adsorption of molecular polar substances, and it is unclear whether it can be directly applied to water purification applications. In either case, the fiber length was not considered, and the performance was not sufficient for use as a material for a water purifier.

[0008] The present invention is intended to solve the above-mentioned problems, and has an object to provide activated carbon fibers that have excellent metal removal performance by suppressing entanglement of the fibers.

[0009] The present inventors have conducted extensive research to solve the above-mentioned problems and have found that an activated carbon fiber having excellent metal removal performance can be obtained by adjusting the content of functional groups derived from carboxylic acid and / or a metal carboxylate and the average fiber length to specific ranges. Based on this finding, the present inventors have conducted further research and completed the present invention. That is, the present invention includes the following features.

[0010] Item 1. An activated carbon fiber having a content of functional groups derived from carboxylic acid and / or carboxylic acid metal salts of 0.60 mmol / g or more and an average fiber length of 10 to 180 μm.

[0011] Item 2. The activated carbon fiber according to Item 1, wherein the metal constituting the functional group derived from the metal carboxylate is at least one metal selected from the group consisting of alkali metals and alkaline earth metals.

[0012] Item 3. The activated carbon fiber according to Item 2, wherein the metal constituting the functional group derived from the metal carboxylate is at least one metal selected from the group consisting of sodium, potassium, calcium, and magnesium.

[0013] Item 4. The activated carbon fiber according to any one of Items 1 to 3, having a packing density of 0.30 g / mL or more as measured by a tapping method.

[0014] Item 5. The activated carbon fiber according to any one of Items 1 to 4, having a soluble lead water flow rate of 800 L / g or more in the following water flow test method. Water flow test method: Test water is passed through a molded body obtained by mixing and molding 3 mass % of the activated carbon fiber, 94 mass % of coconut shell activated carbon, and 3 mass % of acrylic fiber, and the soluble lead concentrations before and after passing through the column are measured. The water flow rate (L / g) per 1 g of metal-adsorbed activated carbon fiber is calculated from the total amount of filtered water (L) up to the breakthrough point, and this is defined as the soluble lead water flow rate. Test water: Space velocity (SV) of an aqueous solution with a soluble lead concentration of 50 ppb: 3200 h －１ Method for measuring soluble lead concentration: atomic absorption spectrometry Breakthrough point: The point at which the concentration of chloroform in the column effluent water relative to the column inflow water exceeds 20%.

[0015] Item 6. The activated carbon fiber according to any one of Items 1 to 5, having an average fiber diameter of 3 to 20 μm.

[0016] Item 7. BET specific surface area is 1600 m ２ Item 7. The activated carbon fiber according to any one of items 1 to 6, wherein the activated carbon fiber has a viscosity of 1000 kJ / g or less.

[0017] Item 8. In a temperature programmed desorption analysis (TPD analysis), the activated carbon fiber is subjected to CO 2 analysis at a temperature of 100 to 400°C. ２Item 8. The activated carbon fiber according to any one of Items 1 to 7, wherein the amount of generated carbon dioxide is 200 μmol / g or more.

[0018] Item 9. The activated carbon fiber according to any one of Items 1 to 8, having an oxygen content of 10% by mass or more.

[0019] Item 10. The activated carbon fiber according to any one of Items 1 to 9, wherein the amount of adsorption of free chlorine measured in accordance with the analytical method described in JIS S3201 is 10 to 100 L / g.

[0020] Item 11. The activated carbon fiber according to any one of Items 1 to 10, wherein the activated carbon fiber has a decomposition initiation temperature of 850°C or lower, as measured in thermogravimetric analysis in the atmosphere at a temperature increase rate of 10°C / min.

[0021] Item 12. The activated carbon fiber according to any one of Items 1 to 11, wherein the pH of the filtrate or aqueous suspension according to JIS K 1477:2007 is 2.0 to 8.0.

[0022] Item 13. A metal adsorbent containing the activated carbon fiber according to any one of Items 1 to 12.

[0023] Item 14. The metal adsorbent according to Item 13, which adsorbs metal ions belonging to Groups 6 to 16 of the periodic table.

[0024] Item 15. A filter medium for a water purifier, comprising the metal adsorbent according to item 13 or 14.

[0025] Item 16. The water purifier filter medium according to Item 15, further comprising a fibrous binder.

[0026] Item 17. The water purifier filter material according to Item 16, wherein the content of the fibrous binder is 2 to 15 parts by mass relative to 100 parts by mass of the activated carbon fiber.

[0027] Item 18. A filter for a water purifier, comprising the filter material for a water purifier according to any one of Items 15 to 17.

[0028] Item 19. A cartridge for a water purifier comprising the filter for a water purifier according to Item 18.

[0029] Item 20. A water purifier comprising the water purifier cartridge according to Item 19.

[0030] Item 21. A system kitchen equipped with the water purifier according to Item 20.

[0031] Item 22. A method for producing an activated carbon fiber according to any one of Items 1 to 12, comprising: (1) a step of oxidizing a raw material activated carbon fiber; and (2) a step of washing the oxidized activated carbon fiber obtained in the step (1) with water.

[0032] Item 23. The production method according to Item 22, wherein the step (1) is a step of oxidizing the raw material activated carbon fiber and then washing it with a basic solution.

[0033] The activated carbon fiber of the present invention can provide activated carbon fiber having excellent metal removal performance by suppressing entanglement of fibers.

[0034] In this specification, the term "containing" is a concept that encompasses all of "comprise," "consist essentially of," and "consist only of."

[0035] In addition, in this specification, when a numerical range is expressed as "A to B," it means A or more and B or less.

[0036] As used herein, "activated carbon fiber" refers to fibrous activated carbon.

[0037] 1. Activated Carbon Fiber The activated carbon fiber of the present invention has a content of functional groups derived from carboxylic acid and / or carboxylic acid metal salts of 0.60 mmol / g or more and an average fiber length of 10 to 180 μm.

[0038] With this configuration, the fibers have an appropriate length, are less likely to entangle with each other, and are uniformly dispersed when mixed with other components. As a result, the activated carbon fibers for metal removal are uniformly dispersed within the molded body, and the metal (especially lead) removal performance can be fully demonstrated.

[0039] Unlike inorganic porous carriers such as zeolite and alumina, activated carbon has a chaotic pore structure, and thus activated carbon fibers also have sites capable of adsorbing metal species that are difficult to adsorb on other inorganic porous carriers.

[0040] Various activated carbon fibers can be used as raw material fibers for the activated carbon fiber of the present invention. Examples include activated carbon fibers made from plant-based or fossil-based raw materials such as wood, wood flour (such as sawdust), bamboo, fruit shells (such as coconut shells), by-products of pulp production, bagasse, blackstrap molasses, graphite, coal (such as peat, lignite, brown coal, and bituminous coal), anthracite, coal pitch, petroleum (particularly petroleum distillation residue components), petroleum pitch, coke, and coal tar; various synthetic resins such as phenolic resin, vinyl chloride resin, vinyl acetate resin, melamine resin, urea resin, resorcinol resin, celluloid, epoxy resin, polyurethane resin, polyester resin, acrylic resin (such as polyacrylonitrile (PAN)), and polyamide resin; synthetic rubbers such as polybutylene, polybutadiene, and polychloroprene; polysaccharides such as cellulose and regenerated cellulose; other synthetic wood; and synthetic pulp. Among these, from the viewpoints of easily improving the metal (particularly lead) removal performance and preventing deterioration of the pore structure of the activated carbon, preferred are plant-based activated carbon fibers, coal-based activated carbon fibers, synthetic resin-derived activated carbon fibers, polysaccharide-derived activated carbon fibers, etc., and more preferred are coconut shell activated carbon fibers, sawdust activated carbon fibers, coal-based activated carbon fibers, phenol-based activated carbon fibers, polyacrylonitrile (PAN)-based activated carbon fibers, cellulose-based activated carbon fibers, etc. These activated carbon fibers can be used alone or in combination of two or more types.

[0041] As the raw material fibers for the activated carbon fiber of the present invention, various commercially available products can usually be used.

[0042] The activated carbon fiber of the present invention can be obtained by subjecting these raw material fibers to, for example, the treatment shown in the production method described below.

[0043] Activated carbon fibers usually have acidic groups present on their surfaces. The type of acidic group on the surface of an activated carbon fiber varies depending on the activated carbon fiber. However, in the activated carbon fiber of the present invention, the content of functional groups derived from carboxylic acid and / or carboxylic acid metal salts is 0.60 mmol / g or more, preferably 0.65 to 5.00 mmol / g, and more preferably 0.70 to 4.00 mmol / g. If the content of functional groups derived from carboxylic acid and / or carboxylic acid metal salts in the activated carbon fiber of the present invention is less than 0.60 mmol / g, the fiber will be less likely to adsorb metals (particularly lead), resulting in poor metal (particularly lead) removal performance and inability to suppress clogging and leakage from the molded article. The content of functional groups derived from carboxylic acid and / or carboxylic acid metal salts in the activated carbon fiber of the present invention is measured by acid-base neutralization titration (Boehm method).

[0044] The functional group derived from a carboxylic acid and / or a metal carboxylate contained in the activated carbon fiber of the present invention may be a functional group derived from a carboxylic acid, i.e., a carboxy group, or a functional group derived from a metal carboxylate. Whether the activated carbon fiber of the present invention has a functional group derived from a carboxylic acid or a functional group derived from a metal carboxylate, the content of the functional group can be adjusted to be within the above range.

[0045] When the activated carbon fiber of the present invention has a functional group derived from a metal carboxylate, the metal species constituting the metal salt as the functional group derived from the metal carboxylate on the surface is not particularly limited, but examples thereof include alkali metals (sodium, potassium, etc.) and alkaline earth metals (calcium, magnesium, etc.). These metal species may be contained alone or in combination of two or more. That is, the surface of the activated carbon of the present invention may contain -COONa, -COOK, -(COO) ２ Ca, -(COO) ２ It may contain one or more groups containing Mg or the like.

[0046] The method for analyzing the functional groups in the activated carbon of the present invention will be described below.

[0047] Typically, the amount of acidic functional groups on the surface of activated carbon can be determined by acid-base neutralization titration (Boehm method) to determine the amount of quinone groups, carboxyl groups, lactone groups, phenolic hydroxyl groups, etc. present on the surface. This acid-base neutralization titration method involves adding various alkalis to activated carbon to cause a reaction, and then back-titrating the alkali concentration after the reaction with an acid to quantify the amount of acidic functional groups present on the surface of the activated carbon. In this method, the amount of each acidic functional group can be separately quantified based on the difference in acidity: alkali metal ethoxides (e.g., sodium ethoxide) react with carboxyl groups, lactone groups, phenolic hydroxyl groups, quinone groups, etc.; alkali metal hydroxides (e.g., sodium hydroxide) react with carboxyl groups, lactone groups, phenolic hydroxyl groups, etc.; alkali metal carbonates (e.g., sodium carbonate) react with carboxyl groups, lactone groups, etc.; and alkali metal bicarbonates (e.g., sodium bicarbonate) react with carboxyl groups, etc.

[0048] However, since this acid-base neutralization titration method (Boehm method) cannot quantify the groups derived from a metal carboxylate, the activated carbon fiber after washing with an acid is subjected to back titration with an aqueous alkali solution, and the groups derived from a carboxylic acid and a metal carboxylate are calculated from the titration amount.

[0049] It is also possible to calculate the content of functional groups derived from carboxylic acids, i.e., carboxy groups, from the amount of carboxylic acids determined by titration for the activated carbon fiber after washing with an alkaline aqueous solution, and to calculate the amount of functional groups derived from carboxylic acid metal salts from the difference between the amount of carboxylic acids determined by titration for the activated carbon fiber after washing with an alkaline aqueous solution and the amount of carboxylic acids determined by titration for the activated carbon fiber before washing with an alkaline aqueous solution.

[0050] The average fiber length of the activated carbon fiber of the present invention is 10 to 180 μm, preferably 20 to 160 μm. If the average fiber length of the activated carbon fiber of the present invention is less than 10 μm, the activated carbon fiber is likely to flow out of the molded body and clog. If the average fiber length of the activated carbon fiber of the present invention exceeds 180 μm, entanglement of the fibers cannot be suppressed, and the metal (particularly lead) removal performance decreases. The average fiber length of the activated carbon fiber of the present invention is calculated by the number average from the number distribution of fiber lengths measured by electron microscope observation.

[0051] The average fiber diameter of the activated carbon fiber of the present invention is preferably 3 to 20 μm, more preferably 5 to 19 μm, from the viewpoints of readily exhibiting excellent metal (particularly lead) removal performance and readily suppressing clogging and outflow from a molded product. The average fiber diameter of the activated carbon fiber of the present invention is measured by calculating the number average from the number distribution of fiber diameters measured by electron microscope observation.

[0052] The average aspect ratio (average fiber length / average fiber diameter) of the activated carbon fiber of the present invention is preferably 3.0 to 11.0, more preferably 4.0 to 10.0, from the viewpoints of easily exhibiting excellent metal (particularly lead) removal performance and easily suppressing clogging and outflow from a molded product.

[0053] The BET specific surface area of ​​the activated carbon fiber of the present invention is set to 1600 m from the viewpoint of easily exhibiting excellent metal (particularly lead) removal performance and easily suppressing clogging and outflow from the molded product. ２ / g or less, and 50 to 1300m ２ / g is more preferable, and 100 to 1100m ２ The BET specific surface area of ​​the activated carbon fiber of the present invention is measured by the BET method.

[0054] The activated carbon fiber of the present invention is likely to have excellent metal (particularly lead) removal performance and is likely to be easily inhibited from leaking from a molded body, so that the packing density in the tapping method is preferably 0.30 g / mL, more preferably 0.31 to 1.00 g / mL, and even more preferably 0.32 to 0.90 g / mL. For details of the tapping method, see the method described in Japanese Patent No. 7453462.

[0055] CO between 100 and 400°C２ The amount of CO generated depends on the functional group derived from the carboxylate metal salt imparted to the activated carbon. From the viewpoint of easily improving the metal (particularly lead) removal performance and easily suppressing clogging and outflow from the molded body, the activated carbon fiber of the present invention is characterized by the fact that the amount of CO generated is determined by temperature-programmed desorption spectroscopy (TPD analysis) at temperatures between 100 and 400°C. ２ The amount of CO generated is preferably 200 μmol / g or more, more preferably 300 to 4000 μmol / g, and even more preferably 500 to 3000 μmol / g. ２ The amount of generated is measured by a mass spectrometer.

[0056] The oxygen content of the activated carbon fiber of the present invention is not particularly limited, but from the viewpoints of easily improving the metal (particularly lead) removal performance and easily suppressing clogging and outflow from the molded product, it is preferably 10% by mass or more, more preferably 11 to 25% by mass, and even more preferably 12 to 20% by mass, based on 100% by mass of the total amount of the activated carbon fiber. The oxygen content of the activated carbon fiber is measured by energy dispersive X-ray spectroscopy.

[0057] The adsorption amount of free chlorine on the activated carbon fiber of the present invention is not particularly limited, but from the viewpoints of easily improving the metal (particularly lead) removal performance and easily suppressing clogging and leakage from the molded product, it is preferably 10 to 100 L / g, more preferably 20 to 80 L / g, and even more preferably 40 to 60 L / g. The adsorption amount of free chlorine on the activated carbon fiber is measured in accordance with the analytical method described in JIS S3201.

[0058] In general, the higher the activation temperature during production of activated carbon, the more developed the hexagonal network structure of the activated carbon becomes, and the fewer the number of highly reactive edge sites becomes. In the activated carbon fiber of the present invention, since the sites where functional groups are introduced are edge sites, it is preferable to select an activated carbon fiber with many edge sites and a developed pore structure. From this perspective, the decomposition onset temperature measured by thermogravimetric analysis (TGA) in air at a temperature rise rate of 10°C / min is preferably 850°C or lower, more preferably 300 to 800°C, and even more preferably 400 to 700°C.

[0059] Furthermore, the activated carbon fiber of the present invention preferably has a pH of 2.0 to 8.0, more preferably 2.2 to 6.0, and even more preferably 2.5 to 4.0 in the form of a filtrate or aqueous suspension as measured in accordance with JIS K 1477: 2007. When the pH of the aqueous suspension is controlled within the above range, even in the case of activated carbon fiber containing a large amount of water, mold growth is easily inhibited and mold growth is easily reduced, and metal removal performance (particularly lead removal performance) is not easily reduced even after long-term storage. In addition, acidic functional groups on the activated carbon fiber are less likely to be anionized, solid-liquid separation is easily performed, and working efficiency is also easily improved. JIS K 1477:2007 describes that approximately 0.5 g of a sample, converted to dry mass, is weighed out and transferred to a 200 mL beaker, tall beaker, or Erlenmeyer flask, 100 mL of water is added, and the mixture is heated gently for 5 minutes so that the boiling continues, then cooled to room temperature, filtered through filter paper type 5A specified in JIS P 3801, water is added to the filtrate to make 100 mL, the mixture is stirred well, and the pH is measured using a pH meter.

[0060] The activated carbon fiber of the present invention, having the above-described configuration, can adsorb metals (particularly lead) particularly efficiently. Specifically, the activated carbon fiber of the present invention can have a soluble lead water flow rate of 800 L / g or more, preferably 900 to 5000 L / g, and more preferably 1000 to 4000 L / g, in the following water flow test method. Water flow test method: Test water is passed through a molded body obtained by mixing and molding 3 mass % of the activated carbon fiber, 94 mass % of coconut shell activated carbon, and 3 mass % of acrylic fiber. The soluble lead concentrations before and after passing through the column are measured, and the water flow rate (L / g) per 1 g of metal-adsorbed activated carbon fiber is calculated from the total amount of filtered water (L) up to the breakthrough point, and this is defined as the soluble lead water flow rate. Test water: Space velocity (SV) of an aqueous solution with a soluble lead concentration of 50 ppb: 3200 h －１ Method for measuring soluble lead concentration: atomic absorption spectrometry Breakthrough point: The point at which the concentration of chloroform in the column effluent water relative to the column inflow water exceeds 20%.

[0061] 2. Method for Producing Activated Carbon Fiber The method for producing the activated carbon fiber of the present invention is not particularly limited, but may be, for example, a method comprising: (1) a step of oxidizing a raw activated carbon fiber; and (2) a step of washing the oxidized activated carbon fiber obtained in the step (1) with water.

[0062] In addition, when the activated carbon fiber of the present invention has a surface functional group derived from a metal carboxylate in the content range described above, it is preferable to wash the raw activated carbon fiber with a basic solution after oxidizing it in the step (1).

[0063] (2-1) Step (1) The oxidation treatment that can be used in step (1) is not particularly limited, and oxidizing agents such as nitric acid, sulfuric acid, hydrogen peroxide, ammonium peroxodisulfide, sodium peroxodisulfate, and ozone can be used. Alternatively, heat treatment in air under an oxygen gas atmosphere or oxidation treatment using oxygen plasma and ultraviolet rays can be performed. These oxidation treatments can be performed alone or in combination of two or more. In particular, when hydrogen peroxide is used as the oxidizing agent, it is preferable to use it in combination with nitric acid, sulfuric acid, ammonium peroxodisulfide, sodium peroxodisulfate, or the like. Among these, from the viewpoint of mass production, it is preferable to use an oxidizing agent.

[0064] When an oxidizing agent is used, the oxidizing agent may be added dropwise to a dispersion of raw activated carbon fibers (particularly, an aqueous dispersion of raw activated carbon fibers), for example, without any particular limitation. In this case, the oxidizing agent may be added dropwise over a period of 10 minutes to 10 hours, particularly 20 minutes to 5 hours, after the temperature has been raised to a reaction temperature described below.

[0065] Here, the amount of the oxidizing agent used is preferably 50 to 1,000 parts by mass, and more preferably 100 to 800 parts by mass, per 100 parts by mass of the raw material activated carbon fiber, from the viewpoints that it is easy to increase the amount of functional groups derived from carboxylic acid and / or carboxylic acid metal salt, it is easy to adjust the average fiber length appropriately, and it is easy to obtain activated carbon fiber that has excellent metal removal performance by suppressing entanglement between fibers and is suppressed from clogging and outflow from the molded product.

[0066] The reaction temperature in step (1) is not particularly limited and can be adjusted appropriately depending on the oxidizing power of the oxidizing agent. However, from the viewpoints of easily increasing the amount of functional groups derived from carboxylic acid and / or carboxylic acid metal salt, easily adjusting the average fiber length to an appropriate value, and easily obtaining activated carbon fibers that have excellent metal removal performance by suppressing entanglement between fibers and are suppressed from clogging and spilling out of the molded product, the reaction temperature is preferably 20 to 150°C, and more preferably 40 to 100°C.

[0067] The reaction time in step (1) is not particularly limited and can be a time long enough to sufficiently oxidize the starting activated carbon fiber and increase the amount of functional groups derived from carboxylic acid and / or carboxylic acid metal salt, for example, 5 minutes to 6 hours, preferably 10 minutes to 3 hours. In the present invention, the reaction time means the time during which the temperature is maintained at the maximum temperature after the completion of the dropwise addition.

[0068] When the content of functional groups derived from metal carboxylates on the surface is set within the above range, it is preferable to wash the raw activated carbon fiber with a basic solution after oxidizing it in step (1).

[0069] In this case, the carboxylic acid-derived group introduced by the above oxidation can be converted to a group derived from a metal carboxylate by washing with a base containing an alkali metal, alkaline earth metal, or the like (an alkali metal hydroxide such as sodium hydroxide or potassium hydroxide; an alkaline earth metal hydroxide such as calcium hydroxide or magnesium hydroxide, or the like) as the base contained in the basic solution. Note that when the oxidizing agent contains an alkali metal, alkaline earth metal, or the like, it is also possible to introduce a group derived from a metal carboxylate without washing with a basic solution.

[0070] In this case, the degree of washing with the basic solution can be adjusted so that the pH of the filtrate after washing is 4 or higher, preferably 5 to 10, and more preferably 6 to 9.

[0071] (2-2) Step (2) Washing with water can be carried out by a conventional method, which can remove the oxidizing agent and basic solution remaining in the pores, and the product formed by the reaction between the oxidizing agent and the basic solution, as well as metals contained in the activated carbon fiber and foreign matter attached to the surface.

[0072] Thereafter, if necessary, the activated carbon fiber of the present invention can be obtained by drying it by a conventional method.

[0073] 3. Uses of Activated Carbon Fiber The activated carbon fiber of the present invention is particularly useful as a metal adsorbent because of its excellent metal removal performance as described above. The metals that can be removed by the activated carbon fiber of the present invention are not particularly limited, but examples thereof include metal ions belonging to Groups 6 to 16 of the periodic table, such as lead, mercury, cadmium, copper, arsenic, zinc, selenium, nickel, manganese, chromium, iron, and aluminum, preferably metal ions belonging to Groups 10 to 15 of the periodic table.

[0074] Thus, since the adsorbent of the present invention is useful as an adsorbent for metals such as lead, it can be used as a filter medium for water purifiers. In this case, the activated carbon fiber of the present invention described above can be filled into a cartridge case as is or as a filter-like water purifier filter, or the activated carbon fiber of the present invention can be added to a desired binder and molded to obtain the water purifier cartridge of the present invention. As described above, when the pH of an aqueous suspension of the activated carbon fiber of the present invention is adjusted to fall within a predetermined range, mold growth is easily inhibited and mold spores are easily reduced, making the activated carbon fiber useful as a water purifier filter medium. Either a dry molding method or a wet molding method can be used as a molding method for producing the water purifier cartridge of the present invention.

[0075] When the dry molding method is employed, the composition containing the activated carbon fiber of the present invention and a thermoplastic resin is preferably molded into a hollow cylinder or a disk. More specifically, the composition containing the activated carbon fiber of the present invention and a thermoplastic resin is preferably placed in a mold made of aluminum or the like as needed, and heated to be molded into a hollow cylinder or a disk.

[0076] Examples of usable thermoplastic resins include polyethylene, polypropylene, polystyrene, ethylene-vinyl acetate copolymer, acrylonitrile-butadiene-styrene copolymer resin, polyethylene terephthalate, polybutylene terephthalate, ethylene-acrylic resin, polymethyl methacrylate, nylon, mesophase pitch, and hydrophilic resins (e.g., polyvinyl alcohol resin, ethylene-vinyl alcohol resin, etc.). The content of the thermoplastic resin is not particularly limited. Specifically, from the viewpoint of the strength and adsorption properties of the molded product, the content is preferably 5 to 20 parts by mass, and more preferably 8 to 18 parts by mass, per 100 parts by mass of the activated carbon fiber of the present invention.

[0077] When a wet molding method is employed, it is preferable that a composition containing the activated carbon fiber of the present invention and a fibrous binder be molded into a hollow cylindrical or disc shape. More specifically, it is preferable that a composition containing the activated carbon fiber of the present invention and a fibrous binder be dispersed in water to prepare a slurry, and the slurry is molded into a hollow cylindrical or disc shape while being aspirated as necessary.

[0078] The fibrous binder is not particularly limited as long as it can entangle and shape the fibrous activated carbon and powdered activated carbon by fibrillation, and a wide range of materials, both synthetic and natural, can be used. Examples of such fibrous binders include acrylic fibers, polyethylene fibers, polypropylene fibers, polyacrylonitrile fibers, cellulose fibers, nylon fibers, and aramid fibers.

[0079] The shape of the fibrous binder is not particularly limited, and from the viewpoint of the strength of the molded product and workability, the average fiber length is preferably 0.5 to 4 mm, more preferably 0.7 to 2 mm.

[0080] The content of the fibrous binder is not particularly limited. Specifically, from the viewpoint of the strength and adsorption characteristics of the molded body, the content is preferably 2 to 15 parts by mass, more preferably 5 to 10 parts by mass, per 100 parts by mass of the activated carbon fiber of the present invention.

[0081] When the activated carbon fiber of the present invention is filled into the cartridge, it is also possible to fill it with ordinary activated carbon or activated carbon fiber. It is also possible to fill it with zeolite, titanosilicate, or the like capable of adsorbing and removing soluble lead, or an adsorbent containing silver ions and / or silver compounds capable of imparting antibacterial properties. In this case, the mass of the activated carbon fiber of the present invention relative to the total amount of adsorbent to be filled is preferably 50% by mass or more (50 to 100% by mass), more preferably 70% by mass or more (70 to 100% by mass), and even more preferably 80% by mass or more (80 to 100% by mass).

[0082] The method for molding the composition into a hollow cylindrical or disc shape is not particularly limited and can be performed according to a conventional method. The size of the resulting hollow cylindrical or disc-shaped molded article is not particularly limited and can be set to a size corresponding to the cartridge to be filled.

[0083] Furthermore, by employing the above-described water purifier cartridge of the present invention, it is possible to make a water purifier in a conventional manner, and it is also possible to make a system kitchen having a normal configuration except for the water purifier.

[0084] The present invention will be specifically described below with reference to examples, but the present invention is not limited to the following examples.

[0085] Example 1 An aqueous solution of sodium peroxodisulfate was prepared by adding 250 g of water to 151.3 g of sodium peroxodisulfate (Fujifilm Wako Pure Chemical Industries, Ltd.). ２ 59 g of water was added to 30 g of activated carbon fiber (0.50 mL / g, pore volume 0.50 mL / g, packing density 0.47 g / mL), and the temperature was raised to 90°C while stirring. The prepared aqueous sodium peroxodisulfate solution was then added dropwise over 50 minutes. After the dropwise addition was completed, the temperature was maintained at 90°C for 20 minutes, and the temperature was confirmed to have dropped to 50°C, followed by filtration. The residue was washed by pouring 3,000 g of water over it. The residue was dried at 115°C for 3 hours, yielding the desired activated carbon fiber for metal adsorption.

[0086] Example 2 An aqueous solution of sodium peroxodisulfate was prepared by adding 250 g of water to 148 g of sodium peroxodisulfate (Fujifilm Wako Pure Chemical Industries, Ltd.). ２ 59 g of water was added to 30 g of activated carbon fiber (0.50 mL / g, pore volume 0.50 mL / g, packing density 0.53 g / mL), and the temperature was raised to 70°C while stirring. The prepared aqueous sodium peroxodisulfate solution was then added dropwise over 50 minutes. After the dropwise addition was completed, the temperature was maintained at 70°C or higher for 20 minutes, and then the temperature was lowered by natural cooling overnight, after which filtration was performed. The filter cake was washed with five times the amount of water. After washing, the filter cake was again dried at 115°C for 3 hours to obtain the desired activated carbon fiber for metal adsorption.

[0087] Example 3 250 g of water was added to 151 g of sodium peroxodisulfate (Fujifilm Wako Pure Chemical Industries, Ltd.) to prepare an aqueous solution of sodium peroxodisulfate. ２ 59 g of water was added to 30 g of activated carbon fiber (0.66 g / mL, pore volume 0.32 mL / g, packing density 0.66 g / mL), and the temperature was raised to 90°C while stirring. The prepared aqueous sodium peroxodisulfate solution was then added dropwise over 50 minutes. After the dropwise addition was completed, the temperature was maintained at 90°C for 20 minutes, and the temperature was confirmed to have dropped to 50°C, followed by filtration. 100 g of water was added to the residue, and an aqueous solution of 4.0 g of sodium hydroxide dissolved in 85 g of water was added, followed by filtering again and washing with 300 g of water. The residue was dried at 115°C for 3 hours to obtain the desired activated carbon fiber for metal adsorption.

[0088] Example 4 An aqueous solution of sodium peroxodisulfate was prepared by adding 250 g of water to 151.3 g of sodium peroxodisulfate (Fujifilm Wako Pure Chemical Industries, Ltd.). ２80 g of water was added to 30 g of activated carbon fiber (0.73 g / g, pore volume 0.32 mL / g, packing density 0.73 g / mL), and the temperature was raised to 91°C while stirring. The prepared aqueous sodium peroxodisulfate solution was then added dropwise over 60 minutes. After completion of the dropwise addition, the temperature was maintained at 90°C or higher for 15 minutes, and the temperature was confirmed to have dropped to 50°C, followed by filtration. 100 g of water was added to the residue, and an aqueous solution of 4.0 g of sodium hydroxide dissolved in 85 g of water was added, followed by filtering again and washing with 300 g of water. The residue was dried at 115°C for 3 hours to obtain the desired activated carbon fiber for metal adsorption.

[0089] Example 5 250 g of water was added to 139.8 g of sodium peroxodisulfate (Fujifilm Wako Pure Chemical Industries, Ltd.) to prepare an aqueous solution of sodium peroxodisulfate. ２ 80 g of water was added to 30 g of activated carbon fiber (0.50 mL / g, pore volume 0.50 mL / g, packing density 0.57 g / mL), and the temperature was raised to 90°C while stirring. The prepared aqueous sodium peroxodisulfate solution was then added dropwise over 30 minutes. After the dropwise addition was completed, the temperature was maintained at 90°C or higher for 15 minutes, and the temperature was confirmed to have dropped to 50°C, after which the mixture was filtered. The residue was washed by pouring 3,000 g of water over it. The residue was dried at 115°C for 3 hours to obtain the desired activated carbon fiber for metal adsorption.

[0090] Example 6 250 g of water was added to 139.6 g of sodium peroxodisulfate (Fujifilm Wako Pure Chemical Industries, Ltd.) to prepare an aqueous solution of sodium peroxodisulfate. ２ 260 g of water was added to 30 g of activated carbon fiber (0.50 mL / g, pore volume 0.50 mL / g, packing density 0.39 g / mL), and the temperature was raised to 91°C while stirring. The prepared aqueous sodium peroxodisulfate solution was then added dropwise over 30 minutes. After completion of the dropwise addition, the temperature was maintained at 90°C or higher for 15 minutes, and the temperature was confirmed to have dropped to 50°C, followed by filtration. The filter cake was washed by pouring 3000 g of water over it. The filter cake was dried at 115°C for 3 hours, yielding the desired activated carbon fiber for metal adsorption.

[0091] Example 7 37.6 g of sodium peroxodisulfate (Fujifilm Wako Pure Chemical Industries, Ltd.) was added to 250 g of water to prepare an aqueous solution of sodium peroxodisulfate. ２ 60 g of water was added to 30 g of activated carbon fiber (0.90 mL / g, pore volume 0.90 mL / g, packing density 0.53 g / mL), and the temperature was raised to 90°C while stirring. The prepared aqueous sodium peroxodisulfate solution was then added dropwise over 60 minutes. After completion of the dropwise addition, the temperature was maintained at 90°C or higher for 15 minutes, and the temperature was confirmed to have dropped to 50°C before filtration. The residue was filtered while pouring 3,000 g of water over it, and washed. The residue was dried at 115°C for 3 hours, yielding the desired activated carbon fiber for metal adsorption.

[0092] Example 8 250 g of water was added to 37.6 g of sodium peroxodisulfate (Fujifilm Wako Pure Chemical Industries, Ltd.) to prepare an aqueous solution of sodium peroxodisulfate. ２ 60 g of water was added to 30 g of activated carbon fiber (1.05 mL / g, pore volume 1.05 mL / g, packing density 0.54 g / mL), and the temperature was raised to 91°C while stirring. The prepared aqueous sodium peroxodisulfate solution was then added dropwise over 60 minutes. After the dropwise addition was completed, the temperature was maintained at 90°C or higher for 15 minutes, and the temperature was confirmed to have dropped to 50°C, after which the mixture was filtered. The residue was washed by pouring 3,000 g of water over it. The residue was dried at 115°C for 3 hours to obtain the desired activated carbon fiber for metal adsorption.

[0093] Example 9 An aqueous solution of sodium peroxodisulfate was prepared by adding 250 g of water to 151.3 g of sodium peroxodisulfate (Fujifilm Wako Pure Chemical Industries, Ltd.). ２80 g of water was added to 30 g of activated carbon fiber (0.58 g / g, pore volume 0.32 mL / g, packing density 0.58 g / mL), and the temperature was raised to 91°C while stirring. The prepared aqueous sodium peroxodisulfate solution was then added dropwise over 60 minutes. After the dropwise addition was completed, the temperature was maintained at 90°C or higher for 15 minutes, and the temperature was confirmed to have dropped to 50°C, followed by filtration. 100 g of water was added to the residue, and an aqueous solution of 3.4 g of sodium hydroxide dissolved in 85 g of water was added, followed by filtering again and washing with 300 g of water. The residue was dried at 115°C for 3 hours to obtain the desired activated carbon fiber for metal adsorption.

[0094] Example 10: 680 g of sodium peroxodisulfate (Fujifilm Wako Pure Chemical Industries, Ltd.) was mixed with 1,031 g of water to prepare an aqueous solution of sodium peroxodisulfate. ２ 128 g of activated carbon fiber (0.46 g / mL, pore volume 0.522 mL / g, packing density 0.46 g / mL) was added with 312 g of water and stirred, and an aqueous sodium peroxodisulfate solution was added dropwise from room temperature over 180 minutes. It was confirmed that the temperature reached after the completion of the dropwise addition was 85°C. After confirming that the temperature in the reaction vessel had dropped to 40°C, an aqueous NaOH solution prepared with 120 g of NaOH and 130 g of water was added to the reaction vessel. After confirming that the temperature had dropped to 40°C after the addition was complete, the mixture was filtered. The filter cake was washed twice by pouring 640 g of hot water at 60°C or higher over the filter cake. The filter cake was dried at 115°C for 3 hours to obtain the desired activated carbon fiber for metal adsorption.

[0095] Example 11 An aqueous solution of sodium peroxodisulfate was prepared by adding 1,308 g of water to 862 g of sodium peroxodisulfate (Fujifilm Wako Pure Chemical Industries, Ltd.). ２100 g of water was added to 50 g of activated carbon fiber (0.46 g / mL, pore volume 0.522 mL / g, packing density 0.46 g / mL), and the resulting aqueous sodium peroxodisulfate solution was added dropwise from room temperature over 180 minutes while stirring. It was confirmed that the temperature reached after the completion of the dropwise addition was 85°C. After confirming that the temperature in the reaction vessel had dropped to 40°C, an aqueous NaOH solution prepared by mixing 207 g of NaOH and 224 g of water was added to the reaction vessel. After confirming that the temperature had dropped to 40°C after the addition was complete, the mixture was filtered. The filter cake was washed by pouring 870 g of hot water at 60°C or higher over the filter cake. The filter cake was dried at 115°C for 3 hours, yielding the desired activated carbon fiber for metal adsorption.

[0096] Example 12 An aqueous solution of sodium peroxodisulfate was prepared by adding 1031 g of water to 680 g of sodium peroxodisulfate (Fujifilm Wako Pure Chemical Industries, Ltd.). ２ To 128 g of activated carbon fiber (0.46 g / g, pore volume 0.522 mL / g, packing density 0.46 g / mL), 312 g of water was added, and the prepared aqueous sodium peroxodisulfate solution was added dropwise from room temperature over 180 minutes while stirring. It was confirmed that the temperature reached after the completion of the dropwise addition was 85°C. After the completion of the addition, it was confirmed that the temperature had dropped to 40°C, and then the mixture was filtered. The filter cake was washed twice by pouring 640 g of hot water at 60°C or higher over it, and then filtered to obtain the target activated carbon fiber for metal adsorption.

[0097] Example 13: 680 g of sodium peroxodisulfate (Fujifilm Wako Pure Chemical Industries, Ltd.) was mixed with 1,031 g of water to prepare an aqueous solution of sodium peroxodisulfate. ２128 g of activated carbon fiber (0.46 g / g, pore volume 0.522 mL / g, packing density 0.46 g / mL) was added with 312 g of water and stirred, and an aqueous sodium peroxodisulfate solution was added dropwise from room temperature over 180 minutes. It was confirmed that the temperature reached after the completion of the dropwise addition was 85°C. After confirming that the temperature in the reaction vessel had dropped to 40°C, an aqueous NaOH solution prepared with 120 g of NaOH and 130 g of water was added to the reaction vessel. After confirming that the temperature had dropped to 40°C after the addition was complete, the mixture was filtered. The filter cake was washed twice by pouring 640 g of hot water at 60°C or higher over the filter cake, and the target activated carbon fiber for metal adsorption was obtained.

[0098] Comparative Example 1 An aqueous solution of sodium peroxodisulfate was prepared by adding 120 g of water to 43.1 g of sodium peroxodisulfate (Fujifilm Wako Pure Chemical Industries, Ltd.). ２ 59 g of water was added to 30 g of activated carbon fiber (0.50 mL / g, pore volume 0.50 mL / g, packing density 0.58 g / mL), and the temperature was raised to 90°C while stirring. The prepared aqueous sodium peroxodisulfate solution was then added dropwise over 50 minutes. After the dropwise addition was completed, the temperature was maintained at 90°C for 20 minutes, and the temperature was confirmed to have dropped to 50°C, after which the mixture was filtered. The residue was washed by pouring 3,000 g of water over it. The residue was dried at 115°C for 3 hours to obtain the desired activated carbon fiber for metal adsorption.

[0099] Comparative Example 2 An aqueous solution of sodium peroxodisulfate was prepared by adding 250 g of water to 151 g of sodium peroxodisulfate (Fujifilm Wako Pure Chemical Industries, Ltd.). ２ 59 g of water was added to 30 g of activated carbon fiber (0.1 g / g, pore volume 0.32 mL / g, packing density 0.50 g / mL), and the temperature was raised to 90°C while stirring. The prepared aqueous sodium peroxodisulfate solution was then added dropwise over 50 minutes. After the dropwise addition was completed, the temperature was maintained at 90°C for 20 minutes, and the temperature was confirmed to have dropped to 50°C, followed by filtration. 100 g of water was added to the residue, and an aqueous solution of 3.4 g of sodium hydroxide dissolved in 85 g of water was added, followed by filtering again and washing with 300 g of water. The residue was dried at 115°C for 3 hours to obtain the desired activated carbon fiber for metal adsorption.

[0100] Reference Example 1 36 g of water was added to 20 g of sodium peroxodisulfate (Fujifilm Wako Pure Chemical Industries, Ltd.) to prepare an aqueous solution of sodium peroxodisulfate. ２ 50 g of water was added to 5 g of the pulverized product (median diameter 45 μm) of 1000 kJ / g, and the mixture was heated to 80°C while stirring, and then the prepared aqueous sodium peroxodisulfate solution was added dropwise over 10 minutes. After the dropwise addition was completed, the mixture was maintained at 80°C or higher for 10 minutes, and then the temperature was confirmed to have dropped to 50°C, followed by filtration. The residue was filtered while pouring 500 g of water over it. The residue was dried at 115°C for 3 hours, and the desired activated carbon fiber for metal adsorption was obtained.

[0101] Test Example 1: Content of Functional Groups Derived from Carboxylic Acid and Carboxylic Acid Metal Salts. 50 mL of water was added to 2 g of the obtained metal-adsorbing activated carbon fiber, and 0.1 mol / L hydrochloric acid was added while stirring until the pH reached 3 or less. The solution containing the metal-adsorbing activated carbon fiber was then filtered, and the resulting metal-adsorbing activated carbon was washed with 100 mL of water. The washed metal-adsorbing activated carbon was dried at 115°C for 3 hours. 50 mL of a 1 mol / L aqueous sodium bicarbonate solution was added to 1 g of the dried metal-adsorbing activated carbon fiber, and the mixture was shaken at room temperature for 24 hours. After shaking, the sodium bicarbonate solution containing the activated carbon fiber was filtered through a membrane filter. 10 mL of the filtrate was diluted with 50 mL of water, and the solution was titrated with 1 mol / L hydrochloric acid. The carboxyl group content was calculated from the titration amount, and this value was used as the total amount of functional groups derived from carboxylic acid and carboxylic acid metal salts.

[0102] Test Example 2: Average fiber length and average fiber diameter The number average fiber length L was calculated from the number distribution of fiber lengths measured using a VHX-7000 manufactured by Keyence Corporation, and the number average fiber diameter D was calculated from the number distribution of fiber diameters, and these were taken as the average fiber length and average fiber diameter.

[0103] Test Example 3: BET specific surface area After heating the activated carbon fiber at 115°C for 3 hours under a reduced pressure atmosphere, the nitrogen gas adsorption isotherm was measured using a Belsorp mini manufactured by Microtrackbell Co., Ltd. at a temperature of 77 K. The obtained nitrogen gas adsorption isotherm was analyzed by the BET method to calculate the specific surface area.

[0104] Test Example 4: Packing density

[0049] The packing density of activated carbon fiber was measured using a tapping bulk density measuring device. The volume of the cylinder was 100 mL, and the number of tappings was 100. The packing density was measured in the same manner as in Japanese Patent No. 7453462.

[0105] Test Example 5: Soluble lead adsorption amount A sample of a molded body for a water purifier was prepared by mixing 100 parts by mass of THC-40 (crushed coconut shell charcoal (granular) manufactured by Osaka Gas Chemicals Co., Ltd.), 3 parts by mass of the functionalized activated carbon of the Examples and Comparative Examples, and 3 parts by mass of a fibrous binder (acrylic fiber manufactured by Nippon Exlan Kogyo Co., Ltd.), and suction molding was carried out into a mold with an inner diameter of 8 mm, an outer diameter of 25.6 mm, and a height of 117 mm, and drying was carried out at 110°C for 12 hours or more to obtain a hollow cylindrical molded body for a water purifier with an inner diameter of 8 mm, an outer diameter of 25.9 mm, and a height of 116.8 mm.

[0106] The water flow method was performed in accordance with the test method for household water purifiers specified in JIS S 3201. Test water with a soluble lead concentration of 50 ppb was flowed toward the activated carbon module at a flow rate of 3 L / min under a pressure of 0.2 MPa. The soluble lead concentration was measured by collecting a sample in a container, adding 1% of 60% by mass nitric acid, and analyzing it with an atomic absorption spectrophotometer. The cumulative amount of water flowed at the time when the soluble lead removal rate fell below 80% of the initial value was evaluated as the removal performance. Furthermore, since cartridge replacement is recommended when the soluble lead removal rate falls below 80% of the initial value, the longer the time until the soluble lead removal rate falls below 80% of the initial value, the better the soluble lead adsorption performance. The molded body for water purifiers was passed through the module at a flow rate of 3 L / min at 20°C to achieve a soluble lead concentration of 50±5 μg / L (50 ppb) in accordance with the test method for household water purifiers. The cumulative amount of water passed was measured at the time when the removal rate of soluble lead fell below 80%.

[0107] The results are shown in Table 1.

[0108]

[0109] Test Example 6: Metal adsorption amount Using the activated carbon fibers for adsorbing metals obtained in Example 10 and Comparative Example 1, the metal adsorption amount was measured as follows.

[0110] Several Erlenmeyer flasks were prepared, and activated carbon was placed in all but one Erlenmeyer flask. 25 mL of a solution prepared by diluting a metal standard solution (lead standard solution, copper standard solution, cadmium standard solution, or zinc standard solution; 1000 ppm) with distilled water to 100 ppm was added, and the mixture was shaken at 150 rpm for 90 minutes at 25 ° C. After that, the solution in the flask was filtered with a syringe, and 2.5 mL of the collected solution and 0.25 mL of 60% HNO were mixed. ３ The aqueous solution was placed in a 25 mL measuring flask, and the volume of the solution was adjusted with distilled water. The metal concentration was analyzed by ICP-OES, and the amount of adsorption at 10 ppm was confirmed from the adsorption isotherm.

[0111] The results are shown in Table 2.

[0112]

[0113] Test Example 7: Evaluation of fungal growth inhibition The fungal growth inhibition effect was evaluated using the activated carbon fibers obtained in Examples 12 and 13. The pH of the aqueous suspensions of the activated carbon fibers obtained in Examples 12 and 13 was measured in accordance with JIS K 1474:2014.

[0114] Activated carbon fiber was weighed out in an amount of 30 g in terms of dry weight and placed in a glass bottle. 0.3 mL of mold (Aspergillus niger) was added as a test bacterium to this activated carbon fiber, and the mixture was left for one week. Next, the mold was added to 9 mL of sterilized water, and 1 g of activated carbon fiber that had been left for one week was added and mixed well (this resulted in a 10-fold dilution). This dilution procedure was repeated until the final dilution ratio reached 10. ３ The diluted solution was diluted stepwise until the concentration reached 1:1. 1 mL of the prepared diluted solution was dispensed into a petri dish, and 15-20 mL of culture medium that had been autoclaved and kept at 50°C was poured in. The mixture was mixed well using a circular motion and then allowed to stand to solidify. The solidified petri dish was left to stand for 3 days to culture the bacteria, and the number of colonies was visually confirmed. The final number of colonies was calculated by multiplying the number of confirmed colonies by the dilution factor (number of colonies = number confirmed visually × dilution factor). The results are shown in Table 3. The mold used is managed as NBRC6341 and can be purchased from the National Institute of Technology and Evaluation.

[0115]

Claims

1. Activated carbon fiber having a content of functional groups derived from carboxylic acid and / or carboxylic acid metal salts of 0.60 mmol / g or more and an average fiber length of 10 to 180 μm.

2. The activated carbon fiber according to claim 1, wherein the metal constituting the functional group derived from the metal carboxylate is at least one metal selected from the group consisting of alkali metals and alkaline earth metals.

3. The activated carbon fiber according to claim 2, wherein the metal constituting the functional group derived from the metal carboxylate is at least one metal selected from the group consisting of sodium, potassium, calcium and magnesium.

4. The activated carbon fiber according to claim 1, which has a packing density of 0.30 g / mL or more when measured by a tapping method.

5. The activated carbon fiber according to claim 1, wherein the soluble lead water flow rate is 800 L / g or more in the following water flow test method. Water flow test method: Test water is passed through a molded body obtained by mixing and molding 3 mass % of the activated carbon fiber, 94 mass % of coconut shell activated carbon, and 3 mass % of acrylic fiber, and the soluble lead concentration is measured before and after passing through the column. The water flow rate (L / g) per 1 g of metal-adsorbed activated carbon fiber is calculated from the total amount of filtered water (L) up to the breakthrough point, and this is defined as the soluble lead water flow rate. Test water: Space velocity (SV) of an aqueous solution with a soluble lead concentration of 50 ppb: 3200 h －１ Method for measuring soluble lead concentration: atomic absorption spectrometry Breakthrough point: The point at which the concentration of chloroform in the column effluent water relative to the column inflow water exceeds 20%.

6. The activated carbon fiber according to claim 1, having an average fiber diameter of 3 to 20 μm.

7. BET specific surface area is 1600m ２ The activated carbon fiber according to claim 1, wherein the activated carbon fiber has a molecular weight of 1 / g or less.

8. In the temperature programmed desorption analysis (TPD analysis), the CO ２ The activated carbon fiber according to claim 1, wherein the amount of generated carbon is 200 μmol / g or more.

9. Activated carbon fiber according to claim 1, having an oxygen content of 10% by mass or more.

10. The activated carbon fiber according to claim 1, which has an adsorption capacity of free chlorine of 10 to 100 L / g as measured in accordance with the analytical method set forth in JIS S3201.

11. The activated carbon fiber according to claim 1, which has a decomposition initiation temperature of 850°C or less when measured in thermogravimetric analysis in the atmosphere at a temperature increase rate of 10°C / min.

12. The activated carbon fiber according to claim 1, wherein the pH of the filtrate or aqueous suspension according to JIS K 1477:2007 is 2.0 to 8.

0.

13. A metal adsorbent containing the activated carbon fiber according to any one of claims 1 to 12.

14. The metal adsorbent according to claim 13, which adsorbs metal ions belonging to groups 6 to 16 of the periodic table.

15. A filter medium for a water purifier containing the metal adsorbent according to claim 13.

16. The water purifier filter medium according to claim 15, further comprising a fibrous binder.

17. The filter medium for a water purifier according to claim 16, wherein the content of the fibrous binder is 2 to 15 parts by mass per 100 parts by mass of the activated carbon fiber.

18. A filter for a water purifier, comprising the filter material for a water purifier according to claim 15.

19. A water purifier cartridge comprising the water purifier filter according to claim 18.

20. A water purifier comprising the water purifier cartridge according to claim 19.

21. A system kitchen equipped with the water purifier according to claim 20.

22. A method for producing activated carbon fiber according to any one of claims 1 to 12, comprising: (1) a step of oxidizing raw activated carbon fiber; and (2) a step of washing the oxidized activated carbon fiber obtained in step (1) with water.

23. The method of claim 22, wherein step (1) is a step of oxidizing the raw activated carbon fiber and then washing it with a basic solution.

Images